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Sample records for large turbostratic crystallites

  1. Turbostratic stacked CVD graphene for high-performance devices

    Science.gov (United States)

    Uemura, Kohei; Ikuta, Takashi; Maehashi, Kenzo

    2018-03-01

    We have fabricated turbostratic stacked graphene with high-transport properties by the repeated transfer of CVD monolayer graphene. The turbostratic stacked CVD graphene exhibited higher carrier mobility and conductivity than CVD monolayer graphene. The electron mobility for the three-layer turbostratic stacked CVD graphene surpassed 10,000 cm2 V-1 s-1 at room temperature, which is five times greater than that for CVD monolayer graphene. The results indicate that the high performance is derived from maintenance of the linear band dispersion, suppression of the carrier scattering, and parallel conduction. Therefore, turbostratic stacked CVD graphene is a superior material for high-performance devices.

  2. Turbostratic-like carbon nitride coatings deposited by industrial-scale direct current magnetron sputtering

    International Nuclear Information System (INIS)

    Louring, S.; Madsen, N.D.; Berthelsen, A.N.; Christensen, B.H.; Almtoft, K.P.; Nielsen, L.P.; Bøttiger, J.

    2013-01-01

    Carbon nitride thin films were deposited by direct current magnetron sputtering in an industrial-scale equipment at different deposition temperatures and substrate bias voltages. The films had N/(N + C) atomic fractions between 0.2 and 0.3 as determined by X-ray photoelectron spectroscopy (XPS). Raman spectroscopy provided insight into the ordering and extension of the graphite-like clusters, whereas nanoindentation revealed information on the mechanical properties of the films. The internal compressive film stress was evaluated from the substrate bending method. At low deposition temperatures the films were amorphous, whereas the film deposited at approximately 380 °C had a turbostratic-like structure as confirmed by high-resolution transmission electron microscopy images. The turbostratic-like film had a highly elastic response when subjected to nanoindentation. When a CrN interlayer was deposited between the film and the substrate, XPS and Raman spectroscopy indicated that the turbostratic-like structure was maintained. However, it was inconclusive whether the film still exhibited an extraordinary elastic recovery. An increased substrate bias voltage, without additional heating and without deposition of an interlayer, resulted in a structural ordering, although not to the extent of a turbostratic-like structure. - Highlights: • Carbon nitride films were deposited by industrial-scale magnetron sputtering. • The deposition temperature and the substrate bias voltage were varied. • A turbostratic-like structure was obtained at an elevated deposition temperature. • The turbostratic-like film exhibited a very high elastic recovery. • The influence of a CrN interlayer on the film properties was investigated

  3. Ammonia induced precipitation of cobalt hydroxide: observation of turbostratic disorder

    Science.gov (United States)

    Ramesh, T. N.; Rajamathi, Michael; Kamath, P. Vishnu

    2003-05-01

    Cobalt hydroxide freshly precipitated from aqueous solutions of Co salts using ammonia, is a layered phase having a 9.17 Å interlayer spacing. DIFFaX simulations of the PXRD pattern reveal that it is turbostratically disordered.

  4. Large-scale fabrication and utilization of novel hexagonal/turbostratic composite boron nitride nanosheets

    KAUST Repository

    Zhong, Bo

    2017-02-15

    In this report, we have developed a scalable approach to massive synthesis of hexagonal/turbostratic composite boron nitride nanosheets (h/t-BNNSs). The strikingly effective, reliable, and high-throughput (grams) synthesis is performed via a facile chemical foaming process at 1400°C utilizing ammonia borane (AB) as precursor. The characterization results demonstrate that high quality of h/t-BNNSs with lateral size of tens of micrometers and thickness of tens of nanometers are obtained. The growth mechanism of h/t-BNNSs is also discussed based on the thermogravimetric analysis of AB which clearly shows two step weight loss. The h/t-BNNSs are further used for making thermoconductive h/t-BNNSs/epoxy resin composites. The thermal conductivity of the composites is obviously improved due to the introduction of h/t-BNNSs. Consideration of the unique properties of boron nitride, these novel h/t-BNNSs are envisaged to be very valuable for future high performance polymer based material fabrication.

  5. Features of structural response of mechanically loaded crystallites to irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Korchuganov, Aleksandr V., E-mail: avkor@ispms.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); National Research Tomsk State University, Tomsk, 634050 (Russian Federation)

    2015-10-27

    A molecular dynamics method is employed to investigate the origin and evolution of plastic deformation in elastically deformed iron and vanadium crystallites due to atomic displacement cascades. Elastic stress states of crystallites result from different degrees of specimen deformation. Crystallites are deformed under constant-volume conditions. Atomic displacement cascades with the primary knock-on atom energy up to 50 keV are generated in loaded specimens. It is shown that irradiation may cause not only the Frenkel pair formation but also large-scale structural rearrangements outside the irradiated area, which prove to be similar to rearrangements proceeding by the twinning mechanism in mechanically loaded specimens.

  6. Structural changes in elastically stressed crystallites under irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Zolnikov, K.P., E-mail: kost@ispms.ru [Institute of Strength Physics and Materials Science SB RAS, 2/4, pr. Akademicheskii, Tomsk (Russian Federation); Tomsk State University, 36 Lenin Ave., Tomsk (Russian Federation); Korchuganov, A.V. [Institute of Strength Physics and Materials Science SB RAS, 2/4, pr. Akademicheskii, Tomsk (Russian Federation); Kryzhevich, D.S. [Institute of Strength Physics and Materials Science SB RAS, 2/4, pr. Akademicheskii, Tomsk (Russian Federation); Tomsk State University, 36 Lenin Ave., Tomsk (Russian Federation); Chernov, V.M. [Tomsk State University, 36 Lenin Ave., Tomsk (Russian Federation); A.A. Bochvar High-Technology Scientific Research Institute for Inorganic Materials, 5a Rogova St., Moscow (Russian Federation); Psakhie, S.G. [Institute of Strength Physics and Materials Science SB RAS, 2/4, pr. Akademicheskii, Tomsk (Russian Federation); Tomsk Polytechnic University, 30 Lenin Ave., Tomsk (Russian Federation); Skolkovo Institute of Science and Technology, 100 Novaya St., Skolkovo (Russian Federation)

    2015-06-01

    The response of elastically stressed iron and vanadium crystallites to atomic displacement cascades was investigated by molecular dynamics simulation. Interatomic interaction in vanadium was described by a many-body potential calculated in the Finnis–Sinclair approximation of the embedded atom method. Interatomic interaction in iron was described by a many-body potential constructed in the approximation of valence-electron gas. The crystallite temperature in the calculations was varied from 100 to 600 K. The elastically stressed state in the crystallites was formed through uniaxial tension by 4–8% such that their volume remained unchanged. The energy of a primary knock-on atom was varied from 0.5 to 50 keV. It is shown that the lower the temperature and the higher the strain degree of an initial crystallite, the lower the threshold primary knock-on atom energy for plastic deformation generation in the crystallite. The structural rearrangements induced in the crystallites by an atomic displacement cascade are similar to those induced by mechanical loading. It is found that the rearrangements are realized through twinning.

  7. Structural changes in elastically stressed crystallites under irradiation

    International Nuclear Information System (INIS)

    Zolnikov, K.P.; Korchuganov, A.V.; Kryzhevich, D.S.; Chernov, V.M.; Psakhie, S.G.

    2015-01-01

    The response of elastically stressed iron and vanadium crystallites to atomic displacement cascades was investigated by molecular dynamics simulation. Interatomic interaction in vanadium was described by a many-body potential calculated in the Finnis–Sinclair approximation of the embedded atom method. Interatomic interaction in iron was described by a many-body potential constructed in the approximation of valence-electron gas. The crystallite temperature in the calculations was varied from 100 to 600 K. The elastically stressed state in the crystallites was formed through uniaxial tension by 4–8% such that their volume remained unchanged. The energy of a primary knock-on atom was varied from 0.5 to 50 keV. It is shown that the lower the temperature and the higher the strain degree of an initial crystallite, the lower the threshold primary knock-on atom energy for plastic deformation generation in the crystallite. The structural rearrangements induced in the crystallites by an atomic displacement cascade are similar to those induced by mechanical loading. It is found that the rearrangements are realized through twinning

  8. Multiscale Modelling of Electronic and Thermal Transport : Thermoelectrics, Turbostratic 2D Materials and Diamond/c-BN HEMT

    Science.gov (United States)

    Narendra, Namita

    in turbostratic MoS2/WS 2 heterostructure is investigated. Since it is a major challenge in controlling the stacking orientation while growing these heterostructures, the electronic transport properties can experience a sizeable impact via misorientation. Small rotation angles lead to large unit cells with thousands of atoms necessiating an analytical tight binding approach. Tight binding model is developed for MoS2/WS2 heterostructure by fitting to DFT data which is extended to the turbostratic case. Cross-plane electronic transport is then analyzed by NEGF and Landauer formalism. It is found that in-plane transport remains largely unaffected, while inter-layer electrical resistance increases upto 10% for holes and 30% for electrons. Finally, diamond/c-BN HEMT is proposed. Diamond is a promising material for high-power electronic applications in both the dc and rf domains. However, the predicted advantages are yet to be realized due to a number of technical challenges. In particular, n-type devices have not been feasible due to the large ionization energies and low thermodynamic solubility limits of n-dopants. Motivated by the recent advances in nonequilibrium processing, we propose and theoretically examine a diamond/c-BN HEMT that can circumvent the critical limitations. A first-principles calculation suggests the desired type-I alignment at the heterojunction of these two nearly lattice matched semiconductors. The investigation also illustrates that a large sheet carrier density in excess of 5 x 1012 cm-2 can be induced in the undoped diamond channel by the gate bias. A subsequent analysis of a simple prototype design indicates that the proposed device can achieve large current drive (˜ 10 A/cm), low Ron (˜ 0.05 mO · cm2), and high f T (˜ 300 GHz) simultaneously.

  9. Crystallite Size Effect on Thermal Conductive Properties of Nonwoven Nanocellulose Sheets.

    Science.gov (United States)

    Uetani, Kojiro; Okada, Takumi; Oyama, Hideko T

    2015-07-13

    The thermal conductive properties, including the thermal diffusivity and resultant thermal conductivity, of nonwoven nanocellulose sheets were investigated by separately measuring the thermal diffusivity of the sheets in the in-plane and thickness directions with a periodic heating method. The cross-sectional area (or width) of the cellulose crystallites was the main determinant of the thermal conductive properties. Thus, the results strongly indicate that there is a crystallite size effect on phonon conduction within the nanocellulose sheets. The results also indicated that there is a large interfacial thermal resistance between the nanocellulose surfaces. The phonon propagation velocity (i.e., the sound velocity) within the nanocellulose sheets was estimated to be ∼800 m/s based on the relationship between the thermal diffusivities and crystallite widths. The resulting in-plane thermal conductivity of the tunicate nanocellulose sheet was calculated to be ∼2.5 W/mK, markedly higher than other plastic films available for flexible electronic devices.

  10. Radiative decay rates in Si crystallites with a donor ion

    Science.gov (United States)

    Derbenyova, Natalia V.; Burdov, Vladimir A.

    2018-04-01

    Within the framework of the time-dependent density functional theory, the radiative recombination rates have been calculated for small, ˜1 nm in diameter, hydrogen-passivated silicon crystallites with a single lithium or phosphorus ion. Sharp increase of the radiative recombination rates with increasing temperature was revealed for the crystallites with the lithium ion. No temperature effect was found for the crystallites with the ion of P. It was also shown that the presence of ionized donors in Si crystallites can substantially accelerate the radiative decay compared to the case of pure crystallites.

  11. X-ray diffraction study of directionally grown perylene crystallites

    DEFF Research Database (Denmark)

    Breiby, Dag W.; Lemke, H. T.; Hammershøj, P.

    2008-01-01

    Using grazing incidence X-ray diffraction, perylene crystallites grown on thin highly oriented poly(tetrafluoroethylene) (PTFE) films on silicon substrates have been investigated. All the perylene crystallites are found to orient with the ab plane of the monoclinic unit cell parallel to the subst......Using grazing incidence X-ray diffraction, perylene crystallites grown on thin highly oriented poly(tetrafluoroethylene) (PTFE) films on silicon substrates have been investigated. All the perylene crystallites are found to orient with the ab plane of the monoclinic unit cell parallel...... to the substrate. The scattering data is interpreted as a trimodal texture of oriented perylene crystallites, induced by interactions between the perylene molecules and the oriented PTFE substrate. Three families of biaxial orientations are seen, with the axes (h = 1, 2, or 3) parallel to the PTFE alignment......, all having the ab-plane parallel to the substrate. About 92% of the scattered intensity corresponds to a population with highly parallel to (PTFE)....

  12. Efficient perovskite light-emitting diodes featuring nanometre-sized crystallites

    Science.gov (United States)

    Xiao, Zhengguo; Kerner, Ross A.; Zhao, Lianfeng; Tran, Nhu L.; Lee, Kyung Min; Koh, Tae-Wook; Scholes, Gregory D.; Rand, Barry P.

    2017-01-01

    Organic-inorganic hybrid perovskite materials are emerging as highly attractive semiconductors for use in optoelectronics. In addition to their use in photovoltaics, perovskites are promising for realizing light-emitting diodes (LEDs) due to their high colour purity, low non-radiative recombination rates and tunable bandgap. Here, we report highly efficient perovskite LEDs enabled through the formation of self-assembled, nanometre-sized crystallites. Large-group ammonium halides added to the perovskite precursor solution act as a surfactant that dramatically constrains the growth of 3D perovskite grains during film forming, producing crystallites with dimensions as small as 10 nm and film roughness of less than 1 nm. Coating these nanometre-sized perovskite grains with longer-chain organic cations yields highly efficient emitters, resulting in LEDs that operate with external quantum efficiencies of 10.4% for the methylammonium lead iodide system and 9.3% for the methylammonium lead bromide system, with significantly improved shelf and operational stability.

  13. Atomic structure and thermal stability of interfaces between metallic glass and embedding nano-crystallites revealed by molecular dynamics simulations

    Energy Technology Data Exchange (ETDEWEB)

    Gao, X.Z.; Yang, G.Q.; Xu, B.; Qi, C.; Kong, L.T., E-mail: konglt@sjtu.edu.cn; Li, J.F.

    2015-10-25

    Molecular dynamics simulations were performed to investigate the atomic structure and thermal stability of interfaces formed between amorphous Cu{sub 50}Zr{sub 50} matrix and embedding B2 CuZr nano-crystallites. The interfaces are found to be rather abrupt, and their widths show negligible dependence on the nano-crystallite size. Local atomic configuration in the interfacial region is dominated by geometry characterized by Voronoi polyhedra <0,5,2,6> and <0,4,4,6>, and the contents of these polyhedra also exhibit apparent size dependence, which in turn results in an increasing trend in the interfacial energy against the nano-crystallite size. Annealing of the interface models at elevated temperatures will also enrich these characterizing polyhedra. While when the temperature is as high as the glass transition temperature of the matrix, growth of the nano-crystallites will be appreciable. The growth activation energy also shows size dependence, which is lower for larger nano-crystallites, suggesting that large nano-crystallites are prone to grow upon thermal disturbance. - Highlights: • Special clusters characterizing the local geometry are abundant in the interfaces. • Their content varies with the size of the embedding nano-crystallite. • In turn, size dependences in interfacial thermodynamics and kinetics are observed.

  14. Turbostratic carbon supported palladium as an efficient catalyst for reductive purification of water from trichloroethylene

    Directory of Open Access Journals (Sweden)

    Emil Kowalewski

    2017-12-01

    Full Text Available This work investigates the catalytic properties of turbostratic carbon supported Pd catalyst in hydrodechlorination of trichloroethylene (TCE HDC in aqueous phase. 1.57 wt% Pd/C was thoroughly characterized by BET, TPHD, CO chemisorption, PXRD, STEM, XPS and used as the catalyst in removal of trichloroethylene from drinking water in batch and continuous-flow reactors. The studies showed that catalytic performance of Pd/C depended on the hydrophobicity and textural properties of carbon support, which influenced noble metal dispersion and increased catalyst tolerance against deactivation by chlorination. Palladium in the form of uniformly dispersed small (~3.5 nm nanoparticles was found to be very active and stable in purification of water from TCE both in batch and continuous-flow operation.

  15. Application of the ellipsoid modeling of the average shape of nanosized crystallites in powder diffraction

    DEFF Research Database (Denmark)

    Katerinopoulou, Anna; Balic Zunic, Tonci; Lundegaard, Lars Fahl

    2012-01-01

    Anisotropic broadening correction in X-ray powder diffraction by an ellipsoidal formula is applied on samples with nanosized crystals. Two cases of minerals with largely anisotropic crystallite shapes are presented. The properly applied formalism not only improves the fitting of the theoretical...

  16. Characterization of crystallite morphology for doped strontium fluoride nanophosphors by TEM and XRD

    Energy Technology Data Exchange (ETDEWEB)

    O' Connell, J.H. [Centre for HRTEM, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth ZA6031 (South Africa); Lee, M.E., E-mail: Michael.lee@nmmu.ac.za [Centre for HRTEM, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth ZA6031 (South Africa); Yagoub, M.Y.A.; Swart, H.C.; Coetsee, E. [Department of Physics, University of the Free State, PO Box 339, Bloemfontein ZA9300 (South Africa)

    2016-01-01

    Crystallite morphology for Eu-doped and undoped SrF{sub 2} nanophosphors have been determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The values for average crystallite size obtained by the application of the Scherrer equation and the full width at half maximum (FWHM) values for XRD peaks are compared to the results obtained using the hollow cone dark field (HCDF) TEM imaging technique. In the case of the TEM analysis, a bimodal crystallite size distribution was revealed with one of the distributions having a measured range of crystallite sizes which was in good agreement with the XRD data. HCDF in combination with FIB specimen preparation was found to be a promising technique for the determination of crystallite size distributions in nanophosphors which might facilitate a better understanding of their scintillation properties.

  17. Characterization of crystallite morphology for doped strontium fluoride nanophosphors by TEM and XRD

    International Nuclear Information System (INIS)

    O'Connell, J.H.; Lee, M.E.; Yagoub, M.Y.A.; Swart, H.C.; Coetsee, E.

    2016-01-01

    Crystallite morphology for Eu-doped and undoped SrF_2 nanophosphors have been determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The values for average crystallite size obtained by the application of the Scherrer equation and the full width at half maximum (FWHM) values for XRD peaks are compared to the results obtained using the hollow cone dark field (HCDF) TEM imaging technique. In the case of the TEM analysis, a bimodal crystallite size distribution was revealed with one of the distributions having a measured range of crystallite sizes which was in good agreement with the XRD data. HCDF in combination with FIB specimen preparation was found to be a promising technique for the determination of crystallite size distributions in nanophosphors which might facilitate a better understanding of their scintillation properties.

  18. Crystallite structure formation at the collapse pressure of fatty acid Langmuir films

    International Nuclear Information System (INIS)

    Valdes-Covarrubias, M A; Cadena-Nava, R D; Vasquez-MartInez, E; Valdez-Perez, D; Ruiz-GarcIa, J

    2004-01-01

    We report isotherm and atomic force microscopy studies of collapsed Langmuir monolayers of fatty acids. The Langmuir monolayers were overcompressed in the range 7-40 deg. C and transferred onto mica after the sharp pressure drop when the collapse pressure was reached. Collapsed material was observed by AFM, which revealed that the multilayers are indeed three-dimensional crystallites. We found that the shape of the crystallites depends on the collapse temperature, the phase from which the collapse occurs and/or the chain length. However, at higher temperatures the collapsed films no longer show a well defined crystallite formation, but rather a more heterogeneous melt-like pattern. We associated the crystallite formation with known bulk crystal phases of the fatty acids

  19. Effect of roll hot press temperature on crystallite size of PVDF film

    Energy Technology Data Exchange (ETDEWEB)

    Hartono, Ambran, E-mail: ambranhartono@yahoo.com; Sanjaya, Edi [Departement of Physics Faculty of Science and Technology, Islamic State University Syarif Hidayatullah , Jl. Juanda 95 Ciputat Jakarta (Indonesia); Djamal, Mitra; Satira, Suparno; Bahar, Herman [Theoretical High Energy Physics and Instrumentation Group Research, Faculty Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesa 10 Bandung (Indonesia); Ramli [Departement of Physics, Faculty of Mathematics and Natural Sciences, Universitas Negeri Padang, Jl.Prof. Hamka, Padang 25131 (Indonesia)

    2014-03-24

    Fabrication PVDF films have been made using Hot Roll Press. Preparation of samples carried out for nine different temperatures. This condition is carried out to see the effect of Roll Hot Press temperature on the size of the crystallite of PVDF films. To obtain the diffraction pattern of sample characterization is performed using X-Ray Diffraction. Furthermore, from the diffraction pattern is obtained, the calculation to determine the crystallite size of the sample by using the Scherrer equation. From the experimental results and the calculation of crystallite sizes obtained for the samples with temperature 130 °C up to 170 °C respectively increased from 7.2 nm up to 20.54 nm. These results show that increasing temperatures will also increase the size of the crystallite of the sample. This happens because with the increasing temperature causes the higher the degree of crystallization of PVDF film sample is formed, so that the crystallite size also increases. This condition indicates that the specific volume or size of the crystals depends on the magnitude of the temperature as it has been studied by Nakagawa.

  20. Crystallite size effects in stacking faulted nickel hydroxide and its electrochemical behaviour

    International Nuclear Information System (INIS)

    Ramesh, T.N.

    2009-01-01

    β-Nickel hydroxide comprises a long range periodic arrangement of atoms with a stacking sequence of AC AC AC-having an ideal composition Ni(OH) 2 . Variation in the preparative conditions can lead to the changes in the stacking sequence (AC AC BA CB AC AC or AC AC AB AC AC). This type of variation in stacking sequence can result in the formation of stacking fault in nickel hydroxide. The stability of the stacking fault depends on the free energy content of the sample. Stacking faults in nickel hydroxide is essential for better electrochemical activity. Also there are reports correlating particle size to the better electrochemical activity. Here we present the effect of crystallite size on the stacking faulted nickel hydroxide samples. The electrochemical performance of stacking faulted nickel hydroxide with small crystallite size exchanges 0.8e/Ni, while the samples with larger crystallite size exchange 0.4e/Ni. Hence a right combination of crystallite size and stacking fault content has to be controlled for good electrochemical activity of nickel hydroxide

  1. On the nature of structural disorder in calcium silicate hydrates with a calcium/silicon ratio similar to tobermorite

    Energy Technology Data Exchange (ETDEWEB)

    Grangeon, Sylvain, E-mail: S.Grangeon@brgm.fr [BRGM, 3, Avenue Claude Guillemin, 45060 Orléans Cedex 2 (France); Claret, Francis; Lerouge, Catherine [BRGM, 3, Avenue Claude Guillemin, 45060 Orléans Cedex 2 (France); Warmont, Fabienne [CRMD, UMR 6619 – CNRS, 1b rue de la férollerie, 45071 Orléans Cedex 2 (France); Sato, Tsutomu; Anraku, Sohtaro [Laboratory of Environmental Geology, Research Group of Geoenvironmental/Engineering Division of Solid Waste, Resources and Geoenvironmental/Engineering Graduate School of Engineering, Hokkaido University, Kita 13 Nishi 8, Sapporo 060-8628 (Japan); Numako, Chiya [Faculty of Integrated Arts and Sciences, The University of Tokushima, 1-1, Minami-Josanjima, Tokushima, 770-8502 (Japan); Linard, Yannick [ANDRA, Centre de Meuse/Haute Marne, 55290 Bure (France); Lanson, Bruno [ISTerre, Grenoble University, CNRS, F-38041 Grenoble (France)

    2013-10-15

    Four calcium silicate hydrates (C-S-H) with structural calcium/silicon (Ca/Si) ratios ranging from 0.82 ± 0.02 to 0.87 ± 0.02 were synthesized at room temperature, 50, 80, and 110 °C. Their structure was elucidated by collating information from electron probe micro-analysis, transmission electron microscopy, extended X-ray absorption fine structure spectroscopy, and powder X-ray diffraction (XRD). A modeling approach specific to defective minerals was used because sample turbostratism prevented analysis using usual XRD refinement techniques (e.g. Rietveld analysis). It is shown that C-S-H with Ca/Si ratio of ∼ 0.8 are structurally similar to nano-crystalline turbostratic tobermorite, a naturally occurring mineral. Their structure thus consists of sheets of calcium atoms in 7-fold coordination, covered by ribbons of silicon tetrahedra with a dreierketten (wollastonite-like) organization. In these silicate ribbons, 0.42 Si per bridging tetrahedron are missing. Random stacking faults occur systematically between successive layers (turbostratic stacking). Layer-to-layer distance is equal to 11.34 Å. Crystallites have a mean size of 10 nm in the a–b plane, and a mean number of 2.6–2.9 layers stacked coherently along the c* axis.

  2. Direct measurement of free-energy barrier to nucleation of crystallites in amorphous silicon thin films

    Science.gov (United States)

    Shi, Frank G.

    1994-01-01

    A method is introduced to measure the free-energy barrier W(sup *), the activation energy, and activation entropy to nucleation of crystallites in amorphous solids, independent of the energy barrier to growth. The method allows one to determine the temperature dependence of W(sup *), and the effect of the preparation conditions of the initial amorphous phase, the dopants, and the crystallization methds on W(sup *). The method is applied to determine the free-energy barrier to nucleation of crystallites in amorphous silicon (a-Si) thin films. For thermally induced nucleation in a-Si thin films with annealing temperatures in the range of from 824 to 983 K, the free-energy barrier W(sup *) to nucleation of silicon crystals is about 2.0 - 2.1 eV regardless of the preparation conditions of the films. The observation supports the idea that a-Si transforms into an intermediate amorphous state through the structural relaxation prior to the onset of nucleation of crystallites in a-Si. The observation also indicates that the activation entropy may be an insignificant part of the free-energy barrier for the nucleation of crystallites in a-Si. Compared with the free-energy barrier to nucleation of crystallites in undoped a-Si films, a significant reduction is observed in the free-energy barrier to nucleation in Cu-doped a-Si films. For a-Si under irradiation of Xe(2+) at 10(exp 5) eV, the free-energy barrier to ion-induced nucleation of crystallites is shown to be about half of the value associated with thermal-induced nucleation of crystallites in a-Si under the otherwise same conditions, which is much more significant than previously expected. The present method has a general kinetic basis; it thus should be equally applicable to nucleation of crystallites in any amorphous elemental semiconductors and semiconductor alloys, metallic and polymeric glasses, and to nucleation of crystallites in melts and solutions.

  3. Crystallite growth in nanocrystalline tungsten; rate determining mechanism and the role of contaminations

    International Nuclear Information System (INIS)

    Hegedűs, Zoltán; Meka, Sai Ramudu; Mittemeijer, Eric J.

    2016-01-01

    The thermal stability of nanocrystalline tungsten was investigated by tracing the evolution of the microstructure as a function of (isothermal) annealing time at different temperatures (800−875 °C). To this end especially in situ X-ray diffraction and transmission electron microscopy methods were applied to ball milled tungsten powder. Initially the dislocation density and the crystallite/domain size decreased and increased rapidly, respectively. Upon prolonged annealing the crystallite growth rate decelerated and even became nil: a saturation crystallite size, increasing with increasing annealing temperature, was attained. Application of all available isothermal growth models to the experimental data resulted in very low values for the activation energy (60−120 kJ/mol) indicating that recovery of the deformed microstructure is the dominantly occurring process, leading to pronounced crystallite/domain growth. The effect on the growth kinetics of different levels of contaminations, which exert a drag force on the moving boundaries, was also investigated.

  4. Influence of crystallographic orientation on the response of copper crystallites to nanoindentation

    Energy Technology Data Exchange (ETDEWEB)

    Korchuganov, Aleksandr V., E-mail: avkor@ispms.tsc.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); Kryzhevich, Dmitrij S., E-mail: kryzhev@ispms.tsc.ru, E-mail: kost@ispms.tsc.ru; Zolnikov, Konstantin P., E-mail: kryzhev@ispms.tsc.ru, E-mail: kost@ispms.tsc.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055, Russia and National Research Tomsk State University, Tomsk, 634050 (Russian Federation); Psakhie, Sergey G., E-mail: sp@ispms.tsc.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055, Russia and National Research Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation)

    2014-11-14

    Molecular dynamics simulation was performed to study the features of nucleation and development of plastic deformation in copper crystallites in nanoindentation with different crystallographic orientations of their loaded surface: (011), (001), and (111). Atomic interaction was described by a potential constructed in terms of the embedded atom method. It is shown that behavior of the crystallite reaction force correlates well with a change in the fraction of atoms involved in local structural rearrangements. The generation of local structural changes decreases the slope of the crystallite reaction force curve or results in an extremum due to internal stress relaxation. Analysis of structural changes in the material being indented demonstrates that the orientation of its loaded surface greatly affects the features of nucleation and development of plastic deformation.

  5. MD simulation of plastic deformation nucleation in stressed crystallites under irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Korchuganov, A. V., E-mail: avkor@ispms.tsc.ru; Zolnikov, K. P., E-mail: kost@ispms.tsc.ru; Kryzhevich, D. S., E-mail: kryzhev@ispms.tsc.ru [Russian Academy of Sciences, Institute of Strength Physics and Materials Science, Siberian Branch (Russian Federation); Chernov, V. M., E-mail: VMChernov@bochvar.ru [National Research Tomsk State University (Russian Federation); Psakhie, S. G., E-mail: sp@ispms.tsc.ru [Russian Academy of Sciences, Institute of Strength Physics and Materials Science, Siberian Branch (Russian Federation)

    2016-12-15

    The investigation of plastic deformation nucleation in metals and alloys under irradiation and mechanical loading is one of the topical issues of materials science. Specific features of nucleation and evolution of the defect system in stressed and irradiated iron, vanadium, and copper crystallites were studied by molecular dynamics simulation. Mechanical loading was performed in such a way that the modeled crystallite volume remained unchanged. The energy of the primary knock-on atom initiating a cascade of atomic displacements in a stressed crystallite was varied from 0.05 to 50 keV. It was found that atomic displacement cascades might cause global structural transformations in a region far larger than the radiation-damaged area. These changes are similar to the ones occurring in the process of mechanical loading of samples. They are implemented by twinning (in iron and vanadium) or through the formation of partial dislocation loops (in copper).

  6. Detrital illite crystals identified from crystallite thickness measurements in siliciclastic sediments

    Science.gov (United States)

    Aldega, L.; Eberl, D.D.

    2005-01-01

    Illite crystals in siliciclastic sediments are heterogeneous assemblages of detrital material coming from various source rocks and, at paleotemperatures >70 ??C, of superimposed diagenetic modification in the parent sediment. We distinguished the relative proportions of 2M1 detrital illite and possible diagenetic 1Md + 1M illite by a combined analysis of crystal-size distribution and illite polytype quantification. We found that the proportions of 1Md + 1M and 2M1 illite could be determined from crystallite thickness measurements (BWA method, using the MudMaster program) by unmixing measured crystallite thickness distributions using theoretical and calculated log-normal and/or asymptotic distributions. The end-member components that we used to unmix the measured distributions were three asymptotic-shaped distributions (assumed to be the diagenetic component of the mixture, the 1Md + 1M polytypes) calculated using the Galoper program (Phase A was simulated using 500 crystals per cycle of nucleation and growth, Phase B = 333/cycle, and Phase C = 250/ cycle), and one theoretical log-normal distribution (Phase D, assumed to approximate the detrital 2M1 component of the mixture). In addition, quantitative polytype analysis was carried out using the RockJock software for comparison. The two techniques gave comparable results (r2 = 0.93), which indicates that the unmixing method permits one to calculate the proportion of illite polytypes and, therefore, the proportion of 2M1 detrital illite, from crystallite thickness measurements. The overall illite crystallite thicknesses in the samples were found to be a function of the relative proportions of thick 2M1 and thin 1Md + 1M illite. The percentage of illite layers in I-S mixed layers correlates with the mean crystallite thickness of the 1Md + 1M polytypes, indicating that these polytypes, rather than the 2M1 polytype, participate in I-S mixed layering.

  7. Determination of Crystallite Size Distribution Histogram in Nanocrystalline Anatase Powders by XRD

    Czech Academy of Sciences Publication Activity Database

    Matěj, Z.; Matějová, Lenka; Novotný, F.; Drahokoupil, Jan; Kužel, R.

    2011-01-01

    Roč. 1, - (2011), s. 87-92 [European Powder Diffraction Conference EPDIC 12 /12./. Darmstadt, 27.08.2010-30.08.2010] R&D Projects: GA AV ČR KAN400720701 Institutional research plan: CEZ:AV0Z40720504; CEZ:AV0Z10100520 Keywords : titanium dioxide * crystallite size * crystallite size distribution Subject RIV: CA - Inorganic Chemistry http://www.oldenbourg-link.com/ toc /zkpr/current

  8. Distinguishing crystallite size effects from those of structural disorder ...

    Indian Academy of Sciences (India)

    Administrator

    Both crystallite size effects and structural disorder contribute to the broadening of lines in .... ple contributions to the peak profiles. ... the fit is then corrected by accounting for sample ... Authors thank the Department of Science and Tech-.

  9. Crystallite size distribution of clay minerals from selected Serbian clay deposits

    Directory of Open Access Journals (Sweden)

    Simić Vladimir

    2006-01-01

    Full Text Available The BWA (Bertaut-Warren-Averbach technique for the measurement of the mean crystallite thickness and thickness distributions of phyllosilicates was applied to a set of kaolin and bentonite minerals. Six samples of kaolinitic clays, one sample of halloysite, and five bentonite samples from selected Serbian deposits were analyzed. These clays are of sedimentary volcano-sedimentary (diagenetic, and hydrothermal origin. Two different types of shape of thickness distribution were found - lognormal, typical for bentonite and halloysite, and polymodal, typical for kaolinite. The mean crystallite thickness (T BWA seams to be influenced by the genetic type of the clay sample.

  10. Formation and characterization of Ni nanostructures in porous InP - from crystallites to wires

    International Nuclear Information System (INIS)

    Gerngross, M.-D.; Hrkac, V.; Kienle, L.; Carstensen, J.; Foell, H.

    2013-01-01

    In this work the galvanic formation of Ni crystallites and Ni nanowires with very high aspect ratios (>1000:1) in porous InP is presented. By depositing a dielectric interlayer on the InP pore walls it is possible to produce very high aspect ratio Ni nanowires. The coercivity of these nanowires is about 100 Oe (in-plane) and 240 Oe (out-of-plane), while the coercivity of the crystallites lies in between these values. The in-plane remanence squareness of the Ni nanowires is very low (S ∼ 0.08), out-of-plane it is 0.36. For the Ni crystallites the remanence squareness lies in between the range given for the Ni nanowires. (author)

  11. Collagen Orientation and Crystallite Size in Human Dentin: A Small Angle X-ray Scattering Study

    Energy Technology Data Exchange (ETDEWEB)

    Pople, John A

    2001-03-29

    The mechanical properties of dentin are largely determined by the intertubular dentin matrix, which is a complex composite of type I collagen fibers and a carbonate-rich apatite mineral phase. The authors perform a small angle x-ray scattering (SAXS) study on fully mineralized human dentin to quantify this fiber/mineral composite architecture from the nanoscopic through continuum length scales. The SAXS results were consistent with nucleation and growth of the apatite phase within periodic gaps in the collagen fibers. These mineralized fibers were perpendicular to the dentinal tubules and parallel with the mineralization growth front. Within the plane of the mineralization front, the mineralized collagen fibers were isotropic near the pulp, but became mildly anisotropic in the mid-dentin. Analysis of the data also indicated that near the pulp the mineral crystallites were approximately needle-like, and progressed to a more plate-like shape near the dentino-enamel junction. The thickness of these crystallites, {approx} 5 nm, did not vary significantly with position in the tooth. These results were considered within the context of dentinogenesis and maturation.

  12. The use of pattern decomposition to study the combined X-ray diffraction effects of crystallite size and stacking faults in ex-oxalate zinc oxide

    International Nuclear Information System (INIS)

    Langford, J.I.; Boultif, A.; Auffredic, J.P.; Louer, D.

    1993-01-01

    The microstructure of ZnO powder, obtained from thermal decomposition of the oxalate and studied previously by electron microscopy and adsorption calorimetry, was investigated by means of X-ray powder diffraction pattern decomposition. A Williamson-Hall plot revealed that some lines were broadened solely due to the effects of crystallite size, whereas other breadths included a contribution due to stacking faults. Spherical and cylindrical models are used to describe the form of the crystallites and procedures are presented for separating 'size' effects from 'mistake' broadening. This leads to estimates of the mean dimensions of the crystallites and the stacking-fault probability. The analysis demonstrates that, with good-quality data for a large number of reflections, a considerable amount of detailed information can be obtained about microstructure. On the other hand, it reveals some of the limitations of current procedures for modelling diffraction line profiles. (orig.)

  13. EFFECTS OF ULTRASOUND ON THE MORPHOLOGY, PARTICLE SIZE, CRYSTALLINITY, AND CRYSTALLITE SIZE OF CELLULOSE

    Directory of Open Access Journals (Sweden)

    SUMARI SUMARI

    2014-05-01

    Full Text Available The aim of this study is to optimize ultrasound treatment to produce fragment of cellulose that is low in particles size, crystallite size, and crystallinity. Slurry of 1 % (w/v the cellulose was sonicated at different time periods and temperatures. An ultrasonic reactor was operated at 300 Watts and 28 kHz to cut down the polymer into smaller particles. We proved that ultrasound damages and fragments the cellulose particles into shorter fibers. The fiber lengths were reduced from in the range of 80-120 µm to 30-50 µm due to an hour ultrasonication and became 20-30 µm after 5 hours. It was also found some signs of erosion on the surface and stringy. The acoustic cavitation also generated a decrease in particle size, crystallinity, and crystallite size of the cellulose along with increasing sonication time but it did not change d-spacing. However, the highest reduction of particle size, crystallite size, and crystallinity of the cellulose occurred within the first hour of ultrasonication, after which the efficiency was decreased. The particle diameter, crystallite size, and crystallinity were decreased from 19.88 µm to 15.96 µm, 5.81 Å to 2.98 Å, and 77.7% to 73.9% respectively due to an hour ultrasound treatment at 40 °C. The treatment that was conducted at 40 °C or 60 °C did not give a different effect significantly. Cellulose with a smaller particle and crystallite size as well as a more amorphous shape is preferred for further study.

  14. Preparation and characterization of graphene/turbostratic carbon derived from chitosan film for supercapacitor electrodes

    Science.gov (United States)

    Hanappi, M. F. Y. M.; Deraman, M.; Suleman, M.; Othman, M. A. R.; Basri, N. H.; Nor, N. S. M.; Hamdan, E.; Sazali, N. E. S.; Tajuddin, N. S. M.

    2018-04-01

    Electrochemical capacitors or supercapacitors are the potential energy storage devices which are known for having higher specific capacitance and specific energy than electrolytic capacitors. Electric double-layer capacitors (EDLCs) also referred as ultracapacitors is a class of supercapacitors that employ different forms of carbon like activated carbon, CNT, graphene etc., as electrodes. The performance of the supercapacitors is determined by its components namely electrolyte, electrode, etc. Carbon electrodes with high surface area and desired pore size distribution are always preferred and which can be tailored by varying the precursor and method of preparation. In recent years, owing to their low cost, ease of synthesis, high stability and conductivity, the activated carbons derived from biomass precursors have been investigated as potential electrode material for the EDLCs. In this report, we present the preparation and characterization of graphene/turbostratic carbon monolith (CM) electrodes from the carbon grains (CGs) obtained by carbonization (under the flow of nitrogen, N2 gas and over a temperature range from 600 °C to 1000 °C) of biomass precursor chitosan film. The procedure to prepare the chitosan film is described elsewhere. The carbon grains are characterized using Raman spectroscopy (RS) and X-ray diffraction (XRD). We expect that the CGs would have the similar characteristics as graphene and would be a potential electrode material for EDLCs application.

  15. Effect of deformation on crystallite characteristic and yield stress of zircaloy-4

    International Nuclear Information System (INIS)

    Sugondo; Futichah

    2007-01-01

    The effect of deformation (rolling) on micro strain, crystallite size, crystallite density, and yield strength of Zircaloy-4 was characterized by x-ray diffraction. The goal of this investigation is to characterize the cladding materials of PWR and the target is to have data on the crystallography of Zircaloy-4. The as-received material with the composition 1.3% Sn, 0.22% Fe, 0.1% Cr, and Zr balanced was cut 10 mm × 100 mm in size using diamond blade. The samples were cleaned and heated at 1100 °C for 2 hours and then quenched in cold water. Then the sample were cleaned and heated at 750 °C for 2 hours. Afterward the samples were cold rolled with 40%, 75%, and 80% reduction in thickness. After the preparation was completed, the crystals of the samples were characterized using X-ray diffraction. The processes being analysed were quenching followed by annealing, plastic deformation of annealing and reduction from 40% to 80%, and the constancy of the c/a ratio. From the analyses, three conclusions were obtained. Firstly, the annealing process at 750 °C of Zircaloy-4 from the quenched samples resulted in the recrystallization and the grain growth which was proven by the increase of micro strain from 25.05% to 32.83%, the increase of crystallite size from 10.1015 Å to 287.4798 Å, the decrease of dislocation density from 2.94E+16 m/m3 to 3.63E+13 m/m3, and the decrease of yield strength from 1125.52 MPa to 304.44 MPa. Secondly, the process of reduction of Zircaloy-4 from the annealed samples reduced to 80% resulted in the plastic deformation and crystallite which was shown by the decrease of micro strain from 32.83% to 3.15%, the decrease of crystallite size from 287.4798 Å to 10.9764 Å, the increase of dislocation density from 3.63E+13 m/m3 to 2.49E+16 m/m3, and the increase of yield strength from 304.44 MPa to 1057.69 MPa. Thirdly, the process of plastic deformation of Zircaloy-4 was limited by the constancy of the c/a ratio which was verified by the decrease

  16. Study of the crystallite size of nitrosylpentacyanoferrate through refinement of structures

    International Nuclear Information System (INIS)

    Jimenez G, J.A.; Yee M, H.T.; Balmaceda E, J.; Reguera R, E.

    2006-01-01

    The development reached in the instrumentation and in the computer science of the diffraction of rays X, it has enlarged the reach of the method of powders considerably, in the resolution of crystalline structures of polycrystalline material converting it in a potent tool that, attended by spectroscopic techniques, it allows the fine characterization to atomic scale of having been accustomed to crystalline. In the thesis it is developed an effective methodology of determination of the crystallite size and structural refinement starting from data of diffraction of powders, based on the use of the equation of Sherrer for the estimate of the crystallite size and the method of Rietveld for the structural refinement; supplemented with the employment of the spectroscopic methods (IR and Moessbauer). The combined use of these techniques in the structural study of having been accustomed to crystalline lens of high complexity provides a novel and advanced work. The estimate of the crystallite size, it has been little explored to study accustomed to crystalline such as the pentacyanonitrosyl ferrates. One of the reasons for the which have intended to study the glass size in these structures it is due to that the molecular materials have attracted the attention of the international scientific community for their promissory properties in fields so diverse as: the absorption, desorption and separation of gases among others. Of the entreated information by means of databases and articles of scientific popularization were refined the structures of two compounds (NPCo and NPNi) obtained by powders diffraction; offering the possibility to develop a titled work: 'Physical description of the desorption of the water in nano structured material of nitrosyl penta cyano ferrates' which is carried out in parallel way to this thesis. This tools supplemented with the spectroscopic methods, potent the reach of the methods of diffraction of powders for the structural study of having been

  17. Influence of composition and structure on the mechanical properties of BCN coatings deposited by thermal CVD

    Energy Technology Data Exchange (ETDEWEB)

    Stoeckel, S.; Weise, K.; Dietrich, D.; Thamm, T.; Braun, M.; Cremer, R.; Neuschuetz, D.; Marx, G

    2002-12-02

    BCN films were deposited by isothermal chemical vapour deposition from gaseous mixtures of trimethylborazine, toluene and ammonia. The films were analysed with respect to chemical state, composition, morphology and microstructure on the one side oxidation behaviour and hardness on the other side. X-ray spectroscopy (WDX), Raman and infrared spectroscopy, differential thermal analysis, X-ray diffraction and transmission electron spectroscopy were employed for film characterization. A microhardness of maximum 20 GPa was achieved, affected by carbon content, by the way of its incorporation into the hexagonal turbostratic lattice as well as by the crystallite size and its texture.

  18. Influence of composition and structure on the mechanical properties of BCN coatings deposited by thermal CVD

    International Nuclear Information System (INIS)

    Stoeckel, S.; Weise, K.; Dietrich, D.; Thamm, T.; Braun, M.; Cremer, R.; Neuschuetz, D.; Marx, G.

    2002-01-01

    BCN films were deposited by isothermal chemical vapour deposition from gaseous mixtures of trimethylborazine, toluene and ammonia. The films were analysed with respect to chemical state, composition, morphology and microstructure on the one side oxidation behaviour and hardness on the other side. X-ray spectroscopy (WDX), Raman and infrared spectroscopy, differential thermal analysis, X-ray diffraction and transmission electron spectroscopy were employed for film characterization. A microhardness of maximum 20 GPa was achieved, affected by carbon content, by the way of its incorporation into the hexagonal turbostratic lattice as well as by the crystallite size and its texture

  19. Nano/micro Sr{sub 2}Bi{sub 4}Ti{sub 5}O{sub 18} crystallites: Size dependent structural, second harmonic and piezoelectric properties

    Energy Technology Data Exchange (ETDEWEB)

    Tukaram, Shet; Bhimireddi, Rajasekhar; Varma, K.B.R., E-mail: kbrvarma@mrc.iisc.ernet.in

    2016-09-15

    Graphical abstract: Synthesis of Sr{sub 2}Bi{sub 4}Ti{sub 5}O{sub 18} nano/micro crystallites and their size dependent non-linear optical and piezoelectric responses. - Highlights: • Nano/microcrystallites of Sr{sub 2}Bi{sub 4}Ti{sub 5}O{sub 18} were synthesized via sol-gel route. • Crystallite size dependent structural and physical properties were studied. • SHG intensity (1.4 times that of KDP powder) from these crystallites was recorded. • PFM studies on isolated crystallite of 480 nm exhibited d{sub 33} as high as 27 pm/V. • Single domain nature of the crystallites below 160 nm was observed. - Abstract: Strontium bismuth titanate (Sr{sub 2}Bi{sub 4}Ti{sub 5}O{sub 18}) powders comprising crystallites of average sizes in the range of 94–1400 nm were prepared via citrate-assisted sol-gel route. With an increase in the average crystallite size there was a change in the lattice parameters and shift in the Raman vibration modes. Second harmonic signal (532 nm) intensity of the Sr{sub 2}Bi{sub 4}Ti{sub 5}O{sub 18} powders increased with the increase in the average crystallite size and the maximum intensity obtained in the reflection mode was 1.4 times as high as that of the powdered KH{sub 2}PO{sub 4}. Piezo Force Microscopic analyses carried out on isolated crystallite of size 74 nm, established a single domain nature with the coercive field as high as 347 kV/cm. There was a systematic increase in the d{sub 33} value with an increase in the size of the isolated crystallites and a high piezoelectric coefficient of ∼27 pm/V was obtained from an isolated crystallite of size 480 nm.

  20. On sub-T(g) dewetting of nanoconfined liquids and autophobic dewetting of crystallites.

    Science.gov (United States)

    Souda, Ryutaro

    2012-03-28

    The glass transition temperature (T(g)) of thin films is reduced by nanoconfinement, but it is also influenced by the free surface and substrate interface. To gain more insights into their contributions, dewetting behaviors of n-pentane, 3-methylpentane, and toluene films are investigated on various substrates as functions of temperature and film thickness. It is found that monolayers of these molecules exhibit sub-T(g) dewetting on a perfluoro-alkyl modified Ni substrate, which is attributable to the evolution of a 2D liquid. The onset temperature of dewetting increases with film thickness because fluidity evolves via cooperative motion of many molecules; sub-T(g) dewetting is observed for films thinner than 5 monolayers. In contrast, monolayers wet substrates of graphite, silicon, and amorphous solid water until crystallization occurs. The crystallites exhibit autophobic dewetting on the substrate covered with a wetting monolayer. The presence of premelting layers is inferred from the fact that n-pentane crystallites disappear on amorphous solid water via intermixing. Thus, the properties of quasiliquid formed on the crystallite surface differ significantly from those of the 2D liquid formed before crystallization.

  1. Magnetic properties of nanocrystalline CoFe{sub 2}O{sub 4} powders prepared at room temperature: variation with crystallite size

    Energy Technology Data Exchange (ETDEWEB)

    Rajendran, M.; Pullar, R.C.; Bhattacharya, A.K. E-mail: ashokbhattacharya@warwick.ac.uk; Das, D.; Chintalapudi, S.N.; Majumdar, C.K

    2001-06-01

    The magnetic properties of nanocrystalline CoFe{sub 2}O{sub 4} powders prepared by a redox process at room temperature have been studied by vibrating sample magnetometer (VSM). The average crystallite size of the powders varied from 6 to 20 nm by changing the synthesis conditions and the corresponding saturation magnetisation (M{sub s}) value ranged from 9 to 38 emu g{sup -1}. On heating, the crystallite size increased with corresponding increase in M{sub s} values. At 1073 K all samples achieved M{sub s} values close to 73 emu g{sup -1}. On increasing the crystallite size, the coercivity (H{sub c}) increased passed through a maximum and dropped. Cobalt ferrite powder with an average crystallite size of 6 nm prepared at room temperature achieved desirable values of M{sub s}=60 emu g{sup -1} and H{sub c}=1.42 kOe after thermal annealing at 973 K. The Moessbauer spectra were recorded for CoFe{sub 2}O{sub 4} having a range of crystallite sizes at room temperature and at low temperatures down to 40 K. The magnetic and Moessbauer results are provided for nanocrystalline CoFe{sub 2}O{sub 4} as a function of crystallite size and measurement temperature.

  2. Influence of crystallite size and shape of zeolite ZSM-22 on its activity and selectivity in the catalytic cracking of n-octane

    Energy Technology Data Exchange (ETDEWEB)

    Bager, F.; Ernst, S. [Kaiserslautern Univ. (Germany). Dept. of Chemistry, Chemical Technology

    2013-11-01

    Light olefins belong to the major building blocks for the petrochemical industry, particularly for the production of polymers. It has become necessary to increase the production of light olefins specifically in the case for propene with so called 'on-purpose propene' technologies. One possible route is to increase the amount of propene that can be obtained from Fluid Catalytic Cracking (FCC) by optimizing the catalyst through introducing new additives, which offer a high selectivity to propene. Zeolite ZSM-22 samples with different crystallite sizes and morphologies have been synthesized via hydrothermal syntheses and characterized by powder X-Ray diffraction, nitrogen physisorption, atomic absorption spectroscopy, scanning electron microscopy and solid-state NMR spectroscopy. The zeolites in the Broensted-acid form have been tested as catalysts in the catalytic cracking of n-octane as a model hydrocarbon. Clear influences of the crystallite size on the deactivation behavior have been observed. Larger crystals of zeolite ZSM-22 produce an increased amount of coke deposits resulting in a faster deactivation of the catalyst. The experimental results suggest that there is probably some influence of pore diffusion on the catalytic activity of the ZSM-22 sample with the large crystallite size. However a noticeable influence on the general product distribution could not be observed. (orig.)

  3. Dependence of crystallite formation and preferential backbone orientations on the side chain pattern in PBDTTPD polymers

    KAUST Repository

    El Labban, Abdulrahman

    2014-11-26

    (Figure Presented) Alkyl substituents appended to the π-conjugated main chain account for the solution-processability and film-forming properties of most π-conjugated polymers for organic electronic device applications, including field-effect transistors (FETs) and bulk-heterojunction (BHJ) solar cells. Beyond film-forming properties, recent work has emphasized the determining role that side-chain substituents play on polymer self-assembly and thin-film nanostructural order, and, in turn, on device performance. However, the factors that determine polymer crystallite orientation in thin-films, implying preferential backbone orientation relative to the device substrate, are a matter of some debate, and these structural changes remain difficult to anticipate. In this report, we show how systematic changes in the side-chain pattern of poly(benzo[1,2-b:4,5-b′]dithiophene-alt-thieno[3,4-c]pyrrole-4,6-dione) (PBDTTPD) polymers can (i) influence the propensity of the polymer to order in the π-stacking direction, and (ii) direct the preferential orientation of the polymer crystallites in thin films (e.g., "face-on" vs "edge-on"). Oriented crystallites, specifically crystallites that are well-ordered in the π-stacking direction, are believed to be a key contributor to improved thin-film device performance in both FETs and BHJ solar cells.

  4. Crystallite size variation of TiO_2 samples depending time heat treatment

    International Nuclear Information System (INIS)

    Galante, A.G.M.; Paula, F.R. de; Montanhera, M.A.; Pereira, E.A.; Spada, E.R.

    2016-01-01

    Titanium dioxide (TiO_2) is an oxide semiconductor that may be found in mixed phase or in distinct phases: brookite, anatase and rutile. In this work was carried out the study of the residence time influence at a given temperature in the TiO_2 powder physical properties. After the powder synthesis, the samples were divided and heat treated at 650 °C with a ramp up to 3 °C/min and a residence time ranging from 0 to 20 hours and subsequently characterized by x-ray diffraction. Analyzing the obtained diffraction patterns, it was observed that, from 5-hour residence time, began the two-distinct phase coexistence: anatase and rutile. It also calculated the average crystallite size of each sample. The results showed an increase in average crystallite size with increasing residence time of the heat treatment. (author)

  5. X-ray determination of crystallite size and effect of lattice strain on ...

    Indian Academy of Sciences (India)

    X-ray diffraction; lattice strain; crystallite size; Debye–Waller factor; vacancy formation energy. 1. Introduction ... In the present investigation, results of a system- atic study of .... that while milling is enough to create strains, it affects the particle ...

  6. Ambient aging of rhenium filaments used in thermal ionization mass spectrometry: Growth of oxo-rhenium crystallites and anti-aging strategies

    Directory of Open Access Journals (Sweden)

    Joseph M. Mannion

    2017-01-01

    Full Text Available Degassing is a common preparation technique for rhenium filaments used for thermal ionization mass spectrometric analysis of actinides, including plutonium. Although optimization studies regarding degassing conditions have been reported, little work has been done to characterize filament aging after degassing. In this study, the effects of filament aging after degassing were explored to determine a “shelf-life” for degassed rhenium filaments, and methods to limit filament aging were investigated. Zone-refined rhenium filaments were degassed by resistance heating under high vacuum before exposure to ambient atmosphere for up to 2 months. After degassing the nucleation and preferential growth of oxo-rhenium crystallites on the surface of polycrystalline rhenium filaments was observed by atomic force microscopy and scanning electron microscopy (SEM. Compositional analysis of the crystallites was conducted using SEM-Raman spectroscopy and SEM energy dispersive X-ray spectroscopy, and grain orientation at the metal surface was investigated by electron back-scatter diffraction mapping. Spectra collected by SEM-Raman suggest crystallites are composed primarily of perrhenic acid. The relative extent of growth and crystallite morphology were found to be grain dependent and affected by the dissolution of carbon into filaments during annealing (often referred to as carbonization or carburization. Crystallites were observed to nucleate in region specific modes and grow over time through transfer of material from the surface. Factors most likely to affect the rates of crystallite growth include rhenium substrate properties such as grain size, orientation, levels of dissolved carbon, and relative abundance of defect sites; as well as environmental factors such as length of exposure to oxygen and relative humidity. Thin (∼180 nm hydrophobic films of poly(vinylbenzyl chloride were found to slow the growth of oxo-rhenium crystallites on the filament

  7. Crystallite size and lattice distortion of human dental enamel estimated from the integral width of x-ray diffraction peak profile

    International Nuclear Information System (INIS)

    Maruyama, Fumiaki; Sakae, Toshiro

    2000-01-01

    Crystallite size and lattice distortion of human dental enamel were estimated by peak profile analysis using x-ray diffraction pattern. Firstly, noises were removed from x-ray diffraction pattern, and deconvolution of overlapping peaks and determination of baseline level were carried out. Then, the instrumental peak broadening and effect of overlapping Kα1 and Kα2 were eliminated to obtain pure peak profile using the Stokes's Fourier method. The integral width method was applied for estimation of crystallite size and 'upper-limit of distortion', assuming the peak profile as Cauchy function. The estimated crystallite size and distortion were ca. 210 A and ca. 0.4% in the a-axis direction and ca. 550 A and ca. 0.7% in the c-axis direction, respectively. The crystallite size value along the a-axis was almost the same to the previously reported values, but the value for along the c-axis was nearly half of the reported values. The crystallite size in this study means the size of coherent domain in contrast to the size of particle which may contain several domains in the case of enamel crystals. The results suggest that human enamel crystals grow in their size along the c-axis by multiplication, fusion of crystallites. It was notable that the distortion value was larger in the c-axis direction. The phenomenon may partly be due to the high carbonate ion content of enamel crystals and partly due to crystal growth mechanism. (author)

  8. Magnetic properties and potential barrier between crystallites model of MgGa2-xFexO4 ceramics

    Directory of Open Access Journals (Sweden)

    V. A. dos S. Ribeiro

    Full Text Available Abstract The aim of this work was to investigate the magnetic properties and the electrical conductivity temperature dependence associated to the potential barrier between the crystallites model. Gallium and magnesium containing spinel ceramic has low magnetic coercivity and high electrical resistivity. MgGa2-xFexO4 samples (x= 0.01, 0.05, 0.15, 0.25, 0.35 were prepared by solid-state method and sintered at 800 °C for 8 h. X-ray diffraction analysis confirmed the formation of a single phase with compact cubic spinel structure. The magnetic measurements show that the saturation magnetization and remanence of all samples increased with increasing iron concentration. The coercive field decreased up to the concentration x= 0.15, and above x= 0.25 it was observed an increase in the coercive field. Through electrical characterization it was found that the samples presented highly insulating behavior for x= 0.01, and further increase in x above 0.15 gives a semiconductor behavior compatible with the potential barrier between the crystallites model, i.e. fulfills the condition L/2 > LD (crystallite size L in comparison with the Debye length LD, and the conduction is limited by potential barriers between the crystallites.

  9. A bioactive coating with submicron-sized titania crystallites fabricated by induction heating of titanium after tensile deformations.

    Science.gov (United States)

    Li, Ning-Bo; Xu, Wen-Hua; Xiao, Gui-Yong; Zhao, Jun-Han; Lu, Yu-Peng

    2017-11-01

    Thermal oxidation technology was widely investigated as one of effective surface modification method for improving the bioactivity and biocompatibility of titanium and its alloys. In this work, the induction heat oxidization method, a fast, efficient, economical and environmental protective technology, was applied to prepare the submicron-morphological oxide coating with variable rutile TiO 2 equiaxed crystallites on the surface of pure Ti substrates after cold-drawing with 10-20% deformations. The results showed the plastic-deformed Ti cylinders recrystallized during induction heating treatment (IHT) for 10-20s which resulted in evolution of microstructures as well as slight improvement of microhardness. The surface characteristics of TiO 2 crystallites in oxidation layers were determined by the microstructural evolutions of Ti substrate in terms of the nucleation and growth of TiO 2 crystallites. Specially, the oxidized surface with 50-75nm roughness and more uniform and finer equiaxed oxide grains remarkablely improved the apatite deposition after bioactive evaluation in 1.5 × SBF for 7 days. This work provided a potential method to create controlled bioactive oxide coatings with submicro-/nano-scaled TiO 2 crystallites on titanium substrate in terms of the role of metallographic microstructure in the formation process of titanium oxides. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Measurement of the single 100 diffraction line and evaluation of the average crystallite sizes along the fiber axis for mesophase-pitch-based carbon fiber P100

    International Nuclear Information System (INIS)

    Yoshida, Akira; Kaburagi, Yutaka; Hishiyama, Yoshihiro

    2007-01-01

    Mesophase-pitch-based carbon fiber P100 is known as a well-oriented carbon fiber in which the partially graphitized crystallites align along the fiber axis. The X-ray powder diffraction pattern for P100 measured by the X-ray diffractometer reveals the 100 diffraction line as a composite peak with the 101 diffraction line. The composite peak is usually not easy to separate into the component peaks of 100 and 101 lines. In the present article, a method to measure the single 100 diffraction line with the X-ray diffractometer using fiber samples of P100 has been developed. It has been found that there exist two types of crystallites oriented to their basal planes along the fiber axis in each of the P100 fibers; the Z-type crystallite with the zigzag boundary planes and the A-type crystallite with the armchair boundary planes, both of the boundary planes are perpendicular to the fiber axis. The average crystallite sizes along the fiber axis evaluated are 53 nm for the Z-type crystallites and 800 nm for the armchair crystallites. The average crystallite thickness for both types is about 120 nm. (author)

  11. Unexpected ferromagnetic ordering enhancement with crystallite size growth observed in La0.5Ca0.5MnO3 nanoparticles

    International Nuclear Information System (INIS)

    Iniama, G.; Ita, B. I.; Presa, P. de la; Hernando, A.; Alonso, J. M.; Multigner, M.; Cortés-Gil, R.; Ruiz-González, M. L.; Gonzalez-Calbet, J. M.

    2014-01-01

    In this paper, the physical properties of half-doped manganite La 0.5 Ca 0.5 MnO 3 with crystallite sizes ranging from 15 to 40 nm are investigated. As expected, ferromagnetic order strengthens at expense of antiferromagnetic one as crystallite size is reduced to 15 nm. However, contrary to previously reported works, an enhancement of saturation magnetization is observed as crystallite size increases from 15 to 22 nm. This unexpected behavior is accompanied by an unusual cell volume variation that seems to induce ferromagnetic-like behavior at expense of antiferromagnetic one. Besides, field cooled hysteresis loops show exchange bias field and coercivity enhancement for increasing cooling fields, which suggest a kind of core-shell structure with AFM-FM coupling for crystallite sizes as small as 15 nm. It is expected that inner core orders antiferromagnetically, whereas uncompensated surface spins behave as spin glass with ferromagnetic-like ordering.

  12. Antiphase Boundaries in the Turbostratically Disordered Misfit Compound (BiSe)(1+δ)NbSe2.

    Science.gov (United States)

    Mitchson, Gavin; Falmbigl, Matthias; Ditto, Jeffrey; Johnson, David C

    2015-11-02

    (BiSe)(1+δ)NbSe2 ferecrystals were synthesized in order to determine whether structural modulation in BiSe layers, characterized by periodic antiphase boundaries and Bi-Bi bonding, occurs. Specular X-ray diffraction revealed the formation of the desired compound with a c-axis lattice parameter of 1.21 nm from precursors with a range of initial compositions and initial periodicities. In-plane X-ray diffraction scans could be indexed as hk0 reflections of the constituents, with a rectangular basal BiSe lattice and a trigonal basal NbSe2 lattice. Electron micrographs showed extensive turbostratic disorder in the samples and the presence of periodic antiphase boundaries (approximately 1.5 nm periodicity) in BiSe layers oriented with the [110] direction parallel to the zone axis of the microscope. This indicates that the structural modulation in the BiSe layers is not due to coherency strain resulting from commensurate in-plane lattices. Electrical transport measurements indicate that holes are the dominant charge carrying species, that there is a weak decrease in resistivity as temperature decreases, and that minimal charge transfer occurs from the BiSe to NbSe2 layers. This is consistent with the lack of charge transfer from the BiX to the TX2 layers reported in misfit layer compounds where antiphase boundaries were observed. This suggests that electronic considerations, i.e., localization of electrons in the Bi-Bi pairs at the antiphase boundaries, play a dominant role in stabilizing the structural modulation.

  13. A Microbeam Small-Angle X-ray Scattering Study on Enamel Crystallites in Subsurface Lesion

    Energy Technology Data Exchange (ETDEWEB)

    Yagi, N; Ohta, N; Matsuo, T [Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5198 (Japan); Tanaka, T; Terada, Y; Kamasaka, H; Kometani, T, E-mail: yagi@spring8.or.j [Ezaki Glico Co. Ltd., 4-6-5 Utajima, Nishiyodogawa-ku, Osaka 555-8502 (Japan)

    2010-10-01

    The early caries lesion in bovine tooth enamel was studied by two different X-ray diffraction systems at the SPring-8 third generation synchrotron radiation facility. Both allowed us simultaneous measurement of the small and large angle regions. The beam size was 6{mu}m at BL40XU and 50{mu}m at BL45XU. The small-angle scattering from voids in the hydroxyapatite crystallites and the wide-angle diffraction from the hydroxyapatite crystals were observed simultaneously. At BL40XU an X-ray image intensifier was used for the small-angle and a CMOS flatpanel detector for the large-angle region. At BL45XU, a large-area CCD detector was used to cover both regions. A linear microbeam scan at BL40XU showed a detailed distribution of voids and crystals and made it possible to examine the structural details in the lesion. The two-dimensional scan at BL45XU showed distribution of voids and crystals in a wider region in the enamel. The simultaneous small- and wide-angle measurement with a microbeam is a powerful tool to elucidate the mechanisms of demineralization and remineralization in the early caries lesion.

  14. A Microbeam Small-Angle X-ray Scattering Study on Enamel Crystallites in Subsurface Lesion

    International Nuclear Information System (INIS)

    Yagi, N; Ohta, N; Matsuo, T; Tanaka, T; Terada, Y; Kamasaka, H; Kometani, T

    2010-01-01

    The early caries lesion in bovine tooth enamel was studied by two different X-ray diffraction systems at the SPring-8 third generation synchrotron radiation facility. Both allowed us simultaneous measurement of the small and large angle regions. The beam size was 6μm at BL40XU and 50μm at BL45XU. The small-angle scattering from voids in the hydroxyapatite crystallites and the wide-angle diffraction from the hydroxyapatite crystals were observed simultaneously. At BL40XU an X-ray image intensifier was used for the small-angle and a CMOS flatpanel detector for the large-angle region. At BL45XU, a large-area CCD detector was used to cover both regions. A linear microbeam scan at BL40XU showed a detailed distribution of voids and crystals and made it possible to examine the structural details in the lesion. The two-dimensional scan at BL45XU showed distribution of voids and crystals in a wider region in the enamel. The simultaneous small- and wide-angle measurement with a microbeam is a powerful tool to elucidate the mechanisms of demineralization and remineralization in the early caries lesion.

  15. Unexpected ferromagnetic ordering enhancement with crystallite size growth observed in La{sub 0.5}Ca{sub 0.5}MnO₃ nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Iniama, G.; Ita, B. I. [Department of Pure and Applied Chemistry, University of Calabar, Calabar (Nigeria); Presa, P. de la, E-mail: pmpresa@ucm.es; Hernando, A. [Instituto de Magnetismo Aplicado, UCM-ADIF-CSIC, 28230 Las Rozas (Spain); Fac. CC Físicas, Dpto. Física de Materiales, Univ. Complutense de Madrid, 28040 Madrid (Spain); Alonso, J. M. [Instituto de Magnetismo Aplicado, UCM-ADIF-CSIC, 28230 Las Rozas (Spain); Instituto de Ciencia de Materiales, CSIC, 28049-Madrid (Spain); Multigner, M. [Instituto de Magnetismo Aplicado, UCM-ADIF-CSIC, 28230 Las Rozas (Spain); Cortés-Gil, R.; Ruiz-González, M. L. [Fac. CC Químicas, Dpto. Química Inorgánica, Univ. Complutense de Madrid, 28040 Madrid (Spain); Gonzalez-Calbet, J. M. [Instituto de Magnetismo Aplicado, UCM-ADIF-CSIC, 28230 Las Rozas (Spain); Fac. CC Químicas, Dpto. Química Inorgánica, Univ. Complutense de Madrid, 28040 Madrid (Spain)

    2014-09-21

    In this paper, the physical properties of half-doped manganite La{sub 0.5}Ca{sub 0.5}MnO₃ with crystallite sizes ranging from 15 to 40 nm are investigated. As expected, ferromagnetic order strengthens at expense of antiferromagnetic one as crystallite size is reduced to 15 nm. However, contrary to previously reported works, an enhancement of saturation magnetization is observed as crystallite size increases from 15 to 22 nm. This unexpected behavior is accompanied by an unusual cell volume variation that seems to induce ferromagnetic-like behavior at expense of antiferromagnetic one. Besides, field cooled hysteresis loops show exchange bias field and coercivity enhancement for increasing cooling fields, which suggest a kind of core-shell structure with AFM-FM coupling for crystallite sizes as small as 15 nm. It is expected that inner core orders antiferromagnetically, whereas uncompensated surface spins behave as spin glass with ferromagnetic-like ordering.

  16. Nanostructured titanium dioxide: a control of crystallite size and content of polymorphic phases

    International Nuclear Information System (INIS)

    Boery, Mirella N. de O.; Ono, Eduardo; Manfrim, Tarcio P.; Santos, Juliana S.; Suzuki, Carlos K.

    2010-01-01

    TiO 2 (titanium dioxide) powders and nanoparticles have been largely used in toners and cosmetics. Nowadays, they are mainly focused in photocatalysis, antibacterial coatings, dye-sensitized solar cells, etc. The efficiency is related to photocatalytic properties of TiO 2 nanoparticles, such as crystallite size and phase (anatasio/rutile). In this research, flame aerosol method was used to synthesize TiO 2 nanoparticles by hydrolysis and oxidation of TiCl 4 (titanium tetrachloride). The oxy-hydrogen flame was provided by a five concentric nozzle silica burner. X-ray diffraction was used to identify each TiO 2 nanoparticles phase and scanning electron microscopy was used to observe the size and morphology of nanoparticles. Pure anatase was obtained with H 2 /O 2 ratio ≤ 1.0, and up to 52 wt% of rutile was obtained with H 2 /O 2 ratio > 2.0. Anatase crystal grain size varied from 25 to 38 nm, estimated by Scherrer formula.(author)

  17. Liesegang bands versus random crystallites in Ag2Cr2O7 - Single and mixed gelled media

    Science.gov (United States)

    Ibrahim, Huria; El-Rassy, Houssam; Sultan, Rabih

    2018-02-01

    Liesegang patterns of silver dichromate (Ag2Cr2O7) are studied in two different gel media: agar and gelatin, based on the work of Lagzi and Ueyama (2009). Whereas in gelatin, standard Liesegang bands are obtained as a result of the interdiffusion of Ag+ and Cr2 O72-, random crystallites with dendritic ramifications are observed in agar. We revisit this phenomenon and demonstrate the proposed mechanism, wherein dense heterogeneous nucleation in gelatin leads to Liesegang bands, as opposed to surface nucleation in agar yielding crystallites. We use viscosity, pH measurements, and notably scanning electron microscopy (SEM) in this endeavor.

  18. Determination of the crystallite orientation distribution from direct pole figures

    International Nuclear Information System (INIS)

    Araujo Gomes, P.A.M. de.

    1977-01-01

    A method is described which allows to calculate the crystallite orientation distribution in polycrystalline material, from direct pole figures data of its crystallographic planes (Roe's Method). The programme was applied to (1010), (0002), (1011) and (1120) complete pole figures data for a commercial, thin sheet Zircaloy-4 tubing specimen. A semi-automatic Rigaku-Denki texture goniometer, which scans the reciprocal lattice sphere pointwise outputting the data in a punched tape, was used to obtain the pole figures. This is consistent with the results obtained through direct conclusion from the pole figures. (author)

  19. Peculiar Li-storage mechanism at graphene edges in turbostratic carbon black and their application in high energy Li-ion capacitor

    Science.gov (United States)

    Anothumakkool, Bihag; Dupré, Nicolas; Moreau, Philippe; Guyomard, Dominique; Brousse, Thierry; Gaubicher, Joel

    2018-02-01

    We report experimental evidence for the specific Li-storage at turbostratic graphene edges of a well-known and cheap Super P® carbon black (Csp) material, which is usually used as a conductive additive in composite electrodes. Indeed, operando XRD and HR-TEM consistently demonstrate Li insertion occurs with zero expansion of graphene layer up to a composition of Li0.4C6 (150 mA h/g) that is reached at 0.01 V vs. Li+/Li. 7Li NMR substantiates these results and suggests that the weak electronic transfer from the carbon host to the intercalant could help local reorganization of the layer order as suggested by the unexpected reversible changes of the (002) Bragg peak intensity during the charge-discharge process. Our observations also indicate this insertion mechanism is kinetically favored resulting in remarkable cycling stability over 1000 cycles and power capability allowing to sustain 110 mA h/g at 8 A/g (21 C) in half cell. The capability of Csp as an efficient anode is ultimately demonstrated in a lithium hybrid capacitor against a positive electrode of activated carbon. The full cell delivers a maximum energy of 120 Wh/kg (4.3-2 V) and remarkable capacity retention over 1800 cycles.

  20. Controlling morphology and crystallite size of Cu(In0.7Ga0.3)Se2 nano-crystals synthesized using a heating-up method

    International Nuclear Information System (INIS)

    Hsu, Wei-Hsiang; Hsiang, Hsing-I; Chia, Chih-Ta; Yen, Fu-Su

    2013-01-01

    CuIn 0.7 Ga 0.3 Se 2 (CIGS) nano-crystals were successfully synthesized via a heating-up process. The non-coordinating solvent (1-octadecene) and selenium/cations ratio effects on the crystalline phase and crystallite size of CIGS nano-crystallites were investigated. It was observed that the CIGS nano-crystallite morphology changed from sheet into spherical shape as the amount of 1-octadecene addition was increased. CIGS nano-crystals were obtained in 9–20 nm sizes as the selenium/cations ratio increased. These results suggest that the monomer reactivity in the solution can be adjusted by changing the solvent type and selenium/cations ratio, hence affecting the crystallite size and distribution. - Graphical abstract: CuIn 0.7 Ga 0.3 Se 2 (CIGS) nano-crystals were successfully synthesized via a heating-up process in this study. The super-saturation in the solution can be adjusted by changing the OLA/ODE ratio and selenium/cation ratio.

  1. Dislocation, crystallite size distribution and lattice strain of magnesium oxide nanoparticles

    Science.gov (United States)

    Sutapa, I. W.; Wahid Wahab, Abdul; Taba, P.; Nafie, N. L.

    2018-03-01

    The oxide of magnesium nanoparticles synthesized using sol-gel method and analysis of the structural properties was conducted. The functional groups of nanoparticles has been analysed by Fourier Transform Infrared Spectroscopy (FT-IR). Dislocations, average size of crystal, strain, stress, the energy density of crystal, crystallite size distribution and morphologies of the crystals were determined based on X-ray diffraction profile analysis. The morphological of the crystal was analysed based on the image resulted from SEM analysis. The crystallite size distribution was calculated with the contention that the particle size has a normal logarithmic form. The most orientations of crystal were determined based on the textural crystal from diffraction data of X-ray diffraction profile analysis. FT-IR results showed the stretching vibration mode of the Mg-O-Mg in the range of 400.11-525 cm-1 as a broad band. The average size crystal of nanoparticles resulted is 9.21 mm with dislocation value of crystal is 0.012 nm-2. The strains, stress, the energy density of crystal are 1.5 x 10-4 37.31 MPa; 0.72 MPa respectively. The highest texture coefficient value of the crystal is 0.98. This result is supported by morphological analysis using SEM which shows most of the regular cubic-shaped crystals. The synthesis method is suitable for simple and cost-effective synthesis model of MgO nanoparticles.

  2. Application of back-propagation artificial neural network (ANN) to predict crystallite size and band gap energy of ZnO quantum dots

    Science.gov (United States)

    Pelicano, Christian Mark; Rapadas, Nick; Cagatan, Gerard; Magdaluyo, Eduardo

    2017-12-01

    Herein, the crystallite size and band gap energy of zinc oxide (ZnO) quantum dots were predicted using artificial neural network (ANN). Three input factors including reagent ratio, growth time, and growth temperature were examined with respect to crystallite size and band gap energy as response factors. The generated results from neural network model were then compared with the experimental results. Experimental crystallite size and band gap energy of ZnO quantum dots were measured from TEM images and absorbance spectra, respectively. The Levenberg-Marquardt (LM) algorithm was used as the learning algorithm for the ANN model. The performance of the ANN model was then assessed through mean square error (MSE) and regression values. Based on the results, the ANN modelling results are in good agreement with the experimental data.

  3. Influence of crystallite size on the magnetic properties of Fe{sub 3}O{sub 4} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Upadhyay, Sneha [Dept of Applied Science, Symbiosis Institute of Technology, SIU, Lavale, Mulshi, Pune 412 115 (India); Parekh, Kinnari [K C Patel R & D Center, Charotar University of Science & Technology, Changa 388421 (India); Pandey, Brajesh, E-mail: bpandey@gmail.com [Dept of Applied Science, Symbiosis Institute of Technology, SIU, Lavale, Mulshi, Pune 412 115 (India)

    2016-09-05

    Structural and magnetic properties of chemically synthesized magnetite nanoparticles have been studied using X-ray diffraction, Transmission Electron Microscopy and Vibrating Sample Magnetometer. Magnetically the synthesized nanoparticles are ranging from superparamagnetic to multi domain state. Average crystallite size of the synthesized magnetite nanoparticles were determined using X-ray line broadening and are found to be in the range of 9–53 nm. On the other hand, the TEM images show that the size is ranging between 7.9 and 200 nm with the transition from spherical superparamagnetic particles to faceted cubic multi domain particles. Magnetic parameters of the samples show a strong dependence on average crystallite size. The ratio of coercive field at 20 K to that at 300 K (H{sub c} (20 K)/H{sub c} (300 K)) increased sharply with decrease in crystallite size. A critical crystallite diameter of order 36 nm may be inferred as boundary between single domain to multi domain transition. Zero-field-cooled (ZFC) and field-cooled (FC) measurements at 10 Oe field validate the same for smallest and largest size samples, confirming that the anisotropy energy is greater than thermal energy upto 300 K temperature. For 9 nm sample broad ZFC curve with overlapping of FC curve is observed just at 300 K, indicating the effect of strong dipolar field in superparamagnetic system. - Graphical abstract: We present our study on magnetite nanoparticles. We observed that the synthesized nanoparticles behave like single domain particles in the range of 14 nm–36 nm. They show superparamagnetic properties if particles are smaller than 14 nm and multi-domain properties when the particles are bigger than 36 nm. - Highlights: • Magnetite nanoparticles have been synthesized using chemical precipitation method. • Smaller magnetite particles below 14 nm in size are in super-paramagnetic state. • Bigger particles show multi-domain character. • Magnetite in the size range 14–36 is

  4. Magnetic properties and potential barrier between crystallites model of MgGa{sub 2-x}Fe{sub x}O{sub 4} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Ribeiro, V.A. dos S.; Rubinger, R.M.; Oliveira, A.F.; Mendonca, C.S.P.; Silva, M.R. da, E-mail: vanderalkmin@gmail.com, E-mail: rero@unifei.edu.br, E-mail: adhimarflavio@unifei.edu.br, E-mail: sales.claudiney21@gmail.com, E-mail: mrsilva@unifei.edu.br [Universidade Federal de Itajuba (UNIFEI), MG (Brazil). Instituto de Fisica e Quimica

    2016-10-15

    The aim of this work was to investigate the magnetic properties and the electrical conductivity temperature dependence associated to the potential barrier between the crystallites model. Gallium and magnesium containing spinel ceramic has low magnetic coercivity and high electrical resistivity. MgGa{sub 2-x}Fe{sub x}O{sub 4} samples (x= 0.01, 0.05, 0.15, 0.25, 0.35) were prepared by solid-state method and sintered at 800 °C for 8 h. X-ray diffraction analysis confirmed the formation of a single phase with compact cubic spinel structure. The magnetic measurements show that the saturation magnetization and remanence of all samples increased with increasing iron concentration. The coercive field decreased up to the concentration x= 0.15, and above x= 0.25 it was observed an increase in the coercive field. Through electrical characterization it was found that the samples presented highly insulating behavior for x= 0.01, and further increase in x above 0.15 gives a semiconductor behavior compatible with the potential barrier between the crystallites model, i.e. fulfills the condition L/2 > L{sub D} (crystallite size L in comparison with the Debye length L{sub D}), and the conduction is limited by potential barriers between the crystallites. (author)

  5. Cauliflower hillock formation through crystallite migration of SnO2 thin films prepared on alumina substrates by using MOCVD

    International Nuclear Information System (INIS)

    Choi, Gwangpyo; Ryu, Hyunwook; Lee, Woosun; Hong, Kwangjun; Shin, Dongcharn; Park, Jinseong; Seo, Yongjin; Akbar, Sheikh A.

    2003-01-01

    Tin-oxide thin films were deposited at 375 .deg. C on α-alumina substrates by using metalorganic chemical vapor deposition (MOCVD) process. A number of hillocks were formed on the film after annealing in air at 500 .deg. C for 30 min, but fewer hillocks were formed for annealing in N 2 . The hillocks on the film and the grains on the alumina substrate were composed of crystallites. The oxygen content and the binding energy after annealing in air came to close to values for the stoichiometric SnO 2 . There was no relationship between the film thickness and the binding energy shift, but the binding energy did change with the annealing atmosphere and the oxygen content. The cauliflower hillocks on the film seem to be formed by the continuous migration of crystallites from cauliflower grains on the substrate to release the stress due to the increased oxygen content and volume. A cauliflower hillock can be grown by continuous migration of crystallites from nearby grains to the hillock.

  6. Quantitative analysis of lattice disorder and crystallite size in organic semiconductor thin films

    KAUST Repository

    Rivnay, Jonathan

    2011-07-07

    The crystallite size and cumulative lattice disorder of three prototypical, high-performing organic semiconducting materials are investigated using a Fourier-transform peak shape analysis routine based on the method of Warren and Averbach (WA). A thorough incorporation of error propagation throughout the multistep analysis and a weighted fitting of Fourier-transformed data to the WA model allows for more accurate results than typically obtained and for determination of confidence bounds. We compare results obtained when assuming two types of column-length distributions, and discuss the benefits of each model in terms of simplicity and accuracy. For strongly disordered materials, the determination of a crystallite size is greatly hindered because disorder dominates the coherence length, not finite size. A simple analysis based on trends of peak widths and Lorentzian components of pseudo-Voigt line shapes as a function of diffraction order is also discussed as an approach to more easily and qualitatively assess the amount and type of disorder present in a sample. While applied directly to organic systems, this methodology is general for the accurate deconvolution of crystalline size and lattice disorder for any material investigated with diffraction techniques. © 2011 American Physical Society.

  7. Effect of sample moisture content on XRD-estimated cellulose crystallinity index and crystallite size

    Science.gov (United States)

    Umesh P. Agarwal; Sally A. Ralph; Carlos Baez; Richard S. Reiner; Steve P. Verrill

    2017-01-01

    Although X-ray diffraction (XRD) has been the most widely used technique to investigate crystallinity index (CrI) and crystallite size (L200) of cellulose materials, there are not many studies that have taken into account the role of sample moisture on these measurements. The present investigation focuses on a variety of celluloses and cellulose...

  8. High-performance porous polylactide stereocomplex crystallite scaffolds prepared by solution blending and salt leaching.

    Science.gov (United States)

    Xie, Yan; Lan, Xiao-Rong; Bao, Rui-Ying; Lei, Yang; Cao, Zhi-Qiang; Yang, Ming-Bo; Yang, Wei; Wang, Yun-Bing

    2018-09-01

    Biodegradable stereocomplex crystallite polylactide (SC-PLA) porous scaffolds with well-defined pore structures, high heat resistance, mechanical strength, and solvent resistance together with good biocompatibility, were obtained through solution casting of mixed poly(l-lactide) and poly(d-lactide) solution and subsequent leaching of sodium chloride particles. The pore structure of the SC-PLA scaffolds can be perfectly maintained after a high-pressure sterilization treatment at 121 °C, owing to the extensive formation of stereocomplex crystallites in the scaffolds. In vivo pilot study demonstrates that the fibroblasts of rats can infiltrate into the SC-PLA scaffolds well through the open pores. Degradation tests in phosphate-buffered saline solution reveal that the structure of SC-PLA scaffolds was quite stable due to the enhanced hydrolysis-resistance and improved mechanical properties of the scaffolds. These results reveal that SC-PLA scaffolds with good biocompatibility are potentially to be used as implanted biomaterials for the regeneration and restoration of tissues or organs. Copyright © 2018 Elsevier B.V. All rights reserved.

  9. [Components of urinary crystallites in urine of uric acid stone formers and its relationship with formation of stones].

    Science.gov (United States)

    Huang, Zhi-jie; Tan, Jin; Ouyang, Jian-ming

    2010-09-01

    The components, zeta potential, morphology of nanocrystallites in urines of 10 uric acid stone formers as well as their relationship with the formation of uric acid stones were comparatively studied using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, nanoparticle size analyzer, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The urine pH of uric acid stone formers was relatively low within the range of 4.8 to 5.7. The main constituent of urinary crystallites was uric acid. Their particle size distribution was highly uneven, ranging from several nanometers to several tens of micrometers, and obvious aggregation was observed. The zeta potential of urinary crystallites in ten lithogenic patients was -6.02 mV, which was higher than that in ten normal subjects (-10.1 mV). After drug therapies (potassium citrate was taken), the urine pH value of the uric acid stone formers increased to 6.5 or so, and at this pH value most of the uric acid had changed to urate. Since the solubility of urate increased greatly than uric acid, the risk of the formation of uric acid stone reduced. The results in this paper showed that there was a close relationship among stone components, urinary crystallites composition and urine pH.

  10. Analysis of crystallite size and microdeformation crystal lattice the tungsten carbide milling in mill high energy

    International Nuclear Information System (INIS)

    Silva, F.T. da; Nunes, M.A.M.; Souza, C.P. de; Gomes, U.U.

    2010-01-01

    The tungsten carbide (WC) has wide application due to its properties like high melting point, high hardness, wear resistance, oxidation resistance and good electrical conductivity. The microstructural characteristics of the starting powders influences the final properties of the carbide. In this context, the use of nanoparticle powders is an efficient way to improve the final properties of the WC. The high energy milling stands out from other processes to obtain nanometric powders due to constant microstructural changes caused by this process. Therefore, the objective is to undertake an analysis of microstructural characteristics on the crystallite size and microdeformations of the crystal lattice using the technique of X-ray diffraction (XRD) using the Rietveld refinement. The results show an efficiency of the milling process to reduce the crystallite size, leading to a significant deformation in the crystal lattice of WC from 5h milling. (author)

  11. Controlling morphology and crystallite size of Cu(In{sub 0.7}Ga{sub 0.3})Se{sub 2} nano-crystals synthesized using a heating-up method

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, Wei-Hsiang [Department of Resources Engineering, Particulate Materials Research Center, National Cheng Kung University, Tainan, 70101 Taiwan (China); Hsiang, Hsing-I, E-mail: hsingi@mail.ncku.edu.tw [Department of Resources Engineering, Particulate Materials Research Center, National Cheng Kung University, Tainan, 70101 Taiwan (China); Chia, Chih-Ta [Department of Physics, National Taiwan Normal University, Taipei, 116 Taiwan (China); Yen, Fu-Su [Department of Resources Engineering, Particulate Materials Research Center, National Cheng Kung University, Tainan, 70101 Taiwan (China)

    2013-12-15

    CuIn{sub 0.7}Ga{sub 0.3}Se{sub 2}(CIGS) nano-crystals were successfully synthesized via a heating-up process. The non-coordinating solvent (1-octadecene) and selenium/cations ratio effects on the crystalline phase and crystallite size of CIGS nano-crystallites were investigated. It was observed that the CIGS nano-crystallite morphology changed from sheet into spherical shape as the amount of 1-octadecene addition was increased. CIGS nano-crystals were obtained in 9–20 nm sizes as the selenium/cations ratio increased. These results suggest that the monomer reactivity in the solution can be adjusted by changing the solvent type and selenium/cations ratio, hence affecting the crystallite size and distribution. - Graphical abstract: CuIn{sub 0.7}Ga{sub 0.3}Se{sub 2}(CIGS) nano-crystals were successfully synthesized via a heating-up process in this study. The super-saturation in the solution can be adjusted by changing the OLA/ODE ratio and selenium/cation ratio.

  12. Theoretical investigation of active sites at the corners of Mgcl 2 crystallites in supported ziegler-natta catalysts

    KAUST Repository

    Correa, Andrea; Credendino, Raffaele; Pater, Jochem T M; Morini, Giampiero; Cavallo, Luigi

    2012-01-01

    We present a theoretical study on possible models of catalytic active species corresponding to Ti-chloride species adsorbed at the corners of MgCl 2 crystallites. First we focused our efforts on the interaction between prototypes of three

  13. Photostimulated luminescence from a fluorobromozirconate glass-ceramic and the effect of crystallite size and phase

    CERN Document Server

    Secu, M; Spaeth, J M; Edgar, A; Williams, G V M; Rieser, U

    2003-01-01

    We report a systematic study of the photoluminescence (PL), photostimulated luminescence (PSL) and thermostimulated luminescence (TSL) from europium-and bromine-doped fluorozirconate glass-ceramics. Eu sup 2 sup + ions in the as-prepared glass show no PL, but after suitable thermal annealing hexagonal phase and orthorhombic phase barium bromide crystallites are precipitated and PL is observed from Eu sup 2 sup + ions in these crystallites. Room temperature PSL is observed from the orthorhombic phase, with an efficiency which is up to 9% of the well known crystalline storage phosphor BaFBr:Eu sup 2 sup +. The emission is at 404 nm, and there is a maximum in the stimulation at 580 nm. We associate the PSL with an optically quenchable peak in the glow curve, which has an activation energy of 1.20 eV and attribute this feature to a perturbed F centre. Room temperature PSL from glass-ceramics containing predominantly the hexagonal phase of BaBr sub 2 has a relative efficiency of less than 0.07%. The resultant trap...

  14. Study of the arrangement of crystallites in γ-irradiated human enamel by electron paramagnetic resonance

    International Nuclear Information System (INIS)

    Cevc, P.; Schara, M.; Ravnik, C.; Skaleric, U.

    1976-01-01

    The arrangement of tooth enamel microcrystals has been studied on CO 3 3- bound electrons by paramagnetic resonance. It was found that noncarious human maxillary central incisors have a greater degree of alignment of tooth enamel microcrystals than the carious ones. The outermost surface layer of enamel showed a greater crystallite degree of alignment than other parts

  15. Direct observation of nanometer-scale amorphous layers and oxide crystallites at grain boundaries in polycrystalline Sr1−xKxFe2As2 superconductors

    KAUST Repository

    Wang, Lei

    2011-06-01

    We report here an atomic resolution study of the structure and composition of the grain boundaries in polycrystallineSr0.6K0.4Fe2As2superconductor. A large fraction of grain boundaries contain amorphous layers larger than the coherence length, while some others contain nanometer-scale crystallites sandwiched in between amorphous layers. We also find that there is significant oxygen enrichment at the grain boundaries. Such results explain the relatively low transport critical current density (Jc) of polycrystalline samples with respect to that of bicrystal films.

  16. Optical properties of La2CuO4 and La2−xCaxCuO4 crystallites in UV–vis–NIR region synthesized by sol–gel process

    International Nuclear Information System (INIS)

    Li Yifeng; Huang Jianfeng; Cao Liyun; Wu Jianpeng; Fei Jie

    2012-01-01

    La 2 CuO 4 and La 2−x Ca x CuO 4 crystallites were prepared via a simple sol–gel process. The as-prepared La 2 CuO 4 and La 2 −x Ca x CuO 4 crystallites were characterized by X-ray diffraction, transmission electron microscope and UV–vis–NIR spectra. Results show that the grain size of La 2 CuO 4 crystallites increases with the increase of heat treatment temperature from 600 °C to 800 °C. Optical properties show that La 2 CuO 4 crystallites have broad absorption both in the UV–vis region and in the NIR region. The band gap of the as-prepared crystallites decreases from 1.367 eV to 1.284 eV with the increase of calcination temperature from 600 °C to 800 °C. In the series of La 2−x Ca x CuO 4 compounds (x = 0.05, 0.08, 0.10, 0.12, 0.15 and 0.20), all of the samples exhibit an orthogonal crystal structure and the solubility limit of Ca 2+ in La 2 CuO 4 is within the range of x = 0.12–0.15. In the whole UV–vis–NIR region, La 2−x Ca x CuO 4 crystallites exhibit a broad absorption and the corresponding band gap first increases and then decreases with increasing of Ca 2+ content. - Highlights: ► The optical band gap can be tuned by adjusting the grain size and Ca 2+ content. ► La 2 CuO 4 crystallites exhibit a broad absorption band both in the UV–vis region and in the NIR region. ► The band gap increases from 1.284 eV to 1.319 eV with the decrease of heat treatment temperature. ► In the whole UV–vis–NIR region, the La 2−x Ca x CuO 4 crystallites displayed a broad absorption. ► The band gap of La 2−x Ca x CuO 4 increases linearly with doping level when 0 ≤ x ≤ 0.12.

  17. Theoretical investigation of active sites at the corners of Mgcl 2 crystallites in supported ziegler-natta catalysts

    KAUST Repository

    Correa, Andrea

    2012-05-08

    We present a theoretical study on possible models of catalytic active species corresponding to Ti-chloride species adsorbed at the corners of MgCl 2 crystallites. First we focused our efforts on the interaction between prototypes of three industrially relevant Lewis bases used as internal donors (1,3-diethers, alkoxysilanes and succinates) and MgCl 2 units at the corner of a MgCl 2 crystallite. Our calculations show that the energetic cost to extract MgCl 2 units at the corner of (104) edged MgCl 2 crystallites is not prohibitive, and that Lewis bases added during catalyst preparation make this process easier. After removal of one MgCl 2 unit, a short (110) stretch joining the (104) edges is formed. Adsorption of TiCl 4 on the generated vacancy originates a Ti-active species. In the second part of this manuscript, we report on the stereo- and regioselective behavior of this model of active species in the absence as well as in the presence of the three Lewis bases indicated above. Surface reconstruction due to the additional adsorption of an extra MgCl 2 layer is also considered. We show that, according to experimental data, Lewis bases coordinated in the proximity of the active Ti center confer a remarkable stereoselectivity. Moreover, surface reconstruction as well as donor coordination would improve regioselectivity by disfavoring secondary propene insertion. While still models of possible active species, our results indicate that defects, corners and surface reconstruction should be considered as possible anchoring sites for the catalytically active Ti-species. © 2012 American Chemical Society.

  18. Analysis of PL spectrum shape of Si-based materials as a tool for determination of Si crystallites' distribution

    Energy Technology Data Exchange (ETDEWEB)

    Khomenkova, L., E-mail: khomen@isp.kiev.ua

    2014-11-15

    This paper represents the analysis of the shape of photoluminescence spectra of Si-based nano-materials vs. energy of excitation light and temperature of measurements as a tool for the estimation of Si nanocrystallites' distribution. The samples fabricated by electrochemical etching (allowed different termination of Si nanocrystallites to be obtained) were used as modeling material. Bright emission at room temperature was observed for oxygen-terminated Si nanocrytallites, whereas hydrogen-terminated samples emit at low temperatures only. For most samples the photoluminescence spectrum was found to be complex, demonstrating competitive emission from Si crystallites and oxide defects. In latter case to separate the contribution of each recombination channel and to obtain information about crystallite distribution, low-temperature measurements of photoluminescence spectra under different excitation light energy were performed.

  19. Quality of Graphite Target for Biological/Biomedical/Environmental Applications of 14C-Accelerator Mass Spectrometry

    Science.gov (United States)

    2010-01-01

    Catalytic graphitization for 14C-accelerator mass spectrometry (14C-AMS) produced various forms of elemental carbon. Our high-throughput Zn reduction method (C/Fe = 1:5, 500 °C, 3 h) produced the AMS target of graphite-coated iron powder (GCIP), a mix of nongraphitic carbon and Fe3C. Crystallinity of the AMS targets of GCIP (nongraphitic carbon) was increased to turbostratic carbon by raising the C/Fe ratio from 1:5 to 1:1 and the graphitization temperature from 500 to 585 °C. The AMS target of GCIP containing turbostratic carbon had a large isotopic fractionation and a low AMS ion current. The AMS target of GCIP containing turbostratic carbon also yielded less accurate/precise 14C-AMS measurements because of the lower graphitization yield and lower thermal conductivity that were caused by the higher C/Fe ratio of 1:1. On the other hand, the AMS target of GCIP containing nongraphitic carbon had higher graphitization yield and better thermal conductivity over the AMS target of GCIP containing turbostratic carbon due to optimal surface area provided by the iron powder. Finally, graphitization yield and thermal conductivity were stronger determinants (over graphite crystallinity) for accurate/precise/high-throughput biological, biomedical, and environmental14C-AMS applications such as absorption, distribution, metabolism, elimination (ADME), and physiologically based pharmacokinetics (PBPK) of nutrients, drugs, phytochemicals, and environmental chemicals. PMID:20163100

  20. Coulomb crystallites from harmonically confined charged bosons in two dimensions

    International Nuclear Information System (INIS)

    Mese, A I; Okan, S E; Capuzzi, P; Akdeniz, Z; Tosi, M P

    2008-01-01

    We exploit rotational-symmetry breaking in the one-body density to examine the formation of structures in systems of N strongly coupled charged bosons with logarithmic repulsions inside isotropic two-dimensional harmonic traps, with N in the range from 2 to 7. The results serve as a map for ordered arrangements of vortices in a trapped Bose-Einstein condensate. Two types of N-body wavefunctions are assumed: (i) a permanent |ψ WM > of N identical Gaussian orbitals centred at variationally determined sites, and (ii) a permanent |ψ SM > of N orthogonal orbitals built from harmonic-oscillator energy eigenstates. With increasing coupling strength, the bosons in the |ψ WM > orbitals localize into polygonal-ringlike crystalline patterns ('Wigner molecules'), whereas the wavefunctions |ψ SM / describe low energy excited states containing delocalized bosons as in supersolid crystallites ('supermolecules'). For N = 2 at strong coupling both states describe a Wigner dimer

  1. X-ray measurements of elastic deformation of individual crystallites in polycrystalline Al-Cu alloys

    International Nuclear Information System (INIS)

    Kato, Hiroshi; Urashima, Ken-ichi; Miyawaki, Noburo; Yoshikawa, Keiji

    1982-01-01

    Equations and angular limits for X-ray stress measurements of individual crystallites in polycrystalline aggregates are obtained, and the stresses in grains of Al-4 -- 5 mass% Cu alloys containing large grains are measured under tension to compare the analytical results. Stresses in grains are not affected by the aging treatment, but diffraction spots are blurred out by the eigen strain occurred during the aging. Deviation angles theta 1 of the principal stress from the tensile direction have a linear relation to the shear factor F sub(S), which consists of the direction cosines of axes of the specimen with respect to axes of the crystallographic grain, and the proportional constant α is about 10 0 . The principal stress σ 1 is not affected by the factor F sub(S). Stress distributions are numerically analized for rectangular grains to clarify quantitatively the relations obtained experimentally. Numerical results also show the linear relation between the angle theta 1 and the factor F sub(S). The proportional constant α increases from zero to a constant αinfinity with the ratio R of the width to the length of the grain. The principal stress σ 1 is not affected by the shear factor F sub(S), but varies with the ratio R. (author)

  2. Development of a routine method for the determination of mean crystallite dimensions in nuclear materials by X-ray diffraction line broadening. An application example using U/sub 3/O/sub 8/ microspheres

    Energy Technology Data Exchange (ETDEWEB)

    Imakuma, K; Sato, I M; Cretella Neto, J; Costa, M I

    1975-03-01

    A method for mean crystallite size determination by X-ray diffraction line broadening was established. Both step-scanning and methods were extensivly tested and the precision of the data obtained as a function of the crystallite size is discussed. Emphasis is given to our contribution in order to eliminate instrumental effects as well as K sub(..cap alpha../sub 1/)/Ksub(..cap alpha../sub 2/) doublet effect upon line broadening. Instrumental correction was performed with a monocrystalline Si sample having mean crystallite size well above 13,000 A improving the accuracy of experimental data. Ksub(..cap alpha../sub 2/) and Ksub(..cap alpha../sub 2/) peaks determined instead of taking it for granted as 5. The mean crystallite dimension of U/sub 3/O/sub 8/ was calculated and the results show the dependence of this parameter on the quality of the microspheres.

  3. Preferential Alignment of Hydroxyapatite Crystallites in Nanocomposites with Chemically Disintegrated Silk Fibroin

    International Nuclear Information System (INIS)

    Nemoto, Rei; Wang Li; Ikoma, Toshiyuki; Tanaka, Junzo; Senna, Mamoru

    2004-01-01

    Hydroxyapatite (HAp) nanocrystals were prepared at room temperature by a coprecipitation method from Ca(OH) 2 and H 3 PO 4 , in the presence of chemically disintegrated silk fibroin (SF). Adsorbed amounts of cations on SF and crystallinity of HAp in the composite were increased by the chemical disintegration of SF higher order structure. Preferential alignment of c-axis of HAp crystallites along the longitudinal direction of ca. 150nm SF fibril was observed. These changes due to disintegration of SF were discussed in terms of the chemical interaction between HAp and SF. The resulted composite with preferential alignment of HAp nanocrystals is a good candidate as a starting material for bone substitutes

  4. Effect of calcination temperature on the crystallite growth of cerium oxide nano-powders prepared by the co-precipitation process

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jian-Chih [Department of Orthopaedics, Kaohsiung Medical University Hospital, Kaohsiung 807, Taiwan (China); Chen, Wen-Cheng [School of Dentistry, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan (China); Tien, Yin-Chun [Department of Orthopaedics, Kaohsiung Medical University Hospital, Kaohsiung 807, Taiwan (China); Shih, Chi-Jen, E-mail: cjshih@kmu.edu.t [Department of Fragrance and Cosmetics Science, Kaohsiung Medical University, 100 Shi-Chuan1st Road, Kaohsiung 80708, Taiwan (China)

    2010-04-30

    Cerium oxide nanocrystallites were synthesized by a co-precipitation process at a relatively low temperature, using cerium (III) nitrate as the starting material in a water solution with pH in the range of 8-9. The effect of calcination temperature on the crystallite growth of cerium oxide nano-powders was investigated by X-ray diffraction, transmission electron microscopy and electron diffraction. The crystallization temperature of the cerium oxide powders was estimated to be about 273 K, by XRD analysis. When calcined at temperatures from 473 to 1273 K, face-centered cubic phase crystallization was observed by XRD. The crystallite size of the cerium oxide increased from 12.0 to 48 nm as the calcining temperature increased from 473 to 1273 K, in the pH range 8-9. The activation energy for the growth of cerium oxide nanoparticles was found to have very low values of 17.5 kJ/mol for pH = 8 and 16.0 kJ/mol for pH = 9.

  5. Crystallite-conjugation regions in polycrystalline transition and noble metals. 1. Composition and properties of point defects in the cores of crystallite-conjugation regions in polycrystalline Cr, Ta and W

    International Nuclear Information System (INIS)

    Klotsman, S.M.; Kajgorodov, V.N.; Ermakov, A.V.; Rudenko, V.K.

    2004-01-01

    With the use of available results of theoretical investigations on structure and properties of crystallite conjugation regions (CCR) the types and relaxation volumes of point defects arising in a core of the CCR of polycrystalline Ta, W and Cr after vacuum annealing (10 -6 - 10 -5 torr) are determined. Temperature dependences are studied for isomer shifts δ 1 and δ 2 of -1 and -2 components of emission spectra of NGR-irradiation 57 Co( 57 Fe) atomic probes localized in a core of the CCR and in adjacent zones of the lattice of polycrystalline solid solutions of O(Ta), O(W) and O(Cr). A comparison of the dependences obtained is carried and the specific features observed are explained for O(Cr) [ru

  6. Structure and properties of vanadium(V)-doped hexagonal turbostratic birnessite and its enhanced scavenging of Pb{sup 2+} from solutions

    Energy Technology Data Exchange (ETDEWEB)

    Yin, Hui; Feng, Xionghan; Tan, Wenfeng [Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070 (China); Koopal, Luuk K. [Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070 (China); Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, 6703HB Wageningen (Netherlands); Hu, Tiandou [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100039 (China); Zhu, Mengqiang, E-mail: mzhu6@uwyo.edu [Department of Ecosystem Science and Management, University of Wyoming, 1000 E. University Ave., Laramie, WY 82071 (United States); Liu, Fan, E-mail: liufan@mail.hzau.edu.cn [Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070 (China)

    2015-05-15

    Highlights: • V was coprecipitated with birnessite at a series of V/Mn molar ratios. • V-doped birnessites have greatly reduced particle sizes and increased SSAs. • V exists as V(V) oxyanions, including [V{sub 6}O{sub 16}] and [VO{sub 4}], on birnessite surfaces. • Scavenging of Pb{sup 2+} by these V-doped birnessites is greatly enhanced. - Abstract: Vanadium(V)-doped hexagonal turbostratic birnessites were synthesized and characterized by multiple techniques and were used to remove Pb{sup 2+} from aqueous solutions. With increasing V content, the V(V)-doped birnessites have significantly decreased crystallinity, i.e., the thickness of crystals in the c axis decreases from 9.8 nm to ∼0.7 nm, and the amount of vacancies slightly increases from 0.063 to 0.089. The specific surface areas of these samples increase after doping while the Mn average oxidation sates are almost constant. V has a valence of +5 and tetrahedral symmetry, and exists as oxyanions, including V{sub 6}O{sub 16}{sup 2−}, and VO{sub 4}{sup 3−} on birnessite edge sites by forming monodentate corning-sharing complexes. Pb L{sub III}-edge extended X-ray absorption fine structure (EXAFS) spectra analysis shows that, at low V contents (V/Mn ≤ 0.07) Pb{sup 2+} mainly binds with birnessite on octahedral vacancy and especially edge sites whereas at higher V contents (V/Mn > 0.07) more Pb{sup 2+} associates with V oxyanions and form vanadinite [Pb{sub 5}(VO{sub 4}){sub 3}Cl]-like precipitates. With increasing V(V) content, the Pb{sup 2+} binding affinity on the V-doped birnessites significantly increases, ascribing to both the formation of the vanadinite precipitates and decreased particle sizes of birnessite. These results are useful to design environmentally benign materials for treatment of metal-polluted water.

  7. Preparation and characterization of palladium nano-crystallite decorated TiO₂ nano-tubes photoelectrode and its enhanced photocatalytic efficiency for degradation of diclofenac.

    Science.gov (United States)

    Cheng, Xiuwen; Liu, Huiling; Chen, Qinghua; Li, Junjing; Wang, Pu

    2013-06-15

    TiO2 has been considered as a versatile candidate for the photoelectrochemical (PECH) application. In this study, Pd nano-crystallite decorated TiO₂ nano-tubes (Pd/TNTs) photoelectrode was prepared through electrochemical deposition. The resulting Pd/TNTs samples were characterized by SEM, XRD, DRS and XPS. It was found that the decorated Pd nano-crystallite existed in the form of Pd(0) with an average diameter of 30 nm, and could improve the light absorption in visible region. In addition, PECH properties of Pd/TNTs photoanode were investigated through transient open circuit potential, photocurrent response, electro-chemical impedance spectroscopy (EIS) and Mott-Schottky analysis. Moreover, the generation rate of hydroxyl radicals (•OH) was detected by a photoluminescence (PL) spectra using terephthalic acid (TA) as a probe molecule. Results showed that Pd/TNTs photoelectrode exhibited high transient photoinduced current of 0.094 mA cm(-2), open circuit photovoltage of -0.339 mV cm(-2) and effective photoelectrocatalytic (PEC) efficiency of 67.7% (0.4V vs. SCE) for the degradation of diclofenac (DCF). The high PC and PEC efficiency could mainly be attributed to the decoration of Pd nano-crystallite which could provide pathway for the transfer of photoinduced charge carriers. Furthermore, the contribution of series of active species was applied to clarify the enhanced PC mechanism. Copyright © 2013 Elsevier B.V. All rights reserved.

  8. Hydrothermal preparation of blue molybdenum bronze nanoribbons: structural changes in mother crystals, related to solid-state conversion and crystallite splitting to nanomorphology

    Science.gov (United States)

    Nishida, Takamasa; Eda, Kazuo

    2018-02-01

    Hydrothermal syntheses of alkali-metal blue molybdenum bronze nanoribbons, which are expected to exhibit unique properties induced by a combined effect of extrinsic and intrinsic low-dimensionalities, from hydrated-alkali-metal molybdenum bronzes were investigated. Nanoribbons grown along the quasi-one-dimensional (1D) conductive direction of Cs0.3MoO3, which is difficult to prepare by the conventional methods, were first synthesized. The nanomorphology formation is achieved by a solid-state conversion (or crystallite splitting) and subsequent crystallite growth, and the structural changes of the starting material related to the conversion were first observed by powder X-ray diffraction and scanning transmission electron microscopy as a result of finely tuned reaction system and preparation conditions. The structural changes were analyzed by model simulations and were attributed to the structural modulations that were concerned with the intralayer packing disorder and with two-dimensional long-range ordered structure, formed in MoO3 sheets of the hydrated molybdenum bronze. Moreover, the modulations were related to displacement defects of the Mo-O framework units generated along the [100] direction in the hydrated molybdenum bronze. Then, it was suggested that the solid-state conversion into blue molybdenum bronze and the crystallite splitting to nanomorphology were initiated by the breaking of the Mo-O-Mo bonds at the defects. [Figure not available: see fulltext.

  9. Crystallite-growth, phase transition, magnetic properties, and sintering behaviour of nano-CuFe2O4 powders prepared by a combustion-like process

    International Nuclear Information System (INIS)

    Köferstein, Roberto; Walther, Till; Hesse, Dietrich; Ebbinghaus, Stefan G.

    2014-01-01

    The synthesis of nano-crystalline CuFe 2 O 4 powders by a combustion-like process is described herein. Phase formation and evolution of the crystallite size during the decomposition process of a (CuFe 2 )—precursor gel were monitored up to 1000 °C. Phase-pure nano-sized CuFe 2 O 4 powders were obtained after reaction at 750 °C for 2 h resulting in a crystallite size of 36 nm, which increases to 96 nm after calcining at 1000 °C. The activation energy of the crystallite growth process was calculated as 389 kJ mol −1 . The tetragonal⇄cubic phase transition occurs between 402 and 419 °C and the enthalpy change (ΔH) was found to range between 1020 and 1229 J mol −1 depending on the calcination temperature. The optical band gap depends on the calcination temperature and was found between 2.03 and 1.89 eV. The shrinkage and sintering behaviour of compacted powders were examined. Dense ceramic bodies can be obtained either after conventional sintering at 950 °C or after a two-step sintering process at 800 °C. Magnetic measurements of both powders and corresponding ceramic bodies show that the saturation magnetization rises with increasing calcination-/sintering temperature up to 49.1 emu g −1 (2.1 µ B fu −1 ), whereas the coercivity and remanence values decrease. - Graphical abstract: A cheap one-pot synthesis was developed to obtain CuFe 2 O 4 nano-powders with different crystallite sizes (36–96 nm). The optical band gaps, phase transition temperatures and enthalpies were determined depending on the particle size. The sintering behaviour of nano CuFe 2 O 4 was studied in different sintering procedures. The magnetic behaviour of the nano-powders as well as the corresponding ceramic bodies were investigated. - Highlights: • Eco-friendly and simple synthesis for nano CuFe 2 O 4 powder using starch as polymerization agent. • Monitoring the phase evolution and crystallite growth kinetics during the synthesis. • Determination of the optical band gap

  10. Study of the crystallite size of nitrosylpentacyanoferrate through refinement of structures; Estudio del tamano de cristalita de nitrosilpentacianoferratos mediante refinamiento de estructuras

    Energy Technology Data Exchange (ETDEWEB)

    Jimenez G, J.A.; Yee M, H.T. [ESFM-IPN, 07738 Mexico D.F. (Mexico); Balmaceda E, J. [IIM-UNAM, 04510 Mexico D.F. (Mexico); Reguera R, E. [CICATA-IPN, Av. Legaria 694, 11500 Mexico D.F. (Mexico)

    2006-07-01

    The development reached in the instrumentation and in the computer science of the diffraction of rays X, it has enlarged the reach of the method of powders considerably, in the resolution of crystalline structures of polycrystalline material converting it in a potent tool that, attended by spectroscopic techniques, it allows the fine characterization to atomic scale of having been accustomed to crystalline. In the thesis it is developed an effective methodology of determination of the crystallite size and structural refinement starting from data of diffraction of powders, based on the use of the equation of Sherrer for the estimate of the crystallite size and the method of Rietveld for the structural refinement; supplemented with the employment of the spectroscopic methods (IR and Moessbauer). The combined use of these techniques in the structural study of having been accustomed to crystalline lens of high complexity provides a novel and advanced work. The estimate of the crystallite size, it has been little explored to study accustomed to crystalline such as the pentacyanonitrosyl ferrates. One of the reasons for the which have intended to study the glass size in these structures it is due to that the molecular materials have attracted the attention of the international scientific community for their promissory properties in fields so diverse as: the absorption, desorption and separation of gases among others. Of the entreated information by means of databases and articles of scientific popularization were refined the structures of two compounds (NPCo and NPNi) obtained by powders diffraction; offering the possibility to develop a titled work: 'Physical description of the desorption of the water in nano structured material of nitrosyl penta cyano ferrates' which is carried out in parallel way to this thesis. This tools supplemented with the spectroscopic methods, potent the reach of the methods of diffraction of powders for the structural study of having

  11. Analysis of the texture of zircaloy-4 sheet by crystallite orientation distribution function

    International Nuclear Information System (INIS)

    Ryoo, Hwei Soo; Hwang Sun Keum

    1990-01-01

    In order to analyze the texture variation of Zircaloy-4 sheet the Roe's method of calculating the crystallite orientation distribution function(CODF) for hcp system was computer programmed. The coefficients W lmn of CODF were calculated from plane-normal distribution pole figures obtained by X-ray diffraction, and the CODF was computed from a series expansion of spherical harmonics. The Legendre function, which is the basis of the harmonics, was computed up to l=16 to account for the symmetry systems of specimen and hcp crystal. A cross-rolling followed by beta-phase heat treatment and furnace cooling increased the density of basal poles along the sheet normal direction and rotated prism poles around the c axis. (Author)

  12. Crystallite Size and Microstrain Measurement of Cathode Material after Mechanical Milling using Neutron Diffraction Technique

    Directory of Open Access Journals (Sweden)

    A. Fajar

    2010-12-01

    Full Text Available The measurements of neutron diffraction patterns of commercially product and 10 hour mechanically milled cathode material lithium cobaltites (LiCoO2 have been performed. Rietveld analysis using FullProf does not show the change of crystal structure due to milling process, but the diffraction pattern has a lower intensity and the diffraction-line was broadening. The results of line-broadening study on milled sample using Rietveld methods detected that the microstrain was occurred in the sample with value 0.127080(35 % and the average crystallite size was 424.78(20 Å.

  13. A colloidal solution of Fe3O4 crystallites to optically locate the magnetic center of multipole magnets

    International Nuclear Information System (INIS)

    Sugahara, Ryuhei; Kubo, Tadashi; Oosawa, Yasunobu.

    1989-09-01

    In the alignment of accelerator components or beam transports components along the beam line, it is important to identify the magnetic center of multipole magnets, which does not necessarily coincide with the mechanical center. The position of the magnetic center of magnets can be located by using a colloidal solution of Fe 3 O 4 crystallites with a high resolution of about 10 μm. This is because the magnetic center can be observed visually and neither elaborate equipment nor accurate adjustment of the colloidal solution is necessary. A colloidal solution of Fe 3 O 4 crystallites is prepared and its performance is examined. The life time of the scattering pattern formed by the scattering of plane-polarized light in the colloidal solution is found to be longer than two days, which is much longer than the pattern life of about 40 minutes for commercial colloidal solution. The reproducibility of the alignment of the hair cross of the telescope onto the cross point of the pattern is less than 20 μm. It is suggested that polydextrose, a soluble derivative of cellulose, can be effective in improving the pattern life. (N.K.)

  14. Ab initio and Molecular Dynamic models of displacement damage in crystalline and turbostratic graphite

    Science.gov (United States)

    McKenna, Alice

    which simulations have been performed on. The difference between the two is at the grain boundaries with one having dangling bonds and the other one being bonded. The cascade showed the grain boundaries acting as a trap for the knock-on atoms which produces more damage compared with the single crystal. Finally the effects of turbostratic disorder on damage is considered. Density functional theory (DFT) was used to look at interstitials in (002) twist boundaries and how they act compared to AB stacked graphite. The results of these calculations show that the spiro interstitial is more stable in these grain boundaries, so at temperatures where the interstitial can migrate along the c direction they will segregate to (002) twist boundaries.

  15. Multiscale investigation of graphene layers on 6H-SiC(000-1

    Directory of Open Access Journals (Sweden)

    Hiebel Fanny

    2011-01-01

    Full Text Available Abstract In this article, a multiscale investigation of few graphene layers grown on 6H-SiC(000-1 under ultrahigh vacuum (UHV conditions is presented. At 100-μm scale, the authors show that the UHV growth yields few layer graphene (FLG with an average thickness given by Auger spectroscopy between 1 and 2 graphene planes. At the same scale, electron diffraction reveals a significant rotational disorder between the first graphene layer and the SiC surface, although well-defined preferred orientations exist. This is confirmed at the nanometer scale by scanning tunneling microscopy (STM. Finally, STM (at the nm scale and Raman spectroscopy (at the μm scale show that the FLG stacking is turbostratic, and that the domain size of the crystallites ranges from 10 to 100 nm. The most striking result is that the FLGs experience a strong compressive stress that is seldom observed for graphene grown on the C face of SiC substrates.

  16. High throughput, high resolution enzymatic lithography process: effect of crystallite size, moisture, and enzyme concentration.

    Science.gov (United States)

    Mao, Zhantong; Ganesh, Manoj; Bucaro, Michael; Smolianski, Igor; Gross, Richard A; Lyons, Alan M

    2014-12-08

    By bringing enzymes into contact with predefined regions of a surface, a polymer film can be selectively degraded to form desired patterns that find a variety of applications in biotechnology and electronics. This so-called "enzymatic lithography" is an environmentally friendly process as it does not require actinic radiation or synthetic chemicals to develop the patterns. A significant challenge to using enzymatic lithography has been the need to restrict the mobility of the enzyme in order to maintain control of feature sizes. Previous approaches have resulted in low throughput and were limited to polymer films only a few nanometers thick. In this paper, we demonstrate an enzymatic lithography system based on Candida antartica lipase B (CALB) and poly(ε-caprolactone) (PCL) that can resolve fine-scale features, (<1 μm across) in thick (0.1-2.0 μm) polymer films. A Polymer Pen Lithography (PPL) tool was developed to deposit an aqueous solution of CALB onto a spin-cast PCL film. Immobilization of the enzyme on the polymer surface was monitored using fluorescence microscopy by labeling CALB with FITC. The crystallite size in the PCL films was systematically varied; small crystallites resulted in significantly faster etch rates (20 nm/min) and the ability to resolve smaller features (as fine as 1 μm). The effect of printing conditions and relative humidity during incubation is also presented. Patterns formed in the PCL film were transferred to an underlying copper foil demonstrating a "Green" approach to the fabrication of printed circuit boards.

  17. Growth kinetics of tetragonal and monoclinic ZrO2 crystallites in 3 mol% yttria partially stabilized ZrO2 (3Y-PSZ) precursor powder

    International Nuclear Information System (INIS)

    Kuo, Chih-Wei; Lee, Kuen-Chan; Yen, Feng-Lin; Shen, Yun-Hwei; Lee, Huey-Er; Wen, Shaw-Bing; Wang, Moo-Chin; Stack, Margaret Mary

    2014-01-01

    Highlights: • The crystalline structures were composed of tetragonal and monoclinic ZrO 2 . • Growth kinetics of t-ZrO 2 in the 3Y-PSZ precursor powder is described as: D te 2 =(4.57±0.55)t 0.12±0.02 exp(-((24.79±0.38)×10 3 )/(RT) ). • Growth kinetics of m-ZrO 2 in the 3Y-PSZ precursor powder is described as: D m 2 =(4.40±1.63)t 0.17±0.08 exp(-((66.47±3.97)×10 3 )/(RT) ). - Abstract: The growth kinetics of tetragonal and monoclinic ZrO 2 crystallites in 3 mol% yttria partially stabilized ZrO 2 (3Y-PSZ) precursor powder has been investigated using X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) specific surface area analysis, transmission electron microscopy (TEM) and high resolution TEM (HRTEM). After calcination of the 3Y-PSZ precursor powder between 773 and 1073 K for 2 h, the crystalline structures were composed of tetragonal and monoclinic ZrO 2 as the primary and secondary phases, respectively. When the 3Y-PSZ precursor powder was calcined at 773 K for 2 h, the BET specific surface area was 97.13 m 2 /g, which is equivalent to a particle size of 10.30 nm. The crystallite sizes determined via XRD and BET agreed well, indicating that the powder was virtually non-agglomerated. The growth kinetics of tetragonal and monoclinic ZrO 2 crystallite isothermal growth in the 3Y-PSZ precursor powder are described by: D te 2 =(4.57±0.55)t 0.12±0.02 exp(-((24.79±0.38)×10 3 )/(RT) ) and D m 2 =(4.40±1.63)t 0.17±0.08 exp(-((66.47±3.97)×10 3 )/(RT) ), respectively, for 773K≤T≤1073K. D te and D m denote the crystallite size of tetragonal and monoclinic ZrO 2 at time t and temperature T, respectively

  18. Homocomposites of Polylactide (PLA) with Induced Interfacial Stereocomplex Crystallites

    Science.gov (United States)

    2015-01-01

    The demand for “green” degradable composite materials increases with growing environmental awareness. The key challenge is achieving the preferred physical properties and maintaining their eco-attributes in terms of the degradability of the matrix and the filler. Herein, we have designed a series of “green” homocomposites materials based purely on polylactide (PLA) polymers with different structures. Film-extruded homocomposites were prepared by melt-blending PLA matrixes (which had different degrees of crystallinity) with PLLA and PLA stereocomplex (SC) particles. The PLLA and SC particles were spherical and with 300–500 nm size. Interfacial crystalline structures in the form of stereocomplexes were obtained for certain particulate-homocomposite formulations. These SC crystallites were found at the particle/matrix interface when adding PLLA particles to a PLA matrix with d-lactide units, as confirmed by XRD and DSC data analyses. For all homocomposites, the PLLA and SC particles acted as nucleating agents and enhanced the crystallization of the PLA matrixes. The SC particles were more rigid and had a higher Young’s modulus compared with the PLLA particles. The mechanical properties of the homocomposites varied with particle size, rigidity, and the interfacial adhesion between the particles and the matrix. An improved tensile strength in the homocomposites was achieved from the interfacial stereocomplex formation. Hereafter, homocomposites with tunable crystalline arrangements and subsequently physical properties, are promising alternatives in strive for eco-composites and by this, creating materials that are completely degradable and sustainable. PMID:26523245

  19. Moessbauer-spectroscopic characterization of the local surrounding of tin dopant cations in the bulk and on the surface of YCrO{sub 3} crystallites

    Energy Technology Data Exchange (ETDEWEB)

    Afanasov, Mikhail I.; Fabritchnyi, Pavel B. [M.V. Lomonosov Moscow State Univ. (Russian Federation). Dept. of Chemistry; Wattiaux, Alain; Labrugere, Christine; Delmas, Claude [CNRS, Bordeaux Univ., Pessac (France). Inst. de Chimie de la Matiere Condensee

    2011-03-15

    {sup 119}Sn Moessbauer spectra of tin-doped YCrO{sub 3}, obtained by annealing in air of an YCr({sup 119}Sn{sup 4+}){sub 0.003}(OH){sub 6} . xH{sub 2}O precursor, provide evidence for the location of Sn{sup 4+} on the Cr{sup 3+} site in the bulk of crystallites. Below the Neel point of YCrO{sub 3} (T{sub N} = 141 K), Sn{sup 4+} ions are spin-polarized, the majority exhibiting a hyperfine field H of 80 kOe at 4.2 K. Analysis of the {sup 119}Sn spectra of another sample, obtained by impregnation of polycrystalline YCrO{sub 3} with a solution of {sup 119}SnCl{sub 4}, shows that annealing in H{sub 2} results in the location of the dopant, in the divalent state, on the surface of the crystallites. The parameters of an in situ {sup 119}Sn spectrum at 295 K (isomer shift {delta} = 2.76 mm s{sup -1} and quadrupole splitting E{sub Q} = 1.95 mm s{sup -1}) reveal the presence of Sn{sup 2+} ions on sites with a coordination number CN < 6. At 100 K these Sn{sup 2+} ions exhibit no spin polarization. Upon contact with air they are rapidly oxidized to the tetravalent state, as demonstrated by their modified isomer shift value {delta} = 0.06 mm s{sup -1}. For the large majority of both the residual 'parent' Sn{sup 2+} ions and the 'daughter' Sn{sup 4+} ones no spin polarization is observed down to 4.2 K. This means that surface-located tin dopant cations, regardless of their oxidation state, occupy the Y{sup 3+} sites with an equal number of Cr{sup 3+} neighbors having mutually opposite spin orientations. (orig.)

  20. Control of crystallite orientation and size in Fe and FeCo nanoneedles

    International Nuclear Information System (INIS)

    Mendoza-Reséndez, Raquel; Luna, Carlos; Diaz Barriga-Castro, Enrique; Bonville, Pierre; Serna, Carlos J

    2012-01-01

    Uniform magnetic nanoneedles have been prepared by hydrogen reduction of elongated nanoarchitectures. These precursors are as-prepared or cobalt-coated aggregates of highly oriented haematite nanocrystals (∼5 nm). The final materials are flattened nanoneedles formed by chains of assembled Fe or FeCo single-domain nanocrystals. The microstructural properties of such nanoneedles were tailored using renewed and improved synthetic strategies. In this fashion, the needle elongation and composition, the crystallite size (from 15 up to 30 nm), the nanocrystal orientation (with the 〈110〉 or 〈001〉 directions roughly along the long axis of the nanoneedle) and their type of arrangement (single chains, frustrated double chains and double chains) were controlled by modifying the reduction time, the axial ratio of the precursor haematite and the presence of additional coatings of aluminum or yttrium compounds. The values of the coercivity H C found for these nanoneedles are compared with the values predicted by the chain of spheres model assuming a symmetric fanning mechanism for magnetization reversal. (paper)

  1. BAND STRUCTURE OF NON-STEIOCHIOMETRIC LARGE-SIZED NANOCRYSTALLITES

    Directory of Open Access Journals (Sweden)

    I.V.Kityk

    2004-01-01

    Full Text Available A band structure of large-sized (from 20 to 35nm non-steichiometric nanocrystallites (NC of the Si2-xCx (1.04 < x < 1.10 has been investigated using different band energy approaches and a modified Car-Parinello molecular dynamics structure optimization of the NC interfaces. The non-steichiometric excess of carbon favors the appearance of a thin prevailingly carbon-contained layer (with thickness of about 1 nm covering the crystallites. As a consequence, one can observe a substantial structure reconstruction of boundary SiC crystalline layers. The numerical modeling has shown that these NC can be considered as SiC reconstructed crystalline films with thickness of about 2 nm covering the SiC crystallites. The observed data are considered within the different one-electron band structure methods. It was shown that the nano-sized carbon sheet plays a key role in a modified band structure. Independent manifestation of the important role played by the reconstructed confined layers is due to the experimentally discovered excitonic-like resonances. Low-temperature absorption measurements confirm the existence of sharp-like absorption resonances originating from the reconstructed layers.

  2. Impact of the Crystallite Orientation Distribution on Exciton Transport in Donor–Acceptor Conjugated Polymers

    KAUST Repository

    Ayzner, Alexander L.; Mei, Jianguo; Appleton, Anthony; DeLongchamp, Dean; Nardes, Alexandre; Benight, Stephanie; Kopidakis, Nikos; Toney, Michael F.; Bao, Zhenan

    2015-01-01

    © 2015 American Chemical Society. Conjugated polymers are widely used materials in organic photovoltaic devices. Owing to their extended electronic wave functions, they often form semicrystalline thin films. In this work, we aim to understand whether distribution of crystallographic orientations affects exciton diffusion using a low-band-gap polymer backbone motif that is representative of the donor/acceptor copolymer class. Using the fact that the polymer side chain can tune the dominant crystallographic orientation in the thin film, we have measured the quenching of polymer photoluminescence, and thus the extent of exciton dissociation, as a function of crystal orientation with respect to a quenching substrate. We find that the crystallite orientation distribution has little effect on the average exciton diffusion length. We suggest several possibilities for the lack of correlation between crystallographic texture and exciton transport in semicrystalline conjugated polymer films.

  3. Impact of the Crystallite Orientation Distribution on Exciton Transport in Donor–Acceptor Conjugated Polymers

    KAUST Repository

    Ayzner, Alexander L.

    2015-12-30

    © 2015 American Chemical Society. Conjugated polymers are widely used materials in organic photovoltaic devices. Owing to their extended electronic wave functions, they often form semicrystalline thin films. In this work, we aim to understand whether distribution of crystallographic orientations affects exciton diffusion using a low-band-gap polymer backbone motif that is representative of the donor/acceptor copolymer class. Using the fact that the polymer side chain can tune the dominant crystallographic orientation in the thin film, we have measured the quenching of polymer photoluminescence, and thus the extent of exciton dissociation, as a function of crystal orientation with respect to a quenching substrate. We find that the crystallite orientation distribution has little effect on the average exciton diffusion length. We suggest several possibilities for the lack of correlation between crystallographic texture and exciton transport in semicrystalline conjugated polymer films.

  4. Scratch-resistant transparent boron nitride films

    Energy Technology Data Exchange (ETDEWEB)

    Dekempeneer, E.H.A.; Kuypers, S.; Vercammen, K.; Meneve, J.; Smeets, J. [Vlaamse Instelling voor Technologisch Onderzoek (VITO), Mol (Belgium); Gibson, P.N.; Gissler, W. [Joint Research Centre of the Commission of the European Communities, Institute for Advanced Materials, Ispra (Vatican City State, Holy See) (Italy)

    1998-03-01

    Transparent boron nitride (BN) coatings were deposited on glass and Si substrates in a conventional capacitively coupled RF PACVD system starting from diborane (diluted in helium) and nitrogen. By varying the plasma conditions (bias voltage, ion current density), coatings were prepared with hardness values ranging from 2 to 12 GPa (measured with a nano-indenter). Infrared absorption measurements indicated that the BN was of the hexagonal type. A combination of glancing-angle X-ray diffraction measurements and simulations shows that the coatings consist of hexagonal-type BN crystallites with different degrees of disorder (nanocrystalline or turbostratic material). High-resolution transmission electron microscopy analysis revealed the presence of an amorphous interface layer and on top of this interface layer a well-developed fringe pattern characteristic for the basal planes in h-BN. Depending on the plasma process conditions, these fringe patterns showed different degrees of disorder as well as different orientational relationships with respect to the substrate surface. These observations were correlated with the mechanical properties of the films. (orig.) 14 refs.

  5. Structural transformation of nanocrystalline titania by sol-gel and the growth kinetics of crystallites

    International Nuclear Information System (INIS)

    Hu Linhua; Dai Songyuan; Wang Kongjia

    2002-05-01

    Structural transformation of nanocrystalline titania prepared by sol-gel with hydrolysis precursor titanium isopropoxide was investigated. At the same time, the growth kinetics of titania powders was also studied here. It was found that the grain size of the powders increased slowly with autoclave heating temperature up to 230 degree C, when hydrolysis pH was 0.9, but grew rapidly when heating temperature was higher that 230 degree C. The activation energies for growth of anatase crystallites in two temperature regions were calculated to be 18.5 kJ/mol and 59.7 kJ/mol respectively. The X-ray diffraction results show that the transformation from anatase phase to rutile phase starts at 230 degree C and structural transformation finished when temperature raises to 270 degree C, which is a temperature much more lower than that of the transformation by conventional literature reports

  6. Growth kinetics of tetragonal and monoclinic ZrO{sub 2} crystallites in 3 mol% yttria partially stabilized ZrO{sub 2} (3Y-PSZ) precursor powder

    Energy Technology Data Exchange (ETDEWEB)

    Kuo, Chih-Wei [Department of Resources Engineering, National Cheng Kung University, 1 Ta-Hsueh Road, Tainan 70101, Taiwan (China); Lee, Kuen-Chan [Department of Fragrance and Cosmetic Science, Kaohsiung Medical University, 100 Shih-Chuan 1st Road, Kaohsiung 807, Taiwan (China); Yen, Feng-Lin, E-mail: flyen@kmu.edu.tw [Department of Fragrance and Cosmetic Science, Kaohsiung Medical University, 100 Shih-Chuan 1st Road, Kaohsiung 807, Taiwan (China); Shen, Yun-Hwei [Department of Resources Engineering, National Cheng Kung University, 1 Ta-Hsueh Road, Tainan 70101, Taiwan (China); Lee, Huey-Er [Department of Dentistry, Kaohsiung Medical University, 100 Shih-Chuan 1st Road, Kaohsiung 807, Taiwan (China); Department of Dentistry, Kaohsiung Medical University, Chung Ho Memorial Hospital, 100 Tzyou 1st Road, Kaohsiung 807, Taiwan (China); Wen, Shaw-Bing [General Education Center, Meiho Institute of Technology, 23 Pingguang Road, Neipu, Pingtung 91202, Taiwan (China); Wang, Moo-Chin, E-mail: mcwang@kmu.edu.tw [Department of Fragrance and Cosmetic Science, Kaohsiung Medical University, 100 Shih-Chuan 1st Road, Kaohsiung 807, Taiwan (China); Stack, Margaret Mary [Department of Mechanical and Aerospace Engineering, University of Strathclyde, 75 Montrose Street, Glasgow (United Kingdom)

    2014-04-01

    Highlights: • The crystalline structures were composed of tetragonal and monoclinic ZrO{sub 2}. • Growth kinetics of t-ZrO{sub 2} in the 3Y-PSZ precursor powder is described as: D{sub te}{sup 2}=(4.57±0.55)t{sup 0.12±0.02}exp(-((24.79±0.38)×10{sup 3})/(RT) ). • Growth kinetics of m-ZrO{sub 2} in the 3Y-PSZ precursor powder is described as: D{sub m}{sup 2}=(4.40±1.63)t{sup 0.17±0.08}exp(-((66.47±3.97)×10{sup 3})/(RT) ). - Abstract: The growth kinetics of tetragonal and monoclinic ZrO{sub 2} crystallites in 3 mol% yttria partially stabilized ZrO{sub 2} (3Y-PSZ) precursor powder has been investigated using X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) specific surface area analysis, transmission electron microscopy (TEM) and high resolution TEM (HRTEM). After calcination of the 3Y-PSZ precursor powder between 773 and 1073 K for 2 h, the crystalline structures were composed of tetragonal and monoclinic ZrO{sub 2} as the primary and secondary phases, respectively. When the 3Y-PSZ precursor powder was calcined at 773 K for 2 h, the BET specific surface area was 97.13 m{sup 2}/g, which is equivalent to a particle size of 10.30 nm. The crystallite sizes determined via XRD and BET agreed well, indicating that the powder was virtually non-agglomerated. The growth kinetics of tetragonal and monoclinic ZrO{sub 2} crystallite isothermal growth in the 3Y-PSZ precursor powder are described by: D{sub te}{sup 2}=(4.57±0.55)t{sup 0.12±0.02}exp(-((24.79±0.38)×10{sup 3})/(RT) ) and D{sub m}{sup 2}=(4.40±1.63)t{sup 0.17±0.08}exp(-((66.47±3.97)×10{sup 3})/(RT) ), respectively, for 773K≤T≤1073K. D{sub te} and D{sub m} denote the crystallite size of tetragonal and monoclinic ZrO{sub 2} at time t and temperature T, respectively.

  7. Large-scale fabrication and utilization of novel hexagonal/turbostratic composite boron nitride nanosheets

    KAUST Repository

    Zhong, Bo; Zhang, Xiaodong; Xia, Long; Yu, Yuanlie; Wen, Guangwu

    2017-01-01

    mechanism of h/t-BNNSs is also discussed based on the thermogravimetric analysis of AB which clearly shows two step weight loss. The h/t-BNNSs are further used for making thermoconductive h/t-BNNSs/epoxy resin composites. The thermal conductivity

  8. Phase separation of acetonitrile-water mixtures and minimizing of ice crystallites from there in confinement of MCM-41.

    Science.gov (United States)

    Kittaka, Shigeharu; Kuranishi, Miki; Ishimaru, Shinji; Umahara, Osamu

    2007-03-07

    The effect of confinement of an acetonitrile-water mixture, whose correlation length was comparable to the pore size of the mesopores of MCM-41 (d=2.4-3.6 nm), on the phase changes was studied. Used techniques were low temperature differential scanning calorimetry and Fourier transform infrared spectroscopy, where the phase separation, lowering of the freezing and melting temperatures, and phase transitions of the acetonitrile were detected. The latter occurred in the mesopores at temperatures similar to that of the pure liquid, while the melting temperature of the water in the mesopores<3.1 nm decreased markedly at higher acetonitrile contents, suggesting a marked lowering of ice crystallite size.

  9. Surfactant-assisted hydrothermal fabrication and visible-light-driven photocatalytic degradation of methylene blue over multiple morphological BiVO4 single-crystallites

    International Nuclear Information System (INIS)

    Meng Xue; Zhang Lei; Dai Hongxing; Zhao Zhenxuan; Zhang Ruzhen; Liu Yuxi

    2011-01-01

    Monoclinic BiVO 4 single-crystallites with polyhedral, rod-like, tubular, leaf-like, and spherical morphologies have been fabricated using the triblock copolymer P123-assisted hydrothermal strategy with bismuth nitrate and ammonium metavanadate as metal source and various bases as pH adjustor. The physicochemical properties of the materials were characterized by means of the XRD, TGA/DSC, Raman, HRSEM, HRTEM/SAED, XPS, and UV-vis techniques. The photocatalytic activities of the as-fabricated BiVO 4 samples were measured for the photodegradation of methylene blue (MB) under visible-light irradiation. It is shown that factors, such as the pH value of precursor solution, the introduction of surfactant, the nature of alkaline source, and the hydrothermal temperature, have a crucial influence on the particle architecture of the BiVO 4 product. Among the as-fabricated BiVO 4 samples, the ones derived hydrothermally with P123 at pH = 6 or 10 possessed excellent optical absorption performance both in UV- and visible-light regions and hence showed outstanding photocatalytic activities for the addressed reaction. The unusually high visible-light-driven catalytic performance of monoclinically crystallized rod-like and tubular BiVO 4 single-crystallites is associated with the higher surface areas and concentrations of surface oxygen defects, and unique particle morphologies. The possible formation mechanisms of such multiple morphological BiVO 4 materials have also been discussed.

  10. Nanostructured titanium dioxide: a control of crystallite size and content of polymorphic phases; Nanoestrutura de dioxido de titanio: controle do tamanho de cristalitos e teor das fases polimorficas

    Energy Technology Data Exchange (ETDEWEB)

    Boery, Mirella N. de O.; Ono, Eduardo; Manfrim, Tarcio P.; Santos, Juliana S.; Suzuki, Carlos K., E-mail: miboery@fem.unicamp.b [Universidade Estadual de Campinas (UNICAMP), SP (Brazil)

    2010-07-01

    TiO{sub 2} (titanium dioxide) powders and nanoparticles have been largely used in toners and cosmetics. Nowadays, they are mainly focused in photocatalysis, antibacterial coatings, dye-sensitized solar cells, etc. The efficiency is related to photocatalytic properties of TiO{sub 2} nanoparticles, such as crystallite size and phase (anatasio/rutile). In this research, flame aerosol method was used to synthesize TiO{sub 2} nanoparticles by hydrolysis and oxidation of TiCl{sub 4} (titanium tetrachloride). The oxy-hydrogen flame was provided by a five concentric nozzle silica burner. X-ray diffraction was used to identify each TiO{sub 2} nanoparticles phase and scanning electron microscopy was used to observe the size and morphology of nanoparticles. Pure anatase was obtained with H{sub 2}/O{sub 2} ratio {<=} 1.0, and up to 52 wt% of rutile was obtained with H{sub 2}/O{sub 2} ratio > 2.0. Anatase crystal grain size varied from 25 to 38 nm, estimated by Scherrer formula.(author)

  11. Oriented monolayer film of Gd2O3:0.05 Eu crystallites: quasi-topotactic transformation of the hydroxide film and drastic enhancement of photoluminescence properties.

    Science.gov (United States)

    Hu, Linfeng; Ma, Renzhi; Ozawa, Tadashi C; Sasaki, Takayoshi

    2009-01-01

    Caught on film: A semitransparent and intensely luminescent monolayer film of oriented Gd(2)O(3):0.05 Eu platelet crystallites is fabricated by annealing the precursor hydroxide film (see scheme). The photoluminescence properties of the as-transformed film are greatly improved over those of the hydroxide film, and are much more pronounced than those of the corresponding Gd(2)O(3):0.05 Eu powder.

  12. X-ray diffraction stress analysis of interrupted titanium nitride films: Combining the sin2ψ and crystallite group methods

    International Nuclear Information System (INIS)

    Sinkovits, Theo; Zhao, Yue; O'Brien, Rebecca; Dowey, Steve

    2014-01-01

    Interruptions during film growth have been discussed by researchers to assist in understanding the evolution of stress in physical vapour deposition films. A change in intrinsic stress is directly related to microstructure, hence careful analysis of stress in films can provide valuable structure–stress correlated information. In this study we discuss the use of combining two X-ray diffraction (XRD) stress analysis methods to elucidate the effect of interruptions during growth on the residual stress of TiN films. The sin 2 ψ and crystallite group method (CGM), scanning the (220) peaks from all grains in the film and only (111) oriented crystallites respectively, were used to analyse residual stress in standard and interrupted cathodic arc TiN films 1.5, 3.5 and 6.5 μm thick, grown on high-speed steel substrates. The sin 2 ψ method does not reveal any changes in stress with interruptions, however, measurements using the CGM show increased compressive stress and increased a 0 in the resultant TiN films. A comparison of results from both XRD methods indicates that an increased compressive stress from interruptions could be due to an increased number of defects in (111) oriented grains during the interruptions which would also affect a 0 as evident. In both methods, compressive stresses are found to decrease with increased thickness of films. - Highlights: • Interrupting TiN film growth increases compressive stress in (111) grains. • Increased stress is believed to be caused by defects incorporated into or not annealed out of (111) grains. • A comparison of sin 2 ψ and CGM results reveals differences in stress. • Compressive stress decreases as TiN films increase in thickness from 1.5 μm to 6.5 μm

  13. Preparation of zinc ferrite nano powders by high energy wet-milling method and investigation of Crystallites size variation during this process

    International Nuclear Information System (INIS)

    Masoudi, H.; Aftabi, A.; Mozafari, M.; Amighian, J.

    2007-01-01

    In this research work ZnFe 2 O 4 nano powders were prepared by high-energy wet-milling process, using metallic Fe and Zn powders. The process was investigated by XRD technique. 10% of the zinc ferrite was formed after 10 h milling. The as-milled sample was annealed at 500, 550 and 600 d egree C . Ultimately a single sample was obtained at 600 d egree C . Using sherrer's formula, the mean crystallite size of the as-milled and annealed powders were calculated. These were in the range of 17.9 to 20.4 nm.

  14. Crystallite size variation of TiO{sub 2} samples depending time heat treatment; Variacao do tamanho de cristalito de amostras de TiO{sub 2} em funcao do tempo de tratamento termico

    Energy Technology Data Exchange (ETDEWEB)

    Galante, A.G.M.; Paula, F.R. de; Montanhera, M.A.; Pereira, E.A., E-mail: amandagmgalante@gmail.com [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Ilha Solteira, SP (Brazil). Departamento de Fisica e Quimica; Spada, E.R. [Universidade de Sao Paulo (USP), Ilha Solteira, SP (Brazil). Instituto de Fisica

    2016-07-01

    Titanium dioxide (TiO{sub 2}) is an oxide semiconductor that may be found in mixed phase or in distinct phases: brookite, anatase and rutile. In this work was carried out the study of the residence time influence at a given temperature in the TiO{sub 2} powder physical properties. After the powder synthesis, the samples were divided and heat treated at 650 °C with a ramp up to 3 °C/min and a residence time ranging from 0 to 20 hours and subsequently characterized by x-ray diffraction. Analyzing the obtained diffraction patterns, it was observed that, from 5-hour residence time, began the two-distinct phase coexistence: anatase and rutile. It also calculated the average crystallite size of each sample. The results showed an increase in average crystallite size with increasing residence time of the heat treatment. (author)

  15. The other prey-capture silk: Fibres made by glow-worms (Diptera: Keroplatidae) comprise cross-β-sheet crystallites in an abundant amorphous fraction.

    Science.gov (United States)

    Walker, Andrew A; Weisman, Sarah; Trueman, Holly E; Merritt, David J; Sutherland, Tara D

    2015-09-01

    Glow-worms (larvae of dipteran genus Arachnocampa) are restricted to moist habitats where they capture flying prey using snares composed of highly extensible silk fibres and sticky mucus droplets. Little is known about the composition or structure of glow-worm snares, or the extent of possible convergence between glow-worm and arachnid capture silks. We characterised Arachnocampa richardsae silk and mucus using X-ray scattering, Fourier transform infrared spectroscopy and amino acid analysis. Silk but not mucus contained crystallites of the cross-β-sheet type, which occur in unrelated insect silks but have not been reported previously in fibres used for prey capture. Mucus proteins were rich in Gly (28.5%) and existed in predominantly a random coil structure, typical of many adhesive proteins. In contrast, the silk fibres were unusually rich in charged and polar residues, particularly Lys (18.1%), which we propose is related to their use in a highly hydrated state. Comparison of X-ray scattering, infrared spectroscopy and amino acid analysis data suggests that silk fibres contain a high fraction of disordered protein. We suggest that in the native hydrated state, silk fibres are capable of extension via deformation of both disordered regions and cross-β-sheet crystallites, and that high extensibility is an adaptation promoting successful prey capture. This study illustrates the rich variety of protein motifs that are available for recruitment into biopolymers, and how convergently evolved materials can nevertheless be based on fundamentally different protein structures. Crown Copyright © 2015. Published by Elsevier Inc. All rights reserved.

  16. Application of nuclear quadrupole resonance relaxometry to study the influence of the environment on the surface of the crystallites of powder

    Energy Technology Data Exchange (ETDEWEB)

    Sinyavsky, Nikolay Ya. [Immanuel Kant Baltic Federal Univ., Kaliningrad (Russian Federation); Kaliningrad State Technical Univ. (Russian Federation); Mershiev, Ivan G.; Kupriyanova, Galina S. [Immanuel Kant Baltic Federal Univ., Kaliningrad (Russian Federation)

    2015-10-01

    The results of the experimental study of the influence of the environment surrounding the surface of the crystallites of a KClO{sub 3} powder on the distribution of the spin-spin and spin-lattice relaxation times for {sup 35}Cl nuclear quadrupole resonance are described. It was found that the distributions of the spin-lattice relaxation times are unimodal and distributions of the spin-spin relaxation times are bimodal for all samples we studied. T{sub 1} - T{sub 2} and T{sub 1ρ} - T{sub 2} correlations by means of the two-dimensional (2D) inverse Laplace transform are obtained. The efficiency of the method for the study of surface phenomena in solids is demonstrated.

  17. Application of nuclear quadrupole resonance relaxometry to study the influence of the environment on the surface of the crystallites of powder

    International Nuclear Information System (INIS)

    Sinyavsky, Nikolay Ya.; Mershiev, Ivan G.; Kupriyanova, Galina S.

    2015-01-01

    The results of the experimental study of the influence of the environment surrounding the surface of the crystallites of a KClO 3 powder on the distribution of the spin-spin and spin-lattice relaxation times for 35 Cl nuclear quadrupole resonance are described. It was found that the distributions of the spin-lattice relaxation times are unimodal and distributions of the spin-spin relaxation times are bimodal for all samples we studied. T 1 - T 2 and T 1ρ - T 2 correlations by means of the two-dimensional (2D) inverse Laplace transform are obtained. The efficiency of the method for the study of surface phenomena in solids is demonstrated.

  18. Characterization of mesoporous carbon prepared from date stems by H{sub 3}PO{sub 4} chemical activation

    Energy Technology Data Exchange (ETDEWEB)

    Hadoun, H., E-mail: hhadoun@hotmail.com [Nuclear Research Center, 2 Bd Frantz Fanon, Algiers (Algeria); Laboratory of Reaction Genius, Mechanical and Processes Genius Faculty, University of Sciences and Technology Houari – Boumediene, BP n°32, El alia, bab ezzouar, 16111 Algiers (Algeria); Sadaoui, Z. [Laboratory of Reaction Genius, Mechanical and Processes Genius Faculty, University of Sciences and Technology Houari – Boumediene, BP n°32, El alia, bab ezzouar, 16111 Algiers (Algeria); Souami, N.; Sahel, D.; Toumert, I. [Nuclear Research Center, 2 Bd Frantz Fanon, Algiers (Algeria)

    2013-09-01

    The present work was focused on the determination of texture, morphology, crystanillity and oxygenated surface groups characteristics of an activated carbon prepared from date stems. Chemical activation of this precursor at different temperatures (450, 550 and 650 °C) was adopted using phosphoric acid as dehydrating agent at (2/1) impregnation ratio. Fourier transform infrared spectroscopy study was carried out to identify surface groups in date stems activated carbons. The microscopic structure was examined by nitrogen adsorption at 77 K. The interlayer spacing (d{sub 200} and d{sub 100}), stack height (L{sub c}), stack width (L{sub a}) and effective dimension L of the turbostratic crystallites (microcrystallite) in the date stems activated carbons were estimated from X-ray diffraction data (XRD). Results yielded a surface area, S{sub BET}, and total pore volume of 682, 1455, 1319 m{sup 2}/g and 0,343, 1,045 and 0.735 cm{sup 3}/g, for the carbon prepared at 450, 550 and 650 °C, respectively. Scanning electron microscopy exhibits a highly developed porosity which is in good agreement with the porous texture derived from gas adsorption data and these results confirm that the activated carbon is dominated by network of slit-shaped mesopores morphology and in some cases by varied micropores morphologies.

  19. Dynamic molecular structure of plant biomass-derived black carbon (biochar)

    Energy Technology Data Exchange (ETDEWEB)

    Keiluweit, M.; Nico, P.S.; Johnson, M.G.; Kleber, M.

    2009-11-15

    Char black carbon (BC), the solid residue of incomplete combustion, is continuously being added to soils and sediments due to natural vegetation fires, anthropogenic pollution, and new strategies for carbon sequestration ('biochar'). Here we present a molecular-level assessment of the physical organization and chemical complexity of biomass-derived chars and, specifically, that of aromatic carbon in char structures. BET-N{sub 2} surface area, X-ray diffraction (XRD), synchrotron-based Near-edge X-ray Absorption Fine Structure (NEXAFS), and Fourier transform infrared (FT-IR) spectroscopy are used to show how two plant materials (wood and grass) undergo analogous, but quantitatively different physical-chemical transitions as charring temperature increases from 100 to 700 C. These changes suggest the existence of four distinct categories of char consisting of a unique mixture of chemical phases and physical states: (i) in transition chars the crystalline character of the precursor materials is preserved, (ii) in amorphous chars the heat-altered molecules and incipient aromatic polycondensates are randomly mixed, (iii) composite chars consist of poorly ordered graphene stacks embedded in amorphous phases, and (iv) turbostratic chars are dominated by disordered graphitic crystallites. The molecular variations among the different char categories translate into differences in their ability to persist in the environment and function as environmental sorbents.

  20. Structural features of various kinds of carbon fibers as determined by small-angle X-ray scattering

    Energy Technology Data Exchange (ETDEWEB)

    Li, Denghua; Du, Sujun [Shanxi Transportation Research Institute, National and Local Joint Engineering Laboratory of Advanced Road Materials, Taiyuan (China); Lu, Chunxiang; Wu, Gangping; Yang, Yu; Wang, Lina [Chinese Academy of Sciences, National Engineering Laboratory for Carbon Fiber Technology, Institute of Coal Chemistry, Taiyuan (China)

    2016-11-15

    The structural features of polyacrylonitrile and pitch-based carbon fibers were analyzed from a comprehensive point of view by X-ray measurements and related techniques. The results indicated that the undulating graphite ribbon with embedded microvoid was the main structural unit for graphitic fibers. The void's parameters for these fibers could be obtained directly by small-angle X-ray scattering following the classic method deduced based on the typical two-phase system (i.e., Porod's law, Guinier's law and Debye's law). The non-graphitic fibers, however, were composed of two-dimensional turbostratic crystallites in the aggregation of microfibril and thus had a quasi two-phase structure (microfibril, interfibrillar amorphous structure and microvoid embedded within the microfibril). The extended Debye or Beaucage model in this case should be applied in order to obtain the structural parameters. It also revealed that the quasi two-phase system would complete its transformation to two-phase system during high-temperature graphitization. Therefore, the degree of graphitization was speculated to be the essential indicator distinguishing graphitic fibers from non-graphitic ones and would be helpful in understanding the transformation of structural features during the graphitization of carbon fibers. (orig.)

  1. Characterization of mesoporous carbon prepared from date stems by H3PO4 chemical activation

    International Nuclear Information System (INIS)

    Hadoun, H.; Sadaoui, Z.; Souami, N.; Sahel, D.; Toumert, I.

    2013-01-01

    The present work was focused on the determination of texture, morphology, crystanillity and oxygenated surface groups characteristics of an activated carbon prepared from date stems. Chemical activation of this precursor at different temperatures (450, 550 and 650 °C) was adopted using phosphoric acid as dehydrating agent at (2/1) impregnation ratio. Fourier transform infrared spectroscopy study was carried out to identify surface groups in date stems activated carbons. The microscopic structure was examined by nitrogen adsorption at 77 K. The interlayer spacing (d 200 and d 100 ), stack height (L c ), stack width (L a ) and effective dimension L of the turbostratic crystallites (microcrystallite) in the date stems activated carbons were estimated from X-ray diffraction data (XRD). Results yielded a surface area, S BET , and total pore volume of 682, 1455, 1319 m 2 /g and 0,343, 1,045 and 0.735 cm 3 /g, for the carbon prepared at 450, 550 and 650 °C, respectively. Scanning electron microscopy exhibits a highly developed porosity which is in good agreement with the porous texture derived from gas adsorption data and these results confirm that the activated carbon is dominated by network of slit-shaped mesopores morphology and in some cases by varied micropores morphologies.

  2. Facile synthesis of both needle-like and spherical hydroxyapatite nanoparticles: effect of synthetic temperature and calcination on morphology, crystallite size and crystallinity.

    Science.gov (United States)

    Wijesinghe, W P S L; Mantilaka, M M M G P G; Premalal, E V A; Herath, H M T U; Mahalingam, S; Edirisinghe, M; Rajapakse, R P V J; Rajapakse, R M G

    2014-09-01

    Synthetic hydroxyapatite (HA) nanoparticles, that mimic natural HA, are widely used as biocompatible coatings on prostheses to repair and substitute human bones. In this study, HA nanoparticles are prepared by precipitating them from a precursor solution containing calcium sucrate and ammonium dihydrogen orthophosphate, at a Ca/P mole ratio of 1.67:1, at temperatures, ranging from 10°C to 95°C. A set of products, prepared at different temperatures, is analyzed for their crystallinity, crystallite size, morphology, thermal stability and composition, by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and Fourier transform infrared (FT-IR) spectroscopic techniques, while the other set is analyzed after calcining the respective products, soon after their synthesis, for 3h, at 700°C. The as-prepared products, after 2h of drying, without any calcination, are not crystalline, but they grow very slowly into needle-like morphologies, as they are ripened with time. The percentage crystallinity of the final products increases from 15% to 52%, with increasing the preparative temperature. The calcined samples always produce spherical nanoparticles of essentially the same diameter, between 90 nm and 100 nm, which does not change due to aging and preparative temperatures. Therefore, the same method can be utilized to synthesize both spherical and needle-like nanoparticles of hydroxyapatite, with well-defined sizes and shapes. The ability to use readily available cheap raw materials, for the synthesis of such well-defined crystallites of hydroxyapatite, is an added advantage of this method, which may be explored further for the scaling up of the procedures to suit to industrial scale synthesis of such hydroxyapatite nanoparticles. Copyright © 2014 Elsevier B.V. All rights reserved.

  3. Analysis of crystallite size and microdeformation crystal lattice the tungsten carbide milling in mill high energy; Analise do tamanho do cristalito e microdeformacao da rede cristalina do carbeto de tugstenio moidos em moinho de alta energia

    Energy Technology Data Exchange (ETDEWEB)

    Silva, F.T. da; Nunes, M.A.M. [Universidade Federal do Rio Grande do Norte (PPGCEM/UFRN), Natal (Brazil). Programa de Pos-Graduacao em Ciencia e Engenharia de Materiais; Oliveira, R.M.V. de; Silva, G.G. da [Instituto Federal do Rio Grande do Norte (IFRN), Natal (Brazil); Souza, C.P. de; Gomes, U.U. [Universidade Federal do Rio Grande do Norte (UFRN), Natal (Brazil)

    2010-07-01

    The tungsten carbide (WC) has wide application due to its properties like high melting point, high hardness, wear resistance, oxidation resistance and good electrical conductivity. The microstructural characteristics of the starting powders influences the final properties of the carbide. In this context, the use of nanoparticle powders is an efficient way to improve the final properties of the WC. The high energy milling stands out from other processes to obtain nanometric powders due to constant microstructural changes caused by this process. Therefore, the objective is to undertake an analysis of microstructural characteristics on the crystallite size and microdeformations of the crystal lattice using the technique of X-ray diffraction (XRD) using the Rietveld refinement. The results show an efficiency of the milling process to reduce the crystallite size, leading to a significant deformation in the crystal lattice of WC from 5h milling. (author)

  4. Synthesis, structure and electrical properties of a new tin vanadium selenide

    International Nuclear Information System (INIS)

    Atkins, Ryan; Disch, Sabrina; Jones, Zachary; Haeusler, Ines; Grosse, Corinna; Fischer, Saskia F.; Neumann, Wolfgang; Zschack, Paul; Johnson, David C.

    2013-01-01

    The turbostratically disordered misfit layer compound (SnSe) 1.15 VSe 2 was synthesized and structurally characterized. Electrical transport measurements suggest this compound undergoes a charge or spin density wave (CDW or SDW) transition, which has not been observed in previous misfit layer compounds. The (SnSe) 1.15 VSe 2 compound, created through the modulated elemental reactants technique, contains highly oriented intergrowths of SnSe bilayers and VSe 2 structured Se–V–Se trilayers with abrupt interfaces between them perpendicular to the c-axis. X-ray diffraction data and transmission electron microscope images show that each constituent has in-plane crystallinity but that there is a random rotational disorder between the constituent layers. Temperature-dependent electrical resistivity data and Hall measurements are consistent with (SnSe) 1.15 VSe 2 being a metal, however an abrupt increase in the resistivity occurs between 30 and 100 K. The carrier concentration decreases by approximately 1 carrier per vanadium atom during this temperature interval. - Graphical abstract: Turbostratically disordered (SnSe) 1.15 VSe 2 . - Highlights: • New compound (SnSe) 1.15 VSe 2 . • Turbostratic disorder. • Charge density wave at 100 K

  5. Chlorine effect on the formation of carbon nanofibers.

    Science.gov (United States)

    Lin, Wang-Hua; Takahashi, Yusuke; Li, Yuan-Yao; Sakoda, Akiyoshi

    2012-12-01

    Platelet graphite nanofibers (GNFs) and turbostratic carbon nanofibers (CNFs) are synthesized by the thermal evaporation and decomposition of a polymer-based mixture at 700 degrees C using Ni as a catalyst. The mixture consists of poly(ethylene glycol) (PEG), serving as the carbon source, and hydrochloric acid solution (HCl(aq)), serving as the promoter/additive for the growth of CNFs. High-purity zigzag-shaped platelet GNFs form with 10 wt% HCl(aq) as an additive in the PEG. The diameters of the platelet GNFs are in the range of 40-60 nm, with lengths of a few micrometers. High-resolution transmission electron microscopy images indicate a high degree of graphitization and well ordered graphene layers along the fiber axis. In contrast, high-purity turbostratic CNFs form with 20 wt% HCl(aq) in the PEG. The diameter and length of the turbostratic CNFs are 20-40 nm and a few micrometers, respectively. The participation of HCl in the thermal process leads to the formation of Ni-Cl compounds. The amount of chlorine affects the shape of the Ni catalyst, which determines the type of CNF formed.

  6. Facile synthesis of both needle-like and spherical hydroxyapatite nanoparticles: Effect of synthetic temperature and calcination on morphology, crystallite size and crystallinity

    International Nuclear Information System (INIS)

    Wijesinghe, W.P.S.L.; Mantilaka, M.M.M.G.P.G.; Premalal, E.V.A.; Herath, H.M.T.U.; Mahalingam, S.; Edirisinghe, M.; Rajapakse, R.P.V.J.; Rajapakse, R.M.G.

    2014-01-01

    Synthetic hydroxyapatite (HA) nanoparticles, that mimic natural HA, are widely used as biocompatible coatings on prostheses to repair and substitute human bones. In this study, HA nanoparticles are prepared by precipitating them from a precursor solution containing calcium sucrate and ammonium dihydrogen orthophosphate, at a Ca/P mole ratio of 1.67:1, at temperatures, ranging from 10 °C to 95 °C. A set of products, prepared at different temperatures, is analyzed for their crystallinity, crystallite size, morphology, thermal stability and composition, by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and Fourier transform infrared (FT-IR) spectroscopic techniques, while the other set is analyzed after calcining the respective products, soon after their synthesis, for 3 h, at 700 °C. The as-prepared products, after 2 h of drying, without any calcination, are not crystalline, but they grow very slowly into needle-like morphologies, as they are ripened with time. The percentage crystallinity of the final products increases from 15% to 52%, with increasing the preparative temperature. The calcined samples always produce spherical nanoparticles of essentially the same diameter, between 90 nm and 100 nm, which does not change due to aging and preparative temperatures. Therefore, the same method can be utilized to synthesize both spherical and needle-like nanoparticles of hydroxyapatite, with well-defined sizes and shapes. The ability to use readily available cheap raw materials, for the synthesis of such well-defined crystallites of hydroxyapatite, is an added advantage of this method, which may be explored further for the scaling up of the procedures to suit to industrial scale synthesis of such hydroxyapatite nanoparticles. - Highlights: • Hydroxyapatite nanoparticles are synthesized using a simple precipitation method. • Both needle-like and spherical hydroxyapatite nanoparticles are synthesized. • The prepared

  7. Facile synthesis of both needle-like and spherical hydroxyapatite nanoparticles: Effect of synthetic temperature and calcination on morphology, crystallite size and crystallinity

    Energy Technology Data Exchange (ETDEWEB)

    Wijesinghe, W.P.S.L.; Mantilaka, M.M.M.G.P.G. [Department of Chemistry, Faculty of Science, University of Peradeniya, Peradeniya 20400 (Sri Lanka); Post-graduate Institute of Science, P.O. Box: 25, University of Peradeniya, Peradeniya 20400 (Sri Lanka); Premalal, E.V.A. [Department of Materials Science, Shizuoka University, Johoku, Naka-ku Hamamatsu, 432-8011 (Japan); Herath, H.M.T.U. [Department of Medical Laboratory Science, Faculty of Allied Health Sciences, University of Peradeniya, Peradeniya 20400 (Sri Lanka); Mahalingam, S.; Edirisinghe, M. [Department of Mechanical Engineering, University College London, London WC1E 7JE (United Kingdom); Rajapakse, R.P.V.J. [Department of Veterinary Pathobiology, Faculty of Veterinary, University of Peradeniya, Peradeniya 20400 (Sri Lanka); Rajapakse, R.M.G., E-mail: rmgr@pdn.ac.lk [Department of Chemistry, Faculty of Science, University of Peradeniya, Peradeniya 20400 (Sri Lanka); Post-graduate Institute of Science, P.O. Box: 25, University of Peradeniya, Peradeniya 20400 (Sri Lanka)

    2014-09-01

    Synthetic hydroxyapatite (HA) nanoparticles, that mimic natural HA, are widely used as biocompatible coatings on prostheses to repair and substitute human bones. In this study, HA nanoparticles are prepared by precipitating them from a precursor solution containing calcium sucrate and ammonium dihydrogen orthophosphate, at a Ca/P mole ratio of 1.67:1, at temperatures, ranging from 10 °C to 95 °C. A set of products, prepared at different temperatures, is analyzed for their crystallinity, crystallite size, morphology, thermal stability and composition, by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and Fourier transform infrared (FT-IR) spectroscopic techniques, while the other set is analyzed after calcining the respective products, soon after their synthesis, for 3 h, at 700 °C. The as-prepared products, after 2 h of drying, without any calcination, are not crystalline, but they grow very slowly into needle-like morphologies, as they are ripened with time. The percentage crystallinity of the final products increases from 15% to 52%, with increasing the preparative temperature. The calcined samples always produce spherical nanoparticles of essentially the same diameter, between 90 nm and 100 nm, which does not change due to aging and preparative temperatures. Therefore, the same method can be utilized to synthesize both spherical and needle-like nanoparticles of hydroxyapatite, with well-defined sizes and shapes. The ability to use readily available cheap raw materials, for the synthesis of such well-defined crystallites of hydroxyapatite, is an added advantage of this method, which may be explored further for the scaling up of the procedures to suit to industrial scale synthesis of such hydroxyapatite nanoparticles. - Highlights: • Hydroxyapatite nanoparticles are synthesized using a simple precipitation method. • Both needle-like and spherical hydroxyapatite nanoparticles are synthesized. • The prepared

  8. The Scherrer equation and the dynamical theory of X-ray diffraction.

    Science.gov (United States)

    Muniz, Francisco Tiago Leitão; Miranda, Marcus Aurélio Ribeiro; Morilla Dos Santos, Cássio; Sasaki, José Marcos

    2016-05-01

    The Scherrer equation is a widely used tool to determine the crystallite size of polycrystalline samples. However, it is not clear if one can apply it to large crystallite sizes because its derivation is based on the kinematical theory of X-ray diffraction. For large and perfect crystals, it is more appropriate to use the dynamical theory of X-ray diffraction. Because of the appearance of polycrystalline materials with a high degree of crystalline perfection and large sizes, it is the authors' belief that it is important to establish the crystallite size limit for which the Scherrer equation can be applied. In this work, the diffraction peak profiles are calculated using the dynamical theory of X-ray diffraction for several Bragg reflections and crystallite sizes for Si, LaB6 and CeO2. The full width at half-maximum is then extracted and the crystallite size is computed using the Scherrer equation. It is shown that for crystals with linear absorption coefficients below 2117.3 cm(-1) the Scherrer equation is valid for crystallites with sizes up to 600 nm. It is also shown that as the size increases only the peaks at higher 2θ angles give good results, and if one uses peaks with 2θ > 60° the limit for use of the Scherrer equation would go up to 1 µm.

  9. Accelerated effects of nano-ZnO on phosphorus removal by Chlorella vulgaris: Formation of zinc phosphate crystallites.

    Science.gov (United States)

    Xiao, Huaixian; Liu, Na; Tian, Ke; Liu, Shixiang; Ge, Fei

    2018-09-01

    Nanoparticles have been reported to induce toxicity to aquatic organisms, however, their potential impacts on phosphorus removal from wastewater by algae are unclear. In this study, the effects of nanoparticle ZnO (nano-ZnO) on phosphate (PO 4 3- ) removal by a green alga Chlorella vulgaris were investigated. We found that PO 4 3- removal efficiency was accelerated with high concentrations of nano-ZnO (0.04-0.15mM) but reduced with low concentrations of nano-ZnO (0.005-0.04mM) compared to the control (without nano-ZnO), suggesting that PO 4 3- removal efficiency by C. vulgaris was related to nano-ZnO concentrations. Moreover, we observed changes of nano-ZnO morphology and detected element P on the surface of nano-ZnO by using transmission electronic microscopy (TEM) combined with energy dispersive X-ray spectroscopy (EDX), indicating that PO 4 3- was interacted with nano-ZnO or the dissolved Zn 2+ from nano-ZnO. Furthermore, we confirmed this interaction induced the formation of Zn 3 (PO 4 ) 2 crystallites sedimentation by employing X-ray diffraction analysis (XRD) and X-ray photoelectron spectroscopy (XPS), which finally accelerates the removal of PO 4 3- . Copyright © 2018 Elsevier B.V. All rights reserved.

  10. Synthesis, structure and electrical properties of a new tin vanadium selenide

    Energy Technology Data Exchange (ETDEWEB)

    Atkins, Ryan, E-mail: atkins@uoregon.edu [Department of Chemistry and Materials Science Institute, University of Oregon, Eugene, OR 97403 (United States); Disch, Sabrina, E-mail: disch@ill.fr [Institut Laue-Langevin (ILL), F-38042 Grenoble (France); Jones, Zachary, E-mail: zjones@chem.ucsb.edu [Department of Chemistry and Materials Science Institute, University of Oregon, Eugene, OR 97403 (United States); Haeusler, Ines, E-mail: haeusler@physik.hu-berlin.de [Novel Materials, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489 Berlin (Germany); Grosse, Corinna, E-mail: Corinna.Grosse@physik.hu-berlin.de [Novel Materials, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489 Berlin (Germany); Fischer, Saskia F., E-mail: Saskia.Fischer@physik.hu-berlin.de [Novel Materials, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489 Berlin (Germany); Neumann, Wolfgang, E-mail: wsn@uoregon.edu [Department of Chemistry and Materials Science Institute, University of Oregon, Eugene, OR 97403 (United States); Zschack, Paul, E-mail: zschack@bnl.gov [Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439 (United States); Johnson, David C., E-mail: davej@uoregon.edu [Department of Chemistry and Materials Science Institute, University of Oregon, Eugene, OR 97403 (United States)

    2013-06-15

    The turbostratically disordered misfit layer compound (SnSe){sub 1.15}VSe{sub 2} was synthesized and structurally characterized. Electrical transport measurements suggest this compound undergoes a charge or spin density wave (CDW or SDW) transition, which has not been observed in previous misfit layer compounds. The (SnSe){sub 1.15}VSe{sub 2} compound, created through the modulated elemental reactants technique, contains highly oriented intergrowths of SnSe bilayers and VSe{sub 2} structured Se–V–Se trilayers with abrupt interfaces between them perpendicular to the c-axis. X-ray diffraction data and transmission electron microscope images show that each constituent has in-plane crystallinity but that there is a random rotational disorder between the constituent layers. Temperature-dependent electrical resistivity data and Hall measurements are consistent with (SnSe){sub 1.15}VSe{sub 2} being a metal, however an abrupt increase in the resistivity occurs between 30 and 100 K. The carrier concentration decreases by approximately 1 carrier per vanadium atom during this temperature interval. - Graphical abstract: Turbostratically disordered (SnSe){sub 1.15}VSe{sub 2}. - Highlights: • New compound (SnSe){sub 1.15}VSe{sub 2}. • Turbostratic disorder. • Charge density wave at 100 K.

  11. Radiation induced growth of micro crystallites

    International Nuclear Information System (INIS)

    Meisel, D.

    1991-01-01

    Generation of colloidal particles during the radiolysis of aqueous solutions was already observed in the early days of radiation chemistry. Systematic studies using radiation chemistry techniques as synthetic tools in the preparation of colloidal particles, primarily metallic particles, were begun approximately a decade ago in conjunction since they were found to catalyze multi-electron redox processes. A large number of metallic colloidal particles were then synthesized, including silver, gold, platinum, iridium, nickel, cadmium, and others. More recently, attention has turned to semiconductor colloidal particles. The stimulus to these studies is the observation of quantum size effects in small semiconductor particles that exhibit hybrid properties between those of the molecular species and the solid state bulk material. In the following we discuss our own observations on the evolution of semiconductor particles whose growth has been initiated by pulse radiolysis. 13 refs., 2 figs

  12. Dimensional confinement in carbon-based structures - from 3D to 1D

    International Nuclear Information System (INIS)

    Richter, Nils; Braatz, Marie-Luise; Klaeui, Mathias; Chen, Zongping; Narita, Akimitsu; Musseau, Fabienne; Weber, Nils-Eike; Muellen, Klaus

    2017-01-01

    We present an overview of charge transport in selected one-, two- and three-dimensional carbon-based materials with exciting properties. The systems are atomically defined bottom-up synthesized graphene nanoribbons, doped graphene and turbostratic graphene micro-disks, where up to 100 graphene layers are rotationally stacked. For turbostratic graphene we show how this system lends itself to spintronic applications. This follows from the inner graphene layers where charge carriers are protected and thus highly mobile. Doped graphene and graphene nanoribbons offer the possibility to tailor the electronic properties of graphene either by introducing heteroatoms or by confining the system geometrically. Herein, we describe the most recent developments of charge transports in these carbon systems. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Dimensional confinement in carbon-based structures - from 3D to 1D

    Energy Technology Data Exchange (ETDEWEB)

    Richter, Nils; Braatz, Marie-Luise; Klaeui, Mathias [Johannes Gutenberg Universitaet, Institut fuer Physik, Mainz (Germany); Graduate School of Excellence Materials Science in Mainz, Mainz (Germany); Chen, Zongping; Narita, Akimitsu [Max Planck Institut fuer Polymerforschung, Mainz (Germany); Musseau, Fabienne [Johannes Gutenberg Universitaet, Institut fuer Physik, Mainz (Germany); Weber, Nils-Eike [Carbon Materials Innovation Center (CMIC), BASF SE, Ludwigshafen (Germany); Muellen, Klaus [Max Planck Institut fuer Polymerforschung, Mainz (Germany); Johannes Gutenberg Universitaet, Institut fuer Physikalische Chemie, Mainz (Germany)

    2017-11-15

    We present an overview of charge transport in selected one-, two- and three-dimensional carbon-based materials with exciting properties. The systems are atomically defined bottom-up synthesized graphene nanoribbons, doped graphene and turbostratic graphene micro-disks, where up to 100 graphene layers are rotationally stacked. For turbostratic graphene we show how this system lends itself to spintronic applications. This follows from the inner graphene layers where charge carriers are protected and thus highly mobile. Doped graphene and graphene nanoribbons offer the possibility to tailor the electronic properties of graphene either by introducing heteroatoms or by confining the system geometrically. Herein, we describe the most recent developments of charge transports in these carbon systems. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. Neutron diffraction on a large block mosaic crystal

    International Nuclear Information System (INIS)

    Kim Chir Sen; Nitts, V.V.

    1985-01-01

    The neutron diffraction by the mosaic single crystal with size of crystallites sufficient to achieve the primary extinction saturation is considered. Two cases where the proportionality between the reflection intensity and the structure amplitude is performed are analysed. Such a dependence is convenient for structure investigations. The difficulties connected with the accounting of the extinction are eliminated considerably

  15. Comparison of Physicochemical Properties of Nano- and Microsized Crystals in the Urine of Calcium Oxalate Stone Patients and Control Subjects

    Directory of Open Access Journals (Sweden)

    Jie Gao

    2014-01-01

    Full Text Available Purpose. To compare the properties of different sizes of urinary crystallites between calcium oxalate (CaOx calculi patients and healthy controls. Methods. We studied the average particle size, size distribution, intensity-autocorrelation curve, zeta potential (ζ, conductivity, mobility, aggregation state, and stability of different sizes of urinary crystallites by nanoparticle size analysis and transmission electron microscopy after filtration through a microporous membrane with an aperture size from 0.22 μm to 0.45, 1.2, 3, and 10 μm. Results. The urinary crystallites of the CaOx calculi patients were uneven and much easy to aggregate than those of controls. The number of large-sized crystallites of the patients was significantly more than that of the controls. The main components of the nanosized urinary crystallites in patients were CaOx monohydrate (COM, uric acid, and β-calcium phosphate, and these components were basically similar to those of the microsized urinary crystallites. The urinary crystallites of the calculi patients were easier to aggregate than that of the controls, and the small-sized urinary crystallites were much easier to agglomerate. Conclusions. The urinary system of CaOx calculi patients is unstable and highly susceptible to urinary crystallite aggregation. The rapid aggregation of urinary crystallites may be the key factor affecting urolithiasis formation.

  16. Identification of a deleterious phase in photocatalyst based on Cd1 - xZnxS/Zn(OH)2 by simulated XRD patterns.

    Science.gov (United States)

    Cherepanova, Svetlana; Markovskaya, Dina; Kozlova, Ekaterina

    2017-06-01

    The X-ray diffraction (XRD) pattern of a deleterious phase in the photocatalyst based on Cd 1 - x Zn x S/Zn(OH) 2 contains two relatively intense asymmetric peaks with d-spacings of 2.72 and 1.56 Å. Very small diffraction peaks with interplanar distances of (d) ≃ 8.01, 5.40, 4.09, 3.15, 2.49 and 1.35 Å are characteristic of this phase but not always observed. To identify this phase, the XRD patterns for sheet-like hydroxide β-Zn(OH) 2 and sheet-like hydrozincite Zn 5 (CO 3 ) 2 (OH) 6 as well as for turbostratic hydrozincite were simulated. It is shown that the XRD pattern calculated on the basis of the last model gives the best correspondence with experimental data. Distances between layers in the turbostratically disordered hydrozincite fluctuate around d ≃ 8.01 Å. This average layer-to-layer distance is significantly higher than the interlayer distance 6.77 Å in the ordered Zn 5 (CO 3 ) 2 (OH) 6 probably due to a deficiency of CO 3 2- anions, excess OH - and the presence of water molecules in the interlayers. It is shown by variable-temperature XRD and thermogravimetric analysis (TGA) that the nanocrystalline turbostratic nonstoichiometric hydrozincite-like phase is quite thermostable. It decomposes into ZnO in air above 473 K.

  17. Effect of iron on the production of high electrocatalytic activity carbons from ferrocene - PFA mixtures

    International Nuclear Information System (INIS)

    Cashion, J.D.; Brown, L.J.; Ozaki, J.; Yamada, K.; Nozawa, K.; Matsui, K.; Oya, A.

    1999-01-01

    Full text: We have previously studied the carbonisation of mixtures of ferrocene and poly(furfury 1 alcohol) (PFA) which, after heating at 700 deg C, produces electrodes with an electrocatalytic activity comparable to that of platinum. The carbons have a distinctive furry structure under the SEM and an XRD profile characteristic of turbostratic carbon. The iron had been converted to a mixture of α- and γiron and cementite, Fe 3 C and we conjectured that the furry carbon could be formed by the exsolution of carbon from the γ iron on cooling. The present experiments have shown that changing the cooling rate has only a small effect so exsolution is not the cause. However, the increased conductivity correlates well with the proportion of turbostratic carbon which, in turn, correlates with the percentage of cementite. The turbostratic carbon forms cages surrounding an iron phase, presumably the cementite. The conductivity data can be fitted well to either a power law or logarithmic behaviour above the percolation theory critical concentration. The normal percolation theory model for conductivity assumes a growing volume of good conductor in an insulating matrix. However, our system has a good conductor in a matrix of moderate conductor, the conductivity of which is not constant but is increasing under heat treatment at the same time as the good conductor volume is increasing. Some possible analyses will be given

  18. Anion mediated polytype selectivity among the basic salts of Co(II)

    Science.gov (United States)

    Ramesh, T. N.; Rajamathi, Michael; Vishnu Kamath, P.

    2006-08-01

    Basic salts of Co(II) crystallize in the rhombohedral structure. Two different polytypes, 3R 1 and 3R 2, with distinct stacking sequences of the metal hydroxide slabs, are possible within the rhombohedral structure. These polytypes are generated by simple translation of successive layers by (2/3, 1/3, z) or (1/3, 2/3, z). The symmetry of the anion and the mode of coordination influences polytype selection. Cobalt hydroxynitrate crystallizes in the structure of the 3R 2 polytype while the hydroxytartarate, hydroxychloride and α-cobalt hydroxide crystallize in the structure of the 3R 1 polytype. Cobalt hydroxysulfate is turbostratically disordered. The turbostratic disorder is a direct consequence of the mismatch between the crystallographically defined interlayer sites generated within the crystal and the tetrahedral symmetry of the SO 42- ions.

  19. Studies of interaction of amines with TOPO/TOP capped CdSe quantum dots: Role of crystallite size and oxidation potential

    International Nuclear Information System (INIS)

    Sharma, Shailesh N.; Sharma, Himani; Singh, Gurmeet; Shivaprasad, S.M.

    2008-01-01

    This work reports the interaction of aliphatic (triethyl amine, butyl amine) and aromatic amines (PPD, aniline) with CdSe quantum dots of varied sizes. The emission properties and lifetime values of CdSe quantum dots were found to be dependent on the oxidation potential of amines and crystallite sizes. Smaller CdSe quantum dots (size ∼5 nm) ensure better surface coverage of amines and hence higher quenching efficiency of amines could be realized as compared to larger CdSe quantum dots (size ∼14 nm). Heterogeneous quenching of amines due to the presence of accessible and inaccessible set of CdSe fluorophores is indicated. PPD owing to its lowest oxidation potential (∼0.26 V) has been found to have higher quenching efficiency as compared to other amines TEA and aniline having oxidation potentials ∼0.66 and >1.0 V, respectively. Butyl amine on the other hand, plays a dual role: its post-addition acts as a quencher for smaller and enhances emission for larger CdSe quantum dots, respectively. The beneficial effect of butyl amine in enhancing emission intensity could be attributed to enhance capping effect and better passivation of surface-traps

  20. In situ characterization of thin film growth: Boron nitride on silicon

    International Nuclear Information System (INIS)

    Fukarek, W.

    2001-01-01

    Real-time ellipsometry (RTE) in combination with particle flux measurement is applied to ion beam assisted deposition of boron nitride (BN) films. RTE is used as a tool for process diagnostic to improve the deposition stability. A novel technique for the determination of absolute density depth profiles from dynamic growth rate data and film forming particle flux is employed. From real-time cantilever curvature measurement and simultaneously recorded film thickness data instantaneous stress depth profiles are derived with a depth resolution in the nm range. The synergistic effects on the information obtained from RTE, particle flux, and cantilever bending data are demonstrated. The density of turbostratic BN (tBN) is found to increase slightly with film thickness while the compressive stress decreases, indicating an increasing quality and/or size of crystallites in the course of film growth. Refractive index and density depth profiles in cubic BN (cBN) films correspond perfectly to structural information obtained from dark field transmission electron microscope graphs. The established tBN/cBN two-layer model is found to be a crude approximation that has to be replaced by a three-layer model including nucleation, grain growth, and coalescence of cBN. The instantaneous compressive stress in a homogeneous tBN film is found to decrease, while the density increases during growth. The instantaneous compressive stress depth profiles in cBN films are more complex and not easy to understand but reliable information on the structural evolution during growth can be extracted

  1. Carboxyl functionalized carbon fibers with preserved tensile strength and electrochemical performance used as anodes of structural lithium-ion batteries

    International Nuclear Information System (INIS)

    Feng, Mengjie; Wang, Shubin; Yu, Yalin; Feng, Qihang; Yang, Jiping; Zhang, Boming

    2017-01-01

    Highlights: • Carboxyl functionalized CF is acquired by simple chemical oxidation method. • These CF have preserved the tensile strength, better electrochemical properties. • The presence of H_3PO_4 prevented the turbostratic carbon from over-oxidization. • There CF can be used as anodes of multifunctional structural battery. • The preservation and improvement is result from the hindered over-oxidization. - Abstract: Carboxyl functionalized carbon fibers with preserved tensile strength and electrochemical properties were acquired through a simple chemical oxidation method, and the proposed underlying mechanism was verified. The surface of carboxyl functionalizing carbon fibers is necessary in acquiring functional groups on the surface of carbon fibers to further improve the thermal, electrical or mechanical properties of the fibers. Functionalization should preserve the tensile strength and electrochemical properties of carbon fibers, because the anodes of structural batteries need to have high strength and electrochemical properties. Functionalized with mixed H_2SO_4/HNO_3 considerably reduced the tensile strength of carbon fibers. By contrast, the appearance of H_3PO_4 preserved the tensile strength of functionalized carbon fibers, reduced the dispersion level of tensile strength values, and effectively increased the concentration of functional acid groups on the surface of carbon fibers. The presence of phosphoric acid hindered the over-oxidation of turbostratic carbon, and consequently preserved the tensile strength of carbon fibers. The increased proportion of turbostratic carbon on the surface of carbon fibers concurrently enhanced the electrochemical properties of carbon fibers.

  2. Sulfonated poly(ether ether ketone)/poly(vinyl alcohol) sensitizing system for solution photogeneration of small Ag, Au, and Cu crystallites.

    Science.gov (United States)

    Korchev, A S; Shulyak, T S; Slaten, B L; Gale, W F; Mills, G

    2005-04-28

    Illumination of air-free aqueous solutions containing sulfonated poly(ether ether ketone) and poly(vinyl alcohol) with 350 nm light results in benzophenone ketyl radicals of the polyketone. The polymer radicals form with a quantum yield 0.02 and decay with a second-order rate constant 6 orders of magnitude lower than that of typical alpha-hydroxy radicals. Evidence is presented that the polymeric benzophenone ketyl radicals reduce Ag+, Cu2+, and AuCl4- to metal particles of nanometer dimensions. Decreases in the reduction rates with increasing Ag(I), Cu(II), and Au(III) concentrations are explained using a kinetic model in which the metal ions quench the excited state of the polymeric benzophenone groups, which forms the macromolecular radicals. Quenching is fastest for Ag+, whereas Cu2+ and AuCl4- exhibit similar rate constants. Particle formation becomes more complex as the number of equivalents needed to reduce the metal ions increases; the Au(III) system is an extreme case where the radical reactions operate in parallel with secondary light-initiated and thermal reduction channels. For each metal ion, the polymer-initiated photoreactions produce crystallites possessing distinct properties, such as a very strong plasmon in the Ag case or the narrow size distribution exhibited by Au particles.

  3. Digital selective growth of a ZnO nanowire array by large scale laser decomposition of zinc acetate.

    Science.gov (United States)

    Hong, Sukjoon; Yeo, Junyeob; Manorotkul, Wanit; Kang, Hyun Wook; Lee, Jinhwan; Han, Seungyong; Rho, Yoonsoo; Suh, Young Duk; Sung, Hyung Jin; Ko, Seung Hwan

    2013-05-07

    We develop a digital direct writing method for ZnO NW micro-patterned growth on a large scale by selective laser decomposition of zinc acetate. For ZnO NW growth, by replacing the bulk heating with the scanning focused laser as a fully digital local heat source, zinc acetate crystallites can be selectively activated as a ZnO seed pattern to grow ZnO nanowires locally on a larger area. Together with the selective laser sintering process of metal nanoparticles, more than 10,000 UV sensors have been demonstrated on a 4 cm × 4 cm glass substrate to develop all-solution processible, all-laser mask-less digital fabrication of electronic devices including active layer and metal electrodes without any conventional vacuum deposition, photolithographic process, premade mask, high temperature and vacuum environment.

  4. Carboxyl functionalized carbon fibers with preserved tensile strength and electrochemical performance used as anodes of structural lithium-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Mengjie [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Wang, Shubin, E-mail: shubinwang@buaa.edu.cn [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Yu, Yalin; Feng, Qihang; Yang, Jiping; Zhang, Boming [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China)

    2017-01-15

    Highlights: • Carboxyl functionalized CF is acquired by simple chemical oxidation method. • These CF have preserved the tensile strength, better electrochemical properties. • The presence of H{sub 3}PO{sub 4} prevented the turbostratic carbon from over-oxidization. • There CF can be used as anodes of multifunctional structural battery. • The preservation and improvement is result from the hindered over-oxidization. - Abstract: Carboxyl functionalized carbon fibers with preserved tensile strength and electrochemical properties were acquired through a simple chemical oxidation method, and the proposed underlying mechanism was verified. The surface of carboxyl functionalizing carbon fibers is necessary in acquiring functional groups on the surface of carbon fibers to further improve the thermal, electrical or mechanical properties of the fibers. Functionalization should preserve the tensile strength and electrochemical properties of carbon fibers, because the anodes of structural batteries need to have high strength and electrochemical properties. Functionalized with mixed H{sub 2}SO{sub 4}/HNO{sub 3} considerably reduced the tensile strength of carbon fibers. By contrast, the appearance of H{sub 3}PO{sub 4} preserved the tensile strength of functionalized carbon fibers, reduced the dispersion level of tensile strength values, and effectively increased the concentration of functional acid groups on the surface of carbon fibers. The presence of phosphoric acid hindered the over-oxidation of turbostratic carbon, and consequently preserved the tensile strength of carbon fibers. The increased proportion of turbostratic carbon on the surface of carbon fibers concurrently enhanced the electrochemical properties of carbon fibers.

  5. Anion mediated polytype selectivity among the basic salts of Co(II)

    International Nuclear Information System (INIS)

    Ramesh, T.N.; Rajamathi, Michael; Vishnu Kamath, P.

    2006-01-01

    Basic salts of Co(II) crystallize in the rhombohedral structure. Two different polytypes, 3R 1 and 3R 2 , with distinct stacking sequences of the metal hydroxide slabs, are possible within the rhombohedral structure. These polytypes are generated by simple translation of successive layers by (2/3, 1/3, z) or (1/3, 2/3, z). The symmetry of the anion and the mode of coordination influences polytype selection. Cobalt hydroxynitrate crystallizes in the structure of the 3R 2 polytype while the hydroxytartarate, hydroxychloride and α-cobalt hydroxide crystallize in the structure of the 3R 1 polytype. Cobalt hydroxysulfate is turbostratically disordered. The turbostratic disorder is a direct consequence of the mismatch between the crystallographically defined interlayer sites generated within the crystal and the tetrahedral symmetry of the SO 4 2- ions. - Graphical abstract: (a) Observed PXRD pattern of cobalt hydroxytartarate compared with the DIFFaX simulated patterns of (b) 3R 1 and (c) 3R 2 polytypes, respectively

  6. The thermal expansion of a highly crystalline hexagonal BC2N compound synthesized under high temperature and pressure

    International Nuclear Information System (INIS)

    Wu Qinghua; Liu Zhongyuan; Hu Qianku; Li Hui; He Julong; Yu Dongli; Li Dongchun; Tian Yongjun

    2006-01-01

    The thermal expansion has been investigated for a highly crystalline hexagonal BC 2 N compound synthesized by the compression of a turbostratic B-C-N precursor with iron catalyst at the high temperature of 1500 deg. C and the high pressure of 5.5 GPa. The thermal expansion in the c direction is large and linear with an expansion coefficient of 35.86 x 10 -6 K -1 up to 1000 deg. C, while in the basal plane, the a dimension displays a slight linear contraction up to 750 deg. C with a contraction coefficient of -8.76 x 10 -7 K -1 , but above 750 deg. C a linear expansion is observed with a larger expansion coefficient of 1.52 x 10 -6 K -1

  7. Electron microprobe analyses of selected samples from deep rock disposal experiment No. 1

    International Nuclear Information System (INIS)

    Hlava, P.F.; Chambers, W.F.

    1976-04-01

    Deep Rock Disposal Experiment No. 1 was designed to provide information about the interaction between a molten, glass-based, nuclear waste simulant and rock material. Selected samples from this experiment were examined by optical microscopy and electron probe microanalysis. Analysis of the homogenized material in the convection cell that was created in the central portion of the melt region shows that an amount of rock equal to about one-half of the original amount of waste simulant was incorporated in the melt during the experiment. Stagnant melt at the sides of the cell formed a glass with large compositional gradients. A white band separated the convected and stagnant materials. The color of the band is attributed to light scattering by small crystallites formed during cooling. Four types of crystallites grew from the melt: two oxides, a Mg--Fe borate, and a silicate. Spinel (MgO, Cr 2 O 3 , FeO (Fe 2 O 3 ), and NiO) was the most common crystallite in the glass. The spinel crystallites found within the convection cell displayed skeletal morphology and oscillatory zoning which indicates growth at varying temperatures as they were carried along by convection. A single cluster of nonskeletal (Fe,Cr) 2 O 3 crystallites was found at the bottom of the melt zone where convection did not occur. Mg--Fe borate crystallites grew in clusters in the central portion of the convection cell after convection ceased. A silicate similar to Fe-rich diopside (CaMgSi 2 O 6 ) with unusual amounts of Ce 2 O 3 and other heavy metal oxides formed as larger crystallites in the stagnant melt at the side of the convection cell and as many very small crystallites in the white band

  8. Influence of Si-doping on heteroepitaxially grown a-plane GaN

    Energy Technology Data Exchange (ETDEWEB)

    Wieneke, Matthias; Bastek, Barbara; Noltemeyer, Martin; Hempel, Thomas; Rohrbeck, Antje; Witte, Hartmut; Veit, Peter; Blaesing, Juergen; Dadgar, Armin; Christen, Juergen; Krost, Alois [Otto-von-Guericke-Universitaet Magdeburg, FNW/IEP, Universitaetsplatz 2, 39106 Magdeburg (Germany)

    2011-07-01

    Si-doped a-plane GaN samples with nominal doping levels up to 10{sup 20} cm{sup -3} were grown on r-plane sapphire by metal organic vapor phase epitaxy. Silane flow rates higher than 59 nmol/min lead to three dimensional grown crystallites as revealed by scanning electron microscopy. High resolution X-ray diffraction, photoluminescence and cathodoluminescence suggest considerably reduced defect densities in the large micrometer-sized GaN crystallites. Especially, transmission electron microscopy images verify a very low density of basal plane stacking faults less than 10{sup 4} cm{sup -1} in these crystallites consisting of heteroepitaxially grown a-plane GaN. In our presentation the influence of the Si doping on the basal plane stacking faults will be discussed.

  9. High Capacity of Hard Carbon Anode in Na-Ion Batteries Unlocked by PO x Doping

    Energy Technology Data Exchange (ETDEWEB)

    Li, Zhifei; Ma, Lu; Surta, Todd Wesley; Bommier, Clement; Jian, Zelang; Xing, Zhenyu; Stickle, William F.; Dolgos, Michelle; Amine, Khalil; Lu, Jun; Wu, Tianpin; Ji, Xiulei

    2016-08-12

    The capacity of hard carbon anodes in Na-ion batteries 2.5 rarely reaches values beyond 300 mAh/g. We report that doping POx into local structures of hard carbon increases its reversible capacity from 283 to 359 mAh/g. We confirm that the doped POx is redox inactive by X-ray adsorption near edge structure measurements, thus not contributing to the higher capacity. We observe two significant changes of hard carbon's local structures caused by doping. First, the (002) d-spacing inside the turbostratic nanodomains is increased, revealed by both laboratory and synchrotron X-ray diffraction. Second, doping turns turbostratic nanodomains more defective along ab planes, indicated by neutron total scattering and the associated pair distribution function studies. The local structural changes of hard carbon are correlated to the higher capacity, where both the plateau and slope regions in the potential profiles are enhanced. Our study demonstrates that Na-ion storage in hard carbon heavily depends on carbon local structures, where such structures, despite being disordered, can be tuned toward unusually high capacities.

  10. A Novel Synthesis Routine for Woodwardite and Its Affinity towards Light (La, Ce, Nd and Heavy (Gd and Y Rare Earth Elements

    Directory of Open Access Journals (Sweden)

    Sirio Consani

    2018-01-01

    Full Text Available A synthetic Cu-Al-SO4 layered double hydroxide (LDH, analogue to the mineral woodwardite [Cu1−xAlx(SO4x/2(OH2·nH2O], with x < 0.5 and n ≤ 3x/2, was synthesised by adding a solution of Cu and Al sulphates to a solution with NaOH. The pH values were kept constant at 8.0 and 10.0 by a continuous addition of NaOH. The material obtained had poor crystallinity, turbostratic structure, and consisted of nanoscopic crystallites. The analyses performed in order to characterise the obtained materials (X-ray diffraction (XRD, thermogravimetry (TG, and Fourier Transform Infra-Red (FTIR spectroscopy showed that the Cu-Al-SO4 LDH is very similar to woodwardite, although it has a smaller layer spacing, presumably due to a lesser water content than in natural samples. The synthesis was performed by adding light rare earth elements (LREEs (La, Ce, and Nd and heavy rare earth elements (HREEs (Gd and Y in order to test the affinity of the Cu-Al-SO4 LDH to the incorporation of REEs. The concentration of rare earth elements (REEs in the solid fraction was in the range of 3.5–8 wt %. The results showed a good affinity for HREE and Nd, especially for materials synthesised at pH 10.0, whereas the affinities for Ce and La were much lower or non-existent. The thermal decomposition of the REE-doped materials generates a mixture of Cu, Al, and REE oxides, making them interesting as precursors in REE oxide synthesis.

  11. Mechanical activation of graphite in air: A way to advanced carbon nanomaterials

    Energy Technology Data Exchange (ETDEWEB)

    Baklanova, O.N., E-mail: baklanova@ihcp.ru; Drozdov, V.A.; Lavrenov, A.V.; Vasilevich, A.V.; Muromtsev, I.V.; Trenikhin, M.V.; Arbuzov, A.B.; Likholobov, V.A.; Gorbunova, O.V.

    2015-10-15

    A high-energy planetary mill AGO-2 was used for mechanical activation of synthetic graphite with the particle size of 25–30 μm and specific surface area S{sub BET} = 3.0 m{sup 2}/g in air for 1–60 min at a 100 g acceleration of milling bodies. The X-ray diffraction, Raman spectroscopy and electron microscopy studies showed that the 60 min mechanical activation of graphite decreases the number of graphene layers in graphite crystallites to 8–12 and induces their turbostratic disorder. The size of graphite particles decreases to 6.9 μm after 30 min of mechanical activation and increases to 12.1 μm when the time of mechanical activation is extended to 60 min. Similar changes are observed for the true density of graphite: after 60 min of mechanical activation it becomes equal to 2.48 ⋅ 10{sup 3} kg/m{sup 3}, which is by 10% higher than the true density of graphite not subjected to such treatment. The specific adsorption surface of graphite (S{sub BET}) reaches its maximum values, 427–460 m{sup 2}/g, after 7–12 min of mechanical activation. A further increase in the activation time to 30–60 min decreases S{sub BET} of graphite to 230–250 m{sup 2}/g. Due to attrition of steel milling bodies caused by mechanical activation, iron is accumulated in the samples and its content exceeds 5%. Iron is distributed uniformly in the graphite as the 30–100 and 3–5 nm particles of hematite and iron carbide. The IR spectroscopy study revealed the formation of 0.8 mEq/g of the hydroxyl, phenolic, lactone and carbonyl groups on the graphite surface in the course of mechanical activation. - Highlights: • Graphite was mechanically activated in air at a 100 g acceleration of milling bodies. • The amount of graphenes in graphite crystallites decreases to 8–12. • Graphite transforms into a nanocrystalline X-ray amorphous state. • A metal–graphite composite with the 30–100 and 3–5 nm iron particles is formed. • Oxygen-containing groups in the amount of

  12. Surface growth mechanisms and structural faulting in the growth of large single and spherulitic titanosilicate ETS-4 crystals

    Science.gov (United States)

    Miraglia, Peter Q.; Yilmaz, Bilge; Warzywoda, Juliusz; Sacco, Albert

    2004-10-01

    Morphological, surface and crystallographic analyses of titanosilicate ETS-4 products, with diverse habits ranging from spherulitic particles composed of submicron crystallites to large single crystals, are presented. Pole figures revealed that crystal surfaces with a-, b- and c- axes corresponded to , and directions, respectively. Thus, technologically important 8-membered ring pores and titania chains in ETS-4 run along the b-axis of single crystals and terminate at the smallest crystal face. Height of the spiral growth steps observed on {1 0 0} and {0 0 1} surfaces corresponded to the interplanar spacings associated with their crystallographic orientation, and is equivalent to the thickness of building units that form the ETS-4 framework. Data suggest that the more viscous synthesis mixtures, with a large driving force for growth, increased the two- and three-dimensional nucleation, while limiting the transport of nutrients to the growth surface. These conditions increase the tendency for stacking fault formation on {1 0 0} surfaces and small angle branching, which eventually results in spherulitic growth. The growth of high quality ETS-4 single crystals (from less viscous synthesis mixtures) occurred at lower surface nucleation rates. Data suggest that these high quality, large crystals grew due to one-dimensional nucleation at spiral hillocks, and indicate that under these conditions un-faulted growth is preferred.

  13. Shungite as the natural pantry of nanoscale reduced graphene oxide

    Directory of Open Access Journals (Sweden)

    Elena F. Sheka

    2014-01-01

    Full Text Available Shungite is presented as a natural carbon allotrope of a multilevel fractal structure that is formed by a successive aggregation of ~1 nm reduced graphene oxide nanosheets. Turbostratic stacks of the sheets of ~1.5 nm in thickness and globular composition of the stacks of ~6 nm in size determine the secondary and tertiary levels of the structure. Aggregates of globules of tens of nanometers complete the structure. Molecular theory of graphene oxide, supported by large experience gained by the modern graphene science, has led to the foundation of the suggested presentation. The microscopic view has found a definite confirmation when analyzing the available empirical appearance of shungite. To our knowledge, this is the first time a geological process is described at quantum level.

  14. Chemical adhesion rather than mechanical retention enhances resin bond durability of a dental glass-ceramic with leucite crystallites

    International Nuclear Information System (INIS)

    Meng, X F; Yoshida, K; Gu, N

    2010-01-01

    This study aims to evaluate the effect of chemical adhesion by a silane coupler and mechanical retention by hydrofluoric acid (HFA) etching on the bond durability of resin to a dental glass ceramic with leucite crystallites. Half of the ceramic plates were etched with 4.8% HFA (HFA group) for 60 s, and the other half were not treated (NoHFA group). The scale of their surface roughness and rough area was measured by a 3D laser scanning microscope. These plates then received one of the following two bond procedures to form four bond test groups: HFA/cement, NoHFA/cement, HFA/silane/cement and NoHFA/silane/cement. The associated micro-shear bond strength and bond failure modes were tested after 0 and 30 000 thermal water bath cycles. Four different silane/cement systems (Monobond S/Variolink II, GC Ceramic Primer/Linkmax HV, Clearfil Ceramic Primer/Clearfil Esthetic Cement and Porcelain Liner M/SuperBond C and B) were used. The data for each silane/cement system were analyzed by three-way ANOVA. HFA treatment significantly increased the surface R a and R y values and the rough area of the ceramic plates compared with NoHFA treatment. After 30 000 thermal water bath cycles, the bond strength of all the test groups except the HFA/Linkmax HV group was significantly reduced, while the HFA/Linkmax HV group showed only adhesive interface failure. The other HFA/cement groups and all NoHFA/cement groups lost bond strength completely, and all NoHFA/silane/cement groups with chemical adhesion had significantly higher bond strength and more ceramic cohesive failures than the respective HFA/cement groups with mechanical retention. The result of the HFA/silane/cement groups with both chemical adhesion and mechanical retention revealed that HFA treatment could enhance the bond durability of resin/silanized glass ceramics, which might result from the increase of the chemical adhesion area on the ceramic rough surface and subsequently reduced degradation speed of the silane coupler

  15. 2D Cross Sectional Analysis and Associated Electrochemistry of Composite Electrodes Containing Dispersed Agglomerates of Nanocrystalline Magnetite, Fe₃O₄.

    Science.gov (United States)

    Bock, David C; Kirshenbaum, Kevin C; Wang, Jiajun; Zhang, Wei; Wang, Feng; Wang, Jun; Marschilok, Amy C; Takeuchi, Kenneth J; Takeuchi, Esther S

    2015-06-24

    When electroactive nanomaterials are fully incorporated into an electrode structure, characterization of the crystallite sizes, agglomerate sizes, and dispersion of the electroactive materials can lend insight into the complex electrochemistry associated with composite electrodes. In this study, composite magnetite electrodes were sectioned using ultramicrotome techniques, which facilitated the direct observation of crystallites and agglomerates of magnetite (Fe3O4) as well as their dispersal patterns in large representative sections of electrode, via 2D cross sectional analysis by Transmission Electron Microscopy (TEM). Further, the electrochemistry of these electrodes were recorded, and Transmission X-ray Microscopy (TXM) was used to determine the distribution of oxidation states of the reduced magnetite. Unexpectedly, while two crystallite sizes of magnetite were employed in the production of the composite electrodes, the magnetite agglomerate sizes and degrees of dispersion in the two composite electrodes were similar to each other. This observation illustrates the necessity for careful characterization of composite electrodes, in order to understand the effects of crystallite size, agglomerate size, and level of dispersion on electrochemistry.

  16. Synthesis and characterization of thermally stable large-pore mesoporous nanocrystallineanatase

    Energy Technology Data Exchange (ETDEWEB)

    Ermokhina, Natalia I.; Nevinskiy, Vitaly A.; Manorik, Piotr A.; Ilyin, Vladimir G. [L.V. Pisarzhevskiy Institute of Physical Chemistry, National Academy of Sciences of Ukraine, 31 Prospekt Nauki, Kyiv 03028 (Ukraine); Novichenko, Viktor N.; Shcherbatiuk, Mykola M.; Klymchuk, Dmitro O. [M.G. Kholodny Institute of Botany, National Academy of Sciences of Ukraine, 2Tereshchenkivska St., 01601, Kyiv (Ukraine); Tsyba, Mykola M. [Institute for Sorption and Problems of Endoecology, National Academy of Sciences of Ukraine, 13 Naumov St., Kyiv 03164 (Ukraine); Puziy, Alexander M., E-mail: alexander.puziy@ispe.kiev.ua [Institute for Sorption and Problems of Endoecology, National Academy of Sciences of Ukraine, 13 Naumov St., Kyiv 03164 (Ukraine)

    2013-04-15

    Thermally stable mesoporous nanocrystalline TiO{sub 2} with a pure anatase structure was obtained by sol–gel synthesis (in combination with hydrothermal treatment) using titanium tetrabutoxide and dibenzo-18-crown-6 as a structure-directing agent in presence of surfactant and/or La{sup 3+} ions additives. Nanocrystalline TiO{sub 2} demonstrates various textures with a well-defined spherical morphology (micro- and nanospheres), a crystallite size of no greater than 10 nm (XRD), and a narrow pore size distribution. Spherical particles of micrometer scale in the presence of La{sup 3+} ions do not form. TiO{sub 2} calcined (at 500 °C) after hydrothermal treatment (at 175 °C) has a significantly more developed porous structure as compared with TiO{sub 2} which was not treated hydrothermally. For example, specific surface area amounts 137 m{sup 2} g{sup −1} and 69 m{sup 2} g{sup −1}, pore volume 0.98 cm{sup 3} g{sup −1} and 0.21 cm{sup 3} g{sup −1}, pore diameter 17.5 nm and 12.5 nm respectively for samples hydrothermally treated and not treated. - Graphical abstract: Large-pore mesoporous nanocristalline anatase. Highlights: ► Large-pore mesoporous nanocrystalline TiO{sub 2} was obtained by sol–gel synthesis. ► Crown ether was used as template in presence of surfactant and/or La{sup 3+} ions. ► Anatase (crystalline size<11 nm) is the only crystalline phase present in TiO{sub 2}. ► TiO{sub 2} shows well-defined homogeneous spherical morphology (micro- and nano-spheres)

  17. Chemical adhesion rather than mechanical retention enhances resin bond durability of a dental glass-ceramic with leucite crystallites

    Energy Technology Data Exchange (ETDEWEB)

    Meng, X F [Department of Prosthodontics, The Stomatological Hospital Affiliated Medical School, Nanjing University, Nanjing 210008 (China); Yoshida, K [Division of Applied Prosthodontics, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki 852-8588 (Japan); Gu, N, E-mail: mengsoar@nju.edu.c [Jiangsu Key Laboratory for Biomaterials and Devices, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096 (China)

    2010-08-01

    This study aims to evaluate the effect of chemical adhesion by a silane coupler and mechanical retention by hydrofluoric acid (HFA) etching on the bond durability of resin to a dental glass ceramic with leucite crystallites. Half of the ceramic plates were etched with 4.8% HFA (HFA group) for 60 s, and the other half were not treated (NoHFA group). The scale of their surface roughness and rough area was measured by a 3D laser scanning microscope. These plates then received one of the following two bond procedures to form four bond test groups: HFA/cement, NoHFA/cement, HFA/silane/cement and NoHFA/silane/cement. The associated micro-shear bond strength and bond failure modes were tested after 0 and 30 000 thermal water bath cycles. Four different silane/cement systems (Monobond S/Variolink II, GC Ceramic Primer/Linkmax HV, Clearfil Ceramic Primer/Clearfil Esthetic Cement and Porcelain Liner M/SuperBond C and B) were used. The data for each silane/cement system were analyzed by three-way ANOVA. HFA treatment significantly increased the surface R{sub a} and R{sub y} values and the rough area of the ceramic plates compared with NoHFA treatment. After 30 000 thermal water bath cycles, the bond strength of all the test groups except the HFA/Linkmax HV group was significantly reduced, while the HFA/Linkmax HV group showed only adhesive interface failure. The other HFA/cement groups and all NoHFA/cement groups lost bond strength completely, and all NoHFA/silane/cement groups with chemical adhesion had significantly higher bond strength and more ceramic cohesive failures than the respective HFA/cement groups with mechanical retention. The result of the HFA/silane/cement groups with both chemical adhesion and mechanical retention revealed that HFA treatment could enhance the bond durability of resin/silanized glass ceramics, which might result from the increase of the chemical adhesion area on the ceramic rough surface and subsequently reduced degradation speed of the silane

  18. Nature of the Ag-Si interface in screen-printed contacts. A detailed transmission electron microscopy study of cross-sectional structures

    Energy Technology Data Exchange (ETDEWEB)

    Ballif, C. [Fraunhofer ISE, Laboratory and Service Center Gelsenkirchen (Germany); Huljic, D.M.; Willeke, G. [Fraunhofer-Institut fuer Solare Energiesysteme (ISE), Freiburg im Breisgau (Germany); Hessler-Wyser, A. [Swiss Federal Inst. of Technology, CIME, Lausanne (Switzerland)

    2002-07-01

    As screen printed contacts are the predominant metallisation technique in industrial production of Si solar cells, a better understanding of their properties is necessary. In this work, we show that high-quality cross-sectional samples can be prepared, whose study by transmission electron microscopy (TEM) reveals precisely the structure of the contact between the silver fingers and the Si. On diffused [100] Si wafers, direct firing of an Ag paste results in interfaces which are mainly composed of shaped Ag crystallites penetrating the emitter up to 120 nm. These crystallites are in epitaxial relation with the Sl substrate. When firing the contacts through a SiN{sub x} layer, larger Ag crystallites are present at the interface with Si and the orientation relation is lost. In both cases, high resolution TEM imaging and EDX analyses reveal a crystalline Ag/Si interface, where neither oxide nor glass frit can be detected. The presence of a significant glass frit layer between the Ag crystallites contacting the Si and the large Ag grains forming the bulk of the fingers can partly explain why lowly doped emitters are difficult to contact by screen-printing. (orig.)

  19. Atomistic structure of cobalt-phosphate nanoparticles for catalytic water oxidation.

    Science.gov (United States)

    Hu, Xiao Liang; Piccinin, Simone; Laio, Alessandro; Fabris, Stefano

    2012-12-21

    Solar-driven water splitting is a key photochemical reaction that underpins the feasible and sustainable production of solar fuels. An amorphous cobalt-phosphate catalyst (Co-Pi) based on earth-abundant elements has been recently reported to efficiently promote water oxidation to protons and dioxygen, a main bottleneck for the overall process. The structure of this material remains largely unknown. We here exploit ab initio and classical atomistic simulations combined with metadynamics to build a realistic and statistically meaningful model of Co-Pi nanoparticles. We demonstrate the emergence and stability of molecular-size ordered crystallites in nanoparticles initially formed by a disordered Co-O network and phosphate groups. The stable crystallites consist of bis-oxo-bridged Co centers that assemble into layered structures (edge-sharing CoO(6) octahedra) as well as in corner- and face-sharing cubane units. These layered and cubane motifs coexist in the crystallites, which always incorporate disordered phosphate groups at the edges. Our computational nanoparticles, although limited in size to ~1 nm, can contain more than one crystallite and incorporate up to 18 Co centers in the cubane/layered structures. The crystallites are structurally stable up to high temperatures. We simulate the extended X-ray absorption fine structure (EXAFS) of our nanoparticles. Those containing several complete and incomplete cubane motifs-which are believed to be essential for the catalytic activity-display a very good agreement with the experimental EXAFS spectra of Co-Pi grains. We propose that the crystallites in our nanoparticles are reliable structural models of the Co-Pi catalyst surface. They will be useful to reveal the origin of the catalytic efficiency of these novel water-oxidation catalysts.

  20. CuInSe2 nano-crystallite reaction kinetics using solid state reaction from Cu2Se and In2Se3 powders

    International Nuclear Information System (INIS)

    Hsiang, Hsing-I; Lu, Li-Hsin; Chang, Yu-Lun; Ray, Dahtong; Yen, Fu-Su

    2011-01-01

    Highlights: → CuInSe 2 phase increased gradually accompanied with a decrease in γ-In 2 Se 3 and no intermediate phase during calcination. → CuInSe 2 formation from Cu 2 Se and In 2 Se 3 powders follows a one-dimensional diffusion-controlled reaction with apparent activation energy of about 122.5 kJ/mol. → The solid reaction kinetics may be dominated by the diffusion of In 3+ ions. - Abstract: The reaction mechanism and CuInSe 2 formation kinetics using a solid state reaction from Cu 2 Se and In 2 Se 3 powders synthesized using a heating up process were investigated using X-ray diffractomy (XRD) and transmission electron microscopy (TEM). It was observed that the CuInSe 2 phase increased gradually, accompanied with a decrease in γ-In 2 Se 3 with no intermediate phase as the calcination temperature and soaking time were increased. The reaction kinetics was analyzed using the Avrami and polynomial kinetic model, suggesting that CuInSe 2 formation from Cu 2 Se and In 2 Se 3 powders follows a diffusion-controlled reaction with an apparent activation energy of about 122.5-182.3 kJ/mol. Cu 2 Se and In 2 Se 3 phases react and directly transform into CIS without the occurrence of any intermediate phase and the size of the newly formed CuInSe 2 crystallites was close to that of the Cu 2 Se reactant particle based on the TEM results, which indicated that the solid reaction kinetics may be dominated by the diffusion of In 3+ ions.

  1. On the peculiarities of galvanomagnetic effects in high magnetic fields in twisting bicrystals of the 3D topological insulator Bi{sub 1–x}Sb{sub x} (0.07 ≤ x ≤ 0.2)

    Energy Technology Data Exchange (ETDEWEB)

    Muntyanu, F. M., E-mail: muntean-teodor@yahoo.com [Academy of Sciences of Moldova, Institute of Electronic Engineering and Industrial Technologies (Moldova, Republic of); Gheorghitsa, E. I. [Technical University of Moldova (Moldova, Republic of); Gilewski, A. [International Laboratory of High Magnetic Fields and Low Temperatures (Poland); Chistol, V. [Tiraspol State University (Moldova, Republic of); Bejan, V. [Technical University of Moldova (Moldova, Republic of); Munteanu, V. [Academy of Sciences of Moldova, Institute of Electronic Engineering and Industrial Technologies (Moldova, Republic of)

    2017-04-15

    Galvanomagnetic effects in twisting bicrystals of Bi{sub 1–x}Sb{sub x} alloys (0.07 ≤ x ≤ 0.2) at low temperatures and in magnetic fields up to 40 T are studied. It is found that, at small crystallite misorientation angles, the semiconductor–semimetal transition is induced in the central layer (~60-nm-thick) and two adjacent layers (each ~20-nm-thick) of the interface at different values of ultraquantum magnetic field. Bicrystals with large misorientation angles, being located in strong magnetic fields, exhibit quantum oscillations of the magnetoresistance and the Hall effect, thus indicating that the density of states is higher and charge carriers are heavier in the adjacent layers of the interfaces than in the crystallites. Our results show also that twisting bicrystals contain regions with different densities of quantum electronic states, which are determined by the crystallite misorientation angle and magnetic-field strength.

  2. Anomalous behavior of B1g mode in highly transparent anatase nano-crystalline Nb-doped Titanium Dioxide (NTO thin films

    Directory of Open Access Journals (Sweden)

    Subodh K. Gautam

    2015-12-01

    Full Text Available The effect of Niobium doping and size of crystallites on highly transparent nano-crystalline Niobium doped Titanium Dioxide (NTO thin films with stable anatase phase are reported. The Nb doping concentration is varied within the solubility limit in TiO2 lattice. Films were annealed in controlled environment for improving the crystallinity and size of crystallites. Elemental and thickness analysis were carried out using Rutherford backscattering spectrometry and cross sectional field emission scanning electron microscopy. Structural characteristics reveal a substitutional incorporation of Nb+5 in the TiO2 lattice which inhibits the anatase crystallites growth with increasing the doping percentage. The micro-Raman (MR spectra of films with small size crystallites shows stiffening of about 4 cm−1 for the Eg(1 mode and is ascribed to phonon confinement and non-stoichiometry. In contrast, B1g mode exhibits a large anomalous softening of 20 cm−1 with asymmetrical broadening; which was not reported for the case of pure TiO2 crystallites. This anomalous behaviour is explained by contraction of the apical Ti-O bonds at the surface upon substitutional Nb5+ doping induced reduction of Ti4+ ions also known as hetero-coordination effect. The proposed hypotheses is manifested through studying the electronic structure and phonon dynamics by performing the near edge x-ray absorption fine structure (NEXAFS and temperature dependent MR down to liquid nitrogen temperature on pure and 2.5 at.% doped NTO films, respectively.

  3. Microwave Assisted Synthesis of Porous NiCo2O4 Microspheres: Application as High Performance Asymmetric and Symmetric Supercapacitors with Large Areal Capacitance

    Science.gov (United States)

    Khalid, Syed; Cao, Chuanbao; Wang, Lin; Zhu, Youqi

    2016-01-01

    Large areal capacitance is essentially required to integrate the energy storage devices at the microscale electronic appliances. Energy storage devices based on metal oxides are mostly fabricated with low mass loading per unit area which demonstrated low areal capacitance. It is still a challenge to fabricate supercapacitor devices of porous metal oxides with large areal capacitance. Herein we report microwave method followed by a pyrolysis of the as-prepared precursor is used to synthesize porous nickel cobaltite microspheres. Porous NiCo2O4 microspheres are capable to deliver large areal capacitance due to their high specific surface area and small crystallite size. The facile strategy is successfully demonstrated to fabricate aqueous-based asymmetric & symmetric supercapacitor devices of porous NiCo2O4 microspheres with high mass loading of electroactive materials. The asymmetric & symmetric devices exhibit maximum areal capacitance and energy density of 380 mF cm−2 & 19.1 Wh Kg−1 and 194 mF cm−2 & 4.5 Wh Kg−1 (based on total mass loading of 6.25 & 6.0 mg) respectively at current density of 1 mA cm−2. The successful fabrication of symmetric device also indicates that NiCo2O4 can also be used as the negative electrode material for futuristic asymmetric devices. PMID:26936283

  4. Study of the effect of residual stress on the microstrain of the crystalline lattice and on the crystallite size of steel Cr-Si-V by shot peening

    International Nuclear Information System (INIS)

    Oliveira, Rene Ramos de

    2016-01-01

    the results, we can notice the difference between the values obtained in the deformations, however, the emphasis of this work was on the characteristics of the distribution profiles and not on the absolute values. In addition, the study of the distribution of the mean crystallite size along the thickness of the X-ray diffraction profile was provided and the results showed that this distribution varies inversely with microstrain. The relationship between the mean crystallite size and the variation of the interplanar distances corresponds directly to changes in the densities of dislocations occurring in the material, which in turn are linked to the microstrain of the crystalline lattice. As a complement to the work, the stress concentration factor and fatigue tests of the material were analyzed. The stress concentration factor did not change according to the use of the S330 and S390 grit, both being applied in the same blasting regime. Fatigue tests indicated that pretensioning increases the useful life of the cyclic stresses of the material studied. (author)

  5. Stability of uranium silicides during high energy ion irradiation

    International Nuclear Information System (INIS)

    Birtcher, R.C; Wang, L.M.

    1991-11-01

    Changes induced by 1.5 MeV Kr ion irradiation of both U 3 Si and U 3 Si 2 have been followed by in situ transmission electron microscopy. When irradiated at sufficiently low temperatures, both alloys transform from the crystalline to the amorphous state. When irradiated at temperatures above the temperature limit for ion beam amorphization, both compounds disorder with the Martensite twin structure in U 3 Si disappearing from view in TEM. Prolonged irradiation of the disordered crystalline phases results in nucleation of small crystallites within the initially large crystal grains. The new crystallites increase in number during continued irradiation until a fine grain structure is formed. Electron diffraction yields a powder-like diffraction pattern that indicates a random alignment of the small crystallites. During a second irradiation at lower temperatures, the small crystallizes retard amorphization. After 2 dpa at high temperatures, the amorphization dose is increased by over twenty times compared to that of initially unirradiated material

  6. In situ X-ray analysis of MoO3 reduction

    International Nuclear Information System (INIS)

    Leisegang, T.; Levin, A.A.; Meyer, D.C.; Walter, J.

    2005-01-01

    The reduction of MoO 3 to MoO 2 under hydrogen/argon atmosphere (5 vol. % H 2 /95 vol. % Ar) in the temperature range 323 K..623 K was studied in situ by means of wide-angle X-ray scattering. It has been found that the starting material, MoO 3 , consists of two different orthorhombic MoO 3 phases A and B with nearly the same structure parameters. The phase A (fraction of 37.1 wt%) describes the larger crystallites whereas the phase B (fraction of 62.9 wt.%) describes the smaller crystallites. Under the reduction to monoclinic MoO 2 phase during the heating, the thermal evolution of the phase fractions is different. A conclusion is drawn that MoO 2 is formed preferably in big crystallites. About 10 wt. % of MoO 2 has been found to form at 623 K resulting in about 69 wt. % after cooling to room temperature followed by holding in Ar/H 2 atmosphere about 24 h. Additionally, about 4.4 wt. % of the Mo 4 O 11 oxide probably formed in large crystallites was detected in the reduced powder after the cooling. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  7. Carbonized Micro- and Nanostructures: Can Downsizing Really Help?

    Science.gov (United States)

    Naraghi, Mohammad; Chawla, Sneha

    2014-01-01

    In this manuscript, we discuss relationships between morphology and mechanical strength of carbonized structures, obtained via pyrolysis of polymeric precursors, across multiple length scales, from carbon fibers (CFs) with diameters of 5–10 μm to submicron thick carbon nanofibers (CNFs). Our research points to radial inhomogeneity, skin–core structure, as a size-dependent feature of polyacrylonitrile-based CFs. This inhomogeneity is a surface effect, caused by suppressed diffusion of oxygen and stabilization byproducts during stabilization through skin. Hence, reducing the precursor diameters from tens of microns to submicron appears as an effective strategy to develop homogeneous carbonized structures. Our research establishes the significance of this downsizing in developing lightweight structural materials by comparing intrinsic strength of radially inhomogeneous CFs with that of radially homogeneous CNF. While experimental studies on the strength of CNFs have targeted randomly oriented turbostratic domains, via continuum modeling, we have estimated that strength of CNFs can reach 14 GPa, when the basal planes of graphitic domains are parallel to nanofiber axis. The CNFs in our model are treated as composites of amorphous carbon (matrix), reinforced with turbostratic domains, and their strength is predicted using Tsai–Hill criterion. The model was calibrated with existing experimental data. PMID:28788651

  8. Property changes of urinary nanocrystallites and urine of uric acid stone formers after taking potassium citrate

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Guang-Na; Ouyang, Jian-Ming, E-mail: toyjm@jnu.edu.cn; Xue, Jun-Fa; Shang, Yun-Feng

    2013-10-15

    The property changes of urinary nanocrystallites in 20 cases of uric acid (UA) stone formers after 1 week of potassium citrate (K{sub 3}cit) intake were comparatively studied by X-ray diffraction analysis, Fourier transform infrared spectroscopy, nanoparticle size analysis, and transmission electron microscopy. Before K{sub 3}cit intake, the urinary crystallites mainly contained UA and calcium oxalate. After K{sub 3}cit intake, the components changed to urate and UA; the qualities, species, and amounts of aggregated crystallites decreased; urine pH, citrate, and glycosaminoglycan excretions increased; and UA excretion, Zeta potential, and crystallite size decreased. The stability of crystallites followed the order: controls > patients after taking K{sub 3}cit > patients before taking K{sub 3}cit. Therefore, the components of urinary stones were closely related to the components of urinary crystallites. - Graphical abstract: The relationships among stone components, urinary crystallite components, and urine pH were established. The crystallites stability order was: controls > patients after taking K{sub 3}cit > patients before taking K{sub 3}cit. Highlights: • Urine crystallite property of uric acid stone former after K{sub 3}cit intake was studied. • The components of crystallites in urine are closely related to type of stones. • After K{sub 3}cit intake the qualities and species of crystallites decreased. • After K{sub 3}cit intake the amount of aggregated crystallites decreased. • The stability of urinary crystallites of UA patients increased after taking K{sub 3}cit.

  9. Property changes of urinary nanocrystallites and urine of uric acid stone formers after taking potassium citrate

    International Nuclear Information System (INIS)

    Zhang, Guang-Na; Ouyang, Jian-Ming; Xue, Jun-Fa; Shang, Yun-Feng

    2013-01-01

    The property changes of urinary nanocrystallites in 20 cases of uric acid (UA) stone formers after 1 week of potassium citrate (K 3 cit) intake were comparatively studied by X-ray diffraction analysis, Fourier transform infrared spectroscopy, nanoparticle size analysis, and transmission electron microscopy. Before K 3 cit intake, the urinary crystallites mainly contained UA and calcium oxalate. After K 3 cit intake, the components changed to urate and UA; the qualities, species, and amounts of aggregated crystallites decreased; urine pH, citrate, and glycosaminoglycan excretions increased; and UA excretion, Zeta potential, and crystallite size decreased. The stability of crystallites followed the order: controls > patients after taking K 3 cit > patients before taking K 3 cit. Therefore, the components of urinary stones were closely related to the components of urinary crystallites. - Graphical abstract: The relationships among stone components, urinary crystallite components, and urine pH were established. The crystallites stability order was: controls > patients after taking K 3 cit > patients before taking K 3 cit. Highlights: • Urine crystallite property of uric acid stone former after K 3 cit intake was studied. • The components of crystallites in urine are closely related to type of stones. • After K 3 cit intake the qualities and species of crystallites decreased. • After K 3 cit intake the amount of aggregated crystallites decreased. • The stability of urinary crystallites of UA patients increased after taking K 3 cit

  10. Fluorination of Isotopically Labeled Turbostratic and Bernal Stacked Bilayer Graphene

    Czech Academy of Sciences Publication Activity Database

    Ek Weis, Johan; da Costa, Sara; Frank, Otakar; Bastl, Zdeněk; Kalbáč, Martin

    2015-01-01

    Roč. 21, č. 3 (2015), s. 1081-1087 ISSN 1521-3765 R&D Projects: GA MŠk LL1301 Institutional support: RVO:61388955 Keywords : fluorination * graphene * bilayers Subject RIV: CF - Physical ; Theoretical Chemistry

  11. Changes in the vibrational energies and interatomic spacings upon the formation of vacancies in the volume and in the cores of crystallite conjugation regions of polycrystalline transition metals with cubic lattices

    International Nuclear Information System (INIS)

    Klotsman, S.M.; Timofeev, A.N.

    2008-01-01

    Measured changes (ε vac ) i,j of vibrational energy on vacancies formation in i-fields (in volumes and nuclei of crystallite conjugation regions of polycrystalline metals (CCR-PM)): Cr, Mo, Ta, W, Cu, Ir are presented. Changes ε vol of vibrational energy of vacancy nearest environment formed in the metal volume, changes ε FCC of vibrational energy when vacancies formation in CCR nuclei of BCC- and FCC lattices transition metals are discussed. Measured changes ε FCC of vibrational energy, u FCC potential energy and determined sign of interatomic distances changes Δa FCC when formation of split vacancy in the FCC-lattice CCR-PM, changes ε BCC of vibrational energy, u BCC potential energy and determined sign of Δa BCC changes of interatomic distances when vacancies formation in the BCC-lattice CCR-PM are demonstrated. It is noted that the increase of interatomic distances when vacancies formation in the BCC-lattice CCR nucleus of transition metals is conditioned by the the appearance of vacancies alternative structure. Properties of CCR-PM nuclei are more sensitive to interatomic distances changes in the vacancies environment, than to changes of its nearest neighbours numbers [ru

  12. Self-Limited Growth in Pentacene Thin Films.

    Science.gov (United States)

    Pachmajer, Stefan; Jones, Andrew O F; Truger, Magdalena; Röthel, Christian; Salzmann, Ingo; Werzer, Oliver; Resel, Roland

    2017-04-05

    Pentacene is one of the most studied organic semiconducting materials. While many aspects of the film formation have already been identified in very thin films, this study provides new insight into the transition from the metastable thin-film phase to bulk phase polymorphs. This study focuses on the growth behavior of pentacene within thin films as a function of film thickness ranging from 20 to 300 nm. By employing various X-ray diffraction methods, combined with supporting atomic force microscopy investigations, one crystalline orientation for the thin-film phase is observed, while three differently tilted bulk phase orientations are found. First, bulk phase crystallites grow with their 00L planes parallel to the substrate surface; second, however, crystallites tilted by 0.75° with respect to the substrate are found, which clearly dominate the former in ratio; third, a different bulk phase polymorph with crystallites tilted by 21° is found. The transition from the thin-film phase to the bulk phase is rationalized by the nucleation of the latter at crystal facets of the thin-film-phase crystallites. This leads to a self-limiting growth of the thin-film phase and explains the thickness-dependent phase behavior observed in pentacene thin films, showing that a large amount of material is present in the bulk phase much earlier during the film growth than previously thought.

  13. Intrinsic stress in ZrN thin films: Evaluation of grain boundary contribution from in situ wafer curvature and ex situ x-ray diffraction techniques

    International Nuclear Information System (INIS)

    Koutsokeras, L. E.; Abadias, G.

    2012-01-01

    Low-mobility materials, like transition metal nitrides, usually undergo large residual stress when sputter-deposited as thin films. While the origin of stress development has been an active area of research for high-mobility materials, atomistic processes are less understood for low-mobility systems. In the present work, the contribution of grain boundary to intrinsic stress in reactively magnetron-sputtered ZrN films is evaluated by combining in situ wafer curvature measurements, providing information on the overall biaxial stress, and ex situ x-ray diffraction, giving information on elastic strain (and related stress) inside crystallites. The thermal stress contribution was also determined from the in situ stress evolution during cooling down, after deposition was stopped. The stress data are correlated with variations in film microstructure and growth energetics, in the 0.13-0.42 Pa working pressure range investigated, and discussed based on existing stress models. At low pressure (high energetic bombardment conditions), a large compressive stress is observed due to atomic peening, which induces defects inside crystallites but also promotes incorporation of excess atoms in the grain boundary. Above 0.3-0.4 Pa, the adatom surface mobility is reduced, leading to the build-up of tensile stress resulting from attractive forces between under-dense neighbouring column boundary and possible void formation, while crystallites can still remain under compressive stress.

  14. Effects of magnetic pre-alignment of nano-powders on formation of high textured barium hexa-ferrite quasi-single crystals via a magnetic forming and liquid participation sintering route

    International Nuclear Information System (INIS)

    Liu, Junliang; Zeng, Yanwei; Zhang, Xingkai; Zhang, Ming

    2015-01-01

    Highly textured barium hexa-ferrite quasi-single crystal with narrow ferromagnetic resonance line-width is believed to be a potential gyromagnetic material for self-biased microwave devices. To fabricate barium hexa-ferrite quasi-single crystal with a high grain orientation degree, a magnetic forming and liquid participation sintering route has been developed. In this paper, the effects of the pre-alignment of the starting nano-powders on the formation of barium quasi-single crystal structures have been investigated. The results indicated that: the crystallites with large sizes and small specific surfaces were easily aligned for they got higher driving forces and lower resistances during magnetic forming. The average restricting magnetic field was about 4.647 kOe to overcome the average friction barrier between crystallites. The pre-aligned crystallites in magnetic forming acted as the “crystal seeds” for oriented growth of the un-aligned crystallites during liquid participation sintering to achieve a high grain orientation. To effectively promote the grain orientation degrees of the sintered pellets, the grain orientation degrees of the green compacts must be higher than a limited value of 15.0%. Barium hexa-ferrite quasi-single crystal with a high grain orientation degree of 98.6% was successfully fabricated after sintering the green compact with its grain orientation degree of 51.1%. - Highlights: • Aligned particles acted as “crystal seeds” for un-aligned ones' oriented growth. • Magnetic field of 4.647 kOe was needed to overcome crystallites' friction barrier. • GOD dramatically increased after sintering if starting GOD exceeded to 15.0%. • Quasi-single crystal was prepared by sintering green compact with GOD of 51.1%

  15. Effects of magnetic pre-alignment of nano-powders on formation of high textured barium hexa-ferrite quasi-single crystals via a magnetic forming and liquid participation sintering route

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Junliang, E-mail: liujunliang@yzu.edu.cn [Key Laboratory of Environmental Materials and Engineering of Jiangsu Province, School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002 (China); Zeng, Yanwei [State Key Laboratory of Materials-Oriented Chemical Engineering, School of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009 (China); Zhang, Xingkai [Key Laboratory of Environmental Materials and Engineering of Jiangsu Province, School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002 (China); Zhang, Ming [Key Laboratory of Environmental Materials and Engineering of Jiangsu Province, School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002 (China); Testing Center of Yangzhou University, Yangzhou 225002 (China)

    2015-05-15

    Highly textured barium hexa-ferrite quasi-single crystal with narrow ferromagnetic resonance line-width is believed to be a potential gyromagnetic material for self-biased microwave devices. To fabricate barium hexa-ferrite quasi-single crystal with a high grain orientation degree, a magnetic forming and liquid participation sintering route has been developed. In this paper, the effects of the pre-alignment of the starting nano-powders on the formation of barium quasi-single crystal structures have been investigated. The results indicated that: the crystallites with large sizes and small specific surfaces were easily aligned for they got higher driving forces and lower resistances during magnetic forming. The average restricting magnetic field was about 4.647 kOe to overcome the average friction barrier between crystallites. The pre-aligned crystallites in magnetic forming acted as the “crystal seeds” for oriented growth of the un-aligned crystallites during liquid participation sintering to achieve a high grain orientation. To effectively promote the grain orientation degrees of the sintered pellets, the grain orientation degrees of the green compacts must be higher than a limited value of 15.0%. Barium hexa-ferrite quasi-single crystal with a high grain orientation degree of 98.6% was successfully fabricated after sintering the green compact with its grain orientation degree of 51.1%. - Highlights: • Aligned particles acted as “crystal seeds” for un-aligned ones' oriented growth. • Magnetic field of 4.647 kOe was needed to overcome crystallites' friction barrier. • GOD dramatically increased after sintering if starting GOD exceeded to 15.0%. • Quasi-single crystal was prepared by sintering green compact with GOD of 51.1%.

  16. Thermal expansivity of highly-stretched linear polyethylene with extended chains irradiated with different doses of γ-rays

    International Nuclear Information System (INIS)

    Turetskij, A.A.; Chvalun, S.N.; Zubov, Yu.A.; Bakeev, N.F.

    1993-01-01

    Temperature begavior of crystal lattice parameters of highly-stretched samples of linear polyethylene with extended chains irradiated with different doses of γ-rays was studied. It was found that transverse vibrations of macromolecular chains are excited at irradiation doses D≥500 Mrad and temperatures close to the melting temperature of the crystallites. These vibrations cause a sharp increase in the latiice parameter a. But no phase transition to the hexagonal packing occurs. It was shown that the thermal expansivity of the lattice parameter c changes its sign at high irradiation doses. These results are explained by the presence in the crystallites of samples irradiated with large doses of a considerable number of intermolecular chemical bonds

  17. Superconductivity in the ferecrystals (PbSe){sub 1.14}(NbSe{sub 2}){sub n}

    Energy Technology Data Exchange (ETDEWEB)

    Grosse, Corinna; Chiatti, Olivio; Fischer, Saskia F. [Novel Materials Group, Humboldt-Universitaet Berlin (Germany); Alemayehu, Matti B.; Falmbigl, Matthias; Johnson, David C. [Department of Chemistry, University of Oregon, Eugene, OR (United States)

    2016-07-01

    The ferecrystals (PbSe){sub 1.14}(NbSe{sub 2}){sub n} are artificially layered materials consisting of n NbSe{sub 2} single-layers stacked alternately with atomic double layers of PbSe. NbSe{sub 2} is a transition metal dichalcogenide with interesting electrical properties such as superconductivity and charge density waves. The influence of turbostratic disorder, a random rotation between the NbSe{sub 2} and PbSe layers, on the superconducting transition temperature has been unknown so far. We investigate the structural and temperature-dependent electrical properties of the ferecrystals (PbSe){sub 1.14}(NbSe{sub 2}){sub n} by means of scanning transmission electron microscopy, X-ray diffraction, in-plane resistivity and Hall measurements and compare them to those of analogous non-disordered misfit layer compound (MLC) polymorphs. We observe a superconducting transition in the resistivity of the ferecrystals. The transition temperatures are reduced by up to 55 % with respect to the analogous MLC polymorphs. This indicates that turbostratic disorder substantially weakens the electron-phonon coupling in (PbSe){sub 1.14}(NbSe{sub 2}){sub n}. We discuss the results of the structural and electrical properties of the ferecrystals with respect to their MLC analogues and also with respect to ultra-thin NbSe{sub 2} layers.

  18. Reliable Piezoelectricity in Bilayer WSe2 for Piezoelectric Nanogenerators.

    Science.gov (United States)

    Lee, Ju-Hyuck; Park, Jae Young; Cho, Eun Bi; Kim, Tae Yun; Han, Sang A; Kim, Tae-Ho; Liu, Yanan; Kim, Sung Kyun; Roh, Chang Jae; Yoon, Hong-Joon; Ryu, Hanjun; Seung, Wanchul; Lee, Jong Seok; Lee, Jaichan; Kim, Sang-Woo

    2017-08-01

    Recently, piezoelectricity has been observed in 2D atomically thin materials, such as hexagonal-boron nitride, graphene, and transition metal dichalcogenides (TMDs). Specifically, exfoliated monolayer MoS 2 exhibits a high piezoelectricity that is comparable to that of traditional piezoelectric materials. However, monolayer TMD materials are not regarded as suitable for actual piezoelectric devices due to their insufficient mechanical durability for sustained operation while Bernal-stacked bilayer TMD materials lose noncentrosymmetry and consequently piezoelectricity. Here, it is shown that WSe 2 bilayers fabricated via turbostratic stacking have reliable piezoelectric properties that cannot be obtained from a mechanically exfoliated WSe 2 bilayer with Bernal stacking. Turbostratic stacking refers to the transfer of each chemical vapor deposition (CVD)-grown WSe 2 monolayer to allow for an increase in degrees of freedom in the bilayer symmetry, leading to noncentrosymmetry in the bilayers. In contrast, CVD-grown WSe 2 bilayers exhibit very weak piezoelectricity because of the energetics and crystallographic orientation. The flexible piezoelectric WSe 2 bilayers exhibit a prominent mechanical durability of up to 0.95% of strain as well as reliable energy harvesting performance, which is adequate to drive a small liquid crystal display without external energy sources, in contrast to monolayer WSe 2 for which the device performance becomes degraded above a strain of 0.63%. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Ion beam induced charge and cathodoluminescence imaging of response uniformity of CVD diamond radiation detectors

    CERN Document Server

    Sellin, P J; Galbiati, A; Maghrabi, M; Townsend, P D

    2002-01-01

    The uniformity of response of CVD diamond radiation detectors produced from high quality diamond film, with crystallite dimensions of >100 mu m, has been studied using ion beam induced charge imaging. A micron-resolution scanning alpha particle beam was used to produce maps of pulse height response across the device. The detectors were fabricated with a single-sided coplanar electrode geometry to maximise their sensitivity to the surface region of the diamond film where the diamond crystallites are highly ordered. High resolution ion beam induced charge images of single crystallites were acquired that demonstrate variations in intra-crystallite charge transport and the termination of charge transport at the crystallite boundaries. Cathodoluminescence imaging of the same crystallites shows an inverse correlation between the density of radiative centres and regions of good charge transport.

  20. Turbostratic boron nitride coated on high-surface area metal oxide templates

    DEFF Research Database (Denmark)

    Klitgaard, Søren Kegnæs; Egeblad, Kresten; Brorson, M.

    2007-01-01

    Boron nitride coatings on high-surface area MgAl2O4 and Al2O3 have been synthesized and characterized by transmission electron microscopy and by X-ray powder diffraction. The metal oxide templates were coated with boron nitride using a simple nitridation in a flow of ammonia starting from ammonium...

  1. Line profile analysis of ODS steels Fe20Cr5AlTiY milled powders at different Y2O3 concentrations

    Science.gov (United States)

    Afandi, A.; Nisa, R.; Thosin, K. A. Z.

    2017-04-01

    Mechanical properties of material are largely dictated by constituent microstructure parameters such as dislocation density, lattice microstrain, crystallite size and its distribution. To develop ultra-fine grain alloys such as Oxide Dispersion Strengthened (ODS) alloys, mechanical alloying is crucial step to introduce crystal defects, and refining the crystallite size. In this research the ODS sample powders were mechanically alloyed with different Y2O3 concentration respectively of 0.5, 1, 3, and 5 wt%. MA process was conducted with High Energy Milling (HEM) with the ball to powder ratio of 15:1. The vial and the ball were made of alumina, and the milling condition is set 200 r.p.m constant. The ODS powders were investigated by X-Ray Diffractions (XRD), Bragg-Brentano setup of SmartLab Rigaku with 40 KV, and 30 mA, step size using 0.02°, with scanning speed of 4°min-1. Line Profile Analysis (LPA) of classical Williamson-Hall was carried out, with the aim to investigate the different crystallite size, and microstrain due to the selection of the full wide at half maximum (FWHM) and integral breadth.

  2. Critical current through grain boundary of metal oxide superconductors YBa2Cu3O7-δ

    International Nuclear Information System (INIS)

    Ermolov, S.N.; Kislov, N.A.; Marchenko, V.A.

    1989-01-01

    Josephson junction with characteristics, corresponding to sandwich type structure is produced at 78 K at the link of large YBa 2 Cu 3 O 7-δ crystallite with fine-grain structure. J c (H) dependence on the thermomagnetic prehistory is explained with regard to scattering fields of magnetic flux captured by grains

  3. Water electrolysis with a conducting carbon cloth: subthreshold hydrogen generation and superthreshold carbon quantum dot formation.

    Science.gov (United States)

    Biswal, Mandakini; Deshpande, Aparna; Kelkar, Sarika; Ogale, Satishchandra

    2014-03-01

    A conducting carbon cloth, which has an interesting turbostratic microstructure and functional groups that are distinctly different from other ordered forms of carbon, such as graphite, graphene, and carbon nanotubes, was synthesized by a simple one-step pyrolysis of cellulose fabric. This turbostratic disorder and surface chemical functionalities had interesting consequences for water splitting and hydrogen generation when such a cloth was used as an electrode in the alkaline electrolysis process. Importantly, this work also gives a new twist to carbon-assisted electrolysis. During electrolysis, the active sites in the carbon cloth allow slow oxidation of its surface to transform the surface groups from COH to COOH and so forth at a voltage as low as 0.2 V in a two-electrode system, along with platinum as the cathode, instead of 1.23 V (plus overpotential), which is required for platinum, steel, or even graphite anodes. The quantity of subthreshold hydrogen evolved was 24 mL cm(-2)  h(-1) at 1 V. Interestingly, at a superthreshold potential (>1.23 V+overpotential), another remarkable phenomenon was found. At such voltages, along with the high rate and quantity of hydrogen evolution, rapid exfoliation of the tiny nanoscale (5-7 nm) units of carbon quantum dots (CQDs) are found in copious amounts due to an enhanced oxidation rate. These CQDs show bright-blue fluorescence under UV light. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Magnetic properties in MnBi alloy of small crystallites for permanent magnet devices

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, S. K.; Prakash, H. R.; Ram, S., E-mail: jms.sanjeev@gmail.com [Materials Science Centre, Indian Institute of Technology, Kharagpur-721302 (India)

    2016-05-06

    A rare-earth free alloy like MnBi is a potential candidate for developing small magnets and devices. In a commercially viable method, a MnBi alloy was prepared by arc melting Mn and Bi metals in a 1:1 ratio. In terms of the X-ray diffraction a single crystalline MnBi phase is formed of the as prepared alloy. FESEM images delineate thin MnBi layers (25 – 40 nm thickness) of average EDX composition throughout the specimen. A large coercivity 5.501 kOe (6.5 emu/g magnetization) observed in an M-H at 300 K is decreased to 0.171 (9.0 emu/g magnetization) at 100 K in decreasing upon cooling.

  5. Synthesis and characterization of Gd{sub 2}O{sub 3} doped UO{sub 2} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Soldati, A.L., E-mail: asoldati@cab.cnea.gov.ar [Centro Atómico Bariloche (CAB) – Comisión Nacional de Energía Atómica (CNEA), Av. Bustillo 9500, CP: 8400 Bariloche (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Av. De los Pioneros 2300, CP: 8400 Bariloche (Argentina); Gana Watkins, I. [Centro Atómico Bariloche (CAB) – Comisión Nacional de Energía Atómica (CNEA), Av. Bustillo 9500, CP: 8400 Bariloche (Argentina); Fernández Zuvich, A. [Centro Atómico Bariloche (CAB) – Comisión Nacional de Energía Atómica (CNEA), Av. Bustillo 9500, CP: 8400 Bariloche (Argentina); Instituto Balseiro, Universidad Nacional de Cuyo, Av. Bustillo 9500, CP: 8400 Bariloche (Argentina); Napolitano, F.; Troiani, H. [Centro Atómico Bariloche (CAB) – Comisión Nacional de Energía Atómica (CNEA), Av. Bustillo 9500, CP: 8400 Bariloche (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Av. De los Pioneros 2300, CP: 8400 Bariloche (Argentina); and others

    2016-10-15

    UO{sub 2} nanoparticles doped with 4, 8, 10 and 15 wt% Gd{sub 2}O{sub 3}were synthesized by a reverse strike method. Crystal structure and chemical homogeneity were evaluated using a combination of X-ray diffraction and microscopy tools. An exhaustive study of the composition and its homogeneity at the micro and at the nanometer level was carried out in this nuclear fuel material. Field Emission Gun Scanning and Transmission Electron Microscopy images revealed the presence of micrometer scale agglomerates of nanoparticles, with rounded morphology and an average crystallite size of 100 nm. Rietveld refinements of high-statistic X-ray Diffraction data determined the crystal structure and composition. Furthermore, Energy Dispersive Spectroscopy using a 2 nm{sup 2} spot on the sample surface determined a Gd concentration variation around the average of ±5% in different spots of a single crystallite and of ±10% between different crystallites. However, when measuring large amounts of nanoparticles the concentration averages, producing a homogeneous composition distribution at the micrometer scale. - Highlights: • Synthesis of 4, 8, 10 and 15wt% Gd{sub 2}O{sub 3} doped UO{sub 2} nanoparticles. • Crystallite sizes around 100 nm and rounded morphology. • 90% Gd distribution homogeneity between particles for the less concentrated sample. • High Statistic X-ray Rietveld analysis determined an U{sub 1−x}Gd{sub x}O{sub 2−δ} fcc structure. • Phases with similar crystal structure and symmetry, but different lattice parameter.

  6. Texture of low temperature isotropic pyrocarbons

    International Nuclear Information System (INIS)

    Pelissier, Joseph; Lombard, Louis.

    1976-01-01

    Isotropic pyrocarbon deposited on fuel particles was studied by transmission electron microscopy in order to determine its texture. The material consists of an agglomerate of spherical growth features similar to those of carbon black. The spherical growth features are formed from the cristallites of turbostratic carbon and the distribution gives an isotropic structure. Neutron irradiation modifies the morphology of the pyrocarbon. The spherical growth features are deformed and the coating becomes strongly anisotropic. The transformation leads to the rupture of the coating caused by strong irradiation doses [fr

  7. Large polaron tunneling, magnetic and impedance analysis of magnesium ferrite nanocrystallite

    Energy Technology Data Exchange (ETDEWEB)

    Mahato, Dev K., E-mail: drdevkumar@yahoo.com [Department of Physics, National Institute of Technology Patna, Patna 800 005 (India); Majumder, Sumit [Department of Physics, Jadavpur University, Kolkata 700032 (India); Surface Physics and Material Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700 064 (India); Banerjee, S. [Surface Physics and Material Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700 064 (India)

    2017-08-15

    Graphical abstract: The diffraction peaks corresponding to the planes (111), (220), (311), (222), (400), (422), (511), (440), (620), (533) and (444) provide a clear evidence for the formation of spinel structure of the ferrites. The lattice parameter ‘a’ determined as 8.392 Å matches well with JCPDS (73-2410) file for MgFe{sub 2}O{sub 4.} The volume of the unit cell is 591.012 Å{sup 3}. The crystallite size of the synthesized powder estimated from X-ray peak broadening of (311) highest intensity diffraction peak using Scherer formula was 56.4 nm. - Highlights: • Both the grain and grain boundaries contribution to conductivity of the Mg-ferrite has been observed. • Polydispersive nature of the material is checked using Cole – Cole relation. • The ac conductivity of magnesium ferrite followed σ{sub ac} ∝ ω{sup n} dependence. • The variation of the exponent ‘n’ with temperature suggests that overlapping large polaron tunnelling is the dominant conduction mechanism. • The superparamagnetic behavior of this Mg-ferrite has been observed for sample S1 annealed at 500 °C. - Abstract: Single phase MgFe{sub 2}O{sub 4} (MFO) ferrite was prepared through sol-gel auto-combustion route. The Rietveld analysis of X-ray patterns reveals that our samples are single phase. The increase in average particle size with annealing temperature and formation of nanoparticle agglomerates is observed in MgFe{sub 2}O{sub 4}. The structural morphology of the nanoparticles is studied using Scanning Electron Microscopy (SEM). Formation of spinel structure is confirmed using Fourier transform infrared spectroscopy (FTIR). The Zero-Field-Cooled (ZFC) and Field-Cooled (FC) magnetization measurements show the maximum irreversibility at 700 °C annealing temperature. The formation of a maximum at blocking temperature, T{sub B}∼ 180 K for sample annealed at 500 °C in the ZFC curve shows the superparamagnetic behavior of the sample. The increase of saturation magnetism (M

  8. Critical current through grain boundary of metal oxide superconductors YBa sub 2 Cu sub 3 O sub 7-. delta. Kriticheskij tok cherez granitsu zeren metallooksidnykh sverkhprovodnikov YBa sub 2 Cu3O sub 7-. delta

    Energy Technology Data Exchange (ETDEWEB)

    Ermolov, S N; Kislov, N A; Marchenko, V A [and others

    1989-06-01

    Josephson junction with characteristics, corresponding to sandwich type structure is produced at 78 K at the link of large YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} crystallite with fine-grain structure. J{sub c}(H) dependence on the thermomagnetic prehistory is explained with regard to scattering fields of magnetic flux captured by grains.

  9. Structure and properties of copper after large strain deformation

    Energy Technology Data Exchange (ETDEWEB)

    Rodak, Kinga; Molak, Rafal M.; Pakiela, Zbigniew

    2010-05-15

    Structure and properties of Cu in dependence on strain (from {epsilon}{proportional_to} 0.9 to {epsilon}{proportional_to} 15) during multi-axial compression processing at room temperature was investigated. The evolution of dislocation structure, misorientation distribution and crystallite size were observed by using transmission electron microscopy (TEM) and scanning electron microscopy (SEM) equipment with electron back scattered diffraction (EBSD) facility. The mechanical properties of yield strength (YS), ultimate tensile strength (UTS) and uniform elongation was performed on MTS QTest/10 machine equipped with digital image correlation method (DIC). The structure-flow stress relationship of multi-axial compression processing material at strains {epsilon}{proportional_to} 3.5 and {epsilon}{proportional_to} 5.5 is discussed. It is found that processing does not produce any drastic changes in deformation structure and the microstructural refinement is slow. These results indicate that dynamic recrystallization plays an important role during multi-axial compression process in this range of deformation (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Size distribution of BaF2 nanocrystallites in transparent glass ceramics

    International Nuclear Information System (INIS)

    Bocker, Christian; Bhattacharyya, Somnath; Hoeche, Thomas; Ruessel, Christian

    2009-01-01

    In glasses with the composition 1.9 Na 2 O-15 K 2 O-7.5 Al 2 O 3 -69.6 SiO 2 -6 BaF 2 (in mol.%), BaF 2 nanocrystalline precipitates are formed upon heat treatment. Using dark-field and bright-field transmission electron micrographs, crystallite size distributions are obtained for samples crystallized at various temperatures. According to the 'tomato-salad problem', the size distributions are corrected and then compared to various theories of grain growth taking into account coarsening of the crystallites during heat treatment. The experimental crystallite size distributions show for smaller mean crystallite sizes a more symmetric shape in comparison to the theories of Lifshitz-Slyozov-Wagner (LSW) or Brailsford and Wynblatt (B and W). With increasing mean crystallite sizes to about 18 nm at higher heat-treatment temperatures, the full width at half maximum of the observed distributions decreases and becomes even narrower than the LSW function. These findings indicate that in the investigated nano glass ceramics no coarsening by Ostwald ripening or coalescence occurs. This is explained by the formation of a diffusion barrier around each nanocrystallite which limits the size of the crystallites and hence results in such a narrow and uniform crystallite size distribution.

  11. The magnetic properties of amorphous and nanocrystalline cobalt-rare earth films

    Science.gov (United States)

    Thomas, Richard Allen

    Magnetic materials are of great technological importance for their use in transformers, electric motors, computer disks and hard drives, etc. Understanding the intrinsic physical properties of magnetic materials is essential in order to develop new and better materials for these applications. Presented here is a study of the magnetic properties of amorphous and nanocrystalline cobalt-rare earth (Co-R, where R = Y, Pr, Gd, and Dy) films composed of very small crystalline grains, about 2--200 nm in size. The films are produced by co-sputtering two single element targets onto a single substrate. Many are then annealed briefly to produce magnetic films composed of nanoscale crystallites. The magnetic properties of these films depend largely on the relative strengths of the exchange interaction, which tends to align the spins within a group of crystallites, and the magnetocrystalline anisotropy, which tends to align the spins within each crystallite to an easy direction defined by the crystal lattice. The ratio of these two competing interactions varies strongly with grain size as predicted by the random magnetic anisotropy model. The coercivity, remanent magnetization, initial magnetization, etc., are discussed in light of the predictions made by the models of Callen et al (1977), Chi and Alben (1977), Chudnovsky (1986), and Fukunaga and Inoue (1992).

  12. Effects of air pollutants on epicuticular wax chemical composition

    International Nuclear Information System (INIS)

    Percy, K.E.; McQuattie, C.J.; Rebbeck, J.A.

    1994-01-01

    There are numerous reports in the literature of modifications to epicuticular wax structure as a consequence of exposure to air pollutants. Most authors have used scanning electron microscopy (SEM) to describe changes in wax crystallite morphology or distribution. ''Erosion'' or ''weathering'' of crystalline structure into an amorphous state is the most common observation, particularly in the case of conifer needles having the characteristic tube crystallites comprised of nonacosan-10-ol. Wax structure is largely determined by its chemical composition. Therefore, many of the reported changes in wax structure due to air pollutants probably arise from direct interactions between pollutants such as ozone and wax biosynthesis. The literature describing changes in wax composition due to pollutants is briefly reviewed. New evidence is introduced in support of the hypothesis for a direct interaction between air pollutants and epicuticular wax Biosynthesis. (orig.)

  13. Physics of Hard Spheres Experiment: Significant and Quantitative Findings Made

    Science.gov (United States)

    Doherty, Michael P.

    2000-01-01

    (Earth's gravity), and the emergence of face-centered-cubic (FCC) crystals late in the coarsening process (as small crystallites lost particles to the slow ripening of large crystallites). Significant quantitative findings from the microgravity experiments have been developed describing complex interactions among crystallites during the growth process, as concentration fields overlap in the surrounding disordered phase. Time-resolved Bragg scattering under microgravity captures one effect of these interactions quite conclusively for the sample at a volume fraction of 0.528. From the earliest time until the sample is almost fully crystalline, the size and overall crystallinity grow monotonically, but the number of crystallites per unit volume (number density) falls. Apparently nucleation is slower than the loss of crystallites because of the transfer of particles from small to large crystals. Thus, coarsening occurs simultaneously with growth, rather than following the completion of nucleation and growth as is generally assumed. In the same sample, an interesting signature appears in the apparent number density of crystallites and the volume fraction within the crystallites shortly before full crystallinity is reached. A brief upturn in both indicates the creation of more domains of the size of the average crystallite simultaneous with the compression of the crystallites. Only the emergence of dendritic arms offers a reasonable explanation. The arms would be "seen" by the light scattering as separate domains whose smaller radii of curvature would compress the interior phase. In fiscal year 1999, numerous papers, a doctoral dissertation, and the PHaSE final report were produced. Although this flight project has been completed, plans are in place for a follow-on colloid experiment by Chaikin and Russel that employs a light microscope within Glenn's Fluids and Combustion Facility on the International Space Station. PHaSE is providing us with a deeper understanding of the

  14. Nucleation and crystallization behaviors of nano-crystalline lithium–mica glass–ceramic prepared via sol–gel method

    Energy Technology Data Exchange (ETDEWEB)

    Tohidifar, M.R. [Department of Materials Science and Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Alizadeh, P., E-mail: p-alizadeh@modares.ac.ir [Department of Materials Science and Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Riello, P. [Department of Molecular Sciences and Nanosystems, University of Ca’Foscari, Venice (Italy)

    2012-06-15

    Graphical abstract: The effects of nucleation and crystallization treatments on nano-crystalline lithium–mica glass–ceramic, synthesized by sol–gel technique, were investigated. It was found that MgF{sub 2} crystals act as nuclei centers for the mica crystallization so that a large quantity of mica crystallites was obtained following nucleation process. The crystallization activation energy for both the un-nucleated and nucleated samples was measured as 400.2 and 229.6 kJ mol{sup −1}, respectively. The calculated Avrami exponents demonstrated that the growth mechanism of mica crystallites changes from the needle-like to three-dimensional growth with applying the appropriate nucleation treatment ▪. Highlights: ► Crystallization temperature shifts to 625 from 680 °C following nucleation process. ► Activation energy of crystallization for the nucleated specimen is 229.6 kJ mol{sup −1}. ► Crystallization activation energy for the un-nucleated specimen is 400.2 kJ mol{sup −1}. ► Needle-like growth is predominant growth mechanism for un-nucleated sample. ► Three-dimensional growth is predominant growth mechanism for nucleated sample. -- Abstract: The paper investigates the effects of nucleation and crystallization treatments on nano-crystalline lithium–mica glass–ceramics, taking the composition LiMg{sub 3}AlSi{sub 3(1+x)}O{sub 10+6x}F{sub 2} (x = 0.5) and 8 mass% MgF{sub 2} synthesized by sol–gel technique. Here, X-ray diffraction, thermal analysis and transmission electron microscopy were used to assess the structural evolutions of as-synthesized nano-crystalline lithium–mica glass–ceramics. It was found that MgF{sub 2} crystals perform as nuclei centers for the mica crystallization hence; a large quantity of mica crystallites obtained following the nucleation process at 400 °C for 12 h. For both the un-nucleated and nucleated samples, the crystallization activation energy was measured as 400.2 and 229.6 kJ mol{sup −1

  15. Structure determination of spider silk from X-ray images

    Energy Technology Data Exchange (ETDEWEB)

    Ulrich, Stephan; Zippelius, Annette [Universitaet Goettingen, Institut fuer Theoretische Physik (Germany); Meling, Martin [Max-Planck-Institut fuer biophysikalische Chemie, Goettingen (Germany); Glisovic, Anja; Salditt, Tim [Universitaet Goettingen, Institut fuer Roentgenphysik (Germany)

    2008-07-01

    Spider silk consists of interconnected crystallites, which are typically aligned along the fiber axis. We present a method to systematically determine the structure of these crystallites. Hereby we introduce a model that calculates the scattering function G(q) which is fitted to the measured X-ray image (silk from nephila clavipes). With it, the crystallites' size, the constitution and dimensions of their unit cell, as well as their tilt with respect to the fiber axis is identified, and furthermore the effect of coherent scattering from different crystallites is investigated. The shown methods and the presented model can easily be generalized to a wide class of composite materials.

  16. BaSnF4 fast ion conductor: Variations versus the method of preparation and anomalous temperature variation of the quadrupole splitting

    International Nuclear Information System (INIS)

    Hantash, Jamil; Bartlett, Alan; Denes, Georges; Muntasar, Abdualhafeed; Oldfield, Philip

    2005-01-01

    A new method of preparation of high performance fluoride ion conductor, BaSnF 4 , by water leaching of newly discovered barium tin(II) chloride fluorides, has been designed, and the materials have been studied and compared to the solid prepared by the usual dry method. The unit-cell parameters and crystallite dimensions were found to vary with the method of preparation. In addition, the crystallite dimensions were found to be highly anisotropic for the samples obtained by the wet method. The Moessbauer spectrum is made of a large tin(II) quadrupole doublet, and a broad tin(IV) oxide peak due to surface oxidation. The tin(II) spectrum is in agreement with covalently bonded tin(II) having a strongly stereoactive lone pair. An unusually high dependence of the quadrupole splitting at low temperatures was observed (5.8 times larger than for α-SnF 2 ).

  17. Nanostructural origin of semiconductivity and large magnetoresistance in epitaxial NiCo2O4/Al2O3 thin films

    Science.gov (United States)

    Zhen, Congmian; Zhang, XiaoZhe; Wei, Wengang; Guo, Wenzhe; Pant, Ankit; Xu, Xiaoshan; Shen, Jian; Ma, Li; Hou, Denglu

    2018-04-01

    Despite low resistivity (~1 mΩ cm), metallic electrical transport has not been commonly observed in inverse spinel NiCo2O4, except in certain epitaxial thin films. Previous studies have stressed the effect of valence mixing and the degree of spinel inversion on the electrical conduction of NiCo2O4 films. In this work, we studied the effect of nanostructural disorder by comparing the NiCo2O4 epitaxial films grown on MgAl2O4 (1 1 1) and on Al2O3 (0 0 1) substrates. Although the optimal growth conditions are similar for the NiCo2O4 (1 1 1)/MgAl2O4 (1 1 1) and the NiCo2O4 (1 1 1)/Al2O3 (0 0 1) films, they show metallic and semiconducting electrical transport, respectively. Post-growth annealing decreases the resistivity of NiCo2O4 (1 1 1)/Al2O3 (0 0 1) films, but the annealed films are still semiconducting. While the semiconductivity and the large magnetoresistance in NiCo2O4 (1 1 1)/Al2O3 (0 0 1) films cannot be accounted for in terms of non-optimal valence mixing and spinel inversion, the presence of anti-phase boundaries between nano-sized crystallites, generated by the structural mismatch between NiCo2O4 and Al2O3, may explain all the experimental observations in this work. These results reveal nanostructural disorder as being another key factor for controlling the electrical transport of NiCo2O4, with potentially large magnetoresistance for spintronics applications.

  18. The relaxational behaviour of poly-(vinylidene fluoride) before and after gamma-irradiation

    International Nuclear Information System (INIS)

    Callens, A.

    The main purpose of this work was to investigate how molecular chain reorganization may affect the physical property of polymers. This may be done by the analysis of the as received and post-irradiation relaxation spectra of the semi-crystalline linear chain polymer polyvinylidene fluoride (PVDF), which has been gamma-irradiated up to doses of 1 grad. The effects of the irradiation on the material are primarly main chain cross-linking production of unsaturated bonds and crystallite degradation. To reach a complete interpretation of the relaxation spectra, it is necessary to incorporate a third phase into the analysis besides the amorphous viscoelastic region (AVR) and the crystalline viscoelastic region (CVR), the intermediate phase. The amorphous phase (AVR) is at the origin of the relaxation effects occurring in the temperature region below room temperature. The saturation like behaviour of the cross-linking in the amorphous phase is at the origin of the intensity decrease, temperature shift and peak broadening of the beta relaxation. There is a large amount of evidence that in the neighbourhood of the beta relaxation, relaxation effects are created through irradiation, as mainly revealed by TSD-spectra (thermalloy stimulated depolarisation). The intensity of the gamma relaxation, gradually increases with dose, which has been attributed to the production of disordered chain from the debris of radiation enhanced crystallite destruction. The relaxation effect, occuring at the temperatures between AVR and CVR, is assigned to the long amorphous chain segments attached partly to the crystallites, mainly from the consideration of the similarity of the dose enhanced decrease in intensity of both beta and βsub(μ)-effects. The increase with dose of the intensity of the α1 relaxation, which has been classified within CVR, confirms the grainboundary hypothesis. The second component of CVR (α2 relaxation) is due to relaxation effects of molecular chains belonging to the

  19. On the solid phase crystallization of In{sub 2}O{sub 3}:H transparent conductive oxide films prepared by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Macco, Bart; Verheijen, Marcel A.; Black, Lachlan E.; Melskens, J. [Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Barcones, Beatriz [NanoLab@TU/e, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Kessels, Wilhelmus M. M., E-mail: w.m.m.kessels@tue.nl [Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Solliance Solar Research, High Tech Campus 5, 5656 AE Eindhoven (Netherlands)

    2016-08-28

    Hydrogen-doped indium oxide (In{sub 2}O{sub 3}:H) has emerged as a highly transparent and conductive oxide, finding its application in a multitude of optoelectronic devices. Recently, we have reported on an atomic layer deposition (ALD) process to prepare high quality In{sub 2}O{sub 3}:H. This process consists of ALD of In{sub 2}O{sub 3}:H films at 100 °C, followed by a solid phase crystallization step at 150–200 °C. In this work, we report on a detailed electron microscopy study of this crystallization process which reveals new insights into the crucial aspects for achieving the large grain size and associated excellent properties of the material. The key finding is that the best optoelectronic properties are obtained by preparing the films at the lowest possible temperature prior to post-deposition annealing. Electron microscopy imaging shows that such films are mostly amorphous, but feature a very low density of embedded crystallites. Upon post-deposition annealing, crystallization proceeds merely from isotropic crystal grain growth of these embedded crystallites rather than by the formation of additional crystallites. The relatively high hydrogen content of 4.2 at. % in these films is thought to cause the absence of additional nucleation, thereby rendering the final grain size and optoelectronic properties solely dependent on the density of embedded crystallites. The temperature-dependent grain growth rate has been determined, from which an activation energy of (1.39 ± 0.04) eV has been extracted. Finally, on the basis of the observed crystallization mechanism, a simple model to fully describe the crystallization process has been developed. This model has been validated with a numerical implementation thereof, which accurately predicts the observed temperature-dependent crystallization behaviour.

  20. Size dependent compressibility of nano-ceria: Minimum near 33 nm

    International Nuclear Information System (INIS)

    Rodenbough, Philip P.; Song, Junhua; Chan, Siu-Wai; Walker, David; Clark, Simon M.; Kalkan, Bora

    2015-01-01

    We report the crystallite-size-dependency of the compressibility of nanoceria under hydrostatic pressure for a wide variety of crystallite diameters and comment on the size-based trends indicating an extremum near 33 nm. Uniform nano-crystals of ceria were synthesized by basic precipitation from cerium (III) nitrate. Size-control was achieved by adjusting mixing time and, for larger particles, a subsequent annealing temperature. The nano-crystals were characterized by transmission electron microscopy and standard ambient x-ray diffraction (XRD). Compressibility, or its reciprocal, bulk modulus, was measured with high-pressure XRD at LBL-ALS, using helium, neon, or argon as the pressure-transmitting medium for all samples. As crystallite size decreased below 100 nm, the bulk modulus first increased, and then decreased, achieving a maximum near a crystallite diameter of 33 nm. We review earlier work and examine several possible explanations for the peaking of bulk modulus at an intermediate crystallite size

  1. Size dependent compressibility of nano-ceria: Minimum near 33 nm

    Energy Technology Data Exchange (ETDEWEB)

    Rodenbough, Philip P. [Department of Applied Physics and Applied Mathematics, Materials Science and Engineering Program, Columbia University, New York, New York 10027 (United States); Chemistry Department, Columbia University, New York, New York 10027 (United States); Song, Junhua; Chan, Siu-Wai, E-mail: sc174@columbia.edu [Department of Applied Physics and Applied Mathematics, Materials Science and Engineering Program, Columbia University, New York, New York 10027 (United States); Walker, David [Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York 10964 (United States); Clark, Simon M. [ARC Center of Excellence for Core to Crust Fluid Systems and Department of Earth and Planetary Sciences, Macquarie University, Sydney, New South Wales 2019, Australia and The Bragg Institute, Australian Nuclear Science and Technology Organisation, Kirrawee DC, New South Wales 2232 (Australia); Kalkan, Bora [Department of Physics Engineering, Hacettepe University, 06800 Beytepe, Ankara (Turkey)

    2015-04-20

    We report the crystallite-size-dependency of the compressibility of nanoceria under hydrostatic pressure for a wide variety of crystallite diameters and comment on the size-based trends indicating an extremum near 33 nm. Uniform nano-crystals of ceria were synthesized by basic precipitation from cerium (III) nitrate. Size-control was achieved by adjusting mixing time and, for larger particles, a subsequent annealing temperature. The nano-crystals were characterized by transmission electron microscopy and standard ambient x-ray diffraction (XRD). Compressibility, or its reciprocal, bulk modulus, was measured with high-pressure XRD at LBL-ALS, using helium, neon, or argon as the pressure-transmitting medium for all samples. As crystallite size decreased below 100 nm, the bulk modulus first increased, and then decreased, achieving a maximum near a crystallite diameter of 33 nm. We review earlier work and examine several possible explanations for the peaking of bulk modulus at an intermediate crystallite size.

  2. Role of stacking disorder in ice nucleation.

    Science.gov (United States)

    Lupi, Laura; Hudait, Arpa; Peters, Baron; Grünwald, Michael; Gotchy Mullen, Ryan; Nguyen, Andrew H; Molinero, Valeria

    2017-11-08

    The freezing of water affects the processes that determine Earth's climate. Therefore, accurate weather and climate forecasts hinge on good predictions of ice nucleation rates. Such rate predictions are based on extrapolations using classical nucleation theory, which assumes that the structure of nanometre-sized ice crystallites corresponds to that of hexagonal ice, the thermodynamically stable form of bulk ice. However, simulations with various water models find that ice nucleated and grown under atmospheric temperatures is at all sizes stacking-disordered, consisting of random sequences of cubic and hexagonal ice layers. This implies that stacking-disordered ice crystallites either are more stable than hexagonal ice crystallites or form because of non-equilibrium dynamical effects. Both scenarios challenge central tenets of classical nucleation theory. Here we use rare-event sampling and free energy calculations with the mW water model to show that the entropy of mixing cubic and hexagonal layers makes stacking-disordered ice the stable phase for crystallites up to a size of at least 100,000 molecules. We find that stacking-disordered critical crystallites at 230 kelvin are about 14 kilojoules per mole of crystallite more stable than hexagonal crystallites, making their ice nucleation rates more than three orders of magnitude higher than predicted by classical nucleation theory. This effect on nucleation rates is temperature dependent, being the most pronounced at the warmest conditions, and should affect the modelling of cloud formation and ice particle numbers, which are very sensitive to the temperature dependence of ice nucleation rates. We conclude that classical nucleation theory needs to be corrected to include the dependence of the crystallization driving force on the size of the ice crystallite when interpreting and extrapolating ice nucleation rates from experimental laboratory conditions to the temperatures that occur in clouds.

  3. Microstructure and initial growth characteristics of the low temperature microcrystalline silicon films on silicon nitride surface

    International Nuclear Information System (INIS)

    Park, Young-Bae; Rhee, Shi-Woo

    2001-01-01

    Microstructure and initial growth characteristics of the hydrogenated microcrystalline Si (μc-Si:H) films grown on hydrogenated amorphous silicon nitride (a-SiN x :H) surface at low temperature were investigated using high resolution transmission electron microscope and micro-Raman spectroscopy. With increasing the Si and Si - H contents in the SiN x :H surfaces, μc-Si crystallites, a few nanometers in size, were directly grown on amorphous nitride surfaces. It is believed that the crystallites were grown through the nucleation and phase transition from amorphous to crystal in a hydrogen-rich ambient of gas phase and growing surface. The crystallite growth characteristics on the dielectric surface were dependent on the stoichiometric (x=N/Si) ratio corresponding hydrogen bond configuration of the SiN x :H surface. Surface facetting and anisotropic growth of the Si crystallites resulted from the different growth rate on the different lattice planes of Si. No twins and stacking faults were observed in the (111) lattice planes of the Si crystallites surrounding the a-Si matrix. This atomic-scale structure was considered to be the characteristic of the low temperature crystallization of the μc-Si:H by the strain relaxation of crystallites in the a-Si:H matrix. [copyright] 2001 American Institute of Physics

  4. In Situ Investigations of Li-MoS2 with Planar Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Wan, Jiayu [Univ. of Maryland, College Park, MD (United States). Dept. of Materials Science and Engineering; Bao, Wenzhong [Univ. of Maryland, College Park, MD (United States). Dept. of Materials Science and Engineering and Dept. of Physics; Liu, Yang [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Center for Integrated Nanotechnologies (CINT); Dai, Jiaqi [Univ. of Maryland, College Park, MD (United States). Dept. of Materials Science and Engineering; Shen, Fei [Univ. of Maryland, College Park, MD (United States). Dept. of Materials Science and Engineering; Zhou, Lihui [Univ. of Maryland, College Park, MD (United States). Dept. of Materials Science and Engineering; Cai, Xinghan [Univ. of Maryland, College Park, MD (United States). Dept. of Physics; Urban, Daniel [Univ. of Maryland, College Park, MD (United States). Dept. of Materials Science and Engineering; Li, Yuanyuan [Univ. of Maryland, College Park, MD (United States). Dept. of Materials Science and Engineering; Jungjohann, Katherine [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Center for Integrated Nanotechnologies (CINT); Fuhrer, Michael S. [Univ. of Maryland, College Park, MD (United States). Dept. of Physics; Monash Univ., Melbourne, VIC (Australia). School of Physics; Hu, Liangbing [Univ. of Maryland, College Park, MD (United States). Dept. of Materials Science and Engineering

    2014-11-25

    For this study, a planar microbattery that enables various in situ measurements of lithiation of 2D materials on the individual-flake scale is developed. A large conductivity increase of thick MoS2 crystallite lithiation due to the formation of a percolative Mo nanoparticle network embedded in a Li2S matrix is observed. The nanoscale study leads to the development of a novel charging strategy for batteries that largely improves the capacity and cycling performance confirmed in bulk MoS2/Li coin cells.

  5. Developpement d'un modele thermodynamique pour les cristallites de coke: Application aux systems carbone-hydrogene et carbone-soufre

    Science.gov (United States)

    Ouzilleau, Philippe

    Carbon materials are essential components of multiple key industrial processes. One example of such a process is the production of aluminum using the Hall-Heroult process. It is well known that important quantities of carbon materials are regularily consumed by the operation of the Hall-Heroult process. In recent years, the increased impurity content of industrial carbon materials motivated the development of a better understanding for the high temperature behavior of these specific materials. The most common forms of carbon materials used in the industry are cokes. Cokes are carbon materials which, following heat treatment, present a crystalline structure similar to that observed in graphite. However, the observed crystallite size of cokes is usually much smaller than the one observed in graphite. For this reason, the chemical and thermodynamic properties of the ordered phase of cokes (i.e. coke crystallites) are very different than those of graphite (although coke crystallites of infinite size would possess properties almost identical to graphite). Coke crystallites consist of hexagonal planes of carbon atoms stacked one above the other. This particular aspect causes strong anisotropic properties in coke crystallites. No thermodynamic model was found for the production of a reliable correlation between the effect of crystallite size and chemical composition for the predictive calculations of the thermodynamic properties (and phase equilibriums) of coke crystallites. It is also difficult to produce predictive calculations that can be compared to experimental results using such a thermodynamic model. The goal of the present work is to propose a thermodynamic model designed to solve this problem. The present model is based on the well-defined geometrical properties of coke cristallites. This geometry allows the development of mathematical equations for the calculation of the mass balances of the crystallite (using a simplified geometry) using only the commonly used

  6. Local structure and defect chemistry of [(SnSe)1.15]m(TaSe2) ferecrystals – A new type of layered intergrowth compound

    International Nuclear Information System (INIS)

    Grosse, Corinna; Atkins, Ryan; Kirmse, Holm; Mogilatenko, Anna; Neumann, Wolfgang; Johnson, David C.

    2013-01-01

    Highlights: •The crystal structure of [(SnSe) 1.15 ] m (TaSe 2 ) ferecrystals was analyzed by TEM. •The layers exhibit turbostratic disorder, but we also observed a local ordering. •The structures of the SnSe and TaSe 2 layers are similar to binary SnSe and 2H-TaSe 2 . •An increasing in-plane SnSe grain size with increasing m was observed. •Defect areas with missing, substituted or additional layers were found. -- Abstract: The atomic structure of the family of ferecrystals [(SnSe) 1.15 ] m (TaSe 2 ) (m = 1, 3, and 6) was investigated by means of transmission electron microscopy. The tantalum in the TaSe 2 layers was observed to have trigonal prismatic coordination similar to that found in the 2H polytype of bulk TaSe 2 . The structure of the SnSe constituent was found to be similar to that of orthorhombic α-SnSe. In the compounds with m = 1 and m = 3, regions with a local ordering of the layers along a commensurate axis, similar to the ordering in conventional misfit layer compounds, were observed. However, on a longer range the ferecrystals were found to exhibit a turbostratically disordered structure. Stacking defects were occasionally found in the samples in which a layer is interrupted and the surrounding layers are bent around these defects, while maintaining abrupt interfaces instead of interdiffusing. Volume defects were found in one sample of [(SnSe) 1.15 ] 1 (TaSe 2 ) 1 in which a SnSe layer locally substitutes a part of a TaSe 2 layer without interrupting the surrounding layers

  7. Misfit Layer Compounds and Ferecrystals: Model Systems for Thermoelectric Nanocomposites

    Directory of Open Access Journals (Sweden)

    Devin R. Merrill

    2015-04-01

    Full Text Available A basic summary of thermoelectric principles is presented in a historical context, following the evolution of the field from initial discovery to modern day high-zT materials. A specific focus is placed on nanocomposite materials as a means to solve the challenges presented by the contradictory material requirements necessary for efficient thermal energy harvest. Misfit layer compounds are highlighted as an example of a highly ordered anisotropic nanocomposite system. Their layered structure provides the opportunity to use multiple constituents for improved thermoelectric performance, through both enhanced phonon scattering at interfaces and through electronic interactions between the constituents. Recently, a class of metastable, turbostratically-disordered misfit layer compounds has been synthesized using a kinetically controlled approach with low reaction temperatures. The kinetically stabilized structures can be prepared with a variety of constituent ratios and layering schemes, providing an avenue to systematically understand structure-function relationships not possible in the thermodynamic compounds. We summarize the work that has been done to date on these materials. The observed turbostratic disorder has been shown to result in extremely low cross plane thermal conductivity and in plane thermal conductivities that are also very small, suggesting the structural motif could be attractive as thermoelectric materials if the power factor could be improved. The first 10 compounds in the [(PbSe1+δ]m(TiSe2n family (m, n ≤ 3 are reported as a case study. As n increases, the magnitude of the Seebeck coefficient is significantly increased without a simultaneous decrease in the in-plane electrical conductivity, resulting in an improved thermoelectric power factor.

  8. Mechanism of pyrrhotite formation from ferric oxyhydroxide catalyst; Kokoritsu sekitan ekika shokubai no kaihatsu (Okishi suisankatetsu shokubai karano pyrrhotite seisei kyodo)

    Energy Technology Data Exchange (ETDEWEB)

    Tazawa, K.; Koyama, T.; Kaneko, T.; Shimasaki, K. [Nippon Brown Coal Liquefaction Co. Ltd., Tokyo (Japan)

    1996-10-28

    It is thought that iron-based catalysts for coal liquefaction exercise their catalytic activity by forming pyrrhotite (Fe(1-x)S). However, there are still a lot of unknown problems remained concerning the formation and agglomeration behaviors of pyrrhotite. These make a difficulty for improving the activity of iron-based catalysts. In this study, sulfiding behaviors of {alpha}-iron oxyhydroxide ({alpha}-FeOOH) and {gamma}-iron oxyhydroxide ({gamma}-FeOOH) were investigated to reveal the formation and agglomeration behaviors of pyrrhotite. It was found that pyrrhotite was easily converted from ferric oxyhydroxide catalysts having large specific surface areas at the sulfiding temperature below 250{degree}C, and fine crystallites of pyrrhotite were formed at the initial stage of sulfiding. Crystal growth of pyrrhotite at the sulfiding temperature over 350{degree}C depended on the catalyst forms. It was also found that smaller crystallites of pyrrhotite were formed from {gamma}-FeOOH than from {alpha}-FeOOH and amorphous iron oxyhydroxide. 5 refs., 7 figs., 1 tab.

  9. Synthesis of some Mg/Co-Al type nano hydrotalcites and characterization

    Directory of Open Access Journals (Sweden)

    Khadijeh Shekoohi

    2017-01-01

    Full Text Available Hydrotalcites are quite prevalent in nature and their importance is growing more and more because of their very wide range of potential applications and uses. Because hydrotalcite does not exist in significant quantities in nature, coprecipitation methods are the most used for prepartion of hydrotalcite. In this study: Two types of Nano hydrotalcite compounds containing one divalent (Mg-Al and two divalent cation(Co-Mg-Al were synthesized based on aqueous solutions of corresponding nitrates by co-precipitation method. The molar ratio influences structure and performance of hydrotalcite largely. The crystallinity and crystallite size of the hydrotalcite were observed to varying with molar of M2+/M3+ ratio. The structure and morphology of the Nano hydrotalcites were characterized by powder X-ray diffraction, scanning electron microscopy, Fourier-transformed Infrared spectroscopy and thermal gravimetric analysis. The crystallite size of the hydrotalcite was observed to increase when the Mg/Al molar ratio increases and, more significantly, when a second divalent cation (cobalt was added.

  10. Photoluminescent properties of single crystal diamond microneedles

    Science.gov (United States)

    Malykhin, Sergey A.; Ismagilov, Rinat R.; Tuyakova, Feruza T.; Obraztsova, Ekaterina A.; Fedotov, Pavel V.; Ermakova, Anna; Siyushev, Petr; Katamadze, Konstantin G.; Jelezko, Fedor; Rakovich, Yury P.; Obraztsov, Alexander N.

    2018-01-01

    Single crystal needle-like diamonds shaped as rectangular pyramids were produced by combination of chemical vapor deposition and selective oxidation with dimensions and geometrical characteristics depending on the deposition process parameters. Photoluminescence spectra and their dependencies on wavelength of excitation radiation reveal presence of nitrogen- and silicon-vacancy color centers in the diamond crystallites. Photoluminescence spectra, intensity mapping, and fluorescence lifetime imaging microscopy indicate that silicon-vacancy centers are concentrated at the crystallites apex while nitrogen-vacancy centers are distributed over the whole crystallite. Dependence of the photoluminescence on excitation radiation intensity demonstrates saturation and allows estimation of the color centers density. The combination of structural parameters, geometry and photoluminescent characteristics are prospective for advantageous applications of these diamond crystallites in quantum information processing and optical sensing.

  11. Features of bicrystal growth during the directional crystallization of metal melts

    Energy Technology Data Exchange (ETDEWEB)

    Gubernatorov, V. V.; Sycheva, T. S., E-mail: sych@imp.uran.ru; Gundyrev, V. M.; Akshentsev, Yu. N. [Russian Academy of Sciences, M.N. Mikheev Institute of Metal Physics, Ural Branch (Russian Federation)

    2017-03-15

    The factors responsible for the formation of different configurations of boundaries between adjacent crystallites during their growth from melt by Bridgman and Czochralski methods have been considered by an of example Fe–20 wt % Ga alloy and Ni bicrystals. It is found that the configuration of intercrystallite boundary is related to the features of crystallite growth, caused by the strained state of intercrystallite and interphase (crystal–melt) boundaries, the difference in the linear thermal expansion coefficients of the crystallite boundaries and bulk, and the shape (geometry) of the bicrystal cross section. It is suggested that the strained state of boundaries and the formation of substructure in crystallites during directional crystallization from metal melt are significantly affected by their deformation under the melt weight.

  12. Large-D gravity and low-D strings.

    Science.gov (United States)

    Emparan, Roberto; Grumiller, Daniel; Tanabe, Kentaro

    2013-06-21

    We show that in the limit of a large number of dimensions a wide class of nonextremal neutral black holes has a universal near-horizon limit. The limiting geometry is the two-dimensional black hole of string theory with a two-dimensional target space. Its conformal symmetry explains the properties of massless scalars found recently in the large-D limit. For black branes with string charges, the near-horizon geometry is that of the three-dimensional black strings of Horne and Horowitz. The analogies between the α' expansion in string theory and the large-D expansion in gravity suggest a possible effective string description of the large-D limit of black holes. We comment on applications to several subjects, in particular to the problem of critical collapse.

  13. Near-infrared emission from mesoporous crystalline germanium

    Energy Technology Data Exchange (ETDEWEB)

    Boucherif, Abderraouf; Aimez, Vincent; Arès, Richard, E-mail: richard.ares@usherbrooke.ca [Institut Interdisciplinaire d’Innovation Technologique (3IT), Université de Sherbrooke, 3000 Boulevard Université, Sherbrooke, J1K OA5, Québec (Canada); Laboratoire Nanotechnologies Nanosystèmes (LN2)-CNRS UMI-3463, Université de Sherbrooke, 3000 Boulevard Université, Sherbrooke, J1K OA5, Québec (Canada); Korinek, Andreas [Canadian Centre for Electron Microscopy, Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario, L8S 4M1 (Canada)

    2014-10-15

    Mesoporous crystalline germanium was fabricated by bipolar electrochemical etching of Ge wafer in HF-based electrolyte. It yields uniform mesoporous germanium layers composed of high density of crystallites with an average size 5-7 nm. Subsequent extended chemical etching allows tuning of crystallites size while preserving the same chemical composition. This highly controllable nanostructure exhibits photoluminescence emission above the bulk Ge bandgap, in the near-infrared range (1095-1360nm) with strong evidence of quantum confinement within the crystallites.

  14. Structure variations of carbonizing lignin

    International Nuclear Information System (INIS)

    Otani, C.; Polidoro, H.A.; Otani, S.; Craievich, A.F.

    1984-01-01

    The studied lignin is a by-product of the process of ethanol production from eucaliptus. It was heat-treated under inert atmosphere conditions at increasing temperatures from 300C up to 2400C. The structural variations were studied by wide-angle X-ray diffraction, small-angle X-ray scattering and infrared absorption spectroscopy. The bulk and 'real' density of the compacted materials have also been determined as functions of the final temperature. These experimental results enabled us to establish a mechanism of structure variation based on the formation of a turbostratic graphite-like and porous structure within the initially amorphous lignin matrix. (Author) [pt

  15. Biomineralization-inspired synthesis of chitosan/hydroxyapatite biocomposites based on a novel bilayer rate-controlling model.

    Science.gov (United States)

    Hu, Jing-Xiao; Ran, Jia-Bing; Chen, Si; Shen, Xin-Yu; Tong, Hua

    2015-12-01

    In order to prepare sophisticated biomaterials using a biomimetic approach, a deeper understanding of biomineralization is needed. Of particular importance is the control and regulation of the mineralization process. In this study, a novel bilayer rate-controlling model was designed to investigate the factors potentially influencing mineralization. In the absence of a rate-controlling layer, nano-scale hydroxyapatite (HA) crystallites exhibited a spherical morphology, whereas, in the presence of a rate-controlling layer, HA crystallites were homogeneously dispersed and spindle-like in structure. The mineralization rate had a significant effect on controlling the morphology of crystals. Furthermore, in vitro tests demonstrated that the reaction layer containing spindle-like HA crystallites possessed superior biological properties. These results suggest that a slow mineralization rate is required for controlling the morphology of inorganic crystallites, and consumption by the rate-controlling layer ensured that the ammonia concentration remained low. This study demonstrates that a biomimetic approach can be used to prepare novel biomaterials containing HA crystallites that have different morphologies and biological properties. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. Crystal structure of pure ZrO2 nanopowders

    International Nuclear Information System (INIS)

    Lamas, D.G.; Rosso, A.M.; Anzorena, M. Suarez; Fernandez, A.; Bellino, M.G.; Cabezas, M.D.; Walsoee de Reca, N.E.; Craievich, A.F.

    2006-01-01

    The crystal structure of pure (undoped) zirconia nanopowders synthesized by different wet-chemical routes has been investigated by synchrotron X-ray diffraction. Whereas some previous authors reported the retention of the cubic phase in similar materials, we demonstrate here that pure zirconia nanopowders with average crystallite sizes ranging from 5 to 10 nm exhibit the tetragonal phase. In addition, our results suggest that a tetragonal-to-cubic transition for decreasing crystallite size could eventually occur at a very small critical crystallite size

  17. Magnetic anisotropy and order parameter in nanostructured CoPt particles

    Science.gov (United States)

    Komogortsev, S. V.; Iskhakov, R. S.; Zimin, A. A.; Filatov, E. Yu.; Korenev, S. V.; Shubin, Yu. V.; Chizhik, N. A.; Yurkin, G. Yu.; Eremin, E. V.

    2013-10-01

    The correlation of magnetic anisotropy energy with order parameter in the crystallites of CoPt nanostructured particles prepared by thermal decomposition and further annealing has been studied by investigation of the approach magnetization to saturation curves and x-ray powder diffraction pattern profiles. It is shown that magnetic anisotropy energy value in partially ordered CoPt crystallite could be described as an intermediate case between two extremes, corresponding to either single or several c-domains of L10 phase in crystallite.

  18. Cavitational synthesis of nanostructured inorganic materials for enhanced heterogeneous catalysis

    Science.gov (United States)

    Krausz, Ivo Michael

    The synthesis of nanostructured inorganic materials by hydrodynamic cavitation processing was investigated. The goal of this work was to develop a general synthesis technique for nanostructured materials with a control over crystallite size in the 1--20 nm range. Materials with crystallite sizes in this range have shown enhanced catalytic activity compared to materials with larger crystallite sizes. Several supported and unsupported inorganic materials were studied to understand the effects of cavitation on crystallite size. Cavitation processing of calcium fluoride resulted in more spherical particles, attached to one another by melted necks. This work produced the first evidence of shock wave heating of nanostructured materials by hydrodynamic cavitation processing. Hydrodynamic cavitation synthesis of various catalytic support materials indicated that their phase composition and purity could be controlled by adjustment of the processing parameters. Zirconia/alumina supports synthesized using hydro-dynamic cavitation and calcined to 1368 K retained a high purity cubic zirconia phase, whereas classically prepared samples showed a phase transformation to monoclinic zirconia. Similarly, the synthesis of alumina resulted in materials with varying Bohmite and Bayerite contents as a function of the process parameters. High temperature calcination resulted in stable alumina supports with varying amounts of delta-, and theta-alumina. Synthesis studies of palladium and silver showed modest variations in crystallite size as a function of cavitation process parameters. Calcination resulted in larger grain materials, indicating a disappearance of intergrain boundaries. Based on these results, a new synthesis method was studied involving controlled agglomeration of small silver crystallites by hydrodynamic cavitation processing, followed by deposition on alumina. The optimal pH, concentration, and processing time for controlling the silver crystallite size in the cavitation

  19. A detailed TEM and SEM study of Ni-base alloys oxide scales formed in primary conditions of pressurized water reactor

    International Nuclear Information System (INIS)

    Sennour, Mohamed; Marchetti, Loic; Martin, Frantz; Perrin, Stephane; Molins, Regine; Pijolat, Michele

    2010-01-01

    The oxide film formed on nickel-based alloys in pressurized water reactors (PWR) primary coolant conditions (325 o C, aqueous media) is very thin, in the range of 1-100 nm thick, depending on the surface state and on the corrosion test duration. The nature and the structure of this scale have been investigated by Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM). TEM observations revealed an oxide layer divided in two parts. The internal layer was mainly composed of a continuous spinel layer, identified as a mixed iron and nickel chromite (Ni (1-x) Fe x Cr 2 O 4 ). Moreover, nodules of Cr 2 O 3 , with a size about 5 nm, were present at the interface between this spinel and the alloy. No chromium depletion was observed in the alloy, at the alloy/oxide interface. The external layer is composed of large crystallites corresponding to a spinel structure rich in iron (Ni (1-z) Fe (2+z) O 4 ) resulting from precipitation phenomena. SEM and TEM observations showed a link between the nucleation and/or the growth of crystallites of nickel ferrite and the crystallographic orientation of the substrate. A link between the presence of surface defects and the nucleation of the crystallites was also underlined by SEM observations. Partially hydrated nickel hydroxide, was also observed by TEM in the external scale. Based on these results, some considerations about the mechanism of formation of this oxide layer are discussed.

  20. Elaboration, caractérisation structurale et mise en forme d'alliages de magnésium vitreux

    OpenAIRE

    Puech , Sylvain

    2008-01-01

    The amorphous structure of metallic glasses results in high mechanical properties at room temperature, high hardness and strength, large elastic deformation domain, but also interesting forming capacity in their supercooled liquid region. Because of their out of equilibrium state, a crystallisation can develop during a heat treatment and lead to the formation of a glass/crystallites composite, for which properties are changed. We investigate in this thesis the Mg based bulk metallic glasses f...

  1. Effect of twins in Ni substrates on the microstructure of La{sub 2}Zr{sub 2}O{sub 7} films for coated conductors

    Energy Technology Data Exchange (ETDEWEB)

    Petit, Sarah [CRETA-CNRS, 25 av. des Martyrs, BP166, 38042 Grenoble Cedex (France); Institut Néel-CNRS, 25 av. des Martyrs, BP166, 38042 Grenoble Cedex (France); Pairis, Sébastien [Institut Néel-CNRS, 25 av. des Martyrs, BP166, 38042 Grenoble Cedex (France); Mikolajczyk, Mélissa [CRETA-CNRS, 25 av. des Martyrs, BP166, 38042 Grenoble Cedex (France); Institut Néel-CNRS, 25 av. des Martyrs, BP166, 38042 Grenoble Cedex (France); Ortega, Luc [Institut Néel-CNRS, 25 av. des Martyrs, BP166, 38042 Grenoble Cedex (France); Soubeyroux, Jean-Louis [CRETA-CNRS, 25 av. des Martyrs, BP166, 38042 Grenoble Cedex (France); Institut Néel-CNRS, 25 av. des Martyrs, BP166, 38042 Grenoble Cedex (France); Odier, Philippe [CRETA-CNRS, 25 av. des Martyrs, BP166, 38042 Grenoble Cedex (France); Institut Néel-CNRS, 25 av. des Martyrs, BP166, 38042 Grenoble Cedex (France)

    2013-03-01

    La{sub 2}Zr{sub 2}O{sub 7} (LZO) films were deposited by chemical solution deposition on Ni{sub 95}Wi{sub 5}rolling assisted bi-axially textured substrates to be used in YBa{sub 2}Cu{sub 3}O{sub 7} (YBCO) coated conductors. These LZO films were proved of good qualities for YBCO deposition by metal organic chemical vapor deposition that is an economic process. The mosaic of LZO films is only slightly degraded by the process of grain-to-grain epitaxial transfer (16% with respect to that of the substrate). The film is composed of small crystallites (20–40 nm) and larger anomalous crystallites (100–400 nm) found in great number in transferred twins from the substrate. The anomalous crystallites are poorly crystallized or amorphous and contain more C than areas with normal crystallites. High temperature in-situ X-ray diffraction shows a sudden crystallization at 860 °C that does not seem to involve a solid state reaction. The anomalous crystallites are analyzed to result from a locally enhanced barrier to nucleation and might reveal poor characteristics of the crystallization. - Highlights: ► La{sub 2}Zr{sub 2}O{sub 7} film on Ni{sub 95}W{sub 5} RABiT. ► Anomalous crystallites (100-400 nm) are amorphous on transferred twins. ► La{sub 2}Zr{sub 2}O{sub 7} crystallization appears above 860 °C.

  2. Nucleation and Early Stages of Layer-by-Layer Growth of Metal Organic Frameworks on Surfaces

    Science.gov (United States)

    2015-01-01

    High resolution atomic force microscopy (AFM) is used to resolve the evolution of crystallites of a metal organic framework (HKUST-1) grown on Au(111) using a liquid-phase layer-by-layer methodology. The nucleation and faceting of individual crystallites is followed by repeatedly imaging the same submicron region after each cycle of growth and we find that the growing surface is terminated by {111} facets leading to the formation of pyramidal nanostructures for [100] oriented crystallites, and triangular [111] islands with typical lateral dimensions of tens of nanometres. AFM images reveal that crystallites can grow by 5–10 layers in each cycle. The growth rate depends on crystallographic orientation and the morphology of the gold substrate, and we demonstrate that under these conditions the growth is nanocrystalline with a morphology determined by the minimum energy surface. PMID:26709359

  3. High capacity orthorhombic LiMnO{sub 2} phases: role of piling up defects; Phases LiMnO{sub 2} orthorhombiques a haute capacite: role des defauts d`empilement

    Energy Technology Data Exchange (ETDEWEB)

    Deniard, P.; Croguennec, L.; Brec, R. [IMN Laboratoire de Chimie des Solides, 44 - Nantes (France); Lecerf, A. [Institut National des Sciences Appliquees (INSA), 35 - Rennes (France)

    1996-12-31

    The electrochemical performances of orthorhombic LiMnO{sub 2} compounds are analyzed in order to find a structural and/or morphological origin to the differences of electrochemical behaviours observed in compounds with different size of crystallites and different amounts of lattice defects. Energy capacity performances of 200 Ah/kg are reached for materials with crystallites of about 10{sup 7} Angstrom{sup 3} and with about 7% of defects, while energy capacities of only 80 Ah/kg are obtained for materials with ten times bigger crystallites. (J.S.) 3 refs.

  4. High capacity orthorhombic LiMnO{sub 2} phases: role of piling up defects; Phases LiMnO{sub 2} orthorhombiques a haute capacite: role des defauts d`empilement

    Energy Technology Data Exchange (ETDEWEB)

    Deniard, P; Croguennec, L; Brec, R [IMN Laboratoire de Chimie des Solides, 44 - Nantes (France); Lecerf, A [Institut National des Sciences Appliquees (INSA), 35 - Rennes (France)

    1997-12-31

    The electrochemical performances of orthorhombic LiMnO{sub 2} compounds are analyzed in order to find a structural and/or morphological origin to the differences of electrochemical behaviours observed in compounds with different size of crystallites and different amounts of lattice defects. Energy capacity performances of 200 Ah/kg are reached for materials with crystallites of about 10{sup 7} Angstrom{sup 3} and with about 7% of defects, while energy capacities of only 80 Ah/kg are obtained for materials with ten times bigger crystallites. (J.S.) 3 refs.

  5. X-ray diffraction study of the structure of detonation nanodiamonds

    International Nuclear Information System (INIS)

    Ozerin, A. N.; Kurkin, T. S.; Ozerina, L. A.; Dolmatov, V. Yu.

    2008-01-01

    The spatial structure of aggregates formed by detonation nanodiamonds is investigated using the wide-angle and small-angle X-ray scattering techniques. The effective sizes of crystallites and the crystallite size distribution function are determined. The shape of scattering aggregates is restored from the small-angle X-ray scattering data. An analysis of the results obtained allowed the conclusion that the nanodiamond aggregates have an extended spatial structure composed of nine to ten clusters, each involving four to five crystallites with a crystal lattice of the diamond type

  6. Influence of Ba/Fe mole ratios on magnetic properties, crystallite size and shifting of X-ray diffraction peaks of nanocrystalline BaFe12O19 powder, prepared by sol gel auto combu

    Science.gov (United States)

    Suastiyanti, Dwita; Sudarmaji, Arif; Soegijono, Bambang

    2012-06-01

    Barium hexaferrite BaFe12O19 (BFO) is of great importance as permanent magnets, particularly for magnetic recording as well as in microwave devices. Nano-crystalline BFO powders were prepared by sol gel auto combustion method in citric acid - metal nitrates system. Hence the mole ratios of Ba/Fe were variated at 1:12; 1:11.5 and 1:11. Ratio of cation to fuel was fixed at 1:1. An appropriate amount of amonia solution was added dropwise to this solution with constant stirring until the PH reached 7 in all cases. Heating at 850oC for 10 hours for each sample to get final formation of BFO nanocrystalline. The data from XRD showing the lattice parameters a,c and the unit-cell volume V, confirm that BFO with ratio 1:12 has same crystall parameters with ratio 1:11. Ratio of Ba/Fe 1:12 and 1:11 have diffraction pattern similarly at almost each 2 θ for each samples. Ratio of Ba/Fe 1: 11.5 has the finest crystallite size 22 nm. Almost diffraction pattern peaks of Ba/Fe 1:11.5 move to the left from of Ba/Fe 1:12 then return to diffraction pattern of Ba/Fe 1:12 for Ba/Fe 1:11. SEM observations show the particle size less than 100 nm and the same shape for each sample. Ratio of Ba/Fe 1: 12 gives the highest intrinsic coercive Hc = 427.3 kA/m. The highest remanent magnetization is at ratio 1:11 with Mr = 0.170 T. BFO with mole ratio 1:11.5 has the finest grain 22 nm, good magnetic properties and the highest value of best FoM 89%.

  7. Computational analysis of electrical conduction in hybrid nanomaterials with embedded non-penetrating conductive particles

    Science.gov (United States)

    Cai, Jizhe; Naraghi, Mohammad

    2016-08-01

    In this work, a comprehensive multi-resolution two-dimensional (2D) resistor network model is proposed to analyze the electrical conductivity of hybrid nanomaterials made of insulating matrix with conductive particles such as CNT reinforced nanocomposites and thick film resistors. Unlike existing approaches, our model takes into account the impenetrability of the particles and their random placement within the matrix. Moreover, our model presents a detailed description of intra-particle conductivity via finite element analysis, which to the authors’ best knowledge has not been addressed before. The inter-particle conductivity is assumed to be primarily due to electron tunneling. The model is then used to predict the electrical conductivity of electrospun carbon nanofibers as a function of microstructural parameters such as turbostratic domain alignment and aspect ratio. To simulate the microstructure of single CNF, randomly positioned nucleation sites were seeded and grown as turbostratic particles with anisotropic growth rates. Particle growth was in steps and growth of each particle in each direction was stopped upon contact with other particles. The study points to the significant contribution of both intra-particle and inter-particle conductivity to the overall conductivity of hybrid composites. Influence of particle alignment and anisotropic growth rate ratio on electrical conductivity is also discussed. The results show that partial alignment in contrast to complete alignment can result in maximum electrical conductivity of whole CNF. High degrees of alignment can adversely affect conductivity by lowering the probability of the formation of a conductive path. The results demonstrate approaches to enhance electrical conductivity of hybrid materials through controlling their microstructure which is applicable not only to carbon nanofibers, but also many other types of hybrid composites such as thick film resistors.

  8. Synthesis of strontium substituted barium titanate nanoparticles by mechanical alloying and high power ultrasonication destruction

    Energy Technology Data Exchange (ETDEWEB)

    Yustanti, Erlina, E-mail: erlina.yustanti@ui.ac.id [Graduate Program of Material Science, Faculty of Mathematics and Natural Sciences University of Indonesia Jl. Salemba Raya No. 04 Jakarta 10430 (Indonesia); Department of Metallurgy, Faculty of Engineering University of Sultan AgengTirtayasa Jl. Jenderal Sudirman KM 03 Cilegon-Banten 65134 (Indonesia); Hafizah, Mas Ayu Elita, E-mail: kemasayu@yahoo.com; Manaf, Azwar, E-mail: azwar@ui.ac.id [Graduate Program of Material Science, Faculty of Mathematics and Natural Sciences University of Indonesia Jl. Salemba Raya No. 04 Jakarta 10430 (Indonesia)

    2016-04-19

    This paper reports the particle and crystallite size characterizations of mechanically alloyed Ba{sub (1-x)}Sr{sub x}TiO{sub 3} (BST) with x = 0.3 and 0.7 prepared with the assistance of a high-power sonicator. Analytical grade BaCO{sub 3}, TiO{sub 2} and SrCO{sub 3} precursors with a purity of greater than 99 wt.% were mixed and milled using a planetary ball mill to a powder weight ratio of 10:1. Powders obtained after 20 hours of milling time were then sintered at 1200°C for 4 hours to form crystalline powders.These powders were further treated ultrasonically under a fixed 6.7 gr/l particle concentration in demineralized water for 1, 3, 5, 7 hours and a fixed ultrasonic irradiation time of 1 hour to the dispersion of 6.7; 20; 33.3 gr/l concentrations. As to the results of crystallite size characterization, it is demonstrated that the mean crystallite size of BST with x = 0.3 and 0.7 undergo a slight change after the first 1 hour irradiation time and then remain almost unchanged. This was in contrary to the particle size in which the mean particle size of BST with x = 0.3 increased from 765 nm to 1405 nm after 7 hours irradiation time, while that of x = 0.7 increased from 505 nm to 1298 nm after 3 hours and then reduced back to the initial size after 7 hours ultra sonication time. The increase in particle size was due to large of cohesive forces among fine particles. It is also demonstrated that the concentration of particles in a dispersion with anionic surfactant do not effective to reduce the particle sizes ultrasonically. Nanoparticles with the mean size respectively 40 and 10 times larger than their respective crystallite size were successfully obtained respectively in x = 0.3 and x = 0.7.

  9. Synthesis of strontium substituted barium titanate nanoparticles by mechanical alloying and high power ultrasonication destruction

    International Nuclear Information System (INIS)

    Yustanti, Erlina; Hafizah, Mas Ayu Elita; Manaf, Azwar

    2016-01-01

    This paper reports the particle and crystallite size characterizations of mechanically alloyed Ba (1-x) Sr x TiO 3 (BST) with x = 0.3 and 0.7 prepared with the assistance of a high-power sonicator. Analytical grade BaCO 3 , TiO 2 and SrCO 3 precursors with a purity of greater than 99 wt.% were mixed and milled using a planetary ball mill to a powder weight ratio of 10:1. Powders obtained after 20 hours of milling time were then sintered at 1200°C for 4 hours to form crystalline powders.These powders were further treated ultrasonically under a fixed 6.7 gr/l particle concentration in demineralized water for 1, 3, 5, 7 hours and a fixed ultrasonic irradiation time of 1 hour to the dispersion of 6.7; 20; 33.3 gr/l concentrations. As to the results of crystallite size characterization, it is demonstrated that the mean crystallite size of BST with x = 0.3 and 0.7 undergo a slight change after the first 1 hour irradiation time and then remain almost unchanged. This was in contrary to the particle size in which the mean particle size of BST with x = 0.3 increased from 765 nm to 1405 nm after 7 hours irradiation time, while that of x = 0.7 increased from 505 nm to 1298 nm after 3 hours and then reduced back to the initial size after 7 hours ultra sonication time. The increase in particle size was due to large of cohesive forces among fine particles. It is also demonstrated that the concentration of particles in a dispersion with anionic surfactant do not effective to reduce the particle sizes ultrasonically. Nanoparticles with the mean size respectively 40 and 10 times larger than their respective crystallite size were successfully obtained respectively in x = 0.3 and x = 0.7.

  10. Reflective metallic coatings for first mirrors on ITER

    International Nuclear Information System (INIS)

    Eren, Baran; Marot, Laurent; Litnovsky, Andrey; Matveeva, Maria; Steiner, Roland; Emberger, Valentin; Wisse, Marco; Mathys, Daniel; Covarel, Gregory; Meyer, Ernst

    2011-01-01

    Metallic mirrors are foreseen to play a crucial role for all optical diagnostics in ITER. Therefore, the development of reliable techniques for the production of mirrors which are able to maintain their optical properties in the harsh ITER environment is highly important. By applying magnetron sputtering and evaporation techniques, rhodium and molybdenum films have been prepared for tokamak tests. The films were characterised in terms of chemical composition, surface roughness, crystallite structure, reflectivity and adhesion. No impurities were detected on the surface after deposition. The effects of deposition parameters and substrate temperature on the resulting crystallite structure, surface roughness and hence on the reflectivity, were investigated. The films are found to exhibit nanometric crystallites with a dense columnar structure. Open boundaries between the crystallite columns, which are sometimes present after evaporation, are found to reduce the reflectivity as compared to rhodium or molybdenum references.

  11. Reflective metallic coatings for first mirrors on ITER

    Energy Technology Data Exchange (ETDEWEB)

    Eren, Baran, E-mail: baran.eren@unibas.ch [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Marot, Laurent [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Litnovsky, Andrey; Matveeva, Maria [Institut fuer Energieforschung (Plasmaphysik), Forschungszentrum Juelich, Association EURATOM-FZJ, D 52425 Juelich (Germany); Steiner, Roland; Emberger, Valentin; Wisse, Marco [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Mathys, Daniel [Centre of Microscopy, University of Basel, Klingelbergstrasse 50/70, CH-4056 Basel (Switzerland); Covarel, Gregory [Laboratoire de Physique et Mecanique Textile EA CNRS 7189, Universite de Haute Alsace, 61 rue Albert Camus, 68093 Mulhouse Cedex (France); Meyer, Ernst [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland)

    2011-10-15

    Metallic mirrors are foreseen to play a crucial role for all optical diagnostics in ITER. Therefore, the development of reliable techniques for the production of mirrors which are able to maintain their optical properties in the harsh ITER environment is highly important. By applying magnetron sputtering and evaporation techniques, rhodium and molybdenum films have been prepared for tokamak tests. The films were characterised in terms of chemical composition, surface roughness, crystallite structure, reflectivity and adhesion. No impurities were detected on the surface after deposition. The effects of deposition parameters and substrate temperature on the resulting crystallite structure, surface roughness and hence on the reflectivity, were investigated. The films are found to exhibit nanometric crystallites with a dense columnar structure. Open boundaries between the crystallite columns, which are sometimes present after evaporation, are found to reduce the reflectivity as compared to rhodium or molybdenum references.

  12. Retention at room temperature of the tetragonal t''-form in Sc{sub 2}O{sub 3}-doped ZrO{sub 2} nanopowders

    Energy Technology Data Exchange (ETDEWEB)

    Abdala, Paula M., E-mail: pabdala@citefa.gov.a [CINSO (Centro de Investigaciones en Solidos), CITEFA-CONICET, J.B. de La Salle 4397, 1603 Villa Martelli, Pcia. de Buenos Aires (Argentina); Lamas, Diego G. [CINSO (Centro de Investigaciones en Solidos), CITEFA-CONICET, J.B. de La Salle 4397, 1603 Villa Martelli, Pcia. de Buenos Aires (Argentina); Fantini, Marcia C.A.; Craievich, Aldo F. [Instituto de Fisica, FAP, USP, Travessa R da Rua do Matao, No. 187, Cidade Universitaria, 05508-900 Sao Paulo (Brazil)

    2010-04-16

    Synchrotron X-ray powder diffraction was applied to the study of the effect of crystallite size on the crystal structure of ZrO{sub 2}-10 mol% Sc{sub 2}O{sub 3} nanopowders synthesized by a nitrate-lysine gel-combustion route. Nanopowders with different average crystallite sizes were obtained by calcination at several temperatures, ranging from 650 to 1200 {sup o}C. The metastable t''-form of the tetragonal phase, exhibiting a cubic unit cell and tetragonal P4{sub 2}/nmc spatial symmetry, was retained at room temperature in fine nanocrystalline powders, completely avoiding the presence of the stable rhombohedral {beta} phase. Differently, this phase was identified in samples calcined at high temperatures and its content increased with increasing crystallite size. The critical maximum crystallite size for the retention of the mestastable t''-form resulted of about 35 nm.

  13. Large deviations

    CERN Document Server

    Varadhan, S R S

    2016-01-01

    The theory of large deviations deals with rates at which probabilities of certain events decay as a natural parameter in the problem varies. This book, which is based on a graduate course on large deviations at the Courant Institute, focuses on three concrete sets of examples: (i) diffusions with small noise and the exit problem, (ii) large time behavior of Markov processes and their connection to the Feynman-Kac formula and the related large deviation behavior of the number of distinct sites visited by a random walk, and (iii) interacting particle systems, their scaling limits, and large deviations from their expected limits. For the most part the examples are worked out in detail, and in the process the subject of large deviations is developed. The book will give the reader a flavor of how large deviation theory can help in problems that are not posed directly in terms of large deviations. The reader is assumed to have some familiarity with probability, Markov processes, and interacting particle systems.

  14. A simple and rapid method for determining orientations and misorientations of crystalline specimens in TEM

    DEFF Research Database (Denmark)

    Liu, Q.

    1995-01-01

    direction, the orientation of any crystallite can be obtained by determining the relative position of the Kikuchi pattern on the screen. Then, for one interesting area containing many crystallites which have closely related orientations (difference less than 15 degrees), the orientations of the different...

  15. Structure of CdTe nanoparticles in glass

    Science.gov (United States)

    Hayes, T. M.; Nagpal, Swati; Persans, P. D.

    2000-03-01

    Optical long-pass wavelength filters are generally made by growing small crystallites of appropriate semiconductors in a transparent glass matrix. Depending on the semiconductor, these systems are candidates for interesting and important nonlinear optical switching applications. The structure of these nanocrystals has been shown to be a valuable indicator of the chemical and thermodynamic processes during crystallite growth and dissolution. We have used x-ray absorption spectroscopy to study the structure of the crystallites produced during heat treatment of filter glasses containing Cd and Te and producing optical absorption edges at the band gap of bulk CdTe. The results will be discussed.

  16. Some structural characteristics of gamma-irradiated pure and Li2O-doped NiO solids

    International Nuclear Information System (INIS)

    Ramadan, A.A.; Dessouki, A.M.

    1989-01-01

    The induced structural changes, due to Li 2 O-doping (2.5 mol%) and γ-irradiation (10-80 Mrad), of NiO were investigated by XRD analyses. The results obtained revealed that lithium-doping resulted in a significant increase in the internal strain and a decrease in lattice parameter. These changes were explained in terms of creation of Ni 3+ ions in the doped solids. γ-Irradiation of pure and doped solids effected a decrease in both crystallite size and microstrain upon subjecting to doses of 20 and 30 Mrad. Higher doses induced an increase in both parameters in the case of pure NiO and a further decrease in case of the doped solid. These results were attributed to splitting of the large strained crystallites and to an activated sintering of the small strained ones. γ-Irradiation effected also an increase in the lattice parameters of pure and doped solids due to removal of some excess oxygen with subsequent decrease in the concentration of Ni 3+ ions. (author)

  17. Structure and Properties of the Aluminide Coatings on the Inconel 625 Superalloy

    Science.gov (United States)

    Adamiak, Stanisław; Bochnowski, Wojciech; Dziedzic, Andrzej; Filip, Ryszard; Szeregij, Eugeniusz

    2016-01-01

    The research samples used in this study were based on the Inconel 625 alloy; the examined samples were coated with aluminide films deposited in a low-activity chemical vapor deposition (CVD) process. The samples' microstructure was investigated with optical and electron microscopy and energy dispersive X-ray spectroscopy analysis. Hardness measurements were performed using Vickers and Berkovich test methods. The adhesion of the aluminide coating was determined by fractography. It was shown that the fracture mechanism was different for the respective zones of the aluminide coating and the substrate material. The outer zone of the aluminide coating is characterized by an intercrystalline fracture, with a small contribution of transcrystalline fracture within individual grains (large crystallites in the bottom of the zone, composed of smaller crystallites, also show an intercrystalline fracture). The substrate material exhibited a ductile intercrystalline fracture. Based on this investigation, an increase of the microhardness of the material occurring at loads below 0.2 N was observed. When determining microhardness of aluminide coating it is necessary to take into account the optimal choice of the indentation tip.

  18. The effect of temperature deposited on the performance of ZnO-CNT-graphite for supercapacitors

    Science.gov (United States)

    Darari, Alfin; Hakim, Istajib S.; Priyono; Subagio, Agus; Pardoyo; Subhan, Achmad

    2017-07-01

    Carbon nanotubes (CNTs), graphite are now widely studied as the electrodes of supercapacitor, owing to their high conductivity, large surface area, chemical stability, etc. A lot of research has been focused on Carbon/metal oxide nanocomposite electrode for Electrode supercapacitor because it will increase the total capacitance. In this research, ZnO nanoparticles were deposited onto substrate CNT:Graphite in different temperatures such as 300°, 350°, and 400°C. The characterization of the crystal size using X-Ray Diffraction (XRD) patterns showed ZnO material peak was detected a ZnO crystallite. The size of ZnO crystallite in 300°, 350°, and 400°C consecutively is 101.1; 103.4; and 116.7 nm. The test results are Electrochemical impedance spectrometry (EIS) high electrical conductivity values obtained on the composition of ZnO-CNT-graphite with a temperature of 350°C 4.6 (S/m); and (2) the highest value of capacitance in 300°C is 1.23 F/g.

  19. High temperature superconducting films by rf magnetron sputtering

    International Nuclear Information System (INIS)

    Kadin, A.M.; Ballentine, P.H.

    1989-01-01

    The authors have produced sputtered films of Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O by rf magnetron sputtering from an oxide target consisting of loose reacted powder. The use of a large 8-inch stoichiometric target in the magnetron mode permits films located above the central region to be free of negative-ion resputtering effects, and hence yields reproducible, uniform stoichiometric compositions for a wide range of substrate temperatures. Superconducting YBCO films have been obtained either by sputtering at low temperatures followed by an 850 0 C oxygen anneal, or alternatively by depositing onto substrates heated to ∼600 - 650 0 C and cooling in oxygen. Films prepared by the former method on cubic zirconia substrate consist of randomly oriented crystallites with zero resistance above 83 K. Those deposited on zirconia at medium temperatures without the high-temperature anneal contain smooth partially oriented crystallites, with a slightly depressed T/sub c/ ∼75K. Finally, superconducting films have been deposited on MgO using a BiSrCaCu/sub 2/O/sub x/ powder target

  20. Observations on the effects of acid rain treatment on needle surfaces of scots pine and Norway spruce seedlings

    International Nuclear Information System (INIS)

    Turunen, M.; Huttunen, S.; Back, J.

    1994-01-01

    Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies L. Karst.) seedlings were subjected to acid rain treatment at pH 3, pH 4 and pH 7 in a field experiment during 1986-1989. SEM+EDS, TEM, and measurements of wax quantity were used to detect changes in needle surfaces. After 5 weeks at pH 3 and pH 4 acid rain treatment, CaSO 4 -crystallites were observed on visibly undamaged pine and spruce needle surfaces. Direct acid rain damage in conjunction with CaSO 4 -crystallites was observed only occasionally in wax structures. Two-month-old pine needles had 50% less wax in early August after exposure at pH 3 and pH 4 than water controls. The occurrence of CaSO 4 -crystallites on acid rain-treated needle surfaces, and more abundant deposition of Ca oxalate crystallites in the inner walls of epi- and hypodermal cells could be involved with acid rain-induced calcium leaching. Calcium sulphate is probably a result of the disturbed wax and cuticle biosynthesis resulting in undeveloped, permeable cuticles. At the end of experiment, no CaSO 4 -crystallites were seen on needle surfaces. Soil analysis revealed an increase in the soluble Ca concentrations at pH 3. (orig.)

  1. Influence of the surroundings conditions on the evolution of elastomers in the nuclear field

    International Nuclear Information System (INIS)

    Davenas, J.; Stevenson, I.; Celette, N.; David, L.; Vigier, G.; David, L.

    2006-01-01

    The evolution under radiations of EPDM elastomers used as cable insulators reveals the determining role of the surrounding atmosphere. The formation of unsaturated bonds and a recovery of the reticulation are revealed for irradiations in inert atmosphere, whereas a lot of oxidized species are formed in presence of oxygen. The dynamic mechanical relaxation spectroscopy shows a decrease of the molecular mobility in all the cases. This ones results of the reticulation under inert atmosphere, but its origin is less clear during the radio-oxidation where the chain cleavages constitute the main process. The evolution of the conservation modulus with the irradiation dose is in agreement with the waited evolution after the melting of the crystallites. The number of reticulation intersection increases until a dose corresponding to the complete consumption of diene, for decreasing then under the influence of the chain cleavages. The crystallites growth due to chain cleavages explains then the evolution at ambient temperature in presence of oxygen. The mechanical properties at the great deformations show the role of reinforcement of the crystallites at ambient temperature which disappears during the crystallites melting. The evolution of the EPDM properties results of a complex equilibrium between reticulations, chain cleavages and crystallites growth, which is controlled by the temperature and the atmosphere. (O.M.)

  2. Wet chemical synthesis of quantum confined nanostructured tin oxide thin films by successive ionic layer adsorption and reaction technique

    Energy Technology Data Exchange (ETDEWEB)

    Murali, K.V., E-mail: kvmuralikv@gmail.com [School of Pure and Applied Physics, Department of Physics, Kannur University, Kerala 670327 (India); Department of Physics, Nehru Arts and Science College, Kanhangad, Kerala 671314 (India); Ragina, A.J. [School of Pure and Applied Physics, Department of Physics, Kannur University, Kerala 670327 (India); Department of Physics, Nehru Arts and Science College, Kanhangad, Kerala 671314 (India); Preetha, K.C. [School of Pure and Applied Physics, Department of Physics, Kannur University, Kerala 670327 (India); Department of Physics, Sree Narayana College, Kannur, Kerala 670007 (India); Deepa, K.; Remadevi, T.L. [School of Pure and Applied Physics, Department of Physics, Kannur University, Kerala 670327 (India); Department of Physics, Pazhassi Raja N.S.S. College, Mattannur, Kerala 670702 (India)

    2013-09-01

    Graphical abstract: - Highlights: • Quantum confined SnO{sub 2} thin films were synthesized at 80 °C by SILAR technique. • Film formation mechanism is discussed. • Films with snow like crystallite morphology offer high specific surface area. • The blue-shifted value of band gap confirmed the quantum confinement effect. • Present synthesis has advantages – low cost, low temperature and green friendly. - Abstract: Quantum confined nanostructured SnO{sub 2} thin films were synthesized at 353 K using ammonium chloride (NH{sub 4}Cl) and other chemicals by successive ionic layer adsorption and reaction technique. Film formation mechanism is discussed. Structural, morphological, optical and electrical properties were investigated and compared with the as-grown and annealed films fabricated without NH{sub 4}Cl solution. SnO{sub 2} films were polycrystalline with crystallites of tetragonal structure with grain sizes lie in the 5–8 nm range. Films with snow like crystallite morphology offer high specific surface area. The blue-shifted value of band gap of as-grown films confirmed the quantum confinement effect of grains. Refractive index of the films lies in the 2.1–2.3 range. Films prepared with NH{sub 4}Cl exhibit relatively lower resistivity of the order of 10{sup 0}–10{sup −1} Ω cm. The present synthesis has advantages such as low cost, low temperature and green friendly, which yields small particle size, large surface–volume ratio, and high crystallinity SnO{sub 2} films.

  3. Precipitation kinetics of a continuous precipitator, with application to the precipitation of ammonium polyuranate

    International Nuclear Information System (INIS)

    Hoyt, R.C.

    1978-04-01

    A mathematical model describing the kinetics of continuous precipitation was developed which accounts for crystal nucleation, crystal growth, primary coagulation, and secondary coagulation. Population density distributions, average particle sizes, dominant particle sizes, and suspension density fractions of the crystallites, primary agglomerates, and secondary agglomerates leaving the continuous precipitator can be determined. This kinetic model was applied to the continuous precipitation of ammonium polyuranate, which consists of: (1) elementary crystals, (2) clusters or primary coagulated particles, and (3) agglomerates or secondary coagulated particles. The crystallites are thin, submicron, hexagonal platelets. The clusters had an upper size limit of about 7 μ in diameter and contained numerous small voids (less than 0.3 μm) due to the packing of the crystallites. The agglomerates had an upper size limit of about 40 μm in diameter and contained large voids (approximately 1 μm). The particle size distribution and particle structure of the ammonium polyuranate precipitate can be controlled through proper regulation of the precipitation conditions. The ratio of clusters to agglomerates can be best controlled through the uranium concentration, and the cohesiveness or internal bonding strength of the particles can be controlled with the ammonium to uranium reacting feed mole ratio. These two conditions, in conjunction with the residence time, will determine the nucleation rates, growth rates, and size distributions of the particles leaving the continuous precipitator. With proper control of these physical particle characteristics, the use of pore formers, ball-milling, and powder blending can probably be eliminated from the nuclear fuel fabrication process, substantially reducing the cost

  4. Precipitation kinetics of a continuous precipitator, with application to the precipitation of ammonium polyuranate

    Energy Technology Data Exchange (ETDEWEB)

    Hoyt, R.C.

    1978-04-01

    A mathematical model describing the kinetics of continuous precipitation was developed which accounts for crystal nucleation, crystal growth, primary coagulation, and secondary coagulation. Population density distributions, average particle sizes, dominant particle sizes, and suspension density fractions of the crystallites, primary agglomerates, and secondary agglomerates leaving the continuous precipitator can be determined. This kinetic model was applied to the continuous precipitation of ammonium polyuranate, which consists of: (1) elementary crystals, (2) clusters or primary coagulated particles, and (3) agglomerates or secondary coagulated particles. The crystallites are thin, submicron, hexagonal platelets. The clusters had an upper size limit of about 7 ..mu.. in diameter and contained numerous small voids (less than 0.3 ..mu..m) due to the packing of the crystallites. The agglomerates had an upper size limit of about 40 ..mu..m in diameter and contained large voids (approximately 1 ..mu..m). The particle size distribution and particle structure of the ammonium polyuranate precipitate can be controlled through proper regulation of the precipitation conditions. The ratio of clusters to agglomerates can be best controlled through the uranium concentration, and the cohesiveness or internal bonding strength of the particles can be controlled with the ammonium to uranium reacting feed mole ratio. These two conditions, in conjunction with the residence time, will determine the nucleation rates, growth rates, and size distributions of the particles leaving the continuous precipitator. With proper control of these physical particle characteristics, the use of pore formers, ball-milling, and powder blending can probably be eliminated from the nuclear fuel fabrication process, substantially reducing the cost.

  5. Bulletin of Materials Science | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Room temperature magnetic properties were studied using vibrating sample magnetometer (VSM) with field strengths up to ± 10 kOe. Lattice constant and crystallite size increased as the annealing temperature was increased. However, the coercivity (c) initially increased and then decreased with the increase of crystallite ...

  6. Biowaste-Derived Hierarchical Porous Carbon Nanosheets for Ultrahigh Power Density Supercapacitors.

    Science.gov (United States)

    Yu, Dengfeng; Chen, Chong; Zhao, Gongyuan; Sun, Lei; Du, Baosheng; Zhang, Hong; Li, Zhuo; Sun, Ye; Besenbacher, Flemming; Yu, Miao

    2018-03-05

    Low-cost activated carbons with high capacitive properties remain desirable for supercapacitor applications. Herein, a three-dimensional scaffolding framework of porous carbon nanosheets (PCNSs) has been produced from a typical biowaste, namely, ground cherry calyces, the specific composition and natural structures of which have contributed to the PCNSs having a very large specific surface area of 1612 m 2  g -1 , a hierarchical pore size distribution, a turbostratic carbon structure with a high degree graphitization, and about 10 % oxygen and nitrogen heteroatoms. A high specific capacitance of 350 F g -1 at 0.1 A g -1 has been achieved in a two-electrode system with 6 m KOH; this value is among the highest specific capacitance of biomass-derived carbon materials. More inspiringly, a high energy density of 22.8 Wh kg -1 at a power density of 198.8 W kg -1 can be obtained with 1 m aqueous solution of Li 2 SO 4 , and an ultrahigh energy density of 81.4 Wh kg -1 at a power density of 446.3 W kg -1 is realized with 1-ethyl-3-methylimidazolium tetrafluoroborate electrolyte. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Size distribution of magnetic iron oxide nanoparticles using Warren-Averbach XRD analysis

    Science.gov (United States)

    Mahadevan, S.; Behera, S. P.; Gnanaprakash, G.; Jayakumar, T.; Philip, J.; Rao, B. P. C.

    2012-07-01

    We use the Fourier transform based Warren-Averbach (WA) analysis to separate the contributions of X-ray diffraction (XRD) profile broadening due to crystallite size and microstrain for magnetic iron oxide nanoparticles. The profile shape of the column length distribution, obtained from WA analysis, is used to analyze the shape of the magnetic iron oxide nanoparticles. From the column length distribution, the crystallite size and its distribution are estimated for these nanoparticles which are compared with size distribution obtained from dynamic light scattering measurements. The crystallite size and size distribution of crystallites obtained from WA analysis are explained based on the experimental parameters employed in preparation of these magnetic iron oxide nanoparticles. The variation of volume weighted diameter (Dv, from WA analysis) with saturation magnetization (Ms) fits well to a core shell model wherein it is known that Ms=Mbulk(1-6g/Dv) with Mbulk as bulk magnetization of iron oxide and g as magnetic shell disorder thickness.

  8. Solid State Formation Mechanism of Li4Ti5O12 from an Anatase TiO2 Source

    DEFF Research Database (Denmark)

    Shen, Yanbin; Søndergaard, Martin; Christensen, Mogens

    2014-01-01

    Solid state synthesis of Li4Ti5O12 anode material for Li ion batteries typically results in products containing rutile TiO2 and Li2TiO3 impurities, and subsequent high calcination temperatures lead to particle growth that reduces capacity and rate ability. Here, the formation and growth of Li4Ti5O......12 particles by a solid-state reaction using anatase TiO2 with various crystallite sizes and Li2CO3 is investigated by in situ high temperature powder X-ray diffraction (HT-PXRD) and thermal gravimetry-differential thermal analysis (TG-DTA). The combined data provide insight into the origin...... crystallite sizes (∼50 nm, ∼30 nm, ∼20 nm, and amorphous) were explored, and decreasing crystallite sizes causes a reduced initial reaction temperature. Using anatase with a crystallite size of ∼20 nm resulted in phase pure Li4Ti5O12 at the lowest temperature (800 °C). PXRD and TG-DTA results also revealed...

  9. Magnetic and critical properties of Pr0.6Sr0.4MnO3 nanocrystals prepared by a combination of the solid state reaction and the mechanical ball milling methods

    Science.gov (United States)

    Dung, Nguyen Thi; Linh, Dinh Chi; Huyen Yen, Pham Duc; Yu, Seong Cho; Van Dang, Nguyen; Dang Thanh, Tran

    2018-06-01

    Influence of the crystallite size on the magnetic and critical properties of nanocrystals has been investigated. The results show that Curie temperature and magnetization slightly decrease with decreasing average crystallite size . Based on the mean-field theory and the magnetic-field dependences of magnetization at different temperatures , we pointed out that the ferromagnetic-paramagnetic phase transition in the samples undergoes the second-order phase transition with the critical exponents (, , and ) close to those of the mean-field theory. However, there is a small deviation from those expected for the mean-field theory of the values of , and obtained for the samples. It means that short-range ferromagnetic interactions appear in the smaller particles. In other words, nanocrystals become more magnetically inhomogeneous with smaller crystallite sizes that could be explained by the presence of surface-related effects, lattice strain and distortions, which lead the strength of ferromagnetic interaction is decreased in the small crystallite sizes.

  10. Presence of glassy state and large exchange bias in nanocrystalline BiFeO3

    Science.gov (United States)

    Srivastav, Simant Kumar; Johari, Anima; Patel, S. K. S.; Gajbhiye, N. S.

    2017-11-01

    We investigated the static and dynamic aspects of the magnetic properties for single phase nanocrystalline BiFeO3 with average crystallite size of 35 nm. The frequency dependence of the peak is observed in the real part of ac susceptibility χ‧ac vs T measurement and described well by the Vogel-Fulcher law as well as the power law. These analyses indicated the existence of cluster glass state with significant interaction among the spin clusters and results in cluster-glass like cooperative freezing at low temperature. The influence of temperature and magnetic field cooling on the exchange bias effect is investigated. A training effect is also observed. We have reported a significantly high ZFC & FC exchange bias of 200 Oe & 450 Oe at 300 K and 900 Oe & 2100 Oe at 5 K. The obtained results are interpreted in the framework of core-shell model, where the core of the BFO nanoparticles shows antiferromagnetic behavior and surrounded by CG-like ferromagnetic (FM) shell associated to uncompensated surface spins.

  11. Nano-crystals of cerium–hafnium binary oxide: Their size-dependent structure

    Energy Technology Data Exchange (ETDEWEB)

    Raitano, Joan M. [Department of Applied Physics and Applied Mathematics, Materials Science and Engineering Program, Columbia University, New York, NY 10027 (United States); Khalid, Syed [National Synchrotron Light Source, Brookhaven National Laboratory, Upton, NY 11973 (United States); Marinkovic, Nebojsa [Chemical Engineering Department, Columbia University, 500 W 120th St, Mudd 801, New York, NY 10027 (United States); Chan, Siu-Wai, E-mail: sc174@columbia.edu [Department of Applied Physics and Applied Mathematics, Materials Science and Engineering Program, Columbia University, New York, NY 10027 (United States)

    2015-09-25

    Highlights: • (1 − x)CeO{sub 2}–xHfO{sub 2} was precipitated (0 < x < 1) and calcined in air. • For x ⩽ 0.14, crystallites ⩽140 nm in size exhibit only the fluorite structure. • This low hafnia solubility is attributable to no auto-reduction (Ce{sup 3+} = 0). • The low solubility is also due to the high temperature required for homogenization. • Coarsening is lessened as Hf{sup 4+} ions slow cation diffusion in these crystallites. - Abstract: Cerium oxide (CeO{sub 2}, “ceria”) and hafnium oxide (HfO{sub 2}, “hafnia”) were aqueously co-precipitated and subsequently calcined to allow for homogenization. The size of the (1−x)CeO{sub 2}–xHfO{sub 2} crystallites, determined by the Scherrer equation, varied from 140 nm for x = 0 to 15 nm for x = 0.73. For x ⩽ 0.14, only cubic structures are visible in X-ray diffractograms, and the lattice parameters are consistent with the values expected for structurally cubic solid solutions of hafnia in ceria. At x = 0.26, tetragonal and monoclinic phases nucleated with the former not being observed in the bulk phase diagram for ceria–hafnia. Therefore, the solubility limit of the cubic structure is between x = 0.14 and x = 0.26 for 40–61 nm crystallites, the sizes of these respective compositions. More specifically, for the 40 nm crystallites of x = 0.26 (1 − x)CeO{sub 2}–xHfO{sub 2}, 15% of the hafnia remains in a structurally cubic solid solution with ceria based on the observed cubic lattice parameter. The compositional domain for the cubic fluorite structure in this study is narrower than other nanostructured (1 − x)CeO{sub 2}–xHfO{sub 2} studies, especially studies with crystallite sizes less than 10 nm, but wider than observed in the bulk and helps to expand the size regime over which the relationship between crystallite size and phase stability is known. The extent of this cubic-structure domain is mainly attributable to the intermediate crystallite size and the roughly zero Ce{sup 3

  12. Sulfide precursor concentration and lead source effect on PbS thin films properties

    Energy Technology Data Exchange (ETDEWEB)

    Beddek, L.; Messaoudi, M.; Attaf, N. [Laboratoire Couche Minces et Interfaces, Université frères Mentouri Constantine, 25000, Constantine (Algeria); Aida, M.S., E-mail: aida_salah2@yahoo.fr [Laboratoire Couche Minces et Interfaces, Université frères Mentouri Constantine, 25000, Constantine (Algeria); Bougdira, J. [Université de Lorraine, Institut Jean Lamour UMR 7198, Vandoeuvre 54506 (France)

    2016-05-05

    Lead sulfide (PbS) thin films were synthesized using chemical bath deposition (CBD). Bath solutions are formed of various concentrations of thiourea, sulfide source, ranged from 0.6 to 1.2 M and two different salts as Pb source (lead acetate and lead nitrate). From the growth mechanism, we inferred that PbS is formed through the ion by ion process when using acetate lead source, while, using nitrate source yields to films growth through the complex-decomposition process. Due to the difference in the involved growth process, lead acetate produces films with larger crystallite size (from 4 to 16 nm), smooth and dense films. However, lead nitrate produces rough films with smaller crystallite size (from 1 to 4 nm). Increasing the thiourea concentration results in crystallinity improvement when using lead acetate and, oppositely, in crystallinity degradation when using lead nitrate. Due to the quantum effect caused by the small crystallite sizes, the films optical gap is varied from 0.5 to 0.9 eV. - Highlights: • PbS thin films were synthesized by chemical bath deposition. • Ion by ion is the growth process when using the acetate lead source. • Deposition process is by complex-decomposition when using nitrate source. • Lead acetate yields to dense films with larger crystallite size. • Lead nitrate produces rough films with smaller crystallite size.

  13. Sulfide precursor concentration and lead source effect on PbS thin films properties

    International Nuclear Information System (INIS)

    Beddek, L.; Messaoudi, M.; Attaf, N.; Aida, M.S.; Bougdira, J.

    2016-01-01

    Lead sulfide (PbS) thin films were synthesized using chemical bath deposition (CBD). Bath solutions are formed of various concentrations of thiourea, sulfide source, ranged from 0.6 to 1.2 M and two different salts as Pb source (lead acetate and lead nitrate). From the growth mechanism, we inferred that PbS is formed through the ion by ion process when using acetate lead source, while, using nitrate source yields to films growth through the complex-decomposition process. Due to the difference in the involved growth process, lead acetate produces films with larger crystallite size (from 4 to 16 nm), smooth and dense films. However, lead nitrate produces rough films with smaller crystallite size (from 1 to 4 nm). Increasing the thiourea concentration results in crystallinity improvement when using lead acetate and, oppositely, in crystallinity degradation when using lead nitrate. Due to the quantum effect caused by the small crystallite sizes, the films optical gap is varied from 0.5 to 0.9 eV. - Highlights: • PbS thin films were synthesized by chemical bath deposition. • Ion by ion is the growth process when using the acetate lead source. • Deposition process is by complex-decomposition when using nitrate source. • Lead acetate yields to dense films with larger crystallite size. • Lead nitrate produces rough films with smaller crystallite size.

  14. Magnetic and structural properties of Fe{sub 65}Co{sub 35} alloys obtained by melting, high-energy milling and heat treatment

    Energy Technology Data Exchange (ETDEWEB)

    Trifu, A.V.; Dorolti, E. [Faculty of Physics, Babes-Bolyai University, 400084 Cluj-Napoca (Romania); Takacs, A.F., E-mail: albert.takacs@phys.ubbcluj.ro [Faculty of Physics, Babes-Bolyai University, 400084 Cluj-Napoca (Romania); Chicinaş, I. [Materials Sciences and Engineering Department, Technical University of Cluj-Napoca, 103-105 Muncii Avenue, 400641 Cluj-Napoca (Romania); Isnard, O. [Institut Néel, CNRS, Université Joseph Fourier, BP 166X, 38042 Grenoble Cédex 9 (France); Pop, V. [Faculty of Physics, Babes-Bolyai University, 400084 Cluj-Napoca (Romania)

    2013-11-20

    The influence of milling and annealing conditions on the structural and magnetic behaviour of mechanically milled Fe{sub 65}Co{sub 35} alloys has been studied. By differential scanning calorimetry measurements we determined the internal stress relaxation temperature, recrystallisation temperature and structural order/disorder transition temperature of bulk and mechanical milled Fe{sub 65}Co{sub 35}. The width of the X-ray diffraction peaks was found to increase with the milling time. Two types of annealing were performed: a conventional heat treatment at 500, 550 and 600 °C for 2 h and a rapid annealing for a maximum of 2 min at 700, 750 or 800 °C followed by quenching. Crystallite size increases with increasing heat treatment temperature and time, as both are parameters that influence the magnetic properties of the sample. Magnetic permeability variations result from internal stress evolution, changes in crystallite size, supposing that the crystallite size of the annealed samples is at the border between viability of the Herzer model and the classical behaviour of the permeability vs. crystallite size.

  15. Microstructural analysis of the {delta} to {alpha}' phase transformation in plutonium alloys using X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Platteau, C; Ravat, B; Texier, G; Oudot, B; Delaunay, F, E-mail: brice.ravat@cea.fr [CEA Valduc 21120 Is sur Tille (France)

    2010-03-15

    The partial martensitic {delta}{yields}{alpha}' transformation in plutonium alloys is sensitive to chemical composition, sample thermal history, as well as crystalline defects. The present work investigates the {delta}-Pu phase microstructure before and after the martensitic transformation {delta}{yields}{delta}+{alpha}'. More precisely, microstructural modifications of the host {delta}-phase, resulting from the stress induced by a cell volume difference of 19% between the {delta} and {alpha}'-phases, were analysed. Microstructural information about crystallite size and microstrain of a highly homogenized Pu-Ga alloy was extracted from x-ray diffraction patterns using a three dimension crystallite size and microstrain model. This is available in Rietveld refinement software and consists in anisotropic broadening analysis of diffraction peaks. Crystallite size doesn't significantly change with the phase transformation contrary to microstrain that is multiplied, on average, by five. Furthermore, internal normal and shear microstress are multiplied, respectively, by 2 and 13 when {alpha}'-phase appears. Last, dislocation densities, calculated from crystallite size and microstrain, are compared to TEM results available in the literature.

  16. Large Neighborhood Search

    DEFF Research Database (Denmark)

    Pisinger, David; Røpke, Stefan

    2010-01-01

    Heuristics based on large neighborhood search have recently shown outstanding results in solving various transportation and scheduling problems. Large neighborhood search methods explore a complex neighborhood by use of heuristics. Using large neighborhoods makes it possible to find better...... candidate solutions in each iteration and hence traverse a more promising search path. Starting from the large neighborhood search method,we give an overview of very large scale neighborhood search methods and discuss recent variants and extensions like variable depth search and adaptive large neighborhood...

  17. About some practical aspects of X-ray diffraction : From single crystal to powders

    Energy Technology Data Exchange (ETDEWEB)

    Giacovazzo, C [Bari Univ. (Italy). Dip. Geomineralogico

    1996-09-01

    An ideal polycrystalline material or power is an ensemble of a very large number of randomly oriented crystallites. It is shown the effect that this random orientation has on the diffraction of a specimen assumed to contain only one reciprocal lattice node. The most remarkable difference with the single-crystal case is that now must think of scattering vectors not as lying on discrete nodes of reciprocal lattice vectors, the distances from the single-crystal reciprocal lattice nodes to the origin of reciprocal space.

  18. About some practical aspects of X-ray diffraction : From single crystal to powders

    International Nuclear Information System (INIS)

    Giacovazzo, C.

    1996-01-01

    An ideal polycrystalline material or power is an ensemble of a very large number of randomly oriented crystallites. It is shown the effect that this random orientation has on the diffraction of a specimen assumed to contain only one reciprocal lattice node. The most remarkable difference with the single-crystal case is that now must think of scattering vectors not as lying on discrete nodes of reciprocal lattice vectors, the distances from the single-crystal reciprocal lattice nodes to the origin of reciprocal space

  19. Study of some Mg-based ferrites as humidity sensors

    International Nuclear Information System (INIS)

    Rezlescu, N; Rezlescu, E; Doroftei, C; Popa, P D

    2005-01-01

    The micostructure and humidity sensitivity of MgFe 2 O 4 + CaO, Mg 0.5 Cu 0.5 Fe 1.8 Ga 0.2 O 4 , Mg 0.5 Zn 0.5 Fe 2 O 4 + KCl and MgMn 0.2 Fe 1.8 O 4 ferrites were investigated. We have found that the humidity sensitivity largely depends on composition, crystallite size, surface area and porosity. The best results concerning humidity sensitivity were obtained for MgMn 0.2 Fe 1.8 O 4 ferrite

  20. Photocatalytic properties of TiO{sub 2} prepared by coprecipitation and by hydrothermal synthesis and study of the effect of doping Gd{sup 3+}; Fotokatalyticke vlastnosti TiO{sub 2} pripraveneho koprecipitaciou a hydrotermalnou syntezou a studium vplyvu dopovania Gd{sup 3+}

    Energy Technology Data Exchange (ETDEWEB)

    Sipos, M [Univerzita Komenskeho v Bratislave, Prirodovedecka fakulta, Katedra anorganickej chemie, 84215 Bratislava (Slovakia)

    2012-04-25

    In this paper we described a synthesis of TiO{sub 2} nanopowders by coprecipitation and by hydrothermal method. We examined the effect of sample preparation procedure, of annealing temperature and doping by Gd{sup 3+} ions on the photocatalytic properties of TiO{sub 2}. We did not observe a correlation between primary micro-crystallites largeness and their photocatalytic activity. Sulfation and samples doping by G{sup d}3{sup +} ions enhances their photodegradation properties. Effect of doping is significantly larger at hydrothermally prepared samples. (authors)

  1. Interatomic potentials and the simulation of lattice defects in metals

    International Nuclear Information System (INIS)

    Heugten, W.F.W.M. van.

    1979-01-01

    The computer simulation technique is applied to investigate the properties of point defects and line defects in metals. For that purpose crystallites are constructed in which these defects are simulated. In the case of line defects (dislocations) the initial positions of the atoms, surrounding the dislocations, are determined using the elastic theory of anisotropic media. Hereafter the atoms in such crystallites are allowed to relax to there minimum potential energy positions under the influence of the interatomic forces. These forces are derived from interatomic interaction potentials. These potentials are together with the boundary conditions of the simulated crystallite the main input data in these computer simulation models. The metals considered include molybdenum, tungsten and tantalum. (Auth.)

  2. Ultrasonic texture characterization of aluminum, zirconium and titanium alloys

    International Nuclear Information System (INIS)

    Anderson, A.J.

    1997-01-01

    This work attempts to show the feasibility of nondestructive characterization of non-ferrous alloys. Aluminum alloys have a small single crystal anisotropy which requires very precise ultrasonic velocity measurements for derivation of orientation distribution coefficients (ODCs); the precision in the ultrasonic velocity measurement required for aluminum alloys is much greater than is necessary for iron alloys or other alloys with a large single crystal anisotropy. To provide greater precision, some signal processing corrections need to be applied to account for the inherent, half-bandwidth offset in triggered pulses when using a zero-crossing technique for determining ultrasonic velocity. In addition, alloys with small single crystal anisotropy show a larger dependence on the single crystal elastic constants (SCECs) when predicting ODCs which require absolute velocity measurements. Attempts were made to independently determine these elastics constants in an effort to improve correlation between ultrasonically derived ODCs and diffraction derived ODCs. The greater precision required to accurately derive ODCs in aluminum alloys using ultrasonic nondestructive techniques is easily attainable. Ultrasonically derived ODCs show good correlation with derivations made by Bragg diffraction techniques, both neutron and X-ray. The best correlation was shown when relative velocity measurements could be used in the derivations of the ODCs. Calculation of ODCs in materials with hexagonal crystallites can also be done. Because of the crystallite symmetries, more information can be extracted using ultrasonic techniques, but at a cost of requiring more physical measurements. Some industries which use materials with hexagonal crystallites, e.g. zirconium alloys and titanium, have traditionally used texture parameters which provide some specialized measure of the texture. These texture parameters, called Kearns factors, can be directly related to ODCs

  3. Large scale electrolysers

    International Nuclear Information System (INIS)

    B Bello; M Junker

    2006-01-01

    Hydrogen production by water electrolysis represents nearly 4 % of the world hydrogen production. Future development of hydrogen vehicles will require large quantities of hydrogen. Installation of large scale hydrogen production plants will be needed. In this context, development of low cost large scale electrolysers that could use 'clean power' seems necessary. ALPHEA HYDROGEN, an European network and center of expertise on hydrogen and fuel cells, has performed for its members a study in 2005 to evaluate the potential of large scale electrolysers to produce hydrogen in the future. The different electrolysis technologies were compared. Then, a state of art of the electrolysis modules currently available was made. A review of the large scale electrolysis plants that have been installed in the world was also realized. The main projects related to large scale electrolysis were also listed. Economy of large scale electrolysers has been discussed. The influence of energy prices on the hydrogen production cost by large scale electrolysis was evaluated. (authors)

  4. Investigation on the structural, magnetic and magnetocaloric properties of nanocrystalline Pr-deficient Pr1-xSrxMnO3-δ manganites

    Science.gov (United States)

    Arun, B.; Athira, M.; Akshay, V. R.; Sudakshina, B.; Mutta, Geeta R.; Vasundhara, M.

    2018-02-01

    We have investigated the structural, magnetic and magnetocaloric properties of nanocrystalline Pr-deficient Pr1-xSrxMnO3-δ Perovskite manganites. Rietveld refinement of the X-ray powder diffraction patterns confirms that all the studied compounds have crystallized into an orthorhombic structure with Pbnm space group. Transmission electron microscopy analysis reveals nanocrystalline compounds with crystallite size less than 50 nm. The selected area electron diffraction patterns reveal the highly crystalline nature of the compounds and energy dispersive X-ray spectroscopic analysis shows that the obtained compositions are nearly identical with the nominal one. The oxygen stoichiometry is estimated by iodometric titration method and stoichiometric compositions are confirmed by X-ray Fluorescence Spectrometry analysis. A large bifurcation is observed in the ZFC/FC curves and Arrott plots not show a linear relation but have a convex curvature nature. The temperature dependence of inverse magnetic susceptibility at higher temperature confirms the existence of ferromagnetic clusters. The experimental results reveal that the reduction of crystallite size to nano metric scale in Pr-deficient manganites adversely influences structural, magnetic and magnetocaloric properties as compared to its bulk counterparts reported earlier.

  5. Challenges in quantitative crystallographic characterization of 3D thin films by ACOM-TEM

    Energy Technology Data Exchange (ETDEWEB)

    Kobler, A. [Institute of Nanotechnology (INT), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen (Germany); Karlsruhe Nano Micro Facility (KNMF), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen (Germany); Kübel, C., E-mail: christian.kuebel@kit.edu [Institute of Nanotechnology (INT), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen (Germany); Karlsruhe Nano Micro Facility (KNMF), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen (Germany)

    2017-02-15

    Automated crystal orientation mapping for transmission electron microscopy (ACOM-TEM) has become an easy to use method for the investigation of crystalline materials and complements other TEM methods by adding local crystallographic information over large areas. It fills the gap between high resolution electron microscopy and electron back scatter diffraction in terms of spatial resolution. Recent investigations showed that spot diffraction ACOM-TEM is a quantitative method with respect to sample parameters like grain size, twin density, orientation density and others. It can even be used in combination with in-situ tensile or thermal testing. However, there are limitations of the current method. In this paper we discuss some of the challenges and discuss solutions, e.g. we present an ambiguity filter that reduces the number of pixels with a ‘180° ambiguity problem’. For that an ACOM-TEM tilt series of nanocrystalline Pd thin films with overlapping crystallites was acquired and analyzed. - Highlights: • Tilt series of nanocrystalline Pd thin films. • Quantitative ACOM-TEM data processing, including a rotation map of crystallites. • Noise filter for orientation data: Ambiguity Filter and min. distance filter.

  6. Structuring of gels of zirconium oxohydrate

    International Nuclear Information System (INIS)

    Sukharev, Yu.I.; Skuratovich, L.P.

    1991-01-01

    Genetic relationship between formation of mesophase states of zirconium oxohydrate gel, coprecipitated with dimethylamine, and ordered macrocrystallites of sorption material after cryogranulation or decryptation granulating is shown. This phenomenon is followed on example of formation of flattened crystallites when preparing granules in the presence of appl. The successive polymerization growth of crystallites leads to the frame ordered aggregation or aggregation of another type

  7. A mechanistic basis for the effect of aluminum content on ethene selectivity in methanol-to-hydrocarbons conversion on HZSM-5

    KAUST Repository

    Khare, Rachit; Liu, Zhaohui; Han, Yu; Bhan, Aditya

    2017-01-01

    Increasing crystallize size or aluminum content in MFI-type zeolites independently enhances the propagation of the aromatics-based methylation/dealkylation cycle relative to that of the olefins-based methylation/cracking cycle in methanol-to-hydrocarbons (MTH) conversion and consequentially results in higher ethene selectivity. Ethene selectivity increases monotonically with increasing aluminum content for HZSM-5 samples with nearly identical crystallite size consequent to an increase in the intracrystalline contact time analogous to our recent report detailing the effects of crystallite size (Khare et al., 2015) on MTH selectivity. The confected effects of crystallite size and site density on MTH selectivity can therefore, be correlated using a descriptor that represents the average number of acid sites that an olefin-precursor will interact with before elution.

  8. The effect of sulphur-terminated GaAs substrates on the MOVPE growth of CuGaS{sub 2} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Berndt, P.R. [Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa)]. E-mail: pearl.berndt@nmmu.ac.za; Botha, J.R. [Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa); Branch, M.S. [Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa); Leitch, A.W.R. [Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa); Kirmse, H. [Institute of Physics, Chair of Crystallography, Humboldt University of Berlin, Berlin (Germany); Neumann, W. [Institute of Physics, Chair of Crystallography, Humboldt University of Berlin, Berlin (Germany); Weber, J. [Institute for Applied Physics-Semiconductor Physics, University of Technology, Dresden (Germany)

    2007-05-31

    In this study, various CuGaS{sub 2} layers were grown on GaAs (001) substrates using metalorganic vapour phase epitaxy, for the purpose of studying the effect of sulphur-termination of the substrate on layer quality. The resultant films were investigated using X-ray diffractometry, and transmission electron microscopy, with high-resolution transmission electron microscopy providing additional insights into crystallite growth on the control substrates. This paper will demonstrate that sulphur-termination limits substrate degradation. In the absence of sulphur-termination, atypical three-dimensional MOVPE growth is observed, with epitaxial crystallites varying in size from 10 nm to 200 nm. Substrate degradation inhibits lateral growth at the interface resulting in amorphous regions, cavities, and epitaxial crystallites demonstrating overgrowth into mushroom-like structures.

  9. Method and article of manufacture corresponding to a composite comprised of ultra nonacrystalline diamond, metal, and other nanocarbons useful for thermoelectric and other applications

    Science.gov (United States)

    Gruen, Dieter M.

    2010-05-18

    One provides (101) disperse ultra-nanocrystalline diamond powder material that comprises a plurality of substantially ordered crystallites that are each sized no larger than about 10 nanometers. One then reacts (102) these crystallites with a metallic component. The resultant nanowire is then able to exhibit a desired increase with respect to its ability to conduct electricity while also substantially preserving the thermal conductivity behavior of the disperse ultra-nanocrystalline diamond powder material. The reaction process can comprise combining (201) the crystallites with one or more metal salts in an aqueous solution and then heating (203) that aqueous solution to remove the water. This heating can occur in a reducing atmosphere (comprising, for example, hydrogen and/or methane) to also reduce the salt to metal.

  10. The dependence of the texture of tellurium thin films on vacuum deposition angle

    International Nuclear Information System (INIS)

    Cocks, F.H.; Peterson, M.J.; Jones, P.L.

    1980-01-01

    Vacuum-deposited tellurium thin films can show substantially different surface morphologies depending on the angle with which the vapor stream impinges on the substrate surface. These tellurium thin films have a tendency to grow as acicular crystallites but as the deposition angle is increased so that the vapor stream becomes tangential to the substrate surface the spacing between crystallites increases and approaches, at stream angles of approximately 80 0 from the normal, dimensions roughly once or twice the average wavelength of visible light. Such films may have application in solar energy collector systems because of the high absorptivity of sunlight shown by such films. Mechanisms which describe the tendency for crystallite spacing to increase with increasing angle are discussed. (Auth.)

  11. Influence of the particle size of zeolite HZSM-5 on the catalytic performance in the ethene-to-propene reaction

    Energy Technology Data Exchange (ETDEWEB)

    Follmann, S.; Ernst, S. [Kaiserslautern Univ. (Germany). Dept. of Chemistry; Vetter, A.; Ripperger, S. [Kaiserslautern Univ. (Germany). Dept. of Mechanical and Process Engineering

    2013-11-01

    In this study, HZSM-5-type zeolites with comparable nSi/nAl-ratios but different crystallite sizes (6 {mu}m, 27 {mu}m, 40 {mu}m and 62 {mu}m) were synthesized and their physicochemical properties characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and nitrogen physisorption. Their catalytic properties were explored in the acid-catalyzed conversion of ethene to propene (and higher hydrocarbons). The results show that there is a significant influence of the crystallite size of the zeolite catalyst on the activity and time-on-steam stability. While the yields of short-chain olefins do not significantly differ for all materials investigated, the formation of aromatics is significantly suppressed over the catalyst with the largest crystallite size. (orig.)

  12. The structure of Cu-Cd alloys obtained by electrolysis on monocrystalline silver substrates

    International Nuclear Information System (INIS)

    Lagiewka, E.

    1981-01-01

    The structure of Cu-Cd alloys obtained by electrolysis on monocrystalline silver cathodes with a surface parallel to the (111), (110) and (100) planes has been investigated. It has been found that depending on the range of the cathode potentials, one-phase (phase α) or two-phase (phase α + cadmium) alloy are obtained. In the alloys the occurrence of twins has been observed, the orientation of which is the result of twinning along the [111] planes of crystallites with epitaxial orientation with respect to the cathode surface and of a random orientation of crystallites. The volume of the layer containing crystallites with a random arrangement increases with the obtaining potential of the alloy and with the decrease in the surface density of the cathode atoms. (author)

  13. X-ray diffraction investigation of self-annealing in nanocrystalline copper electrodeposits

    DEFF Research Database (Denmark)

    Pantleon, Karen; Somers, Marcel A. J.

    2006-01-01

    X-ray diffraction analysis and electrical resistivity measurements were conducted simultaneously for in-situ examination of self-annealing in copper electrodeposits. Considerable growth of the as-deposited nano-sized crystallites occurs with time and the crystallographic texture changes by multip...... twinning during self-annealing. The kinetics of self-annealing depends on the layer thickness as well as on the orientation and/or the size of the as-deposited crystallites. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.......X-ray diffraction analysis and electrical resistivity measurements were conducted simultaneously for in-situ examination of self-annealing in copper electrodeposits. Considerable growth of the as-deposited nano-sized crystallites occurs with time and the crystallographic texture changes by multiple...

  14. The effect of sulphur-terminated GaAs substrates on the MOVPE growth of CuGaS2 thin films

    International Nuclear Information System (INIS)

    Berndt, P.R.; Botha, J.R.; Branch, M.S.; Leitch, A.W.R.; Kirmse, H.; Neumann, W.; Weber, J.

    2007-01-01

    In this study, various CuGaS 2 layers were grown on GaAs (001) substrates using metalorganic vapour phase epitaxy, for the purpose of studying the effect of sulphur-termination of the substrate on layer quality. The resultant films were investigated using X-ray diffractometry, and transmission electron microscopy, with high-resolution transmission electron microscopy providing additional insights into crystallite growth on the control substrates. This paper will demonstrate that sulphur-termination limits substrate degradation. In the absence of sulphur-termination, atypical three-dimensional MOVPE growth is observed, with epitaxial crystallites varying in size from 10 nm to 200 nm. Substrate degradation inhibits lateral growth at the interface resulting in amorphous regions, cavities, and epitaxial crystallites demonstrating overgrowth into mushroom-like structures

  15. TEM characterization of UO2-Gd2O3 nuclear fuels synthesized by coprecipitation method

    International Nuclear Information System (INIS)

    Soldati, A.; Gana Watkins, I.; Menghini, J.; Prado, M.

    2013-01-01

    We present a micro and nano structural characterization of 4% weight doped Gd 2 O 3 -UO 2 pellet using Transmission Electron Microscopy (TEM). Agglomerate morphology and crystallite sizes were determined using light/dark field and high resolution (HR-TEM) images. Convergent beam Energy Dispersive Spectroscopy (EDS) and Electron Diffraction (ED) were used to evaluate sample composition and homogeneity, even at the nanometer scale. We obtained an average crystallite size of 90±20 nm. Moreover, from TEM-EDS analyses we determined the presence of Gadolinium in all the analyzed crystallites but with 25% variation among their concentrations. These results show the capability of TEM analysis to characterize a nuclear fuel pellet with burnable poisons nano structure and homogeneity.(author)

  16. Luminescence kinetics of porous silicon: fluctuation approach

    CERN Document Server

    Bondarev, V N

    2001-01-01

    Theoretical interpretation of the kinetics of the photoluminescence (PL), caused by the tunnel radiative recombination of the photoexcited electron and hole, localized on the crystallite/matrix interface, is given on the basis of the notions on the porous silicon structure as an incidental totality of the Si nanodimensional crystallites, submerged into the SiO sub 2 matrix. The relatively slow (by the stretched exponential type) time drop in the PL intensity is the results of averaging the intensity in each PL elementary act by the electron and hole mutual disposition and by the crystallite dimensions. The good quantitative description of the low-temperature experiments may be obtained through the proposed approach both by the PL kinetics and time evolution of the porous silicon PL spectrum

  17. A mechanistic basis for the effect of aluminum content on ethene selectivity in methanol-to-hydrocarbons conversion on HZSM-5

    KAUST Repository

    Khare, Rachit

    2017-03-20

    Increasing crystallize size or aluminum content in MFI-type zeolites independently enhances the propagation of the aromatics-based methylation/dealkylation cycle relative to that of the olefins-based methylation/cracking cycle in methanol-to-hydrocarbons (MTH) conversion and consequentially results in higher ethene selectivity. Ethene selectivity increases monotonically with increasing aluminum content for HZSM-5 samples with nearly identical crystallite size consequent to an increase in the intracrystalline contact time analogous to our recent report detailing the effects of crystallite size (Khare et al., 2015) on MTH selectivity. The confected effects of crystallite size and site density on MTH selectivity can therefore, be correlated using a descriptor that represents the average number of acid sites that an olefin-precursor will interact with before elution.

  18. Studies on AC Electrical Conductivity of CdCl2 Doped PVA Polymer Electrolyte

    Directory of Open Access Journals (Sweden)

    M. B. Nanda Prakash

    2013-01-01

    Full Text Available PVA-based polymer electrolytes were prepared with various concentrations of CdCl2 using solvent casting method. Prepared polymer films were investigated using line profile analysis employing X-ray diffraction (XRD data. XRD results show that the crystallite size decreases and then increases with increase in CdCl2. AC conductivity in these polymer increases films first and then decreases. These observations are in agreement with XRD results. The highest ionic conductivity of 1.68E − 08 Scm−1 was observed in 4% of CdCl2 in PVA polymer blend. Crystallite ellipsoids for different concentrations of CdCl2 are computed here using whole pattern powder fitting (WPPF indicating that crystallite area decreases with increase in the ionic conductivity.

  19. The large-s field-reversed configuration experiment

    International Nuclear Information System (INIS)

    Hoffman, A.L.; Carey, L.N.; Crawford, E.A.; Harding, D.G.; DeHart, T.E.; McDonald, K.F.; McNeil, J.L.; Milroy, R.D.; Slough, J.T.; Maqueda, R.; Wurden, G.A.

    1993-01-01

    The Large-s Experiment (LSX) was built to study the formation and equilibrium properties of field-reversed configurations (FRCs) as the scale size increases. The dynamic, field-reversed theta-pinch method of FRC creation produces axial and azimuthal deformations and makes formation difficult, especially in large devices with large s (number of internal gyroradii) where it is difficult to achieve initial plasma uniformity. However, with the proper technique, these formation distortions can be minimized and are then observed to decay with time. This suggests that the basic stability and robustness of FRCs formed, and in some cases translated, in smaller devices may also characterize larger FRCs. Elaborate formation controls were included on LSX to provide the initial uniformity and symmetry necessary to minimize formation disturbances, and stable FRCs could be formed up to the design goal of s = 8. For x ≤ 4, the formation distortions decayed away completely, resulting in symmetric equilibrium FRCs with record confinement times up to 0.5 ms, agreeing with previous empirical scaling laws (τ∝sR). Above s = 4, reasonably long-lived (up to 0.3 ms) configurations could still be formed, but the initial formation distortions were so large that they never completely decayed away, and the equilibrium confinement was degraded from the empirical expectations. The LSX was only operational for 1 yr, and it is not known whether s = 4 represents a fundamental limit for good confinement in simple (no ion beam stabilization) FRCs or whether it simply reflects a limit of present formation technology. Ideally, s could be increased through flux buildup from neutral beams. Since the addition of kinetic or beam ions will probably be desirable for heating, sustainment, and further stabilization of magnetohydrodynamic modes at reactor-level s values, neutral beam injection is the next logical step in FRC development. 24 refs., 21 figs., 2 tabs

  20. New anode material for lithium-ion cells produced by catalytic graphitization of glassy carbon at 1000 degrees C

    Energy Technology Data Exchange (ETDEWEB)

    Skowronski, J.M. [Poznan Univ. of Technology, Poznan (Poland). Inst. of Chemistry and Technical Electrochemistry; Central Lab. of Batteries and Cells, Poznan (Poland); Knofczynski, K. [Central Lab. of Batteries and Cells, Poznan (Poland)

    2006-10-15

    This study investigated the conversion of glassy carbon into graphite at relatively low temperature of 1000 degrees C under ambient pressure using iron powder as the catalyst. The composite product of reaction was a graphite and turbostratic carbon whose use was then examined in terms of application in lithium-ion cells. Glassy, hard carbon spheres of 10 to 15 {iota}m were prepared from phenolic resin in a nitrogen atmosphere and then subjected to heat treatment with an iron powder mixture. After cooling down to ambient temperature, the carbon/iron mixture was treated with diluted HCl solution to remove metallic additives. The modified carbon was then washed with distilled water until chloride ions disappeared in a filtrate. All samples were characterized using XRD analysis. Working electrodes for electrochemical measurements were made by mixing carbons with PVDF. Cyclic voltammograms recorded for unmodified and modified carbons were consistent with XRD measurements. SEM analysis revealed that the process of graphitization begins at the external regions of glassy carbon spheres where erosion occurs when the carbon reacts with iron particles. The surface destruction of carbon spheres progresses into the interior of the spheres, resulting in their collapse followed by the transformation into pallets resembling a stack of graphite sheets. It was noted that not all unorganized carbon was conversed to graphite. Rather, only 50 per cent of turbostratic carbon existed in the product of heat treatment. The product of graphitization appeared to be a promising material for the preparation of anodes for lithium-ion cells. The discharge capacity for carbon produced by catalytic treatment was found to be approximately 5 times higher, while the discharge/charge reversibility was 23 per cent higher than values obtained for untreated carbon. The study showed that the uptake of lithium ions by the original carbon depends on the insertion/deinsertion mechanism of hard carbon as well

  1. Organic semiconductors. Fundamental aspects of metal contacts, highly ordered films and the application in field effect transistors; Organische Halbleiter. Fundamentale Aspekte von Metallkontakten, hochgeordneten Schichten und deren Anwendung in Feldeffekttransistoren

    Energy Technology Data Exchange (ETDEWEB)

    Sachs, Soenke

    2010-05-31

    In this thesis, fundamental aspects of organic semiconductor devices are investigated and incorporated into the construction and optimization of an organic semiconductor field effect transistor (OFET). In order to approach the ''high end'' of OFETs, elaborate steps to optimize the devices are taken, despite the fact that they might not be feasible in a direct application. Well-characterized model systems are selected to study fundamental properties of devices, in particular the electronic structure at molecule/metal contacts and in the organic semiconductor bulk, as well as the growth of organic semiconductor molecules on single crystalline insulator substrates. The realization of a high performance OFET is pursued by a comprehensive approach in order to optimize particularly the interfaces of the device. Considerable progress is made towards a working OFET with best possible properties. A primary focus of this work, the investigation of the electronic structure at molecule/metal contacts and in the molecular bulk of the model system PTCDA/Ag(111) is performed using two photon photoelectron spectroscopy (2PPE). Of special interest is the excitation of the lowest unoccupied molecular orbital (LUMO) that shows different energetic relaxation mechanisms, depending on the origin of excitation. In addition to the importance of the molecule/metal contacts, the performance of OFETs is determined to a large extend by the quality of the organic semiconductor/gate insulator interface where the charge carrier channel is established. The morphology and structure of a molecular layer are investigated for diindenoperylene (DIP) molecules, adsorbed on a single crystalline Al{sub 2}O{sub 3} substrate, by atomic force microscopy and optical microscopy. Dependent on the substrate temperature during growth, the morphology shows grains with lateral dimensions of about 200 nm at 350 K which increase up to 700 nm at 450 K. This change in morphology is accompanied by

  2. Crystal growth in zinc borosilicate glasses

    Science.gov (United States)

    Kullberg, Ana T. G.; Lopes, Andreia A. S.; Veiga, João P. B.; Monteiro, Regina C. C.

    2017-01-01

    Glass samples with a molar composition (64+x)ZnO-(16-x)B2O3-20SiO2, where x=0 or 1, were successfully synthesized using a melt-quenching technique. Based on differential thermal analysis data, the produced glass samples were submitted to controlled heat-treatments at selected temperatures (610, 615 and 620 °C) during various times ranging from 8 to 30 h. The crystallization of willemite (Zn2SiO4) within the glass matrix was confirmed by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). Under specific heat-treatment conditions, transparent nanocomposite glass-ceramics were obtained, as confirmed by UV-vis spectroscopy. The influence of temperature, holding time and glass composition on crystal growth was investigated. The mean crystallite size was determined by image analysis on SEM micrographs. The results indicated an increase on the crystallite size and density with time and temperature. The change of crystallite size with time for the heat-treatments at 615 and 620 °C depended on the glass composition. Under fixed heat-treatment conditions, the crystallite density was comparatively higher for the glass composition with higher ZnO content.

  3. Large electrostatic accelerators

    International Nuclear Information System (INIS)

    Jones, C.M.

    1984-01-01

    The paper is divided into four parts: a discussion of the motivation for the construction of large electrostatic accelerators, a description and discussion of several large electrostatic accelerators which have been recently completed or are under construction, a description of several recent innovations which may be expected to improve the performance of large electrostatic accelerators in the future, and a description of an innovative new large electrostatic accelerator whose construction is scheduled to begin next year

  4. Synthesis and Characterization of Nano Scale YBCO

    International Nuclear Information System (INIS)

    Sukirman, E.; Wisnu AA; Yustinus P; Sahidin W, D.; Rina M, Th.

    2009-01-01

    Synthesis and characterization of the nano scale YBCO superconductor have been performed. The nano scale superconductor was synthesized from YBCO system (YBa 2 Cu 3 O 7-X ). Raw materials, namely Y 2 O 3 , BaCO 3 , and Cu°, were balanced and mixed with ethanol using magnetic steering as a churn in a beaker glass. Then, the precursor was calcined at T k = 900°C for 5 hours and repeated it until three times. The resulting precursor was ground by using High Energy Milling (HEM) for t = 0, 30, 50, 70, and 90 hour and hereinafter precursors are successively referred as YKM-00, YKM-30, YKM-50, YKM-70, and YKM-90. The resulting powders phase were characterized by means of x-ray diffraction technique using the Rietveld analysis method. Precursor of YKM-90 was pressed into pellets, and then sintered at various temperatures and periods. The sample phase was then characterized by using the Rietveld analysis method based on the x-ray diffraction data. The crystallites size were calculated using Scherrer formula. Results of analysis indicate that by minimizing crystallites size, period of sinter can be shortened from 10 to 1 hour, resulting crystallite size of D = 925 Å, critical current density of J c = 4 A / cm 2 , and can be grown of about 15 weight % of 211-phase in a matrix of 123-phase. The decrease of crystallite size will generate a change in physical properties dramatically, if the crystallite size of the material, D is smaller or equal to the coherence length of 10 Å. (author)

  5. Enhanced room temperature ferromagnetism in antiferromagnetic NiO nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Ravikumar, Patta; Kisan, Bhagaban; Perumal, A., E-mail: perumal@iitg.ernet.in [Department of Physics, Indian institute of Technology Guwahati, Guwahati 781 039 (India)

    2015-08-15

    We report systematic investigations of structural, vibrational, resonance and magnetic properties of nanoscale NiO powders prepared by ball milling process under different milling speeds for 30 hours of milling. Structural properties revealed that both pure NiO and as-milled NiO powders exhibit face centered cubic structure, but average crystallite size decreases to around 11 nm along with significant increase in strain with increasing milling speed. Vibrational properties show the enhancement in the intensity of one-phonon longitudinal optical (LO) band and disappearance of two-magnon band due to size reduction. In addition, two-phonon LO band exhibits red shift due to size-induced phonon confinement effect and surface relaxation. Pure NiO powder exhibit antiferromagnetic nature, which transforms into induced ferromagnetic after size reduction. The average magnetization at room temperature increases with decreasing the crystallite size and a maximum moment of 0.016 μ{sub B}/f.u. at 12 kOe applied field and coercivity of 170 Oe were obtained for 30 hours milled NiO powders at 600 rotation per minute milling speed. The change in the magnetic properties is also supported by the vibrational properties. Thermomagnetization measurements at high temperature reveal a well-defined magnetic phase transition at high temperature (T{sub C}) around 780 K due to induced ferromagnetic phase. Electron paramagnetic resonance (EPR) studies reveal a good agreement between the EPR results and magnetic properties. The observed results are described on the basis of crystallite size variation, defect density, large strain, oxidation/reduction of Ni and interaction between uncompensated surfaces and particle core with lattice expansion. The obtained results suggest that nanoscale NiO powders with high T{sub C} and moderate magnetic moment at room temperature with cubic structure would be useful to expedite for spintronic devices.

  6. Enhanced room temperature ferromagnetism in antiferromagnetic NiO nanoparticles

    Directory of Open Access Journals (Sweden)

    Patta Ravikumar

    2015-08-01

    Full Text Available We report systematic investigations of structural, vibrational, resonance and magnetic properties of nanoscale NiO powders prepared by ball milling process under different milling speeds for 30 hours of milling. Structural properties revealed that both pure NiO and as-milled NiO powders exhibit face centered cubic structure, but average crystallite size decreases to around 11 nm along with significant increase in strain with increasing milling speed. Vibrational properties show the enhancement in the intensity of one-phonon longitudinal optical (LO band and disappearance of two-magnon band due to size reduction. In addition, two-phonon LO band exhibits red shift due to size-induced phonon confinement effect and surface relaxation. Pure NiO powder exhibit antiferromagnetic nature, which transforms into induced ferromagnetic after size reduction. The average magnetization at room temperature increases with decreasing the crystallite size and a maximum moment of 0.016 μB/f.u. at 12 kOe applied field and coercivity of 170 Oe were obtained for 30 hours milled NiO powders at 600 rotation per minute milling speed. The change in the magnetic properties is also supported by the vibrational properties. Thermomagnetization measurements at high temperature reveal a well-defined magnetic phase transition at high temperature (TC around 780 K due to induced ferromagnetic phase. Electron paramagnetic resonance (EPR studies reveal a good agreement between the EPR results and magnetic properties. The observed results are described on the basis of crystallite size variation, defect density, large strain, oxidation/reduction of Ni and interaction between uncompensated surfaces and particle core with lattice expansion. The obtained results suggest that nanoscale NiO powders with high TC and moderate magnetic moment at room temperature with cubic structure would be useful to expedite for spintronic devices.

  7. Characterization of polymorphic solid-state changes using variable temperature X-ray powder diffraction

    DEFF Research Database (Denmark)

    Karjalainen, Milja; Airaksinen, Sari; Rantanen, Jukka

    2005-01-01

    The aim of this study was to use variable temperature X-ray powder diffraction (VT-XRPD) to understand the solid-state changes in the pharmaceutical materials during heating. The model compounds studied were sulfathiazole, theophylline and nitrofurantoin. This study showed that the polymorph form...... of sulfathiazole SUTHAZ01 was very stable and SUTHAZ02 changed as a function of temperature to SUTHAZ01. Theophylline monohydrate changed via its metastable form to its anhydrous form during heating and nitrofurantoin monohydrate changed via amorphous form to its anhydrous form during heating. The crystallinity...... to the anhydrous form. The average crystallite size of sulfathiazole samples varied only a little during heating. The average crystallite size of both theophylline and nitrofurantoin monohydrate decreased during heating. However, the average crystallite size of nitrofurantoin monohydrate returned back to starting...

  8. EPR of radiation defects in lithium-oxyfluoride glass ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Fedotovs, A; Rogulis, U; Sarakovskis, A; Dimitrocenko, L, E-mail: andris-f@navigator.l [Institute of Solid State Physics, University of Latvia, Kengaraga st. 8, LV-1063, Riga (Latvia)

    2010-11-01

    We studied oxyfluoride composites based on lithium silicate glasses with yttrium fluorides and rare-earth dopants. The electron paramagnetic resonance (EPR) has been used to obtain information about radiation induced defects in these materials. Spectra have been measured before and after X-ray irradiation at room temperature and at liquid nitrogen temperature. Fluoride crystallites within samples were created by means of thermal treatment at specific temperatures. EPR spectra of radiation induced defects in oxyfluoride glass ceramics, in which crystallites have not been yet created, show no explicit hfs interaction of fluorine nuclei. However, in glass ceramics, which already contains fluoride crystallites, the hfs characteristic to fluorine nuclei appears in the EPR spectra. EPR hyperfine structure could be explained within a model of an F-type centre in YF{sub 3} crystalline phase.

  9. EPR of radiation defects in lithium-oxyfluoride glass ceramics

    Science.gov (United States)

    Fedotovs, A.; Rogulis, U.; Sarakovskis, A.; Dimitrocenko, L.

    2010-11-01

    We studied oxyfluoride composites based on lithium silicate glasses with yttrium fluorides and rare-earth dopants. The electron paramagnetic resonance (EPR) has been used to obtain information about radiation induced defects in these materials. Spectra have been measured before and after X-ray irradiation at room temperature and at liquid nitrogen temperature. Fluoride crystallites within samples were created by means of thermal treatment at specific temperatures. EPR spectra of radiation induced defects in oxyfluoride glass ceramics, in which crystallites have not been yet created, show no explicit hfs interaction of fluorine nuclei. However, in glass ceramics, which already contains fluoride crystallites, the hfs characteristic to fluorine nuclei appears in the EPR spectra. EPR hyperfine structure could be explained within a model of an F-type centre in YF3 crystalline phase.

  10. Quantum Mechanical Calculations of Vibrational Sum-Frequency-Generation (SFG) Spectra of Cellulose: Dependence of the CH and OH Peak Intensity on the Polarity of Cellulose Chains within the SFG Coherence Domain.

    Science.gov (United States)

    Lee, Christopher M; Chen, Xing; Weiss, Philip A; Jensen, Lasse; Kim, Seong H

    2017-01-05

    Vibrational sum-frequency-generation (SFG) spectroscopy is capable of selectively detecting crystalline biopolymers interspersed in amorphous polymer matrices. However, the spectral interpretation is difficult due to the lack of knowledge on how spatial arrangements of crystalline segments influence SFG spectra features. Here we report time-dependent density functional theory (TD-DFT) calculations of cellulose crystallites in intimate contact with two different polarities: parallel versus antiparallel. TD-DFT calculations reveal that the CH/OH intensity ratio is very sensitive to the polarity of the crystallite packing. Theoretical calculations of hyperpolarizability tensors (β abc ) clearly show the dependence of SFG intensities on the polarity of crystallite packing within the SFG coherence length, which provides the basis for interpretation of the empirically observed SFG features of native cellulose in biological systems.

  11. Comparative study of Ni and Cu doped ZnO nanoparticles: Structural and optical properties

    Science.gov (United States)

    Thakur, Shaveta; Thakur, Samita; Sharma, Jyoti; Kumar, Sanjay

    2018-05-01

    Nanoparticles of undoped and doped (0.1 M Ni2+ and Cu2+) ZnO are synthesized using chemical precipitation method. The crystallite size, morphology, chemical bonding and optical properties of as prepared nanoparticles are determined by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and UV-visible spectra. XRD analysis shows that the prepared samples are single phase and have hexagonal wurtzite structure. The crystallite size of the doped and undoped nanoparticles is determined using Scherrer method. The crystallite size is found to be increased with concentration of nickel and copper. All stretching and vibrational bands are observed at their specific positions through FTIR. The increase in band gap can be attributed to the different chemical nature of dopant and host cation.

  12. Crystallinity of the epitaxial heterojunction of C60 on single crystal pentacene

    Science.gov (United States)

    Tsuruta, Ryohei; Mizuno, Yuta; Hosokai, Takuya; Koganezawa, Tomoyuki; Ishii, Hisao; Nakayama, Yasuo

    2017-06-01

    The structure of pn heterojunctions is an important subject in the field of organic semiconductor devices. In this work, the crystallinity of an epitaxial pn heterojunction of C60 on single crystal pentacene is investigated by non-contact mode atomic force microscopy and high-resolution grazing incidence x-ray diffraction. Analysis shows that the C60 molecules assemble into grains consisting of single crystallites on the pentacene single crystal surface. The in-plane mean crystallite size exceeds 0.1 μm, which is at least five time larger than the size of crystallites deposited onto polycrystalline pentacene thin films grown on SiO2. The results indicate that improvement in the crystal quality of the underlying molecular substrate leads to drastic promotion of the crystallinity at the organic semiconductor heterojunction.

  13. Mobility and powering of large detectors. Moving large detectors

    International Nuclear Information System (INIS)

    Thompson, J.

    1977-01-01

    The possibility is considered of moving large lepton detectors at ISABELLE for readying new experiments, detector modifications, and detector repair. A large annex (approximately 25 m x 25 m) would be built adjacent to the Lepton Hall separated from the Lepton Hall by a wall of concrete 11 m high x 12 m wide (for clearance of the detector) and approximately 3 m thick (for radiation shielding). A large pad would support the detector, the door, the cryogenic support system and the counting house. In removing the detector from the beam hall, one would push the pad into the annex, add a dummy beam pipe, bake out the beam pipe, and restack and position the wall on a small pad at the door. The beam could then operate again while experimenters could work on the large detector in the annex. A consideration and rough price estimate of various questions and proposed solutions are given

  14. Instantons and Large N

    Science.gov (United States)

    Mariño, Marcos

    2015-09-01

    Preface; Part I. Instantons: 1. Instantons in quantum mechanics; 2. Unstable vacua in quantum field theory; 3. Large order behavior and Borel summability; 4. Non-perturbative aspects of Yang-Mills theories; 5. Instantons and fermions; Part II. Large N: 6. Sigma models at large N; 7. The 1=N expansion in QCD; 8. Matrix models and matrix quantum mechanics at large N; 9. Large N QCD in two dimensions; 10. Instantons at large N; Appendix A. Harmonic analysis on S3; Appendix B. Heat kernel and zeta functions; Appendix C. Effective action for large N sigma models; References; Author index; Subject index.

  15. Influence of bases on hydrothermal synthesis of titanate nanostructures

    Science.gov (United States)

    Sikhwivhilu, Lucky M.; Sinha Ray, Suprakas; Coville, Neil J.

    2009-03-01

    A hydrothermal treatment of titanium dioxide (TiO2) with various bases (i.e., LiOH, NaOH, KOH, and NH4OH) was used to prepare materials with unique morphologies, relatively small crystallite sizes, and large specific surface areas. The experimental results show that the formation of TiO2 is largely dependent on the type, strength and concentration of a base. The effect of the nature of the base used and the concentration of the base on the formation of nanostructures were investigated using X-ray diffraction, Raman spectroscopy, transmission and scanning electron microscopy, as well as surface area measurements. Sodium hydroxide (NaOH) and potassium hydroxide (KOH) were both used to transform the morphology of starting TiO2 material.

  16. Electrochemical fabrication of Sn nanowires on titania nanotube guide layers

    International Nuclear Information System (INIS)

    Djenizian, Thierry; Hanzu, Ilie; Premchand, Yesudas D; Vacandio, Florence; Knauth, Philippe

    2008-01-01

    We describe a novel approach for the fabrication of tailored nanowires using a two-step electrochemical process. It is demonstrated that self-organized TiO 2 nanotubes can be used to activate and guide the electrochemical growth of Sn crystallites, leading to the formation of vertical features with a high aspect ratio. We show that the dimensions and the density of Sn crystallites depend on the electrodeposition parameters

  17. Epitaxial growth of lithium fluoride on the (1 1 1) surface of CaF 2

    Science.gov (United States)

    Klumpp, St; Dabringhaus, H.

    1999-08-01

    Growth of lithium fluoride by molecular beam epitaxy on the (1 1 1) surface of calcium fluoride crystals was studied by TEM and LEED for crystal temperatures from 400 to 773 K and impinging lithium fluoride fluxes from 3×10 11 to 3×10 14 cm -2 s -1. Growth starts, usually, at the steps on the (1 1 1) surface of CaF 2. For larger step distances and at later growth stages also growth on the terraces between the steps is found. Preferably, longish, roof-like crystallites are formed, which can be interpreted by growth of LiF(2 0 1¯)[0 1 0] parallel to CaF 2(1 1 1)[ 1¯ 0 1]. To a lesser extent square crystallites, i.e. growth with LiF(0 0 1), and, rarely, three-folded pyramidal crystallites, i.e. growth with LiF(1 1 1) parallel to CaF 2(1 1 1), are observed. While the pyramidal crystallites show strict epitaxial orientation with LiF[ 1¯ 0 1]‖CaF 2[ 1¯ 0 1] and LiF[ 1¯ 0 1]‖CaF 2[1 2¯ 1], only about 80% of the square crystallites exhibit an epitaxial alignment, where LiF[1 0 0]‖CaF 2[ 1¯ 0 1] is preferred to LiF[1 1 0]‖CaF 2[ 1¯ 0 1]. The epitaxial relationships are discussed on the basis of theoretically calculated adsorption positions of the lithium fluoride monomer and dimer on the terrace and at the steps of the CaF 2(1 1 1) surface.

  18. Effect of surfactants on the properties of hydrotalcites prepared by the reverse micelle method

    Energy Technology Data Exchange (ETDEWEB)

    Holgado, Patricia H., E-mail: h.holgado@usal.es; Holgado, María J., E-mail: holgado@usal.es; San Román, María S., E-mail: sanroman@usal.es; Rives, Vicente, E-mail: vrives@usal.es

    2015-02-01

    Layered double hydroxides with the hydrotalcite-type structure have been prepared by the reverse micelles method. The layer cations were Ni{sup 2+} and Fe{sup 3+} in all cases and the interlayer anion was carbonate. We have studied the effect of the surfactant used (with linear chains of different lengths, or cyclic) and the effect of the pH on the properties of the solids formed. These have been characterized by element chemical analysis, powder X-ray diffraction, thermogravimetric analysis, temperature-programmed reduction, FT-IR and Vis–UV spectroscopies and scanning electron microscopy. It has been found that the samples prepared at pH 9 are more crystalline than those prepared at pH 11 and their crystallite sizes are always larger than for samples prepared by the conventional precipitation method. Surfactants with cyclic organic chains lead to a larger crystallite size, probably because the water pool vesicle where the crystallite grows is larger due to sterical hindrance of the organic chains. - Graphical abstract: Layered double hydroxides with the hydrotalcite-type structure with Ni{sup 2+} and Fe{sup 3+} cations in the layers have been prepared by the reverse micelles method. Different surfactants were used at different pH synthesis. Samples prepared at pH 9 are higher crystalline than those prepared at pH 11. Surfactants with cyclic organic chains lead to a larger crystallite size. - Highlights: • Hydrotalcites were prepared by the micelles reverse method. • Straight alkyl or cyclic chain surfactants were used. • All hydrotalcites are well crystallized at pH = 9 and 11. • The crystallite size depends on the linear/cyclic nature of the surfactant chain.

  19. Effect of surfactants on the properties of hydrotalcites prepared by the reverse micelle method

    International Nuclear Information System (INIS)

    Holgado, Patricia H.; Holgado, María J.; San Román, María S.; Rives, Vicente

    2015-01-01

    Layered double hydroxides with the hydrotalcite-type structure have been prepared by the reverse micelles method. The layer cations were Ni 2+ and Fe 3+ in all cases and the interlayer anion was carbonate. We have studied the effect of the surfactant used (with linear chains of different lengths, or cyclic) and the effect of the pH on the properties of the solids formed. These have been characterized by element chemical analysis, powder X-ray diffraction, thermogravimetric analysis, temperature-programmed reduction, FT-IR and Vis–UV spectroscopies and scanning electron microscopy. It has been found that the samples prepared at pH 9 are more crystalline than those prepared at pH 11 and their crystallite sizes are always larger than for samples prepared by the conventional precipitation method. Surfactants with cyclic organic chains lead to a larger crystallite size, probably because the water pool vesicle where the crystallite grows is larger due to sterical hindrance of the organic chains. - Graphical abstract: Layered double hydroxides with the hydrotalcite-type structure with Ni 2+ and Fe 3+ cations in the layers have been prepared by the reverse micelles method. Different surfactants were used at different pH synthesis. Samples prepared at pH 9 are higher crystalline than those prepared at pH 11. Surfactants with cyclic organic chains lead to a larger crystallite size. - Highlights: • Hydrotalcites were prepared by the micelles reverse method. • Straight alkyl or cyclic chain surfactants were used. • All hydrotalcites are well crystallized at pH = 9 and 11. • The crystallite size depends on the linear/cyclic nature of the surfactant chain

  20. Zinc-Containing Restorations Create Amorphous Biogenic Apatite at the Carious Dentin Interface: A X-Ray Diffraction (XRD) Crystal Lattice Analysis.

    Science.gov (United States)

    Toledano, Manuel; Aguilera, Fátima S; López-López, Modesto T; Osorio, Estrella; Toledano-Osorio, Manuel; Osorio, Raquel

    2016-10-01

    The aim of this research was to assess the ability of amalgam restorations to induce amorphous mineral precipitation at the caries-affected dentin substrate. Sound and caries-affected dentin surfaces were subjected to both Zn-free and Zn-containing dental amalgam restorations. Specimens were submitted to thermocycling (100,000 cycles/5°C-55°C, 3 months). Dentin surfaces were studied by atomic force microscopy (nanoroughness), X-ray diffraction, field emission scanning electron microscopy, and energy-dispersive analysis, for physical and morphological surface characterization. Zn-containing amalgam placement reduced crystallinity, crystallite size, and grain size of calcium phosphate crystallites at the dentin surface. Both microstrain and nanoroughness were augmented in caries-affected dentin restored with Zn-containing amalgams. Caries-affected dentin showed the shortest mineral crystallites (11.04 nm), when Zn-containing amalgams were used for restorations, probably leading to a decrease of mechanical properties which might favor crack propagation and deformation. Sound dentin restored with Zn-free amalgams exhibited a substantial increase in length of grain particles (12.44 nm) embedded into dentin crystallites. Zn-containing amalgam placement creates dentin mineralization and the resultant mineral was amorphous in nature. Amorphous calcium phosphate provides a local ion-rich environment, which is considered favorable for in situ generation of prenucleation clusters, promotong further dentin remineralization.

  1. Size-dependent elastic/inelastic behavior of enamel over millimeter and nanometer length scales.

    Science.gov (United States)

    Ang, Siang Fung; Bortel, Emely L; Swain, Michael V; Klocke, Arndt; Schneider, Gerold A

    2010-03-01

    The microstructure of enamel like most biological tissues has a hierarchical structure which determines their mechanical behavior. However, current studies of the mechanical behavior of enamel lack a systematic investigation of these hierarchical length scales. In this study, we performed macroscopic uni-axial compression tests and the spherical indentation with different indenter radii to probe enamel's elastic/inelastic transition over four hierarchical length scales, namely: 'bulk enamel' (mm), 'multiple-rod' (10's microm), 'intra-rod' (100's nm with multiple crystallites) and finally 'single-crystallite' (10's nm with an area of approximately one hydroxyapatite crystallite). The enamel's elastic/inelastic transitions were observed at 0.4-17 GPa depending on the length scale and were compared with the values of synthetic hydroxyapatite crystallites. The elastic limit of a material is important as it provides insights into the deformability of the material before fracture. At the smallest investigated length scale (contact radius approximately 20 nm), elastic limit is followed by plastic deformation. At the largest investigated length scale (contact size approximately 2 mm), only elastic then micro-crack induced response was observed. A map of elastic/inelastic regions of enamel from millimeter to nanometer length scale is presented. Possible underlying mechanisms are also discussed. (c) 2009 Elsevier Ltd. All rights reserved.

  2. Synthesis of antimony-doped tin oxide (ATO) nanoparticles by the nitrate-citrate combustion method

    International Nuclear Information System (INIS)

    Zhang Jianrong; Gao Lian

    2004-01-01

    Antimony-doped tin oxide (ATO) nanoparticles having rutile structure have been synthesized by the combustion method using citric acid (CA) as fuel and nitrate as an oxidant, the metal sources were granulated tin and Sb 2 O 3 . The influence of citric acid (fuel) to metal ratio on the average crystallite size, specific surface area and morphology of the nanoparticles has been investigated. X-ray diffraction showed the tin ions were reduced to elemental tin during combustion reaction. The average ATO crystallite size increased with the increase of citric acid (fuel). Powder morphology and the comparison of crystallite size and grain size shows that the degree of agglomeration of the powder decreased with an increase of the ratio. The highest specific surface area was 37.5 m 2 /g when the citric acid to tin ratio was about 6

  3. XRD analysis of undoped and Fe doped TiO2 nanoparticles by Williamson Hall method

    International Nuclear Information System (INIS)

    Bharti, Bandna; Barman, P. B.; Kumar, Rajesh

    2015-01-01

    Undoped and Fe doped titanium dioxide (TiO 2 ) nanoparticles were synthesized by sol-gel method at room temperature. The synthesized samples were annealed at 500°C. For structural analysis, the prepared samples were characterized by X-ray diffraction (XRD). The crystallite size of TiO 2 and Fe doped TiO 2 nanoparticles were calculated by Scherer’s formula, and was found to be 15 nm and 11 nm, respectively. Reduction in crystallite size of TiO 2 with Fe doping was observed. The anatase phase of Fe-doped TiO 2 nanoparticles was also confirmed by X-ray diffraction. By using Williamson-Hall method, lattice strain and crystallite size were also calculated. Williamson–Hall plot indicates the presence of compressive strain for TiO 2 and tensile strain for Fe-TiO 2 nanoparticles annealed at 500°C

  4. Structural properties and gas sensing behavior of sol-gel grown nanostructured zinc oxide

    Energy Technology Data Exchange (ETDEWEB)

    Rajyaguru, Bhargav; Gadani, Keval; Kansara, S. B.; Pandya, D. D.; Shah, N. A.; Solanki, P. S., E-mail: piyush.physics@gmail.com [Department of Physics, Saurashtra University, Rajkot – 360 005 (India); Rathod, K. N.; Solanki, Sapana [Department of Physics, Saurashtra University, Rajkot – 360 005 (India); V.V.P. Engineering College, Gujarat Technological University, Rajkot – 360 005 (India)

    2016-05-06

    In this communication, we report the results of the studies on structural properties and gas sensing behavior of nanostructured ZnO grown using acetone precursor based modified sol-gel technique. Final product of ZnO was sintered at different temperatures to vary the crystallite size while their structural properties have been studied using X-ray diffraction (XRD) measurement performed at room temperature. XRD results suggest the single phasic nature of all the samples and crystallite size increases from 11.53 to 20.96 nm with increase in sintering temperature. Gas sensing behavior has been studied for acetone gas which indicates that lower sintered samples are more capable to sense the acetone gas and related mechanism has been discussed in the light of crystallite size, crystal boundary density, defect mechanism and possible chemical reaction between gas traces and various oxygen species.

  5. Hard magnetic properties of rapidly annealed NdFeB thin films on Nb and V buffer layers

    International Nuclear Information System (INIS)

    Jiang, H.; Evans, J.; O'Shea, M.J.; Du Jianhua

    2001-01-01

    NdFeB thin films of the form A (20 nm)/NdFeB(d nm)/A(20 nm), where d ranges from 54 to 540 nm and the buffer layer A is Nb or V were prepared on a Si(1 0 0) substrate by magnetron sputtering. The hard Nd 2 Fe 14 B phase is formed by a 30 s rapid anneal or a 20 min anneal. Average crystallite size ranged from 20 to 35 nm with the rapidly annealed samples having the smaller crystallite size. These samples also exhibited a larger coercivity and energy product than those treated by a 20 min vacuum anneal. A maximum coercivity of 26.3 kOe at room temperature was obtained for a Nb/NdFeB (180 nm)/Nb film after a rapid anneal at 725 deg. C. Initial magnetization curves indicate magnetization rotation rather than nucleation of reverse domains is important in the magnetization process. A Brown's equation analysis of the coercivity as a function of temperature allowed us to compare the rapidly annealed and 20 min annealed samples. This analysis suggests that rapid annealing gives higher quality crystalline grains than the 20 min annealed sample leading to the observed large coercivity in the rapidly annealed samples

  6. Facile Low Temperature Hydrothermal Synthesis of BaTiO3 Nanoparticles Studied by In Situ X-ray Diffraction

    Directory of Open Access Journals (Sweden)

    Ola G. Grendal

    2018-06-01

    Full Text Available Ferroelectric materials are crucial for today’s technological society and nanostructured ferroelectric materials are important for the downscaling of devices. Controlled and reproducible synthesis of these materials are, therefore, of immense importance. Hydrothermal synthesis is a well-established synthesis route, with a large parameter space for optimization, but a better understanding of nucleation and growth mechanisms is needed for full utilization and control. Here we use in situ X-ray diffraction to follow the nucleation and growth of BaTiO3 formed by hydrothermal synthesis using two different titanium precursors, an amorphous titania precipitate slurry and a Ti-citric acid complex solution. Sequential Rietveld refinement was used to extract the time dependency of lattice parameters, crystallite size, strain, and atomic displacement parameters. Phase pure BaTiO3 nanoparticles, 10–15 nm in size, were successfully synthesized at different temperatures (100, 125, and 150 °C from both precursors after reaction times, ranging from a few seconds to several hours. The two precursors resulted in phase pure BaTiO3 with similar final crystallite size. Finally, two different growth mechanisms were revealed, where the effect of surfactants present during hydrothermal synthesis is discussed as one of the key parameters.

  7. Investigation of the stability of glass-ceramic composites containing CeTi2O6 and CaZrTi2O7 after ion implantation

    Science.gov (United States)

    Paknahad, Elham; Grosvenor, Andrew P.

    2017-12-01

    Glass-ceramic composite materials have been investigated for nuclear waste sequestration applications due to their ability to incorporate large amounts of radioactive waste elements. A key property that needs to be understood when developing nuclear waste sequestration materials is how the structure of the material responds to radioactive decay of nuclear waste elements, which can be simulated by high energy ion implantation. Borosilicate glass-ceramic composites containing brannerite-type (CeTi2O6) or zirconolite-type (CaZrTi2O7) oxides were synthesized at different annealing temperatures and investigated after being implanted with high-energy Au ions to mimic radiation induced structural damage. Backscattered electron (BSE) images were collected to investigate the interaction of the brannerite crystallites with the glass matrix before and after implantation and showed that the morphology of the crystallites in the composite materials were not affected by radiation damage. Surface sensitive Ti K-edge glancing angle XANES spectra collected from the implanted composite materials showed that the structures of the CeTi2O6 and CaZrTi2O7 ceramics were damaged as a result of implantation; however, analysis of Si L2,3-edge XANES spectra indicated that the glass matrix was not affected by ion implantation.

  8. Investigation of the stability of glass-ceramic composites containing CeTi 2 O 6 and CaZrTi 2 O 7 after ion implantation

    Energy Technology Data Exchange (ETDEWEB)

    Paknahad, Elham; Grosvenor, Andrew P.

    2017-12-01

    Glass-ceramic composite materials have been investigated for nuclear waste sequestration applications due to their ability to incorporate large amounts of radioactive waste elements. A key property that needs to be understood when developing nuclear waste sequestration materials is how the structure of the material responds to radioactive decay of nuclear waste elements, which can be simulated by high energy ion implantation. Borosilicate glass-ceramic composites containing brannerite-type (CeTi2O6) or zirconolite-type (CaZrTi2O7) oxides were synthesized at different annealing temperatures and investigated after being implanted with high-energy Au ions to mimic radiation induced structural damage. Backscattered electron (BSE) images were collected to investigate the interaction of the brannerite crystallites with the glass matrix before and after implantation and showed that the morphology of the crystallites in the composite materials were not affected by radiation damage. Surface sensitive Ti K-edge glancing angle XANES spectra collected from the implanted composite materials showed that the structures of the CeTi2O6 and CaZrTi2O7 ceramics were damaged as a result of implantation; however, analysis of Si L2,3-edge XANES spectra indicated that the glass matrix was not affected by ion implantation.

  9. Mass fabrication of homogeneously Yb-doped silica nanoparticles and their spectroscopic properties

    International Nuclear Information System (INIS)

    Xiong Liangming; Sekiya, Edson H; Saito, Kazuya

    2009-01-01

    A large number of homogeneously Yb-doped silica nanoparticles were continually fabricated in a vapor synthesis route, in which the Yb doping level can be well controlled by varying either the heating temperature or the carrier gas flow rate of the Yb precursor. The sizes, shapes, and morphologies of the nanoparticles were examined, and no crystallites and no Yb 2 O 3 clusters were observed in the nanoparticles. These nanoparticles exhibit a clear Yb 3+ -derived absorption at around 973-975 nm and a dependence of the emission intensity and decay time on the doping level, much different from that of sintered pellets.

  10. Electrocatalyst advances for hydrogen oxidation in phosphoric acid fuel cells

    Science.gov (United States)

    Stonehart, P.

    1984-01-01

    The important considerations that presently exist for achieving commercial acceptance of fuel cells are centered on cost (which translates to efficiency) and lifetime. This paper addresses the questions of electrocatalyst utilization within porous electrode structures and the preparation of low-cost noble metal electrocatalyst combinations with extreme dispersions of the metal. Now that electrocatalyst particles can be prepared with dimensions of 10 A, either singly or in alloy combinations, a very large percentage of the noble metal atoms in a crystallite are available for reaction. The cost savings for such electrocatalysts in the present commercially driven environment are considerable.

  11. Large electrostatic accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Jones, C.M.

    1984-01-01

    The increasing importance of energetic heavy ion beams in the study of atomic physics, nuclear physics, and materials science has partially or wholly motivated the construction of a new generation of large electrostatic accelerators designed to operate at terminal potentials of 20 MV or above. In this paper, the author briefly discusses the status of these new accelerators and also discusses several recent technological advances which may be expected to further improve their performance. The paper is divided into four parts: (1) a discussion of the motivation for the construction of large electrostatic accelerators, (2) a description and discussion of several large electrostatic accelerators which have been recently completed or are under construction, (3) a description of several recent innovations which may be expected to improve the performance of large electrostatic accelerators in the future, and (4) a description of an innovative new large electrostatic accelerator whose construction is scheduled to begin next year. Due to time and space constraints, discussion is restricted to consideration of only tandem accelerators.

  12. Large electrostatic accelerators

    International Nuclear Information System (INIS)

    Jones, C.M.

    1984-01-01

    The increasing importance of energetic heavy ion beams in the study of atomic physics, nuclear physics, and materials science has partially or wholly motivated the construction of a new generation of large electrostatic accelerators designed to operate at terminal potentials of 20 MV or above. In this paper, the author briefly discusses the status of these new accelerators and also discusses several recent technological advances which may be expected to further improve their performance. The paper is divided into four parts: (1) a discussion of the motivation for the construction of large electrostatic accelerators, (2) a description and discussion of several large electrostatic accelerators which have been recently completed or are under construction, (3) a description of several recent innovations which may be expected to improve the performance of large electrostatic accelerators in the future, and (4) a description of an innovative new large electrostatic accelerator whose construction is scheduled to begin next year. Due to time and space constraints, discussion is restricted to consideration of only tandem accelerators

  13. Structural characterization of graphene layers in various Indian coals by X-Ray Diffraction technique

    Science.gov (United States)

    Manoj, B.; Kunjomana, A. G.

    2015-02-01

    The results of the structural investigation of three Indian coals showed that, the structural parameters like fa & Lc increased where as interlayer spacing d002 decreased with increase in carbon content, aromaticity and coal rank. These structural parameters change just opposite with increase in volatile matter content. Considering the 'turbostratic' structure for coals, the minimum separation between aromatic lamellae was found to vary between 3.34 to 3.61 A° for these coals. As the aromaticity increased, the interlayer spacing decreased an indication of more graphitization of the sample. Volatile matter and carbon content had a strong influence on the aromaticity, interlayer spacing and stacking height on the sample. The average number of carbon atoms per aromatic lamellae and number of layers in the lamellae was found to be 16-21 and 7-8 for all the samples.

  14. Electronic and structural properties of micro-and nanometre-sized crystalline copper monoxide ceramics investigated by positron annihilation

    International Nuclear Information System (INIS)

    Druzhkov, A.P.; Gizhevskii, B.A.; Arbuzov, V.L.; Shalnov, K.V.; Naumov, S.V.; Perminov, D.A.; Kozlov, E.A.

    2002-01-01

    Electronic and structural properties of copper monoxide (CuO) sintered as a common ceramic and nanoceramic are studied by positron annihilation spectroscopy. A CuO nanoceramic with crystallite size ranging from 15 to 90 nm was prepared from a common one by shock-wave loading. It is found that the momentum distribution of valence electrons in CuO is shifted, as compared with metallic copper, towards higher momentum values. This result is related to the effect of the Cu 3d-O 2p hybridization in the Cu-O ionic covalent bond formation. It is found that open volumes, identified mainly as small agglomerates of oxygen vacancies, appear at the nanoceramic crystallite interfaces. The degree of the Cu-O bond covalency decreases locally at the crystallite interfaces because of an oxygen deficit. The nanocrystalline state in CuO is shown to be thermally stable up to 700 K. (author)

  15. Hydrothermal synthesis and magnetic properties of Mn doped ZnS nanoparticles

    Science.gov (United States)

    Rashad, M. M.; Rayan, D. A.; El-Barawy, K.

    2010-01-01

    Nanocrystallite Mn doped Zn1-XS (X = 0 to 0.4) powders have been synthesized through a hydrothermal route. The effect of the hydrothermal temperature and Mn2+ ions substitution on the crystal structure, crystallite size, microstructure and magnetic properties were investigated using (XRD), (SEM) and (VSM). The results revealed that wurtzite zinc sulfide phase was formed using thiourea as a sulfur source at temperature 150- 200oC for 24 h. The crystallite size was (7.9-15.1 nm) was obtained at the same conditions. The doping of Mn2+ ions decreased the crystallite size of the formed ZnS wurtzite phase was in the range between 7.9 and 3.8 nm. SEM micrographs showed that the produced ZnS and Mn doped ZnS particles were appeared as spherical shape. The magnetic properties were improved by substitution of Mn2+ ions up to 0.2.

  16. Hydrothermal synthesis and magnetic properties of Mn doped ZnS nanoparticles

    International Nuclear Information System (INIS)

    Rashad, M M; Rayan, D A; El-Barawy, K

    2010-01-01

    Nanocrystallite Mn doped Zn 1-X S (X = 0 to 0.4) powders have been synthesized through a hydrothermal route. The effect of the hydrothermal temperature and Mn 2+ ions substitution on the crystal structure, crystallite size, microstructure and magnetic properties were investigated using (XRD), (SEM) and (VSM). The results revealed that wurtzite zinc sulfide phase was formed using thiourea as a sulfur source at temperature 150- 200 o C for 24 h. The crystallite size was (7.9-15.1 nm) was obtained at the same conditions. The doping of Mn 2+ ions decreased the crystallite size of the formed ZnS wurtzite phase was in the range between 7.9 and 3.8 nm. SEM micrographs showed that the produced ZnS and Mn doped ZnS particles were appeared as spherical shape. The magnetic properties were improved by substitution of Mn 2+ ions up to 0.2.

  17. Applications of the Warren-Averbach method of X-ray diffraction line profile analysis

    International Nuclear Information System (INIS)

    Ichikawa, Rodrigo Uchida

    2013-01-01

    The objective of this work was to develop and implement a methodology of X-ray Line Profile Analysis (XLPA) for the study and determination of the mean crystallite sizes and microstrains in materials. A computer program was developed to speed up the treatment of diffraction peaks and perform the deconvolution utilizing the Stokes method to correct the instrumental contribution in the X-ray diffraction measurements. The XLPA methods used were the Scherrer, Williamson-Hall and Single-Line methods, which can be called real space methods, and the Fourier space method of Warren-Averbach. Furthermore, considering a mathematical modelling it was possible to calculate the crystallite size distribution, considering the log-normal distribution and spherical crystallites. It was possible to demonstrate the proposed theory can provide reliable results evaluating a dispersion parameter. The methodologies described above were applied in two distinct materials: in the alloy Zircaloy-4 and in ZnO. (author)

  18. α-Sn and β-Sn precipitates in annealed epitaxial Si0.95Sn0.05

    DEFF Research Database (Denmark)

    Fyhn, M.F.; Chevallier, J.; Larsen, A.N.

    1999-01-01

    -Sn and beta-Sn crystallites. The presence of alpha-Sn at temperatures far above the bulk alpha beta transition temperature is explained by interface and pressure effects; the latter is likely to be due to the difference in thermal expansion of the precipitates and the matrix.......-temperature molecular-beam epitaxy on Si (001) and relaxed Si1-xGex substrates. Two different phases of solid Sn were identified in the annealed layers: the semiconductor phase, alpha-Sn, and the metallic phase beta-Sn The precipitates were found to consist of either only beta-Sn or to contain crystallites of both...... solid Sn phases. The orientations, the sizes and the relative number densities of the alpha-Sn and beta-Sn crystallites were investigated. in situ heating and cooling experiments were performed in the transmission electron microscope to study the melting and solidification characteristics of the alpha...

  19. Structural and microstructural characterization of U3Si2 nuclear fuel using X-ray diffraction

    International Nuclear Information System (INIS)

    Ichikawa, Rodrigo U.; Garcia, Rafael H.L.; Silva, Andre S.B. da; Saliba-Silva, Adonis M.; Lima, Nelson B.; Martinez, Luis G.; Turrillas, Xavier

    2017-01-01

    In this work, two uranium silicide powdered samples, containing 67% and 42 mol% of Si, were analyzed using X-ray diffraction (named as 67 Si and 42 Si). For structural characterization, Rietveld refinement was used to estimate cell parameters, volume fraction (weight percent) of crystalline phases and atomic positions. For the main phases, X-ray line profile analysis (XLPA) was used to estimate mean crystallite sizes and micro strains. The 67 Si sample presents higher content of USi 2( tetragonal) and the 42 Si sample presents higher content of U 3 Si 2 (tetragonal) as identified and calculated from the XRD profiles. Overall there are no appreciable structural changes and the parameters refined are in good accordance with the ones reported in the literature. Mean crystallite sizes determined by XLPA revealed small crystallites of the order of 10 1 nm and low micro strain for all samples. (author)

  20. Nanocrystallite characterization of milled simulated dry process fuel powders by neutron diffraction

    International Nuclear Information System (INIS)

    Ryu, Ho Jin; Kang, Kwon Ho; Moon, Je Sun; Song, Kee Chan; Choi, Yong Nam

    2003-01-01

    The nano-scale crystallite sizes of simulated spent fuel powders were measured by the neutron diffraction line broadening method in order to analyze the sintering behavior of the dry process fuel. The mixed U0 2 and fission product oxide powders were dry-milled in an attritor for 30, 60, and 120 min. The diffraction patterns of the powders were obtained by using the high resolution powder diffractometer in the HANARO research reactor. Diffraction line broadening due to crystallite size was measured using various techniques such as the Stokes' deconvolution, profile fitting methods using Cauchy function, Gaussian function, and Voigt function, and the Warren-Averbach method. The r.m.s. strain, stacking fault, twin and dislocation density were measured using the information from the diffraction pattern. The realistic crystallite size can be obtained after separation of the contribution from the non-uniform strain, stacking fault and twin

  1. Electronic and structural properties of micro-and nanometre-sized crystalline copper monoxide ceramics investigated by positron annihilation

    Energy Technology Data Exchange (ETDEWEB)

    Druzhkov, A.P. [Institute of Metal Physics, Ural Branch Russian Academy of Sciences, Ekaterinburg (Russian Federation)]. E-mail: druzhkov@imp.uran.ru; Gizhevskii, B.A.; Arbuzov, V.L.; Shalnov, K.V.; Naumov, S.V.; Perminov, D.A. [Institute of Metal Physics, Ural Branch Russian Academy of Sciences, Ekaterinburg (Russian Federation); Kozlov, E.A. [All-Russian R and D Institute of Technical Physics, Snezhinsk (Russian Federation)

    2002-09-02

    Electronic and structural properties of copper monoxide (CuO) sintered as a common ceramic and nanoceramic are studied by positron annihilation spectroscopy. A CuO nanoceramic with crystallite size ranging from 15 to 90 nm was prepared from a common one by shock-wave loading. It is found that the momentum distribution of valence electrons in CuO is shifted, as compared with metallic copper, towards higher momentum values. This result is related to the effect of the Cu 3d-O 2p hybridization in the Cu-O ionic covalent bond formation. It is found that open volumes, identified mainly as small agglomerates of oxygen vacancies, appear at the nanoceramic crystallite interfaces. The degree of the Cu-O bond covalency decreases locally at the crystallite interfaces because of an oxygen deficit. The nanocrystalline state in CuO is shown to be thermally stable up to 700 K. (author)

  2. The effect of substrate temperature on atomic layer deposited zinc tin oxide

    Energy Technology Data Exchange (ETDEWEB)

    Lindahl, Johan, E-mail: johan.lindahl@angstrom.uu.se; Hägglund, Carl, E-mail: carl.hagglund@angstrom.uu.se; Wätjen, J. Timo, E-mail: timo.watjen@angstrom.uu.se; Edoff, Marika, E-mail: marika.edoff@angstrom.uu.se; Törndahl, Tobias, E-mail: tobias.torndahl@angstrom.uu.se

    2015-07-01

    Zinc tin oxide (ZTO) thin films were deposited on glass substrates by atomic layer deposition (ALD), and the film properties were investigated for varying deposition temperatures in the range of 90 to 180 °C. It was found that the [Sn]/([Sn] + [Zn]) composition is only slightly temperature dependent, while properties such as growth rate, film density, material structure and band gap are more strongly affected. The growth rate dependence on deposition temperature varies with the relative number of zinc or tin containing precursor pulses and it correlates with the growth rate behavior of pure ZnO and SnO{sub x} ALD. In contrast to the pure ZnO phase, the density of the mixed ZTO films is found to depend on the deposition temperature and it increases linearly with about 1 g/cm{sup 3} in total over the investigated range. Characterization by transmission electron microscopy suggests that zinc rich ZTO films contain small (~ 10 nm) ZnO or ZnO(Sn) crystallites embedded in an amorphous matrix, and that these crystallites increase in size with increasing zinc content and deposition temperature. These crystallites are small enough for quantum confinement effects to reduce the optical band gap of the ZTO films as they grow in size with increasing deposition temperature. - Highlights: • Zinc tin oxide thin films were deposited by atomic layer deposition. • The structure and optical properties were studied at different growth temperatures. • The growth temperature had only a small effect on the composition of the films. • Small ZnO or ZnO(Sn) crystallites were observed by TEM in zinc rich ZTO films. • The growth temperature affects the crystallite size, which influences the band gap.

  3. A comparative study of TiN and TiC: Oxidation resistance and retention of xenon at high temperature and under degraded vacuum

    International Nuclear Information System (INIS)

    Gavarini, S.; Bes, R.; Millard-Pinard, N.; Peaucelle, C.; Perrat-Mabilon, A.; Gaillard, C.; Cardinal, S.; Garnier, V.

    2011-01-01

    Dense TiN and TiC samples were prepared by hot pressing using micrometric powders. Xenon species (simulating rare gas fission products) were then implanted into the ceramics. The samples were annealed for 1 h at 1500 deg. C under several degraded vacuums with P O 2 varying from 10 -6 to 2x10 -4 mbars. The oxidation resistance of the samples and their retention properties with respect to preimplanted xenon species were analyzed using scanning electron microscopy, grazing incidence x-ray diffraction, Rutherford backscattering spectrometry, and nuclear backscattering spectrometry. Results indicate that TiC is resistant to oxidation and does not release xenon for P O 2 ≤6x10 -6 mbars. When P O 2 increases, geometric oxide crystallites appear at the surface depending on the orientation and size of TiC grains. These oxide phases are Ti 2 O 3 , Ti 3 O 5 , and TiO 2 . Apparition of oxide crystallites is associated with the beginning of xenon release. TiC surface is completely covered by the oxide phases at P O 2 =2x10 -4 mbars up to a depth of 3 μm and the xenon is then completely released. For TiN samples, the results show a progressive apparition of oxide crystallites (Ti 3 O 5 mainly) at the surface when P O 2 increases. The presence of the oxide crystallites is also directly correlated with xenon release, the more oxide crystallites are growing the more xenon is released. TiN surface is completely covered by an oxide layer at P O 2 =2x10 -4 mbars up to 1 μm. A correlation between the initial fine microstructure of TiN and the properties of the growing layer is suggested.

  4. The effect of substrate temperature on atomic layer deposited zinc tin oxide

    International Nuclear Information System (INIS)

    Lindahl, Johan; Hägglund, Carl; Wätjen, J. Timo; Edoff, Marika; Törndahl, Tobias

    2015-01-01

    Zinc tin oxide (ZTO) thin films were deposited on glass substrates by atomic layer deposition (ALD), and the film properties were investigated for varying deposition temperatures in the range of 90 to 180 °C. It was found that the [Sn]/([Sn] + [Zn]) composition is only slightly temperature dependent, while properties such as growth rate, film density, material structure and band gap are more strongly affected. The growth rate dependence on deposition temperature varies with the relative number of zinc or tin containing precursor pulses and it correlates with the growth rate behavior of pure ZnO and SnO x ALD. In contrast to the pure ZnO phase, the density of the mixed ZTO films is found to depend on the deposition temperature and it increases linearly with about 1 g/cm 3 in total over the investigated range. Characterization by transmission electron microscopy suggests that zinc rich ZTO films contain small (~ 10 nm) ZnO or ZnO(Sn) crystallites embedded in an amorphous matrix, and that these crystallites increase in size with increasing zinc content and deposition temperature. These crystallites are small enough for quantum confinement effects to reduce the optical band gap of the ZTO films as they grow in size with increasing deposition temperature. - Highlights: • Zinc tin oxide thin films were deposited by atomic layer deposition. • The structure and optical properties were studied at different growth temperatures. • The growth temperature had only a small effect on the composition of the films. • Small ZnO or ZnO(Sn) crystallites were observed by TEM in zinc rich ZTO films. • The growth temperature affects the crystallite size, which influences the band gap

  5. Structure and properties of carbon black particles

    Science.gov (United States)

    Xu, Wei

    Structure and properties of carbon black particles were investigated using atomic force microscopy, gas adsorption, Raman spectroscopy, and X-ray diffraction. Supplementary information was obtained using TEM and neutron scattering. The AFM imaging of carbon black aggregates provided qualitative visual information on their morphology, complementary to that obtained by 3-D modeling based on TEM images. Our studies showed that carbon black aggregates were relatively flat. The surface of all untreated carbon black particles was found to be rough and its fractal dimension was 2.2. Heating reduced the roughness and fractal dimension for all samples heat treated at above 1300 K to 2.0. Once the samples were heat treated rapid cooling did not affect the surface roughness. However, rapid cooling reduced crystallite sizes, and different Raman spectra were obtained for carbon blacks of various history of heat treatment. By analyzing the Raman spectra we determined the crystallite sizes and identified amorphous carbon. The concentration of amorphous carbon depends on hydrogen content. Once hydrogen was liberated at increased temperature, the concentration of amorphous carbon was reduced and crystallites started to grow. Properties of carbon blacks at high pressure were also studied. Hydrostatic pressure did not affect the size of the crystallites in carbon black particles. The pressure induced shift in Raman frequency of the graphitic component was a result of increased intermolecular forces and not smaller crystallites. Two methods of determining the fractal dimension, the FHH model and the yardstick technique based on the BET theory were used in the literature. Our study proved that the FHH model is sensitive to numerous assumptions and leads to wrong conclusions. On the other hand the yardstick method gave correct results, which agreed with the AFM results.

  6. 3D equilibrium crystal shapes in the new light of STM and AFM

    International Nuclear Information System (INIS)

    Bonzel, H.P.

    2003-01-01

    A systematic study of 3D equilibrium crystal shapes (ECS) can yield important surface energetic quantities, such as step, kink, surface and step-step interaction free energies. Observations of the ECS, especially of flat facets and adjacent vicinal regions, will provide primarily relative step and surface free energies. An advanced goal is to determine absolute step free energies, kink formation and step interaction energies. Absolute values of these energies are important in governing crystal growth morphologies, high temperature phase changes and kinetic processes associated with shape changes. Furthermore, absolute step and kink energies are the key to absolute surface free energies of well defined low-index orientations. We review new experiments where sections of the ECS are monitored as a function of temperature to extract characteristic morphological parameters, yielding absolute surface energetic quantities. Attention will be paid to the question of attaining true 3D equilibrium of an ensemble of crystallites. The special role of scanning tunneling and atomic force microscopies will be stressed. New ways of overcoming the problem of the activation barrier for facet growth (or shrinkage) through the study of dislocated crystallites will be demonstrated. In the general context of 3D crystallites, the study of 2D nano-crystals, in the form of adatom or vacancy islands on extended flat surfaces, will be discussed. In particular, the connection between the temperature dependent shape of 2D islands and the absolute step and kink formation energies of the bounding steps, complementary to facet shape changes of 3D crystallites, has emerged as an important topic of recent research. Finally, high temperature phase changes, such as surface roughening and surface melting, as they have been observed by scanning electron microscopy on 3D crystallites, will be briefly reviewed

  7. Large bowel resection

    Science.gov (United States)

    ... blockage in the intestine due to scar tissue Colon cancer Diverticular disease (disease of the large bowel) Other reasons for bowel resection are: Familial polyposis (polyps are growths on the lining of the colon or rectum) Injuries that damage the large bowel ...

  8. Self-assembled infrared-luminescent Er-Si-O crystallites on silicon

    International Nuclear Information System (INIS)

    Isshiki, H.; Dood, M.J.A. de; Polman, A.; Kimura, T.

    2004-01-01

    Optically active and electrically excitable erbium complexes on silicon are made by wet-chemical synthesis. The single-crystalline Er-Si-O compound is formed by coating a Si(100) substrate with an ErCl 3 /ethanol solution, followed by rapid thermal oxidation and annealing. Room-temperature Er-related 1.53 μm photoluminescence is observed with a peak linewidth as small as 4 meV. The complexes can be excited directly into the Er intra-4f states, or indirectly, through photocarriers. Er concentrations as high as 14 at. % are achieved, incorporated in a crystalline lattice with a 0.9 nm periodicity. Thermal quenching at room temperature is only a factor 5, and the lifetime at 1.535 μm is 200 μs

  9. Large N Scalars

    DEFF Research Database (Denmark)

    Sannino, Francesco

    2016-01-01

    We construct effective Lagrangians, and corresponding counting schemes, valid to describe the dynamics of the lowest lying large N stable massive composite state emerging in strongly coupled theories. The large N counting rules can now be employed when computing quantum corrections via an effective...

  10. Influence of the molecular modifications on the properties of EPDM elastomers under irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Davenas, J. E-mail: joel.davenas@univ-lyon1.fr; Stevenson, I.; Celette, N.; Vigier, G.; David, L

    2003-08-01

    The degradation of the mechanical behaviour of EPDM elastomers used as cable insulation materials has been investigated by mechanical spectroscopy and tensile tests for different formulations: unvulcanised EPDM, vulcanised and stabilised elastomer with an antioxidant. In all cases, {gamma}-irradiation of EPDM under oxygen leads to a reduction of the molecular mobility indicated by the shift of the glass transition relaxation temperature towards higher temperatures. Moreover, the molecular flow occurring above T{sub g} is suppressed after irradiation for the unvulcanised EPDM providing evidence of cross-linking. The competition between cross-linking and chain scissions is shown by the decrease of the storage modulus above the crystallites melting temperature ({approx}40 deg. C) at doses larger than 100 kGy. A strong increase of the Young modulus and reduction of the elongation at break of the non-vulcanised EPDM becoming more brittle are shown by stress/strain characterisations performed at 80 deg. C. At the opposite vulcanised EPDM exhibits higher elongation at break after crystallites melting. This evolution is interpreted by the competition between cross-linking and chain scissions, being hindered by the crystallites at room temperature. The intrinsic irradiation effects can be isolated after crystallite melting. The reduction of the molecular mobility can be explained by a chemi-crystallisation process assisted by chain scissions, leading to a more rigid phase upon irradiation.

  11. Influence of the molecular modifications on the properties of EPDM elastomers under irradiation

    International Nuclear Information System (INIS)

    Davenas, J.; Stevenson, I.; Celette, N.; Vigier, G.; David, L.

    2003-01-01

    The degradation of the mechanical behaviour of EPDM elastomers used as cable insulation materials has been investigated by mechanical spectroscopy and tensile tests for different formulations: unvulcanised EPDM, vulcanised and stabilised elastomer with an antioxidant. In all cases, γ-irradiation of EPDM under oxygen leads to a reduction of the molecular mobility indicated by the shift of the glass transition relaxation temperature towards higher temperatures. Moreover, the molecular flow occurring above T g is suppressed after irradiation for the unvulcanised EPDM providing evidence of cross-linking. The competition between cross-linking and chain scissions is shown by the decrease of the storage modulus above the crystallites melting temperature (∼40 deg. C) at doses larger than 100 kGy. A strong increase of the Young modulus and reduction of the elongation at break of the non-vulcanised EPDM becoming more brittle are shown by stress/strain characterisations performed at 80 deg. C. At the opposite vulcanised EPDM exhibits higher elongation at break after crystallites melting. This evolution is interpreted by the competition between cross-linking and chain scissions, being hindered by the crystallites at room temperature. The intrinsic irradiation effects can be isolated after crystallite melting. The reduction of the molecular mobility can be explained by a chemi-crystallisation process assisted by chain scissions, leading to a more rigid phase upon irradiation

  12. Regulation of Dental Enamel Shape and Hardness

    Science.gov (United States)

    Simmer, J.P.; Papagerakis, P.; Smith, C.E.; Fisher, D.C.; Rountrey, A.N.; Zheng, L.; Hu, J.C.-C.

    2010-01-01

    Epithelial-mesenchymal interactions guide tooth development through its early stages and establish the morphology of the dentin surface upon which enamel will be deposited. Starting with the onset of amelogenesis beneath the future cusp tips, the shape of the enamel layer covering the crown is determined by five growth parameters: the (1) appositional growth rate, (2) duration of appositional growth (at the cusp tip), (3) ameloblast extension rate, (4) duration of ameloblast extension, and (5) spreading rate of appositional termination. Appositional growth occurs at a mineralization front along the ameloblast distal membrane in which amorphous calcium phosphate (ACP) ribbons form and lengthen. The ACP ribbons convert into hydroxyapatite crystallites as the ribbons elongate. Appositional growth involves a secretory cycle that is reflected in a series of incremental lines. A potentially important function of enamel proteins is to ensure alignment of successive mineral increments on the tips of enamel ribbons deposited in the previous cycle, causing the crystallites to lengthen with each cycle. Enamel hardens in a maturation process that involves mineral deposition onto the sides of existing crystallites until they interlock with adjacent crystallites. Neutralization of acidity generated by hydroxyapatite formation is a key part of the mechanism. Here we review the growth parameters that determine the shape of the enamel crown as well as the mechanisms of enamel appositional growth and maturation. PMID:20675598

  13. Adaptive Large Neighbourhood Search

    DEFF Research Database (Denmark)

    Røpke, Stefan

    Large neighborhood search is a metaheuristic that has gained popularity in recent years. The heuristic repeatedly moves from solution to solution by first partially destroying the solution and then repairing it. The best solution observed during this search is presented as the final solution....... This tutorial introduces the large neighborhood search metaheuristic and the variant adaptive large neighborhood search that dynamically tunes parameters of the heuristic while it is running. Both heuristics belong to a broader class of heuristics that are searching a solution space using very large...... neighborhoods. The tutorial also present applications of the adaptive large neighborhood search, mostly related to vehicle routing problems for which the heuristic has been extremely successful. We discuss how the heuristic can be parallelized and thereby take advantage of modern desktop computers...

  14. Moessbauer study in the glass system PbO. 2B/sub 2/O/sub 3/. Fe/sub 2/O/sub 3/

    Energy Technology Data Exchange (ETDEWEB)

    Sekhon, S S; Kamal, R [Punjabi Univ., Patiala (India). Dept. of Physics

    1978-05-01

    The Moessbauer technique has been employed to study the structure and crystallite formation in the glass system PbO.2B/sub 2/O/sub 3/ containing upto 30 wt% Fe/sub 2/O/sub 3/. Like alkali borate glasses, this glass system also exhibits a broadened quadrupole doublet and iron ions are present in Fe/sup 3 +/ state. Above about 20 wt%, the crystallites of magnetically ordered states have been identified. Susceptibility variation with concentration suggests the formation of a superparamagnetic state.

  15. Evolution of Structural and Optical Properties of ZnO Nanorods Grown on Vacuum Annealed Seed Crystallites

    Directory of Open Access Journals (Sweden)

    Waqar Khan

    2018-01-01

    Full Text Available In this study, the ambient condition for the as-coated seed layer (SL annealing at 350 °C is varied from air or nitrogen to vacuum to examine the evolution of structural and optical properties of ZnO nanorods (NRs. The NR crystals of high surface density (~240 rods/μm2 and aspect ratio (~20.3 show greatly enhanced (002 degree of orientation and crystalline quality, when grown on the SLs annealed in vacuum, compared to those annealed in air or nitrogen ambient. This is due to the vacuum-annealed SL crystals of a highly preferred orientation toward (002 and large grain sizes. X-ray photoelectron spectroscopy also reveals that the highest O/Zn atomic ratio of 0.89 is obtained in the case of vacuum-annealed SL crystals, which is due to the effective desorption of hydroxyl groups and other contaminants adsorbed on the surface formed during aqueous solution-based growth process. Near band edge emission (ultra violet range of 360–400 nm of the vacuum-annealed SLs is also enhanced by 44% and 33% as compared to those annealed in air and nitrogen ambient, respectively, in photoluminescence with significant suppression of visible light emission associated with deep level transition. Due to this improvement of SL optical crystalline quality, the NR crystals grown on the vacuum-annealed SLs produce ~3 times higher ultra violet emission intensity than the other samples. In summary, it is shown that the ZnO NRs preferentially grow along the wurtzite c-axis direction, thereby producing the high crystalline quality of nanostructures when they grow on the vacuum-annealed SLs of high crystalline quality with minimized impurities and excellent preferred orientation. The ZnO nanostructures of high crystalline quality achieved in this study can be utilized for a wide range of potential device applications such as laser diodes, light-emitting diodes, piezoelectric transducers and generators, gas sensors, and ultraviolet detectors.

  16. Large deviations

    CERN Document Server

    Deuschel, Jean-Dominique; Deuschel, Jean-Dominique

    2001-01-01

    This is the second printing of the book first published in 1988. The first four chapters of the volume are based on lectures given by Stroock at MIT in 1987. They form an introduction to the basic ideas of the theory of large deviations and make a suitable package on which to base a semester-length course for advanced graduate students with a strong background in analysis and some probability theory. A large selection of exercises presents important material and many applications. The last two chapters present various non-uniform results (Chapter 5) and outline the analytic approach that allow

  17. X-ray stress analysis in textured polycrystalline materials

    International Nuclear Information System (INIS)

    Yokoyama, Ryouichi; Harada, Jimpei

    2010-01-01

    The relationship between stress and strain in polycrystalline materials with fibre texture is examined on the basis of the strain analysis in the constituent crystallites within the Reuss approximation. By introducing the symmetry of reciprocal lattices for the constituent crystallites, the physical meaning of taking an average of the strains observed by X-ray diffraction (XRD) is made clear. By using formulae obtained by the present treatment for the stress-strain relation in cubic specimens with fibre texture in the Laue classes m3-bar m hkl Bragg reflections with h≠k≠l split into doublets owing to the existence of crystallites with two different orientations under the stress field. This technique was confirmed by the profile analysis in XRD data observed for reflections of 222 and 420 in a cubic TiN thin film sputtered on a polyimide film. The technique of the stress analysis and its confirmation are introduced. (author)

  18. Investigations of magnetoelectric behavior in BiFe0.95Co0.05O3 nanoparticles

    Science.gov (United States)

    Shrimali, V. G.; Gadani, Keval; Rathod, K. N.; Boricha, Hetal; Prajapati, Pooja; Keshvani, M. J.; Kataria, B. R.; Joshi, A. D.; Pandya, D. D.; Shah, N. A.; Solanki, P. S.

    2017-05-01

    Nanophasic BiFe0.95Co0.05O3 (BFCO) particles were synthesized using low cost, easy, simple, environment friendly and low temperature acetate precursor based modified sol-gel method. Influence of particle size and magnetic field on the structural, dielectric, impedance and a.c. conductivity of BFCO is investigated. X-ray diffraction (XRD) measurement has been performed to understand the structural modifications in the samples upon increasing the sintering temperature. Crystallite size (CS) increases from 33.62nm to 39.56nm due to agglomeration effect between the smaller crystallites. Effect of sintering temperature on the dielectric, impedance and conductivity has been studied and understood in the context of the creation of crystallite (particle) size and oxygen vacancies created due to high temperature sintering process. Magnetic field induced modifications in all these electrical properties [magnetoelectric (ME) effects] for the presently studied BFCO samples have been discussed on the basis of magnetostriction effect and charge mobility across the Fe-O lattice in the samples.

  19. Manipulating the Morphology of P3HT–PCBM Bulk Heterojunction Blends with Solvent Vapor Annealing

    KAUST Repository

    Verploegen, Eric; Miller, Chad E.; Schmidt, Kristin; Bao, Zhenan; Toney, Michael F.

    2012-01-01

    Using grazing incidence X-ray scattering, we observe the effects of solvent vapors upon the morphology of poly(3-hexylthiophene)-phenyl-C 61-butyric acid methyl ester (P3HT-PCBM) bulk heterojunction thin film blends in real time; allowing us to observe morphological rearrangements that occur during this process as a function of solvent. We detail the swelling of the P3HT crystallites upon the introduction of solvent and the resulting changes in the P3HT crystallite morphology. We also demonstrate the ability for tetrahydrofuran vapor to induce crystallinity in PCBM domains. Additionally, we measure the nanoscale phase segregated domain size as a function of solvent vapor annealing and correlate this to the changes observed in the crystallite morphology of each component. Finally, we discuss the implications of the morphological changes induced by solvent vapor annealing on the device properties of BHJ solar cells. © 2012 American Chemical Society.

  20. Surface oxidation in glassy arsenic trisulphide induced by high-energy γ-irradiation

    International Nuclear Information System (INIS)

    Shpotyuk, M.; Shpotyuk, O.; Serkiz, R.; Demchenko, P.; Kozhyukhin, S.

    2014-01-01

    Influence of high-energy γ-irradiation with ∼3 MGy dose on glassy g-As 2 S 3 was investigated by a complex of scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction methods. A white layer composed of separate 1–2 μm rhombohedral arsenolite As 2 O 3 crystallites was observed at the surface of γ-irradiated samples. These As 2 O 3 extractions along with crystallised S allotropes are responsible for expansion of the first sharp diffraction peaks in the XRD patterns of g-As 2 S 3 . - Highlights: • As 2 O 3 crystallites are observed at the surface of γ-irradiated As 2 S 3 samples. • Observed crystallites can be removed from the surface after washing and polishing. • γ-Irradiation broadens the FSDP due to satellite lines located on its both sides. • As 2 O 3 and S phases extracted at the surface are responsible for satellite lines

  1. Hydrothermal synthesis and magnetic properties of Mn doped ZnS nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Rashad, M M; Rayan, D A; El-Barawy, K [Central Metallurgical Research and Development Institute PO Box: 87 Helwan, Cairo (Egypt)

    2010-01-01

    Nanocrystallite Mn doped Zn{sub 1-X}S (X = 0 to 0.4) powders have been synthesized through a hydrothermal route. The effect of the hydrothermal temperature and Mn{sup 2+} ions substitution on the crystal structure, crystallite size, microstructure and magnetic properties were investigated using (XRD), (SEM) and (VSM). The results revealed that wurtzite zinc sulfide phase was formed using thiourea as a sulfur source at temperature 150- 200{sup o}C for 24 h. The crystallite size was (7.9-15.1 nm) was obtained at the same conditions. The doping of Mn{sup 2+} ions decreased the crystallite size of the formed ZnS wurtzite phase was in the range between 7.9 and 3.8 nm. SEM micrographs showed that the produced ZnS and Mn doped ZnS particles were appeared as spherical shape. The magnetic properties were improved by substitution of Mn{sup 2+} ions up to 0.2.

  2. Structural and microstructural characterization of U{sub 3}Si{sub 2} nuclear fuel using X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Ichikawa, Rodrigo U.; Garcia, Rafael H.L.; Silva, Andre S.B. da; Saliba-Silva, Adonis M.; Lima, Nelson B.; Martinez, Luis G. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Turrillas, Xavier, E-mail: ichikawa@usp.br, E-mail: rlgarcia@ipen.br, E-mail: andre.santos.silva@usp.br, E-mail: saliba@ipen.br, E-mail: nblima@ipen.br, E-mail: lgallego@ipen.br, E-mail: xturrillas@icmab.es [Institut de Ciència de Materials de Barcelona (ICMAB/CSIC), Cerdanyola de Vallès (Spain)

    2017-07-01

    In this work, two uranium silicide powdered samples, containing 67% and 42 mol% of Si, were analyzed using X-ray diffraction (named as {sup 67}Si and {sup 42}Si). For structural characterization, Rietveld refinement was used to estimate cell parameters, volume fraction (weight percent) of crystalline phases and atomic positions. For the main phases, X-ray line profile analysis (XLPA) was used to estimate mean crystallite sizes and micro strains. The {sup 67}Si sample presents higher content of USi{sub 2(}tetragonal) and the {sup 42}Si sample presents higher content of U{sub 3}Si{sub 2} (tetragonal) as identified and calculated from the XRD profiles. Overall there are no appreciable structural changes and the parameters refined are in good accordance with the ones reported in the literature. Mean crystallite sizes determined by XLPA revealed small crystallites of the order of 10{sup 1} nm and low micro strain for all samples. (author)

  3. Mechanochemically synthesized Al2O3-TiC nanocomposite

    International Nuclear Information System (INIS)

    Mohammad Sharifi, E.; Karimzadeh, F.; Enayati, M.H.

    2010-01-01

    Al 2 O 3 -TiC nanocomposite was synthesized by ball milling of aluminum, titanium oxide and graphite powder mixtures. Effect of the milling time and heat treatment temperatures were investigated. The structural evolution of powder particles after different milling times was studied by X-ray diffractometry and scanning electron microscopy. The results showed that after 40 h of ball milling the Al/TiO 2 /C reacted with a self-propagating combustion mode producing Al 2 O 3 -TiC nanocomposite. In final stage of milling, alumina and titanium carbide crystallite sizes were less than 10 nm. After annealing at 900 o C for 1 h, Al 2 O 3 and TiC crystallite sizes remained constant, however increasing annealing temperature to 1200 o C increased Al 2 O 3 and TiC crystallite size to 65 and 30 nm, respectively. No phase change was observed after annealing of the synthesized Al 2 O 3 -TiC powder.

  4. Manipulating the Morphology of P3HT–PCBM Bulk Heterojunction Blends with Solvent Vapor Annealing

    KAUST Repository

    Verploegen, Eric

    2012-10-23

    Using grazing incidence X-ray scattering, we observe the effects of solvent vapors upon the morphology of poly(3-hexylthiophene)-phenyl-C 61-butyric acid methyl ester (P3HT-PCBM) bulk heterojunction thin film blends in real time; allowing us to observe morphological rearrangements that occur during this process as a function of solvent. We detail the swelling of the P3HT crystallites upon the introduction of solvent and the resulting changes in the P3HT crystallite morphology. We also demonstrate the ability for tetrahydrofuran vapor to induce crystallinity in PCBM domains. Additionally, we measure the nanoscale phase segregated domain size as a function of solvent vapor annealing and correlate this to the changes observed in the crystallite morphology of each component. Finally, we discuss the implications of the morphological changes induced by solvent vapor annealing on the device properties of BHJ solar cells. © 2012 American Chemical Society.

  5. Nanocrystalline (Fe{sub 60}Al{sub 40}){sub 80}Cu{sub 20} alloy prepared by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Krifa, M.; Mhadhbi, M. [Laboratoire de Chimie Inorganique, 99/UR/12-22, FSS – Université de Sfax, B.P. 1171, Sfax 3018 (Tunisia); Escoda, L.; Güell, J.M. [Dept. de Fisica, Universitat de Girona, Campus Montilivi, 17071 Girona (Spain); Suñol, J.J., E-mail: joanjosep.sunyol@udg.edu [Dept. de Fisica, Universitat de Girona, Campus Montilivi, 17071 Girona (Spain); Llorca-Isern, N.; Artieda-Guzmán, C. [Dept. CMEM, Universitat de Barcelona, Martí Franques 1, 08028 Barcelona (Spain); Khitouni, M. [Laboratoire de Chimie Inorganique, 99/UR/12-22, FSS – Université de Sfax, B.P. 1171, Sfax 3018 (Tunisia)

    2013-03-25

    Highlights: ► Nanocrystalline Fe(Al, Cu) powdered alloy (10 nm) has been synthesized by MA. ► Decreasing the crystallite size increases coercivity and squareness ratio. ► As low crystallites size stronger hard ferromagnetic material results. -- Abstract: A nanostructured disordered Fe(Al, Cu) solid solution was obtained from prealloyed FeAl and elemental Cu powders using a high-energy ball mill. The transformations occurring in the material during milling were studied with the use of X-ray diffraction. The transformation of the phase depends upon the milling time. With the increase of milling time all Cu atoms became dissolved in the bcc Fe and the final product of the MA process was the nanocrystalline Fe(Al, Cu) solid solution with a mean crystallite size of 10 nm. Scanning electron microscopy (SEM) was employed to examine the morphology of the samples as a function of milling times. Magnetic properties were also investigated and were related to the microstructural changes. The system showed hard magnetic behavior.

  6. The clinical application of percutaneous large core needle biopsy on large breast mass

    International Nuclear Information System (INIS)

    Peng Songhong; Ma Jie; Wang Guohong; Sun Guoping; Fu Jianmin; Zhou Dongxian

    2005-01-01

    Objective: An evaluation of the clinical application of percutaneous large core needle biopsy on large breast mass. Methods: Mammography and percutaneous large core needle biopsy were performed in 31 cases of large breast mass. Results: Apart from 5 cases showing characteristic calcification of malignancy, the rest cases were lack of diagnostic manifestation. Needle biopsy and pathological examination identified breast canner in 11 cases, suppurative mastitis in 9 case, fibrocystic mammary disorder in 7 cases, tuberculosis in 1 case, and fibroadenoma in 3 cases. Fibrocystic mammary disease was initially identified by biopsy in a case, while the following pathological diagnosis was fibrocystic mammary disorder with cancinoma in sim. Specificity rate of' biopsy was 96.8% and no false positive was observed. Vagotonia occurred in one case during the biopsy and hematoma in another. Conclusion: Percutaneous large core needle biopsy is a less invasive, simple, safe and reliable methods in the diagnosis of the large breast mass. And it may be recommended as a complementary procedure for routine imaging modality or surgical resection. (authors)

  7. The influence of precipitation temperature on the properties of ceria–zirconia solid solution composites

    International Nuclear Information System (INIS)

    Cui, Yajuan; Fang, Ruimei; Shang, Hongyan; Shi, Zhonghua; Gong, Maochu; Chen, Yaoqiang

    2015-01-01

    Highlights: • The crystallite size of precipitate increases as the precipitation temperature rises. • The stack of large crystallite can form nanoparticles with big pore size. • Big pore sizes are advantageous to improve the thermal stability. • Phase segregation is restricted in CZ solid solution precipitated at 70 °C. • The reducibility and OSC of the solid solution precipitated at 70 °C are improved. - Abstract: The ceria–zirconia composites (CZ) with a Ce/Zr mass ratio of 1/1 were synthesized by a back-titration method, in which the influence of precipitation temperature on the properties of ceria–zirconia precipitates was investigated. The resulting precipitation and mixed oxides at different precipitation temperatures were then characterized by a range of techniques, including textural properties, X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), H 2 -temperature programmed reduction (H 2 -TPR) as well as oxygen storage capacity (OSC) measurement. The results revealed that ceria–zirconia composites were formed as solid solution and such structure is favored of thermostability and texture properties. In particular, the composite CZ-70 synthesized at 70 °C exhibited prominent thermostability with a surface area of 32 m 2 /g as well as a pore volume of 0.15 cc/g after aging treatment at 1000 °C for 5 h. And this was found to be associated with the wider pore size distribution which maybe owed to the formation of large crystal at the primary stage of precipitation. Additionally, the composite CZ-70 showed excellent reduction property and OSC benefiting from stable texture and structure

  8. Large-scale solar purchasing

    International Nuclear Information System (INIS)

    1999-01-01

    The principal objective of the project was to participate in the definition of a new IEA task concerning solar procurement (''the Task'') and to assess whether involvement in the task would be in the interest of the UK active solar heating industry. The project also aimed to assess the importance of large scale solar purchasing to UK active solar heating market development and to evaluate the level of interest in large scale solar purchasing amongst potential large scale purchasers (in particular housing associations and housing developers). A further aim of the project was to consider means of stimulating large scale active solar heating purchasing activity within the UK. (author)

  9. Large mass storage facility

    International Nuclear Information System (INIS)

    Peskin, A.M.

    1978-01-01

    The report of a committee to study the questions surrounding possible acquisition of a large mass-storage device is presented. The current computing environment at BNL and justification for an online large mass storage device are briefly discussed. Possible devices to meet the requirements of large mass storage are surveyed, including future devices. The future computing needs of BNL are prognosticated. 2 figures, 4 tables

  10. Electron-Beam Deposition of Superconducting Molybdenum Thin Films for the Development of Mo/Au TES X-Ray Microcalorimeter

    Science.gov (United States)

    Finkbeiner, Fred Michael; Adams, Joseph S.; Bandler, Simon R.; Betancour-Martinez, Gabriele L.; Brown, Ari David; Chang, Meng-Ping; Chervenak, James A.; Chiao, Meng P.; Datesman, Aaron; Eckart, Megan E.; hide

    2016-01-01

    We are exploring the properties of electron-beam evaporated molybdenum thin films on silicon nitride coated silicon wafers at substrate temperatures between room temperature and 650 C. The temperature dependence of film stress, transition temperature, and electrical properties are presented. X-ray diffraction measurements are performed to gain information on molybdenum crystallite size and growth. Results show the dominant influence of the crystallite size on the intrinsic properties of our films. Wafer-scale uniformity, wafer yield, and optimal thermal bias regime for TES fabrication are discussed.

  11. Environment friendly route of iron oxide nanoparticles from Zingiber officinale (ginger) root extract

    Science.gov (United States)

    Xin Hui, Yau; Yi Peng, Teoh; Wei Wen, Liu; Zhong Xian, Ooi; Peck Loo, Kiew

    2016-11-01

    Iron oxide nanoparticles were prepared from the reaction between the Zingiber officinale (ginger) root extracts and ferric chloride solution at 50°C for 2 h in mild stirring condition. The synthesized powder forms of nanoparticles were further characterized by using UV-Vis spectroscopy and X-ray Diffraction spectrometry. UV-Vis analysis shows the absorption peak of iron oxide nanoparticles is appeared at 370 nm. The calculation of crystallite size from the XRD showed that the average particle size of iron oxide nanoparticles was 68.43 nm. Therefore, this eco-friendly technique is low cost and large scale nanoparticles synthesis to fulfill the demand of various applications.

  12. Controlling morphology, mesoporosity, crystallinity, and photocatalytic activity of ordered mesoporous TiO{sub 2} films prepared at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Elgh, Björn; Yuan, Ning; Palmqvist, Anders E. C. [Applied Surface Chemistry, Department of Chemical and Biological Engineering, Chalmers University of Technology, SE 412 96 Göteborg (Sweden); Cho, Hae Sung; Terasaki, Osamu [Graduate School of EEWS (WCU), KAIST, Daejeon 305-701 (Korea, Republic of); Magerl, David; Philipp, Martine; Müller-Buschbaum, Peter [Lehrstuhl für Funktionelle Materialien, Physik-Department, Technische Universität München, 85748 Garching (Germany); Roth, Stephan V. [DESY, Notkestrasse 85, 22603 Hamburg (Germany); Yoon, Kyung Byung [Department of Chemistry, Sogang University, Seoul 121-742 (Korea, Republic of)

    2014-11-01

    Partly ordered mesoporous titania films with anatase crystallites incorporated into the pore walls were prepared at low temperature by spin-coating a microemulsion-based reaction solution. The effect of relative humidity employed during aging of the prepared films was studied using SEM, TEM, and grazing incidence small angle X-ray scattering to evaluate the mesoscopic order, porosity, and crystallinity of the films. The study shows unambiguously that crystal growth occurs mainly during storage of the films and proceeds at room temperature largely depending on relative humidity. Porosity, pore size, mesoscopic order, crystallinity, and photocatalytic activity of the films increased with relative humidity up to an optimum around 75%.

  13. Catalytic Graphitization for Preparation of Porous Carbon Material Derived from Bamboo Precursor and Performance as Electrode of Electrical Double-Layer Capacitor

    Science.gov (United States)

    Tsubota, Toshiki; Maguchi, Yuta; Kamimura, Sunao; Ohno, Teruhisa; Yasuoka, Takehiro; Nishida, Haruo

    2015-12-01

    The combination of addition of Fe (as a catalyst for graphitization) and CO2 activation (a kind of gaseous activation) was applied to prepare a porous carbon material from bamboo powder (a waste product of superheated steam treatment). Regardless of the heat treatment temperature, many macropores were successfully formed after the heating process by removal of Fe compounds. A turbostratic carbon structure was generated in the Fe-added sample heated at 850°C. It was confirmed that the added Fe acted as a template for pore formation. Moreover, it was confirmed that the added Fe acted as a catalyst for graphitization. The resulting electrochemical performance as the electrode of an electrical double-layer capacitor, as demonstrated by cyclic voltammetry, electrochemical impedance spectroscopy, and charge-discharge testing, could be explained based on the graphitization and activation effects. Addition of Fe could affect the electrical properties of carbon material derived from bamboo.

  14. Large deviations and idempotent probability

    CERN Document Server

    Puhalskii, Anatolii

    2001-01-01

    In the view of many probabilists, author Anatolii Puhalskii''s research results stand among the most significant achievements in the modern theory of large deviations. In fact, his work marked a turning point in the depth of our understanding of the connections between the large deviation principle (LDP) and well-known methods for establishing weak convergence results.Large Deviations and Idempotent Probability expounds upon the recent methodology of building large deviation theory along the lines of weak convergence theory. The author develops an idempotent (or maxitive) probability theory, introduces idempotent analogues of martingales (maxingales), Wiener and Poisson processes, and Ito differential equations, and studies their properties. The large deviation principle for stochastic processes is formulated as a certain type of convergence of stochastic processes to idempotent processes. The author calls this large deviation convergence.The approach to establishing large deviation convergence uses novel com...

  15. Health impacts of large dams

    International Nuclear Information System (INIS)

    Lerer, L.B.

    1999-01-01

    Large dams have been criticized because of their negative environmental and social impacts. Public health interest largely has focused on vector-borne diseases, such as schistosomiasis, associated with reservoirs and irrigation projects. Large dams also influence health through changes in water and food security, increases in communicable diseases, and the social disruption caused by construction and involuntary resettlement. Communities living in close proximity to large dams often do not benefit from water transfer and electricity generation revenues. A comprehensive health component is required in environmental and social impact assessments for large dam projects

  16. Neodymium cobalt oxide as a chemical sensor

    Science.gov (United States)

    Abdel-Latif, I. A.; Rahman, Mohammed M.; Khan, Sher Bahadar

    2018-03-01

    Chemical sensing and electrical transport properties of neodymium coblate, NdCoO3, was investigated in this work. It was prepared by using co-precipitation method. Pure neodymium chloride and cobalt chloride were mixing in the presence of sodium hydroxide and the obtained co-precipitated powder was calcined at 850 and 1000 °C. The synthesized composites, as-grown (NdCoO3-I), calcined at 850 °C (NdCoO3-II), and calcined at 1000 °C (NdCoO3-III) were studied in details in terms of their morphological and structural properties. The X-ray analysis confirmed that the synthesized products are well crystalline possessing single phase orthorhombic crystal system of space group Pbnm(62). The crystallite size of NdCoO3-I, NdCoO3-II, and NdCoO3-III is 22, 111, and 338 nm, respectively which reflect that crystallite size is increasing with increase in firing temperature. The DC resistivity was measured as a function of temperature in the temperature range from room temperature up to 200 °C. All NdCoO3 are semiconductor in this range of temperature but showed different activation energy which strongly depends on the crystallite size of the products. The activation energy decreased with increase in crystallite size, 0.798, 0.414 and 0.371 eV for NdCoO3-I, NdCoO3-II, and NdCoO3-III, respectively. Thus resistivity increases with increase in crystallite size of NdCoO3. All NdCoO3 products were tested as chemical sensor for acetone by electrochemical approaches and showed excellent sensitivity. Among the NdCoO3 samples, NdCoO3-III showed the highest sensitivity (3.4722 μAcm-2 mM-1) compared to other compositions and gradually decreased to 3.2407 μAcm-2 mM-1 with decreasing the crystallite size of NdCoO3-II. It is also observed that the sensitivity drastically decreased to 0.76253 μAcm-2 mM-1 in the case of NdCoO3-I. It is introduced an efficient route for the detection of environmental unsafe chemicals by electrochemical approach for the safety of healthcare and environmental

  17. Preparation of ZnO film on p-Si and I-V characteristics of p-Si/n-ZnO

    Directory of Open Access Journals (Sweden)

    Shampa Mondal

    2012-01-01

    Full Text Available Zinc oxide (ZnO thin films were deposited on p-silicon (Si substrate from ammonium zincate bath following a chemical dipping technique called SILAR. Films in the thickness range 0.5-4.5 µm could be prepared by varying the number of dipping for a fixed concentration (0.125 M of zincate bath and fixed pH (11.00-11.10. Higher values of dipping produced nonadherent and poor quality films. Structural characterization by X-ray diffraction (XRD indicates the formation of polycrystalline single phase ZnO with strong c-axis orientation. The structural characteristics of the films were found to be a sensitive function of film thickness. The degree of orientation was found to be a function of film thickness and a maximum was found at around 2.2 µm. Scanning electron microscopy (SEM reveals the formation of sub-micrometer crystallites on silicon substrate. The coverage of crystallites (grains on substrate surface increases with number of dipping. Dense film containing grains distributed throughout the surface is obtained at large thicknesses. The ohmic nature of silver (Ag on ZnO and Aluminum (Al on p-Si was confirmed by I-V measurements. I-V characteristic of the p-Si/n-ZnO heterojunction was studied and rectification was observed. The maximum value of forward to reverse current ratio was ~15 at 3.0 V.

  18. Preparation of ZnO film on p-Si and I-V characteristics of p-Si/n-ZnO

    Directory of Open Access Journals (Sweden)

    Shampa Mondal

    2013-02-01

    Full Text Available Zinc oxide (ZnO thin films were deposited on p-silicon (Si substrate from ammonium zincate bath following a chemical dipping technique called SILAR. Films in the thickness range 0.5-4.5 µm could be prepared by varying the number of dipping for a fixed concentration (0.125 M of zincate bath and fixed pH (11.00-11.10. Higher values of dipping produced nonadherent and poor quality films. Structural characterization by X-ray diffraction (XRD indicates the formation of polycrystalline single phase ZnO with strong c-axis orientation. The structural characteristics of the films were found to be a sensitive function of film thickness. The degree of orientation was found to be a function of film thickness and a maximum was found at around 2.2 µm. Scanning electron microscopy (SEM reveals the formation of sub-micrometer crystallites on silicon substrate. The coverage of crystallites (grains on substrate surface increases with number of dipping. Dense film containing grains distributed throughout the surface is obtained at large thicknesses. The ohmic nature of silver (Ag on ZnO and Aluminum (Al on p-Si was confirmed by I-V measurements. I-V characteristic of the p-Si/n-ZnO heterojunction was studied and rectification was observed. The maximum value of forward to reverse current ratio was ~15 at 3.0 V.

  19. Influence of the processing conditions on the structural properties of ZnO layers obtained by PECVD

    Energy Technology Data Exchange (ETDEWEB)

    Kitova, S; Danev, G, E-mail: skitova@clf.bas.b [Institute of Optical Materials and Technology ' Acad. J. Malinowski' , Bulgarian Academy of Sciences, Acad. G. Bonchev str., bl.109, 1113 Sofia (Bulgaria)

    2010-11-01

    The plasma enhanced chemical vapor deposition (PECVD) is a powerful and flexible instrument for depositing thin layers, nanocomposites or nanostructures. In this work ZnO layers have been grown by metal-organic PECVD (RF - 13.56 MHz) on Si wafers. Zn acetylacetonate has been used as a precursor and oxygen as oxidant. The influence of the oxygen content in gas mixture, the total pressure, substrate temperature and ZnO seed layer on the structural properties of the layers deposited on Si wafers has been studied. ZnO layer properties were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD data have shown that all layers are crystalline with hexagonal wurtzite structure. The crystallites are preferentially oriented along c-axis direction perpendicular to the substrate surfaces. The results obtained indicate that by controlling the oxygen content in gas mixture, the total pressure and substrate temperature during the film growth one can control the formation of c-axis phase and the crystallite grain size. Nanorods with good alignment, vertically orientated to the substrate surface can be observed in the layers deposited at low content of O{sub 2} in plasma at substrate temperature of 400 {sup o}C. Due to their structural characteristics these layers are potential materials for preparing chemical- and biosensors where inherently large surface to volume ratio of structured materials are important prerequisite for enhanced sensitivity.

  20. Structural, magnetic and dielectric investigations in antimony doped nano-phased nickel-zinc ferrites

    Energy Technology Data Exchange (ETDEWEB)

    Lakshmi, Ch.S. [Department of Physics, Regency Institute of Technology, Adivipolam Yanam 533464, Pondicherry (India); Sridhar, Ch.S.L.N. [Department of Physics, Vignana Bharathi Institute of Technology, Aushapur(v) Ghatkesar (M), Hyderabad 501301, Telangana (India); Govindraj, G. [Department of Physics, School of Physical, Chemical and Applied Sciences, Pondicherry University, R.V.Nagar, Kalapet, Pondicherry 605014 (India); Bangarraju, S. [Department of Physics, Andhra University, Visakhapatnam 530003, Andhrapradesh (India); Potukuchi, D.M., E-mail: potukuchidm@yahoo.com [Department of Physics, University College of Engineering, Jawaharlal Nehru Technological University:Kakinada, Kakinada 533003 (India)

    2015-02-15

    Nanocrystalline Ni–Zn–Sb ferrites synthesized by hydrothermal method are reported. Influence of Sb{sup 5+} ions on structural, magnetic and dielectric properties of ferrites is studied. Phase identification, lattice parameter and crystallite size studies are carried out using by X-ray diffraction (XRD). Addition of dopant resulted for decrease in lattice parameter. Crystallite size gets reduced from 62 nm to 38 nm with doping of Antimony. Crystallite size and porosity exhibit similar trends with doping. Morphological study is carried out by Field Emission Scanning Electron Microscopy (FESEM). Strong FTIR absorption bands at 400–600 cm{sup −1} confirm the formation of ferrite structure. Increase of porosity is attributed to the grain size. Doping with Antimony results for decrease in saturation magnetization and increase in coercivity. An initial increase of saturation magnetization for x=0.1 is attributed to the unusually high density. Reversed trend of coercivity with crystallite size are observed. Higher value of dielectric constant ε′(ω) is attributed to the formation of excess of Fe{sup 2+} ions caused by aliovalent doping of Sb{sup 5+} ions. Variation of dielectric constant infers hopping type of conductivity mechanism. The dielectric loss factor tanδ attains lower values of ∼10{sup −2}. High ac resistivity ρ(ω) of 10{sup 8} Ω cm is witnessed for antimony doped ferrites. Higher saturation magnetization and enhanced dielectric response directs for a possible utility as microwave oscillators and switches.

  1. Effect of synthesis conditions on the nanopowder properties of Ce{sub 0.9}Zr{sub 0.1}O{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Zimicz, M.G.; Fabregas, I.O.; Lamas, D.G. [CINSO (Centro de Investigaciones en Solidos) CONICET-CITEFA J.B. de La Salle 4397, 1603 Villa Martelli, Pcia. de Buenos Aires (Argentina); Larrondo, S.A., E-mail: susana@di.fcen.uba.ar [Laboratorio de Procesos Cataliticos, Departamento de Ingenieria Quimica, Facultad de Ingenieria, Universidad de Buenos Aires, Pabellon de Industrias, Ciudad Universitaria, 1428 Buenos Aires (Argentina)

    2011-06-15

    Graphical abstract: . The synthesis of nanocrystalline Ce{sub 0.9}Zr{sub 0.1}O{sub 2} powders via the gel-combustion method, using different fuels, and following either stoichiometric or non-stoichiometric pH-controlled routes is investigated. Research highlights: {yields} All samples exhibited the fluorite-type crystal structure, nanometric average crystallite size and negligible carbon content. {yields} Synthesis conditions strongly affect the average crystallite size, the degree of agglomeration, the specific surface area and the pore volume. {yields} Our results indicate that, by controlling the synthesis conditions it is possible to obtain solids with custom-made morphological properties. -- Abstract: In this work, the synthesis of nanocrystalline Ce{sub 0.9}Zr{sub 0.1}O{sub 2} powders via the gel-combustion method, using different fuels, and following either stoichiometric or non-stoichiometric pH-controlled routes is investigated. The objective is to evaluate the effect of synthesis conditions on the textural and morphological properties, and the crystal structure of the synthesized materials. The solids were characterized by nitrogen physisorption, Scanning Electron Microscopy (SEM), X-ray powder diffraction (XPD), and Carbon-Hydrogen-Nitrogen Elemental Analysis (CHN). All the powders exhibited nanometric crystallite size, fluorite-type structure and negligible carbon content. Synthesis conditions strongly affect the average crystallite size, the degree of agglomeration, the specific surface area and the pore volume. Our results indicate that, by controlling the synthesis conditions it is possible to obtain solids with custom-made morphological properties.

  2. Large-scale grid management

    International Nuclear Information System (INIS)

    Langdal, Bjoern Inge; Eggen, Arnt Ove

    2003-01-01

    The network companies in the Norwegian electricity industry now have to establish a large-scale network management, a concept essentially characterized by (1) broader focus (Broad Band, Multi Utility,...) and (2) bigger units with large networks and more customers. Research done by SINTEF Energy Research shows so far that the approaches within large-scale network management may be structured according to three main challenges: centralization, decentralization and out sourcing. The article is part of a planned series

  3. Large momentum transfer phenomena

    International Nuclear Information System (INIS)

    Imachi, Masahiro; Otsuki, Shoichiro; Matsuoka, Takeo; Sawada, Shoji.

    1978-01-01

    The large momentum transfer phenomena in hadron reaction drastically differ from small momentum transfer phenomena, and are described in this paper. Brief review on the features of the large transverse momentum transfer reactions is described in relation with two-body reactions, single particle productions, particle ratios, two jet structure, two particle correlations, jet production cross section, and the component of momentum perpendicular to the plane defined by the incident protons and the triggered pions and transverse momentum relative to jet axis. In case of two-body process, the exponent N of the power law of the differential cross section is a value between 10 to 11.5 in the large momentum transfer region. The breaks of the exponential behaviors into the power ones are observed at the large momentum transfer region. The break would enable to estimate the order of a critical length. The large momentum transfer phenomena strongly suggest an important role of constituents of hadrons in the hard region. Hard rearrangement of constituents from different initial hadrons induces large momentum transfer reactions. Several rules to count constituents in the hard region have been proposed so far to explain the power behavior. Scale invariant quark interaction and hard reactions are explained, and a summary of the possible types of hard subprocess is presented. (Kato, T.)

  4. Nanocomposites based on thermoplastic elastomers with functional basis of nano titanium dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Yulovskaya, V. D.; Kuz’micheva, G. M., E-mail: galina-kuzmicheva@list.ru [Federal State Budget Educational Institution of Higher Education “Moscow Technological University” (Russian Federation); Klechkovskaya, V. V. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Orekhov, A. S.; Zubavichus, Ya. V. [National Research Centre “Kurchatov Institute” (Russian Federation); Domoroshchina, E. N.; Shegay, A. V. [Federal State Budget Educational Institution of Higher Education “Moscow Technological University” (Russian Federation)

    2016-03-15

    Nanocomposites based on a thermoplastic elastomer (TPE) (low-density polyethylene (LDPE) and 1,2-polybutadiene in a ratio of 60/40) with functional titanium dioxide nanoparticles of different nature, TiO{sub 2}/TPE, have been prepared and investigated by a complex of methods (X-ray diffraction analysis using X-ray and synchrotron radiation beams, scanning electron microscopy, transmission electron microscopy, and X-ray energy-dispersive spectroscopy). The morphology of the composites is found to be somewhat different, depending on the TiO{sub 2} characteristics. It is revealed that nanocomposites with cellular or porous structures containing nano-TiO{sub 2} aggregates with a large specific surface and large sizes of crystallites and nanoparticles exhibit the best deformation‒strength and fatigue properties and stability to the effect of active media under conditions of ozone and vapor‒air aging.

  5. Fabrication of nano ZrO2 dispersed novel W79Ni10Ti5Nb5 alloy by mechanical alloying and pressureless sintering

    Science.gov (United States)

    Sahoo, R. R.; Patra, A.; Karak, S. K.

    2017-02-01

    A high energy planetary ball-mill was employed to synthesize tungsten (W) based alloy with nominal composition of W79Ni10Ti5Nb5(ZrO2)1 (in wt. %) for 20 h with chrome steel as grinding media, toluene as process control agent (PCA) along with compaction at 500 MPa pressure for 5 mins and sintering at 1500°C for 2 h using Ar atmosphere. X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS), elemental mapping and Transmission electron microscopy (TEM) was used to study the phase formation, microstructure of both milled powder and consolidated alloy. The crystallite size of W in W79Ni10Ti5Nb5(ZrO2)1 powder was 37 nm, 14.7 nm at 10 h and 20 h of milling respectively and lattice strain enhances to 0.54% at 20 h of milling. The crystallite size reduction is more at 10 h of milling and the rate drop beyond 10 to 20 h of milling. The intense improvement in dislocation density was evident upto 10 h of milling and the rate decreases between 10 to 20 h of milling. Increase in the lattice parameter of tungsten in W79Ni10Ti5Nb5(ZrO2)1 alloy upto 0.09% was observed at 10 h of milling owing to severe stress assisted deformation followed by contraction upto 0.07% at 20 h of milling due to formation of solid solution. The large spherical particles at 0 h of milling transformed to elongated shape at 10 h of milling and finer morphology at 20 h of milling. The average particle size reduced from 100 µm to 4.5 µm with the progress of milling from 0 to 20 h. Formation of fine polycrystallites of W was revealed by bright field TEM analysis and the observed crystallite size from TEM study was well supported by the evaluated crystallite size from XRD. XRD pattern and SEM micrograph of sintered alloy revealed the formation of NbNi, Ni3Ti intermetallic phases. Densification of 91.5% was attained in the 20 h milled and sintered alloy. Mechanical behaviour of the sintered product was evaluated by hardness and wear study. W79Ni10Ti5Nb5(ZrO2)1 alloy

  6. Large Pelagics Intercept Survey

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Large Pelagics Intercept Survey (LPIS) is a dockside survey of private and charterboat captains who have just completed fishing trips directed at large pelagic...

  7. Growth of apatite on chitosan-multiwall carbon nanotube composite membranes

    Energy Technology Data Exchange (ETDEWEB)

    Yang Jun; Yao Zhiwen [State Key Laboratory of Oral Diseases, West China College of Stomatology, Sichuan University, No 14, 3rd Section South People' s Road, Chengdu 610041 (China); Tang Changyu [Department of Polymer Science and Materials, Sichuan University (China); Darvell, B.W. [Dental Materials Science, Faculty of Dentistry, University of Hong Kong (Hong Kong); Zhang Hualin; Pan Lingzhan; Liu Jingsong [State Key Laboratory of Oral Diseases, West China College of Stomatology, Sichuan University, No 14, 3rd Section South People' s Road, Chengdu 610041 (China); Chen Zhiqing, E-mail: yangj0710@gmail.com [State Key Laboratory of Oral Diseases, West China College of Stomatology, Sichuan University, No 14, 3rd Section South People' s Road, Chengdu 610041 (China)

    2009-07-30

    Bioactive membranes for guided tissue regeneration would be of value for periodontal therapy. Chitosan-multiwall carbon nanotube (CS-MWNT) composites were treated to deposit nanoscopic apatite for MWNT proportions of 0-4 mass%. Fourier-transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray analysis, and X-ray diffraction were used for characterization. Apatite was formed on the CS-MWNT composites at low MWNT concentrations, but the dispersion of the MWNT affects the crystallite size and the Ca/P molar ratio of the composite. The smallest crystallite size was 9 nm at 1 mass% MWNT.

  8. Self-composite comprised of nanocrystalline diamond and a non-diamond component useful for thermoelectric applications

    Science.gov (United States)

    Gruen, Dieter M [Downers Grove, IL

    2009-08-11

    One provides nanocrystalline diamond material that comprises a plurality of substantially ordered diamond crystallites that are sized no larger than about 10 nanometers. One then disposes a non-diamond component within the nanocrystalline diamond material. By one approach this non-diamond component comprises an electrical conductor that is formed at the grain boundaries that separate the diamond crystallites from one another. The resultant nanowire is then able to exhibit a desired increase with respect to its ability to conduct electricity while also preserving the thermal conductivity behavior of the nanocrystalline diamond material.

  9. Shear induced orientation of edible fat and chocolate crystals

    Science.gov (United States)

    Mazzanti, Gianfranco; Welch, Sarah E.; Marangoni, Alejandro G.; Sirota, Eric B.; Idziak, Stefan H. J.

    2003-03-01

    Shear-induced orientation of fat crystallites was observed during crystallization of cocoa butter, milk fat, stripped milk fat and palm oil. This universal effect was observed in systems crystallized under high shear. The minor polar components naturally present in milk fat were found to decrease the shear-induced orientation effect in this system. The competition between Brownian and shear forces, described by the Peclet number, determines the crystallite orientation. The critical radius size, from the Gibbs-Thomson equation, provides a tool to understand the effect of shear at the onset stages of crystallization.

  10. Three-dimensional reciprocal space profile of an individual nanocrystallite inside a thin-film solar cell absorber layer

    International Nuclear Information System (INIS)

    Slobodskyy, Taras; Schroth, Philip; Minkevich, Andrey; Grigoriev, Daniil; Fohtung, Edwin; Riotte, Markus; Baumbach, Tilo; Powalla, Michael; Lemmer, Uli; Slobodskyy, Anatoliy

    2013-01-01

    The strain profile of an individual Cu(In,Ga)Se 2 nanocrystallite in a solar cell absorber layer is accessed using synchrotron radiation. We find that the investigated crystallite is inhomogeneously strained. The strain is most likely produced by a combination of intergranular strain and composition variations in nanocrystals inside the polycrystalline semiconductor film and carries information about the intercrystalline interaction. The measurements are made nondestructively and without additional sample preparation or x-ray beam nanofocusing. This is the first step towards measurements of strain profiles of individual crystallites inside a working solar cell. (paper)

  11. Hysteresis properties of local region of morphous-crystalline alloy. Gisterezisnye svojstva lokal'nogo uchastka amorfnokristallicheskogo splava

    Energy Technology Data Exchange (ETDEWEB)

    Kryukov, I I [Irkutskij Pedagogicheskij Inst., Irkutsk (Russian Federation)

    1991-09-01

    Fields of H{sub 3} domain boundary pinning on an amorphous interlayer d thick, separating neighbouring crystallites, the axes of light magnetization (ALM) of which are disoriented, were calculated by numerical methods for amorpthous-crystalline alloy (ACA). At d=0 and d={infinity} analytical expressions were obtained for H{sub p}. It is shown that ALM dispersion of the crystallites to a considerable extent determines hysteresis properties of ACA and can be responsible for bends on magnetization and remagnetization curves, dependence of hysteresis properties of magnetizing field amplitude and the sample prehistory.

  12. Transmission electron-microscopic studies of structural changes in polycrystalline graphite after high temperature irradiation

    International Nuclear Information System (INIS)

    Platonov, P.A.; Gurovich, B.A.; Shtrombakh, Ya.I.; Karpukhin, V.I.

    1985-01-01

    Transmission electron-microscopic investigation of polycrystalline graphite before and after irradiation is carried out. The direct use of graphite samples after ion thinning, as an inquiry subject is the basic peculiarity of the work. Main structural components of MPG-6 graphite before and after irradiation are revealed, the structural mechanism of the reactor graphite destruction under irradiation is demonstrated. The mean values of L αm and L cm crystallite dimensions are determined. Radiation defects, occuring in some crystallites after irradiation are revealed by the dark-field electron microscopy method

  13. Plan for support of large-plant (post-CRBR) needs in large-leak sodium-water reaction area

    International Nuclear Information System (INIS)

    Whipple, J.C.

    1980-03-01

    Work in the large leak test and analysis area of steam generator development has been carried out at GE-ARSD under 189a SG037 since 1973. The currently planned master schedule for the SG037 program is shown. Principal activities are the large leak testing program being carried out at the Large Leak Test Rig and the analysis methods development. The plan for supporting the large plant (post-CRBR) needs in the large leak sodium-water reaction area is outlined. Most of the needs will be answered in the current SG037 large leak program

  14. Large field radiotherapy

    International Nuclear Information System (INIS)

    Vanasek, J.; Chvojka, Z.; Zouhar, M.

    1984-01-01

    Calculations may prove that irradiation procedures, commonly used in radiotherapy and represented by large-capacity irradiation techniques, do not exceed certain limits of integral doses with favourable radiobiological action on the organism. On the other hand integral doses in supralethal whole-body irradiation, used in the therapy of acute leukemia, represent radiobiological values which without extreme and exceptional further interventions and teamwork are not compatible with life, and the radiotherapeutist cannot use such high doses without the backing of a large team. (author)

  15. Primary cutaneous anaplastic large cell lymphoma masquerading as large pyogenic granuloma

    Directory of Open Access Journals (Sweden)

    Anupama Bains

    2016-01-01

    Full Text Available Primary cutaneous anaplastic large cell lymphoma (pcALCL forms 9% of the cutaneous T-cell lymphomas. It usually presents as solitary reddish brown ulcerating nodule or indurated plaque. Sometimes, it mimics other dermatological diseases such as eczema, pyoderma gangrenosum, pyogenic granuloma, morphea, and squamous cell carcinoma. Our case presented with large pyogenic granuloma like lesion with regional lymphadenopathy. Since pcALCL is rare, one can misdiagnose such cases and therefore high index of suspicion is necessary.

  16. ERP inside Large Organizations

    Directory of Open Access Journals (Sweden)

    Constantin Daniel AVRAM

    2010-01-01

    Full Text Available Many large companies in Romania are still functioning without an ERP system. Instead they are using traditional application systems built around the strong boundaries of specific functions: finance, selling, HR, production. An ERP will offer lots of advantages among which the integration of functionalities and support for top management decisions. Although the total cost of ownership is not small and there are some risks when implementing an ERP inside large and very large organizations, having such a system is mandatory. Choosing the right product and vendor and using a correct risk management strategy, will ensure a successful implementation.

  17. Characterization of titanium silicide thin films by X-ray diffraction techniques

    International Nuclear Information System (INIS)

    Morimoto, N.J.

    1987-01-01

    This thesis deals with characterization techniques of thin films by means of X-ray diffraction. This includes phase identification and residual stress, microstress and crystallite size calculations. The techniques developed were applied on the study of the titanium silicide formation obtained by means of Rapidy Thermal Processing (RTP) pf Ti films deposited on silicon substratum. The different phases were studied in relation with processing temperature and time in one and two anneling steps. The low resistivity TiSi 2 phase was observed for temperature of 700 0 C and higher. The experimental results indicate that the residual stress of TiSi 2 films doesn't vary significantly with the annealing conditions. On the other hand, the microstress is reduced with annealing time at 800 0 C, while the crystallite size is almost not affected. For the microstress and the crystallite size determination technique, two methods were implemented and compared. The Riella's method appeared to be very efficient, while the Gangulle's method seemed to be inadequate, because the results oscillate too much [pt

  18. Structural changes of polytetrafluoroethylene during irradiation in oxygen

    International Nuclear Information System (INIS)

    Liu, Shuling; Fu, Congli; Gu, Aiqun; Yu, Zili

    2015-01-01

    To study the effect of irradiation on PTFE structure and prepare modified PTFE micropowder, PTFE was irradiated with dose up to 4 MGy in oxygen at room temperature. The structures of both irradiated and unirradiated PTFE samples were comparatively characterized by IR, XPS, Raman spectra and XRD measurement. The results showed that new groups of acyl fluoride (COF), carboxylic acid (COOH) and trifluoromethyl (CF 3 ) were formed under heavy radiation exposure in oxygen. In addition, the expansion of crystallite size or crystal lattice was first reported for the irradiated PTFE. The formation of new chemical groups and the expansion of crystallite size were elucidated by structural changes occurring in irradiation. - Highlights: • The structural change of PTFE irradiated in O 2 is different from that in vacuum. • The double bond is not found in PTFE after irradiation in oxygen. • The new groups like COF, COOH and CF 3 are formed in PTFE after irradiation. • The expansion of crystallite size is observed in the irradiated PTFE

  19. Characterization of BaBi2Ta2O9 prepared through amorphous precursor

    International Nuclear Information System (INIS)

    Maczka, M.; Kepinski, L.; Hermanowicz, K.; Dacko, S.; Czapla, Z.; Hanuza, J.

    2011-01-01

    Research highlights: → Formation of Bi-layered BaBi 2 Ta 2 O 9 proceeds via an intermediate fluorite phase. → Mechanochemical activation lowers the synthesis temperature by 150-200 deg. C. → The lateral size of the synthesized plate-like crystallites is about 100-200 nm. → Properties of the synthesized crystallites are different from the bulk material. - Abstract: Formation of ferroelectric BaBi 2 Ta 2 O 9 by annealing of an amorphous precursor prepared by high energy milling in ball mill has been studied by X-ray, scanning electron microscopy (SEM), Raman, infrared spectroscopy (IR), diffuse reflectivity and dielectric measurements. Our results show that formation of Bi-layered BaBi 2 Ta 2 O 9 proceeds via an intermediate fluorite phase. Mechanochemical activation allows obtaining BaBi 2 Ta 2 O 9 at short time and much lower temperatures than those required in a conventional solid state reaction. The lateral size of the plate-like crystallites is about 100-200 nm and properties of the synthesized particles are different compared to the bulk material.

  20. Atomic-scale structure of irradiated GaN compared to amorphised GaP and GaAs

    International Nuclear Information System (INIS)

    Ridgway, M.C.; Everett, S.E.; Glover, C.J.; Kluth, S.M.; Kluth, P.; Johannessen, B.; Hussain, Z.S.; Llewellyn, D.J.; Foran, G.J.; Azevedo, G. de M.

    2006-01-01

    We have compared the atomic-scale structure of ion irradiated GaN to that of amorphised GaP and GaAs. While continuous and homogenous amorphised layers were easily achieved in GaP and GaAs, ion irradiation of GaN yielded both structural and chemical inhomogeneities. Transmission electron microscopy revealed GaN crystallites and N 2 bubbles were interspersed within an amorphous GaN matrix. The crystallite orientation was random relative to the unirradiated epitaxial structure, suggesting their formation was irradiation-induced, while the crystallite fraction was approximately constant for all ion fluences beyond the amorphisation threshold, consistent with a balance between amorphisation and recrystallisation processes. Extended X-ray absorption fine structure measurements at the Ga K-edge showed short-range order was retained in the amorphous phase for all three binary compounds. For ion irradiated GaN, the stoichiometric imbalance due to N 2 bubble formation was not accommodated by Ga-Ga bonding in the amorphous phase or precipitation of metallic Ga but instead by a greater reduction in Ga coordination number

  1. Analyzing the scale of the bainitic ferrite plates by XRD, SEM and TEM

    International Nuclear Information System (INIS)

    Garcia-Mateo, Carlos; Jimenez, Jose A.; Lopez-Ezquerra, Belen; Rementeria, Rosalia; Morales-Rivas, Lucia; Kuntz, Matthias; Caballero, Francisca G.

    2016-01-01

    Since the major strengthening mechanisms in nanocrystalline bainitic steels arise from the exceptionally small size of the bainitc ferrite plate, accurate determination of this parameter is fundamental for quantitative relating the microstructure to the mechanical properties. In this work, the thickness of the bainitic ferrite subunits obtained by different bainitic heat treatments was determined in two steels, with carbon contents of 0.3 and 0.7 wt.%, from SEM and TEM micrographs. As these measurements were made on 2D images taken from random sections, the method includes some stereological correction factors to obtain accurate information. Finally, the determined thicknesses of bainitic ferrite plates were compared with the crystallite size calculated from the analysis of X-ray diffraction peak broadening. Although in some case the values obtained for crystallite size and plate thickness can be similar, this study confirms that indeed they are two different parameters. - Highlights: •Bainitic microstructure in a nanostructured and sub-micron steel •Bainitic ferrite plate thickness measured by SEM and TEM •Crystallite size determined by X-ray analysis

  2. Analyzing the scale of the bainitic ferrite plates by XRD, SEM and TEM

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Mateo, Carlos, E-mail: cgm@cenim.csic.es [Department of Physical Metallurgy, Spanish National Center for Metallurgical Research (CENIM-CSIC), Avda. Gregorio del Amo 8, E-28040 Madrid (Spain); Jimenez, Jose A.; Lopez-Ezquerra, Belen; Rementeria, Rosalia; Morales-Rivas, Lucia [Department of Physical Metallurgy, Spanish National Center for Metallurgical Research (CENIM-CSIC), Avda. Gregorio del Amo 8, E-28040 Madrid (Spain); Kuntz, Matthias [Robert-Bosch GmbH, Materials and Process Engineering Metals, Renningen, 70465 Stuttgart (Germany); Caballero, Francisca G. [Department of Physical Metallurgy, Spanish National Center for Metallurgical Research (CENIM-CSIC), Avda. Gregorio del Amo 8, E-28040 Madrid (Spain)

    2016-12-15

    Since the major strengthening mechanisms in nanocrystalline bainitic steels arise from the exceptionally small size of the bainitc ferrite plate, accurate determination of this parameter is fundamental for quantitative relating the microstructure to the mechanical properties. In this work, the thickness of the bainitic ferrite subunits obtained by different bainitic heat treatments was determined in two steels, with carbon contents of 0.3 and 0.7 wt.%, from SEM and TEM micrographs. As these measurements were made on 2D images taken from random sections, the method includes some stereological correction factors to obtain accurate information. Finally, the determined thicknesses of bainitic ferrite plates were compared with the crystallite size calculated from the analysis of X-ray diffraction peak broadening. Although in some case the values obtained for crystallite size and plate thickness can be similar, this study confirms that indeed they are two different parameters. - Highlights: •Bainitic microstructure in a nanostructured and sub-micron steel •Bainitic ferrite plate thickness measured by SEM and TEM •Crystallite size determined by X-ray analysis.

  3. Effects of solution concentration and capping agents on the properties of potassium titanyl phosphate noparticles synthesized using a co-precipitation method

    Science.gov (United States)

    Gharibshahian, E.; Jafar Tafershi, M.; Fazli, M.

    2018-05-01

    In this study, KTiOPO4 (KTP) nanoparticles were synthesized using a co-precipitation method. The effects of the solution concentration (M) and capping agents, such as PVA, oxalic acid, glycine, triethanolamine, and L-alanine, on the structural, microstructural, and optical properties of the products were investigated using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy. Decreasing the solution concentration decreased the crystallite size from 53.07 nm (for M = 2) to 39.42 nm (for M = 0.5). After applying different capping agents to the sample at the optimum concentration (M = 0.5), the crystallite size decreased again and grains as small as 10.61 nm were obtained. XRD and FTIR analyses indicated the formation of KTP nanoparticles with an orthorhombic structure in all of the samples. The optical band gap increased as the crystallite size decreased. Different morphological patterns such as spherical, needle shaped, polyhedron, and tablet forms were observed in the nanoparticles, which were correlated with the effects of the capping agents employed.

  4. Crystallization of sheared hard spheres at 64.5% volume fraction

    Science.gov (United States)

    Swinney, H. L.; Rietz, F.; Schroeter, M.; Radin, C.

    2017-11-01

    A classic experiment by G.D. Scott Nature 188, 908, 1960) showed that pouring balls into a rigid container filled the volume to an upper limit of 64% of the container volume, which is well below the 74% volume fraction filled by spheres in a hexagonal close packed (HCP) or face center cubic (FCC) lattice. Subsequent experiments have confirmed a ``random closed packed'' (RCP) fraction of about 64%. However, the physics of the RCP limit has remained a mystery. Our experiment on a cubical box filled with 49400 weakly sheared glass spheres reveals a first order phase transition from a disordered to an ordered state at a volume fraction of 64.5%. The ordered state consists of crystallites of mixed FCC and HCP symmetry that coexist with the amorphous bulk. The transition is initiated by homogeneous nucleation: in the shearing process small crystallites with about ten or fewer spheres dissolve, while larger crystallites grow. A movie illustrates the crystallization process. German Academic Exchange Service (DAAD), German Research Foundation (DFG), NSF DMS, and R.A. Welch Foundation.

  5. Understanding the phase separation evolution in efficient P3HT:IC70BA-based bulk-heterojunction polymer solar cells

    International Nuclear Information System (INIS)

    Fan Xi; Guo Shishang; Fang Guojia; Li Songzhan

    2013-01-01

    The effects of solvent and thermal annealing on the morphology of the active layers and the photovoltaic performance of bulk-heterojunction (BHJ) polymer solar cells (PSCs) are investigated systematically, for PSCs based on a blend of poly(3-hexylthiophene) (P3HT) as a donor and indene-C 70 bisadduct (IC 70 BA) as an acceptor. IC 70 BA crystallites are found reasonably well dispersed in the P3HT matrix after spin-coating. However, the IC 70 BA crystallites coarsen in size after annealing, which are clearly evidenced by transmission electron microscopy. Simultaneously, space charge limited current measurements demonstrate that solvent and thermal annealing can improve the hole and electron mobility, which reduces charge-carrier recombination and improves charge-carrier transport in the P3HT and IC 70 BA blend layers. The corresponding current-voltage curves are measured in quantity and we propose a model to show the variation of the ordered structure of P3HT domains and IC 70 BA crystallite characteristics in the phase separation process, expressing a viewpoint on the high performance of BHJ PSCs.

  6. Influence of solution deposition rate on properties of V{sub 2}O{sub 5} thin films deposited by spray pyrolysis technique

    Energy Technology Data Exchange (ETDEWEB)

    Abd–Alghafour, N. M., E-mail: na2013bil@gmail.com [Iraqi Ministry of Education, Anbar (Iraq); Ahmed, Naser M.; Hassan, Zai; Mohammad, Sabah M. [Nano-Optoelectronics Research and Technology Laboratory, School of Physics, University Sains Malaysia,11800 Penang (Malaysia)

    2016-07-19

    Vanadium oxide (V{sub 2}O{sub 5}) thin films were deposited on glass substrates by using a cost-efficient spray pyrolysis technique. The films were grown at 350° through thermal decomposition of VCl{sub 3} in deionized water with different solution spray rates. The high resolution X-ray diffraction results revealed the formation of nanocrystalline films having orthorhombic structures with preferential orientation along (101) direction. The spray rate influenced the surface morphology and crystallite size of the films. The crystallite size was found to increase whereas the micro-strain was decreased by increasing the spray deposition rates. The increase in crystallite size and decrease in the macrostrain resulted in an improvement in the films’ crystallinity. The UV-Visible spectroscopy analysis indicated that the average transmittance of all films lies in the range 75-80 %. The band gap of V{sub 2}O{sub 5} film was decreased from 2.65 to 2.46 eV with increase of the spray deposition rate from 5 ml/min to 10 ml/min. first, second, and third level headings (first level heading).

  7. Influence of solution deposition rate on properties of V_2O_5 thin films deposited by spray pyrolysis technique

    International Nuclear Information System (INIS)

    Abd–Alghafour, N. M.; Ahmed, Naser M.; Hassan, Zai; Mohammad, Sabah M.

    2016-01-01

    Vanadium oxide (V_2O_5) thin films were deposited on glass substrates by using a cost-efficient spray pyrolysis technique. The films were grown at 350° through thermal decomposition of VCl_3 in deionized water with different solution spray rates. The high resolution X-ray diffraction results revealed the formation of nanocrystalline films having orthorhombic structures with preferential orientation along (101) direction. The spray rate influenced the surface morphology and crystallite size of the films. The crystallite size was found to increase whereas the micro-strain was decreased by increasing the spray deposition rates. The increase in crystallite size and decrease in the macrostrain resulted in an improvement in the films’ crystallinity. The UV-Visible spectroscopy analysis indicated that the average transmittance of all films lies in the range 75-80 %. The band gap of V_2O_5 film was decreased from 2.65 to 2.46 eV with increase of the spray deposition rate from 5 ml/min to 10 ml/min. first, second, and third level headings (first level heading).

  8. PbSe nanocubes obtained by high-energy milling

    Energy Technology Data Exchange (ETDEWEB)

    Rojas-Chavez, H., E-mail: hrojasc@ipn.mx [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada - IPN (Mexico); Reyes-Carmona, F. [Facultad de Quimica - UNAM (Mexico); Achimovicova, M. [Slovak Academy of Sciences, Institute of Geotechnics (Slovakia); Daneu, N. [Jozef Stefan Institute, Department for Nanostructured Materials (Slovenia); Jaramillo-Vigueras, D. [Centro de Investigacion e Innovacion Tecnologica - IPN (Mexico)

    2012-06-15

    In this study, PbSe nanocubes were obtained by high-energy milling, and their optical properties were investigated by measuring the UV-VIS-IR spectra in the range of 200-2,000 nm. The optical absorption of all samples showed a strong UV emission band at 1.45 eV. Previously, to obtain only PbSe nanocubes, an intermediate phase was identified, PbSeO{sub 3}. Although both PbSeO{sub 3} and PbSe were traced through this study, a major effort is devoted to characterize the latter. To trace how chemical transitions evolve from precursors to PbSe, X-ray diffraction and Rietveld refinement were carried out. Therefore, the following parameters were evaluated as a function of milling time: phase percentages, area-to-volume ratio, average crystallite dimensions, specific surface area, and morphology changes. To corroborate previous findings, nitrogen adsorption and transmission electron microscopy techniques were used. All the set experimental results unambiguously confirm that crystallites show a cubic morphology, with its average crystallite size distribution being around 24 nm.

  9. Electromagnetic surface waves for large-area RF plasma productions between large-area planar electrodes

    International Nuclear Information System (INIS)

    Nonaka, S.

    1992-01-01

    Recently, large-area plasma production has been tested by means of a 13.56 MHz radio-frequency (RF) discharge between a pair of large-area planar electrodes, approximately 0.5 m x 1.4 m, as one of the semiconductor technologies for fabrication of large-area amorphous silicon solar cells in the ''Sunshine Project'' of the Agency of Industrial Science and Technology in Japan. We also confirmed long plasma production between a pair of long electrodes. In this paper, normal electromagnetic (EM) waves propagating in a region between a planar waveguide with one plasma and two dielectric layers are analyzed in order to study the feasibility of large-area plasma productions by EM wave-discharges between a pair of large-area RF electrodes larger than the half-wavelength of RF wave. In conclusion, plasmas higher than an electron plasma frequency will be produced by an odd TMoo surface mode. (author) 4 refs., 3 figs

  10. Direct observation of nanometer-scale amorphous layers and oxide crystallites at grain boundaries in polycrystalline Sr1−xKxFe2As2 superconductors

    KAUST Repository

    Wang, Lei; Ma, Yanwei; Wang, Qingxiao; Li, Kun; Zhang, Xixiang; Qi, Yanpeng; Gao, Zhaoshun; Zhang, Xianping; Wang, Dongliang; Yao, Chao; Wang, Chunlei

    2011-01-01

    We report here an atomic resolution study of the structure and composition of the grain boundaries in polycrystallineSr0.6K0.4Fe2As2superconductor. A large fraction of grain boundaries contain amorphous layers larger than the coherence length, while

  11. Quenches in large superconducting magnets

    International Nuclear Information System (INIS)

    Eberhard, P.H.; Alston-Garnjost, M.; Green, M.A.; Lecomte, P.; Smits, R.G.; Taylor, J.D.; Vuillemin, V.

    1977-08-01

    The development of large high current density superconducting magnets requires an understanding of the quench process by which the magnet goes normal. A theory which describes the quench process in large superconducting magnets is presented and compared with experimental measurements. The use of a quench theory to improve the design of large high current density superconducting magnets is discussed

  12. The diagenesis-metamorphism limit in pelitic rocks: an X-ray diffraction and decomposition study of illite and interstratified illite/smectite minerals

    International Nuclear Information System (INIS)

    Gharrabi, M.

    1995-01-01

    The definition of the limit between diagenesis and metamorphism has long been debated. Various approaches have been used to describe this limit including mineral reaction such as the appearance of pyrophyllite, illite crystallinity and rock textures (i.e. the development of schistosity). The aim of this study is to characterize the illite clays transformation during this transition. Study of the (001) and (003) XRD peaks of illite and illite-rich interstratified illite/smectite (I/S) by decomposition of XRD spectra allows to define the transformation that affect these minerals in the transition from extensive diagenesis to low grade metamorphism. We studied Paleozoic pelites from the Illinois Basin (USA), Cornwall (UK), Brittany (France) and the Anti-Atlas mountains and the Eastern-Haou/Basin (Morocco) that have undergone this transition. Illite clays pass through three evolutionary stages during the transition from diagenesis to metamorphism: advanced diagenesis where the population of illite particles is composed of the following phases: interstratified illite/smectite (I/S), small illite crystallites (PCI) and large illite crystallites (WCI). The composition of I/S particles that contain approximately 95 % illite layers changes very little at low temperatures even over long periods of time. The most important change during this stage is the reduction in the amount of this phase. These I/S particles (<5% smectite layers) dissolve and furnish the chemical constituents necessary for the growth of PCI and WCI before they are transformed into 100 % illite. Particles of PCI also contain smectite interlayers in their structure. These smectite interlayers may be considered as a characteristic of diagenetic conditions. The second stage, corresponding to anchizone metamorphism is characterized by the disappearance of I/S. The disappearance is caused by higher thermal regime. In the last stage corresponding to epizone metamorphism there exists only one population of illite

  13. Large-scale data analytics

    CERN Document Server

    Gkoulalas-Divanis, Aris

    2014-01-01

    Provides cutting-edge research in large-scale data analytics from diverse scientific areas Surveys varied subject areas and reports on individual results of research in the field Shares many tips and insights into large-scale data analytics from authors and editors with long-term experience and specialization in the field

  14. Effects of crystallite size on the structure and magnetism of ferrihydrite

    NARCIS (Netherlands)

    Wang, Xiaoming; Zhu, Mengqiang; Koopal, L.K.; Li, Wei; Xu, Wenqian; Liu, Fan; Zhang, Jing; Liu, Qingsong; Feng, Xionghan; Sparks, D.L.

    2016-01-01

    The structure and magnetic properties of nano-sized (1.6 to 4.4 nm) ferrihydrite samples are systematically investigated through a combination of X-ray diffraction (XRD), X-ray pair distribution function (PDF), X-ray absorption spectroscopy (XAS) and magnetic analyses. The XRD, PDF and Fe K-edge

  15. Helium ion microscopy of enamel crystallites and extracellular tooth enamel matrix.

    Science.gov (United States)

    Bidlack, Felicitas B; Huynh, Chuong; Marshman, Jeffrey; Goetze, Bernhard

    2014-01-01

    An unresolved problem in tooth enamel studies has been to analyze simultaneously and with sufficient spatial resolution both mineral and organic phases in their three dimensional (3D) organization in a given specimen. This study aims to address this need using high-resolution imaging to analyze the 3D structural organization of the enamel matrix, especially amelogenin, in relation to forming enamel crystals. Chemically fixed hemi-mandibles from wild type mice were embedded in LR White acrylic resin, polished and briefly etched to expose the organic matrix in developing tooth enamel. Full-length amelogenin was labeled with specific antibodies and 10 nm immuno-gold. This allowed us to use and compare two different high-resolution imaging techniques for the analysis of uncoated samples. Helium ion microscopy (HIM) was applied to study the spatial organization of organic and mineral structures, while field emission scanning electron microscopy (FE-SEM) in various modes, including backscattered electron detection, allowed us to discern the gold-labeled proteins. Wild type enamel in late secretory to early maturation stage reveals adjacent to ameloblasts a lengthwise parallel alignment of the enamel matrix proteins, including full-length amelogenin proteins, which then transitions into a more heterogeneous appearance with increasing distance from the mineralization front. The matrix adjacent to crystal bundles forms a smooth and lacey sheath, whereas between enamel prisms it is organized into spherical components that are interspersed with rod-shaped protein. These findings highlight first, that the heterogeneous organization of the enamel matrix can be visualized in mineralized en bloc samples. Second, our results illustrate that the combination of these techniques is a powerful approach to elucidate the 3D structural organization of organic matrix molecules in mineralizing tissue in nanometer resolution.

  16. Helium ion microscopy of enamel crystallites and extracellular tooth enamel matrix

    Directory of Open Access Journals (Sweden)

    Felicitas B Bidlack

    2014-10-01

    Full Text Available An unresolved problem in tooth enamel studies has been to analyze simultaneously and with sufficient spatial resolution both mineral and organic phases in their three dimensional (3D organization in a given specimen. This study aims to address this need using high-resolution imaging to analyze the 3D structural organization of the enamel matrix, especially amelogenin, in relation to forming enamel crystals. Chemically fixed hemi-mandibles from wild type mice were embedded in LR White acrylic resin, polished and briefly etched to expose the organic matrix in developing tooth enamel. Full-length amelogenin was labeled with specific antibodies and 10 nm immuno-gold. This allowed us to use and compare two different high-resolution imaging techniques for the analysis of uncoated samples. Helium ion microscopy (HIM was applied to study the spatial organization of organic and mineral structures, while field emission scanning electron microscopy (FE-SEM in various modes, including backscattered electron detection, allowed us to discern the gold-labeled proteins. Wild type enamel in late secretory to early maturation stage reveals adjacent to ameloblasts a lengthwise parallel alignment of the enamel matrix proteins, including full-length amelogenin proteins, which then transitions into a more heterogeneous appearance with increasing distance from the mineralization front. The matrix adjacent to crystal bundles forms a smooth and lacey sheath, whereas between enamel prisms it is organized into spherical components that are interspersed with rod-shaped protein. These findings highlight first, that the heterogeneous organization of the enamel matrix can be visualized in mineralized en bloc samples. Second, our results illustrate that the combination of these techniques is a powerful approach to elucidate the 3D structural organization of organic matrix molecules in mineralizing tissue in nanometer resolution.

  17. Intrafibrillar Mineral May be Absent in Dentinogenesis Imperfecta Type II (DI-II)

    Energy Technology Data Exchange (ETDEWEB)

    Pople, John A

    2001-03-29

    High-resolution synchrotron radiation computed tomography (SRCT) and small angle x-ray scattering (SAXS) were performed on normal and dentinogenesis imperfecta type II (DI-II) teeth. Three normal and three DI-II human third molars were used in this study. The normal molars were unerupted and had intact enamel; donors were female and ranged in age from 18-21y. The DI-II specimens, which were also unerupted with intact enamel, came from a single female donor age 20y. SRCT showed that the mineral concentration was 33% lower on average in the DI-II dentin with respect to normal dentin. The SAXS spectra from normal dentin exhibited low-angle diffraction peaks at harmonics of 67.6 nm, consistent with nucleation and growth of the apatite phase within gaps in the collagen fibrils (intrafibrillar mineralization). In contrast, the low-angle peaks were almost nonexistent in the DI-II dentin. Crystallite thickness was independent of location in both DI-II and normal dentin, although the crystallites were significantly thicker in DI-II dentin (6.8 nm (s.d. = 0.5) vs 5.1 nm (s.d. = 0.6)). The shape factor of the crystallites, as determined by SAXS, showed a continuous progression in normal dentin from roughly one-dimensional (needle-like) near the pulp to two-dimensional (plate-like) near the dentin-enamel junction. The crystallites in DI-II dentin, on the other hand, remained needle-like throughout. The above observations are consistent with an absence of intrafibrillar mineral in DI-II dentin.

  18. X-ray diffraction microstructural analysis of bimodal size distribution MgO nano powder

    International Nuclear Information System (INIS)

    Suminar Pratapa; Budi Hartono

    2009-01-01

    Investigation on the characteristics of x-ray diffraction data for MgO powdered mixture of nano and sub-nano particles has been carried out to reveal the crystallite-size-related microstructural information. The MgO powders were prepared by co-precipitation method followed by heat treatment at 500 degree Celsius and 1200 degree Celsius for 1 hour, being the difference in the temperature was to obtain two powders with distinct crystallite size and size-distribution. The powders were then blended in air to give the presumably bimodal-size- distribution MgO nano powder. High-quality laboratory X-ray diffraction data for the powders were collected and then analysed using Rietveld-based MAUD software using the lognormal size distribution. Results show that the single-mode powders exhibit spherical crystallite size (R) of 20(1) nm and 160(1) nm for the 500 degree Celsius and 1200 degree Celsius data respectively with the nano metric powder displays narrower crystallite size distribution character, indicated by lognormal dispersion parameter of 0.21 as compared to 0.01 for the sub-nano metric powder. The mixture exhibits relatively more asymmetric peak broadening. Analysing the x-ray diffraction data for the latter specimen using single phase approach give unrealistic results. Introducing two phase models for the double-phase mixture to accommodate the bimodal-size-distribution characteristics give R = 100(6) and σ = 0.62 for the nano metric phase and R = 170(5) and σ= 0.12 for the σ sub-nano metric phase. (author)

  19. Intrafibrillar Mineral May be Absent in Dentinogenesis Imperfecta Type II (DI-II); TOPICAL

    International Nuclear Information System (INIS)

    Pople, John A.

    2001-01-01

    High-resolution synchrotron radiation computed tomography (SRCT) and small angle x-ray scattering (SAXS) were performed on normal and dentinogenesis imperfecta type II (DI-II) teeth. Three normal and three DI-II human third molars were used in this study. The normal molars were unerupted and had intact enamel; donors were female and ranged in age from 18-21y. The DI-II specimens, which were also unerupted with intact enamel, came from a single female donor age 20y. SRCT showed that the mineral concentration was 33% lower on average in the DI-II dentin with respect to normal dentin. The SAXS spectra from normal dentin exhibited low-angle diffraction peaks at harmonics of 67.6 nm, consistent with nucleation and growth of the apatite phase within gaps in the collagen fibrils (intrafibrillar mineralization). In contrast, the low-angle peaks were almost nonexistent in the DI-II dentin. Crystallite thickness was independent of location in both DI-II and normal dentin, although the crystallites were significantly thicker in DI-II dentin (6.8 nm (s.d.= 0.5) vs 5.1 nm (s.d.= 0.6)). The shape factor of the crystallites, as determined by SAXS, showed a continuous progression in normal dentin from roughly one-dimensional (needle-like) near the pulp to two-dimensional (plate-like) near the dentin-enamel junction. The crystallites in DI-II dentin, on the other hand, remained needle-like throughout. The above observations are consistent with an absence of intrafibrillar mineral in DI-II dentin

  20. Mid - infrared transmission of polycrystalline (LaSr) (MnNi)O3

    International Nuclear Information System (INIS)

    Laksanawati, W. D.; Kurniawan, B.; Saptari, S. A.

    2016-01-01

    Polycrystalline (LaSr)(MnNi)O 3 was shintesized using sol gel methods with nitrat precursors La(NO 3 ) 3 , Sr(NO 3 ) 2 , Mn(NO 3 ) 2 .4H 2 O, and Ni(NO3)2.6H2O and the different heating process. Sample (LaSr)(MnNi)O 3 with chemical formulation La 0,67 Sr 0,33 Mn 1-x Ni x O 3 with × = 0,05 and 0,10. We report the crystallite structure of La 0,67 Sr 0,33 Mn 1-x Ni x O 3 with x= 0,00 and 0,10 are single phase with characterization by X-ray diffraction. Refinement has result that crystallite size of La 0,67 Sr 0,33 Mn 0,95 Ni 0,05 O 3 is 24,67 and La 0,67 Sr 0,33 Mn 0,9 Ni 0,1 O 3 is 21,84 with crystallite system rombohedral, it show us that increasing at Ni composition influence of decreased crystallite size. Sampel (LaSr)(MnNi)O3 has been characterization with Fourier Transform Infrared with range of wave number from 450 to 4000 cm -1 were chategories at mid infrared wave. The FTIR pattern show to us that the Mn-O-Mn bounded has absorp infrared at wave number 605 cm -1 and the dominant peak at wave number 3750 cm -1 caused the hidroxy compound in sampel La 0,67 Sr 0,33 Mn 0,95 Ni 0,05 O 3 . (paper)

  1. Tunable conductivity in mesoporous germanium

    Science.gov (United States)

    Beattie, Meghan N.; Bioud, Youcef A.; Hobson, David G.; Boucherif, Abderraouf; Valdivia, Christopher E.; Drouin, Dominique; Arès, Richard; Hinzer, Karin

    2018-05-01

    Germanium-based nanostructures have attracted increasing attention due to favourable electrical and optical properties, which are tunable on the nanoscale. High densities of germanium nanocrystals are synthesized via electrochemical etching, making porous germanium an appealing nanostructured material for a variety of applications. In this work, we have demonstrated highly tunable electrical conductivity in mesoporous germanium layers by conducting a systematic study varying crystallite size using thermal annealing, with experimental conductivities ranging from 0.6 to 33 (×10‑3) Ω‑1 cm‑1. The conductivity of as-prepared mesoporous germanium with 70% porosity and crystallite size between 4 and 10 nm is shown to be ∼0.9 × 10‑3 Ω‑1 cm‑1, 5 orders of magnitude smaller than that of bulk p-type germanium. Thermal annealing for 10 min at 400 °C further reduced the conductivity; however, annealing at 450 °C caused a morphological transformation from columnar crystallites to interconnecting granular crystallites and an increase in conductivity by two orders of magnitude relative to as-prepared mesoporous germanium caused by reduced influence of surface states. We developed an electrostatic model relating the carrier concentration and mobility of p-type mesoporous germanium to the nanoscale morphology. Correlation within an order of magnitude was found between modelled and experimental conductivities, limited by variation in sample uniformity and uncertainty in void size and fraction after annealing. Furthermore, theoretical results suggest that mesoporous germanium conductivity could be tuned over four orders of magnitude, leading to optimized hybrid devices.

  2. Large-group psychodynamics and massive violence

    Directory of Open Access Journals (Sweden)

    Vamik D. Volkan

    2006-06-01

    Full Text Available Beginning with Freud, psychoanalytic theories concerning large groups have mainly focused on individuals' perceptions of what their large groups psychologically mean to them. This chapter examines some aspects of large-group psychology in its own right and studies psychodynamics of ethnic, national, religious or ideological groups, the membership of which originates in childhood. I will compare the mourning process in individuals with the mourning process in large groups to illustrate why we need to study large-group psychology as a subject in itself. As part of this discussion I will also describe signs and symptoms of large-group regression. When there is a threat against a large-group's identity, massive violence may be initiated and this violence in turn, has an obvious impact on public health.

  3. Ku-band electromagnetic wave absorbing properties of polysiloxane derived Si-O-C bulk ceramics

    Science.gov (United States)

    Ding, Donghai; Li, Zipei; Xiao, Guoqing; Yang, Shaoyu

    2018-02-01

    The bulk Si-O-C ceramics were prepared by polymer derived ceramics (PDCs) route using polysiloxane as precursor and their properties were investigated for electromagnetic wave absorbing in the frequency range of 12.4-18 GHz (Ku-band). It was found that the catalytic pyrolysis can enhance substantially the absorbing properties by in situ formation of turbostratic carbon network, ordered carbon, and multi-wall carbon nanotubes. The matching thickness of sample containing 1.5 wt% FeCl3 (FPSO-1.5) is 2.2 mm, and its reflection loss exceeds -10 dB in the whole Ku-band with an absorption peak of -35.48 dB at 14.16 GHz. For sample containing 1.5 wt% FeCl3, its absorption peak increases to -15.78 dB, but its matching thickness decreases significantly to 2.2 mm. The polymer derived Si-O-C ceramics could be used as excellent electromagnetic functional devices working in harsh environments.

  4. Preparation of activated carbon hollow fibers from ramie at low temperature for electric double-layer capacitor applications.

    Science.gov (United States)

    Du, Xuan; Zhao, Wei; Wang, Yi; Wang, Chengyang; Chen, Mingming; Qi, Tao; Hua, Chao; Ma, Mingguo

    2013-12-01

    Activated carbon hollow fibers (ACHFs) with high surface area were prepared from inexpensive, renewable ramie fibers (RFs) by a single-step activation method under lower temperature than that of other reports. The effects of activation conditions on the pore structure and turbostratic structure of ACHFs were investigated systematically. The results show that ACHFs surface area decreased but micropore volume and conductivity increased as the increase of activation temperature and activation time. The electrochemical measurements of supercapacitors fabricated from these ACHFs electrodes reveal that the electrochemical properties improved with the enhancing of activation degree. However, too high activation temperature can make the ion diffusion resistance increase. It suggests that pore structure and conductivity are as important as surface area to decide the electrochemical performances of ACHFs electrode materials. A maximum capacity of 287 F g(-1) at 50 mA g(-1) was obtained for the ACHFs electrode prepared under suitable conditions. Copyright © 2013 Elsevier Ltd. All rights reserved.

  5. High-Flux Carbon Molecular Sieve Membranes for Gas Separation.

    Science.gov (United States)

    Richter, Hannes; Voss, Hartwig; Kaltenborn, Nadine; Kämnitz, Susanne; Wollbrink, Alexander; Feldhoff, Armin; Caro, Jürgen; Roitsch, Stefan; Voigt, Ingolf

    2017-06-26

    Carbon membranes have great potential for highly selective and cost-efficient gas separation. Carbon is chemically stable and it is relative cheap. The controlled carbonization of a polymer coating on a porous ceramic support provides a 3D carbon material with molecular sieving permeation performance. The carbonization of the polymer blend gives turbostratic carbon domains of randomly stacked together sp 2 hybridized carbon sheets as well as sp 3 hybridized amorphous carbon. In the evaluation of the carbon molecular sieve membrane, hydrogen could be separated from propane with a selectivity of 10 000 with a hydrogen permeance of 5 m 3 (STP)/(m 2 hbar). Furthermore, by a post-synthesis oxidative treatment, the permeation fluxes are increased by widening the pores, and the molecular sieve carbon membrane is transformed from a molecular sieve carbon into a selective surface flow carbon membrane with adsorption controlled performance and becomes selective for carbon dioxide. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Surface heterogeneity and ionization of Cs promoter in carbon-based ruthenium catalyst for ammonia synthesis

    International Nuclear Information System (INIS)

    Kotarba, Andrzej; Dmytrzyk, Jaromir; Rarog-Pilecka, Wioletta; Kowalczyk, Zbigniew

    2003-01-01

    Second-generation ammonia synthesis cesium-doped ruthenium catalyst supported on turbostratic carbon was investigated by the species resolved thermal alkali desorption method (SR-TAD). Energetic barriers for cesium ions (2.86 eV), ground state (1.96 eV) and electronically excited atoms (5.76 eV) desorbing from the Cs-Ru/C catalyst were determined. In the case of ruthenium-free Cs/C system, cesium desorbs as ground state atoms only, with an energy barrier of 2.87 eV. The work functions determined by the thermionic emission of electrons from Cs/C and Cs-Ru/C were of the same value (2.9 eV). It was concluded that ruthenium induces heterogeneous distribution of cesium on the catalyst surface. The promoter stability is reduced on low work function areas and its surface ionization on high work function areas opens the ionic desorption channel. The Cs desorption from the catalyst is discussed in terms of the literature data for the cesium/graphite system

  7. Imaging the oxidation of ZnS encapsulated in carbon nanotubes

    DEFF Research Database (Denmark)

    Costa, Pedro M. F. J.; Hansen, Thomas Willum; Wagner, Jakob Birkedal

    2010-01-01

    Cable-to-tube transition: Core–shell sulfide–carbon nanocables have been oxidised to hollow polycrystalline nanowires and further assembled to crystallites inside a transmission electron microscope. The full experimental life cycle (see graphic) was followed for a single nanostructure; this provi......Cable-to-tube transition: Core–shell sulfide–carbon nanocables have been oxidised to hollow polycrystalline nanowires and further assembled to crystallites inside a transmission electron microscope. The full experimental life cycle (see graphic) was followed for a single nanostructure......; this provided extended structural and chemical information that supports a nanocable-to-nanotube transition and the presence of the Kirkendall effect....

  8. Mesoporous high surface area Ce0.9Gd0.1O1.95 synthesized by spray drying

    DEFF Research Database (Denmark)

    Lundberg, Mats; Wang, Hsiang-Jen; Blennow Tullmar, Peter

    2011-01-01

    Mesoporous gadolinium doped cerium dioxide with high surface area was produced by spray drying using Pluronic 123 as surfactant. The powder, when calcined at 400 °C, had a BET surface area of 136 m2 g−1 and was polycrystalline as confirmed by XRD and TEM. XEDS confirmed Ce, Gd and O, as the only......, corresponding to the crystallite size calculated from XRD data. The similar size range of the mesopores and the observed crystallite size indicates that the porosity is partly formed from intergranular mesoporosity. Using the spray drying method of a surfactant assisted liquid precursor solution it can...

  9. Size Fluctuations of Near Critical Nuclei and Gibbs Free Energy for Nucleation of BDA on Cu(001)

    Science.gov (United States)

    Schwarz, Daniel; van Gastel, Raoul; Zandvliet, Harold J. W.; Poelsema, Bene

    2012-07-01

    We present a low-energy electron microscopy study of nucleation and growth of BDA on Cu(001) at low supersaturation. At sufficiently high coverage, a dilute BDA phase coexists with c(8×8) crystallites. The real-time microscopic information allows a direct visualization of near-critical nuclei, determination of the supersaturation and the line tension of the crystallites, and, thus, derivation of the Gibbs free energy for nucleation. The resulting critical nucleus size nicely agrees with the measured value. Nuclei up to 4-6 times larger still decay with finite probability, urging reconsideration of the classic perception of a critical nucleus.

  10. Annealing of TiO2 Films Deposited on Si by Irradiating Nitrogen Ion Beams

    International Nuclear Information System (INIS)

    Yokota, Katsuhiro; Yano, Yoshinori; Miyashita, Fumiyoshi

    2006-01-01

    Thin TiO2 films were deposited on Si at a temperature of 600 deg. C by an ion beam assisted deposition (IBAD) method. The TiO2 films were annealed for 30 min in Ar at temperatures below 700 deg. C. The as-deposited TiO2 films had high permittivities such 200 εo and consisted of crystallites that were not preferentially oriented to the c-axis but had an expanded c-axis. On the annealed TiO2 films, permittivities became lower with increasing annealing temperature, and crystallites were oriented preferentially to the (110) plane

  11. Combined in situ PXRD and PDF study of hydrothermal formation of α- and β-MnO2 nanocrystallites

    DEFF Research Database (Denmark)

    Birgisson, Steinar; Shen, Yanbin; Saha, Dipankar

    resolved powder X-ray diffraction (PXRD) and total scattering (TS) data is then measured using synchrotron radiation.[5, 6] By Rietveld refinement of PXRD data, information about the quantity of different crystalline phases, unit cell size, crystallite size and morphology as function of reaction time...... it looks like the smallest α-MnO2 nanocrystallites transform to β-MnO2 first, before subsequent transformation of larger crystallites. 1. Thackeray, M.M., Manganese oxides for lithium batteries. Progress in Solid State Chemistry, 1997. 25(1–2): p. 1-71. 2. Palomares, V., et al., Update on Na-based battery...

  12. Mechanical alloying of Cu-xCr (x = 3, 5 and 8 wt.%) alloys

    International Nuclear Information System (INIS)

    Aguilar, C.; Ordonez, S.; Guzman, D.; Rojas, P.A.

    2010-01-01

    This work studies the structural evolution of Cu-xCr (x = 3, 5 and 8 wt.%) alloys processed by mechanical alloying using X-ray diffraction profiles, scanning microscopy and microhardness analysis. X-ray diffraction analysis using the modified Williamson-Hall and Warren-Averbach methods were used to determine structural properties, such as crystallite size, stacking fault probability and energy, dislocation density, lattice parameters and crystallite size distribution of metallic powder as a function of Cr amount and milling time. Lattice defects increase the Gibbs free energy and the Gibbs free energy curves shift upward, therefore the solubility limit change.

  13. Nucleation and growth of polycrystalline SiC

    DEFF Research Database (Denmark)

    Kaiser, M.; Schimmel, S.; Jokubavicius, V.

    2014-01-01

    The nucleation and bulk growth of polycrystalline SiC in a 2 inch PVT setup using isostatic and pyrolytic graphite as substrates was studied. Textured nucleation occurs under near-thermal equilibrium conditions at the initial growth stage with hexagonal platelet shaped crystallites of 4H, 6H and 15......R polytypes. It is found that pyrolytic graphite results in enhanced texturing of the nucleating gas species. Reducing the pressure leads to growth of the crystallites until a closed polycrystalline SiC layer containing voids with a rough surface is developed. Bulk growth was conducted at 35 mbar Ar...

  14. Effect of solvent on the synthesis of SnO_2 nanoparticles

    International Nuclear Information System (INIS)

    Kumar, Virender; Singh, Karamjit; Singh, Kulwinder; Kumar, Akshay; Kumari, Sudesh; Thakur, Anup

    2016-01-01

    Tin oxide (SnO_2) nanoparticles have been synthesized by co-precipitation method. The synthesized nanoparticles have been characterized by X-ray diffraction (XRD) and Ultraviolet-Visible spectroscopy (UV-VIS). XRD analysis confirmed the formation of single phase of SnO_2 nanoparticles. It has been found that solvents played important role in controlling the crystallite size of SnO_2 nanoparticles. The XRD analysis showed well crystallized tetragonal SnO_2 nanoparticles. The crystallite size of SnO_2 nanoparticles varies with the solvent. Tauc plot showed that optical band gap was also tailored by controlling the solvent during synthesis.

  15. Exploring the large-scale structure of Taylor–Couette turbulence through Large-Eddy Simulations

    Science.gov (United States)

    Ostilla-Mónico, Rodolfo; Zhu, Xiaojue; Verzicco, Roberto

    2018-04-01

    Large eddy simulations (LES) of Taylor-Couette (TC) flow, the flow between two co-axial and independently rotating cylinders are performed in an attempt to explore the large-scale axially-pinned structures seen in experiments and simulations. Both static and dynamic LES models are used. The Reynolds number is kept fixed at Re = 3.4 · 104, and the radius ratio η = ri /ro is set to η = 0.909, limiting the effects of curvature and resulting in frictional Reynolds numbers of around Re τ ≈ 500. Four rotation ratios from Rot = ‑0.0909 to Rot = 0.3 are simulated. First, the LES of TC is benchmarked for different rotation ratios. Both the Smagorinsky model with a constant of cs = 0.1 and the dynamic model are found to produce reasonable results for no mean rotation and cyclonic rotation, but deviations increase for increasing rotation. This is attributed to the increasing anisotropic character of the fluctuations. Second, “over-damped” LES, i.e. LES with a large Smagorinsky constant is performed and is shown to reproduce some features of the large-scale structures, even when the near-wall region is not adequately modeled. This shows the potential for using over-damped LES for fast explorations of the parameter space where large-scale structures are found.

  16. Neutron-diffraction study of cubic ErC/sub 0.6/ in the temperature range 1.6--296 K

    International Nuclear Information System (INIS)

    Atoji, M.

    1981-01-01

    Neutron-diffraction measurements have shown that the form of ErC/sub 0.6/ that has a cubic, NaCl-type structure is paramagnetic above 90 K, exhibiting a free Er 3+ moment. Below 90 K, ErC/sub 0.6/ becomes a ferromagnet with a saturation moment of 2.5 Bohr magnetons (only 28% of the maximum free-ion moment), indicating a large crystal-field effect. By measuring the preferential crystallite orientation induced by the applied magnetic field, the direction of the ferromagnetically ordered moment was found to be parallel to the axis. A ferromagnetic, short-range ordering coexists with the ferromagnetic long-range ordering at temperatures down to 1.6 K

  17. Conductivity and superconductivity of (Bi,Pb)-Sr-Ca-Cu-O

    International Nuclear Information System (INIS)

    Gazda, M.; Kusz, B.; Klimczuk, T.; Natali, R.; Stizza, S.

    2007-01-01

    The (Bi,Pb)-Sr-Ca-Cu-O glass-ceramics may be considered as disordered metal and superconductor. Depending on the heat treatment conditions the materials are either composed of the oval grains of the 2212 or 2201 phases embedded in the insulating matrix or they mainly contain the 2212 plate-like crystallites weakly connected one with another. The materials have large resistivity and usually large negative temperature coefficient of resistivity (TCR). The granular and disordered character of the materials is also reflected in their superconducting properties. Both the normal-state and superconducting properties correlate one with another. The glass-ceramic samples were obtained by annealing the amorphous solid at temperatures between 840 and 860 deg. C. The measurements of the temperature dependence of resistivity in annealed samples were carried out with the conventional four-terminal method in a temperature range from 3 to 300 K

  18. Large-scale solar heat

    Energy Technology Data Exchange (ETDEWEB)

    Tolonen, J.; Konttinen, P.; Lund, P. [Helsinki Univ. of Technology, Otaniemi (Finland). Dept. of Engineering Physics and Mathematics

    1998-12-31

    In this project a large domestic solar heating system was built and a solar district heating system was modelled and simulated. Objectives were to improve the performance and reduce costs of a large-scale solar heating system. As a result of the project the benefit/cost ratio can be increased by 40 % through dimensioning and optimising the system at the designing stage. (orig.)

  19. Electrochemical Performance of Electrospun carbon nanofibers as free-standing and binder-free anodes for Sodium-Ion and Lithium-Ion Batteries

    International Nuclear Information System (INIS)

    Jin, Juan; Shi, Zhi-qiang; Wang, Cheng-yang

    2014-01-01

    Highlights: • Electrospun carbon nanofiber webs were prepared by pyrolysis of polyacrylonitrile. • The webs as binder-free and current collector-free electrodes for SIBs and LIBs. • Different layer spacing and pore size for Li and Na lead different electrochemical behavior. • Electrochemical performances of the electrodes were high. - Abstract: A series of hard carbon nanofiber-based electrodes derived from electrospun polyacrylonitrile (PAN) nanofibers (PAN-CNFs) have been fabricated by stabilization in air at about 280 °C and then carbonization in N 2 at heat treatment temperatures (HTT) between 800 and 1500 °C. The electrochemical performances of the binder-free, current collector-free carbon nanofiber-based anodes in lithium-ion batteries and sodium-ion batteries are systematically investigated and compared. We demonstrate the presence of similar alkali metal insertion mechanisms in both cases, but just the differences of the layer spacing and pore size available for lithium and sodium ion lead the discharge capacity delivered at sloping region and plateau region to vary from the kinds of alkali elements. Although the anodes in sodium-ion batteries show poorer rate capability than that in lithium-ion batteries, they still achieve a reversible sodium intercalation capacity of 275 mAh g −1 and similar cycling stability due to the conductive 3-D network, weakly ordered turbostratic structure and a large interlayer spacing between graphene sheets. The feature of high capacity and stable cycling performance makes PAN-CNFs to be promising candidates as electrodes in rechargeable sodium-ion batteries and lithium-ion batteries

  20. Laboratory for Large Data Research

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: The Laboratory for Large Data Research (LDR) addresses a critical need to rapidly prototype shared, unified access to large amounts of data across both the...

  1. Hydroelastic analysis of a very large floating plate with large deflections in stochastic seaway

    DEFF Research Database (Denmark)

    Chen, Xu-jun; Jensen, Jørgen Juncher; Cui, Wei-cheng

    2004-01-01

    The hydroelasticity of a very large floating plate with large deflections in multidirectional irregular waves is discussed. After a brief introduction on wave loads on a flexible structure, the paper derives the generalised fluid force acting on a floating structure in multidirectional irregular ...

  2. Ethics of large-scale change

    OpenAIRE

    Arler, Finn

    2006-01-01

      The subject of this paper is long-term large-scale changes in human society. Some very significant examples of large-scale change are presented: human population growth, human appropriation of land and primary production, the human use of fossil fuels, and climate change. The question is posed, which kind of attitude is appropriate when dealing with large-scale changes like these from an ethical point of view. Three kinds of approaches are discussed: Aldo Leopold's mountain thinking, th...

  3. Prospecting direction and favourable target areas for exploration of large and super-large uranium deposits in China

    International Nuclear Information System (INIS)

    Liu Xingzhong

    1993-01-01

    A host of large uranium deposits have been successively discovered abroad by means of geological exploration, metallogenetic model studies and the application of new geophysical and geochemical methods since 1970's. Thorough undertaking geological research relevant to prospecting for super large uranium deposits have attracted great attention of the worldwide geological circle. The important task for the vast numbers of uranium geological workers is to make an afford to discover more numerous large and super large uranium deposits in China. The author comprehensively analyses the regional geological setting and geological metallogenetic conditions for the super large uranium deposits in the world. Comparative studies have been undertaken and the prospecting direction and favourable target areas for the exploration of super large uranium deposits in China have been proposed

  4. Synthesis and characterization of arsenic-doped cysteine-capped thoria-based nanoparticles

    International Nuclear Information System (INIS)

    Pereira, F. J.; Díez, M. T.; Aller, A. J.

    2013-01-01

    Thoria materials have been largely used in the nuclear industry. Nonetheless, fluorescent thoria-based nanoparticles provide additional properties to be applied in other fields. Thoria-based nanoparticles, with and without arsenic and cysteine, were prepared in 1,2-ethanediol aqueous solutions by a simple precipitation procedure. The synthesized thoria-based nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (ED-XRS), Raman spectroscopy, Fourier transform infrared (FT-IR) spectroscopy and fluorescence microscopy. The presence of arsenic and cysteine, as well as the use of a thermal treatment facilitated fluorescence emission of the thoria-based nanoparticles. Arsenic-doped and cysteine-capped thoria-based nanoparticles prepared in 2.5 M 1,2-ethanediol solutions and treated at 348 K showed small crystallite sizes and strong fluorescence. However, thoria nanoparticles subjected to a thermal treatment at 873 K also produced strong fluorescence with a very narrow size distribution and much smaller crystallite sizes, 5 nm being the average size as shown by XRD and TEM. The XRD data indicated that, even after doping of arsenic in the crystal lattice of ThO 2 , the samples treated at 873 K were phase pure with the fluorite cubic structure. The Raman and FT-IR spectra shown the most characteristics vibrational peaks of cysteine together with other peaks related to the bonds of this molecule to thoria and arsenic when present

  5. Synthesis and characterization of PVA blended LiClO4 as electrolyte material for battery Li-ion

    Science.gov (United States)

    Gunawan, I.; Deswita; Sugeng, B.; Sudaryanto

    2017-07-01

    It have been synthesized the materials for Li ion battery electrolytes, namely PVA with the addition of LiClO4 salt were varied 0, 5, 10, 15 and 20% by weight respectively. The objective of this study is to control the ionic conductivity in traditional polymer electrolytes, to improve ionic conductivity with the addition of lithium perchlorat (LiClO4). These electrolyte materials prepared by PVA powder was dissolved into distilled water and added LiClO4 salt were varied. After drying the solution, PVA sheet blended LiClO4 salt as electrolyte material for Li ion battery obtained. PVA blended LiClO4 salt crystallite form was confirmed using X-Ray Difraction (XRD) equipment. Observation of the morphology done by using Scanning Electron Microscope (SEM). While the electrical conductivity of the material is measured using LCR meter. The results of XRD pattern of LiClO4 shows intense peaks at angles 2θ = 23.2, 32.99, and 36.58°, which represent the crystalline nature of the salt. Particles morphology of the sample revealed by scanning electron microscopy are irregular in shape and agglomerated, with mean size 200-300 nm. It can be concluded that polycrystalline particles are composed of large number of crystallites. The study of conductivity by using LCR meter shows that all the graphs represent the DC and AC conductivity phenomena.

  6. Sequentially solution-processed, nanostructured polymer photovoltaics using selective solvents

    KAUST Repository

    Kim, Do Hwan; Mei, Jianguo; Ayzner, Alexander L.; Schmidt, Kristin; Giri, Gaurav; Appleton, Anthony L.; Toney, Michael F.; Bao, Zhenan

    2014-01-01

    We demonstrate high-performance sequentially solution-processed organic photovoltaics (OPVs) with a power conversion efficiency (PCE) of 5% for blend films using a donor polymer based on the isoindigo-bithiophene repeat unit (PII2T-C10C8) and a fullerene derivative [6,6]-phenyl-C[71]-butyric acid methyl ester (PC71BM). This has been accomplished by systematically controlling the swelling and intermixing processes of the layer with various processing solvents during deposition of the fullerene. We find that among the solvents used for fullerene deposition that primarily swell but do not re-dissolve the polymer underlayer, there were significant microstructural differences between chloro and o-dichlorobenzene solvents (CB and ODCB, respectively). Specifically, we show that the polymer crystallite orientation distribution in films where ODCB was used to cast the fullerene is broad. This indicates that out-of-plane charge transport through a tortuous transport network is relatively efficient due to a large density of inter-grain connections. In contrast, using CB results in primarily edge-on oriented polymer crystallites, which leads to diminished out-of-plane charge transport. We correlate these microstructural differences with photocurrent measurements, which clearly show that casting the fullerene out of ODCB leads to significantly enhanced power conversion efficiencies. Thus, we believe that tuning the processing solvents used to cast the electron acceptor in sequentially-processed devices is a viable way to controllably tune the blend film microstructure. © 2014 The Royal Society of Chemistry.

  7. Large-scale multimedia modeling applications

    International Nuclear Information System (INIS)

    Droppo, J.G. Jr.; Buck, J.W.; Whelan, G.; Strenge, D.L.; Castleton, K.J.; Gelston, G.M.

    1995-08-01

    Over the past decade, the US Department of Energy (DOE) and other agencies have faced increasing scrutiny for a wide range of environmental issues related to past and current practices. A number of large-scale applications have been undertaken that required analysis of large numbers of potential environmental issues over a wide range of environmental conditions and contaminants. Several of these applications, referred to here as large-scale applications, have addressed long-term public health risks using a holistic approach for assessing impacts from potential waterborne and airborne transport pathways. Multimedia models such as the Multimedia Environmental Pollutant Assessment System (MEPAS) were designed for use in such applications. MEPAS integrates radioactive and hazardous contaminants impact computations for major exposure routes via air, surface water, ground water, and overland flow transport. A number of large-scale applications of MEPAS have been conducted to assess various endpoints for environmental and human health impacts. These applications are described in terms of lessons learned in the development of an effective approach for large-scale applications

  8. Large Retailers’ Financial Services

    OpenAIRE

    Risso, Mario

    2010-01-01

    Over the last few years, large retailers offering financial services have considerably grown in the financial services sector. Retailers are increasing the wideness and complexity of their offer of financial services. Large retail companies provide financial services to their customers following different strategic ways. The provision of financial services in the retailers offer is implemented in several different ways related to the strategies, the structures and the degree of financial know...

  9. Utility unbundling : large consumer's perspective

    International Nuclear Information System (INIS)

    Block, C.

    1997-01-01

    The perspectives of Sunoco as a large user of electric power on utility unbundling were presented. Sunoco's Sarnia refinery runs up an energy bill of over $60 million per year for electricity, natural gas (used both as a feedstock as well as a fuel), natural gas liquids and steam. As a large customer Sunoco advocates unbundling of all services, leaving only the 'pipes and wires' as true monopolies. In their view, regulation distorts the market place and prevents the lower prices that would result from competition as has been seen in the airline and telephone industries. Sunoco's expectation is that in the post-deregulated environment large and small consumers will have a choice of energy supplier, and large consumers will increasingly turn to co-generation as the most desirable way of meeting their power needs

  10. One-step chemical bath deposition and photocatalytic activity of Cu2O thin films with orientation and size controlled by a chelating agent

    International Nuclear Information System (INIS)

    Xu, HaiYan; Dong, JinKuang; Chen, Chen

    2014-01-01

    Nanocrystalline cuprous oxide (Cu 2 O) thin films were prepared via a one-step chemical bath deposition (CBD) method. The effects of a chelating agent on the orientation, morphology, crystallite size, and photocatalytic activity of the thin films were carefully examined using X-ray diffractometry, scanning electron microscopy, and UV–vis spectrophotometry. The results confirmed that the crystallite size as well as the orientation of the films was dependent on the volume of trisodium citrate (TSC), demonstrating that the band gap ranged from 2.71 eV to 2.49 eV. The morphology and number density of the thin films also depended on the volume of TSC. In addition, the obtained Cu 2 O thin films could degrade methyl orange (MO) efficiently in the presence of H 2 O 2 under visible-light irradiation, and the mechanism for the enhanced photocatalytic activity of the Cu 2 O thin films with the assistance of H 2 O 2 was also explored in detail. - Graphical abstract: Nano-structured Cu 2 O thin films have been prepared by a one-step chemical bath deposition method. The number density, crystallite size, surface morphology and orientation of these thin films could be tailored by chelating agent. The results confirmed that the crystallite size as well as the orientation of the thin films was dependent on the volume of TSC, showed that the band gap ranged from 2.71 eV to 2.49 eV. The formation mechanism of the Cu 2 O particles could be illuminated by an oriented attachment mode. In addition, the obtained Cu 2 O thin films degraded methyl orange efficiently in the presence of H 2 O 2 under the irradiation of visible light, and the mechanism for photocatalytic reaction was also discussed in detail. - Highlights: • Oriented Cu 2 O thin films were prepared by one-step chemical bath deposition. • Orientation and crystallite size were dependent on trisodium citrate volume. • The enhanced visible light degradation mechanism was systematically studied. • Oriented attachment

  11. One-step chemical bath deposition and photocatalytic activity of Cu{sub 2}O thin films with orientation and size controlled by a chelating agent

    Energy Technology Data Exchange (ETDEWEB)

    Xu, HaiYan, E-mail: xuhaiyan@ahjzu.edu.cn; Dong, JinKuang, E-mail: dongjinkuang1988@126.com; Chen, Chen, E-mail: 13865901653@139.com

    2014-01-15

    Nanocrystalline cuprous oxide (Cu{sub 2}O) thin films were prepared via a one-step chemical bath deposition (CBD) method. The effects of a chelating agent on the orientation, morphology, crystallite size, and photocatalytic activity of the thin films were carefully examined using X-ray diffractometry, scanning electron microscopy, and UV–vis spectrophotometry. The results confirmed that the crystallite size as well as the orientation of the films was dependent on the volume of trisodium citrate (TSC), demonstrating that the band gap ranged from 2.71 eV to 2.49 eV. The morphology and number density of the thin films also depended on the volume of TSC. In addition, the obtained Cu{sub 2}O thin films could degrade methyl orange (MO) efficiently in the presence of H{sub 2}O{sub 2} under visible-light irradiation, and the mechanism for the enhanced photocatalytic activity of the Cu{sub 2}O thin films with the assistance of H{sub 2}O{sub 2} was also explored in detail. - Graphical abstract: Nano-structured Cu{sub 2}O thin films have been prepared by a one-step chemical bath deposition method. The number density, crystallite size, surface morphology and orientation of these thin films could be tailored by chelating agent. The results confirmed that the crystallite size as well as the orientation of the thin films was dependent on the volume of TSC, showed that the band gap ranged from 2.71 eV to 2.49 eV. The formation mechanism of the Cu{sub 2}O particles could be illuminated by an oriented attachment mode. In addition, the obtained Cu{sub 2}O thin films degraded methyl orange efficiently in the presence of H{sub 2}O{sub 2} under the irradiation of visible light, and the mechanism for photocatalytic reaction was also discussed in detail. - Highlights: • Oriented Cu{sub 2}O thin films were prepared by one-step chemical bath deposition. • Orientation and crystallite size were dependent on trisodium citrate volume. • The enhanced visible light degradation mechanism

  12. Effect of the Pd/MWCNTs anode catalysts preparation methods on their morphology and activity in a direct formic acid fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Lesiak, B., E-mail: blesiak-orlowska@ichf.edu.pl [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warszawa (Poland); Mazurkiewicz, M.; Malolepszy, A. [Faculty of Chemical and Process Engineering, Warsaw University of Technology, Waryńskiego 1, 00-645 Warszawa (Poland); Stobinski, L. [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warszawa (Poland); Faculty of Chemical and Process Engineering, Warsaw University of Technology, Waryńskiego 1, 00-645 Warszawa (Poland); Mierzwa, B.; Mikolajczuk-Zychora, A.; Juchniewicz, K.; Borodzinski, A. [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warszawa (Poland); Zemek, J.; Jiricek, P. [Institute of Physics, Academy of Sciences of the Czech Republic, 162-53 Prague 6, Cukrovarnicka 10 (Czech Republic)

    2016-11-30

    Highlights: • Catalysts properties studied by XRD, STEM, XPS methods. • Differences in Pd particle size, content of Pd, functional groups, PdC{sub x.}. • Catalytic activity studied in a Direct Formic Acid Fuel Cell. • Highest activity–catalyst prepared using a strong reducing agent (NaBH{sub 4}). - Abstract: Impact of Pd/MWCNTs catalysts preparation method on the catalysts morphology and activity in a formic acid electrooxidation reaction was investigated. Three reduction methods of Pd precursor involving reduction in a high pressure microwave reactor (Pd1), reduction with NaBH{sub 4} (Pd2) and microwave-assisted polyol method (Pd3) were used in this paper. Crystallites size and morphology were studied using the scanning transmission electron microscopy (STEM), X-ray diffraction (XRD), whereas elemental composition, Pd chemical state and functional groups content by the X-ray photoelectron spectroscopy (XPS). The prepared catalysts were tested in a direct formic acid fuel cell (DFAFC) as an anode material. The catalytic activity was correlated with a mean fraction of the total Pd atoms exposed at the surface (FE). The value of FE was calculated from the crystallites size distribution determined by the STEM measurements. Non-linear dependence of a current density versus FE, approaching the maximum at FE≈0.25 suggests that the catalytic process proceeded at Pd nanocrystallites faces, with inactive edges and corners. Pd2 catalyst exhibited highest activity due to its smallest Pd crystallites (3.2 nm), however the absence of Pd crystallites aggregation and low content of carbon in PdC{sub x} phase, i.e. x = 4 at.% may also affect the observed.

  13. Crystallographic Analysis of a Japanese Sword by using Bragg Edge Transmission Spectroscopy

    Science.gov (United States)

    Shiota, Yoshinori; Hasemi, Hiroyuki; Kiyanagi, Yoshiaki

    Neutron imaging using a pulsed neutron source can give crystallographic information over wide area of a sample by analysing position dependent transmission spectra. With the use of a Bragg edge imaging method we non-destructively obtained crystallographic information of a Japanese sword, signed by Bishu Osafune Norimitsu, in order to know position dependent crystallographic characteristics and to check usefulness of the method for the Japanese sword investigation. Strong texture appeared on the back side. On the other hand in the middle area almost isotropic feature appeared and edge side showed feature between them. Rather isotropic area in the centre area gradually reduced from the grip side to the tip side. The crystallite size was smaller near the edge and became larger towards the back side. The smaller crystallite size will be due to quenching around the edge and this trend disappeared in the grip (nakago) area. The larger crystallite size will be due to strong hammering. Coarse grains were also observed directly as transmission images with the use of a high spatial resolution detector. The spatial distribution of the grains was not uniform but the reason have not been understood. Furthermore, a white area around a tip area was proved to be a void by looking at the Brag edge transmission spectra. This void may be formed during forging process of two kinds of steel. It is suggested that consideration on differences in the texture and the crystallite size depending on position will give information to clarify the manufacturing process, and Bragg edge analysis will be a profitable tool for research of Japanese sword.

  14. Effect of the Pd/MWCNTs anode catalysts preparation methods on their morphology and activity in a direct formic acid fuel cell

    International Nuclear Information System (INIS)

    Lesiak, B.; Mazurkiewicz, M.; Malolepszy, A.; Stobinski, L.; Mierzwa, B.; Mikolajczuk-Zychora, A.; Juchniewicz, K.; Borodzinski, A.; Zemek, J.; Jiricek, P.

    2016-01-01

    Highlights: • Catalysts properties studied by XRD, STEM, XPS methods. • Differences in Pd particle size, content of Pd, functional groups, PdC x. . • Catalytic activity studied in a Direct Formic Acid Fuel Cell. • Highest activity–catalyst prepared using a strong reducing agent (NaBH 4 ). - Abstract: Impact of Pd/MWCNTs catalysts preparation method on the catalysts morphology and activity in a formic acid electrooxidation reaction was investigated. Three reduction methods of Pd precursor involving reduction in a high pressure microwave reactor (Pd1), reduction with NaBH 4 (Pd2) and microwave-assisted polyol method (Pd3) were used in this paper. Crystallites size and morphology were studied using the scanning transmission electron microscopy (STEM), X-ray diffraction (XRD), whereas elemental composition, Pd chemical state and functional groups content by the X-ray photoelectron spectroscopy (XPS). The prepared catalysts were tested in a direct formic acid fuel cell (DFAFC) as an anode material. The catalytic activity was correlated with a mean fraction of the total Pd atoms exposed at the surface (FE). The value of FE was calculated from the crystallites size distribution determined by the STEM measurements. Non-linear dependence of a current density versus FE, approaching the maximum at FE≈0.25 suggests that the catalytic process proceeded at Pd nanocrystallites faces, with inactive edges and corners. Pd2 catalyst exhibited highest activity due to its smallest Pd crystallites (3.2 nm), however the absence of Pd crystallites aggregation and low content of carbon in PdC x phase, i.e. x = 4 at.% may also affect the observed.

  15. Strain and grain size of TiO2 nanoparticles from TEM, Raman spectroscopy and XRD: The revisiting of the Williamson-Hall plot method

    Science.gov (United States)

    Kibasomba, Pierre M.; Dhlamini, Simon; Maaza, Malik; Liu, Chuan-Pu; Rashad, Mohamed M.; Rayan, Diaa A.; Mwakikunga, Bonex W.

    2018-06-01

    The Williamson-Hall (W-H) equation, which has been used to obtain relative crystallite sizes and strains between samples since 1962, is revisited. A modified W-H equation is derived which takes into account the Scherrer equation, first published in 1918, (which traditionally gives more absolute crystallite size prediction) and strain prediction from Raman spectra. It is found that W-H crystallite sizes are on average 2.11 ± 0.01 times smaller than the sizes from Scherrer equation. Furthermore the strain from the W-H plots when compared to strain obtained from Raman spectral red-shifts yield factors whose values depend on the phases in the materials - whether anatase, rutile or brookite. Two main phases are identified in the annealing temperatures (350 °C-700 °C) chosen herein - anatase and brookite. A transition temperature of 550 °C has been found for nano-TiO2 to irreversibly transform from brookite to anatase by plotting the Raman peak shifts against the annealing temperatures. The W-H underestimation on the strain in the brookite phase gives W-H/Raman factor of 3.10 ± 0.05 whereas for the anatase phase, one gets 2.46 ± 0.03. The new βtot2cos2θ-sinθ plot and when fitted with a polynomial yield less strain but much better matching with experimental TEM crystallite sizes and the agglomerates than both the traditional Williamson-Hall and the Scherrer methods. There is greater improvement in the model when linearized - that is the βtotcos2θ-sinθ plot rather than the βtot2cos2θ-sinθ plot.

  16. Influence of starting precursors and synthesis methods on the physiochemical properties of zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Gaydhankar, T.R., E-mail: tr.gaydhankar@ncl.res.in [Catalysis Division, National Chemical Laboratory, Pune 411008 (India); Jha, R.K. [Catalysis Division, National Chemical Laboratory, Pune 411008 (India); Nikalje, M.D. [Department of Chemistry, University of Pune, Pune 411 007 (India); Waghmare, K.J. [Catalysis Division, National Chemical Laboratory, Pune 411008 (India)

    2014-07-01

    Graphical abstract: Crystallite size of tetragonal phase of the zirconia samples prepared using different synthesis parameters and precursors as a function of calcination temperature. Surface area values of the zirconia samples calcined at 500 and 700 °C are in given brackets. - Highlights: • Zirconia prepared with modified sol–gel method is less stable compared with zirconia prepared by precipitation method. • Optimized synthesis conditions shifted the glow exotherm to higher temperature range indicating better thermal stability. • Tetragonal-zirconia could be synthesized in cost-effective manner using zirconium oxy-nitrate. • In our studies no co-relation between the surface area and crystallite size was observed. - Abstract: Under identical and judiciously pre-optimized synthesis conditions, the influence of different combinations of zirconium sources and/or post treatment conditions on structural properties, thermal stability, phase composition and morphology of zirconia has been investigated. High surface area tetragonal zirconia could be synthesized in a cost-effective manner from 1 M solution of zirconium oxy-nitrate at pH 11 using aqueous ammonia solution as a precipitant when calcined at 400 °C for 3 h. Irrespective of the preparation method, pH and starting precursor, zirconia samples prepared without digestion contained dominant monoclinic phase with some traces of tetragonal phase when calcined at 700 °C. Even though there is linear decrease in surface area with increase in the crystallite size for each sample as a function of calcination temperature, no co-relation between the surface area and crystallite size could be achieved. SEM images show agglomerated and irregular shape particles between 10 to 20 μm.

  17. Large Break LOCA Accident Management Strategies for Accidents With Large Containment Leaks

    International Nuclear Information System (INIS)

    Sdouz, Gert

    2006-01-01

    The goal of this work is the investigation of the influence of different accident management strategies on the thermal-hydraulics in the containment during a Large Break Loss of Coolant Accident with a large containment leak from the beginning of the accident. The increasing relevance of terrorism suggests a closer look at this kind of severe accidents. Normally the course of severe accidents and their associated phenomena are investigated with the assumption of an intact containment from the beginning of the accident. This intact containment has the ability to retain a large part of the radioactive inventory. In these cases there is only a release via a very small leakage due to the un-tightness of the containment up to cavity bottom melt through. This paper represents the last part of a comprehensive study on the influence of accident management strategies on the source term of VVER-1000 reactors. Basically two different accident sequences were investigated: the 'Station Blackout'- sequence and the 'Large Break LOCA'. In a first step the source term calculations were performed assuming an intact containment from the beginning of the accident and no accident management action. In a further step the influence of different accident management strategies was studied. The last part of the project was a repetition of the calculations with the assumption of a damaged containment from the beginning of the accident. This paper concentrates on the last step in the case of a Large Break LOCA. To be able to compare the results with calculations performed years ago the calculations were performed using the Source Term Code Package (STCP), hydrogen explosions are not considered. In this study four different scenarios have been investigated. The main parameter was the switch on time of the spray systems. One of the results is the influence of different accident management strategies on the source term. In the comparison with the sequence with intact containment it was

  18. Bifurcation of equilibria between with and without a large island in the large helical device

    Energy Technology Data Exchange (ETDEWEB)

    Ohyabu, N; Narushima, Y; Nagayama, Y; Narihara, K; Morisaki, T; Komori, A [National Institute for Fusion Science, Toki, Gifu, 509-5292 (Japan)

    2005-09-01

    A rapid bifurcation of the equilibria with and without a large island (n/m = 1/1) has been observed in the medium to high beta large helical device discharges. A large island imposed by an external resonant field is suddenly suppressed nearly perfectly by the plasma effects when the beta at the {iota}/2{pi} = 1 surface exceeds a critical value. The critical beta value is nearly proportional to the externally imposed resonant field normalized by the main field strength.

  19. P type porous silicon resistivity and carrier transport

    International Nuclear Information System (INIS)

    Ménard, S.; Fèvre, A.; Billoué, J.; Gautier, G.

    2015-01-01

    The resistivity of p type porous silicon (PS) is reported on a wide range of PS physical properties. Al/PS/Si/Al structures were used and a rigorous experimental protocol was followed. The PS porosity (P % ) was found to be the major contributor to the PS resistivity (ρ PS ). ρ PS increases exponentially with P % . Values of ρ PS as high as 1 × 10 9 Ω cm at room temperature were obtained once P % exceeds 60%. ρ PS was found to be thermally activated, in particular, when the temperature increases from 30 to 200 °C, a decrease of three decades is observed on ρ PS . Based on these results, it was also possible to deduce the carrier transport mechanisms in PS. For P % lower than 45%, the conduction occurs through band tails and deep levels in the tissue surrounding the crystallites. When P % overpasses 45%, electrons at energy levels close to the Fermi level allow a hopping conduction from crystallite to crystallite to appear. This study confirms the potential of PS as an insulating material for applications such as power electronic devices

  20. Precipitation-Induced Changes in Microstrain and Its Relation with Hardness and Tempering Parameter in 17-4 PH Stainless Steel

    Science.gov (United States)

    Mahadevan, S.; Manojkumar, R.; Jayakumar, T.; Das, C. R.; Rao, B. P. C.

    2016-06-01

    17-4 PH (precipitation hardening) stainless steel is a soft martensitic stainless steel strengthened by aging at appropriate temperature for sufficient duration. Precipitation of copper particles in the martensitic matrix during aging causes coherency strains which improves the mechanical properties, namely hardness and strength of the matrix. The contributions to X-ray diffraction (XRD) profile broadening due to coherency strains caused by precipitation and crystallite size changes due to aging are separated and quantified using the modified Williamson-Hall approach. The estimated normalized mean square strain and crystallite size are used to explain the observed changes in hardness. Microstructural changes observed in secondary electron images are in qualitative agreement with crystallite size changes estimated from XRD profile analysis. The precipitation kinetics in the age-hardening regime and overaged regime are studied from hardness changes and they follow the Avrami kinetics and Wilson's model, respectively. In overaged condition, the hardness changes are linearly correlated to the tempering parameter (also known as Larson-Miller parameter). Similar linear variation is observed between the normalized mean square strain (determined from XRD line profile analysis) and the tempering parameter, in the incoherent regime which is beyond peak microstrain conditions.

  1. Effect of nanostructure on thermoelectric properties of La0.7Sr0.3MnO3 in 300–600 K temperature range

    Science.gov (United States)

    Singh, Saurabh; Srivastav, Simant Kumar; Patel, Ashutosh; Chatterjee, Ratnamala; Pandey, Sudhir K.

    2018-05-01

    In oxide materials, nanostructuring effect has been found a very promising approach for the enhancement of figure-of-merit, ZT. In the present work, we have synthesized La0.7Sr0.3MnO3 (LSMO) compound using sol-gel method and samples of crystallite size of ∼20, ∼41, and ∼49 nm were obtained by giving different heat treatment. Seebeck coefficient (α), electrical resistivity (ρ), and thermal conductivity (κ) measurements were carried out in 300–600 K temperature range. The systematic change in the values of α from ∼‑19 μV/K to ∼‑24 μV/K and drastic reduction in the values of κ from ∼0.88 W/mK to ∼0.23 W/mK are observed as crystallite size is reduced from 49 nm to 20 nm at ∼600 K. Also, fall in the values of ρ in the paramagnetic (PM) insulator phase (400–600 K) are effectively responsible for the increasing trend in the values of ZT at high temperature. For the crystallite size of 41 nm, the value of ZT at 600 K was found to be ∼0.017.

  2. Effect of Silicon Addition on Microstructure and Mechanical Properties of Chromium and Titanium Based Coatings

    Directory of Open Access Journals (Sweden)

    Luis Carlos Ardila-Téllez

    2014-07-01

    Full Text Available The changes in the microstructure, mechanical properties and residual stresses of AlTiN, AlTiSiN, AlCrN and AlCrSiN coatings, has been studied before and after annealing at 900 ºC and 1100 ºC, using scanning and transmission electron microscopy, along with nano-indentation and X-ray diffraction techniques. The As-deposited coatings show a columnar structure, with a crystallite size between 18 nm and 28 nm. Despite the silicon addition, no effect on the crystallite size refinement was observed.However, the addition of silicon increases hardness, elastic modulus and compressive residual stresses. After annealing at 900 ºC, the crystallite size growth and the residual stress relaxes; therefore, the coating hardness decreases. At 1100 ºC, the oxide layers formed in AlTiN and AlTiSiN, which act as protective layers enhancing oxidation resistance; meanwhile, a complete oxidation of AlCrN and AlCrSiN coatings take place. The Titanium based coatings present some superior mechanical properties and oxidation resistance than the chromium based coatings at 900 ºC and 1100 ºC.

  3. Cobalt Fischer-Tropsch catalysts: influence of cobalt dispersion and titanium oxides promotion

    Energy Technology Data Exchange (ETDEWEB)

    Azib, H

    1996-04-10

    The aim of this work is to study the effect of Sol-Gel preparation parameters which occur in silica supported cobalt catalysts synthesis. These catalysts are particularly used for the waxes production in natural gas processing. The solids have been characterized by several techniques: transmission electron microscopy (TEM), X-ray absorption near edge spectroscopy (XANES), programmed temperature reduction (TPR), infrared spectroscopy (IR), ultraviolet spectroscopy (UV), Magnetism, thermodesorption of H{sub 2} (TPD). The results indicate that the control of the cobalt dispersion and oxide phases nature is possible by modifying Sol-Gel parameters. The catalytic tests in Fischer-Tropsch synthesis were conducted on a pilot unit under pressure (20 atm) and suggested that turnover rates were independent of Co crystallite size, Co phases in the solids (Co deg., cobalt silicate) and titanium oxide promotion. On the other methane, the C{sub 3}{sup +} hydrocarbon selectivity is increased with increasing crystallite size. Inversely, the methane production is favoured by very small crystallites, cobalt silicate increase and titanium addition. However, the latter, used as a cobalt promoter, has a benefic effect on the active phase stability during the synthesis. (author). 149 refs., 102 figs., 71 tabs.

  4. Impact of crystalline defects and size on X-ray line broadening: A phenomenological approach for tetragonal SnO{sub 2} nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Muhammed Shafi, P.; Chandra Bose, A., E-mail: acbose@nitt.edu [Nanomaterials Laboratory, Department of Physics, National Institute of Technology, Trichy – 620015 (India)

    2015-05-15

    Nanocrystalline tin oxide (SnO{sub 2}) powders with different grain size were prepared by chemical precipitation method. The reaction was carried out by varying the period of hydrolysis and the as-prepared samples were annealed at different temperatures. The samples were characterized using X-ray powder diffractometer and transmission electron microscopy. The microstrain and crystallite size were calculated for all the samples by using Williamson-Hall (W-H) models namely, isotropic strain model (ISM), anisotropic strain model (ASM) and uniform deformation energy density model (UDEDM). The morphology and particle size were determined using TEM micrographs. The directional dependant young’s modulus was modified as an equation relating elastic compliances (s{sub ij}) and Miller indices of the lattice plane (hkl) for tetragonal crystal system and also the equation for elastic compliance in terms of stiffness constants was derived. The changes in crystallite size and microstrain due to lattice defects were observed while varying the hydrolysis time and the annealing temperature. The dependence of crystallite size on lattice strain was studied. The results were correlated with the available studies on electrical properties using impedance spectroscopy.

  5. Characterization of WO3-SnO2 Nanocomposites and Application in Humidity Sensing

    Directory of Open Access Journals (Sweden)

    N. K. Pandey

    2011-02-01

    Full Text Available Pellet samples of WO3-SnO2 nanocomposite in the weight % ratio of 85:15 have been prepared and annealed at temperatures 300-600 °C for 3 hours. When exposed to humidity, the sample shows maximum sensitivity of 23.41 MΩ/%RH for the annealing temperature 600 °C. For this annealing temperature of 600 °C, the sample shows low ageing effect after four months. The hysteresis (between humidification and desiccation, measured in the RH range of 15–90 % RH for the annealing temperature of 600 °C is less than 8 % RH. Activation energy measured from Arrhenius plot in 50 to 300 °C and 300 to 600 °C range have been found to be 0.12 and 0.54 eV respectively. The response time and recovery time for the sample annealed at 600 °C are 121 seconds and 912 seconds respectively. The grain size and crystallite size of the pellets are found to be in the nanometer range. An observation of the crystallite size and grain size would suggest that smaller crystallites are getting agglomerated to form larger grains.

  6. Synthesis and Characterization of Some Alkaline-Earth-Oxide Nanoparticles

    Science.gov (United States)

    Singh, Jitendra Pal; Lim, Weon Cheol; Won, Sung Ok; Song, Jonghan; Chae, Keun Hwa

    2018-04-01

    The present work reports the synthesis of MgO and CaO nanoparticles by using the sol-gel autocombustion method. The annealing of the precursor at 1200 °C was observed to lead the formation of MgO nanoparticles having average crystallite size of 31 nm. Annealing the precursor at same temperature produced materials having a CaO phase with a minor impure phase of calcium carbonate ( 3%). The crystallite size corresponding to the CaO phase was 38 nm. A change of thermal history in the precursor was observed not to result in an improvement of the CaO phase. The change of thermal history in the precursor gave rise to mixed phases of CaCO3 and Ca(OH)2 rather than the phase of CaO. Further, annealing at 1200 °C for 12 h resulted in the formation of the CaO phase along with almost 1 - 5% of calcium hydroxide as an impurity phase. X-ray absorption spectroscopic measurements carried out on these materials revealed that the local electronic/atomic structure of these oxides was not only affected by the impurity phases but also influenced by the carbaneous impurities attached to the crystallites.

  7. Solid-state synthesis in the system Na0.8NbyW1-yO3 with 0≤y≤0.4: A new phase, Na0.5NbO2.75, with perovskite-type structure

    International Nuclear Information System (INIS)

    Debnath, Tapas; Ruescher, Claus H.; Gesing, Thorsten M.; Koepke, Juergen; Hussain, Altaf

    2008-01-01

    Series of compounds in the system Na x Nb y W 1-y O 3 were prepared according to the appropriate molar ratio of Na 2 WO 4 , WO 3 , WO 2 and Nb 2 O 5 with x=0.80 and 0.0≤y≤0.4 at 600 deg. C in evacuated silica glass tubes. These compounds were investigated by X-ray powder diffraction, optical microscopy, microprobe analysis, Raman and optical microspectroscopy. A y-dependent separation into three distinct coloured crystallites with cubic perovskite-type structures is observed: (i) red-orange crystallites with composition Na x WO 3 with slightly decreasing x (i.e. 0.8-0.72) with increasing nominal y, (ii) bluish solid solution of composition Na x Nb y W 1-y O 3 and (iii) white crystallites of a new phase having defect perovskite-type structure with composition Na 0.5 NbO 2.75 . - Graphical abstract: Optical micrograph of a polished sample of nominal composition Na 0.8 Nb 0.4 W 0.6 O 3 showing a mixture of three different coloured crystals: red, light blue and white. The scale bar is 30 μm

  8. Mechanically Strain-Induced Modification of Selenium Powders in the Amorphization Process

    International Nuclear Information System (INIS)

    Fuse, Makoto; Shirakawa, Yoshiyuki; Shimosaka, Atsuko; Hidaka, Jusuke

    2003-01-01

    For the fabrication of particles designed in the nanoscale structure, or the nanostructural modification of particles using mechanical grinding process, selenium powders ground by a planetary ball mill at various rotational speeds have been investigated. Structural analyses, such as particle size distributions, crystallite sizes, lattice strains and nearest neighbour distances were performed using X-ray diffraction, scanning electron microscopy and dynamical light scattering.By grinding powder particles became spherical composites consisting of nanocrystalline and amorphous phase, and had a distribution with the average size of 2.7 μm. Integral intensities of diffraction peaks of annealed crystal selenium decreased with increasing grinding time, and these peaks broadened due to lattice strains and reducing crystallite size during the grinding. The ground powder at 200 rpm did not have the lattice strain and showed amorphization for the present grinding periods. It indicates that the amorphization of Se by grinding accompanies the lattice strain, and the lattice strain arises from a larger energy concerning intermolecular interaction. In this process, the impact energy is spent on thermal and structural changes according to energy accumulation in macroscopic (the particle size distribution) and microscopic (the crystallite size and the lattice strain) range

  9. Mechanical and microstructural characterization of dispersion strengthened Al-C system nanocomposites

    International Nuclear Information System (INIS)

    Santos-Beltran, A.; Gallegos-Orozco, V.; Reyes, R. Goytia; Miki-Yoshida, M.; Estrada-Guel, I.; Martinez-Sanchez, R.

    2010-01-01

    Al and different amounts of C and C-Cu mixtures were used to produce Al-C and Al-C-Cu powder samples by mechanical milling. Microhardness tests were carried out to evaluate the mechanical properties of the nanocomposites in the as-milled condition. In general, the measured values were considerably higher than pure Al. In order to determine the causes of this hardening, the crystallite size and dislocation density were measured by means of X-ray analyses coupled with a convolutional multiple whole profile (CMWP) fitting program and a comparison with atomic force microscopy (AFM) observations. In Al-C samples, the hardening is mainly due to the decrease of the crystallite size, however for the Al-C-Cu, an additional strengthening mechanism appears and it seems that it is due by a dispersion of graphite nanoparticles in the Al matrix. The strengthening contributions of dislocation density, crystallite size and particle dispersion were modeled by superposing of every single contribution to strengthening (via hardness analyses). We found a direct relationship between the mechanical properties and the nominal amount of C-Cu, where Cu apparently acts as C nanoparticles integration and dispersion agent.

  10. Synthesis and structural studies of copper sulfide nanocrystals

    Directory of Open Access Journals (Sweden)

    Peter A. Ajibade

    Full Text Available We report the synthesis and structural studies of copper sulfide nanocrystals from copper(II dithiocarbamate single molecule precursors. The optical studies of the as-prepared copper sulfide nanoparticles were carried out using UV–Visible and photoluminescence spectroscopy. The absorption spectra show absorption band edges at 287 nm and exhibit considerable blue shift that could be ascribed to the quantum confinement effects as a result of the small crystallite sizes of the nanoparticles and the photoluminescence spectra show emission curves that are red shifted with respect to the absorption band edges. The structural studies were carried out using powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and atomic force microscopy. The XRD patterns revealed the formation of hexagonal structure of covellite CuS with estimated crystallite sizes of 17.3–18.6 nm. The TEM images showed particles with almost spherical or rod shapes with average crystallite sizes of 3–9.8 nm. SEM images showed morphology with ball-like microsphere on the surfaces and EDS spectra confirmed the presence of CuS nanoparticles. Keywords: CuS, Dithiocarbamate, Nanoparticles, Electron microscopy, AFM

  11. Protein-free formation of bone-like apatite: New insights into the key role of carbonation.

    Science.gov (United States)

    Deymier, Alix C; Nair, Arun K; Depalle, Baptiste; Qin, Zhao; Arcot, Kashyap; Drouet, Christophe; Yoder, Claude H; Buehler, Markus J; Thomopoulos, Stavros; Genin, Guy M; Pasteris, Jill D

    2017-05-01

    The nanometer-sized plate-like morphology of bone mineral is necessary for proper bone mechanics and physiology. However, mechanisms regulating the morphology of these mineral nanocrystals remain unclear. The dominant hypothesis attributes the size and shape regulation to organic-mineral interactions. Here, we present data supporting the hypothesis that physicochemical effects of carbonate integration within the apatite lattice control the morphology, size, and mechanics of bioapatite mineral crystals. Carbonated apatites synthesized in the absence of organic molecules presented plate-like morphologies and nanoscale crystallite dimensions. Experimentally-determined crystallite size, lattice spacing, solubility and atomic order were modified by carbonate concentration. Molecular dynamics (MD) simulations and density functional theory (DFT) calculations predicted changes in surface energy and elastic moduli with carbonate concentration. Combining these results with a scaling law predicted the experimentally observed scaling of size and energetics with carbonate concentration. The experiments and models describe a clear mechanism by which crystal dimensions are controlled by carbonate substitution. Furthermore, the results demonstrate that carbonate substitution is sufficient to drive the formation of bone-like crystallites. This new understanding points to pathways for biomimetic synthesis of novel, nanostructured biomaterials. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Large Scale Self-Organizing Information Distribution System

    National Research Council Canada - National Science Library

    Low, Steven

    2005-01-01

    This project investigates issues in "large-scale" networks. Here "large-scale" refers to networks with large number of high capacity nodes and transmission links, and shared by a large number of users...

  13. Large transverse momentum hadronic processes

    International Nuclear Information System (INIS)

    Darriulat, P.

    1977-01-01

    The possible relations between deep inelastic leptoproduction and large transverse momentum (psub(t)) processes in hadronic collisions are usually considered in the framework of the quark-parton picture. Experiments observing the structure of the final state in proton-proton collisions producing at least one large transverse momentum particle have led to the following conclusions: a large fraction of produced particles are uneffected by the large psub(t) process. The other products are correlated to the large psub(t) particle. Depending upon the sign of scalar product they can be separated into two groups of ''towards-movers'' and ''away-movers''. The experimental evidence are reviewed favouring such a picture and the properties are discussed of each of three groups (underlying normal event, towards-movers and away-movers). Some phenomenological interpretations are presented. The exact nature of away- and towards-movers must be further investigated. Their apparent jet structure has to be confirmed. Angular correlations between leading away and towards movers are very informative. Quantum number flow, both within the set of away and towards-movers, and between it and the underlying normal event, are predicted to behave very differently in different models

  14. Phenomenology of large Nc QCD

    International Nuclear Information System (INIS)

    Lebed, R.F.

    1999-01-01

    These lectures are designed to introduce the methods and results of large N c QCD in a presentation intended for nuclear and particle physicists alike. Beginning with definitions and motivations of the approach, we demonstrate that all quark and gluon Feynman diagrams are organized into classes based on powers of 1/N c . We then show that this result can be translated into definite statements about mesons and baryons containing arbitrary numbers of constituents. In the mesons, numerous well-known phenomenological properties follow as immediate consequences of simply counting powers of N c , while for the baryons, quantitative large N c analyses of masses and other properties are seen to agree with experiment, even when 'large' N c is set equal to its observed value of 3. Large N c reasoning is also used to explain some simple features of nuclear interactions. (author)

  15. Phenomenology of large Nc QCD

    International Nuclear Information System (INIS)

    Richard Lebed

    1998-01-01

    These lectures are designed to introduce the methods and results of large N c QCD in a presentation intended for nuclear and particle physicists alike. Beginning with definitions and motivations of the approach, they demonstrate that all quark and gluon Feynman diagrams are organized into classes based on powers of 1/N c . They then show that this result can be translated into definite statements about mesons and baryons containing arbitrary numbers of constituents. In the mesons, numerous well-known phenomenological properties follow as immediate consequences of simply counting powers of N c , while for the baryons, quantitative large N c analyses of masses and other properties are seen to agree with experiment, even when ''large'' N c is set equal to its observed value of 3. Large N c reasoning is also used to explain some simple features of nuclear interactions

  16. Study of the effect of residual stress on the microstrain of the crystalline lattice and on the crystallite size of steel Cr-Si-V by shot peening; Estudo do efeito da tensão residual na microdeformação da rede cristalina e no tamanho de cristalito em aço Cr-Si-V jateado com granalhas de aço

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Rene Ramos de

    2016-07-01

    observing the results, we can notice the difference between the values obtained in the deformations, however, the emphasis of this work was on the characteristics of the distribution profiles and not on the absolute values. In addition, the study of the distribution of the mean crystallite size along the thickness of the X-ray diffraction profile was provided and the results showed that this distribution varies inversely with microstrain. The relationship between the mean crystallite size and the variation of the interplanar distances corresponds directly to changes in the densities of dislocations occurring in the material, which in turn are linked to the microstrain of the crystalline lattice. As a complement to the work, the stress concentration factor and fatigue tests of the material were analyzed. The stress concentration factor did not change according to the use of the S330 and S390 grit, both being applied in the same blasting regime. Fatigue tests indicated that pretensioning increases the useful life of the cyclic stresses of the material studied. (author)

  17. Workflow management in large distributed systems

    International Nuclear Information System (INIS)

    Legrand, I; Newman, H; Voicu, R; Dobre, C; Grigoras, C

    2011-01-01

    The MonALISA (Monitoring Agents using a Large Integrated Services Architecture) framework provides a distributed service system capable of controlling and optimizing large-scale, data-intensive applications. An essential part of managing large-scale, distributed data-processing facilities is a monitoring system for computing facilities, storage, networks, and the very large number of applications running on these systems in near realtime. All this monitoring information gathered for all the subsystems is essential for developing the required higher-level services—the components that provide decision support and some degree of automated decisions—and for maintaining and optimizing workflow in large-scale distributed systems. These management and global optimization functions are performed by higher-level agent-based services. We present several applications of MonALISA's higher-level services including optimized dynamic routing, control, data-transfer scheduling, distributed job scheduling, dynamic allocation of storage resource to running jobs and automated management of remote services among a large set of grid facilities.

  18. Workflow management in large distributed systems

    Science.gov (United States)

    Legrand, I.; Newman, H.; Voicu, R.; Dobre, C.; Grigoras, C.

    2011-12-01

    The MonALISA (Monitoring Agents using a Large Integrated Services Architecture) framework provides a distributed service system capable of controlling and optimizing large-scale, data-intensive applications. An essential part of managing large-scale, distributed data-processing facilities is a monitoring system for computing facilities, storage, networks, and the very large number of applications running on these systems in near realtime. All this monitoring information gathered for all the subsystems is essential for developing the required higher-level services—the components that provide decision support and some degree of automated decisions—and for maintaining and optimizing workflow in large-scale distributed systems. These management and global optimization functions are performed by higher-level agent-based services. We present several applications of MonALISA's higher-level services including optimized dynamic routing, control, data-transfer scheduling, distributed job scheduling, dynamic allocation of storage resource to running jobs and automated management of remote services among a large set of grid facilities.

  19. Structural and dielectric studies of Ce doped BaSnO3 perovskite nanostructures

    Science.gov (United States)

    Angel, S. Lilly; Deepa, K.; Rajamanickam, N.; Jayakumar, K.; Ramachandran, K.

    2018-04-01

    Undoped and Cerium (Ce) doped BaSnO3(BSO) nanostructures were synthesized by co-precipitation method. The cubic structure and perovskite phase were confirmed by X-ray diffraction (XRD). The crystallite size of BSO is 41nm and when Ce ion concentration is increased, the crystallite sizesdecreased. The nanocube, nanocuboids and nanorods are observed from SEM analysis. The purity of the undoped and doped samples are confirmed by EDS spectrum. For larger defects, wide band gap was obtained from UV-Vis and PL spectrum. The dielectric constants are increased at low frequencies when Ce impurities are introduced in the BSO matrix at Sn site.

  20. The effect of grooves in amorphous substrates on the orientation of metal deposits. I - Carbon substrates

    Science.gov (United States)

    Anton, R.; Poppa, H.; Flanders, D. C.

    1982-01-01

    The graphoepitaxial alignment of vapor-deposited discrete metal crystallites is investigated in the nucleation and growth stages and during annealing by in situ UHV/TEM techniques. Various stages of nucleation, growth and coalescence of vapor deposits of Au, Ag, Pb, Sn, and Bi on amorphous, topographically structured C substrates are analyzed by advanced dark-field techniques to detect preferred local orientations. It is found that the topography-induced orientation of metal crystallites depends strongly on their mobility and their respective tendency to develop pronounced crystallographic shapes. Lowering of the average surface free energies and increasing the crystallographic surface energy anisotropies cause generally improved graphoepitaxial alignments.

  1. Analysis of Polymorphic Nanocrystals of TiO2 by X-Ray Rietveld Refinement and High-Resolution Transmission Electron Microscopy: Acetaldehyde Decomposition

    Directory of Open Access Journals (Sweden)

    R. Carrera

    2008-01-01

    Full Text Available In this work, TiO2 nanocrystals were synthesized by the sol-gel method. These materials were annealed at 200 and 500∘C; and characterized by the XRD-Rietveld refinement; and by BET and TEM. As for the low-temperature-treated sample (200∘C, nanocrystals with small crystallite sizes (7 nm and high abundance of anatase, coexisting with the brookite phase, were obtained. Meanwhile, the sample annealed at 500∘C showed an increased crystallite size (22 nm and an important polymorphic increment. The sample annealed at 200∘C showed a high activity in the photocatalytic decomposition of acetaldehyde.

  2. Organic photovoltaic cells utilizing ultrathin sensitizing layer

    Science.gov (United States)

    Forrest, Stephen R [Ann Arbor, MI; Yang, Fan [Piscataway, NJ; Rand, Barry P [Somers, NY

    2011-09-06

    A photosensitive device includes a plurality of organic photoconductive materials disposed in a stack between a first electrode and a second electrode, including a first continuous layer of donor host material, a second continuous layer of acceptor host material, and at least one other organic photoconductive material disposed as a plurality of discontinuous islands between the first continuous layer and the second continuous layer. Each of these other photoconductive materials has an absorption spectra different from the donor host material and the acceptor host material. Preferably, each of the discontinuous islands consists essentially of a crystallite of the respective organic photoconductive material, and more preferably, the crystallites are nanocrystals.

  3. Defect studies of ZnO films prepared by pulsed laser deposition on various substrates

    International Nuclear Information System (INIS)

    Melikhova, O; Čížek, J; Procházka, I; Kužel, R; Novotný, M; Bulír, J; Lancok, J; Anwand, W; Brauer, G; Connolly, J; McCarthy, E; Krishnamurthy, S; Mosnier, J-P

    2013-01-01

    ZnO thin films deposited on various substrates were characterized by slow positron implantation spectroscopy (SPIS) combined with X-ray diffraction (XRD). All films studied exhibit wurtzite structure and crystallite size 20–100 nm. The mosaic spread of crystallites is relatively small for the films grown on single crystalline substrates while it is substantial for the film grown on amorphous substrate. SPIS investigations revealed that ZnO films deposited on single crystalline substrates exhibit significantly higher density of defects than the film deposited on amorphous substrate. This is most probably due to a higher density of misfit dislocations, which compensate for the lattice mismatch between the film and the substrate.

  4. Dynamic fatigue on repolarization of lead zirconate-titanate base ceramics with various ferroelectric hardness

    International Nuclear Information System (INIS)

    Gavrilyachenko, V.G.; Semenchev, A.F.; Sklyarova, E.N.; Kuznetsova, E.M.

    2006-01-01

    One studied experimentally changes of the residual polarization in lead zirconate-titanate base ceramics with various ferroelectric hardness under the effect of a strong varying field. The twinning and untwinning of crystallites accompanying repolarization is assumed to be the basic mechanism of propagation of the crystalline structure defects governing the fatigue rates of the ferroelectric-soft ceramics. In ferroelectric-hard ceramics crystallites the stable configurations of mechanical twins, the result of the secondary twinning, are formed when the hysteresis loop is formed. At repolarization in the mentioned structures one observes no motion of the twin boundaries, and the fatigue rates are low ones [ru

  5. Electromechanical properties of a textured ceramic material in the (1 - x)PMN- xPT system: Simulation based on the effective-medium method

    Science.gov (United States)

    Aleshin, V. I.; Raevskiĭ, I. P.; Sitalo, E. I.

    2008-11-01

    A complete set of dielectric, piezoelectric, and elastic parameters for the textured ceramic material 0.67PMN-0.33PT is calculated by the self-consistency method with due regard for the anisotropy and piezoelectric activity of the medium. It is shown that the best piezoelectric properties corresponding to those of a single crystal are observed for the ceramic material with a texture in which all crystallites are oriented parallel to the [001] direction of the parent perovskite cubic cell. The simplest models of the polarization of an untextured ceramic material with a random initial orientation of crystallites are considered. The results obtained are compared with experimental data.

  6. In situ synchrotron X-ray diffraction study of surface scale formation during CO2 corrosion of carbon steel at temperatures up to 90 oC

    International Nuclear Information System (INIS)

    Ingham, B.; Ko, M.; Kear, G.; Kappen, P.; Laycock, N.; Kimpton, J.A.; Williams, D.E.

    2010-01-01

    In situ synchrotron X-ray diffraction was used to follow the formation of corrosion product scales on carbon steel in CO 2 saturated brine at temperatures from 40 to 90 o C. The corrosion process was accelerated by applying a small anodic current, and in selected tests a scale inhibitor, amino trimethylene phosphonic acid (ATMPA), was added. Siderite was identified as the major phase in the scale formed in all conditions. With increasing temperature, the scale formation rate increased, while the scale thickness and crystallite size decreased. Above 60 o C, the scale became increasingly protective. The scale thickness and crystallite size decreased with increasing ATMPA concentration.

  7. Molecular dynamics modeling of bonding two materials by atomic scale friction stir welding at different process parameters

    Science.gov (United States)

    Konovalenko S., Iv.; Psakhie, S. G.

    2017-12-01

    Using the molecular dynamics method, we simulated the atomic scale butt friction stir welding on two crystallites and varied the onset FSW tool plunge depth. The effects of the plunge depth value on the thermomechanical evolution of nanosized crystallites and mass transfer in the course of FSW have been studied. The increase of plunge depth values resulted in more intense heating and reducing the plasticized metal resistance to the tool movement. The mass transfer intensity was hardly dependent on the plunge depth value. The plunge depth was recommended to be used as a FSW process control parameter in addition to the commonly used ones.

  8. Reliability of large and complex systems

    CERN Document Server

    Kolowrocki, Krzysztof

    2014-01-01

    Reliability of Large and Complex Systems, previously titled Reliability of Large Systems, is an innovative guide to the current state and reliability of large and complex systems. In addition to revised and updated content on the complexity and safety of large and complex mechanisms, this new edition looks at the reliability of nanosystems, a key research topic in nanotechnology science. The author discusses the importance of safety investigation of critical infrastructures that have aged or have been exposed to varying operational conditions. This reference provides an asympt

  9. Large transverse momentum phenomena

    International Nuclear Information System (INIS)

    Brodsky, S.J.

    1977-09-01

    It is pointed out that it is particularly significant that the quantum numbers of the leading particles are strongly correlated with the quantum numbers of the incident hadrons indicating that the valence quarks themselves are transferred to large p/sub t/. The crucial question is how they get there. Various hadron reactions are discussed covering the structure of exclusive reactions, inclusive reactions, normalization of inclusive cross sections, charge correlations, and jet production at large transverse momentum. 46 references

  10. [Large vessel vasculitides].

    Science.gov (United States)

    Morović-Vergles, Jadranka; Puksić, Silva; Gracanin, Ana Gudelj

    2013-01-01

    Large vessel vasculitis includes Giant cell arteritis and Takayasu arteritis. Giant cell arteritis is the most common form of vasculitis affect patients aged 50 years or over. The diagnosis should be considered in older patients who present with new onset of headache, visual disturbance, polymyalgia rheumatica and/or fever unknown cause. Glucocorticoides remain the cornerstone of therapy. Takayasu arteritis is a chronic panarteritis of the aorta ant its major branches presenting commonly in young ages. Although all large arteries can be affected, the aorta, subclavian and carotid arteries are most commonly involved. The most common symptoms included upper extremity claudication, hypertension, pain over the carotid arteries (carotidynia), dizziness and visual disturbances. Early diagnosis and treatment has improved the outcome in patients with TA.

  11. Physics with large extra dimensions

    Indian Academy of Sciences (India)

    can then be accounted by the existence of large internal dimensions, in the sub- ... strongly coupled heterotic theory with one large dimension is described by a weakly ..... one additional U(1) factor corresponding to an extra 'U(1)' D-brane is ...

  12. 27 CFR 19.915 - Large plants.

    Science.gov (United States)

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Large plants. 19.915... OF THE TREASURY LIQUORS DISTILLED SPIRITS PLANTS Distilled Spirits For Fuel Use Permits § 19.915 Large plants. Any person wishing to establish a large plant shall make application for and obtain an...

  13. Political consultation and large-scale research

    International Nuclear Information System (INIS)

    Bechmann, G.; Folkers, H.

    1977-01-01

    Large-scale research and policy consulting have an intermediary position between sociological sub-systems. While large-scale research coordinates science, policy, and production, policy consulting coordinates science, policy and political spheres. In this very position, large-scale research and policy consulting lack of institutional guarantees and rational back-ground guarantee which are characteristic for their sociological environment. This large-scale research can neither deal with the production of innovative goods under consideration of rentability, nor can it hope for full recognition by the basis-oriented scientific community. Policy consulting knows neither the competence assignment of the political system to make decisions nor can it judge succesfully by the critical standards of the established social science, at least as far as the present situation is concerned. This intermediary position of large-scale research and policy consulting has, in three points, a consequence supporting the thesis which states that this is a new form of institutionalization of science: These are: 1) external control, 2) the organization form, 3) the theoretical conception of large-scale research and policy consulting. (orig.) [de

  14. MPQS with three large primes

    NARCIS (Netherlands)

    Leyland, P.; Lenstra, A.K.; Dodson, B.; Muffett, A.; Wagstaff, S.; Fieker, C.; Kohel, D.R.

    2002-01-01

    We report the factorization of a 135-digit integer by the triple-large-prime variation of the multiple polynomial quadratic sieve. Previous workers [6][10] had suggested that using more than two large primes would be counterproductive, because of the greatly increased number of false reports from

  15. Experimental Benchmarking of Pu Electronic Structure

    International Nuclear Information System (INIS)

    Tobin, J.G.; Moore, K.T.; Chung, B.W.; Wall, M.A.; Schwartz, A.J.; Ebbinghaus, B.B.; Butterfield, M.T.; Teslich, N.E. Jr.; Bliss, R.A.; Morton, S.A.; Yu, S.W.; Komesu, T.; Waddill, G.D.; van der Laan, G.; Kutepov, A.L.

    2008-01-01

    The standard method to determine the band structure of a condensed phase material is to (1) obtain a single crystal with a well defined surface and (2) map the bands with angle resolved photoelectron spectroscopy (occupied or valence bands) and inverse photoelectron spectroscopy (unoccupied or conduction bands). Unfortunately, in the case of Pu, the single crystals of Pu are either nonexistent, very small and/or having poorly defined surfaces. Furthermore, effects such as electron correlation and a large spin-orbit splitting in the 5f states have further complicated the situation. Thus, we have embarked upon the utilization of unorthodox electron spectroscopies, to circumvent the problems caused by the absence of large single crystals of Pu with well-defined surfaces. Our approach includes the techniques of resonant photoelectron spectroscopy, x-ray absorption spectroscopy, electron energy loss spectroscopy, Fano Effect measurements, and Bremstrahlung Isochromat Spectroscopy, including the utilization of micro-focused beams to probe single-crystallite regions of polycrystalline Pu samples.

  16. Sample-path large deviations in credit risk

    NARCIS (Netherlands)

    Leijdekker, V.J.G.; Mandjes, M.R.H.; Spreij, P.J.C.

    2011-01-01

    The event of large losses plays an important role in credit risk. As these large losses are typically rare, and portfolios usually consist of a large number of positions, large deviation theory is the natural tool to analyze the tail asymptotics of the probabilities involved. We first derive a

  17. Decentralized Large-Scale Power Balancing

    DEFF Research Database (Denmark)

    Halvgaard, Rasmus; Jørgensen, John Bagterp; Poulsen, Niels Kjølstad

    2013-01-01

    problem is formulated as a centralized large-scale optimization problem but is then decomposed into smaller subproblems that are solved locally by each unit connected to an aggregator. For large-scale systems the method is faster than solving the full problem and can be distributed to include an arbitrary...

  18. Entanglement transitions induced by large deviations

    Science.gov (United States)

    Bhosale, Udaysinh T.

    2017-12-01

    The probability of large deviations of the smallest Schmidt eigenvalue for random pure states of bipartite systems, denoted as A and B , is computed analytically using a Coulomb gas method. It is shown that this probability, for large N , goes as exp[-β N2Φ (ζ ) ] , where the parameter β is the Dyson index of the ensemble, ζ is the large deviation parameter, while the rate function Φ (ζ ) is calculated exactly. Corresponding equilibrium Coulomb charge density is derived for its large deviations. Effects of the large deviations of the extreme (largest and smallest) Schmidt eigenvalues on the bipartite entanglement are studied using the von Neumann entropy. Effect of these deviations is also studied on the entanglement between subsystems 1 and 2, obtained by further partitioning the subsystem A , using the properties of the density matrix's partial transpose ρ12Γ. The density of states of ρ12Γ is found to be close to the Wigner's semicircle law with these large deviations. The entanglement properties are captured very well by a simple random matrix model for the partial transpose. The model predicts the entanglement transition across a critical large deviation parameter ζ . Log negativity is used to quantify the entanglement between subsystems 1 and 2. Analytical formulas for it are derived using the simple model. Numerical simulations are in excellent agreement with the analytical results.

  19. Measuring happiness in large population

    Science.gov (United States)

    Wenas, Annabelle; Sjahputri, Smita; Takwin, Bagus; Primaldhi, Alfindra; Muhamad, Roby

    2016-01-01

    The ability to know emotional states for large number of people is important, for example, to ensure the effectiveness of public policies. In this study, we propose a measure of happiness that can be used in large scale population that is based on the analysis of Indonesian language lexicons. Here, we incorporate human assessment of Indonesian words, then quantify happiness on large-scale of texts gathered from twitter conversations. We used two psychological constructs to measure happiness: valence and arousal. We found that Indonesian words have tendency towards positive emotions. We also identified several happiness patterns during days of the week, hours of the day, and selected conversation topics.

  20. Large-scale energy consumers pay less

    International Nuclear Information System (INIS)

    Denneman, A.

    2012-01-01

    The price of electricity in the Netherlands rose with 6 percent in the first quarter of 2012, whereas large business consumers are paying less. The natural gas price has risen with about 10 percent in the last year, both for households and for large business consumers. Meanwhile, households are paying twice as much for electricity and gas as large business consumers. [nl

  1. Automating large-scale reactor systems

    International Nuclear Information System (INIS)

    Kisner, R.A.

    1985-01-01

    This paper conveys a philosophy for developing automated large-scale control systems that behave in an integrated, intelligent, flexible manner. Methods for operating large-scale systems under varying degrees of equipment degradation are discussed, and a design approach that separates the effort into phases is suggested. 5 refs., 1 fig

  2. Querying Large Biological Network Datasets

    Science.gov (United States)

    Gulsoy, Gunhan

    2013-01-01

    New experimental methods has resulted in increasing amount of genetic interaction data to be generated every day. Biological networks are used to store genetic interaction data gathered. Increasing amount of data available requires fast large scale analysis methods. Therefore, we address the problem of querying large biological network datasets.…

  3. Large-scale pool fires

    Directory of Open Access Journals (Sweden)

    Steinhaus Thomas

    2007-01-01

    Full Text Available A review of research into the burning behavior of large pool fires and fuel spill fires is presented. The features which distinguish such fires from smaller pool fires are mainly associated with the fire dynamics at low source Froude numbers and the radiative interaction with the fire source. In hydrocarbon fires, higher soot levels at increased diameters result in radiation blockage effects around the perimeter of large fire plumes; this yields lower emissive powers and a drastic reduction in the radiative loss fraction; whilst there are simplifying factors with these phenomena, arising from the fact that soot yield can saturate, there are other complications deriving from the intermittency of the behavior, with luminous regions of efficient combustion appearing randomly in the outer surface of the fire according the turbulent fluctuations in the fire plume. Knowledge of the fluid flow instabilities, which lead to the formation of large eddies, is also key to understanding the behavior of large-scale fires. Here modeling tools can be effectively exploited in order to investigate the fluid flow phenomena, including RANS- and LES-based computational fluid dynamics codes. The latter are well-suited to representation of the turbulent motions, but a number of challenges remain with their practical application. Massively-parallel computational resources are likely to be necessary in order to be able to adequately address the complex coupled phenomena to the level of detail that is necessary.

  4. Crocodilian Nest in a Late Cretaceous Sauropod Hatchery from the Type Lameta Ghat Locality, Jabalpur, India.

    Directory of Open Access Journals (Sweden)

    Rahul Srivastava

    Full Text Available The well-known Late Cretaceous Lameta Ghat locality (Jabalpur, India provides a window of opportunity to study a large stable, near shore sandy beach, which was widely used by sauropod dinosaurs as a hatchery. In this paper, we revisit the eggs and eggshell fragments previously assigned to lizards from this locality and reassign them to crocodylomorphs. Several features point to a crocodilian affinity, including a subspherical to ellipsoidal shape, smooth, uneven external surface, discrete trapezoid shaped shell units with wide top and narrow base, basal knobs and wedge shaped crystallites showing typical inverted triangular extinction under crossed nicols. The crocodylomorph eggshell material presented in this paper adds to the skeletal data of these most probably Cretaceous-Eocene dryosaurid crocodiles.

  5. Chemical synthesis of composite HML / PDMcT / PAni and its application as the trhiodan adsorbent in aqueous solutions

    International Nuclear Information System (INIS)

    Girotto, L.G.; Pacheco, I.; Freitas, L.L. de; Oliveira, R.S.; Amaral, F.A. do; Canobre, S.C.

    2016-01-01

    The mixed hydroxide lamellar [Co -Al- Cl] was synthesize by the co- precipitation method constant pH 8. The synthesis composite HML/PDMcT/PAni was carried out via chemical. The DRX composite HML/PDMcT/PAni showed that one amorphicity in the conductor polymer doesn't hid the diffraction peaks characteristic of HML. The MEV micrographs of composite HDL / PDMcT / PAni showed a large number of crystallites compacts with several shapes characteristic to PDMcT and nanofibers of polyaniline indicating an association between the different constituents forming the composite. The results of the adsorption was 98% of the pesticide in the composite HML / PDMcT / PAni , the composite can contribute so significantly to one Thiodon withdrawal in contaminated pesticide waters. (author)

  6. Chemical synthesis of composite HML / PDMcT / PAni and its application as the trhiodan adsorbent in aqueous solutions; Sintese quimica de compositos de HML/PDMcT/PAni e sua aplicacao como adsorvente do trhiodan em solucoes aquosas

    Energy Technology Data Exchange (ETDEWEB)

    Girotto, L.G.; Pacheco, I.; Freitas, L.L. de; Oliveira, R.S.; Amaral, F.A. do; Canobre, S.C., E-mail: aylagg.eab@gmail.com [Universidade Federal de Uberlandia (UFU), MG (Brazil). Instituto de Quimica

    2016-07-01

    The mixed hydroxide lamellar [Co -Al- Cl] was synthesize by the co- precipitation method constant pH 8. The synthesis composite HML/PDMcT/PAni was carried out via chemical. The DRX composite HML/PDMcT/PAni showed that one amorphicity in the conductor polymer doesn't hid the diffraction peaks characteristic of HML. The MEV micrographs of composite HDL / PDMcT / PAni showed a large number of crystallites compacts with several shapes characteristic to PDMcT and nanofibers of polyaniline indicating an association between the different constituents forming the composite. The results of the adsorption was 98% of the pesticide in the composite HML / PDMcT / PAni , the composite can contribute so significantly to one Thiodon withdrawal in contaminated pesticide waters. (author)

  7. Exchange of deuterium with hydrogen of zeolite catalyst surface

    International Nuclear Information System (INIS)

    Minachev, Kh.M.; Dmitriev, R.V.; Penchev, V.; Kanazirev, V.; Minchev, Kh.; Kasimov, Ch.K.; Bylgarska Akademiya na Naukite, Sofia. Inst. za Obshta i Organichna Khimiya; AN Azerbajdzhanskoj SSR, Baku. Inst. Neftekhimicheskikh Protsessov)

    1981-01-01

    Isotope heteromolecular exchange of hydrogen on the reduced nickel-containing zeolites takes places at the temperatures above 100 deg and it is controlled by activated hydrogen transfer from metal particles on the substrate surface. High-temperature redox treatment of nickel-containing zeolites results in the formation of large nickel crystallites on zeolite external faces. The rest part of nickel remains in zeolite pores and conditions a high promoting effect in the exchange reaction. Catalytic activity of reduced zeolites NiCaNaY in toluene disproportionation increases considerably only in the cases when nickel is introduced into zeolite by means of ion exchange. Close spatial location of nickel particles and OH groups promotes the procedure of both isotope exchange and disproportionation of toluene [ru

  8. Developing Large Web Applications

    CERN Document Server

    Loudon, Kyle

    2010-01-01

    How do you create a mission-critical site that provides exceptional performance while remaining flexible, adaptable, and reliable 24/7? Written by the manager of a UI group at Yahoo!, Developing Large Web Applications offers practical steps for building rock-solid applications that remain effective even as you add features, functions, and users. You'll learn how to develop large web applications with the extreme precision required for other types of software. Avoid common coding and maintenance headaches as small websites add more pages, more code, and more programmersGet comprehensive soluti

  9. The algebras of large N matrix mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Halpern, M.B.; Schwartz, C.

    1999-09-16

    Extending early work, we formulate the large N matrix mechanics of general bosonic, fermionic and supersymmetric matrix models, including Matrix theory: The Hamiltonian framework of large N matrix mechanics provides a natural setting in which to study the algebras of the large N limit, including (reduced) Lie algebras, (reduced) supersymmetry algebras and free algebras. We find in particular a broad array of new free algebras which we call symmetric Cuntz algebras, interacting symmetric Cuntz algebras, symmetric Bose/Fermi/Cuntz algebras and symmetric Cuntz superalgebras, and we discuss the role of these algebras in solving the large N theory. Most important, the interacting Cuntz algebras are associated to a set of new (hidden!) local quantities which are generically conserved only at large N. A number of other new large N phenomena are also observed, including the intrinsic nonlocality of the (reduced) trace class operators of the theory and a closely related large N field identification phenomenon which is associated to another set (this time nonlocal) of new conserved quantities at large N.

  10. Large-bandwidth planar photonic crystal waveguides

    DEFF Research Database (Denmark)

    Søndergaard, Thomas; Lavrinenko, Andrei

    2002-01-01

    A general design principle is presented for making finite-height photonic crystal waveguides that support leakage-free guidance of light over large frequency intervals. The large bandwidth waveguides are designed by introducing line defects in photonic crystal slabs, where the material in the line...... defect has appropriate dispersion properties relative to the photonic crystal slab material surrounding the line defect. A three-dimensional theoretical analysis is given for large-bandwidth waveguide designs based on a silicon-air photonic crystal slab suspended in air. In one example, the leakage......-free single-mode guidance is found for a large frequency interval covering 60% of the photonic band-gap....

  11. Large optics inspection, tilting, and washing stand

    Science.gov (United States)

    Ayers, Marion Jay [Brentwood, CA; Ayers, Shannon Lee [Brentwood, CA

    2010-08-24

    A large optics stand provides a risk free means of safely tilting large optics with ease and a method of safely tilting large optics with ease. The optics are supported in the horizontal position by pads. In the vertical plane the optics are supported by saddles that evenly distribute the optics weight over a large area.

  12. Large area CMOS image sensors

    International Nuclear Information System (INIS)

    Turchetta, R; Guerrini, N; Sedgwick, I

    2011-01-01

    CMOS image sensors, also known as CMOS Active Pixel Sensors (APS) or Monolithic Active Pixel Sensors (MAPS), are today the dominant imaging devices. They are omnipresent in our daily life, as image sensors in cellular phones, web cams, digital cameras, ... In these applications, the pixels can be very small, in the micron range, and the sensors themselves tend to be limited in size. However, many scientific applications, like particle or X-ray detection, require large format, often with large pixels, as well as other specific performance, like low noise, radiation hardness or very fast readout. The sensors are also required to be sensitive to a broad spectrum of radiation: photons from the silicon cut-off in the IR down to UV and X- and gamma-rays through the visible spectrum as well as charged particles. This requirement calls for modifications to the substrate to be introduced to provide optimized sensitivity. This paper will review existing CMOS image sensors, whose size can be as large as a single CMOS wafer, and analyse the technical requirements and specific challenges of large format CMOS image sensors.

  13. The Software Reliability of Large Scale Integration Circuit and Very Large Scale Integration Circuit

    OpenAIRE

    Artem Ganiyev; Jan Vitasek

    2010-01-01

    This article describes evaluation method of faultless function of large scale integration circuits (LSI) and very large scale integration circuits (VLSI). In the article there is a comparative analysis of factors which determine faultless of integrated circuits, analysis of already existing methods and model of faultless function evaluation of LSI and VLSI. The main part describes a proposed algorithm and program for analysis of fault rate in LSI and VLSI circuits.

  14. Effect of gamma-irradiation on some structural characteristics of NiO

    International Nuclear Information System (INIS)

    El-Shabiny, A.M.; El-Shobaky, G.A.; Dessouki, A.M.; Ramadan, A.A.

    1989-01-01

    Pure NiO specimens were prepared by the thermal decomposition of pure basic nickel carbonate in air at 400 and 600 0 C. The obtained solids were exposed to different doses of γ-irradiation ranging between 10-80 Mrad. The change in residual microstrain, lattice parameter and crystallite size due to the irradiation process were investigated by X-ray diffraction analyses. The results revealed that γ-irradiation effected important changes in the structural characteristics of NiO lattice. No detectable change was observed for the crystallite size of NiO-400 0 C; however, the crystallite size of NiO-600 0 C decreased by increasing the dose up to 20 Mrad and increased at higher doses but still remaining smaller than that measured for the unirradiated specimen. The lattice parameters of NiO preheated at 400 or 600 0 C were found to increase as a function of the dose. These results were attributed to progressive removal of Ni 3+ ions acting as lattice defects in NiO solid. The microstrains in NiO specimens precalcined either at 400 or 600 0 C were found to decrease progressively by increasing the dose falling to minimum values at doses of 40 and 80 Mrad for the solids preheated at 600 and 400 0 C, respectively. The augmentation of the exposure dose above 40 Mrad for NiO-600 0 C resulted in an increase in microstrain which, however, remained always smaller than those found for the unirradiated solid. The strain-relief in NiO-600 0 C due to γ-irradiation took place, mainly, via splitting of its crystallites. On the other hand, the progressive removal of lattice defects (Ni 3+ ions) due to the irradiation process might account for the observed strain-relief in NiO-400 0 C. (author)

  15. Introduction of Functional Structures in Nano-Scales into Engineering Polymer Films Using Radiation Technique

    Energy Technology Data Exchange (ETDEWEB)

    Maekawa, Y., E-mail: maekawa.yasunari@jaea.go.jp [Japan Atomic Energy Agency (JAEA), Quantum Beam Science Directorate, High Performance Polymer Group, 1233 Watanuki-Machi, Takasaki, Gunma-ken 370-1292 (Japan)

    2010-07-01

    Introduction of functional regions in nanometer scale in polymeric films using γ-rays, EB, and ion beams are proposed. Two approaches to build nano-scale functional domains in polymer substrates are proposed: 1) Radiation-induced grafting to transfer nano-scale polymer crystalline structures (morphology), acting as a nano-template, to nano-scale graft polymer regions. The obtained polymers with nano structures can be applied to high performance polymer membranes. 2) Fabrication of nanopores and functional domains in engineering plastic films using ion beams, which deposit the energy in very narrow region of polymer films. Hydrophilic grafting polymers are introduced into hydrophobic fluorinated polymers, cross-linked PTFE (cPTFE) and aromatic hydrocarbon polymer, poly(ether ether ketone (PEEK), which is known to have lamella and crystallite in the polymer films. Then, the hierarchical structures of graft domains are analyzed by a small angle neutron scattering (SANS) experiment. From these analyses, the different structures and the different formation of graft domains were observed in fluorinated and hydrocarbon polymer substrates. the grafted domains in the cPTFE film, working as an ion channel, grew as covering the crystallite and the size of domain seems to be similar to that of crystallite. On the other hand, the PEEK-based PEM has a smaller domain size and it seems to grow independently on the crystallites of PEEK substrate. For nano-fabrication of polymer films using heavy ion beams, the energy distribution in radial direction, which is perpendicular to ion trajectory, is mainly concerned. For penumbra, we re-estimated effective radius of penumbra, in which radiation induced grafting took place, for several different ion beams. We observed the different diameters of the ion channels consisting of graft polymers. The channel sizes were quite in good agreement with the effective penumbra which possess the absorption doses more than 1 kGy. (author)

  16. Introduction of Functional Structures in Nano-Scales into Engineering Polymer Films Using Radiation Technique

    International Nuclear Information System (INIS)

    Maekawa, Y.

    2010-01-01

    Introduction of functional regions in nanometer scale in polymeric films using γ-rays, EB, and ion beams are proposed. Two approaches to build nano-scale functional domains in polymer substrates are proposed: 1) Radiation-induced grafting to transfer nano-scale polymer crystalline structures (morphology), acting as a nano-template, to nano-scale graft polymer regions. The obtained polymers with nano structures can be applied to high performance polymer membranes. 2) Fabrication of nanopores and functional domains in engineering plastic films using ion beams, which deposit the energy in very narrow region of polymer films. Hydrophilic grafting polymers are introduced into hydrophobic fluorinated polymers, cross-linked PTFE (cPTFE) and aromatic hydrocarbon polymer, poly(ether ether ketone (PEEK), which is known to have lamella and crystallite in the polymer films. Then, the hierarchical structures of graft domains are analyzed by a small angle neutron scattering (SANS) experiment. From these analyses, the different structures and the different formation of graft domains were observed in fluorinated and hydrocarbon polymer substrates. the grafted domains in the cPTFE film, working as an ion channel, grew as covering the crystallite and the size of domain seems to be similar to that of crystallite. On the other hand, the PEEK-based PEM has a smaller domain size and it seems to grow independently on the crystallites of PEEK substrate. For nano-fabrication of polymer films using heavy ion beams, the energy distribution in radial direction, which is perpendicular to ion trajectory, is mainly concerned. For penumbra, we re-estimated effective radius of penumbra, in which radiation induced grafting took place, for several different ion beams. We observed the different diameters of the ion channels consisting of graft polymers. The channel sizes were quite in good agreement with the effective penumbra which possess the absorption doses more than 1 kGy. (author)

  17. Intrinsically water-repellent copper oxide surfaces; An electro-crystallization approach

    Science.gov (United States)

    Akbari, Raziyeh; Ramos Chagas, Gabriela; Godeau, Guilhem; Mohammadizadeh, Mohammadreza; Guittard, Frédéric; Darmanin, Thierry

    2018-06-01

    Use of metal oxide thin layers is increased due to their good durability under environmental conditions. In this work, the repeatable nanostructured crystalite Cu2O thin films, developed by electrodeposition method without any physical and chemical modifications, demonstrate good hydrophobicity. Copper (I) oxide (Cu2O) layers were fabricated on gold/Si(1 0 0) substrates by different electrodeposition methods i.e. galvanostatic deposition, cyclic voltammetry, and pulse potentiostatic deposition and using copper sulfate (in various concentrations) as a precursor. The greatest crystalline face on prepared Cu2O samples is (1 1 1) which is the most hydrophobic facet of Cu2O cubic structure. Indeed, different crystallite structures such as nanotriangles and truncated octahedrons were formed on the surface for various electrodeposition methods. The increase of the contact angle (θw) measured by the rest time, reaching to about 135°, was seen at different rates and electrodeposition methods. In addition, two-step deposition surfaces were also prepared by applying two of the mentioned methods, alternatively. In general, the morphology of the two-step deposition surfaces showed some changes compared to that of one-step samples, allowing the formation of different crystallite shapes. Moreover, the wettability behavior showd the larger θw of the two-step deposition layers compared to the related one-step deposition layers. Therefore, the highest observed θw was related to the one of two-step deposition layers due to the creation of small octahedral structures on the surface, having narrow and deep valleys. However, there was an exception which was due to the resulted big structures and broad valleys on the surface. So, it is possible to engineer different crystallites shapes using the proposed two-step deposition method. It is expected that hydrophobic crystallite thin films can be used in environmental and electronic applications to save energy and materials properties.

  18. Properties of TiO2 prepared by acid treatment of BaTiO3

    International Nuclear Information System (INIS)

    Okada, Kiyoshi; Yanagisawa, Tomoki; Kameshima, Yoshikazu; Nakajima, Akira

    2007-01-01

    TiO 3 powders were prepared by acid treatment of BaTiO 3 and their properties were investigated. The BaTiO 3 powder was subjected to HNO 3 in concentrations ranging from 10 -3 to 8 M at 90 deg. C for 0.5-6 h. Dissolution of BaTiO 3 and precipitation of TiO 2 occurred at acid concentrations of 2-5 M. BaTiO 3 dissolves completely to form a clear solution at reaction times of 0.5-1 h, but a rutile precipitate is formed after 2 h of acid treatment. By contrast, anatase is precipitated by adjusting the pH of the clear solution to 2-3 using NaOH or NH 4 OH solution. The rutile crystals were small and rod-shaped, consisting of many small coherent domains connected by grain boundaries with small inclination angles and edge dislocations, giving them a high specific surface area (S BET ). With increasing HNO 3 concentration, the S BET value increased from 100 to 170 m 2 /g while the crystallite size decreased from 25 to 11 nm. The anatase crystals obtained here were very small equi-axial particles with a smaller crystallite size than the rutile and S BET values of about 270 m 2 /g (higher than the rutile samples). The photocatalytic activity of these TiO 2 was determined from the decomposition rate of Methylene Blue under ultraviolet irradiation. Higher decomposition rates were obtained with larger crystallite sizes resulting from heat treatment. The maximum decomposition rates were obtained in samples heated at 500-600 deg. C. The photocatalytic activity of the TiO 2 was found to depend more strongly on the sample crystallite size than on S BET

  19. Environmental effects and large space systems

    Science.gov (United States)

    Garrett, H. B.

    1981-01-01

    When planning large scale operations in space, environmental impact must be considered in addition to radiation, spacecraft charging, contamination, high power and size. Pollution of the atmosphere and space is caused by rocket effluents and by photoelectrons generated by sunlight falling on satellite surfaces even light pollution may result (the SPS may reflect so much light as to be a nuisance to astronomers). Large (100 Km 2) structures also will absorb the high energy particles that impinge on them. Altogether, these effects may drastically alter the Earth's magnetosphere. It is not clear if these alterations will in any way affect the Earth's surface climate. Large structures will also generate large plasma wakes and waves which may cause interference with communications to the vehicle. A high energy, microwave beam from the SPS will cause ionospheric turbulence, affecting UHF and VHF communications. Although none of these effects may ultimately prove critical, they must be considered in the design of large structures.

  20. Study of crystallite size of yttria-stabilized zirconia powders by Rietveld method

    International Nuclear Information System (INIS)

    Leite, Wellington Claiton; Brinatti, Andre Mauricio; Ribeiro, Mauricio Aparecido; Andrade, Andre Vitor Chaves de; Chinelatto, Adriana Scoton Antonio; Chinelatto, Adilson Luiz

    2009-01-01

    The yttria-stabilized zirconia (YSZ) is used in a great variety of applications, for example, electrolytes of solid oxide fuel cells and oxygen sensors. In the study of YSZ, the particle size powders and sintering processes are important to define the final properties of the zirconia products. The objectives of this work were to determine the phases and the crystalline size using X-Ray Diffraction (XRD) data and the Rietveld Method (RM) of the YSZ powders obtained by chemical synthesis based on the Pechini method. It was used ZrOCl 2.8 H 2 O and Y(NO 3 ) 3.5 H 2 O as precursors reagents. After calcination at 550 deg C during 24 hours, the powder was analyzed by XRD and scanning electronic microscopy (SEM). From XRD and using Rietveld method were verified that there is only cubic phase with lattice parameter a = 5.1307(1) Å and the space group Fm3m. Due to substitution of the Zr atoms in the Y atoms sites, there were vacancies in 17.72 % of O atoms sites. However, the percentage of substitution of Zr atoms in Y atoms sites in the structure not was determinate because the curves of atomic scattering of them are very similar. Using Scherrer equation and considering anisotropy effect, the average crystalline size was determinate: 10,43 nm (c axis) and 10,39 (b axis). This spherical symmetry also observed for SEM. (author)