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Sample records for high-pressure crystal chemistry

  1. Molecular Surface Chemistry by Metal Single Crystals and Nanoparticles from Vacuum to High Pressure.

    SciTech Connect

    Somorjai, Gabor A.; Park, Jeong Y.

    2008-04-05

    Model systems for studying molecular surface chemistry have evolved from single crystal surfaces at low pressure to colloidal nanoparticles at high pressure. Low pressure surface structure studies of platinum single crystals using molecular beam surface scattering and low energy electron diffraction techniques probe the unique activity of defects, steps and kinks at the surface for dissociation reactions (H-H, C-H, C-C, O{double_bond}O bonds). High-pressure investigations of platinum single crystals using sum frequency generation vibrational spectroscopy have revealed the presence and the nature of reaction intermediates. High pressure scanning tunneling microscopy of platinum single crystal surfaces showed adsorbate mobility during a catalytic reaction. Nanoparticle systems are used to determine the role of metal-oxide interfaces, site blocking and the role of surface structures in reactive surface chemistry. The size, shape and composition of nanoparticles play important roles in determining reaction activity and selectivity.

  2. Crystal Chemistry of Carbonate Apatites from High-Pressure Synthesis

    NASA Astrophysics Data System (ADS)

    Fleet, M. E.; Liu, X.

    2007-12-01

    Relatively large (50-200 μm) crystals of carbonate-bearing hydroxylapatite (CHAP) and fluorapatite (CFAP) have been grown from carbonate-rich melts at 1-3 GPa and used to determine structural details beyond the resolution of Rietveld powder diffraction methods, using X-ray single-crystal structure and FTIR spectroscopy. The new information includes the structural location of the channel (type A) and phosphate group (type B) carbonate ions in various composition series, as well as the location of the excess fluoride anion in francolite, substitution mechanisms, and identification of the hydrogen carbonate (bicarbonate) ion as a new apatite channel species. For equivalent conditions of synthesis, the uptake of A-B carbonate is greater for Na-bearing CHAP (up to 2 carbonate ions pfu) than Na-bearing CFAP (about 0.4 pfu). The Na cation and A and B carbonate ions are locally coupled in ratios of 1:1:1 in CHAP and 1:1:2 in CFAP, to minimize the effects of charge compensation and spatial accommodation. An extensive data base of type A and B site occupancies reveals that the amount of A carbonate in type A-B CHAP and CFAP is considerably under represented by the relative band areas for asymmetric stretching (ν3) and out-of-plane bending (ν2) of carbonate in FTIR spectra. The weaker absorption intensity and shift to higher wavenumbers of type A bands indicates that the carbonate ion is bound more weakly in the apatite channel than in the interior of the crystal structure. Thus literature spectra for apatites, and especially for apatite biomineralisation, showing dominant amounts of B carbonate should be re-evaluated.

  3. Akimotoite in the Tenham meteorite: Crystal chemistry and high-pressure transformation mechanisms

    NASA Astrophysics Data System (ADS)

    Ferroir, Tristan; Beck, Pierre; Van de Moortèle, Bertrand; Bohn, Marcel; Reynard, Bruno; Simionovici, Alexandre; El Goresy, Ahmed; Gillet, Philippe

    2008-10-01

    The transformation of pyroxene to its high-pressure polymorph akimotoite (MgSiO 3 ilmenite type structure) is documented in the shock-induced melt veins of the L6 Tenham chondrite. Four textural relationships between pyroxene and akimotoite are observed in former pyroxene grains entrained in the shear melt vein and in pyroxene grains attached to the wall of the melt vein. In one of the entrained enstatite grains the transformation to akimotoite is partial. One third of the grain is transformed to a polycrystalline aggregate of akimotoite with a scalloped interface with enstatite. Akimotoite (Fe 0,4Mg 1,24Ca 0.07Na 0,12Al 0,14)(Si 1,963Al 0,037)O 6 is slightly enriched in Ca (CaO = 1.74%), Al and Na with respect to enstatite (CaO = 0.71%). Narrow bands of polycrystalline akimotoite with three crystallographic orientations and a chemical composition similar to the surrounding enstatite intersect the other part of the grain. In a second grain entrained in the shear melt vein, tablets of akimotoite are interwoven with a pyroxene glass with a lower Na and Fe content and a higher Mg content compared to the adjacent akimotoite. This pyroxene glass is probably the product of (Mg,Fe)SiO 3-perovskite amorphization. Polycrystalline akimotoite is also formed at the expense of enstatite at the vein wall of the shear melt vein. In that case akimotoite is also enriched in Ca (CaO = 2.85%) Na (NaO = 1.72%) and Al (Al 2O 3 = 4.14%). All these observations suggest that akimotoite is mainly formed by solid-state transformation of former pyroxenes with subsequent diffusion of calcium, aluminum and sodium from the chondritic melt of the shear melt vein. Finally, the first complete X-ray diffraction pattern of natural akimotoite is presented.

  4. High-pressure crystallography of periodic and aperiodic crystals.

    PubMed

    Hejny, Clivia; Minkov, Vasily S

    2015-03-01

    More than five decades have passed since the first single-crystal X-ray diffraction experiments at high pressure were performed. These studies were applied historically to geochemical processes occurring in the Earth and other planets, but high-pressure crystallography has spread across different fields of science including chemistry, physics, biology, materials science and pharmacy. With each passing year, high-pressure studies have become more precise and comprehensive because of the development of instrumentation and software, and the systems investigated have also become more complicated. Starting with crystals of simple minerals and inorganic compounds, the interests of researchers have shifted to complicated metal-organic frameworks, aperiodic crystals and quasicrystals, molecular crystals, and even proteins and viruses. Inspired by contributions to the microsymposium 'High-Pressure Crystallography of Periodic and Aperiodic Crystals' presented at the 23rd IUCr Congress and General Assembly, the authors have tried to summarize certain recent results of single-crystal studies of molecular and aperiodic structures under high pressure. While the selected contributions do not cover the whole spectrum of high-pressure research, they demonstrate the broad diversity of novel and fascinating results and may awaken the reader's interest in this topic. PMID:25866659

  5. High-pressure crystallography of periodic and aperiodic crystals.

    PubMed

    Hejny, Clivia; Minkov, Vasily S

    2015-03-01

    More than five decades have passed since the first single-crystal X-ray diffraction experiments at high pressure were performed. These studies were applied historically to geochemical processes occurring in the Earth and other planets, but high-pressure crystallography has spread across different fields of science including chemistry, physics, biology, materials science and pharmacy. With each passing year, high-pressure studies have become more precise and comprehensive because of the development of instrumentation and software, and the systems investigated have also become more complicated. Starting with crystals of simple minerals and inorganic compounds, the interests of researchers have shifted to complicated metal-organic frameworks, aperiodic crystals and quasicrystals, molecular crystals, and even proteins and viruses. Inspired by contributions to the microsymposium 'High-Pressure Crystallography of Periodic and Aperiodic Crystals' presented at the 23rd IUCr Congress and General Assembly, the authors have tried to summarize certain recent results of single-crystal studies of molecular and aperiodic structures under high pressure. While the selected contributions do not cover the whole spectrum of high-pressure research, they demonstrate the broad diversity of novel and fascinating results and may awaken the reader's interest in this topic.

  6. High-pressure crystallography of periodic and aperiodic crystals

    PubMed Central

    Hejny, Clivia; Minkov, Vasily S.

    2015-01-01

    More than five decades have passed since the first single-crystal X-ray diffraction experiments at high pressure were performed. These studies were applied historically to geochemical processes occurring in the Earth and other planets, but high-pressure crystallography has spread across different fields of science including chemistry, physics, biology, materials science and pharmacy. With each passing year, high-pressure studies have become more precise and comprehensive because of the development of instrumentation and software, and the systems investigated have also become more complicated. Starting with crystals of simple minerals and inorganic compounds, the interests of researchers have shifted to complicated metal–organic frameworks, aperiodic crystals and quasicrystals, molecular crystals, and even proteins and viruses. Inspired by contributions to the microsymposium ‘High-Pressure Crystallography of Periodic and Aperiodic Crystals’ presented at the 23rd IUCr Congress and General Assembly, the authors have tried to summarize certain recent results of single-crystal studies of molecular and aperiodic structures under high pressure. While the selected contributions do not cover the whole spectrum of high-pressure research, they demonstrate the broad diversity of novel and fascinating results and may awaken the reader’s interest in this topic. PMID:25866659

  7. Synthetic chemistry with periodic mesostructures at high pressure.

    PubMed

    Mandal, Manik; Landskron, Kai

    2013-11-19

    Over the last two decades, researchers have studied extensively the synthesis of mesostructured materials, which could be useful for drug delivery, catalytic cracking of petroleum, or reinforced plastics, among other applications. However, until very recently researchers used only temperature as a thermodynamic variable for synthesis, completely neglecting pressure. In this Account, we show how pressure can affect the synthetic chemistry of periodic mesoporous structures with desirable effects. In its simplest application, pressure can crystallize the pore walls of periodic mesoporous silicas, which are difficult to crystallize otherwise. The motivation for the synthesis of periodic mesoporous silica materials (with pore sizes from 2 to 50 nm) 20 years ago was to replace the microporous zeolites (which have pore sizes of <2 nm) in petroleum cracking applications, because the larger pore size of mesoporous materials allows for faster transport of larger molecules. However, these mesoporous materials could not replace zeolite materials because they showed lower hydrothermal stability and lower catalytic activity. This reduced performance has been attributed to the amorphous nature of the mesoporous materials' channel walls. To address this problem, we developed the concept of "nanocasting at high pressure". Through this approach, we produced hitherto-unavailable, periodic mesostructured silicas with crystalline pore walls. In nanocasting, we compress a periodic mesostructured composite (e.g. a periodic mesoporous silica with carbon-filled pores) and subsequently heat it to induce the selective crystallization of one of the two phases. We attain the necessary high pressure for synthesis using piston-cylinder and multianvil apparatuses. Using periodic mesostructured silica/carbon nanocomposites as starting material, we have produced periodic mesoporous coesite and periodic mesoporous quartz. The quartz material is highly stable under harsh hydrothermal conditions (800

  8. High pressure chemistry of substituted acetylenes

    SciTech Connect

    Chellappa, Raja; Dattelbaum, Dana; Sheffield, Stephen; Robbins, David

    2011-01-25

    High pressure in situ synchrotron x-ray diffraction experiments were performed on substituted polyacetylenes: tert-butyl acetylene [TBA: (CH{sub 3}){sub 3}-C{triple_bond}CH] and ethynyl trimethylsilane [ETMS: (CH{sub 3}){sub 3}-Si{triple_bond}CH] to investigate pressure-induced chemical reactions. The starting samples were the low temperature crystalline phases which persisted metastably at room temperature and polymerized beyond 11 GPa and 26 GPa for TBA and ETMS respectively. These reaction onset pressures are considerably higher than what we observed in the shockwave studies (6.1 GPa for TBA and 6.6 GPa for ETMS). Interestingly, in the case of ETMS, it was observed with fluid ETMS as starting sample, reacts to form a semi-crystalline polymer (crystalline domains corresponding to the low-T phase) at pressures less than {approx}2 GPa. Further characterization using vibrational spectroscopy is in progress.

  9. High-pressure chemistry of molecular solids: evidences for novel extended phases of carbon dioxide

    SciTech Connect

    Yoo, C S

    1999-07-22

    At high pressures and temperatures, many molecular solids become unstable and transform into denser extended phases. Recently, we have discovered evidences for two novel extended phases of carbon dioxide at high pressures and temperatures: (1) an ionic form of dimeric CO,, C02+C03*- at 8-13 GPa and above 2000 K [I] and (2) a polymeric phase CO,-V above 35 GPa and 1800 K [2,3]. These extended phases can be quenched at room temperature at low pressures, from which their molecular and crystal structures have been determined. These transitions occur to soften highly repulsive intermolecular potentials via delocalization of electrons at high pressures and temperatures. Based on these and other previous results, we conjecture that three fundamental mechanisms of high-pressure chemistry are ionization, polymerization, and metallization, occurring in high-density molecular solids and fluids. [carbon dioxide, polymeric COZ, ionic CO, dimer, high-pressure chemistry, electron delocalization

  10. High Pressure Cryocooling of Protein Crystals: The Enigma of Water

    NASA Astrophysics Data System (ADS)

    Gruner, Sol M.

    2010-03-01

    A novel high-pressure cryocooling technique for preparation biological samples for x-ray analysis is described. The method, high-pressure cryocooling, involves cooling samples to cryogenic temperatures (e.g., 100 K) in high-pressure Helium gas (up to 200 MPa). It bears both similarities and differences to high-pressure cooling methods that have been used to prepare samples for electron microscopy, and has been especially useful for cryocooling of macromolecular crystals for x-ray diffraction. Examples will be given where the method has been effective in providing high quality crystallographic data for difficult samples, such as cases where ligands needed to be stabilized in binding sites to be visualized, or where very high resolution data were required. The talk concludes with a discussion of data obtained by high-pressure cryocooling that pertains to two of the most important problems in modern science: the enigma of water and how water affects the activity of proteins.

  11. High pressure phase transitions in lawsonite at simultaneous high pressure and temperature: A single crystal study

    NASA Astrophysics Data System (ADS)

    O'Bannon, E. F., III; Vennari, C.; Beavers, C. C. G.; Williams, Q. C.

    2015-12-01

    Lawsonite (CaAl2Si2O7(OH)2.H2O) is a hydrous mineral with a high overall water content of ~11.5 wt.%. It is a significant carrier of water in subduction zones to depths greater than ~150 km. The structure of lawsonite has been extensively studied under room temperature, high-pressure conditions. However, simultaneous high-pressure and high-temperature experiments are scarce. We have conducted synchrotron-based simultaneous high-pressure and temperature single crystal experiments on lawsonite up to a maximum pressure of 8.4 GPa at ambient and high temperatures. We used a natural sample of lawsonite from Valley Ford, California (Sonoma County). At room pressure and temperature lawsonite crystallizes in the orthorhombic system with Cmcm symmetry. Room temperature compression indicates that lawsonite remains in the orthorhombic Cmcm space group up to ~9.0 GPa. Our 5.0 GPa crystal structure is similar to the room pressure structure, and shows almost isotropic compression of the crystallographic axes. Unit cell parameters at 5.0 GPa are a- 5.7835(10), b- 8.694(2), and c- 13.009(3). Single-crystal measurements at simultaneous high-pressure and temperature (e.g., >8.0 GPa and ~100 oC) can be indexed to a monoclinic P-centered unit cell. Interestingly, a modest temperature increase of ~100 oC appears to initiate the orthorhombic to monoclinic phase transition at ~0.6-2.4 GPa lower than room temperature compression studies have shown. There is no evidence of dehydration or H atom disorder under these conditions. This suggests that the orthorhombic to monoclinic transition could be kinetically impeded at 298 K, and that monoclinic lawsonite could be the dominant water carrier through much of the depth range of upper mantle subduction processes.

  12. High pressure chemistry of red phosphorus by photoactivated simple molecules

    NASA Astrophysics Data System (ADS)

    Ceppatelli, Matteo; Bini, Roberto; Fanetti, Samuele; Caporali, Maria; Peruzzini, Maurizio

    2013-06-01

    High pressure (HP) is very effective in reducing intermolecular distances and inducing unexpected chemical reactions. In particular the photoactivation of the reactants in HP conditions can lead to very efficient and selective processes. The chemistry of phosphorus is currently based on the white molecular form. The red polymeric allotrope, despite more stable and much less toxic, has not attracted much attention so far. However, switching from the white to the red form would benefit any industrial procedure, especially from an environmental point of view. On the other side, water and ethanol are renewable, environmental friendly and largely available molecules, usable as reactants and photoactivators in HP conditions. Here we report a study on the HP photoinduced reactivity of red phosphorus with water and ethanol, showing the possibility of very efficient and selective processes, leading to molecular hydrogen and valuable phosphorus compounds. The reactions have been studied by means of FTIR and Raman spectroscopy and pressure has been generated using DAC and SAC. HP reactivity has been activated by the two-photon absorption of near-UV wavelengths and occured in total absence of solvents, catalysts and radical initiators, at room T and mild pressure conditions (0.2-1.5 GPa).

  13. High pressure Raman spectra of monoglycine nitrate single crystal

    NASA Astrophysics Data System (ADS)

    Carvalho, J. O.; Moura, G. M.; Dos Santos, A. O.; Lima, R. J. C.; Freire, P. T. C.; Façanha Filho, P. F.

    2016-05-01

    Single crystal of monoglycine nitrate has been studied by Raman spectroscopy under high pressures up to 5.5 GPa. The results show changes in lattice modes in the pressure ranges of 1.1-1.6 GPa and 4.0-4.6 GPa. The first change occurs with appearance of bands related to the lattice modes as well as discontinuity in the slope of dΩ/dP of these modes. Moreover, bands associated with the skeleton of glycine suggest that the molecule undergoes conformational modifications. The appearance of a strong band at 55 cm- 1 point to a second phase transition associated with the lattice modes, while the internal modes remain unchanged. These anomalies are probably due to rearrangement of hydrogen bonds. Additionally, decompression to ambient pressure shows that the phase transitions are reversible. Finally, the results show that the nitrate anions play an important role on the stability of the monoglycine nitrate crystal.

  14. High pressure Raman spectra of monoglycine nitrate single crystal.

    PubMed

    Carvalho, J O; Moura, G M; Dos Santos, A O; Lima, R J C; Freire, P T C; Façanha Filho, P F

    2016-05-15

    Single crystal of monoglycine nitrate has been studied by Raman spectroscopy under high pressures up to 5.5 GPa. The results show changes in lattice modes in the pressure ranges of 1.1-1.6 GPa and 4.0-4.6 GPa. The first change occurs with appearance of bands related to the lattice modes as well as discontinuity in the slope of dΩ/dP of these modes. Moreover, bands associated with the skeleton of glycine suggest that the molecule undergoes conformational modifications. The appearance of a strong band at 55 cm(-1) point to a second phase transition associated with the lattice modes, while the internal modes remain unchanged. These anomalies are probably due to rearrangement of hydrogen bonds. Additionally, decompression to ambient pressure shows that the phase transitions are reversible. Finally, the results show that the nitrate anions play an important role on the stability of the monoglycine nitrate crystal. PMID:26967511

  15. Inelastic neutron scattering from single crystal Zn under high pressure

    NASA Astrophysics Data System (ADS)

    Morgan, J. G.; von Dreele, R. B.; Wochner, P.; Shapiro, S. M.

    1996-07-01

    Inelastic neutron-scattering experiments have been performed for single crystals of Zn under pressures up to 8.8 GPa at 300 K. The phonon modes q/qmax=ξ=0.075 and ξ=0.10 were measured in the transverse acoustic branch Σ3, where q=0 corresponds with the elastic constant C44. The phonon energy showed a substantial hardening with increasing pressure. The experimental data below 6.8 GPa for ξ=0.075 yield a constant Grüneisen mode γi=-lnωi/lnV of 2.25 in good agreement with a previous calculation [H. Ledbetter, Phys. Status Solidi B 181, 81 (1994)]. Above 6.8 GPa, there is a very rapid increase of γi which is indicative of the presence of a giant Kohn anomaly. This rapid divergence at high pressure indicates that a phonon softening may occur at pressures higher than 8.8 GPa caused by the collapse of the giant Kohn anomaly via an electronic topological transition (ETT). In an earlier Mössbauer Zn study at 4 K [W. Potzel et al., Phys. Rev. Lett. 74, 1139 (1994)], a drastic drop of the Lamb-Mössbauer factor was observed at 6.6 GPa, which was interpreted as being due to phonon softening, indicating this ETT had occurred. This paper also compares the compressibility data for single crystal Zn and Zn powder using neutron scattering. The results were found to be similar to an earlier x-ray Zn powder experiment [O. Schulte et al., High Pressure Res. 6, 169 (1991)].

  16. Deformation of Single Crystal Molybdenum at High Pressure

    SciTech Connect

    Bonner, B P; Aracne, C; Farber, D L; Boro, C O; Lassila, D H

    2004-02-24

    Single crystal samples of micron dimensions oriented in the [001] direction were shortened 10 to 40% in uniaxial compression with superposed hydrostatic pressure to begin investigation of how the onset of yielding evolves with pressure. A testing machine based on opposed anvil geometry with precision pneumatic control of the applied force and capability to measure sub micron displacements was developed to produce shape changing deformation at pressure. The experiments extend observations of pressure dependent deformation to {approx}5Gpa at shortening rates of {approx}2*10{sup -4}. Samples have been recovered for post run characterization and analysis to determine if deformation mechanisms are altered by pressure. Experiments under hydrostatic pressure provide insight into the nature of materials under extreme conditions, and also provide a means for altering deformation behavior in a controlled fashion. The approach has a long history demonstrating that pressure enhances ductility in general, and produces enhanced hardening relative to that expected from normal cold work in the BCC metals Mo, Ta and Nb{sup 2}. The pressure hardening is in excess of that predicted from the measured increase in shear modulus at pressure, and therefore is likely due to a dislocation mechanism, such as suppression of kink pair formation or the interaction of forest dislocation cores, and not from lattice resistance. The effect has not been observed in FCC metals, suggesting a fundamental difference between deformation mechanisms at pressure for the two classes. The purpose of this letter is to investigate the origin of pressure hardening with new experiments that extend the pressure range beyond 3 GPa, the upper limit of conventional large sample (1cm{sup 3}) testing methods. Most previous high pressure deformation studies have been on poly crystals, relying on model dependent analysis to infer the maximum deviatoric stress that a deformed sample can support. In one experiment, a

  17. Iron Catalyst Chemistry in High Pressure Carbon Monoxide Nanotube Reactor

    NASA Technical Reports Server (NTRS)

    Scott, Carl D.; Povitsky, Alexander; Dateo, Christopher; Gokcen, Tahir; Smalley, Richard E.

    2001-01-01

    The high-pressure carbon monoxide (HiPco) technique for producing single wall carbon nanotubes (SWNT) is analyzed using a chemical reaction model coupled with properties calculated along streamlines. Streamline properties for mixing jets are calculated by the FLUENT code using the k-e turbulent model for pure carbon monixide. The HiPco process introduces cold iron pentacarbonyl diluted in CO, or alternatively nitrogen, at high pressure, ca. 30 atmospheres into a conical mixing zone. Hot CO is also introduced via three jets at angles with respect to the axis of the reactor. Hot CO decomposes the Fe(CO)5 to release atomic Fe. Cluster reaction rates are from Krestinin, et aI., based on shock tube measurements. Another model is from classical cluster theory given by Girshick's team. The calculations are performed on streamlines that assume that a cold mixture of Fe(CO)5 in CO is introduced along the reactor axis. Then iron forms clusters that catalyze the formation of SWNTs from the Boudouard reaction on Fe-containing clusters by reaction with CO. To simulate the chemical process along streamlines that were calculated by the fluid dynamics code FLUENT, a time history of temperature and dilution are determined along streamlines. Alternative catalyst injection schemes are also evaluated.

  18. Application of ultra high pressure (UHP) in starch chemistry.

    PubMed

    Kim, Hyun-Seok; Kim, Byung-Yong; Baik, Moo-Yeol

    2012-01-01

    Ultra high pressure (UHP) processing is an attractive non-thermal technique for food treatment and preservation at room temperature, with the potential to achieve interesting functional effects. The majority of UHP process applications in food systems have focused on shelf-life extension associated with non-thermal sterilization and a reduction or increase in enzymatic activity. Only a few studies have investigated modifications of structural characteristics and/or protein functionalities. Despite the rapid expansion of UHP applications in food systems, limited information is available on the effects of UHP on the structural and physicochemical properties of starch and/or its chemical derivatives included in most processed foods as major ingredients or minor additives. Starch and its chemical derivatives are responsible for textural and physical properties of food systems, impacting their end-use quality and/or shelf-life. This article reviews UHP processes for native (unmodified) starch granules and their effects on the physicochemical properties of UHP-treated starch. Furthermore, functional roles of UHP in acid-hydrolysis, hydroxypropylation, acetylation, and cross-linking reactions of starch granules, as well as the physicochemical properties of UHP-assisted starch chemical derivatives, are discussed.

  19. CRYSTAL CHEMISTRY OF HYDROUS MINERALS

    SciTech Connect

    Y. ZHAO; ET AL

    2001-02-01

    Hydrogen has long been appreciated for its role in geological processes of the Earth's crust. However, its role in Earth's deep interior has been neglected in most geophysical thinking. Yet it is now believed that most of our planet's hydrogen may be locked up in high pressure phases of hydrous silicate minerals within the Earth's mantle. This rocky interior (approximately 7/8 of Earth's volume) is conjectured to contain 1-2 orders of magnitude more water than the more obvious oceans (the ''hydrosphere'') and atmosphere. This project is aimed at using the capability of neutron scattering from hydrogen to study the crystal chemistry and stability of hydrogen-bearing minerals at high pressures and temperatures. At the most basic level this is a study of the atomic position and hydrogen bond itself. We have conducted experimental runs on hydrous minerals under high pressure and high temperature conditions. The crystallographic structure of hydrous minerals at extreme conditions and its structural stability, and hydrogen bond at high P-T conditions are the fundamental questions to be addressed. The behavior of the hydrous minerals in the deep interior of the Earth has been discussed.

  20. Final Report. IUT No. B560420 with UC Berkeley. Organic Chemistry at High Pressures &Temperatures

    SciTech Connect

    Montgomery, W; Crowhurst, J C; Zaug, J M; Jeanloz, R

    2007-03-20

    We have successfully completed the research outlined in our proposal: Organic Chemistry at High Pressures and Temperatures. We have experimentally determined a phase diagram which documents the phases and reaction regimes of cyanuric acid , H{sub 3}C{sub 3}N{sub 3}O{sub 3} (1,3,5-triazine-2,4,6-trione), from 300 - 750 K and 0 - 8.1 GPa. We utilized a comparatively new technique to study thin samples of cyanuric acid in the diamond anvil cell in order to collect ambient temperature, high pressure FTIR and Raman data as well as the high-pressure, high-temperature data used in the phase diagram. These experiments made use of the CMLS High-pressure lab's diamond anvil facilities as well as the FTIR and Raman systems.

  1. Combined crystal structure prediction and high-pressure crystallization in rational pharmaceutical polymorph screening

    NASA Astrophysics Data System (ADS)

    Neumann, M. A.; van de Streek, J.; Fabbiani, F. P. A.; Hidber, P.; Grassmann, O.

    2015-07-01

    Organic molecules, such as pharmaceuticals, agro-chemicals and pigments, frequently form several crystal polymorphs with different physicochemical properties. Finding polymorphs has long been a purely experimental game of trial-and-error. Here we utilize in silico polymorph screening in combination with rationally planned crystallization experiments to study the polymorphism of the pharmaceutical compound Dalcetrapib, with 10 torsional degrees of freedom one of the most flexible molecules ever studied computationally. The experimental crystal polymorphs are found at the bottom of the calculated lattice energy landscape, and two predicted structures are identified as candidates for a missing, thermodynamically more stable polymorph. Pressure-dependent stability calculations suggested high pressure as a means to bring these polymorphs into existence. Subsequently, one of them could indeed be crystallized in the 0.02 to 0.50 GPa pressure range and was found to be metastable at ambient pressure, effectively derisking the appearance of a more stable polymorph during late-stage development of Dalcetrapib.

  2. Boron suboxide crystal: high pressure synthesis and hardness measurement

    NASA Astrophysics Data System (ADS)

    He, Duanwei

    2002-03-01

    B6O crystal growth from the B-B2O3 system was investigated at 1700-2200 ¡ãC and 4.5-6.5 GPa by using two different sample assemblies. Single B6O crystals over 100 mm in size have been synthesized at 5.5 GPa and 2100 ¡ãC. This makes it possible to study the properties of this interesting material. The factors affecting the B6O crystal morphology, size, colour, and growth process were discussed. The solubility of B6O in B2O3 flux was estimated at 5.5 GPa and different temperatures. Based on the experimental results, we suggest two methods to grow large B6O crystal.

  3. In situ crystallization of ionic liquid [Emim][PF6] from methanol solution under high pressure.

    PubMed

    Li, Haining; Su, Lei; Zhu, Xiang; Cheng, Xuerui; Yang, Kun; Yang, Guoqiang

    2014-07-24

    The solubility of 1-ethyl-3-methylimidazolium hexafluorophosphate ([Emim][PF6]) in methanol under high pressure is newly measured quantitatively according to the correlation between the ratios of Raman intensity and the concentrations. In situ crystallization and cation conformation of [Emim][PF6] from methanol solution under high pressure have been investigated by using Raman spectroscopy in detail. Remarkably, crystal polymorphism was observed and two crystalline phases (phases I and II) coexisted under high pressure up to ∼ 1.4 GPa. However, only phase II was obtained by recrystallization at ∼ 2 GPa. Our findings may facilitate the development of an effective way for crystallization and purification of ionic liquids under high pressure. PMID:24968114

  4. In situ crystallization of ionic liquid [Emim][PF6] from methanol solution under high pressure.

    PubMed

    Li, Haining; Su, Lei; Zhu, Xiang; Cheng, Xuerui; Yang, Kun; Yang, Guoqiang

    2014-07-24

    The solubility of 1-ethyl-3-methylimidazolium hexafluorophosphate ([Emim][PF6]) in methanol under high pressure is newly measured quantitatively according to the correlation between the ratios of Raman intensity and the concentrations. In situ crystallization and cation conformation of [Emim][PF6] from methanol solution under high pressure have been investigated by using Raman spectroscopy in detail. Remarkably, crystal polymorphism was observed and two crystalline phases (phases I and II) coexisted under high pressure up to ∼ 1.4 GPa. However, only phase II was obtained by recrystallization at ∼ 2 GPa. Our findings may facilitate the development of an effective way for crystallization and purification of ionic liquids under high pressure.

  5. Combined crystal structure prediction and high-pressure crystallization in rational pharmaceutical polymorph screening

    PubMed Central

    Neumann, M. A.; van de Streek, J.; Fabbiani, F. P. A.; Hidber, P.; Grassmann, O.

    2015-01-01

    Organic molecules, such as pharmaceuticals, agro-chemicals and pigments, frequently form several crystal polymorphs with different physicochemical properties. Finding polymorphs has long been a purely experimental game of trial-and-error. Here we utilize in silico polymorph screening in combination with rationally planned crystallization experiments to study the polymorphism of the pharmaceutical compound Dalcetrapib, with 10 torsional degrees of freedom one of the most flexible molecules ever studied computationally. The experimental crystal polymorphs are found at the bottom of the calculated lattice energy landscape, and two predicted structures are identified as candidates for a missing, thermodynamically more stable polymorph. Pressure-dependent stability calculations suggested high pressure as a means to bring these polymorphs into existence. Subsequently, one of them could indeed be crystallized in the 0.02 to 0.50 GPa pressure range and was found to be metastable at ambient pressure, effectively derisking the appearance of a more stable polymorph during late-stage development of Dalcetrapib. PMID:26198974

  6. Properties of beryl single crystals grown by a high pressure hydrothermal method

    SciTech Connect

    Furusaki, T.; Bando, Y.; Kodaira, K. ); Matsushita, T. )

    1989-08-01

    The authors discuss beryl crystals grown under high pressure hydrothermal condition of 1 GPa. The optimum crystal growth was observed at 600{sup 0}C and from 0.1N NaOH solution. The beryl crystals from 0.1 - 0.3N NaOH solutions incorporated water molecules and alkali cations in the channels of the beryl structure. The crystals showed same refractive indices and density as those of natural emerald crystals. These physical properties were very similar to natural emeralds.

  7. Initial development of a high-pressure crystal growth facility: Center director's discretionary fund

    NASA Technical Reports Server (NTRS)

    Szofran, F. R.; Lehoczky, S. L.; Cobb, S. D.; Gillies, D. C.

    1993-01-01

    A low-cost, flexible, high-pressure (600 psi) system for crystal growth and related thermophysical properties measurements was designed, assembled, and tested. The furnace system includes a magnetically coupled translation mechanism that eliminates the need for a high-pressure mechanical feedthru. The system is currently being used for continuing crystal growth experiments and thermophysical properties measurements on several material systems including Hg(1-x)Cd(x)Te, Hg(1-x)Zn(x)Te, and Hg(1-x)Zn(x)Se.

  8. In situ characterization of formation and growth of high-pressure phases in single-crystal silicon during nanoindentation

    NASA Astrophysics Data System (ADS)

    Huang, Hu; Yan, Jiwang

    2016-04-01

    Pressure-induced intermediate phases of silicon exhibit unique characteristics in mechanics, chemistry, optics, and electrics. Clarifying the formation and growth processes of these new phases is essential for the preparation and application of them. For in situ characterization of the formation and growth of high-pressure phases in single-crystal silicon, a quantitative parameter, namely displacement change of indenter (Δ h) during the unloading holding process in nanoindentation, was proposed. Nanoindentation experiments under various unloading holding loads and loading/unloading rates were performed to investigate their effects on Δ h. Results indicate that Δ h varies significantly before and after the occurrence of pop-out; for the same maximum indentation load, it tends to increase with the decrease in the holding load and to increase with the increase in the loading/unloading rate. Thus, the value of Δ h can be regarded as an indicator that reflects the formation and growth processes of the high-pressure phases. Using Δ h, the initial position for the nucleation of the high-pressure phases, their growth, and their correlation to the loading/unloading rate were predictable.

  9. EFFECT OF CROSSLINK DENSITY ON THE HIGH PRESSURE CRYSTALLIZATION OF UHMWPE

    PubMed Central

    Oral, Ebru; Beckos, Christine Godleski; Ghali, Bassem W.; Lozynsky, Andrew J.; Muratoglu, Orhun K.

    2010-01-01

    Ultrahigh molecular weight polyethylene (UHMWPE) is a bearing surface material for total joint implants. It is radiation cross-linked for high wear resistance and is melted or treated with vitamin E for oxidative stability. We investigated high pressure crystallization (HPC) of irradiated UHMWPE as an alternative method to improve the mechanical strength while stabilizing the residual free radicals from radiation crosslinking. HPC of uncross-linked UHMWPE has resulted in the formation of extended chain crystals and increased crystallinity, leading to improved strength. We hypothesized that increased cross-link density would hinder crystallization during HPC due to decreased chain mobility. Therefore, we investigated the crystalline structure and tensile mechanical properties of high pressure crystallized 25-, 65- and 100-kGy irradiated UHMWPE. We also determined free radical content and wear. The strength of 25- and 65-kGy irradiated UHMWPEs was improved by HPC with increased crystallinity and crystal size. 100-kGy irradiated UHMWPE did not show improved strength, supporting our hypothesis that decreased chain mobility would hinder crystal formation and strength improvement. None of the HPC irradiated UHMWPEs contained detectable free radicals and their wear properties were maintained, suggesting oxidative and mechanical stability in the long term. Therefore, HPC can be used effectively for imparting oxidative stability while strength improvement can be achieved for irradiated UHMWPE with low to moderate crosslink density. PMID:19213055

  10. High-pressure hydrogen testing of single crystal superalloys for advanced rocket engine turbopump turbine blades

    NASA Technical Reports Server (NTRS)

    Alter, W. S.; Parr, R. A.; Johnston, M. H.; Strizak, J. P.

    1984-01-01

    A screening program to determine the effects of high pressure hydrogen on selected candidate materials for advanced single crystal turbine blade applications is examined. The alloys chosen for the investigation are CM SX-2, CM SX-4C, Rene N-4, and PWA1480. Testing is carried out in hydrogen and helium at 34 MPa and room temperature, with both notched and unnotched single crystal specimens. Results show a significant variation in susceptibility to Hydrogen Environment Embrittlement (HEE) among the four alloys and a marked difference in fracture topography between hydrogen and helium environment specimens.

  11. High-pressure hydrogen testing of single crystal superalloys for advanced rocket engine turbopump turbine blades

    NASA Technical Reports Server (NTRS)

    Parr, R. A.; Alter, W. S.; Johnston, M. H.; Strizak, J. P.

    1985-01-01

    A screening program to determine the effects of high pressure hydrogen on selected candidate materials for advanced single crystal turbine blade applications is examined. The alloys chosen for the investigation are CM SX-2, CM SX-4C, Rene N-4, and PWA1480. Testing is carried out in hydrogen and helium at 34 MPa and room temperature, with both notched and unnotched single crystal specimens. Results show a significant variation in susceptibility to Hydrogen Environment Embrittlement (HEE) among the four alloys and a marked difference in fracture topography between hydrogen and helium environment specimens.

  12. [Photonic crystals for analytical chemistry].

    PubMed

    Chen, Yi; Li, Jincheng

    2009-09-01

    Photonic crystals, originally created to control the transmission of light, have found their increasing value in the field of analytical chemistry and are probable to become a hot research area soon. This review is hence composed, focusing on their analytical chemistry-oriented applications, including especially their use in chromatography, capillary- and chip-based electrophoresis.

  13. High-Pressure High-Temperature Phase Diagram of the Organic Crystal Paracetamol

    NASA Astrophysics Data System (ADS)

    Smith, Spencer; Montgomery, Jeffrey; Vohra, Yogesh

    High-pressure high-temperature (HPHT) Raman spectroscopy studies have been performed on the organic crystal paracetamol in a diamond anvil cell utilizing boron-doped diamond as heating anvil. The HPHT data obtained from boron-doped diamond heater is cross-checked with data obtained using a standard block heater diamond anvil cell. Isobaric measurements were conducted at pressures up to 8.5 GPa and temperature up to 520 K in a number of different experiments. Solid state phase transitions from monoclinic Form I --> orthorhombic Form II were observed at various pressures and temperatures as well as transitions from Form II --> unknown Form IV. The melting temperature for paracetamol was observed to increase with increasing pressures to 8.5 GPa. Our previous angle dispersive x-ray diffraction studies at the Advanced Photon Source has confirmed the existence of two unknown crystal structures Form IV and Form V of paracetamol at high pressure and ambient temperature. The phase transformation from Form II to Form IV occurs at ~8.5 GPa and from Form IV to Form V occurs at ~11 GPa at ambient temperature. Our new data is combined with the previous ambient temperature high-pressure Raman and X- ray diffraction data to create the first HPHT phase diagram of paracetamol. Doe-NNSA Carnegie DOE Alliance Center (CDAC) under Grant Number DE-NA0002006.

  14. The preparation of BP single crystals by high pressure flux method

    NASA Technical Reports Server (NTRS)

    Kumashiro, Y.; Misawa, S.; Gonda, S.

    1984-01-01

    Single crystals of BP, a III-V compound semiconductor, were obtained by the high pressure flux method. Cu3P and Ni12P5 powders were used as the flux, and mixed with BP powder. Two kinds of mixtures were prepared: (1) 1.8g (BP) + 35 G (Cu3P) and (2) 1.7 g (BP) + 25 g (Ni12P5). They were compressed into pellets, heated at 1300 C for 24 h in an induction furnace under a pressure of 1 MPa using Ar-P2 gas, and slowly cooled to room temperature. In case (1), BP single crystals grew along the (III) plane, and in case (2) they grew as an aggregate of crystallites. The cathodoluminescence spectra of the synthetic BP crystals showed peaks near 680 nm (1.82 eV) for case (1), and 500 nm (2.47 eV) for case (2). By using the high pressure flux method conventional sized crystals were obtained in a relatively short time.

  15. Heteroepitaxial growth of cubic boron nitride single crystal on diamond seed under high pressure

    SciTech Connect

    Taniguchi, T.; Yamaoka, S.

    1997-07-01

    Single crystal cubic boron nitride (cBN) was heteroepitaxially grown on a seed crystal of diamond under static high pressure and high temperature at 5.5GPa and 1,600--1,700 C, respectively, for 10--100 hour. A temperature gradient method was employed for the crystal growth by using lithium boron nitride as a solvent. Initial growth feature of cBN crystal was found on the diamond seed surface after the growing time of 10 minutes. The nucleation sites of the crystals seem to be near the etch pits on the diamond surface which were introduced by the surface dissolution by the solvent for cBN growth. Two types of growth features, island and step growth were typically shown on the surface. It can be seen that grown crystal appearing as a (111) nitrogen face was exhibited with the step growth feature, while the (11n) face exhibited the island growth feature. Considering the growth process under constant P-T growing condition, growth rate of cBN crystal was significantly small as compared to that of diamond.

  16. High-Pressure Crystal Structure, Lattice Vibrations, and Band Structure of BiSbO4.

    PubMed

    Errandonea, Daniel; Muñoz, Alfonso; Rodríguez-Hernández, Placida; Gomis, Oscar; Achary, S Nagabhusan; Popescu, Catalin; Patwe, Sadeque J; Tyagi, Avesh K

    2016-05-16

    The high-pressure crystal structure, lattice-vibrations, and electronic band structure of BiSbO4 were studied by ab initio simulations. We also performed Raman spectroscopy, infrared spectroscopy, and diffuse-reflectance measurements, as well as synchrotron powder X-ray diffraction. High-pressure X-ray diffraction measurements show that the crystal structure of BiSbO4 remains stable up to at least 70 GPa, unlike other known MTO4-type ternary oxides. These experiments also give information on the pressure dependence of the unit-cell parameters. Calculations properly describe the crystal structure of BiSbO4 and the changes induced by pressure on it. They also predict a possible high-pressure phase. A room-temperature pressure-volume equation of state is determined, and the effect of pressure on the coordination polyhedron of Bi and Sb is discussed. Raman- and infrared-active phonons were measured and calculated. In particular, calculations provide assignments for all the vibrational modes as well as their pressure dependence. In addition, the band structure and electronic density of states under pressure were also calculated. The calculations combined with the optical measurements allow us to conclude that BiSbO4 is an indirect-gap semiconductor, with an electronic band gap of 2.9(1) eV. Finally, the isothermal compressibility tensor for BiSbO4 is given at 1.8 GPa. The experimental (theoretical) data revealed that the direction of maximum compressibility is in the (0 1 0) plane at ∼33° (38°) to the c-axis and 47° (42°) to the a-axis. The reliability of the reported results is supported by the consistency between experiments and calculations.

  17. High-Pressure Crystal Structure, Lattice Vibrations, and Band Structure of BiSbO4.

    PubMed

    Errandonea, Daniel; Muñoz, Alfonso; Rodríguez-Hernández, Placida; Gomis, Oscar; Achary, S Nagabhusan; Popescu, Catalin; Patwe, Sadeque J; Tyagi, Avesh K

    2016-05-16

    The high-pressure crystal structure, lattice-vibrations, and electronic band structure of BiSbO4 were studied by ab initio simulations. We also performed Raman spectroscopy, infrared spectroscopy, and diffuse-reflectance measurements, as well as synchrotron powder X-ray diffraction. High-pressure X-ray diffraction measurements show that the crystal structure of BiSbO4 remains stable up to at least 70 GPa, unlike other known MTO4-type ternary oxides. These experiments also give information on the pressure dependence of the unit-cell parameters. Calculations properly describe the crystal structure of BiSbO4 and the changes induced by pressure on it. They also predict a possible high-pressure phase. A room-temperature pressure-volume equation of state is determined, and the effect of pressure on the coordination polyhedron of Bi and Sb is discussed. Raman- and infrared-active phonons were measured and calculated. In particular, calculations provide assignments for all the vibrational modes as well as their pressure dependence. In addition, the band structure and electronic density of states under pressure were also calculated. The calculations combined with the optical measurements allow us to conclude that BiSbO4 is an indirect-gap semiconductor, with an electronic band gap of 2.9(1) eV. Finally, the isothermal compressibility tensor for BiSbO4 is given at 1.8 GPa. The experimental (theoretical) data revealed that the direction of maximum compressibility is in the (0 1 0) plane at ∼33° (38°) to the c-axis and 47° (42°) to the a-axis. The reliability of the reported results is supported by the consistency between experiments and calculations. PMID:27128858

  18. High pressure chemistry of red phosphorus by photo-activated simple molecules

    NASA Astrophysics Data System (ADS)

    Ceppatelli, M.; Fanetti, S.; Bini, R.; Caporali, M.; Peruzzini, M.

    2014-05-01

    High pressure (HP) is very effective in reducing intermolecular distances and inducing unexpected chemical reactions. In addition the photo-activation of the reactants in HP conditions can lead to very efficient and selective processes. The chemistry of phosphorus is currently based on the white molecular form. The red polymeric allotrope, despite more stable and much less toxic, has not attracted much attention so far. However, switching from the white to the red form would benefit any industrial procedure, especially from an environmental point of view. On the other side, water and ethanol are renewable, environmental friendly and largely available molecules, usable as reactants and photo-activators in HP conditions. Here we report a study on the HP photo-induced reactivity of red phosphorus with water and ethanol, showing the possibility of very efficient and selective processes, leading to molecular hydrogen and valuable phosphorus compounds. The reactions have been studied by means of FTIR and Raman spectroscopy and pressure has been generated using membrane Diamond (DAC) and Sapphire (SAC) anvil cells. HP reactivity has been activated by the two-photon absorption of near-UV wavelengths and occurred in total absence of solvents, catalysts and radical initiators, at room T and mild pressure conditions (0.2-1.5 GPa).

  19. CRISTAPRESS: an optical cell for structure development in high-pressure crystallization.

    PubMed

    Boyer, S A E; Fournier, F E J; Gandin, Ch-A; Haudin, J-M

    2014-01-01

    An original optical high-pressure cell, named CRISTAPRESS, has been especially designed to investigate phase transitions of complex liquids, i.e., polymers, polymer blends, nano-composites, etc. The design of the cell is based on the optical properties of morphological entities through in situ light depolarizing microscopic observations. Pressure up to 200 MPa with a fine temperature control up to 300 °C can be applied. A striking advantage of this cell is the possibility to select the pressure transmitting medium that can be water, silicone oil, a fluid in the supercritical state, etc. The potential of the novel technique was demonstrated by carrying out time-resolved measurements during polymer crystallization induced by water pressure. These preliminary experimental investigations permit to discriminate the role of the barometric and thermal histories on the kinetics of polymer growth, as well as on the subsequent morphologies. It should lead to new reliable crystallization kinetics models.

  20. CRISTAPRESS: An optical cell for structure development in high-pressure crystallization

    NASA Astrophysics Data System (ADS)

    Boyer, S. A. E.; Fournier, F. E. J.; Gandin, Ch.-A.; Haudin, J.-M.

    2014-01-01

    An original optical high-pressure cell, named CRISTAPRESS, has been especially designed to investigate phase transitions of complex liquids, i.e., polymers, polymer blends, nano-composites, etc. The design of the cell is based on the optical properties of morphological entities through in situ light depolarizing microscopic observations. Pressure up to 200 MPa with a fine temperature control up to 300 °C can be applied. A striking advantage of this cell is the possibility to select the pressure transmitting medium that can be water, silicone oil, a fluid in the supercritical state, etc. The potential of the novel technique was demonstrated by carrying out time-resolved measurements during polymer crystallization induced by water pressure. These preliminary experimental investigations permit to discriminate the role of the barometric and thermal histories on the kinetics of polymer growth, as well as on the subsequent morphologies. It should lead to new reliable crystallization kinetics models.

  1. Diffusion of oxygen in bulk GaN crystals at high temperature and at high pressure

    NASA Astrophysics Data System (ADS)

    Sadovyi, B.; Nikolenko, A.; Weyher, J. L.; Grzegory, I.; Dziecielewski, I.; Sarzynski, M.; Strelchuk, V.; Tsykaniuk, B.; Belyaev, O.; Petrusha, I.; Turkevich, V.; Kapustianyk, V.; Albrecht, M.; Porowski, S.

    2016-09-01

    Experimental studies of diffusion of oxygen in bulk wurtzite-type GaN crystals grown by Halide Vapor Phase Epitaxy (HVPE) are reported. Oxygen concentration profiles were studied in as-grown GaN crystals and also after annealing of crystals at temperatures up to 3400 K and pressures up to 9 GPa. Investigated crystals contained large conical defects i.e. pinholes of significantly higher oxygen concentration (NO=(2-4)×1019 cm-3) than that in the bulk matrix (NO<1×1017 cm-3). The pinholes were revealed by a photo-etching method in as-grown and annealed GaN samples. Confocal micro-Raman spectroscopy was applied to measure the profiles of free electron concentration, which directly corresponds to the concentration of oxygen impurity. Lateral scanning across the interfaces between pinholes and matrix in the as-grown HVPE GaN crystals showed sharp step-like carrier concentration profiles. Annealing at high temperature and high pressure resulted in the diffusion blurring of the profiles. Analysis of obtained data allowed for the first time for estimation of oxygen diffusion coefficients DO(T, P). The obtained values of DO(T, P) are anomalously small similarly to the values obtained by Harafuji et al. by molecular dynamic calculations for self-diffusion of nitrogen. Whereas oxygen and nitrogen are on the same sublattice it could explain the similarity of their diffusion coefficients.

  2. Removing Impurity of cBN Crystal Prepared at High Pressure and High Temperature

    NASA Astrophysics Data System (ADS)

    Ji, Xiao-Rui; Yang, Xiao-Hong

    2012-03-01

    The black cubic boron nitride (cBN) single crystal is synthesized by using hBN-LiH and hBN-Li3N-B as the raw materials at high temperature and high pressure (HTHP). The colors of the cBN crystal synthesized in an hBN-Li3N-B system vary from transparent yellow, half-transparent and then opaque black with the increasing B content in the raw materials. It is worth noting that a trigonal shadow is presented at the center of the cBN crystal synthesized in the hBN-Li3N-B system but can not be found in the hBN-LiH system. Analyzing the Raman spectrum, we find that the darkening and the trigonal shadow in the cBN crystal may be due to the presence of excess B atoms. The above-mentioned phenomenon can be determined by removing impurity capacity and growth environment of the cBN crystal.

  3. Energy efficient engine high-pressure turbine single crystal vane and blade fabrication technology report

    NASA Technical Reports Server (NTRS)

    Giamei, A. F.; Salkeld, R. W.; Hayes, C. W.

    1981-01-01

    The objective of the High-Pressure Turbine Fabrication Program was to demonstrate the application and feasibility of Pratt & Whitney Aircraft-developed two-piece, single crystal casting and bonding technology on the turbine blade and vane configurations required for the high-pressure turbine in the Energy Efficient Engine. During the first phase of the program, casting feasibility was demonstrated. Several blade and vane halves were made for the bonding trials, plus solid blades and vanes were successfully cast for materials evaluation tests. Specimens exhibited the required microstructure and chemical composition. Bonding feasibility was demonstrated in the second phase of the effort. Bonding yields of 75 percent for the vane and 30 percent for the blade were achieved, and methods for improving these yield percentages were identified. A bond process was established for PWA 1480 single crystal material which incorporated a transient liquid phase interlayer. Bond properties were substantiated and sensitivities determined. Tooling die materials were identified, and an advanced differential thermal expansion tooling concept was incorporated into the bond process.

  4. Single Crystal Preparation for High-Pressure Experiments in the Diamond Anvil Cell

    SciTech Connect

    Aracne, C; Farber, D; Benterou, J; Occelli, F; Krisch, M; Antonangeli, D; Requardt, H; Fiquet, G

    2003-07-01

    Most research conducted in diamond anvil cells (DAC) is performed on polycrystalline samples. While data from polycrystalline samples are sufficient for determining the bulk properties, high-pressure experiments on single crystals allow for measurements on a range of tensor properties such as: thermal and electrical conductivity; magnetic susceptibility; elasticity; and plasticity. However, in order to achieve pressures above 1 Mbar in a DAC, single crystal samples must be <50 m in diameter and <15 m thick while maintaining a high degree of crystallinity. Thus, we have developed new procedures for producing extremely high-quality micro single crystal samples from commercially available material. Our sample preparation steps include cutting, classical metallographic polishing, and laser ablation. The key to our new process is the preservation of crystallinity during cutting and thinning. We have been successful in maintaining orientation, along with an extremely high degree of crystallinity in completed metal samples. To date, we have analyzed cobalt and molybdenum samples with both white-light interferometry and synchrotron x-ray diffraction, and are in the process of extending these methods to other metals and ceramics.

  5. High-pressure crystal growth and electromagnetic properties of 5d double-perovskite Ca₃OsO₆

    SciTech Connect

    Feng, Hai Luke; Shi, Youguo; Guo, Yanfeng; Li, Jun; Sato, Akira; Sun, Ying; Wang, Xia; Yu, Shan; Sathish, Clastin I.; Yamaura, Kazunari

    2013-05-01

    Single crystals of the osmium-containing compound Ca₃OsO₆ have been successfully grown under high-pressure conditions, for the first time. The crystal structure of Ca₃OsO₆ atoms being fully ordered at the perovskite B-site. The electromagnetic analysis shows that the crystal exhibits a semiconductor-like behavior below 300 K and undergoes an antiferromagnetic transition at 50 K. - Graphical Abstract: Schematic image of crystal structure of Ca₃OsO₆ as determined by X-ray diffraction, where the gray and black octahedrons are occupied by Ca and Os, respectively. Top inset reveals an optic image of a typical Ca₃OsO₆ single crystal. Highlights: • Single crystals of Ca₃OsO₆ have been successfully grown under high-pressure. • Ca₃OsO₆ crystalizes into an ordered double-perovskite structure. • The Ca₃OsO₆ undergoes an antiferromagnetic transition at 50 K.

  6. Size and location of ice crystals in pork frozen by high-pressure-assisted freezing as compared to classical methods.

    PubMed

    Martino, M N; Otero, L; Sanz, P D; Zaritzky, N E

    1998-11-01

    In high-pressure-assisted freezing, samples are cooled under pressure (200 MPa) to - 20 °C without ice formation then pressure is released (0.1 MPa) and the high super-cooling reached (approx. 20 °C), promotes uniform and rapid ice nucleation. The size and location of ice crystals in large meat pieces (Longissimus dorsi pork muscle) as a result of high-pressure-assisted freezing were compared to those obtained by air-blast and liquid N(2). Samples from the surface and centre of the frozen muscle were histologically analysed using an indirect technique (isothermal-freeze fixation). Air-blast and cryogenic fluid freezing, having thermal gradients, showed non-uniform ice crystal distributions. High-pressure-assisted frozen samples, both at the surface and at the central zones, showed similar, small-sized ice crystals. This technique is particularly useful for freezing large pieces of food when uniform ice crystal sizes are required.

  7. High-pressure synthesis and crystal structure of silicon phosphate hydroxide, SiPO 4(OH)

    NASA Astrophysics Data System (ADS)

    Stearns, Linda A.; Groy, Thomas L.; Leinenweber, Kurt

    2005-09-01

    A new high-pressure phase, silicon phosphate hydroxide, was prepared at 8.3±0.5 GPa and 1000 °C in >98% purity. From X-ray diffraction on a pseudo-merohedrally twinned crystal, it was found that SiPO 4(OH) crystallizes in a monoclinic cell with space group P21/n (No. 14), a=6.8446(11) Å, b=6.8683(13) Å, c=6.8446(11) Å, β=119.77(1)∘, and Z=4. The refinement gave a conventional Robs of 0.0320 and wRobs of 0.0864 for the overlapped data from both twin components. In the structure, SiO 6 octahedra form chains along [101], with PO 4 tetrahedra alternating along the chain in the b-direction. The parallel chains link up with tetrahedral corners from other chains to form a 3-dimensional network. SiPO 4(OH) belongs to a structural family that includes HgSeO4·H2O. It is also related to the SbOPO 4 structure by a small distortion that lowers the symmetry from C2/c in SbOPO 4 to P21/c (P21/n) in SiPO 4(OH).

  8. Effects of catalyst height on diamond crystal morphology under high pressure and high temperature

    NASA Astrophysics Data System (ADS)

    Ya-Dong, Li; Xiao-Peng, Jia; Bing-Min, Yan; Ning, Chen; Chao, Fang; Yong, Li; Hong-An, Ma

    2016-04-01

    The effect of the catalyst height on the morphology of diamond crystal is investigated by means of temperature gradient growth (TGG) under high pressure and high temperature (HPHT) conditions with using a Ni-based catalyst in this article. The experimental results show that the morphology of diamond changes from an octahedral shape to a cub-octahedral shape as the catalyst height rises. Moreover, the finite element method (FEM) is used to simulate the temperature field of the melted catalyst/solvent. The results show that the temperature at the location of the seed diamond continues to decrease with the increase of catalyst height, which is conducive to changing the morphology of diamond. This work provides a new way to change the diamond crystal morphology. Project supported by the National Natural Science Foundation of China (Grant No. 51172089), the Program for New Century Excellent Talents in University, the Natural Science Foundation of Guizhou Provincial Education Department (Grant No. KY[2013]183), and the Collaborative Fund of Science and Technology Office of Guizhou Province, China (Grant No. LH[2015]7232).

  9. Thermal Diffused Scattering (TDS) - a new tool for determining single crystal elasticity at high-pressure condition

    NASA Astrophysics Data System (ADS)

    Zhang, J.

    2015-12-01

    X-ray thermal diffuse scattering (TDS) has been used to determine phonon dispersion relation of solids since 1940s (Wehinger et al. 2013; Ding et al. 2006; Xu and Chiang 2005). However, its application in high-pressure mineral physics has not been widely recognized. Sound velocities of Earth materials at relevant high pressure (P) and temperature (T) conditions are essential for interpreting seismic data, which provides by now the most accurate image of the Earth interior. Comparing with other commonly used techniques for measuring sound velocities in the high-pressure mineral physics community, it has significant advantages and disadvantages. Firstly, it could be used for measuring any single crystals at extreme P-T conditions using diamond anvil cell (DAC), not limited to transparent samples or nuclear resonant isotopes; Secondly, single-crystal elastic constants could be obtained through TDS, and hence directional dependences of sound velocities are available; Finally, experimental setup for TDS measurement is very easy, essentially identical to what is used for routine high-pressure single-crystal X-ray diffraction experiments. However, TDS is much less straightforward in data interpretation, which usually involves micro force constant modeling between the nearest neighbor atoms. We developed dependable data collection procedures for TDS measurement under high-pressure conditions. Measurements with single-crystal Si and foresterite under ambient and high-pressure conditions are successful. Using the python code package we developed for analyzing TDS data, we successfully reproduced the previously determined single-crystal elastic moduli of Si and foresterite using Brillouin spectroscopy and ultrasonics. The experimental uncertainty of the single crystal elastic moduli determined from TDS approach is within 4% or better.

  10. Evolution of crystal and electronic structures of magnesium dicarbide at high pressure.

    PubMed

    Wang, Dashuai; Yan, Yan; Zhou, Dan; Liu, Yanhui

    2015-01-01

    Carbon-based compounds exhibit unexpected structures and electronic behavior at high pressure arising from various bonding features of carbon (e.g., sp, sp(2) and sp(3) C-C bonds). Here we report evolution of crystal structures of MgC2 in a wide pressure range of 0-200 GPa as predicted through ab-initio calculations in combination with an unbiased swarm structure search. Three pressure-induced structural transformations are unraveled, following the phase sequence of ambient-pressure P42/mnm (α-phase) → Cmcm (β-phase) → C2m (γ-phase) → EuGe2-type P-3m1 (δ-phase), where significant C-C bonding modifications from C-C dimer to quasi 1-dimensionzigzag chain, to polymerized ribbon and then to winkled quasi 2- dimension graphite sheet are evident. The predicted β- and γ-phases with sp(2) C-C hybridization are metals, while the δ- phase characterized by a sp(3)C-C hybridization is a narrow-gap semiconductor with a band gap of 0.667 eV. Strong electron-phonon couplings in the compressed β- and γ- phases arepredicted with β-phase showing a high superconducting critical temperature of 11.2 K. The current results indicate that pressure is effective in tuning the crystal and electronic structures of MgC2, which is expected to have impact on physical properties for potential applications. PMID:26634906

  11. Evolution of crystal and electronic structures of magnesium dicarbide at high pressure

    NASA Astrophysics Data System (ADS)

    Wang, Dashuai; Yan, Yan; Zhou, Dan; Liu, Yanhui

    2015-12-01

    Carbon-based compounds exhibit unexpected structures and electronic behavior at high pressure arising from various bonding features of carbon (e.g., sp, sp2 and sp3 C-C bonds). Here we report evolution of crystal structures of MgC2 in a wide pressure range of 0-200 GPa as predicted through ab-initio calculations in combination with an unbiased swarm structure search. Three pressure-induced structural transformations are unraveled, following the phase sequence of ambient-pressure P42/mnm (α-phase) → Cmcm (β-phase) → C2m (γ-phase) → EuGe2-type P-3m1 (δ-phase), where significant C-C bonding modifications from C-C dimer to quasi 1-dimensionzigzag chain, to polymerized ribbon and then to winkled quasi 2- dimension graphite sheet are evident. The predicted β- and γ-phases with sp2 C-C hybridization are metals, while the δ- phase characterized by a sp3C-C hybridization is a narrow-gap semiconductor with a band gap of 0.667 eV. Strong electron-phonon couplings in the compressed β- and γ- phases arepredicted with β-phase showing a high superconducting critical temperature of 11.2 K. The current results indicate that pressure is effective in tuning the crystal and electronic structures of MgC2, which is expected to have impact on physical properties for potential applications.

  12. Crystal structures of (Mg1-x,Fex)SiO3postperovskite at high pressures

    PubMed Central

    Yamanaka, Takamitsu; Hirose, Kei; Mao, Wendy L.; Meng, Yue; Ganesh, P.; Shulenburger, Luke; Shen, Guoyin; Hemley, Russell J.

    2012-01-01

    X-ray diffraction experiments on postperovskite (ppv) with compositions (Mg0.9Fe0.1)SiO3 and (Mg0.6Fe0.4)SiO3 at Earth core-mantle boundary pressures reveal different crystal structures. The former adopts the CaIrO3-type structure with space group Cmcm, whereas the latter crystallizes in a structure with the Pmcm (Pmma) space group. The latter has a significantly higher density (ρ = 6.119(1) g/cm3) than the former (ρ = 5.694(8) g/cm3) due to both the larger amount of iron and the smaller ionic radius of Fe2+ as a result of an electronic spin transition observed by X-ray emission spectroscopy (XES). The smaller ionic radius for low-spin compared to high-spin Fe2+ also leads to an ordered cation distribution in the M1 and M2 crystallographic sites of the higher density ppv structure. Rietveld structure refinement indicates that approximately 70% of the total Fe2+ in that phase occupies the M2 site. XES results indicate a loss of 70% of the unpaired electronic spins consistent with a low spin M2 site and high spin M1 site. First-principles calculations of the magnetic ordering confirm that Pmcm with a two-site model is energetically more favorable at high pressure, and predict that the ordered structure is anisotropic in its electrical and elastic properties. These results suggest that interpretations of seismic structure in the deep mantle need to treat a broader range of mineral structures than previously considered. PMID:22223656

  13. Piezochromism in nickel salicylaldoximato complexes: tuning crystal-field splitting with high pressure.

    PubMed

    Byrne, Peter J; Richardson, Patricia J; Chang, John; Kusmartseva, Anna F; Allan, David R; Jones, Anita C; Kamenev, Konstantin V; Tasker, Peter A; Parsons, Simon

    2012-06-18

    The crystal structures of bis(3-fluoro-salicylaldoximato)nickel(II) and bis(3-methoxy-salicylaldoximato)nickel(II) have been determined at room temperature between ambient pressure and approximately 6 GPa. The principal effect of pressure is to reduce intermolecular contact distances. In the fluoro system molecules are stacked, and the Ni⋅⋅⋅Ni distance decreases from 3.19 Å at ambient pressure to 2.82 Å at 5.4 GPa. These data are similar to those observed in bis(dimethylglyoximato)nickel(II) over a similar pressure range, though contrary to that system, and in spite of their structural similarity, the salicyloximato does not become conducting at high pressure. Ni-ligand distances also shorten, on average by 0.017 and 0.011 Å for the fluoro and methoxy complexes, respectively. Bond compression is small if the bond in question is directed towards an interstitial void. A band at 620 nm, which occurs in the visible spectrum of each derivative, can be assigned to a transition to an antibonding molecular orbital based on the metal 3d(x(2)-y(2)) orbital. Time-dependent density functional theory calculations show that the energy of this orbital is sensitive to pressure, increasing in energy as the Ni-ligand distances are compressed, and consequently increasing the energy of the transition. The resulting blueshift of the UV-visible band leads to piezochromism, and crystals of both complexes, which are green at ambient pressure, become red at 5 GPa. PMID:22615125

  14. Evolution of crystal and electronic structures of magnesium dicarbide at high pressure

    PubMed Central

    Wang, Dashuai; Yan, Yan; Zhou, Dan; Liu, Yanhui

    2015-01-01

    Carbon-based compounds exhibit unexpected structures and electronic behavior at high pressure arising from various bonding features of carbon (e.g., sp, sp2 and sp3 C-C bonds). Here we report evolution of crystal structures of MgC2 in a wide pressure range of 0–200 GPa as predicted through ab-initio calculations in combination with an unbiased swarm structure search. Three pressure-induced structural transformations are unraveled, following the phase sequence of ambient-pressure P42/mnm (α-phase) → Cmcm (β-phase) → C2m (γ-phase) → EuGe2-type P-3m1 (δ-phase), where significant C-C bonding modifications from C-C dimer to quasi 1-dimensionzigzag chain, to polymerized ribbon and then to winkled quasi 2- dimension graphite sheet are evident. The predicted β- and γ-phases with sp2 C-C hybridization are metals, while the δ- phase characterized by a sp3C-C hybridization is a narrow-gap semiconductor with a band gap of 0.667 eV. Strong electron-phonon couplings in the compressed β- and γ- phases arepredicted with β-phase showing a high superconducting critical temperature of 11.2 K. The current results indicate that pressure is effective in tuning the crystal and electronic structures of MgC2, which is expected to have impact on physical properties for potential applications. PMID:26634906

  15. Stability of amino acids and their oligomerization under high-pressure conditions: implications for prebiotic chemistry.

    PubMed

    Otake, Tsubasa; Taniguchi, Takashi; Furukawa, Yoshihiro; Kawamura, Fumio; Nakazawa, Hiromoto; Kakegawa, Takeshi

    2011-10-01

    The polymerization of amino acids leading to the formation of peptides and proteins is a significant problem for the origin of life. This problem stems from the instability of amino acids and the difficulty of their oligomerization in aqueous environments, such as seafloor hydrothermal systems. We investigated the stability of amino acids and their oligomerization reactions under high-temperature (180-400°C) and high-pressure (1.0-5.5 GPa) conditions, based on the hypothesis that the polymerization of amino acids occurred in marine sediments during diagenesis and metamorphism, at convergent margins on early Earth. Our results show that the amino acids glycine and alanine are stabilized by high pressure. Oligomers up to pentamers were formed, which has never been reported for alanine in the absence of a catalyst. The yields of peptides at a given temperature and reaction time were higher under higher-pressure conditions. Elemental, infrared, and isotopic analyses of the reaction products indicated that deamination is a key degradation process for amino acids and peptides under high-pressure conditions. A possible NH(3)-rich environment in marine sediments on early Earth may have further stabilized amino acids and peptides by inhibiting their deamination.

  16. Stability of amino acids and their oligomerization under high-pressure conditions: implications for prebiotic chemistry.

    PubMed

    Otake, Tsubasa; Taniguchi, Takashi; Furukawa, Yoshihiro; Kawamura, Fumio; Nakazawa, Hiromoto; Kakegawa, Takeshi

    2011-10-01

    The polymerization of amino acids leading to the formation of peptides and proteins is a significant problem for the origin of life. This problem stems from the instability of amino acids and the difficulty of their oligomerization in aqueous environments, such as seafloor hydrothermal systems. We investigated the stability of amino acids and their oligomerization reactions under high-temperature (180-400°C) and high-pressure (1.0-5.5 GPa) conditions, based on the hypothesis that the polymerization of amino acids occurred in marine sediments during diagenesis and metamorphism, at convergent margins on early Earth. Our results show that the amino acids glycine and alanine are stabilized by high pressure. Oligomers up to pentamers were formed, which has never been reported for alanine in the absence of a catalyst. The yields of peptides at a given temperature and reaction time were higher under higher-pressure conditions. Elemental, infrared, and isotopic analyses of the reaction products indicated that deamination is a key degradation process for amino acids and peptides under high-pressure conditions. A possible NH(3)-rich environment in marine sediments on early Earth may have further stabilized amino acids and peptides by inhibiting their deamination. PMID:21961531

  17. Crystal chemistry of meteoritic hibonites

    NASA Technical Reports Server (NTRS)

    Burns, R. G.; Burns, V. M.

    1984-01-01

    The characteristics of cation vacancies and site occupancies of natural hibonites in meteors are discussed. Note is taken of the effect of the specific locations of the hibonites in the matrices on the crystal chemistry, electronic stabilities, and spectral features of the metal ions which replace the Al(3+). Hibonites form beta-alumina hexagonal cells with 26 cation sites. Fe cations are found in octahedral, tetrahedral, and five-fold coordinations. Fe(2+) is found in face-shared Al(3) octahedra, a siting explained in terms of ionic radius and crystal field stabilization energy criteria. Spectral colors are attributed to V(3+) and Ti(3+) field transitions at 400 and 700 nm, respectively, although the 700 nm line may arise from transitions of Ti(3+) to Ti(4+) or Fe(2+) to Fe(3+) during heating. Excesses of Mg-26 can be traced to decay of nebular Al-26.

  18. Elasticity of single-crystal olivine at high pressures and temperatures

    NASA Astrophysics Data System (ADS)

    Mao, Zhu; Fan, Dawei; Lin, Jung-Fu; Yang, Jing; Tkachev, Sergey N.; Zhuravlev, Kirill; Prakapenka, Vitali B.

    2015-09-01

    Elasticity of single-crystal San Carlos olivine has been derived from sound velocity and density measurements at simultaneous high pressure-temperature conditions up to 20 GPa and 900 K using in situ Brillouin spectroscopy and single-crystal X-ray diffraction in externally-heated diamond anvil cells. These experimental results are used to evaluate the combined effect of pressure and temperature on full elastic constants of single-crystal olivine to better understand its velocity profiles and anisotropies in the deep mantle. Analysis of the results shows that the shear moduli display strong concave behaviors as a function of pressure at a given high temperature, while the longitudinal modulus, C11, and the off-diagonal moduli, C12 and C13, exhibit greater temperature dependence at higher pressures than at relatively lower pressures. Using a finite-strain theory and thermal equation of state modeling for a pyrolitic mantle composition along an expected mantle geotherm, our results show that the magnitude of the VP and VS jumps at the 410-km depth are 6% and 6.4%, respectively, which are greater than that found in seismic observations, suggesting a mantle olivine content of 40-50 vol%, which is less than what is expected for the pyrolite model. Our modeled velocity profiles for a metastable olivine wedge in the subduction slabs along a representative cold slab geotherm are 6% and 10% lower than those of wadsleyite and ringwoodite, respectively, at corresponding depths of the normal mantle. Our modeled results also show that metastable olivine in the cold slabs could have strong VP and VS anisotropies. The maximum VP anisotropy is estimated to be 19-22% at transition zone depth, whereas the maximum VS splitting is 13-23% and increases with depth. As a result, the presence of a metastable olivine wedge at the transition zone depth would exhibit a seismic signature of low velocity and strong seismic anisotropy which are consistent with recent seismic observations for

  19. XPS analysis for cubic boron nitride crystal synthesized under high pressure and high temperature using Li3N as catalysis

    NASA Astrophysics Data System (ADS)

    Guo, Xiaofei; Xu, Bin; Zhang, Wen; Cai, Zhichao; Wen, Zhenxing

    2014-12-01

    Cubic boron nitride (cBN) single crystals are synthesized with lithium nitride (Li3N) as catalyst under high pressure and high temperature. The variation of electronic structures from boron nitride of different layers in coating film on the cBN single crystal has been investigated by X-ray photoelectron spectroscopy. Combining the atomic concentration analysis, it was shown that from the film/cBN crystal interface to the inner, the sp2 fractions are decreasing, and the sp3 fractions are increasing in the film at the same time. Moreover, by transmission electron microscopy, a lot of cBN microparticles are found in the interface. For there is no Li3N in the film, it is possible that Li3N first reacts with hexagonal boron nitride to produce Li3BN2 during cBN crystals synthesis under high pressure and high temperature (HPHT). Boron and nitrogen atoms, required for cBN crystals growth, could come from the direct conversion from hexagonal boron nitride with the catalysis of Li3BN2 under high pressure and high temperature, but not directly from the decomposition of Li3BN2.

  20. High-pressure crystal structures of TaAs from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Lu, Mingchun; Guo, Yanan; Zhang, Miao; Liu, Hanyu; Tse, John S.

    2016-08-01

    In this work, we systematically studied the phase transition of TaAs under high pressures and reported three high-pressure structures P-6m2 (hexagonal, stable at 13-32 GPa), P21/c (monoclinic, stable at 32-103 GPa) and Pm-3m (cubic, stable above 103 GPa), by using particle swarm optimization in combination with first principles electronic structure methodology. All predicted structures are dynamically stable, since there is no imaginary mode to be found in the whole Brillouin zone. At high pressures, the TaAs was found to become superconductor with the superconducting critical temperature of ~1 K at about 100 GPa.

  1. Thermoset recycling via high-pressure high-temperature sintering: Revisiting the effect of interchange chemistry

    NASA Astrophysics Data System (ADS)

    Morin, Jeremy Edward

    In 1844 Charles Goodyear obtained U.S. Patent #3,633 for his "Gum Elastic Composition". In a published circular, which describes his patent for the sulfur vulcanization of gum elastic composition, he stated: "No degree of heat, without blaze, can melt it (rubber)... It resists the most powerful chemical reagents. Aquafortis (nitric acid), sulphuric acid, essential and common oils, turpentine and other solvents... ..." Goodyear's sulfur vulcanization of rubber fueled much of the industrial revolution and made transportation possible, as it exists today. In doing so, Goodyear created one of the most difficult materials to recycle. Rubber will not melt, dissolve, or lend itself to the usual methods of chemical decomposition. Ironically, Goodyear recognized this problem and in 1853 he patented the process of adding ground rubber to virgin material, now currently known as regrind blending. Today, scrap tires represent one of the most serious sources of pollution in the world. Studies estimate that there are roughly 2 billion scrap tires in U.S. landfills and more are being added at a rate of over 273 million tires per year. Current methods of recycling waste tires are crude, ineffective, and use rubber powder as a low cost filler instead of a new rubber. The groundwork for a very simple and effective method of producing high-quality rubber goods using 100% scrap rubber was discovered in 1944 by A. V. Tobolsky et al. This application, however, was not recognized until recently in our laboratory. The process as studied to date represents a method of creating quality, high-value added rubber goods with nothing other than heat and pressure. High pressure is required to obtain a void-free compaction of the rubber particles by forcing all of the free surfaces into intimate contact. High temperature then activates the chemical rearrangement, scission, and reformation of the chemical bonds thus providing new bridges between the once fractured interfaces. This occurs both within

  2. A high-pressure cryocooling method for protein crystals and biological samples with reduced background X-ray scatter

    PubMed Central

    Kim, Chae Un; Wierman, Jennifer L.; Gillilan, Richard; Lima, Enju; Gruner, Sol M.

    2013-01-01

    High-pressure cryocooling has been developed as an alternative method for cryopreservation of macromolecular crystals and successfully applied for various technical and scientific studies. The method requires the preservation of crystal hydration as the crystal is pressurized with dry helium gas. Previously, crystal hydration was maintained either by coating crystals with a mineral oil or by enclosing crystals in a capillary which was filled with crystallization mother liquor. These methods are not well suited to weakly diffracting crystals because of the relatively high background scattering from the hydrating materials. Here, an alternative method of crystal hydration, called capillary shielding, is described. The specimen is kept hydrated via vapor diffusion in a shielding capillary while it is being pressure cryocooled. After cryocooling, the shielding capillary is removed to reduce background X-ray scattering. It is shown that, compared to previous crystal-hydration methods, the new hydration method produces superior crystal diffraction with little sign of crystal damage. Using the new method, a weakly diffracting protein crystal may be properly pressure cryo­cooled with little or no addition of external cryoprotectants, and significantly reduced background scattering can be observed from the resulting sample. Beyond the applications for macromolecular crystallography, it is shown that the method has great potential for the preparation of noncrystalline hydrated biological samples for coherent diffraction imaging with future X-ray sources. PMID:23396891

  3. High-pressure chemistry of hydrogen in metals: in situ study of iron hydride.

    PubMed

    Badding, J V; Hemley, R J; Mao, H K

    1991-07-26

    Optical observations and x-ray diffraction measurements of the reaction between iron and hydrogen at high pressure to form iron hydride are described. The reaction is associated with a sudden pressure-induced expansion at 3.5 gigapascals of iron samples immersed in fluid hydrogen. Synchrotron x-ray diffraction measurements carried out to 62 gigapascals demonstrate that iron hydride has a double hexagonal close-packed structure, a cell volume up to 17% larger than pure iron, and a stoichiometry close to FeH. These results greatly extend the pressure range over which the technologically important iron-hydrogen phase diagram has been characterized and have implications for problems ranging from hydrogen degradation and embrittlement of ferrous metals to the presence of hydrogen in Earth's metallic core.

  4. Single-crystal CVD diamonds as small-angle X-ray scattering windows for high-pressure research

    PubMed Central

    Wang, Suntao; Meng, Yu-fei; Ando, Nozomi; Tate, Mark; Krasnicki, Szczesny; Yan, Chih-shiue; Liang, Qi; Lai, Joseph; Mao, Ho-kwang; Gruner, Sol M.; Hemley, Russell J.

    2012-01-01

    Small-angle X-ray scattering (SAXS) was performed on single-crystal chemical vapor deposition (CVD) diamonds with low nitrogen concentrations, which were fabricated by microwave plasma-assisted chemical vapor deposition at high growth rates. High optical quality undoped 500 µm-thick single-crystal CVD diamonds grown without intentional nitrogen addition proved to be excellent as windows on SAXS cells, yielding parasitic scattering no more intense than a 7.5 µm-thick Kapton film. A single-crystal CVD diamond window was successfully used in a high-pressure SAXS cell. PMID:22675230

  5. High-pressure crystal growth and electromagnetic properties of 5d double-perovskite Ca3OsO6

    NASA Astrophysics Data System (ADS)

    Feng, Hai Luke; Shi, Youguo; Guo, Yanfeng; Li, Jun; Sato, Akira; Sun, Ying; Wang, Xia; Yu, Shan; Sathish, Clastin I.; Yamaura, Kazunari

    2013-05-01

    Single crystals of the osmium-containing compound Ca3OsO6 have been successfully grown under high-pressure conditions, for the first time. The crystal structure of Ca3OsO6 were characterized as an ordered double-perovskite structure of space group P21/n with the Ca and Os atoms being fully ordered at the perovskite B-site. The electromagnetic analysis shows that the crystal exhibits a semiconductor-like behavior below 300 K and undergoes an antiferromagnetic transition at 50 K.

  6. One-step green synthesis of cuprous oxide crystals with truncated octahedra shapes via a high pressure flux approach

    SciTech Connect

    Li Benxian; Wang Xiaofeng; Xia Dandan; Chu Qingxin; Liu Xiaoyang; Lu Fengguo; Zhao Xudong

    2011-08-15

    Cuprous oxide (Cu{sub 2}O) was synthesized via reactions between cupric oxide (CuO) and copper metal (Cu) at a low temperature of 300 deg. C. This progress is green, environmentally friendly and energy efficient. Cu{sub 2}O crystals with truncated octahedra morphology were grown under high pressure using sodium hydroxide (NaOH) and potassium hydroxide (KOH) with a molar ratio of 1:1 as a flux. The growth mechanism of Cu{sub 2}O polyhedral microcrystals are proposed and discussed. - Graphical Abstract: The Cu{sub 2}O crystals with truncated octahedral shape were one-step synthesized in high yield via high pressure flux method for the first time, which is green and environmentally friendly. The mechanisms of synthesis and crystal growth were discussed in this paper. Highlights: > Cuprous oxide was one-step green synthesized by high pressure flux method. > The approach was based on the reverse dismutation reactions between cupric oxide and copper metal. > This progress is green, environmentally friendly and energy efficient. > The synthesized Cu2O crystals were of truncated octahedra morphology.

  7. Iron catalyst chemistry in modeling a high-pressure carbon monoxide nanotube reactor

    NASA Technical Reports Server (NTRS)

    Scott, Carl D.; Povitsky, Alexander; Dateo, Christopher; Gokcen, Tahir; Willis, Peter A.; Smalley, Richard E.

    2003-01-01

    The high-pressure carbon monoxide (HiPco) technique for producing single-wall carbon nanotubes (SWNTs) is analyzed with the use of a chemical reaction model coupled with flow properties calculated along streamlines, calculated by the FLUENT code for pure carbon monoxide. Cold iron pentacarbonyl, diluted in CO at about 30 atmospheres, is injected into a conical mixing zone, where hot CO is also introduced via three jets at 30 degrees with respect to the axis. Hot CO decomposes the Fe(CO)5 to release atomic Fe. Then iron nucleates and forms clusters that catalyze the formation of SWNTs by a disproportionation reaction (Boudouard) of CO on Fe-containing clusters. Alternative nucleation rates are estimated from the theory of hard sphere collision dynamics with an activation energy barrier. The rate coefficient for carbon nanotube growth is estimated from activation energies in the literature. The calculated growth was found be about an order of magnitude greater than measured, regardless of the nucleation rate. A study of cluster formation in an incubation zone prior to injection into the reactor shows that direct dimer formation from Fe atoms is not as important as formation via an exchange reaction of Fe with CO in FeCO.

  8. Iron catalyst chemistry in modeling a high-pressure carbon monoxide nanotube reactor.

    PubMed

    Scott, Carl D; Povitsky, Alexander; Dateo, Christopher; Gökçen, Tahir; Willis, Peter A; Smalley, Richard E

    2003-01-01

    The high-pressure carbon monoxide (HiPco) technique for producing single-wall carbon nanotubes (SWNTs) is analyzed with the use of a chemical reaction model coupled with flow properties calculated along streamlines, calculated by the FLUENT code for pure carbon monoxide. Cold iron pentacarbonyl, diluted in CO at about 30 atmospheres, is injected into a conical mixing zone, where hot CO is also introduced via three jets at 30 degrees with respect to the axis. Hot CO decomposes the Fe(CO)5 to release atomic Fe. Then iron nucleates and forms clusters that catalyze the formation of SWNTs by a disproportionation reaction (Boudouard) of CO on Fe-containing clusters. Alternative nucleation rates are estimated from the theory of hard sphere collision dynamics with an activation energy barrier. The rate coefficient for carbon nanotube growth is estimated from activation energies in the literature. The calculated growth was found be about an order of magnitude greater than measured, regardless of the nucleation rate. A study of cluster formation in an incubation zone prior to injection into the reactor shows that direct dimer formation from Fe atoms is not as important as formation via an exchange reaction of Fe with CO in FeCO. PMID:12908231

  9. High-pressure behavior of natural single-crystal epidote and clinozoisite up to 40 GPa

    NASA Astrophysics Data System (ADS)

    Qin, Fei; Wu, Xiang; Wang, Ying; Fan, Dawei; Qin, Shan; Yang, Ke; Townsend, Joshua P.; Jacobsen, Steven D.

    2016-06-01

    The comparative compressibility and high-pressure stability of a natural epidote (0.79 Fe-total per formula unit, Fetot pfu) and clinozoisite (0.40 Fetot pfu) were investigated by single-crystal X-ray diffraction and Raman spectroscopy. The lattice parameters of both phases exhibit continuous compression behavior up to 30 GPa without evidence of phase transformation. Pressure-volume data for both phases were fitted to a third-order Birch-Murnaghan equation of state with V 0 = 461.1(1) Å3, K 0 = 115(2) GPa, and K0' = 3.7(2) for epidote and V 0 = 457.8(1) Å3, K 0 = 142(3) GPa, and K0' = 5.2(4) for clinozoisite. In both epidote and clinozoisite, the b-axis is the stiffest direction, and the ratios of axial compressibility are 1.19:1.00:1.15 for epidote and 1.82:1.00:1.19 for clinozoisite. Whereas the compressibility of the a-axis is nearly the same for both phases, the b- and c-axes of the epidote are about 1.5 times more compressible than in clinozoisite, consistent with epidote having a lower bulk modulus. Raman spectra collected up to 40.4 GPa also show no indication of phase transformation and were used to obtain mode Grüneisen parameters (γ i) for Si-O vibrations, which were found to be 0.5-0.8, typical for hydrous silicate minerals. The average pressure coefficient of Raman frequency shifts for M-O modes in epidote, 2.61(6) cm-1/GPa, is larger than found for clinozoisite, 2.40(6) cm-1/GPa, mainly due to the different compressibility of FeO6 and AlO6 octahedra in M3 sites. Epidote and clinozoisite contain about 2 wt% H2O are thus potentially important carriers of water in subducted slabs.

  10. High-pressure behavior of natural single-crystal epidote and clinozoisite up to 40 GPa

    NASA Astrophysics Data System (ADS)

    Qin, Fei; Wu, Xiang; Wang, Ying; Fan, Dawei; Qin, Shan; Yang, Ke; Townsend, Joshua P.; Jacobsen, Steven D.

    2016-10-01

    The comparative compressibility and high-pressure stability of a natural epidote (0.79 Fe-total per formula unit, Fetot pfu) and clinozoisite (0.40 Fetot pfu) were investigated by single-crystal X-ray diffraction and Raman spectroscopy. The lattice parameters of both phases exhibit continuous compression behavior up to 30 GPa without evidence of phase transformation. Pressure-volume data for both phases were fitted to a third-order Birch-Murnaghan equation of state with V 0 = 461.1(1) Å3, K 0 = 115(2) GPa, and K0' = 3.7(2) for epidote and V 0 = 457.8(1) Å3, K 0 = 142(3) GPa, and K0' = 5.2(4) for clinozoisite. In both epidote and clinozoisite, the b-axis is the stiffest direction, and the ratios of axial compressibility are 1.19:1.00:1.15 for epidote and 1.82:1.00:1.19 for clinozoisite. Whereas the compressibility of the a-axis is nearly the same for both phases, the b- and c-axes of the epidote are about 1.5 times more compressible than in clinozoisite, consistent with epidote having a lower bulk modulus. Raman spectra collected up to 40.4 GPa also show no indication of phase transformation and were used to obtain mode Grüneisen parameters ( γ i) for Si-O vibrations, which were found to be 0.5-0.8, typical for hydrous silicate minerals. The average pressure coefficient of Raman frequency shifts for M-O modes in epidote, 2.61(6) cm-1/GPa, is larger than found for clinozoisite, 2.40(6) cm-1/GPa, mainly due to the different compressibility of FeO6 and AlO6 octahedra in M3 sites. Epidote and clinozoisite contain about 2 wt% H2O are thus potentially important carriers of water in subducted slabs.

  11. Crystal chemistry and real structure of crystals

    NASA Astrophysics Data System (ADS)

    Bartl, H.; Bats, J. W.; Dyck, W.; Fuess, H.; Gregory, A.; Joswig, W.; Lottermoser, W.; Koerfer, M.; Mueller, R.; Schweiss, B. P.

    1984-03-01

    Elastic and inelastic scattering, X-ray diffraction and spectroscopy were combined to obtain a comprehensive picture of the properties of crystals. The electron density distribution allows one to verify the models of the theoretical chemistry. Systematic investigations of chemically similar anions (ClO3 and ClO4; S2O3, SO3 and SO4) show differences in bonding and reaction capability. The X-ray-neutron method applied to these anions shows maxima between 0.2 and 0.4 eXA to the power-3 in the bondings of the unbound electrons on S and D. For the SO3-group good agreement is found with theoretical calculations. The effect of the Mg (two times ionized) cation on the density is demonstrated on the water molecules of MgS2O3.6H2O and MgSO3.6H2O. Magnetic structure and magnetization density were investigated on CO3V2O8, Fe2SiO4 and Mn2SiO4 with polarized neutrons. The differences in magnetic moments of both cation states is also demonstrated for Fe2SiO4 with complementary Mossbauer measurements. Inelastic time of flight experiments allow predictions concerning the motion of the NH3-group in aniliniumbromide and of the water molecule in natural zeolites. The theoretical model to calculate the photon dispersion on CaSO4 shows good agreement with the measured dispersion curves.

  12. Short review of high-pressure crystal growth and magnetic and electrical properties of solid-state osmium oxides

    NASA Astrophysics Data System (ADS)

    Yamaura, Kazunari

    2016-04-01

    High-pressure crystal growth and synthesis of selected solid-state osmium oxides, many of which are perovskite-related types, are briefly reviewed, and their magnetic and electrical properties are introduced. Crystals of the osmium oxides, including NaOsO3, LiOsO3, and Na2OsO4, were successfully grown under high-pressure and high-temperature conditions at 6 GPa in the presence of an appropriate amount of flux in a belt-type apparatus. The unexpected discovery of a magnetic metal-insulator transition in NaOsO3, a ferroelectric-like transition in LiOsO3, and high-temperature ferrimagnetism driven by a local structural distortion in Ca2FeOsO6 may represent unique features of the osmium oxides. The high-pressure and high-temperature synthesis and crystal growth has played a central role in the development of solid-state osmium oxides and the elucidation of their magnetic and electronic properties toward possible use in multifunctional devices.

  13. Crystallization of diamond from a silicate melt of kimberlite composition in high-pressure and high-temperature experiments

    SciTech Connect

    Arima, Makoto; Nakayama, Kazuhiro ); Akaishi, Minoru; Yamaoka, Shinobu; Kanda, Hisao )

    1993-11-01

    In high-pressure and high-temperature experiments (1800-2200[degrees]C and 7.0-7.7 GPa), diamond crystallized and grew in a volatile-rich silicate melt of kimberlite composition. This diamond has well-developed [111] faces, and its morphologic characteristics resemble those of natural diamond but differ from those of synthetic diamond grown from metallic solvent-catalysts. The kimberlite melt has a strong solvent-catalytic effect on diamond formation, supporting the view that some natural diamonds crystallized from volatile-rich melts in the upper mantle. 19 refs., 3 figs., 1 tab.

  14. High-pressure and high-temperature characteristics of a Fabry-Perot interferometer based on photonic crystal fiber.

    PubMed

    Wu, Chuang; Fu, H Y; Qureshi, Khurram Karim; Guan, Bai-Ou; Tam, H Y

    2011-02-01

    A fiber-optic Fabry-Perot interferometer was constructed by splicing a short length of photonic crystal fiber to a standard single-mode fiber. The photonic crystal fiber functions as a Fabry-Perot cavity and serves as a direct sensing probe without any additional components. Its pressure and temperature responses in the range of 0-40 MPa and 25°C-700°C were experimentally studied. The proposed sensor is easy to fabricate, potentially low-cost, and compact in size, which makes it very attractive for high-pressure and high-temperature sensing applications. PMID:21283207

  15. Electronic structure of ytterbium-implanted GaN at ambient and high pressure: experimental and crystal field studies.

    PubMed

    Kaminska, A; Ma, C-G; Brik, M G; Kozanecki, A; Boćkowski, M; Alves, E; Suchocki, A

    2012-03-01

    The results of high-pressure low-temperature optical measurements in a diamond-anvil cell of bulk gallium nitride crystals implanted with ytterbium are reported in combination with crystal field calculations of the Yb(3+) energy levels. Crystal field analysis of splitting of the (2)F(7/2) and (2)F(5/2) states has been performed, with the aim of assigning all features of the experimental luminescence spectra. A thorough analysis of the pressure behavior of the Yb(3+) luminescence lines in GaN allowed the determination of the ambient-pressure positions and pressure dependence of the Yb(3+) energy levels in the trigonal crystal field as well as the pressure-induced changes of the spin-orbit coupling coefficient.

  16. High Pressure Crystallization of Mafic Magma: Field Observations, Compositional Measurements and Computer Modeling

    NASA Astrophysics Data System (ADS)

    Tracy, R. J.

    2009-05-01

    The Cortlandt Complex is a small early Silurian composite, mafic to ultramafic, anorogenic deep crustal pluton about 60 km N of New York City in which most rocks in the six mapped plutonic phases have resulted from either fractionation or contamination or both. Bender et al (AJS-1984) estimated Cortlandt parental composition as an alkalic gabbro based on the nature of early plutons. The youngest and easternmost pluton consists largely of concentrically layered pyroxenites and olivine pyroxenites (with subequal modal proportions of opx and cpx, and only minor ol) and it appears to have had a different parental magma. Samples collected through a series of layers reflecting a few hundred meters of stratigraphy in layered pyroxenites indicate wide variation in F/FM (0.18 to 0.3) and both Al and Ti contents of pyroxenes are unusually high (cpx - Al2O3 from 6-7 wt percent and TiO2 from 1.0 - 1.5 wt percent; opx - Al2O3 from 3.8 - 5.7 wt percent and TiO2 from 0.2 to 0.7 wt percent). All pyroxenes show significant exsolution of ilm lamellae. Crystallization pressure has been well constrained by thermobarometry of metapelites in the thermal aureole at roughly 0.8 GPa, making this a very unusual example of very high P cumulate formation. Several magma compositions were tested as suitable parents by running computer simulations using MELTS (Ghiorso and Sack, 1995, CMP; Asimow and Ghiorso, 1998, Am. Min.). These MELTS runs quickly eliminated the proposed alkalic gabbro parent - it did not crystallize opx at any P. In this preliminary modeling, the most suitable parental magma for the cumulates was a picritic Karoo basalt (SiO2 - 46.9, TiO2 - 1.6, Al2O3 - 9.3, FeO - 12.2, MgO - 15.9, CaO - 9.1; Na2O - 1.3, K2O - 0.6, P2O5 - 0.2). MELTS runs at 8 kbar and FMQ showed a close approximation to both mineral proportions and mineral chemistry of the Cortlandt samples. The initial liquidus phase was opx at 1421C, ol at 1407C (L 4.4percent crystallized), spl at 1301C (L 19.7 percent

  17. The Effect of Iron and Aluminium Incorporation on the Single-Crystal Elasticity of Bridgmanite at High Pressure.

    NASA Astrophysics Data System (ADS)

    Kurnosov, A.; Marquardt, H.; Boffa Ballaran, T.; Frost, D. J.

    2015-12-01

    MgSiO3 bridgmanite constitutes about 70% by volume of the Earth's lower mantle and likely governs the physical behavior of this region. Chemical substitutions in MgSiO3 bridgmanite involving Al and Fe may explain seismic velocity anomalies observed in the Earth's lower mantle [1-3]. However, the effects of these substitutions on the anisotropic elastic properties of bridgmanite at high pressure and temperature are still experimentally unconstrained. Here, we present data of internally consistent measurements of the single-crystal elastic properties of Mg0.88Fe0.12Si0.09Al0.11O3 bridgmanite at high-pressures. Two differently oriented single-crystals of brigmanite have been double-side polished and cut as two semi-disks using a FEI Scios Focused Ion Beam (FIB) machine [4]. Two semi-disks, one for each of the crystallographic orientations, were loaded together in the pressure chamber of a diamond anvil cell with helium as a pressure-transmitting medium. Simultaneous measurements of density and sound velocities have been made on both crystals at high pressures using single-crystal X-ray diffraction and Brillouin spectroscopy in order to obtain self-consistent data, which do not depend on a secondary pressure scale. The Brillouin data at each pressure were fitted for both crystals simultaneously in order to reduce correlations among the elastic constants Cij. Our approach allows determining the single-crystal elastic properties of bridgmanite as a function of pressure, derived independently of a secondary pressure. We will use our results for Al-Fe-bearing bridgmanite to discuss the effects of chemical substitution on the high-pressure elasticity of bridgmanite and implications for the interpretation of seismic heterogeneities in Earth's lower mantle. [1] Ni et al. (2005), Geophys. J. Int. 161, 283-294. [2] Masters et al. (2000), AGU Monograph Series, 117, 63-87. [3] Garnero et al. (2005), The Geological Society of America Special Paper, 430, 79-101. [4] Marquardt et al

  18. Promising dissolution enhancement effect of soluplus on crystallized celecoxib obtained through antisolvent precipitation and high pressure homogenization techniques.

    PubMed

    Homayouni, Alireza; Sadeghi, Fatemeh; Varshosaz, Jaleh; Afrasiabi Garekani, Hadi; Nokhodchi, Ali

    2014-10-01

    Poor solubility and dissolution of hydrophobic drugs have become a major challenge in pharmaceutical development. Drug nanoparticles have been widely accepted to overcome this problem. The aim of this study was to manufacture celecoxib nanoparticles using antisolvent precipitation and high pressure homogenization techniques in the presence of varying concentrations of soluplus(®) as a hydrophilic stabilizer. Antisolvent crystallization followed by freeze drying (CRS-FD) and antisolvent crystallization followed by high pressure homogenization and freeze drying (HPH-FD) were used to obtain celecoxib nanoparticles. The obtained nanoparticles were analyzed in terms of particle size, saturation solubility, morphology (optical and scanning electron microscopy), solid state (DSC, XRPD and FT-IR) and dissolution behavior. The results showed that celecoxib nanoparticle can be obtained when soluplus was added to the crystallization medium. In addition, the results showed that the concentration of soluplus and the method used to prepare nanoparticles can control the size and dissolution of celecoxib. Samples obtained in the presence of 5% soluplus through HPH technique showed an excellent dissolution (90%) within 4min. It is interesting to note that celecoxib samples with high crystallinity showed better dissolution than those celecoxib samples with high amorphous content, although they had the same concentration of soluplus. DSC and XRPD proved that samples obtained via HPH technique are more crystalline than the samples obtained through only antisolvent crystallization technique. PMID:25124835

  19. High-pressure single-crystal studies of pyroxene minerals in metastable compression regime with relevance to cold subducting slabs

    NASA Astrophysics Data System (ADS)

    Dera, P. K.

    2012-12-01

    Our understanding of transformation pathways of rock-forming minerals as a function of depth in the Earth interior derives from analysis of their crystal structures at high pressure and temperature conditions and from the relations between different polymorphic forms of the same material. From this perspective, it is often valuable to consider metastable compression behavior of principal rock-forming minerals in the metastable regime, beyond the thermodynamic stability limits and outside of the PT path established by standard geotherm models. Such metastable compression regime can provide useful crystal chemical clues offering insights into intermediate stages of major geophysically-relevant phase transformations and clarifying the most important aspects of the compression mechanisms. Beyond the crystallographic and crystal chemical aspects, the metastable compression experiments may provide information applicable to deep Earth environments that significantly deviate from the standard geotherm, such as subduction zones. Seismic imaging data indicate that in subduction zones the temperatures in the cold subducted oceanic slab, which is dragged beneath the continental plate can be lower than the geotherm by as much as thousands of degrees. Recent seismic travel time tomography evidence indicates that some of the subduction zones, particularly in the Southeast Asia region, extend within the mantle well beyond the 660 km, discontinuity, perhaps as deep as 800 km. The main source of information about the compression behavior of minerals, the crystallographic experiments at high pressure and temperature, have been constrained by the limitations of the experimental in situ techniques and mostly limited to pressure range below 10 GPa. Recent developments in synchrotron-based high-pressure single-crystal diffraction, which will be reviewed in this presentation, opened possibilities to extend these studies well into the pressure range beyond 50 GPa. I will discuss the latest

  20. Crystal structure and stability of Tl2CO3 at high pressures.

    PubMed

    Grzechnik, A; Friese, K

    2010-03-01

    The crystal structure of dithallium carbonate, Tl(2)CO(3) (C2/m, Z = 4), was investigated at pressures of up to 7.4 GPa using single-crystal X-ray diffraction in a diamond anvil cell. It is stable to at least 5.82 GPa. All atoms except for one of the O atoms lie on crystallographic mirror planes. At higher pressures, the material undergoes a phase transition that destroys the single crystal. PMID:20203393

  1. Improved resistance to wear and fatigue fracture in high pressure crystallized vitamin E-containing ultra-high molecular weight polyethylene

    PubMed Central

    Oral, Ebru; Beckos, Christine A. Godleski; Lozynsky, Andrew J.; Malhi, Arnaz S.; Muratoglu, Orhun K.

    2013-01-01

    Higher crystallinity and extended chain morphology are induced in ultra-high molecular weight polyethylene (UHMWPE) in the hexagonal phase at temperatures and pressures above the triple point, resulting in improved mechanical properties. In this study, we report the effects of the presence of a plasticizing agent, namely vitamin E (α-tocopherol), in UHMWPE during high pressure crystallization. We found that this new vitamin E-blended and high pressure crystallized UHMWPE (VEHPE) has improved fatigue strength and wear resistance compared to virgin high pressure crystallized (HP) UHMWPE. This suggested different mechanisms of wear reduction and fatigue crack propagation resistance in UHMWPE. PMID:19135247

  2. High pressure transformation of single-crystal graphite to form molecular carbon onions

    NASA Astrophysics Data System (ADS)

    Blank, V. D.; Denisov, V. N.; Kirichenko, A. N.; Kulnitskiy, B. A.; Martushov, S. Yu; Mavrin, B. N.; Perezhogin, I. A.

    2007-08-01

    Carbon onions were formed in graphite in the diamond anvil high pressure cell under axial pressure combined with shear deformation at room temperature. The onions were ranging in size from 1-2 nm to 1-2 µm and HREM studies have shown that the amount of their concentric shells tended to increase with pressure and deformation growth. Raman spectra were taken from large-size onions. Narrow bands found between 1400 and 1550 cm-1 correspond to fullerene-related carbon materials. The splitting of the pentagonal pinch mode 1446-1489 cm-1 is considered to be connected with the formation of heptagons.

  3. Effect of crystallization water on the structural and electrical properties of CuWO{sub 4} under high pressure

    SciTech Connect

    Wang, Li; Yan, Jiejuan; Liu, Cailong; Liu, Xizhe; Han, Yonghao E-mail: cc060109@qq.com; Gao, Chunxiao E-mail: cc060109@qq.com; Ke, Feng; Wang, Qinglin; Li, Yanchun; Ma, Yanzhang

    2015-11-16

    The effect of crystallization water on the structural and electrical properties of CuWO{sub 4} under high pressure has been investigated by in situ X-ray diffraction and alternating current impedance spectra measurements. The crystallization water was found to be a key role in modulating the structural stability of CuWO{sub 4} at high pressures. The anhydrous CuWO{sub 4} undergoes two pressure-induced structural transitions at 8.8 and 18.5 GPa, respectively, while CuWO{sub 4}·2H{sub 2}O keeps its original structure up to 40.5 GPa. Besides, the crystallization water makes the electrical transport behavior of anhydrous CuWO{sub 4} and CuWO{sub 4}·2H{sub 2}O quite different. The charge carrier transportation is always isotropic in CuWO{sub 4}·2H{sub 2}O, but anisotropic in the triclinic and the third phase of anhydrous CuWO{sub 4}. The grain resistance of CuWO{sub 4}·2H{sub 2}O is always larger than that of anhydrous CuWO{sub 4} in the entire pressure range. By analyzing the relaxation response, we found that the large number of hydrogen bonds can soften the grain characteristic frequency of CuWO{sub 4}·2H{sub 2}O over CuWO{sub 4} by one order of magnitude.

  4. Crystal lattice and band structure of the intermediate high-pressure phase of PbSe.

    PubMed

    Streltsov, S V; Manakov, A Yu; Vokhmyanin, A P; Ovsyannikov, S V; Shchennikov, V V

    2009-09-23

    In the present paper the results of fitting synchrotron diffraction data are obtained for the intermediate high-pressure phase (9.5 GPa) of the lead selenide based compound Pb(1-x)Sn(x)Se (x = 0.125)-an optoelectronic as well as a thermoelectric material-for two types of lattice symmetries Pnma (space group #62) and Cmcm (space group #63). Both lattice parameters and positions of atoms for the above mentioned structures have been used in calculations of the electron structure of high-pressure phases. The main difference between the electronic properties for Cmcm and Pnma structures established in electronic structure calculations is that in the first one the PbSe compound was found to be a metal, while in the second a small semiconductor gap (E(G) = 0.12 eV) was obtained. Moreover, the forces in the Cmcm structure are an order of magnitude larger than those calculated for the Pnma lattice. In the optimized, Pnma structure within a generalized gradient approximation (GGA), the band gap increases up to E(G) = 0.27 eV. The result coincides with the data on thermoelectric power and electrical resistance data pointing to a semiconductor gap of ∼0.2 eV at ∼9.5 GPa. Thus, the Pmna type of lattice seems to be a preferable version for the intermediate phase compared with the Cmcm one. PMID:21832372

  5. The influence of severe plastic deformation by high pressure torsion on structure and mechanical properties of Hadfield steel single crystals

    NASA Astrophysics Data System (ADS)

    Zakharova, G. G.; Astafurova, E. G.

    2010-07-01

    Hadfield steel single crystals have been deformed by high pressure torsion at room temperature (P=5GPa) for 1, 2, 3 revolutions. The resulting microstructure has been studied by means of transmission electron microscopy (TEM) and X-ray analysis. The size of fragments decreases with increasing number of revolutions due to interaction of slip dislocations, microbands and thin twins. As a result of severe plastic deformation, the microhardness of the Hadfield steel has been increased, and a portion of epsilon, α' martensite has been found.

  6. Structural and vibrational properties of single crystals of Scandia, Sc{sub 2}O{sub 3} under high pressure

    SciTech Connect

    Ovsyannikov, Sergey V. E-mail: sergey2503@gmail.com; Wenz, Michelle D.; Pakhomova, Anna S.; Dubrovinsky, Leonid; Bykova, Elena; Bykov, Maxim; Glazyrin, Konstantin; Liermann, Hanns-Peter

    2015-10-28

    We report the results of single-crystal X-ray diffraction and Raman spectroscopy studies of scandium oxide, Sc{sub 2}O{sub 3}, at ambient temperature under high pressure up to 55 and 28 GPa, respectively. Both X-ray diffraction and Raman studies indicated a phase transition from the cubic bixbyite phase (so-called C-Res phase) to a monoclinic C2/m phase (so-called B-Res phase) at pressures around 25–28 GPa. The transition was accompanied by a significant volumetric drop by ∼6.7%. In addition, the Raman spectroscopy detected a minor crossover around 10–12 GPa, which manifested in the appearance of new and disappearance of some Raman modes, as well as in softening of one Raman mode. We found the bulk modulus values of the both C-Res and B-Res phases as B{sub 0} = 198.2(3) and 171.2(1) GPa (for fixed B′ = 4), respectively. Thus, the denser high-pressure lattice of Sc{sub 2}O{sub 3} is much softer than the original lattice. We discuss possible mechanisms that might be responsible for the pronounced elastic softening in the monoclinic high-pressure phase in this “simple” oxide with an ultra-wide band gap.

  7. High-pressure synthesis, crystal structure and magnetic property of ilmenite-type FeGeO{sub 3}

    SciTech Connect

    Nakatsuka, Daisuke; Yoshino, Takashi; Kano, Jun; Hashimoto, Hideki; Nakanishi, Makoto; Takada, Jun; Fujii, Tatsuo

    2013-02-15

    We synthesized well-crystallized ilmenite-type FeGeO{sub 3} to investigate its structural and magnetic properties. Ilmenite-type FeGeO{sub 3} were synthesized by high-pressure synthesis technique using a Kawai-type multi-anvil apparatus. Their structural and magnetic properties were examined by XRD analysis with Rietveld refinement, transmission electron microscopy, Moessbauer spectroscopy and SQUID-magnetization measurements. The subsequent annealing after the high-pressure synthesis was effective to improve the crystallinity of the ilmenite-type FeGeO{sub 3}. The primary particle size of ilmenite-type FeGeO{sub 3} was {approx}15 nm. Some particles seemed to be covered with non- or poorly crystalline phase even after the annealing, and others showed a lamellar microstructure parallel to the (0 0 1) plane. Theilmenite-type FeGeO{sub 3} showed typical antiferromagnetic behavior with the Neel temperature of 79 K. - Graphical abstract: Crystal structure, transmission electron micrograph and temperature dependent susceptibility of ilmenite-type FeGeO{sub 3}. Highlights: Black-Right-Pointing-Pointer Ilmenite-type FeGeO{sub 3}, a novel polymorphism of FeGeO{sub 3} was successfully synthesized. Black-Right-Pointing-Pointer It was synthesized by using high pressure technique at 23.5 GPa at 500 Degree-Sign C. Black-Right-Pointing-Pointer Subsequent annealing in vacuum was effective to improve the crystallinity. Black-Right-Pointing-Pointer Its primary particle size was {approx}15 nm, and some grains had lamellar microstructure. Black-Right-Pointing-Pointer It showed typical antiferromagnetic behavior with the Neel temperature of 79 K.

  8. High-Pressure Synthesis and Crystal Structure of Ce4B14O27

    PubMed Central

    Hinteregger, Ernst; Perfler, Lukas; Huppertz, Hubert

    2013-01-01

    Ce4B14O27 was synthesized under conditions of 2.6 GPa and 750 °C in a Walker-type multianvil apparatus. The crystal structure was determined on the basis of single-crystal X-ray diffraction data, collected at room temperature, revealing that Ce4B14O27 is isotypic to La4B14O27. Ce4B14O27 crystallizes monoclinically with four formula units in the space group C2/c (No. 15) and the lattice parameters a = 1117.8(2), b = 640.9(2), c = 2531.7(5) pm, and β = 100.2(1)°. The three-dimensional boron-oxygen framework consists of [BO4]5– tetrahedra and trigonal-planar [BO3]3– groups. The structure contains two crystallographically different cerium ions. Furthermore, Raman spectroscopy was performed on single crystals of Ce4B14O27. PMID:25995523

  9. High-pressure high-temperature crystal growth of equiatomic rare earth stannides RENiSn and REPdSn

    NASA Astrophysics Data System (ADS)

    Heymann, Gunter; Heying, Birgit; Rodewald, Ute Ch.; Janka, Oliver; Huppertz, Hubert; Pöttgen, Rainer

    2016-04-01

    The two series of equiatomic rare earth (RE) stannides RENiSn and REPdSn were systematically studied with respect to high-pressure modifications. The normal-pressure (NP) low-temperature (LT) modifications were synthesized by arc-melting and subsequently treated under high-pressure (Pmax=11.5 GPa) and high-temperature (Tmax=1570 K) conditions in a Walker-type multi-anvil press. The pressure and temperature conditions were systematically varied in order to improve the crystallization conditions. The new ZrNiAl-type high-pressure modifications HP-RENiSn (RE=Sc, Y, La, Gd-Lu) and HP-REPdSn (RE=Y, Sm-Dy) were obtained in 80 mg quantities, several of them in X-ray pure form. Some of the REPdSn stannides with the heavy rare earth elements show high-temperature (HT) modifications. The structures of HP-ScNiSn, HP-GdNiSn, HP-DyNiSn (both ZrNiAl-type), NP-YbNiSn, and HT-ErPdSn (both TiNiSi-type) were refined from single crystal diffractometer data, indicating full ordering of the transition metal and tin sites. TiNiSi-type NP-EuPdSn transforms to MgZn2-type HP-EuPdSn: P63/mmc, a=588.5(2), c=917.0(3) pm, wR2=0.0769, 211 F2 values, 11 variables. The structure refinement indicated statistical occupancy of the palladium and tin sites on the tetrahedral network. The X-ray pure high-pressure phases were studied with respect to their magnetic properties. HP-YPdSn is a Pauli paramagnet. The susceptibility data of HP-TbNiSn, HP-DyNiSn, HP-GdPdSn, and HP-TbPdSn show experimental magnetic moments close to the free ion values of RE3+ and antiferromagnetic ordering at low temperature with the highest Néel temperature of 15.8 K for HP-TbPdSn. HP-SmPdSn shows the typical Van Vleck type behavior along with antiferromagnetic ordering at TN=5.1 K. HP-EuPdSn shows divalent europium and antiferromagnetic ordering at 8.9 K followed by a spin reorientation at 5.7 K.

  10. Use of a miniature diamond-anvil cell in high-pressure single-crystal neutron Laue diffraction.

    PubMed

    Binns, Jack; Kamenev, Konstantin V; McIntyre, Garry J; Moggach, Stephen A; Parsons, Simon

    2016-05-01

    The first high-pressure neutron diffraction study in a miniature diamond-anvil cell of a single crystal of size typical for X-ray diffraction is reported. This is made possible by modern Laue diffraction using a large solid-angle image-plate detector. An unexpected finding is that even reflections whose diffracted beams pass through the cell body are reliably observed, albeit with some attenuation. The cell body does limit the range of usable incident angles, but the crystallographic completeness for a high-symmetry unit cell is only slightly less than for a data collection without the cell. Data collections for two sizes of hexamine single crystals, with and without the pressure cell, and at 300 and 150 K, show that sample size and temperature are the most important factors that influence data quality. Despite the smaller crystal size and dominant parasitic scattering from the diamond-anvil cell, the data collected allow a full anisotropic refinement of hexamine with bond lengths and angles that agree with literature data within experimental error. This technique is shown to be suitable for low-symmetry crystals, and in these cases the transmission of diffracted beams through the cell body results in much higher completeness values than are possible with X-rays. The way is now open for joint X-ray and neutron studies on the same sample under identical conditions.

  11. Use of a miniature diamond-anvil cell in high-pressure single-crystal neutron Laue diffraction

    PubMed Central

    Binns, Jack; Kamenev, Konstantin V.; McIntyre, Garry J.; Moggach, Stephen A.; Parsons, Simon

    2016-01-01

    The first high-pressure neutron diffraction study in a miniature diamond-anvil cell of a single crystal of size typical for X-ray diffraction is reported. This is made possible by modern Laue diffraction using a large solid-angle image-plate detector. An unexpected finding is that even reflections whose diffracted beams pass through the cell body are reliably observed, albeit with some attenuation. The cell body does limit the range of usable incident angles, but the crystallographic completeness for a high-symmetry unit cell is only slightly less than for a data collection without the cell. Data collections for two sizes of hexamine single crystals, with and without the pressure cell, and at 300 and 150 K, show that sample size and temperature are the most important factors that influence data quality. Despite the smaller crystal size and dominant parasitic scattering from the diamond-anvil cell, the data collected allow a full anisotropic refinement of hexamine with bond lengths and angles that agree with literature data within experimental error. This technique is shown to be suitable for low-symmetry crystals, and in these cases the transmission of diffracted beams through the cell body results in much higher completeness values than are possible with X-rays. The way is now open for joint X-ray and neutron studies on the same sample under identical conditions. PMID:27158503

  12. Analysis of CZT crystals and detectors grown in Russia and the Ukraine by high-pressure Bridgman methods

    SciTech Connect

    H. Hermon; M. Schieber; R. B. James; E. Y. Lee; N. Yang; A. J. Antolak; D. H. Morse; C. Hackett; E. Tarver; N. N. P. Kolesnikov; Yu N. Ivanov; V. Komar; M. S. Goorsky; H. Yoon

    2000-01-10

    Sandia National Laboratories (SNL) is leading an effort to evaluate vertical high pressure Bridgman (VHPB) Cd{sub 1-x}Zn{sub x}Te (CZT) crystals grown in the former Soviet Union (FSU) (Ukraine and Russia), in order to study the parameters limiting the crystal quality and the radiation detector performance. The stoichiometry of the CZT crystals, with 0.04 < x < 0.25, has been determined by methods such as proton-induced X-ray emission (PIXE), X-ray diffraction (XRD), microprobe analysis and laser ablation ICP mass spectroscopy (LA-ICP/MS). Other methods such as triaxial double crystal x-ray diffraction (TADXRD), infrared transmission spectroscopy (IR), atomic force microscopy (AFM), thermoelectric emission spectroscopy (TEES) and laser induced transient charge technique (TCT) were also used to evaluate the material properties. The authors have measured the zinc distribution in a CZT ingot along the axial direction and also its homogeneity. The (Cd+Zn)/Te average ratio measured on the Ukraine crystals was 1.2, compared to the ratio of 0.9-1.06 on the Russian ingots. The IR transmission showed highly decorated grain boundaries with precipitates and hollow bubbles. Microprobe elemental analysis and LA-ICP/MS showed carbon precipitates in the CZT bulk and carbon deposits along grain boundaries. The higher concentration of impurities and the imperfect crystallinity lead to shorter electron and hole lifetimes in the range of 0.5--2 {micro}s and 0.1 {micro}s respectively, compared to 3--20 {micro}s and 1--7 {micro}s measured on US spectrometer grade CZT detectors. These results are consistent with the lower resistivity and worse crystalline perfection of these crystals, compared to US grown CZT. However, recently grown CZT from FSU exhibited better detector performance and good response to alpha particles.

  13. Experiments with phase transitions at very high pressure. [compressed solidifed gases, semiconductors, superconductors, and molecular crystals

    NASA Technical Reports Server (NTRS)

    Spain, I. L.

    1983-01-01

    Diamond cells were constructed for use to 1 Mbar. A refrigerator for cooling diamond cells was adapted for studies between 15 and 300 K. A cryostat for superconductivity studies between 1.5 to 300 K was constructed. Optical equipment was constructed for fluorescence, transmission, and reflectance studies. X-ray equipment was adapted for use with diamond cells. Experimental techniques were developed for X-ray diffraction studies using synchrotron radiation. AC susceptibility techniques were developed for detecting superconducting transitions. The following materials were studied: compressed solidified gases (Xe, Ar), semiconductors (Ge, Si, GaAs), superconductors (Nb3Ge, Nb3Si, Nb3As, CuCl), molecular crystals (I).

  14. Crystal grain growth during room temperature high pressure Martensitic alpha to omega transformation in zirconium

    SciTech Connect

    Velisavljevic, Nenad; Chesnut, Gary N; Stevens, Lewis L; Dattelbaum, Dana M

    2008-01-01

    Systematic increase in transition pressure with increase in interstitial impurities is observed for the martensitic {alpha} {yields} {omega} structural phase transition in Zr. Significant room temperature crystal grain growth is also observed for the two highest purity samples at this transition, while in the case of the lowest purity sample interstitial impurities obstruct grain growth even as the sample is heated to 1279 K. Our results show the importance of impurities in controlling structural phase stability and other mechanical properties associated with the {alpha} {yields} {omega} structural phase transition.

  15. First-principles study of MoHn (n =1, 2 and 3) crystal structures under high pressure

    NASA Astrophysics Data System (ADS)

    Feng, Xiaolei; Zhang, Jurong; Liu, Hanyu; Wang, Hui

    Hydrogen-rich materials have attracted attention recently, owing to their fascinating chemical bonding and potential high superconducting critical temperatures temperature. Inspired by the recent identification of polyhydrides of d metals and molybdenum hydride molecules with a high H content, we explored the crystal structures of MoHn (n = 1, 2, and 3) under high pressures using particle swarm optimization combined with first-principles electronic structure calculations. Several novel structures of MoH2 and MoH3 are predicted at high pressures. MoH is calculated to be stable at ambient pressure; at P >2.3 GPa the hexagonal phase of MoH2 becomes stable, and at 24 GPa it transforms into an orthorhombic structure, which remains stable up to 100 GPa. All three stable structures show metallic behavior under pressure. The calculated electronic properties suggest that the d-orbitals of the Mo atoms provide the dominant contribution to the density of states at the Fermi level, which is different from the density of states previously predicted for H-rich materials. The present results offer insights in understanding of chemical and physical properties in hydrogen-rich materials, especially in extreme environments.

  16. Single-crystal elasticity of natural Fe-bearing orthoenstatite across a high-pressure phase transition

    NASA Astrophysics Data System (ADS)

    Zhang, Jin S.; Bass, Jay D.

    2016-08-01

    Sound velocities and elastic moduli have been measured on Fe-bearing orthoenstatite (OEN) single crystals up to 12 GPa by Brillouin spectroscopy. The ambient adiabatic bulk modulus (Ks0) and shear modulus (G0) are determined to be 113(1) GPa and 75.9(7) GPa, respectively. A fourth-order finite strain fit to the data yields pressure derivatives of Ks0' = 8.8(1), Ks0″ = -0.68(6), G0' = 2.9(1), and G0″ = -0.40(2). These values are significantly higher than those for other major mantle minerals up to 10.5 GPa but lower than some previous measurements on OEN. A pronounced increase of shear anisotropy was observed at a pressure of 12.06(9) GPa, coinciding with a phase transition from orthoenstatite to a recently discovered high-pressure phase with space group P21/c. A high-pressure phase transition in OEN is unlikely to be the cause of the X discontinuity in the 250-325 km depth range. Rather, a change in seismic anisotropy would be expected to accompany the orthoenstatite-to-P21/c phase transition in the upper mantle at greater depths.

  17. Molecular dynamics and electronic spectrum of C{sub 60} crystals at high pressure

    SciTech Connect

    Meletov, K.P.; Kourouklis, G.; Christofilos, D.; Ves, S.

    1995-10-01

    The Raman scattering, luminescence, and absorption spectra of C{sub 60} single crystals at T= 300 K and pressures up to 15 GPa were measured. The pressure dependence of the frequencies of the Raman-active intramolecular optical phonons were determined and it was shown that phase transitions associated with orientational ordering of the molecules in a cubic lattice of fullerite occur at pressures of 0.4 and 2.4 GPa. The pressure shifts {partial_derivative}{omega}{sub i}/{partial_derivative}P and the Gruneisen parameters {gamma}{sub i}={minus} ({partial_derivative}{omega}{sub i}/{omega}{sub i})/({partial_derivative}V/V) of the intramolecular phonon modes in the orientationally ordered phase were determined. The magnitudes of the pressure shifts {partial_derivative}E/{partial_derivative}P of the luminescence and absorption spectra were measured. The deformation potential D= {partial_derivative}E{sub g}/{partial_derivative}ln(V{sub 0}/V) determined from these data is equal to 1.3{+-}0.1 eV. 33 refs., 6 figs., 1 tab.

  18. Elasticity of single-crystal superhydrous phase B at simultaneous high pressure-temperature conditions

    NASA Astrophysics Data System (ADS)

    Li, Xinyang; Mao, Zhu; Sun, Ningyu; Liao, Yifan; Zhai, Shuangmeng; Wang, Yi; Ni, Huaiwei; Wang, Jingyun; Tkachev, Sergey N.; Lin, Jung-Fu

    2016-08-01

    We investigated the combined effect of pressure and temperature on the elasticity of single-crystal superhydrous phase B (Shy-B) using Brillouin scattering and X-ray diffraction up to 12 GPa and 700 K. Using the obtained elasticity, we modeled the anisotropy of Shy-B along slab geotherms, showing that Shy-B has a low anisotropy and cannot be the major cause of the observed anisotropy in the region. Modeled velocities of Shy-B show that Shy-B will be shown as positive velocity anomalies at the bottom transition zone. Once Shy-B is transported to the topmost lower mantle, it will exhibit a seismic signature of lower velocities than topmost lower mantle. We speculate that an accumulation of hydrous phases, such as Shy-B, at the topmost lower mantle with a weight percentage of ~17-26% in the peridotite layer as subduction progresses could help explain the observed 2-3% low shear velocity anomalies in the region.

  19. Single-crystal elasticity of the deep-mantle magnesite at high pressure and temperature

    NASA Astrophysics Data System (ADS)

    Yang, Jing; Mao, Zhu; Lin, Jung-Fu; Prakapenka, Vitali B.

    2014-04-01

    Magnesite (MgCO3) is considered to be a major candidate carbon host in the Earth's mantle, and has been found to exist as an accessory mineral in carbonated peridotite and eclogite. Studying the thermal elastic properties of magnesite under relevant pressure-temperature conditions of the upper mantle is thus important for our understanding of the deep-carbon storage in the Earth's interior. Here we have measured the single-crystal elasticity of a natural magnesite using in situ Brillouin spectroscopy and X-ray diffraction in a diamond anvil cell up to 14 GPa at room temperature and up to 750 K at ambient pressure, respectively. Using the third-order Eulerian finite-strain equations to model the elasticity data, we have derived the aggregate adiabatic bulk, KS0, and shear moduli, G0, at ambient conditions: KS0=114.7 (±1.3) GPa and G0=69.9 (±0.6) GPa. The pressure derivatives of the bulk and shear moduli at 300 K are (∂KS/∂P)T=4.82 (±0.10) and (∂G/∂P)T=1.75 (±0.10), respectively, while their temperature derivatives at ambient pressure are (∂Ks/∂T)P=-24.0 (±0.2) MPa/K and (∂G/∂T)P=-14.8 (±0.7) MPa/K. Based on the thermal elastic modeling of the measured elastic constants along an expected normal upper-mantle geotherm and a cold subducting slab, magnesite exhibits compressional wave (VP) anisotropy of approximately 46-49% and shear wave (VS) splitting of 37-41% that are much larger than those of major constituent minerals in the Earth's upper mantle including olivine, pyroxene, and garnet. The modeled aggregate VP and VS velocity in moderately carbonated peridotite and eclogite containing approximately 10 wt.% magnesite (approximately 5 wt.% CO2) show minimal effects of magnesite on the seismic profiles of these rock assemblages at upper mantle conditions, suggesting that the presence of magnesite is likely difficult to be detected seismically. However, due to its unusually high VP and VS anisotropies, magnesite with strong preferred orientations

  20. Some recent advances in the design and the use of miniaturized droplet-based continuous process: applications in chemistry and high-pressure microflows.

    PubMed

    Lorber, Nicolas; Sarrazin, Flavie; Guillot, Pierre; Panizza, Pascal; Colin, Annie; Pavageau, Bertrand; Hany, Cindy; Maestro, Patrick; Marre, Samuel; Delclos, Thomas; Aymonier, Cyril; Subra, Pascale; Prat, Laurent; Gourdon, Christophe; Mignard, Emmanuel

    2011-03-01

    This mini-review focuses on two different miniaturizing approaches: the first one describes the generation and use of droplets flowing within a millifluidic tool as individual batch microreactors. The second one reports the use of high pressure microflows in chemistry. Millifluidics is an inexpensive, versatile and easy to use approach which is upscaled from microfluidics. It enables one to produce hierarchically organized multiple emulsions or particles with a good control over sizes and shapes, as well as to provide a convenient data acquisition platform dedicated to slow or rather fast chemical reactions, i.e., from hours to a few minutes. High-pressure resistant devices were recently fabricated and used to generate stable droplets from pressurized fluids such as supercritical fluid-liquid systems. We believe that supercritical microfluidics is a promising tool to develop sustainable processes in chemistry.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  2. High-pressure behavior of bromine confined in the one-dimensional channels of zeolite AlPO4-5 single crystals

    NASA Astrophysics Data System (ADS)

    Liu, Zhaodong; Yao, Zhen; Yao, Mingguang; Lv, Jiayin; Chen, Shuanglong; Li, Quanjun; Lv, Hang; Wang, Tianyi; Lu, Shuangchen; Liu, Ran; Liu, Bo; Liu, Jing; Chen, Zhiqiang; Zou, Bo; Cui, Tian; Liu, Bingbing

    2016-09-01

    We present a joint experimental and theoretical study on the high-pressure behavior of bromine confined in the one-dimensional (1D) nanochannels of zeolite AlPO4-5 (AFI) single crystals. Raman scattering experiments indicate that loading bromine into AFI single crystals can lead to the formation of bromine molecular chains inside the nanochannels of the crystals. High-pressure Raman and X-ray diffraction studies demonstrate that high pressure can increase the length of the confined bromine molecular chains and modify the inter- and intramolecular interactions of the molecules. The confined bromine shows a considerably different high-pressure behavior to that of bulk bromine. The pressure-elongated bromine molecular chains can be preserved when the pressure is reduced to ambient pressure. Theoretical simulations explain the experimental results obtained from the Raman spectroscopy and X-ray diffraction studies. Furthermore, we find that the intermolecular distance between confined bromine molecules gradually becomes comparable to the intramolecular bond length in bromine molecules upon compression. This may result in the dissociation of the bromine molecules and the formation of 1D bromine atomic chains at pressures above 24 GPa. Our study suggests that the unique nanoconfinement has a considerable effect on the high-pressure behavior of bromine, and the confined bromine species concomitantly enhance the structural stability of the host AFI single crystals.

  3. Water-Shale interactions in bench-top and high pressure/high temperature autoclave experiments: Identifying geochemical reaction controlling flow back water chemistry

    NASA Astrophysics Data System (ADS)

    Mickler, P. J.; Lu, J.; Nicot, J.

    2013-12-01

    An important side effect of hydraulic fracturing (HF) in shale gas wells is the production of saline flow-back water. This water often contains total dissolved soil (TDS) concentrations greater than 100,000 ppm which requires expensive treatment and disposal of the produced water. Possible origins of the high TDS content include: 1. Mixing of fresh HF-fluids with highly saline pore fluids in the targeted shale. 2. Migration and mixing of saline brines by newly-formed fractures into the HF-water from neighboring formations. 3. Water rock interactions between the targeted shale and HF-water that include mineral dissolution, pyrite oxidation buffered by carbonate dissolution and cation exchange in newly hydrated clay minerals.. These possibilities are not mutually exclusive and all may be operating to alter flow-back water chemistry. This study will examine geochemical reactions between a productive Gulf Coast shale and manufactured HF-waters using sealed bench top experiments and high temperature/high pressure autoclave experiments. The samples of the shale were collected from core material housed at The Bureau of Economic Geology collected from two wells. The manufactured HF-waters were produced by mixing NaCl, KCl and CaCl2 salts with De-ionized water at approximately 0, 2000 and 20,000 ppm. During experiments, elements that show large increases in aqueous concentrations are Na, Cl, Ca and SO4. Simultaneous increases in Na and Cl, coupled with high Cl/Br ratios, suggest halite dissolution rather than pore space brine is responsible for Na and Cl concentrations. Simultaneous increase in Ca and SO4 suggest anhydrite dissolution. (SEM imaging shows that anhydrite crystals are usually embedded with the framework mineral grains, rather than precipitated in pores during sample drying, which suggests mineral source of Ca and SO4, possibly for Na and Cl as well). Pyrite oxidation and calcium carbonate dissolution were not significant due to no decrease in pH and no

  4. Water-Shale interactions in bench-top and high pressure/high temperature autoclave experiments: Identifying geochemical reaction controlling flow back water chemistry

    NASA Astrophysics Data System (ADS)

    Molnar, I. L.; O'Carroll, D. M.; Willson, C. S.; Gerhard, J.

    2011-12-01

    An important side effect of hydraulic fracturing (HF) in shale gas wells is the production of saline flow-back water. This water often contains total dissolved soil (TDS) concentrations greater than 100,000 ppm which requires expensive treatment and disposal of the produced water. Possible origins of the high TDS content include: 1. Mixing of fresh HF-fluids with highly saline pore fluids in the targeted shale. 2. Migration and mixing of saline brines by newly-formed fractures into the HF-water from neighboring formations. 3. Water rock interactions between the targeted shale and HF-water that include mineral dissolution, pyrite oxidation buffered by carbonate dissolution and cation exchange in newly hydrated clay minerals.. These possibilities are not mutually exclusive and all may be operating to alter flow-back water chemistry. This study will examine geochemical reactions between a productive Gulf Coast shale and manufactured HF-waters using sealed bench top experiments and high temperature/high pressure autoclave experiments. The samples of the shale were collected from core material housed at The Bureau of Economic Geology collected from two wells. The manufactured HF-waters were produced by mixing NaCl, KCl and CaCl2 salts with De-ionized water at approximately 0, 2000 and 20,000 ppm. During experiments, elements that show large increases in aqueous concentrations are Na, Cl, Ca and SO4. Simultaneous increases in Na and Cl, coupled with high Cl/Br ratios, suggest halite dissolution rather than pore space brine is responsible for Na and Cl concentrations. Simultaneous increase in Ca and SO4 suggest anhydrite dissolution. (SEM imaging shows that anhydrite crystals are usually embedded with the framework mineral grains, rather than precipitated in pores during sample drying, which suggests mineral source of Ca and SO4, possibly for Na and Cl as well). Pyrite oxidation and calcium carbonate dissolution were not significant due to no decrease in pH and no

  5. Crystal chemistry of birefringent hydrogrossular

    NASA Astrophysics Data System (ADS)

    Antao, Sytle M.

    2015-06-01

    Crystal structure refinements of two fine-grained, massive, birefringent hydrogarnet samples from South Africa [1. green "jade" and 2. pink "jade"] were carried out with the Rietveld method, cubic space group and monochromatic synchrotron high-resolution powder X-ray diffraction (HRPXRD) data. Electron-microprobe analysis (EMPA) gave bulk compositions as follows: (1) (Ca2.997Mg0.003)Σ3{Al1.794Fe{0.196/3+}Cr{0.004/3+}Mn{0.003/3+}Ti{0.002/4+}}Σ2[(SiO4)2.851(O4H4)0.151]Σ3 and (2) (Ca2.993Mg0.007)Σ3{Al1.977Fe{0.020/3+}Mn{0.003/3+}Cr{0.001/3+}}Σ2[(SiO4)2.272(O4H4)0.730]Σ3. Their crystal structure was modeled well as indicated by the Rietveld refinement statistical indicators where the reduced χ2 and overall R ( F 2) values are 1.133 and 0.0467, respectively, for sample 1 and 1.308 and 0.0342 for sample 2. Two cubic phases are contained in each sample. For phase 1a in sample 1, the weight fraction (%), unit-cell parameter (Å), and O-H bond distance (Å) are as follows: 74.4(1), a = 11.88874(4), and O-H = 0.98(9); the corresponding data for phase 1b are 25.6(1), a = 11.9280(5), and O-H = 0.91(9). For phase 2a in sample 2, the corresponding data are 52.0(1), a = 12.0591(1), and O-H = 0.90(6); the corresponding data for phase 2b are 48.0(1), a = 11.9340(2), and O-H = 0.90(7). The anisotropic displacement ellipsoids for the O atoms show no unusual features and are not elongated along the "Si-O" bond direction, which is written as Z-O, because of the general formula, X3Y2Z3O12, for garnet. Phase 1a is near end-member grossular, ideally Ca3Al2Si3O12. The deficiencies of the site occupancy factors ( sofs) for the Si (=Z) site indicate that there are significant [O4H4]4- replacing [SiO4]4-. The Z-O distance is large in phase 1b, phases 2a, and 2b compared to a typical Z-O distance in anhydrous grossular or phase 1a. The H atoms occur in different environments around the vacant Z site in the two samples, and they may also bond to the O atoms surrounding the X and Y sites

  6. Magnetic Measurements of Superconducting KxFe2-ySe2 Single Crystals Under High Pressure

    NASA Astrophysics Data System (ADS)

    Miyoshi, K.; Kondo, M.; Morishita, K.; Takeuchi, J.

    Measurements of DC magnetization for single crystal specimens of KxFe2-ySe2 both under hydrostatic and uniaxial pressure have been performed using liquid Ar and NaCl as pressure transmitting media to generate hydrostatic and nearly uniaxial pressure, respectively. It has been found that TC is pressure independent below 2 GPa but decreases rapidly above 3 GPa under hydrostatic pressure, indicating that the bulk superconductivity disappears above 6 GPa. We have also observed a very weak diamagnetic response below ∽10 K for P≥6 GPa, suggesting that non-bulk superconductivity survives even under high pressure. On the other hand, TC is found to decrease rapidly above 1.5 GPa by the application of uniaxial pressure along c-axis, indicating that the lattice compression along c-axis suppresses the superconductivity more effectively. This suggests that c-axis lattice constant is an important factor to determine TC in KxFe2-ySe2.

  7. Crystal structures of (Mg1;#8722;x,Fex)SiO[subscript 3] postperovskite at high pressures

    SciTech Connect

    Yamanaka, Takamitsu; Hirose, Kei; Mao, Wendy L.; Meng, Yue; Ganesh, P.; Shulenburger, Luke; Shen, Guoyin; Hemley, Russell J.

    2012-03-15

    X-ray diffraction experiments on postperovskite (ppv) with compositions (Mg{sub 0.9}Fe{sub 0.1})SiO{sub 3} and (Mg{sub 0.6}Fe{sub 0.4})SiO{sub 3} at Earth core-mantle boundary pressures reveal different crystal structures. The former adopts the CaIrO{sub 3}-type structure with space group Cmcm, whereas the latter crystallizes in a structure with the Pmcm (Pmma) space group. The latter has a significantly higher density ({rho} = 6.119(1) g/cm{sup 3}) than the former ({rho} = 5.694(8) g/cm{sup 3}) due to both the larger amount of iron and the smaller ionic radius of Fe{sup 2+} as a result of an electronic spin transition observed by X-ray emission spectroscopy (XES). The smaller ionic radius for low-spin compared to high-spin Fe{sup 2+} also leads to an ordered cation distribution in the M1 and M2 crystallographic sites of the higher density ppv structure. Rietveld structure refinement indicates that approximately 70% of the total Fe{sup 2+} in that phase occupies the M2 site. XES results indicate a loss of 70% of the unpaired electronic spins consistent with a low spin M2 site and high spin M1 site. First-principles calculations of the magnetic ordering confirm that Pmcm with a two-site model is energetically more favorable at high pressure, and predict that the ordered structure is anisotropic in its electrical and elastic properties. These results suggest that interpretations of seismic structure in the deep mantle need to treat a broader range of mineral structures than previously considered.

  8. High-pressure microfluidics

    NASA Astrophysics Data System (ADS)

    Hjort, K.

    2015-03-01

    When using appropriate materials and microfabrication techniques, with the small dimensions the mechanical stability of microstructured devices allows for processes at high pressures without loss in safety. The largest area of applications has been demonstrated in green chemistry and bioprocesses, where extraction, synthesis and analyses often excel at high densities and high temperatures. This is accessible through high pressures. Capillary chemistry has been used since long but, just like in low-pressure applications, there are several potential advantages in using microfluidic platforms, e.g., planar isothermal set-ups, large local variations in geometries, dense form factors, small dead volumes and precisely positioned microstructures for control of reactions, catalysis, mixing and separation. Other potential applications are in, e.g., microhydraulics, exploration, gas driven vehicles, and high-pressure science. From a review of the state-of-art and frontiers of high pressure microfluidics, the focus will be on different solutions demonstrated for microfluidic handling at high pressures and challenges that remain.

  9. Benzene under high pressure: A story of molecular crystals transforming to saturated networks, with a possible intermediate metallic phase

    SciTech Connect

    Wen, Xiao-Dong; Hoffmann, Roald; Ashcroft, N. W.

    2011-01-01

    In a theoretical study, benzene is compressed up to 300 GPa. The transformations found between molecular phases generally match the experimental findings in the moderate pressure regime (<20 GPa): phase I (Pbca) is found to be stable up to 4 GPa, while phase II (P43212) is preferred in a narrow pressure range of 4–7 GPa. Phase III (P21/c) is at lowest enthalpy at higher pressures. Above 50 GPa, phase V (P21 at 0 GPa; P21/c at high pressure) comes into play, slightly more stable than phase III in the range of 50–80 GP, but unstable to rearrangement to a saturated, four-coordinate (at C), one-dimensional polymer. Actually, throughout the entire pressure range, crystals of graphane possess lower enthalpy than molecular benzene structures; a simple thermochemical argument is given for why this is so. In several of the benzene phases there nevertheless are substantial barriers to rearranging the molecules to a saturated polymer, especially at low temperatures. Even at room temperature these barriers should allow one to study the effect of pressure on the metastable molecular phases. Molecular phase III (P21/c) is one such; it remains metastable to higher pressures up to ~200 GPa, at which point it too rearranges spontaneously to a saturated, tetracoordinate CH polymer. At 300 K the isomerization transition occurs at a lower pressure. Nevertheless, there may be a narrow region of pressure, between P = 180 and 200 GPa, where one could find a metallic, molecular benzene state. We explore several lower dimensional models for such a metallic benzene. We also probe the possible first steps in a localized, nucleated benzene polymerization by studying the dimerization of benzene molecules. Several new (C6H6)2 dimers are predicted.

  10. In situ Raman and synchrotron X-ray diffraction study on crystallization of Choline chloride/Urea deep eutectic solvent under high pressure

    NASA Astrophysics Data System (ADS)

    Yuan, Chaosheng; Chu, Kunkun; Li, Haining; Su, Lei; Yang, Kun; Wang, Yongqiang; Li, Xiaodong

    2016-09-01

    Pressure-induced crystallization of Choline chloride/Urea (ChCl/Urea) deep eutectic solvent (DES) has been investigated by in-situ Raman spectroscopy and synchrotron X-ray diffraction. The results indicated that high pressure crystals appeared at around 2.6 GPa, and the crystalline structure was different from that formed at ambient pressure. Upon increasing the pressure, the Nsbnd H stretching modes of Urea underwent dramatic change after liquid-solid transition. It appears that high pressures may enhance the hydrogen bonds formed between ChCl and Urea. P versus T phase diagram of ChCl/Urea DES was constructed, and the crystallization mechanism of ChCl/Urea DES was discussed in view of hydrogen bonds.

  11. High pressure Raman and single crystal X-ray diffraction of the alkali/calcium carbonate, shortite

    NASA Astrophysics Data System (ADS)

    Williams, Q. C.; Vennari, C.; O'Bannon, E. F., III

    2015-12-01

    Raman and synchrotron-based single crystal x-ray diffraction data have been collected on shortite (Na2Ca2(CO3)3) up to 10 GPa at 300 K. Shortite is of geological importance due to its presence in the ground-mass of kimberlites, and the alkaline-/carbon-rich character of kimberlitic eruptions. This investigation focuses on shortite's high pressure behavior and is relevant to the behavior of alkali-carbonate systems within Earth's upper mantle. X-ray data demonstrate that shortite's symmetry remains stable at high pressures—retaining orthorhombic C crystal system (Amm2) up to 10 GPa; diffraction data show a 12% volume decrease from room pressure, and a bulk modulus of 71.0(3) GPa. These also demonstrate that the c-axis is twice as compressible as the a- and b-axes. This anisotropic compression is likely due to the orientation of the relatively stiff carbonate groups, a third of which are oriented close to the plane of the a- and b-axes, c axis compression primarily involves the compaction of the 9-fold coordinate sodium and calcium polyhedral. The two distinct carbonate sites within the unit cell give rise to two Raman symmetric stretching modes of the symmetric stretch; the carbonate group stretching vibration which is close to in plane with the a- and b-axes shifts at 3.75 cm-1/GPa as opposed to the carbonate groups which is closer to in plane with the b- and c-axes which shift at 4.25 cm-1/GPa. This furthers evidence for anisotropic compression observed using x-ray diffraction--as the carbonate in plane with the a- and b-axes is compressed, the strength of oxygen bonds along the c-axis with the cations increases, thus decreasing the pressure shift of the mode. The out of plane bending vibration shifts at -0.48 cm-1/GPa, indicating an enhanced interaction of the oxygens with the cations. The multiple in plane bending modes all shift positively, as do at the low frequency lattice modes, indicating that major changes in bonding do not occur up to 10 GPa. The data

  12. Phonon density of states of single-crystal SrF e2A s2 across the collapsed phase transition at high pressure

    NASA Astrophysics Data System (ADS)

    Wang, Y. Q.; Lu, P. C.; Wu, J. J.; Liu, J.; Wang, X. C.; Zhao, J. Y.; Bi, W.; Alp, E. E.; Park, C. Y.; Popov, D.; Jin, C. Q.; Sun, J.; Lin, J. F.

    2016-07-01

    To help our understanding of the structural and superconducting transitions in ferropnictides, partial phonon density of states (PDOS) of iron in a single-crystal SrF e2A s2 pnictide have been investigated from both out-of-plane and in-plane polarizations with respect to the basal plane of the crystal structure using nuclear resonant inelastic x-ray scattering in a high-pressure diamond anvil cell at ambient temperature. The partial PDOS of iron in the pnictide crystal changes dramatically at approximately 8 GPa, which can be associated with the tetragonal (T) to collapsed tetragonal (CT) isostructural transition as evidenced in high-pressure x-ray diffraction measurements and theoretical calculations. Across the T-CT phase transition, analysis of the PDOS spectra shows a rapid stiffening of the optical phonon modes and a dramatic increase of the Lamb-Mössbauer factor (fLM) and mean force constant which can be associated with the rapid decrease of the c axis and the anomalous expansion of the a axis. Theoretically calculated Fe partial PDOS and lattice parameters of SrF e2A s2 further reveal the strong correlation between the lattice parameters and phonons. Our results show that the T-CT transition can induce significant changes in the vibrational, elastic, and thermodynamic properties of SrF e2A s2 single crystal at high pressure.

  13. The crystal structure and crystal chemistry of fernandinite and corvusite

    USGS Publications Warehouse

    Evans, H.T.; Post, J.E.; Ross, D.R.; Nelen, J.A.

    1994-01-01

    Using type material of fernandinite from Minasragra, Peru, and corvusite from the Jack Claim, La Sal Mountains, Utah, the properties and crystal chemistry of these minerals have been determined by Rietveld analysis of the powder X-ray-diffraction patterns. The crystal structure of both species is isotypic with the V2O5 -type layer first found for ??-Ag0.68V2O5; it consists of chains of VO6 octahedra linked by opposite corners (parallel to b) condensed by edge-sharing to form the layer. The vanadium has average valence 4.8, and the resulting layer-charge is balanced by varying amounts of Ca, Na, and K in the interlayer region accompanied by labile water. This study has confirmed the validity of fernandinite as a unique mineral species. It is closely related to corvusite, from which it is distinguished on the basis of the dominant interlayer cation: Ca for fernandinite, Na for curvusite. -Authors

  14. High pressure single crystal x-ray and neutron powder diffraction study of the ferroelectric-paraelectric phase transition in PbTiO3

    NASA Astrophysics Data System (ADS)

    Al-Zein, A.; Bouvier, P.; Kania, A.; Levelut, C.; Hehlen, B.; Nassif, V.; Hansen, T. C.; Fertey, P.; Haines, J.; Rouquette, J.

    2015-12-01

    The results obtained by high pressure neutron powder diffraction and single-crystal x-ray diffraction for the P4mm-Pm \\bar{3} m phase transition in the prototype ferroelectric perovskite lead titanate are shown. Neutron diffraction is found to be strongly sensitive to the dipolar moment in the PbTiO3 unit cell due to the gradual reduction of the displacement of the Ti and O atoms from centrosymmetric positions in the cubic perovskite structure which exhibits anti-phase scattering of Pb, Ti and O atoms. From applying both techniques, the anomalously high Debye-Waller factor for the lead atoms confirms the disordered character of the cubic phase. High pressure single crystal x-ray diffraction also perfectly describes the ferroelectric-paraelectric transition and will be the technique of choice to solve higher pressure structures for PbTiO3.

  15. High-pressure synthesis and crystal structure of the lithium borate HP-LiB{sub 3}O{sub 5}

    SciTech Connect

    Neumair, Stephanie C.; Vanicek, Stefan; Kaindl, Reinhard; Toebbens, Daniel M.; Wurst, Klaus; Huppertz, Hubert

    2011-09-15

    The new lithium borate HP-LiB{sub 3}O{sub 5} was synthesized under high-pressure/high-temperature conditions of 6 GPa and 1050 deg. C in a multianvil press with a Walker-type module. The compound crystallizes in the space group Pnma (no. 62) with the lattice parameters a=829.7(2), b=759.6(2), and c=1726.8(4) pm (Z=16). The high-pressure compound HP-LiB{sub 3}O{sub 5} is built up from a three-dimensional network of BO{sub 4} tetrahedra and BO{sub 3} groups, which incorporates Li{sup +} ions in channels along the b-axis. Band assignments of measured IR- and Raman spectra were done via quantum-mechanical calculations. Additionally, the thermal behavior of HP-LiB{sub 3}O{sub 5} was investigated. - Graphical abstract: The new high-pressure compound HP-LiB{sub 3}O{sub 5} is built up from a three-dimensional network of BO4 tetrahedra and BO{sub 3} groups, which incorporates Li{sup +} ions in channels along the b-axis. In this paper, the synthesis, the crystal structure, and the properties of HP-LiB{sub 3}O{sub 5} are described. Highlights: > Synthesis of a new lithium borate with the composition HP-LiB{sub 3}O{sub 5} at high pressure. > In contrast to the non-centrosymmetric phase LiB{sub 3}O{sub 5}, this high-pressure phase is centrosymmetric. > First example of ternary alkali borates exhibiting threefold bridging oxygen atoms.

  16. [Recent advancement of photonic-crystal-based analytical chemistry].

    PubMed

    Chen, Yun; Guo, Zhenpeng; Wang, Jinyi; Chen, Yi

    2014-04-01

    Photonic crystals are a type of novel materials with ordered structure, nanopores/channels and optical band gap. They have hence important applications in physics, chemistry, biological science and engineering fields. This review summarizes the recent advancement of photonic crystals in analytical chemistry applications, with focus on sensing and separating fields happening in the nearest 5 years.

  17. Crystal chemistry of the natural vanadium bronzes

    USGS Publications Warehouse

    Evans, H.T.; Hughes, J.M.

    1990-01-01

    The crystal chemistry of the natural vanadium bronze minerals is reviewed on the basis of published information and new studies (mainly by X-ray powder-diffraction methods) using type material wherever possible. The known V bronze minerals are divided into three categories: 1) the hewettite group, 2) the straczekite group, 3) other structure types including navajoite, schubnelite, fervanite, shcherbinaite, bannermanite, and melanovanadite. All known structures associated with the fibrous V bronzes (fiber spacing 3.6 A??) can be considered as various lateral linkages (into sheets or networks) of only two types of polyvanadate chains: 1) a divanadate chain (V2O6)n consisting of alternating square pyramids, and 2) a tetravanadate chain (V4O12)n consisting of four highly condensed single octahedral chains. -from Authors

  18. Magnetocaloric effect in a dual-phase coupled LaFe11Si2 crystal prepared by a modified high-pressure zone-melting technique

    NASA Astrophysics Data System (ADS)

    Feng, Shutong; Fang, Yue; Zhai, Qijie; Luo, Zhiping; Zheng, Hongxing

    2016-10-01

    A modified high-pressure optical zone-melting technique was adopted to grow a rare-earth-based LaFe11Si2 crystal in the present work. Dual-phase coupled microstructure was obtained where aligned α(Fe) phase distributed in the La(Fe,Si)13 matrix. Magnetic measurements showed that the produced crystal underwent a second-order magnetic transition in the vicinity of 250 K. Under a magnetic field change of 30 kOe, the refrigeration capacity (RC) of the produced crystal reached up to 162 J/kg. It was confirmed that zone-melting crystal growth technique is an effective approach to strikingly enhance the magnetocaloric effect of La-Fe-Si refrigeration materials.

  19. High-Pressure Single-Crystal Structures of 3D Lead-Halide Hybrid Perovskites and Pressure Effects on their Electronic and Optical Properties.

    PubMed

    Jaffe, Adam; Lin, Yu; Beavers, Christine M; Voss, Johannes; Mao, Wendy L; Karunadasa, Hemamala I

    2016-04-27

    We report the first high-pressure single-crystal structures of hybrid perovskites. The crystalline semiconductors (MA)PbX3 (MA = CH3NH3 (+), X = Br(-) or I(-)) afford us the rare opportunity of understanding how compression modulates their structures and thereby their optoelectronic properties. Using atomic coordinates obtained from high-pressure single-crystal X-ray diffraction we track the perovskites' precise structural evolution upon compression. These structural changes correlate well with pressure-dependent single-crystal photoluminescence (PL) spectra and high-pressure bandgaps derived from density functional theory. We further observe dramatic piezochromism where the solids become lighter in color and then transition to opaque black with compression. Indeed, electronic conductivity measurements of (MA)PbI3 obtained within a diamond-anvil cell show that the material's resistivity decreases by 3 orders of magnitude between 0 and 51 GPa. The activation energy for conduction at 51 GPa is only 13.2(3) meV, suggesting that the perovskite is approaching a metallic state. Furthermore, the pressure response of mixed-halide perovskites shows new luminescent states that emerge at elevated pressures. We recently reported that the perovskites (MA)Pb(Br x I1-x )3 (0.2 < x < 1) reversibly form light-induced trap states, which pin their PL to a low energy. This may explain the low voltages obtained from solar cells employing these absorbers. Our high-pressure PL data indicate that compression can mitigate this PL redshift and may afford higher steady-state voltages from these absorbers. These studies show that pressure can significantly alter the transport and thermodynamic properties of these technologically important semiconductors. PMID:27163050

  20. High-Pressure Single-Crystal Structures of 3D Lead-Halide Hybrid Perovskites and Pressure Effects on their Electronic and Optical Properties

    PubMed Central

    2016-01-01

    We report the first high-pressure single-crystal structures of hybrid perovskites. The crystalline semiconductors (MA)PbX3 (MA = CH3NH3+, X = Br– or I–) afford us the rare opportunity of understanding how compression modulates their structures and thereby their optoelectronic properties. Using atomic coordinates obtained from high-pressure single-crystal X-ray diffraction we track the perovskites’ precise structural evolution upon compression. These structural changes correlate well with pressure-dependent single-crystal photoluminescence (PL) spectra and high-pressure bandgaps derived from density functional theory. We further observe dramatic piezochromism where the solids become lighter in color and then transition to opaque black with compression. Indeed, electronic conductivity measurements of (MA)PbI3 obtained within a diamond-anvil cell show that the material’s resistivity decreases by 3 orders of magnitude between 0 and 51 GPa. The activation energy for conduction at 51 GPa is only 13.2(3) meV, suggesting that the perovskite is approaching a metallic state. Furthermore, the pressure response of mixed-halide perovskites shows new luminescent states that emerge at elevated pressures. We recently reported that the perovskites (MA)Pb(BrxI1–x)3 (0.2 < x < 1) reversibly form light-induced trap states, which pin their PL to a low energy. This may explain the low voltages obtained from solar cells employing these absorbers. Our high-pressure PL data indicate that compression can mitigate this PL redshift and may afford higher steady-state voltages from these absorbers. These studies show that pressure can significantly alter the transport and thermodynamic properties of these technologically important semiconductors. PMID:27163050

  1. High-Pressure Single-Crystal Structures of 3D Lead-Halide Hybrid Perovskites and Pressure Effects on their Electronic and Optical Properties.

    PubMed

    Jaffe, Adam; Lin, Yu; Beavers, Christine M; Voss, Johannes; Mao, Wendy L; Karunadasa, Hemamala I

    2016-04-27

    We report the first high-pressure single-crystal structures of hybrid perovskites. The crystalline semiconductors (MA)PbX3 (MA = CH3NH3 (+), X = Br(-) or I(-)) afford us the rare opportunity of understanding how compression modulates their structures and thereby their optoelectronic properties. Using atomic coordinates obtained from high-pressure single-crystal X-ray diffraction we track the perovskites' precise structural evolution upon compression. These structural changes correlate well with pressure-dependent single-crystal photoluminescence (PL) spectra and high-pressure bandgaps derived from density functional theory. We further observe dramatic piezochromism where the solids become lighter in color and then transition to opaque black with compression. Indeed, electronic conductivity measurements of (MA)PbI3 obtained within a diamond-anvil cell show that the material's resistivity decreases by 3 orders of magnitude between 0 and 51 GPa. The activation energy for conduction at 51 GPa is only 13.2(3) meV, suggesting that the perovskite is approaching a metallic state. Furthermore, the pressure response of mixed-halide perovskites shows new luminescent states that emerge at elevated pressures. We recently reported that the perovskites (MA)Pb(Br x I1-x )3 (0.2 < x < 1) reversibly form light-induced trap states, which pin their PL to a low energy. This may explain the low voltages obtained from solar cells employing these absorbers. Our high-pressure PL data indicate that compression can mitigate this PL redshift and may afford higher steady-state voltages from these absorbers. These studies show that pressure can significantly alter the transport and thermodynamic properties of these technologically important semiconductors.

  2. Single-crystal diffraction at the Extreme Conditions beamline P02.2: procedure for collecting and analyzing high-pressure single-crystal data.

    PubMed

    Rothkirch, André; Gatta, G Diego; Meyer, Mathias; Merkel, Sébastien; Merlini, Marco; Liermann, Hanns Peter

    2013-09-01

    Fast detectors employed at third-generation synchrotrons have reduced collection times significantly and require the optimization of commercial as well as customized software packages for data reduction and analysis. In this paper a procedure to collect, process and analyze single-crystal data sets collected at high pressure at the Extreme Conditions beamline (P02.2) at PETRA III, DESY, is presented. A new data image format called `Esperanto' is introduced that is supported by the commercial software package CrysAlis(Pro) (Agilent Technologies UK Ltd). The new format acts as a vehicle to transform the most common area-detector data formats via a translator software. Such a conversion tool has been developed and converts tiff data collected on a Perkin Elmer detector, as well as data collected on a MAR345/555, to be imported into the CrysAlis(Pro) software. In order to demonstrate the validity of the new approach, a complete structure refinement of boron-mullite (Al5BO9) collected at a pressure of 19.4 (2) GPa is presented. Details pertaining to the data collections and refinements of B-mullite are presented. PMID:23955034

  3. Experimental evidence of bulk chemistry constraint on SiO2 solubility in clinopyroxene at high-pressure conditions

    NASA Astrophysics Data System (ADS)

    Kawasaki, Toshisuke; Osanai, Yasuhito

    2015-06-01

    We have experimentally confirmed that the solubility of SiO2 in clinopyroxene at ultrahigh-pressure metamorphic conditions is buffered by coesite and kyanite. The present findings were derived from high-pressure experiments on metapelite glass, powdered andesite and eclogite glass under anhydrous conditions. The metapelite glass and powdered andesite were recrystallised in boron nitride capsules at 8 GPa and 1100-1500 °C. The eclogite glass was heated in an AuPd capsule, both ends of which were welded, at 3 GPa and 1000 °C. Clinopyroxene nucleated from metapelite glass, the bulk composition of which is saturated in both SiO2 and Al2SiO5 components plotting within the Jd (Na,K)(Al,Cr)(Si,Ti)2O6-Qtz (Si,Ti)O2-Grt M3(Al,Cr)2(Si,Ti)3O12-Als (Al,Cr)2(Si,Ti)O5 tetrahedron (M = Fe, Mn, Mg, Ni, Zn, Ca), coexists with garnet, coesite and kyanite. The average excess silica content of the clinopyroxene ranges from 23.4 to 35.4 mol%. In contrast, an andesite experiment saturated in SiO2 but undersaturated in Al2SiO5 within the Jd-Qtz-Aug M(Si,Ti)O3-Grt tetrahedron produced clinopyroxene, garnet and coesite but no kyanite. The average excess silica in the clinopyroxene was 9.7-15.5 mol%, which is comparable to previous experimental data. Experiment on the eclogite glass with similar composition to andesite yielded clinopyroxene, garnet and coesite. An average excess silica content in clinopyroxene counts 6.4 mol%, which is much lower than that obtained from the andesite. The SiO2 content of clinopyroxene coexisting with garnet, coesite and kyanite is much higher than that of clinopyroxene coexisting with garnet and coesite without kyanite. Although the temperature dependence is unclear, the SiO2 solubility increases with pressure and Fe/(Fe+Mg). Clinopyroxene forms the solid solution series Jd-Es □0.5M0.5Al(Si,Ti)2O6 and Aug-Es, rather than Jd-Ts MAl2(Si,Ti)O6 and Es-Ts joins. Our experimental data suggest the probable existence of octahedral Si which may accompany the M2

  4. High-Pressure Geoscience Special Feature: Dynamic pressure-induced dendritic and shock crystal growth of ice VI

    NASA Astrophysics Data System (ADS)

    Lee, Geun Woo; Evans, William J.; Yoo, Choong-Shik

    2007-05-01

    Crystal growth mechanisms are crucial to understanding the complexity of crystal morphologies in nature and advanced technological materials, such as the faceting and dendrites found in snowflakes and the microstructure and associated strength properties of structural and icy planetary materials. In this article, we present observations of pressure-induced ice VI crystal growth, which have been predicted theoretically, but had never been observed experimentally to our knowledge. Under modulated pressure conditions in a dynamic-diamond anvil cell, rough single ice VI crystal initially grows into well defined octahedral crystal facets. However, as the compression rate increases, the crystal surface dramatically changes from rough to facet, and from convex to concave because of a surface instability, and thereby the growth rate suddenly increases by an order of magnitude. Depending on the compression rate, this discontinuous jump in crystal growth rate or "shock crystal growth" eventually produces 2D carpet-type fractal morphology, and moreover dendrites form under sinusoidal compression, whose crystal morphologies are remarkably similar to those predicted in theoretical simulations under a temperature gradient field. The observed strong dependence of the growth mechanism on compression rate, therefore, suggests a different approach to developing a comprehensive understanding of crystal growth dynamics.

  5. Synthesis and crystal structure of the high-pressure iron borate {alpha}-FeB{sub 2}O{sub 4}

    SciTech Connect

    Knyrim, Johanna S.; Huppertz, Hubert

    2008-08-15

    The high-pressure iron borate {alpha}-FeB{sub 2}O{sub 4} was synthesized under high-pressure and high-temperature conditions in a Walker-type multianvil apparatus at 7.5 GPa and 1100 deg. C. The monoclinic iron borate crystallizes with eight formula units in the space group P2{sub 1}/c with the lattice parameters a=715.2(2), b=744.5(2), c=862.3(2) pm, and {beta}=94.71(3){sup o}. The compound is built up exclusively from corner-sharing BO{sub 4}-tetrahedra, isotypic to the monoclinic phases {beta}-SrGa{sub 2}O{sub 4}, CaAl{sub 2}O{sub 4}-II, and CaGa{sub 2}O{sub 4}. Additionally, the structure is closely related to the orthorhombic compound BaFe{sub 2}O{sub 4}. The structure consists of layers of six-membered rings, which are interconnected to a three-dimensional network. The iron cations are coordinated by six and seven oxygen atoms. Next to synthesis and crystal structure of the new high-pressure borate, structural coherences to other structure types are discussed. - Abstract: High-pressure/high-temperature synthesis (multianvil technique) led to the new phase {alpha}-FeB{sub 2}O{sub 4}, which is exclusively built up from corner-sharing BO{sub 4}-tetrahedra, isotypic to the monoclinic phases {beta}-SrGa{sub 2}O{sub 4}, CaAl{sub 2}O{sub 4}-II, and CaGa{sub 2}O{sub 4}. Display Omitted.

  6. High-pressure crystal growth and magnetic and electrical properties of the quasi-one dimensional osmium oxide Na{sub 2}OsO{sub 4}

    SciTech Connect

    Shi, Y.G.; Guo, Y.F.; Yu, S.; Arai, M.; Belik, A.A.; Sato, A.; Yamaura, K.; Takayama-Muromachi, E.

    2010-02-15

    Na{sub 2}OsO{sub 4} crystals were grown by a NaCl flux method under high pressure. It crystallizes in the Ca{sub 2}IrO{sub 4}-type structure without having additional elements or metal vacancies, which are usually accommodated. It appears that Na{sub 2}OsO{sub 4} is a metal-stoichiometric Ca{sub 2}IrO{sub 4}-type compound never been synthesized to date. Na{sub 2}OsO{sub 4} has the octahedral environment of Os{sup 6+}O{sub 6} so that the electronic configuration is 5d{sup 2}, suggesting the magnetic S=1 ground state. However, magnetization, electrical resistivity, and specific heat measurements indicated that the non-magnetic S=0 state is much likely for Na{sub 2}OsO{sub 4} than the S=1 state. Band structure calculations and the structure analysis found that the disagreement is probably due to the statically uniaxial compression of the OsO{sub 6} octahedra, resulting in splitting of the t{sub 2{sub g}} band. - Graphical abstract: Na{sub 2}OsO{sub 4} crystals were grown by a NaCl flux method under high pressure. It crystallizes in the Ca{sub 2}IrO{sub 4}-type structure comprising infinite Os{sup 6+}O{sub 6} octahedra (5d{sup 2}) chains. The crystal growth, the crystal structure, and the magnetic and electrical properties are reported.

  7. High-pressure phase diagram and equation of state of solid helium from single-crystal X-ray diffraction to 23.3 GPa

    NASA Technical Reports Server (NTRS)

    Mao, H. K.; Hemley, R. J.; Jephcoat, A. P.; Finger, L. W.; Wu, Y.

    1988-01-01

    Single-crystal X-ray diffraction measurements have been performed on solid He-4 from 15.6 to 23.3 GPa at 300 K with synchrotron radiation. The diffraction patterns demonstrate that the structure of the solid is hexagonal close packed over this pressure-temperature range, contrary to both the interpretation of high-pressure optical studies and to theoretical predictions. The solid is more compressible than is indicated by equations of state calculated with recently determined helium pair potentials. The results suggest that a significant revision of current views of the phase diagram and energetics of dense solid helium is in order.

  8. High-Pressure Single-Crystal Neutron Scattering Study of Magnetic and Fe Vacancy Orders in (Tl,Rb)2Fe4Se5 Superconductor

    NASA Astrophysics Data System (ADS)

    Ye, Feng; Bao, Wei; Chi, Song-Xue; Antonio, M. dos Santos; Jamie, J. Molaison; Fang, Ming-Hu; Wang, Hang-Dong; Mao, Qian-Hui; Wang, Jin-Chen; Liu, Juan-Juan; Sheng, Jie-Ming

    2014-12-01

    The magnetic and iron vacancy orders in superconducting (Tl,Rb)2Fe4Se5 single-crystals are investigated by using a high-pressure neutron diffraction technique. Similar to the temperature effect, the block antiferromagnetic order gradually decreases upon increasing pressure while the Fe vacancy superstructural order remains intact before its precipitous disappearance at the critical pressure Pc = 8.3 GPa. Combined with previously determined Pc for superconductivity, our phase diagram under pressure reveals the concurrence of the block AFM order, the √5 × √5 iron vacancy order and superconductivity for the 245 superconductor. A synthesis of current experimental data in a coherent physical picture is attempted.

  9. From crystal chemistry to colloid stability

    NASA Astrophysics Data System (ADS)

    Gilbert, B.; Burrows, N.; Penn, R. L.

    2008-12-01

    Aqueous suspensions of ferrihydrite nanoparticles form a colloid with properties that can be understood using classical theories but which additionally exhibit the distinctive phenomenon of nanocluster formation. While use of in situ light and x-ray scattering methods permit the quantitative determination of colloid stability, interparticle interactions, and cluster or aggregate geometry, there are currently few approaches to predict the colloidal behavior of mineral nanoparticles. A longstanding goal of aqueous geochemistry is the rationalization and prediction of the chemical properties of hydrated mineral interfaces from knowledge of interface structure at the molecular scale. Because interfacial acid-base reactions typically lead to the formation of a net electrostatic charge at the surfaces of oxide, hydroxide, and oxyhydroxide mineral surfaces, quantitative descriptions of this behavior have the potential to permit the prediction of long-range interactions between mineral particles. We will evaluate the feasibility of this effort by constructing a model for surface charge formation for ferrihydrite that combines recent insights into the crystal structure of this phase and proposed methods for estimating the pKa of acidic surface groups. We will test the ability of this model to predict the colloidal stability of ferrihydrite suspensions as a function of solution chemistry.

  10. High-pressure effects on single crystals of electron-doped Pr2-xCexCuO4

    NASA Astrophysics Data System (ADS)

    Rotundu, C. R.; Struzhkin, V. V.; Somayazulu, M. S.; Sinogeikin, S.; Hemley, Russell J.; Greene, R. L.

    2013-01-01

    We present high-pressure diamond-anvil cell synchrotron x-ray, resistivity, and ac-susceptibility measurements on the electron-doped cuprate Pr2-xCexCuO4 to much higher pressures than previously reported. At 2.72 GPa between 88 and 98% of the superconducting T' phase of the optimally doped Pr1.85Ce0.15CuO4 transforms into the insulating phase T. With application of pressure, the T phase becomes more insulating, so we present here an example of electron doping in the T structure. The results have implications for the search for ambipolar high-Tc cuprate superconductors. The Tc of the remaining 2-12% T' phase is suppressed continuously from 22 to 18.5 K at about 14 GPa. Remarkably, the Tc of the overdoped Pr1.83Ce0.17CuO4 remains practically unchanged even at 32 GPa.

  11. Nanocrystalline diamond micro-anvil grown on single crystal diamond as a generator of ultra-high pressures

    NASA Astrophysics Data System (ADS)

    Samudrala, Gopi K.; Moore, Samuel L.; Velisavljevic, Nenad; Tsoi, Georgiy M.; Baker, Paul A.; Vohra, Yogesh K.

    2016-09-01

    By combining mask-less lithography and chemical vapor deposition (CVD) techniques, a novel two-stage diamond anvil has been fabricated. A nanocrystalline diamond (NCD) micro-anvil 30 μ m in diameter was grown at the center of a [100]-oriented, diamond anvil by utilizing microwave plasma CVD method. The NCD micro-anvil has a diamond grain size of 115 nm and micro-focused Raman and X-ray Photoelectron spectroscopy analysis indicate sp3-bonded diamond content of 72%. These CVD grown NCD micro-anvils were tested in an opposed anvil configuration and the transition metals osmium and tungsten were compressed to high pressures of 264 GPa in a diamond anvil cell.

  12. Experimental verification of the high pressure crystal structures in NH{sub 3}BH{sub 3}

    SciTech Connect

    Huang, Yanping; Huang, Xiaoli; Zhao, Zhonglong; Li, Wenbo; Jiang, Shuqing; Duan, Defang; Bao, Kuo; Zhou, Qiang; Liu, Bingbing; Cui, Tian

    2014-06-28

    A detailed high-pressure study on NH{sub 3}BH{sub 3} has been carried out using in situ synchrotron X-ray diffraction (XRD) and Raman scattering with a diamond anvil cell up to 20 and 33 GPa, respectively. The Rietveld refinement based on the XRD pattern and analysis of Raman data indicate two first-order phase transitions from the ambient pressure I4 mm structure (α-NH{sub 3}BH{sub 3}) to a high pressure Cmc2{sub 1} phase (β-NH{sub 3}BH{sub 3}) at 2.14 GPa, and further into a monoclinic P2{sub 1} (Z = 2) phase (γ-NH{sub 3}BH{sub 3}) at 9.67 GPa. Fitting the measured volumetric compression data to the third order Birch-Murnaghan equation of state reveals a bulk modulus of B{sub 0} = 9.9 ± 0.5 and 17.0 ± 3.0 GPa (with fixed B{sub 0}{sup ′} = 4) for the β-NH{sub 3}BH{sub 3} below and above 5 GPa, respectively. Still, with the splitting of the NBH rock mode in Raman experiment, it is concluded that a second-order isostructural phase transition occurs at 5 GPa. By analyzing the dihydrogen bonding framework, the origin of the isostructural phase transition is attributed to the number of dihydrogen bondings per molecule in the Cmc2{sub 1} phase increasing from 12 to 14 at 5 GPa.

  13. Synthesis, crystal structure, and electronic properties of high-pressure PdF2-type oxides MO2 (M = Ru, Rh, Os, Ir, Pt).

    PubMed

    Shirako, Yuichi; Wang, Xia; Tsujimoto, Yoshihiro; Tanaka, Kie; Guo, Yanfeng; Matsushita, Yoshitaka; Nemoto, Yoshihiro; Katsuya, Yoshio; Shi, Youguo; Mori, Daisuke; Kojitani, Hiroshi; Yamaura, Kazunari; Inaguma, Yoshiyuki; Akaogi, Masaki

    2014-11-01

    The polycrystalline MO2's (HP-PdF2-type MO2, M = Rh, Os, Pt) with high-pressure PdF2 compounds were successfully synthesized under high-pressure conditions for the first time, to the best of our knowledge. The crystal structures and electromagnetic properties were studied. Previously unreported electronic properties of the polycrystalline HP-PdF2-type RuO2 and IrO2 were also studied. The refined structures clearly indicated that all compounds crystallized into the HP-PdF2-type structure, M(4+)O(2-)2, rather than the pyrite-type structure, M(n+)(O2)(n-) (n < 4). The MO2 compounds (M = Ru, Rh, Os, Ir) exhibited metallic conduction, while PtO2 was highly insulating, probably because of the fully occupied t2g band. Neither superconductivity nor a magnetic transition was detected down to a temperature of 2 K, unlike the case of 3d transition metal chalcogenide pyrites. PMID:25337807

  14. Structural and elastic anisotropy of crystals at high pressures and temperatures from quantum mechanical methods: The case of Mg{sub 2}SiO{sub 4} forsterite

    SciTech Connect

    Erba, A. Dovesi, R.; Maul, J.; De La Pierre, M.

    2015-05-28

    We report accurate ab initio theoretical predictions of the elastic, seismic, and structural anisotropy of the orthorhombic Mg{sub 2}SiO{sub 4} forsterite crystal at high pressures (up to 20 GPa) and temperatures (up to its melting point, 2163 K), which constitute earth’s upper mantle conditions. Single-crystal elastic stiffness constants are evaluated up to 20 GPa and their first- and second-order pressure derivatives reported. Christoffel’s equation is solved at several pressures: directional seismic wave velocities and related properties (azimuthal and polarization seismic anisotropies) discussed. Thermal structural and average elastic properties, as computed within the quasi-harmonic approximation of the lattice potential, are predicted at high pressures and temperatures: directional thermal expansion coefficients, first- and second-order pressure derivatives of the isothermal bulk modulus, and P-V-T equation-of-state. The effect on computed properties of five different functionals, belonging to three different classes of approximations, of the density functional theory is explicitly investigated.

  15. Structural and elastic anisotropy of crystals at high pressures and temperatures from quantum mechanical methods: The case of Mg2SiO4 forsterite.

    PubMed

    Erba, A; Maul, J; De La Pierre, M; Dovesi, R

    2015-05-28

    We report accurate ab initio theoretical predictions of the elastic, seismic, and structural anisotropy of the orthorhombic Mg2SiO4 forsterite crystal at high pressures (up to 20 GPa) and temperatures (up to its melting point, 2163 K), which constitute earth's upper mantle conditions. Single-crystal elastic stiffness constants are evaluated up to 20 GPa and their first- and second-order pressure derivatives reported. Christoffel's equation is solved at several pressures: directional seismic wave velocities and related properties (azimuthal and polarization seismic anisotropies) discussed. Thermal structural and average elastic properties, as computed within the quasi-harmonic approximation of the lattice potential, are predicted at high pressures and temperatures: directional thermal expansion coefficients, first- and second-order pressure derivatives of the isothermal bulk modulus, and P-V-T equation-of-state. The effect on computed properties of five different functionals, belonging to three different classes of approximations, of the density functional theory is explicitly investigated. PMID:26026453

  16. Synthesis, crystal structure, and electronic properties of high-pressure PdF2-type oxides MO2 (M = Ru, Rh, Os, Ir, Pt).

    PubMed

    Shirako, Yuichi; Wang, Xia; Tsujimoto, Yoshihiro; Tanaka, Kie; Guo, Yanfeng; Matsushita, Yoshitaka; Nemoto, Yoshihiro; Katsuya, Yoshio; Shi, Youguo; Mori, Daisuke; Kojitani, Hiroshi; Yamaura, Kazunari; Inaguma, Yoshiyuki; Akaogi, Masaki

    2014-11-01

    The polycrystalline MO2's (HP-PdF2-type MO2, M = Rh, Os, Pt) with high-pressure PdF2 compounds were successfully synthesized under high-pressure conditions for the first time, to the best of our knowledge. The crystal structures and electromagnetic properties were studied. Previously unreported electronic properties of the polycrystalline HP-PdF2-type RuO2 and IrO2 were also studied. The refined structures clearly indicated that all compounds crystallized into the HP-PdF2-type structure, M(4+)O(2-)2, rather than the pyrite-type structure, M(n+)(O2)(n-) (n < 4). The MO2 compounds (M = Ru, Rh, Os, Ir) exhibited metallic conduction, while PtO2 was highly insulating, probably because of the fully occupied t2g band. Neither superconductivity nor a magnetic transition was detected down to a temperature of 2 K, unlike the case of 3d transition metal chalcogenide pyrites.

  17. X-ray photoelectron spectroscopy study of cubic boron nitride single crystals grown under high pressure and high temperature

    NASA Astrophysics Data System (ADS)

    Hou, Lixin; Chen, Zhanguo; Liu, Xiuhuan; Gao, Yanjun; Jia, Gang

    2012-02-01

    The defects, impurities and their bonding states of unintentionally doped cubic boron nitride (cBN) single crystals were investigated by X-ray photoelectron spectroscopy (XPS). The results indicate that nitrogen vacancy (VN) is the main native defect of the cBN crystals since the atomic ratio of B:N is always larger than 1 before Ar ion sputtering. After sputter cleaning, around 6 at% carbon, which probably comes from the growth chamber, remains in the samples as the main impurity. Carbon can substitute nitrogen lattice site and form the bonding states of Csbnd Bsbnd N or Csbnd B, which can be verified by the XPS spectra of C1s, B1s and N1s. The C impurity (acceptor) and N vacancy (donor) can compose the donor-acceptor complex to affect the electrical and optical properties of cBN crystals.

  18. Applications of the Cambridge Structural Database in organic chemistry and crystal chemistry.

    PubMed

    Allen, Frank H; Motherwell, W D Samuel

    2002-06-01

    The Cambridge Structural Database (CSD) and its associated software systems have formed the basis for more than 800 research applications in structural chemistry, crystallography and the life sciences. Relevant references, dating from the mid-1970s, and brief synopses of these papers are collected in a database, DBUse, which is freely available via the CCDC website. This database has been used to review research applications of the CSD in organic chemistry, including supramolecular applications, and in organic crystal chemistry. The review concentrates on applications that have been published since 1990 and covers a wide range of topics, including structure correlation, conformational analysis, hydrogen bonding and other intermolecular interactions, studies of crystal packing, extended structural motifs, crystal engineering and polymorphism, and crystal structure prediction. Applications of CSD information in studies of crystal structure precision, the determination of crystal structures from powder diffraction data, together with applications in chemical informatics, are also discussed.

  19. High Pressure Scanning Tunneling Microscopy and High PressureX-ray Photoemission Spectroscopy Studies of Adsorbate Structure,Composition and Mobility during Catalytic Reactions on A Model SingleCrystal

    SciTech Connect

    Montano, Max O.

    2006-01-01

    Our research focuses on taking advantage of the ability of scanning tunneling microscopy (STM) to operate at high-temperatures and high-pressures while still providing real-time atomic resolution images. We also utilize high-pressure x-ray photoelectron spectroscopy (HPXPS) to monitor systems under identical conditions thus giving us chemical information to compare and contrast with the structural and dynamic data provided by STM.

  20. The phase diagram of water at high pressures as obtained by computer simulations of the TIP4P/2005 model: the appearance of a plastic crystal phase.

    PubMed

    Aragones, J L; Conde, M M; Noya, E G; Vega, C

    2009-01-21

    In this work the high pressure region of the phase diagram of water has been studied by computer simulation by using the TIP4P/2005 model of water. Free energy calculations were performed for ices VII and VIII and for the fluid phase to determine the melting curve of these ices. In addition, molecular dynamics simulations were performed at high temperatures (440 K) observing the spontaneous freezing of the liquid into a solid phase at pressures of about 80,000 bar. The analysis of the structure obtained lead to the conclusion that a plastic crystal phase was formed. In the plastic crystal phase the oxygen atoms were arranged forming a body center cubic structure, as in ice VII, but the water molecules were able to rotate almost freely. Free energy calculations were performed for this new phase, and it was found that for TIP4P/2005 this plastic crystal phase is thermodynamically stable with respect to ices VII and VIII for temperatures higher than about 400 K, although the precise value depends on the pressure. By using Gibbs-Duhem simulations, all coexistence lines were determined, and the phase diagram of the TIP4P/2005 model was obtained, including ices VIII and VII and the new plastic crystal phase. The TIP4P/2005 model is able to describe qualitatively the phase diagram of water. It would be of interest to study if such a plastic crystal phase does indeed exist for real water. The nearly spherical shape of water makes possible the formation of a plastic crystal phase at high temperatures. The formation of a plastic crystal phase at high temperatures (with a bcc arrangements of oxygen atoms) is fast from a kinetic point of view occurring in about 2 ns. This is in contrast to the nucleation of ice Ih which requires simulations of the order of hundreds of ns. PMID:19283272

  1. The phase diagram of water at high pressures as obtained by computer simulations of the TIP4P/2005 model: the appearance of a plastic crystal phase.

    PubMed

    Aragones, J L; Conde, M M; Noya, E G; Vega, C

    2009-01-21

    In this work the high pressure region of the phase diagram of water has been studied by computer simulation by using the TIP4P/2005 model of water. Free energy calculations were performed for ices VII and VIII and for the fluid phase to determine the melting curve of these ices. In addition, molecular dynamics simulations were performed at high temperatures (440 K) observing the spontaneous freezing of the liquid into a solid phase at pressures of about 80,000 bar. The analysis of the structure obtained lead to the conclusion that a plastic crystal phase was formed. In the plastic crystal phase the oxygen atoms were arranged forming a body center cubic structure, as in ice VII, but the water molecules were able to rotate almost freely. Free energy calculations were performed for this new phase, and it was found that for TIP4P/2005 this plastic crystal phase is thermodynamically stable with respect to ices VII and VIII for temperatures higher than about 400 K, although the precise value depends on the pressure. By using Gibbs-Duhem simulations, all coexistence lines were determined, and the phase diagram of the TIP4P/2005 model was obtained, including ices VIII and VII and the new plastic crystal phase. The TIP4P/2005 model is able to describe qualitatively the phase diagram of water. It would be of interest to study if such a plastic crystal phase does indeed exist for real water. The nearly spherical shape of water makes possible the formation of a plastic crystal phase at high temperatures. The formation of a plastic crystal phase at high temperatures (with a bcc arrangements of oxygen atoms) is fast from a kinetic point of view occurring in about 2 ns. This is in contrast to the nucleation of ice Ih which requires simulations of the order of hundreds of ns.

  2. A Physical Chemistry Experiment in Polymer Crystallization Kinetics

    ERIC Educational Resources Information Center

    Singfield, Kathy L.; Chisholm, Roderick A.; King, Thomas L.

    2012-01-01

    A laboratory experiment currently used in an undergraduate physical chemistry lab to investigate the rates of crystallization of a polymer is described. Specifically, the radial growth rates of typical disc-shaped crystals, called spherulites, growing between microscope glass slides are measured and the data are treated according to polymer…

  3. SINGLE CRYSTAL DIFFRACTION OF SIDERITE UP TO 54 GPA AND HIGH PRESSURE-HIGH TEMPERATURE PHASES IN THE Fe-C-O SYSTEM (Invited)

    NASA Astrophysics Data System (ADS)

    Lavina, B.; Dera, P. K.; Downs, R. T.

    2009-12-01

    Phases in the Fe-C-O system are of interest for the deep carbon cycle, they might play an important role in buffering the mantle fO2. Carbon is also common in the fluid phases that greatly influence the Earth’s processes. The study of the high pressure behavior of siderite and of the phases synthesized after laser heating offers a good opportunity to illustrate the advantages and importance of single crystal diffraction in the high pressure science. The structure of siderite, FeCO3, has been refined up to 54 GPa across the spin pairing transition. Splitting of the diffraction peaks at the transition pressure provides unequivocal evidence of the sharpness of the spin crossover and of the absence of any intermediate volume and therefore of an intermediate spin state at ambient temperature. Diffraction intensities were collected in about 30 minutes at a bending magnet station (HPCAT, APS) and in about one minute at an insertion device station (GSECARS, APS). The quality of the refinement is unvaried in the investigated range, and the results obtained from the two different radiation and detectors are consistent. The refinements provide an accurate and robust determination of the dependence of bond distances and angles with pressure. Subtle structural rearrangements associated with the collapse of the octahedral cation size will be discussed. In situ laser heating is a very powerful method to study minerals at the actual P-T of the Earth’s deep interior. Overcoming the kinetic barriers required for bond breaking and atom diffusion, high pressure-high temperature phases may be synthesized. The analysis of high-pressure phases is very challenging. Diffraction patterns are usually of moderate quality and resolution, furthermore in addition to the sample, the pattern contains the contribution of other phases such as those used to insulate the anvils, to provide a pressure medium and a pressure marker. In several cases after laser heating, we observed phase transitions

  4. High-pressure synthesis and crystal structure analysis of NaMn{sub 2}O{sub 4} with the calcium ferrite-type structure

    SciTech Connect

    Akimoto, Junji . E-mail: j.akimoto@aist.go.jp; Awaka, Junji; Kijima, Norihito; Takahashi, Yasuhiko; Maruta, Yuichi; Tokiwa, Kazuyasu; Watanabe, Tsuneo

    2006-01-15

    Single crystals of a new sodium manganese oxide, NaMn{sub 2}O{sub 4}, were synthesized for the first time using a high-temperature and high-pressure technique. The NaMn{sub 2}O{sub 4} single crystal is black, has a needle shape, and crystallizes in the orthorhombic calcium ferrite-type structure, space group Pnam with a=8.9055(18)A, b=11.0825(22)A, c=2.8524(5)A, V=281.52(9)A{sup 3}, and Z=4. The structure was determined from a single-crystal X-ray study and refined to the conventional values R=0.041 and wR=0.034 for 1190 observed reflections. The framework structure is built up from edge-sharing chains of MnO{sub 6} octahedra that condense to form one-dimensional tunnels in which the sodium atoms are located. The Mn-O bond distance and bond valence analyses revealed the manganese valence Mn{sup 3+}/Mn{sup 4+} ordering in the two 'double rutile' chains of NaMn{sub 2}O{sub 4}.

  5. Crystal chemistry of thorium nitrates and chromates

    SciTech Connect

    Sigmon, Ginger E.; Burns, Peter C.

    2010-07-15

    The structures and infrared spectra of six novel thorium compounds are reported. Th(NO{sub 3}){sub 2}(OH){sub 2}(H{sub 2}O){sub 2} (1) crystallizes in space group C2/c, a=14.050(1), b=8.992(7), c=5.954(5) A, {beta}=101.014(2){sup o}. K{sub 2}Th(NO{sub 3}){sub 6} (2), P-3, a=13.606(1), c=6.641(6) A. (C{sub 12}H{sub 28}N){sub 2}Th(NO{sub 3}){sub 6} (3), P2{sub 1}/c, a=14.643(4), b=15.772(5), c=22.316(5) A, {beta}=131.01(1){sup o}. KTh(NO{sub 3}){sub 5}(H{sub 2}O){sub 2} (4), P2{sub 1}/c, a=10.070(8), b=12.731(9), c=13.231(8) A, {beta}=128.647(4){sup o}. Th(CrO{sub 4}){sub 2}(H{sub 2}O){sub 2} (5), P2{sub 1}/n, a=12.731(1), b=9.469(8), c=12.972(1) A, {beta}=91.793(2){sup o}. K{sub 2}Th{sub 3}(CrO{sub 4}){sub 7}(H{sub 2}O){sub 10} (6), Ama2, a=19.302(8), b=15.580(6), c=11.318(6) A. The coordination polyhedra about Th in these structures are diverse. Th is coordinated by 9 O atoms in 5 and 6, seven of which are from monodentate (CrO{sub 4}) tetrahedra and two are (H{sub 2}O). The Th in compound 1 is coordinated by ten O atoms, four of which are O atoms of two bidentate (NO{sub 3}) triangles and six of which are (OH) and (H{sub 2}O). In compounds 2, 3 and 4 the Th is coordinate by 12 O atoms. In 2 and 3 there are six bidentate (NO{sub 3}) triangles, and in 4 ten of the O atoms are part of five bidentate (NO{sub 3}) triangles and the others are (H{sub 2}O) groups. The structural units of these compounds consist of a chain of thorium and nitrate polyhedra (1), isolated thorium hexanitrate clusters (2, 3), an isolated thorium pentanitrate dihydrate cluster (4), and a sheet (6) and framework (5) of thorium and chromate polyhedra. These structures illustrate the complexity inherent in the crystal chemistry of Th. - Graphical Abstract: The structures and infrared spectra of four new Th nitrates and two Th chromates are reported. The coordination numbers of the Th cations range from nine to 12 in these compounds. Structural units consist of isolated clusters, chains, sheets and

  6. Crystal structure of magnesium dichloride decahydrate determined by X-ray and neutron diffraction under high pressure.

    PubMed

    Komatsu, Kazuki; Shinozaki, Ayako; Machida, Shinichi; Matsubayashi, Takuto; Watanabe, Mao; Kagi, Hiroyuki; Sano-Furukawa, Asami; Hattori, Takanori

    2015-02-01

    Magnesium dichloride decahydrate (MgCl2·10H2O) and its deuterated counterpart (MgCl2·10D2O) are identified for the first time by in-situ powder synchrotron X-ray and spallation neutron diffraction. These substances are crystallized from a previously unidentified nanocrystalline compound, which originates from an amorphous state at low temperature. A combination of a recently developed autoindexing procedure and the charge-flipping method reveals that the crystal structure of MgCl2·10H2O consists of an ABCABC··· sequence of Mg(H2O)6 octahedra. The Cl(-) anions and remaining water molecules unconnected to the Mg(2+) cations bind the octahedra, similar to other water-rich magnesium dichloride hydrates. The D positions in MgCl2·10D2O, determined by the difference Fourier methods using the neutron powder diffraction patterns at 2.5 GPa, show the features such as bifurcated hydrogen bonds and tetrahedrally coordinated O atoms, which were not found in other forms of magnesium chloride hydrates.

  7. Effects of gate insulator using high pressure annealing on the characteristics of solid phase crystallized polycrystalline silicon thin-film transistors

    NASA Astrophysics Data System (ADS)

    Kim, Moojin; Jin, GuangHai

    2009-04-01

    The oxidizing ambient was built using high pressure H2O vapor at 550 °C. For the solid phase crystallization (SPC) polycrystalline silicon (poly-Si) that is annealed for 1 h at 2 MPa, the oxide thickness is about 150 Å. The oxide layer is approximately 90 Å above the original surface of the poly-Si and 60 Å below the original surface. The oxide layer is used as the first gate insulator layer of thin-film transistors (TFTs). The heating at 550 °C with 2 MPa H2O vapor increased the carrier mobility from 17.6 cm2/V s of the conventional SPC process to 30.4 cm2/V s, and it reduced the absolute value of the threshold voltage (Vth) from 4.13 to 3.62 V. The subthreshold swing also decreased from 0.72 to 0.60 V/decade. This improvement is attributed mainly to the reduction in defect density at the oxide/poly-Si interface and in the poly-Si film by the high pressure annealing (HPA) process. Since the realization of excellent performance at the oxide/poly-Si interface and in poly-Si depends on the defect density, the poly-Si having the thermal oxide formed by a combined process of SPC and HPA may be well suited for fabrication of poly-Si TFTs for flat panel displays such as active matrix organic light emitting diodes.

  8. High-temperature treatment of In-doped CZT crystals grown by the high-pressure Bridgman method

    SciTech Connect

    Bolotnikov A.; Fochuk, P.; Nakonechnyi, I.; Kopach, O.; Verzhak, Ye.; Panchuk, O.; Komar, V.; Terzin, I.; Kutnij, V.; Rybka, A.; Nykoniuk, Ye.; Camarda, G.C.; Cui, Y.; Hossain, A.; Kim, K.H.; Yang, G.; James, R.B.

    2012-08-12

    We evaluated the effect of high-temperature treatment of Cd0.9Zn0.1Te:In single crystals using Hall-effect measurements, medium- and high-temperature annealing under various deviations from stoichiometry, and infra-red (IR) transmission microscopy Annealing at ~730 K sharply increased the electrical conductivity (by ~1-2 orders-of-magnitude). Plots of the temperature- and cadmium-pressure dependences of the electrical conductivity, carrier concentration, and mobility were obtained. Treating previously annealed Cd-samples under a Te overpressure at 1070 K allowed us to restore their resistance to its initial high values. The main difference in comparing this material with CdTe was its lowered electron density. We explained our results within the framework of Kröger’s theory of quasi-chemical reactions between point defects in solids.

  9. High-pressure single-crystal elasticity study of CO{sub 2} across phase I-III transition

    SciTech Connect

    Zhang, Jin S. Bass, Jay D.; Shieh, Sean R.; Dera, Przemyslaw; Prakapenka, Vitali

    2014-04-07

    Sound velocities and elastic moduli of solid single-crystal CO{sub 2} were measured at pressures up to 11.7(3) GPa by Brillouin spectroscopy. The aggregate adiabatic bulk modulus (K{sub S}), shear modulus (G), and their pressure derivatives for CO{sub 2} Phase I are K{sub S0} = 3.4(6) GPa, G{sub 0} = 1.8(2) GPa, (dK{sub S}/dP){sub 0} = 7.8(3), (dG/dP){sub 0} = 2.5(1), (d{sup 2}K{sub S}/dP{sup 2}){sub 0} = −0.23(3) GPa{sup −1}, and (d{sup 2}G/dP{sup 2}){sub 0} = −0.10(1) GPa{sup −1}. A small increase of elastic properties was observed between 9.8(1) and 10.5(3) GPa, in agreement with the CO{sub 2} I-III transition pressure determined from previous x-ray diffraction experiments. Above the transition pressure P{sub T}, we observed a mixture dominated by CO{sub 2}-I, with minor CO{sub 2}-III. The CO{sub 2}-I + III mixture shows slightly increased sound velocities compared to pure CO{sub 2}-I. Elastic anisotropy calculated from the single-crystal elasticity tensor exhibits a decrease with pressure beginning at 7.9(1) GPa, which is lower than P{sub T}. Our results coincide with recent X-ray Raman observations, suggesting that a pressure-induced electronic transition is related to local structural and optical changes.

  10. High-Pressure Single-Crystal Neutron Scattering Study of Magnetic and Fe Vacancy Orders in (Tl,Rb)2 Fe4 Se5 Superconductor

    DOE PAGESBeta

    Ye, Feng; Bao, Wei; Chi, Song-Xue; Santos, Antonio M. dos; Molaison, Jamie J.; Fang, Ming-Hu; Wang, Hang-Dong; Mao, Qian-Hui; Wang, Jin-Chen; Liu, Juan-Juan; et al

    2014-12-01

    We investigate the magnetic and iron vacancy orders in superconducting (Tl,Rb)2Fe4Se5 single-crystals by using a high-pressure neutron diffraction technique. Similar to the temperature effect, the block antiferromagnetic order gradually decreases upon increasing pressure while the Fe vacancy superstructural order remains intact before its precipitous disappearance at the critical pressure Pc = 8.3 GPa. Combined with previously determined Pc for superconductivity, our phase diagram under pressure reveals the concurrence of the block AFM order, the √5 × √5 iron vacancy order and superconductivity for the 245 superconductor. Lastly, a synthesis of current experimental data in a coherent physical picture is attempted.

  11. Relaxation of the normal electrical resistivity induced by high-pressure in strongly underdoped YBa2Cu3O7-δ single crystals

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

    We investigate the relaxation of the normal electrical resistivity, induced by high-pressure in YBa2Cu3O6.45 single crystals. It is determined that the pressure affects to the phase composition of the sample. Under pressure phases with different (but similar) critical temperatures form. It is determined that the application-removal pressure process is completely reversible. Above Tc the temperature dependence of the resistivity in the layers' plane at different hydrostatic pressures can be approximated with high accuracy with the scattering of electrons by phonons model. With increasing pressure, the residual resistance is reduced and the contribution of intraband s-s scattering increases. Additionally, the role of the interband s-d scattering and the Debye temperature is enhanced.

  12. Development of a Fluid-Particle Model in Simulating the Motion of External Solidified Crystals and the Evolution of Defect Bands in High-Pressure Die Casting

    NASA Astrophysics Data System (ADS)

    Bi, Cheng; Xiong, Shoumei; Li, Xiaobo; Guo, Zhipeng

    2016-04-01

    A numerical fluid-particle model was developed to simulate the motion of external solidified crystals (ESCs) in the melt during the filling process of high-pressure die casting (HPDC). Simulation results on a tensile bar casting with two types of ingates (semi-circle and circle) revealed that for a long time scale the ESCs tended to distribute in a ring pattern around the specimen center, whereas for a short time scale the ESC distribution changed constantly from the ring pattern to either the center pattern or the ring-center pattern. It was proposed that the defect bands would form at these areas where two solidification fronts met (where solidification shrinkage occurred), including one originating from the skin layer of the specimen and the other from the ESC region. Accordingly, three types of defect band patterns, which were commonly observed in HPDC experiment, could be successfully simulated and explained using this model.

  13. Adsorption Device Based on a Langatate Crystal Microbalance for High Temperature High Pressure Gas Adsorption in Zeolite H-ZSM-5.

    PubMed

    Ding, Wenjin; Baracchini, Giulia; Klumpp, Michael; Schwieger, Wilhelm; Dittmeyer, Roland

    2016-01-01

    We present a high-temperature and high-pressure gas adsorption measurement device based on a high-frequency oscillating microbalance (5 MHz langatate crystal microbalance, LCM) and its use for gas adsorption measurements in zeolite H-ZSM-5. Prior to the adsorption measurements, zeolite H-ZSM-5 crystals were synthesized on the gold electrode in the center of the LCM, without covering the connection points of the gold electrodes to the oscillator, by the steam-assisted crystallization (SAC) method, so that the zeolite crystals remain attached to the oscillating microbalance while keeping good electroconductivity of the LCM during the adsorption measurements. Compared to a conventional quartz crystal microbalance (QCM) which is limited to temperatures below 80 °C, the LCM can realize the adsorption measurements in principle at temperatures as high as 200-300 °C (i.e., at or close to the reaction temperature of the target application of one-stage DME synthesis from the synthesis gas), owing to the absence of crystalline-phase transitions up to its melting point (1,470 °C). The system was applied to investigate the adsorption of CO2, H2O, methanol and dimethyl ether (DME), each in the gas phase, on zeolite H-ZSM-5 in the temperature and pressure range of 50-150 °C and 0-18 bar, respectively. The results showed that the adsorption isotherms of these gases in H-ZSM-5 can be well fitted by Langmuir-type adsorption isotherms. Furthermore, the determined adsorption parameters, i.e., adsorption capacities, adsorption enthalpies, and adsorption entropies, compare well to literature data. In this work, the results for CO2 are shown as an example. PMID:27585356

  14. Bench-Scale Development of a Hot Carbonate Absorption Process with Crystallization-Enabled High-Pressure Stripping for Post-Combustion CO{sub 2} Capture

    SciTech Connect

    Lu, Yongqi; DeVries, Nicholas; Ruhter, David; Manoranjan, Sahu; Ye, Qing; Ye, Xinhuai; Zhang, Shihan; Chen, Scott; Li, Zhiwei; O'Brien, Kevin

    2014-03-31

    A novel Hot Carbonate Absorption Process with Crystallization-Enabled High-Pressure Stripping (Hot-CAP) has been developed by the University of Illinois at Urbana-Champaign and Carbon Capture Scientific, LLC in this three-year, bench-scale project. The Hot-CAP features a concentrated carbonate solution (e.g., K{sub 2}CO{sub 3}) for CO{sub 2} absorption and a bicarbonate slurry (e.g., KHCO{sub 3}) for high-pressure CO{sub 2} stripping to overcome the energy use and other disadvantages associated with the benchmark monoethanolamine (MEA) process. The project was aimed at performing laboratory- and bench-scale experiments to prove its technical feasibility and generate process engineering and scale-up data, and conducting a techno-economic analysis (TEA) to demonstrate its energy use and cost competitiveness over MEA. To meet project goals and objectives, a combination of experimental, modeling, process simulation, and economic analysis studies were applied. Carefully designed and intensive experiments were conducted to measure thermodynamic and reaction engineering data relevant to four major unit operations in the Hot-CAP (i.e., CO{sub 2} absorption, CO{sub 2} stripping, bicarbonate crystallization, and sulfate reclamation). The rate promoters that could accelerate the CO{sub 2} absorption rate into the potassium carbonate/bicarbonate (PCB) solution to a level greater than that into the 5 M MEA solution were identified, and the superior performance of CO{sub 2} absorption into PCB was demonstrated in a bench-scale packed-bed column. Kinetic data on bicarbonate crystallization were developed and applied for crystallizer design and sizing. Parametric testing of high-pressure CO{sub 2} stripping with concentrated bicarbonate-dominant slurries at high temperatures ({>=}140{degrees}C) in a bench-scale stripping column demonstrated lower heat use than with MEA. The feasibility of a modified process for combining SO{sub 2} removal with CO{sub 2} capture was preliminarily

  15. High-pressure synthesis, crystal structure, and unusual valence state of novel perovskite oxide CaCu3Rh4O12.

    PubMed

    Yamada, Ikuya; Ochi, Mikiko; Mizumaki, Masaichiro; Hariki, Atsushi; Uozumi, Takayuki; Takahashi, Ryoji; Irifune, Tetsuo

    2014-07-21

    A novel perovskite oxide, CaCu3Rh4O12, has been synthesized under high-pressure and high-temperature conditions (15 GPa and 1273 K). Rietveld refinement of synchrotron X-ray powder diffraction data indicates that this compound crystallizes in a cubic AA'3B4O12-type perovskite structure. Synchrotron X-ray absorption and photoemission spectroscopy measurements reveal that the Cu and Rh valences are nearly trivalent. The spectroscopic analysis based on calculations suggests that the appropriate ionic model of this compound is Ca(2+)Cu(∼2.8+)3Rh(∼3.4+)4O12, as opposed to the conventional Ca(2+)Cu(2+)3Rh(4+)4O12. The uncommon valence state of this compound is attributed to the relative energy levels of the Cu 3d and Rh 4d orbitals, in which the large crystal-field splitting energy of the Rh 4d orbitals is substantial.

  16. High-pressure crystal growth and magnetic and electrical properties of the quasi-one dimensional osmium oxide Na{sub 2}OsO{sub 4}.

    SciTech Connect

    Shi, Y. G.; Guo, Y. F.; Yu, S.; Arai, M.; Belik, A. A.; Sato, A.; Yamaura, K.; Takayama-Muromachi, E.; Varga, T.; Mitchell, J. F.; Materials Science Division; National Inst. for Materials Science; JST, Transformative Research Project on Iron Pnictides; Hokkaido Univ.

    2010-02-01

    Na{sub 2}OsO{sub 4} crystals were grown by a NaCl flux method under high pressure. It crystallizes in the Ca{sub 2}IrO{sub 4}-type structure without having additional elements or metal vacancies, which are usually accommodated. It appears that Na{sub 2}OsO{sub 4} is a metal-stoichiometric Ca{sub 2}IrO{sub 4}-type compound never been synthesized to date. Na{sub 2}OsO{sub 4} has the octahedral environment of Os{sup 6+}O{sub 6} so that the electronic configuration is 5d{sup 2}, suggesting the magnetic S=1 ground state. However, magnetization, electrical resistivity, and specific heat measurements indicated that the non-magnetic S=0 state is much likely for Na{sub 2}OsO{sub 4} than the S=1 state. Band structure calculations and the structure analysis found that the disagreement is probably due to the statically uniaxial compression of the OsO{sub 6} octahedra, resulting in splitting of the t{sub 2{sub g}} band.

  17. On the induction of homogeneous bulk crystallization in Eu-doped calcium aluminosilicate glass by applying simultaneous high pressure and temperature

    NASA Astrophysics Data System (ADS)

    Muniz, R. F.; de Ligny, D.; Le Floch, S.; Martinet, C.; Rohling, J. H.; Medina, A. N.; Sandrini, M.; Andrade, L. H. C.; Lima, S. M.; Baesso, M. L.; Guyot, Y.

    2016-06-01

    From initial calcium aluminosilicate glass, transparent glass-ceramics have been successfully synthesized under simultaneous high pressure and temperature (SHPT). Possible homogeneous volumetric crystallization of this glassy system, which was not achieved previously by means of conventional heat treatment, has been put in evidence with a SHPT procedure. Structural, mechanical, and optical properties of glass and glass-ceramic obtained were investigated. Raman spectroscopy and X-ray diffraction allowed to identify two main crystalline phases: merwinite [Ca3Mg(SiO4)2] and diopside [CaMgSi2O6]. A Raman scanning profile showed that the formation of merwinite is quite homogeneous over the bulk sample. However, the sample surface also contains significant diopside crystals. Instrumented Berkovich nanoindentation was applied to determine the effect of SHPT on hardness from glass to glass-ceramic. For Eu-doped samples, the broadband emission due to 4f65d1 → 4f7 transition of Eu2+ was studied in both host systems. Additionally, the 5D0 → 7FJ transition of Eu3+ was used as an environment probe in the pristine glass and the glass-ceramic.

  18. High-pressure synthesis and crystal structure of the mixed-valent titanium borate Ti{sub 5}B{sub 12}O{sub 26}

    SciTech Connect

    Haberer, Almut; Huppertz, Hubert

    2009-03-15

    The new titanium borate was synthesized under high-pressure/high-temperature conditions in a Walker-type multianvil apparatus at 7.5 GPa and 1350 deg. C. Ti{sub 5}B{sub 12}O{sub 26} is built up exclusively from corner-sharing BO{sub 4}-tetrahedra and shows a structural relation to the Zintl phase NaTl. Consisting of B{sub 12}O{sub 26}-clusters as fundamental building blocks, the structure of Ti{sub 5}B{sub 12}O{sub 26} can be described via two interpenetrating diamond structures as in NaTl, where each atom corresponds to one B{sub 12}O{sub 26}-cluster. The tetragonal titanium borate crystallizes with eight formula units in the space group I4{sub 1}/acd and exhibits lattice parameters of a=1121.1(2) pm and c=2211.5(4) pm. Ti{sub 5}B{sub 12}O{sub 26} is a mixed-valent compound with Ti{sup III} and Ti{sup IV} cations. The environment of the titanium cations, as well as charge distribution calculations, leads us to the assumption that Ti{sup III} and Ti{sup IV} are located on different crystallographic sites. - Graphical abstract: High-pressure/high-temperature synthesis (multianvil technique) led to the first mixed-valent titanium borate Ti{sub 5}B{sub 12}O{sub 26}, which is exclusively built up from corner-sharing BO{sub 4}-tetrahedra, showing structural relations to the Zintl phase NaTl.

  19. High-pressure synthesis, crystal structure and magnetic properties of double perovskite oxide Ba{sub 2}CuOsO{sub 6}

    SciTech Connect

    Feng, Hai L.; Arai, Masao; Matsushita, Yoshitaka; Tsujimoto, Yoshihiro; Yuan, Yahua; Sathish, Clastin I.; He, Jianfeng; Tanaka, Masahiko; Yamaura, Kazunari

    2014-09-15

    A new compositional double perovskite oxide Ba{sub 2}CuOsO{sub 6} was synthesized under high-pressure (6 GPa) and high-temperature (1500 °C) conditions. The polycrystalline Ba{sub 2}CuOsO{sub 6} was characterized by synchrotron X-ray diffraction, thermogravimetric analysis, and magnetic susceptibility, isothermal magnetization, and specific heat measurements. The oxide crystallizes in a double-perovskite structure with an I4/m space group, in which Os(VI) and Cu(II) are ordered in the perovskite B-site. Ba{sub 2}CuOsO{sub 6} is electrically insulating with an activation energy of 0.813(2) eV and shows antiferromagnetic-like characteristics at temperatures of ∼55 K and ∼70 K. The results of the first-principle calculation suggested that the spin–orbit interaction of Os(VI) plays a substantial role in the insulating state. The Jahn–Teller distortion of CuO{sub 6} octahedra influences the magnetic characteristics with regard to possible two-dimensional magnetic correlations. - Graphical abstract: A new compositional double perovskite oxide Ba{sub 2}CuOsO{sub 6} synthesized by a high-pressure (6 GPa) and high-temperature (1500 °C) method. - Highlights: • A new compositional double perovskite oxide Ba{sub 2}CuOsO{sub 6} was synthesized. • Ba{sub 2}CuOsO{sub 6} is electrically insulating and antiferromagnetic below ∼70 K. • The Jahn–Teller distortion of CuO{sub 6} has relevance to possible magnetic anisotropy.

  20. First-principles high-pressure unreacted equation of state and heat of formation of crystal 2,6-diamino-3, 5-dinitropyrazine-1-oxide (LLM-105)

    SciTech Connect

    Manaa, M. Riad Kuo, I-Feng W.; Fried, Laurence E.

    2014-08-14

    We report dispersion-corrected density functional theoretical calculations of the unreacted equation of state (EOS) of crystal 2,6-diamino-3, 5-dinitropyrazine-1-oxide (LLM-105) under hydrostatic compression of up to 45 GPa. Convergence tests for k-points sampling in the Brillouin zone show that a 3 × 1 × 2 mesh is required to reproduce the X-ray crystal structure at ambient conditions, and we confirm our finding with a separate supercell calculation. Our high-pressure EOS yields a bulk modulus of 19.2 GPa, and indicates a tendency towards anisotropic compression along the b lattice vector due to molecular orientations within the lattice. We find that the electronic energy band gap decreases from a semiconductor type of 1.3 eV at 0 GPa to quasi-metallic type of 0.6 eV at 45 GPa. The extensive intermolecular hydrogen bonds involving the oxide (–NO) and dioxide (–NO{sub 2}) interactions with the amine (–NH{sub 2}) group showed enhanced interactions with increasing pressure that should be discernible in the mid IR spectral region. We do not find evidence for structural phase transitions or chemically induced transformations within the pressure range of our study. The gas phase heat of formation is calculated at the G4 level of theory to be 22.48 kcal/mol, while we obtain 25.92 kcal/mol using the ccCA-PS3 method. Density functional theory calculations of the crystal and the gas phases provided an estimate for the heat of sublimation of 32.4 kcal/mol. We thus determine the room-temperature solid heat of formation of LLM-105 to be −9.9 or −6.5 kcal/mol based on the G4 or ccCA-PS3 methods, respectively.

  1. High-pressure stabilization of argon fluorides.

    PubMed

    Kurzydłowski, Dominik; Zaleski-Ejgierd, Patryk

    2016-01-28

    On account of the rapid development of noble gas chemistry in the past half-century both xenon and krypton compounds can now be isolated in macroscopic quantities. The same does not hold true for the next lighter group 18 element, argon, which forms only isolated molecules stable solely in low temperature matrices or supersonic jet streams. Here we present theoretical investigations into a new high-pressure reaction pathway, which enables synthesis of argon fluorides in bulk and at room temperature. Our hybrid DFT calculations (employing the HSE06 functional) indicate that above 60 GPa ArF2-containing molecular crystals can be obtained by a reaction between argon and molecular fluorine. PMID:26742478

  2. LiNbO3-Type Oxide (Tl(1-x)Sc(x))ScO3: High-Pressure Synthesis, Crystal Structure, and Electronic Properties.

    PubMed

    Belik, Alexei A; Yi, Wei; Kumagai, Yu; Katsuya, Yoshio; Tanaka, Masahiko; Oba, Fumiyasu

    2016-02-15

    We investigate the synthesis of a thallium scandate, TlScO3, under high-pressure (6-7.7 GPa) and high-temperature (1373-1773 K) conditions. At 6 GPa, a LiNbO3-type phase appears in a narrow temperature range and in mixtures with other phases. At 7.7 GPa and 1673 K, a new LiNbO3-type oxide is found with a composition of (Tl(1-x)Sc(x))ScO3 and x ≈ 0.26 as determined by structural analysis from X-ray powder diffraction data. It crystallizes in space group R3c (No. 161) with lattice parameters of a = 5.50283(7) Å and c = 14.4606(2) Å. It is stable at least up to 800 K at ambient pressure. The point-charge model gives an electric polarization of 60 μC/cm(2). First-principles calculations show that centrosymmetric ilmenite-type and polar LiNbO3-type structures of stoichiometric TlScO3 have almost the same lowest energy, and the next stable structure is a GdFeO3-type perovskite structure. PMID:26840839

  3. Magnetocaloric effect study of SrFe0.8Co0.2O3 single crystal prepared under high pressure

    NASA Astrophysics Data System (ADS)

    Xia, Hai-Liang; Qin, Xiao-Mei; Yang, Jun-Ye; Yin, Yun-Yu; Dai, Jian-Hong; Shi, Wang-Zhou; Long, You-Wen

    2015-05-01

    A high-quality SrFe0.8Co0.2O3 single crystal is prepared by combining floating-zone and high-pressure treatment methods. Its Magnetocaloric effect is investigated by magnetic measurements. A paramagnetism-to-ferromagnetism transition is found at about 270 K and this transition is a second-order one in nature as confirmed by Arrott plots. The saturated moment obtained at 2 K and 7 T is 3.63 μB/f.u. The maximal value of magnetic entropy change measured at 5 T is about 4.0 J·kg-1·K-1. The full wide at half maximum for a magnetic entropy change peak observed in SrFe0.8Co0.2O3 is considerably large. As a consequence, the relative cooling power value of SrFe0.8Co0.2O3 obtained at 5 T is 331 J/kg, which is greatly higher than those observed in other perovskite oxides. The present work therefore provides a promising candidate for magnetic refrigeration near room temperature. Project supported by the National Basic Research Program of China (Grant No. 2014CB921500) and the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB07030300).

  4. Crystallization Processes in Mercury's Core Inferred from In-situ High-Pressure Melting Experiments in the Fe-S-Si-C System

    NASA Astrophysics Data System (ADS)

    Martin, A. M.; Van Orman, J. A.; Hauck, S. A., II; Sun, N.; Yu, T.; Wang, Y.

    2014-12-01

    Based upon the high pressure melting temperatures in the Fe-FeS system, an iron "snow" process has been suggested to occur in Mercury's core. However, recent results from the MESSENGER mission indicate very reducing conditions in Mercury, under which a substantial amount of silicon should also dissolve into the core. The presence of Si can significantly modify the chemical and physical properties of Mercury's core (e.g., phase relations, crystallization, density). Moreover, up to 4 wt% C could have been incorporated into the core during the planet formation. In order to test the iron snow hypothesis in a system that is likely to be closer to the actual core composition, we performed in situ high-pressure, high-temperature experiments in the Fe-FeS-Fe2Si-Fe3C system using a multi-anvil press on a synchrotron (Advanced Photon Source, Argonne). To observe low degree eutectic melting, we separated the samples in two parts: (1) an iron rod presaturated with Si and C and (2) a mixture of FeS, Fe2Si and Fe3C. Eutectic melting temperature and phase relations were determined at various pressures between 4.5 and 15.5 GPa using energy dispersive X-ray diffraction and imaging. Temperature was quenched soon after melting in order to preserve the eutectic melt composition. The X-ray images, diffraction spectra and back-scattered electron images of the recovered samples show that eutectic melting occurs in the range of 800 - 900°C in all our experiments. These temperatures are close to the eutectic temperatures in the Fe-FeS-Fe3C system, indicating that Si does not change the eutectic temperatures significantly. Melting therefore occurs at much lower temperature than suggested for the Fe-S-Si system at similar pressures. This difference may be explained by the presence of C and by the higher silicon content in our starting composition. Our experimental setup may also be more suitable for detecting the low degrees of melting in metallic systems. Such low eutectic melting

  5. Crystal structure and properties of high-pressure-synthesized BiRhO{sub 3}, LuRhO{sub 3}, and NdRhO{sub 3}

    SciTech Connect

    Yi, Wei; Liang, Qifeng; Matsushita, Yoshitaka; Tanaka, Masahiko; Hu, Xiao; Belik, Alexei A.

    2013-04-15

    GdFeO{sub 3}-type orthorhombic perovskite compounds BiRhO{sub 3}, LuRhO{sub 3}, and NdRhO{sub 3} were prepared using a high-pressure and high-temperature technique at 6 GPa and 1300–1600 K. Their crystal structures were investigated using synchrotron X-ray powder diffraction data: a=5.8098(3) Å, b=7.7720(4) Å, and c=5.3510(3) Å for BiRhO{sub 3}; a=5.75519(1) Å, b=7.77218(2) Å, and c=5.37572(1) Å for NdRhO{sub 3}, and a=5.66981(1) Å, b=7.51205(2) Å, and c=5.18520(1) Å for LuRhO{sub 3}. BiRhO{sub 3} crystallizes in the centrosymmetric space group Pnma (No. 62) similar to LuRhO{sub 3} and NdRhO{sub 3} despite the presence of the lone electron pair of Bi{sup 3+} and the non-magnetic ground state of Rh{sup 3+}. BiRhO{sub 3} and LuRhO{sub 3} are non-magnetic, and NdRhO{sub 3} shows paramagnetic behavior from Nd{sup 3+} ions. The specific heat of BiRhO{sub 3}, LuRhO{sub 3}, and NdRhO{sub 3} in different applied magnetic fields was also investigated. An energy gap of BiRhO{sub 3} was estimated to be about 1.3 eV from diffuse reflectance spectra and 0.95 eV from first-principle calculations with U=3.5 eV. - Graphical abstract: A fragment of the crystal structure of BiRhO{sub 3} in the Pnma (along b axis) model, 2×2×2 unit cell. The RhO{sub 6} octahedra are shown in gray. The Bi atoms are shown by big black circles. Highlights: ► BiRhO{sub 3}, LuRhO{sub 3}, and NdRhO{sub 3} were prepared using a high-pressure technique. ► Structure of three compounds was determined: centrosymmetric space group Pnma. ► BiRhO{sub 3} and LuRhO{sub 3} are non-magnetic, and NdRhO{sub 3} shows paramagnetic behavior. ► Specific heat of BiRhO{sub 3}, LuRhO{sub 3}, and NdRhO{sub 3} was investigated. ► BiRhO{sub 3} has an energy gap of about 1.3 eV.

  6. High-pressure synthesis and crystal structures of the strontium oxogallates Sr2Ga2O5 and Sr5Ga6O14

    NASA Astrophysics Data System (ADS)

    Kahlenberg, Volker; Goettgens, Valerie; Mair, Philipp; Schmidmair, Daniela

    2015-08-01

    High-pressure synthesis experiments in a piston-cylinder apparatus at 1.5 GPa/3.0 GPa and 1000 °C resulted in the formation of single-crystals of Sr2Ga2O5 and Sr5Ga6O14, respectively. The structures of both compounds have been solved from single-crystal diffraction data sets using direct methods. The first compound is orthorhombic with space group type Pbca (a=10.0021(4) Å, b=9.601(4) Å, c=10.6700(4) Å, V=1024.6(4) Å3, Mr=394.68 u, Z=8, Dx=5.12 g/cm3) and belongs to the group of single layer gallates. Individual sheets are parallel to (0 0 1) and can be built from the condensation of unbranched vierer single chains running along [0 1 0]. The layers are characterized by the presence of four- and strongly elliptical eight-membered rings of corner connected tetrahedra in UUDD and UUUUDDDD conformation. Strontium atoms are sandwiched between the tetrahedral layers for charge compensation and are coordinated by six and seven oxygen ligands, respectively. Sr2Ga2O5 is isotypic with several other double sulfides and selenides. To the best of our knowledge, it is the first example of an oxide with this structure type. From a structural point of view, Sr5Ga6O14 is a phyllogallate as well. The crystal structure adopts the monoclinic space group P21/c (a=8.1426(3) Å, b=8.1803(3) Å, c=10.8755(4) Å, β=91.970(4)° V=723.98(5) Å3, Mr=1080.42 u, Z=2, Dx=4.96 g/cm3). Individual sheets extend along (0 0 1). Basic building units are unbranched dreier single chains parallel to [1 0 0]. The layers contain tertiary (Q3) und quaternary (Q4) connected [GaO4]-tetrahedra in the ratio 2:1 resulting in a Ga:O ratio of 3:7 and the formation of exclusively five-membered rings. Linkage between adjacent tetrahedral sheets is provided by three symmetrically independent strontium ions which are surrounded by six to eight oxygen atoms. The layers in Sr5Ga6O14 are similar to those observed in the melilite structure-type. Crystallochemical relationships between the present phases and other

  7. Some applications of thermodynamics in crystal chemistry

    NASA Astrophysics Data System (ADS)

    Herbstein, Frank H.

    1996-01-01

    The integrated study of polymorphic phase changes in crystals by combining thermodynamic and crystallographic data is illustrated for four one-component systems — tin, carbon, adamantane and fullerene C 60 Ih — of increasing complexity. A brief review of the basic thermodynamics of the solid state (laws of thermodynamics, polymorphism, order of transitions) reminds the reader that enthalpy ( H) and entropy ( S) are experimental quantities derivable from the values of the heat capacity at constant pressure ( CP) measured as a function of temperature ( T). Combination of H and S through the Gibbs function gives the free energy as a function of T ( G = H - TS). For a one-component crystal with two polymorphic forms, the separate roles of the enthalpy and entropy differences between the polymorphs can be distinguished. This is illustrated in quantitative fashion for the two polymorphs of tin at atmospheric pressure, where there is a first-order phase transformation from grey (diamond) to white (metallic) at 286 K. Application of the Clausius-Clapeyron equation ( {dP }/{dT } = {ΔS}/{ΔV}) shows that metallic tin is the stable phase above ≈ 5 kbar at 0 K. This is entirely analogous to the treatment of the pressure dependence of the melting point of ice. In the next stage, pressure is added as a variable in order to treat the graphite-diamond polymorphism of carbon. Adamantane, for which calorimetric, phase-diagram and crystallographic data are available over a considerable range of temperature and pressure, is next reviewed in detail. The polymorphic change from tetragonal (stable below 208.6 K at atmospheric pressure) to cubic is almost, but not quite, first-order in character. A somewhat similar analysis is applied to available calorimetric and crystallographic data for fullerene C60 Ih, where the transition shows appreciable deviations from ideal first-order character. The next stage, not considered here, would be to proceed from the methods of

  8. Elasticity of single-crystal NAL phase at high pressure: A potential source of the seismic anisotropy in the lower mantle

    NASA Astrophysics Data System (ADS)

    Wu, Ye; Yang, Jing; Wu, Xiang; Song, Maoshuang; Yoshino, Takashi; Zhai, Shuangmeng; Qin, Shan; Huang, Haijun; Lin, Jung-Fu

    2016-08-01

    The new hexagonal aluminous phase, named the NAL phase, is expected to be stable at depths of <1200 km in subducted slabs and believed to constitute 10~30 wt% of subducted mid-ocean ridge basalt together with the CaFe2O4-type aluminous phase. Here elasticity of the single-crystal NAL phase is investigated using Brillouin light scattering coupled with diamond anvil cells up to 20 GPa at room temperature. Analysis of the results shows that the substitution of iron lowers the shear modulus of the NAL phase by ~5% (~6 GPa) but does not significantly affect the adiabatic bulk modulus. The NAL phase exhibits high-velocity anisotropies with AVP = 14.7% and AVS = 15.12% for the Fe-bearing phase at ambient conditions. The high AVS of the NAL phase mainly results from the high anisotropy of the faster VS1 (13.9~15.8%), while the slower VS2 appears almost isotropic (0.1~2.8%) at ambient and high pressures. The AVP and AVS of the NAL phase decrease with increasing pressure but still have large values with AVP = 11.4% and AVS = 14.12% for the Fe-bearing sample at 20.4 GPa. The extrapolated AVP and AVS of the Fe-free and Fe-bearing NAL phases at 40 GPa are larger than those of bridgmanite at the same pressure. Together with its spin transition of iron and structural transition to the CF phase, the presence of the NAL phase with high-velocity anisotropies may contribute to the observed seismic anisotropy around subducted slabs in the uppermost lower mantle.

  9. Bench-Scale Development of a Hot Carbonate Absorption Process with Crystallization-Enabled High Pressure Stripping for Post-Combustion CO{sub 2} Capture

    SciTech Connect

    Lu, Yongqi

    2014-02-01

    This report summarizes the methodology and preliminary results of a techno-economic analysis on a hot carbonate absorption process (Hot-CAP) with crystallization-enabled high pressure stripping for post-combustion CO{sub 2} capture (PCC). This analysis was based on the Hot-CAP that is fully integrated with a sub-critical steam cycle, pulverized coal-fired power plant adopted in Case 10 of the DOE/NETL’s Cost and Performance Baseline for Fossil Energy Plants. The techno-economic analysis addressed several important aspects of the Hot-CAP for PCC application, including process design and simulation, equipment sizing, technical risk and mitigation strategy, performance evaluation, and cost analysis. Results show that the net power produced in the subcritical power plant equipped with Hot-CAP is 611 MWe, greater than that with Econoamine (550 MWe). The total capital cost for the Hot-CAP, including CO{sub 2} compression, is $399 million, less than that for the Econoamine PCC ($493 million). O&M costs for the power plant with Hot-CAP is $175 million annually, less than that with Econoamine ($178 million). The 20-year levelized cost of electricity (LCOE) for the power plant with Hot-CAP, including CO2 transportation and storage, is 119.4 mills/kWh, a 59% increase over that for the plant without CO2 capture. The LCOE increase caused by CO{sub 2} capture for the Hot-CAP is 31% lower than that for its Econoamine counterpart.

  10. High pressure ices

    PubMed Central

    Hermann, Andreas; Ashcroft, N. W.; Hoffmann, Roald

    2012-01-01

    H2O will be more resistant to metallization than previously thought. From computational evolutionary structure searches, we find a sequence of new stable and meta-stable structures for the ground state of ice in the 1–5 TPa (10 to 50 Mbar) regime, in the static approximation. The previously proposed Pbcm structure is superseded by a Pmc21 phase at p = 930 GPa, followed by a predicted transition to a P21 crystal structure at p = 1.3 TPa. This phase, featuring higher coordination at O and H, is stable over a wide pressure range, reaching 4.8 TPa. We analyze carefully the geometrical changes in the calculated structures, especially the buckling at the H in O-H-O motifs. All structures are insulating—chemistry burns a deep and (with pressure increase) lasting hole in the density of states near the highest occupied electronic levels of what might be component metallic lattices. Metallization of ice in our calculations occurs only near 4.8 TPa, where the metallic C2/m phase becomes most stable. In this regime, zero-point energies much larger than typical enthalpy differences suggest possible melting of the H sublattice, or even the entire crystal. PMID:22207625

  11. The crystal chemistry of four thorium sulfates

    SciTech Connect

    Albrecht, Amanda J.; Sigmon, Ginger E.; Moore-Shay, Laura; Wei, Rebecca; Dawes, Colleen; Szymanowski, Jennifer; Burns, Peter C.

    2011-07-15

    Four thorium sulfate compounds have been synthesized and characterized. [Th(SO{sub 4}){sub 2}(H{sub 2}O){sub 7}].2H{sub 2}O (ThS1) crystallizes in space group P2{sub 1}/m, a=7.2488(4), b=12.1798(7), c=8.0625(5) A, {beta}=98.245(1){sup o}; Na{sub 10}[Th{sub 2}(SO{sub 4}){sub 9}(H{sub 2}O){sub 2}].3H{sub 2}O (ThS2), Pna2{sub 1}, a=17.842(2), b=6.9317(8), c=27.550(3) A; Na{sub 2}[Th{sub 2}(SO{sub 4}){sub 5}(H{sub 2}O){sub 3}].H{sub 2}O (ThS3), C2/c, a=16.639(2), b=9.081(1), c=25.078(3) A, {beta}= 95.322(2){sup o}; [Th{sub 4}(SO{sub 4}){sub 7}(OH){sub 2}(H{sub 2}O){sub 6}].2H{sub 2}O (ThS4), Pnma, a=18.2127(9), b=11.1669(5), c=14.4705(7) A. In all cases the Th cations are coordinated by nine O atoms corresponding to SO{sub 4} tetrahedra, OH groups, and H{sub 2}O groups. The structural unit of ThS1 is an isolated cluster consisting of a single Th polyhedron with two monodentate SO{sub 4} tetrahedra and seven H{sub 2}O groups. A double-wide Th sulfate chain is the basis of ThS2. The structures of ThS3 and ThS4 are frameworks of Th polyhedra and sulfate tetrahedra, and each contains channels that extend through the framework. One of the Th cations in ThS3 is coordinated by a bidentate SO{sub 4} tetrahedron, and ThS4 is unusual in the presence of a pair of Th cations that share a polyhedral face. - Graphical abstract: The structures of four hydrous thorium sulfates are reported that have structural units consisting of finite clusters, chains, and frameworks. Highlights: > Four hydrous thorium sulfates have structural units consisting of finite clusters, chains, and frameworks. > In each the Th cations are coordinated by nine O atoms from SO{sub 4} tetrahedra, OH groups, and H{sub 2}O groups. > The details of the linkages of ThO{sub 9} polyhedra and sulfate tetrahedra vary considerably in these structures.

  12. Constraining 17O and 27Al NMR spectra of high-pressure crystals and glasses: New data for jadeite, pyrope, grossular, and mullite

    USGS Publications Warehouse

    Kelsey, K.E.; Stebbins, J.F.; Du, L.-S.; Hankins, B.

    2007-01-01

    The 17O NMR spectra of glasses quenched from melts at high pressure are often difficult to interpret due to overlapping peaks and lack of crystalline model compounds. High-pressure aluminosilicate glasses often contain significant amounts of [5]Al and [6]Al, thus these high-pressure glasses must contain oxygen bonded to high-coordinated aluminum. The 17O NMR parameters for the minerals jadeite, pyrope, grossular, and mullite are presented to assist interpretation of glass spectra and to help test quantum chemical calculations. The 17O NMR parameters for jadeite and grossular support previous peak assignments of oxygen bonded to Si and high-coordinated Al in high-pressure glasses as well as quantum chemical calculations. The oxygen tricluster in mullite is very similar to the previously observed tricluster in grossite (CaAl4 O7) and suspected triclusters in glasses. We also present 27Al NMR spectra for pyrope, grossular, and mullite.

  13. The evolution of model catalytic systems; studies of structure, bonding and dynamics from single crystal metal surfaces to nanoparticles, and from low pressure (<10(-3) Torr) to high pressure (>10(-3) Torr) to liquid interfaces.

    PubMed

    Somorjai, Gabor A; York, Roger L; Butcher, Derek; Park, Jeong Y

    2007-07-21

    The material and pressure gap has been a long standing challenge in the field of heterogeneous catalysis and have transformed surface science and biointerfacial research. In heterogeneous catalysis, the material gap refers to the discontinuity between well-characterized model systems and industrially relevant catalysts. Single crystal metal surfaces have been useful model systems to elucidate the role of surface defects and the mobility of reaction intermediates in catalytic reactivity and selectivity. As nanoscience advances, we have developed nanoparticle catalysts with lithographic techniques and colloidal syntheses. Nanoparticle catalysts on oxide supports allow us to investigate several important ingredients of heterogeneous catalysis such as the metal-oxide interface and the influence of noble metal particle size and surface structure on catalytic selectivity. Monodispersed nanoparticle and nanowire arrays were fabricated for use as model catalysts by lithographic techniques. Platinum and rhodium nanoparticles in the 1-10 nm range were synthesized in colloidal solutions in the presence of polymer capping agents. The most catalytically active systems are employed at high pressure or at solid-liquid interfaces. In order to study the high pressure and liquid interfaces on the molecular level, experimental techniques with which we bridged the pressure gap in catalysis have been developed. These techniques include the ultrahigh vacuum system equipped with high pressure reaction cell, high pressure Sum Frequency Generation (SFG) vibration spectroscopy, High Pressure Scanning Tunneling Microscopy (HP-STM), and High Pressure X-ray Photoemission Spectroscopy (HP-XPS), and Quartz Crystal Microbalance (QCM). In this article, we overview the development of experimental techniques and evolution of the model systems for the research of heterogeneous catalysis and biointerfacial studies that can shed light on the long-standing issues of materials and pressure gaps.

  14. Crystal structure, equation of state, and elasticity of hydrous aluminosilicate phase, topaz-OH (Al2SiO4(OH)2) at high pressures

    NASA Astrophysics Data System (ADS)

    Mookherjee, Mainak; Tsuchiya, Jun; Hariharan, Anant

    2016-02-01

    We examined the equation of state and high-pressure elasticity of the hydrous aluminosilicate mineral topaz-OH (Al2SiO4(OH)2) using first principles simulation. Topaz-OH is a hydrous phase in the Al2O3-SiO2-H2O (ASH) ternary system, which is relevant for the mineral phase relations in the hydrated sedimentary layer of subducting slabs. Based on recent neutron diffraction experiments, it is known that the protons in the topaz-OH exhibit positional disorder with half occupancy over two distinct crystallographic sites. In order to adequately depict the proton environment in the topaz-OH, we examined five crystal structure models with distinct configuration for the protons in topaz-OH. Upon full geometry optimization we find two distinct space group, an orthorhombic Pbnm and a monoclinic P21/c for topaz-OH. The topaz-OH with the monoclinic P21/c space group has a lower energy compared to the orthorhombic Pbmn space group symmetry. The pressure-volume results for the monoclinic topaz-OH is well represented by a third order Birch-Murnaghan formulation, with V0mon = 348.63 (±0.04) Å3, K0mon = 164.7 (±0.04) GPa, and K0mon = 4.24 (±0.05). The pressure-volume results for the orthorhombic topaz-OH is well represented by a third order Birch-Murnaghan formulation, with V0orth = 352.47 (±0.04) Å3, K0orth = 166.4 (±0.06) GPa, and K0orth = 4.03 (±0.04). While the bulk moduli are very similar for both the monoclinic and orthorhombic topaz-OH, the shear elastic constants and the shear moduli are very sensitive to the position of the proton, orientation of the O-H dipole, and the space group symmetry. The S-wave anisotropy for the orthorhombic and monoclinic topaz-OH are also quite distinct. In the hydrated sedimentary layer of subducting slabs, transformation of a mineral assemblage consisting of coesite (SiO2) and diaspore (AlOOH) to topaz-OH (Al2SiO4(OH)2) is likely to be accompanied by an increase in density, compressional velocity, and shear wave velocity. However

  15. Occurrence and mineral chemistry of high pressure phases, Portrillo basalt, southcentral New Mexico. M.S. Thesis. Final Technical Report, 1 Jun. 1978 - 31 May 1980

    NASA Technical Reports Server (NTRS)

    Hoffer, J. M.; Ortiz, T. S.

    1980-01-01

    Inclusions of clinopyroxenite, kaersutiteclinopyroxenite, kaersutite-rich inclusions, wehrlite and olivine-clinopyroxenite together with megacrysts of feldspar, kaersutite and spinel are found loose on the flanks of cinder cones, as inclusions within lava flows and within the cores of volcanic bombs in the Quaternary alkali-olivine basalt of the West Potrillo Mountains, southcentral New Mexico. Based on petrological and geochemical evidence the megacysts are interpreted to be phenocrysts which formed at great depth rather that xenocrysts of larger crystal aggregates. These large crystals are believed to have formed as stable phases at high temperature and pressure and have partially reacted with the basalt to produce subhedral to anhedral crystal boundaries. It can be demonstrated that the mafic and ultramafic crystal aggregates were derived from an alkali-basalt source rock generated in the mantle. The inclusions are believed to represent a cumulus body or bodies injected within the lower crust or upper mantle.

  16. Electronic phenomena at high pressure

    SciTech Connect

    Drickamer, H.G.

    1981-01-01

    High pressure research is undertaken either to investigate intrinsically high pressure phenomena or in order to get a better understanding of the effect of the chemical environment on properties or processes at one atmosphere. Studies of electronic properties which fall in each area are presented. Many molecules and complexes can assume in the excited state different molecular arrangements and intermolecular forces depending on the medium. Their luminescence emission is then very different in a rigid or a fluid medium. With pressure one can vary the viscosity of the medium by a factor of 10/sup 7/ and thus control the distribution and rate of crossing between the excited state conformations. In rare earth chelates the efficiency of 4f-4f emission of the rare earth is controlled by the feeding from the singlet and triplet levels of the organic ligand. These ligand levels can be strongly shifted by pressure. A study of the effect of pressure on the emission efficiency permits one to understand the effect of ligand chemistry at one atmosphere. At high pressure electronic states can be sufficiently perturbed to provide new ground states. In EDA complexes these new ground states exhibit unusual chemical reactivity and new products.

  17. High-pressure synthesis and single-crystal structure refinement of gadolinium holmium silicate hydroxyapatite Gd{sub 4.33}Ho{sub 4.33}(SiO{sub 4}){sub 6}(OH){sub 2}

    SciTech Connect

    Wang Chao; Liu Xiaoyang . E-mail: liuxy@jlu.edu.cn; Fleet, M.E.; Feng, Shouhua; Xu Ruren

    2006-07-15

    Single crystals of gadolinium holmium silicate hydroxyapatite Gd{sub 4.33}Ho{sub 4.33}(SiO{sub 4}){sub 6}(OH){sub 2} have been synthesized at 2.0GPa and 1450 deg. C using a piston-cylinder-type high-pressure apparatus. The crystal symmetry by single-crystal X-ray diffraction analysis is hexagonal, space group P6{sub 3}/m (No. 176), with a=9.3142(5)A, c=6.7010(4)A, Z=1. Gadolinium and Ho are disordered over the two large cation positions, A(1) and A(2), and charge balance in this silicate apatite is maintained by cation vacancies in A(1). Two other apatite-structure crystals investigated have P3-bar and Imma symmetry, and represent either partially ordered Gd-Ho distributions or crystal strain induced during quenching.

  18. Single-Crystal X-Ray Diffraction of Orthoenstatite to 48 GPa: New High-Pressure Phases with 4-, 5-, and 6-Coordinated Silicon

    NASA Astrophysics Data System (ADS)

    Finkelstein, G. J.; Dera, P. K.; Duffy, T. S.

    2013-12-01

    Orthopyroxene (opx, (Mg,Fe)SiO3) is one of the major phases in Earth's upper mantle, comprising ~20% of the region by volume. At high pressures and temperatures, this phase undergoes several well-characterized phase transitions. Its behavior at low temperature is less well known, but may be important for cold subducting slabs (1, 2). Previous studies (3, 4) reported that MgSiO3 orthoenstatite persists up to ~12 GPa, and a phase transition above this pressure was recently discovered by Zhang et al. (5). This structure, which we call β-opx (designated HPCEN2 in previous studies), is related to one predicted by theory (6), and has P21/c monoclinic symmetry. It retains an opx topology despite its lower symmetry, distinguishing it from a true clinopyroxene. We conducted single-crystal X-ray diffraction experiments in a diamond anvil cell at GSECARS and HPCAT at the APS. Mg0.91Fe0.09SiO3 orthopyroxene was compressed in a neon pressure medium with a gold pressure standard. In addition to the orthopyroxene to β-opx transition, we observe two further phase changes at ~28 GPa and ~38 GPa. The transitions result in volume reductions of ~2.5% and ~3.9%, respectively. The Si layers in both new structures are intermediate between the opx structure and that of the ilmenite-structured akimotoite polymorph. Akimotoite consists of edge-sharing MgO6 and SiO6 octahedra arranged in alternating honeycomb sheets. A theoretical study suggested clinoenstatite could transform directly to akimotoite at low temperatures through a shear-based mechanism (7). Here, we observe that the path toward akimotoite-like Si layers is stepwise. In the new MgSiO3 structures, the initial chains of SiO4 tetrahedra are partially converted to the characteristic 6-coordinated honeycomb layers. This results in some 5-coordinated Si sites in both structures. Due to the increased coordination number, we are calling the new structures α- and β-post-orthopyroxene (α-popx and β-popx). The Mg layers, however, do

  19. High pressure melt ejection

    SciTech Connect

    Tarbell, W.W.; Brockmann, J.E.; Pilch, M.

    1983-01-01

    Recent probabilistic risk assessments have identified the potential for reactor pressure vessel failure while the reactor coolant system is at elevated pressure. The analyses postulate that the blowdown of steam and hydrogen into the reactor cavity will cause the core material to be swept from the cavity region into the containment building. The High Pressure Melt Streaming (HIPS) program is an experimental study of the high pressure ejection of molten material and subsequent interactions within a concrete cavity. The program focuses on using prototypic system conditions and scaled models of reactor geometries to accurately simulate the ex-vessel processes during high-pressure accident sequences. Scaling analyses of the experiment show that the criteria established for core debris removal from the cavity are met or exceeded. Tests are performed at two scales, representing 1/10th and 1/20th linear reproductions of the Zion reactor plant. Results of the 1/20th scale tests are presented.

  20. High-Pressure Research in Mineral Physics

    NASA Astrophysics Data System (ADS)

    Hazen, Robert M.

    Advances in high-pressure science and technology have transformed solid Earth geophysics. In the last decade, high-pressure researchers have reproduced the full range of Earth pressure and temperature conditions in the laboratory, and they have synthesized single crystals of dense silicate phases, unknown at the Earth's surface yet suspected to comprise most of the Earth's volume. These and other extraordinary accomplishments are chronicled in High-Pressure Research in Mineral Physics, an outgrowth of the third U.S.-Japan High-Pressure seminar, held in Kahuku, Hawaii, January, 13-16, 1986. The well produced and reasonably priced volume is dedicated to Syun-iti Akimoto, dean of Japanese high-pressure research, who recently retired from the University of Tokyo. Akimoto's fascinating historical account of pressure research at the Institute for Solid State Physics at the University of Tokyo is the leadoff article.

  1. Chromium crystal chemistry mullite-spinel refractory ceramics

    SciTech Connect

    Levy, D.; Gualtieri, A.; Quartieri, S.; Artioli, G.; Valle, M.

    1999-03-15

    A small amount of chromium oxide was added to a mullite-spinel refractory mixture to improve its thermal and mechanical properties. Two different compositions of mullite-spinel refractory were studied to define the crystal structures hosting the chromium cations, and the chromium solubility in spinel (MgAl{sub 2{minus}x}Cr{sub x}O{sub 4}) was determined. Powder X-ray diffraction (XRD), X-ray absorption near edge spectroscopy (XANES), and scanning electron microscopy (SEM) elemental distribution maps were used to determine the chromium crystal chemistry in the system. The observed maximum solubility of chromium in spinel was found at x = 1.2, but the presence of mullite in the mixture caused a strong decrease of this value. The chromium distribution among the crystal phases reflects the different reaction paths of the two samples: a stage involving spinel and melt drives all present chromium in the spinel, while a simultaneous crystallization of spinel-mullite distributes chromium cations between mullite, spinel, and secondary corundum.

  2. Direct arylation of benzene with aryl bromides using high-temperature/high-pressure process windows: expanding the scope of C-H activation chemistry.

    PubMed

    Pieber, Bartholomäus; Cantillo, David; Kappe, C Oliver

    2012-04-16

    A detailed investigation on the direct arylation of benzene with aryl bromides by using first-row transition metals under high-temperature/high-pressure (high-T/p) conditions is described. By employing a parallel reactor platform for rapid reaction screening and discovery at elevated temperatures, various metal/ligand/base combinations were evaluated for their ability to enable biaryl formation through C-H activation. The combination of cobalt(III) acetylacetonate and lithium bis(trimethylsilyl)amide was subjected to further process intensification at 200 °C (15 bar), allowing a significant reduction of the catalyst/base loading and a dramatic increase in catalytic efficiency (turnover frequency) by a factor of 1000 compared to traditional protocols. The high-throughput screening additionally identified novel nickel- and copper-based metal/ligand combinations that favored an amination pathway competing with C-H activation, with the addition of ligands, such as 1,10-phenanthroline, having a profound influence on the selectivity. In addition to metal-based catalysts, high-T/p process windows were also successfully applied to transition-metal-free systems, utilizing 1,10-phenanthroline as organocatalyst.

  3. Secondary metabolites isolation in natural products chemistry: comparison of two semipreparative chromatographic techniques (high pressure liquid chromatography and high performance thin-layer chromatography).

    PubMed

    Do, Thi Kieu Tiên; Hadji-Minaglou, Francis; Antoniotti, Sylvain; Fernandez, Xavier

    2014-01-17

    Chemical investigations on secondary metabolites in natural products chemistry require efficient isolation techniques for characterization purpose as well as for the evaluation of their biological properties. In the case of phytochemical studies, the performance of the techniques is critical (resolution and yield) since the products generally present a narrow range of polarity and physicochemical properties. Several techniques are currently available, but HPLC (preparative and semipreparative) is the most widely used. To compare the performance of semipreparative HPLC and HPTLC for the isolation of secondary metabolites in different types of extracts, we have chosen carvone from spearmint essential oil (Mentha spicata L.), resveratrol from Fallopia multiflora (Thunb.) Haraldson, and rosmarinic acid from rosemary (Rosmarinus officinalis L.) extracts. The comparison was based on the chromatographic separation, the purity and quantity of isolated compounds, the solvent consumption, the duration and the cost of the isolation operations. The results showed that semipreparative HPTLC can in some case offer some advantages over conventional semipreparative HPLC.

  4. High pressure furnace

    DOEpatents

    Morris, D.E.

    1993-09-14

    A high temperature high pressure furnace has a hybrid partially externally heated construction. A metallic vessel fabricated from an alloy having a composition of at least 45% nickel, 15% chrome, and 10% tungsten is utilized (the preferred alloy including 55% nickel, 22% chrome, 14% tungsten, 2% molybdenum, 3% iron (maximum) and 5% cobalt (maximum)). The disclosed alloy is fabricated into 11/4 or 2 inch, 32 mm or 50 mm bar stock and has a length of about 22 inches, 56 cm. This bar stock has an aperture formed therein to define a closed high temperature, high pressure oxygen chamber. The opposite and closed end of the vessel is provided with a small blind aperture into which a thermocouple can be inserted. The closed end of the vessel is inserted into an oven, preferably heated by standard nickel chrome electrical elements and having a heavily insulated exterior. 19 figures.

  5. High pressure furnace

    DOEpatents

    Morris, Donald E.

    1993-01-01

    A high temperature high pressure furnace has a hybrid partially externally heated construction. A metallic vessel fabricated from an alloy having a composition of at least 45% nickel, 15% chrome, and 10% tungsten is utilized (the preferred alloy including 55% nickel, 22% chrome, 14% tungsten, 2% molybdenum, 3% iron (maximum) and 5% cobalt (maximum). The disclosed alloy is fabricated into 11/4 or 2 inch, 32 mm or 50 mm bar stock and has a length of about 22 inches, 56 cm. This bar stock has an aperture formed therein to define a closed high temperature, high pressure oxygen chamber. The opposite and closed end of the vessel is provided with a small blind aperture into which a thermocouple can be inserted. The closed end of the vessel is inserted into an oven, preferably heated by standard nickel chrome electrical elements and having a heavily insulated exterior.

  6. High pressure oxygen furnace

    DOEpatents

    Morris, D.E.

    1992-07-14

    A high temperature high pressure oxygen furnace having a hybrid partially externally heated construction is disclosed. A metallic bar fabricated from an alloy having a composition of at least 45% nickel, 15% chrome, and 10% tungsten is utilized, the preferred alloy including 55% nickel, 22% chrome, 14% tungsten, 2% molybdenum, 3% iron (maximum) and 5% cobalt (maximum). The disclosed alloy is fabricated into 11/4 inch bar stock and has a length of about 17 inches. This bar stock is gun drilled for over 16 inches of its length with 0.400 inch aperture to define a closed high temperature, high pressure oxygen chamber. The opposite and closed end of the bar is provided with a small support aperture into which both a support and a thermocouple can be inserted. The closed end of the gun drilled bar is inserted into an oven, preferably heated by standard nickel chrome electrical elements and having a heavily insulated exterior. 5 figs.

  7. High pressure oxygen furnace

    DOEpatents

    Morris, Donald E.

    1992-01-01

    A high temperature high pressure oxygen furnace having a hybrid partially externally heated construction is disclosed. A metallic bar fabricated from an alloy having a composition of at least 45% nickel, 15% chrome, and 10% tungsten is utilized (the preferred alloy including 55% nickel, 22% chrome, 14% tungsten, 2% molybdenum, 3% iron (maximum) and 5% cobalt (maximum). The disclosed alloy is fabricated into 11/4 inch bar stock and has a length of about 17 inches. This bar stock is gun drilled for over 16 inches of its length with 0.400 inch aperture to define a closed high temperature, high pressure oxygen chamber. The opposite and closed end of the bar is provided with a small support aperture into which both a support and a thermocouple can be inserted. The closed end of the gun drilled bar is inserted into an oven, preferably heated by standard nickel chrome electrical elements and having a heavily insulated exterior.

  8. High pressure ratio turbocharger

    SciTech Connect

    Woollenweber, W.E.

    1991-06-25

    This patent describes a turbocharger system for an internal combustion engine. It comprises means forming a turbine adapted to be driven by exhaust gas from an internal combustion engine comprising: a turbine wheel having a central core and outwardly extending vanes, the turbine wheel being rotatable about a central axis; a meridionally divided volute for exhaust gas surrounding the turbine wheel, the meridionally divided volute including a divider wall defining first and second volute passageways with openings at the turbine wheel; means forming a high-pressure compressor driven by the turbine means, the high-pressure compressor comprising: rotating compressor blades, the compressor blades adapted to be driven in rotation about the central axis by the turbine means to deliver a flow of air at high pressures for an internal combustion engine, and blades being moveable about longitudinal axes generally transverse to the central axis to impart positive or negative pre-whirl motion to the air leaving the stator blades prior to entering the rotating blades of the compressor stage; closure means for providing a flow of engine exhaust gas from one of the first and second volute passageways into the turbine wheel; and a control means for operating the closure means and the stator blades in synchronization.

  9. Enhanced polarization properties of ferrielectric AgNbO3 single crystals grown by Czochralski method under high-pressure oxygen atmosphere

    NASA Astrophysics Data System (ADS)

    Kitanaka, Yuuki; Egawa, Takuya; Noguchi, Yuji; Miyayama, Masaru

    2016-10-01

    We report crystal growth under high oxygen pressure (P O2) atmosphere that yields high-quality single crystals of AgNbO3. X-ray fluorescence analysis reveals that an increase in P O2 during crystal growth effectively suppresses the deficiency of Ag and then leads to low leakage currents. Single crystals grown via the Czochralski method at a P O2 of 0.9 MPa are demonstrated to show ferrielectric switching with enhanced polarization under electric fields along the [110] direction.

  10. Ammothermal Growth of Gan Substrates For Leds: High-Pressure Ammonothermal Process for Bulk Gallium Nitride Crystal Growth for Energy Efficient Commercially Competitive Lighting

    SciTech Connect

    2011-01-01

    Broad Funding Opportunity Announcement Project: The new GaN crystal growth method is adapted from that used to grow quartz crystals, which are very inexpensive and represent the second-largest market for single crystals for electronic applications (after silicon). More extreme conditions are required to grow GaN crystals and therefore a new type of chemical growth chamber was invented that is suitable for large-scale manufacturing. A new process was developed that grows GaN crystals at a rate that is more than double that of current processes. The new technology will enable GaN substrates with best-in-world quality at lowest-in-world prices, which in turn will enable new generations of white LEDs, lasers for full-color displays, and high-performance power electronics.

  11. Crystal-chemistry and partitioning of REE in whitlockite

    NASA Technical Reports Server (NTRS)

    Colson, R. O.; Jolliff, B. L.

    1993-01-01

    Partitioning of Rare Earth Elements (REE) in whitlockite is complicated by the fact that two or more charge-balancing substitutions are involved and by the fact that concentrations of REE in natural whitlockites are sufficiently high such that simple partition coefficients are not expected to be constant even if mixing in the system is completely ideal. The present study combines preexisting REE partitioning data in whitlockites with new experiments in the same compositional system and at the same temperature (approximately 1030 C) to place additional constraints on the complex variations of REE partition coefficients and to test theoretical models for how REE partitioning should vary with REE concentration and other compositional variables. With this data set, and by combining crystallographic and thermochemical constraints with a SAS simultaneous-equation best-fitting routine, it is possible to infer answers to the following questions: what is the speciation on the individual sites Ca(B), Mg, and Ca(IIA) (where the ideal structural formula is Ca(B)18 Mg2Ca(IIA)2P14O56); how are REE's charge-balanced in the crystal; and is mixing of REE in whitlockite ideal or non-ideal. This understanding is necessary in order to extrapolate derived partition coefficients to other compositional systems and provides a broadened understanding of the crystal chemistry of whitlockite.

  12. High pressure atomization

    NASA Astrophysics Data System (ADS)

    Bracco, F. V.

    1982-03-01

    The main objective of these grants has been to study the fundamental processes which lead to the atomization of high pressure jets injected into compressed gases through single hole nozzles. Specific topics include: Dependence of Spray Angle and Other Spray Parameters on Nozzle Design and Operating Conditions; Ultra High Speed Filming of Atomizing Jets; Mechanism of Breakup of Highly Super Heated Liquid Jets; Measurements of the Spray Angle of Atomizing Jets; Mechanism of Atomization of a Liquid Jet; Scaling of Transient Laminar, Turbulent, and Spray Jets; Computations of Drop Sizes in Pulsating Sprays and of Liquid Core Length in Vaporizing Sprays; and Scaling of Impulsively Started Sprays.

  13. HIGH PRESSURE DIES

    DOEpatents

    Wilson, W.B.

    1960-05-31

    A press was invented for subjecting specimens of bismuth, urania, yttria, or thoria to high pressures and temperatures. The press comprises die parts enclosing a space in which is placed an electric heater thermally insulated from the die parts so as not to damage them by heat. The die parts comprise two opposed inner frustoconical parts and an outer part having a double frustoconical recess receiving the inner parts. The die space decreases in size as the inner die parts move toward one another against the outer part and the inner parts, though very hard, do not fracture because of the mode of support provided by the outer part.

  14. Crystal chemistry of Ti-bearing garnets with volcanic origin

    NASA Astrophysics Data System (ADS)

    Scordari, F.; Schingaro, E.; Malitesta, C.; Pedrazzi, G.

    2003-04-01

    The crystal chemistry of Ti-bearing andradites ("melanites") belonging to different pyroclastic units of Albani Hills (Lazio, Italy) has been investigated electron probe microanalysis (EPMA), single crystal X-ray diffraction (SCXRD), Mössbauer spectroscopy (MS) and X-ray Photoelectron Spectroscopy (XPS). The aim is to determine the correct cations distribution over the X(8-fold), Y(6-fold) and Z(4-fold) sites and accurate values of cations site populations. The analysed samples are characterized by a low Ti-content ( TiO_2 in the range 1.76-3.59 wt%) and cell edges in the range 11.996(3)-12.014(1). MS investigation reveald Fe to be present predominantly as Fe3+(Y) and subordinately as Fe2+(X). XPS analysis was accomplished according to the procedure developed by Malitesta et al.(1989). The fitting of Ti2p signals seem to indicate that two (octahedral Ti3+ and Ti4+) or three (octahedral Ti3+ and Ti4+, tetrahedral Ti4+) Ti species may occur in these specimen. From the combination of the results from different techniques the distribution of Al over the Y and Z sites has been deduced. By comparing the Albani Hills samples crystal chemistry with that of melanites from Mt. Vulture (Scordari et al., 1999), it has been found that in the latter samples the Z sites is occupied by Si, Fe3+ and Ti4+, whereas in the former by Si,Ti4+ and Al3+. Substitution mechanisms through which Fe and Ti enter the garnet structure are expected to be related to the geologic environment in which they occurr. It has been recently proposed that in samples from volcanic rocks schorlomite substitution, Ti4+(Y) + Fe3+(Z) leftrightarrow Si4+(Z) + Fe3+(Y) is predominant, associated to a low degree of hydrogarnet component, (SiO_4)4- leftrightarrow (O_4H_4)4-; on the contrary Ti-garnets from metamorphic rocks should be affected by morimotoite substitution Ti4+(Y) + Fe2+(Y) leftrightarrow 2Fe3+(Y) and a high degree of hydrogarnet component (Armbruster et al., 1998). The result obtained in the present

  15. High pressure effects on U L3 x-ray absorption in partial fluorescence yield mode and single crystal x-ray diffraction in the heavy fermion compound UCd11

    NASA Astrophysics Data System (ADS)

    Nasreen, Farzana; Antonio, Daniel; VanGennep, Derrick; Booth, Corwin H.; Kothapalli, Karunakar; Bauer, Eric D.; Sarrao, John L.; Lavina, Barbara; Iota-Herbei, Valentin; Sinogeikin, Stanislav; Chow, Paul; Xiao, Yuming; Zhao, Yusheng; Cornelius, Andrew L.

    2016-03-01

    We report a study of high pressure x-ray absorption (XAS) performed in the partial fluorescence yield mode (PFY) at the U L3 edge (0-28.2 GPa) and single crystal x-ray diffraction (SXD) (0-20 GPa) on the UCd11 heavy fermion compound at room temperature. Under compression, the PFY-XAS results show that the white line is shifted by  +4.1(3) eV at the highest applied pressure of 28.2 GPa indicating delocalization of the 5f electrons. The increase in full width at half maxima and decrease in relative amplitude of the white line with respect to the edge jump point towards 6d band broadening under high pressure. A bulk modulus of K 0  =  62(1) GPa and its pressure derivative, K0\\prime   =  4.9(2) was determined from high pressure SXD results. Both the PFY-XAS and diffraction results do not show any sign of a structural phase transition in the applied pressure range.

  16. Combined single crystal polarized XAFS and XRD at high pressure: probing the interplay between lattice distortions and electronic order at multiple length scales in high T c cuprates

    DOE PAGESBeta

    Fabbris, G.; Hücker, M.; Gu, G. D.; Tranquada, J. M.; Haskel, D.

    2016-07-14

    Some of the most exotic material properties derive from electronic states with short correlation length (~10-500 Å), suggesting that the local structural symmetry may play a relevant role in their behavior. In this study, we discuss the combined use of polarized x-ray absorption fine structure and x-ray diffraction at high pressure as a powerful method to tune and probe structural and electronic orders at multiple length scales. Besides addressing some of the technical challenges associated with such experiments, we illustrate this approach with results obtained in the cuprate La1.875Ba0.125CuO4, in which the response of electronic order to pressure can onlymore » be understood by probing the structure at the relevant length scales.« less

  17. Analysis of voids in crystal structures: the methods of 'dual' crystal chemistry.

    PubMed

    Blatov, V A; Shevchenko, A P

    2003-01-01

    The theoretical basics of the analysis of voids in crystal structures by means of Voronoi-Dirichlet polyhedra (VDP) and of the graph theory are stated. Topological relations are considered between VDPs and atomic domains in a crystal field. These relations allow the separation of two non-intersecting topological subspaces in a crystal structure, whose connectednesses are defined by two finite 'reduced' graphs. The first, 'direct', subspace includes the atoms (VDP centres) and the network of interatomic bonds (VDP faces), the second, 'dual', one comprises the void centres (VDP vertices) and the system of channels (VDP edges) between them. Computer methods of geometrical-topological analysis of the 'dual' subspace are developed and implemented within the program package TOPOS. They are designed for automatically restoring the system of channels, visualizing and sizing voids and void conglomerates, dimensional analysis of continuous void systems, and comparative topological analysis of 'dual' subspaces for various substances. The methods of analysis of 'dual' and 'direct' subspaces are noted to differ from each other only in some details that allows the term 'dual' crystal chemistry to be introduced. The efficiency of the methods is shown with the analysis of compounds of different chemical nature: simple substances, ionic structures, superionic conductors, zeolites, clathrates, organic supramolecular complexes. PMID:12496460

  18. HIGH PRESSURE GAS REGULATOR

    DOEpatents

    Ramage, R.W.

    1962-05-01

    A gas regulator operating on the piston and feedback principle is described. The device is particularly suitable for the delicate regulation of high pressure, i.e., 10,000 psi and above, gas sources, as well as being perfectly adaptable for use on gas supplies as low as 50 psi. The piston is adjustably connected to a needle valve and the movement of the piston regulates the flow of gas from the needle valve. The gas output is obtained from the needle valve. Output pressure is sampled by a piston feedback means which, in turn, regulates the movement of the main piston. When the output is other than the desired value, the feedback system initiates movement of the main piston to allow the output pressure to be corrected or to remain constant. (AEC)

  19. High pressure mechanical seal

    NASA Technical Reports Server (NTRS)

    Babel, Henry W. (Inventor); Fuson, Phillip L. (Inventor); Chickles, Colin D. (Inventor); Jones, Cherie A. (Inventor); Anderson, Raymond H. (Inventor)

    1995-01-01

    A relatively impervious mechanical seal is formed between the outer surface of a tube and the inside surface of a mechanical fitting of a high pressure fluid or hydraulic system by applying a very thin soft metal layer onto the outer surface of the hard metal tube and/or inner surface of the hard metal fitting, prior to swaging the fitting onto the tube. The thickness of such thin metal layer is independent of the size of the tube and/or fittings. Many metals and alloys of those metals exhibit the requisite softness, including silver, gold, nickel, tin, platinum, indium, rhodium and cadmium. Suitably, the coating is about 0.0025 millimeters (0.10 mils) in thickness. After swaging, the tube and fitting combination exhibits very low leak rates on the order or 10.sup.-8 cubic centimeters per second or less as meaured using the Helium leak test.

  20. High pressure mechanical seal

    NASA Technical Reports Server (NTRS)

    Babel, Henry W. (Inventor); Anderson, Raymond H. (Inventor)

    1996-01-01

    A relatively impervious mechanical seal is formed between the outer surface of a tube and the inside surface of a mechanical fitting of a high pressure fluid or hydraulic system by applying a very thin soft metal layer onto the outer surface of the hard metal tube and/or inner surface of the hard metal fitting. The thickness of such thin metal layer is independent of the size of the tube and/or fittings. Many metals and alloys of those metals exhibit the requisite softness, including silver, gold, tin, platinum, indium, rhodium and cadmium. Suitably, the coating is about 0.0025 millimeters (0.10 mils) in thickness. After compression, the tube and fitting combination exhibits very low leak rates on the order or 10.sup.-8 cubic centimeters per second or less as measured using the Helium leak test.

  1. Simultaneous crystallization of diamond and cubic boron nitride from the graphite relative BC[sub 2]N under high pressure/high temperature conditions

    SciTech Connect

    Takayoshi Sasaki; Minoru Akaishi; Shinobu Yamaoka; Yoshinori Fujiki; Tetsuo Oikawa )

    1993-05-01

    Graphite BC[sub 2]N has been compressed with Co metal at a pressure of 5.5 GPa and temperatures of 1400-1600[degrees]C. The principal resulting products were crystals (average dimension 3 [mu]m) with cubiclike facets. The powder X-ray diffraction pattern revealed two kinds of cubic phase, in approximately equal amounts, which were identified as diamond and cBN on the basis of their lattice parameters. Microelemental analyses on individual crystal fragments by K-edge electron energy-loss spectroscopy confirmed this disproportionating crystallization scheme: half of the grains were composed of carbon-only signals of which gave fine-structure characteristic of sp[sup 3] bonding and the other half gave spectra characteristic of sp[sup 3] boron and nitrogen. The crystallization of cBN as well as diamond in the catalytic solvent of pure Co metal is observed here for the first time and is of relevance to the mechanism of the accepted catalytic action of cobalt on the hexagonal/cubic transformation. 26 refs., 4 figs., 2 tabs.

  2. High-pressure phase transitions of strontianite

    NASA Astrophysics Data System (ADS)

    Speziale, S.; Biedermann, N.; Reichmann, H. J.; Koch-Mueller, M.; Heide, G.

    2015-12-01

    Strontianite (SrCO3) is isostructural to aragonite, a major high-pressure polymorph of calcite. Thus it is a material of interest to investigate the high-pressure phase behavior of aragonite-group minerals. SrCO3 is a common component of natural carbonates and knowing its physical properties at high pressures is necessary to properly model the thermodynamic properties of complex carbonates, which are major crustal minerals but are also present in the deep Earth [Brenker et al., 2007] and control carbon cycling in the Earth's mantle. The few available high-pressure studies of SrCO3 disagree regarding both pressure stability and structure of the post-aragonite phase [Lin & Liu, 1997; Ono et al., 2005; Wang et al. 2015]. To clarify such controversies we investigated the high-pressure behavior of synthetic SrCO3 by Raman spectroscopy. Using a diamond anvil cell we compressed single-crystals or powder of strontianite (synthesized at 4 GPa and 1273 K for 24h in a multi anvil apparatus), and measured Raman scattering up to 78 GPa. SrCO3 presents a complex high-pressure behavior. We observe mode softening above 20 GPa and a phase transition at 25 - 26.9 GPa, which we interpret due to the CO3 groups rotation, in agreement with Lin & Liu [1997]. The lattice modes in the high-pressure phase show dramatic changes which may indicate a change from 9-fold coordinated Sr to a 12-fold-coordination [Ono, 2007]. Our results confirm that the high-pressure phase of strontianite is compatible with Pmmn symmetry. References Brenker, F.E. et al. (2007) Earth and Planet. Sci. Lett., 260, 1; Lin, C.-C. & Liu, L.-G. (1997) J. Phys. Chem. Solids, 58, 977; Ono, S. et al. (2005) Phys. Chem. Minerals, 32, 8; Ono, S. (2007) Phys. Chem. Minerals, 34, 215; Wang, M. et al. (2015) Phys Chem Minerals 42, 517.

  3. [High Pressure Gas Tanks

    NASA Technical Reports Server (NTRS)

    Quintana, Rolando

    2002-01-01

    Four high-pressure gas tanks, the basis of this study, were especially made by a private contractor and tested before being delivered to NASA Kennedy Space Center. In order to insure 100% reliability of each individual tank the staff at KSC decided to again submit the four tanks under more rigorous tests. These tests were conducted during a period from April 10 through May 8 at KSC. This application further validates the predictive safety model for accident prevention and system failure in the testing of four high-pressure gas tanks at Kennedy Space Center, called Continuous Hazard Tracking and Failure Prediction Methodology (CHTFPM). It is apparent from the variety of barriers available for a hazard control that some barriers will be more successful than others in providing protection. In order to complete the Barrier Analysis of the system, a Task Analysis and a Biomechanical Study were performed to establish the relationship between the degree of biomechanical non-conformities and the anomalies found within the system on particular joints of the body. This relationship was possible to obtain by conducting a Regression Analysis to the previously generated data. From the information derived the body segment with the lowest percentage of non-conformities was the neck flexion with 46.7%. Intense analysis of the system was conducted including Preliminary Hazard Analysis (PHA), Failure Mode and Effect Analysis (FMEA), and Barrier Analysis. These analyses resulted in the identification of occurrences of conditions, which may be becoming hazardous in the given system. These conditions, known as dendritics, may become hazards and could result in an accident, system malfunction, or unacceptable risk conditions. A total of 56 possible dendritics were identified. Work sampling was performed to observe the occurrence each dendritic. The out of control points generated from a Weighted c control chart along with a Pareto analysis indicate that the dendritics "Personnel not

  4. High-pressure synthesis, long-term stability of single crystals of diboron trioxide, B2O3, and an empirical electronic polarizability of [3]B3+

    NASA Astrophysics Data System (ADS)

    Burianek, Manfred; Birkenstock, Johannes; Mair, Philipp; Kahlenberg, Volker; Medenbach, Olaf; Shannon, Robert D.; Fischer, Reinhard X.

    2016-07-01

    Single crystals of B2O3 are needed for the precise determination of the refractive indices used to calculate the electronic polarizability α of 3-coordinated boron. The α(B) values in turn are used to predict mean refractive indices of borate minerals. Since the contribution of boron to the total polarizability of a mineral is very low, the synthetic compound B2O3 represents an ideal model system because of its high molar content of boron. Millimeter-sized crystals were synthesized at 1 GPa in a piston-cylinder apparatus. The samples were heated above the liquidus (800 °C), subsequently cooled at 15 °C/h to 500 °C and finally quenched. The refractive indices were determined by the immersion method using a microrefractometer spindle stage. The refractive indices n o = 1.653 (3) and n e = 1.632 (3) correspond to a total polarizability for B2O3 of α = 4.877 Å3. These values were used to determine the electronic polarizability of boron of α(B) = 0.16 Å3. Although the surface of the B2O3 crystals was coated with a hydrous film immediately after being exposed to air, its bulk crystallinity is retained for a period of at least 2 months.

  5. High pressure capillary connector

    DOEpatents

    Renzi, Ronald F.

    2005-08-09

    A high pressure connector capable of operating at pressures of 40,000 psi or higher is provided. This connector can be employed to position a first fluid-bearing conduit that has a proximal end and a distal end to a second fluid-bearing conduit thereby providing fluid communication between the first and second fluid-bearing conduits. The connector includes (a) an internal fitting assembly having a body cavity with (i) a lower segment that defines a lower segment aperture and (ii) an interiorly threaded upper segment, (b) a first member having a first member aperture that traverses its length wherein the first member aperture is configured to accommodate the first fluid-bearing conduit and wherein the first member is positioned in the lower segment of the internal fitting assembly, and (c) a second member having a second member aperture that traverses its length wherein the second member is positioned in the upper segment of the fitting assembly and wherein a lower surface of the second member is in contact with an upper surface of the first member to assert a compressive force onto the first member and wherein the first member aperture and the second member aperture are coaxial.

  6. Laser techniques in high-pressure geophysics

    NASA Technical Reports Server (NTRS)

    Hemley, R. J.; Bell, P. M.; Mao, H. K.

    1987-01-01

    Laser techniques in conjunction with the diamond-anvil cell can be used to study high-pressure properties of materials important to a wide range of problems in earth and planetary science. Spontaneous Raman scattering of crystalline and amorphous solids at high pressure demonstrates that dramatic changes in structure and bonding occur on compression. High-pressure Brillouin scattering is sensitive to the pressure variations of single-crystal elastic moduli and acoustic velocities. Laser heating techniques with the diamond-anvil cell can be used to study phase transitions, including melting, under deep-earth conditions. Finally, laser-induced ruby fluorescence has been essential for the development of techniques for generating the maximum pressures now possible with the diamond-anvil cell, and currently provides a calibrated in situ measure of pressure well above 100 gigapascals.

  7. Atomic and electronic structure transformations in SnS2 at high pressures: a joint single crystal X-ray diffraction and DFT study.

    PubMed

    Filsø, M Ø; Eikeland, E; Zhang, J; Madsen, S R; Iversen, B B

    2016-03-01

    The layered semiconductor SnS2 spurs much interest for both intercalation and optoelectronic applications. Despite the wealth of research in the field of metal dichalcogenides, the structure-property relationship of this compound remains unclear. Here we present a thorough study combining single-crystal X-ray diffraction and DFT calculations on SnS2 in the pressure range 0 < p < 20 GPa. The anisotropic compression of the unit cell is clearly linked to the van der Waals interactions between the S-Sn-S sandwich layers, as the compression mainly affects the interlayer distance. This compression behavior is coincidal with the compression of other well-known layered compounds (graphite and boron nitride) but differs significantly from the compression of other MS2 compounds, making it clear that SnS2 presents a unique and interesting case in the field of metal dichalcogenides. The compression leads to a significant increase in S···S interlayer interaction which in turn results in a change in the electronic structure, documented through DFT band structure calculations. The calculated narrowing of the band gap is supported by a significant, reversible color change of the single crystal. At 20 GPa, the size of the band gap has decreased from 2.15 to 0.88 eV, and band gap closure is predicted to occur at 33 GPa.

  8. Multianvil high-pressure/high-temperature synthesis, crystal structure, and thermal behaviour of the rare-earth borogermanate Ce{sub 6}(BO{sub 4}){sub 2}Ge{sub 9}O{sub 22}

    SciTech Connect

    Heymann, Gunter; Huppertz, Hubert . E-mail: huh@cup.uni-muenchen.de

    2006-02-15

    The new monoclinic cerium borogermanate Ce{sub 6}(BO{sub 4}){sub 2}Ge{sub 9}O{sub 22} was synthesized under high-pressure and high-temperature conditions in a Walker-type multianvil apparatus at 10.5GPa and 1200 deg. C. Ce{sub 6}(BO{sub 4}){sub 2}Ge{sub 9}O{sub 22} crystallizes with two formula units in the space group P2{sub 1}/n with lattice parameters a=877.0(2), b=1079.4(2), c=1079.1(2) pm, and {beta}=95.94(3){sup o}. As the parameter pressure favours the formation of compounds with cations possessing high coordination numbers, it was possible to produce simultaneously BO{sub 4}-tetrahedra and GeO{sub 6}-octahedra in one and the same borogermanate for the first time. Furthermore, the cerium atoms show high coordination numbers (C.N.: 9 and 11), and one oxygen site bridges one boron and two germanium atoms (O{sup [3]}), which is observed here for the first time. Besides a structural discussion, temperature-dependent X-ray powder diffraction data are presented, demonstrating the metastable character of this high-pressure phase.

  9. Specific features of insulator-metal transitions under high pressure in crystals with spin crossovers of 3d ions in tetrahedral environment

    SciTech Connect

    Lobach, K. A. Ovchinnikov, S. G.; Ovchinnikova, T. M.

    2015-01-15

    For Mott insulators with tetrahedral environment, the effective Hubbard parameter U{sub eff} is obtained as a function of pressure. This function is not universal. For crystals with d{sup 5} configuration, the spin crossover suppresses electron correlations, while for d{sup 4} configurations, the parameter U{sub eff} increases after a spin crossover. For d{sup 2} and d{sup 7} configurations, U{sub eff} increases with pressure in the high-spin (HS) state and is saturated after the spin crossover. Characteristic features of the insulator-metal transition are considered as pressure increases; it is shown that there may exist cascades of several transitions for various configurations.

  10. High-Pressure Single-Crystal Neutron Scattering Study of Magnetic and Fe Vacancy Orders in (Tl,Rb)2 Fe4 Se5 Superconductor

    SciTech Connect

    Ye, Feng; Bao, Wei; Chi, Song-Xue; Santos, Antonio M. dos; Molaison, Jamie J.; Fang, Ming-Hu; Wang, Hang-Dong; Mao, Qian-Hui; Wang, Jin-Chen; Liu, Juan-Juan; Sheng, Jie-Ming

    2014-12-01

    We investigate the magnetic and iron vacancy orders in superconducting (Tl,Rb)2Fe4Se5 single-crystals by using a high-pressure neutron diffraction technique. Similar to the temperature effect, the block antiferromagnetic order gradually decreases upon increasing pressure while the Fe vacancy superstructural order remains intact before its precipitous disappearance at the critical pressure Pc = 8.3 GPa. Combined with previously determined Pc for superconductivity, our phase diagram under pressure reveals the concurrence of the block AFM order, the √5 × √5 iron vacancy order and superconductivity for the 245 superconductor. Lastly, a synthesis of current experimental data in a coherent physical picture is attempted.

  11. High-pressure neutron diffraction

    SciTech Connect

    Xu, Hongwu

    2011-01-10

    This lecture will cover progress and prospect of applications of high-pressure neutron diffraction techniques to Earth and materials sciences. I will first introduce general high-pressure research topics and available in-situ high-pressure techniques. Then I'll talk about high-pressure neutron diffraction techniques using two types of pressure cells: fluid-driven and anvil-type cells. Lastly, I will give several case studies using these techniques, particularly, those on hydrogen-bearing materials and magnetic transitions.

  12. Effect of high pressure on the electrical resistivity of optimally doped YBa2Cu3O7-δ single crystals with unidirectional planar defects

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

    In the present work the effect of hydrostatic pressure up to 10 kbar on in-plane electrical resistivity of well-structured YBa2Cu3O7-δ (δ<0.15, Тс≈91 K, ΔТс≈0.3 K) single crystals was investigated. The influence of the twin boundaries on the electrical resistivity was minimized. The resistivities temperature dependences in the interval Тс up to 300 K can be approximated by taking into account the linear term at high temperatures and the fluctuation conductivity (Maki-Thompson model) near Тс. The parameters of the linear dependence of R(T) are decreasing as the pressure is increasing. Тс increases linearly when the pressure increases with the derivative dTc/dP≈0.080 K/kbar. Among the Maki-Thompson model parameters the inter-layer distance, d, can be considered to be independent from pressure, the transverse coherence length, ξc(0)∼0.1d.

  13. Information-theoretic approach for the discovery of design rules for crystal chemistry.

    PubMed

    Kong, Chang Sun; Luo, Wei; Arapan, Sergiu; Villars, Pierre; Iwata, Shuichi; Ahuja, Rajeev; Rajan, Krishna

    2012-07-23

    In this work, it is shown that for the first time that, using information-entropy-based methods, one can quantitatively explore the relative impact of a wide multidimensional array of electronic and chemical bonding parameters on the structural stability of intermetallic compounds. Using an inorganic AB2 compound database as a template data platform, the evolution of design rules for crystal chemistry based on an information-theoretic partitioning classifier for a high-dimensional manifold of crystal chemistry descriptors is monitored. An application of this data-mining approach to establish chemical and structural design rules for crystal chemistry is demonstrated by showing that, when coupled with first-principles calculations, statistical inference methods can serve as a tool for significantly accelerating the prediction of unknown crystal structures.

  14. Electrokinetically pumped high pressure sprays

    DOEpatents

    Schoeniger, Joseph S.; Paul, Phillip H.; Schoeniger, Luke

    2005-11-01

    An electrokinetic pump capable of producing high pressure is combined with a nozzle having a submicron orifice to provide a high pressure spray device. Because of its small size, the device can be contained within medical devices such as an endoscope for delivering biological materials such as DNA, chemo therapeutic agents, or vaccines to tissues and cells.

  15. Electrokinetically pumped high pressure sprays

    SciTech Connect

    Schoeniger, Joseph S.; Paul, Phillip H.; Schoeniger, Luke

    2002-01-01

    An electrokinetic pump capable of producing high pressure is combined with a nozzle having a submicron orifice to provide a high pressure spray device. Because of its small size, the device can be contained within medical devices such as an endoscope for delivering biological materials such as DNA, chemo therapeutic agents, or vaccines to tissues and cells.

  16. Crystal structures and compressibility of novel iron borides Fe{sub 2}B{sub 7} and Fe{sub x}B{sub 50} synthesized at high pressure and high temperature

    SciTech Connect

    Bykova, E.; Gou, H.; Bykov, M.; Hanfland, M.; Dubrovinsky, L.; Dubrovinskaia, N.

    2015-10-15

    We present here a detailed description of the crystal structures of novel iron borides, Fe{sub 2}B{sub 7} and Fe{sub x}B{sub 50} with various iron content (x=1.01(1), 1.04(1), 1.32(1)), synthesized at high pressures and high temperatures. As revealed by high-pressure single-crystal X-ray diffraction, the structure of Fe{sub 2}B{sub 7} possesses short incompressible B–B bonds, which make it as stiff as diamond in one crystallographic direction. The volume compressibility of Fe{sub 2}B{sub 7} (the bulk modulus K{sub 0}= 259(1.8) GPa, K{sub 0}′= 4 (fixed)) is even lower than that of FeB{sub 4} and comparable with that of MnB{sub 4}, known for high bulk moduli among 3d metal borides. Fe{sub x}B{sub 50} adopts the structure of the tetragonal δ-B, in which Fe atoms occupy an interstitial position. Fe{sub x}B{sub 50} does not show considerable anisotropy in the elastic behavior. - Graphical abstract: Crystal structures of novel iron borides, Fe{sub 2}B{sub 7} and Fe{sub x}B{sub 50} (x=1.01(1), 1.04(1), 1.32(1)). - Highlights: • Novel iron borides, Fe{sub 2}B{sub 7} and Fe{sub x}B{sub 50}, were synthesized under HPHT conditions. • Fe{sub 2}B{sub 7} has a unique orthorhombic structure (space group Pbam). • Fe{sub 2}B{sub 7} possesses short incompressible B–B bonds that results in high bulk modulus. • Fe{sub x}B{sub 50} adopts the structure of the tetragonal δ-B composed of B{sub 12} icosahedra. • In Fe{sub x}B{sub 50} intraicosahedral bonds are stiffer than intericosahedral ones.

  17. High-pressure synthesis and crystal structures of the strontium oxogallates Sr{sub 2}Ga{sub 2}O{sub 5} and Sr{sub 5}Ga{sub 6}O{sub 14}

    SciTech Connect

    Kahlenberg, Volker; Goettgens, Valerie; Mair, Philipp; Schmidmair, Daniela

    2015-08-15

    High-pressure synthesis experiments in a piston–cylinder apparatus at 1.5 GPa/3.0 GPa and 1000 °C resulted in the formation of single-crystals of Sr{sub 2}Ga{sub 2}O{sub 5} and Sr{sub 5}Ga{sub 6}O{sub 14}, respectively. The structures of both compounds have been solved from single-crystal diffraction data sets using direct methods. The first compound is orthorhombic with space group type Pbca (a=10.0021(4) Å, b=9.601(4) Å, c=10.6700(4) Å, V=1024.6(4) Å{sup 3}, M{sub r}=394.68 u, Z=8, D{sub x}=5.12 g/cm{sup 3}) and belongs to the group of single layer gallates. Individual sheets are parallel to (0 0 1) and can be built from the condensation of unbranched vierer single chains running along [0 1 0]. The layers are characterized by the presence of four- and strongly elliptical eight-membered rings of corner connected tetrahedra in UUDD and UUUUDDDD conformation. Strontium atoms are sandwiched between the tetrahedral layers for charge compensation and are coordinated by six and seven oxygen ligands, respectively. Sr{sub 2}Ga{sub 2}O{sub 5} is isotypic with several other double sulfides and selenides. To the best of our knowledge, it is the first example of an oxide with this structure type. From a structural point of view, Sr{sub 5}Ga{sub 6}O{sub 14} is a phyllogallate as well. The crystal structure adopts the monoclinic space group P2{sub 1}/c (a=8.1426(3) Å, b=8.1803(3) Å, c=10.8755(4) Å, β=91.970(4)° V=723.98(5) Å{sup 3}, M{sub r}=1080.42 u, Z=2, D{sub x}=4.96 g/cm{sup 3}). Individual sheets extend along (0 0 1). Basic building units are unbranched dreier single chains parallel to [1 0 0]. The layers contain tertiary (Q{sup 3}) und quaternary (Q{sup 4}) connected [GaO{sub 4}]-tetrahedra in the ratio 2:1 resulting in a Ga:O ratio of 3:7 and the formation of exclusively five-membered rings. Linkage between adjacent tetrahedral sheets is provided by three symmetrically independent strontium ions which are surrounded by six to eight oxygen atoms. The layers

  18. Wine chemistry and flavor: looking into the crystal glass.

    PubMed

    Ebeler, Susan E; Thorngate, John H

    2009-09-23

    Over the past century, advances in analytical chemistry have played a significant role in understanding wine chemistry and flavor. Whereas the focus in the 19th and early 20th centuries was on determining major components (ethanol, organic acids, sugars) and detecting fraud, more recently the emphasis has been on quantifying trace compounds including those that may be related to varietal flavors. In addition, over the past 15 years, applications of combined analytical and sensory techniques (e.g., gas chromatography-olfactometry) have improved the ability to relate chemical composition to sensory properties, whether identifying impact compounds or elucidating matrix effects. Many challenges remain, however. This paper discusses some of the recent research aimed at understanding how viticultural and enological practices influence grape and wine volatiles. In addition, the challenges in linking composition to sensory properties will also be reviewed. Finally, future advances in linking grape, yeast, and human genomics to wine chemistry and flavor will be briefly discussed. PMID:19719127

  19. Wine chemistry and flavor: looking into the crystal glass.

    PubMed

    Ebeler, Susan E; Thorngate, John H

    2009-09-23

    Over the past century, advances in analytical chemistry have played a significant role in understanding wine chemistry and flavor. Whereas the focus in the 19th and early 20th centuries was on determining major components (ethanol, organic acids, sugars) and detecting fraud, more recently the emphasis has been on quantifying trace compounds including those that may be related to varietal flavors. In addition, over the past 15 years, applications of combined analytical and sensory techniques (e.g., gas chromatography-olfactometry) have improved the ability to relate chemical composition to sensory properties, whether identifying impact compounds or elucidating matrix effects. Many challenges remain, however. This paper discusses some of the recent research aimed at understanding how viticultural and enological practices influence grape and wine volatiles. In addition, the challenges in linking composition to sensory properties will also be reviewed. Finally, future advances in linking grape, yeast, and human genomics to wine chemistry and flavor will be briefly discussed.

  20. High-pressure synthesis, crystal structure, and structural relationship of the first ytterbium fluoride borate Yb{sub 5}(BO{sub 3}){sub 2}F{sub 9}

    SciTech Connect

    Haberer, Almut; Huppertz, Hubert

    2009-04-15

    Yb{sub 5}(BO{sub 3}){sub 2}F{sub 9} was synthesized under high-pressure/high-temperature conditions in a Walker-type multianvil apparatus at 7.5 GPa and 1100 deg. C, representing the first known ytterbium fluoride borate. The compound exhibits isolated BO{sub 3}-groups next to ytterbium cations and fluoride anions, showing a structure closely related to the other known rare-earth fluoride borates RE{sub 3}(BO{sub 3}){sub 2}F{sub 3} (RE=Sm, Eu, Gd) and Gd{sub 2}(BO{sub 3})F{sub 3}. Monoclinic Yb{sub 5}(BO{sub 3}){sub 2}F{sub 9} crystallizes in space group C2/c with the lattice parameters a=2028.2(4) pm, b=602.5(2) pm, c=820.4(2) pm, and beta=100.63(3){sup o} (Z=4). Three different ytterbium cations can be identified in the crystal structure, each coordinated by nine fluoride and oxygen anions. None of the five crystallographically independent fluoride ions is coordinated by boron atoms, solely by trigonally-planar arranged ytterbium cations. In close proximity to the above mentioned compounds RE{sub 3}(BO{sub 3}){sub 2}F{sub 3} (RE=Sm, Eu, Gd) and Gd{sub 2}(BO{sub 3})F{sub 3}, Yb{sub 5}(BO{sub 3}){sub 2}F{sub 9} can be described via alternating layers with the formal compositions 'YbBO{sub 3}' and 'YbF{sub 3}' in the bc-plane. - Graphical abstract: High-pressure/high-temperature synthesis (multianvil technique) led to the first ytterbium fluoride borate Yb{sub 5}(BO{sub 3}){sub 2}F{sub 9}, built up from isolated BO{sub 3}-groups. The compound shows structural relations to the known rare-earth fluoride borates RE{sub 3}(BO{sub 3}){sub 2}F{sub 3} (RE=Sm, Eu, Gd) and Gd{sub 2}(BO{sub 3})F{sub 3}.

  1. High pressure synthesis gas fermentation

    SciTech Connect

    Not Available

    1992-01-01

    The construction of the high pressure gas phase fermentation system has been completed. Photographs of the various components of the system are presented, along with an operating procedure for the equipment.

  2. High pressure studies of potassium perchlorate

    NASA Astrophysics Data System (ADS)

    Pravica, Michael; Wang, Yonggang; Sneed, Daniel; Reiser, Sharissa; White, Melanie

    2016-09-01

    Two experiments are reported on KClO4 at extreme conditions. A static high pressure Raman study was first conducted to 18.9 GPa. Evidence for at least two new phases was observed: one between 2.4 and 7.7 GPa (possibly sluggish), and the second near 11.7 GPa. Then, the X-ray induced decomposition rate of potassium perchlorate (KClO4 → hν KCl + 2O2) was studied up to 15.2 GPa. The time-dependent growth of KCl and O2 was monitored. The decomposition rate slowed at higher pressures. We present the first direct evidence for O2 crystallization at higher pressures, demonstrating that O2 molecules aggregate at high pressure.

  3. High-pressure synthesis, crystal structure, and magnetic properties of KSbO3-type 5d oxides K0.84OsO3 and Bi2.93Os3O11

    NASA Astrophysics Data System (ADS)

    Yuan, Yahua; Feng, Hai L.; Shi, Youguo; Tsujimoto, Yoshihiro; Belik, Alexei A.; Matsushita, Yoshitaka; Arai, Masao; He, Jianfeng; Tanaka, Masahiko; Yamaura, Kazunari

    2014-12-01

    5d Solid-state oxides K0.84OsO3 (Os5.16+; 5d 2.84) and Bi2.93Os3O11 (Os4.40+; 5d 3.60) were synthesized under high-pressure and high-temperature conditions (6 GPa and 1500-1700 °C). Their crystal structures were determined by synchrotron x-ray diffraction and their 5d electronic properties and tunnel-like structure motifs were investigated. A KSbO3-type structure with a space group of Im-3 and Pn-3 was determined for K0.84OsO3 and Bi2.93Os3O11, respectively. The magnetic and electronic transport properties of the polycrystalline compounds were compared with those obtained theoretically. It was revealed that the 5d tunnel-like structures are paramagnetic with metallic charge conduction at temperatures above 2 K. This was similar to what was observed for structurally relevant 5d oxides, including Bi3Re3O11 (Re4.33+; 5d 2.66) and Ba2Ir3O9 (Ir4.66+; 5d 4.33). The absence of long-range magnetic order seems to be common among 5d KSbO3-like oxides, regardless of the number of 5d electrons (between 2.6 and 4.3 per 5d atom).

  4. High pressure synthesis gas conversion. Task 3: High pressure profiles

    SciTech Connect

    Not Available

    1993-05-01

    The purpose of this research project was to build and test a high pressure fermentation system for the production of ethanol from synthesis gas. The fermenters, pumps, controls, and analytical system were procured or fabricated and assembled in our laboratory. This system was then used to determine the effects of high pressure on growth and ethanol production by C. 1jungdahlii. The limits of cell concentration and mass transport relationships were found in CSTR and immobilized cell reactors (ICR). The minimum retention times and reactor volumes were found for ethanol production in these reactors.

  5. Crystal chemistry and structure refinement of five hydrated calcium borates

    USGS Publications Warehouse

    Clark, J.R.; Appleman, D.E.; Christ, C.L.

    1964-01-01

    The crystal structures of the five known members of the series Ca2B6O11??xH2O (x = 1, 5, 5, 7, 9, and 13) have been refined by full-matrix least-squares techniques, yielding bond distances and angles with standard errors of less than 0??01 A?? and 0??5??, respectively. The results illustrate the crystal chemical principles that govern the structures of hydrated borate compounds. The importance of hydrogen bonding in the ferroelectric transition of colemanite is confirmed by more accurate proton assignments. ?? 1964.

  6. Green chemistry strategies using crystal-to-crystal photoreactions: stereoselective synthesis and decarbonylation of trans-alpha,alpha'-dialkenoylcyclohexanones.

    PubMed

    Mortko, Christopher J; Garcia-Garibay, Miguel A

    2005-06-01

    This paper describes steps to develop green chemistry strategies to prepare compounds with adjacent quaternary centers by stereospecific photodecarbonylation of crystalline ketones bearing radical-stabilizing alkenyl substituents in their alpha-positions. Crystals of trans-2,6-dimethyl-2,6-di(benzyloxycarbonyl-trans-ethenyl)-cyclohexanone, trans-2, prepared by double Michael addition of benzyl propiolate to 2,6-dimethyl-cyclohexanone iso-butylimine (1), were investigated along with those of the dicarboxylic acid (trans-3) and a dibenzylammonium salt derivative (trans-4) to establish the best substrates for the solid-state reaction. While reactions of the ester and the acid lose CO to give radical combination products with high selectivity at low conversions, the crystalline salt gave a similar product in >97% yield. Explorative reactions carried out under sunlight and in semipreparative (1.5 g) scale highlight the potential of reactions in crystals as a viable strategy for the development of green chemistry. PMID:15926806

  7. Chemistry at high pressures and temperatures: in-situ synthesis and characterization of {beta}-Si{sub 3}N{sub 4} by DAC X-ray/laser-heating studies

    SciTech Connect

    Yoo, C.-S.; Akella, J.; Nicol, M.

    1996-01-01

    We have developed in-situ XRD technique at high pressures and temperatures by integrating the angle-resolved synchrotron XRD method, laser-heating system, and diamond anvil cell together. Using this technique, we have studied the direct elementary reactions of nitrogen with Si, yielding technologically important {beta}-Si{sub 3}N{sub 4}. These reactions do not occur at ambient temperatures at high pressures up to 50 GPa, but proceed exothermically at high temperatures at moderate pressures. It implies that the reaction is kinetically limited by a large activation barrier.

  8. Crystal chemistry of hydrothermally grown ternary alkali rare earth fluorides.

    PubMed

    McMillen, Colin D; Comer, Sara; Fulle, Kyle; Sanjeewa, Liurukara D; Kolis, Joseph W

    2015-12-01

    The structural variations of several alkali metal rare earth fluoride single crystals are summarized. Two different stoichiometric formulations are considered, namely those of ARE2F7 and ARE3F10 (A = K, Rb, Cs; RE = Y, La-Lu), over a wide range of ionic radii of both the alkali and rare earth (RE) ions. Previously reported and several new single-crystal structures are considered. The new single crystals are grown using hydrothermal methods and the structures are compared with literature reports of structures grown from both melts and hydrothermal fluids. The data reported here are combined with the literature data to gain a greater understanding of structural subtleties surrounding these systems. The work underscores the importance of the size of the cations to the observed structure type and also introduces synthetic technique as a contributor to the same. New insights based on single-crystal structure analysis in the work introduce a new disordered structure type in the case of ARE2F7, and examine the trends and boundaries of the ARE3F10 stoichiometry. Such fundamental structural information is useful in understanding the potential applications of these compounds as optical materials. PMID:26634734

  9. Crystal chemistry of hydrothermally grown ternary alkali rare earth fluorides.

    PubMed

    McMillen, Colin D; Comer, Sara; Fulle, Kyle; Sanjeewa, Liurukara D; Kolis, Joseph W

    2015-12-01

    The structural variations of several alkali metal rare earth fluoride single crystals are summarized. Two different stoichiometric formulations are considered, namely those of ARE2F7 and ARE3F10 (A = K, Rb, Cs; RE = Y, La-Lu), over a wide range of ionic radii of both the alkali and rare earth (RE) ions. Previously reported and several new single-crystal structures are considered. The new single crystals are grown using hydrothermal methods and the structures are compared with literature reports of structures grown from both melts and hydrothermal fluids. The data reported here are combined with the literature data to gain a greater understanding of structural subtleties surrounding these systems. The work underscores the importance of the size of the cations to the observed structure type and also introduces synthetic technique as a contributor to the same. New insights based on single-crystal structure analysis in the work introduce a new disordered structure type in the case of ARE2F7, and examine the trends and boundaries of the ARE3F10 stoichiometry. Such fundamental structural information is useful in understanding the potential applications of these compounds as optical materials.

  10. Crystal Model Kits for Use in the General Chemistry Laboratory.

    ERIC Educational Resources Information Center

    Kildahl, Nicholas J.; And Others

    1986-01-01

    Dynamic crystal model kits are described. Laboratory experiments in which students use these kits to build models have been extremely successful in providing them with an understanding of the three-dimensional structures of the common cubic unit cells as well as hexagonal and cubic closest-packing of spheres. (JN)

  11. High pressure synthesis and crystal structure of a ternary superconductor Ca{sub 2}Al{sub 3}Si{sub 4} containing layer structured calcium sub-network isomorphous with black phosphorus

    SciTech Connect

    Tanaka, Masashi; Zhang, Shuai; Tanaka, Yuki; Inumaru, Kei; Yamanaka, Shoji

    2013-02-15

    The Zintl compound CaAl{sub 2}Si{sub 2} is peritectically decomposed to a mixture of Ca{sub 2}Al{sub 3}Si{sub 4} and aluminum metal at temperatures above 600 Degree-Sign C under a pressure of 5 GPa. The new ternary compound Ca{sub 2}Al{sub 3}Sl{sub 4} crystalizes with the space group Cmc2{sub 1} and the lattice parameters a=5.8846(8), b=14.973(1), and c=7.7966(5) A. The structure is composed of aluminum silicide framework [Al{sub 3}Si{sub 4}] and layer structured [Ca{sub 2}] network interpenetrating with each other. The electron probe microanalysis (EPMA) shows the formation of solid solutions Ca{sub 2}Al{sub 3-x}Si{sub 4+x} (x<0.6). The layer structured [Ca{sub 2}] sub-network is isomorphous with black phosphorus. The new ternary compound shows superconductivity with a transition temperature (T{sub c}) of 6.4 K. The band structure calculation suggests that the superconductivity should occur through the conduction bands mainly composed of 3p orbitals of the aluminum silicide framework. - Graphical abstract: A new ternary superconductor Ca{sub 2}Al{sub 3}Si{sub 4} has been prepared under high pressure and high temperature conditions, which includes layer structured calcium sub-network isomorphous with black phosphorus. Highlights: Black-Right-Pointing-Pointer A typical Zintl compound CaAl{sub 2}Si{sub 2} melts congruently at ambient pressure. Black-Right-Pointing-Pointer Under high pressure CaAl{sub 2}Si{sub 2} decomposes to Ca{sub 2}Al{sub 3}Si{sub 4} and Al at {approx}600 Degree-Sign C. Black-Right-Pointing-Pointer Ca{sub 2}Al{sub 3}Si{sub 4} contains Ca sub-network isomorphous with black phosphorus. Black-Right-Pointing-Pointer Ca{sub 2}Al{sub 3}Si{sub 4} shows superconductivity with a transition temperature of 6.4 K.

  12. Visualizing Molecular Chirality in the Organic Chemistry Laboratory Using Cholesteric Liquid Crystals

    ERIC Educational Resources Information Center

    Popova, Maia; Bretz, Stacey Lowery; Hartley, C. Scott

    2016-01-01

    Although stereochemistry is an important topic in second-year undergraduate organic chemistry, there are limited options for laboratory activities that allow direct visualization of macroscopic chiral phenomena. A novel, guided-inquiry experiment was developed that allows students to explore chirality in the context of cholesteric liquid crystals.…

  13. Deformation Twinning of a Silver Nanocrystal under High Pressure

    SciTech Connect

    Huang, Xiaojing; Yang, Wenge; Harder, Ross; Sun, Yugang; Liu, Ming; Chu, Yong S.; Robinson, Ian K.; Mao, Ho-kwang

    2015-11-01

    Within a high-pressure environment, crystal deformation is controlled by complex processes such as dislocation motion, twinning, and phase transitions, which change materials' microscopic morphology and alter their properties. Understanding a crystal's response to external stress provides a unique opportunity for rational tailoring of its functionalities. It is very challenging to track the strain evolution and physical deformation from a single nanoscale crystal under high-pressure stress. Here, we report an in situ three-dimensional mapping of morphology and strain evolutions in a single-crystal silver nanocube within a high-pressure environment using the Bragg Coherent Diffractive Imaging (CDI) method. We observed a continuous lattice distortion, followed by a deformation twining process at a constant pressure. The ability to visualize stress-introduced deformation of nanocrystals with high spatial resolution and prominent strain sensitivity provides an important route for interpreting and engineering novel properties of nanomaterials.

  14. Deformation Twinning of a Silver Nanocrystal under High Pressure.

    PubMed

    Huang, Xiaojing; Yang, Wenge; Harder, Ross; Sun, Yugang; Lu, Ming; Chu, Yong S; Robinson, Ian K; Mao, Ho-Kwang

    2015-11-11

    Within a high-pressure environment, crystal deformation is controlled by complex processes such as dislocation motion, twinning, and phase transitions, which change materials' microscopic morphology and alter their properties. Understanding a crystal's response to external stress provides a unique opportunity for rational tailoring of its functionalities. It is very challenging to track the strain evolution and physical deformation from a single nanoscale crystal under high-pressure stress. Here, we report an in situ three-dimensional mapping of morphology and strain evolutions in a single-crystal silver nanocube within a high-pressure environment using the Bragg Coherent Diffractive Imaging (CDI) method. We observed a continuous lattice distortion, followed by a deformation twining process at a constant pressure. The ability to visualize stress-introduced deformation of nanocrystals with high spatial resolution and prominent strain sensitivity provides an important route for interpreting and engineering novel properties of nanomaterials. PMID:26484941

  15. Electrokinetic high pressure hydraulic system

    DOEpatents

    Paul, Phillip H.; Rakestraw, David J.; Arnold, Don W.; Hencken, Kenneth R.; Schoeniger, Joseph S.; Neyer, David W.

    2003-06-03

    An electrokinetic high pressure hydraulic pump for manipulating fluids in capillary-based system. The pump uses electro-osmotic flow to provide a high pressure hydraulic system, having no moving mechanical parts, for pumping and/or compressing fluids, for providing valve means and means for opening and closing valves, for controlling fluid flow rate, and manipulating fluid flow generally and in capillary-based systems (microsystems), in particular. The compact nature of the inventive high pressure hydraulic pump provides the ability to construct a micro-scale or capillary-based HPLC system that fulfills the desire for small sample quantity, low solvent consumption, improved efficiency, the ability to run samples in parallel, and field portability. Control of pressure and solvent flow rate is achieved by controlling the voltage applied to an electrokinetic pump.

  16. Electrokinetic high pressure hydraulic system

    DOEpatents

    Paul, Phillip H.; Rakestraw, David J.; Arnold, Don W.; Hencken, Kenneth R.; Schoeniger, Joseph S.; Neyer, David W.

    2001-01-01

    An electrokinetic high pressure hydraulic pump for manipulating fluids in capillary-based systems. The pump uses electro-osmotic flow to provide a high pressure hydraulic system, having no moving mechanical parts, for pumping and/or compressing fluids, for providing valve means and means for opening and closing valves, for controlling fluid flow rate, and manipulating fluid flow generally and in capillary-based systems (Microsystems), in particular. The compact nature of the inventive high pressure hydraulic pump provides the ability to construct a micro-scale or capillary-based HPLC system that fulfills the desire for small sample quantity, low solvent consumption, improved efficiency, the ability to run samples in parallel, and field portability. Control of pressure and solvent flow rate is achieved by controlling the voltage applied to an electrokinetic pump.

  17. High pressure liquid level monitor

    DOEpatents

    Bean, Vern E.; Long, Frederick G.

    1984-01-01

    A liquid level monitor for tracking the level of a coal slurry in a high-pressure vessel including a toroidal-shaped float with magnetically permeable bands thereon disposed within the vessel, two pairs of magnetic field generators and detectors disposed outside the vessel adjacent the top and bottom thereof and magnetically coupled to the magnetically permeable bands on the float, and signal processing circuitry for combining signals from the top and bottom detectors for generating a monotonically increasing analog control signal which is a function of liquid level. The control signal may be utilized to operate high-pressure control valves associated with processes in which the high-pressure vessel is used.

  18. Exotic stable cesium polynitrides at high pressure

    DOE PAGESBeta

    Peng, Feng; Han, Yunxia; Liu, Hanyu; Yao, Yansun

    2015-11-19

    New polynitrides containing metastable forms of nitrogen are actively investigated as potential high energy-density materials. Using a structure search method based on the CALYPSO methodology, we investigated the stable stoichiometries and structures of cesium polynitrides at high pressures. Along with the CsN3, we identified five new stoichiometric compounds (Cs3N, Cs2N, CsN, CsN2, and CsN5) with interesting structures that may be experimentally synthesizable at modest pressures (i.e., less than 50 GPa). Nitrogen species in the predicted structures have various structural forms ranging from single atom (N) to highly endothermic molecules (N2, N3 , N4, N5, N6) and chains (N∞). Polymeric chainsmore » of nitrogen were found in the high-pressure C2/c phase of CsN2. This structure contains a substantially high content of single N-N bonds that exceeds the previously known nitrogen chains in pure forms, and also exhibit metastability at ambient conditions. We also identified a very interesting CsN crystal that contains novel N44- anion. In conclusion, to our best knowledge, this is the first time a charged N4 species being reported. Results of the present study suggest that it is possible to obtain energetic polynitrogens in main-group nitrides under high pressure.« less

  19. Exotic stable cesium polynitrides at high pressure

    NASA Astrophysics Data System (ADS)

    Peng, Feng; Han, Yunxia; Liu, Hanyu; Yao, Yansun

    2015-11-01

    New polynitrides containing metastable forms of nitrogen are actively investigated as potential high-energy-density materials. Using a structure search method based on the CALYPSO methodology, we investigated the stable stoichiometries and structures of cesium polynitrides at high pressures. Along with the CsN3, we identified five new stoichiometric compounds (Cs3N, Cs2N, CsN, CsN2, and CsN5) with interesting structures that may be experimentally synthesizable at modest pressures (i.e., less than 50 GPa). Nitrogen species in the predicted structures have various structural forms ranging from single atom (N) to highly endothermic molecules (N2, N3, N4, N5, N6) and chains (N∞). Polymeric chains of nitrogen were found in the high-pressure C2/c phase of CsN2. This structure contains a substantially high content of single N-N bonds that exceeds the previously known nitrogen chains in pure forms, and also exhibit metastability at ambient conditions. We also identified a very interesting CsN crystal that contains novel N44- anion. To our best knowledge, this is the first time a charged N4 species being reported. Results of the present study suggest that it is possible to obtain energetic polynitrogens in main-group nitrides under high pressure.

  20. Exotic stable cesium polynitrides at high pressure

    PubMed Central

    Peng, Feng; Han, Yunxia; Liu, Hanyu; Yao, Yansun

    2015-01-01

    New polynitrides containing metastable forms of nitrogen are actively investigated as potential high-energy-density materials. Using a structure search method based on the CALYPSO methodology, we investigated the stable stoichiometries and structures of cesium polynitrides at high pressures. Along with the CsN3, we identified five new stoichiometric compounds (Cs3N, Cs2N, CsN, CsN2, and CsN5) with interesting structures that may be experimentally synthesizable at modest pressures (i.e., less than 50 GPa). Nitrogen species in the predicted structures have various structural forms ranging from single atom (N) to highly endothermic molecules (N2, N3, N4, N5, N6) and chains (N∞). Polymeric chains of nitrogen were found in the high-pressure C2/c phase of CsN2. This structure contains a substantially high content of single N-N bonds that exceeds the previously known nitrogen chains in pure forms, and also exhibit metastability at ambient conditions. We also identified a very interesting CsN crystal that contains novel N44− anion. To our best knowledge, this is the first time a charged N4 species being reported. Results of the present study suggest that it is possible to obtain energetic polynitrogens in main-group nitrides under high pressure. PMID:26581175

  1. High pressure synthesis gas fermentation

    SciTech Connect

    Not Available

    1991-01-01

    Construction of the high pressure gas phase fermentation system is nearing completion. All non-explosion proof components will be housed separately in a gas-monitored plexiglas cabinet. A gas-monitoring system has been designed to ensure the safety of the operations in case of small or large accidental gas releases. Preliminary experiments investigating the effects of high pressure on Clostridium 1jungdahlii have shown that growth and CO uptake are not negatively affected and CO uptake by an increased total pressure of 100 psig at a syngas partial pressure of 10 psig.

  2. Electrokinetic high pressure hydraulic system

    DOEpatents

    Paul, Phillip H.; Rakestraw, David J.

    2000-01-01

    A compact high pressure hydraulic pump having no moving mechanical parts for converting electric potential to hydraulic force. The electrokinetic pump, which can generate hydraulic pressures greater than 2500 psi, can be employed to compress a fluid, either liquid or gas, and manipulate fluid flow. The pump is particularly useful for capillary-base systems. By combining the electrokinetic pump with a housing having chambers separated by a flexible member, fluid flow, including high pressure fluids, is controlled by the application of an electric potential, that can vary with time.

  3. Water solubility in pyrope at high pressures

    NASA Astrophysics Data System (ADS)

    Mookherjee, M.; Karato, S.-

    2006-12-01

    To address how much water is stored within the Earth's mantle, we need to understand the water solubility in the nominally anhydrous minerals. Much is known about olivine and pyroxene. Garnet is another important component, approaching 40% by volume in the transition zone. Only two studies on water solubility in pyrope at high-pressures exist which contradict each other. Lu and Keppler (1997) observed increase in water solubility in a natural pyrope up to 200 ppm wt of water, till 10 GPa. They concluded that the proton is located in the interstitial site. Withers et al. (1998) on the contrary, observed increasing water content in Mg-rich pyrope till 6 GPa, then sudden decrease of water, beyond detection, at 7 GPa. Based on infrared spectra, Withers et al. (1998), concluded hydrogarnet (Si^{4+} replaced by 4H+ to form O4H4) substitution in synthetic magnesium rich pyrope. They argued that at high pressure owing to larger volume, hydrogarnet substitution is unstable and water is expelled out of garnet. In transition zone conditions, however, majorite garnet seems to contain around 600-700 ppm wt of water (Bolfan-Casanova et al. 2000; Katayama et al. 2003). The cause for such discrepancy is not clear and whether garnet could store a significant amount of water at mantle condition is unconstrained. In order to understand the solubility mechanism of water in pyrope at high-pressure, we have conducted high- pressure experiments on naturally occurring single crystals of pyrope garnet (from Arizona, Aines and Rossman, 1984). To ascertain water-saturated conditions, we use olivine single-crystal as an internal standard. Preliminary results indicate that natural pyrope is capable of dissolving water at high-pressures, however, water preferentially enters olivine than in pyrope. We are undertaking systematic study to estimate the solubility of water in pyrope as a function of pressure. This will enable us to develop solubility models to understand the defect mechanisms

  4. High pressure neon arc lamp

    DOEpatents

    Sze, Robert C.; Bigio, Irving J.

    2003-07-15

    A high pressure neon arc lamp and method of using the same for photodynamic therapies is provided. The high pressure neon arc lamp includes a housing that encloses a quantity of neon gas pressurized to about 500 Torr to about 22,000 Torr. At each end of the housing the lamp is connected by electrodes and wires to a pulse generator. The pulse generator generates an initial pulse voltage to breakdown the impedance of the neon gas. Then the pulse generator delivers a current through the neon gas to create an electrical arc that emits light having wavelengths from about 620 nanometers to about 645 nanometers. A method for activating a photosensitizer is provided. Initially, a photosensitizer is administered to a patient and allowed time to be absorbed into target cells. Then the high pressure neon arc lamp is used to illuminate the target cells with red light having wavelengths from about 620 nanometers to about 645 nanometers. The red light activates the photosensitizers to start a chain reaction that may involve oxygen free radicals to destroy the target cells. In this manner, a high pressure neon arc lamp that is inexpensive and efficiently generates red light useful in photodynamic therapy is provided.

  5. High-pressure well design

    SciTech Connect

    Krus, H.; Prieur, J.M. )

    1991-12-01

    Shell U.K. E and P (Shell Expro), operator in the U.K. North Sea on behalf of Shell and Esso, plans to drill 20 high-pressure oil and gas wells during the next 2 years. This paper reports that the well design is based on new standards developed after the U.K. Dept. of Energy restriction on high-pressure drilling in the autumn of 1988. Studies were carried out to optimize casing design and drilling performance on these wells. Several casing schemes, including a slim-hole option, were analyzed. The material specifications for casing and drillpipe were reviewed to ensure that they met the loads imposed during drilling, well- control, and well-testing operations. The requirement for sour-service material was weighted against possible H{sub 2}S adsorption by the mud film. As a result, a new drillstring and two high-pressure casing schemes have been specified. The high-pressure casing scheme used depends on the maximum expected surface pressure.

  6. High-pressure water facility

    NASA Technical Reports Server (NTRS)

    2006-01-01

    NASA Test Operations Group employees, from left, Todd Pearson, Tim Delcuze and Rodney Wilkinson maintain a water pump in Stennis Space Center's high-pressure water facility. The three were part of a group of employees who rode out Hurricane Katrina at the facility and helped protect NASA's rocket engine test complex.

  7. High pressure volumetric measurements in dipalmitoylphosphatidylcholine bilayers.

    PubMed

    Tosh, R E; Collings, P J

    1986-07-10

    The one previously reported high pressure volumetric experiment on a phospholipid bilayer investigated a region of pressure between 0 and 25 MPa and obtained isothermal compressibility values for the liquid crystal and intermediate phases which differed by more than a factor of ten. We report new volumetric measurements around the main transition in dipalmitoylphosphatidylcholine (DPPC) from 0 to 100 MPa. The isothermal compressibility data for the two phases are of the same order of magnitude, and the experimentally determined coexistence curve, specific volume dependence, and volume discontinuity values are compared with the predictions of the phenomenological theory according to Sugar and Tarjan ((1982) Sov. Phys. Crystallogr. 27, 4-5). Significant discrepancies between this theory and experiment are found. Finally, the data indicate that steric interactions play a more dominant role in the main transition of phospholipid bilayers than in transitions in most thermotropic liquid crystals.

  8. High-pressure synthesis, crystal structures, and magnetic properties of 5d double-perovskite oxides Ca2MgOsO6 and Sr2MgOsO6.

    PubMed

    Yuan, Yahua; Feng, Hai L; Ghimire, Madhav Prasad; Matsushita, Yoshitaka; Tsujimoto, Yoshihiro; He, Jianfeng; Tanaka, Masahiko; Katsuya, Yoshio; Yamaura, Kazunari

    2015-04-01

    Double-perovskite oxides Ca2MgOsO6 and Sr2MgOsO6 have been synthesized under high-pressure and high-temperature conditions (6 GPa and 1500 °C). Their crystal structures and magnetic properties were studied by a synchrotron X-ray diffraction experiment and by magnetic susceptibility, specific heat, isothermal magnetization, and electrical resistivity measurements. Ca2MgOsO6 and Sr2MgOsO6 crystallized in monoclinic (P21/n) and tetragonal (I4/m) double-perovskite structures, respectively; the degree of order of the Os and Mg arrangement was 96% or higher. Although Ca2MgOsO6 and Sr2MgOsO6 are isoelectric, a magnetic-glass transition was observed for Ca2MgOsO6 at 19 K, while Sr2MgOsO6 showed an antiferromagnetic transition at 110 K. The antiferromagnetic-transition temperature is the highest in the family. A first-principles density functional approach revealed that Ca2MgOsO6 and Sr2MgOsO6 are likely to be antiferromagnetic Mott insulators in which the band gaps open, with Coulomb correlations of ∼1.8-3.0 eV. These compounds offer a better opportunity for the clarification of the basis of 5d magnetic sublattices, with regard to the possible use of perovskite-related oxides in multifunctional devices. The double-perovskite oxides Ca2MgOsO6 and Sr2MgOsO6 are likely to be Mott insulators with a magnetic-glass (MG) transition at ∼19 K and an antiferromagnetic (AFM) transition at ∼110 K, respectively. This AFM transition temperature is the highest among double-perovskite oxides containing single magnetic sublattices. Thus, these compounds offer valuable opportunities for studying the magnetic nature of 5d perovskite-related oxides, with regard to their possible use in multifunctional devices. PMID:25751088

  9. High-pressure neutron diffraction studies at LANSCE

    NASA Astrophysics Data System (ADS)

    Zhao, Yusheng; Zhang, Jianzhong; Xu, Hongwu; Lokshin, Konstantin A.; He, Duanwei; Qian, Jiang; Pantea, Cristian; Daemen, Luke L.; Vogel, Sven C.; Ding, Yang; Xu, Jian

    2010-06-01

    The development of neutron diffraction under extreme pressure ( P) and temperature ( T) conditions is highly valuable to condensed matter physics, crystal chemistry, materials science, and earth and planetary sciences. We have incorporated a 500-ton press TAP-98 into the HiPPO diffractometer at the Los Alamos Neutron Science Center (LANSCE) to conduct in situ high- P- T neutron diffraction experiments. We have developed a large gem-crystal anvil cell, ZAP, to conduct neutron diffraction experiments at high P. The ZAP cell can be used to integrate multiple experimental techniques such as neutron diffraction, laser spectroscopy, and ultrasonic interferometery. More recently, we have developed high- P low- T gas/liquid cells in conjunction with neutron diffraction. These techniques enable in situ and real-time examination of gas uptake/release processes and allow accurate, time-dependent determination of changes in crystal structure and related reaction kinetics. We have successfully used these techniques to study the equations of state, structural phase transitions, and thermo-mechanical properties of metals, ceramics, and minerals. We have conducted researches on the formation/decomposition kinetics of methane, CO2 and hydrogen hydrate clathrates, and hydrogen/CO2 adsorption of inclusion compounds such as metal-organic frameworks (MOFs). The aim of our research is to accurately map out phase relations and determine structural parameters (lattice constants, atomic positions, atomic thermal parameters, bond lengths, bond angles, etc.) in the P- T- X space. We are developing further high- P- T technology with a new 2000-ton press, TAPLUS-2000, and a ZIA (Deformation-DIA type) cubic anvil package to routinely achieve pressures up to 20 GPa and temperatures up to 2000 K. The design of a dedicated high- P neutron beamline, LAPTRON, is also underway for simultaneous high- P- T neutron diffraction, ultrasonic, calorimetry, radiography, and tomography studies. Studies based

  10. Crystal chemistry of diagenetic zeolites in volcanoclastic deposits of Italy

    NASA Astrophysics Data System (ADS)

    Passaglia, Elio; Vezzalini, Giovanna

    1985-07-01

    Zeolites from the most important volcanoclastic deposits of Italy include: (1) phillipsite and heulandite from the cinerite of the central northern Apennines; (2) chabazite and phillipsite from the phonolitic tephritic ignimbrite with black pumices; (3) phillipsite from the “tufo lionato” of Vulcano Laziale; (4) chabazite and phillipsite from the Campanian ignimbrite; (5) phillipsite from the Neapolitan yellow tuff; and (6) chabazite and phillipsite from the pyroclastics of Monte Vulture. Compared with sedimentary phillipsites and chabazites described in the literature, the chabazites and phillipsites studied here have lower Si/Al ratios and higher K contents. These chemical peculiarities are correlated with both the K-rich vesuvitic-leucititic, latitic-phonolitic, and potassic alkali-trachytic chemistry of the ash from which they were derived and, very likely, with the character of the hydrologically open system environment in which they formed. The zeolite of the heulandite-clinoptilolite group from the cinerite of the central northern Apennines is classified as a true heulandite on the basis of its chemical composition and thermal behavior.

  11. High pressure rinsing system comparison

    SciTech Connect

    D. Sertore; M. Fusetti; P. Michelato; Carlo Pagani; Toshiyasu Higo; Jin-Seok Hong; K. Saito; G. Ciovati; T. Rothgeb

    2007-06-01

    High pressure rinsing (HPR) is a key process for the surface preparation of high field superconducting cavities. A portable apparatus for the water jet characterization, based on the transferred momentum between the water jet and a load cell, has been used in different laboratories. This apparatus allows to collected quantitative parameters that characterize the HPR water jet. In this paper, we present a quantitative comparison of the different water jet produced by various nozzles routinely used in different laboratories for the HPR process

  12. High pressure synthesis gas conversion

    SciTech Connect

    Not Available

    1992-01-01

    A high pressure gas phase fermentation system has been constructed for the biological production of ethanol from coal synthesis gas. The reactors in the system consist of a 650 mL continuous stirred tank reactor and a 1 L continuous column reactor. The reactors are designed for individual or dual operation in series or parallel, with continuous gas and liquid feed. The system is housed in a constant temperature, explosion-proof room, equipped with gas leak detectors.

  13. [Study on crystal chemistry and spectra of feldspar from Zhoukoudian granodiorite].

    PubMed

    Zhang, Yong-wang; Zeng, Jian-hui; Liu, Yan; Guo, Jian-yu

    2009-09-01

    The chemical composition and spectra characteristic of feldspar from Zhoukoudian granodiorite were systematically analyzed. Based on the field work, some feldspar samples were selected for crystal chemistry and structure analysis through EMPA, IR, LRM and XRD. The compositions of the feldspar range between Ab (85.21) Or (0.18) An (9.11) and Ab (90.06) Or (3.00) An (13.27) by electronic microscope probe analysis. According to the XRD peak and its diffraction intensity, the mineral species was found the unit cell parameters were calculated. The absorption bands and peaks of infrared and Raman spectra were also assigned and the results show that the characteristics of its infrared and Raman spectra are in accordance with the ideal atlas of albite. The infrared spectra show that all the analyzed feldspar grains contain structural hydrogen, which occur as OH-. On the basis of the above analyses, the crystal chemistry and structure characteristics of feldspar were summarized.

  14. Exotic stable cesium polynitrides at high pressure

    SciTech Connect

    Peng, Feng; Han, Yunxia; Liu, Hanyu; Yao, Yansun

    2015-11-19

    New polynitrides containing metastable forms of nitrogen are actively investigated as potential high energy-density materials. Using a structure search method based on the CALYPSO methodology, we investigated the stable stoichiometries and structures of cesium polynitrides at high pressures. Along with the CsN3, we identified five new stoichiometric compounds (Cs3N, Cs2N, CsN, CsN2, and CsN5) with interesting structures that may be experimentally synthesizable at modest pressures (i.e., less than 50 GPa). Nitrogen species in the predicted structures have various structural forms ranging from single atom (N) to highly endothermic molecules (N2, N3 , N4, N5, N6) and chains (N). Polymeric chains of nitrogen were found in the high-pressure C2/c phase of CsN2. This structure contains a substantially high content of single N-N bonds that exceeds the previously known nitrogen chains in pure forms, and also exhibit metastability at ambient conditions. We also identified a very interesting CsN crystal that contains novel N44- anion. In conclusion, to our best knowledge, this is the first time a charged N4 species being reported. Results of the present study suggest that it is possible to obtain energetic polynitrogens in main-group nitrides under high pressure.

  15. Measurement of the Order Parameter in a Room Temperature Liquid Crystal: An Experiment for the Physical Chemistry Laboratory.

    ERIC Educational Resources Information Center

    DuPre, Donald B.; Chapoy, L. Lawrence

    1979-01-01

    Presented here is a laboratory experiment for a course in physical chemistry. Students are requested to directly measure the degree of orientational order in a liquid crystal at room temperature. A minimum amount of equipment is necessary. (Author/SA)

  16. Electrokinetic high pressure hydraulic system

    SciTech Connect

    Paul, P.H.; Rakestraw, D.J.

    2000-01-11

    A compact high pressure hydraulic system having no moving parts for converting electric potential to hydraulic force and for manipulating fluids. Electro-osmotic flow is used to provide a valve and means to compress a fluid or gas in a capillary-based system. By electro-osmotically moving an electrolyte between a first position opening communication between a fluid inlet and outlet and a second position closing communication between the fluid inlet and outlet the system can be configured as a valve. The system can also be used to generate forces as large as 2500 psi that can be used to compress a fluid, either a liquid or a gas.

  17. Brillouin scattering at high pressures

    SciTech Connect

    Grimsditch, M.; Polian, A.

    1988-02-01

    Technical advances which have made Brillouin scattering a useful tool in high pressure diamond anvil cell (DAC) studies, viz. multipassing and tandem operation of Fabry-Perot interferometers, are reviewed. Experimental aspects, such as allowed scattering geometries, are outlined and the data analysis required to transform Brillouin spectra into sound velocities and elastic constants is presented. Experimental results on H/sub 2/, N/sub 2/, Ar, and He are presented, and the close relationship between the Brillouin scattering results and equations of state is highlighted.

  18. Spray patternation at high pressure

    NASA Astrophysics Data System (ADS)

    Cohen, J. M.; Rosfjord, T. J.

    1989-07-01

    The spatial distribution of the fuel spray created by a gas turbine fuel injector has been measured at high pressure and temperature. A patternation system for measuring fuel spray mass flux distributions at high power conditions has been designed and operated. The facility has been designed to simulate the environment inside a gas turbine combustor as closely as possible. Results for a full scale gas turbine fuel injector have been obtained at high levels of pressure, temperature and liquid flowrate and compared with visual observations.

  19. Electokinetic high pressure hydraulic system

    DOEpatents

    Paul, Phillip H.; Rakestraw, David J.

    2000-01-01

    A compact high pressure hydraulic system having no moving parts for converting electric potential to hydraulic force and for manipulating fluids. Electro-osmotic flow is used to provide a valve and means to compress a fluid or gas in a capillary-based system. By electro-osmotically moving an electrolyte between a first position opening communication between a fluid inlet and outlet and a second position closing communication between the fluid inlet and outlet the system can be configured as a valve. The system can also be used to generate forces as large as 2500 psi that can be used to compress a fluid, either a liquid or a gas.

  20. Improved high pressure turbine shroud

    NASA Technical Reports Server (NTRS)

    Bessen, I. I.; Rigney, D. V.; Schwab, R. C.

    1977-01-01

    A new high pressure turbine shroud material has been developed from the consolidation of prealloyed powders of Ni, Cr, Al and Y. The new material, a filler for cast turbine shroud body segments, is called Genaseal. The development followed the identification of oxidation resistance as the primary cause of prior shroud deterioration, since conversion to oxides reduces erosion resistance and increases spalling under thermal cycled engine conditions. The NICrAlY composition was selected in preference to NIAL and FeCRALY alloys, and was formulated to a prescribed density range that offers suitable erosion resistance, thermal conductivity and elastic modulus for improved behavior as a shroud.

  1. Stable Lithium Argon compounds under high pressure

    PubMed Central

    Li, Xiaofeng; Hermann, Andreas; Peng, Feng; Lv, Jian; Wang, Yanchao; Wang, Hui; Ma, Yanming

    2015-01-01

    High pressure can fundamentally alter the bonding patterns of chemical elements. Its effects include stimulating elements thought to be “inactive” to form unexpectedly stable compounds with unusual chemical and physical properties. Here, using an unbiased structure search method based on CALYPSO methodology and density functional total energy calculations, the phase stabilities and crystal structures of Li−Ar compounds are systematically investigated at high pressure up to 300 GPa. Two unexpected LimArn compounds (LiAr and Li3Ar) are predicted to be stable above 112 GPa and 119 GPa, respectively. A detailed analysis of the electronic structure of LiAr and Li3Ar shows that Ar in these compounds attracts electrons and thus behaves as an oxidizing agent. This is markedly different from the hitherto established chemical reactivity of Ar. Moreover, we predict that the P4/mmm phase of Li3Ar has a superconducting transition temperature of 17.6 K at 120 GPa. PMID:26582083

  2. Structure and stability of hydrous minerals at high pressure

    NASA Technical Reports Server (NTRS)

    Duffy, T. S.; Fei, Y.; Meade, C.; Hemley, R. J.; Mao, H. K.

    1994-01-01

    The presence of even small amounts of hydrogen in the Earth's deep interior may have profound effects on mantle melting, rheology, and electrical conductivity. The recent discovery of a large class of high-pressure H-bearing silicates further underscores the potentially important role for hydrous minerals in the Earth's mantle. Hydrogen may also be a significant component of the Earth's core, as has been recently documented by studies of iron hydride at high pressure. In this study, we explore the role of H in crystal structures at high pressure through detailed Raman spectroscopic and x ray diffraction studies of hydrous minerals compressed in diamond anvil cells. Brucite, Mg(OH)2, has a simple structure and serves as an analogue for the more complex hydrous silicates. Over the past five years, this material has been studied at high pressure using shock-compression, powder x ray diffraction, infrared spectroscopy, Raman spectroscopy, and neutron diffraction. In addition, we have recently carried out single-crystal synchrotron x-ray diffraction on Mg(OH)2 and Raman spectroscopy on Mg(OD)2 at elevated pressure. From all these studies, an interesting picture of the crystal chemical behavior of this material at high pressure is beginning to emerge. Some of the primary conclusions are as follows: First, hydrogen bonding is enhanced by the application of pressure. Second, layered minerals which are elastically anisotropic at low pressure may not be so at high pressure. Furthermore, the brucite data place constraints on the effect of hydrogen on seismic velocities and density at very high pressure. Third, the stability of hydrous minerals may be enhanced at high P by subtle structural rearrangements that are difficult to detect using traditional probes and require detailed spectroscopic analyses. Finally, brucite appears to be unique in that it undergoes pressure-induced disordering that is confined solely to the H-containing layers of the structure.

  3. New trends in chemistry and materials science in extremely tight space

    DOE PAGESBeta

    Song, Yang; Manaa, M. Riad

    2012-01-26

    Pressure plays a critical role in regulating the structures and properties of materials. Since Percy Bridgeman was recognized by the 1946 Nobel Prize in Physics for his contribution in high-pressure physics, high-pressure research has remained an interdisciplinary scientific frontier with many extraordinary breakthroughs. Over the past decade or so, in particular, high-pressure chemistry and materials research has undergone major advances with the discovery of numerous exotic structures and properties. Furthermore, brand new classes of inorganic materials of unusual stoichiometries and crystal structures, which have a wide range of optical, mechanical, electronic and magnetic properties, have been produced at high pressures.

  4. Crystal structure of coesite, a high-pressure form of SiO/sub 2/, at 15 and 298 K from single-crystal neutron and x-ray diffraction data: test of bonding models

    SciTech Connect

    Smyth, J.R.; Smith, J.V.; Artioli, G.; Kvick, A.

    1987-02-12

    The crystal structure of a natural coesite from an eclogite rock fragment in the Roberts Victor kimberlite, South Africa, was determined at 15 K by neutron diffraction (a = 7.1357 (13) A, b = 12.3835 (26) A, c = 7.1859 (11) A, ..beta.. = 120.375 (16)/sup 0/, C2/c), and at approx.298 K by X-ray diffraction. Cell dimensions measured by neutron diffraction at 292 K (7.1464 (9), 12.3796 (19), and 7.1829 (8) A, 120.283 (9)/sup 0/) differed from those determined by X-ray diffraction, probably because of a systematic absorption error for the latter. The strongly anisotropic nature of the thermal expansion is explained qualitatively by the relatively large changes (approx.1%) in the distances between the nonbonded oxygen neighbors and the relatively small changes of Si-O-Si and O-Si-O angles in the compact three-dimensional framework. There is a good, but not perfect, negative correlation between the eight independent Si-O distances and the five independent values for sec theta(Si-O-Si) at 15 K. It is weaker than that for 298 K, and the scatter from a straight-line prediction from molecular-orbital models for small clusters (e.g., H/sub 6/Si/sub 2/O/sub 7/) implies that it is desirably to consider additional forces, including repulsive forces between nonbonded oxygen neighbors. The combined at a for Si-O and Si-O-Si in coesite, quartz, and cristobalite at 10-15 K show less scatter than those for approx.298 K, in accordance with the greater thermal response of framework geometry in the more open structures.

  5. High pressure xenon ionization detector

    DOEpatents

    Markey, J.K.

    1989-11-14

    A method is provided for detecting ionization comprising allowing particles that cause ionization to contact high pressure xenon maintained at or near its critical point and measuring the amount of ionization. An apparatus is provided for detecting ionization, the apparatus comprising a vessel containing a ionizable medium, the vessel having an inlet to allow high pressure ionizable medium to enter the vessel, a means to permit particles that cause ionization of the medium to enter the vessel, an anode, a cathode, a grid and a plurality of annular field shaping rings, the field shaping rings being electrically isolated from one another, the anode, cathode, grid and field shaping rings being electrically isolated from one another in order to form an electric field between the cathode and the anode, the electric field originating at the anode and terminating at the cathode, the grid being disposed between the cathode and the anode, the field shaping rings being disposed between the cathode and the grid, the improvement comprising the medium being xenon and the vessel being maintained at a pressure of 50 to 70 atmospheres and a temperature of 0 to 30 C. 2 figs.

  6. High pressure xenon ionization detector

    DOEpatents

    Markey, John K.

    1989-01-01

    A method is provided for detecting ionization comprising allowing particles that cause ionization to contact high pressure xenon maintained at or near its critical point and measuring the amount of ionization. An apparatus is provided for detecting ionization, the apparatus comprising a vessel containing a ionizable medium, the vessel having an inlet to allow high pressure ionizable medium to enter the vessel, a means to permit particles that cause ionization of the medium to enter the vessel, an anode, a cathode, a grid and a plurality of annular field shaping rings, the field shaping rings being electrically isolated from one another, the anode, cathode, grid and field shaping rings being electrically isolated from one another in order to form an electric field between the cathode and the anode, the electric field originating at the anode and terminating at the cathode, the grid being disposed between the cathode and the anode, the field shaping rings being disposed between the cathode and the grid, the improvement comprising the medium being xenon and the vessel being maintained at a pressure of 50 to 70 atmospheres and a temperature of 0.degree. to 30.degree. C.

  7. Steam Oxidation at High Pressure

    SciTech Connect

    Holcomb, Gordon R.; Carney, Casey

    2013-07-19

    A first high pressure test was completed: 293 hr at 267 bar and 670{degrees}C; A parallel 1 bar test was done for comparison; Mass gains were higher for all alloys at 267 bar than at 1 bar; Longer term exposures, over a range of temperatures and pressures, are planned to provide information as to the commercial implications of pressure effects; The planned tests are at a higher combination of temperatures and pressures than in the existing literature. A comparison was made with longer-term literature data: The short term exposures are largely consistent with the longer-term corrosion literature; Ferritic steels--no consistent pressure effect; Austenitic steels--fine grain alloys less able to maintain protective chromia scale as pressure increases; Ni-base alloys--more mass gains above 105 bar than below. Not based on many data points.

  8. High pressure hollow electrode discharges

    SciTech Connect

    Schoenbach, K.H.; El-Habachi, A.; Shi, W.; Ciocca, M.

    1997-12-31

    Reduction of the cathode hole diameter into the submillimeter range has allowed the authors to extend the pressure range for hollow electrode discharge operation to values on the order of 50 Torr. In recent experiments with cathode holes of 0.2 mm diameter they obtained stable glow discharge operation up to approximately 900 Torr in argon. The current-voltage (I-V) characteristics of these discharges (with currents ranging from the ten`s of {micro}A to ten mA) show three distinct discharge modes: at low current, a discharge with positive differential resistivity, followed by a range with strong increase in current and reduction in voltage, and, at high current, again a resistive discharge mode. For low pressure (< 100 Torr) these modes correspond to the predischarge, hollow cathode discharge (sustained by pendulum electrons), and abnormal glow discharge, respectively. At higher pressure the discharge in the short gap system (anode-cathode distance: 0.25 mm) changes from a hollow cathode discharge to, what seems to be a pulseless partial glow discharge. In hollow cathode discharges operated in the torr range the electron energy distribution is known to be strongly non-maxwellian with a large concentration of electrons at energies greater than 30 eV. This holds also for hollow cathode discharge at high pressure and for partial discharges as indicated by the presence of strong excimer lines in the VUV spectrum of Ar-discharges at 128 nm and Xe-discharges at 172 nm. The resistive characteristic of high pressure hollow electrode discharges over a large range of current allows them to generate arrays of these discharges for use as flat panel, direct current, excimer lamps.

  9. Quantitative chemistry and the discrete geometry of conformal atom-thin crystals.

    PubMed

    Pacheco Sanjuan, Alejandro A; Mehboudi, Mehrshad; Harriss, Edmund O; Terrones, Humberto; Barraza-Lopez, Salvador

    2014-02-25

    When flat or on a firm mechanical substrate, the atomic composition and atomistic structure of two-dimensional crystals dictate their chemical, electronic, optical, and mechanical properties. These properties change when the two-dimensional and ideal crystal structure evolves into arbitrary shapes, providing a direct and dramatic link among geometry and material properties due to the larger structural flexibility when compared to bulk three-dimensional materials. We describe methods to understand the local geometrical information of two-dimensional conformal crystals quantitatively and directly from atomic positions, even in the presence of atomistic defects. We then discuss direct relations among the discrete geometry and chemically relevant quantities--mean bond lengths, hybridization angles, and σ-π hybridization. These concepts are illustrated for carbon-based materials and ionic crystals. The pyramidalization angle turns out to be linearly proportional to the mean curvature for relevant crystalline configurations. Discrete geometry provides direct quantitative information on the potential chemistry of conformal two-dimensional crystals.

  10. Crystal chemistry of layered structures formed by linear rigid silyl-capped molecules

    PubMed Central

    Lumpi, Daniel; Kautny, Paul; Stöger, Berthold; Fröhlich, Johannes

    2015-01-01

    The crystallization behavior of methylthio- or methylsulfonyl-containing spacer extended Z,Z-bis-ene–yne molecules capped with trimethylsilyl groups obtained by (tandem) thiophene ring fragmentation and of two non-spacer extended analogs were investigated. The rigid and linear molecules generally crystallized in layers whereby the flexibility of the layer interfaces formed by the silyl groups leads to a remarkably rich crystal chemistry. The molecules with benzene and thiophene spacers both crystallized with C2/c symmetry and can be considered as merotypes. Increasing the steric bulk of the core by introduction of ethylenedioxythiophene (EDOT) gave a structure incommensurately modulated in the [010] direction. Further increase of steric demand in the case of a dimethoxythiophene restored periodicity along [010] but resulted in a doubling of the c vector. Two different polytypes were observed, which feature geometrically different layer interfaces (non-OD, order–disorder, polytypes), one with a high stacking fault probability. Oxidation of the methylthio groups of the benzene-based molecule to methylsulfonyl groups led to three polymorphs (two temperature-dependent), which were analyzed by Hirshfeld surface d e/d i fingerprint plots. The analogously oxidized EDOT-based molecule crystallized as systematic twins owing to its OD polytypism. Shortening of the backbone by removal of the aryl core resulted in an enantiomorphic structure and a further shortening by removal of a methylthio-ene fragment again in a systematically twinned OD polytype. PMID:26306200

  11. Crystal chemistry of natural and synthetic trioctahedral micas: Exploring the limits of geometric crystal chemical models

    NASA Astrophysics Data System (ADS)

    Mercier, Patrick H. J.

    Seventy-five synthetic powder trioctahedral mica samples (between Mg, Co, Ni, and Fe end members, with different degrees of oxidation, vacancy and Al/Si contents, and including an OH/F substitution series) were studied by room-temperature powder X-ray diffraction. The iron-bearing samples were studied by 57Fe Mossbauer spectroscopy. Subsets of the samples were also characterized by scanning electron microscopy combined with energy dispersive spectroscopy, optical microscopy, X-ray fluorescence spectroscopy, and gas chromatography. Lattice parameters (refined under the 1M stacking polytype, space group C2/m) were determined for all powder samples and iron site populations ([4]Fe 3+, [6]Fe2+, and [6]Fe 2+) were obtained from Mossbauer spectroscopy. The relation (c/a)cosbeta* = 113 was found to hold exactly (within experimental error) for all synthetic powders whereas it does not hold in general for synthetic and natural 1M single-crystals. The above relation is predicted to hold for geometric home-octahedral sheets (having equal M1 and M2 site bond lengths) and not to hold for geometric meso-octahedral sheets (having unequal M1 and M2 site bond lengths). The counter-rotation of the M2 site of 1M single-crystals exactly (within experimental error) follows the geometric meso-octahedral sheet model, which, assuming a uniform octahedral sheet height and site-specific M1 and M2 bond lengths, predicts site-specific flattening angles and a counter-rotation angle for the M2 site which is uniquely determined by the bond length difference between the M1 and M2 sites. A geometric meso-octahedral 2:1 layer silicate was shown to require corrugated tetrahedral sheets composed of bond-distorted tetrahedra. Key geometric meso-octahedral distortions in 1M single-crystals were identified and elucidated: (i) intra-layer top-bottom displacements within a TOT layer; and (ii) a tetrahedral bending angle between the apical bond and the pyramidal base formed by the three basal bonds. Plots

  12. Effects of Mg on diamond growth and properties in Fe-C system under high pressure and high temperature condition

    NASA Astrophysics Data System (ADS)

    Huang, Guo-Feng; Zheng, You-Jin; Li, Zhan-Chang; Gao, Qiang; Ma, Zhuo; Shi, Si-Ming; Jiang, Bao-Gang; Zhao, He

    2016-08-01

    Diamond crystal crystallized in Fe-Mg-C system with Archimedes buoyancy as a driving force is established under high pressure and high temperature conditions. The experimental results indicate that the addition of the Mg element results in the nitrogen concentration increasing from 87 ppm to 271 ppm in the diamond structure. The occurrence of the {100} plane reveals that the surface character is remarkably changed due to the addition of Mg. Micro-Raman spectra indicate that the half width of full maximum is in a range of 3.01 cm-1-3.26 cm-1, implying an extremely good quality of diamond specimens in crystallization. Project supported by the Natural Science Foundation of Inner Mongolia Autonomous Region, China (Grant No. 2013MS0809) and the Open Project of Key Laboratory of Functional Materials Physics and Chemistry (Jilin Normal University) of the Ministry of Education of China (Grant No. 201608).

  13. Effects of Mg on diamond growth and properties in Fe–C system under high pressure and high temperature condition

    NASA Astrophysics Data System (ADS)

    Huang, Guo-Feng; Zheng, You-Jin; Li, Zhan-Chang; Gao, Qiang; Ma, Zhuo; Shi, Si-Ming; Jiang, Bao-Gang; Zhao, He

    2016-08-01

    Diamond crystal crystallized in Fe–Mg–C system with Archimedes buoyancy as a driving force is established under high pressure and high temperature conditions. The experimental results indicate that the addition of the Mg element results in the nitrogen concentration increasing from 87 ppm to 271 ppm in the diamond structure. The occurrence of the {100} plane reveals that the surface character is remarkably changed due to the addition of Mg. Micro-Raman spectra indicate that the half width of full maximum is in a range of 3.01 cm‑1–3.26 cm‑1, implying an extremely good quality of diamond specimens in crystallization. Project supported by the Natural Science Foundation of Inner Mongolia Autonomous Region, China (Grant No. 2013MS0809) and the Open Project of Key Laboratory of Functional Materials Physics and Chemistry (Jilin Normal University) of the Ministry of Education of China (Grant No. 201608).

  14. From the Wood-Shop to Crystal Engineering: Teaching Three-Dimensional Chemistry

    NASA Astrophysics Data System (ADS)

    Martin, James D.

    2001-09-01

    Understanding structure and bonding in chemistry requires an ability to visualize in three dimensions. Proper 3-D perspective provides important insight into chemical structure and reactivity, necessary for the design of advanced materials. Working from a textbook or computer screen, however, requires that we translate 2-D images into 3-D perception. Skills traditionally taught in industrial arts for 3-D visualization from 2-D images, and the 2-D description of 3-D objects, can be readily adapted to enhance student mastery of 3-D chemistry. By teaching students to draw a series of geometric blocks, analogous to those utilized in a wood-shop class, skills are gained that significantly augment a computer-based drawing assignment used to understand complex molecular structures required for crystal engineering. Developing skills in drawing and understanding the blueprints of chemical structure prepares students to be chemical architects.

  15. Transition Metals in the Transition Zone: Crystal Chemistry of Minor Element Substitution in Wadsleyite

    NASA Astrophysics Data System (ADS)

    Zhang, L.

    2015-12-01

    As the most abundant solid phase at depths of 410 to 525 km, wadsleyite constitutes a large geochemical reservoir in the Earth. In order to better understand minor element substitution and cation ordering in wadsleyite, we have synthesized wadsleyite coexisting with pyroxene with 2 to 3 weight percent each of TiO2, Cr2O3, V2O3, CoO, NiO, and ZnO under hydrous conditions in separate experiments at 1300ºC and 15GPa. We have refined the crystal structures of these wadsleyites, analyzed the compositions by electron microprobe, and estimated M3 vacancy contents from b/a cell-parameter ratios. Trivalent cations, Fe, Cr and V, show a strong preference for M3 over M1 and M2 and significant substitution up to 2.8% at the tetrahedral site. Divalent Ni, Co, and Zn show site preferences similar to those of Fe2+ with M1≈ M3 > M2 > T. This site preference appears to be due crystal field stabilization energies rather than cation radius effects. Trivalent Cr, and V have much greater solubilities in wadsleyite than in olivine and so may be enriched in a melt or an accessory phase if hydrous melting occurs on upward convection across the wadsleyite-olivine boundary and may be useful as indicators of high pressure origin.

  16. Electrical Transport Experiments at High Pressure

    SciTech Connect

    Weir, S

    2009-02-11

    High-pressure electrical measurements have a long history of use in the study of materials under ultra-high pressures. In recent years, electrical transport experiments have played a key role in the study of many interesting high pressure phenomena including pressure-induced superconductivity, insulator-to-metal transitions, and quantum critical behavior. High-pressure electrical transport experiments also play an important function in geophysics and the study of the Earth's interior. Besides electrical conductivity measurements, electrical transport experiments also encompass techniques for the study of the optoelectronic and thermoelectric properties of materials under high pressures. In addition, electrical transport techniques, i.e., the ability to extend electrically conductive wires from outside instrumentation into the high pressure sample chamber have been utilized to perform other types of experiments as well, such as high-pressure magnetic susceptibility and de Haas-van Alphen Fermi surface experiments. Finally, electrical transport techniques have also been utilized for delivering significant amounts of electrical power to high pressure samples, for the purpose of performing high-pressure and -temperature experiments. Thus, not only do high-pressure electrical transport experiments provide much interesting and valuable data on the physical properties of materials extreme compression, but the underlying high-pressure electrical transport techniques can be used in a number of ways to develop additional diagnostic techniques and to advance high pressure capabilities.

  17. Dissociation of methane under high pressure

    NASA Astrophysics Data System (ADS)

    Gao, Guoying; Oganov, Artem R.; Ma, Yanming; Wang, Hui; Li, Peifang; Li, Yinwei; Iitaka, Toshiaki; Zou, Guangtian

    2010-10-01

    Methane is an extremely important energy source with a great abundance in nature and plays a significant role in planetary physics, being one of the major constituents of giant planets Uranus and Neptune. The stable crystal forms of methane under extreme conditions are of great fundamental interest. Using the ab initio evolutionary algorithm for crystal structure prediction, we found three novel insulating molecular structures with P212121, Pnma, and Cmcm space groups. Remarkably, under high pressure, methane becomes unstable and dissociates into ethane (C2H6) at 95 GPa, butane (C4H10) at 158 GPa, and further, carbon (diamond) and hydrogen above 287 GPa at zero temperature. We have computed the pressure-temperature phase diagram, which sheds light into the seemingly conflicting observations of the unusually low formation pressure of diamond at high temperature and the failure of experimental observation of dissociation at room temperature. Our results support the idea of diamond formation in the interiors of giant planets such as Neptune.

  18. Dissociation of methane under high pressure.

    PubMed

    Gao, Guoying; Oganov, Artem R; Ma, Yanming; Wang, Hui; Li, Peifang; Li, Yinwei; Iitaka, Toshiaki; Zou, Guangtian

    2010-10-14

    Methane is an extremely important energy source with a great abundance in nature and plays a significant role in planetary physics, being one of the major constituents of giant planets Uranus and Neptune. The stable crystal forms of methane under extreme conditions are of great fundamental interest. Using the ab initio evolutionary algorithm for crystal structure prediction, we found three novel insulating molecular structures with P2(1)2(1)2(1), Pnma, and Cmcm space groups. Remarkably, under high pressure, methane becomes unstable and dissociates into ethane (C(2)H(6)) at 95 GPa, butane (C(4)H(10)) at 158 GPa, and further, carbon (diamond) and hydrogen above 287 GPa at zero temperature. We have computed the pressure-temperature phase diagram, which sheds light into the seemingly conflicting observations of the unusually low formation pressure of diamond at high temperature and the failure of experimental observation of dissociation at room temperature. Our results support the idea of diamond formation in the interiors of giant planets such as Neptune.

  19. Dissociation of methane under high pressure.

    PubMed

    Gao, Guoying; Oganov, Artem R; Ma, Yanming; Wang, Hui; Li, Peifang; Li, Yinwei; Iitaka, Toshiaki; Zou, Guangtian

    2010-10-14

    Methane is an extremely important energy source with a great abundance in nature and plays a significant role in planetary physics, being one of the major constituents of giant planets Uranus and Neptune. The stable crystal forms of methane under extreme conditions are of great fundamental interest. Using the ab initio evolutionary algorithm for crystal structure prediction, we found three novel insulating molecular structures with P2(1)2(1)2(1), Pnma, and Cmcm space groups. Remarkably, under high pressure, methane becomes unstable and dissociates into ethane (C(2)H(6)) at 95 GPa, butane (C(4)H(10)) at 158 GPa, and further, carbon (diamond) and hydrogen above 287 GPa at zero temperature. We have computed the pressure-temperature phase diagram, which sheds light into the seemingly conflicting observations of the unusually low formation pressure of diamond at high temperature and the failure of experimental observation of dissociation at room temperature. Our results support the idea of diamond formation in the interiors of giant planets such as Neptune. PMID:20950018

  20. Carbon Nanotubes as High-Pressure Cylinders and Nanoextruders

    NASA Astrophysics Data System (ADS)

    Sun, L.; Banhart, F.; Krasheninnikov, A. V.; Rodríguez-Manzo, J. A.; Terrones, M.; Ajayan, P. M.

    2006-05-01

    Closed-shell carbon nanostructures, such as carbon onions, have been shown to act as self-contracting high-pressure cells under electron irradiation. We report that controlled irradiation of multiwalled carbon nanotubes can cause large pressure buildup within the nanotube cores that can plastically deform, extrude, and break solid materials that are encapsulated inside the core. We further showed by atomistic simulations that the internal pressure inside nanotubes can reach values higher than 40 gigapascals. Nanotubes can thus be used as robust nanoscale jigs for extruding and deforming hard nanomaterials and for modifying their properties, as well as templates for the study of individual nanometer-sized crystals under high pressure.

  1. Crystal chemistry of hydroxyl and water in silicate minerals. Final technical report

    SciTech Connect

    Smyth, J.R.

    1998-06-01

    This was a project to investigate the crystal chemistry of OH and H{sub 2}O substitution in silicate minerals by use of X-ray and neutron diffraction methods combined with IR spectroscopy and to interpret and generalize the results using an electrostatic model for these mineral structures. Using these data together with published H position data electrostatic parameters for H sites were calculated from a simple electrostatic model. The data were then used to refine the model for incorporation of H into the wadsleyite structure. This has led to recent work on the synthesis and characterization of hydrous wadsleyites.

  2. Phase equilibria and crystal chemistry of rubidium niobates and rubidium tantalates

    NASA Technical Reports Server (NTRS)

    Minor, D. B.; Roth, R. S.; Parker, H. S.; Brower, W. S.

    1977-01-01

    The phase equilibria relations and crystal chemistry of portions of the Rb2O-Nb2O5 and Rb2O-Ta2O5 systems were investigated for structures potentially useful as ionic conductors. A hexagonal tungsten bronze-type (HTB) structure was found in both systems as well as three hexagonal phases with mixed HTB-pyrochlore type structures. Ion exchange experiments between various alkali ions are described for several phases. Unit cell dimensions and X-ray diffraction powder patterns are reported.

  3. Structural changes in thermoelectric SnSe at high pressures.

    PubMed

    Loa, I; Husband, R J; Downie, R A; Popuri, S R; Bos, J-W G

    2015-02-25

    The crystal structure of the thermoelectric material tin selenide has been investigated with angle-dispersive synchrotron x-ray powder diffraction under hydrostatic pressure up to 27 GPa. With increasing pressure, a continuous evolution of the crystal structure from the GeS type to the higher-symmetry TlI type was observed, with a critical pressure of 10.5(3) GPa. The orthorhombic high-pressure modification, β'-SnSe, is closely related to the pseudo-tetragonal high-temperature modification at ambient pressure. The similarity between the changes of the crystal structure at elevated temperatures and at high pressures suggests the possibility that strained thin films of SnSe may provide a route to overcoming the problem of the limited thermal stability of β-SnSe at high temperatures.

  4. Crystal structure and crystal chemistry of melanovanadite, a natural vanadium bronze.

    USGS Publications Warehouse

    Konnert, J.A.; Evans, H.T.

    1987-01-01

    The crystal structure of melanovanadite from Minas Ragra, Peru, has been determined in space group P1. The triclinic unit cell (non-standard) has a 6.360(2), b 18.090(9), c 6.276(2) A, alpha 110.18(4)o, beta 101.62(3)o, gamma 82.86(4)o. A subcell with b' = b/2 was found by crystal-structure analysis to contain CaV4O10.5H2O. The subcell has a layer structure in which the vanadate sheet consists of corner-shared tetrahedral VO4 and double square-pyramidal V2O8 groups, similar to that previously found in synthetic CsV2O5. Refinement of the full structure (R = 0.056) showed that the Ca atom, which half-occupies a general position in the subcell, is 90% ordered at one of these sites in the whole unit cell. Bond length-bond strength estimates indicate that the tetrahedra contain V5+, and the square pyramids, V4+.-J.A.Z.

  5. Hibonite: Crystal Chemistry and Origin of Blue Coloration in Meteoritic Assemblages

    NASA Technical Reports Server (NTRS)

    Burns, R. G.; Burns, V. M.

    1985-01-01

    The blue color and optical spectra of hibonite, a common constituent of refractory inclusions in carbonaceous chondrites, are discussed. Because they may be manifestations of exotic cation species stabilized in unusual coordination sites in the hibonite crystalstructure. Hibonite, ideally CaAl12O19, is conducive to atomic substitution of host Ca2+ and Al3+ ions by a variety of lanthanide and first series transition elements. The latter cations are responsible for the colors of many rock-forming minerals as a result of intraelectronic or intervalence transitions. The visible-region spectra of most oxide and silicate minerals are generally well understood. Assignments of absorption bands in meteoritic hibonite optical spectra due to uncertainties of cation valencies and complexities in the crystal structure are examined. The crystal chemistry of hibonite is reviewed, Mossbauer spectral measurements of iron-bearing hibonite and electronic transitions that may be responsible for the blue coloration of meteoritic hibonites are discussed.

  6. Topaz and Kyanite Luminescence Under High Pressure

    NASA Astrophysics Data System (ADS)

    O'Bannon, E. F., III; Williams, Q. C.

    2014-12-01

    The luminescence spectra of Cr3+ in heat-treated topaz Al2SiO4(OH,F)2 and natural kyanite Al2SiO5 were measured from 650 - 800 nm in a hydrostatic environment up to pressures of 15 GPa. The R1 and R2 peaks of topaz shift at average rates of 0.30 nm/GPa and 0.22 nm/GPa, respectively, implying that the deformation of the Cr3+ octahedra increases with pressure. Three peaks are fit under each R line of topaz at both room and high pressure, and these peaks are associated with different Al sites into which the Cr substitutes. The shift of the R lines in topaz under pressure is remarkably linear, which appears to be a general feature of many Cr3+-bearing oxides: the underlying cause of this linearity may lie in anharmonic coupling with lattice vibrations. In this context, we also characterize the frequency shifts of two vibronic peaks within topaz. The R1 and R2 peaks of kyanite shift at 0.37 nm/GPa and 0.88 nm/GPa respectively. Two peaks are fit under R1 and three peaks are fit under R2 of kyanite at both room and high pressure; this result is also consistent with three different Cr3+ sites in this material. The R lines in kyanite are notably optically anisotropic, depending strongly on crystallographic orientation: this is most strongly manifested in the R2 peak. The Cr3+ luminescence in these materials provides a sensitive probe of pressure-dependent shifts in the local geometry of the Al-sites in these materials, which are analyzed in the context of previous single-crystal x-ray diffraction measurements.

  7. High Pressure Electrolyzer System Evaluation

    NASA Technical Reports Server (NTRS)

    Prokopius, Kevin; Coloza, Anthony

    2010-01-01

    This report documents the continuing efforts to evaluate the operational state of a high pressure PEM based electrolyzer located at the NASA Glenn Research Center. This electrolyzer is a prototype system built by General Electric and refurbished by Hamilton Standard (now named Hamilton Sunstrand). It is capable of producing hydrogen and oxygen at an output pressure of 3000 psi. The electrolyzer has been in storage for a number of years. Evaluation and testing was performed to determine the state of the electrolyzer and provide an estimate of the cost for refurbishment. Pressure testing was performed using nitrogen gas through the oxygen ports to ascertain the status of the internal membranes and seals. It was determined that the integrity of the electrolyzer stack was good as there were no appreciable leaks in the membranes or seals within the stack. In addition to the integrity testing, an itemized list and part cost estimate was produced for the components of the electrolyzer system. An evaluation of the system s present state and an estimate of the cost to bring it back to operational status was also produced.

  8. Single crystal structures of thallium (I) thorium fluorides and crystal chemistry of monovalent tetravalent cation pentafluorides

    NASA Astrophysics Data System (ADS)

    Oudahmane, Abdelghani; El-Ghozzi, Malika; Jouffret, Laurent; Avignant, Daniel

    2015-12-01

    Two thallium (I) thorium (IV) fluorides, TlTh3F13 and TlThF5 were obtained by solid state synthesis and their crystal structures determined from single crystal X-ray diffraction data recorded at room temperature with an APEX-II CCD diffractometer. TlTh3F13 is orthorhombic, space group Pmc21, with a=8.1801(2) Å, b=7.4479(2) Å, c=8.6375(2) Å, V=526.24(2) Å3, Z=2 and TlThF5 is monoclinic, space group P21/n, with a=8.1128(5) Å, b=7.2250(4) Å, c=8.8493(6) Å, β=116.683(3)°, V=463.46(5) Å3, Z=4. The structure of TlTh3F13 comprises layers of corner and edge-sharing ThF9 polyhedra further linked by chains of trans connected tricapped trigonal prisms ThF9 through corners and edges. The three dimensional thorium frameworks delimits channels parallel to [0 0 1] where the 11-coordinated Tl+ ions are arranged into double columns located in mirror planes of the structure. TlTh3F13 is isotypic with RbTh3F13, RbU3F13 and with one of the two polymorphs of CsTh3F13. The structure of TlThF5 may be regarded as a layer structure built up from the regular succession of 2∞[ M ‧F5 ] - corrugated layers further held by the Tl+ ions along the [1 0 1 ̅] direction. The layers are built up from edge and corner-sharing thorium polyhedra where each (ThF9)5- monocapped square antiprism is connected to five others by sharing three edges and two corners. TlThF5 is isostructural with β-NH4UF5 and with one of the polymorphs of CsThF5. A comparison of the different structural types of MM‧F5 pentafluorides is presented and a diagram of repartition of their structures is given. From the comparison of the Tl structures with their Rb or Cs homologs, where very similar monovalent cation environments are observed it should be concluded to a stereochemically inactivity of the 6s2 lone pair of Tl(I) in both TlTh3F13 and TlThF5, contrary to what is observed in richer Tl(I) content Tl3ThF7 fluorothorate.

  9. Crystal structure and chemistry of lithium-bearing trioctahedral micas-3T

    USGS Publications Warehouse

    Brigatti, M.F.; Kile, D.E.; Poppi, L.

    2003-01-01

    Chemical analyses and crystal structure refinements were performed on lithian siderophyllite-3T crystals from granitic pegmatites of the anorogenic Pikes Peak batholith (Colorado) to characterize the crystal chemistry and relations with trioctahedral lithium-bearing micas showing different stacking sequences. Chemical data show that the studied samples fall on the siderophyllite-polylithionite join, closer to the siderophyllite end-member. Single-crystal X-ray refinements were carried out on three samples (two of which were taken from core and rim of the same crystal) in space-group P31 12 (the agreement factor, Robs, varies between 0.034 and 0.036). Mean bond distances and mean electron counts of M1, M2 and M3 octahedral sites indicate an ordered cation distribution with M1 and M3 positions substantially larger than M2. In the sample with the largest iron content, the M2 mean electron count increases as well as the mean distance, whereas remains smaller than or . The tetrahedral cation-oxygen atom mean distances range from 1.614 to 1.638 A?? and from 1.663 to 1.678 A?? for T1 and T2 sites, respectively, being consistent with Al3+ enrichment in the T2 sites. The tetrahedral rotation angle, ??, is generally small (3.1 ??? ?? ??? 4.6??) and decreases with siderophyllite content. As Fe increases, the T1 tetrahedron becomes flatter (112.4 ??? t??1 ??? 110.5??), whereas T2 tetrahedron distortion appears unchanged (110.7 ??? t??T2 ??? 110.9).

  10. Gd{sub 4}B{sub 4}O{sub 11}F{sub 2}: Synthesis and crystal structure of a rare-earth fluoride borate exhibiting a new 'fundamental building block' in borate chemistry

    SciTech Connect

    Haberer, Almut; Kaindl, Reinhard; Huppertz, Hubert

    2010-02-15

    A new gadolinium fluoride borate Gd{sub 4}B{sub 4}O{sub 11}F{sub 2} was yielded in a Walker-type multianvil apparatus at 7.5 GPa and 1100 deg. C. Gd{sub 4}B{sub 4}O{sub 11}F{sub 2} crystallizes monoclinically in the space group C2/c with the lattice parameters a=1361.3(3) pm, b=464.2(2) pm, c=1374.1(3) pm, and beta=91.32(3){sup o} (Z=4). The crystal structure exhibits a structural motif not yet reported from borate chemistry: two BO{sub 4}-tetrahedra (square) and two BO{sub 3}-groups (DELTA) are connected via common corners, leading to the fundamental building block 2DELTA2square:DELTAsquaresquareDELTA. In the two crystallographically identical BO{sub 4}-tetrahedra, a distortion resulting in a very long B-O-bond is found. - Graphical abstract: A new gadolinium fluoride borate Gd{sub 4}B{sub 4}O{sub 11}F{sub 2} could be synthesized via high-pressure/high-temperature synthesis (multianvil technique). The crystal structure exhibits a structural motif not yet reported from borate chemistry: two BO{sub 4}-tetrahedra (square) and two BO{sub 3}-groups (DELTA) are connected via common corners, leading to the fundamental building block 2DELTA2square:DELTAsquaresquareDELTA.

  11. Rare-earth-metal nitridophosphates through high-pressure metathesis.

    PubMed

    Kloss, Simon David; Schnick, Wolfgang

    2015-09-14

    Developing a synthetic method to target an broad spectrum of unknown phases can lead to fascinating discoveries. The preparation of the first rare-earth-metal nitridophosphate LiNdP4 N8 is reported. High-pressure solid-state metathesis between LiPN2 and NdF3 was employed to yield a highly crystalline product. The in situ formed LiF is believed to act both as the thermodynamic driving force and as a flux to aiding single-crystal formation in dimensions suitable for crystal structure analysis. Magnetic properties stemming from Nd(3+) ions were measured by SQUID magnetometry. LiNdP4 N8 serves as a model system for the exploration of rare-earth-metal nitridophosphates that may even be expanded to transition metals. High-pressure metathesis enables the systematic study of these uncharted regions of nitride-based materials with unprecedented properties. PMID:26352033

  12. Rare-earth-metal nitridophosphates through high-pressure metathesis.

    PubMed

    Kloss, Simon David; Schnick, Wolfgang

    2015-09-14

    Developing a synthetic method to target an broad spectrum of unknown phases can lead to fascinating discoveries. The preparation of the first rare-earth-metal nitridophosphate LiNdP4 N8 is reported. High-pressure solid-state metathesis between LiPN2 and NdF3 was employed to yield a highly crystalline product. The in situ formed LiF is believed to act both as the thermodynamic driving force and as a flux to aiding single-crystal formation in dimensions suitable for crystal structure analysis. Magnetic properties stemming from Nd(3+) ions were measured by SQUID magnetometry. LiNdP4 N8 serves as a model system for the exploration of rare-earth-metal nitridophosphates that may even be expanded to transition metals. High-pressure metathesis enables the systematic study of these uncharted regions of nitride-based materials with unprecedented properties.

  13. Crystallographic and magnetic properties of (Cu{sub 1-x}V{sub x})V{sub 2}S{sub 4} (x{approx}0.3) single crystals with the layered defect NiAs structure synthesized under high pressure

    SciTech Connect

    Klein, Y.; Moutaabbid, H.; Soyer, A.; D'Astuto, M.; Rousse, G.; Vigneron, J.; Etcheberry, A.; Gauzzi, A.

    2011-09-15

    We report on the reproducible growth of (Cu{sub 1-x}V{sub x})V{sub 2}S{sub 4} single crystals of sizable dimensions ({approx}0.3 mm) and homogeneous composition (x{approx}0.3) by means of high-pressure synthesis. The refinement of single crystal X-ray diffraction data indicates that the crystal structure is of the monoclinic defect NiAs-type, which consists of a stacking of VS{sub 2} layers with CdI{sub 2}-type structure and chains of edge-sharing (Cu{sub 1-x}V{sub x})S{sub 6} octahedra. Layers and chains form a network of face-sharing octahedra with no Cu-V intra-chain ordering. A combined X-ray photoelectron spectroscopy and bond valence sum analysis indicates that the valence of the V and Cu ions are 3+ and 1+, respectively. Magnetic susceptibility measurements unveil the coexistence of a large Pauli-like and of a small Curie-like paramagnetic contributions, with no evidence of any long range order down to 2 K. This result suggests a picture of predominantly itinerant 3d V electrons with significant electron-electron correlations. - Graphical Abstract: Crystallographic structure of (Cu{sub 0.69}V{sub 0.31})V{sub 2}S{sub 4}. For clarity, the octahedral environment of (Cu{sub 0.69}V{sub 0.31}) site is not shown. Highlights: > Synthesis of new single-crystals in the Cu-V-S system using high pressure and high temperature. > Structural analysis revealed the single-crystals to be of the defect NiAs-type structure. > Bond valence sum analysis combined to X-ray photoemission spectroscopy revealed Cu{sup 1+} and a majority of V{sup 3+}. > Magnetic susceptibility has been measured. > Charge carriers are of two types, localized and itinerant.

  14. High-Pressure Lightweight Thrusters

    NASA Technical Reports Server (NTRS)

    Holmes, Richard; McKechnie, Timothy; Shchetkovskiy, Anatoliy; Smirnov, Alexander

    2013-01-01

    Returning samples of Martian soil and rock to Earth is of great interest to scientists. There were numerous studies to evaluate Mars Sample Return (MSR) mission architectures, technology needs, development plans, and requirements. The largest propulsion risk element of the MSR mission is the Mars Ascent Vehicle (MAV). Along with the baseline solid-propellant vehicle, liquid propellants have been considered. Similar requirements apply to other lander ascent engines and reaction control systems. The performance of current state-ofthe- art liquid propellant engines can be significantly improved by increasing both combustion temperature and pressure. Pump-fed propulsion is suggested for a single-stage bipropellant MAV. Achieving a 90-percent stage propellant fraction is thought to be possible on a 100-kg scale, including sufficient thrust for lifting off Mars. To increase the performance of storable bipropellant rocket engines, a high-pressure, lightweight combustion chamber was designed. Iridium liner electrodeposition was investigated on complex-shaped thrust chamber mandrels. Dense, uniform iridium liners were produced on chamber and cylindrical mandrels. Carbon/carbon composite (C/C) structures were braided over iridium-lined mandrels and densified by chemical vapor infiltration. Niobium deposition was evaluated for forming a metallic attachment flange on the carbon/ carbon structure. The new thrust chamber was designed to exceed state-of-the-art performance, and was manufactured with an 83-percent weight savings. High-performance C/Cs possess a unique set of properties that make them desirable materials for high-temperature structures used in rocket propulsion components, hypersonic vehicles, and aircraft brakes. In particular, more attention is focused on 3D braided C/Cs due to their mesh-work structure. Research on the properties of C/Cs has shown that the strength of composites is strongly affected by the fiber-matrix interfacial bonding, and that weakening

  15. High-pressure phase transition in {gamma}-hexanitrohexaazaisowurtzitane

    SciTech Connect

    Russell, T.P.; Miller, P.J.; Piermarini, G.J.; Block, S.

    1992-06-25

    FTIR, EDXD, and PLM; data for a new high-pressure polymorph, {zeta}-HNIW, which is formed from {gamma}-HNIW at 0.7 +/- 0.05 GPa and room temperature. The {gamma}-{zeta} transformation is rapid and reversible in single crystals in a hydrostatic pressure transmitting medium, but the {zeta} form could not be retrieved to ambient conditions. 12 refs., 6 figs., 2 tabs.

  16. Computational chemistry modeling and design of photoswitchable alignment materials for optically addressable liquid crystal devices

    NASA Astrophysics Data System (ADS)

    Marshall, K. L.; Sekera, E. R.; Xiao, K.

    2015-09-01

    Photoalignment technology based on optically switchable "command surfaces" has been receiving increasing interest for liquid crystal optics and photonics device applications. Azobenzene compounds in the form of low-molar-mass, watersoluble salts deposited either directly on the substrate surface or after dispersion in a polymer binder have been almost exclusively employed for these applications, and ongoing research in the area follows a largely empirical materials design and development approach. Recent computational chemistry advances now afford unprecedented opportunities to develop predictive capabilities that will lead to new photoswitchable alignment layer materials with low switching energies, enhanced bistability, write/erase fatigue resistance, and high laser-damage thresholds. In the work described here, computational methods based on the density functional theory and time-dependent density functional theory were employed to study the impact of molecular structure on optical switching properties in photoswitchable methacrylate and acrylamide polymers functionalized with azobenzene and spiropyran pendants.

  17. NETL- High-Pressure Combustion Research Facility

    ScienceCinema

    None

    2016-07-12

    NETL's High-Pressure Combustion Facility is a unique resource within the National Laboratories system. It provides the test capabilities needed to evaluate new combustion concepts for high-pressure, high-temperature hydrogen and natural gas turbines. These concepts will be critical for the next generation of ultra clean, ultra efficient power systems.

  18. NETL- High-Pressure Combustion Research Facility

    SciTech Connect

    2013-07-08

    NETL's High-Pressure Combustion Facility is a unique resource within the National Laboratories system. It provides the test capabilities needed to evaluate new combustion concepts for high-pressure, high-temperature hydrogen and natural gas turbines. These concepts will be critical for the next generation of ultra clean, ultra efficient power systems.

  19. Phase Transitions of Triflate-Based Ionic Liquids under High Pressure.

    PubMed

    Faria, Luiz F O; Ribeiro, Mauro C C

    2015-11-01

    Raman spectroscopy has been used to study phase transitions of ionic liquids based on the triflate anion, [TfO](-), as a function of pressure or temperature. Raman spectra of ionic liquids containing the cations 1-butyl-3-methylimidazolium, [C4C1Im](+), 1-octyl-3-methylimidazolium, [C8C1Im](+), 1-butyl-2,3-dimethylimidazolium, [C4C1C1Im](+), and 1-butyl-1-methylpyrrolidinium, [C4C1Pyr](+), were compared. Vibrational frequencies and binding energy of ionic pairs were calculated by quantum chemistry methods. The ionic liquids [C4C1Im][TfO] and [C4C1Pyr][TfO] crystallize at 1.0 GPa when the pressure is increased in steps of ∼ 0.2 GPa from the atmospheric pressure, whereas [C8C1Im][TfO] and [C4C1C1Im][TfO] do not crystallize up to 2.3 GPa of applied pressure. The low-frequency range of the Raman spectrum of [C4C1Im][TfO] indicates that the system undergoes glass transition, rather than crystallization, when the pressure applied on the liquid has been increased above 2.0 GPa in a single step. Strong hysteresis of spectral features (frequency shift and bandwidth) of the high-pressure crystalline phase when the pressure was released stepwise back to the atmospheric pressure has been found .

  20. High pressure Raman spectroscopy of H2O-CH3OH mixtures.

    PubMed

    Hsieh, Wen-Pin; Chien, Yu-Hsiang

    2015-02-23

    Complex intra-molecular interactions and the hydrogen-bonding network in H2O-volatile mixtures play critical roles in many dynamics processes in physical chemistry, biology, and Earth and planetary sciences. We used high pressure Raman spectroscopy to study the pressure evolution of vibrational frequencies and bonding behavior in H2O-CH3OH mixtures. We found that the presence of low CH3OH content in H2O increases the transition pressure where water crystallizes to ice VI, but does not significantly change the pressure where ice VI transforms to ice VII. Furthermore, the stiffening rates of C-H stretching frequencies dω/dP in CH3OH significantly decrease upon the crystallization of water, and the softening rates of the O-H stretching frequencies of ice VII are suppressed over a narrow pressure range, after which the frequencies of these modes shift with pressure in ways similar to pure CH3OH and ice VII, respectively. Such complex pressure evolution of Raman frequencies along with pronounced variations in Raman intensities of CH3OH within the sample, and the hysteresis of the water-ice VI phase transition suggest pressure-induced segregation of low content CH3OH from ice VII. These findings indicate the significant influence of volatiles on the crystallization of sub-surface ocean and thermal evolution within large icy planets and satellites.

  1. Enhanced microwave absorption properties in BiFeO 3 ceramics prepared by high-pressure synthesis

    NASA Astrophysics Data System (ADS)

    Wen, Fusheng; Wang, Nan; Zhang, Fang

    2010-10-01

    Multiferroic BiFeO 3 nanoparticles and ceramics have been successfully prepared by sol-gel method and following high-pressure synthesis. The denser samples, good crystallization and crystal structure deformation have been obtained via high-pressure synthesis proved by XRD, SEM and Raman spectra. The enhanced magnetization of high-pressure samples attributes to crystal structure deformation; moreover, the enhanced dielectric loss of high-pressure samples results from good crystallization. The better microwave absorption properties can be obtained by high-pressure synthesis, and the minimum reflection loss elevates from -13 dB at 12.4 GHz to -17 dB at 11.2 GHz. It means that the high-pressure synthesis can effectively improve microwave absorption properties of multiferroic materials.

  2. Infrared Spectra of High Pressure Carbon Monoxide

    SciTech Connect

    Evans, W J; Lipp, M J; Lorenzana, H E

    2001-09-21

    We report infrared (IR) spectroscopic measurements of carbon monoxide (CO) at high pressures. Although CO is one of the simplest heteronuclear diatomic molecules, it displays surprisingly complex behavior at high pressures and has been the subject of several studies [1-5]. IR spectroscopic studies of high pressures phases of CO provide data complementing results from previous studies and elucidating the nature of these phases. Though a well-known and widely utilized diagnostic of molecular systems, IR spectroscopy presents several experimental challenges to high pressure diamond anvil cell research. We present measurements of the IR absorption bands of CO at high pressures and experimentally illustrate the crucial importance of accurate normalization of IR spectra specially within regions of strong absorptions in diamond.

  3. Nanoscale coherent intergrowthlike defects in a crystal of La1.9Ca1.1Cu2O6+δ made superconducting by high-pressure oxygen annealing

    DOE PAGESBeta

    Hu, Hefei; Zhu, Yimei; Shi, Xiaoya; Li, Qiang; Zhong, Ruidan; Schneeloch, John A.; Gu, Genda; Tranquada, John M.; Billinge, Simon J. L.

    2014-10-28

    Superconductivity with Tc = 53.5 K has been induced in a large La₁.₉Ca₁.₁Cu₂O₆ (La-2126) single crystal by annealing in a high partial-pressure of oxygen at 1200°C. Using transmission electron microscopy (TEM) techniques, we show that a secondary Ca-doped La₂CuO₄ (La-214) phase, not present in the as-grown crystal, appears as a coherent “intergrowth” as a consequence of the annealing. A corresponding secondary superconducting transition near 13 K is evident in the magnetization measurement. In this study, electron energy loss spectroscopy (EELS) reveals a pre-edge peak at the O K edge in the superconducting La-2126 phase, which is absent in the as-grownmore » crystal, confirming the hole-doping by interstitial oxygen.« less

  4. Ultra high pressure liquid chromatography for crude plant extract profiling.

    PubMed

    Eugster, Philippe J; Guillarme, Davy; Rudaz, Serge; Veuthey, Jean-Luc; Carrupt, Pierre-Alain; Wolfender, Jean-Luc

    2011-01-01

    Ultra high pressure liquid chromatography (UHPLC) systems operating at very high pressures and using sub-2 microm packing columns have allowed a remarkable decrease in analysis time and increase in peak capacity, sensitivity, and reproducibility compared to conventional HPLC. This technology has rapidly been widely accepted by the analytical community and is being gradually applied to various fields of plant analysis such as QC, profiling and fingerprinting, dereplication, and metabolomics. For many applications, an important improvement of the overall performances has been reported. In this review, the basic principles of UHPLC are summarized, and practical information on the type of columns used and phase chemistry available is provided. An overview of the latest applications to natural product analysis in complex mixtures is given, and the potential and limitations as well as some new trends in the development of UHPLC are discussed.

  5. Crystal-chemistry of alteration products of vitrified wastes: implications on the retention of polluting elements.

    PubMed

    Sterpenich, Jérôme

    2008-01-01

    Alteration products of vitrified wastes coming from the incineration of household refuse (MSW) are described. Two vitrified wastes containing 50% and 70% of fly ash and a synthetic stained-glass with a composition close to that of an ancient glass (medieval stained-glass) were altered under different pH conditions (1, 5.5 corresponding to demineralized water and 10) during 181 days. Under acidic condition, the alteration layer is made of an amorphous hydrated silica gel impoverished in most of the initial elements. A minor phase MPO(4)*nH(2)O, where M represents Fe, Ti, Al, Ca and K cations, also constitutes the altered layer of the synthetic stained-glass. Under neutral and basic conditions, the altered layer is made of an amorphous hydrated silica gel and a crystallized calcium phosphate phase. The silica gel is depleted in alkalis and alkali-earth elements but contains significant amounts of aluminium, magnesium and transition elements, whereas the calcium phosphate is a hydroxylapatite-like phase with P-Si substitutions and a Ca/P ratio depending on the pH of the solution. This study shows: (i) the strong influence of pH conditions on the crystal-chemistry of alteration products and thus on the mechanisms of weathering resulting in different trapping of polluting elements, and (ii) that glass alteration does not necessary produce thermodynamically stable phases which has to be taken into account for the prediction of the long-term behavior.

  6. Properties Data for Adhesion and Surface Chemistry of Aluminum: Sapphire-Aluminum, Single-Crystal Couple

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Pohlchuck, Bobby; Whitle, Neville C.; Hector, Louis G., Jr.; Adams, Jim

    1998-01-01

    An investigation was conducted to examine the adhesion and surface chemistry of single-crystal aluminum in contact with single-crystal sapphire (alumina). Pull-off force (adhesion) measurements were conducted under loads of 0. I to I mN in a vacuum of 10(exp -1) to 10(exp -9) Pa (approx. 10(exp -10) to 10(exp -11) torr) at room temperature. An Auger electron spectroscopy analyzer incorporated directly into an adhesion-measuring vacuum system was primarily used to define the chemical nature of the surfaces before and after adhesion measurements. The surfaces were cleaned by argon ion sputtering. With a clean aluminum-clean -sapphire couple the mean value and standard deviation of pull-off forces required to separate the surfaces were 3015 and 298 micro-N, respectively. With a contaminated aluminum-clean sapphire couple these values were 231 and 241 micro-N. The presence of a contaminant film on the aluminum surface reduced adhesion by a factor of 13. Therefore, surfaces cleanliness, particularly aluminum cleanliness, played an important role in the adhesion of the aluminum-sapphire couples. Pressures on the order of 10(exp -8) to 10(exp -9) Pa (approx. 10(exp -10) to 10(exp -11) torr) maintained a clean aluminum surface for only a short time (less then 1 hr) but maintained a clean sapphire surface, once it was achieved, for a much longer time.

  7. Method of producing a high pressure gas

    DOEpatents

    Bingham, Dennis N.; Klingler, Kerry M.; Zollinger, William T.

    2006-07-18

    A method of producing a high pressure gas is disclosed and which includes providing a container; supplying the container with a liquid such as water; increasing the pressure of the liquid within the container; supplying a reactant composition such as a chemical hydride to the liquid under pressure in the container and which chemically reacts with the liquid to produce a resulting high pressure gas such as hydrogen at a pressure of greater than about 100 pounds per square inch of pressure; and drawing the resulting high pressure gas from the container.

  8. Crystallization of pegmatites: Insights from chemistry of garnet, Jacumba pegmatites, San Diego County, California

    NASA Astrophysics Data System (ADS)

    Thompson, M.; Sirbescu, M. C.

    2013-12-01

    Systematic mineral and textural variations from the border zone to the core of a zoned pegmatite sheet may reflect the kinetic or equilibrium fractionation processes that occurred during sequential crystallization of the pegmatite magma. Rhythmic layering, also named 'line rock', is a salient textural feature of world famous San Diego Co. pegmatites, that consists of alternating garnet × tourmaline layers and albite - quartz layers, mm's to cm's thick. Slowly diffusing, incompatible elements in the felsic magma including B, Fe, and Mn may become enriched in boundary layers formed ahead of rapidly crystallized quartzo-felspathic assemblages. This study explores whether the chemistry of garnet concentrated in the border and foot-wall zones and dispersed in the graphic feldspar, core, and pocket zones of Garnet Ledge pegmatite, Jacumba district, might fingerprint the diffusion-controlled oscillatory boundary layers. The lithium-cesium-tantalum (LCT) Jacumba pegmatite district, late product of the Eastern Peninsular Ranges Batholith, consists of numerous subparallel dikes, 3 to 7 m thick, intruding pre-batholitic metasedimentary rocks. The composite aplite-pegmatite dikes are texturally diverse. Comb-textured tourmaline, other unidirectional textures, garnet × tourmaline 'line rock', and coarse graphic K-feldspar crystals occur in the outer zones, followed by massive feldspar-quartz cores, vuggy cleavlandite- euhedral garnet, and miarolitic cavities. The Jacumba pegmatites have produced gem spodumene, beryl, and garnet from several open cuts such as the Beebe Hole and Pack Rat - Garnet Ledge workings. Systematic mineralogical and textural variations, and SEM-EDS garnet compositions were recorded from border to core at Garnet Ledge outcrop and thin section scale, focusing on continuous traverses across the line rock. Garnet from Garnet Ledge belongs to the spessartine-almandine series (Sp42 to Sp65) with minor contents of Mg, Ca, and Ti, consistent with garnet

  9. Design of high pressure waterjet nozzles

    NASA Technical Reports Server (NTRS)

    Mazzoleni, Andre P.

    1994-01-01

    The Hydroblast Research Cell at Marshall Space Flight Center is used to investigate the use of high pressure waterjets to strip paint, grease, adhesive and thermal spray coatings from various substrates. Current methods of cleaning often use ozone depleting chemicals (ODC) such as chlorinated solvents. High pressure waterjet cleaning has proven to be a viable alternative to the use of solvents. A popular method of waterjet cleaning involves the use of a rotating, multijet, high pressure water nozzle which is robotically controlled. This method enables rapid cleaning of a large area, but problems such as incomplete coverage and damage to the substrate from the waterjet have been observed. This report summarizes research consisting of identifying and investigating the basic properties of rotating, multijet, high pressure water nozzles, and how particular designs and modes of operation affect such things as stripping rate, standoff distance and completeness of coverage. The study involved computer simulations, an extensive literature review, and experimental studies of different nozzle designs.

  10. Design of high pressure waterjet nozzles

    NASA Astrophysics Data System (ADS)

    Mazzoleni, Andre P.

    1994-10-01

    The Hydroblast Research Cell at Marshall Space Flight Center is used to investigate the use of high pressure waterjets to strip paint, grease, adhesive and thermal spray coatings from various substrates. Current methods of cleaning often use ozone depleting chemicals (ODC) such as chlorinated solvents. High pressure waterjet cleaning has proven to be a viable alternative to the use of solvents. A popular method of waterjet cleaning involves the use of a rotating, multijet, high pressure water nozzle which is robotically controlled. This method enables rapid cleaning of a large area, but problems such as incomplete coverage and damage to the substrate from the waterjet have been observed. This report summarizes research consisting of identifying and investigating the basic properties of rotating, multijet, high pressure water nozzles, and how particular designs and modes of operation affect such things as stripping rate, standoff distance and completeness of coverage. The study involved computer simulations, an extensive literature review, and experimental studies of different nozzle designs.

  11. Cagelike diamondoid nitrogen at high pressures.

    PubMed

    Wang, Xiaoli; Wang, Yanchao; Miao, Maosheng; Zhong, Xin; Lv, Jian; Cui, Tian; Li, Jianfu; Chen, Li; Pickard, Chris J; Ma, Yanming

    2012-10-26

    Under high pressure, triply bonded molecular nitrogen dissociates into singly bonded polymeric nitrogen, a potential high-energy-density material. The discovery of stable high-pressure forms of polymeric nitrogen is of great interest. We report the striking stabilization of cagelike diamondoid nitrogen at high pressures predicted by first-principles structural searches. The diamondoid structure of polymeric nitrogen has not been seen in any other elements, and it adopts a highly symmetric body-centered cubic structure with lattice sites occupied by diamondoids, each of which consists of ten nitrogen atoms, forming a N(10) tetracyclic cage. Diamondoid nitrogen possesses a wide energy gap and is energetically most stable among all known polymeric structures above 263 GPa, a pressure that is accessible to a high-pressure experiment. Our findings represent a significant step toward the understanding of the behavior of solid nitrogen at extreme conditions.

  12. Cagelike diamondoid nitrogen at high pressures.

    PubMed

    Wang, Xiaoli; Wang, Yanchao; Miao, Maosheng; Zhong, Xin; Lv, Jian; Cui, Tian; Li, Jianfu; Chen, Li; Pickard, Chris J; Ma, Yanming

    2012-10-26

    Under high pressure, triply bonded molecular nitrogen dissociates into singly bonded polymeric nitrogen, a potential high-energy-density material. The discovery of stable high-pressure forms of polymeric nitrogen is of great interest. We report the striking stabilization of cagelike diamondoid nitrogen at high pressures predicted by first-principles structural searches. The diamondoid structure of polymeric nitrogen has not been seen in any other elements, and it adopts a highly symmetric body-centered cubic structure with lattice sites occupied by diamondoids, each of which consists of ten nitrogen atoms, forming a N(10) tetracyclic cage. Diamondoid nitrogen possesses a wide energy gap and is energetically most stable among all known polymeric structures above 263 GPa, a pressure that is accessible to a high-pressure experiment. Our findings represent a significant step toward the understanding of the behavior of solid nitrogen at extreme conditions. PMID:23215200

  13. High pressure processing for food safety.

    PubMed

    Fonberg-Broczek, Monika; Windyga, B; Szczawiński, J; Szczawińska, M; Pietrzak, D; Prestamo, G

    2005-01-01

    Food preservation using high pressure is a promising technique in food industry as it offers numerous opportunities for developing new foods with extended shelf-life, high nutritional value and excellent organoleptic characteristics. High pressure is an alternative to thermal processing. The resistance of microorganisms to pressure varies considerably depending on the pressure range applied, temperature and treatment duration, and type of microorganism. Generally, Gram-positive bacteria are more resistant to pressure than Gram-negative bacteria, moulds and yeasts; the most resistant are bacterial spores. The nature of the food is also important, as it may contain substances which protect the microorganism from high pressure. This article presents results of our studies involving the effect of high pressure on survival of some pathogenic bacteria -- Listeria monocytogenes, Aeromonas hydrophila and Enterococcus hirae -- in artificially contaminated cooked ham, ripening hard cheese and fruit juices. The results indicate that in samples of investigated foods the number of these microorganisms decreased proportionally to the pressure used and the duration of treatment, and the effect of these two factors was statistically significant (level of probability, P high pressure treatment than L. monocytogenes and A. hydrophila. Mathematical methods were applied, for accurate prediction of the effects of high pressure on microorganisms. The usefulness of high pressure treatment for inactivation of microorganisms and shelf-life extention of meat products was also evaluated. The results obtained show that high pressure treatment extends the shelf-life of cooked pork ham and raw smoked pork loin up to 8 weeks, ensuring good micro-biological and sensory quality of the products.

  14. Multicomponent fuel vaporization at high pressures.

    SciTech Connect

    Torres, D. J.; O'Rourke, P. J.

    2002-01-01

    We extend our multicomponent fuel model to high pressures using a Peng-Robinson equation of state, and implement the model into KIVA-3V. Phase equilibrium is achieved by equating liquid and vapor fugacities. The latent heat of vaporization and fuel enthalpies are also corrected for at high pressures. Numerical simulations of multicomponent evaporation are performed for single droplets for a diesel fuel surrogate at different pressures.

  15. Manufacturing Diamond Under Very High Pressure

    NASA Technical Reports Server (NTRS)

    Voronov, Oleg

    2007-01-01

    A process for manufacturing bulk diamond has been made practical by the invention of the High Pressure and Temperature Apparatus capable of applying the combination of very high temperature and high pressure needed to melt carbon in a sufficiently large volume. The apparatus includes a reaction cell wherein a controlled static pressure as high as 20 GPa and a controlled temperature as high as 5,000 C can be maintained.

  16. An Inexpensive Sampleable Reactor for High-Pressure Chemistry.

    ERIC Educational Resources Information Center

    Shumate, R. E.; Riley, D. P.

    1984-01-01

    Describes how to modify the commercially available and inexpensive Griffin-Worden (Kontes) glass pressure reactors to permit sampling of homogeneous reactions, without changing the relative concentration of species present. All required parts necessary for the modification are commercially available. (JN)

  17. High-pressure polymorphism of acetylsalicylic acid (aspirin): Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Crowell, Ethan L.; Dreger, Zbigniew A.; Gupta, Yogendra M.

    2015-02-01

    Micro-Raman spectroscopy was used to elucidate the high-pressure polymorphic behavior of acetylsalicylic acid (ASA), an important pharmaceutical compound known as aspirin. Using a diamond anvil cell (DAC), single crystals of the two polymorphic phases of aspirin existing at ambient conditions (ASA-I and ASA-II) were compressed to 10 GPa. We found that ASA-I does not transform to ASA-II, but instead transforms to a new phase (ASA-III) above ∼2 GPa. It is demonstrated that this transformation primarily introduces structural changes in the bonding and arrangement of the acetyl groups and is reversible upon the release of pressure. In contrast, a less dense ASA-II shows no transition in the pressure range studied, though it appears to exhibit a disordered structure above 7 GPa. Our results suggest that ASA-III is the most stable polymorph of aspirin at high pressures.

  18. High Pressure Materials Research: Novel Extended Phases of Molecular Triatomics

    SciTech Connect

    Yoo, C

    2004-05-26

    Application of high pressure significantly alters the interatomic distance and thus the nature of intermolecular interaction, chemical bonding, molecular configuration, crystal structure, and stability of solid [1]. With modern advances in high-pressure technologies [2], it is feasible to achieve a large (often up to a several-fold) compression of lattice, at which condition material can be easily forced into a new physical and chemical configuration [3]. The high-pressure thus offers enhanced opportunities to discover new phases, both stable and metastable ones, and to tune exotic properties in a wide-range of atomistic length scale, substantially greater than (often being several orders of) those achieved by other thermal (varying temperatures) and chemical (varying composition or making alloys) means. Simple molecular solids like H{sub 2}, C, CO{sub 2}, N{sub 2}, O{sub 2}, H{sub 2}O, CO, NH{sub 3}, and CH{sub 4} are bounded by strong covalent intramolecular bonds, yet relatively weak intermolecular bonds of van der Waals and/or hydrogen bonds. The weak intermolecular bonds make these solids highly compressible (i.e., low bulk moduli typically less than 10 GPa), while the strong covalent bonds make them chemically inert at least initially at low pressures. Carbon-carbon single bonds, carbon-oxygen double bonds and nitrogen-nitrogen triple bonds, for example, are among the strongest. These molecular forms are, thus, often considered to remain stable in an extended region of high pressures and high temperatures. High stabilities of these covalent molecules are also the basis of which their mixtures are often presumed to be the major detonation products of energetic materials as well as the major constituents of giant planets. However, their physical/chemical stabilities are not truly understood at those extreme pressure-temperature conditions. In fact, an increasing amount of experimental evidences contradict the assumed stability of these materials at high

  19. Crystal-chemistry of alteration products of vitrified wastes: Implications on the retention of polluting elements

    SciTech Connect

    Sterpenich, Jerome

    2008-07-01

    Alteration products of vitrified wastes coming from the incineration of household refuse (MSW) are described. Two vitrified wastes containing 50% and 70% of fly ash and a synthetic stained-glass with a composition close to that of an ancient glass (medieval stained-glass) were altered under different pH conditions (1, 5.5 corresponding to demineralized water and 10) during 181 days. Under acidic condition, the alteration layer is made of an amorphous hydrated silica gel impoverished in most of the initial elements. A minor phase MPO{sub 4} . nH{sub 2}O, where M represents Fe, Ti, Al, Ca and K cations, also constitutes the altered layer of the synthetic stained-glass. Under neutral and basic conditions, the altered layer is made of an amorphous hydrated silica gel and a crystallized calcium phosphate phase. The silica gel is depleted in alkalis and alkali-earth elements but contains significant amounts of aluminium, magnesium and transition elements, whereas the calcium phosphate is a hydroxylapatite-like phase with P-Si substitutions and a Ca/P ratio depending on the pH of the solution. This study shows: (i) the strong influence of pH conditions on the crystal-chemistry of alteration products and thus on the mechanisms of weathering resulting in different trapping of polluting elements, and (ii) that glass alteration does not necessary produce thermodynamically stable phases which has to be taken into account for the prediction of the long-term behavior.

  20. Ternary clathrates Ba Cd Ge: phase equilibria, crystal chemistry and physical properties

    NASA Astrophysics Data System (ADS)

    Melnychenko-Koblyuk, N.; Grytsiv, A.; Berger, St.; Kaldarar, H.; Michor, H.; Röhrbacher, F.; Royanian, E.; Bauer, E.; Rogl, P.; Schmid, H.; Giester, G.

    2007-01-01

    The present paper describes the formation, phase relations at subsolidus temperatures and at 800 °C, crystal chemistry and physical properties of a series of ternary clathrates as part of the solid solution {\\mathrm {Ba_{8}Cd}}_{x}\\mathrm {Ge}_{43-5x/8}\\square _{3-3x/8} , derived from binary {\\mathrm {Ba_{8}Ge_{43}}}\\square_{3} with a solubility limit of 8 Cd per formula unit at 800 °C. Structural investigations in all cases confirm cubic primitive symmetry with a lattice parameter aap1.1 nm, consistent with the space group type Pm{\\bar {3}}n . Both the temperature dependent x-ray spectra and the heat capacity define a low-lying, almost localized, phonon branch. Studies of transport properties show electrons to be the majority charge carriers in the systems. As the Cd content increases, the system is driven towards a metal-to-insulator transition, causing \\mathrm {Ba_{8}Cd_{4.7}Ge_{40.3}}\\square_{1.0} , for example, to show metallic behaviour at low temperatures while at high temperatures semiconducting features become obvious. A model based on a gap of the electronic density of states slightly above the Fermi energy perfectly explains such a scenario. Thermal conductivity exhibits a pronounced low temperature maximum, dominated by the lattice contribution, while at higher temperatures the electronic part becomes more important.

  1. OH defects in high-pressure kyanite

    NASA Astrophysics Data System (ADS)

    Wieczorek, A. K.; Beran, A.

    2003-04-01

    The close-packed mineral structures of nominally anhydrous minerals, likely to be present within the Earth's upper mantle, may offer important storage sites for trace hydrogen (Ingrin and Skogby, 2000). Kyanite may indeed incorporate essential amounts of hydrogen (Beran et al., 1993). The IR spectrum in the OH stretching vibrational region of a gem-quality kyanite from an eclogite xenolith in a kimberlite from the Roberts Victor mine, South Africa, is characterized by a band triplet consisting of sharp bands centered at 3440, 3410 and 3387 cm-1 showing similar intensities (band group I). In comparison with kyanites from crustal occurrences, the similar intensities of these bands is a characteristic feature of this high-pressure kyanite, probably related to the enhanced Mg and Ti contents (ca. 0.06 wt.% MgO, 0.09 wt.% TiO_2). A second group of bands (band group II) is characterized by a broad absorption centered around 3270 cm-1. Band deconvolution revealed two maxima at 3276 and 3260 cm-1. Heating experiments indicate diffusion processes of hydrogen to preferred structural oxygen positions. Up to temperatures of 600^oC, the band at 3387 cm-1 shows a significant increase of its intensity, while the intensities of the bands at 3440 and 3410 cm-1 slightly decrease. No changes of intensity were observed for the low-energy band group II. Above heating temperatures of 600^oC all bands show a decrease of their intensities. The two groups of bands suggest that at least two types of OH positions exist simultaneously in the structure of kyanite. The pleochroic scheme of the two band groups, measured on oriented sections cut parallel to (100) and perpendicular to b direction, allows to develop a model for the OH defect incorporation, where the two crystallographically different oxygen atoms, not bound to Si, are preferred candidates for the partial OH replacement. The analytical H_2O content was determined on the basis of Beer's law from polarized spectral data and amounts to

  2. Single crystal X-ray diffraction study of a mixed-valence gold compound, Cs{sub 2}Au{sup I}Au{sup III}Cl{sub 6} under high pressures up to 18 GPa: Pressure-induced phase transition coupled with gold valence transition

    SciTech Connect

    Matsushita, Nobuyuki Ahsbahs, Hans; Hafner, Stefan S.; Kojima, Norimichi

    2007-04-15

    We performed the single-crystal X-ray diffraction study of a perovskite-type gold mixed-valence compound, Cs{sub 2}Au{sup I}Au{sup III}Cl{sub 6}, under high pressures up to 18 GPa by using a diamond-anvil-cell with helium gas as an ideal hydrostatic pressure-transmitting medium. The lattice parameters and the variable atomic positional parameters were obtained with reasonable accuracy at various pressures. A structural phase transition at ca. 12.5 GPa from I4/mmm to Pm3m was found. The lattice parameters a {sub 0} and c {sub 0}, denoted in the tetragonal cell setting, result in the relationship 2{sup 1/2} a {sub 0}=c {sub 0}, and the superstructure reflections h k l (l is odd), caused by the shift of the Cl ions from the midpoint of the Au ions, disappeared at pressures above the phase transition. Both elongated [Au{sup III}Cl{sub 6}] and compressed [Au{sup I}Cl{sub 6}] octahedra in the low-pressure phase smoothly approach regular octahedra with increasing pressure. Above the structural phase transition at 12.5 GPa, all the [AuCl{sub 6}] octahedra are crystallographically equivalent, which shows that the tetragonal-to-cubic phase transition accompanies the valence transition from the Au{sup I}/Au{sup III} mixed-valence state to the Au{sup II} single-valence state. - Graphical abstract: Single-crystal X-ray diffraction study under high pressures up to 18 GPa by using a diamond-anvil-cell with helium gas as an ideal hydrostatic pressure medium has revealed that a perovskite-type gold mixed-valence compound, Cs{sub 2}Au{sup I}Au{sup III}Cl{sub 6}, exhibits the structural phase transition from tetragonal to cubic at 12.5 GPa accompanying gold valence transition.

  3. High-pressure high-temperature synthesis and crystal structure of the isotypic rare earth (RE)-thioborate-sulfides RE{sub 9}[BS{sub 3}]{sub 2}[BS{sub 4}]{sub 3}S{sub 3}, (RE=Dy-Lu)

    SciTech Connect

    Borna, Marija; Hunger, Jens; Ormeci, Alim; Zahn, Dirk; Burkhardt, Ulrich; Carrillo-Cabrera, Wilder; Cardoso-Gil, Raul; Kniep, Ruediger

    2011-02-15

    Application of high-pressure high-temperature conditions (3.5 GPa at 1673 K for 5 h) to mixtures of the elements (RE:B:S=1:3:6) yielded crystalline samples of the isotypic rare earth-thioborate-sulfides RE{sub 9}[BS{sub 3}]{sub 2}[BS{sub 4}]{sub 3}S{sub 3}, (RE=Dy-Lu), which crystallize in space group P6{sub 3} (Z=2/3) and adopt the Ce{sub 6}Al{sub 3.33}S{sub 14} structure type. The crystal structures were refined from X-ray powder diffraction data by applying the Rietveld method. Dy: a=9.4044(2) A, c=5.8855(3) A; Ho: a=9.3703(1) A, c=5.8826(1) A; Er: a=9.3279(12) A, c=5.8793(8) A; Tm: a=9.2869(3) A, c=5.8781(3) A; Yb: a=9.2514(5) A, c=5.8805(6) A; Lu: a=9.2162(3) A, c=5.8911(3) A. The crystal structure is characterized by the presence of two isolated complex ions [BS{sub 3}]{sup 3-} and [BS{sub 4}]{sup 5-} as well as [{open_square}(S{sup 2-}){sub 3}] units. -- Graphical abstract: Isotypic rare earth-thioborate-sulfides RE{sub 9}[BS{sub 3}]{sub 2}[BS{sub 4}]{sub 3}S{sub 3}, (RE=Dy-Lu) were prepared by application of high-pressure high-temperature conditions to mixtures of the elements. Their crystal structures are characterized by presence of the two isolated complex ions [BS{sub 3}]{sup 3-} and [BS{sub 4}]{sup 5-} as well as [{open_square}(S{sup 2-}){sub 3}] units. Quantum mechanical calculations revealed the arrangement of the intrinsic vacancies. Display Omitted Research Highlights: {yields} Application of high-pressure high-temperature conditions to mixtures of the elements yields crystalline samples of the isotypic rare earth-thioborate-sulfides RE{sub 9}[BS{sub 3}]{sub 2}[BS{sub 4}]{sub 3}S{sub 3}, (RE=Dy-Lu). {yields} RE{sub 9}[BS{sub 3}]{sub 2}[BS{sub 4}]{sub 3}S{sub 3}, (RE=Dy-Lu) crystallize in space group P6{sub 3} (Z=2/3) and adopt the Ce{sub 6}Al{sub 3.33}S{sub 14} structure type. {yields} The crystal structure of RE{sub 9}[BS{sub 3}]{sub 2}[BS{sub 4}]{sub 3}S{sub 3}, (RE=Dy-Lu) is characterized by the presence of two isolated complex ions [BS{sub 3

  4. Fuel droplet burning rates at high pressures.

    NASA Technical Reports Server (NTRS)

    Canada, G. S.; Faeth, G. M.

    1973-01-01

    Combustion of methanol, ethanol, propanol-1, n-pentane, n-heptane, and n-decane was observed in air under natural convection conditions, at pressures up to 100 atm. The droplets were simulated by porous spheres, with diameters in the range from 0.63 to 1.90 cm. The pressure levels of the tests were high enough so that near-critical combustion was observed for methanol and ethanol. Due to the high pressures, the phase-equilibrium models of the analysis included both the conventional low-pressure approach as well as high-pressure versions, allowing for real gas effects and the solubility of combustion-product gases in the liquid phase. The burning-rate predictions of the various theories were similar, and in fair agreement with the data. The high-pressure theory gave the best prediction for the liquid-surface temperatures of ethanol and propanol-1 at high pressure. The experiments indicated the approach of critical burning conditions for methanol and ethanol at pressures on the order of 80 to 100 atm, which was in good agreement with the predictions of both the low- and high-pressure analysis.

  5. Novel Stable Compounds in the C-H-O Ternary System at High Pressure.

    PubMed

    Saleh, Gabriele; Oganov, Artem R

    2016-01-01

    The chemistry of the elements is heavily altered by high pressure, with stabilization of many new and often unexpected compounds, the emergence of which can profoundly change models of planetary interiors, where high pressure reigns. The C-H-O system is one of the most important planet-forming systems, but its high-pressure chemistry is not well known. Here, using state-of-the-art variable-composition evolutionary searches combined with quantum-mechanical calculations, we explore the C-H-O system at pressures up to 400 GPa. Besides uncovering new stable polymorphs of high-pressure elements and known molecules, we predicted the formation of new compounds. A 2CH4:3H2 inclusion compound forms at low pressure and remains stable up to 215 GPa. Carbonic acid (H2CO3), highly unstable at ambient conditions, was predicted to form exothermically at mild pressure (about 1 GPa). As pressure rises, it polymerizes and, above 314 GPa, reacts with water to form orthocarbonic acid (H4CO4). This unexpected high-pressure chemistry is rationalized by analyzing charge density and electron localization function distributions, and implications for general chemistry and planetary science are also discussed. PMID:27580525

  6. Novel Stable Compounds in the C-H-O Ternary System at High Pressure

    PubMed Central

    Saleh, Gabriele; Oganov, Artem R.

    2016-01-01

    The chemistry of the elements is heavily altered by high pressure, with stabilization of many new and often unexpected compounds, the emergence of which can profoundly change models of planetary interiors, where high pressure reigns. The C-H-O system is one of the most important planet-forming systems, but its high-pressure chemistry is not well known. Here, using state-of-the-art variable-composition evolutionary searches combined with quantum-mechanical calculations, we explore the C-H-O system at pressures up to 400 GPa. Besides uncovering new stable polymorphs of high-pressure elements and known molecules, we predicted the formation of new compounds. A 2CH4:3H2 inclusion compound forms at low pressure and remains stable up to 215 GPa. Carbonic acid (H2CO3), highly unstable at ambient conditions, was predicted to form exothermically at mild pressure (about 1 GPa). As pressure rises, it polymerizes and, above 314 GPa, reacts with water to form orthocarbonic acid (H4CO4). This unexpected high-pressure chemistry is rationalized by analyzing charge density and electron localization function distributions, and implications for general chemistry and planetary science are also discussed. PMID:27580525

  7. Novel Stable Compounds in the C-H-O Ternary System at High Pressure

    NASA Astrophysics Data System (ADS)

    Saleh, Gabriele; Oganov, Artem R.

    2016-09-01

    The chemistry of the elements is heavily altered by high pressure, with stabilization of many new and often unexpected compounds, the emergence of which can profoundly change models of planetary interiors, where high pressure reigns. The C-H-O system is one of the most important planet-forming systems, but its high-pressure chemistry is not well known. Here, using state-of-the-art variable-composition evolutionary searches combined with quantum-mechanical calculations, we explore the C-H-O system at pressures up to 400 GPa. Besides uncovering new stable polymorphs of high-pressure elements and known molecules, we predicted the formation of new compounds. A 2CH4:3H2 inclusion compound forms at low pressure and remains stable up to 215 GPa. Carbonic acid (H2CO3), highly unstable at ambient conditions, was predicted to form exothermically at mild pressure (about 1 GPa). As pressure rises, it polymerizes and, above 314 GPa, reacts with water to form orthocarbonic acid (H4CO4). This unexpected high-pressure chemistry is rationalized by analyzing charge density and electron localization function distributions, and implications for general chemistry and planetary science are also discussed.

  8. Energy efficient engine high-pressure turbine detailed design report

    NASA Technical Reports Server (NTRS)

    Thulin, R. D.; Howe, D. C.; Singer, I. D.

    1982-01-01

    The energy efficient engine high-pressure turbine is a single stage system based on technology advancements in the areas of aerodynamics, structures and materials to achieve high performance, low operating economics and durability commensurate with commercial service requirements. Low loss performance features combined with a low through-flow velocity approach results in a predicted efficiency of 88.8 for a flight propulsion system. Turbine airfoil durability goals are achieved through the use of advanced high-strength and high-temperature capability single crystal materials and effective cooling management. Overall, this design reflects a considerable extension in turbine technology that is applicable to future, energy efficient gas-turbine engines.

  9. Piston cylinder cell for high pressure ultrasonic pulse echo measurements.

    PubMed

    Kepa, M W; Ridley, C J; Kamenev, K V; Huxley, A D

    2016-08-01

    Ultrasonic techniques such as pulse echo, vibrating reed, or resonant ultrasound spectroscopy are powerful probes not only for studying elasticity but also for investigating electronic and magnetic properties. Here, we report on the design of a high pressure ultrasonic pulse echo apparatus, based on a piston cylinder cell, with a simplified electronic setup that operates with a single coaxial cable and requires sample lengths of mm only. The design allows simultaneous measurements of ultrasonic velocities and attenuation coefficients up to a pressure of 1.5 GPa. We illustrate the performance of the cell by probing the phase diagram of a single crystal of the ferromagnetic superconductor UGe2. PMID:27587156

  10. Piston cylinder cell for high pressure ultrasonic pulse echo measurements

    NASA Astrophysics Data System (ADS)

    Kepa, M. W.; Ridley, C. J.; Kamenev, K. V.; Huxley, A. D.

    2016-08-01

    Ultrasonic techniques such as pulse echo, vibrating reed, or resonant ultrasound spectroscopy are powerful probes not only for studying elasticity but also for investigating electronic and magnetic properties. Here, we report on the design of a high pressure ultrasonic pulse echo apparatus, based on a piston cylinder cell, with a simplified electronic setup that operates with a single coaxial cable and requires sample lengths of mm only. The design allows simultaneous measurements of ultrasonic velocities and attenuation coefficients up to a pressure of 1.5 GPa. We illustrate the performance of the cell by probing the phase diagram of a single crystal of the ferromagnetic superconductor UGe2.

  11. The sound velocity measurement in diacylglycerol oil under high pressure

    NASA Astrophysics Data System (ADS)

    Rostocki, A. J.; Malanowski, A.; Tarakowski, R.; Szlachta, K.; Kiełczyński, P.; Szalewski, M.; Balcerzak, A.; Ptasznik, S.

    2013-03-01

    In this article, the influence of high pressure on sound velocity at 293 K has been presented. The investigated diacylglycerol oil (DAG - [D82T18]AG) was composed of 82% DAGs and 18% triacylglycerols. The variation of sound velocity with hydrostatic pressure for DAG was evaluated up to 400 MPa. The phase transformation in DAG has been observed as a discontinuity of the dependence of sound velocity on pressure. The sound velocity during the phase transition has shown distinct increment. Also the volume changes have been measured. It has shown the rapid drop of the volume at the phase transformation pressure due to the possible crystallization of DAG oil.

  12. Structural Behaviour of Uranium Sulfide under High Pressure

    SciTech Connect

    Shareef, F.; Singh, S.; Gour, A.; Bhardwaj, P.; Sarwan, M.; Dubey, R.; Singh, R. K.

    2011-07-15

    The study of pressure induced structural phase transition of uranium sulphide, which crystallizes in rock salt (B1) structure, has been performed using the well described three body interaction model (TBIPM). Our present TBIP model consists of long range coulombic interaction, three body interactions, Hafemeister and Flygare type short-range overlap repulsion extended upto the second neighbor ions and the van der Waals interaction. The present results are in good agreement with the available experimental data on the phase transition pressure (Pt = 80.2 GPa). So it can be considered as an adequate and suitable model to perform high pressure studies.

  13. Pr{sub 4}B{sub 10}O{sub 21}: A new composition of rare-earth borates by high-pressure/high-temperature synthesis

    SciTech Connect

    Haberer, Almut; Heymann, Gunter; Huppertz, Hubert

    2007-05-15

    High-pressure chemistry led to the synthesis of the rare-earth borate Pr{sub 4}B{sub 10}O{sub 21} using a Walker-type multianvil apparatus at 3.5 GPa and 1050 deg. C. The tetra-praseodymium(III)-decaborate crystallizes monoclinicly with four formula units in the space group P2{sub 1}/n and lattice parameters of a=710.2(2), b=1948.8(4), c=951.6(2) pm, and {beta}=93.27(3){sup o}. The boron-oxygen network consists of [BO{sub 4}]{sup 5-} tetrahedra and [BO{sub 3}]{sup 3-} groups; however, the [BO{sub 4}]{sup 5-} groups represent the major part (80%) due to the high-pressure conditions during the synthesis. The praseodymium ions are coordinated by 10 and 12 oxygen atoms. Along with a detailed description of the crystal structure, temperature programmed X-ray powder diffraction data are shown, demonstrating the metastable character of this compound. - Graphical abstract: Synthesis of Pr{sub 4}B{sub 10}O{sub 21} via the multianvil high-pressure/high-temperature technique representing a new composition of rare-earth borates.

  14. Curved and conformal high-pressure vessel

    DOEpatents

    Croteau, Paul F.; Kuczek, Andrzej E.; Zhao, Wenping

    2016-10-25

    A high-pressure vessel is provided. The high-pressure vessel may comprise a first chamber defined at least partially by a first wall, and a second chamber defined at least partially by the first wall. The first chamber and the second chamber may form a curved contour of the high-pressure vessel. A modular tank assembly is also provided, and may comprise a first mid tube having a convex geometry. The first mid tube may be defined by a first inner wall, a curved wall extending from the first inner wall, and a second inner wall extending from the curved wall. The first inner wall may be disposed at an angle relative to the second inner wall. The first mid tube may further be defined by a short curved wall opposite the curved wall and extending from the second inner wall to the first inner wall.

  15. High pressure electrical insulated feed thru connector

    DOEpatents

    Oeschger, Joseph E.; Berkeland, James E.

    1979-11-13

    A feed-thru type hermetic electrical connector including at least one connector pin feeding through an insulator block within the metallic body of the connector shell. A compression stop arrangement coaxially disposed about the insulator body is brazed to the shell, and the shoulder on the insulator block bears against this top in a compression mode, the high pressure or internal connector being at the opposite end of the shell. Seals between the pin and an internal bore at the high pressure end of the insulator block and between the insulator block and the metallic shell at the high pressure end are hermetically brazed in place, the first of these also functioning to transfer the axial compressive load without permitting appreciable shear action between the pin and insulator block.

  16. High-pressure distillation is different

    SciTech Connect

    Brierley, R.J.P.

    1994-07-01

    Many fluid systems perform differently at higher pressures than at lower ones. This makes high-pressure distillation different, too. But it also offers significant opportunities to engineers, both those deciding on the types of equipment to specify at the design stage, and those responsible for making high-pressure columns work, getting the best out of them, and assessing whether they can be uprated. Indeed, in a number of cases, it has been possible to uprate columns substantially (in one case by 70%) by redesign of the trays, and by replacement of trays with packing. This article provides practical guidance, based on the author's 20 years of experience as a distillation specialist, on how to get the best out of high-pressure distillation.

  17. High pressure studies on nanometer sized clusters: Structural, optical, and cooperative properties

    SciTech Connect

    Tolbert, S.H.

    1995-05-01

    High-pressure Se EXAFS is used to study pressure-induced structural transformations in CdSe nanocrystals. The transformation is wurtzite to rock salt, at a pressure much higher than in bulk. High-pressure XRD is used to confirm the EXAFS results. Diffraction peak widths indicate that nanocrystals do not fragment upon transformation. Optical absorption correlates with structural transformations and is used to measure transition pressures; transformation pressure increases smoothly as nanocrystal size decreases. Thermodynamics of transformation is modeled using an elevated surface energy in the high-pressure phase. High-pressure study of Si nanocrystals show large increases in transformation pressure in crystallites to 500{angstrom} diameter, and an overall change in crystallite shape upon transformation is seen from XRD line widths. C{sub 60} single crystals were studied using Raman scattering; results provide information about the clusters` rotational state. Optical properties of high-pressure phase CdSe clusters were studied.

  18. Elasticity of methane hydrate phases at high pressure.

    PubMed

    Beam, Jennifer; Yang, Jing; Liu, Jin; Liu, Chujie; Lin, Jung-Fu

    2016-04-21

    Determination of the full elastic constants (cij) of methane hydrates (MHs) at extreme pressure-temperature environments is essential to our understanding of the elastic, thermodynamic, and mechanical properties of methane in MH reservoirs on Earth and icy satellites in the solar system. Here, we have investigated the elastic properties of singe-crystal cubic MH-sI, hexagonal MH-II, and orthorhombic MH-III phases at high pressures in a diamond anvil cell. Brillouin light scattering measurements, together with complimentary equation of state (pressure-density) results from X-ray diffraction and methane site occupancies in MH from Raman spectroscopy, were used to derive elastic constants of MH-sI, MH-II, and MH-III phases at high pressures. Analysis of the elastic constants for MH-sI and MH-II showed intriguing similarities and differences between the phases' compressional wave velocity anisotropy and shear wave velocity anisotropy. Our results show that these high-pressure MH phases can exhibit distinct elastic, thermodynamic, and mechanical properties at relevant environments of their respective natural reservoirs. These results provide new insight into the determination of how much methane exists in MH reservoirs on Earth and on icy satellites elsewhere in the solar system and put constraints on the pressure and temperature conditions of their environment. PMID:27389226

  19. Elasticity of methane hydrate phases at high pressure

    NASA Astrophysics Data System (ADS)

    Beam, Jennifer; Yang, Jing; Liu, Jin; Liu, Chujie; Lin, Jung-Fu

    2016-04-01

    Determination of the full elastic constants (cij) of methane hydrates (MHs) at extreme pressure-temperature environments is essential to our understanding of the elastic, thermodynamic, and mechanical properties of methane in MH reservoirs on Earth and icy satellites in the solar system. Here, we have investigated the elastic properties of singe-crystal cubic MH-sI, hexagonal MH-II, and orthorhombic MH-III phases at high pressures in a diamond anvil cell. Brillouin light scattering measurements, together with complimentary equation of state (pressure-density) results from X-ray diffraction and methane site occupancies in MH from Raman spectroscopy, were used to derive elastic constants of MH-sI, MH-II, and MH-III phases at high pressures. Analysis of the elastic constants for MH-sI and MH-II showed intriguing similarities and differences between the phases' compressional wave velocity anisotropy and shear wave velocity anisotropy. Our results show that these high-pressure MH phases can exhibit distinct elastic, thermodynamic, and mechanical properties at relevant environments of their respective natural reservoirs. These results provide new insight into the determination of how much methane exists in MH reservoirs on Earth and on icy satellites elsewhere in the solar system and put constraints on the pressure and temperature conditions of their environment.

  20. Theoretical Predictions of Phase Transitions at Ultra-high Pressures

    NASA Astrophysics Data System (ADS)

    Boates, Brian

    2013-06-01

    We present ab initio calculations of the high-pressure phase diagrams of important planetary materials such as CO2, MgSiO3, and MgO. For CO2, we predict a series of distinct liquid phases over a wide pressure (P) and temperature (T) range, including a first-order transition to a dense polymer liquid. We have computed finite-temperature free energies of liquid and solid CO2 phases to determine the melting curve beyond existing measurements and investigate possible phase separation transitions. The interaction of these phase boundaries with the mantle geotherm will also be discussed. Furthermore, we find evidence for a vast pressure-temperature regime where molten MgSiO3 decomposes into liquid SiO2 and solid MgO, with a volume change of approximately 1.2 percent. The demixing transition is driven by the crystallization of MgO ? the reaction only occurs below the high-pressure MgO melting curve. The predicted transition pressure at 10,000 K is in close proximity to an anomaly reported in recent laser-driven shock experiments of MgSiO3. We also present new results for the high-pressure melting curve of MgO and its B1-B2 solid phase transition, with a triple point near 364 GPa and 12,000 K.

  1. High-pressure Raman study of fully deuterated methane hydrate

    NASA Astrophysics Data System (ADS)

    Yabashi, Ryo; Yoshida, Masashi; Kume, Tetsuji; Sasaki, Shigeo

    2013-06-01

    Methane hydrate (MH: CH4- nH2O) crystallizes in a cubic structure I (sI) which consists of hydrogen-bonded water cages which enclathrate methane molecules as guests. With increasing pressure, the initial sI of MH transforms to a hexagonal structure H (sH) at 0.9 GPa, and eventually to an orthorhombic cage-less structure O at 1.9 GPa. The sH consists of three small S1, two small S2, and one large LL water cages in a hexagonal unit cell. The previous high-pressure Raman measurements for C-H stretching vibration of MH-sH indicated that the capacity of methane molecules in the large LL cage abruptly increased at 1.3 GPa, and its occupation number of methane molecule was about 2.5 above 1.3 GPa. However, this result disagrees with the previous high-pressure neutron diffraction experiments for sH of fully deutarated methane hydrate (FDMH: CD4- nD2O). To solve this discrepancy, we have carried out the high pressure Raman measurements for C-D stretching vibration in the sI and sH phases of FDMH. As a result, we have obtained the different Raman spectral patterns between FDMH and MH, which suggests that the occupancy of CD4 in water cages is somewhat different from CH4.

  2. High pressure water jet mining machine

    DOEpatents

    Barker, Clark R.

    1981-05-05

    A high pressure water jet mining machine for the longwall mining of coal is described. The machine is generally in the shape of a plowshare and is advanced in the direction in which the coal is cut. The machine has mounted thereon a plurality of nozzle modules each containing a high pressure water jet nozzle disposed to oscillate in a particular plane. The nozzle modules are oriented to cut in vertical and horizontal planes on the leading edge of the machine and the coal so cut is cleaved off by the wedge-shaped body.

  3. High pressure water jet cutting and stripping

    NASA Technical Reports Server (NTRS)

    Hoppe, David T.; Babai, Majid K.

    1991-01-01

    High pressure water cutting techniques have a wide range of applications to the American space effort. Hydroblasting techniques are commonly used during the refurbishment of the reusable solid rocket motors. The process can be controlled to strip a thermal protective ablator without incurring any damage to the painted surface underneath by using a variation of possible parameters. Hydroblasting is a technique which is easily automated. Automation removes personnel from the hostile environment of the high pressure water. Computer controlled robots can perform the same task in a fraction of the time that would be required by manual operation.

  4. Superelastic carbon spheres under high pressure

    NASA Astrophysics Data System (ADS)

    Li, Meifen; Guo, Junjie; Xu, Bingshe

    2013-03-01

    We report a superelastic deformation behavior of carbon spheres by the in situ Raman spectroscopy in a high-pressure diamond anvil cell. The carbon spheres produced by arc discharging in toluene have a mean diameter of 200 nm and an onion-like multilayer graphitic structure. We find that the elastic coefficients, during both the compression and decompression processes, remain a constant up to 10 GPa, indicating a superior high-pressure structural stability. Such superelastic behavior is related to the isotropic and concentric configuration of carbon spheres and provides additional insight into improving the microscopic mechanical properties of small-scale particles.

  5. High pressure freon decontamination of remote equipment

    SciTech Connect

    Wilson, C.E.

    1987-01-01

    A series of decontamination tests using high pressure FREON 113 was conducted in the 200 Area of the Hanford site. The intent of these tests was to evaluate the effectiveness of FREON 113 in decontamination of manipulator components, tools, and equipment items contaminated with mixed fission products. The test results indicated that high pressure FREON 113 is very effective in removing fissile material from a variety of objects and can reduce both the quantity and the volume of the radioactive waste material presently being buried.

  6. A new structure type of RE{sub 4}B{sub 4}O{sub 11}F{sub 2}: High-pressure synthesis and crystal structure of La{sub 4}B{sub 4}O{sub 11}F{sub 2}

    SciTech Connect

    Haberer, Almut; Kaindl, Reinhard; Oeckler, Oliver; Huppertz, Hubert

    2010-09-15

    The first lanthanum fluoride borate La{sub 4}B{sub 4}O{sub 11}F{sub 2} was obtained in a Walker-type multianvil apparatus at 6 GPa and 1300 {sup o}C. La{sub 4}B{sub 4}O{sub 11}F{sub 2} crystallizes in the monoclinic space group P2{sub 1}/c with the lattice parameters a=778.1(2) pm, b=3573.3(7) pm, c=765.7(2) pm, {beta}=113.92(3){sup o} (Z=8), and represents a new structure type in the class of compounds with the composition RE{sub 4}B{sub 4}O{sub 11}F{sub 2}. The crystal structure contains BO{sub 4}-tetrahedra interconnected with two BO{sub 3}-groups via common vertices, B{sub 2}O{sub 5}-pyroborate units, and isolated BO{sub 3}-groups. The structure shows a wave-like modulation along the b-axis. The crystal structure and properties of La{sub 4}B{sub 4}O{sub 11}F{sub 2} are discussed and compared to Gd{sub 4}B{sub 4}O{sub 11}F{sub 2}. - Graphical abstract: A new structure type of RE{sub 4}B{sub 4}O{sub 11}F{sub 2}: high-pressure synthesis and crystal structure of La{sub 4}B{sub 4}O{sub 11}F{sub 2}.

  7. Small, high-pressure liquid hydrogen turbopump

    NASA Technical Reports Server (NTRS)

    Csomor, A.; Sutton, R.

    1977-01-01

    A high pressure, liquid hydrogen turbopump was designed, fabricated, and tested to a maximum speed of 9739 rad/s and a maximum pump discharge pressure of 2861 N/sq. cm. The approaches used in the analysis and design of the turbopump are described, and fabrication methods are discussed. Data obtained from gas generator tests, turbine performance calibration, and turbopump testing are presented.

  8. High Pressure Solution Kinetics of Metal Complexes.

    ERIC Educational Resources Information Center

    Suvachittanont, Surapong

    1983-01-01

    Describes use of activation volumes derived from the effect of pressure reaction rates in aiding the understanding of reaction mechanism. Topics discussed include determination and interpretation of activation volumes, high pressure equipment/techniques, and application of activation volumes in mechanistic elucidation of several inorganic…

  9. High-pressure differential scanning microcalorimeter.

    PubMed

    Senin, A A; Dzhavadov, L N; Potekhin, S A

    2016-03-01

    A differential scanning microcalorimeter for studying thermotropic conformational transitions of biopolymers at high pressure has been designed. The calorimeter allows taking measurements of partial heat capacity of biopolymer solutions vs. temperature at pressures up to 3000 atm. The principles of operation of the device, methods of its calibration, as well as possible applications are discussed. PMID:27036806

  10. High Pressure Inactivation of HAV within Mussels

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The potential of hepatitis A virus (HAV) to be inactivated within Mediterranean mussels (Mytilus galloprovincialis) and blue mussels (Mytilus edulis) by high pressure processing was evaluated. HAV was bioaccumulated within mussels to approximately 6-log10 PFU by exposure of mussels to HAV-contamina...

  11. High-pressure lubricity at the meso- and nanoscale

    NASA Astrophysics Data System (ADS)

    Vanossi, A.; Benassi, A.; Varini, N.; Tosatti, E.

    2013-01-01

    The increase of sliding friction upon increasing load is a classic in the macroscopic world. Here we discuss the possibility that friction rise might sometimes turn into a drop when, at the mesoscale and nanoscale, a confined lubricant film separating crystalline sliders undergoes strong layering and solidification. Under pressure, transitions from N to N-1 layers may imply a change of lateral periodicity of the crystallized lubricant sufficient to alter the matching of crystal structures, influencing the ensuing friction jump. A pressure-induced friction drop may occur as the shear gradient maximum switches from the lubricant middle, marked by strong stick-slip with or without shear melting, to the crystalline slider-lubricant interface, characterized by smooth superlubric sliding. We present high-pressure sliding simulations to display examples of frictional drops, suggesting their possible relevance to the local behavior in boundary lubrication.

  12. High Pressure Transport Studies of NdIn3

    NASA Astrophysics Data System (ADS)

    Purcell, Kenneth; Graf, David; Ebihara, Takao

    2015-03-01

    NdIn3 is a cubic antiferromagnetic metal that orders with a Neel temperature of 5.9 K and belongs to a family of rare earth intermetallic compounds RIn3 that have a cubic AuCu3-type crystal structure. At 0.5 K and the magnetic field applied in 100 direction, NdIn3 exhibits metamagnetic transitions at 7.8 T and 8.9 T before entering a field induced paramagnetic state at 11.1 T. We report high pressure transport studies of single crystal NdIn3 and the effect that pressure has on the Neel temperature, critical field, and metamagnetic transitions observed in the magnetoresistance. Comparisons to the behavior of the pressure induced superconductor CeIn3 will be discussed.

  13. Advanced Diagnostics for High Pressure Spray Combustion.

    SciTech Connect

    Skeen, Scott A.; Manin, Julien Luc; Pickett, Lyle M.

    2014-06-01

    The development of accurate predictive engine simulations requires experimental data to both inform and validate the models, but very limited information is presently available about the chemical structure of high pressure spray flames under engine- relevant conditions. Probing such flames for chemical information using non- intrusive optical methods or intrusive sampling techniques, however, is challenging because of the physical and optical harshness of the environment. This work details two new diagnostics that have been developed and deployed to obtain quantitative species concentrations and soot volume fractions from a high-pressure combusting spray. A high-speed, high-pressure sampling system was developed to extract gaseous species (including soot precursor species) from within the flame for offline analysis by time-of-flight mass spectrometry. A high-speed multi-wavelength optical extinction diagnostic was also developed to quantify transient and quasi-steady soot processes. High-pressure sampling and offline characterization of gas-phase species formed following the pre-burn event was accomplished as well as characterization of gas-phase species present in the lift-off region of a high-pressure n-dodecane spray flame. For the initial samples discussed in this work several species were identified, including polycyclic aromatic hydrocarbons (PAH); however, quantitative mole fractions were not determined. Nevertheless, the diagnostic developed here does have this capability. Quantitative, time-resolved measurements of soot extinction were also accomplished and the novel use of multiple incident wavelengths proved valuable toward characterizing changes in soot optical properties within different regions of the spray flame.

  14. Recent Advances in High Pressure and Temperature Rheological Studies

    SciTech Connect

    Wang, Yanbin; Hilairet, Nadege; Dera, Przemyslaw

    2012-01-20

    Rheological studies at high pressure and temperature using in-situ X-ray diffraction and imaging have made significant progresses in recent years, thanks to a combination of recent developments in several areas: (1) advances in synchrotron X-ray techniques, (2) advances in deformation devices and the abilities to control pressure, temperature, stress, strain and strain rates, (3) theoretical and computational advances in stress determination based on powder and single crystal diffraction, (4) theoretical and computational advances in modeling of grain-level micromechanics based on elasto-plastic and visco-plastic self-consistent formulations. In this article, we briefly introduce the experimental techniques and theoretical background for in-situ high pressure, high temperature rheological studies, and then review recent studies of rheological properties of major mantle materials. Some currently encountered issues have prompted developments in single-crystal quasi-Laue diffraction for complete stress tensor determination and textural evolution of poly-phased composites based on X-ray microtomography. Future prospects are discussed.

  15. High pressure x-ray diffraction techniques with synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Jing, Liu

    2016-07-01

    This article summarizes the developments of experimental techniques for high pressure x-ray diffraction (XRD) in diamond anvil cells (DACs) using synchrotron radiation. Basic principles and experimental methods for various diffraction geometry are described, including powder diffraction, single crystal diffraction, radial diffraction, as well as coupling with laser heating system. Resolution in d-spacing of different diffraction modes is discussed. More recent progress, such as extended application of single crystal diffraction for measurements of multigrain and electron density distribution, time-resolved diffraction with dynamic DAC and development of modulated heating techniques are briefly introduced. The current status of the high pressure beamline at BSRF (Beijing Synchrotron Radiation Facility) and some results are also presented. Project supported by the National Natural Science Foundation of China (Grant Nos. 10875142, 11079040, and 11075175). The 4W2 beamline of BSRF was supported by the Chinese Academy of Sciences (Grant Nos. KJCX2-SW-N20, KJCX2-SW-N03, and SYGNS04).

  16. Methane and ethane at high pressures: structure and stability

    NASA Astrophysics Data System (ADS)

    Goncharov, A.; Stavrou, E.; Lobanov, S.; Oganov, A. R.; Chanyshev, A.; Litasov, K.; Konopkova, Z.; Prakapenka, V.

    2013-12-01

    Methane is one of the most abundant hydrocarbon molecules in the universe and is expected to be a significant part of the icy giant planets (Uranus and Neptune) and their satellites. Ethane is one of the most predictable products of chemical reactivity of methane at extreme pressures and temperatures. In spite of numerous experimental and theoretical studies, the structure and relative stability of these materials even at room temperature remains controversial. We have performed a combined experimental, using x-ray diffraction and Raman spectroscopy, and theoretical, using the ab-initio evolutionary algorithm, study of both methane and ethane up at high pressures up to 120 GPa at 300 K. In the case of methane we have successfully solved the structure of phase B by determining the space group and the positional parameters of carbon atoms, and by completing these results for the hydrogen positions using the theoretical calculations. The general structural behavior under pressure and the relation between phase B and phases A and pre-B will be also discussed. For ethane we have determined the crystallization point, for room temperature, at 1.7 GPa and also the low pressure crystal structure (Phase I). This crystal structure is orientationally disordered (plastic phase) and deviates from the known crystal structures for ethane at low temperatures. Moreover, a pressure induced phase transition has been indentified, for the first time, at 18 GPa to a monoclinic phase II, the structure of which is solved based on a good agreement of the experimental results and theoretical predictions. We have determined the equations of state of methane and ethane, which provides a solid basis for the discussion of their relative stability at high pressures.

  17. Development of Designer Diamond Technology for High Pressure High Temperature Experiments in Support of Stockpile Stewardship Program

    SciTech Connect

    Vohra, Yogesh, K.

    2009-10-28

    The role of nitrogen in the fabrication of designer diamond was systematically investigated by adding controlled amount of nitrogen in hydrogen/methane/oxygen plasma. This has led to a successful recipe for reproducible fabrication of designer diamond anvils for high-pressure high-temperature research in support of stockpile stewardship program. In the three-year support period, several designer diamonds fabricated with this new growth chemistry were utilized in high-pressure experiments at UAB and Lawrence Livermore National Laboratory. The designer diamond anvils were utilized in high-pressure studies on heavy rare earth metals, high pressure melting studies on metals, and electrical resistance measurements on iron-based layered superconductors under high pressures. The growth chemistry developed under NNSA support can be adapted for commercial production of designer diamonds.

  18. High-Pressure Neutron Diffraction Studies for Materials Sciences and Energy Sciences

    NASA Astrophysics Data System (ADS)

    Zhao, Y.; Los Alamos High Pressure Materials Research Team

    2013-05-01

    The development of neutron diffraction under extreme pressure (P) and temperature (T) conditions is highly valuable to condensed matter physics, crystal chemistry, materials sciences, as well as earth and planetary sciences. We have incorporated a 500-ton press TAP-98 into the HiPPO diffractometer at LANSCE to conduct in situ high P-T neutron diffraction experiments. We have worked out a large gem-crystal anvil cell, ZAP, to conduct neutron diffraction experiments at high-P and low-T. The ZAP cell can be used to integrate multiple experimental techniques such as neutron diffraction, laser spectroscopy, and ultrasonic interferometery. Recently, we have developed high-P low-T gas/fluid cells in conjunction with neutron diffraction and inelastic neutron scattering instruments. These techniques enable in-situ and real-time examination of gas uptake/release processes and allow high-resolution time-dependent determination of changes in crystal structure and related reaction kinetics. We have successfully used these techniques to study the equation of state, structural phase transition, and thermo-mechanical properties of metals, ceramics, and minerals. We have conducted researches on the formation of methane and hydrogen clathrates, and hydrogen adsorption of the inclusion compounds such as the recently discovered metal-organic frameworks (MOFs). The aim of our research is to accurately map phase diagram, lattice parameters, thermal parameters, bond lengths, bond angles, neighboring atomic environments, and phase stability in P-T-X space. We are currently developing further high P-T technology with a new "true" triaxial loading press, TAP_6x, to compress cubic sample package to achieve pressures up to 20 GPa and temperatures up to 2000 K in routine experiments. The implementation of TAP_6x300 with high-pressure neutron beamlines is underway for simultaneous high P-T neutron diffraction, ultrasonic, calorimetry, radiography, and tomography studies. Studies based on high-pressure

  19. Deformation twinning of a silver nanocrystal under high pressure. Supplementary materials

    SciTech Connect

    Huang, X. J.; Yang, W. G.; Harder, R.; Sun, Y.; Lu, M.; Chu, Y. S.; Robinson, I. K.; Mao, H. K.

    2015-10-20

    Within a high-pressure environment, crystal deformation is controlled by complex processes such as dislocation motion, twinning, and phase transitions, which change materials’ microscopic morphology and alter their properties. Likewise, understanding a crystal’s response to external stress provides a unique opportunity for rational tailoring of its functionalities. It is very challenging to track the strain evolution and physical deformation from a single nanoscale crystal under high-pressure stress. Here, we report an in situ three-dimensional mapping of morphology and strain evolutions in a single-crystal silver nanocube within a high-pressure environment using the Bragg Coherent Diffractive Imaging (CDI) method. We also observed a continuous lattice distortion, followed by a deformation twining process at a constant pressure. The ability to visualize stress-introduced deformation of nanocrystals with high spatial resolution and prominent strain sensitivity provides an important route for interpreting and engineering novel properties of nanomaterials.

  20. Deformation twinning of a silver nanocrystal under high pressure. Supplementary materials

    DOE PAGESBeta

    Huang, X. J.; Yang, W. G.; Harder, R.; Sun, Y.; Lu, M.; Chu, Y. S.; Robinson, I. K.; Mao, H. K.

    2015-10-20

    Within a high-pressure environment, crystal deformation is controlled by complex processes such as dislocation motion, twinning, and phase transitions, which change materials’ microscopic morphology and alter their properties. Likewise, understanding a crystal’s response to external stress provides a unique opportunity for rational tailoring of its functionalities. It is very challenging to track the strain evolution and physical deformation from a single nanoscale crystal under high-pressure stress. Here, we report an in situ three-dimensional mapping of morphology and strain evolutions in a single-crystal silver nanocube within a high-pressure environment using the Bragg Coherent Diffractive Imaging (CDI) method. We also observed amore » continuous lattice distortion, followed by a deformation twining process at a constant pressure. The ability to visualize stress-introduced deformation of nanocrystals with high spatial resolution and prominent strain sensitivity provides an important route for interpreting and engineering novel properties of nanomaterials.« less

  1. Magnetic and Superconducting Materials at High Pressures

    SciTech Connect

    Struzhkin, Viktor V.

    2015-03-24

    The work concentrates on few important tasks in enabling techniques for search of superconducting compressed hydrogen compounds and pure hydrogen, investigation of mechanisms of high-Tc superconductivity, and exploring new superconducting materials. Along that route we performed several challenging tasks, including discovery of new forms of polyhydrides of alkali metal Na at very high pressures. These experiments help us to establish the experimental environment that will provide important information on the high-pressure properties of hydrogen-rich compounds. Our recent progress in RIXS measurements opens a whole field of strongly correlated 3d materials. We have developed a systematic approach to measure major electronic parameters, like Hubbard energy U, and charge transfer energy Δ, as function of pressure. This technique will enable also RIXS studies of magnetic excitations in iridates and other 5d materials at the L edge, which attract a lot of interest recently. We have developed new magnetic sensing technique based on optically detected magnetic resonance from NV centers in diamond. The technique can be applied to study superconductivity in high-TC materials, to search for magnetic transitions in strongly correlated and itinerant magnetic materials under pressure. Summary of Project Activities; development of high-pressure experimentation platform for exploration of new potential superconductors, metal polyhydrides (including newly discovered alkali metal polyhydrides), and already known superconductors at the limit of static high-pressure techniques; investigation of special classes of superconducting compounds (high-Tc superconductors, new superconducting materials), that may provide new fundamental knowledge and may prove important for application as high-temperature/high-critical parameter superconductors; investigation of the pressure dependence of superconductivity and magnetic/phase transformations in 3d transition metal compounds, including

  2. Sample injector for high pressure liquid chromatography

    DOEpatents

    Paul, Phillip H.; Arnold, Don W.; Neyer, David W.

    2001-01-01

    Apparatus and method for driving a sample, having a well-defined volume, under pressure into a chromatography column. A conventional high pressure sampling valve is replaced by a sample injector composed of a pair of injector components connected in series to a common junction. The injector components are containers of porous dielectric material constructed so as to provide for electroosmotic flow of a sample into the junction. At an appropriate time, a pressure pulse from a high pressure source, that can be an electrokinetic pump, connected to the common junction, drives a portion of the sample, whose size is determined by the dead volume of the common junction, into the chromatographic column for subsequent separation and analysis. The apparatus can be fabricated on a substrate for microanalytical applications.

  3. Combustion of liquid sprays at high pressures

    NASA Technical Reports Server (NTRS)

    Shearer, A. J.; Faeth, G. M.

    1977-01-01

    The combustion of pressure atomized fuel sprays in high pressure stagnant air was studied. Measurements were made of flame and spray boundaries at pressures in the range 0.1-9 MPa for methanol and n-pentane. At the higher test pressure levels, critical phenomena are important. The experiments are compared with theoretical predictions based on a locally homogeneous two-phase flow model. The theory correctly predicted the trends of the data, but underestimates flame and spray boundaries by 30-50 percent, indicating that slip is still important for the present experiments (Sauter mean diameters of 30 microns at atmospheric pressure under cold flow conditions). Since the sprays are shorter at high pressures, slip effects are still important even though the density ratio of the phases approach one another as the droplets heat up. The model indicates the presence of a region where condensed water is present within the spray and provides a convenient means of treating supercritical phenomena.

  4. Design guide for high pressure oxygen systems

    NASA Technical Reports Server (NTRS)

    Bond, A. C.; Pohl, H. O.; Chaffee, N. H.; Guy, W. W.; Allton, C. S.; Johnston, R. L.; Castner, W. L.; Stradling, J. S.

    1983-01-01

    A repository for critical and important detailed design data and information, hitherto unpublished, along with significant data on oxygen reactivity phenomena with metallic and nonmetallic materials in moderate to very high pressure environments is documented. This data and information provide a ready and easy to use reference for the guidance of designers of propulsion, power, and life support systems for use in space flight. The document is also applicable to designs for industrial and civilian uses of high pressure oxygen systems. The information presented herein are derived from data and design practices involving oxygen usage at pressures ranging from about 20 psia to 8000 psia equal with thermal conditions ranging from room temperatures up to 500 F.

  5. Wound cleansing by high pressure irrigation.

    PubMed

    Rodeheaver, G T; Pettry, D; Thacker, J G; Edgerton, M T; Edlich, R F

    1975-09-01

    All traumatic wounds are contaminated to some degree by both soil and bacteria. Specific infection potentiating factors in soil impair the defenses of the tissue and invite infection. These factors are small in size and resist removal by low pressure irrigation. The efficiency of wound irrigation is markedly improved by delivering the irrigant to the wound under continuous high pressure. Irrigation of the wound with saline solution delivered at 15 pounds per square inch removed 84.8 per cent of the soil infection potentiating factors from the wound. The residual infection potentiating factors remaining in the wound did not significantly impair tissue defenses. On the basis of these experimental studies, clinical studies are now being initiated to test the therapeutic value of high pressure irrigation in traumatic wounds in humans.

  6. Material Strength at High Pressure LDRD Strategic Initiative Final Report

    SciTech Connect

    Lassila, D H; Bonner, B P; Bulatov, V V; Cazamias, J U; Chandler, E A; Farber, D L; Moriarty, J A; Zaug, J M

    2004-03-02

    Various aspects of the Laboratory's national security mission are now highly dependent on accurate computer code simulations of plastic flow (i.e., non-reversible deformation) of materials under conditions of high hydrostatic pressure. Strength models are typically dependent on pressure, temperature, and strain rate. Current strength models can not be extrapolated to high pressure because they are not based on the underlying mechanisms of plastic deformation. The critical need for predictive models of material strength, which describe flow stress in computer code simulations, has motivated LLNL's multiscale modeling efforts. Over the past three years, the ''Material Strength at High Pressure'' LDRD Strategic Initiative has established a framework for the development of predictive strength models for deformation of metals under conditions of high hydrostatic pressure. Deformation experiments have been developed to measure the effect of high pressure on the yield strength and work hardening behavior of high purity Mo and Ta single crystals. The over arching goal of the SI is to experimentally validate multiscale-modeling capabilities for deformation of metals under conditions of high pressure. The work performed and accomplished is a necessary next step in the development of predictive strength models. Our initial experimental results show that the influence of pressure is to dramatically increase the work hardening rate of Ta. Bridgman also observed this in experiments performed in the 1950's. Currently there is very little modern data on this phenomena, or theoretical understanding. The work started by this SI is a first step in a comprehensive understanding of plasticity under conditions of high pressure and we expect eventually to be able to incorporate the proper physics into dislocation dynamics (DD) simulations to capture the increase in work hardening that we observe experimentally. In the following sections we briefly describe the work that was performed in

  7. High pressure hydrogen time projection chamber

    SciTech Connect

    Goulianos, K.

    1983-01-01

    We describe a high pressure hydrogen gas time projection chamber which consists of two cylindrical drift regions each 45 cm in diameter and 75 cm long. Typically, at 15 atm of H/sub 2/ with 2 kV/cm drift field and 7 kV on the 35..mu.. sense wires, the drift velocity is about 0.5 cm/..mu..sec and the spatial resolution +-200..mu...

  8. High-pressure mechanical instability in rocks

    USGS Publications Warehouse

    Byerlee, J.D.; Brace, W.F.

    1969-01-01

    At a confining pressure of a few kilobars, deformation of many sedimentary rocks, altered mafic rocks, porous volcanic rocks, and sand is ductile, in that instabilities leading to audible elastic shocks are absent. At pressures of 7 to 10 kilobars, however, unstable faulting and stick-slip in certain of these rocks was observed. This high pressure-low temperature instability might be responsible for earthquakes in deeply buried sedimentary or volcanic sequences.

  9. Small, high pressure liquid hydrogen turbopump

    NASA Technical Reports Server (NTRS)

    Csomor, A.; Warren, D. J.

    1980-01-01

    A high pressure, low capacity, liquid hydrogen turbopump was designed, fabricated, and tested. The design configuration of the turbopump is summarized and the results of the analytical and test efforts are presented. Approaches used to pin point the cause of poor suction performance with the original design are described and performance data are included with an axial inlet design which results in excellent suction capability.

  10. Raman spectroscopy of triolein under high pressures

    NASA Astrophysics Data System (ADS)

    Tefelski, D. B.; Jastrzębski, C.; Wierzbicki, M.; Siegoczyński, R. M.; Rostocki, A. J.; Wieja, K.; Kościesza, R.

    2010-03-01

    This article presents results of the high pressure Raman spectroscopy of triolein. Triolein, a triacylglyceride (TAG) of oleic acid, is an unsaturated fat, present in natural oils such as olive oil. As a basic food component and an energy storage molecule, it has considerable importance for food and fuel industries. To generate pressure in the experiment, we used a high-pressure cylindrical chamber with sapphire windows, presented in (R.M. Siegoczyński, R. Kościesza, D.B. Tefelski, and A. Kos, Molecular collapse - modification of the liquid structure induced by pressure in oleic acid, High Press. Res. 29 (2009), pp. 61-66). Pressure up to 750 MPa was applied. A Raman spectrometer in "macro"-configuration was employed. Raman spectroscopy provides information on changes of vibrational modes related to structural changes of triolein under pressure. Interesting changes in the triglyceride C‒H stretching region at 2650-3100 cm-1 were observed under high-pressures. Changes were also observed in the ester carbonyl (C˭ O) stretching region 1700-1780 cm-1 and the C‒C stretching region at 1050-1150 cm-1. The overall luminescence of the sample decreased under pressure, making it possible to set longer spectrum acquisition time and obtain more details of the spectrum. The registered changes suggest that the high-pressure solid phase of triolein is organized as β-polymorphic, as was reported in (C. Akita, T. Kawaguchi, and F. Kaneko, Structural study on polymorphism of cis-unsaturated triacylglycerol: Triolein, J. Phys. Chem. B 110 (2006), pp. 4346-4353; E. Da Silva and D. Rousseau, Molecular order and thermodynamics of the solid-liquid transition in triglycerides via Raman spectroscopy, Phys. Chem. Chem. Phys. 10 (2008), pp. 4606-4613) (with temperature-induced phase transitions). The research has shown that Raman spectroscopy in TAGs under pressure reveals useful information about its structural changes.

  11. (High-pressure structural studies of promethium)

    SciTech Connect

    Haire, R.G.

    1988-11-15

    The primary object of the foreign travel was to carry out collaborative high-pressure structural studies at the European Institute for Transuranium Elements (EITU), Karlsruhe, Federal Republic of Germany. These studies reestablished previous collaborative investigations by ORNL and EITU that have been very productive scientifically during the past few years. The study during the present travel period was limited to a structural study of promethium metal under pressure.

  12. High-pressure mechanical instability in rocks.

    PubMed

    Byerlee, J D; Brace, W F

    1969-05-01

    At a confining pressure of a few kilobars, deformation of many sedimentary rocks, altered mafic rocks, porous volcanic rocks, and sand is ductile, in that instabilities leading to audible elastic shocks are absent. At pressures of 7 to 10 kilobars, however, unstable faulting and stick-slip in certain of these rocks was observed. This high pressure-low temperature instability might be responsible for earthquakes in deeply buried sedimentary or volcanic sequences.

  13. Soft chemistry synthesis and crystal structure of Mg{sub x}Cu{sub 3-x}V{sub 2}O{sub 6}(OH){sub 4}.2H{sub 2}O

    SciTech Connect

    Melghit, Khaled

    2009-04-02

    Mg{sub x}Cu{sub 3-x}V{sub 2}O{sub 6}(OH){sub 4}.2H{sub 2}O (x {approx} 1), with similar crystal structure as volborthite Cu{sub 3}V{sub 2}O{sub 7}(OH){sub 2}.2H{sub 2}O, was successfully prepared by a soft chemistry technique. The method consists of mixing magnesium nitrate and copper nitrate with a boiling solution of vanadium oxide (obtained by reacting V{sub 2}O{sub 5} with few mL of 30 vol.% H{sub 2}O{sub 2} followed by addition of distilled water). When ammonium hydroxide NH{sub 4}OH 10% was added (pH 7.8), a green yellowish precipitate was obtained. Using X-ray powder diffraction data, its crystal structure has been determined by Rietveld refinement. Compared to volborthite, the vanadium coordination changes from tetrahedral VO{sub 4} to trigonal bipyramidal VO{sub 5}, and magnesium replaces copper, preferably, in the less distorted octahedron. At 300 deg. C, the phase formed is similar to the high pressure (HP) monoclinic Cu{sub 3}V{sub 2}O{sub 8} phase. However at higher temperature, 600 deg. C, the phase obtained is different from known Cu{sub 3}V{sub 2}O{sub 8} phases.

  14. High pressure synthesis gas conversion. Final report

    SciTech Connect

    Not Available

    1993-05-01

    The purpose of this research project is to build and test a high pressure fermentation system for the production of ethanol from synthesis gas. The fermenters, pumps, controls, and analytical system were procured or fabricated and assembled in our laboratory. This system was then used to determine the effects of high pressure on growth and ethanol production by Clostridium ljungdahlii. The limits of cell concentration and mass transport relationships were found in CSTR and immobilized cell reactors (ICR). The minimum retention times and reactor volumes were found for ethanol production in these reactors. A maximum operating pressure of 150 psig has been shown to be possible for C. ljungdahlli with the medium of Phillips et al. This medium was developed for atmospheric pressure operation in the CSTR to yield maximum ethanol concentrations and thus is not best for operation at elevated pressures. It is recommended that a medium development study be performed for C. ljungdahlii at increased pressure. Cell concentration, gas conversion and product concentration profiles were presented for C. ljungdahlii as a function of gas flow rate, the variable which affects bacterium performance the most. This pressure was chosen as a representative pressure over the 0--150 psig operating pressure range for the bacterium. Increased pressure negatively affected ethanol productivity probably due to the fact that medium composition was designed for atmospheric pressure operation. Medium development at increased pressure is necessary for high pressure development of the system.

  15. Apparatus for testing high pressure injector elements

    NASA Technical Reports Server (NTRS)

    Myers, William Neill (Inventor); Scott, Ewell M. (Inventor); Forbes, John C. (Inventor); Shadoan, Michael D. (Inventor)

    1995-01-01

    An apparatus for testing and evaluating the spray pattern of high pressure fuel injector elements for use in supplying fuel to combustion engines is presented. Prior art fuel injector elements were normally tested by use of low pressure apparatuses which did not provide a purge to prevent mist from obscuring the injector element or to prevent frosting of the view windows; could utilize only one fluid during each test; and had their viewing ports positioned one hundred eighty (180 deg) apart, thus preventing optimum use of laser diagnostics. The high pressure fluid injector test apparatus includes an upper hub, an upper weldment or housing, a first clamp and stud/nut assembly for securing the upper hub to the upper weldment, a standoff assembly within the upper weldment, a pair of window housings having view glasses within the upper weldment, an injector block assembly and purge plate within the upper weldment for holding an injector element to be tested and evaluated, a lower weldment or housing, a second clamp and stud/nut assembly for securing the lower weldment to the upper hub, a third clamp and stud/nut assembly for securing the lower hub to the lower weldment, mechanisms for introducing fluid under high pressure for testing an injector element, and mechanisms for purging the apparatus to prevent frosting of view glasses within the window housings and to permit unobstructed viewing of the injector element.

  16. [The high pressure life of piezophiles].

    PubMed

    Oger, Philippe; Cario, Anaïs

    2014-01-01

    The deep biosphere is composed of very different biotopes located in the depth of the oceans, the ocean crust or the lithosphere. Although very different, deep biosphere biotopes share one common feature, high hydrostatic pressure. The deep biosphere is colonized by specific organisms, called piezophiles, that are able to grow under high hydrostatic pressure. Bacterial piezophiles are mainly psychrophiles belonging to five genera of γ-proteobacteria, Photobacterium, Shewanella, Colwellia, Psychromonas and Moritella, while piezophilic Archaea are mostly (hyper)thermophiles from the Thermococcales. None of these genera are specific for the deep biosphere. High pressure deeply impacts the activity of cells and cellular components, and reduces the activity of numerous key processes, eventually leading to cell death of piezosensitive organisms. Biochemical and genomic studies yield a fragmented view on the adaptive mechanisms in piezophiles. It is yet unclear whether piezophilic adaptation requires the modification of a few genes, or metabolic pathways, or a more profound reorganization of the genome, the fine tuning of gene expression to compensate the pressure-induced loss of activity of the proteins most affected by high pressure, or a stress-like physiological cell response. In contrast to what has been seen for thermophily or halophily, the adaptation to high pressure is diffuse in the genome and may concern only a small fraction of the genes. PMID:25474000

  17. Raman study of opal at high pressure

    NASA Astrophysics Data System (ADS)

    Farfan, G.; Wang, S.; Mao, W. L.

    2011-12-01

    More commonly known for their beauty and lore as gemstones, opals are also intriguing geological materials which may have potential for materials science applications. Opal lacks a definite crystalline structure, and is composed of an amorphous packing of hydrated silica (SiO2) spheroids, which provides us with a unique nano-scaled mineraloid with properties unlike those of other amorphous materials like glass. Opals from different localities were studied at high pressure using a diamond anvil cell to apply pressure and Raman spectroscopy to look at changes in bonding as pressure was increased. We first tested different samples from Virgin Valley, NV, Spencer, ID, Juniper Ridge, OR, and Australia, which contain varying amounts of water at ambient conditions, using Raman spectroscopy to determine if they were opal-CT (semicrystalline cristobalite-trydimite volcanic origin) or opal-A (amorphous sedimentary origin). We then used x-ray diffraction and Raman spectroscopy in a diamond anvil cell to see how their bonding and structure changed under compression and to determine what effect water content had on their high pressure behavior. Comparison of our results on opal to other high pressure studies of amorphous materials like glass has implications from a geological and materials science standpoint.

  18. Single Molecule Raman Spectroscopy Under High Pressure

    NASA Astrophysics Data System (ADS)

    Fu, Yuanxi; Dlott, Dana

    2014-06-01

    Pressure effects on surface-enhanced Raman scattering spectra of Rhdoamine 6G adsorbed on silver nanoparticle surfaces was studied using a confocal Raman microscope. Colloidal silver nanoparticles were treated with Rhodamine 6G (R6G) and its isotopically substituted partner, R6G-d4. Mixed isotopomers let us identify single-molecule spectra, since multiple-molecule spectra would show vibrational transitions from both species. The nanoparticles were embedded into a poly vinyl alcohol film, and loaded into a diamond anvil cell for the high-pressure Raman scattering measurement. Argon was the pressure medium. Ambient pressure Raman scattering spectra showed few single-molecule spectra. At moderately high pressure ( 1GPa), a surprising effect was observed. The number of sites with observable spectra decreased dramatically, and most of the spectra that could be observed were due to single molecules. The effects of high pressure suppressed the multiple-molecule Raman sites, leaving only the single-molecule sites to be observed.

  19. Apparatus for testing high pressure injector elements

    NASA Technical Reports Server (NTRS)

    Myers, William Neill (Inventor); Scott, Ewell M. (Inventor); Forbes, John C. (Inventor); Shadoan, Michael D. (Inventor)

    1993-01-01

    An apparatus for testing and evaluating the spray pattern of high pressure fuel injector elements for use in supplying fuel to combustion engines is presented. Prior art fuel injector elements were normally tested by use of low pressure apparatuses which did not provide a purge to prevent mist from obscuring the injector element or to prevent frosting of the view windows; could utilize only one fluid during each test; and had their viewing ports positioned one hundred eighty (180 deg) apart, thus preventing optimum use of laser diagnostics. The high pressure fluid injector test apparatus includes an upper hub, an upper weldment or housing, a first clamp and stud/nut assembly for securing the upper hub to the upper weldment, a standoff assembly within the upper weldment, a pair of window housings having view glasses within the upper weldment, an injector block assembly and purge plate within the upper weldment for holding an injector element to be tested and evaluated, a lower weldment or housing, a second clamp and stud/nut assembly for securing the lower weldment to the upper weldment, a lower hub, a third clamp and stud/nut assembly for securing the lower hub to the lower weldment, mechanisms for introducing fluid under high pressure for testing an injector element, and mechanisms for purging the apparatus to prevent frosting of view glasses within the window housings and to permit unobstructed viewing of the injector element.

  20. High pressure effects on allergen food proteins.

    PubMed

    Somkuti, Judit; Smeller, László

    2013-12-15

    There are several proteins, which can cause allergic reaction if they are inhaled or ingested. Our everyday food can also contain such proteins. Food allergy is an IgE-mediated immune disorder, a growing health problem of great public concern. High pressure is known to affect the structure of proteins; typically few hundred MPa pressure can lead to denaturation. That is why several trials have been performed to alter the structure of the allergen proteins by high pressure, in order to reduce its allergenicity. Studies have been performed both on simple protein solutions and on complex food systems. Here we review those allergens which have been investigated under or after high pressure treatment by methods capable of detecting changes in the secondary and tertiary structure of the proteins. We focus on those allergenic proteins, whose structural changes were investigated by spectroscopic methods under pressure in correlation with the observed allergenicity (IgE binding) changes. According to this criterion we selected the following allergen proteins: Mal d 1 and Mal d 3 (apple), Bos d 5 (milk), Dau c 1 (carrot), Gal d 2 (egg), Ara h 2 and Ara h 6 (peanut), and Gad m 1 (cod).

  1. Fracture strength of glass chips for high-pressure microfluidics

    NASA Astrophysics Data System (ADS)

    Andersson, Martin; Hjort, Klas; Klintberg, Lena

    2016-09-01

    High-pressure microfluidics exposes new areas in chemistry. In this paper, the reliability of transparent borosilicate glass chips is investigated. Two designs of circular cavities are used for fracture strength tests, either 1.6 mm wide with rounded corners to the fluid inlets, or 2.0 mm wide with sharp inlet corners. Two kinds of tests are done, either short-term, e.g. pressurization to fracture at room temperature, or long-term, with fracture at constant pressurization for up to one week, in the temperature region 11-125 °C. The speed of crack fronts is measured using a high-speed camera. Results show fracture stresses in the range of 129 and 254 MPa for short-term measurements. Long-term measurements conclude the presences of a temperature and stress dependent delayed fracture. For a reliability of one week at 11-38 °C, a pressure limit is found at the lower end of the short-term measurements, or 15% lower than the average. At 80 °C, this pressure limit is 45% lower. Crack speeds are measured to be 10-5 m s-1 during short-term fracture. These measurements are comparable with estimations based on slow crack growth and show that the growth affects the reliability of glass chips. This effect is strongly affected by high temperatures, thus lowers the operating window of high-pressure glass microfluidic devices.

  2. Proton delocalization under extreme conditions of high pressure and temperature

    SciTech Connect

    Goncharov, Alexander F.; Crowhurst, Jonathan

    2008-10-02

    Knowledge of the behaviour of light hydrogen-containing molecules under extreme conditions of high pressure and temperature is crucial to a comprehensive understanding of the fundamental physics and chemistry that is relevant under such conditions. It is also vital for interpreting the results of planetary observations, in particular those of the gas giants, and also for various materials science applications. On a fundamental level, increasing pressure causes the redistribution of the electronic density, which results in a modification of the interatomic potentials followed by a consequent qualitative change in the character of the associated bonding. Ultimately, at sufficiently high pressure, one may anticipate a transformation to a homogeneously bonded material possessing unusual physical properties (e.g. a quantum fluid). As temperature increases so does the concentration of ionised species leading ultimately to a plasma. Considerable improvements have recently been made in both the corresponding experimental and theoretical investigations. Here we review recent results for hydrogen and water that reveal unexpected routes of transformation to nonmolecular materials. We stress the importance of quantum effects, which remain significant even at high temperatures.

  3. Fracture strength of glass chips for high-pressure microfluidics

    NASA Astrophysics Data System (ADS)

    Andersson, Martin; Hjort, Klas; Klintberg, Lena

    2016-09-01

    High-pressure microfluidics exposes new areas in chemistry. In this paper, the reliability of transparent borosilicate glass chips is investigated. Two designs of circular cavities are used for fracture strength tests, either 1.6 mm wide with rounded corners to the fluid inlets, or 2.0 mm wide with sharp inlet corners. Two kinds of tests are done, either short-term, e.g. pressurization to fracture at room temperature, or long-term, with fracture at constant pressurization for up to one week, in the temperature region 11–125 °C. The speed of crack fronts is measured using a high-speed camera. Results show fracture stresses in the range of 129 and 254 MPa for short-term measurements. Long-term measurements conclude the presences of a temperature and stress dependent delayed fracture. For a reliability of one week at 11–38 °C, a pressure limit is found at the lower end of the short-term measurements, or 15% lower than the average. At 80 °C, this pressure limit is 45% lower. Crack speeds are measured to be 10‑5 m s‑1 during short-term fracture. These measurements are comparable with estimations based on slow crack growth and show that the growth affects the reliability of glass chips. This effect is strongly affected by high temperatures, thus lowers the operating window of high-pressure glass microfluidic devices.

  4. Equation of state of unreacted high explosives at high pressures

    SciTech Connect

    Yoo, C-S

    1998-08-14

    Isotherms of unreacted high explosives (HMX, RDX, and PETN) have been determined to quasi-hydrostatic high pressures below 45 GPa, by using a diamond-anvil cell angle-resolved synchrotron x-ray diffraction method. The equation-of-state parameters (bulk modulus Bo, and its derivatives B' ) are presented for the 3rd-order Birch-Murnaghan formula based on the measured isotherms. The results are also used to retrieve unreacted Hugoniots in these high explosives and to develop the equations of state and kinetic models for composite high explolsivcs such as XTX-8003 and LX-04. The evidence of shear-induced chemistry of HMX in non-hydrostatic conditions is also presented.

  5. Structural and Vibrational Properties of Nitrogen-Hydrogen Mixtures at High Pressure

    NASA Astrophysics Data System (ADS)

    Spaulding, Dylan; Weck, Gunnar; Loubeyre, Paul; Datchi, Frederic; Dumas, Paul; Hanfland, Michael

    2013-06-01

    The chemistry and equations of state of simple molecular systems (e.g. N2, H2, H2O, CO2, CH4 etc.) in the dense fluid state are of extreme importance to planetary astrophysics and are model systems for understanding the effects of pressure on chemical bonding, reactivity in the solid solution and potentially new routes to pressure-induced metallization. Here, we present the first comprehensive study of the binary N2/H2 system in the diamond anvil cell using Raman spectroscopy, synchrotron infrared micro-spectroscopy and visual observation. We find a eutectic-type binary phase diagram with two stable high-pressure compounds which we identify as (N2)6(H2)7 (R-3m) and N2(H2)2 (Pm-3m) using single-crystal x-ray diffraction. The former has a novel rhombohedral structure in which groups of hydrogen molecules are contained by the nitrogen lattice. We discuss further infrared absorption studies on this compound, including evidence for a gradual transformation from van der Waals to ionic interactions with pressure. A phase transition to an ionic compound with the same stoichiometry is observed at 55 GPa. Compression of this compound was carried out up to 200 GPa to investigate possible metallization.

  6. 7 CFR 58.219 - High pressure pumps and lines.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 3 2013-01-01 2013-01-01 false High pressure pumps and lines. 58.219 Section 58.219....219 High pressure pumps and lines. High pressure lines may be cleaned-in-place and shall be of such construction that dead ends, valves and the high pressure pumps can be disassembled for hand cleaning. The...

  7. 7 CFR 58.219 - High pressure pumps and lines.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 3 2011-01-01 2011-01-01 false High pressure pumps and lines. 58.219 Section 58.219....219 High pressure pumps and lines. High pressure lines may be cleaned-in-place and shall be of such construction that dead ends, valves and the high pressure pumps can be disassembled for hand cleaning. The...

  8. 7 CFR 58.219 - High pressure pumps and lines.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 3 2012-01-01 2012-01-01 false High pressure pumps and lines. 58.219 Section 58.219....219 High pressure pumps and lines. High pressure lines may be cleaned-in-place and shall be of such construction that dead ends, valves and the high pressure pumps can be disassembled for hand cleaning. The...

  9. 7 CFR 58.219 - High pressure pumps and lines.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 3 2014-01-01 2014-01-01 false High pressure pumps and lines. 58.219 Section 58.219....219 High pressure pumps and lines. High pressure lines may be cleaned-in-place and shall be of such construction that dead ends, valves and the high pressure pumps can be disassembled for hand cleaning. The...

  10. Dissolution rates and surface chemistry of feldspar glass and crystal. Final technical report, June 15, 1995 - August 14, 2001

    SciTech Connect

    Brantley, S.; Pantano, C.

    2002-06-11

    Final report summarizing the completed work of the project entitled 'Dissolution of Feldspar in the Field and Laboratory.' One of the highly debated questions today in low-temperature geochemical kinetics centers upon the rate and mechanism of dissolution of feldspar, the most common mineral in the crust. In this project, the mechanisms of feldspar dissolution were investigated by emphasizing experiments with feldspar glass and crystal while comparing surface and solution chemistry. Specifically, laboratory work focused on the structure of altered surface layers on feldspars, the rate of dissolution of feldspar crystal and glass, and the presence of porosity and surface coatings on feldspars. In a complementary field project, the use of Sr concentrations and isotopic ratios were used to calculate feldspar dissolution rates.

  11. Structural investigation of ribonuclease A conformational preferences using high pressure protein crystallography

    NASA Astrophysics Data System (ADS)

    Kurpiewska, Katarzyna; Dziubek, Kamil; Katrusiak, Andrzej; Font, Josep; Ribò, Marc; Vilanova, Maria; Lewiński, Krzysztof

    2016-04-01

    Hydrostatic pressure in range 0.1-1.5 GPa is used to modify biological system behaviour mostly in biophysical studies of proteins in solution. Due to specific influence on the system equilibrium high pressure can act as a filter that enables to identify and investigate higher energy protein conformers. The idea of the presented experiments is to examine the behaviour of RNase A molecule under high pressure before and after introduction of destabilizing mutation. For the first time crystal structures of wild-type bovine pancreatic ribonuclease A and its markedly less stable variant modified at position Ile106 were determined at different pressures. X-ray diffraction experiments at high pressure showed that the secondary structure of RNase A is well preserved even beyond 0.67 GPa at room temperature. Detailed structural analysis of ribonuclease A conformation observed under high pressure revealed that pressure influences hydrogen bonds pattern, cavity size and packing of molecule.

  12. High pressure structural phase transitions of TiO2 nanomaterials

    NASA Astrophysics Data System (ADS)

    Quan-Jun, Li; Bing-Bing, Liu

    2016-07-01

    Recently, the high pressure study on the TiO2 nanomaterials has attracted considerable attention due to the typical crystal structure and the fascinating properties of TiO2 with nanoscale sizes. In this paper, we briefly review the recent progress in the high pressure phase transitions of TiO2 nanomaterials. We discuss the size effects and morphology effects on the high pressure phase transitions of TiO2 nanomaterials with different particle sizes, morphologies, and microstructures. Several typical pressure-induced structural phase transitions in TiO2 nanomaterials are presented, including size-dependent phase transition selectivity in nanoparticles, morphology-tuned phase transition in nanowires, nanosheets, and nanoporous materials, and pressure-induced amorphization (PIA) and polyamorphism in ultrafine nanoparticles and TiO2-B nanoribbons. Various TiO2 nanostructural materials with high pressure structures are prepared successfully by high pressure treatment of the corresponding crystal nanomaterials, such as amorphous TiO2 nanoribbons, α-PbO2-type TiO2 nanowires, nanosheets, and nanoporous materials. These studies suggest that the high pressure phase transitions of TiO2 nanomaterials depend on the nanosize, morphology, interface energy, and microstructure. The diversity of high pressure behaviors of TiO2 nanomaterials provides a new insight into the properties of nanomaterials, and paves a way for preparing new nanomaterials with novel high pressure structures and properties for various applications. Project supported by the National Basic Research Program of China (Grant No. 2011CB808200), the National Natural Science Foundation of China (Grant Nos. 11374120, 11004075, 10979001, 51025206, 51032001, and 21073071), and the Cheung Kong Scholars Programme of China.

  13. High pressure liquid chromatographic gradient mixer

    DOEpatents

    Daughton, Christian G.; Sakaji, Richard H.

    1985-01-01

    A gradient mixer which effects the continuous mixing of any two miscible solvents without excessive decay or dispersion of the resultant isocratic effluent or of a linear or exponential gradient. The two solvents are fed under low or high pressure by means of two high performance liquid chromatographic pumps. The mixer comprises a series of ultra-low dead volume stainless steel tubes and low dead volume chambers. The two solvent streams impinge head-on at high fluxes. This initial nonhomogeneous mixture is then passed through a chamber packed with spirally-wound wires which cause turbulent mixing thereby homogenizing the mixture with minimum "band-broadening".

  14. HIGH PRESSURE COAL COMBUSTON KINETICS PROJECT

    SciTech Connect

    Stefano Orsino

    2005-03-30

    As part of the U.S. Department of Energy (DoE) initiative to improve the efficiency of coal-fired power plants and reduce the pollution generated by these facilities, DOE has funded the High-Pressure Coal Combustion Kinetics (HPCCK) Projects. A series of laboratory experiments were conducted on selected pulverized coals at elevated pressures with the specific goals to provide new data for pressurized coal combustion that will help extend to high pressure and validate models for burnout, pollutant formation, and generate samples of solid combustion products for analyses to fill crucial gaps in knowledge of char morphology and fly ash formation. Two series of high-pressure coal combustion experiments were performed using SRI's pressurized radiant coal flow reactor. The first series of tests characterized the near burner flame zone (NBFZ). Three coals were tested, two high volatile bituminous (Pittsburgh No.8 and Illinois No.6), and one sub-bituminous (Powder River Basin), at pressures of 1, 2, and 3 MPa (10, 20, and 30 atm). The second series of experiments, which covered high-pressure burnout (HPBO) conditions, utilized a range of substantially longer combustion residence times to produce char burnout levels from 50% to 100%. The same three coals were tested at 1, 2, and 3 MPa, as well as at 0.2 MPa. Tests were also conducted on Pittsburgh No.8 coal in CO2 entrainment gas at 0.2, 1, and 2 MPa to begin establishing a database of experiments relevant to carbon sequestration techniques. The HPBO test series included use of an impactor-type particle sampler to measure the particle size distribution of fly ash produced under complete burnout conditions. The collected data have been interpreted with the help of CFD and detailed kinetics simulation to extend and validate devolatilization, char combustion and pollutant model at elevated pressure. A global NOX production sub-model has been proposed. The submodel reproduces the performance of the detailed chemical reaction

  15. High pressure luminescence probes in polymers

    SciTech Connect

    Drickamer, H.G.

    1980-01-01

    High pressure luminescence has proved to be a very powerful tool for characterizing crystalline solids and liquids. Two problems involving glassy polymers are analyzed. In the first problem the excited states of azulene and its derivatives are used to probe intermolecular interactions in PMMA and PS. In the second problem the change in emission intensity with pressure from two excimer states of polyvinylcarbazole as a pure polymer and in dilute solution in polystyrene (PS), polymethylmethacrylate (PMMA) and polyisoliutylene (PIB) is studied. The relative emission from the two states depends strongly on the possibility for motion of polymer segments. The observations are related to the proximity to the glass transition.

  16. High-pressure liquid chromatographic gradient mixer

    DOEpatents

    Daughton, C.G.; Sakaji, R.H.

    1982-09-08

    A gradient mixer effects the continuous mixing of any two miscible solvents without excessive decay or dispersion of the resultant isocratic effluent or of a linear or exponential gradient. The two solvents are fed under low or high pressure by means of two high performance liquid chromatographic pumps. The mixer comprises a series of ultra-low dead volume stainless steel tubes and low dead volume chambers. The two solvent streams impinge head-on at high fluxes. This initial nonhomogeneous mixture is then passed through a chamber packed with spirally-wound wires which cause turbulent mixing thereby homogenizing the mixture with minimum band-broadening.

  17. Very high-pressure orogenic garnet peridotites

    PubMed Central

    Liou, J. G.; Zhang, R. Y.; Ernst, W. G.

    2007-01-01

    Mantle-derived garnet peridotites are a minor component in many very high-pressure metamorphic terranes that formed during continental subduction and collision. Some of these mantle rocks contain trace amounts of zircon and micrometer-sized inclusions. The constituent minerals exhibit pre- and postsubduction microstructures, including polymorphic transformation and mineral exsolution. Experimental, mineralogical, petrochemical, and geochronological characterizations using novel techniques with high spatial, temporal, and energy resolutions are resulting in unexpected discoveries of new phases, providing better constraints on deep mantle processes. PMID:17519341

  18. High-pressure layered structure of carbon disulfide

    NASA Astrophysics Data System (ADS)

    Naghavi, S. Shahab; Crespo, Yanier; MartoÅák, Roman; Tosatti, Erio

    2015-06-01

    Solid CS2 is superficially similar to CO2, with the same C m c a molecular crystal structure at low pressures, which has suggested similar phases also at high pressures. We carried out an extensive first-principles evolutionary search in order to identify the zero-temperature lowest-enthalpy structures of CS2 for increasing pressure up to 200 GPa. Surprisingly, the molecular C m c a phase does not evolve into β -cristobalite as in CO2 but transforms instead into phases HP2 and HP1, both recently described in high-pressure SiS2. HP1 in particular, with a wide stability range, is a layered P 21/c structure characterized by pairs of edge-sharing tetrahedra and is theoretically more robust than all other CS2 phases discussed so far. Its predicted Raman spectrum and pair correlation function agree with experiment better than those of β -cristobalite, and further differences are predicted between their respective IR spectra. The band gap of HP1-CS2 is calculated to close under pressure, yielding an insulator-metal transition near 50 GPa, in agreement with experimental observations. However, the metallic density of states remains modest above this pressure, suggesting a different origin for the reported superconductivity.

  19. Nonmetallization and band inversion in beryllium dicarbide at high pressure

    NASA Astrophysics Data System (ADS)

    Du, Henan; Feng, Wanxiang; Li, Fei; Wang, Dashuai; Zhou, Dan; Liu, Yanhui

    2016-05-01

    Carbides have attracted much attention owing to their interesting physical and chemical properties. Here, we systematically investigated global energetically stable structures of BeC2 in the pressure range of 0–100 GPa using a first-principles structural search. A transition from the ambient-pressure α-phase to the high-pressure β-phase was theoretically predicted. Chemical bonding analysis revealed that the predicted phase transition is associated with the transformation from sp2 to sp3 C-C hybridization. The electrical conductivity of the high-pressure phase changed from a metal (α-phase) to a narrow bandgap semiconductor (β-phase), and the β-phase had an inverted band structure with positive pressure dependence. Interestingly, the β-phase was a topological insulator with the metallic surface states protected by the time-reversal symmetry of the crystal. The results indicate that pressure modulates the electronic band structure of BeC2, which is an important finding for fundamental physics and for a wide range of potential applications in electronic devices.

  20. Vanadium and V-Ti alloys at high pressure

    NASA Astrophysics Data System (ADS)

    Jenei, Zsolt; Cynn, Hyunchae; Evans, William J.; MacLeod, Simon; Sinogeikin, Stanislav; Meng, Yue

    2013-03-01

    Experimental studies of vanadium found that during compression it undergoes a phase transition from the low pressure body centered cubic crystal structure to a rhombohedral phase at 65 GPa when compressed under quasihydrostatic conditions (PRB 83, 054101). Theoretical studies are in reasonable agreement with the transition pressure and predict that upon further compression above 200 GPa the bcc phase becomes stable again. The latest study (PRL 103, 235501) predicts that alloying vanadium with small amounts of the neighboring elements can increase or decrease the stability of the bcc phase relative to the rhombohedral phase. We performed powder x-ray diffraction experiments in diamond anvil cell of pure vanadium and V-Ti alloys at ambient temperature to very high pressures. We will discuss our results, including the equation of state and the stability of the rhombohedral phase at high pressures. This work performed under the auspices of the US DOE by LLNL under Contract DE-AC52-07NA27344. HPCAT use is supported by DOE-BES, DOE-NNSA, NSF, and the W.M. Keck Foundation. APS is supported by DOE-BES, under Contract No. DE-AC02-06CH11357.

  1. Enhancement of Superconductivity of Beryllium at High Pressure

    NASA Astrophysics Data System (ADS)

    Shimizu, Katsuya; Kubota, Kazuhisa; Katsuoka, Takahiro; Miyake, Atsushi; Sakata, Masafumi; Nakamoto, Yuki; Ohishi, Yasuo

    2013-06-01

    Among elements shows superconductivity at high pressure, some elements show the large enhancement of the transition temperature (Tc) at higher pressures. In the case of lithium, the Tc at ambient pressure is 0.4 mK which is the lowest observed value in whole elements, however, is enhanced by pressure up to near 20 K. And calcium, which is on the same group II and not superconductive at ambient pressure, shows the highest Tc of elements at 29 K under pressure. Then we focused on beryllium which is near to them on the periodic table. At ambient pressure, Tc of beryllium is 24 mK. We measured the electrical resistance at high pressure (P < 50 GPa) and low temperature (T > 100 mK) and found that the Tc rose up to few Kelvin at pressure above 20 GPa and reached up to 3.7 K at 30 GPa. In this pressure range the hcp crystal structure is stable at room temperature. We performed a powder X-ray diffraction measurement at room temperature and low temperature in BL10XU at SPring-8 and found a discontinuous change in c/a ratio at around 25 GPa.

  2. Nonmetallization and band inversion in beryllium dicarbide at high pressure

    PubMed Central

    Du, Henan; Feng, Wanxiang; Li, Fei; Wang, Dashuai; Zhou, Dan; Liu, Yanhui

    2016-01-01

    Carbides have attracted much attention owing to their interesting physical and chemical properties. Here, we systematically investigated global energetically stable structures of BeC2 in the pressure range of 0–100 GPa using a first-principles structural search. A transition from the ambient-pressure α-phase to the high-pressure β-phase was theoretically predicted. Chemical bonding analysis revealed that the predicted phase transition is associated with the transformation from sp2 to sp3 C-C hybridization. The electrical conductivity of the high-pressure phase changed from a metal (α-phase) to a narrow bandgap semiconductor (β-phase), and the β-phase had an inverted band structure with positive pressure dependence. Interestingly, the β-phase was a topological insulator with the metallic surface states protected by the time-reversal symmetry of the crystal. The results indicate that pressure modulates the electronic band structure of BeC2, which is an important finding for fundamental physics and for a wide range of potential applications in electronic devices. PMID:27198492

  3. Nonmetallization and band inversion in beryllium dicarbide at high pressure.

    PubMed

    Du, Henan; Feng, Wanxiang; Li, Fei; Wang, Dashuai; Zhou, Dan; Liu, Yanhui

    2016-01-01

    Carbides have attracted much attention owing to their interesting physical and chemical properties. Here, we systematically investigated global energetically stable structures of BeC2 in the pressure range of 0-100 GPa using a first-principles structural search. A transition from the ambient-pressure α-phase to the high-pressure β-phase was theoretically predicted. Chemical bonding analysis revealed that the predicted phase transition is associated with the transformation from sp(2) to sp(3) C-C hybridization. The electrical conductivity of the high-pressure phase changed from a metal (α-phase) to a narrow bandgap semiconductor (β-phase), and the β-phase had an inverted band structure with positive pressure dependence. Interestingly, the β-phase was a topological insulator with the metallic surface states protected by the time-reversal symmetry of the crystal. The results indicate that pressure modulates the electronic band structure of BeC2, which is an important finding for fundamental physics and for a wide range of potential applications in electronic devices. PMID:27198492

  4. High-pressure electrides: the chemical nature of interstitial quasiatoms.

    PubMed

    Miao, Mao-sheng; Hoffmann, Roald

    2015-03-18

    Building on our previous chemical and physical model of high-pressure electrides (HPEs), we explore the effects of interaction of electrons confined in crystals but off the atoms, under conditions of extreme pressure. Electrons in the quantized energy levels of voids or vacancies, interstitial quasiatoms (ISQs), effectively interact with each or with other atoms, in ways that are quite chemical. With the well-characterized Na HPE as an example, we explore the ionic limit, ISQs behaving as anions. A detailed comparison with known ionic compounds points to high ISQ charge density. ISQs may also form what appear to be covalent bonds with neighboring ISQs or real atoms, similarly confined. Our study looks specifically at quasimolecular model systems (two ISQs, a Li atom and a one-electron ISQ, a Mg atom and two ISQs), in a compression chamber made of He atoms. The electronic density due to the formation of bonding and antibonding molecular orbitals of the compressed entities is recognizable, and a bonding stabilization, which increases with pressure, is estimated. Finally, we use the computed Mg electride to understand metallic bonding in one class of electrides. In general, the space confined between atoms in a high pressure environment offers up quantized states to electrons. These ISQs, even as they lack centering nuclei, in their interactions with each other and neighboring atoms may show anionic, covalent, or metallic bonding, all the chemical features of an atom.

  5. Stable Calcium Nitrides at Ambient and High Pressures.

    PubMed

    Zhu, Shuangshuang; Peng, Feng; Liu, Hanyu; Majumdar, Arnab; Gao, Tao; Yao, Yansun

    2016-08-01

    The knowledge of stoichiometries of alkaline-earth metal nitrides, where nitrogen can exist in polynitrogen forms, is of significant interest for understanding nitrogen bonding and its applications in energy storage. For calcium nitrides, there were three known crystalline forms, CaN2, Ca2N, and Ca3N2, at ambient conditions. In the present study, we demonstrated that there are more stable forms of calcium nitrides than what is already known to exist at ambient and high pressures. Using a global structure searching method, we theoretically explored the phase diagram of CaNx and discovered a series of new compounds in this family. In particular, we found a new CaN phase that is thermodynamically stable at ambient conditions, which may be synthesized using CaN2 and Ca2N. Four other stoichiometries, namely, Ca2N3, CaN3, CaN4, and CaN5, were shown to be stable under high pressure. The predicted CaNx compounds contain a rich variety of polynitrogen forms ranging from small molecules (N2, N4, N5, and N6) to extended chains (N∞). Because of the large energy difference between the single and triple nitrogen bonds, dissociation of the CaNx crystals with polynitrogens is expected to be highly exothermic, making them as potential high-energy-density materials. PMID:27428707

  6. Ionic high-pressure form of elemental boron.

    PubMed

    Oganov, Artem R; Chen, Jiuhua; Gatti, Carlo; Ma, Yanzhang; Ma, Yanming; Glass, Colin W; Liu, Zhenxian; Yu, Tony; Kurakevych, Oleksandr O; Solozhenko, Vladimir L

    2009-02-12

    Boron is an element of fascinating chemical complexity. Controversies have shrouded this element since its discovery was announced in 1808: the new 'element' turned out to be a compound containing less than 60-70% of boron, and it was not until 1909 that 99% pure boron was obtained. And although we now know of at least 16 polymorphs, the stable phase of boron is not yet experimentally established even at ambient conditions. Boron's complexities arise from frustration: situated between metals and insulators in the periodic table, boron has only three valence electrons, which would favour metallicity, but they are sufficiently localized that insulating states emerge. However, this subtle balance between metallic and insulating states is easily shifted by pressure, temperature and impurities. Here we report the results of high-pressure experiments and ab initio evolutionary crystal structure predictions that explore the structural stability of boron under pressure and, strikingly, reveal a partially ionic high-pressure boron phase. This new phase is stable between 19 and 89 GPa, can be quenched to ambient conditions, and has a hitherto unknown structure (space group Pnnm, 28 atoms in the unit cell) consisting of icosahedral B(12) clusters and B(2) pairs in a NaCl-type arrangement. We find that the ionicity of the phase affects its electronic bandgap, infrared adsorption and dielectric constants, and that it arises from the different electronic properties of the B(2) pairs and B(12) clusters and the resultant charge transfer between them.

  7. Toward a Role of Light Absorption in Initiation Chemistry of Shocked HMX single Crystals and Crystalline High Explosives

    NASA Astrophysics Data System (ADS)

    Plaksin, Igor; Rodrigues, L.

    2013-06-01

    Question which mechanism is driving radiation-induced reactions, thermal or athermal becomes a subject of conflicting discussions. Major challenge of this work is to identify at micro- (sub-granular), meso- (grain level) and macro-scale roles of these two mechanisms in triggering initiation chemistry in HMX-based HEs. Four acceptor-patterns were tested at 20 GPa input pressure: single HMX crystal-in-water, HMX/water-slurry, PBX(HMX/HTPB) & inert PBX-simulant (HMX-particles replaced by crystalline sucrose). Scenario of reaction onset-localizations-dissipation was spatially resolved using Multi-Channel Optical Analyzer MCOA-UC (96 channels, 100um-spatial accuracy, 0.2ns-timeresolution, 450-850 nm-spectral range) through real-time panoramic recording emitted reaction light and shock field in standard optic monitor. Experiments reveal a dual nature of initiation chemistry: athermal and thermal. Single-crystal tests disclose origination of photo-induced reactions downstream of emitting reaction spot due to intensified radiation absorption in surface micro-defects. Polycrystalline samples reveal cyclic reproducibility of radiation-induced thermal precursors in which radiation absorption causes thermal expansion/phase-changes of HMX-grains resulting in oscillating detonation. Work was supported by the Office of Naval Research under the ONR and ONR Global Grants N00014-12-1-0477 and N62909-12-1-7131 with Drs. Cliff Bedford and Shawn Thorne Program Managers.

  8. Elasticity of Pyrope at High Pressures and Temperatures by Brillouin Scattering and X-ray Diffraction

    NASA Astrophysics Data System (ADS)

    Lu, C.; Mao, Z.; Lin, J.; Prakapenka, V.

    2011-12-01

    Iron-containing pyrope ((Fe,Mg)3Al2Si3O12)) is believed to be an abundant rock-forming mineral in the Earth's interior, ranging from the crust to the top of the lower mantle. Based on the pyrolite mineralogical model, pyrope accounts for 13% by volume in the upper mantle and 10% in the transition zone. Therefore, laboratory measurements on the elasticity of pyrope at relevant pressure and temperature conditions are critical in understanding the seismic images and in constraining the chemistry and mineralogy of the region. The elasticity of single-crystal pyrope has been studied up to 20 GPa at 300 K and up to 1100 K at 1 bar, yet it has never been investigated at simultaneous high pressure-temperature conditions. Thus, much of our knowledge of the upper mantle and transition zone seismic profiles largely relies on extrapolated experimental results or theoretical calculations. Here we have measured the single-crystal elasticity of garnet, ((Mg2.04Ca0.16Fe0.74)Al2.02(SiO4)3) up to 20 GPa and 750 K using combined Brillouin scattering and synchrontron X-ray diffraction in an externally-heated diamond anvil cell at GSECARS of the Advanced Photon Source, Argonne National Laboratory. We have derived full elastic constants (Cij) of the sample as a function of pressure and temperature at relevant conditions of the deep mantle. The temperature derivatives of the Cijs are similar to that at ambient pressure, indicating a minimal pressure effect. Together with the elasticity of other major mantle minerals, we have used a thermoelastic model to reconstruct the seismic velocity profile of the upper mantle and the transition zone and to reference the mineralogy of the regions.

  9. Unusual electronic and mechanical properties of sodium chlorides at high pressures

    NASA Astrophysics Data System (ADS)

    Bu, Hongxia; Zhao, Mingwen; Zhou, Hongcai; Du, Yanling

    2016-04-01

    Using first-principles calculations, we performed systematic investigation on the electronic and mechanical properties of sodium chlorides with different stoichiometries at high pressures. It was found that most of the phases are metallic except the Pnma-NaCl3 with a gap of 2.155 eV. The extended Cl (or Na) sublattice at Cl-rich (or Na-rich) conditions contributes to the metallization. Accompanied by metallization, the NamCln crystals exhibit good ductility in contrast to the brittle NaCl crystal, due to the changes of binding features induced by high pressure. These results are expected to be useful for understanding the exotic properties of NaCl at high pressures.

  10. Electronic Structure of Crystalline 4He at High Pressures

    SciTech Connect

    Mao, Ho Kwang; Shirley, Eric L.; Ding, Yang; Eng, Peter; Cai, Yong Q.; Chow, Paul; Xiao, Yuming; Jinfu Shu, A=Kao, Chi-Chang; Hemley, Russell J.; Kao, Chichang; Mao, Wendy L.; /Stanford U., Geo. Environ. Sci. /SLAC

    2011-01-10

    Using inelastic X-ray scattering techniques, we have succeeded in probing the high-pressure electronic structure of helium crystal at 300 K which has the widest known electronic energy bandgap of all materials, that was previously inaccessible to measurements due to the extreme energy and pressure range. We observed rich electron excitation spectrum, including a cut-off edge above 23 eV, a sharp exciton peak showing linear volume dependence, and a series of excitations and continuum at 26 to 45 eV. We determined electronic dispersion along the {Gamma}-M direction over two Brillouin zones, and provided a quantitative picture of the helium exciton beyond the simplified Wannier-Frenkel description.

  11. High-pressure Raman spectroscopy of phase change materials

    SciTech Connect

    Hsieh, Wen-Pin Mao, Wendy L.; Zalden, Peter; Wuttig, Matthias; Lindenberg, Aaron M.

    2013-11-04

    We used high-pressure Raman spectroscopy to study the evolution of vibrational frequencies of the phase change materials (PCMs) Ge{sub 2}Sb{sub 2}Te{sub 5}, GeSb{sub 2}Te{sub 4}, and SnSb{sub 2}Te{sub 4}. We found that the critical pressure for triggering amorphization in the PCMs decreases with increasing vacancy concentration, demonstrating that the presence of vacancies, rather than differences in the atomic covalent radii, is crucial for pressure-induced amorphization in PCMs. Compared to the as-deposited amorphous phase, the pressure-induced amorphous phase has a similar vibrational spectrum but requires much lower laser power to transform into the crystalline phase, suggesting different kinetics of crystallization, which may have implications for applications of PCMs in non-volatile data storage.

  12. Phonon triggered rhombohedral lattice distortion in vanadium at high pressure.

    PubMed

    Antonangeli, Daniele; Farber, Daniel L; Bosak, Alexei; Aracne, Chantel M; Ruddle, David G; Krisch, Michael

    2016-01-01

    In spite of the simple body-centered-cubic crystal structure, the elements of group V, vanadium, niobium and tantalum, show strong interactions between the electronic properties and lattice dynamics. Further, these interactions can be tuned by external parameters, such as pressure and temperature. We used inelastic x-ray scattering to probe the phonon dispersion of single-crystalline vanadium as a function of pressure to 45 GPa. Our measurements show an anomalous high-pressure behavior of the transverse acoustic mode along the (100) direction and a softening of the elastic modulus C44 that triggers a rhombohedral lattice distortion occurring between 34 and 39 GPa. Our results provide the missing experimental confirmation of the theoretically predicted shear instability arising from the progressive intra-band nesting of the Fermi surface with increasing pressure, a scenario common to all transition metals of group V. PMID:27539662

  13. Phonon triggered rhombohedral lattice distortion in vanadium at high pressure

    NASA Astrophysics Data System (ADS)

    Antonangeli, Daniele; Farber, Daniel L.; Bosak, Alexei; Aracne, Chantel M.; Ruddle, David G.; Krisch, Michael

    2016-08-01

    In spite of the simple body-centered-cubic crystal structure, the elements of group V, vanadium, niobium and tantalum, show strong interactions between the electronic properties and lattice dynamics. Further, these interactions can be tuned by external parameters, such as pressure and temperature. We used inelastic x-ray scattering to probe the phonon dispersion of single-crystalline vanadium as a function of pressure to 45 GPa. Our measurements show an anomalous high-pressure behavior of the transverse acoustic mode along the (100) direction and a softening of the elastic modulus C44 that triggers a rhombohedral lattice distortion occurring between 34 and 39 GPa. Our results provide the missing experimental confirmation of the theoretically predicted shear instability arising from the progressive intra-band nesting of the Fermi surface with increasing pressure, a scenario common to all transition metals of group V.

  14. Phonon triggered rhombohedral lattice distortion in vanadium at high pressure

    PubMed Central

    Antonangeli, Daniele; Farber, Daniel L.; Bosak, Alexei; Aracne, Chantel M.; Ruddle, David G.; Krisch, Michael

    2016-01-01

    In spite of the simple body-centered-cubic crystal structure, the elements of group V, vanadium, niobium and tantalum, show strong interactions between the electronic properties and lattice dynamics. Further, these interactions can be tuned by external parameters, such as pressure and temperature. We used inelastic x-ray scattering to probe the phonon dispersion of single-crystalline vanadium as a function of pressure to 45 GPa. Our measurements show an anomalous high-pressure behavior of the transverse acoustic mode along the (100) direction and a softening of the elastic modulus C44 that triggers a rhombohedral lattice distortion occurring between 34 and 39 GPa. Our results provide the missing experimental confirmation of the theoretically predicted shear instability arising from the progressive intra-band nesting of the Fermi surface with increasing pressure, a scenario common to all transition metals of group V. PMID:27539662

  15. Prediction of Production Power for High-pressure Hydrogen by High-pressure Water Electrolysis

    NASA Astrophysics Data System (ADS)

    Kyakuno, Takahiro; Hattori, Kikuo; Ito, Kohei; Onda, Kazuo

    Recently the high attention for fuel cell electric vehicle (FCEV) is pushing to construct the hydrogen supplying station for FCEV in the world. The hydrogen pressure supplied at the current test station is intended to be high for increasing the FCEV’s driving distance. The water electrolysis can produce cleanly the hydrogen by utilizing the electricity from renewable energy without emitting CO2 to atmosphere, when it is compared to be the popular reforming process of fossil fuel in the industry. The power required for the high-pressure water electrolysis, where water is pumped up to high-pressure, may be smaller than the power for the atmospheric water electrolysis, where the produced atmospheric hydrogen is pumped up by compressor, since the compression power for water is much smaller than that for hydrogen gas. In this study the ideal water electrolysis voltage up to 70MPa and 523K is estimated referring to both the results by LeRoy et al up to 10MPa and 523K, and to the latest steam table. By using this high-pressure water electrolysis voltage, the power required for high-pressure hydrogen produced by the high-pressure water electrolysis method is estimated to be about 5% smaller than that by the atmospheric water electrolysis method, by assuming the compressor and pump efficiency of 50%.

  16. Prediction of production power for high-pressure hydrogen by high-pressure water electrolysis

    NASA Astrophysics Data System (ADS)

    Onda, Kazuo; Kyakuno, Takahiro; Hattori, Kikuo; Ito, Kohei

    Recent attention focused on fuel cell electric vehicles (FCEVs) has created demand for the construction of hydrogen supply stations for FCEVs throughout the world. The hydrogen pressure supplied at the supply stations is intentionally high to increase the FCEVs driving mileage. Water electrolysis can produce clean hydrogen by utilizing electricity from renewable energy without CO 2 emission to the atmosphere when compared with the industrial fossil fuel reforming process. The power required for high-pressure water electrolysis, wherein water is pumped up to a high-pressure, may be less than the power required for atmospheric water electrolysis, wherein the produced atmospheric hydrogen is pumped by a compressor, since the compression power for water is much less than that for hydrogen-gas. In this study, the ideal water electrolysis voltage of up to 70 MPa and 250 °C is estimated by referring to both the results of LeRoy et al. up to 10 MPa and 250 °C, and the latest steam tables. Using this high-pressure water electrolysis voltage, the power required to produce high-pressure hydrogen by high-pressure water electrolysis is estimated to be about 5% less than that required for atmospheric water electrolysis, assuming compressor and pump efficiencies of 50%.

  17. Sounding experiments of high pressure gas discharge

    SciTech Connect

    Biele, Joachim K.

    1998-07-10

    A high pressure discharge experiment (200 MPa, 5{center_dot}10{sup 21} molecules/cm{sup 3}, 3000 K) has been set up to study electrically induced shock waves. The apparatus consists of the combustion chamber (4.2 cm{sup 3}) to produce high pressure gas by burning solid propellant grains to fill the electrical pump chamber (2.5 cm{sup 3}) containing an insulated coaxial electrode. Electrical pump energy up to 7.8 kJ at 10 kV, which is roughly three times of the gas energy in the pump chamber, was delivered by a capacitor bank. From the current-voltage relationship the discharge develops at rapidly decreasing voltage. Pressure at the combustion chamber indicating significant underpressure as well as overpressure peaks is followed by an increase of static pressure level. These data are not yet completely understood. However, Lorentz forces are believed to generate pinching with subsequent pinch heating, resulting in fast pressure variations to be propagated as rarefaction and shock waves, respectively. Utilizing pure axisymmetric electrode initiation rather than often used exploding wire technology in the pump chamber, repeatable experiments were achieved.

  18. High Pressure Hydrogen from First Principles

    NASA Astrophysics Data System (ADS)

    Morales, M. A.

    2014-12-01

    Typical approximations employed in first-principles simulations of high-pressure hydrogen involve the neglect of nuclear quantum effects (NQE) and the approximate treatment of electronic exchange and correlation, typically through a density functional theory (DFT) formulation. In this talk I'll present a detailed analysis of the influence of these approximations on the phase diagram of high-pressure hydrogen, with the goal of identifying the predictive capabilities of current methods and, at the same time, making accurate predictions in this important regime. We use a path integral formulation combined with density functional theory, which allows us to incorporate NQEs in a direct and controllable way. In addition, we use state-of-the-art quantum Monte Carlo calculations to benchmark the accuracy of more approximate mean-field electronic structure calculations based on DFT, and we use GW and hybrid DFT to calculate the optical properties of the solid and liquid phases near metallization. We present accurate predictions of the metal-insulator transition on the solid, including structural and optical properties of the molecular phase. This work was supported by the U.S. Department of Energy at the Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and by LDRD Grant No. 13-LW-004.

  19. Elasticity of Hydrogen at High Pressures

    NASA Astrophysics Data System (ADS)

    Goncharov, A. F.; Decremps, F.; Gauthier, M.; Ayrinhac, S.; Antonangeli, D.; Freiman, Y. A.; Grechnev, A.; Tretyak, S. M.

    2015-12-01

    High-pressure elastic properties of hydrogen give insight into anisotropy, equation of state, thermodynamic properties, and intermolecular potentials of this material providing an important link to ultrahigh pressure behavior approaching transformation to metallic monatomic or molecular state. Here we present picosecond acoustics measurements of compressional sound velocities [1] combined with optical interferometry and Raman spectroscopy of H2 and D2 at 295 K up to 55 GPa. Using the equation of state determined previously [2], we deduced the transverse sound velocities and the Poisson's ratio up to 55 GPa. The latter shows a broad minimum near 45 GPa (c.f. Ref. [3]) providing a new experimentally proven insight into lattice dynamics of hydrogen at high pressure that can be compared to theoretical calculations of various levels [4]. [1] F. Decremps, M. Gauthier, S. Ayrinhac, L. Bove, L. Belliard, B. Perrin, M. Morand, G. Le Marchand, F. Bergame, J. Philippe, Ultrasonics, 56 (2015) 129-140. [2] P. Loubeyre, R. LeToullec, D. Hausermann, M. Hanfland, R.J. Hemley, H.K. Mao, L.W. Finger, Nature, 383 (1996) 702-704. [3] C.-s. Zha, T.S. Duffy, H.-k. Mao, R.J. Hemley, Phys. Rev. B, 48 (1993) 9246-9255. [4] Y.A. Freiman, A. Grechnev, S.M. Tretyak, A.F. Goncharov, E. Gregoryanz, Fizika Nizkikh Temperatur, 41 (2015) 571.

  20. A picosecond high pressure gas switch

    SciTech Connect

    Cravey, W.R.; Poulsen, P.P.; Pincosy, P.A.

    1992-06-01

    Work is being done to develop a high pressure gas switch (HPGS) with picosecond risetimes for UWB applications. Pulse risetimes on the order of 200 picoseconds have been observed at 1 kHz prf and 1 atmosphere. Calculations show that switching closure times on the order of tens of picoseconds can be achieved at high pressures and higher electric fields. A voltage hold-off of 1 MV/cm has been measured at 10 atmospheres and several MV/cm appears possible with the HPGS. With these high electric field levels, energy storage of tens of Joules in a reasonably sized package is achievable. Initial HPGS performance has been characterized on the WASP pulse generator at LLNL. A detailed description of the switch used for initial testing is given. Switch recovery times of 1-ms have been measured at 1 atmosphere. Data on the switching uniformity, voltage hold-off recovery, and pulse repeatability, is presented. In addition, a physics switch model is described and results are compared with lab data.

  1. High-pressure droplet combustion studies

    NASA Technical Reports Server (NTRS)

    Mikami, Masato; Kono, M.; Sato, Junichi; Dietrich, Daniel L.; Williams, Forman A.

    1993-01-01

    This is a joint research program, pursued by investigators at the University of Tokyo, UCSD, and NASA Lewis Research Center. The focus is on high-pressure combustion of miscible binary fuel droplets. It involves construction of an experimental apparatus in Tokyo, mating of the apparatus to a NASA-Lewis 2.2-second drop-tower frame in San Diego, and performing experiments in the 2.2-second tower in Cleveland, with experimental results analyzed jointly by the Tokyo, UCSD, and NASA investigators. The project was initiated in December, 1990 and has now involved three periods of drop-tower testing by Mikami at Lewis. The research accomplished thus far concerns the combustion of individual fiber-supported droplets of mixtures of n-heptane and n-hexadecane, initially about 1 mm diameter, under free-fall microgravity conditions. Ambient pressures ranged up to 3.0 MPa, extending above the critical pressures of both pure fuels, in room-temperature nitrogen-oxygen atmospheres having oxygen mole fractions X of 0.12 and 0.13. The general objective is to study near-critical and super-critical combustion of these droplets and to see whether three-stage burning, observed at normal gravity, persists at high pressures in microgravity. Results of these investigations will be summarized here; a more complete account soon will be published.

  2. High pressure turbomachinery ground test facility

    NASA Technical Reports Server (NTRS)

    Scheuermann, Patrick E.

    1992-01-01

    Turbomachinery test facilities are at present scarce to non-existent world-wide. The turbomachinery test facility at Stennis Space Center will provide for advanced development and research and development capabilities for liquid hydrogen/liquid oxygen propellant rocket engine components. The facility will provide ultra-high pressure via gas generators to deliver the needed turbine drive on various turbomachinery. State of the art process control systems will provide the vital pressure, temperature and flow requirements during tests. These systems will better control adverse transient conditions during start-up and shutdown, and by using advanced control theory, as well as incorporate test article health monitoring. Also, digital data acquisition systems will obtain high frequency (up to 20 KHz) and low frequency (up to 1 KHz) data during the test. Pressures of up to 15,000 psi will be generated to pressurize high pressure tanks supplying cryogens to various test article inlets thus pushing turbopump materials and manufacturing processes to their limits. By planning for future projects the test facility will be easily adaptable to multi-program test configurations over a range of thermodynamic positions.

  3. High Pressure X-Ray Diffraction Studies of Nanocrystalline Materials

    NASA Technical Reports Server (NTRS)

    Palosz, B.; Stel'makh, S.; Grzanka, E.; Gierlotka, S.; Palosz, W.

    2004-01-01

    Experimental evidence obtained for a variety of nanocrystalline materials suggest that the crystallographic structure of a very small size particle deviates from that in the bulk crystals. In this paper we show the effect of the surface of nanocrystals on their structure by the analysis of generation and distribution of macro- and micro-strains at high pressures and their dependence on the grain size in nanocrystalline powders of Sic. We studied the structure of Sic nanocrystals by in-situ high-pressure powder diffraction technique using synchrotron and neutron sources and hydrostatic or isostatic pressure conditions. The diffraction measurements were done in HASYLAB at DESY using a Diamond Anvil Cell (DAC) in the energy dispersive geometry in the diffraction vector range up to 3.5 - 4/A and under pressures up to 50 GPa at room temperature. In-situ high pressure neutron diffraction measurements were done at LANSCE in Los Alamos National Laboratory using the HIPD and HIPPO diffractometers with the Paris-Edinburgh and TAP-98 cells, respectively, in the diffraction vector range up to 26 Examination of the response of the material to external stresses requires nonstandard methodology of the materials characterization and description. Although every diffraction pattern contains a complete information on macro- and micro-strains, a high pressure experiment can reveal only those factors which contribute to the characteristic diffraction patterns of the crystalline phases present in the sample. The elastic properties of powders with the grain size from several nm to micrometers were examined using three methodologies: (l), the analysis of positions and widths of individual Bragg reflections (used for calculating macro- and micro-strains generated during densification) [I], (2). the analysis of the dependence of the experimental apparent lattice parameter, alp, on the diffraction vector Q [2], and (3), the atomic Pair Distribution Function (PDF) technique [3]. The results

  4. (Ultra) high pressure homogenization for continuous high pressure sterilization of pumpable foods - a review.

    PubMed

    Georget, Erika; Miller, Brittany; Callanan, Michael; Heinz, Volker; Mathys, Alexander

    2014-01-01

    Bacterial spores have a strong resistance to both chemical and physical hurdles and create a risk for the food industry, which has been tackled by applying high thermal intensity treatments to sterilize food. These strong thermal treatments lead to a reduction of the organoleptic and nutritional properties of food and alternatives are actively searched for. Innovative hurdles offer an alternative to inactivate bacterial spores. In particular, recent technological developments have enabled a new generation of high pressure homogenizer working at pressures up to 400 MPa and thus, opening new opportunities for high pressure sterilization of foods. In this short review, we summarize the work conducted on (ultra) high pressure homogenization (U)HPH to inactivate endospores in model and food systems. Specific attention is given to process parameters (pressure, inlet, and valve temperatures). This review gathers the current state of the art and underlines the potential of UHPH sterilization of pumpable foods while highlighting the needs for future work.

  5. (Ultra) High Pressure Homogenization for Continuous High Pressure Sterilization of Pumpable Foods – A Review

    PubMed Central

    Georget, Erika; Miller, Brittany; Callanan, Michael; Heinz, Volker; Mathys, Alexander

    2014-01-01

    Bacterial spores have a strong resistance to both chemical and physical hurdles and create a risk for the food industry, which has been tackled by applying high thermal intensity treatments to sterilize food. These strong thermal treatments lead to a reduction of the organoleptic and nutritional properties of food and alternatives are actively searched for. Innovative hurdles offer an alternative to inactivate bacterial spores. In particular, recent technological developments have enabled a new generation of high pressure homogenizer working at pressures up to 400 MPa and thus, opening new opportunities for high pressure sterilization of foods. In this short review, we summarize the work conducted on (ultra) high pressure homogenization (U)HPH to inactivate endospores in model and food systems. Specific attention is given to process parameters (pressure, inlet, and valve temperatures). This review gathers the current state of the art and underlines the potential of UHPH sterilization of pumpable foods while highlighting the needs for future work. PMID:25988118

  6. Sealed Rotors for In Situ High Temperature High Pressure MAS NMR†

    PubMed Central

    Hu, Jian Zhi; Hu, Mary Y.; Zhao, Zhenchao; Xu, Suochang; Vjunov, Aleksei; Shi, Hui; Camaioni, Donald M.; Peden, Charles H. F.; Lercher, Johannes A.

    2015-01-01

    Here we present the design of reusable and perfectly-sealed all-zircornia MAS rotors. The rotors are used to study AlPO4-5 molecular sieve crystallization under hydrothermal conditions, high temperature high pressure cyclohexanol dehydration reaction, and low temperature metabolomics of intact biological tissue. PMID:26171928

  7. TOPICAL REVIEW: High-pressure synthesis, crystal growth, phase diagrams, structural and magnetic properties of Y2Ba4CunO2n+x, HgBa2Can- 1CunO2n+2+delta and quasi-one-dimensional cuprates

    NASA Astrophysics Data System (ADS)

    Karpinski, J.; Meijer, G. I.; Schwer, H.; Molinski, R.; Kopnin, E.; Conder, K.; Angst, M.; Jun, J.; Kazakov, S.; Wisniewski, A.; Puzniak, R.; Hofer, J.; Alyoshin, V.; Sin, A.

    1999-09-01

    In this paper we present a review of high-gas-pressure single crystal growth studies of YBa2Cu4O8 and Y2Ba4Cu7O15-x performed in oxygen pressure up to 3000 bar and Hg1-xMxBa2Can- 1CunO2n+2+icons/Journals/Common/delta" ALT="delta" ALIGN="MIDDLE"/> (M = Pb, Re; n = 1-7) compounds in argon pressure up 11 000 bar at temperature up to 1200 °C. Chain compounds A1-xCuO2 (A = Sr, Ca, Ba) have been synthesized at high oxygen pressure up to 2000 bar. High-pressure phase diagram studies of the investigated systems are also discussed. Structure analyses of Y2Ba4CunO2n+x (n = 6-8), Hg1-xMxBa2Can- 1CunO2n+2+icons/Journals/Common/delta" ALT="delta" ALIGN="MIDDLE"/> (M = Pb, Re; n = 1-8), Sr0.73CuO2 and (Sr,Ca)4Cu6O10 single crystals have been performed. The effects of substitutions and trends in bondlengths are discussed. The vortex state properties of HgBa2Ca2Cu3O8+icons/Journals/Common/delta" ALT="delta" ALIGN="MIDDLE"/> and YBa2Cu4O8 single crystals are compared. For Hg-based compounds, the influence of oxygen content, chemical substitutions and radiation defects on vortex pinning were determined. The quasi-one-dimensional cuprates Ca0.83CuO2 and Sr0.73CuO2 show an antiferromagnetically ordered state of long-range 3D character at T < 10 K. The spin dynamics of Sr0.73CuO2, measured by inelastic neutron scattering, indicate that this ordered state coexists with a dimerized singlet ground state.

  8. New developments in high pressure x-ray spectroscopy beamline at High Pressure Collaborative Access Team

    SciTech Connect

    Xiao, Y. M. Chow, P.; Boman, G.; Bai, L. G.; Rod, E.; Bommannavar, A.; Kenney-Benson, C.; Sinogeikin, S.; Shen, G. Y.

    2015-07-15

    The 16 ID-D (Insertion Device - D station) beamline of the High Pressure Collaborative Access Team at the Advanced Photon Source is dedicated to high pressure research using X-ray spectroscopy techniques typically integrated with diamond anvil cells. The beamline provides X-rays of 4.5-37 keV, and current available techniques include X-ray emission spectroscopy, inelastic X-ray scattering, and nuclear resonant scattering. The recent developments include a canted undulator upgrade, 17-element analyzer array for inelastic X-ray scattering, and an emission spectrometer using a polycapillary half-lens. Recent development projects and future prospects are also discussed.

  9. Synthesis of sodium polyhydrides at high pressures.

    PubMed

    Struzhkin, Viktor V; Kim, Duck Young; Stavrou, Elissaios; Muramatsu, Takaki; Mao, Ho-Kwang; Pickard, Chris J; Needs, Richard J; Prakapenka, Vitali B; Goncharov, Alexander F

    2016-01-01

    The only known compound of sodium and hydrogen is archetypal ionic NaH. Application of high pressure is known to promote states with higher atomic coordination, but extensive searches for polyhydrides with unusual stoichiometry have had only limited success in spite of several theoretical predictions. Here we report the first observation of the formation of polyhydrides of Na (NaH3 and NaH7) above 40 GPa and 2,000 K. We combine synchrotron X-ray diffraction and Raman spectroscopy in a laser-heated diamond anvil cell and theoretical random structure searching, which both agree on the stable structures and compositions. Our results support the formation of multicenter bonding in a material with unusual stoichiometry. These results are applicable to the design of new energetic solids and high-temperature superconductors based on hydrogen-rich materials. PMID:27464650

  10. Synthesis of sodium polyhydrides at high pressures

    DOE PAGESBeta

    Struzhkin, Viktor V.; Kim, Duck Young; Stavrou, Elissaios; Muramatsu, Takaki; Mao, Ho-kwang; Pickard, Chris J.; Needs, Richard J.; Prakapenka, Vitali B.; Goncharov, Alexander F.

    2016-07-28

    Archetypal ionic NaH is the only known compound of sodium and hydrogen. Application of high pressure is known to promote states with higher atomic coordination, but extensive searches for polyhydrides with unusual stoichiometry have had only limited success in spite of several theoretical predictions. Here we report the first observation of the formation of polyhydrides of Na (NaH3 and NaH7) above 40 GPa and 2,000 K. Moreover, we combine synchrotron X-ray diffraction and Raman spectroscopy in a laser-heated diamond anvil cell and theoretical random structure searching, which both agree on the stable structures and compositions. Our results support the formationmore » of multicenter bonding in a material with unusual stoichiometry. These results are applicable to the design of new energetic solids and high-temperature superconductors based on hydrogen-rich materials.« less

  11. Synthesis of sodium polyhydrides at high pressures

    NASA Astrophysics Data System (ADS)

    Struzhkin, Viktor V.; Kim, Duck Young; Stavrou, Elissaios; Muramatsu, Takaki; Mao, Ho-Kwang; Pickard, Chris J.; Needs, Richard J.; Prakapenka, Vitali B.; Goncharov, Alexander F.

    2016-07-01

    The only known compound of sodium and hydrogen is archetypal ionic NaH. Application of high pressure is known to promote states with higher atomic coordination, but extensive searches for polyhydrides with unusual stoichiometry have had only limited success in spite of several theoretical predictions. Here we report the first observation of the formation of polyhydrides of Na (NaH3 and NaH7) above 40 GPa and 2,000 K. We combine synchrotron X-ray diffraction and Raman spectroscopy in a laser-heated diamond anvil cell and theoretical random structure searching, which both agree on the stable structures and compositions. Our results support the formation of multicenter bonding in a material with unusual stoichiometry. These results are applicable to the design of new energetic solids and high-temperature superconductors based on hydrogen-rich materials.

  12. Safety improvements in high pressure thermal machines

    SciTech Connect

    Otters, J.L.

    1988-02-09

    In a thermal machine of the type including a machine body having a main axis extending between a thermal end and a work end, a working fluid at relatively high pressure in a working fluid chamber defined in the body and a displacer element reciprocable within the chamber for subjecting the fluid to a thermodynamic cycle in cooperation with a reciprocable work piston, the improvement is described comprising outer shell means enclosing the machine body for maintaining a substantially sealed atmosphere about the machine body, and diffuser means arranged between the machine body and the outer shell means for diffusing a shock wave traveling towards the outer shell means resulting from explosive failure of the machine body and for shielding the outer shell means against fragments projected upon such failure.

  13. Synthesis of sodium polyhydrides at high pressures.

    PubMed

    Struzhkin, Viktor V; Kim, Duck Young; Stavrou, Elissaios; Muramatsu, Takaki; Mao, Ho-Kwang; Pickard, Chris J; Needs, Richard J; Prakapenka, Vitali B; Goncharov, Alexander F

    2016-07-28

    The only known compound of sodium and hydrogen is archetypal ionic NaH. Application of high pressure is known to promote states with higher atomic coordination, but extensive searches for polyhydrides with unusual stoichiometry have had only limited success in spite of several theoretical predictions. Here we report the first observation of the formation of polyhydrides of Na (NaH3 and NaH7) above 40 GPa and 2,000 K. We combine synchrotron X-ray diffraction and Raman spectroscopy in a laser-heated diamond anvil cell and theoretical random structure searching, which both agree on the stable structures and compositions. Our results support the formation of multicenter bonding in a material with unusual stoichiometry. These results are applicable to the design of new energetic solids and high-temperature superconductors based on hydrogen-rich materials.

  14. Low energy high pressure miniature screw valve

    DOEpatents

    Fischer, Gary J.; Spletzer, Barry L.

    2006-12-12

    A low energy high pressure screw valve having a valve body having an upper portion and a lower portion, said lower portion of said valve body defining an inlet flow passage and an outlet flow passage traversing said valve body to a valve seat, said upper portion of said valve body defining a cavity at said valve seat, a diaphragm restricting flow between said upper portion of said valve body and said lower portion, said diaphragm capable of engaging said valve seat to restrict fluid communication between said inlet passage and said outlet passage, a plunger within said cavity supporting said diaphragm, said plunger being capable of engaging said diaphragm with said valve seat at said inlet and outlet fluid passages, said plunger being in point contact with a drive screw having threads engaged with opposing threads within said upper portion of said valve body such engagement allowing motion of said drive screw within said valve body.

  15. High pressure and high temperature apparatus

    DOEpatents

    Voronov, Oleg A.

    2005-09-13

    A design for high pressure/high temperature apparatus and reaction cell to achieve .about.30 GPa pressure in .about.1 cm volume and .about.100 GPa pressure in .about.1 mm volumes and 20-5000.degree. C. temperatures in a static regime. The device includes profiled anvils (28) action on a reaction cell (14, 16) containing the material (26) to be processed. The reaction cell includes a heater (18) surrounded by insulating layers and screens. Surrounding the anvils are cylindrical inserts and supporting rings (30-48) whose hardness increases towards the reaction cell. These volumes may be increased considerably if applications require it, making use of presses that have larger loading force capability, larger frames and using larger anvils.

  16. Small, high-pressure liquid oxygen turbopump

    NASA Technical Reports Server (NTRS)

    Csomor, A.; Sutton, R.

    1977-01-01

    A small, high-pressure, liquid oxygen turbopump was designed, fabricated, and tested. The pump was of a single-stage, centrifugal type; power to the pump was supplied by a single-stage, partial emission, axial-impulse turbine. Design conditions included an operating speed of 70,000 rpm, pump discharge pressure of 2977 N/sq cm (4318 psia), and a pump flowrate of 16.4 kg/s (36.21 lb/sec). The turbine was propelled by LO2/LH2 combustion products at 1041 K (1874 R) inlet temperature, and at a design pressure ratio of 1.424. The approaches used in the detail analysis and design of the turbopump are described, and fabrication methods are discussed. Data obtained from gas generator tests, turbine performance calibration, and turbopump testing are presented.

  17. High pressure study of acetophenone azine

    NASA Astrophysics Data System (ADS)

    Tang, X. D.; Ding, Z. J.; Zhang, Z. M.

    2009-02-01

    High pressure Raman spectra of acetophenone azine (APA) have been measured up to 17.7 GPa with a diamond anvil cell. Two crystalline-to-crystalline phase transformations are found at pressures about 3.6 and 5.8 GPa. A disappearance of external modes and the C-H vibration at pressures higher than 8.7 GPa suggests that the sample undergoes a phase transition to amorphous or orientationally disordered (plastic) state, and the amorphization was completed at about 12.1 GPa. The disordered state is unstable and, then, a polymerization transformation reaction occurs with a further pressure increase. After the pressure has been released, the polymerization state can remain at the ambient condition, indicating that the virgin crystalline state is not recovered. The results show that the phenomenon underlying the pressure induced phase transition of APA may involve profound changes in the coordination environments of the symmetric aromatic azine.

  18. High pressure combustion synthesis of aluminum nitride

    SciTech Connect

    Costantino, M.; Firpo, C. )

    1991-11-01

    We report initial results on the synthesis of monolithic aluminum nitride by burning Al--AlN mixtures in high pressure nitrogen. The objective is to synthesize economically large, near-theoretical density AlN parts. In this work, we begin with compacted mixtures of 10 {mu}m Al and 3 {mu}m AlN powder formed into 7.62 cm diameter by 3.81 cm thick disks having densities up to 60% of theoretical. Then, at N{sub 2} pressures up to 180 MPa (26 000 psi), we ignite the disk on one face. The fraction of Al converted to AlN, density, and severity of macroscopic cracking vary with N{sub 2} pressure and heat transfer from the sample. Presently, products are inhomogeneous, showing regions of relatively high porosity, regions with no porosity but with AlN in a matrix of Al, and regions of nearly theoretical density AlN.

  19. Ceramic high pressure gas path seal

    NASA Technical Reports Server (NTRS)

    Liotta, G. C.

    1987-01-01

    Stage 1 ceramic shrouds (high pressure turbine gas path seal) were developed for the GE T700 turbine helicopter engine under the Army/NASA Contract NAS3-23174. This contract successfully proved the viability and benefits of a Stage 1 ceramic shroud for production application. Stage 1 ceramic shrouds were proven by extensive component and engine testing. This Stage 1 ceramic shroud, plasma sprayed ceramic (ZrOs-BY2O3) and bond coating (NiCrAlY) onto a cast metal backing, offers significant engine performance improvement. Due to the ceramic coating, the amount of cooling air required is reduced 20% resulting in a 0.5% increase in horsepower and a 0.3% decrease in specific fuel consumption. This is accomplished with a component which is lower in cost than the current production shroud. Stage 1 ceramic shrouds will be introduced into field service in late 1987.

  20. Synthesis of sodium polyhydrides at high pressures

    PubMed Central

    Struzhkin, Viktor V.; Kim, Duck Young; Stavrou, Elissaios; Muramatsu, Takaki; Mao, Ho-kwang; Pickard, Chris J.; Needs, Richard J.; Prakapenka, Vitali B.; Goncharov, Alexander F.

    2016-01-01

    The only known compound of sodium and hydrogen is archetypal ionic NaH. Application of high pressure is known to promote states with higher atomic coordination, but extensive searches for polyhydrides with unusual stoichiometry have had only limited success in spite of several theoretical predictions. Here we report the first observation of the formation of polyhydrides of Na (NaH3 and NaH7) above 40 GPa and 2,000 K. We combine synchrotron X-ray diffraction and Raman spectroscopy in a laser-heated diamond anvil cell and theoretical random structure searching, which both agree on the stable structures and compositions. Our results support the formation of multicenter bonding in a material with unusual stoichiometry. These results are applicable to the design of new energetic solids and high-temperature superconductors based on hydrogen-rich materials. PMID:27464650

  1. Urea and deuterium mixtures at high pressures

    SciTech Connect

    Donnelly, M. Husband, R. J.; Frantzana, A. D.; Loveday, J. S.; Bull, C. L.; Klotz, S.

    2015-03-28

    Urea, like many network forming compounds, has long been known to form inclusion (guest-host) compounds. Unlike other network formers like water, urea is not known to form such inclusion compounds with simple molecules like hydrogen. Such compounds if they existed would be of interest both for the fundamental insight they provide into molecular bonding and as potential gas storage systems. Urea has been proposed as a potential hydrogen storage material [T. A. Strobel et al., Chem. Phys. Lett. 478, 97 (2009)]. Here, we report the results of high-pressure neutron diffraction studies of urea and D{sub 2} mixtures that indicate no inclusion compound forms up to 3.7 GPa.

  2. High Pressure Quick Disconnect Particle Impact Tests

    NASA Technical Reports Server (NTRS)

    Rosales, Keisa R.; Stoltzfus, Joel M.

    2009-01-01

    NASA Johnson Space Center White Sands Test Facility (WSTF) performed particle impact testing to determine whether there is a particle impact ignition hazard in the quick disconnects (QDs) in the Environmental Control and Life Support System (ECLSS) on the International Space Station (ISS). Testing included standard supersonic and subsonic particle impact tests on 15-5 PH stainless steel, as well as tests performed on a QD simulator. This paper summarizes the particle impact tests completed at WSTF. Although there was an ignition in Test Series 4, it was determined the ignition was caused by the presence of a machining imperfection. The sum of all the test results indicates that there is no particle impact ignition hazard in the ISS ECLSS QDs. KEYWORDS: quick disconnect, high pressure, particle impact testing, stainless steel

  3. Small, high-pressure, liquid oxygen turbopump

    NASA Technical Reports Server (NTRS)

    Csomor, A.

    1978-01-01

    A small, high-pressure, LOX turbopump was designed, fabricated, and tested. The pump was of a single-stage, centrifugal type; power to the pump was supplied by a single-stage, partial-admission, axial-impulse turbine. Design conditions included an operating speed of 7330 rad/sec (70,000 rpm) pump discharge pressure of 2977 N/sq cm (4318 psia), and a pump flowrate of 16.4 kg/s (36.21 lb/sec). The turbine was propelled by LOX/LH2 combustion products at 1041 K (1874 R) inlet temperature, and at a design pressure ratio of 1.424. Test data obtained with the turbopump are presented and mechanical performance is discussed.

  4. High-Pressure Research Applications Seminar

    NASA Astrophysics Data System (ADS)

    Manghnani, Murli H.; Akimoto, Syun-iti; Ahrens, Thomas J.; Syono, Yasuhiko; Jeanloz, Raymond; Yagi, Takehiko

    The United States-Japan seminar on “High-Pressure Research Applications in Geophysics and Geochemistry” was held in Honolulu, Hawaii, January 13-16, 1986, under the auspices of the National Science Foundation (NSF) and the Japan Society for the Promotion of Science (JSPS). The seminar, the third in a series, was cocovened by Murli H. Manghnani (University of Hawaii, Honolulu) and Syun-iti Akimoto (University of Tokyo). Coming together for this symposium were 25 researchers from Japan, 22 from the United States, and four others, from Australia, the People's Republic of China, the Netherlands, and the Federal Republic of Germany. Of the 52 papers presented, 38 were presented orally at seven scientific sessions, and the rest were displayed at a poster session.

  5. High-pressure coal fuel processor development

    SciTech Connect

    Greenhalgh, M.L.

    1992-11-01

    The objective of Subtask 1.1 Engine Feasibility was to conduct research needed to establish the technical feasibility of ignition and stable combustion of directly injected, 3,000 psi, low-Btu gas with glow plug ignition assist at diesel engine compression ratios. This objective was accomplished by designing, fabricating, testing and analyzing the combustion performance of synthesized low-Btu coal gas in a single-cylinder test engine combustion rig located at the Caterpillar Technical Center engine lab in Mossville, Illinois. The objective of Subtask 1.2 Fuel Processor Feasibility was to conduct research needed to establish the technical feasibility of air-blown, fixed-bed, high-pressure coal fuel processing at up to 3,000 psi operating pressure, incorporating in-bed sulfur and particulate capture. This objective was accomplished by designing, fabricating, testing and analyzing the performance of bench-scale processors located at Coal Technology Corporation (subcontractor) facilities in Bristol, Virginia. These two subtasks were carried out at widely separated locations and will be discussed in separate sections of this report. They were, however, independent in that the composition of the synthetic coal gas used to fuel the combustion rig was adjusted to reflect the range of exit gas compositions being produced on the fuel processor rig. Two major conclusions resulted from this task. First, direct injected, ignition assisted Diesel cycle engine combustion systems can be suitably modified to efficiently utilize these low-Btu gas fuels. Second, high pressure gasification of selected run-of-the-mine coals in batch-loaded fuel processors is feasible. These two findings, taken together, significantly reduce the perceived technical risks associated with the further development of the proposed coal gas fueled Diesel cycle power plant concept.

  6. Yield strength of molybdenum at high pressures.

    PubMed

    Jing, Qiumin; Bi, Yan; Wu, Qiang; Jing, Fuqian; Wang, Zhigang; Xu, Jian; Jiang, Sheng

    2007-07-01

    In the diamond anvil cell technology, the pressure gradient approach is one of the three major methods in determining the yield strength for various materials at high pressures. In the present work, by in situ measuring the thickness of the sample foil, we have improved the traditional technique in this method. Based on this modification, the yield strength of molybdenum at pressures has been measured. Our main experimental conclusions are as follows: (1) The measured yield strength data for three samples with different initial thickness (100, 250, and 500 microm) are in good agreement above a peak pressure of 10 GPa. (2) The measured yield strength can be fitted into a linear formula Y=0.48(+/-0.19)+0.14(+/-0.01)P (Y and P denote the yield strength and local pressure, respectively, both of them are in gigapascals) in the local pressure range of 8-21 GPa. This result is in good agreement with both Y=0.46+0.13P determined in the pressure range of 5-24 GPa measured by the radial x-ray diffraction technique and the previous shock wave data below 10 GPa. (3) The zero-pressure yield strength of Mo is 0.5 GPa when we extrapolate our experimental data into the ambient pressure. It is close to the tensile strength of 0.7 GPa determined by Bridgman [Phys. Rev. 48, 825 (1934)] previously. The modified method described in this article therefore provides the confidence in determination of the yield strength at high pressures. PMID:17672772

  7. Test facility for high pressure plasmas

    SciTech Connect

    Block, R.; Laroussi, M.; Schoenbach, K.H.

    1999-07-01

    High pressure nonthermal plasmas are gaining increasing importance because of their wide range of applications, e.g. in air plasma ramparts, gas processing, surface treatment, thin film deposition, and chemical and biological decontamination. In order to compare various methods of plasma generation with respect to efficiency, development of instabilities, homogeneity, lifetime etc., a central test facility for high pressure plasmas is being established. The facility will allow one to study large volume (> 100 cm{sup 3}), nonthermal (gas temperature: < 2,000 K) plasmas over a large pressure range (10{sup {minus}6} Torr up to more than 1 atmosphere) in a standardized discharge cell. The setup was designed to generate plasmas in air as well as in gas mixtures. The available voltage range extends to 25 kV dc (10 kW power). The electrodes can be water cooled. Electrical diagnostics include a 400 Mhz, 2 GS/s 4-channel oscilloscope for current and voltage measurements and the detection of the onset of instabilities. For optical diagnostics, a CCD video camera is used to record the appearance of dc discharges. A high-speed light intensified CCD-camera (25 mm MCP with photocathode, gating speed: 200 ps, adjustable in 10 ps steps) allows to study the development of instabilities and can also be utilized in temporally resolved spectroscopic measurements. Optical emission spectroscopy allows one to determine plasma parameters such as electron density (through Stark broadening measurements) and gas temperature measurements. Interferometry is well suited for electron density measurements especially in weakly ionized plasmas.

  8. High-pressure coal fuel processor development

    SciTech Connect

    Greenhalgh, M.L. )

    1992-12-01

    Caterpillar shares DOE/METC interest in demonstrating the technology required to displace petroleum-based engine fuels with various forms of low cost coal. Current DOE/METC programs on mild gasification and coal-water-slurries are addressing two approaches to this end. Engine and fuel processor system concept studies by Caterpillar have identified a third, potentially promising, option. This option includes high-pressure fuel processing of run-of-the-mine coal and direct injection of the resulting low-Btu gas stream into an ignition assisted, high compression ratio diesel engine. The compactness and predicted efficiency of the system make it suitable for application to line-haul railroad locomotives. Two overall conclusions resulted from Task 1. First direct injected, ignition assisted Diesel cycle engine combustion systems can be suitably modified to efficiently utilize low-Btu gas fuels. Second, high pressure gasification of selected run-of-the-mine coals in batch-loaded fuel processors is feasible. These two findings, taken together, significantly reduce the perceived technical risk associated with the further development of the proposed coal gas fueled Diesel cycle power plant concept. The significant conclusions from Task 2 were: An engine concept, derived from a Caterpillar 3600 series engine, and a fuel processor concept, based on scaling up a removable-canister configuration from the test rig, appear feasible; and although the results of this concept study are encouraging, further, full-scale component research and development are required before attempting a full-scale integrated system demonstration effort.

  9. High pressure microhollow cathode discharges in air

    SciTech Connect

    Khedr, M.A.; Stark, R.H.; Watson, B.; Schoenbach, K.H.

    1998-12-31

    Research on high pressure, large volume glow discharges in air is motivated by applications such as reflectors and absorbers for electromagnetic radiation, plasma processing, and the remediation of gaseous pollution. In order to prevent glow-to-arc transitions, which in high-pressure glow discharges start in the cathode region, it is proposed to use a plasma cathode consisting of an array of microhollow cathode discharges. To explore the conditions for stable operation of single 100 {micro}m microhollow cathode discharges in flowing air, the current-voltage characteristics, and the visual appearance of a 100 {micro}m microhollow cathode discharge were studied. The results show that the threshold current for the transition from a glow into a filamentary discharge varies inversely with pressure. At pressures of 400 Torr the current in the 100 {micro}m hollow cathode discharge must not exceed 0.5 mA in order for the discharge to be stable. The type of instability, which causes the transition from dc to fluctuating currents, is not known at this time, but the observed dependence of the threshold current from the gas pressure points to a thermal instability. Assuming that the White-Allis scaling law still holds for air discharges at pressures close to atmospheric, it is expected that reducing the cathode hole diameter to 50 {micro}m will allow us to operate microhollow cathode discharges at atmospheric air with currents of up to 0.25 mA. Experimental studies on the effect of the cathode dimensions and cathode material are underway and results will be discussed at the conference.

  10. Novel high-pressure phase of ZrO{sub 2}: An ab initio prediction

    SciTech Connect

    Durandurdu, Murat

    2015-10-15

    The high-pressure behavior of the orthorhombic cotunnite type ZrO{sub 2} is explored using an ab initio constant pressure technique. For the first time, a novel hexagonal phase (Ni{sub 2}In type) within P6{sub 3}/mmc symmetry is predicted through the simulation. The Ni{sub 2}In type crystal is the densest high-pressure phase of ZrO{sub 2} proposed so far and has not been observed in other metal dioxides at high pressure before. The phase transformation is accompanied by a small volume drop and likely to occur around 380 GPa in experiment. - Graphical abstract: Post-cotunnite Ni{sub 2}In type hexagonal phase forms in zirconia at high pressure. - Highlights: • A post-cotunnite phase is predicted for ZrO{sub 2} through an ab initio simulation. • Cotunnite ZrO{sub 2} adopts the Ni{sub 2}In type structure at high pressure. • The Ni{sub 2}In type structure is the densest high-pressure phase of ZrO{sub 2} proposed so far. • The preferred mechanism in ZrO{sub 2} differs from the other metal dioxides.

  11. High pressure/high temperature thermogravimetric apparatus. Final report

    SciTech Connect

    Calo, J.M.; Suuberg, E.M.

    1999-12-01

    The purpose of this instrumentation grant was to acquire a state-of-the-art, high pressure, high temperature thermogravimetric apparatus (HP/HT TGA) system for the study of the interactions between gases and carbonaceous solids for the purpose of solving problems related to coal utilization and applications of carbon materials. The instrument that we identified for this purpose was manufactured by DMT (Deutsche Montan Technologies)--Institute of Cokemaking and Coal Chemistry of Essen, Germany. Particular features of note include: Two reactors: a standard TGA reactor, capable of 1100 C at 100 bar; and a high temperature (HT) reactor, capable of operation at 1600 C and 100 bar; A steam generator capable of generating steam to 100 bar; Flow controllers and gas mixing system for up to three reaction gases, plus a separate circuit for steam, and another for purge gas; and An automated software system for data acquisition and control. The HP/TP DMT-TGA apparatus was purchased in 1996 and installed and commissioned during the summer of 1996. The apparatus was located in Room 128 of the Prince Engineering Building at Brown University. A hydrogen alarm and vent system were added for safety considerations. The system has been interfaced to an Ametek quadruple mass spectrometer (MA 100), pumped by a Varian V250 turbomolecular pump, as provided for in the original proposed. With this capability, a number of gas phase species of interest can be monitored in a near-simultaneous fashion. The MS can be used in a few different modes. During high pressure, steady-state gasification experiments, it is used to sample, measure, and monitor the reactant/product gases. It can also be used to monitor gas phase species during nonisothermal temperature programmed reaction (TPR) or temperature programmed desorption (TPD) experiments.

  12. Chemistry Notes.

    ERIC Educational Resources Information Center

    School Science Review, 1981

    1981-01-01

    Describes 13 activities, experiments and demonstrations, including the preparation of iron (III) chloride, simple alpha-helix model, investigating camping gas, redox reactions of some organic compounds, a liquid crystal thermometer, and the oxidation number concept in organic chemistry. (JN)

  13. 30 CFR 57.13021 - High-pressure hose connections.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false High-pressure hose connections. 57.13021... Air and Boilers § 57.13021 High-pressure hose connections. Except where automatic shutoff valves are...-pressure hose lines of 3/4-inch inside diameter or larger, and between high-pressure hose lines of...

  14. 30 CFR 57.13021 - High-pressure hose connections.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false High-pressure hose connections. 57.13021... Air and Boilers § 57.13021 High-pressure hose connections. Except where automatic shutoff valves are...-pressure hose lines of 3/4-inch inside diameter or larger, and between high-pressure hose lines of...

  15. 30 CFR 57.13021 - High-pressure hose connections.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false High-pressure hose connections. 57.13021... Air and Boilers § 57.13021 High-pressure hose connections. Except where automatic shutoff valves are...-pressure hose lines of 3/4-inch inside diameter or larger, and between high-pressure hose lines of...

  16. 30 CFR 57.13021 - High-pressure hose connections.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false High-pressure hose connections. 57.13021... Air and Boilers § 57.13021 High-pressure hose connections. Except where automatic shutoff valves are...-pressure hose lines of 3/4-inch inside diameter or larger, and between high-pressure hose lines of...

  17. 30 CFR 57.13021 - High-pressure hose connections.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false High-pressure hose connections. 57.13021... Air and Boilers § 57.13021 High-pressure hose connections. Except where automatic shutoff valves are...-pressure hose lines of 3/4-inch inside diameter or larger, and between high-pressure hose lines of...

  18. Structural chemistry and number theory amalgamized: crystal structure of Na11Hg52.

    PubMed

    Hornfeck, Wolfgang; Hoch, Constantin

    2015-12-01

    The recently elucidated crystal structure of the technologically important amalgam Na11Hg52 is described by means of a method employing some fundamental concept of number theory, namely modular arithmetical (congruence) relations observed between a slightly idealized set of atomic coordinates. In combination with well known ideas from group theory, regarding lattice-sublattice transformations, these allow for a deeper mutual understanding of both and provide the structural chemist with a slightly different kind of spectacles, thus enabling a distinct viw on complex crystal structures in general.

  19. High-Pressure Equation of State for Partially Ionic Solids

    NASA Technical Reports Server (NTRS)

    Schlosser, Herbert; Ferrante, John

    1993-01-01

    Recently, we showed that the cohesive energy of partially ionic solids may be characterized by a two-term energy relationship consisting of a Coulomb term arising from the valence-charge transfer delta Z between the atoms, and a scaled universal energy function E(sup *)(a(sup *)), which accounts for the partially covalent character of the bond and for the repulsion between the atomic cores for small R; a(sup *) is a scaled length. Normalized cohesive-energy curves of alkali halide crystals and of Ti and Ag halide crystals were obtained, and the cohesive-energy-curve parameters were used to generate theoretical equation-of-state (EOS) curves for the Li, Na, K, Cs, and Ag halides. Good agreement was obtained with the experimental isothermal compression curves over a wide pressure range (0-90 kbar). In this paper we verify that the cohesive-energy relationship is valid for divalent partially ionic solids; physically reasonable charge-transfer values (1.80 less than delta Z less than 2.0) are obtained for MgO, CaO, and CaS. Next, EOS curves for LiF, NaF, Nal, CsCl, Csl, MgO, CaO, and CaS are generated in terms of the cohesive-energy parameters. These EOS's yield excellent fits to experimental isothermal-compression data and to shock-wave data to very high pressures (P(sub max)= 250-1350 kbar).

  20. High-Pressure Effects in Benzoic Acid Dimers: Vibrational Spectroscopy

    NASA Astrophysics Data System (ADS)

    Tao, Yuchuan; Dreger, Zbigniew; Gupta, Yogendra

    2013-06-01

    To understand pressure effects on dimer structure stability, Raman and FTIR spectroscopy were used to examine changes in hydrogen bonded dimers of benzoic acid crystals up to 31 GPa. Raman measurements indicated a phase transition around 7-8 GPa. It is proposed that this transition is caused by a rearrangement of molecules within the dimer leading to a symmetry change from C2h to likely C2 or Cs. This change was reversible upon pressure release from 15 GPa. Pressures above 15 GPa, induced gradual changes in luminescence and a color change in the crystal from white to brownish. FTIR measurements at 31 GPa revealed the formation of a new broad band centered around 3250 cm-1, which was attributed to the stretching vibrations of the O -H bond. It is proposed that hydrogen bonded dimers of benzoic acid transform partially to a covalently bonded compound composed of benzoic anhydride-like molecules and H2O. This study demonstrates that application of high pressure can lead to significant changes in the H-bonded dimer structure, including formation of chemical bonding. Work supported by DOE/NNSA and ONR/MURI.

  1. High-Pressure Polymorph of NaBiO3.

    PubMed

    Naa, Octavianti; Kumada, Nobuhiro; Miura, Akira; Takei, Takahiro; Azuma, Masaki; Kusano, Yoshihiro; Oka, Kengo

    2016-06-20

    A new high-pressure polymorph of NaBiO3 (hereafter β-NaBiO3) was synthesized under the conditions of 6 GPa and 600 °C. The powder X-ray diffraction pattern of this new phase was indexed with a hexagonal cell of a = 9.968(1) Å and c = 3.2933(4) Å. Crystal structure refinement using synchrotron powder X-ray diffraction data led to RWP = 8.53% and RP = 5.55%, and the crystal structure was closely related with that of Ba2SrY6O12. No photocatalytic activity for phenol decomposition was observed under visible-light irradiation in spite of a good performance for its mother compound, NaBiO3. The optical band-gap energy of β-NaBiO3 was narrower than that of NaBiO3, which was confirmed with density of states curves simulated by first-principles density functional theory calculation. PMID:27243818

  2. Insertion of N2 into the Channels of AFI Zeolite under High Pressure.

    PubMed

    Lv, Hang; Yao, Mingguang; Li, Quanjun; Liu, Ran; Liu, Bo; Yao, Zhen; Liu, Dedi; Liu, Zhaodong; Liu, Jing; Chen, Zhiqiang; Zou, Bo; Cui, Tian; Liu, Bingbing

    2015-01-01

    We present an experimental study of a new hybrid material where nitrogen is encapsulated in the channels of porous zeolite AlPO4-5 (AFI) single crystals by a high-pressure method. The high-pressure behavior of nitrogen confined inside the AFI nano-channels is then investigated by Raman spectroscopy up to 44 GPa. Under pressure, the Raman modes of confined nitrogen show behaviors different from those of the bulk nitrogen. After the return to atmospheric pressure, it is demonstrated that non-gaseous nitrogen can be effectively stabilized by being confined inside the intact AFI sample. This result provides new insight into nitrogen capture and storage technologies.

  3. Chemistry Notes.

    ERIC Educational Resources Information Center

    School Science Review, 1981

    1981-01-01

    Outlines laboratory procedures, demonstrations, teaching suggestions, and content information related to chemistry. Topics include polarizing power; calorimetry and momentum; microcomputers in school chemistry; a constant-volume dispenser for liquids, floating magnets, and crystal lattices; preparation of chromium; and solvent polarity and…

  4. High-pressure powder x-ray diffraction study of EuVO{sub 4}

    SciTech Connect

    Garg, Alka B.; Errandonea, D.

    2015-03-15

    The high-pressure structural behavior of europium orthovanadate has been studied using in-situ, synchrotron based, high-pressure x-ray powder diffraction technique. Angle-dispersive x-ray diffraction measurements were carried out at room temperature up to 34.7 GPa using a diamond-anvil cell, extending the pressure range reported in previous experiments. We confirmed the occurrence of zircon–scheelite phase transition at 6.8 GPa and the coexistence of low- and high-pressure phases up to 10.1 GPa. In addition, clear evidence of a scheelite–fregusonite transition is found at 23.4 GPa. The fergusonite structure remains stable up to 34.7 GPa, the highest pressure reached in the present measurements. A partial decomposition of EuVO{sub 4} was also observed from 8.1 to 12.8 GPa; however, this fact did not preclude the identification of the different crystal structures of EuVO{sub 4}. The crystal structures of the different phases have been Rietveld refined and their equations of state (EOS) have been determined. The results are compared with the previous experimental data and theoretical calculations. - Graphical abstract: The high-pressure structural sequence of EuVO{sub 4}. - Highlights: • EuVO{sub 4} is studied under pressure up to 35 GPa using synchrotron XRD. • The zircón–scheelite–fergusonite structural sequence is observed. • Crystal structures are refined and equations of state determined.

  5. High Pressure Electrochemistry: Application to silver halides

    NASA Astrophysics Data System (ADS)

    Havens, K.; Kavner, A.

    2007-12-01

    Electron and ion charge transfer processes help govern electrical conductivity and diffusive mass and heat transport properties in deep Earth minerals. In an attempt to understand how pressure influences charge transfer behavior, the halide silver bromide (AgBr) was studied under the influence of an electric potential difference applied across two electrodes in a diamond anvil cell. This study follows our previous work on AgI, which was found to dissociate to molecular iodine and silver metal due to pressure and voltage influences. We performed two sets of experiments on AgBr at high pressure in a diamond anvil cell: electrochemical dissociation and electrical resistance measurements. In our study, we were able to electrochemically dissociate AgBr at pressures of 0.25-1.6 GPa by applying a voltage across the electrodes in the diamond cell sample chamber. Ag metal grew visibly on the negatively-charged electrode when voltages varying from 0.1 V to 5 V were applied. Additionally, a dark blue color appeared in low pressure areas of the diamond cell and grew darker from both voltage application and light exposure, indicating photochemical effects. We found that the reaction area and growth rate of both metal and dark blue color strongly increased as voltage increased, but tended to decrease with greater pressure. The resistance across the cell was observed to be influenced by both pressure and light exposure. As the AgBr sample was exposed to visible light, the resistance dropped instantaneously, and after the light was turned off, the resistance increased on a timescale of 10's of seconds to minutes. Notably, at higher pressures, the AgBr showed less photosensitivity. Exploration of these metal halide systems has many potential applications. First, these experiments explore the pressure-dependence of photochemical and photovoltaic processes, and may spur development of pressure-tuned microscale electronic devices. Second, these experimental results can be used to

  6. An ionic model of the crystal chemistry in the superconducting copper oxides of stoichiometry (RE) 2CuO 4

    NASA Astrophysics Data System (ADS)

    Bringley, Joseph F.; Trail, Steven S.; Scott, Bruce A.

    1990-06-01

    The mixed rare earth systems La 2- xRE xCuO 4 (RE = NdY) have been investigated in an effort to understand the crystal chemistry and phase stability of the related K 2NiF 4 ( T)-, Nd 2CuO 4 ( T')-, and hybrid T∗-type structures. The crystal chemistry of these (RE) 2CuO 4 phases is then discussed on the basis of a simple ionic model. A definitive correlation between the size of the RE cation and structure is found, and the stability limits of the T, T', and T∗ phases are defined in terms of a perovskite-like tolerance factor ( t). The T structure is found to exist for 0.87 ≤ t ≤ 0.99, while the T' structure occurs for 0.83 ≤ t ≤ 0.86. The smallest rare earths, or t ≤ 0.83, do not form stable (RE) 2CuO 4 compounds. The T∗ structure occurs in a very narrow region adjacent to the boundary of the {T}/{T'} stability field and is seen as resulting from a thermodynamic competition between the T and T' structures, due to a tendency toward {T}/{T'}- site ordering. Metastable T∗ phases are observed for the larger rare earths Nd, Eu, and Gd, but the structure becomes quite stable for RE = Tb, Dy. Where both T' and T∗ are of comparable thermodynamic stability, high oxygen activity is found to stabilize T∗, whereas low oxygen activity favors T'. The role of RE coordination preferences and the influence of the REO framework upon the structure and properties of these materials are discussed.

  7. Crystals size and surface chemistry dependent phase diagram for nanocrystals of rutile and anatase: Experimental studies and computer modeling

    NASA Astrophysics Data System (ADS)

    Xu, H.; Barnard, A. S.

    2008-12-01

    It is well known that rutile is the thermodynamically stable phase of TiO2 under ambient conditions at the macroscale, and that anatase is the thermodynamically stable phase at the nanoscale. Both anatase and rutile have superior performance in a range of advanced photochemical applications. It is important for our understanding of the stability of nanostructures in different chemical and physical environments, because both rutile and anatase nanocrystals are used in different chemical and engineering environments. Using a size-, shape- and temperature-dependent thermodynamic model we have generated the first phase diagram for anatase and rutile nanocrystals by incorporating more experimentally relevant parameters (both the equilibrium shape and surface chemistry). Results from hydrothermal synthesis and DFT-based computer modeling show acidic environment favors rutile formation. The acidic solution also favors OH2-terminated surfaces of both anatase and rutile. The boundary between rutile an danatase ranges from ~ 10 nm to ~ 50 nm, depending on temperature and surface composition. The calculated phase map indicates that the equilibrium boundary between anatase and rutile nano-crystals is surface charge chemistry dependent, which relates to both their formation and post-synthesis environments.

  8. Thermal chemistry of copper(I)-N,N '-di-sec-butylacetamidinate on Cu(110) single-crystal surfaces

    SciTech Connect

    Ma Qiang; Zaera, Francisco; Gordon, Roy G.

    2012-01-15

    The surface chemistry of copper(I)-N,N'-di-sec-butylacetamidinate on Cu(110) single-crystal surfaces has been characterized under ultrahigh vacuum by temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy. A series of thermal stepwise conversions were identified, starting with the partial dissociative adsorption of the copper acetamidinate dimers into a mixture of monomers and dimers on the surface. An early dissociation of a C-N bond leads to the production of N-sec-butylacetamidine, which is detected in TPD experiments in three temperature regimes, the last one centered around 480 K. Butene, and a small amount of butane, is also detected above approximately 500 K, and hydrogen production, an indication of dehydrogenation of surface fragments, is observed at 460, 550 and 670 K. In total, only about 10% of the initial copper(I)-N,N'-di-sec-butylacetamidinate adsorbed monolayer decomposes, and only about {approx}3% of carbon is left behind on the surface after heating to high temperatures. The implications of this surface chemistry to the design of chemical film growth processes using copper acetamidinates as precursors are discussed.

  9. High pressure electrides: a predictive chemical and physical theory.

    PubMed

    Miao, Mao-Sheng; Hoffmann, Roald

    2014-04-15

    Electrides, in which electrons occupy interstitial regions in the crystal and behave as anions, appear as new phases for many elements (and compounds) under high pressure. We propose a unified theory of high pressure electrides (HPEs) by treating electrons in the interstitial sites as filling the quantized orbitals of the interstitial space enclosed by the surrounding atom cores, generating what we call an interstitial quasi-atom, ISQ. With increasing pressure, the energies of the valence orbitals of atoms increase more significantly than the ISQ levels, due to repulsion, exclusion by the atom cores, effectively giving the valence electrons less room in which to move. At a high enough pressure, which depends on the element and its orbitals, the frontier atomic electron may become higher in energy than the ISQ, resulting in electron transfer to the interstitial space and the formation of an HPE. By using a He lattice model to compress (with minimal orbital interaction at moderate pressures between the surrounding He and the contained atoms or molecules) atoms and an interstitial space, we are able to semiquantitatively explain and predict the propensity of various elements to form HPEs. The slopes in energy of various orbitals with pressure (s > p > d) are essential for identifying trends across the entire Periodic Table. We predict that the elements forming HPEs under 500 GPa will be Li, Na (both already known to do so), Al, and, near the high end of this pressure range, Mg, Si, Tl, In, and Pb. Ferromagnetic electrides for the heavier alkali metals, suggested by Pickard and Needs, potentially compete with transformation to d-group metals. PMID:24702165

  10. Robert Boyle's chiral crystal chemistry: computational re-evaluation of enantioselective adsorption on quartz.

    PubMed

    Kahr, Bart; Chittenden, Brianne; Rohl, Andrew

    2006-02-01

    While searching for early examples of interactions of organic chromophores with minerals in the context of a systematic study of the process of dyeing crystals, we came across Robert Boyle's description of an experiment that may have been evidence of the enantioselective adsorption of a natural product, carminic acid (7-beta-D-glucopyranosyl-9,10-dihydro-3,5,6,8-tetrahydroxy-1-methyl-9,10-dioxo-2-anthracenecarboxylic acid), to the chiral surfaces of alpha-quartz, three centuries before such interactions became the subject of active chemical investigations. In order to determine whether Boyle did indeed observe enantioselective adsorption--albeit unbeknownst to him--we attempted to dye quartz with carminic acid according to his recipe. Quartz adsorbs carminic acid only because on heating it develops a network of microfissures that adsorb dye. This process depends on capillarity, not on specific non-covalent interactions; there is no evidence of enantioselectivity adsorption to heated crystals or enantioselective epitaxy to unheated crystals. These failures changed the focus of our inquiry: Why have almost all attempts to demonstrate the enantioselective adsorption of additives to quartz crystal surfaces been generally confounding and equivocal? In order to answer this question, we complement our experimental historical re-investigation with contemporary computational techniques for modeling crystal surface structure and the adsorption of additives. Minimizations of the energies associated with the adsorption of carminic acid to relaxed, hydrated d- and l-quartz {10(-)0} surfaces are analyzed in light of quartz's abysmal record as an enantioselective stationary phase.

  11. Robert Boyle's chiral crystal chemistry: computational re-evaluation of enantioselective adsorption on quartz.

    PubMed

    Kahr, Bart; Chittenden, Brianne; Rohl, Andrew

    2006-02-01

    While searching for early examples of interactions of organic chromophores with minerals in the context of a systematic study of the process of dyeing crystals, we came across Robert Boyle's description of an experiment that may have been evidence of the enantioselective adsorption of a natural product, carminic acid (7-beta-D-glucopyranosyl-9,10-dihydro-3,5,6,8-tetrahydroxy-1-methyl-9,10-dioxo-2-anthracenecarboxylic acid), to the chiral surfaces of alpha-quartz, three centuries before such interactions became the subject of active chemical investigations. In order to determine whether Boyle did indeed observe enantioselective adsorption--albeit unbeknownst to him--we attempted to dye quartz with carminic acid according to his recipe. Quartz adsorbs carminic acid only because on heating it develops a network of microfissures that adsorb dye. This process depends on capillarity, not on specific non-covalent interactions; there is no evidence of enantioselectivity adsorption to heated crystals or enantioselective epitaxy to unheated crystals. These failures changed the focus of our inquiry: Why have almost all attempts to demonstrate the enantioselective adsorption of additives to quartz crystal surfaces been generally confounding and equivocal? In order to answer this question, we complement our experimental historical re-investigation with contemporary computational techniques for modeling crystal surface structure and the adsorption of additives. Minimizations of the energies associated with the adsorption of carminic acid to relaxed, hydrated d- and l-quartz {10(-)0} surfaces are analyzed in light of quartz's abysmal record as an enantioselective stationary phase. PMID:16385623

  12. High Pressure Research With the Diamond Anvil Cell at GSECARS

    NASA Astrophysics Data System (ADS)

    Shen, G.; Prakapenka, V.; Rivers, M.; Sutton, S.; Eng, P.

    2002-12-01

    The high pressure diamond anvil cell (DAC) program at GSECARS started with a combination of commissioning and experiments from December 1996. Since early 1999, it has been running proposal-based experiments full time. These experiments address key geochemical and geophysical problems in the Earth's deep interior. Research topics include: - equations of state, crystal structures, and phase relations of mantle and core materials, - high PT studies of melts, glasses, and other non-crystalline materials, - properties of light elements relevant to the outer planets, - rheology of minerals at high pressure, - pressure effects on magnetic and electronic properties of deep Earth materials, - ultra high pressure-temperature experiments, - kinetics of phase transitions and chemical reactions at high PT. Meanwhile, major technical advances have been made, providing a unique facility at the third generation synchrotron source. Some examples include: - providing small and intense x-ray beam suitable for miniature sample in the diamond anvil cell (beam size <10 μm at FWHM and <30 μm at FW1%M), - a double-sided laser heating system combined with x-ray area detectors for high-resolution diffraction applications at high PT and a feedback system incorporated to dramatically improve long-term temperature stability, - the implementation of amorphous boron gaskets, making it possible to use x-ray area detectors for strain measurements and resulting in high quality texture and rheology investigations, - using x-radiography in the DAC for accurate melt volume determinations, - a high-resolution Rowland circle spectrometer for high resolution spectroscopic experiments, - a pair of 1-meter long focusing mirrors focusing almost the entire undulator x-ray beam to a size of 30x70 μm FWHM, making it possible for collecting weak signals in x-ray inelastic scattering experiments. These developments will be presented together with some highlights of scientific results. Acknowledgments: We

  13. The Incorporation of Single Crystal X-Ray Diffraction into the Undergraduate Chemistry Curriculum Using Internet-Facilitated Remote Diffractometer Control

    ERIC Educational Resources Information Center

    Szalay, P. S.; Hunter, A. D.; Zeller, M.

    2005-01-01

    The benefits of integrating single crystal X-ray diffraction into the curricula of the disciplines of science such as chemistry, biology, biochemistry physics, and many more are addressed. The results showed that students were able to complete all report requirements with the aid of handouts and instructor inputs, and remote control of the…

  14. High pressure waterjet cutting industrial needs survey

    NASA Astrophysics Data System (ADS)

    Klavuhn, John; Baker, Bruce

    1989-08-01

    The results are presented of a survey conducted by personnel of the National Center for Excellence in Metalworking Technology (NCEMT) to assess the industrial needs in high pressure water jet cutting (WJC) technology. Survey forms were mailed to approximately 1400 individuals obtained from three mailing lists. The respondents included approximately 200 individuals associated with a variety of industries: 12 percent were WJC equipment suppliers, 40 percent were WJC users, and 48 percent were neither suppliers nor users. The survey addressed five specific areas of WJC technology: research and development, standards, systems, new products, and training and service. Results show that the need having the highest priority is the establishment of a database on WJC that contains the cutting parameters for a wide range of materials. Associated with this objective is the expressed need for an independent demonstration and test center for testing, data generation and operator training. A further need was found for establishing organized efforts in hardware development and research in mechanisms of cutting.

  15. Stable magnesium peroxide at high pressure.

    PubMed

    Lobanov, Sergey S; Zhu, Qiang; Holtgrewe, Nicholas; Prescher, Clemens; Prakapenka, Vitali B; Oganov, Artem R; Goncharov, Alexander F

    2015-09-01

    Rocky planets are thought to comprise compounds of Mg and O as these are among the most abundant elements, but knowledge of their stable phases may be incomplete. MgO is known to be remarkably stable to very high pressure and chemically inert under reduced condition of the Earth's lower mantle. However, in exoplanets oxygen may be a more abundant constituent. Here, using synchrotron x-ray diffraction in laser-heated diamond anvil cells, we show that MgO and oxygen react at pressures above 96 GPa and T = 2150 K with the formation of I4/mcm MgO2. Raman spectroscopy detects the presence of a peroxide ion (O2(2-)) in the synthesized material as well as in the recovered specimen. Likewise, energy-dispersive x-ray spectroscopy confirms that the recovered sample has higher oxygen content than pure MgO. Our finding suggests that MgO2 may be present together or instead of MgO in rocky mantles and rocky planetary cores under highly oxidized conditions.

  16. Stable magnesium peroxide at high pressure

    NASA Astrophysics Data System (ADS)

    Lobanov, Sergey S.; Zhu, Qiang; Holtgrewe, Nicholas; Prescher, Clemens; Prakapenka, Vitali B.; Oganov, Artem R.; Goncharov, Alexander F.

    2015-09-01

    Rocky planets are thought to comprise compounds of Mg and O as these are among the most abundant elements, but knowledge of their stable phases may be incomplete. MgO is known to be remarkably stable to very high pressure and chemically inert under reduced condition of the Earth’s lower mantle. However, in exoplanets oxygen may be a more abundant constituent. Here, using synchrotron x-ray diffraction in laser-heated diamond anvil cells, we show that MgO and oxygen react at pressures above 96 GPa and T = 2150 K with the formation of I4/mcm MgO2. Raman spectroscopy detects the presence of a peroxide ion (O22-) in the synthesized material as well as in the recovered specimen. Likewise, energy-dispersive x-ray spectroscopy confirms that the recovered sample has higher oxygen content than pure MgO. Our finding suggests that MgO2 may be present together or instead of MgO in rocky mantles and rocky planetary cores under highly oxidized conditions.

  17. Stable magnesium peroxide at high pressure.

    PubMed

    Lobanov, Sergey S; Zhu, Qiang; Holtgrewe, Nicholas; Prescher, Clemens; Prakapenka, Vitali B; Oganov, Artem R; Goncharov, Alexander F

    2015-01-01

    Rocky planets are thought to comprise compounds of Mg and O as these are among the most abundant elements, but knowledge of their stable phases may be incomplete. MgO is known to be remarkably stable to very high pressure and chemically inert under reduced condition of the Earth's lower mantle. However, in exoplanets oxygen may be a more abundant constituent. Here, using synchrotron x-ray diffraction in laser-heated diamond anvil cells, we show that MgO and oxygen react at pressures above 96 GPa and T = 2150 K with the formation of I4/mcm MgO2. Raman spectroscopy detects the presence of a peroxide ion (O2(2-)) in the synthesized material as well as in the recovered specimen. Likewise, energy-dispersive x-ray spectroscopy confirms that the recovered sample has higher oxygen content than pure MgO. Our finding suggests that MgO2 may be present together or instead of MgO in rocky mantles and rocky planetary cores under highly oxidized conditions. PMID:26323635

  18. Amorphous boron nitride at high pressure

    NASA Astrophysics Data System (ADS)

    Durandurdu, Murat

    2016-06-01

    The pressure-induced phase transformation in hexagonal boron nitrite and amorphous boron nitrite is studied using ab initio molecular dynamics simulations. The hexagonal-to-wurtzite phase transformation is successfully reproduced in the simulation with a transformation mechanism similar to one suggested in experiment. Amorphous boron nitrite, on the other hand, gradually transforms to a high-density amorphous phase with the application of pressure. This phase transformation is irreversible because a densified amorphous state having both sp3 and sp2 bonds is recovered upon pressure release. The high-density amorphous state mainly consists of sp3 bonds and its local structure is quite similar to recently proposed intermediate boron nitrite phases, in particular tetragonal structure (P42/mnm), rather than the known the wurtzite or cubic boron nitrite due to the existence of four membered rings and edge sharing connectivity. On the basis of this finding we propose that amorphous boron nitrite might be best candidate as a starting structure to synthesize the intermediate phase(s) at high pressure and temperature (probably below 800 °C) conditions.

  19. Stable magnesium peroxide at high pressure

    PubMed Central

    Lobanov, Sergey S.; Zhu, Qiang; Holtgrewe, Nicholas; Prescher, Clemens; Prakapenka, Vitali B.; Oganov, Artem R.; Goncharov, Alexander F.

    2015-01-01

    Rocky planets are thought to comprise compounds of Mg and O as these are among the most abundant elements, but knowledge of their stable phases may be incomplete. MgO is known to be remarkably stable to very high pressure and chemically inert under reduced condition of the Earth’s lower mantle. However, in exoplanets oxygen may be a more abundant constituent. Here, using synchrotron x-ray diffraction in laser-heated diamond anvil cells, we show that MgO and oxygen react at pressures above 96 GPa and T = 2150 K with the formation of I4/mcm MgO2. Raman spectroscopy detects the presence of a peroxide ion (O22−) in the synthesized material as well as in the recovered specimen. Likewise, energy-dispersive x-ray spectroscopy confirms that the recovered sample has higher oxygen content than pure MgO. Our finding suggests that MgO2 may be present together or instead of MgO in rocky mantles and rocky planetary cores under highly oxidized conditions. PMID:26323635

  20. High-pressure structural properties of tetramethylsilane

    NASA Astrophysics Data System (ADS)

    Zhen-Xing, Qin; Xiao-Jia, Chen

    2016-02-01

    High-pressure structural properties of tetramethylsilane are investigated by synchrotron powder x-ray diffraction at pressures up to 31.1 GPa and room temperature. A phase with the space group of Pnma is found to appear at 4.2 GPa. Upon compression, the compound transforms to two following phases: the phase with space groups of P21/c at 9.9 GPa and the phase with P2/m at 18.2 GPa successively via a transitional phase. The unique structural character of P21/c supports the phase stability of tetramethylsilane without possible decomposition upon heavy compression. The appearance of the P2/m phase suggests the possible realization of metallization for this material at higher pressure. Project supported by the Cultivation Fund of the Key Scientific and Technical Innovation Project from Ministry of Education of China (Grant No. 708070), the Fundamental Research Funds for the Central Universities, South China University of Technology (Grant No. 2014ZZ0069), the National Natural Science Foundation of China (Grant No. 51502189), and the Doctoral Project of Taiyuan University of Science and Technology, China (Grant No. 20132010).

  1. Picosecond High Pressure Gas Switch experiment

    SciTech Connect

    Cravey, W.R.; Freytag, E.K.; Goerz, D.A.; Poulsen, P.; Pincosy, P.A.

    1993-08-01

    A high Pressure Gas Switch has been developed and tested at LLNL. Risetimes on the order of 200 picoseconds have been observed at 1 kHz prf and 1 atmosphere pressures. Calculations show that switching closure times on the order of tens of picoseconds can be achieved at higher pressures and electric fields. A voltage hold-off of 1 MV/cm has been measured at 10 atmospheres and several MV/cm appears possible with the HPGS. With such high electric field levels, energy storage of tens of Joules in a reasonably sized package is achievable. Initial HPGS performance has been characterized using the WASP pulse generator at LLNL. A detailed description of the switch used for initial testing is given. Switch recovery times of 1-ms have been measured at 1 atmosphere. Data on the switching uniformity, voltage hold-off recovery, and pulse repeatability, is presented. In addition, a physics switch model is described and results are compared with experimental data. Modifications made to the WASP HV pulser in order to drive the HPGS will also be discussed. Recovery times of less than 1 ms were recorded without gas flow in the switch chambers. Low pressure synthetic air was used as the switch dielectric. Longer recovery times were required when it was necessary to over-voltage the switch.

  2. Glow discharges in high pressure microhollow cathodes

    NASA Astrophysics Data System (ADS)

    Boeuf, J.-P.; Pitchford, L. C.; Schoenbach, K. H.

    2004-09-01

    We have developed a model of high-pressure, microhollow cathode discharges (MHCDs) which has been used to predict the electrical characteristics and other properties of these discharges for comparison with experiment. The configuration studied here is an anode/dielectric/cathode sandwich in which a cylindrical hole with a diameter of some 100's of microns is pierced in the dielectric and in the cathode. Results from the model calculations in xenon at 100 torr and higher pressures show that the positive V-I (voltage-current) characteristic observed experimentally at low current corresponds to an abnormal glow discharge inside the cathode hole. At higher current, the V-I characteristic is that of a normal to slightly abnormal glow discharge between the anode and the outer face of the cathode. The change in slope of the V-I characteristic is consistent with experiment (provided metastables are taken into account). This shape was previously attribed to the onset of the classical hollow cathode effect, but we find no hollow cathode effect for pressures above about 30 torr and for 200 micron hole diameters.

  3. A New Scanning Tunneling Microscope Reactor Used for High Pressure and High Temperature Catalysis Studies

    SciTech Connect

    Tao, Feng; Tang, David C.; Salmeron, Miquel; Somorjai, Gabor A.

    2008-05-12

    We present the design and performance of a home-built high-pressure and high-temperature reactor equipped with a high-resolution scanning tunneling microscope (STM) for catalytic studies. In this design, the STM body, sample, and tip are placed in a small high pressure reactor ({approx}19 cm{sup 3}) located within an ultrahigh vacuum (UHV) chamber. A sealable port on the wall of the reactor separates the high pressure environment in the reactor from the vacuum environment of the STM chamber and permits sample transfer and tip change in UHV. A combination of a sample transfer arm, wobble stick, and sample load-lock system allows fast transfer of samples and tips between the preparation chamber, high pressure reactor, and ambient environment. This STM reactor can work as a batch or flowing reactor at a pressure range of 10{sup -13} to several bars and a temperature range of 300-700 K. Experiments performed on two samples both in vacuum and in high pressure conditions demonstrate the capability of in situ investigations of heterogeneous catalysis and surface chemistry at atomic resolution at a wide pressure range from UHV to a pressure higher than 1 atm.

  4. Better Actuation Through Chemistry: Using Surface Coatings to Create Uniform Director Fields in Nematic Liquid Crystal Elastomers.

    PubMed

    Xia, Yu; Lee, Elaine; Hu, Hao; Gharbi, Mohamed Amine; Beller, Daniel A; Fleischmann, Eva-Kristina; Kamien, Randall D; Zentel, Rudolf; Yang, Shu

    2016-05-18

    Controlling the molecular alignment of liquid crystal monomers (LCMs) within nano- and microstructures is essential in manipulating the actuation behavior of nematic liquid crystal elastomers (NLCEs). Here, we study how to induce uniformly vertical alignment of nematic LCMs within a micropillar array to maximize the macroscopic shape change using surface chemistry. Landau-de Gennes numerical modeling suggests that it is difficult to perfectly align LCMs vertically in every pore within a poly(dimethylsiloxane) (PDMS) mold with porous channels during soft lithography. In an untreated PDMS mold that provides homeotropic anchoring of LCMs, a radially escaped configuration of LCMs is observed. Vertically aligned LCMs, a preferred configuration for actuation, are only observed when using a PDMS mold with planar anchoring. Guided by the numerical modeling, we coat the PDMS mold with a thin layer of poly(2-hydroxyethyl methacrylate) (PHEMA), leading to planar anchoring of LCM. Confirmed by polarized optical microscopy, we observe monodomains of vertically aligned LCMs within the mold, in agreement with modeling. After curing and peeling off the mold, the resulting NLCE micropillars showed a relatively large and reversible radial strain (∼30%) when heated above the nematic to isotropic transition temperature. PMID:27152975

  5. Toxicity of TiO2 Nanoparticles to Escherichia coli: Effects of Particle Size, Crystal Phase and Water Chemistry

    PubMed Central

    Lin, Xiuchun; Li, Jingyi; Ma, Si; Liu, Gesheng; Yang, Kun; Tong, Meiping; Lin, Daohui

    2014-01-01

    Controversial and inconsistent results on the eco-toxicity of TiO2 nanoparticles (NPs) are commonly found in recorded studies and more experimental works are therefore warranted to elucidate the nanotoxicity and its underlying precise mechanisms. Toxicities of five types of TiO2 NPs with different particle sizes (10∼50 nm) and crystal phases were investigated using Escherichia coli as a test organism. The effect of water chemistry on the nanotoxicity was also examined. The antibacterial effects of TiO2 NPs as revealed by dose-effect experiments decreased with increasing particle size and rutile content of the TiO2 NPs. More bacteria could survive at higher solution pH (5.0–10.0) and ionic strength (50–200 mg L−1 NaCl) as affected by the anatase TiO2 NPs. The TiO2 NPs with anatase crystal structure and smaller particle size produced higher content of intracellular reactive oxygen species and malondialdehyde, in line with their greater antibacterial effect. Transmission electron microscopic observations showed the concentration buildup of the anatase TiO2 NPs especially those with smaller particle sizes on the cell surfaces, leading to membrane damage and internalization. These research results will shed new light on the understanding of ecological effects of TiO2 NPs. PMID:25310452

  6. Better Actuation Through Chemistry: Using Surface Coatings to Create Uniform Director Fields in Nematic Liquid Crystal Elastomers.

    PubMed

    Xia, Yu; Lee, Elaine; Hu, Hao; Gharbi, Mohamed Amine; Beller, Daniel A; Fleischmann, Eva-Kristina; Kamien, Randall D; Zentel, Rudolf; Yang, Shu

    2016-05-18

    Controlling the molecular alignment of liquid crystal monomers (LCMs) within nano- and microstructures is essential in manipulating the actuation behavior of nematic liquid crystal elastomers (NLCEs). Here, we study how to induce uniformly vertical alignment of nematic LCMs within a micropillar array to maximize the macroscopic shape change using surface chemistry. Landau-de Gennes numerical modeling suggests that it is difficult to perfectly align LCMs vertically in every pore within a poly(dimethylsiloxane) (PDMS) mold with porous channels during soft lithography. In an untreated PDMS mold that provides homeotropic anchoring of LCMs, a radially escaped configuration of LCMs is observed. Vertically aligned LCMs, a preferred configuration for actuation, are only observed when using a PDMS mold with planar anchoring. Guided by the numerical modeling, we coat the PDMS mold with a thin layer of poly(2-hydroxyethyl methacrylate) (PHEMA), leading to planar anchoring of LCM. Confirmed by polarized optical microscopy, we observe monodomains of vertically aligned LCMs within the mold, in agreement with modeling. After curing and peeling off the mold, the resulting NLCE micropillars showed a relatively large and reversible radial strain (∼30%) when heated above the nematic to isotropic transition temperature.

  7. Molecular Docking Study of Conformational Polymorph: Building Block of Crystal Chemistry

    PubMed Central

    Dubey, Rashmi; Tewari, Ashish Kumar; Singh, Ved Prakash; Singh, Praveen; Dangi, Jawahar Singh; Puerta, Carmen; Valerga, Pedro; Kant, Rajni

    2013-01-01

    Two conformational polymorphs of novel 2-[2-(3-cyano-4,6-dimethyl-2-oxo-2H-pyridin-1-yl)-ethoxy]-4,6-dimethyl nicotinonitrile have been developed. The crystal structure of both polymorphs (1a and 1b) seems to be stabilized by weak interactions. A difference was observed in the packing of both polymorphs. Polymorph 1b has a better binding affinity with the cyclooxygenase (COX-2) receptor than the standard (Nimesulide). PMID:24250264

  8. Distortions and stabilization of simple-cubic calcium at high pressure and low temperature

    SciTech Connect

    Mao, Wendy L.; Wang, Lin; Ding, Yang; Yang, Wenge; Liu, Wenjun; Kim, Duck Young; Luo, Wei; Ahuja, R.; Meng, Yue; Sinogeikin, Stanislav V.; Shu, Jinfu; Mao, Ho-kwang

    2010-06-01

    Ca-III, the first superconducting calcium phase under pressure, was identified as simple-cubic (sc) by previous X-ray diffraction (XRD) experiments. In contrast, all previous theoretical calculations showed that sc had a higher enthalpy than many proposed structures and had an imaginary (unstable) phonon branch. By using our newly developed submicrometer high-pressure single-crystal XRD, cryogenic high-pressure XRD, and theoretical calculations, we demonstrate that Ca-III is neither exactly sc nor any of the lower-enthalpy phases, but sustains the sc-like, primitive unit by a rhombohedral distortion at 300 K and a monoclinic distortion below 30 K. This surprising discovery reveals a scenario that the high-pressure structure of calcium does not go to the zero-temperature global enthalpy minimum but is dictated by high-temperature anharmonicity and low-temperature metastability fine-tuned with phonon stability at the local minimum.

  9. Distortions and Stabilization of Simple Cubic Calcium at High Pressure and Low Temperature

    SciTech Connect

    Veith, Alison A.

    2012-04-18

    Ca-III, the first superconducting calcium phase under pressure, was identified as simple-cubic (sc) by previous X-ray diffraction (XRD) experiments. In contrast, all previous theoretical calculations showed that sc had a higher enthalpy than many proposed structures and had an imaginary (unstable) phonon branch. By using our newly developed submicrometer high-pressure single-crystal XRD, cryogenic high-pressure XRD, and theoretical calculations, we demonstrate that Ca-III is neither exactly sc nor any of the lower-enthalpy phases, but sustains the sc-like, primitive unit by a rhombohedral distortion at 300 K and a monoclinic distortion below 30 K. This surprising discovery reveals a scenario that the high-pressure structure of calcium does not go to the zero-temperature global enthalpy minimum but is dictated by high-temperature anharmonicity and low-temperature metastability fine-tuned with phonon stability at the local minimum.

  10. On the relative stability of orthorhombic and hcp phases of beryllium at high pressures

    NASA Astrophysics Data System (ADS)

    Palanivel, B.; Rao, R. S.; Godwal, B. K.; Sikka, S. K.

    2000-10-01

    High-pressure electronic properties of Be have been investigated theoretically by means of ab initio electronic structure calculations. The calculations have been carried out by the semi-relativistic full-potential, linear muffin-tin orbital (FPLMTO) method, within the local density approximation. The crystal structure stability among the hcp, bcc and orthorhombic (distorted hcp) phases has been studied as a function of compression. The bcc structure is found to be energetically stable at pressures above 180 GPa. From the results of our calculations, the orthorhombic phase cannot occur as an intermediate phase between the ambient pressure hcp phase and the high-pressure bcc structure. Our work thus suggests the need for more accurate high-pressure x-ray data.

  11. Pressure Dome for High-Pressure Electrolyzer

    NASA Technical Reports Server (NTRS)

    Norman, Timothy; Schmitt, Edwin

    2012-01-01

    A high-strength, low-weight pressure vessel dome was designed specifically to house a high-pressure [2,000 psi (approx. = 13.8 MPa)] electrolyzer. In operation, the dome is filled with an inert gas pressurized to roughly 100 psi (approx. = 690 kPa) above the high, balanced pressure product oxygen and hydrogen gas streams. The inert gas acts to reduce the clamping load on electrolyzer stack tie bolts since the dome pressure acting axially inward helps offset the outward axial forces from the stack gas pressure. Likewise, radial and circumferential stresses on electrolyzer frames are minimized. Because the dome is operated at a higher pressure than the electrolyzer product gas, any external electrolyzer leak prevents oxygen or hydrogen from leaking into the dome. Instead the affected stack gas stream pressure rises detectably, thereby enabling a system shutdown. All electrical and fluid connections to the stack are made inside the pressure dome and require special plumbing and electrical dome interfaces for this to be accomplished. Further benefits of the dome are that it can act as a containment shield in the unlikely event of a catastrophic failure. Studies indicate that, for a given active area (and hence, cell ID), frame outside diameter must become ever larger to support stresses at higher operating pressures. This can lead to a large footprint and increased costs associated with thicker and/or larger diameter end-plates, tie-rods, and the frames themselves. One solution is to employ rings that fit snugly around the frame. This complicates stack assembly and is sometimes difficult to achieve in practice, as its success is strongly dependent on frame and ring tolerances, gas pressure, and operating temperature. A pressure dome permits an otherwise low-pressure stack to operate at higher pressures without growing the electrolyzer hardware. The pressure dome consists of two machined segments. An O-ring is placed in an O-ring groove in the flange of the bottom

  12. Gas Hydrate Stability at Low Temperatures and High Pressures with Applications to Mars and Europa

    NASA Technical Reports Server (NTRS)

    Marion, G. M.; Kargel, J. S.; Catling, D. C.

    2004-01-01

    Gas hydrates are implicated in the geochemical evolution of both Mars and Europa [1- 3]. Most models developed for gas hydrate chemistry are based on the statistical thermodynamic model of van der Waals and Platteeuw [4] with subsequent modifications [5-8]. None of these models are, however, state-of-the-art with respect to gas hydrate/electrolyte interactions, which is particularly important for planetary applications where solution chemistry may be very different from terrestrial seawater. The objectives of this work were to add gas (carbon dioxide and methane) hydrate chemistries into an electrolyte model parameterized for low temperatures and high pressures (the FREZCHEM model) and use the model to examine controls on gas hydrate chemistries for Mars and Europa.

  13. Origins of life and biochemistry under high-pressure conditions.

    PubMed

    Daniel, Isabelle; Oger, Philippe; Winter, Roland

    2006-10-01

    Life on Earth can be traced back to as far as 3.8 billion years (Ga) ago. The catastrophic meteoritic bombardment ended between 4.2 and 3.9 Ga ago. Therefore, if life emerged, and we know it did, it must have emerged from nothingness in less than 400 million years. The most recent scenarios of Earth accretion predict some very unstable physico-chemical conditions at the surface of Earth, which, in such a short time period, would impede the emergence of life from a proto-biotic soup. A possible alternative would be that life originated in the depth of the proto-ocean of the Hadean Earth, under high hydrostatic pressure. The large body of water would filter harmful radiation and buffer physico-chemical variations, and therefore would provide a more stable radiation-free environment for pre-biotic chemistry. After a short introduction to Earth history, the current tutorial review presents biological and physico-chemical arguments in support of high-pressure origin for life on Earth.

  14. A novel method to create molecular mixtures at high pressures

    NASA Astrophysics Data System (ADS)

    Pravica, Michael; Smith, Quinlan; Sneed, Daniel; Wang, Yonggang; White, Melanie

    2015-06-01

    We have successfully created a segregated mixture of hydrogen and oxygen at high pressure in a diamond anvil cell (DAC) using useful hard x-ray photochemistry. A keyhole (two holes connected by an opening) sample chamber was created in a metallic gasket to support two segregated powders of ammonia borane and potassium perchlorate in each hole, respectively at ~ 5.0 GPa. Both holes were separately irradiated with synchrotron hard x-rays to release molecular oxygen (via KClO4 + hv --> KCl +2O2) and molecular hydrogen respectively. Upon irradiation of the first KClO4 - containing hole, solid reddish-orange O2 appeared in the irradiated region and molecular oxygen diffused throughout the entire sample region. The second ammonia borane-containing hole was then irradiated and H2 was observed to form via Raman spectroscopy. Water was observed in the ammonia borane-containing hole and possibly (in the form of ice VII) in the second hole. This unique experiment demonstrates the ability to easily create solid mixtures of simple molecular systems via x-ray irradiation and then react them via further irradiation which will aid chemistry at extreme conditions. In particular, the ability to easily determine intermolecular potentials of detonation products and better understand diffusion and molecular mixing or segregation under extreme conditions.

  15. Cobalt ferrite nanoparticles under high pressure

    SciTech Connect

    Saccone, F. D.; Ferrari, S.; Grinblat, F.; Bilovol, V.; Errandonea, D.

    2015-08-21

    We report by the first time a high pressure X-ray diffraction and Raman spectroscopy study of cobalt ferrite (CoFe{sub 2}O{sub 4}) nanoparticles carried out at room temperature up to 17 GPa. In contrast with previous studies of nanoparticles, which proposed the transition pressure to be reduced from 20–27 GPa to 7.5–12.5 GPa (depending on particle size), we found that cobalt ferrite nanoparticles remain in the spinel structure up to the highest pressure covered by our experiments. In addition, we report the pressure dependence of the unit-cell parameter and Raman modes of the studied sample. We found that under quasi-hydrostatic conditions, the bulk modulus of the nanoparticles (B{sub 0} = 204 GPa) is considerably larger than the value previously reported for bulk CoFe{sub 2}O{sub 4} (B{sub 0} = 172 GPa). In addition, when the pressure medium becomes non-hydrostatic and deviatoric stresses affect the experiments, there is a noticeable decrease of the compressibility of the studied sample (B{sub 0} = 284 GPa). After decompression, the cobalt ferrite lattice parameter does not revert to its initial value, evidencing a unit cell contraction after pressure was removed. Finally, Raman spectroscopy provides information on the pressure dependence of all Raman-active modes and evidences that cation inversion is enhanced by pressure under non-hydrostatic conditions, being this effect not fully reversible.

  16. Effect of Water on High Pressure Olivine Slip Systems Activity

    NASA Astrophysics Data System (ADS)

    Girard, J.; Chen, J.; Raterron, P. C.; Holyoke, C. W.

    2012-12-01

    Seismologic studies of the Earth's shallow (Z<220 km) upper mantle have observed seismic anisotropy parallel to the direction of plate movement and have related this observation to alignment of olivine [100] due to shearing related to convection. These observations have been reinforced by field-based and experimental investigations which observe evidence that [100] slip is dominant at low pressures and water contents. However, direct evidence of the dominant slip system in the deep upper mantle (Z>220 km) is limited to a few studies of xenoliths which have LPOs consistent with [001] slip. Experimental studies of dry single crystals and polycrystals indicate that [001] slip becomes dominant at pressures > 8 GPa. However, water contents in the mantle are significant (~1000 H/106 Si) and we do not know how the slip systems of olivine are affected by higher water contents at high pressures. In order to investigate the effect of pressure on slip systems activities in olivine deformed in wet conditions, deformation experiments were carried out on single crystals, at pressure ranging from 4 to 8 GPa and temperature between 1373 and 1473 K in the Deformation-DIA apparatus (D-DIA) of the X17B2 beamline of the NSLS (NY, USA). Specimen were deformed in uniaxial compression along [110]c, [011]c and [101]c crystallographic directions, promoting the activation of, respectively, [100](010), [001](010) slip systems, and simultaneously [100](001) and [001](100) slip systems. Talc sleeves about the annulus of the single crystals were used as source of water during deformation. In addition, run products investigation using a micro-focused IR beam at the U2 beamline enables accurate mapping of the water content across the deformed single crystals using FTIR spectroscopy, while specimen deformation microstructures were investigated by TEM. We observe a slip-system transition in wet specimen occurring at lower pressure than that observed by Raterron et al. (2007) in dry specimens. For

  17. High-pressure compressibility and thermal expansion of aragonite

    NASA Astrophysics Data System (ADS)

    Palaich, S.; Heffern, R. A.; Kavner, A.; Manning, C. E.; Merlini, M.; Hanfland, M.

    2015-12-01

    An important component of Earth's deep carbon cycle is the return of surficial carbon to the planet's interior. Most recycled carbon is bound in CaCO3 minerals, of which aragonite is the most significant at upper mantle pressures. It is therefore essential to understand the phase stability and compressibility of aragonite at high pressures and temperatures. Aragonite has an orthorhombic 2/m 2/m 2/m structure and a Z of 4. The high-pressure behavior of aragonite has been studied under dynamic and static compression using both X-ray diffraction and spectroscopic techniques, but these results have been contradictory and inconclusive. To address these issues, a single-crystal synchrotron X-ray diffraction study of aragonite under hydrostatic compression was performed to 40 GPa in a diamond anvil cell at ambient temperature. To supplement the compressional experiment, thermal expansion was also measured via powder X-ray diffraction at ambient pressure between 298-673 K. Ambient-pressure single-crystal measurements confirm the orthorhombic 2/m 2/m 2/m structure and yield a unit cell volume of 226.932(5) Å3. At room temperature, aragonite is stable in the orthorhombic structure to 40 GPa, with an isothermal bulk modulus of 66.5(7) GPa and K' = 5.0(1). The a-axis is most compressible and the c-axis is the least compressible. The b-axis is intermediate, but starts to decrease in compressibility at ~15 GPa. Between 25-30 GPa the aragonite unit cell distorts due to the stiffening of the b-axis, which is controlled by the orientation and distortion of the carbonate groups, layered in the aragonite structure parallel to the a-axis. The carbonate groups elongate and deform from equilateral to isosceles between 15 and 30 GPa, thus influencing the compressibility of the b-axis. The thermal expansion measurements yield expansion coefficients a0 = 4.9(2) x 10-5 and a1 =3.7(5) x 10-8, in agreement with previous data. The combination of the isothermal and isobaric studies allows the

  18. Insights into the crystal chemistry of Earth materials rendered by electron density distributions: Pauling's rules revisited

    SciTech Connect

    Gibbs, Gerald V.; Ross, Nancy L.; Cox, David F.; Rosso, Kevin M.

    2014-05-20

    Pauling's first two rules are examined in terms of the accumulation of the electron density between bonded pairs of atoms for a relatively large number of oxide and silicate crystals and siloxane molecules. The distribution of the electron density shows that the radius of the oxygen atom is not fixed, but that it actually decreases systematically from ~1.40 Å to ~ 0.65 Å as the polarizing power and the electronegativity of the bonded metal atoms increase and the distribution of the O atom is progressively polarized and contracted along the bond vectors by the impact of the bonded interactions. The contractions result in an aspherical oxygen atom that displays as many different bonded “radii” as it has bonded interactions. The bonded radii for the metal atoms match the Shannon and Prewitt ionic radii for the more electropositive atoms like potassium and sodium, but they are systematically larger for the more electronegative atoms like aluminum, silicon and phosphorous. Pauling's first rule is based on the assumption that the radius of the oxide anion is fixed and that the radii of the cations are such that radius sum of the spherical oxide anion and a cation necessarily equals the separation between the cation-anion bonded pair with the coordination number of the cation being determined by the ratio of the radii of the cation and anion. In the case of the bonded radii, the sum of the bonded radii for the metal atoms and the oxide anion necessarily equals the bond lengths by virtue of the way that the bonded radii were determined in the partitioning of the electron density along the bond path into metal and O atom parts. But, the radius ratio for the O and M atoms is an unsatisfactory rule for determining the coordination number of the metal atom inasmuch as a bonded O atom is not, in general, spherical, and its size varies substantially along its bonded directions. But by counting the number of bond paths that radiate from a bonded atom, the coordination

  19. Structural control on displacive phase transitions in minerals at high pressures

    NASA Astrophysics Data System (ADS)

    Miletich, Ronald

    2010-05-01

    High-pressure phase transformations resemble discontinuous thermodynamic and structural changes of materials, which can be assigned to configurational instabilities and lattice-related boundary conditions. In particular transformations, which are predominantely displacive in character, reveal structural control across the critical transition pressures through the structures of the polymorphs involved. Three examples of high-pressure phase transitions will be presented, which have been subject to a series of experimental studies at high pressures using diamond-anvil cells. The first example deals with clinopyroxenes, their static elasticities and elastic anomalies associated with occuring first-order transition. The example of spodumene will demonstrate in particular the structural role of the silicate-chain units, and exemplifies the pronounced deviation from conventional equation-of-state behaviour in the proximity of the critical transition pressure. The second example deals with the high-pressure phase transition of behoite and the structural control of hydrogen bridging on first-order transformations in simple (hydr)oxide phases. The third example will present the second-order transition in the silicate mineral benitoite, which has been chosen to demonstrate the need for high-precision single-crystal techniques in order to track down subtle structural changes related to high-pressure transitions.

  20. Elastic properties of solids at high pressure

    NASA Astrophysics Data System (ADS)

    Vekilov, Yu Kh; Krasilnikov, O. M.; Lugovskoy, A. V.

    2015-11-01

    This review examines the elastic response of solids under load. The definitions of isothermal and adiabatic elastic constants of ( n≥2) for a loaded crystal are given. For the case of hydrostatic pressure, two techniques are proposed for calculating the second-, third-, and fourth-order elastic constants from the energy-strain and stress-strain relations. As an example, using the proposed approach within the framework of the density functional theory, the second- to fourth-order elastic constants of bcc tungsten are calculated for the pressure range of 0-600 GPa.