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Sample records for crystalline phases formed

  1. Naturally occurring crystalline phases: analogues for radioactive waste forms

    Energy Technology Data Exchange (ETDEWEB)

    Haaker, R.F.; Ewing, R.C.

    1981-01-01

    Naturally occurring mineral analogues to crystalline phases that are constituents of crystalline radioactive waste forms provide a basis for comparison by which the long-term stability of these phases may be estimated. The crystal structures and the crystal chemistry of the following natural analogues are presented: baddeleyite, hematite, nepheline; pollucite, scheelite;sodalite, spinel, apatite, monazite, uraninite, hollandite-priderite, perovskite, and zirconolite. For each phase in geochemistry, occurrence, alteration and radiation effects are described. A selected bibliography for each phase is included.

  2. Microscopic characterization of crystalline phases in waste forms

    Energy Technology Data Exchange (ETDEWEB)

    Buck, E.C.; Dietz, N.L.; Wronkiewicz, D.J.; Bates, J.K. [Argonne National Lab., IL (United States); Millar, A. [Purdue Univ., West Lafayette, IN (United States)

    1995-07-01

    Transmission electron microscopy (TEM) has been used to determine the microstructure of crystalline phases present in zirconium- and titanium-bearing glass crystalline composite (GCC) waste forms. The GCC materials were found to contain spinels (maghemite), zirconolites, perovskites (CaTiO{sub 3}) and plagiociase feldspar (anorthite) mineral phases. The structure of the uranium and cerium-bearing monoclinic zirconolite was characterized by medium resolution TEM imaging and electron and X-ray diffraction (XRD). The phase was found to contain high levels of iron in comparison to Synroc-type zirconolites. Excess zirconium in zirconolite has resulted in martensitic baddeleyite (ZrO{sub 2}) formation. Anorthite (CaAl{sub 2}Si{sub 2}O{sub 8}) was present as elongated crystallites within a calcium-rich aluminosilicate glass. Lead and iron-bearing anorthite lying along distinct precipitates were occasionally observed within the an crystallographic planes.

  3. Review of crystalline structures of some selected homologous series of rod-like molecules capable of forming liquid crystalline phases.

    Science.gov (United States)

    Zugenmaier, Peter

    2011-01-01

    The crystal structures of four homologous series of rod-like molecules are reviewed, two of which form hydrogen bonds and two with a symmetric chemical constitution. Many of the compounds investigated turn into liquid crystalline phases upon temperature increase. It is of valuable interest to know possible conformations and possible packing arrangements as prerequisites to model liquid crystalline structures. The hydrogen bonds of homologous series of pure 4-(ω-hydroxyalkyloxy)-4'-hydroxybiphenyl (HnHBP, n the alkyloxy tail length) are realized through head to tail arrangements of the hydroxyl groups and crystallize except one compound in chiral space groups without the molecules containing any asymmetric carbon. The hydrogen bonds of the homologous series of 4-substituted benzoic acids with various lengths of the tail provide dimers through strong polar bonding of adjacent carboxyl groups and thus provide the stiff part of a mesogenic unit prerequisite for liquid crystalline phases. The homologous series of dialkanoyloxybiphenyls (BP-n, n = 1, 19), of which nine compounds could be crystallized, show liquid crystalline behavior for longer alkane chain lengths, despite the high mobility of the alkane chain ends already detectable in the crystal phase. A single molecule, half a molecule or two half molecules form the asymmetric unit in a centrosymmetric space group. The homologous series of 1,4-terephthalidene-bis-N-(4'-n-alkylaniline) (TBAA-n) exhibit a large variety of packing arrangements in the crystalline state, with or without relying on the symmetry center within the molecules.

  4. Review of Crystalline Structures of Some Selected Homologous Series of Rod-Like Molecules Capable of Forming Liquid Crystalline Phases

    Directory of Open Access Journals (Sweden)

    Peter Zugenmaier

    2011-10-01

    Full Text Available The crystal structures of four homologous series of rod-like molecules are reviewed, two of which form hydrogen bonds and two with a symmetric chemical constitution. Many of the compounds investigated turn into liquid crystalline phases upon temperature increase. It is of valuable interest to know possible conformations and possible packing arrangements as prerequisites to model liquid crystalline structures. The hydrogen bonds of homologous series of pure 4-(ω-hydroxyalkyloxy-4′-hydroxybiphenyl (HnHBP, n the alkyloxy tail length are realized through head to tail arrangements of the hydroxyl groups and crystallize except one compound in chiral space groups without the molecules containing any asymmetric carbon. The hydrogen bonds of the homologous series of 4-substituted benzoic acids with various lengths of the tail provide dimers through strong polar bonding of adjacent carboxyl groups and thus provide the stiff part of a mesogenic unit prerequisite for liquid crystalline phases. The homologous series of dialkanoyloxybiphenyls (BP-n, n = 1, 19, of which nine compounds could be crystallized, show liquid crystalline behavior for longer alkane chain lengths, despite the high mobility of the alkane chain ends already detectable in the crystal phase. A single molecule, half a molecule or two half molecules form the asymmetric unit in a centrosymmetric space group. The homologous series of 1,4-terephthalidene-bis-N-(4′-n-alkylaniline (TBAA-n exhibit a large variety of packing arrangements in the crystalline state, with or without relying on the symmetry center within the molecules.

  5. Suppressed Release of Clarithromycin from Tablets by Crystalline Phase Transition of Metastable Polymorph Form I.

    Science.gov (United States)

    Fujiki, Sadahiro; Watanabe, Narumi; Iwao, Yasunori; Noguchi, Shuji; Mizoguchi, Midori; Iwamura, Takeru; Itai, Shigeru

    2015-08-01

    The pharmaceutical properties of clarithromycin (CAM) tablets containing the metastable form I of crystalline CAM were investigated. Although the dissolution rate of form I was higher than that of stable form II, the release of CAM from form I tablet was delayed. Disintegration test and liquid penetration test showed that the disintegration of the tablet delayed because of the slow penetration of an external solution into form I tablet. Investigation by scanning electron microscopy revealed that the surface of form I tablet was covered with fine needle-shaped crystals following an exposure to the external solution. These crystals were identified as form IV crystals by powder X-ray diffraction. The phenomenon that CAM releases from tablet was inhibited by fine crystals spontaneously formed on the tablet surface could be applied to the design of sustained-release formulation systems with high CAM contents by minimizing the amount of functional excipients. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

  6. Form-stable crystalline polymer pellets for thermal energy storage. Phase 1

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    Botham, R.A.; Jenkins, G.H.; Ball, G.L. III; Salyer, I.O.

    1977-07-01

    The objective of this project was to develop a form-stable, crystalline polymer pellet TES bed material, useful in the 120 to 140/sup 0/C temperature range suitable for solar absorption air conditioning applications. This objective was achieved with a Si-O-Si crosslinked HDPE pellet material, demonstrated to have a high heat of fusion value (46 cal/g, approximately 98% of the HDPE's heat of fusion value prior to crosslinking). Further, on melt/freeze cycling of these TES pellets through 400 cycles in ethylene glycol, they retained nearly 100% of their initial heat of fusion value, and had excellent form-stability characteristics, with little or no inter-particle adhesion. Appropriate testing of this TES pellet material, from analytical (DSC) to a one gallon lab-scale TES unit, and finally to a 60 gallon prototype TES demonstration unit, consistently verified these results. C-C crosslinked PE products, which were slightly inferior to the Si-O-Si crosslinked PE in terms of good heat of fusion and form-stability properties, were also developed and are potential alternatives to the prime PE TES product.

  7. Phase Structure and Properties of a Biodegradable Block Copolymer Coalesced from It's Crystalline Inclusion Compound Formed with alpha-Cyclodextrin

    Science.gov (United States)

    Shuai, Xintao; Wei, Min; Probeni, Francis; Bullions, Todd A.; Shin, I. Daniel; Tonelli, Alan E.

    2002-03-01

    A well-defined biodegradable block copolymer of poly(epsilon caprolactone) (PCL) and poly(L-lactic acid) (PLLA) was synthesized and characterized and then included as a guest in an inclusion compound (IC) formed with the host alpha-cyclodextrin (CD). The PCL-b-PLLA block copolymer was subsequently coalesced from it's CD-IC crystals by either treatment with hot water (50 C) or an aqueous amylase solution at 25 C. The coalesced PCL-b-PLLA was examined by FTIR, DSC, TGA, and WAXD and was found to be much more homogeneosly organized, with much less segregation and crystallinity of the PCL and PLLA microphases. The morpholgy, crystallization kinetics, thermal behavior, and biodegradability of the coalesced PCL-b-PLLA block copolymer was studied by comparison to similar observations made on as-synthesized PCL-b-PLLA, PCL and PLLA homopolymers, and their solution-cast blend. The PCL and PLLA blocks are found to be more intimately mixed, with less phase segregation, in the coalesced diblock copolymer, and this leads to homogeneous bulk crystallization, which is not observed for the as-synthesized diblock copolymer. The coalesced PCL-b-PLLA was also found to be more quickly biodegraded (lipase from Rhizopus arrhizus)than the as-synthesized PCL-b-PLLA or the physical blend of PCL and PLLA homopolymers. Overall, the coalescence of the inherently phase segregated diblock copolymer PCL-b-PLLA results in a small amount of compact, chain-extended PCL and PLLA crystals embedded in an amorphous phase, largely consisting of well-mixed PCL and PLLA blocks. Thus, we have demonstrated that it is possible to control the morpholgy of a biodegradable diblock copolymer, thereby significantly modifying it's properties, by coalescence from it's CD-IC crystals.

  8. Nanostructures having crystalline and amorphous phases

    Science.gov (United States)

    Mao, Samuel S; Chen, Xiaobo

    2015-04-28

    The present invention includes a nanostructure, a method of making thereof, and a method of photocatalysis. In one embodiment, the nanostructure includes a crystalline phase and an amorphous phase in contact with the crystalline phase. Each of the crystalline and amorphous phases has at least one dimension on a nanometer scale. In another embodiment, the nanostructure includes a nanoparticle comprising a crystalline phase and an amorphous phase. The amorphous phase is in a selected amount. In another embodiment, the nanostructure includes crystalline titanium dioxide and amorphous titanium dioxide in contact with the crystalline titanium dioxide. Each of the crystalline and amorphous titanium dioxide has at least one dimension on a nanometer scale.

  9. CRYSTALLINE CERAMIC WASTE FORMS: REFERENCE FORMULATION REPORT

    Energy Technology Data Exchange (ETDEWEB)

    Brinkman, K.; Fox, K.; Marra, J.

    2012-05-15

    The research conducted in this work package is aimed at taking advantage of the long term thermodynamic stability of crystalline ceramics to create more durable waste forms (as compared to high level waste glass) in order to reduce the reliance on engineered and natural barrier systems. Durable ceramic waste forms that incorporate a wide range of radionuclides have the potential to broaden the available disposal options and to lower the storage and disposal costs associated with advanced fuel cycles. Assemblages of several titanate phases have been successfully demonstrated to incorporate radioactive waste elements, and the multiphase nature of these materials allows them to accommodate variation in the waste composition. Recent work has shown that they can be successfully produced from a melting and crystallization process. The objective of this report is to explain the design of ceramic host systems culminating in a reference ceramic formulation for use in subsequent studies on process optimization and melt property data assessment in support of FY13 melter demonstration testing. The waste stream used as the basis for the development and testing is a combination of the projected Cs/Sr separated stream, the Trivalent Actinide - Lanthanide Separation by Phosphorous reagent Extraction from Aqueous Komplexes (TALSPEAK) waste stream consisting of lanthanide fission products, the transition metal fission product waste stream resulting from the transuranic extraction (TRUEX) process, and a high molybdenum concentration with relatively low noble metal concentrations. In addition to the combined CS/LN/TM High Mo waste stream, variants without Mo and without Mo and Zr were also evaluated. Based on the results of fabricating and characterizing several simulated ceramic waste forms, two reference ceramic waste form compositions are recommended in this report. The first composition targets the CS/LN/TM combined waste stream with and without Mo. The second composition targets

  10. Electrical transport in crystalline phase change materials

    Energy Technology Data Exchange (ETDEWEB)

    Woda, Michael

    2012-01-06

    In this thesis, the electrical transport properties of crystalline phase change materials are discussed. Phase change materials (PCM) are a special class of semiconducting and metallic thin film alloys, typically with a high amount of the group five element antimony or the group six element tellurium, such as Ge{sub 2}Sb{sub 2}Te{sub 5}. The unique property portfolio of this material class makes it suitable for memory applications. PCMs reveal fast switching between two stable room-temperature phases (amorphous and crystalline) realized by optical laser or electrical current pulses in memory devices. Additionally, a pronounced property contrast in form of optical reflectivity and electrical conductivity between the amorphous and crystalline phase is the characteristic fingerprint of PCMs. The emerging electrical solid state memory PCRAM is a very promising candidate to replace Flash memory in the near future or to even become a universal memory, which is non-volatile and shows the speed and cyclability of DRAM. One of the main technological challenges is the switching process into the amorphous state, which is the most power demanding step. In order to reduce the switching power, the crystalline resistivity needs to be increased at a given voltage. Thus understanding and tayloring of this property is mandatory. In this work, first the technological relevance, i.e. optical and electrical memory concepts based on PCMs are introduced. Subsequently a description of the physical properties of PCMs in four categories is given. Namely, structure, kinetics, optical properties and electrical properties are discussed. Then important recent developments such as the identification of resonant bonding in crystalline PCMs and a property predicting coordination scheme are briefly reviewed. The following chapter deals with the theoretical background of electrical transport, while the next chapter introduces the experimental techniques: Sputtering, XRR, XRD, DSC, thermal annealing

  11. Phase diagrams of binary crystalline-crystalline polymer blends.

    Science.gov (United States)

    Matkar, Rushikesh A; Kyu, Thein

    2006-08-17

    A thermodynamically self-consistent theory has been developed to establish binary phase diagrams for two-crystalline polymer blends by taking into consideration all interactions including amorphous-amorphous, crystal-amorphous, amorphous-crystal, and crystal-crystal interactions. The present theory basically involves combination of the Flory-Huggins free energy for amorphous-amorphous isotropic mixing and the Landau free energy of polymer solidification (e.g., crystallization) of the crystalline constituents. The self-consistent solution via minimization of the free energy of the mixture affords determination of eutectic, peritectic, and azeotrope phase diagrams involving various coexistence regions such as liquid-liquid, liquid-solid, and solid-solid coexistence regions bound by liquidus and solidus lines. To validate the present theory, the predicted eutectic phase diagrams have been compared with the reported experimental binary phase diagrams of blends such as polyethylene fractions as well as polycaprolactone/trioxane mixtures.

  12. Stamp forming optimization for formability and crystallinity

    Science.gov (United States)

    Donderwinkel, T. G.; Rietman, B.; Haanappel, S. P.; Akkerman, R.

    2016-10-01

    The stamp forming process is well suited for high volume production of thermoplastic composite parts. The process can be characterized as highly non-isothermal as it involves local quench-cooling of a molten thermoplastic composite blank where it makes contact with colder tooling. The formability of the thermoplastic composite depends on the viscoelastic material behavior of the matrix material, which is sensitive to temperature and degree of crystallinity. An experimental study was performed to determine the effect of temperature and crystallinity on the storage modulus during cooling for a woven glass fiber polyamide-6 composite material. An increase of two decades in modulus was observed during crystallization. As this will significantly impede the blank formability, the onset of crystallization effectively governs the time available for forming. Besides the experimental work, a numerical model is developed to study the temperature and crystallinity throughout the stamp forming process. A process window can be determined by feeding the model with the experimentally obtained data on crystallization.

  13. Monolithic aerogels with nanoporous crystalline phases

    Science.gov (United States)

    Daniel, Christophe; Guerra, Gaetano

    2015-05-01

    High porosity monolithic aerogels with nanoporous crystalline phases can be obtained from syndiotactic polystyrene and poly(2,6-dimethyl-1,4-phenylene)oxide thermoreversible gels by removing the solvent with supercritical CO2. The presence of crystalline nanopores in the aerogels based on these polymers allows a high uptake associated with a high selectivity of volatile organic compounds from vapor phase or aqueous solutions even at very low activities. The sorption and the fast kinetics make these materials particularly suitable as sorption medium to remove traces of pollutants from water and moist air.

  14. A new crystalline phase in magnetar crusts

    CERN Document Server

    Bedaque, Paulo F; Ng, Nathan; Sen, Srimoyee

    2013-01-01

    We show that ions at the low densities and high magnetic fields relevant to the outer crust of magnetars form a novel crystalline phase where ions are strongly coupled along the magnetic field and loosely coupled in the transverse direction. The underlying cause is the anisotropic screening of the Coulomb force by electrons in the presence of a strongly quantizing magnetic field which leads to Friedel oscillations in the ion-ion potential. In particular, the Friedel oscillations are much longer-ranged in the direction of the magnetic field than is the case in the absence of magnetic fields, a factor that has been neglected in previous studies. These "Friedel crystals" have very anisotropic elastic moduli, with potentially interesting implications for the Quasi-periodic Oscillations seen in the X-ray flux of magnetars during their giant flares. We find the minimum energy configuration of ions taking into account these anisotropic effects and find that, depending on the density, temperature and magnetic field s...

  15. Polymorphism of Alprazolam (Xanax): a review of its crystalline phases and identification, crystallographic characterization, and crystal structure of a new polymorph (form III).

    Science.gov (United States)

    de Armas, Héctor Novoa; Peeters, Oswald M; Van den Mooter, Guy; Blaton, Norbert

    2007-05-01

    A new polymorphic form of Alprazolam (Xanax), 8-chloro-1-methyl-6-phenyl-4H-[1,2,4]triazolo-[4,3-alpha][1,4]benzodiazepine, C(17)H(13)ClN(4), has been investigated by means of X-ray powder diffraction (XRPD), single crystal X-ray diffraction, and differential scanning calorimetry (DSC). This polymorphic form (form III) was obtained during DSC experiments after the exothermic recrystallization of the melt of form I. The crystal unit cell dimensions for form III were determined from diffractometer methods. The monoclinic unit cell found for this polymorph using XRPD after indexing the powder diffractogram was confirmed by the cell parameters obtained from single crystal X-ray diffractometry on a crystal isolated from the DSC pans. The single crystal unit cell parameters are: a = 28.929(9), b = 13.844(8), c = 7.361(3) angstroms, beta = 92.82(3) degrees , V = 2944(2) angstroms(3), Z = 8, space group P2(1) (No.4), Dx = 1.393 Mg/m(3). The structure obtained from single crystal X-ray diffraction was used as initial model for Rietveld refinement on the powder diffraction data of form III. The temperature phase transformations of alprazolam were also studied using high temperature XRPD. A review of the different phases available in the Powder Diffraction File (PDF) database for this drug is described bringing some clarification and corrections.

  16. Phase diagrams and kinetics of solid-liquid phase transitions in crystalline polymer blends

    Science.gov (United States)

    Matkar, Rushikesh A.

    A free energy functional has been formulated based on an order parameter approach to describe the competition between liquid-liquid phase separation and solid-liquid phase separation. In the free energy description, the assumption of complete solvent rejection from the crystalline phase that is inherent in the Flory diluent theory was removed as solvent has been found to reside in the crystalline phase in the form of intercalates. Using this approach, we have calculated various phase diagrams in binary blends of crystalline and amorphous polymers that show upper or lower critical solution temperature. Also, the discrepancy in the chi values obtained from different experimental methods reported in the literature for the polymer blend of poly(vinylidenefluoride) and poly(methylmethacrylate) has been discussed in the context of the present model. Experimental phase diagram for the polymer blend of poly(caprolactone) and polystyrene has also been calculated. Of particular importance is that the crystalline phase concentration as a function of temperature has been calculated using free energy minimization methods instead of assuming it to be pure. In the limit of complete immiscibility of the solvent in the crystalline phase, the Flory diluent theory is recovered. The model is extended to binary crystalline blends and the formation of eutectic, peritectic and azeotrope phase diagrams has been explained on the basis of departure from ideal solid solution behavior. Experimental eutectic phase diagram from literature of a binary blend of crystalline polymer poly(caprolactone) and trioxane were recalculated using the aforementioned approach. Furthermore, simulations on the spatio temporal dynamics of crystallization in blends of crystalline and amorphous polymers were carried out using the Ginzburg-Landau approach. These simulations have provided insight into the distribution of the amorphous polymer in the blends during the crystallization process. The simulated results

  17. Assessment of analytical techniques for characterization of crystalline clopidogrel forms in patent applications

    Directory of Open Access Journals (Sweden)

    Luiz Marcelo Lira

    2014-04-01

    Full Text Available The aim of this study was to evaluate two important aspects of patent applications of crystalline forms of drugs: (i the physicochemical characterization of the crystalline forms; and (ii the procedure for preparing crystals of the blockbuster drug clopidogrel. To this end, searches were conducted using online patent databases. The results showed that: (i the majority of patent applications for clopidogrel crystalline forms failed to comply with proposed Brazilian Patent Office guidelines. This was primarily due to insufficient number of analytical techniques evaluating the crystalline phase. In addition, some patent applications lacked assessment of chemical/crystallography purity; (ii use of more than two analytical techniques is important; and (iii the crystallization procedure for clopidogrel bisulfate form II were irreproducible based on the procedure given in the patent application.

  18. The influence of glass composition on crystalline phase stability in glass-ceramic wasteforms

    Energy Technology Data Exchange (ETDEWEB)

    Maddrell, Ewan, E-mail: ewan.r.maddrell@nnl.co.uk [National Nuclear Laboratory, Sellafield, Seascale, Cumbria CA20 1PG (United Kingdom); Thornber, Stephanie; Hyatt, Neil C. [Department of Materials Science and Engineering, The University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom)

    2015-01-15

    Highlights: • Crystalline phase formation shown to depend on glass matrix composition. • Zirconolite forms as the sole crystalline phase only for most aluminous glasses. • Thermodynamics indicate that low silica activity glasses stabilise zirconolite. - Abstract: Zirconolite glass-ceramic wasteforms were prepared using a suite of Na{sub 2}O–Al{sub 2}O{sub 3}–B{sub 2}O{sub 3}–SiO{sub 2} glass matrices with variable Al:B ratios. Zirconolite was the dominant crystalline phase only for the most alumina rich glass compositions. As the Al:B ratio decreased zirconolite was replaced by sphene, zircon and rutile. Thermodynamic data were used to calculate a silica activity in the glass melt below which zirconolite is the favoured crystalline phase. The concept of the crystalline reference state of glass melts is then utilised to provide a physical basis for why silica activity varies with the Al:B ratio.

  19. Polymorphic phases of galactocerebrosides: spectroscopic evidence of lamellar crystalline structures.

    Science.gov (United States)

    Bou Khalil, M; Carrier, D; Wong, P T; Tanphaichitr, N

    2001-06-06

    Fourier transform infrared spectroscopy was applied to study the structural and thermal properties of bovine brain galactocerebroside (GalCer) containing amide linked non-hydroxylated or alpha-hydroxy fatty acids (NFA- and HFA-GalCer, respectively). Over the temperature range 0-90 degrees C, both GalCer displayed complex thermal transitions, characteristic of polymorphic phase behavior. Upon heating, aqueous dispersions of NFA- and HFA-GalCer exhibited high order-disorder transition temperatures near 80 and 72 degrees C, respectively. En route to the chain melting transition, the patterns of the amide I band of NFA-GalCer were indicative of two different lamellar crystalline phases, whereas those of HFA-GalCer were suggestive of lamellar gel and crystalline bilayers. Cooling from the liquid-crystalline phase resulted in the formation of another crystalline phase of NFA-GalCer and a gel phase of HFA-GalCer, with a phase transition near 62 and 66 degrees C, respectively. Prolonged incubation of GalCer bilayers at 38 degrees C revealed conversions among lamellar crystalline phases (NFA-GalCer) or between lamellar gel and crystalline bilayer structures (HFA-GalCer). Spectral changes indicated that the temperature and/or time induced formation of the lamellar crystalline structures of NFA- and HFA-GalCer was accompanied by partial dehydration and by rearrangements of the hydrogen bonding network and bilayer packing mode of GalCer.

  20. Solvated crystalline forms of nevirapine: thermoanalytical and spectroscopic studies.

    Science.gov (United States)

    Chadha, Renu; Arora, Poonam; Saini, Anupam; Jain, Dharamvir Singh

    2010-09-01

    The study is aimed at exploring the utility of thermoanalytical methods in the solid-state characterization of various crystalline forms of nevirapine. The different forms obtained by recrystallization of nevirapine from various solvents were identified using differential scanning calorimetry and thermogravimetric analysis (TGA). The appearance of desolvation peak accompanied by weight loss in TGA indicated the formation of solvates: hemi-ethanolate (Form I), hemi-acetonitrilate (Form II), hemi-chloroformate (Form III), hemi-THF solvate (Form IV), mixed hemi-ethanolate hemi-hydrate (Form V), and hemi-toluenate (Form VI). The higher desolvation temperatures of all the solvates except toluenate than their respective boiling point indicate tighter binding of solvent. Emphasis has been laid on the determination of heat capacity and heat of solution utilizing microreaction calorimeter to further distinguish the various forms. The enthalpy of solution (ΔH(sol)), an indirect measure of the lattice energy of a solid, was well correlated with the crystallinity of all the solid forms obtained. The magnitude of ΔH(sol) was found to be -14.14 kJ/mol for Form I and -2.83 kJ/mol for Form V in phosphate buffer of pH 2, exhibiting maximum ease of molecular release from the lattice in Form I. The heat capacity for solvation (ΔC(p)) was found to be positive, providing information about the state of solvent molecules in the host lattice. The solubility and dissolution rate of the forms were also found to be in agreement with their enthalpy of solution. Form (I), being the most exothermic, was found to be the most soluble of all the forms.

  1. Gemini型表面活性剂在离子液体中构筑的溶致液晶%Lyotropic liquid crystalline phases formed by Gemini surfactants in anionic liquid

    Institute of Scientific and Technical Information of China (English)

    宋冰蕾; 陈涛; 田金年; 裴晓梅; 孟丽

    2015-01-01

    通过差示扫描量热仪(DSC)、X 射线衍射仪(XRD)、热台偏光显微镜(POM)和红外光谱仪等手段研究了Gemini表面活性剂在硝酸乙基铵(EAN)中构筑的溶致液晶体系(lyotropic liquid crystal,LLc)的性质.结果表明,在液晶区内,所形成的溶致液晶均为层状介晶A相(SmA),且EAN主要存在于液晶相分子层的极性亚层中;液晶相稳定存在的温度区间随Gemini表面活性剂的浓度、尾链长度的增加而变大,随联接链的增加表现出先增大再减小的趋势;羟基削弱了离子头基与反离子间的相互作用,进而缩小了液晶相稳定存在的温度区间.%The lyotropic liquid crystals formed by Gemini surfactants in ethyl ammonium nitrate (EAN) were investigated by differential scanning calorimetry(DSC),X ray diffractometer(XRD),polarizing microscope(POM) equipped with a hot stage and FTIR. All the surfactants form smectic A phase(SmA) in liquid crystalline region. The EAN molecules mainly exist in the polar sublayers of liquid crystals. The temperature ranges of liquid crystal phase increase with increasing Gemini surfactant alkyl chain length while show maximum with the increase of spacer length. The hydroxyl groups decrease the interactions between the ionic head groups and counterions. The temperature range of liquid crystal state is thus narrowed.

  2. Multiple Melting Endotherms of Syndiotactic Polystyrene in β Crystalline Form

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A series of syndiotactic polystyrene (SPS) samples in β crystalline form were prepared by cooling from the melt at various cooling rates. The effects of cooling rate from the melt, and DSC heating rate on the multiple melting behaviors of β crystals were investigated by differential scanning calorimetry (DSC) and modulated differential scanning calorimetry (MDSC), from which the nature of the multiple melting behavior was ascribed to the occurring of a recrystallization process.

  3. Radiation stability test on multiphase glass ceramic and crystalline ceramic waste forms

    Science.gov (United States)

    Tang, Ming; Kossoy, Anna; Jarvinen, Gordon; Crum, Jarrod; Turo, Laura; Riley, Brian; Brinkman, Kyle; Fox, Kevin; Amoroso, Jake; Marra, James

    2014-05-01

    A radiation stability study was performed on glass ceramic and crystalline ceramic waste forms. These materials are candidate host materials for immobilizing alkali/alkaline earth (Cs/Sr-CS) + lanthanide (LN) + transition metal (TM) fission product waste streams from nuclear fuel reprocessing. In this study, glass ceramics were fabricated using a borosilicate glass as a matrix in which to incorporate CS/LN/TM combined waste streams. The major phases in these multiphase materials are powellite, oxyaptite, pollucite, celsian, and durable residual glass phases. Al2O3 and TiO2 were combined with these waste components to produce multiphase crystalline ceramics containing hollandite-type phases, perovskites, pyrochlores and other minor metal titanate phases. For the radiation stability test, selected glass ceramic and crystalline ceramic samples were exposed to different irradiation environments including low fluxes of high-energy (∼1-5 MeV) protons and alpha particles generated by an ion accelerator, high fluxes of low-energy (hundreds of keV) krypton particles generated by an ion implanter, and in-situ electron irradiations in a transmission electron microscope. These irradiation experiments were performed to simulate self-radiation effects in a waste form. Ion irradiation-induced microstructural modifications were examined using X-ray diffraction and transmission electron microscopy. Our preliminary results reveal different radiation tolerance in different crystalline phases under various radiation damage environments. However, their stability may be rate dependent which may limit the waste loading that can be achieved.

  4. Crystalline ceramics: Waste forms for the disposal of weapons plutonium

    Energy Technology Data Exchange (ETDEWEB)

    Ewing, R.C.; Lutze, W. [New Mexico Univ., Albuquerque, NM (United States); Weber, W.J. [Pacific Northwest Lab., Richland, WA (United States)

    1995-05-01

    At present, there are three seriously considered options for the disposition of excess weapons plutonium: (i) incorporation, partial burn-up and direct disposal of MOX-fuel; (ii) vitrification with defense waste and disposal as glass ``logs``; (iii) deep borehole disposal (National Academy of Sciences Report, 1994). The first two options provide a safeguard due to the high activity of fission products in the irradiated fuel and the defense waste. The latter option has only been examined in a preliminary manner, and the exact form of the plutonium has not been identified. In this paper, we review the potential for the immobilization of plutonium in highly durable crystalline ceramics apatite, pyrochlore, monazite and zircon. Based on available data, we propose zircon as the preferred crystalline ceramic for the permanent disposition of excess weapons plutonium.

  5. Nonionic diethanolamide amphiphiles with isoprenoid-type hydrocarbon chains: thermotropic and lyotropic liquid crystalline phase behaviour

    Energy Technology Data Exchange (ETDEWEB)

    Sagnella, Sharon M.; Conn, Charlotte E.; Krodkiewska, Irena; Drummond, Calum J. (CSIRO/MSE)

    2014-09-24

    The thermotropic and lyotropic liquid crystalline phase behaviour of a series of diethanolamide amphiphiles with isoprenoid-type hydrocarbon chains (geranoyl, H-farnesoyl, and phytanoyl) has been investigated. When neat, both H-farnesoyl and phytanoyl diethanolamide form a smectic liquid crystalline structure at sub-zero temperatures. In addition, all three diethanolamides exhibit a glass transition temperature at around -73 C. Geranoyl diethanolamide forms a lamellar crystalline phase with a lattice parameter of 17.4 {angstrom} following long term storage accompanied by the loss of the glass transition. In the presence of water, H-farnesoyl and phytanoyl diethanolamide form lyotropic liquid crystalline phases, whilst geranoyl diethanolamide forms an L{sub 2} phase. H-farnesoyl diethanolamide forms a fluid lamellar phase (L{sub {alpha}}) at room temperature and up to {approx} 40 C. Phytanoyl diethanolamide displays a rich mesomorphism forming the inverse diamond (Q{sub II}{sup D}) and gyroid (Q{sub II}{sup G}) bicontinuous cubic phases in addition to an L{sub {alpha}} phase.

  6. Electrospinning of PVDF nanofibrous membranes with controllable crystalline phases

    Science.gov (United States)

    Lei, Tingping; Zhu, Ping; Cai, Xiaomei; Yang, Le; Yang, Fan

    2015-07-01

    Effectively controlling crystalline phases of electrospun polyvinylidene fluoride (PVDF) nanofibers is crucial to produce membranes with special properties for specific applications. Here, the heating treatment during or after electrospinning has been investigated to determine an effective way to control crystalline phase of PVDF nanofibers. By simultaneously controlling the collector temperature and the flow rate during the fiber deposition, a comparatively lower temperature (≤70 °C) is required for obtaining α-, β-, or γ-phase-dominant nanofibrous membranes, whereas a much higher temperature (≥150 °C) is necessary for post-heating of already-deposited fibers. On the other hand, through finely tuning the heating during or after electrospinning, crosslinked nanofibrous membranes can be also obtained, which undoubtedly enhance mechanical performance of the membranes. Therefore, it is hopeful to fabricate high-performance electrospun PVDF nanofibrous membranes with synchronous control of crystalline phases and morphologies, which will further broaden the applications of PVDF materials.

  7. Entropy calculations for a supercooled liquid crystalline blue phase

    Energy Technology Data Exchange (ETDEWEB)

    Singh, U [Physics Department, University of the West Indies, PO Box 64, Bridgetown (Barbados)

    2007-01-15

    We observed, using polarized light microscopy, the supercooling of the blue phase (BPI) of cholesteryl proprionate and measured the corresponding liquid crystalline phase transition temperatures. From these temperatures and additional published data we have provided, for the benefit of undergraduate physics students, a nontraditional example involving entropy calculations for an irreversible transition.

  8. Local Crystalline Structure in an Amorphous Protein Dense Phase.

    Science.gov (United States)

    Greene, Daniel G; Modla, Shannon; Wagner, Norman J; Sandler, Stanley I; Lenhoff, Abraham M

    2015-10-20

    Proteins exhibit a variety of dense phases ranging from gels, aggregates, and precipitates to crystalline phases and dense liquids. Although the structure of the crystalline phase is known in atomistic detail, little attention has been paid to noncrystalline protein dense phases, and in many cases the structures of these phases are assumed to be fully amorphous. In this work, we used small-angle neutron scattering, electron microscopy, and electron tomography to measure the structure of ovalbumin precipitate particles salted out with ammonium sulfate. We found that the ovalbumin phase-separates into core-shell particles with a core radius of ∼2 μm and shell thickness of ∼0.5 μm. Within this shell region, nanostructures comprised of crystallites of ovalbumin self-assemble into a well-defined bicontinuous network with branches ∼12 nm thick. These results demonstrate that the protein gel is comprised in part of nanocrystalline protein.

  9. Crystalline-crystalline phase transformation in two-dimensional In2Se3 thin layers.

    Science.gov (United States)

    Tao, Xin; Gu, Yi

    2013-08-14

    We report, for the first time, the fabrication of single-crystal In2Se3 thin layers using mechanical exfoliation and studies of crystalline-crystalline (α → β) phase transformations as well as the corresponding changes of the electrical properties in these thin layers. Particularly, using electron microscopy and correlative in situ micro-Raman and electrical measurements, we show that, in contrast to bulk single crystals, the β phase can persist in single-crystal thin layers at room temperature (RT). The single-crystal nature of the layers before and after the phase transition allows for unambiguous determination of changes in the electrical resistivity. Specifically, the β phase has an electrical resistivity about 1-2 orders of magnitude lower than the α phase. Furthermore, we find that the temperature of the α → β phase transformation increases by as much as 130 K with the layer thickness decreasing from ~87 nm to ~4 nm. These single-crystal thin layers are ideal for studying the scaling behavior of the phase transformations and associated changes of the electrical properties. For these In2Se3 thin layers, the accessibility of the β phase at RT, with distinct electrical properties than the α phase, provides the basis for multilevel phase-change memories in a single material system.

  10. Casimir Force Contrast Between Amorphous and Crystalline Phases of AIST

    NARCIS (Netherlands)

    Torrichelli, G.; Zwol, van P.J.; Shpak, O.; Palasantzas, G.; Svetovoy, V.B.; Binns, C.; Kooi, B.J.; Jost, P.; Wittig, M.

    2012-01-01

    Phase change materials (PCMs) can be rapidly and reversibly switched between the amorphous and crystalline state. The structural transformation is accompanied by a signifi cant change of optical and electronic properties rendering PCMs suitable for rewritable optical data storage and nonvolatile ele

  11. Crystalline Ceramic Waste Forms: Comparison Of Reference Process For Ceramic Waste Form Fabrication

    Energy Technology Data Exchange (ETDEWEB)

    Brinkman, K. S. [Savannah River National Laboratory; Marra, J. C. [Savannah River National Laboratory; Amoroso, J. [Savannah River National Laboratory; Tang, M. [Los Alamos National Laboratory

    2013-08-22

    The research conducted in this work package is aimed at taking advantage of the long term thermodynamic stability of crystalline ceramics to create more durable waste forms (as compared to high level waste glass) in order to reduce the reliance on engineered and natural barrier systems. Durable ceramic waste forms that incorporate a wide range of radionuclides have the potential to broaden the available disposal options and to lower the storage and disposal costs associated with advanced fuel cycles. Assemblages of several titanate phases have been successfully demonstrated to incorporate radioactive waste elements, and the multiphase nature of these materials allows them to accommodate variation in the waste composition. Recent work has shown that they can be produced from a melting and crystallization process. The objective of this report is to explore the phase formation and microstructural differences between lab scale melt processing in varying gas environments with alternative densification processes such as Hot Pressing (HP) and Spark Plasma Sintering (SPS). The waste stream used as the basis for the development and testing is a simulant derived from a combination of the projected Cs/Sr separated stream, the Trivalent Actinide - Lanthanide Separation by Phosphorous reagent Extraction from Aqueous Komplexes (TALSPEAK) waste stream consisting of lanthanide fission products, the transition metal fission product waste stream resulting from the transuranic extraction (TRUEX) process, and a high molybdenum concentration with relatively low noble metal concentrations. Melt processing as well as solid state sintering routes SPS and HP demonstrated the formation of the targeted phases; however differences in microstructure and elemental partitioning were observed. In SPS and HP samples, hollandite, pervoskite/pyrochlore, zirconolite, metallic alloy and TiO{sub 2} and Al{sub 2}O{sub 3} were observed distributed in a network of fine grains with small residual pores

  12. Minerals as natural analogues for crystalline nuclear waste forms

    Energy Technology Data Exchange (ETDEWEB)

    Giere, R. [Purdue University West Lafayette, Earth and Atmospheric Sciences (United States)

    2000-07-01

    Between the mining of uranium ore (mostly as uraninite) and the final disposal of nuclear waste, there are many processes and steps which together comprise the nuclear fuel cycle. Radioactive waste will be generated as long as nuclear reactors are in operation, but it is also produced by other means, e.g., during certain medical, scientific and industrial procedures. The most dangerous wastes are those resulting from the reprocessing of spent nuclear fuel and from some processes in the production and dismantling of nuclear weapons. A large part of this highly radioactive waste is present as a liquid and thus, its safe isolation from the biosphere requires immobilization of the radionuclides in a durable matrix (waste form). This is a solid which must be resistant to heat, radiation and corrosion over a geologic time scale. Three main categories of waste forms have been developed for the immobilization of radioactive waste, namely glasses, crystalline and multibarrier waste forms. One of the key properties of a nuclear waste form is its chemical durability (or resistance to corrosion), because the waste form represents the primary barrier to radionuclide release. The sciences of mineralogy and petrology have both contributed significantly to the development, characterization and performance assessment of such waste forms. The most important goal of safe nuclear waste disposal is to ensure that practically no radioactive materials reach the biosphere and, ultimately, human beings. Therefore, the design of final repositories is based on an approach that places several obstacles, or barriers, between waste and biosphere, whereby each barrier has a specific role in preventing or delaying migration of radioactive material. This multibarrier concept is different for each type of waste but, for the option of geological disposal, it generally comprises the following five barriers: (1) waste form (contains the actual waste); (2) canister (surrounds waste form; composed of a

  13. Viscous friction between crystalline and amorphous phase of dragline silk.

    Directory of Open Access Journals (Sweden)

    Sandeep P Patil

    Full Text Available The hierarchical structure of spider dragline silk is composed of two major constituents, the amorphous phase and crystalline units, and its mechanical response has been attributed to these prime constituents. Silk mechanics, however, might also be influenced by the resistance against sliding of these two phases relative to each other under load. We here used atomistic molecular dynamics (MD simulations to obtain friction forces for the relative sliding of the amorphous phase and crystalline units of Araneus diadematus spider silk. We computed the coefficient of viscosity of this interface to be in the order of 10(2 Ns/m(2 by extrapolating our simulation data to the viscous limit. Interestingly, this value is two orders of magnitude smaller than the coefficient of viscosity within the amorphous phase. This suggests that sliding along a planar and homogeneous surface of straight polyalanine chains is much less hindered than within entangled disordered chains. Finally, in a simple finite element model, which is based on parameters determined from MD simulations including the newly deduced coefficient of viscosity, we assessed the frictional behavior between these two components for the experimental range of relative pulling velocities. We found that a perfectly relative horizontal motion has no significant resistance against sliding, however, slightly inclined loading causes measurable resistance. Our analysis paves the way towards a finite element model of silk fibers in which crystalline units can slide, move and rearrange themselves in the fiber during loading.

  14. A Study of Ca-Mg Silicate Crystalline Glazes--An Analysis on Forms of Crystals

    Institute of Scientific and Technical Information of China (English)

    LIU Pei-de; YU Ping-li; WU Ji-huai

    2004-01-01

    In the study on Ca-Mg silicate crystalline glazes, we found some disequilibrated crystallization phenomena,such as non-crystallographic small angle forking and spheroidal growth, parasitism and wedging-form of crystals, dendritic growth, secondary nucleation, etc. Those phenomena possibly resulted from two factors:(1) partial temperature gradient, which is caused by heat asymmetry in the electrical resistance furnace,when crystals crystalize from silicate melt ; (2) constitutional supercooling near the surface of crystals. The disparity of disequilibrated crystallization phenomena in different main crystalline phases causes various morphological features of the crystal aggregates. At the same time, disequilibrated crystallization causes great stress retained in the crystals, which results in cracks in glazes when the temperature drops. According to the results, the authors analyzed those phenomena and displayed correlative figures and data.

  15. Cold crucible induction melter test for crystalline ceramic waste form fabrication: A feasibility assessment

    Science.gov (United States)

    Amoroso, Jake W.; Marra, James; Dandeneau, Christopher S.; Brinkman, Kyle; Xu, Yun; Tang, Ming; Maio, Vince; Webb, Samuel M.; Chiu, Wilson K. S.

    2017-04-01

    The first scaled proof-of-principle cold crucible induction melter (CCIM) test to process a multiphase ceramic waste form from a simulated combined (Cs/Sr, lanthanide and transition metal fission products) commercial used nuclear fuel waste stream was recently conducted in the United States. X-ray diffraction, 2-D X-ray absorption near edge structure (XANES), electron microscopy, inductively coupled plasma-atomic emission spectroscopy (and inductively coupled plasma-mass spectroscopy for Cs), and product consistency tests were used to characterize the fabricated CCIM material. Characterization analyses confirmed that a crystalline ceramic with a desirable phase assemblage was produced from a melt using a CCIM. Primary hollandite, pyrochlore/zirconolite, and perovskite phases were identified in addition to minor phases rich in Fe, Al, or Cs. The material produced in the CCIM was chemically homogeneous and displayed a uniform phase assemblage with acceptable aqueous chemical durability.

  16. Perhydroazulene-based liquid-crystalline materials with smectic phases.

    Science.gov (United States)

    Hussain, Zakir; Hopf, Henning; Eichhorn, S Holger

    2012-01-01

    New liquid-crystalline materials with a perhydroazulene core were synthesized and the stereochemistry of these compounds was investigated. The mesomorphic properties of the new LC compounds were investigated by differential scanning colorimetry, polarizing optical microscopy and X-ray diffraction. We report here on the LC properties of nonchiral materials, which predominantly exhibit smectic phases and display nematic phases only within narrow temperature ranges. The dependence of the mesogenic behavior of the new materials on the stereochemistry of the core system was also investigated. All newly synthesized compounds were fully characterized by the usual spectroscopic and analytical methods.

  17. Perhydroazulene-based liquid-crystalline materials with smectic phases

    Directory of Open Access Journals (Sweden)

    Zakir Hussain

    2012-03-01

    Full Text Available New liquid-crystalline materials with a perhydroazulene core were synthesized and the stereochemistry of these compounds was investigated. The mesomorphic properties of the new LC compounds were investigated by differential scanning colorimetry, polarizing optical microscopy and X-ray diffraction. We report here on the LC properties of nonchiral materials, which predominantly exhibit smectic phases and display nematic phases only within narrow temperature ranges. The dependence of the mesogenic behavior of the new materials on the stereochemistry of the core system was also investigated. All newly synthesized compounds were fully characterized by the usual spectroscopic and analytical methods.

  18. Crystalline structures of poly(L-lactide) formed under pressure and structure transitions with heating

    DEFF Research Database (Denmark)

    Huang, Shaoyong; Li, Hongfei; Yu, Donghong;

    2013-01-01

    The isothermally crystallized poly(L-lactide) (PLLA) samples were obtained at 135 °C under pressures (Pc) ranging from 1 bar to 2.5 kbar. The crystalline structures, the structure transition, and thermal properties of the prepared samples were investigated by wide-angle X-ray diffraction (WAXD...... on the peculiarities of crystalline structure and crystallization behaviors, low and high pressure regions were revealed: disordered α crystal was formed in the high pressure region (>1 kbar). A layer located intermediate between crystalline and melt-like regions was observed, which finally took on crystalline order....... Reformation, disorder to order transformation, and recrystallization during heating completely changed the previous crystalline and stacking structure, a more stable crystalline structure was newly formed. The melting behaviors of samples indicate the crystalline and stacking structure formed under high...

  19. Growth of crystalline Al2O3 via thermal atomic layer deposition: Nanomaterial phase stabilization

    Directory of Open Access Journals (Sweden)

    S. M. Prokes

    2014-03-01

    Full Text Available We report the growth of crystalline Al2O3 thin films deposited by thermal Atomic Layer Deposition (ALD at 200 °C, which up to now has always resulted in the amorphous phase. The 5 nm thick films were deposited on Ga2O3, ZnO, and Si nanowire substrates 100 nm or less in diameter. The crystalline nature of the Al2O3 thin film coating was confirmed using Transmission Electron Microscopy (TEM, including high-resolution TEM lattice imaging, selected area diffraction, and energy filtered TEM. Al2O3 coatings on nanowires with diameters of 10 nm or less formed a fully crystalline phase, while those with diameters in the 20–25 nm range resulted in a partially crystalline coating, and those with diameters in excess of 50 nm were fully amorphous. We suggest that the amorphous Al2O3 phase becomes metastable with respect to a crystalline alumina polymorph, due to the nanometer size scale of the film/substrate combination. Since ALD Al2O3 films are widely used as protective barriers, dielectric layers, as well as potential coatings in energy materials, these findings may have important implications.

  20. Nucleation and growth studies of crystalline carbon phases at nanoscale

    Science.gov (United States)

    Mani, Radhika C.

    Understanding the nucleation and early stage growth of crystals from the vapor phase is important for realizing large-area single-crystal quality films, controlled synthesis of nanocrystals, and the possible discovery of new phases of materials. Carbon provides the most interesting system because all its known crystalline phases (diamond, graphite and carbon nanotubes) are technologically important materials. Hence, this dissertation is focused on studying the nucleation and growth of carbon phases synthesized from the vapor phase. Nucleation experiments were performed in a microwave plasma chemical vapor deposition (CVD) reactor, and the resulting carbon nanocrystals were analyzed primarily using electron nanodiffraction and Raman spectroscopy. These studies led to the discovery of two new crystalline phases of sp 3 carbon other than diamond: face-centered and body-centered cubic carbon. Nanodiffraction results revealed possible hydrogen substitution into diamond-cubic lattices, indicating that these new phases probably act as intermediates in diamond nucleation. Nucleation experiments also led to the discovery of two new morphologies for sp2 carbon: nanocrystals of graphite and tapered, hollow 1-D structures termed here as "carbon nanopipettes". A Kinetic Monte Carlo (KMC) algorithm was developed to simulate the growth of individual diamond crystals from the vapor phase, starting with small clusters of carbon atoms (or seeds). Specifically, KMC simulations were used to distinguish the kinetic rules that give rise to a star-shaped decahedral morphology compared to decahedral crystals. KMC simulations revealed that slow adsorption on the {111} step-propagation sites compared to kink sites leads to star-decahedral crystals, and higher adsorption leads to decahedral crystals. Since the surfaces of the nanocrystals of graphite and nanopipettes were expected to be composed primarily of edge-plane sites, the electrochemical behavior of both these materials were

  1. Formation of nano quasicrystalline and crystalline phases by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Shamah, A.M.; Ibrahim, S. [Faculty of Petroleum and Mining Engineering, Suez Canal University, Suez (Egypt); Hanna, F.F., E-mail: fariedhanna@yahoo.com [Faculty of Petroleum and Mining Engineering, Suez Canal University, Suez (Egypt)

    2011-02-03

    Research highlights: > Mechanical alloying (MA) is an important method to investigate the formation of nano sized quasicrystalline phases in Al{sub 86}Cr{sub 14}, Al{sub 84}Fe{sub 16} and Al{sub 62.5}Cu{sub 25}Fe{sub 12.5} compounds. The second part of the present work is an attempt to examine the possibility of formation of the i-phase of the Al{sub 62.5}Cu{sub 25}Fe{sub 12.5}, which lies in the region of the perfect i-phase in the ternary phase diagram, by rapid solidification method. To perform the obtained quasi phase mechanical alloying and heat treatment at the rapid solidified sample were done. - Abstract: In the present work, the formation of nano quasicrystalline icosahedral phase in Al{sub 86}Cr{sub 14}, Al{sub 84}Fe{sub 16} and Al{sub 62.5}Cu{sub 25}Fe{sub 12.5} alloys has been investigated by mechanical alloying. Mixtures of quasicrystalline and related crystalline phases have been observed under various milling conditions. The X-ray diffraction, differential thermal analysis and electrical resistivity techniques have been used for characterization and physical property measurements. The particle size was calculated by X-ray profile using Williamson-Hall plot method and it was found to be 25-50 nm size.

  2. Spatial distribution of crystalline corrosion products formed during corrosion of stainless steel in concrete

    Energy Technology Data Exchange (ETDEWEB)

    Serdar, Marijana [Department of Materials, Faculty of Civil Engineering, University of Zagreb, 10000 Zagreb (Croatia); Meral, Cagla [Middle East Technical University, Department of Civil Engineering, Ankara (Turkey); Kunz, Martin [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Bjegovic, Dubravka [Department of Materials, Faculty of Civil Engineering, University of Zagreb, 10000 Zagreb (Croatia); Wenk, Hans-Rudolf [Department of Earth and Planetary Science, University of California, Berkeley, CA 94720 (United States); Monteiro, Paulo J.M., E-mail: monteiro@ce.berkeley.edu [Department of Civil and Environmental Engineering, University of California, Berkeley, CA 94720 (United States)

    2015-05-15

    The mineralogy and spatial distribution of nano-crystalline corrosion products that form in the steel/concrete interface were characterized using synchrotron X-ray micro-diffraction (μ-XRD). Two types of low-nickel high-chromium reinforcing steels embedded into mortar and exposed to NaCl solution were investigated. Corrosion in the samples was confirmed by electrochemical impedance spectroscopy (EIS). μ-XRD revealed that goethite (α-FeOOH) and akaganeite (β-FeOOH) are the main iron oxide–hydroxides formed during the chloride-induced corrosion of stainless steel in concrete. Goethite is formed closer to the surface of the steel due to the presence of chromium in the steel, while akaganeite is formed further away from the surface due to the presence of chloride ions. Detailed microstructural analysis is shown and discussed on one sample of each type of steel. - Highlights: • Synchrotron micro-diffraction used to map the distribution of crystalline phases. • Goethite and akaganeite are the main corrosion products during chloride induced corrosion in mortar. • Layers of goethite and akaganeite are negatively correlated. • EDS showed Cr present in corrosion products identified by SEM.

  3. Electronic phases of substances. Phase transitions with change of electron and crystalline structure

    Directory of Open Access Journals (Sweden)

    Nadykto Boris

    2015-01-01

    Full Text Available There is plenty of experimental data on high-pressure phase transformations in various materials. Variations in materials characteristics (for example, equilibrium density and bulk modulus, while the crystalline structure remains unchanged, are indicative of energy variations in outer-shell electrons of solid atoms. In experiments with crystalline structure variations, the dependence of pressure on density in some cases can be described by the same curve, the parameters of which are independent of the crystalline structure. Examples of such transformations in some materials at static compression and in shock-wave experiments are given.

  4. Spectral descriptors for bulk metallic glasses based on the thermodynamics of competing crystalline phases

    CERN Document Server

    Perim, Eric; Liu, Yanhui; Toher, Cormac; Gong, Pan; Li, Yanglin; Simmons, W Neal; Levy, Ohad; Vlassak, Joost J; Schroers, Jan; Curtarolo, Stefano

    2016-01-01

    Metallic glasses have attracted considerable interest in recent years due to their unique combination of superb properties and processability. Predicting bulk metallic glass formers from known parameters remains a challenge and the search for new systems is still performed by trial and error. It has been speculated that some sort of "confusion" during crystallization of the crystalline phases competing with glass formation could play a key role. Here, we propose a heuristic descriptor quantifying confusion and demonstrate its validity by detailed experiments on two well-known glass forming alloy systems. With the insight provided by these results, we develop a robust model for predicting glass formation ability based on the spectral decomposition of geometrical and energetic features of crystalline phases calculated ab-initio in the AFLOW high throughput framework. Our findings indicate that the formation of metallic glass phases could be a much more common phenomenon than currently estimated, with more than ...

  5. Topological Crystalline Insulator in a New Bi Semiconducting Phase

    Science.gov (United States)

    Munoz, F.; Vergniory, M. G.; Rauch, T.; Henk, J.; Chulkov, E. V.; Mertig, I.; Botti, S.; Marques, M. A. L.; Romero, A. H.

    2016-02-01

    Topological crystalline insulators are a type of topological insulators whose topological surface states are protected by a crystal symmetry, thus the surface gap can be tuned by applying strain or an electric field. In this paper we predict by means of ab initio calculations a new phase of Bi which is a topological crystalline insulator characterized by a mirror Chern number nM = -2, but not a strong topological insulator. This system presents an exceptional property: at the (001) surface its Dirac cones are pinned at the surface high-symmetry points. As a consequence they are also protected by time-reversal symmetry and can survive against weak disorder even if in-plane mirror symmetry is broken at the surface. Taking advantage of this dual protection, we present a strategy to tune the band-gap based on a topological phase transition unique to this system. Since the spin-texture of these topological surface states reduces the back-scattering in carrier transport, this effective band-engineering is expected to be suitable for electronic and optoelectronic devices with reduced dissipation.

  6. Volume phase transitions of cholesteric liquid crystalline gels

    Energy Technology Data Exchange (ETDEWEB)

    Matsuyama, Akihiko, E-mail: matuyama@bio.kyutech.ac.jp [Department of Bioscience and Bioinformatics, Faculty of Computer Science and Systems Engineering, Kyushu Institute of Technology, Kawazu 680-4, Iizuka, Fukuoka 820-8502 (Japan)

    2015-05-07

    We present a mean field theory to describe anisotropic deformations of a cholesteric elastomer without solvent molecules and a cholesteric liquid crystalline gel immersed in isotropic solvents at a thermal equilibrium state. Based on the neoclassical rubber theory of nematic elastomers, we derive an elastic energy and a twist distortion energy, which are important to determine the shape of a cholesteric elastomer (or gel). We demonstrate that when the elastic energy dominates in the free energy, the cholesteric elastomer causes a spontaneous compression in the pitch axis and elongates along the director on the plane perpendicular to the pitch axis. Our theory can qualitatively describe the experimental results of a cholesteric elastomer. We also predict the first-order volume phase transitions and anisotropic deformations of a gel at the cholesteric-isotropic phase transition temperature. Depending on a chirality of a gel, we find a prolate or oblate shape of cholesteric gels.

  7. Conformer of the peroxynitrite ion formed under photolysis of crystalline alkali nitrates – cis or trans?

    Science.gov (United States)

    Pak, V. Kh; Anan’ev, V. A.; Dyagileva, E. P.; Lyrshchikov, S. Yu; Miklin, M. B.; Rezvova, M. A.

    2017-01-01

    The optical and infrared reflectance spectra of the crystalline powders prepared by co-crystallization of caesium nitrate, nitrite, and peroxynitrite from alkali solution have been studied. We find that the trans conformer forms under photolysis of crystalline pure caesium nitrate. Under its dissolution the trans conformer transforms to the cis conformer.

  8. Smectic Phase Formed by DNA Dimers

    Science.gov (United States)

    Salamonczyk, Miroslaw; Gleeson, James; Jakli, Antal; Sprunt, Samuel; Dhont, Jan; Stiakakis, Emmanuel

    The rapidly expanding bio market is driving the development and characterization of new multifunctional materials. In particular, nucleic acids are under intense study for gene therapy, drug delivery and other bio-safe applications [1,2,3]. DNA is well-known to form a cholesteric nematic liquid crystal in its native form; however, much recent research has focused on self-assembly and mesomorphic behavior in concentrated solutions of short DNA helices [4]. Our work focuses on DNA dimers, consisting of 48 base-pair double-stranded helices connected by a 5 to 20 base flexible single strand, and suspended in a natural buffer. Depending on temperature, concentration and length of the flexible spacer, polarizing optical microscopy and small angle x-ray scattering reveal cholesteric nematic and, remarkably, smectic liquid crystalline phases. A model for smectic phase formation in this system will be presented. 1] J.-L. Lim et al., Int. J. of. Pharm. 490 (2015) 2652] D.-H. Kim et al., Nature Biotech. 23 (2005) 2223] K. Liu et al., Chem. Eur. J. 21 (2015) 48984] M. Nakata et al., Science 318 (2007) 1276 NSF DMR 1307674.

  9. Selective Sequence for the Peptide-Triggered Phase Transition of Lyotropic Liquid-Crystalline Structures.

    Science.gov (United States)

    Liu, Qingtao; Dong, Yao-Da; Boyd, Ben J

    2016-05-24

    A novel concept of using mixed lipids to construct selective peptide-sequence-sensing lyotropic liquid-crystalline (LLC) dispersion systems was investigated. The LLC systems were constructed using a mixture of phytantriol, a lipid that forms lyotropic liquid-crystalline phases, and a novel synthesized peptide-lipid (peplipid) for sensing a target peptide with the RARAR sequence. The internal structure of the dispersed LLC particles was converted from the lamellar structure (liposomes) to the inverse bicontinuous cubic phase (cubosomes) in the presence of the target peptide. The addition of common human proteins did not induce any structural change, indicating a high selectivity of interaction with the target peptide. The concept has potential for the design of targeted controlled release drug delivery agents.

  10. Wettability and surface chemistry of crystalline and amorphous forms of a poorly water soluble drug.

    Science.gov (United States)

    Puri, Vibha; Dantuluri, Ajay K; Kumar, Mahesh; Karar, N; Bansal, Arvind K

    2010-05-12

    The present study compares energetics of wetting behavior of crystalline and amorphous forms of a poorly water soluble drug, celecoxib (CLB) and attempts to correlate it to their surface molecular environment. Wettability and surface free energy were determined using sessile drop contact angle technique and water vapor sorption energetics was measured by adsorption calorimetry. The surface chemistry was elucidated by X-ray photoelectron spectroscopy (XPS) and crystallographic evaluation. The two solid forms displayed distinctly different wetting with various probe liquids and in vitro dissolution media. The crystalline form surface primarily exhibited dispersive surface energy (47.3mJ/m(2)), while the amorphous form had a slightly reduced dispersive (45.2mJ/m(2)) and a small additional polar (4.8mJ/m(2)) surface energy. Calorimetric measurements, revealed the amorphous form to possess a noticeably high differential heat of absorption, suggesting hydrogen bond interactions between its polar energetic sites and water molecules. Conversely, the crystalline CLB form was found to be inert to water vapor sorption. The relatively higher surface polarity of the amorphous form could be linked to its greater oxygen-to-fluorine surface concentration ratio of 1.27 (cf. 0.62 for crystalline CLB), as determined by XPS. The crystallographic studies of the preferred cleavage plane (020) of crystalline CLB further supported its higher hydrophobicity. In conclusion, the crystalline and amorphous forms of CLB exhibited disparate surface milieu, which in turn can have implications on the surface mediated events.

  11. Formation of liquid crystalline phases in aqueous suspensions of platelet-like tripalmitin nanoparticles

    Science.gov (United States)

    Schmiele, Martin; Gehrer, Simone; Westermann, Martin; Steiniger, Frank; Unruh, Tobias

    2014-06-01

    Suspensions of platelet-like shaped tripalmitin nanocrystals stabilized by the pure lecithin DLPC and the lecithin blend S100, respectively, have been studied by small-angle x-ray scattering (SAXS) and optical observation of their birefringence at different tripalmitin (PPP) concentrations φPPP. It could be demonstrated that the platelets of these potential drug delivery systems start to form a liquid crystalline phase already at pharmaceutically relevant concentrations φPPP of less than 10 wt. %. The details of this liquid crystalline phase are described here for the first time. As in a previous study [A. Illing et al., Pharm. Res. 21, 592 (2004)] some platelets are found to self-assemble into lamellar stacks above a critical tripalmitin concentration \\varphi _{PPP}^{st} of 4 wt. %. In this study another critical concentration \\varphi _{PPP}^{lc}≈ 7 wt. % for DLPC and \\varphi _{PPP}^{lc}≈ 9 wt. % for S100 stabilized dispersions, respectively, has been observed. \\varphi _{PPP}^{lc} describes the transition from a phase of randomly oriented stacked lamellae and remaining non-assembled individual platelets to a phase in which the stacks and non-assembled platelets exhibit an overall preferred orientation. A careful analysis of the experimental data indicates that for concentrations above \\varphi _{PPP}^{lc} the stacked lamellae start to coalesce to rather small liquid crystalline domains of nematically ordered stacks. These liquid crystalline domains can be individually very differently oriented but possess an overall preferred orientation over macroscopic length scales which becomes successively more expressed when further increasing φPPP. The lower critical concentration for the formation of liquid crystalline domains of the DLPC-stabilized suspension compared to \\varphi _{PPP}^{lc} of the S100-stabilized suspension can be explained by a larger aspect ratio of the corresponding tripalmitin platelets. A geometrical model based on the excluded volumes of

  12. Electric-field triggered controlled release of bioactive volatiles from imine-based liquid crystalline phases.

    Science.gov (United States)

    Herrmann, Andreas; Giuseppone, Nicolas; Lehn, Jean-Marie

    2009-01-01

    Application of an electric field to liquid crystalline film forming imines with negative dielectric anisotropy, such as N-(4-methoxybenzylidene)-4-butylaniline (MBBA, 1), results in the expulsion of compounds that do not participate in the formation of the liquid crystalline phase. Furthermore, amines and aromatic aldehydes undergo component exchange with the imine by generating constitutional dynamic libraries. The strength of the electric field and the duration of its application to the liquid crystalline film influence the release rate of the expelled compounds and, at the same time, modulate the equilibration of the dynamic libraries. The controlled release of volatile organic molecules with different chemical functionalities from the film was quantified by dynamic headspace analysis. In all cases, higher headspace concentrations were detected in the presence of an electric field. These results point to the possibility of using imine-based liquid crystalline films to build devices for the controlled release of a broad variety of bioactive volatiles as a direct response to an external electric signal.

  13. Evidence of a new crystalline phase in U–Gd–O phase diagram

    Energy Technology Data Exchange (ETDEWEB)

    Pieck, Darío [CEA, DEN, DEC, SESC – Laboratoire des Lois de Comportement des Combustibles (France); Desgranges, Lionel, E-mail: lionel.desgranges@cea.fr [CEA, DEN, DEC, SESC – Laboratoire des Lois de Comportement des Combustibles (France); Matheron, Pierre [CEA, DEN, DEC, SPUA – Laboratoire Combustibles Uranium (France); Palancher, Hervé [CEA, DEN, DEC, SESC – Laboratoire des Lois de Comportement des Combustibles (France)

    2015-06-15

    The U–Gd–O phase diagram was investigated in its high Gd content part. Several samples with the general (U{sub 1−y}, Gd{sub y})O{sub 2±x} composition were prepared by sintering under Ar H{sub 2} 5% atmosphere. The samples were characterized by SEM–EDS and X-ray diffraction. A new cubic crystalline phase was evidenced at high a Gd content that was not expected from previous literature. Rietveld refinements showed that its crystalline structure is related to C-Gd{sub 2}O{sub 3} phase. The existence of this compound has to be taken into account in the sintering of (U,Gd)O{sub 2} nuclear fuel.

  14. Quasiparticle specific heats for the crystalline color superconducting phase of QCD

    CERN Document Server

    Casalbuoni, R; Mannarelli, M; Nardulli, G; Ruggieri, M; Stramaglia, S; 10.1016/j.physletb.2003.09.071

    2003-01-01

    We calculate the specific heats of quasiparticles of two-flavor QCD in its crystalline phases for low temperature. We show that for the different crystalline structures considered here there are gapless modes contributing linearly in temperature to the specific heat. We evaluate also the phonon contributions which are cubic in temperature. These features might be relevant for compact stars with an inner shell in a color superconducting crystalline phase. (21 refs).

  15. Quasi-particle Specific Heats for the Crystalline Color Superconducting Phase of QCD

    CERN Document Server

    Casalbuoni, Roberto; Mannarelli, M; Nardulli, Giuseppe; Ruggieri, Marco; Stramaglia, S

    2003-01-01

    We calculate the specific heats of quasi-particles of two-flavor QCD in its crystalline phases for low temperature. We show that for the different crystalline structures considered here there are gapless modes contributing linearly in temperature to the specific heat. We evaluate also the phonon contributions which are cubic in temperature. These features might be relevant for compact stars with an inner shell in a color superconducting crystalline phase.

  16. Quasi-particle specific heats for the crystalline color superconducting phase of QCD

    Energy Technology Data Exchange (ETDEWEB)

    Casalbuoni, R.; Gatto, R.; Mannarelli, M.; Nardulli, G.; Ruggieri, M.; Stramaglia, S

    2003-11-27

    We calculate the specific heats of quasi-particles of two-flavor QCD in its crystalline phases for low temperature. We show that for the different crystalline structures considered here there are gapless modes contributing linearly in temperature to the specific heat. We evaluate also the phonon contributions which are cubic in temperature. These features might be relevant for compact stars with an inner shell in a color superconducting crystalline phase.

  17. Crystalline behaviors and phase transition during the manufacture of fine denier PA6 fibers

    Institute of Scientific and Technical Information of China (English)

    ZHANG ChengFeng; LIU YuHai; LIU ShaoXuan; LI HuiZhen; HUANG Kun; PAN QingHua; HUA XiaoHui; HAO ChaoWei; MA QingFang; LV ChangYou; LI WeiHong; YANG ZhanLan; ZHAO Ying; WANG DuJin; LAI GuoQiao; JIANG JianXiong; XU YiZhuang; WU JinGuang

    2009-01-01

    Recently we have successfully produced fine denier PA6 fibers by using additives containing lanthanide compounds.Meanwhile,crystallization and phase transition of PA6 fibers during spinning and drawing processes were investigated.During the spinning process,β phase crystal could be obtained In as-spun PA6 fibers which were produced with relatively high melt draw ratio,while γ phase crystal predominated when the melt draw ratio was relatively low.β phase crystal,whose behaviors ere similar with those of γ phase by FT-IR and XRD characterization,could be transformed to α form easily when PA6 fibers are immersed in boiling water.However,γ phase crystal of PA6 remains unchanged in boiling water.Thus,β and γ phase crystals of PA6 can be differentiated by the crystalline behaviors of PA6 fibers after treatment in boiling water.Further experiments demonstrate that the β phase can also be produced during a drawing process where a phase transformation from γ to α occurs.In other words,βphase may act as an intermediate state during the phase transformation.

  18. Crystalline structures of poly(L-lactide) formed under pressure and structure transitions with heating

    DEFF Research Database (Denmark)

    Huang, Shaoyong; Li, Hongfei; Yu, Donghong

    2013-01-01

    . Reformation, disorder to order transformation, and recrystallization during heating completely changed the previous crystalline and stacking structure, a more stable crystalline structure was newly formed. The melting behaviors of samples indicate the crystalline and stacking structure formed under high......The isothermally crystallized poly(L-lactide) (PLLA) samples were obtained at 135 °C under pressures (Pc) ranging from 1 bar to 2.5 kbar. The crystalline structures, the structure transition, and thermal properties of the prepared samples were investigated by wide-angle X-ray diffraction (WAXD......), real time synchrotron small-angle X-ray scattering (SR-SAXS) and differential scanning calorimetry (DSC) during this process. The structural parameters, such as the size of crystallites, the inverse spacing, the long periods and lamellae thicknesses decrease with pressure increasing. Based...

  19. The devitrification of artificial fibers: a multimethodic approach to quantify the temperature-time onset of cancerogenic crystalline phases.

    Science.gov (United States)

    Comodi, Paola; Cera, Fabio; Gatta, Giacomo Diego; Rotiroti, Nicola; Garofani, Patrizia

    2010-11-01

    A variety of artificial fibers extensively employed as lining in high-temperature apparatus may undergo a devitrification process that leads to significant changes in the chemical-physical properties of the materials. Among them, the crystallization of carcinogenic minerals, such as cristobalite, has already been documented for alumino-silicate ceramic fibers. Five fibrous samples with different compositions were treated over a wide range of temperatures (20-1500°C) and times (24-336 h) to investigate the rate and the crystalline phases that are formed as well their onset temperatures. The new phases were characterized by using a multimethodic approach: phase transformations were monitored together with thermal analysis and the new phases were investigated by using X-ray powder diffraction analysis. The crystalline:amorphous ratio was monitored by Rietveld refinement of X-ray diffraction data. Scanning electron microscopy was used to study the effect of heat treatments on the morphology of fibers, and the nanostructures were investigated by transmission electron microscopy (TEM). The results show that the main crystalline phases are cristobalite, diopside, mullite, and zirconia. The onset of cristobalite was observed at temperature lower than that thermodynamically expected. The TEM analysis showed that protostructures were present in the material vitrified from sol-gel-derived products, which can act as crystallization nuclei. The study shows that the devitrification leads to health hazard due to the formation of inhalable powder of cancerogenic crystalline phases.

  20. Comparison of Oxidative Stresses Mediated by Different Crystalline Forms and Surface Modification of Titanium Dioxide Nanoparticles

    Directory of Open Access Journals (Sweden)

    Karim Samy El-Said

    2015-01-01

    Full Text Available Titanium dioxide nanoparticles (TiO2 NPs are manufactured worldwide for use in a wide range of applications. There are two common crystalline forms of TiO2 anatase and rutile with different physical and chemical characteristics. We previously demonstrated that an increased DNA damage response is mediated by anatase crystalline form compared to rutile. In the present study, we conjugated TiO2 NPs with polyethylene glycol (PEG in order to reduce the genotoxicity and we evaluated some oxidative stress parameters to obtain information on the cellular mechanisms of DNA damage that operate in response to TiO2 NPs different crystalline forms exposure in hepatocarcinoma cell lines (HepG2. Our results indicated a significant increase in oxidative stress mediated by the anatase form of TiO2 NPs compared to rutile form. On the other hand, PEG modified TiO2 NPs showed a significant decrease in oxidative stress as compared to TiO2 NPs. These data suggested that the genotoxic potential of TiO2 NPs varies with crystalline form and surface modification.

  1. Phase behavior and crystalline structures of cholesteryl ester mixtures: a C-13 MASNMR study.

    Science.gov (United States)

    Guo, W; Hamilton, J A

    1995-06-01

    Cholesteryl esters are a transport and storage form of cholesterol in normal physiology but also a significant lipid in atherosclerotic plaques. To understand better the molecular properties of cholesteryl esters in tissues and plaques, we have studied the polymorphic and mesomorphic features of pure and mixed cholesteryl esters by solid state C-13 NMR with magic angle sample spinning (MASNMR). The temperature-dependent properties of two single components (cholesteryl linoleate (CL, C18:2) and cholesteryl linolenate (CLL, C18:3)), four binary systems (cholesteryl palmitate (CP, C16:0) with CL, CLL or cholesteryl oleate (CO, C18:1), and CO/CL), one ternary system (CO/CP/CL), and one quaternary system (CO/CP/CL/CLL) were studied. The mixing ratios were based on the composition of an atherosclerosis plaque dissected from a cholesterol-fed New Zealand white rabbit. C-13 MASNMR determined the phase transition temperatures, identified the phases present in all systems, and provided novel information about molecular structures. For example, solid CL exhibited a disordered structure with multiple molecular conformations, whereas pure CLL had a crystalline structure different from the three most commonly characterized forms (MLII, MLI, BL). In binary mixtures, the crystalline structure of each cholesteryl ester species was identified by its own characteristic resonances. It was found that CP always existed in its native BL form, but CL and CO were influenced by the composition of the mixture. CL was induced to form MLII crystals by the coexisting CP (55 wt%). When CO was cooled from the isotropic phase, it existed as a mixture of MLII and an amorphous form. The presence of CP significantly accelerated the conversion of the amorphous form to the MLII form. For the ternary mixture co-dried from chloroform, CL cocrystallized with CO in the MLII form and CP existed in BL form. Addition of a small amount of CLL slightly increased the heterogeneity of the solid mixture, but had

  2. Molecular dynamics simulation of calcium fluoride——Crystalline, superionic, molten and quenched-amorphous phases

    Institute of Scientific and Technical Information of China (English)

    程兆年; 郏正明; 张静; 陈念贻

    1995-01-01

    The results from the molecular dynamics simulations on crystalline, superionic, molten and quenched-amorphous states of calcium fluoride system are reported. The Ca++ and F- sublattices are studied by using the method of bond order parameters. The result shows that both Ca++ and F- sublattices can be described with the bond-orientation normal distribution model. In the superionic phase the Ca++ cations keep their original stable fcc frame, but in the F- case random distortion generates from their original simple cubic (sc) structure. The simulation on the molten phase gives three radial distribution functions that are difficult to separate from the experimental X-ray diffraction data. The simulation of quenched-amorphous state shows that a dense random packing of equivalent spheres centered by Ca++ cations occurs in the system simulated. However, the system quenched is not stable enough because the Ca++ cation and F- anions around it do not form themselves into a certain configuration.

  3. Ore-forming fluid constraints on illite crystallinity (IC) at Dexing porphyry copper deposit, Jiangxi Province

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Illite, a distinctive kind of clay minerals of potassiumalteration within the hydrothermal alteration zone, frequently occurs at the Tongchang porphyry copper deposit ore field. The illite crystallinity (IC) value and expandability are mainly affected by water/rock ratio or fluid flux. It was formed by illitization of plagioclase and micas during hydrothermal fluid-rock interaction within the porphyry body and near the contact zone with wall rocks. Moreover, the negative correlation between illite index (IC) and copper grade indicates that within the alteration zone, the smaller the illite crystallinity value, the higher the alteration degree, and the higher the copper grade due to higher water/rock ratio. At lower levels of the porphyry body, however, the illite crystallinity (IC) values are mainly controlled by temperature and time duration.

  4. Nanostructures formed on carbon-based materials with different levels of crystallinity using oxygen plasma treatment

    Energy Technology Data Exchange (ETDEWEB)

    Ko, Tae-Jun [Institute for Multidisciplinary Convergence of Matter, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Department of Materials Science and Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of); Jo, Wonjin; Lee, Heon Ju [Institute for Multidisciplinary Convergence of Matter, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Oh, Kyu Hwan [Department of Materials Science and Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of); Moon, Myoung-Woon, E-mail: mwmoon@kist.re.kr [Institute for Multidisciplinary Convergence of Matter, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of)

    2015-09-01

    Nanostructure formation was explored for various carbon-based materials, such as diamond, carbon fiber, polyethylene terephthalate and poly (methyl methacrylate), which have different levels of crystallinity, ranging from perfect crystal to polymeric amorphous. After treatment of oxygen plasma glow discharge, the nanostructures on these carbon-based materials were found to evolve via preferential etching due to the co-deposition of metal elements sputtered from the metal cathode plate. Local islands or clusters formed by the metal co-deposition have a low etching rate compared to pristine regions on each material, resulting in anisotropic patterns on the carbon-based materials. This pattern formation mechanism was confirmed by covering the cathode or preventing the co-deposition of metallic sources with a polymeric material. Regardless of the level of crystallinity of the carbon-based materials, no patterns were observed on the surfaces covered with the polymeric material, and the surfaces were uniformly etched. It was found that the materials with low crystallinity had a high etching rate due to low carbon atom density, which thus easily formed high-aspect-ratio nanostructures for the same plasma treatment duration. - Highlight: • Reactive ion etching & metal deposition were occurred in oxygen plasma treatment. • High-aspect-ratio nanostructures can be fabricated on carbon-based materials. • Materials with low crystallinity easily formed high-aspect-ratio nanostructure. • Amount of etching inhibitors affects the pattern formation and configuration.

  5. Evidences of the existence of SiTe2 crystalline phase and a proposed new Si-Te phase diagram

    Science.gov (United States)

    Mishra, R.; Mishra, P. K.; Phapale, S.; Babu, P. D.; Sastry, P. U.; Ravikumar, G.; Yadav, A. K.

    2016-05-01

    The existence of two distinct crystalline phases viz., Si2Te3 and SiTe2, in the Si-Te system is established from differential thermal analysis (DTA) studies. Thermo-gravimetric (TG) data on SiTe2 indicate that the compound decomposes to Si in multiple steps via intermediate Si2Te3 phase. X-ray diffraction (XRD) reveals that SiTe2 crystallizes in P 3 ̅m1 space group with CdI2 trigonal structure, whereas Si2Te3 crystallizes in trigonal structure with space group P 3 ̅1c with varying occupation of octahedral voids. Single Si atoms fill only 1/2 of the octahedral voids in SiTe2 structure whereas in Si2Te3, Si atoms are arranged in pairs occupying 2/3 of the octahedral voids in alternating planes along c-axis. Further, X-ray absorption near edge structure (XANES) and X-ray photoelectron spectroscopy (XPS) confirm the distinctness of the chemical environment in the two crystalline structures confirming the uniqueness of both the phases. DTA results on the two compounds indicate the presence of one crystallographic phase-transition in each of the compound with transition temperatures at 441 °C for Si2Te3 and 392 °C for SiTe2. At the same time both Si2Te3 and SiTe2 undergo peritectic decomposition at 683 °C and 432 °C forming [Si(s)+Te(liq)] and [α-Si2Te3(s)+Te(liq)], respectively. The system revealed eutectic reaction between β-SiTe2 and Te at 398 °C [L=Te+SiTe2]. Consequently, the phase diagram in the Si-Te system has been delineated.

  6. Process induced disorder in crystalline materials: differentiating defective crystals from the amorphous form of griseofulvin.

    Science.gov (United States)

    Feng, Tao; Pinal, Rodolfo; Carvajal, M Teresa

    2008-08-01

    This research investigates milling induced disorder in crystalline griseofulvin. Griseofulvin was subjected to cryogenic milling for various lengths of time. For comparison, the amorphous form of griseofulvin was also prepared by the quench melt method. Different analytical techniques were used to study the differences between the cryomilled, amorphous and crystalline forms of the drug. Cryogenic milling of griseofulvin progressively reduces the crystallinity of the drug by inducing crystal defects, rather than amorphous materials. Raman analysis provides evidence of structural differences between the two. The differences between the defective crystals produced by milling and the amorphous form are significant enough as to be measurable in their bulk thermal properties. Defective crystals show significant decrease in the heat of fusion as a function of milling time but do not exhibit a glass transition nor recrystallization from the amorphous form. Crystal defects undergo recrystallization upon heating at temperatures well below the glass transition temperature (T(g)) in a process that is separate and completely independent from the crystallization of the amorphous griseofulvin, observed above T(g). Physical mixtures of defective crystals and amorphous drug demonstrate that the thermal events associated with each form persist in the mixtures, unaffected by the presence of the other form.

  7. Light-Driven Liquid Crystalline Materials: From Photo-Induced Phase Transitions and Property Modulations to Applications.

    Science.gov (United States)

    Bisoyi, Hari Krishna; Li, Quan

    2016-12-28

    Light-driven phenomena both in living systems and nonliving materials have enabled truly fascinating and incredible dynamic architectures with terrific forms and functions. Recently, liquid crystalline materials endowed with photoresponsive capability have emerged as enticing systems. In this Review, we focus on the developments of light-driven liquid crystalline materials containing photochromic components over the past decade. Design and synthesis of photochromic liquid crystals (LCs), photoinduced phase transitions in LC, and photoalignment and photoorientation of LCs have been covered. Photomodulation of pitch, polarization, lattice constant and handedness inversion of chiral LCs is discussed. Light-driven phenomena and properties of liquid crystalline polymers, elastomers, and networks have also been analyzed. The applications of photoinduced phase transitions, photoalignment, photomodulation of chiral LCs, and photomobile polymers have been highlighted wherever appropriate. The combination of photochromism, liquid crystallinity, and fabrication techniques has enabled some fascinating functional materials which can be driven by ultraviolet, visible, and infrared light irradiation. Nanoscale particles have been incorporated to widen and diversify the scope of the light-driven liquid crystalline materials. The developed materials possess huge potential for applications in optics, photonics, adaptive materials, nanotechnology, etc. The challenges and opportunities in this area are discussed at the end of the Review.

  8. Sensitivity of micromechanical actuation on amorphous to crystalline phase transformations under the influence of Casimir forces

    NARCIS (Netherlands)

    Sedighi Ghozotkhar, Mehdi; Broer, W. H.; Palasantzas, G.; Kooi, B. J.

    2013-01-01

    Amorphous to crystalline phase transitions in phase change materials (PCM) can have strong influence on the actuation of microelectromechanical systems under the influence of Casimir forces. Indeed, the bifurcation curves of the stationary equilibrium points and the corresponding phase portraits of

  9. Indomethacin nanocrystals prepared by different laboratory scale methods: effect on crystalline form and dissolution behavior

    Energy Technology Data Exchange (ETDEWEB)

    Martena, Valentina; Censi, Roberta [University of Camerino, School of Pharmacy (Italy); Hoti, Ela; Malaj, Ledjan [University of Tirana, Department of Pharmacy (Albania); Di Martino, Piera, E-mail: piera.dimartino@unicam.it [University of Camerino, School of Pharmacy (Italy)

    2012-12-15

    The objective of this study is to select very simple and well-known laboratory scale methods able to reduce particle size of indomethacin until the nanometric scale. The effect on the crystalline form and the dissolution behavior of the different samples was deliberately evaluated in absence of any surfactants as stabilizers. Nanocrystals of indomethacin (native crystals are in the {gamma} form) (IDM) were obtained by three laboratory scale methods: A (Batch A: crystallization by solvent evaporation in a nano-spray dryer), B (Batch B-15 and B-30: wet milling and lyophilization), and C (Batch C-20-N and C-40-N: Cryo-milling in the presence of liquid nitrogen). Nanocrystals obtained by the method A (Batch A) crystallized into a mixture of {alpha} and {gamma} polymorphic forms. IDM obtained by the two other methods remained in the {gamma} form and a different attitude to the crystallinity decrease were observed, with a more considerable decrease in crystalline degree for IDM milled for 40 min in the presence of liquid nitrogen. The intrinsic dissolution rate (IDR) revealed a higher dissolution rate for Batches A and C-40-N, due to the higher IDR of {alpha} form than {gamma} form for the Batch A, and the lower crystallinity degree for both the Batches A and C-40-N. These factors, as well as the decrease in particle size, influenced the IDM dissolution rate from the particle samples. Modifications in the solid physical state that may occur using different particle size reduction treatments have to be taken into consideration during the scale up and industrial development of new solid dosage forms.

  10. Indomethacin nanocrystals prepared by different laboratory scale methods: effect on crystalline form and dissolution behavior

    Science.gov (United States)

    Martena, Valentina; Censi, Roberta; Hoti, Ela; Malaj, Ledjan; Di Martino, Piera

    2012-12-01

    The objective of this study is to select very simple and well-known laboratory scale methods able to reduce particle size of indomethacin until the nanometric scale. The effect on the crystalline form and the dissolution behavior of the different samples was deliberately evaluated in absence of any surfactants as stabilizers. Nanocrystals of indomethacin (native crystals are in the γ form) (IDM) were obtained by three laboratory scale methods: A (Batch A: crystallization by solvent evaporation in a nano-spray dryer), B (Batch B-15 and B-30: wet milling and lyophilization), and C (Batch C-20-N and C-40-N: Cryo-milling in the presence of liquid nitrogen). Nanocrystals obtained by the method A (Batch A) crystallized into a mixture of α and γ polymorphic forms. IDM obtained by the two other methods remained in the γ form and a different attitude to the crystallinity decrease were observed, with a more considerable decrease in crystalline degree for IDM milled for 40 min in the presence of liquid nitrogen. The intrinsic dissolution rate (IDR) revealed a higher dissolution rate for Batches A and C-40-N, due to the higher IDR of α form than γ form for the Batch A, and the lower crystallinity degree for both the Batches A and C-40-N. These factors, as well as the decrease in particle size, influenced the IDM dissolution rate from the particle samples. Modifications in the solid physical state that may occur using different particle size reduction treatments have to be taken into consideration during the scale up and industrial development of new solid dosage forms.

  11. Phases formed during rapid quenching of liquid carbon

    Science.gov (United States)

    Basharin, A. Yu.; Dozhdikov, V. S.; Dubinchuk, V. T.; Kirillin, A. V.; Lysenko, I. Yu.; Turchaninov, M. A.

    2009-05-01

    Pulsed laser action upon a sample of highly oriented pyrolytic graphite (HOPG) in a gasostat filled with helium at a pressure above that corresponding to the triple point of carbon, followed by rapid quenching of the liquid phase at a rate of about 106 K/s leads to the formation of a crater with a periodic spatial structure at the surface. The composition and structure of nongraphite carbon phases in the near-surface region of the crater have been studied using the Raman scattering spectroscopy, electron microdiffraction, and energy-dispersive X-ray analysis. It is established that rapidly quenched carbon possesses predominantly a hybrid structure of glassy carbon formed as a result of the high-temperature treatment, with inclusions of crystalline carbyne, chaoite, and a hybrid cubic phase of ultradense carbon (C8). The hybrid phases of glassy carbon and C8 had not been reported until now as possible products of solidification of liquid carbon.

  12. Determination of Crystallinity and Crystal Structure of Hylamer™ Polyethylene after in vivo Wear

    OpenAIRE

    Visentin, M; Stea, S.; De Clerico, M.; Reggiani, M.; Fagnano, C.; Squarzoni, S.; De Toni, A

    2006-01-01

    Abstract Hylamer? polyethylene is a crystalline form of polyethylene of 70% crystallinity whereas conventional polyethylene (PE) has 50% crystallinity. Crystallinity is the percentage by weight of the crystalline phase present in the whole polymer, which comprises both amorphous and crystalline phases. Clinical experience has shown that Hylamer? components used in joint prostheses, if sterilized ...

  13. Determination of Crystallinity and Crystal Structure of Hylamer™ Polyethylene after in vivo Wear

    OpenAIRE

    Visentin, M; Stea, S.; Clerico, M; Reggiani, M.; Fagnano, C.; Squarzoni, S.; Toni, A.

    2006-01-01

    Abstract Hylamer? polyethylene is a crystalline form of polyethylene of 70% crystallinity whereas conventional polyethylene (PE) has 50% crystallinity. Crystallinity is the percentage by weight of the crystalline phase present in the whole polymer, which comprises both amorphous and crystalline phases. Clinical experience has shown that Hylamer? components used in joint prostheses, if sterilized ...

  14. Frustrated smectic liquid crystalline phases in lactic acid derivatives

    Science.gov (United States)

    Glogarová, M.; Novotná, V.

    2016-08-01

    We have prepared and studied a series of compounds with different types of molecular core and lactate unit in the chiral terminal chain. We draw a survey and comparison of their mesomorphic properties with respect to the occurrence of twist grain boundary (TGB) phases. The materials exhibit extremely wide TGBA phase more than 60K broad, unique TGBA-TGBC-SmC*-SmCA* phase sequence and unique re-entrant TGBA phase below the SmA phase. TGB phases have been induced in binary mixtures of molecules with different molecular shape and chirality (chiral lactic acid derivative and non-chiral hockey-stick mesogen). Unique effect is observed for compounds with TGBA phase, where the applied electric field transforms the planar texture into the homeotropic one, homogeneously dark in crossed polarizers. The process is analogy of the Frederiks transition so far known only for nematics. This effect, changing the bright state to the dark one, is promising for applications.

  15. Preparation and crystalline phase of a TiO2 porous film by anodic oxidation

    Institute of Scientific and Technical Information of China (English)

    WANG Wei; TAO Jie; ZHANG Weiwei; TAO Haijun; WANG Ling

    2005-01-01

    Anatase titanium dioxide is an active photocatalyst, but it is difficult to immobilize on the substrate. A crystalline TiO2 porous film was prepared directly on the surface of pure titanium by anodic oxidation in this work. Constant voltage and constant current anodic oxidation were adopted with sulphuric acid used as the electrolyte, pure titanium as the anode and copper as the cathode. The morphology and structure of the porous film on the substrate were analyzed with the aid of Field Emission Scanning Electron Microscopy (FESEM) and X-ray Diffraction (XRD). The effects of the parameters of anodic oxidation (such as voltage, the concentration of sulphuric acid, anodization time and current density) on the aperture and the crystalline phase of the TiO2 porous film were systematically investigated. The results indicate that the increase of current density facilitates the augment of the aperture and the generation of anatase and rutile. In addition, the forming mechanism of anatase and rutile TiO2 porous films was discussed.

  16. Structural phase study in un-patterned and patterned PVDF semi-crystalline films

    Energy Technology Data Exchange (ETDEWEB)

    Pramod, K., E-mail: rameshg.phy@pondiuni.edu.in; Gangineni, Ramesh Babu, E-mail: rameshg.phy@pondiuni.edu.in [Department of Physics, Pondicherry University, R. V. Nagar, Kalapet, Puducherry - 605014 (India)

    2014-04-24

    This work explores the structural phase studies of organic polymer- polyvinylidene fluoride (PVDF) thin films in semi-crystallized phase and nano-patterned PVDF thin films. The nanopatterns are transferred with the CD layer as a master using soft lithography technique. The semi-crystalline PVDF films were prepared by a still and hot (SH) method, using a homemade spin coater that has the proficiency of substrate heating by a halogen lamp. Using this set up, smooth PVDF thin films in semi-crystalline α-phase were prepared using 2-Butanone as solvent. XRD, AFM and confocal Raman microscope have been utilized to study the structural phase, crystallinity and quality of the films.

  17. Effect of heat and film thickness on a photoinduced phase transition in azobenzene liquid crystalline polyesters

    DEFF Research Database (Denmark)

    Sanchez, C; Alcala, R; Hvilsted, Søren

    2003-01-01

    The liquid crystal to isotropic phase transition induced with 488 nm light in films of liquid crystalline azobenzene polyesters has been studied as a function of temperature, light intensity, and film thickness. That phase transition is associated with the photoinduced trans-cis-trans isomerizati...

  18. STUDY ON THE PHASE TRANSITION KINETICS OF THERMOTROPIC LIQUID CRYSTALLINE AROMATIC-ALIPHATIC COPOLYESTER

    Institute of Scientific and Technical Information of China (English)

    LI Minhui; WANG Xiaogong; LIU Deshan; ZHOU Qixiang

    1991-01-01

    The phase transition kinetics of thermotropic liquid crystalline aromatic-aliphatic regular copolyester:(X) were studied by DSC. By means of Kissinger's method the kinetic equation and parameters including activation energy, rate order and preexponential factor for phase transition from nematic to isotropic were obtained. The activation energy from crystal to nematic was also presented.

  19. Tuning Eu{sup 3+} emission in europium sesquioxide films by changing the crystalline phase

    Energy Technology Data Exchange (ETDEWEB)

    Mariscal, A., E-mail: antonio.mariscal@csic.es [Laser Processing Group, Instituto de Óptica, CSIC, C/ Serrano 121, 28006 Madrid (Spain); Quesada, A. [Ceramics for Smart Systems Group, Instituto de Cerámica y Vidrio, C/ Kelsen 5, 28049 Madrid (Spain); Camps, I. [Laser Processing Group, Instituto de Óptica, CSIC, C/ Serrano 121, 28006 Madrid (Spain); Palomares, F.J. [Instituto de Ciencia de Materiales de Madrid, C/ Sor Juana Inés de la Cruz 3, 28049 Madrid (Spain); Fernández, J.F. [Ceramics for Smart Systems Group, Instituto de Cerámica y Vidrio, C/ Kelsen 5, 28049 Madrid (Spain); Serna, R. [Laser Processing Group, Instituto de Óptica, CSIC, C/ Serrano 121, 28006 Madrid (Spain)

    2016-06-30

    Highlights: • PLD production of high quality europium sesquioxide (Eu{sub 2}O{sub 3}) films. • The deposition of Al{sub 2}O{sub 3} capping and/or buffer layers modifies the crystallization for Eu{sub 2}O{sub 3} films upon annealing. • The formation of cubic or monoclinic phases can be favored. • Eu{sup 3+} emission tuning is achieved as a consequence of crystal field effects. - Abstract: We report the growth of europium sesquioxide (Eu{sub 2}O{sub 3}) thin films by pulsed laser deposition (PLD) in vacuum at room temperature from a pure Eu{sub 2}O{sub 3} ceramic bulk target. The films were deposited in different configurations formed by adding capping and/or buffer layers of amorphous aluminum oxide (a-Al{sub 2}O{sub 3}). The optical properties, refractive index and extinction coefficient of the as deposited Eu{sub 2}O{sub 3} layers were obtained. X-ray photoelectron spectroscopy (XPS) measurements were done to assess its chemical composition. Post-deposition annealing was performed at 500 °C and 850 °C in air in order to achieve the formation of crystalline films and to accomplish photoluminescence emission. According to the analysis of X-ray diffraction (XRD) spectra, cubic and monoclinic phases were formed. It is found that the relative amount of the phases is related to the different film configurations, showing that the control over the crystallization phase can be realized by adequately designing the structures. All the films showed photoluminescence emission peaks (under excitation at 355 nm) that are attributed to the intra 4f-transitions of Eu{sup 3+} ions. The emission spectral shape depends on the crystalline phase of the Eu{sub 2}O{sub 3} layer. Specifically, changes in the hypersensitive {sup 5}D{sub 0} → {sup 7}F{sub 2} emission confirm the strong influence of the crystal field effect on the Eu{sup 3+} energy levels.

  20. Synthesis and characterization of organic-inorganic hybrids formed between conducting polymers and crystalline antimonic acid

    Directory of Open Access Journals (Sweden)

    Beleze Fábio A.

    2001-01-01

    Full Text Available In this paper we report the synthesis and characterization of novel organic-inorganic hybrid materials between the crystalline antimonic acid (CAA and two conductive polymers: polypyrrole and polyaniline. The hybrids were obtained by in situ oxidative polymerization of monomers by the Sb(V present in the pyrochlore-like CAA structure. The materials were characterized by infrared and Raman spectroscopy, X-ray diffraction, cyclic voltammetry, CHN elemental analysis and electronic paramagnetic resonance spectroscopy. The results showed that both polymers were formed in their oxidized form, with the CAA structure acting as a counter anion.

  1. Alignment engineering in liquid crystalline elastomers: Free-form microstructures with multiple functionalities

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Hao; Cerretti, Giacomo; Wiersma, Diederik S., E-mail: camilla.parmeggiani@lens.unifi.it, E-mail: wiersma@lens.unifi.it [European Laboratory for Non Linear Spectroscopy (LENS), University of Florence, via Nello Carrara 1, 50019 Sesto Fiorentino (Italy); Wasylczyk, Piotr [European Laboratory for Non Linear Spectroscopy (LENS), University of Florence, via Nello Carrara 1, 50019 Sesto Fiorentino (Italy); Faculty of Physics, Institute of Experimental Physics, University of Warsaw, ul. Hoza 69, Warszawa 00-681 (Poland); Martella, Daniele [European Laboratory for Non Linear Spectroscopy (LENS), University of Florence, via Nello Carrara 1, 50019 Sesto Fiorentino (Italy); Dipartimento di Chimica “Ugo Schiff,” University of Florence, via della Lastruccia 3-13, 50019 Sesto Fiorentino (Italy); Parmeggiani, Camilla, E-mail: camilla.parmeggiani@lens.unifi.it, E-mail: wiersma@lens.unifi.it [European Laboratory for Non Linear Spectroscopy (LENS), University of Florence, via Nello Carrara 1, 50019 Sesto Fiorentino (Italy); CNR-INO, via Nello Carrara 1, 50019 Sesto Fiorentino (Italy)

    2015-03-16

    We report a method to fabricate polymer microstructures with local control over the molecular orientation. Alignment control is achieved on molecular level in a structure of arbitrary form that can be from 1 to 100 μm in size, by fixing the local boundary conditions with micro-grating patterns. The method makes use of two-photon polymerization (Direct Laser Writing) and is demonstrated specifically in liquid-crystalline elastomers. This concept allows for the realization of free-form polymeric structures with multiple functionalities which are not possible to realize with existing techniques and which can be locally controlled by light in the micrometer scale.

  2. Crystalline phase transition information induced by high temperature susceptibility transformations in bulk PMP-YBCO superconductor growth in-situ

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, C.P., E-mail: zhangcp6813@126.com [SMRC, Northwest Institute for Non-ferrous Metal Research, Xi’an (China); Physics Department, Université Joseph Fourier, Grenoble (France); State Key Lab of Solidification Processing, Northwest Polytechnical University, Xi’an (China); Chaud, X. [CRETA/CNRS, 25 avenue des martyrs, 38042 Grenoble Cedex 9 (France); Beaugnon, E. [Physics Department, Université Joseph Fourier, Grenoble (France); CRETA/CNRS, 25 avenue des martyrs, 38042 Grenoble Cedex 9 (France); Zhou, L. [SMRC, Northwest Institute for Non-ferrous Metal Research, Xi’an (China); State Key Lab of Solidification Processing, Northwest Polytechnical University, Xi’an (China)

    2015-01-15

    Highlights: • It was the first time we measured the susceptibility of bulk YBCO in powder-melting-process at high temperature up to 1060 °C. • It revealed that the crystalline phase transition of bulk PMP-YBCO growth in process. • A new discovery of Y123 phase pre-formed then melted in heating stage has been found. • It discovered that Y123 crystal solidification started at 1004 °C in cooling stage in PMP route. - Abstract: The dynamic susceptibility transformations of bulk HTSC PMP-YBCO growth have been investigated from 200 °C up to 1060 °C by the Faraday Balance in-situ. It revealed that the crystalline phase transitions of bulk PMP-YBCO growth in process. A new discovery of Y123 phase pre-formed then melted in heating stage has been found. It also discovered that Y123 crystal solidification started at 1004 °C in cooling stage. Before Y123 solidification the liquid phase CuO change to Cu{sub 2}O reciprocally as well as the copper ion valence changed between divalent Cu{sup 2+} and trivalent Cu{sup 1+} each other. It was essential to keep quantities of CuO phase instead of the Cu{sub 2}O for Y123 crystal solidification.

  3. Improvement of multilayer graphene crystallinity by solid-phase precipitation with current stress application during annealing

    Science.gov (United States)

    Sahab Uddin, Md.; Ichikawa, Hiroyasu; Sano, Shota; Ueno, Kazuyoshi

    2016-06-01

    To improve the crystallinity of multilayer graphene (MLG) films by solid-phase precipitation, a new method by which current stress is introduced during annealing of a carbon-doped cobalt (Co-C) layer using cobalt (Co) as the catalyst has been investigated. The effects of current stress on the formation and crystallinity of MLG films were investigated by comparing the characteristics of the films annealed at the same temperature with and without current by taking into account the temperature rise due to Joule heating. The characteristics obtained by Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) measurements revealed that the MLG films produced were crystalline in nature and their crystallinity increased with applied current stress at the same temperature. From SEM observations, beside Joule heating, enhancement of Co grain size by agglomeration induced by current stress may be the potential reason for the improvement of the crystallinity of MLG films. We have also improved the uniformity of MLG films by depositing an additional copper (Cu) capping layer over the Co-C layer. Current stress application can lead to low-temperature fabrication of MLG with higher crystallinity by solid-phase precipitation.

  4. Fullerene-based one-dimensional crystalline nanopolymer formed through topochemical transformation of the parent nanowire

    DEFF Research Database (Denmark)

    Geng, Junfeng; Solov'yov, Ilia; Reid, David G.

    2010-01-01

    displays a well-defined crystalline nanostructure, exceptionally large length-to-width ratio and excellent thermal stability. The material is prepared by first growing the corresponding nanowire through a solution phase of C_60 followed by a topochemical polymerization reaction in the solid state. Gas...... chromatography, mass spectrometry and ^13C nuclear magnetic resonance evidence is provided for the nature of the covalent bonding mode adopted by the polymeric chains. Theoretical analysis based on detailed calculations of the reaction energetics and structural analysis provides an in-depth understanding...

  5. 77 FR 35425 - Crystalline Silicon Photovoltaic Cells and Modules From China; Scheduling of the Final Phase of...

    Science.gov (United States)

    2012-06-13

    ... silicon photovoltaic cells, and modules, laminates, and panels, consisting of crystalline silicon... COMMISSION Crystalline Silicon Photovoltaic Cells and Modules From China; Scheduling of the Final Phase of... crystalline silicon photovoltaic cells and modules, provided for in subheadings 8501.31.80, 8501.61.00,...

  6. Electrostriction and Crystalline Phase Transformations in a Vinylidene Flouride Terpolymer

    Science.gov (United States)

    Roland, C. M.; Garrett, J. T.; Qadri, S. B.

    Substantial electrostrictive strains can be obtained from terpolymers of vinylidene fluoride, trifluoroethylene, and chlorotrifluoroethylene. The mechanism of the electromechanical response was investigated using x-ray diffraction and infrared absorption measurements on the polymer under an electric field. While application of the field is found to induce changes in the crystal phase structure, the phase transition that can effect dimensional changes is too small to account for the magnitude of the electrostriction. Thus, the origin of the exceptional electromechanical properties of this material remains to be fully elucidated.

  7. Amorphous and crystalline phase interaction during the Brill transition in nylon 66

    Directory of Open Access Journals (Sweden)

    2009-07-01

    Full Text Available A prominent α' process in specifically treated nylon 66 and microcomposite samples is identified by dynamic mechanical analysis and proposed to be an amorphous phase counterpart of the Brill transition identified by synchrotron wide-angle X-ray diffraction (WAXD. It is suggested that this α' process, which marks a critical free volume change and an onset of segmental chain movement in the amorphous phase, precedes and prompts the Brill transition in the crystalline phase.

  8. Tuning the phase diagrams: the miscibility studies of multilactate liquid crystalline compounds

    Science.gov (United States)

    Bubnov, Alexej; Tykarska, Marzena; Hamplová, Věra; Kurp, Katarzyna

    2016-09-01

    Design of binary and multicomponent liquid crystalline mixtures is a very powerful tool to reach the desired self-assembling properties. Beyond many advantages, this method has a distinct negativity - it is very material-consuming. While working with unique chiral materials in the research laboratory, this problem can be solved by applying miscibility study by the contact preparation method. In this work, the miscibility studies of lactic acid derivatives and non-chiral/chiral liquid crystalline molecules of different structure have been done in order to establish the phase diagrams. Special attention is focused on the ferro(antiferro)electric smectic phases.

  9. Spatial distribution of crystalline corrosion products formed during corrosion of stainless steel in concrete

    KAUST Repository

    Serdar, Marijana

    2015-05-01

    © 2015 Elsevier Ltd All rights reserved. The mineralogy and spatial distribution of nano-crystalline corrosion products that form in the steel/concrete interface were characterized using synchrotron X-ray micro-diffraction (μ-XRD). Two types of low-nickel high-chromium reinforcing steels embedded into mortar and exposed to NaCl solution were investigated. Corrosion in the samples was confirmed by electrochemical impedance spectroscopy (EIS). μ-XRD revealed that goethite (α-FeOOH) and akaganeite (β-FeOOH) are the main iron oxide-hydroxides formed during the chloride-induced corrosion of stainless steel in concrete. Goethite is formed closer to the surface of the steel due to the presence of chromium in the steel, while akaganeite is formed further away from the surface due to the presence of chloride ions. Detailed microstructural analysis is shown and discussed on one sample of each type of steel.

  10. Low-pressure phase diagram of crystalline benzene from quantum Monte Carlo

    Science.gov (United States)

    Azadi, Sam; Cohen, R. E.

    2016-08-01

    We studied the low-pressure (0-10 GPa) phase diagram of crystalline benzene using quantum Monte Carlo and density functional theory (DFT) methods. We performed diffusion quantum Monte Carlo (DMC) calculations to obtain accurate static phase diagrams as benchmarks for modern van der Waals density functionals. Using density functional perturbation theory, we computed the phonon contributions to the free energies. Our DFT enthalpy-pressure phase diagrams indicate that the Pbca and P21/c structures are the most stable phases within the studied pressure range. The DMC Gibbs free-energy calculations predict that the room temperature Pbca to P21/c phase transition occurs at 2.1(1) GPa. This prediction is consistent with available experimental results at room temperature. Our DMC calculations give 50.6 ± 0.5 kJ/mol for crystalline benzene lattice energy.

  11. Two crystalline polymorphic forms of α-( N-benzoxazolin-2-one)acetic acid

    Science.gov (United States)

    Ashurov, J. M.; Izotova, L. Yu.; Ibragimov, B. T.; Mukhamedov, N. S.

    2017-01-01

    Two crystalline polymorphic forms of α-( N-benzoxazolin-2-one)acetic acid (BAA) are prepared by changing the temperature of its crystallization from solution in ethanol. Crystallographic data of the α-form are determined: a = 12.7769(17) Å, b = 8.2574(9) Å, c = 16.7390(19) Å, β = 105.087(13)°, space group C2/ c, V = 1705.2(4) Å3, and Z = 8, while those of β form are a = 5.2854(4) Å, b = 5.9880(4) Å, c = 13.4509(5) Å, β = 94.666(4)°, space group P21, V = 424.30(4) Å3, and Z = 2. It is found that BAA molecules of the α form combine into infinite one-dimensional chains arranged along axis b by means of O‒H···O and C‒H···O hydrogen bonds, and these chains are crosslinked via C‒H···O hydrogen bonds to form a threedimensional structure. The β form has another system of hydrogen bonds, one of which is bifurcated (O4···O2, O4···O3), and the π-π-interactions between the benzoxazolinone fragments of BAA molecules combined into a chain also arranged along axis b are observed. Calorimetric analysis shows that the polymorphic transition from the α form to the β form occurs at 129°C.

  12. Chemical composition of glass and crystalline phases in coarse coal gasification ash

    Energy Technology Data Exchange (ETDEWEB)

    R.H. Matjie; Zhongsheng Li; Colin R. Ward; David French [Sasol Technology (Pty) Ltd., Sasolburg (South Africa)

    2008-05-15

    A procedure has been developed for determining the chemical composition and relative abundance of the amorphous or glassy material, as well as crystalline phases, present in coarse coal gasification ash, in order to assist in predicting the behaviour of the material in cement/brick/concrete applications. The procedure is based on a combination of quantitative X-ray diffraction (XRD), chemical analysis and electron microprobe studies. XRD analysis indicates that the clinker samples contain a number of crystalline high temperature phases, including anorthite, mullite, cristobalite, quartz and diopside. Quantitative evaluation using Rietveld-based techniques has been used to determine the percentages of both the individual crystalline phases and the glass component. These data were then combined with the chemistry of the crystalline phases and the overall chemical composition of the ash to estimate the chemical composition of the glass phase, which is typically the most abundant component present in the different materials. Although there is some degree of scatter, comparison between the inferred glass composition from XRD and bulk chemistry and actual data on the glass composition using electron microprobe techniques suggest that the two approaches are broadly consistent. The microprobe further indicates that a range of compositions are present in the glassy and crystalline components of the ashes, including Si-Al-rich glass, metakaolin and Fe-Ca-Mg-Ti phases, as well as quartz, anorthite and an aluminophosphate material. Electron microprobe and XRD studies also show that pyrrhotite (FeS), representing a high temperature transformation product of pyrite, is present in some clinker and partially burnt carbonaceous shale samples. 27 refs., 5 figs., 7 tabs.

  13. Formation Mechanism and Control of Perovskite Films from Solution to Crystalline Phase Studied by in Situ Synchrotron Scattering.

    Science.gov (United States)

    Chang, Chun-Yu; Huang, Yu-Ching; Tsao, Cheng-Si; Su, Wei-Fang

    2016-10-12

    Controlling the crystallization and morphology of perovskite films is crucial for the fabrication of high-efficiency perovskite solar cells. For the first time, we investigate the formation mechanism of the drop-cast perovskite film from its precursor solution, PbCl2 and CH3NH3I in N,N-dimethylformamide, to a crystalline CH3NH3PbI3-xClx film at different substrate temperatures from 70 to 180 °C in ambient air and humidity. We employed an in situ grazing-incidence wide-angle X-ray scattering (GIWAXS) technique for this study. When the substrate temperature is at or below 100 °C, the perovskite film is formed in three stages: the initial solution stage, transition-to-solid film stage, and transformation stage from intermediates into a crystalline perovskite film. In each stage, the multiple routes for phase transformations are preceded concurrently. However, when the substrate temperature is increased from 100 to 180 °C, the formation mechanism of the perovskite film is changed from the "multistage formation mechanism" to the "direct formation mechanism". The proposed mechanism has been applied to understand the formation of a perovskite film containing an additive. The result of this study provides a fundamental understanding of the functions of the solvent and additive in the solution and transition states to the crystalline film. It provides useful knowledge to design and fabricate crystalline perovskite films for high-efficiency solar cells.

  14. Shadow wave-function variational calculations of crystalline and liquid phases of 4He

    Science.gov (United States)

    Vitiello, S. A.; Runge, K. J.; Chester, G. V.; Kalos, M. H.

    1990-07-01

    A new class of variational wave functions for boson systems, shadow wave functions, is used to investigate the properties of solid and liquid 4He. The wave function is translationally invariant and symmetric under particle interchange. In principle, the calculations for the crystalline phase do not require the use of any auxiliary lattice. Using the Metropolis Monte Carlo algorithm, we show that the additional variational degrees of freedom in the wave function lower the energy significantly. This wave function also allows the crystalization of an equilibrated liquid phase when a crystalline seed is used. The pair correlation function and structure factor S(k) are determined in the liquid phase. The condensate fraction is calculated as well. Results are given for the single-particle distribution function around the lattice positions in the solid phase.

  15. Quantitative Phase Development of crystalline, nano-crystalline and amorphous phases during hydration of OPC blended with siliceous fly ash

    OpenAIRE

    Dittrich, Sebastian

    2015-01-01

    Ambitious efforts driven by political and environmental considerations to reduce carbon dioxide emission are currently present, amongst other branches in the construction material industry as well. One possible solution concentrates on the replacement of cement by supplementary cementitious materials like fly ash or granulated blast furnace slag. Due to its high amorphous phase content and the related reactivity potential fly ash seems well suited for being used in cement or concrete. Unfortu...

  16. Crystalline phase transition information induced by high temperature susceptibility transformations in bulk PMP-YBCO superconductor growth in-situ

    Science.gov (United States)

    Zhang, C. P.; Chaud, X.; Beaugnon, E.; Zhou, L.

    2015-01-01

    The dynamic susceptibility transformations of bulk HTSC PMP-YBCO growth have been investigated from 200 °C up to 1060 °C by the Faraday Balance in-situ. It revealed that the crystalline phase transitions of bulk PMP-YBCO growth in process. A new discovery of Y123 phase pre-formed then melted in heating stage has been found. It also discovered that Y123 crystal solidification started at 1004 °C in cooling stage. Before Y123 solidification the liquid phase CuO change to Cu2O reciprocally as well as the copper ion valence changed between divalent Cu2+ and trivalent Cu1+ each other. It was essential to keep quantities of CuO phase instead of the Cu2O for Y123 crystal solidification.

  17. Distinct Topological Crystalline Phases in Models for the Strongly Correlated Topological Insulator SmB_{6}.

    Science.gov (United States)

    Baruselli, Pier Paolo; Vojta, Matthias

    2015-10-09

    SmB_{6} was recently proposed to be both a strong topological insulator and a topological crystalline insulator. For this and related cubic topological Kondo insulators, we prove the existence of four different topological phases, distinguished by the sign of mirror Chern numbers. We characterize these phases in terms of simple observables, and we provide concrete tight-binding models for each phase. Based on theoretical and experimental results for SmB_{6} we conclude that it realizes the phase with C_{k_{z}=0}^{+}=+2, C_{k_{z}=π}^{+}=+1, C_{k_{x}=k_{y}}^{+}=-1, and we propose a corresponding minimal model.

  18. The structure and dynamics of amorphous and crystalline phases of ice

    Energy Technology Data Exchange (ETDEWEB)

    Klug, D. D.; Tse, J. S.; Tulk, C. A.; Svensson, E. C.; Swainson, I.; Loong, C.-K.

    2000-07-14

    The structures of the high and low-density amorphous phases of ice are studied using several techniques. The diffraction patterns of high and low density amorphous ice are analyzed using reverse Monte Carlo methods and compared with molecular dynamics simulations of these phases. The spectra of crystalline and amorphous phases of ice obtained by Raman and incoherent inelastic neutron scattering are analyzed to yield structural features for comparison with the results of molecular dynamics and Reverse Monte Carlo analysis. The structural details obtained indicate that there are significant differences between the structure of liquid water and the amorphous phases of ice.

  19. Optical and electrical characterization of crystalline silicon films formed by rapid thermal annealing of amorphous silicon

    Energy Technology Data Exchange (ETDEWEB)

    Baldus-Jeursen, Christopher, E-mail: cjbaldus@uwaterloo.ca; Tarighat, Roohollah Samadzadeh, E-mail: rsamadza@uwaterloo.ca; Sivoththaman, Siva, E-mail: sivoththaman@uwaterloo.ca

    2016-03-31

    The effect of rapid thermal annealing (RTA) on n-type hydrogenated amorphous silicon (a-Si:H) films deposited on single-crystal silicon (c-Si) wafers was studied by electrical and optical methods. Deposition of a-Si:H films by plasma-enhanced chemical vapor deposition (PECVD) was optimized for high deposition rate and maximum film uniformity. RTA processed films were characterized by spreading resistance profiling (SRP), Hall effect, spectroscopic ellipsometry, defect etching, and transmission electron microscopy (TEM). It was found that the films processed between 600 °C and 1000 °C were highly crystalline and that the defect density in the films diminished with increasing thermal budget. Junctions formed by the RTA processed n-type a-Si:H films on p-type c-Si wafers were tested for device applicability. It was established that these films can be used as the emitter layer in n{sup +}p photovoltaic (PV) devices with over 14% conversion efficiency. - Highlights: • Rapid thermal annealing of doped amorphous silicon deposited on single-crystal silicon (c-Si) wafers resulted in highly crystalline films for photovoltaic devices. • As the annealing temperature increased, the electrical and optical properties of the films became increasingly similar to single-crystal silicon. • Annealing temperatures between 500-1000 oC were investigated. Solar cell devices fabricated after annealing at 750 oC were found to be the most suitable compromise between good quality crystalline films and minimal dopant diffusion into the c-Si wafer. • Annealed films were highly conductive without the need for a transparent conducting oxide.

  20. High-Quality Single Crystalline Ge(111) Growth on Si(111) Substrates by Solid Phase Epitaxy

    Institute of Scientific and Technical Information of China (English)

    SUN Bing; CHANG Hu-Dong; LU Li; LIU Hong-Gang; WU De-Xin

    2012-01-01

    Heterogeneous integration of crystalline Ge layers on cleaned and H-terminated Si(111) substrates are demonstrated by employing a combination of e-beam evaporation and solid phase epitaxy techniques. High-quality single crystalline Ge(111) layers on Si(111) substrates with a smooth Ge surface and an abrupt interface between Ge and Si are obtained.An XRD rocking curve scan of the Ge(111) diffraction peak shovs a FWHM of only 260 arcsec for a 50-nm-thick Ge layer annealed at 600℃ with a ramp-up rate of 20℃/s and a holding time of 1 min. The AFM images exhibit that the rms surface roughness of all the crystalline Ge layers are less than 2.1 nm.

  1. Toward an anisotropic atom-atom model for the crystalline phases of the molecular S8 compound

    OpenAIRE

    Pastorino, C.; Gamba, Z.

    2000-01-01

    We analize two anisotropic atom-atom models used to describe the crystalline alpha,beta and gamma phases of S8 crystals, the most stable compound of elemental sulfur in solid phases, at ambient pressure and T

  2. Fullerene-based one-dimensional crystalline nanopolymer formed through topochemical transformation of the parent nanowire

    DEFF Research Database (Denmark)

    Geng, Junfeng; Solov'yov, Ilia; Reid, David G.;

    2010-01-01

    Large-scale practical applications of fullerene (C_60) in nanodevices could be significantly facilitated if the commercially available micrometer-scale raw C_60 powder were further processed into a one-dimensional nanowire-related polymer displaying covalent bonding as molecular interlinks...... and resembling traditional important conjugated polymers. However, there has been little study thus far in this area despite the abundant literature on fullerene. Here we report the preparation and characterization of such a C_60-based polymer nanowire, (-C_60.TMB-)_n, where TMB=1,2,4-trimethylbenzene, which...... displays a well-defined crystalline nanostructure, exceptionally large length-to-width ratio and excellent thermal stability. The material is prepared by first growing the corresponding nanowire through a solution phase of C_60 followed by a topochemical polymerization reaction in the solid state. Gas...

  3. A method for the quantitative determination of crystalline phases by X-ray

    Science.gov (United States)

    Petzenhauser, I.; Jaeger, P.

    1988-01-01

    A mineral analysis method is described for rapid quantitative determination of crystalline substances in those cases in which the sample is present in pure form or in a mixture of known composition. With this method there is no need for prior chemical analysis.

  4. Change in the crystalline structure during the phase transition of the palladium-hydrogen system.

    Science.gov (United States)

    Kawasaki, Akio; Itoh, Satoshi; Shima, Kunihiro; Kato, Kenichi; Ohashi, Haruhiko; Ishikawa, Tetsuya; Yamazaki, Toshimitsu

    2015-10-14

    We performed an X-ray diffraction experiment while a palladium bulk absorbed and desorbed hydrogen to investigate the behavior of the crystalline lattice during the phase transition between the α phase and the β phase. Fast growth of the β phase was observed at around x = 0.1 and x = 0.45 of PdHx, and the phase transition rate has an exponential behavior in between. In addition, slight compression of the lattice at a high hydrogen concentration, an increase in the lattice constant, and broadening of the line width of the α phase after a cycle of absorption and desorption of hydrogen were observed. These behaviors correlated with the change in the sample length, which may infer that the change in shape was related to the phase transition.

  5. High-quality single crystalline NiO with twin phases grown on sapphire substrate by metalorganic vapor phase epitaxy

    Directory of Open Access Journals (Sweden)

    Kazuo Uchida

    2012-12-01

    Full Text Available High-quality single crystalline twin phase NiO grown on sapphire substrates by metalorganic vapor phase epitaxy is reported. X-ray rocking curve analysis of NiO films grown at different temperatures indicates a minimum full width at half maximum of the cubic (111 diffraction peak of 0.107° for NiO film grown at as low as 550 °C. Detailed microstructural analysis by Φ scan X-ray diffraction and transmission electron microscopy reveal that the NiO film consists of large single crystalline domains with two different crystallographic orientations which are rotated relative to each other along the [111] axis by 60°. These single crystal domains are divided by the twin phase boundaries.

  6. Use of X-ray tomography to map crystalline and amorphous phases in frozen biomaterials.

    Science.gov (United States)

    Bischof, J C; Mahr, B; Choi, J H; Behling, M; Mewes, D

    2007-02-01

    The outcome of both cryopreservation and cryosurgical freezing applications is influenced by the concentration and type of the cryoprotective agent (CPA) or the cryodestructive agent (i.e., the chemical adjuvants referred to here as CDA) added prior to freezing. It also depends on the amount and type of crystalline, amorphous and/or eutectic phases formed during freezing which can differentially affect viability. This work describes the use of X-ray computer tomography (CT) for non-invasive, indirect determination of the phase, solute concentration and temperature within biomaterials (CPA, CDA loaded solutions and tissues) by X-ray attenuation before and after freezing. Specifically, this work focuses on establishing the feasibility of CT (100-420 kV acceleration voltage) to accurately measure the concentration of glycerol or salt as model CPA and CDAs in unfrozen solutions and tissues at 20 degrees C, or the phase in frozen solutions and tissue systems at -78.5 and -196 degrees C. The solutions are composed of water with physiological concentrations of NaCl (0.88% wt/wt) and DMEM (Dulbecco's Modified Eagle's Medium) with added glycerol (0-8 M). The tissue system is chosen as 3 mm thick porcine liver slices as well as 2 cm diameter cores which were either imaged fresh (3-4 h cold ischemia) or after loading with DMEM based glycerol solutions (0-8 M) for times ranging from hours to 7 days at 4 degrees C. The X-ray attenuation is reported in Hounsfield units (HU), a clinical measurement which normalizes X-ray attenuation values by the difference between those of water and air. NaCl solutions from 0 to 23.3% wt/wt (i.e. water to eutectic concentration) were found to linearly correspond to HU in a range from 0 to 155. At -196 degrees C the variation was from -80 to 95 HU while at -78.5 degrees C all readings were roughly 10 HU lower. At 20 degrees C NaCl and DMEM solutions with 0-8 M glycerol loading show a linear variation from 0 to 145 HU. After freezing to -78

  7. Amorphous and crystalline aerosol particles interacting with water vapor – Part 1: Microstructure, phase transitions, hygroscopic growth and kinetic limitations

    Directory of Open Access Journals (Sweden)

    T. Koop

    2009-03-01

    Full Text Available Interactions with water are crucial for the properties, transformation and climate effects of atmospheric aerosols. Here we outline characteristic features and differences in the interaction of amorphous and crystalline aerosol particles with water vapor. Using a hygroscopicity tandem differential mobility analyzer (H-TDMA, we performed hydration, dehydration and cyclic hydration&dehydration experiments with aerosol particles composed of levoglucosan, oxalic acid and ammonium sulfate (diameters ~100–200 nm, relative uncertainties <0.4%, relative humidities <5% to 95% at 298 K. The measurements and accompanying Köhler model calculations provide new insights into particle microstructure, surface adsorption, bulk absorption, phase transitions and hygroscopic growth. The results of these and related investigations lead to the following main conclusions: 1. Many organic substances (including carboxylic acids, carbohydrates and proteins tend to form amorphous rather than crystalline phases upon drying of aqueous solution droplets. Depending on viscosity and microstructure, the amorphous phases can be classified as glasses, rubbers, gels or viscous liquids. 2. Amorphous organic substances tend to absorb water vapor and undergo gradual deliquescence and hygroscopic growth at much lower relative humidity than their crystalline counterparts. 3. In the course of hydration and dehydration, certain organic substances can form rubber- or gel-like structures (supra-molecular networks and undergo stepwise transitions between swollen and collapsed network structures. 4. Organic gels or (semi-solid amorphous shells (glassy, rubbery, ultra-viscous with low molecular diffusivity can kinetically limit the uptake and release of water by submicron aerosol particles on (multi-second time scales, which may influence the hygroscopic growth and activation of aerosol particles as cloud condensation nuclei (CCN and ice nuclei (IN. 5. The shape and porosity of amorphous

  8. Anchoring Strength of Thin Aligned-Polymer Films Formed by Liquid Crystalline Monomer

    Science.gov (United States)

    Murashige, Takeshi; Fujikake, Hideo; Ikehata, Seiichiro; Sato, Fumio

    2003-04-01

    We have evaluated the polar anchoring strength of a thin molecule-aligned polymer film formed by a liquid crystalline monomer. The polymer film was obtained by photopolymerization of the monomer oriented by a rubbed polyimide alignment layer in a chamber filled with N2 gas. We fabricated a nematic liquid crystal cell using the thin aligned-polymer films as alignment layers, and then evaluated the anchoring strength of the polymer by measuring the optical retardation curve of the cell driven by voltages. The experimental result showed that the anchoring strength was one order of magnitude lower than that of a conventional rubbed polyimide alignment layer, and decreased with increasing the cure temperature of the monomer film.

  9. Investigations on the liquid crystalline phases of cation-induced condensed DNA

    Indian Academy of Sciences (India)

    C K S Pillai; Neethu Sundaresan; M Radhakrishnan Pillai; T Thomas; T J Thomas

    2005-10-01

    Viral and nonviral condensing agents are used in gene therapy to compact oligonucleotides and plasmid DNA into nanostructures for their efficient transport through the cell membranes. Whereas viral vectors are best by the toxic effects on the immune system, most of the nonviral delivery vehicles are not effective for use in clinical system. Recent investigations indicate that the supramolecular organization of DNA in the condensed state is liquid crystalline. The present level of understanding of the liquid crystalline phase of DNA is inadequate and a thorough investigation is required to understand the nature, stability, texture and the influence of various environmental conditions on the structure of the phase. The present study is mainly concerned with the physicochemical investigations on the liquid crystalline transitions during compaction of DNA by cationic species such as polyamines and metallic cations. As a preliminary to the above investigation, studies were conducted on the evolution of mesophase transitions of DNA with various cationic counterion species using polarized light microscopy. These studies indicated significant variations in the phase behaviour of DNA in the presence of Li and other ions. Apart from the neutralization of the charges on the DNA molecule, these ions are found to influence selectively the hydration sphere of DNA that in turn influences the induction and stabilization of the LC phases. The higher stability observed with the liquid crystalline phases of Li-DNA system could be useful in the production of nanostructured DNA. In the case of the polyamine, a structural specificity effect depending on the nature, charge and structure of the polyamine used has been found to be favoured in the crystallization of DNA.

  10. Investigations on the liquid crystalline phases of cation-induced condensed DNA

    Science.gov (United States)

    Pillai, C. K. S.; Sundaresan, Neethu; Radhakrishnan Pillai, M.; Thomas, T.; Thomas, T. J.

    2005-10-01

    Viral and nonviral condensing agents are used in gene therapy to compact oligonucleotides and plasmid DNA into nanostructures for their efficient transport through the cell membranes. Whereas viral vectors are best by the toxic effects on the immune system, most of the nonviral delivery vehicles are not effective for use in clinical system. Recent investigations indicate that the supramolecular organization of DNA in the condensed state is liquid crystalline. The present level of understanding of the liquid crystalline phase of DNA is inadequate and a thorough investigation is required to understand the nature, stability, texture and the influence of various environmental conditions on the structure of the phase. The present study is mainly concerned with the physico-chemical investigations on the liquid crystalline transitions during compaction of DNA by cationic species such as polyamines and metallic cations. As a preliminary to the above investigation, studies were conducted on the evolution of mesophase transitions of DNA with various cationic counterion species using polarized light microscopy. These studies indicated significant variations in the phase behaviour of DNA in the presence of Li and other ions. Apart from the neutralization of the charges on the DNA molecule, these ions are found to influence selectively the hydration sphere of DNA that in turn influences the induction and stabilization of the LC phases. The higher stability observed with the liquid crystalline phases of Li--DNA system could be useful in the production of nanostructured DNA. In the case of the polyamine, a structural specificity effect depending on the nature, charge and structure of the polyamine used has been found to be favoured in the crystallization of DNA.

  11. Spray Forming Aluminum - Final Report (Phase II)

    Energy Technology Data Exchange (ETDEWEB)

    D. D. Leon

    1999-07-08

    The U.S. Department of Energy - Office of Industrial Technology (DOE) has an objective to increase energy efficient and enhance competitiveness of American metals industries. To support this objective, ALCOA Inc. entered into a cooperative program to develop spray forming technology for aluminum. This Phase II of the DOE Spray Forming Program would translate bench scale spray forming technology into a cost effective world class process for commercialization. Developments under DOE Cooperative Agreement No. DE-FC07-94ID13238 occurred during two time periods due to budgetary constraints; April 1994 through September 1996 and October 1997 and December 1998. During these periods, ALCOA Inc developed a linear spray forming nozzle and specific support processes capable of scale-up for commercial production of aluminum sheet alloy products. Emphasis was given to alloys 3003 and 6111, both being commercially significant alloys used in the automotive industry. The report reviews research performed in the following areas: Nozzel Development, Fabrication, Deposition, Metal Characterization, Computer Simulation and Economics. With the formation of a Holding Company, all intellectual property developed in Phases I and II of the Project have been documented under separate cover for licensing to domestic producers.

  12. Low-pressure phase diagram of crystalline benzene from quantum Monte Carlo

    CERN Document Server

    Azadi, Sam

    2016-01-01

    We study the low-pressure (0 to 10 GPa) phase diagram of crystalline benzene using quantum Monte Carlo (QMC) and density functional theory (DFT) methods. We consider the $Pbca$, $P4_32_12$, and $P2_1/c$ structures as the best candidates for phase I and phase II. We perform diffusion quantum Monte Carlo (DMC) calculations to obtain accurate static phase diagrams as benchmarks for modern van der Waals density functionals. We use density functional perturbation theory to compute phonon contribution in the free-energy calculations. Our DFT enthalpy-pressure phase diagram indicates that the $Pbca$ and $P2_1/c$ structures are the most stable phases within the studied pressure range. The DMC Gibbs free-energy calculations predict that the room temperature $Pbca$ to $P2_1/c$ phase transition occurs at 2.1(1) GPa. This prediction is consistent with available experimental results at room temperature. Our DMC calculations show an estimate of 50.6$\\pm$0.5 kJ/mol for crystalline benzene lattice energy.

  13. Transitions between imperfectly ordered crystalline structures: A phase switch Monte Carlo study

    OpenAIRE

    Wilms, Dorothea; Wilding, Nigel B.; Binder, Kurt

    2012-01-01

    A model for two-dimensional colloids confined laterally by "structured boundaries" (i.e., ones that impose a periodicity along the slit) is studied by Monte Carlo simulations. When the distance D between the confining walls is reduced at constant particle number from an initial value D_0, for which a crystalline structure commensurate with the imposed periodicity fits, to smaller values, a succession of phase transitions to imperfectly ordered structures occur. These structures have a reduced...

  14. Computing phase diagrams for a quasicrystal-forming patchy-particle system.

    Science.gov (United States)

    Reinhardt, Aleks; Romano, Flavio; Doye, Jonathan P K

    2013-06-21

    We introduce an approach to computing the free energy of quasicrystals, which we use to calculate phase diagrams for systems of two-dimensional patchy particles with five regularly arranged patches that have previously been shown to form dodecagonal quasicrystals. We find that the quasicrystal is a thermodynamically stable phase for a wide range of conditions and remains a robust feature of the system as the potential's parameters are varied. We also demonstrate that the quasicrystal is entropically stabilized over its crystalline approximants.

  15. Structure of 1,5-Anhydro-D-Fructose: X-ray Analysis of Crystalline Acetylated Dimeric Forms

    DEFF Research Database (Denmark)

    Lundt, Inge; Andersen, Søren Møller; Marcussen, Jan

    1998-01-01

    Acetylation of 1,5-anhydro-D-fructose under acidic conditions gave two crystalline acetylated dimeric forms, which by X-ray analysis were shown to be diastereomeric spiroketals formed between C-2 and C-2´/C-3´. The structures of the compounds differed only at the configuration at C-2. Acetylation...

  16. Crystalline Precipitate in a Bulk Glass Forming Zr-Based Alloy and Its Effect on Mechanical Properties

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Cylindrical and sheet samples of bulk metallic glass with a nominal composition of Zr52.5Ni14.6Al10Cu17.9Ti5 (at. pct) were prepared by melt injection casting. The crystalline precipitates formed during the casting were studied by metallographic observations and selected-area electron diffractions. The effect of crystalline precipitates on the mechanical properties were investigated by tensile and compressive tests at room temperature. Oxygen contents and the sample sizes (or cooling rates) strongly affect the formation of the crystalline precipitates. Overheating the alloy melt up to 200 K above its melting temperature can effectively prevent the formation of the crystalline precipitates to get fully glass samples with diameters up to 2 mm for cylinders and thickness up to 1 mm for sheets even the oxygen content is as higher as 0.08 wt pct.With increasing the sample sizes, the crystalline precipitates increase in volume fraction and size. The formation of the precipitates experienced two stages, i.e., initially nucleation and isotropic growth, and then anisotropic growth, finally forming faceted morphologies. Fully glassy Zr52.5Ni14.6Al10Cu17.9Ti5 alloy exhibits excellent tensile and compressive properties at room temperature. The presence of crystalline precipitates significantly decreases the tensile and compressive properties. With increasing the crystalline precipitates, the area of vein patterns on the fracture surface decreases, but the fracture steps increase, and the fracture mode changes from ductile to brittle resulting from the larger stress concentration caused by the larger sizes and faceted shapes of the crystalline precipitates.

  17. Nature of phase transitions in crystalline and amorphous GeTe-Sb2Te3 phase change materials.

    Science.gov (United States)

    Kalkan, B; Sen, S; Clark, S M

    2011-09-28

    The thermodynamic nature of phase stabilities and transformations are investigated in crystalline and amorphous Ge(1)Sb(2)Te(4) (GST124) phase change materials as a function of pressure and temperature using high-resolution synchrotron x-ray diffraction in a diamond anvil cell. The phase transformation sequences upon compression, for cubic and hexagonal GST124 phases are found to be: cubic → amorphous → orthorhombic → bcc and hexagonal → orthorhombic → bcc. The Clapeyron slopes for melting of the hexagonal and bcc phases are negative and positive, respectively, resulting in a pressure dependent minimum in the liquidus. When taken together, the phase equilibria relations are consistent with the presence of polyamorphism in this system with the as-deposited amorphous GST phase being the low entropy low-density amorphous phase and the laser melt-quenched and high-pressure amorphized GST being the high entropy high-density amorphous phase. The metastable phase boundary between these two polyamorphic phases is expected to have a negative Clapeyron slope. © 2011 American Institute of Physics

  18. Collagen films with stabilized liquid crystalline phases and concerns on osteoblast behaviors

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Minjian; Ding, Shan; Min, Xiang; Jiao, Yanpeng, E-mail: tjiaoyp@jnu.edu.cn; Li, Lihua; Li, Hong; Zhou, Changren, E-mail: tcrz9@jnu.edu.cn

    2016-01-01

    To duplicate collagen's in vivo liquid crystalline (LC) phase and investigate the relationship between the morphology of LC collagen and osteoblast behavior, a self-assembly method was introduced for preparing collagen films with a stabilized LC phase. The LC texture and topological structure of the films before and after stabilization were observed with polarizing optical microscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM). The relationship between the collagen films and osteoblast behavior was studied with the 3-(4,5)-dimethylthiahiazo(-z-y1)-3,5-di-phenytetrazoliumromide method, proliferation index detection, alkaline phosphatase measurements, osteocalcin assay, inverted microscopy, SEM observation, AFM observation, and cytoskeleton fluorescence staining. The results showed that the LC collagen film had continuously twisting orientations in the cholesteric phase with a typical series of arced patterns. The collagen fibers assembled in a well-organized orientation in the LC film. Compared to the non-LC film, the LC collagen film can promote cell proliferation, and increase ALP and osteocalcin expression, revealing a contact guide effect on osteoblasts. - Highlights: • Collagen film with liquid crystalline (LC) phase was observed by POM, SEM and AFM. • The effect of LC collagen film on osteoblasts behaviors was studied in detail. • LC collagen film promoted osteoblast proliferation and osteogenesis activity.

  19. Insect attachment on crystalline bioinspired wax surfaces formed by alkanes of varying chain lengths

    Directory of Open Access Journals (Sweden)

    Elena Gorb

    2014-07-01

    Full Text Available The impeding effect of plant surfaces covered with three-dimensional wax on attachment and locomotion of insects has been shown previously in numerous experimental studies. The aim of this study was to examine the effect of different parameters of crystalline wax coverage on insect attachment. We performed traction experiments with the beetle Coccinella septempunctata and pull-off force measurements with artificial adhesive systems (tacky polydimethylsiloxane semi-spheres on bioinspired wax surfaces formed by four alkanes of varying chain lengths (C36H74, C40H82, C44H90, and C50H102. All these highly hydrophobic coatings were composed of crystals having similar morphologies but differing in size and distribution/density, and exhibited different surface roughness. The crystal size (length and thickness decreased with an increase of the chain length of the alkanes that formed these surfaces, whereas the density of the wax coverage, as well as the surface roughness, showed an opposite relationship. Traction tests demonstrated a significant, up to 30 fold, reduction of insect attachment forces on the wax surfaces when compared with the reference glass sample. Attachment of the beetles to the wax substrates probably relied solely on the performance of adhesive pads. We found no influence of the wax coatings on the subsequent attachment ability of beetles. The obtained data are explained by the reduction of the real contact between the setal tips of the insect adhesive pads and the wax surfaces due to the micro- and nanoscopic roughness introduced by wax crystals. Experiments with polydimethylsiloxane semi-spheres showed much higher forces on wax samples when compared to insect attachment forces measured on these surfaces. We explain these results by the differences in material properties between polydimethylsiloxane probes and tenent setae of C. septempunctata beetles. Among wax surfaces, force experiments showed stronger insect attachment and higher

  20. Liquid crystalline phase transitions in virus and virus/polymer suspensions

    Science.gov (United States)

    Dogic, Zvonimir

    Using experimental, theoretical, and simulation methods, we investigate the relationship between the intermolecular interactions of rod-like colloids and the resulting liquid crystalline phase diagrams. As a model system of rod-like particles we use bacteriophage fd, which is a charge stabilized colloid. We are able to engineer complex attractive and repulsive intermolecular interactions by changing the ionic strengths of the suspensions, attaching covalently bound polymers and adding nonadsorbing polymers. Using standard molecular cloning techniques it is also shown that the aspect ratio of the rod-like particle can be manipulated. In the limit of high ionic strength the fd virus quantitatively agrees with the Onsager theory for the isotropic-nematic (I-N) phase transition in hard rods. The role of attractive interaction on the nature of the I-N phase transition is investigated. As the strength of the attraction is increased we observe isotropic-smectic (I-S) phase transitions. Using an optical microscope we follow the kinetics of the I-S phase transition and observe a wide range of novel structures of unexpected complexity. We also investigate the influence of adding hard spheres, or polymers on the nematic-smectic phase transition. We conclude that adding small spheres stabilizes the smectic phase and destabilizes the nematic phase.

  1. Morphology and crystalline-phase-dependent electrical insulating properties in tailored polypropylene for HVDC cables

    Science.gov (United States)

    Zha, Jun-Wei; Yan, Hong-Da; Li, Wei-Kang; Dang, Zhi-Min

    2016-11-01

    Polypropylene (PP) has become one promising material to potentially replace the cross-link polyethylene used for high voltage direct current cables. Besides the isotactic polypropylene, the block polypropylene (b-PP) and random polypropylene (r-PP) can be synthesized through the copolymerization of ethylene and propylene molecules. In this letter, the effect of morphology and crystalline phases on the insulating electrical properties of PP was investigated. It was found that the introduction of polyethylene monomer resulted in the formation of β and γ phases in b-PP and r-PP. The results from the characteristic trap energy levels indicated that the β and γ phases could induce deep electron traps which enable to capture the carriers. And the space charge accumulation was obviously suppressed. Besides, the decreased electrical conductivity was observed in b-PP and r-PP. It is attributed to the existence of deep traps which can effectively reduce the carrier mobility and density in materials.

  2. Two-dimensional topological crystalline insulator phase in quantum wells of trivial insulators

    Science.gov (United States)

    Niu, Chengwang; Buhl, Patrick M.; Bihlmayer, Gustav; Wortmann, Daniel; Blügel, Stefan; Mokrousov, Yuriy

    2016-06-01

    The realization of two-dimensional (2D) topological insulators (TIs) in HgTe/CdTe quantum wells (QWs) has generated an explosion of research on TIs and novel topologically nontrivial phases. Here we predict, based on first-principles calculations, that the newly discovered 2D topological crystalline insulators (TCIs) phase exists even in the QWs of trivial insulators, e.g. (Sn/Pb)Te and Na(Cl/Br), with mirror Chern number {n}{{M}}=-2. Tunable nontrivial energy gaps ranging from 4 to 238 meV are obtained, guaranteeing further room-temperature observations and applications. The combined effect of strain and electrostatic interaction that can be engineered by the cladding layers leads to a band inversion, resulting in the phase transition from trivial insulator to 2D TCIs. Our work provides a new strategy for engineering topological states in 2D materials.

  3. Sensitivity of micromechanical actuation on amorphous to crystalline phase transformations under the influence of Casimir forces

    Science.gov (United States)

    Sedighi, M.; Broer, W. H.; Palasantzas, G.; Kooi, B. J.

    2013-10-01

    Amorphous to crystalline phase transitions in phase change materials (PCM) can have strong influence on the actuation of microelectromechanical systems under the influence of Casimir forces. Indeed, the bifurcation curves of the stationary equilibrium points and the corresponding phase portraits of the actuation dynamics between gold and AIST (Ag5In5Sb60Te30) PCM, where an increase of the Casimir force of up ˜25% has been measured upon crystallization, show strong sensitivity to changes of the Casimir force as the stiffness of the actuating component decreases and/or the effective interaction area of the Casimir force increases, which can also lead to stiction. However, introduction of intrinsic energy dissipation (associated with a finite quality factor of the actuating system) can prevent stiction by driving the system to attenuated motion towards stable equilibrium depending on the PCM state and the system quality factor.

  4. Multiple phase transitions in single-crystalline Na_{1-delta}FeAs.

    Science.gov (United States)

    Chen, G F; Hu, W Z; Luo, J L; Wang, N L

    2009-06-01

    Specific heat, resistivity, susceptibility, and Hall coefficient measurements were performed on high-quality single-crystalline Na_{1-delta}FeAs. This compound is found to undergo three successive phase transitions at around 52, 41, and 23 K, which correspond to structural, magnetic, and superconducting transitions, respectively. The Hall effect result indicates the development of energy gap at low temperature due to the occurrence of spin-density-wave instability. Our results provide direct experimental evidence of the magnetic ordering in the nearly stoichiometric NaFeAs.

  5. Molecular structure of the discotic liquid crystalline phase of hexa-peri-hexabenzocoronene/oligothiophene hybrid and their charge transport properties

    Energy Technology Data Exchange (ETDEWEB)

    Bag, Saientan; Maingi, Vishal; Maiti, Prabal K., E-mail: maiti@physics.iisc.ernet.in [Department of Physics, Center for Condensed Matter Theory, Indian Institute of Science, Bangalore 560012 (India); Yelk, Joe; Glaser, Matthew A.; Clark, Noel A. [Department of Physics, University of Colorado, Boulder, Colorado 80309 (United States); Walba, David M. [Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309 (United States)

    2015-10-14

    Using atomistic molecular dynamics simulation, we study the discotic columnar liquid crystalline (LC) phases formed by a new organic compound having hexa-peri-Hexabenzocoronene (HBC) core with six pendant oligothiophene units recently synthesized by Nan Hu et al. [Adv. Mater. 26, 2066 (2014)]. This HBC core based LC phase was shown to have electric field responsive behavior and has important applications in organic electronics. Our simulation results confirm the hexagonal arrangement of columnar LC phase with a lattice spacing consistent with that obtained from small angle X-ray diffraction data. We have also calculated various positional and orientational correlation functions to characterize the ordering of the molecules in the columnar arrangement. The molecules in a column are arranged with an average twist of 25° having an average inter-molecular separation of ∼5 Å. Interestingly, we find an overall tilt angle of 43° between the columnar axis and HBC core. We also simulate the charge transport through this columnar phase and report the numerical value of charge carrier mobility for this liquid crystal phase. The charge carrier mobility is strongly influenced by the twist angle and average spacing of the molecules in the column.

  6. Dynamic characterization of crystalline and glass phases of deuterated 1,1,2,2 tetrachloroethane

    Energy Technology Data Exchange (ETDEWEB)

    Pérez, Silvina C., E-mail: clyde@famaf.unc.edu.ar; Zuriaga, Mariano, E-mail: zuriaga@famaf.unc.edu.ar; Serra, Pablo, E-mail: serra@famaf.unc.edu.ar; Wolfenson, Alberto, E-mail: wolf@famaf.unc.edu.ar [Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba and IFEG-CONICET, Ciudad Universitaria, X5016LAE Córdoba (Argentina); Negrier, Philippe, E-mail: philippe.negrier@u-bordeaux.fr [Université Bordeaux, LOMA, UMR 5798, F-33400 Talence, France and LOMA, UMR 5798, F-33400 Talence (France); Tamarit, Josep Lluis, E-mail: josep.lluis.tamarit@upc.edu [Grup de Caracterització de Materials, Departament de Física i Enginyeria Nuclear, ETSEIB, Diagonal 647, Universitat Politècnica de Catalunya, 08028 Barcelona, Catalonia (Spain)

    2015-10-07

    A thorough characterization of the γ, β, and glass phases of deuterated 1,1,2,2 tetrachloroethane (C{sub 2}D{sub 2}Cl{sub 4}) via nuclear quadrupole resonance and Molecular Dynamic Simulations (MDSs) is reported. The presence of molecular reorientations was experimentally observed in the glass phase and in the β phase. In the β phase, and from MDS, these reorientations are attributed to two possible movements, i.e., a 180°  reorientation around the C{sub 2} molecular symmetry axis and a reorientation of the molecule between two non-equivalent positions. In the glass phase, the spin-lattice relaxation time T{sub 1} is of the order of 16 times lower than in the crystalline phase and varies as T{sup −1} below 100 K in good agreement with the strong quadrupolar relaxation observed in amorphous materials and in the glassy state of molecular organic systems. The activation energy of molecular reorientations in the glass phase (19 kJ/mol) is comparable to that observed in the glassy crystal of a “molecular cousin” compound, Freon 112 (C{sub 2}F{sub 2}Cl{sub 4}), for the secondary β-relaxation. Moreover, the on-site orientational motion of tetrachloroethane molecules offers a new indirect evidence of the prominent role of such orientational disorder in glassy dynamics.

  7. Dynamic characterization of crystalline and glass phases of deuterated 1,1,2,2 Tetrachloroethane

    CERN Document Server

    Perez, Silvina; Serra, Pablo; Wolfenson, Alberto; Negrier, Philippe; Tamarit, Josep

    2015-01-01

    A thorough characterization of the {\\gamma}, {\\beta} and glass phases of deuterated 1,1,2,2 Tetrachloroethane (C2D2Cl4) via Nuclear Quadrupole Resonance and Molecular Dynamic Simulations (MDS) is reported. The presence of molecular reorientations was experimentally observed in the glass phase and in the {\\beta} phase. In the {\\beta} phase, and from MDS, these reorientations are attributed to two possible movements, i.e. a $180^o$ reorientation around the C2 molecular symmetry axis and a reorientation of the molecule between non-equivalent positions. In the glass phase, the spin-lattice relaxation time T1 is of the order of 16 times lower that T1 in the crystalline phase and varies as $T^{-1}$ below 100 K in good agreement with the strong quadrupolar relaxation observed in amorphous materials and in the glassy state of molecular organic systems. The activation energy of molecular reorientations in the glass phase (19 kJ/mol) is comparable to that observed in the glassy crystal of a "molecular cousin" compound,...

  8. Protective colloids and polylactic acid co-affecting the polymorphic crystal forms and crystallinity of indomethacin encapsulated in microspheres.

    Science.gov (United States)

    Lin, S Y; Chen, K S; Teng, H H

    1999-01-01

    The co-effect of protective colloids and polylactic acid (PLA) on the polymorphic crystal forms and crystallinity of indomethacin (IMC) in IMC-loaded PLA microspheres was investigated with differential scanning calorimetry, infrared spectroscopy and x-ray diffractometry, to evaluate the polymorphic crystal forms and crystallinity of IMC encapsulated in PLA microspheres. The surfactant, sodium dodecyl sulphate (SDS), was also used as a dispersing agent. The results indicate that the polymorphism and crystallinity of IMC encapsulated in IMC-loaded PLA microspheres was dependent on the type of protective colloid and PLA used. The amorphous state and alpha-form of IMC were found in the IMC-loaded PLA microspheres prepared using polysaccharide (pectin or beta-cyclodextrin) as a protective colloid or SDS as a dispersing agent. However, the amorphous and methylene chloride solvate of IMC seemed to exist in the IMC-loaded PLA microspheres prepared with the proteins (gelatin or albumin), synthetic cellulose derivative (methyl cellulose or hydroxylpropyl methylcellulose) or the synthetic nonionic polymer (polyvinyl alcohol, polyvinyl pyrrolidone or biosoluble polymer) as a protective colloid. PLA was found to express a certain crystallinity in microspheres and not be affected by the protective colloids, but it played a more important role in influencing the crystallization of IMC during microencapsulation than the protective colloids. No interaction occurred in the physical mixture of IMC and PLA, nor in the IMC-loaded PLA microspheres.

  9. Fabrication of tensile-strained single-crystalline GeSn on transparent substrate by nucleation-controlled liquid-phase crystallization

    Science.gov (United States)

    Oka, Hiroshi; Amamoto, Takashi; Koyama, Masahiro; Imai, Yasuhiko; Kimura, Shigeru; Hosoi, Takuji; Shimura, Takayoshi; Watanabe, Heiji

    2017-01-01

    We developed a method of forming single-crystalline germanium-tin (GeSn) alloy on transparent substrates that is based on liquid-phase crystallization. By controlling and designing nucleation during the melting growth process, a highly tensile-strained single-crystalline GeSn layer was grown on a quartz substrate without using any crystal-seeds or catalysts. The peak field-effect hole mobility of 423 cm2/V s was obtained for a top-gate single-crystalline GeSn MOSFET on a quartz substrate with a Sn content of 2.6%, indicating excellent crystal quality and mobility enhancement due to Sn incorporation and tensile strain.

  10. Nanoscale characteristics of triacylglycerol oils: phase separation and binding energies of two-component oils to crystalline nanoplatelets.

    Science.gov (United States)

    MacDougall, Colin J; Razul, M Shajahan; Papp-Szabo, Erzsebet; Peyronel, Fernanda; Hanna, Charles B; Marangoni, Alejandro G; Pink, David A

    2012-01-01

    Fats are elastoplastic materials with a defined yield stress and flow behavior and the plasticity of a fat is central to its functionality. This plasticity is given by a complex tribological interplay between a crystalline phase structured as crystalline nanoplatelets (CNPs) and nanoplatelet aggregates and the liquid oil phase. Oil can be trapped within microscopic pores within the fat crystal network by capillary action, but it is believed that a significant amount of oil can be trapped by adsorption onto crystalline surfaces. This, however, remains to be proven. Further, the structural basis for the solid-liquid interaction remains a mystery. In this work, we demonstrate that the triglyceride liquid structure plays a key role in oil binding and that this binding could potentially be modulated by judicious engineering of liquid triglyceride structure. The enhancement of oil binding is central to many current developments in this area since an improvement in the health characteristics of fat and fat-structured food products entails a reduction in the amount of crystalline triacylglycerols (TAGs) and a relative increase in the amount of liquid TAGs. Excessive amounts of unbound, free oil, will lead to losses in functionality of this important food component. Engineering fats for enhanced oil binding capacity is thus central to the design of more healthy food products. To begin to address this, we modelled the interaction of triacylglycerol oils, triolein (OOO), 1,2-olein elaidin (OOE) and 1,2-elaidin olein (EEO) with a model crystalline nanoplatelet composed of tristearin in an undefined polymorphic form. The surface of the CNP in contact with the oil was assumed to be planar. We considered pure OOO and mixtures of OOO + OOE and OOO + EEO with 80% OOO. The last two cases were taken as approximations to high oleic sunflower oil (HOSO). The intent was to investigate whether phase separation on a nanoscale took place. We defined an "oil binding capacity" parameter, B

  11. Local order and orientational correlations in liquid and crystalline phases of carbon tetrabromide from neutron powder diffraction measurements

    CERN Document Server

    Temleitner, László

    2010-01-01

    The liquid, plastic crystalline and ordered crystalline phases of CBr$_4$ were studied using neutron powder diffraction. The measured total scattering differential cross-sections were modelled by Reverse Monte Carlo simulation techniques (RMC++ and RMCPOW). Following successful simulations, the single crystal diffraction pattern of the plastic phase, as well as partial radial distribution functions and orientational correlations for all the three phases have been calculated from the atomic coordinates ('particle configurations'). The single crystal pattern, calculated from a configuration that had been obtained from modelling the powder pattern, shows identical behavior to the recent single crystal data of Folmer et al. (Phys. Rev. {\\bf B77}, 144205 (2008)). The BrBr partial radial distribution functions of the liquid and plastic crystalline phases are almost the same, while CC correlations clearly display long range ordering in the latter phase. Orientational correlations also suggest strong similarities bet...

  12. Gasification slag rheology and crystalline phase formation in titanium-calcium-alumina-silica-rich glass

    Energy Technology Data Exchange (ETDEWEB)

    Brooker, D.D. [Texaco, Inc., Beacon, NY (United States); Oh, M.S. [Hongik Univ., Seoul (Korea, Republic of)

    1996-10-01

    The Texaco Gasification Process employs a high temperature and pressure slagging gasifier, in which the viscosity of the slag plays a key role in determining operating conditions. The empirical models available in the literature as well as laboratory testing have concentrated on low titanium feeds. During the gasification of waste material, titanium oxide will become an important element in controlling the ash and slag behavior. Slag viscosity was measured at temperatures in the range of 1150-1500{degrees}C under reducing atmosphere with 0-30% titanium in combination with calcium-alumina-silica rich feeds to gain a better understanding of the slag theology. The slag viscosities with most titanium-rich slags showed the behavior of a crystalline slag with T{sub cv} of 1250{degrees}C. Crystalline phase analyses of the slag samples revealed that titanium oxide crystal will nucleate, but the glass phase is dominated by calcium-titanium-silicate and calcium-alumina-silicate glasses which have low melting points.

  13. Improving the performance of polymer solar cells by adjusting the crystallinity and nanoscale phase separation

    Institute of Scientific and Technical Information of China (English)

    Chen Wei-Bing; Xu Zong-Xiang; Li Kai; Chui Stephen Sin-Yin; Roy V.A.L.; Lai Pui-To; Che Chi-Ming

    2012-01-01

    In this paper,we report a high-performance P3HT/PCBM bulk-heterojunction solar cell with a power conversion efficiency of 4.85% fabricated by adjusting the polymer crystallinity and nanoscale phase separation using an ultrasonic irradiation mixing approach for the polymer.The grazing incidence X-ray diffraction,UV/Vis spectroscopic,and atomic force microscopic measurement results for the P3HT/PCBM blend films reveal that the P3HT/PCBM film fabricated by ultrasonic irradiation mixing of the P3HT and PCBM solutions for 10 min has a higher degree of cryetallinity,a higher absorption efficiency,and better phase separation,which together account for the higher charge transport properties and photovoltaic cell performance.

  14. Shifting Phases for Patchy Particles - Effect of mutagenesis and chemical modification on the phase diagram of human gamma D crystallin

    Science.gov (United States)

    McManus, Jennifer J.; James, Susan; McNamara, Ruth; Quinn, Michelle

    2014-03-01

    Single mutations in human gamma D crystallin (HGD), a protein found in the eye lens are associated with several childhood cataracts. Phase diagrams for several of these protein mutants have been measured and reveal that phase boundaries are shifted compared with the native protein, leading to condensation of protein in a physiologically relevant regime. Using HGD as a model protein, we have constructed phase diagrams for double mutants of the protein, incorporating two single amino acid substitutions for which phase diagrams are already known. In doing so, the characteristics of each of the single mutations are maintained but both are now present in the same protein particle. While these proteins are not of interest physiologically, this strategy allows the controlled synthesis of nano-scale patchy particles in which features associated with a known phase behavior can be included. It can also provide a strategy for the controlled crystallisation of proteins. Phase boundaries also change after the chemical modification of the protein, through the covalent attachment of fluorescent labels, for example, and this will also be discussed. The authors acknowledge Science Foundation Ireland Stokes Lectureship and Grant 11/RFP.1/PHY/3165. The authors also acknowledge the Irish Research Council and the John and Pat Hume Scholarship.

  15. Relaxation process and phase transition of lanthanide liquid crystalline complexes by photoacoustic spectroscopy

    Institute of Scientific and Technical Information of China (English)

    LI Junjia; YANG Yuetao; LIU Xiaojun; ZHANG Shuyi; ZHANG Zhongning

    2008-01-01

    Lanthanide-containing liquid crystals exhibiting smectic A phase close to room temperature were obtained. Photoacoustic (PA) spectroscopy was used to study the spectral properties and phase transitions of liquid crystalline metal complexes. It was found that PA intensity of the ligand had a relationship with the probability of nonradiative transitions, which increased in the order of Eu(tta)3L2Phase transitions of europium(III) and erbium(III) complexes, in the temperature range of 383-358 K, could be clearly monitored by both PA amplitude and PA phase signals. As the temperature crossed the transition point, PA amplitude showed a minimum and PA phase a maximum. The results indicated that PA technique could serve as a new tool for investigating the physicochemical properties of liquid crystals containing metal ions.

  16. Gradient measurement technique to identify phase transitions in nano-dispersed liquid crystalline compounds

    Science.gov (United States)

    Pardhasaradhi, P.; Madhav, B. T. P.; Venugopala Rao, M.; Manepalli, R. K. N. R.; Pisipati, V. G. K. M.

    2016-09-01

    Characterization and phase transitions in pure and 0.5% BaTiO3 nano-dispersed liquid crystalline (LC) N-(p-n-heptyloxybenzylidene)-p-n-nonyloxy aniline, 7O.O9, com-pounds are carried out using a polarizing microscope attached with hot stage and camera. We observed that when any of these images are distorted, different local structures suffer from various degradations in a gradient magnitude. So, we examined the pixel-wise gradient magnitude similarity between the reference and distorted images combined with a novel pooling strategy - the standard deviation of the GMS map - to determine the overall phase transition variations. In this regard, MATLAB software is used for gradient measurement technique to identify the phase transitions and transition temperature of the pure and nano-dispersed LC compounds. The image analysis of this method proposed is in good agreement with the standard methods like polarizing microscope (POM) and differential scanning calorimeter (DSC). 0.5% BaTiO3 nano-dispersed 7O.O9 compound induces cholesteric phase quenching the nematic phase, which the pure compound exhibits.

  17. Monodisperse nonionic isoprenoid-type hexahydrofarnesyl ethylene oxide surfactants: high throughput lyotropic liquid crystalline phase determination.

    Science.gov (United States)

    Fong, Celesta; Weerawardena, Asoka; Sagnella, Sharon M; Mulet, Xavier; Krodkiewska, Irena; Chong, Josephine; Drummond, Calum J

    2011-03-15

    The neat and lyotropic phase behavior of eight new ethylene oxide amphiphiles (EO = 1-8) with a hexahydrofarnesyl chain (3,7,11-trimethyldodecyl) and narrow polydispersity (>98.5% purity) is reported. Below five EO units the behavior of the neat surfactants show only a glass transition, Tg ∼ -90 °C. Above four EO units, crystallization (Tcrys) and crystal-isotropic liquid (Tm) transitions are also observed that increase with degree of ethoxylation of the surfactant headgroup. The lyotropic liquid crystalline phase behavior spans a complex spectrum of surfactant-water interfacial curvatures. Specifically, inverse phases are present below ambient temperatures for EO ethoxylation, with the crossover to normal phases occurring at HFarn(EO)(7-8) which exhibits normal hexagonal (H(I)) and cubic (Q(I)) phases at ambient temperatures. The toxicity of colloidal dispersions of these EO amphiphiles was assayed against normal breast epithelial (HMEpiC) and breast cancer (MCF7) cell lines. The IC50 of the EO amphiphiles was similar in both cell lines with moderate toxicity ranging from ca. <5 to 140 μM in an in vitro cell viability assay. Observations are qualitatively rationalized in terms of the molecular geometry of the surfactant. The physicochemical behavior of the HFarnesyl ethylene oxide amphiphiles is compared to other ethylene oxide surfactants.

  18. The evolution of strength and crystalline phases for alkali-activated ground blast furnace slag and fly ash-based geopolymers

    KAUST Repository

    Oh, Jae Eun

    2010-02-01

    The increase in strength and evolution of crystalline phases in inorganic polymer cement, made by the alkali activation of slag, Class C and Class F fly ashes, was followed using compressive strength test and synchrotron X-ray diffraction. In order to increase the crystallinity of the product the reactions were carried out at 80 °C. We found that hydrotalcite formed in both the alkali-activated slag cements and the fly ash-based geopolymers. Hydroxycancrinite, one member of the ABC-6 family of zeolites, was found only in the fly ash geopolymers. Assuming that the predominantly amorphous geopolymer formed under ambient conditions relates to the crystalline phases found when the mixture is cured at high temperature, we propose that the structure of this zeolitic precursor formed in Na-based high alkaline environment can be regarded as a disordered form of the basic building unit of the ABC-6 group of zeolites which includes poly-types such as hydroxycancrinite, hydroxysodalite and chabazite-Na. © 2009 Elsevier Ltd.

  19. Implications of transmutation on the defect chemistry in crystalline waste forms

    Energy Technology Data Exchange (ETDEWEB)

    Uberuaga, B.P., E-mail: blas@lanl.go [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Jiang, C.; Stanek, C.R.; Sickafus, K.E. [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Marks, N.A. [Nanochemistry Research Institute, Curtin University of Technology, P.O. Box U1987, Perth, WA 6845 (Australia); Carter, D.J.; Rohl, A.L. [Nanochemistry Research Institute, Curtin University of Technology, P.O. Box U1987, Perth, WA 6845 (Australia); iVEC, Technology Park, Kensington, WA 6151 (Australia)

    2010-10-01

    Radioactive decay within the solid state creates chemical environments which are typically incommensurate with the initial host structure. Using a combined theoretical and computational approach, we discuss this 'transmutation problem' in the context of the short-lived fission products Cs-137 and Sr-90. We show how a Kroeger-Vink treatment is insufficient for understanding defects arising from transmutation, and present density functional theory data for chemical evolution within two prototypical hosts, CsCl and SrTiO{sub 3}. While the latter has a strong driving force for phase separation with increasing Zr content, the Cs(Ba)Cl system is surprisingly stable. The sharp difference between these two findings points to the need for better understanding of novel chemistry in nuclear waste forms.

  20. Liquid crystalline dihydroazulene photoswitches

    DEFF Research Database (Denmark)

    Petersen, Anne Ugleholdt; Jevric, Martyn; Mandle, Richard J.

    2015-01-01

    A large selection of photochromic dihydroazulene (DHA) molecules incorporating various substituents at position 2 of the DHA core was prepared and investigated for their ability to form liquid crystalline phases. Incorporation of an octyloxy-substituted biphenyl substituent resulted in nematic...

  1. Solvation Dynamics in Different Phases of the Lyotropic Liquid Crystalline System.

    Science.gov (United States)

    Roy, Bibhisan; Satpathi, Sagar; Gavvala, Krishna; Koninti, Raj Kumar; Hazra, Partha

    2015-09-03

    Reverse hexagonal (HII) liquid crystalline material based on glycerol monooleate (GMO) is considered as a potential carrier for drugs and other important biomolecules due to its thermotropic phase change and excellent morphology. In this work, the dynamics of encapsulated water, which plays important role in stabilization and formation of reverse hexagonal mesophase, has been investigated by time dependent Stokes shift method using Coumarin-343 as a solvation probe. The formation of the reverse hexagonal mesophase (HII) and transformation to the L2 phase have been monitored using small-angle X-ray scattering and polarized light microscopy experiments. REES studies suggest the existence of different polar regions in both HII and L2 systems. The solvation dynamics study inside the reverse hexagonal (HII) phase reveals the existence of two different types of water molecules exhibiting dynamics on a 120-900 ps time scale. The estimated diffusion coefficients of both types of water molecules obtained from the observed dynamics are in good agreement with the measured diffusion coefficient collected from the NMR study. The calculated activation energy is found to be 2.05 kcal/mol, which is associated with coupled rotational-translational water relaxation dynamics upon the transition from "bound" to "quasi-free" state. The observed ∼2 ns faster dynamics of the L2 phase compared to the HII phase may be associated with both the phase transformation as well as thermotropic effect on the relaxation process. Microviscosities calculated from time-resolved anisotropy studies infer that the interface is almost ∼22 times higher viscous than the central part of the cylinder. Overall, our results reveal the unique dynamical features of water inside the cylinder of reverse hexagonal and inverse micellar phases.

  2. Durability of crystalline phase in concrete microstructure modified by the mineral powders: evaluation by nanoindentation tests

    Directory of Open Access Journals (Sweden)

    Rajczakowska Magdalena

    2016-03-01

    Full Text Available This paper presents the nanoindentation investigation of the evolution of concrete microstructure modified by the Internal Crystallization Technology mineral powders. The samples under study were retrieved from a fragment of a circular concrete lining of the vertical mine shaft at a depth of approximately 1,000 m. Due to the aggressive environment and exposure to contaminated water, the internal surface of the structure was deteriorated, decreasing its strength significantly. The mineral powders were applied directly on the surface lining. The specimens were investigated one month, three months and one year after the application of the aforementioned substance in order to verify the time dependence of the strengthening processes and durability of the crystalline phase. The microstructural changes of concrete were assessed with the use of nanoindentation technique. The testing procedure involved including the previously cut specimens in the epoxy resin and grinding and polishing in order to reduce the surface roughness. As a result of the nanoindentation tests the hardness as well as Young’s modulus of the material were evaluated. The results were then compared and statistically analyzed. As a consequence, the disintegration time of the crystalline network in the pores of concrete was identified.

  3. MORPHOLOGICAL AND KINETIC STUDIES OF PHASE TRANSITIONS OF A SIDE-CHAIN LIQUID CRYSTALLINE POLYMER

    Institute of Scientific and Technical Information of China (English)

    Chi-bing Tan; Shu-fan Zhang; Mao Xu

    1999-01-01

    The morphological changes of a side-chain liquid-crystalline polymethacrylate during isotropization and liquid-crystallization transitions were studied by means of polarizing microscopy. These transitions were found to be composed of the initiation of a new phase at local places of the old phase matrix and the growth of the new phase domains. The kinetics of the liquid-crystallization of the polymer from an isotropic melt to a smectic mesophase was also investigated. The isothermal process of the transition can be described by the Avrami equation. The values of the Avrami exponent were found to be around 2.6. which is lower than the value usually obtained for crystallization transition of polymers, but larger than that reported for liquid-crystallization transition of main-chain polymers. These results may indicate the difference in growth geometry of new phase during transition between crystallization and liquid-crystallization in general and between liquid-crystallization of main-chain and side-chain polymers. It was found that the liquidcrystallization of the used side-chain polymethacrylate may occur at small undercoolings with high transformation rate similar to that of main-chain polymers and small-molecule liquid crystals, while the crystallization of polymers can only proceed at large undercoolings. These phenomena can be explained by the idea that the surface free energy of nucleus during liquid-crystallization transition is less than that for crystallization, and evidence was obtained from analysis of the temperature dependence of the transformation rate.

  4. Mechanochemical spinodal decomposition: a phenomenological theory of phase transformations in multi-component, crystalline solids

    Science.gov (United States)

    Rudraraju, Shiva; van der Ven, Anton; Garikipati, Krishna

    2016-06-01

    We present a phenomenological treatment of diffusion-driven martensitic phase transformations in multi-component crystalline solids that arise from non-convex free energies in mechanical and chemical variables. The treatment describes diffusional phase transformations that are accompanied by symmetry-breaking structural changes of the crystal unit cell and reveals the importance of a mechanochemical spinodal, defined as the region in strain-composition space, where the free-energy density function is non-convex. The approach is relevant to phase transformations wherein the structural order parameters can be expressed as linear combinations of strains relative to a high-symmetry reference crystal. The governing equations describing mechanochemical spinodal decomposition are variationally derived from a free-energy density function that accounts for interfacial energy via gradients of the rapidly varying strain and composition fields. A robust computational framework for treating the coupled, higher-order diffusion and nonlinear strain gradient elasticity problems is presented. Because the local strains in an inhomogeneous, transforming microstructure can be finite, the elasticity problem must account for geometric nonlinearity. An evaluation of available experimental phase diagrams and first-principles free energies suggests that mechanochemical spinodal decomposition should occur in metal hydrides such as ZrH2-2c. The rich physics that ensues is explored in several numerical examples in two and three dimensions, and the relevance of the mechanism is discussed in the context of important electrode materials for Li-ion batteries and high-temperature ceramics.

  5. Phase field modeling of grain structure evolution during directional solidification of multi-crystalline silicon sheet

    Science.gov (United States)

    Lin, H. K.; Lan, C. W.

    2017-10-01

    Evolution of grain structures and grain boundaries (GBs), especially the coincident site lattice GBs, during directional solidification of multi-crystalline silicon sheet are simulated by using a phase field model for the first time. Since the coincident site lattice GBs having lower mobility, tend to follow their own crystallographic directions despite thermal gradients, the anisotropic energy and mobility of GBs are considered in the model. Three basic interactions of GBs during solidification are examined and they are consistent with experiments. The twinning process for new grain formation is further added in the simulation by considering twin nucleation. The effect of initial distribution of GB types and grain orientations is also investigated for the twinning frequency and the evolution of grain size and GB types.

  6. The dielectric behavior of vapor-deposited amorphous solid water and of its crystalline forms

    Science.gov (United States)

    Johari, G. P.; Hallbrucker, Andreas; Mayer, Erwin

    1991-08-01

    The dielectric permittivity and loss of vapor-deposited amorphous solid water (ASW) have been measured for fixed frequencies of 1 and 10 kHz from 80 K to its crystallization temperature. Similar measurements have also been made on the cubic ice formed after the crystallization of ASW and the hexagonal ice formed on heating the cubic ice. The loss tangent shows a broad sub-Tg relaxation peak centered at about 100 K and an approach towards a plateau value which appears as a shoulder. The peak is attributed to thermally activated rotation of H2O molecules with one or two dangling OH groups on the surface of the pores of the microporous sample, and the shoulder to localized motions within the network structure. Sintering of the samples on thermal cycling between 77 and ≊120 K in vacuo causes the broad peak to vanish. With increase in temperature, above Tg, the loss tangent shows the emergence of the expected α-relaxation peak of a liquid at T>Tg, whose completion is terminated by the onset of crystallization to cubic ice at about the same temperature for 1 kHz and for 10 kHz measurements. Thereafter, crystallization becomes slower, thus allowing further observation of the low-temperature part of the α-relaxation peak. The dielectric loss of amorphous solid water at 80 K is nearly 20 times that of the cubic ice formed on its crystallization after heating to 193 K, and nearly 3.5 times higher at Tg. The dielectric loss of the cubic ice formed on crystallization tends towards a plateau value prior to rapidly increasing with increase in temperature, an evidence for a low temperature relaxation which vanishes on conversion to hexagonal ice. This relaxation indicates a remnant topologically disordered structure of intergranular water and/or stacking faults in cubic ice. Samples sintered by thermal cycling in vacuo to ≊120 K crystallized in one step, whereas those without prior thermal cycling crystallized in two steps to cubic ice. Annealing of the ASW at 130 K

  7. Effect of Preparation Method on Surface Area and Crystalline Form of CeO2-ZrO2 Solid Solution

    Institute of Scientific and Technical Information of China (English)

    王晓红; 郭耘; 卢冠忠; 郭杨龙; 王筠松; 张志刚; 刘晓晖

    2004-01-01

    The CeO2-ZrO2 solid solutions were prepared by a reverse microemulsion method. The effect of preparation parameters on the surface area and crystalline form of the solid solutions were studied by the BET surface area and XRD analysis. The studies indicate that the separation of the microemulsion phase during the preparation procedure can decrease the specific surface area of sample, adding hydrogen peroxide in the matrix solution can increase the specific surface area and stability of sample. The surface area of sample calcined at 550 ℃ for 5 h is 149 m2·g-1, and that calcined at 900 ℃ for 6 h is 88 m2·g-1.The sample with tetragonal symmetry Ce0.5Zr0.5O2 phase has a higher stability.

  8. Transitions between imperfectly ordered crystalline structures: a phase switch Monte Carlo study.

    Science.gov (United States)

    Wilms, Dorothea; Wilding, Nigel B; Binder, Kurt

    2012-05-01

    A model for two-dimensional colloids confined laterally by "structured boundaries" (i.e., ones that impose a periodicity along the slit) is studied by Monte Carlo simulations. When the distance D between the confining walls is reduced at constant particle number from an initial value D(0), for which a crystalline structure commensurate with the imposed periodicity fits, to smaller values, a succession of phase transitions to imperfectly ordered structures occur. These structures have a reduced number of rows parallel to the boundaries (from n to n-1 to n-2, etc.) and are accompanied by an almost periodic strain pattern, due to "soliton staircases" along the boundaries. Since standard simulation studies of such transitions are hampered by huge hysteresis effects, we apply the phase switch Monte Carlo method to estimate the free energy difference between the structures as a function of the misfit between D and D(0), thereby locating where the transitions occur in equilibrium. For comparison, we also obtain this free energy difference from a thermodynamic integration method: The results agree, but the effort required to obtain the same accuracy as provided by phase switch Monte Carlo would be at least three orders of magnitude larger. We also show for a situation where several "candidate structures" exist for a phase, that phase switch Monte Carlo can clearly distinguish the metastable structures from the stable one. Finally, applying the method in the conjugate statistical ensemble (where the normal pressure conjugate to D is taken as an independent control variable), we show that the standard equivalence between the conjugate ensembles of statistical mechanics is violated.

  9. Multi-technique Approach for the Evaluation of the Crystalline Phase of Ultrathin High-k Gate Oxide Films

    Science.gov (United States)

    Bersch, E.; LaRose, J. D.; Wells, I.; Consiglio, S.; Clark, R. D.; Leusink, G. J.; Matyi, R. J.; Diebold, A. C.

    2011-11-01

    In order to continue scaling metal oxide semiconductor field effect transistors (MOSFETs) with HfO2 gate oxides, efforts are being made to further improve the deposited high-k film properties. Recently, a process whereby an HfO2 film is deposited through a series of depositions and anneals (so-called DADA process) has been shown to result in films that give rise to MOS capacitors (MOSCAPs) which are electrically scaled compared to MOSCAPs with HfO2 films that only received post deposition anneals (PDA) or no anneals. We have measured as-deposited, DADA and PDA HfO2 films using four measurement techniques, all of which are non-destructive and capable of being used for in-line processing, to evaluate their crystallinity and crystalline phases. Grazing incidence in-plane X-ray diffraction was used to determine the crystalline phases of the HfO2 films. We observed the crystalline phases of these films to be process dependent. Additionally, X-ray and UV photoelectron spectroscopy were used to show the presence of crystallinity in the films. As a fourth technique, spectroscopic ellipsometry was used to determine if the crystalline phases were monoclinic. The combination of techniques was useful in that XPS and UPS were able to confirm the amorphous nature of a 30 cycle DADA film, as measured by GIIXRD, and GIIXRD was able to help us interpret the SE data as being an indication of the monoclinic phase of HfO2.

  10. Emergence of topological and topological crystalline phases in TlBiS2 and TlSbS2

    KAUST Repository

    Zhang, Qingyun

    2015-02-11

    Using first-principles calculations, we investigate the band structure evolution and topological phase transitions in TlBiS2 and TlSbS2 under hydrostatic pressure as well as uniaxial and biaxial strain. The phase transitions are identified by parity analysis and by calculating the surface states. Zero, one, and four Dirac cones are found for the (111) surfaces of both TlBiS2 and TlSbS2 when the pressure grows, which confirms trivial-nontrivial-trivial phase transitions. The Dirac cones at the (M) over bar points are anisotropic with large out-of-plane component. TlBiS2 shows normal, topological, and topological crystalline insulator phases under hydrostatic pressure, thus being the first compound to exhibit a phase transition from a topological to a topological crystalline insulator.

  11. Effect of NiO crystallinity on forming characteristics in Pt/NiO/Pt cells as resistive switching memories

    Science.gov (United States)

    Nishi, Yusuke; Kimoto, Tsunenobu

    2016-09-01

    Resistive switching (RS) in metal/oxide/metal stack structures plays a key role in resistive RAM. The formation and rupture of conductive filaments have been widely accepted as an origin of RS mechanism especially in binary transition metal oxides. Forming exhibits some analogies with a dielectric breakdown of SiO2 thin films. In this study, Time-Dependent Forming (TDF) characteristics of Pt/NiO/Pt stack structures have been investigated. The results revealed that the formation of conductive filaments at the forming process by applying constant voltage followed a weakest-link theory and that the weakest spots were almost randomly distributed in NiO thin films according to the Poisson statistics. Furthermore, the distribution of TDF characteristics depends on NiO crystallinity. A small variation of initial resistance tends to result in a large variation of time to forming and vice versa.

  12. Control of crystalline phases in magnetic Fe nanoparticles inserted inside a matrix of porous carbon

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, M.P., E-mail: fernandezpaz.uo@uniovi.e [Dpto. de Fisica, Universidad de Oviedo, Calvo Sotelo, s/n, 33007 Oviedo (Spain); Schmool, D.S. [IN-IFIMUP, Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal); Dpto. de Fisica, Universidade do Porto, Rua do Campo Alegre 687, 4440-661 Porto (Portugal); Silva, A.S. [Dpto. de Fisica, Universidade do Porto, Rua do Campo Alegre 687, 4440-661 Porto (Portugal); Sevilla, M.; Fuertes, A.B. [Instituto Nacional del Carbon (CSIC), Apartado 73, 33080 Oviedo (Spain); Gorria, P.; Blanco, J.A. [Dpto. de Fisica, Universidad de Oviedo, Calvo Sotelo, s/n, 33007 Oviedo (Spain)

    2010-05-15

    Two magnetic composites made up of Fe nanoparticles (Fe-NPs) embedded in a porous amorphous carbon matrix are presented. One of the samples, Fe-S-AC, was obtained with the aid of sucrose and the other, Fe-AC, in the absence of this substance. The XRD patterns show Bragg diffraction peaks associated with alpha-Fe and gamma-Fe crystalline phases in the Fe-AC sample, while only peaks corresponding to the alpha-Fe phase are observed for Fe-S-AC powders. The Fe-NPs exhibit broad particle-size distributions for both samples, 5-50 nm for Fe-AC, whereas two populations (2-8 and 10-70 nm) for the Fe-S-AC composite are found. This fact gives rise to poorly defined blocking temperatures, as it can be deduced from the broad maxima observed in M{sub ZFC}(T) variations. In addition, M(H) curves for both Fe-AC and Fe-S-AC samples reveal the existence of exchange-bias effect for T<60 K, probably due to a magnetic coupling within a core/shell structure of the Fe-NPs, although this effect was observed to be less significant for Fe-S-AC.

  13. Liquid crystalline phase as a probe for crystal engineering of lactose: carrier for pulmonary drug delivery.

    Science.gov (United States)

    Patil, Sharvil S; Mahadik, Kakasaheb R; Paradkar, Anant R

    2015-02-20

    The current work was undertaken to assess suitability of liquid crystalline phase for engineering of lactose crystals and their utility as a carrier in dry powder inhalation formulations. Saturated lactose solution was poured in molten glyceryl monooleate which subsequently transformed into gel. The gel microstructure was analyzed by PPL microscopy and SAXS. Lactose particles recovered from gels after 48 h were analyzed for polymorphism using techniques such as FTIR, XRD, DSC and TGA. Particle size, morphology and aerosolisation properties of prepared lactose were analyzed using Anderson cascade impactor. In situ seeding followed by growth of lactose crystals took place in gels with cubic microstructure as revealed by PPL microscopy and SAXS. Elongated (size ∼ 71 μm) lactose particles with smooth surface containing mixture of α and β-lactose was recovered from gel, however percentage of α-lactose was more as compared to β-lactose. The aerosolisation parameters such as RD, ED, %FPF and % recovery of lactose recovered from gel (LPL) were found to be comparable to Respitose® ML001. Thus LC phase (cubic) can be used for engineering of lactose crystals so as to obtain particles with smooth surface, high elongation ratio and further they can be used as carrier in DPI formulations.

  14. Substrate Biasing during Plasma-Assisted ALD for Crystalline Phase-Control of TiO(2) Thin Films

    NARCIS (Netherlands)

    Profijt, H. B.; M. C. M. van de Sanden,; Kessels, W. M. M.

    2012-01-01

    Substrate biasing has been implemented in a remote plasma atomic layer deposition (ALD) reactor, enabling control of the ion energy up to 260 eV. For TiO(2) films deposited from Ti(Cp(Me))(NMe(2))(3) and O(2) plasma it is demonstrated that the crystalline phase can be tailored by tuning the ion ener

  15. Appearance of large crystalline domains in VO{sub 2} films grown on sapphire (001) and their phase transition characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Azhan, Nurul Hanis; Su, Kui; Okimura, Kunio, E-mail: okifn@keyaki.cc.u-tokai.ac.jp [Graduate School of Science and Technology, Tokai University, Hiratsuka 259-1292 (Japan); Zaghrioui, Mustapha; Sakai, Joe [GREMAN, UMR 7347 CNRS, Université François Rabelais de Tours, Parc de Grandmont 37200 Tours (France)

    2015-06-28

    We report the first observation of large crystalline domains of several μm-size in VO{sub 2} films deposited on Al{sub 2}O{sub 3} (001) substrates by rf-biased reactive sputtering technique. The large crystalline domains, dominated with random in-plane oriented growth of (011){sub M1}-orientation, appear only under adequate substrate biasing, such as 10 W, while most biasing conditions result in conventional nanosized grains of highly oriented (010){sub M1}-orientation. Two temperature-controlled analyses, x-ray diffraction and micro-Raman spectroscopy, have revealed that some parts of large crystalline domains undergo intermediate monoclinic (M2) phase during the thermally-induced structural phase transition from monoclinic (M1) to rutile-tetragonal (R) phase. As an effect of the appearance of large crystalline domains, the film showed in-plane tensile stress, resulting in high T{sub IMT} of 69 °C due to the elongation of the V-V distance in its low-temperature monoclinic phase.

  16. Solid-state NMR analysis of a complex crystalline phase of ronacaleret hydrochloride.

    Science.gov (United States)

    Vogt, Frederick G; Williams, Glenn R; Strohmeier, Mark; Johnson, Matthew N; Copley, Royston C B

    2014-08-28

    A crystalline phase of the pharmaceutical compound ronacaleret hydrochloride is studied by solid-state nuclear magnetic resonance (SSNMR) spectroscopy and single-crystal X-ray diffraction. The crystal structure is determined to contain two independent cationic molecules and chloride anions in the asymmetric unit, which combine with the covalent structure of the molecule to yield complex SSNMR spectra. Experimental approaches based on dipolar correlation, chemical shift tensor analysis, and quadrupolar interaction analysis are employed to obtain detailed information about this phase. Density functional theory (DFT) calculations are used to predict chemical shielding and electric field gradient (EFG) parameters for comparison with experiment. (1)H SSNMR experiments performed at 16.4 T using magic-angle spinning (MAS) and homonuclear dipolar decoupling provide information about hydrogen bonding and molecular connectivity that can be related to the crystal structure. (19)F and (13)C assignments for the Z' = 2 structure are obtained using DFT calculations, (19)F homonuclear dipolar correlation, and (13)C-(19)F heteronuclear dipolar correlation experiments. (35)Cl MAS experiments at 16.4 T observe two chlorine sites that are assigned using calculated chemical shielding and EFG parameters. SSNMR dipolar correlation experiments are used to extract (1)H-(13)C, (1)H-(15)N, (1)H-(19)F, (13)C-(19)F, and (1)H-(35)Cl through-space connectivity information for many positions of interest. The results allow for the evaluation of the performance of a suite of SSNMR experiments and computational approaches as applied to a complex but typical pharmaceutical solid phase.

  17. Crystalline-to-plastic phase transitions in molecularly thin n-dotriacontane films adsorbed on solid surfaces

    DEFF Research Database (Denmark)

    Cisternas, Edgardo; Corrales, T. P.; del Campo, V.;

    2009-01-01

    Crystalline-to-rotator phase transitions have been widely studied in bulk hydrocarbons, in particular in normal alkanes. But few studies of these transitions deal with molecularly thin films of pure n-alkanes on solid substrates. In this work, we were able to grow dotriacontane (n-C32H66) films...... identify with a solid-solid phase transition. At higher coverages, we observed additional steps in the ellipsometric signal that we identify with a solid-solid phase transition in multilayer islands (similar to 333 K) and with the transition to the rotator phase in bulk crystallites (similar to 337 K...

  18. A novel technique for production of nano-crystalline mono tungsten carbide single phase via mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Razavi, Mansour, E-mail: m-razavi@merc.ac.ir [Materials and Energy Research Center (MERC), P.O. Box 14155-4777, Tehran (Iran, Islamic Republic of); Rahimipour, Mohammad Reza; Yazdani-Rad, Rahim [Materials and Energy Research Center (MERC), P.O. Box 14155-4777, Tehran (Iran, Islamic Republic of)

    2011-06-09

    Highlights: > By adding WC to mixture of tungsten and carbon black unlike the system which does not contain any additive, it can lead to synthesized mono carbide tungsten. > However, the synthesize time has been reduced significantly. > Crystalline size of two systems were in nano-meter scale, this amount in system contain primary WC which was smaller than system without WC. - Abstract: Due to simultaneous synthesis of WC and W{sub 2}C phases in most of the synthesis processes and lower mechanical properties of W{sub 2}C than WC, in this work the possibility of production of nano-crystalline WC single phase as a useful refractory ceramic by means of mechanical alloying has been investigated. The raw materials containing W and C with WC were milled in a planetary ball mill. The sampling has been done in different times. As it was expected, XRD studies showed that after 75 h of milling the WC with W{sub 2}C were produced. By adding WC to the raw materials in the beginning of the process it led to the fact that after 50 h of milling WC was synthesized only without any other phases which remained stable at the higher times while milling. During broadening of XRD peaks, the size of synthesized crystalline WC was estimated in the order of nano-meter. Crystalline size and mean strain of synthesized WC in the system without additive were higher and lower than the system containing WC, respectively.

  19. Coarse-grained electrostatic interactions of coronene: Towards the crystalline phase

    Energy Technology Data Exchange (ETDEWEB)

    Heinemann, Thomas, E-mail: thomas.heinemann@tu-berlin.de; Klapp, Sabine H. L., E-mail: klapp@physik.tu-berlin.de [Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin (Germany); Palczynski, Karol, E-mail: karol.palczynski@helmholtz-berlin.de; Dzubiella, Joachim, E-mail: joachim.dzubiella@helmholtz-berlin.de [Institut für Physik, Humboldt Universität zu Berlin, Newtonstraße 15, 12489 Berlin (Germany); Institut für Weiche Materie und Funktionale Materialen, Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner Platz 1, 14109 Berlin (Germany)

    2015-11-07

    In this article, we present and compare two different, coarse-grained approaches to model electrostatic interactions of disc-shaped aromatic molecules, specifically coronene. Our study builds on our previous work [T. Heinemann et al., J. Chem. Phys. 141, 214110 (2014)], where we proposed, based on a systematic coarse-graining procedure starting from the atomistic level, an anisotropic effective (Gay-Berne-like) potential capable of describing van der Waals contributions to the interaction energy. To take into account electrostatics, we introduce, first, a linear quadrupole moment along the symmetry axis of the coronene disc. The second approach takes into account the fact that the partial charges within the molecules are distributed in a ring-like fashion. We then reparametrize the effective Gay-Berne-like potential such that it matches, at short distances, the ring-ring potential. To investigate the validity of these two approaches, we perform many-particle molecular dynamics simulations, focusing on the crystalline phase (karpatite) where electrostatic interaction effects are expected to be particularly relevant for the formation of tilted stacked columns. Specifically, we investigate various structural parameters as well as the melting transition. We find that the second approach yields consistent results with those from experiments despite the fact that the underlying potential decays with the wrong distance dependence at large molecule separations. Our strategy can be transferred to a broader class of molecules, such as benzene or hexabenzocoronene.

  20. Coarse-grained electrostatic interactions of coronene: Towards the crystalline phase.

    Science.gov (United States)

    Heinemann, Thomas; Palczynski, Karol; Dzubiella, Joachim; Klapp, Sabine H L

    2015-11-07

    In this article, we present and compare two different, coarse-grained approaches to model electrostatic interactions of disc-shaped aromatic molecules, specifically coronene. Our study builds on our previous work [T. Heinemann et al., J. Chem. Phys. 141, 214110 (2014)], where we proposed, based on a systematic coarse-graining procedure starting from the atomistic level, an anisotropic effective (Gay-Berne-like) potential capable of describing van der Waals contributions to the interaction energy. To take into account electrostatics, we introduce, first, a linear quadrupole moment along the symmetry axis of the coronene disc. The second approach takes into account the fact that the partial charges within the molecules are distributed in a ring-like fashion. We then reparametrize the effective Gay-Berne-like potential such that it matches, at short distances, the ring-ring potential. To investigate the validity of these two approaches, we perform many-particle molecular dynamics simulations, focusing on the crystalline phase (karpatite) where electrostatic interaction effects are expected to be particularly relevant for the formation of tilted stacked columns. Specifically, we investigate various structural parameters as well as the melting transition. We find that the second approach yields consistent results with those from experiments despite the fact that the underlying potential decays with the wrong distance dependence at large molecule separations. Our strategy can be transferred to a broader class of molecules, such as benzene or hexabenzocoronene.

  1. Germanium ion implantation to Improve Crystallinity during Solid Phase Epitaxy and the effect of AMU Contamination

    Science.gov (United States)

    Lee, K. S.; Yoo, D. H.; Son, G. H.; Lee, C. H.; Noh, J. H.; Han, J. J.; Yu, Y. S.; Hyung, Y. W.; Yang, J. K.; Song, D. G.; Lim, T. J.; Kim, Y. K.; Lee, S. C.; Lee, H. D.; Moon, J. T.

    2006-11-01

    Germanium ion implantation was investigated for crystallinity enhancement during solid phase epitaxial regrowth (SPE) using high current implantation equipment. Electron back-scatter diffraction(EBSD) measurement showed numerical increase of 19 percent of signal, which might be due to pre-amorphization effect on silicon layer deposited by LPCVD process with germanium ion implantation. On the other hand, electrical property such as off-leakage current of NMOS transistor degraded in specific regions of wafers, which implied non-uniform distribution of donor-type impurities into channel area. It was confirmed that arsenic atoms were incorporated into silicon layer during germanium ion implantation. Since the equipment for germanium pre-amorphization implantation(PAI) was using several source gases such as BF3 and AsH3, atomic mass unit(AMU) contamination during PAI of germanium with AMU 74 caused the incorporation of arsenic with AMU 75 which resided in arc-chamber and other parts of the equipment. It was effective to use germanium isotope of AMU 72 to suppress AMU contamination, however it led serious reduction of productivity because of decrease in beam current by 30 percent as known to be difference in isotope abundance. It was effective to use enriched germanium source gas with AMU 72 in order to improve productivity. Spatial distribution of arsenic impurities in wafers was closely related to hardware configuration of ion implantation equipment.

  2. Effect of Alkali Ions on the Amorphous to Crystalline Phase Transition of Silica

    Science.gov (United States)

    Venezia, A. M.; La Parola, V.; Longo, A.; Martorana, A.

    2001-11-01

    The effect of the addition of alkali ions to commercial amorphous silica, generally used as support for heterogeneous catalysts, has been investigated from the point of view of morphological and structural changes. Samples of alkali-doped silica were prepared by impregnation and subsequent calcination at various temperatures. The structural effect of Li, Na, K, and Cs was determined by use of techniques such as wide-angle (WAXS) and small-angle X-ray scattering (SAXS). The WAXS diffractograms, analyzed with the Rietveld method using the GSAS program, allowed qualitative and quantitative identification of the fraction of the different silica polymorphs like quartz, tridymite, and cristobalite. SAXS measurements, using the classical method based on Porod's law, yielded the total surface area of the systems. The calculated areas were compared with the surface areas determined by the nitrogen adsorption technique using the analytical method of Brunauer-Emmett-Teller. The results are explained in terms of sizes of the alkali ions and cell volume of the different crystalline phases.

  3. Second amorphous-to-crystalline phase transformation in Cu60Ti20Zr20 bulk metallic glass

    DEFF Research Database (Denmark)

    Cao, Q.P.; Li, J.F.; Zhang, P.N.

    2007-01-01

    is estimated to be about 2.46 kJ mol(-1) at 753 K, much smaller than the 61 kJ mol(-1) obtained assuming that it is a polymorphic transformation. It was revealed that the phase transformation occurs through a eutectic crystallization of Cu51Zr14 and Cu2TiZr14 having an effective activation energy of the order......The second amorphous-to-crystalline phase transformation in Cu60Ti20Zr20 bulk metallic glass was investigated by differential scanning calorimetry and x-ray diffractometry. The difference of the Gibbs free energies between the amorphous phase and the crystalline products during the transformation...

  4. Analysis of coal tar polycyclic aromatic hydrocarbon LC-fractions by capillary SFC on a liquid crystalline stationary phase

    Energy Technology Data Exchange (ETDEWEB)

    Kithinji, J.P.; Raynor, M.W.; Egia, B.; Davies, I.L.; Bartle, K.D.; Clifford, A.A. (University of Leeds, Leeds (UK). School of Chemistry)

    1990-01-01

    Supercritical fluid chromatography (SFC) on a capillary column coated with a smectic mesomorphic crystalline phase is shown to exhibit a typical turnover effect (retention versus column temperature) for polycyclic aromatic hydrocarbons (PAHs) at lower temperatures than are found on a methylpolysiloxane phase. Liquid chromatography is used to separate various fractions from a coal tar, which are analyzed by high resolution capillary SFC. Different density and temperature programs were investigated to optimize the separations. Simultaneous density and temperature programs gave the best results, and this is thought to be due to increased solute diffusion coefficients which yield highly efficient separations for the high molecular weight polycyclic aromatic hydrocarbons. The separation mechanism is based on the shape of the liquid crystalline phase, solubility, volatility, and molecular geometry of the PAHs.

  5. First-principles computation of mantle materials in crystalline and amorphous phases

    Science.gov (United States)

    Karki, Bijaya B.

    2015-03-01

    First-principles methods based on density functional theory are used extensively in the investigation of the behavior and properties of mantle materials over broad ranges of pressure, temperature, and composition that are relevant. A review of computational results reported during the last couple of decades shows that essentially all properties including structure, phase transition, equation of state, thermodynamics, elasticity, alloying, conductivity, defects, interfaces, diffusivity, viscosity, and melting have been calculated from first principles. Using MgO, the second most abundant oxide of Earth's mantle, as a primary example and considering many other mantle materials in their crystalline and amorphous phases, we have found that most properties are strongly pressure dependent, sometimes varying non-monotonically and anomalously, with the effects of temperature being systematically suppressed with compression. The overall agreement with the available experimental data is excellent; it is remarkable that the early-calculated results such as shear wave velocities of two key phases, MgO and MgSiO3 perovskite, were subsequently reproduced by experimentation covering almost the entire mantle pressure regime. As covered in some detail, the defect formation and migration enthalpies of key mantle materials increase with pressure. The predicted trend is that partial MgO Schottky defects are energetically most favorable in Mg-silicates but their formation enthalpies are high. So, the diffusion in the mantle is likely to be in the extrinsic regime. Preliminary results on MgO and forsterite hint that the grain boundaries can accommodate point defects (including impurities) and enhance diffusion rates at all pressures. The structures are highly distorted in the close vicinity of the defects and at the interface with excess space. Recent simulations of MgO-SiO2 binary and other silicate melts have found that the melt self-diffusion and viscosity vary by several orders of

  6. Integrating superconducting phase and topological crystalline quantum spin Hall effect in hafnium intercalated gallium film

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Jian, E-mail: jzhou2@vcu.edu, E-mail: pjena@vcu.edu; Jena, Puru, E-mail: jzhou2@vcu.edu, E-mail: pjena@vcu.edu [Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284 (United States); Zhang, Shunhong [Center for Applied Physics and Technology, College of Engineering, Peking University, Beijing 100871 (China); Wang, Qian [Center for Applied Physics and Technology, College of Engineering, Peking University, Beijing 100871 (China); Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284 (United States)

    2016-06-20

    Motivated by the growth of superconducting atomic hexagonal Ga layers on GaN surface we have calculated the electronic properties of Hf intercalated honeycomb Ga layers using first-principles theory. In contrast to the hexagonal Ga layers where substrate is necessary for their stability, we find the above structure to be dynamically stable in its freestanding form with small formation energy. In particular, six Dirac cones composed of Hf-d{sub xy}/d{sub x2-y2} orbitals are observed in the first Brillouin zone, slightly below the Fermi energy. Spin-orbit coupling opens a large band gap of 177 meV on these Dirac cones. By calculating its mirror Chern number, we demonstrate that this band gap is topologically nontrivial and protected by mirror symmetry. Such mirror symmetry protected band gaps are rare in hexagonal lattice. A large topological crystalline quantum spin Hall conductance σ{sub SH} ∼ −4 e{sup 2}/h is also revealed. Moreover, electron-phonon coupling calculations reveal that this material is superconducting with a transition temperature T{sub c} = 2.4 K, mainly contributed by Ga out-of-plane vibrations. Our results provide a route toward manipulating quantum spin Hall and superconducting behaviors in a single material which helps to realize Majorana fermions and topological superconductors.

  7. A new micro scale FE model of crystalline materials in micro forming process

    Directory of Open Access Journals (Sweden)

    Luo Liang

    2016-01-01

    Full Text Available Micro forming of metals has drawn global attention due to the increasing requirement of micro metal products. However, the size effects become significant in micro forming processes and affect the application of finite element (FE simulation of micro forming processes. Dividing samples into small areas according to their microstructures and assigning individual properties to each small area are a possible access to micro forming simulation considering material size effects. In this study, a new model that includes both grains and their boundaries was developed based on the observed microstructures of samples. The divided subareas in the model have exact shapes and sizes with real crystals on the sample, and each grain and grain boundaries have their own properties. Moreover, two modelling methods using different information from the microstructural images were introduced in detail. The two modelling methods largely increase the availability of various microstructural images. The new model provides accurate results which present the size effects well.

  8. Characterization of single crystalline ZnTe and ZnSe grown by vapor phase transport

    Energy Technology Data Exchange (ETDEWEB)

    Trigubo, A B; Di Stefano, M C [FRBA-UTN, (1179) Buenos Aires (Argentina); Aguirre, M H [Dpto de Quim Inorg, Fac de Cs Quim, Univ Complutense, (28040) Madrid (Spain); Martinez, A M; D' Elia, R; Canepa, H; Heredia, E, E-mail: atrigubo@citefa.gov.a [CINSO-CITEFA: (1603) Villa Martelli, Pcia de Buenos Aires (Argentina)

    2009-05-01

    Tubular furnaces were designed and built to obtain single crystalline ZnTe and ZnSe ingots using respectively physical and chemical transport methods. Different temperature profiles and growth rates were analyzed in order to optimize the necessary crystalline quality for device development. Optical and scanning electron micrographs of the corrosion figures produced by chemical etching were used to obtain the dislocation density and the misorientation between adjacent subgrains in ZnTe and ZnSe wafers. Structural quality of the single crystalline material was determined by transmission electronic microscopy. Optical transmittance was measured by infrared transmission spectrometry and the resulting values were compared to commercial samples.

  9. Metastable Phases of Dross Particles Formed in a Molten Zinc Bath and Prediction of Soluble Aluminum During Galvannealing Processes

    Science.gov (United States)

    Paik, Doo-Jin; Hong, Moon-Hi; Huh, Yoon; Park, Joo Hyun; Chae, Hong-Kook; Park, Seok-Ho; Choun, Si-Youl

    2012-06-01

    The morphology, chemistry, and crystallographic characteristics of metastable dross particles were identified. These particles are formed during the initial stage of precipitation. The particles had aluminum concentrations of 15 to 80 mass pct, with values that decreased gradually as particle size increased. These metastable dross particles were a mixture of the crystalline phase of FeZn10, which is called the "delta phase," and the high-aluminum amorphous phase, which covered the surface of the crystalline phase. The new "meta Q" concept was proposed to predict the amount of soluble aluminum in the zinc bath by considering nucleation kinetics and particle growth. The results calculated using the "meta Q" concept were compared with the values measured by the aluminum sensor, which were taken during the same period at the commercial galvanizing line. The mean of the absolute values of the differences between the calculated and measured values was 9.7 ppm.

  10. Dielectrophoretic manipulation and solubility of protein nanofibrils formed from crude crystallins

    DEFF Research Database (Denmark)

    Domigan, Laura; Andersen, Karsten B.; Sasso, Luigi

    2013-01-01

    Protein nanofibrils and nanotubes are now widely accepted as having potential for use in the field of bionanotechnology. For this to be a feasible alternative to existing technologies, there is a need for a commercially viable source. Previous work has identified amyloid fibrils formed from crude...

  11. Ore-forming fluid constraints on illite crystallinity (IC) at Dexing porphyry copper deposit, Jiangxi Province

    Institute of Scientific and Technical Information of China (English)

    JIN; Zhangdong

    2001-01-01

    [1]uatier, M. D., Peacor, D. R., O’Neil, J. R., Smectite-illite transition in Barbados accretionary wedge sediments: TEM and AEM evidence for dissolution/crystallization at low temperature, Clays and Clay Minerals, 1992, 40(1): 65.[2]Eberl, D., Hower, J., Kinetics of illite formation, Geological Society of America Bulletin, 1976, 9: 1326[3]Elliott, W. C., Matisoff, G., Evaluation of kinetic models for smectite to illite transformation, Clays and Clay Minerals, 1996, 44(1): 77.[4]Ji Junfeng, Browne, P. R. L., Liu Yingjun et al., Kinetic model for the smectite to illite transformation in active geothermal system, Chinese Science Bulletin (in Chinese), 1997, 42 (21): 2313[5]Pollastro, R. M., Considerations and applications of the illite/smectite geothermometer in hydrocarbonbearing rocks of Miocene to Mississippian age, Clays and Clay Minerals, 1993, 41(1): 119[6]Harvey, C. C., Browne, P. R. L., Mixed-layer clay geothermometry in the Wairakei geothermal field, New Zealand, Clays and Clay Minerals, 1991, 39(3): 614[7]Whitney, G., Role of water in the smectite-to-illite reaction, Clays and Clay Minerals, 1990, 38 (2): 343.[8]Inoue, A., Kitagawa, R., Morphological characteristics of illitic clay minerals from a hydrothermal system, American Mineralogist, 1994, 79: 700.[9]Velde, B., Vasseur, G., Estimation of the diagenetic smectite to illite in time-temperature space, American Mineralogist, 1992, 77: 967.[10]hu Xun, Huang Chongke, Rui Zongyao et al., Dexing Porphyry Copper Deposit (in Chinese), Beijing: Geological Publishing House, 1983.[11]Kisch, H. J., Illite crystallinity: recommendation on sample preparation, X-ray diffraction settings and interlaboratory samples, Journal of Metamorphic Geology, 1991, 9: 665.[12]Eberl, D. D., Velde, B., Beyond the Kübler Index, Clay Minerals, 1989, 24(3): 571.[13]Srodon, J., Eberl, D. D., Illite. Micas, Reviews in Mineralogy (ed. Bailey, S. W.), 1984, 13: 495.[14]Yao, Y. C

  12. Phase Retrieval Algorithm for Form Testing Metrology in Production Environment

    Directory of Open Access Journals (Sweden)

    Stephan Stuerwald

    2010-08-01

    Full Text Available Form testing interferometry permits a fast, non-tactile and full- field quantitative phase imaging of components in ultra precise manufacturing. To reduce the influence of vibrations under manufacturing conditions, it is most common to use the FT- based spatial carrier phase measurement technique (SCPM which requires only a single interferogram recording. The utilization of a generalized, relatively new spatial phase-shifting method operating in the position space opens up prospects for reduced phase noise and less reconstruction errors of the calculated phase-map under production conditions. Therefore this phase-shifting technique is investigated for applicability in machine integrated interferometric form testing of optical lenses. A characterization of the algorithm and a comparison with the commonly used FT-based algorithm is performed. As a reference, measurements are carried out with a coordinate measuring machine with nanometre accuracy.

  13. Melt processed crystalline ceramic waste forms for advanced nuclear fuel cycles: CRP T21027 1813: Processing technologies for high level waste, formulation of matrices and characterization of waste forms, Task 17208: Final report

    Energy Technology Data Exchange (ETDEWEB)

    Amoroso, J. W. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Marra, J. C. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-08-26

    A multi-phase ceramic waste form is being developed at the Savannah River National Laboratory (SRNL) for treatment of secondary waste streams generated by reprocessing commercial spent nuclear. The envisioned waste stream contains a mixture of transition, alkali, alkaline earth, and lanthanide metals. Ceramic waste forms are tailored (engineered) to incorporate waste components as part of their crystal structure based on knowledge from naturally found minerals containing radioactive and non-radioactive species similar to the radionuclides of concern in wastes from fuel reprocessing. The ability to tailor ceramics to mimic naturally occurring crystals substantiates the long term stability of such crystals (ceramics) over geologic timescales of interest for nuclear waste immobilization [1]. A durable multi-phase ceramic waste form tailored to incorporate all the waste components has the potential to broaden the available disposal options and thus minimize the storage and disposal costs associated with aqueous reprocessing. This report summarizes results from three years of work on the IAEA Coordinated Research Project on “Processing technologies for high level waste, formulation of matrices and characterization of waste forms” (T21027), and specific task “Melt Processed Crystalline Ceramic Waste Forms for Advanced Nuclear Fuel Cycles” (17208).

  14. Melt processed crystalline ceramic waste forms for advanced nuclear fuel cycles: CRP T21027 1813: Processing technologies for high level waste, formulation of matrices and characterization of waste forms, task 17208: Final report

    Energy Technology Data Exchange (ETDEWEB)

    Amoroso, J. W. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Marra, J. C. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-08-26

    A multi-phase ceramic waste form is being developed at the Savannah River National Laboratory (SRNL) for treatment of secondary waste streams generated by reprocessing commercial spent nuclear. The envisioned waste stream contains a mixture of transition, alkali, alkaline earth, and lanthanide metals. Ceramic waste forms are tailored (engineered) to incorporate waste components as part of their crystal structure based on knowledge from naturally found minerals containing radioactive and non-radioactive species similar to the radionuclides of concern in wastes from fuel reprocessing. The ability to tailor ceramics to mimic naturally occurring crystals substantiates the long term stability of such crystals (ceramics) over geologic timescales of interest for nuclear waste immobilization [1]. A durable multi-phase ceramic waste form tailored to incorporate all the waste components has the potential to broaden the available disposal options and thus minimize the storage and disposal costs associated with aqueous reprocessing. This report summarizes results from three years of work on the IAEA Coordinated Research Project on “Processing technologies for high level waste, formulation of matrices and characterization of waste forms” (T21027), and specific task “Melt Processed Crystalline Ceramic Waste Forms for Advanced Nuclear Fuel Cycles” (17208).

  15. Ultrasonic study of the shear mechanical impedance of butyloxybenzylidene octylaniline near the crystalline-B-smectic-A phase transition

    OpenAIRE

    Thiriet, Y.; Martinoty, P.

    1982-01-01

    We report a detailed study of the shear mechanical impedance near the crystalline-B-smectic-A transition in butyloxybenzylidene octylaniline (40.8). The measurements were performed at various frequencies from 5 to 85 MHz for shear waves propagating along the normal to the layers. In both phases the material response presents strong relaxation effects. The structure change at the transition is indicated by an increase in the real part of the shear impedance. The results at 85 MHz are those exp...

  16. The surface quasiliquid melt acceleration and the role of thermodynamic phase in the thermal decomposition of crystalline organic explosives

    Energy Technology Data Exchange (ETDEWEB)

    Henson, Bryan F [Los Alamos National Laboratory

    2010-01-01

    We show that melt acceleration in the thermal decomposition of crystalline organic solids is a manifestation of the surface quasiliquid phase. We derive a single universal rate law for melt acceleration that is a simple function of the metastable liquid activity below the melting point, and has a zero order term proportional to the quasiliquid thickness. We argue that the underlying mechanisms of this model will provide a molecular definition for the stability of the class of secondary explosives.

  17. A METHOD OF PREPARING SPHERICAL NANO-CRYSTAL CELLULOSE WITH MIXED CRYSTALLINE FORMS OF CELLULOSE Ⅰ AND Ⅱ

    Institute of Scientific and Technical Information of China (English)

    Xiao-fang Li; En-yong Ding; Guo-kang Li

    2001-01-01

    A new kind of nano-crystal cellulose (NCC) prepared from natural cotton fiber has been obtained by the method of acid hydrolysis. Compared to most other nanophase materials that derive from inorganic materials, our products are prepared from natural cotton fibers. The products are of spherical shape with mixed crystal forms of cellulose Ⅰ and Ⅱ. The preparation conditions determine the properties of the products. Prior treatment is a critical procedure. The properties of the products are also strongly affected by such conditions as the kinds of acids used, the ratio of the acid mixture, the acid concentration, the ultrasonic agitation time and hydrolysis temperature. The number average molecular weight of NCC is determined by gel permeation chromatography (GPC). The particle size and shape were determined by transmission electron microscopy (TEM). X-ray diffraction was used to detect the crystallinity and average crystallite size of the particle.

  18. Predicting primary crystalline phase and liquidus temperature above or below 1050{degrees}C as functions of glass composition

    Energy Technology Data Exchange (ETDEWEB)

    Redgate, P.E.; Piepel, G.F.

    1996-02-01

    This report presents the results of applying statistical empirical modeling techniques to primary crystalline phase at the liquidus temperature (T{sub L}) and (ii) whether liquidus temperature is above or below 1050{degree}C (1OO{degree}C below a melting temperature of 1150{degree}C). Data used in modeling primary crystalline phase and liquidus temperate are from the Composition Variability Study (CVS) of Hanford waste glass compositions and properties. The majority of the 123 CVS glasses are categorized into one of 13 primary crystalline phases (at the liquidus temperature). They are also classified as to having T{sub L} Above or Below 1050{degree}C. Two common statistical methods used to model such categorical data are the multinomial logit and classification tree models. The classification tree models provided an overall better modeling approach than did the multinomial logit models. The performance of models in this report should be compared to the performance of the revised ``Development of Models and Software for Liquidus Temperature of Glasses of HWVP Products`` models from Ecole Polytechnique. If the Ecole Polytechnique models perform better than the models discussed in this report, no additional effort on these models would be needed. However, if the converse is true, it may be worthwhile to invest additional effort on statistical empirical modeling methods.

  19. Selecting polymers for two-phase partitioning bioreactors (TPPBs): Consideration of thermodynamic affinity, crystallinity, and glass transition temperature.

    Science.gov (United States)

    Bacon, Stuart L; Peterson, Eric C; Daugulis, Andrew J; Parent, J Scott

    2015-01-01

    Two-phase partitioning bioreactor technology involves the use of a secondary immiscible phase to lower the concentration of cytotoxic solutes in the fermentation broth to subinhibitory levels. Although polymeric absorbents have attracted recent interest due to their low cost and biocompatibility, material selection requires the consideration of properties beyond those of small molecule absorbents (i.e., immiscible organic solvents). These include a polymer's (1) thermodynamic affinity for the target compound, (2) degree of crystallinity (wc ), and (3) glass transition temperature (Tg ). We have examined the capability of three thermodynamic models to predict the partition coefficient (PC) for n-butyric acid, a fermentation product, in 15 polymers. Whereas PC predictions for amorphous materials had an average absolute deviation (AAD) of ≥16%, predictions for semicrystalline polymers were less accurate (AAD ≥ 30%). Prediction errors were associated with uncertainties in determining the degree of crystallinity within a polymer and the effect of absorbed water on n-butyric acid partitioning. Further complications were found to arise for semicrystalline polymers, wherein strongly interacting solutes increased the polymer's absorptive capacity by actually dissolving the crystalline fraction. Finally, we determined that diffusion limitations may occur for polymers operating near their Tg , and that the Tg can be reduced by plasticization by water and/or solute. This study has demonstrated the impact of basic material properties that affects the performance of polymers as sequestering phases in TPPBs, and reflects the additional complexity of polymers that must be taken into account in material selection.

  20. The influence of heat treatment on the semi-crystalline structure of polyaniline Emeraldine-salt form

    Science.gov (United States)

    de Oliveira, Lilian R.; Manzato, Lizandro; Mascarenhas, Yvonne P.; Sanches, Edgar A.

    2017-01-01

    Polyaniline emeraldine-salt form (PANI-ES) was chemically synthesized using hydrochloric acid and subjected to heat treatment for 1 h at 50, 100, 200 and 300 °C. X-ray Diffraction (XRD), Le Bail method structural refinement, Infrared-transform Fourier Spectroscopy (FTIR), Small-angle X-ray Scattering (SAXS), Scanning Electron Microscopy (SEM) and Electrical Conductivity measurements were used to evaluate the influence of heat treatment on the semi-crystalline structure of PANI. The heat treatment has resulted in a progressive decrease of crystallinity from 50 to 22%. A crosslinking process during heat treatment was observed by FTIR at 200 °C, revealing some chemical changes in molecular structure of PANI such as elimination of HCl on the imino groups and the simultaneous chlorination of the aromatic rings. Le Bail method showed that crystal structure of the unheated ES-PANI is strongly dependent on the molecular size of the counter ion, so the unit cell volume needed to be increased for their accommodation in the polymer structure. The refined parameters suggested a decomposition from tetrameric to dimeric-folded chains, accompanied by a decrease in the crystallite anisotropy and average size and shape, which reduced from 36 Å to 16 Å and acquired oblate shape. The pair-distance distribution function (p(r)) curves suggested particles tending from oblate to prolate form over heat treatment. Well-defined nanofibers were observed in unheated ES-PANI, which decreased and lost progressively their initial morphology over heat treatment. Electrical conductivity showed a decreasing of about 90% due to the loss of emeraldine sequences and removal of chloride ions.

  1. Effect of trans-cis photoisomerization on phase equilibria and phase transition of liquid-crystalline azobenzene chromophore and its blends with reactive mesogenic diacrylate.

    Science.gov (United States)

    Kim, Namil; Li, Quan; Kyu, Thein

    2011-03-01

    Photoisomerization-induced phase transition of neat liquid-crystalline azobenzene chromophore (LCAC) and its effect on phase diagrams of its mixtures with reactive mesogenic diacrylate monomer (RM257) have been investigated experimentally and theoretically. Upon irradiation with ultraviolet light, the nematic phase of LCAC transformed to isotropic, while the crystal phase showed corrugated textures on the surface (i.e., ripples). The phase-transition temperatures and corresponding morphologies of the blends have been investigated by means of differential scanning calorimetry and optical microscopy. A theoretical phase diagram of a binary nematic and crystalline system was constructed by self-consistently solving the combined free energies of Flory-Huggins, Maier-Saupe, and phase-field theory. The calculation revealed various coexistence regions such as nematic + liquid (N₁ + L₂), crystal + liquid (Cr₁ + L₂), crystal + nematic (Cr₁ + N₂), and crystal + crystal (Cr₁ + Cr₂) over a broad range of compositions including the single-phase nematic (N₁, N₂) of the corresponding constituents. The calculated liquidus lines were in good accord with the depressed mesophase-isotropic transition points. The present paper demonstrates the effect of trans-cis photoisomerization on the mesophase transitions of neat LCAC and the phase diagram of LCAC-RM257 as well as on the ripple formation (i.e., periodic undulation) on the azobenzene crystals.

  2. Short-Range Order of Mesomorphic Phase of a Semi-crystalline Polymer by Solid-State NMR: Isotactic Polypropylene

    Science.gov (United States)

    Yuan, Shichen; Miyoshi, Toshikazu

    2015-03-01

    Mesophase is intermediate phase between crystalline and melt state. Characterization of short-range structures of disordered mesomorphic phase without long-range order is challenging issue in polymer characterization. The short range order was considered same as α or β i PP, or neither. In this work, a new strategy using 13C-13C through space interactions as well as molecular dynamics based on chemical shift anisotropy (CSA) re-orientation is proposed for evaluating short-range order of mesophase of isotactic-polypropylene (iPP). 13C-13C double quantum (DQ) build up curves of 13C 15 percent CH3 selectively labeled iPP and spin dynamics simulations elucidate that local packing structures in mesophase is very close to that in β phase. Moreover, exchange NMR proves that the crystalline chains perform large amplitude motions in all α, β, and mesophase. The correlation time of overall dynamics of stems in mesophase follows the same Arrhenius line with that of β phase but is largely deviated from the Arrhenius line of the α phase. Through the obtained results, it is concluded that short-range order in mesophase is exceedingly close or same to those in β phase. This work was financially supported by the National Science Foundation (Grant No. DMR-1105829) and by UA startup funds.

  3. The influence of dipalmitoyl phosphatidylserine on phase behaviour of and cellular response to lyotropic liquid crystalline dispersions.

    Science.gov (United States)

    Shen, Hsin-Hui; Crowston, Jonathan G; Huber, Florian; Saubern, Simon; McLean, Keith M; Hartley, Patrick G

    2010-12-01

    Lyotropic liquid crystalline nanoparticles (cubosomes) have the potential to act as amphiphilic scaffolds for the presentation of lipids and subsequent application in, for example, bioseparations and therapeutic delivery. In this work we have formulated lyotropic liquid crystalline systems based on the synthetic amphiphile 1,2,3-trihydroxy-3,7,11,15-tetramethylhexadecane (phytantriol) and containing the lipid dipalmitoyl phosphatidylserine (DPPS). We have prepared a range of DPPS-containing phytantriol cubosome formulations and characterized them using Small Angle X-ray Scattering and Cryo-transmission electron microscopy. These techniques show that increased DPPS content induces marked changes in lyotropic liquid crystalline phase behaviour, characterized by changes in crystallographic dimensions and increases in vesicle content. Furthermore, in vitro cell culture studies indicate that these changes correlate with lipid/surfactant cellular uptake and cytotoxicity. A model cell membrane based on a surface supported phospholipid bilayer was used to gain insights into cubosome-bilayer interactions using Quartz Crystal Microgravimetry. The data show that mass uptake at the supported bilayer increased with DPPS content. We propose that the cytotoxicity of the DPPS-containing dispersions results from changes in lipid/surfactant phase behaviour and the preferential attachment and fusion of vesicles at the cell membrane.

  4. Efficient and Stable Ternary Organic Solar Cells Based on Two Planar Nonfullerene Acceptors with Tunable Crystallinity and Phase Miscibility.

    Science.gov (United States)

    Wang, Jialin; Peng, Jiajun; Liu, Xiaoyu; Liang, Ziqi

    2017-06-21

    Planar perylene diimides (PDIs), when used as nonfullerene acceptors for organic photovoltaics, are constrained by their large π-aggregation in solid state. To tackle this issue, another planar nonfullerene acceptor 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone)-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']dithiophene (ITIC) with weak crystallinity and near-infrared light absorption is introduced into the PTB7-Th:PDI binary blend to fabricate efficient and stable ternary solar cells. We have finely tuned the PDI/ITIC weight ratio to investigate the influences of individual ITIC and PDI on the optical, electronic, and morphological properties of the PTB7-Th:ITIC:PDI ternary blend. Compared to the binary blend, complementary optical absorption is achieved in all ternary blends. More importantly, it is found that ITIC plays a critical role on largely suppressing the PDI aggregates in the PTB7-Th:PDI blend, while PDI aids to form an interpenetrating network morphology to facilitate charge transport in the PTB7-Th:ITIC blend. Consequently, when the PDI/ITIC ratio is 3:7 (w/w), the PTB7-Th:ITIC:PDI based inverted solar cells exhibit the highest power conversion efficiency of 8.64% due to their favorable out-of-plane π-π stacking, finest phase-separation morphology, and highest charge mobility. Remarkably, the optimal cells that are solution-processed in air show the promising efficiency of 7.09%, suggesting good ambient stability of such ternary solar cells.

  5. Influence of growth parameters on the surface morphology and crystallinity of InSb epilayers grown by liquid phase epitaxy

    Indian Academy of Sciences (India)

    N K Udayashankar; H L Bhat

    2003-12-01

    Unintentionally doped homoepitaxial InSb films have been grown by liquid phase epitaxy employing ramp cooling and step cooling growth modes. The effect of growth temperature, degree of supercooling and growth duration on the surface morphology and crystallinity were investigated. The major surface features of the grown film like terracing, inclusions, meniscus lines, etc are presented step-by-step and a variety of methods devised to overcome such undesirable features are described in sufficient detail. The optimization of growth parameters have led to the growth of smooth and continuous films. From the detailed morphological, X-ray diffraction, scanning electron microscopic and Raman studies, a correlation between the surface morphology and crystallinity has been established.

  6. The fabrication of quantum wires in silicon utilising the characteristics of solid phase epitaxial regrowth of crystalline silicon

    Energy Technology Data Exchange (ETDEWEB)

    Liu, A.C.Y.; McCallum, J.C. [Melbourne Univ. Parkville, VIC (Australia). School of Physics, Microanalytical Research Centre

    1998-06-01

    The process of solid phase epitaxy (SPE) in semiconductor materials is one which has been intensively researched due to possible applications in the semiconductor industry. SPE is a solid phase transformation, in which an amorphous layer can be recrystallized either through heating or a combination of heating and ion bombardment. The transformation is believed to occur exclusively at the interface between the amorphous and crystalline layers, with individual atoms from the amorphous phase being incorporated into the crystalline phase by some point defect mechanism. The process has been observed to follow an Arrhenius temperature dependence. A wafer silicon was subjected to a multi-energy silicon implant through a fine nickel grid to amorphise region to a depth of 5{mu}m creating an array of amorphous wells. Metal impurity atoms were then implanted in this region at energy of 500 keV. Samples were examined using an optical microscope and the Alphastep profiler at RMIT. It was confirmed that burgeoning wells were about 2 {mu}m wide and rose about 0.01 {mu}m above the silicon substrate. Extended abstract. 4 refs., 3 figs.

  7. Studies of phase transitions in the aripiprazole solid dosage form.

    Science.gov (United States)

    Łaszcz, Marta; Witkowska, Anna

    2016-01-05

    Studies of the phase transitions in an active substance contained in a solid dosage form are very complicated but essential, especially if an active substance is classified as a BCS Class IV drug. The purpose of this work was the development of sensitive methods for the detection of the phase transitions in the aripiprazole tablets containing initially its form III. Aripiprazole exhibits polymorphism and pseudopolymorphism. Powder diffraction, Raman spectroscopy and differential scanning calorimetry methods were developed for the detection of the polymorphic transition between forms III and I as well as the phase transition of form III into aripiprazole monohydrate in tablets. The study involved the initial 10 mg and 30 mg tablets, as well as those stored in Al/Al blisters, a triplex blister pack and HDPE bottles (with and without desiccant) under accelerated and long term conditions. The polymorphic transition was not observed in the initial and stored tablets but it was visible on the DSC curve of the Abilify(®) 10 mg reference tablets. The formation of the monohydrate was observed in the diffractograms and Raman spectra in the tablets stored under accelerated conditions. The monohydrate phase was not detected in the tablets stored in the Al/Al blisters under long term conditions. The results showed that the Al/Al blisters can be recommended as the packaging of the aripiprazole tablets containing form III.

  8. Mechanisms of zinc incorporation in aluminosilicate crystalline structures and the leaching behaviour of product phases.

    Science.gov (United States)

    Tang, Yuanyuan; Shih, Kaimin

    2015-01-01

    This study quantitatively evaluates a waste-to-resource strategy of blending zinc-laden sludge and clay material for low-cost ceramic products. Using ZnO as the simulated zinc-laden sludge to sinter with kaolinite, both zinc aluminate spinel (ZnAl₂O₄) and willemite (Zn₂SiO₄) phases were formed during the sintering process. To analyse the details of zinc incorporation reactions, γ-Al₂O₃and quartz were further used as precursors to observe ZnAl₂O₄and Zn₂SiO₄formations. By firing the ZnO mixtures and their corresponding precursors at 750-1350°C for 3 h, the efficiency of zinc transformation was determined through Rietveld refinement analyses of X-ray diffraction data. The results also show different incorporation behaviour for kaolinite and mullite precursors during the formation of ZnAl2O₄and Zn2SiO₄in the system. In addition, with a competitive formation between ZnAl₂O₄and Zn₂SiO₄, the ZnAl₂O₄spinel phase is predominant at temperatures higher than 1050°C. This study used a prolonged leaching test modified from the US Environmental Protection Agency's toxicity characteristic leaching procedure to evaluate ZnO, ZnAl₂O₄, and Zn₂SiO₄product phases. The zinc concentrations in ZnO and Zn₂SiO₄leachates were about two orders of magnitude higher than that of ZnAl₂O₄ leachate at the end of the experiment, indicating that ZnAl₂O₄formation is the preferred stabilization mechanism for incorporating zinc in ceramic products.

  9. Phase behaviour of macromolecular liquid crystalline materials. Computational studies at the molecular level

    CERN Document Server

    Stimson, L M

    2003-01-01

    Molecular simulations provide an increasingly useful insight into the static and dynamic characteristics of materials. In this thesis molecular simulations of macro-molecular liquid crystalline materials are reported. The first liquid crystalline material that has been investigated is a side chain liquid crystal polymer (SCLCP). In this study semi-atomistic molecular dynamics simulations have been conducted at a range of temperatures and an aligning potential has been applied to mimic the effect of a magnetic field. In cooling the SCLCP from an isotropic melt, microphase separation was observed yielding a domain structure. The application of a magnetic field to this structure aligns the domains producing a stable smectic mesophase. This is the first study in which mesophases have been observed using an off-lattice model of a SCLCP. The second material that has been investigated is a dendrimer with terminal mesogenic functionalization. Here, a multi-scale approach has been taken with Monte Carlo studies of a s...

  10. Rheology of the lamellar liquid-crystalline phase in polyethoxylated alcohol/water/heptane systems.

    Directory of Open Access Journals (Sweden)

    Gallegos, C.

    2005-06-01

    Full Text Available Linear viscoelastic tests as well as transient and steady flow experiments were carried out on lamellar liquid crystalline samples of poly (oxyethylene alcohol/water/heptane systems. The effect of surfactant and heptane concentrations on the rheological properties of the lamellar mesophase was investigated. The mechanical spectrum inside the linear viscoelastic regime shows, in all cases, a well-developed plateau region in the whole frequency range studied. The values of the dynamic functions were higher for intermediate surfactant or heptane concentrations indicative of a major development of the elastic network in the midrange of existence of the lamellar phase. Transient and steady flow experiments point out a shear-induced evolution of the lamellar microstructure. Different power law regions with different values of the flow index were detected in the viscosity versus shear rate plots. These shear-induced structural modifications were confirmed by using polarizing microscopy in an optical shearing cell. Structural modifications appear to be highly influenced by shear rate. In general, applying relatively high constant shear rates, the alignment of the bilayers followed by the appearance of the “oily streaks” structure was observed. Appearance of shear-induced vesicles occurs at high heptane content, as indicates the texture of close-packed monodisperse spherulites detected by polarizing microscopy.n este trabajo se han estudiado las propiedades reológicas de una fase líquido-cristalina laminar contenida en un sistema alcohol polietoxilado/agua/heptano, mediante ensayos viscoelásticos lineales, estacionarios y transitorios. El efecto de distintas variables como la composición de tensioactivo y heptano sobre dichas propiedades reológicas ha sido analizado. El espectro mecánico obtenido de la fase laminar muestra en todos los casos una región “plateau” en el intervalo de frecuencias estudiado así como mayores valores

  11. Mechano-chemical spinodal decomposition: A phenomenological theory of phase transformations in multi-component, crystalline solids

    CERN Document Server

    Rudraraju, Shiva; Garikipati, Krishna

    2015-01-01

    We present a new phenomenological treatment of phase transformations in multi-component crystalline solids driven by free energy density functions that are non-convex in mechanical and chemical variables. We identify the mechano-chemical spinodal as the region in strain-composition space where the free energy density function is non-convex. Our treatment describes diffusional phase transformations that are accompanied by symmetry breaking structural changes of the crystal unit cell due to mechanical instabilities in the mechano-chemical spinodal. This approach is relevant to phase transformations wherein the structural order parameters can be expressed as linear combinations of strains relative to a high-symmetry reference crystal. Because the local strains in an inhomogeneous, transforming microstructure can be finite, the elasticity problem must account for geometric nonlinearity. Furthermore, for physical consistency and mathematical well-posedness, we regularize the free energy density functions by interf...

  12. Effect of co-solutes and process variables on crystallinity and the crystal form of freeze-dried myo-inositol.

    Science.gov (United States)

    Izutsu, Ken-Ichi; Kusano, Riho; Arai, Ryoko; Yoshida, Hiroyuki; Ito, Masataka; Shibata, Hiroko; Sugano, Kiyohiko; Goda, Yukihiro; Terada, Katsuhide

    2016-07-25

    The purpose of this study was to elucidate how co-solutes affect the crystallization of small solute molecules during freeze-drying and subsequent storage. Crystallization profiles of myo-inositol and its mixture with dextran 40k in frozen solutions and dried solids were assessed by thermal analysis (DSC), powder-X-ray diffraction, and simultaneous DSC and PXRD analysis. Higher mass ratios of dextran maintained myo-inositol in the non-crystalline mixture state, in frozen solutions, during freeze-drying process, and exposure of dried solids to higher temperatures. Co-lyophilization with a lower mass ratio of dextran resulted in solids containing a variety of myo-inositol crystal forms and crystallinity depending on the composition and thermal history of the process. Heating of some inositol-rich amorphous solids showed crystallization of myo-inositol in the metastable form and its transition to stable form before melting. Heat-treatment of inositol-rich frozen solutions resulted in high crystallinity stable-form inositol solids, leaving dextran in the amorphous state. Sufficient direct molecular interactions (e.g., hydrogen bonding) should explain the stability of dextran-rich amorphous solids. Optimizing solute composition and processes should be a potent way to control crystal form and crystallinity of components in freeze-dried formulations.

  13. Single-Crystalline Silicon Solar Cell with Selective Emitter Formed by Screen Printing and Chemical Etching Method: A Feasibility Study

    Directory of Open Access Journals (Sweden)

    Yen-Po Chen

    2013-01-01

    Full Text Available A new method for fabricating crystalline silicon solar cells with selective emitters is presented. In this method, shallow trenches corresponding to metal contact area are first formed by screen printing and chemical etching, followed by heavy doping over the whole front surface of the silicon wafer. After a polymer mask is pasted by aligned screen-printing to cover the shallow trenches, the silicon wafer is etched such that the heavy doping remains at the shallow trench area, while other areas become lightly doped. With the presented method, two screening printing steps are required for obtaining a selective emitter structure on a solar wafer. Compared with existing etch-back methods, the presented one is believed to be able to easily conform with present industrial process. Experimental results show that optical responses at the short and long wavelengths were both improved by applying the proposed selective emitter technique to fabricate solar cells with an a-Si:H film deposited on the back surface. The selective emitter cell with a-Si:H back surface deposition had improvements of 1.66 mA/cm2 and 1.23% absolute in Jsc and conversion efficiency, respectively, compared to the reference cell that had a homogeneous emitter and no a-Si:H on the back surface.

  14. Gibbs free-energy difference between the glass and crystalline phases of a Ni-Zr alloy

    Science.gov (United States)

    Ohsaka, K.; Trinh, E. H.; Holzer, J. C.; Johnson, W. L.

    1993-01-01

    The heats of eutectic melting and devitrification, and the specific heats of the crystalline, glass, and liquid phases have been measured for a Ni24Zr76 alloy. The data are used to calculate the Gibbs free-energy difference, Delta G(AC), between the real glass and the crystal on an assumption that the liquid-glass transition is second order. The result shows that Delta G(AC) continuously increases as the temperature decreases in contrast to the ideal glass case where Delta G(AC) is assumed to be independent of temperature.

  15. Formation of liquid-crystalline structures in the bile salt-chitosan system and triggered release from lamellar phase bile salt-chitosan capsules.

    Science.gov (United States)

    Tangso, Kristian J; Lindberg, Seth; Hartley, Patrick G; Knott, Robert; Spicer, Patrick; Boyd, Ben J

    2014-08-13

    Nanostructured capsules comprised of the anionic bile salt, sodium taurodeoxycholate (STDC), and the biocompatible cationic polymer, chitosan, were prepared to assess their potential as novel tailored release nanomaterials. For comparison, a previously studied system, sodium dodecyl sulfate (SDS), and polydiallyldimethylammonium chloride (polyDADMAC) was also investigated. Crossed-polarizing light microscopy (CPLM) and small-angle X-ray scattering (SAXS) identified the presence of lamellar and hexagonal phase at the surfactant-polymer interface of the respective systems. The hydrophobic and electrostatic interactions between the oppositely charged components were studied by varying temperature and salt concentration, respectively, and were found to influence the liquid-crystalline nanostructure formed. The hexagonal phase persisted at high temperatures, however the lamellar phase structure was lost above ca. 45 °C. Both mesophases were found to dissociate upon addition of 4% NaCl solution. The rate of release of the model hydrophilic drug, Rhodamine B (RhB), from the lamellar phase significantly increased in response to changes in the solution conditions studied, suggesting that modulating the drug release from these bile salt-chitosan capsules is readily achieved. In contrast, release from the hexagonal phase capsules had no appreciable response to the stimuli applied. These findings provide a platform for these oppositely charged surfactant and polymer systems to function as stimuli-responsive or sustained-release drug delivery systems.

  16. Highly efficient molecular simulation methods for evaluation of thermodynamic properties of crystalline phases

    Science.gov (United States)

    Moustafa, Sabry Gad Al-Hak Mohammad

    Molecular simulation (MS) methods (e.g. Monte Carlo (MC) and molecular dynamics (MD)) provide a reliable tool (especially at extreme conditions) to measure solid properties. However, measuring them accurately and efficiently (smallest uncertainty for a given time) using MS can be a big challenge especially with ab initio-type models. In addition, comparing with experimental results through extrapolating properties from finite size to the thermodynamic limit can be a critical obstacle. We first estimate the free energy (FE) of crystalline system of simple discontinuous potential, hard-spheres (HS), at its melting condition. Several approaches are explored to determine the most efficient route. The comparison study shows a considerable improvement in efficiency over the standard MS methods that are known for solid phases. In addition, we were able to accurately extrapolate to the thermodynamic limit using relatively small system sizes. Although the method is applied to HS model, it is readily extended to more complex hard-body potentials, such as hard tetrahedra. The harmonic approximation of the potential energy surface is usually an accurate model (especially at low temperature and large density) to describe many realistic solid phases. In addition, since the analysis is done numerically the method is relatively cheap. Here, we apply lattice dynamics (LD) techniques to get the FE of clathrate hydrates structures. Rigid-bonds model is assumed to describe water molecules; this, however, requires additional orientation degree-of-freedom in order to specify each molecule. However, we were able to efficiently avoid using those degrees of freedom through a mathematical transformation that only uses the atomic coordinates of water molecules. In addition, the proton-disorder nature of hydrate water networks adds extra complexity to the problem, especially when extrapolating to the thermodynamic limit is needed. The finite-size effects of the proton disorder contribution is

  17. Effective surface passivation of p-type crystalline silicon with silicon oxides formed by light-induced anodisation

    Energy Technology Data Exchange (ETDEWEB)

    Cui, Jie, E-mail: j.cui@unsw.edu.au [School of Photovoltaic and Renewable Energy Engineering, The University of New South Wales, Sydney 2052 (Australia); Grant, Nicholas [Centre for Sustainable Energy Systems, Australian National University, Canberra, A.C.T. 0200 (Australia); Lennon, Alison [School of Photovoltaic and Renewable Energy Engineering, The University of New South Wales, Sydney 2052 (Australia)

    2014-12-30

    Highlights: • The surface passivation by anodic SiO{sub 2} formed by light-induced anodisation is investigated. • The anodic SiO{sub 2} grows lower temperatures with shorter growth times. After annealing in oxygen and then forming gas the effective minority carrier lifetime is increased to 150 μs. • It shows a very low positive Q{sub eff} of 3.4 × 10{sup 11} cm{sup −2}, a moderate D{sub it} of 6 × 10{sup 11} eV{sup −1} cm{sup −2}. • It has a very low leakage current density suggesting its application in solar cell as a functional dielectric. - Abstract: Electronic surface passivation of p-type crystalline silicon by anodic silicon dioxide (SiO{sub 2}) was investigated. The anodic SiO{sub 2} was grown by light-induced anodisation (LIA) in diluted sulphuric acid at room temperature, a process that is significantly less-expensive than thermal oxidation which is widely-used in silicon solar cell fabrication. After annealing in oxygen and then forming gas at 400 °C for 30 min, the effective minority carrier lifetime of 3–5 Ω cm, boron-doped Czochralski silicon wafers with a phosphorus-doped 80 Ω/□ emitter and a LIA anodic SiO{sub 2} formed on the p-type surface was increased by two orders of magnitude to 150 μs. Capacitance–voltage measurements demonstrated a very low positive charge density of 3.4 × 10{sup 11} cm{sup −2} and a moderate density of interface states of 6 × 10{sup 11} eV{sup −1} cm{sup −2}. This corresponded to a silicon surface recombination velocity of 62 cm s{sup −1}, which is comparable with values reported for other anodic SiO{sub 2} films, which required higher temperatures and longer growth times, and significantly lower than oxides grown by chemical vapour deposition techniques. Additionally, a very low leakage current density of 3.5 × 10{sup −10} and 1.6 × 10{sup −9} A cm{sup −2} at 1 and −1 V, respectively, was measured for LIA SiO{sub 2} suggesting its potential application as insulation layer in

  18. Amorphous-crystalline dual-layer structures resulting from metastable liquid phase separation in (Fe50Co25B15Si10)8oCu20 melt-spun ribbons

    Institute of Scientific and Technical Information of China (English)

    Cao Chong-De; Gong Su-Lian; Guo Jin-Bo; Song Rui-Bo; Sun Zhan-Bo; Yang Sen; Wang Wei-Min

    2012-01-01

    (Fe50Co25B15Si10)80Cu20 ribbons are prepared by using the single-roller melt-spinning method.A dual-layer structure consisting of a (Fe,Co)-rich amorphous phase and a Cu-rich crystalline phase forms due to metastable liquid phase separation before solidification.The magnetic hysteresis loops of the as-quenched and annealed samples are measured at room temperature.It is indicated that the coercivity of the ribbon is almost zero in the as-quenched state.The crystallization leads to the increase of coercivity and decrease of saturation magnetization.

  19. Identifying the crystallinity, phase, and arsenic uptake of the nanomineral schwertmannite using analytical high resolution transmission electron microscopy

    Science.gov (United States)

    French, R. A.; Kim, B.; Murayama, M.; Hochella, M. F.

    2010-12-01

    Schwertmannite, an iron oxyhydroxide sulfate nanomineral, plays a significant role in the geochemistry of acid mine drainage (AMD) as a metastable phase with respect to goethite and by retaining toxic metals, e.g. arsenic [1]. Schwertmannite’s characteristic morphology is needles 100-300 nm long and only 5-10 nm in diameter extending from a dense aggregate. The poorly-and nano-crystalline nature of this mineral requires using high resolution electron microscopy (HRTEM) to be fully characterized. We used HRTEM to identify the polyphasic nature of natural samples of schwertmannite collected from the Iberian Pyrite Belt in Spain. In order to analyze the dense core, samples were prepared in thin section using an ultramicrotome. Data on a sample identified as pure schwertmannite through powder XRD shows the presence of 5-10 nm goethite nanocrystals making up a significant portion of one of the nanoneedle tips (Figure 1). These nanocrystals exhibit lattice fringes and faceted surfaces, both of which match that expected for goethite. The great majority of the nanoneedles are poorly-crystalline (no lattice fringes) with atomically rough surfaces which may be highly active in the uptake of As. The presence of a range of phases and crystallinities in this sample demonstrate incipient stages of the mechanism that results in transformation of schwertmannite to goethite. Further analytical TEM analyses will help us track sorption/desorption, as well as the specific locations of As within these materials upon initial formation, as well as during transformation. [1] Acero et al. (2006) GCA 70, 4130-4139. Figure 1. HRTEM image of 'schwertmannite' nanoneedle with FFT data (inset).

  20. Fast Atomic-Scale Chemical Imaging of Crystalline Materials and Dynamic Phase Transformations.

    Science.gov (United States)

    Lu, Ping; Yuan, Ren Liang; Ihlefeld, Jon F; Spoerke, Erik David; Pan, Wei; Zuo, Jian Min

    2016-04-13

    Atomic-scale phenomena fundamentally influence materials form and function that makes the ability to locally probe and study these processes critical to advancing our understanding and development of materials. Atomic-scale chemical imaging by scanning transmission electron microscopy (STEM) using energy-dispersive X-ray spectroscopy (EDS) is a powerful approach to investigate solid crystal structures. Inefficient X-ray emission and collection, however, require long acquisition times (typically hundreds of seconds), making the technique incompatible with electron-beam sensitive materials and study of dynamic material phenomena. Here we describe an atomic-scale STEM-EDS chemical imaging technique that decreases the acquisition time to as little as one second, a reduction of more than 100 times. We demonstrate this new approach using LaAlO3 single crystal and study dynamic phase transformation in beam-sensitive Li[Li0.2Ni0.2Mn0.6]O2 (LNMO) lithium ion battery cathode material. By capturing a series of time-lapsed chemical maps, we show for the first time clear atomic-scale evidence of preferred Ni-mobility in LNMO transformation, revealing new kinetic mechanisms. These examples highlight the potential of this approach toward temporal, atomic-scale mapping of crystal structure and chemistry for investigating dynamic material phenomena.

  1. Gas Phase Hydration of Methyl Glyoxal to Form the Gemdiol

    Science.gov (United States)

    Kroll, Jay A.; Axson, Jessica L.; Vaida, Veronica

    2016-06-01

    Methylglyoxal is a known oxidation product of volatile organic compounds (VOCs) in Earth's atmosphere. While the gas phase chemistry of methylglyoxal is fairly well understood, its modeled concentration and role in the formation of secondary organic aerosol (SOA) continues to be controversial. The gas phase hydration of methylglyoxal to form a gemdiol has not been widely considered for water-restricted environments such as the atmosphere. However, this process may have important consequences for the atmospheric processing of VOCs. We will report on spectroscopic work done in the Vaida laboratory studying the hydration of methylglyoxal and discuss the implications for understanding the atmospheric processing and fate of methylglyoxal and similar molecules.

  2. Vapor-phase hydrothermal transformation of HTiOF3 intermediates into {001} faceted anatase single-crystalline nanosheets.

    Science.gov (United States)

    Liu, Porun; Wang, Yun; Zhang, Haimin; An, Taicheng; Yang, Huagui; Tang, Zhiyong; Cai, Weiping; Zhao, Huijun

    2012-12-07

    For the first time, a facile, one-pot hydrofluoric acid vapor-phase hydrothermal (HF-VPH) method is demonstrated to directly grow single-crystalline anatase TiO(2) nanosheets with 98.2% of exposed {001} faceted surfaces on the Ti substrate via a distinctive two-stage formation mechanism. The first stage produces a new intermediate crystal (orthorhombic HTiOF(3) ) that is transformed into anatase TiO(2) nanosheets during the second stage. The findings reveal that the HF-VPH reaction environment is unique and differs remarkably from that of liquid-phase hydrothermal processes. The uniqueness of the HF-VPH conditions can be readily used to effectively control the nanostructure growth.

  3. Combined toxicity of two crystalline phases (anatase and rutile) of Titania nanoparticles towards freshwater microalgae: Chlorella sp

    Energy Technology Data Exchange (ETDEWEB)

    Iswarya, V.; Bhuvaneshwari, M.; Alex, Sruthi Ann; Iyer, Siddharth; Chaudhuri, Gouri [Centre for Nanobiotechnology, VIT University, Vellore (India); Chandrasekaran, Prathna Thanjavur [Department of Materials Engineering, Indian Institute of Science, Bangalore (India); Bhalerao, Gopalkrishna M.; Chakravarty, Sujoy [UGC-DAE CSR, Kalpakkam Node, Kokilamedu (India); Raichur, Ashok M. [Department of Materials Engineering, Indian Institute of Science, Bangalore (India); Chandrasekaran, N. [Centre for Nanobiotechnology, VIT University, Vellore (India); Mukherjee, Amitava, E-mail: amit.mookerjea@gmail.com [Centre for Nanobiotechnology, VIT University, Vellore (India)

    2015-04-15

    Highlights: • Toxicity of two crystalline phases of titania NPs on freshwater microalgae studied. • (Anatase, Rutile) mixture showed additive and antagonistic effect on microalgae. • Rutile had more colloidal stability than anatase and binary mixtures. • ROS generation varied with the crystallinity of the NPs. • Ultrastructural damages observed in TEM images. - Abstract: In view of the increasing usage of anatase and rutile crystalline phases of titania NPs in the consumer products, their entry into the aquatic environment may pose a serious risk to the ecosystem. In the present study, the possible toxic impact of anatase and rutile nanoparticles (individually and in binary mixture) was investigated using freshwater microalgae, Chlorella sp. at low exposure concentrations (0.25, 0.5 and 1 mg/L) in freshwater medium under UV irradiation. Reduction of cell viability as well as a reduction in chlorophyll content were observed due to the presence of NPs. An antagonistic effect was noted at certain concentrations of binary mixture such as (0.25, 0.25), (0.25, 0.5), and (0.5, 0.5) mg/L, and an additive effect for the other combinations, (0.25, 1), (0.5, 0.25), (0.5, 1), (1, 0.25), (1, 0.5), and (1, 1) mg/L. The hydrodynamic size analyses in the test medium revealed that rutile NPs were more stable in lake water than the anatase and binary mixtures [at 6 h, the sizes of anatase (1 mg/L), rutile NPs (1 mg/L), and binary mixture (1, 1 mg/L) were 948.83 ± 35.01 nm, 555.74 ± 19.93 nm, and 1620.24 ± 237.87 nm, respectively]. The generation of oxidative stress was found to be strongly dependent on the crystallinity of the nanoparticles. The transmission electron microscopic images revealed damages in the nucleus and cell membrane of algal cells due to the interaction of anatase NPs, whereas rutile NPs were found to cause chloroplast and internal organelle damages. Mis-shaped chloroplasts, lack of nucleus, and starch-pyrenoid complex were noted in binary

  4. [Influence of mutant genes on crystallin synthesis in the forming mouse lens. II. Fidget and ocular retardation genes].

    Science.gov (United States)

    Iakovlev, M I; Platonov, E S; Koniukhov, B V

    1977-01-01

    The beginning of synthesis and the localization of alpha- and gamma-crystallins in the developing lenses of the 10-13 and 15 days old mouse embryos of the genotypes fi/fi +/+, +/+ or/or, fi/fi or/or and +/+ +/+ were studied by means of indirect immunofluorescence. The synthesis of crystallins in the mutant embryos with the exception of the embryo +/+ or/or was shown to begin somewhat later than in the normal ones but to proceed in all defective lenses, irrespective of the degree of defect. Hence, the activation of the genes controlling the synthesis of alpha-crystallins begins at the early stages of lens development and the synthesis of these proteins proceeds even during the abnormal with the slowing down of the formation of primary lens fibers. In the cases of strong defects of morphogenesis in the fi/fi +/+ and, especially, fi/fi or/or, embryos gamma-crystallins were not detected. The synthesis of gamma-crystallins appears to begin at the final stages of lens fiber differentiation.

  5. Stereodynamic control of star-epoxy/anhydride crosslinking actuated by liquid-crystalline phase transitions.

    Science.gov (United States)

    Pin, Jean-Mathieu; Mija, Alice; Sbirrazzuoli, Nicolas

    2017-02-07

    The epoxy/anhydride copolymerization kinetics of an original star-epoxy monomer (TriaEP) was explored in dynamic heating mode using a series of isoconversional methods. Negative values of the apparent activation energy (Eα) related to an anti-Arrhenius behavior were observed. The transition from Arrhenius to anti-Arrhenius behavior and vice versa depending on the Eα of polymerization was correlated with the dynamics of mesophasic fall-in/fall-out events, physically induced transition (PIT) and chemically induced transition (CIT). This self-assembly phenomenon induces the generation of an anisotropic crosslinked architecture exhibiting both nematic discotic (ND) and nematic columnar (NC) organization. Particular emphasis was placed on evaluating the juxtaposition/contribution of the liquid-crystalline transitions to crosslinking, considering both the reaction dynamics and the macromolecular vision.

  6. Chemistry in a Forming Protoplanetary Disk: Main Accretion Phase

    Science.gov (United States)

    Yoneda, Haruaki; Tsukamoto, Yusuke; Furuya, Kenji; Aikawa, Yuri

    2016-12-01

    We investigate the chemistry in a radiation-hydrodynamics model of a star-forming core that evolves from a cold (˜10 K) prestellar core to the main accretion phase in ˜105 years. A rotationally supported gravitationally unstable disk is formed around a protostar. We extract the temporal variation of physical parameters in ˜1.5 × 103 SPH particles that end up in the disk, and perform post-processing calculations of the gas-grain chemistry adopting a three-phase model. Inside the disk, the SPH particles migrate both inward and outward. Since a significant fraction of volatiles such as CO can be trapped in the water-dominant ice in the three-phase model, the ice mantle composition depends not only on the current position in the disk, but also on whether the dust grain has ever experienced higher temperatures than the water sublimation temperature. Stable molecules such as H2O, CH4, NH3, and CH3OH are already abundant at the onset of gravitational collapse and are simply sublimated as the fluid parcels migrate inside the water snow line. On the other hand, various molecules such as carbon chains and complex organic molecules (COMs) are formed in the disk. The COMs abundance sensitively depends on the outcomes of photodissociation and diffusion rates of photofragments in bulk ice mantle. As for S-bearing species, H2S ice is abundant in the collapse phase. In the warm regions in the disk, H2S is sublimated to be destroyed, while SO, H2CS, OCS, and SO2 become abundant.

  7. [Preparation and evaluation of press-coated aminophylline tablet using crystalline cellulose and polyethylene glycol in the outer shell for timed-release dosage forms].

    Science.gov (United States)

    Watanabe, Yoshiteru; Mukai, Baku; Kawamura, Ken-ichi; Ishikawa, Tatsuya; Namiki, Michihiro; Utoguchi, Naoki; Fujii, Makiko

    2002-02-01

    In an attempt to achieve chronopharmacotherapy for asthma, press-coated tablets (250 mg), which contained aminophylline in the core tablet in the form of low-substituted hydroxypropylcellulose (L-HPC) and coated with crystalline cellulose (PH-102) and polyethylene glycol (PEG) at various molecular weights and mixing ratios in the amounts of PH-102 and PEG as the outer shell (press-coating material), were prepared (chronopharmaceutics). Their applicability as timed-release (delayed-release) tablets with a lag time of disintegration and a subsequent rapid drug release phase was investigated. Various types of press-coated tablets were prepared using a tableting machine, and their aminophylline dissolution profiles were evaluated by the JP paddle method. Tablets with the timed-release characteristics could be prepared, and the lag time of disintegration was prolonged as the molecular weight and the amount of PEG, for example PEG 500,000, in the outer shell were increased. The lag time of disintegration could be controlled by the above-mentioned method, however, the pH of the medium had no effect on disintegration of the tablet and dissolution behavior of theophylline. The press-coated tablet (core tablet:aminophylline 50 mg, L-HPC and PEG 6000; outer shell:PH-102:PEG = 8:2 200 mg) with the timed-release characteristics was administered orally to rabbits for an in vivo test. Theophylline was first detected in plasma more than 2 h after administration; thus, this tablet showed a timed-release characteristics in the gastrointestinal tract. The time (tmax) required to reach the maximum plasma theophylline concentration (Cmax) observed after administration of the press-coated tablet was significantly (p 24) between the press-coated tablet and aminophylline solution. These results suggest that the press-coated aminophylline tablet (with the timed-release characteristic) offers a promising forms of theophylline chronotherapy for asthma.

  8. Chemistry in a forming protoplanetary disk: main accretion phase

    CERN Document Server

    Yoneda, Haruaki; Furuya, Kenji; Aikawa, Yuri

    2016-01-01

    We investigate the chemistry in a radiation-hydrodynamics model of star-forming core which evolves from a cold ($\\sim 10$ K) prestellar core to the main accretion phase in $\\sim 10^5$ yr. A rotationally-supported gravitationally unstable disk is formed around a protostar. We extract the temporal variation of physical parameters in $\\sim 1.5 \\times 10^3$ SPH particles which end up in the disk, and perform post-processing calculations of the gas-grain chemistry adopting a three-phase model. Inside the disk, the SPH particles migrate both inward and outward. Since a significant fraction of volatiles such as CO can be trapped in the water-dominant ice in the three-phase model, the ice mantle composition depends not only on the current position in the disk but also on whether the dust grain has ever experienced higher temperatures than the water sublimation temperature. Stable molecules such as H$_2$O, CH$_4$, NH$_3$ and CH$_3$OH are already abundant at the onset of gravitational collapse and simply sublimated as ...

  9. Structural mechanisms of the Ih–II and II → Ic transitions between the crystalline phases of aqueous ice

    Energy Technology Data Exchange (ETDEWEB)

    Zheligovskaya, E. A., E-mail: lmm@phyche.ac.ru [Russian Academy of Sciences, Frumkin Institute of Physical Chemistry and Electrochemistry (Russian Federation)

    2015-09-15

    Structural mechanisms are proposed for experimentally observed phase transitions between crystalline modifications of aqueous ice, Ih and II, as well as II and Ic. It is known that the Ih–II transition occurs with the conservation of large structural units (hexagonal channels) common for these ices. It is shown that the Ih → II transition may occur with the conservation of 5/6 of all hydrogen bonds in crystal, including all hydrogen bonds in the retained channels (3/4 of the total number of bonds in crystal) and 1/3 of the bonds between these channels (1/12 of the total number). The transformation of other hydrogen bonds between the retained channels leads to the occurrence of proton order in ice II. A structural mechanism is proposed to explain the transformation of single crystals of ice Ih either into single crystals of ice II or into crystalline twins of ice II with c axes rotated by 180° with respect to each other, which is often observed at the Ih → II transition. It is established that up to 7/12 of all hydrogen bonds are retained at the irreversible cooperative II → Ic transition.

  10. Effect of fabrication technique on the crystalline phase and electrical properties of PVDF films

    Directory of Open Access Journals (Sweden)

    Mahato P. K.

    2015-03-01

    Full Text Available The effect of different fabrication techniques on the formation of electroactive β-phase polyvinylidene fluoride (PVDF has been investigated. Films with varying concentration of PVDF and solvent - dimethyl formamide (DMF were synthesized by tape casting and solvent casting techniques. The piezoelectric β-phase as well as non polar β-phase were observed for both the tape cast and solvent cast films from X-ray diffraction (XRD micrographs and Fourier transform infra-red spectroscopy (FT-IR spectra. A maximum percentage (80 % of β-phase was obtained from FT-IR analysis for a solvent cast PVDF film. The surface morphology of the PVDF films was analyzed by FESEM imaging. The dielectric properties as a function of temperature and frequency and the ferroelectric hysteresis loop as a function of voltage were measured. An enhancement in the value of the dielectric constant and polarization was obtained in solvent cast films.

  11. Atomic-level simulations of nanoindentation-induced phase transformation in mono-crystalline silicon

    Science.gov (United States)

    Lin, Yen-Hung; Chen, Tei-Chen; Yang, Ping-Feng; Jian, Sheng-Rui; Lai, Yi-Shao

    2007-12-01

    Molecular dynamics (MD) simulations of nanoindentation are carried out to investigate the phase transformations in Si with a spherical indenter. Since the phase transformation induced by deformation in micro-scale is closely related to the carrier mobility of the material, it has become a key issue to be investigated for the chips especially with smaller feature size. Up to now, however, it is not possible to carry out the nanoindentation experimentally in such a small feature. Consequently, molecular dynamic simulation on nanoindentation is resorted to and becomes a powerful tool to understand the detailed mechanisms of stress-induced phase transformation in nano-scale. In this study, the inter-atomic interaction of Si atoms is modeled by Tersoff's potential, while the interaction between Si atoms and diamond indenter atoms is modeled by Morse potential. It is found that the diamond cubic structure of Si in the indentation zone transforms into a phase with body-centred tetragonal structure (β-Si) just underneath the indenter during loading stage and then changes to amorphous after unloading. By using the technique of coordinate number the results reveal that indentation on the (0 0 1) surface exhibits significant phase transformation along the direction. In addition, indentation on the (1 1 0) surface shows more significant internal slipping and spreading of phase transformation than on the (0 0 1) surface. Furthermore, during the indentation process phase transformations of Si are somewhat reversible. Parts of transformed phases that are distributed over the region of elastic deformation can be gradually recovered to original mono-crystal structure after unloading.

  12. Role of the crystalline form of titanium dioxide nanoparticles: Rutile, and not anatase, induces toxic effects in Balb/3T3 mouse fibroblasts.

    Science.gov (United States)

    Uboldi, Chiara; Urbán, Patricia; Gilliland, Douglas; Bajak, Edyta; Valsami-Jones, Eugenia; Ponti, Jessica; Rossi, François

    2016-03-01

    The wide use of titanium dioxide nanoparticles (TiO2 NPs) in industrial applications requires the investigation of their effects on human health. In this context, we investigated the effects of nanosized and bulk titania in two different crystalline forms (anatase and rutile) in vitro. By colony forming efficiency assay, a dose-dependent reduction of the clonogenic activity of Balb/3T3 mouse fibroblasts was detected in the presence of rutile, but not in the case of anatase NPs. Similarly, the cell transformation assay and the micronucleus test showed that rutile TiO2 NPs were able to induce type-III foci formation in Balb/3T3 cells and appeared to be slightly genotoxic, whereas anatase TiO2 NPs did not induce any significant neoplastic or genotoxic effect. Additionally, we investigated the interaction of TiO2 NPs with Balb/3T3 cells and quantified the in vitro uptake of titania using mass spectrometry. Results showed that the internalization was independent of the crystalline form of TiO2 NPs but size-dependent, as nano-titania were taken up more than their respective bulk materials. In conclusion, we demonstrated that the cytotoxic, neoplastic and genotoxic effects triggered in Balb/3T3 cells by TiO2 NPs depend on the crystalline form of the nanomaterial, whereas the internalization is regulated by the particle size.

  13. A 4F2-cross-point phase change memory using nano-crystalline doped GeSbTe material

    Science.gov (United States)

    Takaura, Norikatsu; Kinoshita, Masaharu; Tai, Mitsuharu; Ohyanagi, Takasumi; Akita, Kenichi; Morikawa, Takahiro

    2015-04-01

    This paper reports on the use of nano-crystalline doped GeSbTe, or nano-GST, to fabricate a cross-point phase change memory with 4F2 cell size and test results obtained for it. We show the characteristics of a poly-Si diode select device with a high on-off ratio and data writing in a 4F2 memory cell array. The advantages of nano-GST over conventional GeSbTe are presented in terms of neighboring disturbance and 4F2 cross-point array formation. The memory cells’ high drivability, low power, and selective write and read performances are demonstrated. The scalability of the diode current density is also presented.

  14. Cataract-associated P23T γD-crystallin retains a native-like fold in amorphous-looking aggregates formed at physiological pH

    Science.gov (United States)

    Boatz, Jennifer C.; Whitley, Matthew J.; Li, Mingyue; Gronenborn, Angela M.; van der Wel, Patrick C. A.

    2017-05-01

    Cataracts cause vision loss through the large-scale aggregation of eye lens proteins as a result of ageing or congenital mutations. The development of new treatments is hindered by uncertainty about the nature of the aggregates and their mechanism of formation. We describe the structure and morphology of aggregates formed by the P23T human γD-crystallin mutant associated with congenital cataracts. At physiological pH, the protein forms aggregates that look amorphous and disordered by electron microscopy, reminiscent of the reported formation of amorphous deposits by other crystallin mutants. Surprisingly, solid-state NMR reveals that these amorphous deposits have a high degree of structural homogeneity at the atomic level and that the aggregated protein retains a native-like conformation, with no evidence for large-scale misfolding. Non-physiological destabilizing conditions used in many in vitro aggregation studies are shown to yield qualitatively different, highly misfolded amyloid-like fibrils.

  15. An advanced regime of the anomalous acousto-optical interaction with tangential phase matching in crystalline materials

    Science.gov (United States)

    Shcherbakov, Alexandre S.; Arellanes, Adan O.

    2016-09-01

    Regime of effective non-collinear acousto-optical interaction with tangential phase matching had been identified and previously observed only in two limiting cases: in tellurium dioxide (TeO2) at low acoustic frequencies ( 60 MHz) and in rutile (TiO2) at ultra-high frequencies ( 5 GHz). Both these limits are motivated by optical properties of the chosen materials. Low frequencies in TeO2 admit designing a wide-aperture acousto-optical cell, but limit the frequency bandwidth. While an acousto-optical cell made of TiO2 has very small aperture and exhibits low spectral resolution due to the effect of linear acoustic attenuation. Instead of those limits, we propose an advanced regime of the anomalous acousto-optical interaction with tangential phase matching, which allows us varying the frequency range and optimizing all the performances (for instance, the spectral resolution) of a wide-aperture acousto-optical cell made of the chosen crystal, as the case requires. Recently, we had suggested and successfully tested experimentally the revealed additional degree of freedom, i.e. the action of the tilt angle within the refractive indices ellipsoids to manipulate by the performances of crystalline acousto-optical cells. Now, we consider an opportunity of refining this additional degree of freedom within those ellipsoids of crystalline acousto-optical cell through some declination of the acoustic beam. For our investigations, the lithium niobate (LiNbO3) and rutile (TiO2) crystals of about 5 cm length, operating with the slow-shear acoustic mode along the acoustic axes had been selected. The needed theoretical analysis, numerical estimations, and 3D-vector diagrams have been developed to reveal potential benefits of the proposed technique.

  16. Study of crystalline morphology and phase structure in poly(styrene-b-ethylene oxide-b-styrene) triblock copolymers bu solid state RMN spin diffusion

    Energy Technology Data Exchange (ETDEWEB)

    Mantovani, Gerson L., E-mail: gerson.mantovani@ufabc.edu.b [Universidade Federal do ABC (UFABC), Santo Andre, SP (Brazil). Centro de Engenharia, Modelagem e Ciencias Sociais Aplicadas; Bonk, Fabio A. [Universidade Estadual de Campinas (IQ/UNICAMP) SP (Brazil). Inst. de Quimica; Caldarelli, Stefano Caldarelli [Aix-Marseille Universite ISm2, Site de Saint Jerome, Marseille (France); Phan, Trang; Bertin, Denis [Universite de Provence, Site de Saint Jerome, Marseille (France); Azevedo, Eduardo R. de; Bonagamba, Tito J. [Universidade de Sao Paulo (IF/USP), Sao Carlos, SP (Brazil). Inst. de Fisica

    2009-07-01

    The phase structure and crystalline morphology of a series of polystyrene-b-polyethylene oxide-b-polystyrene (PS-b- PEO-b-PS) triblock copolymers, with different compositions and molecular weights, has been studied by solid-state NMR. WAXS and DSC measurements were used to detect the presence of crystalline domains of polyethylene oxide (PEO) blocks at room temperature as a function of the copolymer composition. {sup 1}H NMR spin diffusion analyses provided an estimation of the size of the dispersed phases of the nano structured copolymers. (author)

  17. Collective stringlike motion of semiflexible filamentous particles in columnar liquid crystalline phases

    NARCIS (Netherlands)

    Naderi, S.; van der Schoot, P. P. A. M.

    2013-01-01

    We study, by means of Brownian dynamics simulations, heterogeneous dynamics in a dense columnar phase of monodisperse hard filamentous particles, and find that in a background of barely moving particles, some particles occasionally engage in a fast coherent string-type motion similar to what is

  18. 不同晶型BiVO_4微球的制备及其对光催化性能的影响%Synthesis and photocatalytic activities of BiVO_4 microspheres with different crystalline forms

    Institute of Scientific and Technical Information of China (English)

    朱振峰; 杜娟; 李军奇; 张艳丽; 刘佃光; 于红光

    2011-01-01

    以Bi(NO3)3、NH4VO3为原料,NaOH为pH调节剂,采用微波水热法在180℃制备了BiVO4微球,分析了不同煅烧温度对晶型、形貌的影响,并进一步探讨了BiVO4晶型与其光催化性能的关系。采用XRD、SEM和UV-Vis吸收光谱对产品进行了分析表征,并以光催化降解亚甲基蓝为模型反应研究BiVO4的光催化性能。结果表明所制备的BiVO4微球是四方相结构,球的直径在1~3μm之间,将其在500℃煅烧后发生晶型转变,600℃煅烧可得到纯单斜相BiVO4微球,且具有良好的可见光催化活性。而且,不同晶型的BiVO4影响亚甲基蓝的降解效果。%Bismuth vanadate(BiVO4) microspheres were prepared with Bi(NO3)3 and NH4VO3 as starting materials and with NaOH to adjust pH through the microwave hydrothermal method at 180℃.The effect of different calcination temperatures on the crystalline phase and morphology was investigated,and the relationship between crystalline phase of BiVO4 and its photocatalytic performance was further studied.The as-prepared BiVO4 samples were characterized by XRD,SEM and UV-Vis.The photocatalytic activity of the BiVO4 microspheres was determined by degradation of methylene blue molecules under visible light irradiation.The results indicated that the crystalline phase of as-prepared BiVO4 microspheres was tetragonal phase,and the diameter of microspheres was 1-3μm.It is found that the phase transition had undergone after being calcined at 500℃,and monoclinic scheelite BiVO4 microspheres obtained by being calcined at 600℃ had the excellent visible-light photocatalysis.Besides,BiVO4 with different crystalline forms can affect the degradation of methylene blue molecules.

  19. Encapsulation of CO2 into amorphous and crystalline α-cyclodextrin powders and the characterization of the complexes formed.

    Science.gov (United States)

    Ho, Thao M; Howes, Tony; Bhandari, Bhesh R

    2015-11-15

    Carbon dioxide complexation was undertaken into solid matrices of amorphous and crystalline α-cyclodextrin (α-CD) powders, under various pressures (0.4-1.6 MPa) and time periods (4-96 h). The results show that the encapsulation capacity of crystalline α-CD was significantly lower than that of amorphous α-CD at low pressure and short time (0.4-0.8 MPa and 4-24 h), but was markedly enhanced with an increase of pressure and prolongation of encapsulation time. For each pressure level tested, the time required to reach a near equilibrium encapsulation capacity of the crystalline powder was around 48 h, which was much longer than that of the amorphous one, which only required about 8h. The inclusion complex formation of both types of α-CD powders was confirmed by the appearance of a CO2 peak on the FTIR and NMR spectra. Moreover, inclusion complexes were also characterized by DSC, TGA, SEM and X-ray analyses.

  20. Polymorphism: characterization and study of the properties of a crystalline phase

    Directory of Open Access Journals (Sweden)

    Gilson da Silva

    2010-09-01

    Full Text Available Despite the same chemical composition, the physicochemical properties of polymorphs can be totally different, such as leading or not electricity. The legality of recognize them as completely new products is discussed, in front of the characteristics that a polymorph may have over another. The fact is that the differential solubility and stability and formation of active sites in different phases of a substance engage the interest of many active sectors of the economy. There are no few polymorphic energetic materials, or their precursors, which also have therapeutic applications. Therefore, some of the techniques developed by the lucrative pharmaceutical industry to study the polymorphism can be tailored to the needs of the war industry. This paper presents energetic and pharmacological materials recognized for their polymorphism and discuss properties, characterization techniques and the study of phase transition in these materials.

  1. Cooperative effect of electrospinning and nanoclay on formation of polar crystalline phases in poly(vinylidene fluoride).

    Science.gov (United States)

    Liu, Yi-Liao; Li, Ying; Xu, Jun-Ting; Fan, Zhi-Qiang

    2010-06-01

    Poly(vinylidene difluoride)/organically modified montmorillonite (PVDF/OMMT) composite nanofibers were prepared by electrospinning the solution of PVDF/OMMT precursor in DMF. Wide-angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM) show that in the bulk of the PVDF/OMMT precursor OMMT platelets are homogeneously dispersed in PVDF and can be both intercalated and exfoliated. It is found that the diameter of the PVDF/OMMT composite nanofibers is smaller than that of the neat PVDF fibers because the lower viscosity of PVDF/OMMT solution, which is attributed to the possible adsorption of PVDF chains on OMMT layers and thus reduction in number of entanglement. The crystal structure of the composite nanofibers was investigated using WAXD and Fourier transform infrared (FT-IR) and compared with that of thin film samples. The results show that the nonpolar alpha phase is completely absent in the electrospun PVDF/OMMT composite nanofibers, whereas it is still present in the neat PVDF electrospun fibers and in the thin films of PVDF/OMMT nanocomposites. The cooperative effect between electrospinning and nanoclay on formation of polar beta and gamma crystalline phases in PVDF is discussed. The IR result reveals that electrospinning induces formation of long trans conformation, whereas OMMT platelets can retard relaxation of PVDF chains and stabilize such conformation due to the possible interaction between the PVDF chains and OMMT layers. This cooperative effect leads to extinction of nonpolar alpha phase and enhances the polar beta and gamma phases in the electrospun PVDF/OMMT composite nanofibers.

  2. Phospholipid barrier to fibrinolysis: role for the anionic polar head charge and the gel phase crystalline structure.

    Science.gov (United States)

    Váradi, Balázs; Kolev, Krasimir; Tenekedjiev, Kiril; Mészáros, Gyöngyi; Kovalszky, Ilona; Longstaff, Colin; Machovich, Raymund

    2004-09-17

    The massive presence of phospholipids is demonstrated in frozen sections of human arterial thrombi. Purified platelet phospholipids and synthetic phospholipids retard in vitro tissue-type plasminogen activator (tPA)-induced fibrinolysis through effects on plasminogen activation and plasmin function. The inhibition of plasminogen activation on the surface of fibrin correlates with the fraction of anionic phospholipid. The phospholipids decrease the amount of tPA penetrating into the clot by 75% and the depth of the reactive surface layer occupied by the activator by up to 30%, whereas for plasmin both of these parameters decrease by approximately 50%. The phospholipids are not only a diffusion barrier, they also bind the components of the fibrinolytic system. Isothermal titration calorimetry shows binding characterized with dissociation constants in the range 0.35-7.64 microm for plasmin and tPA (lower values with more negative phospholipids). The interactions are endothermic and thermodynamically driven by an increase in entropy, probably caused by the rearrangements in the ordered gel structure of the phospholipids (in line with the stronger inhibition at gel phase temperatures compared with liquid crystalline phase temperatures). These findings show a phospholipid barrier, which should be overcome during lysis of arterial thrombi.

  3. Detachment of CVD-grown graphene from single crystalline Ni films by a pure gas phase reaction

    Science.gov (United States)

    Zeller, Patrick; Henß, Ann-Kathrin; Weinl, Michael; Diehl, Leo; Keefer, Daniel; Lippmann, Judith; Schulz, Anne; Kraus, Jürgen; Schreck, Matthias; Wintterlin, Joost

    2016-11-01

    Despite great previous efforts there is still a high need for a simple, clean, and upscalable method for detaching epitaxial graphene from the metal support on which it was grown. We present a method based on a pure gas phase reaction that is free of solvents and polymer supports and avoids mechanical transfer steps. The graphene was grown on 150 nm thick, single crystalline Ni(111) films on Si(111) wafers with YSZ buffer layers. Its quality was monitored by using low energy electron diffraction and scanning tunneling microscopy. The gas phase etching uses a chemical transport reaction, the so-called Mond process, based on the formation of gaseous nickel tetracarbonyl in ~ 1 bar of CO at ~ 75 °C and by adding small amounts of sulfide catalysts. X-ray photoelectron spectroscopy, Raman spectroscopy and scanning electron microscopy were used to characterize the detached graphene. It was found that the method successfully removes the nickel from underneath the graphene layer, so that the graphene lies on the insulating oxide buffer layer. Small residual particles of nickel sulfide and cracks in the obtained graphene layer were identified. The defect concentrations were comparable to graphene samples obtained by wet chemical etching and by the bubbling transfer.

  4. A Phase Field Technique for Modeling and Predicting Flow Induced Crystallization Morphology of Semi-Crystalline Polymers

    Directory of Open Access Journals (Sweden)

    Xiaodong Wang

    2016-06-01

    Full Text Available Flow induced crystallization of semi-crystalline polymers is an important issue in polymer science and engineering because the changes in morphology strongly affect the properties of polymer materials. In this study, a phase field technique considering polymer characteristics was established for modeling and predicting the resulting morphologies. The considered crystallization process can be divided into two stages, which are nucleation upon the flow induced structures and subsequent crystal growth after the cessation of flow. Accordingly, the proposed technique consists of two parts which are a flow induced nucleation model based on the calculated information of molecular orientation and stretch, and a phase field crystal growth model upon the oriented nuclei. Two-dimensional simulations are carried out to predict the crystallization morphology of isotactic polystyrene under an injection molding process. The results of these simulations demonstrate that flow affects crystallization morphology mainly by producing oriented nuclei. Specifically, the typical skin-core structures along the thickness direction can be successfully predicted. More importantly, the results reveal that flow plays a dominant part in generating oriented crystal morphologies compared to other parameters, such as anisotropy strength, crystallization temperature, and physical noise.

  5. High Energy Rate Forming Induced Phase Transition in Austenitic Steel

    Science.gov (United States)

    Kovacs, T.; Kuzsella, L.

    2017-02-01

    In this study, the effects of explosion hardening on the microstructure and the hardness of austenitic stainless steel have been studied. The optimum explosion hardening technology of austenitic stainless steel was researched. In case of the explosive hardening used new idea means indirect hardening setup. Austenitic stainless steels have high plasticity and can be cold formed easily. However, during cold processing the hardening phenomena always occurs. Upon the explosion impact, the deformation mechanism indicates a plastic deformation and this deformation induces a phase transformation (martensite). The explosion hardening enhances the mechanical properties of the material, includes the wear resistance and hardness [1]. In case of indirect hardening as function of the setup parameters specifically the flayer plate position the hardening increased differently. It was find a relationship between the explosion hardening setup and the hardening level.

  6. Effects of initial layers on surface roughness and crystallinity of microcrystalline silicon thin films formed by remote electron cyclotron resonance silane plasma

    CERN Document Server

    Murata, K; Hori, Masaki; Goto, T; Ito, M

    2002-01-01

    We have observed mu c-Si:H films grown in the glass substrate in electron cyclotron resonance plasma-enhanced chemical vapor deposition employing two-step growth (TSG) method, where the seed layer was formed without charged species firstly, and subsequently, the film with charged species. The mu c-Si:H films with smooth surface and high crystallinity were synthesized with a relatively high deposition rate at a low substrate temperature by TSG. By Fourier transform infrared attenuated-total reflection, it was found that the surface roughness and crystallinity of seed layer were related to the ratio of SiH bonds over SiH sub 2 ones in the film. Consequently, the control of chemical bonds at the initial layer is of importance and TSG method is effective for the formation of mu c-Si:H film with high quality.

  7. Oxidation of Alumina-Forming MAX Phases in Turbine Environments

    Science.gov (United States)

    Smialek, James; Garg, Anita; Harder, Bryan; Nesbitt, James; Gabb, Timothy; Gray, SImon

    2017-01-01

    Protective coatings for high temperature turbine components are based on YSZ thermal barriers and oxidation resistant, alumina-forming NiAl or NiCoCrAlY bond coats. Ti2AlC and Cr2AlC MAX phases are thus of special interest because of good oxidation resistance and CTE that can match Al2O3 and YSZ. Their alumina scales grow according to cubic kinetics due to grain growth in the scale, with initial heating dominated by fast TiO2 growth. Protective cubic kinetics are also found in high pressure burner rig tests of MAXthal 211 Ti2AlC, but with reduced rates due to volatile TiO(OH)2 formation in water vapor. YSZ-coatings on bulk Ti2AlC exhibit remarkable durability up to 1300C in furnace tests and at least a 25x life advantage compared to superalloys. At another extreme, Cr2AlC is resistant to low temperature Na2SO4 hot corrosion and exhibits thermal cycling stability bonded to a superalloy disk material. Accordingly, sputtered Cr2AlC coatings on disk specimens prevented hot corrosion detriments on LCF. Breakaway oxidation (Ti2AlC), scale spallation (Cr2AlC), interdiffusion, and processing as coatings still present serious challenges. However the basic properties of MAX phases provide some unusual opportunities for use in high temperature turbines.

  8. Synthesis of TiO2 visible light catalysts with controllable crystalline phase and morphology from Ti-bearing electric arc furnace molten slag.

    Science.gov (United States)

    Li, Yang; Liu, Lulu; Guo, Min; Zhang, Mei

    2016-09-01

    TiO2 visible light catalysts with different crystalline phases and morphologies were synthesized from titanium-bearing electric arc furnace molten slag (Ti-bearing EAF slag) by using a simple acidolysis process. The effects of the pH of the HCl solution, liquid to solid ratio (RL/S, HCl solution to the residue ratio, mL/g) and acidolysis time on the micro-morphology and crystalline phase of as-prepared TiO2 photocatalysts were systematically investigated. The results indicated that with decreasing pH in the HCl solution and increasing RL/S, the crystalline phase and micro-morphology of the obtained TiO2 nanostructures tended to transform from anatase type TiO2 with spherical nanoparticle structures to rutile type TiO2 with needle-like nanorod structures. The acidolysis time had little influence on the crystalline phase but great impact on the size of the obtained TiO2. The growth mechanism of TiO2 from Ti-bearing EAF slag during the acidolysis process was also discussed. In addition, the influence of RL/S on the photocatalytic properties of the synthesized nanostructured TiO2 was studied. The results showed that the photodegradation efficiency for Rhodamine B solution could reach 91.00% in 120min when the RL/S was controlled at 50:1.

  9. Reversible amorphous-crystalline phase changes in a wide range of Se1-xTex alloys studied using ultrafast differential scanning calorimetry

    NARCIS (Netherlands)

    Vermeulen, Paul. A.; Momand, Jamo; Kooi, Bart J.

    2014-01-01

    The reversible amorphous-crystalline phase change in a chalcogenide material, specifically the Se1-xTex alloy, has been investigated for the first time using ultrafast differential scanning calorimetry. Heating rates and cooling rates up to 5000 K/s were used. Repeated reversible amorphous-crystalli

  10. Reversible electrical resistance switching in GeSbTe thin films : An electrolytic approach without amorphous-crystalline phase-change

    NARCIS (Netherlands)

    Pandian, Ramanathaswamy; Kooi, Bart J.; Palasantzas, George; De Hosson, Jeff Th. M.; Wouters, DJ; Hong, S; Soss, S; Auciello, O

    2008-01-01

    Besides the well-known resistance switching originating from the amorphous-crystalline phase-change in GeSbTe thin films, we demonstrate another switching mechanism named 'polarity-dependent resistance (PDR) switching'. 'Me electrical resistance of the film switches between a low- and high-state whe

  11. The magnetic and crystalline structure of the Laves phase superconductor CeRu{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Huxley, A.; Boucherle, J.X.; Bonnet, M.; Bourdarot, F.; Schustler, I.; Caplan, D. [CEA, Departement de Recherche Fondamental sur la Matiere Condensee, SPSMS, Grenoble 38054 (France); Lelievre, E.; Bernhoeft, N. [Institut Laue - Langevin, Grenoble (France); Lejay, P. [Centre de Recherche sur les Tres Basses Temperatures, CNRS, Grenoble (France); Gillon, B. [CEA, Laboratoire Leon Brillouin, Saclay (France)

    1997-05-19

    We report measurements of the field-induced magnetization density in CeRu{sub 2}. The main results of the study are that the magnetic density is located equally at the Ce and Ru sites, and that the distribution of the induced magnetization about the Ce site extends to larger distances than predicted for Ce{sup 3+} ions with well localized f electrons. Our measurements also cover the superconducting state, where we do not observe any suppression of the spin susceptibility. In an accompanying structural study (in zero field) of our single crystal we detect a small deviation from the ideal Laves phase structure. These results are discussed in relation to the unusual electronic and magnetic properties of this compound. (author)

  12. The effect of heating power on impurity formation and transport during the holding phase in a Bridgman furnace for directional solidification of multi-crystalline silicon

    Science.gov (United States)

    Ellingsen, Kjerstin; Lindholm, Dag; M`Hamdi, Mohammed

    2016-06-01

    Oxygen and carbon are the most common impurities in multi-crystalline silicon. The general mechanism for formation and transport of O and C in the solidification furnace is as follows: oxygen from the silica crucible comes into the melt and combines with a silicon atom and evaporates at the gas/melt interface in the form of silicon oxide (SiO). Argon inert gas, injected into the furnace chamber, carries the SiO to the hot graphite fixtures, where it reacts with carbon to form carbon monoxide (CO) and silicon carbide (SiC). CO is carried by the gas to the melt free surface, where it dissociates into carbon and oxygen. Finally, during solidification oxygen and carbon are incorporated into the crystal. A global furnace model accounting for heat transfer, melt flow, gas flow and impurity transport has been applied to investigate the oxygen and carbon formation and transport in a vertical Bridgman furnace during the holding phase when the furnace is at its hottest. A case study is performed to investigate the effect of the applied heating power on the carbon and oxygen concentrations in the melt prior to solidification.

  13. Interaction of fibrinogen and albumin with titanium dioxide nanoparticles of different crystalline phases

    Science.gov (United States)

    Marucco, Arianna; Fenoglio, Ivana; Turci, Francesco; Fubini, Bice

    2013-04-01

    TiO2 nanoparticles (NPs) are contained in different kinds of industrial products including paints, self-cleaning glasses, sunscreens. TiO2 is also employed in photocatalysis and it has been proposed for waste water treatment. Micrometric TiO2 is generally considered a safe material, while there is concern on the possible health effects of nanometric titania. Due to their small size NPs may migrate within the human body possibly entering in the blood stream. Therefore studies on the interaction of NPs with plasma proteins are needed. In fact, the interaction with proteins is believed to ultimately influences the NPs biological fate. Fibrinogen and albumin are two of the most abundant plasma proteins. They are involved in several important physiological functions. Furthermore, fibrinogen is known to trigger platelet adhesion and inflammation. For these reasons the study of the interaction between these protein and nanoparticles is an important step toward the understanding of the behavior of NPs in the body. In this study we investigated the interaction of albumin and fibrinogen with TiO2 nanoparticles of different crystal phases (rutile and anatase) using an integrated set of techniques. The amount of adsorbed fibrinogen and albumin for each TiO2 surface was investigated by using the bicinchoninic acid assay (BCA). The variation of the surface charge of the NP-protein conjugates respect to the naked NPs was used to indirectly estimate both surface coverage and reversibility of the adsorption upon dilution. Surface charge was monitored by measuring the ζ potential with a conventional electrophoretic light scattering (ELS) system. The extent of protein deformation was evaluated by Raman Spectroscopy. We found that both proteins adsorb irreversibly against electrostatic repulsion, likely undergoing conformational changes or selective orientation upon adsorption. The size of primary particles and the particles aggregation rather than the crystal phase modulate the

  14. Crystalline Confinement

    CERN Document Server

    Banerjee, D; Jiang, F -J; Wiese, U -J

    2013-01-01

    We show that exotic phases arise in generalized lattice gauge theories known as quantum link models in which classical gauge fields are replaced by quantum operators. While these quantum models with discrete variables have a finite-dimensional Hilbert space per link, the continuous gauge symmetry is still exact. An efficient cluster algorithm is used to study these exotic phases. The $(2+1)$-d system is confining at zero temperature with a spontaneously broken translation symmetry. A crystalline phase exhibits confinement via multi-stranded strings between charge-anti-charge pairs. A phase transition between two distinct confined phases is weakly first order and has an emergent spontaneously broken approximate $SO(2)$ global symmetry. The low-energy physics is described by a $(2+1)$-d $\\mathbb{R}P(1)$ effective field theory, perturbed by a dangerously irrelevant $SO(2)$ breaking operator, which prevents the interpretation of the emergent pseudo-Goldstone boson as a dual photon. This model is an ideal candidat...

  15. The human crystallin gene families

    Directory of Open Access Journals (Sweden)

    Wistow Graeme

    2012-12-01

    Full Text Available Abstract Crystallins are the abundant, long-lived proteins of the eye lens. The major human crystallins belong to two different superfamilies: the small heat-shock proteins (α-crystallins and the βγ-crystallins. During evolution, other proteins have sometimes been recruited as crystallins to modify the properties of the lens. In the developing human lens, the enzyme betaine-homocysteine methyltransferase serves such a role. Evolutionary modification has also resulted in loss of expression of some human crystallin genes or of specific splice forms. Crystallin organization is essential for lens transparency and mutations; even minor changes to surface residues can cause cataract and loss of vision.

  16. Liquid crystalline phases in suspensions of pigments in non-polar solvents

    Science.gov (United States)

    Klein, Susanne; Richardson, Robert M.; Eremin, Alexey

    We will discuss colloid suspensions of pigments and compare their electro-optic properties with those of traditional dyed low molecular weight liquid crystal systems. There are several potential advantages of colloidal suspensions over low molecular weight liquid crystal systems: a very high contrast because of the high orientational order parameter of suspensions of rod shaped nano-particles, the excellent light fastness of pigments as compared to dyes and high colour saturations resulting from the high loading of the colour stuff. Although a weak `single-particle' electro-optic response can be observed in dilute suspensions, the response is very much enhanced when the concentration of the particles is sufficient to lead to a nematic phase. Excellent stability of suspensions is beneficial for experimental observation and reproducibility, but it is a fundamental necessity for display applications. We therefore discuss a method to achieve long term stability of dispersed pigments and the reasons for its success. Small angle X-ray scattering was used to determine the orientational order parameter of the suspensions as a function of concentration and the dynamic response to an applied electric field. Optical properties were investigated for a wide range of pigment concentrations. Electro-optical phenomena, such as field-induced birefringence and switching, were characterised. In addition, mixtures of pigment suspensions with small amounts of ferrofluids show promise as future magneto-optical materials.

  17. Structural phase analysis of a sol-gel nano-crystalline lithium-mica glass-ceramic through different compositions

    Energy Technology Data Exchange (ETDEWEB)

    Tohidifar, M.R., E-mail: tohidifar@znu.ac.ir [Faculty of Engineering, University of Zanjan, P.O. Box 45371-38791, Zanjan (Iran, Islamic Republic of); Alizadeh, P. [Department of Materials Science and Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of)

    2016-08-15

    The current paper attempts to study the influence of chemical composition on the phase development of nano-crystalline lithium-mica glass-ceramic. For this purpose, aqueous sol-gel technique was employed to prepare the glass-ceramics. The synthesis process was accomplished using two chemical compositions of Li{sub (1+x)}Mg{sub 3}AlSi{sub 3(1+x)}O{sub 10+6.5x}F{sub 2} and LiMg{sub 3}AlSi{sub 3(1+x)}O{sub 10+6x}F{sub 2} at different x values along with various mass% of MgF{sub 2} inclusion. It was found that considering an optimized amount of MgF{sub 2}, the specimens synthesized through a new formulation of LiMg{sub 3}AlSi{sub 3(1+x)}O{sub 10+6x}F{sub 2} composition are more appropriate for the sol-gel synthesis method, especially because of intensifying the lithium-mica precipitation and also omission of the secondary phase (i.e. lithium aluminum silicate). The results also indicated that any deviation from the optimized amount of MgF{sub 2} (8%) would cause degradation in the intensity of the precipitated lithium-mica, following the nucleation treatment. - Highlights: • Higher intensity of mica phase obtains through LiMg{sub 3}AlSi{sub 3(1+x)}O{sub 10+6x}F{sub 2} composition. • LiMg{sub 3}AlSi{sub 3(1+x)}O{sub 10+6x}F{sub 2} composition offers mica phase without applying excess MgF{sub 2}. • Applying LiMg{sub 3}AlSi{sub 3(1+x)}O{sub 10+6x}F{sub 2} composition leads to omission of minor phases. • Li{sub (1+x)}Mg{sub 3}AlSi{sub 3(1+x)}O{sub 10+6.5x}F{sub 2} formula cannot be useful in mica nucleation process. • Optimum amount of MgF{sub 2} was obtained as 8% following the nucleation process.

  18. Congenital cataract causing mutants of αA-crystallin/sHSP form aggregates and aggresomes degraded through ubiquitin-proteasome pathway.

    Directory of Open Access Journals (Sweden)

    Ilangovan Raju

    Full Text Available BACKGROUND: Mutations of human αA-crystallin cause congenital cataract by protein aggregation. How mutations of αA-crystallin cause disease pathogenesis through protein aggregation is not well understood. To better understand the cellular events leading to protein aggregation, we transfected cataract causing mutants, R12C, R21L, R21W, R49C, R54C, R116C and R116H, of human αA-crystallin in HeLa cells and examined the formation of intracellular protein aggregates and aggresomes by confocal microscopy. METHODOLOGY/PRINCIPAL FINDINGS: YFP-tagged human αA-wild-type (αA-wt was sub-cloned and the mutants were generated by site-directed mutagenesis. The αA-wt and the mutants were individually transfected or co-transfected with CFP-tagged αA-wt or αB-wild-type (αB-wt in HeLa cells. Overexpression of these mutants forms multiple small dispersed cytoplasmic aggregates as well as aggresomes. Co-expression of αB-wt with these mutants significantly inhibited protein aggregates where as co-expression with αA-wt enhanced protein aggregates which seems to be due to co-aggregation of the mutants with αA-wt. Aggresomes were validated by double immunofluorescence by co-localization of γ-tubulin, a centrosome marker protein with αA-crystallin. Furthermore, increased ubiquitination was detected in R21W, R116C and R116H as assessed by western blot analyses. Immunostaining with an ubiquitin antibody revealed that ubiquitin inclusions in the perinuclear regions were evident only in R116C transfected cells. Pulse chase assay, after cycloheximide treatment, suggested that R116C degraded faster than the wild-type control. CONCLUSIONS/SIGNIFICANCE: Mutants of αA-crystallin form aggregates and aggresomes. Co-expression of αA-wt with the mutants increased aggregates and co-expression of αB-wt with the mutants significantly decreased the aggregates. The mutant, R116C protein degraded faster than wild-type control and increased ubiquitination was evident in R

  19. Effect of long range order on sheared liquid crystalline materials: flow regimes, transitions, and rheological phase diagrams

    Science.gov (United States)

    Tsuji; Rey

    2000-12-01

    A generalized theory that includes short-range elasticity, long-range elasticity, and flow effects is used to simulate and characterize the shear flow of liquid crystalline materials as a function of the Deborah (De) and Ericksen (Er) numbers in the presence of fixed planar director boundary conditions; the results are also interpreted as a function of the ratio R between short-range and long-range elasticity. The results are effectively summarized into rheological phase diagrams spanned by De and Er, and also by R and Er, where the stability region of four distinct flow regimes are indicated. The four regimes for planar (two-dimensional orientation) shear flow are (1) the elastic-driven steady state, (2) the composite tumbling-wagging periodic state, (3) the wagging periodic state, and (4) the viscous-driven steady state. The coexistence of the four regimes at a quacritical point is shown to be due to the emergence of a defect structure. The origin, the significant steady and dynamical features, and the transitions between these regimes are thoroughly characterized and analyzed. Quantitative and qualitative comparisons between the present complete model predictions and those obtained from the classical theories of nematodynamics (Leslie-Ericksen and Doi theories) are presented and the main physical mechanisms that drive the observed deviations between the predictions of these models are identified. The presented results fill the previously existing gap between the classical Leslie-Ericksen theory and the Doi theory, and present a unified description of nematodynamics.

  20. Controlled vapor phase growth of single crystalline, two-dimensional GaSe crystals with high photoresponse.

    Science.gov (United States)

    Li, Xufan; Lin, Ming-Wei; Puretzky, Alexander A; Idrobo, Juan C; Ma, Cheng; Chi, Miaofang; Yoon, Mina; Rouleau, Christopher M; Kravchenko, Ivan I; Geohegan, David B; Xiao, Kai

    2014-06-30

    Compared with their bulk counterparts, atomically thin two-dimensional (2D) crystals exhibit new physical properties, and have the potential to enable next-generation electronic and optoelectronic devices. However, controlled synthesis of large uniform monolayer and multi-layer 2D crystals is still challenging. Here, we report the controlled synthesis of 2D GaSe crystals on SiO2/Si substrates using a vapor phase deposition method. For the first time, uniform, large (up to ~60 μm in lateral size), single-crystalline, triangular monolayer GaSe crystals were obtained and their structure and orientation were characterized from atomic scale to micrometer scale. The size, density, shape, thickness, and uniformity of the 2D GaSe crystals were shown to be controllable by growth duration, growth region, growth temperature, and argon carrier gas flow rate. The theoretical modeling of the electronic structure and Raman spectroscopy demonstrate a direct-to-indirect bandgap transition and progressive confinement-induced bandgap shifts for 2D GaSe crystals. The 2D GaSe crystals show p-type semiconductor characteristics and high photoresponsivity (~1.7 A/W under white light illumination) comparable to exfoliated GaSe nanosheets. These 2D GaSe crystals are potentially useful for next-generation electronic and optoelectronic devices such as photodetectors and field-effect transistors.

  1. Study of the terahertz spectra of crystalline materials using NDDO semi-empirical methods: polyethylene, poly(vinylidene fluoride) form II and $\\alpha$-D-glucose

    CERN Document Server

    Chamorro-Posada, P

    2016-01-01

    Semi-empirical quantum chemistry methods offer a very interesting compromise between accuracy and computational load. In order to assess the performance of NDDO methods in the interpretation of terahertz spectra, the low frequency vibration modes of three crystalline materials, namely, polyethylene, poly(vinylidene fluoride) form II and $\\alpha$-D-glucose have been studied using the PM6 and PM7 Hamiltonians and the results have been compared with the experimental data and former calculations. The results show good qualitative or semi-quantitative agreement with the experimentally observed terahertz spectra.

  2. Preliminary treatment of chlorinated streams containing fission products: mechanisms leading to crystalline phases in molten chloride media; Pretraitement pyrochimique de flux charges en produits de fission: mecanismes conduisant a l'obtention de phases cristallines en milieux chlorures fondus

    Energy Technology Data Exchange (ETDEWEB)

    Hudry, D

    2008-10-15

    The world of the nuclear power gets ready for profound modifications so that 'the atom' can aspire in conformance with long-lasting energy: it is what we call the development of generation IV nuclear systems. So, the new pyrochemical separation processes for the spent fuel reprocessing are currently being investigated. Techniques in molten chloride media generate an ultimate flow (with high chlorine content) which cannot be incorporated in conventional glass matrices. This flow is entirely water-soluble and must be conditioned in a chemical form which is compatible with a long-term disposal. This work of thesis consists in studying new ways for the management of the chlorinated streams loaded with fission products (FP). To do it, a strategy of selective FP extraction via the in situ formation of crystalline phases was retained. The possibility of extracting rare earths in the eutectic LiCl-KCl was demonstrated via the development of a new way of synthesis of rare earth phosphates (TRPO{sub 4}). As regards alkaline earths, the conversion of strontium and barium chlorides to the corresponding tungstates or molybdates was studied in different solvents. Mechanisms leading to the crystalline phases in molten chloride media were studied via the coupling of NMR and XRD techniques. First of all, it has been shown that these mechanisms are dependent on the stability of the used precursors. So in the case of the formation of rare earth phosphates the solvent is chemically active. On the other hand, in the case of the formation of alkaline earth tungstates it would seem that the solvent plays the role of structuring agent which can control the ability to react of chlorides. (author)

  3. Combined toxicity of two crystalline phases (anatase and rutile) of Titania nanoparticles towards freshwater microalgae: Chlorella sp.

    Science.gov (United States)

    Iswarya, V; Bhuvaneshwari, M; Alex, Sruthi Ann; Iyer, Siddharth; Chaudhuri, Gouri; Chandrasekaran, Prathna Thanjavur; Bhalerao, Gopalkrishna M; Chakravarty, Sujoy; Raichur, Ashok M; Chandrasekaran, N; Mukherjee, Amitava

    2015-04-01

    In view of the increasing usage of anatase and rutile crystalline phases of titania NPs in the consumer products, their entry into the aquatic environment may pose a serious risk to the ecosystem. In the present study, the possible toxic impact of anatase and rutile nanoparticles (individually and in binary mixture) was investigated using freshwater microalgae, Chlorella sp. at low exposure concentrations (0.25, 0.5 and 1mg/L) in freshwater medium under UV irradiation. Reduction of cell viability as well as a reduction in chlorophyll content were observed due to the presence of NPs. An antagonistic effect was noted at certain concentrations of binary mixture such as (0.25, 0.25), (0.25, 0.5), and (0.5, 0.5) mg/L, and an additive effect for the other combinations, (0.25, 1), (0.5, 0.25), (0.5, 1), (1, 0.25), (1, 0.5), and (1, 1) mg/L. The hydrodynamic size analyses in the test medium revealed that rutile NPs were more stable in lake water than the anatase and binary mixtures [at 6h, the sizes of anatase (1mg/L), rutile NPs (1mg/L), and binary mixture (1, 1mg/L) were 948.83±35.01nm, 555.74±19.93nm, and 1620.24±237.87nm, respectively]. The generation of oxidative stress was found to be strongly dependent on the crystallinity of the nanoparticles. The transmission electron microscopic images revealed damages in the nucleus and cell membrane of algal cells due to the interaction of anatase NPs, whereas rutile NPs were found to cause chloroplast and internal organelle damages. Mis-shaped chloroplasts, lack of nucleus, and starch-pyrenoid complex were noted in binary-treated cells. The findings from the current study may facilitate the environmental risk assessment of titania NPs in an aquatic ecosystem.

  4. Pure, single phase, high crystalline, chamfered-edge zeolite 4A synthesized from coal fly ash for use as a builder in detergents.

    Science.gov (United States)

    Hui, K S; Chao, C Y H

    2006-09-01

    Single phase chamfered-edge zeolite 4A samples in pure form with a high crystallinity were synthesized by applying step-change of synthesis temperature during hydrothermal treatment of coal fly ash. The calcium binding capacity of these zeolite 4A samples (prepared from coal fly ash) and the commercial detergent grade zeolite 4A were tested for usage as a detergent builder. The results show that these zeolite 4A samples behaved similarly as the commercial one in removing calcium ions during the washing cycle. Moreover, from the leaching tests (evaluation of toxicological safety), the results show that these zeolite 4A samples leached the same elements (Sb, As, Se and Tl) as the commercial one with the concentrations in the same order of magnitude. This shows that the toxicological effect of the coal fly ash converted zeolite 4A was not worse than that of the commercial sample. Finally, economic and environmental aspects of converting coal fly ash to useful products were discussed.

  5. Crystalline phases during the melting of Bi sub 2 Sr sub 2 CaCu sub 2 O sub x

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Ming; Polonka, J.; Goldman, A.I.; Finnemore, D.K.; Li, Qiang; Laabs, F.C.

    1991-01-01

    The melting of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x} material has been studied by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) in order to study the phases that formed in the high temperature regions. Two distinct phases of (Sr{sub 1-x}Ca{sub x})CuO{sub 2} and (Sr{sub 1-x}Ca{sub x}){sub 2}CuO{sub 3} have been observed in the Bi-rich matrix depending upon quenching temperatures. Crystallization from the melt by fast cooling usually produce the co-existence of Bi (2201) and these Sr-Ca-Cu-O phases. 12 refs., 2 figs.

  6. The effects of sulfate content on crystalline phase, microstructure, and chemical durability of zirconolite−barium borosilicate glass-ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Lang, E-mail: lang.wu@163.com [State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010 (China); Wang, Xin; Li, Huidong; Teng, Yuancheng [State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010 (China); Peng, Long [Sichuan Province Key Laboratory of Information Materials and Devices Application, Chengdu University of Information Technology, Chengdu 610225 (China)

    2016-09-15

    The effects of sulfate content on structure and chemical durability of barium borosilicate glass-ceramics were studied. The results show that the glass-ceramics with 0–1.10 mol% SO{sub 3} possess mainly CaZrTi{sub 2}O{sub 7}-2M phase along with a small amount of CaZrTi{sub 2}O{sub 7}-3T and ZrO{sub 2} phases. The hexagonal CaZrTi{sub 2}O{sub 7}-3T crystals crystallize on the surface of glass-ceramics. For the samples with 1.24–1.55 mol% SO{sub 3}, the main crystalline phases are CaTiSiO{sub 5} and CaZrTi{sub 2}O{sub 7}-2M in the bulk, while a separate sulfate layer containing Na{sub 2}SO{sub 4} and BaSO{sub 4} is observed on the surface. X-ray fluorescence analysis indicates that about 2/3 of the SO{sub 3} originally added has been lost by volatility. The normalized mass loss (NL{sub i}) for Na, B, Ca elements remains almost unchanged (∼10{sup −2} g/m{sup 2}) after 7 days for the samples with 0–1.10 mol% SO{sub 3}. The NL{sub i} for both Na and B increases gradually after 7 days when the SO{sub 3} content is 1.24 mol%. - Highlights: • Strip-shaped CaZrTi{sub 2}O{sub 7}-2M and plate-like CaTiSiO{sub 5} crystals crystallize in the bulk. • CaZrTi{sub 2}O{sub 7}-3T crystals crystallize on the surface for samples with 0–1.10 mol% SO{sub 3}. • A separate sulfate layer crystallizes on the surface when SO{sub 3} exceeds solubility.

  7. On the relationship between crystalline structure and amorphous phase dynamics during isothermal crystallization of bacterial poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolymers.

    Science.gov (United States)

    Sics, I; Ezquerra, T A; Nogales, A; Baltá-Calleja, F J; Kalniņs, M; Tupureina, V

    2001-01-01

    The isothermal crystallization process of a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolymer, P(HB-co-HV) with a HB/HV ratio 78/22 was investigated by simultaneous small-angle X-ray scattering (SAXS), wide-angle X-ray scattering (WAXS), and dielectric spectroscopy (DS). By use of this experimental setup (SWD), we have obtained simultaneous information about changes occurring in both the crystalline and the amorphous phases during crystallization. By using the Havriliak-Negami formalism to analyze the dielectric relaxation data, a strong dependence of the relaxation curve shape with the development of the crystalline phase was found. However, in this particular copolymer, the developing crystalline domains do not affect significantly the average segmental mobility in the amorphous phase. This effect is discussed in the light of the enrichment of amorphous phase by HV comonomer units during primary crystallization, hindering the secondary crystallization processes. Results support the hypothesis that the decrease of the physical-aging-like behavior, observed in P(HB-co-HV) copolymers as the amount of HV increases, can be attributed to the progressive inhibition of secondary crystallization mechanisms.

  8. Filling the gap in Ca input-output budgets in base-poor forest ecosystems: The contribution of non-crystalline phases evidenced by stable isotopic dilution

    Science.gov (United States)

    van der Heijden, Gregory; Legout, Arnaud; Mareschal, Louis; Ranger, Jacques; Dambrine, Etienne

    2017-07-01

    In terrestrial ecosystems, plant-available pools of magnesium and calcium are assumed to be stored in the soil as exchangeable cations adsorbed on the surface of mineral and/or organic particles. The pools of exchangeable magnesium and calcium are measured by ion-exchange soil extractions. These pools are sustained in the long term by the weathering of primary minerals in the soil and atmospheric inputs. This conceptual model is the base of input-output budgets from which soil acidification and the sustainability of soil chemical fertility is inferred. However, this model has been questioned by data from long-term forest ecosystem monitoring sites, particularly for calcium. Quantifying the contribution of atmospheric inputs, ion exchange and weathering of both primary, secondary and non-crystalline phases to tree nutrition in the short term is challenging. In this study, we developed and applied a novel isotopic dilution technique using the stable isotopes of magnesium and calcium to study the contribution of the different soil phases to soil solution chemistry in a very acidic soil. The labile pools of Mg and Ca in the soil (pools in equilibrium with the soil solution) were isotopically labeled by spraying a solution enriched in 26Mg and 44Ca on the soil. Labeled soil columns were then percolated with a dilute acid solution during a 3-month period and the isotopic dilution of the tracers was monitored in the leaching solution, in the exchangeable (2 sequential 1 mol L-1 ammonium acetate extractions) and non-crystalline (2 sequential soil digestions: oxalic acid followed by nitric acid) phases. Significant amounts of Mg and Ca isotope tracer were recovered in the non-crystalline soil phases. These phases represented from 5% to 25% and from 24% to 50%, respectively, of the Mg and Ca labile pools during the experiment. Our results show that non-crystalline phases act as both a source and a sink of calcium and magnesium in the soil, and contribute directly to soil

  9. Indocyanine Green Angiographic and Multifocal Electroretinographic Features in the Diffuse and Regional Form of Bietti′s Crystalline Retinopathy

    Institute of Scientific and Technical Information of China (English)

    Libin Jiang; Feng Wen; Lezheng Wu; Hong Yan; Shixing Hu

    2002-01-01

    Prpose: To observe different features of indocyanine green angiography(ICGA) andtifocal electroretinography (ERG) in the diffuse and regional type of Bieti′sc stalline retinopathy (BCR). Thods: ICGA and the multifocal ERG were performed in two cases of the diffuse andregional type of BCR respectively. These data were compared with fluoresceinangiography (FA), standard Ganzfeld ERG, and visual field testing. Results: In the regional case, ICGA revealed reduced perfusion of the choroidalcirculation in the early phase and multiple hypofluorescent spots in the posterior pole in the late phase, due to choriocapillaris filling defect; the extent of choroiocapillaris losswas shown in early phase of ICGA and there were multifocal hyperfluorescent dotssurrounding hypofluorescent spots in late phase in the diffuse case. The multifocal ERGshowed that the central responses were markedly depressed, corresponding to the visualfield defects, while the findings of Ganzfeld ERG were normal in the regional BCR;however, both the multifocal ERG and Ganzfeld ERG were severely subnormal in thediffuse case.Conclusions: The features of ICGA and multifocal ERG are different between the diffuseand regional BCR. In the meantime, the two tools are also useful to differentiate the typeand assess the extentof evolution in BCR.

  10. Congenital Cataract-Causing Mutation G129C in γC-Crystallin Promotes the Accumulation of Two Distinct Unfolding Intermediates That Form Highly Toxic Aggregates.

    Science.gov (United States)

    Xi, Yi-Bo; Chen, Xiang-Jun; Zhao, Wei-Jie; Yan, Yong-Bin

    2015-08-28

    Cataract is a lens opacification disease prevalent worldwide. Cataract-causing mutations in crystallins generally lead to the formation of light-scattering particles in the lens. However, it remains unclear for the detailed structural and pathological mechanisms of most mutations. In this study, we showed that the G129C mutation in γC-crystallin, which is associated with autosomal dominant congenital nuclear cataract, perturbed the unfolding process by promoting the accumulation of two distinct aggregation-prone intermediates under mild denaturing conditions. The abnormally accumulated intermediates escaped from the chaperone-like function of αA-crystallin during refolding. Molecular dynamics simulations indicated that the mutation altered domain pairing geometry and allowed the penetration of extra solvent molecules into the domain binding interface, thereby weakening domain binding energy. Under mild denaturation conditions, the increased domain movements may facilitate the formation of non-native oligomers via domain swapping, which further assembled into amyloid-like fibrils. The intermediate that appeared at 1.6M guanidine hydrochloride was more compact and less aggregatory than the one populated at 0.9 M guanidine hydrochloride, which was caused by the increased solvation of acidic residues in the ion-pairing network via the competitive binding of guanidinium ions. More importantly, both the amyloid-like fibrils preformed in vitro and intracellular aggresomes formed by exogenously overexpressed mutant proteins significantly inhibited cell proliferation and induced cell death. The combined data from spectroscopic, structural and cellular studies strongly suggest that both the formation of light-scattering aggregates and the toxic effects of the aggregates may contribute to the onset and development of cataract.

  11. Achieving balanced intermixed and pure crystalline phases in PDI-based non-fullerene organic solar cells via selective solvent additives.

    Science.gov (United States)

    Li, Mingguang; Liu, Jiangang; Cao, Xinxiu; Zhou, Ke; Zhao, Qiaoqiao; Yu, Xinhong; Xing, Rubo; Han, Yanchun

    2014-12-28

    Herein, balanced intermixed and pure crystalline phases in N,N'-bis(1-ethylpropyl)-perylene-3,4,9,10-tetracarboxylic diimide (EP-PDI)-based non-fullerene organic solar cells (OSCs) were achieved via selective solvent additives (SAs). Poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl

  12. Phase equilibria in model surfactants forming Langmuir monolayers.

    Science.gov (United States)

    Ramírez, E; Santana, A; Cruz, A; López, G E

    2007-12-14

    The study of Langmuir monolayers has generated the attention of researchers because of their unique properties and their not well understood phase equilibrium. These monolayers exhibit interesting phase diagrams where the unusual liquid-liquid equilibrium can be observed for a single component monolayer. Monte Carlo computer simulations in the virtual Gibbs ensemble were used to obtain the phase diagram of Langmuir monolayers. The liquid-vapor and liquid-liquid phase equilibria were considered by constructing the Cailletet-Mathias phase diagrams. By using the Ising model and the rectilinear approximations the identification of the critical properties for both equilibria was determined. These critical parameters were calculated as a function of the strength of the interaction between the surfactant molecules and the aqueous subphase. As a result, we have identified the coexistence between a liquid expanded state (LES)-vapor and the liquid condensed state-LES, in agreement with experimental and theoretical evidence in the literature. We obtained a clear separation of phases and a strong dependence on the strength of the solvent used. Namely, as the interaction between the solvent and the head of the surfactant increases, the critical properties also increase. Equilibrium states were characterized by computing thermodynamic quantities as a function of temperature and solvent strength.

  13. Benzocaine polymorphism: pressure-temperature phase diagram involving forms II and III.

    Science.gov (United States)

    Gana, Inès; Barrio, Maria; Do, Bernard; Tamarit, Josep-Lluís; Céolin, René; Rietveld, Ivo B

    2013-11-18

    Understanding the phase behavior of an active pharmaceutical ingredient in a drug formulation is required to avoid the occurrence of sudden phase changes resulting in decrease of bioavailability in a marketed product. Benzocaine is known to possess three crystalline polymorphs, but their stability hierarchy has so far not been determined. A topological method and direct calorimetric measurements under pressure have been used to construct the topological pressure-temperature diagram of the phase relationships between the solid phases II and III, the liquid, and the vapor phase. In the process, the transition temperature between solid phases III and II and its enthalpy change have been determined. Solid phase II, which has the highest melting point, is the more stable phase under ambient conditions in this phase diagram. Surprisingly, solid phase I has not been observed during the study, even though the scarce literature data on its thermal behavior appear to indicate that it might be the most stable one of the three solid phases.

  14. Liquid-crystalline rigid-core semiconductor oligothiophenes: influence of molecular structure on phase behaviour and thin-film properties.

    Science.gov (United States)

    Melucci, Manuela; Favaretto, Laura; Bettini, Christian; Gazzano, Massimo; Camaioni, Nadia; Maccagnani, Piera; Ostoja, Paolo; Monari, Magda; Barbarella, Giovanna

    2007-01-01

    The design, synthesis and properties of liquid-crystalline semiconducting oligothiophenes containing dithienothiophene (DTT), benzothiadiazole (BTZ) and carbazole (CBZ) rigid cores are described. The effect of molecular structure (shape, size and substitution) on their thermal behaviour and electrical properties has been investigated. Polarised optical microscopy (POM) and differential scanning calorimetry (DSC) analyses have revealed highly ordered smectic mesophases for most of the newly synthesised compounds. X-ray diffraction (XRD) studies performed at various temperatures have shown that the smectic order is retained in the crystalline state upon cooling across the transition temperature, affording cast films with a more favourable morphology for FET applications.

  15. InAsSb on GaAs (001): influence of the arsenic molecules form on composition and crystalline properties of MBE layers

    Science.gov (United States)

    Emel'yanov, E. A.; Vasev, A. V.; Semyagin, B. R.; Vasilenko, A. P.; Komanov, A. A.; Gutakovskii, A. K.; Putyato, M. A.; Preobrazhenskii, V. V.

    2015-11-01

    The influence of As molecular form on the composition and crystalline properties of InAsxSb1-x solid solutions with MBE has been experimentally investigated. A series of samples has been grown at different growth temperatures. The grown samples were studied with the HRXRD and TEM methods. The incorporation coefficient of As4 and As2 molecules were determined at different growth temperatures. It has been found that the incorporation coefficient of As4 much more dependent on growth temperature compared to As2. It has been found that at a low growth temperature a step-like increase of Sb fraction in an InAsxSb1-x film leads to a decrease of threading dislocations density in a layer with a smaller x.

  16. The potential for the fabrication of wires embedded in the crystalline silicon substrate using the solid phase segregation of gold in crystallising amorphous volumes

    Energy Technology Data Exchange (ETDEWEB)

    Liu, A.C.Y.; McCallum, J.C

    2004-05-15

    The refinement of gold in crystallising amorphous silicon volumes was tested as a means of creating a conducting element embedded in the crystalline matrix. Amorphous silicon volumes were created by self-ion-implantation through a mask. Five hundred kiloelectronvolt Au{sup +} was then implanted into the volumes. The amorphous volumes were crystallised on a hot stage in air, and the crystallisation was characterised using cross sectional transmission electron microscopy. It was found that the amorphous silicon volumes crystallised via solid phase epitaxy at all the lateral and vertical interfaces. The interplay of the effects of the gold and also the hydrogen that infilitrated from the surface oxide resulted in a plug of amorphous material at the surface. Further annealing at this temperature demonstrated that the gold, once it had reached a certain critical concentration nucleated poly-crystalline growth instead of solid phase epitaxy. Time resolved reflectivity and Rutherford backscattering and channeling measurements were performed on large area samples that had been subject to the same implantation regime to investigate this system further. It was discovered that the crystallisation dynamics and zone refinement of the gold were complicated functions of both gold concentration and temperature. These findings do not encourage the use of this method to obtain conducting elements embedded in the crystalline silicon substrate.

  17. The structure and functional properties of Ti2 NiCu alloy rapidly quenched ribbons with different fractions of crystalline phase

    Science.gov (United States)

    Belyaev, S. P.; Istomin-Kastrovskiy, V. V.; Koledov, V. V.; Kuchin, D. S.; Resnina, N. N.; Shavrov, V. G.; Shelyakov, A. V.; Ivanov, S. E.

    The samples of Ti2NiCu rapidly quenched alloy with different fractions of crystalline phase have been prepared by electric pulse technique from as spun amorphous ribbons. The structure and thermomechanical properties of these samples have been studied. The mixture of amorphous and nanocrystalline structures with mean grains size less than 10 nm has been observed by HRTEM. The remarkable thermomechanical properties of the samples with the ratio of crystalline fraction in the range of r = 0.4 - 0.6 (determined by electrical resistivity measurements) have been found. The two-way shape memory effect with the reverse deformation Δε = 0.31 % has been induced in the sample with r = 0.46 by single deformation at cooling below the temperature of martensite transformation. The prototype of microtweezers based on amorphous-nanocrystalline Ti2NiCu melt-spun ribbon alloy with two-way shape memory effect has been designed and tested.

  18. New tellurite glasses and crystalline phases in the Bi{sub 2}O{sub 3}-CaO-TeO{sub 2} system: Synthesis and characterization

    Energy Technology Data Exchange (ETDEWEB)

    Chagraoui, Abdeslam; Tairi, Abdelmjid; Ajebli, Kaltoum; Bensaid, Hanane; Moussaoui, Abdenajib [Laboratoire de Chimie Analytique et Physico-chimie des Materiaux, Departement de Chimie, Faculte des Sciences Ben M' sik, Universite HassanII-Mohammedia Casablanca (Morocco)

    2010-04-09

    Tellurite glasses containing calcium and bismuth oxides have been prepared at 800 {sup o}C and investigated by X-ray diffraction, DSC, IR and Raman spectroscopy. The crystalline phases of glasses in TeO{sub 2}-CaO revealed {gamma}TeO{sub 2} phase which transforms into the stable {alpha}TeO{sub 2} phase up to 500 {sup o}C. IR and Raman studies show the transition of TeO{sub 4}, TeO{sub 3+1} and TeO{sub 3} units with increasing CaO content. The value of refractive index and density of glasses have been measured. The investigation in the system using XRD reveals new phases.

  19. Hierarchical architectures TiO2: pollen-inducted synthesis, remarkable crystalline-phase stability, tunable size, and reused photo-catalysis.

    Science.gov (United States)

    Dou, Lingling; Gao, Lishuang; Yang, Xiaohui; Song, Xiuqin

    2012-02-15

    TiO(2) with hierarchical architectures, tunable crystalline phase and thermal stability is successfully fabricated on a large scale through a facile hydrolysis process of TiCl(4) combining with inducing of pollen. The structure of the as-prepared TiO(2) is characterized by X-ray diffraction, Raman spectroscopy, infrared spectra, and scanning electron microscopy. The experimental results indicate that different phases (anatase, rutile or mixed crystallite) of TiO(2) can be synthesized by controlling the experimental conditions. The pure phase of rutile or anatase can be obtained at 100°C, while the pure phase of anatase can be retained after being annealed at 900°C. The hierarchical structures TiO(2) are constitute through self-assembly of nanoparticles or nanorods TiO(2), which exhibit high and reused photo-catalytic properties for degradation of methylene blue.

  20. SYNTHESIS AND PROPERTIES OF NEW SIDE-CHAIN LIQUID CRYSTALLINE POLYMER WITH LATERALLY ATTACHED MESOGENS BY ESTER GROUP

    Institute of Scientific and Technical Information of China (English)

    Qi-ding Mi; Qi-feng Zhou

    1999-01-01

    New liquid crystalline monomer, 2,5-bis[(4'-methoxyphenoxy)carbonyl]phenyl acrylate was successfully synthesized. Polyacrylate with laterally attached mesogens via ester linkage was also derived.This polymer forms an enantiotropic liquid crystal phase while its monomer exhibits a metastable nematic phase with respect to the crystalline state. However, its liquid crystallinity is very low as compared to that of poly { 2,5-bis[(4'-methoxyphenoxy)carbonyl] -styrene }.

  1. Nanocrystalline calcitic lens arrays fabricated by self-assembly followed by amorphous-to-crystalline phase transformation.

    Science.gov (United States)

    Schmidt, Ingo; Lee, Kyubock; Zolotoyabko, Emil; Werner, Peter; Shim, Tae Soup; Oh, You-Kwan; Fratzl, Peter; Wagermaier, Wolfgang

    2014-09-23

    Natural calcium carbonate-based nanocomposites often have superior physical properties and provide a comprehensive source for bioinspired synthetic materials. Here we present thermodynamically stable, transparent CaCO3 microlens arrays (MLA) produced by transforming an amorphous CaCO3 phase into nanocrystalline calcite. We analyze the structure and properties of crystallized MLA by X-ray scattering, transmitted and polarized light microscopy, and electron microscopy and find that MLA are crystallized in spherulite-like patterns without changing the shape of the microlens. The key finding is that nanocrystallinity of the calcite formed diminishes structural anisotropy on the wavelength scale and results in greatly reduced birefringent effects. The remnant preferred orientation of the optical axes of calcite crystals in the plane of the microlens arrays leads to some directionality of optical properties, which may be beneficial for technical applications.

  2. Optical tweezers formed by pure phase pupil filter

    Science.gov (United States)

    Lv, Wei; You, Chenglong; Wang, Mei; Yun, Maojin

    2013-09-01

    The focusing properties of vector beams have attracted great attention and quickly became the subject of extensive worldwide research due to their applications in lithography, optical storage, microscopy, material processing, and optical trapping. Focusing properties of the radially polarized beam and generalized cylindrical vector beams in high numerical aperture system with designed pure phase filter are analyzed in detail by using vector Debye diffraction theory. By utilizing diffractive optical element to partly change the polarization of vector beams, the energy density of light field in the vicinity of focus is studied by the numerical analysis. Numerical simulation result shows that optical bubbles can be obtained by changing the composition and polarization of the incident beams. At last, optical tweezers are constituted by two optical bubbles around the focus.

  3. Enhanced Crystalline Phase Purity of CH3NH3PbI3-xClx Film for High-Efficiency Hysteresis-Free Perovskite Solar Cells.

    Science.gov (United States)

    Yang, Yingguo; Feng, Shanglei; Xu, Weidong; Li, Meng; Li, Li; Zhang, Xingmin; Ji, Gengwu; Zhang, Xiaonan; Wang, Zhaokui; Xiong, Yimin; Cao, Liang; Sun, Baoquan; Gao, Xingyu

    2017-07-12

    Despite rapid successful developments toward promising perovskite solar cells (PSCs) efficiency, they often suffer significant hysteresis effects. Using synchrotron-based grazing incidence X-ray diffraction (GIXRD) with different probing depths by varying the incident angle, we found that the perovskite films consist of dual phases with a parent phase dominant in the interior and a child phase with a smaller (110) interplanar space (d(110)) after rapid thermal annealing (RTA), which is a widely used post treatment to improve the crystallization of solution-processed perovskite films for high-performance planar PSCs. In particular, the child phase composition gradually increases with decreasing depth till it becomes the majority on the surface, which might be one of the key factors related to hysteresis in fabricated PSCs. We further improve the crystalline phase purity of the solution-processed CH3NH3PbI3-xClx perovskite film (referred as g-perovskite) by using a facile gradient thermal annealing (GTA), which shows a uniformly distributed phase structure in pinhole-free morphology with less undercoordinated Pb and I ions determined by synchrotron-based GIXRD, grazing incidence small-angle X-ray scattering, scanning electron microscopy, and X-ray photoelectron spectroscopy. Regardless of device structures (conventional and inverted types), the planar heterojunction PSCs employing CH3NH3PbI3-xClx g-perovskite films exhibit negligible hysteresis with a champion power conversion efficiency of 17.04% for TiO2-based conventional planar PSCs and 14.83% for poly(3,4-ethylenedioxythiophene:poly(styrenesulfonate) (PEDOT:PSS)-based inverted planar PSCs. Our results indicate that the crystalline phase purity in CH3NH3PbI3-xClx perovskite film, especially in the surface region, plays a crucial role in determining the hysteresis effect and device performance.

  4. Charge-coupled Substituted Garnets (Y3-xCa0.5xM0.5x)Fe5O12 (M = Ce, Th): Structure and Stability as Crystalline Nuclear Waste Forms

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Xiaofeng; Kukkadapu, Ravi K.; Lanzirotti, Anthony; Newville, Mathew; Engelhard, Mark H.; Sutton , Steven R.; Navrotsky, Alexandra

    2015-04-20

    The garnet structure has been proposed as a potential crystalline nuclear waste form for accommodation of actinide elements, especially uranium (U). In this study, yttrium iron garnet (YIG) as a model garnet host was studied for the incorporation of U analogs, cerium (Ce), and thorium (Th), incorporated by a charge-coupled substitution with calci-um (Ca) for yttrium (Y) in YIG, namely 2Y3+ = Ca2+ + M4+, where M4+ = Ce4+ or Th4+. Single phase garnets Y3-xCa0.5xM0.5xFe5O12, synthesized by the citrate-nitrate combustion method, were obtained up to x = 0.7. Ce was confirmed to be tetravalent by X-ray absorption spectroscopy and X-ray photoelectron spectroscopy. X-ray diffraction and 57Fe-Mössbauer spectroscopy indicated that the samples are single phase, M4+ and Ca2+ cations are restricted to the c-site, the nature of M4+ has only a minor effect on the structure, and the local environments of both the tetrahedral and octahedral Fe3+ are systematically affected by the extent of substitution, especially on the tetrahedral sublattice. The charge coupled substitution has advantages in incorporating Ce/Th and in stabilizing the substituted phases, compared to a single substitution strategy. Enthalpies of formation of garnets were obtained by high temperature oxide melt solution calorimetry, and the enthalpies of substitution of Ce and Th were determined. The thermodynamic analysis demonstrates that the substituted garnets are entropically rather than energetically stabilized. This suggests that such garnets may form and persist in repositories at high temperature but might decompose near room temperature. These structural and thermodynamic findings shed light on possible incorporation of U in this garnet system.

  5. Detection of a minor amorphous phase in crystalline etoricoxib by dynamic mechanical analysis: comparison with Raman spectroscopy and modulated differential scanning calorimetry.

    Science.gov (United States)

    Clas, Sophie-Dorothee; Lalonde, Karine; Khougaz, Karine; Dalton, Chad R; Bilbeisi, Rana

    2012-02-01

    Detection and quantification of the amorphous phase of etoricoxib bulk drug substances, a selective cycloogenase-2 inhibitor used for the treatment of osteoarthritis, rheumatoid arthritis, and dental pain, was carried out using modulated differential scanning calorimetry (MDSC), dynamic mechanical analysis (DMA), and Raman spectroscopy. Detection of amorphous content in pharmaceutical powders by DMA is a special application of dynamic mechanical spectroscopy. DMA was found to be a sensitive technique, able to detect the presence of an amorphous phase in a crystalline phase at concentrations as low as 0.5%. The limit of detection (LOD) determined for DMA was 2.5%. In comparison, Raman spectroscopy and MDSC had LOD values of 2% and 5% amorphous, respectively.

  6. Cubic-to-monoclinic phase transition during the epitaxial growth of crystalline Gd2O3 films on Ge(001) substrates

    Science.gov (United States)

    Molle, Alessandro; Wiemer, Claudia; Bhuiyan, Md. Nurul Kabir; Tallarida, Grazia; Fanciulli, Marco; Pavia, Giuseppe

    2007-05-01

    Thin crystalline films of Gd2O3 are grown on an atomically flat Ge(001) surface by molecular beam epitaxy and are characterized in situ by reflection high energy electron diffraction and x-ray photoelectron spectroscopy, and ex situ by x-ray diffraction (XRD), atomic force microscopy (AFM), and transmission electron microscopy. The first stage of the growth corresponds to a cubic (110) structure, with two equiprobable, 90° rotated, in-plane domains. Increasing the thickness of the films, a phase transition from cubic (110) to monoclinic (100) oriented crystallites is observed which keeps the in-plane domain rotation, as evidenced by XRD and AFM.

  7. Potential of ITO nanoparticles formed by hydrogen treatment in PECVD for improved performance of back grid contact crystalline silicon solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Mandal, Sourav; Mitra, Suchismita; Dhar, Sukanta; Ghosh, Hemanta; Banerjee, Chandan, E-mail: chandanbanerjee74@gmail.com; Datta, Swapan K.; Saha, Hiranmoy

    2015-09-15

    Highlights: • Indium tin oxide (ITO) nanoparticles as back scatterers in c-Si solar cells. • ITO NP have comparatively low dissipative losses and tunable optical properties. • ITO NP formed by hydrogen plasma treatment on sputtered ITO film. • Enhanced absorption and carrier collection at longer wavelengths due to enhanced light trapping. - Abstract: This paper discusses the prospect of using indium tin oxide (ITO) nanoparticles as back scatterers in crystalline silicon solar cells instead of commonly used metal nanoparticles as ITO nanoparticles have comparatively low dissipative losses and tunable optical properties. ITO nanoparticles of ∼5–10 nm size is developed on the rear side of the solar cell by deposition of ∼5–10 nm thick ITO layer by DC magnetron sputtering followed by hydrogen treatment in PECVD. The silicon solar cell is fabricated in the laboratory using conventional method with grid metal contact at the back surface. Various characterizations like FESEM, TEM, AFM, XRD, EQE and IV characteristics are performed to analyze the morphology, chemical composition, optical characteristics and electrical performance of the device. ITO nanoparticles at the back surface of the solar cell significantly enhances the short circuit current, open circuit voltage and efficiency of the solar cell. These enhancements may be attributed to the increased absorption and carrier collection at longer wavelengths of solar spectrum due to enhanced light trapping by the ITO nanoparticles and surface passivation by the hydrogen treatment of the back surface.

  8. Thermal and structural studies of imidazolium-based ionic liquids with and without liquid-crystalline phases: the origin of nanostructure.

    Science.gov (United States)

    Nemoto, Fumiya; Kofu, Maiko; Yamamuro, Osamu

    2015-04-16

    To clarify the origin of the nanostructure of ionic liquids (ILs), we have investigated two series of ILs 1-alkyl-3-methylimidazolium hexafluorophosphate (CnmimPF6, n = 4-16, n is an alkyl-carbon number) and 1-alkyl-3-methylimidazolium chloride (CnmimCl, n = 4-14) using differential scanning calorimetry and X-ray diffraction techniques. The PF6 samples with n > 13 and the Cl samples with n > 10 exhibited the liquid-crystalline (LC) to liquid (L) phase transitions, as reported before. We found that both samples with smaller n also exhibited the LC to L transitions under supercooled states as far as the ionic motions were not frozen-in at the glass transition temperatures Tg. The Tg of the LC phase was close to that of the L phase, indicating that the characteristic length of the glass transition is shorter than that of the nanostructure. A low-Q peak due to the nanostructure in the L phase and a diffraction peak due to the layer structure in the LC phase appeared at almost the same Q positions in both samples. On the basis of the above results and some thermodynamic analysis, we argue that the nanostructures of ILs are essentially the same as the layer structures in the LC phases.

  9. Primordial hexagonal phase formation during the bcc dezincification of the {beta} Cu-Zn single crystalline surface: Matrix instabilization and transformation path

    Energy Technology Data Exchange (ETDEWEB)

    Baruj, A. [Centro Atomico Bariloche and Instituto Balseiro, Comision Nacional de Energia Atomica (CNEA), (8400) San Carlos de Bariloche, Rio Negro (Argentina); CONICET (Argentina)], E-mail: baruj@cab.cnea.gov.ar; Granada, M.; Arneodo Larochette, P. [Centro Atomico Bariloche and Instituto Balseiro, Comision Nacional de Energia Atomica (CNEA), (8400) San Carlos de Bariloche, Rio Negro (Argentina); CONICET (Argentina); Sommadossi, S. [F. Ingenieria, U. N. Comahue, Buenos Aires 1400, (8300) Neuquen (Argentina); CONICET (Argentina); Troiani, H.E. [Centro Atomico Bariloche and Instituto Balseiro, Comision Nacional de Energia Atomica (CNEA), (8400) San Carlos de Bariloche, Rio Negro (Argentina); CONICET (Argentina)

    2009-07-29

    Subjecting Cu-Zn samples to annealing under dynamical vacuum produces the evaporation of Zn, a process known as dezincification. Here, we study the phase transitions related to dezincification of Cu-48 at.% Zn (bcc, Beta phase) single crystalline surfaces with residual stresses due to mechanical polishing. In order to identify different steps in the dezincification process of these deformed samples we apply a combination of in situ optical microscopy and transmission electron microscopy (TEM) observations. The former allows us to control and stop the dezincification process at a specific stage of evolution while the latter allows relating surface features with structure and composition changes. Due to dezincification, the formation of an on average 4H hexagonal phase and the fcc equilibrium phase take place. TEM observations show that the bcc to 4H phase transformation occurs by a mechanism of nucleation and growth. In particular, we show evidence of the mechanism of embryo formation for the first time. During the subsequent growth process, the coalescence of transformed zones defines regions in the micron range which after subsequent prolonged dezincification transform to the final fcc equilibrium structure. These experiments provide an insight on the reason for the formation of the non-equilibrium hexagonal phase during the dezincification of electropolished (non-deformed) samples. The new experimental results evidence the heterogeneous character of the dezincification.

  10. Synchrotron X-Ray Study of Novel Crystalline-B Phases in Heptyloxybenzylidene-Heptylaniline (70.7)

    DEFF Research Database (Denmark)

    Collet, J.; Sorensen, L. B.; Pershan, P. S.;

    1982-01-01

    This paper reports an x-ray diffraction study of structures and restacking transitions within the B phases of heptyloxybenzylidene-heptylaniline. The system evolves from a hexagonal close-packed structure, through intermediate orthorhombic and monoclinic phases, to a simple hexagonal structure. T....... The monoclinic phase has a temperature-dependent shear which transforms the system from orthorhombic to hexagonal. The latter three phases exhibit a single-q⃗ sinusoidal modulation of the molecular layers....

  11. Improved Cross Validation of a Static Ubiquitin Structure Derived from High Precision Residual Dipolar Couplings Measured in a Drug-Based Liquid Crystalline Phase

    OpenAIRE

    2014-01-01

    The antibiotic squalamine forms a lyotropic liquid crystal at very low concentrations in water (0.3-3.5% w/v), which remains stable over a wide range of temperature (1-40 °C) and pH (4-8). Squalamine is positively charged, and comparison of the alignment of ubiquitin relative to 36 previously reported alignment conditions shows that it differs substantially from most of these, but is closest to liquid crystalline cetyl pyridinium bromide. High precision residual dipolar couplings (RDCs) measu...

  12. Charge-coupled substituted garnets (Y3-xCa0.5xM0.5x)Fe5O12 (M = Ce, Th): structure and stability as crystalline nuclear waste forms.

    Science.gov (United States)

    Guo, Xiaofeng; Kukkadapu, Ravi K; Lanzirotti, Antonio; Newville, Matthew; Engelhard, Mark H; Sutton, Stephen R; Navrotsky, Alexandra

    2015-04-20

    The garnet structure has been proposed as a potential crystalline nuclear waste form for accommodation of actinide elements, especially uranium (U). In this study, yttrium iron garnet (YIG) as a model garnet host was studied for the incorporation of U analogs, cerium (Ce) and thorium (Th), incorporated by a charge-coupled substitution with calcium (Ca) for yttrium (Y) in YIG, namely, 2Y(3+) = Ca(2+) + M(4+), where M(4+) = Ce(4+) or Th(4+). Single-phase garnets Y3-xCa0.5xM0.5xFe5O12 (x = 0.1-0.7) were synthesized by the citrate-nitrate combustion method. Ce was confirmed to be tetravalent by X-ray absorption spectroscopy and X-ray photoelectron spectroscopy. X-ray diffraction and (57)Fe-Mössbauer spectroscopy indicated that M(4+) and Ca(2+) cations are restricted to the c site, and the local environments of both the tetrahedral and the octahedral Fe(3+) are systematically affected by the extent of substitution. The charge-coupled substitution has advantages in incorporating Ce/Th and in stabilizing the substituted phases compared to a single substitution strategy. Enthalpies of formation of garnets were obtained by high temperature oxide melt solution calorimetry, and the enthalpies of substitution of Ce and Th were determined. The thermodynamic analysis demonstrates that the substituted garnets are entropically rather than energetically stabilized. This suggests that such garnets may form and persist in repositories at high temperature but might decompose near room temperature.

  13. Improved Josephson Qubits incorporating Crystalline Silicon Dielectrics

    Science.gov (United States)

    Gao, Yuanfeng; Maurer, Leon; Hover, David; Patel, Umeshkumar; McDermott, Robert

    2010-03-01

    Josephson junction phase quibts are a leading candidate for scalable quantum computing in the solid state. Their energy relaxation times are currently limited by microwave loss induced by a high density of two-level state (TLS) defects in the amorphous dielectric films of the circuit. It is expected that the integration of crystalline, defect-free dielectrics into the circuits will yield substantial improvements in qubit energy relaxation times. However, the epitaxial growth of a crystalline dielectric on a metal underlayer is a daunting challenge. Here we describe a novel approach in which the crystalline silicon nanomembrane of a Silicon-on-Insulator (SOI) wafer is used to form the junction shunt capacitor. The SOI wafer is thermocompression bonded to the device wafer. The handle and buried oxide layers of the SOI are then etched away, leaving the crystalline silicon layer for subsequent processing. We discuss device fabrication issues and present microwave transport data on lumped-element superconducting resonators incorporating the crystalline silicon.

  14. Synthesis, characterization and structural control of nano crystalline molybdenum oxide MoO{sub 3} single phase by low cost technique

    Energy Technology Data Exchange (ETDEWEB)

    Afify, H.H.; Hassan, S.A. [Solid State Department, Physics Division, National Research Centre, 33 El Bohouthst. (fromer El Tahrirst.), Dokki, P.O. 12622, Giza (Egypt); Abouelsayed, A., E-mail: as.abouelsayed@gmail.com [Spectroscopy Department, Physics Division, National Research Centre, 33 El Bohouthst. (fromer El Tahrirst.), Dokki, P.O. 12622, Giza (Egypt); Demian, S.E. [Solid State Department, Physics Division, National Research Centre, 33 El Bohouthst. (fromer El Tahrirst.), Dokki, P.O. 12622, Giza (Egypt); Zayed, H.A. [Physics Department, Faculty of Girls for Art, Sciences and Education, Ain Shams University (Egypt)

    2016-06-15

    Thermodynamically stable α- MoO{sub 3} thin film is prepared without any other phases of the molybdenum oxides. Simple and low coast spray pyrolysis technique is used. Growth conditions are optimized to produce pure α- MoO{sub 3} with controlled crystallite size and surface morphology. Small angle (GAXRD) diffractometer is used to elucidate the structure. Profile shape function (PSF) model is made for the experimental data. WinFit software is going first to fit (PSF) to use the refined profile parameters for determination of crystallite size and internal residual strain. The (GAXRD) patterns prove the existence of α- MoO{sub 3} only with layered structure, indicated by the appearance of only (0k0). The calculated crystallite sizes and the strain are found to range from 10 to 28 nm and 0.28%–0.05% respectively. Ultraviolet and Visible transmission measurements were performed over a wavelength range 190–2500 nm on the MoO{sub 3} thin films synthesized by spray pyrolysis technique at different substrate temperature. The two sub-bands corresponds to the electronic transition between the molybdenum oxidation states Mo{sup 4+}, Mo{sup 5+} and Mo{sup 6+} are observed. Quantitative information on the temperature-induced blue shift of the sub-bands was obtained by fitting the spectra with Lorentz functions. The transition from Mo{sup 5+} to Mo{sup 6+} oxidation states show a blue shift up to Tc = 325 °C. Above Tc, the transition Mo{sup 5+} to Mo{sup 6+} increases more drastically, resulting in an anomaly in the temperature-induced shift at Tc. The anomaly can be attributed to the amorphous-to-crystalline phase transition at 325 °C. In addition, both refractive index and extinction coefficient are calculated as a function of substrate temperature. - Highlights: • Single phase α-MoO{sub 3} nano crystalline MoO{sub 3} thin films have been synthesized. • Amorphous-to-crystalline phase transition occurs at 325 °C for MoO{sub 3} thin films. • A clear

  15. Noether-Form Invariance of Nonholonomic Controllable Mechanical Systems in Phase Space

    Institute of Scientific and Technical Information of China (English)

    XIA Li-Li; LI Yuan-Cheng

    2007-01-01

    In this paper, we study the Noether-form invariance of nonholonomic mechanical controllable systems in phase space. Equations of motion of the controllable mechanical systems in phase space are presented. The definition and the criterion for this system are presented. A new conserved quantity and the Noether conserved quantity deduced from the Noether-form invariance are obtained. An example is given to illustrate the application of the results.

  16. Thermodynamics of Crystalline States

    CERN Document Server

    Fujimoto, Minoru

    2010-01-01

    Thermodynamics is a well-established discipline of physics for properties of matter in thermal equilibrium surroundings. Applying to crystals, however, the laws encounter undefined properties of crystal lattices, which therefore need to be determined for a clear and well-defined description of crystalline states. Thermodynamics of Crystalline States explores the roles played by order variables and dynamic lattices in crystals in a wholly new way. This book is divided into three parts. The book begins by clarifying basic concepts for stable crystals. Next, binary phase transitions are discussed to study collective motion of order variables, as described mostly as classical phenomena. In the third part, the multi-electron system is discussed theoretically, as a quantum-mechanical example, for the superconducting state in metallic crystals. Throughout the book, the role played by the lattice is emphasized and examined in-depth. Thermodynamics of Crystalline States is an introductory treatise and textbook on meso...

  17. Crystallization and Characterization of Galdieria sulphuraria RUBISCO in Two Crystal Forms: Structural Phase Transition Observed in P21 Crystal Form

    Directory of Open Access Journals (Sweden)

    Boguslaw Stec

    2007-10-01

    Full Text Available We have isolated ribulose-1,5-bisphosphate-carboxylase/oxygenase (RUBISCOfrom the red algae Galdieria Sulphuraria. The protein crystallized in two different crystalforms, the I422 crystal form being obtained from high salt and the P21 crystal form beingobtained from lower concentration of salt and PEG. We report here the crystallization,preliminary stages of structure determination and the detection of the structural phasetransition in the P21 crystal form of G. sulphuraria RUBISCO. This red algae enzymebelongs to the hexadecameric class (L8S8 with an approximate molecular weight 0.6MDa.The phase transition in G. sulphuraria RUBISCO leads from two hexadecamers to a singlehexadecamer per asymmetric unit. The preservation of diffraction power in a phasetransition for such a large macromolecule is rare.

  18. Field-Induced Crystalline-to-Amorphous Phase Transformation on the Si Nano-Apex and the Achieving of Highly Reliable Si Nano-Cathodes

    Science.gov (United States)

    Huang, Yifeng; Deng, Zexiang; Wang, Weiliang; Liang, Chaolun; She, Juncong; Deng, Shaozhi; Xu, Ningsheng

    2015-05-01

    Nano-scale vacuum channel transistors possess merits of higher cutoff frequency and greater gain power as compared with the conventional solid-state transistors. The improvement in cathode reliability is one of the major challenges to obtain high performance vacuum channel transistors. We report the experimental findings and the physical insight into the field induced crystalline-to-amorphous phase transformation on the surface of the Si nano-cathode. The crystalline Si tip apex deformed to amorphous structure at a low macroscopic field (0.6~1.65 V/nm) with an ultra-low emission current (1~10 pA). First-principle calculation suggests that the strong electrostatic force exerting on the electrons in the surface lattices would take the account for the field-induced atomic migration that result in an amorphization. The arsenic-dopant in the Si surface lattice would increase the inner stress as well as the electron density, leading to a lower amorphization field. Highly reliable Si nano-cathodes were obtained by employing diamond like carbon coating to enhance the electron emission and thus decrease the surface charge accumulation. The findings are crucial for developing highly reliable Si-based nano-scale vacuum channel transistors and have the significance for future Si nano-electronic devices with narrow separation.

  19. Fluorine-containing triphenylenes. Liquid crystalline properties and surface ordering

    NARCIS (Netherlands)

    Umesh, C.P.; Marcelis, A.T.M.; Zuilhof, H.

    2014-01-01

    The synthesis and liquid crystalline properties of two novel series of triphenylenes with 4 or 5 pentafuoropentyloxy tails and 1 or 2 alkoxy tails of varying length are reported. All compounds form wide-range hexagonal columnar phases. The isotropisation temperatures and the corresponding enthalpy

  20. Pressure-induced lattice collapse in the tetragonal phase of single-crystalline Fe(1.05)Te

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Chao [Beijing National Laboratory for Condensed Matter Physics/Chinese Academy of Scie; Yi, Wei [Beijing National Laboratory for Condensed Matter Physics/Chinese Academy of Scie; Sun, Liling [Beijing National Laboratory for Condensed Matter Physics/Chinese Academy of Scie; Chen, Xiao-Jia [Carnegie Institution of Washington; Hemley, Russell [Carnegie Institution of Washington; Mao, Ho-Kwang [Carnegie Institution of Washington; Lu, Wei [Beijing National Laboratory for Condensed Matter Physics/Chinese Academy of Scie; Dong, Xiaoli [Beijing National Laboratory for Condensed Matter Physics/Chinese Academy of Scie; Ligang, Bai [Institute of High Energy Physics, Chinese Academy of Sciences, China; Jing, Liu [Institute of High Energy Physics, Chinese Academy of Sciences, China; Moreira Dos Santos, Antonio F [ORNL; Molaison, Jamie J [ORNL; Tulk, Christopher A [ORNL; Chen, Genfu [Beijing National Laboratory for Condensed Matter Physics/Chinese Academy of Scie; Wang, Nanlin [The Institute of Physics, Chinese Academy of Sciences; Zhao, Zhongxian [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics

    2009-01-01

    Pressure-induced lattice collapse was discovered in tetragonal T phase of single crystal Fe{sub 1.05}Te at room temperature through x-ray and neutron-diffraction measurements. A remarkable compression along the c axis {approx}5% was observed upon increasing pressure from the ambient condition to 4 GPa. Indexed results demonstrate that the crystallographic structure remains unchanged after the collapse, revealing that the collapse does not break symmetry of crystal structure. The Fe-spin state change was proposed to account for the lattice collapse. The equations of state for the T phase and pressure-induced collapsed T phase were determined from the diffraction measurements.

  1. Magnetic and magnetothermal properties and the magnetic phase diagram of high purity single crystalline terbium along the easy magnetization direction.

    Science.gov (United States)

    Zverev, V I; Tishin, A M; Chernyshov, A S; Mudryk, Ya; Gschneidner, K A; Pecharsky, V K

    2014-02-12

    The magnetic and magnetothermal properties of a high purity terbium single crystal have been re-investigated from 1.5 to 350 K in magnetic fields ranging from 0 to 75 kOe using magnetization, ac magnetic susceptibility and heat capacity measurements. The magnetic phase diagram has been refined by establishing a region of the fan-like phase broader than reported in the past, by locating a tricritical point at 226 K, and by a more accurate definition of the critical fields and temperatures associated with the magnetic phases observed in Tb.

  2. Phase diagram of one-patch colloids forming tubes and lamellae.

    Science.gov (United States)

    Preisler, Zdenek; Vissers, Teun; Smallenburg, Frank; Munaò, Gianmarco; Sciortino, Francesco

    2013-08-15

    We numerically calculate the equilibrium phase diagram of one-patch particles with 30% patch coverage. It has been previously shown that in the fluid phase these particles organize into extremely long tubelike aggregates (G. Munaò et al. Soft Matter 2013, 9, 2652). Here, we demonstrate by means of free-energy calculations that such a disordered tube phase, despite forming spontaneously from the fluid phase below a density-dependent temperature, is always metastable against a lamellar crystal. We also show that a crystal of infinitely long packed tubes is thermodynamically stable, but only at high pressure. The full phase diagram of the model, beside the fluid phase, displays four different stable crystals. A gas-liquid critical point, and hence a liquid phase, is not detected.

  3. Hexagonal Close-Packed ^4{He} as Crystalline Multilayered Polytype: An Alternative for `Supersolid' or `Glassy-Like' Phase

    Science.gov (United States)

    Chishko, K. A.; Antsygina, T. N.; Poltavskaya, M. I.

    2017-01-01

    We apply the model of a crystalline polytype built of close-packed 2D monoatomic basal planes with triangular lattice to interpret the anomalous thermodynamical and mechanical properties of solid hexagonal close-packed (HCP) ^4{He} . The polytype is a 3D stack of the basal planes, and its structure can be built from the simplest periodic packing (HCP, FCC, 4H, 5H, 6R, ldots etc.) up to random stacking fault system (RSFS) totally aperiodic in only c-direction perpendicular to the basal planes. RSFS is a crystal without microscopic translation symmetry along c-axis, i.e., entirely disordered in only one spatial direction. Despite of packing disorder, c-direction remains the crystallographic axis of third order at arbitrary sequence of the 2D plates in the whole stack. In a long-wave limit the HCP polytype can be treated as 3D anisotropic continuum, as a result its phonon spectrum and Helmholtz free energy have been calculated. The temperature dependence of the phonon pressure is calculated theoretically and compared with experimental data. A quantitative agreement between the theory and the experiment is achieved. Mechanical properties of ^4{He} crystals in the framework of the polytype model are briefly discussed.

  4. Atomic-scale study of the amorphous-to-crystalline phase transition mechanism in GeTe thin films

    CERN Document Server

    Mantovan, R.; Mokhles Gerami, A.; Mølholt, T. E.; Wiemer, C.; Longo, M.; Gunnlaugsson, H. P.; Johnston, K.; Masenda, H.; Naidoo, D.; Ncube, M.; Bharuth-Ram, K.; Fanciulli, M.; Gislason, H. P.; Langouche, G.; Ólafsson, S.; Weyer, G.

    The underlying mechanism driving the structural amorphous-to-crystalline transition in Group VI chalcogenides is still a matter of debate even in the simplest GeTe system. We exploit the extreme sensitivity of 57Fe emission Mössbauer spectroscopy, following dilute implantation of 57Mn (T½ = 1.5 min) at ISOLDE/CERN, to study the electronic charge distribution in the immediate vicinity  of the 57Fe probe substituting Ge (FeGe), and to interrogate the local environment of FeGe over the amorphous-crystalline phase transition in GeTe thin films. Our results show that the local structure  of as-sputtered amorphous GeTe is a combination of tetrahedral and defect-octahedral sites. The main effect of the crystallization is the conversion from tetrahedral to defect-free octahedral sites.  We discover that only the tetrahedral fraction in amorphous GeTe participates to the change of the FeGe-Te chemical bond...

  5. Distinct molecular structures and hydrogen bond patterns of α,α-diethyl-substituted cyclic imide, lactam, and acetamide derivatives in the crystalline phase

    Science.gov (United States)

    Krivoshein, Arcadius V.; Ordonez, Carlos; Khrustalev, Victor N.; Timofeeva, Tatiana V.

    2016-10-01

    α,α-Dialkyl- and α-alkyl-α-aryl-substituted cyclic imides, lactams, and acetamides show promising anticonvulsant, anxiolytic, and anesthetic activities. While a number of crystal structures of various α-substituted cyclic imides, lactams, and acetamides were reported, no in-depth comparison of crystal structures and solid-state properties of structurally matched compounds have been carried out so far. In this paper, we report molecular structure and intermolecular interactions of three α,α-diethyl-substituted compounds - 3,3-diethylpyrrolidine-2,5-dione, 3,3-diethylpyrrolidin-2-one, and 2,2-diethylacetamide - in the crystalline phase, as studied using single-crystal X-ray diffraction and IR spectroscopy. We found considerable differences in the patterns of H-bonding and packing of the molecules in crystals. These differences correlate with the compounds' melting points and are of significance to physical pharmacy and formulation development of neuroactive drugs.

  6. Understanding the Crystallinity Indices Behavior of Burned Bones and Teeth by ATR-IR and XRD in the Presence of Bioapatite Mixed with Other Phosphate and Carbonate Phases

    Directory of Open Access Journals (Sweden)

    Giampaolo Piga

    2016-01-01

    Full Text Available We have critically investigated the ATR-IR spectroscopy data behavior of burned human teeth as opposed to the generally observed behavior in human bones that were subjected to heat treatment, whether deliberate or accidental. It is shown that the deterioration of the crystallinity index (CI behavior sometimes observed in bones subjected to high temperature appears to be of higher frequency in the case of bioapatite from teeth. This occurs because the formation of the β-tricalcium phosphate (β-TCP phase, otherwise known as whitlockite, clearly ascertained by the X-ray diffraction (XRD patterns collected on the same powdered specimens investigated by ATR-IR. These results point to the need of combining more than one physicochemical technique even if apparently well suitable, in order to verify whether the assumed conditions assessed by spectroscopy are fully maintained in the specimens after temperature and/or mechanical processing.

  7. Role of sintering time, crystalline phases and symmetry in the piezoelectric properties of lead-free KNN-modified ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Rubio-Marcos, F., E-mail: frmarcos@icv.csic.es [Electroceramic Department, Instituto de Ceramica y Vidrio, CSIC, Kelsen 5, 28049 Madrid (Spain); Marchet, P.; Merle-Mejean, T. [SPCTS, UMR 6638 CNRS, Universite de Limoges, 123, Av. A. Thomas, 87060 Limoges (France); Fernandez, J.F. [Electroceramic Department, Instituto de Ceramica y Vidrio, CSIC, Kelsen 5, 28049 Madrid (Spain)

    2010-09-01

    Lead-free KNN-modified piezoceramics of the system (Li,Na,K)(Nb,Ta,Sb)O{sub 3} were prepared by conventional solid-state sintering. The X-ray diffraction patterns revealed a perovskite phase, together with some minor secondary phase, which was assigned to K{sub 3}LiNb{sub 6}O{sub 17}, tetragonal tungsten-bronze (TTB). A structural evolution toward a pure tetragonal structure with the increasing sintering time was observed, associated with the decrease of TTB phase. A correlation between higher tetragonality and higher piezoelectric response was clearly evidenced. Contrary to the case of the LiTaO{sub 3} modified KNN, very large abnormal grains with TTB structure were not detected. As a consequence, the simultaneous modification by tantalum and antimony seems to induce during sintering a different behaviour from the one of LiTaO{sub 3} modified KNN.

  8. Crystalline products isolated from solutions with commercially available 2,3-bis(2-pyridyl)pyrazine (dpp) as reactant: Detection of a dimerized form of dpp

    Science.gov (United States)

    Grove, Hilde; Frøystein, Nils Åge; Sæthre, Leif J.; Sletten, Jorunn

    2006-12-01

    From reaction mixtures of commercially available 2,3-bis(2-pyridyl)pyrazine (dpp) and perchloric acid four different solid products have been isolated and structurally characterized by X-ray crystallography; (dppH 2)(ClO 4) 2·3H 2O ( 1), (dppH 2)(ClO 4) 2 ( 2), (ddppH 2)(ClO 4) 2 ( 3) and (dppH)(ClO 4) ( 4) (dppH is monoprotonated dpp, dppH 2 is the diprotonated dication of dpp, ddppH 2 is the dication 5,5'-bis(2,3-bis(2-pyridyl)pyrazinium), i.e. dimerized dppH). In 1 and 2 the nitrogen atom in both of the pyridyl rings in dpp is protonated. Hydrogen bonding and packing arrangements differ in the two compounds. In 3 a protonated and dimerized form of dpp is found; two 2,3-bis(2-pyridyl)pyrazinium units are connected by a C(sp 2) sbnd C(sp 2) bond in the 5-positions of the pyrazine rings, one pyridyl ring in each dpp moiety being protonated at the nitrogen. Strong intra-cation N sbnd H⋯N bonds between pyridyl rings are present. In 4 the monomeric dppH moieties display the same type of intramolecular hydrogen bonds as found in 3. Upon reacting dpp with copper(II) salts and oxalate, a dinuclear copper (II) complex, [Cu 2(ddpp)(ox) 2(H 2O) 2] (ddpp = 5,5'-bis(2,3-bis(2-pyridyl)pyrazine)), as well as mononuclear [Cu(dpp)(ox)(H 2O)] have been obtained in the same reaction mixtures. In one of the isolated crystalline products a dimer of dpp is found, as described in the case of compound 3, but no protonation has occurred. The crystal structure determination reveals a dinuclear complex with the neutral ddpp (dimerized dpp) as bridging ligand. Oxalate occurs as a bidentate, terminal ligand; water completes the copper coordination sphere. The dinuclear complex cocrystallizes with a mononuclear Cu-dpp-ox complex; in the mixed crystal two mononuclear units replace one dinuclear unit in 25% of the unit cells, thus the average formula is [Cu 2(ddpp)(ox) 2(H 2O) 2] 0.75[{Cu(dpp)(ox)(H 2O)} 2] 0.25·8H 2O ( 5). The monomeric species also crystallizes in the form of compound

  9. Electrical induction and optical erasure of birefringence in the isotropic liquid phase of a dichiral azobenzene liquid-crystalline compound (Presentation Recording)

    Science.gov (United States)

    Yamamoto, Takahiro; Nishiyama, Isa

    2015-10-01

    Liquid crystal is a representative soft matter, which has physical properties between those of conventional liquid and those of crystal in a temperature range above a melting point. A liquid-crystal display (LCD) employs the response of the liquid-crystal alignment to the electric field and is a key device of an information display. For common LCDs, the precise control of the initial alignment of LC molecules is needed so that a good dark state, thus a high contrast ratio, can be obtained. If the birefringence can be induced in the liquid phase by the application of electric field, it is of great use as a material for the LCD application. In this study, we will report a unique property of dichiral azobenzene liquid crystals: an electric induction of birefringence in a liquid phase of an antiferroelectric dichiral azobenzene liquid crystal. The optically isotropic texture changes into the homogenous birefringent texture by the application of the in-plane electric field above the clearing temperature of the liquid crystal. We find that one of the possible reasons of the induction of the birefringence in the isotropic phase is the electrically-induced increase of the phase transition temperature between the antiferroelectric liquid-crystalline and "liquid" phases, i.e., increase in the clearing temperature. The resulting birefringence can be disappeared by the irradiation of UV light, due to the photoinduced isomerization of the azobenzene compound, thus dual control of the birefringent structure, by the irradiation of light and/or by the application of the electric field, is achieved.

  10. Bietti's Crystalline Dystrophy

    Science.gov (United States)

    ... Dystrophy > Facts About Bietti's Crystalline Dystrophy Facts About Bietti's Crystalline Dystrophy This information was developed by the ... is the best person to answer specific questions. Bietti’s Crystalline Dystrophy Defined What is Bietti’s Crystalline Dystrophy? ...

  11. Crystalline systems. [Book chapter

    Energy Technology Data Exchange (ETDEWEB)

    Kispert, L.D.

    The use of two double resonance methods, electron-nuclear double resonance (ENDOR) and electron-electron double resonance (ELDOR) in the study of free radicals in solids is reviewed. Included are descriptions of how crystalline-phase ENDOR is used to determine small hyperfine splittings, quadrupoly couplings, and reaction mechanisms or radical formation and how crystalline phase ELDOR is used to determine large hyperfine splittings, to identify radicals with large quadrupole moments and to study spin exchange processes. The complementary role played by the ENDOR and ELDOR spectroscopy in the separation of overlapping EPR spectra, in the study of proton-deuterium exchange, in the study of methyl groups undergoing tunneling rotation, and in the determination of the rates of intermolecular motion are dealt with. 13 figures, 1 table. (DP)

  12. Thermodynamics of Crystalline States

    CERN Document Server

    Fujimoto, Minoru

    2013-01-01

    Thermodynamics is a well-established discipline of physics for properties of matter in thermal equilibrium with the surroundings. Applying to crystals, however, the laws encounter undefined properties of crystal lattice, which therefore need to be determined for a clear and well-defined description of crystalline states. Thermodynamics of Crystalline States explores the roles played by order variables and dynamic lattices in crystals in a wholly new way. The book begins by clarifying basic concepts for stable crystals. Next, binary phase transitions are discussed to study collective motion of order variables, as described mostly as classical phenomena. New to this edition is the examination of magnetic crystals, where magnetic symmetry is essential for magnetic phase transitions. The multi-electron system is also discussed  theoretically, as a quantum-mechanical example, for superconductivity in metallic crystals. Throughout the book, the role played by the lattice is emphasized and studied in-depth. Thermod...

  13. Theoretical study of phase behaviour of DLVO model for lysozyme and γ-crystalline aqueous electrolyte solutions

    Directory of Open Access Journals (Sweden)

    R. Melnyk

    2015-03-01

    Full Text Available Mean spherical approximation (MSA, second-order Barker-Henderson (BH perturbation theory and thermodynamic perturbation theory (TPT for associating fluids in combination with BH perturbation theory are applied to the study of the structural properties and phase behaviour of the Derjaguin-Landau-Verwey-Overbeek (DLVO model of lysozyme and γ-cristalline aqueous electrolyte solutions. Predictions of the MSA for the structure factors are in good agreement with the corresponding computer simulation predictions. The agreement between theoretical results for the liquid-gas phase diagram and the corresponding results of the experiment and computer simulation is less satisfactory, with predictions of the combined BH-TPT approach being the most accurate.

  14. Crystalline phase of Y2O3:Eu particles generated in a substrate-free flame process

    Institute of Scientific and Technical Information of China (English)

    Bing Guo; Hoon Yim; Wonjoong Hwang; Matt Nowell; Zhiping Luo

    2011-01-01

    In this study, factors affecting the crystal structure of flame-synthesized Y2O3:Eu particles were investigated, especially the particle size effect and its interaction with Eu doping concentration. Polydisperse Y2O3:Eu (size range 200nm to 3 μm) powder samples with Eu doping concentrations from 2.5 mol% to 25 mol% were generated in either H2/air or H2/O2 substrate-free flames. The crystal structure of the powder samples was determined by powder X-ray diffraction (XRD),which was complemented by photoluminescence (PL) measurements. Single particle crystal structure was determined by single particle selected area electron diffraction (SAED),and for the first time,by electron backscatter diffraction (EBSD).H2/air flames resulted in cubic phase Y2O3:Eu particles with hollow morphology and irregular shapes.Particles from H2/O2 flames had dense and spherical morphology; samples with lower Eu doping concentrations had mixed cubic/monoclinic phases: samples with the highest Eu doping concentrations were phase-pure monoclinic. For samples generated from H2/O2 flames,a particle size effect and its interaction with Eu doping concentration were found: particles smaller than a critical diameter had the monoclinic phase,and this critical diameter increased with increasing Eu doping concentration. These findings suggest that the formation of monoclinic Y2O3:Eu is inevitable when extremely hot substrate-free flames are used,because typical flame-synthesized Y2O3:Eu particle sizes are well below the critical diameter.However,it may be possible to generate particles with dense,spherical morphology and the desired cubic structure by using a moderately high flame temperature that enables fast sintering without melting the particles.

  15. Quasicritical behavior of the low-frequency dielectric permittivity in the isotropic phase of liquid crystalline materials.

    Science.gov (United States)

    Drozd-Rzoska, A; Rzoska, S J; Zioło, J; Jadzyn, J

    2001-05-01

    Results presented give evidence of the existence of quasicritical, fluidlike behavior in the isotropic phase of 4-cyano-4-pentyl-biphenyl (5CB) for frequencies ranging from the static to the ionic-dominated [low-frequency (LF)] region. Despite the boost of dielectric permittivity on lowering the frequency below 1 kHz, values of the isotropic-nematic transition discontinuity (approximately 1.1 K) and the critical exponent alpha (approximately 0.5) remain constant. It is shown that the contribution from residual ionic impurities is a linear function of temperature in the critical, prenematic fluctuation-dominated region. The validity of the fluidlike and critical behavior for LF dielectric permittivity confirmed results of a derivative analysis of the experimental data: d(epsilon)/dT proportional to (T-T*)(-alpha), originally proposed for critical mixtures. Results of a preliminary test in the isotropic phase of 4-decyl-4'-isothiocyanatobiphenyl (10BT), on approaching the smectic-E phase, may indicate a general validity of results obtained.

  16. Smooth/rough layering in liquid-crystalline/gel state of dry phospholipid film, in relation to its ability to generate giant vesicles

    CERN Document Server

    Hishida, M; Yoshikawa, K; Hishida, Mafumi; Seto, Hideki; Yoshikawa, Kenichi

    2005-01-01

    Morphological changes in a dry phospholipid film on a solid substrate were studied below and above the main transition temperature, between the gel and liquid-crystalline phases by phase-contrast microscopy and AFM. A Phospholipid film in the liquid-crystalline phase exhibits flat, smooth layering, whereas that in the gel phase shows rough, random layering. These film morphologies are discussed in relation to the ability to form giant vesicles through the natural swelling method.

  17. On the polymorphism of benzocaine; a low-temperature structural phase transition for form (II).

    Science.gov (United States)

    Chan, Eric J; Rae, A David; Welberry, T Richard

    2009-08-01

    A low-temperature structural phase transition has been observed for form (II) of benzocaine (BZC). Lowering the temperature doubles the b-axis repeat and changes the space group from P2(1)2(1)2(1) to P112(1) with gamma now 99.37 degrees. The structure is twinned, the twin rule corresponding to a 2(1) screw rotation parallel to a. The phase transition is associated with a sequential displacement parallel to a of zigzag bi-layers of ribbons perpendicular to b*. No similar phase transition was observed for form (I) and this was attributed to the different packing symmetries of the two room-temperature polymorphic forms.

  18. Effect of Ce2O3 on Structure, Viscosity, and Crystalline Phase of CaO-Al2O3-Li2O-Ce2O3 Slags

    Science.gov (United States)

    Qi, Jie; Liu, Chengjun; Zhang, Chi; Jiang, Maofa

    2017-02-01

    Aiming at devising new mold flux for Ce-bearing stainless steel, a fundamental investigation on the effect of Ce2O3 on properties of the CaO-Al2O3-Li2O-Ce2O3 slag was provided by the present work. The results show that adding Ce2O3 could decrease the viscosity of the slag due to its effects on decreasing the polymerization of the slag. The crystalline process was restrained by increasing the content of Ce2O3, and the crystalline phases also can be influenced by the slag structure. The crystalline phases were transferred from LiAlO2 and CaO to LiAlO2 and CaCeAlO4 with the addition of Ce2O3 to the slag, which could be well confirmed by the structure of the unit cell of the crystals.

  19. Final waste forms project: Performance criteria for phase I treatability studies

    Energy Technology Data Exchange (ETDEWEB)

    Gilliam, T.M. [Oak Ridge National Lab., TN (United States); Hutchins, D.A. [Martin Marietta Energy Systems, Inc., Oak Ridge, TN (United States); Chodak, P. III [Massachusetts Institute of Technology (United States)

    1994-06-01

    This document defines the product performance criteria to be used in Phase I of the Final Waste Forms Project. In Phase I, treatability studies will be performed to provide {open_quotes}proof-of-principle{close_quotes} data to establish the viability of stabilization/solidification (S/S) technologies. This information is required by March 1995. In Phase II, further treatability studies, some at the pilot scale, will be performed to provide sufficient data to allow treatment alternatives identified in Phase I to be more fully developed and evaluated, as well as to reduce performance uncertainties for those methods chosen to treat a specific waste. Three main factors influence the development and selection of an optimum waste form formulation and hence affect selection of performance criteria. These factors are regulatory, process-specific, and site-specific waste form standards or requirements. Clearly, the optimum waste form formulation will require consideration of performance criteria constraints from each of the three categories. Phase I will focus only on the regulatory criteria. These criteria may be considered the minimum criteria for an acceptable waste form. In other words, a S/S technology is considered viable only if it meet applicable regulatory criteria. The criteria to be utilized in the Phase I treatability studies were primarily taken from Environmental Protection Agency regulations addressed in 40 CFR 260 through 265 and 268; and Nuclear Regulatory Commission regulations addressed in 10 CFR 61. Thus the majority of the identified criteria are independent of waste form matrix composition (i.e., applicable to cement, glass, organic binders etc.).

  20. Gamma-irradiation effects to posttranslational modification and chaperon function of bovine {alpha}-crystalline

    Energy Technology Data Exchange (ETDEWEB)

    Hiroki, K; Matsumoto, S.; Awakura, M. [Kyoto Univ., Graduate School of Science, Kyoto (Japan); Fujii, N. [Kyoto Univ., Kumatori, Osaka (Japan). Research Reactor Inst

    2001-01-01

    The formation of D-asparate (D-Asp) in {alpha}A-crystallin of the aged human eye and the cataract crystalline lens has been reported. Crystalline lens keeps the transparency by forming {alpha}-crystallin which consists of a high order association of {alpha}A-and {alpha}B-crystallin. Bovine {alpha}-crystallin for investigating a chaperone function which protects the crystalline lens from getting to opaque or disordered agglutination with heat or light, is irradiated by gamma-ray (Co-60) at 0, 1, 2, 3, and 4 kGy, respectively. The irradiated bovine {alpha}-crystallin are analyzed with electrophoresis, gel permeation chromatograph, and UV absorption spectrometer for checking on the agglutination and the isomerization of macromolecules. Oxidation of methionine residues (Met-1) and isomerization of asparagine residues (Asp-151) in the {alpha}A-crystallin are ascertained in molecular levels with reversed phase liquid chromatography. The Met-1 oxidation and the Asp-151 isomerization depend on gamma-irradiation doses. It is thought that OH radical and H radical in water generated by the irradiation lead to the oxidation and the isomerization. Stereoinversion in the {alpha}-crystallin following to such a chemical change are considered to lead to the agglutination of polymer and the reduction of chaperon function. (M. Suetake)

  1. 宽温域蓝相液晶材料%Wide Temperature Range Blue Phase Liquid Crystalline Materials

    Institute of Scientific and Technical Information of China (English)

    何万里; 王玲; 王乐; 崔晓鹏; 谢谟文; 杨槐

    2012-01-01

    Blue phases (BPs) are mesophases usually exhibited by highly chiral materials and commonly occur in a narrow temperature range below the isotropic phase. They are optically active and non-birefringent, while exhibit Bragg diffraction of light in the visible wavelength. Recently, BPs have attracted growing attention in the field of optoelectronics and photonics. This paper reviews the recent research advances in BPs liquid crystals, also with a brief introduction of the history of the blue phase studies, and some special properties, especially the frustration in the double twist molecular alignment. Finally, the current challenges for applications of BPs materials are highlighted, and the focus of future research and development are proposed%蓝相常在高手性液晶体系的清亮点附近温度区间出现,由于具有优异的光学特性如无双折射现象和选择性反射可见光等,近年来蓝相在光电和光子领域越来越受到人们的关注。本文综述了蓝相的发现、分子排列和光学特性等,详细介绍了宽温域蓝相液晶材料在国内外的研究进展和应用现状。最后分析了蓝相液晶用于平板显示领域在技术方面存在的主要问题和未来发展方向。

  2. On the Evolution of Quasicrystalline and Crystalline Phases in Rapidly Quenched Al-Co-Cu-Ni Alloy

    OpenAIRE

    Yadav, T. P.; Mukhopadhyay, N. K.; Tiwari, R. S.; O. N. Srivastava

    2006-01-01

    The occurrence of stable decagonal quasicrystalline phase in Al-Co-Ni and Al-Cu-Co alloys through conventional solidification is well established. Earlier, we have studied the effect of Cu substitution in place of Co in the Al70 Co15Ni15 alloy. Here we report the structural/micro-structural changes with substitution of Cu for Ni in rapidly solidified Al-Co-Ni alloys. The melt-spun ribbons have been characterized using X-ray diffractometry (XRD), Scanning and transmission electron microscopy (...

  3. Fabrication of pure and Ag-doped TiO2 nanorods and study of the lattice strain and the activation energy of the crystalline phases

    Science.gov (United States)

    Riazian, Mehran; Rad, Shima Daliri; Azinabadi, Reza Ramezani

    2013-02-01

    TiO2 nanorods can be used as dye-sensitized solar cells and as various sensors and photocatalysts. These nanorods are synthesized by using a thermal corrosion process in a NaOH solution at 200 °C with TiO2 powder as a source material. In the present work, the synthesis of TiO2 nanorods in anatase, rutile and Ti8O15 phases and the synthesis of TiO2 nanorods by using the sol-gel method and alkaline corrosion to incorporate silver and silver-oxide dopants are reported. The morphologies and the crystalline structures of the TiO2 nanorods are characterized using field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), tunneling electron microscopy (TEM) and X-ray diffraction (XRD) techniques. The obtained results show an aggregation structure at high calcining temperatures with spherical particles and with Ti-O-Ti, Ti-O and Ag-O bonds. The effects of the chemical composition and the calcining temperature on the surface topography, lattice strain and phase crystallization are studied. The activation energy (E) of nanoparticle formation in a pure state during thermal treatment is calculated.

  4. Aqueous Two-Phase Systems formed by Biocompatible and Biodegradable Polysaccharides and Acetonitrile.

    Science.gov (United States)

    de Brito Cardoso, Gustavo; Souza, Isabela Nascimento; Pereira, Matheus M; Freire, Mara G; Soares, Cleide Mara Faria; Lima, Álvaro Silva

    2014-11-05

    In this work, it is shown that novel aqueous two-phase systems can be formed by the combination of acetonitrile and polysaccharides, namely dextran. Several ternary phase diagrams were determined at 25 °C for the systems composed of water + acetonitrile + dextran. The effect of the dextran molecular weight (6,000, 40,000 and 100,000 g.mol(-1)) was ascertained toward their ability to undergo liquid-liquid demixing. An increase in the dextran molecular weight favors the phase separation. Furthermore, the effect of temperature (25, 35 and 45 °C) was evaluated for the system constituted by the dextran of higher molecular weight. Lower temperatures are favorable for phase separation since lower amounts of dextran and acetonitrile are required for the creation of aqueous two-phase systems. In general, acetonitrile is enriched in the top phase while dextran is majorly concentrated in the bottom phase. The applicability of this new type of two-phase systems as liquid-liquid extraction approaches was also evaluated by the study of the partition behavior of a well-known antioxidant - vanillin - and used here as a model biomolecule. The optimized conditions led to an extraction efficiency of vanillin of 95% at the acetonitrile-rich phase.

  5. Investigation of the Influence of PLA Molecular Structure on the Crystalline Forms (α’ and α and Mechanical Properties of Wet Spinning Fibres

    Directory of Open Access Journals (Sweden)

    Michał Puchalski

    2017-01-01

    Full Text Available In this paper, the influence of the molecular structure of polylactide (PLA—characterised by its molar mass and content of d-lactide isomer—on the molecular ordering and α’–α form transition during fibre manufacturing by the wet spinning method is described. Fibres were studied by wide-angle X-ray diffraction (WAXD and differential scanning calorimetry (DSC. Additionally, the physical and mechanical properties of the fibres were determined. This study also examines the preliminary molecular ordering and crystallisation of PLA fibres at various draw ratios. The performed experiments clearly show the dependence of the molecular ordering of PLA on the molar mass and d-lactide content during the wet spinning process. The fibres manufactured from PLA with the lowest content of d-lactide and the lowest molar mass were characterised by a higher tendency for crystallisation and a higher possibility to undergo the disorder-to-order phase transition (α’ to α form. The structural changes in PLA explain the observed changes in the physical and mechanical properties of the obtained fibres.

  6. Paramagnetic defect centres in crystalline Alq{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Grecu, M N [National Institute for Materials Physics, POB MG-7, 077125 Magurele-Bucharest (Romania); Mirea, A [Experimental Physics II, Bayreuth University, 95440 Bayreuth (Germany); Ghica, C [National Institute for Materials Physics, POB MG-7, 077125 Magurele-Bucharest (Romania); Coelle, M [Philips Research, Laboratories, NL-5656 AA Eindhoven (Netherlands); Schwoerer, M [Experimental Physics II, Bayreuth University, 95440 Bayreuth (Germany)

    2005-10-05

    X- and Q-band electron paramagnetic resonance (EPR) investigation of different crystalline Alq{sub 3} (tris(8-hydroxyquinoline)aluminium (III)) fractions formed by a train sublimation method are reported. Several paramagnetic defect centres corresponding to 1/2, 1, and 3/2 spin are observed at room temperature. Their intensity is dependent on the temperature, nature of the crystalline phase, and preparation conditions. Spectra simulation and analysis based on the spin Hamiltonian appropriate to a high spin system (S{>=}1) suggest the existence of randomly oriented triplets and quartets in annealed Alq{sub 3} fractions. The crystalline Alq{sub 3} phases responsible for the EPR powder spectra have been identified by transmission electron microscopy measurements performed on these sample fractions.

  7. Initiating the Validation of CCIM Processability for Multi-phase all Ceramic (SYNROC) HLW Form: Plan for Test BFY14CCIM-C

    Energy Technology Data Exchange (ETDEWEB)

    Maio, Vince [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2014-08-01

    This plan covers test BFY14CCIM-C which will be a first–of–its-kind demonstration for the complete non-radioactive surrogate production of multi-phase ceramic (SYNROC) High Level Waste Forms (HLW) using Cold Crucible Induction Melting (CCIM) Technology. The test will occur in the Idaho National Laboratory’s (INL) CCIM Pilot Plant and is tentatively scheduled for the week of September 15, 2014. The purpose of the test is to begin collecting qualitative data for validating the ceramic HLW form processability advantages using CCIM technology- as opposed to existing ceramic–lined Joule Heated Melters (JHM) currently producing BSG HLW forms. The major objectives of BFY14CCIM-C are to complete crystalline melt initiation with a new joule-heated resistive starter ring, sustain inductive melting at temperatures between 1600 to 1700°C for two different relatively high conductive materials representative of the SYNROC ceramic formation inclusive of a HLW surrogate, complete melter tapping and pouring of molten ceramic material in to a preheated 4 inch graphite canister and a similar canister at room temperature. Other goals include assessing the performance of a new crucible specially designed to accommodate the tapping and pouring of pure crystalline forms in contrast to less recalcitrant amorphous glass, assessing the overall operational effectiveness of melt initiation using a resistive starter ring with a dedicated power source, and observing the tapped molten flow and subsequent relatively quick crystallization behavior in pans with areas identical to standard HLW disposal canisters. Surrogate waste compositions with ceramic SYNROC forming additives and their measured properties for inductive melting, testing parameters, pre-test conditions and modifications, data collection requirements, and sampling/post-demonstration analysis requirements for the produced forms are provided and defined.

  8. Beam Forming HF Radar Beam Pattern Measurements and Phase Offset Calibration Using a UAV

    Science.gov (United States)

    Cahl, D.; Voulgaris, G.

    2016-12-01

    It has been shown that measuring antenna patterns for direction finding radars improves surface current measurements. For beam forming radars, the beam pattern of the receive array is assumed to be similar to that derived using theoretical calculations. However, local environmental conditions may lead to deviations (i.e., larger sidelobes and beamwidth) from this idealized beam pattern. This becomes particularly important for wave measurements that are sensitive to interference from sidelobes. Common techniques for beam forming HF radar phase calibration include "cross calibration", using a secondary beam forming site as the signal source, or calibration using a ship. The former method is limited to only one direction; on straight coastlines this is often at a large angle from the radar bore site where the beam width and uncertainty in phase calibration might be large. The latter technique requires chartering a ship with an appropriate reflector or transmitter, or the identification of ships of opportunity. Recent advances in UAV technology combined with an easement of FAA restrictions (Part 107) allows phase calibrations and beam pattern measurements to be completed on an HF radar site using a small transmitter attached to a UAV. This presentation describes the use of a UAV and the development of a method for beam forming phase calibration and beam pattern measurements. This method uses the UAV as a moving signal source to provide true sidelobe and beamwidth measurements. Results are shown from a calibration carried out at a beam forming (WERA) radar site (8.3 MHz) located in Georgetown, SC and are compared with results from a cross calibration. Phase calibrations acquired by the UAV showed a dependence on azimuthal angle from the radar bore site. Also, the beam patterns obtained were found to be narrower than those derived using the stationary source method. The effect of the new phase values derived using this method on the accuracy of radial velocities will be

  9. Preparation of Porous Crystalline Spherical Titania under Atmospheric Liquid Phase Conditions%结晶二氧化钛多孔球的常压液相制备

    Institute of Scientific and Technical Information of China (English)

    申乾宏; 黎胜; 宗建娟; 杨辉

    2009-01-01

    Porous crystalline spherical titania was facilely prepared by treating the organic titanium precursor spheres with boiling water. The spherical titania was characterized by X-ray diffraction, scanning electron mi-croscopy and transmission electron microscopy. The probable mechanism for formation of anatase nanocrystal and the morphology change of precursor spheres was also discussed. The results demonstrate that extending the treating time in boiling water is helpful for the formation of porous structure as well as the crystallization of nanoparticles. With increasing in treating time, the surface of the procursor spheres become rougher and rougher, and the crys-tallinity of anatase titania improves gradually. The forming mechanism of porous structure and anatase nanoerystal is attributed to the complete in-situ hydrolysis and condensation of the organic titanium precursor spheres in boiling water.%利用沸水处理有机钛前驱体球较为便捷地制备出结晶二氧化钛多孔球,采用XRD、SEM和TEM对二氧化钛球进行表征,并探讨了二氧化钛球锐钛矿纳米晶形成以及形貌变化的机理.结果表明:延长沸水处理时间有利于多孔结构的形成和纳米粒子的晶化,随处理时间的增加,前驱体球表面变得越来越粗糙,二氧化钛结晶度也逐渐增强.其形成机理主要归因于沸水处理过程中有机钛前驱体球原位发生的完全水解和聚合.

  10. A fresh look at dense hydrogen under pressure. IV. Two structural models on the road from paired to monatomic hydrogen, via a possible non-crystalline phase.

    Science.gov (United States)

    Labet, Vanessa; Hoffmann, Roald; Ashcroft, N W

    2012-02-21

    In this paper, we examine the transition from a molecular to monatomic solid in hydrogen over a wide pressure range. This is achieved by setting up two models in which a single parameter δ allows the evolution from a molecular structure to a monatomic one of high coordination. Both models are based on a cubic Bravais lattice with eight atoms in the unit cell; one belongs to space group Pa3, the other to space group R3m. In Pa3 one moves from effective 1-coordination, a molecule, to a simple cubic 6-coordinated structure but through a very special point (the golden mean is involved) of 7-coordination. In R3m, the evolution is from 1 to 4 and then to 3 to 6-coordinate. If one studies the enthalpy as a function of pressure as these two structures evolve (δ increases), one sees the expected stabilization of minima with increased coordination (moving from 1 to 6 to 7 in the Pa3 structure, for instance). Interestingly, at some specific pressures, there are in both structures relatively large regions of phase space where the enthalpy remains roughly the same. Although the structures studied are always higher in enthalpy than the computationally best structures for solid hydrogen - those emerging from the Pickard and Needs or McMahon and Ceperley numerical laboratories - this result is suggestive of the possibility of a microscopically non-crystalline or "soft" phase of hydrogen at elevated pressures, one in which there is a substantial range of roughly equi-enthalpic geometries available to the system. A scaling argument for potential dynamic stabilization of such a phase is presented.

  11. Positronium diffusion in crystalline polyethylene

    Energy Technology Data Exchange (ETDEWEB)

    Serna, J. (Dept. de Fisica de Materiales, Univ. Complutense, Madrid (Spain))

    1990-12-16

    The analysis in four components of the positron lifetime spectra of nine different and structurally well characterised lamellar polyethylene samples has allowed to associate the two longest-lived components to positronium annihilation in the crystalline and amorphous phases. Further assumption on positronium tunneling through the interface between both phases, and a simple geometrical model, led to a value for the positronium diffusion coefficient in the crystalline phase of the order of 10{sup -4} cm{sup 2}/s. Interfaces have thicknesses around 1.5 nm and are shallow traps for positronium. (orig.).

  12. Looking for phase-space structures in star-forming regions: an MST-based methodology

    Science.gov (United States)

    Alfaro, Emilio J.; González, Marta

    2016-03-01

    We present a method for analysing the phase space of star-forming regions. In particular we are searching for clumpy structures in the 3D sub-space formed by two position coordinates and radial velocity. The aim of the method is the detection of kinematic segregated radial velocity groups, that is, radial velocity intervals whose associated stars are spatially concentrated. To this end we define a kinematic segregation index, tilde{Λ }(RV), based on the Minimum Spanning Tree graph algorithm, which is estimated for a set of radial velocity intervals in the region. When tilde{Λ }(RV) is significantly greater than 1 we consider that this bin represents a grouping in the phase space. We split a star-forming region into radial velocity bins and calculate the kinematic segregation index for each bin, and then we obtain the spectrum of kinematic groupings, which enables a quick visualization of the kinematic behaviour of the region under study. We carried out numerical models of different configurations in the sub-space of the phase space formed by the coordinates and the that various case studies illustrate. The analysis of the test cases demonstrates the potential of the new methodology for detecting different kind of groupings in phase space.

  13. Design of a ring resonator-based optical beam forming network for phased array receive antennas

    NARCIS (Netherlands)

    Klooster, van 't J.W.; Roeloffzen, C.G.H.; Meijerink, A.; Zhuang, L.; Marpaung, D.A.I.; Etten, van W.C.; Heideman, R.G.; Leinse, A.; Schippers, H.; Verpoorte, J.; Wintels, M.

    2008-01-01

    A novel squint-free ring resonator-based optical beam forming network (OBFN) for phased array antennas (PAA) is proposed. It is intended to provide broadband connectivity to airborne platforms via geostationary satellites. In this paper, we present the design of the OBFN and its control system. Our

  14. On some liquid crystalline phases exhibited by compounds made of bent-core molecules and their mixtures with rod-like molecules

    Indian Academy of Sciences (India)

    R Pratibha; N V Madhusudana; B K Sadashiva

    2003-08-01

    In most homologous series of compounds made of bent-core (BC) molecules, the B2, B1 and B6 phases occur as the chain length decreases. We have studied binary mixtures of the compound 1,3-phenylene bis[4-(3-methylbenzoyloxy)]4'--dodecylbiphenyl 4'-carboxylate (BC12) which exhibits the B2 phase with the compound 4-biphenylyl 4''--undecyloxybenzoate (BO11) made of rod-like (R) molecules. We find the above sequence of occurrence of the B phases with increasing concentration of BO11. In this paper we describe the physical origin for the formation of these phases in both pure compounds and in the mixtures. We have also found the occurrence of the biaxial smectic A phase when the BO11 concentration is increased to 87–95.5 mol%. We also report on another binary system composed of BC12 and 4--octyloxy 4'- cyanobiphenyl (8OCB) made of R molecules. This system exhibits the biaxial smectic A phase down to 30°C. Using polarized infrared spectroscopy we find that the mutual orientation of the R and BC molecules in the SmAdb liquid crystal is such that the arrow axes of the BC molecules are along the layer normal of the partial bilayer smectic structure formed by the rods. We also describe unusual growth patterns obtained when the nematic phase transforms to the SmAdb phase in a mixture with 24 mol% of BC12.

  15. Discovery of a Frank-Kasper sigma phase in sphere-forming block copolymer melts.

    Science.gov (United States)

    Lee, Sangwoo; Bluemle, Michael J; Bates, Frank S

    2010-10-15

    Sphere-forming block copolymers are known to self-assemble into body-centered cubic crystals near the order-disorder transition temperature. Small-angle x-ray scattering and transmission electron microscopy experiments on diblock and tetrablock copolymer melts have revealed an equilibrium phase characterized by a large tetragonal unit cell containing 30 microphase-separated spheres. This structure, referred to as the sigma (σ) phase by Frank and Kasper more than 50 years ago, nucleates and grows from the body-centered cubic phase similar to its occurrence in metal alloys and is a crystal approximant to dodecagonal quasicrystals. Formation of the σ phase in undiluted linear block copolymers (and certain branched dendrimers) appears to be mediated by macromolecular packing frustration, an entropic contribution to the interparticle interactions that control the sphere-packing geometry.

  16. A New, More Stable Polymorphic Form of Otilonium Bromide: Solubility, Crystal Structure, and Phase Transformation.

    Science.gov (United States)

    Vega, Daniel R; Halac, Emilia; Segovia, Luciano; Baggio, Ricardo

    2016-10-01

    A new polymorphic form of otilonium bromide is presented (Form I), and a thorough analysis of its crystal and molecular structure is performed. The compound suffers a temperature-driven first-order phase transition at about 396 K, which transforms it into the polymorph reported by Dapporto P and Sega A (Acta Cryst. 1986;C42:474-478) (Form II). Through thermal analysis and solubility experiments the relative stability of both crystal modifications were determined, confirming that at room temperature this new Form I is the more stable one, Form II existing just in a metastable state. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

  17. Current induced polycrystalline-to-crystalline transformation in vanadium dioxide nanowires

    Science.gov (United States)

    Jeong, Junho; Yong, Zheng; Joushaghani, Arash; Tsukernik, Alexander; Paradis, Suzanne; Alain, David; Poon, Joyce K. S.

    2016-11-01

    Vanadium dioxide (VO2) exhibits a reversible insulator-metal phase transition that is of significant interest in energy-efficient nanoelectronic and nanophotonic devices. In these applications, crystalline materials are usually preferred for their superior electrical transport characteristics as well as spatial homogeneity and low surface roughness over the device area for reduced scattering. Here, we show applied electrical currents can induce a permanent reconfiguration of polycrystalline VO2 nanowires into crystalline nanowires, resulting in a dramatically reduced hysteresis across the phase transition and reduced resistivity. Low currents below 3 mA were sufficient to cause the local temperature in the VO2 to reach about 1780 K to activate the irreversible polycrystalline-to-crystalline transformation. The crystallinity was confirmed by electron microscopy and diffraction analyses. This simple yet localized post-processing of insulator-metal phase transition materials may enable new methods of studying and fabricating nanoscale structures and devices formed from these materials.

  18. Magneto-thermal conduction and magneto-caloric effect in poly and nano crystalline forms of multiferroic GdCrO3

    Science.gov (United States)

    Uma, S.; Philip, J.

    2014-09-01

    Gadolinium chromite, GdCrO3, belongs to the family of rare earth chromites, exhibiting multiferroism with coupling between electric polarization and magnetic ordering. It is understood that the interaction between Gd3+ and Cr3+ ions is responsible for switchable polarization in this system. Below Néel temperature the spins of Cr3+ ions interact in anti-parallel through super exchange mechanism, giving rise to antiferromagnetic ordering at around 169 K in poly and nanocrystalline phases of this material. In order to understand the nature of spin-lattice coupling and magnon-phonon interaction in the intermediate temperature range (150-250 K), the magneto-thermal conduction and magneto-caloric effect in poly and nanocrystalline forms of this material are reported. These properties show anomalies around 169 K, which is described as due to spin-phonon coupling. When particle sizes are reduced to nanometer scales, thermal conductivity decreases significantly while specific heat capacity increases. The former is explained as due to reduction in phonon mean free path and phonon scattering from nanoparticle interfaces, while the latter is ascribed to contributions from Einstein oscillators at weakly bound atoms at the interfaces of nanocrystals.

  19. Ge Implantation to Improve Crystallinity and Productivity for Solid Phase Epitaxy Prepared by Atomic Mass Unit Cross Contamination-Free Technique

    Science.gov (United States)

    Lee, Kong-Soo; Yoo, Dae-Han; Han, Jae-Jong; Son, Gil-Hwan; Lee, Chang-Hun; Noh, Ju-Hee; Kim, Seok-Jae; Kim, Yong-Kwon; You, Young-Sub; Hyung, Yong-Woo; Lee, Hyeon-Deok

    2006-11-01

    Germanium (Ge) ion implantation was investigated for crystallinity enhancement during solid phase epitaxial (SPE) regrowth. Electron back-scatter diffraction (EBSD) measurement showed numerical increase of 19% of (100) signal, which might be due to the effect of pre-amorphization implantation (PAI) on silicon layer. On the other hand, electrical property such as off-leakage current of n-channel metal oxide semiconductor (NMOS) transistor degraded in specific regions of wafers. It was confirmed that arsenic (As) atoms were incorporated into channel area during Ge ion implantation. Since the equipment for Ge PAI was using several source gases such as BF3 and AsH3, atomic mass unit (AMU) contamination during PAI of Ge with AMU 74 caused the incorporation of As with AMU 75 which resided in arc-chamber and other parts of the equipment. It was effective to use Ge isotope of AMU 72 to suppress AMU contamination. It was effective to use enriched Ge source gas with AMU 72 in order to improve productivity.

  20. Terahertz and direct current losses and the origin of non-Drude terahertz conductivity in the crystalline states of phase change materials

    Science.gov (United States)

    Shimakawa, Koichi; Wagner, Tomas; Frumar, Miloslav; Kadlec, Filip; Kadlec, Christelle; Kasap, Safa

    2013-12-01

    THz and DC losses in crystalline states of GeSbTe and AgInSbTe phase-change material systems are re-examined and discussed. Although a simple free carrier transport has been assumed so far in the GeSbTe (GST) system, it is shown through recent experimental results that a series sequence of intragrain and intergrain (tunneling) transport, as recently formulated in Shimakawa et al., "The origin of non-Drude terahertz conductivity in nanomaterials," Appl. Phys. Lett. 100, 132102 (2012) may dominate the electronic transport in the commercially utilized GST system, producing a non-Drude THz conductivity. The extracted physical parameters such as the free-carrier density and mobility are significantly different from those obtained from the Drude law. These physical parameters are consistent with those obtained from the DC loss data, and provide further support for the model. Negative temperature coefficient of resistivity is found even in the metallic state, similar to amorphous metals, when the mean free path is short. It is shown that the concept of minimum metallic conductivity, often used in the metal-insulator transition, cannot be applied to electronic transport in these materials.

  1. Terahertz and direct current losses and the origin of non-Drude terahertz conductivity in the crystalline states of phase change materials

    Energy Technology Data Exchange (ETDEWEB)

    Shimakawa, Koichi [Department of General and Inorganic Chemistry, University of Pardubice, Pardubice (Czech Republic); Department of Electrical Engineering, Gifu University (Japan); Wagner, Tomas; Frumar, Miloslav [Department of General and Inorganic Chemistry, University of Pardubice, Pardubice (Czech Republic); Kadlec, Filip; Kadlec, Christelle [Institute of Physics, Academy of Sciences of the Czech Republic, Prague (Czech Republic); Kasap, Safa [Department of Electrical Engineering, University of Saskatchewan, Saskatoon SK S7N 5A9 (Canada)

    2013-12-21

    THz and DC losses in crystalline states of GeSbTe and AgInSbTe phase-change material systems are re-examined and discussed. Although a simple free carrier transport has been assumed so far in the GeSbTe (GST) system, it is shown through recent experimental results that a series sequence of intragrain and intergrain (tunneling) transport, as recently formulated in Shimakawa et al., “The origin of non-Drude terahertz conductivity in nanomaterials,” Appl. Phys. Lett. 100, 132102 (2012) may dominate the electronic transport in the commercially utilized GST system, producing a non-Drude THz conductivity. The extracted physical parameters such as the free-carrier density and mobility are significantly different from those obtained from the Drude law. These physical parameters are consistent with those obtained from the DC loss data, and provide further support for the model. Negative temperature coefficient of resistivity is found even in the metallic state, similar to amorphous metals, when the mean free path is short. It is shown that the concept of minimum metallic conductivity, often used in the metal-insulator transition, cannot be applied to electronic transport in these materials.

  2. Activated kinetics of the Crystalline to Nematic (K-N) and Nematic to Isotropic (N-I) phase transitions of Pentylcyanobiphenyl (5CB) liquid crystal

    Science.gov (United States)

    Sharma, Dipti

    2011-04-01

    Activated kinetics of the crystalline to Nematic (K-N) and the Nematic to Isotropic (N-I) phase transitions of the Pentylcyanobiphenyl (5CB) liquid crystal are discussed here. A kinetic comparison of the same types of transitions of other family member with higher number of carbon atoms i.e. Octylcyanobiphenyl (8CB) are also made to see the difference between the kinetic behavior of the above two transitions of the liquid crystals. Experiments were performed using high resolution calorimetric technique for heating and cooling runs. Two different scans i.e. Temperature scans and Rate scans were performed for 5CB and 8CB from 280 to 333 K at various rates to get the detailed behavior of the transitions. As a result, Double activation was observed for 5CB for two heating rate regimes whereas 8CB indicated single activation only. The 5CB has smaller enthalpy and entropy of the transitions and needs larger activation than 8CB. This kinetic change can be explained in terms of the length scale and mobility of the liquid crystal molecules.

  3. Evidence for variable crystallinity in bivalve shells

    Science.gov (United States)

    Jacob, D. E.; Wehrmeister, U.

    2012-04-01

    Bivalve shells are used as important palaeoclimate proxy archives and monitor regional climate variations. The shells mostly exist of two crystalline polymorphic phases of calcium carbonate calcite (rombohedric) and aragonite (orthorhombic). Calcite is the most stable polymorph at standard conditions, whereas vaterite (hexagonal) is the least stable and only rarely found in these structures. Shells are characterized by organized structures and several micro architectures of mollusc shell structures have been identified: Nacre shows different types: columnar and bricked forms and consists of composite inorganic- organic at the nano-scale. They are well known to display a "brick and mortar" structure. By AFM and FIB/TEM methods it could be shown, that its nanostructure consists of the structures in the range of 50 - 100 nm [1, 2]. These structures are vesicles, consisting of CaCO3 and are individually coated by a membrane. Most probably, the mantle epithelian cells of the bivalve extrude CaCO3 vesicles. By Raman spectroscopic investigations the crystalline CaCO3 polymorphs calcite, aragonite and vaterite, as well as ACC were determined. For some species (Diplodon chilensis patagonicus, Hyriopsis cumingii) pure ACC (i.e. not intermingled with a crystalline phase) could be identified. The presence of an amorphous phase is generally deduced from the lack of definite lattice modes, whereas a broad Raman band in this region is to observe. In most of the cultured pearls (Pinctada maxima and genus Hyriopsis) the ν1-Raman band of ACC clearly displays an asymmetric shape and splits into two different bands according to a nanocrystalline and an amorphous fraction. The FWHMs of most of the crystalline fractions are too high for well crystallized materials and support the assumption of nanocrystalline calcium carbonate polymorph clusters in ACC. They are primarily composed of amorphous calcium carbonate (ACC) which is later transformed into a crystalline modification [3

  4. Spin Forming Aluminum Crew Module (CM) Metallic Aft Pressure Vessel Bulkhead (APVBH) - Phase II

    Science.gov (United States)

    Hoffman, Eric K.; Domack, Marcia S.; Torres, Pablo D.; McGill, Preston B.; Tayon, Wesley A.; Bennett, Jay E.; Murphy, Joseph T.

    2015-01-01

    The principal focus of this project was to assist the Multi-Purpose Crew Vehicle (MPCV) Program in developing a spin forming fabrication process for manufacture of the Orion crew module (CM) aft pressure vessel bulkhead. The spin forming process will enable a single piece aluminum (Al) alloy 2219 aft bulkhead resulting in the elimination of the current multiple piece welded construction, simplify CM fabrication, and lead to an enhanced design. Phase I (NASA TM-2014-218163 (1)) of this assessment explored spin forming the single-piece CM forward pressure vessel bulkhead. The Orion MPCV Program and Lockheed Martin (LM) recently made two critical decisions relative to the NESC Phase I work scope: (1) LM selected the spin forming process to manufacture a single-piece aft bulkhead for the Orion CM, and (2) the aft bulkhead will be manufactured from Al 2219. Based on the Program's new emphasis related to the spin forming process, the NESC was asked to conduct a Phase II assessment to assist in the LM manufacture of the aft bulkhead and to conduct a feasibility study into spin forming the Orion CM cone. This activity was approved on June 19, 2013. Dr. Robert Piascik, NASA Technical Fellow for Materials at the Langley Research Center (LaRC), was selected to lead this assessment. The project plan was approved by the NASA Engineering and Safety Center (NESC) Review Board (NRB) on July 18, 2013. The primary stakeholders for this assessment were the NASA and LM MPCV Program offices. Additional benefactors are commercial launch providers developing CM concepts.

  5. Elements of style: consent form language and the therapeutic misconception in phase 1 gene transfer trials.

    Science.gov (United States)

    Kimmelman, Jonathan; Levenstadt, Aaron

    2005-04-01

    The therapeutic misconception arises wherever human subjects misinterpret the primary purpose of a clinical trial as therapeutic. Such misconceptions are particularly prevalent in trials involving severely ill subjects or novel and well-publicized investigational agents. In order to identify possible sources of the therapeutic misconception in gene transfer trials, 286 phase 1 human gene transfer consent documents were analyzed for their description of purpose, alternatives, and their use of the term gene transfer. We report that 20% of trials fail to explain their purpose as safety and dosage, only 41% of oncology trials identify comfort care as an alternative to participation, and that the term gene therapy is used with twice the frequency of the term gene transfer. Trends and coherence in consent form language were analyzed as well. Our results indicate that consent forms used in gene transfer phase 1 trials often contain language that promotes, or does little to deter, therapeutic misconceptions.

  6. Unified constitutive modelling for two-phase lamellar titanium alloys at hot forming conditions

    Directory of Open Access Journals (Sweden)

    Yang Lei

    2016-01-01

    Full Text Available In this paper, a set of mechanism based unified viscoplastic constitutive equations have been established for two-phase titanium alloys with initial lamellar microstructure, which models the softening mechanisms of the alloys in hot forming conditions. The dislocation density, rotation and globularization of lamellar α-phase and their effects on flow behaviour can also be modelled. The values of material constants in the equation set have been calibrated, according to stress-strain curves and globularization fractions of lamellar α-phase obtained from compression tests at a range of temperatures and strain rates, using a genetic algorithm (GA based optimisation method. Based on the determined constitutive equations, flow stress and globularization evolution of Ti-17 and TA15 alloys at different temperatures and strain rates were predicted. Good agreements between the experimental and computed results were obtained.

  7. Design and Implementation of a Beam Forming Network for a Phased Array Antenna

    Directory of Open Access Journals (Sweden)

    S. Devimeena

    2015-03-01

    Full Text Available This dissertation presents a beam forming network (BFN for phased array antenna-based on coherently radiating periodic structure (CORPS. The elements of CORPS are selected in such a way to obtain broad band characteristics, good return loss and good isolation between the radiating elements. These elements were arranged in such a way that the BFN naturally produces Gaussian amplitude. This methodology reduces the complexity of the conventional phased array design making it more flexible and minimizing the loss of energy inside the structure. A phase shifter design is proposed for the CORPS. The entire BFN’s sub-blocks have been designed for the frequency band of 5.925 GHz to 6.425 GHz, which find applications in communication satellite, fixed wireless systems.Defence Science Journal, Vol. 65, No. 1, January 2015, pp.46-52, DOI:http://dx.doi.org/10.14429/dsj.65.6940

  8. Studies of Nucleation and Growth, Specific Heat and Viscosity of Undercooled Melts of Quasicrystals and Polytetrahedral-Phase-Forming Alloys

    Science.gov (United States)

    Kelton, K. F.; Gangopadhyay, A. K.; Lee, G. W.; Hyers, R. W.; Rogers, J. R.; Robinson, M. B.; Rathz, T. J.; Krishnan, S.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    The local atomic structures of undercooled liquid metals are presumed to be icosahedral; this order is incompatible with translational periodicity, constituting a barrier to the nucleation of the crystal phase. The extended atomic structure of the icosahedral quasicrystal (i-phase) is similar to that presumed in the undercooled liquid. Therefore, a comparison of the maximum undercooling in alloys that form the i-phase with those that form crystal phases provides a probe of the liquid structure.

  9. Phase-space structures and stellar populations in the star-forming region NGC 2264

    Science.gov (United States)

    González, Marta; Alfaro, Emilio J.

    2017-02-01

    In this work, we analyse the structure of a subspace of the phase space of the star-forming region NGC 2264 using the spectrum of kinematic groupings (SKG). We show that the SKG can be used to process a collection of star data to find substructure at different scales. We have found structure associated with the NGC 2264 region and also with the background area. In the NGC 2264 region, a hierarchical analysis shows substructure compatible with that found in previous specific studies of the area but with an objective, compact methodology that allows us to homogeneously compare the structure of different clusters and star-forming regions. Moreover, this structure is compatible with the different ages of the main NGC 2264 star-forming populations. The structure found in the field can be roughly associated with giant stars far in the background, dynamically decoupled from NGC 2264, which could be related either with the Outer Arm or Monoceros Ring. The results in this paper confirm the relationship between structure in the radial velocity phase-space subspace and different kinds of populations, defined by other variables not necessarily analysed with the SKG, such as age or distance, showing the importance of detecting phase-space substructure in order to trace stellar populations in the broadest sense of the word.

  10. Looking for phase-space structures in star-forming regions: An MST-based methodology

    CERN Document Server

    Alfaro, Emilio J

    2015-01-01

    We present a method for analysing the phase space of star-forming regions. In particular we are searching for clumpy structures in the 3D subspace formed by two position coordinates and radial velocity. The aim of the method is the detection of kinematic segregated radial velocity groups, that is, radial velocity intervals whose associated stars are spatially concentrated. To this end we define a kinematic segregation index, $\\tilde{\\Lambda}$(RV), based on the Minimum Spanning Tree (MST) graph algorithm, which is estimated for a set of radial velocity intervals in the region. When $\\tilde{\\Lambda}$(RV) is significantly greater than 1 we consider that this bin represents a grouping in the phase space. We split a star-forming region into radial velocity bins and calculate the kinematic segregation index for each bin, and then we obtain the spectrum of kinematic groupings, which enables a quick visualization of the kinematic behaviour of the region under study. We carried out numerical models of different config...

  11. Improved cross validation of a static ubiquitin structure derived from high precision residual dipolar couplings measured in a drug-based liquid crystalline phase.

    Science.gov (United States)

    Maltsev, Alexander S; Grishaev, Alexander; Roche, Julien; Zasloff, Michael; Bax, Ad

    2014-03-12

    The antibiotic squalamine forms a lyotropic liquid crystal at very low concentrations in water (0.3-3.5% w/v), which remains stable over a wide range of temperature (1-40 °C) and pH (4-8). Squalamine is positively charged, and comparison of the alignment of ubiquitin relative to 36 previously reported alignment conditions shows that it differs substantially from most of these, but is closest to liquid crystalline cetyl pyridinium bromide. High precision residual dipolar couplings (RDCs) measured for the backbone (1)H-(15)N, (15)N-(13)C', (1)H(α)-(13)C(α), and (13)C'-(13)C(α) one-bond interactions in the squalamine medium fit well to the static structural model previously derived from NMR data. Inclusion into the structure refinement procedure of these RDCs, together with (1)H-(15)N and (1)H(α)-(13)C(α) RDCs newly measured in Pf1, results in improved agreement between alignment-induced changes in (13)C' chemical shift, (3)JHNHα values, and (13)C(α)-(13)C(β) RDCs and corresponding values predicted by the structure, thereby validating the high quality of the single-conformer structural model. This result indicates that fitting of a single model to experimental data provides a better description of the average conformation than does averaging over previously reported NMR-derived ensemble representations. The latter can capture dynamic aspects of a protein, thus making the two representations valuable complements to one another.

  12. REVERSE PHASE HIGH PERFORMANCE LIQUID CHROMATOGRAPHIC METHOD FOR THE ANALYSIS OF GLIPIZIDE IN PHARMACEUTICAL DOSAGE FORMS

    Directory of Open Access Journals (Sweden)

    Sheikh Rahila

    2010-12-01

    Full Text Available A rapid and sensitive reverse phase high performance liquid chromatographic methods depicted for the qualitative and quantitative assay of glipizide in pharmaceutical dosage forms. Glipizide was chromatographed on reverse phase C18 column with mobile phase consisting of 0.05 M Potassium Dihydrogen Orthophosphate: Methanol [15: 85 %v/v, pH 7.0 ± 0.05, adjusted with 1% Triethylamine]. The mobile phase was pumped at a flow rate 1 mL/min. Quantification was achieved by monitoring the ultraviolet absorbance at 225 ηm. The average retention time for Glipizide was found to be 3.21 ± 0.07. With this method, linearity was observed in the range of 10 – 2000 ηg/ml. The LOD and LOQ were found to be 5 ηg/ml and 15 ηg/ml respectively. The method was applicable for the analysis of drug in tablet formulation. The results of analysis were validated statistically.

  13. Iron oxyhydroxide nanoparticles formed by forced hydrolysis: dependence of phase composition on solution concentration.

    Science.gov (United States)

    Fu, Dong; Keech, Peter G; Sun, Xueliang; Wren, J Clara

    2011-11-07

    Nanoparticles of single-phase lepidocrocite (γ-FeOOH) and goethite (α-FeOOH) have been synthesized by forced hydrolysis of ferric nitrate with no other additives, and the particles have been characterized by XRD, FT-IR and TEM. At low Fe(NO(3))(3) concentrations the hydrolysis product is predominantly γ-FeOOH, while at high concentrations it is α-FeOOH. These particles are nanometers in size and fall within narrow particle size distributions. The dependence of the oxyhydoxide phase on ferric nitrate concentration is attributed to two thermodynamic factors, the enthalpy of formation and the surface enthalpy of hydration at the oxide-water interface (which is a function of surface area). Two potential mechanisms for the phase-specific growth are proposed that explain the solution concentration dependence of the phase formed. Three other common nanoscale particles (α-Fe(2)O(3), Fe(3)O(4) and γ-Fe(2)O(3)) have also been prepared by relatively simple thermal/chemical treatment of the γ-FeOOH nanoparticles.

  14. Study on polyethylene glycol/epoxy resin composite as a form-stable phase change material

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Yutang; Kang, Huiying; Wang, Weilong; Liu, Hong; Gao, Xuenong [The Key Laboratory of Enhanced Heat Transfer and Energy Conservation, Ministry of Education, South China University of Technology, Guangzhou 510640 (China)

    2010-12-15

    Form-stable polyethylene glycol (PEG)/epoxy resin (EP) composite as a novel phase change material (PCM) was prepared using casting molding method. In this new material, PEG acts as the latent heat storage material and EP polymer serves as the supporting material, which provides structural strength and prevents the leakage of the melted PEG. The structure and morphology of the novel composite were observed using Fourier transformation infrared spectroscope (FTIR) and scanning electronic microscope (SEM). The thermo-mechanical property and transition behavior were characterized by polarizing optical microscope (POM), static thermo-mechanical analysis (TMA) and differential scanning calorimeter (DSC). The experimental results show that, as a result of the physical tangled function of the epoxy resin carrier to the PEG segment, the composite macroscopically presents the solid-solid phase change characteristic. (author)

  15. Study on polyethylene glycol/epoxy resin composite as a form-stable phase change material

    Energy Technology Data Exchange (ETDEWEB)

    Fang Yutang, E-mail: ppytfang@scut.edu.c [Key Laboratory of Enhanced Heat Transfer and Energy Conservation, Ministry of Education, South China University of Technology, Guangzhou 510640 (China); Kang Huiying; Wang Weilong; Liu Hong; Gao Xuenong [Key Laboratory of Enhanced Heat Transfer and Energy Conservation, Ministry of Education, South China University of Technology, Guangzhou 510640 (China)

    2010-12-15

    Form-stable polyethylene glycol (PEG)/epoxy resin (EP) composite as a novel phase change material (PCM) was prepared using casting molding method. In this new material, PEG acts as the latent heat storage material and EP polymer serves as the supporting material, which provides structural strength and prevents the leakage of the melted PEG. The structure and morphology of the novel composite were observed using Fourier transformation infrared spectroscope (FTIR) and scanning electronic microscope (SEM). The thermo-mechanical property and transition behavior were characterized by polarizing optical microscope (POM), static thermo-mechanical analysis (TMA) and differential scanning calorimeter (DSC). The experimental results show that, as a result of the physical tangled function of the epoxy resin carrier to the PEG segment, the composite macroscopically presents the solid-solid phase change characteristic.

  16. Corrosion properties of S-phase layers formed on medical grade austenitic stainless steel.

    Science.gov (United States)

    Buhagiar, Joseph; Dong, Hanshan

    2012-02-01

    The corrosion properties of S-phase surface layers formed in AISI 316LVM (ASTM F138) and High-N (ASTM F1586) medical grade austenitic stainless steels by plasma surface alloying with nitrogen (at 430°C), carbon (at 500°C) and both carbon and nitrogen (at 430°C) has been investigated. The corrosion behaviour of the S-phase layers in Ringer's solutions was evaluated using potentiodynamic and immersion corrosion tests. The corrosion damage was evaluated using microscopy, hardness testing, inductive coupled plasma mass spectroscopy and X-ray diffraction. The experimental results have demonstrated that low-temperature nitriding, carburising and carbonitriding can improve the localised corrosion resistance of both industrial and medical grade austenitic stainless steels as long as the threshold sensitisation temperature is not reached. Carburising at 500°C has proved to be the best hardening treatment with the least effect on the corrosion resistance of the parent alloy.

  17. Subsolutions of Elliptic Operators in Divergence Form and Application to Two-Phase Free Boundary Problems

    Directory of Open Access Journals (Sweden)

    Sandro Salsa

    2006-12-01

    Full Text Available Let L be a divergence form operator with Lipschitz continuous coefficients in a domain Ω, and let u be a continuous weak solution of Lu=0 in {u≠0}. In this paper, we show that if φ satisfies a suitable differential inequality, then vφ(x=supBφ(x(xu is a subsolution of Lu=0 away from its zero set. We apply this result to prove C1,γ regularity of Lipschitz free boundaries in two-phase problems.

  18. PHASE STRUCTURE AND THERMAL BEHAVIOR OF LIQUID CRYSTALLINE MULTI-BLOCK COPOLYMERS,POLY[1,6-BIS(4-OXYBENZOYL-OXY)HEXANE TEREPHTHALATE]-b-BISPHENOL A POLYCARBONATE

    Institute of Scientific and Technical Information of China (English)

    Hui-qing Zhang; Xiong-yan Zhao; De-shan Liu; Qi-xiang Zhou

    1999-01-01

    Liquid crystalline multi-block copolymers poly[1,6-bis(4-oxybenzoyl-oxy)hexane terephthalate]-b-bisphenol A polycarbonate (PHTH-6-b-PC) with different segments of polycarbonate (PC) and thermotropic polyester PHTH-6 were synthesized in tetrachloroethane at 144~146℃. The influence of segment length on the resulting phase structure and thermal behavior of block copolymers was also discussed. It is demonstrated by TEM and DMA that the resulting block copolymers show a considerable microphase separation. The degree of phase separation and the thermal behavior of the block copolymers are strongly dependent on the molecular weight of the segments incorporated.

  19. A structural study of lamellar phases formed by nucleoside-functionalized lipids

    CERN Document Server

    Berti, D; Baglioni, P; Dante, S; Hauss, T

    2002-01-01

    We report a neutron-scattering investigation of lamellar phases formed by novel phospholipids bearing nucleosides at the polar-head-group region. These nucleolipids can interact through stacking and H-bond interactions, following a pattern that resembles base-base coupling in natural nucleic acids (DNA, RNA), i.e. they have similar recognition properties. Bilayer stacks formed of DPP-adenosine, DPP-uridine and their 1:1 mixture were investigated after equilibration in a 98% relative humidity atmosphere. The DPP-adenosine spectrum can be accounted for (in analogy to DPPC) by a lamellar phase with a smectic period of about 60 A. DPP-uridine displays a not so straightforward behavior that we have tentatively ascribed to the coexistence of lamellae with different smectic periods. In the 1:1 mixture the lamellar mesophase of DPP-uridine is retained, suggesting a specific interaction of the uridine polar-head group with the adenosine moiety of DPP-adenosine. It should be stressed that this behavior can be considere...

  20. A global sensitivity analysis of two-phase flow between fractured crystalline rock and bentonite with application to spent nuclear fuel disposal

    Science.gov (United States)

    Dessirier, Benoît; Frampton, Andrew; Jarsjö, Jerker

    2015-11-01

    Geological disposal of spent nuclear fuel in deep crystalline rock is investigated as a possible long term solution in Sweden and Finland. The fuel rods would be cased in copper canisters and deposited in vertical holes in the floor of deep underground tunnels, embedded within an engineered bentonite buffer. Recent experiments at the Äspö Hard Rock Laboratory (Sweden) showed that the high suction of unsaturated bentonite causes a de-saturation of the adjacent rock at the time of installation, which was also independently predicted in model experiments. Remaining air can affect the flow patterns and alter bio-geochemical conditions, influencing for instance the transport of radionuclides in the case of canister failure. However, thus far, observations and model realizations are limited in number and do not capture the conceivable range and combination of parameter values and boundary conditions that are relevant for the thousands of deposition holes envisioned in an operational final repository. In order to decrease this knowledge gap, we introduce here a formalized, systematic and fully integrated approach to study the combined impact of multiple factors on air saturation and dissolution predictions, investigating the impact of variability in parameter values, geometry and boundary conditions on bentonite buffer saturation times and on occurrences of rock de-saturation. Results showed that four parameters consistently appear in the top six influential factors for all considered output (target) variables: the position of the fracture intersecting the deposition hole, the background rock permeability, the suction representing the relative humidity in the open tunnel and the far field pressure value. The combined influence of these compared to the other parameters increases as one targets a larger fraction of the buffer reaching near-saturation. Strong interaction effects were found, which means that some parameter combinations yielded results (e.g., time to

  1. A global sensitivity analysis of two-phase flow between fractured crystalline rock and bentonite with application to spent nuclear fuel disposal.

    Science.gov (United States)

    Dessirier, Benoît; Frampton, Andrew; Jarsjö, Jerker

    2015-11-01

    Geological disposal of spent nuclear fuel in deep crystalline rock is investigated as a possible long term solution in Sweden and Finland. The fuel rods would be cased in copper canisters and deposited in vertical holes in the floor of deep underground tunnels, embedded within an engineered bentonite buffer. Recent experiments at the Äspö Hard Rock Laboratory (Sweden) showed that the high suction of unsaturated bentonite causes a de-saturation of the adjacent rock at the time of installation, which was also independently predicted in model experiments. Remaining air can affect the flow patterns and alter bio-geochemical conditions, influencing for instance the transport of radionuclides in the case of canister failure. However, thus far, observations and model realizations are limited in number and do not capture the conceivable range and combination of parameter values and boundary conditions that are relevant for the thousands of deposition holes envisioned in an operational final repository. In order to decrease this knowledge gap, we introduce here a formalized, systematic and fully integrated approach to study the combined impact of multiple factors on air saturation and dissolution predictions, investigating the impact of variability in parameter values, geometry and boundary conditions on bentonite buffer saturation times and on occurrences of rock de-saturation. Results showed that four parameters consistently appear in the top six influential factors for all considered output (target) variables: the position of the fracture intersecting the deposition hole, the background rock permeability, the suction representing the relative humidity in the open tunnel and the far field pressure value. The combined influence of these compared to the other parameters increases as one targets a larger fraction of the buffer reaching near-saturation. Strong interaction effects were found, which means that some parameter combinations yielded results (e.g., time to

  2. The GM1 Ganglioside Forms GM1-Rich Gel Phase Microdomains within Lipid Rafts

    Directory of Open Access Journals (Sweden)

    Lucia Becucci

    2014-07-01

    Full Text Available Mercury-supported, self-assembled monolayers (SAMs of the sole dioleoylphosphatidylcholine (DOPC and of a raft-forming mixture of DOPC, cholesterol (Chol and palmitoylsphingomyelin (PSM of (59:26:15 mol% composition, were investigated by electrochemical impedance spectroscopy (EIS, both in the absence and in the presence of the monosialoganglioside GM1. The impedance spectra of these four SAMs were fitted by a series of parallel combinations of a resistance and a capacitance (RC meshes and displayed on plots of ωZ′ against −ωZ″, where Z′ and Z″ are the in-phase and quadrature components of the impedance and ω is the angular frequency. A comparison among these different impedance spectra points to the formation of GM1-rich gel phase microdomains within the lipid rafts of the DOPC/Chol/PSM mixture, thanks to the unique molecular-level smooth support provided by mercury, which allows EIS to detect the protruding gel phase microdomains by averaging them over a macroscopically large area.

  3. Laser assisted conical spin forming of dual phase automotive steel. Experimental demonstration of work hardening reduction and forming limit extension

    Science.gov (United States)

    Romero, P.; Otero, N.; Cabrera, J. M.; Masagué, D.

    Laser Assisted Spin Forming is investigated for improving the poor formability of Advanced High Strength Steel DP-800 and Aeronautic Grade Titanium alloy, with minor or no change in microstructure, final properties improvements and no damage to coating, thanks to controlled energy input and fast thermal cycles. IR imaging and force-torque monitoring are used to characterise the forming process. Residual stress measurement, microstructure, microhardness and EBSD are used to study the formed parts under the combined action of laser and mechanical force. A micromechanism of laser assisted spinning is proposed, as well as advantages and limitations of the technique.

  4. Crystalline and Crystalline International Disposal Activities

    Energy Technology Data Exchange (ETDEWEB)

    Viswanathan, Hari S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Chu, Shaoping [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Reimus, Paul William [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Makedonska, Nataliia [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hyman, Jeffrey De' Haven [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Karra, Satish [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dittrich, Timothy M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-12-21

    This report presents the results of work conducted between September 2014 and July 2015 at Los Alamos National Laboratory in the crystalline disposal and crystalline international disposal work packages of the Used Fuel Disposition Campaign (UFDC) for DOE-NE’s Fuel Cycle Research and Development program.

  5. Phase-space structures and stellar populations in the star-forming region NGC~ 2264

    CERN Document Server

    Gonzalez, Marta

    2016-01-01

    In this work we analyse the structure of a subspace of the phase space of the star-forming region NGC~ 2264 using the Spectrum of Kinematic Groupings (SKG). We show that the SKG can be used to process a collection of star data to find substructure at different scales. We have found structure associated with the NGC~ 2264 region and also with the background area. In the NGC~ 2264 region, a hierarchical analysis shows substructure compatible with that found in previous specific studies of the area but with an objective, compact methodology that allows us to homogeneously compare the structure of different clusters and star-forming regions. Moreover, this structure is compatible with the different ages of the main NGC~ 2264 star-forming populations. The structure found in the field can be roughly associated with giant stars far in the background, dynamically decoupled from NGC~ 2264, which could be related either with the Outer Arm or Monoceros Ring. The results in this paper confirm the relationship between str...

  6. Effect of Flame Conditions on Crystalline Structure of TiO2 in Liquid Flame Spraying

    Institute of Scientific and Technical Information of China (English)

    LI Chang-jiu; YANG Guan-jun; WANG Yu-yue

    2004-01-01

    Nanostructured TiO2 is a most promising functional ceramic owing to its potential utilization in photocatalytical, optical and electrical applications. Nanostructured TiO2 coating was deposited through thermal spraying with liquid feedstock. Two types of crystalline structures were present in the synthesized TiO2 coating including anatase phase and rutile phase.The effect of spray flame conditions on the crystalline structure was investigated in order to control the crystalline structure of the coating. The results showed that spray distance, flame power and precursor concentration in the liquid feedstock significantly influenced phase constitutions and grain size in the coating. Anatase phase was formed at spray distance from 150 to 250mm, while rutile phase was evidently observed in the coating deposited at 100 mm. The results suggested that anatase phase was firstly formed in the coating, and rutile phase resulted from the transformation of the deposited anatase phase. The phase transformation from anatase to rutile occurred through the annealing effect of spraying flame. The control of the phase formation can be realized through flame condition and spray distance.

  7. Crystalline 'Genes' in Metallic Liquids

    CERN Document Server

    Sun, Yang; Ye, Zhuo; Fang, Xiaowei; Ding, Zejun; Wang, Cai-Zhuang; Mendelev, Mikhail I; Ott, Ryan T; Kramer, M J; Ho, Kai-Ming

    2014-01-01

    The underlying structural order that transcends the liquid, glass and crystalline states is identified using an efficient genetic algorithm (GA). GA identifies the most common energetically favorable packing motif in crystalline structures close to the alloy's Al-10 at.% Sm composition. These motifs are in turn compared to the observed packing motifs in the actual liquid structures using a cluster-alignment method which reveals the average topology. Conventional descriptions of the short-range order, such as Voronoi tessellation, are too rigid in their analysis of the configurational poly-types when describing the chemical and topological ordering during transition from undercooled metallic liquids to crystalline phases or glass. Our approach here brings new insight into describing mesoscopic order-disorder transitions in condensed matter physics.

  8. Influence of coupling with calculation of phase diagrams on microsegregation forming simulation of Al-4.5%Cu alloy

    Institute of Scientific and Technical Information of China (English)

    LIU Yong-gang; CHEN Guang; SUN Guo-xiong

    2006-01-01

    The effect of coupling with calculation of phase diagrams on microsegregation forming simulation was investigated. The traditional simplified phase diagram and calculated phase diagram were introduced into the numerical models respectively and simulation on microsegregation forming of the Al-4.5%Cu alloy ingot was also presented. The simulation results were both compared with the experiment results. The results show that the calculated sencondary arm spacing with these two kinds of phase diagram are almost the same because relationship between the coarsening model and the information of phase diagram is not close. The calculated eutectic phase volume fractions of different locations in the ingot coupled with different phase diagrams are discrepant. The calculated volume fractions are consistent with the experiment results when calculated phase diagram couples, but are far from the experiment results and obviously inacceptable when traditional simplified phase diagram couples. So, coupling with accurate calculated phase diagrams is very significant for microsegregation forming simulation since much information of the phase diagram is used in the models and it can improve the precision of simulation results.

  9. New disordering mode for TFSI- anions: the nonequilibrium, plastic crystalline structure of Et4NTFSI.

    Science.gov (United States)

    Henderson, Wesley A; Herstedt, Marie; Young, Victor G; Passerini, Stefano; De Long, Hugh C; Trulove, Paul C

    2006-02-20

    A new TFSI- anion disordering mode has been discovered in a supercooled plastic crystalline phase of Et4NTFSI, which may, in part, account for the low melting points of TFSI- salts with organic cations, thereby forming ionic liquids, and the intriguing properties of LiTFSI for lithium battery applications.

  10. A metastable liquid melted from a crystalline solid under decompression

    Science.gov (United States)

    Lin, Chuanlong; Smith, Jesse S.; Sinogeikin, Stanislav V.; Kono, Yoshio; Park, Changyong; Kenney-Benson, Curtis; Shen, Guoyin

    2017-01-01

    A metastable liquid may exist under supercooling, sustaining the liquid below the melting point such as supercooled water and silicon. It may also exist as a transient state in solid–solid transitions, as demonstrated in recent studies of colloidal particles and glass-forming metallic systems. One important question is whether a crystalline solid may directly melt into a sustainable metastable liquid. By thermal heating, a crystalline solid will always melt into a liquid above the melting point. Here we report that a high-pressure crystalline phase of bismuth can melt into a metastable liquid below the melting line through a decompression process. The decompression-induced metastable liquid can be maintained for hours in static conditions, and transform to crystalline phases when external perturbations, such as heating and cooling, are applied. It occurs in the pressure–temperature region similar to where the supercooled liquid Bi is observed. Akin to supercooled liquid, the pressure-induced metastable liquid may be more ubiquitous than we thought. PMID:28112152

  11. Can Pearlite form Outside of the Hultgren Extrapolation of the Ae3 and Acm Phase Boundaries?

    Science.gov (United States)

    Aranda, M. M.; Rementeria, R.; Capdevila, C.; Hackenberg, R. E.

    2016-02-01

    It is usually assumed that ferrous pearlite can form only when the average austenite carbon concentration C 0 lies between the extrapolated Ae3 ( γ/ α) and Acm ( γ/ θ) phase boundaries (the "Hultgren extrapolation"). This "mutual supersaturation" criterion for cooperative lamellar nucleation and growth is critically examined from a historical perspective and in light of recent experiments on coarse-grained hypoeutectoid steels which show pearlite formation outside the Hultgren extrapolation. This criterion, at least as interpreted in terms of the average austenite composition, is shown to be unnecessarily restrictive. The carbon fluxes evaluated from Brandt's solution are sufficient to allow pearlite growth both inside and outside the Hultgren Extrapolation. As for the feasibility of the nucleation events leading to pearlite, the only criterion is that there are some local regions of austenite inside the Hultgren Extrapolation, even if the average austenite composition is outside.

  12. Double-bilayer: a new phase formed by lysophospholipids and the corresponding fatty acid

    Directory of Open Access Journals (Sweden)

    Sérgio S. Funari

    2009-01-01

    Full Text Available The product of catalytic activity of the enzyme phospholipase A2, which resembles the core unit of animal toxins, on phospholipids is a 1:1 mixture of lysolipid and fatty acid. This mixture was studied by time-resolved simultaneous small- and wide angle x-ray diffraction over the temperature range from 23 to 53.5ºC. An unusually large lamellar structure was observed, with d = 11 nm, contradicting the complex functional dimer model between lysolipid and fatty acid. It can be explained by formation of a "double-bilayer", a new phase consisting of two different bilayers, one formed by lysophospholipid and other by fatty acid, bound together by head group interactions. Its strucutre was confirmed by simulations of the X-ray scattering pattern.

  13. Coarse-grained models of stripe forming systems: phase diagrams, anomalies, and scaling hypothesis.

    Science.gov (United States)

    Mendoza-Coto, Alejandro; Stariolo, Daniel A

    2012-11-01

    Two coarse-grained models which capture some universal characteristics of stripe forming systems are studied. At high temperatures, the structure factors of both models attain their maxima on a circle in reciprocal space, as a consequence of generic isotropic competing interactions. Although this is known to lead to some universal properties, we show that the phase diagrams have important differences, which are a consequence of the particular k dependence of the fluctuation spectrum in each model. The phase diagrams are computed in a mean field approximation and also after inclusion of small fluctuations, which are shown to modify drastically the mean field behavior. Observables like the modulation length and magnetization profiles are computed for the whole temperature range accessible to both models and some important differences in behavior are observed. A stripe compression modulus is computed, showing an anomalous behavior with temperature as recently reported in related models. Also, a recently proposed scaling hypothesis for modulated systems is tested and found to be valid for both models studied.

  14. TiO{sub 2} nanoparticles obtained by laser ablation in water: Influence of pulse energy and duration on the crystalline phase

    Energy Technology Data Exchange (ETDEWEB)

    Giorgetti, E., E-mail: emilia.giorgetti@fi.isc.cnr.it [Istituto dei Sistemi Complessi (ISC) CNR, Via Madonna del Piano 10, 50019 Sesto Fiorentino (Italy); Muniz Miranda, M.; Caporali, S. [Dipartimento di Chimica “Ugo Schiff”, Università di Firenze, Via della Lastruccia 3, 50019 Sesto Fiorentino (Italy); Canton, P. [Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari, Via Torino, 30170 Venezia-Mestre (Italy); Marsili, P. [Istituto dei Sistemi Complessi (ISC) CNR, Via Madonna del Piano 10, 50019 Sesto Fiorentino (Italy); Dipartimento di Fisica, Università di Pisa, Largo Bruno Pontecorvo 3, 56127 Pisa (Italy); Vergari, C.; Giammanco, F. [Dipartimento di Fisica, Università di Pisa, Largo Bruno Pontecorvo 3, 56127 Pisa (Italy)

    2015-09-15

    Highlights: • Laser ablation of Ti in water at 1064 nm and comparison of ns and ps temporal regimes. • Structural and spectroscopic characterization of the colloids: TiO{sub 2} is the predominant phase. • Determination of an energy window where ps ablation produces more anatase than rutile. • Modelling of the experimental dependence of anatase/rutile yield on pulse length and energy. - Abstract: We fabricated Ti oxide nanoparticles by laser ablation of a Ti target in doubly deionized water with ps or ns pulses at a laser wavelength of 1064 nm. Electron microscopy, Raman, X-ray diffraction and X-ray photoelectron spectroscopy showed that, while with ns pulses the dominant oxide phase is rutile, with ps pulses anatase is the most abundant form in an intermediate energy window centered around 25 mJ per pulse. This experimental behavior can be described by a theoretical model which calculates the pressure and temperature evolution of the ablated material and, from this, the rutile and anatase yield.

  15. Isomers and conformational barriers of gas phase nicotine, nornicotine and their protonated forms

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, Tomoki; Farone, William A.; Xantheas, Sotiris S.

    2014-07-17

    We report extensive conformational searches of the neutral nicotine, nornicotine and their protonated analogs that are based on ab-initio second order Møller-Plesset perturbation (MP2) electronic structure calculations. Initial searches were performed with the 6-31G(d,p) and the energetics of the most important structures were further refined from geometry optimizations with the aug-cc-pVTZ basis set. Based on the calculated free energies at T=298 K for the gas phase molecules, neutral nicotine has two dominant trans conformers, whereas neutral nornicotine is a mixture of several conformers. For nicotine, the protonation on both the pyridine and the pyrrolidine sites is energetically competitive, whereas nornicotine prefers protonation on the pyridine nitrogen. The protonated form of nicotine is mainly a mixture of two pyridine-protonated trans conformers and two pyrrolidine-protonated trans conformers, whereas the protonated form of nornicotine is a mixture of four pyridine-protonated trans conformers. Nornicotine is conformationally more flexible than nicotine, however it is less protonated at the biologically important pyrrolidine nitrogen site. The lowest energy isomers for each case were found to interconvert via low (< 6 kcal/mol) rotational barriers around the pyridine-pyrrolidine bond.

  16. Removal of pyridine from liquid and gas phase by copper forms of natural and synthetic zeolites

    Energy Technology Data Exchange (ETDEWEB)

    Rehakova, Maria, E-mail: maria.rehakova@upjs.sk [Institute of Chemistry, Faculty of Science, P.J. Safarik University, 041 54 Kosice (Slovakia); Fortunova, Lubica [Institute of Chemistry, Faculty of Science, P.J. Safarik University, 041 54 Kosice (Slovakia); Bastl, Zdenek [J. Heyrovsky Institute of Physical Chemistry, ASCR, v.v.i., 18223 Prague 8 (Czech Republic); Nagyova, Stanislava [Department of Physics, Electrotechnical Faculty, Technical University, 042 00 Kosice (Slovakia); Dolinska, Silvia [Institute of Geotechnics, Slovak Academy of Sciences, 043 53 Kosice (Slovakia); Jorik, Vladimir [Department of Inorganic Chemistry, Faculty of Chemical and Food Technology, Slovak University of Technology, 81237 Bratislava (Slovakia); Jona, Eugen [Department of Chemistry and Technology of Inorganic Materials, Faculty of Industrial Technologies, Trencin University of Alexander Dubcek, 02032 Puchov (Slovakia)

    2011-02-15

    Zeoadsorbents on the basis of copper forms of synthetic zeolite ZSM5 and natural zeolite of the clinoptilolite type (CT) have been studied taking into account their environmental application in removing harmful pyridine (py) from liquid and gas phase. Sorption of pyridine by copper forms of zeolites (Cu-ZSM5 and Cu-CT) has been studied by CHN, X-ray photoelectron spectroscopy, X-ray powder diffractometry, FTIR spectroscopy, thermal analysis (TG, DTA and DTG) and analysis of the surface areas and the pore volumes by low-temperature adsorption of nitrogen. The results of thermal analyses of Cu-ZSM5, Cu-(py){sub x}ZSM5, Cu-CT and Cu-(py){sub x}CT zeolitic products with different composition (x depends on the experimental conditions of sorption of pyridine) clearly confirmed their different thermal properties as well as the sorption of pyridine. In the zeolitic pyridine containing samples the main part of the pyridine release process occurs at considerably higher temperatures than is the boiling point of pyridine, which proves strong bond and irreversibility of py-zeolite interaction. FTIR spectra of Cu-(py){sub x}zeolite samples showed well resolved bands of pyridine. The results of thermal analysis and FTIR spectroscopy are in a good agreement with the results of other used methods.

  17. Removal of pyridine from liquid and gas phase by copper forms of natural and synthetic zeolites.

    Science.gov (United States)

    Reháková, Mária; Fortunová, Lubica; Bastl, Zdeněk; Nagyová, Stanislava; Dolinská, Silvia; Jorík, Vladimír; Jóna, Eugen

    2011-02-15

    Zeoadsorbents on the basis of copper forms of synthetic zeolite ZSM5 and natural zeolite of the clinoptilolite type (CT) have been studied taking into account their environmental application in removing harmful pyridine (py) from liquid and gas phase. Sorption of pyridine by copper forms of zeolites (Cu-ZSM5 and Cu-CT) has been studied by CHN, X-ray photoelectron spectroscopy, X-ray powder diffractometry, FTIR spectroscopy, thermal analysis (TG, DTA and DTG) and analysis of the surface areas and the pore volumes by low-temperature adsorption of nitrogen. The results of thermal analyses of Cu-ZSM5, Cu-(py)(x)ZSM5, Cu-CT and Cu-(py)(x)CT zeolitic products with different composition (x depends on the experimental conditions of sorption of pyridine) clearly confirmed their different thermal properties as well as the sorption of pyridine. In the zeolitic pyridine containing samples the main part of the pyridine release process occurs at considerably higher temperatures than is the boiling point of pyridine, which proves strong bond and irreversibility of py-zeolite interaction. FTIR spectra of Cu-(py)(x)zeolite samples showed well resolved bands of pyridine. The results of thermal analysis and FTIR spectroscopy are in a good agreement with the results of other used methods.

  18. Scanning tunneling microscopic and spectroscopic studies on a crystalline silica monolayer epitaxially formed on hexagonal SiC(0001¯) surfaces

    Science.gov (United States)

    Tochihara, Hiroshi; Shirasawa, Tetsuroh; Suzuki, Takayuki; Miyamachi, Toshio; Kajiwara, Takashi; Yagyu, Kazuma; Yoshizawa, Shunsuke; Takahashi, Toshio; Tanaka, Satoru; Komori, Fumio

    2014-02-01

    An epitaxial silicon-oxide monolayer of chemical composition of Si2O3 (the Si2O3 layer) formed on hexagonal SiC(0001¯) surfaces has been observed by scanning tunneling microscopy (STM). Filled- and empty-state STM images with atomic resolution support the previously reported model. Typical structural defects in the Si2O3 layer are found to be missing SiOn (n = 1, 2, 3) molecules. The band gap of the Si2O3 layer obtained by point tunneling spectroscopy is 5.5±0.5 eV, exhibiting considerable narrowing from that of bulk SiO2, 8.9 eV. It is proposed that the Si2O3 layer is suitable as a relevant interface material for formation of SiC-based metal-oxide-semiconductor devices.

  19. Mixed phases during the phase transitions

    CERN Document Server

    Tatsumi, Toshitaka; Maruyama, Toshiki

    2011-01-01

    Quest for a new form of matter inside compact stars compels us to examine the thermodynamical properties of the phase transitions. We closely consider the first-order phase transitions and the phase equilibrium on the basis of the Gibbs conditions, taking the liquid-gas phase transition in asymmetric nuclear matter as an example. Characteristic features of the mixed phase are figured out by solving the coupled equations for mean-fields and densities of constituent particles self-consistently within the Thomas-Fermi approximation. The mixed phase is inhomogeneous matter composed of two phases in equilibrium; it takes a crystalline structure with a unit of various geometrical shapes, inside of which one phase with a characteristic shape, called "pasta", is embedded in another phase by some volume fraction. This framework enables us to properly take into account the Coulomb interaction and the interface energy, and thereby sometimes we see the mechanical instability of the geometric structures of the mixed phase...

  20. Scanning tunneling microscopic and spectroscopic studies on a crystalline silica monolayer epitaxially formed on hexagonal SiC(0001{sup ¯}) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Tochihara, Hiroshi, E-mail: tochihara@fukuoka-u.ac.jp, E-mail: tochihara.hiroshi.146@m.kyushu-u.ac.jp; Suzuki, Takayuki; Yagyu, Kazuma [Department of Electronics Engineering and Computer Science, Fukuoka University, Fukuoka 814-0180 (Japan); Shirasawa, Tetsuroh; Takahashi, Toshio [Laser and Synchrotron Research Center, Institute for Solid State Physics, University of Tokyo, Chiba 277-8581 (Japan); Miyamachi, Toshio; Yoshizawa, Shunsuke; Komori, Fumio [Nanoscale Science Division, Institute for Solid State Physics, University of Tokyo, Chiba 277-8581 (Japan); Kajiwara, Takashi; Tanaka, Satoru [Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Fukuoka 819-0395 (Japan)

    2014-02-03

    An epitaxial silicon-oxide monolayer of chemical composition of Si{sub 2}O{sub 3} (the Si{sub 2}O{sub 3} layer) formed on hexagonal SiC(0001{sup ¯}) surfaces has been observed by scanning tunneling microscopy (STM). Filled- and empty-state STM images with atomic resolution support the previously reported model. Typical structural defects in the Si{sub 2}O{sub 3} layer are found to be missing SiO{sub n} (n = 1, 2, 3) molecules. The band gap of the Si{sub 2}O{sub 3} layer obtained by point tunneling spectroscopy is 5.5±0.5 eV, exhibiting considerable narrowing from that of bulk SiO{sub 2}, 8.9 eV. It is proposed that the Si{sub 2}O{sub 3} layer is suitable as a relevant interface material for formation of SiC-based metal-oxide-semiconductor devices.

  1. Structure of olefin-imidacloprid and gas-phase fragmentation chemistry of its protonated form.

    Science.gov (United States)

    Fusetto, Roberto; White, Jonathan M; Hutton, Craig A; O'Hair, Richard A J

    2016-02-01

    One of the major insect metabolites of the widely used neonicotinoid insecticide imidacloprid, 1 (1-[(6-chloro-3-pyridinyl)methyl]-N-nitro-1H-imidazol-2-amine), is the olefin 2. To better understand how the structure of olefin 2 relates to the gas-phase fragmentation of its protonated form, 2H(+), X-ray crystallography, tandem mass spectrometry experiments and DFT calculations were carried out. Olefin 2 was found to be in a tautomeric form where the proton is on the N(1) position of the imidazole ring and forms a hydrogen bond to one of the oxygen atoms of the coplanar nitroamine group. Under conditions of low-energy collision-induced dissociation (CID) in a linear ion trap, 2H(+), formed via electrospray ionization (ESI), fragments via a major loss of water, together with minor competing losses of HNO2 and NO2•.This contrasts with 1H+, which mainly undergoes bond homolysis via NO2• loss. Thus, installation of the double bond in 2 plays a key role in facilitating the loss of water. DFT calculations, carried out using the B3LYP/6-311G++(d,p) level of theory, revealed that loss of water was energetically more favourable compared to HNO2 and NO2• loss. Three multistep, energetically accessible mechanisms were identified for loss of water from 2H(+), and these have the following barriers: (I) direct proton transfer from N(5) of the pyridine to O(1) on the NO2 group (119 kJ mol(-1)); (II) rotation of the N(2)-N(4) bond (117 kJ mol(-1)); (III) 1,3-intramolecular proton transfer between the two oxygen atoms of the NO2 group (145 kJ mol(-1)). Given that the lowest barrier for the losses of HNO2 and NO2• is 156 kJ mol(-1), it is likely that all three water loss mechanisms occur concurrently.

  2. Ion-irradiation-assisted phase selection in single crystalline Fe7Pd3 ferromagnetic shape memory alloy thin films: from fcc to bcc along the Nishiyama-Wassermann path.

    Science.gov (United States)

    Arabi-Hashemi, A; Mayr, S G

    2012-11-09

    When processing Fe-Pd ferromagnetic shape memory thin films, selection of the desired phases and their transformation temperatures constitutes one of the largest challenges from an application point of view. In the present contribution we demonstrate that irradiation with 1.8 MeV Kr(+) ions is the method of choice to achieve this goal: Single crystalline Fe(7)Pd(3) thin films that are grown with molecular beam epitaxy on MgO (001) substrates and subsequently irradiated with ions reveal a phase transformation along the whole phase transformation path ranging from fcc austenite to bcc martensite. While for 10(14) ions/cm(2) a fcc-fct phase transformation is observed, increasing the fluence to 5 × 10(14) ions/cm(2) and 5 × 10(15) ions/cm(2) leads to a phase transformation to the bcc phase. Pole figure measurements reveal an orientation relationship for the fcc-bcc phase transformation according to Nishiyama and Wassermann.

  3. EVALUATION OF THOR MINERALIZED WASTE FORMS FOR THE DOE ADVANCED REMEDIATION TECHNOLOGIES PHASE 2 PROJECT

    Energy Technology Data Exchange (ETDEWEB)

    Crawford, C.; Jantzen, C.

    2012-02-02

    , sulfates/sulfides, chlorides, fluorides, volatile radionuclides or other aqueous components. The FBSR technology can process these wastes into a crystalline ceramic (mineral) waste form. The mineral waste form that is produced by co-processing waste with kaolin clay in an FBSR process has been shown to be as durable as LAW glass. Monolithing of the granular FBSR product, which is one of the objectives of this current study, is being investigated to prevent dispersion during transport or burial/storage but is not necessary for performance. FBSR testing of a Hanford LAW simulant and a WTP-SW simulant at the pilot scale was performed by THOR Treatment Technologies, LLC at Hazen Research Inc. in April/May 2008. The Hanford LAW simulant was the Rassat 68 tank blend and the target concentrations for the LAW was increased by a factor of 10 for Sb, As, Ag, Cd, and Tl; 100 for Ba and Re (Tc surrogate); 1,000 for I; and 254,902 for Cs based on discussions with the DOE field office and the environmental regulators and an evaluation of the Hanford Tank Waste Envelopes A, B, and C. It was determined through the evaluation of the actual tank waste metals concentrations that some metal levels were not sufficient to achieve reliable detection in the off-gas sampling. Therefore, the identified metals concentrations were increased in the Rassat simulant processed by TTT at HRI to ensure detection and enable calculation of system removal efficiencies, product retention efficiencies, and mass balance closure without regard to potential results of those determinations or impacts on product durability response such as Toxicity Characteristic Leach Procedure (TCLP). A WTP-SW simulant based on melter off-gas analyses from Vitreous State Laboratory (VSL) was also tested at HRI in the 15-inch diameter Engineering Scale Test Demonstration (ESTD) dual reformer at HRI in 2008. The target concentrations for the Resource Conservation and Recovery Act (RCRA) metals were increased by 16X for Se, 29X for

  4. EVALUATION OF THOR MINERALIZED WASTE FORMS FOR THE DOE ADVANCED REMEDIATION TECHNOLOGIES PHASE 2 PROJECT

    Energy Technology Data Exchange (ETDEWEB)

    Crawford, C.; Jantzen, C.

    2012-02-02

    , sulfates/sulfides, chlorides, fluorides, volatile radionuclides or other aqueous components. The FBSR technology can process these wastes into a crystalline ceramic (mineral) waste form. The mineral waste form that is produced by co-processing waste with kaolin clay in an FBSR process has been shown to be as durable as LAW glass. Monolithing of the granular FBSR product, which is one of the objectives of this current study, is being investigated to prevent dispersion during transport or burial/storage but is not necessary for performance. FBSR testing of a Hanford LAW simulant and a WTP-SW simulant at the pilot scale was performed by THOR Treatment Technologies, LLC at Hazen Research Inc. in April/May 2008. The Hanford LAW simulant was the Rassat 68 tank blend and the target concentrations for the LAW was increased by a factor of 10 for Sb, As, Ag, Cd, and Tl; 100 for Ba and Re (Tc surrogate); 1,000 for I; and 254,902 for Cs based on discussions with the DOE field office and the environmental regulators and an evaluation of the Hanford Tank Waste Envelopes A, B, and C. It was determined through the evaluation of the actual tank waste metals concentrations that some metal levels were not sufficient to achieve reliable detection in the off-gas sampling. Therefore, the identified metals concentrations were increased in the Rassat simulant processed by TTT at HRI to ensure detection and enable calculation of system removal efficiencies, product retention efficiencies, and mass balance closure without regard to potential results of those determinations or impacts on product durability response such as Toxicity Characteristic Leach Procedure (TCLP). A WTP-SW simulant based on melter off-gas analyses from Vitreous State Laboratory (VSL) was also tested at HRI in the 15-inch diameter Engineering Scale Test Demonstration (ESTD) dual reformer at HRI in 2008. The target concentrations for the Resource Conservation and Recovery Act (RCRA) metals were increased by 16X for Se, 29X for

  5. Organic solvents vapor pressure and relative humidity effects on the phase transition rate of α and β forms of tegafur.

    Science.gov (United States)

    Petkune, Sanita; Bobrovs, Raitis; Actiņš, Andris

    2012-01-01

    The objective of this work was to investigate the relative humidity (RH) and solvent vapor pressure effects on the phase transition dynamics between tegafur polymorphic forms that do not form hydrates and solvates. The commercially available α and β modifications of 5-fluoro-1-(tetrahydro-2-furyl)-uracil, known as the antitumor agent tegafur, were used as model materials for this study. While investigating the phase transitions of α and β tegafur under various partial pressures of methanol, n-propanol, n-butanol, and water vapor, it was determined that the phase transition rate increased in the presence of solvent vapors, even though no solvates were formed. By increasing the relative air humidity from 20% to 80%, the phase transition rate constant of α and β tegafur was increased about 60 times. After increasing the partial pressure of methanol, n-propanol, or n-butanol vapor, the phase transition rate constant did not change, but the extent of phase transformation was increased. In the homologous row of n-alcohols, the phase transition rate constant decreased with increasing carbon chain length. The dependence of phase transformation extent versus the RH corresponded to the polymolecular adsorption isotherm with a possible capillary condensation effect.

  6. STUDIES ON THE PORE FORMATION MECHANISM OF β-CRYSTALLINE POLYPROPYLENE UNDER STRETCHING

    Institute of Scientific and Technical Information of China (English)

    Shao-feng Ran; Mao Xu

    2004-01-01

    The pore formation mechanism of β-crystalline polypropylene under stretching was investigated. The porosity of the samples increases rapidly with stretching, having a maximum at draw ratios around 2 and then decreases monotonically.An abrupt formation process of initial micropores at very low draw ratios was evidenced by in situ SAXS measurements. At the same time the phase transition from β-crystal to a-crystal proceeds slowly in the whole deformation process up to large draw ratios around 5. Comparative studies of a- and β-crystalline polypropylene samples before stretching indicate that in addition to difference in crystal forms the a- and β-crystalline polypropylene samples exhibit quite different morphological features. There are a lot of interfaces in β-crystalline polypropylene samples, which may have a lower density value and can be easily etched by argon ions and penetrated by small molecules. It was concluded from these experimental facts that the pore formation and crystal transition are two independent phenomena during the deformation of β-crystalline polypropylene samples, and phase transition from β-crystal to a-crystal could hardly be the origin of pore formation. A defect initiation mechanism was proposed to understand the pore formation behavior of β-crystalline polypropylenes.

  7. Preparation of porous microsphere-scaffolds by electrohydrodynamic forming and thermally induced phase separation

    Energy Technology Data Exchange (ETDEWEB)

    Ghanbar, Hanif; Luo, C.J.; Bakhshi, Poonam [Department of Mechanical Engineering, University College London, Torrington Place, London, WC1E 7JE (United Kingdom); Day, Richard [Division of Medicine, University College London, Rockefeller Building, 21 University Street, London, WC1E 6JJ (United Kingdom); Edirisinghe, Mohan, E-mail: m.edirisinghe@ucl.ac.uk [Department of Mechanical Engineering, University College London, Torrington Place, London, WC1E 7JE (United Kingdom)

    2013-07-01

    The availability of forming technologies able to mass produce porous polymeric microspheres with diameters ranging from 150 to 300 μm is significant for some biomedical applications where tissue augmentation is required. Moreover, appropriate assembly of microspheres into scaffolds is an important challenge to enable direct usage of the as-formed structures in treatments. This work reports the production of poly (glycolic-co-lactic acid) and poly (ε-caprolactone) microspheres under ambient conditions using one-step electrohydrodynamic jetting (traditionally known as atomisation) and thermally induced phase separation (TIPS). To ensure robust production for practical uses, this work presents 12 comprehensive parametric mode mappings of the diameter distribution profiles of the microspheres obtained over a broad range of key processing parameters and correlating of this with the material parameters of 5 different polymer solutions of various concentrations. Poly (glycolic-co-lactic acid) (PLGA) in Dimethyl carbonate (DMC), a low toxicity solvent with moderate conductivity and low dielectric constant, generated microspheres within the targeted diameter range of 150–300 μm. The fabrication of the microspheres suitable for formation of the scaffold structure is achieved by changing the collection method from distilled water to liquid nitrogen and lyophilisation in a freeze dryer. Highlights: ► EHDA is a unique method for production of the desired size of microspheres. ► Polymer solution properties are used to tailor the size distribution of spheres. ► Process control parameters (flow rate and applied voltage) are key in size control. ► Combination of EHDA with TIPS provides porous microspheres for assembly of scaffold.

  8. Photocontrollable liquid-crystalline actuators

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Haifeng [Top Runner Incubation Center for Academia-Industry Fusion and Department of Materials and Technology, Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka 940-2188 (Japan); Ikeda, Tomiki [Chemical Resources Laboratory, Tokyo Institute of Technology, R1-11, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan)

    2011-05-17

    Coupling photochromic molecules with liquid crystalline (LC) materials enables one to reversibly photocontrol unique LC features such as phase transition, photoalignment, and molecular cooperative motion. LC elastomers show photomechanical and photomobile properties, directly converting light energy into mechanical energy. In well-defined LC block copolymers, regular patternings of nanostructures in macroscopic scales are fabricated by photo-manipulation of LC actuators. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Liquid Crystalline Esters of Dibenzophenazines

    Directory of Open Access Journals (Sweden)

    Kevin John Anthony Bozek

    2015-01-01

    Full Text Available A series of esters of 2,3,6,7-tetrakis(hexyloxydibenzo[a,c]phenazine-11-carboxylic acid was prepared in order to probe the effects of the ester groups on the liquid crystalline behavior. These compounds exhibit columnar hexagonal phases over broad temperature ranges. Variations in chain length, branching, terminal groups, and the presence of cyclic groups were found to modify transition temperatures without substantially destabilizing the mesophase range.

  10. Heavy ion irradiation of crystalline water ice

    CERN Document Server

    Dartois, E; Boduch, P; Brunetto, R; Chabot, M; Domaracka, A; Ding, J J; Kamalou, O; Lv, X Y; Rothard, H; da Silveira, E F; Thomas, J C

    2015-01-01

    Under cosmic irradiation, the interstellar water ice mantles evolve towards a compact amorphous state. Crystalline ice amorphisation was previously monitored mainly in the keV to hundreds of keV ion energies. We experimentally investigate heavy ion irradiation amorphisation of crystalline ice, at high energies closer to true cosmic rays, and explore the water-ice sputtering yield. We irradiated thin crystalline ice films with MeV to GeV swift ion beams, produced at the GANIL accelerator. The ice infrared spectral evolution as a function of fluence is monitored with in-situ infrared spectroscopy (induced amorphisation of the initial crystalline state into a compact amorphous phase). The crystalline ice amorphisation cross-section is measured in the high electronic stopping-power range for different temperatures. At large fluence, the ice sputtering is measured on the infrared spectra, and the fitted sputtering-yield dependence, combined with previous measurements, is quadratic over three decades of electronic ...

  11. A study on the properties of C-doped Ge8Sb2Te11 thin films during an amorphous-to-crystalline phase transition

    Science.gov (United States)

    Park, Cheol-Jin; Kong, Heon; Lee, Hyun-Yong; Yeo, Jong-Bin

    2016-04-01

    In this work, we evaluated the structural, electrical and optical properties of carbon-doped Ge8Sb2Te11 thin films. In a previous work, GeSbTe alloys were doped with different materials in an attempt to improve the thermal stability. Ge8Sb2Te11 and carbon-doped Ge8Sb2Te11 films of 250 nm in thickness were deposited on p-type Si (100) and glass substrates by using a RF magnetron reactive co-sputtering system at room temperature. The fabricated films were annealed in a furnance in the 0 ~ 400°C temperature range. The structural properties were analyzed by using X-ray diffraction (XRD), and the result showed that the carbon-doped Ge8Sb2Te11 had a face-centeredcubic (fcc) crystalline structure and an increased crystallization temperature ( T c ). An increase in the T c leads to thermal stability in the amorphous state. The optical properties were analyzed by using an UV-Vis-IR spectrophotometer, and the result showed an increase in the optical-energy band gap ( E op ) in the crystalline materials and an increase in the E op difference (Δ E op ), which is a good effect for reducing the noise in the memory device. The electrical properties were analyzed by using a 4-point probe, which showed an increase in the sheet resistance ( R s ) in the amorphous state and the crystalline state, which means a reduced programming current in the memory device.

  12. MICROPOROUS PVDF-HFP-BASED POLYMER MEMBRANES FORMED FROM SUPERCRITICAL CO2 INDUCED PHASE SEPARATION

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Microporous poly(vinylidene fluoride-co-hexafluoropropylene)(PVDF-HFP)membranes following supercritical CO2 induced phase separation process were prepared using four solvents.The solid electrolytes of PVDF-HFP were formed by microporous PVDF-HFP membranes filled and swollen by a liquid electrolyte.The effect of the solvents on the morphology and structure,electrolyte absorptions and lithium ionic conductivity of the activated membranes were investigated.It was approved that all the membrane had the similar"sponge-like"and asymmetric structure when different solvent was used.As the mutual affinity between solvent and supercritical CO2 decreased,the membrane porosity and the average pore diameter increased.The PVDF-HFP membrane with porosity at 88% and pore size at 10 μm were successfully prepared.The uptake of electrolyte solution and lithium ionic conductivity could reach 487 wt% and 3.09×10-3 S/cm respectively for obtained membrane.

  13. Drop coating deposition Raman spectroscopy of proteinogenic amino acids compared with their solution and crystalline state

    Science.gov (United States)

    Pazderka, Tomáš; Kopecký, Vladimír

    2017-10-01

    The Raman spectra of 20 proteinogenic amino acids were recorded in the solution, glass phase (as drop coating deposition Raman (DCDR) samples) and crystalline forms in the wide spectral range of 200-3200 cm- 1. The most apparent spectral differences between the Raman spectra of the crystalline forms, glass phases and aqueous solutions of amino acids were briefly discussed and described in the frame of published works. The possible density dependencies of spectral bands were noted. In some cases, a strong influence of the sample density, as well as of the organization of the water envelope, was observed. The most apparent changes were observed for Ser and Thr. Nevertheless, for the majority of amino acids, the DCDR sample form is an intermediate between the solution and crystalline forms. In contrast, aromatic amino acids have only a small sensitivity to the form of the sample. Our reference set of Raman spectra is useful for revealing discrepancies between the SERS and solid/solution spectra of amino acids. We also found that some previously published Raman spectra of polycrystalline samples resemble glassy state rather than crystalline spectra. Therefore, this reference set of spectra will find application in every branch of Raman spectroscopy where the spectra of biomolecules are collected from coatings.

  14. Crystalline Scaling Geometries from Vortex Lattices

    CERN Document Server

    Bao, Ning

    2013-01-01

    We study magnetic geometries with Lifshitz and/or hyperscaling violation exponents (both with a hard wall cutoff in the IR and a smooth black brane horizon) which have a complex scalar field which couples to the magnetic field. The complex scalar is unstable to the production of a vortex lattice in the IR. The lattice is a normalizable mode which is relevant (i.e. grows into the IR.) When one considers linearized backreaction of the lattice on the metric and gauge field, the metric forms a crystalline structure. We analyze the scaling of the free energy, thermodynamic entropy, and entanglement in the lattice phase and find that in the smeared limit, the leading order correction to thermodynamic properties due to the lattice has the scaling behavior of a theory with a hyperscaling violation exponent between 0 and 1, indicating a flow to an effectively lower-dimensional theory in the deep IR.

  15. Crystalline and Crystalline International Disposal Activities

    Energy Technology Data Exchange (ETDEWEB)

    Viswanathan, Hari S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Chu, Shaoping [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dittrich, Timothy M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hyman, Jeffrey De' Haven [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Karra, Satish [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Makedonska, Nataliia [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Reimus, Paul William [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-03-06

    This report presents the results of work conducted between September 2015 and July 2016 at Los Alamos National Laboratory in the crystalline disposal and crystalline international disposal work packages of the Used Fuel Disposition Campaign (UFDC) for DOE-NE’s Fuel Cycle Research and Development program. Los Alamos focused on two main activities during this period: Discrete fracture network (DFN) modeling to describe flow and radionuclide transport in complex fracture networks that are typical of crystalline rock environments, and a comprehensive interpretation of three different colloid-facilitated radionuclide transport experiments conducted in a fractured granodiorite at the Grimsel Test Site in Switzerland between 2002 and 2013. Chapter 1 presents the results of the DFN work and is divided into three main sections: (1) we show results of our recent study on the correlation between fracture size and fracture transmissivity (2) we present an analysis and visualization prototype using the concept of a flow topology graph for characterization of discrete fracture networks, and (3) we describe the Crystalline International work in support of the Swedish Task Force. Chapter 2 presents interpretation of the colloidfacilitated radionuclide transport experiments in the crystalline rock at the Grimsel Test Site.

  16. Crystalline Silica Primer

    Science.gov (United States)

    ,

    1992-01-01

    Crystalline silica is the scientific name for a group of minerals composed of silicon and oxygen. The term crystalline refers to the fact that the oxygen and silicon atoms are arranged in a threedimensional repeating pattern. This group of minerals has shaped human history since the beginning of civilization. From the sand used for making glass to the piezoelectric quartz crystals used in advanced communication systems, crystalline silica has been a part of our technological development. Crystalline silica's pervasiveness in our technology is matched only by its abundance in nature. It's found in samples from every geologic era and from every location around the globe. Scientists have known for decades that prolonged and excessive exposure to crystalline silica dust in mining environments can cause silicosis, a noncancerous lung disease. During the 1980's, studies were conducted that suggested that crystalline silica also was a carcinogen. As a result of these findings, crystalline silica has been regulated under the Occupational Safety and Health Administration's (OSHA) Hazard Communication Standard (HCS). Under HCS, OSHAregulated businesses that use materials containing 0.1% or more crystalline silica must follow Federal guidelines concerning hazard communication and worker training. Although the HCS does not require that samples be analyzed for crystalline silica, mineral suppliers or OSHAregulated

  17. Nano-titanium dioxide bioreactivity with human alveolar type-I-like epithelial cells: Investigating crystalline phase as a critical determinant.

    Science.gov (United States)

    Sweeney, Sinbad; Berhanu, Deborah; Ruenraroengsak, Pakatip; Thorley, Andrew J; Valsami-Jones, Eugenia; Tetley, Teresa D

    2015-05-01

    There can be significant variability between bioreactivity studies of nanomaterials that are apparently the same, possibly reflecting differences in the models used and differing sources of experimental material. In this study, we have generated two crystal forms of titanium dioxide nanoparticles (nano-TiO2), pure anatase and pure rutile to address the hypothesis that the bioreactivity of these nanoparticles with human alveolar epithelium will depend on their crystal phase. We used a human alveolar type-I-like epithelial cell model (TT1; generated in-house from primary human alveolar epithelial type II cells); these cells cover 95% of the alveolar epithelial surface area and are an important target cell for inhaled nanomaterials. Using literature as a guide, we hypothesised that pure anatase nano-TiO2 would display greater bioreactivity with TT1 cells in comparison to pure rutile nano-TiO2. However, we found the profile and pattern of inflammatory mediator release was similar between these two nano-TiO2 formats, although pure rutile treatment caused a small, but consistently greater, response for IL-6, IL-8 and MCP-1. Interestingly, the temporal induction of oxidative stress (increased reactive oxygen species levels and depleted glutathione) varied markedly between the different nano-TiO2 formats. We have shown that a combination of using nanomaterials synthesised specifically for toxicological study and the use of a highly relevant, reproducible human lung cell model, offers a useful approach to delineating the physicochemical properties of nanomaterials that may be important in their cellular reactivity.

  18. Crystallization of calcium carbonate (CaCO3) in a flowing system: Influence of Cu2+ additives on induction time and crystalline phase transformation

    Science.gov (United States)

    Usmany, Y.; Putranto, W. A.; Bayuseno, A. P.; Muryanto, S.

    2016-04-01

    Scaling of calcium carbonate (CaCO3) is commonly found in piping systems in oil, gas, desalination and other chemical processes. The scale may create technical problems, leading to the reduction of heat transfer, increase of energy consumption and unscheduled equipment shutdown. This paper presents crystallization scaling experiments and evaluation of the effect of Cu2+ additives on the induction time and calcium carbonate transformation. The crystals precursors were prepared using equimolar of CaCl2 and Na2CO3 resulted in concentrations of 3000 ppm Ca2+ in the solution. The Cu2+ in amounts of 0, 1 and 10 ppm was separately added in the solution. The flow rates (20, 35, and 60 mL/min) and elevated temperatures (27, 35 and 45°C) were selected in the study. The induction time for crystallization of CaCO3 was observed by measuring the solution conductivity over time, while the phase transformation of calcium carbonate was examined by XRD method and SEM/EDX. It was found that the conductivity remained steady for a certain period reflecting to the induction time of crystal formation, and then decreased sharply afterwards,. The induction time was increased from 34 and 48 minutes in the presence of Cu additives (1 and 10 ppm), depending on the flow rates and temperature observed. In all the experiments, the Cu2+ addition leads to the reduction of mass of crystals. Apparently, the presence of Cu2+ could inhibit the CaCO3 crystallization. In the absence of Cu2+ and at elevated temperature, the crystals obtained were a mixture of vaterite and calcite. In the presence of Cu2+ and at elevated temperature, the crystals formed were aragonite and calcite. Here, the presence of Cu2+ additives might have controlled the crystal transformation of CaCO3.

  19. Mössbauer study of oxide phase distributions in rust formed on steel constructions near the Black Sea in Sochi

    Energy Technology Data Exchange (ETDEWEB)

    Filippov, V. P., E-mail: vpfilippov@mephi.ru; Lauer, Yu. A. [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute) (Russian Federation); Goloborodko, P. G.; Polyakov, A. M. [Sanatorium “Progress” (Russian Federation)

    2016-12-15

    The phase composition of the intermediate oxide layers formed on elements of steel structures at different positions relative to the sea water of the Black Sea near Sochi are investigated. The differences of the phase composition of these oxide layers are shown, depending on the location of the design details in relation to the sea and the abundancies of certain types of oxides in the studied layers are discussed.

  20. Mulled coal: A beneficiated coal form for use as a fuel or fuel intermediate. Phase 3, Final report

    Energy Technology Data Exchange (ETDEWEB)

    1993-08-01

    Energy International Corporation (El) was awarded a contract to evaluate a new concept for utilization of the fine coal wetcake produced by many of the physical beneficiation processes now under development. EI proposed development of a stabilized wetcake with properties that would facilitate storage, handling, transport, and subsequent conversion of the material into Coal-Water Fuel (CWF) at the point of use. The effort was performed in three phases. Phase I established the technical feasibility of stabilizing the fine coal ``wetcake`` in a form that can be readily handled and converted into a desired fuel form at the combustion site. The preferred form of stabilized ``wetcake`` was a granular free flowing material with the moisture encapsulated with the fine coal particles. The product was termed Mulled Coal. Phase I results indicated that the Mulled Coal was not only suitable as a CWF intermediate, but also had potential as a solid fuel. Phase II demonstrated the utilization of the Mulled Coal process to store and move fine coal products as a stable ``wetcake.`` Tasks in this phase tested components of the various systems required for storage, handling and combustion of the fine coals. Phase III expanded the technology by: 1. Evaluating Mulled Coal from representative coals from all producing regions in the US. 2. Development of bench-scale tests. 3. Design, construction, and operation of a 1 ton/hr continuous processing unit. 4. Evaluation of the effects of beneficiation. and 5. Developing an estimate of capital and operating costs for commercial units.

  1. The cephalic phase insulin response to nutritive and low-calorie sweeteners in solid and beverage form.

    Science.gov (United States)

    Dhillon, Jaapna; Lee, Janice Y; Mattes, Richard D

    2017-09-09

    The purpose of the study was to examine the role of the cephalic phase insulin response (CPIR) following exposure to nutritive and low-calorie sweeteners in solid and beverage form in overweight and obese adults. In addition, the role of learning on the CPIR to nutritive and low-calorie sweetener exposure was tested. Sixty-four overweight and obese adults (age: 18-50years, BMI: 24-37kg/m(2), body fat percentage>25% for men and >32% for women) were sham-fed (at 2-minute intervals for 14min) a randomly assigned test load comprised of a nutritive (sucrose) or low calorie sweetener (sucralose) in beverage or solid form in phase 1 of the study. A 2-3ml blood sample was collected before and 2, 6, 10, 14, 61, 91 and 121min after oral exposure for serum insulin and glucose analysis. During phase 2, participants underwent a 2-week training period to facilitate associative learning between the sensory properties of test loads and their post-ingestive effects. In phase 3, participants were retested for their cephalic phase responses as in phase 1. Participants were classified as responders if they demonstrated a positive insulin response (rise of serum insulin above baseline i.e. Δ insulin) 2min post-stimulus in phase 1. Among responders exposed to the same sweetener in Phases 1 and 3, the proportion of participants that displayed a rise of insulin with oral exposure to sucralose was significantly greater when the stimulus was in the solid form compared to the beverage form. Sucralose and sucrose exposure elicited similarly significant increases in serum insulin 2min after exposure and significant decreases after 2min in responders in both food forms. The solid food form elicited greater CPIR over 2, 6 and 10min than the beverage form. There was no effect of learning on insulin responses after training. The results indicate the presence of a significant CPIR in a subset of individuals with overweight or obesity after oral exposure to sucralose, especially when present in

  2. Crystalline Bioceramic Materials

    Directory of Open Access Journals (Sweden)

    de Aza, P. N.

    2005-06-01

    Full Text Available A strong interest in the use of ceramics for biomedical engineering applications developed in the late 1960´s. Used initially as alternatives to metallic materials in order to increase the biocompatibility of implants, bioceramics have become a diverse class of biomaterials, presently including three basic types: relatively bioinert ceramics; bioactive or surface reactive bioceramics and bioresorbable ceramics. This review will only refer to bioceramics “sensus stricto”, it is to say, those ceramic materials constituted for nonmetallic inorganic compounds, crystallines and consolidated by thermal treatments of powders to high temperatures. Leaving bioglasses, glass-ceramics and biocements apart, since, although all of them are obtained by thermal treatments to high temperatures, the first are amorphous, the second are obtained by desvitrification of a glass and in them vitreous phase normally prevails on the crystalline phases and the third are consolidated by means of a hydraulic or chemical reaction to room temperature. A review of the composition, physiochemical properties and biological behaviour of the principal types of crystalline bioceramics is given, based on the literature data and on the own experience of the authors.

    A finales de los años sesenta se despertó un gran interés por el uso de los materiales cerámicos para aplicaciones biomédicas. Inicialmente utilizados como una alternativa a los materiales metálicos, con el propósito de incrementar la biocompatibilidad de los implantes, las biocerámicas se han convertido en una clase diversa de biomateriales, incluyendo actualmente tres tipos: cerámicas cuasi inertes; cerámicas bioactivas o reactivas superficialmente y cerámicas reabsorbibles o biodegradables. En la presente revisión se hace referencia a las biocerámicas en sentido estricto, es decir, a aquellos materiales constitutitos por compuestos inorgánicos no metálicos, cristalinos y consolidados

  3. Research on the Mineral Phase and Component of Non-Crystalline and Nano-Crystalline Corrosion Products on Bronzes Unearthed from Shang Tomb in Xingan%新干商墓青铜器非晶与纳米晶锈蚀产物结构的分析研究

    Institute of Scientific and Technical Information of China (English)

    成小林; 潘路

    2012-01-01

    应用微区X射线衍射仪(μXRD)及高分辨透射电镜(HTEM)分析江西新干商墓出土的青铜器粉状锈蚀产物,结果表明锈蚀产物主要为具有锡石结构的SnO2,晶态形式为非晶与晶粒尺寸为4~5.7 nm的纳米晶共混;能谱分析表明样品中除含有大量锡外,还有少量的铜、硅、铅与铁等元素.通过对锈蚀产物的高分辨透射电镜晶格条纹像计算,说明纳米晶SnO2的晶格中并没有其他原子的掺杂;对该锈蚀产物拉曼光谱的分析研究表明,样品不含有表征SnO2的体相拉曼峰,更具有非晶SnO2的特征,而973 cm-1的弱而宽的峰表明样品含有非晶的硅酸盐类的锈蚀物,推测锈蚀产物中的少量铜、硅、铅与铁等元素应以非晶的形式存在.%The patinas on bronzes in Shang Tomb of Xingan were powdery, pale green, which were more like "bronze disease", but the mineral composition of patinas was not paratacamite or atacamite. Micro X-ray diffraction (XRD) and high performance transmission electroscope ( HTEM) showed that the patinas were mainly composed of non-crystalline and nano-crystalline SnO2, and the size of nano-crystalline particle was in the range of 4 ~ 5. 7 nm; Moreover, the energy-dispersive X-ray spectrometry showed that element tin is the primary ingredient of the sample, as well as little copper, silicon, lead and iron were detected. By studying the crystal lattice stripe image of the nanometer SnQ2, it was deduced that the chemical formula of nano-crystalline SnO2 did not include other elements; The Raman spectrum of the sample showed that there were not any characteristic peaks of SnO2, the spectrum was more like non-crystalline SnO2, and the weak and broad peak of 973 cm-1 indicated that the sample may contain silicate grains, It was inferred that little of copper, silicon, lead and iron should exist in the form of non-crystalline silicate particles.

  4. Crystalline boron nitride aerogels

    Science.gov (United States)

    Zettl, Alexander K.; Rousseas, Michael; Goldstein, Anna P.; Mickelson, William; Worsley, Marcus A.; Woo, Leta

    2017-04-04

    This disclosure provides methods and materials related to boron nitride aerogels. In one aspect, a material comprises an aerogel comprising boron nitride. The boron nitride has an ordered crystalline structure. The ordered crystalline structure may include atomic layers of hexagonal boron nitride lying on top of one another, with atoms contained in a first layer being superimposed on atoms contained in a second layer.

  5. Crystalline boron nitride aerogels

    Energy Technology Data Exchange (ETDEWEB)

    Zettl, Alexander K.; Rousseas, Michael; Goldstein, Anna P.; Mickelson, William; Worsley, Marcus A.; Woo, Leta

    2017-04-04

    This disclosure provides methods and materials related to boron nitride aerogels. In one aspect, a material comprises an aerogel comprising boron nitride. The boron nitride has an ordered crystalline structure. The ordered crystalline structure may include atomic layers of hexagonal boron nitride lying on top of one another, with atoms contained in a first layer being superimposed on atoms contained in a second layer.

  6. Charge-Coupled Substituted Garnets (Y3-xCa0.5xM0.5x)Fe5O12 (M = Ce, Th): Structure and Stability as Crystalline Nuclear Waste Forms

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Xiaofeng; Kukkadapu, Ravi K.; Lanzirotti, Antonio; Newville, Matthew; Engelhard, Mark H.; Sutton, Stephen R.; Navrotsky, Alexandra [UCD; (UC); (PNNL)

    2015-06-08

    The garnet structure has been proposed as a potential crystalline nuclear waste form for accommodation of actinide elements, especially uranium (U). In this study, yttrium iron garnet (YIG) as a model garnet host was studied for the incorporation of U analogs, cerium (Ce) and thorium (Th), incorporated by a charge-coupled substitution with calcium (Ca) for yttrium (Y) in YIG, namely, 2Y3+ = Ca2+ + M4+, where M4+ = Ce4+ or Th4+. Single-phase garnets Y3–xCa0.5xM0.5xFe5O12 (x = 0.1–0.7) were synthesized by the citrate–nitrate combustion method. Ce was confirmed to be tetravalent by X-ray absorption spectroscopy and X-ray photoelectron spectroscopy. X-ray diffraction and 57Fe–Mössbauer spectroscopy indicated that M4+ and Ca2+ cations are restricted to the c site, and the local environments of both the tetrahedral and the octahedral Fe3+ are systematically affected by the extent of substitution. The charge-coupled substitution has advantages in incorporating Ce/Th and in stabilizing the substituted phases compared to a single substitution strategy. Enthalpies of formation of garnets were obtained by high temperature oxide melt solution calorimetry, and the enthalpies of substitution of Ce and Th were determined. The thermodynamic analysis demonstrates that the substituted garnets are entropically rather than energetically stabilized. This suggests that such garnets may form and persist in repositories at high temperature but might decompose near room temperature.

  7. Influence of deposition temperature and bias voltage on the crystalline phase of Er{sub 2}O{sub 3} thin films deposited by filtered cathodic arc

    Energy Technology Data Exchange (ETDEWEB)

    Adelhelm, Christoph, E-mail: christoph.adelhelm@ipp.mpg.de [Max-Planck-Institut fuer Plasmaphysik, Materials Research, EURATOM Association, Boltzmannstrasse 2, 85748 Garching (Germany); Pickert, Thomas [Max-Planck-Institut fuer Plasmaphysik, Materials Research, EURATOM Association, Boltzmannstrasse 2, 85748 Garching (Germany); Koch, Freimut, E-mail: freimut.koch@ipp.mpg.de [Max-Planck-Institut fuer Plasmaphysik, Materials Research, EURATOM Association, Boltzmannstrasse 2, 85748 Garching (Germany); Balden, Martin; Jahn, Stephan [Max-Planck-Institut fuer Plasmaphysik, Materials Research, EURATOM Association, Boltzmannstrasse 2, 85748 Garching (Germany); Rinke, Monika [Forschungszentrum Karlsruhe, Institute for Materials Research I, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Maier, Hans [Max-Planck-Institut fuer Plasmaphysik, Materials Research, EURATOM Association, Boltzmannstrasse 2, 85748 Garching (Germany)

    2011-10-01

    Er{sub 2}O{sub 3} thin films on Eurofer steel substrates were produced by a filtered cathodic arc device, varying the substrate temperature (RT - 700 deg. C) and sample bias (0 to -450 V). The crystallographic phase was analyzed by X-ray diffraction and Raman spectroscopy. Deposition at {>=}600 deg. C without bias lead to solely formation of the cubic Er{sub 2}O{sub 3} phase. Thin films of the uncommon, monoclinic B-phase were prepared with a negative bias voltage of {>=}100 V at RT, and at temperatures {<=}500 deg. C for -250 V bias. The B-phase films exhibit a strongly textured film structure. Residual stress measurements show high compressive stress for B-phase films deposited at RT.

  8. Influence of the oxygen concentration on the formation of crystalline phases of TiO2 during the low-pressure arc-discharge plasma synthesis

    Science.gov (United States)

    Ushakov, A. V.; Karpov, I. V.; Lepeshev, A. A.

    2016-02-01

    The synthesis of titanium dioxide (TiO2) nanoparticles with different percentage of anatase and rutile phases is investigated. The synthesis is performed by controlling the oxygen percentage in the gas mixture in the plasmachemical evaporation-condensation process employing a low-pressure arc discharge. In all our experiments, the pressure in the plasmachemical reactor and the average size of particles remain constant and are 60 Pa and 6 nm, respectively. The crystal structure of synthesized TiO2 is studied using X-ray diffraction; the morphology of the particles is analyzed employing transmission electron microscopy. Using X-ray phase analysis, it is established that the concentration of the TiO2 anatase phase decreases upon a decrease in the oxygen concentration in the gas mixture. It is shown that the TiO2 anatase phase is more efficient for photocatalytic decomposition of methylene blue than the rutile phase.

  9. Phase evolution in zirconolite glass-ceramic wasteforms

    Science.gov (United States)

    Maddrell, Ewan R.; Paterson, Hannah C.; May, Sarah E.; Burns, Kerry M.

    2017-09-01

    The evolution of crystalline phases in a model glass-ceramic wasteform system has been studied as a function of temperature and time. The work has shown that perovskite and sphene form as transient phases before final formation of zirconolite. The study also suggests some evidence for subtle structural transformations within the zirconolite phase.

  10. Generic Crystalline Disposal Reference Case

    Energy Technology Data Exchange (ETDEWEB)

    Painter, Scott Leroy [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Chu, Shaoping [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Harp, Dylan Robert [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Perry, Frank Vinton [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Wang, Yifeng [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-02-20

    A generic reference case for disposal of spent nuclear fuel and high-level radioactive waste in crystalline rock is outlined. The generic cases are intended to support development of disposal system modeling capability by establishing relevant baseline conditions and parameters. Establishment of a generic reference case requires that the emplacement concept, waste inventory, waste form, waste package, backfill/buffer properties, EBS failure scenarios, host rock properties, and biosphere be specified. The focus in this report is on those elements that are unique to crystalline disposal, especially the geosphere representation. Three emplacement concepts are suggested for further analyses: a waste packages containing 4 PWR assemblies emplaced in boreholes in the floors of tunnels (KBS-3 concept), a 12-assembly waste package emplaced in tunnels, and a 32-assembly dual purpose canister emplaced in tunnels. In addition, three failure scenarios were suggested for future use: a nominal scenario involving corrosion of the waste package in the tunnel emplacement concepts, a manufacturing defect scenario applicable to the KBS-3 concept, and a disruptive glaciation scenario applicable to both emplacement concepts. The computational approaches required to analyze EBS failure and transport processes in a crystalline rock repository are similar to those of argillite/shale, with the most significant difference being that the EBS in a crystalline rock repository will likely experience highly heterogeneous flow rates, which should be represented in the model. The computational approaches required to analyze radionuclide transport in the natural system are very different because of the highly channelized nature of fracture flow. Computational workflows tailored to crystalline rock based on discrete transport pathways extracted from discrete fracture network models are recommended.

  11. Epitaxial layers of 2122 BCSCO superconductor thin films having single crystalline structure

    Science.gov (United States)

    Pandey, Raghvendra K. (Inventor); Raina, Kanwal K. (Inventor); Solayappan, Narayanan (Inventor)

    1995-01-01

    A substantially single phase, single crystalline, highly epitaxial film of Bi.sub.2 CaSr.sub.2 Cu.sub.2 O.sub.8 superconductor which has a T.sub.c (zero resistance) of 83K is provided on a lattice-matched substrate with no intergrowth. This film is produced by a Liquid Phase Epitaxy method which includes the steps of forming a dilute supercooled molten solution of a single phase superconducting mixture of oxides of Bi, Ca, Sr, and Cu having an atomic ratio of about 2:1:2:2 in a nonreactive flux such as KCl, introducing the substrate, e.g., NdGaO.sub.3, into the molten solution at 850.degree. C., cooling the solution from 850.degree. C. to 830.degree. C. to grow the film and rapidly cooling the substrate to room temperature to maintain the desired single phase, single crystalline film structure.

  12. First-leaflet phase effect on properties of phospholipid bilayer formed through vesicle adsorption on LB monolayer.

    Science.gov (United States)

    Park, Jin-Won

    2010-10-01

    Phospholipid bilayers were formed on mica using the Langmuir-Blodgett technique and liposome fusion, as a model system for biomembranes. Nanometer-scale surface physical properties of the bilayers were quantitatively characterized upon the different phases of the first leaflets. Lower hydration/steric forces on the bilayers were observed at the liquid phase of the first leaflet than at the solid phase. The forces appear to be related to the low mechanical stability of the lipid bilayer, which was affected by the first leaflet phase. The first leaflet phase also influenced the long-range repulsive forces over the second leaflet. Surface forces, measured using a modified probe with an atomic force microscope, showed that lower long-range repulsive forces were also found at the liquid phase of the first leaflet. Force measurements were performed at 300 mM sodium chloride solution so that the effect of the phase on the long-range repulsive forces could be investigated by reducing the effect of the repulsion between the second-leaflet lipid headgroups on the long-range repulsive forces. Forces were analyzed using the Derjaguin-Landau-Verwey-Overbeek theory so that the surface potential and surface charge density of the lipid bilayers were quantitatively acquired for each phase of the first leaflet.

  13. Crystallization of metastable beta glycine from gas phase via the sublimation of alpha or gamma form in vacuum.

    Science.gov (United States)

    Liu, Zhimin; Zhong, Lin; Ying, Pinliang; Feng, Zhaochi; Li, Can

    2008-01-01

    It is found that beta glycine, the metastable polymorph of glycine, can be rapidly formed from gas phase via the sublimation of its stable alpha or gamma form in vacuum. The transformation process was monitored by infrared spectroscopy and the crystal structure of the sublimate was identified by X-ray diffraction techniques. It is the first report about the transformation of stable alpha or gamma glycine into metastable beta form in "one-step" (heating then cool down spontaneously). Crystallization of beta glycine from gas phase is very different from other methods that require additives in solution. The hydrogen-bonding interaction and self-assembling of amino acid were discussed based on the observations.

  14. Role of interface in forming non-equilibrium hcp phase by ion mixing in an immiscible Au-Co system

    CERN Document Server

    Yan, H F; Liu, B X

    2003-01-01

    In an equilibrium immiscible Au-Co system characterized by a positive heat of formation of +11 kJ mol sup - sup 1 , a non-equilibrium Au-Co phase of hcp structure was formed by 200 keV xenon ion mixing at 77 K in the Au sub 5 sub 0 Co sub 5 sub 0 multilayered films. Based on the free energy calculation, the excess interfacial free energy stored in the Au-Co multilayered films could provide adequate thermodynamic driving force for alloying between Au and Co and forming the non-equilibrium Au-Co hcp phase. Besides, the average magnetic moment per Co atom in the newly formed hcp structure was reduced by 22% of its equilibrium value, within a measuring error of 8%.

  15. Separation of chiral primary amino compounds by forming a sandwiched complex in reversed-phase high performance liquid chromatography.

    Science.gov (United States)

    Zhang, Chen; Huang, Wei X; Chen, Zhi; Rustum, Abu M

    2010-07-23

    Separation of chiral primary amino compounds was efficiently achieved under reversed-phase high performance liquid chromatography (RP-HPLC) conditions using a mixture of non-chiral crown ether (18-crown-6) and dimethyl-beta-cyclodextrin (DM-beta-CD) in the mobile phase. Under these conditions, the amino group of the chiral compound was protonated in a low pH mobile phase, and then interacted with 18-crown-6 and DM-beta-CD to form a sandwiched complex [18-crown-6+amine+CD]. Enantiomers of the compound in the sandwiched complex were separated with good enantioselectivity. Formation of the sandwiched complex among the chiral compound and additives in the mobile phase is a key step of the chiral separation. Four different chiral amino compounds namely, 1-aminoindan (AI), 1,2,3,4-tetrahydro-1-naphthylamine (THNA), tyrosine (Tyr), and phenylalanine (Phe), were selected to demonstrate the separation using the sandwiched complex mechanism in RP-HPLC.

  16. Studies of Nucleation, Growth, Specific Heat, and Viscosity of Undercooled Melts of Quasicrystals and Polytetrahedral-Phase-Forming Alloys

    Science.gov (United States)

    Kelton, K. F.; Croat, T. K.; Gangopadhyay, A.; Holland-Moritz, D.; Hyers, Robert W.; Rathz, Thomas J.; Robinson, Michael B.; Rogers, Jan R.

    2001-01-01

    Undercooling experiments and thermal physical property measurements of metallic alloys on the International Space Station (ISS) are planned. This recently-funded research focuses on fundamental issues of the formation and structure of highly-ordered non-crystallographic phases (quasicrystals) and related crystal phases (crystal approximants), and the connections between the atomic structures of these phases and those of liquids and glasses. It extends studies made previously by us of the composition dependence of crystal nucleation processes in silicate and metallic glasses, to the case of nucleation from the liquid phase. Motivating results from rf-levitation and drop-tube measurements of the undercooling of Ti/Zr-based liquids that form quasicrystals and crystal approximants are discussed. Preliminary measurements by electrostatic levitation (ESL) are presented.

  17. Matched-filtering generalized phase contrast using LCoS pico-projectors for beam-forming

    DEFF Research Database (Denmark)

    Bañas, Andrew Rafael; Palima, Darwin; Glückstad, Jesper

    2012-01-01

    We report on a new beam-forming system for generating high intensity programmable optical spikes using so-called matched-filtering Generalized Phase Contrast (mGPC) applying two consumer handheld pico-projectors. Such a system presents a low-cost alternative for optical trapping and manipulation......, optical lattices and other beam-shaping applications usually implemented with high-end spatial light modulators. Portable pico-projectors based on liquid crystal on silicon (LCoS) devices are used as binary phase-only spatial light modulators by carefully setting the appropriate polarization of the laser...... patterns suited for different requirements. Despite imperfections in these consumer pico-projectors, the mGPC approach tolerates phase aberrations that would have otherwise been hard to overcome by standard phase projection....

  18. Preparation and Characterization of Membranes Formed by Nonsolvent Induced Phase Separation: A Review

    KAUST Repository

    Guillen, Gregory R.

    2011-04-06

    The methods and mechanisms of nonsolvent induced phase separation have been studied for more than fifty years. Today, phase inversion membranes are widely used in numerous chemical industries, biotechnology, and environmental separation processes. The body of knowledge has grown exponentially in the past fifty years, which suggests the need for a critical review of the literature. Here we present a review of nonsolvent induced phase separation membrane preparation and characterization for many commonly used membrane polymers. The key factors in membrane preparation discussed include the solvent type, polymer type and concentration, nonsolvent system type and composition, additives to the polymer solution, and film casting conditions. A brief introduction to membrane characterization is also given, which includes membrane porosity and pore size distribution characterization, membrane physical and chemical properties characterization, and thermodynamic and kinetic evaluation of the phase inversion process. One aim of this review is to lay out the basics for selecting polymer solvent nonsolvent systems with appropriate film casting conditions to produce membranes with the desired performance, morphology, and stability, and to choose the proper way to characterize these properties of nonsolvent induced phase inversion membranes. © 2011 American Chemical Society.

  19. Synthesis and crystalline phase of monazite-type Ce{sub 1−x}Gd{sub x}PO{sub 4} solid solutions for immobilization of minor actinide curium

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Hang; Teng, Yuancheng, E-mail: tyc239@163.com; Ren, Xuetan; Wu, Lang; Liu, Haichang; Wang, Shanlin; Xu, Liuyang

    2014-01-15

    Gadolinium (Gd{sup 3+}) was used to simulate trivalent minor actinide curium (Cm{sup 3+}), and monazite-type solid solutions with composition of Ce{sub 1−x}Gd{sub x}PO{sub 4} (x = 0–1) were prepared by the solid state reaction method using Ce{sub 2}(C{sub 2}O{sub 4}){sub 3}·10H{sub 2}O, NH{sub 4}H{sub 2}PO{sub 4}, and Gd{sub 2}O{sub 3} as starting materials. The effects of Gd content on the crystalline phase and microstructure of Ce{sub 1−x}Gd{sub x}PO{sub 4} solid solutions were investigated, and the calcining parameters of Ce{sub 0.9}Gd{sub 0.1}PO{sub 4} solid solution were optimized by means of XRD, TG-DSC and SEM. The results show that pure monazite-type crystalline phase was obtained for the Ce{sub 1−x}Gd{sub x}PO{sub 4} with x = 0–1, and the incorporation of minor actinide curium simulated by gadolinium in monazite was confirmed. The change of Gd content had no significant effect on the microstructure of Ce{sub 1−x}Gd{sub x}PO{sub 4} solid solutions, and the grain size was approximately 0.1–1 μm. Besides, the optimal calcining temperature and holding time of Ce{sub 0.9}Gd{sub 0.1}PO{sub 4} solid solution were 1000 °C and 2 h, respectively.

  20. Solubility, dissolution rate and phase transition studies of ranitidine hydrochloride tautomeric forms.

    Science.gov (United States)

    Mirmehrabi, M; Rohani, S; Murthy, K S K; Radatus, B

    2004-09-10

    Understanding the polymorphic behavior of pharmaceutical solids during the crystallization process and further in post-processing units is crucial to meet medical and legal requirements. In this study, an analytical technique was developed for determining the composition of two solid forms of ranitidine hydrochloride using two peaks of Fourier transform infrared (FTIR) spectra without the need to grind the samples. Solubility studies of ranitidine hydrochloride showed that Form 2 has a higher solubility than Form 1. Solution-mediated transformation is very slow and occurs from Form 2 to Form 1 and not the reverse. No solid-solid transformation was observed due to grinding or compressing the pure samples of either forms and of a 50/50 wt.% mixture. Grinding was found to be a proper technique for increasing the bulk solid density of the ranitidine hydrochloride without the risk of solid-solid transformation. Dissolution rate found to be equally fast for both forms. The solubility data were modeled using the group contribution parameters and UNIversal QUAsi-Chemical (UNIQUAC) theory. There was a good agreement between the experimental solubility data of ranitidine hydrochloride and the results of UNIQUAC equation.

  1. Low-temperature polymorphic phase transition in a crystalline tripeptide L-Ala-L-Pro-Gly·H2O revealed by adiabatic calorimetry.

    Science.gov (United States)

    Markin, Alexey V; Markhasin, Evgeny; Sologubov, Semen S; Ni, Qing Zhe; Smirnova, Natalia N; Griffin, Robert G

    2015-02-05

    We demonstrate application of precise adiabatic vacuum calorimetry to observation of phase transition in the tripeptide L-alanyl-L-prolyl-glycine monohydrate (APG) from 6 to 320 K and report the standard thermodynamic properties of the tripeptide in the entire range. Thus, the heat capacity of APG was measured by adiabatic vacuum calorimetry in the above temperature range. The tripeptide exhibits a reversible first-order solid-to-solid phase transition characterized by strong thermal hysteresis. We report the standard thermodynamic characteristics of this transition and show that differential scanning calorimetry can reliably characterize the observed phase transition with <5 mg of the sample. Additionally, the standard entropy of formation from the elemental substances and the standard entropy of hypothetical reaction of synthesis from the amino acids at 298.15 K were calculated for the studied tripeptide.

  2. Low-Temperature Polymorphic Phase Transition in a Crystalline Tripeptide l-Ala-l-Pro-Gly·H2O Revealed by Adiabatic Calorimetry

    Science.gov (United States)

    Markin, Alexey V.; Markhasin, Evgeny; Sologubov, Semen S.; Ni, Qing Zhe; Smirnova, Natalia N.; Griffin, Robert G.

    2015-01-01

    We demonstrate application of precise adiabatic vacuun calorimetry to observation of phase transition in the tripeptide l-alanyl-l-prolyl-glycine monohydrate (APG) from 6 to 320 K and report the standard thermodynamic properties of the tripeptide in the entire range. Thus, the heat capacity of APG was measured by adiabatic vacuun calorimetry in the above temperature range. The tripeptide exhibits a reversible first-order solid-to-solid phase transition characterized by strong thermal hysteresis. We report the standard thermodynamic characteristics of this transition and show that differential scanning calorimetry can reliably characterize the observed phase transition with <5 mg of the sample. Additionally, the standard entropy of formation from the elemental substances and the standard entropy of hypothetical reaction of synthesis from the amino acids at 298.15 K were calculated for the studied tripeptide. PMID:25588051

  3. Liquid crystalline thermosetting polyimides. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Hoyt, A.E.; Huang, S.J. [Connecticut Univ., Storrs, CT (United States). Inst. of Materials Science

    1993-07-01

    Phase separation of rodlike reinforcing polymers and flexible coil matrix polymers is a common problem in formulating molecular composites. One way to reduce phase separation might be to employ liquid crystalline thermosets as the matrix material. In this work, functionally terminated polyimide oligomers which exhibit lyotropic liquid crystalline behavior were successfully prepared. Materials based on 2,2{prime}-bis(trifluoromethyl)-4,4{prime}-diaminobiphenyl and 3,3{prime},4,4{prime}-biphenylenetetra-carboxylic dianhydride have been synthesized and characterized.

  4. Triblock polyphiles through click chemistry: self-assembled thermotropic cubic phases formed by micellar and monolayer vesicular aggregates.

    Science.gov (United States)

    Tan, Xiaoping; Kong, Leiyang; Dai, Heng; Cheng, Xiaohong; Liu, Feng; Tschierske, Carsten

    2013-11-25

    Three series of triblock polyphiles consisting of a rigid 4-phenyl-1,2,3-triazole or 1,4-diphenyl-1,2,3-triazole core with three lipophilic and flexible alkoxyl chains at one end and a polar glycerol group at the opposite end were synthesized by copper-catalyzed azide-alkyne click reactions. Their mesophase behavior was studied by polarizing optical microscopy, differential scanning calorimetry, and XRD. Depending on alkyl chain length and core length, a transition from hexagonal columnar to Pm3n-type cubic phases was observed. In the cubic phases, the molecules are organized as spherical objects. Remarkably, compounds with a longer core unit have a higher tendency to form these cubic phases, and their stability is strongly enhanced over those of the compounds with a shorter core, despite longer cores having a smaller cone angle and therefore being expected to disfavor the formation of spherical objects. There is a large difference in the number of molecules involved in the spherical aggregates formed by compounds with long and short cores. Whereas the aggregates in the cubic phases of the compounds with short rod units are small and could be regarded as micellar, the long-core compounds form much larger aggregates which are regarded as a kind of monolayer vesicular aggregate.

  5. Swelling equilibrium of dentin adhesive polymers formed on the water-adhesive phase boundary: Experiments and micromechanical model

    Science.gov (United States)

    Misra, Anil; Parthasarathy, Ranganathan; Ye, Qiang; Singh, Viraj; Spencer, Paulette

    2013-01-01

    During their application to the wet, oral environment, dentin adhesives can experience phase separation and composition change which can compromise the quality of the hybrid layer formed at the dentin-adhesive interface. The chemical composition of polymer phases formed in the hybrid layer can be represented using a ternary water-adhesive phase diagram. In this paper, these polymer phases have been characterized using a suite of mechanical tests and swelling experiments. The experimental results were evaluated using granular micromechanics based model that incorporates poro-mechanical effects and polymer-solvent thermodynamics. The variation of the model parameters and model-predicted polymer properties has been studied as a function of composition along the phase boundary. The resulting structure-property correlations provide insight into interactions occurring at the molecular level in the saturated polymer system. These correlations can be used for modeling the mechanical behavior of hybrid layer, and are expected to aid in the design and improvement of water-compatible dentin adhesive polymers. PMID:24076070

  6. Study of clay chemical composition in formation of new phases in crystalline materials ceramic; Estudo da composicao quimica de argilas na formacao de novas fases cristalinas em materiais ceramicos

    Energy Technology Data Exchange (ETDEWEB)

    Lima, L.K.S.; Goncalves, W.P.; Silva, V.J.; Dias, G.; Neves, G.A.; Santana, L.N.L., E-mail: lizandralima15@gmail.com, E-mail: lisiane@dema.ufcg.edu.br [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Unidade Academica de Engenharia dos Materiais

    2016-07-01

    The knowledge of the characteristics of raw materials and the behavior of these during the heat treatment is crucial before starting any manufacturing process of clay-based products. The objective of this work was to study phase transformations of clay under different heat treatments using conventional oven. To achieve the same were used two clays coming from the municipality of Cubati - PB and kaolin from an industry in the Northeast. The samples were subjected to beneficiation process, crushing, grinding and sieving and further characterized: chemical analysis, particle size, thermal and mineralogical. For heat treatment temperatures employed were 1000, 1100 and 1200 ° C, heating rate 5 ° C / min and residence time of 60min. After this step, the mineralogical characterization was performed by x-ray diffraction technique. Clays with larger particle size fraction below 2um and greater amount of flux oxides showed higher amount of mullite for the temperatures studied. The results also showed nucleation of mullite phase from 1100 °C, a band 2theta in the range of between 20 and 25°, characteristic of amorphous silica and the temperature rise was observed intensification of crystalline phases. (author)

  7. Evolution of the crystalline structure in (Bi{sub 0}.5Na{sub 0}.5){sub 1}-xBaxTiO{sub 3} thin films around the Morpho tropic Phase Boundary

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Mezcua, D.; Calzada, M. L.; Bretos, I.; Ricote, J.; Chateigner, D.; Escobar-Galindo, R.; Jimenez, R.; Sirera, R.

    2014-02-01

    (Bi{sub 0}.5Na{sub 0}.5){sub 1}-xBa{sub x}TiO{sub 3} (BNBT), which exhibits compositions for the morphotropic phase boundary (MPB) where exist an intimate coexistence of the rhombohedral and tetragonal structures, is being considered as promising lead-free alternative to the well known Pb(Zr{sub x},Ti{sub 1}-x)O{sub 3} (PZT). In this work, BNBT thin films were fabricated by chemical solution deposition (CSD) with a wide range of compositions (x{approx}{approx}0.050-0.150) onto Pt/TiO{sub 2}/SiO{sub 2}/(100)Si substrates. Structural studies by X-ray diffraction ({lambda}Cu{approx}1.5406 A) using a four-circle goniometer were carried out to determine the crystalline structure of the films. Rietveld analysis of the experimental X-ray patterns showed different volume fractions of the rhombohedral and tetragonal phases as a function of the Ba{sup 2}+ content and the coexistence of both phases, characteristic of a MPB region, for x{approx}­0.055-0.080. Finally, Rutherford backscattering experiments (RBS) were performed to determine the compositional profile of the films. This study revealed a homogenous composition of the BNBT films with abrupt film/substrate interfaces. (Author)

  8. STUDIES ON CRITICAL CONCENTRATION OF LIQUID CRYSTALLINE ETHYLCELLULOSE

    Institute of Scientific and Technical Information of China (English)

    DONG Yanming; ZHANG Shiying

    1996-01-01

    Critical concentrations of lyotropic liquid crystalline ethylcellulose in more than ten cal concentration Ccrit of forming liquid crystal phase decreased with increasing solubility parameter δ of solvent until approaching the δ of polymer. Although the alcohols used as solvents had the same variation rule, the critical concentration values of their solutions were much higher, due to their excessive large hydrogen bond component of δ. The experiments of using mixed solvents which showed good linear relation between Ccrit and δ also proved this rule. A technique of Transmission Optical Analysis was first used to estimate the concentration dependence of critical phase transition temperature Tcrit of EC, and a T-C phase diagram could be drawn.

  9. Matched-filtering generalized phase contrast using LCoS pico-projectors for beam-forming.

    Science.gov (United States)

    Bañas, Andrew; Palima, Darwin; Glückstad, Jesper

    2012-04-23

    We report on a new beam-forming system for generating high intensity programmable optical spikes using so-called matched-filtering Generalized Phase Contrast (mGPC) applying two consumer handheld pico-projectors. Such a system presents a low-cost alternative for optical trapping and manipulation, optical lattices and other beam-shaping applications usually implemented with high-end spatial light modulators. Portable pico-projectors based on liquid crystal on silicon (LCoS) devices are used as binary phase-only spatial light modulators by carefully setting the appropriate polarization of the laser illumination. The devices are subsequently placed into the object and Fourier plane of a standard 4f-setup according to the mGPC spatial filtering configuration. Having a reconfigurable spatial phase filter, instead of a fixed and fabricated one, allows the beam shaper to adapt to different input phase patterns suited for different requirements. Despite imperfections in these consumer pico-projectors, the mGPC approach tolerates phase aberrations that would have otherwise been hard to overcome by standard phase projection.

  10. Effect of Cycle Duration and Phasing on Thermomechanical Fatigue of Dog-Bone Specimens Made form Steel

    Directory of Open Access Journals (Sweden)

    Achegaf Zineb

    2010-01-01

    Full Text Available Problem statement: Lifetime of standard dog-bone specimens made form steel as affected by phasing between thermal cycles and strains cycles and by cycle duration in thermomechanical fatigue is assessed under various conditions of loading. Approach: The methodology used was based on finite element post-processing analysis by specialized fatigue software package that takes into account coupling of damage from three primary sources: Fatigue, oxidation and creep. Results: A parametric study has been conducted for various thermomechanical loadings and effects of phasing and cycle duration on lifetime have been evaluated. The associated percentages of damage mechanisms due to fatigue, oxidation and creep have been determined. Conclusion: It has been shown that both phasing and cycle duration have considerable effect on lifetime. In the range of parameters investigated, the in-phase cycles were found to reduce considerably damage in the specimen for low pressures and low temperatures. The results have shown also that there was no way of unique comparison of the various phasing configurations, since there exists always a case of thermomechanical loading for which one phasing configuration yields higher damage than any another configuration.

  11. Trilayered Morphology of an ABC Triple Crystalline Triblock Terpolymer

    KAUST Repository

    Palacios, Jordana K.

    2017-09-07

    Triple crystalline triblock terpolymers are materials with remarkable semicrystalline superstructures. In this work, we report for first time the alternating triple lamellar morphology that self-assembles inside spherulites of a triblock terpolymer composed of poly(ethylene oxide) (PEO), poly(ε-caprolactone) (PCL), and poly(l-lactide) (PLLA). The morphology of the PEO-b-PCL-b-PLLA triblock terpolymer is compared to an analogous PCL-b-PLLA diblock copolymer. Both diblock and triblock form a single phase in the melt. Two crystallization protocols were employed to create particular crystalline morphologies. In both cases, the isothermal crystallization of the PLA block is induced first (at 81 °C, a temperature above the melting points of both PCL and PEO blocks) and PLLA spherulites form a template, whereupon cooling the other two blocks can crystallize within the PLLA interlamellar spaces. WAXS analysis demonstrated the double crystalline and triple crystalline nature of the materials. The lamellar structure was evaluated by AFM observations and SAXS measurements. Moreover, theoretical SAXS curves of one-dimensional structural models were calculated. AFM micrographs of the triblock terpolymer evidenced the three different lamellae of PLLA, PCL and PEO that coexist together within the same spherulite. Three different lamellar thickness were determined, and their dimensions suggested that all blocks crystallized in chain-folded conformations. The evolution of the triple lamellar morphology during heating of tricrystalline samples was followed by in situ synchrotron SAXS measurements. The theoretical analysis of the SAXS curves of the triblock terpolymer allowed us to propose a stacking morphological model, in which a particular trilayer structure exists, where one lamella of PCL or one lamella of PEO is inserted randomly between two adjacent PLLA lamellae.

  12. Studies of Nucleation and Growth, Specific Heat and Viscosity of Undercooled Melts of Quasicrystals and Polytetrehedral-Phase-Forming Alloys

    Science.gov (United States)

    2003-01-01

    By investigating the properties of quasicrystals and quasicrystal-forming liquid alloys, we may determine the role of ordering of the liquid phase in the formation of quasicrystals, leading to a better fundamental understanding of both the quasicrystal and the liquid. A quasicrystal is solid characterized by a symmetric but non-periodic arrangement of atoms, usually in the form of an icosahedron (12 atoms, 20 triangular faces). It is theorized that the short-range order in liquids takes this same form. The degree of ordering depends on the temperature of the liquid, and affects many of the liquid s properties, including specific heat, viscosity, and electrical resistivity. The MSFC role in this project includes solidification studies, phase diagram determination, and thermophysical property measurements on the liquid quasicrystal-forming alloys, all by electrostatic levitation (ESL). The viscosity of liquid quasicrystal-forming alloys is measured by the oscillating drop method, both in the stable and undercooled liquid state. The specific heat of solid, undercooled liquid, and stable liquid are measured by the radiative cooling rate of the droplets.

  13. Inclusion complexes of ionic liquids and cyclodextrins: are they formed in the gas phase?

    Science.gov (United States)

    Fernandes, Ana M; Schröder, Bernd; Barata, Tânia; Freire, Mara G; Coutinho, João A P

    2014-05-01

    The interaction of imidazolium-based ionic liquids with α- and β-cyclodextrins was investigated by electrospray ionization mass spectrometry with variable collision induced dissociation energy and quantum chemical gas-phase calculations. The center-of-mass energy at which 50% of a precursor ion decomposes (Ecm,1/2) was determined for the isolated [cyclodextrin + cation](+) or [cyclodextrin + anion](-) adduct ions of imidazolium-based ionic liquids with different alkyl chain lengths combined with a large set of anions, such as chloride, bromide, bis(trifluoromethylsulfonyl)imide, tetrafluoroborate, hexafluorophosphate, trifluoromethanesulfonate, methanesulfonate, dicyanamide, and hydrogensulfate. Moreover, both symmetric and asymmetric imidazolium cationic cores were evaluated. The relative interaction energies in the adduct ions were interpreted in terms of the influence of cation/anion structures and their inherent properties, such as hydrophobicity and hydrogen bond accepting ability, in the complexation process with the cyclodextrins. The trends observed in the mass spectral data together with quantum-chemical calculations suggest that in the gas phase, cations and anions will preferentially interact with the lower or upper rim of the cyclodextrin, respectively, as opposed to what has been reported in condensed phase where the formation of an inclusion complex between ionic liquid and cyclodextrin is assumed.

  14. Is uracil aromatic? The enthalpies of hydrogenation in the gaseous and crystalline phases, and in aqueous solution, as tools to obtain an answer.

    Science.gov (United States)

    Galvão, Tiago L P; Rocha, Inês M; da Silva, Maria D M C Ribeiro; da Silva, Manuel A V Ribeiro

    2013-07-18

    The enthalpy of hydrogenation of uracil was derived from the experimental enthalpies of formation, in the gaseous phase, of uracil and 5,6-dihydrouracil, in order to analyze its aromaticity. The enthalpy of formation of 5,6-dihydrouracil was obtained from combustion calorimetry, Knudsen effusion technique and Calvet microcalorimetry results. High-level computational methods were tested for the enthalpy of hydrogenation of uracil, but only with G3 was possible to obtain results in agreement with the experimental ones. It was found that uracil possesses 30.0% of aromatic character in the gaseous phase. Using both implicit, explicit, and hybrid solvation methods, it was possible to obtain a reference value for the enthalpy of hydrogenation of uracil in the aqueous solution and the effect of polarity and hydrogen bonds on the aromaticity of uracil was analyzed. The value of the hydrogenation enthalpy of uracil in aqueous solution was compared with the experimental value in the crystal phase, also dominated by polarity and hydrogen bonds, derived from combustion calorimetry results. The supramolecular effects on the crystal lattice were explored by the computational simulation of π-π staking dimers and hydrogen bonded dimers.

  15. Tunable structures of mixtures of magnetic particles in liquid-crystalline matrices.

    Science.gov (United States)

    Peroukidis, Stavros D; Lichtner, Ken; Klapp, Sabine H L

    2015-08-14

    We investigate the self-organization of a binary mixture of similar sized rods and dipolar soft spheres by means of Monte-Carlo simulations. We model interparticle interactions by employing anisotropic Gay-Berne, dipolar and soft-sphere interactions. In the limit of vanishing magnetic moments we obtain a variety of fully miscible liquid crystalline phases including nematic, smectic and lamellar phases. For the magnetic mixture, we find that the liquid crystalline matrix supports the formation of orientationally ordered ferromagnetic chains. Depending on the relative size of the species the chains align parallel or perpendicular to the director of the rods forming uniaxial or biaxial nematic, smectic and lamellar phases. As an exemplary external perturbation we apply a homogeneous magnetic field causing uniaxial or biaxial ordering to an otherwise isotropic state.

  16. Rad52 forms DMA repair and recombination centers during S phase

    DEFF Research Database (Denmark)

    Lisby, M.; Rothstein, R.; Mortensen, Uffe Hasbro

    2001-01-01

    fluorescent protein (GFP) is fully functional in DNA repair and recombination. After induction of DNA double-strand breaks by gamma -irradiation, meiosis, or the HO endonuclease, Rad52-GFP relocalizes from a diffuse nuclear distribution to distinct foci. Interestingly, Rad52 foci are formed almost exclusively...

  17. Simple determination of ranitidine in dosage forms by in-phase selective AC polarography.

    Science.gov (United States)

    Squella, J A; Zuñiga, L A; Lemus, I; Nuñez-Vergara, L J

    1988-01-01

    A new AC polarographic method for the determination of pharmaceutical forms of ranitidine is proposed, based on the electroactivity of the ranitidine nitro group. Individual and composite assays as well as recovery studies are described. Results show adequate precision and accuracy. Sample preparation is easy and no excipient separation is required.

  18. Structure of the carbon nanofilaments formed by liquid phase carbonization in porous anodic alumina template

    Energy Technology Data Exchange (ETDEWEB)

    Habazaki, H. [Graduate School of Engineering, Hokkaido University, N13-W8, Sapporo 060-8628 (Japan)], E-mail: habazaki@eng.hokudai.ac.jp; Kiriu, M.; Hayashi, M.; Konno, H. [Graduate School of Engineering, Hokkaido University, N13-W8, Sapporo 060-8628 (Japan)

    2007-10-15

    Platelet structure carbon nanofilaments of {approx}30 nm in diameter have been prepared by heating a mixture of porous anodic alumina template and poly(vinyl)chloride (PVC) powders in an argon atmosphere, and the change in their structure and morphology with heat treatment temperature, ranging from 600 to 2800 deg. C, has been examined using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen gas adsorption measurements. The diameter of the carbon nanofilaments formed does not change with heat treatment temperature, being in agreement with the pore diameter of the template, while their length is reduced with the temperature. The platelet-type orientation of graphene layers is evident even at 600 deg. C with the layer structure further developing with increasing heat treatment temperature. The carbon nanofilaments formed at lower temperatures have micropores, while those formed at higher temperatures do not have porosity. Highly graphitized carbon nanofilaments have been obtained after heat treatment at 2800 deg. C, with another characteristic structural feature being presence of loops at the edge of graphene layers formed at 2800 deg. C.

  19. Distributed beam forming with phase-only control for green cognitive radio networks

    NARCIS (Netherlands)

    Lian, X.; Nikookar, H.; Ligthart, L.P.

    2012-01-01

    Cognitive radio (CR) is an intelligent radio system and is able to share the spectrum with licensed users (LU). By adopting adaptive beam forming techniques, CR can reuse the spectrum with LU via directing main beams towards CR users while displaying nulls towards LU. In this article, we present a n

  20. Stabilization of NaCl-containing cuttings wastes in cement concrete by in situ formed mineral phases.

    Science.gov (United States)

    Filippov, Lev; Thomas, Fabien; Filippova, Inna; Yvon, Jacques; Morillon-Jeanmaire, Anne

    2009-11-15

    Disposal of NaCl-containing cuttings is a major environmental concern due to the high solubility of chlorides. The present work aims at reducing the solubility of chloride by encapsulation in low permeability matrix as well as lowering its solubility by trapping into low-solubility phases. Both the studied materials were cuttings from an oil-based mud in oil drillings containing about 50% of halite, and cuttings in water-based mud from gas drilling containing 90% of halite. A reduction in the amount of dissolved salt from 41 to 19% according to normalized leaching tests was obtained by addition of potassium ortho-phosphate in the mortar formula of oil-based cuttings, while the aluminium dihydrogeno-phosphate is even more efficient for the stabilization of water-based cuttings with a NaCl content of 90%. Addition of ortho-phosphate leads to form a continuous and weakly soluble network in the cement matrix, which reduces the release of salt. The formed mineralogical phases were apatite and hydrocalumite. These phases encapsulate the salt grains within a network, thus lowering its interaction with water or/and trap chloride into low-solubility phases. The tested approaches allow to develop a confinement process of NaCl-containing waste of various compositions that can be applied to wastes, whatever the salt content and the nature of the drilling fluids (water or oil).

  1. Synthesis and Phase Behavior of Branched-Arm Liquid Crystalline-Containing Isosorbide with Chiral Core%以手性核为中心的枝臂液晶的合成与相行为

    Institute of Scientific and Technical Information of China (English)

    何晓智; 韩丽; 姚丹姝; 田梅

    2013-01-01

    In this paper, three branched-arm liquid crystalline:bi-10-(4(4-(4-ethoxyl)benzoxy)biphenyl) decylic acid isosorbide ester(MA1) , bi-4-[10-(4(4-(4-ethoxyl)biphenyl)biphenyl)oxycarbonyl capryloxy] benzoic isosorbide ester(MA2), bi-3,4,5-三-[l0-(4(4-(4-ethoxyl)benzoxy)biphenyl)oxycarbonyl capryloxy] benzoic isosorbide ester (MA3), were synthesized. The structures, optical and thermodynamic properties of the liquid crystalline were investigated by FT-IR spectroscopy, 1H-NMR, differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). MA1 ~ MA3 all show the cholesteric phase. MA3 which has six-arms owns more liquid crystalline texture and wide scopes of liquid crystalline phase. MA1 and MA2 have the right-hand rotation, but MA3 owns the left-hand rotation, which is opposite to the rotation of the chiral core. These branched-arm molecules turn out good fluidity and clear characteristic texture.%设计与合成了3种以异山梨醇为手性核中心的枝臂液晶分子——双-10-(4-(4-(4-乙氧基)苯甲酰氧基)联苯)氧羰基癸酸异山梨醇酯(MA1)、双-4-[10-(4-(4-(4-乙氧基)苯甲酰氧基)联苯)氧羰基癸酰氧基]苯甲(酸)异山梨醇酯(MA2)、双-3,4,5-三-[10-(4-(4-(4-乙氧基)苯甲酰氧基)联苯)氧羰基癸酰氧基]苯甲酸异山梨醇酯(MA3).通过红外光谱、核磁共振、偏光显微镜、差示扫描量热和X射线衍射等手段研究了枝臂液晶分子的结构和性能.MA1~MA3均为胆甾相液晶,且具有6个臂的MA3织构较丰富且液晶相范围也较宽.手性分子MA1、MA2为右旋,而MA3为左旋,与手性核的旋光度方向相反,具有很好的流动性及清晰的特征织构.

  2. ZrNi5-based hydrogenated phases formed under high hydrogen pressure conditions

    Energy Technology Data Exchange (ETDEWEB)

    Filipek, Stanislaw M., E-mail: sfilipek@ichf.edu.pl [Institute of Physical Chemistry PAS, ul. Kasprzaka 44, 01-224 Warsaw (Poland); Paul-Boncour, Valerie [Laboratoire de Chimie Metallurgique des Terres Rares, CNRS, 2-8 rue H. Dunant, 94320 Thiais (France); Liu, Ru-Shi [Department of Chemistry, National Taiwan University, Taipei, Taiwan (China)

    2011-07-15

    Formation of novel hydrides from ZrNi{sub 5} alloy has been confirmed experimentally. After exposure of ZrNi{sub 5} at 0.9 GPa(H{sub 2}) and 100 {sup o}C for 6 days the alloy transformed into two hydrogenated phases {alpha} and {beta} containing initially more than 0.38 and 0.86 hydrogen atoms per formula unit respectively. At ambient conditions both hydrides were extremely unstable. Major part of hydrogen desorbed within few minutes. During this desorption the lattice parameters of both hydrides were continuously reduced what confirms their solid solution character.

  3. Investigation of the amorphous to crystalline phase transition of chemical solution deposited Pb(Zr30Ti70)O3 thin films by soft x-ray absorption and soft x-ray emission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Schneller, T.; Schneller, T.; Kohlstedt, H.; Petraru, A.; Waser, R.; Guo, J.; Denlinger, J.; Learmonth, T.; Glans, Per-Andres; Smith, K. E.

    2008-08-01

    Chemical solution deposited (CSD) complex oxide thin films attract considerable interest in various emerging fields as for example, fuel cells, ferroelectric random access memories or coated conductors. In the present paper the results of soft-x-ray spectroscopy between 100 eV and 500 eV on the amorphous to crystalline phase transition of ferroelectric PbZr{sub 0.3}Ti{sub 0.7}O{sub 3} (PZT) thin films are presented. Five CSD samples derived from the same wafer coated with a PZT film pyrolyzed at 350 C were heat treated at different temperatures between 400 C and 700 C. At first the sample were morphologically and electrically characterized. Subsequently the soft-x-ray absorption and emission experiments were performed at the undulator beamline 8.0 of the Advanced Light Source of the Lawrence Berkeley National Laboratory. Soft-x-ray absorption spectra were acquired for the Ti L{sub 2,3-}, O K-, and C K-edge thresholds by using simultaneously the total electron yield (TEY) and total fluorescence yield (TFY) detection methods. For two samples, annealed at 400 C and 700 C, respectively, the resonant inelastic soft-x-ray spectroscopy (RIXS) was applied for various excitation energies near the Ti L-, O K-edges. We observed clear evidence of a rutile phase at untypically low temperatures. This rutile phase transforms into the perovskite phase upon increasing annealing temperature. These results are discussed in the framework of current microscopic models of the PZT (111) texture selection.

  4. Crystalline Silicon Dielectrics for Superconducting Qubit Circuits

    Science.gov (United States)

    Hover, David; Peng, Weina; Sendelbach, Steven; Eriksson, Mark; McDermott, Robert

    2009-03-01

    Superconducting qubit energy relaxation times are limited by microwave loss induced by a continuum of two-level state (TLS) defects in the dielectric materials of the circuit. State-of-the-art phase qubit circuits employ a micron-scale Josephson junction shunted by an external capacitor. In this case, the qubit T1 time is directly proportional to the quality factor (Q) of the capacitor dielectric. The amorphous capacitor dielectrics that have been used to date display intrinsic Q of order 10^3 to 10^4. Shunt capacitors with a Q of 10^6 are required to extend qubit T1 times well into the microsecond range. Crystalline dielectric materials are an attractive candidate for qubit capacitor dielectrics, due to the extremely low density of TLS defects. However, the robust integration of crystalline dielectrics with superconducting qubit circuits remains a challenge. Here we describe a novel approach to the realization of high-Q crystalline capacitor dielectrics for superconducting qubit circuits. The capacitor dielectric is a crystalline silicon nanomembrane. We discuss characterization of crystalline silicon capacitors with low-power microwave transport measurements at millikelvin temperatures. In addition, we report progress on integrating the crystalline capacitor process with Josephson qubit fabrication.

  5. Separación de fases y cristalinidad en mezclas epoxy/poli-3-hidroxibutirato Phase separation and crystallinity in epoxy/poly-3-hydroxybutyrate blends

    Directory of Open Access Journals (Sweden)

    Sebastián Tognana

    2013-01-01

    Full Text Available En este trabajo se estudiaron mezclas epoxy/poli-3-hidroxibutirato (PHB en dos proporciones distintas 90/10 y 85/15. Para ello se prepararon muestras sometiéndolas a temperaturas de 80 ºC y 120 ºC, a efectos de producir el curado del epoxy. Se analizó la separación de fases y la cristalización del PHB mediante microscopía óptica y calorimetría diferencial de barrido. Asimismo la estructura lamelar del PHB se caracterizó mediante dispersión de rayos X de bajo ángulo. Se encontraron diferencias significativas entre las dos proporciones estudiadas; mientras que la muestra 90/10 presenta miscibilidad, la muestra 85/15 indica una separación de fases. Asimismo se encontró que, sobre todo para la muestra 90/10, el epoxy afecta considerablemente la estructura lamelar del PHB. Los resultados se analizaron en términos de la competencia entre los procesos de cristalización y separación de fases.In this work, epoxy/poly-3-hydroxybutyrate (PHB blends in two different proportions, 90/10 and 85/15, were studied. For this purpose, the samples were submitted to 80ºC and 120ºC for the curing process of epoxy. The phase separation and the crystallization were analyzed using optical microscopy and differential scanning calorimetry. Likewise, the lamellar structure of PHB was characterized using small angle X-ray scattering. Significant differences between the two proportions studied were found; while the 90/10 sample presents miscibility, the 85/15 sample indicates a phase separation. Besides, the lamellar structure of PHB is affected due to the epoxy, mainly in the 90/10 sample. The results were analyzed on the basis of the competition between crystallization and phase separation processes.

  6. Confocal Raman studies in determining crystalline nature of PECVD grown Si nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, Nafis; Bhargav, P. Balaji; Ramasamy, P. [SSN Research Centre, Kalavakkam-603110, Tamilnadu (India); Department of Physics, SSN College of Engineering, Kalavakkam-603110, Tamilnadu (India); Sivadasan, A. K.; Tyagi, A. K.; Dhara, S., E-mail: dhara@igcar.gov.in [Surface and Nanoscience Division, Indira Gandhi Centre for Atomic Research, Kalpakkam-603102 (India); Amirthapandian, S.; Panigrahi, B. K. [Materials Physics Division, Indira Gandhi Centre for Atomic Research, Kalpakkam-603102 (India); Bhattacharya, S. [SSN Research Centre, Kalavakkam-603110, Tamilnadu (India)

    2015-06-24

    Silicon nanowires of diameter ∼200 nm and length of 2-4 µm are grown in the plasma enhanced chemical vapour deposition technique using nanoclustered Au catalyst assisted vapour-liquid-solid process. The crystallinity in the as-grown and annealed samples is studied using confocal Raman spectroscopic studies. Amorphous phase is formed in the as-grown samples. Structural studies using high resolution transmission electron microscopy confirm the polycrystalline nature in the annealed sample.

  7. First detection of gas-phase ammonia in a planet-forming disk

    CERN Document Server

    Salinas, Vachail N; Bergin, Edwin A; Cleeves, L Ilsedore; Brinch, Christian; Blake, Geoffrey A; Lis, Dariusz C; Melnick, Gary J; Panić, Olja; Pearson, John C; Kristensen, Lars; Yıldız, Umut A; van Dishoeck, Ewine F

    2016-01-01

    Nitrogen chemistry in protoplanetary disks and the freeze-out on dust particles is key to understand the formation of nitrogen bearing species in early solar system analogs. So far, ammonia has not been detected beyond the snowline in protoplanetary disks. We aim to find gas-phase ammonia in a protoplanetary disk and characterize its abundance with respect to water vapor. Using HIFI on the Herschel Space Observatory we detect, for the first time, the ground-state rotational emission of ortho-NH$_3$ in a protoplanetary disk, around TW Hya. We use detailed models of the disk's physical structure and the chemistry of ammonia and water to infer the amounts of gas-phase molecules of these species. We explore two radial distributions ( confined to $<$60 au like the millimeter-sized grains) and two vertical distributions (near the midplane where water is expected to photodesorb off icy grains) to describe the (unknown) location of the molecules. These distributions capture the effects of radial drift and vertical...

  8. New milarite/osumilite-type phase formed during ancient glazing of an Egyptian scarab

    Science.gov (United States)

    Artioli, G.; Angelini, I.; Nestola, F.

    2013-02-01

    A scarab found in grave 25 of the Monte Prama necropolis, near Cabras, Oristano, Sardinia, is of special importance for the archaeological interpretation and dating of this important archaeological site. The object has been misinterpreted in the past as composed by bone: recent archaeometric analyses showed that it is a glazed steatite of Egyptian origin and that the altered surface contains interesting phases crystallized during the high-temperature interaction of the Mg-rich talc core with the alkali-rich glass used for glazing. A novel single crystal X-ray diffraction analysis of one of the phases indicates that it is a new compound having the milarite-osumilite structure type, with a peculiar composition close to (Na1.52K0.12□0.36)(Mg3)(Mg1.72Cu0.16Fe0.12)(Si11.4Al0.6)O30, not reported for naturally occurring minerals. The structural and crystal chemical features of the compound, together with the known high-temperature stability of the series, allow a complete interpretation of the glazing process and conditions, based on direct application of the glaze on the steatite core with subsequent treatment at temperatures above 1000 °C.

  9. Synergistic Effects of Sm and C Co-Doped Mixed Phase Crystalline TiO2 for Visible Light Photocatalytic Activity

    Directory of Open Access Journals (Sweden)

    Fuchang Peng

    2017-02-01

    Full Text Available Mixed phase TiO2 nanoparticles with element doping by Sm and C were prepared via a facile sol-gel procedure. The UV-Vis light-diffuse reflectance spectroscopy analysis showed that the absorption region of co-doped TiO2 was shifted to the visible-light region, which was attributed to incorporation of samarium and carbon into the TiO2 lattice during high-temperature reaction. Samarium effectively decreased the anatase-rutile phase transformation. The grain size can be controlled by Sm doping to achieve a large specific surface area useful for the enhancement of photocatalytic activity. The photocatalytic activities under visible light irradiation were evaluated by photocatalytic degradation of methylene blue (MB. The degradation rate of MB over the Sm-C co-doped TiO2 sample was the best. Additionally, first-order apparent rate constants increased by about 4.3 times compared to that of commercial Degusssa P25 under the same experimental conditions. Using different types of scavengers, the results indicated that the electrons, holes, and •OH radicals are the main active species for the MB degradation. The high visible-light photocatalytic activity was attributed to low recombination of the photo-generated electrons and holes which originated from the synergistic effect of the co-doped ions and the heterostructure.

  10. Dry Powder Precursors of Cubic Liquid Crystalline Nanoparticles (cubosomes)

    Science.gov (United States)

    Spicer, Patrick T.; Small, William B.; Small, William B.; Lynch, Matthew L.; Burns, Janet L.

    2002-08-01

    Cubosomes are dispersed nanostructured particles of cubic phase liquid crystal that have stimulated significant research interest because of their potential for application in controlled-release and drug delivery. Despite the interest, cubosomes can be difficult to fabricate and stabilize with current methods. Most of the current work is limited to liquid phase processes involving high shear dispersion of bulk cubic liquid crystalline material into sub-micron particles, limiting application flexibility. In this work, two types of dry powder cubosome precursors are produced by spray-drying: (1) starch-encapsulated monoolein is produced by spray-drying a dispersion of cubic liquid crystalline particles in an aqueous starch solution and (2) dextran-encapsulated monoolein is produced by spray-drying an emulsion formed by the ethanol-dextran-monoolein-water system. The encapsulants are used to decrease powder cohesion during drying and to act as a soluble colloidal stabilizer upon hydration of the powders. Both powders are shown to form (on average) 0.6 μm colloidally-stable cubosomes upon addition to water. However, the starch powders have a broader particle size distribution than the dextran powders because of the relative ease of spraying emulsions versus dispersions. The developed processes enable the production of nanostructured cubosomes by end-users rather than just specialized researchers and allow tailoring of the surface state of the cubosomes for broader application.

  11. Smeared gap equations in crystalline color superconductivity

    CERN Document Server

    Ruggieri, M

    2006-01-01

    In the framework of HDET, we discuss an averaging procedure of the NJL quark-quark interaction lagrangian, treated in the mean field approximation, for the two flavor LOFF phase of QCD. This procedure gives results which are valid in domains where Ginzburg-Landau results may be questionable. We compute and compare the free energy for different LOFF crystalline structures.

  12. Crystalline damage development during martensitic transformations

    NARCIS (Netherlands)

    Suiker, A.S.J.; Turteltaub, S.R.

    2006-01-01

    A recently developed thermo-mechanical model [1] is presented that can be used to simulate the interactions between martensitic phase transformations and crystalline damage growth at the austenitic grain level. Subgrain information is included in the model via the crystallographic theory of martensi

  13. Defect structure of erbium-doped <1 1 1> silicon layers formed by solid phase epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Kyutt, R.N.; Sobolev, Nikolai A. E-mail: nick@sobolev.ioffe.rssi.ru; Nikolaev, Yu. A.; Vdovin, V.I

    2001-01-01

    Erbium-doped layers have been produced on <1 1 1>-oriented silicon wafers using high-energy amorphizing Er implants and solid phase epitaxy (SPE). Transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques, used to study the microstructure of these layers, revealed the presence of microtwins and dislocations. The twins were found to be platelets with lateral dimensions of 15-30 nm and a thickness of about 2-9 nm, and their density throughout the regrown layer was nonuniform. The dislocation densities observed in the regrown layers were very high with densities exceeding 10{sup 10} cm{sup -2}. Within the implant fluence range studied, between 1x10{sup 14} and 9x10{sup 14} Er cm{sup -2}, the twin and dislocation densities were observed to increase with fluence, while the twin dimensions were found to decrease.

  14. Sintering activation of 316L powder using a liquid phase forming powder

    Directory of Open Access Journals (Sweden)

    Nattaya Tosangthum

    2010-03-01

    Full Text Available It was found that the addition of a liquid forming powder (up to 6 wt.% of a gas-atomized tin powder to 316L powdercould activate the sintering process. Sintering activation could be observed by an increase of the sintered density and selected mechanical properties. When optimized tin powder content was used, shorter sintering time and lower sintering temperaturecould produce sintered 316L+tin materials with excellent mechanical properties. Electron dispersive spectroscopy analyses across 316L-tin-316L grains indicated that Ni transportation during the sintering process was enhanced by the presence of liquid tin.

  15. Anisotropic phase diagram and superconducting fluctuations of single-crystalline SmFeAsO0.85F0.15

    Science.gov (United States)

    Welp, U.; Chaparro, C.; Koshelev, A. E.; Kwok, W. K.; Rydh, A.; Zhigadlo, N. D.; Karpinski, J.; Weyeneth, S.

    2011-03-01

    We report on the specific-heat determination of the anisotropic phase diagram of single crystals of optimally doped SmFeAsO1-xFx. In zero field, we find a clear cusplike anomaly in C/T with ΔC/Tc=24 mJ/mol K2 at Tc=49.5 K. In magnetic fields along the c axis, pronounced superconducting fluctuations induce broadening and suppression of the specific-heat anomaly which can be described using three-dimensional lowest-Landau-level scaling with an upper critical field slope of -3.5 T/K and an anisotropy of Γ =8. The small value of ΔC/Tc yields a Sommerfeld coefficient γ ˜ 8 mJ/mol K2, indicating that SmFeAsO1-xFx is characterized by a modest density of states and strong coupling.

  16. The determination of the phase transition temperatures of a semifluorinated liquid crystalline biphenyl ester by impedance spectroscopy as an alternative method

    Science.gov (United States)

    Yıldız, Alptekin; Canli, Nimet Yilmaz; Karanlık, Gürkan; Ocak, Hale; Okutan, Mustafa; Eran, Belkız Bilgin

    2016-12-01

    Dielectric spectroscopy (DS) is a very powerful and important for better understanding of the molecular dynamics and relaxation phenomena in liquid crystals. The dielectric and impedance characteristics Ethyl 4-(7,7,8,8,9,9,10,10,10-nonafluorodecyloxy)biphenyl-4‧-carboxylate (ENBC) liquid crystal have been analyzed over the frequency range of 100 Hz to MHz in the temperature region from room temperature to 180 °C. The compound ENBC shows enantiotropic a smectic mesophase in a wide temperature range. The phase transition temperatures T (°C) of the liquid crystal ENBC, which were characterized by Differential Scanning Calorimetry (DSC), have been verified by the dielectric measurements and conductivity mechanisms of the ENBC. The activation energies for some selected angular frequencies have also been calculated.

  17. Photodegradation of sugarcane vinasse: evaluation of the effect of vinasse pre-treatment and the crystalline phase of TiO2

    Directory of Open Access Journals (Sweden)

    Renata Padilha de Souza

    2016-04-01

    Full Text Available In this work, photocatalysis was employed in the treatment of vinasse using TiO2 and UV light. The parameters investigated were: TiO2 phases (anatase and rutile and vinasse pre-treatments (coagulation/flocculation and dilution. The TiO2 catalysts employed were: Kronos without thermal treatment (100% anatase, calcined at 1000°C (33.5% anatase and immobilized on glass slides (100% anatase; and P25 Degussa without thermal treatment (86.6% anatase. The results showed that natural coagulant removed about 50, 85 and 97% of COD, color and turbidity, respectively. However, pre-treatment followed by photocatalysis with TiO2 87% anatase removed 67% of COD within 48h of irradiation. Bioassays with Artemia salina confirmed the efficacy of the methodology. The treatments reduced the toxicity of vinasse by up to 10 times.

  18. The determination of the phase transition temperatures of a semifluorinated liquid crystalline biphenyl ester by impedance spectroscopy as an alternative method

    Energy Technology Data Exchange (ETDEWEB)

    Yıldız, Alptekin [Istanbul Technical University, Department of Physics Engineering, Maslak, 34469 Istanbul (Turkey); Yildiz Technical University, Department of Physics, 34220 Istanbul (Turkey); Canli, Nimet Yilmaz, E-mail: niyilmaz@yahoo.com [Yildiz Technical University, Department of Physics, 34220 Istanbul (Turkey); Karanlık, Gürkan; Ocak, Hale [Yildiz Technical University, Department of Chemistry, 34220 Istanbul (Turkey); Okutan, Mustafa [Yildiz Technical University, Department of Physics, 34220 Istanbul (Turkey); Eran, Belkız Bilgin [Yildiz Technical University, Department of Chemistry, 34220 Istanbul (Turkey)

    2016-12-15

    Dielectric spectroscopy (DS) is a very powerful and important for better understanding of the molecular dynamics and relaxation phenomena in liquid crystals. The dielectric and impedance characteristics Ethyl 4-(7,7,8,8,9,9,10,10,10-nonafluorodecyloxy)biphenyl-4′-carboxylate (ENBC) liquid crystal have been analyzed over the frequency range of 100 Hz to MHz in the temperature region from room temperature to 180 °C. The compound ENBC shows enantiotropic a smectic mesophase in a wide temperature range. The phase transition temperatures T (°C) of the liquid crystal ENBC, which were characterized by Differential Scanning Calorimetry (DSC), have been verified by the dielectric measurements and conductivity mechanisms of the ENBC. The activation energies for some selected angular frequencies have also been calculated.

  19. Аnodic formation of nanoporous crystalline niobium oxide

    Directory of Open Access Journals (Sweden)

    LEONID SKATKOV

    2014-05-01

    Full Text Available The research results of anodic deposition of crystalline niobium oxide are presented in this work. The factors that have an impact on crystalline phase nucleation and its primary growth are revealed. Dependence of morphology and properties of nanoporous niobium oxide on modes of its formation is shown.

  20. Radionuclide Retention Mechanisms in Secondary Waste-Form Testing: Phase II

    Energy Technology Data Exchange (ETDEWEB)

    Um, Wooyong; Valenta, Michelle M.; Chung, Chul-Woo; Yang, Jungseok; Engelhard, Mark H.; Serne, R. Jeffrey; Parker, Kent E.; Wang, Guohui; Cantrell, Kirk J.; Westsik, Joseph H.

    2011-09-26

    This report describes the results from laboratory tests performed at Pacific Northwest National Laboratory (PNNL) for Washington River Protection Solutions (WRPS) to evaluate candidate stabilization technologies that have the potential to successfully treat liquid secondary waste stream effluents produced by the Hanford Tank Waste Treatment and Immobilization Plant (WTP). WRPS is considering the design and construction of a Solidification Treatment Unit (STU) for the Effluent Treatment Facility (ETF) at Hanford. The ETF, a multi-waste, treatment-and-storage unit that has been permitted under the Resource Conservation and Recovery Act (RCRA), can accept dangerous, low-level, and mixed wastewaters for treatment. The STU needs to be operational by 2018 to receive secondary liquid waste generated during operation of the WTP. The STU will provide the additional capacity needed for ETF to process the increased volume of secondary waste expected to be produced by WTP. This report on radionuclide retention mechanisms describes the testing and characterization results that improve understanding of radionuclide retention mechanisms, especially for pertechnetate, {sup 99}TcO{sub 4}{sup -} in four different waste forms: Cast Stone, DuraLith alkali aluminosilicate geopolymer, encapsulated fluidized bed steam reforming (FBSR) product, and Ceramicrete phosphate bonded ceramic. These data and results will be used to fill existing data gaps on the candidate technologies to support a decision-making process that will identify a subset of the candidate waste forms that are most promising and should undergo further performance testing.

  1. DEVELOPMENT OF CRYSTALLINE CERAMICS FOR IMMOBILIZATION OF ADVANCED FUEL CYCLE REPROCESSING WASTES

    Energy Technology Data Exchange (ETDEWEB)

    Fox, K.; Brinkman, K.

    2011-09-22

    The Savannah River National Laboratory (SRNL) is developing crystalline ceramic waste forms to incorporate CS/LN/TM high Mo waste streams consisting of perovskite, hollandite, pyrochlore, zirconolite, and powellite phase assemblages. Simple raw materials, including Al{sub 2}O{sub 3}, CaO, and TiO{sub 2} were combined with simulated waste components to produce multiphase crystalline ceramics. Fiscal Year 2011 (FY11) activities included (i) expanding the compositional range by varying waste loading and fabrication of compositions rich in TiO{sub 2}, (ii) exploring the processing parameters of ceramics produced by the melt and crystallize process, (iii) synthesis and characterization of select individual phases of powellite and hollandite that are the target hosts for radionuclides of Mo, Cs, and Rb, and (iv) evaluating the durability and radiation stability of single and multi-phase ceramic waste forms. Two fabrication methods, including melting and crystallizing, and pressing and sintering, were used with the intent of studying phase evolution under various sintering conditions. An analysis of the XRD and SEM/EDS results indicates that the targeted crystalline phases of the FY11 compositions consisting of pyrochlore, perovskite, hollandite, zirconolite, and powellite were formed by both press and sinter and melt and crystallize processing methods. An evaluation of crystalline phase formation versus melt processing conditions revealed that hollandite, perovskite, zirconolite, and residual TiO{sub 2} phases formed regardless of cooling rate, demonstrating the robust nature of this process for crystalline phase development. The multiphase ceramic composition CSLNTM-06 demonstrated good resistance to proton beam irradiation. Electron irradiation studies on the single phase CaMoO{sub 4} (a component of the multiphase waste form) suggested that this material exhibits stability to 1000 years at anticipated self-irradiation doses (2 x 10{sup 10}-2 x 10{sup 11} Gy), but that

  2. Chemical characterization of the main secondary organic aerosol (SOA products formed through aqueous-phase photonitration of guaiacol

    Directory of Open Access Journals (Sweden)

    Z. Kitanovski

    2014-04-01

    Full Text Available Guaiacol (2-methoxyphenol and its derivatives can be emitted into the atmosphere by thermal degradation (i.e. burning of wood lignins. Due to its volatility, guaiacol is predominantly distributed in the atmospheric gaseous phase. Recent studies have shown the importance of aqueous-phase reactions in addition to the dominant gas-phase and heterogeneous reactions of guaiacol, in the formation of secondary organic aerosol (SOA in the atmosphere. The main objectives of the present study were to chemically characterize the low-volatility SOA products of the aqueous-phase photonitration of guaiacol and examine their possible presence in urban atmospheric aerosols. The aqueous-phase reactions were carried out under simulated sunlight and in the presence of H2O2 and nitrite. The formed guaiacol reaction products were concentrated by using solid-phase extraction (SPE and then purified by means of semi-preparative high-performance liquid chromatography (HPLC. The fractionated individual compounds were isolated as pure solids and further analyzed with liquid-state 1H, 13C and 2D nuclear magnetic resonance (NMR spectroscopy and direct infusion negative ion electrospray ionization tandem mass spectrometry ((–ESI-MS/MS. The NMR and product ion (MS2 spectra were used for unambiguous product structure elucidation. The main products of guaiacol photonitration are 4-nitroguaiacol (4NG, 6-nitroguaiacol (6NG, and 4,6-dinitroguaiacol (4,6DNG. Using the isolated compounds as standards, 4NG and 4,6DNG were unambiguously identified in winter PM10 aerosols from the city of Ljubljana (Slovenia by means of HPLC/(–ESI-MS/MS. Owing to the strong absorption of UV and visible light, 4,6DNG could be an important constituent of atmospheric "brown" carbon, especially in regions affected by biomass burning.

  3. Spray forming -- Aluminum: Third annual report (Phase 2). Technical progress -- Summary

    Energy Technology Data Exchange (ETDEWEB)

    Kozarek, R.L.

    1998-04-20

    Commercial production of aluminum sheet and plate by spray atomization and deposition is a potentially attractive manufacturing alternative to conventional ingot metallurgy/hot-milling and to continuous casting processes because of reduced energy requirements and reduced cost. To realize the full potential of the technology, the Aluminum Company of America (Alcoa), under contract by the US Department of Energy, is investigating currently available state-of-the-art atomization devices to develop nozzle design concepts whose spray characteristics are tailored for continuous sheet production. This third technical progress report will summarize research and development work conducted during the period 1997 October through 1998 March. Included are the latest optimization work on the Alcoa III nozzle, results of spray forming runs with 6111 aluminum alloy and preliminary rolling trials of 6111 deposits.

  4. X-Ray Diffraction Reference Intensity Ratios of Amorphous and Poorly Crystalline Phases: Implications for CheMin on the Mars Science Laboratory

    Science.gov (United States)

    Morris, R. V.; Achilles, C. N.; Chipera, S. J.; Ming, D. W.; Rampe, E. B.

    2013-01-01

    The CheMin instrument on the Mars Science Laboratory (MSL) rover Curiosity is an X-ray diffraction (XRD) and X-ray fluorescence (XRF) instrument capable of providing the mineralogical and chemical compositions of rocks and soils on the surface of Mars. CheMin uses a microfocus X-ray tube with a Co target, transmission geometry, and an energy-discriminating X-ray sensitive CCD to produce simultaneous 2-D XRD patterns and energy-dispersive X-ray histograms from powdered samples. Piezoelectric vibration of the cell is used to randomize the sample to reduce preferred orientation effects. Instrument details are provided in [1, 2, 3]. Analyses of rock and soil samples by the Mars Exploration Rovers (MER) show nanophase ferric oxide (npOx) is a significant component of the Martian global soil [4] and is thought to be one of the major contributing phases that the Curiosity rover will encounter if a soil sample is analyzed in Gale Crater. Because of the nature of this material, npOx will likely contribute to an X-ray amorphous or short-order component of a XRD pattern measured by the CheMin instrument.

  5. Electron beam-formed ferromagnetic defects on MoS2 surface along 1 T phase transition

    Science.gov (United States)

    Han, Sang Wook; Park, Youngsin; Hwang, Young Hun; Jekal, Soyoung; Kang, Manil; Lee, Wang G.; Yang, Woochul; Lee, Gun-Do; Hong, Soon Cheol

    2016-12-01

    1 T phase incorporation into 2H-MoS2 via an optimal electron irradiation leads to induce a weak ferromagnetic state at room temperature, together with the improved transport property. In addition to the 1T-like defects, the electron irradiation on the cleaved MoS2 surface forms the concentric circle-type defects that are caused by the 2 H/1 T phase transition and the vacancies of the nearby S atoms of the Mo atoms. The electron irradiation-reduced bandgap is promising in vanishing the Schottky barrier to attaining spintronics device. The simple method to control and improve the magnetic and electrical properties on the MoS2 surface provides suitable ways for the low-dimensional device applications.

  6. Early Phases Of Galaxy Assembly Revealed By Young Star-Forming Dwarfs At Z 3

    Science.gov (United States)

    Amorín, Ricardo; VUDS Collaboration

    2017-06-01

    Studying lower-redshift analogs of the first galaxies is essential to scrutinize the details of galaxy formation and cosmic reionization, paving the way for a better interpretation of observations of primeval galaxies with the James Webb Space Telescope. In this talk I will present a thorough study of a recently discovered population of small, sub-L* star-forming galaxies at redshift z 2-4 that exhibit all the rest-frame properties expected for early galaxies in their first epoch of assembling and chemical enrichment. Selected by their strong nebular emission in the UV (including emission lines such as CIII]1908, CIV1550 and OIII]1664) from thousands of galaxies in the VIMOS Ultra Deep Survey, these young low mass systems are extremely metal-deficient galaxies that are likely experiencing their first significant starburst episode. I will discuss their rest-frame properties, hard radiations fields, strong Lyman-alpha emission, HST morphologies and strongly sub-solar chemical abundances. Finally, I will compare their properties with that of galaxies observed at the edge of the reionization epoch, which pose interesting prospects for JWST studies.

  7. CO observations of massive star forming regions at different evolutionary phases

    Institute of Scientific and Technical Information of China (English)

    CHEN; Xi; XU; Ye; SHEN; Zhiqiang; LI; Jingjing

    2006-01-01

    The 12CO (J=1-0), 13CO (J=1-0) and C18O (J=1-0) emissions in 9 massive star forming regions, which are believed to be at different stages of massive star formation,were mapped with the 13.7 m millimeter wave telescope at Qinghai Station of Purple Mountain Observatory. Of the observed 9 sources, 13CO cores were detected in seven of them, and C18O cores in five of them. And only two sources associated with C18O cores and H2O masers showed the extended structures and strong outflows. This is the first detection of outflow associated with IRAS 22566+5828 in the observing field of S152/S153.The physical parameters of cores and outflows for these sources, derived from Local Thermal Equilibrium (LTE) analysis, are presented. These observing results suggest that the C18O cores will only appear when the gas density is high enough and the probability to have an outflow is very high when the clumps show the C18O and H2O maser simultaneously.

  8. The use of surfactants to enhance the solubility and stability of the water-insoluble anticancer drug SN38 into liquid crystalline phase nanoparticles.

    Science.gov (United States)

    Ranneh, Abdul-Hackam; Iwao, Yasunori; Noguchi, Shuji; Oka, Toshihiko; Itai, Shigeru

    2016-12-30

    Cubosomes were used to increase the aqueous solubility of the water insoluble anticancer drug SN38. The results showed that the use of a common cubosome formulation consisting of phytantriol (PHYT) as the matrix amphiphile (PHYT-cubosome) led to a 6-fold increase in the solubility of SN38. However, mean hydrodynamic diameter (DH) and polydispersity index (PDI) of these PHYT-cubosome particles were 345±49nm and 0.37±0.05, respectively, making them unsuitable for intravenous applications. Several additives were investigated to increase the solubility of SN38 and reduce the DH and PDI values of the resulting particles. Charged additives such as didodecyldimethyl ammonium bromide (DDAB) and sodium dodecyl sulfate (SDS) led to improvements in the physiochemical properties of the cubosomes. Notably, the PHYT-DDAB and PHT-SDS cubosomes led to 15- and 14-fold increases in the aqueous solubility of SN38, respectively. Moreover, the SN38 loaded into the PHYT-DDAB and PHYT-SDS cubosomes was found to be highly stable, with very little hydrolysis to its inactive acid form. In summary, the addition of DDAB and SDS to PHYT-cubosome nanoparticle drug delivery systems not only led to considerable improvements in their physiochemical properties, but also enhanced the aqueous solubility of SN38 and increased its chemical stability. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Recent progress in understanding the hot and warm gas phases in the halos of star-forming galaxies

    CERN Document Server

    Strickland, D K; Colbert, E J M; Hoopes, C G; Weaver, K A

    2002-01-01

    In this contribution we present a few selected examples of how the latest generation of space-based instrumentation -- NASA's Chandra X-ray Observatory and the Far-Ultraviolet Spectroscopic Explorer (FUSE) -- are finally answering old questions about the influence of massive star feedback on the warm and hot phases of the ISM and IGM. In particular, we discuss the physical origin of the soft thermal X-ray emission in the halos of star-forming and starburst galaxies, its relationship to extra-planar H-alpha emission, and plasma diagnostics using FUSE observations of O VI absorption and emission.

  10. Effects of Polybenzoxazine on Shape Memory Properties of Polyurethanes with Amorphous and Crystalline Soft Segments

    Directory of Open Access Journals (Sweden)

    Senlong Gu

    2014-04-01

    Full Text Available This paper evaluates the role of minor component polybenzoxazine (PB on shape-memory properties of polyurethanes (PU with glassy and crystalline soft segments. The polymer compounds were prepared in two steps. In the first step, benzoxazine, polyurethane pre-polymer, and chain extender butanediol (BD were mixed into a solution followed by chain-extension of the pre-polymer with BD. In the second step, benzoxazine was polymerized at 180 °C for 3 h to obtain shape memory polymer compounds. The atomic force microscopy images revealed that the PB-phase formed uniform dispersions in PU. The presence of PB-phase induced shape-memory behavior in non-shape memory PU with amorphous soft segment and significantly improved the values of shape fixity, recovery ratio, and recovery stress in shape memory polyurethane with crystalline soft segment.

  11. Electrochemical studies of redox probes in self-organized lyotropic liquid crystalline systems

    Indian Academy of Sciences (India)

    P Suresh Kumar; V Lakshminarayanan

    2009-09-01

    Lyotropic liquid crystalline phases formed by surfactants are of special importance due to their close resemblance to biological systems. The redox reactions in such ordered media are of fundamental interest in understanding several complex processes occurring in the biological media, where the former can act as model systems. In this work, we have carried out the redox reactions of benzoquinone| hydroquinone, methyl viologen and ferrocenemethanol probes in a lyotropic hexagonal columnar phase (H1 phase) using cyclic voltammetry and electrochemical impedance spectroscopic studies. The liquid crystalline phase we have studied is made up of the non-ionic surfactant, Triton X-100 and water. Polarizing optical microscopic examination confirmed that the columnar hexagonal phase is retained even after the addition of redox probe as well as the supporting electrolyte. Our studies show a significant shift in the half-peak potentials of the redox probes in the H1 phase as compared to the solvent phase. The diffusion coefficient values for different redox probes in the H1 phase were also found to be significantly reduced when compared to the corresponding solvent media.

  12. Significance of crystallinity on the photoelectrochemical and photocatalytic activity of TiO{sub 2} nanotube arrays

    Energy Technology Data Exchange (ETDEWEB)

    Nishanthi, S.T.; Iyyapushpam, S.; Sundarakannan, B. [Department of Physics, Manonmaniam Sundaranar University, Tirunelveli 627012, Tamil Nadu (India); Subramanian, E. [Department of Chemistry, Manonmaniam Sundaranar University, Tirunelveli 627012, Tamil Nadu (India); Pathinettam Padiyan, D., E-mail: dppadiyan@msuniv.ac.in [Department of Physics, Manonmaniam Sundaranar University, Tirunelveli 627012, Tamil Nadu (India)

    2014-09-15

    Highlights: • Increase in anodization time improves the crystallinity of nanotubes. • Higher crystalline one showed lower band gap for TiO{sub 2}. • Photoelectrochemical and photocatalytic activity depends on crystallinity. - Abstract: We report the significance of crystallinity on photoelectrochemical and the photocatalytic degradation of methyl orange of titanium dioxide (TiO{sub 2}) nanotube arrays. The TiO{sub 2} nanotube arrays are fabricated by electrochemical anodization of titanium substrates in fluoride based aqueous electrolyte for various anodization time. The degree of crystallinity and phase purity (anatase) is confirmed from X-ray diffraction and Raman spectra. High resolution scanning electron microscope is used to analyze the surface morphology of forming nanotubes. The UV–vis absorption spectrum shows the enhanced absorption in the visible region which is further confirmed using photoluminescence spectra. The photoelectrochemical properties of the prepared samples are studied from linear sweep photovoltammetry measurements and a maximum photocurrent density of 1.32 mA/cm{sup 2} is observed. The enhanced photoelectrochemical activity is attributed to the higher crystallinity which increases the charge carrier separation and extends its light absorption from ultraviolet to visible region owing to lower band gap of 2.751(7) eV.

  13. Nanoscale crystallinity modulates cell proliferation on plasma sprayed surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Alan M. [School of Applied Sciences, University of Huddersfield, Huddersfield HD1 3DH (United Kingdom); Paxton, Jennifer Z.; Hung, Yi-Pei; Hadley, Martin J.; Bowen, James; Williams, Richard L. [School of Chemical Engineering, University of Birmingham, Edgbaston, B15 2TT (United Kingdom); Grover, Liam M., E-mail: l.m.grover@bham.ac.uk [School of Chemical Engineering, University of Birmingham, Edgbaston, B15 2TT (United Kingdom)

    2015-03-01

    Calcium phosphate coatings have been applied to the surface of metallic prostheses to mediate hard and soft tissue attachment for more than 40 years. Most coatings are formed of high purity hydroxyapatite, and coating methods are often designed to produce highly crystalline surfaces. It is likely however, that coatings of lower crystallinity can facilitate more rapid tissue attachment since the surface will exhibit a higher specific surface area and will be considerably more reactive than a comparable highly crystalline surface. Here we test this hypothesis by growing a population of MC3T3 osteoblast-like cells on the surface of two types of hip prosthesis with similar composition, but with differing crystallinity. The surfaces with lower crystallinity facilitated more rapid cell attachment and increased proliferation rate, despite having a less heterogeneous surface topography. This work highlights that the influence of the crystallinity of HA at the nano-scale is dominant over macro-scale topography for cell adhesion and growth. Furthermore, crystallinity could be easily adjusted by without compromising coating purity. These findings could facilitate designing novel coated calcium phosphate surfaces that more rapidly bond tissue following implantation. - Highlights: • Crystallinity of HA at the nano-scale was dominant over macro-scale topography. • Lower crystallinity caused rapid cell attachment and proliferation rate. • Crystallinity could be easily adjusted by without compromising coating purity.

  14. The crystalline fraction of interstellar silicates in starburst galaxies

    CERN Document Server

    Kemper, F; Woods, Paul M

    2010-01-01

    We present a model using the evolution of the stellar population in a starburst galaxy to predict the crystallinity of the silicates in the interstellar medium of this galaxy. We take into account dust production in stellar ejecta, and amorphisation and destruction in the interstellar medium and find that a detectable amount of crystalline silicates may be formed, particularly at high star formation rates, and in case supernovae are efficient dust producers. We discuss the effect of dust destruction and amorphisation by supernovae, and the effect of a low dust-production efficiency by supernovae, and find that when taking this into account, crystallinity in the interstellar medium becomes hard to detect. Levels of 6.5-13% crystallinity in the interstellar medium of starburst galaxies have been observed and thus we conclude that not all these crystalline silicates can be of stellar origin, and an additional source of crystalline silicates associated with the Active Galactic Nucleus must be present.

  15. Preparation and thermal energy storage properties of paraffin/calcined diatomite composites as form-stable phase change materials

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Zhiming [School of Chemical and Environmental Engineering, China University of Mining and Technology, Beijing 100083 (China); Chemistry Discipline, Faculty of Science and Technology, Queensland University of Technology, 2 George Street, GPO Box 2434, Brisbane, Queensland 4001 (Australia); Zhang, Yuzhong [School of Chemical and Environmental Engineering, China University of Mining and Technology, Beijing 100083 (China); Zheng, Shuilin, E-mail: shuilinzh@yahoo.com.cn [School of Chemical and Environmental Engineering, China University of Mining and Technology, Beijing 100083 (China); Park, Yuri [Chemistry Discipline, Faculty of Science and Technology, Queensland University of Technology, 2 George Street, GPO Box 2434, Brisbane, Queensland 4001 (Australia); Frost, Ray L., E-mail: r.frost@qut.edu.au [Chemistry Discipline, Faculty of Science and Technology, Queensland University of Technology, 2 George Street, GPO Box 2434, Brisbane, Queensland 4001 (Australia)

    2013-04-20

    Highlights: ► Composite phase change material (PCM) was prepared by blending composite paraffin and calcined diatomite. ► The optimum mixed proportion was obtained through differential scanning calorimetry. ► Thermal energy storage properties of the composite PCMs were determined by DSC. ► Thermal cycling test showed that the prepared PCMs are thermally reliable and chemically stable. - Abstract: A composite paraffin-based phase change material (PCM) was prepared by blending composite paraffin and calcined diatomite through the fusion adsorption method. In this study, raw diatomite was purified by thermal treatment in order to improve the adsorption capacity of diatomite, which acted as a carrier material to prepare shape-stabilized PCMs. Two forms of paraffin (paraffin waxes and liquid paraffin) with different melting points were blended together by the fusion method, and the optimum mixed proportion with a suitable phase-transition temperature was obtained through differential scanning calorimetry (DSC) analysis. Then the prepared composite paraffin was adsorbed in calcined diatomite. The prepared paraffin/calcined diatomite composites were characterized by the scanning electron microscope (SEM) and Fourier transformation infrared (FT-IR) analysis techniques. Thermal energy storage properties of the composite PCMs were determined by DSC method. DSC results showed that there was an optimum adsorption ratio between composite paraffin and calcined diatomite and the phase-transition temperature and the latent heat of the composite PCMs were 33.04 °C and 89.54 J/g, respectively. Thermal cycling test of composite PCMs showed that the prepared material is thermally reliable and chemically stable. The obtained paraffin/calcined diatomite composites have proper latent heat and melting temperatures, and show practical significance and good potential application value.

  16. Liquid Crystalline Thermosets from Ester, Ester-imide, and Ester-amide Oligomers

    Science.gov (United States)

    Dingemans, Theodorus J. (Inventor); Weiser, Erik S. (Inventor); St. Clair, Terry L. (Inventor)

    2009-01-01

    Main chain thermotropic liquid crystal esters, ester-imides, and ester-amides were prepared from AA, BB, and AB type monomeric materials and end-capped with phenylacetylene, phenylmaleimide, or nadimide reactive end-groups. The end-capped liquid crystal oligomers are thermotropic and have, preferably, molecular weights in the range of approximately 1000-15,000 grams per mole. The end-capped liquid crystaloligomers have broad liquid crystalline melting ranges and exhibit high melt stability and very low melt viscosities at accessible temperatures. The end-capped liquid crystal oli-gomers are stable forup to an hour in the melt phase. They are highly processable by a variety of melt process shape forming and blending techniques. Once processed and shaped, the end-capped liquid crystal oigomers were heated to further polymerize and form liquid crystalline thermosets (LCT). The fully cured products are rubbers above their glass transition temperatures.

  17. Electron impact ionization of H{sub 2}O molecule in crystalline ice

    Energy Technology Data Exchange (ETDEWEB)

    Vinodkumar, Minaxi; Joshipura, K.N. E-mail: knjoshipura@yahoo.com; Limbachiya, C.G.; Antony, B.K

    2003-12-01

    The present work focuses on electron impact scattering in crystalline ice, which is an exotic solid. The major difference between crystalline form and amorphous form lies in its structure. Here we consider the H{sub 2}O molecule to possess properties consistent with the ice structure. Our basic calculation rests on the complex optical potential for the e-molecule system, with the molecular charge density as an input. To examine a single scattering event in condensed phases, we build up a model scattering potential to determine total inelastic cross-section Q{sub inel}. Finally an estimate of the total ionization cross-section, Q{sub ion} for H{sub 2}O (free), H{sub 2}O (amorphous) and H{sub 2}O (ice) in the energy range from threshold to 2000 eV, is obtained through semi-empirical arguments.

  18. Molecular and atomic line surveys of galaxies I: the dense, star-forming phase as a beacon

    CERN Document Server

    Geach, James E

    2012-01-01

    We predict the space density of molecular gas reservoirs in the Universe, and place a lower limit on the number counts of carbon monoxide (CO), hydrogen cyanide (HCN) molecular and [CII] atomic emission lines in blind redshift surveys in the submillimeter-centimeter spectral regime. Our model uses: (a) recently available HCN Spectral Line Energy Distributions (SLEDs) of local Luminous Infrared Galaxies (LIRGs, L_IR>10^11 L_sun), (b) a value for epsilon=SFR/M_dense(H_2) provided by new developments in the study of star formation feedback on the interstellar medium and (c) a model for the evolution of the infrared luminosity density. Minimal 'emergent' CO SLEDs from the dense gas reservoirs expected in all star-forming systems in the Universe are then computed from the HCN SLEDs since warm, HCN-bright gas will necessarily be CO-bright, with the dense star-forming gas phase setting an obvious minimum to the total molecular gas mass of any star-forming galaxy. We include [CII] as the most important of the far-inf...

  19. BaO/Al2O3/NiAl(110) Model NOx Storage Materials. The effect of BaO film thickness on the amorphous-to-crystalline Ba(NO3)2 phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Yi, Cheol-Woo W. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Szanyi, Janos [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2008-12-18

    The reaction of NO2 with BaO (0.15 – 2 ML and > 30 ML)/Al2O3(12 ML)/NiAl(110) model NOx storage materials was studied. A thick (~12 ML), ordered Al2O3 film was prepared as the support oxide on a NiAl(110) substrate in order to minimize the effect of the intermixing between the two oxide phases (BaO and Al2O3) on the NOx chemistry of BaO. The growth of a thick alumina film, prepared by atomic oxygen deposition onto NiAl(110), follows a layer-by-layer growth mode and the resulting film is much more stable when exposed to NO2 than the ultra-thin alumina films studied before. The interaction of NO2 with the model NOx storage systems at low coverages of BaO show fundamentally different behaviors from a thick BaO film, as nitrite species form at low exposures of NO2, followed by nitrate formation at high NO2 exposures. In contrast, on the thick BaO layer nitrite-nitrate ion pairs form at 300 K under UHV conditions (PNO2 ~ 1 x 10-9 Torr). However, at elevated NO2 pressures (≥ 1 x 10-5 Torr) the thick BaO film is gradually converted into amorphous Ba(NO3)2 at 300 K. Raising the temperature of the samples with ΘBaO > 1 ML after NO2 exposure (in the absence of gas phase NO2) leads to the phase transformation of the amorphous Ba(NO3)2 layer into crystalline Ba(NO3)2 particles in the temperature range of 500 – 600 K. No phase transformation is observed in samples with ΘBaO < 1 ML.

  20. Theoretical and Computational Studies of Condensed-Phase Phenomena: The Origin of Biological Homochirality, and the Liquid-Liquid Phase Transition in Network-Forming Fluids

    Science.gov (United States)

    Ricci, Francesco

    This dissertation describes theoretical and computational studies of the origin of biological homochirality, and the existence of a liquid-liquid phase transition in pure-component network-forming fluids. A common theme throughout these studies is the use of sophisticated computer simulation and statistical mechanics techniques to study complex condensed-phase phenomena. In the first part of this dissertation, we use an elementary lattice model with molecular degrees of freedom, and satisfying microscopic reversibility, to investigate the effect of reaction reversibility on the evolution of stochastic symmetry breaking via autocatalysis and mutual inhibition in a closed system. We identify conditions under which the system's evolution towards racemic equilibrium becomes extremely slow, allowing for long-time persistence of a symmetry-broken state. We also identify a "monomer purification" mechanism, due to which a nearly homochiral state can persist for long times, even in the presence of significant reverse reaction rates. Order of magnitude estimates show that with reasonable physical parameters a symmetry broken state could persist over geologically-relevant time scales. In the second part of this dissertation, we study a chiral-symmetry breaking mechanism known as Viedma ripening. We develop a Monte Carlo model to gain further insights into the mechanisms capable of reproducing key experimental signatures associated with this phenomenon. We also provide a comprehensive investigation of how the model parameters impact the system's overall behavior. It is shown that size-dependent crystal solubility alone is insufficient to reproduce most experimental signatures, and that some form of a solid-phase chiral feedback mechanism (e.g., agglomeration) must be invoked in our model. In the third part of this dissertation, we perform rigorous free energy calculations to investigate the possibility of a liquid-liquid phase transition (LLPT) in the Stillinger-Weber (SW

  1. Formation of carbide phases upon the mechanosynthesis of the (Fe0.93Cr0.07)75C25 alloy compared with other carbide-forming processes

    Science.gov (United States)

    Volkov, V. A.; Chulkina, A. A.; El'kin, I. A.; Elsukov, E. P.

    2016-02-01

    Methods of X-ray diffraction, differential thermal analysis, and measurements of the dynamic magnetic susceptibility have been used to investigate the sequence of phase transformations upon the mechanical alloying of a mixture of powders of the initial components of the composition (Fe0.93Cr.07)75C25. It has been shown that, at later stages of mechanical alloying, the phase composition is determined by the conditions of the dynamic equilibrium between the crystalline and amorphous phases. A change in the conditions of mechanical alloying leads to a shift in this equilibrium and to a change in the phase composition of the alloy. A comparison of carbide formation in the Fe-C system upon the mechanosynthesis, tempering of martensite, the saturation of iron with carbon from the gaseous medium, the quenching of the melt, and the sputtering deposition of films has been performed. Some general regularities have been established, from which it follows that an important role in phase formation upon the mechanosynthesis, just as in other abovementioned processes, is played by the thermally activated phenomena.

  2. Melt Processed Single Phase Hollandite Waste Forms For Nuclear Waste Immobilization: Ba{sub 1.0}Cs{sub 0.3}A{sub 2.3}Ti{sub 5.7}O{sub 16}; A = Cr, Fe, Al

    Energy Technology Data Exchange (ETDEWEB)

    Brinkman, Kyle [Savannah River National Laboratory, Aiken, SC 29808 (United States); Marra, James [Savannah River National Laboratory, Aiken, SC 29808 (United States); Amoroso, Jake [Savannah River National Laboratory, Aiken, SC 29808 (United States); Conradson, Steven D. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Tang, Ming [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2013-09-23

    Cs is one of the more problematic fission product radionuclides to immobilize due to its high volatility at elevated temperatures, ability to form water soluble compounds, and its mobility in many host materials. The hollandite structure is a promising crystalline host for Cs immobilization and has been traditionally fabricated by solid state sintering methods. This study presents the structure and performance of Ba{sub 1.0}Cs{sub 0.3}A{sub 2.3}Ti{sub 5.7}O{sub 16}; A = Cr, Fe, Al hollandite fabricated by melt processing. Melt processing is considered advantageous given that melters are currently in use for High Level Waste (HLW) vitrification in several countries. This work details the impact of Cr additions that were demonstrated to i) promote the formation of a Cs containing hollandite phase and ii) maintain the stability of the hollandite phase in reducing conditions anticipated for multiphase waste form processing.

  3. Nanoconfinement crystallization of frustrated alkyl groups: crossover of mesophase to crystalline structure.

    Science.gov (United States)

    Shi, Haifeng; Wang, Haixia; Xin, John H; Zhang, Xingxiang; Wang, Dujin

    2011-04-07

    Crossover of mesophase to crystalline structure in the nanoconfinement crystallization process of frustrated side groups elucidates the critical crystal thickness d(c) or the length scale of side groups, which defines the transition process from mesophase (hexagonal and monoclinic phase) to crystalline phase (orthorhombic phase) of confined CH(2) sequences in a given crystal size restriction.

  4. A Significant Amount of Crystalline Silica in Returned Cometary Samples: Bridging the Gap between Astrophysical and Meteoritical Observations

    Science.gov (United States)

    Roskosz, Mathieu; Leroux, Hugues

    2015-03-01

    Crystalline silica (SiO2) is recurrently identified at the percent level in the infrared spectra of protoplanetary disks. By contrast, reports of crystalline silica in primitive meteorites are very unusual. This dichotomy illustrates the typical gap existing between astrophysical observations and meteoritical records of the first solids formed around young stars. The cometary samples returned by the Stardust mission in 2006 offer an opportunity to have a closer look at a silicate dust that experienced a very limited reprocessing since the accretion of the dust. Here, we provide the first extended study of silica materials in a large range of Stardust samples. We show that cristobalite is the dominant form. It was detected in 5 out of 25 samples. Crystalline silica is thus a common minor phase in Stardust samples. Furthermore, olivine is generally associated with this cristobalite, which put constraints on possible formation mechanisms. A low-temperature subsolidus solid-solid transformation of an amorphous precursor is most likely. This crystallization route favors the formation of olivine (at the expense of pyroxenes), and crystalline silica is the natural byproduct of this transformation. Conversely, direct condensation and partial melting are not expected to produce the observed mineral assemblages. Silica is preserved in cometary materials because they were less affected by thermal and aqueous alterations than their chondritic counterparts. The common occurrence of crystalline silica therefore makes the cometary material an important bridge between the IR-based mineralogy of distant protoplanetary disks and the mineralogy of the early solar system.

  5. A SIGNIFICANT AMOUNT OF CRYSTALLINE SILICA IN RETURNED COMETARY SAMPLES: BRIDGING THE GAP BETWEEN ASTROPHYSICAL AND METEORITICAL OBSERVATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Roskosz, Mathieu; Leroux, Hugues [Unité Matériaux et Transformations, Université Lille 1, CNRS, UMR 8207, F-59655 Villeneuve d’Ascq (France)

    2015-03-01

    Crystalline silica (SiO{sub 2}) is recurrently identified at the percent level in the infrared spectra of protoplanetary disks. By contrast, reports of crystalline silica in primitive meteorites are very unusual. This dichotomy illustrates the typical gap existing between astrophysical observations and meteoritical records of the first solids formed around young stars. The cometary samples returned by the Stardust mission in 2006 offer an opportunity to have a closer look at a silicate dust that experienced a very limited reprocessing since the accretion of the dust. Here, we provide the first extended study of silica materials in a large range of Stardust samples. We show that cristobalite is the dominant form. It was detected in 5 out of 25 samples. Crystalline silica is thus a common minor phase in Stardust samples. Furthermore, olivine is generally associated with this cristobalite, which put constraints on possible formation mechanisms. A low-temperature subsolidus solid–solid transformation of an amorphous precursor is most likely. This crystallization route favors the formation of olivine (at the expense of pyroxenes), and crystalline silica is the natural byproduct of this transformation. Conversely, direct condensation and partial melting are not expected to produce the observed mineral assemblages. Silica is preserved in cometary materials because they were less affected by thermal and aqueous alterations than their chondritic counterparts. The common occurrence of crystalline silica therefore makes the cometary material an important bridge between the IR-based mineralogy of distant protoplanetary disks and the mineralogy of the early solar system.

  6. Determination of glibenclamide, metformin hydrochloride and rosiglitazone maleate by reversed phase liquid chromatographic technique in tablet dosage form

    Directory of Open Access Journals (Sweden)

    Havele Shweta S.

    2014-01-01

    Full Text Available A simple, precise and accurate high performance liquid chromatography (HPLC method was developed for the simultaneous estimation of metformin hydrochloride, rosiglitazone maleate, glibenclamide present in multicomponent dosage forms. Chromatography was performed on a 25 cm × 4.6 mm i.d., 5-μm particle, C18 column with 78:22 (v/v methanol: 20 mM potassium dihydrogen phosphate buffer as mobile phase at a flow rate of 1.0 ml/min and UV detection at 238 nm for metformin hydrochloride, rosiglitazone maleate, and glibenclamide. The total elution time was shorter than 9 min. This method was found to be precise and reproducible. This proposed method was successfully applied for the analysis of metformin hydrochloride, rosiglitazone maleate, glibenclamide as a bulk drug and in pharmaceutical formulation without any interference from the excipients.

  7. New high statistics measurement of $K_{e4}$ decay form factors and $\\pi \\pi$ scattering phase shifts

    CERN Document Server

    Batley, J Richard; Kalmus, George Ernest; Lazzeroni, C; Munday, D J; Slater, M W; Wotton, S A; Arcidiacono, R; Bocquet, G; Cabibbo, Nicola; Ceccucci, A; Cundy, Donald C; Falaleev, V; Fidecaro, Maria; Gatignon, L; Gonidec, A; Kubischta, Werner; Norton, A; Maier, A; Patel, M; Peters, A; Balev, S; Frabetti, P L; Goudzovski, E; Khristov, P Z; Kekelidze, V; Kozhuharov, V; Litov, L; Madigozhin, D T; Marinova, E; Molokanova, N; Polenkevich, I; Potrebenikov, Yu; Stoynev, S; Zinchenko, A; Monnier, E; Swallow, E; Winston, R; Rubin, P; Walker, A; Baldini, W; Cotta-Ramusino, A; Dalpiaz, P; Damiani, C; Fiorini, M; Gianoli, A; Martini, M; Petrucci, F; Savrié, M; Scarpa, M; Wahle, H; Bizzeti, A; Calvetti, M; Celeghini, E; Iacopini, E; Lenti, M; Martelli, F; Ruggiero, G; Veltri, M; Behler, M; Eppard, K; Kleinknecht, K; Marouelli, P; Masetti, L; Moosbrugger, U; Morales-Morales, C; Renk, B; Wache, M; Wanke, R; Winhart, A; Coward, D; Dabrowski, A; Fonseca-Martin, T; Shieh, M; Szleper, M; Velasco, M; Wood, M D; Anzivino, Giuseppina; Cenci, P; Imbergamo, E; Nappi, A; Pepé, M; Petrucci, M C; Piccini, M; Raggi, M; Valdata-Nappi, M; Cerri, C; Collazuol, G; Costantini, F; Di Lella, L; Doble, N; Fantechi, R; Fiorini, L; Giudici, S; Lamanna, G; Mannelli, I; Michetti, A; Pierazzini, G; Sozzi, M; Bloch-Devaux, B; Cheshkov, C; Chèze, J B; De Beer, M; Derré, J; Marel, Gérard; Mazzucato, E; Peyaud, B; Vallage, B; Holder, M; Ziolkowski, M; Bifani, S; Biino, C; Cartiglia, N; Clemencic, M; Goy-Lopez, S; Marchetto, F; Dibon, Heinz; Jeitler, Manfred; Markytan, Manfred; Mikulec, I; Neuhofer, G; Widhalm, L

    2008-01-01

    We report results from a new measurement of the K_{e4} decay K^{+-} -> \\pi^+ \\pi^- e^{+-} v by the NA48/2 collaboration at the CERN SPS, based on a partial sample of more than 670000 Ke4 decays in both charged modes collected in 2003. The form factors of the hadronic current (F, G, H) and pi pi scattering phase shift delta00-delta11 have been measured using a model-independent method and their variation with the pi pi mass has been investigated. Thanks to a sizeable acceptance at large pi pi mass, a low background and a very good resolution, an improved accuracy (+- 0.006 stat +- 0.002 syst), a factor two better than in the previous measurement, is reached when extracting the pi pi scattering length a00.

  8. H-Bonded Liquid Crystalline Polymer Network Materials

    Institute of Scientific and Technical Information of China (English)

    LIN Hong-Cheu; HENDRIANTO Jemmy

    2001-01-01

    @@Side-chain copolymers, poly(mOBA-co-mStilb)s, composed of proton acceptors (stilbazoles) and proton donors (benzoic acids) connected to polyacrylate backbone with different methylene spacer lengths (m = 6 and 10) were prepared in different donor/acceptor molar ratios. The H-bonded copolymeric networks were formed once they were synthesized, and showed more homogenous phase than the physical-blended supramolecular networks consisting of donor and acceptor homopolymers, i.e.H-bonded blends of PmOBA and PmStilb. In order to compare the effects of the backbone connection of these H-bonded copolymers and blends, we also built monomer-monomer and polymer-monomer H-bonded complexes of similar structures (shown in Fig. 1). DSC, POM, and powder XRD studies reveal that the copolymers (m = 10)with mole fractions of benzoic acids between 0.33-0.83 show the smectic A (SMA) phase with layer spacing values between 42.22A-50.47A (increases with higher H-bonded crosslinking density between benzoic acids and stilbazoles), while for m = 6, liquid crystalline behavior still can be observed at 0.89 molar fraction of benzoic acids. However, on the basis of powder XRD study it is found that the d spacing values of H-bonded copolymers with m = 6 in the SmA phase increase with higher molar ratios of benzoic acids, which is agreed with the formation of microphase separation due to the hydrogen bonds of benzoic acids connected themselves from the same backbone. The isotropization temperatures of the H-bonded copolymers and blends increase as the molar ratios of benzoic acids increase, while the higher crosslinking density of the H-bonded copolymeric networks and blends can stabilize the liquid crystalline phase.

  9. H-Bonded Liquid Crystalline Polymer Network Materials

    Institute of Scientific and Technical Information of China (English)

    LIN; Hong-Cheu

    2001-01-01

    Side-chain copolymers, poly(mOBA-co-mStilb)s, composed of proton acceptors (stilbazoles) and proton donors (benzoic acids) connected to polyacrylate backbone with different methylene spacer lengths (m = 6 and 10) were prepared in different donor/acceptor molar ratios. The H-bonded copolymeric networks were formed once they were synthesized, and showed more homogenous phase than the physical-blended supramolecular networks consisting of donor and acceptor homopolymers, i.e.H-bonded blends of PmOBA and PmStilb. In order to compare the effects of the backbone connection of these H-bonded copolymers and blends, we also built monomer-monomer and polymer-monomer H-bonded complexes of similar structures (shown in Fig. 1). DSC, POM, and powder XRD studies reveal that the copolymers (m = 10)with mole fractions of benzoic acids between 0.33-0.83 show the smectic A (SMA) phase with layer spacing values between 42.22A-50.47A (increases with higher H-bonded crosslinking density between benzoic acids and stilbazoles), while for m = 6, liquid crystalline behavior still can be observed at 0.89 molar fraction of benzoic acids. However, on the basis of powder XRD study it is found that the d spacing values of H-bonded copolymers with m = 6 in the SmA phase increase with higher molar ratios of benzoic acids, which is agreed with the formation of microphase separation due to the hydrogen bonds of benzoic acids connected themselves from the same backbone. The isotropization temperatures of the H-bonded copolymers and blends increase as the molar ratios of benzoic acids increase, while the higher crosslinking density of the H-bonded copolymeric networks and blends can stabilize the liquid crystalline phase.……

  10. Oxidation-induced phase transformations and lifetime limits of chromia-forming nickel-base alloy 625

    Energy Technology Data Exchange (ETDEWEB)

    Chyrkin, Anton

    2011-12-05

    For its high creep resistance the commercial nickel-base alloy 625 relies on solid solution strengthening in combination with precipitation hardening by formation of δ-Ni{sub 3}Nb and (Ni,Mo,Si){sub 6}C precipitates during high-temperature service. In oxidizing environments the alloy forms a slow growing, continuous chromia layer on the material surface which protects the alloy against rapid oxidation attack. The growth of the chromia base oxide scale results during exposure at 900-1000 C in oxidation-induced chromium depletion in the subsurface zone of the alloy. Microstructural analyses of the cross-sectioned specimens revealed that this process results in formation of a wide subsurface zone in which the mentioned strengthening phases are dissolved, in spite of the fact that both phases do not contain substantial amounts of the scale-forming element chromium. The cross-sectional analyses revealed that, in parallel to the formation of a precipitate depleted zone, a thin, continuous layer of niobium-rich intermetallic precipitates formed in the immediate vicinity of the scale/alloy interface. The Subsurface Phase Enrichment (abbreviated as SPE) was shown to be the result of an uphill-diffusion of niobium, i.e. the element stabilizing the strengthening precipitates δ-Ni{sub 3}Nb, in the chromium activity gradient and is thus a natural consequence of the oxidation-induced chromium depletion beneath the chromia scale. The thermodynamic calculations carried out using the Thermo-Calc/DICTRA software packages revealed that in alloy 625 the chemical activity of niobium decreases with decreasing chromium content. As chromium is being continuously removed from the alloy as the result of the chromia scale growth, the zone of lowest Nb-activity is formed in the location with the lowest chromium concentration, i.e. the scale/alloy interface. This creates a driving force for Nb to diffuse towards the scale/alloy interface against its own concentration gradient, which is known

  11. Oxidation-induced phase transformations and lifetime limits of chromia-forming nickel-base alloy 625

    Energy Technology Data Exchange (ETDEWEB)

    Chyrkin, Anton

    2011-12-05

    For its high creep resistance the commercial nickel-base alloy 625 relies on solid solution strengthening in combination with precipitation hardening by formation of δ-Ni{sub 3}Nb and (Ni,Mo,Si){sub 6}C precipitates during high-temperature service. In oxidizing environments the alloy forms a slow growing, continuous chromia layer on the material surface which protects the alloy against rapid oxidation attack. The growth of the chromia base oxide scale results during exposure at 900-1000 C in oxidation-induced chromium depletion in the subsurface zone of the alloy. Microstructural analyses of the cross-sectioned specimens revealed that this process results in formation of a wide subsurface zone in which the mentioned strengthening phases are dissolved, in spite of the fact that both phases do not contain substantial amounts of the scale-forming element chromium. The cross-sectional analyses revealed that, in parallel to the formation of a precipitate depleted zone, a thin, continuous layer of niobium-rich intermetallic precipitates formed in the immediate vicinity of the scale/alloy interface. The Subsurface Phase Enrichment (abbreviated as SPE) was shown to be the result of an uphill-diffusion of niobium, i.e. the element stabilizing the strengthening precipitates δ-Ni{sub 3}Nb, in the chromium activity gradient and is thus a natural consequence of the oxidation-induced chromium depletion beneath the chromia scale. The thermodynamic calculations carried out using the Thermo-Calc/DICTRA software packages revealed that in alloy 625 the chemical activity of niobium decreases with decreasing chromium content. As chromium is being continuously removed from the alloy as the result of the chromia scale growth, the zone of lowest Nb-activity is formed in the location with the lowest chromium concentration, i.e. the scale/alloy interface. This creates a driving force for Nb to diffuse towards the scale/alloy interface against its own concentration gradient, which is known

  12. A closed-form solution for moving source localization using LBI changing rate of phase difference only

    Directory of Open Access Journals (Sweden)

    Zhang Min

    2014-04-01

    Full Text Available Due to the deficiencies in the conventional multiple-receiver localization systems based on direction of arrival (DOA such as system complexity of interferometer or array and amplitude/phase unbalance between multiple receiving channels and constraint on antenna configuration, a new radiated source localization method using the changing rate of phase difference (CRPD measured by a long baseline interferometer (LBI only is studied. To solve the strictly nonlinear problem, a two-stage closed-form solution is proposed. In the first stage, the DOA and its changing rate are estimated from the CRPD of each observer by the pseudolinear least square (PLS method, and then in the second stage, the source position and velocity are found by another PLS minimization. The bias of the algorithm caused by the correlation between the measurement matrix and the noise in the second stage is analyzed. To reduce this bias, an instrumental variable (IV method is derived. A weighted IV estimator is given in order to reduce the estimation variance. The proposed method does not need any initial guess and the computation is small. The Cramer–Rao lower bound (CRLB and mean square error (MSE are also analyzed. Simulation results show that the proposed method can be close to the CRLB with moderate Gaussian measurement noise.

  13. Paleogene-early miocene deformations of Bukulja-Venčac crystalline (Vardar zone, Serbia

    Directory of Open Access Journals (Sweden)

    Marović Milun

    2007-01-01

    Full Text Available Low-grade metamorphic rocks of the crystalline of Mts. Bukulja and Venčac, which are integral parts of the Vardar Zone, are of Late Cretaceous age. From the Middle Paleogene to the beginning of the Miocene, they were subjected to three phases of intensive deformations. In the first phase, during the Middle Paleogene, these rocks were subjected to intense shortening (approximately in the E-W direction, regional metamorphism and deformations in the ductile and brittle domains, when first-generation folds with NNE-SSW striking fold hinges were formed. In the second phase, during the Late Oligocene and up to the Early Miocene, extensional unroofing and exhumation of the crystalline occurred, which was followed by intrusion of the granitoid of Bukulja and refolding of the previously formed folds in a simple brachial form of Bukulja and Venčac with an ESE-WNW striking B-axis. The third phase was expressed in the Early lowermost Miocene (before the Ottnanghian, under conditions of NE-SW compression and NW-SE tension. It was characterized by wrench-tectonic activity, particularly by dextral movements along NNW-SSE striking faults.

  14. Characterization and in vitro permeation study of microemulsions and liquid crystalline systems containing the anticholinesterase alkaloidal extract from Tabernaemontana divaricata

    DEFF Research Database (Denmark)

    Chaiyana, Wantida; Rades, Thomas; Okonogi, Siriporn

    2013-01-01

    and water with the oil:surfactant ratios of 1:5 and 2:5. The formulations were characterized by photon correlation spectroscopy, polarizing light microscopy, differential scanning calorimetry, and viscosity measurement. A reverse micellar phase, w/o microemulsions, liquid crystalline systems, liquid crystal...... in microemulsion systems and coarse emulsions were formed along the aqueous dilution line of both oil:surfactant ratios. Formulations with the ratio of 1:5 containing 0.1μg/ml extract showed a significantly higher acetylcholinesterase inhibition than those with the ratio of 2:5. The skin of stillborn piglet...... was used in the permeation study. The liquid crystalline and microemulsion systems significantly increased the transdermal delivery of the extract within 24h. It was concluded that the alkaloidal extract from T. divaricata stem loaded in liquid crystalline or microemulsion systems comprising Z. cassumunar...

  15. Fatty acid eutectic/polymethyl methacrylate composite as form-stable phase change material for thermal energy storage

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Lijiu; Meng, Duo [School of Civil Engineering, Dalian University of Technology, Dalian 116024 (China)

    2010-08-15

    This work is focused on the preparation and characterization of fatty acid eutectic/polymethyl methacrylate (PMMA) form-stable phase change material (PCM). Capric acid (CA), lauric acid (LA), myristic acid (MA) and stearic acid (SA) were selected to prepare binary fatty acid eutectic for the sake of decreasing the phase change temperature. Using the method of self-polymerization, CA-LA, CA-MA, CA-SA and LA-MA eutectics acting as the heat-absorbing materials and PMMA serving as the supporting material were compounded in the ratio of 50/50 wt.%. The relations between mass fraction of LA-MA eutectic and latent heat and compressive strength of LA-MA/PMMA composite were discussed, and the feasible maximum mass fraction of LA-MA eutectic was determined to be 70%. CA-LA/PMMA, CA-MA/PMMA, CA-SA/PMMA and LA-MA/PMMA composites were examined to investigate their potential application in building energy conservation. Scanning electron microscope and polarizing optical microscope observations showed that fatty acid eutectic was coated by PMMA thus the composite remained solid when the sample was heated above the melted point of the fatty acid. Fourier-transform infrared results indicated that fatty acid and PMMA had no chemical reaction and exhibited good compatibility with each other. According to the differential scanning calorimetry results, phase change temperatures of CA-LA/PMMA, CA-MA/PMMA, CA-SA/PMMA and LA-MA/PMMA composites were 21.11 C, 25.16 C, 26.38 C and 34.81 C and their latent heat values were determined to be 76.3 kJ/kg, 69.32 kJ/kg, 59.29 kJ/kg and 80.75 kJ/kg, respectively. Moreover, thermal stability and expansibility of the form-stable PCMs were characterized by thermogravimetric analysis and volume expansion coefficient respectively, and the results indicated that the composites were available for building energy conservation. (author)

  16. In Situ Formed Phase Transited Drug Delivery System of Ketoprofen for Achieving Osmotic, Controlled and Level A In Vitro In Vivo Correlation

    OpenAIRE

    2008-01-01

    A dry process induced phase transited, non disintegrating, controlled release, in situ formed asymmetric membrane capsular system for poorly water soluble drug, ketoprofen, was developed and evaluated both in vitro and in vivo for osmotic and controlled release of the drug. In situ formed asymmetric membrane capsules were prepared using fabricated glass capsule holders via dry, phase inversion process. Effect of varying osmotic pressure of the dissolution medium on drug release was studied. M...

  17. Crystalline mesoporous metal oxide

    Institute of Scientific and Technical Information of China (English)

    Wenbo Yue; Wuzong Zhou

    2008-01-01

    Since the discovery of many types of mesoporous silicas, such as SBA-15, KIT-6, FDU-12 and SBA-16, porous crystalline transition metal oxides, such as Cr2O3, Co3O4, In2O3, NiO, CeO2, WO3, Fe2O3 and MnO2, have been synthesized using the mesoporous silicas as hard templates. Several synthetic methods have been developed. These new porous materials have high potential applications in catalysis, Li-ion rechargeable batteries and gas sensors. This article gives a brief review of the research of porous crystals of metal oxides in the last four years.

  18. Effect of substrate materials on rutile crystalline orientation in plasma-sprayed TiO2 coatings

    Institute of Scientific and Technical Information of China (English)

    YANG Guan-jun; LI Chang-jiu; WANG Yu-yue

    2004-01-01

    TiO2 coatings are of technical importance owing to their promising applications to photocatalytical, electrical, optical and tribological coatings. Thermal spraying process has been widely used to deposit both metallic and nonmetallic coatings. During thermal spraying, spray particle at fully or partially melted condition is projected to a substrate and subsequently flattens, rapidly cools and solidifies. Therefore, a coating in lamellar structure is usually formed as a quenched microstructure. TiO2 coatings were deposited on different substrates through plasma spraying with fused-crushed powder in rutile phase as feedstock to reveal the crystalline orientation in the coatings. XRD results show that the coatings consist of rutile phase with a fraction of anatase phase, and the rutile phase presents a preferable crystalline orientation along [101] direction. It is found that the orientation factors of rutile phase in the thin coatings are significantly influenced by substrate materials. The thick coatings yield the same orientation factors of 0.22 to 0.23 on all substrates in spite of substrate materials. It is considered that the thermal properties of substrate materials are the dominant factors for the preferable crystalline orientation in rutile phase within plasmasprayed TiO2 coating.

  19. The contents and forms of solid-phase species of radioactive strontium and cesium in Taiwan soils.

    Science.gov (United States)

    Chien, S W Chang; Wang, M C; Chiu, C L; Lin, Yu-Ming; Lai, Shu-Ying

    2007-02-01

    This study was to investigate the activities and contents of (137)Cs in the profiles of selected arable and forest soils in Taiwan and various solid-phase species of (85)Sr and (137)Cs in selected arable soils in Taiwan. The gamma (gamma) ray spectra of the collected soil samples and some of the soils amended with (85)Sr and (137)Cs were measured. The data indicate that the arable soils from Sanhsing series, Sanhsing Township and Chuangwei series, Chuangwei Township, Ilan County, and from Tunglochuan series, Pinglin Township, Taipei County shows significantly higher radioactivity of (137)Cs (ND - 11.0 +/- 0.2 Bq kg(-1)). Furthermore, the radioactivity of (137)Cs in the mountain soils (1.24 +/- 0.07 - 42 +/- 1 Bq kg(-1)) from Yuanyang Lake Nature Preserve among Ilan, Taoyuan, and Hsinchu Counties is the highest among the investigated mountain forest soils. This may be mainly attributed to the fact that Ilan County is located in the northeastern part of Taiwan and faces the northeastern and northern seasonal winds with lots of precipitation annually from mid-autumn through mid-spring next year and is receiving greater amount of fallouts yearly. Due to longer reaction period (>or=3 y) of (137)Cs with soil components, (137)Cs was mainly in the forms bound to oxides and to organic matter in the soil amended with (137)Cs and in the soil contaminated with (137)Cs. On the contrary, due to shorter reaction period (<60 d) of (85)Sr with soil components, (85)Sr was mainly in exchangeable form and partially in the forms bound to carbonates and oxides in the soils amended with (85)Sr.

  20. Liquid crystalline systems for transdermal delivery of celecoxib: in vitro drug release and skin permeation studies.

    Science.gov (United States)

    Estracanholli, Eder André; Praça, Fabíola Silva Garcia; Cintra, Ana Beatriz; Pierre, Maria Bernadete Riemma; Lara, Marilisa Guimarães

    2014-12-01

    Liquid crystalline systems of monoolein/water could be a promising approach for the delivery of celecoxib (CXB) to the skin because these systems can sustain drug release, improve drug penetration into the skin layers and minimize side effects. This study evaluated the potential of these systems for the delivery of CXB into the skin based on in vitro drug release and skin permeation studies. The amount of CXB that permeated into and/or was retained in the skin was assayed using an HPLC method. Polarizing light microscopy studies showed that liquid crystalline systems of monoolein/water were formed in the presence of CXB, without any changes in the mesophases. The liquid crystalline systems decreased drug release when compared to control solution. Drug release was independent of the initial water content of the systems and CXB was released from cubic phase systems, irrespective of the initial water content. The systems released the CXB following zero-order release kinetics. In vitro drug permeation studies showed that cubic phase systems allowed drug permeation and retention in the skin layers. Cubic phase systems of monoolein/water may be promising vehicles for the delivery of CXB in/through the skin because it improved CXB skin permeation compared with the control solution.

  1. Liquid-Crystalline Mesophases of Plasmid DNA in Bacteria

    Science.gov (United States)

    Reich, Ziv; Wachtel, Ellen J.; Minsky, Abraham

    1994-06-01

    Bacterial plasmids may often reach a copy number larger than 1000 per cell, corresponding to a total amount of DNA that may exceed the amount of DNA within the bacterial chromosome. This observation highlights the problem of cellular accommodation of large amounts of closed-circular nucleic acids, whose interwound conformation offers negligible DNA compaction. As determined by x-ray scattering experiments conducted on intact bacteria, supercoiled plasmids segregate within the cells into dense clusters characterized by a long-range order. In vitro studies performed at physiological DNA concentrations indicated that interwound DNA spontaneously forms liquid crystalline phases whose macroscopic structural properties are determined by the features of the molecular supercoiling. Because these features respond to cellular factors, DNA supercoiling may provide a sensitive regulatory link between cellular parameters and the packaging modes of interwound DNA in vivo.

  2. DECOVALEX-THMC Project. Task D. Long-Term Permeability/Porosity Changes in the EDZ and Near Field due to THM and THC Processes in Volcanic and Crystalline-Bentonite Systems. Phase 1 Report

    Energy Technology Data Exchange (ETDEWEB)

    Birkholzer, J.; Rutqvist, J.; Sonnenthal, E. [Lawrence Berkeley National Laboratory, CA (United States); Barr, D. [Office of Repository Development, DOE (United States)

    2007-02-15

    The general goal of this project is to encourage multidisciplinary interactive and cooperative research on modeling coupled processes in geologic formations in support of the performance assessment for underground storage of radioactive waste. Three multi-year project stages of DECOVALEX have been completed in the past decade, mainly focusing on coupled thermal-hydrological-mechanical processes. Currently, a fourth three-year project stage of DECOVALEX is under way, referred to as DECOVALEX-THMC. THMC stands for Thermal, Hydrological, Mechanical, and Chemical processes. The new project stage aims at expanding the traditional geomechanical scope of the previous DECOVALEX project stages by incorporating geochemical processes important for repository performance. The U.S. Department of Energy (DOE) leads Task D of the new DECOVALEX phase, entitled 'Long-term Permeability/Porosity Changes in the EDZ and Near Field due to THC and THM Processes for Volcanic and Crystalline-Bentonite Systems.' In its leadership role for Task D, DOE coordinates and sets the direction for the cooperative research activities of the international research teams engaged in Task D. The research program developed for Task D of DECOVALEX-THMC involves geomechanical and geochemical research areas. THM and THC processes may lead to changes in hydrological properties that are important for performance because the flow processes in the vicinity of emplacement tunnels will be altered from their initial state. Some of these changes can be permanent (irreversible), in which case they persist after the thermal conditions have returned to ambient; i.e., they will affect the entire regulatory compliance period. Geochemical processes also affect the water and gas chemistry close to the waste packages, which are relevant for waste package corrosion, buffer stability, and radionuclide transport. Research teams participating in Task D evaluate long-term THM and THC processes in two generic geologic

  3. Photoconductivity studies on amorphous and crystalline TiO{sub 2} films doped with gold nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Valverde-Aguilar, G.; Garcia-Macedo, J.A. [Universidad Nacional Autonoma de Mexico, Departamento de Estado Solido, Instituto de Fisica, Mexico D.F. (Mexico); Renteria-Tapia, V. [Universidad de Guadalajara, Centro Universitario de los Valles, Departamento de Ciencias Naturales y Exactas, Ameca, Jalisco (Mexico); Aguilar-Franco, M. [Universidad Nacional Autonoma de Mexico, Departamento de Fisica Quimica, Instituto de Fisica, Mexico D.F. (Mexico)

    2011-06-15

    In this work, amorphous and crystalline TiO{sub 2} films were synthesized by the sol-gel process at room temperature. The TiO{sub 2} films were doped with gold nanoparticles. The films were spin-coated on glass wafers. The crystalline samples were annealed at 100 C for 30 minutes and sintered at 520 C for 2 h. All films were characterized using X-ray diffraction, transmission electronic microscopy and UV-Vis absorption spectroscopy. Two crystalline phases, anatase and rutile, were formed in the matrix TiO{sub 2} and TiO{sub 2}/Au. An absorption peak was located at 570 nm (amorphous) and 645 nm (anatase). Photoconductivity studies were performed on these films. The experimental data were fitted with straight lines at darkness and under illumination at 515 nm and 645 nm. This indicates an ohmic behavior. Crystalline TiO{sub 2}/Au films are more photoconductive than the amorphous ones. (orig.)

  4. Preparation and properties of lauric acid/silicon dioxide composites as form-stable phase change materials for thermal energy storage

    Energy Technology Data Exchange (ETDEWEB)

    Fang Guiyin, E-mail: gyfang@nju.edu.cn [Department of Physics, Nanjing University, Hankou Road 22, Nanjing, Jiangsu 210093 (China); Li Hui [Department of Material Science and Engineering, Nanjing University, Nanjing 210093 (China); Liu Xu [Department of Physics, Nanjing University, Hankou Road 22, Nanjing, Jiangsu 210093 (China)

    2010-08-01

    Form-stable lauric acid (LA)/silicon dioxide (SiO{sub 2}) composite phase change materials were prepared using sol-gel methods. The LA was used as the phase change material for thermal energy storage, with the SiO{sub 2} acting as the supporting material. The structural analysis of these form-stable LA/SiO{sub 2} composite phase change materials was carried out using Fourier transformation infrared spectroscope (FT-IR). The microstructure of the form-stable composite phase change materials was observed by a scanning electronic microscope (SEM). The thermal properties and thermal stability were investigated by a differential scanning calorimeter (DSC) and a thermogravimetric analysis apparatus (TGA), respectively. The SEM results showed that the LA was well dispersed in the porous network of SiO{sub 2}. The DSC results indicated that the melting latent heat of the form-stable composite phase change material is 117.21 kJ kg{sup -1} when the mass percentage of the LA in the SiO{sub 2} is 64.8%. The results of the TGA showed that these materials have good thermal stability. The form-stable composite phase change materials can be used for thermal energy storage in waste heat recovery and solar heating systems.

  5. Yb9+xCuMg4-x (x = 0.034): A κ-Phase Formed by Lanthanoids.

    Science.gov (United States)

    De Negri, Serena; Romaka, Vitaliy; Solokha, Pavlo; Saccone, Adriana; Giester, Gerald; Michor, Herwig; Rogl, Peter F

    2016-08-15

    Atom order in the crystal structures of Yb2Cu2-xMg (x = 0.17; Mo2FeB2-type; P4/mbm; a = 0.75592(2) nm; c = 0.40282(1) nm) and Yb9+xCuMg4-x (x = 0.034; Hf9Mo4B-type; P63/mmc; a = 1.0169(5) nm; c = 1.0290(5) nm) was determined from powder and X-ray single-crystal counter data analyses supported by electron probe microanalyses. Among the group of the so-called κ-phases, Yb9+xCuMg4-x is the first representative formed by a lanthanoid element. The structure of this κ-phase can be viewed as a typical network of corner-connected empty Yb6-octahedra, which encompass Yb6Mg6-icosahedra (filled by a mix of Mg/Yb atoms) and Yb6-trigonal prisms centered by Cu atoms to complete the three-dimensional metal framework. From another point of view, the same structure is considered as built from infinite polyicosahedral columns of Yb9Mg4 composition with Cu atoms located in trigonal prismatic interstices, highlighting similarities with other Yb-rich Yb-Cu-Mg phases. Density functional theory (DFT) calculations classify Yb9CuMg4 as a polar intermetallic. Metallic-like behavior is inferred from the Sommerfeld constant, γ = 49.2 mJ/mol·K(2), derived from the electronic density of states, calculated at the Fermi level. DFT integration of the f-density of states indicates almost completely filled f-states, revealing 13.6 and 13.7 electrons in the valence band for Yb1 and Yb2 atoms, respectively, close to the Yb(2+) ground state ((1)S0) for both Yb atoms. Magnetic susceptibility data recorded on the same compound are consistent with a nonmagnetic divalent Yb(2+) state. Temperature-dependent heat capacity data display a metallic behavior characterized by a small Sommerfeld constant γ = 64.8 mJ/mol·K(2) and a rather low Debye temperature ΘD = 140 K as typical for soft materials.

  6. Liquid crystalline order in polymers

    CERN Document Server

    Blumstein, Alexandre

    1978-01-01

    Liquid Crystalline Order in Polymers examines the topic of liquid crystalline order in systems containing rigid synthetic macromolecular chains. Each chapter of the book provides a review of one important area of the field. Chapter 1 discusses scattering in polymer systems with liquid crystalline order. It also introduces the field of liquid crystals. Chapter 2 treats the origin of liquid crystalline order in macromolecules by describing the in-depth study of conformation of such macromolecules in their unassociated state. The chapters that follow describe successively the liquid crystalli

  7. FTIR studies of BPO 4·2SiO 2, BPO 4·SiO 2 and 2BPO 4·SiO 2 joints in amorphous and crystalline forms

    Science.gov (United States)

    Adamczyk, A.; Handke, M.; Mozgawa, W.

    1999-11-01

    The MIR spectra of glasses and devitrificates of BPO 4·2SiO 2, BPO 4 SiO 2 and 2BPO 4·SiO 2 compositions have been shown. The bands arising from the Si-O, B-O and P-O bonds vibrations can be assigned in the spectra of the above samples. All bands appear almost at the same wavenumber range: what causes their coincidence? Therefore, all spectra of crystalline and amorphous materials were decomposed into component bands. The decomposed MIR spectra of these samples, as well as the tetragonal boron orthophosphate BPO 4 and the low temperature crystobalite spectra, were then compared. Therefore, one can estimate the probability of the existence of any compounds within the BPO 4-SiO 2 (P 2O 5-B 2O 3-SiO 2) system. The presence of BPO 4·2SiO 2 was reported in a few papers. The results obtained in this work can be treated as an attempt to verify the above hypothesis verifying because of the opposed information existing on this subject in literature.

  8. DECOVALEX-THMC Project. Task D. Long-Term Permeability/Porosity Changes in the EDZ and Near Field due to THM and THC Processes in Volcanic and Crystalline-Bentonite Systems. Phase 1 Report

    Energy Technology Data Exchange (ETDEWEB)

    Birkholzer, J.; Rutqvist, J.; Sonnenthal, E. [Lawrence Berkeley National Laboratory, CA (United States); Barr, D. [Office of Repository Development, DOE (United States)

    2007-02-15

    The general goal of this project is to encourage multidisciplinary interactive and cooperative research on modeling coupled processes in geologic formations in support of the performance assessment for underground storage of radioactive waste. Three multi-year project stages of DECOVALEX have been completed in the past decade, mainly focusing on coupled thermal-hydrological-mechanical processes. Currently, a fourth three-year project stage of DECOVALEX is under way, referred to as DECOVALEX-THMC. THMC stands for Thermal, Hydrological, Mechanical, and Chemical processes. The new project stage aims at expanding the traditional geomechanical scope of the previous DECOVALEX project stages by incorporating geochemical processes important for repository performance. The U.S. Department of Energy (DOE) leads Task D of the new DECOVALEX phase, entitled 'Long-term Permeability/Porosity Changes in the EDZ and Near Field due to THC and THM Processes for Volcanic and Crystalline-Bentonite Systems.' In its leadership role for Task D, DOE coordinates and sets the direction for the cooperative research activities of the international research teams engaged in Task D. The research program developed for Task D of DECOVALEX-THMC involves geomechanical and geochemical research areas. THM and THC processes may lead to changes in hydrological properties that are important for performance because the flow processes in the vicinity of emplacement tunnels will be altered from their initial state. Some of these changes can be permanent (irreversible), in which case they persist after the thermal conditions have returned to ambient; i.e., they will affect the entire regulatory compliance period. Geochemical processes also affect the water and gas chemistry close to the waste packages, which are relevant for waste package corrosion, buffer stability, and radionuclide transport. Research teams participating in Task D evaluate long-term THM and THC processes in two generic geologic

  9. COLD DRAWING IN CRYSTALLINE POLYMERS

    Science.gov (United States)

    alcohols, phenol) in Nylon 6 produced changes in the crystalline structure as well as plasticizer action; these two effects must therefore be carefully...distinguished. Changes in the crystalline structure were followed by changes in the infrared spectrum. Dynamic mechanical and thermogravimetric analysis

  10. Preferential Incorporation of Azelaic Acid Units into the Crystalline Phase of the Copoly(Alkylene Dicarboxylate Derived from 1,9-Nonanediol and an Equimolar Mixture of Pimelic and Azelaic Acids

    Directory of Open Access Journals (Sweden)

    Angélica Díaz

    2015-09-01

    Full Text Available The crystalline structure of two biodegradable odd-odd polyesters (i.e., poly(nonamethylene pimelate (PES 9,7 and poly(nonamethylene azelate (PES 9,9 was investigated by means of electron and X-ray diffraction of single crystals and oriented fibers, respectively. Truncated rhombic crystals were obtained with an aspect ratio that was strongly depended on the supercooling degree. The crystalline structure of both homopolyesters was defined by an orthorhombic P21ab space group and a large unit cell containing four molecular segments with an all-trans conformation. Nevertheless, the structure in the chain axis projection was equivalent to a simpler cell containing only two segments. Crystalline lamellae were effectively degraded by lipases, starting the enzymatic attack on the lamellar surfaces. The random copolymer constituted by an equimolar amount of pimelate and azelate units (COPES 9,7/9 crystallized according to regular lamellae with a similar molecular arrangement in the chain axis projection. The structure of this copolymer was preferably conditioned by the azelate component as could be deduced from both, diffraction and spectroscopic data. Analysis of small angle X-ray scattering patterns pointed out that less crystalline lamellae with higher amorphous thickness had developed in the copolymer. This feature was interpreted as a consequence of the preferential incorporation of pimelate comonomer units in the folding surface.

  11. Role of Disclinations and Nanocrystalline State in the Formation of Quasicrystalline Phases on Mechanical Alloying of Cu-Fe Powders

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    @@Elemental powders of Cu and Fe were ball milled for various time durations up to 100 h. The various stages of forced alloying by ball milling, leading to instability of elemental crystalline phases and formation of quasicrystalline phases were monitored using X-ray diffraction. Diffusion of Fe into the Cu matrix is proposed as the cause which triggers the instability of crystalline phases and leads to the formation of quasicrystalline phases after 10 h of milling. Milling for 100 h resulted in two different quasicrystalline phases with different lattice constants. Role of the nanocrystalline microstructure as an important criterion for the destabilisation of crystalline phases is explained. It is suggested that the formation of nanocrystalline microstructure and their subsequent transformation into quasicrystalline phases may be associated with a continuous increase in the disclination content of the system, which had formed as a result of continued milling and mechanical deformation.

  12. Formation of single-crystalline aragonite tablets/films via an amorphous precursor.

    Science.gov (United States)

    Amos, Fairland F; Sharbaugh, Denise M; Talham, Daniel R; Gower, Laurie B; Fricke, M