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Sample records for calcite crystal orientation

  1. Calcite crystal growth rate inhibition by polycarboxylic acids

    Science.gov (United States)

    Reddy, M.M.; Hoch, A.R.

    2001-01-01

    Calcite crystal growth rates measured in the presence of several polycarboxyclic acids show that tetrahydrofurantetracarboxylic acid (THFTCA) and cyclopentanetetracarboxylic acid (CPTCA) are effective growth rate inhibitors at low solution concentrations (0.01 to 1 mg/L). In contrast, linear polycarbocylic acids (citric acid and tricarballylic acid) had no inhibiting effect on calcite growth rates at concentrations up to 10 mg/L. Calcite crystal growth rate inhibition by cyclic polycarboxyclic acids appears to involve blockage of crystal growth sites on the mineral surface by several carboxylate groups. Growth morphology varied for growth in the absence and in the presence of both THFTCA and CPTCA. More effective growth rate reduction by CPTCA relative to THFTCA suggests that inhibitor carboxylate stereochemical orientation controls calcite surface interaction with carboxylate inhibitors. ?? 20O1 Academic Press.

  2. Mechanism of Calcite Co-Orientation in the Sea Urchin Tooth

    Energy Technology Data Exchange (ETDEWEB)

    Killian, Christopher; Metzler, Rebecca; Gong, Y. U. T.; Olson, Ian; Aizenberg, Joanna; Politi, Yael; Wilt, Fred; Scholl, Andreas; Young, Anthony; Doran, Andrew; Kunz, Martin; Tamura, Nobumichi; Coppersmith, Susan; Gilbert, P. U. P. A.

    2009-12-01

    Sea urchin teeth are remarkable and complex calcite structures, continuously growing at the forming end and self-sharpening at the mature grinding tip. The calcite (CaCO{sub 3}) crystals of tooth components, plates, fibers, and a high-Mg polycrystalline matrix, have highly co-oriented crystallographic axes. This ability to co-orient calcite in a mineralized structure is shared by all echinoderms. However, the physico-chemical mechanism by which calcite crystals become co-oriented in echinoderms remains enigmatic. Here, we show differences in calcite c-axis orientations in the tooth of the purple sea urchin (Strongylocentrotus purpuratus), using high-resolution X-ray photoelectron emission spectromicroscopy (X-PEEM) and microbeam X-ray diffraction ({mu}XRD). All plates share one crystal orientation, propagated through pillar bridges, while fibers and polycrystalline matrix share another orientation. Furthermore, in the forming end of the tooth, we observe that CaCO{sub 3} is present as amorphous calcium carbonate (ACC). We demonstrate that co-orientation of the nanoparticles in the polycrystalline matrix occurs via solid-state secondary nucleation, propagating out from the previously formed fibers and plates, into the amorphous precursor nanoparticles. Because amorphous precursors were observed in diverse biominerals, solid-state secondary nucleation is likely to be a general mechanism for the co-orientation of biomineral components in organisms from different phyla.

  3. Monoclinic deformation of calcite crystals at ambient conditions

    Science.gov (United States)

    Przeniosło, R.; Fabrykiewicz, P.; Sosnowska, I.

    2016-09-01

    High resolution synchrotron radiation powder diffraction shows that the average crystal structure of calcite at ambient conditions is described with the trigonal space group R 3 bar c but there is a systematic hkl-dependent Bragg peak broadening. A modelling of this anisotropic peak broadening with the microstrain model from Stephens (1999) [15] is presented. The observed lattice parameters' correlations can be described by assuming a monoclinic-type deformation of calcite crystallites. A quantitative model of this monoclinic deformation observed at ambient conditions is described with the space group C 2 / c . The monoclinic unit cell suggested at ambient conditions is related with the monoclinic unit cell reported in calcite at high pressure (Merrill and Bassett (1975) [10]).

  4. Radiation damage in diopside and calcite crystals from uranothorianite inclusions

    OpenAIRE

    A.-M. Seydoux-Guillaume; J.-M. Montel; Richard Wirth; Moine, B.

    2009-01-01

    Combining observation and simulation, radiohalos formed around urano-thorianite (UTh) from the Tranomaro granulitic skarns (SE-Madagascar) were studied. These structures consist of UTh grains surrounded by both aluminous diopside (Cpx) and calcite (Cc1) crystals. Optical microscope and Scanning Electron Microscope (SEM) images revealed (1) the presence of radiating cracks around the UTh probably due to swelling of the metamict UTh, (2) a diffuse optical halo at the Cc1/UTh interface, and (3) ...

  5. On the origin of fiber calcite crystals in moonmilk deposits.

    Science.gov (United States)

    Cañaveras, Juan Carlos; Cuezva, Soledad; Sanchez-Moral, Sergio; Lario, Javier; Laiz, Leonila; Gonzalez, Juan Miguel; Saiz-Jimenez, Cesareo

    2006-01-01

    In this study, we show that moonmilk subaerial speleothems in Altamira Cave (Spain) consist of a network of fiber calcite crystals and active microbial structures. In Altamira moonmilks, the study of the typology and distribution of fiber crystals, extracellular polymeric substances, and microorganisms allowed us to define the initial stages of fiber crystal formation in recent samples as well as the variations in the microstructural arrangement in more evolved stages. Thus, we have been able to show the existence of a relationship among the different types of fiber crystals and their origins. This allowed us to outline a model that illustrates the different stages of formation of the moonmilk, developed on different substrata, concluding that microbes influence physicochemical precipitation, resulting in a variety of fiber crystal morphologies and sizes. PMID:16240102

  6. Crystal growth of calcite from calcium bicarbonate solutions at constant PCO2 and 25°C: a test of a calcite dissolution model

    Science.gov (United States)

    Reddy, Michael M.; Plummer, L. Neil; Busenberg, E.

    1981-01-01

    A highly reproducible seeded growth technique was used to study calcite crystallization from calcium bicarbonate solutions at 25°C and fixed carbon dioxide partial pressures between 0.03 and 0.3 atm. The results are not consistent with empirical crystallization models that have successfully described calcite growth at low PCO2 (crystallization rates and those calculated from the calcite dissolution rate law and mechanism proposed by Plummer et al. (1978).

  7. Origin of platy calcite crystals in hot-spring deposits in the Kenya Rift Valley

    Energy Technology Data Exchange (ETDEWEB)

    Jones, B. [Univ. of Alberta, Edmonton, Alberta (Canada). Dept. of Earth and Atmospheric Sciences; Renault, R.W. [Univ. of Saskatchewan, Saskatoon, Saskatchewan (Canada). Dept. of Geological Sciences

    1998-09-01

    Platy calcite crystals, which have their c axis parallel to their shortest length axis, are common components of travertine deposits found around some hot springs in the Kenya Rift Valley. They are composite crystals formed of numerous paper-thin subcrystals. Individual plates allowed to grow without obstruction develop a hexagonal motif. The Kenyan crystals typically form in hot (>75 C) waters that have a low Ca content (<10 mg/l), a high CO{sub 2} content, and a high rate of CO{sub 2} degassing. At Chemurkeu, aggregates of numerous small platy crystals collectively form lattice crystals that superficially resemble ray crystals. The walls of the lattice crystals are formed of large platy crystals that have their long and intermediate length axes aligned parallel to the plane of the long axis of the lattice crystal. Internally, the lattice crystals are formed of small platy calcite crystals arranged in a boxlike pattern that creates the appearance of a lattice when viewed in thin section. Lattice crystals are highly porous, with each pore being enclosed by platy crystals. At Lorusio, travertines are mainly formed of pseudodentrites that are constructed by numerous small platy crystals attached to a main stem which is a large platy crystal that commonly curves along its long axis. The pseudodentrites are the main construction blocks in ledges and lilypads that form in the vent pool and spring outflow channels, where the water is too hot for microbes other than hyperthermophiles. The platy calcite crystals in the Kenyan travertines are morphologically similar to platy calcite crystals that form as scale in pipes in the geothermal fields of New Zealand and hydrothermal angel wing calcite from the La Fe mine in Mexico. Comparison of the Kenyan and New Zealand crystals indicates that platy calcite crystals form from waters with a low Ca{sup 2+} content and a high CO{sub 3}/Ca ratio due to rapid rates of CO{sub 2} degassing.

  8. Skeletal crystals of calcite and trona from hot-spring deposits in Kenya and New Zealand

    Energy Technology Data Exchange (ETDEWEB)

    Jones, B. [Univ. of Alberta, Edmonton, Alberta (Canada). Dept. of Earth and Atmospheric Sciences; Renaut, R.W. [Univ. of Saskatchewan, Saskatoon, Saskatchewan (Canada). Dept. of Geological Sciences

    1996-01-01

    Skeletal crystals are hollow crystals that develop because their outer walls grow before their cores. The presence of skeletal crystals of calcite (three types--trigonal prisms, hexagonal prisms, and plates) and trona in hot (> 90 C) spring deposits in New Zealand (Waikite Springs and Ohaaki Pool) and Kenya (Lorusio hot springs) shows that they can form in natural sedimentary regimes. Analysis of samples from these deposits shows that this crystal morphology develops under disequilibrium conditions that are unrelated to a specific environmental or diagenetic setting. Skeletal crystals transform into solid crystals when subsequent precipitation fills their hollow cores. In some cases, this may involve precipitation of crystalline material that has a sieve-like texture. In other examples, the skeletal crystal provides a framework upon which other materials can be precipitated. Walls in the skeletal trigonal calcite prisms from Waikite Springs are formed of subcrystals that mimic the shape of the parent crystal. Similarly, plate-like skeletal crystals from Lorusio are formed of densely packed subcrystals that are < 0.5 {micro}m long. Conversely, the walls of the skeletal hexagonal calcite crystals from Ohaaki Pool and the skeletal trona crystals from Lorusio are not formed of subcrystals. Recognition of skeletal crystals is important because they represent growth that follows the reverse pattern of normal growth. Failure to recognize that crystal growth followed the skeletal motif may lead to false interpretations concerning the growth of a crystal.

  9. Accurate measurement of the main refractive indices and thermo-optical coefficients of the calcite crystal

    Institute of Scientific and Technical Information of China (English)

    Shuang Zhao; Fuquan Wu; Haifeng Wang; Weigang Zhong; Xiuzhen Li; Hengjing Tang; Meng Shi; Hongyan Deng

    2007-01-01

    The main refractive indices of calcite crystal are measured by the means of auto-collimation, and the thermo-optical coefficients are calculated. The coefficient expression of Sellmeier equation is obtained by solving Sellmeier equation strictly and the refractive indices of different wavelengths are calculated, which accord with experimental esultsery well. The measured main refractive indices of calcite at 488-nm wavelength are identical with the values obtained by Sellmeier equation.

  10. Strain-relief by single dislocation loops in calcite crystals grown on self-assembled monolayers

    Science.gov (United States)

    Ihli, Johannes; Clark, Jesse N.; Côté, Alexander S.; Kim, Yi-Yeoun; Schenk, Anna S.; Kulak, Alexander N.; Comyn, Timothy P.; Chammas, Oliver; Harder, Ross J.; Duffy, Dorothy M.; Robinson, Ian K.; Meldrum, Fiona C.

    2016-06-01

    Most of our knowledge of dislocation-mediated stress relaxation during epitaxial crystal growth comes from the study of inorganic heterostructures. Here we use Bragg coherent diffraction imaging to investigate a contrasting system, the epitaxial growth of calcite (CaCO3) crystals on organic self-assembled monolayers, where these are widely used as a model for biomineralization processes. The calcite crystals are imaged to simultaneously visualize the crystal morphology and internal strain fields. Our data reveal that each crystal possesses a single dislocation loop that occupies a common position in every crystal. The loops exhibit entirely different geometries to misfit dislocations generated in conventional epitaxial thin films and are suggested to form in response to the stress field, arising from interfacial defects and the nanoscale roughness of the substrate. This work provides unique insight into how self-assembled monolayers control the growth of inorganic crystals and demonstrates important differences as compared with inorganic substrates.

  11. In situ AFM crystal growth and dissolution study of calcite in the presence of aqueous fluoride

    Science.gov (United States)

    Vavouraki, A.; Putnis, C. V.; Putnis, A.; Koutsoukos, P. G.

    2009-04-01

    Fluoride is naturally abundant, encountered in rocks, soil and fresh and ocean water. Calcite crystals, during crystal growth may incorporate fluoride ions into their lattice (Okumura et al., 1983). In situ atomic force microscopy (AFM) has been used to study the growth and dissolution of calcite {104} surfaces in aqueous solutions in the presence of fluoride, using a fluid cell in which the supersaturated and the understaturated solutions respectively, flow over a freshly cleaved calcite crystal. For growth experiments, supersaturation index (S.I.) with respect to calcite was equal to 0.89 and the initial solution pH 10.2. The crystal growth rates were measured from the closure of the rhombohedral etch pits along the [010] direction induced by an initial dissolution step using pure water. The spreading rate of 2-dimensional nuclei was also measured along the same direction. In the presence of low fluoride concentrations (≤0.33 mM), the crystal growth rate of calcite was unaffected. At higher concentrations (up to 5 mM) growth rate decreased substantially to 50% of the rate in the absence of fluoride. Potential fluoride sorption over the calcite surface may ascribe the decrease of growth rates. Dissolution experiments were conducted at pH= 7.2 and dissolution rates of calcite were measured from the spreading of rhombohedral etch pits along both [010] and [42] directions. The presence of low concentrations of fluoride (≤1.1 mM) in the undersaturated solutions enhanced the dissolution rate along the [42] direction by 50% in comparison with pure water. The morphology of rhombohedral etch pits changed to hexagonal in the presence of fluoride in the undersaturated solutions. The AFM dissolution experiments suggested that the fluoride ions adsorbed onto the calcite surface. Further increase of fluoride concentrations (up to 1.6 mM) resulted in the decrease of the calcite dissolution rate by 60% in both [010] and [42] directions. Reference: Okumura, M, Kitano, Y

  12. From nanometer aggregates to micrometer crystals: Insight into the coarsening mechanism of calcite

    OpenAIRE

    Schultz L.N., Dideriksen K., Lakshtanov L., Hakim S.S., Müter D., Haußer F., Bechgaard K. and Stipp S.L.S.

    2013-01-01

    Grain size increases when crystals respond to dynamic equilibrium in a saturated solution. The pathway to coarsening is generally thought to be driven by Ostwald ripening, that is, simultaneous dissolution and reprecipitation, but models to describe Ostwald ripening neglect solid−solid interactions and crystal shapes. Grain coarsening of calcite, CaCO3, is relevant for biomineralization and commercial products and is an important process in diagenesis of ...

  13. Experimental study of the effect of mica on pressure solution of single crystal calcite

    Science.gov (United States)

    Karcz, Z.; Laronne, L.; Polizzotti, R. S.; Ertas, D.; Aharonov, E.

    2007-12-01

    Field and experimental studies suggest that clays and micas accelerate the rate of pressure solution in various geomaterials. It is not clear however whether the "clay effect" is purely mechanical (i.e., maintaining a thick conduit for fluids at the contact) or whether its surface chemistry plays a critical role. A case in point is the insoluble clay filling of stylolites, which are thought by some to be merely an inert byproduct of dissolution, or by others to be a necessary feature for the propagation of the seam. To study the effect of mica on carbonate pressure solution, the corner of a cleaved calcite single crystal rhomb was polished into a triangular face (edge length ~ 200micron) and pressed against either muscovite or quartz discs to yield a nominal stress of 10-20MPa. Immersing the contact in pre-saturated (with respect to microcrystalline calcite) solutions of distilled water or 0.25M NH4Cl caused axial shortening of the crystal. This axial strain was measured with a capacitance sensor (perimeter roughens. The second stage is distinguished by high axial strain rates (~40nm/h) and changes in the size and spatial position of isolated contacts (diameterfaces adjacent to it. At this point we see no significant difference between the calcite quartz and calcite muscovite experiments under similar load conditions.

  14. The effect of fluid composition, salinity, and acidity on subcritical crack growth in calcite crystals

    Science.gov (United States)

    Bergsaker, Anne Schad; Røyne, Anja; Ougier-Simonin, Audrey; Aubry, Jérôme; Renard, François

    2016-03-01

    Chemically activated processes of subcritical cracking in calcite control the time-dependent strength of this mineral, which is a major constituent of the Earth's brittle upper crust. Here experimental data on subcritical crack growth are acquired with a double torsion apparatus to characterize the influence of fluid pH (range 5-7.5) and ionic strength and species (Na2SO4, NaCl, MgSO4, and MgCl2) on the propagation of microcracks in calcite single crystals. The effect of different ions on crack healing has also been investigated by decreasing the load on the crack for durations up to 30 min and allowing it to relax and close. All solutions were saturated with CaCO3. The crack velocities reached during the experiments are in the range 10-9-10-2 m/s and cover the range of subcritical to close to dynamic rupture propagation velocities. Results show that for calcite saturated solutions, the energy necessary to fracture calcite is independent of pH. As a consequence, the effects of fluid salinity, measured through its ionic strength, or the variation of water activity have stronger effects on subcritical crack propagation in calcite than pH. Consequently, when considering the geological sequestration of CO2 into carbonate reservoirs, the decrease of pH within the range of 5-7.5 due to CO2 dissolution into water should not significantly alter the rate of fracturing of calcite. Increase in salinity caused by drying may lead to further reduction in cracking and consequently a decrease in brittle creep. The healing of cracks is found to vary with the specific ions present.

  15. Calcite crystal growth inhibition by humic substances with emphasis on hydrophobic acids from the Florida Everglades

    Science.gov (United States)

    Hoch, A.R.; Reddy, M.M.; Aiken, G.R.

    2000-01-01

    The crystallization of calcium carbonate minerals plays an integral role in the water chemistry of terrestrial ecosystems. Humic substances, which are ubiquitous in natural waters, have been shown to reduce or inhibit calcite crystal growth in experiments. The purpose of this study is to quantify and understand the kinetic effects of hydrophobic organic acids isolated from the Florida Everglades and a fulvic acid from Lake Fryxell, Antarctica, on the crystal growth of calcite (CaCO3). Highly reproducible calcite growth experiments were performed in a sealed reactor at constant pH, temperature, supersaturation (?? = 4.5), P(CO2) (10-3.5atm), and ionic strength (0.1 M) with various concentrations of organic acids. Higher plant-derived aquatic hydrophobic acids from the Everglades were more effective growth inhibitors than microbially derived fulvic acid from Lake Fryxell. Organic acid aromaticity correlated strongly with growth inhibition. Molecular weight and heteroatom content correlated well with growth inhibition, whereas carboxyl content and aliphatic nature did not. Copyright (C) 1999 Elsevier Science Ltd.

  16. Flux Growth and Crystal Structure Refinement of Calcite Type Borate GaBO3

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    Shichao Wang

    2015-05-01

    Full Text Available A single crystal of gallium borate, GaBO3, 4 × 4 × 0.2 mm3 in size has been grown by spontaneous crystallization with a molten flux based on a Bi2O3-3B2O3 solvent. From single crystal X-ray diffraction measurement, GaBO3 was found to crystallize in the trigonal calcite type, space group R-3c, with cell dimensions a = 4.56590(10 and c = 14.1764(4 Å, Z = 6. Layers of distorted [GaO6] octahedra are interleaved by layers of triangular planar [BO3] unites. The transmission spectrum on a single crystal indicated that the band gap of GaBO3 is 3.62 eV.

  17. Morphological tranformation of calcite crystal growth by prismatic "acidic" polypeptide sequences.

    Energy Technology Data Exchange (ETDEWEB)

    Kim, I; Giocondi, J L; Orme, C A; Collino, J; Evans, J S

    2007-02-13

    Many of the interesting mechanical and materials properties of the mollusk shell are thought to stem from the prismatic calcite crystal assemblies within this composite structure. It is now evident that proteins play a major role in the formation of these assemblies. Recently, a superfamily of 7 conserved prismatic layer-specific mollusk shell proteins, Asprich, were sequenced, and the 42 AA C-terminal sequence region of this protein superfamily was found to introduce surface voids or porosities on calcite crystals in vitro. Using AFM imaging techniques, we further investigate the effect that this 42 AA domain (Fragment-2) and its constituent subdomains, DEAD-17 and Acidic-2, have on the morphology and growth kinetics of calcite dislocation hillocks. We find that Fragment-2 adsorbs on terrace surfaces and pins acute steps, accelerates then decelerates the growth of obtuse steps, forms clusters and voids on terrace surfaces, and transforms calcite hillock morphology from a rhombohedral form to a rounded one. These results mirror yet are distinct from some of the earlier findings obtained for nacreous polypeptides. The subdomains Acidic-2 and DEAD-17 were found to accelerate then decelerate obtuse steps and induce oval rather than rounded hillock morphologies. Unlike DEAD-17, Acidic-2 does form clusters on terrace surfaces and exhibits stronger obtuse velocity inhibition effects than either DEAD-17 or Fragment-2. Interestingly, a 1:1 mixture of both subdomains induces an irregular polygonal morphology to hillocks, and exhibits the highest degree of acute step pinning and obtuse step velocity inhibition. This suggests that there is some interplay between subdomains within an intra (Fragment-2) or intermolecular (1:1 mixture) context, and sequence interplay phenomena may be employed by biomineralization proteins to exert net effects on crystal growth and morphology.

  18. Liquid crystal orientation control in photonic liquid crystal fibers

    Science.gov (United States)

    Chychlowski, M. S.; Nowinowski-Kruszelnicki, E.; Woliński, T. R.

    2011-05-01

    Similarly to liquid crystal displays technology in photonic liquid crystal fibers (PLCFs) a molecular orientation control is a crucial issue that influences proper operation of PLCF-based devices. The paper presents two distinct configurations: planar and radial escaped orientation of the LC molecules inside capillaries as well as methods of their application to photonic liquid crystal fibers. Possibilities of LC orientation control influence both: attenuation and transmitting spectra of the PLCF The orienting method is based on creation of an additional orienting layer on the inner surface of the capillary or air hole of the photonic liquid crystal fiber. Aligning materials used in the experiment are commercially available polyimides SE1211 and SE130 which induce liquid crystal homeotropic and planar anchoring conditions. The orienting layer increase an order parameter of the liquid crystal improving propagation properties and stability of photonic liquid crystal fiber-based devices.

  19. Effect of annealing on natural calcitic crystals-A thermostimulated luminescence (TSL) study

    Energy Technology Data Exchange (ETDEWEB)

    Ponnusamy, V., E-mail: ponnu@mitindia.edu [Department of Physics, Division of Applied Sciences and Humanities, M.I.T. Campus, Anna University, Chennai 600044, Tamilnadu (India); Ramasamy, V. [Department of Physics, Annamalai University, Annamalainagar 608002, Tamilnadu (India); Jose, M.T. [Radiological Safety Division, IGCAR, Kalpakkam, Tamilnadu (India); Anandalakshmi, K. [Department of Physics, Annamalai University, Annamalainagar 608002, Tamilnadu (India)

    2012-04-15

    The quality crystals (Calcitic limestone) were selected using the UV-visible methylene blue adsorption method. The thermostimulated luminescence (TSL) glow curve characteristics of six well crystallized limestone samples were analyzed. The glow curves of unannealed sample show only one peak in the range 320-330 Degree-Sign C. The sample irradiated with a gamma dose of 100 Gy shows two additional peaks in the range of 113-125 Degree-Sign C and 242-260 Degree-Sign C when recorded with linear heating rate of 10 Degree-Sign C/s. The annealed sample also shows the same trend as that of irradiated sample. Annealing treatment above 250 Degree-Sign C increases the sensitivity of all TSL peaks except 320 Degree-Sign C. On the other hand, annealing at 750 Degree-Sign C caused a collapse in the TSL sensitivity. The enhancement in TSL sensitivity was found to depend on the annealing temperature and time. Annealing treatment at 650 Degree-Sign C for 4 h followed by quenching in air is the optimum condition for TSL sensitization. The response to gamma irradiation is linear in the range from 0.5 Gy to 10{sup 4} Gy. The emission spectra of all the samples show an emission at around 610 nm but with different intensities for each TSL peak. With reference to earlier work, it may be assumed that the recombination site always involves Mn{sup 2+} ions. The observation made through infra-red (IR) and X-ray diffraction (XRD) studies with thermal treatment shows the structural changes of calcite from D{sub 3h} to C{sub s} symmetry at 750 Degree-Sign C. The Thermogravimetric-Differential Thermal Analysis (TG-DTA) analysis shows the calcite gets disordered at 760 Degree-Sign C. Hence, the collapse in the TSL sensitivity at 750 Degree-Sign C is due to structural change or structural disorderedness. - Highlights: Black-Right-Pointing-Pointer Normally, the synthetic material was used as radiation dosimeter but the natural material can also be used for the same application. Black

  20. Puzzling calcite-III dimorphism: crystallography, high-pressure behavior, and pathway of single-crystal transitions

    Science.gov (United States)

    Pippinger, T.; Miletich, R.; Merlini, M.; Lotti, P.; Schouwink, P.; Yagi, T.; Crichton, W. A.; Hanfland, M.

    2015-01-01

    High-pressure phase transformations between the polymorphic forms I, II, III, and IIIb of CaCO3 were investigated by analytical in situ high-pressure high-temperature experiments on oriented single-crystal samples. All experiments at non-ambient conditions were carried out by means of Raman scattering, X-ray, and synchrotron diffraction techniques using diamond-anvil cells in the pressure range up to 6.5 GPa. The composite-gasket resistive heating technique was applied for all high-pressure investigations at temperatures up to 550 K. High-pressure Raman spectra reveal distinguishable characteristic spectral differences located in the wave number range of external modes with the occurrence of band splitting and shoulders due to subtle symmetry changes. Constraints from in situ observations suggest a stability field of CaCO3-IIIb at relatively low temperatures adjacent to the calcite-II field. Isothermal compression of calcite provides the sequence from I to II, IIIb, and finally, III, with all transformations showing volume discontinuities. Re-transformation at decreasing pressure from III oversteps the stability field of IIIb and demonstrates the pathway of pressure changes to determine the transition sequence. Clausius-Clapeyron slopes of the phase boundary lines were determined as: Δ P/Δ T = -2.79 ± 0.28 × 10-3 GPa K-1 (I-II); +1.87 ± 0.31 × 10-3 GPa K-1 (II/III); +4.01 ± 0.5 × 10-3 GPa K-1 (II/IIIb); -33.9 ± 0.4 × 10-3 GPa K-1 (IIIb/III). The triple point between phases II, IIIb, and III was determined by intersection and is located at 2.01(7) GPa/338(5) K. The pathway of transition from I over II to IIIb can be interpreted by displacement with small shear involved (by 2.9° on I/II and by 8.2° on II/IIIb). The former triad of calcite-I corresponds to the [20-1] direction in the P21/ c unit cell of phase II and to [101] in the pseudomonoclinic C setting of phase IIIb. Crystal structure investigations of triclinic CaCO3-III at non-ambient pressure

  1. Semiconductor monolayer assemblies with oriented crystal faces

    KAUST Repository

    Ma, Guijun

    2012-01-01

    Fabrication of two-dimensional monolayers of crystalline oxide and oxynitride particles was attempted on glass plate substrates. X-Ray diffraction patterns of the assemblies show only specific crystal facets, indicative of the uniform orientation of the particles on the substrate. The selectivity afforded by this immobilization technique enables the organization of randomly distributed polycrystalline powders in a controlled manner.

  2. Characteristic crystal orientation of folia in oyster shell, Crassostrea gigas

    International Nuclear Information System (INIS)

    The thin sheets of calcite, termed folia, that make up much of the shell of an oyster are composed of foliated lath. Folia of the giant Pacific oyster (Crassostrea gigas) were examined using TEM (transmission electron microscopy) and tested using microindentation and nanoindentation techniques. Analysis of the Kikuchi patterns obtained from the folia showed that there are two types (type I and type II) of preferred orientation, with an angle of around 70o between them. Nanoindentation tests showed that the folia exhibit a hardness of about 3 GPa and elastic modulus of about 73 GPa. Microcracks were generated using a microindenter in order to study the fracture mechanisms of the folia. Following on from these investigations, fracture mechanisms are discussed in conjunction with the correlation between preferred orientation and structural characteristics during cracking of the folia. Comparing the morphology and the polymorphism with nacre (also known as mother of pearl), the advantages of the relatively fast crystal growth and less amount of organic matrix in folia may have interesting implications for the development of sophisticated synthetic materials

  3. Characteristic crystal orientation of folia in oyster shell, Crassostrea gigas

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Seung Woo [Department of Chemical and Biomolecular Engineering, Sogang University, Seoul (Korea, Republic of); Kim, Gyeung Ho [Nano-Materials Reserch Center, Korea Institute of Science and Technology, Seoul (Korea, Republic of); Choi, Cheong Song [Department of Chemical and Biomolecular Engineering, Sogang University, Seoul (Korea, Republic of)], E-mail: cschoi@sogang.ac.kr

    2008-03-10

    The thin sheets of calcite, termed folia, that make up much of the shell of an oyster are composed of foliated lath. Folia of the giant Pacific oyster (Crassostrea gigas) were examined using TEM (transmission electron microscopy) and tested using microindentation and nanoindentation techniques. Analysis of the Kikuchi patterns obtained from the folia showed that there are two types (type I and type II) of preferred orientation, with an angle of around 70{sup o} between them. Nanoindentation tests showed that the folia exhibit a hardness of about 3 GPa and elastic modulus of about 73 GPa. Microcracks were generated using a microindenter in order to study the fracture mechanisms of the folia. Following on from these investigations, fracture mechanisms are discussed in conjunction with the correlation between preferred orientation and structural characteristics during cracking of the folia. Comparing the morphology and the polymorphism with nacre (also known as mother of pearl), the advantages of the relatively fast crystal growth and less amount of organic matrix in folia may have interesting implications for the development of sophisticated synthetic materials.

  4. Modification of calcite crystal morphology by designed phosphopeptides and primary structures and substrate specifities of the cysteine proteases mexicain and chymomexicain

    Science.gov (United States)

    Lian, Zhirui

    In order to better understand the mechanism of biomineralization, we have undertaken to synthesize polypeptide model compounds of well-defined structure that can interact with specific faces of calcite and alter its crystal morphology. These peptides were designed based on the structure of alpha-helical winter flounder antifreeze polypeptide HPLC-6. In these peptides, from one to three of the threonine residues in HPLC-6 were substituted by phosphoserine or phosphotyrosine. CD spectra show that all the peptides have virtually the same alpha-helicity, i.e., about 90% at 4°C and 50% at 25°C. However, only peptides which contain at least two phosphate groups spaced 16.8-A apart can modify the crystal morphology of the calcite. The newly developed surface has been tentatively identified as the (001) basal face. Molecular modeling indicates that the spacing of phosphate groups allows for a good match with crystal lattice ions on the (001) plane. Another peptide, CBP-3D, in which the three threonine residues in HPLC-6 were substituted by aspartic acids, appears to bind only to {104} rhombohedral faces of calcite. These experiments suggest that conformation and orientation of the binding ligands in the peptide are important factors governing the mutual recognition of crystal surface and proteins. The complete amino acid sequences of the cysteine proteases mexicain and chymomexicain, isolated from the latex of the plant Pileus mexicanus , were determined by Edman degradation of proteolytic fragments. Mexicain and chymomexicain show-high sequence homology to the papain family of cysteine protease. Mexicain and chymomexicain are monomeric polypeptides, with molecular masses of 23,762 Da and 23,694 Da, respectively, and both contain three deduced disulfide bonds. The proteolytic substrate specificities of mexicain and chymomexicain were studied by digesting a series of synthetic peptides and analyzing the fragments by mass spectrometry. The two proteases showed virtually

  5. Crystal Dislocations with Different Orientations and Collisions

    Science.gov (United States)

    Patrizi, Stefania; Valdinoci, Enrico

    2015-07-01

    We study a parabolic differential equation whose solution represents the atom dislocation in a crystal for a general type of Peierls-Nabarro model with possibly long range interactions and an external stress. Differently from the previous literature, we treat here the case in which such dislocation is not the superposition of transitions all occurring with the same orientations (i.e. opposite orientations are allowed as well). We show that, at a long time scale, and at a macroscopic space scale, the dislocations have the tendency to concentrate as pure jumps at points which evolve in time, driven by the external stress and by a singular potential. Due to differences in the dislocation orientations, these points may collide in finite time. More precisely, we consider the evolutionary equation where is the atom dislocation function at time t > 0 at the point is an integro-differential operator of order is a periodic potential, is an external stress and is a small parameter that takes into account the small periodicity scale of the crystal. We suppose that is the superposition of N- K transition layers in the positive direction and K in the negative one (with ); more precisely, we fix points and we take Here is either -1 or 1, depending on the orientation of the transition layer u, which in turn solves the stationary equation . We show that our problem possesses a unique solution and that, as , it approaches the sum of Heaviside functions H with different orientations centered at points x i ( t), namely The point x i evolves in time from , being subject to the external stress and a singular potential, which may be either attractive or repulsive, according to the different orientation of the transitions; more precisely, the speed is proportional to The evolution of such a dynamical system may lead to collisions in finite time. We give a detailed description of such collisions when N = 2, 3 and we show that the solution itself keeps track of such collisions; indeed, at

  6. High surface area calcite

    Science.gov (United States)

    Schultz, L. N.; Andersson, M. P.; Dalby, K. N.; Müter, D.; Okhrimenko, D. V.; Fordsmand, H.; Stipp, S. L. S.

    2013-05-01

    Calcite (CaCO3) is important in many fields—in nature, because it is a component of aquifers, oil reservoirs and prospective CO2 storage sites, and in industry, where it is used in products as diverse as paper, toothpaste, paint, plastic and aspirin. It is difficult to obtain high purity calcite with a high surface area but such material is necessary for industrial applications and for fundamental calcite research. Commercial powder is nearly always contaminated with growth inhibitors such as sugars, citrate or pectin and most laboratory synthesis methods deliver large precipitates, often containing vaterite or aragonite. To address this problem, we (i) adapted the method of carbonating a Ca(OH)2 slurry with CO2 gas to develop the first simple, cheap, safe and reproducible procedure using common laboratory equipment, to obtain calcite that reproducibly had a surface area of 14-17 m2/g and (ii) conducted a thorough characterization of the product. Scanning electron microscopy (SEM) revealed nanometer scale, rhombohedral crystals. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR) confirmed highly crystalline, pure calcite that more closely resembles the dimensions of the biogenic calcite produced by algae in coccoliths than other methods for synthesizing calcite. We suggest that this calcite is useful when purity and high surface area are important.

  7. Control of liquid crystal molecular orientation using ultrasound vibration

    Science.gov (United States)

    Taniguchi, Satoki; Koyama, Daisuke; Shimizu, Yuki; Emoto, Akira; Nakamura, Kentaro; Matsukawa, Mami

    2016-03-01

    We propose a technique to control the orientation of nematic liquid crystals using ultrasound and investigate the optical characteristics of the oriented samples. An ultrasonic liquid crystal cell with a thickness of 5-25 μm and two ultrasonic lead zirconate titanate transducers was fabricated. By exciting the ultrasonic transducers, the flexural vibration modes were generated on the cell. An acoustic radiation force to the liquid crystal layer was generated, changing the molecular orientation and thus the light transmission. By modulating the ultrasonic driving frequency and voltage, the spatial distribution of the molecular orientation of the liquid crystals could be controlled. The distribution of the transmitted light intensity depends on the thickness of the liquid crystal layer because the acoustic field in the liquid crystal layer is changed by the orientational film.

  8. Evolution and the Calcite Eye Lens

    CERN Document Server

    Williams, Vernon L

    2013-01-01

    Calcite is a uniaxial, birefringent crystal, which in its optically transparent form, has been used for animal eye lenses, the trilobite being one such animal. Because of the calcite birefringence there is a difficulty in using calcite as a lens. When the propagation direction of incoming light is not exactly on the c-axis, the mages blur. In this paper, calcite blurring is evaluated, and the non-blurring by a crystallin eye lens is compared to a calcite one.

  9. Investigation on the Orientation Transition of Oriented Magnetostrictive TbDyFe Crystals

    Institute of Scientific and Technical Information of China (English)

    LIU Wei; JIANG Cheng-bao

    2006-01-01

    and TbDyFe magnetostrictive oriented crystals were prepared by the zone-melting unidirectional solidification method at 240 mm/h and 720 mm/h respectively. oriented crystals were also obtained with oriented seeds with the same technique as for growing the oriented crystals. It is confirmed that this technique is stable for growing the oriented crystals in the TbDyFe alloys. Meanwhile, the variation of orientation, the solidification morphology and the magnetostriction were studied during the transition from oriented seeds to the oriented crystal growth. As the growth speeds up, the preferred orientation changed from to , and its morphology develops from of initial cellular to dendritic gradually. When an axial compressive pre-stress of 10 MPa is applied, the magnetostriction at the bottom, the middle and the top are 972×10-6, 918×10-6 and 900×10-6 at 100 mT respectively. The middle sections with mixed orientations have the same high magnetostriction performance as those with a single preferred orientation, which may be due to its celluar-dendritic morphology.

  10. Preparing polished crystal slices with high precision orientation

    DEFF Research Database (Denmark)

    Mathiesen, S. Ipsen; Gerward, Leif; Pedersen, O.

    1974-01-01

    A polishing procedure is described which utilizes a high precision Laue technique for crystal orientation. Crystal slices with their final polished surfaces parallel to a crystallographic plane within 0.02° can be prepared. ©1974 The American Institute of Physics......A polishing procedure is described which utilizes a high precision Laue technique for crystal orientation. Crystal slices with their final polished surfaces parallel to a crystallographic plane within 0.02° can be prepared. ©1974 The American Institute of Physics...

  11. X-ray scattering of calcite thin films deposited by atomic layer deposition: Studies in air and in calcite saturated water solution

    International Nuclear Information System (INIS)

    Carbonates are one of the most abundant groups of minerals in earth systems and are important in many geological settings and industrial processes. Calcite (CaCO3) thin films produced by atomic layer deposition offer a method to evaluate the surficial properties of carbonates as well as interactions at the carbonate–fluid interface. Using synchrotron X-ray reflectivity and X-ray diffraction, these films are observed to be porous, polycrystalline, and have crystallites oriented with the major (104) calcite cleavage plane parallel to the surface of the z-cut single crystal quartz substrate. An Al2O3 buffer layer, present between quartz and the calcite film, does not affect the as-deposited film, but does influence how the films reorganize in contact with fluid. Without a buffer layer, calcite reorients its crystallites to have populations of (006) and (030) parallel to the substrate, while those with an Al2O3 buffer layer become more amorphous. Amorphous films may represent an analog to amorphous calcium carbonate and provide insights into that material's thermophysical behavior. Due to a higher percentage of pore spaces available for fluid infiltration, films deposited at higher temperature make the calcite thin films more susceptible to amorphization. These films are chemically similar, but structurally dissimilar to bulk natural calcite. Nevertheless, they can be a complementary system to traditional single crystal X-ray surface scattering studies on carbonates, particularly for important but less common minerals, to evaluate mineral–fluid interfacial interactions. - Highlights: • Atomic layer deposition (ALD) used to produce calcite films. • Calcite film orientation and crystallinity depend on ALD parameters. • ALD calcite films can be both crystalline and amorphous. • Interaction of water with films can re-orient or amorphize the films. • ALD calcite films may be useful to study carbonate–fluid interfacial interactions

  12. CRYSTALLIZATION BEHAVIOR OF POLYLACTIDE ON HIGHLY ORIENTED POLYETHYLENE THIN FILMS

    Institute of Scientific and Technical Information of China (English)

    Yu-kuan An; Shi-dong Jiang; Shou-ke Yan; Jing-ru Sun; Xue-si Chen

    2011-01-01

    The crystalline structure and morphology of the PLA crystallized isothermally from the glassy state on highly oriented PE substrates at 130℃ were investigated by means of optical microscopy, AFM and X-ray diffraction. The results indicate that the PE substrate influences the crystallization behavior of PLA remarkably, which leads to the growth of PLA crystals on PE substrate always in edge-on form rather than the twisted lamellar crystals from edge-on to flat-on when crystallizing the PLA on glass surface under the same condition. The edge-on PLA lamellae on the PE substrate are preferentially arranged with their long axes in the chain direction of the PE substrate crystals. It is further demonstrated that except for the different crystal orientation, the PE does not influence the crystalline modification and crystallinity of the PLA.

  13. Calcite sealing in a fractured geothermal reservoir: Insights from combined EBSD and chemistry mapping

    Science.gov (United States)

    McNamara, David D.; Lister, Aaron; Prior, Dave J.

    2016-09-01

    Fractures play an important role as fluid flow pathways in geothermal resources hosted in indurated greywacke basement of the Taupo Volcanic Zone, New Zealand, including the Kawerau Geothermal Field. Over time, the permeability of such geothermal reservoirs can be degraded by fracture sealing as minerals deposit out of transported geothermal fluids. Calcite is one such fracture sealing mineral. This study, for the first time, utilises combined data from electron backscatter diffraction and chemical mapping to characterise calcite vein fill morphologies, and gain insight into the mechanisms of calcite fracture sealing in the Kawerau Geothermal Field. Two calcite sealing mechanisms are identified 1) asymmetrical syntaxial growth of calcite, inferred by the presence of single, twinned, calcite crystals spanning the entire fracture width, and 2) 3D, interlocking growth of bladed vein calcite into free space as determined from chemical and crystallographic orientation mapping. This study also identifies other potential uses of combined EBSD and chemical mapping to understand geothermal field evolution including, potentially informing on levels of fluid supersaturation from the study of calcite lattice distortion, and providing information on a reservoir's history of stress, strain, and deformation through investigation of calcite crystal deformation and twinning patterns.

  14. Unified rotational dynamics of molecular crystals with orientational phase transition

    NARCIS (Netherlands)

    Michel, K.H.; Raedt, H. De

    1976-01-01

    A unified theory for the rotational dynamics of molecular crystals with orientational phase transitions is given. As basic secular variables one takes symmetry adapted functions, which describe the molecular orientations, and the angular momenta of the molecules. Using Mori’s projection operator tec

  15. Deformation microstructure and orientation of F.C.C. crystals

    DEFF Research Database (Denmark)

    Liu, Q.; Hansen, N.

    1995-01-01

    The effect of crystallographic orientation on the microstructural evolution in f.c.c. metals with medium to high stacking fault energy is analyzed. This analysis is based on a literature review of the behaviour of single crystals and polycrystals supplemented with an experimental study of cold-rolled...... that dependent on the crystallographic orientation of the crystal the subdividing boundaries may be nearly parallel to slip planes or they may have a non-crystallographic orientation. This difference is discussed on the basis of an analysis of potential slip planes identified by a Schmid factor...

  16. Crystal-Orientation Dependent Evolution of Edge Dislocations from a Void in Single Crystal Gu

    Institute of Scientific and Technical Information of China (English)

    SONG Zhen-Fei; ZHU Wen-Jun; DENG Xiao-Liang; HE Hong-Liang

    2006-01-01

    @@ The micro-void growth by dislocation emission under tensile loading is explored with focus on the influence of crystal orientations. Based on the elastic theory, a dislocation emission criterion is formulated. It is predicted that the preferential location of dislocation nucleation and its threshold stress are dependent on the crystal orientation.Large-scale molecular dynamics (MD) simulations are also performed for single crystal copper to illustrate the dislocation evolution pattern associated with a nano-void growth. The results are in line with those given by the theoretical prediction. As revealed by MD simulations, the characteristics of void growth at micro-scale depend greatly on the crystal-orientation.

  17. Sulfated Macromolecules as Templates for Calcite Nucleation and Growth

    Science.gov (United States)

    David, M.; Passalacqua, K.; Neira, A. C.; Fernandez, M. S.

    2003-12-01

    Mineralization of egg and seashells is controlled by an intimate association of inorganic materials with organic macromolecules. Among them, particular polyanionic sulfated macromolecules referred to as proteoglycans have been described to be involved in the calcification of these biominerals. The sulfated moieties of the proteoglycans are part of polymer chains constituted of building-blocks of disaccharide units, referred to as sulfated glycosaminoglycans (GAGs), which are covalently attached to a protein core. By using a sitting drop crystallization assay under controlled conditions of time, pH and reactants concentration, we have tested several sulfated and non-sulfated GAGs (i.e.: dermatan and keratan sulfate, hyaluronic acid and heparin), differing in their sulfonate and carboxylate degree and pattern, in their ability to modify calcium carbonate crystal morphology as observed under scanning electron microscopy. Without the addition of GAGs, regular \\{104\\} rhombohedral calcite crystals were obtained. When hyaluronic acid (HA), a non-sulfated but carboxylated GAG, was added, 20 mm long piles of unmodified calcite crystals were observed. When desulfated dermatan, which is an epimeric form of HA but shorter polymer, having their carboxylate groups in an inverted configuration, was added, isolated rhombohedral \\{104\\} calcite crystals showing rounded corners with planes oriented parallel to the c axis were observed. When dermatan sulfated was added, isolated calcite crystals exhibit a columnar morphology as a \\{hk0\\} cylinder with three \\{104\\} faces forming a cap at both ends. Heparin activity depends on the fraction added. Fast-moving heparin fraction (FM), is an undersulfated, low-molecular-weight heterogeneous polymer, while slow-moving heparin fraction (SM) is an high-molecular-weight homogeneous polymer rich in trisulfated-disaccharide units. When FM was added, isolated calcite crystals displayed rhombohedrical \\{104\\} faces but flat corners of

  18. The Crystal Hotel: A Microfluidic Approach to Biomimetic Crystallization.

    Science.gov (United States)

    Gong, Xiuqing; Wang, Yun-Wei; Ihli, Johannes; Kim, Yi-Yeoun; Li, Shunbo; Walshaw, Richard; Chen, Li; Meldrum, Fiona C

    2015-12-01

    A "crystal hotel" microfluidic device that allows crystal growth in confined volumes to be studied in situ is used to produce large calcite single crystals with predefined crystallographic orientation, microstructure, and shape by control of the detailed physical environment, flow, and surface chemistry. This general approach can be extended to form technologically important, nanopatterned single crystals. PMID:26479157

  19. Crystal orientation dependent thermoelectric properties of highly oriented aluminum-doped zinc oxide thin films

    KAUST Repository

    Abutaha, Anas I.

    2013-02-06

    We demonstrate that the thermoelectric properties of highly oriented Al-doped zinc oxide (AZO) thin films can be improved by controlling their crystal orientation. The crystal orientation of the AZO films was changed by changing the temperature of the laser deposition process on LaAlO3 (100) substrates. The change in surface termination of the LaAlO3 substrate with temperature induces a change in AZO film orientation. The anisotropic nature of electrical conductivity and Seebeck coefficient of the AZO films showed a favored thermoelectric performance in c-axis oriented films. These films gave the highest power factor of 0.26 W m−1 K−1 at 740 K.

  20. Automated determination of crystal orientations from electron backscattering patterns

    DEFF Research Database (Denmark)

    Lassen, Niels Christian Krieger

    1994-01-01

    pattern recognition procedure which enables 8 to 12 bands to be localized in typical EBSPs from a modern system. It will be described, how these automatically localized bands can be indexed and used for optimal estimation of the unknown crystal orientations. A necessary prerequisite for precise......The electron backscattering pattern (EBSP) technique is widely accepted as being an extremely powerful tool for measuring the crystallographic orientation of individual crystallites in polycrystalline materials. Procedures which allow crystal orientations to be calculated on the bases of the...... determination of crystallographic orientations from EBSPs is accurate knowledge of three calibration parameters which describe the position of the point from which the patterns are emitted relative to the phosphor screen on which they are recorded. This thesis will describe a novel method by which these...

  1. Radiation-induced cathodoluminescent signatures in calcite

    International Nuclear Information System (INIS)

    At ambient temperatures, a permanent change due to neutron irradiation has been identified in the luminescent properties of the common mineral calcite. Calcite is one of many ubiquitous minerals that are known to exhibit luminescence under electron bombardment, a process known as cathodoluminescence (CL). The UV–Visible spectra of individual calcite grains were measured with CL spectroscopy before and after neutron irradiation. Exposure to neutrons causes additional crystal lattice defects (beyond those naturally-occurring) that leave a permanent, readily-measurable CL signature in the 515 nm region of the spectrum. Dose response results following irradiation have been measured and a spectroscopic signature is described that increases proportionately to neutron dose. The CL measurements are complicated by a dependence on the orientation relative to direction of excitation. When taken into account, the total dose to the crystal can be estimated, and possibly even the direction of the neutron source can be determined. This signature could potentially be developed into a nuclear forensics tool to help identify locations where special nuclear materials have been stored.

  2. Director orientation of nematic liquid crystal using orientated nanofibers obtained by electrospinning

    Science.gov (United States)

    Toan, Duong Quoc; Ozaki, Ryotaro; Moritake, Hiroshi

    2014-01-01

    Nanofibers with diameters less than 1000 nm assembled by electrospinning and with a large surface area per unit mass have been attracting considerable attention and are expected to affect the orientation of liquid crystals (LCs). Firstly, to determine the orientated nanofibers on an indium-tin-oxide (ITO) glass surface, the spectral analysis technique of using fast Fourier transform is applied. Optical observation is performed to confirm the orientation of LC molecules in a twisted nematic LC cell. Finally, optical measurement of an LC cell is carried out to estimate the threshold voltage of the LC in two types of twisted nematic LC cell: one with rubbed polyimide and the other with orientated nanofibers as the alignment layer. A twisted nematic LC is oriented in the cell using orientated nanofibers as the alignment layer and the threshold voltage of this cell agrees with that of the conventional polyimide rubbed cell.

  3. Direction-specific interactions control crystal growth by oriented attachment

    DEFF Research Database (Denmark)

    Li, Dongsheng; Nielsen, Michael H; Lee, Jonathan R.I.;

    2012-01-01

    The oriented attachment of molecular clusters and nanoparticles in solution is now recognized as an important mechanism of crystal growth in many materials, yet the alignment process and attachment mechanism have not been established. We performed high-resolution transmission electron microscopy ...

  4. Crystal orientation effects on wurtzite quantum well electromechanical fields

    DEFF Research Database (Denmark)

    Duggen, Lars; Willatzen, Morten

    2010-01-01

    A one-dimensional continuum model for calculating strain and electric field in wurtzite semiconductor heterostructures with arbitrary crystal orientation is presented and applied to GaN/AlGaN and ZnO/MgZnO heterostructure combinations. The model is self-consistent involving feedback couplings of...

  5. Direction-Specific Interactions Control Crystal Growth by Oriented Attachment

    Science.gov (United States)

    Li, Dongsheng; Nielsen, Michael H.; Lee, Jonathan R. I.; Frandsen, Cathrine; Banfield, Jillian F.; De Yoreo, James J.

    2012-05-01

    The oriented attachment of molecular clusters and nanoparticles in solution is now recognized as an important mechanism of crystal growth in many materials, yet the alignment process and attachment mechanism have not been established. We performed high-resolution transmission electron microscopy using a fluid cell to directly observe oriented attachment of iron oxyhydroxide nanoparticles. The particles undergo continuous rotation and interaction until they find a perfect lattice match. A sudden jump to contact then occurs over less than 1 nanometer, followed by lateral atom-by-atom addition initiated at the contact point. Interface elimination proceeds at a rate consistent with the curvature dependence of the Gibbs free energy. Measured translational and rotational accelerations show that strong, highly direction-specific interactions drive crystal growth via oriented attachment.

  6. The Effect of Orientation Relaxation on Polymer Melt Crystallization Studied by Monte Carlo Simulations

    Institute of Scientific and Technical Information of China (English)

    WANG Mao-Xiang

    2009-01-01

    We use dynamic Monte Carlo simulations to study the athermal relaxation of bulk extended chains and the isothermal crystallization in intermediately relaxed melts. It is found that the memory of chain orientations in the melt can significantly enhance the crystallization rates. The crystal orientation and lamellar thickness essentially depend on the orientational relaxation. Moreover, there is a transition of the nucleation mechanism during the isothermal crystallization from the intermediately relaxed melts. These results explain the mechanism of the self-nucleation by orientation and suggest that in flow-induced polymer crystallization, the orientational relaxation of chains decides the crystal orientation.

  7. Orientational bistability in ferronematic liquid crystals with negative diamagnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Zakhlevnykh, A.N., E-mail: anz@psu.ru; Petrov, D.A.

    2015-11-01

    In the framework of continuum theory we study magnetic field induced orientational transitions in a ferronematic, i.e. suspension of single-domain magnetic particles in a nematic liquid crystal. We consider the case of negative diamagnetic susceptibility anisotropy of a liquid crystal and soft planar coupling of impurity particles with a liquid crystal matrix. We found tricritical behavior of the threshold transition in a magnetic field from perturbed state into uniform planar state. This transition can be the first or second order, depending on the parameter of the magnetic phase segregation. We analytically derive the expression for the tricritical segregation parameter that determines the character of a transition. We show that ferronematic has a large magneto-optical non-linearity which is the result of the director reorientation under external field. Comparison of results of numerical calculations with experimental data has been carried out. - Highlights: • We study orientational and magnetooptical properties of ferronematics. • We obtain the phase diagram for soft coupling of nanoparticles and liquid crystal. • We examine the character of magnetic field induced orientational transitions. • We found tricritical behavior of the transition from perturbed to uniform state. • We study the optical phase lag and the capacity of ferronematic cell.

  8. Composite Magnetite and Protein Containing CaCO3 Crystals. External Manipulation and Vaterite → Calcite Recrystallization-Mediated Release Performance.

    Science.gov (United States)

    Sergeeva, Alena; Sergeev, Roman; Lengert, Ekaterina; Zakharevich, Andrey; Parakhonskiy, Bogdan; Gorin, Dmitry; Sergeev, Sergey; Volodkin, Dmitry

    2015-09-30

    Biocompatibility and high loading capacity of mesoporous CaCO3 vaterite crystals give an option to utilize the polycrystals for a wide range of (bio)applications. Formation and transformations of calcium carbonate polymorphs have been studied for decades, aimed at both basic and applied research interests. Here, composite multilayer-coated calcium carbonate polycrystals containing Fe3O4 magnetite nanoparticles and model protein lysozyme are fabricated. The structure of the composite polycrystals and vaterite → calcite recrystallization kinetics are studied. The recrystallization results in release of both loaded protein and Fe3O4 nanoparticles (magnetic manipulation is thus lost). Fe3O4 nanoparticles enhance the recrystallization that can be induced by reduction of the local pH with citric acid and reduction of the polycrystal crystallinity. Oppositely, the layer-by-layer assembled poly(allylamine hydrochloride)/poly(sodium styrenesulfonate) polyelectrolyte coating significantly inhibits the vaterite → calcite recrystallization (from hours to days) most likely due to suppression of the ion exchange giving an option to easily tune the release kinetics for a wide time scale, for example, for prolonged release. Moreover, the recrystallization of the coated crystals results in formulation of multilayer capsules keeping the feature of external manipulation. This study can help to design multifunctional microstructures with tailor-made characteristics for loading and controlled release as well as for external manipulation. PMID:26348458

  9. Effect of the Surface Affinity of Liquid Crystals and Monomers on the Orientation of Polymer-Dispersed Liquid Crystal

    Science.gov (United States)

    Lee, Ji-Hoon; Yoon, Tae-Hoon

    2013-09-01

    We investigated the effect of the surface affinity of liquid crystals and reactive monomers on liquid crystal orientation. Liquid crystals and monomers having different contact angles with the vertical alignment polyimide were mixed and photo-polymerized using a UV light. Liquid crystals with smaller contact angles and reactive monomers with greater contact angles promoted a uniform vertical orientation of liquid crystals with a vertical polymer morphology. On the other hand, liquid crystals with greater contact angles and monomers with smaller contact angles resulted in a deformed liquid crystal orientation with an elliptical polymer structure.

  10. Effect of Crystal Orientation on Fatigue Failure of Single Crystal Nickel Base Turbine Blade Superalloys

    Science.gov (United States)

    Arakere, N. K.; Swanson, G.

    2002-01-01

    High cycle fatigue (HCF) induced failures in aircraft gas turbine and rocket engine turbopump blades is a pervasive problem. Single crystal nickel turbine blades are being utilized in rocket engine turbopumps and jet engines throughout industry because of their superior creep, stress rupture, melt resistance, and thermomechanical fatigue capabilities over polycrystalline alloys. Currently the most widely used single crystal turbine blade superalloys are PWA 1480/1493, PWA 1484, RENE' N-5 and CMSX-4. These alloys play an important role in commercial, military and space propulsion systems. Single crystal materials have highly orthotropic properties making the position of the crystal lattice relative to the part geometry a significant factor in the overall analysis. The failure modes of single crystal turbine blades are complicated to predict due to the material orthotropy and variations in crystal orientations. Fatigue life estimation of single crystal turbine blades represents an important aspect of durability assessment. It is therefore of practical interest to develop effective fatigue failure criteria for single crystal nickel alloys and to investigate the effects of variation of primary and secondary crystal orientation on fatigue life. A fatigue failure criterion based on the maximum shear stress amplitude /Delta(sub tau)(sub max))] on the 24 octahedral and 6 cube slip systems, is presented for single crystal nickel superalloys (FCC crystal). This criterion reduces the scatter in uniaxial LCF test data considerably for PWA 1493 at 1200 F in air. Additionally, single crystal turbine blades used in the alternate advanced high-pressure fuel turbopump (AHPFTP/AT) are modeled using a large-scale three-dimensional finite element model. This finite element model is capable of accounting for material orthotrophy and variation in primary and secondary crystal orientation. Effects of variation in crystal orientation on blade stress response are studied based on 297

  11. Calcite growth kinetics: Modeling the effect of solution stoichiometry

    NARCIS (Netherlands)

    Wolthers, M.; Nehrke, G.; Gustafsson, J.P.; Van Cappellen, P.

    2012-01-01

    Until recently the influence of solution stoichiometry on calcite crystal growth kinetics has attracted little attention, despite the fact that in most aqueous environments calcite precipitates from non-stoichiometric solution. In order to account for the dependence of the calcite crystal growth rat

  12. Effect of the interaction between bovine serum albumin Langmuir monolayer and calcite on the crystallization of CaCO3 nanoparticles

    International Nuclear Information System (INIS)

    Calcium carbonate nanoparticles were generated beneath the Langmuir monolayer of bovine serum albumin (BSA) via templated mineralization. The BSA monolayer and calcium carbonate nanoparticles were characterized based on the measurement of surface pressure-area (π-A) isotherms and area-time curve, and analyses of transmission electron microscopy (TEM), selected area electron diffraction (SAED), scanning electron microscopy (SEM), and X-ray diffraction (XRD) as well. The interaction mechanisms between BSA and calcium carbonate and the role of amorphous calcium carbonate (abridged as ACC) and lattice match in controlling the morphologies and microstructures of the target Calcium carbonate (CaCO3) crystals were discussed, and a model was suggested to illustrate the formation of CaCO3 crystals in the presence of the BSA monolayer. Results indicated that the calcium carbonate nanoparticles were formed through a multi-step process in the presence of the BSA monolayer. Both the amorphous calcium carbonate and lattice match played important roles in terms of the controlled biomineralization and organic matrix-mediated synthesis of CaCO3 nanoparticles. The transformation of amorphous calcium carbonate phase to calcite crystal phase could provide direct evidences to the multistep crystallization process in biomineralization. And the present approach could be used to guide the synthesis of advanced inorganic nanomaterials via simulated biomineralization under mild conditions

  13. Effect of Crystal Orientation on Analysis of Single-Crystal, Nickel-Based Turbine Blade Superalloys

    Science.gov (United States)

    Swanson, G. R.; Arakere, N. K.

    2000-01-01

    High-cycle fatigue-induced failures in turbine and turbopump blades is a pervasive problem. Single-crystal nickel turbine blades are used because of their superior creep, stress rupture, melt resistance, and thermomechanical fatigue capabilities. Single-crystal materials have highly orthotropic properties making the position of the crystal lattice relative to the part geometry a significant and complicating factor. A fatigue failure criterion based on the maximum shear stress amplitude on the 24 octahedral and 6 cube slip systems is presented for single-crystal nickel superalloys (FCC crystal). This criterion greatly reduces the scatter in uniaxial fatigue data for PWA 1493 at 1,200 F in air. Additionally, single-crystal turbine blades used in the Space Shuttle main engine high pressure fuel turbopump/alternate turbopump are modeled using a three-dimensional finite element (FE) model. This model accounts for material orthotrophy and crystal orientation. Fatigue life of the blade tip is computed using FE stress results and the failure criterion that was developed. Stress analysis results in the blade attachment region are also presented. Results demonstrate that control of crystallographic orientation has the potential to significantly increase a component's resistance to fatigue crack growth without adding additional weight or cost.

  14. Effect of Crystal Orientation on Nanoindentation Behavior in Magnesium

    Science.gov (United States)

    Somekawa, Hidetoshi; Schuh, Christopher A.

    2016-04-01

    The effect of crystal orientation on nanoindentation behavior at both quasi-static and high strain rates was investigated using single-crystalline magnesium oriented in basal and prismatic configurations. Both the basal and prismatic planes had similar activation volumes, 55 and 73b 3 for deformation at room temperature, as well as a small temperature dependence up to 423 K (150 °C). Microstructural observations beneath the indentations revealed that { 10bar{1}2 } type deformation twins were formed in both orientations irrespective of testing temperature. With twins forming beneath the indenter and multiple orientations of loading, it is believed that cross-slip and/or multiple slip are likely rate-controlling for global deformation, which also aligns with observations on nanoindentation of polycrystalline coarse-grained magnesium. The locations of the twins were consistent with expectations based on indentation mechanics as assessed by finite element simulations. The finite element simulations also predicted that an indenter tip with a shaper tip radius would tend to promote { 10bar{1}2 } twins.

  15. Micromechanical Behavior of Single-Crystal Superalloy with Different Crystal Orientations by Microindentation

    Directory of Open Access Journals (Sweden)

    Jinghui Li

    2015-01-01

    Full Text Available In order to investigate the anisotropic micromechanical properties of single-crystal nickel-based superalloy DD99 of four crystallographic orientations, (001, (215, (405, and (605, microindentation test (MIT was conducted with different loads and loading velocities by a sharp Berkovich indenter. Some material parameters reflecting the micromechanical behavior of DD99, such as microhardness H, Young’s modulus E, yield stress σy, strain hardening component n, and tensile strength σb, can be obtained from load-displacement relations. H and E of four different crystal planes evidently decrease with the increase of h. The reduction of H is due to dislocation hardening while E is related to interplanar spacing and crystal variable. σy of (215 is the largest among four crystal planes, followed by (605, and (001 has the lowest value. n of (215 is the lowest, followed by (605, and that of (001 is the largest. Subsequently, a simplified elastic-plastic material model was employed for 3D microindentation simulation of DD99 with various crystal orientations. The simulation results agreed well with experimental, which confirmed the accuracy of the simplified material model.

  16. Surface-induced and oriented textures of smectic liquid crystals: effect of thin films

    International Nuclear Information System (INIS)

    In this work, the effect of YBa2Cu3O7-x complex compound thin films on the morphological, thermotropical, optical and orientational properties of smectic liquid crystals have been studied. The peculiarities of surface-induced textures and dynamics of their temperature transformations have been investigated. Stable, homogeneous and reproducible oriented textures of smectic liquid crystals have been obtained

  17. Synthesis and characterization of spider silk calcite composite

    Directory of Open Access Journals (Sweden)

    Svetlana Dmitrović

    2016-03-01

    Full Text Available Spider silk poses excellent mechanical properties, tenacity and elasticity and it has been used as a template for calcite mineralization to improve load bearing strength of osteoconductive calcite. The samples were obtained by mimicking biomineralization for five days in order to follow formation and growth of calcite on the surface of spider silk. Crystal phase was detected by XRD and FTIR spectroscopy. Microstructure, crystal size and its morphology were studied by means of FESEM. After two days of processing, pure calcite phase was obtained, and a size of the formed crystals increased with prolongation of biomineralization.

  18. Interdiffusion behavior between NiAlHf coating and Ni-based single crystal superalloy with different crystal orientations

    International Nuclear Information System (INIS)

    Highlights: • The interdiffusion behavior between the NiAlHf coating and the superalloy substrate was influenced by the crystal orientation of the substrate alloy. • The structure of TCP phases formed in SRZ and IDZ was studied. • Studying the effect of orientation crystal of substrate on the formation of SRZ. - Abstract: NiAlHf coatings were deposited onto Ni-based single crystal (SC) superalloy with different crystal orientations by electron beam physical vapor deposition (EB-PVD). The effects of the crystal orientations of the superalloy substrate on inter-diffusion behavior between the substrate and the NiAlHf coating were investigated. Substrate diffusion zone (SDZ) containing needle-like μ phases and interdiffusion zone (IDZ) mainly consisting of the ellipsoidal and rod-like μ phases were formed in the SC alloy after heat-treatment 10 h at 1100 °C. The thickness of secondary reaction zone (SRZ) formed in the SC alloy with (0 1 1) crystal orientation is about 14 μm after 50 h heat-treatment at 1100 °C, which is relatively thicker than that in the SC alloy with (0 0 1) crystal orientation, whereas the IDZ revealed similar thickness

  19. Orientation of crystals in alanine dosimeter assessed by DRS, as seen in EPR spectra evaluation

    International Nuclear Information System (INIS)

    The alanine dosimeter made for evaluation by diffuse light reflection spectrophotometry (ALA/DRS) does not show the effect of orientation of crystals. Supposed deviation from random orientation has been investigated by EPR spectroscopy. EPR investigation shows that in spite of the very fine size of L-alanine crystals, they are oriented in thin layers of the polyethylene matrix. Specially prepared films with deliberately well oriented crystals have confirmed this observation. Our ALA/DRS dosimeter can be evaluated by the EPR method for the concentration of free radicals, providing that the dominating crystal orientation in the dosimetric film is indicated on it as an arrow, and the sample is inserted into the magnetic cavity always in the same orientation as has been done during the calibration operation. (author). 6 refs., 2 figs

  20. Effect of crystal orientation on low flux helium and hydrogen ion irradiation in polycrystalline tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Fangshu [Department of Physics, Beihang University, Beijing 100191 (China); School of Material Engineering, Panzhihua University, Panzhihua 617000 (China); Ren, Haitao; Peng, Shixiang [State Key Laboratory of Nuclear Physics and Technology, Institute of Heavy Ion Physics, Peking University, Beijing 100871 (China); Zhu, Kaigui, E-mail: kgzhu@buaa.edu.cn [Department of Physics, Beihang University, Beijing 100191 (China)

    2014-08-15

    Blistering behavior in polycrystalline tungsten is investigated under low flux helium and hydrogen ion irradiation. Subsequent to irradiation, the grain orientations near (0 1 1), (1 0 1) and (1 1 1) planes on the surface are analyzed by SEM and EBSD. It is found that blister density is the greatest on the grain orientation near (1 1 1) plane, and the smallest on the grain orientation near (0 0 1) plane. Experiments suggest that blistering degree highly depends upon the grain orientation, blisters are easily formed on the grain orientation near (1 1 1) plane, and medium on the grain orientation near (1 0 1) plane, and the most rare on the grain orientation near (0 1 1) plane. The surface resistant orientation of tungsten is orientation near (0 0 1) plane. The atom binding energy in the crystal plane in combination with the channeling effect of adjacent crystal planes may play an important role for the difference of the surface morphology.

  1. Interaction of alcohols with the calcite surface

    DEFF Research Database (Denmark)

    Bovet, Nicolas Emile; Yang, Mingjun; Javadi, Meshkat Sadat;

    2015-01-01

    A clearer understanding of calcite interactions with organic molecules would contribute to a range of fields including harnessing the secrets of biomineralisation where organisms produce hard parts, increasing oil production from spent reservoirs, remediating contaminated soils and drinking water...... aquifers and improving manufacturing methods for industrial products such as pigments, soft abrasives, building materials and optical devices. Biomineralisation by some species of blue green algae produces beautifully elaborate platelets of calcite where the individual crystals are of nanometer scale...

  2. Intergranular precipitation in aluminium-copper oriented bi-crystals

    International Nuclear Information System (INIS)

    In the first part of this research thesis, the author addresses the fabrication of aluminium-copper oriented bi-crystals by discussing the specific problems raised by this fabrication, and by describing the aspect after a thermal treatment chosen to reach a defined objective: the visibility of precipitates in all grain boundaries, and a secondary role of kinetic parameters. The second part addresses the density of intergranular precipitates by reporting and commenting the results of precipitate numbering in symmetric and asymmetric boundaries performed by using optic microscopy. The third part addresses the dimensions and shapes of intergranular precipitates. The author there reports the study of the average dimensions of precipitates with respect to boundary nature. Some additional remarks are made regarding their shape and crystallographic nature. Numerical results are obtained from measurements performed on photographs of carbon replicates taken by using an electronic microscope. The author then reports the study of the width of the area of low precipitation density at the edge of boundaries. A copper assessment in the intergranular band is performed which shows the type of relationship which seems to exist between previously studied phenomena. Finally, the author reports the study of the relationship between boundary atomic structure and intergranular precipitation. A grain boundary model has been developed and allows a definition of intergranular germination sites to be obtained

  3. Microstructural analysis of calcite-filled fractures inherited from basement structures, southern Ontario, Canada: long term instability of the craton?

    Science.gov (United States)

    Spalding, Jennifer; Schneider, David

    2016-04-01

    Intra-cratonic regions are generally characterized by tectonic stability and low seismicity. In southern Ontario, Canada, moderate levels of seismicity have been recorded over the last few decades reaching magnitudes of 5 MN, indicating that the geosphere is not as stable as predicted. The stratigraphy of the region consists of Ordovician limestone with a thickness of ~200 m that unconformably overlays the Mesoproterozoic crystalline Grenville Province. Subsequent tectonism including repeated Paleozoic orogenies and rifting along the east coast of North America has reactivated Proterozoic structures that have propagated into the overlying carbonate platform forming mesoscopic-scale brittle structures. Exposed along the shores of Lake Ontario are decameter-scale fracture zones, with a fracture spacing of 0.5 to 10 meters. The dominant fracture set trends E-W, and often forms conjugate sets with less prominent NNE-oriented fractures. More locally, an older NW-oriented fracture set is cross cut by the E-W and NNE oriented fractures. Regionally, there have been six directions of maximum horizontal stress in southern Ontario since the Precambrian, with the current orientation of maximum stress oriented ENE as a consequence of far field Atlantic ridge-push forces generated at distant plate boundaries. Calcite mineralization along fractured surfaces locally form sub-horizontal slickenside fabrics which are covered by a layer of euhedral calcite crystals, suggesting that fracture dilation (and fluid flow) occurred after fracture slip to allow the growth of calcite crystals. Due to the proximity of the carbonate units to the crystalline basement, we expect the calcitic veins to be enriched in rare earth elements and are presently conducting geochemical analyses. The calcite veins and surfaces vary from 2.5 cm to 1 mm thicknesses, often with larger calcite crystals in the center of the vein and smaller crystals at the vein boundaries, likely representing nucleation on small

  4. Standard test method for determining the orientation of a metal crystal

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2009-01-01

    1.1 This test method covers the back-reflection Laue procedure for determining the orientation of a metal crystal. The back-reflection Laue method for determining crystal orientation (1, 2) may be applied to macrograins (3) (0.5-mm diameter or larger) within polycrystalline aggregates, as well as to single crystals of any size. The method is described with reference to cubic crystals; it can be applied equally well to hexagonal, tetragonal, or orthorhombic crystals. 1.2 Most natural crystals have well developed external faces, and the orientation of such crystals can usually be determined from inspection. The orientation of a crystal having poorly developed faces, or no faces at all (for example, a metal crystal prepared in the laboratory) must be determined by more elaborate methods. The most convenient and accurate of these involves the use of X-ray diffraction. The “orientation of a metal crystal” is known when the positions in space of the crystallographic axes of the unit cell have been located with...

  5. Crystal orientation mapping via ion channeling: An alternative to EBSD

    International Nuclear Information System (INIS)

    A new method, which we name ion CHanneling ORientation Determination (iCHORD), is proposed to obtain orientation maps on polycrystals via ion channeling. The iChord method exploits the dependence between grain orientation and ion beam induced secondary electron image contrast. At each position of the region of interest, intensity profiles are obtained from a series of images acquired with different orientations with respect to the ion beam. The profiles are then compared to a database of theoretical profiles of known orientation. The Euler triplet associated to the most similar theoretical profile gives the orientation at that position. The proof-of-concept is obtained on a titanium nitride sample. The potentialities of iCHORD as an alternative to EBSD are then discussed. - Highlights: • A new method is proposed to obtain orientation maps via ion channeling. • This method exploits the dependence between grain orientation and SE image contrast. • Intensity profiles are obtained from images acquired with different orientations. • The profiles are then compared to a database of theoretical profiles of known orientation. • The potentialities of this method as an alternative to EBSD are discussed

  6. Crystal orientation mapping via ion channeling: An alternative to EBSD

    Energy Technology Data Exchange (ETDEWEB)

    Langlois, C.; Douillard, T.; Yuan, H. [University of Lyon – INSA de Lyon – CNRS, MATEIS, UMR 5510, Bât. Blaise Pascal, 20 Avenue Albert Einstein, 69621 Villeurbanne (France); Blanchard, N.P. [University of Lyon – CNRS, ILM, UMR 5306, Université Lyon I, Bât. A. Kastler, 10 rue A. Byron, 69622 Villeurbanne (France); Descamps-Mandine, A. [University of Lyon – CNRS, INL, UMR 5510, Bât. B. Pascal, INSA de Lyon/Université Lyon I, 69621 Villeurbanne (France); Van de Moortèle, B. [Ecole Normale Supérieure de Lyon – CNRS, LGL, 46 allée d’Italie, 69364 Lyon (France); Rigotti, C. [University of Lyon – INSA de Lyon – CNRS, LIRIS, UMR 5205, INRIA, Bât. Blaise Pascal, 20 Avenue Albert Einstein, 69621 Villeurbanne (France); Epicier, T. [University of Lyon – INSA de Lyon – CNRS, MATEIS, UMR 5510, Bât. Blaise Pascal, 20 Avenue Albert Einstein, 69621 Villeurbanne (France)

    2015-10-15

    A new method, which we name ion CHanneling ORientation Determination (iCHORD), is proposed to obtain orientation maps on polycrystals via ion channeling. The iChord method exploits the dependence between grain orientation and ion beam induced secondary electron image contrast. At each position of the region of interest, intensity profiles are obtained from a series of images acquired with different orientations with respect to the ion beam. The profiles are then compared to a database of theoretical profiles of known orientation. The Euler triplet associated to the most similar theoretical profile gives the orientation at that position. The proof-of-concept is obtained on a titanium nitride sample. The potentialities of iCHORD as an alternative to EBSD are then discussed. - Highlights: • A new method is proposed to obtain orientation maps via ion channeling. • This method exploits the dependence between grain orientation and SE image contrast. • Intensity profiles are obtained from images acquired with different orientations. • The profiles are then compared to a database of theoretical profiles of known orientation. • The potentialities of this method as an alternative to EBSD are discussed.

  7. Coupled crystal orientation-size effects on the strength of nano crystals.

    Science.gov (United States)

    Yuan, Rui; Beyerlein, Irene J; Zhou, Caizhi

    2016-01-01

    We study the combined effects of grain size and texture on the strength of nanocrystalline copper (Cu) and nickel (Ni) using a crystal-plasticity based mechanics model. Within the model, slip occurs in discrete slip events exclusively by individual dislocations emitted statistically from the grain boundaries. We show that a Hall-Petch relationship emerges in both initially texture and non-textured materials and our values are in agreement with experimental measurements from numerous studies. We find that the Hall-Petch slope increases with texture strength, indicating that preferred orientations intensify the enhancements in strength that accompany grain size reductions. These findings reveal that texture is too influential to be neglected when analyzing and engineering grain size effects for increasing nanomaterial strength. PMID:27185364

  8. Surface Tension Drives the Orientation of Crystals at the Air-Water Interface.

    Science.gov (United States)

    Chevalier, Nicolas R; Guenoun, Patrick

    2016-07-21

    The fabrication of oriented crystalline thin films is essential for a range of applications ranging from semiconductors to optical components, sensors, and catalysis. Here we show by depositing micrometric crystal particles on a liquid interface from an aerosol phase that the surface tension of the liquid alone can drive the crystallographic orientation of initially randomly oriented particles. The X-ray diffraction patterns of the particles at the interface are identical to those of a monocrystalline sample cleaved along the {104} (CaCO3) or {111} (CaF2) face. We show how this orientation effect can be used to produce thin coatings of oriented crystals on a solid substrate. These results also have important implications for our understanding of heterogeneous crystal growth beneath amphiphile monolayers and for 2D self-assembly processes at the air-liquid interface. PMID:27389283

  9. Orientation dependence of shock induced dislocations in tantalum single crystals

    International Nuclear Information System (INIS)

    A planar shock wave with a peak pressure of 6.2 GPa and duration of 1.7 μs followed by a lateral release wave generates profuse dislocations in single crystalline tantalum. Three orientations [100], [110], [111] were tested to examine the orientation dependence of the dislocation generation. The dislocations were characterised by transmission electron microscopy. The Burgers vectors and morphology of the primary dislocations in the specimens with different orientations showed a distinct orientation dependence and will be discussed in light of the model of slip behaviour in one-dimensional strain of C.S. Smith [1

  10. Influence of some crystal orientations in mechanical behaviour of zircaloy-4 tubes

    International Nuclear Information System (INIS)

    Zircaloy-4 tubing used in water cooled reactors work under biaxial loading due primarily to the circunferencial swelling of the fuel elements approximating a plane-strain behaviour. The tube is produced to have crystal orientations with high yield strengths under biaxial loading and principally in transverse plane strain. The contribution of individual crystal orientations to that specific yield strength is analysed based on crystallographic lower bound yield loci. (Author)

  11. Cyclic saturation dislocation structures of multiple-slip-oriented copper single crystals

    International Nuclear Information System (INIS)

    The dislocation structures of [011] and [ anti 111] multiple-slip-oriented Cu single crystals cyclically saturated at constant plastic strain amplitudes were investigated through transmission electron microscopy. The results obtained on [001] multiple-slip-oriented Cu single crystals were also included for summarization. Unlike the case for single-slip-oriented Cu single crystals, the crystallographic orientation has a strong effect on the saturation dislocation structure in these three multiple-slip-oriented crystals. For the [011] crystal, different dislocation patterns such as veins, PSB walls, labyrinths and PSB ladders were observed. The formation of PSB ladders is believed to be a major reason for the existence of a plateau region in the cyclic stress-strain (CSS) curve for the [011] crystal. The cyclic saturation dislocation structure of a [ anti 111] crystal cycled at a low applied strain amplitude γpl of 2.0 x 10-4 was found to consist of irregular cells, which would develop into a more regular arrangement (e. g. PSB ladder-like) and the scale of which tends to decrease with increasing γpl. Finally, three kinds of representative micro-deformation mode were summarized and termed as labyrinth-mode (or [001]-mode), cell-mode (or [ anti 111]-mode) and PSB ladder-mode (or [011]-mode). (orig.)

  12. Identification of biogenetic calcite and aragonite using SEM

    OpenAIRE

    Bermanec, Vladimir; Posilović, Hrvoje; Žigovečki Gobac, Željka

    2009-01-01

    Identification of calcite and aragonite is very important for studying different fossil or recent biomineralized skeletons. Problem occurs when scanning electron microscopy is used for studying calcite and aragonite present in the same part of skeleton. The same chemical composition of these two minerals produces the same contrast on SEM images. There are three possible ways how to distinguish calcite and aragonite in such mixture. (1) It is possible to recognize the crystal habits of the...

  13. Fracture calcites at Olkiluoto. Evidence from quaternary infills for palaeohydrogeology

    Energy Technology Data Exchange (ETDEWEB)

    Gehoer, S.; Kaerki, A.; Taikina-aho, O. [Kivitieto Oy (Finland); Karhu, J. [Helsinki Univ. (Finland); Loefman, J. [VTT Processes, Espoo (Finland); Pitkaenen, P. [VTT Building and Transport, Espoo (Finland); Ruotsalainen, P. [TUKES, Helsinki (Finland)

    2002-02-01

    Recently formed secondary minerals, predominantly calcite, occur in varying amounts as fracture infills, and the calcite types, their chemical compositions and isotope ratios reflect the compositions and physicochemical factors of the groundwater system in which they were formed. Fluid inclusions trapped in calcites give direct evidence of trapping temperatures and past salinities and of the chemical compositions of the palaeo fluids. A wide range of mineralogical and geochemical examinations were carried out within the EQUIP project to examine features of this kind. The fracture calcites at the Olkiluoto site are of various origins and represent several textural types. The exact number of calcite-producing events is unknown, but the duration of the period that was appropriate for the precipitation of low temperature calcite is estimated to have exceeded 1000 Ma. Thus the number of genetically related calcite units is assumed to be considerable. This study was focused on the petrogenesis of calcites crystallized in fractures of high water conductivity during the latest stages of geological evolution. The majority of these late stage calcites form physically homogeneous, scaly layers, and in a few cases thin layers composed of idiomorphic crystals. Chemically these are almost stoichiometric calcites (CaCO{sub 3}). The MnO content may exceed 1%, while the amounts of other elements present are minor, although the trace element concentrations, particularly those of large ionic trace elements, can be used as distinguishing features for the recognition of individual precipitates representing different calcite generations. Evidence from fluid inclusions, or more correctly from the absence of these in the late stage calcites, can be interpreted as an indication of slow rates of crystallization under cool conditions. Many chemical variables, e.g. oxygen isotope ratios, demonstrate an equilibrium between the latest calcites and water similar to the present groundwater. Older

  14. Fracture calcites at Olkiluoto. Evidence from quaternary infills for palaeohydrogeology

    International Nuclear Information System (INIS)

    Recently formed secondary minerals, predominantly calcite, occur in varying amounts as fracture infills, and the calcite types, their chemical compositions and isotope ratios reflect the compositions and physicochemical factors of the groundwater system in which they were formed. Fluid inclusions trapped in calcites give direct evidence of trapping temperatures and past salinities and of the chemical compositions of the palaeo fluids. A wide range of mineralogical and geochemical examinations were carried out within the EQUIP project to examine features of this kind. The fracture calcites at the Olkiluoto site are of various origins and represent several textural types. The exact number of calcite-producing events is unknown, but the duration of the period that was appropriate for the precipitation of low temperature calcite is estimated to have exceeded 1000 Ma. Thus the number of genetically related calcite units is assumed to be considerable. This study was focused on the petrogenesis of calcites crystallized in fractures of high water conductivity during the latest stages of geological evolution. The majority of these late stage calcites form physically homogeneous, scaly layers, and in a few cases thin layers composed of idiomorphic crystals. Chemically these are almost stoichiometric calcites (CaCO3). The MnO content may exceed 1%, while the amounts of other elements present are minor, although the trace element concentrations, particularly those of large ionic trace elements, can be used as distinguishing features for the recognition of individual precipitates representing different calcite generations. Evidence from fluid inclusions, or more correctly from the absence of these in the late stage calcites, can be interpreted as an indication of slow rates of crystallization under cool conditions. Many chemical variables, e.g. oxygen isotope ratios, demonstrate an equilibrium between the latest calcites and water similar to the present groundwater. Older

  15. The effect of crystal orientation on damage accumulation in chromium-implanted Al2O3

    International Nuclear Information System (INIS)

    Chromium-implantation of single crystal aluminium oxide (Al2O3) has been shown to be anisotropic with respect to damage accumulation. Ultra-low load indentation and Rutherford Backscattering Spectroscopy (RBS) have been used to demonstrate the dependence of radiation damage on fluence and crystal orientation. Single crystal Al2O3 specimens of c-axis ([0001] normal to the surface) and a-axis ([1120] normal to the surface) orientations were ion-implanted simultaneously and found to possess different near-surface mechanical properties. Subsequent RBS-ion channeling examination indicated different amounts of disorder in both the aluminum and oxygen sublattices for the two orientations. These results imply a higher amorphization threshold in terms of implantation fluence for the a-axis oriented samples. 15 refs., 6 figs

  16. Calcite twin morphology : a low-temperature deformation geothermometer

    OpenAIRE

    Ferrill, David A.; Morris, Alan P.; Evans, Mark A; Burkhard, Martin; Groshong Jr., Richard H.; Onasch, Charles M.

    2005-01-01

    Twinning of the e-plane is the dominant crystal–plastic deformation mechanism in calcite deformed below about 400 °C. Calcite in a twin domain has a different crystallographic orientation from the host calcite grain. So-called thin twins appear as thin black lines when viewed parallel to the twin plane at 200–320× magnification under a petrographic microscope. Thick twins viewed in the same way have a microscopically visible width of twinned material between black lines. Calcite e-twin width ...

  17. Dependence of characteristics of relativistic electron coherent X-radiation in thick crystal on its input surface orientation

    International Nuclear Information System (INIS)

    The influence of single crystal input surface orientation on the diffracted transition radiation (DTR) under fixed orientation of atomic planes relative to relativistic electron beam is investigated. The analytical expressions of relativistic electrons DTR and parametric X-radiation spectral-angular density are deduced. Calculations f DTR silicon and germanium crystals reveal the significant dependence of DTR parameters on input surface orientation

  18. Effect of crystal orientation on shock initiation sensitivity of pentaerythritol tetranitrate explosive

    International Nuclear Information System (INIS)

    Pentaerythritol tetranitrate single crystals were shocked in four different orientations with the shock direction parallel to the , , , or crystallographic directions. Input stresses were 8.6 or 12.4 GPa. At 12.4 GPa detonation occurred in less than 10-mm run distance of the shock for the and orientations. For the and orientations, denotation was not observed. There is a difference of more than a factor of 2 in run distance to detonation with crystal orientation. The effect can be understood in terms of the available slip systems in the uniaxial strain associated with plane shock compression. In addition, an intermediate velocity transition was observed at 8.6-GPa shock stress for orientation

  19. Effect of orientation stability on recrystallization textures of deformed aluminium single crystals

    International Nuclear Information System (INIS)

    High purity Al single crystals of the Cube (0 0 1)[1 0 0] and rotated Cube (0 1 1)[0 1 1-bar] orientations have been deformed in plane strain compression in a channel die. Deformation was carried out at temperatures between 25 and 600 deg. C up to strains of 1.2. The as-deformed microstructure has been characterised using electron microscopy and electron backscattered diffraction (EBSD). Annealing was carried out for various times and temperatures. The recrystallized microstructure has been studied using electron microscopy, and the orientation of recrystallized grains determined using EBSD. After cold deformation and annealing both orientations exhibited a random recrystallization texture component. After hot deformation both orientations retained a similar annealing texture to their starting deformation texture. The annealing texture of deformed single crystals was found to be more sensitive to the temperature of deformation than the stability of the orientation

  20. Surface chemistry and preferential crystal orientation on the H and Cl terminated silicon surface

    International Nuclear Information System (INIS)

    Surface chemistry and determining factors of the preferential crystal orientation are discussed through the deposition studies on hydrogenated chlorinated crystalline silicon films by rf plasma-enhanced chemical vapor deposition of a dichlorosilane, SiH2Cl2, and H2 mixture. The growth of randomly oriented crystal Si films occurred from the initial growth stage. On the other hand, the incubation layer of amorphous Si was formed in the initial stage, and subsequently, the growth of (220) preferred crystal orientation proceeded. They are determined by the thermal abstraction of H from the growing surface at substrate temperature above 350 degree sign C. Higher degree of Cl termination was effective in suppressing the oxygen incorporation into the Si network, although it did not contribute directly to the preferred crystal orientation. The insertion of atomic hydrogen to the Si-Si back bond in the subsurface region promoted the SiHClx complex formation, which was the most possible nucleation site for promoting the (220) preferential crystal orientation

  1. Investigating the orientational order in smectic liquid crystals

    Science.gov (United States)

    Wang, Shun

    This thesis is composed of two projects. The first one is the investigation of a reversed phase sequence, which subsequently leads to the discovery of a novel Smectic-C liquid crystal phase. The 10OHFBBB1M7 (10OHF) compound shows a reversed phase sequence with the SmC*d4 phase occurring at a higher temperature than the SmC* phase. This phase sequence is stabilized by moderate doping of 9OTBBB1M7 (C9) or 11OTBBB1M7 (C11). To further study this unique phase sequence, the mixtures of 10OHFBBB1M7 and its homologs have been characterized by optical techniques. In order to perform the resonant X-ray diffraction experiment, we have added C9 and C11 compounds to the binary mixtures and pure 10OHF. In two of the studied mixtures, a new smectic-C* liquid crystal phase with six-layer periodicity has been discovered. Upon cooling, the new phase appears between the SmC*a phase having a helical structure and the SmC*d4 phase with four-layer periodicity. The SmC*d6 phase shows a distorted clock structure. Three theoretical models have predicted the existence of a six-layer phase. However, our experimental findings are not consistent with the theories. The second project involves the mixtures of liquid crystals with different shapes. The role of different interactions in stabilizing the antiferroelectric smectic liquid crystal phases have been a long-standing questions in the community. By mixing the antiferroelectric smectic liquid crystal with achiral liquid crystal molecules with rod and hockey-stick shapes, distinct different behaviors are obtained. In the case of the mixtures of chiral smectic liquid crystals with rod-like molecules, all the smectic-C* variant phases vanish with a small amount of doping. However, the hockey-stick molecule is much less destructive compared to the rod-like molecule. This suggests that the antiferroelectric smectic liquid crystal molecules may have a shape closer to a hockey-stick rather than a rod.

  2. Effect of YBa2Cu3O7-x thin films on the textures and orientational properties of liquid crystals

    International Nuclear Information System (INIS)

    In the present work, the effect of thin films of YBa2Cu3O7-x complex compound on the mesomorphic and orientational properties of thermotropic nematic liquid crystals has been studied. Homogeneous, stable and reproducible homeotropic and tilted oriented textures of nematic liquid crystals were obtained. The effect of YBa2Cu3O7-x thin films on the morphologic, orientational and optical properties of thermotropic nematic liquid crystals are discussed. (orig.)

  3. Orientational fluctuation study in nematic liquid crystals by high speed micrograph

    Science.gov (United States)

    Yoon, Beom-Jin; Park, Min Sang; Park, Jung O.; Srinivasarao, Mohan

    2009-03-01

    The orientational fluctuations in uniaxial and biaxial nematic liquid crystals were investigated with a polarized microscope and a high speed TV camera. Liquid crystals usually have fluctuations with respect to their director, even when the molecular axes tend to be aligned to each other. These fluctuations are sufficiently slow and large, have long wave length and increase with temperature. Herein, we describe our study on fluctuation dynamics by direct observations in real space, while it has been typically done by the photon scattering in reciprocal space. The twinkling of liquid crystals due to orientational fluctuations was observed with a high speed camera up to 500 frames/sec. The time correlation function of the intensity was computed via 2D spatial Fourier transform of each image and then the relaxation frequency was estimated from it. The elastic constant to the viscosity ratio was computed from the relaxation frequency. This approach provides facile route to analyze fluctuation dynamics in liquid crystals.

  4. Insights Into the Solution Crystallization of Oriented Alq3 and Znq2 Microprisms and Nanorods.

    Science.gov (United States)

    Boulet, Joel; Mohammadpour, Arash; Shankar, Karthik

    2015-09-01

    Optimized solution-based methods to grow high quality micro- and nanocrystals of organic semi-conductors with defined size, shape and orientation are important to a variety of optoelectronic applications. In this context, we report the growth of single crystal micro- and nanostructures of the organic semiconductors Tris(8-hydroxyquinoline)aluminum (Alq3) and bis(8-hydroxyquinoline)zinc (Znq2) terminating in flat crystal planes using a combination of evaporative and antisolvent crystallization. By controlling substrate-specific nucleation and optimizing the conditions of growth, we generate vertically-oriented hexagonal prism arrays of Alq3, and vertical half-disks and sharp-edged rectangular prisms of Znq2. The effect of process variables such as ambient vapour pressure, choice of anti-solvent and temperature on the morphology and crystal habit of the nanostructures were studied and the results of varying them catalogued to gain a better understanding of the mechanism of growth. PMID:26716228

  5. Crystal orientation mapping applied to the Y-TZP/WC composite

    CERN Document Server

    Faryna, M; Sztwiertnia, K

    2002-01-01

    Crystal orientation measurements made by electron backscattered diffraction (EBSD) in the scanning electron microscope (SEM) and microscopic observations provided the basis for a quantitative investigation of microstructure in an yttria stabilized, tetragonal zirconia-based (Y-TZP) composite. Automatic crystal orientation mapping (ACOM) in a SEM can be preferable to transmission electron microscopy (TEM) for microstructural characterization, since no sample thinning is required, extensive crystal data is already available, and the analysis area is greatly increased. A composite with a 20 vol.% tungsten carbide (WC) content was chosen since it revealed crystal relationships between the matrix and carbide phase already established by TEM analysis. However, this composite was difficult to investigate in the EBSD/ SEM since it is non-conductive, the Y-TZP grain size is of the order of the system resolution, and the sample surface, though carefully prepared, reveals a distinctive microtopography. In this paper, so...

  6. Theoretical characterization of a model of aragonite crystal orientation in red abalone nacre

    OpenAIRE

    Coppersmith, S N; Gilbert, P. U. P. A.; Metzler, R. A.

    2009-01-01

    Nacre, commonly known as mother-of-pearl, is a remarkable biomineral that in red abalone consists of layers of 400-nm thick aragonite crystalline tablets confined by organic matrix sheets, with the $(001)$ crystal axes of the aragonite tablets oriented to within $\\pm$ 12 degrees from the normal to the layer planes. Recent experiments demonstrate that this orientational order develops over a distance of tens of layers from the prismatic boundary at which nacre formation begins. Our previous si...

  7. Formation of oriented nitrides by N+ ion implantation in iron single crystals

    International Nuclear Information System (INIS)

    Iron single crystals were implanted with nitrogen at room temperature, with a fluence of 5×1017 cm−2 and 50 keV energy, to produce iron nitride phases and characterize the influence of the crystal orientation. The stability and evolution of the nitride phases and diffusion of implanted nitrogen were studied as a function of successive annealing treatments at 250 °C in vacuum. The composition, structure and magnetic properties were characterized using RBS/channeling, X-Ray Diffraction, Magnetic Force Microscopy, Magneto-optical Kerr Effect and Conversion Electron Mössbauer Spectroscopy. In the as-implanted state the formation of Fe2N phase was clearly identified in all single crystals. This phase is not stable at 250 °C and annealing at this temperature promotes the formation of ε-Fe3N, or γ′-Fe4N, depending on the orientation of the substrate. - Highlights: • Oriented magnetic iron nitrides were obtained by nitrogen implantation into iron single crystals. • The stable magnetic nitride phase at 250 °C depends on the orientation of the host single crystal, being γ'-Fe4N or ε-Fe3N. • The easy magnetization axis was found to lay in the (100) plane for cubic γ'-Fe4N and out of (100) plane for hexagonal ε-Fe3N

  8. Faraday rotator based on TSAG crystal with orientation.

    Science.gov (United States)

    Yasuhara, Ryo; Snetkov, Ilya; Starobor, Aleksey; Mironov, Evgeniy; Palashov, Oleg

    2016-07-11

    A Faraday isolator (FI) for high-power lasers with kilowatt-level average power and 1-µm wavelength was demonstrated using a terbium scandium aluminum garnet (TSAG) with its crystal axis aligned in the direction. Furthermore, no compensation scheme for thermally induced depolarization in a magnetic field was used. An isolation ratio of 35.4 dB (depolarization ratio γ of 2.9 × 10-4) was experimentally observed at a maximum laser power of 1470 W. This result for room-temperature FIs is the best reported, and provides a simple, practical solution for achieving optical isolation in high-power laser systems. PMID:27410823

  9. Preferential Crystal Growth of (100)-Oriented BiFeO3 Films on Si Substrate

    Science.gov (United States)

    Hayashi, M.; Yasui, S.; Funakubo, H.; Uchida, H.

    2011-10-01

    Bi-based perovskite-type oxide materials such as BiFeO3 (BFO) and the related compounds receive much attention and have been developed actively as important candidates for Pb-free ferroelectric / piezoelectric materials instead of toxic Pb-based perovskite oxide materials. Recently, many researches have been reported for thin films of BFO by various film-deposition techniques for actual application of semiconductive devices, microactuators, etc. In this report, we tried preferential crystal growth of BFO films on semiconductive silicon substrates using uniaxial-(100)-oriented LaNiO3 (LNO) buffer layer. BFO films were fabricated via chemical solution deposition (CSD) technique on platinized silicon wafer [(111)Pt/TiO2/(100)Si] and (100)LNO-coated platinized silicon [(100)LNO/(111)Pt/TiO2/(100)Si] substrates. XRD analysis indicated that the films fabricated on (111)Pt/TiO2/(100)Si substrate consisted of randomly-oriented BFO crystal with lower crystallinity and trace amount of the second Bi2Fe4O9 phase. On the other hand, the films on (100)LNO/(111)Pt/TiO2/(100)Si consisted of uniaxial-(100)-oriented BFO crystal with higher crystallinity. The crystallization temperature these films were 450 and 400°C, respectively. These results suggest that the BFO crystal was grown epitaxially on uniaxial oriented (100)LNO plane which also had perovskite-type crystal structure. Consequently, (100)-oriented BFO films were prepared on Si substrate successfully using (100)LNO buffer layer.

  10. Preferential Crystal Growth of (100)-Oriented BiFeO3 Films on Si Substrate

    International Nuclear Information System (INIS)

    Bi-based perovskite-type oxide materials such as BiFeO3 (BFO) and the related compounds receive much attention and have been developed actively as important candidates for Pb-free ferroelectric / piezoelectric materials instead of toxic Pb-based perovskite oxide materials. Recently, many researches have been reported for thin films of BFO by various film-deposition techniques for actual application of semiconductive devices, microactuators, etc. In this report, we tried preferential crystal growth of BFO films on semiconductive silicon substrates using uniaxial-(100)-oriented LaNiO3 (LNO) buffer layer. BFO films were fabricated via chemical solution deposition (CSD) technique on platinized silicon wafer [(111)Pt/TiO2/(100)Si] and (100)LNO-coated platinized silicon [(100)LNO/(111)Pt/TiO2/(100)Si] substrates. XRD analysis indicated that the films fabricated on (111)Pt/TiO2/(100)Si substrate consisted of randomly-oriented BFO crystal with lower crystallinity and trace amount of the second Bi2Fe4O9 phase. On the other hand, the films on (100)LNO/(111)Pt/TiO2/(100)Si consisted of uniaxial-(100)-oriented BFO crystal with higher crystallinity. The crystallization temperature these films were 450 and 400deg. C, respectively. These results suggest that the BFO crystal was grown epitaxially on uniaxial oriented (100)LNO plane which also had perovskite-type crystal structure. Consequently, (100)-oriented BFO films were prepared on Si substrate successfully using (100)LNO buffer layer.

  11. Crystal Orientation Controlled Photovoltaic Properties of Multilayer GaAs Nanowire Arrays.

    Science.gov (United States)

    Han, Ning; Yang, Zai-Xing; Wang, Fengyun; Yip, SenPo; Li, Dapan; Hung, Tak Fu; Chen, Yunfa; Ho, Johnny C

    2016-06-28

    In recent years, despite significant progress in the synthesis, characterization, and integration of various nanowire (NW) material systems, crystal orientation controlled NW growth as well as real-time assessment of their growth-structure-property relationships still presents one of the major challenges in deploying NWs for practical large-scale applications. In this study, we propose, design, and develop a multilayer NW printing scheme for the determination of crystal orientation controlled photovoltaic properties of parallel GaAs NW arrays. By tuning the catalyst thickness and nucleation and growth temperatures in the two-step chemical vapor deposition, crystalline GaAs NWs with uniform, pure ⟨110⟩ and ⟨111⟩ orientations and other mixture ratios can be successfully prepared. Employing lift-off resists, three-layer NW parallel arrays can be easily attained for X-ray diffraction in order to evaluate their growth orientation along with the fabrication of NW parallel array based Schottky photovoltaic devices for the subsequent performance assessment. Notably, the open-circuit voltage of purely ⟨111⟩-oriented NW arrayed cells is far higher than that of ⟨110⟩-oriented NW arrayed counterparts, which can be interpreted by the different surface Fermi level pinning that exists on various NW crystal surface planes due to the different As dangling bond densities. All this indicates the profound effect of NW crystal orientation on physical and chemical properties of GaAs NWs, suggesting the careful NW design considerations for achieving optimal photovoltaic performances. The approach presented here could also serve as a versatile and powerful platform for in situ characterization of other NW materials. PMID:27223050

  12. Structural Correspondence of the Oriented Attachment Growth Mechanism of Crystals of the Pharmaceutical Dirithromycin.

    Science.gov (United States)

    Liang, Zuozhong; Wang, Yuan; Wang, Wei; Han, Xianglong; Chen, Jian-Feng; Xue, Chunyu; Zhao, Hong

    2015-12-29

    The oriented attachment (OA) mechanism is promising for designing novel nanomaterials, yet an intensive understanding of the relationship between the crystal structure and attachment orientation is still lacking. In this work, we report layered hexagonal crystals of the pharmaceutical dirithromycin (DIR) containing multiple layers fabricated via a solvothermal method for a certain period of time at 40 °C. These elongated hexagonal crystals experience an OA that is preferentially on the face (001) of the initial crystals to assemble the final crystals into layered stacks. Through agreement with molecular modeling calculations, we predicted the final crystal growth morphology and confirmed the favored attachment surface based on the energy change ΔE following an OA event. These simulation results at the molecular level yielded good agreement with the crystal growth experiments. This study demonstrates the critical importance of combining experiments with a computational approach to understand the intrinsic molecular details of the OA growth mechanism of other compounds and to design nanomaterials with a desirable morphology and physical and chemical properties. PMID:26632998

  13. Cyclic growth and branching phenomena of calcite grown in Mg(2+) containing solutions and in natural systems

    Science.gov (United States)

    Wiethoff, Felix; Richter, Detlef K.; Neuser, Rolf D.; Immenhauser, Adrian; Gies, Hermann; Schreuer, Jürgen

    2016-04-01

    Undulosity in calcites (radiaxial fibrous calcite (RFC) and fascicular-optic fibrous calcite (FOFC)) is a common phenomenon in paleozoic and mesozoic limestones. Despite their importance as archives for climate reconstruction the underlying mechanisms and processes of their formation are still poorly understood [1]. To improve the application of such archives for climate reconstruction a better knowledge of their formation and possible alteration scenarios is necessary. In Mg2+ containing gel based growth experiments calcite crystals develop pathological morphologies. The morphology can be described as a product of a geometrical selective branching process at the rhombohedral crystal faces. Multiple sheet like building blocks evolve at the branching crystal face; each slightly tilted in respect to their substrate. The product is a crystal aggregate consisting out of several misoriented sub domains. In polarized light thin section microscopy the extinction behaviour of these sub units resemble the optical undulosity of radiaxial fibrous cements. In a multi method approach the local Mg2+ concentration was measured using EMPA and compared with maps of the local crystal orientation (via electron backscatter diffraction (EBSD)) and thin section microscopy. We found that Mg2+ is enriched at the sub-domain boundaries and deduced that lattice misfit as a consequence of impurity incorporation causes the crystal branching. We propose that this process is cyclic and each new misoriented sheet represents a growth period after a phase of inhibited growth caused by crystal faces covered by Mg2+‑ions. In comparison to natural systems we found that radiaxial-fibrous cave cements show a pathological morphology based on the same formation principles. [1] Richter et al. (2011) Sediment. Geol. 239, 23-36 [2] Reeder & Paquette (1989) Sediment. Geol. 65, 239-247 [3] Davis et al. (2004) Am. Min. 89, 714-720

  14. Adaptation of BAp crystal orientation to stress distribution in rat mandible during bone growth

    International Nuclear Information System (INIS)

    Biological apatite (BAp) c-axis orientation strongly depends on stress distribution in vivo and tends to align along the principal stress direction in bones. Dentulous mandible is subjected to a complicated stress condition in vivo during chewing but few studies have been carried out on the BAp c-axis orientation; so the adaptation of BAp crystal orientation to stress distribution was examined in rat dentulous mandible during bone growth and mastication. Female SD rats 4 to 14 weeks old were prepared, and the bone mineral density (BMD) and BAp crystal orientation were analyzed in a cross-section of mandible across the first molar focusing on two positions: separated from and just under the tooth root on the same cross-section perpendicular to the mesiodistal axis. The degree of BAp orientation was analyzed by a microbeam X-ray diffractometer using Cu-Kα radiation equipped with a detector of curved one-dimensional PSPC and two-dimensional PSPC in the reflection and transmission optics, respectively. BMD quickly increased during bone growth up to 14 weeks, although it was independent of the position from the tooth root. In contrast, BAp crystal orientation strongly depended on the age and the position from the tooth root, even in the same cross-section and direction, especially along the mesiodistal and the biting axes. With increased biting stress during bone growth, the degree of BAp orientation increased along the mesiodistal axis in a position separated from the tooth root more than that near the tooth root. In contrast, BAp preferential alignment clearly appeared along the biting axis near the tooth root. We conclude that BAp orientation rather than BMD sensitively adapts to local stress distribution, especially from the chewing stress in vivo in the mandible.

  15. Preferential {100} grain orientation in 10 micrometer-thick laser crystallized multicrystalline silicon on glass

    International Nuclear Information System (INIS)

    Liquid phase crystallization of 10 μm thin silicon layers on glass substrates was performed with a line-shaped continuous wave laser beam. The process window was investigated in terms of the scanning velocity of the laser, the pre-heating of the specimens and the applied laser intensity. We have identified the entire process window, in which large-scale crystallization without deformation or destruction of the substrate and cracking of the silicon layer can be obtained. The grain orientations of the resulting Si layers were analyzed using both electron backscatter diffraction (EBSD) and X-ray diffraction (XRD). The influence of the critical crystallization parameters on the grain orientation of the silicon film was examined. EBSD and XRD measurements show that a preferential {100} surface texture and {100} and {101} orientations in scanning direction of the laser can be achieved if appropriate crystallization parameters are used. This texture formation is accompanied with a substantial decrease of high angle grain boundaries. - Highlights: • Zone melting of thin silicon films (10 μm) directly on glass substrates. • The process window was examined in dependence of all process parameters. • A preferential {100} orientation was obtained within a specific parameter range. • A reduction of high angle boundaries is accompanied with the texture formation

  16. Preferential {100} grain orientation in 10 micrometer-thick laser crystallized multicrystalline silicon on glass

    Energy Technology Data Exchange (ETDEWEB)

    Kühnapfel, S., E-mail: sven.kuehnapfel@helmholtz-berlin.de [Helmholtz-Zentrum Berlin für Materialien und Energie, Institut für Silizium-Photovoltaik, Kekuléstr. 5, 12489 Berlin (Germany); Nickel, N.H.; Gall, S. [Helmholtz-Zentrum Berlin für Materialien und Energie, Institut für Silizium-Photovoltaik, Kekuléstr. 5, 12489 Berlin (Germany); Klaus, M.; Genzel, C. [Helmholtz-Zentrum Berlin für Material und Energie, Abteilung Mikrostruktur- und Eigenspannungsanalyse, Albert-Einstein-Str. 15, 12489 Berlin (Germany); Rech, B.; Amkreutz, D. [Helmholtz-Zentrum Berlin für Materialien und Energie, Institut für Silizium-Photovoltaik, Kekuléstr. 5, 12489 Berlin (Germany)

    2015-02-02

    Liquid phase crystallization of 10 μm thin silicon layers on glass substrates was performed with a line-shaped continuous wave laser beam. The process window was investigated in terms of the scanning velocity of the laser, the pre-heating of the specimens and the applied laser intensity. We have identified the entire process window, in which large-scale crystallization without deformation or destruction of the substrate and cracking of the silicon layer can be obtained. The grain orientations of the resulting Si layers were analyzed using both electron backscatter diffraction (EBSD) and X-ray diffraction (XRD). The influence of the critical crystallization parameters on the grain orientation of the silicon film was examined. EBSD and XRD measurements show that a preferential {100} surface texture and {100} and {101} orientations in scanning direction of the laser can be achieved if appropriate crystallization parameters are used. This texture formation is accompanied with a substantial decrease of high angle grain boundaries. - Highlights: • Zone melting of thin silicon films (10 μm) directly on glass substrates. • The process window was examined in dependence of all process parameters. • A preferential {100} orientation was obtained within a specific parameter range. • A reduction of high angle boundaries is accompanied with the texture formation.

  17. Orientation dependence of deformation and penetration behavior of tungsten single-crystal rods

    International Nuclear Information System (INIS)

    This paper reports on the performance of tungsten single crystals as kinetic energy penetrator materials that was investigated in a high length-to-diameter (L/D) rod geometry at sub-scale (1/4 geometric scale). The [111]. [110], and [100] crystal orientations were tested in this 74-g LD = 15 geometry penetrator (6.90-mm diameter x 102.5-mm length). Several 93% tungsten alloy and uranium 3/4 titanium rod geometries were also tested to baseline expected performance of typical penetrator material/geometry combinations. Performance was determined for semi-infinite penetration into RHA steel and finite penetration into 76.20-mm RHA steel. Of the orientation tested, the [100] orientation provided the best ballistic results, with superior performance to mass and geometric equivalent 93% tungsten alloy rods. The [100] orientation also provided similar performance to geometric equivalent uranium 3/4 titanium rods. Favorable slip/cleavage during the compressive loading of the penetration process to allow penetrator material flow without large scale plastic deformation, and final shear localization at a favorable angle for easy material flow away from the penetration interface, contribute to the [100] orientation crystals' excellent performance. The net result was less energy expenditure during penetrator flow and, therefore, more energy for deformation of RHA

  18. Influence of Substrate on Crystal Orientation of Large-Grained Si Thin Films Formed by Metal-Induced Crystallization

    Directory of Open Access Journals (Sweden)

    Kaoru Toko

    2015-01-01

    Full Text Available Producing large-grained polycrystalline Si (poly-Si film on glass substrates coated with conducting layers is essential for fabricating Si thin-film solar cells with high efficiency and low cost. We investigated how the choice of conducting underlayer affected the poly-Si layer formed on it by low-temperature (500°C Al-induced crystallization (AIC. The crystal orientation of the resulting poly-Si layer strongly depended on the underlayer material: (100 was preferred for Al-doped-ZnO (AZO and indium-tin-oxide (ITO; (111 was preferred for TiN. This result suggests Si heterogeneously nucleated on the underlayer. The average grain size of the poly-Si layer reached nearly 20 µm for the AZO and ITO samples and no less than 60 µm for the TiN sample. Thus, properly electing the underlayer material is essential in AIC and allows large-grained Si films to be formed at low temperatures with a set crystal orientation. These highly oriented Si layers with large grains appear promising for use as seed layers for Si light-absorption layers as well as for advanced functional materials.

  19. Critical CuI buffer layer surface density for organic molecular crystal orientation change

    International Nuclear Information System (INIS)

    We have determined the critical surface density of the CuI buffer layer inserted to change the preferred orientation of copper phthalocyanine (CuPc) crystals grown on the buffer layer. X-ray reflectivity measurements were performed to obtain the density profiles of the buffer layers and out-of-plane and 2D grazing-incidence X-ray diffraction measurements were performed to determine the preferred orientations of the molecular crystals. Remarkably, it was found that the preferred orientation of the CuPc film is completely changed from edge-on (1 0 0) to face-on (1 1 −2) by a CuI buffer layer with a very low surface density, so low that a large proportion of the substrate surface is bare

  20. Influence of the orientation of methylammonium lead iodide perovskite crystals on solar cell performance

    Directory of Open Access Journals (Sweden)

    Pablo Docampo

    2014-08-01

    Full Text Available Perovskite solar cells are emerging as serious candidates for thin film photovoltaics with power conversion efficiencies already exceeding 16%. Devices based on a planar heterojunction architecture, where the MAPbI3 perovskite film is simply sandwiched between two charge selective extraction contacts, can be processed at low temperatures (<150 °C, making them particularly attractive for tandem and flexible applications. However, in this configuration, the perovskite crystals formed are more or less randomly oriented on the surface. Our results show that by increasing the conversion step temperature from room temperature to 60 °C, the perovskite crystal orientation on the substrate can be controlled. We find that films with a preferential orientation of the long axis of the tetragonal unit cell parallel to the substrate achieve the highest short circuit currents and correspondingly the highest photovoltaic performance.

  1. Theory of two-dimensional self-assembly of Janus colloids: crystallization and orientational ordering.

    Science.gov (United States)

    Shin, Homin; Schweizer, Kenneth S

    2014-01-14

    We study the rich crystalline phase behavior of amphiphilic spherical Janus colloids using a new formulation of self-consistent phonon theory that includes coupled translational and rotational entropic and enthalpic contributions to the free energy. In contrast to homogeneous spheres, broken rotational symmetry can result in more exotic crystals that possess distinct orientational patterns, and also plastic crystals. Ground states are identified based on the compatibility between the patch geometry of particles (e.g., patch coverage, number, shape) and lattice symmetry. We derive the explicit coupled self-consistent equations for translational and rotational localization parameters for effectively 2-dimensional dense monolayers of Janus crystals. The equations are numerically solved for a given crystal symmetry, thermodynamic state, and patch orientational order, and the thermodynamic stability of different phases is determined. For hexagonal packing, we predict with increasing temperature or decreasing attraction strength the possibility of a phase sequence of maximally bonded zigzag stripe, trimer, and rotationally disordered plastic crystal phases (or a phase sequence of trimer, dimer, and plastic crystal), which depends sensitively on particle chemical composition (Janus balance) and pressure. The role of rotational entropy in stabilizing the intermediate trimer (or dimer) phase at intermediate temperatures and high pressures is discussed in detail. Evolution of the center-of-mass vibrational and rotational amplitudes with thermodynamic state and Janus balance is also determined. PMID:24651877

  2. The role of crystal orientation and surface proximity in the self-similar behavior of deformed Cu single crystals

    International Nuclear Information System (INIS)

    We report on novel 3D spatially resolved X-ray diffraction microscopy studies of self-affine behavior in deformed single crystals. This study extends surface profile measurements of self-affined morphology changes in single crystals during deformation to include local lattice rotations and sub-surface behavior. Investigations were made on the spatial correlation of the local lattice rotations in 8% tensile deformed Cu single crystals oriented with [1 2 3], [1 1 1] and [0 0 1] axes parallel to the tensile axis. The nondestructive depth-resolved measurements were made over a length scale of one to hundreds of micrometers. Self-affined correlation was found both at the surface and below the surface of the samples. A universal exponent for the power-law similar to that observed with surface profile methods is found at the surface of all samples but crystallographically sensitive changes are observed as a function of depth. Correlation lengths of the self-affine behavior vary with the [1 2 3] crystal exhibiting the longest self-affine length scale of 70 μm with only 18 μm for the [1 1 1] and [0 0 1] crystals. These measurements illuminate the transition from surface-like to bulk-like deformation behavior and provide new quantitative information to guide emerging models of self-organized structures in plasticity.

  3. New type of instrument for the orientation of the optical axis of crystal

    Science.gov (United States)

    Cao, Tianning

    1992-10-01

    In modern optical industry and optical research the anisotropic crystals, such as iceland, KDP, ADP, LiNbO3, crystalline quartz, etc., have been widely used for making various types of polarizers, optical shutters, interference polarization filters, and light modulators, etc. In order to improve the quality of crystal elements, the accuracy of crystal optical axis orientation must be improved. In this paper a new type of instrument is described for determining the perpendicular orientation of the crystal optical axis of a crystal plate to the plate surface. A converging bundle of polarized rays passes through the plate and forms a set of ring interferogram and a dark cross image in the interferogram. As the working stage is rotated, the center of the cross and the rings move along a circle, if the surface of the plate is not perpendicular to the optical axis. The accuracy of data read directly from a beeswax screen of (phi) 150 mm does not exceed six arc minutes. If the data and other parameters are input to a microcomputer IBM/PC to remove the theoretical deviations of the instrument the accuracy of two arc minutes can be obtained. The size of crystal under test can be (phi) 100 X (0.5 - 100) mm. Theoretical calculation shows that the accuracy of a thick crystal plate under test and the data read from an interferential ring of lower order of interference are improved. In this instrument the crystal cone interferogram, clean and bright, is projected on a screen, and it is suitable for teaching demonstration and shop testing. The cost of this instrument is lower because of its simple structure.

  4. Single-contact pressure solution creep on calcite monocrystals

    CERN Document Server

    Zubtsov, Sergei; Gratier, Jean-Pierre; Dysthe, Dag; Traskine, Vladimir

    2005-01-01

    Pressure solution creep rates and interface structures have been measured by two methods on calcite single crystals. In the first kind of experiments, calcite monocrystals were indented at 40 degrees C for six weeks using ceramic indenters under stresses in the 50-200 MPa range in a saturated solution of calcite and in a calcite-saturated aqueous solution of NH4Cl. The deformation (depth of the hole below the indenter) is measured ex-situ at the end of the experiment. In the second type of experiment, calcite monocrystals were indented by spherical glass indenters for 200 hours under stresses in the 0-100 MPa range at room temperature in a saturated aqueous solution of calcite. The displacement of the indenter was continuously recorded using a specially constructed differential dilatometer. The experiments conducted in a calcite-saturated aqueous solution of NH4Cl show an enhanced indentation rate owing to the fairly high solubility of calcite in this solution. In contrast, the experiments conducted in a calc...

  5. Determination of crystal grain orientations by optical microscopy at textured surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Lausch, D.; Gläser, M.; Hagendorf, C. [Team Mikrostrukturdiagnostik und Analytik, Fraunhofer-Center für Silizium-Photovoltaik CSP, Walter-Hülse-Straße 1 Halle (Saale), Sachsen-Anhalt D-06120 (Germany)

    2013-11-21

    In this contribution, a new method to determine the crystal orientation with the example of chemical treated silicon wafers by means of optical microscopy has been demonstrated. The introduced procedure represents an easy method to obtain all relevant parameters to describe the crystal structure of the investigated material, i.e., the crystal grain orientation and the grain boundary character. The chemical treatment is a standard mono-texture for solar cells, well known in the solar industry. In general, this concept can also be applied to other crystalline materials, i.e., GaAs, SiC, etc., the only thing that needs to be adjusted is the texturing method to reveal specific crystal planes and the calculation model. In conclusion, an application of this method is shown with the example of the defect classification of recombination active defects in mc-Si solar cell. The introduced method demonstrates a simple and quick opportunity to improve the crystallization process and the quality of electronic devices by means of an optical microscope and a chemical treatment of the material.

  6. Determination of the Crystal Axis Orientations of Ge detectors for the Majorana Demonstrator

    Science.gov (United States)

    Xu, Wenqin; Busch, Matthew; Elliott, Steven; Green, Matthew; Hegai, Alex; Henning, Reyco; Ronquest, Michael; Snavely, Kyle; Zitin, Ari

    2013-04-01

    High purity germanium (HPGe) crystals will be used for the Majorana Demonstrator, where they serve as both the source and the detector for neutrinoless double beta decays. Sophisticated pulse shape analysis (PSA) is crucial in distinguishing certain background events in the energy region of interest. It is also well known that the charge-carrier mobility in Ge crystals has considerable dependence on the crystallographic axes, resulting in a crystal axis dependence of the PSA. Meanwhile, as within the Peccei-Quinn solution to the strong CP problem and as a dark matter candidate, axions have been searched for in many experiments. It has been suggested that the postulated solar axions could coherently covert to photons by the Primakeoff effect in a periodic lattice, such as that found in the Ge crystals used by the Demonstrator, with conversion rates depending on the crystal axis orientation. In order to use the Demonstrator to search for solar axions, the Ge crystal axes need to be measured. In this talk, we will present our experimental measurements to characterize crystal axes with P-type point contact (PPC) HPGe detectors, which are cylindrical in shape with point contacts at the bottom.

  7. Characterization of the influence of polarization orientation on bulk damage in KDP crystals at different wavelengths

    Science.gov (United States)

    Zheng, YinBo; Ding, Lei; Zhou, XinDa; Ba, RongSheng; Yuan, Jing; Xu, HongLei; Na, Jin; Li, YaJun; Yang, XiaoYu; Chai, Liqun; Chen, Bo; Zheng, WanGuo

    2016-08-01

    The investigation of polarization orientation on damage performance of type I doubler KDP crystals under different wavelengths pulses irradiation is presented in this work. Pinpoints densities (PPD) and the size distribution of pinpoints are extracted through light scattering pictures captured by microscope. The obtained results indicate that the measured PPD as a function of the fluence is both wavelength and polarization dependent, although neither fluence nor polarization have impact on the size distribution of pinpoints. We also find that the damage performances can separate into three groups depending on the wavelength, which suggests the existence of different categories of precursors and different mechanisms responsible for bulk damage initiation in SHG KDP crystals.

  8. Optical properties of planar nematic liquid crystals samples which are parallel oriented by nanofibers

    Science.gov (United States)

    Yusuf, Yusril; Kusumasari, Ervanggis Minggar; Ula, Nur Mufidatul; Jahidah, Khannah; Triyana, Kuwat; Sosiati, Harini; Harsojo

    2016-04-01

    Optical properties of two nematic liquid crystals, i.e., 4-methoxybenzylidene-4-butylaniline (MBBA) and 4-cyano-4'-pentylbiphenyl (5 CB) which are parallel oriented by nanofibers has been successfully performed. Planar samples of liquid crystals were made using polyvinyl alcohol (PVA) nanofiber from electrospinning process. Electrospinning method was modified using copper (Cu) as gap collector. These planar samples area are 15 mm x 25 mm. Optical characteristic of these samples were studied by using optical polarizing microscope. The optical intensity changes by a rotationof crossed polarizers is observed. The sinusoidal intensity change was observedin these samples as such as in the planar sample prepared by the rubbing method.

  9. Nondispersion polaritons on symmetrically oriented surfaces of two-axis crystals

    International Nuclear Information System (INIS)

    One derived system of dispersion equations describing surface polaritons in optic two-axis crystals on surfaces parallel to symmetry planes of ε permittivity tensor. One analyzes ranges of occurrence, value and orientation of sectors of propagation directions of nondispersion surface polaritons occurring at positive values of ε tensor components. For slightly anisotropic crystals one determined three noncrossing values of dielectric anisotropy parameters where nondispersion polariton may occur. One traced evolution of configuration of optic axis at variation of anisotropy parameters within ranges of occurrence of polaritons

  10. Homeotropic orientation of a nematic liquid crystal by bent-core molecules adsorbed on its surface

    Science.gov (United States)

    Hwang, Jiyong; Yang, Seungbin; Lee, Hyojin; Kim, Jongyoon; Lee, Ji-Hoon; Kang, Shin-Woong; Choi, E.-Joon

    2015-06-01

    We reported the promotion of a homeotropic alignment of a nematic liquid crystal (NLC) by bent-core liquid-crystal (BLC) Molecules adsorbed its surface. The BLC was mixed at various concentrations with the NLC, and the mixtures were injected into an empty cell with a cell gap of 13 μm. Although the pure NLC showed a heterogeneous orientation, the BLC-NLC mixture was gradually transformed to a homeotropic alignment with increasing concentration of the BLC. We investigated the surface topography of the samples by using an atomic force microscopy (AFM) and found that the BLC molecules were segregated into a polyimide (PI) surface and formed protrusion domains with diameters of 50-100 nm. The BLC protrusions might promote the homeotropic orientation of the NLC molecules.

  11. Imprints of air bubbles and crystal orientation fabric on RES signature ?

    OpenAIRE

    Drews, Reinhard; Bohleber, Pascal; Eisen, Olaf; Steinhage, Daniel; Weikusat, Ilka; Wilhelms, Frank; Freitag, Johannes

    2009-01-01

    Radio echo sounding (RES) enables mapping of bedrock topography and internal structure in large ice bodies. Via multi-frequency and multi-polarization sounding, internal reflections can be assigned to non-uniformities in density, conductivity and crystal orientation fabric (COF). This allows to deduce a multitude of glaciological parameters (e.g. accumulation, linking of ice cores). Similar as [1], [2], and [3], we analyse polarization dependent backscatter from ground based measurements in A...

  12. Analysis of rolling texture in commercial titanium using crystal orientation distribution functions

    International Nuclear Information System (INIS)

    Description method for texture state of materials with hexagonal symmetry of the lattice with the help of distribution functions of crystal orientation is described. Texture development in VT1-0 titanium sheets is analyzed depending on the deformation degree during rolling. Crystallographical analysis of the mechanism of plastic deformation is carried out and a ''dynamical model'' of rolling texture development in industrial titanium is proposed

  13. Orientational dynamics and energy landscape features of thermotropic liquid crystals: An analogy with supercooled liquids

    Indian Academy of Sciences (India)

    Biman Jana; Biman Bagchi

    2007-09-01

    Recent optical kerr effect (OKE) studies have revealed that orientational relaxation of rodlike nematogens near the isotropic-nematic (I-N) phase boundary and also in the nematic phase exhibit temporal power law decay at intermediate times. Such behaviour has drawn an intriguing analogy with supercooled liquids. Here, we have investigated the single-particle and collective orientational dynamics of a family of model system of thermotropic liquid crystals using extensive computer simulations. Several remarkable features of glassy dynamics are on display including non-exponential relaxation, dynamical heterogeneity, and non-Arrhenius temperature dependence of the orientational relaxation time. Over a temperature range near the I-N phase boundary, the system behaves like a fragile glass-forming liquid. Using proper scaling, we construct the usual relaxation time versus inverse temperature plot and explicitly demonstrate that one can successfully define a density dependent fragility of liquid crystals. The fragility of liquid crystals shows a temperature and density dependence which is remarkably similar to the fragility of glass forming supercooled liquids. Energy landscape analysis of inherent structures shows that the breakdown of the Arrhenius temperature dependence of relaxation rate occurs at a temperature that marks the onset of the growth of the depth of the potential energy minima explored by the system.

  14. Early oriented isothermal crystallization of polyethylene studied by high-time-resolution SAXS/WAXS.

    Science.gov (United States)

    Stribeck, N; Almendarez Camarillo, A; Nöchel, U; Bösecke, P; Bayer, R K

    2007-01-01

    During cooling from the quiescent melt of a highly oriented polyethylene rod, highly oriented proto-lamellae are formed first, which are not crystalline. This is shown in scattering data which are recorded on two-dimensional detectors with a cycle time of 1 s and an exposure of 0.1 s. In the experiments small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) are registered simultaneously during the first 3 min after quenching to a crystallization temperature. A non-uniform thickness between 20 and 100 nm is characteristic for the ensemble of proto-lamellae. During the first minute of isothermal treatment the number of proto-lamellae slowly increases without a change of the thickness distribution. As crystallization starts, the crystallites are not oriented in contrast to the proto-lamellae. During crystallization the layer thickness distribution narrows. The number of lamellae rapidly increases during the following 2 min of isothermal treatment (at 128 degrees C and 124 degrees C). The results are obtained by interpretation of the WAXS and of the multidimensional chord distribution function (CDF), a model-free real-space visualization of the nanostructure information contained in the SAXS data. PMID:17089099

  15. Direct evidence for radar reflector originating from changes in crystal-orientation fabric

    Directory of Open Access Journals (Sweden)

    O. Eisen

    2007-06-01

    Full Text Available The origin of a strong continuous radar reflector observed with airborne radio-echo sounding (RES at the EPICA deep-drilling site in Dronning Maud Land, Antarctica, is identified as a transition in crystal fabric orientation from a vertical girdle- to increased single-pole orientation seen along the ice core. The reflector is observed with a 60 ns and 600 ns long pulse at a frequency of 150 MHz, spans one pulse length, is continuous over 5 km, and occurs at a depth of about 2020–2030 m at the drill site. Changes in conductivity as reflector origin are excluded by investigating the ice-core profile and synthetic RES data. Our observations allow to extrapolate the crystal orientation feature along the reflector in space, with implications for ice-sheet dynamics. As the conductivity profile of the EPICA shows no distinctive peak at this depths, we exclude changes in conductivity as the reflector origin. This is supported by application of numerical forward modelling of electromagnetic wave propagation, based on the conductivity profile, which is able to reproduce nearby reflections, but fails to reproduce this one. Because of background noise, the permittivity profile based on dielectric does not show prominent signals at these depths. We therefore interpret the observed reflector to originate from this change in crystal fabric.

  16. Solvent minimization induces preferential orientation and crystal clustering in serial micro-crystallography on micro-meshes, in situ plates and on a movable crystal conveyor belt

    Energy Technology Data Exchange (ETDEWEB)

    Soares, Alexei S., E-mail: soares@bnl.gov [Brookhaven National Laboratory, Upton, NY 11973 (United States); Mullen, Jeffrey D. [Brookhaven National Laboratory, Upton, NY 11973 (United States); University of Oregon, Eugene, OR 97403-1274 (United States); Parekh, Ruchi M. [Brookhaven National Laboratory, Upton, NY 11973 (United States); Suffolk County Community College, Selden, NY 11784 (United States); McCarthy, Grace S.; Roessler, Christian G.; Jackimowicz, Rick; Skinner, John M. [Brookhaven National Laboratory, Upton, NY 11973 (United States); Orville, Allen M. [Brookhaven National Laboratory, Upton, NY 11973 (United States); Brookhaven National Laboratory, Upton, NY 11973 (United States); Allaire, Marc [Brookhaven National Laboratory, Upton, NY 11973 (United States); Sweet, Robert M. [Brookhaven National Laboratory, Upton, NY 11973 (United States); Brookhaven National Laboratory, Upton, NY 11973 (United States)

    2014-10-09

    Strategies are described for optimizing the signal-to-noise of diffraction data, and for combining data from multiple crystals. One challenge that must be overcome is the non-random orientation of crystals with respect to one another and with respect to the surface that supports them. X-ray diffraction data were obtained at the National Synchrotron Light Source from insulin and lysozyme crystals that were densely deposited on three types of surfaces suitable for serial micro-crystallography: MiTeGen MicroMeshes™, Greiner Bio-One Ltd in situ micro-plates, and a moving kapton crystal conveyor belt that is used to deliver crystals directly into the X-ray beam. 6° wedges of data were taken from ∼100 crystals mounted on each material, and these individual data sets were merged to form nine complete data sets (six from insulin crystals and three from lysozyme crystals). Insulin crystals have a parallelepiped habit with an extended flat face that preferentially aligned with the mounting surfaces, impacting the data collection strategy and the design of the serial crystallography apparatus. Lysozyme crystals had a cuboidal habit and showed no preferential orientation. Preferential orientation occluded regions of reciprocal space when the X-ray beam was incident normal to the data-collection medium surface, requiring a second pass of data collection with the apparatus inclined away from the orthogonal. In addition, crystals measuring less than 20 µm were observed to clump together into clusters of crystals. Clustering required that the X-ray beam be adjusted to match the crystal size to prevent overlapping diffraction patterns. No additional problems were encountered with the serial crystallography strategy of combining small randomly oriented wedges of data from a large number of specimens. High-quality data able to support a realistic molecular replacement solution were readily obtained from both crystal types using all three serial crystallography strategies.

  17. Solvent minimization induces preferential orientation and crystal clustering in serial micro-crystallography on micro-meshes, in situ plates and on a movable crystal conveyor belt

    International Nuclear Information System (INIS)

    Strategies are described for optimizing the signal-to-noise of diffraction data, and for combining data from multiple crystals. One challenge that must be overcome is the non-random orientation of crystals with respect to one another and with respect to the surface that supports them. X-ray diffraction data were obtained at the National Synchrotron Light Source from insulin and lysozyme crystals that were densely deposited on three types of surfaces suitable for serial micro-crystallography: MiTeGen MicroMeshes™, Greiner Bio-One Ltd in situ micro-plates, and a moving kapton crystal conveyor belt that is used to deliver crystals directly into the X-ray beam. 6° wedges of data were taken from ∼100 crystals mounted on each material, and these individual data sets were merged to form nine complete data sets (six from insulin crystals and three from lysozyme crystals). Insulin crystals have a parallelepiped habit with an extended flat face that preferentially aligned with the mounting surfaces, impacting the data collection strategy and the design of the serial crystallography apparatus. Lysozyme crystals had a cuboidal habit and showed no preferential orientation. Preferential orientation occluded regions of reciprocal space when the X-ray beam was incident normal to the data-collection medium surface, requiring a second pass of data collection with the apparatus inclined away from the orthogonal. In addition, crystals measuring less than 20 µm were observed to clump together into clusters of crystals. Clustering required that the X-ray beam be adjusted to match the crystal size to prevent overlapping diffraction patterns. No additional problems were encountered with the serial crystallography strategy of combining small randomly oriented wedges of data from a large number of specimens. High-quality data able to support a realistic molecular replacement solution were readily obtained from both crystal types using all three serial crystallography strategies

  18. Influence of crystal orientation on hardness and nanoindentation deformation in ion-irradiated stainless steels

    Science.gov (United States)

    Miura, Terumitsu; Fujii, Katsuhiko; Fukuya, Koji; Takashima, Keisuke

    2011-10-01

    The influence of crystal orientation on hardness and the range of plastic deformation caused by nanoindentation was investigated in a solution annealed type 316 stainless steel irradiated with Fe 2+ ions. The hardness was a function of grain orientation and was correlated with the Taylor factor averaged over three normal directions of the contact surface of the Berkovich indenter. The transmission electron microscope observations of the deformation microstructure under the indentations showed that the range of plastic deformation reached up to 10 times the indent depth for unirradiated material and depended on the orientation relation between the contact surface of the indenter and the slip directions. The range of plastic deformation decreased as the damage structure developed in ion irradiation.

  19. Influence of crystal orientation on hardness and nanoindentation deformation in ion-irradiated stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Miura, Terumitsu, E-mail: miura@inss.co.jp [Institute of Nuclear Safety System, Incorporated, 64 Sata, Mihama-cho, Mikata-gun, Fukui 919-1205 (Japan); Fujii, Katsuhiko, E-mail: fujiik@inss.co.jp [Institute of Nuclear Safety System, Incorporated, 64 Sata, Mihama-cho, Mikata-gun, Fukui 919-1205 (Japan); Fukuya, Koji, E-mail: fukuya@inss.co.jp [Institute of Nuclear Safety System, Incorporated, 64 Sata, Mihama-cho, Mikata-gun, Fukui 919-1205 (Japan); Takashima, Keisuke, E-mail: maestro@mech.fukui-u.ac.jp [Graduate School of Nuclear Power and Energy Safety Engineering, University of Fukui, 910-8507, 3-9-1 Bunkyo, Fukui (Japan)

    2011-10-01

    The influence of crystal orientation on hardness and the range of plastic deformation caused by nanoindentation was investigated in a solution annealed type 316 stainless steel irradiated with Fe{sup 2+} ions. The hardness was a function of grain orientation and was correlated with the Taylor factor averaged over three normal directions of the contact surface of the Berkovich indenter. The transmission electron microscope observations of the deformation microstructure under the indentations showed that the range of plastic deformation reached up to 10 times the indent depth for unirradiated material and depended on the orientation relation between the contact surface of the indenter and the slip directions. The range of plastic deformation decreased as the damage structure developed in ion irradiation.

  20. Orientational behavior of a nematic liquid crystal filled with inorganic oxide nanoparticles

    International Nuclear Information System (INIS)

    We report the results of dielectric spectroscopy, Fourier transformed infrared spectroscopy (FTIR) and atomic force microscopy (AFM) studies performed on the nematic liquid crystal (LC) mixture Merck ZLI-1132 filled with TiO2 (rutile and anatase) and SiO2 nanoparticles. The observed static dielectric permittivities are interpreted in terms of orientation of the LC with respect to the measuring electric field. Adding of SiO2 particles mainly induces a statistical orientation of LC molecules, whereas TiO2 particles promote the perpendicular orientation. The dynamics of LC molecules in all systems is very similar. The reason for the slightly faster reorientation observed in the mixtures may be connected with a disturbed nematic order near the surface of solid particles

  1. Influence of crystal orientation on hardness and nanoindentation deformation in ion-irradiated stainless steels

    International Nuclear Information System (INIS)

    The influence of crystal orientation on hardness and the range of plastic deformation caused by nanoindentation was investigated in a solution annealed type 316 stainless steel irradiated with Fe2+ ions. The hardness was a function of grain orientation and was correlated with the Taylor factor averaged over three normal directions of the contact surface of the Berkovich indenter. The transmission electron microscope observations of the deformation microstructure under the indentations showed that the range of plastic deformation reached up to 10 times the indent depth for unirradiated material and depended on the orientation relation between the contact surface of the indenter and the slip directions. The range of plastic deformation decreased as the damage structure developed in ion irradiation.

  2. Calculation of inelastic scattering processes of relativistic electrons in oriented crystals

    Energy Technology Data Exchange (ETDEWEB)

    Hinderks, Dieter; Kohl, Helmut

    2015-04-15

    The inelastic scattering of electrons in oriented crystals has been used to determine the positions of atoms within a crystal, to obtain site-dependent electron energy loss spectra and, more recently, to obtain an energy loss signal corresponding to the circular dichroism in X-ray absorption spectroscopy. The theoretical approaches currently used for the description of these processes are based on the nonrelativistic Schrödinger equation. Nowadays many experiments, however, are conducted with incident energies of 200 or 300 keV. Therefore it is indispensable to use a relativistic description for such processes based on the Dirac equation. Using the Coulomb gauge it is shown, that the fully relativistic cross sections for plane wave scattering are given by the modulus square of a sum of two terms: one describing the electrostatic interactions similar to the nonrelativistic theory plus one additional term describing the interaction of the specimen with the magnetic field produced by the incident electron. In crystals both terms can interfere leading to large deviations from nonrelativistic theory. - Highlights: • Inelastic scattering of relativistic electrons in oriented crystals is described. • We have derived equations for relativistic Bloch waves. • Strong deviations from nonrelativistic theory have been demonstrated.

  3. Surface relief and its relation to the crystallographic orientation in fatigued copper single crystals

    International Nuclear Information System (INIS)

    The typical feature of the response of metallic materials to cyclic loading is the localisation of cyclic slip determining the formation of the surface relief. It is also the main reason for the initiation of fatigue cracks and, consequently, fatigue fracture. This localisation is most evident in the case of single crystals, especially in orientation for simple slip. In the cyclic loading of the single crystals in the controlled deformation regime, there is a short stage of homogeneous deformation during which the material hardens, and this stage is followed by the stage of localisation of plastic deformation. The surface photography, associated with the persistent slip bands in single crystals was studied by means of various microscopic techniques

  4. Offset-free Measurement of Dipolar Couplings in a Single Crystal and Determination of Molecular Orientation

    CERN Document Server

    Jayanthi, S

    2010-01-01

    Dipolar couplings are an important source of structure as they provide site specific dipolar splittings for aligned samples and hence are extensively used for the study of membrane proteins in lipid bilayers, liquid crystals and single crystals. Of the many Separated Local Field (SLF) techniques existing to avail this information for static oriented systems, PISEMA (Polarization Inversion Spin Exchange at Magic Angle) has found to have wide application due to its many favorable characteristics. However the pulse sequence suffers from its inherent sensitivity to proton resonance frequency offset. We have recently proposed a sequence named DAPT (Dipolar Assisted Polarization Transfer: S. Jayanthi et al. Chem. Phys. Lett. 439, 407, 2007.) for dipolar coupling measurement which is found to be insensitive to proton offsets over wide range. In this presentation, we report the first implementation of the sequence on rigid systems. Experiments were done on a single crystal of N-Acetyl DL-Valine (NAV). Dipolar couplin...

  5. Protein crystal structure from non-oriented, single-axis sparse X-ray data

    Directory of Open Access Journals (Sweden)

    Jennifer L. Wierman

    2016-01-01

    Full Text Available X-ray free-electron lasers (XFELs have inspired the development of serial femtosecond crystallography (SFX as a method to solve the structure of proteins. SFX datasets are collected from a sequence of protein microcrystals injected across ultrashort X-ray pulses. The idea behind SFX is that diffraction from the intense, ultrashort X-ray pulses leaves the crystal before the crystal is obliterated by the effects of the X-ray pulse. The success of SFX at XFELs has catalyzed interest in analogous experiments at synchrotron-radiation (SR sources, where data are collected from many small crystals and the ultrashort pulses are replaced by exposure times that are kept short enough to avoid significant crystal damage. The diffraction signal from each short exposure is so `sparse' in recorded photons that the process of recording the crystal intensity is itself a reconstruction problem. Using the EMC algorithm, a successful reconstruction is demonstrated here in a sparsity regime where there are no Bragg peaks that conventionally would serve to determine the orientation of the crystal in each exposure. In this proof-of-principle experiment, a hen egg-white lysozyme (HEWL crystal rotating about a single axis was illuminated by an X-ray beam from an X-ray generator to simulate the diffraction patterns of microcrystals from synchrotron radiation. Millions of these sparse frames, typically containing only ∼200 photons per frame, were recorded using a fast-framing detector. It is shown that reconstruction of three-dimensional diffraction intensity is possible using the EMC algorithm, even with these extremely sparse frames and without knowledge of the rotation angle. Further, the reconstructed intensity can be phased and refined to solve the protein structure using traditional crystallographic software. This suggests that synchrotron-based serial crystallography of micrometre-sized crystals can be practical with the aid of the EMC algorithm even in cases

  6. Studies on Crystal Orientation of ZnO Film on Sapphire Using High-throughout X-ray Diffraction

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The orientation of the nano-columnar ZnO films grown on sapphire using the technique of metal-organic chemical vapor deposition (MOCVD) exhibits deviation because of the mismatch between the crystal lattices of the films and the sapphire substrate. A high-throughout X-ray diffraction method was employed to determine the crystal orientation of the ZnO films at a time scale of the order of minutes based on the general area detection diffraction system (GADDS). This rapid, effective, and ready method, adapted for characterizing the orientation of the nano-columnar crystals is used to directly explain the results of observation of the X-ray diffraction images, by the measurements of the orientations of the crystal columns of the ZnO films along c-axis and in parallel to ab plane.

  7. Improved crystal orientation and physical properties from single-shot XFEL stills

    International Nuclear Information System (INIS)

    X-ray free-electron laser crystallography relies on the collection of still-shot diffraction patterns. New methods are developed for optimal modeling of the crystals’ orientations and mosaic block properties. X-ray diffraction patterns from still crystals are inherently difficult to process because the crystal orientation is not uniquely determined by measuring the Bragg spot positions. Only one of the three rotational degrees of freedom is directly coupled to spot positions; the other two rotations move Bragg spots in and out of the reflecting condition but do not change the direction of the diffracted rays. This hinders the ability to recover accurate structure factors from experiments that are dependent on single-shot exposures, such as femtosecond diffract-and-destroy protocols at X-ray free-electron lasers (XFELs). Here, additional methods are introduced to optimally model the diffraction. The best orientation is obtained by requiring, for the brightest observed spots, that each reciprocal-lattice point be placed into the exact reflecting condition implied by Bragg’s law with a minimal rotation. This approach reduces the experimental uncertainties in noisy XFEL data, improving the crystallographic R factors and sharpening anomalous differences that are near the level of the noise

  8. Orientation dependent oxygen exchange kinetics on single crystal SrTiO3 surfaces.

    Science.gov (United States)

    Kerman, Kian; Ko, Changhyun; Ramanathan, Shriram

    2012-09-14

    The perovskite SrTiO(3) is arguably one of the most important oxide systems in condensed matter research. In this study, we report measurement of the orientation dependence of oxygen exchange on SrTiO(3) single crystal surfaces by dynamic conductivity measurements under electrochemical perturbations. Activation energy for electrical conduction in the 923-1223 K range at an oxygen partial pressure of ∼10(-11) Pa of (100), (111), and (110) single crystals was found to be 2.6 eV, 2.7 eV, and 3.1 eV, respectively. The equilibration kinetics show profound dependence on the surface orientation and are modelled using a heterogeneous relaxation process. All surfaces show similar cationic sub-lattice limited rate behavior with (111), (100), and (110) having the fastest, intermediate, and slowest rates, respectively. We discuss the orientation dependence and its relation to local atomic structure in light of previous experimental and theoretical studies. PMID:22850487

  9. Recording of polarization holograms in a liquid crystal cell with a photosensitive chalcogenide orientation layer [Invited].

    Science.gov (United States)

    Sheremet, Nina; Kurioz, Yuriy; Slyusarenko, Kostyantyn; Trunov, Michael; Reznikov, Yuriy

    2013-08-01

    Polarization gratings have been recorded in a combined liquid crystal (LC) cell made of a substrate covered with a photosensitive chalcogenide orientation layer and a reference substrate covered with a rubbed polyimide film. The gratings are formed due to the spatially modulated light-induced easy orientation axis on the chalcogenide surface recorded by two beams with opposite circular polarizations. The gratings are permanent, but they can be erased by one of the recording beams and re-recorded. The diffraction intensity of the circularly polarized light is achromatic and does not depend on the birefringence of the LC. The diffraction efficiency of the grating is of the order of a few percents. Application of an ac field causes a strong increase of the diffraction efficiency up to 45%. PMID:23913086

  10. Graphite edge controlled registration of monolayer MoS2 crystal orientation

    International Nuclear Information System (INIS)

    Transition metal dichalcogenides such as the semiconductor MoS2 are a class of two-dimensional crystals. The surface morphology and quality of MoS2 grown by chemical vapor deposition are examined using atomic force and scanning tunneling microscopy techniques. By analyzing the moiré patterns from several triangular MoS2 islands, we find that there exist at least five different superstructures and that the relative rotational angles between the MoS2 adlayer and graphite substrate lattices are typically less than 3°. We conclude that since MoS2 grows at graphite step-edges, it is the edge structure which controls the orientation of the islands, with those growing from zig-zag (or armchair) edges tending to orient with one lattice vector parallel (perpendicular) to the step-edge

  11. Orientation dependent deformation by slip and twinning in magnesium during single crystal indentation

    International Nuclear Information System (INIS)

    We present the orientation dependent indentation response of pure magnesium during single grain indentation. A conical indenter and maximum loads between 50 mN and 900 mN were employed. Indent topographies were acquired by confocal microscopy. The indents were also characterized by electron backscatter orientation microscopy for their microstructures. Pronounced activation of specific twinning systems was observed around the impressions. The resulting data were compiled into the inverse pole figure presentation of indent microstructures and topographies after Zambaldi and Raabe, Acta Mater. (2010). Three-dimensional crystal plasticity finite element simulation of the indentation deformation supports the interpretation of the orientation dependent slip and twinning patterns around the indents. The match between the activation of observed and simulated twinning variants is discussed with respect to the conditions for nucleation and growth of extension twins. Furthermore, the compatibility of the twinning strains with the imposed deformation is discussed based on the expanding cavity model of indentation. The orientation dependent response of magnesium during indentation is compared to the literature data for indentation of alpha-titanium and beryllium. Recommendations are given on how to exploit the characteristic nature of the observed indentation patterns to rapidly assess the relative activity of deformation mechanisms and their critical shear stresses during alloy development

  12. Theoretical characterization of a model of aragonite crystal orientation in red abalone nacre

    Energy Technology Data Exchange (ETDEWEB)

    Coppersmith, S N; Gilbert, P U P A; Metzler, R A [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States)

    2009-03-27

    Nacre, commonly known as mother-of-pearl, is a remarkable biomineral that in red abalone consists of layers of 400 nm thick aragonite crystalline tablets confined by organic matrix sheets, with the [0 0 1] crystal axes of the aragonite tablets oriented to within {+-}12 deg. from the normal to the layer planes. Recent experiments demonstrate that greater orientational order develops over a distance of tens of layers from the prismatic boundary at which nacre formation begins. Our previous simulations of a model in which the order develops because of differential tablet growth rates (oriented tablets growing faster than misoriented ones) yield patterns of tablets that agree qualitatively and quantitatively with the experimental measurements. This paper presents an analytical treatment of this model, focusing on how the dynamical development and eventual degree of order depend on model parameters. Dynamical equations for the probability distributions governing tablet orientations are introduced whose form can be determined from symmetry considerations and for which substantial analytic progress can be made. Numerical simulations are performed to relate the parameters used in the analytic theory to those in the microscopic growth model. The analytic theory demonstrates that the dynamical mechanism is able to achieve a much higher degree of order than naive estimates would indicate.

  13. Theoretical characterization of a model of aragonite crystal orientation in red abalone nacre

    International Nuclear Information System (INIS)

    Nacre, commonly known as mother-of-pearl, is a remarkable biomineral that in red abalone consists of layers of 400 nm thick aragonite crystalline tablets confined by organic matrix sheets, with the [0 0 1] crystal axes of the aragonite tablets oriented to within ±12 deg. from the normal to the layer planes. Recent experiments demonstrate that greater orientational order develops over a distance of tens of layers from the prismatic boundary at which nacre formation begins. Our previous simulations of a model in which the order develops because of differential tablet growth rates (oriented tablets growing faster than misoriented ones) yield patterns of tablets that agree qualitatively and quantitatively with the experimental measurements. This paper presents an analytical treatment of this model, focusing on how the dynamical development and eventual degree of order depend on model parameters. Dynamical equations for the probability distributions governing tablet orientations are introduced whose form can be determined from symmetry considerations and for which substantial analytic progress can be made. Numerical simulations are performed to relate the parameters used in the analytic theory to those in the microscopic growth model. The analytic theory demonstrates that the dynamical mechanism is able to achieve a much higher degree of order than naive estimates would indicate

  14. Formation of oriented nickel aggregates in rutile single crystals by Ni implantation

    International Nuclear Information System (INIS)

    The magnetic and electrical properties of Ni implanted single crystalline TiO2 rutile were studied for nominal implanted fluences between 0.5×1017 cm−2 and 2.0×1017 cm−2 with 150 keV energy, corresponding to maximum atomic concentrations between 9 at% and 27 at% at 65 nm depth, in order to study the formation of metallic oriented aggregates. The results indicate that the as implanted crystals exhibit superparamagnetic behavior for the two higher fluences, which is attributed to the formation of nanosized nickel clusters with an average size related with the implanted concentration, while only paramagnetic behavior is observed for the lowest fluence. Annealing at 1073 K induces the aggregation of the implanted nickel and enhances the magnetization in all samples. The associated anisotropic behavior indicates preferred orientations of the nickel aggregates in the rutile lattice consistent with Rutherford backscattering spectrometry—channelling results. Electrical conductivity displays anisotropic behavior but no magnetoresistive effects were detected. - Author-Highlights: • Ni nano-aggregates were grown on TiO2 using Ni implantation with different fluences. • In the as implanted state, the aggregates size is a function of the implanted fluence. • Ni aggregates are oriented within the rutile structure-2 orientations are proposed

  15. Rapid, all-optical crystal orientation imaging of two-dimensional transition metal dichalcogenide monolayers

    Energy Technology Data Exchange (ETDEWEB)

    David, Sabrina N. [Materials Science and Engineering Program, University of Colorado, Boulder, Colorado 80309 (United States); Zhai, Yao [Department of Mechanical Engineering, University of Colorado, Boulder, Colorado 80309 (United States); Zande, Arend M. van der [Department of Mechanical Engineering, Columbia University, New York, New York 10027 (United States); Department of Mechanical Science and Engineering, University of Illinois, Urbana, Illinois 61801 (United States); O' Brien, Kevin [NSF Nanoscale Science and Engineering Center (NSEC), University of California, Berkeley 3112 Etcheverry Hall, UC Berkeley, California 94720 (United States); Huang, Pinshane Y. [Department of Mechanical Science and Engineering, University of Illinois, Urbana, Illinois 61801 (United States); Chenet, Daniel A.; Hone, James C. [Department of Mechanical Engineering, Columbia University, New York, New York 10027 (United States); Zhang, Xiang [NSF Nanoscale Science and Engineering Center (NSEC), University of California, Berkeley 3112 Etcheverry Hall, UC Berkeley, California 94720 (United States); Department of Physics, King Abdulaziz University, Jeddah (Saudi Arabia); Materials Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States); Yin, Xiaobo, E-mail: Xiaobo.Yin@Colorado.Edu [Materials Science and Engineering Program, University of Colorado, Boulder, Colorado 80309 (United States); Department of Mechanical Engineering, University of Colorado, Boulder, Colorado 80309 (United States)

    2015-09-14

    Two-dimensional (2D) atomic materials such as graphene and transition metal dichalcogenides (TMDCs) have attracted significant research and industrial interest for their electronic, optical, mechanical, and thermal properties. While large-area crystal growth techniques such as chemical vapor deposition have been demonstrated, the presence of grain boundaries and orientation of grains arising in such growths substantially affect the physical properties of the materials. There is currently no scalable characterization method for determining these boundaries and orientations over a large sample area. We here present a second-harmonic generation based microscopy technique for rapidly mapping grain orientations and boundaries of 2D TMDCs. We experimentally demonstrate the capability to map large samples to an angular resolution of ±1° with minimal sample preparation and without involved analysis. A direct comparison of the all-optical grain orientation maps against results obtained by diffraction-filtered dark-field transmission electron microscopy plus selected-area electron diffraction on identical TMDC samples is provided. This rapid and accurate tool should enable large-area characterization of TMDC samples for expedited studies of grain boundary effects and the efficient characterization of industrial-scale production techniques.

  16. Liquid crystal orientation on solution processed zinc oxide inorganic films according to molecular concentration

    Science.gov (United States)

    Lee, Jong-Jin; Han, Jae-Jun; Park, Hong-Gyu; Kim, Dai-Hyun; Byun, Sang-Un; Seo, Dae-Shik

    2013-10-01

    In this paper we present the characteristics of molar concentration-dependent zinc oxide (ZnO) inorganic films deposited by the solution process for application in liquid crystal displays. ZnO surfaces supported homogeneously aligned liquid crystal (LC) molecules based on an ion-beam (IB) irradiation system. Uniform LC alignment was obtained at ZnO molar concentrations greater than 0.25 mol l-1. X-ray photoelectron spectroscopic (XPS) analysis revealed that changes in the orientation of LC molecules occurred on the ZnO layer. The electro-optic characteristics of the aligned homogenous LCs and twisted nematic (TN) mode based on the ZnO layer were comparable to those based on polyimide, which showed good potential as ZnO surfaces as an alignment layer.

  17. Surface-assisted unidirectional orientation of ZnO nanorods hybridized with nematic liquid crystals.

    Science.gov (United States)

    Kubo, Shoichi; Taguchi, Rei; Hadano, Shingo; Narita, Mamiko; Watanabe, Osamu; Iyoda, Tomokazu; Nakagawa, Masaru

    2014-01-22

    Inorganic semiconductor nanorods are regarded as the primary components of optical and electrical nanoscale devices. In this paper, we demonstrate the unidirectional alignment of monolayered and dispersed ZnO nanorods on a rubbed polyimide alignment layer, which was achieved by a conventional liquid crystal alignment technique. The outermost surfaces of the ZnO nanorods (average diameter 7 nm; length 50 nm) were modified by polymerization initiator moieties, and nematic liquid crystalline (LC) methacrylate polymers were grown by atom transfer radical polymerization. By regulating the densities of the polymerization initiator moieties, we successfully hybridized LC-polymer-grafted ZnO nanorods and small nematic LC molecules. The LC-polymer-modified ZnO nanorods were hierarchically aligned on the substrate via cooperative molecular interactions among the liquid crystal mesogens, which induced molecular orientation on the rubbed polyimide alignment layer. PMID:24299205

  18. A positron source using an axially oriented crystal associated to a granular amorphous converter

    Institute of Scientific and Technical Information of China (English)

    XU Cheng-Hai; Robert Chehab; Peter Sievers; Xavier Artru; Michel Chevallier; Olivier Dadoun; PEI Guo-Xi; Vladimir M. Strakhovenko; Alessandro Variola

    2012-01-01

    A non-conventional positron source using the intense γ radiation from an axially oriented monocrystal which materializes into e+e- pairs in a granular amorphous converter is described.The enhancement of photon radiation by multi-GeV electrons crossing a tungsten crystal along its 〈111〉 axis is reported.The resulting enhancement of pair production in an amorphous converter placed 2 meters downstream,is also reported.Sweeping off the charged particles from the crystal by a bending magnet upstream of the converter allows a significant reduction of the deposited energy density.Substituting a granular target made of small spheres for the usual compact one,makes the energy dissipation easier.The deposited energy and corresponding heating are analyzed and solutions for cooling are proposed.The configurations studied here for this kind of positron source allow its consideration for unpolarized positrons for the ILC.

  19. Shape-controlled orientation and assembly of colloids with sharp edges in nematic liquid crystals.

    Science.gov (United States)

    Beller, Daniel A; Gharbi, Mohamed A; Liu, Iris B

    2015-02-14

    The assembly of colloids in nematic liquid crystals via topological defects has been extensively studied for spherical particles, and investigations of other colloid shapes have revealed a wide array of new assembly behaviors. We show, using Landau-de Gennes numerical modeling, that nematic defect configurations and colloidal assembly can be strongly influenced by fine details of colloid shape, in particular the presence of sharp edges. For cylinder, microbullet, and cube colloid geometries, we obtain the particles' equilibrium alignment directions and effective pair interaction potentials as a function of simple shape parameters. We find that defects pin at sharp edges, and that the colloid consequently orients at an oblique angle relative to the far-field nematic director that depends on the colloid's shape. This shape-dependent alignment, which we confirm in experimental measurements, raises the possibility of selecting self-assembly outcomes for colloids in liquid crystals by tuning particle geometry. PMID:25523158

  20. Transfer of the in-plane molecular orientation of polyimide film surface to liquid crystal monolayer

    OpenAIRE

    Usami, Kiyoaki; Sakamoto, Kenji; Uehara, Yoichi; Ushioda, Sukekatsu

    2005-01-01

    We have determined the relationship between the in-plane molecular orientations of a polyimide film and the liquid crystal (LC) monolayer in contact with it. A photoaligned film of polyimide, containing azobenzene in the backbone structure, was used, because its in-plane molecular order can be varied over a wide range without change in the morphology and the chemical nature of the film surface. The in-plane order parameter of the LC molecule was found to be almost equal to that of the polyimi...

  1. Is There Something of Mode Coupling Theory in Orientationally Disordered Crystals?

    International Nuclear Information System (INIS)

    Molecular dynamics simulations have been performed on the orientationally disordered crystal chloroadamantane. We stress that universal behavior, relatively well described by the mode coupling theory, is shared by systems whose dynamics are almost completely controlled by translations or rotations. This investigation also shows the existence of a second remarkable dynamical crossover at the temperature Tx>Tc , consistent with a previous NMR and molecular dynamics study [F. Affouard et al., Europhys. Lett.53, 611 (2001)]. This allows us to support clearly the existence of a ''landscape-influenced'' regime as recently proposed [S. Sastry et al., Nature 393, 554 (1998)

  2. Chaotic orientational behavior of a nematic liquid crystal subjected to a steady shear flow.

    Science.gov (United States)

    Rienäcker, Götz; Kröger, Martin; Hess, Siegfried

    2002-10-01

    Based on a relaxation equation for the second rank alignment tensor characterizing the molecular orientation in liquid crystals, we report on a number of symmetry-breaking transient states and simple periodic and irregular, chaotic out-of-plane orbits under steady flow. Both an intermittency route and a period-doubling route to chaos are found for this five-dimensional dynamic system in a certain range of parameters (shear rate, tumbling parameter at isotropic-nematic coexistence, and reduced temperature). A link to the corresponding rheochaotic states, present in complex fluids, is made. PMID:12443167

  3. Analysis of diffuse orientation transition parameters in C60 crystals at 250-260 K

    International Nuclear Information System (INIS)

    The analysis of the orientation-structural transformation parameters in the C60 crystals within the temperature range of 250-260 K is carried out on the basis of the analysis of temperature dependences of thermal capacity and velocity of inelastic (ferroelectric) deformation, observed in the transition area experience. The value of the transformation elementary volume by the C60 (11-83 nm3) correlated molecular motion and the value of spontaneous shear deformation of the lattice 2.4 x 10-2 by its restructuring from a simple cubical one into a face-centered one are determined in the course of the analysis

  4. Unoccupied electronic structure and molecular orientation of rubrene; from evaporated films to single crystals

    Science.gov (United States)

    Ueba, T.; Park, J.; Terawaki, R.; Watanabe, Y.; Yamada, T.; Munakata, T.

    2016-07-01

    Two-photon photoemission (2PPE) spectroscopy and ultraviolet photoemission spectroscopy (UPS) have been performed for rubrene single crystals and evaporated thin films on highly oriented pyrolytic graphite (HOPG). The changes in the 2PPE intensity from the single crystals by the polarization of the light and by the angle of the light incident plane against the crystalline axes indicate that the molecular arrangement on the surface is similar to that in the bulk crystal. On the other hand, in the case of evaporated films, the polarization dependence of 2PPE indicates that the tetracene backbone becomes standing upright as the thickness increases. In spite of the alignment of molecules, the broadened 2PPE spectral features for thick films suggest that the films are amorphous and molecules are in largely different environments. The film structures are confirmed by scanning tunneling microscopy (STM). The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) derived levels of the single crystal are shifted by + 0.18 and - 0.20 eV, respectively, from those of the 0.8 ML film. The shifts are attributed to the packing density of molecules. It is shown that the unoccupied electronic structure is more sensitively affected by the film structure than the occupied electronic structure.

  5. Biogenic calcite granules--are brachiopods different?

    Science.gov (United States)

    Pérez-Huerta, Alberto; Dauphin, Yannicke; Cusack, Maggie

    2013-01-01

    Brachiopods are still one of the least studied groups of organisms in terms of biomineralization despite recent studies indicating the presence of highly complex biomineral structures, particularly in taxa with calcitic shells. Here, we analyze the nanostructure of calcite biominerals, fibers and semi-nacre tablets, in brachiopod shells by high-resolution scanning electron microscopy (SEM) and atomic force microscopy (AFM). We demonstrate that basic mechanisms of carbonate biomineralization are not uniform within the phylum, with semi-nacre tablets composed of spherical aggregates with sub-rounded granules and fibers composed of large, triangular or rod-like particles composed of small sub-rounded granules (40-60 nm). Additionally, proteinaceous envelopes surrounding calcite fibers have been shown for the first time to have a dual function: providing a micro-environment in which granules are produced and acting as the organic template for particle orientation as fiber components. In summary, these new findings in brachiopod shells reveal a complex and distinctive style of biomineralization among carbonate-producing organisms. PMID:23026148

  6. Oxygen isotope fractionation in synthetic magnesian calcite

    Science.gov (United States)

    Jiménez-López, Concepción; Romanek, Christopher S.; Huertas, F. Javier; Ohmoto, Hiroshi; Caballero, Emilia

    2004-08-01

    Mg-bearing calcite was precipitated at 25°C in closed system free-drift experiments from solutions containing NaHCO 3, CaCl 2 and MgCl 2. The chemical and isotope composition of the solution and precipitate were investigated during time course experiments of 24-h duration. Monohydrocalcite and calcite precipitated early in the experiments (95%) thereafter. Solid collected at the end of the experiments displayed compositional zoning from pure calcite in crystal cores to up to 23 mol% MgCO 3 in the rims. Smaller excursions in Mg were superimposed on this chemical record, which is characteristic of oscillatory zoning observed in synthetic and natural solid-solution carbonates of differing solubility. Magnesium also altered the predominant morphology of crystals over time from the {104} to {100} and {110} growth forms. The oxygen isotope fractionation factor for the magnesian-calcite-water system (as 10 3lnα Mg-cl-H 2O ) displayed a strong dependence on the mol% MgCO 3 in the solid phase, but quantification of the relationship was difficult due to the heterogeneous nature of the precipitate. Considering only the Mg-content and δ 18O values for the bulk solid, 10 3lnα Mg-cl-H 2O increased at a rate of 0.17 ± 0.02 per mol% MgCO 3; this value is a factor of three higher than the single previous estimate (Tarutani T., Clayton R.N., and Mayeda T. K. (1969) The effect of polymorphims and magnesium substitution on oxygen isotope fractionation between calcium carbonate and water. Geochim. Cosmochim. Acta 33, 987-996). Nevertheless, extrapolation of our relationship to the pure calcite end member yielded a value of 27.9 ± 0.02, which is similar in magnitude to published values for the calcite-water system. Although no kinetic effect was observed on 10 3lnα Mg-cl-H 2O for precipitation rates that ranged from 10 3.21 to 10 4.60 μmol · m -2 · h -1, it was impossible to disentangle the potential effect(s) of precipitation rate and Mg-content on 10 3lnα Mg-cl-H 2O due to

  7. Molecular Dynamics Simulations of the Orientation Effect on the Initial Plastic Deformation of Magnesium Single Crystals

    Institute of Scientific and Technical Information of China (English)

    Qun Zu; Ya-Fang Guo; Shuang Xu; Xiao-Zhi Tang; Yue-Sheng Wang

    2016-01-01

    Molecular dynamics simulation is employed to study the tension and compression deformation behaviors of magnesium single crystals with different orientations.The angle between the loading axis and the basal direction ranges from 0° to 90°.The simulation results show that the initial defects usually nucleate at free surfaces,but the initial plastic deformation and the subsequent microstructural evolutions are various due to different loading directions.The tension simulations exhibit the deformation mechanisms of twinning,slip,crystallographic reorientation and basal/prismatic transformation.The twinning,crystallographic reorientation and basal/prismatic transformation can only appear in the crystal model loaded along or near the a-axis or c-axis.For the compression simulations,the basal,prismatic and pyramidal slips are responsible for the initial plasticity,and no twinning is observed.Moreover,the plastic deformation models affect the yield strengths for the samples with different orientations.The maximum yield stresses for the samples loaded along the c-axis or a-axis are much higher than those loaded in other directions.

  8. Orientations of Chromonic Liquid Crystals by Imprinted or Rubbed Polymer Films

    Science.gov (United States)

    Yi, Youngwoo; McGuire, Aya; Clark, Noel

    2014-03-01

    A variety of novel alignment effects of chromonic liquid crystal phases of sunset yellow (SSY)/water, disodium cromoglycate (DSCG)/water, and their mixtures by thiol-ene polymer films topographically imprinted with linear channels are observed using polarizing optical microscopy. Nematic DSCG and SSY at low concentration and their nematic mixtures orient with the long axes of stacked chromonic aggregates on average parallel to the channels, that is, with the molecular planes normal to the channel axis. On the contrary, nematic SSY in contact with the rubbed polyimide films orients with the long axes on average in-plane perpendicular to the rubbing direction, arguably, due to a tongue-groove interaction between SSY and the stretched PI chains. Furthermore, multi-stable alignments are observed in SSY solutions of sufficiently high concentration, including preferential in-plane orientation of the long axes of the aggregates parallel to, perpendicular to, and 45° rotated from the channels. This work was supported by NSF grant DMR 1207606, NSF MRSEC grant DMR 0820579, and NSF Research Experience for Undergraduate programs.

  9. Orientation dependence of deformation and penetration behavior of tungsten single crystal rods

    International Nuclear Information System (INIS)

    This paper reports on deformation and flow at a target/penetrator interface that occurs under conditions of high hydrostatic pressure and associated heat generation. To further elucidate the role of material structure in the penetration process, oriented single crystals of tungsten have been launched into steel targets and the residual penetrators recovered and analyzed. Both the penetration depth and the deformation characteristics were strongly influenced by the crystallographic orientation. Deformation modes for the left-angle 100 right-angle rod, which exhibited the best performance, appeared to involve considerable localized slip/cleavage and relatively less plastic working; the residual penetrator was extensively cracked and the eroded penetrator material was extruded in a smooth tube lined with an oriented array of discrete particle exhibiting cleavage fractures. Deformation appeared to be much less localized and to involve more extensive plastic working in the left-angle 011 right-angle rod, which exhibited the poorest penetration, while the left-angle 111 right-angle behaved in an intermediate fashion

  10. Characterization of tin crystal orientation evolution during thermal cycling in lead-free solder joints

    Science.gov (United States)

    Zhou, Bite

    To address the long term reliability of lead-free solder joints in electronic devices during thermal cycling, the fundamental understanding of deformation mechanisms was studied using polarized light optical microscopy (PLM), electron backscatter diffraction (EBSD) in scanning electron microscopy (SEM), and synchrotron X-ray diffraction (XRD). Near-eutectic Sn-3.0(wt %) Ag-0.5(wt %) Cu (SAC305) lead-free solder joints were assessed in three different package designs: low-strain plastic ball grid array (PBGA), medium-strain fine-pitch ball grid array (BGA), and high-strain wafer-level-chip-scale package (WLCSP). The effect of microstructure evolution on solder failure is correlated with dislocation slip activities. The major failure mode in lead-free solder joints during thermal cycling that causes the electrical failure of the device is cracking in the bulk Sn near the Si chip/solder interface. Microstructure and Sn grain orientation evolution usually precedes crack development. A combined approach of both statistical analysis of a large number of solder joints, and detailed studies of individual solder balls was used to investigate the causes of fracture. Sn crystal orientation evolution and its effect on deformation was characterized in solder joints with different thermal histories, and compared with those from other package designs with different effective strain levels. The relationship between the initial dominant and localized recrystallized Sn grain orientations on crack development was investigated. It is found that in the low-strain package design, cracking is strongly correlated with Sn grain orientations with the [001] direction (c-axis) nearly aligned with the chip/solder interface. But no cracks were observed in solder balls with dominant orientations that have the c-axis normal to the interface plane. In higher-strain packages, however, cracking occurred in a variety of Sn grain orientations, and even solder balls with dominant orientations that are

  11. Neutron single crystal diffraction studies of orientational glass state in the [Rbx(NH4)1-x]3H(SO4)2 mixed crystals

    International Nuclear Information System (INIS)

    The [Rbx(NH4)1-x]3H(SO4)2 mixed crystal with the concentration x=0.0 at room temperature crystallizes in a monoclinic C2/c with sp.gr. (space group), which is stabilized for x>0.09 down to low temperatures. This system is transformed in the orientational glass state below the freezing temperature Tg=30 K. The differential Fourier maps for the [Rbx(NH4)1-x]3H(SO4)2 mixed crystals show that if for x=0.0 and 0.11 at 293 K the obtained maps reflect different orientational positions of crystallographically independent NH4(1) and NH4(2) groups, then the differential Fourier maps for x=0.20 at 9 K in the orientational glass state are similar for both ammonium groups reflecting their static disorder. The existence of the modulated structure in the [Rbx(NH4)1-x]3H(SO4)2 mixed crystals with x=0.11 at 2 K is discovered, while the modulated structure for x=0.20 at 2 K is absent. This observation supposes that there should be two different regions of the orientational glass state on x-T phase diagram of the [Rbx(NH4)1-x]3H(SO4)2 mixed crystals

  12. Influence of aluminum nitride crystal orientation on MEMS energy harvesting device performance

    International Nuclear Information System (INIS)

    Aluminum nitride (AlN) is a widely researched piezoelectric material due to its CMOS compatibility. One of the most common applications for AlN is in the area of vibrational energy harvesting. The piezoelectric quality of AlN is related to the crystal orientation of the film and optimal conditions are obtained when AlN is c-axis aligned with a (0 0 2) orientation. AlN can be a challenging material to integrate into a fabrication process due to orientation dependency of the fabrication process. This paper reports on the effects of non-(0 0 2) oriented AlN peaks on an energy harvesting MEMS cantilever structure. Results show that FWHM values of the AlN films from different wafers were approximately the same 8.5°, 8.7°, and 9°, however wafer 1 had additional peaks at (1 0 2) and (1 0 3), which significantly affected the piezoelectric constants and the amount of power generated. The measured d31 value for the wafers were 2.04, 1.97, and 0.84 pm V−1, and the power generated was 0.67, 0.64, and 0.24 µW respectively. These values show that non-peaks of AlN can cause a significant decrease in the piezoelectric constant, which causes significant decrease in the ability to generate power from an AlN film. (paper)

  13. On the complex conductivity signatures of calcite precipitation

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Yuxin; Hubbard, Susan; Williams, Kenneth Hurst; Ajo-Franklin, Jonathan

    2009-11-01

    Calcite is a mineral phase that frequently precipitates during subsurface remediation or geotechnical engineering processes. This precipitation can lead to changes in the overall behavior of the system, such as flow alternation and soil strengthening. Because induced calcite precipitation is typically quite variable in space and time, monitoring its distribution in the subsurface is a challenge. In this research, we conducted a laboratory column experiment to investigate the potential of complex conductivity as a mean to remotely monitor calcite precipitation. Calcite precipitation was induced in a glass bead (3 mm) packed column through abiotic mixing of CaCl{sub 2} and Na{sub 2}CO{sub 3} solutions. The experiment continued for 12 days with a constant precipitation rate of {approx}0.6 milimole/d. Visual observations and scanning electron microscopy imaging revealed two distinct phases of precipitation: an earlier phase dominated by well distributed, discrete precipitates and a later phase characterized by localized precipitate aggregation and associated pore clogging. Complex conductivity measurements exhibited polarization signals that were characteristic of both phases of calcite precipitation, with the precipitation volume and crystal size controlling the overall polarization magnitude and relaxation time constant. We attribute the observed responses to polarization at the electrical double layer surrounding calcite crystals. Our experiment illustrates the potential of electrical methods for characterizing the distribution and aggregation state of nonconductive minerals like calcite. Advancing our ability to quantify geochemical transformations using such noninvasive methods is expected to facilitate our understanding of complex processes associated with natural subsurface systems as well as processes induced through engineered treatments (such as environmental remediation and carbon sequestration).

  14. Molecular orientation of hydrogen-bonded liquid crystal (6BA)2-(BPy)x as Studied by 2H NMR

    International Nuclear Information System (INIS)

    The thermal properties of hydrogen-bonded liquid crystal (6BA)2-(BPy)x (6BA: 4-n-hexylbenzoicacid, BPy: 4,4’-bipyridine) were investigated by DSC. Two liquid crystal phases (LCI, LCII) were found for (6BA)2-(BPy)0.5. In LCII, the distribution of the orientation of molecules was larger than in LCI. The order parameter S of molecular orientation in the liquid crystal phase was estimated from a 2H NMR spectrum. S decreased rapidly around the LCI-LCII phase transition. The increase in orientational fluctuation of the 6BA dimer with an open dimer structure is predicted to cause the rapid decrease of S

  15. Bioengineering single crystal growth.

    Science.gov (United States)

    Wu, Ching-Hsuan; Park, Alexander; Joester, Derk

    2011-02-16

    Biomineralization is a "bottom-up" synthesis process that results in the formation of inorganic/organic nanocomposites with unrivaled control over structure, superior mechanical properties, adaptive response, and the capability of self-repair. While de novo design of such highly optimized materials may still be out of reach, engineering of the biosynthetic machinery may offer an alternative route to design advanced materials. Herein, we present an approach using micro-contact-printed lectins for patterning sea urchin embryo primary mesenchyme cells (PMCs) in vitro. We demonstrate not only that PMCs cultured on these substrates show attachment to wheat germ agglutinin and concanavalin A patterns but, more importantly, that the deposition and elongation of calcite spicules occurs cooperatively by multiple cells and in alignment with the printed pattern. This allows us to control the placement and orientation of smooth, cylindrical calcite single crystals where the crystallographic c-direction is parallel to the cylinder axis and the underlying line pattern. PMID:21265521

  16. Assessment of crystal quality and unit cell orientation in epitaxial Cu₂ZnSnSe₄ layers using polarized Raman scattering.

    Science.gov (United States)

    Krämmer, Christoph; Lang, Mario; Redinger, Alex; Sachs, Johannes; Gao, Chao; Kalt, Heinz; Siebentritt, Susanne; Hetterich, Michael

    2014-11-17

    We use polarization-resolved Raman spectroscopy to assess the crystal quality of epitaxial kesterite layers. It is demonstrated for the example of epitaxial Cu₂ZnSnSe₄ layers on GaAs(001) that "standing" and "lying" kesterite unit cell orientations (c'-axis parallel / perpendicular to the growth direction) can be distinguished by the application of Raman tensor analysis. From the appearance of characteristic intensity oscillations when the sample is rotated one can distinguish polycrystalline and epitaxial layers. The method can be transferred to kesterite layers oriented in any crystal direction and can shed light on the growth of such layers in general. PMID:25402065

  17. Growth and Raman spectra of single-crystal trilayer graphene with different stacking orientations.

    Science.gov (United States)

    Zhao, Haiming; Lin, Yung-Chang; Yeh, Chao-Hui; Tian, He; Chen, Yu-Chen; Xie, Dan; Yang, Yi; Suenaga, Kazu; Ren, Tian-Ling; Chiu, Po-Wen

    2014-10-28

    Understanding the growth mechanism of graphene layers in chemical vapor deposition (CVD) and their corresponding Raman properties is technologically relevant and of importance for the application of graphene in electronic and optoelectronic devices. Here, we report CVD growth of single-crystal trilayer graphene (TLG) grains on Cu and show that lattice defects at the center of each grain persist throughout the growth, indicating that the adlayers share the same nucleation site with the upper layers and these central defects could also act as a carbon pathway for the growth of a new layer. Statistics shows that ABA, 30-30, 30-AB, and AB-30 make up the major stacking orientations in the CVD-grown TLG, with distinctive Raman 2D characteristics. Surprisingly, a high level of lattice defects results whenever a layer with a twist angle of θ = 30° is found in the multiple stacks of graphene layers. PMID:25295851

  18. Molecular conformation and orientational order in nCB liquid crystals

    Science.gov (United States)

    Kobinata, Shunsuke; Kobayashi, Takamichi; Yoshida, Hiroshi; Chandani, A. D. L.; Maeda, Shiro

    1986-08-01

    A resonance Raman probe method for determining the second and fourth orientational order parameters ( P¯2 and P¯4) in liquid crystals is described. The method was applied to a series of nematic nCB near the nematic—isotropic transition temperature, using all trans β-carotene as a resonant probe. Both P¯2 and P¯4, thus obtained show a distinct even—odd effect, that is, zigzag change of the parameter value against the length of alkyl end chain. The origin of the even—odd effect was investigated by the mean field theory, taking the conformation variety of end chain into account following the method of Marcelja. On the basis of calculation, the function of the alkyl chain in the formation of the liquid crystalline state is discussed.

  19. Characterization of the crystal orientation in mono-oriented films of HDPE/LLDPE blends by IR dichroism

    Science.gov (United States)

    Canevarolo, Sebastião V.; Elias, Marcelo; Ravazzi, Camila; Silva, Jorge

    2016-03-01

    Polyethylene films are a common packaging material. The level and type of chain orientation in these films are a very important property which is of great care and concern of the converter personnel during the conformation process. Usually bi-orientation is the conventional procedure but when easy tear in one direction is needed mono-orientation is sought. This paper deal with the characterization of the crystalline orientation in films of polyethylene blends (HDPE/LLDPE) which have being oriented in two steps: initially the polymer was bi-oriented via extrusion-blown, cooled, and then in a second process hot stretched along the machine direction in order to produce mono-oriented films. In order to evaluate the orientation of the film, the polarization of the FT-IR beam was rotated 360° in steps of 5° by rotating the polarizer. In each step the absorbance spectrum was recorded and the corresponding dichroic ratio (DR) calculated after subtracting the baseline. With differential scanning calorimetry (DSC) was possible to infer about the changes in the morphology caused by the stretching.

  20. Creep property and microstructure evolution of a nickel-base single crystal superalloy in [011] orientation

    International Nuclear Information System (INIS)

    The creep property and microstructure evolution of a single crystal superalloy with [011] orientation were investigated at the temperatures of 700 °C, 900 °C and 1040 °C. It is shown that there exist stages of primary, steady-state, and tertiary creep under the lower temperature 700 °C. As the temperature increases to high temperatures of 900 °C and 1040 °C, steady-state creep stage is reduced or disappears and the shape of creep curves is dominated by an extensive tertiary stage. The minimum creep strain rate exhibits power law dependence on the applied stress; the stress exponents at 700 °C, 900 °C and 1040 °C are 28, 13 and 6.5, respectively. Microstructure observation shows that the morphologies of γ′ phase almost keep original shape at the lower temperature 700 °C and high applied stress. With the increasing creep temperature, γ′ precipitates tend to link together and form lamellar structure at an angle of 45° inclined to the applied stress. Transmission electron microscopy (TEM) investigations reveal that multiple (111) slip systems gliding in the matrix channels and shearing γ′ precipitates by stacking faults or bending dislocation pairs are the main deformation mechanism at the lower temperature of 700 °C. At the high temperatures of 900 °C and 1040 °C, dislocation networks are formed at γ/γ′ interfaces and the γ′ rafts are sheared by dislocation pairs. - Highlights: • Creep properties of -oriented single crystal superalloys were investigated. • γ′ phases become rafting at an angle of 45° inclined to the applied stress. • Creep deformation mechanisms depend on temperature and stress

  1. Biotic control of skeletal growth by scleractinian corals in aragonite-calcite seas.

    Directory of Open Access Journals (Sweden)

    Tomihiko Higuchi

    Full Text Available Modern scleractinian coral skeletons are commonly composed of aragonite, the orthorhombic form of CaCO3. Under certain conditions, modern corals produce calcite as a secondary precipitate to fill pore space. However, coral construction of primary skeletons from calcite has yet to be demonstrated. We report a calcitic primary skeleton produced by the modern scleractinian coral Acropora tenuis. When uncalcified juveniles were incubated from the larval stage in seawater with low mMg/Ca levels, the juveniles constructed calcitic crystals in parts of the primary skeleton such as the septa; the deposits were observable under Raman microscopy. Using scanning electron microscopy, we observed different crystal morphologies of aragonite and calcite in a single juvenile skeleton. Quantitative analysis using X-ray diffraction showed that the majority of the skeleton was composed of aragonite even though we had exposed the juveniles to manipulated seawater before their initial crystal nucleation and growth processes. Our results indicate that the modern scleractinian coral Acropora mainly produces aragonite skeletons in both aragonite and calcite seas, but also has the ability to use calcite for part of its skeletal growth when incubated in calcite seas.

  2. Biotic Control of Skeletal Growth by Scleractinian Corals in Aragonite–Calcite Seas

    Science.gov (United States)

    Higuchi, Tomihiko; Fujimura, Hiroyuki; Yuyama, Ikuko; Harii, Saki; Agostini, Sylvain; Oomori, Tamotsu

    2014-01-01

    Modern scleractinian coral skeletons are commonly composed of aragonite, the orthorhombic form of CaCO3. Under certain conditions, modern corals produce calcite as a secondary precipitate to fill pore space. However, coral construction of primary skeletons from calcite has yet to be demonstrated. We report a calcitic primary skeleton produced by the modern scleractinian coral Acropora tenuis. When uncalcified juveniles were incubated from the larval stage in seawater with low mMg/Ca levels, the juveniles constructed calcitic crystals in parts of the primary skeleton such as the septa; the deposits were observable under Raman microscopy. Using scanning electron microscopy, we observed different crystal morphologies of aragonite and calcite in a single juvenile skeleton. Quantitative analysis using X-ray diffraction showed that the majority of the skeleton was composed of aragonite even though we had exposed the juveniles to manipulated seawater before their initial crystal nucleation and growth processes. Our results indicate that the modern scleractinian coral Acropora mainly produces aragonite skeletons in both aragonite and calcite seas, but also has the ability to use calcite for part of its skeletal growth when incubated in calcite seas. PMID:24609012

  3. Robustness of the periodic and chaotic orientational behavior of tumbling nematic liquid crystals.

    Science.gov (United States)

    Heidenreich, Sebastian; Ilg, Patrick; Hess, Siegfried

    2006-06-01

    The dynamical behavior of molecular alignment strongly affects physical properties of nematic liquid crystals. A theoretical description can be made by a nonlinear relaxation equation of the order parameter and leads to the prediction that rather complex even chaotic orientational behavior occur. Here the influence of fluctuating shear rates on the orientational dynamics especially on chaotic solutions is discussed. With the help of phase portraits and time evolution diagrams, we investigated the influence of different fluctuation strengths on the flow aligned, isotropic, and periodic solutions. To explore the effect of fluctuations on the chaotic behavior, we calculated the largest Lyapunov exponent for different fluctuation strengths. We found in all cases that small fluctuations of the shear rate do not affect the basic features of the dynamics of tumbling nematics. Furthermore, we present an amended potential modeling the isotropic to nematic transition and discuss the equivalence and difference to the commonly used Landau-de Gennes potential. In contrast to the Landau-de Gennes potential, our potential has the advantage to restrict the order parameter to physically admissible values. In the case of extensional flow, we show that the amended potential leads for increasing extensional rate to a better agreement with experimental results. PMID:16906852

  4. Robustness of the periodic and chaotic orientational behavior of tumbling nematic liquid crystals

    International Nuclear Information System (INIS)

    The dynamical behavior of molecular alignment strongly affects physical properties of nematic liquid crystals. A theoretical description can be made by a nonlinear relaxation equation of the order parameter and leads to the prediction that rather complex even chaotic orientational behavior occur. Here the influence of fluctuating shear rates on the orientational dynamics especially on chaotic solutions is discussed. With the help of phase portraits and time evolution diagrams, we investigated the influence of different fluctuation strengths on the flow aligned, isotropic, and periodic solutions. To explore the effect of fluctuations on the chaotic behavior, we calculated the largest Lyapunov exponent for different fluctuation strengths. We found in all cases that small fluctuations of the shear rate do not affect the basic features of the dynamics of tumbling nematics. Furthermore, we present an amended potential modeling the isotropic to nematic transition and discuss the equivalence and difference to the commonly used Landau-de Gennes potential. In contrast to the Landau-de Gennes potential, our potential has the advantage to restrict the order parameter to physically admissible values. In the case of extensional flow, we show that the amended potential leads for increasing extensional rate to a better agreement with experimental results

  5. Zinc isotope fractionation during adsorption on calcite

    Science.gov (United States)

    Dong, S.; Wasylenki, L. E.

    2013-12-01

    Zinc is an important element as a nutrient in the marine biosphere. However, our understanding of its biogeochemical cycling in the oceans is relatively limited. The Zn stable isotope system holds the promise of providing novel insights, since published Zn isotopic values for various natural samples reveal significant fractionations in the marine environment. Surface seawater, basalts, shales, deep-sea clay sediments, sediment trap material, bulk plankton and zooplankton samples, and eolian dust fall within a tight range (δ66/64Zn from -0.1 to 0.5‰), but modern ferromanganese crusts (δ66/64Zn from 0.5 to 1.2‰), as well as carbonates (δ66/64Zn from 0.3 to 1.4‰), are notably enriched in heavy Zn isotopes [1-4]. In this study we seek to constrain the mechanism by which carbonates are enriched in heavier isotopes. In particular, we have conducted experiments to quantify isotope fractionation during adsorption of Zn onto the surfaces of calcite crystals that are in equilibrium with solution. The adsorption experiments were carried out in a series of small-volume batch reactions in a clean laboratory environment, using high-purity reagents and calcite seed crystals. The calcite was equilibrated with the solution prior to addition of Zn at atmospheric CO2 pressure (i.e., in air) for 5 days until a stable pH of 8.3 was reached. Later, a small aliquot of dissolved ZnCl2 was added such that the solution remained undersaturated with respect to hydrozincite. Experimental duration varied among the replicates from 6 to 144 hours, and then all solids and solutions were separated by filtration, purified by ion exchange chromatography, and analyzed by MC-ICP-MS. Zn adsorbed on calcite is isotopically heavier than in the co-existing solutions, with Δ68/66Zncalcite-solution of approximately 0.3‰. The variation of Δ68/66Zncalcite-solution beyond 24 hours is insignificant, so we infer that isotopic equilibrium is reached by this time. Previous work strongly suggests that a

  6. Peculiar orientational disorder in 4-bromo-4'-nitrobiphenyl (BNBP) and 4-bromo-4'-cyanobiphenyl (BCNBP) leading to bipolar crystals.

    Science.gov (United States)

    Burgener, Matthias; Aboulfadl, Hanane; Labat, Gaël Charles; Bonin, Michel; Sommer, Martin; Sankolli, Ravish; Wübbenhorst, Michael; Hulliger, Jürg

    2016-05-01

    180° orientational disorder of molecular building blocks can lead to a peculiar spatial distribution of polar properties in molecular crystals. Here we present two examples [4-bromo-4'-nitrobiphenyl (BNBP) and 4-bromo-4'-cyanobiphenyl (BCNBP)] which develop into a bipolar final growth state. This means orientational disorder taking place at the crystal/nutrient interface produces domains of opposite average polarity for as-grown crystals. The spatial inhomogeneous distribution of polarity was investigated by scanning pyroelectric microscopy (SPEM), phase-sensitive second harmonic microscopy (PS-SHM) and selected volume X-ray diffraction (SVXD). As a result, the acceptor groups (NO2 or CN) are predominantly present at crystal surfaces. However, the stochastic process of polarity formation can be influenced by adding a symmetrical biphenyl to a growing system. For this case, Monte Carlo simulations predict an inverted net polarity compared with the growth of pure BNBP and BCNBP. SPEM results clearly demonstrate that 4,4'-dibromobiphenyl (DBBP) can invert the polarity for both crystals. Phenomena reported in this paper belong to the most striking processes seen for molecular crystals, demonstrated by a stochastic process giving rise to symmetry breaking. We encounter here further examples supporting the general thesis that monodomain polar molecular crystals for fundamental reasons cannot exist. PMID:27158508

  7. Tuning hardness in calcite by incorporation of amino acids

    Science.gov (United States)

    Kim, Yi-Yeoun; Carloni, Joseph D.; Demarchi, Beatrice; Sparks, David; Reid, David G.; Kunitake, Miki E.; Tang, Chiu C.; Duer, Melinda J.; Freeman, Colin L.; Pokroy, Boaz; Penkman, Kirsty; Harding, John H.; Estroff, Lara A.; Baker, Shefford P.; Meldrum, Fiona C.

    2016-08-01

    Structural biominerals are inorganic/organic composites that exhibit remarkable mechanical properties. However, the structure-property relationships of even the simplest building unit--mineral single crystals containing embedded macromolecules--remain poorly understood. Here, by means of a model biomineral made from calcite single crystals containing glycine (0-7 mol%) or aspartic acid (0-4 mol%), we elucidate the origin of the superior hardness of biogenic calcite. We analysed lattice distortions in these model crystals by using X-ray diffraction and molecular dynamics simulations, and by means of solid-state nuclear magnetic resonance show that the amino acids are incorporated as individual molecules. We also demonstrate that nanoindentation hardness increased with amino acid content, reaching values equivalent to their biogenic counterparts. A dislocation pinning model reveals that the enhanced hardness is determined by the force required to cut covalent bonds in the molecules.

  8. Preferred orientation of n-hexane crystallized in silicon nanochannels: A combined x-ray diffraction and sorption isotherm study

    CERN Document Server

    Henschel, Anke; Hofmann, Tommy; Knorr, Klaus; Huber, Patrick; 10.1103/PhysRevE.79.032601

    2009-01-01

    We present an x-ray diffraction study on n-hexane in tubular silicon channels of approximately 10 nm diameter both as a function of the filling fraction f of the channels and as a function of temperature. Upon cooling, confined n-hexane crystallizes in a triclinic phase typical of the bulk crystalline state. However, the anisotropic spatial confinement leads to a preferred orientation of the confined crystallites, where the crystallographic direction coincides with the long axis of the channels. The magnitude of this preferred orientation increases with the filling fraction, which corroborates the assumption of a Bridgman-type crystallization process being responsible for the peculiar crystalline texture. This growth process predicts for a channel-like confinement an alignment of the fastest crystallization direction parallel to the long channel axis. It is expected to be increasingly effective with the length of solidifying liquid parcels and thus with increasing f. In fact, the fastest solidification front...

  9. Processing of X-ray snapshots from crystals in random orientations

    Energy Technology Data Exchange (ETDEWEB)

    Kabsch, Wolfgang, E-mail: kabsch@mpimf-heidelberg.mpg.de [Max-Planck-Institut für medizinische Forschung, Jahnstrasse 29, D-69120 Heidelberg (Germany)

    2014-08-01

    A new method for the treatment of partial reflections from X-ray snapshots is implemented in the program package nXDS, which yields intensity data of almost the same quality as those obtained by the classical rotation method. A functional expression is introduced that relates scattered X-ray intensities from a still or a rotation snapshot to the corresponding structure-factor amplitudes. The new approach was implemented in the program nXDS for processing monochromatic diffraction images recorded by a multi-segment detector where each exposure could come from a different crystal. For images containing indexable spots, the intensities of the expected reflections and their variances are obtained by profile fitting after mapping the contributing pixel contents to the Ewald sphere. The varying intensity decline owing to the angular distance of the reflection from the surface of the Ewald sphere is estimated using a Gaussian rocking curve. This decline is dubbed ‘Ewald offset correction’, which is well defined even for still images. Together with an image-scaling factor and other corrections, an explicit expression is defined that predicts each recorded intensity from its corresponding structure-factor amplitude. All diffraction parameters, scaling and correction factors are improved by post-refinement. The ambiguous case of a lower point group than the lattice symmetry is resolved by a method reminiscent of the technique of ‘selective breeding’. It selects the indexing alternative for each image that yields, on average, the highest correlation with intensities from all other images. Processing a test set of rotation images by XDS and treating the same images by nXDS as snapshots of crystals in random orientations yields data of comparable quality, clearly indicating an anomalous signal from Se atoms.

  10. Crystal Orientation and Temperature Effects on the Double Hysteresis Loop Behavior of a PVDF- g-PS Graft Copolymer

    Science.gov (United States)

    Zhu, Lei; Yang, Lianyun; Guan, Fangxiao

    2013-03-01

    In a recent report, double hysteresis loop behavior is observed in a nanoconfined poly(vinylidene fluoride-co-trifluoroethylene-co-chlorotrifluoroethylene)-graft-polystyrene [P(VDF-TrFE-CTFE)- g-PS] copolymer. It is considered that the PS grafts are capable of reducing the compensation polarization and thus the polarization electric field during the reverse poling process, resulting in the double hysteresis loop behavior. In this study, we further investigated crystal orientation and temperature effects on this novel ferroelectric behavior. It is observed that with increasing the orientation factor, the electric displacement-electric field (D-E) loop changes from linear for non-oriented film to double loop for the well-oriented film. With increasing the temperature, the double hysteresis loop is gradually replaced by the single and open loop, which is attributed to the impurity ion migrational loss in the sample. This work is supported by NSF (DMR-0907580).

  11. On the stability of homogenous orientation in a plane-parallel cell of a liquid crystal doped with nanoparticles

    International Nuclear Information System (INIS)

    The problems of molecules homogenous orientations stability of nematic liquid crystal (NLC) doped with small amount of cholesteric LC are considered. The LC cell with homeotropic orientation on the wall and the cell with a twist-oriented molecules on the boundaries are studied. The problems are solved using the Noether theorem for LC. The invariance of the form of free energy to translation according to the Noether theorem leads to conservation of the momentum flux, and invariance with respect to the rotation group leads to conservation of the angular momentum flux. These conservation laws are used to get thresholds of molecules homogenous orientation stability of mentioned mixture and the influence of nanoparticles on this thresholds

  12. Computational modeling of intrinsically induced strain gradients during compression of c-axis-oriented magnesium single crystal

    International Nuclear Information System (INIS)

    A finite-deformation strain gradient crystal plasticity model is implemented in a three-dimensional finite-element framework in order to analyze the deformation behavior and the stress–strain response of magnesium single crystals under c-axis orientation. The potential-based and thermodynamically consistent material model is formulated in a non-local and non-linear inelastic context in which dislocation densities are introduced via plastic strain gradients. Experiments have shown that the internal length scale of the microstructure starts to affect the overall stress–strain response when the sample size decreases to the micron scale. As a consequence, strain gradients develop, leading to an additional energetic-like hardening effect which results in an increase of the macroscopic strength with decreasing crystal size. In the case of uniaxial compression of c-axis-oriented single-crystal micropillars, the model is able to predict the discrete dislocation glide in terms of a band-shaped slip zone. Two different pillar sample sizes are taken into account in order to investigate the intrinsic size effect during plastic deformation where the crystallographic orientation leads to the activation of pyramidal {112¯2}〈112¯3〉 slip systems as reported in various experimental studies. The interaction of those slip systems is expressed in terms of latent hardening and excess dislocation development. A comparison between numerical results and corresponding experimental data is presented

  13. Utilization of oriented crystal growth for screening of aromatic carboxylic acids cocrystallization with urea

    Science.gov (United States)

    Przybyłek, Maciej; Ziółkowska, Dorota; Kobierski, Mirosław; Mroczyńska, Karina; Cysewski, Piotr

    2016-01-01

    The possibility of molecular complex formation in the solid state of urea with benzoic acid analogues was measured directly on the crystallite films deposited on the glass surface using powder X-ray diffractometry (PXRD). Obtained solid mixtures were also analyzed using Fourier transform infrared spectroscopy (FTIR). The simple droplet evaporation method was found to be efficient, robust, fast and cost-preserving approach for first stage cocrystal screening. Additionally, the application of orientation effect to cocrystal screening simplifies the analysis due to damping of majority of diffraction signals coming from coformers. During validation phase the proposed approach successfully reproduced both positive cases of cocrystallization (urea:salicylic acid and urea:4-hydroxy benzoic acid) as well as pairs of co-formers immiscible in the solid state (urea:benzoic acid and urea:acetylsalicylic acids). Based on validated approach new cocrystals of urea were identified in complexes with 3-hydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 2,6-dihydroxybenzoic acid and 3,5-dihydroxybenzoic acid. In all cases formation of multicomponent crystal phase was confirmed by the appearance of new reflexes on the diffraction patterns and FTIR absorption band shifts of O-H and N-H groups.

  14. Calcite formation in soft coral sclerites is determined by a single reactive extracellular protein.

    Science.gov (United States)

    Rahman, M Azizur; Oomori, Tamotsu; Wörheide, Gert

    2011-09-01

    Calcium carbonate exists in two main forms, calcite and aragonite, in the skeletons of marine organisms. The primary mineralogy of marine carbonates has changed over the history of the earth depending on the magnesium/calcium ratio in seawater during the periods of the so-called "calcite and aragonite seas." Organisms that prefer certain mineralogy appear to flourish when their preferred mineralogy is favored by seawater chemistry. However, this rule is not without exceptions. For example, some octocorals produce calcite despite living in an aragonite sea. Here, we address the unresolved question of how organisms such as soft corals are able to form calcitic skeletal elements in an aragonite sea. We show that an extracellular protein called ECMP-67 isolated from soft coral sclerites induces calcite formation in vitro even when the composition of the calcifying solution favors aragonite precipitation. Structural details of both the surface and the interior of single crystals generated upon interaction with ECMP-67 were analyzed with an apertureless-type near-field IR microscope with high spatial resolution. The results show that this protein is the main determining factor for driving the production of calcite instead of aragonite in the biocalcification process and that -OH, secondary structures (e.g. α-helices and amides), and other necessary chemical groups are distributed over the center of the calcite crystals. Using an atomic force microscope, we also explored how this extracellular protein significantly affects the molecular-scale kinetics of crystal formation. We anticipate that a more thorough investigation of the proteinaceous skeleton content of different calcite-producing marine organisms will reveal similar components that determine the mineralogy of the organisms. These findings have significant implications for future models of the crystal structure of calcite in nature. PMID:21768106

  15. Near-Field Birefringence Response of Liquid Crystal Molecules in Thickness Direction of Liquid Crystal Thin Film Orientated by Shear Force

    Institute of Scientific and Technical Information of China (English)

    Jing QIN; Norihiro UMEDA

    2007-01-01

    Information of molecular orientation in nematic liquid crystal (LC) is attractive and important for applications in the field of display devices. We demonstrate a novel method using a birefringence scanning near-field optical microscope (Bi-SNOM) with a probe which is inserted into the LC thin film to detect the molecular orientation from its birefringence responses in the thickness direction of the LC thin film. The probe is laterally vibrated when going forward into the LC thin film, and the retardation and azimuth angle are recorded as the probe going down. Firstly, the thickness of the LC thin film is measured by the shear force detection. Since the shear force acts as a stimulation to reorientate the LC molecules above the substrate surface, we can detect the molecular orientation caused by a polyimide alignment substrate and the effect to molecular orientation caused by vibration of fibre probe. As a result, the orientation profiling of the LC film in depth direction is obtained in both the cases that the direction of probe vibrating is vertical/parallel to the rubbing direction of the alignment film.Furthermore, the thickness of completely orientated layers just above the substrate surface can also be obtained by either vibrating probe or no-vibrating probe. Ultimately, the LC thin film can be modelled in thickness direction from all the results using this method.

  16. Analysis of the variation in nanohardness of pearlitic steel: Influence of the interplay between ferrite crystal orientation and cementite morphology

    Energy Technology Data Exchange (ETDEWEB)

    Debehets, Jolien, E-mail: jolien.debehets@mtm.kuleuven.be [Department of Materials Engineering, KU Leuven, University of Leuven, Kasteelpark Arenberg 44 bus 2450, B-3001 Leuven (Belgium); Tacq, Jeroen [Department of Materials Engineering, KU Leuven, University of Leuven, Kasteelpark Arenberg 44 bus 2450, B-3001 Leuven (Belgium); Favache, Audrey; Jacques, Pascal [Institute of Mechanics, Materials and Civil Engineering, Université catholique de Louvain, Place Sainte Barbe 2 L5.02.02, 1348 Louvain-la-Neuve (Belgium); Seo, Jin Won; Verlinden, Bert; Seefeldt, Marc [Department of Materials Engineering, KU Leuven, University of Leuven, Kasteelpark Arenberg 44 bus 2450, B-3001 Leuven (Belgium)

    2014-10-20

    The influence of the relative orientation of the ferrite crystallite lattice and the cementite lamellae on the hardness of pearlitic steel has been investigated by a combination of nanoindentation and electron microscopy (electron back scatter diffraction (EBSD) and scanning electron microscopy (SEM)). Three pearlitic samples, each with a different interlamellar spacing, and one ferritic sample were nanoindented. Although the hardness of the ferritic sample is very similar at different spots on the sample, a large variation in hardness is obtained on each of the pearlitic samples. It has been found that this variation cannot be accounted for solely by the variation in interlamellar spacing and is related to differences in ferrite crystal orientation. As to explain the observed large variation in hardness, the ferrite crystal orientation was considered relative to the cementite lamellae orientation by calculation of the distance dislocations can glide between adjacent lamellae in the slip direction. However, no clear correlation was found for a scaling of this orientation factor with the hardness. Possible interpretations of this discrepancy are suggested.

  17. Analysis of the variation in nanohardness of pearlitic steel: Influence of the interplay between ferrite crystal orientation and cementite morphology

    International Nuclear Information System (INIS)

    The influence of the relative orientation of the ferrite crystallite lattice and the cementite lamellae on the hardness of pearlitic steel has been investigated by a combination of nanoindentation and electron microscopy (electron back scatter diffraction (EBSD) and scanning electron microscopy (SEM)). Three pearlitic samples, each with a different interlamellar spacing, and one ferritic sample were nanoindented. Although the hardness of the ferritic sample is very similar at different spots on the sample, a large variation in hardness is obtained on each of the pearlitic samples. It has been found that this variation cannot be accounted for solely by the variation in interlamellar spacing and is related to differences in ferrite crystal orientation. As to explain the observed large variation in hardness, the ferrite crystal orientation was considered relative to the cementite lamellae orientation by calculation of the distance dislocations can glide between adjacent lamellae in the slip direction. However, no clear correlation was found for a scaling of this orientation factor with the hardness. Possible interpretations of this discrepancy are suggested

  18. Nickel adsorption on chalk and calcite

    DEFF Research Database (Denmark)

    Belova, Dina Alexandrovna; Lakshtanov, Leonid; Carneiro, J.F.;

    2014-01-01

    Nickel uptake from solution by two types of chalk and calcite was investigated in batch sorption studies. The goal was to understand the difference in sorption behavior between synthetic and biogenic calcite. Experiments at atmospheric partial pressure of CO2, in solutions equilibrated with calcite...

  19. The orientation of the mineral crystals in the radius and tibia of the sheep, and its variation with age.

    OpenAIRE

    Bacon, G. E.; Goodship, A E

    1991-01-01

    The direction of preferred orientation of the hydroxyapatite crystals in both the tibia and radius of the sheep is close to the long axis of the bone, notwithstanding the angle of about 30 degrees which, for the tibia, exists between the long axis and the direction of principal dynamic strain during locomotion. For both bones the orientation of the cranial cortex, which is a tension surface during locomotion, is about 40% larger than the caudal. The variation with age of the magnitude of the ...

  20. Grain orientation distribution and development of grain line in highly ordered Bi4Si3O12 micro-crystals

    OpenAIRE

    Zhang Z.G.; Wang X.F.; Tian Q.Q.

    2010-01-01

    Bismuth silicate (Bi4Si3O12) micro-crystals with a grain line structure were grown by a sintering method under atmosphere pressure. The as-grown products were studied using Xray diffraction (XRD) and Environmental scanning electron microscopy (ESEM). The grain orientation law was tested by the One-Sample Kolmogorov-Smirnov (K-S) test. The result shows Bi4Si3O12 grains are always distributed in pairs on both sides of a stable line. On one side of a line, the angle between grain orientation and...

  1. Conductivity type and crystal orientation of GaAs nanocrystals fabricated in silicon by ion implantation and flash lamp annealing

    International Nuclear Information System (INIS)

    The integration of III–V semiconductor material within silicon technology is crucial for performance of advanced electronic devices. This paper presents the investigations of microstructural and opto-electronic properties of GaAs quantum dots (QDs) formed in silicon by means of sequential ion implantation and flash lamp annealing (FLA). Formation of crystalline GaAs QDs with well-defined crystal orientation and conductivity type was confirmed by high resolution transmission electron microscopy and μ-Raman spectroscopy. The influence of the post implantation millisecond-range annealing on the evolution of the nanoparticles size, shape, crystallographic orientation and doping type of GaAs QDs is discussed

  2. Orientational bonding of phases accompanying directed crystallization of the eutectic of the system Si-TiSi2

    Science.gov (United States)

    Derevyagina, L. S.; Butkevich, L. M.

    1987-09-01

    The characteristic features of structure formation in cast and direct crystallized alloys of the system Si-TiSi2 were studied. It is shown that the predominant orientation of the bonding of the phases in directionally crystallized eutectics (DE) of the system Si-TiSi2, observed at the stage of steady-state growth, already appears on the surface of nucleation, which apparently indicates that the nucleation of the phases in the alloys of this system is of an epitaxial character.

  3. Low limit of Mn 2+-activated cathodoluminescence of calcite: state of the art

    Science.gov (United States)

    Habermann, Dirk; Neuser, Rolf D.; Richter, Detlev K.

    1998-02-01

    In the literature, the lower limit for Mn 2+-activated cathodoluminescence (CL) of calcite is variously reputed to over a very wide range of values above 10 ppm Mn. Our spectroscopic investigations of the CL response in natural calcite reveal that below 10 ppm manganese content Mn 2+-activation is also present. Using the Quantitative High Resolution Spectral analysis of CL (QHRS-CL) an activation by Mn 2+ in the range of 700 ppb is proved, which cannot be determined visually. So, if not quenched, the minimum Mn 2+ content for Mn 2+-activation is one atom in the irradiated calcite crystal lattice volume. As the intrinsic (background blue) luminescence is used to determine non-altered biogenic calcite, the limit of Mn 2+-activation plays an important role in the interpretation of diagenetic processes. Our results of spectroscopic analyses require a revision of current opinions about the diagenesis of calcite as revealed by CL investigation.

  4. In situ crystallization of b-oriented MFI films on plane and curved substrates coated with a mesoporous silica layer

    KAUST Repository

    Deng, Zhiyong

    2013-05-01

    A simple and reproducible method is presented for preparing b-oriented MFI films on plane (disc) and curved (hollow fiber) supports by in situ hydrothermal synthesis. A mesoporous silica (sub-)layer was pre-coated on the supports by dip coating followed by a rapid thermal calcination step (973 K during 1 min) to reduce the number of grain boundaries while keeping the hydrophilic behavior of silica. The role of the silica sub-layer is not only to smoothen the substrate surface, but also to provide a silica source to promote the nucleation and growth of zeolite crystals via a heterogeneous nucleation mechanism (zeolitization), and adsorb zeolite moieties generated in the synthesis solution via a homogeneous nucleation mechanism. A monolayer of b-oriented MFI crystals was obtained on both supports after 3 h synthesis time with a moderate degree of twinning on the surface. © 2013 Elsevier Ltd.

  5. Smectic C liquid crystal growth through surface orientation by ZnxCd1–xSe thin films

    International Nuclear Information System (INIS)

    A smectic C liquid crystal (LC) texture, consisting of distinct local single crystals (DLSCs) was grown using predefined orientation of ternary nanocrystalline thin films of ZnxCd1−xSe. The surface morphology and orientation features of the ZnxCd1−xSe films were investigated by AFM measurements and micro-texture polarization analysis. The ZnxCd1−xSe surface causes a substantial enlargement of the smectic C DLSCs and induction of a surface bistable state. The specific character of the morphology of this coating leads to the decrease of the corresponding anchoring energy. Two new chiral states, not typical for this LC were indicated. The physical mechanism providing these new effects is presented.

  6. Thermoluminescence measurement of calcite shells

    International Nuclear Information System (INIS)

    Thermoluminescence (TL) measurements of calcite derived from shells or shell fragments are relevant to the detection of irradiated shellfish for enforcement of food labelling regulations, and to dating of archaeological and fossil materials. The bio-inorganic nature of the material, which is both micro-porous and an intimate mixture of organic and inorganic phases, presents problems for direct TL measurements. This paper discusses the optimal conditions for direct TL measurements on dried, powdered samples from modern shells. (Author)

  7. Quasicharacteristic radiation of relativistic electrons at orientation motion in lithium halides crystals along charged planes and axes

    Science.gov (United States)

    Maksyuta, N. V.; Vysotskii, V. I.; Efimenko, S. V.

    2016-07-01

    The paper deals with the investigation of the orientation motion of relativistic electrons in charged (111) planes and charged [110] axes of lithium halides ionic crystals of LiF, LiCl, LiBr and LiI. On the basis of these investigations the spectra of quasicharacteristic radiation for the electron beams with various Lorentz-factors both in planar and axial cases have been calculated numerically.

  8. Bond orientational ordering in a metastable supercooled liquid: a shadow of crystallization and liquid–liquid transition

    International Nuclear Information System (INIS)

    It is widely believed that a liquid state can be characterized by a single order parameter, density, and that a transition from a liquid to solid can be described by density ordering (translational ordering). For example, this type of theory has had great success in describing the phase behaviour of hard spheres. However, there are some features that cannot be captured by such theories. For example, hard spheres crystallize into either hcp or fcc structures, without a tendency of bcc ordering which is expected by the Alexander–McTague theory based on the Landau-type free energy of the density order parameter. We also found hcp-like bond orientational ordering in a metastable supercooled liquid, which promotes nucleation of hcp crystals. Furthermore, theories based on the single order parameter cannot explain water-like thermodynamic and kinetic anomalies of a liquid and liquid–liquid transition in a single-component liquid. Based on these facts, we argue that we need an additional order parameter to describe a liquid state. It is bond orientational order, which is induced by dense packing in hard spheres or by directional bonding in molecular and atomic liquids. Bond orientational order is intrinsically of local nature, unlike translational order which is of global nature. This feature plays a unique role in crystallization and quasicrystal formation. We also reveal that bond orientational ordering is a cause of dynamic heterogeneity near a glass transition and is linked to slow dynamics. In relation to this, we note that, for describing the structuring of a highly disordered liquid, we need a structural signature of low configurational entropy, which is more general than bond orientational order. Finally, the water-like anomaly and liquid–liquid transition can be explained by bond orientational ordering due to hydrogen or covalent bonding and its cooperativity, respectively. So we argue that bond orientational ordering is a key to the physical understanding

  9. Influences of ruthenium and crystallographic orientation on creep behavior of aluminized nickel-base single crystal superalloys

    Energy Technology Data Exchange (ETDEWEB)

    Latief, F.H., E-mail: fahamsyah78@gmail.com [Department of Mechanical Engineering, Tokyo Metropolitan University, 1-1 Minami-osawa, Hachioji-shi, Tokyo 192-0397 (Japan); Kakehi, K. [Department of Mechanical Engineering, Tokyo Metropolitan University, 1-1 Minami-osawa, Hachioji-shi, Tokyo 192-0397 (Japan); An-Chou Yeh, H. [Department of Materials Science and Engineering, National TsingHua University, 101, Section 2, Kuang-Fu Road, Hsinchu 30013, Taiwan (China); Murakami, H. [Hybrid Materials Center, National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan)

    2014-01-13

    The influences of ruthenium and surface orientation on creep behavior of aluminized Ni-base single crystal superalloys were investigated by comparing two different types of NKH superalloys. The aluminized coated specimens were then subjected to creep rupture tests at a temperature of 900 °C and a stress of 392 MPa. The coating treatment resulted in a significant decrease in creep rupture lives for both superalloys. The diffusion zones between the coating and substrate led to changes in microstructure, which diminished the creep behavior of the aluminized superalloys. Because of the interdiffusion of Ru, Al and Ni, the solubility of some of the refractory elements, such as W, Re. Mo, Co and Cr decreased in the diffusion zone; the precipitation of topologically close-packed (TCP) phases was thus inevitable. In the present study, the addition of Ru increased the degree of Re and Cr supersaturation in the γ matrix. Consequently, the addition of Ru indirectly promoted the precipitation of TCP phases in aluminized Ni-base single crystal superalloys. Furthermore, the growth of TCP precipitates was greatly influenced by the specific surface orientations of the Ni-base single crystal superalloys. In conclusion, the {110} specimens showed shorter creep rupture life than the {100} specimens, this was due to the difference in the crystallographic geometry of {111}〈101〉 slip system and TCP precipitates between the two side-surface orientations of the specimens.

  10. (U-Th)/He dating and He diffusion in calcite from veins and breccia

    Science.gov (United States)

    Gautheron, C.; Cros, A.; Pagel, M.; Berthet, P.; Tassan-Got, L.; Douville, E.; Pinna-Jamme, R.; Sarda, P.

    2013-12-01

    Knowledge of He retention in crystalline calcite is mandatory to estimate the possibility of (U-Th)/He dating of calcite. To this aim, fault-filling calcite crystals from the Eocene/Oligocene Gondrecourt graben, Paris Basin, Eastern France, have been sampled, based on their relatively old, Eocene-Oligocene, precipitation age and cold thermal history (agreement with the He-retentive character of calcite as determined by Copeland et al. (2007), and these ages were obtained for the most recently precipitated crystals. To better understand the large He-age scatter and why calcites precipitated earlier show younger ages, He diffusion experiments have been conducted on 10 Gondrecourt calcite fragments from 3 samples with He ages of 0.2 to 6 Ma. In addition, a crystallographic investigation by X-Ray Diffraction (XRD) performed on similar samples reveals that the crystal structure evolves with increasing temperature, showing with micro-cracks and cleavage opening. These XRD results indicate that, in fault-filling calcite, He retention is controlled by multiple diffusion domains (MDD, Lovera et al., 1991) with various sizes, and therefore, evolves through time with strong consequences on (U-Th)/He age. We thus interpret the Gondrecourt calcite (U-Th)/He age scatter of older samples as a consequence of cleavage opening due to a succession of calcite crystallization phases related to the deformation history. Finally, we propose that the crystallization age of a calcite crystal with a known thermal history can nevertheless be retrieved by the (U-Th)/He method provided the He diffusion pattern can be measured by careful step-heating degassing analysis. Copeland, P., Watson, E.B., Urizar, S.C., Patterson, D., Lapen, T.J., 2007. Alpha thermochronology of carbonates. Geochim. Cosmochim. Acta, 71: 4488-4511. Cros, A. Gautheron, C., Pagel, M., Berthet, P., Tassan-Got, L., Douville, E., Pinna-Jamme, R., Sarda, P., submitted GCA, He behavior in calcite filling viewed by (U

  11. Calcite growth-rate inhibition by fulvic acids isolated from Big Soda Lake, Nevada, USA, The Suwannee River, Georgia, USA and by polycarboxylic acids

    Science.gov (United States)

    Reddy, Michael M.; Leenheer, Jerry

    2011-01-01

    Calcite crystallization rates are characterized using a constant solution composition at 25°C, pH=8.5, and calcite supersaturation (Ω) of 4.5 in the absence and presence of fulvic acids isolated from Big Soda Lake, Nevada (BSLFA), and a fulvic acid from the Suwannee River, Georgia (SRFA). Rates are also measured in the presence and absence of low-molar mass, aliphatic-alicyclic polycarboxylic acids (PCA). BSLFA inhibits calcite crystal-growth rates with increasing BSLFA concentration, suggesting that BSLFA adsorbs at growth sites on the calcite crystal surface. Calcite growth morphology in the presence of BSLFA differed from growth in its absence, supporting an adsorption mechanism of calcite-growth inhibition by BSLFA. Calcite growth-rate inhibition by BSLFA is consistent with a model indicating that polycarboxylic acid molecules present in BSLFA adsorb at growth sites on the calcite crystal surface. In contrast to published results for an unfractionated SRFA, there is dramatic calcite growth inhibition (at a concentration of 1 mg/L) by a SRFA fraction eluted by pH 5 solution from XAD-8 resin, indicating that calcite growth-rate inhibition is related to specific SRFA component fractions. A cyclic PCA, 1, 2, 3, 4, 5, 6-cyclohexane hexacarboxylic acid (CHXHCA) is a strong calcite growth-rate inhibitor at concentrations less than 0.1 mg/L. Two other cyclic PCAs, 1, 1 cyclopentanedicarboxylic acid (CPDCA) and 1, 1 cyclobutanedicarboxylic acid (CBDCA) with the carboxylic acid groups attached to the same ring carbon atom, have no effect on calcite growth rates up to concentrations of 10 mg/L. Organic matter ad-sorbed from the air onto the seed crystals has no effect on the measured calcite crystal-growth rates.

  12. Magnesium stable isotope fractionation in marine biogenic calcite and aragonite

    Science.gov (United States)

    Wombacher, F.; Eisenhauer, A.; Böhm, F.; Gussone, N.; Regenberg, M.; Dullo, W.-Chr.; Rüggeberg, A.

    2011-10-01

    activation energy required for cation incorporation, which probably reflects the dehydration of the cation and the crystal surface and bond formation at the incorporation site. This kinetic incorporation model predicts (i) no intrinsic dependence on growth rate, unless significant back reaction upon slow growth reduces the isotope fractionation towards that characteristic for equilibrium isotope partitioning (this may be observed for Ca isotopes in calcites), (ii) a small decrease of isotope fractionation with increasing temperature that may be amplified if higher temperatures promote back reaction and (iii) a sensitivity to changes in the activation barrier caused by additives such as anions or biomolecules or by the initial formation of amorphous CaCO 3.

  13. 57Fe Moessbauer investigation of oriented single-crystal and polycrystalline PbFe12O19

    International Nuclear Information System (INIS)

    57Fe Moessbauer spectra of PbFe12O19 have been obtained at 295 K on polycrystalline and single-crystal thin sections oriented with the c-axis parallel and perpendicular, respectively, to the γ-ray propagation direction. Due to the lower Neel temperature, the internal magnetic fields (Heff) in PbFe12O19 are lower than those in BaFe12O19 and SrFe12O19 but the systematics of the hyperfine interactions are similar to those in other hexaferrites. For example, the relative values of Heff exhibit the following sequence: 2b 1 2 and the isomer shifts (δ) exhibit the following ordering: 4f1 2. The large dynamic displacement of the 2b Fe3+ ion parallel to the c-axis is clearly demonstrated by the relative intensity of the 2b site for the two oriented single crystals, being negligible for the crystal perpendicular to the c-axis, and equal to its population fraction for the crystal parallel to the c-axis. The lower value for the electric quadrupole splitting of the 2b site is believed to be related to the larger dynamic displacements at this site compared to other hexaferrites

  14. Comparison in internal strain sensitivity between polariscopy and Raman scattering spectroscopy in a (110)-oriented ZnTe single crystal

    International Nuclear Information System (INIS)

    We present the experimental fact that, in a (110)-oriented ZnTe single crystal, polariscopy is highly sensitive to the internal strain, comparing with Raman scattering spectroscopy. We utilized X-ray topography and X-ray diffraction analysis to thoroughly investigate the crystal structure that is intimately associated with the internal strain. The two X-ray structure analyses clarified that the misalignment from the [110] direction is formed in some regions. We obtained the following main result: The polariscopic analysis detects the internal strain formed by the misalignment, whereas the Raman scattering measurement is insensitive to the internal strain. We, therefore, conclude that polariscopy has the strain-detection sensitivity higher than the Raman scattering spectroscopy. We have confirmed that the polariscopic analysis can detect the internal strain less than 0.5% in the ZnTe crystal. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. Microstratigraphic logging of calcite fabrics in speleothems as tool for palaeoclimate studies

    OpenAIRE

    Silvia Frisia

    2015-01-01

    The systematic documentation of calcite fabrics in stalagmites and flowstones provides robustness to palaeoclimate interpretation based on geochemical proxies, but it has been neglected because it is difficult to transform crystal morphologies into numerical values, and construct fabric time series. Here, general criteria that allow for coding fabrics of calcite composing stalagmites and flowstones is provided. Being based on known models of fabric development, the coding ascribes sequential ...

  16. High orientation Al films growth on LiNbO3 single crystal and its adhesion

    Institute of Scientific and Technical Information of China (English)

    LI Dong-mei; CHEN Jing-jing; PAN Feng

    2004-01-01

    High orientation Al films were deposited on 64°Y-XLiNbO3 substrate by DC magnetron sputtering and the influence of deposition temperature on microstructure and adhesion properties of Al films were investigated. The results show that crystallographic orientation of films varies with substrate temperature and the adhesion strength between LiNbO3 and Al films strongly depends on crystallographic orientation of Al films. The (111) orientated Al films shows stronger adhesion strength to LiNbO3 substrate than (100) orientated films. There is an optimum substrate temperature of 60 ℃ and hardening temperature of 200 ℃ for obtaining high (111) orientated Al films with good surface structure and adhesion property. Using this Al film, we have successfully fabricated the SAW filters with high frequency of about 1.89 GHz.

  17. Epitaxially-crystallized oriented naphthalene bis(dicarboximide) morphology for significant performance improvement of electron-transporting thin-film transistors.

    Science.gov (United States)

    Liu, Lili; Ren, Zhongjie; Xiao, Chengyi; He, Bing; Dong, Huanli; Yan, Shouke; Hu, Wenping; Wang, Zhaohui

    2016-04-01

    Large-area highly-ordered F-NDI films were obtained by epitaxial-crystallization on highly-oriented PE substrates through vacuum deposition. An electron mobility of 0.2 cm(2) V(-1) s(-1) was achieved based on such epitaxially-crystallized F-NDI films, which is 4 times higher than that of its un-oriented thin film devices. PMID:26974522

  18. Calcite Twins, a Tool for Tectonic Studies in Thrust Belts and Stable Orogenic Forelands Les macles de la calcite, un outil pour les études tectoniques dans les chaînes plissées et les avant-pays peu déformés des orogènes

    OpenAIRE

    Lacombe O.

    2010-01-01

    Calcite twins have been used for a long time as indicators of stress/strain orientations and magnitudes. Recent developments during the last 15 years point toward significant improvements of existing techniques as well as new applications of calcite twin analysis in thrust belts and forelands. This paper summarizes the principles of the most common techniques in this tectonic field and illustrates some aspects of the use of calcite twins to constrain not only stress/strain orientations a...

  19. A database of crystal preferred orientation of olivine in upper mantle rocks

    Science.gov (United States)

    Mainprice, D.

    2012-12-01

    Olivine is the most volumetrically abundant mineral in the Earth's upper mantle, as such it dominates the mechanical and physical properties and has a controlling influence of the geodynamics of plate tectonics. Since the pioneering work of Hess and others we know that seismic anisotropy of the shallow mantle is related to olivine and it's crystal preferred orientation (CPO). With advent of plate tectonics the understanding of the key role of peridotite rocks became a major scientific objective and the measurement CPO of olivine in upper mantle samples became an important tool for studying the kinematics of these rocks. Our group originally lead by Adolphe Nicolas introduced the systematic use of CPO measured by U-stage for field studies all over the world for over 30 years, this tradition was extended in last 15 years by the use of electron back-scattered diffraction (EBSD) to study of CPO and the associated digital microstructure. It is an appropriate time to analysis this significant database of olivine CPO, which represents the work of our group, both present and former members, as well as collaborating colleagues. It is also interesting to compare the natural record as illustrated by our database in the light of recent experimental results stimulated by the extended ranges in temperature, pressure and finite strain, as well as intrinsic olivine variables such as hydrogen content. To analysis the database, which is heterogeneous because it is constructed from the individual work of many people over a 45 year period containing U-stage data and EBSD measurements (manual indexing point per grain, automatic indexing one point per grain, automatic indexing gridded mapping data) of various formats, we need a flexible software tool that can handle large volumes of data in consistent way. We have used the state-of-art open source MTEX toolbox for quantitative texture analysis. MTEX is a scriptable MATLAB toolbox, which permits all aspects of quantitative texture

  20. Thermoluminescence dating of stalagmitic calcite

    International Nuclear Information System (INIS)

    The thermoluminescence (TL) method of dating stalagmitic calcite has been applied to twenty-seven samples from two paleolithic cave sites; Pontnewydd, Wales, and Caune de L'Arago, Tautavel, France. Environmental dose-rates were evaluated mainly by means of CaF2 capsule burials. The ages of the stalagmitic samples were independently determined by means of the uranium series disequilibrium method. In general, good agreement is found between the TL and uranium series dates, which cover a range from approximately 15 000 to 300 000 years B.P. It is estimated that the TL method should extend to the order of a million years in good circumstances. (author)

  1. Effect of crystal plane orientation on the friction-induced nanofabrication on monocrystalline silicon

    OpenAIRE

    Yu, Bingjun; Qian, Linmao

    2013-01-01

    Although monocrystalline silicon reveals strong anisotropic properties on various crystal planes, the friction-induced nanofabrication can be successfully realized on Si(100), Si(110), and Si(111) surfaces. Under the same loading condition, the friction-induced hillock produced on Si(100) surface is the highest, while that produced on Si(111) surface is the lowest. The formation mechanism of hillocks on various silicon crystal planes can be ascribed to the structural deformation of crystal ma...

  2. In-situ observation of ettringite crystals

    Science.gov (United States)

    Komatsu, Ryuichi; Mizukoshi, Norihiro; Makida, Koji; Tsukamoto, Katsuo

    2009-01-01

    In-situ observation of growing ettringite crystals in solution has been carried out and the morphology change of ettringite has been investigated under various conditions. In particular, the acceleration behavior of ettringite growth in the presence of calcite, the cause of which is not yet understood, is examined. Spherulite with calcite in its core is formed first followed by the generation of acicular crystals. Compared with the in-situ observation result of crystal growth in a solution with no calcite, the effect of added calcite can be explained as a decrease in the activation energy of nucleation for ettringite around calcite.

  3. Fabrication of well ordered Zn nanorod arrays by ion irradiation method at room temperature and effect on crystal orientations

    International Nuclear Information System (INIS)

    Highly oriented and densely packed one-dimensional (1D) polycrystalline Zn nanorods were fabricated on zinc plate without any catalyst at room temperature by bombardment with obliquely incident Ar+ ion via ion irradiation method. The sputtered surfaces were fully covered with Zn nanostructures with diameter and the length around 60 nm and 1.3 μm, respectively, confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The crystal orientation of the Zn plate was investigated by electron back scattering pattern method (EBSP). The numerical density and morphology of Zn nanostructures (nanoneedle or nanorods) were found to be 2.1 x 106 to 9 x 106/mm2 depending upon the crystal orientation and the atomic density on different crystallographic faces. (21-bar 1-bar 0) faces of Zn polycrystal tended to form more dense nanostructures compared to (0001-bar) faces. This is because of lower atomic density on (21-bar 1-bar 0) faces in comparison with (0001-bar) faces. This indicates that lower atomic density on any crystallographic faces is favorable to form nanostructure of higher density. The outstanding feature of this growth technique is that it provides a new direction for the controllable growth of desired nanostructures of variable density at room temperature without any catalyst. These well-aligned arrays of Zn nanorods/nanoneedle might be a promising material for the future application in nanodevices.

  4. Controlled synthesis of highly orientation-ordered single crystal Cd1−xZnxS nanorod array

    International Nuclear Information System (INIS)

    Graphical abstract: Well-aligned Cd1−xZnxS nanorod arrays. - Highlights: • Single crystal Cd1−xZnxS nanorods arrays were fabricated by chemical vapor deposition method. • The as-synthesized products are high uniformity. • The possible growth mechanism and process of arrays nanostructure has been discussed. - Abstract: In this article, a catalyst-free method for the preparation of orientation-ordered single-crystal Cd1−xZnxS nanorod arrays on graphite substrates has been reported. The morphology and crystal structure of the Cd1−xZnxS nanorod arrays were studied using scanning electron microscopy and transmission electron microscopy. The results showed that the nanorods with 40–100 nm in diameter and 2000 nm in length grew along the [0 0 1] direction of the hexagonal crystalline phase. A vapor–solid (VS) growth mechanism was proposed for the formation of the Cd1−xZnxS nanorod arrays. The photoluminescence characterizations showed a strong blue emission at 420 nm for the Cd1−xZnxS nanorod arrays when the value of x is 0.5. Thus, with a simple CVD technique, the high-density and orientation-ordered nanorod arrays would become a promising candidate in many applications such as building blocks for optoelectronics

  5. Application of orientation imaging to the study of substructural development in cold deformed Al-0.3%Mn single crystal of {l_brace}110{r_brace}<112> orientation

    Energy Technology Data Exchange (ETDEWEB)

    Paul, H; Miszczyk, M [Polish Academy of Sciences, Institute of Metallurgy and Materials Science, ul. Reymonta 25, PL-30059 Krakow (Poland); Maurice, C; Driver, J H, E-mail: nmpaul@imim-pan.krakow.pl [Ecole Nationale Superieure des Mines de Saint Etienne, Centre SMS, 158 Cours Fauriel, FR-42023 Saint Etienne (France)

    2010-02-15

    A systematic study of the deformation microstructures over 3 perpendicular surfaces was carried out in the present work in order to correlate better the substructure with slip patterns, initial and final crystal orientation, and the macroscopic coordinate system. The microstructure and texture evolution of high purity Al-0.3 wt% Mn alloy of initial near brass {l_brace}110{r_brace}<112> (or Bs) orientation, channel-die compressed to the strain level of 1.5, were studied by TEM (including TEM orientation mapping) and high-resolution FEG-SEM/EBSD techniques to observe crystal subdivision deformation patterns at the microscopic scale. The grain orientation dependent structures were analyzed in terms of active slip systems focussing on the crystallography of extended planar boundaries. It was concluded that the type of dislocation structure (one or two sets of microbands) in {l_brace}110{r_brace}<112> oriented crystallites, at moderate strains (< 1.5) depended strongly on the crystallographic grain orientation. In this non-ideal initial crystal orientation the applied deformation mode activates a double slip, of which one system predominates and leads to further rotation away from Bs. A general rotation combined with a wide orientation spread is observed after a strain up to 1.5. The microband boundary alignment corresponds very well to the traces of crystallographic {l_brace}111{r_brace} planes, on which most of the slip occurs.

  6. NMR spectroscopic study of organic phosphate esters coprecipitated with calcite

    Science.gov (United States)

    Phillips, Brian L.; Zhang, Zelong; Kubista, Laura; Frisia, Silvia; Borsato, Andrea

    2016-06-01

    signals occur with characteristics consistent with phosphate monoesters. The results of this study indicate that trace- to minor concentrations of dissolved organic molecules can be effectively taken up during calcite precipitation and incorporated in the structure, leaving a resilient record of materials present during crystallization.

  7. Orientation-dependent hardness and nanoindentation-induced deformation mechanisms of WC crystals

    International Nuclear Information System (INIS)

    The orientation dependence of hardness and nanoindentation-induced deformation mechanisms of differently orientated tungsten carbide (WC) grains in WC–Co hardmetal were studied. Electron backscatter diffraction, atomic force microscopy and scanning electron microscopy investigations were performed to determine the grain orientation, and to study the surface morphology and the resulting deformation fields around the indents. The hardness of the differently orientated WC grains showed significant angle dependence from the basal towards the prismatic directions, but there was only a slight change in hardness between the two types of prismatic orientations ((101¯0) and (21¯1¯0)). Sink-in and pile-up effects, together with highly deformed regions and dislocation steps, were revealed around the imprints in the case of basal and prismatic orientations, respectively. A theoretical model is proposed in which the critical force for slip activation is determined as a function of orientation, based on the possible slip systems of WC. The predictions of the present model concerning the measured hardness values and the deformation field around the indents together with the sink-in effect are in good agreement with the experimental results

  8. Direct nanoscale observations of the coupled dissolution of calcite and dolomite and the precipitation of gypsum.

    Science.gov (United States)

    Offeddu, Francesco Giancarlo; Cama, Jordi; Soler, Josep Maria; Putnis, Christine V

    2014-01-01

    In-situ atomic force microscopy (AFM) experiments were performed to study the overall process of dissolution of common carbonate minerals (calcite and dolomite) and precipitation of gypsum in Na2SO4 and CaSO4 solutions with pH values ranging from 2 to 6 at room temperature (23 ± 1 °C). The dissolution of the carbonate minerals took place at the (104) cleavage surfaces in sulfate-rich solutions undersaturated with respect to gypsum, by the formation of characteristic rhombohedral-shaped etch pits. Rounding of the etch pit corners was observed as solutions approached close-to-equilibrium conditions with respect to calcite. The calculated dissolution rates of calcite at pH 4.8 and 5.6 agreed with the values reported in the literature. When using solutions previously equilibrated with respect to gypsum, gypsum precipitation coupled with calcite dissolution showed short gypsum nucleation induction times. The gypsum precipitate quickly coated the calcite surface, forming arrow-like forms parallel to the crystallographic orientations of the calcite etch pits. Gypsum precipitation coupled with dolomite dissolution was slower than that of calcite, indicating the dissolution rate to be the rate-controlling step. The resulting gypsum coating partially covered the surface during the experimental duration of a few hours. PMID:25161860

  9. Choice of scalar measure for crystal curvature to image dislocation substructure in terms of discrete orientation data

    Science.gov (United States)

    Zisman, Alexander

    2016-04-01

    Starting from Nye's tensor, alternative characteristics of crystal curvature indicative of dislocation content are considered subject to very low thickness of investigated matter under the free surface and discreteness of orientation sampling. Analysis within the framework of continuum mechanics, undertaken to allow for such conditions peculiar to the electron backscatter diffraction (EBSD) technique, has shown the variable part of orientations expressed in a vector form to be most sensitive to lattice defects when projected to the free surface plane. Hence, as verified with EBSD data on a grain junction in a low deformed IF steel, magnitude of the projected field allows one to map plastic strains inhomogeneous within grains whereas divergence of this field distinctly images and quantifies low-angle dislocation boundaries formed at low strains.

  10. Development of non-destructive Young's modulus measurement techniques in non-oriented CeF$_{3}$ crystals

    CERN Document Server

    Pietroni, P; Lebeau, M; Majni, G; Rinaldi, D

    2005-01-01

    For a reliable mechanical assembly of scintillating crystals for the application to radiographic systems such as Positron Emission Tomographer (PET) and high-energy physics calorimeters (e.g. in CMS at CERN LHC), the evaluation of the monocrystal elastic constant (Young's modulus) is needed. Its knowledge is also essential in the photoelastic analysis for the determination of residual stresses. In this work non-destructive techniques based on elastic wave propagation are tested. They differ in the mechanical excitation device: instrumented hammer, traditional ultrasonic probes and laser- generated ultrasound. We have analysed three non-oriented cerium fluoride crystal samples produced for scintillation applications. Finally, we have validated the experimental results comparing them with the elastic constant calculated by using the stiffness matrix.

  11. NH4+-mediated growth of hematite tire-like single crystals by oriented attachment and their unique photocatalytic properties

    Science.gov (United States)

    Ma, J.; Chen, K.

    2014-04-01

    In this work, hematite tire-like single crystals were fabricated by a facile hydrothermal procedure. The presence of NH4+ cations in the reaction was proved to be decisive to the formation of hematite single-crystalline tires. It was found that the (001) crystallographic plane, doubly-coordinated by surface hydroxyl groups, preferably distributes at the edge of originally-formed oblate spheroids and dynamically adsorbs NH4+ cations in solution, which would greatly protect this plane from being etched by [Fe(HPO4)]+ and H+ cations during the reaction. Meanwhile, these remanent etch-proof nanoparticles would co-align, followed by the oriented attachment mechanism, and finally form tire-like single crystals enclosed by (001) surface. Even though these single-crystalline tires were bound by low-index facet, their photocatalytic properties were quite unique due to their high density of surface hydroxyl radicals.

  12. Magnetocrystalline Anisotropy and Magnetoelasticity of Preferentially Oriented Martensitic Variants in Ni52Mn24Ga24 Single Crystals

    Institute of Scientific and Technical Information of China (English)

    曲静萍; 王文洪; 孟凡斌; 刘宝丹; 柳祝红; 陈京兰; 李养贤; 吴光恒

    2002-01-01

    The magnetocrystalline anisotropy and magnetoelasticity of preferentially oriented martensitic variants in an off-stoichiometric Nis2Mn24Ga24 single crystal have been investigated. We found that the easy magnetization direction of the martensite phase is the [110] direction, and the hard magnetization exhibited in [001], the growth direction of single crystals. The temperature dependence of the anisotropy fields and constants of Ni52Mn24 Ga24 have been determined. It was found that, at the martensite phase, the anisotropy field increases monotonically with decreasing temperature, but the anisotropy constant first increases rapidly and then the increasing rate becomes smaller and smaller. Based on a previous model, the present results suggest that the competition between the Zeeman energy and the magnetocrystalline anisotropy energy is mainly responsible for the magnitude of magnetic-field-induced strain in this material.

  13. NH4+-mediated growth of hematite tire-like single crystals by oriented attachment and their unique photocatalytic properties

    International Nuclear Information System (INIS)

    In this work, hematite tire-like single crystals were fabricated by a facile hydrothermal procedure. The presence of NH4+ cations in the reaction was proved to be decisive to the formation of hematite single-crystalline tires. It was found that the (001) crystallographic plane, doubly-coordinated by surface hydroxyl groups, preferably distributes at the edge of originally-formed oblate spheroids and dynamically adsorbs NH4+ cations in solution, which would greatly protect this plane from being etched by [Fe(HPO4)]+ and H+ cations during the reaction. Meanwhile, these remanent etch-proof nanoparticles would co-align, followed by the oriented attachment mechanism, and finally form tire-like single crystals enclosed by (001) surface. Even though these single-crystalline tires were bound by low-index facet, their photocatalytic properties were quite unique due to their high density of surface hydroxyl radicals. (papers)

  14. Development of non-destructive Young's modulus measurement techniques in non-oriented CeF3 crystals

    International Nuclear Information System (INIS)

    For a reliable mechanical assembly of scintillating crystals for the application to radiographic systems such as Positron Emission Tomographer (PET) and high-energy physics calorimeters (e.g. in CMS at CERN LHC), the evaluation of the monocrystal elastic constant (Young's modulus) is needed. Its knowledge is also essential in the photoelastic analysis for the determination of residual stresses. In this work non-destructive techniques based on elastic wave propagation are tested. They differ in the mechanical excitation device: instrumented hammer, traditional ultrasonic probes and laser-generated ultrasound. We have analysed three non-oriented cerium fluoride crystal samples produced for scintillation applications. Finally, we have validated the experimental results comparing them with the elastic constant calculated by using the stiffness matrix

  15. Birefringence imaging and orientation of laser patterned β-BaB2O4 crystals with bending and curved shapes in glass

    International Nuclear Information System (INIS)

    Nonlinear optical β-BaB2O4 crystals (β-BBO) with bending and curved shapes were patterned at the surface of 8Sm2O3–42BaO–50B2O3 glass by laser irradiations (Yb:YVO4 laser with a wavelength of 1080 nm, power of 0.8 W, and scanning speed of 4 μm/s), and the orientation state of β-BBO crystals was examined from the birefringence imaging obtained by polarization optical microscope (POM) observations. The formation (crystallization) of β-BBO crystals follows along laser scanning direction even if the laser scanning direction changes at a certain point within the bending angle of 60°. The birefringence images indicate that the formation of highly c-axis oriented β-BBO crystals follows along laser scanning direction even if the laser scanning direction changes, and in particular the direction of the c-axis of β-BBO crystals changes gradually at the bending point. The model for the orientation of the c-axis of β-BBO near the bending point is proposed. The present study proposes that the laser-induced crystallization opens a new door for the science and technology in crystal growth engineering. - Graphical abstract: This figure shows the birefringence images obtained by the Abrio IM imaging system (λ=546 nm) for the laser-patterned β-BaB2O4 crystal line with the bending angle of 45° in the glass. The relation between the direction of slow axis and color is also shown. It is demonstrated that the formation (crystallization) of highly c-axis oriented β-BaB2O4 crystals follows along laser scanning direction even if the laser scanning direction changes. Display Omitted - Highlights: • β-BaB2O4 crystals with bending and curved shapes were patterned by laser irradiations. • The orientation was examined from the birefringence imaging. • Highly c-axis oriented crystals follows along laser scanning direction. • The c-axis direction changes gradually at the bending point. • The laser-induced crystallization opens a new door in crystal growth engineering

  16. Birefringence imaging and orientation of laser patterned β-BaB{sub 2}O{sub 4} crystals with bending and curved shapes in glass

    Energy Technology Data Exchange (ETDEWEB)

    Ogawa, Kazuki; Honma, Tsuyoshi; Komatsu, Takayuki, E-mail: komatsu@mst.nagaokaut.ac.jp

    2013-11-15

    Nonlinear optical β-BaB{sub 2}O{sub 4} crystals (β-BBO) with bending and curved shapes were patterned at the surface of 8Sm{sub 2}O{sub 3}–42BaO–50B{sub 2}O{sub 3} glass by laser irradiations (Yb:YVO{sub 4} laser with a wavelength of 1080 nm, power of 0.8 W, and scanning speed of 4 μm/s), and the orientation state of β-BBO crystals was examined from the birefringence imaging obtained by polarization optical microscope (POM) observations. The formation (crystallization) of β-BBO crystals follows along laser scanning direction even if the laser scanning direction changes at a certain point within the bending angle of 60°. The birefringence images indicate that the formation of highly c-axis oriented β-BBO crystals follows along laser scanning direction even if the laser scanning direction changes, and in particular the direction of the c-axis of β-BBO crystals changes gradually at the bending point. The model for the orientation of the c-axis of β-BBO near the bending point is proposed. The present study proposes that the laser-induced crystallization opens a new door for the science and technology in crystal growth engineering. - Graphical abstract: This figure shows the birefringence images obtained by the Abrio IM imaging system (λ=546 nm) for the laser-patterned β-BaB{sub 2}O{sub 4} crystal line with the bending angle of 45° in the glass. The relation between the direction of slow axis and color is also shown. It is demonstrated that the formation (crystallization) of highly c-axis oriented β-BaB{sub 2}O{sub 4} crystals follows along laser scanning direction even if the laser scanning direction changes. Display Omitted - Highlights: • β-BaB{sub 2}O{sub 4} crystals with bending and curved shapes were patterned by laser irradiations. • The orientation was examined from the birefringence imaging. • Highly c-axis oriented crystals follows along laser scanning direction. • The c-axis direction changes gradually at the bending point. • The

  17. Model study of initial adsorption of SO2 on calcite and dolomite

    International Nuclear Information System (INIS)

    The rate of calcareous stone degradation is to a significant extent controlled by their surface chemistry with SO2. Initial surface sulphite is converted to a harmful gypsum upon, e.g. NO2 catalysed oxidation. However, it has been observed by scanning electron microscopy that the lateral distributions of gypsum crystals differ between calcitic and dolomitic marbles. The first-principles density functional theory is employed to understand the origin of these fundamentally different morphologies. Here, the stability differences of surface sulphite at calcite CaCO3 (s) and dolomite CaxMg1-xCO3 (s) are determined. A qualitative difference in surface sulphite stability, favouring the former, is reported. This is taken to imply that calcitic micro-crystals embedded in a dolomitic matrix act as sinks in the surface sulphation process, controlled by SO2 diffusion. The subsequent formation of gypsum under such conditions will not require SO42- (aq) ion transport. This explains the homogeneous distribution of gypsum observed on the calcitic micro-crystals in dolomite. In contrast, sulphation on purely calcitic marbles never reaches such high SO2 coverage. Rather, upon oxidation, SO42- (aq) transport to nucleation centres, such as grain boundaries, is required for the growth of gypsum crystals

  18. Photoanodes with Fully Controllable Texture: The Enhanced Water Splitting Efficiency of Thin Hematite Films Exhibiting Solely (110) Crystal Orientation.

    Science.gov (United States)

    Kment, Stepan; Schmuki, Patrik; Hubicka, Zdenek; Machala, Libor; Kirchgeorg, Robin; Liu, Ning; Wang, Lei; Lee, Kiyoung; Olejnicek, Jiri; Cada, Martin; Gregora, Ivan; Zboril, Radek

    2015-07-28

    Hematite, α-Fe2O3, is considered as one of the most promising materials for sustainable hydrogen production via photoelectrochemical water splitting with a theoretical solar-to-hydrogen efficiency of 17%. However, the poor electrical conductivity of hematite is a substantial limitation reducing its efficiency in real experimental conditions. Despite of computing models suggesting that the electrical conductivity is extremely anisotropic, revealing up to 4 orders of magnitude higher electron transport with conduction along the (110) hematite crystal plane, synthetic approaches allowing the sole growth in that direction have not been reported yet. Here, we present a strategy for controlling the crystal orientation of very thin hematite films by adjusting energy of ion flux during advanced pulsed reactive magnetron sputtering technique. The texture and effect of the deposition mode on the film properties were monitored by XRD, conversion electron Mössbauer spectroscopy, XPS, SEM, AFM, PEC water splitting, IPCE, transient photocurrent measurements, and Mott-Schottky analysis. The precise control of the synthetic conditions allowed to fabricate hematite photoanodes exhibiting fully textured structures along (110) and (104) crystal planes with huge differences in photocurrents of 0.65 and 0.02 mA cm(-2) (both at 1.55 V versus RHE), respectively. The photocurrent registered for fully textured (110) film is among record values reported for thin planar films. Moreover, the developed fine-tuning of crystal orientation having a huge impact on the photoefficiency would induce further improvement of thin hematite films mainly if cation doping will be combined with the controllable texture. PMID:26083741

  19. Crystal orientation effects on the piezoelectric field of strained zinc-blende quantum-well structures

    DEFF Research Database (Denmark)

    Duggen, Lars; Willatzen, Morten; Lassen, Benny

    2008-01-01

    A three-layered zinc-blende quantum-well structure is analyzed subject to both static and dynamic conditions for different crystal growth directions taking into account piezoelectric effects and lattice mismatch. It is found that the strain component Szz in the quantum-well region strongly depends...... on the crystal growth direction and that a piezoelectric strain contribution exists in zinc blende as in wurtzite, albeit smaller. It is also found in the absence of loss effects that resonance frequencies, giving large strains in the structure, depend strongly on the crystal growth direction. Due to the higher...... symmetry of the zinc-blende structure, we find in a one-dimensional model that piezoelectric effects do not affect strain values for zinc-blende structures grown along the [001] direction in contrast to the corresponding wurtzite result. However, zinc-blende structures grown along a general crystal...

  20. Low-magnesium uranium-calcite with high degree of crystallinity and gigantic luminescence emission

    Energy Technology Data Exchange (ETDEWEB)

    Valle-Fuentes, Francisco-Jose [Instituto de Ceramica y Vidrio, CSIC. Cantoblanco, 28049 Madrid (Spain); Garcia-Guinea, Javier [Museo Nacional Ciencias Naturales, CSIC, 28006 Madrid (Spain)]. E-mail: guinea@mncn.csic.es; Cremades, Ana [Departmento Fisica de Materiales, Facultad de Fisicas, University Complutense de Madrid, 28040 Madrid (Spain); Correcher, Virgilio [CIEMAT, Laboratory Dosimetria de Radiaciones, 28040 Madrid (Spain); Sanchez-Moral, Sergio [Museo Nacional Ciencias Naturales, CSIC, 28006 Madrid (Spain); Gonzalez-Martin, Rafael [Museo Nacional Ciencias Naturales, CSIC, 28006 Madrid (Spain); Sanchez-Munoz, Luis [CIEMAT, Laboratory Dosimetria de Radiaciones, 28040 Madrid (Spain); Lopez-Arce, Paula [Getty Conservation Institute, 1200 Getty Center Drive, Suite 700, Los Angeles, CA 90049 (United States)

    2007-01-15

    Cabrera (Madrid) low-Mg calcites exhibit: (i) an unusual twofold elevation in X-ray diffraction pattern intensity; (ii) a 60-fold elevation of luminescence emission, compared to six common natural calcites selected for comparison purposes; (iii) a natural relatively high radiation level of circa 200 nSv h{sup -1} not detected in 1300 other calcites from the Natural History Museum of Madrid. Calcites were analysed by the X-ray diffraction powder method (XRD), cathodo-luminescence spectroscopy in scanning electron microscopy (CL-SEM), thermoluminescence (TL), differential thermal analysis (DTA), X-ray fluorescence spectrometry (XRF) and particle size distribution (PSD). The Cabrera calcite study shows: (i) helicoidally distributed steps along the (0 0 0 1) orientation; (ii) protuberance defects onto the (0 0 0 1) surface, observed by SEM; (iii) XRF chemical contents of 0.03% MgO, 0.013% of Y{sub 2}O{sub 3}, and 0.022% of U{sub 3}O{sub 8}, with accessory amounts of rare earth elements (REE); (iv) DTA dissociation temperature of 879 {sup o}C; (v) TL maxima peaks at 233 and 297 {sup o}C whose areas are 60 times compared to other calcites; (vi) spectra CL-SEM bands at 2.0 and 3.4 eV in the classic structure of Mn{sup 2+} activators; (vii) a twofold XRD pattern explained given that sample is a low-Mg calcite. The huge TL and CL emissions of the Cabrera calcite sample must be linked with the uranyl group presence. This intense XRD pattern in low-Mg calcites could bring into being analytical errors.

  1. The potential for phosphorus pollution remediation by calcite precipitation in UK freshwaters

    Directory of Open Access Journals (Sweden)

    C. Neal

    2001-01-01

    Full Text Available This paper examines the potential for calcium carbonate to reduce phosphate pollution in freshwaters by co-precipitation, a process known as a "self cleansing mechanism". Calcium carbonate saturation levels and phosphate concentrations (SRP - soluble reactive phosphate across the major eastern UK river basins are examined to test for solubility controls. The study shows that calcite saturation varies for each catchment as a function of flow and biological activity rather than by direct regulation by SRP. Indeed, there is no evidence, for any of the rivers studied, that calcite solubility controls hold. However, for groundwater and groundwater-fed springs in the Chalk of the Thames basin, calcite saturation is observed with associated low SRP levels. A self-cleansing mechanism may well be operative within the Chalk due to two factors. Firstly, there is a high potential for nucleation on the calcite micro-crystals in the aquifer. Secondly, there are within aquifer reactions that remove the calcite nucleating inhibitors (SRP and dissolved organic carbon, DOC to levels lower than those occurring within the rivers do. These inhibitors enter the catchment at very high concentrations in association with agricultural pollution (fertilizer application and animal slurry and household contamination (e.g. sewage sources from septic tanks. Under low flow conditions, when the saturation index for calcite is at its highest, so too is the concentration of the nucleation inhibitor SRP. Companion work shows that calcite precipitation can occur at the water-sediment interface of the river and this may involve SRP removal. The data, as a whole, define an apparent bound for calcite solubility control where in the presence of nucleating centres, SRP must be less than 4 mM-P l-1 and DOC must be less than 150 mM-C l-1: a condition that does not seem to pertain within most UK rivers. Keywords: calcite, calcium carbonate, phosphate, soluble reactive phosphate, dissolved

  2. Orientation-dependent crystal instability of gamma-TiAl in nanoindentation investigated by a multiscale interatomic potential finite-element model

    International Nuclear Information System (INIS)

    The anisotropic mechanical behavior of γ-TiAl alloys has been observed and repeatedly reported, but the effect of crystallographic orientations on the crystal instability of γ-TiAl is still unclear. In this paper, the orientation-dependent crystal instability of γ-TiAl single crystals was investigated by performing nanoindentation on different crystal surfaces. All the nanoindentations are simulated using an interatomic potential finite-element model (IPFEM). Simulation results show that the load–displacement curves, critical indentation depth and critical load for crystal instability as well as indentation modulus, are all associated with surface orientations. The active slip systems and the location of crystal instability in five typical nanoindentations are analyzed in detail, i.e. the (0 0 1), (1 0 0), (1 0 1), (1 1 0) and (1 1 1) crystal surfaces. The predicted crystal instability sites and the activated slipping systems in the IPFEM simulations are in good agreement with the dislocation nucleation in molecular dynamics simulations. (paper)

  3. Birefringence imaging and orientation of laser patterned β-BaB2O4 crystals with bending and curved shapes in glass

    Science.gov (United States)

    Ogawa, Kazuki; Honma, Tsuyoshi; Komatsu, Takayuki

    2013-11-01

    Nonlinear optical β-BaB2O4 crystals (β-BBO) with bending and curved shapes were patterned at the surface of 8Sm2O3-42BaO-50B2O3 glass by laser irradiations (Yb:YVO4 laser with a wavelength of 1080 nm, power of 0.8 W, and scanning speed of 4 μm/s), and the orientation state of β-BBO crystals was examined from the birefringence imaging obtained by polarization optical microscope (POM) observations. The formation (crystallization) of β-BBO crystals follows along laser scanning direction even if the laser scanning direction changes at a certain point within the bending angle of 60°. The birefringence images indicate that the formation of highly c-axis oriented β-BBO crystals follows along laser scanning direction even if the laser scanning direction changes, and in particular the direction of the c-axis of β-BBO crystals changes gradually at the bending point. The model for the orientation of the c-axis of β-BBO near the bending point is proposed. The present study proposes that the laser-induced crystallization opens a new door for the science and technology in crystal growth engineering.

  4. Bond orientational order in the blue phases of chiral liquid crystals

    OpenAIRE

    Longa, Lech; Trebin, Hans-Rainer

    1993-01-01

    It is proposed to describe blue phases by two order parameters: the standard alignment tensor field Q αβ(r) and a bond orientational tensor order parameter of octahedral point group symmetry scrO(432). The yet mysterious blue fog then emerges as a liquid of purely cubic bond orientational order. In the transition from the cubic blue phases to the blue fog the cubic space group symmetry is being reduced to its octahedral factor group. Because of the new order parameter the scrO 5(scr...

  5. Seismic Anisotropy in Salt Structures Due to Preferred Crystal Orientation Anisotropie sismique dans les structures salifères due à l'orientation préférentielle des cristaux

    OpenAIRE

    Raymer D. G.; Kendall J. M.

    2006-01-01

    Texture analysis of natural rock salt and experimentally deformed halite have shown that lattice preferred orientation of halite crystals does occur. The elastic parameters for a range of halite polycrystalline aggregates are calculated using orientation distribution functions. These are used to construct seismic models which are ray-traced through to investigate the potential effects of seismic anisotropy in salt structures. Anisotropic salt models show significant variation in travel time f...

  6. Pyroelectric and electrocaloric effect of <1 1 1>-oriented 0.9PMN-0.1PT single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Luo Laihui, E-mail: llhsic@126.com [Department of Physics, Ningbo University, Ningbo 315211 (China); Chen Hongbing [Institute of Materials Science and Engineering, Ningbo University, Ningbo 315211 (China); Zhu Yuejin; Li Weiping [Department of Physics, Ningbo University, Ningbo 315211 (China); Luo Haosu [Shanghai Institute of ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Zhang Yuepin [Department of Physics, Ningbo University, Ningbo 315211 (China)

    2011-08-11

    Highlights: > Here, we use indirect method to measure pyroelectric and electrocaloric effect. > The largest temperature change achieves {approx}1 deg. C with a small field change. > The mechanism of electrocaloric effect of PMN-PT is explained. > The largest ({partial_derivative}P/{partial_derivative}T){sub E} value achieves -0.5 {mu}C/cm{sup 2} K. > PMN-PT has excellent pyroelectric effect. - Abstract: In this paper, the polarization vs. electric field hysteresis loops of <1 1 1>-oriented 0.9PbMg{sub 1/3}Nb{sub 2/3}O{sub 3}-0.1PbTiO{sub 3} (0.9PMN-0.1PT) single crystal at different temperatures (20-110 deg. C) were measured. The adiabatic temperature change {Delta}T of <1 1 1>-oriented 0.9PMN-0.1PT single crystal due to the application or withdraw of electric field were calculated through the thermodynamic relation. The largest temperature change {Delta}T achieves {approx}1 K with only a change of 40 kV/cm electric field, the mechanism of the electrocaloric effect (ECE) is discussed for 0.9PMN-0.1PT crystal. The pyroelectric coefficient of 0.9PMN-0.1PT under bias field was calculated according to the data of hysteresis loop. The result shows that 0.9PMN-0.1PT have large pyroelectric coefficient under bias field, the largest ({partial_derivative}P/{partial_derivative}T){sub E} value achieves -0.5 {mu}C/cm{sup 2} K.

  7. Orientation dependence of high energy electron multiple scattering at small angles of incidence to crystal

    International Nuclear Information System (INIS)

    Experimental investigations is carried out for the orientational dependence of the mean square of the multiple scattering angle at small incidence angles of 4.5 GeV electrons relative to crystallographic (110) planes of diamond. A theoretical discussion of the experiment is reported. 4 refs.; 2 figs

  8. Heterogeneous growth of cadmium and cobalt carbonate phases at the (101¯4) calcite surface

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Man; Ilton, Eugene S.; Engelhard, Mark H.; Qafoku, Odeta; Felmy, Andrew R.; Rosso, Kevin M.; Kerisit, Sebastien N.

    2015-03-01

    The ability of surface precipitates to form heteroepitaxially is an important factor that controls the extent of heterogeneous growth. In this work, the growth of cadmium and cobalt carbonate phases on (10-14) calcite surfaces is compared for a range of initial saturation states with respect to otavite (CdCO3) and sphaerocobaltite (CoCO3), two isostructural metal carbonates that exhibit different lattice misfits with respect to calcite. Calcite single crystals were reacted in static conditions for 16 hours with CdCl2 and CoCl2 aqueous solutions with initial concentrations 0.3 ≤ [Cd2+]0 ≤ 100 μM and 25 ≤ [Co2+]0 ≤ 200 μM. The reacted crystals were imaged in situ with atomic force microscopy (AFM) and analyzed ex situ with X-ray photoelectron spectroscopy (XPS). AFM images of Cd-reacted crystals showed the formation of large islands elongated along the direction, clear evidence of heteroepitaxial growth, whereas surface precipitates on Co-reacted crystals were small round islands. Deformation of calcite etch pits in both cases indicated the incorporation of Cd and Co at step edges. XPS analysis pointed to the formation of a Cd-rich (Ca,Cd)CO3 solid solution coating atop the calcite substrate. In contrast, XPS measurements of the Co-reacted crystals provided evidence for the formation of a mixed hydroxy-carbonate cobalt phase. The combined AFM and XPS results suggest that the lattice misfit between CoCO3 and CaCO3 ( 15% based on surface areas) is too large to allow for heteroepitaxial growth of a pure cobalt carbonate phase on calcite surfaces in aqueous solutions and at ambient conditions. The use of the satellite structure of the Co 2p3/2 photoelectron line as a tool for determining the nature of cobalt surface precipitates is also discussed.

  9. Influence of the structure and orientation of the parent phase on the hysteresis of single-crystal shape memory alloys

    International Nuclear Information System (INIS)

    The results of high-resolution electron microscopy, calorimetry and tension-compression tests on the Cu-Zn-Al single-crystals, of calorimetry on the Mn-Cu, NiTi single-crystal and on the NiTi polycrystals are presented. The features of the pseudo-plastic (ferroelastic) hysteresis by the deformation of the single-crystals in the martensitic state are investigated in detail. The similarity of ferroelastic and ferromagnetic hysteresis, the strongly orientation dependence of the ferroelastic hysteresis and its independence on the temperature are shown experimentally, which are well known peculiarities of the ferroelastic hysteresis. The dissipated energy during a one cycle of the ferroelastic deformation has parabolic dependence on the strain with an proportionality coefficient which is determined as an effective modulus of the martensitic polydomain. The hysteresis of the thermal-induced, stress-free transformation of all samples is also investigated. Two equilibrium lines bracketing the permanent hysteresis inside the major hysteresis loop are found during the partial cycling. The dissipated energy involves two terms: the one, describing the permanent hysteresis, depends linear on the martensite phase fraction and the other, parabolic. The influence of the transformation type, polycristallinity and scanning rate on the thermal hysteresis are discussed. (orig.)

  10. Liquid crystal quenched orientational disorder at an AFM-scribed alignment surface.

    Science.gov (United States)

    Pendery, J S; Atherton, T J; Nobili, M; Petschek, R G; Lacaze, E; Rosenblatt, C

    2015-03-21

    A polyimide substrate was scribed using the stylus of an atomic force microscope, then covered with a nematic liquid crystal. The fiber from a near field scanning optical microscope was immersed into the liquid crystal and rastered approximately 80 nm above the surface, thereby obviating smearing effects that occur in thicker samples. By appropriate averaging of multiple data sets, a histogram of the "frozen-in" director deviation Δφ from the average easy axis was obtained, having a full-width-half-maximum of ∼0.02 rad. Additionally, the spatial autocorrelation function of Δφ was extracted, where the primary correlation length was found to be comparable to, but larger than, the liquid crystal's extrapolation length. A secondary characteristic length scale of a few μm was observed, and is thought to be an artifact due to material ejection during the scribing process. Our results demonstrate the utility of nanoscale imaging of the interface behavior inside the liquid crystal. PMID:25643289

  11. Orientation effect of coulomb interactions in superconducting phase of Rb3 C60 crystal

    International Nuclear Information System (INIS)

    Calculating the Coulomb interaction energies in superconducting phase of Rb3 C60 we find the essential dependences of the ground state energy on rotational angles of spheroidal anions of C603-. The results obtained assume of frozen rotations of fullerene ions in the crystal due to Coulomb fields. 17 refs., 3 figs

  12. Texture evolution in oriented magnesium single crystals processed by equal channel angular pressing

    Czech Academy of Sciences Publication Activity Database

    Šedá, Petra; Ostapovets, Andriy; Jäger, Aleš; Lejček, Pavel

    2012-01-01

    Roč. 92, č. 10 (2012), s. 1223-1237. ISSN 1478-6435 R&D Projects: GA AV ČR KAN300100801 Institutional research plan: CEZ:AV0Z10100520 Keywords : ECAP * texture * EBSD * magnesium * single crystal Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.596, year: 2012

  13. Effect of crystal orientation on the phase diagrams, dielectric and piezoelectric properties of epitaxial BaTiO{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Huaping, E-mail: wuhuaping@gmail.com, E-mail: hpwu@zjut.edu.cn [Key Laboratory of E& M (Zhejiang University of Technology), Ministry of Education & Zhejiang Province, Hangzhou 310014 (China); State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology, Dalian 116024 (China); Ma, Xuefu; Zhang, Zheng; Zeng, Jun; Chai, Guozhong [Key Laboratory of E& M (Zhejiang University of Technology), Ministry of Education & Zhejiang Province, Hangzhou 310014 (China); Wang, Jie [Department of Engineering Mechanics, School of Aeronautics and Astronautics, Zhejiang University, Hangzhou 310027 (China)

    2016-01-15

    The influence of crystal orientations on the phase diagrams, dielectric and piezoelectric properties of epitaxial BaTiO{sub 3} thin films has been investigated using an expanded nonlinear thermodynamic theory. The calculations reveal that crystal orientation has significant influence on the phase stability and phase transitions in the misfit strain-temperature phase diagrams. In particular, the (110) orientation leads to a lower symmetry and more complicated phase transition than the (111) orientation in BaTiO{sub 3} films. The increase of compressive strain will dramatically enhance the Curie temperature T{sub C} of (110)-oriented BaTiO{sub 3} films, which matches well with previous experimental data. The polarization components experience a great change across the boundaries of different phases at room temperature in both (110)- and (111)-oriented films, which leads to the huge dielectric and piezoelectric responses. A good agreement is found between the present thermodynamics calculation and previous first-principles calculations. Our work provides an insight into how to use crystal orientation, epitaxial strain and temperature to tune the structure and properties of ferroelectrics.

  14. Effect of crystal orientation on the phase diagrams, dielectric and piezoelectric properties of epitaxial BaTiO3 thin films

    International Nuclear Information System (INIS)

    The influence of crystal orientations on the phase diagrams, dielectric and piezoelectric properties of epitaxial BaTiO3 thin films has been investigated using an expanded nonlinear thermodynamic theory. The calculations reveal that crystal orientation has significant influence on the phase stability and phase transitions in the misfit strain-temperature phase diagrams. In particular, the (110) orientation leads to a lower symmetry and more complicated phase transition than the (111) orientation in BaTiO3 films. The increase of compressive strain will dramatically enhance the Curie temperature TC of (110)-oriented BaTiO3 films, which matches well with previous experimental data. The polarization components experience a great change across the boundaries of different phases at room temperature in both (110)- and (111)-oriented films, which leads to the huge dielectric and piezoelectric responses. A good agreement is found between the present thermodynamics calculation and previous first-principles calculations. Our work provides an insight into how to use crystal orientation, epitaxial strain and temperature to tune the structure and properties of ferroelectrics

  15. Cloud radar with hybrid mode towards estimation of shape and orientation of ice crystals

    Science.gov (United States)

    Myagkov, A.; Seifert, P.; Bauer-Pfundstein, M.; Wandinger, U.

    2016-02-01

    This paper is devoted to the experimental quantitative characterization of the shape and orientation distribution of ice particles in clouds. The characterization is based on measured and modeled elevation dependencies of the polarimetric parameters differential reflectivity and correlation coefficient. The polarimetric data are obtained using a newly developed 35 GHz cloud radar MIRA-35 with hybrid polarimetric configuration and scanning capabilities. The full procedure chain of the technical implementation and the realization of the setup of the hybrid-mode cloud radar for the shape determination are presented. This includes the description of phase adjustments in the transmitting paths, the introduction of the general data processing scheme, correction of the data for the differences of amplifications and electrical path lengths in the transmitting and receiving channels, the rotation of the polarization basis by 45°, the correction of antenna effects on polarimetric measurements, the determination of spectral polarimetric variables, and the formulation of a scheme to increase the signal-to-noise ratio. Modeling of the polarimetric variables is based on existing back-scattering models assuming the spheroidal representation of cloud scatterers. The parameters retrieved from the model are polarizability ratio and degree of orientation, which can be assigned to certain particle orientations and shapes. The developed algorithm is applied to a measurement of the hybrid-mode cloud radar taken on 20 October 2014 in Cabauw, the Netherlands, in the framework of the ACCEPT (Analysis of the Composition of Clouds with Extended Polarization Techniques) campaign. The case study shows the retrieved polarizability ratio and degree of orientation of ice particles for a cloud system of three cloud layers at different heights. Retrieved polarizability ratios are 0.43, 0.85, and 1.5 which correspond to oblate, quasi-spherical, and columnar ice particles, respectively. It is shown

  16. Cloud radar with hybrid mode towards estimation of shape and orientation of ice crystals

    Directory of Open Access Journals (Sweden)

    A. Myagkov

    2015-09-01

    Full Text Available This paper is devoted to the experimental quantitative characterization of the shape and orientation distribution of ice particles in clouds. The characterization is based on measured and modeled elevation dependencies of the polarimetric parameters differential reflectivity and correlation coefficient. The polarimetric data is obtained using a newly developed 35 GHz cloud radar MIRA-35 with hybrid polarimetric configuration and scanning capabilities. The full procedure chain of the technical implementation and the realization of the setup of the hybrid-mode cloud radar for the shape determination are presented. This includes the description of phase adjustments in the transmitting paths, the introduction of the general data processing scheme, correction of the data for the differences of amplifications and electrical path lengths in the transmitting and receiving channels, the rotation of the polarization basis by 45°, the correction of antenna effects on polarimetric measurements, the determination of spectral polarimetric variables, and the formulation of a scheme to increase the signal-to-noise ratio. Modeling of the polarimetric variables is based on existing back-scattering models assuming the spheroidal representation of cloud scatterers. The parameters retrieved from the model are polarizability ratio and degree of orientation, which can be assigned to certain particle orientations and shapes. The developed algorithm is applied to a measurement of the hybrid-mode cloud radar taken on 20 October 2014 in Cabauw, the Netherlands, in the frame of the ACCEPT (Analysis of the Composition of Clouds with Extended Polarization Techniques campaign. The case study shows the retrieved polarizability ratio and degree of orientation of ice particles for a cloud system of three cloud layers at different heights. Retrieved polarizability ratios are 0.43, 0.85, and 1.5 which correspond to oblate, quasi-spherical, and columnar ice particles, respectively

  17. Slip, Crystal Orientation, and Damage Evolution During Thermal Cycling in High-Strain Wafer-Level Chip-Scale Packages

    Science.gov (United States)

    Zhou, Bite; Zhou, Quan; Bieler, Thomas R.; Lee, Tae-kyu

    2015-03-01

    Wafer-level chip-scale package samples with pre-cross-sectioned edge rows were thermally cycled to study microstructure evolution and damage development. Electron backscattered diffraction (EBSD) and high-energy x-ray diffraction were used to obtain Sn grain orientations and the average coefficient of thermal expansion normal to the board in every joint of the package for samples in the as-fabricated and thermally cycled conditions. The results indicated a near-random distribution of joint orientation. Optical, scanning electron microscopy, and EBSD methods were used to characterize microstructure changes in pre-cross-sectioned samples due to thermal cycling. Slip trace analysis and Orientation Imaging Microscopy™ (OIM) show that slip systems with high Schmid factors (estimated global shear stress based on the package neutral point) are responsible for the observed microstructure evolution during thermal cycling, which provides information about slip systems that are more easily activated. Two joints were analyzed in detail to evaluate slip activity at different stages of their thermal history. The first case showed that a solidification twin grain boundary misorientation deviated from the twin relationship due to slip activity during thermal cycling, which can influence damage development and the path of crack propagation. The second case showed a new grain orientation developing due to gradual lattice rotation about the Sn [110] axis by a continuous recrystallization mechanism. This rotation was correlated with the operation of slip system . Small tin whiskers emerged from the initially polished chip interface and grew with increasing thermal cycles until a crack developed in the solder that relieved the stress. As the local stresses are not known experimentally, this analysis provides observations that can be compared with a crystal plasticity model simulation.

  18. Preferred Ice Crystal Orientation Fabric Measurements within the Greenland Ice Sheet Using Multi-Polarization Radar Data

    Science.gov (United States)

    Velez-Gonzalez, J. A.; JiLu, L.; Leuschen, C.; Gogineni, P.; Van der Veen, C. J.; Tsoflias, G. P.; Drews, R.; Harish, A. R.

    2013-12-01

    Discharge of ice from the Greenland Ice Sheet to the ocean has increased significantly over the last 25 years due to the acceleration of important outlet glaciers. It was reported that the Greenland Ice Sheet contributed about 2.5 m out of about 6 m of sea-level rise during the Eemian interglacial period. The temperatures during Eemian were reported to be about 8o×4o C higher than the mean of the past millennium. Laboratory measurements have shown that glacial ice, characterized by preferred crystal orientation fabric (COF), is three times more deformable than ice with randomly oriented crystalline structures. Layers characterized by preferred ice COF can influence the flow behavior of a glacier or ice sheet. However, COF measurements are typically obtained from ice cores, and thus are very spatially limited and mostly constrained to areas with little ice flow. A more efficient technique to map the extent of ice fabric over larger regions of ice sheets is needed to better understand the effects on large scale ice flow processes. Radar measurements are capable of discriminating between reflections caused by changes in density, electrical permittivity and COF by exploiting the anisotropic and birefringent properties of ice crystals. For this investigation two radar datasets were collected during the survey of the Greenland Eemian Ice Drilling Site (77.45°N 51.06°W) in August 2008, using a ground-based and chirped-pulse Multi-Channel Radar Depth Sounder (MCRDS) developed by the Center for Remote Sensing of Ice Sheets (CReSIS). The radar used two transmit and eight receive antennas at the center frequency of 150 MHz with a bandwidth of 30 MHz. The first data set consisted of polarimatric measurements acquired in a circular pattern (radius: 35 m) with two co-polarized antenna orientations (one transmitter and four receivers oriented with 90° offsets in the directions of the incident H-Field and E-Field, respectively). Analysis of the circular data shows a periodic

  19. Electrical characterization of YBCO single crystal surfaces oriented in any crystallographic direction

    International Nuclear Information System (INIS)

    Although considerable studies have been carried out, the true nature of high-Tc superconductors (HTSC) is still not clear. Pseudogap phase at high temperature as well as possible time reversal symmetry breaking at low temperature need further investigations. The need of carefully made samples showing the intrinsic properties of superconductivity is essential to test new theoretical developments. We present in this paper how to control crystallographic orientation in the junction and a technique developed to determine the quality of the interface barrier between a gold electrode and a HTSC: YBa2Cu3O7-δ. This potentially allows us to perform Andreev spectroscopy in the CuO2 planes of cuprate superconductors as a function of temperature, crystallographic orientation and doping

  20. Molecular orientation of hydrogen-bonded liquid crystal (6BA){sub 2}-(BPy){sub x} as Studied by {sup 2}H NMR

    Energy Technology Data Exchange (ETDEWEB)

    Mizuno, M., E-mail: mizuno@se.kanazawa-u.ac.jp; Higashima, Y.; Yamashita, A.; Ishida, Y.; Miyatou, T.; Kumagai, Y.; Ohashi, R.; Ida, T. [Kanazawa University, Kakuma, Department of Chemistry, Graduate School of Natural Science & Technology (Japan)

    2015-04-15

    The thermal properties of hydrogen-bonded liquid crystal (6BA){sub 2}-(BPy){sub x} (6BA: 4-n-hexylbenzoicacid, BPy: 4,4’-bipyridine) were investigated by DSC. Two liquid crystal phases (LC{sub I}, LC{sub II}) were found for (6BA){sub 2}-(BPy){sub 0.5}. In LC{sub II}, the distribution of the orientation of molecules was larger than in LC{sub I}. The order parameter S of molecular orientation in the liquid crystal phase was estimated from a {sup 2}H NMR spectrum. S decreased rapidly around the LC{sub I}-LC{sub II} phase transition. The increase in orientational fluctuation of the 6BA dimer with an open dimer structure is predicted to cause the rapid decrease of S.

  1. Properties of boron-doped epitaxial diamond layers grown on (110) oriented single crystal substrates

    Czech Academy of Sciences Publication Activity Database

    Mortet, Vincent; Pernot, J.; Jomard, F.; Soltani, A.; Remeš, Zdeněk; Barjon, J.; D´Haen, J.; Haenen, K.

    2015-01-01

    Roč. 35, Mar (2015), s. 29-34. ISSN 0925-9635 R&D Projects: GA ČR GA13-31783S Grant ostatní: EU(XE) CZ.1.07/2.3.00/20.0306 Institutional support: RVO:68378271 Keywords : diamond * boron * doping * crystalline orientation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.919, year: 2014

  2. Electrical characterization of YBCO single crystal surfaces oriented in any crystallographic direction

    OpenAIRE

    Guillou, H.; Chaussy, J.; Charalambous, M.; Pissas, M.

    2002-01-01

    Although considerable studies have been carried out, the true nature of high-Tc superconductors (HTCS) is still not clear. Pseudogap phase at high temperature as well as possible time reversal symmetry breaking at low temperature need further investigations. The need of carefully made samples showing the intrinsic properties of superconductivity is essential to test new theoretical developments. We present in this paper how to control crystallographic orientation in the junction and a techniq...

  3. Modeling the effect of subgrain rotation recrystallization on the evolution of olivine crystal preferred orientations in simple shear

    Science.gov (United States)

    Signorelli, Javier; Tommasi, Andréa

    2015-11-01

    Homogenization models are widely used to predict the evolution of texture (crystal preferred orientations) and resulting anisotropy of physical properties in metals, rocks, and ice. They fail, however, in predicting two main features of texture evolution in simple shear (the dominant deformation regime on Earth) for highly anisotropic crystals, like olivine: (1) the fast rotation of the CPO towards a stable position characterized by parallelism of the dominant slip system and the macroscopic shear and (2) the asymptotical evolution towards a constant intensity. To better predict CPO-induced anisotropy in the mantle, but limiting computational costs and use of poorly-constrained physical parameters, we modified a viscoplastic self-consistent code to simulate the effects of subgrain rotation recrystallization. To each crystal is associated a finite number of fragments (possible subgrains). Formation of a subgrain corresponds to introduction of a disorientation (relative to the parent) and resetting of the fragment strain and internal energy. The probability of formation of a subgrain is controlled by comparison between the local internal energy and the average value in the polycrystal. A two-level mechanical interaction scheme is applied for simulating the intracrystalline strain heterogeneity allowed by the formation of low-angle grain boundaries. Within a crystal, interactions between subgrains follow a constant stress scheme. The interactions between grains are simulated by a tangent viscoplastic self-consistent approach. This two-level approach better reproduces the evolution of olivine CPO in simple shear in experiments and nature. It also predicts a marked weakening at low shear strains, consistently with experimental data.

  4. Template Adaptability is Key in the Oriented Crystallization of CaCO3

    International Nuclear Information System (INIS)

    In CaCO3, biomineralization nucleation and growth of the crystals are related to the presence of carboxylate-rich proteins within a macromolecular matrix, often with organized β-sheet domains. To understand the interplay between the organic template and the mineral crystal it is important to explicitly address the issue of structural adaptation of the template during mineralization. To this end we have developed a series of self-organizing surfactants (1-4) consisting of a dodecyl chain connected via a bisureido-heptylene unit to an amino acid head group. In Langmuir monolayers the spacing of these molecules in one direction is predetermined by the hydrogen-bonding distances between the bis-urea units. In the other direction, the intermolecular distance is determined by steric interactions introduced by the side groups (-R) of the amino acid moiety. Thus, by the choice of the amino acid we can systematically alter the density of the surfactant molecules in a monolayer and their ability to respond to the presence of calcium ions. The monolayer films are characterized by surface pressure-surface area (p-A) isotherms, Brewster angle microscopy, in-situ synchrotron X-ray scattering at fixed surface area, and also infrared reflection absorption spectroscopy (IRRAS) of films transferred to solid substrates. The developing crystals are studied with scanning and transmission electron microscopy (SEM, TEM), selected area electron diffraction (SAED), and crystal modeling. The results demonstrate that although all compounds are active in the nucleation of calcium carbonate, habit modification is only observed when the size of the side group allows the molecules to rearrange and adapt their organization in response to the mineral phase.

  5. Vertical Liquid Crystal Orientation on Amorphous Tantalum Pentoxide Surfaces Depending on Anisotropic Dipole-Dipole Interaction via Ion Beam Irradiation

    Science.gov (United States)

    Lee, Jong-Jin; Kim, Hyung-Jun; Kang, Young-Gu; Kim, Young-Hwan; Park, Hong-Gyu; Kim, Byoung-Yong; Seo, Dae-Shik

    2011-03-01

    We achieved vertically aligned (VA) liquid crystals (LCs) on amorphous tantalum pentoxide (Ta2O5) alignment films deposited by radio frequency (rf) magnetron sputtering using ion beam (IB) irradiation. By analyzing measurements by X-ray photoelectron spectroscopy (XPS), we confirmed the bond breaking, as detected from the O 1s spectra, which caused an isotropic dipole-dipole interaction between the LC molecules and the Ta2O5 alignment film to uniformly align the vertical LC molecular orientation as a function of IB energy density. Moreover, by examining the electro-optical (EO) characteristics of the Ta2O5 surfaces compared with those of the polyimide (PI) alignment layer, we confirmed that Ta2O5 has a low threshold voltage and a low power consumption when used as an LC alignment layer.

  6. High temperature oxidation behavior of aluminide on a Ni-based single crystal superalloy in different surface orientations

    Institute of Scientific and Technical Information of China (English)

    Fahamsyah H.Latief; Koji Kakehi; El-Sayed M.Sherif

    2014-01-01

    An investigation on oxidation behavior of coated Ni-based single crystal superalloy in different surface orientations has been carried out at 1100 1C. It has been found that the {100} surface shows a better oxidation resistance than the {110} one, which is attributed that the {110}surface had a slightly higher oxidation rate when compared to the {100} surface. The experimental results also indicated that the anisotropic oxidation behavior took place even with a very small difference in the oxidation rates that was found between the two surfaces. The differences of the topologically close packed phase amount and its penetration depth between the two surfaces, including the ratio of α-Al2O3 after 500 h oxidation, were responsible for the oxidation anisotropy.

  7. Macroscopic shape effect due to quadrupole orientation in single crystals of Mg with heavy RE impurities

    International Nuclear Information System (INIS)

    The magnetostriction of dilute MgTb, MgDy, MgHo and MgTm alloys was measured at 4.2 K and found to be comparable, per RE ion, to that of concentrated RE systems. The contribution of these impurities to the low-temperature thermal expansion of Mg was also measured between 1.5 and 15 K. Quadrupole orientation accounts only for the results on MgTb; in MgHo we find very strong indications for an effect of higher-order multipoles. (orig.)

  8. Vorticity analysis in calcite tectonites: An example from the Attico-Cycladic massif (Attica, Greece)

    Science.gov (United States)

    Spanos, D.; Xypolias, P.; Koukouvelas, I.

    2015-11-01

    Although calcite tectonites are widespread in nature their use to quantify flow vorticity is limited. We use new (micro-)structural, petrofabric and vorticity data to analyse the kinematics of flow in outcrop-scale calcite mylonite zones. These zones are genetically related to a crustal-scale NE-directed ductile thrust (Basal Thrust) that emplaced the Blueschist over the Basal unit during the exhumation of the Attico-Cycladic Massif. Calcite microstructures reveal that the last stage of deformation occurred at temperatures 200-300 °C achieved by mild heating, which is possibly related with the reburial of the Basal Thrust's footwall. Vorticity analyses were based on the degree of asymmetry of calcite c-axis fabrics as well as on the assumption that the orientation of the long axes of calcite neoblasts within an oblique foliation delineates the direction of instantaneous stretching axis. Both methodological approaches provide consistent estimates with a simple shear component between 55% and 82% (Wn = 0.76-0.96). The use of the stress axis (σ1) orientation recorded by twin-c-axis-pairs to quantify vorticity generally gives significantly lower simple shear component. Comparison of our vorticity estimates with previous estimates inferred from quartz fabrics and rigid porphyroclasts reveals that exhumation-related deformation in the nappe pile was steady state.

  9. Microbially Induced Calcite Precipitation Employing Environmental Isolates

    OpenAIRE

    Gunjo Kim; Heejung Youn

    2016-01-01

    In this study, five microbes were employed to precipitate calcite in cohesionless soils. Four microbes were selected from calcite-precipitating microbes isolated from calcareous sand and limestone cave soils, with Sporosarcina pasteurii ATCC 11859 (standard strain) used as a control. Urease activities of the four microbes were higher than that of S. pasteurii. The microbes and urea–CaCl2 medium were injected at least four times into cohesionless soils of two different relative densities (60% ...

  10. Unravelling the enigmatic origin of calcitic nanofibres in soils and caves: purely physicochemical or biogenic processes?

    Directory of Open Access Journals (Sweden)

    S. Bindschedler

    2014-01-01

    Full Text Available Calcitic nanofibres are ubiquitous habits of secondary calcium carbonate (CaCO3 accumulations observed in calcareous vadose environments. Despite their widespread occurrence, the origin of these nanofeatures remains enigmatic. Three possible mechanisms fuel the debate: (i purely physicochemical processes, (ii mineralization of rod-shaped bacteria, and (iii crystal precipitation on organic templates. Nanofibres can be either mineral (calcitic or organic in nature. They are very often observed in association with Needle Fibre Calcite (NFC, another typical secondary CaCO3 habit in terrestrial environments. This association has contributed to some confusion between both habits, however they are truly two distinct calcitic features and their recurrent association is likely to be an important fact to help understanding the origin of nanofibres. In this manuscript the different hypotheses that currently exist to explain the origin of calcitic nanofibres are critically reviewed. In addition to this, a new hypothesis for the origin of nanofibres is proposed based on the fact that current knowledge attributes a fungal origin to NFC. As this feature and nanofibres are recurrently observed together, a possible fungal origin for nanofibres which are associated with NFC is investigated. Sequential enzymatic digestion of the fungal cell wall of selected fungal species demonstrates that the fungal cell wall can be a source of organic nanofibres. The obtained organic nanofibres show a striking morphological resemblance when compared to their natural counterparts, emphasizing a fungal origin for part of the organic nanofibres observed in association with NFC. It is further hypothesized that these organic nanofibres may act as templates for calcite nucleation in a biologically-influenced mineralization process, generating calcitic nanofibres. This highlights the possible involvement of Fungi in CaCO3 biomineralization processes, a role still poorly documented at

  11. The potential for phosphorus pollution remediation by calcite precipitation in UK freshwaters

    Science.gov (United States)

    Neal, Colin

    This paper examines the potential for calcium carbonate to reduce phosphate pollution in freshwaters by co-precipitation, a process known as a "self cleansing mechanism". Calcium carbonate saturation levels and phosphate concentrations (SRP - soluble reactive phosphate) across the major eastern UK river basins are examined to test for solubility controls. The study shows that calcite saturation varies for each catchment as a function of flow and biological activity rather than by direct regulation by SRP. Indeed, there is no evidence, for any of the rivers studied, that calcite solubility controls hold. However, for groundwater and groundwater-fed springs in the Chalk of the Thames basin, calcite saturation is observed with associated low SRP levels. A self-cleansing mechanism may well be operative within the Chalk due to two factors. Firstly, there is a high potential for nucleation on the calcite micro-crystals in the aquifer. Secondly, there are within aquifer reactions that remove the calcite nucleating inhibitors (SRP and dissolved organic carbon, DOC) to levels lower than those occurring within the rivers do. These inhibitors enter the catchment at very high concentrations in association with agricultural pollution (fertilizer application and animal slurry) and household contamination (e.g. sewage sources from septic tanks). Under low flow conditions, when the saturation index for calcite is at its highest, so too is the concentration of the nucleation inhibitor SRP. Companion work shows that calcite precipitation can occur at the water-sediment interface of the river and this may involve SRP removal. The data, as a whole, define an apparent bound for calcite solubility control where in the presence of nucleating centres, SRP must be less than 4 mM-P l-1 and DOC must be less than 150 mM-C l-1: a condition that does not seem to pertain within most UK rivers.

  12. Surface-Controlled Orientational Transitions in Elastically Strained Films of Liquid Crystal That Are Triggered by Vapors of Toluene.

    Science.gov (United States)

    Bedolla Pantoja, Marco A; Abbott, Nicholas L

    2016-05-25

    We report the fabrication of chemically patterned microwells that enable the rapid and facile preparation (by spin coating and patterned dewetting) of thin films of liquid crystals (LCs) that have precise thicknesses (0.7-30 μm), are supported on chemically defined substrates, and have free upper surfaces. We use these microwells to prepare elastically strained nematic LC films supported on silica glass, gold, or polystyrene substrates and thereby characterize the response of the strained LC films to vapors of toluene. We report that low concentrations of toluene vapor (film to drive the LC films through an orientational transition. The central role of the toluene-induced change in surface anchoring energy is supported by additional experiments in which the response of the nematic LC to changes in film thickness and substrate identity are quantified. A simple thermodynamic model captures these trends and yielded estimates of anchoring energies (8-22 μJ/m(2)). Significantly, the orientational transitions observed in these strained LC thin films occur at concentrations of toluene vapor that are almost 1 order of magnitude below those which lead to bulk phase transitions, and they are not triggered by exposure to water vapor. Overall, these results hint at principles for the design of responsive LC-based materials that can be triggered by concentrations of aromatic, volatile organic compounds that are relevant to human health. PMID:27070511

  13. Molecular Dynamics Simulation of the Crystal Orientation and Temperature Influences in the Hardness on Monocrystalline Silicon

    Directory of Open Access Journals (Sweden)

    Hongwei Zhao

    2014-01-01

    Full Text Available A nanoindentation simulation using molecular dynamic (MD method was carried out to investigate the hardness behavior of monocrystalline silicon with a spherical diamond indenter. In this study, Tersoff potential was used to model the interaction of silicon atoms in the specimen, and Morse potential was used to model the interaction between silicon atoms in the specimen and carbon atoms in the indenter. Simulation results indicate that the silicon in the indentation zone undergoes phase transformation from diamond cubic structure to body-centred tetragonal and amorphous structure upon loading of the diamond indenter. After the unloading of the indenter, the crystal lattice reconstructs, and the indented surface with a residual dimple forms due to unrecoverable plastic deformation. Comparison of the hardness of three different crystal surfaces of monocrystalline silicon shows that the (0 0 1 surface behaves the hardest, and the (1 1 1 surface behaves the softest. As for the influence of the indentation temperature, simulation results show that the silicon material softens and adhesiveness of silicon increases at higher indentation temperatures.

  14. Orientational Coherent Effects of High-Energy Particles in a LiNbO3 Crystal

    Science.gov (United States)

    Bagli, E.; Guidi, V.; Mazzolari, A.; Bandiera, L.; Germogli, G.; Sytov, A. I.; De Salvador, D.; Argiolas, A.; Bazzan, M.; Carnera, A.; Berra, A.; Bolognini, D.; Lietti, D.; Prest, M.; Vallazza, E.

    2015-07-01

    A bent lithium niobate strip was exposed to a 400 -GeV /c proton beam at the external lines of CERN Super Proton Synchrotron to probe its capabilities versus coherent interactions of the particles with the crystal such as channeling and volume reflection. Lithium niobate (LiNbO3 ) exhibits an interplanar electric field comparable to that of Silicon (Si) and remarkable piezoelectric properties, which could be exploited for the realization of piezo-actuated devices for the control of high-energy particle beams. In contrast to Si and germanium (Ge), LiNbO3 shows an intriguing effect; in spite of a low channeling efficiency (3%), the volume reflection maintains a high deflection efficiency (83%). Such discrepancy was ascribed to the high concentration (1 04 per cm2 ) of dislocations in our sample, which was obtained from a commercial wafer. Indeed, it has been theoretically shown that a channeling efficiency comparable with that of Si or Ge would be attained with a crystal at low defect concentration (less than ten per cm2 ). To better understand the role of dislocations on volume reflection, we have worked out computer simulation via dynecharm++ Monte Carlo code to study the effect of dislocations on volume reflection. The results of the simulations agree with experimental records, demonstrating that volume reflection is more robust than channeling in the presence of dislocations.

  15. Aging characteristics of 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 single crystals with different crystal orientations

    International Nuclear Information System (INIS)

    In this work, the time and temperature dependence of the piezoelectric and ferroelectric properties of the 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (0.7PMN-0.3PT) single crystals were investigated in order to search for an effective method to improve their properties further. The piezoelectric properties of the [001]-, [110]- and [111]-oriented 0.7PMN-0.3PT single crystals exhibit excellent time stability during the 2-month room-temperature aging process. The re-poling process leads to the improvement of piezoelectric constant d33 for the [001]-, [110]- and [111]-oriented 0.7PMN-0.3PT single crystals, while the values of electromechanical coupling coefficient kt change little. During the thermal aging, the values of the measured d33, calculated converse piezoelectric constant d33*, maximum strain Smax% and longitudinal electrostrictive coefficient Q of the [001]-, [110]- and [111]-oriented crystal plates increase gradually before the ferroelectric phase transition temperatures (TFPT, TR-M, TR-O and TR-T) and then decline continuously. The increase in these values before the TFPT is a result of the phase instability. In general, the [001]- and [110]-oriented 0.7PMN-0.3PT single crystals exhibit large piezoelectricity, excellent time stability and relatively high thermal stability between 20 and 80 C, which is favorable to the piezoelectric applications. (orig.)

  16. Microstructure evolution and FEM analysis of a [0 1 1] oriented single crystal nickel-based superalloy during compressive creep

    International Nuclear Information System (INIS)

    Highlights: ► We study microstructure evolution of [0 1 1] SC superalloy during compressive creep. ► We analyze the γ′ phase evolution regularity with the aid of finite element method. ► We constitute the γ′ phase existence mode in three-dimensional space during creep. ► Compressive strain may repel Al, Ti atoms to promote directional growth of γ′ phase. ► Driving forces of elements diffusion and γ′ phase directional growth are investigated. -- Abstract: By means of the stress–strain finite element method (FEM) in elastic–plastic regime, the influences of the applied stress on the distribution of von Mises stress and evolution of shape regularity of γ′ phase in a [0 1 1] oriented single crystal nickel-based superalloy are investigated. Results show that, after full heat treatment, the microstructure of [0 1 1] oriented single crystal superalloy consists of the cuboidal γ′ phase embedded coherently in the γ matrix phase, and on (1 0 0) plane aligned regularly at angle of 45° relative to the [0 1 1] orientation. During compressive creep, the cuboidal γ′ phase is transformed into the mesh-like lamellar rafted structure on (1 0 0) plane. Therefore, the changes of the lattice strain, the strain energy density and interfacial energy are thought to be the driving forces of the element diffusion and γ′ phase directional growth. During compressive creep, the lattice contraction occurs on (1 0 0) plane of the cuboidal γ′ phase along [0 0 1] and [0 1 0] directions, whose extruding effect may repel Al, Ti atoms with bigger radius. Therefore, the expanding strain of lattices along [1 0 0] direction on (0 1 0) and (0 0 1) planes of the cuboidal γ′ phase may trap Al, Ti atoms to promote the directional growth of γ′ phase on (1 0 0) plane along [0 0 1] and [0 1 0] directions, which is thought to be the main reason for the γ′ phase growing directionally into the mesh-like lamellar structure

  17. Effects of dopant concentration, crystallographic orientation, and crystal morphology on secondary electron emission from diamond

    International Nuclear Information System (INIS)

    Secondary electron emission properties from crystalline and polycrystalline diamond films containing different boron concentrations were measured. The secondary electron yields δ were high. Yields were independent of incident beam angle and crystallographic orientation. The secondary electron yields were greatest for boron concentrations of 1019 endash 1020 cm-3. The angular distribution was peaked about the surface normal with a half width at half maximum of 37±7 degree. The secondary electron yield decreased with prolonged energetic electron beam bombardment. The energy distribution of the emitted electrons contained a large, relatively narrow, low energy peak that disappeared with extended electron beam bombardment. The large secondary electron yields and narrow energy distributions of the emitted electrons were consistent with nearly thermalized electron emission from negative electron affinity states. copyright 1997 American Institute of Physics

  18. Modeling of MnS precipitation during the crystallization of grain oriented silicon steel

    Directory of Open Access Journals (Sweden)

    D. Kalisz

    2015-01-01

    Full Text Available The process of manganese sulfide formation in the course of grain-oriented silicon steel solidification process is described in the paper. Fine dispersive MnS inclusions are grain growth inhibitors and apart from AlN inclusions they contribute to the formation of a privileged texture, i.e. Goss texture. A computer simulation of a high-silicon steel ingot solidification with the use of author’s software has been performed. Ueshima model was adapted for simulating the 3 % Si steel ingot solidification. The calculations accounted for the back diffusion effect according to Wołczyński equation. The computer simulation results are presented in the form of plots representing the process of steel components segregation in a solidifying ingot and curves illustrating the inclusion separation process.

  19. Orientational dynamics of a ferronematic liquid crystal in a rotating magnetic field

    International Nuclear Information System (INIS)

    The behavior of the orientational structure of a ferronematic in a rotating uniform magnetic field is investigated using the continual theory. The time-dependent system of equations describing the dynamics of the ferronematic is derived. The dependences of the angles of rotation of the director and of the magnetization of the ferronematic on the velocity of field rotation are determined for various values of the material parameters. Two regimes (synchronous and asynchronous) of rotation of the ferronematic structure are detected. In the synchronous regime, the director rotates with the frequency of the magnetic field and a constant phase delay. The asynchronous regime is characterized by a time-dependent phase delay. The dependence of the critical angular velocity of magnetic field rotation, which determines the boundary between the synchronous and asynchronous regimes, on the magnetic field strength is derived

  20. Performance Analysis of Silicon and Germanium Nanowire Transistor using Crystal Orientation and Oxide Thickness

    Directory of Open Access Journals (Sweden)

    P.Theres Mary

    2014-09-01

    Full Text Available Nanowire Transistors have attracted attention due to the probable high performance and excellent controllability of device current. In this paper, we investigate the performance analysis of nanowire transistors made of silicon and germanium materials. The nanowire transistor has a 3D distribution of electron density and electrostatic potential, therefore self-consistent 3D simulations are used. Nanowire (tool is 3D Poisson self-consistent simulator which can study the 3D transport in nanowire transistor considering phonon scattering based on the effective-mass approximation. The output characteristics of the nanowire transistors are studied in detail for both Si and Ge materials for different transport orientation (i.e., 100,110,111 and varying the oxide thickness.

  1. Orientational order and translational dynamics of magnetic particle assemblies in liquid crystals.

    Science.gov (United States)

    Peroukidis, Stavros D; Klapp, Sabine H L

    2016-08-10

    Implementing extensive molecular dynamics simulations we explore the organization of magnetic particle assemblies (clusters) in a uniaxial liquid crystalline matrix comprised of rodlike particles. The magnetic particles are modelled as soft dipolar spheres with diameter significantly smaller than the width of the rods. Depending on the dipolar strength coupling the magnetic particles arrange into head-to-tail configurations forming various types of clusters including rings (closed loops) and chains. In turn, the liquid crystalline matrix induces long range orientational ordering to these structures and promotes their diffusion along the director of the phase. Different translational dynamics are exhibited as the liquid crystalline matrix transforms either from isotropic to nematic or from nematic to smectic state. This is caused due to different collective motion of the magnetic particles into various clusters in the anisotropic environments. Our results offer a physical insight for understanding both the structure and dynamics of magnetic particle assemblies in liquid crystalline matrices. PMID:27460190

  2. Acceleration of calcite kinetics by abalone nacre proteins

    Energy Technology Data Exchange (ETDEWEB)

    Fu, G; Qiu, S R; Orme, C A; Morse, D E; De Yoreo, J J

    2005-06-09

    The fascinating shapes and hierarchical designs of biomineralized structures have long been an inspiration to materials scientists because of the potential they suggest for biomolecular control over synthesis of crystalline materials. One prevailing view is that mineral-associated macromolecules are responsible for initiating and stabilizing non-equilibrium crystal polymorphs and morphologies through interactions between anionic moieties and cations in solution or at mineral surfaces. Indeed, numerous studies have demonstrated that bio-organic additives can dramatically alter crystal shapes and growth-rates in vitro. However, previous molecular-scale studies revealing mechanisms of growth modification focused on small molecules such as amino acids or peptides and always observed growth inhibition. In contrast, studies using full proteins were non-quantitative and underlying sources of growth modification were ill-defined. Here we investigate interactions between proteins isolated from abalone shell nacre and growing surfaces of calcite. We find that these proteins significantly accelerate the molecular-scale kinetics and, though much larger than atomic steps, alter growth morphology through step-specific interactions that lower their free energies. We propose that these proteins act as surfactants to promote ion attachment at calcite surfaces.

  3. The role of grain boundary structure and crystal orientation on crack growth asymmetry in aluminum

    International Nuclear Information System (INIS)

    Atomistic simulations have shown that the grain boundary (GB) structure affects a number of physical, mechanical, thermal, and chemical properties, which can have a profound effect on macroscopic properties of polycrystalline materials. The research objective herein is to use atomistic simulations to explore the role that GB structure and the adjacent crystallographic orientations have on the directional asymmetry of an intergranular crack (i.e. cleavage behavior is favored along one direction, while ductile behavior along the other direction of the interface) for aluminum grain boundaries. Simulation results from seven 〈110〉 symmetric tilt grain boundaries (STGBs) show that the GB structure and the associated free volume directly influence the stress–strain response, crack growth rate, and crack tip plasticity mechanisms for middle-tension (M(T)) crack propagation specimens. In particular, the structural units present within the GB promote whether a dislocation or twinning-based mechanism operates at the crack tip during intergranular fracture along certain GBs (e.g., the ‘E’ structural unit promotes twinning at the crack tip in Al). Furthermore, the crystallography of the adjacent grains, and therefore the available slip planes, can significantly affect the crack growth rates in both directions of the crack – this creates a strong directional asymmetry in the crack growth rate in the Σ11 (113) and the Σ27 (552) STGBs. Upon comparing these results with the theoretical Rice criterion, it was found that certain GBs in this study (Σ9 (221), Σ11 (332) and Σ33 (441)) show an absence of directional asymmetry in the observed crack growth behavior, in conflict with the Rice criterion. The significance of the present research is that it provides a physical basis for the role of GB character and crystallographic orientation on intergranular crack tip deformation behavior

  4. Peculiar orientational disorder in 4-bromo-4′-nitrobiphenyl (BNBP and 4-bromo-4′-cyanobiphenyl (BCNBP leading to bipolar crystals

    Directory of Open Access Journals (Sweden)

    Matthias Burgener

    2016-05-01

    Full Text Available 180° orientational disorder of molecular building blocks can lead to a peculiar spatial distribution of polar properties in molecular crystals. Here we present two examples [4-bromo-4′-nitrobiphenyl (BNBP and 4-bromo-4′-cyanobiphenyl (BCNBP] which develop into a bipolar final growth state. This means orientational disorder taking place at the crystal/nutrient interface produces domains of opposite average polarity for as-grown crystals. The spatial inhomogeneous distribution of polarity was investigated by scanning pyroelectric microscopy (SPEM, phase-sensitive second harmonic microscopy (PS-SHM and selected volume X-ray diffraction (SVXD. As a result, the acceptor groups (NO2 or CN are predominantly present at crystal surfaces. However, the stochastic process of polarity formation can be influenced by adding a symmetrical biphenyl to a growing system. For this case, Monte Carlo simulations predict an inverted net polarity compared with the growth of pure BNBP and BCNBP. SPEM results clearly demonstrate that 4,4′-dibromobiphenyl (DBBP can invert the polarity for both crystals. Phenomena reported in this paper belong to the most striking processes seen for molecular crystals, demonstrated by a stochastic process giving rise to symmetry breaking. We encounter here further examples supporting the general thesis that monodomain polar molecular crystals for fundamental reasons cannot exist.

  5. Peculiar orientational disorder in 4-bromo-4′-nitrobiphenyl (BNBP) and 4-bromo-4′-cyanobiphenyl (BCNBP) leading to bipolar crystals

    Science.gov (United States)

    Burgener, Matthias; Aboulfadl, Hanane; Labat, Gaël Charles; Bonin, Michel; Sommer, Martin; Sankolli, Ravish; Wübbenhorst, Michael; Hulliger, Jürg

    2016-01-01

    180° orientational disorder of molecular building blocks can lead to a peculiar spatial distribution of polar properties in molecular crystals. Here we present two examples [4-bromo-4′-nitrobiphenyl (BNBP) and 4-bromo-4′-cyanobiphenyl (BCNBP)] which develop into a bipolar final growth state. This means orientational disorder taking place at the crystal/nutrient interface produces domains of opposite average polarity for as-grown crystals. The spatial inhomogeneous distribution of polarity was investigated by scanning pyroelectric microscopy (SPEM), phase-sensitive second harmonic microscopy (PS-SHM) and selected volume X-ray diffraction (SVXD). As a result, the acceptor groups (NO2 or CN) are predominantly present at crystal surfaces. However, the stochastic process of polarity formation can be influenced by adding a symmetrical biphenyl to a growing system. For this case, Monte Carlo simulations predict an inverted net polarity compared with the growth of pure BNBP and BCNBP. SPEM results clearly demonstrate that 4,4′-dibromobiphenyl (DBBP) can invert the polarity for both crystals. Phenomena reported in this paper belong to the most striking processes seen for molecular crystals, demonstrated by a stochastic process giving rise to symmetry breaking. We encounter here further examples supporting the general thesis that monodomain polar molecular crystals for fundamental reasons cannot exist. PMID:27158508

  6. Determination of the orientation of pieces of zigzag-Bloch walls in bulk FeSi-single crystals by neutron small-angle scattering

    International Nuclear Information System (INIS)

    Small-angle scattering of neutrons allows the determination of the orientation of Bloch walls in the interior of bulk single crystals. The zigzag angle psi=280 of the 900 Bloch wall and its field dependence are measured. We also observe walls or wall pieces with psi=00. With 1800 walls we measure zigzag angles of psi approximately equal to 300. (orig.)

  7. Smaller Calcite Lattice Deformation Caused by Occluded Organic Material in Coccoliths than in Mollusk Shell

    DEFF Research Database (Denmark)

    Froelich, Simon; Sørensen, H.O.; Hakim, S.S.;

    2015-01-01

    The growth and nucleation of biominerals are directed and affected by associated biological molecules. In this paper, we investigate the influence of occluded biomolecules on biogenic calcite from the coccolithophorid Pleurochrysis carterae and from chalk, a rock composed predominantly of fossil...... suggests that the interaction between biomolecules and calcite is not as tight in the coccoliths as in the shell. Although the shape of chalk has been preserved over millions of years, no major influence on the crystal lattice was observed in the chalk samples....

  8. Do organic ligands affect calcite dissolution rates?

    Science.gov (United States)

    Oelkers, Eric H.; Golubev, Sergey V.; Pokrovsky, Oleg S.; Bénézeth, Pascale

    2011-04-01

    Steady state Iceland-spar calcite dissolution rates were measured at 25 °C in aqueous solutions containing 0.1 M NaCl and up to 0.05 M dissolved bicarbonate at pH from 7.9 to 9.1 in the presence of 13 distinct dissolved organic ligands in mixed-flow reactors. The organic ligands considered in this study include those most likely to be present in either (1) aquifers at the conditions pertinent to CO 2 sequestration or (2) soil/early diagenetic environments: acetate, phthalate, citrate, EDTA 4-, succinate, D-glucosaminate, L-glutamate, D-gluconate, 2,4-dihydroxybenzoate, 3,4-dihydroxybenzoate, fumarate, malonate, and gallate. Results show that the presence of extract, humic acid, pectin, and gum xanthan. In no case did the presence of <100 ppm of these organics change calcite dissolution rates by more than a factor of 2.5. Results obtained in this study suggest that the presence of aqueous organic anions negligibly affects calcite forward dissolution rates in most natural environments. Some effect on calcite reactivity may be observed, however, by the presence of organic anions if they change substantially the chemical affinity of the fluid with respect to calcite.

  9. Calcite solubility in simulated geothermal brines

    Energy Technology Data Exchange (ETDEWEB)

    Pool, K.H.; Raney, P.J.; Shannon, D.W.

    1987-02-01

    The deposition of scale on geothermal piping surfaces has been recognized as a cause of increased pressure drop and diminished fluid flow. The two most common scales encountered in the geothermal energy field are silica and calcite. The main purpose of this study was to obtain accurate, reliable calcite solubility data in brines similar to natural geothermal brines over the temperature range of most known exploitable geothermal resources. In addition, geothermal fluid equilibrium modeling efforts and data bases can be refined and fine-turned with respect to the commercially important calcite-geothermal fluid stability problem with these data. The effect of sodium chloride and sodium bicarbonate on the solubility of CaCO/sub 3/ (calcite) in high temperature solutions was measured over the 100 to 300/sup 0/C temperature range. The brines studied contained 0 to 5 wt % NaCl, 0 to 5 mM NaHCO/sub 3/, and 0.003 to 0.1 M CO/sub 2/. The data detailing calcite solubility at various temperatures are presented in tabular, graphical, and regression-equation form for each brine composition tested.

  10. Magnetoelectric effect in FeCo/PMN-PT/FeCo trilayers prepared by electroless deposition of FeCo on PMN-PT crystals with various orientations

    Energy Technology Data Exchange (ETDEWEB)

    Shen, H.Q.; Wang, Y.G., E-mail: yingang.wang@nuaa.edu.cn; Xie, D.; Cheng, J.H.

    2014-10-15

    Highlights: • The composites FeCo/PMN-PT/FeCo were prepared by electroless deposition. • The influence of the crystal cut of PMN-PT on ME coupling is discussed. • Optimizing the crystal cut of the piezoelectric substrate, proper resonant frequency and ME effect could be obtained. - Abstract: The magnetoelectric (ME) effect was studied in the FeCo/PMN-PT/FeCo trilayer composites prepared by electroless deposition of the FeCo layers on the single crystal PMN-PT substrates with various crystal cuts. X-ray diffraction reveals that the orientation of PMN-PT substrate has no effect on the growth of FeCo layer. The structures with PMN-PT crystals of various orientations have different acoustic resonance frequencies. FeCo/PMN-PT/FeCo composites with PMN-PT of 〈0 0 1〉{sup L} × 〈01{sup ‾}1〉{sup W} × 〈0 1 1〉{sup T} crystal cut shows superior ME performance, which is due to the highest piezoelectric module of PMN-PT.

  11. Structural point defects in 'Iceland spar' calcite

    International Nuclear Information System (INIS)

    Trace element concentrations by micro-PIXE, cathodoluminescence (CL) emission spectra and electron spin resonance (ESR) spectra of Mn2+ in 'Iceland spar' calcite have been measured. The average rare earth elements (REE) abundances of the Iceland spar calcite revealed a concave shape with positive Eu and Tb anomalies. All samples show comparable average REE abundances compared to average chondrites standard. The REE signal in hydrothermal solution seems to be similar for the different locations and age of formation although the absolute REE concentration in the solution was certainly different. The CL-properties of investigated Iceland spar varied from orange to green. The orange luminescence is based on Mn2+ in Ca-position of calcite while this uncommon green luminescence is most likely attributed to UO22+ complex ions associated with electron-hole centres

  12. Calcite Biohybrids as Microenvironment for Stem Cells

    Directory of Open Access Journals (Sweden)

    Razi Vago

    2012-04-01

    Full Text Available A new type of composite 3D biomaterial that provides extracellular cues that govern the differentiation processes of mesenchymal stem cells (MSCs has been developed. In the present study, we evaluated the chondrogenecity of a biohybrid composed of a calcium carbonate scaffold in its calcite polymorph and hyaluronic acid (HA. The source of the calcite scaffolding is an exoskeleton of a sea barnacle Tetraclita rifotincta (T. rifotincta, Pilsbry (1916. The combination of a calcium carbonate-based bioactive scaffold with a natural polymeric hydrogel is designed to mimic the organic-mineral composite of developing bone by providing a fine-tuned microenvironment. The results indicate that the calcite-HA interface creates a suitable microenvironment for the chondrogenic differentiation of MSCs, and therefore, the biohybrid may provide a tool for tissue-engineered cartilage.

  13. Silver as Seed-Particle Material for GaAs Nanowires—Dictating Crystal Phase and Growth Direction by Substrate Orientation

    Science.gov (United States)

    2016-01-01

    Here we investigate the feasibility of silver as seed-particle material to synthesize GaAs nanowires and show that both crystal phase and growth direction can be controlled by choice of substrate orientation. A (111)B substrate orientation can be used to form vertically aligned wurtzite GaAs nanowires and a (100) substrate orientation to form vertically aligned zinc blende GaAs nanowires. A 45–50% yield of vertical nanowire growth is achieved on the (100) substrate orientation without employing any type of surface modification or nucleation strategy to promote a vertical growth direction. In addition, photoluminescence measurements reveal that the photon emission from the silver seeded wurtzite GaAs nanowires is characterized by a single and narrow emission peak at 1.52 eV. PMID:26998550

  14. Radially oriented mesoporous TiO2 microspheres with single-crystal-like anatase walls for high-efficiency optoelectronic devices.

    Science.gov (United States)

    Liu, Yong; Che, Renchao; Chen, Gang; Fan, Jianwei; Sun, Zhenkun; Wu, Zhangxiong; Wang, Minghong; Li, Bin; Wei, Jing; Wei, Yong; Wang, Geng; Guan, Guozhen; Elzatahry, Ahmed A; Bagabas, Abdulaziz A; Al-Enizi, Abdullah M; Deng, Yonghui; Peng, Huisheng; Zhao, Dongyuan

    2015-05-01

    Highly crystalline mesoporous materials with oriented configurations are in demand for high-performance energy conversion devices. We report a simple evaporation-driven oriented assembly method to synthesize three-dimensional open mesoporous TiO2 microspheres with a diameter of ~800 nm, well-controlled radially oriented hexagonal mesochannels, and crystalline anatase walls. The mesoporous TiO2 spheres have a large accessible surface area (112 m(2)/g), a large pore volume (0.164 cm(3)/g), and highly single-crystal-like anatase walls with dominant (101) exposed facets, making them ideal for conducting mesoscopic photoanode films. Dye-sensitized solar cells (DSSCs) based on the mesoporous TiO2 microspheres and commercial dye N719 have a photoelectric conversion efficiency of up to 12.1%. This evaporation-driven approach can create opportunities for tailoring the orientation of inorganic building blocks in the assembly of various mesoporous materials. PMID:26601185

  15. Morphology and orientation of β-BaB2O4 crystals patterned by laser in the inside of samarium barium borate glass

    International Nuclear Information System (INIS)

    Nonlinear optical β-BaB2O4 crystal lines (β-BBO) were patterned in the inside of 8Sm2O3–42BaO–50B2O3 glass by irradiations of continuous-wave Yb:YVO4 lasers with a wavelength of 1080 nm (power: P=0.8–1.0 W, scanning speed: S=0.2–2.5 μm/s), in which the laser focal position was moved gradually from the surface to the inside. The morphology, size, and orientation of β-BBO crystals were examined from polarization optical microscope and birefringence imaging observations. It was demonstrated that c-axis oriented β-BBO crystals with long lengths (e.g., 20 mm) were patterned in the inside of the glass. The morphology of β-BBO in the cross-section of lines was a rectangular shape with rounded corners, and the volume of β-BBO formed increased with increasing laser power and with decreasing laser scanning speed. The maximum depth in the inside from the surface for β-BBO patterning increased with increasing laser power, e.g., Dmax∼100 μm at P=0.8 W, Dmax∼170 μm at P=0.9 W, and Dmax∼200 μm at P=1 W. The present study proposes that the laser-induced crystallization opens a new door for applied engineering in glassy solids. - Graphical abstract: This figure shows the POM photographs for β-BaB2O4 crystal lines patterned by cw Yb:YVO4 fiber laser irradiations with a laser power of P=0.8 W and a laser scanning speed S=2 μm/s in the glass. The laser focal point was moved gradually from the surface into the inside. The results shown in Fig. 1 demonstrate that it is possible to pattern highly oriented β-BaB2O4 crystals even in the inside of glasses. - Highlights: • β-BaB2O4 crystal lines were patterned in the inside of a glass by lasers. • Laser focal position was moved gradually from the surface to the inside. • Birefringence imaging was observed. • Morphology, size, and orientation of crystals were clarified. • Crystal lines with long lengths (e.g., 20 mm) were patterned at the depth of 200 μm

  16. Morphology and orientation of β-BaB{sub 2}O{sub 4} crystals patterned by laser in the inside of samarium barium borate glass

    Energy Technology Data Exchange (ETDEWEB)

    Nishii, Akihito; Shinozaki, Kenji; Honma, Tsuyoshi; Komatsu, Takayuki, E-mail: komatsu@mst.nagaokaut.ac.jp

    2015-01-15

    Nonlinear optical β-BaB{sub 2}O{sub 4} crystal lines (β-BBO) were patterned in the inside of 8Sm{sub 2}O{sub 3}–42BaO–50B{sub 2}O{sub 3} glass by irradiations of continuous-wave Yb:YVO{sub 4} lasers with a wavelength of 1080 nm (power: P=0.8–1.0 W, scanning speed: S=0.2–2.5 μm/s), in which the laser focal position was moved gradually from the surface to the inside. The morphology, size, and orientation of β-BBO crystals were examined from polarization optical microscope and birefringence imaging observations. It was demonstrated that c-axis oriented β-BBO crystals with long lengths (e.g., 20 mm) were patterned in the inside of the glass. The morphology of β-BBO in the cross-section of lines was a rectangular shape with rounded corners, and the volume of β-BBO formed increased with increasing laser power and with decreasing laser scanning speed. The maximum depth in the inside from the surface for β-BBO patterning increased with increasing laser power, e.g., D{sub max}∼100 μm at P=0.8 W, D{sub max}∼170 μm at P=0.9 W, and D{sub max}∼200 μm at P=1 W. The present study proposes that the laser-induced crystallization opens a new door for applied engineering in glassy solids. - Graphical abstract: This figure shows the POM photographs for β-BaB{sub 2}O{sub 4} crystal lines patterned by cw Yb:YVO{sub 4} fiber laser irradiations with a laser power of P=0.8 W and a laser scanning speed S=2 μm/s in the glass. The laser focal point was moved gradually from the surface into the inside. The results shown in Fig. 1 demonstrate that it is possible to pattern highly oriented β-BaB{sub 2}O{sub 4} crystals even in the inside of glasses. - Highlights: • β-BaB{sub 2}O{sub 4} crystal lines were patterned in the inside of a glass by lasers. • Laser focal position was moved gradually from the surface to the inside. • Birefringence imaging was observed. • Morphology, size, and orientation of crystals were clarified. • Crystal lines with long lengths

  17. Low-magnesium calcite produced by coralline algae in seawater of Late Cretaceous composition.

    Science.gov (United States)

    Stanley, Steven M; Ries, Justin B; Hardie, Lawrence A

    2002-11-26

    Shifts in the MgCa ratio of seawater driven by changes in midocean ridge spreading rates have produced oscillations in the mineralogy of nonskeletal carbonate precipitates from seawater on time scales of 10(8) years. Since Cambrian time, skeletal mineralogies of anatomically simple organisms functioning as major reef builders or producers of shallow marine limestones have generally corresponded in mineral composition to nonskeletal precipitates. Here we report on experiments showing that the ambient MgCa ratio actually governs the skeletal mineralogy of some simple organisms. In modern seas, coralline algae produce skeletons of high-Mg calcite (>4 mol % MgCO(3)). We grew three species of these algae in artificial seawaters having three different MgCa ratios. All of the species incorporated amounts of Mg into their skeletons in proportion to the ambient MgCa ratio, mimicking the pattern for nonskeletal precipitation. Thus, the algae calcified as if they were simply inducing precipitation from seawater through their consumption of CO(2) for photosynthesis; presumably organic templates specify the calcite crystal structure of their skeletons. In artificial seawater with the low MgCa ratio of Late Cretaceous seas, the algae in our experiments produced low-Mg calcite (MgCO(3)), the carbonate mineral formed by nonskeletal precipitation in those ancient seas. Our results suggest that many taxa that produce high-Mg calcite today produced low-Mg calcite in Late Cretaceous seas. PMID:12399549

  18. Discovery of room-temperature spin-glass behaviors in two-dimensional oriented attached single crystals

    Science.gov (United States)

    Ma, Ji; Chen, Kezheng

    2016-05-01

    In this study, room-temperature spin-glass behaviors were observed in flake-like oriented attached hematite (α-Fe2O3) and iron phosphate hydroxide hydrate (Fe5(PO4)4(OH)3·2H2O) single crystals. Remarkably, their coercivity (HC) values were found to be almost invariable at various given temperatures from 5 to 300 K. The spin topographic map in these flakes was assumed as superparamagnetic (SPM) "islands" isolated by spin glass (SG)-like "bridges". A spin-glass model was then proposed to demonstrate the spin frustration within these "bridges", which were formed by the staggered atomic planes in the uneven surfaces belonging to different attached nanoparticles. Under the spatial limitation and coupling shield of these "bridges", the SPM "islands" were found to be collectively frozen to form a superspin glass (SSG) state below 80 K in weak applied magnetic fields; whereas, when strong magnetic fields were applied, the magnetic coupling of these "islands" would become superferromagnetic (SFM) through tunneling superexchange, so that, these SFM spins could antiferromagnetically couple with the SG-like "bridges" to yield pronounced exchange bias (EB) effect.

  19. Low-energy electron diffraction study of potassium adsorbed on single-crystal graphite and highly oriented pyrolytic graphite

    International Nuclear Information System (INIS)

    Potassium adsorption on graphite has been a model system for the understanding of the interaction of alkali metals with surfaces. The geometries of the (2x2) structure of potassium on both single-crystal graphite (SCG) and highly oriented pyrolytic graphite (HOPG) were investigated for various preparation conditions for graphite temperatures between 55 and 140 K. In all cases, the geometry was found to consist of K atoms in the hollow sites on top of the surface. The K-graphite average perpendicular spacing is 2.79±0.03 A , corresponding to an average C-K distance of 3.13±0.03 A , and the spacing between graphite planes is consistent with the bulk spacing of 3.35 A. No evidence was observed for a sublayer of potassium. The results of dynamical LEED studies for the clean SCG and HOPG surfaces indicate that the surface structures of both are consistent with the truncated bulk structure of graphite

  20. Upscaling Calcite Growth Rates From the Mesoscale to the Macroscale

    Energy Technology Data Exchange (ETDEWEB)

    Bracco, Jacquelyn N [ORNL; Stack, Andrew G [ORNL; Steefel, Carl I [Lawrence Berkeley National Laboratory (LBNL)

    2013-01-01

    Quantitative prediction of mineral reaction rates in the subsurface remains a daunting task partly because a key parameter for macroscopic models, the reactive site density, is poorly constrained. Here we report atomic force microscopy (AFM) measurements on the calcite surface of monomolecular step densities, treated as equivalent to the reactive site density, as a function of aqueous calcium-to-carbonate ratio and saturation index. Data for the obtuse step orientation are combined with existing step velocity measurements to generate a model that predicts overall macroscopic calcite growth rates. The model is quantitatively consistent with several published macroscopic rates under a range of alkaline solution conditions, particularly for two of the most comprehensive data sets without the need for additional fit parameters. The model reproduces peak growth rates and its functional form is simple enough to be incorporated into reactive transport or other macroscopic models designed for predictions in porous media. However, it currently cannot model equilibrium, pH effects, and may overestimate rates at high aqueous calcium-to-carbonate ratios. The discrepancies in rates at high calcium-to-carbonate ratios may be due to differences in pre-treatment, such as exposing the seed material to SI 1.0 to generate/develop growth hillocks, or other factors.

  1. Orientation and temperature dependence of some mechanical properties of the single-crystal nickel-base superalloy Rene N4. II - Low cycle fatigue behavior

    Science.gov (United States)

    Gabb, T. P.; Gayda, J.; Miner, R. V.

    1986-01-01

    The low cycle fatigue (LCF) properties of a single-crystal nickel-base superalloy Rene N4, have been examined at 760 and 980 C in air. Specimens having crystallographic orientations near the 001, 011, -111, 023, -236, and -145 lines were tested in fully reversed, total-strain-controlled LCF tests at a frequency of 0.1 Hz. At 760 C, this alloy exhibited orientation dependent tension-compression anisotropies of yielding which continued to failure. Also at 760 C, orientations exhibiting predominately single slip exhibited serrated yielding for many cycles. At 980 C, orientation dependencies of yielding behavior were smaller. In spite of the tension-compression anisotropies, cyclic stress range-strain range behavior was not strongly orientation dependent for either test temperature. Fatigue life on a total strain range basis was highly orientation dependent at 760 and 980 C and was related chiefly to elastic modulus, low modulus orientations having longer lives. Stage I crack growth on 111 planes was dominant at 760 C, while Stage II crack growth occurred at 980 C. Crack initiation generally occurred at near-surface micropores, but occasionally at oxidation spikes in the 980 C tests.

  2. Carbon isotope fractionation in synthetic magnesian calcite

    Science.gov (United States)

    Jimenez-Lopez, Concepción; Romanek, Christopher S.; Caballero, Emilia

    2006-03-01

    Mg-calcite was precipitated at 25 °C in closed system, free-drift experiments, from solutions containing NaHCO 3, CaCl 2 and MgCl 2. The carbon stable isotope composition of bulk solid and solution were analyzed from subsamples collected during time course experiments of 24 h duration. Considering only the Mg-content and δ 13C values for the bulk solid, the carbon isotope fractionation factor for the Mg-calcite-HCO 3(aq)- system (as 103lnα) increased with average mol percentage of Mg (X Mg) in the solid at a rate of (0.024 ± 0.011) per mol% MgCO 3. Extrapolation of this relationship to the pure calcite end member yields a value of 0.82 ± 0.09, which is similar to published values for the calcite-HCO 3(aq)- system. Although 103lnα did not vary for precipitation rates that ranged from 10 3.21 to 10 4.60 μmol m -2 h -1, it was not possible to hold Mg-content of the solid constant, so kinetic effect on 10 3 ln α could not be evaluated from these experiments.

  3. Growing spherulitic calcite grains in saline, hyperalkaline lakes: experimental evaluation of the effects of Mg-clays and organic acids

    Science.gov (United States)

    Mercedes-Martín, R.; Rogerson, M. R.; Brasier, A. T.; Vonhof, H. B.; Prior, T. J.; Fellows, S. M.; Reijmer, J. J. G.; Billing, I.; Pedley, H. M.

    2016-04-01

    The origin of spherical-radial calcite bodies - spherulites - in sublacustrine, hyperalkaline and saline systems is unclear, and therefore their palaeoenvironmental significance as allochems is disputed. Here, we experimentally investigate two hypotheses concerning the origin of spherulites. The first is that spherulites precipitate from solutions super-saturated with respect to magnesium-silicate clays, such as stevensite. The second is that spherulite precipitation happens in the presence of dissolved, organic acid molecules. In both cases, experiments were performed under sterile conditions using large batches of a synthetic and cell-free solution replicating waters found in hyperalkaline, saline lakes (such as Mono Lake, California). Our experimental results show that a highly alkaline and highly saline solution supersaturated with respect to calcite (control solution) will precipitate euhedral to subhedral rhombic and trigonal bladed calcite crystals. The same solution supersaturated with respect to stevensite precipitates sheet-like stevensite crystals rather than a gel, and calcite precipitation is reduced by ~ 50% compared to the control solution, producing a mixture of patchy prismatic subhedral to euhedral, and minor needle-like, calcite crystals. Enhanced magnesium concentration in solution is the likely the cause of decreased volumes of calcite precipitation, as this raised equilibrium ion activity ratio in the solution. On the other hand, when alginic acid was present then the result was widespread development of micron-size calcium carbonate spherulite bodies. With further growth time, but falling supersaturation, these spherules fused into botryoidal-topped crusts made of micron-size fibro-radial calcite crystals. We conclude that the simplest tested mechanism to deposit significant spherical-radial calcite bodies is to begin with a strongly supersaturated solution that contains specific but environmentally-common organic acids. Furthermore, we found

  4. Aging characteristics of 0.7Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}-0.3PbTiO{sub 3} single crystals with different crystal orientations

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xing [Changzhou University, School of Materials Science and Engineering, Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering, Changzhou (China); Chinese Academy of Sciences, Key Laboratory of Inorganic Function Material and Device, Shanghai (China); Wu, Dun; Fang, Bijun [Changzhou University, School of Materials Science and Engineering, Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering, Changzhou (China); Ding, Jianning [Changzhou University, School of Materials Science and Engineering, Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering, Changzhou (China); Jiangsu University, School of Material Science and Engineering, Zhenjiang (China); Li, Xiaobing; Zhao, Xiangyong; Luo, Haosu [Chinese Academy of Sciences, Key Laboratory of Inorganic Function Material and Device, Shanghai (China); Ko, Jae-Hyeon [Hallym University, Department of Physics, Chuncheon (Korea, Republic of); Ahn, Chang Won [University of Ulsan, Department of Physics and EHSRC, Ulsan (Korea, Republic of)

    2015-06-15

    In this work, the time and temperature dependence of the piezoelectric and ferroelectric properties of the 0.7Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}-0.3PbTiO{sub 3} (0.7PMN-0.3PT) single crystals were investigated in order to search for an effective method to improve their properties further. The piezoelectric properties of the [001]-, [110]- and [111]-oriented 0.7PMN-0.3PT single crystals exhibit excellent time stability during the 2-month room-temperature aging process. The re-poling process leads to the improvement of piezoelectric constant d{sub 33} for the [001]-, [110]- and [111]-oriented 0.7PMN-0.3PT single crystals, while the values of electromechanical coupling coefficient k{sub t} change little. During the thermal aging, the values of the measured d{sub 33}, calculated converse piezoelectric constant d{sub 33}{sup *}, maximum strain S{sub max}% and longitudinal electrostrictive coefficient Q of the [001]-, [110]- and [111]-oriented crystal plates increase gradually before the ferroelectric phase transition temperatures (T{sub FPT}, T{sub R-M}, T{sub R-O} and T{sub R-T}) and then decline continuously. The increase in these values before the T{sub FPT} is a result of the phase instability. In general, the [001]- and [110]-oriented 0.7PMN-0.3PT single crystals exhibit large piezoelectricity, excellent time stability and relatively high thermal stability between 20 and 80 C, which is favorable to the piezoelectric applications. (orig.)

  5. Modelling how incorporation of divalent cations affects calcite wettability-implications for biomineralisation and oil recovery.

    Science.gov (United States)

    Andersson, M P; Dideriksen, K; Sakuma, H; Stipp, S L S

    2016-01-01

    Using density functional theory and geochemical speciation modelling, we predicted how solid-fluid interfacial energy is changed, when divalent cations substitute into a calcite surface. The effect on wettability can be dramatic. Trace metal uptake can impact organic compound adsorption, with effects for example, on the ability of organisms to control crystal growth and our ability to predict the wettability of pore surfaces. Wettability influences how easily an organic phase can be removed from a surface, either organic compounds from contaminated soil or crude oil from a reservoir. In our simulations, transition metals substituted exothermically into calcite and more favourably into sites at the surface than in the bulk, meaning that surface properties are more strongly affected than results from bulk experiments imply. As a result of divalent cation substitution, calcite-fluid interfacial energy is significantly altered, enough to change macroscopic contact angle by tens of degrees. Substitution of Sr, Ba and Pb makes surfaces more hydrophobic. With substitution of Mg and the transition metals, calcite becomes more hydrophilic, weakening organic compound adsorption. For biomineralisation, this provides a switch for turning on and off the activity of organic crystal growth inhibitors, thereby controlling the shape of the associated mineral phase. PMID:27352933

  6. Modelling how incorporation of divalent cations affects calcite wettability–implications for biomineralisation and oil recovery

    Science.gov (United States)

    Andersson, M. P.; Dideriksen, K.; Sakuma, H.; Stipp, S. L. S.

    2016-01-01

    Using density functional theory and geochemical speciation modelling, we predicted how solid-fluid interfacial energy is changed, when divalent cations substitute into a calcite surface. The effect on wettability can be dramatic. Trace metal uptake can impact organic compound adsorption, with effects for example, on the ability of organisms to control crystal growth and our ability to predict the wettability of pore surfaces. Wettability influences how easily an organic phase can be removed from a surface, either organic compounds from contaminated soil or crude oil from a reservoir. In our simulations, transition metals substituted exothermically into calcite and more favourably into sites at the surface than in the bulk, meaning that surface properties are more strongly affected than results from bulk experiments imply. As a result of divalent cation substitution, calcite-fluid interfacial energy is significantly altered, enough to change macroscopic contact angle by tens of degrees. Substitution of Sr, Ba and Pb makes surfaces more hydrophobic. With substitution of Mg and the transition metals, calcite becomes more hydrophilic, weakening organic compound adsorption. For biomineralisation, this provides a switch for turning on and off the activity of organic crystal growth inhibitors, thereby controlling the shape of the associated mineral phase. PMID:27352933

  7. Isotopic tracer evidence for the amorphous calcium carbonate to calcite transformation by dissolution-reprecipitation

    Science.gov (United States)

    Giuffre, Anthony J.; Gagnon, Alexander C.; De Yoreo, James J.; Dove, Patricia M.

    2015-09-01

    Observations that some biogenic and sedimentary calcites grow from amorphous calcium carbonate (ACC) raise the question of how this mineralization process influences composition. However, the detailed pathway and geochemical consequences of the ACC to calcite transformation are not well constrained. This experimental study investigated the formation of calcite from ACC by using magnesium and calcium stable isotope labeling to directly probe the transformation pathway and controls on composition. Four processes were considered: dissolution-reprecipitation, solid state transformation, and combinations of these end-members. To distinguish between these scenarios, ACC was synthesized from natural isotope abundance solutions and subsequently transferred to spiked solutions that were enriched in 43Ca and 25Mg for the transformation to calcite. Isotope measurements by NanoSIMS determined the 43Ca/40Ca, and 25Mg/24Mg ratios of the resulting calcite crystals. Analysis of the data shows the transformation is best explained by a dissolution-reprecipitation process. We find that when a small amount of ACC is transferred, the isotopic signals in the resulting calcite are largely replaced by the composition of the surrounding spiked solution. When larger amounts of ACC are transferred, calcite compositions reflect a mixture between the ACC and initial solution end-member. Comparisons of the measurements to the predictions of a simple mixing model indicate that calcite compositions (1) are sensitive to relative amounts of ACC and the surrounding solution reservoir and (2) are primarily governed by the conditions at the time of ACC transformation rather than the initial ACC formation. Shifts in calcite composition over the duration of the transformation period reflect the progressive evolution of the local solution conditions. This dependence indicates the extent to which there is water available would change the end point composition on the mixing line. While these findings have

  8. Shock-induced effects in calcite from Cactus Crater

    Science.gov (United States)

    Vizgirda, J.; Ahrens, T. J.; Tsay, F.-D.

    1980-01-01

    The paper discusses shock metamorphism of calcite from coralline limestone samples retrieved from a borehole drilled into rocks beneath Cactus Crater, a nuclear explosion crater at Eniwetok Atoll. The metamorphism was detected and quantified using electron spin resonance (ESR); the ESR spectra of Mn(+) present as a trace constituent in the coral samples, show a consistent decrease in hyperfine peak splitting with decreasing depth of sample. It is suggested that the decrease in hyperfine peak splitting reflects a decrease in crystal field splitting, and therefore, small increases on cation-anion distances produced by mechanical energy input during the shock process. Two alternative crater models suggested by the ESR results are a depiction of a steady decay of the shock wave, and a delineation of a breccia lens with a breccia-bedrock interface at 20 plus or minus 5 m.

  9. Oriented crystalline monolayers and bilayers of 2 x 2 silver(1) grid architectures at the air-solution interface: Their assembly and crystal structure elucidation

    DEFF Research Database (Denmark)

    Weissbuch, J.; Baxter, P.N.W.; Kuzmenko, I.; Cohen, H.; Cohen, S.; Kjær, K.; Howes, P.B.; Als-Nielsen, J.; Lehn, J.M.; Leiserowitz, L.; Lahav, M.

    2000-01-01

    Oriented crystalline monolayers, similar to 14 Angstrom thick, of a 2 x 2 Ag+ grid complex, self-assembled at the air-solution interface starting from an water-insoluble ligand 3,6-bis[2-(6-phenylpyridine)]pyridazine spread on silver-ion-containing solutions,were examined by grazing-incidence X....... Such a phase transition is of relevance to the understanding of crystal nucleation....

  10. Molecular orientation behavior of chiral nematic liquid crystals based on the presence of blue phases using polarized microscopic FT-IR spectroscopy

    Science.gov (United States)

    Matsumura, Masanori; Katayama, Norihisa

    2016-07-01

    Study on molecular orientation behavior of highly twisted chiral nematic liquid crystals (N∗LCs) expressing blue phases (BPs) is important for developing new devices. This study examines the change of molecular orientation of N∗LCs due to the presence of BPs. Polarized microscopic FT-IR spectroscopy was used to study the in- and out-of-plane molecular orientations of N∗LCs that undergo a phase transition involving BPs. The band intensity ratio of CN to CH2 stretching modes (CN/CH2) in the IR spectra was used to determine the orientation of N∗LC molecules. The measured spectra indicated that the helical axis of N∗LC molecules was perpendicular to the substrate before heating and inclined on the substrate after cooling the sample which has phase transition from BP I to chiral nematic (N∗). The N∗LC molecule in the cell of rubbed orientation film exhibited the in-plane anisotropy after a heating-cooling ramp only in samples that passed through BP I. These results indicate that the changes of molecular orientation of N∗LC by phase transition are affected by BP I.

  11. Thermodynamics of magnesian calcite solid-solutions at 25°C and 1 atm total pressure

    Science.gov (United States)

    Busenberg, Eurybiades; Plummer, L. Niel

    1989-01-01

    protodolomite. Group I and II solid-solutions differ significantly in stability. The rate of crystal growth and the chemical composition of the aqueous solutions from which the solids were formed are the main factors controlling stoichiometric solubility of the magnesian calcites and the density of crystal defects. The literature on the occurrence and behavior of magnesian calcites in sea water and other aqueous solutions is also examined.

  12. in situ Calcite Precipitation for Contaminant Immobilization

    Energy Technology Data Exchange (ETDEWEB)

    Yoshiko Fujita; Robert W. Smith

    2009-08-01

    in situ Calcite Precipitation for Contaminant Immobilization Yoshiko Fujita (Yoshiko.fujita@inl.gov) (Idaho National Laboratory, Idaho Falls, Idaho, USA) Robert W. Smith (University of Idaho-Idaho Falls, Idaho Falls, Idaho, USA) Subsurface radionuclide and trace metal contaminants throughout the U.S. Department of Energy (DOE) complex pose one of DOE’s greatest challenges for long-term stewardship. One promising stabilization mechanism for divalent trace ions, such as the short-lived radionuclide strontium-90, is co-precipitation in calcite. Calcite, a common mineral in the arid western U.S., can form solid solutions with trace metals. The rate of trace metal incorporation is susceptible to manipulation using either abiotic or biotic means. We have previously demonstrated that increasing the calcite precipitation rate by stimulating the activity of urea hydrolyzing microorganisms can result in significantly enhanced Sr uptake. Urea hydrolysis causes the acceleration of calcium carbonate precipitation (and trace metal co-precipitation) by increasing pH and alkalinity, and also by liberating the reactive cations from the aquifer matrix via exchange reactions involving the ammonium ion derived from urea: H2NCONH2 + 3H2O ? 2NH4+ + HCO3- + OH- urea hydrolysis >X:2Ca + 2NH4+ ? 2>X:NH4 + Ca2+ ion exchange Ca2+ + HCO3- + OH- ? CaCO3(s) + H2O calcite precipitation where >X: is a cation exchange site on the aquifer matrix. This contaminant immobilization approach has several attractive features. Urea hydrolysis is catalyzed by the urease enzyme, which is produced by many indigenous subsurface microorganisms. Addition of foreign microbes is unnecessary. In turn the involvement of the native microbes and the consequent in situ generation of reactive components in the aqueous phase (e.g., carbonate and Ca or Sr) can allow dissemination of the reaction over a larger volume and/or farther away from an amendment injection point, as compared to direct addition of the reactants at

  13. Morphology and orientation of β-BaB2O4 crystals patterned by laser in the inside of samarium barium borate glass

    Science.gov (United States)

    Nishii, Akihito; Shinozaki, Kenji; Honma, Tsuyoshi; Komatsu, Takayuki

    2015-01-01

    Nonlinear optical β-BaB2O4 crystal lines (β-BBO) were patterned in the inside of 8Sm2O3-42BaO-50B2O3 glass by irradiations of continuous-wave Yb:YVO4 lasers with a wavelength of 1080 nm (power: P=0.8-1.0 W, scanning speed: S=0.2-2.5 μm/s), in which the laser focal position was moved gradually from the surface to the inside. The morphology, size, and orientation of β-BBO crystals were examined from polarization optical microscope and birefringence imaging observations. It was demonstrated that c-axis oriented β-BBO crystals with long lengths (e.g., 20 mm) were patterned in the inside of the glass. The morphology of β-BBO in the cross-section of lines was a rectangular shape with rounded corners, and the volume of β-BBO formed increased with increasing laser power and with decreasing laser scanning speed. The maximum depth in the inside from the surface for β-BBO patterning increased with increasing laser power, e.g., Dmax~100 μm at P=0.8 W, Dmax~170 μm at P=0.9 W, and Dmax~200 μm at P=1 W. The present study proposes that the laser-induced crystallization opens a new door for applied engineering in glassy solids.

  14. Linear-dichroic infrared spectroscopy—Validation and experimental design of the new orientation technique of solid samples as suspension in nematic liquid crystal

    Science.gov (United States)

    Ivanova, B. B.; Simeonov, V. D.; Arnaudov, M. G.; Tsalev, D. L.

    2007-05-01

    A validation of the developed new orientation method of solid samples as suspension in nematic liquid crystal (NLC), applied in linear-dichroic infrared (IR-LD) spectroscopy has been carried out using a model system DL-isoleucine ( DL-isoleu). Accuracy, precision and the influence of the liquid crystal medium on peak positions and integral absorbances of guest molecules have been presented. Optimization of experimental conditions has been performed as well. An experimental design for quantitative evaluation of the impact of four input factors: the number of scans, the rubbing-out of KBr-pellets, the amount of studied compounds included in the liquid crystal medium and the ratios of Lorentzian to Gaussian peak functions in the curve fitting procedure on the spectroscopic signal at five different frequencies, indicating important specifities of the system has been studied.

  15. Growth of Large-Size SnS Thin Crystals Driven by Oriented Attachment and Applications to Gas Sensors and Photodetectors.

    Science.gov (United States)

    Wang, Jun; Lian, Gang; Xu, Zhenghao; Fu, Chen; Lin, Zhaojun; Li, Liyi; Wang, Qilong; Cui, Deliang; Wong, Ching-Ping

    2016-04-20

    Freestanding large-size SnS thin crystals are synthesized via two-dimensional oriented attachment (OA) growth of colloidal quantum dots (CQDs) in a novel high-pressure solvothermal reaction. The SnS thin crystals present a uniform rectangular shape with a lateral size of 20-30 um and thickness of SnS thin single crystals, are also prepared. The sensing devices present high sensitivity, superior selectivity, low detection limit (≪100 ppb) and reversibility to NO2 at room temperature. The fabricated photodetector devices exhibit a high responsivity of 2.04 × 10(3) A W(1-) and high external quantum efficiency of ∼4.75 × 10(5) % at 532 nm, which are much higher than most of the photodetector devices. PMID:27054920

  16. Calcite growth-rate inhibition by fulvic acid and magnesium ion—Possible influence on biogenic calcite formation

    Science.gov (United States)

    Reddy, Michael M.

    2012-01-01

    Increases in ocean surface water dissolved carbon dioxide (CO2) concentrations retard biocalcification by reducing calcite supersaturation (Ωc). Reduced calcification rates may influence growth-rate dependent magnesium ion (Mg) incorporation into biogenic calcite modifying the use of calcifying organisms as paleoclimate proxies. Fulvic acid (FA) at biocalcification sites may further reduce calcification rates. Calcite growth-rate inhibition by FA and Mg, two common constituents of seawater and soil water involved in the formation of biogenic calcite, was measured separately and in combination under identical, highly reproducible experimental conditions. Calcite growth rates (pH=8.5 and Ωc=4.5) are reduced by FA (0.5 mg/L) to 47% and by Mg (10−4 M) to 38%, compared to control experiments containing no added growth-rate inhibitor. Humic acid (HA) is twice as effective a calcite growth-rate inhibitor as FA. Calcite growth rate in the presence of both FA (0.5 mg/L) and Mg (10−4 M) is reduced to 5% of the control rate. Mg inhibits calcite growth rates by substitution for calcium ion at the growth site. In contrast, FA inhibits calcite growth rates by binding multiple carboxylate groups on the calcite surface. FA and Mg together have an increased affinity for the calcite growth sites reducing calcite growth rates.

  17. Magnesian calcite sorbent for carbon dioxide capture

    Energy Technology Data Exchange (ETDEWEB)

    Mabry, J.C.; Mondal, K. [Southern Illinois University, Carbondale, IL (United States)

    2011-07-01

    Magnesian calcite with controlled properties was synthesized for the removal of carbon dioxide. The results from characterization, reactivity and CO{sub 2} capture capacity for different synthesis conditions are reported. The magnesian calcite samples (CaCO{sub 3}:MgCO{sub 3}) were synthesized by the coprecipitation of specific amounts of commercially available CaO and MgO by carbon dioxide. Characterization was done with BET, SEM/EDS, particle size analysis and XRD. The capacity was measured using TGA cycles at 800 {sup o}C and compared for different preparation conditions. The effects of CaO, MgO and surfactant loading on the physical properties and carbonation activity were studied to determine the optimal synthesis condition. A long-term carbonation-calcination cycling test was conducted on the optimal sample. It was observed that the sample maintained its capacity to 86% of its original uptake even after 50 cycles.

  18. Recovery of crystallinity in ground calcite

    Energy Technology Data Exchange (ETDEWEB)

    Gammage, R.B.; Glasson, D.R.

    1976-01-01

    Recovery processes by thermal treatment and recrystallization are examined in a calcite specimen severely disordered by ball milling. As the annealing temperature is increased, restructuring in the bulk lags behind the recovery of crystalline perfection in the surface regions. Surface reordering is significant at temperatures as low as 150 to 175/sup 0/C and is rapidly completed at 400/sup 0/C. Annealing at 600/sup 0/C is required for removal of all lattice strain. Before loss of surface can occur by sintering, the temperature needs to exceed 300/sup 0/C. The corresponding temperature for a high-area precipitated calcite is 400/sup 0/C. Recovery of crystallinity is also promoted by light-etching with aqueous acid when extensive whisker growth occurs. Aging over a period of twelve years has led to loss of the ultrareactive characteristics.

  19. [Study on Mineralogical Characteristics of Quartz and Calcite from Feieling Skarn-Type Pb-Zn Deposit in Southwest Margin of Yunkai Massif].

    Science.gov (United States)

    Zeng, Chang-yu; Zhao, Ming-zhen; Li, Hong-zhong; Niu, Jia; Zhang, Jie-tang; He, Jun-guo; Zhou, Yong-zhang; Yang, Zhi-jun

    2015-09-01

    The Feieling Pb-Zn deposit of skarn-type is located the in Southwest margin of Yunkai massif, China. This ore deposit can be divided into wall rock near ore, concealed rock mass, endoskarn, exoskarn and orebody. The Raman and FTIR spectrum are conducted to study the mineralogical characteristics of quartz and calcite from five types of rocks from Feieling skarn-type deposit. The analysis shows that the quartz included in the near ore wall rock, endoskarn and exoskarn, comparing with recrystallized quartz of concealed rock mass, has a tend to change into low symmetry quartz in varying degrees. The crystalinity and order degree of quartz from near ore wall rock to concealed rock mass and to endoskarn are becoming higher, but that of quartz from different exoskarn samples display no regular. The origin or the quartz microstructure changes may be related to the multi-stage evolution of skarn mineralization process. The quartz, included in near ore wall rock, endoskarn and exoskarn, become easier to recrystallize and adjust microstructure under the influence of the multi-stage hydrothermal and temperature effect. In anyone sample, the earlier crystalline calcite, showing subhedral-euhedral crystal, display higher crystalinity and order degree. On the contrary, the later crystalline calcite, showing xenomorphic crystal, display lower crystalinity and order degree. Calcite crystal of exoskarn rock contains some silica impurity, while endoskarn and orebody rock is pure. The purity of calcite crystal may relate to Multi-stage evolution of skarn mineralization process. At the early and late skarn stage, active silica-containing fluid is easier to join into calcite, which is under higher temperature environments. On the contrary, at the late quartz-surfide stage, the later crystalized calcite displays higher purity, which is under lower temperature environments. Therefore, spectral characteristics of quartz and calcite reflect multi-stage evolution of skarn mineralization

  20. Mechanistic aspects of the calcite precipitation reaction and supercritical fluid movements in calcite lattice: implication for mineral storage of CO2

    International Nuclear Information System (INIS)

    crystal surface. These movements can occur through the grain boundaries of the crystals or the microstructures at a velocity ten times superior to the crystalline diffusion in conditions of standard temperature and pressure. Moreover, it has been shown that this phenomenon affects significantly the surface properties of the calcite and has to be taken into account during the predictive modelling of the reactivity and transport of the fluids in the storage medium. (O.M.)

  1. Textural properties of synthetic nano-calcite produced by hydrothermal carbonation of calcium hydroxide

    Science.gov (United States)

    Montes-Hernandez, G.; Fernández-Martínez, A.; Charlet, L.; Tisserand, D.; Renard, F.

    2008-05-01

    The hydrothermal carbonation of calcium hydroxide (Ca(OH) 2) at high pressure of CO 2 (initial P=55 bar) and moderate to high temperature (30 and 90 °C) was used to synthesize fine particles of calcite. This method allows a high carbonation efficiency (about 95% of Ca(OH) 2-CaCO 3 conversion), a significant production rate (48 kg/m 3 h) and high purity of product (about 96%). However, the various initial physicochemical conditions have a strong influence on the crystal size and surface area of the synthesized calcite crystals. The present study is focused on the estimation of the textural properties of synthesized calcite (morphology, specific surface area, average particle size, particle size distribution and particle size evolution with reaction time), using Rietveld refinements of X-ray diffraction (XRD) spectra, Brunauer-Emmett-Teller (BET) measurements, and scanning electron microscope (SEM) and transmission electron microscope (TEM) observations. This study demonstrate that the pressure, the temperature and the dissolved quantity of CO 2 have a significant effect on the average particle size, specific surface area, initial rate of precipitation, and on the morphology of calcium carbonate crystals. In contrast, these PT x conditions used herein have an insignificant effect on the carbonation efficiency of Ca(OH) 2. Finally, the results presented here demonstrate that nano-calcite crystals with high specific surface area ( SBET=6-10 m 2/g) can be produced, with a high potential for industrial applications such as adsorbents and/or filler in papermaking industry.

  2. Evolution of calcite growth morphology in the presence of magnesium: Implications for the dolomite problem

    Science.gov (United States)

    Hong, Mina; Xu, Jie; Teng, Henry H.

    2016-01-01

    The effect of magnesium on calcite growth morphology was known to occur as step rounding in some cases and surface segmentation in others. What remains unknown are the conditions for and the relations between the different effects, suggesting a lack of comprehensive understanding of the fundamental cause. Here we investigated the evolution of spiral hillock morphology on calcite cleavage surfaces in solutions with increasing Ca to Mg ratios and supersaturation levels using in situ atomic force microscopy. We isolated the effects of Mg and saturation by conducting experiments under conditions of constant pH, ionic strength, and Ca2+/CO32-. Our results revealed three types of morphological variations, ranging from step rounding in one direction (type I), to all directions (type II), and finally to a mosaic-like surface segmentation associated with monolayer buckling and step bunching (type III). These results suggest that the effect of magnesium on calcite growth depends upon multiple parameters including the concentration of Mg in solution, the step speed, as well as the extensiveness of Mg for Ca substitution in calcite lattice. We propose that the morphological variation may be understood by a model taken into consideration of (1) the lifespan and flux size of Mg ions at kinks in comparison to step kinetics, and (2) the diffusion and alignment of point defects created by the substitution of Mg for Ca in the crystal lattice. Stress calculations show that the maximum amount of Mg which calcite lattice can sustain before plastic deformation is ∼40%, suggesting that lattice stress due to the mismatch between MgCO3 and CaCO3 is likely the ultimate cause for the difficulty of ambient condition dolomite crystallization.

  3. Ice crystal c-axis orientation and mean grain size measurements from the Dome Summit South ice core, Law Dome, East Antarctica

    Science.gov (United States)

    Treverrow, Adam; Jun, Li; Jacka, Tim H.

    2016-06-01

    We present measurements of crystal c-axis orientations and mean grain area from the Dome Summit South (DSS) ice core drilled on Law Dome, East Antarctica. All measurements were made on location at the borehole site during drilling operations. The data are from 185 individual thin sections obtained between a depth of 117 m below the surface and the bottom of the DSS core at a depth of 1196 m. The median number of c-axis orientations recorded in each thin section was 100, with values ranging from 5 through to 111 orientations. The data from all 185 thin sections are provided in a single comma-separated value (csv) formatted file which contains the c-axis orientations in polar coordinates, depth information for each core section from which the data were obtained, the mean grain area calculated for each thin section and other data related to the drilling site. The data set is also available as a MATLAB™ structure array. Additionally, the c-axis orientation data from each of the 185 thin sections are summarized graphically in figures containing a Schmidt diagram, histogram of c-axis colatitudes and rose plot of c-axis azimuths. All these data are referenced by doi:10.4225/15/5669050CC1B3B and are available free of charge at https://data.antarctica.gov.au.<

  4. Ice crystal c-axis orientation and mean grain size measurements from the Dome Summit South ice core, Law Dome, East Antarctica

    Science.gov (United States)

    Treverrow, Adam; Jun, Li; Jacka, Tim H.

    2016-06-01

    We present measurements of crystal c-axis orientations and mean grain area from the Dome Summit South (DSS) ice core drilled on Law Dome, East Antarctica. All measurements were made on location at the borehole site during drilling operations. The data are from 185 individual thin sections obtained between a depth of 117 m below the surface and the bottom of the DSS core at a depth of 1196 m. The median number of c-axis orientations recorded in each thin section was 100, with values ranging from 5 through to 111 orientations. The data from all 185 thin sections are provided in a single comma-separated value (csv) formatted file which contains the c-axis orientations in polar coordinates, depth information for each core section from which the data were obtained, the mean grain area calculated for each thin section and other data related to the drilling site. The data set is also available as a MATLAB™ structure array. Additionally, the c-axis orientation data from each of the 185 thin sections are summarized graphically in figures containing a Schmidt diagram, histogram of c-axis colatitudes and rose plot of c-axis azimuths. All these data are referenced by doi:10.4225/15/5669050CC1B3B and are available free of charge at https://data.antarctica.gov.au" target="_blank">https://data.antarctica.gov.au.<

  5. Effects of crystal orientation on the optical gain characteristics of blue AlInGaN/InGaN quantum-well structures

    Energy Technology Data Exchange (ETDEWEB)

    Park, S. H. [Catholic University of Daegu, Hayang (Korea, Republic of); Cho, Y. H.; Shim, M. B.; Kim, S. J. [Samsung Electronics, Suwon (Korea, Republic of); Park, C. Y.; Pak, Y. E. [Seoul National University, Suwon (Korea, Republic of); Mishra, D.; Yoo, S. H. [Ajou University, Suwon (Korea, Republic of); Kang, K. W. [Yonsei University, Seoul (Korea, Republic of)

    2014-08-15

    The effects of crystal orientation on the optical gain characteristics of blue AlInGaN/InGaN quantum-well (QW) structures with a reduced internal field were investigated by using the non-Markovian model with many-body effects. The AlInGaN/InGaN system has a larger matrix element than the conventional InGaN/GaN system because the former has a smaller internal field than the latter for relatively small crystal angles. As a result, for QW structures with a relatively small crystal angle (θ = 30 .deg. ), the AlInGaN/InGaN system is shown to have a much larger optical gain than the conventional InGaN/GaN system. On the other hand, in the case of QW structures with a large crystal angle (θ = 90 .deg. ), the AlInGaN/InGaN system is shown to have a smaller optical gain than the conventional InGaN/GaN system. Hence, we expect that we can obtain high-efficiency optoelectronic devices by using quaternary AlInGaN QW for relatively small crystal angles.

  6. Calcite microcrystals in the pineal gland of the human brain: second harmonic generators and possible piezoelectric transducers

    International Nuclear Information System (INIS)

    Full text: A new form of biomineralization in the pineal gland of the human brain has been studied. It consists of small crystals that are less than 20 μm in length and that are completely distinct from the often-observed mulberry-type hydroxyapatite concretions. Cubic, hexagonal and cylindrical morphologies have been identified using scanning electron microscopy. Energy dispersive spectroscopy, selected-area electron diffraction and near infrared Raman spectroscopy established that the crystals were calcite. Experiments at the European Synchrotron Radiation Facility (ESRF) to study the biomineralization showed the presence of sulfur originating from both sugars and proteins. Other studies at the ESRF furnished information on the complex texture crystallization of the calcite. With the exception of the otoconia structure of the inner ear, this is the only known non-pathological occurrence of calcite in the human body. The calcite microcrystals are believed to be responsible for the previously observed second harmonic generation (SHG) in pineal tissue sections. There is a strong possibility that the complex twinned structure of the crystals may lower their symmetry and permit the existence of a piezoelectric effect

  7. Origin of zoning within dedolomite and calcitized gypsum of the Mississippian Arroyo Penasco Group

    Energy Technology Data Exchange (ETDEWEB)

    Ulmer, D.S.

    1985-01-01

    The Mississippian Arroyo Penasco Group carbonates are the oldest Paleozoic rocks present in north-central New Mexico. These supratidal to shallow,subtidal sediments exhibit complex diagenetic fabrics produced by periods of pre-Pennsylvanian subaerial exposure. Both extensive recrystallization of the Espiritu Santo carbonates and brecciation of the overlying Macho Member of the Tererro Formation resulted from an extended period of Mississippian subaerial exposure of broad, low-relief tidal flats. Cathodoluminescent petrography indicates that the recrystallized limestones consist of calcite pseudomorphs of dolomite and gypsum. Dedolomite and calcitized gypsum crystals, with /sup 13/C//sup 12/C ratios of -2 to +1.5% PDB, range from highly zoned to uniformly luminescent. Electron microprobe analyses reveals variable Mn and Fe contents across the pseudomorphs which are responsible for differences in observed luminosity. These features are interpreted to reflect a period of subaerial exposure after deposition of Macho Member sediments, which caused dissolution of gypsum and dolomite by sulfate and Mg depleted meteoric fluids and produced the collapse breccia. Preservation of zoning within some pseudomorphs required simultaneous dissolution of gypsum and dolomite and precipitation of calcite. C-isotope data indicates a meteoric to mixed phreatic origin for pore fluids which precipitated calcite; repetitive zoning within dolomite and gypsum pseudomorphs is indicative of interactions between marine and meteoric phreatic fluids in the intertidal environment.

  8. Microstratigraphic logging of calcite fabrics in speleothems as tool for palaeoclimate studies

    Directory of Open Access Journals (Sweden)

    Silvia Frisia

    2015-01-01

    Full Text Available The systematic documentation of calcite fabrics in stalagmites and flowstones provides robustness to palaeoclimate interpretation based on geochemical proxies, but it has been neglected because it is difficult to transform crystal morphologies into numerical values, and construct fabric time series. Here, general criteria that allow for coding fabrics of calcite composing stalagmites and flowstones is provided. Being based on known models of fabric development, the coding ascribes sequential numbers to each fabric, which reflect climate-related parameters, such as changes in drip rate variability, bio-mediation or diagenetic modifications. Acronyms are proposed for Columnar types, Dendritic, Micrite, Microsparite and Mosaic fabrics, whose use could then render possible comparison of calcite fabrics in stalagmites and flowstones from diverse latitudinal and altitudinal settings. The climatic and environmental significance of similarities in the geochemical signals and trends analysed in coeval stalagmites and flowstones (or differences in the signals and trends will be more robust when compared with fabric time series. This is particularly true where, such as in the Holocene, changes in geochemical values may be subtle, yet fabrics may show changes related to variations in supersaturation, drip rate or input of detrital particles or organic compounds. The proposed microstratigraphic logging allows recognition of changes in stable isotope ratio or trace element values that can be ascribed to hydrology and diagenesis, with considerable improvement of reconstructions based on the chemical proxies of stalagmites and flowstones composed of calcite.

  9. Effect of electrolysis conditions on the morphology and crystal orientation of zinc electrodeposit; Denki Zn mekki himaku no kessho keitai, haikosei ni oyobosu denkai joken no eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Nakano, H.; Araga, K.; Iwai, M.; Kawafuku, J. [Kobe Steel, Ltd., Kobe (Japan)

    1997-12-01

    The effect of electrolysis condition on the morphology and crystal orientation of zinc electrodeposit was investigated by using the polycrystal commercial low carbon Al-killed steel sheet as a base material and the sulfate bath under the current density of 50-200A/dm{sup 2}, flow rate of 1-2m/s and bath temperature of 50-70degC. Under the conditions where overvoltage of electrodeposit is high, such as high current density, low flow rate and low temperature, heteroepitaxy of steel/zinc decreases, so that zinc crystals become fine and random in size and growth direction. Under the high overvoltage conditions, orientation indexes of (0002)Zn and (1013)Zn decrease but those of (1011)Zn and (1010)Zn increase. When zinc electrodeposits grow heteroepitaxially, (0002)Zn and (0013)Zn planes are preferred. From these results, zinc electrodeposits are thought to progress as follows: At initial stage of plating, zinc electrodeposits grow heteroepitaxially at preferred orientations of (0002) Zn and (1013) Zn. Then, random growth of zinc begins partly on the (0002) Zn and (1013) Zn and finally random growth of (1011) Zn and (1010)Zn occurs partly on the (0002)Zn and (1013)Zn. 16 refs., 11 figs., 1 tab.

  10. Effect of water absorption of dielectric underlayers on crystal orientation in Al-Si-Cu/Ti/TiN/Ti metallization

    Science.gov (United States)

    Yoshida, Tomoyuki; Hashimoto, Shoji; Hosokawa, Hideki; Ohwaki, Takeshi; Mitsushima, Yasuichi; Taga, Yasunori

    1997-05-01

    The influence of the exposure of underlying dielectric (phophosilicate glass and borophosphosilicate glass) films to a humid air ambient on crystallographic orientations in Al-Si-Cu/Ti/TiN/Ti layered structures has been investigated as a function of the boron content and exposure time of the dielectric films. The Al(111) orientation in the layered structures was found to improve drastically with increasing boron content and exposure time of the dielectric films. The full width at half maximum value of an Al(111) x-ray rocking curve reached less than 1°. It was also found that the Al-Si-Cu surface becomes smoother and the average grain size increases as the Al(111) orientation improves. The improved Al(111) orientation was attributed to the improved Ti(002) orientation of the bottom Ti films. The mechanism of the improved Ti(002) orientation was investigated. It was confirmed that the improved orientation is closely related with the surface concentration of the absorbed water in the dielectric films. Further, it was demonstrated that interconnects fabricated from the improved layered structure have excellent electromigration performance.

  11. STUDY ON MAGNETIC FIELD-INDUCED ORIENTATION OF A CHIRAL SIDE-CHAIN LIQUID CRYSTAL POLYACRYLATE USING INFRARED DICHROISM

    Institute of Scientific and Technical Information of China (English)

    HE Liu; JIN Shunzi; ZHANG Shufan; QI Zongneng; WANG Fosong

    1996-01-01

    Magnetic field-induced orientation of a chiral side chain liquid crystalline polyacrylate (P-11) was studied by using IR dichroism. For the investigated P-11, it has been shown that the magnetic alignment takes place over the entire temperature range between its melting point and clearing point and the orientation level is strongly temperature-dependent, the development with time of the magnetic orientation follows an exponential-type relation,and the smectic phase state influences the thermal relaxation process in the absence of the magnetic field.

  12. High-performance poly-Si thin film transistors with highly biaxially oriented poly-Si thin films using double line beam continuous-wave laser lateral crystallization

    Science.gov (United States)

    Yamano, Masayuki; Kuroki, Shin-Ichiro; Sato, Tadashi; Kotani, Koji

    2014-01-01

    Highly biaxially oriented poly-Si thin films were formed by double-line beam continuous-wave laser lateral crystallization (DLB-CLC). The crystallinities of the DLB-CLC poly-Si thin films were (110), (111), and (211) for the laser scan, transverse, and surface directions, respectively, and an energetically stable Σ3 grain boundary was observed to be dominant. All silicon grains were elongated in the laser scan direction and one-dimensionally very large silicon grains with lengths of more than 100 µm were fabricated. Using these biaxially oriented polycrystalline silicon (poly-Si) films, low-temperature poly-Si TFTs (LTPS-TFTs) were fabricated at low temperatures (≦550 °C) by a metal gate self-aligned process. As a result, a TFT with a high electron field effect mobility of μFE = 450 cm2 V-1 s-1 in a linear region was realized.

  13. The creep behaviour of single-crystal turbine blade alloys basing on nickel SC 16 with [011] orientation; Das Kriechverhalten der einkristallinen Nickelbasisturbinenschaufellegierung SC 16 MIT [011]-Orientierung

    Energy Technology Data Exchange (ETDEWEB)

    Klingelhoeffer, H.; Chrzanowski, U.; Kraemer, E.; Frenz, H.; Ziebs, J. [Bundesanstalt fuer Materialforschung und -pruefung, Berlin (Germany)

    1997-12-31

    This paper describes the creep behaviour of single-crystal turbine blade alloys basing on nickel SC 16 compared to the material IN 738 LC while submitted to creep strain. The creep properties of samples with [011] and [001]-orientation are compared with each other. (orig./MM) [Deutsch] In der vorliegenden Arbeit wird das Kriechverhalten der einkristallinen Nickelbasissuperlegierung SC 16 im Vergleich zum Werkstoff IN 738 LC unter Kriechbeanspruchung dargestellt. Dabei werden die Kriecheigenschaften von Proben mit [011]- und [001]-Orientierung gegenuebergestellt. (orig./MM)

  14. The relationship between chemistry, texture and anisotropy of magnetic susceptibility for a set of calcite mylonites

    International Nuclear Information System (INIS)

    Complete text of publication follows. Magnetic susceptibility and its anisotropy (AMS) are sensitive indicators for trace amounts of paramagnetic impurities and second-phase minerals in rocks that display diamagnetic bulk susceptibility. To illustrate this relationship a set of highly strained calcite mylonites has been collected from the overturned limb (shear zone) of the Morcles Nappe (Helvetic Alps, southwestern Switzerland). The sample set consists of white and gray fine-grained calcite mylonites (Upper and Lower Urgonian) with less than 10 vol% of secondary phase content and varying amounts of paramagnetic Fe and Mn impurities. The AMS of these specimens are studied using a combination of low- and high-field magnetic susceptibility measurements. In addition, high-field AMS measurements are performed at 77 K. The use of these methods illustrates a strong relationship between the magnetic susceptibility, the development of crystallographic preferred orientation (CPO) of calcite and the Fe plus Mn impurity content. The bulk magnetic susceptibility and AMS varies systematically according to the amount of Fe and Mn. At room-temperature the AMS results from a combination of the diamagnetic and paramagnetic sub-fabrics, whereas at 77 K the paramagnetic sub-fabric is dominant. The k1 and k3 axes invert positions when comparing the AMS at room temperature and 77 K. The degree of anisotropy is shown to be related to bulk susceptibility, which in itself is directly dependent on the amount of Fe incorporated into the calcite's lattice, and the strength of the calcite's CPO. Our results indicate that AMS can be used as a sensitive tool for studying the relationship between trace element chemistry and deformation.

  15. A study of the crystal orientation dependence of the solid-phase epitaxial growth of amorphized GaAs

    International Nuclear Information System (INIS)

    In-situ transmission electron microscopy (TEM) has been utilized in conjunction with conventional in-situ time resolved reflectivity (TRR) and ex-situ TEM to study the influence of substrate orientation on the solid-phase epitaxial growth (SPEG) of amorphized GaAs. A thin amorphous layer was produced on semi-insulating (100), (110) and (111) GaAs substrates, maintained at liquid nitrogen temperature, by As and Ga co-implantation. Sample were annealed at ∼260 deg C in the electron microscope and the dynamic events of the recrystallization process for the different substrates were video-captured. By quantitatively analyzing the in-situ TEM data, it has been demonstrated that the non-planarity of the amorphous-crystalline (a/c)-interface was greatest for the (111) and least for the (110) substrate orientations. The roughness was measured in terms of the length of the a/c-interface in a given window as a function of depth on a frame captured from the video recorded in-situ. This has been further analyzed and substantiated by measuring the size of the angle subtended by a microtwin with respect to the interface on ex-situ TEM micrographs of each orientation. The angle was both calculated and measured and was the largest in (111) orientation and smallest in (110) orientation. This has ensured that the a/c-interface was the roughest and most planar for (111) and (110) orientations, respectively. (authors)

  16. Cryogenic and non-cryogenic pool calcites indicating permafrost and non-permafrost periods: a case study from the Herbstlabyrinth-Advent Cave system (Germany

    Directory of Open Access Journals (Sweden)

    D. K. Richter

    2010-11-01

    Full Text Available Weichselian cryogenic calcites collected in what is referred to as the Rätselhalle of the Herbstlabyrinth-Advent Cave system are structurally classified as rhombohedral crystals and spherulitic aggregates. The carbon and oxygen isotopic composition of these precipitates (δ13C = +0.6 to −7.3‰ δ18O = −6.9 to −18.0‰ corresponds to those of known slowly precipitated cryogenic cave calcites under conditions of isotopic equilibrium between water and ice of Central European caves. The carbon and oxygen isotopic composition varies between different caves which is attributed to the effects of cave air ventilation before the freezing started.

    By petrographic and geochemical comparisons of Weichselian cryogenic calcite with recent to sub-recent precipitates as well as Weichselian non-cryogenic calcites of the same locality, a model for the precipitation of these calcites is proposed. While the recent and sub-recent pool-calcites isotopically match the composition of interglacial speleothems (stalagmites, etc., isotope ratios of Weichselian non-cryogenic pool-calcites reflect cooler conditions. Weichselian cryogenic calcites show a trend towards low δ18O values with higher carbon isotope ratios reflecting slow freezing of the precipitating solution. In essence, the isotope geochemistry of the Weichselian calcites reflects the climate history changing from overall initial permafrost conditions to permafrost-free and subsequently to renewed permafrost conditions. Judging from the data compiled here, the last permafrost stage in the Rätselhalle is followed by a warm period (interstadial and/or Holocene. During this warmer period, the cave ice melted and cryogenic and non-cryogenic Weichselian calcite precipitates were deposited on the cave ground or on fallen blocks, respectively.

  17. Biosorption of divalent Pb, Cd and Zn on aragonite and calcite mollusk shells

    Energy Technology Data Exchange (ETDEWEB)

    Du Yang; Lian Fei [Key Laboratory of Pollution Process and Environmental Criteria, Ministry of Education, Tianjin Key Laboratory of Urban Ecology Environmental Remediation and Pollution Control, College of Environmental Science and Engineering, Nankai University, Tianjin 300071 (China); Zhu Lingyan, E-mail: zhuly@nankai.edu.cn [Key Laboratory of Pollution Process and Environmental Criteria, Ministry of Education, Tianjin Key Laboratory of Urban Ecology Environmental Remediation and Pollution Control, College of Environmental Science and Engineering, Nankai University, Tianjin 300071 (China)

    2011-07-15

    The potential of using mollusk shell powder in aragonite (razor clam shells, RCS) and calcite phase (oyster shells, OS) to remove Pb{sup 2+}, Cd{sup 2+} and Zn{sup 2+} from contaminated water was investigated. Both biogenic sorbents displayed very high sorption capacities for the three metals except for Cd on OS. XRD, SEM and XPS results demonstrated that surface precipitation leading to crystal growth took place during sorption. Calcite OS displayed a remarkably higher sorption capacity to Pb than aragonite RCS, while the opposite was observed for Cd. However, both sorbents displayed similar sorption capacities to Zn. These could be due to the different extent of matching in crystal lattice between the metal bearing precipitate and the substrates. The initial pH of the solution, sorbent's dosage and grain size affected the removal efficiency of the heavy meals significantly, while the organic matter in mollusk shells affected the removal efficiency to a lesser extent. - Highlights: > Mollusk shells display high removal efficiency to heavy metals in contaminated water. > Surface precipitation leading to crystal growth takes place during the sorption. > Crystal structure similarity between precipitates and substrates affects the sorption. > pH, sorbent dosage and grain size of adsorbent affects the removal efficiency. > Organic matter in mollusk shells affects the removal efficiency to a less extent. - Mollusk shells display high sorption ability to heavy metals and crystal structure similarity between precipitates and substrates affects the sorption.

  18. Origin of calcite in the glacigenic Virttaankangas complex

    Directory of Open Access Journals (Sweden)

    Nina M. Kortelainen

    2007-01-01

    Full Text Available Groundwaters of the glacigenic Virttaankangas complex in southern Finland are characterized by high pH values ranging up to 9.5. These values are significantly higher than those observed in silicate-rich shallow groundwater formations in crystalline bedrock areas. TheVirttaankangas sediments were discovered to contain small amounts of fine grained, dispersed calcite, which has a high tendency to increase the pH of local groundwaters. The primary goal of this study was to determine the mode of occurrence of calcite and to identifyits sources. The mineralogy of the glacigenic Virttaankangas complex was studied using material from 21 sediment drill cores. Fine-grained calcite is present in trace amounts (<< 1.4 % in the glaciofluvial and glaciolacustrine depositional units of the Virttaankangas complex. The topmost littoral sands were practically devoid of calcite. The isotope records of carbon and oxygen, the angular morphology of the grains and the uniform dispersion of calcite in the complex suggest a clastic origin for calcite, with no evidence for in-situ precipitation. In order to constrain the source of calcite, the isotopic composition of carbon and oxygen in five calcite samples was compared to the isotopic data from five carbonate rock erratics and eight crystalline bedrock samples from the region. Based on carbon and oxygen isotope ratios and chemical compositions, the dispersed calcite grains of the Virttaankangas complex appear to have been derived from the Mesoproterozoic Satakunta Formation, some 30 km NW from the Virttaankangas area. In sandstone, calcite is predominantly present as diagenetic cement in grain interspaces, concretions and interlayers. The source of detrital calcite was unexpected, as prior to this study the Satakunta sandstone hasnot been known to contain calcite.

  19. Impact of trace metals on the water structure at the calcite surface

    Science.gov (United States)

    Wolthers, Mariette; Di Tommaso, Devis; De Leeuw, Nora

    2014-05-01

    Carbonate minerals play an important role in regulating the chemistry of aquatic environments, including the oceans, aquifers, hydrothermal systems, soils and sediments. Through mineral surface processes such as dissolution, precipitation and sorption, carbonate minerals affect the biogeochemical cycles of not only the constituent elements of carbonates, such as Ca, Mg, Fe and C, but also H, P and trace elements. Surface charging of the calcite mineral-water interface, and its reactivity towards foreign ions can be quantified using a surface structural model that includes, among others, the water structure at the interface (i.e. hydrogen bridging) [1,2] in accordance with the CD-MUSIC formalism [3]. Here we will show the impact of foreign metals such as Mg and Sr on the water structure around different surface sites present in etch pits and on growth terraces at the calcite (10-14) surface. We have performed Molecular Dynamics simulations of metal-doped calcite surfaces, using different interatomic water potentials. Results show that the local environment around the structurally distinct sites differs depending on metal presence, suggesting that metal substitutions in calcite affect its reactivity. The information obtained in this study will help in improving existing macroscopic surface model for the reactivity of calcite [2] and give more general insight in mineral surface reactivity in relation to crystal composition. [1] Wolthers, Charlet, & Van Cappellen (2008). Am. J. Sci., 308, 905-941. [2] Wolthers, Di Tommaso, Du, & de Leeuw (2012). Phys. Chem. Chem. Phys. 14, 15145-15157. [3] Hiemstra and Van Riemsdijk (1996) J. Colloid Interf. Sci. 179, 488-508.

  20. Textural properties of synthetic nano-calcite produced by hydrothermal carbonation of calcium hydroxide

    CERN Document Server

    Montes-Hernandez, German; Charlet, L; Tisserand, Delphine; Renard, F

    2008-01-01

    The hydrothermal carbonation of calcium hydroxide (Ca(OH)2) at high pressure of CO2 (initial PCO2 1/4 55 bar) and moderate to high temperature (30 and 90 1C) was used to synthesize fine particles of calcite. This method allows a high carbonation efficiency (about 95% of Ca(OH)2-CaCO3 conversion), a significant production rate (48 kg/m3 h) and high purity of product (about 96%). However, the various initial physicochemical conditions have a strong influence on the crystal size and surface area of the synthesized calcite crystals. The present study is focused on the estimation of the textural properties of synthesized calcite (morphology, specific surface area, average particle size, particle size distribution and particle size evolution with reaction time), using Rietveld refinements of X-ray diffraction (XRD) spectra, Brunauer-Emmett-Teller (BET) measurements, and scanning electron microscope (SEM) and transmission electron microscope (TEM) observations. This study demonstrate that the pressure, the temperatu...

  1. Seismic Anisotropy in Salt Structures Due to Preferred Crystal Orientation Anisotropie sismique dans les structures salifères due à l'orientation préférentielle des cristaux

    Directory of Open Access Journals (Sweden)

    Raymer D. G.

    2006-12-01

    Full Text Available Texture analysis of natural rock salt and experimentally deformed halite have shown that lattice preferred orientation of halite crystals does occur. The elastic parameters for a range of halite polycrystalline aggregates are calculated using orientation distribution functions. These are used to construct seismic models which are ray-traced through to investigate the potential effects of seismic anisotropy in salt structures. Anisotropic salt models show significant variation in travel time from the isotropic salt model and large shear-wave splitting is predicted. L'analyse de la texture du sel gemme naturel et du halite déformé expérimentalement a montré qu'il se produit une orientation préférentielle du réseau dans les cristaux de halite. Les paramètres d'élasticité pour une série d'agrégats polycristallins de halite sont calculés en utilisant les fonctions de distribution d'orientation. Ils sont alors utilisés pour élaborer des modèles sismiques dans lesquels sont tracés des rayons afin d'étudier les effets potentiels de l'anisotropie sismique dans les structures salifères. Les modèles salifères anisotropes montrent une variation significative dans le temps de propagation par rapport au modèle salifère isotrope, et un effet important de biréfringence des ondes transversales est prédit.

  2. A Reacidification Model for Acidified Lakes Neutralized With Calcite

    Science.gov (United States)

    Sverdrup, Harald; Warfvinge, Per

    1985-09-01

    In lake liming operations in Sweden, acidified lakes are reclaimed by neutralization with calcite powder. The amount added is intended to neutralize the water column as well as to delay the reacidification. The reacidification of limed lakes is dependent on the dilution of the dissolved calcium carbonate with time and, for a limited period of time, the dissolution of calcite from the lake sediments. Calcite on the lake bottom will, in addition to being covered by sedimentation, become inactivated by precipitates of humus and clay minerals clogging the calcite surfaces. A model has been developed to calculate the reacidification of a limed lake which includes the following mechanisms: (1) the dissolution of calcite and a subsequent neutralization of acid water, (2) owing to the increase inpH value, occurrence of precipitation of humus and dissolved metals onto the calcite surface and inhibition of the dissolution of calcite (3) reversible sorbtion of calcium from the water column by sediments not covered with calcite, and (4) diffusive transport through a boundary bottom layer to the water column. In a first approach the lake was modeled as a continuously stirred tank. The equations were derived from a mass balance and the dissolution kinetics for calcite to describe the long-term development ofpH, alkalinity, and calcium concentration in the lake. The differential equations describing the mechanisms were solved with the help of a computer code. The model accurately describes the reacidification and the mass balances observed in several limed lakes.

  3. Sorption and desorption of arsenate and arsenite on calcite

    DEFF Research Database (Denmark)

    Sø, Helle Ugilt; Postma, Diederik Jan; Jakobsen, Rasmus;

    2008-01-01

    The adsorption and desorption of arsenate (As(V)) and arsenite (As(111)) oil calcite was investigated in a series of batch experiments in calcite-equilibrated solutions. The solutions covered a broad range of pH, alkalinity, calcium concentration and ionic strength. The initial arsenic concentrat......The adsorption and desorption of arsenate (As(V)) and arsenite (As(111)) oil calcite was investigated in a series of batch experiments in calcite-equilibrated solutions. The solutions covered a broad range of pH, alkalinity, calcium concentration and ionic strength. The initial arsenic...

  4. Rare Earth element (REE) incorporation in natural calcite. Upper limits for actinide uptake in a secondary phase

    Energy Technology Data Exchange (ETDEWEB)

    Stipp, S.L.S.; Christensen, J.T.; Waight, T.E. [Geological Inst., Univ. of Copenhagen (Denmark); Lakshtanov, L.Z. [Geological Inst., Univ. of Copenhagen (Denmark); Inst. of Experimental Mineralogy, Russian Academy of Science, Chernogolovka (Russian Federation); Baker, J.A. [School of Earth Sciences, Victoria Univ. of Wellington (New Zealand)

    2006-07-01

    Secondary minerals have the potential to sequester escaped actinides in the event of a radioactive waste repository failure, but currently, data to define their maximum uptake capacity are generally lacking. To estimate a maximum limit for solid solution in calcite, we took advantage of the behavioural similarities of the 4f-orbital lanthanides with some of the 5f-orbital actinides and used rare Earth element (REE) concentration as an analogue. A suite of 65 calcite samples, mostly pure single crystals, was assembled from a range of geological settings, ages and locations and analysed by isotope dilution MC-ICP-MS (multiple-collector inductively-coupled plasma mass spectroscopy). All samples were shown to contain significant lanthanide concentrations. The highest were in calcite formed from hydrothermal solutions and from carbonatite magma. Maximum total mole fraction of REE was 4.72 x 10{sup -4}, which represents one substituted atom for about 2000 Ca sites. In comparison, synthetic calcite, precipitated at growth rates slow enough to insure solid solution formation, incorporated 7.5 x 10{sup -4} mole fraction Eu(III). For performance assessment, we propose that 7.5 mmole substitution/kg calcite should be considered the upper limit for actinide incorporation in secondary calcite. The largest source of uncertainty in this estimate results from extrapolating lanthanide data to actinides. However, the data offer confidence that for waters in the hydrothermal temperature range, such as in the near-field, or at groundwater temperatures, such as in the far-field, if calcite formation is favoured and actinides are present, those with behaviour like the trivalent lanthanides, especially Am{sup 3+} and Cm{sup 3+}, will be incorporated. REE are abundant and widely distributed, and they have remained in calcite for millions of years. Thus, one can be certain that incorporated actinides will also remain immobilised in calcite formed in fractures and pore spaces, as long as

  5. Calcite surface structure and reactivity: molecular dynamics simulations and macroscopic surface modelling of the calcite-water interface

    OpenAIRE

    Wolthers, M.; Di Tommaso, D.; Du, Z; de Leeuw, N. H.

    2012-01-01

    Calcite–water interactions are important not only in carbon sequestration and the global carbon cycle, but also in contaminant behaviour in calcite-bearing host rock and in many industrial applications. Here we quantify the effect of variations in surface structure on calcite surface reactivity. Firstly, we employ classical Molecular Dynamics simulations of calcite surfaces containing an etch pit and a growth terrace, to show that the local environment in water around structurally different s...

  6. Joint investigation of the local material rotation and lattice spin in a cube {l_brace}100{r_brace} <001> oriented single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Darrieulat, M; Fillit, R Y; Mondon, M; Sao-Joao, S, E-mail: darrieulat@emse.f [Ecole Nationale Superieure des Mines de Saint-Etienne, SMS Centre, UMR CNRS n0 5146, 158 cours Fauriel 42023 Saint-Etienne, cedex 2 (France)

    2010-07-01

    Cube {l_brace}100{r_brace} <001> oriented single crystals of Al 1% Mn were compressed in channel-die. Their lateral faces were covered with transferable carbon grids with a step of 100mm . At a deformation of about 0.3, the vertical bars of the grids show undulations whose characteristic length is of the order of the millimetre and which become sharper and smaller as the deformation proceeds. Fiducial golden grids with a step of 20 mm remain largely unaffected. This shows that the investigated heterogeneity is typical of the mesoscopic scale and has no directly related patterns at the macroscopic and microscopic level. Microfocussed X-rays were used to measure the crystallographic rotations during the process. The investigated spot was a few 0.1 mm{sup 2}. At a deformation of 0.6, the lateral faces of the crystal undergo a split into two Cube orientations each rotated of about 15{sup 0} around the transverse axis. This is put in relation with the undulations of the bars. At 0.9 an additional rotation around the longitudinal axis appears. The local material rotation and the lattice spin at the mesoscopic scale are interpreted in accordance with previous analyses of the evolution of the Cube texture based on EBSD and the observation of the traces of slip systems.

  7. One-on-One and R-on-One Tests on KDP and DKDP Crystals with Different Orientations

    Institute of Scientific and Technical Information of China (English)

    HU Guo-Hang; ZHAO Yuan-An; SUN Shao-Tao; LI Da-Wei; SUN Xun; SHAO Jian-Da; FAN Zheng-Xiu

    2009-01-01

    By testing a substantial number of tripler and z-cut KDP and DKDP crystals,we have observed that at 355 nm,the laser induced damage threshold in the R-on-one test is higher than that in the one-on-one test.It is proved that laser conditioning is an efficient way to improve the damage resistance.The efficiency of laser conditioning becomes increasingly good with smaller ramping fluence steps.We have also found that the damage resistance of the z-cut crystal is higher than the tripler cut,and the pinpoint number is definitely less in the z-cut crystal.The reason for these observations is discussed.

  8. The role of the crystal orientation (c-axis) on switching field distribution and the magnetic domain configuration in electrodeposited hcp Co–Pt nanowires

    Science.gov (United States)

    Shahid Arshad, Muhammad; Proenca, Mariana P.; Trafela, Spela; Neu, Volker; Wolff, Ulrike; Stienen, Sven; Vazquez, Manuel; Kobe, Spomenka; Žužek Rožman, Kristina

    2016-05-01

    In this report, Co–Pt nanowires (NWs) were produced via potentiostatic electrodeposition into commonly used commercial ordered-alumina and disordered-polycarbonate membranes with similar pore diameters (≈200 nm). The pore diameter of the membranes and the deposition conditions were chosen such that the Co–Pt NWs fabricated into both membranes had a hexagonal close packed (hcp) crystal structure with a crystallographic texturing of the c-axis in the direction perpendicular to the NWs’ long axis; this effect was more pronounced in the alumina membranes. Due to the local fluctuation in electrodeposition conditions (pore diameter, pore shape), we have found a small variation in the c-axis orientations in the plane perpendicular to the NWs’ long axis. Magnetic characterizations suggested that there is uniaxial anisotropy perpendicular to the Co–Pt NWs’ long axis and the small variation in the orientation of the hcp c-axis plays an important role in the switching-field distribution and the magnetic domain structure of the Co–Pt NWs. First order reversal curves (FORCs) revealed week magnetostatic interactions between Co–Pt NWs, thus suggesting that the different pore alignments are not influencing much the magnetic properties in both membranes. The micromagnetic simulation revealed that the transverse-stripe (TS) and longitudinal stripe (LS) domains are energetically most favorable structures in such NWs. This study accentuates the influence of the crystal orientation (c-axis) of the high-anisotropy materials on their functional magnetic properties and thus is of great importance for the fabrication of nanodevices based on such NWs.

  9. Relationship between the orientation of texture and heteroepitaxy of diamond and related materials films on silicon single crystal and the valence electron structure of the interface

    Institute of Scientific and Technical Information of China (English)

    LI; ZhiLin; LI; ZhiFeng; HUANG; Qin

    2007-01-01

    Diamond and cubic boron nitride films have already been applied practically because of their excellent properties. The specific orientations of the films have special meaning on their application in optics and microelectronics fields. In this paper, the relative electron density differences of the interface between the different crystal planes of silicon substrate and those of diamond and cubic boron films are calculated with the empirical electron theory in solids and molecules. Analyses on the calculation results show that in the range of the researched films, the smaller the relative electron density difference between the film and the substrate is, the stabler the film is in thermodynamics. Therefore, the electron density difference is the essential factor of determining the orientation of the texture and heteroepitaxy of the films. The deductions accord well with the experimental facts. The calculation methods and the theory not only provide a new angle of view for the research of the growth mechanism of diamond film and cubic boron nitride film on the silicon substrate, but also provide a possible direction for the prediction of the orientation of other films.

  10. Controlled sputtering of AlN (002) and (101) crystal orientations on epitaxial 3C-SiC-on-Si (100) substrate

    Science.gov (United States)

    Iqbal, A.; Walker, G.; Iacopi, A.; Mohd-Yasin, F.

    2016-04-01

    Aluminum Nitride (AlN) thin films are successfully deposited on epitaxial 3C-SiC-on-Si (100) substrates using DC magnetron sputterer. The sputtered films are characterized on the following parameters: crystal orientations (Siemens D500 X-Ray diffraction tool), deposition rate (Nanospec AFT 180), surface roughness (Park NX20 Atomic Force Microscopy), refractive index (Rudolph AutoEL IV Ellipsometer), in-plane stress (Tencor Flexus 2320 System) and Raman Spectra (Rennishaw InVia Spectrometer). XRD results demonstrate that the orientation of the AlN thin films can be changed from (002) to (101) by increasing the Nitrogen to Argon ratio from 40% to 80% at the total gas flow of 50 sccm. We are also able to tune the in-plane stress via RF biasing on the substrate. Both controlling abilities enable the applications of these thin films for low cost longitudinal piezoelectric devices and a quasi-shear mode devices using (002) and (101) orientations, respectively.

  11. The role of silicate surfaces on calcite precipitation kinetics

    DEFF Research Database (Denmark)

    Stockmann, Gabrielle J.; Wolff-Boenisch, Domenik; Bovet, Nicolas Emile;

    2014-01-01

    H equal to 9.1. Although the inlet fluid composition, flow rate, and temperature were identical for all experiments, the onset of calcite precipitation depended on the identity of the seeds present in the reactor. Calcite precipitated instantaneously and at a constant rate in the presence of calcite......The aim of this study is to illuminate how calcite precipitation depends on the identity and structure of the growth substrate. Calcite was precipitated at 25°C from supersaturated aqueous solutions in the presence of seeds of either calcite or one of six silicate materials: augite, enstatite......, labradorite, olivine, basaltic glass and peridotite rock. Calcite saturation was achieved by mixing a CaCl2-rich aqueous solution with a NaHCO3-Na2CO3 aqueous buffer in mixed-flow reactors containing 0.5-2g of mineral, rock, or glass seeds. This led to an inlet fluid calcite saturation index of 0.6 and a p...

  12. Calcite and dolomite in intrusive carbonatites. II. Trace-element variations

    Science.gov (United States)

    Chakhmouradian, Anton R.; Reguir, Ekaterina P.; Couëslan, Christopher; Yang, Panseok

    2016-04-01

    The composition of calcite and dolomite from several carbonatite complexes (including a large set of petrographically diverse samples from the Aley complex in Canada) was studied by electron-microprobe analysis and laser-ablation inductively-coupled-plasma mass-spectrometry to identify the extent of substitution of rare-earth and other trace elements in these minerals and the effects of different igneous and postmagmatic processes on their composition. Analysis of the newly acquired and published data shows that the contents of rare-earth elements (REE) and certain REE ratios in magmatic calcite and dolomite are controlled by crystal fractionation of fluorapatite, monazite and, possibly, other minerals. Enrichment in REE observed in some samples (up to ~2000 ppm in calcite) cannot be accounted for by coupled substitutions involving Na, P or As. At Aley, the REE abundances and chondrite-normalized (La/Yb)cn ratios in carbonates decrease with progressive fractionation. Sequestration of heavy REE from carbonatitic magma by calcic garnet may be responsible for a steeply sloping "exponential" pattern and lowered Ce/Ce* ratios of calcite from Magnet Cove (USA) and other localities. Alternatively, the low levels of Ce and Mn in these samples could result from preferential removal of these elements by Ce4+- and Mn3+-bearing minerals (such as cerianite and spinels) at increasing f(O2) in the magma. The distribution of large-ion lithophile elements (LILE = Sr, Ba and Pb) in rock-forming carbonates also shows trends indicative of crystal fractionation effects (e.g., concomitant depletion in Ba + Pb at Aley, or Sr + Ba at Kerimasi), although the phases responsible for these variations cannot be identified unambiguously at present. Overall, element ratios sensitive to the redox state of the magma and its complexing characteristics (Eu/Eu*, Ce/Ce* and Y/Ho) are least variable and in both primary calcite and dolomite, approach the average chondritic values. In consanguineous

  13. From nanometer aggregates to micrometer crystals

    DEFF Research Database (Denmark)

    Schultz, Logan Nicholas; Dideriksen, Knud; Lakshtanov, Leonid;

    2014-01-01

    and crystal shapes. Grain coarsening of calcite, CaCO3, is relevant for biomineralization and commercial products and is an important process in diagenesis of sediments to rock during geological time. We investigated coarsening of pure, synthetic calcite powder of sub-micrometer diameter crystals and...... one growth mechanism to the other. This has been poorly described by mean field coarsening models and offers predictive power to grain coarsening models. © 2014 American Chemical Society....

  14. Differences in the immobilization of arsenite and arsenate by calcite

    Science.gov (United States)

    Yokoyama, Yuka; Tanaka, Kazuya; Takahashi, Yoshio

    2012-08-01

    The sorption and coprecipitation experiments of arsenic (As) with calcite coupled with determinations of the chemical state of As both in the reaction fluid and in calcite were conducted to investigate the influence of the As oxidation state on its immobilization into calcite. The oxidation states of As in calcite and water were determined via As K-edge XANES and HPLC-ICP-MS analysis, respectively. The results of the sorption experiments at pH 8.2 show that only As(V) is distributed to calcite regardless of the As oxidation state in the solution. In coprecipitation experiments, As(V) is preferentially incorporated into calcite over a wide range of pH (7-12). On the other hand, the incorporation of As(III) into calcite is not observed at circumneutral pH. This difference between As(III) and As(V) is attributed to the fact that their dissolved species are neutral vs. negatively charged, respectively, at circumneutral pH (arsenite as H3AsO3; arsenate as H2AsO4- or HAsO42-). As the pH increases (>9), up to 33% of As(III)/Astotal ratio is partitioned into calcite or a precursor of calcite (metastable vaterite formed during the early stage of precipitation). The higher interaction of As with calcite at an alkaline pH compared with circumneutral pH is due to the negative charge of As(III) at alkaline pH. However, the As(III)/Astotal ratio decreases as time progresses and only As(V) can be found finally in calcite. The ratio of distribution coefficients of As(III) and As(V) into calcite (KAs(V)/KAs(III)) at pH ˜7 is larger than 2.1 × 103, suggesting that the oxidation state of As is a significant issue in considering the interaction between As and calcite in groundwater. Moreover, low KAs(III) shows that the sequestration of As via coprecipitation with calcite is not an important chemical process under reducing conditions, such as in the groundwaters in Bangladesh and other As-contaminated areas where As(III) is the dominant dissolved species of As. In the system spiked

  15. Molecular modeling studies of interactions between sodium polyacrylate polymer and calcite surface

    International Nuclear Information System (INIS)

    The interactions between calcite pigment and sodium polyacrylate dispersing agent, widely used in papermaking as paper coating components, were investigated using classical force field and quantum chemical approaches. The objective was to understand interactions between the calcite surface and sodium polyacrylate polymer at 300 K using molecular dynamics simulations. A quantum mechanical ab initio Hartree–Fock method was also used to obtain detailed information about the sodium polyacrylate polymer structure. The effect of water molecules (moisture) on the interactions was also examined. Calculations showed that molecular weight, branching and the orientation of sodium polyacrylate polymers influence the interactions between the calcite surface and the polymer. The force field applied, and also water molecules, were found to have an impact on all systems studied. Ab initio Hartree–Fock calculations indicated that there are two types of coordination between sodium atoms and carboxylate groups of the sodium polyacrylate polymer, inter- and intra-carboxylate group coordination. In addition, ab initio Hartree–Fock calculations of the structure of the sodium polyacrylate polymer produced important information regarding interactions between the polymers and carboxylated styrene-butadiene latex particles.

  16. Molecular modeling studies of interactions between sodium polyacrylate polymer and calcite surface

    Energy Technology Data Exchange (ETDEWEB)

    Ylikantola, A. [University of Jyväskylä, Department of Chemistry, P.O. Box 35, University of Jyväskylä, FI-40014 (Finland); Linnanto, J., E-mail: juha.m.linnanto@gmail.com [University of Jyväskylä, Department of Chemistry, P.O. Box 35, University of Jyväskylä, FI-40014 (Finland); University of Tartu, Institute of Physics, Riia 142, EE-51014 Tartu (Estonia); Knuutinen, J.; Oravilahti, A. [University of Jyväskylä, Department of Chemistry, P.O. Box 35, University of Jyväskylä, FI-40014 (Finland); Toivakka, M. [Åbo Akademi University, Laboratory of Paper Coating and Converting and Center for Functional Materials, FI-20500 Turku/Åbo (Finland)

    2013-07-01

    The interactions between calcite pigment and sodium polyacrylate dispersing agent, widely used in papermaking as paper coating components, were investigated using classical force field and quantum chemical approaches. The objective was to understand interactions between the calcite surface and sodium polyacrylate polymer at 300 K using molecular dynamics simulations. A quantum mechanical ab initio Hartree–Fock method was also used to obtain detailed information about the sodium polyacrylate polymer structure. The effect of water molecules (moisture) on the interactions was also examined. Calculations showed that molecular weight, branching and the orientation of sodium polyacrylate polymers influence the interactions between the calcite surface and the polymer. The force field applied, and also water molecules, were found to have an impact on all systems studied. Ab initio Hartree–Fock calculations indicated that there are two types of coordination between sodium atoms and carboxylate groups of the sodium polyacrylate polymer, inter- and intra-carboxylate group coordination. In addition, ab initio Hartree–Fock calculations of the structure of the sodium polyacrylate polymer produced important information regarding interactions between the polymers and carboxylated styrene-butadiene latex particles.

  17. Molecular modeling studies of interactions between sodium polyacrylate polymer and calcite surface

    Science.gov (United States)

    Ylikantola, A.; Linnanto, J.; Knuutinen, J.; Oravilahti, A.; Toivakka, M.

    2013-07-01

    The interactions between calcite pigment and sodium polyacrylate dispersing agent, widely used in papermaking as paper coating components, were investigated using classical force field and quantum chemical approaches. The objective was to understand interactions between the calcite surface and sodium polyacrylate polymer at 300 K using molecular dynamics simulations. A quantum mechanical ab initio Hartree-Fock method was also used to obtain detailed information about the sodium polyacrylate polymer structure. The effect of water molecules (moisture) on the interactions was also examined. Calculations showed that molecular weight, branching and the orientation of sodium polyacrylate polymers influence the interactions between the calcite surface and the polymer. The force field applied, and also water molecules, were found to have an impact on all systems studied. Ab initio Hartree-Fock calculations indicated that there are two types of coordination between sodium atoms and carboxylate groups of the sodium polyacrylate polymer, inter- and intra-carboxylate group coordination. In addition, ab initio Hartree-Fock calculations of the structure of the sodium polyacrylate polymer produced important information regarding interactions between the polymers and carboxylated styrene-butadiene latex particles.

  18. Existence and release of fluid inclusions in bornite and its associated quartz and calcite

    Science.gov (United States)

    Deng, Jiu-shuai; Wen, Shu-ming; Wu, Dan-dan; Liu, Jian; Zhang, Xiao-lin; Shen, Hai-ying

    2013-09-01

    The existence and release of fluid inclusions in bornite and its associated minerals, namely, quartz and calcite were investigated and confirmed. The structures, forms, and phases of these large quantities of fluid inclusions were also studied. A mass of fluid inclusions with various sizes, distributions, shapes, and phases exist in bornite and its associated minerals. Their sizes vary from a few micrometers to tens of micrometers, and the forms appear as negative crystals, or elongated, elliptical, and irregular. At room temperature, fluid inclusions were mainly characterized as gas-liquid twophase. However, small amounts of fluid inclusions with pure gas phase and pure liquid single-phase were also observed in quartz and calcite. These fluid inclusions initially broke during the ore crushing and grinding process and then released into the flotation pulp in the flotation process. The quantitative analysis of fluid inclusions in the solution and the comparisons of mineral dissolution show that the amount of copper and iron released by fluid inclusions in the bornite sample is higher than the amount dissolved by the mineral; fluid inclusions in the associated gangue minerals, quartz, and calcite also make contribution.

  19. Unique 1D Co3O4 crystallized nanofibers with (220) oriented facets as high-performance lithium ion battery anode material

    Science.gov (United States)

    Tan, Yanli; Gao, Qiuming; Li, Zeyu; Tian, Weiqian; Qian, Weiwei; Yang, Chunxiao; Zhang, Hang

    2016-01-01

    A novel one-step hydrothermal and calcination strategy was developed to synthesize the unique 1D oriented Co3O4 crystal nanofibers with (220) facets on the carbon matrix derived from the natural, abundant and low cost wool fibers acting as both carbon precursor and template reagent. The resultant W2@Co3O4 nanocomposite exhibited very high specific capacity and favorable high-rate capability when used as anode material of lithium ion battery. The high reversible Li+ ion storage capacity of 986 mAh g−1 was obtained at 100 mA g−1 after 150 cycles, higher than the theoretical capacity of Co3O4 (890 mAh g−1). Even at the higher current density of 1 A g−1, the electrode could still deliver a remarkable discharge capacity of 720 mAh g−1 over 150 cycles. PMID:27217201

  20. Unique 1D Co3O4 crystallized nanofibers with (220) oriented facets as high-performance lithium ion battery anode material.

    Science.gov (United States)

    Tan, Yanli; Gao, Qiuming; Li, Zeyu; Tian, Weiqian; Qian, Weiwei; Yang, Chunxiao; Zhang, Hang

    2016-01-01

    A novel one-step hydrothermal and calcination strategy was developed to synthesize the unique 1D oriented Co3O4 crystal nanofibers with (220) facets on the carbon matrix derived from the natural, abundant and low cost wool fibers acting as both carbon precursor and template reagent. The resultant W2@Co3O4 nanocomposite exhibited very high specific capacity and favorable high-rate capability when used as anode material of lithium ion battery. The high reversible Li(+) ion storage capacity of 986 mAh g(-1) was obtained at 100 mA g(-1) after 150 cycles, higher than the theoretical capacity of Co3O4 (890 mAh g(-1)). Even at the higher current density of 1 A g(-1), the electrode could still deliver a remarkable discharge capacity of 720 mAh g(-1) over 150 cycles. PMID:27217201

  1. The control of the growth orientations of electrodeposited single-crystal nanowire arrays: a case study for hexagonal CdS

    International Nuclear Information System (INIS)

    The controllable growth of highly aligned and ordered semiconductor nanowire arrays is crucial for their potential applications in nanodevices. In the present study, both the growth orientation and the microstructure of hexagonal CdS nanowire arrays electrodeposited in a porous alumina template with 40 nm diameter pores have been controlled by simply tuning the deposition current density. An extremely low current density of 0.05 mA cm-2 is favorable for the growth of single-crystal CdS nanowires along the normal direction of the intrinsic low-surface-energy (103) face. This can be understood well by a modified critical dimension model given in the present work

  2. Microstructure and Sn crystal orientation evolution in Sn-3.5Ag lead-free solders in high temperature packaging applications

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Bite [ORNL; Muralidharan, Govindarajan [ORNL; Kurumaddali, Nalini Kanth [ORNL; Parish, Chad M [ORNL; Leslie, Dr Scott [Powerex Inc; Bieler, T. R. [Michigan State University, East Lansing

    2014-01-01

    Understanding the reliability of eutectic Sn-3.5Ag lead-free solders in high temperature packaging applications is of significant interest in power electronics for the next generation electric grid. Large area (2.5mm 2.5mm) Sn-3.5Ag solder joints between silicon dies and direct bonded copper substrates were thermally cycled between 5 C and 200 C. Sn crystal orientation and microstructure evolution during thermal cycling were characterized by electron backscatter diffraction (EBSD) in scanning electron microscope (SEM). Comparisons are made between observed initial texture and microstructure and its evolution during thermal cycling. Gradual lattice rotation and grain boundary misorientation evolution suggested the continuous recrystallization mechanism. Recrystallization behavior was correlated with dislocation slip activities.

  3. Calcite Twins, a Tool for Tectonic Studies in Thrust Belts and Stable Orogenic Forelands Les macles de la calcite, un outil pour les études tectoniques dans les chaînes plissées et les avant-pays peu déformés des orogènes

    Directory of Open Access Journals (Sweden)

    Lacombe O.

    2010-10-01

    Full Text Available Calcite twins have been used for a long time as indicators of stress/strain orientations and magnitudes. Recent developments during the last 15 years point toward significant improvements of existing techniques as well as new applications of calcite twin analysis in thrust belts and forelands. This paper summarizes the principles of the most common techniques in this tectonic field and illustrates some aspects of the use of calcite twins to constrain not only stress/strain orientations and magnitudes, but also to some extent paleotemperature or paleoburial in orogenic forelands. This review is based in a large part on the studies that I conducted in various geological settings such as the forelands of Taiwan, Pyrenees, Zagros, Rockies and Albanides orogens. The contribution of calcite twin analysis to the understanding of the intraplate stress transmission away from plate boundaries is also emphasized. Les macles de la calcite sont utilisees depuis longtemps comme indicateurs de paleocontraintes et comme marqueurs de la deformation finie, en orientations comme en grandeurs. Au cours des 15 dernieres annees, des ameliorations importantes des methodes d’analyses existantes ont ete realisees et ont donne lieu a de nouvelles applications dans les chaines plissees et les avant-pays peu deformes des orogenes. Cet article resume le principe des methodes les plus utilisees en tectonique et illustre quelques apports de l’analyse des macles de la calcite pour la caracterisation non seulement des orientations et des grandeurs des paleocontraintes et de la deformation finie, mais egalement dans une certaine mesure de la paleotemperature et du paleoenfouissement. Cette revue se fonde en grande partie sur les etudes regionales que j’ai effectuees dans des contextes geologiques varies, comme les avant-pays des chaines de Taiwan, des Pyrenees, du Zagros, des Rocheuses et des Albanides. Cet article discutera egalement la contribution de l’etude des

  4. Uranyl incorporation into calcite and aragonite: XAFS and luminescence studies

    International Nuclear Information System (INIS)

    X-ray absorption, luminescence, and Raman spectroscopic studies of U(VI)-containing calcite and aragonite show that the UO22+ ion, the dominant and mobile form of dissolved uranium in near-surface waters, has a disordered and apparently less stable coordination environment when incorporated into calcite in comparison to aragonite, both common polymorphs of CaCO3. Their findings suggest that calcite, a widely distributed authigenic mineral in soils and near-surface sediments and a principal weathering product of concrete-based containment structures, is not likely to be a suitable host for the long-term sequestration of U(VI). The more stable coordination provided by aragonite suggests that its long-term retention should be favored in this phase, until it inverts to calcite. Consequently, future remobilization of U(VI) coprecipitated with calcium carbonate minerals should not be ruled out in assessments of contaminated sites. Their observation of a similar equatorial coordination of UO22+ in aragonite and the dominant aqueous species [UO2(CO3)34-] but a different coordination in calcite indicates that a change in UO22+ coordination is required for its incorporation into calcite. This may explain the observed preferential uptake of U(VI) by aragonite relative to calcite

  5. Assessment of the potential for dating secondary calcite and quartz in fault zones

    International Nuclear Information System (INIS)

    Calcite and quartz occur frequently as secondary minerals in faults. In many instances these minerals are not deformed. Calcite, for example, often exhibits an undisturbed fibrous habit or appears as euhedral crystals. Direct dating of euhedral crystals would provide a minimum age of the last movement along a fault, whereas dating of fibrous crystals would furnish the real age of the last movement. This information would be essential in the evaluation and selection of sites for both nuclear power reactors and nuclear waste disposal. In the Canadian context, to be successful, the technique should be able to date minerals as old as tens of millions of years. In this study both isotopic and radioactive damage techniques were considered. It was found that thermoluminescence, thermally stimulated current, and electron spin resonance offer possibilities. Recent electron spin resonance studies of ancient flints have yielded dates of several hundred million years. It is anticipated that in the near future a combination of the above techniques will be extensively used in the field of geochronology

  6. Surface analysis of free-standing GaN substrates with polar, nonpolar,and semipolar crystal orientations

    Czech Academy of Sciences Publication Activity Database

    Romanyuk, Olexandr; Jiříček, Petr; Mutombo, Pingo; Paskova, T.; Bartoš, Igor

    Bellingham: SPIE, 2013 - (Chyi, J.; Nanishi, Y.; Morkoc, H.; Piprek, J.; Yoon, E.; Fujioka, H.), "862521-1"-"862521-9". (Proceedings of SPIE. 8625). ISBN 978-0-8194-9394-1. ISSN 0277-786X. [SPIE Symposium on Gallium Nitride Materials and Devices /8./. San Francisco (US), 04.02.2013-07.02.2013] Grant ostatní: AV ČR(CZ) M100101201 Institutional support: RVO:68378271 Keywords : surface structure * non-polar GaN * semipolar GaN * LEED * photoelectron diffraction * crystal polarity Subject RIV: BM - Solid Matter Physics ; Magnetism http://dx.doi.org/10.1117/12.2006400

  7. Deposition-rate dependence of orientation growth and crystallization of Ti thin films prepared by magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Chen, A.Y.; Bu, Y.; Tang, Y.T. [School of Materials Science and Engineering, University of Shanghai for Science and Technology, Shanghai 200093 (China); Wang, Y., E-mail: wangye@smmu.edu.cn [Information Center, Second Military Medical University, Shanghai 200433 (China); Liu, F. [School of Materials Science and Engineering, University of Shanghai for Science and Technology, Shanghai 200093 (China); Xie, X.F. [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Gu, J.F. [School of Materials Science & Engineering, Shanghai Jiao Tong University, Shanghai 200030 (China)

    2015-01-01

    The effect of deposition rate on the microstructure of Ti thin films prepared by magnetron sputtering was investigated. The microstructure of Ti thin films was characterized by X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy and atomic force microscopy. The Ti thin films exhibit a composite structure of amorphous matrix embodied with nanocrystallines. The nanocrystallization is improved with the increase of deposition rate. XRD patterns show that the crystallographic orientation transits from random distribution to (002) preferred orientation, and this crystallographic growth texture is enhanced with increasing deposition rate. Three-dimensional hexagonal particles are formed at the deposition rate of 0.35 nm/s, while flaky slices occur at the surface at larger deposition rate. Moreover, the growth process of Ti thin films controlled by the deposition rate is discussed. - Highlights: • Deposition rate-controlled microstructure of Ti thin films was studied. • The microstructure is characterized by amorphous–nanocrystalline composite. • Crystallinity and texture are enhanced with increasing deposition rate. • A transition of growth mode from 3D islands to 2D flaky slices is observed.

  8. Deposition-rate dependence of orientation growth and crystallization of Ti thin films prepared by magnetron sputtering

    International Nuclear Information System (INIS)

    The effect of deposition rate on the microstructure of Ti thin films prepared by magnetron sputtering was investigated. The microstructure of Ti thin films was characterized by X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy and atomic force microscopy. The Ti thin films exhibit a composite structure of amorphous matrix embodied with nanocrystallines. The nanocrystallization is improved with the increase of deposition rate. XRD patterns show that the crystallographic orientation transits from random distribution to (002) preferred orientation, and this crystallographic growth texture is enhanced with increasing deposition rate. Three-dimensional hexagonal particles are formed at the deposition rate of 0.35 nm/s, while flaky slices occur at the surface at larger deposition rate. Moreover, the growth process of Ti thin films controlled by the deposition rate is discussed. - Highlights: • Deposition rate-controlled microstructure of Ti thin films was studied. • The microstructure is characterized by amorphous–nanocrystalline composite. • Crystallinity and texture are enhanced with increasing deposition rate. • A transition of growth mode from 3D islands to 2D flaky slices is observed

  9. Ionic conductivity in gem-quality single-crystal alkali feldspar from the Eifel: temperature, orientation and composition dependence

    Science.gov (United States)

    El Maanaoui, Hamid; Wilangowski, Fabian; Maheshwari, Aditya; Wiemhöfer, Hans-Dieter; Abart, Rainer; Stolwijk, Nicolaas A.

    2016-05-01

    We measured the ion conductivity of single-crystal alkali feldspar originating from two different locations in the Eifel/Germany, named Volkesfeld and Rockeskyller sanidine and having potassium site fractions C_K of 0.83 and 0.71, respectively. The dc conductivities resulting from electrochemical impedance spectroscopy over the temperature range of 300-900°C show a weak composition dependence but pronounced differences between the b-direction [perp (010)] and c^{*}-direction [perp (001)] of the monoclinic feldspar structure. Conductivity activation energies obtained from the observed linear Arrhenius plots are close to 1.2 eV in all cases, which is closely similar to the activation energies of the ^{22}Na tracer diffusivity in the same crystals. Taking into account literature data on K tracer diffusion and diffusion correlation effects, the present results point to a predominance of the interstitialcy mechanism over the vacancy mechanism in mass and charge transport on the alkali sublattice in potassium-rich alkali feldspar.

  10. Orientation and Temperature Dependence of Piezoelectric Properties for Sillenite-Type Bi12TiO20 and Bi12SiO20 Single Crystals

    Directory of Open Access Journals (Sweden)

    Chuanying Shen

    2014-06-01

    Full Text Available The full matrix of electro-elastic constants of sillenite-type crystals Bi12TiO20 (BTO and Bi12SiO20 (BSO were determined by the resonance method, with d14 and k14 being on the order of 40–48 pC/N and 31%–36%, respectively. In addition, double-rotated orientation dependence of d33 was investigated, with the maximum values of 25–28 pC/N being achieved in ZXtl45°/54°-cut samples. The electrical resistivity of BSO was found to be two orders higher than that of BTO, being on the order of 7 × 105 Ω cm at 500 °C. The temperature dependence of dielectric and piezoelectric properties were investigated. BSO exhibited a high thermal stability in the temperature range of 25–500 °C, while BTO showed a variation of ~3% in the range of 25–350 °C. The high values of d14 and k14, together with the good thermal stability, make BTO and BSO crystals potential candidates for electromechanical applications in medium temperature range.

  11. One-dimensional photonic crystals with a planar oriented nematic layer: Temperature and angular dependence of the spectra of defect modes

    International Nuclear Information System (INIS)

    Transmission spectra of a one-dimensional photonic crystal (PC) formed by two multilayer dielectric mirrors and a planar oriented layer of 5CB nematic liquid crystal (LC) that is sandwiched between these mirrors and serves as a structure defect are investigated experimentally. Specific features of the behavior of the spectrum of defect modes as a function of the angle of incidence of light on the crystal are studied for two polarizations: parallel and perpendicular to the director of the LC; the director either lies in the plane of incidence or is perpendicular to it. It is shown that, for the configurations considered, the maxima of the defect modes shift toward the short-wavelength region as the tilt angle of incidence radiation increases; this tendency is more manifest for the parallel-polarized component, when the director lies in the plane of incidence. In the latter case, the width of the photonic band gap (PBG) appreciably decreases. The temperature dependence of the polarization components of the transmission spectra of a PC is investigated in the case of normal incidence of light. The spectral shift of defect modes due to the variation of the refractive index of the LC at the nematic-isotropic liquid phase transition point is measured. It is shown that, in real PCs, the amplitude of defect modes decreases when approaching the center of the band gap, as well as when the number of layers in the dielectric mirrors increases. Theoretical transmission spectra of the PCs calculated by the method of recurrence relations with regard to the decay of defect modes are in good agreement with experimental data.

  12. One-dimensional photonic crystals with a planar oriented nematic layer: Temperature and angular dependence of the spectra of defect modes

    International Nuclear Information System (INIS)

    Transmission spectra of a one-dimensional photonic crystal (PC) formed by two multilayer dielectric mirrors and a planar oriented layer of 5CB nematic liquid crystal (LC) that is sandwiched between these mirrors and serves as a structure defect are investigated experimentally. Specific features of the behavior of the spectrum of defect modes as a function of the angle of incidence of light on the crystal are studied for two polarizations: parallel and perpendicular to the director of the LC; the director either lies in the plane of incidence or is perpendicular to it. It is shown that, for the configurations considered, the maxima of the defect modes shift toward the short-wavelength region as the tilt angle of incidence radiation increases; this tendency is more manifest for the parallel-polarized component, when the director lies in the plane of incidence. In the latter case, the width of the photonic band gap (PBG) appreciably decreases. The temperature dependence of the polarization components of the transmission spectra of a PC is investigated in the case of normal incidence of light. The spectral shift of defect modes due to the variation of the refractive index of the LC at the nematic-isotropic liquid phase transition point is measured. It is shown that, in real PCs, the amplitude of defect modes decreases when approaching the center of the band gap, as well as when the number of layers in the dielectric mirrors increases. Theoretical transmission spectra of the PCs calculated by the method of recurrence relations with regard to the decay of defect modes are in good agreement with experimental data

  13. One-dimensional photonic crystals with a planar oriented nematic layer: Temperature and angular dependence of the spectra of defect modes

    Science.gov (United States)

    Arkhipkin, V. G.; Gunyakov, V. A.; Myslivets, S. A.; Gerasimov, V. P.; Zyryanov, V. Ya.; Vetrov, S. Ya.; Shabanov, V. F.

    2008-02-01

    Transmission spectra of a one-dimensional photonic crystal (PC) formed by two multilayer dielectric mirrors and a planar oriented layer of 5CB nematic liquid crystal (LC) that is sandwiched between these mirrors and serves as a structure defect are investigated experimentally. Specific features of the behavior of the spectrum of defect modes as a function of the angle of incidence of light on the crystal are studied for two polarizations: parallel and perpendicular to the director of the LC; the director either lies in the plane of incidence or is perpendicular to it. It is shown that, for the configurations considered, the maxima of the defect modes shift toward the short-wavelength region as the tilt angle of incidence radiation increases; this tendency is more manifest for the parallel-polarized component, when the director lies in the plane of incidence. In the latter case, the width of the photonic band gap (PBG) appreciably decreases. The temperature dependence of the polarization components of the transmission spectra of a PC is investigated in the case of normal incidence of light. The spectral shift of defect modes due to the variation of the refractive index of the LC at the nematic-isotropic liquid phase transition point is measured. It is shown that, in real PCs, the amplitude of defect modes decreases when approaching the center of the band gap, as well as when the number of layers in the dielectric mirrors increases. Theoretical transmission spectra of the PCs calculated by the method of recurrence relations with regard to the decay of defect modes are in good agreement with experimental data.

  14. Calcite surface structure and reactivity: molecular dynamics simulations and macroscopic surface modelling of the calcite-water interface.

    Science.gov (United States)

    Wolthers, M; Di Tommaso, D; Du, Z; de Leeuw, N H

    2012-11-21

    Calcite-water interactions are important not only in carbon sequestration and the global carbon cycle, but also in contaminant behaviour in calcite-bearing host rock and in many industrial applications. Here we quantify the effect of variations in surface structure on calcite surface reactivity. Firstly, we employ classical Molecular Dynamics simulations of calcite surfaces containing an etch pit and a growth terrace, to show that the local environment in water around structurally different surface sites is distinct. In addition to observing the expected formation of more calcium-water interactions and hydrogen-bonds at lower-coordinated sites, we also observed subtle differences in hydrogen bonding around acute versus obtuse edges and corners. We subsequently used this information to refine the protonation constants for the calcite surface sites, according to the Charge Distribution MUltiSite Ion Complexation (CD-MUSIC) approach. The subtle differences in hydrogen bonding translate into markedly different charging behaviour versus pH, in particular for acute versus obtuse corner sites. The results show quantitatively that calcite surface reactivity is directly related to surface topography. The information obtained in this study is not only crucial for the improvement of existing macroscopic surface models of the reactivity of calcite towards contaminants, but also improves our atomic-level understanding of mineral-water interactions. PMID:23042085

  15. Biomineralisation in the Palaeozoic oceans: evidence for simultaneous crystallisation of high and low magnesium calcite by phacopine trilobites

    OpenAIRE

    Lee, M.; Torney, C.; Owen, A. W.

    2012-01-01

    The chemical composition and microstructure of the calcite cuticles of eleven species of phacopine trilobites have been investigated by electron beam imaging, diffraction, and microanalysis, and results reveal that the lenses of their schizochroal eyes differed significantly in chemical composition from the rest of the cuticle in vivo. Apart from the eye lenses, most cuticles are inferred to have escaped extensive recrystallisation because their constituent crystals are sub-micrometre in size ...

  16. Calcite fabric development during the spatial and temporal evolution of a high-strain zone

    Science.gov (United States)

    Buchan, C.; Reddy, S.

    2003-04-01

    High-strain zones commonly have complex deformation histories because of the spatial and temporal localisation of deformation during their development. Linking microstructural development to particular stages of this progressive deformation may provide a significant advance in our understanding of how high-strain zones develop but such studies are difficult unless the temporal framework of deformation can be constrained. The Gressoney Shear Zone (GSZ) in the Italian Alps is a kilometre-wide, calcite-dominated high strain zone characterised by top-SE movement related to crustal extension. Rb-Sr dating of micas within different fabrics recrystallised below their blocking temperature thus recording the time of deformation, show that the GSZ developed between c. 45 -- 36 Ma ago. This well constrained temporal and kinematic framework provides an excellent opportunity to investigate the microstructural evolution of high strain rocks. Electron Backscatter Diffraction (EBSD) has been utilised to: 1) characterise the effects of grain size on crystallographic preferred orientations (CPO); 2) establish the relationship of calcite deformation mechanisms to misorientations; and 3) compare deformation processes in naturally-deformed samples with experimental data. In most cases, samples record a similar CPO with (0001) lying parallel to the shear zone boundary. Coarser grains (>200 μm) record e-twinning but also the development of low-angle boundaries and core/mantle structures indicative of sub-grain rotation. Smaller grains (10--200 μm) show no evidence of twinning and generally record similar (0001) CPO to coarser grains. The samples with older mica ages exhibit more variability with significant differences in CPO. Within all samples, r- and f- planes show no preferred orientation and slip directions associated with these calcite slip planes are randomly distributed. Our data indicates considerably more complexity than experimentally deformed calcite and are not readily

  17. Calcite Twinning in the Ordovician Martinsburg Formation, Delaware Water Gap, New Jersey, USA: Implications for Cleavage Formation and Tectonic Shortening in the Appalachian Piedmont Province

    Directory of Open Access Journals (Sweden)

    John P. Craddock

    2016-02-01

    Full Text Available A traverse across the Stone Church syncline in the Ordovician Martinsburg turbidites reveals an axial planar cleavage (N40°E, SE dips in regional thrust-related folds (N40°E, shallow plunges and five phases of sparry calcite. Calcite fillings are bedding-parallel, cleavage-parallel, and one vein set cross-cuts both earlier phases; the youngest calcite filling is a bedding-parallel fault gouge that crosscuts the cleavage and preserves top-down-to-the-southeast normal fault kinematics. Calcite veins unique to disharmonically-folded calcareous siltstones (Maxwell, 1962 were also analyzed. Stable isotopic analysis (O, C of all of the calcite phases indicates a uniform fluid source (δ13C −2.0, δ18O −13.3 VPDB and, potentially, a similar precipitation and mechanical twinning age. The twinning strains (n = 1341; average Δσ = −32 MPa; average ε1 = −2.9% in the calcite suite are consistent with SE-NW thrust shortening, and sub-horizontal shortening perpendicular to evolving axial planar cleavage planes in the Stone Church syncline. Calcareous siltstone layers within the Martinsburg Fm. turbidites share concordant bedding planes and are unique, chemically (XRF, but folded and cleaved differently than the surrounding clay-rich Martinsburg turbidites. Neither sediment type yielded detrital zircons. Electron backscatter X-ray diffraction (EBSD and calcite twinning results in a folded calcareous siltstone layer preserving a layer-normal SE-NW shortening strain and Lattice Preferred Orientation (LPO. Shortening axes for the five-phase calcite suite trends ~N40°W, consistent with tectonic transport associated with crystalline nappe emplacement of the Reading Prong within the Piedmont province.

  18. Molecular ordering of ethanol at the calcite surface

    DEFF Research Database (Denmark)

    Pasarín, I. S.; Yang, M.; Bovet, Nicolas Emile;

    2012-01-01

    dynamics (MD) simulations, the structuring on calcite of a layer of the simplest carbon chain molecule that contains an OH group, ethanol (CH 3-CH2-OH). We found evidence that EtOH forms a highly ordered structure at the calcite surface, where the first layer molecules bond with calcite. The ethanol...... molecules stand up perpendicularly at the interface or nearly so. As a consequence, the fatty, CH3 ends form a new surface, about 6 Å from the termination of the bulk calcite, and beyond that, there is a thin gap where ethanol density is low. Following is a more disordered layer that is two to three...... ethanol molecules thick, about 14 Å, where density more resembles that of bulk liquid ethanol. The good agreement between theory and experiment gives confidence that a theoretical approach can offer information about behavior in more complex systems. © 2012 American Chemical Society....

  19. Nuclear anomalies in the buccal cells of calcite factory workers

    OpenAIRE

    Songül Budak Diler; Serap Ergene

    2010-01-01

    The micronucleus (MN) assay on exfoliated buccal cells is a useful and minimally invasive method for monitoring genetic damage in humans. To determine the genotoxic effects of calcite dust that forms during processing, MN assay was carried out in exfoliated buccal cells of 50 (25 smokers and 25 non-smokers) calcite factory workers and 50 (25 smokers and 25 non-smokers) age- and sex-matched control subjects. Frequencies of nuclear abnormalities (NA) other than micronuclei, such as binucleates,...

  20. Kinetics and Mechanisms of Calcite Reactions with Saline Waters

    Energy Technology Data Exchange (ETDEWEB)

    Chapman, Piers; *Morse, John W. (*/deceased)

    2010-11-15

    1. Objective The general objective of this research was to determine the kinetics and mechanisms of calcite reactions with saline waters over a wide range of saline water composition, carbon dioxide partial pressure (pCO2), and modest ranges of T and P. This would be done by studying both reaction rates and solubility from changes in solution chemistry. Also, nanoscale observations of calcite surface morphology and composition would be made to provide an understanding of rate controlling mechanisms.

  1. Effects of crystal orientation on the tensile and shear deformation of nickel–silicon interfaces: A molecular dynamics simulation

    International Nuclear Information System (INIS)

    Highlights: ► The deformation and fracture mechanisms of Si–Ni interfaces under tensile and shear loads were studied by MD simulations. ► A higher tensile strength is obtained for interface planes with higher density. ► Sliding of atomic planes occurs at planes with a high density that leads to a fluctuation in the stress–strain curve. ► Amorphization of the interface region was observed when sliding of low density planes was not easy to occur. ► The relationship between the interface strength and the planar density and the width of the disorder zone was demonstrated. - Abstract: Atomistic simulation was used to study the deformation and fracture mechanisms of Ni–Si interfaces under tensile and shear loads dependent on the crystal structure of interface zone. Modified embedded atom method (MEAM) potential was utilized for molecular dynamics (MD) modeling. The simulation includes analysis of common neighbors, coordination number, least-square atomic local strain, and radial distribution function. The profound effect of interface crystallography on the tensile and shear deformation is shown. The highest tensile strength is obtained for interfaces with high plane density due to lowest atomic disorder while under shear loading planes with low density exhibit a high local deformation as a result of regional atomic amorphization. The deformation mechanism in shear mode is shown to be controlled by planner sliding and local amorphization at the interface zone. A general agreement between the strength and atomic planar density at the interface is demonstrated.

  2. Palaeotemperature reconstruction during the Last Glacial from δ18O of earthworm calcite granules from Nussloch loess sequence, Germany

    Science.gov (United States)

    Prud'homme, Charlotte; Lécuyer, Christophe; Antoine, Pierre; Moine, Olivier; Hatté, Christine; Fourel, François; Martineau, François; Rousseau, Denis-Didier

    2016-05-01

    The Nussloch loess-palaeosol sequence (Rhine Valley, Germany) is considered to be one of the most complete records of the last glacial period in Western Europe due to its very high sedimentation rate and its good chronological control. This sequence is therefore a good framework in which to develop new proxies for palaeoenvironmental reconstructions. In this study, we explore, for the first time, the potential of earthworm calcite granules as a new bio-indicator and climatic proxy of absolute air and soil temperature in the context of Last Glacial loess. These granules are composed of rhomboedric calcite crystals, organized in a radial crystalline structure. As these granules are individually generated by earthworms at a relative fast rate, they are expected to record intra-annual variations in the available sources of oxygen: percolating waters of meteoric origin. We extracted thirty earthworm calcite granules from 11 of 5 cm layers thick from tundra gley and brown soil horizons previously, dated at 45 to 23 ka. Oxygen isotope ratios were measured on each individual granule. The δ18O of calcite granules and interlinked transfer functions between water cycle, air and soil temperatures allowed us to estimate air temperatures ranging from 10 to 12 ± 4°C, which most likely reflect the warm periods of the year when earthworms were the most active.

  3. Orientation Dependence of Functional Properties in Heterophase Single Crystals of the Ti36.5Ni51.0Hf12.5 and Ti48.5Ni51.5 Alloys

    Science.gov (United States)

    Panchenko, E. Yu.; Chumlyakov, Yu. I.; Surikov, N. Yu.; Tagiltsev, A. I.; Vetoshkina, N. G.; Osipovich, K. S.; Maier, H.; Sehitoglu, H.

    2016-03-01

    The features of orientation dependence of stress-induced thermoelastic B2-( R)- B19'-martensitic transformations in single crystals of the Ti48.5Ni51.5 and Ni51.0Ti36.5Hf12.5 (at.%) alloys, which contain disperse particles of the Ti3Ni4 and H-phase, respectively, are revealed along with those of their shape-memory effects (SME) and superelasticity (SE). It is experimentally demonstrated that irrespective of the crystal structure of disperse particles measuring more than 100 nm, for their volume fraction f > 16% there is a weaker orientation dependence of the reversible strain in the cases of manifestation of SME and SE. In the orientations of Class I, wherein martensitic detwinning introduces a considerable contribution into transformation strain, the values of SME |ɛ SME | and SE |ɛ SE | decrease by over a factor of two compared to the theoretical lattice strain value |ɛ tr0 | for a B2- B19'-transformation and the experimental values of reversible strain for quenched TiNi crystals. In the orientations of Class 2, wherein detwinning of the martensite is suppressed as is the case in quenched single-phase single crystals, the reversible strain is maintained close to its theoretical value |ɛ tr0 |. Micromechanical models of interaction between the martensite and the disperse particles are proposed, which account for the weaker orientation dependence of |ɛ SME | and |ɛ SE | due to suppression of detwinning of the B19'-martensite crystals by the particles and a transition from a single-variant evolution of the stress-induced martensitic transformations to a multiple-variant evolution of transformations in the cases of increased size of the particles and their larger volume fractions.

  4. The effect of substrate orientation on the kinetics of ultra-thin oxide-film growth on Al single crystals

    International Nuclear Information System (INIS)

    The kinetics of ultra-thin (O2=1x10-4Pa was investigated by real-time in situ spectroscopic ellipsometry. It follows that the oxide-film growth kinetics depends strongly on the parent metal substrate orientation. On Al{1 0 0} and Al{1 1 0}, the growth kinetics can be subdivided into an initial, very fast oxidation stage and a subsequent very slow oxidation stage, which is characterized by the occurrence of a near-limiting oxide-film thickness that increases with increasing temperature. On Al{1 1 1}, the initial, very fast growth rate decreases more gradually with increasing oxidation time and an unexpected decrease of oxide-film thickness, for an oxidation time of 6000 s, with increasing temperature up to 475 K is observed. The rate-limiting step(s) and mechanism(s) of the oxidation process were identified by a quantitative model description of the oxide-film growth kinetics on the basis of coupled currents of electrons (by both tunneling and thermionic emission) and cations under influence of a surface-charge field. It followed that the unexpected decrease of the oxide-film thickness with increasing temperature on Al{1 1 1} is due to a slow increase of the (relatively low) activation energy barrier for cation transport in combination with a constant kinetic potential due to the surface-charge field within the amorphous oxide-film regime (up to T ≤ 450 K). For Al{1 0 0} and Al{1 1 0}, the energy barrier for cation transport, as well as the kinetic potential, increase with increasing temperature due to, as compared to Al{1 1 1}, a more gradual amorphous-to-crystalline transition, which already starts at lower temperatures T < 400 K

  5. Calcite precipitation on glass substrates and active stalagmites in Katerloch Cave (Austria): Constraints from environmental monitoring

    Science.gov (United States)

    Sakoparnig, Marlene; Boch, Ronny; Wang, Xianfeng; Lin, Ke; Spötl, Christoph; Leis, Albrecht; Gollowitsch, Anna; Dietzel, Martin

    2016-04-01

    Located near Graz at the SE-rim of the Alps Katerloch is well-known for its impressive dripstone decoration, e.g. several metres tall and relatively fast growing (0.2-0.7 mm/yr on average) candle-stick-type stalagmites. In the course of an ongoing multi-annual and partially high-resolution cave monitoring program we study modern (active) sites of carbonate deposition focusing on the site-specific growth dynamics and connection of modern regional and cave environmental conditions with petrographic, chemical and stable isotopic information captured in the speleothems. Fresh calcite precipitates on artificial (glass) substrates underneath active drip sites were collected continuously from 2006 to 2014 (eight years!). The samples (up to 7 mm thick) represent cave sections of different temperature and drip sites of partially different characteristics (e.g. drip rate). We also recovered short drill cores (up to 3 cm length, 1 cm diameter) from the top of active stalagmites probably representing the last decades to centuries of calcite crystallization. Moreover, an actively growing stalagmite (K10) comprising both modern and past calcite deposition was collected. 238U-234U-230Th dating using MC-ICP-MS of K10 (71 cm long) revealed several distinct growth intervals (separated by growth interruptions) starting at 129.1 ±1.2 kyr BP (Last Interglacial) up to now, mostly reflecting warm and humid climate intervals. High-resolution (100 μm) isotope profiles micromilled from the multi-annual modern calcite precipitates on artificial substrates revealed low δ13C values of -12.8 to -8.3 ‰ (VPDB) and relatively high δ18O of -6.9 to -4.9 ‰Ṫhe δ18O curves from all collection sites (different growth rate) record a pronounced decrease during their most recent growth period most likely corresponding to a significant decrease towards lower oxygen isotope values observed in drip waters collected in the year 2014 compared with samples from 2005 to 2007. Drip water δ2H /δ18O

  6. THE ORIENTATION OF CaCO3 ARAGONITE CRYSTALS FROM SEVERAL ORGANISMS%几种生物CaCO3霰石结晶的取向性

    Institute of Scientific and Technical Information of China (English)

    蒋新农; 李敬之; 徐学红

    2001-01-01

    The CaCO3 crystals are widely distributed in organisms. Thecalcite, aragonite and vaterite are the main crystal polymorphisms of CaCO3. In this paper, CaCO3 crystals were obtained from the nacreous layers of Hyriopsis cumingii Lea and Pinctada martensii Dunker, the internal shell of a cuttlefish and the otolith of Pseudosciaena crocea. X-ray diffraction measurement was used to analyze the crystal orientation of CaCO3 crystals: The results showed that each kind of natural CaCO3 crystal has an orientation on specific plane. In detail, the crystal orientations of the nacreous layers are higher than the internal shell, and the orientation of the otolith is the lowest. Except the nacreous layers of Pinctada martensii, whose highest peak is on the crystal plane (312), all the other three natural samples have the highest peak on the crystal plane (012). As to ground CaCO3 crystals, the differences between their corresponding d values are very small, so each ground sample has the CaCO3 aragonite structure characterized by the JCPDS card (5-0453).%CaCO3结晶广泛分布于生物界,其主要结晶形式为方解石、霰石及球霰石。用X-射线衍射法对三角帆蚌及合浦珍珠母贝的珍珠层、墨鱼骨和大黄鱼耳石的CaCO3结晶进行测定,发现各样品均有一定取向性,以三角帆蚌和合浦珍珠母贝珍珠层的取向性为最强,墨鱼骨的取向性次之,大黄鱼耳石的取向性最小,以上材料粉末样的衍射分析表明,各样品对应d值间差异极小,均为X射线衍射卡(5-0453)所表征的CaCO3霰石结构。

  7. Effects of electrolysis and bath conditions on the surface roughness, morphology and crystal orientation of zinc electrodeposit. Denki aen mekki himaku no hyomen arasa to kessho jotai ni oyobosu denkai joken, yokujoken no eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Sagiyama, M.; Kawabe, M.; Watanabe, T. (NKK Corporation, Tokyo (Japan). Steel Research Center)

    1990-08-01

    Under controlled plating conditions zinc metal coatings were electrodeposited on steel substrates from a bath or a chloride bath. The surface roughness of a zinc electrodeposit was measured by means of tracer method and an aggregation of its crystals was analyzed by means of electronmicroscopy and X-ray diffraction. It is found that with increasing current density increases the surface roughness of the zinc metal coatings deposited from the sulfate bath and also the chloride bath except when current density is less than 0.4A/cm {sup 2}. A detailed description is given of the result that as the mass transfer of Zn {sup 2 {plus}} is promoted in the sulfate bath, a decrease in the surface roughness of zinc electrodeposit results from the growth of stacked platy crystals whose (0001) basal planes are oriented in the direction parallel or slightly oblique to the substrate surface, while as the mass transfer of Zn {sub 2 {plus}} is retarded in the same bath, the surface roughness of the deposit increases due to the growth of minute platy crystals whose <1120> direction is oriented in the direction pependicular to the substrate surface. In this connection, an account is given of the preferred orientation of crystals in zinc electrodeposits. 14 refs., 13 figs., 1 tab.

  8. Blistering and exfoliation during annealing of a-axis oriented α-Al2O3 single crystals implanted with oxygen ions

    International Nuclear Information System (INIS)

    During a study of damage accumulation and its annealing in α-Al2O3 implanted with oxygen self ions, blister formation has been observed beyond a critical dose. Damage-free α-axis oriented single crystals of Al2O3 were implanted at liquid-nitrogen temperature with 55 keV oxygen ions to doses of (0.1-6)x1016 ions/cm2. Annealing was performed in argon ambient at 700, 800 and 900degC. At the highest dose, the as-implanted samples were amorphous and exhibited blistering and exfoliation effects after annealing at all temperatures. The threshold critical doses for amorphisation and for thermal blistering at 700degC have been evaluated and are both found to be (3-4)x1016 ions/cm2. This similarity and the absence of blistering without annealing indicates that excess implanted oxygen behaves like an inert gas in Al2O3 which does not permit any deviations from stoichiometry. Negligibly small solubility or reactivity of excess oxygen is thus demonstrated. (orig.)

  9. Desired crystal oriented LiFePO4 nanoplatelets in situ anchored on a graphene cross-linked conductive network for fast lithium storage.

    Science.gov (United States)

    Wang, Bo; Liu, Anmin; Abdulla, Wael Al; Wang, Dianlong; Zhao, X S

    2015-05-21

    Electron transfer and lithium ion diffusion rates are the key factors limiting the lithium ion storage in anisotropic LiFePO4 electrodes. In this work, we employed a facile solvothermal method to synthesize a "platelet-on-sheet" LiFePO4/graphene composite (LFP@GNs), which is LiFePO4 nanoplatelets in situ grown on graphene sheets with highly oriented (010) facets of LiFePO4 crystals. Such a two-phase contact mode with graphene sheets cross-linked to form a three-dimensional porous network is favourable for both fast lithium ion and electron transports. As a result, the designed LFP@GNs displayed a high rate capability (∼56 mA h g(-1) at 60 C) and long life cycling stability (∼87% capacity retention over 1000 cycles at 10 C). For comparison purposes, samples ex situ modified with graphene (LFP/GNs) as well as pure LiFePO4 platelets (LFP) were also prepared and investigated. More importantly, the obtained LFP@GNs can be used as a basic unit for constructing more complex structures to further improve electrochemical performance, such as coating the exposed LFP surface with a thin layer of carbon to build a C@LFP@GN composite to further enhance its cycling stability (∼98% capacity retention over 1000 cycles at 10 C). PMID:25908535

  10. A Raman spectroscopic comparison of calcite and dolomite.

    Science.gov (United States)

    Sun, Junmin; Wu, Zeguang; Cheng, Hongfei; Zhang, Zhanjun; Frost, Ray L

    2014-01-01

    Raman spectroscopy was used to characterize and differentiate the two minerals calcite and dolomite and the bands related to the mineral structure. The (CO3)(2-) group is characterized by four prominent Raman vibrational modes: (a) the symmetric stretching, (b) the asymmetric deformation, (c) asymmetric stretching and (d) symmetric deformation. These vibrational modes of the calcite and dolomite were observed at 1440, 1088, 715 and 278 cm(-1). The significant differences between the minerals calcite and dolomite are observed by Raman spectroscopy. Calcite shows the typical bands observed at 1361, 1047, 715 and 157 cm(-1), and the special bands at 1393, 1098, 1069, 1019, 299, 258 and 176 cm(-1) for dolomite are observed. The difference is explained on the basis of the structure variation of the two minerals. Calcite has a trigonal structure with two molecules per unit cell, and dolomite has a hexagonal structure. This is more likely to cause the splitting and distorting of the carbonate groups. Another cause for the difference is the cation substituting for Mg in the dolomite mineral. PMID:23988531

  11. Photoinduced synthesis of single-digit micrometer-size spheroidal calcite composites in the presence of partially hydrolyzed poly(vinyl alcohol)

    Science.gov (United States)

    Nishio, Takashi; Naka, Kensuke

    2015-06-01

    Photoinduced crystallization of calcium carbonate (CaCO3), which was based on the photodecarboxylation of ketoprofen (KP, 2-(3-benzoylphyenyl)propionic acid) under alkaline conditions of pH 8.4 and 10 was studied for preparation of CaCO3 composite particles in single-digit micrometer-sizes. In this method, a homogeneous solution comprising KP, calcium chloride, ammonia, and partially hydrolyzed poly(vinyl alcohol) (PVAPS, degree of saponification: 86.5-89.0 mol%) was used as a precursor solution and was exposed to ultraviolet (UV) irradiation for different time periods. After the UV irradiation for 50 min, calcite spheroids in single-digit micrometer-sizes were obtained as major products at pH 8.4. The obtained calcite spheroids contained organic components of about 10 wt%. The comparison of the characteristics of the CaCO3 obtained at pH 8.4 and 10 suggests that the nucleation and crystallization of both vaterite and calcite continuously took place in a moderated supersaturation owing to the CO2 hydration equilibrium as long as the photodecarboxylation of KP continued. Consequently, the aggregation-based crystal growth in the presence of PVAPS seemed to enable the formation of the spheroidal composites of calcite in single-digit micrometer-sizes.

  12. Separation of deviatoric stress tensors from heterogeneous calcite twin data using a statistical mixture model

    Science.gov (United States)

    Yamaji, Atsushi

    2016-04-01

    It is essential for the techniques of paleostress analysis to separate stresses from heterogeneous data (e.g., Tikoff et al., 2013). A statistical mixture model is shown in this paper to be effective for calcite twinning paleopiezometry: Given the orientations of twinned e-planes and their gliding directions, the present inverse method based on the mixture model determines not only deviatoric stress tensors, but also estimates the number of tensors that should be read from a data set using Bayesian information criterion. The present method is based on the fact that mechanical twinning occurs on an e-plane if the resolved shear stress along its gliding direction, τ, is greater than a critical value, τc (e.g., Lacombe, 2010). The orientation data from e-planes corresponds to points on a 5-dimensional unit sphere, a spherical cap on which indicates a deviatoric stress tensor. The twinning condition, τ > τc, is identical with the condition that the points corresponding to the orientation data are distributed upon the spherical cap (Yamaji, 2015a). It means that the paleostress analysis of calcite twins comes down to the problem of fitting a spherical cap to data points on the sphere (Yamaji, 2015b). Given a heterogeneous data set, two or more spherical caps should be fitted to the data point on the sphere. A statistical mixture model is employed for this fitting in the present work. Such a statistical model enables us to evaluate the number of stresses recorded in the data set. The present method was tested with artificial data sets and a natural data set obtained from a Miocene graben in central Japan. From the former type of data sets, the method determined the deviatoric stress tensors that were assumed to generate the data sets. The natural data were inverted to give two stresses that appeared appropriate for the tectonic setting of the area where the data were obtained.

  13. Study of delta18O calcite-dolomite mixtures

    International Nuclear Information System (INIS)

    Isotope ratio of oxygen in carbonate mixtures has been studied. For the purpose samples of calcite and dolomite with the known values delta18O are mixed in the ratios 9:1, 3:1, 1:1, 1:3, 1:9. Then from the mixtures prepared CO2 gas is separated using the McCrea method, delta18O of the gas is measured using mass-srectrometer. It has been established that to obtain delta18O calcite in the mixtures with calcite excess CO2 gas should be collected in the interval 15-30 min of the reaction duration and for the mixtures with dolomite excess - in the interval 5-15 min. To determine delta18O of dolomite the optimum time of CO2 gas collection for all the mixtures is 4-24 h

  14. Carbon isotopic thermometry calibrated by dolomite-calcite solvus temperatures

    International Nuclear Information System (INIS)

    The temperature dependence of carbon isotopic fractionations between calcite and graphite, and between dolomite and graphite are calibrated by the calcite-dolomite solvus geothermometry using marbles collected from the contact metamorphic aureole in the Kasuga area, central Japan. The carbon isotopic fractionations systematically decrease with increasing metamorphic temperature. The concordant relationships between the fractionations and solvus temperatures which are presented, are approximately linear with T-2 over the temperature range, 400 deg to 680 deg C. They suggest that carbon isotopic equilibria between carbonates and graphite were attained in many cases. The equation for the calcite-graphite system has a slope steeper than Bottinga's (1969) results. It is, however, in good agreement with that of Valley and O'Neil (1981) in the temperature range from 600 deg to 800 deg C. Because of the relatively high sensitivity to temperature, these isotopic geothermometers are useful for determining the temperatures in moderate- to high-grade metamorphosed carbonate rocks. (author)

  15. Crystal orientation dependence of band matching in all-B2-trilayer current-perpendicular-to-plane giant magnetoresistance pseudo spin-valves using Co{sub 2}Fe(Ge{sub 0.5}Ga{sub 0.5}) Heusler alloy and NiAl spacer

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jiamin; Hono, K., E-mail: kazuhiro.hono@nims.go.jp [National Institute for Materials Science, 1-2-1, Sengen, Tsukuba 305-0047 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-2-1, Sengen, Tsukuba 305-0047 (Japan); Furubayashi, T.; Takahashi, Y. K.; Sasaki, T. T. [National Institute for Materials Science, 1-2-1, Sengen, Tsukuba 305-0047 (Japan)

    2015-05-07

    We have experimentally investigated the crystal orientation dependence of band matching in current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) pseudo-spin-valves using Co{sub 2}Fe(Ge{sub 0.5}Ga{sub 0.5}) (CFGG) Heusler alloy ferromagnetic layer and NiAl spacer. The high quality epitaxial CFGG/NiAl/CFGG all-B2-trilayers structure devices were fabricated on both MgO(001) and sapphire (112{sup ¯}0) single crystal substrates to create (001) and (110) crystal orientations. Same magneto-transport properties were observed from these two differently orientated devices indicating that there is no or little orientation dependence of band matching on MR output. We also found that all-B2-trilayer structure was free of lattice matching influence depending on the crystal orientation, which made it a good candidate for CPP-GMR device.

  16. Crystal orientation dependence of band matching in all-B2-trilayer current-perpendicular-to-plane giant magnetoresistance pseudo spin-valves using Co2Fe(Ge0.5Ga0.5) Heusler alloy and NiAl spacer

    International Nuclear Information System (INIS)

    We have experimentally investigated the crystal orientation dependence of band matching in current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) pseudo-spin-valves using Co2Fe(Ge0.5Ga0.5) (CFGG) Heusler alloy ferromagnetic layer and NiAl spacer. The high quality epitaxial CFGG/NiAl/CFGG all-B2-trilayers structure devices were fabricated on both MgO(001) and sapphire (112¯0) single crystal substrates to create (001) and (110) crystal orientations. Same magneto-transport properties were observed from these two differently orientated devices indicating that there is no or little orientation dependence of band matching on MR output. We also found that all-B2-trilayer structure was free of lattice matching influence depending on the crystal orientation, which made it a good candidate for CPP-GMR device

  17. Climate proxies from Sr/Ca of coccolith calcite: calibrations from continuous culture of Emiliania huxleyi

    Science.gov (United States)

    Stoll, Heather M.; Rosenthal, Yair; Falkowski, Paul

    2002-03-01

    Continuous culture of the coccolithophorid Emiliania huxleyi reveals that coccolith Sr/Ca ratios depend on temperature and growth rate. At a constant temperature of 18°C, coccolith Sr/Ca ratios increased nearly 15% as growth rate increased from 0.1 to 1.5 divisions per day and calcification rate increased from 1.5 to 50 pg calcite per cell per day. When temperature increased from 7 to 26°C, Sr/Ca ratios increased by more than 25% (i.e., 1%/1°C), although the range in growth and calcification rates was the same as for experiments at constant temperature. The temperature dependence of Sr/Ca ratios in coccoliths is consistent with that observed in planktonic foraminifera and abiogenic calcites, suggesting that it is controlled by thermodynamic processes. However, the positive correlation of coccolith Sr/Ca with temperature contrasts with field studies in the equatorial Pacific, where Sr/Ca ratios are highest at the locus of maximum upwelling and productivity despite depressed temperatures. This paradox may reflect different calcification rate effects between E. huxleyi and the other species dominating assemblages in the equatorial Pacific sediments, which may be resolved by new techniques for separation of monospecific coccolith samples from sediments. Models of crystal growth indicate that kinetic effects on Sr partitioning in calcite due to surface enrichment could explain the Sr/Ca variations observed in constant temperature experiments but not the larger amplitude calcification rate effects observed in equatorial Pacific sediments. Despite the dual influence of temperature and growth rate on coccolith Sr/Ca, coccolith Sr/Ca correlates with "b," the slope of the dependence of carbon isotope fractionation in biomarkers (ɛ p) on CO 2(aq) at a range of growth rates and temperatures. Consequently, using coccolith Sr/Ca in combination with alkenone ɛ p may improve paleo-CO 2 determinations.

  18. Surface tension alteration on calcite, induced by ion substitution

    DEFF Research Database (Denmark)

    Sakuma, Hiroshi; Andersson, Martin Peter; Bechgaard, Klaus;

    2014-01-01

    , where particles are smaller than the smallest droplet? We investigated the energy required to exchange Mg2+ and SO4 2- from aqueous solution into calcite {10.4} surfaces using density functional theory. Mg2+ substitution for Ca2+ is favored but only when SO4 2- is also present and MgSO4 incorporates...... the pore water. Incorporation of MgSO4 into calcite, which is energetically favored, decreases surface tension and releases polar oil compounds. © 2014 American Chemical Society....

  19. Magnesium incorporation in calcite in the presence of organic ligands

    Science.gov (United States)

    Mavromatis, Vasileios; Baldermann, Andre; Purgstaller, Bettina; Dietzel, Martin

    2015-04-01

    The formation of authigenic Mg-calcites in marine early diagenetic environments is commonly driven by a bio-induced process, the anaerobic oxidation of methane (AOM), which provides inorganic carbon required for the precipitation of such authigenic carbonates. In such settings the availability of major and/or trace divalent metal cations (Me2+) incorporated in calcite and their aqueous speciation are controlled by the presence of aqueous organic molecules that are produced either as (by-)products of biological activity (i.e. exopolymeric substances) or during degradation of allochthonous organic matter in the sediments. Despite the fact that the presence of aqueous organic ligands strongly affects the growth rates and the mineralogy of precipitating CaCO3 polymorphs, till now no study addresses the role of Me2+-ligand aqueous complexes on the extent of Mg and/or other trace element content of Mg-calcites. In order to shed light on this process, relevant to authigenic calcite formation in organic-rich marine sediments and continental soils, we precipitated calcite in the presence of aqueous Mg and a variety of low molecular weight carboxylic- and aminoacids. Our experimental data indicate that the presence of organic ligands augments significantly the saturation state of calcite in the parent fluid during its precipitation. Moreover, they suggest that the higher the ligand concentration, the higher the obtained distribution coefficient of Mg in calcite. The latter is directly proportional to the ratio of Mg2+/Ca2+ aqueous ions for all ligands used. Hydrogeochemical modelling of the aqueous fluids indicate that the observed correlation can be explained by the stronger complexation of Ca2+ with organic ligands compared to Mg2+, which results in higher availability of Mg2+ vs. Ca2+ aqueous ions. Overall the obtained results suggest that the higher the organic ligand aqueous concentration the higher the Mg content of calcite forming from this fluid. These findings are

  20. Effect of tensile orientation on stress corrosion cracking in SUS 316 steel single crystals. SUS 316 hagane tankessho no oryoku fushoku ware ni oyobosu hippari jiku hoi no eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Uchida, H.; Inoue, S.; Koterazawa, K. (Himeji Inst. of Tech., Hyogo (Japan). Faculty of Engineering); Oido, T. (Matsushita Electric Works, Ltd., Osaka (Japan))

    1991-07-15

    Influence of tensile axis orientation on SCC susceptibility and cracked surface of SUS 316 steel single crystal was examined. The threshold stress to SCC initiation depends on the tensile axis direction. Mostly, however, SCC susceptibility increases as Schmid factor increases. SCC threshold stress roughly corresponds to 60-80% of the yield strength. (001) oriented single crystal differs much in the SCC susceptibility depending on the manner of selection of main slipping direction. The crack susceptibility increases if its direction is more parallel to the front and the size surface of the specimen. SCC generates from a microscopic pitting corrosion formed along the slipping step, and propagates to (211) direction roughly along the (210) direction irrespective of tensile axial direction. 8 refs., 12 figs., 2 tabs.

  1. Desired crystal oriented LiFePO4 nanoplatelets in situ anchored on a graphene cross-linked conductive network for fast lithium storage

    Science.gov (United States)

    Wang, Bo; Liu, Anmin; Abdulla, Wael Al; Wang, Dianlong; Zhao, X. S.

    2015-05-01

    Electron transfer and lithium ion diffusion rates are the key factors limiting the lithium ion storage in anisotropic LiFePO4 electrodes. In this work, we employed a facile solvothermal method to synthesize a ``platelet-on-sheet'' LiFePO4/graphene composite (LFP@GNs), which is LiFePO4 nanoplatelets in situ grown on graphene sheets with highly oriented (010) facets of LiFePO4 crystals. Such a two-phase contact mode with graphene sheets cross-linked to form a three-dimensional porous network is favourable for both fast lithium ion and electron transports. As a result, the designed LFP@GNs displayed a high rate capability (~56 mA h g-1 at 60 C) and long life cycling stability (~87% capacity retention over 1000 cycles at 10 C). For comparison purposes, samples ex situ modified with graphene (LFP/GNs) as well as pure LiFePO4 platelets (LFP) were also prepared and investigated. More importantly, the obtained LFP@GNs can be used as a basic unit for constructing more complex structures to further improve electrochemical performance, such as coating the exposed LFP surface with a thin layer of carbon to build a C@LFP@GN composite to further enhance its cycling stability (~98% capacity retention over 1000 cycles at 10 C).Electron transfer and lithium ion diffusion rates are the key factors limiting the lithium ion storage in anisotropic LiFePO4 electrodes. In this work, we employed a facile solvothermal method to synthesize a ``platelet-on-sheet'' LiFePO4/graphene composite (LFP@GNs), which is LiFePO4 nanoplatelets in situ grown on graphene sheets with highly oriented (010) facets of LiFePO4 crystals. Such a two-phase contact mode with graphene sheets cross-linked to form a three-dimensional porous network is favourable for both fast lithium ion and electron transports. As a result, the designed LFP@GNs displayed a high rate capability (~56 mA h g-1 at 60 C) and long life cycling stability (~87% capacity retention over 1000 cycles at 10 C). For comparison purposes, samples

  2. Epifluorescence microscopy: a sensitive tool for studying the morphology and oriented growth of europium precipitates in KI single-crystal hosts.

    Science.gov (United States)

    Cordero-Borboa, A E; Unda-Angeles, R

    2015-06-01

    The morphology and oriented growth of europium precipitates in well-annealed Eu²⁺-doped KI single crystals are investigated by epifluorescence microscopy using the proper doping ions as fluorochromes. To make this, electronic spatial reconstructions of some fields of precipitates and of some individual precipitates were built from epifluorescence microscope images of different optical cross-sections of these objects. The building procedures are carefully explained. Previously, the KI:Eu²⁺ system was characterized by fluorescence spectrophotometry and the KI-host long-range translational order was tested by single-plate X-ray diffraction. Precipitates are shaped as plates, with their broad faces being parallel to host lattice planes of either {100}- or {110}-forms (the {100}- or {110}-plates, respectively) and as rods lying along host lattice -directions. The {100}-plates have rhomboidal broad faces with a side lying along a -direction, an internal angle of about 45°, as measured on the corresponding {100}-plane, and, consequently, another side (the {100}-side) lying along a direction on this plane. The {110}-plates have rectangular broad faces with a side lying along a -direction and with another side (the {110}-side) lying along a -direction on the corresponding {110}-plane. Spatial reconstructions of a typical precipitate field, a typical {100}-plate, a typical {110}-plate and a typical rod are described in detail. Precipitates were measured in their different dimensions and the measuring procedures are explained. The plate thicknesses and rod diameters are into a common narrow range of values (0.5-0.2 μm) which contains also the inferior limits of the obtained length ranges for the {100}- and {110}-sides (5.1-0.3 and 4.9-0.3 μm, respectively). It is discussed that that three different europium precipitation states are responsible for the studied precipitation and that plates grew from rods during annealing. PMID:25703500

  3. Geochemical signatures of fluid paleo-transfer in fracture filling calcite from low permeability rock masses: examples taken from Bure's and Tournemire's site in France and northern Switzerland; Signatures geochimiques de paleocirculations aqueuses dans la calcite de remplissage de fracture de massifs argileux peu permeables et de leurs encaissants: exemples pris sur les sites de Bure, Tournemire et Suisse du nord

    Energy Technology Data Exchange (ETDEWEB)

    Lecocq, D

    2002-12-15

    Fractures in rock masses represent preferential path for fluid transfer and, as such, are the most efficient way for migration of radionuclides at a regional scale. The impact of fracturing on hydrogeological system is a major challenge for underground radioactive waste storage projects. In this context, geochemistry of fracture-filling calcite is used to better understand physical and chemical properties of palaeo-fluids. A new methodology has been developed to analyze Mg, Mn, Fe, Sr and Rare Earth Elements REE (La, Ce, Nd, Sm, Eu, Dy and Yb) in calcite by Secondary Ion Mass Spectrometry. Analyses of calcite crystals have been performed in fractures from Jurassic clays and limestones in France (Bure and Tournemire sites) and northern Switzerland (Mt Terri's tunnel and deep borehole). On each case, several geochemical signatures are observed, according to REE partitioning and Mn and Fe concentrations. In the Bure site, a dependence of calcite geochemistry from fracture host rock has been evidenced. On the other hand, speciation of REE in solution equilibrated with clayey or calcareous rocks at circum-neutral pH (7 to 8) is not significantly influenced by the media: speciation is dominated by carbonate species in both cases and phosphate complexes can modify heavy REE availability in relatively to light REE. These results point out that in fractures in clays, calcite crystallizes at equilibrium with a fluid expulsed during diagenesis from clay minerals, recording the effect of clays and accessory phases. In limestone fractures, calcite records a later event related to the past functioning of the present aquifer, and the fluid has reached equilibrium with the rock minerals. In secondary filling calcite from Toarcian Argilites faults close to Tournemire's tunnel, three successive generations of calcite are observed in an extensive fault, and a fourth in a compressive one. In Aalenian Opalinus Clays veins, comparison between existing isotopic data and Mn, Fe

  4. Ion microprobe assessment of the heterogeneity of Mg/Ca, Sr/Ca and Mn/Ca ratios in Pecten maximus and Mytilus edulis (bivalvia shell calcite precipitated at constant temperature

    Directory of Open Access Journals (Sweden)

    P. S. Freitas

    2009-07-01

    Full Text Available Small-scale heterogeneity of biogenic carbonate elemental composition can be a significant source of error in the accurate use of element/Ca ratios as geochemical proxies. In this study ion microprobe (SIMS profiles showed significant small-scale variability of Mg/Ca, Sr/Ca and Mn/Ca ratios in new shell calcite of the marine bivalves Pecten maximus and Mytilus edulis that was precipitated during a constant-temperature culturing experiment. Elevated Mg/Ca, Sr/Ca and Mn/Ca ratios were found to be associated with the deposition of elaborate shell features, i.e. a shell surface stria in P. maximus and surface shell disturbance marks in both species, the latter a common occurrence in bivalve shells. In both species the observed small-scale elemental heterogeneity most likely was not controlled by variable transport of ions to the extra-pallial fluid, but by factors such as the influence of shell organic content and/or crystal size and orientation, the latter reflecting conditions at the shell crystal-solution interface. In the mid and innermost regions of the P. maximus shell the lack of significant small-scale variation of Mg/Ca ratios, which is consistent with growth at constant temperature, suggest a potential application as a palaeotemperature proxy. Cross-growth band element/Ca ratio profiles in the interior of bivalve shells may provide more promising palaeo-environmental tools than sampling from the outer region of bivalve shells.

  5. Ion microprobe assessment of the heterogeneity of Mg/Ca, Sr/Ca and Mn/Ca ratios in Pecten maximus and Mytilus edulis (bivalvia) shell calcite precipitated at constant temperature

    Science.gov (United States)

    Freitas, P. S.; Clarke, L. J.; Kennedy, H.; Richardson, C. A.

    2009-07-01

    Small-scale heterogeneity of biogenic carbonate elemental composition can be a significant source of error in the accurate use of element/Ca ratios as geochemical proxies. In this study ion microprobe (SIMS) profiles showed significant small-scale variability of Mg/Ca, Sr/Ca and Mn/Ca ratios in new shell calcite of the marine bivalves Pecten maximus and Mytilus edulis that was precipitated during a constant-temperature culturing experiment. Elevated Mg/Ca, Sr/Ca and Mn/Ca ratios were found to be associated with the deposition of elaborate shell features, i.e. a shell surface stria in P. maximus and surface shell disturbance marks in both species, the latter a common occurrence in bivalve shells. In both species the observed small-scale elemental heterogeneity most likely was not controlled by variable transport of ions to the extra-pallial fluid, but by factors such as the influence of shell organic content and/or crystal size and orientation, the latter reflecting conditions at the shell crystal-solution interface. In the mid and innermost regions of the P. maximus shell the lack of significant small-scale variation of Mg/Ca ratios, which is consistent with growth at constant temperature, suggest a potential application as a palaeotemperature proxy. Cross-growth band element/Ca ratio profiles in the interior of bivalve shells may provide more promising palaeo-environmental tools than sampling from the outer region of bivalve shells.

  6. Porosity and hydric behavior of typical calcite microfabrics in stalagmites

    OpenAIRE

    Muñoz García, Mercedes; López Arce, Paula; Fernández Valle, Mª Encarnación; Martín Chivelet, Javier; Fort González, Rafael

    2012-01-01

    Petrophysical techniques commonly used for material characterization are applied for the first time to speleothem samples to investigate the porosity and hydric behavior of calcite stalagmites used in paleoclimatology. These techniques allow the determination of the stalagmites' potential to undergo diagenetic transformations when substantial changes in drip waters occur in the cave environment. The petrophysical techniques include water absorption under vacuum and by capillarity,...

  7. Removal of trace elements from landfill leachate by calcite precipitation

    Czech Academy of Sciences Publication Activity Database

    Ettler, V.; Zelená, O.; Mihaljevič, M.; Šebek, O.; Strnad, L.; Coufal, P.; Bezdička, Petr

    2006-01-01

    Roč. 88, 1-3 (2006), s. 28-31. ISSN 0375-6742 R&D Projects: GA AV ČR(CZ) KJB3111402 Institutional research plan: CEZ:AV0Z40320502 Keywords : landfill leachate * calcite * scavenging Subject RIV: CA - Inorganic Chemistry Impact factor: 0.922, year: 2006

  8. Isolation and identification of Pseudomonas azotoformans for induced calcite precipitation.

    Science.gov (United States)

    Heidari Nonakaran, Siamak; Pazhouhandeh, Maghsoud; Keyvani, Abdullah; Abdollahipour, Fatemeh Zahra; Shirzad, Akbar

    2015-12-01

    Biomineralization is a process by which living organisms produce minerals. The extracellular production of these biominerals by microbes has potential for various bioengineering applications. For example, crack remediation and improvement of durability of concrete is an important goal for engineers and biomineral-producing microbes could be a useful tool in achieving this goal. Here we report the isolation, biochemical characterization and molecular identification of Pseudomonas azotoformans, a microbe that produces calcite and which potentially be used to repair cracks in concrete structures. Initially, 38 bacterial isolates were isolated from soil and cements. As a first test, the isolates were screened using a urease assay followed by biochemical tests for the rate of urea hydrolysis, calcite production and the insolubility of calcite. Molecular amplification and sequencing of a 16S rRNA fragment of selected isolates permitted us to identify P. azotoformans as a good candidate for preparation of biotechnological concrete. This species was isolated from soil and the results show that among the tested isolates it had the highest rate of urea hydrolysis, produced the highest amount of calcite, which, furthermore was the most adhesive and insoluble. This species is thus of interest as an agent with the potential ability to repair cracks in concrete. PMID:26386580

  9. Adsorption of polar aromatic hydrocarbons on synthetic calcite

    DEFF Research Database (Denmark)

    Madsen, Lene; Grahl-Madsen, Laila; Grøn, Christian; Lind, Ida; Engell, John

    1996-01-01

    The wettability of hydrocarbon reservoirs depends on how and to what extent the organic compounds are adsorbed onto the surfaces of calcite, quartz and clay. A model system of synthetic call cite, cyclohexane and the three probe molecules: benzoic acid, benzyl alcohol and benzylamine, have been...

  10. Is bicarbonate stable in and on the calcite surface?

    DEFF Research Database (Denmark)

    Andersson, Martin Peter; Rodriguez Blanco, Juan Diego; Stipp, Susan Louise Svane

    2016-01-01

    We have used density functional theory with the COSMO-RS implicit solvent model to predict the pKa for the deprotonation of bicarbonate to carbonate, i.e. HCO3− <=> CO32− + H+, when HCO3− is included in, and adsorbed on, a calcite surface. We have used cluster models (80–100 atoms) to represent t...

  11. Aragonite / Calcite seas and the evolution of biomineralization

    Science.gov (United States)

    Balthasar, Uwe

    2015-04-01

    The vast majority of marine invertebrate skeletons are composed of the CaCO3 polymorphs aragonite and calcite, yet the influence of seawater composition on the evolution of calcareous skeletal composition is poorly understood. The main theoretical framework in which the evolution of CaCO3 shell mineralogy is assessed is the aragonite-calcite sea hypothesis with conventional thinking suggesting that a threshold in the marine Mg:Ca ratio determines CaCO3 polymorph formation. I present data from CaCO3 precipitation experiments to show that the concept of a distinct threshold is misleading because Mg:Ca ratio and temperature combined result in a Phanerozoic continuum of co-existing aragonite-calcite seas with aragonite-facilitating conditions existing throughout the Phanerozoic in shallow warm-water (>20° C) environments. The stable reservoir of aragonite-favouring conditions in shallow warm water environments potentially explains the trend of increasing occurrences of skeletal aragonite throughout the Phanerozoic, particularly in the context of the 'out of the tropics' hypothesis. By contrast, the most prominent fluctuations with respect to aragonite-calcite sea conditions can be expected to have occurred in mid- to high latitudes.

  12. Quasi-homoepitaxial growth of a-axis oriented PrBa sub 2 Cu sub 3 O sub 7 sub - subdelta thick film on (100) YBa sub 2 Cu sub 3 O sub 7 sub - subdelta single crystal

    CERN Document Server

    Sato, M; Morishita, T

    2003-01-01

    The structural characterizations of the quasi-homoepitaxial growth of a-axis oriented PrBa sub 2 Cu sub 3 O sub 7 sub - subdelta thick film grown on (100) YBa sub 2 Cu sub 3 O sub 7 sub - subdelta single crystal were investigated in comparison with those of the film grown on (001) YBa sub 2 Cu sub 3 O sub 7 sub - subdelta single crystal. The a-axis oriented PrBa sub 2 Cu sub 3 O sub 7 sub - subdelta films, expected to be a barrier layer, were prepared using a dc-95 MHz hybrid plasma sputtering on (100) and (001) YBa sub 2 Cu sub 3 O sub 7 sub - subdelta single crystals that are superconducting ground planes. The atomic force microscopy image revealed that the surfaces of 700-nm-thick a-axis PrBa sub 2 Cu sub 3 O sub 7 sub - subdelta films on (100) YBa sub 2 Cu sub 3 O sub 7 sub - subdelta single crystals were smooth with a mean roughness of 2.8 nm. X-ray diffraction scans showed that a-axis PrBa sub 2 Cu sub 3 O sub 7 sub - subdelta films deposited on (100) YBa sub 2 Cu sub 3 O sub 7 sub - subdelta single cry...

  13. Reconstructing Cambro-Ordovician Seawater Composition using Clumped Isotope Paleothermometry on Calcitic and Phosphatic Brachiopods

    Science.gov (United States)

    Bergmann, K.; Robles, M.; Finnegan, S.; Hughes, N. C.; Eiler, J. M.; Fischer, W. W.

    2012-12-01

    A secular increase in δ18O values of marine fossils through early Phanerozoic time raises questions about the evolution of climate and the water cycle. This pattern suggests two end-member hypotheses 1) surface temperatures during early Paleozoic time were very warm, in excess of 40°C (tropical MAT), or 2) the isotopic composition of seawater increased by up to 7-8‰. It has been difficult to evaluate these hypotheses because the δ18O composition of fossils depends on both temperature and the δ18O of water. Furthermore, primary isotopic signatures can be overprinted by diagenetic processes that modify geological materials. This too could explain the decrease in δ18O values of marine fossils with age. Carbonate clumped isotope thermometry can constrain this problem by providing an independent measure of crystallization temperature and, when paired with classical δ18O paleothermometry, can determine the isotopic composition of the fluid the mineral last equilibrated with. Combined with traditional tools, this method has the potential to untangle primary isotopic signatures from diagenetic signals. We measured the isotopic ordering of CO3 groups (Δ47) substituted into the phosphate lattice of phosphatic brachiopods in Cambrian strata. Phosphatic fossils are generally less soluble than carbonates in surface and diagenetic environments, and so are hypothesized to provide a more robust record of primary growth conditions. They also provide an archive prior to the rise of thick shelled calcitic fossils during the Ordovician Radiation. Additionally, measurements of the δ18O of the CO3 groups can be compared with the δ18O of PO4 groups to test whether their mutual fractionation is consistent with primary growth and the apparent temperature recorded by carbonate clumped isotope measurements. We are constructing a phosphatic brachiopod calibration for carbonate clumped isotope thermometry, and Δ47 values of CO2 extracted from modern phosphatic brachiopods suggest

  14. New inversion of calcite twin data for paleostress tested and calibrated on numerically-generated and natural data

    Science.gov (United States)

    Parlangeau, Camille; Lacombe, Olivier; Schueller, Sylvie; Daniel, Jean-Marc

    2016-04-01

    The inversion of calcite twin data is a powerful tool to reconstruct paleostresses sustained by carbonate rocks during their geological history. Following Etchecopar's (1984) pioneering work, this study presents a new technique of inversion of calcite twin data, which allows reconstructing the 5 parameters of the deviatoric stress tensor. In order to determine the applicability domain of the technique as well as to estimate the uncertainties on the reconstructed stress tensors, we first carried out tests on numerically generated calcite twin data and tested the separability of superimposed stress tensors with various degrees of similarity and the influence of optical bias, heterogeneities and occurrence of different grain size classes as met in natural samples. For monophase datasets with homogeneous grain size, the errors on the different stress parameters (orientation of principal stress axes, stress ratio and differential stresses) are negligible except for the differential stress (error of 5%). In cases displaying distinct grain sizes, misfits remain negligible but may reach 20% for the differential stress if the differential stress applied is greater than 60-65 MPa. Incorporation of optical bias slightly increases uncertainties up to 25% for the differential stress, 5% for the stress ratio and 8° for the orientation of the principal stress axes. For polyphase datasets with homogeneous grain size, the misfit on the orientation of the principal stress axes increases up to 10°, the stress ratio remains well constrained and the misfit on differential stress reaches 20% (applied differential stress > 70 MPa). Incorporation of optical bias increases the misfit of the orientation of the principal stress axes (average misfit: 6-8°; maximum: 17°), the misfit on stress ratio (average misfit: 2%; maximum: 26%) and the misfit on the differential stress (average misfit: 15%; maximum: 30%) These tests demonstrate that it is better to analyze twin data from subsets of

  15. Experimental study of the replacement of calcite by calcium sulphates

    Science.gov (United States)

    Ruiz-Agudo, E.; Putnis, C. V.; Hövelmann, J.; Álvarez-Lloret, P.; Ibáñez-Velasco, A.; Putnis, A.

    2015-05-01

    Among the most relevant mineral replacement reactions are those involving sulphates and carbonates, which have important geological and technological implications. Here it is shown experimentally that during the interaction of calcite (CaCO3) cleavage surfaces with sulphate-bearing acidic solutions, calcite is ultimately replaced by gypsum (CaSO4 2H2O) and anhydrite (CaSO4), depending on the reaction temperature. Observations suggest that this occurs most likely via an interface-coupled dissolution-precipitation reaction, in which the substrate is replaced pseudomorphically by the product. At 120 and 200 °C gypsum and/or bassanite (CaSO4·0.5H2O) form as precursor phases for the thermodynamically stable anhydrite. Salinity promotes the formation of less hydrated precursor phases during the replacement of calcite by anhydrite. The reaction stops before equilibrium with respect to calcite is reached and during the course of the reaction most of the bulk solutions are undersaturated with respect to the precipitating phase(s). A mechanism consisting of the dissolution of small amounts of solid in a thin layer of fluid at the mineral-fluid interface and the subsequent precipitation of the product phase from this layer is in agreement with these observations. PHREEQC simulations performed in the framework of this mechanism highlight the relevance of transport and surface reaction kinetics on the volume change associated with the CaCO3-CaSO4 replacement. Under our experimental conditions, this reaction occurs with a positive volume change, which ultimately results in passivation of the unreacted substrate before calcite attains equilibrium with respect to the bulk solution.

  16. Impact-Induced Devolatilization or Melting of Calcite? Or Both? Answers from MEMIN Experiments

    Science.gov (United States)

    Hamann, C.; Hecht, L.; Deutsch, A.

    2015-07-01

    Calcite was experimentally shocked in a series of MEMIN hypervelocity impact and laser melting experiments. Evidence for the formation of calcite melts in both types of experiments is presented and discussed.

  17. On the Shock Behavior of Calcite: Recent Results from MEMIN Experiments

    Science.gov (United States)

    Hamann, C.; Hecht, L.; Deutsch, A.

    2015-09-01

    Hypervelocity impact and laser melting experiments, aiming at a better understanding of the shock behavior of calcite, suggest that both melting and decomposition of calcite can occur at P-T conditions commensurate with impact processes.

  18. Effect of annealing on natural calcitic crystals—A thermostimulated luminescence (TSL) study

    International Nuclear Information System (INIS)

    The quality crystals (Calcitic limestone) were selected using the UV–visible methylene blue adsorption method. The thermostimulated luminescence (TSL) glow curve characteristics of six well crystallized limestone samples were analyzed. The glow curves of unannealed sample show only one peak in the range 320–330 °C. The sample irradiated with a gamma dose of 100 Gy shows two additional peaks in the range of 113–125 °C and 242–260 °C when recorded with linear heating rate of 10 °C/s. The annealed sample also shows the same trend as that of irradiated sample. Annealing treatment above 250 °C increases the sensitivity of all TSL peaks except 320 °C. On the other hand, annealing at 750 °C caused a collapse in the TSL sensitivity. The enhancement in TSL sensitivity was found to depend on the annealing temperature and time. Annealing treatment at 650 °C for 4 h followed by quenching in air is the optimum condition for TSL sensitization. The response to gamma irradiation is linear in the range from 0.5 Gy to 104 Gy. The emission spectra of all the samples show an emission at around 610 nm but with different intensities for each TSL peak. With reference to earlier work, it may be assumed that the recombination site always involves Mn2+ ions. The observation made through infra-red (IR) and X-ray diffraction (XRD) studies with thermal treatment shows the structural changes of calcite from D3h to Cs symmetry at 750 °C. The Thermogravimetric-Differential Thermal Analysis (TG-DTA) analysis shows the calcite gets disordered at 760 °C. Hence, the collapse in the TSL sensitivity at 750 °C is due to structural change or structural disorderedness. - Highlights: ►Normally, the synthetic material was used as radiation dosimeter but the natural material can also be used for the same application. ► A wide dose linear response to gamma radiation is observed in the range of 0.5–104 Gy. ► The natural material is not harmful to human body and more eco-friendly so

  19. Stability of Basalt plus Anhydrite plus Calcite at HP-HT: Implications for Venus, the Earth and Mars

    Science.gov (United States)

    Martin, A. M.; Righter, K.; Treiman, A. H.

    2010-01-01

    "Canali" observed at Venus surface by Magellan are evidence for very long melt flows, but their composition and origin remain uncertain. The hypothesis of water-rich flow is not reasonable regarding the temperature at Venus surface. The length of these channels could not be explained by a silicate melt composition but more likely, by a carbonate-sulfate melt which has a much lower viscosity (Kargel et al 1994). One hypothesis is that calcite CaCO3 and anhydrite CaSO4 which are alteration products of basalts melted during meteorite impacts. A famous example recorded on the Earth (Chicxulub) produced melt and gas rich in carbon and sulfur. Calcite and sulfate evaporites are also present on Mars surface, associated with basalts. An impact on these materials might release C- and S-rich melt or fluid. Another type of planetary phenomenon (affecting only the Earth) might provoke a high pressure destabilization of basalt+anhydrite+calcite. Very high contents of C and S are measured in some Earth s magmas, either dissolved or in the form of crystals (Luhr 2008). As shown by the high H content and high fO2 of primary igneous anhydrite-bearing lavas, the high S content in their source may be explained by subduction of an anhydrite-bearing oceanic crust, either directly (by melting followed by eruption) or indirectly (by release of S-rich melt or fluid that metasomatize the mantle) . Calcite is a major product of oceanic sedimentation and alteration of the crust. Therefore, sulfate- and calcite-rich material may be subducted to high pressures and high temperatures (HP-HT) and release S- and C-rich melts or fluids which could influence the composition of subduction zone lavas or gases. Both phenomena - meteorite impact and subduction - imply HP-HT conditions - although the P-T-time paths are different. Some HP experimental/theoretical studies have been performed on basalt/eclogite, calcite and anhydrite separately or on a combination of two. In this study we performed piston

  20. Lithofacies palaeogeography and sedimentology Beef and cone-in-cone calcite fibrous cements associated with the end-Permian and end-Triassic mass extinctions:Reassessment of processes of formation

    Institute of Scientific and Technical Information of China (English)

    Stephen Kershaw; Li Guo

    2016-01-01

    This paper reassesses published interpretation that beef and cone-in-cone (B-CIC) fibrous calcite cements were precipitated contemporaneously just below the sea floor in uncon-solidated sediment, in limestones associated with the end-Permian (P/T) and end-Triassic (T/J) mass extinctions. That interpretation introduced the concept of a sub-seafloor car-bonate factory associated with ocean acidification by raised carbon dioxide driven by volcanic eruption, coinciding with mass extinction. However, our new fieldwork and petrographic analysis, with literature comparison, reveals several problems with this concept. Two key points based on evidence in the T/J transition of the UK are:(1) that B-CIC calcite deposits form thin scattered layers and lenses at several horizons, not a distinct deposit associated with volcanic activity; and (2) B-CIC calcite is more common in Early Jurassic sediments after the extinction and after the end of the Central Atlantic Magmatic Province volcanism proposed to have supplied the carbon dioxide required. Our samples from Late Triassic, Early Jurassic and Early Cretaceous limestones in southern UK show that B-CIC calcite occurs in both marine and non-marine sediments, therefore ocean processes are not mandatory for its formation. There is no proof that fibrous calcite was formed before lithification, but our Early Jurassic samples do prove fibrous calcite formed after compaction, thus interpretation of crystal growth in uncon-solidated sediment is problematic. Furthermore, B-CIC crystals mostly grew both upwards and downwards equally, contradicting the interpretation of the novel carbonate factory that they grew preferentially upwards in soft sediment. Finally, Early Jurassic and Early Cretaceous examples are not associated with mass extinction. Three further key points derived from the literature include: (1) B-CIC calcite is wide-spread geographically and stratigraphically, not clustered around mass extinctions or the Paleocene

  1. Growth rate controlled barium partitioning in calcite and aragonite

    Science.gov (United States)

    Goetschl, Katja Elisabeth; Mavromatis, Vasileios; Baldermann, Andre; Purgstaller, Bettina; Dietzel, Martin

    2016-04-01

    The barium (Ba) content and the Ba/Ca molar ratios in biogenic and abiotic carbonates have been widely used from the scientific community as a geochemical proxy especially in marine and early diagenetic settings. The Ba content of carbonate minerals has been earlier associated to changes in oceanic circulation that may have been caused by upwelling, changes in weathering regimes and river-runoff as well as melt water discharge. The physicochemical controls of Ba ion incorporation in the two most abundant CaCO3 polymorphs found in Earth's surface environments, i.e. calcite and aragonite, have adequately been studied only for calcite. These earlier studies (i.e. [1]) suggest that at increasing growth rate, Ba partitioning in calcite is increasing as well. In contrast, to date the effect of growth rate on the partitioning of Ba in aragonite remains questionable, despite the fact that this mineral phase is the predominant carbonate-forming polymorph in shallow marine environments. To shed light on the mechanisms controlling Ba ion uptake in carbonates in this study we performed steady-state Ba co-precipitation experiments with calcite and aragonite at 25°C. The obtained results for the partitioning of Ba in calcite are in good agreement with those reported earlier by [1], whereas those for aragonite indicate a reduction of Ba partitioning at elevated aragonite growth rates, with the partitioning coefficient value between solid and fluid to be approaching the unity. This finding is good agreement with the formation of a solid solution in the aragonite-witherite system, owing to the isostructural crystallography of the two mineral phases. Moreover, our data set provides new insights that are required for reconstructing the evolution of the Ba content of pristine marine versus diagenetically altered carbonate minerals commonly occurring in marine subfloor settings, as the thermodynamically less stable aragonite will transform to calcite enriched in Ba, whilst affecting

  2. Orientation dependence of the probability of close collisions during passage of high-energy negatively charged particle through a bent crystal

    International Nuclear Information System (INIS)

    The probability of close collisions of high-energy negatively charged particle with atoms in a bent crystal was considered as a function of the angle between the initial particle momentum and the bending plane. This allowed to compare the probability of close collisions of high-energy negatively charged particle in a bent crystal in two different regimes of deflection: planar channeling and stochastic deflection. The results of simulation of negatively charged particle motion in a bent crystal shown the great efficiency of high-energy negatively charged particle beam deflection by a bent crystal due to stochastic deflection and small efficiency of deflection due to planar channeling

  3. Enzyme-accelerated and structure-guided crystallization of calcium carbonate: role of the carbonic anhydrase in the homologous system.

    Science.gov (United States)

    Müller, Werner E G; Schlossmacher, Ute; Schröder, Heinz C; Lieberwirth, Ingo; Glasser, Gunnar; Korzhev, Michael; Neufurth, Meik; Wang, Xiaohong

    2014-01-01

    The calcareous spicules from sponges, e.g. from Sycon raphanus, are composed of almost pure calcium carbonate. In order to elucidate the formation of those structural skeletal elements, the function of the enzyme carbonic anhydrase (CA), isolated from this species, during the in vitro calcium carbonate-based spicule formation, was investigated. It is shown that the recombinant sponge CA substantially accelerates calcium carbonate formation in the in vitro diffusion assay. A stoichiometric calculation revealed that the turnover rate of the sponge CA during the calcification process amounts to 25 CO2s(-1) × molecule CA(-1). During this enzymatically driven process, initially pat-like particles are formed that are subsequently transformed to rhomboid/rhombohedroid crystals with a dimension of ~50 μm. The CA-catalyzed particles are smaller than those which are formed in the absence of the enzyme. The Martens hardness of the particles formed is ~4 GPa, a value which had been determined for other biogenic calcites. This conclusion is corroborated by energy-dispersive X-ray spectroscopy, which revealed that the particles synthesized are composed predominantly of the elements calcium, oxygen and carbon. Surprising was the finding, obtained by light and scanning electron microscopy, that the newly formed calcitic crystals associate with the calcareous spicules from S. raphanus in a highly ordered manner; the calcitic crystals almost perfectly arrange in an array orientation along the two opposing planes of the spicules, leaving the other two plane arrays uncovered. It is concluded that the CA is a key enzyme controlling the calcium carbonate biomineralization process, which directs the newly formed particles to existing calcareous spicular structures. It is expected that with the given tools new bioinspired materials can be fabricated. PMID:23978410

  4. Adsorption of polar aromatic hydrocarbons on synthetic calcite

    DEFF Research Database (Denmark)

    Madsen, Lene; Grahl-Madsen, Laila; Grøn, Christian;

    1996-01-01

    The wettability of hydrocarbon reservoirs depends on how and to what extent the organic compounds are adsorbed onto the surfaces of calcite, quartz and clay. A model system of synthetic call cite, cyclohexane and the three probe molecules: benzoic acid, benzyl alcohol and benzylamine, have been...... studied by adsorption experiments. The results clearly demonstrate the differences in the adsorption behaviour between probes with different functional groups of varying polarity and acidity. The maximum adsorption decreases in the order: benzoic acid, benzyl alcohol and benzylamine. The order of...... magnitude of Delta G degrees for the adsorption process implies the formation of a strong bond between the calcite surface and the adsorbate molecules. Copyright (C) 1996 Elsevier Science Ltd....

  5. Calcite production by coccolithophores in the south east Pacific Ocean

    OpenAIRE

    Beaufort, L.; Couapel, M.; Buchet, N.; H. Claustre; Goyet, C

    2008-01-01

    BIOSOPE cruise covered an oceanographic transect through the centre of the South Pacific Gyre (SPG) from the Marquesas archipelago to the Peru-Chile upwelling (PCU). Water samples from 6 depths in the euphotic zone were collected at 20 stations. The concentrations of suspended calcite particles, coccolithophores cells and detached coccoliths were estimated together with size and weight using an automatic polarizing microscope, a digital camera, and a collection of softwares performing morphom...

  6. The effect of dissolved magnesium on diffusion creep in calcite

    Science.gov (United States)

    Herwegh, Marco; Xiao, Xiaohui; Evans, Brian

    2003-07-01

    We experimentally tested a series of synthetic calcite marbles with varying amounts of dissolved magnesium in a standard triaxial deformation machine at 300 MPa confining pressure, temperatures between 700 and 850°C, stresses between 2 and 100 MPa, and strain rates between 10 -7 and 10 -3 s -1. The samples were fabricated by hot isostatic pressing of a mixture of calcite and dolomite at 850°C and 300 MPa. The fabrication protocol resulted in a homogeneous, fine-grained high-magnesian calcite aggregate with minimal porosity and with magnesium contents between 0.07 and 0.17 mol% MgCO 3. At stresses below 40 MPa the samples deformed with linear viscosity that depended inversely on grain size to the 3.26±0.51 power, suggesting that the mechanisms of deformation were some combination of grain boundary diffusion and grain boundary sliding. Because small grain sizes tended to occur in the high-magnesium calcite, the strength also appeared to vary inversely with magnesium content. However, the strength at constant grain size does not depend on the amount of dissolved magnesium, and thus, the impurity effect seems to be indirect. At stresses higher than 40 MPa, the aggregates become non-linearly viscous, a regime we interpret to be dislocation creep. The transition between the two regimes depends on grain size, as expected. The activation energy for diffusion creep is 200±30 kJ/mol and is quite similar to previous measurements in natural and synthetic marbles deformed at similar conditions with no added magnesium.

  7. Origin of calcite in the glacigenic Virttaankangas complex

    OpenAIRE

    Nina M. Kortelainen; Petri J. Korkeakoski; Karhu, Juha A.

    2007-01-01

    Groundwaters of the glacigenic Virttaankangas complex in southern Finland are characterized by high pH values ranging up to 9.5. These values are significantly higher than those observed in silicate-rich shallow groundwater formations in crystalline bedrock areas. TheVirttaankangas sediments were discovered to contain small amounts of fine grained, dispersed calcite, which has a high tendency to increase the pH of local groundwaters. The primary goal of this study was to determine the mode of...

  8. Biogenic calcite structures in Green Lake, James Ross Island, Antarctica

    Czech Academy of Sciences Publication Activity Database

    Elster, Josef; Nedbalová, Linda; Komárek, Jiří; Vodrážka, R.

    Brno: Masarykova Univerzita, 2009 - (Barták, M.; Hájek, J.; Váczi, P.), s. 38-40 ISBN 978-80-210-4987-1. [Electronic Conference on Interactions between Antarctic Life and Environmental Factors. Brno (CZ), 22.10.2009-23.10.2009] R&D Projects: GA MŠk(CZ) ME 945 Institutional research plan: CEZ:AV0Z60050516 Keywords : Green Lake * James Ross * Biogenic calcite structures Subject RIV: EF - Botanics

  9. Magnetic Separation of Calcite Using Selective Magnetite Coating

    OpenAIRE

    Prakash, S; Das, B.; R. Venugopal

    1999-01-01

    Magnetic separation of naturally occurring calcite (98.2% CaCO3) using selective coating of synthetic colloidal magnetite with sodium oleate has been investigated as a function of pH, concentration of colloidal magnetite, magnetic intensity and particle size. Colloidal magnetite treated with sodium oleate (oleate magnetite) is found to be a better coating agent than the natural magnetite. The mechanism of oleate magnetite coating has been investigated through adsorption and electrokinetics me...

  10. Arsenite sorption and co-precipitation with calcite

    CERN Document Server

    Roman-Ross, Gabriela; Turrillas, Xavier; Fernandez-Martinez, Alejandro; Charlet, Laurent

    2008-01-01

    Sorption of As(III) by calcite was investigated as a function of As(III) concentration, time and pH. The sorption isotherm, i.e. the log As(III) vs. log [As(OH)3 degrees / Assat] plot is S-shaped and has been modelled on an extended version of the surface precipitation model. At low concentrations, As(OH)3 degrees is adsorbed by complexation to surface Ca surface sites, as previously described by the X-ray standing wave technique. The inflexion point of the isotherm, where As(OH)3 degrees is limited by the amount of surface sites (ST), yields 6 sites nm-2 in good agreement with crystallographic data. Beyond this value, the amount of sorbed arsenic increases linearly with solution concentration, up to the saturation of arsenic with respect to the precipitation of CaHAsO3(s). The solid solutions formed in this concentration range were examined by X-ray and neutron diffraction. The doped calcite lattice parameters increase with arsenic content while c/a ratio remains constant. Our results made on bulk calcite on...

  11. Synthetic Calcite as a Scaffold for Osteoinductive Bone Substitutes.

    Science.gov (United States)

    Chróścicka, Anna; Jaegermann, Zbigniew; Wychowański, Piotr; Ratajska, Anna; Sadło, Jarosław; Hoser, Grażyna; Michałowski, Sławomir; Lewandowska-Szumiel, Malgorzata

    2016-07-01

    Although a wide variety of biomaterials have been already proposed for use in bone tissue engineering, there is still need for man-made materials, which would combine support for osteogenesis with simplicity desirable for upscaling and costs reduction. In this study we have shown that synthetic calcite may serve as a scaffold for human osteoblasts transplantation. A simple dynamic system allows uniform and effective cell distribution. Cell viability and osteogenic phenotype were confirmed by XTT assay, alkaline phosphatase activity and selected osteoblast-specific genes expression. Extracellular matrix deposited by cells improved elasticity and made the whole system similar to the flexible composite material rather than to the brittle ceramic implants. It was revealed in the compression tests and also by the improved samples handling. Subcutaneous implantation of the cell-seeded calcite scaffolds to immunodeficient mice resulted in mineralized bone formation, which was confirmed histologically and by EPR analysis. The latter we propose as a method supplementary to histological analysis, for bone regeneration investigations. It specifically confirms the presence of bone mineral with a unique sensitivity and using bulk samples, which eliminates the risk of missing the material in the preparation. Our study resulted in development of a new osteogenic tissue engineered product based on man-made calcite. PMID:26666226

  12. PVC mixtures’ mechanical properties with the addition of modified calcite as filler

    Directory of Open Access Journals (Sweden)

    Vučinić Dušica R.

    2012-01-01

    Full Text Available In this study mechanical properties of PVC mixtures (PVC, stabilizer, lubricant, filler such as tensile strength, tensile elongation, breaking strength, and breaking elongation were investigated. Unmodified calcite, as well as calcite modified by stearic acid, were used as fillers in wet and dry processes. The PVC mixtures containing the calcite modified by wet procedure have better mechanical properties compared to those with the calcite modified by the dry process. Tensile and breaking strength of the PVC mixture containing the calcite modified with 1.5% stearic acid using wet process, are higher for 2.8% and 5.2%, respectively, compared to the PVC mixture containing the calcite modified with the same amount of acid used in the dry process. The tensile strength difference between the mixtures increases with the increase of the concentration of used stearic acid up to 3%. The strength of PVC mixture with the calcite modified by wet process is 3.1% higher compared to the mixture containing calcite modified by dry process. The results showed that the bonding strength between calcite and the adsorbed organic component affected tensile strength, tensile elongation and breaking strength of the PVC mixtures. The best filler was obtained by wet modification using 1.5% stearic acid solution that provided the formation of a stearate monolayer chemisorbed on calcite. The PVC mixtures containing the calcite modified by wet process using 1.5% stearic acid solution exhibited the best mechanical properties. This calcite was completely hydrophobic with dominant chemically adsorbed surfactant, which means that stearate chemisorbed on calcite provided stronger interaction in the calcite-stearic acid-PVC system.

  13. Field-Induced Domain Reorientation and Polarization Rotation of Oriented Pb(Mg1/3Nb2/3)O3-PbTiO3 Single Crystals

    Institute of Scientific and Technical Information of China (English)

    CHEN Ke-Pi; ZHANG Xiao-Wen; FANG Fei

    2006-01-01

    Polarization hysteresis loops, x-ray diffraction and temperature dependent dielectric constant under different electric Gelds for oriented 0.7PMN-0.3PT crystals are measured. The field-induced phase transition and the process of depolarization are discussed. The results show that with the electric field E increasing, the single-crystal form changes from the relaxor state of rhombohedral to normal rhombohedral, then to a monoclinic state via polar-axis reorientation and polarization rotation. Orthorhombic phase may present when E≥ 10 kV, but it is an unstable form after E removal. The depolarization process is not just the reversal of the polarization process. It is noticed that only the temperature-dependent dielectric behaviour is not enough to judge the processes of the E-field induced phase transition.

  14. Stable isotope (C, O) and monovalent cation fractionation upon synthesis of carbonate-bearing hydroxyl apatite (CHAP) via calcite transformation

    Science.gov (United States)

    Böttcher, Michael E.; Schmiedinger, Iris; Wacker, Ulrike; Conrad, Anika C.; Grathoff, Georg; Schmidt, Burkhard; Bahlo, Rainer; Gehlken, Peer-L.; Fiebig, Jens

    2016-04-01

    Carbonate-bearing hydroxyl-apatite (CHAP) is of fundamental and applied interest to the (bio)geochemical, paleontological, medical and material science communities, since it forms the basic mineral phase in human and animal teeth and bones. In addition, it is found in non-biogenic phosphate deposits. The stable isotope and foreign element composition of biogenic CHAP is widely used to estimate the formation conditions. This requires careful experimental calibration under well-defined boundary conditions. Within the DFG project EXCALIBOR, synthesis of carbonate-bearing hydroxyapatite was conducted via the transformation of synthetic calcite powder in aqueous solution as a function of time, pH, and temperature using batch-type experiments. The aqueous solution was analyzed for the carbon isotope composition of dissolved inorganic carbonate (gas irmMS), the oxygen isotope composition of water (LCRDS), and the cationic composition. The solid was characterized by powder X-ray diffraction, micro Raman and FTIR spectroscopy, SEM-EDX, elemental analysis (EA, ICP-OES) and gas irmMS. Temperature was found to significantly impact the transformation rate of calcite to CHAP. Upon complete transformation, CHAP was found to contain up to 5% dwt carbonate, depending on the solution composition (e.g., pH), both incorporated on the A and B type position of the crystal lattice. The oxygen isotope fractionation between water and CHAP decreased with increasing temperature with a tentative slope shallower than those reported in the literature for apatite, calcite or aragonite. In addition, the presence of dissolved NH4+, K+ or Na+ in aqueous solution led to partial incorporation into the CHAP lattice. How these distortions of the crystal lattice may impact stable isotope discrimination is subject of future investigations.

  15. EDITORIAL: Optical orientation Optical orientation

    Science.gov (United States)

    SAME ADDRESS *, Yuri; Landwehr, Gottfried

    2008-11-01

    priority of the discovery in the literature, which was partly caused by the existence of the Iron Curtain. I had already enjoyed contact with Boris in the 1980s when the two volumes of Landau Level Spectroscopy were being prepared [2]. He was one of the pioneers of magneto-optics in semiconductors. In the 1950s the band structure of germanium and silicon was investigated by magneto-optical methods, mainly in the United States. No excitonic effects were observed and the band structure parameters were determined without taking account of excitons. However, working with cuprous oxide, which is a direct semiconductor with a relative large energy gap, Zakharchenya and his co-worker Seysan showed that in order to obtain correct band structure parameters, it is necessary to take excitons into account [3]. About 1970 Boris started work on optical orientation. Early work by Hanle in Germany in the 1920s on the depolarization of luminescence in mercury vapour by a transverse magnetic field was not appreciated for a long time. Only in the late 1940s did Kastler and co-workers in Paris begin a systematic study of optical pumping, which led to the award of a Nobel prize. The ideas of optical pumping were first applied by Georges Lampel to solid state physics in 1968. He demonstrated optical orientation of free carriers in silicon. The detection method was nuclear magnetic resonance; optically oriented free electrons dynamically polarized the 29Si nuclei of the host lattice. The first optical detection of spin orientation was demonstrated by with the III-V semiconductor GaSb by Parsons. Due to the various interaction mechanisms of spins with their environment, the effects occurring in semiconductors are naturally more complex than those in atoms. Optical detection is now the preferred method to detect spin alignment in semiconductors. The orientation of spins in crystals pumped with circularly polarized light is deduced from the degree of circular polarization of the recombination

  16. Oriented single-crystal nuclear resonance vibrational spectroscopy of [Fe(TPP)(MI)(NO)] : quantitative sssessment of the trans effect of NO.

    Energy Technology Data Exchange (ETDEWEB)

    Lehnert, N.; Sage, J. T.; Silvernail, N.; Scheidt, W. R.; Alp, E. E.; Sturhahn, W.; Zhao, J. (X-Ray Science Division); (Univ. of Michigan); (Northeastern Univ.); (Univ. of Notre Dame)

    2010-01-01

    This paper presents oriented single-crystal Nuclear Resonance Vibrational Spectroscopy (NRVS) data for the six-coordinate (6C) ferrous heme-nitrosyl model complex [{sup 57}Fe(TPP)(MI)(NO)] (1; TPP{sup 2-} = tetraphenylporphyrin dianion; MI = 1-methylimidazole). The availability of these data enables for the first time the detailed simulation of the complete NRVS data, including the porphyrin-based vibrations, of a 6C ferrous heme-nitrosyl, using our quantum chemistry centered normal coordinate analysis (QCC-NCA). Importantly, the Fe-NO stretch is split by interaction with a porphyrin-based vibration into two features, observed at 437 and 472 cm{sup -1}. The 437 cm{sup -1} feature is strongly out-of-plane (oop) polarized and shows a {sup 15}N{sup 18}O isotope shift of 8 cm{sup -1} and is therefore assigned to v(Fe-NO). The admixture of Fe-N-O bending character is small. Main contributions to the Fe-N-O bend are observed in the 520-580 cm{sup -1} region, distributed over a number of in-plane (ip) polarized porphyrin-based vibrations. The main component, assigned to {delta}{sub ip}(Fe-N-O), is identified with the feature at 563 cm{sup -1}. The Fe-N-O bend also shows strong mixing with the Fe-NO stretching internal coordinate, as evidenced by the oop NRVS intensity in the 520-580 cm{sup -1} region. Very accurate normal mode descriptions of ?(Fe-NO) and {delta}{sub ip}(Fe-N-O) have been obtained in this study. These results contradict previous interpretations of the vibrational spectra of 6C ferrous heme-nitrosyls where the higher energy feature at {approx}550 cm{sup -1} had usually been associated with v(Fe-NO). Furthermore, these results provide key insight into NO binding to ferrous heme active sites in globins and other heme proteins, in particular with respect to (a) the effect of hydrogen bonding to the coordinated NO and (b) changes in heme dynamics upon NO coordination. [Fe(TPP)(MI)(NO)] constitutes an excellent model system for ferrous NO adducts of myoglobin

  17. Oriented single-crystal nuclear resonance vibrational spectroscopy of [Fe(TPP)(MI)(NO)]: quantitative assessment of the trans effect of NO.

    Science.gov (United States)

    Lehnert, Nicolai; Sage, J Timothy; Silvernail, Nathan; Scheidt, W Robert; Alp, E Ercan; Sturhahn, Wolfgang; Zhao, Jiyong

    2010-08-01

    This paper presents oriented single-crystal Nuclear Resonance Vibrational Spectroscopy (NRVS) data for the six-coordinate (6C) ferrous heme-nitrosyl model complex [(57)Fe(TPP)(MI)(NO)] (1; TPP(2-) = tetraphenylporphyrin dianion; MI = 1-methylimidazole). The availability of these data enables for the first time the detailed simulation of the complete NRVS data, including the porphyrin-based vibrations, of a 6C ferrous heme-nitrosyl, using our quantum chemistry centered normal coordinate analysis (QCC-NCA). Importantly, the Fe-NO stretch is split by interaction with a porphyrin-based vibration into two features, observed at 437 and 472 cm(-1). The 437 cm(-1) feature is strongly out-of-plane (oop) polarized and shows a (15)N(18)O isotope shift of 8 cm(-1) and is therefore assigned to nu(Fe-NO). The admixture of Fe-N-O bending character is small. Main contributions to the Fe-N-O bend are observed in the 520-580 cm(-1) region, distributed over a number of in-plane (ip) polarized porphyrin-based vibrations. The main component, assigned to delta(ip)(Fe-N-O), is identified with the feature at 563 cm(-1). The Fe-N-O bend also shows strong mixing with the Fe-NO stretching internal coordinate, as evidenced by the oop NRVS intensity in the 520-580 cm(-1) region. Very accurate normal mode descriptions of nu(Fe-NO) and delta(ip)(Fe-N-O) have been obtained in this study. These results contradict previous interpretations of the vibrational spectra of 6C ferrous heme-nitrosyls where the higher energy feature at approximately 550 cm(-1) had usually been associated with nu(Fe-NO). Furthermore, these results provide key insight into NO binding to ferrous heme active sites in globins and other heme proteins, in particular with respect to (a) the effect of hydrogen bonding to the coordinated NO and (b) changes in heme dynamics upon NO coordination. [Fe(TPP)(MI)(NO)] constitutes an excellent model system for ferrous NO adducts of myoglobin (Mb) mutants where the distal histidine (His64

  18. Carbonate "clumped" isotope signatures in aragonitic scleractinian and calcitic gorgonian deep-sea corals

    Directory of Open Access Journals (Sweden)

    J. Kimball

    2015-12-01

    between the corals of different mineralogy is in the same direction as published theoretical predictions for the offset between calcite and aragonite, although the magnitude of the offset is different. One possibility is that the deep-sea coral results reflect that crystals may attain nominal mineral equilibrium clumped isotope signatures only under conditions of extremely slow growth. In that case, a possible explanation for the attainment of disequilibrium bulk isotope signatures and equilibrium clumped isotope signatures by deep-sea corals is that extraordinarily slow growth rates can promote the occurrence of isotopic reordering in the interfacial region of growing crystals. We also cannot rule out a component of a biological "vital-effect" influencing clumped isotope signatures in one or both orders of coral. Based on published experimental data and theoretical calculations, these biological "vital" effects could arise from kinetic isotope effects due to the source of carbon used for calcification, temperature- and pH-dependent rates of CO2 hydration and/or hydroxylation, calcifying fluid pH, the activity of carbonic anhydrase, the residence time of dissolved inorganic carbon in the calcifying fluid, and calcification rate. A third possible explanation is the occurrence of variable acid digestion fractionation factors. Although a recent study has suggested that dolomite, calcite, and aragonite may have similar clumped isotope acid digestion fractionation factors, the influence of acid digestion kinetics on Δ47 is a subject that warrants further investigation.

  19. Carbonate "clumped" isotope signatures in aragonitic scleractinian and calcitic gorgonian deep-sea corals

    Science.gov (United States)

    Kimball, J.; Tripati, R. E.; Dunbar, R.

    2015-12-01

    corals of different mineralogy is in the same direction as published theoretical predictions for the offset between calcite and aragonite, although the magnitude of the offset is different. One possibility is that the deep-sea coral results reflect that crystals may attain nominal mineral equilibrium clumped isotope signatures only under conditions of extremely slow growth. In that case, a possible explanation for the attainment of disequilibrium bulk isotope signatures and equilibrium clumped isotope signatures by deep-sea corals is that extraordinarily slow growth rates can promote the occurrence of isotopic reordering in the interfacial region of growing crystals. We also cannot rule out a component of a biological "vital-effect" influencing clumped isotope signatures in one or both orders of coral. Based on published experimental data and theoretical calculations, these biological "vital" effects could arise from kinetic isotope effects due to the source of carbon used for calcification, temperature- and pH-dependent rates of CO2 hydration and/or hydroxylation, calcifying fluid pH, the activity of carbonic anhydrase, the residence time of dissolved inorganic carbon in the calcifying fluid, and calcification rate. A third possible explanation is the occurrence of variable acid digestion fractionation factors. Although a recent study has suggested that dolomite, calcite, and aragonite may have similar clumped isotope acid digestion fractionation factors, the influence of acid digestion kinetics on Δ47 is a subject that warrants further investigation.

  20. Patterns of biomediated CaCO3 crystal bushes in hot spring deposits

    Science.gov (United States)

    Peng, Xiaotong; Jones, Brian

    2013-08-01

    In the Eryuan hot spring, located in south China, the vent pool is covered with “crystal bushes”, up to 2 cm high, 1 cm in diameter, that grew in the biofilms that thrive in the spring waters that have a pH of 7.5 and a temperature of 88 °C. The biofilms are formed largely of phototrophic purple bacteria and green bacteria. Growth of the crystal bushes, which are formed of aragonite crystals (wheat-sheaves, radiating clusters), rhombohedral and dodecahedral calcite crystals, amorphous CaCO3 (ACC), and opal-A, is attributed to precipitation in the micro-domains of the biofilms where physiochemical conditions can vary on the sub-micron scale. There is no evidence that the calcite was formed through recrystallization of the metastable aragonite and most of the calcite crystals developed as mesocrystals that are characterized by incomplete growth and porous crystal faces. With the onset of diagenesis, there is a high probability that the crystal bushes will lose much of their identity as the (1) biofilm is lost through decay, (2) ACC and aragonite change to calcite, (3) identities of the mesocrystals and incompletely formed crystals are lost through continued precipitation and/or recrystallization, and (4) porous crystal faces are converted to solid crystal faces. This means that most of the features considered indicative of biomediated calcite precipitation have a low preservation potential and that the recognition of biomediated precipitates in old spring deposits may remain problematical.

  1. EDITORIAL: Optical orientation Optical orientation

    Science.gov (United States)

    SAME ADDRESS *, Yuri; Landwehr, Gottfried

    2008-11-01

    priority of the discovery in the literature, which was partly caused by the existence of the Iron Curtain. I had already enjoyed contact with Boris in the 1980s when the two volumes of Landau Level Spectroscopy were being prepared [2]. He was one of the pioneers of magneto-optics in semiconductors. In the 1950s the band structure of germanium and silicon was investigated by magneto-optical methods, mainly in the United States. No excitonic effects were observed and the band structure parameters were determined without taking account of excitons. However, working with cuprous oxide, which is a direct semiconductor with a relative large energy gap, Zakharchenya and his co-worker Seysan showed that in order to obtain correct band structure parameters, it is necessary to take excitons into account [3]. About 1970 Boris started work on optical orientation. Early work by Hanle in Germany in the 1920s on the depolarization of luminescence in mercury vapour by a transverse magnetic field was not appreciated for a long time. Only in the late 1940s did Kastler and co-workers in Paris begin a systematic study of optical pumping, which led to the award of a Nobel prize. The ideas of optical pumping were first applied by Georges Lampel to solid state physics in 1968. He demonstrated optical orientation of free carriers in silicon. The detection method was nuclear magnetic resonance; optically oriented free electrons dynamically polarized the 29Si nuclei of the host lattice. The first optical detection of spin orientation was demonstrated by with the III-V semiconductor GaSb by Parsons. Due to the various interaction mechanisms of spins with their environment, the effects occurring in semiconductors are naturally more complex than those in atoms. Optical detection is now the preferred method to detect spin alignment in semiconductors. The orientation of spins in crystals pumped with circularly polarized light is deduced from the degree of circular polarization of the recombination

  2. Pyrite-pyrrhotite intergrowths in calcite marble from Bistriški Vintgar, Slovenia

    Science.gov (United States)

    Zavašnik, J.

    2016-02-01

    Roman marble quarry in Bistrica gorge in southern Pohorje Mt. (north-eastern Slovenia) is situated in a 20 m thick lens of layered marble, at the contact zone between granodiorite and metamorphites. Grey and yellowish non-homogenous calcite marble is heavily included by mica, quartz, feldspars, zoisite, pyrite and amphiboles. In the present research, we have studied numerous pyrite (FeS2) crystals associated with yellowish-bronze non-stoichiometric pyrrhotite (Fe1-xS), not previously reported from this locality. SEM investigation revealed unusual sequence of crystallisation: primary skeletal pyrrhotite matrix is sparsely overgrown by well-crystalline pyrite, both being overgrown by smaller, well-developed hexagonal pyrrhotite crystals of the second generation. With TEM we identify the pyrrhotite as 5T-Fe1-xS phase, where x is about 0.1 and is equivalent to Fe9S10. The pyrite-pyrrhotite coexistence allows us a construction of fO2-pH diagram of stability fields, which reflects geochemical conditions at the time of marble re-crystallisation.

  3. Radiation does response of calcium carbonate crystal in marine shells samples

    OpenAIRE

    Changkian, S.; Kaewtubtim, P.

    2002-01-01

    A study of the evolution of element, crystal structure and thermoluminescence signal versus gamma irradiation dose were carried out for calcite shells samples. The composition of element was studied by X-ray fluorescence spectrometer. As identified by X-ray diffraction and SEM/EDS analysis, two polymorphs of calcium-carbonate were extracted: calcite and aragonite. The evolution of TL signal versus gamma irradiation dose using the TL reader (Harshaw 2000) was initially dependent on crystal str...

  4. Kinetical and thermodynamical parametars of crystallization of iPP nucleated with mixed α-nucleators

    OpenAIRE

    Janevski, Aco; Bogoeva-Gaceva, Gordana

    2013-01-01

    It is well known that the presence of a solid surface (substrate) in contact with thermoplastic polymers during the crystallization from the melt, generally favors the heterogeneous nucleation. Isothermal and nonisothermal crystallization of isotactic polypropylene (iPP) nucleated with 0.1 %wt. talc (average dimension of 20 µ) (assign. PPT), 0.1 %wt. calcite (average dimension of 5µ) (assign. PPC) and polymer nucleated with 0.1 %wt. talc plus 0.1 % wt. calcite (assign. PPTC), were studied...

  5. Three-Dimensional Reciprocal-Lattice Analysis Using Azimuth-Scan Reflection High-Energy Electron Diffraction: Determination of Complex Crystal Orientations of Al Grains on Si(111) Surface

    Science.gov (United States)

    Hattori, Ken; Oi, Hideo; Tanaka, Kota; Kumagai, Tomohiro; Daimon, Hiroshi

    2012-05-01

    We have applied a three-dimensional (3D) reciprocal-lattice analysis method using a typical reflection high-energy electron diffraction (RHEED) system - all RHEED patterns in scanning sample-surface azimuth are converted into 3D reciprocal-lattice space. This analysis method can determine complex crystal orientations of nanoclusters, islands, and grains with multiple domains, which are difficult to obtain from a small number of non-converted two-dimensional RHEED patterns. For an Al-deposited Si(111) surface followed by annealing, we successfully determined new crystal orientations of Al grains: Al(001), Al(012) and Al(011) ∥ Si(111) with Al[100] ∥ Si. The typical acquisition time of 3D RHEED patterns is 10-20 min, which is shorter than that by a standard X-ray diffraction system with φ and ω scans for 3D reciprocal-lattice mapping. This is one of the advantages of this analysis method, in addition to the convenient observation of in situ vacuum-fabricated nanocrystals on substrate surfaces with high sensitivity.

  6. 3D imaging using X-Ray tomography and SEM combined FIB to study non isothermal creep damage of (111) oriented samples of γ / γ ′ nickel base single crystal superalloy MC2

    KAUST Repository

    Jouiad, Mustapha

    2012-01-01

    An unprecedented investigation consisting of the association of X-Ray tomography and Scanning Electron Microscopy combined with Focus Ion Beam (SEM-FIB) is conducted to perform a 3D reconstruction imaging. These techniques are applied to study the non-isothermal creep behavior of close (111) oriented samples of MC2 nickel base superalloys single crystal. The issue here is to develop a strategy to come out with the 3D rafting of γ\\' particles and its interaction whether with dislocation structures or/and with the preexisting voids. This characterization is uncommonly performed away from the conventional studied orientation [001] in order to feed the viscoplastic modeling leading to its improvement by taking into account the crystal anisotropy. The creep tests were performed at two different conditions: classical isothermal tests at 1050°C under 140 MPa and a non isothermal creep test consisting of one overheating at 1200°C and 30 seconds dwell time during the isothermal creep life. The X-Ray tomography shows a great deformation heterogeneity that is pronounced for the non-isothermal tested samples. This deformation localization seems to be linked to the preexisting voids. Nevertheless, for both tested samples, the voids coalescence is the precursor of the observed damage leading to failure. SEM-FIB investigation by means of slice and view technique gives 3D views of the rafted γ\\' particles and shows that γ corridors evolution seems to be the main creep rate controlling parameter. © 2012 Trans Tech Publications, Switzerland.

  7. Dielectric properties and phase transitions of [001], [110], and [111] oriented Pb(Zn1/3Nb2/3)O3-6%PbTiO3 single crystals

    Science.gov (United States)

    Amin Hentati, Mouhamed; Dammak, Hichem; Khemakhem, Hamadi; Pham Thi, Mai

    2013-06-01

    Phase transformations of [001], [110], and [111] oriented Pb(Zn1/3Nb2/3)O3-6%PbTiO3 (PZN-6%PT) single crystals have been investigated by means of dielectric permittivity and loss, x-ray diffraction and depolarization current as function of temperature (from 250 to 500 K). The unpoled samples undergo R-T-C phase transition sequence during zero field heating (ZFH), where R, T, and C are rhombohedral, tetragonal, and cubic phases, respectively. Under electric field (0.5 kV/cm), an intermediate orthorhombic (O) phase is induced between the T and R phases in the field cooling (FC) process. This phase reappears during subsequent zero field heating of the poled sample (zero field heating after field cooling: ZFHaFC). The existence range of this O phase depends on both the crystal orientation and the measurement conditions (FC or ZFHaFC). Finally, for the [001] direction, it was found that the piezoelectric activity of the intermediate phase is the highest.

  8. Calcite production by coccolithophores in the south east Pacific Ocean

    Directory of Open Access Journals (Sweden)

    L. Beaufort

    2008-08-01

    Full Text Available BIOSOPE cruise covered an oceanographic transect through the centre of the South Pacific Gyre (SPG from the Marquesas archipelago to the Peru-Chile upwelling (PCU. Water samples from 6 depths in the euphotic zone were collected at 20 stations. The concentrations of suspended calcite particles, coccolithophores cells and detached coccoliths were estimated together with size and weight using an automatic polarizing microscope, a digital camera, and a collection of softwares performing morphometry and pattern recognition. Some of these softwares are new and described here for the first time. The coccolithophores standing stocks were usually low and reached maxima west of the PCU. The coccoliths of Emiliania huxleyi, Gephyrocapsa spp. and Crenalithus spp. (Order Isochrysidales represented more than 30% of all the suspended calcite particles detected in the size range 0.1–46 μm (22% of PIC in term of calcite weight. These species grew preferentially in the Chlorophyll maximum zone. In the SPG their maximum cell concentrations were recorded between depth of 150 and 200 m, which is unusually deep for these taxa. The weight of coccoliths and coccospheres were correlated to their size. Large and heavy coccoliths and coccospheres were found in regions with relatively high fertility in the Marquises Island and in the PCU. Small and light coccoliths and coccospheres were found west of the PCU. This distribution is strongly related to ocean chemistry in particular to alkalinity and to carbonate ions concentration. The biotic (coccolithophores production influence on calcification is mainly driven at the local scale (depth whereas the abiotic (carbonate chemistry plays its most important role at the regional (horizontal level. Here 94% of the variability of coccolith and coccosphere weight can be explained by a change in 7 environmental variables.

  9. Calcite production by coccolithophores in the south east Pacific Ocean

    Science.gov (United States)

    Beaufort, L.; Couapel, M.; Buchet, N.; Claustre, H.; Goyet, C.

    2008-08-01

    BIOSOPE cruise covered an oceanographic transect through the centre of the South Pacific Gyre (SPG) from the Marquesas archipelago to the Peru-Chile upwelling (PCU). Water samples from 6 depths in the euphotic zone were collected at 20 stations. The concentrations of suspended calcite particles, coccolithophores cells and detached coccoliths were estimated together with size and weight using an automatic polarizing microscope, a digital camera, and a collection of softwares performing morphometry and pattern recognition. Some of these softwares are new and described here for the first time. The coccolithophores standing stocks were usually low and reached maxima west of the PCU. The coccoliths of Emiliania huxleyi, Gephyrocapsa spp. and Crenalithus spp. (Order Isochrysidales) represented more than 30% of all the suspended calcite particles detected in the size range 0.1 46 μm (22% of PIC in term of calcite weight). These species grew preferentially in the Chlorophyll maximum zone. In the SPG their maximum cell concentrations were recorded between depth of 150 and 200 m, which is unusually deep for these taxa. The weight of coccoliths and coccospheres were correlated to their size. Large and heavy coccoliths and coccospheres were found in regions with relatively high fertility in the Marquises Island and in the PCU. Small and light coccoliths and coccospheres were found west of the PCU. This distribution is strongly related to ocean chemistry in particular to alkalinity and to carbonate ions concentration. The biotic (coccolithophores production) influence on calcification is mainly driven at the local scale (depth) whereas the abiotic (carbonate chemistry) plays its most important role at the regional (horizontal) level. Here 94% of the variability of coccolith and coccosphere weight can be explained by a change in 7 environmental variables.

  10. Principles of calcite dissolution in human and artificial otoconia.

    Directory of Open Access Journals (Sweden)

    Leif Erik Walther

    Full Text Available Human otoconia provide mechanical stimuli to deflect hair cells of the vestibular sensory epithelium for purposes of detecting linear acceleration and head tilts. During lifetime, the volume and number of otoconia are gradually reduced. In a process of degeneration morphological changes occur. Structural changes in human otoconia are assumed to cause vertigo and balance disorders such as benign paroxysmal positional vertigo (BPPV. The aim of this study was to investigate the main principles of morphological changes in human otoconia in dissolution experiments by exposure to hydrochloric acid, EDTA, demineralized water and completely purified water respectively. For comparison reasons artificial (biomimetic otoconia (calcite gelatin nanocomposits and natural calcite were used. Morphological changes were detected in time steps by the use of environmental scanning electron microscopy (ESEM. Under in vitro conditions three main dissolution mechanisms were identified as causing characteristic morphological changes of the specimen under consideration: pH drops in the acidic range, complex formation with calcium ions and changes of ion concentrations in the vicinity of otoconia. Shifts in pH cause a more uniform reduction of otoconia size (isotropic dissolution whereas complexation reactions and changes of the ionic concentrations within the surrounding medium bring about preferred attacks at specific areas (anisotropic dissolution of human and artificial otoconia. Owing to successive reduction of material, all the dissolution mechanisms finally produce fragments and remnants of otoconia. It can be assumed that the organic component of otoconia is not significantly attacked under the given conditions. Artificial otoconia serve as a suitable model system mimicking chemical attacks on biogenic specimens. The underlying principles of calcite dissolution under in vitro conditions may play a role in otoconia degeneration processes such as BPPV.

  11. Arsenite sorption and co-precipitation with calcite

    OpenAIRE

    Roman-Ross, Gabriela; Cuello, Gabriel; Turrillas, Xavier; Fernandez-Martinez, Alejandro; Charlet, Laurent

    2008-01-01

    Sorption of As(III) by calcite was investigated as a function of As(III) concentration, time and pH. The sorption isotherm, i.e. the log As(III) vs. log [As(OH)3 degrees / Assat] plot is S-shaped and has been modelled on an extended version of the surface precipitation model. At low concentrations, As(OH)3 degrees is adsorbed by complexation to surface Ca surface sites, as previously described by the X-ray standing wave technique. The inflexion point of the isotherm, where As(OH)3 degrees is ...

  12. Recombinant sea urchin vascular endothelial growth factor directs single-crystal growth and branching in vitro.

    Science.gov (United States)

    Knapp, Regina T; Wu, Ching-Hsuan; Mobilia, Kellen C; Joester, Derk

    2012-10-31

    Biomineralization in sea urchin embryos is a crystal growth process that results in oriented single-crystalline spicules with a complex branching shape and smoothly curving surfaces. Uniquely, the primary mesenchyme cells (PMCs) that construct the endoskeleton can be cultured in vitro. However, in the absence of morphogenetic cues secreted by other cells in the embryo, spicules deposited in PMC culture lack the complex branching behavior observed in the embryo. Herein we demonstrate that recombinant sea urchin vascular endothelial growth factor (rVEGF), a signaling molecule that interacts with a cell-surface receptor, induces spiculogenesis and controls the spicule shape in PMC culture. Depending on the rVEGF concentration, PMCs deposit linear, "h"- and "H"-shaped, or triradiate spicules. Remarkably, the change from linear to triradiate occurs with a switch from bidirectional crystal growth parallel to the calcite c axis to growth along the three a axes. This finding has implications for our understanding of how cells integrate morphogenesis on the multi-micrometer scale with control over lattice orientation on the atomic scale. The PMC model system is uniquely suited to investigate this mechanism and develop biotechnological approaches to single-crystal growth. PMID:23066927

  13. Inversion of calcite twin data, paleostress reconstruction and multiphase weak deformation in cratonic interior - Evidence from the Proterozoic Cuddapah basin, India

    Science.gov (United States)

    Tripathy, Vikash; Saha, Dilip

    2015-08-01

    Paleostress orientations from mechanically twinned calcite in carbonate rocks and veins in the neighborhood of large faults were investigated to comment on the nature of weak upper crustal stresses affecting sedimentary successions within the Proterozoic Cuddapah basin, India. Application of Turner's P-B-T method and Spang's Numerical dynamic analysis on Cuddapah samples provided paleostress orientations comparable to those derived from fault-slip inversion. Results from the neighborhood of E-W faults cutting through the Paleoproterozoic Papaghni and Chitravati groups and the Neoproterozoic Kurnool Group in the western Cuddapah basin, reveal existence of multiple deformation events - (1) NE-SW σ3 in strike-slip to extensional regime along with an additional event having NW-SE σ3, for lower Cuddapah samples; (2) compressional/transpressional event with ESE-WNW or NNE-SSW σ1 mainly from younger Kurnool samples. Integrating results from calcite twin data inversion, fault-slip analysis and regional geology we propose that late Mesoproterozoic crustal extension led to initial opening of the Kurnool sub-basin, subsequently influenced by weak compressional deformation. The dynamic analysis of calcite twins thus constrains the stress regimes influencing basin initiation in the southern Indian cratonic interior and subsequent basin inversion in relation to craton margin mobile belts and plausible global tectonic events in the Proterozoic.

  14. First-Principles Study on Influences of Crystal Structure and Orientation on Band Offsets at the CdS/Cu2ZnSnS4 Interface

    OpenAIRE

    Wujisiguleng Bao; Masaya Ichimura

    2012-01-01

    Cu2ZnSnS4 (CZTS) has attracted much attention recently as an absorber layer material in a heterojunction solar cell. Using the first-principles method, we calculate the band offsets for the CdS/CZTS heterojunction. The valence band offset is 1.2 eV for the (001) CdS/CZTS heterointerface and 1.0 eV for the (010) heterointerface, when CZTS is considered to crystallize in the kesterite structure. When CZTS is considered to crystallize in the stannite structure,  eV for the (001) heterointerface...

  15. Thermoluminescent of induced calcite by gamma and ultraviolet radiation

    International Nuclear Information System (INIS)

    Samples of brazilian calcite, exposed to gamma radiation in laboratory and heated at constant rate of 2.70 C/s, showed three glow peaks at 150, 250 and 350 0C in their thermoluminescent emission curves. The analysis of these peaks, using different models, indicated that they follow a second order kinetics; it has been obtained, for the activation energy, 1.3, 1.5 and 1.7 eV, and, for the pre-exponential factors, 8.1 x 10 14, 6.8 x10 13 and 2.4 x 1012 s-1. Although the total thermoluminescent emission has stayed constant, the relative height of glow peaks has changed with the temperature of annealing in the range of 400 to 700 0C. Exposed samples were also illuminated with ultraviolet light and the resultant curves showed partial or total bleaching or some glow peaks and the growth of peaks at lower temperatures. Samples of virgin calcite, submited to increasing exposures of gamma rays, showed a corresponding enhancement of the optical absorption bands in the range of 25000 to 47000 cm-1 A subsequent illumination of these samples with ultraviolet light produced a decrease of the optical absorption bands at the same range. (author)

  16. Prediction of calcite Cement Distribution in Shallow Marine Sandstone Reservoirs using Seismic Data

    Energy Technology Data Exchange (ETDEWEB)

    Bakke, N.E.

    1996-12-31

    This doctoral thesis investigates how calcite cemented layers can be detected by reflection seismic data and how seismic data combined with other methods can be used to predict lateral variation in calcite cementation in shallow marine sandstone reservoirs. Focus is on the geophysical aspects. Sequence stratigraphy and stochastic modelling aspects are only covered superficially. Possible sources of calcite in shallow marine sandstone are grouped into internal and external sources depending on their location relative to the presently cemented rock. Well data and seismic data from the Troll Field in the Norwegian North Sea have been analysed. Tuning amplitudes from stacks of thin calcite cemented layers are analysed. Tuning effects are constructive or destructive interference of pulses resulting from two or more closely spaced reflectors. The zero-offset tuning amplitude is shown to depend on calcite content in the stack and vertical stack size. The relationship is found by regression analysis based on extensive seismic modelling. The results are used to predict calcite distribution in a synthetic and a real data example. It is found that describing calcite cemented beds in shallow marine sandstone reservoirs is not a deterministic problem. Hence seismic inversion and sequence stratigraphy interpretation of well data have been combined in a probabilistic approach to produce models of calcite cemented barriers constrained by a maximum amount of information. It is concluded that seismic data can provide valuable information on distribution of calcite cemented beds in reservoirs where the background sandstones are relatively homogeneous. 63 refs., 78 figs., 10 tabs.

  17. Titania single crystals with a curved surface

    Science.gov (United States)

    Yang, Shuang; Yang, Bing Xing; Wu, Long; Li, Yu Hang; Liu, Porun; Zhao, Huijun; Yu, Yan Yan; Gong, Xue Qing; Yang, Hua Gui

    2014-11-01

    Owing to its scientific and technological importance, crystallization as a ubiquitous phenomenon has been widely studied over centuries. Well-developed single crystals are generally enclosed by regular flat facets spontaneously to form polyhedral morphologies because of the well-known self-confinement principle for crystal growth. However, in nature, complex single crystalline calcitic skeleton of biological organisms generally has a curved external surface formed by specific interactions between organic moieties and biocompatible minerals. Here we show a new class of crystal surface of TiO2, which is enclosed by quasi continuous high-index microfacets and thus has a unique truncated biconic morphology. Such single crystals may open a new direction for crystal growth study since, in principle, crystal growth rates of all facets between two normal {101} and {011} crystal surfaces are almost identical. In other words, the facet with continuous Miller index can exist because of the continuous curvature on the crystal surface.

  18. Impact of cooling condition on the crystal structure and surface quality of preferred c-axis-oriented AIN films for SAW devices

    Institute of Scientific and Technical Information of China (English)

    ZHANG Geng-yu; YANG Bao-he; ZHAO Jian; LI Cui-ping; LI Ming-ji

    2011-01-01

    AIN films with preferred c-axis orientation are deposited on Si substrates using the radio frequency (RF) magnetron sputtering method. The post-processing is carried out under the cooling conditions including high vacuum, low vacuum under deposition gas ambient and low vacuum under dynamic N2 ambient. Structures and morphologies of the films are analyzed by X-ray diffraction (XRD) and atomic force microscopy (AFM). The hardness and Young's modulus are investigated by the nanoindenter. The experimental results indicate that the (100) and (110) peak intensities decrease in the XRD spectra and the root-mean-square of roughness (Rrms) of the film decreases gradually with the increase of the cooling rate. The maximum values of the hardness and Young's modulus are obtained by cooling in low vacuum under deposition gas ambient. The reason for orientation variation of the films is explained from the perspective of the Al-N bond formation.

  19. Thermal properties of halogen-ethane glassy crystals: Effects of orientational disorder and the role of internal molecular degrees of freedom

    Science.gov (United States)

    Vdovichenko, G. A.; Krivchikov, A. I.; Korolyuk, O. A.; Tamarit, J. Ll.; Pardo, L. C.; Rovira-Esteva, M.; Bermejo, F. J.; Hassaine, M.; Ramos, M. A.

    2015-08-01

    The thermal conductivity, specific heat, and specific volume of the orientational glass former 1,1,2-trichloro-1,2,2-trifluoroethane (CCl2F-CClF2, F-113) have been measured under equilibrium pressure within the low-temperature range, showing thermodynamic anomalies at ca. 120, 72, and 20 K. The results are discussed together with those pertaining to the structurally related 1,1,2,2-tetrachloro-1,2-difluoroethane (CCl2F-CCl2F, F-112), which also shows anomalies at 130, 90, and 60 K. The rich phase behavior of these compounds can be accounted for by the interplay between several of their degrees of freedom. The arrest of the degrees of freedom corresponding to the internal molecular rotation, responsible for the existence of two energetically distinct isomers, and the overall molecular orientation, source of the characteristic orientational disorder of plastic phases, can explain the anomalies at higher and intermediate temperatures, respectively. The soft-potential model has been used as the framework to describe the thermal properties at low temperatures. We show that the low-temperature anomaly of the compounds corresponds to a secondary relaxation, which can be associated with the appearance of Umklapp processes, i.e., anharmonic phonon-phonon scattering, that dominate thermal transport in that temperature range.

  20. Thermal properties of halogen-ethane glassy crystals: Effects of orientational disorder and the role of internal molecular degrees of freedom

    International Nuclear Information System (INIS)

    The thermal conductivity, specific heat, and specific volume of the orientational glass former 1,1,2-trichloro-1,2,2-trifluoroethane (CCl2F–CClF2, F-113) have been measured under equilibrium pressure within the low-temperature range, showing thermodynamic anomalies at ca. 120, 72, and 20 K. The results are discussed together with those pertaining to the structurally related 1,1,2,2-tetrachloro-1,2-difluoroethane (CCl2F–CCl2F, F-112), which also shows anomalies at 130, 90, and 60 K. The rich phase behavior of these compounds can be accounted for by the interplay between several of their degrees of freedom. The arrest of the degrees of freedom corresponding to the internal molecular rotation, responsible for the existence of two energetically distinct isomers, and the overall molecular orientation, source of the characteristic orientational disorder of plastic phases, can explain the anomalies at higher and intermediate temperatures, respectively. The soft-potential model has been used as the framework to describe the thermal properties at low temperatures. We show that the low-temperature anomaly of the compounds corresponds to a secondary relaxation, which can be associated with the appearance of Umklapp processes, i.e., anharmonic phonon-phonon scattering, that dominate thermal transport in that temperature range

  1. Thermal properties of halogen-ethane glassy crystals: Effects of orientational disorder and the role of internal molecular degrees of freedom

    Energy Technology Data Exchange (ETDEWEB)

    Vdovichenko, G. A.; Krivchikov, A. I.; Korolyuk, O. A. [B. Verkin Institute for Low Temperature Physics and Engineering of NAS Ukraine, 47 Lenin Ave., 61103 Kharkov (Ukraine); Tamarit, J. Ll., E-mail: josep.lluis.tamarit@upc.edu; Pardo, L. C.; Rovira-Esteva, M. [Grup de Caracterització de Materials, Departament de Física i Enginyeria Nuclear, ETSEIB, Universitat Politècnica de Catalunya, Diagonal 647, 08028 Barcelona, Catalonia (Spain); Bermejo, F. J. [Instituto de Estructura de la Materia, CSIC, Consejo Superior de Investigaciones Cientificas, Serrano 123, 28006 Madrid (Spain); Hassaine, M.; Ramos, M. A. [Laboratorio de Bajas Temperaturas, Departamento de Física de la Materia Condensada, Condensed Matter Physics Center (IFIMAC) and Instituto Nicolás Cabrera, Universidad Autónoma de Madrid, Francisco Tomás y Valiente 7, 28049 Madrid (Spain)

    2015-08-28

    The thermal conductivity, specific heat, and specific volume of the orientational glass former 1,1,2-trichloro-1,2,2-trifluoroethane (CCl{sub 2}F–CClF{sub 2}, F-113) have been measured under equilibrium pressure within the low-temperature range, showing thermodynamic anomalies at ca. 120, 72, and 20 K. The results are discussed together with those pertaining to the structurally related 1,1,2,2-tetrachloro-1,2-difluoroethane (CCl{sub 2}F–CCl{sub 2}F, F-112), which also shows anomalies at 130, 90, and 60 K. The rich phase behavior of these compounds can be accounted for by the interplay between several of their degrees of freedom. The arrest of the degrees of freedom corresponding to the internal molecular rotation, responsible for the existence of two energetically distinct isomers, and the overall molecular orientation, source of the characteristic orientational disorder of plastic phases, can explain the anomalies at higher and intermediate temperatures, respectively. The soft-potential model has been used as the framework to describe the thermal properties at low temperatures. We show that the low-temperature anomaly of the compounds corresponds to a secondary relaxation, which can be associated with the appearance of Umklapp processes, i.e., anharmonic phonon-phonon scattering, that dominate thermal transport in that temperature range.

  2. CHARACTERIZATION METHODS AND RESEARCH PROGRESSES FOR STRETCHING ORIENTATION AND STRAIN-INDUCED CRYSTALLIZATION OF ELASTOMERS%弹性体拉伸取向和应变诱导结晶研究进展

    Institute of Scientific and Technical Information of China (English)

    徐志强; 卢咏来; 张立群; 闫寿科

    2011-01-01

    橡胶拉伸取向和应变诱导结晶被公认为是天然橡胶和一些合成橡胶(如氯丁橡胶、丁基橡胶、氢化丁腈橡胶等)高效自增强的关键所在,研究该现象和行为规律对理解橡胶增强机理具有十分重要的意义.本文总结了常用于研究橡胶拉伸取向和应变诱导结晶的表征方法,对其原理、特点和适用范围进行了对比分析;综述了纳米填料(炭黑,二氧化硅,黏土,碳纳米管)增强橡胶的拉伸取向和应变诱导结晶以及热塑性弹性体拉伸取向的研究进展;并展望了该领域的未来发展方向.%Stretching orientation and strain-induced crystallization of rubber is widely recognized to play key role in the self-reinforcement of natural rubber and some synthetic rubbers (such as chloroprene rubber, butyl rubber and hydrogenated nitrile-butadiene rubber). Therefore, studying these phenomena and behavior has substantial significance for understanding the mechanism of the rubber reinforcing. In this review, various characterization methods concerning stretching orientation and strain-induced crystallization of polymer materials as well as principles, features and applicable scope of these methods were summarized and compared.Current progresses in the research about stretching orientation and strain-induced crystallization of nano-fillers (including carbon black, silica, nano clay and carbon nanotube) reinforced rubber composites as well as thermoplastic elastomers were surveyed. Finally, the future developing trend in this research field was prospected.

  3. Structure and interactions of calcite spherulites with {alpha}-chitin in the brown shrimp (Penaeus aztecus) shell

    Energy Technology Data Exchange (ETDEWEB)

    Heredia, A. [Instituto de Ciencias Nucleares, Departamento de Quimica de Radiaciones y Radioquimica, UNAM, Circuito Exterior C.U. Apdo., Postal 70-543, 04510 Mexico, D.F. (Mexico); Physikalisches Institut and Center for Nanotechnology, Universitaet Muenster, Gievenbecker Weg 11, 48149 Muenster (Germany); Aguilar-Franco, M. [Instituto de Fisica, Depto de Fisicoquimica, UNAM, Circuito Exterior s/n, Ciudad Universitaria Apartado Postal 20-364 01000 Mexico D.F. (Mexico); Magana, C. [Instituto de Fisica, Depto de Estado Solido, UNAM, Circuito Exterior s/n, Ciudad Universitaria Apartado Postal 20-364 01000 Mexico D.F. (Mexico); Flores, C. [Instituto de Investigaciones en Materiales, Depto de Estado Solido, Laboratorio de Biomateriales, UNAM, Circuito Exterior C.U. S/N CP 04510 Mexico, D.F. (Mexico); Pina, C. [Instituto de Investigaciones en Materiales, Depto de Estado Solido, Laboratorio de Biomateriales, UNAM, Circuito Exterior C.U. S/N CP 04510 Mexico, D.F. (Mexico); Velazquez, R. [Centro de Fisica Aplicada Tecnologia Avanzada, UNAM, Km. 15 Carretera Queretaro-San Luis Potosi, C.P. 76230, Queretaro, Qro. (Mexico); Schaeffer, T.E. [Physikalisches Institut and Center for Nanotechnology, Universitaet Muenster, Gievenbecker Weg 11, 48149 Muenster (Germany); Bucio, L. [Instituto de Fisica, Depto de Estado Solido, UNAM, Circuito Exterior s/n, Ciudad Universitaria Apartado Postal 20-364 01000 Mexico D.F. (Mexico); Basiuk, V.A. [Instituto de Ciencias Nucleares, Departamento de Quimica de Radiaciones y Radioquimica, UNAM, Circuito Exterior C.U. Apdo., Postal 70-543, 04510 Mexico, D.F. (Mexico)

    2007-01-15

    White spots form in the brown shrimp (Penaeus aztecus, Decapoda) shell during frozen storage. The mineral formed consists of calcite incorporated into an amorphous {alpha}-chitin matrix. We studied mechanisms of interaction of amorphous {alpha}-chitin macromolecules with hkl crystal planes to form highly ordered structures, as well as the role of specific sites in the biopolymer, which can be related to nucleation and spheroidal crystal growth. We used low vacuum scanning electron microscopy (LVSEM), X-ray powder diffraction (XRD), atomic force microscopy (AFM), Fourier-transform infrared spectroscopy (FT-IR), and molecular mechanics modeling (MM+ method). AFM images showed fingerprint distances in the biopolymer and a highly layered structure in the crystalline material. The presence of {alpha}-chitin, with a specific spatial distribution of radicals, is thought to be responsible for nucleation and to thermodynamically stabilize ions to form the spherulite crystalline phase, which are usually oval to spherical (0.10 to 200 {mu}m in diameter). Our models of crystal-biopolymer interaction found high affinity of CO{sub 3} {sup 2-} anions in the (104) crystalline plane (the main plane in calcite monocrystals) to NH- groups of the biopolymer, as well as of the C=O in the biopolymer to Ca{sup 2+} cations in the crystalline structure. These interactions explain the spherical growth and inhibition in some planes. The specific physicochemical interactions (docking of groups depending on their geometrical distribution) suggest that the biomineral structure is controlled by the biopolymer on a local scale. This information is useful for further design and improvement of (hybrid) materials for versatile application, from nanotechnology to biomedicine and engineering.

  4. First-Principles Study on Influences of Crystal Structure and Orientation on Band Offsets at the CdS/Cu2ZnSnS4 Interface

    Directory of Open Access Journals (Sweden)

    Wujisiguleng Bao

    2012-01-01

    Full Text Available Cu2ZnSnS4 (CZTS has attracted much attention recently as an absorber layer material in a heterojunction solar cell. Using the first-principles method, we calculate the band offsets for the CdS/CZTS heterojunction. The valence band offset is 1.2 eV for the (001 CdS/CZTS heterointerface and 1.0 eV for the (010 heterointerface, when CZTS is considered to crystallize in the kesterite structure. When CZTS is considered to crystallize in the stannite structure,  eV for the (001 heterointerface and  eV for the (010 heterointerface. In any case, the conduction band minimum of CZTS is higher than that of CdS, and the conduction band offset is in a range between 0.1 and 0.4 eV.

  5. Kinetics and Mechanisms of Calcite Reactions with Saline Waters

    Energy Technology Data Exchange (ETDEWEB)

    Gorman, Brian P [Colorado School of Mines, Golden, CO (United States)

    2015-09-02

    Project Description: The general objective of the proposed research is to determine the kinetics and mechanisms of calcite reactions with saline waters over a wide range of saline water composition, pCO2, and modest ranges in T and P. This will be accomplished by studying both reaction rates and solubility from changes in solution chemistry, and making nanoscale observations of calcite precipitate surface morphology and composition at the micro-to-nano-scale to provide an understanding of controlling reaction mechanisms and pathways. The specific objectives necessary to reach the general objective are: a) determination of how pCO2, Ca2+, ionic strength and “foreign” ions influence reaction rates; and b) investigate the influence of these parameters on apparent kinetic solubility from dissolution and precipitation reactions. This information will clearly be central to the construction of reliable reaction-transport models to predict reservoir and formation response to increased CO2 in saline waters. This program was initially collaborative with John Morse at Texas A&M, however his passing shortly after the beginning of this program resulted in abbreviated research time and effort. Summary of Results: Early studies using electron microscopy and spectroscopy indicated that carbonate precipitation from natural seawater (NSW) conditions onto aragonite substrates was mediated by a surface amorphous calcium carbonate layer. It was hypothesized that this ACC layer (observed after < 5days reaction time) was responsible for the abnormal reaction kinetics and also served as a metastable seed layer for growth of epitaxial aragonite. Further studies of the ACC formation mechanism indicated a strong dependence on the Mg concentration in solution. Subsequent studies at shorter times (10 hrs) on calcite substrates and in a wide range of supersaturation conditions did not indicate any ACC layer. Instead, an epitaxial layer by layer

  6. Crystallization and self-assembly of flowerlike superstructures of calcium carbonate regulated by pepsin Langmuir monolayers

    International Nuclear Information System (INIS)

    Flowerlike superstructures of calcium carbonate were synthesized at air–water interface in the presence of pepsin Langmuir monolayers as the biomimetic template. The phase structure, morphology, and microstructure of the products obtained at various crystallization stages were characterized by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, selected area electron diffraction and high resolution transmission electron microscopy. The structural and morphological evolution processes of the products from monodispersed nanoparticles to nanoparticle aggregates and flowerlike superstructures were investigated. Results indicate that the flowerlike superstructures of calcium carbonate are assembled from amorphous calcium carbonate nanoparticles. The growth and assembly of calcium carbonate minerals are significantly regulated by the pepsin Langmuir monolayers. Namely, the pepsin Langmuir monolayers stabilize amorphous calcium carbonate nanoparticles and direct their transformation to amorphous aggregates via non-oriented aggregation. The present approach presents a feasible way to manipulate the growth of inorganic crystal, which, hopefully, is to help better reveal the role of proteins in mineralization process and understand the mechanism of biomineralization. -- Highlights: ► Pepsin Langmuir monolayer as biomimetic template. ► Flower-like calcite crystals experience a novel assembly and growth process. ► The morphologic evolution and phase transformation were observed. ► The trace of initial nucleation site of CaCO3 at the interface was observed. ► The template directs the crystallization and growth process.

  7. Crystallization and self-assembly of flowerlike superstructures of calcium carbonate regulated by pepsin Langmuir monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Xue, Zhonghui [Key Laboratory for Special Functional Materials of Ministry of Education, Henan University, Kaifeng 475004 (China); School of Physics and Chemistry, Henan Polytechnic University, Jiaozuo 454000 (China); Hu, Binbin; Dai, Shuxi [Key Laboratory for Special Functional Materials of Ministry of Education, Henan University, Kaifeng 475004 (China); Du, Zuliang, E-mail: zld@henu.edu.cn [Key Laboratory for Special Functional Materials of Ministry of Education, Henan University, Kaifeng 475004 (China)

    2012-10-15

    Flowerlike superstructures of calcium carbonate were synthesized at air-water interface in the presence of pepsin Langmuir monolayers as the biomimetic template. The phase structure, morphology, and microstructure of the products obtained at various crystallization stages were characterized by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, selected area electron diffraction and high resolution transmission electron microscopy. The structural and morphological evolution processes of the products from monodispersed nanoparticles to nanoparticle aggregates and flowerlike superstructures were investigated. Results indicate that the flowerlike superstructures of calcium carbonate are assembled from amorphous calcium carbonate nanoparticles. The growth and assembly of calcium carbonate minerals are significantly regulated by the pepsin Langmuir monolayers. Namely, the pepsin Langmuir monolayers stabilize amorphous calcium carbonate nanoparticles and direct their transformation to amorphous aggregates via non-oriented aggregation. The present approach presents a feasible way to manipulate the growth of inorganic crystal, which, hopefully, is to help better reveal the role of proteins in mineralization process and understand the mechanism of biomineralization. -- Highlights: Black-Right-Pointing-Pointer Pepsin Langmuir monolayer as biomimetic template. Black-Right-Pointing-Pointer Flower-like calcite crystals experience a novel assembly and growth process. Black-Right-Pointing-Pointer The morphologic evolution and phase transformation were observed. Black-Right-Pointing-Pointer The trace of initial nucleation site of CaCO{sub 3} at the interface was observed. Black-Right-Pointing-Pointer The template directs the crystallization and growth process.

  8. Determination of the tectonic evolution from fractures, faults, and calcite twins on the southwestern margin of the Indochina Block

    Science.gov (United States)

    Arboit, Francesco; Amrouch, Khalid; Collins, Alan S.; King, Rosalind; Morley, Christopher

    2015-08-01

    In polyphase tectonic zones, integrating a study of fault and fracture with calcite twin analysis can determine the evolving paleostress magnitudes and principle stress directions that affected the area. This paper presents the results of the analyses of fractures, striated faults, and calcite twins collected within the Khao Khwang Fold-Thrust Belt in central Thailand (SE Asia). Here we attempt to reconstruct the orientation of the principal stresses that developed during the tectonic evolution of this highly deformed, polyphase orogen. Tectonic data were collected in the Permian carbonates of the Khao Khad Formation of the Saraburi Group, and five successive tectonic stages are determined that are interpreted to have developed before, during, and after, the Triassic Indosinian Orogeny. The first three stages predate the main deformation event: the first stage is interpreted as a pre-Indosinian N-S extensional stage, the second stage described a N-S strike-slip and compressional regime, largely perpendicular to the fold axes of the main structures, while the third stage is associated with an E-W compressional strike-slip phase. A further two stages took place after, or during, the main folding event and correspond to N-S compression and to an E-W composite strike-slip/contractional stage, the latter which is interpreted to represent Cenozoic deformation related to the India-Asia collision.

  9. Stable carbon isotopes and lipid biomarkers provide new insight into the formation of calcite and siderite concretions in organic-matter rich deposits

    Science.gov (United States)

    Baumann, Lydia; Birgel, Daniel; Wagreich, Michael; Peckmann, Jörn

    2015-04-01

    Carbonate concretions from two distinct settings have been studied for their petrography, stable carbon and oxygen isotopes, and lipid biomarker content. Carbonate concretions are in large part products of microbial degradation of organic matter, as for example by sulfate-reducing bacteria, iron-reducing bacteria, and methanogenic archaea. For these prokaryotes certain lipid biomarkers such as hopanoids, terminally-branched fatty acids (bacteria) and isoprenoids (archaea) are characteristic. Two different types of concretions were studied: a) Upper Miocene septarian calcite concretions of the southern Vienna Basin embedded in brackish sediments represented by partly bituminous calcareous sands, silts and clays; b) Paleocene-Eocene siderite concretions enclosed in marine, sandy to silty turbidites with varying carbonate contents and marl layers from the Upper Gosau Subgroup in northern Styria. Calcite concretions consist of abundant calcite microspar (80-90 vol.%), as well as detrital minerals and iron oxyhydroxides. The septarian cracks show beginning cementation with dog-tooth calcite to varying degrees. Framboidal pyrite occurs in some of the calcite concretions, pointing to bacterial sulfate reduction. Siderite concretions consist of even finer carbonate crystals, mainly siderite (40-70 vol.%) but also abundant ferroan calcite, accompanied by iron oxyhydroxides and detrital minerals. The δ13C values of the calcite concretions (-6.8 to -4.1o ) most likely reflect a combination of bacterial organic matter oxidation and input of marine biodetrital carbonate. The δ18O values range from -8.9 to -7.8o agreeing with a formation within a meteoric environment. The surrounding host sediment shows about 1-2o higher δ13C and δ18O values. The siderite δ13C values (-11.1 to -7.5o ) point to microbial respiration of organic carbon and the δ18O values (-3.5 to +2.2o ) agree with a marine depositional environment. In contrast to the calcite concretions, the stable isotope

  10. X-ray dose response of calcite-A comprehensive analysis for optimal application in TL dosimetry

    Science.gov (United States)

    Kalita, J. M.; Wary, G.

    2016-09-01

    The effect of various annealing treatments on dosimetric characteristics of orange calcite (CaCO3) mineral has been studied in detail. Quantitative analysis on the dose response shows that the 573 K annealed sample showed sublinear dose response from 10 mGy to 1 Gy. The fading and reproducibility of this sample are also good enough for dosimetric application. However, a specific annealing treatment after irradiation shows some significant improvements in the dosimetric characteristics of the sample. The 773 K pre-annealed sample, after X-ray irradiation post-annealing at 340 K for 6 min provides linear dose response from 10 mGy to 3.60 Gy, very less fading and good reproducibility. Moreover, this sample after post-annealing at 380 K for 6 min shows linear dose response from 10 mGy to 5.40 Gy when analyzed from the ∼408 K thermoluminescence (TL) glow peak. Analysis of TL glow curves confirmed that the 1.30 eV trap center in calcite crystal is the most effective trapping site for dosimetric application.

  11. Sorption of cesium on bentonite: The role of calcite

    International Nuclear Information System (INIS)

    Full text: Since bentonite is investigated for its use in Engineered Barriers Systems as backfill material, many studies of their surfaces properties have been performed in the past years to qualify and quantify adsorption on their surfaces, which can be one of the major processes limiting migration of radionuclides away from a disposal site. Nevertheless, most of these studies concerned simplified systems, such as Na-montmorillonite in mono-electrolyte solution. As ion-exchange processes are of importance in water-clays interactions, adsorption of natural major ions has also to be taken into account for natural systems. The aim of this work is (i) to quantify the sorption of the natural major cations on the montmorillonite surface, (ii) to compare the sorption of cesium, in two different systems, a simple one (Na-montmorillonite in NaNO3 0.05 Mol.L-1) and a complex one (natural bentonite in a synthetic natural water) and then (iii) to assess the influence of the natural major ions on this sorption, and to identify the role of the calcite phase present in bentonite. The methodology used consists in several batch experiments, first considering a very simple solution (NaNO3), then using mixtures of two different electrolytes, and lastly using a synthetic natural water. A surface complexation model, describing the surface of clays as a mixture of ion-exchange and complexation surface sites, is used to provide interpretations and quantifications of the sorption processes. Observed results indicate that affinity for the montmorillonite surface is greatest for Ca, then Mg and then K. The sorption of cesium is strongly affected by the presence in solution of Ca, witch can come from the partial dissolution of calcite. (author)

  12. Sorption of cesium on bentonite: The role of calcite

    International Nuclear Information System (INIS)

    Full text: Since bentonite is investigated for its use in Engineered Barriers Systems as backfill material, many studies of their surfaces properties have been performed in the past years to qualify and quantify adsorption on their surfaces, which can be one of the major processes limiting migration of radionuclides away from a disposal site. Nevertheless, most of these studies concerned simplified systems, such as Na-montmorillonite in mono-electrolyte solution. As ion-exchange processes are of importance in water-clays interactions, adsorption of natural major ions has also to be taken into account for natural systems. The aim of this work is (i) to quantify the sorption of the natural major cations on the montmorillonite surface; (ii) to compare the sorption of cesium, in two different systems, a simple one ( Na-montmorillonite in NaNO3 0.05 Mol.L-1) and a complex one (natural bentonite in a synthetic natural water) and then; (iii) to assess the influence of the natural major ions on this sorption, and to identify the role of the calcite phase present in bentonite. The methodology used consists in several batch experiments, first considering a very simple solution (NaNO3), then using mixtures of two different electrolytes, and lastly using a synthetic natural water. A surface complexation model, describing the surface of clays as a mixture of ion-exchange and complexation surface sites, is used to provide interpretations and quantifications of the sorption processes. Observed results indicate that affinity for the montmorillonite surface is greatest for Ca, then Mg and then K. The sorption of cesium is strongly affected by the presence in solution of Ca, witch can come from the partial dissolution of calcite. This study is one part of a work supported by ANDRA on the retention properties of bentonite materials. (author)

  13. Carbon and oxygen isotopes in apatite CO2 and co-existing calcite

    International Nuclear Information System (INIS)

    Carbon and oxygen isotopes were analyzed in carbonate apatite CO2 and in co-existing calcite. Both C and O in apatite CO2 are enriched in the respective light isotopes relative to calcite. These results confirm the proposition that carbonate is part of the apatite structure

  14. Enhancement of exchange bias with crystal orientation in NiFe/CoO and CoO/NiFe bilayers grown on MgO(100) and MgO(111)

    International Nuclear Information System (INIS)

    We present the comparative study of the structural and magnetic properties of the NiFe/CoO and CoO/NiFe bilayers grown on both MgO(111) and MgO(100) substrates by using the ion beam sputtering technique. We observed that crystallographic orientation and crystal quality strongly affected the exchange bias properties of the bilayers. The NiFe layers showed fourfold magnetocrystalline anisotropy when we used MgO(100) substrate and uniaxial anisotropy when we used MgO(111) substrate. When the CoO layer is grown on MgO(111) and MgO(100) substrates as a first layer, instead of the NiFe, the increase of the crystalline quality and stoichiometric CoO phase has been achieved so that the exchange bias field increases by five and three times for NiFe/CoO/MgO(111) and NiFe/CoO/MgO(100) systems, respectively. The blocking temperature significantly increases for NiFe/CoO on MgO(111) and (100) substrates, indicating the increase of the stoichiometric stable Co1O1 phase in the exchange-biased system. The magnitude of the exchange bias field is 800 Oe at 10 K for NiFe/CoO/MgO(111) and more than two times as compared to that of NiFe/CoO/MgO(100). This high exchange bias value observed for NiFe/CoO/MgO(111) was explained with the uncompensated spins in CoO(111) surface. We also carried out training effect measurements to observe the durability of the exchange bias for technological applications. - Highlights: • This paper analyses magnetization dynamic of exchange biased of NiFe/CoO thin films. • Exchange bias is enhanced by crystal orientation and quallity. • High exchange bias value observed due to the uncompensated spins in CoO(111) surface

  15. Influence of surface conductivity on the apparent zeta potential of calcite

    CERN Document Server

    Li, Shuai; Heberling, Frank; Devau, Nicolas; Jougnot, Damien; Chiaberge, Christophe

    2016-01-01

    Zeta potential is a physicochemical parameter of particular importance in describing the surface electrical properties of charged porous media. However, the zeta potential of calcite is still poorly known because of the difficulty to interpret streaming potential experiments. The Helmholtz-Smoluchowski (HS) equation is widely used to estimate the apparent zeta potential from these experiments. However, this equation neglects the influence of surface conductivity on streaming potential. We present streaming potential and electrical conductivity measurements on a calcite powder in contact with an aqueous NaCl electrolyte. Our streaming potential model corrects the apparent zeta potential of calcite by accounting for the influence of surface conductivity and flow regime. We show that the HS equation seriously underestimates the zeta potential of calcite, particularly when the electrolyte is diluted (ionic strength < 0.01 M) because of calcite surface conductivity. The basic Stern model successfully predicted ...

  16. High-pressure phase transition in Mn2O3: Application for the crystal structure and preferred orientation of the CaIrO3 type

    Science.gov (United States)

    Santillán, Javier; Shim, Sang-Heon; Shen, Guoyin; Prakapenka, Vitali B.

    2006-08-01

    Our X-ray diffraction measurements reveal that Mn2O3 undergoes a phase transition to the CaIrO3 type, which is proposed for the post-perovskite in MgSiO3, at 27-38 GPa and 300 K, bypassing the other phase transitions observed in sesquioxides. Small distortions in the polyhedra after the transition indicate that the Jahn-Teller effect, which is strong at ambient conditions, is suppressed during the transition. The CaIrO3-type phase exhibits strong preferred orientation of the (010) plane perpendicular to the loading axis before annealing whereas preferred orientation of the (100) and (110) planes was observed after annealing. The pre-annealing texture may result from either the deformation under strong differential stresses or the phase transition. The post-annealing texture may be related to either lower differential stresses or thermal annealing. Our result shows that the texture of the CaIrO3 type can be sensitive to phase transition and annealing as well as differential stresses.

  17. Highly birefringent crystal for Raman transitions with phase modulators

    Science.gov (United States)

    Arias, Nieves; Abediyeh, Vahide; Hamzeloui, Saeed; Jeronimo-Moreno, Yasser; Gomez, Eduardo

    2016-05-01

    We present a system to excite Raman transitions with minimum phase noise. The system uses a phase modulator to generate the phase locked beams required for the transition. We use a long calcite crystal to filter out one of the sidebands, avoiding the cancellation that appears at high detunings for phase modulation. The measured phase noise is limited by the quality of the microwave synthesizer. We use the calcite crystal a second time to produce a co-propagating Raman pair with perpendicular polarizations to drive velocity insensitive Raman transitions. Support from CONACYT and Fundacion Marcos Moshinsky.

  18. Interfacial dislocations in (111) oriented (Ba{sub 0.7}Sr{sub 0.3})TiO{sub 3} films on SrTiO{sub 3} single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Xuan [National Laboratory of Solid State Microstructures, Department of Materials Science and Engineering, College of Engineering and Applied Science, and Collaborative Innovation Center of Advanced Materials, Nanjing University, Nanjing 210093 (China); Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973 (United States); Yamada, Tomoaki [Department of Materials, Physics and Energy Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan); Department of Innovative and Engineered Materials, Tokyo Institute of Technology, Yokohama 226-8502 (Japan); Lin, Ruoqian; Xin, Huolin L.; Su, Dong, E-mail: dsu@bnl.gov [Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973 (United States); Kamo, Takafumi; Funakubo, Hiroshi [Department of Innovative and Engineered Materials, Tokyo Institute of Technology, Yokohama 226-8502 (Japan); Wu, Di [National Laboratory of Solid State Microstructures, Department of Materials Science and Engineering, College of Engineering and Applied Science, and Collaborative Innovation Center of Advanced Materials, Nanjing University, Nanjing 210093 (China)

    2015-10-05

    We have investigated the interfacial structure of epitaxial (Ba,Sr)TiO{sub 3} films grown on (111)-oriented SrTiO{sub 3} single-crystal substrates using transmission electron microscopy (TEM) techniques. Compared with the (100) epitaxial perovskite films, we observe dominant dislocation half-loop with Burgers vectors of a〈110〉 comprised of a misfit dislocation along 〈112〉, and threading dislocations along 〈110〉 or 〈100〉. The misfit dislocation with Burgers vector of a〈110〉 can dissociate into two ½a〈110〉 partial dislocations and one stacking fault. We found the dislocation reactions occur not only between misfit dislocations, but also between threading dislocations. Via three-dimensional electron tomography, we retrieved the configurations of the threading dislocation reactions. The reactions between threading dislocations lead to a more efficient strain relaxation than do the misfit dislocations alone in the near-interface region of the (111)-oriented (Ba{sub 0.7}Sr{sub 0.3})TiO{sub 3} films.

  19. Interactions between acidic proteins and crystals: stereochemical requirements in biomineralization.

    OpenAIRE

    Addadi, L; Weiner, S

    1985-01-01

    Acidic matrix macromolecules are intimately involved in biological crystal growth. In vitro experiments, in which crystals of calcium dicarboxylate salts were grown in the presence of aspartic acid-rich proteins, revealed a stereochemical property common to all the interacting faces. Calcite crystals are nucleated on stereochemically analogous faces when proteins are adsorbed onto a rigid substrate. The importance of this property in biomineralization is discussed.

  20. Transformation of Mg-bearing amorphous calcium carbonate to Mg-calcite - In situ monitoring

    Science.gov (United States)

    Purgstaller, Bettina; Mavromatis, Vasileios; Immenhauser, Adrian; Dietzel, Martin

    2016-02-01

    The formation of Mg-bearing calcite via an amorphous precursor is a poorly understood process that is of relevance for biogenic and abiogenic carbonate precipitation. In order to gain an improved insight on the controls of Mg incorporation in calcite formed via an Mg-rich amorphous calcium carbonate (Mg-ACC) precursor, the precipitation of Mg-ACC and its transformation to Mg-calcite was monitored by in situ Raman spectroscopy. The experiments were performed at 25.0 ± 0.03 °C and pH 8.3 ± 0.1 and revealed two distinct pathways of Mg-calcite formation: (i) At initial aqueous Mg/Ca molar ratios ⩽ 1:6, Mg-calcite formation occurs via direct precipitation from solution. (ii) Conversely, at higher initial Mg/Ca molar ratios, Mg-calcite forms via an intermediate Mg-rich ACC phase. In the latter case, the final product is a calcite with up to 20 mol% Mg. This Mg content is significant higher than that of the Mg-rich ACC precursor phase. Thus, a strong net uptake of Mg ions from the solution into the crystalline precipitate throughout and also subsequent to ACC transformation is postulated. Moreover, the temporal evolution of the geochemical composition of the reactive solution and the Mg-ACC has no significant effect on the obtained "solubility product" of Mg-ACC. The enrichment of Mg in calcite throughout and subsequent to Mg-ACC transformation is likely affected by the high aqueous Mg/Ca ratio and carbonate alkalinity concentrations in the reactive solution. The experimental results have a bearing on the formation mechanism of Mg-rich calcites in marine early diagenetic environments, where high carbonate alkalinity concentrations are the rule rather than the exception, and on the insufficiently investigated inorganic component of biomineralisation pathways in many calcite secreting organisms.

  1. STRONTIUM ISOTOPE EVOLUTION OF PORE WATER AND CALCITE IN THE TOPOPAH SPRING TUFF, YUCCA MOUNTAIN, NEVADA

    International Nuclear Information System (INIS)

    Yucca Mountain, a ridge of Miocene volcanic rocks in southwest Nevada, is being characterized as a site for a potential high-level radioactive waste repository. One issue of concern for the future performance of the potential repository is the movement of water in and around the potential repository horizon. Past water movement in this unsaturated zone is indicated by fluid inclusions trapped in calcite coatings on fracture footwall surfaces and in some lithophysal cavities. Some of the fluid inclusions have homogenization temperatures above the present-day geotherm (J.F. Whelan, written communication), so determining the ages of the calcite associated with those fluid inclusions is important in understanding the thermal history of the potential repository site. Calcite ages have been constrained by uranium-lead dating of silica polymorphs (opal and chalcedony) that are present in most coatings. The opal and chalcedony ages indicate that deposition of the calcite and opal coatings in the welded part of the Topopah Spring Tuff (TSw hydrogeologic unit) spanned nearly the entire history of the 12.8-million-year-old rock mass at fairly uniform overall long-term rates of deposition (within a factor of five). Constraining the age of a layer of calcite associated with specific fluid inclusions is complicated. Calcite is commonly bladed with complex textural relations, and datable opal or chalcedony may be millions of years older or younger than the calcite layer or may be absent from the coating entirely. Therefore, a more direct method of dating the calcite is presented in this paper by developing a model for strontium evolution in pore water in the TSw as recorded by the strontium coprecipitated with calcium in the calcite. Although the water that precipitated the calcite in fractures and cavities may not have been in local isotopic equilibrium with the pore water, the strontium isotope composition of all water in the TSw is primarily controlled by water

  2. Preferred orientation of ettringite in concrete fractures

    KAUST Repository

    Wenk, Hans-Rudolf

    2009-05-15

    Sulfate attack and the accompanying crystallization of fibrous ettringite [Ca6Al2(OH)12(SO4) 3·26H2O] cause cracking and loss of strength in concrete structures. Hard synchrotron X-ray microdiffraction is used to quantify the orientation distribution of ettringite crystals. Diffraction images are analyzed using the Rietveld method to obtain information on textures. The analysis reveals that the c axes of the trigonal crystallites are preferentially oriented perpendicular to the fracture surfaces. By averaging single-crystal elastic properties over the orientation distribution, it is possible to estimate the elastic anisotropy of ettringite aggregates. © 2009 International Union of Crystallography.

  3. Preferred orientation of ettringite in concrete fractures

    International Nuclear Information System (INIS)

    Sulfate attack and the accompanying crystallization of fibrous ettringite (Ca6Al2(OH)12(SO4)3 · 26H2O) cause cracking and loss of strength in concrete structures. Hard synchrotron X-ray microdiffraction is used to quantify the orientation distribution of ettringite crystals. Diffraction images are analyzed using the Rietveld method to obtain information on textures. The analysis reveals that the c axes of the trigonal crystallites are preferentially oriented perpendicular to the fracture surfaces. By averaging single-crystal elastic properties over the orientation distribution, it is possible to estimate the elastic anisotropy of ettringite aggregates.

  4. Holographic liquid crystal devices

    OpenAIRE

    Pavani, Kotakonda, (Thesis)

    2009-01-01

    Liquid crystals have become natural candidates for use in electro-optic devices for their ability to change the orientation of the director with the application of an electric field, and exhibiting large range of refractive index. The aim of the work presented in this thesis is to fabricate liquid crystal optoelectronic devices such as electrically switchable liquid crystal diffraction gratings and polarization rotators by exploiting the holographic surface relief effect in photopolymer and b...

  5. Uranium isotope fractionation during coprecipitation with aragonite and calcite

    Science.gov (United States)

    Chen, Xinming; Romaniello, Stephen J.; Herrmann, Achim D.; Wasylenki, Laura E.; Anbar, Ariel D.

    2016-09-01

    Natural variations in 238U/235U of marine calcium carbonates might provide a useful way of constraining redox conditions of ancient environments. In order to evaluate the reliability of this proxy, we conducted aragonite and calcite coprecipitation experiments at pH ∼7.5 and ∼8.5 to study possible U isotope fractionation during incorporation into these minerals. Small but significant U isotope fractionation was observed in aragonite experiments at pH ∼8.5, with heavier U isotopes preferentially enriched in the solid phase. 238U/235U of dissolved U in these experiments can be fit by Rayleigh fractionation curves with fractionation factors of 1.00007 + 0.00002/-0.00003, 1.00005 ± 0.00001, and 1.00003 ± 0.00001. In contrast, no resolvable U isotope fractionation was observed in an aragonite experiment at pH ∼7.5 or in calcite experiments at either pH. Equilibrium isotope fractionation among different aqueous U species is the most likely explanation for these findings. Certain charged U species are preferentially incorporated into calcium carbonate relative to the uncharged U species Ca2UO2(CO3)3(aq), which we hypothesize has a lighter equilibrium U isotope composition than most of the charged species. According to this hypothesis, the magnitude of U isotope fractionation should scale with the fraction of dissolved U that is present as Ca2UO2(CO3)3(aq). This expectation is confirmed by equilibrium speciation modeling of our experiments. Theoretical calculation of the U isotope fractionation factors between different U species could further test this hypothesis and our proposed fractionation mechanism. These findings suggest that U isotope variations in ancient carbonates could be controlled by changes in the aqueous speciation of seawater U, particularly changes in seawater pH, PCO2 , Ca2+, or Mg2+ concentrations. In general, these effects are likely to be small (<0.13‰), but are nevertheless potentially significant because of the small natural range of

  6. U-Th dating of calcitic corals from the Red Sea

    Science.gov (United States)

    Stein, M.; Yehudai, M.; Kohn, N.; Shaked, Y.; Agnon, A.; Lazar, B.

    2013-12-01

    Pristine aragonite skeletons of reef building corals can be rapidly recrystallized to calcite by the interaction of the corals with freshwater in coastal aquifers. The aragonite/calcite transformation is accompanied by opening the coral's U-Th isotope system in which uranium is partly lost while Th remains adsorbed and reincorporates into the newly formed calcite. Depending on the geological setting of the reef, the corals may incorporate secondary aragonite with higher U and 234U/238U isotope ratio, while still submerged, before the recrystallization process. Recrystallization to calcite occurs during sea level drop or coast tectonic uplift and later may follow a subaerial closed system decay scheme. In this study we examine the behavior of the U and Th in calcitic corals from the last interglacial reefs at the northern Gulf of Aqaba. We analyzed several subsamples from selected reef coral skeletons in an attempt to follow the recrystallization scheme of the corals and find a reliable method to estimate the age of these heavily altered corals. The main assumptions were that all subsamples from the same coral have identical deposition age and the sub-samples Th (and hence 230Th) was fully preserved during recrystallization to calcite (increasing the 230Th/238U isotope ratio). Diagenesis to calcite occurred several thousand years after the initial precipitation of the aragonitic skeleton. This calls for wetter (than present) conditions during the last interglacial in the currently hyperarid northern Red Sea.

  7. Paleohydrogeological implications from fracture calcites in fissures of low transmissivity. A report of investigations in 2011

    International Nuclear Information System (INIS)

    Samples of fracture fillings were collected from 26 bedrock fractures at Olkiluoto. Special attention was paid to fractures having low transmissivities of <1E-8 m2/s. The chemical composition and the C and O isotopic composition of the fracture filling calcite were analysed. In addition, fluid inclusions were studied and microthermometric measurements conducted on fracture filling calcite. The most common minor element in calcite fillings was Mn, having concentrations up to 3.4 wt-%. The δ13C values had a wide range, from -13.0 to 14.5 per mille, and the δ18O values a narrower range, from -13.4 to -7.3 per mille. The δ18O values of late-stage calcite appear to be independent of the transmissivity of the fractures, ranging from -11.2 to -7.3 per mille over a T range from 3E-6 to 1.6E-11 m2/s. The δ13C values of late-stage calcite appear to have more variation at high transmissivities of >1E-8 m2/s. Unusually low and high δ13C values in late-stage calcite fillings occur in the upper ∼ 400 m of the bedrock and are probably related to microbial reduction processes, at near surface (<60 m) conditions to oxidation of organic matter resulting in low δ13C values and at ∼ 55-400 m to methanogenesis, causing high δ 13C values. A relatively low spread in the δ 13C values of late-stage calcite precipitates in low transmissivity (<1E-8 m2/s) fractures is most likely caused by stable conditions in the areas of low conductivity in the bedrock, reflecting slow dissolution/reprecipitation of older carbonate fillings. Fluid inclusion data indicate variation in fracture water types from high temperature, ∼ 200 deg C, low salinity fluid with < 4 wt-% of NaCleq to low temperature, <100 deg C, high salinity fluid with 17-29 wt-% of NaCleq. The high temperature fluid is associated with Group 5 calcite fillings and the low temperature fluid with Group 3 calcite. The composition of fluids related to Group 4 calcite falls roughly between the compositions representing Group 5

  8. Comparison of galvanic displacement and electroless methods for deposition of gold nanoparticles on synthetic calcite

    Indian Academy of Sciences (India)

    Chamarthi K Srikanth; P Jeevanandam

    2012-11-01

    Gold nanoparticles have been deposited on synthetic calcite substrate by galvanic displacement reaction and electroless deposition methods. A comparative study has shown that electroless deposition is superior compared to galvanic displacement reaction for uniform deposition of gold nanoparticles on calcite. Characterization of the samples, prepared by two different deposition methods, was carried out by X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy (FE–SEM) and diffuse reflectance spectroscopy (DRS) measurements. FE–SEM studies prove that smaller nanoparticles of gold are deposited uniformly on calcite if electroless deposition method was employed and DRS measurements show the characteristic surface plasmon resonance of gold nanoparticles.

  9. Paleohydrogeological implications from fracture calcites in fissures of low transmissivity. A report of investigations in 2011

    Energy Technology Data Exchange (ETDEWEB)

    Sahlstedt, E.; Karhu, J. [Univ. of Helsinki (Finland)

    2014-07-15

    Samples of fracture fillings were collected from 26 bedrock fractures at Olkiluoto. Special attention was paid to fractures having low transmissivities of <1E-8 m{sup 2}/s. The chemical composition and the C and O isotopic composition of the fracture filling calcite were analysed. In addition, fluid inclusions were studied and microthermometric measurements conducted on fracture filling calcite. The most common minor element in calcite fillings was Mn, having concentrations up to 3.4 wt-%. The δ13C values had a wide range, from -13.0 to 14.5 per mille, and the δ18O values a narrower range, from -13.4 to -7.3 per mille. The δ18O values of late-stage calcite appear to be independent of the transmissivity of the fractures, ranging from -11.2 to -7.3 per mille over a T range from 3E{sup -6} to 1.6E{sup -1}1 m{sup 2}/s. The δ13C values of late-stage calcite appear to have more variation at high transmissivities of >1E-8 m{sup 2}/s. Unusually low and high δ13C values in late-stage calcite fillings occur in the upper ∼ 400 m of the bedrock and are probably related to microbial reduction processes, at near surface (<60 m) conditions to oxidation of organic matter resulting in low δ13C values and at ∼ 55-400 m to methanogenesis, causing high δ 13C values. A relatively low spread in the δ 13C values of late-stage calcite precipitates in low transmissivity (<1E-8 m{sup 2}/s) fractures is most likely caused by stable conditions in the areas of low conductivity in the bedrock, reflecting slow dissolution/reprecipitation of older carbonate fillings. Fluid inclusion data indicate variation in fracture water types from high temperature, ∼ 200 deg C, low salinity fluid with < 4 wt-% of NaCl{sub eq} to low temperature, <100 deg C, high salinity fluid with 17-29 wt-% of NaCl{sub eq}. The high temperature fluid is associated with Group 5 calcite fillings and the low temperature fluid with Group 3 calcite. The composition of fluids related to Group 4 calcite falls roughly

  10. Distribution of Minor Elements in Calcite From the Unsaturated Zone at Yucca Mountain, Nevada

    Science.gov (United States)

    Marshall, B. D.; Whelan, J. F.

    2001-12-01

    Calcite is sporadically distributed in fractures and cavities in the volcanic rocks that form the 500- to 700-m-thick unsaturated zone at Yucca Mountain. Previous work has shown that the calcite precipitated from water moving downward through the unsaturated zone since the volcanic rocks were emplaced approximately 13 Ma. Calcite thus serves as a proxy for the chemistry and amounts of past percolation, two parameters that are important in predictions of the future behavior of the potential radioactive waste repository at Yucca Mountain. Latest calcite, which began forming between approximately 5 and 2 Ma, typically displays fine-scale growth zoning defined by distributions of Mn (inferred from cathodoluminescence), Mg, and Sr. Electron microprobe (EPMA) mapping of outermost calcite reveals Mg growth zoning1 and higher overall concentrations of Mg in late calcite than in older calcite. Micro X-ray fluorescence (micro-XRF) maps were obtained by slow rastering of the samples over a 100-watt X-ray source collimated through a final aperture of 100 μ m. Although the spatial resolution of the micro-XRF mapping is much less than that of EPMA, this technique reveals distributions of some elements to which EPMA is less sensitive. Micro-XRF maps show that Sr is spatially correlated with Mg; Sr concentrations range to 500 μ g/g at the resolution of the 100-μ m collimator. Because both Mg and Sr have similar calcite-water distribution coefficients much less than one, the Mg/Sr in calcite reflects the Mg/Sr of the water that precipitated the calcite. The distribution coefficient for Mn is greater than one and variations in Mn are not correlated with Mg and Sr. Covariation of Mg and Sr in the percolating water may be explained by reactions that affect the rate of uptake of chemical constituents from the overlying rock and soil, and/or evaporation. Late calcite has lower δ 13C values, probably due to a regional change from wetter to drier climate conditions. The higher Mg and

  11. Alkaline flocculation of Phaeodactylum tricornutum induced by brucite and calcite.

    Science.gov (United States)

    Vandamme, Dries; Pohl, Philip I; Beuckels, Annelies; Foubert, Imogen; Brady, Patrick V; Hewson, John C; Muylaert, Koenraad

    2015-11-01

    Alkaline flocculation holds great potential as a low-cost harvesting method for marine microalgae biomass production. Alkaline flocculation is induced by an increase in pH and is related to precipitation of calcium and magnesium salts. In this study, we used the diatom Phaeodactylum tricornutum as model organism to study alkaline flocculation of marine microalgae cultured in seawater medium. Flocculation started when pH was increased to 10 and flocculation efficiency reached 90% when pH was 10.5, which was consistent with precipitation modeling for brucite or Mg(OH)2. Compared to freshwater species, more magnesium is needed to achieve flocculation (>7.5mM). Zeta potential measurements suggest that brucite precipitation caused flocculation by charge neutralization. When calcium concentration was 12.5mM, flocculation was also observed at a pH of 10. Zeta potential remained negative up to pH 11.5, suggesting that precipitated calcite caused flocculation by a sweeping coagulation mechanism. PMID:26310384

  12. Stress remagnetization in pyrrhotite-calcite synthetic aggregates

    Science.gov (United States)

    Robion, Philippe; Borradaile, Graham J.

    2001-01-01

    Stress-induced remagnetization has been applied to multidomain pyrrhotite-calcite synthetic aggregates in a triaxial rig. Experimental deformation used 150MPa confining pressure, a constant strain rate of 10-5 s-1 and applied differential stresses of up to 70MPa. New components of magnetization, parallel to the direction of the pressure vessel field, were added to the pre-deformational magnetization. The intensity of remagnetization (M'-M0) increases with the intensity of the applied differential stress and affects the coercivity fraction below 15mT. Bulk shortening is less than 8 per cent, thus grain rotation cannot explain selective remagnetization of the low-coercivity fraction. Remagnetization is thus attributed to deformational viscous remanent magnetization (DVRM). It is observed that high-coercivity (>15mT) grains do not remagnetize. There is, however, slight progressive rotation of pre-deformational magnetization with increasing strain up to 8 per cent of bulk shortening. The lack of piezoremanent magnetization in the high-coercivity range may be due to defects introduced in pyrrhotite during sample preparation. Experiments using synthetic pyrrhotite, expected to show low dislocation densities, would be necessary to test this effect.

  13. Microbiologically Induced Calcite Precipitation Mediated by Sporosarcina pasteurii.

    Science.gov (United States)

    Bhaduri, Swayamdipta; Debnath, Nandini; Mitra, Sushanta; Liu, Yang; Kumar, Aloke

    2016-01-01

    The particular bacterium under investigation here (S. pasteurii) is unique in its ability, under the right conditions, to induce the hydrolysis of urea (ureolysis) in naturally occurring environments through secretion of an enzyme urease. This process of ureolysis, through a chain of chemical reactions, leads to the formation of calcium carbonate precipitates. This is known as Microbiologically Induced Calcite Precipitation (MICP). The proper culture protocols for MICP are detailed here. Finally, visualization experiments under different modes of microscopy were performed to understand various aspects of the precipitation process. Techniques like optical microscopy, Scanning Electron Microscopy (SEM) and X-Ray Photo-electron Spectroscopy (XPS) were employed to chemically characterize the end-product. Further, the ability of these precipitates to clog pores inside a natural porous medium was demonstrated through a qualitative experiment where sponge bars were used to mimic a pore-network with a range of length scales. A sponge bar dipped in the culture medium containing the bacterial cells hardens due to the clogging of its pores resulting from the continuous process of chemical precipitation. This hardened sponge bar exhibits superior strength when compared to a control sponge bar which becomes compressed and squeezed under the action of an applied external load, while the hardened bar is able to support the same weight with little deformation. PMID:27167458

  14. Studies on cyanobacterial extracellular polymeric substances: functional groups, calcite biomineralization and formation of capsular polymeric substances

    Science.gov (United States)

    Dittrich, M.; Sibler, S.; Matsko, N.

    2006-12-01

    Extracellular polymeric substances (EPS) of microbial origin are an important class of polymeric materials which have been involved in different processes such as biofilm development or mineral precipitation. Cyanobacteria have been known as potential EPS producers for a long time. Despite their ubiquitous distribution, there is still a great lack of knowledge concerning the diversity of EPS binding sites of different picocyanobacterial strains on the one hand and the specific components of EPS which are responsible for calcite precipitation and crystal morphology on the other hand. It is generally accepted that capsular extracellular polymeric substances are the main components of biofilm matrixes. In this context, it is important to understand under which conditions cyanobacteria produce surface polysaccharides. In a recent study, we characterized the binding sites of EPS of three unicellular autotrophic picocyanobacterial strains of the Synechococcus-type. Potentiometric titrations were conducted to determine different types of functional groups present at the various sites. Precipitation experiments with EPS of different strains allowed for estimating the potential of EPS to precipitate calcium carbonate and the impact of functional groups composition on crystal morphology. In order to clarify the conditions under which cyanobacteria formed capsular EPS, we performed growth experiments in nutrients medium with different phosphorus concentrations (0.4, 4.1, 8.2 and 41 mgP/l). Cyanobacterial cells produced capsular EPS under phosphorus concentrations of 0.4, 4.1 and 8.2 mgP/l, while no capsular EPS were observed for the highest P concentration (41 mgP/l). At this concentration, however, calcium rich storage products were detected in the cells. The results thus suggest that both extracellular and intracellular products are regulated through phosphorus concentrations in growth solutions. Titrations reveal five or six distinct sites on surfaces of picocyanobacterial

  15. Nanoscale observations of the effect of citrate on calcium oxalate precipitation on calcite surfaces.

    Science.gov (United States)

    Burgos-Cara, Alejandro; Ruiz-Agudo, Encarnacion; Putnis, Christine V.

    2016-04-01

    Calcium oxalate (CaC2O4ṡxH2O) minerals are naturally occurring minerals found in fossils, plants, kidney stones and is a by-product in some processes such as paper, food and beverage production [1,2]. In particular, calcium oxalate monohydrate phase (COM) also known as whewellite (CaC2O4ṡH2O), is the most frequently reported mineral phase found in urinary and kidney stones together with phosphates. Organic additives are well known to play a key role in the formation of minerals in both biotic and abiotic systems, either facilitating their precipitation or hindering it. In this regard, recent studies have provided direct evidence demonstrating that citrate species could enhance dissolution of COM and inhibit their precipitation. [3,4] The present work aims at evauate the influence of pH, citrate and oxalic acid concentrations in calcium oxalate precipitation on calcite surfaces (Island Spar, Chihuahua, Mexico) through in-situ nanoscale observation using in situ atomic force microscopy (AFM, Multimode, Bruker) in flow-through experiments. Changes in calcium oxalate morphologies and precipitated phases were observed, as well as the inhibitory effect of citrate on calcium oxalate precipitation, which also lead to stabilization an the amorphous calcium oxalate phase. [1] K.D. Demadis, M. Öner, Inhibitory effects of "green"additives on the crystal growth of sparingly soluble salts, in: J.T. Pearlman (Ed.), Green Chemistry Research Trends, Nova Science Publishers Inc., New York, 2009, pp. 265-287. [2] M. Masár, M. Zuborová, D. Kaniansky, B. Stanislawski, Determination of oxalate in beer by zone electrophoresis on a chip with conductivity detection, J. Sep. Sci. 26 (2003) 647-652. [3] Chutipongtanate S, Chaiyarit S, Thongboonkerd V. Citrate, not phosphate, can dissolve calcium oxalate monohydrate crystals and detach these crystals from renal tubular cells. Eur J Pharmacol 2012;689:219-25. [4] Weaver ML, Qiu SR, Hoyer JR, Casey WH, Nancollas GH, De Yoreo JJ

  16. Differential early diagenetic low-Mg calcite cementation and rhythmic hardground development in Campanian-Maastrichtian chalk

    DEFF Research Database (Denmark)

    Molenaar, Nicolaas; J.J.P., Zijlstra

    1997-01-01

    and differences in the degree of early diagenesis. Cemented layers and hardgrounds are the result of differential early marine calcite cementation. In these limestones early calcite cementation cannot be explained by the supply of cementing materials from saturated seawater, An alternative model for...... early marine calcite cementation is proposed, in which early calcite cementation occurred within the sediment at some distance below the seafloor as a result of organic matter degradation and internal redistribution of bioclastic carbonate. Bacterial organic matter degradation caused dissolution of...... relatively unstable high-Mg calcite (and/or aragonite) in the oxic zone followed by precipitation of calcite cement as a consequence of bacterial iron reduction. During periods with a lower sedimentation rate, any significant early cementation and replacement of high-Mg calcite occurred when younger oxic...

  17. Calcium sulfoaluminate (Ye'elimite) hydration in the presence of gypsum, calcite, and vaterite

    International Nuclear Information System (INIS)

    Six calcium sulfoaluminate-based cementitious systems composed of calcium sulfoaluminate, calcite, vaterite, and gypsum were cured as pastes and mortars for 1, 7, 28 and 84 days. Pastes were analyzed with X-ray diffraction, thermogravimetric and differential thermal analyses. Mortars were tested for compressive strength, dimensional stability and setting time. Furthermore, pastes with a water/cementitious material mass ratio of 0.80 were tested for heat evolution during the first 48 h by means of isothermal conduction calorimetry. It has been found that: (1) both calcite and vaterite reacted with monosulfoaluminate to give monocarboaluminate and ettringite, with vaterite being more reactive; (2) gypsum lowered the reactivity of both carbonates; (3) expansion was reduced by calcite and vaterite, irrespective of the presence of gypsum; and (4) both carbonates increased compressive strength in the absence of gypsum and decreased compressive strength less in the presence of gypsum, with vaterite's action more effective than that of calcite

  18. Calcium sulfoaluminate (Ye'elimite) hydration in the presence of gypsum, calcite, and vaterite

    Energy Technology Data Exchange (ETDEWEB)

    Hargis, Craig W. [Department of Civil and Environmental Engineering, University of California, Berkeley, CA (United States); Telesca, Antonio [School of Engineering, University of Basilicata, Potenza (Italy); Monteiro, Paulo J.M., E-mail: monteiro@ce.berkeley.edu [Department of Civil and Environmental Engineering, University of California, Berkeley, CA (United States)

    2014-11-15

    Six calcium sulfoaluminate-based cementitious systems composed of calcium sulfoaluminate, calcite, vaterite, and gypsum were cured as pastes and mortars for 1, 7, 28 and 84 days. Pastes were analyzed with X-ray diffraction, thermogravimetric and differential thermal analyses. Mortars were tested for compressive strength, dimensional stability and setting time. Furthermore, pastes with a water/cementitious material mass ratio of 0.80 were tested for heat evolution during the first 48 h by means of isothermal conduction calorimetry. It has been found that: (1) both calcite and vaterite reacted with monosulfoaluminate to give monocarboaluminate and ettringite, with vaterite being more reactive; (2) gypsum lowered the reactivity of both carbonates; (3) expansion was reduced by calcite and vaterite, irrespective of the presence of gypsum; and (4) both carbonates increased compressive strength in the absence of gypsum and decreased compressive strength less in the presence of gypsum, with vaterite's action more effective than that of calcite.

  19. Precipitation of Calcite during the Deposition of Paleogene Sangkarewang Oil Shale, Ombilin Basin, West Sumatra, Indonesia

    Directory of Open Access Journals (Sweden)

    Agus Haris Widayat

    2015-12-01

    Full Text Available Geochemical and petrographical analyses were carried out to investigate the occurrence of calcite in theformer Ombilin lacustrine lake. The study involves eight samples taken from a 56 m long drill core of Sangkarewangoil shale. Geochemical investigation showed that the samples consist of varied terrigenous input represented by Si, Al, K, and Ti, and autochthonous input represented by S, total organic carbon (TOC, and d13C of bulk organic matter. Along the drill core profile the abundance of autochthonous input decreases upwards, while that of terrigenous input oppositely increases upwards. Petrographical analysis revealed that calcite is a major mineral in the samples. In this study, the abundance of calcite could be represented by the abundance of Ca, as calcite is the only significant Ca containing mineral. Ca is abundant in the samples (8.4% in average and its concentration varies similarly with those of S, TOC, and d13C, suggesting that the element as well as calcite incorporates the autochthonous input. Thevariation of calcite abundance in the drill core profile is considered to be related with primary productivity changes during the development of the former lake. Higher primary productivity represented by more positive of d13C value(-24.8‰ during the deposition of the lower part of the drill core profile promoted the higher amount of deposited organic matter. In such environment, the supersaturation of carbonate ion in lake water was also reached and significant precipitation of authigenic calcite occurred. As the lake developed, the primary productivity decreased as indicated by more negative of d13C value (eventually -26.8‰. This condition led to the decreases of deposited organic matterand calcite in the lake sediments.

  20. Molecular dynamics simulation of adsorption of an oil-water-surfactant mixture on calcite surface

    Institute of Scientific and Technical Information of China (English)

    Lu Guiwu; Zhang Xuefen; Shao Changjin; Yang Hong

    2009-01-01

    An interface super molecular structure model for oil-water-surfactant mixture and calcite was established. By using a molecular dynamics method, the effects of rhamnolipid, sodium dodecyl benzene sulfonate and sodium hexadecyl sulfonate on the interface adsorption behavior of oil molecules were investigated. It was found that these three surfactants could reduce oil-calcite interface binding energy, and play a role of oil-displacing agent.

  1. Origin of sulfate in barite and calcite cements in the Jebel Madar salt dome (Oman)

    Science.gov (United States)

    Vandeginste, V.; John, C. M.; Gilhooly, W. P.

    2012-12-01

    Jebel Madar is a 500-m high mountain rising in the desert at the Oman Foothills. The Jebel consists of Triassic to Cretaceous carbonate host rocks forming the carapace of a salt dome. Halokinesis caused major fracturing and faulting at Jebel Madar, and the resulting structures acted as the main pathways for fluids that generated diagenetic cements composed of both barite and calcite. The spatial distribution of calcite and barite occurrences shows that calcite is formed in large abundance along the three main faults, whereas barite is more concentrated along faults further away from the three main ones. The stable carbon and oxygen isotope composition of calcite and fluid inclusion data from both calcite and barite show a distinct evolution of the fluid with a highly saline component towards more mixing with meteoric water. This is in agreement with clumped isotopes data on calcite cements indicating an evolution towards lower temperatures, consistent with doming of the Jebel and greater input of lower-temperature descending meteoric fluids. Here, we present sulphur and oxygen isotopic data on barite that suggest a link between the barite formation and the Precambrian salt underlying Jebel Madar. The average δ34S measured in barite is 33‰ CDT (1σ = 5‰; n = 33), which falls at the lower end of the δ34S range reported for the Ara Group anhydrite. The average δ18O in the same barite samples is 23‰ VSMOW (1σ = 2‰; n = 33). Data from the barite will be compared with sulphur isotopes from the carbonate-associate sulfate in the calcite cements. The overall goal of our research is to gain a better insight in the formation process of barite and calcite in Jebel Madar and its link with salt tectonics. We would like to acknowledge the financial support of QCCSRC (funded jointly by Qatar Petroleum, Shell and the Qatar Science & Technology Park) and the GSA Laubach fund for this study.

  2. Calcite Formation in Soft Coral Sclerites Is Determined by a Single Reactive Extracellular Protein*

    OpenAIRE

    Rahman, M. Azizur; Oomori, Tamotsu; Wörheide, Gert

    2011-01-01

    Calcium carbonate exists in two main forms, calcite and aragonite, in the skeletons of marine organisms. The primary mineralogy of marine carbonates has changed over the history of the earth depending on the magnesium/calcium ratio in seawater during the periods of the so-called “calcite and aragonite seas.” Organisms that prefer certain mineralogy appear to flourish when their preferred mineralogy is favored by seawater chemistry. However, this rule is not without exceptions. For example, so...

  3. Stimulated Globular Scattering of Laser Radiation in Photonic Crystals: Temperature Dependences

    CERN Document Server

    Gorelik, V S; Tcherniega, N V; Vodchits, A I

    2007-01-01

    Stimulated globular scattering (SGS) characteristics (frequency shifts, threshold, conversion efficiency) have been studied in photonic crystals (synthetic opal matrices and opal nanocomposites) at different temperatures. Results have been compared with stimulated Raman scattering investigations in calcite single crystals. In both cases temperature lowering from +20 C to -196 C resulted in the stimulated scattering energy increase and its redistribution to the higher order components.

  4. Low-Temperature Plasticity of Naturally Deformed Calcite Rocks

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Optical, cathodoluminescence and transmission electron microscope (TEM) analyses were conducted onfour groups of calcite fault rocks, a cataclastic limestone, cataclastic coarse-grained marbles from two fault zones, and afractured mylonite. These fault rocks show similar microstructural characteristics and give clues to similar processes ofrock deformation. They are characterized by the structural contrast between macroscopic cataclastic (brittle) andmicroscopic mylonitic (ductile) microstructures. Intragranular deformation microstructures (i.e. deformation twins, kinkbands and microfractures) are well preserved in the deformed grains in clasts or in primary rocks. The matrix materials areof extremely fine grains with diffusive features. Dislocation microstructures for co-existing brittle deformation andcrystalline plasticity were revealed using TEM. Tangled dislocations are often preserved at the cores of highly deformedclasts, while dislocation walls form in the transitions to the fine-grained matrix materials and free dislocations, dislocationloops and dislocation dipoles are observed both in the deformed clasts and in the fine-grained matrix materials. Dynamicrecrystallization grains from subgrain rotation recrystallization and subsequent grain boundary migration constitute themajor parts of the matrix materials. Statistical measurements of densities of free dislocations, grain sizes of subgrains anddynamically recrystallized grains suggest an unsteady state of the rock deformation. Microstructural andcathodoluminescence analyses prove that fluid activity is one of the major parts of faulting processes. Low-temperatureplasticity, and thereby induced co-existence of macroscopic brittle and microscopic ductile microstmctures are attributedto hydrolytic weakening due to the involvement of fluid phases in deformation and subsequent variation of rock rheology.During hydrolytic weakening, fluid phases, e.g. water, enhance the rate of dislocation slip and climb, and

  5. Ion beam modifications of defect sub-structure of calcite cleavages

    Indian Academy of Sciences (India)

    E Venkateshwar Rao; M Ramakrishna Murthy

    2008-04-01

    Experimental investigations on the defect sub-structure and surface modifications, brought about by He+ ion-bombardment of calcite cleavages (100), have been carried out. Optical and scanning electron microscopic investigations revealed drastic modifications on the surface morphology, local symmetry and defect concentration. Additional structural defects on ion-bombardment of calcite surfaces also have been observed. Changes in shape and form of chemical etch pits are found to be a function of ion-beam energy, as studied by optical microscopy. Radiation damage in calcite has been attributed mainly due to desorption of CO$^{-2}_{3}$ ions from the calcite surfaces, on irradiation. Measurements of surface conductivity on irradiated calcite surfaces have been made employing a four-probe technique. Enhancement of surface conductivity has been considered to be due to an increase in concentration of CO$^{-2}_{3}$ ions formed, on ion irradiation and subsequent thermal stimulation. Planar plastic anisotropy has been studied on irradiated calcite cleavages by measurement of microhardness.

  6. NMR characterization of hydrocarbon adsorption on calcite surfaces: A first principles study

    Energy Technology Data Exchange (ETDEWEB)

    Bevilaqua, Rochele C. A.; Miranda, Caetano R. [Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, UFABC, Santo André, SP (Brazil); Rigo, Vagner A. [Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, UFABC, Santo André, SP (Brazil); Universidade Tecnológica Federal do Paraná, UTFPR, Cornélio Procópio, PR (Brazil); Veríssimo-Alves, Marcos [Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, UFABC, Santo André, SP (Brazil); Departamento de Física, ICEx, Universidade Federal Fluminense, UFF, Volta Redonda, RJ (Brazil)

    2014-11-28

    The electronic and coordination environment of minerals surfaces, as calcite, are very difficult to characterize experimentally. This is mainly due to the fact that there are relatively few spectroscopic techniques able to detect Ca{sup 2+}. Since calcite is a major constituent of sedimentary rocks in oil reservoir, a more detailed characterization of the interaction between hydrocarbon molecules and mineral surfaces is highly desirable. Here we perform a first principles study on the adsorption of hydrocarbon molecules on calcite surface (CaCO{sub 3} (101{sup ¯}4)). The simulations were based on Density Functional Theory with Solid State Nuclear Magnetic Resonance (SS-NMR) calculations. The Gauge-Including Projector Augmented Wave method was used to compute mainly SS-NMR parameters for {sup 43}Ca, {sup 13}C, and {sup 17}O in calcite surface. It was possible to assign the peaks in the theoretical NMR spectra for all structures studied. Besides showing different chemical shifts for atoms located on different environments (bulk and surface) for calcite, the results also display changes on the chemical shift, mainly for Ca sites, when the hydrocarbon molecules are present. Even though the interaction of the benzene molecule with the calcite surface is weak, there is a clearly distinguishable displacement of the signal of the Ca sites over which the hydrocarbon molecule is located. A similar effect is also observed for hexane adsorption. Through NMR spectroscopy, we show that aromatic and alkane hydrocarbon molecules adsorbed on carbonate surfaces can be differentiated.

  7. NMR characterization of hydrocarbon adsorption on calcite surfaces: A first principles study

    International Nuclear Information System (INIS)

    The electronic and coordination environment of minerals surfaces, as calcite, are very difficult to characterize experimentally. This is mainly due to the fact that there are relatively few spectroscopic techniques able to detect Ca2+. Since calcite is a major constituent of sedimentary rocks in oil reservoir, a more detailed characterization of the interaction between hydrocarbon molecules and mineral surfaces is highly desirable. Here we perform a first principles study on the adsorption of hydrocarbon molecules on calcite surface (CaCO3 (101¯4)). The simulations were based on Density Functional Theory with Solid State Nuclear Magnetic Resonance (SS-NMR) calculations. The Gauge-Including Projector Augmented Wave method was used to compute mainly SS-NMR parameters for 43Ca, 13C, and 17O in calcite surface. It was possible to assign the peaks in the theoretical NMR spectra for all structures studied. Besides showing different chemical shifts for atoms located on different environments (bulk and surface) for calcite, the results also display changes on the chemical shift, mainly for Ca sites, when the hydrocarbon molecules are present. Even though the interaction of the benzene molecule with the calcite surface is weak, there is a clearly distinguishable displacement of the signal of the Ca sites over which the hydrocarbon molecule is located. A similar effect is also observed for hexane adsorption. Through NMR spectroscopy, we show that aromatic and alkane hydrocarbon molecules adsorbed on carbonate surfaces can be differentiated

  8. Orienteering club

    CERN Multimedia

    Club d'orientation

    2015-01-01

    Course d'orientation La reprise des courses d’orientation était attendue dans la région puisque près de 150 coureurs ont participé à la première épreuve automnale organisée par le club d’orientation du CERN sur le site de La Faucille. Les circuits ont été remportés par Yann Locatelli du club d’Orientation Coeur de Savoie avec 56 secondes d’avance sur Damien Berguerre du club SOS Sallanches pour le parcours technique long, Marie Vuitton du club CO CERN (membre également de l’Equipe de France Jeune) pour le parcours technique moyen avec presque 4 minutes d’avance sur Jeremy Wichoud du club Lausanne-Jorat, Victor Dannecker pour le circuit technique court devant Alina Niggli, Elliot Dannecker pour le facile moyen et Alice Merat sur le facile court, tous membres du club O’Jura. Les résultats comp...

  9. Tropical Silurian Paleotemperatures from Clumped Isotope Analysis of Coexisting Dolomite and Calcite

    Science.gov (United States)

    Winkelstern, I. Z.; Lohmann, K. C.

    2013-12-01

    In many instances, pervasive diagenetic alteration of original material prevents the use of quantitative climate proxies on Paleozoic or older rocks. As an inherently diagenetic phase, dolomite may provide a more resilient paleotemperature resource. The Δ47 carbonate clumped isotope thermometer has been shown to be an accurate paleothermometer and, in a limited way, has been shown to be applicable to dolomites. The shallow water carbonates of the Pipe Creek Jr. Reef in central Indiana offer an opportunity to test the viability of the technique in ancient dolomite. After formation in the late Silurian, a sea level drop resulted in a diagenetic sequence of meteoric phreatic alteration of marine cement and biotic components, which included precipitation of dolomite cements inter-grown within the meteoric phreatic calcite cement. This was post-dated by a coarse void filling calcite spar formed at burial temperatures of ~100°C (based on fluid inclusion analysis). Preliminary analyses of coexisting dolomite and calcite suggest that near-surface temperatures are preserved in dolomites despite having experienced elevated thermal diagenetic effects.. In contrast, co-existing early-formed calcites exhibit resetting of earth surface temperatures to elevated values. Δ47 measurements in dolomites yield temperatures around 30°C using the Guo et al., (2009) theoretical calibration. This contrasts with analyses of early (original) and late (hydrothermal) calcites, which record temperatures greater than ~80°C using the Δ47-calcite calibration of Dennis and Schrag (2010). These data support the hypothesis that dolomite can be a more resilient paleotemperature proxy relative to calcite in deep-time studies. Temperatures from dolomites compare reasonably with other late Silurian paleoclimate studies, and offer insight into regional-scale paleoclimate.

  10. FORMATION OF CALCITE AND SILICA FROM PERCOLATION IN A HYDROLOGICALLY UNSATURATED SETTING, YUCCA MOUNTAIN, NEVADA

    International Nuclear Information System (INIS)

    Geological, mineralogical, chemical, and isotopic evidence from coatings of calcite and silica on open fractures and lithophysal cavities within welded tuffs at Yucca Mountain indicate an origin from meteoric water percolating through a thick (500 to 700 m) unsaturated zone (UZ) rather than from pulses of ascending ground water. Geologic evidence for a UZ setting includes the presence of coatings in only a small percentage of cavities, the restriction of coatings to fracture footwalls and cavity floors, and an absence of mineral high-water marks indicative of water ponding. Systematic mineral sequences (early calcite, followed by chalcedony with minor quartz and fluorite, and finally calcite with intercalated opal forming the bulk of the coatings) indicate progressive changes in UZ conditions through time, rather than repeated saturation by flooding. Percolation under the influence of gravity also results in mineral textures that vary between steeply dipping sites (thinner coatings of blocky calcite) and shallowly dipping sites (thicker coatings of coarse, commonly bladed calcite, with globules and sheets of opal). Micrometer-scale growth banding in both calcite and opal reflects slow average growth rates (scale of mm/m.y.) over millions of years rather than only a few rapidly deposited growth episodes. Isotopic compositions of C, O, Sr, and U from calcite and opal indicate a percolation-modified meteoric water source, and collectively refute a deeper ground-water source. Chemical and isotopic variations in coatings also indicate long-term evolution of water compositions. Although some compositional changes are related to shifts in climate, growth rates in the deeper UZ are buffered from large changes in meteoric input. Coatings most likely formed from films of water flowing down connected fracture pathways. Mineral precipitation is consistent with water vapor and carbon dioxide loss from films at very slow rates. Data collectively indicate that mineral coatings

  11. Dispersion properties of transverse anisotropic liquid crystal core photonic crystal fibers

    Science.gov (United States)

    Karasawa, Naoki

    2016-04-01

    The dispersion properties of liquid crystal core photonic crystal fibers for different core diameters have been calculated by a full vectorial finite difference method. In calculations, air holes are assumed to be arranged in a regular hexagonal array in fused silica and a central hole is filled with liquid crystal to create a core. In this study, three types of transverse anisotropic configurations, where liquid crystal molecules are oriented in a transverse plane, and a planar configuration, where liquid crystal molecules are oriented in a propagation direction, are considered. The large changes of the dispersion properties are found when the orientation of the liquid crystal molecules is changed from a planar configuration to a uniform configuration, where all molecules are oriented in the same direction in a transverse plane. Since the orientation of liquid crystal molecules may be controlled by applying an electric field, it could be utilized for various applications including the spectral control of supercontinuum generation.

  12. The influence of final repository relevant electrolyte on the interaction of trivalent lanthanides and actinides with calcite; Der Einfluss endlagerrelevanter Elektrolyte auf die Wechselwirkung dreiwertiger Lanthanide und Actinide mit Calcit

    Energy Technology Data Exchange (ETDEWEB)

    Hofmann, Sascha

    2015-10-21

    Calcite, a naturally occurring and very abundant mineral, is considered a potential retentive geochemical barrier regarding nuclear waste disposal. In this work, the reactivity of calcite towards trivalent Ln and An has been determined by spectroscopic, microscopic and X-ray scattering techniques. This, in connection with the use of luminescent probes Eu(III) and Cm(III), allowed for the understanding of electrolyte influences on the retention potential of calcite.

  13. Orienteering Club

    CERN Multimedia

    Club d'orientation

    2013-01-01

    Courses d’orientation Une bonne dizaine de clubs étaient représentés samedi dernier à La Faucille pour participer à la  2e manche de la coupe genevoise organisée par le club du CERN. Les 120 coureurs ont pu découvrir des parcours classés "technique". Ceux du Haut-Jura familiarisés à ce type de terrain ont pu sortir leur épingle du jeu et se sont octroyé la victoire sur 4 des 5 circuits. Samedi 21 septembre, la montagne du Haut-Jura était encore plébiscitée puisque les coureurs étaient attendus à Saint Cergue sur la carte des Pralies. Pour les résultats complets de La Faucille et les informations sur la prochaine étape, consultez le site du club http://cern.ch/club-orientation.

  14. Orienteering Club

    CERN Multimedia

    Club d'orientation

    2013-01-01

    Courses d’orientation ce printemps Le Club d’orientation du CERN vous invite à venir découvrir la course d’orientation et vous propose, en partenariat avec d’autres clubs de la région, une dizaine de courses populaires. Celles-ci ont lieu les samedis après-midi, elles sont ouvertes à tous, quel que soit le niveau, du débutant au sportif confirmé, en famille ou en individuel, en promenade ou en course. Si vous êtes débutant vous pouvez profiter d’une petite initiation offerte par l’organisateur avant de vous lancer sur un parcours. Divers types de parcours sont à votre choix lors de chaque épreuve : facile court (2-3 km), facile moyen (3-5 km), technique court (3-4 km), technique moyen (4-5 km) et technique long (5-7 km). Les dates à retenir sont les suivantes : Samedi 23 mars: Pully (Vd) Samedi 13 avril: Pougny...

  15. Orientation Club

    CERN Multimedia

    Club d'orientation

    2014-01-01

    COURSE ORIENTATION Résultats de samedi 10 mai    C’est sur une carte entièrement réactualisée dans les bois de Versoix, que plus de 100 coureurs sont venus participer à la course d’orientation, type longue distance, préparée par des membres du club du CERN. Le terrain plutôt plat nécessitait une orientation à grande vitesse, ce qui a donné les podiums suivants :  Technique long avec 17 postes : 1er Jurg Niggli, O’Jura en 52:48, 2e Beat Muller, COLJ Lausanne-Jorat en 58:02, 3e Christophe Vuitton, CO CERN en 58:19 Technique moyen avec 13 postes : 1er Jean-Bernard Zosso, CO CERN, en 46:05 ; 2e Yves Rousselot, Balise 25 Besançon, en 55:11 ; 3e Laurent Merat, O'Jura, en 55:13 Technique court avec 13 postes : 1er Julien Vuitton, CO CERN en 40:59, 2e Marc Baumgartner, CO CERN en 43:18, 3e Yaelle Mathieu en 51:42 Su...

  16. Towards a Mechanism-Based Understanding of Vital Effects: Biomolecules Influence Mg/Ca in Calcite

    Science.gov (United States)

    Stephenson, A. E.; Nelson, E. J.; Wu, K. J.; de Yoreo, J. J.; Dove, P. M.

    2006-12-01

    Recent findings from our group suggest that the chemistry of biomolecules present at sites of mineral formation have a strong influence on the structure of water near calcite surfaces (Elhadj et al., CGD, 2006) and exercise predictable controls on the rate of calcite growth (Elhadj et al., submitted). Observing the extent to which biomolecules can mediate growth processes leads us to hypothesize that they also have measurable influence over impurity (Mg, Sr) contents. If true, this could be a significant contributor to the widely documented 'vital effects' that complicate interpretations of paleoenvironments, largely based on chemical signatures found in the skeletal remains of organisms. We use in situ AFM to measure the growth rate of calcite at the nanoscale under controlled solution compositions and at characterized chemical driving force. The relationship between the presence of carboxyl- rich peptides in solution during growth and the magnesium content in the resulting calcite was quantified using time-of-flight SIMS. This new work with tof-SIMS has validated previous compositional maps of Mg distributions collected by electron microprobe, and has yielded new insights into controls on impurity content. We are using similar methods to also determine factors that influence impurity contents of calcites grown in solutions at seawater ionic strength.

  17. Dolomite-magnesian calcite relations at elevated temperatures and CO2 pressures

    Science.gov (United States)

    Graf, D.L.; Goldsmith, J.R.

    1955-01-01

    The equilibrium thermal decomposition curve of dolomite has been determined up to a CO2 pressure of 20,000 lb/in.2, at which pressure dolomite decomposes at 857??C. Equilibrium was approached from both directions, by the breakdown and by the solid-state synthesis of dolomite. At elevated temperatures and pressures, calcites in equilibrium with periclase as well as those in equilibrium with dolomite contain Mg in solid solution. In the former, the Mg content increases with increasing CO2 pressure, and decreases with increasing temperature. In the latter, it is a function of temperature only. The exsolution curve of dolomite and magnesian calcite has been determined between 500?? and 800??C; at 500?? dolomite is in equilibrium with a magnesian calcite containing ~6 mol per cent MgCO2; at 800??, ~22 mol per cent. There appears to be a small but real deviation from the ideal 1 : 1 Ca : Mg ratio of dolomite, in the direction of excess Ca, for material in equilibrium with magnesian calcite at high temperature. The experimental findings indicate that very little Mg is stable in the calcites of sedimentary environments, but that an appreciable amount is stable under higher-temperature metamorphic conditions, if sufficient CO2 pressure is maintained. ?? 1955.

  18. Bioleaching of cobalt and zinc from pyrite ore in relation to calcitic gangue content.

    Science.gov (United States)

    Baldi, F; Bralia, A; Riccobono, F; Sabatini, G

    1991-05-01

    Bioleaching of a pyrite ore containing high concentrations of cobalt (0.1%) and zinc (0.065%) was affected by small amounts of calcitic gangue (from 0.01 to 1.01%). Results from an air-lift percolator and from Erlenmeyer flask experiments show that a small percentage of calcite raises the pH and arrests the growth of the acidophilic bacterium Thiobacillus ferrooxidans. In percolator experiments, when calcite is completely removed by the continuous addition of small quantities of acid, and the pH of the liquor becomes acid, the micro-organism begins to grow and to bio-oxidize the pyrite ore. The growth of T. ferrooxidans shows different lag phase spans (from 13 to 190 days) depending on carbonate dissolution. The metals Fe, Zn and Co are released into the leaching solution together at different rates after a lag-time which depends on calcite concentrations in pyrite gangue. Metal ratios in the mineral bulk are different from those in the liquor, Zn dissolving 5 times more readily than Co. Bioleaching rates for metal removal from pyrite are higher in percolator (for Fe, from 5 to 15 mg/l/h) than in flask experiments (from 0.5 to 2 mg/l/h), but the lag phases are shorter (from 2 to 65 days). The differences between the two systems are related to calcite dissolution and gypsum precipitation. PMID:24425016

  19. The influence of final repository relevant electrolyte on the interaction of trivalent lanthanides and actinides with calcite

    International Nuclear Information System (INIS)

    Calcite, a naturally occurring and very abundant mineral, is considered a potential retentive geochemical barrier regarding nuclear waste disposal. In this work, the reactivity of calcite towards trivalent Ln and An has been determined by spectroscopic, microscopic and X-ray scattering techniques. This, in connection with the use of luminescent probes Eu(III) and Cm(III), allowed for the understanding of electrolyte influences on the retention potential of calcite.

  20. First-principles calculations of structural, electronic, optical and elastic properties of magnesite MgCO 3 and calcite CaCO 3

    Science.gov (United States)

    Brik, M. G.

    2011-02-01

    Detailed ab initio calculations of the structural, electronic, optical and elastic properties of two crystals - magnesite (MgCO 3) and calcite (CaCO 3) - are reported in the present paper. Both compounds are important natural minerals, playing an important role in the carbon dioxide cycling. The optimized crystal structures, band gaps, density of states diagrams, elastic constants, optical absorption spectra and refractive indexes dependence on the wavelength all have been calculated and compared, when available, with literature data. Both crystals are indirect band compounds, with calculated band gaps of 5.08 eV for MgCO 3 and 5.023 eV for CaCO 3. Both values are underestimated by approximately 1.0 eV with respect to the experimental data. Although both crystals have the same structure, substitution of Mg by Ca ions leads to certain differences, which manifest themselves in noticeable change in the electronic bands profiles and widths, shape of the calculated absorption spectra, and values of the elastic constants. Response of both crystals to the applied hydrostatic pressure was analyzed in the pressure range of phase stability, variations of the lattice parameters and characteristic interionic distances were considered. The obtained dependencies of lattice constants and calculated band gap on pressure can be used for prediction of properties of these two hosts at elevated pressures that occur in the Earth's mantle.