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Sample records for crystal structure-ionic conductivity

  1. Structure, ionic conductivity and mobile carrier density in fast ionic conducting chalcogenide glasses

    SciTech Connect

    Yao, Wenlong

    2006-01-01

    This thesis consists of six sections. The first section gives the basic research background on the ionic conduction mechanism in glass, polarization in the glass, and the method of determining the mobile carrier density in glass. The proposed work is also included in this section. The second section is a paper that characterizes the structure of MI + M2S + (0.1 Ga2S3 + 0.9 GeS2) (M = Li, Na, K and Cs) glasses using Raman and IR spectroscopy. Since the ionic radius plays an important role in determining the ionic conductivity in glasses, the glass forming range for the addition of different alkalis into the basic glass forming system 0.1 Ga2S3 + 0.9 GeS2 was studied. The study found that the change of the alkali radius for the same nominal composition causes significant structure change to the glasses. The third section is a paper that investigates the ionic conductivity of MI + M2S + (0.1Ga2S3 + 0.9 GeS2) (M = Li, Na, K and Cs) glasses system. Corresponding to the compositional changes in these fast ionic conducting glasses, the ionic conductivity shows changes due to the induced structural changes. The ionic radius effect on the ionic conductivity in these glasses was investigated. The fourth section is a paper that examines the mobile carrier density based upon the measurements of space charge polarization. For the first time, the charge carrier number density in fast ionic conducting chalcogenide glasses was determined. The experimental impedance data were fitted using equivalent circuits and the obtained parameters were used to determine the mobile carrier density. The influence of mobile carrier density and mobility on the ionic conductivity was separated. The fifth section is a paper that studies the structures of low-alkali-content Na2S + B2S3 (x ≤ 0.2) glasses by neutron and synchrotron x-ray diffraction

  2. Liquid crystal-templated conducting organic polymers

    DOEpatents

    Stupp, Samuel I.; Hulvat, James F.

    2004-01-20

    A method of preparing a conductive polymeric film, includes providing a liquid crystal phase comprising a plurality of hydrophobic cores, the phase on a substrate, introducing a hydrophobic component to the phase, the component a conductive polymer precursor, and applying an electric potential across the liquid crystal phase, the potential sufficient to polymerize the said precursor.

  3. Conduction mechanism of single-crystal alumina

    NASA Technical Reports Server (NTRS)

    Will, Fritz G.; Delorenzi, Horst G.; Janora, Kevin H.

    1992-01-01

    The fully guarded three-terminal technique was used to perform conductivity measurements on single-crystal alumina at temperatures of 400-1300 C. The conductivity was also determined as a function of time at various temperatures and applied fields. Further, the fractions of the current carried by Al and O ions (ionic transference numbers) were determined from long-term transference experiments in the temperature range 1100-1300 C. A mathematical model of the conduction mechanism is proposed, and model predictions are compared with experimental results.

  4. Thermal Conductivity and Liquid Crystal Thermometers.

    ERIC Educational Resources Information Center

    Edge, R. D., Ed.

    1993-01-01

    Describes using stock liquid crystal postcards as inexpensive classroom thermometers. Also suggests using these postcards as a good visual temperature indicator for classroom demonstrations such as temperature gradients. One such activity is provided. (MVL)

  5. Reduction of Thermal Conductivity by Nanoscale 3D Phononic Crystal

    PubMed Central

    Yang, Lina; Yang, Nuo; Li, Baowen

    2013-01-01

    We studied how the period length and the mass ratio affect the thermal conductivity of isotopic nanoscale three-dimensional (3D) phononic crystal of Si. Simulation results by equilibrium molecular dynamics show isotopic nanoscale 3D phononic crystals can significantly reduce the thermal conductivity of bulk Si at high temperature (1000 K), which leads to a larger ZT than unity. The thermal conductivity decreases as the period length and mass ratio increases. The phonon dispersion curves show an obvious decrease of group velocities in 3D phononic crystals. The phonon's localization and band gap is also clearly observed in spectra of normalized inverse participation ratio in nanoscale 3D phononic crystal. PMID:23378898

  6. Reduction of thermal conductivity by nanoscale 3D phononic crystal.

    PubMed

    Yang, Lina; Yang, Nuo; Li, Baowen

    2013-01-01

    We studied how the period length and the mass ratio affect the thermal conductivity of isotopic nanoscale three-dimensional (3D) phononic crystal of Si. Simulation results by equilibrium molecular dynamics show isotopic nanoscale 3D phononic crystals can significantly reduce the thermal conductivity of bulk Si at high temperature (1000 K), which leads to a larger ZT than unity. The thermal conductivity decreases as the period length and mass ratio increases. The phonon dispersion curves show an obvious decrease of group velocities in 3D phononic crystals. The phonon's localization and band gap is also clearly observed in spectra of normalized inverse participation ratio in nanoscale 3D phononic crystal.

  7. Remarkable reduction of thermal conductivity in phosphorene phononic crystal

    NASA Astrophysics Data System (ADS)

    Xu, Wen; Zhang, Gang

    2016-05-01

    Phosphorene has received much attention due to its interesting physical and chemical properties, and its potential applications such as thermoelectricity. In thermoelectric applications, low thermal conductivity is essential for achieving a high figure of merit. In this work, we propose to reduce the thermal conductivity of phosphorene by adopting the phononic crystal structure, phosphorene nanomesh. With equilibrium molecular dynamics simulations, we find that the thermal conductivity is remarkably reduced in the phononic crystal. Our analysis shows that the reduction is due to the depressed phonon group velocities induced by Brillouin zone folding, and the reduced phonon lifetimes in the phononic crystal. Interestingly, it is found that the anisotropy ratio of thermal conductivity could be tuned by the ‘non-square’ pores in the phononic crystal, as the phonon group velocities in the direction with larger projection of pores is more severely suppressed, leading to greater reduction of thermal conductivity in this direction. Our work provides deep insight into thermal transport in phononic crystals and proposes a new strategy to reduce the thermal conductivity of monolayer phosphorene.

  8. Remarkable reduction of thermal conductivity in phosphorene phononic crystal.

    PubMed

    Xu, Wen; Zhang, Gang

    2016-05-05

    Phosphorene has received much attention due to its interesting physical and chemical properties, and its potential applications such as thermoelectricity. In thermoelectric applications, low thermal conductivity is essential for achieving a high figure of merit. In this work, we propose to reduce the thermal conductivity of phosphorene by adopting the phononic crystal structure, phosphorene nanomesh. With equilibrium molecular dynamics simulations, we find that the thermal conductivity is remarkably reduced in the phononic crystal. Our analysis shows that the reduction is due to the depressed phonon group velocities induced by Brillouin zone folding, and the reduced phonon lifetimes in the phononic crystal. Interestingly, it is found that the anisotropy ratio of thermal conductivity could be tuned by the 'non-square' pores in the phononic crystal, as the phonon group velocities in the direction with larger projection of pores is more severely suppressed, leading to greater reduction of thermal conductivity in this direction. Our work provides deep insight into thermal transport in phononic crystals and proposes a new strategy to reduce the thermal conductivity of monolayer phosphorene.

  9. Engineering thermal conductance using a two-dimensional phononic crystal

    PubMed Central

    Zen, Nobuyuki; Puurtinen, Tuomas A.; Isotalo, Tero J.; Chaudhuri, Saumyadip; Maasilta, Ilari J.

    2014-01-01

    Controlling thermal transport has become relevant in recent years. Traditionally, this control has been achieved by tuning the scattering of phonons by including various types of scattering centres in the material (nanoparticles, impurities, etc). Here we take another approach and demonstrate that one can also use coherent band structure effects to control phonon thermal conductance, with the help of periodically nanostructured phononic crystals. We perform the experiments at low temperatures below 1 K, which not only leads to negligible bulk phonon scattering, but also increases the wavelength of the dominant thermal phonons by more than two orders of magnitude compared to room temperature. Thus, phononic crystals with lattice constants ≥1 μm are shown to strongly reduce the thermal conduction. The observed effect is in quantitative agreement with the theoretical calculation presented, which accurately determined the ballistic thermal conductance in a phononic crystal device. PMID:24647049

  10. Photon assisted hopping conduction mechanism in Tl2SSe crystals

    NASA Astrophysics Data System (ADS)

    Qasrawi, A. F.; Ziqan, Abdelhalim M.; Jazzar, Suha Kh.; Gasanly, N. M.

    2015-02-01

    In this article, the powder X-ray diffraction data and the dark and the photo-excited electrical conduction parameters of Tl2SSe crystal are reported. The dark and photon excited electrical conduction in the tetragonal crystal are found to be dominated by thermionic emission assisted variable range hopping conduction (VRH). The dark Mott's VRH parameters representing by the degree of disorder (To), the density of localized states near the Fermi level (N (EF)), the average hopping range (R) and average hopping energy (W) exhibited wide tunability via incremental photon intensity. Particularly, while the dark values of T0 , W and R significantly decreased from 2.32 ×108 to 1.52 ×105 K, 114 to 18.25 meV and from 66.15 to 10.58 A°, respectively, the values of N (EF) increased from 7.23 ×1018 to 1.10 ×1022cm-3 /eV when the crystal was photo-excited with a 53.6 mW/cm2 light intensity. These variations in the hopping parameters via photon excitations are promisig for using the crystal in the fabrication of well controlled, widely tunable, low energy consuming and highly efficient electronic devices.

  11. Electrochemical growth of linear conducting crystals in microgravity

    NASA Technical Reports Server (NTRS)

    Cronise, Raymond J., IV

    1988-01-01

    Much attention has been given to the synthesis of linear conducting materials. These inorganic, organic, and polymeric materials have some very interesting electrical and optical properties, including low temperature superconductivity. Because of the anisotropic nature of these compounds, impurities and defects strongly influences the unique physical properties of such crystals. Investigations have demonstrated that electrochemical growth has provided the most reproducible and purest crystals. Space, specifically microgravity, eliminates phenomena such as buoyancy driven convection, and could permit formation of crystals many times purer than the ones grown to date. Several different linear conductors were flown on Get Away Special G-007 on board the Space Shuttle Columbia, STS 61-C, the first of a series of Project Explorer payloads. These compounds were grown by electrochemical methods, and the growth was monitored by photographs taken throughout the mission. Due to some thermal problems, no crystals of appreciable size were grown. The experimental results will be incorporated into improvements for the next 2 missions of Project Explorer. The results and conclusions of the first mission are discussed.

  12. Electrical conduction in nanodomains in congruent lithium tantalate single crystal

    SciTech Connect

    Cho, Yasuo

    2014-01-27

    The electrical current flow behavior was investigated for nanodomains formed in a thin congruent lithium tantalate (LiTaO{sub 3}) single-crystal plate. When the nanodomains were relatively large, with diameters of about 100 nm, current flow was detected along the domain wall. However, when they were about 40 nm or smaller, the current flowed through the entire nanodomain. Schottky-like rectifying behavior was observed. Unlike the case of LiNbO{sub 3}, optical illumination was not required for current conduction in LiTaO{sub 3}. A clear temperature dependence of the current was found indicating that the conduction mechanism for nanodomains in LiTaO{sub 3} may involve thermally activated carrier hopping.

  13. Lithium-cation conductivity and crystal structure of lithium diphosphate

    SciTech Connect

    Voronin, V.I.; Sherstobitova, E.A.; Blatov, V.A.; Shekhtman, G.Sh.

    2014-03-15

    The electrical conductivity of lithium diphosphate Li{sub 4}P{sub 2}O{sub 7} has been measured and jump-like increasing of ionic conductivity at 913 K has been found. The crystal structure of Li{sub 4}P{sub 2}O{sub 7} has been refined using high temperature neutron diffraction at 300–1050 K. At 913 K low temperature triclinic form of Li{sub 4}P{sub 2}O{sub 7} transforms into high temperature monoclinic one, space group P2{sub 1}/n, a=8.8261(4) Å, b=5.2028(4) Å, c=13.3119(2) Å, β=104.372(6)°. The migration maps of Li{sup +} cations based on experimental data implemented into program package TOPOS have been explored. It was found that lithium cations in both low- and high temperature forms of Li{sub 4}P{sub 2}O{sub 7} migrate in three dimensions. Cross sections of the migrations channels extend as the temperature rises, but at the phase transition point have a sharp growth showing a strong “crystal structure – ion conductivity” correlation. -- Graphical abstract: Crystal structure of Li{sub 4}P{sub 2}O{sub 7} at 950 K. Red balls represent oxygen atoms; black lines show Li{sup +} ion migration channels in the layers perpendicular to [001] direction. Highlights: • Structure of Li{sub 4}P{sub 2}O{sub 7} has been refined using high temperature neutron diffraction. • At 913 K triclinic form of Li{sub 4}P{sub 2}O{sub 7} transforms into high temperature monoclinic one. • The migration maps of Li{sup +} implemented into program package TOPOS have been explored. • Cross sections of the migrations channels at the phase transition have a sharp growth.

  14. Conductivity of boules of single crystal sodium beta-alumina

    NASA Technical Reports Server (NTRS)

    Fielder, W. L.; Kautz, H. E.; Fordyce, J. S.; Singer, J.

    1974-01-01

    The ionic and electrochemical polarization characteristics of two boules of single crystal sodium beta-alumina (Na2O.8Al2O3), 2 cm in diameter, were investigated over the range of 25 to 300 C using 2- and 4-probe ac and dc techniques with reversible and ion-blocking electrodes. Textural (or internal) polarization at 27 C was present only in boule 1 which cleaved easily. Interfacial polarization, using solid sodium electrodes, was present at 27 C in the 2-probe conductivities for both boules. Cleaning with liquid sodium at 300 C reduced its magnitude, but some interfacial polarization was still present in the 2-probe conductivities for boule 2 below about 140 C. Above 140 C, with liquid sodium electrodes, the 2-probe conductivities, essentially polarization-free, were given by KT = 3300 exp(-3650/RT). The conductivity of boule 2 at 180 C remained essentially constant with increasing current density up to about 140 milliamps per square centimeter.

  15. Acceptor conductivity in bulk zinc oxide (0001) crystals

    NASA Astrophysics Data System (ADS)

    Adekore, Bababunmi Tolu

    ZnO is a promising wide bandgap semiconductor. Its renowned and prominent properties as its bandgap of 3.37eV at 4.2K; its very high excitonic binding energy, 60meV; its high melting temperature, 2248K constitute the basis for the recently renewed and sustained scientific interests in the material. In addition to the foregoing, the availability of bulk substrates of industrially relevant sizes provides important opportunities such as homoepitaxial deposition of the material which is a technological asset in the production of efficient optoelectronic and electronic devices. The nemesis of wide bandgap materials cannot be more exemplified than in ZnO. The notorious limitation of asymmetric doping and the haunting plague of electrically active point defects dim the bright future of the material. In this case, the search for reliable and consistent acceptor conductivity in bulk substrates has been hitherto, unsuccessful. In the dissertation that now follows, our efforts have been concerted in the search for a reliable acceptor. We have carefully investigated the science of point defects in the material, especially those responsible for the high donor conductivity. We also investigated and herein report variety of techniques of introducing acceptors into the material. We employ the most relevant and informative characterization techniques in verifying both the intended conductivity and the response of intrinsic crystals to variation in temperature and strain. And finally we explain deviations, where they exist, from ideal acceptor characteristics. Our work on reliable acceptor has been articulated in four papers. The first establishing capacitance based methods of monitoring electrically active donor defects. The second investigates the nature of anion acceptors on the oxygen sublattice. A study similar to the preceding study was conducted for cation acceptors on the zinc sublattice and reported in the third paper. Finally, an analysis of the response of the crystal to

  16. Polaron conductivity mechanism in potassium acid phthalate crystal: AC-conductivity investigation

    NASA Astrophysics Data System (ADS)

    Filipič, Cene; Levstik, Iva; Levstik, Adrijan; Hadži, Dušan

    2016-08-01

    The complex dielectric constant, \\varepsilon *(ν ,T), of potassium acid phthalate monocrystal (KAP) was investigated over the broad frequency and temperature range. While the imaginary part of dielectric constant ε‧‧(ν) increases rapidly with increasing temperature in the studied temperature range, the real part of dielectric constant ε‧(ν) increases only at high temperatures; there is almost no change of ε‧(ν) below 200 K. Both values of ε‧ and ε‧‧ are frequency dependent; the values increase with decreasing frequencies. At temperatures below 450 K the ac electrical conductivity and dielectric constant follow simultaneously the universal dielectric response (UDR). The analysis of the temperature dependence of the UDR parameter s in terms of the theoretical model for small polarons revealed that this mechanism governs the charge transport in KAP crystal in the studied temperature range.

  17. Low temperature dc electrical conduction in reduced lithium niobate single crystals

    NASA Astrophysics Data System (ADS)

    Dhar, Ajay; Singh, Nidhi; Singh, Rajiv K.; Singh, Ramadhar

    2013-01-01

    The direct current (dc) electrical conductivity of unreduced and reduced lithium niobate (LiNbO3) single crystals has been measured at room temperature (˜300 K). The dc conductivity and activation energy show strong dependence on the degree of oxygen reduction in LiNbO3 single crystals. The dc conductivity exhibits a peak as a function of increasing degree of oxygen reduction. These results have been analysed assuming small polaron hopping conduction between Nb4+ and Nb5+ ion sites. The temperature dependence of dc conductivity of reduced LiNbO3 single crystal, exhibiting the highest dc conductivity, has been examined in the temperature range 77-373 K. The observed dc conductivity data has been analyzed and explained in terms of Mott’s variable range hopping (VRH) conduction model involving a single phonon hopping process.

  18. Catalytic synthesis of metal crystals using conductive polymers

    DOEpatents

    Wang, Hsing-Lin; Li, Wenguang

    2008-01-15

    A method of forming metal nanoparticles using a polymer colloid that includes at least one conductive polymer and at least one polyelectrolyte. Metal ions are reduced in water by the conductive polymer to produce the nanoparticles, which may be then incorporated in the colloidal structure to form a colloid composite. The method can also be used to separate selected metal ions from aqueous solutions.

  19. Anisotropic ionic conductivities in lyotropic supramolecular liquid crystals.

    PubMed

    Huang, Youju; Cong, Yuanhua; Li, Junjun; Wang, Daoliang; Zhang, Jingtuo; Xu, Lu; Li, Weili; Li, Liangbin; Pan, Guoqiang; Yang, Chuanlu

    2009-12-28

    The designed aromatic amide discotic molecule with sulfonic acid groups at its periphery exhibits a hexagonal supramolecular columnar liquid crystalline phase, which leads to the achievement of anisotropic ionic conductivity through macroscopically aligning the ionic channels.

  20. Mechanical tension and electrical conductivity of liquid crystal filaments

    NASA Astrophysics Data System (ADS)

    Kress, Oliver H.

    During the NSF funded IRES internship at the Otto-von-Geuricke Univeristy in Magdeburg, Germany, I studied the optical properties and mechanical behavior in the form of line tension of bent-core liquid crystal fiber bundles and verified previously published tension values and temperature dependent behavior. Then, carbon nanotubes were added and it as found that the tension in the fibers decreased by a factor of two instead of increasing as was hoped. A new device for pulling fibers and measuring tension by deflection due to the adhesion of glass beads was built at the LCI. The device was meant to improve upon the device used at O.v.G. Improvements included a smaller heating chamber with better insulation, temperature control, large viewing windows, more stable mounting interface, easier disassembly and the option to quickly modify the device in order to perform a variety of other experiments such as observing behavior due to acoustic driving (based on previous literature), observing optical behavior under a polarizing microscope and introducing probes to measure the electrical properties of fibers. The platform remains modular and makes the addition of new components for carrying out new experiments very simple and straightforward. The addition of carbon nanotubes has scattered results regarding the modulation of fiber tension. It seems that the addition of CNTs to BLC1571 may slightly be decreasing tension while the addition to BLC1688 may be increasing it. In both mesogens, 10wt% CNT yielded the highest tension value above the theoretical surface tension contribution. A reversal of temperature dependence was observed for fibers containing CNT; their tension increased with temperature instead of decreased. A driving rod attached to a speaker was used to acoustically drive a filament of pure BLC1571 in an attempt to replicate the tension values in a different way. The movement of the fiber and the driving rod were captured using a high-speed camera and MATLAB code

  1. Correlating crystallization and ionic conductivity of PEO/graphene oxide nanocomposite

    NASA Astrophysics Data System (ADS)

    Cheng, Shan; Smith, Derrick; Hsuan, Grace; Li, Christopher

    2012-02-01

    Polyethylene oxide (PEO) is one of the best candidates for solid state electrolyte due to its chemical stability and strong ability to form complex with lithium salts. Crystallization behavior of PEO directly affects the lithium ion transport, and in turn the ionic conductivity of the electrolyte. By adding two dimensional graphene oxide nanosheets into PEO matrix, mechanical property of the latter is significantly strengthened, while the crystallization behavior of PEO is also altered by the graphene oxide sheets. The crystallization of PEO/graphene oxide nanocomposites was studied by differential scanning calorimetry (DSC) and the orientations of graphene oxide and PEO crystal were studied by small angle X-ray scattering and wide angle X-ray diffraction. PEO/graphene oxide nanocomposite doped with lithium salt was further fabricated and characterized by electrochemical impedance spectroscopy. Anisotropic ionic conductivity was observed for the nanocomposite electrolyte due to the orientation of graphene oxide and directional growth of PEO crystals.

  2. Enhancing proton conduction via doping of supramolecular liquid crystals (4-alkoxybenzoic acids) with imidazole

    NASA Astrophysics Data System (ADS)

    Liang, Ting; Wu, Yong; Tan, Shuai; Yang, Xiaohui; Wei, Bingzhuo

    2015-09-01

    Enhancing proton conduction via doping was first achieved in hydrogen-bonded liquid crystals consisting of benzoic acids. Supramolecular liquid crystals formed by pure 4-alkoxybenzoic acids (nAOBA, n = 8, 10, 12) exhibited the maximum proton conductivity of 5.0 × 10-8 S cm-1. Doping of nAOBA with 25 mol% imidazole (Im0.25) had little impact on mesomorphism but increased proton conductivities by at least 3 orders of magnitude. The liquid crystals formed by nAOBA-Im0.25 exhibited the maximum proton conductivity of 1.9 × 10-4 S cm-1. It was proposed that structure diffusion of imidazole bridged interdimer proton transfer to form continuous conducting pathways in mesomorphic nAOBA-Im0.25.

  3. DC electrical conductivity measurements for pure and titanium oxide doped KDP Crystals grown by gel medium

    NASA Astrophysics Data System (ADS)

    Mareeswaran, S.; Asaithambi, T.

    2016-10-01

    Now a day's crystals are the pillars of current technology. Crystals are applied in various fields like fiber optic communications, electronic industry, photonic industry, etc. Crystal growth is an interesting and innovative field in the subject of physics, chemistry, material science, metallurgy, chemical engineering, mineralogy and crystallography. In recent decades optically good quality of pure and metal doped KDP crystals have been grown by gel growth method in room temperature and its characterizations were studied. Gel method is a very simple and one of the easiest methods among the various crystal growth methods. Potassium dihydrogen phosphate KH2PO4 (KDP) continues to be an interesting material both academically and technologically. KDP is a delegate of hydrogen bonded materials which possess very good electrical and nonlinear optical properties in addition to interesting electro-optic properties. We made an attempt to grow pure and titanium oxide doped KDP crystals with various doping concentrations (0.002, 0.004, 0.006, 0.008 and 0.010) using gel method. The grown crystals were collected after 20 days. We get crystals with good quality and shaped crystals. The dc electrical conductivity (resistance, capacitance and dielectric constant) values of the above grown crystals were measured at two different frequencies (1KHz and 100 Hz) with a temperature range of 500C to 1200C using simple two probe setup with Q band digital LCR meter present in our lab. The electrical conductivity increases with the increase of temperature. Dielectric constants value of titanium oxide doped KDP crystal was slightly decreased compared with pure KDP crystals. Results were discussed in details.

  4. Electrical conductivity of MgO crystals implanted with lithium ions

    NASA Astrophysics Data System (ADS)

    Tardío, M.; Ramírez, R.; González, R.; Chen, Y.; Alves, E.

    2002-05-01

    MgO single crystals were implanted with a fluence of 1×10 17 Li +/cm 2 with 175 keV. Using ac and dc techniques, the electrical conductivity of these crystals was investigated in the temperature range 296-440 K. The electrical conductivity of the implanted region was 14 orders of magnitude higher than the unimplanted area. Measurements at different temperatures suggest a thermally activated process with an activation energy of about 0.33 eV. In the implanted area, electrical contacts are found to be ohmic whereas contacts are blocking in unimplanted crystals. Removal of thin layers of the implanted region by immersing the crystal in hot phosphoric acid suggests that the enhancement in conductivity in the implanted region is associated with the intrinsic defects created by the implantation, rather than with the Li ions.

  5. Switchable photoluminescence liquid crystal coated bacterial cellulose films with conductive response.

    PubMed

    Tercjak, Agnieszka; Gutierrez, Junkal; Barud, Hernane S; Ribeiro, Sidney J L

    2016-06-05

    Three different low molecular weight nematic liquid crystals (LCs) were used to impregnate bacterial cellulose (BC) film. This simple fabrication pathway allows to obtain highly transparent BC based films. The coating of BC film with different liquid crystals changed transmittance spectra in ultraviolet-visible region and allows to design UVC and UVB shielding materials. Atomic force microscopy results confirmed that liquid crystals coated BC films maintain highly interconnected three-dimensional network characteristic of BC film and simultaneously, transversal cross-section scanning electron microscopy images indicated penetration of liquid crystals through the three-dimensional network of BC nanofibers. Investigated BC films maintain nematic liquid crystal properties being switchable photoluminiscence as a function of temperature during repeatable heating/cooling cycles. Conductive response of the liquid crystal coated BC films was proved by tunneling atomic force microscopy measurement. Moreover, liquid crystal coated BC films maintain thermal stability and mechanical properties of the BC film. Designed thermoresponsive materials possessed interesting optical and conductive properties opening a novel simple pathway of fabrication liquid crystal coated BC films with tuneable properties.

  6. Heat conduction and phonon localization in disordered harmonic crystals

    NASA Astrophysics Data System (ADS)

    Kundu, A.; Chaudhuri, A.; Roy, D.; Dhar, A.; Lebowitz, J. L.; Spohn, H.

    2010-05-01

    We investigate the steady-state heat current in two- and three-dimensional isotopically disordered harmonic lattices. Using localization theory as well as kinetic theory we estimate the system size dependence of the current. These estimates are compared with numerical results obtained using an exact formula for the current given in terms of a phonon transmission function, as well as by direct nonequilibrium simulations. We find that heat conduction by high frequency modes is suppressed by localization while low frequency modes are strongly affected by boundary conditions. Our heuristic arguments show that Fourier's law is valid in a three-dimensional disordered solid except for special boundary conditions. We also study the pinned case relevant to localization in quantum systems and often used as a model system to study the validity of Fourier's law. Here we provide the first numerical verification of Fourier's law in three dimensions. In the two-dimensional pinned case we find that localization of phonon modes leads to a heat insulator.

  7. The contribution of surfaces and interfaces to the crystal thermal conductivity

    NASA Astrophysics Data System (ADS)

    Kazan, M.; Masri, P.

    This review provides theoretical understanding of the role of the surface and interface in the thermal conductivity of solids. An attempt is made to collect the various methods used in the analysis of experiments. The adequacy and range of validity of these methods are evaluated, and suggestions are made concerning possible theoretical and experimental investigations which seem desirable. A major part of the paper is devoted to the description of the surface vibrational modes, the surface thermal conductivity, the interaction of defects with crystal surfaces, and the phonon scattering from crystal surfaces. First, a review is made of the general form of the interatomic potential energy and lattice vibrations. Certain aspects related to the three- and four-phonon processes are discussed. Then, the heat current is calculated in the presence of scattering processes described by a relaxation time, and a general formalism for the lattice thermal conductivity is derived. A special consideration is given to the effect of boundary scattering and boundary thermal conductance. In the first sections, despite the consideration of boundary scattering, the calculation of the thermal conductivity is carried out with adopting of the cyclic boundary conditions. Such a treatment, while mathematically convenient, eliminates the possibility of studying the dynamical properties of atoms in the neighborhood of a free surface of a real crystal because the crystal structure in the surface layers may differ from the structures in the bulk of the crystal. The forces acting on atoms in the surface layers will be different from the forces acting on atoms in the bulk since an atom in the surface layers has fewer nearest neighbors, next-nearest neighbors, etc., than an atom in the interior of a crystal. Therefore, one would expect that the dynamical properties and the resultant thermal conductivity are different for atoms in the surface layers of a crystal than for atoms in the bulk of the

  8. Conductive Hybrid Crystal Composed from Polyoxomolybdate and Deprotonatable Ionic-Liquid Surfactant.

    PubMed

    Kobayashi, Jun; Kawahara, Ryosuke; Uchida, Sayaka; Koguchi, Shinichi; Ito, Takeru

    2016-06-23

    A polyoxomolybdate inorganic-organic hybrid crystal was synthesized with deprotonatable ionic-liquid surfactant. 1-dodecylimidazolium cation was employed for its synthesis. The hybrid crystal contained δ-type octamolybdate (Mo₈) isomer, and possessed alternate stacking of Mo₈ monolayers and interdigitated surfactant bilayers. The crystal structure was compared with polyoxomolybdate hybrid crystals comprising 1-dodecyl-3-methylimidazolium surfactant, which preferred β-type Mo₈ isomer. The less bulky hydrophilic moiety of the 1-dodecylimidazolium interacted with the δ-Mo₈ anion by N-H···O hydrogen bonds, which presumably induced the formation of the δ-Mo₈ anion. Anhydrous conductivity of the hybrid crystal was estimated to be 5.5 × 10(-6) S·cm(-1) at 443 K by alternating current (AC) impedance spectroscopy.

  9. Conductive Hybrid Crystal Composed from Polyoxomolybdate and Deprotonatable Ionic-Liquid Surfactant

    PubMed Central

    Kobayashi, Jun; Kawahara, Ryosuke; Uchida, Sayaka; Koguchi, Shinichi; Ito, Takeru

    2016-01-01

    A polyoxomolybdate inorganic-organic hybrid crystal was synthesized with deprotonatable ionic-liquid surfactant. 1-dodecylimidazolium cation was employed for its synthesis. The hybrid crystal contained δ-type octamolybdate (Mo8) isomer, and possessed alternate stacking of Mo8 monolayers and interdigitated surfactant bilayers. The crystal structure was compared with polyoxomolybdate hybrid crystals comprising 1-dodecyl-3-methylimidazolium surfactant, which preferred β-type Mo8 isomer. The less bulky hydrophilic moiety of the 1-dodecylimidazolium interacted with the δ-Mo8 anion by N–H···O hydrogen bonds, which presumably induced the formation of the δ-Mo8 anion. Anhydrous conductivity of the hybrid crystal was estimated to be 5.5 × 10−6 S·cm−1 at 443 K by alternating current (AC) impedance spectroscopy. PMID:27347926

  10. Thermal conductivity of γ-irradiated LiF single crystals

    NASA Astrophysics Data System (ADS)

    Basiev, T. T.; Konyushkin, V. A.; Kuznetsov, S. V.; Osiko, V. V.; Popov, P. A.; Fedorov, P. P.

    2008-08-01

    The thermal conductivity of γ-irradiated lithium fluoride (LiF) single crystals has been studied using the method of stationary longitudinal heat flux in a temperature range of 50 300 K. An increase in the irradiation dose to 2 × 109 rad is accompanied by a monotonic decrease in the thermal conductivity by 10% at 300 K and by a factor of 10 at 50 K. This increase in the irradiation dose also leads to an increase in the microhardness of LiF crystals from 140 to 222.5 kgf/mm2.

  11. Low-temperature conductivity in CuGaS{sub 2} single crystals

    SciTech Connect

    Abdullaev, N. A. Aliguliyeva, Kh. V.; Aliyeva, L. N.; Qasimoglu, I.; Kerimova, T. G.

    2015-04-15

    CuGaS{sub 2} single crystals are grown by the Bridgman-Stockbarger method. X-ray diffraction and Raman studies are performed. It is shown that the conductivity at low temperatures has an activation mechanism: in the range of 100–300 K, impurity conduction with an acceptor activation energy of 12 meV dominates; at temperatures below 100 K, Mott conductivity, i.e., so-called hopping conductivity with a variable hop length prevails. The density of localized states and the average carrier hop length are estimated.

  12. Thermal Conductance of a Surface Phonon-Polariton Crystal Made up of Polar Nanorods

    NASA Astrophysics Data System (ADS)

    Ordonez-Miranda, Jose; Joulain, Karl; Ezzahri, Younes

    2017-02-01

    We demonstrate that the energy transport of surface phonon-polaritons can be large enough to be observable in a crystal made up of a three-dimensional assembly of nanorods of silicon carbide. The ultralow phonon thermal conductivity of this nanostructure along with its high surface area-to-volume ratio allows the predominance of the polariton energy over that generated by phonons. The dispersion relation, propagation length, and thermal conductance of polaritons are numerically determined as functions of the radius and temperature of the nanorods. It is shown that the thermal conductance of a crystal with nanorods at 500 K and diameter (length) of 200 nm (20 μm) is 0.55 nW·K-1, which is comparable to the quantum of thermal conductance of polar nanowires.

  13. From crystal to glass-like thermal conductivity in crystalline minerals.

    PubMed

    Bouyrie, Y; Candolfi, C; Pailhès, S; Koza, M M; Malaman, B; Dauscher, A; Tobola, J; Boisron, O; Saviot, L; Lenoir, B

    2015-08-14

    The ability of some materials with a perfectly ordered crystal structure to mimic the heat conduction of amorphous solids is a remarkable physical property that finds applications in numerous areas of materials science, for example, in the search for more efficient thermoelectric materials that enable to directly convert heat into electricity. Here, we unveil the mechanism in which glass-like thermal conductivity emerges in tetrahedrites, a family of natural minerals extensively studied in geology and, more recently, in thermoelectricity. By investigating the lattice dynamics of two tetrahedrites of very close compositions (Cu12Sb2Te2S13 and Cu10Te4S13) but with opposite glasslike and crystal thermal transport by means of powder and single-crystal inelastic neutron scattering, we demonstrate that the former originates from the peculiar chemical environment of the copper atoms giving rise to a strongly anharmonic excess of vibrational states.

  14. Explicitly Solvable Model of the Charge Carriers' Phenomena in Isotropic Conducting Crystals

    NASA Astrophysics Data System (ADS)

    Budzak, Yaroslav S.; Wacławski, Tadeusz

    2017-01-01

    In this paper, a theoretical analysis of the kinetic properties of the isotropic conducting crystals is presented. The general formulas for these kinetic properties are expressed in terms of the Fermi integrals. These integrals were obtained using methods of statistical ensembles with varying number of particles and the Gibbs's grand canonical distribution. The determination of the scattering function and the exploration of its relation with the mobility of the current carriers inside these crystals have been made. Together with the results of theoretical analysis of the scattering function and its relation with the current carriers' mobility, these formulas constitute the mathematical model of the charge carriers' transport phenomena in conducting crystals (where a non-parabolic energy spectrum is described by Kane's formula) and provide algorithms for the calculation of these properties.

  15. Explicitly Solvable Model of the Charge Carriers' Phenomena in Isotropic Conducting Crystals

    NASA Astrophysics Data System (ADS)

    Budzak, Yaroslav S.; Wacławski, Tadeusz

    2017-04-01

    In this paper, a theoretical analysis of the kinetic properties of the isotropic conducting crystals is presented. The general formulas for these kinetic properties are expressed in terms of the Fermi integrals. These integrals were obtained using methods of statistical ensembles with varying number of particles and the Gibbs's grand canonical distribution. The determination of the scattering function and the exploration of its relation with the mobility of the current carriers inside these crystals have been made. Together with the results of theoretical analysis of the scattering function and its relation with the current carriers' mobility, these formulas constitute the mathematical model of the charge carriers' transport phenomena in conducting crystals (where a non-parabolic energy spectrum is described by Kane's formula) and provide algorithms for the calculation of these properties.

  16. Heat, Light, and Videotapes: Experiments in Heat Conduction Using Liquid Crystal Film.

    ERIC Educational Resources Information Center

    Bacon, Michael E.; And Others

    1995-01-01

    Presents a range of experiments in heat conduction suitable for upper-level undergraduate laboratories that make use of heat sensitive liquid crystal film to measure temperature contours. Includes experiments mathematically described by Laplace's equation, experiments theoretically described by Poisson's equation, and experiments that involve…

  17. Anisotropy of thermal conductivities in non- and Mg-doped near-stoichiometric LiTaO 3 crystals

    NASA Astrophysics Data System (ADS)

    Nakamura, Masaru; Takekawa, Shunji; Kitamura, Kenji

    2010-09-01

    We investigated the thermal conductivities of non-doped near-stoichiometric LiTaO 3 (SLT) and Mg (1 mol%)-doped near-stoichiometric LiTaO 3 (Mg:SLT) crystals along the X-, Y-, and Z-axes at room temperature. Those of non-doped congruent LiTaO 3 (CLT) crystal along the same axes were also estimated to investigate the effect of non-stoichiometric defects. The thermal conductivities were determined by measuring the thermal diffusivity using a laser-flash method and measuring the specific heat using a differential scanning calorimeter. Anisotropy of the thermal conductivities was found for all three crystals. That is, the thermal conductivities along the X-axis were the same as those along the Y-axis and less than those along the Z-axis. The thermal conductivities of the SLT crystal were the highest and were twice those of the CLT crystal. The thermal conductivities of the Mg:SLT crystal were slightly lower than those of the SLT crystal apparently due to the Mg-doping. We also investigated the effect of the difference in domain structure on thermal conductivity using as-grown Mg:SLT crystal with randomly distributed multi-domains and found that it did not affect the thermal conductivity along any axis. These findings regarding thermal conductivity should be useful for designing high-power laser applications using SLT and Mg:SLT crystals.

  18. Dielectric and conducting behavior of gadolinium-terbium fumarate heptahydrate crystals

    NASA Astrophysics Data System (ADS)

    Shah, M. D.; Want, B.

    2015-07-01

    Gadolinium-terbium fumarate heptahydrate crystals were grown in silica gel by using single gel diffusion technique. The crystals were characterized by different physico-chemical techniques of characterization. Powder X-ray diffraction results showed that the grown material is purely crystalline in nature. Elemental analyses suggested the chemical formula of the compound to be Gd Tb (C4H2O4)3ṡ7H2O. Energy dispersive X-ray analysis confirmed the presence of Gd and Tb in the title compound. The dielectric and conductivity studies of the grown compound were carried as function of frequency of applied field and the temperature. The grown material showed a dielectric anomaly which was correlated with its thermal behavior. The ac conductivity of the material showed Jonscher's power law behavior: σ(ω)=σo+Aωs, with a temperature-dependent power exponent s(<1). The conductivity was found to be a function of temperature and frequency.

  19. One-way Tamm plasmon polaritons at the interface between magnetophotonic crystals and conducting metal oxides

    NASA Astrophysics Data System (ADS)

    Dong, Hui Yuan; Wang, Jin; Cui, Tie Jun

    2013-01-01

    We demonstrate theoretically the existence of one-way Tamm plasmon polaritons on the interface between magnetophotonic crystals and conducting metal oxides. In contrast to conventional surface plasmon-polaritons (SPPs), Tamm plasmon polaritons (TPPs) occur at frequencies above the bulk plasma frequency of the conducting materials, provided that the dispersion curves of such surface modes lie outside the light cone for the conducting oxides and simultaneously fall into the photonic band gap of the magnetophotonic crystal. The nonreciprocal properties of TPPs are caused by violation of the periodicity and time-reversal symmetry in the structure. Calculations on the field distribution and transmission spectra through the structure are employed to confirm the theoretical results, which could potentially impact on a broad range of SPP-related phenomena in applications.

  20. Fergusonite-type CeNbO4+δ: Single crystal growth, symmetry revision and conductivity

    NASA Astrophysics Data System (ADS)

    Bayliss, Ryan D.; Pramana, Stevin S.; An, Tao; Wei, Fengxia; Kloc, Christian L.; White, Andrew J. P.; Skinner, Stephen J.; White, Timothy J.; Baikie, Tom

    2013-08-01

    Large fergusonite-type (ABO4, A=Ce, B=Nb) oxide crystals, a prototype electrolyte composition for solid oxide fuel cells (SOFC), were prepared for the first time in a floating zone mirror furnace under air or argon atmospheres. While CeNbO4 grown in air contained CeNbO4.08 as a minor impurity that compromised structural analysis, the argon atmosphere yielded a single phase crystal of monoclinic CeNbO4, as confirmed by selected area electron diffraction, powder and single crystal X-ray diffraction. The structure was determined in the standard space group setting C12/c1 (No. 15), rather than the commonly adopted I12/a1. AC impedance spectroscopy conducted under argon found that stoichiometric CeNbO4 single crystals showed lower conductivity compared to CeNbO4+δ confirming interstitial oxygen can penetrate through fergusonite and is responsible for the higher conductivity associated with these oxides.

  1. Extreme low thermal conductivity in nanoscale 3D Si phononic crystal with spherical pores.

    PubMed

    Yang, Lina; Yang, Nuo; Li, Baowen

    2014-01-01

    In this work, we propose a nanoscale three-dimensional (3D) Si phononic crystal (PnC) with spherical pores, which can reduce the thermal conductivity of bulk Si by a factor up to 10,000 times at room temperature. Thermal conductivity of Si PnCs depends on the porosity, for example, the thermal conductivity of Si PnCs with porosity 50% is 300 times smaller than that of bulk Si. The phonon participation ratio spectra demonstrate that more phonons are localized as the porosity increases. The thermal conductivity is insensitive to the temperature changes from room temperature to 1100 K. The extreme-low thermal conductivity could lead to a larger value of ZT than unity as the periodic structure affects very little the electric conductivity.

  2. Influence of the growth and annealing atmosphere on the electrical conductivity of LTG crystals

    NASA Astrophysics Data System (ADS)

    Alani, M.; Batis, N.; Laroche, T.; Nehari, A.; Cabane, H.; Lebbou, K.; Boy, J. J.

    2017-03-01

    We present the electrical conductivity measurements of La3Ga5.5Ta0.5O14 (LGT) crystals grown by Czochralski (Cz) technique in Ir crucibles and N2 atmosphere containing few percent of O2. In addition, we have studied the effect of thermal annealing on the stability and the thermal conductivity. The electrical conductivity depends on the stoichiometry, the inhomogeneous impurities levels, the growth atmosphere and the post-growth annealing conditions. Furthermore, we recorded the UV-Vis transmission spectra of the LGT samples and we note that the less resistive LGT samples have an edge of the intrinsic absorption at the highest wavelengths.

  3. The crystallization kinetics and thermal conductivity of alumina/fluorescein sodium salt (Al2O3/FSS) composites

    NASA Astrophysics Data System (ADS)

    Yakuphanoglu, Fahrettin; Sekerci, M.

    2005-01-01

    The thermal conductivity and crystallization mechanism of alumina (Al2O3)/fluorescein sodium salt (FSS) composites prepared by the powder metallurgy method have been investigated by means of differential thermal analysis. The Kissinger method is applied to determine the crystallization kinetics from the endotherm peaks. The activation energy E and Avrami parameter n were calculated. The kinetic parameters (E and n) have made it possible to postulate the type of crystal growth exhibited in the crystallization process. The crystallization growth is found to be one-dimensional for the composite system. The thermal conductivity of the composite system was also determined by differential scanning calorimetry.

  4. Data Mining-Aided Crystal Engineering for the Design of Transparent Conducting Oxides: Preprint

    SciTech Connect

    Suh, C.; Kim, K.; Berry, J. J.; Lee, J.; Jones, W. B.

    2010-12-01

    The purpose of this paper is to accelerate the pace of material discovery processes by systematically visualizing the huge search space that conventionally needs to be explored. To this end, we demonstrate not only the use of empirical- or crystal chemistry-based physical intuition for decision-making, but also to utilize knowledge-based data mining methodologies in the context of finding p-type delafossite transparent conducting oxides (TCOs). We report on examples using high-dimensional visualizations such as radial visualization combined with machine learning algorithms such as k-nearest neighbor algorithm (k-NN) to better define and visualize the search space (i.e. structure maps) of functional materials design. The vital role of search space generated from these approaches is discussed in the context of crystal chemistry of delafossite crystal structure.

  5. Anisotropy of thermal conductivity in single crystals YBa 2Cu 3O 7

    NASA Astrophysics Data System (ADS)

    Gusakov, Vasilii; Jezowski, Andrzej; Barilo, Sergey; Kalanda, Nikolay; Saiko, Alexandr

    2000-07-01

    The anisotropy of thermal conductivity k in single crystals YBa 2Cu 3O 7 has been studied. The temperature dependence of k in c-direction is well described by the lattice thermal conductivity ( T max=60 K; k max=4 W/ mK; T D=140 K) . The precise measurements reveal the hysteretic behavior of out-of-plane thermal conductivity. In ab-direction the upturn in k for temperatures below Tc is observed and temperatures of thermal conductivity peaks in ab- and c-direction coincide. Theoretical analysis suggests a model in which an observed peak below Tc in thermal conductivity for ab-direction is ascribed to a quasiparticle contribution.

  6. Anisotropy of thermal conductivity in YBaCuO single crystals

    NASA Astrophysics Data System (ADS)

    Gusakov, V.; Jezowski, A.; Barilo, S.; Kalanda, N.; Saiko, A.

    2000-11-01

    The anisotropy of thermal conductivity (k) in single crystals YBa 2Cu 3O 7 have been studied. The temperature dependence of k in c-direction is well described by the lattice thermal conductivity ( Tmax = 60K; k max = 4W/mK; T D = 140K). The precise measurements reveal the hysteretic behavior of out-of-plane thermal conductivity. In ab-direction the upturn in k for temperatures below T c is observed and temperatures of thermal conductivity peaks in ab- and c-direction are coincided. Theoretical analysis suggests a model in which an observed peak below T c in thermal conductivity for ab-direction is ascribed to a quasiparticle contribution.

  7. Interface shape in Czochralski grown crystals - Effect of conduction and radiation

    NASA Technical Reports Server (NTRS)

    Srivastava, R. K.; Ramachandran, P. A.; Dudukovic, M. P.

    1985-01-01

    A sequential modular computational scheme has been proposed for the calculation of temperature profiles in the melt and crystal including the melt-crystal interface shape and the crystal pulling rate for a fixed crystal radius. The heat transfer in the melt is assumed to occur by conduction only. The shape of melt-gas meniscus, described by Laplace-Young equation, is incorporated in the model and its effects on interface shape and pulling rate are examined. Further, the model incorporates the detailed radiation interaction among the various surfaces in the puller using the Gebhart enclosure theory which accounts for both direct and reflected radiation. The effects of various process parameters on the interface shape and the pulling rate have been investigated. The results of this study indicate that the shape of the melt-gas meniscus has a significant effect on the pulling rate and the interface shape in conformity with earlier studies. Further, it is shown that a simple radiation model (Stefan's model) is inadequate to model the radiation heat exchange in the Czochralski puller apparatus and the detailed Gebhart analysis is necessary for accurate calculation of both the temperature profile in the crystal as well as the interface shape.

  8. Conductive properties of switchable photoluminescence thermosetting systems based on liquid crystals.

    PubMed

    Tercjak, Agnieszka; Gutierrez, Junkal; Ocando, Connie; Mondragon, Iñaki

    2010-03-16

    Conductive properties of different thermosetting materials modified with nematic 4'-(hexyl)-4-biphenyl-carbonitrile (HBC) liquid crystal and rutile TiO(2) nanoparticles were successfully studied by means of tunneling atomic force miscroscopy (TUNA). Taking into account the liquid crystal state of the HBC at room temperature, depending on both the HBC content and the presence of TiO(2) nanoparticles, designed materials showed different TUNA currents passed through the sample. The addition of TiO(2) nanoparticles into the systems multiply the detected current if compared to the thermosetting systems without TiO(2) nanoparticles and simultaneously stabilized the current passed through the sample, making the process reversible since the absolute current values were almost the same applying both negative and positive voltage. Moreover, thermosetting systems modified with liquid crystals with and without TiO(2) nanoparticles are photoluminescence switchable materials as a function of temperature gradient during repeatable heating/cooling cycle. Conductive properties of switchable photoluminescence thermosetting systems based on liquid crystals can allow them to find potential application in the field of photoresponsive devices, with a high contrast ratio between transparent and opaque states.

  9. Geometric tuning of thermal conductivity in three-dimensional anisotropic phononic crystals.

    PubMed

    Wei, Zhiyong; Wehmeyer, Geoff; Dames, Chris; Chen, Yunfei

    2016-10-07

    Molecular dynamics simulations are performed to investigate the thermal transport properties of a three-dimensional (3D) anisotropic phononic crystal consisting of silicon nanowires and films. The calculation shows that the in-plane thermal conductivity is negatively correlated with the out-of-plane thermal conductivity upon making geometric changes, whether varying the nanowire diameter or the film thickness. This enables the anisotropy ratio of thermal conductivity to be tailored over a wide range, in some cases by more than a factor of 20. Similar trends in thermal conductivity are also observed from an independent phonon ray tracing simulation considering only diffuse boundary scattering effects, though the range of anisotropy ratios is smaller than that obtained in MD simulation. By analyzing the phonon dispersion relation with varied geometric parameters, it is found that increasing the nanowire diameter increases the out-of-plane acoustic phonon group velocities, but reduces the in-plane longitudinal and fast transverse acoustic phonon group velocities. The calculated phonon irradiation further verified the negative correlation between the in-plane and the out-of-plane thermal conductivity. The proposed 3D phononic crystal may find potential application in thermoelectrics, energy storage, catalysis and sensing applications owing to its widely tailorable thermal conductivity.

  10. Polystyrene colloidal crystals: Interface controlled thermal conductivity in an open-porous mesoparticle superstructure.

    PubMed

    Nutz, Fabian A; Ruckdeschel, Pia; Retsch, Markus

    2015-11-01

    Colloidal crystals typically consist of sub-micron sized monodisperse particles, which are densely packed on a face centered cubic lattice. While many properties of this material class have been studied over the past decades, little is known about their thermal transport properties. The high amount of interfaces and their small interparticle contact area should result in efficient thermal insulation. Using laser flash analysis we report for the first time on the temperature dependent thermal conductivity of a freestanding 366 nm polystyrene (PS) colloidal crystal. Macroscopic monoliths of these samples were fabricated by colloidal self-assembly. We demonstrate a very low thermal conductivity κ of 51 mW K(-1) m(-1) (κ of bulk PS∼140 mW K(-1) m(-1)). Remarkably, this low thermal conductivity is reached at a comparatively high density of 750 kg m(-3). It can be further increased by almost 300% upon film formation and loss of the colloidal mesostructure. Additionally, this open porous structure is largely independent of the surrounding atmosphere. This can be rationalized by the small size (∼100 nm) of the pores present within this colloidal crystal.

  11. Electrical conductivity of α-LiIO 3 acid type crystals at 1 kHz

    NASA Astrophysics Data System (ADS)

    Galez, C.; Rosso, C.; Teisseyre, Y.; Crettez, J. M.; Bourson, P.; Medeiros-Ribeiro, G.; Righi, A.; Moreira, R. L.

    1995-03-01

    The temperature dependence of the electrical conductivity of α-LiIO 3 acid type crystals is studied. By applying a very low amplitude electric field at 1 kHz and performing a continuous sampling of measurements, differences, reproducible for all the investigated samples, appeared between the first and subsequent heatings The anomalies occurring during the first heating are attributed mainly to inclusions of mother liquor, HIO 3 and Li 1-xH xIO 3. The 'intrinsic' conductivity is measured after a first annealing at about 470 K; the activation energies are then calculated.

  12. Optimization of liquid crystal devices based on weakly conductive layers for lensing and beam steering

    NASA Astrophysics Data System (ADS)

    Beeckman, Jeroen; Nys, Inge; Willekens, Oliver; Neyts, Kristiaan

    2017-01-01

    Liquid crystals are mostly known for their use in displays, but over the past decade these materials have been applied in a number of other devices such as tunable lenses or beam steering devices. A common technique to realize a gradual electric field profile as is required to obtain a gradual refractive index profile in these applications is the use of weakly conductive materials. The weakly conductive layers are able to spread the voltage profile which is applied through well-conductive electrodes at the side of the weakly conductive layer. The simulation and design of such structures is not trivial because two or three dimensional quasi-static electric field profiles need to be calculated. This is due to the fact that the resistivity of the conductive layers and the dielectric properties of the liquid crystal are coupled. An exact solution requires solving a number of coupled differential equations. In this paper, we develop a model to simulate the RC-effects with an approximate model.

  13. Universal conductance fluctuations in three dimensional metallic single crystals of Si

    PubMed

    Ghosh; Raychaudhuri

    2000-05-15

    In this paper we report the measurement of conductance fluctuations in 3D crystals of Si made metallic by heavy doping. ( L/L(straight phi) approximately 10(3), where L(straight phi) is the phase coherence length.) Temperature and magnetic field dependence of noise strongly indicate the universal conductance fluctuations as a predominant source of the observed magnitude of noise. Conductance fluctuations within a single phase coherent region of L(3)(straight phi) were found to be saturated at <(deltaG(straight phi))(2)> approximately (e(2)/h)(2). An accurate knowledge of the level of disorder enables us to calculate the change in conductance deltaG1 due to movement of a single scatterer as <(deltaG1)(2)> approximately (e(2)/h)(2), which is approximately 2 orders of magnitude higher than its theoretically expected value in 3D systems.

  14. Optical, electrical and ac conductivity measurements of nonlinear optical Dimethylaminomethylphthalimide doped with cadmium chloride single crystal for nano applications

    NASA Astrophysics Data System (ADS)

    Subramani, K.; Joseph, P. S.; Shankar, G.

    2013-07-01

    Single crystals of Dimethylaminomethylphthalimide cadmium chloride (DAMPCC) were grown by a slow evaporation technique. The unit cell parameters and crystal structure were measured by the powder X-ray diffraction analysis. The modes of vibrations of different molecular groups present in the DAMPCC crystal have been identified by FTIR spectral analysis. The UV-vis-NIR spectral analysis is used to study the optical behaviors like absorption and transmission properties of the crystal. The diffuse reflectance spectrum in absorption studies is calculated. The optical band gap of the DAMPCC crystal is calculated to be cut off wavelength 360 nm at photon energy 4.772 eV. The optical conductivity, electrical conductivity and ac conductivity are also calculated. Finally the nonlinear optics (NLO) property of DAMPCC crystal was confirmed by second harmonic generation (SHG) test using the Nd:YAG laser of fundamental wavelength 1064 nm.

  15. Rubrene crystal field-effect mobility modulation via conducting channel wrinkling.

    PubMed

    Reyes-Martinez, Marcos A; Crosby, Alfred J; Briseno, Alejandro L

    2015-05-05

    With the impending surge of flexible organic electronic technologies, it has become essential to understand how mechanical deformation affects the electrical performance of organic thin-film devices. Organic single crystals are ideal for the systematic study of strain effects on electrical properties without being concerned about grain boundaries and other defects. Here we investigate how the deformation affects the field-effect mobility of single crystals of the benchmark semiconductor rubrene. The wrinkling instability is used to apply local strains of different magnitudes along the conducting channel in field-effect transistors. We discover that the mobility changes as dictated by the net strain at the dielectric/semiconductor interface. We propose a model based on the plate bending theory to quantify the net strain in wrinkled transistors and predict the change in mobility. These contributions represent a significant step forward in structure-function relationships in organic semiconductors, critical for the development of the next generation of flexible electronic devices.

  16. Conductance of a quantum wire in the Wigner-crystal regime.

    PubMed

    Matveev, K A

    2004-03-12

    We study the effect of Coulomb interactions on the conductance of a single-mode quantum wire connecting two bulk leads. When the density of electrons in the wire is very low, they arrange in a finite-length Wigner crystal. In this regime the electron spins form an antiferromagnetic Heisenberg chain with an exponentially small coupling J. An electric current in the wire perturbs the spin chain and gives rise to a temperature-dependent contribution of the spin subsystem to the resistance. At low temperature Tconductance of the wire remains close to 2e2/h. At T>J the spin effect reduces the conductance to e2/h.

  17. Vertically Conductive Single-Crystal SiC-Based Bragg Reflector Grown on Si Wafer

    PubMed Central

    Massoubre, David; Wang, Li; Hold, Leonie; Fernandes, Alanna; Chai, Jessica; Dimitrijev, Sima; Iacopi, Alan

    2015-01-01

    Single-crystal silicon carbide (SiC) thin-films on silicon (Si) were used for the fabrication and characterization of electrically conductive distributed Bragg reflectors (DBRs) on 100 mm Si wafers. The DBRs, each composed of 3 alternating layers of SiC and Al(Ga)N grown on Si substrates, show high wafer uniformity with a typical maximum reflectance of 54% in the blue spectrum and a stopband (at 80% maximum reflectance) as large as 100 nm. Furthermore, high vertical electrical conduction is also demonstrated resulting to a density of current exceeding 70 A/cm2 above 1.5 V. Such SiC/III-N DBRs with high thermal and electrical conductivities could be used as pseudo-substrate to enhance the efficiency of SiC-based and GaN-based optoelectronic devices on large Si wafers. PMID:26601894

  18. Effects of β-sheet crystals and a glycine-rich matrix on the thermal conductivity of spider dragline silk.

    PubMed

    Park, Jinju; Kim, Duckjong; Lee, Seung-Mo; Choi, Ji-Ung; You, Myungil; So, Hye-Mi; Han, Junkyu; Nah, Junghyo; Seol, Jae Hun

    2017-03-01

    We measured the thermal conductivity of Araneus ventricosus' spider dragline silk using a suspended microdevice. The thermal conductivity of the silk fiber was approximately 0.4Wm(-1)K(-1) at room temperature and gradually increased with an increasing temperature in a manner similar to that of other disordered crystals or proteins. In order to elucidate the effect of β-sheet crystals in the silk, thermal denaturation was used to reduce the quantity of the β-sheet crystals. A calculation with an effective medium approximation supported this measurement result showing that the thermal conductivity of β-sheet crystals had an insignificant effect on the thermal conductivity of SDS. Additionally, the enhancement of bonding strength in a glycine-rich matrix by atomic layer deposition did not increase the thermal conductivity. Thus, this study suggests that the disordered part of the glycine-rich matrix prevented the peptide chains from being coaxially extended via the cross-linking covalent bonds.

  19. Facet-dependent electrical conductivity properties of Cu2O crystals.

    PubMed

    Tan, Chih-Shan; Hsu, Shih-Chen; Ke, Wei-Hong; Chen, Lih-Juann; Huang, Michael H

    2015-03-11

    It is interesting to examine facet-dependent electrical properties of single Cu2O crystals, because such study greatly advances our understanding of various facet effects exhibited by semiconductors. We show a Cu2O octahedron is highly conductive, a cube is moderately conductive, and a rhombic dodecahedron is nonconductive. The conductivity differences are ascribed to the presence of a thin surface layer having different degrees of band bending. When electrical connection was made on two different facets of a rhombicuboctahedron, a diode-like response was obtained, demonstrating the potential of using single polyhedral nanocrystals as functional electronic components. Density of state (DOS) plots for three layers of Cu2O (111), (100), and (110) planes show respective metallic, semimetal, and semiconducting band structures. By examining DOS plots for varying number of planes, the surface layer thicknesses responsible for the facet-dependent electrical properties of Cu2O crystals have been determined to be below 1.5 nm for these facets.

  20. Hopping conductivity in Mn-doped β-FeSi2 single crystals

    NASA Astrophysics Data System (ADS)

    Arushanov, E.; Lisunov, K. G.; Vinzelberg, H.; Behr, G.; Schumann, J.; Schmidt, O. G.

    2008-09-01

    The article gives a report on resistivity measurements on Mn-doped p-type FeSi2 single crystals and analyzes the data within the framework of different hopping conductivity models. Both the Mott [N. Mott and E. A. Davies, Electron Processes in Non-Crystalline Materials (Clarendon, Oxford, 1979)] and the Shklovskii-Efros [B. I. Shklovskii and A. L. Efros, Electronic Properties o0066 Doped Semiconductors (Springer, Berlin, 1984)] regimes of the variable-range hopping (VRH) conductivity are observed. It is shown that the temperature dependence of the resistivity of Mn-doped β-FeSi2 crystals, which follows a VRH conduction mechanism, can be expressed by a scaling expression of the form ln(ρ /ρ0)=Af(T /Tx). The characteristic and transition temperatures, as well as the complete set of parameters describing the properties of the localized holes (the localization radius, the dielectric permittivity, the width of the Coulomb gap Δ, and the values of the density of states at the Fermi level) are determined. The data above indicate existence of a rigid gap δ in the spectrum of the DOS in addition to Δ and point out to the polaronic nature of the charge carriers in the investigated compound.

  1. Crystal Structure Effects on the Thermal Conductivity of Cu-Ge-Se Compounds

    NASA Astrophysics Data System (ADS)

    Skoug, Eric; Cain, Jeffrey; Morelli, Donald

    2010-03-01

    One approach to increasing the efficiency of a thermoelectric material is to decrease its thermal conductivity without degrading its electronic properties. Traditionally this has been accomplished, for instance, by forming solid solutions between compounds with similar crystal structures, or, more recently, by inducing nanostructure in the crystal lattice. These methods have proven effective in many cases; however discovering compounds with intrinsically low thermal conductivity provides a fundamental solution to the same problem. Here we describe our initial efforts in synthesis and characterization of compounds of the series Cu2Ge1+xSe3, in which we observe a transition from orthorhombic to cubic symmetry at x = 0.55. The lattice thermal conductivity of the cubic phase is significantly lower than that of the orthorhombic phase, which we discuss here in relation to vacancies and anti-site defects. A simple valence argument is presented suggesting a change in the nominal valence of Ge as x approaches 1.0, which we speculate contributes to increased bond anharmonicity in the cubic-structure compounds.

  2. Mechanism of the Reduced Thermal Conductivity of Fishbone-Type Si Phononic Crystal Nanostructures

    NASA Astrophysics Data System (ADS)

    Nomura, M.; Maire, J.

    2014-09-01

    The mechanism of the reduced thermal conductivity of fishbone-type phononic crystal (PnC) nanostructures, in which ballistic phonon transport is dominant, was investigated with consideration of both the wave and particle nature of phonons. Phononic band diagrams were calculated for an Si nanowire and a fishbone-type PnC structure with a period of 100 nm, and a clear reduction of the group velocity of phonons, because of a zone-folding effect, was shown. Air-suspended Si nanowires and fishbone-type PnC structures were fabricated by electron beam (EB) lithography, and their thermal conductivities were measured by use of the originally developed micro time-domain thermoreflectance method. The PnC structure had a much lower thermal conductivity. We measured the thermal conductivity of a variety of PnC structures with different fin widths to investigate the mechanism of the reduced thermal conductivity observed. The result indicates that the increase of the phonon traveling distance. as a result of the fins, also results in reduced thermal conductivity.

  3. Mechanism of the Reduced Thermal Conductivity of Fishbone-Type Si Phononic Crystal Nanostructures

    NASA Astrophysics Data System (ADS)

    Nomura, M.; Maire, J.

    2015-06-01

    The mechanism of the reduced thermal conductivity of fishbone-type phononic crystal (PnC) nanostructures, in which ballistic phonon transport is dominant, was investigated with consideration of both the wave and particle nature of phonons. Phononic band diagrams were calculated for an Si nanowire and a fishbone-type PnC structure with a period of 100 nm, and a clear reduction of the group velocity of phonons, because of a zone-folding effect, was shown. Air-suspended Si nanowires and fishbone-type PnC structures were fabricated by electron beam (EB) lithography, and their thermal conductivities were measured by use of the originally developed micro time-domain thermoreflectance method. The PnC structure had a much lower thermal conductivity. We measured the thermal conductivity of a variety of PnC structures with different fin widths to investigate the mechanism of the reduced thermal conductivity observed. The result indicates that the increase of the phonon traveling distance. as a result of the fins, also results in reduced thermal conductivity.

  4. Enhancing ionic conductivity of bulk single-crystal yttria-stabilized zirconia by tailoring dopant distribution

    SciTech Connect

    Lee, E.; Prinz, F. B.; Cai, W.

    2011-02-11

    We present an ab initio–based kinetic Monte Carlo model for ionic conductivity in single-crystal yttria-stabilized zirconia. Ionic interactions are taken into account by combining density functional theory calculations and the cluster expansion method and are found to be essential in reproducing the effective activation energy observed in experiments. The model predicts that the effective energy barrier can be reduced by 0.15–0.25 eV by arranging the dopant ions into a superlattice.

  5. Real-time crystallization in fluorinated parylene probed by conductivity spectra

    SciTech Connect

    Khazaka, R. Diaham, S.; Locatelli, M. L.; Tenailleau, C.

    2014-03-17

    Dielectric relaxation spectroscopy experiments were performed at high temperature on fluorinated parylene films during the occurrence of the isothermal crystalline phase transition. For this polymer, since the difference between the glass transition temperature (T{sub g}) and the phase transition temperature (T{sub c}) is very strong (T{sub c} ≥ 4T{sub g}), segmental and dipolar relaxation usually used to probe the crystallization are not shown in the experiment frequency window (10{sup −1} to 10{sup 6} Hz) during the crystallization. The charge diffusion becomes the only electrical marker that allows probing the phase transition. During the transition phase, a continuous decrease of about two orders of magnitude is observed in the conductivity values below an offset frequency (f{sub c}) with a tendency to stabilization after 600 min. Below the offset frequency, the decrease of the normalized conductivity to the initial value as function of time is frequency independent. The same behavior is also observed for the f{sub c} values that decrease from 160 Hz to about 20 Hz. Above the offset frequency, the electronic hopping mechanism is also affected by the phase transition and the power law exponent (n) of the AC conductivity shows a variation from 0.7 to 0.95 during the first 600 min that tend to stabilize thereafter. Accordingly, three parameters (n, f{sub c}, and AC conductivity values for frequencies below f{sub c}) extracted from the AC conductivity spectra in different frequency windows seem suitable to probe the crystalline phase transition.

  6. Liquid crystal behavior induced assembling fabrication of conductive chiral MWCNTs@NCC nanopaper

    NASA Astrophysics Data System (ADS)

    Ren, Yumei; Wang, Tianjiao; Chen, Zhimin; Li, Jing; Tian, Qiuge; Yang, Hongxia; Xu, Qun

    2016-11-01

    The conductive chiral MWCNTs@NCC nanopapers obtained by the assembly of nanocrystalline cellulose liquid crystals (NCC LCs) host matrix along with one-dimensional (1-D) multi-walled carbon nanotubes (MWCNTs) have been studied in this work. Circular dichroism (CD) studies show strong signals stemming from the chiral nematic structure. Notably, the introduction of the MWCNTs has a pronounced effect on the chiral structure of the as-prepared nanopaper. Our experimental results indicate the multiple weak molecular interactions existing between MWCNTs and NCC are responsible for the effective dispersion and stabilization of MWCNTs. Moreover it also confirms the resulting nanopaper has an increased conductivity of 4.2 S/m at 1.96 wt% MWCNTs. So the co-assembly of the nanocomposite herein opens a gateway for preparing functional materials combining the photonic properties of the NCC LCs matrix with other building blocks that can supply other advantageous functions.

  7. Surface electrical conductivity of single crystal spinel in cesium vapor. Final report

    SciTech Connect

    Agnew, P.; Ing, J.L.

    1995-04-02

    The operation of a thermionic fuel element (TFE) requires the maintenance of good electrical resistance between the anode and cathode, and between the electrodes and the TFE body. A program of research was established as part of the TOPAZ International Program (TIP) with the purpose of investigating the degradation of TFE electrical insulators. The major emphasis of this research has been on the interactions of oxide ceramics with cesium (Cs) vapor, and the resurfacing decrease of surface resistivity. Previous work has studied the surface electrical conductivity of sapphire exposed to Cs. In this report the authors describe the results of an experimental investigation of the surface electrical conductivity of single crystal magnesium aluminate spinel at temperatures ranging from 573K to 923K, in the presence of cesium vapor at pressures up to 1 Torr. The interest in spinel has arisen in view of its apparent resistance to radiation damage.

  8. Crystal structure and ion conducting properties of La5NbMo2O16

    NASA Astrophysics Data System (ADS)

    Vu, T. D.; Krichen, F.; Barre, M.; Busselez, R.; Adil, K.; Jouanneaux, A.; Suard, E.; Goutenoire, F.

    2016-05-01

    The new compound La5NbMo2O16 with high ionic conduction has been discovered during the study of the ternary phase diagram of La2O3-MoO3-Nb2O5. The material crystallizes in the cubic space group Pn 3 bar n (no 222) with the unit cell parameter a=11.2250(1) Å. La5NbMo2O16 is a new analogue of the R5Mo3O16 series (R=Pr, Nd). The structure was refined from a combined data X-ray and neutron powder diffraction. The ionic conductivity of the compound is then measured on sintered pellets, by means of complex impedance spectroscopy.

  9. Point defect distribution in high-mobility conductive SrTiO{sub 3} crystals

    SciTech Connect

    Gentils, A.; Copie, O.; Bibes, M.; Bouzehouane, K.; Jacquet, E.; Carretero, C.; Barthelemy, A.; Fortuna, F.; Basletic, M.; Tafra, E.; Hamzic, A.

    2010-04-01

    We have carried out positron-annihilation spectroscopy to characterize the spatial distribution and the nature of vacancy defects in insulating as-received as well as in reduced SrTiO{sub 3} substrates exhibiting high-mobility conduction. The substrates were reduced either by ion etching the substrate surfaces or by doping with vacancies during thin-film deposition at low pressure and high temperature. We show that Ti vacancies are native defects homogeneously distributed in as-received substrates. In contrast, the dominant vacancy defects are the same both in ion etched crystals and substrates reduced during the film growth, and they consist of nonhomogeneous distributions of cation-oxygen vacancy complexes. Their spatial extension is tuned from a few microns in ion-etched samples to the whole substrate in specimens reduced during film deposition. Our results shed light on the transport mechanisms of conductive SrTiO{sub 3} crystals and on strategies for defect-engineered oxide quantum wells, wires, and dots.

  10. Automated optical inspection of liquid crystal display anisotropic conductive film bonding

    NASA Astrophysics Data System (ADS)

    Ni, Guangming; Du, Xiaohui; Liu, Lin; Zhang, Jing; Liu, Juanxiu; Liu, Yong

    2016-10-01

    Anisotropic conductive film (ACF) bonding is widely used in the liquid crystal display (LCD) industry. It implements circuit connection between screens and flexible printed circuits or integrated circuits. Conductive microspheres in ACF are key factors that influence LCD quality, because the conductive microspheres' quantity and shape deformation rate affect the interconnection resistance. Although this issue has been studied extensively by prior work, quick and accurate methods to inspect the quality of ACF bonding are still missing in the actual production process. We propose a method to inspect ACF bonding effectively by using automated optical inspection. The method has three steps. The first step is that it acquires images of the detection zones using a differential interference contrast (DIC) imaging system. The second step is that it identifies the conductive microspheres and their shape deformation rate using quantitative analysis of the characteristics of the DIC images. The final step is that it inspects ACF bonding using a back propagation trained neural network. The result shows that the miss rate is lower than 0.1%, and the false inspection rate is lower than 0.05%.

  11. Electrical and thermal conductivities of rapidly crystallized Cu-Zr alloys: The effect of anharmonicity

    NASA Astrophysics Data System (ADS)

    Uporov, S.; Bykov, V.; Estemirova, S.

    2016-10-01

    We present a comprehensive study of electrical and thermal conductivities, specific heat and magnetic susceptibility of rapidly crystallized Cu100-xZrx (x = 20-90) alloys. X-ray diffraction analysis has revealed that all the prepared compositions had strongly textured and distorted crystal structures. Different monoclinic and other non-equilibrium phases were detected in the case of glass-forming samples, whereas the alloys without a tendency to form glassy state show almost equilibrium phase content. Metallic type of electrical conductivity and the Kondo anomaly were observed for all the examined samples. It was found that the electrical resistance data cannot be adequately described within the standard Bloch-Grüneisen theory. We use the Debye characteristic temperature as a linear function to fit the electrical conductivity accurately. The composition dependence of the electron density of states at the Fermi level (DOS) has been extracted from room temperature magnetic susceptibility. We found that the glass-forming alloys are characterized by abnormally large values of DOS, which are comparable to those of glassy analogues. Noticeable anharmonic contribution in total specific heat has been revealed for all the studied compositions. In order to estimate the effect of anharmonicity in the system under consideration, we analyzed composition and temperature dependencies of the studied thermal characteristics related to the Grüneisen coefficient. Basing on the results obtained in this study we propose a phenomenological concept to explain abnormal behavior of physical properties of glass-forming Cu-Zr alloys within the standard solid state theory taking into account anharmonic effects.

  12. Rubrene crystal field-effect mobility modulation via conducting channel wrinkling

    PubMed Central

    Reyes-Martinez, Marcos A.; Crosby, Alfred J.; Briseno, Alejandro L.

    2015-01-01

    With the impending surge of flexible organic electronic technologies, it has become essential to understand how mechanical deformation affects the electrical performance of organic thin-film devices. Organic single crystals are ideal for the systematic study of strain effects on electrical properties without being concerned about grain boundaries and other defects. Here we investigate how the deformation affects the field-effect mobility of single crystals of the benchmark semiconductor rubrene. The wrinkling instability is used to apply local strains of different magnitudes along the conducting channel in field-effect transistors. We discover that the mobility changes as dictated by the net strain at the dielectric/semiconductor interface. We propose a model based on the plate bending theory to quantify the net strain in wrinkled transistors and predict the change in mobility. These contributions represent a significant step forward in structure–function relationships in organic semiconductors, critical for the development of the next generation of flexible electronic devices. PMID:25939864

  13. Geometric treatment of conduction electron scattering by crystal lattice strains and dislocations

    SciTech Connect

    Viswanathan, Koushik; Chandrasekar, Srinivasan

    2014-12-28

    The problem of conduction electron scattering by inhomogeneous crystal lattice strains is addressed using a tight-binding formalism and the differential geometric treatment of deformations in solids. In this approach, the relative positions of neighboring atoms in a strained lattice are naturally taken into account, even in the presence of crystal dislocations, resulting in a fully covariant Schrödinger equation in the continuum limit. Unlike previous work, the developed formalism is applicable to cases involving purely elastic strains as well as discrete and continuous distributions of dislocations—in the latter two cases, it clearly demarcates the effects of the dislocation strain field and core. It also differentiates between elastic and plastic strain contributions, respectively. The electrical resistivity due to the strain field of edge dislocations is then evaluated and the resulting numerical estimate for Cu shows good agreement with reported experimental values. This indicates that the electrical resistivity of edge dislocations in metals is not entirely due to the core, contrary to current models. Application to the study of strain effects in constrained quantum systems is also discussed.

  14. Copper and silver selenide crystal growth rate measurements as a method for determination of ionic conductivity

    NASA Astrophysics Data System (ADS)

    Vučić, Zlatko; Lovrić, Davorin; Gladić, Jadranko; Etlinger, Božidar

    2004-03-01

    The motivation behind this work is the discrepancy between the measured and calculated growth rates of copper selenide spherical single crystals between 740 and 800 K. The growth of cylindrical polycrystalline samples of copper selenide at high temperatures was monitored in experiments that enabled full control of the geometry of growth. Together with the calculations based on Yokota's transport equation, these measurements eliminated ionic conductivity data as a possible reason behind too high values of the calculated growth rates. The equivalent growth experiments on polycrystalline silver selenide samples were performed as a test of the method, yielding excellent agreement with the results obtained by extrapolation of existing data. On the basis of these measurements and associated analysis, this method is proposed as a method for determination of ionic conductivity of mixed superionic conductors on temperatures up to the temperatures of melting, i.e. in the range in which other methods of ionic conductivity measurements either do not work or are not accurate enough.

  15. Fluctuation conductivity of oxygen underdoped YBa2Cu3O7-δ single crystals

    NASA Astrophysics Data System (ADS)

    Vovk, R. V.; Khadzhai, G. Ya.; Goulatis, I. L.; Chroneos, A.

    2014-03-01

    The electrical resistance in the range of ТC-300 K in the layer planes of YВа2Сu3О7-δ single crystals with a range of oxygen deficiency (providing a range of TC from 78 to 92 K) was investigated. The experimental data is approximated by an expression that accounts for the scattering of electrons on phonons, as well as on defects and the fluctuation conductivity in a 3-D model of the Aslamazov-Larkin theory. According to this approximation, depending upon the oxygen deficiency, the Debye temperature varies from 245 to 400 K, coherence length ξС(0)≈0.5 Å.

  16. Fast dynamic holographic recording based on conductive ionic metal-alkanoate liquid crystals and smectic glasses.

    PubMed

    Klimusheva, G; Bugaychuk, S; Garbovskiy, Yu; Kolesnyk, O; Mirnaya, T; Ishchenko, A

    2006-01-15

    Recordings of dynamic holograms with microsecond relaxation times under the action of nanosecond laser pulses are obtained in composites on the base of a novel class of liquid crystals (LCs) in ionic metal-alkanoates. Holographic parameters and relaxation characteristics are measured for doped lyotropic ionic LC, for sandwichlike cells (consisting of a dye layer and a layer of the lyotropic ionic LC), and for colored ionic smectic glasses. The structure of the materials is investigated by use of the small-angle x-ray technique. The mechanism of resonance nonlinearity in photosensitive centers and mechanisms of the grating erasure connected with a charge transport in the ionic conductive LC matrix are discussed.

  17. Single-Crystal X-ray Structures of conductive π-Stacking Dimers of Tetrakis(alkylthio)benzene Radical Cations

    PubMed Central

    Chen, Xiaoyu; Gao, Feng; Yang, Wuqin

    2016-01-01

    Salts containing radical cations of 1,2,4,5-tetrakis(isopropylthio)benzene (TPB) and 1,2,4,5-tetrakis(ethylthio) benzene (TEB) have been successfully synthesized with . These newly synthesized salts have been characterized by UV-Vis absorption, EPR spectroscopy, conductivity measurement, single crystal X-ray diffraction analysis as well as DFT calculation. This study raises the first crystal structure of conductive π-stacking radical cation with single phenyl ring and reveals their conductivity has relationship with the stack structure which affected by the substituent. PMID:27403720

  18. Decoupling mass adsorption from fluid viscosity and density in quartz crystal microbalance measurements using normalized conductance modeling

    NASA Astrophysics Data System (ADS)

    Parlak, Z.; Biet, C.; Zauscher, S.

    2013-08-01

    We describe the physical understanding of a method which differentiates between the frequency shift caused by fluid viscosity and density from that caused by mass adsorption in the resonance of a quartz crystal resonator. This method uses the normalized conductance of the crystal to determine a critical frequency at which the fluid mass and fluid loss compensate each other. Tracking the shift in this critical frequency allows us to determine purely mass adsorption on the crystal. We extended this method to Maxwellian fluids for understanding the mass adsorption in non-Newtonian fluids. We validate our approach by real-time mass adsorption measurements using glycerol and albumin solutions.

  19. Ionic conductivity of single crystals of sodium aluminium germanate Na8Al6Ge6O24(OH)2

    NASA Astrophysics Data System (ADS)

    Sorokin, N. I.

    2015-09-01

    The electrical conductivity of single crystals of sodium aluminium germanate Na8Al6Ge6O24(OH)2 (cubic system, sp. gr. ), which is a germanium analog of sodalite, has been studied in the temperature range of 468‒758 K. Na8Al6Ge6O24(OH)2 crystals are obtained by hydrothermal synthesis (temperature in the dissolution zone 573‒673 K, temperature gradient ~1.5 K/cm). NaAlO2 and GeO2В oxides are used as starting reagents; NaOH hydroxide serves as a solvent. The ionic conductivity of Na8Al6Ge6O24(OH)2 crystals is 2 × 10-4 S/cm (at 758 K); the activation energy of ionic transfer is 0.46 ± 0.03 eV.

  20. Two-dimensional superconductivity of SmFeAsO0.85 single crystals: A fluctuation-conductivity study

    NASA Astrophysics Data System (ADS)

    Lee, Hyun-Sook; Park, Jae-Hyun; Lee, Jae-Yeap; Kim, Ju-Young; Sung, Nak-Heon; Cho, B. K.; Lee, Hu-Jong

    2010-12-01

    Temperature dependence of the in-plane conductance of a SmFeAsO0.85 single crystal is measured in c-axis and planar magnetic fields up to 7 T. The conductivity near the superconducting transition is well described by two-dimensional (2D) thermal-fluctuation theory. The 2D superconductivity arises as the c-axis coherence length is much shorter than the spacing between neighboring FeAs layers.

  1. Analysis of the nature of electrical conductivity in nominally undoped LiNbO{sub 3} crystals

    SciTech Connect

    Pritulenko, A. S. Yatsenko, A. V.; Yevdokimov, S. V.

    2015-03-15

    The temperature dependence of electrical conductivity and admittance of two nominally undoped lithium niobate crystals of congruent composition has been investigated in the temperature range of 293–450 K and simulated in the range of 350–700 K. It is shown that the ion conductivity at T < 450 K is mainly determined by OH{sup −} groups; however, some other mechanisms may manifest themselves at higher temperatures; a likely one is diffusion of oxygen vacancies, which leads to an increase in the “averaged” conductivity activation energy.

  2. On the solid phase crystallization of In2O3:H transparent conductive oxide films prepared by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Macco, Bart; Verheijen, Marcel A.; Black, Lachlan E.; Barcones, Beatriz; Melskens, J.; Kessels, Wilhelmus M. M.

    2016-08-01

    Hydrogen-doped indium oxide (In2O3:H) has emerged as a highly transparent and conductive oxide, finding its application in a multitude of optoelectronic devices. Recently, we have reported on an atomic layer deposition (ALD) process to prepare high quality In2O3:H. This process consists of ALD of In2O3:H films at 100 °C, followed by a solid phase crystallization step at 150-200 °C. In this work, we report on a detailed electron microscopy study of this crystallization process which reveals new insights into the crucial aspects for achieving the large grain size and associated excellent properties of the material. The key finding is that the best optoelectronic properties are obtained by preparing the films at the lowest possible temperature prior to post-deposition annealing. Electron microscopy imaging shows that such films are mostly amorphous, but feature a very low density of embedded crystallites. Upon post-deposition annealing, crystallization proceeds merely from isotropic crystal grain growth of these embedded crystallites rather than by the formation of additional crystallites. The relatively high hydrogen content of 4.2 at. % in these films is thought to cause the absence of additional nucleation, thereby rendering the final grain size and optoelectronic properties solely dependent on the density of embedded crystallites. The temperature-dependent grain growth rate has been determined, from which an activation energy of (1.39 ± 0.04) eV has been extracted. Finally, on the basis of the observed crystallization mechanism, a simple model to fully describe the crystallization process has been developed. This model has been validated with a numerical implementation thereof, which accurately predicts the observed temperature-dependent crystallization behaviour.

  3. Acoustoelectric effects in reflection of leaky-wave-radiated bulk acoustic waves from piezoelectric crystal-conductive liquid interface.

    PubMed

    Rimeika, Romualdas; Čiplys, Daumantas; Jonkus, Vytautas; Shur, Michael

    2016-01-01

    The leaky surface acoustic wave (SAW) propagating along X-axis of Y-cut lithium tantalate crystal strongly radiates energy in the form of an obliquely propagating narrow bulk acoustic wave (BAW) beam. The reflection of this beam from the crystal-liquid interface has been investigated. The test liquids were solutions of potassium nitrate in distilled water and of lithium chloride in isopropyl alcohol with the conductivity varied by changing the solution concentration. The strong dependences of the reflected wave amplitude and phase on the liquid conductivity were observed and explained by the acoustoelectric interaction in the wave reflection region. The novel configuration of an acoustic sensor for liquid media featuring important advantages of separate measuring and sensing surfaces and rigid structure has been proposed. The application of leaky-SAW radiated bulk waves for identification of different brands of mineral water has been demonstrated.

  4. Strong tendency of homeotropic alignment and anisotropic lithium ion conductivity of sulfonate functionalized zwitterionic imidazolium ionic liquid crystals.

    PubMed

    Rondla, Rohini; Lin, Joseph C Y; Yang, C T; Lin, Ivan J B

    2013-09-17

    Here, we report the first attempt to investigate the liquid crystal (LC) behavior of SO3(-) functionalized imidazolium zwitterionic (SO3(-)ImZI) salts, which display homeotropic alignment on a glass slide without the aid of any aligning approach. Doping lithium salt to ImZI salts lowers the melting temperatures and raises the clearing temperatures substantially to form room temperature ImZILCs. Excellent anisotropic lithium ion conductivity is achieved; which is strengthened by their tendency for homeotropic alignment.

  5. Thermal conductivity of Glycerol’s liquid, glass, and crystal states, glass-liquid-glass transition, and crystallization at high pressures

    SciTech Connect

    Andersson, Ove; Johari, G. P.

    2016-02-14

    To investigate the effects of local density fluctuations on phonon propagation in a hydrogen bonded structure, we studied the thermal conductivity κ of the crystal, liquid, and glassy states of pure glycerol as a function of the temperature, T, and the pressure, p. We find that the following: (i) κ{sub crystal} is 3.6-times the κ{sub liquid} value at 140 K at 0.1 MPa and 2.2-times at 290 K, and it varies with T according to 138 × T{sup −0.95}; (ii) the ratio κ{sub liquid} (p)/κ{sub liquid} (0.1 MPa) is 1.45 GPa{sup −1} at 280 K, which, unexpectedly, is about the same as κ{sub crystal} (p)/κ{sub crystal} (0.1 MPa) of 1.42 GPa{sup −1} at 298 K; (iii) κ{sub glass} is relatively insensitive to T but sensitive to the applied p (1.38 GPa{sup −1} at 150 K); (iv) κ{sub glass}-T plots show an enhanced, pressure-dependent peak-like feature, which is due to the glass to liquid transition on heating; (v) continuous heating cold-crystallizes ultraviscous glycerol under pressure, at a higher T when p is high; and (vi) glycerol formed by cooling at a high p and then measured at a low p has a significantly higher κ than the glass formed by cooling at a low p. On heating at a fixed low p, its κ decreases before its glass-liquid transition range at that p is reached. We attribute this effect to thermally assisted loss of the configurational and vibrational instabilities of a glass formed at high p and recovered at low p, which is different from the usual glass-aging effect. While the heat capacity, entropy, and volume of glycerol crystal are less than those for its glass and liquid, κ{sub crystal} of glycerol, like its elastic modulus and refractive index, is higher. We discuss these findings in terms of the role of fluctuations in local density and structure, and the relations between κ and the thermodynamic quantities.

  6. Spherical 3D photonic crystal with conducting nanoshell and particle core

    NASA Astrophysics Data System (ADS)

    Zamudio-Lara, A.; Sánchez-Mondragón, J.; Escobedo-Alatorre, J.; Pérez-Careta, E.; Torres-Cisneros, M.; Tecpoyotl-Torres, Margarita; Vázquez-Buenos Aires, O.

    2009-06-01

    We discuss a structured 3D Dielectric Photonic Crystal with both a metallic core and a metallic shell. We discuss the role of each one, the stack, the core as well as the cavity formed between the core and the shell. The low frequency metallic core features becomes much more significant as it gets smaller and get diluted by the cavity.

  7. Optical reflectance, optical refractive index and optical conductivity measurements of nonlinear optics for L-aspartic acid nickel chloride single crystal

    NASA Astrophysics Data System (ADS)

    Anbazhagan, G.; Joseph, P. S.; Shankar, G.

    2013-03-01

    Single crystals of L-aspartic acid nickel chloride (LANC) were grown by the slow evaporation technique at room temperature. The grown crystals were subjected to Powder X-ray diffraction studies to confirm the crystal structure. The modes of vibration of different molecular groups present in LANC have been identified by FTIR spectral analysis. Optical transferency of the grown crystal was investigated by UV-Vis-NIR spectrum. The lower optical cut off wavelength for this crystal is observed at 240 nm and energy band gap 5.179 eV. The optical reflectance and optical refractive index studies have been carried out in this crystal. Finally, the optical conductivity and electrical conductivity studies have been carried out on LANC single crystal.

  8. FORTRAN 77 programs for conductive cooling of dikes with temperature-dependent thermal properties and heat of crystallization

    USGS Publications Warehouse

    Delaney, P.T.

    1988-01-01

    Temperature histories obtained from transient heat-conduction theory are applicable to most dikes despite potential complicating effects related to magma flow during emplacement, groundwater circulation, and metamorphic reaction during cooling. Here. machine-independent FORTRAN 77 programs are presented to calculate temperatures in and around dikes as they cool conductively. Analytical solutions can treat thermal-property contrasts between the dike and host rocks, but cannot address the release of magmatic heat of crystallization after the early stages of cooling or the appreciable temperature dependence of thermal conductivity and diffusivity displayed by most rock types. Numerical solutions can incorporate these additional factors. The heat of crystallization can raise the initial temperature at the dike contact, ??c1, about 100??C above that which would be estimated if it were neglected, and can decrease the rate at which the front of solidified magma moves to the dike center by a factor of as much as three. Thermal conductivity and diffusivity of rocks increase with decreasing temperature and, at low temperatures, these properties increase more if the rocks are saturated with water. Models that treat these temperature dependencies yield estimates of ??c1 that are as much as 75??C beneath those which would be predicted if they were neglected. ?? 1988.

  9. Transition from semiconducting to metallic-like conducting and weak antilocalization effect in single crystals of LuPtSb

    SciTech Connect

    Hou, Zhipeng; Wang, Yue; Xu, Guizhou; Zhang, Xiaoming; Liu, Enke; Xi, Xuekui; Wang, Wenhong Wu, Guangheng; Wang, Wenquan; Liu, Zhongyuan

    2015-03-09

    High quality half-Heusler single crystals of LuPtSb have been synthesized by a Pb flux method. The temperature dependent resistivity and Hall effects indicate that the LuPtSb crystal is a p-type gapless semiconductor showing a transition from semiconducting to metallic conducting at 150 K. Moreover, a weakly temperature-dependent positive magnetoresistance (MR) as large as 109% and high carrier mobility up to 2950 cm{sup 2}/V s are experimentally observed at temperatures below 150 K. The low-field MR data show evidence for weak antilocalization (WAL) effect at temperatures even up to 150 K. Analysis of the temperature and angle dependent magnetoconductance manifests that the WAL effect originates from the bulk contribution owing to the strong spin-orbital coupling.

  10. Thermal conductivity prediction of nanoscale phononic crystal slabs using a hybrid lattice dynamics-continuum mechanics technique

    NASA Astrophysics Data System (ADS)

    Reinke, Charles M.; Su, Mehmet F.; Davis, Bruce L.; Kim, Bongsang; Hussein, Mahmoud I.; Leseman, Zayd C.; Olsson-III, Roy H.; El-Kady, Ihab

    2011-12-01

    Recent work has demonstrated that nanostructuring of a semiconductor material to form a phononic crystal (PnC) can significantly reduce its thermal conductivity. In this paper, we present a classical method that combines atomic-level information with the application of Bloch theory at the continuum level for the prediction of the thermal conductivity of finite-thickness PnCs with unit cells sized in the micron scale. Lattice dynamics calculations are done at the bulk material level, and the plane-wave expansion method is implemented at the macrosale PnC unit cell level. The combination of the lattice dynamics-based and continuum mechanics-based dispersion information is then used in the Callaway-Holland model to calculate the thermal transport properties of the PnC. We demonstrate that this hybrid approach provides both accurate and efficient predictions of the thermal conductivity.

  11. Effect of Fe doping on the terahertz conductivity of GaN single crystals

    NASA Astrophysics Data System (ADS)

    Kadlec, Filip; Kadlec, Christelle; Paskova, Tanya; Evans, Keith

    2010-04-01

    Bulk single crystals of GaN with different degrees of Fe doping were studied using time-domain terahertz spectroscopy at high temperatures. Features due to free carriers were observed in the complex permittivity spectra with a pronounced dependence on both doping and temperature. Fitting the spectra using the Drude model made it possible to deduce a defect ionization energy of 16 meV in the undoped sample while the spectra of doped samples are consistent with an ionization energy of 60 meV. Also, the free carrier concentrations at temperatures from 300 to 900 K were estimated.

  12. Small polaron hopping conduction mechanism in LiFePO4 glass and crystal

    NASA Astrophysics Data System (ADS)

    Banday, Azeem; Murugavel, Sevi

    2017-01-01

    The optimization of a cathode material is the most important criterion of lithium ion battery technology, which decides the power density. In order to improve the rate capability, a cathode material must possess high electronic and ionic conductivities. Therefore, it is important to understand the charge transport mechanism in such an advanced cathode material in its intrinsic state before modifying it by various means. In this work, we report the thermal, structural, and electrical conductivity studies on lithium iron phosphate, LiFePO4, both in its polycrystalline (LFPC) and glassy (LFPG) counterpart states. The vibrational spectroscopic measurements reveal the characteristic vibrational modes, which are the intrinsic part of LFPC, whereas in LFPG, the phonon modes become broader and overlap with each other due to the lattice disorder. The electrical conductivity measurements reveal that LFPG exhibits a higher polaronic conductivity of 1.6 orders than the LFPC sample. The temperature dependent dc conductivity has been analyzed with the Mott model of polarons and reveals the origin of enhanced polaronic conductivity in LFPG. Based on the analysis, the enhanced polaronic conductivity in LFPG has been attributed to the combined effect of reduced hopping length, decreased activation energy, and enhanced polaron concentration.

  13. Realisation of an all solid state lithium battery using solid high temperature plastic crystal electrolytes exhibiting liquid like conductivity.

    PubMed

    Shekibi, Youssof; Rüther, Thomas; Huang, Junhua; Hollenkamp, Anthony F

    2012-04-07

    Replacement of volatile and combustible electrolytes in conventional lithium batteries is desirable for two reasons: safety concerns and increase in specific energy. In this work we consider the use of an ionic organic plastic crystal material (IOPC), N-ethyl-N-methylpyrrolidinium tetrafluoroborate, [C2mpyr][BF(4)], as a solid-state electrolyte for lithium battery applications. The effect of inclusion of 1 to 33 mol% lithium tetrafluoroborate, LiBF(4), into [C2mpyr][BF(4)] has been investigated over a wide temperature range by differential scanning calorimetry (DSC), impedance spectroscopy, cyclic voltammetry and cycling of full Li|LiFePO(4) batteries. The increases in ionic conductivity by orders of magnitude observed at higher temperature are most likely associated with an increase in Li ion mobility in the highest plastic phase. At concentrations >5 mol% LiBF(4) the ionic conductivity of these solid-state composites is comparable to the ionic conductivity of room temperature ionic liquids. Galvanostatic cycling of Li|Li symmetrical cells showed that the reversibility of the lithium metal redox reaction at the interface of this plastic crystal electrolyte is sufficient for lithium battery applications. For the first time we demonstrate an all solid state lithium battery incorporating solid electrolytes based on IOPC as opposed to conventional flammable organic solvents.

  14. The special features of the crystal structure and properties of oxides with mixed conductivity based on lanthanum gallate

    NASA Astrophysics Data System (ADS)

    Politova, E. D.; Ivanov, S. A.; Kaleva, G. M.; Mosunov, A. V.; Rusakov, V. S.

    2008-10-01

    The paper presents a review of works on the synthesis, structural composition effects, phase transitions, and electrical conductivity properties of multicomponent solid solutions based on heterosubstituted lanthanum gallate (La,A)(Ga,M)O3 - y . High-temperature phase transitions and structural and charge ordering effects were studied. The presence of iron cations in different valence states was proved; the relative contents of these cations depended on the x parameter and nonstoichiometry parameter y of the base composition. For M = Fe, antiferromagnetic ordering was observed; its temperature interval was determined by the concentration of iron cations in the high-spin state. The total conductivity was found to increase as the concentration of transition metal cations grew because of an increase in the electronic conductivity component. The data on structural parameters and dc and ac conductivity substantiated the conclusion that the highest ionic conductivity and permeability to oxygen were characteristic of iron-containing oxides. The results obtained are evidence that crystal chemical factors play a determining role in the formation of the ion-conducting properties of anion-deficient perovskite-like oxides.

  15. Anomalous three-dimensional bulk ac conduction within the Kondo gap of SmB6 single crystals

    NASA Astrophysics Data System (ADS)

    Laurita, N. J.; Morris, C. M.; Koohpayeh, S. M.; Rosa, P. F. S.; Phelan, W. A.; Fisk, Z.; McQueen, T. M.; Armitage, N. P.

    2016-10-01

    The Kondo insulator SmB6 has long been known to display anomalous transport behavior at low temperatures, T <5 K. In this temperatures range, a plateau is observed in the dc resistivity, contrary to the exponential divergence expected for a gapped system. Recent theoretical calculations suggest that SmB6 may be the first topological Kondo insulator (TKI) and propose that the residual conductivity is due to topological surface states which reside within the Kondo gap. Since the TKI prediction many experiments have claimed to observe high mobility surface states within a perfectly insulating hybridization gap. Here, we investigate the low energy optical conductivity within the hybridization gap of single crystals of SmB6 via time domain terahertz spectroscopy. Samples grown by both optical floating zone and aluminum flux methods are investigated to probe for differences originating from sample growth techniques. We find that both samples display significant three-dimensional bulk conduction originating within the Kondo gap. Although SmB6 may be a bulk dc insulator, it shows significant bulk ac conduction that is many orders of magnitude larger than any known impurity band conduction. The nature of these in-gap states and their coupling with the low energy spin excitons of SmB6 is discussed. Additionally, the well-defined conduction path geometry of our optical experiments allows us to show that any surface states, which lie below our detection threshold if present, must have a sheet resistance of R /square≥ 1000 Ω .

  16. Thermal conductance at the interface between crystals using equilibrium and nonequilibrium molecular dynamics

    NASA Astrophysics Data System (ADS)

    Merabia, Samy; Termentzidis, Konstantinos

    2012-09-01

    In this article, we compare the results of nonequilibrium (NEMD) and equilibrium (EMD) molecular dynamics methods to compute the thermal conductance at the interface between solids. We propose to probe the thermal conductance using equilibrium simulations measuring the decay of the thermally induced energy fluctuations of each solid. We also show that NEMD and EMD give generally speaking inconsistent results for the thermal conductance: Green-Kubo simulations probe the Landauer conductance between two solids which assumes phonons on both sides of the interface to be at equilibrium. On the other hand, we show that NEMD give access to the out-of-equilibrium interfacial conductance consistent with the interfacial flux describing phonon transport in each solid. The difference may be large and reaches typically a factor 5 for interfaces between usual semiconductors. We analyze finite size effects for the two determinations of the interfacial thermal conductance, and show that the equilibrium simulations suffer from severe size effects as compared to NEMD. We also compare the predictions of the two above-mentioned methods—EMD and NEMD—regarding the interfacial conductance of a series of mass mismatched Lennard-Jones solids. We show that the Kapitza conductance obtained with EMD can be well described using the classical diffuse mismatch model (DMM). On the other hand, NEMD simulation results are consistent with an out-of-equilibrium generalization of the acoustic mismatch model (AMM). These considerations are important in rationalizing previous results obtained using molecular dynamics, and help in pinpointing the physical scattering mechanisms taking place at atomically perfect interfaces between solids, which is a prerequisite to understand interfacial heat transfer across real interfaces.

  17. Large Scale Laser Crystallization of Solution-based Alumina-doped Zinc Oxide (AZO) Nanoinks for Highly Transparent Conductive Electrode

    PubMed Central

    Nian, Qiong; Callahan, Michael; Saei, Mojib; Look, David; Efstathiadis, Harry; Bailey, John; Cheng, Gary J.

    2015-01-01

    A new method combining aqueous solution printing with UV Laser crystallization (UVLC) and post annealing is developed to deposit highly transparent and conductive Aluminum doped Zinc Oxide (AZO) films. This technique is able to rapidly produce large area AZO films with better structural and optoelectronic properties than most high vacuum deposition, suggesting a potential large-scale manufacturing technique. The optoelectronic performance improvement attributes to UVLC and forming gas annealing (FMG) induced grain boundary density decrease and electron traps passivation at grain boundaries. The physical model and computational simulation developed in this work could be applied to thermal treatment of many other metal oxide films. PMID:26515670

  18. Large Scale Laser Crystallization of Solution-based Alumina-doped Zinc Oxide (AZO) Nanoinks for Highly Transparent Conductive Electrode.

    PubMed

    Nian, Qiong; Callahan, Michael; Saei, Mojib; Look, David; Efstathiadis, Harry; Bailey, John; Cheng, Gary J

    2015-10-30

    A new method combining aqueous solution printing with UV Laser crystallization (UVLC) and post annealing is developed to deposit highly transparent and conductive Aluminum doped Zinc Oxide (AZO) films. This technique is able to rapidly produce large area AZO films with better structural and optoelectronic properties than most high vacuum deposition, suggesting a potential large-scale manufacturing technique. The optoelectronic performance improvement attributes to UVLC and forming gas annealing (FMG) induced grain boundary density decrease and electron traps passivation at grain boundaries. The physical model and computational simulation developed in this work could be applied to thermal treatment of many other metal oxide films.

  19. Large Scale Laser Crystallization of Solution-based Alumina-doped Zinc Oxide (AZO) Nanoinks for Highly Transparent Conductive Electrode

    NASA Astrophysics Data System (ADS)

    Nian, Qiong; Callahan, Michael; Saei, Mojib; Look, David; Efstathiadis, Harry; Bailey, John; Cheng, Gary J.

    2015-10-01

    A new method combining aqueous solution printing with UV Laser crystallization (UVLC) and post annealing is developed to deposit highly transparent and conductive Aluminum doped Zinc Oxide (AZO) films. This technique is able to rapidly produce large area AZO films with better structural and optoelectronic properties than most high vacuum deposition, suggesting a potential large-scale manufacturing technique. The optoelectronic performance improvement attributes to UVLC and forming gas annealing (FMG) induced grain boundary density decrease and electron traps passivation at grain boundaries. The physical model and computational simulation developed in this work could be applied to thermal treatment of many other metal oxide films.

  20. Quantum transport in strongly disordered crystals: Electrical conductivity with large negative vertex corrections

    NASA Astrophysics Data System (ADS)

    Janiš, Václav; Pokorný, Vladislav

    2012-12-01

    We propose a renormalization scheme of the Kubo formula for the electrical conductivity with multiple backscatterings contributing to the electron-hole irreducible vertex derived from the asymptotic limit to high spatial dimensions. We use this vertex to represent the two-particle Green function via a symmetrized Bethe-Salpeter equation in momentum space. We further utilize the dominance of a pole in the irreducible vertex to an approximate diagonalization of the Bethe-Salpeter equation and a non-perturbative representation of the electron-hole correlation function. The latter function is then used to derive a compact representation for the electrical conductivity at zero temperature without the necessity to evaluate separately the Drude term and vertex corrections. The electrical conductivity calculated in this way remains nonnegative also in the strongly disordered regime where the localization effects become significant and the negative vertex corrections in the standard Kubo formula overweight the Drude term.

  1. Reciprocated suppression of polymer crystallization toward improved solid polymer electrolytes: Higher ion conductivity and tunable mechanical properties

    SciTech Connect

    Bi, Sheng; Sun, Che-Nan; Zawodzinski, Thomas A.; Ren, Fei; Keum, Jong Kahk; Ahn, Suk-Kyun; Li, Dawen; Chen, Jihua

    2015-08-06

    Solid polymer electrolytes based on lithium bis(trifluoromethanesulfonyl) imide and polymer matrix were extensively studied in the past due to their excellent potential in a broad range of energy related applications. Poly(vinylidene fluoride) (PVDF) and polyethylene oxide (PEO) are among the most examined polymer candidates as solid polymer electrolyte matrix. In this paper, we study the effect of reciprocated suppression of polymer crystallization in PVDF/PEO binary matrix on ion transport and mechanical properties of the resultant solid polymer electrolytes. With electron and X-ray diffractions as well as energy filtered transmission electron microscopy, we identify and examine the appropriate blending composition that is responsible for the diminishment of both PVDF and PEO crystallites. Laslty, a three-fold conductivity enhancement is achieved along with a highly tunable elastic modulus ranging from 20 to 200 MPa, which is expected to contribute toward future designs of solid polymer electrolytes with high room-temperature ion conductivities and mechanical flexibility.

  2. Conducting glasses recovered from thin film transistor liquid crystal display wastes for dye-sensitized solar cell cathodes.

    PubMed

    Chen, C-C; Chang, F-C; Peng, C Y; Wang, H Paul

    2015-01-01

    Transparent conductive glasses such as thin film transistor (TFT) array and colour filter glasses were recovered from the TFT-liquid crystal display panel wastes by dismantling and sonic cleaning. Noble metals (i.e. platinum (Pt)) and indium tin oxide (ITO) are generally used in the cathode of a dye-sensitized solar cell (DSSC). To reduce the DSSC cost, Pt was replaced with nano nickel-encapsulated carbon-shell (Ni@C) nanoparticles, which were prepared by carbonization of Ni²⁺-β-cyclodextrin at 673 K for 2 h. The recovered conductive glasses were used in the DSSC electrodes in the substitution of relatively expensive ITO. Interestingly, the efficiency of the DSSC having the Ni@C-coated cathode is as high as 2.54%. Moreover, the cost of the DSSC using the recovered materials can be reduced by at least 24%.

  3. Metal induced crystallized poly-Si-based conductive bridge resistive switching memory device with one transistor and one resistor architecture

    NASA Astrophysics Data System (ADS)

    Chand, Umesh; Huang, Chun-Yang; Kumar, Dayanand; Tseng, Tseung-Yuen

    2015-11-01

    In this letter, the metal induced crystallization (MIC) process is used in the Si-based conductive bridging resistive random access memory (CBRAM) application. The amorphous Si (a-Si) is transformed to crystallized poly-silicon (poly-Si) at a low temperature by using Ni metal for inducing poly-Si to provide the resistive switching. The MIC process can produce a highly preferred orientation poly-Si film, which can create the exact paths or grain boundaries through the top and down electrodes in the present CBRAM device. The grain boundary in MIC poly-Si layer can confine the conductive filament of metal bridging growth in it, which can improve the switching fluctuation behavior in the nonvolatile memory application. Compared with the a-Si based device, a significant improvement in terms of resistive switching parameters such as stability and resistance distribution is demonstrated in the MIC poly-Si CBRAM device. Moreover, the well-behaved memory performance, such as high ON/OFF resistance ratio (4 order), a large AC endurance (106), and good retention characteristics (104 s at 125 °C) are achieved in the Cu/poly-Si/n+-Si CMOS compatible cross bar structure.

  4. Coupled effects of conduction in the crystal and thermo-solutal convection in a rectangular inclined enclosure

    NASA Technical Reports Server (NTRS)

    Mennetrier, Christophe; Duval, Walter M. B.

    1990-01-01

    To date modeling of crystal growth of optoelectronic materials using Physical Vapor Transport has been limited to the study of the fluid phase. To achieve it, the equations of coupled heat, mass and momentum transfer in the gas have to be solved. The first objective of this study is to examine the effect of heat conduction in the crystal on the fluid flow in the neighborhood of the interface. Heat transfer boundary conditions on both interfaces were modified to take into account the additional heat flux between gas and solid. It is proved that heat conduction does not affect the fluid flow. In the presence of gravity, density gradients in the fluid phase generate convection responsible for the problem of a nonplanar growth of the interface. The second objective is to study systematically under one-g the different possible flows in order to solve this problem. Depending on the parameters, a diffusive mode and three convective modes (thermal, solutal and thermo-solutal) are observed. The competition between thermal and solutal convections leads to a mathematical condition which can be used to achieve a planar growth. It is proven that, under the physical conditions chosen, this mathematical condition cannot be thermodynamically satisfied.

  5. Hydrogen centers and the conductivity of In2O3 single crystals

    DOE PAGES

    Yin, Weikai; Smithe, Kirby; Weiser, Philip; ...

    2015-02-24

    A series of infrared absorption experiments and complementary theory have been performed in order to determine the properties of OH and OD centers in In2O3 single crystals. Annealing In2O3 samples in H2 or D2 at temperatures near 450°C produces an n-type layer ≈0.06mm thick with an n-type doping of 1.6×1019 cm-3. The resulting free-carrier absorption is correlated with an OH center with a vibrational frequency of 3306 cm-1 that we associate with interstitial H+. Additional O-H (O-D) vibrational lines are assigned to metastable configurations of the interstitial H+(D+) center and complexes of H (D) with In vacancies. In addition, unlikemore » other oxides studied recently where H trapped at an oxygen vacancy is the dominant shallow donor (ZnO and SnO2, for example), interstitial H+ is found to be the dominant H-related shallow donor in In2O3.« less

  6. Effects of dispersion, correction term, and isotopes on the thermal conductivity of LiF crystal

    NASA Astrophysics Data System (ADS)

    Singh, B. K.; Roy, M. K.; Menon, V. J.; Sood, K. C.

    2003-01-01

    We have adapted the Callaway-Holland model so that the dispersive effect and correction term κc can be included in the theoretical analysis of the lattice thermal conductivity of LiF over the temperature range 1 300 K, for varying concentration of the isotopic content 7Li. Some different empirical expressions for different three-phonon relaxation rates τ-13ph for the entire temperature range have been proposed. Anisotropic and dispersive point defect scattering relaxation rate for LiF is also introduced. Our main findings are as follows: κc even for moderate isotopic concentration of 7Li in LiF gives sizable contribution at temperatures where τ-13ph umklapp U processes dominate, which was considered to be negligible by earlier workers; contribution of longitudinal phonons is substantial beyond the conductivity maximum; theoretical value of the isotope scattering parameter A1 has to be increased only by 1.8 1.9 times in going from 50.8% to 97.2% of 7Li content as against 5 times increase taken by Callaway and Baeyer; and in conformity with Callaway’s findings the presence of small chemical impurities has to be assumed to explain the phonon-conductivity data of the isotopically pure sample (7Li 99.99%) of LiF. Theoretically justified parameters are used to obtain excellent agreement with the results reported by Thacher as well as by Berman and Brock.

  7. Thermal and Electrical Conduction of Single-crystal Bi2Te3 Nanostructures grown using a one step process

    PubMed Central

    Park, Dambi; Park, Sungjin; Jeong, Kwangsik; Jeong, Hong-Sik; Song, Jea Yong; Cho, Mann–Ho

    2016-01-01

    Single-crystal Bi2Te3 nanowires (NWs) and nanoribbons (NRs) were synthesized by a vapor-liquid-solid (VLS) method from Bi2Te3 powder. To investigate the thermal properties of the Bi2Te3 nanostructure, a nondestructive technique based on temperature dependent Raman mapping was carried out. The Raman peaks were red shifted with increasing temperature. In addition, the fraction of the laser power absorbed inside the Bi2Te3 nanostructures was estimated by optical simulation and used to calculate the thermal conductivity value (κ). The thermal conductivity value obtained for the Bi2Te3 NW and NR was 1.47 Wm−1K−1 and 1.81 Wm−1K−1 at 300 K, respectively. The electrical conductivity of the Bi2Te3 nanostructure was also measured. In particular, an excellent electrical conductivity value of 1.22 * 103 Ω−1 cm−1 was obtained for the Bi2Te3 NW at 300 K. This result can be attributed to topological insulator surface states. As a result of our study, the figure of merit (ZT) for the Bi2Te3 NW and NR can be significantly improved. PMID:26750563

  8. Thermal and Electrical Conduction of Single-crystal Bi2Te3 Nanostructures grown using a one step process.

    PubMed

    Park, Dambi; Park, Sungjin; Jeong, Kwangsik; Jeong, Hong-Sik; Song, Jea Yong; Cho, Mann-Ho

    2016-01-11

    Single-crystal Bi2Te3 nanowires (NWs) and nanoribbons (NRs) were synthesized by a vapor-liquid-solid (VLS) method from Bi2Te3 powder. To investigate the thermal properties of the Bi2Te3 nanostructure, a nondestructive technique based on temperature dependent Raman mapping was carried out. The Raman peaks were red shifted with increasing temperature. In addition, the fraction of the laser power absorbed inside the Bi2Te3 nanostructures was estimated by optical simulation and used to calculate the thermal conductivity value (κ). The thermal conductivity value obtained for the Bi2Te3 NW and NR was 1.47 Wm(-1)K(-1) and 1.81 Wm(-1)K(-1) at 300 K, respectively. The electrical conductivity of the Bi2Te3 nanostructure was also measured. In particular, an excellent electrical conductivity value of 1.22 * 10(3 )Ω(-1) cm(-1) was obtained for the Bi2Te3 NW at 300 K. This result can be attributed to topological insulator surface states. As a result of our study, the figure of merit (ZT) for the Bi2Te3 NW and NR can be significantly improved.

  9. Hierarchical self-assembly of hexagonal single-crystal nanosheets into 3D layered superlattices with high conductivity

    NASA Astrophysics Data System (ADS)

    Tao, Yulun; Shen, Yuhua; Yang, Liangbao; Han, Bin; Huang, Fangzhi; Li, Shikuo; Chu, Zhuwang; Xie, Anjian

    2012-05-01

    While the number of man-made nano superstructures realized by self-assembly is growing in recent years, assemblies of conductive polymer nanocrystals, especially for superlattices, are still a significant challenge, not only because of the simplicity of the shape of the nanocrystal building blocks and their interactions, but also because of the poor control over these parameters in the fabrication of more elaborate nanocrystals. Here, we firstly report a facile and general route to a new generation of 3D layered superlattices of polyaniline doped with CSA (PANI-CSA) and show how PANI crystallize and self-assemble, in a suitable single solution environment. In cyclohexane, 1D amorphous nanofibers transformed to 1D nanorods as building blocks, and then to 2D single-crystal nanosheets with a hexagonal phase, and lastly to 3D ordered layered superlattices with the narrowest polydispersity value (Mw/Mn = 1.47). Remarkably, all the instructions for the hierarchical self-assembly are encoded in the layered shape in other non-polar solvents (hexane, octane) and their conductivity in the π-π stacking direction is improved to about 50 S cm-1, which is even higher than that of the highest previously reported value (16 S cm-1). The method used in this study is greatly expected to be readily scalable to produce superlattices of conductive polymers with high quality and low cost.While the number of man-made nano superstructures realized by self-assembly is growing in recent years, assemblies of conductive polymer nanocrystals, especially for superlattices, are still a significant challenge, not only because of the simplicity of the shape of the nanocrystal building blocks and their interactions, but also because of the poor control over these parameters in the fabrication of more elaborate nanocrystals. Here, we firstly report a facile and general route to a new generation of 3D layered superlattices of polyaniline doped with CSA (PANI-CSA) and show how PANI crystallize and

  10. The first BETS radical cation salts with dicyanamide anion: Crystal growth, structure and conductivity study

    SciTech Connect

    Kushch, N.D.; Buravov, L.I.; Chekhlov, A.N.; Spitsina, N.G.; Kushch, P.P.; Yagubskii, E.B.; Herdtweck, E.; Kobayashi, A.

    2011-11-15

    Electrochemical oxidation of bis(ethylenedithio)tetraselenafulvalene (BETS) has been investigated. Simple and complex dicyanamides of transition metals (Mn{sup 2+}, Ni{sup 2+} and Fe{sup 2+}) were used as electrolytes. The correlation between composition of prepared radical cation salts and metal nature in electrolytes was established. Manganese dicyanamides provide the formation of BETS salts with the {l_brace}Mn[N(CN){sub 2}]{sub 3}{r_brace}- and [N(CN){sub 2}]-XH{sub 2}O anions. When Ni- or Fe-containing electrolytes were used only metalless BETS salts, {alpha}''-BETS{sub 2}[N(CN){sub 2}].2H{sub 2}O (I) and {theta}-BETS{sub 2}[N(CN){sub 2}].3.6H{sub 2}O (II), formed. Structures and conducting properties of these salts were analyzed. Both salts exhibit layered structure. Conducting radical cation layers have {alpha}'' (I)- or {theta}-type (II). Anion sheets appear as two-dimensional polymer networks of different types. These networks are formed by [N(CN)]{sub 2}{sup -} anions and water molecules interlinked by hydrogen bonds. Salt I is a semiconductor and II demonstrates resistance drop down to150 K at normal pressure and down to 72 K at {approx}0.4 kbar pressure. - Graphical abstract: We studied electrochemical oxidation of BETS donor in the presence of simple and/or complex dicyanamides of transition metals (Ni, Fe, Mn) as electrolytes. New conducting salts {alpha}''-BETS{sub 2}[N(CN){sub 2}].2H{sub 2}O and {theta}-BETS{sub 2}[N(CN){sub 2}].3.8H{sub 2}O have been synthesized and characterized. Highlights: > We studied electrochemical oxidation of BETS donor. > Dicyanamides of transition metals (Ni, Fe, Mn) were used as electrolytes. > We found a well-reproducible synthesis of magnetic superconductor BETS{sub 2}Mn[N(CN){sub 2}]{sub 3}. > Two new metalless BETS salts form when Ni and Fe electrolytes were used. > Their structure and conductivity were investigated.

  11. Electrically continuous graphene from single crystal copper verified by terahertz conductance spectroscopy and micro four-point probe.

    PubMed

    Buron, Jonas D; Pizzocchero, Filippo; Jessen, Bjarke S; Booth, Timothy J; Nielsen, Peter F; Hansen, Ole; Hilke, Michael; Whiteway, Eric; Jepsen, Peter U; Bøggild, Peter; Petersen, Dirch H

    2014-11-12

    The electrical performance of graphene synthesized by chemical vapor deposition and transferred to insulating surfaces may be compromised by extended defects, including for instance grain boundaries, cracks, wrinkles, and tears. In this study, we experimentally investigate and compare the nano- and microscale electrical continuity of single layer graphene grown on centimeter-sized single crystal copper with that of previously studied graphene films, grown on commercially available copper foil, after transfer to SiO2 surfaces. The electrical continuity of the graphene films is analyzed using two noninvasive conductance characterization methods: ultrabroadband terahertz time-domain spectroscopy and micro four-point probe, which probe the electrical properties of the graphene film on different length scales, 100 nm and 10 μm, respectively. Ultrabroadband terahertz time-domain spectroscopy allows for measurement of the complex conductance response in the frequency range 1-15 terahertz, covering the entire intraband conductance spectrum, and reveals that the conductance response for the graphene grown on single crystalline copper intimately follows the Drude model for a barrier-free conductor. In contrast, the graphene grown on commercial copper foil shows a distinctly non-Drude conductance spectrum that is better described by the Drude-Smith model, which incorporates the effect of preferential carrier backscattering associated with extended, electronic barriers with a typical separation on the order of 100 nm. Micro four-point probe resistance values measured on graphene grown on single crystalline copper in two different voltage-current configurations show close agreement with the expected distributions for a continuous 2D conductor, in contrast with previous observations on graphene grown on commercial copper foil. The terahertz and micro four-point probe conductance values of the graphene grown on single crystalline copper shows a close to unity correlation, in

  12. Crystal Structure and Ionic Conductivity of Three Polymorphic Phases of Rubidium Trefluoromethyl Sulfonate, RbSO3CF3

    SciTech Connect

    Hildebrandt,L.; Dinnebier, R.; Jansen, M.

    2006-01-01

    The crystal structures of three polymorphic phases of rubidium trifluoromethyl sulfonate (RbSO{sub 3}CF{sub 3}, rubidium 'triflate') were solved from X-ray powder diffraction data. At room temperature, rubidium triflate crystallizes in the monoclinic space group Cm with lattice parameters of a = 19.9611(5) Angstroms, b = 23.4913(7) Angstroms, c = 5.1514(2) Angstroms, = 102.758(2); Z = 16. At T = 321 K, a first-order phase transition occurs toward a monoclinic phase in space group P2{sub 1} with lattice parameters at T = 344 K of a = 10.3434(5) Angstroms, b = 5.8283(3) Angstroms, c = 5.1982(3) Angstroms, = 104.278(6); Z = (2). At T = 461 K, another phase transition, this time of second order, occurs toward an orthorhombic phase in space group Cmcm with lattice parameters at T = 510 K of a = 5.3069(2) Angstroms, b = 20.2423(10) Angstroms, c = 5.9479(2) Angstroms; Z = 4. As a common feature within all three crystal structures of rubidium triflate, the triflate anions are arranged in double layers with the lipophilic CF{sub 3} groups facing each other. The rubidium ions are located between the SO{sub 3} groups. The general packing is similar to the packing in cesium triflate. Rubidium triflate can be classified as a solid electrolyte with a specific ionic conductivity of = 9.89 x 10{sup -9} S/cm at T = 384 K and = 3.84 x 10{sup -6} S/cm at T = 481 K.

  13. "Dual-template" synthesis of one-dimensional conductive nanoparticle superstructures from coordination metal-peptide polymer crystals.

    PubMed

    Rubio-Martínez, Marta; Puigmartí-Luis, Josep; Imaz, Inhar; Dittrich, Petra S; Maspoch, Daniel

    2013-12-20

    Bottom-up fabrication of self-assembled structures made of nanoparticles may lead to new materials, arrays and devices with great promise for myriad applications. Here a new class of metal-peptide scaffolds is reported: coordination polymer Ag(I)-DLL belt-like crystals, which enable the dual-template synthesis of more sophisticated nanoparticle superstructures. In these biorelated scaffolds, the self-assembly and recognition capacities of peptides and the selective reduction of Ag(I) ions to Ag are simultaneously exploited to control the growth and assembly of inorganic nanoparticles: first on their surfaces, and then inside the structures themselves. The templated internal Ag nanoparticles are well confined and closely packed, conditions that favour electrical conductivity in the superstructures. It is anticipated that these Ag(I)-DLL belts could be applied to create long (>100 μm) conductive Ag@Ag nanoparticle superstructures and polymetallic, multifunctional Fe3 O4 @Ag nanoparticle composites that marry the magnetic and conductive properties of the two nanoparticle types.

  14. Comparison of the local and the average crystal structure of proton conducting lanthanum tungstate and the influence of molybdenum substitution.

    PubMed

    Magrasó, Anna; Frontera, Carlos

    2016-03-07

    We report on the comparison of the local and average structure reported recently for proton conducting lanthanum tungstate, of general formula La28-xW4+xO54+δv2-δ, and the impact of molybdenum-substitution on the crystal structure of the material. Partial replacement of W with 10 and 30 mol% Mo is investigated here, i.e. La27(W1-xMox)5O55.5 for x = 0.1 and 0.3. This study addresses the interpretation and the description of a disordered cation and anion sublattice in this material, which enables the understanding of the fundamental properties related to hydration, transport properties and degradation in lanthanum tungstate. The report shows that Mo-substituted lanthanum tungstate is a promising material as a dense oxide membrane for hydrogen separation at intermediate temperatures.

  15. Electron scattering in the Δ{sub 1} model of the conduction band of germanium single crystals

    SciTech Connect

    Luniov, S. V. Burban, O. V.; Nazarchuk, P. F.

    2015-05-15

    Electron scattering in the possible Δ{sub 1} models of the conduction band in germanium crystals formed by hydrostatic or uniaxial pressure is investigated. On the basis of the theory of anisotropic scattering, the temperature dependences of the anisotropy parameter of the relaxation times and electron mobility for these models under conditions of scattering at impurity ions, as well as at acoustic and intervalley phonons are obtained. Analysis of the temperature dependences indicates that, in the temperature range of 77–300 K, intervalley scattering becomes substantial. Only for the Δ{sub 1} model formed by uniaxial pressure along the crystallographic direction [100], the electron scattering at intervalley phonons, which correspond to the g transitions, is minor with respect to scattering at acoustic phonons (the intravalley scattering) and impurity ions.

  16. See-through amorphous silicon solar cells with selectively transparent and conducting photonic crystal back reflectors for building integrated photovoltaics

    SciTech Connect

    Yang, Yang; O’Brien, Paul G.; Ozin, Geoffrey A. E-mail: kherani@ecf.utoronto.ca; Kherani, Nazir P. E-mail: kherani@ecf.utoronto.ca

    2013-11-25

    Thin semi-transparent hydrogenated amorphous silicon (a-Si:H) solar cells with selectively transparent and conducting photonic crystal (STCPC) back-reflectors are demonstrated. Short circuit current density of a 135 nm thick a-Si:H cell with a given STCPC back-reflector is enhanced by as much as 23% in comparison to a reference cell with an ITO film functioning as its rear contact. Concurrently, solar irradiance of 295 W/m{sup 2} and illuminance of 3480 lux are transmitted through the cell with a given STCPC back reflector under AM1.5 Global tilt illumination, indicating its utility as a source of space heating and lighting, respectively, in building integrated photovoltaic applications.

  17. Selectively transparent and conducting photonic crystal rear-contacts for thin-film silicon-based building integrated photovoltaics

    NASA Astrophysics Data System (ADS)

    O'Brien, P. G.; Chutinan, A.; Mahtani, P.; Leong, K.; Ozin, G. A.; Kherani, N. P.

    2011-08-01

    Wave-optics analysis is performed to show that selectively transparent and conducting photonic crystals (STCPCs) can be utilized as rear contacts to enhance the performance of building-integrated photovoltaics (BIPV). For instance, the current generated in an a-Si:H cell with an STCPC functioning as its rear contact is comparable to that of a similar cell with an optimized ZnO/Ag rear contact. However, the solar lumens (~3.5 klm/m2) and power (~430W/m2) transmitted through the cell with the STCPC rear contact can potentially provide indoor heating and lighting, respectively. Moreover, experimental results show that STCPC rear contacts could be used to control the color temperature of light transmitted through BIPV panels.

  18. Selectively transparent and conducting photonic crystal rear-contacts for thin-film silicon-based building integrated photovoltaics.

    PubMed

    O'Brien, P G; Chutinan, A; Mahtani, P; Leong, K; Ozin, G A; Kherani, N P

    2011-08-29

    Wave-optics analysis is performed to show that selectively transparent and conducting photonic crystals (STCPCs) can be utilized as rear contacts to enhance the performance of building-integrated photovoltaics (BIPV). For instance, the current generated in an a-Si:H cell with an STCPC functioning as its rear contact is comparable to that of a similar cell with an optimized ZnO/Ag rear contact. However, the solar lumens (~3.5 klm/m2) and power (~430W/m2) transmitted through the cell with the STCPC rear contact can potentially provide indoor heating and lighting, respectively. Moreover, experimental results show that STCPC rear contacts could be used to control the color temperature of light transmitted through BIPV panels.

  19. On the growth of conductive aluminum doped zinc oxide on 001 strontium titanate single crystals

    NASA Astrophysics Data System (ADS)

    Trinca, L. M.; Galca, A. C.; Aldica, G.; Radu, R.; Mercioniu, I.; Pintilie, L.

    2016-02-01

    Aluminum doped zinc oxide (AZO) thin films were obtained by pulsed laser deposition on (001) SrTiO3 (STO) on a range of substrate temperatures during ablation between 300 °C and 600 °C. A hexagonal system lying on a cubic one should be difficult to be obtained in epitaxial form. The geometrical selection of the AZO growth on (001) STO is not giving a unique preferential orientation. Two orientations, c-axis (along [001]) and 110, have been observed experimentally with different ratios at different substrate temperature. Discussions are made with respect to the temperature dependence of lattice mismatch between the two cases and the cubic surface of the substrate, and to the substrate surface morphology and terminating atomic layer composition. The 110 AZO is the main phase at deposition temperature of 550 °C, while for other substrate temperatures the 001 is the preferential orientation. The conductive character of 110 AZO thin film have been inferred from both ellipsometry spectra and current-voltage measurements. Excepting the samples deposited at 300 °C, the lowest resistivity is recorded for the samples with 110 AZO as the main phase.

  20. Ionic conductivity of Bi12(V,Bi)O20 + δ single crystal (δ = 0.27) with a sillenite-type structure

    NASA Astrophysics Data System (ADS)

    Sorokin, N. I.

    2012-11-01

    The ionic conductivity of nonstoichiometric Bi12(V0.89Bi0.03)O20.27 single crystal with a sillenite-type structure has been investigated by impedance spectroscopy; its conductivity at 673 K is 2 × 10-3 S/cm, which is about two orders of magnitude higher than the conductivity of oxide superionic conductor single crystal Zr0.88Y0.12O1.94. As follows from crystallochemical analysis, ion transport in Bi12(V0.89Bi0.03)O20.27 is due to additional O2- ions, which arise due to oxygen nonstoichiometry.

  1. Reciprocated suppression of polymer crystallization toward improved solid polymer electrolytes: Higher ion conductivity and tunable mechanical properties

    DOE PAGES

    Bi, Sheng; Sun, Che-Nan; Zawodzinski, Thomas A.; ...

    2015-08-06

    Solid polymer electrolytes based on lithium bis(trifluoromethanesulfonyl) imide and polymer matrix were extensively studied in the past due to their excellent potential in a broad range of energy related applications. Poly(vinylidene fluoride) (PVDF) and polyethylene oxide (PEO) are among the most examined polymer candidates as solid polymer electrolyte matrix. In this paper, we study the effect of reciprocated suppression of polymer crystallization in PVDF/PEO binary matrix on ion transport and mechanical properties of the resultant solid polymer electrolytes. With electron and X-ray diffractions as well as energy filtered transmission electron microscopy, we identify and examine the appropriate blending composition thatmore » is responsible for the diminishment of both PVDF and PEO crystallites. Laslty, a three-fold conductivity enhancement is achieved along with a highly tunable elastic modulus ranging from 20 to 200 MPa, which is expected to contribute toward future designs of solid polymer electrolytes with high room-temperature ion conductivities and mechanical flexibility.« less

  2. Anomalous enhancement of proton conductivity for water molecular clusters stabilized in interstitial spaces of porous molecular crystals.

    PubMed

    Tadokoro, Makoto; Ohhata, Yuki; Shimazaki, Yuriko; Ishimaru, Shin'ichi; Yamada, Teppei; Nagao, Yuki; Sugaya, Tomoaki; Isoda, Kyosuke; Suzuki, Yuta; Kitagawa, Hiroshi; Matsui, Hiroshi

    2014-10-13

    In an investigation into the proton conductivity of crystallized water clusters confined within low-dimensional nanoporous materials, we have found that water-stable nanoporous crystals are formed by complementary hydrogen bonding between [Co(III) (H2 bim)3 ](3+) (H2 bim: 2,2'-biimidazole) and TATC(3-) (1,3,5- tricarboxyl-2,4,6-triazinate); the O atoms in the -COO(-) groups of TATC(3-) in the porous outer wall are strongly hydrogen bonded with H2 O, forming two types of WMCs (water molecular clusters): a spirocyclic tetramer chain (SCTC) that forms infinite open 1D channels, and an isolated cyclic tetramer (ICT) present in the void space. The ICT is constructed from four H2 O molecules as a novel C2 -type WMC, which are hydrogen bonded with four-, three-, and two-coordination spheres, respectively. The largest structural fluctuation is observed at elevated temperatures from the two-coordinated H2 O molecules, which begin to rapidly and isotropically fluctuate on heating. This behavior can be rationalized by a simple model for the elucidation of pre-melting phenomena, similar to those in ice surfaces as the temperature increases. Moreover, high proton conductivity of SCTCs (ca. 10(-5) S cm(-1) at 300 K with an activation energy of 0.30 eV) through a proton-hole mechanism was observed for pellet samples using the alternating impedance method. The proton conductivity exhibits a slight enhancement of about 0.1×10(-5) S cm(-1) at 274 K due to a structural transition upon approaching this temperature that elongates the unit cell along the b-axis. The proton-transfer route can be predicted in WMCs, as O(4) of an H2 O molecule at the center of an SCTC shows a motion that rotates the dipole in the b-axis direction, but not the c-axis; the thermal ellipsoids of O(4) based on anisotropic temperature factors obtained by X-ray crystallography reflect a structural fluctuation along the b-axis direction induced by [Co(III) (H2 bim)3 ](3+) .

  3. Electromagnetic Characterization of YBa2Cu3O7-Delta Thin Films with Calcium Doping for Bi-Crystal Grain Boundary Conductivity Enhancement (Postprint)

    DTIC Science & Technology

    2008-02-08

    boundary of a vicinal and donor- doped 5 SrTiO3 bi-crystal results in a depletion zone ∼200 nm wide, with the interface potential at the middle of the...AFRL-RZ-WP-TP-2012-0146 ELECTROMAGNETIC CHARACTERIZATION OF YBa2Cu3O7−δ THIN FILMS WITH CALCIUM DOPING FOR BI-CRYSTAL GRAIN BOUNDARY...WITH CALCIUM DOPING FOR BI-CRYSTAL GRAIN BOUNDARY CONDUCTIVITY ENHANCEMENT (POSTPRINT) 5a. CONTRACT NUMBER In-house 5b. GRANT NUMBER 5c

  4. Electrical conductivity of {gamma}-irradiated crystals of La{sub 0.95}Ba{sub 0.05}F{sub 2.95} superionic conductor

    SciTech Connect

    Sorokin, N. I. Sobolev, B. P.

    2012-03-15

    The electrical conductivity of single crystals of the La{sub 0.95}Ba{sub 0.05}F{sub 2.95} superionic conductor subjected to irradiation by {gamma} quanta (source {gamma}-{sup 60}Co, dose 2 Multiplication-Sign 10{sup 6} rad) has been investigated. It is shown that the radiation defects do not have a great effect on the ionic conductivity of nonstoichiometric La{sub 0.95}Ba{sub 0.05}F{sub 2.95} crystals, which is caused by the heterovalent replacements of La{sup 3+} cations with Ba{sup 2+} cations.

  5. Silver transfer in proustite Ag{sub 3}AsS{sub 3} at high temperatures: Conductivity and single-crystal X-ray studies

    SciTech Connect

    Gagor, Anna Pawlowski, Antoni; Pietraszko, Adam

    2009-03-15

    Single crystals of proustite Ag{sub 3}AsS{sub 3} have been characterised by impedance spectroscopy and single-crystal X-ray diffraction in the temperature ranges of 295-543 and 295-695 K, respectively. An analysis of the one-particle potential of silver atoms shows that in the whole measuring temperature range defects in the silver substructure play a major role in the conduction mechanism. Furthermore, the silver transfer is equally probable within silver chains and spirals, as well as between chains and spirals. The trigonal R3c room temperature phase does not change until the decomposition of the crystal. The electric anomaly of the first-order character which appears near 502 K is related to an increase in the electronic component of the total conductivity resulting from Ag{sub 2}S deposition at the sample surface. - Joint probability density function map of silver atoms at T=695 K.

  6. Correction: Decrease in thermal conductivity in polymeric P3HT nanowires by size-reduction induced by crystal orientation: new approaches towards thermal transport engineering of organic materials

    NASA Astrophysics Data System (ADS)

    Rojo, Miguel Muñoz; Martín, Jaime; Grauby, Stéphane; Borca-Tasciuc, Theodorian; Dilhaire, Stefan; Martin-Gonzalez, Marisol

    2015-02-01

    Correction for `Decrease in thermal conductivity in polymeric P3HT nanowires by size-reduction induced by crystal orientation: new approaches towards thermal transport engineering of organic materials' by Miguel Muñoz Rojo et al., Nanoscale, 2014, 6, 7858-7865.

  7. Electrical conduction mechanism in La3Ta0.5Ga5.3Al0.2O14 single crystals.

    PubMed

    Yaokawa, Ritsuko; Aota, Katsumi; Uda, Satoshi

    2013-12-14

    The electrical conduction mechanism in La3Ta0.5Ga5.3Al0.2O14 (LTGA) single crystals was studied by nonstoichiometric defect formation during crystal growth. Since stoichiometric LTGA is not congruent, the single crystal grown from the stoichiometric melt was Ta-poor and Al-rich, where Al atoms were substituted not only in Ga sites but also in Ta sites. The population of the substitutional Al in Ta sites increased with increasing oxygen partial pressure during growth (growth-pO2) in the range from 0.01 to 1 atm. Below 600 °C, substitutional Al atoms in Ta sites were ionized to yield holes, and thus the electrical conductivity of the LTGA crystal depended on temperature and the growth-pO2. The dependence of the electrical conductivity on the growth-pO2 decreased as temperature increased. The temperature rise increases ionic conductivity, for which the dominant carriers are oxygen defects formed by the anion Frenkel reaction.

  8. SrxBa1-xNb2O6-δ Ferroelectric-thermoelectrics: Crystal anisotropy, conduction mechanism, and power factor

    NASA Astrophysics Data System (ADS)

    Lee, Soonil; Wilke, Rudeger H. T.; Trolier-McKinstry, Susan; Zhang, Shujun; Randall, Clive A.

    2010-01-01

    Nonstoichiometric tungsten bronze-structured ferroelectric SrxBa1-xNb2O6-δ (SBN) single crystals were found to be a promising n-type thermoelectric oxide. Thermopower anomalies were observed at the phase transition temperatures, depending on the degree of reduction as well as crystal anisotropy. Above 500 K, heavily reduced SBN crystals show high thermoelectric power factors (˜20 μW/cm K2 at 516 K) with both thermopower and electrical conductivity higher parallel to the c-axis. It is noted that the power factor increases with temperature due to the semiconducting behavior with high carrier concentration. The carrier transport mechanism also varies with the degree of reduction and temperature.

  9. Crystal structure, NMR study, dielectric relaxation and AC conductivity of a new compound [Cd3(SCN)2Br6(C2H9N2)2]n

    NASA Astrophysics Data System (ADS)

    Saidi, K.; Kamoun, S.; Ayedi, H. Ferid; Arous, M.

    2013-11-01

    The crystal structure, the 13C NMR spectroscopy and the complex impedance have been carried out on [Cd3(SCN)2Br6(C2H9N2)2]n. Crystal structure shows a 2D polymeric network built up of two crystallographically independent cadmium atoms with two different octahedral coordinations. This compound exhibits a phase transition at (T=355±2 K) which has been characterized by differential scanning calorimetry (DSC), X-rays powder diffraction, AC conductivity and dielectric measurements. Examination of 13C CP/MAS line shapes shows indirect spin-spin coupling (14N and 13C) with a dipolar coupling constant of 1339 Hz. The AC conductivity of this compound has been carried out in the temperature range 325-376 K and the frequency range from 10-2 Hz to 10 MHz. The impedance data were well fitted to two equivalent electrical circuits. The results of the modulus study reveal the presence of two distinct relaxation processes. One, at low frequency side, is thermally activated due to the ionic conduction of the crystal and the other, at higher frequency side, gradually disappears when temperature reaches 355 K which is attributed to the localized dipoles in the crystal. Moreover, the temperature dependence of DC-conductivity in both phases follows the Arrhenius law and the frequency dependence of σ(ω,T) follows Jonscher's universal law. The near values of activation energies obtained from the conductivity data and impedance confirm that the transport is through the ion hopping mechanism.

  10. Ultraviolet laser crystallized ZnO:Al films on sapphire with high Hall mobility for simultaneous enhancement of conductivity and transparency

    SciTech Connect

    Nian, Qiong; Zhang, Martin Y.; Schwartz, Bradley D.; Cheng, Gary J.

    2014-05-19

    One of the most challenging issues in transparent conductive oxides (TCOs) is to improve their conductivity without compromising transparency. High conductivity in TCO films often comes from a high carrier concentration, which is detrimental to transparency due to free carrier absorption. Here we show that UV laser crystallization (UVLC) of aluminum-doped ZnO (AZO) films prepared by pulsed laser deposition on sapphire results in much higher Hall mobility, allowing relaxation of the constraints of the conductivity/transparency trade-off. X-ray diffraction patterns and morphological characterizations show grain growth and crystallinity enhancement during UVLC, resulting in less film internal imperfections. Optoelectronic measurements show that UVLC dramatically improves the electron mobility, while the carrier concentration decreases which in turn simultaneously increases conductivity and transparency. AZO films under optimized UVLC achieve the highest electron mobility of 79 cm{sup 2}/V s at a low carrier concentration of 7.9 × 10{sup +19} cm{sup −3}. This is realized by a laser crystallization induced decrease of both grain boundary density and electron trap density at grain boundaries. The infrared (IR) to mid-IR range transmittance spectrum shows UVLC significantly enhances the AZO film transparency without compromising conductivity.

  11. An efficient light trapping scheme based on textured conductive photonic crystal back reflector for performance improvement of amorphous silicon solar cells

    SciTech Connect

    Chen, Peizhuan; Hou, Guofu Huang, Qian; Zhao, Jing; Zhang, Jianjun Ni, Jian; Zhang, Xiaodan; Zhao, Ying; Fan, QiHua

    2014-08-18

    An efficient light trapping scheme named as textured conductive photonic crystal (TCPC) has been proposed and then applied as a back-reflector (BR) in n-i-p hydrogenated amorphous silicon (a-Si:H) solar cell. This TCPC BR combined a flat one-dimensional photonic crystal and a randomly textured surface of chemically etched ZnO:Al. Total efficiency enhancement was obtained thanks to the sufficient conductivity, high reflectivity and strong light scattering of the TCPC BR. Unwanted intrinsic losses of surface plasmon modes are avoided. An initial efficiency of 9.66% for a-Si:H solar cell was obtained with short-circuit current density of 14.74 mA/cm{sup 2}, fill factor of 70.3%, and open-circuit voltage of 0.932 V.

  12. Temperature-dependent thermal conductivity and diffusivity of a Mg-doped insulating β-Ga2O3 single crystal along [100], [010] and [001

    NASA Astrophysics Data System (ADS)

    Handwerg, M.; Mitdank, R.; Galazka, Z.; Fischer, S. F.

    2016-12-01

    The monoclinic crystal structure of β-{{Ga}}2{{{O}}}3 leads to significant anisotropy of the thermal properties. The 2ω-method is used to measure the thermal diffusivity D in [010] and [001] direction respectively and to determine the thermal conductivity values λ of the [100], [010] and [001] direction from the same insulating Mg-doped β-{{Ga}}2{{{O}}}3 single crystal. We detect a temperature independent anisotropy factor of both the thermal diffusivity and conductivity values of {D}[010]/{D}[001]={λ }[010]/{λ }[001]=1.4+/- 0.1. The temperature dependence is in accord with phonon-phonon-Umklapp-scattering processes from 300 K down to 150 K. Below 150 K point-defect-scattering lowers the estimated phonon-phonon-Umklapp-scattering values.

  13. Effect of Praseodymium Concentration on the Excess Conductivity Near the Critical Temperature of Y1- z Pr z Ba2Cu3O7- δ Single Crystals

    NASA Astrophysics Data System (ADS)

    Vovk, R. V.; Nazyrov, Z. F.; Goulatis, L. I.; Chroneos, A.

    2013-02-01

    The evolution of the excess conductivity in Y1- z Pr z Ba2Cu3O7- δ single crystals has been studied by systematically increasing the praseodymium concentration (0.05≤ z≤0.5). The concentration dependence of the coherence length along c axis ξ c (0) on the praseodymium content has been determined. The praseodymium concentration reduction from 0.0 to 0.5 results in a substantial broadening of the temperature interval where the excess conductivity takes place. The ξ c (0) value increases more than fourfold and the 2D-3D crossover point is shifted in temperature.

  14. Conductivity anisotropy in Y1-yPryBa2Cu3O7-δ single crystals in a wide range of praseodymium concentrations

    NASA Astrophysics Data System (ADS)

    Vovk, Ruslan V.; Khadzhai, Georgij Ya.; Dobrovolskiy, Oleksandr V.

    2014-12-01

    Anisotropies of different conductivity mechanisms in Y1-yPryBa2Cu3O7-δ single crystals in a wide range of praseodymium concentrations are reported, assuming a transition from the metallic conductivity to the semiconductor-like regime, in conjunction with the fluctuation conductivity within the 3D Aslamazov-Larkin model. The Tc anisotropy grows with increasing y, with a most drastic rise when approaching the non-superconducting composition. As the praseodymium concentration increases, the ideal resistance anisotropy passes through a maximum at y ≈ 0.19. The temperature dependence of the semiconductor-like resistance anisotropy exhibits a maximum associated with variable-range jumps along the c-axis. The temperature dependence of the fluctuation conductivity anisotropy passes through a maximum due to a significant anisotropy of the coherence length.

  15. CRYSTAL STRUCTURE, ELECTRICAL CONDUCTIVITY AND THERMAL EXPANSION OF Pr1-xSrxFeO3-δ(0 ≤ x ≤ 0.6)

    NASA Astrophysics Data System (ADS)

    Prashanth Kumar, V.; Reddy, Y. S.; Kistaiah, P.; Vishnuvardhan Reddy, C.

    2012-12-01

    The crystal structure at room temperature (RT), thermal expansion from RT to 1000°C and electrical conductivity, from RT to 600°C, of the perovskite-type oxides in the system Pr1-xSrxFeO3(x = 0, 0.2, 0.4, 0.6) were studied. All the compounds have the orthorhombic perovskite GdFeO3-type structure with space group Pbnm. The lattice parameters were determined by X-ray powder diffraction. The Pseudo cubic lattice parameter decreases with an increase in x, while the coefficient of linear thermal expansion increases. The thermal expansion is almost linear for x = 0 and 0.2. The electrical conductivity increases with increasing x while the activation energy decreases. The electrical conductivity can be described by the small polaron hopping conductivity model.

  16. A molecular dynamics study of the effect of thermal boundary conductance on thermal transport of ideal crystal of n-alkanes with different number of carbon atoms

    NASA Astrophysics Data System (ADS)

    Rastgarkafshgarkolaei, Rouzbeh; Zeng, Yi; Khodadadi, J. M.

    2016-05-01

    Phase change materials such as n-alkanes that exhibit desirable characteristics such as high latent heat, chemical stability, and negligible supercooling are widely used in thermal energy storage applications. However, n-alkanes have the drawback of low thermal conductivity values. The low thermal conductivity of n-alkanes is linked to formation of randomly oriented nano-domains of molecules in their solid structure that is responsible for excessive phonon scattering at the grain boundaries. Thus, understanding the thermal boundary conductance at the grain boundaries can be crucial for improving the effectiveness of thermal storage systems. The concept of the ideal crystal is proposed in this paper, which describes a simplified model such that all the nano-domains of long-chain n-alkanes are artificially aligned perfectly in one direction. In order to study thermal transport of the ideal crystal of long-chain n-alkanes, four (4) systems (C20H42, C24H50, C26H54, and C30H62) are investigated by the molecular dynamics simulations. Thermal boundary conductance between the layers of ideal crystals is determined using both non-equilibrium molecular dynamics (NEMD) and equilibrium molecular dynamics (EMD) simulations. Both NEMD and EMD simulations exhibit no significant change in thermal conductance with the molecular length. However, the values obtained from the EMD simulations are less than the values from NEMD simulations with the ratio being nearly three (3) in most cases. This difference is due to the nature of EMD simulations where all the phonons are assumed to be in equilibrium at the interface. Thermal conductivity of the n-alkanes in three structures including liquid, solid, and ideal crystal is investigated utilizing NEMD simulations. Our results exhibit a very slight rise in thermal conductivity values as the number of carbon atoms of the chain increases. The key understanding is that thermal transport can be significantly altered by how the molecules and the

  17. Synthesis, crystal structure, NMR study and AC conductivity of [(C3H7)4N]2Cd2ClF5 compound

    NASA Astrophysics Data System (ADS)

    Hajji, Rachid; Oueslati, Abderrazak; Body, Monique; Hlel, Faouzi

    2015-08-01

    The [(C3H7)4N]2Cd2ClF5 compound was crystallized in the triclinic system with space group P1. The crystal structure consists of organic-inorganic layers, stacked along direction. The organic part consists of two cations types. The inorganic layer is made up of Cd2ClF5 dimmers composed of two in-equivalent irregular tetrahedra sharing one edge (Cl-F). The MAS NMR spectra showed two, three and five isotropic resonances relative to 111Cd, 13C and 19F nuclei, respectively. DSC measurement disclosed a phase transition at around 380 K. The impedance spectroscopy and AC electrical conductivity measurements of our compound were taken from 209 Hz to 5 MHz over the temperature range of 350-381 K. Nyquist plots ( Z″ vs Z') show semicircle arcs at different temperatures, and an electrical equivalent circuit has been proposed to explain the impedance results. The circuits consist of the parallel combination of bulk resistance ( R), capacitance ( C) and fractal capacitance (CPE). The conductivity σ p follows the Arrhenius relation. The near value of activation energies obtained from the conductivity data and circuit equivalent confirms that the transport is through hopping mechanism. The analysis of the experimental data shows that the reorientation motion of [N(C3H7)4]+ cations and/or [Cd2ClF5]2- anions is probably responsible for the observed conductivity.

  18. Decrease in thermal conductivity in polymeric P3HT nanowires by size-reduction induced by crystal orientation: new approaches towards thermal transport engineering of organic materials.

    PubMed

    Rojo, Miguel Muñoz; Martín, Jaime; Grauby, Stéphane; Borca-Tasciuc, Theodorian; Dilhaire, Stefan; Martin-Gonzalez, Marisol

    2014-07-21

    To date, there is no experimental characterization of thermal conductivity of semiconductor polymeric individual nanowires embedded in a matrix. This work reports on scanning thermal microscopy measurements in a 3ω configuration to determine how the thermal conductivity of individual nanowires made of a model conjugated polymer (P3HT) is modified when decreasing their diameters. We observe a reduction of thermal conductivity, from λNW = 2.29 ± 0.15 W K(-1) m(-1) to λNW = 0.5 ± 0.24 W K(-1) m(-1), when the diameter of nanowires is reduced from 350 nm to 120 nm, which correlates with the polymer crystal orientation measured by WAXS. Through this work, the foundations for future polymer thermal transport engineering are presented.

  19. A single crystal X-ray and powder neutron diffraction study on NASICON-type Li1+xAlxTi2-x(PO4)3 (0 ≤ x ≤ 0.5) crystals: Implications on ionic conductivity

    NASA Astrophysics Data System (ADS)

    Redhammer, G. J.; Rettenwander, D.; Pristat, S.; Dashjav, E.; Kumar, C. M. N.; Topa, D.; Tietz, F.

    2016-10-01

    Single crystals of NASICON-type material Li1+xTi2-xAlx(PO4)3 (LATP) with 0 ≤ x ≤ 0.5 were successfully grown using long-term sintering techniques. Sample material was studied by chemical analysis, single crystal X-ray and neutron diffraction. The Ti4+ replacement scales very well with the Al3+ and Li+ incorporation. The additional Li+ thereby enters the M3 cavity of the NASICON framework at x, y, z ∼ (0.07, 0.34, 0.09) and is regarded to be responsible for the enhanced Li+ conduction of LATP as compared to Al-free LTP. Variations in structural parameters, associated with the Ti4+ substitution with Al3+ + Li+ will be discussed in detail in this paper.

  20. Conductivity of single-crystal Y1-yPryBa2Cu3O7-δ over a wide range of temperatures and Pr concentrations

    NASA Astrophysics Data System (ADS)

    Khadzhai, G. Ya.; Vovk, N. R.; Vovk, R. V.

    2014-06-01

    The in-plane electrical resistance of Y1-yPryBa2Cu3O7-δ single crystals with a high degree of perfection is studied for temperatures in the range TC-300 K, where TC ranges from 92 to 52 K, with varying praseodymium content. The experimental data are approximated by an expression that takes electron scattering on phonons and defects into account, as well as fluctuation conductivity in a 3D Aslamazov-Larkin model. According to the approximation data the Debye temperature ranges from 350-370 K, depending on the praseodymium content. The transverse coherence length is ˜1 Å.

  1. COEXISTENCE OF DIFFERENT TYPES OF TRANSVERSE CONDUCTIVITY IN Y1-xPrxBa2Cu3 O7-δ SINGLE CRYSTALS WITH DIFFERENT PRASEODYMIUM CONCENTRATIONS

    NASA Astrophysics Data System (ADS)

    Vovk, R. V.; Vovk, N. R.; Goulatis, I. L.; Chroneos, A.

    2013-10-01

    In this paper, the influence of praseodymium doping on the conductivity across (transverse) the basal plane of high-temperature superconducting Y1-xPrxBa2Cu3O7-δ single crystals is investigated. It is determined that an increase of praseodymium doping leads to increased localization effects and the implementation of a metal-insulator transition Y1-xPrxBa2Cu3O7-δ, which always precedes the superconducting transition. The increase of the praseodymium concentration also leads to a significant displacement of the point of the metal-insulator transition to the low temperature region.

  2. Effect of conducting polymer poly (3,4-ethylenedioxythiophene) (PEDOT) nanotubes on electro-optical and dielectric properties of a ferroelectric liquid crystal.

    PubMed

    Ghosh, S; Nayek, P; Roy, S K; Gangopadhyay, R; Rahaman Molla, M; Majumder, T P

    2011-04-01

    A detailed comparative study of the dielectric and electro-optical properties of a ferroelectric liquid crystal (FLC) and FLC after having doped with conducting polymer Poly (3,4-ethylenedioxythiophene) (PEDOT) nanotubes is done. The electro-optic study reveals a lower electrical response time, rotational viscosity and spontaneous polarization in the FLC/PEDOT nanocomposite system. By fitting the capacitance with voltage in a Preisach model, four dipolar species in both FLC and composites system have been obtained. The orientation of the four dipolar species in the composites system is such that the effective dipole moment in the transverse direction of the FLC molecule is less than that in FLC compound.

  3. Measurement of the topological surface state optical conductance in bulk-insulating Sn-doped Bi1.1Sb0.9Te2S single crystals

    NASA Astrophysics Data System (ADS)

    Cheng, Bing; Wu, Liang; Kushwaha, S. K.; Cava, R. J.; Armitage, N. P.

    2016-11-01

    Topological surface states have been extensively observed via optics in thin films of topological insulators. However, in typical thick single crystals of these materials, bulk states are dominant and it is difficult for optics to verify the existence of topological surface states definitively. In this Rapid Communication, we study the charge dynamics of the newly formulated bulk-insulating Sn-doped Bi1.1Sb0.9Te2S crystal by using time-domain terahertz spectroscopy. This compound shows much better insulating behavior than any other bulk-insulating topological insulators reported previously. The transmission can be enhanced an amount which is 5 % of the zero-field transmission by applying magnetic field to 7 T, an effect which we believe is due to the suppression of topological surface states. This suppression is essentially independent of the thicknesses of the samples, showing the two-dimensional nature of the transport. The suppression of surface states in field allows us to use the crystal slab itself as a reference sample to extract the surface conductance, mobility, charge density, and scattering rate. Our measurements set the stage for the investigation of phenomena out of the semiclassical regime, such as the topological magnetoelectric effect.

  4. Encapsulating Mobile Proton Carriers into Structural Defects in Coordination Polymer Crystals: High Anhydrous Proton Conduction and Fuel Cell Application.

    PubMed

    Inukai, Munehiro; Horike, Satoshi; Itakura, Tomoya; Shinozaki, Ryota; Ogiwara, Naoki; Umeyama, Daiki; Nagarkar, Sanjog; Nishiyama, Yusuke; Malon, Michal; Hayashi, Akari; Ohhara, Takashi; Kiyanagi, Ryoji; Kitagawa, Susumu

    2016-07-13

    We describe the encapsulation of mobile proton carriers into defect sites in nonporous coordination polymers (CPs). The proton carriers were encapsulated with high mobility and provided high proton conductivity at 150 °C under anhydrous conditions. The high proton conductivity and nonporous nature of the CP allowed its application as an electrolyte in a fuel cell. The defects and mobile proton carriers were investigated using solid-state NMR, XAFS, XRD, and ICP-AES/EA. On the basis of these analyses, we concluded that the defect sites provide space for mobile uncoordinated H3PO4, H2PO4(-), and H2O. These mobile carriers play a key role in expanding the proton-hopping path and promoting the mobility of protons in the coordination framework, leading to high proton conductivity and fuel cell power generation.

  5. Effects of the amino acid sequence on thermal conduction through β-sheet crystals of natural silk protein.

    PubMed

    Zhang, Lin; Bai, Zhitong; Ban, Heng; Liu, Ling

    2015-11-21

    Recent experiments have discovered very different thermal conductivities between the spider silk and the silkworm silk. Decoding the molecular mechanisms underpinning the distinct thermal properties may guide the rational design of synthetic silk materials and other biomaterials for multifunctionality and tunable properties. However, such an understanding is lacking, mainly due to the complex structure and phonon physics associated with the silk materials. Here, using non-equilibrium molecular dynamics, we demonstrate that the amino acid sequence plays a key role in the thermal conduction process through β-sheets, essential building blocks of natural silks and a variety of other biomaterials. Three representative β-sheet types, i.e. poly-A, poly-(GA), and poly-G, are shown to have distinct structural features and phonon dynamics leading to different thermal conductivities. A fundamental understanding of the sequence effects may stimulate the design and engineering of polymers and biopolymers for desired thermal properties.

  6. One-dimensional ion-conductive polymer films: alignment and fixation of ionic channels formed by self-organization of polymerizable columnar liquid crystals.

    PubMed

    Yoshio, Masafumi; Kagata, Takayoshi; Hoshino, Koji; Mukai, Tomohiro; Ohno, Hiroyuki; Kato, Takashi

    2006-04-26

    We have prepared two types of one-dimensional ion-conductive polymer films containing ion nanochannels that are both perpendicular and parallel to the film surface. These films have been obtained by photopolymerization of aligned columnar liquid crystals of a fan-shaped imidazolium salt having acrylate groups at the periphery. In the columnar structure, the ionic part self-assembles into the inner part of the column. The column is oriented macroscopically in two directions by different methods: orientation perpendicular to the modified surfaces of glass and indium tin oxide with 3-(aminopropyl)triethoxysilane and orientation parallel to a glass surface by mechanical shearing. Ionic conductivities have been measured for the films with columnar orientation vertical and parallel to the surface. Anisotropic ionic conductivities are observed for the oriented films fixed by photopolymerization. The ionic conductivities parallel to the columnar axis are higher than those perpendicular to the columnar axis because the lipophilic part functions as an ion-insulating part. The film with the columns oriented vertically to the surface shows an anisotropy of ionic conductivities higher than that of the film with the columns aligned parallel to the surface.

  7. Synthesis, Electrical Conductivity, and Crystal Structure of Cu 4Sn 7S 16and Structure Refinement of Cu 2SnS 3

    NASA Astrophysics Data System (ADS)

    Chen, Xue-an; Wada, Hiroaki; Sato, Akira; Mieno, Masahiro

    1998-08-01

    Single crystals of Cu 4Sn 7S 16and Cu 2SnS 3were prepared by the conventional solid state reaction method. Their crystal structures were determined from single-crystal X-ray data. Cu 4Sn 7S 16is of a new structure type with rhombohedral symmetry: R-3 m, a=7.372(1), c=36.010(7) Å, Z=3, R=0.018 for 522 structure factors and 36 variable parameters. Its crystal structure may be described as a defect variant of the spinel-type. In the unit cell, 3/4 of the tetrahedral sites and 1/8 of the octahedral sites are occupied by Cu +, while 7/8 of the octahedral sites are occupied by Sn 4+ions. The compound can therefore be formulated as (Cu 0.75□ 0.25)(Sn 1.75Cu 0.25)S 4. Cu 2SnS 3has the unit cell formula Cu 2.665(7)Sn 1.335(7)S 4( Z=2) and it is isotypic with the tetragonal stannite [Cu 2(Fe, Zn)SnS 4] structure: I-42 m, a=5.413(1), c=10.824(1) Å, R=0.030 for 281 reflections and 16 variables. In the case of Cu 2SnS 3, the positions of the Cu and Sn atoms of stannite are occupied by the composite atoms M1 [43.6(2) at.% Sn+56.4(2) at.% Cu] and M2 [46.3(3) at.% Sn+53.7(3) at.% Cu], respectively, while those of the (Fe, Zn) atoms are replaced by only Cu atoms. Electrical conductivity measurements confirm the expected semiconducting behavior of Cu 4Sn 7S 16, and XPS analysis reveals the presence of only Cu +in Cu 4Sn 7S 16.

  8. Role of twins in variations in the conductivity characteristics of single-crystal HoBa2Cu3O7-δ during reversible changes in hydrostatic pressure

    NASA Astrophysics Data System (ADS)

    Khadzhai, G. Ya.; Nazyrov, Z. F.; Vovk, R. V.

    2016-09-01

    The in-plane electrical resistivity of single-crystal HoBa2Cu3O7-δ (Tc = 62-66 K) is studied at temperatures Tc-300 K under conditions such that the measurement current flows parallel to twins or at an angle of 45° to them during reversible changes in hydrostatic pressure. The variations in Tc, in the parameters of the Bloch-Grueneisen equations, and in the parameters of the Aslamasov-Larkin model for fluctuation conductivity are analyzed. Application of a pressure facilitates the formation of a second phase with lower Tc that shows up more clearly when the measurement current flows across the twinning plane. In this case, the transverse coherence length and the interval within which the fluctuation conductivity exists are smaller than in the first configuration. The relaxation of the parameters characterizing the scatting of charge carriers on phonons and defects is related to the redistribution of oxygen between the two phases.

  9. Manipulation of the crystal structure defects: An alternative route to the reduction in lattice thermal conductivity and improvement in thermoelectric performance of CuGaTe2

    NASA Astrophysics Data System (ADS)

    Wu, Wenchang; Li, Yapeng; Du, Zhengliang; Meng, Qingsen; Sun, Zheng; Ren, Wei; Cui, Jiaolin

    2013-07-01

    Here, we present the manipulation of the crystal structure defects: an alternative route to reduce the lattice thermal conductivity (κL) on an atomic scale and improve the thermoelectric performance of CuGaTe2. This semiconductor with defects, represented by anion position displacement (u) and tetragonal deformation (η), generally gives low κL values when u and η distinctly deviate from 0.25 and 1 in the ideal zinc-blende structure, respectively. However, this semiconductor will show high Seebeck coefficients and low electrical conductivities when u and η are close to 0.25 and 1, respectively, due to the electrical inactivity caused by an attractive interaction between donor-acceptor defect pairs (GaCu2+ + 2VCu-).

  10. Ionic conductivity of crystallization products of Ba1- x Yb x F2 + x melts ( x = 0.1, 0.2, 0.25)

    NASA Astrophysics Data System (ADS)

    Sorokin, N. I.; Sul'yanova, E. A.; Sobolev, B. P.

    2016-05-01

    The ionic conductivity σ of the crystallization products of Ba1 - x Yb x F2 + x melts with 10, 20 and 25 mol % YbF3 has been studied. A Ba0.9Yb0.1F2.1 sample is a solid solution with the CaF2 structure type, sp. gr. Fmoverline 3 m. A Ba0.8Yb0.2F2.2 sample contains two cubic forms with sp. gr. Fmoverline 3 m and Pmoverline 3 m. The σ values for Ba0.9Yb0.1F2.1 and Ba0.8Yb0.2F2.2 coincide and are equal to 3 × 10-5 S/cm at 500 K. A Ba0.75Yb0.25F2.25 sample is heterogeneous, despite its monolithic nature and transparency. A greater part of its volume has a cubic lattice with sp. gr. Pmoverline 3 m, while the smaller part is a phase crystallizing in the orthorhombic system. A change of composition from x = 0.2 to 0.25 leads to a change in the symmetry group and type of the cluster defects in the Ba1 - x Yb x F2 + x phase. The sp. gr. Fmoverline 3 m is replaced by the sp. gr. Pmoverline 3 m, and octahedral‒cubic {Ba8Yb6F69} clusters are transformed into "inverse" octahedral‒cubic {Yb8Ba6F71} clusters. These changes in the defect structure lead to an increase in conductivity by a factor of about 100. The fluorine-ionic conductivity of Ba0.75Yb0.25F2.25 is 2.5 × 10-3 S/cm at 500 K. This value exceeds the conductivity of Ba0.69La0.31F2.31 crystal by a factor of 15 (Ba0.69La0.31F2.31 has the best conducting properties among the fluorite phases of the Ba1 - x R x F2 + x family, for which σ was found to increase with a decrease in the atomic number of rare earth element (REE)).

  11. Inhibited crystallization and its effect on conductivity in a nano-sized Fe oxide composite PEO solid electrolyte

    NASA Astrophysics Data System (ADS)

    Reddy, M. Jaipal; Chu, Peter P.; Kumar, J. Siva; Rao, U. V. Subba

    Crystallinity and conductivity results for a new nanocomposite PEO:LiClO 4 with nano-sized Fe 3O 4 particles are presented in this paper. The DSC measurements have shown a decrease in the degree of crystallinity of PEO by the inclusion of LiClO 4 salt and further decrease with the addition of Fe 3O 4 nanoparticles. The nano-sized Fe 3O 4 surface has a Lewis acidic group capable of interaction with Lewis base centers of the polymer PEO chain in the nanocomposite electrolyte, resulting in decrease in PEO crystallinity and enhancement of miscibility in the presence of LiClO 4 salt. Annealed at 125 °C of the PEO:LiClO 4 electrolyte shows melting endotherm at 175 °C, but this endotherm is absent with the incorporation of nano-sized Fe oxide particles. This electrolyte system has a one and a half order of magnitude higher ionic conductivity compared to a standard PEO:LiClO 4 electrolyte. Optimized conductivity is found at a 10 wt.% Fe 3O 4 composition while above this concentration, the conductivity is decreased due to aggregation of a Fe 3O 4:Li rich phase.

  12. Thermal Conductivity of Ultrahigh Molecular Weight Polyethylene Crystal: Defect Effect Uncovered by 0 K Limit Phonon Diffusion.

    PubMed

    Liu, Jing; Xu, Zaoli; Cheng, Zhe; Xu, Shen; Wang, Xinwei

    2015-12-16

    Crystalline ultrahigh molecular weight polyethylene (UHMWPE) has the highest reported thermal conductivity at room temperature: 104 W/(m·K), while theoretical predictions proposed an even higher value of 300 W/(m·K). Defects and amorphous fraction in practical UHMWPE fibers significantly reduces the thermal conductivity from the ideal value. Although the amorphous effect can be readily analyzed based on the effective medium theory, the defect effects are poorly understood. This work reports on the temperature-dependent behavior (down to 22 K) of thermal diffusivity and conductivity of UHMWPE fibers in anticipation of observing the reduction in phonon density and scattering rate against temperature and of freezing out high-momentum phonons to clearly observe the defect effects. By studying the temperature-dependent behavior of thermal reffusivity (Θ, inverse of thermal diffusivity) of UHMWPE fibers, we are able to quantify the defect effects on thermal conductivity. After taking out the amorphous region's effect, the residual thermal reffusivities (Θ0) for the studied two samples at the 0 K limit are determined as 3.45 × 10(4) and 2.95 × 10(4) s/m(2), respectively. For rare-/no-defects crystalline materials, Θ0 should be close to zero at the 0 K limit. The defect-induced low-momentum phonon mean free paths are determined as 8.06 and 9.42 nm for the two samples. They are smaller than the crystallite size in the (002) direction (19.7 nm) determined by X-ray diffraction. This strongly demonstrates the diffuse phonon scattering at the grain boundaries. The grain boundary thermal conductance (G) can be evaluated as G ≈ βρc(p)v with sound accuracy. At room temperature, G is around 3.73 GW/(m(2)·K) for S2, comparable to that of interfaces with tight atomic bonding.

  13. Anisotropy of electrical conductivity in dc due to intrinsic defect formation in α-Al2O3 single crystal implanted with Mg ions

    NASA Astrophysics Data System (ADS)

    Tardío, M.; Egaña, A.; Ramírez, R.; Muñoz-Santiuste, J. E.; Alves, E.

    2016-07-01

    The electrical conductivity in α-Al2O3 single crystals implanted with Mg ions in two different crystalline orientations, parallel and perpendicular to c axis, was investigated. The samples were implanted at room temperature with energies of 50 and 100 keV and fluences of 1 × 1015, 5 × 1015 and 5 × 1016 ions/cm2. Optical characterization reveals slight differences in the absorption bands at 6.0 and 4.2 eV, attributed to F type centers and Mie scattering from Mg precipitates, respectively. DC electrical measurements using the four and two-point probe methods, between 295 and 490 K, were used to characterize the electrical conductivity of the implanted area (Meshakim and Tanabe, 2001). Measurements in this temperature range indicate that: (1) the electrical conductivity is thermally activated independently of crystallographic orientation, (2) resistance values in the implanted region decrease with fluence levels, and (3) the I-V characteristic of electrical contacts in samples with perpendicular c axis orientation is clearly ohmic, whereas contacts are blocking in samples with parallel c axis. When thin layers are sequentially removed from the implanted region by immersing the sample in a hot solution of nitric and fluorhydric acids the electrical resistance increases until reaching the values of non-implanted crystal (Jheeta et al., 2006). We conclude that the enhancement in conductivity observed in the implanted regions is related to the intrinsic defects created by the implantation rather than to the implanted Mg ions (da Silva et al., 2002; Tardío et al., 2001; Tardío et al., 2008).

  14. Passing Current through Electrically Conducting Lyotropic Liquid Crystals and Micelles Assembled from Hybrid Surfactants with π-Conjugated Tail and Polyoxometalate Head

    PubMed Central

    2016-01-01

    The solvent-mediated ability for molecularly encoded self-assembly into states of higher order (micelles, lyotropic liquid crystals) embodies the basis for many applications of surfactants in science and society. Surfactants are used frequently in recipes for nanoparticle synthesis. Because ordinary surfactants comprise insulating constituents (alkyl groups as side-chains and charged organic heads), such nanostructures are wrapped in an electrically inactive barrier, and this is a large disadvantage for future developments in nanotechnology. Implications of micelles with electrically conducting walls made from either “metallic” or “semiconducting” surfactants are huge, also in other areas such as nanoelectrocatalysis or micellar energy storage. We cross this frontier by replacing not only the hydrophilic chain but also the hydrophilic head by electronically conducting entities. We report the synthesis of surfactants with oligo para-phenylene-ethynylene as a π-conjugated side-chain attached to a redox-active, inorganic polyoxometalate cluster as charged head. It is proven that electronic communication between head and tail takes place. Hybridization on the molecular level leads to the emergence of advanced surfactant features such as semiconductor properties (Egap = 2.6 eV) in soft lyotropic systems (micelles, liquid crystals). PMID:27809472

  15. Effects of conducting polymer poly(3, 4-ethylenedioxythiophene) nanotubes on the electro-optical and dielectric properties of a nematic liquid crystal 4-n-pentyl-4'-cyanobiphenyl host

    NASA Astrophysics Data System (ADS)

    Ghosh, Sharmistha; Nayek, Prasenjit; Roy, Subir Kr.; Gangopadhyay, Rupali; Molla, Mijanur Rahaman; Dabrowski, Roman

    2010-02-01

    We report the results of the optical transmission and the capacitance behavior as a function dc electric field of a pristine liquid crystal and conducting polymer nanotube-liquid crystal composite measured in twisted nematic cells. The threshold and driving voltages have been determined from transmission-voltage curve. There is remarkable reduction in the threshold and driving voltage in the polymer nanotube doped liquid crystal cell which is good from application point of view. The residual dc is also reduced significantly in the doped cell and the reduction is even more than that observed in the carbon nanotube doped same liquid crystal system.

  16. Transverse conductivity in Y_{1-y}Pr_{y}Ba_{2}Cu_{3}O_{7-\\delta } single crystals

    NASA Astrophysics Data System (ADS)

    Vovk, R. V.; Khadzhai, G. Ya; Dobrovolskiy, O. V.; Nazyrov, Z. F.; Goulatis, I. L.

    2014-04-01

    The out-of-plane resistivity of high-quality Y_{1-y}Pr_{y}Ba_{2}Cu_{3}O_{7-\\delta } single crystals was measured and analyzed within the range {{T}_{{\\rm{c}}}}-300 K. The temperature dependence of the resistivity \\rho \\left( T \\right) can be described well by a model that takes into account scattering of electrons by phonons and defects, in conjunction with a transition to the ‘semiconductor’-type behavior with increasing praseodymium concentration. The effect of fluctuations is described well by the 3D Aslamazov-Larkin model. The electron-phonon interaction in the Y_{1-y}PryBa_{2}Cu_{3}O_{7-\\delta } is strong, but it is weakened with increasing praseodymium concentration. A parabolic correlation between the critical temperature {{T}_{{\\rm{c}}}} and the parameter characterizing the volume fraction of the ‘semiconductor’ phase was observed. The quantified scattering and fluctuation parameters in the investigated interval of praseodymium concentrations (y<0.35) are reported.

  17. Revealing surface oxidation on the organic semi-conducting single crystal rubrene with time of flight secondary ion mass spectroscopy.

    PubMed

    Thompson, Robert J; Fearn, Sarah; Tan, Ke Jie; Cramer, Hans George; Kloc, Christian L; Curson, Neil J; Mitrofanov, Oleg

    2013-04-14

    To address the question of surface oxidation in organic electronics the chemical composition at the surface of single crystalline rubrene is spatially profiled and analyzed using Time of Flight - Secondary Ion Mass Spectroscopy (ToF-SIMS). It is seen that a uniform oxide (C42H28O) covers the surface while there is an increased concentration of peroxide (C42H28O2) located at crystallographic defects. By analyzing the effects of different primary ions, temperature and sputtering agents the technique of ToF-SIMS is developed as a valuable tool for the study of chemical composition variance both at and below the surface of organic single crystals. The primary ion beams C60(3+) and Bi3(+) are found to be most appropriate for mass spectroscopy and spatial profiling respectively. Depth profiling of the material is successfully undertaken maintaining the molecular integrity to a depth of ~5 μm using an Ar cluster ion source as the sputtering agent.

  18. Hydrogen centers and the conductivity of In2O3 single crystals

    SciTech Connect

    Yin, Weikai; Smithe, Kirby; Weiser, Philip; Stavola, Michael; Fowler, W. Beall; Boatner, Lynn A.; Pearton, Stephen J.; Hays, David C.; Koch, Sandro G.

    2015-02-24

    A series of infrared absorption experiments and complementary theory have been performed in order to determine the properties of OH and OD centers in In2O3 single crystals. Annealing In2O3 samples in H2 or D2 at temperatures near 450°C produces an n-type layer ≈0.06mm thick with an n-type doping of 1.6×1019 cm-3. The resulting free-carrier absorption is correlated with an OH center with a vibrational frequency of 3306 cm-1 that we associate with interstitial H+. Additional O-H (O-D) vibrational lines are assigned to metastable configurations of the interstitial H+(D+) center and complexes of H (D) with In vacancies. In addition, unlike other oxides studied recently where H trapped at an oxygen vacancy is the dominant shallow donor (ZnO and SnO2, for example), interstitial H+ is found to be the dominant H-related shallow donor in In2O3.

  19. Noncovalent approach to one-dimensional ion conductors: enhancement of ionic conductivities in nanostructured columnar liquid crystals.

    PubMed

    Shimura, Harutoki; Yoshio, Masafumi; Hoshino, Koji; Mukai, Tomohiro; Ohno, Hiroyuki; Kato, Takashi

    2008-02-06

    Noncovalent design of new liquid-crystalline (LC) columnar assemblies based on an ionic liquid has shown to be useful to achieve anisotropic high ionic conductivities. An equimolar mixture of an ionic liquid, 1-butyl-3-methylimidazolium bromide, and 3-[3,4,5-tri(octyloxy)benzoyloxy]propane-1,2-diol, which is partially miscible with the ionic liquid, exhibits an LC hexagonal columnar phase from -4 to 63 degrees C. This columnar supramolecular assembly forming the nanostructures shows the one-dimensional (1D) ionic conductivity of 3.9 x 10(-3) S cm(-1) at 50 degrees C along the column, which is more than 700 times higher than that of the corresponding covalent-type columnar ionic liquid, 1-methyl-3-[3,4,5-tri(octyloxy)benzyl]imidazolium bromide, which is 5.3 x 10(-6) S cm(-1) at 50 degrees C. This significant enhancement of the ionic conductivity is attributed to the increase of the mobility of the ionic part.

  20. Experimental determination of single-crystal halite thermal conductivity, diffusivity and specific heat from -75°C to 300°C

    SciTech Connect

    Urquhart, Alexander; Bauer, Stephen

    2015-05-19

    The thermal properties of halite have broad practical importance, from design and long-term modeling of nuclear waste repositories to analysis and performance assessment of underground natural gas, petroleum and air storage facilities. Using a computer-controlled transient plane source method, single-crystal halite thermal conductivity, thermal diffusivity and specific heat were measured from -75°C to 300°C. These measurements reproduce historical high-temperature experiments and extend the lower temperature extreme into cryogenic conditions. Measurements were taken in 25-degree increments from -75°C to 300°C. Over this temperature range, thermal conductivity decreases by a factor of 3.7, from 9.975 to 2.699 W/mK , and thermal diffusivity decreases by a factor of 3.6, from 5.032 to 1.396 mm²/s. Specific heat does not appear to be temperature dependent, remaining near 2.0 MJ/m³K at all temperatures. This work is intended to develop and expand the existing dataset of halite thermal properties, which are of particular value in defining the parameters of salt storage thermophysical models. The work was motivated by a need for thermal conductivity values in a mixture theory model used to determine bulk thermal conductivity of reconsolidating crushed salt.

  1. Self-compensation limited conductivity in semi-insulating indium-doped Cd0.9Zn0.1Te crystals

    NASA Astrophysics Data System (ADS)

    Kosyachenko, L. A.; Melnychuk, S. V.; Maslyanchuk, O. L.; Sklyarchuk, V. M.; Sklyarchuk, O. F.; Fiederle, M.; Lambropoulos, C. P.

    2012-07-01

    Cd0.9Zn0.1Te:In crystals with semi-intrinsic conductivity have been investigated. Temperature dependence of their electrical characteristics shows a number of unconventional peculiarities: the thermal activation energy of conductivity is "anomalously" low (0.60-0.62 eV); the resistivity at elevated temperatures is greater than its intrinsic value for Cd0.9Zn0.1Te; the inversion of the conduction from n- to p-type occurs at a temperature slightly above 300 K, etc. The observed features are explained in terms of statistics of electrons and holes in a semiconductor containing a self-compensation complex, whose concentration is much higher than those of uncontrolled (background) impurities and defects. Comparison of the calculation results and experimental data leads to the conclusion that the donor level, which is far distant from the middle of the band gap, dominates in the conductivity of the material and its compensation is virtually complete (Na/Nd = 0.99996-0.99998) as predicted by theory.

  2. Robust random telegraph conductivity noise in single crystals of the ferromagnetic insulating manganite La0.86Ca0.14MnO3

    NASA Astrophysics Data System (ADS)

    Przybytek, J.; Fink-Finowicki, J.; Puźniak, R.; Shames, A.; Markovich, V.; Mogilyansky, D.; Jung, G.

    2017-03-01

    Robust random telegraph conductivity fluctuations have been observed in La0.86Ca0.14MnO3 manganite single crystals. At room temperatures, the spectra of conductivity fluctuations are featureless and follow a 1 /f shape in the entire experimental frequency and bias range. Upon lowering the temperature, clear Lorentzian bias-dependent excess noise appears on the 1 /f background and eventually dominates the spectral behavior. In the time domain, fully developed Lorentzian noise appears as pronounced two-level random telegraph noise with a thermally activated switching rate, which does not depend on bias current and applied magnetic field. The telegraph noise is very robust and persists in the exceptionally wide temperature range of more than 50 K. The amplitude of the telegraph noise decreases exponentially with increasing bias current in exactly the same manner as the sample resistance increases with the current, pointing out the dynamic current redistribution between percolation paths dominated by phase-separated clusters with different conductivity as a possible origin of two-level conductivity fluctuations.

  3. Experimental determination of single-crystal halite thermal conductivity, diffusivity and specific heat from -75°C to 300°C

    DOE PAGES

    Urquhart, Alexander; Bauer, Stephen

    2015-05-19

    The thermal properties of halite have broad practical importance, from design and long-term modeling of nuclear waste repositories to analysis and performance assessment of underground natural gas, petroleum and air storage facilities. Using a computer-controlled transient plane source method, single-crystal halite thermal conductivity, thermal diffusivity and specific heat were measured from -75°C to 300°C. These measurements reproduce historical high-temperature experiments and extend the lower temperature extreme into cryogenic conditions. Measurements were taken in 25-degree increments from -75°C to 300°C. Over this temperature range, thermal conductivity decreases by a factor of 3.7, from 9.975 to 2.699 W/mK , and thermal diffusivitymore » decreases by a factor of 3.6, from 5.032 to 1.396 mm²/s. Specific heat does not appear to be temperature dependent, remaining near 2.0 MJ/m³K at all temperatures. This work is intended to develop and expand the existing dataset of halite thermal properties, which are of particular value in defining the parameters of salt storage thermophysical models. The work was motivated by a need for thermal conductivity values in a mixture theory model used to determine bulk thermal conductivity of reconsolidating crushed salt.« less

  4. Hydrogen-bond-dynamics-based switching of conductivity and magnetism: a phase transition caused by deuterium and electron transfer in a hydrogen-bonded purely organic conductor crystal.

    PubMed

    Ueda, Akira; Yamada, Shota; Isono, Takayuki; Kamo, Hiromichi; Nakao, Akiko; Kumai, Reiji; Nakao, Hironori; Murakami, Youichi; Yamamoto, Kaoru; Nishio, Yutaka; Mori, Hatsumi

    2014-08-27

    A hydrogen bond (H-bond) is one of the most fundamental and important noncovalent interactions in chemistry, biology, physics, and all other molecular sciences. Especially, the dynamics of a proton or a hydrogen atom in the H-bond has attracted increasing attention, because it plays a crucial role in (bio)chemical reactions and some physical properties, such as dielectricity and proton conductivity. Here we report unprecedented H-bond-dynamics-based switching of electrical conductivity and magnetism in a H-bonded purely organic conductor crystal, κ-D3(Cat-EDT-TTF)2 (abbreviated as κ-D). This novel crystal κ-D, a deuterated analogue of κ-H3(Cat-EDT-TTF)2 (abbreviated as κ-H), is composed only of a H-bonded molecular unit, in which two crystallographically equivalent catechol-fused ethylenedithiotetrathiafulvalene (Cat-EDT-TTF) skeletons with a +0.5 charge are linked by a symmetric anionic [O···D···O](-1)-type strong H-bond. Although the deuterated and parent hydrogen systems, κ-D and κ-H, are isostructural paramagnetic semiconductors with a dimer-Mott-type electronic structure at room temperature (space group: C2/c), only κ-D undergoes a phase transition at 185 K, to change to a nonmagnetic insulator with a charge-ordered electronic structure (space group: P1). The X-ray crystal structure analysis demonstrates that this dramatic switching of the electronic structure and physical properties originates from deuterium transfer or displacement within the H-bond accompanied by electron transfer between the Cat-EDT-TTF π-systems, proving that the H-bonded deuterium dynamics and the conducting TTF π-electron are cooperatively coupled. Furthermore, the reason why this unique phase transition occurs only in κ-D is qualitatively discussed in terms of the H/D isotope effect on the H-bond geometry and potential energy curve.

  5. Proton Conduction Path in Rb3H(SeO4)2 Studied by High Temperature Neutron Single Crystal Diffraction

    NASA Astrophysics Data System (ADS)

    Kiyanagi, Ryoji; Ishikawa, Yoshihisa; Noda, Yukio

    A superprotonic conductor, Rb3H(SeO4)2, was structurally investigated by means of neutron single crystal diffraction. The hydrogen bond length was found to gradually elongate as the temperature approaches the superprotonic phase transition temperature and jumps to a much longer value upon the transition. The structure of SeO4 tetrahedron remains unchanged below the transition temperature and becomes more distorted upon the transition with disordered apical oxygen forming three disordered hydrogen bonds. Consequently, the hydrogen atoms (protons) in the hydrogen bonds are significantly delocalized two-dimensionally being indicative of the proton migration. In the proton distribution map, there found small bumps between the adjacent hydrogen bonds. They may be interstitial sites for the conducting protons corresponding to a monomer state of [HSeO4]-.

  6. Influence of gas atmosphere and temperature on the conductivity and the photoconductivity of a TiO2 single crystal in the surface region.

    PubMed

    Amade, R; Heitjans, P; Indris, S; Finger, M; Haeger, A; Hesse, D

    2006-02-14

    The electrical photoconductivity and conductivity at (and near) the surface of a TiO(2) single crystal (rutile) was studied in a range of temperatures between 300 and 573 K and under different ambient gases (oxygen and nitrogen) by means of impedance spectroscopy. The long times required (many hours) to reach steady state photoconductivity can be explained by the reduction of the material upon illumination. At about 475 K a maximum is observed in the equilibrium photoconductivity and a minimum in the rate constants of the rise and decay after switching on and off, respectively, the light. After switching off the light a fast decay takes place during the first milliseconds followed by a slow exponential decay. The first one is related to recombination through defects, while the latter is due to re-oxidation processes of the material. The results are correlated with measurements of photocatalytic activity.

  7. Effect of hydrostatic pressure on the conductivity of YBa2Cu3O7-δsingle crystals in a broad range of temperature and oxygen content

    NASA Astrophysics Data System (ADS)

    Vovk, R. V.; Khadzhai, G. Ya.; Dobrovolskiy, O. V.; Nazyrov, Z. F.; Kamchatnaya, S. N.

    2017-04-01

    The effect of external hydrostatic pressure on the electrical resistance of optimally doped and underdoped YBa2Cu3O7-δ single crystals is investigated in a broad temperature range, which includes the normal state and the region of superconducting fluctuations. The temperature dependences of the resistivity in the normal state are determined by scattering of charge carriers by phonons and defects. The application of pressure leads to significant changes in the electronic structure of the sample and reduces the degree of their defectiveness. This is accompanied by changeû in the lattice characteristics as the sample volume decreases. The fluctuation conductivity only exists within the range of ∼ 0.1Tc . With increasing δ the superconducting characteristics are close to the values typical for conventional low-temperature superconductors.

  8. Effects of internal molecular degrees of freedom on the thermal conductivity of some glasses and disordered crystals

    NASA Astrophysics Data System (ADS)

    Krivchikov, A. I.; Korolyuk, O. A.; Sharapova, I. V.; Tamarit, J. Ll.; Bermejo, F. J.; Pardo, L. C.; Rovira-Esteva, M.; Ruiz-Martin, M. D.; Jezowski, A.; Baran, J.; Davydova, N. A.

    2012-01-01

    The thermal conductivity κ(T) of the fully ordered stable phase II, the metastable phase III, the orientationally disordered (plastic) phase I, as well as the nonergodic orientational glass (OG) phase, of the glass former cyclohexanol (C6H11OH) has been measured under equilibrium vapor pressure within the 2-200 K temperature range. The main emphasis is here focused on the influence of the conformational disorder upon the thermal properties of this material. Comparison of results with those regarding cyanoclyclohexane (C6H11CN), a chemically related compound, serves to quantify the role played by the terminal groups -OH and -CN on the phonon scattering processes. The picture that emerges shows that motions of such groups do play a minor role as scattering centers, both within the low-temperature orientationally ordered phases as well as in the OG states. The results are analyzed within the Debye-Peierls relaxation time model for isotropic solids comprising mechanisms for long-wave phonon scattering within the OG and orientational ordered low-temperature phases, as well as others arising from localized short-wavelength vibrational modes as pictured by the Cahill-Pohl model. By means of complementary neutron and Raman scattering we show that in the OG state the energy landscapes for both compounds are very similar.

  9. Synthesis, crystal structure, and ionic conductivity of a new layered metal phosphate, Li2Sr2Al(PO4)3

    NASA Astrophysics Data System (ADS)

    Kim, Sung-Chul; Kwak, Hyun-Jung; Yoo, Chung-Yul; Yun, Hoseop; Kim, Seung-Joo

    2016-11-01

    A new layered metal phosphate, Li2Sr2Al(PO4)3, was synthesized in the form of either a single-crystal or polycrystalline powder using the molten hydroxide flux method or a solid-state reaction, respectively. Li2Sr2Al(PO4)3 crystallizes to the P21/n (Z=4) monoclinic space group with lattice parameters a≈4.95 Å, b≈22.06 Å, c≈8.63 Å, and β≈91.5°. The structure is composed of stacked [LiSrAl(PO4)2] layers alternating regularly with [LiSrPO4] layers. In the [LiSrAl(PO4)2] sublattice, the AlO6 octahedra and PO4 tetrahedra are tilted cooperatively to form an anionic, corrugated, two-dimensional [Al(PO4)2]3- framework that can be regarded as a "distorted-glaserite" structure. The [LiSrPO4] sublattice is that of a layered block containing a six-membered ring formed from alternating linkages of LiO4 and PO4 tetrahedra. The six-membered rings show a boat-type arrangement with the up(U) or down(D) pointing sequence, UUDUUD. The interspace between the two sublattices generates a two-dimensional pathway for Li+ ion conduction. The impedance measurement indicated that Li2Sr2Al(PO4)3 had a moderate ion conductivity (σ≈1.30×10-4 S cm-1 at 667 K), with an activation energy Ea≈1.02 eV.

  10. Selectively Transparent and Conducting Photonic Crystals and their Potential to Enhance the Performance of Thin-Film Silicon-Based Photovoltaics and Other Optoelectronic Devices

    NASA Astrophysics Data System (ADS)

    O'Brien, Paul G.

    2011-12-01

    The byproducts of human engineered energy production are increasing atmospheric CO2 concentrations well above their natural levels and accompanied continual decline in the natural reserves of fossil fuels necessitates the development of green energy alternatives. Solar energy is attractive because it is abundant, can be produced in remote locations and consumed on site. Specifically, thin-film silicon-based photovoltaic (PV) solar cells have numerous inherent advantages including their availability, non-toxicity, and they are relatively inexpensive. However, their low-cost and electrical performance depends on reducing their thickness to as great an extent as possible. This is problematic because their thickness is much less than their absorption length. Consequently, enhanced light trapping schemes must be incorporated into these devices. Herein, a transparent and conducting photonic crystal (PC) intermediate reflector (IR), integrated into the rear side of the cell and serving the dual function as a back-reflector and a spectral splitter, is identified as a promising method of boosting the performance of thin-film silicon-based PV. To this end a novel class of PCs, namely selectively transparent and conducting photonic crystals (STCPC), is invented. These STCPCs are a significant advance over existing 1D PCs because they combine intense wavelength selective broadband reflectance with the transmissive and conductive properties of sputtered ITO. For example, STCPCs are made to exhibit Bragg-reflectance peaks in the visible spectrum of 95% reflectivity and have a full width at half maximum that is greater than 200nm. At the same time, the average transmittance of these STCPCs is greater than 80% over the visible spectrum that is outside their stop-gap. Using wave-optics analysis, it is shown that STCPC intermediate reflectors increase the current generated in micromorph cells by 18%. In comparison, the more conventional IR comprised of a single homogeneous

  11. Single-scan measurement of conductance of a quartz crystal microbalance array coupled with resonant markers for biosensing in liquid phase

    SciTech Connect

    Hsiao, Hsien-Yi; Chen, Richie L. C.; Cheng, Tzong-Jih

    2009-04-15

    This work presents a method for sensing the viscoelastic property of liquid/solid interface using a quartz crystal microbalance (QCM) array. Each sensor in a QCM array has a unique resonant frequency and can be identified by a single-scan measurement of admittance (or impedance). The resonant frequency encoding at each sensor in an array was realized by connecting a capacitor with a known capacitance, called a resonant marker, to the sensor in series. Changes in the resonant frequency of all sensors in an array can be determined using an impedance analyzer and a program that determines the frequencies at which the conductance is at a local maximum. The sensing method allows every sensor output (resonant frequency) to be obtained without the use of time-consuming multiplexed hardware and software. Adsorptions of biomolecules by multiple sensor are monitored in the liquid phase to demonstrate the feasibility of frequency encoding using resonant markers and the single-scan measurement of conductance of a QCM array.

  12. Critical increase in Na-doping facilitates acceptor band movements that yields ~180 meV shallow hole conduction in ZnO bulk crystals

    PubMed Central

    Parmar, Narendra S.; Yim, Haena; Choi, Ji-Won

    2017-01-01

    Stable p-type conduction in ZnO has been a long time obstacle in utilizing its full potential such as in opto-electronic devices. We designed a unique experimental set-up in the laboratory for high Na-doping by thermal diffusion in the bulk ZnO single crystals. SIMS measurement shows that Na concentration increases by 3 orders of magnitude, to ~3 × 1020 cm−3 as doping temperature increases to 1200 °C. Electronic infrared absorption was measured for Na-acceptors. Absorption bands were observed near (0.20–0.24) eV. Absorption bands blue shifted by 0.04 eV when doped at 1200 °C giving rise to shallow acceptor level. NaZn band movements as a function of doping temperature are also seen in Photoluminescence emission (PL), Photoluminescence excitation (PLE) and UV-Vis transmission measurements. Variable temperature Hall measurements show stable p-type conduction with hole binding energy ~0.18 eV in ZnO samples that were Na-doped at 1200 °C. PMID:28272444

  13. Insight into Understanding Dielectric Behavior of a Zn-MOF Using Variable-Temperature Crystal Structures, Electrical Conductance, and Solid-State (13)C NMR Spectra.

    PubMed

    Tong, Yuan-Bo; Liu, Shao-Xian; Zou, Yang; Xue, Chen; Duan, Hai-Bao; Liu, Jian-Lan; Ren, Xiao-Ming

    2016-11-21

    A Zn-based metal-organic framework (MOF)/porous coordination polymer (PCP), (EMIM)[Zn(SIP)] (1) (SIP(3-) = 5-sulfoisophthalate, EMIM(+) = 1-ethyl-3-methylimidazolium), was synthesized using the ionothermal reaction. The Zn(2+) ion adopts distorted square pyramid coordination geometry with five oxygen atoms from three carboxylates and one sulfo group. One of two carboxylates in SIP(3-) serves as a μ2-bridge ligand to link two Zn(2+) ions and form the dinuclear SBU, and such SBUs are connected by SIP(3-) ligands to build the three-dimensional framework with rutile (rtl) topology. The cations from the ion-liquid fill the channels. This MOF/PCP shows two-step dielectric anomalies together with two-step dielectric relaxations; the variable-temperature single-crystal structure analyses disclosed the dielectric anomaly occurring at ca. 280 K is caused by an isostructural phase transition. Another dielectric anomaly is related to the dynamic disorder of the cations in the channels. Electric modulus, conductance, and variable-temperature solid-state (13)C CP/MAS NMR spectra analyses revealed that two-step dielectric relaxations result from the dynamic motion of the cations as well as the direct-current conduction and electrode effect, respectively.

  14. Critical increase in Na-doping facilitates acceptor band movements that yields ~180 meV shallow hole conduction in ZnO bulk crystals

    NASA Astrophysics Data System (ADS)

    Parmar, Narendra S.; Yim, Haena; Choi, Ji-Won

    2017-03-01

    Stable p-type conduction in ZnO has been a long time obstacle in utilizing its full potential such as in opto-electronic devices. We designed a unique experimental set-up in the laboratory for high Na-doping by thermal diffusion in the bulk ZnO single crystals. SIMS measurement shows that Na concentration increases by 3 orders of magnitude, to ~3 × 1020 cm‑3 as doping temperature increases to 1200 °C. Electronic infrared absorption was measured for Na-acceptors. Absorption bands were observed near (0.20–0.24) eV. Absorption bands blue shifted by 0.04 eV when doped at 1200 °C giving rise to shallow acceptor level. NaZn band movements as a function of doping temperature are also seen in Photoluminescence emission (PL), Photoluminescence excitation (PLE) and UV-Vis transmission measurements. Variable temperature Hall measurements show stable p-type conduction with hole binding energy ~0.18 eV in ZnO samples that were Na-doped at 1200 °C.

  15. Comments on the paper: 'Optical reflectance, optical refractive index and optical conductivity measurements of nonlinear optics for L-aspartic acid nickel chloride single crystal'

    NASA Astrophysics Data System (ADS)

    Srinivasan, Bikshandarkoil R.; Naik, Suvidha G.; Dhavskar, Kiran T.

    2016-02-01

    We argue that the 'L-aspartic acid nickel chloride' crystal reported by the authors of the title paper (Optics Communications, 291 (2013) 304-308) is actually the well-known diaqua(L-aspartato)nickel(II) hydrate crystal.

  16. Thermal Conductivity Investigation of {Ca}_{9} {RE}({VO}_{4})_{7} (RE = La, Nd, Gd) and {Ca}_{10}M(VO_{4})_{7} (M = Li, Na, K) Single Crystals

    NASA Astrophysics Data System (ADS)

    Popov, P. A.; Skrobov, S. A.; Matovnikov, A. V.; Kosmyna, M. B.; Puzikov, V. M.; Nazarenko, B. P.; Shekhovtsov, A. N.; Behrooz, A.; Paszkowicz, W.; Khodasevich, I. A.; Shereshovets, N. N.; Voitikov, S. V.; Orlovich, V. A.

    2017-01-01

    The {Ca}9{RE}({VO}4)7 (RE = La, Nd, Gd) and {Ca}_{10}{M}({VO}4)7 (M = Li, Na, K) single crystals have been grown by the Czochralski method. The binary vanadates are isostructural to "whitlockite" mineral (rhombohedral symmetry, R3 c space group). Their thermal conductivity has been investigated in the range 50 K-300 K parallel to the c axis. For {Ca}9{Gd}({VO}4)7 crystals, the thermal conductivity has been investigated in the range 300 K-550 K also. Additionally, for the {Ca}_{10}{M}({VO}4)7 (M = Li, Na, K) crystals the heat capacity has been studied in the temperature range 80 K-300 K. The character of the temperature dependence of thermal conductivity is close to that of glasses. The possible reasons of the observed features of the thermal conductivity have been analyzed. Raman spectra of {Ca}_{10}{M}({VO}4)7 (M = Li, Na, K) crystals have been measured and discussed. The spectral lines were broad and similar to polycrystalline or amorphous solids. These crystals are expected to be suitable for application as efficient nonlinear optic and laser materials.

  17. Hydrothermal synthesis, crystal structure, conductivity, and thermal decomposition of [Cu(4,4'-bipy)(H2O)(Mo3O10)].H2O.

    PubMed

    Kong, Zuping; Weng, Linhong; Tan, Dejun; He, Heyong; Zhang, Biao; Kong, Jilie; Yue, Bin

    2004-09-06

    The hydrothermal reaction of (NH(4))(6)Mo(7)O(24).4H(2)O, CuCl(2).2H(2)O, and 4,4'-bipyridine yields bipyridine-ligated copper-trimolybdate monohydrate [Cu(4,4'-bipy)(H(2)O)(Mo(3)O(10))].H(2)O in the monoclinic system with space group of C(2/c) and cell parameters of a = 15.335(2) A, b = 15.535(2) A, c = 15.106(2) A, beta = 101.162(2) degrees, V = 3530.7(9) A(3), and Z = 8. Its structure consists of one-dimensional infinite ([Mo3O10]2-)( infinity ) chains linked through [Cu2(H2O)2(4,4'-bipy)] units. The Mo-O chain contains distorted [MoO(6)] octahedra connected through corner-sharing oxygen atoms into infinite chains along the c direction and each chain is located in the channel formed by four adjacent crossing chains of [Cu(4,4'-bipy)(H2O)](n)(2n+). The crystal shows weak conductivity through Mo-O chain along the c direction and insulating property along either a or b direction. Furthermore, a crystalline bimetallic oxide, CuMo3O10, forms when the title compound undergoes thermal treatment in N(2) atmosphere after the complete removal of the ligands.

  18. Synthesis, crystal structure, phase transition and electrical conduction mechanism of the new [(C3H7)4N]2MnCl4 compound

    NASA Astrophysics Data System (ADS)

    Gzaiel, M. Ben; Oueslati, A.; Hlel, F.; Gargouri, M.

    2016-09-01

    Bis tetrapropylammonium tetrchloro-monganete has been synthesized and characterized by X-ray, differential scanning calorimetry, vibrational spectroscopy and impedance spectroscopy. At room temperature, the latter is crystallized in the monoclinic phase, with P2/c space group. The projection of atomic arrangement along b axis shows that all nitrogen atoms are disposed linearly along [001] direction. Differential scanning calorimetry (DSC) disclosed three order-disorder phase transitions at T1=333 K, T2=356 K and T3=379 K. Besides, impedance measurements indicate that the electrical and dielectric properties are strongly dependent on both temperature and frequency. Nyquist plots (Z″ versus Z‧) show that the conductivity behavior is accurately represented by an equivalent circuit model which consists of a series combination of grains interior and grains boundary. The evolution of the dielectric constant as a function of temperature shows a distribution of relaxation times which is probably due to the reorientational dynamics of alkyl chains. On the other hand, the dependency of m(T) with temperature has been discussed in terms of the correlated barrier hopping (CBH) model in phase (I and IV). The quantum mechanical tunneling (QMT) model describes the second phase (II), whereas the third one (III) is characterized by the non-overlapping small Polaron tunneling (NSPT) model.

  19. Electrical conduction mechanism in La{sub 3}Ta{sub 0.5}Ga{sub 5.3}Al{sub 0.2}O{sub 14} single crystals

    SciTech Connect

    Yaokawa, Ritsuko Aota, Katsumi; Uda, Satoshi

    2013-12-14

    The electrical conduction mechanism in La{sub 3}Ta{sub 0.5}Ga{sub 5.3}Al{sub 0.2}O{sub 14} (LTGA) single crystals was studied by nonstoichiometric defect formation during crystal growth. Since stoichiometric LTGA is not congruent, the single crystal grown from the stoichiometric melt was Ta-poor and Al-rich, where Al atoms were substituted not only in Ga sites but also in Ta sites. The population of the substitutional Al in Ta sites increased with increasing oxygen partial pressure during growth (growth-pO{sub 2}) in the range from 0.01 to 1 atm. Below 600 °C, substitutional Al atoms in Ta sites were ionized to yield holes, and thus the electrical conductivity of the LTGA crystal depended on temperature and the growth-pO{sub 2}. The dependence of the electrical conductivity on the growth-pO{sub 2} decreased as temperature increased. The temperature rise increases ionic conductivity, for which the dominant carriers are oxygen defects formed by the anion Frenkel reaction.

  20. Crystal structure, phase transition and conductivity study of two new organic - inorganic hybrids: [(CH2)7(NH3)2]X2, X = Cl/Br

    NASA Astrophysics Data System (ADS)

    Mostafa, Mohga Farid; El-khiyami, Shimaa Said; Abd-Elal, Seham Kamal

    2017-01-01

    Two hybrids 1,7-heptanediammonium di-halide, [(C7H20N2]X2,X = Cl/Br crystallize in monoclinic P21/c, Z = 4. [(C7H20N2]Cl2: a = 4.7838 (2) Å, b = 16.9879 (8) Å, c = 13.9476 (8) Å, β = 97.773 (2)°, V = 1203.58(10) Å3, D = 1.137 g/cm3, λ = 0.71073 Å, R = 0.052 for 1055 reflections with I > 2σ(I), T = 298(2) K. [(C7H20N2]Br2: a = 4.7952 (10) Å, b = 16.9740 (5) Å, c = 13.9281 (5) Å, β = 97.793 (2)°, V = 1203.83(6) Å3, D = 1.612 g/cm3, λ = 0.71073 Å, R = 0.03 for 1959 reflections with I > 2σ(I) T = 298(2) K. Asymmetric unit cell of [(C7H20N2]X2,X = Cl/Br, each consist of one heptane-1,7-diammonium cation and two halide anions. The organic hydrocarbon layers pack in a stacked herring-bone manner, hydrogen bonded to the halide ions. Lattice potential energy is 1568.59 kJ/mol and 1560.78 kJ/mol, and cation molar volumes are 0.295 nm3 and 0.300 nm3 for chloride and bromide respectively. DTA confirmed chain melting transitions for both hybrids below T ∼ 340 K. Dielectric and ac conductivity measurements (290 < T K < 410; 0.080 < f kHz<100) indicated higher conductivity and activation energy of bromide for T > 340 K. Cross over from Jonscher's universal dielectric response at low temperatures T < 340 K to super-linear power law for T > 340 K is observed. At high temperatures halide ion hopping in accordance with the jump relaxation model prevails.

  1. Determination of the concentration of conduction electrons in Y{sub 3}Fe{sub 5}O{sub 12} garnet crystals

    SciTech Connect

    Lomako, I. D.

    2013-07-15

    Ferrites (garnets) are a model object of study and a promising material to be used in magneto-optical devices for data recording and processing and IR modulators. Due to the narrow ferromagnetic resonance line, optical transparency, and high elastic Q factor of ferrite single crystals, they are promising for solid-state microwave, optoelectronic, and computation devices. To ensure the optimal application of ferromagnetic materials, it is necessary to complete the following important task: develop a certification for samples with allowance for the degree of their imperfection caused by the deviation of crystals with garnet structure from stoichiometry, the competitive incorporation of process and dominant impurities, oxygen vacancies, etc.

  2. Crystal structure and ionic conductivity of ruthenium diphosphate ARu{sub 2}(P{sub 2}O{sub 7}){sub 2}, A=Li, Na, and Ag, with a tunnel structure

    SciTech Connect

    Fukuoka, Hiroshi; Matsunaga, Hideyuki; Yamanaka, Shoji

    2003-05-26

    Crystal structure and ionic conductivity of ruthenium diphosphates, ARu{sub 2}(P{sub 2}O{sub 7}){sub 2} A=Li, Na, and Ag, were investigated. The structure of the Ag compound was determined by single crystal X-ray diffraction techniques. It crystallized in the triclinic space group P-1 with a=4.759(2) A, b=6.843(2) A, c=8.063(1) A, {alpha}=90.44(2) deg., {beta}=92.80(2) deg., {gamma}=104.88(2) deg., V=253.4(1) A{sup 3}. The host structure of it was composed of RuO{sub 6} and P{sub 2}O{sub 7} groups and formed tunnels running along the a-axis, in which Ag{sup +} ions were situated. The ionic conductivities have been measured on pellets of the polycrystalline powders. The Li and Ag compounds showed the conductivities of 1.0x10{sup -4} and 3.5x10{sup -5} S cm{sup -1} at 150 deg. C, respectively. Magnetic susceptibility measurement of the Ag compound showed that it did not obey the Curie-Weiss law and the effective magnetic moment decreased as temperature decreased due to the large spin-orbital coupling effect of Ru{sup 4+} ions.

  3. Nanostructured crystals of fluorite phases Sr{sub 1-x}R{sub x}F{sub 2+x} (R are rare earth elements) and their ordering: 5. A study of the ionic conductivity of as-grown Sr{sub 1-x}R{sub x}F{sub 2+x} crystals

    SciTech Connect

    Sorokin, N. I. Karimov, D. N.; Sulyanova, E. A.; Zhmurova, Z. I.; Sobolev, B. P.

    2010-07-15

    The ionic conductivity {sigma} of Sr{sub 1-x}R{sub x}F{sub 2+x} crystals (R = Y, La-Lu) has been measured in the temperature range of 324-933 K. The isomorphic introduction of R{sup 3+} ions into SrF{sub 2} is accompanied by an increase in conductivity up to four orders of magnitude, which makes these crystals superionic conductors. It is shown that the conduction mechanism in Sr{sub 1-x}R{sub x}F{sub 2+x} crystals changes when passing from R = La-Nd to R = Sm-Lu. A change in the type of cluster of structural defects between Nd and Sm is suggested. The concentration dependences of {sigma} and the activation energy of charge-carrier migration (E{sub a}) for Sr{sub 1-x}R{sub x}F{sub 2+x} are nonlinear. For crystals with R = La or Nd, these dependences are interpreted within the percolation model of 'defect regions,' the minimum size of which is estimated to be {approx}700 A{sup 3}. It is shown that the electrical properties of the crystals can be controlled by varying the RF{sub 3} type and concentration. The Sr{sub 1-x}R{sub x}F{sub 2+x} crystals (R = La-Nd, 0.3 {<=} x {<=} 0.5), for which {sigma} = (2-3) x 10{sup -2} S/cm at 673 K and E{sub a} = 0.6-0.7 eV, have the best electrolytic characteristics.

  4. The incommensurately modulated crystal structure of beta-Pb2BiVO6: interpretation of the phase transition alpha --> beta --> delta and conduction properties of related materials.

    PubMed

    Roussel, Pascal; Labidi, Olfa; Huve, Marielle; Drache, Michel; Wignacourt, Jean Pierre; Petricek, Vaclav

    2009-08-01

    A new polymorph of Pb(2)BiVO(6) was prepared under ambient conditions and its crystal structure was determined by single-crystal X-ray diffraction. The phase transitions alpha --> beta and beta --> delta were identified in the mother phase; the high-temperature form delta-Pb(2)BiVO(6) eventually decomposes at 753 K to a mixture of Pb(4)BiVO(8) and the high-temperature form of PbBiVO(5) before showing recombination at 923 K. beta-Pb(2)BiVO(6) has an incommensurate monoclinic modulated structure. This crystal structure is twinned and complementary structural investigations of a powder sample of beta-Pb(2)BiVO(6) by TEM diffraction studies confirmed the lattice and incommensurate modulation character. Log sigma = f(T(-1)) dependences for Pb(2)BiVO(6)-related materials (6% M-for-V-substituted compositions; M = Cr, Mn, P) are reported, which allow the characterization (E(a) and isothermal sigma values) of the beta- as well as the delta- and alpha-Pb(2)BiVO(6) varieties.

  5. Anisotropic electrical and thermal conductivity in Bi2AE2Co2O8+δ [AE = Ca, Sr1-xBax (x = 0.0, 0.25, 0.5, 0.75, 1.0)] single crystals

    NASA Astrophysics Data System (ADS)

    Dong, Song-Tao; Zhang, Bin-Bin; Xiong, Ye; Lv, Yang-Yang; Yao, Shu-Hua; Chen, Y. B.; Zhou, Jian; Zhang, Shan-Tao; Chen, Yan-Feng

    2015-09-01

    Bi2AE2Co2O8+δ (AE represents alkaline earth), constructed by stacking of rock-salt Bi2AE2O4 and triangle CoO2 layers alternatively along c-axis, is one of promising thermoelectric oxides. The most impressive feature of Bi2AE2Co2O8+δ, as reported previously, is their electrical conductivity mainly lying along CoO2 plane, adjusting Bi2AE2O4 layer simultaneously manipulates both thermal conductivity and electrical conductivity. It in turn optimizes thermoelectric performance of these materials. In this work, we characterize the anisotropic thermal and electrical conductivity along both ab-plane and c-direction of Bi2AE2Co2O8+δ (AE = Ca, Sr, Ba, Sr1-xBax) single crystals. The results substantiate that isovalence replacement in Bi2AE2Co2O8+δ remarkably modifies their electrical property along ab-plane; while their thermal conductivity along ab-plane only has a slightly difference. At the same time, both the electrical conductivity and thermal conductivity along c-axis of these materials also have dramatic changes. Certainly, the electrical resistance along c-axis is too high to be used as thermoelectric applications. These results suggest that adjusting nano-block Bi2AE2O4 layer in Bi2AE2Co2O8+δ cannot modify the thermal conductivity along high electrical conductivity plane (ab-plane here). The evolution of electrical property is discussed by Anderson localization and electron-electron interaction U. And the modification of thermal conductivity along c-axis is attributed to the microstructure difference. This work sheds more light on the manipulation of the thermal and electrical conductivity in the layered thermoelectric materials.

  6. Evidence of a pseudogap for superconducting iron-pnictide Ba0.6+δK0.4-δFe2As2 single crystals from optical conductivity measurements

    NASA Astrophysics Data System (ADS)

    Kwon, Yong Seung; Hong, Jong Beom; Jang, Yu Ran; Oh, Hyun Jin; Song, Yun Young; Min, Byeong Hun; Iizuka, Takeuya; Kimura, Shin-ichi; Balatsky, A. V.; Bang, Yunkyu

    2012-06-01

    We report the observation of pseudogap (PG) behavior in optical conductivity in an underdoped Ba0.6+δK0.4-δFe2As2 (Tonsetc ≈ 36 K) single crystal far above Tc, up to 100 K (≈3Tc). Wide separation of the energy scales of the magnetic and superconducting (SC) correlations in the Ba0.6+δK0.4-δFe2As2 sample enabled us to establish that the PG structures observed in optical conductivity in the range of 50-150 cm-1 are uniquely driven by the SC correlation, and the magnetic correlation coexists in the far separated range of about 700 cm-1. Theoretical calculations, based on the preformed Cooper pair model, provided an excellent description of the temperature evolution of the SC correlation in optical conductivity data from below to above Tc.

  7. Conducting a thermal conductivity survey

    NASA Technical Reports Server (NTRS)

    Allen, P. B.

    1985-01-01

    A physically transparent approximate theory of phonon decay rates is presented starting from a pair potential model of the interatomic forces in an insulator or semiconductor. The theory applies in the classical regime and relates the 3-phonon decay rate to the third derivative of the pair potential. Phonon dispersion relations do not need to be calculated, as sum rules relate all the needed quantities directly to the pair potential. The Brillouin zone averaged phonon lifetime turns out to involve a dimensionless measure of the anharmonicity multiplied by an effective density of states for 3-phonon decay. Results are given for rare gas and alkali halide crystals. For rare gases, the results are in good agreement with more elaborate perturbation calculations. Comparison to experimental data on phonon linewidths and thermal conductivity are made.

  8. Crystal structure and ionic conductivity of Mg-doped apatite-type lanthanum silicates La10Si6-xMgxO27-x (x = 0-0.4)

    NASA Astrophysics Data System (ADS)

    Yin, Guang-Chao; Yin, Hong; Zhong, Lin-Hong; Sun, Mei-Ling; Zhang, Jun-Kai; Xie, Xiao-Jun; Cong, Ri-Dong; Wang, Xin; Gao, Wei; Cui, Qi-Liang

    2014-04-01

    Lanthanum silicates La10Si6-xMgxO27-x (x = 0-0.4) were prepared by solid state synthesis to investigate the effect of Mg doping on crystal structure and ionic conductivity. Rietveld analysis of the powder XRD patterns reveals that Mg substitution on Si site results in significant enlargement of channel triangles, favoring oxide-ion conduction. Furthermore, an increase of Mg concentration significantly influences the linear density of interstitial oxygen, which plays an important role in ionic conductivity. The Arrhenius plots of La10Si6-xMgxO27-x (x = 0-0.4) suggest that Mg-doped samples present higher conductivity and lower activation energy than non-doped La10Si6O27, and La10Si5.8Mg0.2O26.8 exhibits the highest conductivity with a value of 3.0×10-2 S ·cm-1 at 700 °C. Such conductive behavior agrees well with the refined results. The corresponding mechanism has been discussed in this paper.

  9. Apparatus for mounting crystal

    DOEpatents

    Longeway, Paul A.

    1985-01-01

    A thickness monitor useful in deposition or etching reactor systems comprising a crystal-controlled oscillator in which the crystal is deposited or etched to change the frequency of the oscillator. The crystal rests within a thermally conductive metallic housing and arranged to be temperature controlled. Electrode contacts are made to the surface primarily by gravity force such that the crystal is substantially free of stress otherwise induced by high temperature.

  10. Defect structure and ionic conductivity of Ca{sub 1-x}Sc{sub x}F{sub 2+x} (0.02 {<=} x {<=} 0.15) single crystals

    SciTech Connect

    Sulyanova, E. A. Molchanov, V. N.; Sorokin, N. I.; Karimov, D. N.; Sulyanov, S. N.; Sobolev, B. P.

    2009-07-15

    Single crystals of the Ca{sub 1-x}Sc{sub x}F{sub 2+x}(x = 0.106, 0.132, 0.156) solid solutions (CaF{sub 2} structure type, space group Fm3-barm) are investigated using X-ray diffraction. It is revealed that the crystals under investigation contain vacancies in the 8c positions and interstitial fluorine ions in the 48i positions. The coordination number of Sc{sup 3+} ions in the structure of the Ca{sub 1-x}Sc{sub x}F{sub 2+x} solid solutions is equal to eight. The specific features of the concentration dependences of the ionic conductivity and the activation energy of ion transfer for the Ca{sub 1-x}Sc{sub x}F{sub 2+x}(0.02 {<=} x {<=} 0.15) solid solutions are explained in the framework of the percolation model of conducting 'defect regions.' The percolation threshold equal to 3-5 mol % ScF{sub 3} corresponds to the model of [Ca{sub 14-n}Sc{sub n}F{sub 68}] octacubic clusters containing fluorine ions in the 48i positions. The ionic conductivity of the Ca{sub 1-x}Sc{sub x}F{sub 2+x} solid solutions is analyzed in comparison with the change in this characteristic for the series of Ca{sub 0.8}R{sub 0.2}F{sub 2.2} crystals with rare-earth elements.

  11. Phononic crystal devices

    DOEpatents

    El-Kady, Ihab F [Albuquerque, NM; Olsson, Roy H [Albuquerque, NM

    2012-01-10

    Phononic crystals that have the ability to modify and control the thermal black body phonon distribution and the phonon component of heat transport in a solid. In particular, the thermal conductivity and heat capacity can be modified by altering the phonon density of states in a phononic crystal. The present invention is directed to phononic crystal devices and materials such as radio frequency (RF) tags powered from ambient heat, dielectrics with extremely low thermal conductivity, thermoelectric materials with a higher ratio of electrical-to-thermal conductivity, materials with phononically engineered heat capacity, phononic crystal waveguides that enable accelerated cooling, and a variety of low temperature application devices.

  12. The sensitivity of the electron transport within bulk zinc-blende gallium nitride to variations in the crystal temperature, the doping concentration, and the non-parabolicity coefficient associated with the lowest energy conduction band valley

    NASA Astrophysics Data System (ADS)

    Siddiqua, Poppy; O'Leary, Stephen K.

    2016-09-01

    Within the framework of a semi-classical three-valley Monte Carlo simulation approach, we analyze the steady-state and transient electron transport that occurs within bulk zinc-blende gallium nitride. In particular, we examine how the steady-state and transient electron transport that occurs within this material changes in response to variations in the crystal temperature, the doping concentration, and the non-parabolicity coefficient associated with the lowest energy conduction band valley. These results are then contrasted with those corresponding to a number of other compound semiconductors of interest.

  13. Liquid crystal self-assembly of halloysite nanotubes in ionic liquids: a novel soft nanocomposite ionogel electrolyte with high anisotropic ionic conductivity and thermal stability

    NASA Astrophysics Data System (ADS)

    Zhao, Ningning; Liu, Yulin; Zhao, Xiaomeng; Song, Hongzan

    2016-01-01

    We report a novel class of liquid crystalline (LC) nanohybrid ionogels fabricated via self-assembly of natural halloysite nanotubes (HNTs) in ionic liquids (ILs). The obtained ionogels are very stable and nonvolatile and show LC phases over a wide temperature range. Remarkably, the nanocomposite ionogels exhibit high anisotropic ionic conductivity after shear, and their room temperature ionic conductivity can reach 3.8 × 10-3 S cm-1 for aligned nanotubes perpendicular to the electrode even when the HNTs content increases to 40 wt%, which is 380 times higher than that obtained for aligned nanotubes parallel to the electrode, which is 1.0 × 10-5 S cm-1. Crucially, the obtained LC nanocomposite ionogels have very high thermal stability, which can sustain 400 °C thermal treatment. The findings will promote the development of novel nanocomposite ionogel electrolytes with faster ion transport and larger anisotropic conductivity.We report a novel class of liquid crystalline (LC) nanohybrid ionogels fabricated via self-assembly of natural halloysite nanotubes (HNTs) in ionic liquids (ILs). The obtained ionogels are very stable and nonvolatile and show LC phases over a wide temperature range. Remarkably, the nanocomposite ionogels exhibit high anisotropic ionic conductivity after shear, and their room temperature ionic conductivity can reach 3.8 × 10-3 S cm-1 for aligned nanotubes perpendicular to the electrode even when the HNTs content increases to 40 wt%, which is 380 times higher than that obtained for aligned nanotubes parallel to the electrode, which is 1.0 × 10-5 S cm-1. Crucially, the obtained LC nanocomposite ionogels have very high thermal stability, which can sustain 400 °C thermal treatment. The findings will promote the development of novel nanocomposite ionogel electrolytes with faster ion transport and larger anisotropic conductivity. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06888f

  14. Desired crystal oriented LiFePO4 nanoplatelets in situ anchored on a graphene cross-linked conductive network for fast lithium storage.

    PubMed

    Wang, Bo; Liu, Anmin; Abdulla, Wael Al; Wang, Dianlong; Zhao, X S

    2015-05-21

    Electron transfer and lithium ion diffusion rates are the key factors limiting the lithium ion storage in anisotropic LiFePO4 electrodes. In this work, we employed a facile solvothermal method to synthesize a "platelet-on-sheet" LiFePO4/graphene composite (LFP@GNs), which is LiFePO4 nanoplatelets in situ grown on graphene sheets with highly oriented (010) facets of LiFePO4 crystals. Such a two-phase contact mode with graphene sheets cross-linked to form a three-dimensional porous network is favourable for both fast lithium ion and electron transports. As a result, the designed LFP@GNs displayed a high rate capability (∼56 mA h g(-1) at 60 C) and long life cycling stability (∼87% capacity retention over 1000 cycles at 10 C). For comparison purposes, samples ex situ modified with graphene (LFP/GNs) as well as pure LiFePO4 platelets (LFP) were also prepared and investigated. More importantly, the obtained LFP@GNs can be used as a basic unit for constructing more complex structures to further improve electrochemical performance, such as coating the exposed LFP surface with a thin layer of carbon to build a C@LFP@GN composite to further enhance its cycling stability (∼98% capacity retention over 1000 cycles at 10 C).

  15. Synthesis, crystal structure and mono-dimensional thallium ion conduction of TlFe{sub 0.22}Al{sub 0.78}As{sub 2}O{sub 7}

    SciTech Connect

    Ouerfelli, Najoua; Guesmi, Abderrahmen Mazza, Daniele; Madani, Adel; Zid, Mohamed Faouzi; Driss, Ahmed

    2007-04-15

    A new solid solution TlFe{sub 0.22}Al{sub 0.78}As{sub 2}O{sub 7} has been synthesized by a solid-state reaction. The structure of the title compound has been determined from a single-crystal X-ray diffraction and refined to final values of the reliability factors: R(F {sup 2})=0.030 and wR(F {sup 2})=0.081 for 1343 independent reflections with I>2{sigma}(I). It crystallizes in the triclinic space group P-1, with a=6.296(2) A, b=6.397(2) A, c=8.242(2) A, {alpha}=96.74(2){sup o}, {beta}=103.78(2){sup o}, {gamma}=102.99(3){sup o}, V=309.0(2) A{sup 3} and Z=2. The structure can be described as a three-dimensional framework containing (Fe/Al)O{sub 6} octahedra connected through As{sub 2}O{sub 7} groups. The metallic units and diarsenate groups share oxygen corners to form a three-dimensional framework with interconnected tunnels parallel to the a, b and c directions, where Tl{sup +} cations are located. The ionic conductivity measurements are performed on pellets of the polycrystalline powder. At 683 K, The conductivity value is 5.23x10{sup -6} S cm{sup -1} and the ionic jump activation energy is 0.656 eV. The bond valence analysis reveals that the ionic conductivity is ensured by Tl{sup +} along the [001] direction. - Graphical abstract: Optimized trajectory for Tl(1)-Tl(2) jump.

  16. Mean carrier transport properties and charge collection dynamics of single-crystal, natural type IIa diamonds from ion-induced conductivity measurements

    SciTech Connect

    Han, Sung Su

    1993-09-01

    Ion-induced conductivity has been used to investigate the detector characteristics of diamond detectors. Both integrated-charge, and time-resolved current measurements were performed to examine the mean carrier transport properties of diamond and the dynamics of charge collection under highly-localized and high-density excitation conditions. The integrated-charge measurements were conducted with a standard pulse-counting system with 241Am radioactivity as the excitation source for the detectors. The time-resolved current measurements were performed using a 70 GHz random sampling oscilloscope with the detectors incorporated into high-speed microstrip transmission lines and the excitation source for these measurements was an ion beam of either 5-MeV He+ or 10-MeV Si3+. The detectors used in both experiments can be described as metal-semiconductor-metal (MSM) devices where a volume of the detector material is sandwiched between two metal plates. A charge collection model was developed to interpret the integrated-charge measurements which enabled estimation of the energy required to produce an electron-hole pair (ϵdi) and the mean carrier transport properties in diamond, such as carrier mobility and lifetime, and the behavior of the electrical contacts to diamond.

  17. Quasi-one-dimensional hopping conductivity of the spin-ladder CaCu2O3 single crystals: Influence of the cation and oxygen nonstoichiometry

    NASA Astrophysics Data System (ADS)

    Lisunov, K. G.; Wizent, N.; Waske, A.; Werner, J.; Tristan, N.; Sekar, C.; Krabbes, G.; Behr, G.; Arushanov, E.; Büchner, B.

    2008-06-01

    The resistivity ρ(T) of the spin-ladder compound CaCu2O3 measured along the Cu-O-Cu leg (j ∥b) exhibits a strongly activated character. It increases from ˜104 to ˜109 Ωm if T decreases from 350 to 100 K. The charge transfer above T ˜200 K is governed by a quasi-one-dimensional (1D) nearest-neighbor hopping (NNH) conductivity mechanism characterized by the law ρ(T )˜exp(Ea/kT). Below 200 K a novel quasi-1D variable-range hopping (VRH) conductivity law ρ(T )˜exp[(T0/T)3/4] is observed, predicted recently by Fogler, Teber, and Shklovskii [Phys. Rev. B 69, 035413 (2004)]. The NNH activation energy Ea and the VRH characteristic temperature T0 exhibit high sensitivity to the cation (Ca, Cu) content, decreasing by 2.3-2.5 times and by 3.0-3.2 times, respectively, when the composition of Ca is changed from 0.854 to 0.786-0.798 and the composition of Cu from 2.039 to 2.159-2.163. The behavior of Ea and T0 can be attributed to a corresponding variation of the concentration of intrinsic defects associated with Cu vacancies. On the other hand, no direct dependence of Ea and T0 to the excess oxygen concentration is observed.

  18. High frequency cut-off in 1/f conductivity noise of hole-doped La1-x Ca x MnO3 manganite single crystals

    NASA Astrophysics Data System (ADS)

    Przybytek, Jacek; Fink-Finowicki, Jan; Puźniak, Roman; Jung, Grzegorz

    2016-05-01

    High frequency bias and temperature-dependent Lorentzian cut-off has been observed in the 1/f spectra of the conductivity fluctuations in low hole-doped ferromagnetic insulating La1-x Ca x MnO3 manganite at low temperatures. The cut-off frequency depends on dc current bias and temperature. The high frequency cut-off has been tentatively associated with intrinsic limits of the appearance of 1/f noise in the hopping regime of the Coulomb glass state. The assumption is validated by the fact that the Efros-Shklovskii temperature {{T}\\text{ES}} , estimated from the fit of the model to the experimentally measured temperature dependence of the cut-off frequency, has the same value as the temperature {{T}\\text{ES}} evaluated independently from the temperature dependence of the resistivity in the corresponding temperature range.

  19. Phase behavior of 1-dodecyl-3-methylimidazolium fluorohydrogenate salts (C12MIm(FH)(n)F, n = 1.0-2.3) and their anisotropic ionic conductivity as ionic liquid crystal electrolytes.

    PubMed

    Xu, Fei; Matsumoto, Kazuhiko; Hagiwara, Rika

    2012-08-23

    The effects of the HF composition, n, in 1-dodecyl-3-methylimidazolium fluorohydrogenate salts (C(12)MIm(FH)(n)F, n = 1.0-2.3) on their physicochemical and structural properties have been investigated using infrared spectroscopy, thermal analysis, polarized optical microscopy, X-ray diffraction, and anisotropic ionic conductivity measurements. The phase diagram of C(12)MIm(FH)(n)F (n vs transition temperature) suggests that C(12)MIm(FH)(n)F is a mixed crystal system that has a boundary around n = 1.9. For all compositions, a liquid crystalline mesophase with a smectic A interdigitated bilayer structure is observed. The temperature range of the mesophase decreases with increasing n value (from 61.8 °C for C(12)MIm(FH)(1.0)F to 37.0 °C for C(12)MIm(FH)(2.3)F). The layer spacing of the smectic structure decreases with increasing n value or increasing temperature. Two structural types with different layer spacings are observed in the crystalline phase (type I, 1.0 ≤ n ≤ 1.9, and type II, 1.9 ≤ n ≤ 2.3). Ionic conductivities parallel and perpendicular to the smectic layers (σ(||) and σ([perpendicular])) increase with increasing n value, whereas the anisotropy of the ionic conductivities (σ(||)/σ([perpendicular])) is independent of the n value, since the thickness of the insulating sheet formed by the dodecyl group remains nearly unchanged.

  20. Crystal structure of new Li + ion conducting perovskites: Li 2 xCa 0.5- xTaO 3 and Li 0.2[Ca 1- ySr y] 0.4TaO 3

    NASA Astrophysics Data System (ADS)

    Pham, Quoc Nghi; Crosnier-Lopez, Marie-Pierre; Le Berre, Françoise; Fauth, François; Fourquet, Jean-Louis

    2004-09-01

    Two new solid solutions—Li 2 xCa 0.5- xTaO 3 (0.05⩽ x⩽0.25) and Li 0.2[Ca 1- ySr y] 0.4TaO 3 (0< y⩽0.15)—based on the A defective ABO 3 perovskite structural type, are synthesized. The crystal structures of these Li + ion conducting compounds are solved from synchrotron radiation and conventional X-ray powder diffraction data. The unit cells exhibit a classical orthorhombic distortion of the cubic perovskite model (space group Pnma No. 62) with parameters close to 2a p, 2 ap, 2a p ( ap, primitive cubic cell parameter). The distortion of the cubic aristotype arises from the three tilts system a+b-b- of the TaO 6 octahedra. For the same lithium content ( x=0.10), the Sr 2+ substitution to Ca 2+ is found to enhance the electrical conductivity by quasi-one order of magnitude (at 200 °C, bulk dc conductivity values are close to 2.3×10 -6 and 1.1×10 -5 S cm -1 for Li 0.2Ca 0.4TaO 3 and Li 0.2[Ca 0.9Sr 0.1] 0.4TaO 3, respectively).

  1. Synthesis, crystal structure, electronic structure and electrical conductivity of La3GeSb0.31Se7 and La3SnFe0.61Se7

    NASA Astrophysics Data System (ADS)

    Assoud, Abdeljalil; Sankar, Cheriyedath Raj; Kleinke, Holger

    2014-12-01

    The selenides La3EM1-xSe7 (La6E2M2-xSe14) adopt the Ce6Al3.33S14 structure type. La3GeSb0.31Se7 and La3SnFe0.61Se7 crystallize in the non-centrosymmetric space group P63 with La replacing Ce in the 6c site, E = Ge or Sn replacing Al in the 2b site and M = Fe or Sb replacing the other, deficient Al site (2a). The structure contains La atoms in square antiprisms of Se atoms, isolated distorted [ESe4] tetrahedra, and face sharing distorted [MSe6] octahedra forming a linear chain along the c-axis with short M-M distances. Band structure calculations predict semiconducting character with different gaps, which was demonstrated by electrical conductivity measurements and reflected in their different colors.

  2. Crystal structure of the cystic fibrosis transmembrane conductance regulator inhibitory factor Cif reveals novel active-site features of an epoxide hydrolase virulence factor.

    PubMed

    Bahl, Christopher D; Morisseau, Christophe; Bomberger, Jennifer M; Stanton, Bruce A; Hammock, Bruce D; O'Toole, George A; Madden, Dean R

    2010-04-01

    Cystic fibrosis transmembrane conductance regulator (CFTR) inhibitory factor (Cif) is a virulence factor secreted by Pseudomonas aeruginosa that reduces the quantity of CFTR in the apical membrane of human airway epithelial cells. Initial sequence analysis suggested that Cif is an epoxide hydrolase (EH), but its sequence violates two strictly conserved EH motifs and also is compatible with other alpha/beta hydrolase family members with diverse substrate specificities. To investigate the mechanistic basis of Cif activity, we have determined its structure at 1.8-A resolution by X-ray crystallography. The catalytic triad consists of residues Asp129, His297, and Glu153, which are conserved across the family of EHs. At other positions, sequence deviations from canonical EH active-site motifs are stereochemically conservative. Furthermore, detailed enzymatic analysis confirms that Cif catalyzes the hydrolysis of epoxide compounds, with specific activity against both epibromohydrin and cis-stilbene oxide, but with a relatively narrow range of substrate selectivity. Although closely related to two other classes of alpha/beta hydrolase in both sequence and structure, Cif does not exhibit activity as either a haloacetate dehalogenase or a haloalkane dehalogenase. A reassessment of the structural and functional consequences of the H269A mutation suggests that Cif's effect on host-cell CFTR expression requires the hydrolysis of an extended endogenous epoxide substrate.

  3. Crystal Structure of the Cystic Fibrosis Transmembrane Conductance Regulator Inhibitory Factor Cif Reveals Novel Active-Site Features of an Epoxide Hydrolase Virulence Factor

    SciTech Connect

    Bahl, C.; Morisseau, C; Bomberger, J; Stanton, B; Hammock, B; O' Toole, G; Madden, D

    2010-01-01

    Cystic fibrosis transmembrane conductance regulator (CFTR) inhibitory factor (Cif) is a virulence factor secreted by Pseudomonas aeruginosa that reduces the quantity of CFTR in the apical membrane of human airway epithelial cells. Initial sequence analysis suggested that Cif is an epoxide hydrolase (EH), but its sequence violates two strictly conserved EH motifs and also is compatible with other {alpha}/{beta} hydrolase family members with diverse substrate specificities. To investigate the mechanistic basis of Cif activity, we have determined its structure at 1.8-{angstrom} resolution by X-ray crystallography. The catalytic triad consists of residues Asp129, His297, and Glu153, which are conserved across the family of EHs. At other positions, sequence deviations from canonical EH active-site motifs are stereochemically conservative. Furthermore, detailed enzymatic analysis confirms that Cif catalyzes the hydrolysis of epoxide compounds, with specific activity against both epibromohydrin and cis-stilbene oxide, but with a relatively narrow range of substrate selectivity. Although closely related to two other classes of {alpha}/{beta} hydrolase in both sequence and structure, Cif does not exhibit activity as either a haloacetate dehalogenase or a haloalkane dehalogenase. A reassessment of the structural and functional consequences of the H269A mutation suggests that Cif's effect on host-cell CFTR expression requires the hydrolysis of an extended endogenous epoxide substrate.

  4. Nanostructured crystals of fluorite phases Sr1- x R x F2 + x and their ordering: 11. Influence of structural cluster ordering on fluorine ionic conductivity of the Sr1- x Lu x F2 + x Phase

    NASA Astrophysics Data System (ADS)

    Sorokin, N. I.; Sobolev, B. P.

    2015-11-01

    Ionic conductivity σ of the ordered phase (binary compound) Sr4Lu3F17 (sp. gr. Roverline 3 , Z = 6) with a fluorite-derivative structure obtained from a melt has been studied for the first time by impedance spectroscopy. The octahedral-cubic clusters {Sr8[Lu6F37]F32} formed in the structure of the disordered (fluorite) phase Sr1- x Lu x F2 + x (sp. gr. Fmoverline 3 m, Z = 4) become structural blocks with long-range order in the Sr4Lu3F17 compound. The effect of the clusters on the conductivity of nonstoichiometric phases Sr1- x Lu x F2 + x (2-25 mol % LuF3) and Sr4Lu3F17 (42.86 mol % LuF3) has been studied for the first time. Cluster ordering in Sr4Lu3F17 is accompanied by a decrease in the conductivity (σ = 6.3 × 10-7 S/cm at 673 K and Δ H σ = 1.12 eV) by a factor of 25 with respect to a disordered Sr0.75Lu0.25F2.75 crystal (experiment) and by a factor of 125 with respect to the saturated fluorite phase Sr0.63Lu0.37F2.37 (extrapolation). The unit-cell volume changes per F- ion during ordering are small and should not significantly affect the fluorine ion conductivity.

  5. Indicators: Conductivity

    EPA Pesticide Factsheets

    Conductivity is a measure of the ability of water to pass an electrical current. Because dissolved salts and other inorganic chemicals conduct electrical current, conductivity increases as salinity increases.

  6. Minimizing radiation damage in nonlinear optical crystals

    DOEpatents

    Cooke, D.W.; Bennett, B.L.; Cockroft, N.J.

    1998-09-08

    Methods are disclosed for minimizing laser induced damage to nonlinear crystals, such as KTP crystals, involving various means for electrically grounding the crystals in order to diffuse electrical discharges within the crystals caused by the incident laser beam. In certain embodiments, electrically conductive material is deposited onto or into surfaces of the nonlinear crystals and the electrically conductive surfaces are connected to an electrical ground. To minimize electrical discharges on crystal surfaces that are not covered by the grounded electrically conductive material, a vacuum may be created around the nonlinear crystal. 5 figs.

  7. Minimizing radiation damage in nonlinear optical crystals

    DOEpatents

    Cooke, D. Wayne; Bennett, Bryan L.; Cockroft, Nigel J.

    1998-01-01

    Methods are disclosed for minimizing laser induced damage to nonlinear crystals, such as KTP crystals, involving various means for electrically grounding the crystals in order to diffuse electrical discharges within the crystals caused by the incident laser beam. In certain embodiments, electrically conductive material is deposited onto or into surfaces of the nonlinear crystals and the electrically conductive surfaces are connected to an electrical ground. To minimize electrical discharges on crystal surfaces that are not covered by the grounded electrically conductive material, a vacuum may be created around the nonlinear crystal.

  8. Crystal structure and ion conductivity of a new mixed-anion phosphate LiMg{sub 3}(PO{sub 4})P{sub 2}O{sub 7}

    SciTech Connect

    Kim, Sung-Chul; Lee, Mi-Sun; Kang, Jinyeong; Kim, Young-Il; Kim, Seung-Joo

    2015-05-15

    A new lithium-containing phosphate, LiMg{sub 3}(PO{sub 4})P{sub 2}O{sub 7}, was prepared by a solid-state reaction, and it was characterized by an ab initio structure determination method on the basis of synchrotron powder X-ray diffraction data. LiMg{sub 3}(PO{sub 4})P{sub 2}O{sub 7} was found to be orthorhombic (space group Pnma) with lattice parameters a=9.0387(1) Å, b=10.6072(1) Å, c=8.3065(1) Å, and V=796.39(1) Å{sup 3}. The structure features infinite [Mg{sub 3}O{sub 10}]{sub ∞} layers that are parallel to the bc plane and that are interconnected along the a axis by PO{sub 4} and P{sub 2}O{sub 7} groups. The [Mg{sub 3}O{sub 10}]{sub ∞} layer contains Mg{sub 3}O{sub 14} trimers that are formed by three edge-shared MgO{sub 6} octahedra. The PO{sub 4} and P{sub 2}O{sub 7} groups are located alternatively between [Mg{sub 3}O{sub 10}]{sub ∞} layers. This gives rise to a three-dimensional framework that contains large tunnels along the directions [1 0 0] and [0 1 0]; the Li{sup +} ions are stabilized in these tunnels. AC impedance spectroscopy shows that LiMg{sub 3}(PO{sub 4})P{sub 2}O{sub 7} has an ionic conductivity of 3.40×10{sup −5} S cm{sup −1} at 769 K, with an activation energy of 1.17 eV. - Graphical abstract: Polyhedral view of LiMg3(PO4)P2O7. Li+ ions are represented by orange spheres, MgO6 groups by octahedra, and PO4 groups by tetrahedra. - Highlights: • New compound LiMg{sub 3}(PO{sub 4})P{sub 2}O{sub 7} is reported. • The crystal structure is investigated by synchrotron XRD analysis. • The structure features [Mg{sub 3}O{sub 10}]{sub ∞} layers with interconnecting PO{sub 4} and P{sub 2}O{sub 7} groups. • Correlation between the crystal structure and ionic conductivity is discussed.

  9. Protein crystallization in microgravity.

    PubMed

    Aibara, S; Shibata, K; Morita, Y

    1997-12-01

    A space experiment involving protein crystallization was conducted in a microgravity environment using the space shuttle "Endeavour" of STS-47, on a 9-day mission from September 12th to 20th in 1992. The crystallization was carried out according to a batch method, and 5 proteins were selected as flight samples for crystallization. Two of these proteins: hen egg-white lysozyme and co-amino acid: pyruvate aminotransferase from Pseudomonas sp. F-126, were obtained as single crystals of good diffraction quality. Since 1992 we have carried out several space experiments for protein crystallization aboard space shuttles and the space station MIR. Our experimental results obtained mainly from hen egg-white lysozyme are described below, focusing on the effects of microgravity on protein crystal growth.

  10. Crystal Meth

    MedlinePlus

    ... from Other Parents Stories of Hope Crystal meth Crystal meth Story of Hope by giovanni January 3, ... about my drug addiction having to deal with Crystal meth. I am now in recovery and fighting ...

  11. Crystal Meth

    MedlinePlus

    ... Navigation Home / Stories of Hope / Crystal meth Crystal meth Story Of Hope By giovanni January 3rd, 2013 ... my drug addiction having to deal with Crystal meth. I am now in recovery and fighting my ...

  12. Crystal Creations.

    ERIC Educational Resources Information Center

    Whipple, Nona; Whitmore, Sherry

    1989-01-01

    Presents a many-faceted learning approach to the study of crystals. Provides instructions for performing activities including crystal growth and patterns, creating miniature simulations of crystal-containing rock formations, charcoal and sponge gardens, and snowflakes. (RT)

  13. DANCE (Detector for Advanced Neutron Capture Experiments) is a 4π array of BaF2 crystals installed at LANSCE, Lujan Center. Neutron capture measurements on ^157Gd and ^89Y nuclei were conducted using this facility.

    NASA Astrophysics Data System (ADS)

    Chyzh, A.; Mitchell, G.; Vieira, D.; Bredeweg, T.; Ullmann, J.; Jandel, M.; Couture, A.; Keksis, A.; Rundberg, R.; Wilhelmy, J.; O'Donnell, J.; Baramsai, B.; Haight, R.; Wouters, J.; Krticka, M.; Parker, W.; Becker, J.; Agvaanlusan, U.

    2009-10-01

    DANCE (Detector for Advanced Neutron Capture Experiments) is a 4π array of BaF2 crystals installed at LANSCE, Lujan Center. Neutron capture measurements on ^157Gd and ^89Y nuclei were conducted using this facility. The absolute cross sections of the ^89Y(n,γ) reaction was measured for the first time ever in the neutron energy range of 10 eV -- 10 keV and improvements were made in the 10 -- 300 keV range. The error bars were significantly reduced and number of cross section points was increased since the past ^89Y(n,γ) experiments. The ^157Gd(n,γ) cross section was determined at En = 20 eV -- 300 keV by normalizing the experimental DANCE data to a well known resonance taken from the ENDF/B-VII library. Computer simulations of the ^157Gd(n,γ) cascades and DANCE pulse height function were made using DICEBOX and GEANT4 codes and simulated Esum and Eγ spectra are compared to the experimental DANCE data. Values of spin and photon strength function (PSF) of the ^157Gd(n,γ) resonances are provided in the range of En = 2 -- 300 eV using spin dependence upon a γ-ray multiplicity.

  14. Electrical Conductivity.

    ERIC Educational Resources Information Center

    Allen, Philip B.

    1979-01-01

    Examines Drude's classical (1900) theory of electrical conduction, details the objections to and successes of the 1900 theory, and investigates the Quantum (1928) theory of conduction, reviewing its successes and limitations. (BT)

  15. Thermal evolution of the crystal structure of proton conducting BaCe0.8Y0.2O3-δ from high-resolution neutron diffraction in dry and humid atmosphere.

    PubMed

    Eriksson Andersson, Annika K; Selbach, Sverre M; Grande, Tor; Knee, Christopher S

    2015-06-21

    The crystal structure of the proton conducting perovskite BaCe(0.8)Y(0.2)O(3-δ) (BCY20) has been studied via high-resolution in situ neutron diffraction performed in controlled dry and humid (heavy water) oxygen flow. Two phase transitions, cubic Pm3[combining macron]m→R3[combining macron]c (775 °C)→Imma (250 °C) were observed on cooling from 1000 °C in dry O(2). A significant shift of the phase stability fields was observed on cooling in wet oxygen (pD(2)O ≈ 0.2 atm) with the R3[combining macron]c structure stabilised at 900 °C, and the R3[combining macron]c→Imma transition occurring at 675 °C. On cooling below 400 °C a monoclinic, I2/m, phase started to appear. The structural dependence on hydration level is primarily due to the de-stabilisation of the correlated, octahedra tilts as a consequence of structural relaxation around the oxygen vacancies present in the non-hydrated phase. The tendency of hydrated BaCe(0.8)Y(0.2)O(3-δ) to show octahedral tilting is also found to be enhanced, indicating that the deuteronic (protonic) defects influence the crystal structure, possibly via hydrogen bonding. Stabilisation of the monoclinic I2/m phase is attributed to the structural effect of deuterons that is inferred to increase on cooling as deuterons localise to a greater extent. Changing from wet oxidising (O(2) + D2O(g)) to wet reducing (5% H2 in Ar + D2O(g)) atmosphere did not influence the structure or the phase stability, indicating that Ce(4+) was not reduced under the present conditions. Based on the observed cell volume expansion protonic defects are present in the material at 900 °C at a D(2)O partial pressure of ∼0.2 atm. The origin of the chemical expansion is explained by the effective size of the oxygen vacancy being significantly smaller than the [OD] defect. Rietveld analysis has been used to locate possible sites for the deuterons in the high temperature, R3[combining macron]c and Imma, phases that are most relevant for proton transport.

  16. Electrical Conductivity.

    ERIC Educational Resources Information Center

    Hershey, David R.; Sand, Susan

    1993-01-01

    Explains how electrical conductivity (EC) can be used to measure ion concentration in solutions. Describes instrumentation for the measurement, temperature dependence and EC, and the EC of common substances. (PR)

  17. Virtual Crystallizer

    SciTech Connect

    Land, T A; Dylla-Spears, R; Thorsness, C B

    2006-08-29

    Large dihydrogen phosphate (KDP) crystals are grown in large crystallizers to provide raw material for the manufacture of optical components for large laser systems. It is a challenge to grow crystal with sufficient mass and geometric properties to allow large optical plates to be cut from them. In addition, KDP has long been the canonical solution crystal for study of growth processes. To assist in the production of the crystals and the understanding of crystal growth phenomena, analysis of growth habits of large KDP crystals has been studied, small scale kinetic experiments have been performed, mass transfer rates in model systems have been measured, and computational-fluid-mechanics tools have been used to develop an engineering model of the crystal growth process. The model has been tested by looking at its ability to simulate the growth of nine KDP boules that all weighed more than 200 kg.

  18. Crystal growing

    NASA Technical Reports Server (NTRS)

    Neville, J. P.

    1990-01-01

    One objective is to demonstrate the way crystals grow and how they affect the behavior of material. Another objective is to compare the growth of crystals in metals and nonmetals. The procedures, which involve a supersaturated solution of a salt that will separate into crystals on cooling and the pouring off of an eutectic solution to expose the crystals formed by a solid solution when an alloy of two metals forms a solid and eutectic solution on cooling, are described.

  19. Appropriate Conduct

    ERIC Educational Resources Information Center

    Di Lullo, Louis

    2004-01-01

    Many years ago when the author assumed the role of assistant principal for school climate, discipline, and attendance, he inherited many school policies and guidelines that were outdated, unfair, and without merit in the current school climate. Because the school conduct code had not been revised since the school opened in 1960, many of the…

  20. Apoferritin crystals

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Dr. Alexander Chernov, of the Universities Space Research Association (USRA) and based at Marshall Space Flight Center, is investigating why protein crystals grown in space are, in about 20 percent of cases, better-ordered than those grown on the ground. They are testing the idea that the amount of impurities trapped by space-grown crystals may be different than the amount trapped by crystals grown on Earth because convection is negligible in microgravity. The concentrations or impurities in many space-grown crystals turned out to be several times lower than that in the terrestrial ones, sometimes below the detection limit. The ground-based experiment also showed that the amount of impurities per unit volume of the crystals was usually higher than the amount per unit volume of the solution. This means that a growing crystal actually purifies the solution in its immediate vicinity. Here, an impurity depletion zone is created around apoferritin crystals grown in gel, imitating microgravity conditions.

  1. The Effect of Ionic Liquids on Protein Crystallization and X-ray Diffraction Resolution

    SciTech Connect

    Judge, Russell A.; Takahashi, Sumiko; Longenecker, Kenton L.; Fry, Elizabeth H.; Abad-Zapatero, Cele; Chiu, Mark L.

    2009-09-08

    Ionic liquids exhibit a variety of properties that make them attractive solvents for biomaterials. Given the potential for productive interaction between ionic liquids and biological macromolecules, we investigated the use of ionic liquids as precipitating agents and additives for protein crystallization for six model proteins (lysozyme, catalase, myoglobin, trypsin, glucose isomerase, and xylanase). The ionic liquids produced changes in crystal morphology and mediated significant increases in crystal size in some cases. Crystals grown using ionic liquids as precipitating agents or as additives provided X-ray diffraction resolution similar to or better than that obtained without ionic liquids. Based upon the experiments performed with model proteins, the ionic liquids were used as additives for the crystallization of the poorly diffracting monoclonal antibody 106.3 Fab in complex with the B-type natriuretic peptide (5-13). The ionic liquids improved the crystallization behavior and provided improved diffraction resulting in the determination of the structure. Ionic liquids should be considered as useful additives for the crystallization of other proteins.

  2. Lysozyme Crystal

    NASA Technical Reports Server (NTRS)

    2004-01-01

    To the crystallographer, this may not be a diamond but it is just as priceless. A Lysozyme crystal grown in orbit looks great under a microscope, but the real test is X-ray crystallography. The colors are caused by polarizing filters. Proteins can form crystals generated by rows and columns of molecules that form up like soldiers on a parade ground. Shining X-rays through a crystal will produce a pattern of dots that can be decoded to reveal the arrangement of the atoms in the molecules making up the crystal. Like the troops in formation, uniformity and order are everything in X-ray crystallography. X-rays have much shorter wavelengths than visible light, so the best looking crystals under the microscope won't necessarily pass muster under the X-rays. In order to have crystals to use for X-ray diffraction studies, crystals need to be fairly large and well ordered. Scientists also need lots of crystals since exposure to air, the process of X-raying them, and other factors destroy them. Growing protein crystals in space has yielded striking results. Lysozyme's structure is well known and it has become a standard in many crystallization studies on Earth and in space.

  3. Crystallization-induced properties from morphology-controlled organic crystals.

    PubMed

    Park, Chibeom; Park, Ji Eun; Choi, Hee Cheul

    2014-08-19

    During the past two decades, many materials chemists have focused on the development of organic molecules that can serve as the basis of cost-effective and flexible electronic, optical, and energy conversion devices. Among the potential candidate molecules, metal-free or metal-containing conjugated organic molecules offer high-order electronic conjugation levels that can directly support fast charge carrier transport, rapid optoelectric responses, and reliable exciton manipulation. Early studies of these molecules focused on the design and synthesis of organic unit molecules that exhibit active electrical and optical properties when produced in the form of thin film devices. Since then, researchers have worked to enhance the properties upon crystallization of the unit molecules as single crystals provide higher carrier mobilities and exciton recombination yields. Most recently, researchers have conducted in-depth studies to understand how crystallization induces property changes, especially those that depend on specific crystal surfaces. The different properties that depend on the crystal facets have been of particular interest. Most unit molecules have anisotropic structures, and therefore produce crystals with several unique crystal facets with dissimilar molecular arrangements. These structural differences would also lead to diverse electrical conductance, optical absorption/emission, and even chemical interaction properties depending on the crystal facet investigated. To study the effects of crystallization and crystal facet-dependent property changes, researchers must grow or synthesize crystals of highly conjugated molecules that have both a variety of morphologies and high crystallinity. Morphologically well-defined organic crystals, that form structures such as wires, rods, disks, and cubes, provide objects that researchers can use to evaluate these material properties. Such structures typically occur as single crystals with well-developed facets with

  4. Electrical Conductivity in Transition Metals

    ERIC Educational Resources Information Center

    Talbot, Christopher; Vickneson, Kishanda

    2013-01-01

    The aim of this "Science Note" is to describe how to test the electron-sea model to determine whether it accurately predicts relative electrical conductivity for first-row transition metals. In the electron-sea model, a metal crystal is viewed as a three-dimensional array of metal cations immersed in a sea of delocalised valence…

  5. RNA Crystallization

    NASA Technical Reports Server (NTRS)

    Golden, Barbara L.; Kundrot, Craig E.

    2003-01-01

    RNA molecules may be crystallized using variations of the methods developed for protein crystallography. As the technology has become available to syntheisize and purify RNA molecules in the quantities and with the quality that is required for crystallography, the field of RNA structure has exploded. The first consideration when crystallizing an RNA is the sequence, which may be varied in a rational way to enhance crystallizability or prevent formation of alternate structures. Once a sequence has been designed, the RNA may be synthesized chemically by solid-state synthesis, or it may be produced enzymatically using RNA polymerase and an appropriate DNA template. Purification of milligram quantities of RNA can be accomplished by HPLC or gel electrophoresis. As with proteins, crystallization of RNA is usually accomplished by vapor diffusion techniques. There are several considerations that are either unique to RNA crystallization or more important for RNA crystallization. Techniques for design, synthesis, purification, and crystallization of RNAs will be reviewed here.

  6. Protein Crystallization

    NASA Technical Reports Server (NTRS)

    Chernov, Alexander A.

    2005-01-01

    Nucleation, growth and perfection of protein crystals will be overviewed along with crystal mechanical properties. The knowledge is based on experiments using optical and force crystals behave similar to inorganic crystals, though with a difference in orders of magnitude in growing parameters. For example, the low incorporation rate of large biomolecules requires up to 100 times larger supersaturation to grow protein, rather than inorganic crystals. Nucleation is often poorly reproducible, partly because of turbulence accompanying the mixing of precipitant with protein solution. Light scattering reveals fluctuations of molecular cluster size, its growth, surface energies and increased clustering as protein ages. Growth most often occurs layer-by-layer resulting in faceted crystals. New molecular layer on crystal face is terminated by a step where molecular incorporation occurs. Quantitative data on the incorporation rate will be discussed. Rounded crystals with molecularly disordered interfaces will be explained. Defects in crystals compromise the x-ray diffraction resolution crucially needed to find the 3D atomic structure of biomolecules. The defects are immobile so that birth defects stay forever. All lattice defects known for inorganics are revealed in protein crystals. Contribution of molecular conformations to lattice disorder is important, but not studied. This contribution may be enhanced by stress field from other defects. Homologous impurities (e.g., dimers, acetylated molecules) are trapped more willingly by a growing crystal than foreign protein impurities. The trapped impurities induce internal stress eliminated in crystals exceeding a critical size (part of mni for ferritin, lysozyme). Lesser impurities are trapped from stagnant, as compared to the flowing, solution. Freezing may induce much more defects unless quickly amorphysizing intracrystalline water.

  7. Computational crystallization.

    PubMed

    Altan, Irem; Charbonneau, Patrick; Snell, Edward H

    2016-07-15

    Crystallization is a key step in macromolecular structure determination by crystallography. While a robust theoretical treatment of the process is available, due to the complexity of the system, the experimental process is still largely one of trial and error. In this article, efforts in the field are discussed together with a theoretical underpinning using a solubility phase diagram. Prior knowledge has been used to develop tools that computationally predict the crystallization outcome and define mutational approaches that enhance the likelihood of crystallization. For the most part these tools are based on binary outcomes (crystal or no crystal), and the full information contained in an assembly of crystallization screening experiments is lost. The potential of this additional information is illustrated by examples where new biological knowledge can be obtained and where a target can be sub-categorized to predict which class of reagents provides the crystallization driving force. Computational analysis of crystallization requires complete and correctly formatted data. While massive crystallization screening efforts are under way, the data available from many of these studies are sparse. The potential for this data and the steps needed to realize this potential are discussed.

  8. Crystal Chemistry of Melanite Garnet

    NASA Technical Reports Server (NTRS)

    Nguyen, Dawn Marie

    1999-01-01

    This original project resulted in a detailed crystal chemical data map of a titanium rich garnet (melanite) suite that originates from the Crowsnest Volcanics of Alberta Canada. Garnet is typically present during the partial melting of the earth's mantle to produce basalt. Prior studies conducted at Youngstown State University have yielded questions as to the crystal structure of the melanite. In the Studies conducted at Youngstown State University, through the use of single crystal x-ray diffraction, the c-axis appears to be distorted creating a tetragonal crystal instead of the typical cubic crystal of garnets. The micro probe was used on the same suite of titanium rich garnets as used in the single crystal x-ray diffraction. The combination of the single crystal x-ray research and the detailed microprobe research will allow us to determine the exact crystal chemical structure of the melanite garnet. The crystal chemical data was gathered through the utilization of the SX100 Electron Probe Micro Analyzer. Determination of the exact chemical nature may prove useful in modeling the ultramafic source rock responsible for the formation of the titanium rich lunar basalts.

  9. Crystal Structure of Garnet-Related Li-Ion Conductor Li7-3x Ga x La3Zr2O12: Fast Li-Ion Conduction Caused by a Different Cubic Modification?

    PubMed

    Wagner, Reinhard; Redhammer, Günther J; Rettenwander, Daniel; Senyshyn, Anatoliy; Schmidt, Walter; Wilkening, Martin; Amthauer, Georg

    2016-03-22

    Li-oxide garnets such as Li7La3Zr2O12 (LLZO) are among the most promising candidates for solid-state electrolytes to be used in next-generation Li-ion batteries. The garnet-structured cubic modification of LLZO, showing space group Ia-3d, has to be stabilized with supervalent cations. LLZO stabilized with Ga(3+) shows superior properties compared to LLZO stabilized with similar cations; however, the reason for this behavior is still unknown. In this study, a comprehensive structural characterization of Ga-stabilized LLZO is performed by means of single-crystal X-ray diffraction. Coarse-grained samples with crystal sizes of several hundred micrometers are obtained by solid-state reaction. Single-crystal X-ray diffraction results show that Li7-3x Ga x La3Zr2O12 with x > 0.07 crystallizes in the acentric cubic space group I-43d. This is the first definite record of this cubic modification for LLZO materials and might explain the superior electrochemical performance of Ga-stabilized LLZO compared to its Al-stabilized counterpart. The phase transition seems to be caused by the site preference of Ga(3+). (7)Li NMR spectroscopy indicates an additional Li-ion diffusion process for LLZO with space group I-43d compared to space group Ia-3d. Despite all efforts undertaken to reveal structure-property relationships for this class of materials, this study highlights the potential for new discoveries.

  10. Crystal Structure of Garnet-Related Li-Ion Conductor Li7–3xGaxLa3Zr2O12: Fast Li-Ion Conduction Caused by a Different Cubic Modification?

    PubMed Central

    2016-01-01

    Li-oxide garnets such as Li7La3Zr2O12 (LLZO) are among the most promising candidates for solid-state electrolytes to be used in next-generation Li-ion batteries. The garnet-structured cubic modification of LLZO, showing space group Ia-3d, has to be stabilized with supervalent cations. LLZO stabilized with Ga3+ shows superior properties compared to LLZO stabilized with similar cations; however, the reason for this behavior is still unknown. In this study, a comprehensive structural characterization of Ga-stabilized LLZO is performed by means of single-crystal X-ray diffraction. Coarse-grained samples with crystal sizes of several hundred micrometers are obtained by solid-state reaction. Single-crystal X-ray diffraction results show that Li7–3xGaxLa3Zr2O12 with x > 0.07 crystallizes in the acentric cubic space group I-43d. This is the first definite record of this cubic modification for LLZO materials and might explain the superior electrochemical performance of Ga-stabilized LLZO compared to its Al-stabilized counterpart. The phase transition seems to be caused by the site preference of Ga3+. 7Li NMR spectroscopy indicates an additional Li-ion diffusion process for LLZO with space group I-43d compared to space group Ia-3d. Despite all efforts undertaken to reveal structure–property relationships for this class of materials, this study highlights the potential for new discoveries. PMID:27019548

  11. Crystal growth of a series of lithium garnets Ln{sub 3}Li{sub 5}Ta{sub 2}O{sub 12} (Ln=La, Pr, Nd): Structural properties, Alexandrite effect and unusual ionic conductivity

    SciTech Connect

    Roof, Irina P.; Smith, Mark D.; Cussen, Edmund J.; Loye, Hans-Conrad zur

    2009-02-15

    We report the single crystal structures of a series of lanthanide containing tantalates, Ln{sub 3}Li{sub 5}Ta{sub 2}O{sub 12} (Ln=La, Pr, Nd) that were obtained out of a reactive lithium hydroxide flux. The structures of Ln{sub 3}Li{sub 5}Ta{sub 2}O{sub 12} were determined by single crystal X-ray diffraction, where the Li{sup +} positions and Li{sup +} site occupancies were fixed based on previously reported neutron diffraction data for isostructural compounds. All three oxides crystallize in the cubic space group Ia3-bard (No. 230) with lattice parameters a=12.7735(1), 12.6527(1), and 12.5967(1) A for La{sub 3}Li{sub 5}Ta{sub 2}O{sub 12}, Pr{sub 3}Li{sub 5}Ta{sub 2}O{sub 12}, and Nd{sub 3}Li{sub 5}Ta{sub 2}O{sub 12}, respectively. A UV-Vis diffuse reflectance spectrum of Nd{sub 3}Li{sub 5}Ta{sub 2}O{sub 12} was collected to explain its unusual Alexandrite-like optical behavior. To evaluate the transport properties of Nd{sub 3}Li{sub 5}Ta{sub 2}O{sub 12}, the impedance data were collected in air in the temperature range 300{<=}T(deg. C){<=}500. - Graphical abstract: Crystal structure of garnets Ln{sub 3}Li{sub 5}Ta{sub 2}O{sub 12} (Ln=La, Pr, Nd). TaO{sub 6} polyhedra are shown in yellow and Ln{sup 3+} are shown as light blue spheres. Octahedrally and tetrahedrally coordinated Li{sup +} ions are shown in green and brown, respectively. Oxygen atoms are omitted for clarity.

  12. Pressure sensor using liquid crystals

    NASA Technical Reports Server (NTRS)

    Parmar, Devendra S. (Inventor); Holmes, Harlan K. (Inventor)

    1994-01-01

    A pressure sensor includes a liquid crystal positioned between transparent, electrically conductive films (18 and 20), that are biased by a voltage (V) which induces an electric field (E) that causes the liquid crystal to assume a first state of orientation. Application of pressure (P) to a flexible, transparent film (24) causes the conductive film (20) to move closer to or farther from the conductive film (18), thereby causing a change in the electric field (E'(P)) which causes the liquid crystal to assume a second state of orientation. Polarized light (P.sub.1) is directed into the liquid crystal and transmitted or reflected to an analyzer (A or 30). Changes in the state of orientation of the liquid crystal induced by applied pressure (P) result in a different light intensity being detected at the analyzer (A or 30) as a function of the applied pressure (P). In particular embodiments, the liquid crystal is present as droplets (10) in a polymer matrix (12) or in cells (14) in a polymeric or dielectric grid (16) material in the form of a layer (13) between the electrically conductive films (18 and 20). The liquid crystal fills the open wells in the polymer matrix (12) or grid (16) only partially.

  13. Crystal growth of a series of lithium garnets Ln3Li 5Ta 2O 12 ( Ln=La, Pr, Nd): Structural properties, Alexandrite effect and unusual ionic conductivity

    NASA Astrophysics Data System (ADS)

    Roof, Irina P.; Smith, Mark D.; Cussen, Edmund J.; zur Loye, Hans-Conrad

    2009-02-01

    We report the single crystal structures of a series of lanthanide containing tantalates, Ln3Li 5Ta 2O 12 ( Ln=La, Pr, Nd) that were obtained out of a reactive lithium hydroxide flux. The structures of Ln3Li 5Ta 2O 12 were determined by single crystal X-ray diffraction, where the Li + positions and Li + site occupancies were fixed based on previously reported neutron diffraction data for isostructural compounds. All three oxides crystallize in the cubic space group Ia3¯d (No. 230) with lattice parameters a=12.7735(1), 12.6527(1), and 12.5967(1) Å for La 3Li 5Ta 2O 12, Pr 3Li 5Ta 2O 12, and Nd 3Li 5Ta 2O 12, respectively. A UV-Vis diffuse reflectance spectrum of Nd 3Li 5Ta 2O 12 was collected to explain its unusual Alexandrite-like optical behavior. To evaluate the transport properties of Nd 3Li 5Ta 2O 12, the impedance data were collected in air in the temperature range 300⩽ T(°C)⩽500.

  14. Crystal Data

    National Institute of Standards and Technology Data Gateway

    SRD 3 NIST Crystal Data (PC database for purchase)   NIST Crystal Data contains chemical, physical, and crystallographic information useful to characterize more than 237,671 inorganic and organic crystalline materials. The data include the standard cell parameters, cell volume, space group number and symbol, calculated density, chemical formula, chemical name, and classification by chemical type.

  15. Importance of C-H-donor and C-H-anion contact interactions for the crystal packing, the lattice softness and the superconducting transition temperatures of organic conducting salts

    SciTech Connect

    Whangbo, M.-H.; Novoa, J.J.; Jung, D. . Dept. of Chemistry); Williams, J.M.; Kinj, A.M.; Wang, H.H.; Geiser, U.; Beno, M.A.; Carlson, K.D. )

    1990-01-01

    The organic donor molecule BEDT-TTF and its analogs 2--4 have yielded a number of ambient-pressure superconducting salts. What structural and electronic factors govern the magnitudes of their superconducting transition temperature {Tc} has been a topic of intense studies. Examination of the band electronic structures of closely related superconducting salts shows, that the magnitudes of their {Tc}'s are primarily determined by the softness of their crystal lattices. The crystal packing and the lattice softness of organic donor salts are strongly influenced by the donor{hor ellipsis}donor and donor{hor ellipsis}anion contact interactions involving the donor-molecule C-H bonds. In the present work, we briefly review the electronic structures of some representative organic salt superconductors and discuss the softness of their crytsal lattices on the basis of the interaction energies calculated for the C-H{hor ellipsis}donor and C-H{hor ellipsis}anion contact interactions. 34 refs., 14 figs., 8 tabs.

  16. Crystal clear

    NASA Astrophysics Data System (ADS)

    2012-02-01

    A semiconductor is usually opaque to any light whose photon energy is larger than the semiconductor bandgap. Nature Photonics spoke to Stephen Durbin about how to render GaAs semiconductor crystals transparent using intense X-ray pulses.

  17. Copper sulfate: Liquid or crystals?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Two separate experiments were conducted to evaluate copper toxicity to channel catfish and free-swimming Ichthyophthirius multifiliis or Ich (the stage of Ich that can be treated); the compounds we used were CuSO4 crystals and a non-chelated liquid CuSO4 product. In 96 hr tests conducted in aquaria...

  18. Shape Evolution of Detached Bridgman Crystals Grown in Microgravity

    NASA Technical Reports Server (NTRS)

    Volz, M. P.; Mazuruk, K.

    2015-01-01

    A theory describing the shape evolution of detached Bridgman crystals in microgravity has been developed. A starting crystal of initial radius r0 will evolve to one of the following states: Stable detached gap; Attachment to the crucible wall; Meniscus collapse. Only crystals where alpha plus omega is great than 180 degrees will achieve stable detached growth in microgravity. Results of the crystal shape evolution theory are consistent with predictions of the dynamic stability of crystallization (Tatarchenko, Shaped Crystal Growth, Kluwer, 1993). Tests of transient crystal evolution are planned for ICESAGE, a series of Ge and GeSi crystal growth experiments planned to be conducted on the International Space Station (ISS).

  19. Ionic Conduction in Nanocrystalline Materials

    DTIC Science & Technology

    2000-02-10

    photo- largely due to oxygen desorption from particle voltaic cells and as the photocatalyst in water surfaces. The latter interpretation...and Tuller [22] prepared dense (-95%) temperature, where bulk reduction was observed. At compacts of TiO2 with the anatase phase. The lower... TiO2 , evidence preparation. is mixed. Nanocrystalline rutile appears to exhibit higher ionic conductivity than single crystal rutile while

  20. Liquid Crystals

    NASA Technical Reports Server (NTRS)

    1990-01-01

    Thermochromic liquid crystals, or TLCs, are a type of liquid crystals that react to changes in temperature by changing color. The Hallcrest/NASA collaboration involved development of a new way to visualize boundary layer transition in flight and in wind tunnel testing of aircraft wing and body surfaces. TLCs offered a new and potentially better method of visualizing the boundary layer transition in flight. Hallcrest provided a liquid crystal formulation technique that afforded great control over the sensitivity of the liquid crystals to varying conditions. Method is of great use to industry, government and universities for aerodynamic and hydrodynamic testing. Company's principal line is temperature indicating devices for industrial use, such as non-destructive testing and flaw detection in electric/electronic systems, medical application, such as diagnostic systems, for retail sale, such as room, refrigerator, baby bath and aquarium thermometers, and for advertising and promotion specials. Additionally, Hallcrest manufactures TLC mixtures for cosmetic applications, and liquid crystal battery tester for Duracell batteries.

  1. SYMMETRICAL LASER CRYSTALS.

    DTIC Science & Technology

    CRYSTAL GROWTH , SYMMETRY(CRYSTALLOGRAPHY), LASERS, SYNTHESIS, FERROELECTRIC CRYSTALS , FLUORESCENCE, IMPURITIES, BARIUM COMPOUNDS, ZIRCONATES...STRONTIUM COMPOUNDS, TITANATES, STANNATES, SAMARIUM, MANGANESE, REFRACTORY MATERIALS, OXIDES, SINGLE CRYSTALS .

  2. A 3D POM-MOF composite based on Ni(ΙΙ) ion and 2,2‧-bipyridyl-3,3‧-dicarboxylic acid: Crystal structure and proton conductivity

    NASA Astrophysics Data System (ADS)

    Wei, Meilin; Wang, Xiaoxiang; Sun, Jingjing; Duan, Xianying

    2013-06-01

    We have succeeded in constructing a 3D POM-MOF, {H[Ni(Hbpdc)(H2O)2]2[PW12O40]·8H2O}n (H2bpdc=2,2'-bipyridyl-3,3'-dicarboxylic acid), by the controllable self-assembly of H2bpdc, Keggin-anions and Ni2+ ions based on the electrostatic and coordination interactions. Interestingly, Hbpdc- as polydentate organic ligands and Keggin-anion as polydentate inorganic ligands are covalently linked transition-metal nickel at the same time. The title complex represents a new example of introducing the metal N-heterocyclic multi-carboxylic acid frameworks into POMs chemistry. Based on Keggin-anions being immobilized as part of the metal N-heterocyclic multi-carboxylic acid framework, the title complex realizes four approaches in the 1D hydrophilic channel used to engender proton conductivity in MOFs. Its water adsorption isotherm at room temperature and pressure shows that the water content in it was 31 cm3 g-1 at the maximum allowable humidity, corresponding to 3.7 water molecules per unit formula. It exhibits good proton conductivities (10-4-10-3 S cm-1) at 100 °C in the relative humidity range 35-98%. The corresponding activation energy (Ea) of conductivity was estimated to be 1.01 eV.

  3. Anisotropic electrical and thermal conductivity in Bi{sub 2}AE{sub 2}Co{sub 2}O{sub 8+δ} [AE = Ca, Sr{sub 1−x}Ba{sub x} (x = 0.0, 0.25, 0.5, 0.75, 1.0)] single crystals

    SciTech Connect

    Dong, Song-Tao; Zhang, Bin-Bin; Lv, Yang-Yang; Zhou, Jian; Zhang, Shan-Tao; Xiong, Ye; Yao, Shu-Hua E-mail: ybchen@nju.edu.cn; Chen, Y. B. E-mail: ybchen@nju.edu.cn; Chen, Yan-Feng

    2015-09-28

    Bi{sub 2}AE{sub 2}Co{sub 2}O{sub 8+δ} (AE represents alkaline earth), constructed by stacking of rock-salt Bi{sub 2}AE{sub 2}O{sub 4} and triangle CoO{sub 2} layers alternatively along c-axis, is one of promising thermoelectric oxides. The most impressive feature of Bi{sub 2}AE{sub 2}Co{sub 2}O{sub 8+δ}, as reported previously, is their electrical conductivity mainly lying along CoO{sub 2} plane, adjusting Bi{sub 2}AE{sub 2}O{sub 4} layer simultaneously manipulates both thermal conductivity and electrical conductivity. It in turn optimizes thermoelectric performance of these materials. In this work, we characterize the anisotropic thermal and electrical conductivity along both ab-plane and c-direction of Bi{sub 2}AE{sub 2}Co{sub 2}O{sub 8+δ} (AE = Ca, Sr, Ba, Sr{sub 1−x}Ba{sub x}) single crystals. The results substantiate that isovalence replacement in Bi{sub 2}AE{sub 2}Co{sub 2}O{sub 8+δ} remarkably modifies their electrical property along ab-plane; while their thermal conductivity along ab-plane only has a slightly difference. At the same time, both the electrical conductivity and thermal conductivity along c-axis of these materials also have dramatic changes. Certainly, the electrical resistance along c-axis is too high to be used as thermoelectric applications. These results suggest that adjusting nano-block Bi{sub 2}AE{sub 2}O{sub 4} layer in Bi{sub 2}AE{sub 2}Co{sub 2}O{sub 8+δ} cannot modify the thermal conductivity along high electrical conductivity plane (ab-plane here). The evolution of electrical property is discussed by Anderson localization and electron-electron interaction U. And the modification of thermal conductivity along c-axis is attributed to the microstructure difference. This work sheds more light on the manipulation of the thermal and electrical conductivity in the layered thermoelectric materials.

  4. Crystal structure and proton conductivity of BaSn0.6Sc0.4O3-δ : insights from neutron powder diffraction and solid-state NMR spectroscopy.

    PubMed

    Kinyanjui, Francis G; Norberg, Stefan T; Knee, Christopher S; Ahmed, Istaq; Hull, Stephen; Buannic, Lucienne; Hung, Ivan; Gan, Zhehong; Blanc, Frédéric; Grey, Clare P; Eriksson, Sten G

    2016-04-14

    The solid-state synthesis and structural characterisation of perovskite BaSn1-x Sc x O3-δ (x = 0.0, 0.1, 0.2, 0.3, 0.4) and its corresponding hydrated ceramics are reported. Powder and neutron X-ray diffractions reveal the presence of cubic perovskites (space group Pm3m) with an increasing cell parameter as a function of scandium concentration along with some indication of phase segregation. (119)Sn and (45)Sc solid-state NMR spectroscopy data highlight the existence of oxygen vacancies in the dry materials, and their filling upon hydrothermal treatment with D2O. It also indicates that the Sn(4+) and Sc(3+) local distribution at the B-site of the perovskite is inhomogeneous and suggests that the oxygen vacancies are located in the scandium dopant coordination shell at low concentrations (x ≤ 0.2) and in the tin coordination shell at high concentrations (x ≥ 0.3). (17)O NMR spectra on (17)O enriched BaSn1-x Sc x O3-δ materials show the existence of Sn-O-Sn, Sn-O-Sc and Sc-O-Sc bridging oxygen environments. A further room temperature neutron powder diffraction study on deuterated BaSn0.6Sc0.4O3-δ refines the deuteron position at the 24k crystallographic site (x, y, 0) with x = 0.579(3) and y = 0.217(3) which leads to an O-D bond distance of 0.96(1) Å and suggests tilting of the proton towards the next nearest oxygen. Proton conduction was found to dominate in wet argon below 700 °C with total conductivity values in the range 1.8 × 10(-4) to 1.1 × 10(-3) S cm(-1) between 300 and 600 °C. Electron holes govern the conduction process in dry oxidizing conditions, whilst in wet oxygen they compete with protonic defects leading to a wide mixed conduction region in the 200 to 600 °C temperature region, and a suppression of the conductivity at higher temperature.

  5. A 3D POM–MOF composite based on Ni(ΙΙ) ion and 2,2´-bipyridyl-3,3´-dicarboxylic acid: Crystal structure and proton conductivity

    SciTech Connect

    Wei, Meilin; Wang, Xiaoxiang; Sun, Jingjing; Duan, Xianying

    2013-06-01

    We have succeeded in constructing a 3D POM–MOF, (H[Ni(Hbpdc)(H₂O)₂]₂[PW₁₂O₄₀]·8H₂O)n (H₂bpdc=2,2´-bipyridyl-3,3´-dicarboxylic acid), by the controllable self-assembly of H₂bpdc, Keggin-anions and Ni²⁺ ions based on the electrostatic and coordination interactions. Interestingly, Hbpdc⁻ as polydentate organic ligands and Keggin-anion as polydentate inorganic ligands are covalently linked transition-metal nickel at the same time. The title complex represents a new example of introducing the metal N-heterocyclic multi-carboxylic acid frameworks into POMs chemistry. Based on Keggin-anions being immobilized as part of the metal N-heterocyclic multi-carboxylic acid framework, the title complex realizes four approaches in the 1D hydrophilic channel used to engender proton conductivity in MOFs. Its water adsorption isotherm at room temperature and pressure shows that the water content in it was 31 cm³ g⁻¹ at the maximum allowable humidity, corresponding to 3.7 water molecules per unit formula. It exhibits good proton conductivities (10⁻⁴–10⁻³ S cm⁻¹) at 100 °C in the relative humidity range 35–98%. The corresponding activation energy (E{sub a}) of conductivity was estimated to be 1.01 eV. - Graphical abstract: A POM–MOF composite constructed by Keggin-type polyanion, Ni²⁺ and H₂bpdc shows good proton conductivities of 10⁻⁴–10⁻³ S cm⁻¹ at 100 °C under 35–98% RH. - Highlights: • A POM–MOF was constructed by combining metal N-heterocyclic multi-carboxylic acid framework and Keggin anion. • It opens a pathway for design and synthesis of multifunctional hybrid materials based on two building units. • Three types of potential proton-carriers have been assembled in the 1D hydrophilic channels of the POM–MOF. • It achieved such proton conductivities as 10⁻⁴–10⁻³ S cm⁻¹ at 100 °C in the RH range 35–98%.

  6. Therapeutic Crystals

    ERIC Educational Resources Information Center

    Bond, Charles S.

    2014-01-01

    Some readers might not fully know what the difference is between crystallography, and the "new age" practice of dangling crystals around the body to capitalise on their healing energy. The latter is often considered to be superstition, while ironically, the former has actually resulted in real rationally-based healing of human diseases…

  7. Comparing Crystals

    ERIC Educational Resources Information Center

    Sharp, Janet; Hoiberg, Karen; Chumbley, Scott

    2003-01-01

    This standard lesson on identifying salt and sugar crystals expands into an opportunity for students to develop their observation, questioning, and modeling skills. Although sugar and salt may look similar, students discovered that they looked very different under a magnifying glass and behaved differently when dissolved in water. In addition,…

  8. Optical Crystals

    ERIC Educational Resources Information Center

    Bergsten, Ronald

    1974-01-01

    Discusses the production and structure of a sequence of optical crystals which can serve as one-, two-, and three-dimensional diffraction plates to illustrate diffraction patterns by using light rather than x-rays or particles. Applications to qualitative presentations of Laue theory at the secondary and college levels are recommended. (CC)

  9. Conducting nanowires in insulating ceramics.

    PubMed

    Nakamura, Atsutomo; Matsunaga, Katsuyuki; Tohma, Jun; Yamamoto, Takahisa; Ikuhara, Yuichi

    2003-07-01

    Low-dimensional structures, such as microclusters, quantum dots and one- or two-dimensional (1D or 2D) quantum wires, are of scientific and technological interest due to their unusual physical properties, which are quite different from those in the bulk. Here we present a successful method for fabricating conducting nanowire bundles inside an insulating ceramic single crystal by using unidirectional dislocations. A high density of dislocations (10(9) cm(-2)) was introduced by activating a primary slip system in sapphire (alpha-Al2O3 single crystal) using a two-stage deformation technique. Plate specimens cut out from the deformed sapphire were then annealed to straighten the dislocations. Finally, the plates on which metallic Ti was evaporated were heat-treated to diffuse Ti atoms inside sapphire. As a result of this process, Ti atoms segregated along the unidirectional dislocations within about 5 nm diameter, forming unidirectional Ti-enriched nanowires, which exhibit excellent electrical conductivity. This simple technique could potentially to be applied to any crystal, and may give special properties to commonly used materials.

  10. Heat conduction in conducting polyaniline nanofibers

    NASA Astrophysics Data System (ADS)

    Nath, Chandrani; Kumar, A.; Syu, K.-Z.; Kuo, Y.-K.

    2013-09-01

    Thermal conductivity and specific heat of conducting polyaniline nanofibers are measured to identify the nature of heat carrying modes combined with their inhomogeneous structure. The low temperature thermal conductivity results reveal crystalline nature while the high temperature data confirm the amorphous nature of the material suggesting heterogeneous model for conducting polyaniline. Extended acoustic phonons dominate the low temperature (<100 K) heat conduction, while localized optical phonons hopping, assisted by the extended acoustic modes, account for the high temperature (>100 K) heat conduction.

  11. Conductive dense hydrogen

    NASA Astrophysics Data System (ADS)

    Eremets, M.; Troyan, I.

    2012-12-01

    Hydrogen at ambient pressures and low temperatures forms a molecular crystal which is expected to display metallic properties under megabar pressures. This metal is predicted to be superconducting with a very high critical temperature Tc of 200-400 K. The superconductor may potentially be recovered metastably at ambient pressures, and it may acquire a new quantum state as a metallic superfluid and a superconducting superfluid. Recent experiments performed at low temperatures T < 100 K showed that at record pressures of 300 GPa, hydrogen remains in the molecular state and is an insulator with a band gap of appr 2 eV. Given our current experimental and theoretical understanding, hydrogen is expected to become metallic at pressures of 400-500 GPa, beyond the current limits of static pressures achievable using diamond anvil cells. We found that at room temperature and pressure > 220 GPa, new Raman modes arose, providing evidence for the transformation to a new opaque and electrically conductive phase IV. Above 260 GPa, in the next phase V, hydrogen reflected light well. Its resistance was nearly temperature-independent over a wide temperature range, down to 30 K, indicating that the hydrogen was metallic. Releasing the pressure induced the metallic phase to transform directly into molecular hydrogen with significant hysteresis at 200 GPa and 295 K. These data were published in our paper: M. I. Eremets and I. A. Troyan "Conductive dense hydrogen." Nature Materials 10: 927-931. We will present also new results on hydrogen: phase diagram with phases IV and V determined in P,T domain up to 300 GPa and 350 K. We will also discuss possible structures of phase IV based on our Raman and infrared measurements up to 300 GPa.

  12. Effect of Strontium-Doped Lanthanum Vanadate on Crystal Structure, Conductivity and Vanadium Valence State of a La1- x Sr x VO3 Anode in a Reducing Environment

    NASA Astrophysics Data System (ADS)

    Liu, Chi-Yang; Tsai, Shu-Yi; Ni, Chung-Ta; Fung, Kuan-Zong

    2017-04-01

    La1- x Sr x VO3 (where x = 0, 0.1, 0.3, 0.5, 0.7, and 1) exhibits a transition from an antiferromagnetic insulator to a paramagnetic metallic conductor and has been synthesized as a potential anode material for solid oxide fuel cells (SOFCs). La1- x Sr x VO3 was synthesized by a solid-state reaction process followed by heat treatment under a reducing atmosphere (Ar:80/H2:20). X-ray diffraction (XRD) results indicate that LaVO3 was substituted with various amounts of Sr2+ in the cation sublattice. Pure LaVO3 shows an orthorhombic structure. After Sr2+ substitution, a more symmetrical cubic perovskite structure was obtained because the tolerance factor is close to 1. The valence state of the vanadium ions of the La1- x Sr x VO3 was further verified by x-ray photoelectron spectroscopy (XPS). According to the XPS results, when the lanthanum ion was substituted by a strontium ion, the negatively charged defect, SrLa', was compensated for by changing the valence of vanadium from a trivalent to a tetravalent or pentavalent state. The dependence of conduction behavior of La1- x Sr x VO3 on the amount of Sr addition is discussed in terms of the hopping process with super/double exchange interaction and a charge transfer mechanism.

  13. Crystal quality and differential crystal-growth behaviour of three proteins crystallized in gel at high hydrostatic pressure.

    PubMed

    Kadri, A; Lorber, B; Charron, C; Robert, M-C; Capelle, B; Damak, M; Jenner, G; Giegé, R

    2005-06-01

    Pressure is a non-invasive physical parameter that can be used to control and influence protein crystallization. It is also found that protein crystals of superior quality can be produced in gel. Here, a novel crystallization strategy combining hydrostatic pressure and agarose gel is described. Comparative experiments were conducted on hen and turkey egg-white lysozymes and the plant protein thaumatin. Crystals could be produced under up to 75-100 MPa (lysozymes) and 250 MPa (thaumatin). Several pressure-dependent parameters were determined, which included solubility and supersaturation of the proteins, number, size and morphology of the crystals, and the crystallization volume. Exploration of three-dimensional phase diagrams in which pH and pressure varied identified growth conditions where crystals had largest size and best morphology. As a general trend, nucleation and crystal-growth kinetics are altered and nucleation is always enhanced under pressure. Further, solubility of the lysozymes increases with pressure while that of thaumatin decreases. Likewise, changes in crystallization volumes at high and atmospheric pressure are opposite, being positive for the lysozymes and negative for thaumatin. Crystal quality was estimated by analysis of Bragg reflection profiles and X-ray topographs. While the quality of lysozyme crystals deteriorates as pressure increases, that of thaumatin crystals improves, with more homogeneous crystal morphology suggesting that pressure selectively dissociates ill-formed nuclei. Analysis of the thaumatin structure reveals a less hydrated solvent shell around the protein when pressure increases, with approximately 20% less ordered water molecules in crystals grown at 150 MPa when compared with those grown at atmospheric pressure (0.1 MPa). Noticeably, the altered water distribution is seen in depressurized crystals, indicating that pressure triggers a stable structural alteration on the protein surface while its polypeptide backbone

  14. Crystallization of struvite from metastable region with different types of seed crystal

    NASA Astrophysics Data System (ADS)

    Ali, Imtiaj; Schneider, Phil Andrew

    2005-05-01

    The main feature of this paper was to recognize struvite crystallization in the metastable region of supersaturation. Thermodynamic equilibria of struvite were simulated to identify the minimum struvite solubility limit, thereafter validated by existing thermodynamic modelling packages such as PHREEQC and the derived data from existing struvite solubility curve. Using laser light scattering detection, spontaneous nucleation was identified by the slow increase of pH in a supersaturated solution of struvite. The crystallization experiment, conducted close to the saturation region in metastable zone, initiated struvite growth. The conducted experiment showed that mother crystal (struvite) was more effective as seeds for struvite crystallization.

  15. Thermophysical parameters of the LBO crystal

    SciTech Connect

    Grechin, Sergei G; Zuev, A V; Fokin, A S; Kokh, Aleksandr E; Moiseev, N V; Popov, Petr A; Sidorov, Aleksei A

    2010-08-27

    The thermophysical parameters (linear thermal expansion coefficients, thermal conductivities, and heat capacity) of the lithium triborate (LBO) crystal are measured and compared with previously published data. (nonlinear-optics phenomena)

  16. DC electrical conductivity study of cerium doped conducting glass systems

    NASA Astrophysics Data System (ADS)

    Barde, R. V.; Waghuley, S. A.

    2013-06-01

    The glass samples of composition 60V2O5-5P2O5-(35-x)B2O3-xCeO2, (1 ≤ x ≤ 5) were prepared by the conventional melt quench method. The samples were characterized by X-ray diffraction and thermo gravimetric-differential thermal analysis. The glass transition temperature and crystallization temperature determined from TG-DTA analysis. The DC electrical conductivity has been carried out in the temperature range 303-473 K. The maximum conductivity and minimum activation energy were found to be 0.039 Scm-1 and 0.15 eV at 473 K for x=1, respectively.

  17. Pressure dependence of electrical conductivity in forsterite

    NASA Astrophysics Data System (ADS)

    Yoshino, Takashi; Zhang, Baohua; Rhymer, Brandon; Zhao, Chengcheng; Fei, Hongzhan

    2017-01-01

    Electrical conductivity of dry forsterite has been measured in muli-anvil apparatus to investigate the pressure dependence of ionic conduction in forsterite. The starting materials for the conductivity experiments were a synthetic forsterite single crystal and a sintered forsterite aggregate synthesized from oxide mixture. Electrical conductivities were measured at 3.5, 6.7, 9.6, 12.1, and 14.9 GPa between 1300 and 2100 K. In the measured temperature range, the conductivity of single crystal forsterite decreases in the order of [001], [010], and [100]. In all cases, the conductivity decreases with increasing pressure and then becomes nearly constant for [100] and [001] and slightly increases above 7 GPa for [010] orientations and a polycrystalline forsterite sample. Pressure dependence of forsterite conductivity was considered as a change of the dominant conduction mechanism composed of migration of both magnesium and oxygen vacancies in forsterite. The activation energy (ΔE) and activation volume (ΔV) for ionic conduction due to migration of Mg vacancy were 1.8-2.7 eV and 5-19 cm3/mol, respectively, and for that due to O vacancy were 2.2-3.1 eV and -1.1 to 0.3 cm3/mol, respectively. The olivine conductivity model combined with small polaron conduction suggests that the most part of the upper mantle is controlled by ionic conduction rather than small polaron conduction. The previously observed negative pressure dependence of the conductivity of olivine with low iron content (Fo90) can be explained by ionic conduction due to migration of Mg vacancies, which has a large positive activation volume.

  18. Biological Macromolecule Crystallization Database

    National Institute of Standards and Technology Data Gateway

    SRD 21 Biological Macromolecule Crystallization Database (Web, free access)   The Biological Macromolecule Crystallization Database and NASA Archive for Protein Crystal Growth Data (BMCD) contains the conditions reported for the crystallization of proteins and nucleic acids used in X-ray structure determinations and archives the results of microgravity macromolecule crystallization studies.

  19. Crystallization process

    DOEpatents

    Adler, Robert J.; Brown, William R.; Auyang, Lun; Liu, Yin-Chang; Cook, W. Jeffrey

    1986-01-01

    An improved crystallization process is disclosed for separating a crystallizable material and an excluded material which is at least partially excluded from the solid phase of the crystallizable material obtained upon freezing a liquid phase of the materials. The solid phase is more dense than the liquid phase, and it is separated therefrom by relative movement with the formation of a packed bed of solid phase. The packed bed is continuously formed adjacent its lower end and passed from the liquid phase into a countercurrent flow of backwash liquid. The packed bed extends through the level of the backwash liquid to provide a drained bed of solid phase adjacent its upper end which is melted by a condensing vapor.

  20. Liquid Crystal Devices.

    ERIC Educational Resources Information Center

    Bradshaw, Madeline J.

    1983-01-01

    The nature of liquid crystals and several important liquid crystal devices are described. Ideas for practical experiments to illustrate the properties of liquid crystals and their operation in devices are also described. (Author/JN)

  1. Liquid Crystal Inquiries.

    ERIC Educational Resources Information Center

    Marroum, Renata-Maria

    1996-01-01

    Discusses the properties and classification of liquid crystals. Presents a simple experiment that illustrates the structure of liquid crystals and the differences between the various phases liquid crystals can assume. (JRH)

  2. Curved branching crystals and differentiation in comb-layered rocks

    NASA Technical Reports Server (NTRS)

    Lofgren, G. E.; Donaldson, C. H.

    1975-01-01

    An investigation is conducted concerning two common features of comb layered rocks. Attention is given to the curvature of oriented, elongate, branching crystals and the tendency to form highly differentiated layers. Crystallization studies of plagioclase show that some degree of supercooling is necessary to produce the skeletal, curved, and branching plagioclase crystal morphologies found in comb-layered rocks and that curved crystals can be grown without the presence of a directed stress.

  3. PARAMAGNETIC RELAXATION IN CRYSTALS.

    DTIC Science & Technology

    CRYSTALS, PARAMAGNETIC RESONANCE, RELAXATION TIME , CRYSTAL DEFECTS, QUARTZ, GLASS, STRAIN(MECHANICS), TEMPERATURE, NUCLEAR SPINS, HYDROGEN, CALCIUM COMPOUNDS, FLUORIDES, COLOR CENTERS, PHONONS, OXYGEN.

  4. Surface Electrical Conductivity of Single Crystal Spinel in Cesium Vapour.

    DTIC Science & Technology

    2007-11-02

    Agnew TOPAZ international Program 901 University Blvd. Albuquerque, NM 87106 USA. 1-9990219 0 4 5 DISTRIBUTION STATEMENT A: Approved for Public...Office of Aerospace Research and Development of the U.S. Air Force under contract number F61708-95-C0002. 2nd April 1995 P. Agnew TOPAZ International...and between the electrodes and the TFE body. A program of research was established as part of the TOPAZ International Program (TIP) with the purpose

  5. Using Inorganic Crystals To Grow Protein Crystals

    NASA Technical Reports Server (NTRS)

    Shlichta, Paul J.; Mcpherson, Alexander A.

    1989-01-01

    Solid materials serve as nucleating agents. Protein crystals induced by heterogeneous nucleation and in some cases by epitaxy to grow at lower supersaturations than needed for spontaneous nucleation. Heterogeneous nucleation makes possible to grow large, defect-free single crystals of protein more readily. Such protein crystals benefits research in biochemistry and pharmacology.

  6. Laser-induced crystallization and crystal growth.

    PubMed

    Sugiyama, Teruki; Masuhara, Hiroshi

    2011-11-04

    Recent streams of laser studies on crystallization and crystal growth are summarized and reviewed. Femtosecond multiphoton excitation of solutions leads to their ablation at the focal point, inducing local bubble formation, shockwave propagation, and convection flow. This phenomenon, called "laser micro tsunami" makes it possible to trigger crystallization of molecules and proteins from their supersaturated solutions. Femtosecond laser ablation of a urea crystal in solution triggers the additional growth of a single daughter crystal. Intense continuous wave (CW) near infrared laser irradiation at the air/solution interface of heavy-water amino acid solutions results in trapping of the clusters and evolves to crystallization. A single crystal is always prepared in a spatially and temporally controlled manner, and the crystal polymorph of glycine depends on laser power, polarization, and solution concentration. Upon irradiation at the glass/solution interface, a millimeter-sized droplet is formed, and a single crystal is formed by shifting the irradiation position to the surface. Directional and selective crystal growth is also possible with laser trapping. Finally, characteristics of laser-induced crystallization and crystal growth are summarized.

  7. Crystal structure, thermal expansion and high-temperature electrical conductivity of A-site deficient La{sub 2−z}Co{sub 1+y}(Mg{sub x}Nb{sub 1−x}){sub 1−y}O{sub 6} double perovskites

    SciTech Connect

    Shafeie, S.; Dreyer, B.; Awater, R.H.P; Golod, T.; Grins, J.; Biendicho, J.J.; Istomin, S.Ya.; Svensson, G.

    2015-09-15

    New La-deficient double perovskites with P2{sub 1}/n symmetry, La{sub ∼1.90}(Co{sup 2+}{sub 1−x}Mg{sup 2+}{sub x})(Co{sup 3+}{sub 1/3}Nb{sup 5+}{sub 2/3})O{sub 6} with x=0, 0.13 and 0.33, and La{sub 2}(Co{sup 2+}{sub 1/2}Mg{sup 2+}{sub 1/2}) (Co{sup 3+}{sub 1/2}Nb{sup 5+}{sub 1/2})O{sub 6} were prepared by solid state reaction at 1450 °C. Their crystal structures were refined using time-of-flight neutron powder diffraction data. Our results show that certain cations such as Nb{sup 5+}, with very strong B–O bonds in the perovskite structure, can induce A-site vacancies in double perovskites. Upon heating in N{sub 2} gas atmosphere at 1200 °C ∼1% O atom vacancies are formed together with a partial reduction of the Co{sup 3+} content. The average thermal expansion coefficient between 25 and 900 °C of La{sub 1.90}(Co{sup 2+}{sub 2/3}Mg{sup 2+}{sub 1/3})(Co{sup 3+}{sub 1/3}Nb{sup 5+}{sub 2/3})O{sub 6} was determined to be 17.4 ppm K{sup −1}. Four-point electronic conductivity measurements showed that the compounds are semiconductors, with conductivities varying between 3.7·10{sup −2} and 7.7·10{sup −2} S cm{sup −1} at 600 °C and activation energies between 0.77 and 0.81 eV. Partial replacement of La{sup 3+} with Sr{sup 2+} does not lead to any increase of conductivity, while replacement of Mg{sup 2+} with Cu{sup 2+} in La{sub 1.9}CoCu{sub 1/3}Nb{sub 2/3}O{sub 6} and La{sub 1.8}CoCu{sub 1/2}Nb{sub 1/2}O{sub 6} leads to ∼100 times larger conductivities at 600 °C, 0.35 and 1.0 S cm{sup −1}, respectively, and lower activation energies, 0.57 and 0.73 eV, respectively. - Highlights: • Double perovskites, P2{sub 1}/n, La{sub 2−z}(Co{sup 2+}{sub 1−x}Mg{sup 2+}{sub x})(Co{sup 3+}{sub 1/3}Nb{sup 5+}{sub 2/3})O{sub 6} have been synthesized. • Crystal structures have been refined using neutron powder diffraction data. • Strong Nb–O bond and size ordering of Mg{sup 2+}/Co{sup 2+} and Nb{sup 5+}/Co{sup ~3+} leads to La-deficiency. • The

  8. Manipulating Heat Flow through 3 Dimensional Nanoscale Phononic Crystal Structure

    DTIC Science & Technology

    2014-06-02

    Nanoscale Phononic Crystal Structure 5a. CONTRACT NUMBER FA23861214047 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Baowen Li 5d...through computer simulation, how the three dimensional (3D) phononic crystal structures can confine phonon and thus reduce thermal conductivity...phononic crystal (PnC) with spherical pores, which can reduce thermal conductivity of bulk Si by a factor up to 10,000 times at room temperature. The

  9. Molecular tectonics: from crystals to crystals of crystals.

    PubMed

    Marinescu, Gabriela; Ferlay, Sylvie; Kyritsakas, Nathalie; Hosseini, Mir Wais

    2013-12-11

    The in situ combination of M(II) cations (Co, Ni, Cu or Zn) with 2,4,6-pyridinetricarboxylic acid as a ligand, a bisamidinium dication as a H-bond donor tecton and NaOH leads to the formation of anionic metal complexes ML2(2-) and their interconnection into isomorphous 3D H-bonded networks displaying different colours which were used as preformed seed crystals for the formation of crystals of crystals by 3D epitaxial growth.

  10. Synthetic thermoelectric materials comprising phononic crystals

    DOEpatents

    El-Kady, Ihab F; Olsson, Roy H; Hopkins, Patrick; Reinke, Charles; Kim, Bongsang

    2013-08-13

    Synthetic thermoelectric materials comprising phononic crystals can simultaneously have a large Seebeck coefficient, high electrical conductivity, and low thermal conductivity. Such synthetic thermoelectric materials can enable improved thermoelectric devices, such as thermoelectric generators and coolers, with improved performance. Such synthetic thermoelectric materials and devices can be fabricated using techniques that are compatible with standard microelectronics.

  11. Conducting compositions of matter

    NASA Technical Reports Server (NTRS)

    Viswanathan, Tito (Inventor)

    2000-01-01

    The invention provides conductive compositions of matter, as well as methods for the preparation of the conductive compositions of matter, solutions comprising the conductive compositions of matter, and methods of preparing fibers or fabrics having improved anti-static properties employing the conductive compositions of matter.

  12. Conducting Compositions of Matter

    NASA Technical Reports Server (NTRS)

    Viswanathan, Tito (Inventor)

    1999-01-01

    The invention provides conductive compositions of matter, as well as methods for the preparation of the conductive compositions of matter, solutions comprising the conductive compositions of matter, and methods of preparing fibers or fabrics having improved anti-static properties employing the conductive compositions of matter.

  13. Heat transfer in vertical Bridgman growth of oxides - Effects of conduction, convection, and internal radiation

    NASA Technical Reports Server (NTRS)

    Brandon, S.; Derby, J. J.

    1992-01-01

    In the present investigation of crystalline phase internal radiation and heat conduction during the vertical Bridgman growth of a YAG-like oxide crystal, where transport through the melt is dominated by convection and conduction, heat is also noted to be conducted through ampoule walls via natural convection and enclosure radiation. The results of a quasi-steady-state axisymmetric Galerkin FEM indicate that heat transfer through the system is powerfully affected by the optical absorption coefficient of the crystal. The coupling of internal radiation through the crystal with conduction through the ampoule walls promotes melt/crystal interface shapes that are highly reflected near the ampoule wall.

  14. Drilling technique for crystals

    NASA Technical Reports Server (NTRS)

    Hunter, T.; Miyagawa, I.

    1977-01-01

    Hole-drilling technique uses special crystal driller in which drill bit rotates at fixed position at speed of 30 rpm while crystal slowly advances toward drill. Technique has been successfully applied to crystal of Rochell salt, Triglycine sulfate, and N-acetyglycine. Technique limits heat buildup and reduces strain on crystal.

  15. Polyaniline Based Conductive Textiles

    NASA Astrophysics Data System (ADS)

    Teli, M.; Dash, S.; Desai, P.

    2014-12-01

    The conductive polymers were mixed with binder and coated on cotton, polyester and wool fabric, keeping conductive polymer concentration at 5 %. Conductive woven fabrics were obtained by pad-dry-cure coating technique. The surface and bulk conductivity behaviour of the coating paste with respect to temperature were studied using four probe and two probe technique. The conductivity studies show that the coated fabrics have good electrical conductivity in the range of 33.2 μS/cm-3281 μS/cm and there was an increase in conductivity with rise in temperature.

  16. Mixed crystal organic scintillators

    DOEpatents

    Zaitseva, Natalia P; Carman, M Leslie; Glenn, Andrew M; Hamel, Sebastien; Hatarik, Robert; Payne, Stephen A; Stoeffl, Wolfgang

    2014-09-16

    A mixed organic crystal according to one embodiment includes a single mixed crystal having two compounds with different bandgap energies, the organic crystal having a physical property of exhibiting a signal response signature for neutrons from a radioactive source, wherein the signal response signature does not include a significantly-delayed luminescence characteristic of neutrons interacting with the organic crystal relative to a luminescence characteristic of gamma rays interacting with the organic crystal. According to one embodiment, an organic crystal includes bibenzyl and stilbene or a stilbene derivative, the organic crystal having a physical property of exhibiting a signal response signature for neutrons from a radioactive source.

  17. Pressure cryocooling protein crystals

    DOEpatents

    Kim, Chae Un; Gruner, Sol M.

    2011-10-04

    Preparation of cryocooled protein crystal is provided by use of helium pressurizing and cryocooling to obtain cryocooled protein crystal allowing collection of high resolution data and by heavier noble gas (krypton or xenon) binding followed by helium pressurizing and cryocooling to obtain cryocooled protein crystal for collection of high resolution data and SAD phasing simultaneously. The helium pressurizing is carried out on crystal coated to prevent dehydration or on crystal grown in aqueous solution in a capillary.

  18. Fabrication of polypyrrole nano-arrays in lysozyme single crystals

    NASA Astrophysics Data System (ADS)

    England, Matt W.; Lambert, Elizabeth M.; Li, Mei; Turyanska, Lyudmila; Patil, Avinash J.; Mann, Stephen

    2012-10-01

    A template-directed method for the synthesis and organization of partially oxidized polypyrrole (PPy) nanoscale arrays within the solvent channels of glutaraldehyde-cross-linked lysozyme single crystals is presented. Macroscopic single crystals of the periodically arranged protein-polymer superstructure are electrically conductive, insoluble in water and organic solvents, and display increased levels of mechanical plasticity compared with native cross-linked lysozyme crystals.A template-directed method for the synthesis and organization of partially oxidized polypyrrole (PPy) nanoscale arrays within the solvent channels of glutaraldehyde-cross-linked lysozyme single crystals is presented. Macroscopic single crystals of the periodically arranged protein-polymer superstructure are electrically conductive, insoluble in water and organic solvents, and display increased levels of mechanical plasticity compared with native cross-linked lysozyme crystals. Electronic supplementary information (ESI) available: Optical microscopy, SEM, TEM images, FTIR spectra and tables, conductivity plot. Experimental methods. See DOI: 10.1039/c2nr32413j

  19. Anisotropic thermal conductivity in uranium dioxide

    NASA Astrophysics Data System (ADS)

    Gofryk, K.; Du, S.; Stanek, C. R.; Lashley, J. C.; Liu, X.-Y.; Schulze, R. K.; Smith, J. L.; Safarik, D. J.; Byler, D. D.; McClellan, K. J.; Uberuaga, B. P.; Scott, B. L.; Andersson, D. A.

    2014-08-01

    The thermal conductivity of uranium dioxide has been studied for over half a century, as uranium dioxide is the fuel used in a majority of operating nuclear reactors and thermal conductivity controls the conversion of heat produced by fission events to electricity. Because uranium dioxide is a cubic compound and thermal conductivity is a second-rank tensor, it has always been assumed to be isotropic. We report thermal conductivity measurements on oriented uranium dioxide single crystals that show anisotropy from 4 K to above 300 K. Our results indicate that phonon-spin scattering is important for understanding the general thermal conductivity behaviour, and also explains the anisotropy by coupling to the applied temperature gradient and breaking cubic symmetry.

  20. Growth and characterization of diammonium copper disulphate hexahydrate single crystal

    SciTech Connect

    Siva Sankari, R.; Perumal, Rajesh Narayana

    2014-03-01

    Graphical abstract: Diammonium copper disulphate hexahydrate (DACS) is one of the most promising inorganic dielectric crystals with exceptional mechanical properties. Good quality crystals of DACS were grown by using solution method in a period of 30 days. The grown crystals were subjected to single crystal X-ray diffraction analysis in order to establish their crystalline nature. Thermo gravimetric, differential thermal analysis, FTIR, and UV–vis–NIR analysis were performed for the crystal. Several solid state physical parameters have been determined for the grown crystals. The dielectric constant and the dielectric loss and AC conductivity of the grown crystal were studied as a function of frequency and temperature has been calculated and plotted. - Highlights: • Diammonium copper disulphate is grown for the first time and CCDC number obtained. • Thermal analysis is done to see the stability range of the crystals. • Band gap and UV cut off wavelength of the crystal are determined to be 2.4 eV and 472.86 nm, respectively. • Dielectric constant, dielectric loss and AC conductivity are plotted as a function of applied field. - Abstract: Diammonium copper disulphate hexahydrate is one of the most promising inorganic crystals with exceptional dielectric properties. A good quality crystal was harvested in a 30-day period using solution growth method. The grown crystal was subjected to various characterization techniques like single crystal X-ray diffraction analysis, thermo gravimetric, differential thermal analysis, FTIR, and UV–vis–NIR analysis. Unit cell dimensions of the grown crystal have been identified from XRD studies. Functional groups of the title compounds have been identified from FTIR studies. Thermal stability of the samples was checked by TG/DTA studies. Band gap of the crystal was calculated. The dielectric constant and dielectric loss were studied as a function of frequency of the applied field. AC conductivity was plotted as a function

  1. Growth and characterization of hexamethylenetetramine crystals grown from solution

    NASA Astrophysics Data System (ADS)

    Babu, B.; Chandrasekaran, J.; Balaprabhakaran, S.

    2014-06-01

    Organic nonlinear optical single crystals of hexamethylenetetramine (HMT; 10 × 10 × 5 mm3) were prepared by crystallization from methanol solution. The grown crystals were subjected to various characterization techniques such as single crystal XRD, powder XRD, UV-Vis and electrical studies. Single crystal XRD analysis confirmed the crystalline structure of the grown crystals. Their crystalline nature was also confirmed by powder XRD technique. The optical transmittance property was identified from UV-Vis spectrum. Dielectric measurements were performed as a function of frequency at different temperatures. DC conductivity and photoconductivity studies were also carried out for the crystal. The powder second harmonic generation efficiency (SHG) of the crystal was measured using Nd:YAG laser and the efficiency was found to be two times greater than that of potassium dihydrogen phosphate (KDP).

  2. The Conductivity of Solutions.

    ERIC Educational Resources Information Center

    Rayner-Canham, Geoff

    1993-01-01

    Presents historical background and modern explanations for the popular demonstration of showing conductivity of solutions through the insertion of a light-bulb conductivity tester into deionized water and water with salt in it. (PR)

  3. Preliminary crystallographic studies of four crystal forms of serum albumin

    NASA Technical Reports Server (NTRS)

    Carter, D. C.; Chang, B.; Ho, J. X.; Keeling, K.; Krishnasami, Z.

    1994-01-01

    Several crystal forms of serum albumin suitable for three-dimensional structure determination have been grown. These forms include crystals of recombinant and wild-type human serum albumin, baboon serum albumin, and canine serum albumin. The intrinsic limits of X-ray diffraction for these crystals are in the range 0.28-0.22 nm. Two of the crystal forms produced from human and canine albumin include incorporated long-chain fatty acids. Molecular replacement experiments have been successfully conducted on each crystal form using the previously determined atomic coordinates of human serum albumin illustrating the conserved tertiary structure.

  4. Surface Conductive Glass.

    ERIC Educational Resources Information Center

    Tanaka, John; Suib, Steven L.

    1984-01-01

    Discusses the properties of surface-conducting glass and the chemical nature of surface-conducting stannic (tin) oxide. Also provides the procedures necessary for the preparation of surface-conducting stannic oxide films on glass substrates. The experiment is suitable for the advanced inorganic chemistry laboratory. (JN)

  5. CRYSTALLIZATION IN MULTICOMPONENT GLASSES

    SciTech Connect

    KRUGER AA; HRMA PR

    2009-10-08

    In glass processing situations involving glass crystallization, various crystalline forms nucleate, grow, and dissolve, typically in a nonuniform temperature field of molten glass subjected to convection. Nuclear waste glasses are remarkable examples of multicomponent vitrified mixtures involving partial crystallization. In the glass melter, crystals form and dissolve during batch-to-glass conversion, melter processing, and product cooling. Crystals often agglomerate and sink, and they may settle at the melter bottom. Within the body of cooling glass, multiple phases crystallize in a non-uniform time-dependent temperature field. Self-organizing periodic distribution (the Liesegnang effect) is common. Various crystallization phenomena that occur in glass making are reviewed.

  6. Electrically conductive composite material

    DOEpatents

    Clough, R.L.; Sylwester, A.P.

    1988-06-20

    An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistent pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like. 2 figs.

  7. Electrically conductive composite material

    SciTech Connect

    Clough, R.L.; Sylwester, A.P.

    1989-05-23

    An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistent pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like. 2 figs.

  8. Electrically conductive composite material

    DOEpatents

    Clough, Roger L.; Sylwester, Alan P.

    1989-01-01

    An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistant pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like.

  9. Phonon manipulation with phononic crystals.

    SciTech Connect

    Kim Bongsang; Hopkins, Patrick Edward; Leseman, Zayd C.; Goettler, Drew F.; Su, Mehmet F.; El-Kady, Ihab Fathy; Reinke, Charles M.; Olsson, Roy H., III

    2012-01-01

    In this work, we demonstrated engineered modification of propagation of thermal phonons, i.e. at THz frequencies, using phononic crystals. This work combined theoretical work at Sandia National Laboratories, the University of New Mexico, the University of Colorado Boulder, and Carnegie Mellon University; the MESA fabrication facilities at Sandia; and the microfabrication facilities at UNM to produce world-leading control of phonon propagation in silicon at frequencies up to 3 THz. These efforts culminated in a dramatic reduction in the thermal conductivity of silicon using phononic crystals by a factor of almost 30 as compared with the bulk value, and about 6 as compared with an unpatterned slab of the same thickness. This work represents a revolutionary advance in the engineering of thermoelectric materials for optimal, high-ZT performance. We have demonstrated the significant reduction of the thermal conductivity of silicon using phononic crystal structuring using MEMS-compatible fabrication techniques and in a planar platform that is amenable to integration with typical microelectronic systems. The measured reduction in thermal conductivity as compared to bulk silicon was about a factor of 20 in the cross-plane direction [26], and a factor of 6 in the in-plane direction. Since the electrical conductivity was only reduced by a corresponding factor of about 3 due to the removal of conductive material (i.e., porosity), and the Seebeck coefficient should remain constant as an intrinsic material property, this corresponds to an effective enhancement in ZT by a factor of 2. Given the number of papers in literature devoted to only a small, incremental change in ZT, the ability to boost the ZT of a material by a factor of 2 simply by reducing thermal conductivity is groundbreaking. The results in this work were obtained using silicon, a material that has benefitted from enormous interest in the microelectronics industry and that has a fairly large thermoelectric power

  10. Between Crystal and Glass: Thermal Transport in C60 Molecular Crystals

    NASA Astrophysics Data System (ADS)

    Lu, Simon; Kumar, Sushant; McGaughey, Alan

    Molecular crystals of the fullerene C60 and its derivatives [e.g., phenyl-C61-butyric acid methyl ester (PCBM)] are candidate materials for use in photovoltaics and thermoelectrics. In thermoelectrics, their usefulness is due in part to their exceptionally low thermal conductivities (0.4 W/m-K for C60 and 0.05 W/m-K for PCBM) at room temperature. Little is known regarding the microscopic physics underlying these low thermal conductivities. An important question is whether thermal transport in the C60 molecular crystal is (i) crystal-like, where energy is transported as collective vibrations of the centers of mass of the molecules, or (ii) amorphous-like, where energy diffuses from molecule to molecule. We use molecular dynamics (MD) simulations and the Green-Kubo method to probe this question by predicting the relative contributions of crystal-like and amorphous-like transport to the thermal conductivity of the C60 molecular crystal. To isolate crystal-like transport, we perform simulations on C60 crystals where molecular rotations and intra-molecular vibrations are prohibited. To isolate amorphous-like transport, we fix the centers of mass of the molecules. We compare the MD results to predictions from a fully diffusive network resistance model. This work is supported by the National Science Foundation (Grant DMR-1507325).

  11. Apparatus for growing crystals

    NASA Technical Reports Server (NTRS)

    Jasinski, Thomas J. (Inventor); Witt, August F. (Inventor)

    1986-01-01

    An improved apparatus and method for growing crystals from a melt employing a heat pipe, consisting of one or more sections, each section serving to control temperature and thermal gradients in the crystal as it forms inside the pipe.

  12. Crystal structure and prediction.

    PubMed

    Thakur, Tejender S; Dubey, Ritesh; Desiraju, Gautam R

    2015-04-01

    The notion of structure is central to the subject of chemistry. This review traces the development of the idea of crystal structure since the time when a crystal structure could be determined from a three-dimensional diffraction pattern and assesses the feasibility of computationally predicting an unknown crystal structure of a given molecule. Crystal structure prediction is of considerable fundamental and applied importance, and its successful execution is by no means a solved problem. The ease of crystal structure determination today has resulted in the availability of large numbers of crystal structures of higher-energy polymorphs and pseudopolymorphs. These structural libraries lead to the concept of a crystal structure landscape. A crystal structure of a compound may accordingly be taken as a data point in such a landscape.

  13. Growth of dopamine crystals

    NASA Astrophysics Data System (ADS)

    Patil, Vidya; Patki, Mugdha

    2016-05-01

    Many nonlinear optical (NLO) crystals have been identified as potential candidates in optical and electro-optical devices. Use of NLO organic crystals is expected in photonic applications. Hence organic nonlinear optical materials have been intensely investigated due to their potentially high nonlinearities, and rapid response in electro-optic effect compared to inorganic NLO materials. There are many methods to grow organic crystals such as vapor growth method, melt growth method and solution growth method. Out of these methods, solution growth method is useful in providing constraint free crystal. Single crystals of Dopamine have been grown by evaporating the solvents from aqueous solution. Crystals obtained were of the size of orders of mm. The crystal structure of dopamine was determined using XRD technique. Images of crystals were obtained using FEG SEM Quanta Series under high vacuum and low KV.

  14. Crystal Structure and Prediction

    NASA Astrophysics Data System (ADS)

    Thakur, Tejender S.; Dubey, Ritesh; Desiraju, Gautam R.

    2015-04-01

    The notion of structure is central to the subject of chemistry. This review traces the development of the idea of crystal structure since the time when a crystal structure could be determined from a three-dimensional diffraction pattern and assesses the feasibility of computationally predicting an unknown crystal structure of a given molecule. Crystal structure prediction is of considerable fundamental and applied importance, and its successful execution is by no means a solved problem. The ease of crystal structure determination today has resulted in the availability of large numbers of crystal structures of higher-energy polymorphs and pseudopolymorphs. These structural libraries lead to the concept of a crystal structure landscape. A crystal structure of a compound may accordingly be taken as a data point in such a landscape.

  15. Crystallization Pathways in Biomineralization

    NASA Astrophysics Data System (ADS)

    Weiner, Steve; Addadi, Lia

    2011-08-01

    A crystallization pathway describes the movement of ions from their source to the final product. Cells are intimately involved in biological crystallization pathways. In many pathways the cells utilize a unique strategy: They temporarily concentrate ions in intracellular membrane-bound vesicles in the form of a highly disordered solid phase. This phase is then transported to the final mineralization site, where it is destabilized and crystallizes. We present four case studies, each of which demonstrates specific aspects of biological crystallization pathways: seawater uptake by foraminifera, calcite spicule formation by sea urchin larvae, goethite formation in the teeth of limpets, and guanine crystal formation in fish skin and spider cuticles. Three representative crystallization pathways are described, and aspects of the different stages of crystallization are discussed. An in-depth understanding of these complex processes can lead to new ideas for synthetic crystallization processes of interest to materials science.

  16. Thermal Conductance through Sapphire-Sapphire Bonding

    NASA Astrophysics Data System (ADS)

    Suzuki, T.; Tomaru, T.; Haruyama, T.; Shintomi, T.; Uchinyama, T.; Miyoki, S.; Ohashi, M.; Kuroda, K.

    2003-07-01

    Thermal conductance on sapphire-sapphire bonded interface has been investigated. Two pieces of single crystal sapphire bar with square cross section were bonded together by adhesion free bonding. In two sections of the bar, thermal conductivity was measured between 5 K to 300K. One section contains a bonded interface and the other section measured a thermal conductivity of the sapphire as a reference. No significant thermal resistance due to bonded interface was found from this measurement. Obtained thermal conductivity reaches κ 1 × 104 [W/m·K] in temperature range of T = 20 ˜ 30 K which is a planned operating temperature of a cryogenic mirror of the Large scale Cryogenic Gravitational wave telescope. It looks promising for sapphire bonding technique to improve a heat transfer from a large cryogenic mirror to susp ension wires.

  17. Photonic Crystal Fibers

    DTIC Science & Technology

    2005-12-01

    passive and active versions of each fiber designed under this task. Crystal Fibre shall provide characteristics of the fiber fabricated to include core...passive version of multicore fiber iteration 2. 15. SUBJECT TERMS EOARD, Laser physics, Fibre Lasers, Photonic Crystal, Multicore, Fiber Laser 16...9 00* 0 " CRYSTAL FIBRE INT ODUCTION This report describes the photonic crystal fibers developed under agreement No FA8655-o5-a- 3046. All

  18. CRYSTAL FILTER TEST SET

    DTIC Science & Technology

    CRYSTAL FILTERS, *HIGH FREQUENCY, *RADIOFREQUENCY FILTERS, AMPLIFIERS, ELECTRIC POTENTIAL, FREQUENCY, IMPEDANCE MATCHING , INSTRUMENTATION, RADIOFREQUENCY, RADIOFREQUENCY AMPLIFIERS, TEST EQUIPMENT, TEST METHODS

  19. Crystallization from Gels

    NASA Astrophysics Data System (ADS)

    Narayana Kalkura, S.; Natarajan, Subramanian

    Among the various crystallization techniques, crystallization in gels has found wide applications in the fields of biomineralization and macromolecular crystallization in addition to crystallizing materials having nonlinear optical, ferroelectric, ferromagnetic, and other properties. Furthermore, by using this method it is possible to grow single crystals with very high perfection that are difficult to grow by other techniques. The gel method of crystallization provides an ideal technique to study crystal deposition diseases, which could lead to better understanding of their etiology. This chapter focuses on crystallization in gels of compounds that are responsible for crystal deposition diseases. The introduction is followed by a description of the various gels used, the mechanism of gelling, and the fascinating phenomenon of Liesegang ring formation, along with various gel growth techniques. The importance and scope of study on crystal deposition diseases and the need for crystal growth experiments using gel media are stressed. The various crystal deposition diseases, viz. (1) urolithiasis, (2) gout or arthritis, (3) cholelithiasis and atherosclerosis, and (4) pancreatitis and details regarding the constituents of the crystal deposits responsible for the pathological mineralization are discussed. Brief accounts of the theories of the formation of urinary stones and gallstones and the role of trace elements in urinary stone formation are also given. The crystallization in gels of (1) the urinary stone constituents, viz. calcium oxalate, calcium phosphates, uric acid, cystine, etc., (2) the constituents of the gallstones, viz. cholesterol, calcium carbonate, etc., (3) the major constituent of the pancreatic calculi, viz., calcium carbonate, and (4) cholic acid, a steroidal hormone are presented. The effect of various organic and inorganic ions, trace elements, and extracts from cereals, herbs, and fruits on the crystallization of major urinary stone and gallstone

  20. Solubility, thermal, photoconductivity and laser damage threshold studies on L-serine acetate (LSA) single crystal

    NASA Astrophysics Data System (ADS)

    Rajesh, K.; Thayanithi, V.; Mani, A.; Amudha, M.; Kumar, P. Praveen

    2015-06-01

    L-serine acetate crystal was grown by slow evaporation technique. Solubility of L-Serine Acetate was determined at different temperatures. L-Serine Acetate was characterized by SEM is to identify the morphology of the crystal. TG and DTA study reveals the thermal stability of the grown crystal. Dielectric measurement was carried out for different temperature ranges. Photo conductivity study revealed the nature of conductivity of the crystal under halogen light. Laser damage threshold of the crystal was measured using Nd:YAG laser source. NLO property of the crystal is confirmed by Kurtz-Perry powder technique.

  1. High conductance surge cable

    DOEpatents

    Murray, M.M.; Wilfong, D.H.; Lomax, R.E.

    1998-12-08

    An electrical cable for connecting transient voltage surge suppressors to electrical power panels. A strip of electrically conductive foil defines a longitudinal axis, with a length of an electrical conductor electrically attached to the metallic foil along the longitudinal axis. The strip of electrically conductive foil and the length of an electrical conductor are covered by an insulating material. For impedance matching purposes, triangular sections can be removed from the ends of the electrically conductive foil at the time of installation. 6 figs.

  2. High conductance surge cable

    DOEpatents

    Murray, Matthew M.; Wilfong, Dennis H.; Lomax, Ralph E.

    1998-01-01

    An electrical cable for connecting transient voltage surge suppressers to ectrical power panels. A strip of electrically conductive foil defines a longitudinal axis, with a length of an electrical conductor electrically attached to the metallic foil along the longitudinal axis. The strip of electrically conductive foil and the length of an electrical conductor are covered by an insulating material. For impedance matching purposes, triangular sections can be removed from the ends of the electrically conductive foil at the time of installation.

  3. Protein crystal growth in microgravity: Temperature induced large scale crystallization of insulin

    NASA Technical Reports Server (NTRS)

    Long, Marianna M.; Delucas, Larry J.; Smith, C.; Carson, M.; Moore, K.; Harrington, Michael D.; Pillion, D. J.; Bishop, S. P.; Rosenblum, W. M.; Naumann, R. J.

    1994-01-01

    One of the major stumbling blocks that prevents rapid structure determination using x-ray crystallography is macro-molecular crystal growth. There are many examples where crystallization takes longer than structure determination. In some cases, it is impossible to grow useful crystals on earth. Recent experiments conducted in conjuction with NASA on various Space Shuttle missions have demonstrated that protein crystals often grow larger and display better internal molecular order than their earth-grown counterparts. This paper reports results from three Shuttle flights using the Protein Crystallization Facility (PCF). The PCF hardware produced large, high-quality insulin crystals by using a temperature change as the sole means to affect protein solubility and thus, crystallization. The facility consists of cylinders/containers with volumes of 500, 200, 100, and 50 ml. Data from the three Shuttle flights demonstrated that larger, higher resolution crystals (as evidenced by x-ray diffraction data) were obtained from the microgravity experiments when compared to earth-grown crystals.

  4. Food Crystalization and Eggs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Food Crystalization and Eggs Deana R. Jones, Ph.D. USDA Agricultural Research Service Egg Safety and Quality Research Unit Athens, Georgia, USA Deana.Jones@ars.usda.gov Sugar, salt, lactose, tartaric acid and ice are examples of constituents than can crystallize in foods. Crystallization in a foo...

  5. Artistic Crystal Creations

    ERIC Educational Resources Information Center

    Lange, Catherine

    2008-01-01

    In this inquiry-based, integrative art and science activity, Grade 5-8 students use multicolored Epsom salt (magnesium sulfate) crystallizing solutions to reveal beautiful, cylindrical, 3-dimensional, needle-shaped structures. Through observations of the crystal art, students analyze factors that contribute to crystal size and formation, compare…

  6. Annealing macromolecular crystals.

    PubMed

    Hanson, B Leif; Bunick, Gerard J

    2007-01-01

    The process of crystal annealing has been used to improve the quality of diffraction from crystals that would otherwise be discarded for displaying unsatisfactory diffraction after flash cooling. Although techniques and protocols vary, macromolecular crystals are annealed by warming the flash-cooled crystal, then flash cooling it again. To apply macromolecular crystal annealing, a flash-cooled crystal displaying unacceptably high mosaicity or diffraction from ice is removed from the goniometer and immediately placed in cryoprotectant buffer. The crystal is incubated in the buffer at either room temperature or the temperature at which the crystal was grown. After about 3 min, the crystal is remounted in the loop and flash cooled. In situ annealing techniques, where the cold stream is diverted and the crystal allowed to warm on the loop prior to flash cooling, are variations of annealing that appears to work best when large solvent channels are not present in the crystal lattice or the solvent content of the crystal is relatively low.

  7. Protein Crystal Based Nanomaterials

    NASA Technical Reports Server (NTRS)

    Bell, Jeffrey A.; VanRoey, Patrick

    2001-01-01

    This is the final report on a NASA Grant. It concerns a description of work done, which includes: (1) Protein crystals cross-linked to form fibers; (2) Engineering of protein to favor crystallization; (3) Better knowledge-based potentials for protein-protein contacts; (4) Simulation of protein crystallization.

  8. Electrically conductive cellulose composite

    DOEpatents

    Evans, Barbara R.; O'Neill, Hugh M.; Woodward, Jonathan

    2010-05-04

    An electrically conductive cellulose composite includes a cellulose matrix and an electrically conductive carbonaceous material incorporated into the cellulose matrix. The electrical conductivity of the cellulose composite is at least 10 .mu.S/cm at 25.degree. C. The composite can be made by incorporating the electrically conductive carbonaceous material into a culture medium with a cellulose-producing organism, such as Gluconoacetobacter hansenii. The composites can be used to form electrodes, such as for use in membrane electrode assemblies for fuel cells.

  9. Tuning thermal conductivity in molybdenum disulfide by electrochemical intercalation

    PubMed Central

    Zhu, Gaohua; Liu, Jun; Zheng, Qiye; Zhang, Ruigang; Li, Dongyao; Banerjee, Debasish; Cahill, David G.

    2016-01-01

    Thermal conductivity of two-dimensional (2D) materials is of interest for energy storage, nanoelectronics and optoelectronics. Here, we report that the thermal conductivity of molybdenum disulfide can be modified by electrochemical intercalation. We observe distinct behaviour for thin films with vertically aligned basal planes and natural bulk crystals with basal planes aligned parallel to the surface. The thermal conductivity is measured as a function of the degree of lithiation, using time-domain thermoreflectance. The change of thermal conductivity correlates with the lithiation-induced structural and compositional disorder. We further show that the ratio of the in-plane to through-plane thermal conductivity of bulk crystal is enhanced by the disorder. These results suggest that stacking disorder and mixture of phases is an effective mechanism to modify the anisotropic thermal conductivity of 2D materials. PMID:27767030

  10. Tuning thermal conductivity in molybdenum disulfide by electrochemical intercalation.

    PubMed

    Zhu, Gaohua; Liu, Jun; Zheng, Qiye; Zhang, Ruigang; Li, Dongyao; Banerjee, Debasish; Cahill, David G

    2016-10-21

    Thermal conductivity of two-dimensional (2D) materials is of interest for energy storage, nanoelectronics and optoelectronics. Here, we report that the thermal conductivity of molybdenum disulfide can be modified by electrochemical intercalation. We observe distinct behaviour for thin films with vertically aligned basal planes and natural bulk crystals with basal planes aligned parallel to the surface. The thermal conductivity is measured as a function of the degree of lithiation, using time-domain thermoreflectance. The change of thermal conductivity correlates with the lithiation-induced structural and compositional disorder. We further show that the ratio of the in-plane to through-plane thermal conductivity of bulk crystal is enhanced by the disorder. These results suggest that stacking disorder and mixture of phases is an effective mechanism to modify the anisotropic thermal conductivity of 2D materials.

  11. Synthesis, crystal growth and characterization of nonlinear optical organic crystal: p-Toluidinium p-toluenesulphonate

    SciTech Connect

    Vijayakumar, P.; Anandha Babu, G.; Ramasamy, P.

    2012-04-15

    been determined using Kurtz powder technique. Thermo gravimetric and differential thermal analyses were used to study its thermal properties. Dielectric constant, dielectric loss and AC conductivity of the grown p-TTS single crystal has been studied.

  12. Maximizing Macromolecule Crystal Size for Neutron Diffraction Experiments

    NASA Technical Reports Server (NTRS)

    Judge, R. A.; Kephart, R.; Leardi, R.; Myles, D. A.; Snell, E. H.; vanderWoerd, M.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    A challenge in neutron diffraction experiments is growing large (greater than 1 cu mm) macromolecule crystals. In taking up this challenge we have used statistical experiment design techniques to quickly identify crystallization conditions under which the largest crystals grow. These techniques provide the maximum information for minimal experimental effort, allowing optimal screening of crystallization variables in a simple experimental matrix, using the minimum amount of sample. Analysis of the results quickly tells the investigator what conditions are the most important for the crystallization. These can then be used to maximize the crystallization results in terms of reducing crystal numbers and providing large crystals of suitable habit. We have used these techniques to grow large crystals of Glucose isomerase. Glucose isomerase is an industrial enzyme used extensively in the food industry for the conversion of glucose to fructose. The aim of this study is the elucidation of the enzymatic mechanism at the molecular level. The accurate determination of hydrogen positions, which is critical for this, is a requirement that neutron diffraction is uniquely suited for. Preliminary neutron diffraction experiments with these crystals conducted at the Institute Laue-Langevin (Grenoble, France) reveal diffraction to beyond 2.5 angstrom. Macromolecular crystal growth is a process involving many parameters, and statistical experimental design is naturally suited to this field. These techniques are sample independent and provide an experimental strategy to maximize crystal volume and habit for neutron diffraction studies.

  13. Conduction in Polydiacetylene Bilayers.

    DTIC Science & Technology

    1979-12-04

    This indicates that the polymer backbone has little effect in the conduction machanism of a dark undoped sample but only comes into play upon...almost none to doping. This indicates that the polymer backbone has little effect in the conduction machanism of a dark undoped sample but only comes into

  14. Electrically conductive diamond electrodes

    DOEpatents

    Swain, Greg; Fischer, Anne ,; Bennett, Jason; Lowe, Michael

    2009-05-19

    An electrically conductive diamond electrode and process for preparation thereof is described. The electrode comprises diamond particles coated with electrically conductive doped diamond preferably by chemical vapor deposition which are held together with a binder. The electrodes are useful for oxidation reduction in gas, such as hydrogen generation by electrolysis.

  15. Conductive Critical Thinking

    ERIC Educational Resources Information Center

    Paetkau, Mark

    2007-01-01

    One of my goals as an instructor is to teach students critical thinking skills. This paper presents an example of a student-led discussion of heat conduction at the first-year level. Heat loss from a human head is calculated using conduction and radiation models. The results of these plausible (but wrong) models of heat transfer contradict what…

  16. Protein crystallization with paper

    NASA Astrophysics Data System (ADS)

    Matsuoka, Miki; Kakinouchi, Keisuke; Adachi, Hiroaki; Maruyama, Mihoko; Sugiyama, Shigeru; Sano, Satoshi; Yoshikawa, Hiroshi Y.; Takahashi, Yoshinori; Yoshimura, Masashi; Matsumura, Hiroyoshi; Murakami, Satoshi; Inoue, Tsuyoshi; Mori, Yusuke; Takano, Kazufumi

    2016-05-01

    We developed a new protein crystallization method that incorporates paper. A small piece of paper, such as facial tissue or KimWipes, was added to a drop of protein solution in the traditional sitting drop vapor diffusion technique, and protein crystals grew by incorporating paper. By this method, we achieved the growth of protein crystals with reducing osmotic shock. Because the technique is very simple and the materials are easy to obtain, this method will come into wide use for protein crystallization. In the future, it could be applied to nanoliter-scale crystallization screening on a paper sheet such as in inkjet printing.

  17. Improving marginal crystals.

    PubMed

    Carter, Charles W; Riès-Kautt, Madeleine

    2007-01-01

    The physical chemistry of crystal growth can help to identify directions in which to look for improved crystal properties. In this chapter, we summarize how crystal growth depends on parameters that can be controlled experimentally, and relate them to the tools available for optimizing a particular crystal form for crystal shape, volume, and diffraction quality. Our purpose is to sketch the conceptual basis of optimization and to provide sample protocols derived from those foundations. We hope to assist even those who chose not to use systematic methods by enabling them to carry out rudimentary optimization searches armed with a better understanding of how the underlying physical chemistry operates.

  18. Manganese olivine I: Electrical conductivity

    NASA Astrophysics Data System (ADS)

    Bai, Quan; Wang, Z.-C.; Kohlstedt, D. L.

    1995-12-01

    To investigate the point defect chemistry and the kinetic properties of manganese olivine Mn2SiO4, electrical conductivity ( ’) of single crystals was measured along either the [100] or the [010] direction. The experiments were carried out at temperatures T=850 1200 °C and oxygen fugacities f_{{text{O}}_{text{2}} } = 10^{ - 11} - 10^2 atm under both Mn oxide ( MO) buffered and MnSiO3 ( MS) buffered conditions. Under the same thermodynamic conditions, charge transport along [100] is 2.5 3.0 times faster than along [010]. At high oxygen fugacities, the electrical conductivity of samples buffered against MS is ˜1.6 times larger than that of samples buffered against MO; while at low oxygen fugacities, the electrical conductivity is nearly identical for the two buffer cases. The dependencies of electrical conductivity on oxygen fugacity and temperature are essentially the same for conduction along the [100] and [010] directions, as well as for samples coexisting with a solid-state buffer of either MO or MS. Hence, it is proposed that the same conduction mechanisms operate for samples of either orientation in contact with either solid-state buffer. The electrical conductivity data lie on concave upward curves on a log-log plot of σ vs f_{{text{O}}_{text{2}} } , giving rise to two f_{{text{O}}_{text{2}} } = 10^{ - 11} - 10^2 regimes with different oxygen fugacity exponents. In the low-f_{{text{O}}_{text{2}} } = 10^{ - 11} - 10^2 regime left( {f_{{text{O}}_{text{2}} } < 10^{ - 7} {text{atm}}} right), the f_{{text{O}}_{text{2}} } = 10^{ - 11} - 10^2 exponent, m, is 0, the MnSiO3-activity exponent, q, is ˜0, and the activation energy, Q, is 45 kJ/mol. In the high f_{{text{O}}_{text{2}} } = 10^{ - 11} - 10^2 regime left( {f_{{text{O}}_{text{2}} } > 10^{ - 7} {text{atm}}} right), m=1/6, q=1/4 1/3, and Q=45 and 200 kJ/mol for T<1100 °C and T>1100 °C, respectively. Based on a comparison of experimental data with results from point defect chemistry calculations, it is

  19. Conductive fabric seal

    DOEpatents

    Livesay, Ronald Jason; Mason, Brandon William; Kuhn, Michael Joseph; Rowe, Nathan Carl

    2015-10-13

    Disclosed are several examples of a system and method for detecting if an article is being tampered with. Included is a covering made of a substrate that is coated with a layer of an electrically conductive material that forms an electrically conductive surface having an electrical resistance. The covering is configured to at least partially encapsulate the article such that the article cannot be tampered with, without modifying the electrical resistance of the electrically conductive surface of the covering. A sensing device is affixed to the electrically conductive surface of the covering and the sensing device monitors the condition of the covering by producing a signal that is indicative of the electrical resistance of the electrically conductive surface of the covering. A measured electrical resistance that differs from a nominal electrical resistance is indicative of a covering that is being tampered with and an alert is communicated to an observer.

  20. Conductive fabric seal

    DOEpatents

    Livesay, Ronald Jason; Mason, Brandon William; Kuhn, Michael Joseph; Rowe, Nathan Carl

    2017-04-04

    Disclosed are several examples of a system and method for detecting if an article is being tampered with. Included is a covering made of a substrate that is coated with a layer of an electrically conductive material that forms an electrically conductive surface having an electrical resistance. The covering is configured to at least partially encapsulate the article such that the article cannot be tampered with, without modifying the electrical resistance of the electrically conductive surface of the covering. A sensing device is affixed to the electrically conductive surface of the covering and the sensing device monitors the condition of the covering by producing a signal that is indicative of the electrical resistance of the electrically conductive surface of the covering. A measured electrical resistance that differs from a nominal electrical resistance is indicative of a covering that is being tampered with and an alert is communicated to an observer.

  1. Photonic crystal light source

    DOEpatents

    Fleming, James G.; Lin, Shawn-Yu; Bur, James A.

    2004-07-27

    A light source is provided by a photonic crystal having an enhanced photonic density-of-states over a band of frequencies and wherein at least one of the dielectric materials of the photonic crystal has a complex dielectric constant, thereby producing enhanced light emission at the band of frequencies when the photonic crystal is heated. The dielectric material can be a metal, such as tungsten. The spectral properties of the light source can be easily tuned by modification of the photonic crystal structure and materials. The photonic crystal light source can be heated electrically or other heating means. The light source can further include additional photonic crystals that exhibit enhanced light emission at a different band of frequencies to provide for color mixing. The photonic crystal light source may have applications in optical telecommunications, information displays, energy conversion, sensors, and other optical applications.

  2. Protein Crystal Growth

    NASA Technical Reports Server (NTRS)

    2003-01-01

    In order to rapidly and efficiently grow crystals, tools were needed to automatically identify and analyze the growing process of protein crystals. To meet this need, Diversified Scientific, Inc. (DSI), with the support of a Small Business Innovation Research (SBIR) contract from NASA s Marshall Space Flight Center, developed CrystalScore(trademark), the first automated image acquisition, analysis, and archiving system designed specifically for the macromolecular crystal growing community. It offers automated hardware control, image and data archiving, image processing, a searchable database, and surface plotting of experimental data. CrystalScore is currently being used by numerous pharmaceutical companies and academic and nonprofit research centers. DSI, located in Birmingham, Alabama, was awarded the patent Method for acquiring, storing, and analyzing crystal images on March 4, 2003. Another DSI product made possible by Marshall SBIR funding is VaporPro(trademark), a unique, comprehensive system that allows for the automated control of vapor diffusion for crystallization experiments.

  3. Macromolecular Crystallization in Microgravity

    NASA Technical Reports Server (NTRS)

    Snell, Edward H.; Helliwell, John R.

    2004-01-01

    The key concepts that attracted crystal growers, macromolecular or solid state, to microgravity research is that density difference fluid flows and sedimentation of the growing crystals are greatly reduced. Thus, defects and flaws in the crystals can be reduced, even eliminated, and crystal volume can be increased. Macromolecular crystallography differs from the field of crystalline semiconductors. For the latter, crystals are harnessed for their electrical behaviors. A crystal of a biological macromolecule is used instead for diffraction experiments (X-ray or neutron) to determine the three-dimensional structure of the macromolecule. The better the internal order of the crystal of a biological macromolecule then the more molecular structure detail that can be extracted. This structural information that enables an understanding of how the molecule functions. This knowledge is changing the biological and chemical sciences with major potential in understanding disease pathologies. Macromolecular structural crystallography in general is a remarkable field where physics, biology, chemistry, and mathematics meet to enable insight to the basic fundamentals of life. In this review, we examine the use of microgravity as an environment to grow macromolecular crystals. We describe the crystallization procedures used on the ground, how the resulting crystals are studied and the knowledge obtained from those crystals. We address the features desired in an ordered crystal and the techniques used to evaluate those features in detail. We then introduce the microgravity environment, the techniques to access that environment, and the theory and evidence behind the use of microgravity for crystallization experiments. We describe how ground-based laboratory techniques have been adapted to microgravity flights and look at some of the methods used to analyze the resulting data. Several case studies illustrate the physical crystal quality improvements and the macromolecular structural

  4. Electrical Conductivity in Insulator

    NASA Astrophysics Data System (ADS)

    Sinha, Anil Kumar

    2003-03-01

    ABSTRACT In insulating solid(Plastic Sheet)of 0.73mm thickness, the conduction process was ohmic at low D.C. electric feilds, but the feild strength increased the conductivity became feild dependent at high feilds and it exhibited some conductivity and the variation in conduction current was none-ohmic.The mechanism of electron transfer between two metallic electrodes separated by insulating material has received considerable attention. The electron transfer current was studied on 0.73mm plastic sheet and(I-V),(log I-log V),(log J-E^1/2)and (log o- 1/T) relations have been studied and the value of slope,electronic dielectric constant and activation energy for nature of conduction mechanism and process have been determined.The electrical conductivity measurements were carried out at room temperature (32.5 celcius)under high D.C. electric feilds of the order of 10^6 volt/meter.The sample of insulator(plastic sheet) was sandwiched between the aluminium electrodes of designed experimental cell,The effect of very high varying feilds at 32.5 celcius temperature,the electrical conduction has been proposed on the data obtained.The non-ohmic behavior in the sample seemed to start at an electric feild 3x10^6 volt/meter.In this case on data obtained it was concluded that "SCHOTTKY EMISSION MECHANISM" has been proposed. The activation energy was calculated by plotting(log o-1/T)characterstics at running temperature and it was found 0.325ev which is less than 1.0,It confirms predominance of Electronic Conduction. I=current in ampere V=volt T=temperature O=conductivity

  5. Some Properties Of Synthetic Single Crystal And Thin Film Diamonds

    NASA Astrophysics Data System (ADS)

    Yazu, Shuji; Sato, Shuichi; Fujimori, Naoji

    1989-01-01

    Large synthetic diamond single crystals, in sizes up to 1.4 ct, are produced on 4 commercial basis for some industrial application fields by Sumitomo Electric. The crystals are yellow colored type Ib stones which contain lower amounts of nitrogen (up to about 100 ppm) dispersed through the crystal structure in the form of singly substituting atoms. The impurity controlled type lb crystals have the highest thermal conductivity which is equivalent to that of pure type IIa crystals. Optical and thermal properties of diamond crystals are strongly affected by dispersed impurities. We studied the kinds of dispersed impurities and amounts of those impurity atoms in our synthesized crystals by SIMS. A relation of the thermal conductivities and the nitrogen concentrations of the crystals was examined. The state of nitrogen impurity in the crystals could be transformed by electron irradiation and subsequent high temperature annealing. The reaction rates for the transformation Ib nitrogen to type IaA aggregates and differences in crystal growth sectors have been studied. Vapor phase deposited diamond films are hopeful candidates for optical application of diamond. Preliminary spectroscopic analysis has been done for the free standing polycrystalline films.

  6. Crystal Polymorphism and Multiple Crystal Forms

    NASA Astrophysics Data System (ADS)

    Braga, Dario; Grepioni, Fabrizia; Maini, Lucia; Polito, Marco

    This chapter discusses the phenomenon of polymorphism in organic and organometallic compounds. Polymorphism is first introduced and then, to give the work some context, background information is given concerning properties and techniques for characterizing the solid phases. In particular, desolvation and interconverstion are examined, and the gas-solid reactions are presented as a successful route to obtaining new crystalline phases. Co-crystal definition is then described and the problem in distinguishing co-crystals and salts is evaluated.

  7. Dislocation conduction in Bi-Sb topological insulators

    NASA Astrophysics Data System (ADS)

    Hamasaki, Hiromu; Tokumoto, Yuki; Edagawa, Keiichi

    2017-02-01

    Previous theoretical works have predicted that when a specific condition is satisfied, dislocations in three-dimensional topological insulators form one-dimensional gapless states, which are topologically protected against disorder scattering. Here, the predicted dislocation conduction is experimentally investigated in Bi-Sb topological insulators. High-density dislocations with the Burgers vector satisfying the conductivity condition are introduced into Bi-Sb single crystals by plastic deformation. Conductivity measurements for deformed and undeformed samples and those for the deformed samples in different orientations show excess conductivity due to dislocation conduction.

  8. Cardiac conduction system

    MedlinePlus Videos and Cool Tools

    ... cardiac muscle cells in the walls of the heart that send signals to the heart muscle causing it to contract. The main components ... the cardiac conduction system's electrical activity in the heart.

  9. Conductive open frameworks

    DOEpatents

    Yaghi, Omar M.; Wan, Shun; Doonan, Christian J.; Wang, Bo; Deng, Hexiang

    2016-02-23

    The disclosure relates generally to materials that comprise conductive covalent organic frameworks. The disclosure also relates to materials that are useful to store and separate gas molecules and sensors.

  10. Electrically conductive material

    DOEpatents

    Singh, Jitendra P.; Bosak, Andrea L.; McPheeters, Charles C.; Dees, Dennis W.

    1993-01-01

    An electrically conductive material for use in solid oxide fuel cells, electrochemical sensors for combustion exhaust, and various other applications possesses increased fracture toughness over available materials, while affording the same electrical conductivity. One embodiment of the sintered electrically conductive material consists essentially of cubic ZrO.sub.2 as a matrix and 6-19 wt. % monoclinic ZrO.sub.2 formed from particles having an average size equal to or greater than about 0.23 microns. Another embodiment of the electrically conductive material consists essentially at cubic ZrO.sub.2 as a matrix and 10-30 wt. % partially stabilized zirconia (PSZ) formed from particles having an average size of approximately 3 microns.

  11. Electrically conductive material

    DOEpatents

    Singh, J.P.; Bosak, A.L.; McPheeters, C.C.; Dees, D.W.

    1993-09-07

    An electrically conductive material is described for use in solid oxide fuel cells, electrochemical sensors for combustion exhaust, and various other applications possesses increased fracture toughness over available materials, while affording the same electrical conductivity. One embodiment of the sintered electrically conductive material consists essentially of cubic ZrO[sub 2] as a matrix and 6-19 wt. % monoclinic ZrO[sub 2] formed from particles having an average size equal to or greater than about 0.23 microns. Another embodiment of the electrically conductive material consists essentially at cubic ZrO[sub 2] as a matrix and 10-30 wt. % partially stabilized zirconia (PSZ) formed from particles having an average size of approximately 3 microns. 8 figures.

  12. Protein crystal growth

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Atomic force microscopy uses laser technology to reveal a defect, a double-screw dislocation, on the surface of this crystal of canavalin, a major source of dietary protein for humans and domestic animals. When a crystal grows, attachment kinetics and transport kinetics are competing for control of the molecules. As a molecule gets close to the crystal surface, it has to attach properly for the crystal to be usable. NASA has funded investigators to look at those attachment kinetics from a theoretical standpoint and an experimental standpoint. Dr. Alex McPherson of the University of California, Irvine, is one of those investigators. He uses X-ray diffraction and atomic force microscopy in his laboratory to answer some of the many questions about how protein crystals grow. Atomic force microscopy provides a means of looking at how individual molecules are added to the surface of growing protein crystals. This helps McPherson understand the kinetics of protein crystal growth. McPherson asks, How fast do crystals grow? What are the forces involved? Investigators funded by NASA have clearly shown that such factors as the level of supersaturation and the rate of growth all affect the habit [characteristic arrangement of facets] of the crystal and the defects that occur in the crystal.

  13. Thermoelectric Properties of Conducting Polymers

    DTIC Science & Technology

    1994-07-01

    polyphenylene sulfide , all of which are made conductive by addition of carbon. Polymers made conductive in this way do not have a high Seebeck...merit. KEYWORDS: Polyaniline, conducting polymer, conductive vinyl, conductive nylon, conductive polyphenylene sulfide , polyoctylthiophene, Schiff’s...directions. Polyphenylene sulfide (Ryton) A conductive form of this material, which is commercially available, is made conductive by the presence of carbon

  14. Optical conductivity of alpha-Mn

    NASA Technical Reports Server (NTRS)

    Scoles, K. J.; Christy, R. W.

    1982-01-01

    The optical constants were measured at room temperature in the photon-energy range 0.6 to 6.5 eV on evaporated thin films. Evaporation conditions were chosen that gave the alpha-Mn crystal structure with reasonably large grains. The optical conductivity was separated into intraband and interband contributions by fitting to the Drude formula at low energies. The results are anomalous in comparison to other 3d transition metals. The free-electron lifetime is exceptionally sort (in agreement with the large dc resistivity of Mn), and the interband transitions seem unusually weak at the lower energies. Possible explanations related to the complicated crystal structure of alpha-Mn are discussed.

  15. Nonequilibrium mesoscopic conductance fluctuations

    NASA Astrophysics Data System (ADS)

    Ludwig, T.; Blanter, Ya. M.; Mirlin, A. D.

    2004-12-01

    We investigate the amplitude of mesoscopic fluctuations of the differential conductance of a metallic wire at arbitrary bias voltage V . For noninteracting electrons, the variance ⟨δg2⟩ increases with V . The asymptotic large- V behavior is ⟨δg2⟩˜V/Vc (where eVc=D/L2 is the Thouless energy), in agreement with the earlier prediction by Larkin and Khmelnitskii. We find, however, that this asymptotics has a very small numerical prefactor and sets in at very large V/Vc only, which strongly complicates its experimental observation. This high-voltage behavior is preceded by a crossover regime, V/Vc≲30 , where the conductance variance increases by a factor ˜3 as compared to its value in the regime of universal conductance fluctuations (i.e., at V→0 ). We further analyze the effect of dephasing due to the electron-electron scattering on ⟨δg2⟩ at high voltages. With the Coulomb interaction taken into account, the amplitude of conductance fluctuations becomes a nonmonotonic function of V . Specifically, ⟨δg2⟩ drops as 1/V for voltages V≫gVc , where g is the dimensionless conductance. In this regime, the conductance fluctuations are dominated by quantum-coherent regions of the wire adjacent to the reservoirs.

  16. Epithelial Conduction in Hydromedusae

    PubMed Central

    Mackie, G. O.; Passano, L. M.

    1968-01-01

    Sarsia, Euphysa, and other hydromedusae have been studied by electrophysiological techniques and are found to have nonnervous conducting epithelia resembling those described earlier for siphonophores. Simple, non-muscular epithelia fire singly or repetitively following brief electrical stimuli. The pulses recorded with suction electrodes are biphasic, initially positive, and show amplitudes of 0.75–2.0 mv, durations of 5–15 msec, and velocities of 15–35 cm/sec with short refractory periods. In the swimming muscle (myoepithelium) 2.0–4.0 mv composite events lasting 150–300 msec are associated with contraction waves. Propagation in nonnervous epithelia is typically all-or-none, nondecremental, and unpolarized. The subumbrellar endoderm lamella conducts independently of the adjacent ectoderm. The lower regions of the tentacles do not show propagated epithelial events. The spread of excitation in conducting epithelia and associated effector responses are described. Examples are given of interaction between events seemingly conducted in the nervous system and those in nonnervous epithelia. Either system may excite the other. Spontaneous activity, however, appears to originate in the nervous system. Conduction in nonnervous tissues is unaffected by excess Mg++ in concentrations suppressing presumed nervous activity, although this may not be a wholly adequate criterion for distinguishing components of the two systems. Evidence from old work by Romanes is considered in the light of these findings and the general significance of epithelial conduction is discussed. PMID:4386662

  17. Crystal-Growing Crucible To Suppress Convection

    NASA Technical Reports Server (NTRS)

    Richter, R.

    1986-01-01

    Platform under growth region stabilizes melt for more uniform crystal growth. In new crucible, platform just below growth interface so melt is too shallow to support convection. Critical depth for onset of pertinent instability calculated from heat flux through surface of melt, volume coefficient of thermal expansion, thermal conductivity, thermal diffusivity, and kinematic viscosity.

  18. Electrochemical Quartz Crystal Nanobalance

    NASA Astrophysics Data System (ADS)

    Inzelt, György

    The method of piezoelectric microgravimetry (nanogravimetry) using an electrochemical quartz crystal microbalance (EQCM) or nanobalance (EQCN) can be considered as a novel and much more sensitive version of electrogravimetry. The EQCN technique has become a widely used technique in several areas of electrochemistry, electroanalytical chemistry, bioelectrochemistry, etc. [1-10]. Obviously, mass changes occurring during adsorption, sorption, electrosorption, electrodeposition, or spontaneous deposition can be followed, which is very helpful for the elucidation of reaction mechanism via identification of the species accumulated on the surface. These investigations include metal and alloy deposition, underpotential deposition, electroplating, synthesis of conducting polymers by electropolymerization, adsorption of biologically active materials, and analytical determination of small ions and biomolecules. Of course, the opposite processes, i.e., spontaneous dissolution, electrodissolution, corrosion, can also be studied. Electrochemical oscillations, in which the formation and oxidation of chemisorbed molecular fragments play a determining role, have been studied, too. The majority of the investigations have been devoted to ion and solvent transport associated with the redox transformations of electrochemically active polymers. Similar studies have been carried out regarding polynuclear surface layers such as metal hexacyanometalates as well as inorganic and organic microcrystals of different compositions.

  19. Proton conducting cerate ceramics

    SciTech Connect

    Coffey, G.W.; Pederson, L.R.; Armstrong, T.R.; Bates, J.L.; Weber, W.J.

    1995-08-01

    Cerate perovskites of the general formula AM{sub x}Ce{sub 1-x}O{sub 3-{delta}}, where A = Sr or Ba and where M = Gd, Nd, Y, Yb or other rare earth dopant, are known to conduct a protonic current. Such materials may be useful as the electrolyte in a solid oxide fuel cell operating at intermediate temperatures, as an electrochemical hydrogen separation membrane, or as a hydrogen sensor. Conduction mechanisms in these materials were evaluated using dc cyclic voltammetry and mass spectrometry, allowing currents and activation energies for proton, electron, and oxygen ion contributions to the total current to be determined. For SrYb{sub 0.05}Ce{sub 0.95}O{sub 3-{delta}}, one of the best and most environmentally stable compositions, proton conduction followed two different mechanisms: a low temperature process, characterized by an activation energy of 0.42{+-}0.04 eV, and a high temperature process, characterized by an activation energy of 1.38{+-}0.13 eV. It is believed that the low temperature process is dominated by grain boundary conduction while bulk conduction is responsible for the high temperature process. The activation energy for oxygen ion conduction (0.97{+-}0.10 eV) agrees well with other oxygen conductors, while that for electronic conduction, 0.90{+-}0.09 eV, is affected by a temperature-dependent electron carrier concentration. Evaluated by direct measurement of mass flux through a dense ceramic with an applied dc field, oxygen ions were determined to be the majority charge carrier except at the lowest temperatures, followed by electrons and then protons.

  20. Automated macromolecular crystallization screening

    DOEpatents

    Segelke, Brent W.; Rupp, Bernhard; Krupka, Heike I.

    2005-03-01

    An automated macromolecular crystallization screening system wherein a multiplicity of reagent mixes are produced. A multiplicity of analysis plates is produced utilizing the reagent mixes combined with a sample. The analysis plates are incubated to promote growth of crystals. Images of the crystals are made. The images are analyzed with regard to suitability of the crystals for analysis by x-ray crystallography. A design of reagent mixes is produced based upon the expected suitability of the crystals for analysis by x-ray crystallography. A second multiplicity of mixes of the reagent components is produced utilizing the design and a second multiplicity of reagent mixes is used for a second round of automated macromolecular crystallization screening. In one embodiment the multiplicity of reagent mixes are produced by a random selection of reagent components.

  1. Antarctic stratospheric ice crystals

    NASA Technical Reports Server (NTRS)

    Goodman, J.; Toon, O. B.; Pueschel, R. F.; Snetsinger, K. G.; Verma, S.

    1989-01-01

    Ice crystals were replicated over the Palmer Peninsula at approximately 72 deg S on six occasions during the 1987 Airboirne Antarctic Ozone Experiment. The sampling altitude was between 12.5 and 18.5 km (45-65 thousand ft pressure altitude) with the temperature between 190 and 201 K. The atmosphere was subsaturated with respect to ice in all cases. The collected crystals were predominantly solid and hollow columns. The largest crystals were sampled at lower altitudes where the potential temperature was below 400 K. While the crystals were larger than anticipated, their low concentration results in a total surface area that is less than one tenth of the total aerosol surface area. The large ice crystals may play an important role in the observed stratospheric dehydration processes through sedimentation. Evidence of scavenging of submicron particles further suggests that the ice crystals may be effective in the removal of stratospheric chemicals.

  2. Crystallization of Macromolecules

    PubMed Central

    Friedmann, David; Messick, Troy; Marmorstein, Ronen

    2014-01-01

    X-ray crystallography has evolved into a very powerful tool to determine the three-dimensional structure of macromolecules and macromolecular complexes. The major bottleneck in structure determination by X-ray crystallography is the preparation of suitable crystalline samples. This unit outlines steps for the crystallization of a macromolecule, starting with a purified, homogeneous sample. The first protocols describe preparation of the macromolecular sample (i.e., proteins, nucleic acids, and macromolecular complexes). The preparation and assessment of crystallization trials is then described, along with a protocol for confirming whether the crystals obtained are composed of macromolecule as opposed to a crystallization reagent. Next, the optimization of crystallization conditions is presented. Finally, protocols that facilitate the growth of larger crystals through seeding are described. PMID:18429252

  3. Crystallization of Macromolecules

    PubMed Central

    Friedmann, David; Messick, Troy; Marmorstein, Ronen

    2014-01-01

    X-ray crystallography has evolved into a very powerful tool to determine the three-dimensional structure of macromolecules and macromolecular complexes. The major bottleneck in structure determination by X-ray crystallography is the preparation of suitable crystalline samples. This unit outlines steps for the crystallization of a macromolecule, starting with a purified, homogeneous sample. The first protocols describe preparation of the macromolecular sample (i.e., proteins, nucleic acids, and macromolecular complexes). The preparation and assessment of crystallization trials is then described, along with a protocol for confirming whether the crystals obtained are composed of macromolecule as opposed to a crystallization reagent . Next, the optimization of crystallization conditions is presented. Finally, protocols that facilitate the growth of larger crystals through seeding are described. PMID:22045560

  4. Cartilage conduction hearing.

    PubMed

    Shimokura, Ryota; Hosoi, Hiroshi; Nishimura, Tadashi; Yamanaka, Toshiaki; Levitt, Harry

    2014-04-01

    Sound information is known to travel to the cochlea via either air or bone conduction. However, a vibration signal, delivered to the aural cartilage via a transducer, can also produce a clearly audible sound. This type of conduction has been termed "cartilage conduction." The aural cartilage forms the outer ear and is distributed around the exterior half of the external auditory canal. In cartilage conduction, the cartilage and transducer play the roles of a diaphragm and voice coil of a loudspeaker, respectively. There is a large gap between the impedances of cartilage and skull bone, such that cartilage vibrations are not easily transmitted through bone. Thus, these methods of conduction are distinct. In this study, force was used to apply a transducer to aural cartilage, and it was found that the sound in the auditory canal was amplified, especially for frequencies below 2 kHz. This effect was most pronounced at an application force of 1 N, which is low enough to ensure comfort in the design of hearing aids. The possibility of using force adjustments to vary amplification may also have applications for cell phone design.

  5. Liquid Crystal Optofluidics

    SciTech Connect

    Vasdekis, Andreas E.; Cuennet, J. G.; Psaltis, D.

    2012-10-11

    By employing anisotropic fluids and namely liquid crystals, fluid flow becomes an additional degree of freedom in designing optofluidic devices. In this paper, we demonstrate optofluidic liquid crystal devices based on the direct flow of nematic liquid crystals in microfluidic channels. Contrary to previous reports, in the present embodiment we employ the effective phase delay acquired by light travelling through flowing liquid crystal, without analysing the polarisation state of the transmitted light. With this method, we demonstrate the variation in the diffraction pattern of an array of microfluidic channels acting as a grating. We also discuss our recent activities in integrating mechanical oscillators for on-chip peristaltic pumping.

  6. Automation in biological crystallization.

    PubMed

    Stewart, Patrick Shaw; Mueller-Dieckmann, Jochen

    2014-06-01

    Crystallization remains the bottleneck in the crystallographic process leading from a gene to a three-dimensional model of the encoded protein or RNA. Automation of the individual steps of a crystallization experiment, from the preparation of crystallization cocktails for initial or optimization screens to the imaging of the experiments, has been the response to address this issue. Today, large high-throughput crystallization facilities, many of them open to the general user community, are capable of setting up thousands of crystallization trials per day. It is thus possible to test multiple constructs of each target for their ability to form crystals on a production-line basis. This has improved success rates and made crystallization much more convenient. High-throughput crystallization, however, cannot relieve users of the task of producing samples of high quality. Moreover, the time gained from eliminating manual preparations must now be invested in the careful evaluation of the increased number of experiments. The latter requires a sophisticated data and laboratory information-management system. A review of the current state of automation at the individual steps of crystallization with specific attention to the automation of optimization is given.

  7. Tunable plasmonic crystal

    DOEpatents

    Dyer, Gregory Conrad; Shaner, Eric A.; Reno, John L.; Aizin, Gregory

    2015-08-11

    A tunable plasmonic crystal comprises several periods in a two-dimensional electron or hole gas plasmonic medium that is both extremely subwavelength (.about..lamda./100) and tunable through the application of voltages to metal electrodes. Tuning of the plasmonic crystal band edges can be realized in materials such as semiconductors and graphene to actively control the plasmonic crystal dispersion in the terahertz and infrared spectral regions. The tunable plasmonic crystal provides a useful degree of freedom for applications in slow light devices, voltage-tunable waveguides, filters, ultra-sensitive direct and heterodyne THz detectors, and THz oscillators.

  8. Liquid crystal optofluidics

    NASA Astrophysics Data System (ADS)

    Vasdekis, A. E.; Cuennet, J. G.; Psaltis, D.

    2012-10-01

    By employing anisotropic fluids and namely liquid crystals, fluid flow becomes an additional degree of freedom in designing optofluidic devices. In this paper, we demonstrate optofluidic liquid crystal devices based on the direct flow of nematic liquid crystals in microfluidic channels. Contrary to previous reports, in the present embodiment we employ the effective phase delay acquired by light travelling through flowing liquid crystal, without analysing the polarisation state of the transmitted light. With this method, we demonstrate the variation in the diffraction pattern of an array of microfluidic channels acting as a grating. We also discuss our recent activities in integrating mechanical oscillators for on-chip peristaltic pumping.

  9. Heroin crystal nephropathy.

    PubMed

    Bautista, Josef Edrik Keith; Merhi, Basma; Gregory, Oliver; Hu, Susie; Henriksen, Kammi; Gohh, Reginald

    2015-06-01

    In this paper we present an interesting case of acute kidney injury and severe metabolic alkalosis in a patient with a history of heavy heroin abuse. Urine microscopy showed numerous broomstick-like crystals. These crystals are also identified in light and electron microscopy. We hypothesize that heroin crystalizes in an alkaline pH, resulting in tubular obstruction and acute kidney injury. Management is mainly supportive as there is no known specific therapy for this condition. This paper highlights the utility of urine microscopy in diagnosing the etiology of acute kidney injury and proposes a novel disease called heroin crystal nephropathy.

  10. Automation in biological crystallization

    PubMed Central

    Shaw Stewart, Patrick; Mueller-Dieckmann, Jochen

    2014-01-01

    Crystallization remains the bottleneck in the crystallographic process leading from a gene to a three-dimensional model of the encoded protein or RNA. Automation of the individual steps of a crystallization experiment, from the preparation of crystallization cocktails for initial or optimization screens to the imaging of the experiments, has been the response to address this issue. Today, large high-throughput crystallization facilities, many of them open to the general user community, are capable of setting up thousands of crystallization trials per day. It is thus possible to test multiple constructs of each target for their ability to form crystals on a production-line basis. This has improved success rates and made crystallization much more convenient. High-throughput crystallization, however, cannot relieve users of the task of producing samples of high quality. Moreover, the time gained from eliminating manual preparations must now be invested in the careful evaluation of the increased number of experiments. The latter requires a sophisticated data and laboratory information-management system. A review of the current state of automation at the individual steps of crystallization with specific attention to the automation of optimization is given. PMID:24915074

  11. Crystals in magma chambers

    NASA Astrophysics Data System (ADS)

    Higgins, M.

    2011-12-01

    Differentiation processes in igneous systems are one way in which the diversity of igneous rocks is produced. Traditionally, magmatic diversity is considered as variations in the overall chemical composition, such as basalt and rhyolite, but I want to extend this definition to include textural diversity. Such textural variations can be manifested as differences in the amount of crystalline (and immiscible liquid) phases and in the origin and identity of such phases. One important differentiation process is crystal-liquid separation by floatation or decantation, which clearly necessitates crystals in the magma. Hence, it is important to determine if magmas in chambers (sensu lato) have crystals. The following discussion is framed in generalities - many exceptions occur. Diabase (dolerite) dykes are a common, widespread result of regional mafic magmatism. The rims of most diabase dykes have few or no phenocrysts and crystals in the cores are commonly thought to have crystallized in place. Hence, this major mafic magmatic source did not have crystals, although compositional diversity of these dykes is commonly explained by crystal-liquid separation. This can be resolved if crystallisation was on the walls on the magma chamber. Similarly, most flood basalts are low in crystals and separation of those that are present cannot always explain the observed compositional diversity. Crystal-rich flows do occur, for example the 'Giant Plagioclase Basalts' of the Deccan series, but the crystals are thought to form or accumulate in a crystal-rich zone beneath the roof of the chamber - the rest of the chamber probably has few crystals. Some magmas from Hawaii contain significant amounts of olivine crystals, but most of these are deformed and cannot have crystallised in the chamber. In this case the crystals are thought to grow as the magma passes through a decollement zone. They may have grown on the walls or been trapped by filters. Basaltic andesite ignimbrites generally have

  12. Quantum Conductivity of Nanosystems

    NASA Astrophysics Data System (ADS)

    Pozhar, Liudmila

    2004-03-01

    Quantum statistical mechanical method of Bogoliubov-Tyablikov two-time Green's functions (TTGFs) suggested by Zubarev and Tserkovnikov is generalized to include spatially inhomogeneous systems, such as small semiconductor quantum dots, artificial atoms, etc. The developed formalism is applied to derive a fundamental quantum theory of conductivity of spatially inhomogeneous systems in weak external electromagnetic fields. Conservation equations for the charge and current densities are derived and analyzed. Explicit expressions for the linear (in the field potentials) longitudal and transverse quantum conductivity, dielectric and magnetic susceptibilities are also derived in terms of the equilibrium/steady state charge density - charge density and microcurrent-microcurrent retarded TTGFs. The obtained results are used in conjunction with quantum computations of electronic energy spectra of small clusters of In, Ga and As atoms to predict the quantum conductivity of such clusters.

  13. Proliferating conduction by isomerism

    NASA Astrophysics Data System (ADS)

    Kaur, Rupan Preet; Sawhney, Ravinder Singh; Engles, Derick

    2015-01-01

    The electrical conduction of isomers of anthracene molecule attached between two semi-infinite gold electrodes was simulated using extended Huckel theory (EHT)-based on semi-empirical model in this research work. The electron transport parameters were examined in two epochs by buffering anthracene and its isomer phenanthrene alternatively between gold electrodes using sulphur as an alligator clip, under variegated bias voltages. Differential NDR effect was observed in both the cases but phenanthrene exhibited more linear I-V curve than its counterpart, anthracene. The simulated results discovered phenanthrene as a better candidate than anthracene towards contributing to electrical conduction in molecular junctions. Phenanthrene reported maximum conductance of 0.74G0 whereas anthracene exhibited 0.03G0 at 0.8V.

  14. Anisotropy of electrical conductivity in dry olivine

    SciTech Connect

    Du Frane, W L; Roberts, J J; Toffelmier, D A; Tyburczy, J A

    2005-04-13

    [1] The electrical conductivity ({sigma}) was measured for a single crystal of San Carlos olivine (Fo{sub 89.1}) for all three principal orientations over oxygen fugacities 10{sup -7} < fO{sub 2} < 10{sup 1} Pa at 1100, 1200, and 1300 C. Fe-doped Pt electrodes were used in conjunction with a conservative range of fO{sub 2}, T, and time to reduce Fe loss resulting in data that is {approx}0.15 log units higher in conductivity than previous studies. At 1200 C and fO{sub 2} = 10{sup -1} Pa, {sigma}{sub [100]} = 10{sup -2.27} S/m, {sigma}{sub [010]} = 10{sup -2.49} S/m, {sigma}{sub [001]} = 10{sup -2.40} S/m. The dependences of {sigma} on T and fO{sub 2} have been simultaneously modeled with undifferentiated mixed conduction of small polarons and Mg vacancies to obtain steady-state fO{sub 2}-independent activation energies: Ea{sub [100]} = 0.32 eV, Ea{sub [010]} = 0.56 eV, Ea{sub [001]} = 0.71 eV. A single crystal of dry olivine would provide a maximum of {approx}10{sup 0.4} S/m azimuthal {sigma} contrast for T < 1500 C. The anisotropic results are combined to create an isotropic model with Ea = 0.53 eV.

  15. Electrical Conductivity in Textiles

    NASA Technical Reports Server (NTRS)

    2006-01-01

    Copper is the most widely used electrical conductor. Like most metals, though, it has several drawbacks: it is heavy, expensive, and can break. Fibers that conduct electricity could be the solutions to these problems, and they are of great interest to NASA. Conductive fibers provide lightweight alternatives to heavy copper wiring in a variety of settings, including aerospace, where weight is always a chief concern. This is an area where NASA is always seeking improved materials. The fibers are also more cost-effective than metals. Expenditure is another area where NASA is always looking to make improvements. In the case of electronics that are confined to small spaces and subject to severe stress, copper is prone to breaking and losing connection over time. Flexible conductive fibers eliminate that problem. They are more supple and stronger than brittle copper and, thus, find good use in these and similar situations. While clearly a much-needed material, electrically conductive fibers are not readily available. The cost of new technology development, with all the pitfalls of troubleshooting production and the years of testing, and without the guarantee of an immediate market, is often too much of a financial hazard for companies to risk. NASA, however, saw the need for electrical fibers in its many projects and sought out a high-tech textile company that was already experimenting in this field, Syscom Technology, Inc., of Columbus, Ohio. Syscom was founded in 1993 to provide computer software engineering services and basic materials research in the areas of high-performance polymer fibers and films. In 1999, Syscom decided to focus its business and technical efforts on development of high-strength, high-performance, and electrically conductive polymer fibers. The company developed AmberStrand, an electrically conductive, low-weight, strong-yet-flexible hybrid metal-polymer YARN.

  16. Transparent Conductive Nanostructures

    SciTech Connect

    2008-06-22

    The objectives of this program between UT-Battelle, LLC (the ''Contractor'') and (Battelle Memorial Institute) (the "Participant") were directed towards achieving significant improvement: in the electrical conductivity and optical/infrared transmission of single-wall carbon nanotube (SWNT)-based composite materials. These materials will be used in coating applications that range from aircraft canopies to display applications. The goal of the project was to obtain supported mats of SWNTs with sheet conductivities approaching 10 ohms/square combined with high optical transmission (>85% transmission at 550 nm), thereby permitting their application as a replacement for indium tin oxide (ITO) in a variety of applications such as flexible displays.

  17. Advanced Protein Crystallization Facility (APCF)

    NASA Technical Reports Server (NTRS)

    1998-01-01

    This section of the Life and Microgravity Spacelab (LMS) publication contains articles entitled: (1) Crystallization of EGFR-EGF; (2) Crystallization of Apocrustacyanin C1; (3) Crystallization and X-ray Analysis of 5S rRNA and the 5S rRNA Domain A; (4) Growth of Lysozyme Crystals at Low Nucleation Density; (5) Comparative Analysis of Aspartyl tRNA-synthetase and Thaumatin Crystals Grown on Earth and In Microgravity; (6) Lysosome Crystal Growth in the Advanced Protein Crystallization Facility Monitored via Mach-Zehnder Interferometry and CCD Video; (7) Analysis of Thaumatin Crystals Grown on Earth and in Microgravity; (8) Crystallization of the Nucleosome Core Particle; (9) Crystallization of Photosystem I; (10) Mechanism of Membrane Protein Crystal Growth: Bacteriorhodopsin-mixed Micelle Packing at the Consolution Boundary, Stabilized in Microgravity; (11) Crystallization in a Microgravity Environment of CcdB, a Protein Involved in the Control of Cell Death; and (12) Crystallization of Sulfolobus Solfataricus

  18. Channeling through Bent Crystals

    SciTech Connect

    Mack, Stephanie; /Ottawa U. /SLAC

    2012-09-07

    Bent crystals have demonstrated potential for use in beam collimation. A process called channeling is when accelerated particle beams are trapped by the nuclear potentials in the atomic planes within a crystal lattice. If the crystal is bent then the particles can follow the bending angle of the crystal. There are several different effects that are observed when particles travel through a bent crystal including dechanneling, volume capture, volume reflection and channeling. With a crystal placed at the edge of a particle beam, part of the fringe of the beam can be deflected away towards a detector or beam dump, thus helping collimate the beam. There is currently FORTRAN code by Igor Yazynin that has been used to model the passage of particles through a bent crystal. Using this code, the effects mentioned were explored for beam energy that would be seen at the Facility for Advanced Accelerator Experimental Tests (FACET) at a range of crystal orientations with respect to the incoming beam. After propagating 5 meters in vacuum space past the crystal the channeled particles were observed to separate from most of the beam with some noise due to dechanneled particles. Progressively smaller bending radii, with corresponding shorter crystal lengths, were compared and it was seen that multiple scattering decreases with the length of the crystal therefore allowing for cleaner detection of the channeled particles. The input beam was then modified and only a portion of the beam sent through the crystal. With the majority of the beam not affected by the crystal, most particles were not deflected and after propagation the channeled particles were seen to be deflected approximately 5mm. After a portion of the beam travels through the crystal, the entire beam was then sent through a quadrupole magnet, which increased the separation of the channeled particles from the remainder of the beam to a distance of around 20mm. A different code, which was developed at SLAC, was used to

  19. Protein crystal growth

    NASA Technical Reports Server (NTRS)

    Bugg, Charles E.

    1993-01-01

    Proteins account for 50% or more of the dry weight of most living systems and play a crucial role in virtually all biological processes. Since the specific functions of essentially all biological molecules are determined by their three-dimensional structures, it is obvious that a detailed understanding of the structural makeup of a protein is essential to any systematic research pertaining to it. At the present time, protein crystallography has no substitute, it is the only technique available for elucidating the atomic arrangements within complicated biological molecules. Most macromolecules are extremely difficult to crystallize, and many otherwise exciting and promising projects have terminated at the crystal growth stage. There is a pressing need to better understand protein crystal growth, and to develop new techniques that can be used to enhance the size and quality of protein crystals. There are several aspects of microgravity that might be exploited to enhance protein crystal growth. The major factor that might be expected to alter crystal growth processes in space is the elimination of density-driven convective flow. Another factor that can be readily controlled in the absence of gravity is the sedimentation of growing crystal in a gravitational field. Another potential advantage of microgravity for protein crystal growth is the option of doing containerless crystal growth. One can readily understand why the microgravity environment established by Earth-orbiting vehicles is perceived to offer unique opportunities for the protein crystallographer. The near term objectives of the Protein Crystal Growth in a Microgravity Environment (PCG/ME) project is to continue to improve the techniques, procedures, and hardware systems used to grow protein crystals in Earth orbit.

  20. Lithium ion conducting electrolytes

    DOEpatents

    Angell, C.A.; Liu, C.

    1996-04-09

    A liquid, predominantly lithium-conducting, ionic electrolyte is described having exceptionally high conductivity at temperatures of 100 C or lower, including room temperature, and comprising the lithium salts selected from the group consisting of the thiocyanate, iodide, bromide, chloride, perchlorate, acetate, tetrafluoroborate, perfluoromethane sulfonate, perfluoromethane sulfonamide, tetrahaloaluminate, and heptahaloaluminate salts of lithium, with or without a magnesium-salt selected from the group consisting of the perchlorate and acetate salts of magnesium. Certain of the latter embodiments may also contain molecular additives from the group of acetonitrile (CH{sub 3}CN), succinnonitrile (CH{sub 2}CN){sub 2}, and tetraglyme (CH{sub 3}--O--CH{sub 2}--CH{sub 2}--O--){sub 2} (or like solvents) solvated to a Mg{sup +2} cation to lower the freezing point of the electrolyte below room temperature. Other particularly useful embodiments contain up to about 40, but preferably not more than about 25, mol percent of a long chain polyether polymer dissolved in the lithium salts to provide an elastic or rubbery solid electrolyte of high ambient temperature conductivity and exceptional 100 C conductivity. Another embodiment contains up to about but not more than 10 mol percent of a molecular solvent such as acetone. 2 figs.

  1. Conductive Education Perspectives.

    ERIC Educational Resources Information Center

    Spivack, Frieda

    1995-01-01

    This article describes conductive education for children with neuromotor disabilities and identifies its major concepts, including orthofunction, rhythmic intention, and verbal regulation. Also addressed are the role of the conductor and the group and the training of conductors at the Peto Institute in Hungary. Research on the method's…

  2. Lithium ion conducting electrolytes

    DOEpatents

    Angell, Charles Austen; Liu, Changle; Xu, Kang; Skotheim, Terje A.

    1999-01-01

    The present invention relates generally to highly conductive alkali-metal ion non-crystalline electrolyte systems, and more particularly to novel and unique molten (liquid), rubbery, and solid electrolyte systems which are especially well suited for use with high current density electrolytic cells such as primary and secondary batteries.

  3. Conductive elastomeric extensometer

    NASA Technical Reports Server (NTRS)

    Gause, F. L.; Glenn, C. G.

    1971-01-01

    Bridge circuit, in which conductive elastomeric material is the variable leg, precisely measures surface area changes in the human body. Circuits are used singularly, or in quantity by adding elements and amplifier circuits. Elastomeric strips can be located in a form-fitting garment.

  4. Conductance Steamflow relationship

    SciTech Connect

    Whitney Trainor-Guitton

    2015-04-01

    These histograms represent our calibration of conductance of a volcanic geothermal field (with a clay cap) and the observed steam flow rates. See the following paper for further description: Trainor-Guitton, Hoversten,Nordquist, Intani, Value of information analysis using geothermal field data: accounting for multiple interpretations & determining new drilling locations. SEG Abstracts 2015.

  5. Conducting the Heat

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Heat conduction plays an important role in the efficiency and life span of electronic components. To keep electronic components running efficiently and at a proper temperature, thermal management systems transfer heat generated from the components to thermal surfaces such as heat sinks, heat pipes, radiators, or heat spreaders. Thermal surfaces absorb the heat from the electrical components and dissipate it into the environment, preventing overheating. To ensure the best contact between electrical components and thermal surfaces, thermal interface materials are applied. In addition to having high conductivity, ideal thermal interface materials should be compliant to conform to the components, increasing the surface contact. While many different types of interface materials exist for varying purposes, Energy Science Laboratories, Inc. (ESLI), of San Diego, California, proposed using carbon velvets as thermal interface materials for general aerospace and electronics applications. NASA s Johnson Space Center granted ESLI a Small Business Innovation Research (SBIR) contract to develop thermal interface materials that are lightweight and compliant, and demonstrate high thermal conductance even for nonflat surfaces. Through Phase II SBIR work, ESLI created Vel-Therm for the commercial market. Vel-Therm is a soft, carbon fiber velvet consisting of numerous high thermal conductivity carbon fibers anchored in a thin layer of adhesive. The velvets are fabricated by precision cutting continuous carbon fiber tows and electrostatically flocking the fibers into uncured adhesive, using proprietary techniques.

  6. Lithium ion conducting electrolytes

    DOEpatents

    Angell, C. Austen; Liu, Changle

    1996-01-01

    A liquid, predominantly lithium-conducting, ionic electrolyte having exceptionally high conductivity at temperatures of 100.degree. C. or lower, including room temperature, and comprising the lithium salts selected from the group consisting of the thiocyanate, iodide, bromide, chloride, perchlorate, acetate, tetrafluoroborate, perfluoromethane sulfonate, perfluoromethane sulfonamide, tetrahaloaluminate, and heptahaloaluminate salts of lithium, with or without a magnesium-salt selected from the group consisting of the perchlorate and acetate salts of magnesium. Certain of the latter embodiments may also contain molecular additives from the group of acetonitrile (CH.sub.3 CN) succinnonitrile (CH.sub.2 CN).sub.2, and tetraglyme (CH.sub.3 --O--CH.sub.2 --CH.sub.2 --O--).sub.2 (or like solvents) solvated to a Mg.sup.+2 cation to lower the freezing point of the electrolyte below room temperature. Other particularly useful embodiments contain up to about 40, but preferably not more than about 25, mol percent of a long chain polyether polymer dissolved in the lithium salts to provide an elastic or rubbery solid electrolyte of high ambient temperature conductivity and exceptional 100.degree. C. conductivity. Another embodiment contains up to about but not more than 10 mol percent of a molecular solvent such as acetone.

  7. Conducting Educational Design Research

    ERIC Educational Resources Information Center

    McKenney, Susan; Reeves, Thomas

    2012-01-01

    Educational design research blends scientific investigation with systematic development and implementation of solutions to educational problems. Empirical investigation is conducted in real learning settings--not laboratories--to craft usable and effective solutions. At the same time, the research is carefully structured to produce theoretical…

  8. Benefits of Conducting Research.

    ERIC Educational Resources Information Center

    Anderson, Frances E.

    2001-01-01

    Metaphors for researchers, such as a crusader; a traveler; an explorer; a miner; an astronaut; a biblical Daniel; a Samurai; and an archaeologist are discussed. Benefits of conducting research are enumerated, including building the knowledge base for art therapy; increasing professional opportunities; improving client care; and advancing the…

  9. Thermally conductive support structure

    NASA Technical Reports Server (NTRS)

    Herzl, Alfred (Inventor)

    2000-01-01

    A structure for supporting and at least transferring heat energy away from at least a first heat source interconnected thereto is disclosed. In one embodiment, the structure includes a deck member having a plurality of layers of thermally conductive fibers packed within a matrix material. Fibers of at least a first layer are orientable to transfer heat energy toward at least a first sidewall of the deck member, and fibers of at least a second layer are orientable about .+-.45.degree. relative to the fibers of the first layer to enhance the structural strength of the deck member. In another embodiment, fibers of at least a first layer of thermally conductive fibers of the deck member are orientable to transfer heat energy from a first heat source to a second, cooler heat source, both of which are interconnectable to the deck member, such that the first and second heat sources operate at substantially uniform temperatures. In this embodiment, fibers of at least a second layer of thermally conductive fibers are orientable about .+-.45.degree. relative to the fibers of the first layer to enhance the structural strength of the deck member. Fibers of at least a third layer of thermally conductive fibers are orientable substantially orthogonally relative to the fibers of the first layer to transfer heat energy away from at least the first heat source to at least a first sidewall of the deck member.

  10. Graphene chiral liquid crystals and macroscopic assembled fibres

    PubMed Central

    Xu, Zhen; Gao, Chao

    2011-01-01

    Chirality and liquid crystals are both widely expressed in nature and biology. Helical assembly of mesophasic molecules and colloids may produce intriguing chiral liquid crystals. To date, chiral liquid crystals of 2D colloids have not been explored. As a typical 2D colloid, graphene is now receiving unprecedented attention. However, making macroscopic graphene fibres is hindered by the poor dispersibility of graphene and by the lack of an assembly method. Here we report that soluble, chemically oxidized graphene or graphene oxide sheets can form chiral liquid crystals in a twist-grain-boundary phase-like model with simultaneous lamellar ordering and long-range helical frustrations. Aqueous graphene oxide liquid crystals were continuously spun into metres of macroscopic graphene oxide fibres; subsequent chemical reduction gave the first macroscopic neat graphene fibres with high conductivity and good mechanical performance. The flexible, strong graphene fibres were knitted into designed patterns and into directionally conductive textiles. PMID:22146390

  11. Crystals for stellar spectrometers

    NASA Technical Reports Server (NTRS)

    Alexandropoulos, N. G.; Cohen, G. G.

    1974-01-01

    Crystal evaluation as it applies to instrumentation employed in X-ray astronomy is reviewed, and some solutions are offered to problems that are commonly encountered. A general approach for selecting the most appropriate crystals for a given problem is also suggested. The energy dependence of the diffraction properties of (002) PET, (111) Ge, (101) ADP, (101) KAP, and (001) RAP are reported.

  12. Walkout in Crystal City

    ERIC Educational Resources Information Center

    Barrios, Greg

    2009-01-01

    When students take action, they create change that extends far beyond the classroom. In this article, the author, who was a former teacher from Crystal City, Texas, remembers the student walkout that helped launch the Latino civil rights movement 40 years ago. The Crystal City student walkout remains a high point in the history of student activism…

  13. Crystal growth and crystallography

    NASA Technical Reports Server (NTRS)

    Chernov, A. A.

    1998-01-01

    Selected topics that may be of interest for both crystal-structure and crystal-growth communities are overviewed. The growth of protein crystals, along with that of some other compounds, is one of the topics, and recent insights into related phenomena are considered as examples of applications of general principles. The relationship between crystal growth shape and structure is reviewed and an attempt to introduce semiquantitative characterization of binding for proteins is made. The concept of kinks for complex structures is briefly discussed. Even at sufficiently low supersaturations, the fluctuation of steps may not be sufficient to implement the Gibbs-Thomson law if the kink density is low enough. Subsurface ordering of liquids and growth of rough interfaces from melts is discussed. Crystals growing in microgravity from solution should be more perfect if they preferentially trap stress-inducing impurities, thus creating an impurity-depleted zone around themselves. Evidently, such a zone is developed only around the crystals growing in the absence of convection. Under terrestrial conditions, the self-purified depleted zone is destroyed by convection, the crystal traps more impurity and grows stressed. The stress relief causes mosaicity. In systems containing stress-inducing but poorly trapped impurities, the crystals grown in the absence of convection should be worse than those of their terrestrial counterparts.

  14. Crystal Shape Bingo.

    ERIC Educational Resources Information Center

    Rule, Audrey C.

    This document describes a game that provides students with practice in recognizing three dimensional crystal shapes and planar geometric shapes of crystal faces. It contains information on the objective of the game, game preparation, and rules for playing. Play cards are included (four to a page). (ASK)

  15. Demonstration of Crystal Structure.

    ERIC Educational Resources Information Center

    Neville, Joseph P.

    1985-01-01

    Describes an experiment where equal parts of copper and aluminum are heated then cooled to show extremely large crystals. Suggestions are given for changing the orientation of crystals by varying cooling rates. Students are more receptive to concepts of microstructure after seeing this experiment. (DH)

  16. Cluster Mechanism of Homogeneous Crystallization (Computer Study)

    NASA Astrophysics Data System (ADS)

    Belashchenko, D. K.

    2008-12-01

    A molecular dynamics (MD) study of homogeneous crystallization of liquid rubidium is conducted with an inter-particle pair potential. The equilibrium crystallization temperature of the models was 313 K. Models consisted of 500, 998, and 1968 particles in a basic cube. The main investigation method was as follows: to detect (along the MD run) the atoms with Voronoi polyhedrons (VP) of 0608 type (“0608-atoms,” as in a bcc crystal) and to detect the bound groups of 0608-atoms (“0608-clusters”) that could play the role of the seeds in crystallization. Full crystallization was observed only at temperatures lower than 185 K with the creation of a predominant bcc crystal. The crystallization mechanism of Rb models differs drastically from the mechanism adopted in classical nucleation theory. It consists of the growth of the total number of 0608-atoms on cooling and the formation of 0608-clusters, analogous to the case of coagulation of solute for a supersaturated two-component solution. At the first stage of the process the clusters have a very loose structure (something like medusa or octopus with many tentacles) and include inside atoms with other Voronoi polyhedron types. The dimensions of clusters quickly increase and approach those of the basic cube. 0608-atoms play the leading role in the crystallization process and activate the transition of the atoms involved in the 0608-coordination. The fast growth of the maximum cluster begins after it attains a critical size (about 150 0608-atoms). The fluctuations of cluster sizes are very important in the creation of a 0608-cluster of critical (threshold) size. These fluctuations are especially large in the interval from 180 K to 185 K.

  17. DHS Internship Summary-Crystal Assembly at Different Length Scales

    SciTech Connect

    Mishchenko, L

    2009-08-06

    I was part of a project in which in situ atomic force microscopy (AFM) was used to monitor growth and dissolution of atomic and colloidal crystals. At both length scales, the chemical environment of the system greatly altered crystal growth and dissolution. Calcium phosphate was used as a model system for atomic crystals. A dissolution-reprecipitation reaction was observed in this first system, involving the conversion of brushite (DCPD) to octacalcium phosphate (OCP). In the second system, polymeric colloidal crystals were dissolved in an ionic solvent, revealing the underlying structure of the crystal. The dissolved crystal was then regrown through an evaporative step method. Recently, we have also found that colloids can be reversibly deposited in situ onto an ITO (indium tin oxide) substrate via an electrochemistry setup. The overall goal of this project was to develop an understanding of the mechanisms that control crystallization and order, so that these might be controlled during material synthesis. Controlled assembly of materials over a range of length scales from molecules to nanoparticles to colloids is critical for designing new materials. In particular, developing materials for sensor applications with tailorable properties and long range order is important. In this work, we examine two of these length scales: small molecule crystallization of calcium phosphate (whose crystal phases include DCPD, OCP, and HAP) and colloidal crystallization of Poly(methyl methacrylate) beads. Atomic Force Microscopy is ideal for this line of work because it allows for the possibility of observing non-conducting samples in fluid during growth with high resolution ({approx} 10 nm). In fact, during atomic crystal growth one can observe changes in atomic steps, and with colloidal crystals, one can monitor the individual building blocks of the crystal. Colloids and atoms crystallize under the influence of different forces acting at different length scales as seen in Table 1

  18. Inverse heat conduction problems

    NASA Astrophysics Data System (ADS)

    Orlande, Helcio Rangel Barreto

    We present the solution of the following inverse problems: (1) Inverse Problem of Estimating Interface Conductance Between Periodically Contacting Surfaces; (2) Inverse Problem of Estimating Interface Conductance During Solidification via Conjugate Gradient Method; (3) Determination of the Reaction Function in a Reaction-Diffusion Parabolic Problem; and (4) Simultaneous Estimation of Thermal Diffusivity and Relaxation Time with Hyperbolic Heat Conduction Model. Also, we present the solution of a direct problem entitled: Transient Thermal Constriction Resistance in a Finite Heat Flux Tube. The Conjugate Gradient Method with Adjoint Equation was used in chapters 1-3. The more general function estimation approach was treated in these chapters. In chapter 1, we solve the inverse problem of estimating the timewise variation of the interface conductance between periodically contacting solids, under quasi-steady-state conditions. The present method is found to be more accurate than the B-Spline approach for situations involving small periods, which are the most difficult on which to perform the inverse analysis. In chapter 2, we estimate the timewise variation of the interface conductance between casting and mold during the solidification of aluminum. The experimental apparatus used in this study is described. In chapter 3, we present the estimation of the reaction function in a one dimensional parabolic problem. A comparison of the present function estimation approach with the parameter estimation technique, wing B-Splines to approximate the reaction function, revealed that the use of function estimation reduces the computer time requirements. In chapter 4 we present a finite difference solution for the transient constriction resistance in a cylinder of finite length with a circular contact surface. A numerical grid generation scheme was used to concentrate grid points in the regions of high temperature gradients in order to reduce discretization errors. In chapter 6, we

  19. Nanostructured conductive polymeric materials

    NASA Astrophysics Data System (ADS)

    Al-Saleh, Mohammed H.

    Conductive polymer composites (CPCs) are a suitable alternative to metals in many applications due to their light-weight, corrosion resistance, low cost, ease of processing and design flexibility. CPCs have been formulated using different types of conductive fillers. In this PhD thesis, the focus is on CPCs for electrostatic discharge (ESD) protection and electromagnetic interference (EMI) attenuation. Despite the versatility of conductive fillers, carbon black (CB) has been the dominant filler to make CPCs for ESD protection applications because CB/polymer composites have a cost advantage over all other CPCs. For EMI shielding, stainless steel fibres and metal coated fibers are the preferred fillers, however CPCs made of those fibers are not the dominant EMI shielding materials. Metal coated and polymer plated polymers are the most widely used EMI shielding options. The limited use of CPCs in the EMI shielding market is because the high filler loading required to formulate a composite with an adequate level of shielding remarkably increases the composite price. In order to increase the competitiveness of CPCs, percolation threshold should be minimized as much as possible and composites with high EMI shielding capabilities at low filler loading should be formulated because all conductive fillers are expensive compared to polymers. In this thesis, two different methodologies to reduce percolation threshold in CPCs have been successfully developed and a CPC with exceptional EMI shielding capability has been formulated using copper nanowires as conductive filler. The first percolation threshold reduction technique is based on the selective localization of CB at the interface of immiscible polymer blend. The technique requires adding a copolymer that prefers the blend's interface and for which CB nanoparticles has the highest affinity. The second method is based on producing a CPC powder and then using this powder as a conductive filler to produce composite by dry

  20. Photonic crystals, amorphous materials, and quasicrystals

    PubMed Central

    Edagawa, Keiichi

    2014-01-01

    Photonic crystals consist of artificial periodic structures of dielectrics, which have attracted much attention because of their wide range of potential applications in the field of optics. We may also fabricate artificial amorphous or quasicrystalline structures of dielectrics, i.e. photonic amorphous materials or photonic quasicrystals. So far, both theoretical and experimental studies have been conducted to reveal the characteristic features of their optical properties, as compared with those of conventional photonic crystals. In this article, we review these studies and discuss various aspects of photonic amorphous materials and photonic quasicrystals, including photonic band gap formation, light propagation properties, and characteristic photonic states. PMID:27877676

  1. Bioengineered magnetic crystals

    NASA Astrophysics Data System (ADS)

    Kasyutich, O.; Sarua, A.; Schwarzacher, W.

    2008-07-01

    In this paper we report on the successful application of a protein crystallization technique to fabricate a three-dimensionally ordered array of magnetic nanoparticles, i.e. a novel type of metamaterial with unique magnetic properties. We utilize ferritin protein cages for the template-constrained growth of superparamagnetic nanoparticles of magnetite/maghemite Fe3O4-γ-Fe2O3 (magnetoferritin), followed by thorough nanoparticle bioprocessing and purification, and finally by protein crystallization. Protein crystallization is driven by the natural response of proteins to the supersaturation of the electrolyte, which leads to spontaneous nucleation and 3D crystal growth. Within a short period of time (hours to days) we were able to grow functional crystals on the meso-scale, with sizes of the order of tens, up to a few hundred micrometres. We present initial magnetic and Raman spectroscopy characterization results for the obtained 3D arrays of magnetic nanoparticles.

  2. Polymer Crystallization under Confinement

    NASA Astrophysics Data System (ADS)

    Floudas, George

    Recent efforts indicated that polymer crystallization under confinement can be substantially different from the bulk. This can have important technological applications for the design of polymeric nanofibers with tunable mechanical strength, processability and optical clarity. However, the question of how, why and when polymers crystallize under confinement is not fully answered. Important studies of polymer crystallization confined to droplets and within the spherical nanodomains of block copolymers emphasized the interplay between heterogeneous and homogeneous nucleation. Herein we report on recent studies1-5 of polymer crystallization under hard confinement provided by model self-ordered AAO nanopores. Important open questions here are on the type of nucleation (homogeneous vs. heterogeneous), the size of critical nucleus, the crystal orientation and the possibility to control the overall crystallinity. Providing answers to these questions is of technological relevance for the understanding of nanocomposites containing semicrystalline polymers. In collaboration with Y. Suzuki, H. Duran, M. Steinhart, H.-J. Butt.

  3. Development of a high conductivity intercalated graphite composite wire

    NASA Astrophysics Data System (ADS)

    Singhal, S. C.

    1982-02-01

    Composite wires previously fabricated by swaging and claimed to possess conductivity equal to or greater than that of copper were analyzed. Intercalation of HOPG crystals with SbF5+HF mixtures was studied to assess the effect of defects in the starting graphite on the final conductivity and also to determine the conductivity as a function of the stage of the compound. Composite wires consisting of copper, aluminum or lead outer sheath and SbF5+HF-or AsF5-intercalated graphite in the core were fabricated by swaging and/or drawing and then analyzed for their electrical conductivity.

  4. Growth and electrical properties on NLO crystal: 4-N,N-dimethylamino 4′-N′-methylstilbazolium iodide

    SciTech Connect

    Kumar, M. Krishna Sudhahar, S. Kumar, R. Mohan

    2014-04-24

    4-N,N-Dimethylamino-4′-N′-methylstilbazolium tosylate single crystals were grown by solution crystal growth method. The cell parameters of grown crystal have been estimated using single crystal-X-ray diffraction analysis. The variation of real (´ε) and imaginary (´ε) part of dielectric constants and dielectric loss were observed for different frequencies and temperatures. The ac and dc electrical conductivities and activation energy were determined for DMSI crystal using dielectric studies.

  5. Protein Crystal Growth With the Aid of Microfluidics

    NASA Technical Reports Server (NTRS)

    vanderWoerd, Mark

    2003-01-01

    Protein crystallography is one of three well-known methods to obtain the structure of proteins. A major rate limiting step in protein crystallography is protein crystal nucleation and growth, which is still largely a process conducted by trial-and-error methods. Many attempts have been made to improve protein crystal growth by performing growth in microgravity. Although the use of microgravity appears to improve crystal quality in some attempts, this method has been inefficient because several reasons: we lack a fundamental understanding of macromolecular crystal growth in general and of the influence of microgravity in particular, we have to start with crystal growth conditions in microgravity based on conditions on the ground and finally the hardware does not allow for experimental iteration without reloading samples on the ground. To partially accommodate the disadvantages of the current hardware, we have used microfluidic technology (Lab-on-a-Chip devices) to design the concept of a more efficient crystallization device, suitable for use on the International Space Station and in high-throughput applications on the ground. The concept and properties of microfluidics, the application design process, and the advances in protein crystal growth hardware will be discussed in this presentation. Some examples of proteins crystallized in the new hardware will be discussed, including the differences between conventional crystallization versus crystallization in microfluidics.

  6. Oxygen ion conducting materials

    DOEpatents

    Vaughey, John; Krumpelt, Michael; Wang, Xiaoping; Carter, J. David

    2005-07-12

    An oxygen ion conducting ceramic oxide that has applications in industry including fuel cells, oxygen pumps, oxygen sensors, and separation membranes. The material is based on the idea that substituting a dopant into the host perovskite lattice of (La,Sr)MnO.sub.3 that prefers a coordination number lower than 6 will induce oxygen ion vacancies to form in the lattice. Because the oxygen ion conductivity of (La,Sr)MnO.sub.3 is low over a very large temperature range, the material exhibits a high overpotential when used. The inclusion of oxygen vacancies into the lattice by doping the material has been found to maintain the desirable properties of (La,Sr)MnO.sub.3, while significantly decreasing the experimentally observed overpotential.

  7. Oxygen ion conducting materials

    DOEpatents

    Carter, J. David; Wang, Xiaoping; Vaughey, John; Krumpelt, Michael

    2004-11-23

    An oxygen ion conducting ceramic oxide that has applications in industry including fuel cells, oxygen pumps, oxygen sensors, and separation membranes. The material is based on the idea that substituting a dopant into the host perovskite lattice of (La,Sr)MnO.sub.3 that prefers a coordination number lower than 6 will induce oxygen ion vacancies to form in the lattice. Because the oxygen ion conductivity of (La,Sr)MnO.sub.3 is low over a very large temperature range, the material exhibits a high overpotential when used. The inclusion of oxygen vacancies into the lattice by doping the material has been found to maintain the desirable properties of (La,Sr)MnO.sub.3, while significantly decreasing the experimentally observed overpotential.

  8. Super ionic conductive glass

    DOEpatents

    Susman, S.; Volin, K.J.

    Described is an ionically conducting glass for use as a solid electrolyte in a power or secondary cell containing an alkali metal-containing anode and a cathode separated by an alkali metal ion conducting glass having an ionic transference number of unity and the general formula: A/sub 1 + x/D/sub 2-x/3/Si/sub x/P/sub 3 - x/O/sub 12 - 2x/3/, wherein A is a network modifier for the glass and is an alkali metal of the anode, D is an intermediate for the glass and is selected from the class consisting of Zr, Ti, Ge, Al, Sb, Be, and Zn and X is in the range of from 2.25 to 3.0. Of the alkali metals, Na and Li are preferred and of the intermediate, Zr, Ti and Ge are preferred.

  9. Super ionic conductive glass

    DOEpatents

    Susman, Sherman; Volin, Kenneth J.

    1984-01-01

    An ionically conducting glass for use as a solid electrolyte in a power or secondary cell containing an alkali metal-containing anode and a cathode separated by an alkali metal ion conducting glass having an ionic transference number of unity and the general formula: A.sub.1+x D.sub.2-x/3 Si.sub.x P.sub.3-x O.sub.12-2x/3, wherein A is a network modifier for the glass and is an alkali metal of the anode, D is an intermediate for the glass and is selected from the class consisting of Zr, Ti, Ge, Al, Sb, Be, and Zn and X is in the range of from 2.25 to 3.0. Of the alkali metals, Na and Li are preferred and of the intermediate, Zr, Ti and Ge are preferred.

  10. Highly Thermal Conductive Nanocomposites

    NASA Technical Reports Server (NTRS)

    Sun, Ya-Ping (Inventor); Connell, John W. (Inventor); Veca, Lucia Monica (Inventor)

    2015-01-01

    Disclosed are methods for forming carbon-based fillers as may be utilized in forming highly thermal conductive nanocomposite materials. Formation methods include treatment of an expanded graphite with an alcohol/water mixture followed by further exfoliation of the graphite to form extremely thin carbon nanosheets that are on the order of between about 2 and about 10 nanometers in thickness. Disclosed carbon nanosheets can be functionalized and/or can be incorporated in nanocomposites with extremely high thermal conductivities. Disclosed methods and materials can prove highly valuable in many technological applications including, for instance, in formation of heat management materials for protective clothing and as may be useful in space exploration or in others that require efficient yet light-weight and flexible thermal management solutions.

  11. Conductance of Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Datta, Supriyo; Anatram, M. P.

    1998-01-01

    The recent report of quantized conductance in a 4 m long multiwalled nanotube (MWNT) raises the exciting possibility of ballistic transport at room temperature over relatively long distances. We argue that this is made possible by the special symmetry of the eigenstates of the lowest propagating modes in metallic nanotubes which suppresses backscattering. This unusual effect is absent for the higher propagating modes so that transport is not ballistic once the bias exceeds the cut-off energy for the higher modes, which is estimated to be approximately 75 meV for nanotubes of diameter approximately 15 nm. Also, we show that the symmetry of the eigenstates can significantly affect their coupling to the reservoir and hence the contact resistance. A simple model is presented that can be used to understand the observed conductance-voltage characteristics.

  12. Oxygen ion conducting materials

    DOEpatents

    Vaughey, John; Krumpelt, Michael; Wang, Xiaoping; Carter, J. David

    2003-01-01

    An oxygen ion conducting ceramic oxide that has applications in industry including fuel cells, oxygen pumps, oxygen sensors, and separation membranes. The material is based on the idea that substituting a dopant into the host perovskite lattice of (La,Sr)MnO.sub.3 that prefers a coordination number lower than 6 will induce oxygen ion vacancies to form in the lattice. Because the oxygen ion conductivity of (La,Sr)MnO.sub.3 is low over a very large temperature range, the material exhibits a high overpotential when used. The inclusion of oxygen vacancies into the lattice by doping the material has been found to maintain the desirable properties of (La,Sr)MnO.sub.3, while significantly decreasing the experimentally observed overpotential.

  13. Conducting effective tailgate trainings.

    PubMed

    Harrington, David; Materna, Barbara; Vannoy, Jim; Scholz, Peter

    2009-07-01

    The California Department of Health Services' Occupational Health Branch and others have identified the construction industry as being at high risk for injuries, illnesses, and fatalities. Effective tailgate trainings (brief job site safety meetings) can be a powerful tool to promote hazard awareness and safe work practices. The authors found that many contractors and supervisors conducted ineffective tailgate trainings. They developed the BuildSafe California Project to assist contractors to have more effective programs by holding 25 training-of-trainers sessions reaching 1,525 participants. The needs assessment, intervention, and evaluation results from the first 18 trainings are presented. Eighty-six percent of the participants found the program "very helpful." Participants used the materials and made improvements in the quality and frequency of trainings. Supervisors must be skilled at conducting tailgate trainings as part of their responsibilities. There is a serious need to provide more culturally appropriate safety training in a workforce increasingly made up of Latino workers.

  14. Measurement & Minimization of Mount Induced Strain on Double Crystal Monochromator Crystals

    NASA Astrophysics Data System (ADS)

    Kelly, J.; Alcock, S. G.

    2013-03-01

    Opto-mechanical mounts can cause significant distortions to monochromator crystals and mirrors if not designed or implemented carefully. A slope measuring profiler, the Diamond-NOM [1], was used to measure the change in tangential slope as a function of crystal clamping configuration and load. A three point mount was found to exhibit the lowest surface distortion (< 2μrad peak-to-valley) over the whole length of the monochromator 2nd crystal. A thermal circuit, comprising the liquid nitrogen manifold to the crystal, was modelled using experimental data for the 2nd crystal absorbed beam power and braid link thermal conductance. In the case of the I09 monochromator 2nd crystal assembly, the temperature drop across the 3 indium mount pads was calculated to be 25% of the total 0.22 K. Less than 1% loss of flux due to the 2nd crystal strain is expected at 25keV. This three pad mount will be used in the monochromators on the I09 and I23 beamlines at Diamond Light Source.

  15. Conduction cooled tube supports

    DOEpatents

    Worley, Arthur C.; Becht, IV, Charles

    1984-01-01

    In boilers, process tubes are suspended by means of support studs that are in thermal contact with and attached to the metal roof casing of the boiler and the upper bend portions of the process tubes. The support studs are sufficiently short that when the boiler is in use, the support studs are cooled by conduction of heat to the process tubes and the roof casing thereby maintaining the temperature of the stud so that it does not exceed 1400.degree. F.

  16. Thermally conductive polymers

    NASA Technical Reports Server (NTRS)

    Byrd, N. R.; Jenkins, R. K.; Lister, J. L. (Inventor)

    1971-01-01

    A thermally conductive polymer is provided having physical and chemical properties suited to use as a medium for potting electrical components. The polymer is prepared from hydroquinone, phenol, and formaldehyde, by conventional procedures employed for the preparation of phenol-formaldehyde resins. While the proportions of the monomers can be varied, a preferred polymer is formed from the monomers in a 1:1:2.4 molar or ratio of hydroquinone:phenol:formaldehyde.

  17. High conductivity composite metal

    DOEpatents

    Zhou, Ruoyi; Smith, James L.; Embury, John David

    1998-01-01

    Electrical conductors and methods of producing them, where the conductors possess both high strength and high conductivity. Conductors are comprised of carbon steel and a material chosen from a group consisting of copper, nickel, silver, and gold. Diffusion barriers are placed between these two materials. The components of a conductor are assembled and then the assembly is subjected to heat treating and mechanical deformation steps.

  18. High conductivity composite metal

    DOEpatents

    Zhou, R.; Smith, J.L.; Embury, J.D.

    1998-01-06

    Electrical conductors and methods of producing them are disclosed, where the conductors possess both high strength and high conductivity. Conductors are comprised of carbon steel and a material chosen from a group consisting of copper, nickel, silver, and gold. Diffusion barriers are placed between these two materials. The components of a conductor are assembled and then the assembly is subjected to heat treating and mechanical deformation steps. 10 figs.

  19. Conductive dense hydrogen.

    PubMed

    Eremets, M I; Troyan, I A

    2011-11-13

    Molecular hydrogen is expected to exhibit metallic properties under megabar pressures. This metal is predicted to be superconducting with a very high critical temperature, T(c), of 200-400 K, and it may acquire a new quantum state as a metallic superfluid and a superconducting superfluid. It may potentially be recovered metastably at ambient pressures. However, experiments carried out at low temperatures, T<100 K, showed that at record pressures of 300 GPa, hydrogen remains in the molecular insulating state. Here we report on the transformation of normal molecular hydrogen at room temperature (295 K) to a conductive and metallic state. At 200 GPa the Raman frequency of the molecular vibron strongly decreased and the spectral width increased, evidencing a strong interaction between molecules. Deuterium behaved similarly. Above 220 GPa, hydrogen became opaque and electrically conductive. At 260-270 GPa, hydrogen transformed into a metal as the conductance of hydrogen sharply increased and changed little on further pressurizing up to 300 GPa or cooling to at least 30 K; and the sample reflected light well. The metallic phase transformed back at 295 K into molecular hydrogen at 200 GPa. This significant hysteresis indicates that the transformation of molecular hydrogen into a metal is accompanied by a first-order structural transition presumably into a monatomic liquid state. Our findings open an avenue for detailed and comprehensive studies of metallic hydrogen.

  20. Canopy stomatal conductance

    SciTech Connect

    Baldocchi, D.D.; Luxmoore, R.J.; Hatfield, J.L.

    1989-07-14

    Stomata are major conduits for the diffusion of many trace gas species between leaves and the atmosphere. The role of the stomata on controlling gas exchange between the terrestrial biosphere and the atmosphere at the landscape, meso- and global-scales has only recently been recognized. Further advances in modelling large-scale trace gas exchange will depend on our ability to understand and model stomatal mechanics at the scale of the pertinent sub-unit, which is typically that of the canopy. This paper describes two approaches for estimating canopy stomatal conductance. One approach is based on 'bottom-up' scaling. This approach computes canopy stomatal conductance by integrating detailed leaf-level and environmentally-driven, physiological processes with the use of a detailed canopy micrometeorology model. The other approach is based on 'top-down' scaling. It interprets the integrated canopy stomatal conductance from measured fluxes of trace gas exchange. Frameworks for extending these scaling approaches to non-idea conditions are given. 96 refs., 5 figs.

  1. Conduction heat transfer solutions

    SciTech Connect

    VanSant, J.H.

    1983-08-01

    This text is a collection of solutions to a variety of heat conduction problems found in numerous publications, such as textbooks, handbooks, journals, reports, etc. Its purpose is to assemble these solutions into one source that can facilitate the search for a particular problem solution. Generally, it is intended to be a handbook on the subject of heat conduction. There are twelve sections of solutions which correspond with the class of problems found in each. Geometry, state, boundary conditions, and other categories are used to classify the problems. Each problem is concisely described by geometry and condition statements, and many times a descriptive sketch is also included. The introduction presents a synopsis on the theory, differential equations, and boundary conditions for conduction heat transfer. Some discussion is given on the use and interpretation of solutions. Supplementary data such as mathematical functions, convection correlations, and thermal properties are included for aiding the user in computing numerical values from the solutions. 155 figs., 92 refs., 9 tabs.

  2. Conductive dense hydrogen

    NASA Astrophysics Data System (ADS)

    Eremets, M. I.; Troyan, I. A.

    2011-12-01

    Molecular hydrogen is expected to exhibit metallic properties under megabar pressures. This metal is predicted to be superconducting with a very high critical temperature, Tc, of 200-400 K (ref. ), and it may acquire a new quantum state as a metallic superfluid and a superconducting superfluid. It may potentially be recovered metastably at ambient pressures. However, experiments carried out at low temperatures, T<100 K (refs , ), showed that at record pressures of 300 GPa, hydrogen remains in the molecular insulating state. Here we report on the transformation of normal molecular hydrogen at room temperature (295 K) to a conductive and metallic state. At 200 GPa the Raman frequency of the molecular vibron strongly decreased and the spectral width increased, evidencing a strong interaction between molecules. Deuterium behaved similarly. Above 220 GPa, hydrogen became opaque and electrically conductive. At 260-270 GPa, hydrogen transformed into a metal as the conductance of hydrogen sharply increased and changed little on further pressurizing up to 300 GPa or cooling to at least 30 K and the sample reflected light well. The metallic phase transformed back at 295 K into molecular hydrogen at 200 GPa. This significant hysteresis indicates that the transformation of molecular hydrogen into a metal is accompanied by a first-order structural transition presumably into a monatomic liquid state. Our findings open an avenue for detailed and comprehensive studies of metallic hydrogen.

  3. Transparent conductive coatings

    NASA Technical Reports Server (NTRS)

    Ashok, S.

    1983-01-01

    Thin film transparent conductors are discussed. Materials with electrical conductivity and optical transparency are highly desirable in many optoelectronic applications including photovoltaics. Certain binary oxide semiconductors such as tin oxide (SnO2) and indium oxide (In2O3) offer much better performance tradeoff in optoelectronics as well as better mechanical and chemical stability than thin semitransparent films. These thin-film transparent conductors (TC) are essentially wide-bandgap degenerate semiconductors - invariably n-type - and hence are transparent to sub-bandgap (visible) radiation while affording high electrical conductivity due to the large free electron concentration. The principal performance characteristics of TC's are, of course, electrical conductivity and optical transmission. The TC's have a refractive index of around 2.0 and hence act as very efficient antireflection coatings. For using TC's in surface barrier solar cells, the photovoltaic barrier is of utmost importance and so the work function or electron affinity of the TC is also a very important material parameter. Fabrication processes are discussed.

  4. Crystallization of macromolecular complexes: combinatorial complex crystallization

    NASA Astrophysics Data System (ADS)

    Stura, Enrico A.; Graille, Marc; Charbonnier, Jean-Baptiste

    2001-11-01

    The usefulness of antibody complexation, as a way of increasing the chances of crystallization needs to be re-evaluated after many antibody complexes have been crystallized and their structure determined. It is somewhat striking that among these, only a small number is a complex with a large protein antigen. The problem is that the effort of raising, cleaving and purifying an Fab is rewarded only by an extra chance of getting crystals; depending on the relative likelihood of crystallization of the complexed and uncomplexed protein. The example of the complex between HIV gp120, CD4 and an Fab fragment from a neutralizing antibody suggests that further complexation of an antigen-antibody complex with a third protein could, by increasing the number of possible combinations, improve the likelihood of crystallization. We propose the use of Ig-binding proteins as a way of extending the method from HIV gp120 to all proteins for which there are monoclonal antibodies. We discuss this technique, combinatorial complex crystallization (CCC), as part of a multi-component system for the enhancement of crystallization of macromolecular complexes. The method makes use of single Ig-binding domains from Staphylococcus aureus protein A (SpA), Peptostreptococcus magnus protein L (PpL) and the streptococcal protein G (SpG). The generality of the method depends on the ability of these domains to interact with a large repertoire of antibodies without affecting antigen binding. There is strong evidence to suggest that these Ig-binding domains bind outside the antigen-combining site of the antibody without perturbing antigen binding. It is clear from the crystal structure of the single SpG domain complexed with an Fab that the interaction involves mainly the immunoglobulin CH1 domain, a region not involved in antigen recognition. We have recently determined the structure of the complex between a human Fab and the domain D from SpA and found that steric hindrance is unlikely even for large

  5. Conductance fluctuations in nanostructures

    NASA Astrophysics Data System (ADS)

    Zhu, Ningjia

    1997-12-01

    In this Ph.D thesis the conductance fluctuations of different physical origins in semi-conductor nanostructures were studied using both diagrammatic analytical methods and large scale numerical techniques. In the "mixed" transport regime where both mesoscopic and ballistic features play a role, for the first time I have analytically calculated the non-universal conductance fluctuations. This mixed regime is reached when impurities are distributed near the walls of a quantum wire, leaving the center region ballistic. I have discovered that the existence of a ballistic region destroys the universal conductance fluctuations. The crossover behavior of the fluctuation amplitude from the usual quasi-1D situation to that of the mixed regime is clearly revealed, and the role of various length scales are identified. My analytical predictions were confirmed by a direct numerical simulation by evaluating the Landauer formula. In another direction, I have made several studies of conductance or resistance oscillations and fluctuations in systems with artificial impurities in the ballistic regime. My calculation gave explanations of all the experimental results concerning the classical focusing peaks of the resistance versus magnetic field, the weak localization peak in a Sinai billiard system, the formation of a chaotic billiard, and predicted certain transport features which were indeed found experimentally. I have further extended the calculation to study the Hall resistance in a four-terminal quantum dot in which there is an antidot array. From my numerical data I analyzed the classical paths of electron motion and its quantum oscillations. The results compare well with recent experimental studies on similar systems. Since these billiard systems could provide quantum chaotic dynamics, I have made a detailed study of the consequence of such dynamics. In particular I have investigated the resonant transmission of electrons in these chaotic systems, and found that the level

  6. Shaped Crystal Growth

    NASA Astrophysics Data System (ADS)

    Tatartchenko, Vitali A.

    Crystals of specified shape and size (shaped crystals) with controlled crystal growth (SCG) defect and impurity structure have to be grown for the successful development of modern engineering. Since the 1950s many hundreds of papers and patents concerned with shaped growth have been published. In this chapter, we do not try to enumerate the successful applications of shaped growth to different materials but rather to carry out a fundamental physical and mathematical analysis of shaping as well as the peculiarities of shaped crystal structures. Four main techniques, based on which the lateral surface can be shaped without contact with the container walls, are analyzed: the Czochralski technique (CZT), the Verneuil technique (VT), the floating zone technique (FZT), and technique of pulling from shaper (TPS). Modifications of these techniques are analyzed as well. In all these techniques the shape of the melt meniscus is controlled by surface tension forces, i.e., capillary forces, and here they are classified as capillary shaping techniques (CST). We look for conditions under which the crystal growth process in each CST is dynamically stable. Only in this case are all perturbations attenuated and a crystal of constant cross section shaping technique (CST) grown without any special regulation. The dynamic stability theory of the crystal growth process for all CST is developed on the basis of Lyapunov's dynamic stability theory. Lyapunov's equations for the crystal growth processes follow from fundamental laws. The results of the theory allow the choice of stable regimes for crystal growth by all CST as well as special designs of shapers in TPS. SCG experiments by CZT, VT, and FZT are discussed but the main consideration is given to TPS. Shapers not only allow crystal of very complicated cross section to be grown but provide a special distribution of impurities. A history of TPS is provided later in the chapter, because it can only be described after explanation of the

  7. Dispersion in photonic crystals

    NASA Astrophysics Data System (ADS)

    Witzens, Jeremy

    2005-11-01

    Investigations on the dispersive properties of photonic crystals, modified scattering in ring-resonators, monolithic integration of vertical-cavity surface-emitting lasers and advanced data processing techniques for the finite-difference time-domain method are presented. Photonic crystals are periodic mesoscopic arrays of scatterers that modify the propagation properties of electromagnetic waves in a similar way as "natural" crystals modify the properties of electrons in solid-state physics. In this thesis photonic crystals are implemented as planar photonic crystals, i.e., optically thin semiconductor films with periodic arrays of holes etched into them, with a hole-to-hole spacing of the order of the wavelength of light in the dielectric media. Photonic crystals can feature forbidden frequency ranges (the band-gaps) in which light cannot propagate. Even though most work on photonic crystals has focused on these band-gaps for application such as confinement and guiding of light, this thesis focuses on the allowed frequency regions (the photonic bands) and investigates how the propagation of light is modified by the crystal lattice. In particular the guiding of light in bulk photonic crystals in the absence of lattice defects (the self-collimation effect) and the angular steering of light in photonic crystals (the superprism effect) are investigated. The latter is used to design a planar lightwave circuit for frequency domain demultiplexion. Difficulties such as efficient insertion of light into the crystal are resolved and previously predicted limitations on the resolution are circumvented. The demultiplexer is also fabricated and characterized. Monolithic integration of vertical-cavity surface-emitting lasers by means of resonantly enhanced grating couplers is investigated. The grating coupler is designed to bend light through a ninety-degree angle and is characterized with the finite-difference time-domain method. The vertical-cavity surface-emitting lasers are

  8. Ultralow Thermal Conductivity in Full Heusler Semiconductors.

    PubMed

    He, Jiangang; Amsler, Maximilian; Xia, Yi; Naghavi, S Shahab; Hegde, Vinay I; Hao, Shiqiang; Goedecker, Stefan; Ozoliņš, Vidvuds; Wolverton, Chris

    2016-07-22

    Semiconducting half and, to a lesser extent, full Heusler compounds are promising thermoelectric materials due to their compelling electronic properties with large power factors. However, intrinsically high thermal conductivity resulting in a limited thermoelectric efficiency has so far impeded their widespread use in practical applications. Here, we report the computational discovery of a class of hitherto unknown stable semiconducting full Heusler compounds with ten valence electrons (X_{2}YZ, X=Ca, Sr, and Ba; Y=Au and Hg; Z=Sn, Pb, As, Sb, and Bi) through high-throughput ab initio screening. These new compounds exhibit ultralow lattice thermal conductivity κ_{L} close to the theoretical minimum due to strong anharmonic rattling of the heavy noble metals, while preserving high power factors, thus resulting in excellent phonon-glass electron-crystal materials.

  9. Fluctuations of thermal conductivity and morphological stability

    NASA Technical Reports Server (NTRS)

    Mazuruk, K.; Gillies, D. C.; Lehoczky, S. L.

    1995-01-01

    Compositional fluctuations of the binary alloy result in the corresponding fluctuations of the thermal conductivity of the material. During crystal growth, these fluctuations can significantly modify the local temperature fields at the liquid-solid interface. This, in turn, will affect the morphological stability of the growing interface. In this work, the temperature dependence of the thermal conductivity of the solid phase has been included into the Mullins-Sekerka formalism. A significant effect on the onset of the instability of planar interface has been predicted. It has been found, in particular, that for binary systems with the segregation coefficient above unity a flat interface is always unstable. The shape of the interface fluctuation should have a single harmonic character with a well defined wavelength.

  10. Ultralow Thermal Conductivity in Full Heusler Semiconductors

    NASA Astrophysics Data System (ADS)

    He, Jiangang; Amsler, Maximilian; Xia, Yi; Naghavi, S. Shahab; Hegde, Vinay I.; Hao, Shiqiang; Goedecker, Stefan; OzoliĆš, Vidvuds; Wolverton, Chris

    2016-07-01

    Semiconducting half and, to a lesser extent, full Heusler compounds are promising thermoelectric materials due to their compelling electronic properties with large power factors. However, intrinsically high thermal conductivity resulting in a limited thermoelectric efficiency has so far impeded their widespread use in practical applications. Here, we report the computational discovery of a class of hitherto unknown stable semiconducting full Heusler compounds with ten valence electrons (X2Y Z , X =Ca , Sr, and Ba; Y =Au and Hg; Z =Sn , Pb, As, Sb, and Bi) through high-throughput ab initio screening. These new compounds exhibit ultralow lattice thermal conductivity κL close to the theoretical minimum due to strong anharmonic rattling of the heavy noble metals, while preserving high power factors, thus resulting in excellent phonon-glass electron-crystal materials.

  11. Protein crystal growth in microgravity

    NASA Technical Reports Server (NTRS)

    Delucas, Lawrence J.; Smith, Craig D.; Smith, H. Wilson; Vijay-Kumar, Senadhi; Senadhi, Shobha E.; Ealick, Steven E.; Carter, Daniel C.; Snyder, Robert S.

    1989-01-01

    The crystals of most proteins or other biological macromolecules are poorly ordered and diffract to lower resolutions than those observed for most crystals of simple organic and inorganic compounds. Crystallization in the microgravity environment of space may improve crystal quality by eliminating convection effects near growing crystal surfaces. A series of 11 different protein crystal growth experiments was performed on U.S. Space Shuttle flight STS-26 in September 1988. The microgravity-grown crystals of gamma-interferon D1, porcine elastase, and isocitrate lyase are larger, display more uniform morphologies, and yield diffraction data to significantly higher resolutions than the best crystals of these proteins grown on earth.

  12. Quartz crystal growth

    DOEpatents

    Baughman, Richard J.

    1992-01-01

    A process for growing single crystals from an amorphous substance that can undergo phase transformation to the crystalline state in an appropriate solvent. The process is carried out in an autoclave having a lower dissolution zone and an upper crystallization zone between which a temperature differential (.DELTA.T) is maintained at all times. The apparatus loaded with the substance, solvent, and seed crystals is heated slowly maintaining a very low .DELTA.T between the warmer lower zone and cooler upper zone until the amorphous substance is transformed to the crystalline state in the lower zone. The heating rate is then increased to maintain a large .DELTA.T sufficient to increase material transport between the zones and rapid crystallization. .alpha.-Quartz single crystal can thus be made from fused quartz in caustic solvent by heating to 350.degree. C. stepwise with a .DELTA.T of 0.25.degree.-3.degree. C., increasing the .DELTA.T to about 50.degree. C. after the fused quartz has crystallized, and maintaining these conditions until crystal growth in the upper zone is completed.

  13. Infrared transparent conductive oxides

    NASA Astrophysics Data System (ADS)

    Johnson, Linda F.; Moran, Mark B.

    2001-09-01

    A novel class of complex metal oxides that have potential as transparent conducting oxides (TCOs) for the electromagnetic-interference (EMI) shielding on IR-seeker windows and missile domes has been identified. These complex metal oxides exhibit the rhombohedral (R3m) crystalline structure of naturally occurring delafossite, CuFeO2. The general chemical formula is ABO2 where A is a monovalent metal (Me+1 such as Cu, Ag, Au, Pt or Pd, and B is a trivalent metal (Me3+) such as Al,Ti,Cr,Co,Fe,Ni,Cs,Rh,Ga,Sn,In,Y,La,Pr,Nd,Sm or Eu. By adjusting the oxygen content, the conductivity can be varied over a wide range so that the delafossites behave as insulators, semiconductors or metals. This paper presents results for films of p-type CuxAlyOz and n-type CuxCryOz deposited by reactive magnetron co-sputtering from high-purity-metal targets. Films have been deposited using conventional RF- and DC-power supplies, and a new asymmetric-bipolar-pulsed- DC-power supply. Similar to the high-temperature-copper- oxide superconductors, the presence of Cu-O bonds is critical for the unique properties. Fourier transform infrared (FTIR) and electron spectroscopy for chemical analysis (ESCA) are used to understand the relationship between the optoelectornic properties and the molecular structure of the films. For example, FTIR absorption bands at 1470 and 1395cm-1 are present only in CuxAlyOz films that exhibit enhanced electrical conductivity. When these bands are absent, the CuxAlyOz films have high values of resistivity. In addition to the 1470 and 1395cm-1 bands observed in CuxAlyOz films, another pair of bands at 1040 and 970cm-1 is present in CuxCryOz films.

  14. Electrically Conductive Porous Membrane

    NASA Technical Reports Server (NTRS)

    Burke, Kenneth Alan (Inventor)

    2014-01-01

    The present invention relates to an electrically conductive membrane that can be configured to be used in fuel cell systems to act as a hydrophilic water separator internal to the fuel cell, or as a water separator used with water vapor fed electrolysis cells, or as a water separator used with water vapor fed electrolysis cells, or as a capillary structure in a thin head pipe evaporator, or as a hydrophobic gas diffusion layer covering the fuel cell electrode surface in a fuel cell.

  15. Conducting polymer ultracapacitor

    DOEpatents

    Shi, Steven Z.; Davey, John R.; Gottesfeld, Shimshon; Ren, Xiaoming

    2002-01-01

    A sealed ultracapacitor assembly is formed with first and second electrodes of first and second conducting polymers electrodeposited on porous carbon paper substrates, where the first and second electrodes each define first and second exterior surfaces and first and second opposing surfaces. First and second current collector plates are bonded to the first and second exterior surfaces, respectively. A porous membrane separates the first and second opposing surfaces, with a liquid electrolyte impregnating the insulating membrane. A gasket formed of a thermoplastic material surrounds the first and second electrodes and seals between the first and second current collector plates for containing the liquid electrolyte.

  16. Aluminum Nitride Crystal Growth

    DTIC Science & Technology

    1979-12-01

    increase the growth rate of AiN crystals from the vapor phase, and some new experiments to test this model conjecture are needed. if one’could operate...walls is much less severe,, and hence the crucible lifetime is about 88 times greater than for the -slycrystalline tungsten. In an effort to test this...added H2 to increase the growth rate is a better idea. One growth run, W253, Was made to test the single-crystal crucible method. The crystal from

  17. Analysis of Crystallization Kinetics

    NASA Technical Reports Server (NTRS)

    Kelton, Kenneth F.

    1997-01-01

    A realistic computer model for polymorphic crystallization (i.e., initial and final phases with identical compositions), which includes time-dependent nucleation and cluster-size-dependent growth rates, is developed and tested by fits to experimental data. Model calculations are used to assess the validity of two of the more common approaches for the analysis of crystallization data. The effects of particle size on transformation kinetics, important for the crystallization of many systems of limited dimension including thin films, fine powders, and nanoparticles, are examined.

  18. Crystallization on prestructured seeds.

    PubMed

    Jungblut, Swetlana; Dellago, Christoph

    2013-01-01

    The crystallization transition of an undercooled monodisperse Lennard-Jones fluid in the presence of small prestructured seeds is studied with transition path sampling combined with molecular dynamics simulations. Compared to the homogeneous crystallization, clusters of a few particles arranged into a face- and body-centered cubic structure enhance the crystallization, while icosahedrally ordered seeds do not change the reaction rate. We identify two distinct nucleation regimes-close to the seed and in the bulk. Crystallites form close to the face- and body-centered structures and tend to stay away from the icosahedrally ordered seeds.

  19. Crystals in light.

    PubMed

    Kahr, Bart; Freudenthal, John; Gunn, Erica

    2010-05-18

    We have made images of crystals illuminated with polarized light for almost two decades. Early on, we abandoned photosensitive chemicals in favor of digital electrophotometry with all of the attendant advantages of quantitative intensity data. Accurate intensities are a boon because they can be used to analytically discriminate small effects in the presence of larger ones. The change in the form of our data followed camera technology that transformed picture taking the world over. Ironically, exposures in early photographs were presumed to correlate simply with light intensity, raising the hope that photography would replace sensorial interpretation with mechanical objectivity and supplant the art of visual photometry. This was only true in part. Quantitative imaging accurate enough to render the separation of crystalloptical quantities had to await the invention of the solid-state camera. Many pioneers in crystal optics were also major figures in the early history of photography. We draw out the union of optical crystallography and photography because the tree that connects the inventors of photography is a structure unmatched for organizing our work during the past 20 years, not to mention that silver halide crystallites used in chemical photography are among the most consequential "crystals in light", underscoring our title. We emphasize crystals that have acquired optical properties such as linear birefringence, linear dichroism, circular birefringence, and circular dichroism, during growth from solution. Other crystalloptical effects were discovered that are unique to curiously dissymmetric crystals containing embedded oscillators. In the aggregate, dyed crystals constitute a generalization of single crystal matrix isolation. Simple crystals provided kinetic stability to include guests such as proteins or molecules in excited states. Molecular lifetimes were extended for the preparation of laser gain media and for the study of the photodynamics of single

  20. Swimming in a crystal.

    PubMed

    Brown, Aidan T; Vladescu, Ioana D; Dawson, Angela; Vissers, Teun; Schwarz-Linek, Jana; Lintuvuori, Juho S; Poon, Wilson C K

    2016-01-07

    We study catalytic Janus particles and Escherichia coli bacteria swimming in a two-dimensional colloidal crystal. The Janus particles orbit individual colloids and hop between colloids stochastically, with a hopping rate that varies inversely with fuel (hydrogen peroxide) concentration. At high fuel concentration, these orbits are stable for 100s of revolutions, and the orbital speed oscillates periodically as a result of hydrodynamic, and possibly also phoretic, interactions between the swimmer and the six neighbouring colloids. Motile E. coli bacteria behave very differently in the same colloidal crystal: their circular orbits on plain glass are rectified into long, straight runs, because the bacteria are unable to turn corners inside the crystal.

  1. Single crystals of chitosan.

    PubMed

    Cartier, N; Domard, A; Chanzy, H

    1990-10-01

    Lamellar single crystals of chitosan were prepared at 125 degrees C by adding ammonia to a low DP fraction of chitosan dissolved in water. The crystals gave sharp electron diffraction diagrams which could be indexed in an orthorhombic P2(1)2(1)2(1) unit cell with a = 8.07 A, b = 8.44 A, c = 10.34 A. The unit cell contained two anti-parallel chitosan chains and no water molecules. It was found that cellulose microfibrils from Valonia ventricosa could act as nuclei for inducing the crystallization of chitosan on cellulose. This produced a shish-kebab morphology.

  2. Molecules in crystals

    NASA Astrophysics Data System (ADS)

    Spackman, Mark A.

    2013-04-01

    Hirshfeld surface analysis has developed from the serendipitous discovery of a novel partitioning of the crystal electron density into discrete molecular fragments, to a suite of computational tools used widely for the identification, analysis and discussion of intermolecular interactions in molecular crystals. The relationship between the Hirshfeld surface and very early ideas on the internal structure of crystals is outlined, and applications of Hirshfeld surface analysis are presented for three molecules of historical importance in the development of modern x-ray crystallography: hexamethylbenzene, hexamethylenetetramine and diketopiperazine.

  3. Crystallization kinetics of alkali feldspars in cooling and decompression-induced crystallization experiments in trachytic melt

    NASA Astrophysics Data System (ADS)

    Arzilli, Fabio; Carroll, Michael R.

    2013-10-01

    Cooling and decompression experiments have been carried out on trachytic melts in order to investigate crystallization kinetics of alkali feldspar, the effect of the degree of undercooling ( ΔT = T liquidus - T experimental) and time on nucleation and crystal growth process. This experimental work gives us new data about crystallization kinetics of trachytic melts, and it that will be useful to better understand the natural system of Campi Flegrei volcanoes. Experiments have been conducted using cold seal pressure vessel apparatus, at pressure between 30 and 200 MPa, temperature between 750 and 855 °C, time between 7,200 and 57,600 s and redox condition close to the NNO +0.8 buffer. These conditions are ideal to reproducing pre- and syn-eruptive conditions of the Campi Flegrei volcanoes, where the "conditions" pertain to the complete range of pressures, temperatures and time at which the experiments were performed. Alkali feldspar is the main phase present in this trachyte, and its abundance can strongly vary with small changes in pressure, temperature and water content in the melt, implying appreciable variations in the textures and in the crystallization kinetics. The obtained results show that crystallization kinetics are strictly related to ΔT, time, final pressure, superheating (- ΔT) and water content in the melt. ΔT is the driving force of the crystallization, and it has a strong influence on nucleation and growth processes. In fact, the growth process dominates crystallization at small ΔT, whereas the nucleation dominates crystallization at large ΔT. Time also is an important variable during crystallization process, because long experiment durations involve more nucleation events of alkali feldspar than short experiment durations. This is an important aspect to understand magma evolution in the magma chamber and in the conduit, which in turn has strong effects on magma rheology.

  4. Conduction heat transfer solutions

    SciTech Connect

    VanSant, James H.

    1980-03-01

    This text is a collection of solutions to a variety of heat conduction problems found in numerous publications, such as textbooks, handbooks, journals, reports, etc. Its purpose is to assemble these solutions into one source that can facilitate the search for a particular problem solution. Generally, it is intended to be a handbook on the subject of heat conduction. This material is useful for engineers, scientists, technologists, and designers of all disciplines, particularly those who design thermal systems or estimate temperatures and heat transfer rates in structures. More than 500 problem solutions and relevant data are tabulated for easy retrieval. There are twelve sections of solutions which correspond with the class of problems found in each. Geometry, state, boundary conditions, and other categories are used to classify the problems. A case number is assigned to each problem for cross-referencing, and also for future reference. Each problem is concisely described by geometry and condition statements, and many times a descriptive sketch is also included. At least one source reference is given so that the user can review the methods used to derive the solutions. Problem solutions are given in the form of equations, graphs, and tables of data, all of which are also identified by problem case numbers and source references.

  5. Radiative thermal conduction fronts

    NASA Astrophysics Data System (ADS)

    Borkowski, Kazimierz J.; Balbus, Steven A.; Fristrom, Carl C.

    1990-07-01

    The discovery of the O VI interstellar absorption lines in our Galaxy by the Copernicus observatory was a turning point in our understanding of the Interstellar Medium (ISM). It implied the presence of widespread hot (approx. 10 to the 6th power K) gas in disk galaxies. The detection of highly ionized species in quasi-stellar objects' absorption spectra may be the first indirect observation of this hot phase in external disk galaxies. Previous efforts to understand extensive O VI absorption line data from our Galaxy were not very successful in locating the regions where this absorption originates. The location at interfaces between evaporating ISM clouds and hot gas was favored, but recent studies of steady-state conduction fronts in spherical clouds by Ballet, Arnaud, and Rothenflug (1986) and Bohringer and Hartquist (1987) rejected evaporative fronts as the absorption sites. Researchers report here on time-dependent nonequilibrium calculations of planar conductive fronts whose properties match well with observations, and suggest reasons for the difference between the researchers' results and the above. They included magnetic fields in additional models, not reported here, and the conclusions are not affected by their presence.

  6. Radiative thermal conduction fronts

    NASA Technical Reports Server (NTRS)

    Borkowski, Kazimierz J.; Balbus, Steven A.; Fristrom, Carl C.

    1990-01-01

    The discovery of the O VI interstellar absorption lines in our Galaxy by the Copernicus observatory was a turning point in our understanding of the Interstellar Medium (ISM). It implied the presence of widespread hot (approx. 10 to the 6th power K) gas in disk galaxies. The detection of highly ionized species in quasi-stellar objects' absorption spectra may be the first indirect observation of this hot phase in external disk galaxies. Previous efforts to understand extensive O VI absorption line data from our Galaxy were not very successful in locating the regions where this absorption originates. The location at interfaces between evaporating ISM clouds and hot gas was favored, but recent studies of steady-state conduction fronts in spherical clouds by Ballet, Arnaud, and Rothenflug (1986) and Bohringer and Hartquist (1987) rejected evaporative fronts as the absorption sites. Researchers report here on time-dependent nonequilibrium calculations of planar conductive fronts whose properties match well with observations, and suggest reasons for the difference between the researchers' results and the above. They included magnetic fields in additional models, not reported here, and the conclusions are not affected by their presence.

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

    PubMed

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

    2015-12-02

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

  8. NOVEL GRAPHITE SALTS AND THEIR ELECTRICAL CONDUCTIVITIES

    SciTech Connect

    Bartlett, N.; McCarron, E.M.; McQuillan, B.W.; Thompson, T.E.

    1980-02-01

    A set of novel first stage graphite salts of general formula C{sub 8}{sup +}MF{sub 6}{sup -} has been prepared (M = Os, Ir, As). Single crystal X-ray diffraction studies indicate that these salts are hexagonal with a {approx} 4.9 and c {approx} 8.1 {angstrom}. The unit cell volume indicates that the anions are closely packed in the galleries. Platinum hexafluoride, which is the most powerful oxidizer of the third transition series, forms a first stage compound, which analytical, structural, and magnetic studies establish as C{sub 12}{sup 2+}PtF{sub 6}{sup 2-}. In this salt the anions are not close packed, but the electron withdrawal from the graphite planes is greater than for the C{sub 8}{sup +}MF{sub 6}{sup -} series. The variation in the electrical conductivity (in the a-b plane), as a function of composition, has been investigated with the OsF{sub 6}, IrF{sub 6}, PtF{sub 6} and AsF{sub 5} intercalates. For OsF{sub 6} and IrF{sub 6}, the conductance per plane of graphite is found to be a maximum at approximately C{sub 24}MF{sub 6} (second stage); the conductivity being an order of magnitude greater than that of the parent material. Intercalation beyond C{sub 24}MF{sub 6} leads to a marked decrease in conductivity. C{sub 8}MF{sub 6} is comparable in conductivity with the parent graphite. This behavior contrasts with the graphite/AsF{sub 5} system in which a steady increase in conductance per graphite plane with increasing AsF{sub 5} content is observed. For the PtF{sub 6} system, the second as well as the first stage materials are poorly conducting.

  9. Crystallization force--a density functional theory concept for revealing intermolecular interactions and molecular packing in organic crystals.

    PubMed

    Li, Tonglei; Ayers, Paul W; Liu, Shubin; Swadley, Matthew J; Aubrey-Medendorp, Clare

    2009-01-01

    Organic molecules are prone to polymorphic formation in the solid state due to the rich diversity of functional groups that results in comparable intermolecular interactions, which can be greatly affected by the selection of solvent and other crystallization conditions. Intermolecular interactions are typically weak forces, such as van der Waals and stronger short-range ones including hydrogen bonding, that are believed to determine the packing of organic molecules during the crystal-growth process. A different packing of the same molecules leads to the formation of a new crystal structure. To disclose the underlying causes that drive the molecule to have various packing motifs in the solid state, an electronic concept or function within the framework of conceptual density functional theory has been developed, namely, crystallization force. The concept aims to describe the local change in electronic structure as a result of the self-assembly process of crystallization and may likely quantify the locality of intermolecular interactions that directs the molecular packing in a crystal. To assess the applicability of the concept, 5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile, so-called ROY, which is known to have the largest number of solved polymorphs, has been examined. Electronic calculations were conducted on the seven available crystal structures as well as on the single molecule. The electronic structures were analyzed and crystallization force values were obtained. The results indicate that the crystallization forces are able to reveal intermolecular interactions in the crystals, in particular, the close contacts that are formed between molecules. Strong correlations exist between the total crystallization force and lattice energy of a crystal structure, further suggesting the underlying connection between the crystallization force and molecular packing.

  10. Shaping Crystal-Crystal Phase Transitions

    NASA Astrophysics Data System (ADS)

    Du, Xiyu; van Anders, Greg; Dshemuchadse, Julia; Glotzer, Sharon

    Previous computational and experimental studies have shown self-assembled structure depends strongly on building block shape. New synthesis techniques have led to building blocks with reconfigurable shape and it has been demonstrated that building block reconfiguration can induce bulk structural reconfiguration. However, we do not understand systematically how this transition happens as a function of building block shape. Using a recently developed ``digital alchemy'' framework, we study the thermodynamics of shape-driven crystal-crystal transitions. We find examples of shape-driven bulk reconfiguration that are accompanied by first-order phase transitions, and bulk reconfiguration that occurs without any thermodynamic phase transition. Our results suggest that for well-chosen shapes and structures, there exist facile means of bulk reconfiguration, and that shape-driven bulk reconfiguration provides a viable mechanism for developing functional materials.

  11. Computer Modeling of Crystallization and Crystal Size distributions

    NASA Astrophysics Data System (ADS)

    Amenta, R. V.

    2002-05-01

    The crystal size distribution of an igneous rock has been shown to be related to the crystallization kinetics. In order to better understand crystallization processes, the nucleation and growth of crystals in a closed system is modeled computationally and graphically. Units of volume analogous to unit cells are systematically attached to stationary crystal nuclei. The number of volume units attached to each crystal per growth stage is proportional to the crystal size insuring that crystal dimensional growth rates are constant regardless of their size. The number of new crystal nuclei per total system volume that form in each growth stage increases exponentially Cumulative crystal size distributions (CCSD) are determined for various stages of crystallization (30 percent, 60 pct, etc) from a database generated by the computer model, and each distribution is fit to an exponential function of the same form. Simulation results show that CCSD functions appear to fit the data reasonably well (R-square) with the greatest misfit at 100 pct crystallization. The crystal size distribution at each pct crystallization can be obtained from the derivative of the respective CCSD function. The log form of each crystal size distribution (CSD) is a linear function with negative slope. Results show that the slopes of the CSD functions at pcts crystallization up to 90 pct are parallel, but the slope at 100 pct crystallization differs from the others although still in approximate alignment. We suggest that real crystallization of igneous rocks may show this pattern. In the early stages of crystallization crystals are far apart and CSD's are ideal as predicted by theory based on growth of crystals in a brine. At advanced stages of crystallization growth collision boundaries develop between crystals. As contiguity increases crystals become blocked and inactive because they can no longer grow. As crystallization approaches 100 pct a significant number of inactive crystals exist resulting in

  12. No warmup crystal oscillator

    NASA Technical Reports Server (NTRS)

    Phillips, D. H.

    1982-01-01

    During warmup, crystal oscillators often show a frequency offset as large as 1 part in 10 to the 5th power. If timing information is transferred to the oscillator and then the oscillator is allowed to warmup, a timing error greater than 1 millisecond will occur. For many applications, it is unsuitable to wait for the oscillator to warmup. For medium accuracy timing requirements where overall accuracies in the order of 1 millisecond are required, a no warmup crystal concept was developed. The concept utilizes two crystal oscillator, used sequentially to avoid using a crystal oscillator for timing much higher frequency accuracy once warmed up. The accuracy achieved with practical TCXOs at initial start over a range of temperatures is discussed. A second design utilizing two oven controlled oscillators is also discussed.

  13. Diffusion in Coulomb crystals

    SciTech Connect

    Hughto, J.; Schneider, A. S.; Horowitz, C. J.; Berry, D. K.

    2011-07-15

    Diffusion in Coulomb crystals can be important for the structure of neutron star crusts. We determine diffusion constants D from molecular dynamics simulations. We find that D for Coulomb crystals with relatively soft-core 1/r interactions may be larger than D for Lennard-Jones or other solids with harder-core interactions. Diffusion, for simulations of nearly perfect body-centered-cubic lattices, involves the exchange of ions in ringlike configurations. Here ions ''hop'' in unison without the formation of long lived vacancies. Diffusion, for imperfect crystals, involves the motion of defects. Finally, we find that diffusion, for an amorphous system rapidly quenched from Coulomb parameter {Gamma}=175 to Coulomb parameters up to {Gamma}=1750, is fast enough that the system starts to crystalize during long simulation runs. These results strongly suggest that Coulomb solids in cold white dwarf stars, and the crust of neutron stars, will be crystalline and not amorphous.

  14. Diffusion in Coulomb crystals.

    PubMed

    Hughto, J; Schneider, A S; Horowitz, C J; Berry, D K

    2011-07-01

    Diffusion in Coulomb crystals can be important for the structure of neutron star crusts. We determine diffusion constants D from molecular dynamics simulations. We find that D for Coulomb crystals with relatively soft-core 1/r interactions may be larger than D for Lennard-Jones or other solids with harder-core interactions. Diffusion, for simulations of nearly perfect body-centered-cubic lattices, involves the exchange of ions in ringlike configurations. Here ions "hop" in unison without the formation of long lived vacancies. Diffusion, for imperfect crystals, involves the motion of defects. Finally, we find that diffusion, for an amorphous system rapidly quenched from Coulomb parameter Γ=175 to Coulomb parameters up to Γ=1750, is fast enough that the system starts to crystalize during long simulation runs. These results strongly suggest that Coulomb solids in cold white dwarf stars, and the crust of neutron stars, will be crystalline and not amorphous.

  15. Crystal-Clear Technology.

    ERIC Educational Resources Information Center

    Ondris-Crawford, Renate J.; And Others

    1993-01-01

    Provides diagrams to aid in discussing polymer dispersed liquid crystal (PDLC) technology. Equipped with a knowledge of PDLC, teachers can provide students with insight on how the gap between basic science and technology is bridged. (ZWH)

  16. Crystallization behavior of anorthite

    NASA Technical Reports Server (NTRS)

    Klein, L.; Uhlmann, D. R.

    1974-01-01

    The growth rate of anorthite crystals from the melt is studied as a function of temperature with undercooling in the ranges 52-152 and 402-652 degrees C. The triclinic form is invariably observed as the crystallization product, growth is preferentially in the c direction, and the interface morphology is faceted. Significant growth rate anisotropy is indicated. The maximum growth rate of anorthite from the melt is higher than for anorthite-rich lunar compositions. Recent computer studies are combined with experimental data to estimate the heat of fusion of anorthite as 28000-45000 cal/mol; the corresponding range for entropy of fusion is (7.8-12)R (where R is the gas constant). The observations and kinetic data support Jackson's predictions concerning materials with large entropies of fusion and his suggestion that entropy of fusion is an important parameter for characterizing the crystal-liquid interface and the nature of the crystallization process.

  17. Crystallization of Silicon Ribbons

    NASA Technical Reports Server (NTRS)

    Leipold, M. H.

    1984-01-01

    Purity constraints for reasonable solar-cell efficiency require that silicon-ribbon growth for photovoltaics occur in a regime in which constitutional supercooling or other compositional effects on the crystallization front are not important. A major consideration in the fundamentals of crystallization is the removal of the latent heat of fusion. The direction of removal, compared with the growth direction, has a major influence on the crystallization rate and the development of localized stresses. The detailed shape of the crystallization front appears to have two forms: that required for dendritic-web growth, and that occurring in all others. After the removal of the latent heat of fusion, the thermal-mechanical behavior of all ribbons appears similar within the constraints of the exothermal gradient. The technological constraints in achieving the required thermal and mechanical conditions vary widely among the growth processes.

  18. Shaping Crystals using Electrophoresis

    NASA Astrophysics Data System (ADS)

    Palacci, Jeremie; Mackiewicz, Kristian

    2016-11-01

    Electrophoresis is size and shape independent as stressed by Morrison in his seminal paper. Here we present an original approach to reshape colloidal crystals using an electric field as a carving tool.

  19. Ion-conducting membranes

    DOEpatents

    Masel, Richard I.; Chen, Qingmei; Liu, Zengcai; Kutz, Robert

    2017-02-28

    An ion conducting polymeric composition mixture comprises a copolymer of styrene and vinylbenzyl-R.sub.s. R.sub.s is selected from the group consisting of imidazoliums, pyridiniums, pyrazoliums, pyrrolidiniums, pyrroliums, pyrimidiums, piperidiniums, indoliums, and triaziniums. The composition contains 10%-90% by weight of vinylbenzyl-R.sub.s. The composition can further comprise a polyolefin comprising substituted polyolefins, a polymer comprising cyclic amine groups, a polymer comprising at least one of a phenylene group and a phenyl group, a polyamide, and/or the reaction product of a constituent having two carbon-carbon double bonds. The composition can be in the form of a membrane. In a preferred embodiment, the membrane is a Helper Membrane that increases the faradaic efficiency of an electrochemical cell into which the membrane is incorporated, and also allows product formation at lower voltages than in cells without the Helper Membrane.

  20. Ion-conducting membranes

    DOEpatents

    Masel, Richard L.; Chen, Qingmei; Liu, Zengcai; Kutz, Robert

    2016-06-21

    An ion conducting polymeric composition mixture comprises a copolymer of styrene and vinylbenzyl-R.sub.s. R.sub.s is selected from the group consisting of imidazoliums and pyridiniums. The composition contains 10%-90% by weight of vinylbenzyl-R.sub.s. The composition can further comprise a polyolefin comprising substituted polyolefins, a polymer comprising cyclic amine groups, a polymer comprising at least one of a phenylene group and a phenyl group, a polyamide, and/or the reaction product of a constituent having two carbon-carbon double bonds. The composition can be in the form of a membrane. In a preferred embodiment, the membrane is a Helper Membrane that increases the faradaic efficiency of an electrochemical cell into which the membrane is incorporated, and also allows product formation at lower voltages than in cells without the Helper Membrane.

  1. Lateral conduction infrared photodetector

    DOEpatents

    Kim, Jin K.; Carroll, Malcolm S.

    2011-09-20

    A photodetector for detecting infrared light in a wavelength range of 3-25 .mu.m is disclosed. The photodetector has a mesa structure formed from semiconductor layers which include a type-II superlattice formed of alternating layers of InAs and In.sub.xGa.sub.1-xSb with 0.ltoreq.x.ltoreq.0.5. Impurity doped regions are formed on sidewalls of the mesa structure to provide for a lateral conduction of photo-generated carriers which can provide an increased carrier mobility and a reduced surface recombination. An optional bias electrode can be used in the photodetector to control and vary a cut-off wavelength or a depletion width therein. The photodetector can be formed as a single-color or multi-color device, and can also be used to form a focal plane array which is compatible with conventional read-out integrated circuits.

  2. SINGLE CRYSTAL NEUTRON DIFFRACTION.

    SciTech Connect

    KOETZLE,T.F.

    2001-03-13

    Single-crystal neutron diffraction measures the elastic Bragg reflection intensities from crystals of a material, the structure of which is the subject of investigation. A single crystal is placed in a beam of neutrons produced at a nuclear reactor or at a proton accelerator-based spallation source. Single-crystal diffraction measurements are commonly made at thermal neutron beam energies, which correspond to neutron wavelengths in the neighborhood of 1 Angstrom. For high-resolution studies requiring shorter wavelengths (ca. 0.3-0.8 Angstroms), a pulsed spallation source or a high-temperature moderator (a ''hot source'') at a reactor may be used. When complex structures with large unit-cell repeats are under investigation, as is the case in structural biology, a cryogenic-temperature moderator (a ''cold source'') may be employed to obtain longer neutron wavelengths (ca. 4-10 Angstroms). A single-crystal neutron diffraction analysis will determine the crystal structure of the material, typically including its unit cell and space group, the positions of the atomic nuclei and their mean-square displacements, and relevant site occupancies. Because the neutron possesses a magnetic moment, the magnetic structure of the material can be determined as well, from the magnetic contribution to the Bragg intensities. This latter aspect falls beyond the scope of the present unit; for information on magnetic scattering of neutrons see Unit 14.3. Instruments for single-crystal diffraction (single-crystal diffractometers or SCDs) are generally available at the major neutron scattering center facilities. Beam time on many of these instruments is available through a proposal mechanism. A listing of neutron SCD instruments and their corresponding facility contacts is included in an appendix accompanying this unit.

  3. Protein Crystal Quality Studies

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Eddie Snell, Post-Doctoral Fellow the National Research Council (NRC) uses a reciprocal space mapping diffractometer for macromolecular crystal quality studies. The diffractometer is used in mapping the structure of macromolecules such as proteins to determine their structure and thus understand how they function with other proteins in the body. This is one of several analytical tools used on proteins crystallized on Earth and in space experiments. Photo credit: NASA/Marshall Space Flight Center (MSFC)

  4. Macromolecular Crystal Quality

    NASA Technical Reports Server (NTRS)

    Snell, Edward H.; Borgstahl, Gloria E. O.; Bellamy, Henry D.; Curreri, Peter A. (Technical Monitor)

    2001-01-01

    There are many ways of judging a good crystal. Which we use depends on the qualities we seek. For gemstones size, clarity and impurity levels (color) are paramount. For the semiconductor industry purity is probably the most important quality. For the structural crystallographer the primary desideratum is the somewhat more subtle concept of internal order. In this chapter we discuss the effect of internal order (or the lack of it) on the crystal's diffraction properties.

  5. Liquid Crystal Airborne Display

    DTIC Science & Technology

    1977-08-01

    81/2X 11- 10 -9 .8 display using a large advertising alphanimeric ( TCI ) has been added to the front of the optical box used in the F-4 aircraft for HUD...properties over a wide range of tempera - tures, including normal room temperature. What are Liquid Crystals? Liquid crystals have been classified in three...natic fanctions and to present data needed for the semi- automatic and manual control of system functions. Existing aircraft using CRT display

  6. Normal Conducting CLIC Technology

    SciTech Connect

    Jensen, Erk

    2006-01-03

    The CLIC (Compact Linear Collider) multi-lateral study group based at CERN is studying the technology for an electron-positron linear collider with a centre-of-mass energy up to 5 TeV. In contrast to the International Linear Collider (ILC) study which has chosen to use super-conducting cavities with accelerating gradients in the range of 30-40 MV/m to obtain centre-of-mass collision energies of 0.5-1 TeV, the CLIC study aims to use a normal-conducting system based on two-beam technology with gradients of 150 MV/m. It is generally accepted that this change in technology is not only necessary but the only viable choice for a cost-effective multi-TeV collider. The CLIC study group is studying the technology issues of such a machine, and is in particular developing state-of-the-art 30 GHz molybdenum-iris accelerating structures and power extraction and transfer structures (PETS). The accelerating structure has a new geometry which includes fully-profiled RF surfaces optimised to minimize surface fields, and hybrid damping using both iris slots and radial waveguides. A newly-developed structure-optimisation procedure has been used to simultaneously balance surface fields, power flow, short and long-range transverse wakefields, RF-to-beam efficiency and the ratio of luminosity to input power. The slotted irises allow a simple structure fabrication by high-precision high-speed 3D milling of just four pieces, and an even easier bolted assembly in a vacuum chamber.

  7. Electrical and Thermal Conductivity

    NASA Astrophysics Data System (ADS)

    Ventura, Guglielmo; Perfetti, Mauro

    After a Sect. 1.1 devoted to electrical conductivity and a section that deals with magnetic and dielectric losses ( 1.2 ), this chapter explores the theory of thermal conduction in solids. The examined categories of solids are: metals Sect. 1.3.2 , Dielectrics Sects. 1.3.3 and 1.3.4 and Nanocomposites Sect. 1.3.5 . In Sect. 1.3.6 the problem of thermal and electrical contact between materials is considered because contact resistance occurring at conductor joints in magnets or other high power applications can lead to undesirable electrical losses. At low temperature, thermal contact is also critical in the mounting of temperature sensors, where bad contacts can lead to erroneous results, in particular when superconductivity phenomena are involved.

  8. Normal Conducting CLIC Technology

    NASA Astrophysics Data System (ADS)

    Jensen, Erk

    2006-01-01

    The CLIC (Compact Linear Collider) multi-lateral study group based at CERN is studying the technology for an electron-positron linear collider with a centre-of-mass energy up to 5 TeV. In contrast to the International Linear Collider (ILC) study which has chosen to use super-conducting cavities with accelerating gradients in the range of 30-40 MV/m to obtain centre-of-mass collision energies of 0.5-1 TeV, the CLIC study aims to use a normal-conducting system based on two-beam technology with gradients of 150 MV/m. It is generally accepted that this change in technology is not only necessary but the only viable choice for a cost-effective multi-TeV collider. The CLIC study group is studying the technology issues of such a machine, and is in particular developing state-of-the-art 30 GHz molybdenum-iris accelerating structures and power extraction and transfer structures (PETS). The accelerating structure has a new geometry which includes fully-profiled RF surfaces optimised to minimize surface fields, and hybrid damping using both iris slots and radial waveguides. A newly-developed structure-optimisation procedure has been used to simultaneously balance surface fields, power flow, short and long-range transverse wakefields, RF-to-beam efficiency and the ratio of luminosity to input power. The slotted irises allow a simple structure fabrication by high-precision high-speed 3D milling of just four pieces, and an even easier bolted assembly in a vacuum chamber.

  9. Protein conducting nanopores

    NASA Astrophysics Data System (ADS)

    Harsman, Anke; Krüger, Vivien; Bartsch, Philipp; Honigmann, Alf; Schmidt, Oliver; Rao, Sanjana; Meisinger, Christof; Wagner, Richard

    2010-11-01

    About 50% of the cellular proteins have to be transported into or across cellular membranes. This transport is an essential step in the protein biosynthesis. In eukaryotic cells secretory proteins are transported into the endoplasmic reticulum before they are transported in vesicles to the plasma membrane. Almost all proteins of the endosymbiotic organelles chloroplasts and mitochondria are synthesized on cytosolic ribosomes and posttranslationally imported. Genetic, biochemical and biophysical approaches led to rather detailed knowledge on the composition of the translocon-complexes which catalyze the membrane transport of the preproteins. Comprehensive concepts on the targeting and membrane transport of polypeptides emerged, however little detail on the molecular nature and mechanisms of the protein translocation channels comprising nanopores has been achieved. In this paper we will highlight recent developments of the diverse protein translocation systems and focus particularly on the common biophysical properties and functions of the protein conducting nanopores. We also provide a first analysis of the interaction between the genuine protein conducting nanopore Tom40SC as well as a mutant Tom40SC (\\mathrm {S}_{54} \\to E ) containing an additional negative charge at the channel vestibule and one of its native substrates, CoxIV, a mitochondrial targeting peptide. The polypeptide induced a voltage-dependent increase in the frequency of channel closure of Tom40SC corresponding to a voltage-dependent association rate, which was even more pronounced for the Tom40SC S54E mutant. The corresponding dwelltime reflecting association/transport of the peptide could be determined with \\bar {t}_{\\mathrm {off}} \\cong 1.1 ms for the wildtype, whereas the mutant Tom40SC S54E displayed a biphasic dwelltime distribution (\\bar {t}_{\\mathrm {off}}^1 \\cong 0.4 ms \\bar {t}_{\\mathrm {off}}^2 \\cong 4.6 ms).

  10. Crystal growth of drug materials by spherical crystallization

    NASA Astrophysics Data System (ADS)

    Szabó-Révész, P.; Hasznos-Nezdei, M.; Farkas, B.; Göcző, H.; Pintye-Hódi, K.; Erős, I.

    2002-04-01

    One of the crystal growth processes is the production of crystal agglomerates by spherical crystallization. Agglomerates of drug materials were developed by means of non-typical (magnesium aspartate) and typical (acetylsalicylic acid) spherical crystallization techniques. The growth of particle size and the spherical form of the agglomerates resulted in formation of products with good bulk density, flow, compactibility and cohesivity properties. The crystal agglomerates were developed for direct capsule-filling and tablet-making.

  11. Periodic nanowire array at the crystal interface.

    PubMed

    Nakamura, Atsutomo; Mizoguchi, Teruyasu; Matsunaga, Katsuyuki; Yamamoto, Takahisa; Shibata, Naoya; Ikuhara, Yuichi

    2013-07-23

    A dislocation in a crystalline material has dangling bonds at its core and a strong strain field in its vicinity. Consequently, the dislocation attracts solute atoms and forms a so-called Cottrell atmosphere along the dislocation. A crystalline dislocation can be used as a template to produce nanowires by selectively doping foreign atoms along the dislocation. However, control of the configuration, spacing, and density of the formed periodic nanowire array has heretofore been extremely difficult. Here we show a method for fabricating ordered, electrically conductive nanowire arrays using periodic dislocations at crystal interfaces. As a demonstration, we fabricated arrays of titanium nanowires arranged at intervals of either 13 or 90 nm and then confirmed by scanning probe microscopy that they exhibit electrical conductivity inside an insulating aluminum oxide. Significantly, we were able to precisely control nanowire periodicity by the choice of crystal orientation and/or crystal planes at the crystal interface. This simple method for the fabrication of periodic nanowire arrays of highly controlled density should be widely applicable to electrical, magnetic, and optical devices.

  12. Engineering Crystal Morphology

    NASA Astrophysics Data System (ADS)

    Dandekar, Preshit; Kuvadia, Zubin B.; Doherty, Michael F.

    2013-07-01

    Crystallization is an important separation and particle formation technique in the manufacture of high-value-added products. During crystallization, many physicochemical characteristics of the substance are established. Such characteristics include crystal polymorph, shape and size, chemical purity and stability, reactivity, and electrical and magnetic properties. However, control over the physical form of crystalline materials has remained poor, due mainly to an inadequate understanding of the basic growth and dissolution mechanisms, as well as of the influence of impurities, additives, and solvents on the growth rate of individual crystal faces. Crystal growth is a surface-controlled phenomenon in which solute molecules are incorporated into surface lattice sites to yield the bulk long-range order that characterizes crystalline materials. In this article, we describe some recent advances in crystal morphology engineering, with a special focus on a new mechanistic model for spiral growth. These mechanistic ideas are simple enough that they can be made to work and accurate enough that they are useful.

  13. Phononic crystal diffraction gratings

    NASA Astrophysics Data System (ADS)

    Moiseyenko, Rayisa P.; Herbison, Sarah; Declercq, Nico F.; Laude, Vincent

    2012-02-01

    When a phononic crystal is interrogated by an external source of acoustic waves, there is necessarily a phenomenon of diffraction occurring on the external enclosing surfaces. Indeed, these external surfaces are periodic and the resulting acoustic diffraction grating has a periodicity that depends on the orientation of the phononic crystal. This work presents a combined experimental and theoretical study on the diffraction of bulk ultrasonic waves on the external surfaces of a 2D phononic crystal that consists of a triangular lattice of steel rods in a water matrix. The results of transmission experiments are compared with theoretical band structures obtained with the finite-element method. Angular spectrograms (showing frequency as a function of angle) determined from diffraction experiments are then compared with finite-element simulations of diffraction occurring on the surfaces of the crystal. The experimental results show that the diffraction that occurs on its external surfaces is highly frequency-dependent and has a definite relation with the Bloch modes of the phononic crystal. In particular, a strong influence of the presence of bandgaps and deaf bands on the diffraction efficiency is found. This observation opens perspectives for the design of efficient phononic crystal diffraction gratings.

  14. Intrinsic electrical conductivity of nanostructured metal-organic polymer chains

    PubMed Central

    Hermosa, Cristina; Vicente Álvarez, Jose; Azani, Mohammad-Reza; Gómez-García, Carlos J.; Fritz, Michelle; Soler, Jose M.; Gómez-Herrero, Julio; Gómez-Navarro, Cristina; Zamora, Félix

    2013-01-01

    One-dimensional conductive polymers are attractive materials because of their potential in flexible and transparent electronics. Despite years of research, on the macro- and nano-scale, structural disorder represents the major hurdle in achieving high conductivities. Here we report measurements of highly ordered metal-organic nanoribbons, whose intrinsic (defect-free) conductivity is found to be 104 S m−1, three orders of magnitude higher than that of our macroscopic crystals. This magnitude is preserved for distances as large as 300 nm. Above this length, the presence of structural defects (~ 0.5%) gives rise to an inter-fibre-mediated charge transport similar to that of macroscopic crystals. We provide the first direct experimental evidence of the gapless electronic structure predicted for these compounds. Our results postulate metal-organic molecular wires as good metallic interconnectors in nanodevices. PMID:23591876

  15. Effects of impurities on membrane-protein crystallization in different systems

    SciTech Connect

    Kors, Christopher A.; Wallace, Ellen; Davies, Douglas R.; Li, Liang; Laible, Philip D.; Nollert, Peter

    2009-10-01

    The effects of commonly encountered impurities on various membrane-protein crystallization regimes are investigated and it is found that the lipidic cubic phase crystallization methodology is the most robust, tolerating protein contamination levels of up to 50%, with little effect on crystal quality. If generally applicable, this tolerance may be exploited (i) in initial crystallization trials to determine the ‘crystallizability’ of a given membrane-protein and (ii) to subject partially pure membrane-protein samples to crystallization trials. When starting a protein-crystallization project, scientists are faced with several unknowns. Amongst them are these questions: (i) is the purity of the starting material sufficient? and (ii) which type of crystallization experiment is the most promising to conduct? The difficulty in purifying active membrane-protein samples for crystallization trials and the high costs associated with producing such samples require an extremely pragmatic approach. Additionally, practical guidelines are needed to increase the efficiency of membrane-protein crystallization. In order to address these conundrums, the effects of commonly encountered impurities on various membrane-protein crystallization regimes have been investigated and it was found that the lipidic cubic phase (LCP) based crystallization methodology is more robust than crystallization in detergent environments using vapor diffusion or microbatch approaches in its ability to tolerate contamination in the forms of protein, lipid or other general membrane components. LCP-based crystallizations produced crystals of the photosynthetic reaction center (RC) of Rhodobacter sphaeroides from samples with substantial levels of residual impurities. Crystals were obtained with protein contamination levels of up to 50% and the addition of lipid material and membrane fragments to pure samples of RC had little effect on the number or on the quality of crystals obtained in LCP

  16. Macromolecular crystal growth experiments on International Microgravity Laboratory--1.

    PubMed Central

    Day, J.; McPherson, A.

    1992-01-01

    Macromolecular crystal growth experiments, using satellite tobacco mosaic virus (STMV) and canavalin from jack beans as samples, were conducted on a US Space Shuttle mission designated International Microgravity Laboratory--1 (IML-1), flown January 22-29, 1992. Parallel experiments using identical samples were carried out in both a vapor diffusion-based device (PCG) and a liquid-liquid diffusion-based instrument (CRYOSTAT). The experiments in each device were run at 20-22 degrees C and at colder temperatures. Crystals were grown in virtually every trial, but the characteristics of the crystals were highly dependent on the crystallization technique employed and the temperature experience of the sample. In general, very good results, based on visual inspection of the crystals, were obtained in both PCG and CRYOSTAT. Unusually impressive results were, however, achieved for STMV in the CRYOSTAT instrument. STMV crystals grown in microgravity by liquid-liquid diffusion were more than 10-fold greater in total volume than any STMV crystals previously grown in the laboratory. X-ray diffraction data collected from eight STMV crystals grown in CRYOSTAT demonstrated a substantial improvement in diffraction quality over the entire resolution range when compared to data from crystals grown on Earth. In addition, the extent of the diffraction pattern for the STMV crystals grown in space extended to 1.8 A resolution, whereas the best crystals that were ever grown under conditions of Earth's gravity produced data limited to 2.3 A resolution. Other observations indicate that the growth of macromolecular crystals is indeed influenced by the presence or absence of gravity. These observations further suggest, consistent with earlier results, that the elimination of gravity provides a more favorable environment for such processes. PMID:1303744

  17. Effect of crystal shape on neutron rocking curves of perfect single crystals designed for ultra-small-angle scattering experiments

    NASA Astrophysics Data System (ADS)

    Freund, A. K.; Rehm, C.

    2014-07-01

    The present study has been conducted in the framework of the channel-cut crystal design for the Kookaburra ultra-small-angle neutron scattering (USANS) instrument to be installed at the OPAL reactor of ANSTO. This facility is based on the classical Bonse-Hart method that uses two multiple-reflection crystal systems. The dynamical theory of diffraction by perfect crystals distinguishes two cases: the Darwin case applying to infinitely thick crystals and the Ewald solution for very small absorption taking into account the reflection from the rear face of a plane-parallel crystal reflecting in Bragg geometry. The former is preferable because it yields narrower rocking curves. To prevent the neutrons to "see" the rear face, grooves were machined into the backside of perfect Si test crystals for single reflection and filled with neutron absorbing material. These samples were examined at the S18 instrument of the Institut Laue-Langevin. Unexpectedly the crystals with empty slots showed an increase of the rocking curve width. When filling the slots with an absorber the widths decreased, but without reaching that of the Darwin curve. Understanding the results and achieving a successful crystal design call for the development of a theory that permits to describe neutron diffraction from crystals with a structured back face.

  18. Thermal conductivity of hydrate-bearing sediments

    USGS Publications Warehouse

    Cortes, D.D.; Martin, A.I.; Yun, T.S.; Francisca, F.M.; Santamarina, J.C.; Ruppel, C.

    2009-01-01

    A thorough understanding of the thermal conductivity of hydrate-bearing sediments is necessary for evaluating phase transformation processes that would accompany energy production from gas hydrate deposits and for estimating regional heat flow based on the observed depth to the base of the gas hydrate stability zone. The coexistence of multiple phases (gas hydrate, liquid and gas pore fill, and solid sediment grains) and their complex spatial arrangement hinder the a priori prediction of the thermal conductivity of hydrate-bearing sediments. Previous studies have been unable to capture the full parameter space covered by variations in grain size, specific surface, degree of saturation, nature of pore filling material, and effective stress for hydrate-bearing samples. Here we report on systematic measurements of the thermal conductivity of air dry, water- and tetrohydrofuran (THF)-saturated, and THF hydrate-saturated sand and clay samples at vertical effective stress of 0.05 to 1 MPa (corresponding to depths as great as 100 m below seafloor). Results reveal that the bulk thermal conductivity of the samples in every case reflects a complex interplay among particle size, effective stress, porosity, and fluid-versus-hydrate filled pore spaces. The thermal conductivity of THF hydrate-bearing soils increases upon hydrate formation although the thermal conductivities of THF solution and THF hydrate are almost the same. Several mechanisms can contribute to this effect including cryogenic suction during hydrate crystal growth and the ensuing porosity reduction in the surrounding sediment, increased mean effective stress due to hydrate formation under zero lateral strain conditions, and decreased interface thermal impedance as grain-liquid interfaces are transformed into grain-hydrate interfaces. Copyright 2009 by the American Geophysical Union.

  19. Thermal conductivity of hydrate-bearing sediments

    NASA Astrophysics Data System (ADS)

    Cortes, Douglas D.; Martin, Ana I.; Yun, Tae Sup; Francisca, Franco M.; Santamarina, J. Carlos; Ruppel, Carolyn

    2009-11-01

    A thorough understanding of the thermal conductivity of hydrate-bearing sediments is necessary for evaluating phase transformation processes that would accompany energy production from gas hydrate deposits and for estimating regional heat flow based on the observed depth to the base of the gas hydrate stability zone. The coexistence of multiple phases (gas hydrate, liquid and gas pore fill, and solid sediment grains) and their complex spatial arrangement hinder the a priori prediction of the thermal conductivity of hydrate-bearing sediments. Previous studies have been unable to capture the full parameter space covered by variations in grain size, specific surface, degree of saturation, nature of pore filling material, and effective stress for hydrate-bearing samples. Here we report on systematic measurements of the thermal conductivity of air dry, water- and tetrohydrofuran (THF)-saturated, and THF hydrate-saturated sand and clay samples at vertical effective stress of 0.05 to 1 MPa (corresponding to depths as great as 100 m below seafloor). Results reveal that the bulk thermal conductivity of the samples in every case reflects a complex interplay among particle size, effective stress, porosity, and fluid-versus-hydrate filled pore spaces. The thermal conductivity of THF hydrate-bearing soils increases upon hydrate formation although the thermal conductivities of THF solution and THF hydrate are almost the same. Several mechanisms can contribute to this effect including cryogenic suction during hydrate crystal growth and the ensuing porosity reduction in the surrounding sediment, increased mean effective stress due to hydrate formation under zero lateral strain conditions, and decreased interface thermal impedance as grain-liquid interfaces are transformed into grain-hydrate interfaces.

  20. Intrinsic low thermal conductivity in weakly ionic rocksalt structures

    DOE PAGES

    Zhang, Yi; Dong, Jianjun; Kent, Paul R. C.; ...

    2015-07-06

    A fundamental challenge in thermoelectric (TE) material research is meeting the simultaneous requirements of high carrier mobility and low thermal conductivity. Simple crystal structures are ideal for maintaining high carrier mobility, but they usually have high thermal conductivity. In this paper, we show by first-principles lattice dynamics and Boltzmann transport calculations that weakly ionic rocksalt structures exhibit strong lattice anharmonicity and low acoustic-phonon group velocity, which combine to produce intrinsic low thermal conductivity. Finally, we unveil microscopic mechanisms that explain experimental observations and provide insights for TE material design and discovery.

  1. Thermal properties of UO2 single crystal

    NASA Astrophysics Data System (ADS)

    Gofryk, K.; Du, S.; Andersson, A. D.; Stanek, C. R.; Schulze, R.; Safarik, D.; Mihaila, B.; Lashley, J. C.; Smith, J. L.

    2013-03-01

    For decades UO2 has been the most widely studied actinide oxide because of its technological importance as fuel material for nuclear reactors. Therefore there is a large interest in understanding its thermal, transport and thermodynamic properties. We present recent experimental results for the thermal conductivity and thermal expansion of high quality UO2 single crystal, obtained for different crystallographic directions, and compare with results of molecular dynamics simulations. We will discuss the implications of this study.

  2. Conducting Wall Hall Thrusters

    NASA Technical Reports Server (NTRS)

    Goebel, Dan M.; Hofer, Richard R.; Mikellides, Ioannis G.; Katz, Ira; Polk, James E.; Dotson, Brandon

    2013-01-01

    A unique configuration of the magnetic field near the wall of Hall thrusters, called Magnetic Shielding, has recently demonstrated the ability to significantly reduce the erosion of the boron nitride (BN) walls and extend the life of Hall thrusters by orders of magnitude. The ability of magnetic shielding to minimize interactions between the plasma and the discharge chamber walls has for the first time enabled the replacement of insulating walls with conducting materials without loss in thruster performance. The boron nitride rings in the 6 kW H6 Hall thruster were replaced with graphite that self-biased to near the anode potential. The thruster efficiency remained over 60% (within two percent of the baseline BN configuration) with a small decrease in thrust and increase in Isp typical of magnetically shielded Hall thrusters. The graphite wall temperatures decreased significantly compared to both shielded and unshielded BN configurations, leading to the potential for higher power operation. Eliminating ceramic walls makes it simpler and less expensive to fabricate a thruster to survive launch loads, and the graphite discharge chamber radiates more efficiently which increases the power capability of the thruster compared to conventional Hall thruster designs.

  3. Thermal Contact Conductance

    NASA Technical Reports Server (NTRS)

    Salerno, Louis J.; Kittel, Peter

    1997-01-01

    The performance of cryogenic instruments is often a function of their operating temperature. Thus, designers of cryogenic instruments often are required to predict the operating temperature of each instrument they design. This requires accurate thermal models of cryogenic components which include the properties of the materials and assembly techniques used. When components are bolted or otherwise pressed together, a knowledge of the thermal performance of such joints are also needed. In some cases, the temperature drop across these joints represents a significant fraction of the total temperature difference between the instrument and its cooler. While extensive databases exist on the thermal properties of bulk materials, similar databases for pressed contacts do not. This has often lead to instrument designs that avoid pressed contacts or to the over-design of such joints at unnecessary expense. Although many people have made measurements of contact conductances at cryogenic temperatures, this data is often very narrow in scope and even more often it has not been published in an easily retrievable fashion, if published at all. This paper presents a summary of the limited pressed contact data available in the literature.

  4. Liquid/Liquid interfacial polymerization to grow single crystalline nanoneedles of various conducting polymers.

    PubMed

    Nuraje, Nurxat; Su, Kai; Yang, Nan-Loh; Matsui, Hiroshi

    2008-03-01

    Single crystalline nanoneedles of polyaniline (PANI) and polypyrrole (PPY) were synthesized using an interfacial polymerization for the first time. The interfacial crystallization of conductive polymers at the liquid/liquid interface allowed PANI and PPY polymers to form single crystalline nanocrystals in a rice-like shape in the dimensions of 63 nm x 12 nm for PANI and 70 nm x 20 nm for PPY. Those crystalline nanoneedles displayed a fast conductance switching in the time scale of milliseconds. An important growth condition necessary to yield highly crystalline conductive polymers was the extended crystallization time at the liquid/liquid interfaces to increase the degree of crystallization. As compared to other interfacial polymerization methods, lower concentrations of monomer and oxidant solutions were employed to further extend the crystallization time. While other interfacial growth of conducting polymers yielded noncrystalline polymer fibers, our interfacial method produced single crystalline nanocrystals of conductive polymers. We recently reported the liquid/liquid interfacial synthesis of conducting PEDOT nanocrystals; however, this liquid/liquid interfacial method needs to be extended to other conductive polymer nanocrystal syntheses in order to demonstrate that our technique could be applied as the general fabrication procedure for the single crystalline conducting polymer growth. In this report, we showed that the liquid/liquid interfacial crystallization could yield PANI nanocrystals and PPY nanocrystals, other important conductive polymers, in addition to PEDOT nanocrystals. The resulting crystalline polymers have a fast conductance switching time between the insulating and conducting states on the order of milliseconds. This technique will be useful to synthesize conducting polymers via oxidative coupling processes in a single crystal state, which is extremely difficult to achieve by other synthetic methods.

  5. Facilitated Ion Transport in Smectic Ordered Ionic Liquid Crystals

    SciTech Connect

    Lee, Jin Hong; Han, Kee Sung; Lee, Je Seung; Lee, Albert S.; Park, Seo Kyung; Hong, Sung Yun; Lee, Jong-Chan; Mueller, Karl T.; Hong, Soon Man; Koo, Chong Min

    2016-09-08

    We investigated a novel ionic mixture of an imidazolium-based room temperature IL containing ethylene oxide functionalized phosphite anion and a lithium salt that self-assembles into a smectic-ordered IL crystal. The two key features in this work are the unique origin of the smectic order of the ionic mixtures and the facilitated ion transport behavior in the smectic ordered IL crystal. In fact, the IL crystals are self-assembled through Coulombic interactions between ion species, not through the hydrophilic-phobic interactions between charged ion heads and hydrophobic long alkyl pendants or the steric interaction between mesogenic moieties. Furthermore, the smectic order in the IL crystal ionogel facilitates exceptional and remarkable ionic transport. Large ionic conductivity, viscoelastic robustness, and additional electrochemical stability of the IL crystal ionogels provide promising opportunities for future electrochemical applications.

  6. Human serum albumin crystals and method of preparation

    NASA Technical Reports Server (NTRS)

    Carter, Daniel C. (Inventor)

    1989-01-01

    Human serum albumin (HSA) crystals are provided in the form of tetragonal plates having the space groups P42(sub 1)2, the crystals being grown to sizes in excess of 0.5 mm in two dimensions and a thickness of 0.1 mm. Growth of the crystals is carried out by a hanging drop method wherein a precipitant solution containing polyethylene glycol (PEG) and a phosphate buffer is mixed with an HSA solution, and a droplet of mixed solution is suspended over a well of precipitant solution. Crystals grow to the desired size in 3 to 7 days. Concentration of reagents, pH and other parameters are controlled within prescribed limits. The resulting crystals exhibit a size and quality such as to allow performance of x ray diffraction studies and enable the conduct of drug binding studies as well as genetic engineering studies.

  7. Manifestations of two-dimensional electron gas in molecular crystals

    NASA Astrophysics Data System (ADS)

    Kuklja, Maija M.; Sharia, Onise; Tsyshevsky, Roman

    2017-03-01

    The existence of two-dimensional electron gas in molecular materials has not been reported or discussed. Intriguing properties of two-dimensional electron gas observed on interfaces of polar and nonpolar oxides spurred oxide electronics and advanced nanotechnology. Here we discover how an electrostatic instability occurs on polar surfaces of molecular crystals and explore its manifestations, chemical degradation of surfaces, charge separation, electrical conductivity, optical band-gap closure and surface metallization. A thin layer of polar surface of a dielectric molecular crystal becomes metallic due to interactions of polar molecules. Our findings are illustrated with two polymorphs of cyclotetramethylene-tetranitramine crystals, the polar δ-phase and nonpolar β-phase. Our theory offers an explanation to a relative stability of the β-phase versus the explosive reactivity of δ-phase and to the experimentally observed difference in conductivity of these crystals. We predict that the electrostatic instability takes place on all polar molecular materials.

  8. Humidity control and hydrophilic glue coating applied to mounted protein crystals improves X-ray diffraction experiments

    PubMed Central

    Baba, Seiki; Hoshino, Takeshi; Ito, Len; Kumasaka, Takashi

    2013-01-01

    Protein crystals are fragile, and it is sometimes difficult to find conditions suitable for handling and cryocooling the crystals before conducting X-ray diffraction experiments. To overcome this issue, a protein crystal-mounting method has been developed that involves a water-soluble polymer and controlled humid air that can adjust the moisture content of a mounted crystal. By coating crystals with polymer glue and exposing them to controlled humid air, the crystals were stable at room temperature and were cryocooled under optimized humidity. Moreover, the glue-coated crystals reproducibly showed gradual transformations of their lattice constants in response to a change in humidity; thus, using this method, a series of isomorphous crystals can be prepared. This technique is valuable when working on fragile protein crystals, including membrane proteins, and will also be useful for multi-crystal data collection. PMID:23999307

  9. Humidity control and hydrophilic glue coating applied to mounted protein crystals improves X-ray diffraction experiments.

    PubMed

    Baba, Seiki; Hoshino, Takeshi; Ito, Len; Kumasaka, Takashi

    2013-09-01

    Protein crystals are fragile, and it is sometimes difficult to find conditions suitable for handling and cryocooling the crystals before conducting X-ray diffraction experiments. To overcome this issue, a protein crystal-mounting method has been developed that involves a water-soluble polymer and controlled humid air that can adjust the moisture content of a mounted crystal. By coating crystals with polymer glue and exposing them to controlled humid air, the crystals were stable at room temperature and were cryocooled under optimized humidity. Moreover, the glue-coated crystals reproducibly showed gradual transformations of their lattice constants in response to a change in humidity; thus, using this method, a series of isomorphous crystals can be prepared. This technique is valuable when working on fragile protein crystals, including membrane proteins, and will also be useful for multi-crystal data collection.

  10. Extremes of heat conduction-Pushing the boundaries of the thermal conductivity of materials

    SciTech Connect

    Cahill, DG

    2012-09-12

    Thermal conductivity is a familiar property of materials: silver conducts heat well, and plastic does not. In recent years, an interdisciplinary group of materials scientists, engineers, physicists, and chemists have succeeded in pushing back long-established limits in the thermal conductivity of materials. Carbon nanotubes and graphene are at the high end of the thermal conductivity spectrum due to their high sound velocities and relative lack of processes that scatter phonons. Unfortunately, the superlative thermal properties of carbon nanotubes have not found immediate application in composites or interface materials because of difficulties in making good thermal contact with the nanotubes. At the low end of the thermal conductivity spectrum, solids that combine order and disorder in the random stacking of two-dimensional crystalline sheets, so-called "disordered layered crystals," show a thermal conductivity that is only a factor of 2 larger than air. The cause of this low thermal conductivity may be explained by the large anisotropy in elastic constants that suppresses the density of phonon modes that propagate along the soft direction. Low-dimensional quantum magnets demonstrate that electrons and phonons are not the only significant carriers of heat. Near room temperature, the spin thermal conductivity of spin-ladders is comparable to the electronic thermal conductivities of metals. Our measurements of nanoscale thermal transport properties employ a variety of ultrafast optical pump-probe metrology tools that we have developed over the past several years. We are currently working to extend these techniques to high pressures (60 GPa), high magnetic fields (5 T), and high temperatures (1000 K).

  11. Crystal growth and electrical properties of CuFeO 2 single crystals

    NASA Astrophysics Data System (ADS)

    Dordor, P.; Chaminade, J. P.; Wichainchai, A.; Marquestaut, E.; Doumerc, J. P.; Pouchard, M.; Hagenmuller, P.; Ammar, A.

    1988-07-01

    Delafossite-type CuFeO 2 single crystals have been prepared by a flux method: crystals obtained in a Cu crucible with LiBO 2 as flux are n-type whereas those prepared in a Pt crucible with a Cu 2O flux are p-type. Electrical measurements have revealed that n-type crystals exhibit weak anisotropic conductivities with large activation energies and small mobilities (r.t. values perpendicular and parallel to the c-axis: μ⊥ = 5 × 10 -5 and μ‖ = 10 -7 cm -2 V -1 sec -1). p-type crystals, less anisotropic, are characterized by low activation energies and higher mobilities ( μ⊥ = 34 and μ‖ = 8.9 cm 2 V -1 sec -1). A two -conduction-band model is proposed to account for the difference observed between the energy gap value deduced from photoelectrochemical measurements and the activation energy of the electrical conductivity in the intrinsic domain.

  12. Excimer laser crystallization of hydrogenated amorphous silicon

    SciTech Connect

    Dai Yongbing; Xu Zhongyang; Wang Changan; Zhang Shaoqiang; An Chengwu; Li Xingjiao; Wan Xinheng; Ding Hui

    1996-12-31

    Hydrogenated amorphous silicon (a-Si:H) films have been crystallized by the irradiations of XeCl excimer laser. The crystallized films have been examined by scanning electron microscopy (SEM), x-ray diffraction (XRD) and conductivity measurements to clarify their morphologies, structure and electrical properties. The results show that a high conductive super thin layer is formed by a single pulse laser irradiation with the energy density of 75mJ/cm{sup 2}. The conductivity increases quickly at laser energy density threshold which decreases when the hydrogen in a-Si:H films is removed by pre-annealing. During crystallization process, oxygen atoms from the air ambient have been introduced into the films and such an introducing process is hindered by the hydrogen eruption. When the oxygen content is high enough, the carrier-transport mechanism includes thermionic emission (TE) and thermionic field emission (TFE) in the vicinity of room temperature, which is similar to semi-insulating polycrystalline silicon (SIPOS).

  13. Effect of several processing parameters on material removal ratio in the deliquescent polishing of KDP crystals

    NASA Astrophysics Data System (ADS)

    Zhang, Feihu; Guo, Shaolong; Zhang, Yong; Luan, Dianrong

    2009-05-01

    A new ultraprecision machining technology for potassium dihydrogen phosphate (KDP) crystals, deliquescent polishing technology for KDP crystals, which utilizes deliquescent effect for ultraprecision machining KDP crystals, is proposed. The principle and the advantages of technology are introduced. The deliquescent polishing procedure of KDP crystals is given. The deliquescent polishing experiments of KDP crystals are conducted, and the material removal ratios are calculated. Through the experiments, the effect of four processing parameters (velocity of polishing plate, velocity of drip, volume percentage of water in the deliquescent polishing fluid, polishing pressure) on material removal ratio in the deliquescent polishing of KDP crystals is researched. The plot of material removal ratio versus every processing parameter in the deliquescent polishing of KDP crystals is obtained, and the rules of material removal ratio in the deliquescent polishing of KDP crystals are reached.

  14. Crystal Growth Control

    NASA Technical Reports Server (NTRS)

    Duval, Walter M. B.; Batur, Celal; Bennett, Robert J.

    1997-01-01

    We present an innovative design of a vertical transparent multizone furnace which can operate in the temperature range of 25 C to 750 C and deliver thermal gradients of 2 C/cm to 45 C/cm for the commercial applications to crystal growth. The operation of the eight zone furnace is based on a self-tuning temperature control system with a DC power supply for optimal thermal stability. We show that the desired thermal profile over the entire length of the furnace consists of a functional combination of the fundamental thermal profiles for each individual zone obtained by setting the set-point temperature for that zone. The self-tuning system accounts for the zone to zone thermal interactions. The control system operates such that the thermal profile is maintained under thermal load, thus boundary conditions on crystal growth ampoules can be predetermined prior to crystal growth. Temperature profiles for the growth of crystals via directional solidification, vapor transport techniques, and multiple gradient applications are shown to be easily implemented. The unique feature of its transparency and ease of programming thermal profiles make the furnace useful for scientific and commercial applications for the determination of process parameters to optimize crystal growth conditions.

  15. Introduction to protein crystallization

    PubMed Central

    McPherson, Alexander; Gavira, Jose A.

    2014-01-01

    Protein crystallization was discovered by chance about 150 years ago and was developed in the late 19th century as a powerful purification tool and as a demonstration of chemical purity. The crystallization of proteins, nucleic acids and large biological complexes, such as viruses, depends on the creation of a solution that is supersaturated in the macromolecule but exhibits conditions that do not significantly perturb its natural state. Supersaturation is produced through the addition of mild precipitating agents such as neutral salts or polymers, and by the manipulation of various parameters that include temperature, ionic strength and pH. Also important in the crystallization process are factors that can affect the structural state of the macromolecule, such as metal ions, inhibitors, cofactors or other conventional small molecules. A variety of approaches have been developed that combine the spectrum of factors that effect and promote crystallization, and among the most widely used are vapor diffusion, dialysis, batch and liquid–liquid diffusion. Successes in macromolecular crystallization have multiplied rapidly in recent years owing to the advent of practical, easy-to-use screening kits and the application of laboratory robotics. A brief review will be given here of the most popular methods, some guiding principles and an overview of current technologies. PMID:24419610

  16. Crystal Ball Functional Model

    NASA Astrophysics Data System (ADS)

    Plotnick, David

    2016-09-01

    The A2 collaboration of the MAinz MIkrotron is dedicated to studying meson production and nucleon structure and behavior via photon scattering. The photons are made via bremsstrahlung process and energy-tagged using the Glasgow Photon tagger. The photon beam then interacts in a variety of targets: cryogenic, polarized or solid state, and scattered particles deposit their energy within the NaI crystals. Scintillators are able to give results on particles energy and time. Events are reconstructed by combining information from the Tagging spectrometer, the Crystal Ball detector, the TAPS forward wall spectrometer, a Cherenkov detector, and multi-wire proportional chambers. To better understand the detector and experimental events, a live display was built to show energies deposited in crystals in real-time. In order to show a range of energies and particles, addressable LEDs that are individually programmable were used. To best replicate the Crystal Ball, 3D printing technology was employed to build a similar highly segmented icosahedron that can hold each LED, creating a 3D representation of what photons see during experiments. The LEDs were controlled via Arduino microcontroller. Finally, we implemented the Experimental Physics and Industrial Control System to grab live event data, and a simple program converts this data in to color and crystal number data that is able to communicate with the Arduino. Using these simple parts, we can better visualize and understand the tools used in nuclear physics. This material is based upon work supported by the National Science Foundation Grant No. IIA-1358175.

  17. Definition study for temperature control in advanced protein crystal growth

    NASA Astrophysics Data System (ADS)

    Nyce, Thomas A.; Rosenberger, Franz; Sowers, Jennifer W.; Monaco, Lisa A.

    1990-09-01

    Some of the technical requirements for an expedient application of temperature control to advanced protein crystal growth activities are defined. Lysozome was used to study the effects of temperature ramping and temperature gradients for nucleation/dissolution and consecutive growth of sizable crystals and, to determine a prototype temperature program. The solubility study was conducted using equine serum albumin (ESA) which is an extremely stable, clinically important protein due to its capability to bind and transport many different small ions and molecules.

  18. Definition study for temperature control in advanced protein crystal growth

    NASA Technical Reports Server (NTRS)

    Nyce, Thomas A.; Rosenberger, Franz; Sowers, Jennifer W.; Monaco, Lisa A.

    1990-01-01

    Some of the technical requirements for an expedient application of temperature control to advanced protein crystal growth activities are defined. Lysozome was used to study the effects of temperature ramping and temperature gradients for nucleation/dissolution and consecutive growth of sizable crystals and, to determine a prototype temperature program. The solubility study was conducted using equine serum albumin (ESA) which is an extremely stable, clinically important protein due to its capability to bind and transport many different small ions and molecules.

  19. Electrically Conductive Paints for Satellites

    NASA Technical Reports Server (NTRS)

    Gilligan, J. E.; Wolf, R. E.; Ray, C.

    1977-01-01

    A program was conducted to develop and test electrically conductive paint coatings for spacecraft. A wide variety of organic and inorganic coatings were formulated using conductive binders, conductive pigments, and similar approaches. Z-93, IITRI's standard specification inorganic thermal control coating, exhibits good electrical properties and is a very space-stable coating system. Several coatings based on a conductive pigment (antimony-doped tin oxide) in silicone and silicate binders offer considerable promise. Paint systems using commercially available conductive polymers also appear to be of interest, but will require substantial development. Evaluations were made based on electrical conductivity, paint physical properties, and the stability of spectral reflectance in space environment testing.

  20. Crystal engineering through halogen bonding

    NASA Astrophysics Data System (ADS)

    Walsh, Rosa Daneen Bailey

    tetraiodoethylene. Organoiodides can also be used to build very interesting layered 'pseudo polyiodides', as well. Traditional coordination polymers consist of a Lewis acid metal center and Lewis base bridging ligands. The shapes that can be made using these coordination polymers include, but are not limited to, chains, ladders, bricks, square or rectangular grids and hexagonal grids. We have been able to build many of these same motifs using a Lewis base iodide center and Lewis acid organoiodide. The diverse structures seen are dependent on factors such as the nature of the cation, the bridging organoiodide, stoichiometry, and the nature of the anion (e.g. I- vs. I3 -). These complexes may exhibit ionic conductivity as well as the possibility of cation exchange. Polymorphism can be a major problem for crystal engineering as it can make prediction of structure very difficult. George Whitesides states "truly rational solid-state design will not be possible until polymorphism is understood and controlled." We have used halogen bonding interactions for interconversion between polymorphic forms of a donor molecule. Polymorphic forms of tetrapyridylpyrazine and acridine, their charge-transfer complexes with iodine, and their interconversion through decomposition of the complexes will be discussed. Through systematic studies of halogen bonding, numerous donors and acceptors have been used to show the structural diversity possible. Our purpose is to define the fundamental structural motifs adopted by these systems. An understanding of these patterns is essential for ongoing crystal engineering projects.

  1. Dynamic crystallization and kinetic melting of the lunar soil

    NASA Technical Reports Server (NTRS)

    Lofgren, G. E.; Smith, D. P.; Brown, R. W.

    1978-01-01

    Dynamic crystallization and kinetic melting tests have been conducted for a lunar soil that resembles the bulk composition of the matrices of melt-rock breccias. The melting tests indicate that plagioclase and olivine can exist for finite times above their equilibrium liquidus temperatures; within 20-30 C below its liquidus temperature the sample is choked with crystals. A range of textures from radiate to porphyritic pyroxene-plagioclase granophyric to subophitic to intergranular to intersertal to very fine-grained poikilitic is found in the dynamic crystallization experiments. The number of nuclei, as deduced from the textures, increases as the melting temperature deceases from above the liquidus to below.

  2. Conductive lithium storage electrode

    DOEpatents

    Chiang, Yet-Ming; Chung, Sung-Yoon; Bloking, Jason T.; Andersson, Anna M.

    2008-03-18

    A compound comprising a composition A.sub.x(M'.sub.1-aM''.sub.a).sub.y(XD.sub.4).sub.z, A.sub.x(M'.sub.1-aM''.sub.a).sub.y(DXD.sub.4).sub.z, or A.sub.x(M'.sub.1-aM''.sub.a).sub.y(X.sub.2D.sub.7).sub.z, and have values such that x, plus y(1-a) times a formal valence or valences of M', plus ya times a formal valence or valence of M'', is equal to z times a formal valence of the XD.sub.4, X.sub.2D.sub.7, or DXD.sub.4 group; or a compound comprising a composition (A.sub.1-aM''.sub.a).sub.xM'.sub.y(XD.sub.4).sub.z, (A.sub.1-aM''.sub.a).sub.xM'.sub.y(DXD.sub.4).sub.z(A.sub.1-aM''.sub.a).s- ub.xM'.sub.y(X.sub.2D.sub.7).sub.z and have values such that (1-a).sub.x plus the quantity ax times the formal valence or valences of M'' plus y times the formal valence or valences of M' is equal to z times the formal valence of the XD.sub.4, X.sub.2D.sub.7 or DXD.sub.4 group. In the compound, A is at least one of an alkali metal and hydrogen, M' is a first-row transition metal, X is at least one of phosphorus, sulfur, arsenic, molybdenum, and tungsten, M'' any of a Group IIA, IIIA, IVA, VA, VIA, VIIA, VIIIA, IB, IIB, IIIB, IVB, VB, and VIB metal, D is at least one of oxygen, nitrogen, carbon, or a halogen, 0.0001conductivity at 27.degree. C. of at least about 10.sup.-8 S/cm. The compound can be a doped lithium phosphate that can intercalate lithium or hydrogen. The compound can be used in an electrochemical device including electrodes and storage batteries and can have a gravimetric capacity of at least about 80 mAh/g while being charged/discharged at greater than about C rate of the compound.

  3. Conductive lithium storage electrode

    DOEpatents

    Chiang, Yet-Ming [Framingham, MA; Chung, Sung-Yoon [Incheon, KR; Bloking, Jason T [Mountain View, CA; Andersson, Anna M [Vasteras, SE

    2012-04-03

    A compound comprising a composition A.sub.x(M'.sub.1-aM''.sub.a).sub.y(XD.sub.4).sub.z, A.sub.x(M'.sub.1-aM''.sub.a).sub.y(DXD.sub.4).sub.z, or A.sub.x(M'.sub.1-aM''.sub.a).sub.y(X.sub.2D.sub.7).sub.z, and have values such that x, plus y(1-a) times a formal valence or valences of M', plus ya times a formal valence or valence of M'', is equal to z times a formal valence of the XD.sub.4, X.sub.2D.sub.7, or DXD.sub.4 group; or a compound comprising a composition (A.sub.1-aM''.sub.a).sub.xM'.sub.y(XD.sub.4).sub.z, (A.sub.1-aM''.sub.a).sub.xM'.sub.y(DXD.sub.4).sub.z (A.sub.1-aM''.sub.a).sub.xM'.sub.y(X.sub.2D.sub.7).sub.z and have values such that (1-a).sub.x plus the quantity ax times the formal valence or valences of M'' plus y times the formal valence or valences of M' is equal to z times the formal valence of the XD.sub.4, X.sub.2D.sub.7 or DXD.sub.4 group. In the compound, A is at least one of an alkali metal and hydrogen, M' is a first-row transition metal, X is at least one of phosphorus, sulfur, arsenic, molybdenum, and tungsten, M'' any of a Group IIA, IIIA, IVA, VA, VIA, VIIA, VIIIA, IB, IIB, IIIB, IVB, VB, and VIB metal, D is at least one of oxygen, nitrogen, carbon, or a halogen, 0.0001conductivity at 27.degree. C. of at least about 10.sup.-8 S/cm. The compound can be a doped lithium phosphate that can intercalate lithium or hydrogen. The compound can be used in an electrochemical device including electrodes and storage batteries and can have a gravimetric capacity of at least about 80 mAh/g while being charged/discharged at greater than about C rate of the compound.

  4. Protein Crystals and their Growth

    NASA Technical Reports Server (NTRS)

    Chernov, A. A.

    2004-01-01

    Recent results on binding between protein molecules in crystal lattice, crystal-solution surface energy, elastic properties and strength and spontaneous crystal cracking are reviewed and discussed in the first half of this paper (Sea 2-4). In the second par&, some basic approaches to solubility of proteins are followed by overview on crystal nucleation and growth (Sec 5). It is argued that variability of mixing in batch crystallization may be a source for scattering of crystal number ultimately appearing in the batch. Frequency at which new molecules join crystal lattice is measured by kinetic coefficient and related to the observable crystal growth rate. Numerical criteria to discriminate diffusion and kinetic limited growth are discussed on this basis in Sec 7. In Sec 8, creation of defects is discussed with the emphasis on the role of impurities and convection on macromolecular crystal I;erfection.

  5. Flexible ferroelectric organic crystals

    PubMed Central

    Owczarek, Magdalena; Hujsak, Karl A.; Ferris, Daniel P.; Prokofjevs, Aleksandrs; Majerz, Irena; Szklarz, Przemysław; Zhang, Huacheng; Sarjeant, Amy A.; Stern, Charlotte L.; Jakubas, Ryszard; Hong, Seungbum; Dravid, Vinayak P.; Stoddart, J. Fraser

    2016-01-01

    Flexible organic materials possessing useful electrical properties, such as ferroelectricity, are of crucial importance in the engineering of electronic devices. Up until now, however, only ferroelectric polymers have intrinsically met this flexibility requirement, leaving small-molecule organic ferroelectrics with room for improvement. Since both flexibility and ferroelectricity are rare properties on their own, combining them in one crystalline organic material is challenging. Herein, we report that trisubstituted haloimidazoles not only display ferroelectricity and piezoelectricity—the properties that originate from their non-centrosymmetric crystal lattice—but also lend their crystalline mechanical properties to fine-tuning in a controllable manner by disrupting the weak halogen bonds between the molecules. This element of control makes it possible to deliver another unique and highly desirable property, namely crystal flexibility. Moreover, the electrical properties are maintained in the flexible crystals. PMID:27734829

  6. Photonic Crystal Microchip Laser

    NASA Astrophysics Data System (ADS)

    Gailevicius, Darius; Koliadenko, Volodymyr; Purlys, Vytautas; Peckus, Martynas; Taranenko, Victor; Staliunas, Kestutis

    2016-09-01

    The microchip lasers, being very compact and efficient sources of coherent light, suffer from one serious drawback: low spatial quality of the beam strongly reducing the brightness of emitted radiation. Attempts to improve the beam quality, such as pump-beam guiding, external feedback, either strongly reduce the emission power, or drastically increase the size and complexity of the lasers. Here it is proposed that specially designed photonic crystal in the cavity of a microchip laser, can significantly improve the beam quality. Experiments show that a microchip laser, due to spatial filtering functionality of intracavity photonic crystal, improves the beam quality factor M2 reducing it by a factor of 2, and increase the brightness of radiation by a factor of 3. This comprises a new kind of laser, the “photonic crystal microchip laser”, a very compact and efficient light source emitting high spatial quality high brightness radiation.

  7. Photonic Crystal Microchip Laser.

    PubMed

    Gailevicius, Darius; Koliadenko, Volodymyr; Purlys, Vytautas; Peckus, Martynas; Taranenko, Victor; Staliunas, Kestutis

    2016-09-29

    The microchip lasers, being very compact and efficient sources of coherent light, suffer from one serious drawback: low spatial quality of the beam strongly reducing the brightness of emitted radiation. Attempts to improve the beam quality, such as pump-beam guiding, external feedback, either strongly reduce the emission power, or drastically increase the size and complexity of the lasers. Here it is proposed that specially designed photonic crystal in the cavity of a microchip laser, can significantly improve the beam quality. Experiments show that a microchip laser, due to spatial filtering functionality of intracavity photonic crystal, improves the beam quality factor M(2) reducing it by a factor of 2, and increase the brightness of radiation by a factor of 3. This comprises a new kind of laser, the "photonic crystal microchip laser", a very compact and efficient light source emitting high spatial quality high brightness radiation.

  8. Flexible ferroelectric organic crystals

    NASA Astrophysics Data System (ADS)

    Owczarek, Magdalena; Hujsak, Karl A.; Ferris, Daniel P.; Prokofjevs, Aleksandrs; Majerz, Irena; Szklarz, Przemysław; Zhang, Huacheng; Sarjeant, Amy A.; Stern, Charlotte L.; Jakubas, Ryszard; Hong, Seungbum; Dravid, Vinayak P.; Stoddart, J. Fraser

    2016-10-01

    Flexible organic materials possessing useful electrical properties, such as ferroelectricity, are of crucial importance in the engineering of electronic devices. Up until now, however, only ferroelectric polymers have intrinsically met this flexibility requirement, leaving small-molecule organic ferroelectrics with room for improvement. Since both flexibility and ferroelectricity are rare properties on their own, combining them in one crystalline organic material is challenging. Herein, we report that trisubstituted haloimidazoles not only display ferroelectricity and piezoelectricity--the properties that originate from their non-centrosymmetric crystal lattice--but also lend their crystalline mechanical properties to fine-tuning in a controllable manner by disrupting the weak halogen bonds between the molecules. This element of control makes it possible to deliver another unique and highly desirable property, namely crystal flexibility. Moreover, the electrical properties are maintained in the flexible crystals.

  9. Photonic Crystal Microchip Laser

    PubMed Central

    Gailevicius, Darius; Koliadenko, Volodymyr; Purlys, Vytautas; Peckus, Martynas; Taranenko, Victor; Staliunas, Kestutis

    2016-01-01

    The microchip lasers, being very compact and efficient sources of coherent light, suffer from one serious drawback: low spatial quality of the beam strongly reducing the brightness of emitted radiation. Attempts to improve the beam quality, such as pump-beam guiding, external feedback, either strongly reduce the emission power, or drastically increase the size and complexity of the lasers. Here it is proposed that specially designed photonic crystal in the cavity of a microchip laser, can significantly improve the beam quality. Experiments show that a microchip laser, due to spatial filtering functionality of intracavity photonic crystal, improves the beam quality factor M2 reducing it by a factor of 2, and increase the brightness of radiation by a factor of 3. This comprises a new kind of laser, the “photonic crystal microchip laser”, a very compact and efficient light source emitting high spatial quality high brightness radiation. PMID:27683066

  10. Frequency doubling crystals

    DOEpatents

    Wang, Francis; Velsko, Stephan P.

    1989-01-01

    A systematic approach to the production of frequency conversion crystals is described in which a chiral molecule has attached to it a "harmonic generating unit" which contributes to the noncentrosymmetry of the molecule. Certain preferred embodiments of such harmonic generating units include carboxylate, guanadyly and imidazolyl units. Certain preferred crystals include L-arginine fluoride, deuterated L-arginine fluoride, L-arginine chloride monohydrate, L-arginine acetate, dithallium tartrate, ammonium N-acetyl valine, N-acetyl tyrosine and N-acetyl hydroxyproline. Chemical modifications of the chiral molecule, such as deuteration, halogenation and controlled counterion substitution are available to adapt the dispersive properties of a crystal in a particular wavelength region.

  11. Microgravity crystal growth

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Advanced finite element models are used to study three-dimensional, time-dependent flow and segregation in crystal growth systems. In this image of a prototypical model for melt and crystal growth, pathlines at one instant in time are shown for the flow of heated liquid silicon in a cylindrical container. The container is subjected to g-jitter disturbances along the vertical axis. A transverse magnetic field is applied to control them. Such computations are extremely powerful for understanding melt growth in microgravity where g-jitter drives buoyant flows. The simulation is part of the Theoretical Analysis of 3D, Transient Convection and Segregation in Microgravity Bridgman Crystal Growth investigation by Dr. Jeffrey J. Derby of the University of Mirnesota, Minneapolis.

  12. Theoretic analysis on electric conductance of nano-wire transistors

    NASA Astrophysics Data System (ADS)

    Tsai, N.-C.; Chiang, Y.-R.; Hsu, S.-L.

    2010-01-01

    By employing the commercial software nanoMos and Vienna ab Initio Simulation Package ( VASP), the performance of nano-wire field-effect transistors is investigated. In this paper, the Density-Gradient Model (DG Model) is used to describe the carrier transport behavior of the nano-wire transistor under quantum effects. The analysis of the drain current with respect to channel length, body dielectric constant and gate contact work function is presented. In addition, Fermi energy and DOS (Density of State) are introduced to explore the relative stability of carrier transport and electrical conductance for the silicon crystal with dopants. Finally, how the roughness of the surface of the silicon-based crystal is affected by dopants and their allocation can be illuminated by a few broken bonds between atoms near the skin of the crystal.

  13. Thin transparent conducting films of cadmium stannate

    DOEpatents

    Wu, Xuanzhi; Coutts, Timothy J.

    2001-01-01

    A process for preparing thin Cd.sub.2 SnO.sub.4 films. The process comprises the steps of RF sputter coating a Cd.sub.2 SnO.sub.4 layer onto a first substrate; coating a second substrate with a CdS layer; contacting the Cd.sub.2 SnO.sub.4 layer with the CdS layer in a water- and oxygen-free environment and heating the first and second substrates and the Cd.sub.2 SnO.sub.4 and CdS layers to a temperature sufficient to induce crystallization of the Cd.sub.2 SnO.sub.4 layer into a uniform single-phase spinel-type structure, for a time sufficient to allow full crystallization of the Cd.sub.2 SnO.sub.4 layer at that temperature; cooling the first and second substrates to room temperature; and separating the first and second substrates and layers from each other. The process can be conducted at temperatures less than 600.degree. C., allowing the use of inexpensive soda lime glass substrates.

  14. CBr4 vapor growth morphologies near the polymorphic transition point. I - Single crystals. II - Crystals with large-angle grain boundaries

    NASA Technical Reports Server (NTRS)

    Xiao, Rong-Fu; Rosenberger, Franz

    1991-01-01

    High-resolution microscopy and image processing were used to investigate morphological changes in CBr4 single crystals during growth from the vapor at various levels of supersaturation and at temperatures below the compound's polymorphic phase transition. It was found that, as the temperature increased at fixed supersaturations, the corners of the crystals became rounded as a result of thermal roughening; the rounding temperatures were different for crystallographically different corners. A study of CBr4 crystals with large-angle grain boundaries or twin boundaries (extended macrodefects), conducted at the temperature of polymorphic phase transition showed that the phase transition temperature, T(tr) and crystal surface morphology of these crystals depended on the presence or absence of extended macrodefects. Unlike the case of a perfect single crystal, where the T(tr) was about 46.75 C, the phase transition in crystals with extended macrodefects occurred significantly below 46.75.

  15. Preparation and electrochemical characterization of ionic-conducting lithium lanthanum titanate oxide/polyacrylonitrile submicron composite fiber-based lithium-ion battery separators

    NASA Astrophysics Data System (ADS)

    Liang, Yinzheng; Ji, Liwen; Guo, Bingkun; Lin, Zhan; Yao, Yingfang; Li, Ying; Alcoutlabi, Mataz; Qiu, Yiping; Zhang, Xiangwu

    Lithium lanthanum titanate oxide (LLTO)/polyacrylonitrile (PAN) submicron composite fiber-based membranes were prepared by electrospinning dispersions of LLTO ceramic particles in PAN solutions. These ionic-conducting LLTO/PAN composite fiber-based membranes can be directly used as lithium-ion battery separators due to their unique porous structure. Ionic conductivities were evaluated after soaking the electrospun LLTO/PAN composite fiber-based membranes in a liquid electrolyte, 1 M lithium hexafluorophosphate (LiPF 6) in ethylene carbonate (EC)/ethyl methyl carbonate (EMC) (1:1 vol). It was found that, among membranes with various LLTO contents, 15 wt.% LLTO/PAN composite fiber-based membranes provided the highest ionic conductivity, 1.95 × 10 -3 S cm -1. Compared with pure PAN fiber membranes, LLTO/PAN composite fiber-based membranes had greater liquid electrolyte uptake, higher electrochemical stability window, and lower interfacial resistance with lithium. In addition, lithium//1 M LiPF 6/EC/EMC//lithium iron phosphate cells containing LLTO/PAN composite fiber-based membranes as the separator exhibited high discharge specific capacity of 162 mAh g -1 and good cycling performance at 0.2 C rate at room temperature.

  16. Polymer Crystallization at Curved Liquid/Liquid Interface

    NASA Astrophysics Data System (ADS)

    Wang, Wenda

    -assembly behavior of single-walled carbon nanotubes (SWCNTs) at curved liquid/liquid interface and the crystallization behavior of polymers at curved liquid/liquid interface while SWCNTs in presence. A few crystalline polymers, such as polyethylene (PE), poly(l-lactic acid) (PLLA), and poly(3-hexylthiophene-2,5-diyl) (P3HT), and water/oil systems were used to study the behavior. The formation of nano speckle structure is a crystallization-driven process due to heterogeneous nucleation and crystal growth of polymers at curved liquid/liquid interface. The second part deals with the homogeneous nucleation and crystal growth at curved liquid/liquid interface. Both PE and PLLA were used to conduct the study. For PE, 1,2-dichlorobenzene (DCB), water, and sodium dodecylsulfate (SDS) were used for the emulsion system. The emulsification system for PLLA is p-xylene, water, and hexadecyltrimethylammonium bromide (CTAB). Surfactant concentration can be employed to control the droplet size, thus controlling the final crystal vesicle's size. By controlling the initial polymer concentration, crystal shells with different morphology, such as curved crystal, bowl-like crystals, and crystal vesicles (named lamellaesome) can be obtained. The formation of these unique structures was templated by the curved interface. The formation process and detailed crystal structure are analyzed based on electron diffraction data from different sized lamellaesomes. Mechanical properties of the crystal vesicles and their encapsulation abilities will be discussed. At the end of this dissertation, a summary of my work and future outlook will be given.

  17. The peculairities of material crystallization experiments in the CF-18 centrifuge under high gravity

    NASA Astrophysics Data System (ADS)

    Burdin, B. V.; Regel, L. L.; Turchaninov, A. M.; Shumaev, O. V.

    1992-04-01

    This paper presents data on the crystallization of various materials using the CF-18 centrifuge at the Gagarin Cosmonaut Center. The geometry and equipment are described. Consideration is given to some peculiarities of preparing and conducting crystal growth experiments in this centrifuge. Vibration in a coordinate system fixed to the crystal growth equipment and the reasons for its initiation are shown. From the results of experiments conducted during the last 10 years, it was concluded that there are many possibilities of using various classes of model materials to study crystal growth processes under high gravity conditions.

  18. FRACTIONAL CRYSTALLIZATION FEED ENVELOPE

    SciTech Connect

    HERTING DL

    2008-03-19

    Laboratory work was completed on a set of evaporation tests designed to establish a feed envelope for the fractional crystallization process. The feed envelope defines chemical concentration limits within which the process can be operated successfully. All 38 runs in the half-factorial design matrix were completed successfully, based on the qualitative definition of success. There is no feed composition likely to be derived from saltcake dissolution that would cause the fractional crystallization process to not meet acceptable performance requirements. However, some compositions clearly would provide more successful operation than other compositions.

  19. Protein Crystal Malic Enzyme

    NASA Technical Reports Server (NTRS)

    1992-01-01

    Malic Enzyme is a target protein for drug design because it is a key protein in the life cycle of intestinal parasites. After 2 years of effort on Earth, investigators were unable to produce any crystals that were of high enough quality and for this reason the structure of this important protein could not be determined. Crystals obtained from one STS-50 were of superior quality allowing the structure to be determined. This is just one example why access to space is so vital for these studies. Principal Investigator is Larry DeLucas.

  20. Protein Crystal Quality Studies

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Eddie Snell (standing), Post-Doctoral Fellow the National Research Council (NRC),and Marc Pusey of Marshall Space Flight Center (MSFC) use a reciprocal space mapping diffractometer for marcromolecular crystal quality studies. The diffractometer is used in mapping the structure of marcromolecules such as proteins to determine their structure and thus understand how they function with other proteins in the body. This is one of several analytical tools used on proteins crystalized on Earth and in space experiments. Photo credit: NASA/Marshall Space Flight Center (MSFC)