WorldWideScience

Sample records for accompanying high-pressure phase

  1. High-pressure phases of alumina

    Science.gov (United States)

    Lyle, Matthew; Pickard, Chris; Needs, Richard

    2014-03-01

    Alumina (Al2O3) has been widely used as a pressure standard in static diamond anvil cell experiments and is a major chemical component of the Earth. So a detailed knowledge of its high-pressure stability is of great importance in both materials science and deep Earth science. A phase transition is known to occur at roughly 80-100 GPa between corundum and the Rh2O3 (II) structure. A second phase transition to the CaIrO3 structure occurs at even higher pressures. Here we present a computational structure search to reveal three additional structures which are competitive at these pressures but hitherto unknown to be stable in high-pressure alumina.

  2. Phase Transition and Structure of Silver Azide at High Pressure

    Energy Technology Data Exchange (ETDEWEB)

    D Hou; F Zhang; C Ji; T Hannon; H Zhu; J Wu; V Levitas; Y Ma

    2011-12-31

    Silver azide (AgN{sub 3}) was compressed up to 51.3 GPa. The results reveal a reversible second-order orthorhombic-to-tetragonal phase transformation starting from ambient pressure and completing at 2.7 GPa. The phase transition is accompanied by a proximity of cell parameters a and b, a 3{sup o} rotation of azide anions, and a change of coordination number from 4-4 (four short, four long) to eight fold. The crystal structure of the high pressure phase is determined to be in I4/mcm space group, with Ag at 4a, N{sub 1} at 4d, and N{sub 2} at 8h Wyckoff positions. Both of the two phases have anisotropic compressibility: the orthorhombic phase exhibits an anomalous expansion under compression along a-axis and is more compressive along b-axis than c-axis; the tetragonal phase is more compressive along the interlayer direction than the intralayer directions. The bulk moduli of the orthorhombic and tetragonal phases are determined to be K{sub OT} = 39{+-}5 GPa with K{sub OT'} = 10{+-}7 and K{sub OT} = 57 {+-}2 GPa with K{sub OT'} = 6.6{+-}0.2, respectively.

  3. Equations of state for barium in high-pressure phases

    International Nuclear Information System (INIS)

    The universal equation of state with an arbitrary reference point presented by the author (Fang Zheng-Hua 1998 Phys. Rev. B 50 16 238) is applied successfully to the analysis of the experimental compression data of barium in different structural phases (I, II, and V). The comparison given in this paper shows that this equation suits for the isothermal compression behaviour of barium in the high-pressure phases (II and V) better than the Birch-Murnaghan equation. The applicability of equations of state for solids in high-pressure phases is also discussed. (author)

  4. Novel high-pressure phase of ZrO2: An ab initio prediction

    International Nuclear Information System (INIS)

    The high-pressure behavior of the orthorhombic cotunnite type ZrO2 is explored using an ab initio constant pressure technique. For the first time, a novel hexagonal phase (Ni2In type) within P63/mmc symmetry is predicted through the simulation. The Ni2In type crystal is the densest high-pressure phase of ZrO2 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 Ni2In type hexagonal phase forms in zirconia at high pressure. - Highlights: • A post-cotunnite phase is predicted for ZrO2 through an ab initio simulation. • Cotunnite ZrO2 adopts the Ni2In type structure at high pressure. • The Ni2In type structure is the densest high-pressure phase of ZrO2 proposed so far. • The preferred mechanism in ZrO2 differs from the other metal dioxides

  5. Novel high-pressure phase of ZrO{sub 2}: An ab initio prediction

    Energy Technology Data Exchange (ETDEWEB)

    Durandurdu, Murat, E-mail: murat.durandurdu@agu.edu.tr

    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.

  6. Experimental methods for phase equilibria at high pressures.

    Science.gov (United States)

    Dohrn, Ralf; Fonseca, José M S; Peper, Stephanie

    2012-01-01

    Knowledge of high-pressure phase equilibria is crucial in many fields, e.g., for the design and optimization of high-pressure chemical and separation processes, carbon capture and storage, hydrate formation, applications of ionic liquids, and geological processes. This review presents the variety of methods to measure phase equilibria at high pressures and, following a classification, discusses the measurement principles, advantages, challenges, and error sources. Examples of application areas are given. A detailed knowledge and understanding of the different methods is fundamental not only for choosing the most suitable method for a certain task but also for the evaluation of experimental data. The discrepancy between the (sometimes low) true accuracy of published experimental data and the (high) accuracy claimed by authors is addressed. Some essential requirements for the generation of valuable experimental results are summarized.

  7. High-Pressure Phase Transition in Cyclo-octane

    Institute of Scientific and Technical Information of China (English)

    GAO Ling-Ling; ZOU Guang-Tian; JIANG Sheng; LIU Dan; HAO Jian; JIN Yun-Xia; WANG Feng; WANG Qiu-Shi; LIU Jing; CUI Qi-Liang

    2008-01-01

    Structural behaviour of cyclo-octane under high pressure is studied by using a synchrotron x-ray source in a diamond anvil cell (DAC) up to 40.2 GPa at room temperature. The cyclo-octane firstly solidifies to the triclinic phase at 0.87 GPa. With the increasing pressure, the phase of cyclo-octane changes to the tetragonal phase at about 6.0 GPa and then transforms to amorphous phase above 18.2 GPa, which is kept till to 40.2 GPa. All the phase transitions of cyclo-octane are irreversible.

  8. High pressure phase transformation in iron under fast compression

    Energy Technology Data Exchange (ETDEWEB)

    Bastea, M; Bastea, S; Becker, R

    2009-07-07

    We present experimental results on the solid-solid, {alpha} to {epsilon} phase transformation kinetics of iron under high pressure dynamic compression. We observe kinetic features - velocity loops - similar with the ones recently reported to occur when water is frozen into its ice VII phase under comparable experimental conditions. We analyze this behavior in terms of general ideas coupling the steady sample compression with phase nucleation and growth with a pressure dependent phase interface velocity. The model is used to predict the response of iron when steadily driven across the {alpha} - {epsilon} phase boundary on very short time scales, including those envisioned to be achieved in ultra-fast laser experiments.

  9. Elasticity of methane hydrate phases at high pressure.

    Science.gov (United States)

    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

  10. Isostructural Phase Transition of TiN under High Pressure

    Institute of Scientific and Technical Information of China (English)

    ZHAO Jing-Geng; LI Yan-Chun; LIU Jing; YANG Liu-Xiang; YU Yong; YOU Shu-Jie; YU Ri-Cheng; LI Feng-Ying; CHEN Liang-Chcn; JIN Chang-Qing; LI Xiao-Dong

    2005-01-01

    @@ In situ high-pressure energy dispersive x-ray diffraction experiments on polycrystalline powder TiN with NaC1type structure have been conducted with the pressure up to 30.1 GPa by using a diamond anvil cell instrument with synchrotron radiation at room temperature. The experimental results suggest that an isostructural phase transition might exist at about 7GPa as revealed by the discontinuity of V/Vo with pressure.

  11. High pressure phase transition in Pr-monopnictides

    Energy Technology Data Exchange (ETDEWEB)

    Raypuria, Gajendra Singh, E-mail: sosfizix@gmail.com, E-mail: gsraypuria@gmail.com; Gupta, Dinesh Chandra [Condensed Matter Theory Group, School of Studies in Physics, Jiwaji University, Gwalior - 474011 (India); Department of Physics, Govt. K.R.G. P.G. Autonomous College, Gwalior - 474001 (India)

    2015-06-24

    The Praseodymium-monopnictides compounds have been found to undergo transition from their initial NaCl-type structure to high pressure body centered tetragonal (BCT) structure (distorted CsCl-type P4/mmm) using CTIP model. The calculated values of cohesive energy, lattice constant, phase transition pressure, relative volume collapse agree well with the available measured data and better than those computed by earlier workers.

  12. A subdivision algorithm for phase equilibrium calculations at high pressures

    Directory of Open Access Journals (Sweden)

    M. L. Corazza

    2007-12-01

    Full Text Available Phase equilibrium calculations at high pressures have been a continuous challenge for scientists and engineers. Traditionally, this task has been performed by solving a system of nonlinear algebraic equations originating from isofugacity equations. The reliability and accuracy of the solutions are strongly dependent on the initial guess, especially due to the fact that the phase equilibrium problems frequently have multiple roots. This work is focused on the application of a subdivision algorithm for thermodynamic calculations at high pressures. The subdivision algorithm consists in the application of successive subdivisions at a given initial interval (rectangle of variables and a systematic test to verify the existence of roots in each subinterval. If the interval checked passes in the test, then it is retained; otherwise it is discharged. The algorithm was applied for vapor-liquid, solid-fluid and solid-vapor-liquid equilibrium as well as for phase stability calculations for binary and multicomponent systems. The results show that the proposed algorithm was capable of finding all roots of all high-pressure thermodynamic problems investigated, independent of the initial guess used.

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

    Energy Technology Data Exchange (ETDEWEB)

    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

  14. High-pressure phase transitions - Examples of classical predictability

    Science.gov (United States)

    Celebonovic, Vladan

    1992-09-01

    The applicability of the Savic and Kasanin (1962-1967) classical theory of dense matter to laboratory experiments requiring estimates of high-pressure phase transitions was examined by determining phase transition pressures for a set of 19 chemical substances (including elements, hydrocarbons, metal oxides, and salts) for which experimental data were available. A comparison between experimental and transition points and those predicted by the Savic-Kasanin theory showed that the theory can be used for estimating values of transition pressures. The results also support conclusions obtained in previous astronomical applications of the Savic-Kasanin theory.

  15. New High-Pressure Phase in Fe2O3

    Science.gov (United States)

    Tsuchiya, T.; Nishiyama, N.; Yusa, H.; Tsuchiya, J.; Funakoshi, K.

    2009-12-01

    Hematite Fe2O3, a prototype of trivalent transition metal oxides, crystallizes in the antiferromagnetic (AFM) insulating phase with the corundum structure at ambient conditions. Extensive studies have been carried out to clarify its structural, magnetic, and electronic evolutions under high pressure due to the broad interests in hematite from condensed matter physics to geosciences. The high-pressure phase relation in Fe2O3 is also substantial to understand geophysically important MgSiO3-Fe2O3 phase equilibria. Those are however still yet to be clarified as for example, some in situ X-ray diffraction measurements using the diamond anvil cell (DAC) reported a phase change from Rh2O3(II) (or orthorhombic Pv) to the CaIrO3-type structure over 60 GPa, while an experiment using the Kawai-type apparatus with sintered diamond (SD) anvils suggested to stabilize a different phase with an unidentified orthorhombic structure at much lower pressure of 40~45 GPa. On the other hand, recent theoretical and experimental investigations of non-magnetic sesquioxide compounds have revealed an emerging systematics of their high-pressure phase sequence (Tsuchiya et al., 2005; Tsuchiya et al., 2007; Yusa et al., 2008; Yusa et al., 2009). While the CaIrO3-type phase with six and eight disproportionate coordination polyhedra was found to stabilize in Al2O3 and Ga2O3 at megabar pressure, several other compounds such as In2O3 and Sc2O3 were reported to transform directly to a further denser phase with the α-Gd2S3 structure composed only of high eight-fold coordination polyhedra at much lower pressure. Similarly to these studies, we searched for a stable form of Fe2O3 under pressure theoretically by means of the density-functional structurally consistent LDA+U method and succeeded to discover a new phase transformation from Rh2O3(II) at the pressure fairly close to that reported by the SD experiment. The high-pressure phase however has different lattice constants suggested experimentally and

  16. Anomalous thermal expansion in the metallic phase of SmS under high pressure

    International Nuclear Information System (INIS)

    SmS exhibits a pressure-induced phase transition at 0.6 GPa from a semiconducting state to a rather metallic state accompanied with a change of Sm valence and volume compression. Using the X-ray diffraction technique under high pressures, we found local minima of the lattice constant of SmS in the metallic phase up to near 2 GPa. The pressure region of the volume minima coincides with that of the low-temperature increase and the humps of electrical resistivity. We succeeded in reproducing the volume minima by a phenomenological model of a Schottky-type behavior due to electronic gap suppressed by pressure

  17. High pressure equation of state for condensed phase thermodynamics

    OpenAIRE

    Nogva, Stig-Erik

    2012-01-01

    In this study a search for an equation of state (EOS) that accurately predicts solids behaviour at both high pressure and temperature has been performed. Firstly, several two-parameter isothermal EOSs for solids under high pressure were investigated. The EOSs evaluated were the Murnaghan, Birch?Murnaghan, Vinet and pseudo-spinodal. The input parameters needed were found through parameter fitting of experimental data. The parameter fitting was done through a second order Murnagh...

  18. A New High Pressure Phase and the Equation of State of YbH2

    DEFF Research Database (Denmark)

    Staun Olsen, J.; Buras, B.; Gerward, Leif;

    1984-01-01

    High-pressure X-ray diffraction studies have been performed on YbH2 up to 28 GPa. A first order phase transition from an orthorhombic structure to a collapsed hexagonal structure with c/a = 1.34 has been observed at about 15 GPa. The transition is accompanied by a 5.2% decrease in volume. Fitting...... the V(P) data to Murnaghan's equation of state yields the bulk modulus B0 = 40.2 GPa and its pressure derivative B'0 = 4.75 for the orthorhombic phase. For the hexagonal phase we find the bulk modulus to be B = B0 = 138 GPa independent of pressure, i.e. B'0 = 0....

  19. High-pressure phase relations of CsD2PO4

    International Nuclear Information System (INIS)

    The high-pressure phase diagram of CsD2PO4 to 4.5 GPa and temperatures between 0 and 4700C is reported. Comparisons are made with CsH2PO4 and correlated with the isotope effect on the high-temperature high-pressure phase relations of KH2PO4

  20. High-pressure phases and compressibility of neptunium and plutonium compounds

    International Nuclear Information System (INIS)

    In this paper the diamond anvil technique for generation of pressure and its potential are briefly introduced. An overview is given on recent studies of the behavior of neptunium and plutonium compounds of the Bl (NaCl) and Cl (CaF2) types under high pressure. Most Bl-type compounds adopt the B2 (CsCl) form as a high-pressure structure, but tetragonal and rhombohedral high-pressure phases occur as well. Orthorhombic high-pressure phases exist for the dioxides. Bulk moduli were determined for all compounds studied. PuO2 is less compressible than dioxides of lighter actinides

  1. High pressure structural phase transitions of TiO2 nanomaterials

    Institute of Scientific and Technical Information of China (English)

    李全军; 刘冰冰

    2016-01-01

    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 re-cent 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 mi-crostructures. 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.

  2. Phase transition of solid bismuth under high pressure

    Science.gov (United States)

    Chen, Hai-Yan; Xiang, Shi-Kai; Yan, Xiao-Zhen; Zheng, Li-Rong; Zhang, Yi; Liu, Sheng-Gang; Bi, Yan

    2016-10-01

    As a widely used pressure calibrator, the structural phase transitions of bismuth from phase I, to phase II, to phase III, and then to phase V with increasing pressure at 300 K have been widely confirmed. However, there are different structural versions for phase III, most of which are determined by x-ray diffraction (XRD) technology. Using x-ray absorption fine structure (XAFS) measurements combined with ab initio calculations, we show that the proposed incommensurate composite structure of bismuth of the three configurations is the best option. An abnormal continuous increase of the nearest-neighbor distance of phase III with elevated pressure is also observed. The electronic structure transformation from semimetal to metal is responsible for the complex behavior of structure transformation. Project supported by the National Natural Science Foundation of China (Grant Nos. 10904133, 11304294, 11274281, 11404006, and U1230201), the Development Foundation of China Academy of Engineering Physics (Grant Nos. 2015B0101004, 2013B0401062, and 2012A0101001), the Research Foundation of the Laboratory of Shock Wave and Detonation, China (Grant No. 9140C670201140C67282).

  3. High pressure phase transitions for CdSe

    Indian Academy of Sciences (India)

    Bo Kong; Ti-Xian Zeng; Zhu-Wen Zhou; De-Liang Chen; Xiao-Wei Sun

    2014-05-01

    The structure and pressure-induced phase transitions for CdSe are investigated using first-principles calculations. The pressure-induced phase transition sequence WZ/ZB $\\to$ Rs $\\to$ $\\to$ CsCl for CdSe is drawn reasonably for the fist time, the corresponding transition pressures are 3.8, 29 and 107 GPa, respectively and the intermediate states between the structure and the CsCl structure should exist.

  4. Phase diagram of Mo at high pressure and temperature

    Energy Technology Data Exchange (ETDEWEB)

    Ross, M

    2008-10-01

    We report values of the Poisson Ratios for shock compressed Mo, calculated from the sound speed measurements, which provide evidence that the 210 GPa ({approx}4100K) transition cannot be a bcc-hcp transition, as originally proposed. Instead, we find the transition is from the bcc to a noncrystalline phase. For pressures above 210 GPa, the Poisson Ratio increases steadily with increasing temperature, approaching the liquid value of 0.5 at 390 GPa({approx}10,000K), suggesting the presence of a noncrystalline solid-liquid mixture. Free energy model calculations were used to show that the low melting slope of Mo, and the phase diagram, can be explained by the presence of local liquid structures. A new phase diagram is proposed for Mo that is constrained by the experimental evidence.

  5. High pressure phase transition and elastic properties of Lutetium chalcogenide

    International Nuclear Information System (INIS)

    Using first-principles density functional calculation, the pressure induced structural phase transformation and mechanical properties of NaCl type (B1) structure in Lutetium chalcogenides (LuX: X=S, Se, Te) were studied by means of the full-potential augmented plane wave plus local orbitals (FP-APW+lo) method. The calculations were performed within the generalized gradient approximation (GGA) for the exchange-correlation potential. The calculated ground state properties such us lattice constants agree quit well with the experimental findings. We have determined the full set of first-order elastic constants and their pressure dependence, which have not been calculated and measured yet. The Debye temperature is estimated from the average sound velocity. To our knowledge this is the first quantitative theoretical prediction of the structural phase transition and elastic properties for these compounds and still awaits experimental confirmations.

  6. High pressure phase diagram of MgO

    Science.gov (United States)

    French, Martin; Cebulla, Daniel; Redmer, Ronald

    2015-06-01

    In order to improve the understanding of the interior of super-Earths (planets in the range of 1-10 Earth masses) and other exoplanets, ab inito calculations for the planetary materials and the equation of state (EOS) and phase diagram of planetary materials are needed. A typical representative is MgO, which is an abundant material in the Earth's mantle and is also expected to be important for the mantle of exoplanets as well as for the rocky cores of gas giants such as Jupiter. Using ab initio molecular dynamic simulations, we have determined the phase diagram for MgO up to 20000 K and 1.5 TPa. In particular, the transition from the solid to the molten salt has been studied using diffusion analyses and pair distribution functions. The transition from the B1 to the B2 structure in solid MgO is determined by calculating the respective free enthalpies. The phase diagram of MgO is constructed based on accurate EOS data. We compare with results from (decaying) shock and ramp compression experiments and theoretical calculations for the B1-B2 and the liquid-solid transition line.

  7. Rheology of phase A at high pressure and high temperature

    Science.gov (United States)

    Hilairet, N.; Amiguet, E.; Wang, Y.; Merkel, S.

    2013-12-01

    Subduction zones are locations where a tectonic plate slides and bends under another one. Materials there undergo large and heterogeneous deformations and stresses which are released through seismicity, occasionally. Thus plasticity of minerals filling faults and shear zones is a critical parameter for understanding the stress balance of whole subduction zones. We present a deformation study on a hexagonal hydrous phase that can exist in shear zones within subducting slabs, phase A, after dehydration of serpentine into pyroxene + phase A. Pure phase A samples were synthesized at 11 GPa and ca. 1100K, in the multi-anvil facility in Clermont-Ferrand, France, with N. Bolfan and D. Andrault. Three samples were deformed at 11 GPa confining pressure, and 673K or 973K, using a D-DIA apparatus [1] at 13B-MD at GSE-CARS, APS, in uniaxial shortening up to -0.24 strain and at 5.10-5 s-1. Lattice strains (a proxy for macro-stress), texture and strain were measured in-situ, using synchrotron radiation. Results from lattice strain and texture analysis show a decrease in flow stress and a change in deformation mechanisms with temperature, coherent with the findings in transmission electron microscopy on samples recovered in relaxation experiments from [2]. The slip systems involved during deformation were further analyzed using Visco-Plastic Self-Consistent (VPSC) simulations [3]. The model inputs were known slip systems for hexagonal materials, including the ones observed by [2], with tunable strengths, the strain rate, final strain, and either a random texture or the starting experimental texture. The final experimental textures could be reproduced. The slip systems that had to be activated for matching the experimental texture confirm the observations by [2]: at 673K, the most active slip systems are prismatic and pyramidal, with the requirement of a smaller activity on the basal system, and at 973K the basal system is the main slip system activated. [1] Wang et al, Review for

  8. Application of Finite Strain Landau Theory To High Pressure Phase Transitions

    OpenAIRE

    Tröster, A.; Schranz, W.; Karsai, F.; Blaha, P.

    2013-01-01

    In this paper we explain how to set up what is in fact the only possible consistent construction scheme for a Landau theory of high pressure phase transitions that systematically allows to take into account elastic nonlinearities. We also show how to incorporate available information on the pressure dependence of elastic constants taken from experiment or simulation. We apply our new theory to the example of the high pressure cubic-tetragonal phase transition in Strontium Titanate, a model pe...

  9. Mechanical behaviors and phase transition of Ho2O3 nanocrystals under high pressure

    International Nuclear Information System (INIS)

    Mechanical properties and phase transition often show quite large crystal size dependent behavior, especially at nanoscale under high pressure. Here, we have investigated Ho2O3 nanocrystals with in-situ x-ray diffraction and Raman spectroscopy under high pressure up to 33.5 GPa. When compared to the structural transition routine cubic -> monoclinic -> hexagonal phase in bulk Ho2O3 under high pressure, the nano-sized Ho2O3 shows a much higher onset transition pressure from cubic to monoclinic structure and followed by a pressure-induced-amorphization under compression. The detailed analysis on the Q (Q = 2π/d) dependent bulk moduli reveals the nanosized Ho2O3 particles consist of a clear higher compressible shell and a less compressible core. Insight into these phenomena shed lights on micro-mechanism studies of the mechanical behavior and phase evolution for nanomaterials under high pressure, in general.

  10. High pressure structural phase transitions of TiO2 nanomaterials

    Science.gov (United States)

    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.

  11. Preparation of high-pressure phase boron nitride films by physical vapor deposition

    CERN Document Server

    Zhu, P W; Zhao, Y N; Li, D M; Liu, H W; Zou Guang Tian

    2002-01-01

    The high-pressure phases boron nitride films together with cubic, wurtzic, and explosive high-pressure phases, were successfully deposited on the metal alloy substrates by tuned substrate radio frequency magnetron sputtering. The percentage of cubic boron nitride phase in the film was about 50% as calculated by Fourier transform infrared measurements. Infrared peak position of cubic boron nitride at 1006.3 cm sup - sup 1 , which is close to the stressless state, indicates that the film has very low internal stress. Transition electron microscope micrograph shows that pure cubic boron nitride phase exits on the surface of the film. The growth mechanism of the BN films was also discussed.

  12. High-pressure phases of group-IV, III-V, and II-VI compounds

    OpenAIRE

    Mujica, A.; Rubio Secades, Ángel; A. Muñoz; Needs, R. J.

    2003-01-01

    Advances in the accuracy and efficiency of first-principles electronic structure calculations have allowed detailed studies of the energetics of materials under high pressures. At the same time, improvements in the resolution of powder x-ray diffraction experiments and more sophisticated methods of data analysis have revealed the existence of many new and unexpected high-pressure phases. The most complete set of theoretical and experimental data obtained to date is for the group-IVA elements ...

  13. First-Principles Prediction of High-Pressure Phase of CaC6

    Institute of Scientific and Technical Information of China (English)

    LI Yan; ZHANG Li-Jun; GUI Tian; LIU Yan-Hui; MA Yan-Ming; ZOU Guang-Tian

    2007-01-01

    The lattice dynamics of rhombohedral CaCe is studied as a function of pressure to probe its high pressure phase with low superconducting transition temperature using the density functional liner-response theory. The pressure-induced phase transition in CaC6 is attributable to the softening transverse acoustic (TA) phonon mode at the zone boundary X (0.5, 0.0, 0.5) point. The high pressure phase is then explored by performing fully structural optimization in the supercell which accommodates the atomic displacements corresponding to the eigenvectors of the unstable mode of TA(X). The high-pressure phase is predicted to be a monoclinic unit cell with space group P21/m.

  14. On the relative stability of orthorhombic and hcp phases of beryllium at high pressures

    Energy Technology Data Exchange (ETDEWEB)

    Palanivel, B.; Rao, R.S.; Godwal, B.K.; Sikka, S.K. [High Pressure Physics Division, Bhabha Atomic Research Center, Mumbai (India)

    2000-10-16

    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. (author)

  15. Phase transitions in Cd3P2 at high pressures and high temperatures

    DEFF Research Database (Denmark)

    Yel'kin, F.S.; Sidorov, V.A.; Waskowska, A.;

    2008-01-01

    The high-pressure, high-temperature structural behaviour of Cd3P2 has been studied using electrical resistance measurements, differential thermal analysis, thermo baric analysis and X-ray diffraction. At room temperature, a phase transformation is observed at 4.0 GPa in compression....... The experimental zero-pressure bulk modulus of the low-pressure phase is 64.7(7) GPa, which agrees quite well with the calculated value of 66.3 GPa using the tight-binding linear muffin-tin orbital method within the local density approximation. Tentatively, the high-pressure phase has an orthorhombic crystal...

  16. Modeling and Experimental Studies on Phase and Chemical Equilibria in High-Pressure Methanol Synthesis

    NARCIS (Netherlands)

    van Bennekom, Joost G.; Winkelman, Jozef G. M.; Venderbosch, Robertus H.; Nieland, Sebastiaan D. G. B.; Heeres, Hero J.

    2012-01-01

    A solution method was developed to calculate the simultaneous phase and chemical equilibria in high-pressure methanol synthesis (P = 20 MPa, 463 phase and include dew point calculations. A modification of the

  17. Phase Transformation of BN Nanoparticles Under High Pressure Low Temperature Conditions

    Science.gov (United States)

    Chen, Z.; Lai, Z. F.; Li, K.; Cui, D. L.; Lun, N.; Wang, Q. L.; Jiang, M. H.

    Phase transformation of BN nanoparticles under high pressure (580~860MPa) and low temperature (270~325°C) hot press conditions was investigated. It was found that the contents of orthorhombic boron nitride (oBN) and cubic boron nitride (cBN) increased with the increase of temperature and the prolonging of hot pressing time under high pressure conditions. At the same time, because of the intergrowth of hBN, oBN and cBN. there are strong interactions among these three phases.

  18. Superconducting phase prepared from Ta{sub 3}Si under high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Murao, R; Kusaba, K; Fukuoka, K; Sugiyama, K; Syono, Y [IMR, Tohoku University 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Kikuchi, M [Kansei Fukushi Research Center, Tohoku Fukushi University1-8-1 Kunimi, Aoba-ku, Sendai, Miyagi 981-8522 (Japan); Atou, T [SMC, Materials and Structures Lab. Tokyo Tech. 4259 Nagatsuta-cho Midori-ku, Yokohama, Kanagawa 226-8503 (Japan); Kikegawa, T, E-mail: r_murao@imr.tohoku.ac.j [IMSS, KEK, Oho 1-1, Tsukuba, Ibaraki 305-0801 (Japan)

    2010-03-01

    High-pressure behaviour of Ta{sub 3}Si intermetallic compound was investigated by shock compression and static compression methods. Superconducting phase with T{sub C} = 9.3 K was found in the sample shocked to 50-61 GPa, however most of the shock recovered sample indicated the starting stable phase with the Ti{sub 3}P-type structure. The new superconducting phase was not obtained from static compression up to 15 GPa and 800 {sup 0}C. Bulk modulus of Ta{sub 3}Si with the Ti{sub 3}P-type structure was determined to be K{sub 0} = 246(4) GPa. The present results suggest that a rapid phase transformation occurred during shock compression, but most of the high-pressure phase was reverted to the stable phase in the decompression process.

  19. Structural and magnetic phase transitions in NdCoAsO under high pressures

    International Nuclear Information System (INIS)

    We have investigated structural and magnetic phase transitions under high pressures in a quaternary rare-earth transition-metal arsenide oxide NdCoAsO compound that is isostructural to the high temperature superconductor parent phase NdFeAsO. The four-probe electrical resistance measurements carried out in a designer diamond anvil cell show that the ferromagnetic Curie temperature and antiferromagnetic Neel temperature increase with an increase in pressure. High pressure x-ray diffraction studies using a synchrotron source show a structural phase transition from a tetragonal phase to a new crystallographic phase at a pressure of 23 GPa at 300 K. The NdCoAsO sample remained antiferromagnetic and non-superconducting down to 10 K and up to the highest pressure achieved in this experiment, 53 GPa. A P-T phase diagram for NdCoAsO is presented from ambient conditions to P = 53 GPa and T = 10 K.

  20. Structural and magnetic phase transitions in NdCoAsO under high pressures

    Energy Technology Data Exchange (ETDEWEB)

    Uhoya, Walter; Tsoi, Georgiy M.; Vohra, Yogesh K.; McGuire, Michael A.; Sefat, Athena S.; Sales, Brian C.; Mandrus, David; Weir, Samuel T. (UAB); (ORNL); (LLNL)

    2010-05-04

    We have investigated structural and magnetic phase transitions under high pressures in a quaternary rare-earth transition-metal arsenide oxide NdCoAsO compound that is isostructural to the high temperature superconductor parent phase NdFeAsO. The four-probe electrical resistance measurements carried out in a designer diamond anvil cell show that the ferromagnetic Curie temperature and antiferromagnetic Neel temperature increase with an increase in pressure. High pressure x-ray diffraction studies using a synchrotron source show a structural phase transition from a tetragonal phase to a new crystallographic phase at a pressure of 23 GPa at 300 K. The NdCoAsO sample remained antiferromagnetic and non-superconducting down to 10 K and up to the highest pressure achieved in this experiment, 53 GPa. A P-T phase diagram for NdCoAsO is presented from ambient conditions to P = 53 GPa and T = 10 K.

  1. Structural and magnetic phase transitions in NdCoAsO under high pressures

    Energy Technology Data Exchange (ETDEWEB)

    Uhoya, Walter [University of Alabama, Birmingham; Tsoi, Georgiy [University of Alabama, Birmingham; Vohra, Y. K. [University of Alabama, Birmingham; McGuire, Michael A [ORNL; Sefat, A. S. [Oak Ridge National Laboratory (ORNL); Sales, Brian C [ORNL; Mandrus, David [ORNL; Weir, S. T. [Lawrence Livermore National Laboratory (LLNL)

    2010-01-01

    We have investigated structural and magnetic phase transitions under high pressures in a quaternary rare-earth transition-metal arsenide oxide NdCoAsO compound that is isostructural to the high temperature superconductor parent phase NdFeAsO. The four-probe electrical resistance measurements carried out in a designer diamond anvil cell show that the ferromagnetic Curie temperature and antiferromagnetic Neel temperature increase with an increase in pressure. High pressure x-ray diffraction studies using a synchrotron source show a structural phase transition from a tetragonal phase to a new crystallographic phase at a pressure of 23 GPa at 300 K. The NdCoAsO sample remained antiferromagnetic and non-superconducting down to 10 K and up to the highest pressure achieved in this experiment, 53 GPa. A P-T phase diagram for NdCoAsO is presented from ambient conditions to P = 53 GPa and T = 10 K.

  2. High-pressure fluid-phase equilibria: Experimental methods and systems investigated (2000-2004)

    DEFF Research Database (Denmark)

    Dohrn, Ralf; Peper, Stephanie; Fonseca, José

    2010-01-01

    As a part of a series of reviews, a compilation of systems for which high-pressure phase-equilibrium data were published between 2000 and 2004 is given. Vapor-liquid equilibria, liquid-liquid equilibria, vapor-liquid-liquid equilibria,solid-liquid equilibria, solid-vapor equilibria, solid-vapor-l...

  3. The high-pressure phase of alumina and implications for Earth's D″ layer

    OpenAIRE

    Artem R. Oganov; Ono, Shigeaki

    2005-01-01

    Using ab initio simulations and high-pressure experiments in a diamond anvil cell, we show that alumina (Al2O3) adopts the CaIrO3-type structure above 130 GPa. This finding substantially changes the picture of high-pressure behavior of alumina; in particular, we find that perovskite structure is never stable for Al2O3 at zero Kelvin. The CaIrO3-type phase suggests a reinterpretation of previous shock-wave experiments and has important implications for the use of alumina as a window material i...

  4. First-principles prediction of a high-pressure hydrous phase of AlOOH

    Science.gov (United States)

    Tsuchiya, Jun; Tsuchiya, Taku

    2011-02-01

    We have predicted a high-pressure hydrous phase of AlOOH stabilizing at ˜170 GPa by first-principles density-functional calculations. The structure predicted has a cubic pyrite-type AlO2 framework with interstitial H atoms forming symmetric hydrogen bonds, whose symmetry is assigned to the space group Pa3¯ (No. 205). The predicted δ-AlOOH to the pyrite-type phase sequence is analogous to a recent theoretical and experimental discovery of high-pressure phase evolution in InOOH and invokes the high-pressure phase relationship in SiO2, but the transition pressure is much greater in AlOOH than in InOOH. Relative enthalpies also indicate that the dissociation of this phase into a CaIrO3-type phase of Al2O3 plus ice X finally occurs at a further pressure of 300 GPa. The present results suggest that AlOOH has an unexpectedly wide stability range in pressure compared to common hydrous materials.

  5. Phase Stability of Epsilon and Gamma Hniw (CL-20) at High-Pressure and Temperature

    Science.gov (United States)

    Gump, Jared C.; Stoltz, Chad A.; Peiris, Suhithi M.

    2007-12-01

    Hexanitrohexaazaisowurtzitane (CL-20) is one of the few ingredients developed since World War II to be considered for transition to military use. Five polymorphs have been identified for CL-20 by FTIR measurements (α, β, γ, ɛ, ζ). As CL-20 is transitioned into munitions it will become necessary to predict its response under conditions of detonation, for performance evaluation. Such predictive modeling requires a phase diagram and basic thermodynamic properties of the various phases at high pressure and temperature. Therefore, the epsilon and gamma phases of CL-20 at static high-pressure and temperature were investigated using synchrotron angle-dispersive x-ray diffraction experiments. The samples were compressed and heated using diamond anvil cells (DAC). Pressures and temperatures achieved were around 5 GPa and 240 °C, respectively. The epsilon phase was stable to 6.3 GPa at ambient temperature. When heated at ambient pressure the epsilon phase was sustained to a temperature of 120 °C then underwent a transition to the gamma phase above 125 °C and then thermal decomposition occurred above 150 °C. Upon compression, the gamma phase underwent a phase transition at both ambient temperature and 140 °C. Pressure—volume data for the epsilon and gamma phase at ambient temperature and the epsilon phase at 75 °C were fit to the Birch-Murnaghan formalism to obtain isothermal equations of state.

  6. High pressure phase transition in Zr–Ni binary system: A first principle study

    Energy Technology Data Exchange (ETDEWEB)

    Mukherjee, Debojyoti, E-mail: debojyoti@barc.gov.in; Sahoo, B.D.; Joshi, K.D.; Gupta, Satish C.

    2015-11-05

    Total energy calculations have been performed on zirconium–nickel (with 50% nickel by atom) binary system to examine its structural stability under high pressure. The evolutionary structure search method in conjunction with density functional theory based projector augmented wave (PAW) method suggested that at zero pressure an orthorhombic phase with space group symmetry Cmcm is the lowest enthalpy structure, in agreement with the experiments. Further, it has been predicted that upon compression at ∼10 GPa, this structure will transform to a lower symmetry triclinic phase (space group P-1) which will remain stable up to ∼50 GPa, the maximum pressure of the present calculations. To support the results of our static lattice calculations, we performed lattice dynamic calculations also on Cmcm and P-1 structures. Lattice dynamic calculations correctly showed that at ambient condition the Cmcm phase is dynamically stable. Further, these calculations carried around the Cmcm to P-1 transition pressure predicted that the Cmcm phase will become unstable dynamically due to failure of acoustic zone boundary phonons, suggesting that the Cmcm to P-1 transition is phonon driven. For P-1 phase our calculations showed that this structure is dynamically stable not only at high pressures but also at ambient condition, indicating that at pressure lower than 10 GPa this phase could be a metastable structure. Further, we have calculated the elastic constants for both the phase at various pressures. - Highlights: • Pressure induced phonon driven orthorhombic to triclinic phase transformations in Zr–Ni binary system at ∼10 GPa. • Elastic and lattice dynamic stability of orthorhombic and triclinic phase. • Exploitation of evolutionary structure searching method to explore high pressure phase of Zr–Ni material.

  7. The Phase Transition of Eu2O3 under High Pressures

    Institute of Scientific and Technical Information of China (English)

    JIANG Sheng; BAI Li-Gang; LIU Jing; XIAO Wan-Sheng; LI Xiao-Dong; LI Yan-Chun; TANG Ling-Yun; ZHANG Yu-Feng; ZHANG De-Chun; ZHENG Li-Rong

    2009-01-01

    Pressure-induced phase transition of cubic Eu2Oa is studied by angle-dispersive x-ray diffraction (ADXD) up to 42.3 GPa at room temperature. A structural transformation from a cubic phase to a hexagonal phase is observed,which starts at 5.0 GPa and finishes at about 13.1 GPa. The phase transition leads to a volume collapse of 9.0% at 8.6 GPa. The hexagonal phase of Eu2O3 maintains stable up to the highest experiment pressure. After release of pressure, the high-pressure phase transforms to a monoclinic phase. The pressure-volume data are fitted with the Birch-Murnaghan equation of state. The bulk moduli obtained upon compression from the fitting are 145(2) GPa and 151(6) GPa for the cubic and hexagonal phases, respectively, when their first pressure derivatives are fixed at 4.

  8. High-pressure fluid-phase equilibria: Experimental methods and systems investigated (2005-2008)

    DEFF Research Database (Denmark)

    Fonseca, José; Dohrn, Ralf; Peper, Stephanie

    2011-01-01

    A review of systems is given, for which experimental high-pressure phase-equilibrium data were published in the period between 2005 and 2008, continuing a series of reviews. To find candidates for articles that are of interest for this survey a three-stage search strategy was used including...... a systematic search of the contents of the 17 most important journals of the field. Experimental methods for the investigation of high-pressure phase equilibria were classified, described and illustrated using examples from articles of the period between 2005 and 2008. For the systems investigated......%) have carbon dioxide as one of the components. Information on 206 pure components, 535 ternary systems of which 355 (66%) contain carbon dioxide, 163 multicomponent and complex systems, and 207 systems with hydrates is given. A continuation of the review series is planned, covering the years from 2009...

  9. High-pressure high-temperature phase diagram of organic crystal paracetamol

    International Nuclear Information System (INIS)

    High-pressure high-temperature (HPHT) Raman spectroscopy studies have been performed on the organic crystal paracetamol in a diamond anvil cell utilizing boron-doped heating diamond anvil. Isobaric measurements were conducted at pressures up to 8.5 GPa and temperature up to 520 K in five 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. This new data is combined with previous ambient temperature high-pressure Raman and x-ray diffraction data to create the first HPHT phase diagram of paracetamol. (paper)

  10. Simulation of the high-pressure phase equilibria of hydrocarbon-water/brine systems

    DEFF Research Database (Denmark)

    Zuo, You-Xiang; Stenby, Erling Halfdan; Guo, Tian-Min

    1996-01-01

    The major objectives of this work are: (1) extend the modified Patel-Teja (MPT) equation of state proposed for aqueous electrolyte systems (Zuo and Guo, 1991) to describe the liquid-liquid and vapor-liquid-liquid equilibria of hydrocarbon-water/brine systems through introducing an unconventional...... mixing rule to the energy parameter "a", (2) apply the revised MPT model (MPT2 model) to predict the effects of the coexisting water/formation water phase on the high-pressure phase behavior of reservoir oils/gas condensates, of which no experimental data is available.The predicted results indicate...... that the influence of the coexisting aqueous phase is not negligible....

  11. Free energy model for solid high-pressure phases of carbon.

    Science.gov (United States)

    Schöttler, Manuel; French, Martin; Cebulla, Daniel; Redmer, Ronald

    2016-04-13

    Analytic free energy models for three solid high-pressure phases--diamond, body centered cubic phase with eight atoms in the unit cell (BC8), and simple cubic (SC)--are developed using density functional theory. We explicitly include anharmonic effects by performing molecular dynamics simulations and investigate their density and temperature dependence in detail. Anharmonicity in the nuclear motion shifts the phase transitions significantly compared to the harmonic approximation. Furthermore, we apply a thermodynamically constrained correction that brings the equation of state in accordance with diamond anvil cell experiments. The performance of our thermodynamic functions is validated against Hugoniot experiments. PMID:26974530

  12. Phase transition and elastic properties of zinc sulfide under high pressure from first principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Wei [Hubei Univ. of Education, Wuhan (China). Dept. of Physics and Electronics; Chinese Academy of Engineering Physics, Mianyang (China). Inst. of Fluid Physics; Song, Jin-Fan; Wang, Ping; Lu, Cheng; Lu, Zhi-Wen [Nanyang Normal Univ. (China). Dept. of Physics; Tan, Xiao-Ming [Ludong Univ., Yantai (China). Dept. of Physics

    2011-10-15

    A theoretical investigation on structural and elastic properties of zinc sulfide semiconductor under high pressure is performed by employing the first-principles method based on the density functional theory. The calculated results show that the transition pressure P{sub t} for the structural phase transition from the B3 structure to the B1 structure is 17.04 GPa. The calculated values are generally speaking in good agreement with experiments and with similar theoretical calculations. (orig.)

  13. A new high-pressure phase transition in natural Fe-bearing orthoenstatite

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jin S.; Dera, Przemyslaw; Bass, Jay D. (UC); (UIUC)

    2016-07-29

    Single-crystal X-ray structure refinements have been carried out on natural Fe-bearing orthoenstatite (OEN) at pressures up to 14.53 GPa. We report a new high-pressure phase transition from OEN to a monoclinic phase (HPCEN2) with space group P2{sub 1}/c, with a density change of {approx}1.9(3)%. The HPCEN2 phase is crystallographically different from low-pressure clinoenstatite (LPCEN), which also has P2{sub 1}/c symmetry. Upon release of pressure HPCEN2 reverts to OEN, and the transition pressure is bracketed between 9.96 and 14.26 GPa at room temperature. We find no evidence for a C2/c phase at high pressure. The lattice constants for the new phase at 14.26 GPa are a = 17.87(2), b = 8.526(9), c = 4.9485(10) {angstrom}, {beta} = 92.88(4){sup o} [{rho} = 3.658(9) g/cm{sup 3}]. Refinement of the new structure indicates rotation of tetrahedral chain as the key characteristic of this transition. This experiment points to the possibility of OEN and HPCEN2 as the stable phases in Earth's upper mantle.

  14. Phase stability and structural distortion of NiO under high pressure

    Institute of Scientific and Technical Information of China (English)

    ZHANG Wei-bing; HU Yu-lin; TANG Bi-yu

    2006-01-01

    The phase stability and structural distortion of NiO under high pressure were investigated using first-principles calculations based on density-functional theory. Different forms of exchange-correlation functional including LDA,GGA and GGA+U were used in the present calculations. All of the three methods predict NiO to be AFM II ordering with the cell slightly compressed along [111] direction and also indicate that there is no structural phase transition of NiO under pressure up to 140 GPa,which are in agreement with the experiment. However,both LDA and GGA incorrectly predict the structural distortion under pressure especially above 60 GPa. Only when strong correlations are included in form of GGA+U,structural distortion under high pressure can qualitatively agree with the experiment. The related mechanism was also analyzed and discussed. These results suggest that the strong electronic correlations still play a very important role in the properties of NiO under high pressure.

  15. High-Pressure Low-Symmetry Phases of Cesium Halides from First Principle Techniques

    OpenAIRE

    Nardelli, M. Buongiorno; Baroni, S.; Giannozzi, P.

    1994-01-01

    The relative stability of different high-pressure phases of various Cesium Halides is studied from first principles and analyzed using the Landau theory of phase transitions. We present results for CsI, CsBr, and CsCl up to pressures of about 100 GPa. A cubic-to-orthorhombic transition, driven by the softening of an acoustic phonon at the M point of the Brillouin zone, is competing with the cubic-to-tetragonal martensitic transition typical of these compounds. The phonon softening takes place...

  16. Computation of Space Shuttle high-pressure cryogenic turbopump ball bearing two-phase coolant flow

    Science.gov (United States)

    Chen, Yen-Sen

    1990-01-01

    A homogeneous two-phase fluid flow model, implemented in a three-dimensional Navier-Stokes solver using computational fluid dynamics methodology is described. The application of the model to the analysis of the pump-end bearing coolant flow of the high-pressure oxygen turbopump of the Space Shuttle main engine is studied. Results indicate large boiling zones and hot spots near the ball/race contact points. The extent of the phase change of the liquid oxygen coolant flow due to the frictional and viscous heat fluxes near the contact areas has been investigated for the given inlet conditions of the coolant.

  17. Free energy model for solid high-pressure phases of carbon

    International Nuclear Information System (INIS)

    Analytic free energy models for three solid high-pressure phases—diamond, body centered cubic phase with eight atoms in the unit cell (BC8), and simple cubic (SC)—are developed using density functional theory. We explicitly include anharmonic effects by performing molecular dynamics simulations and investigate their density and temperature dependence in detail. Anharmonicity in the nuclear motion shifts the phase transitions significantly compared to the harmonic approximation. Furthermore, we apply a thermodynamically constrained correction that brings the equation of state in accordance with diamond anvil cell experiments. The performance of our thermodynamic functions is validated against Hugoniot experiments. (paper)

  18. Development of high pressure two-phase choked flow analysis methodology in complex piping system

    International Nuclear Information System (INIS)

    Choked flow mechanism, characteristics of two-phase flow sound velocity and compressibility effects on flow through various piping system components are studied to develop analysis methodology for high pressure two-phase choked flow in complex piping system which allows choking flow rate evaluation and piping system design related analysis. Piping flow can be said choked if Mach number is equal to 1 and compressibility effects can be accounted through modified incompressible formula in momentum equation. Based on these findings, overall analysis system is developed to study thermal-hydraulic effects on steady-state piping system flow and future research items are presented. (Author)

  19. The high-pressure phase of alumina and implications for Earth's D″ layer

    Science.gov (United States)

    Oganov, Artem R.; Ono, Shigeaki

    2005-01-01

    Using ab initio simulations and high-pressure experiments in a diamond anvil cell, we show that alumina (Al2O3) adopts the CaIrO3-type structure above 130 GPa. This finding substantially changes the picture of high-pressure behavior of alumina; in particular, we find that perovskite structure is never stable for Al2O3 at zero Kelvin. The CaIrO3-type phase suggests a reinterpretation of previous shock-wave experiments and has important implications for the use of alumina as a window material in shock-wave experiments. In particular, the conditions of the stability of this phase correspond to those at which shock-wave experiments indicated an increase of the electrical conductivity. If this increase is caused by high ionic mobility in the CaIrO3-type phase of Al2O3, similar effect can be expected in the isostructural postperovskite phase of MgSiO3 (which is the dominant mineral phase in the Earth's D″ layer). The effect of the incorporation of Al on the perovskite/postperovskite transition of MgSiO3 is discussed. PMID:16040809

  20. High-pressure structural phase transitions in chromium-doped BaFe2As2

    Energy Technology Data Exchange (ETDEWEB)

    Uhoya, Walter [University of Alabama, Birmingham; Brill, Joseph W. [University of Kentucky; Montgomery, Jeffrey M [University of Alabama, Birmingham; Samudrala, G K [University of Alabama, Birmingham; Tsoi, Georgiy [University of Alabama, Birmingham; Vohra, Y. K. [University of Alabama, Birmingham; Weir, S. T. [Lawrence Livermore National Laboratory (LLNL); Safa-Sefat, Athena [ORNL

    2012-01-01

    We report on the results from high pressure x-ray powder diffraction and electrical resistance measurements for hole doped BaFe{sub 2-x}Cr{sub x}As{sub 2} (x = 0, 0.05, 0.15, 0.4, 0.61) up to 81 GPa and down to 10 K using a synchrotron source and diamond anvil cell (DAC). At ambient temperature, an isostructural phase transition from a tetragonal (T) phase (I4/mmm) to a collapsed tetragonal (CT) phase is observed at 17 GPa. This transition is found to be dependent on ambient pressure unit cell volume and is slightly shifted to higher pressure upon increase in the Cr-doping. Unlike BaFe{sub 2}As{sub 2} which superconduct under high pressure, we have not detected any evidence of pressure induced superconductivity in chromium doped samples in the pressure and temperature range of this study. The measured equation of state parameters are presented for both the tetragonal and collapsed tetragonal phases for x = 0.05, 0.15, 0.40 and 0.61.

  1. Phase transformation and fluorescent enhancement of ErF3 at high pressure

    Science.gov (United States)

    Li, Wentao; Ren, Xiangting; Huang, Yanwei; Yu, Zhenhai; Mi, Zhongying; Tamura, Nobumichi; Li, Xiaodong; Peng, Fang; Wang, Lin

    2016-09-01

    Pressure-induced phase transformation and fluorescent properties of ErF3 were investigated here using in-situ synchrotron X-ray diffraction and photoluminescence up to 32.1 GPa at room temperature. Results showed that ErF3 underwent a reversible pressure-induced phase transition from the β-YF3-type to the fluocerite LaF3-type at 9.8 GPa. The bulk moduli B0 for low- and high-pressure phases were determined to be 130 and 208 GPa, respectively. Photoluminescencent studies showed that new emission lines belonging to the transition of 2H11/2→4I15/2, 4S3/2→4I15/2, and 4F9/2→4I15/2 appeared during phase transition, suggesting pressure-induced electronic band splitting. Remarkably, significant pressure-induced enhancement of photoluminescence was observed, which was attributed to lattice distortion of the material under high pressure.

  2. Anomalous phase transition of InN nanowires under high pressure

    Science.gov (United States)

    Tang, Shun-Xi; Zhu, Hong-Yang; Jiang, Jun-Ru; Wu, Xiao-Xin; Dong, Yun-Xuan; Zhang, Jian; Yang, Da-Peng; Cui, Qi-Liang

    2015-09-01

    Uniform InN nanowires were studied under pressures up to 35.5 GPa by using in situ synchrotron radiation x-ray diffraction technique at room temperature. An anomalous phase transition behavior has been discovered. Contrary to the results in the literature, which indicated that InN undergoes a fully reversible phase transition from the wurtzite structure to the rocksalt type structure, the InN nanowires in this study unusually showed a partially irreversible phase transition. The released sample contained the metastable rocksalt phase as well as the starting wurtzite one. The experimental findings of this study also reveal the potentiality of high pressure techniques to synthesize InN nanomaterials with the metastable rocksalt type structure, in addition to the generally obtained zincblende type one. Project supported by the National Natural Science Foundation of China (Grant Nos. 50772043, 51172087, and 11074089).

  3. High-Pressure Torsion of Ti: Synchrotron characterization of phase volume fraction and domain sizes

    Science.gov (United States)

    Bolmaro, Raúl E.; Sordi, Vitor L.; Ferrante, Maurizio; Brokmeier, Heinz-Günter; Kawasaki, Megumi; Langdon, Terence G.

    2014-08-01

    Rods of grade 2 Ti were processed by Equal-Channel Angular Pressing (ECAP) (phi = 120° at 573 K) employing 2, 4 and 6 passes. The same billets were further deformed by High- Pressure Torsion (HPT) at room temperature, varying both the hydrostatic pressure (1 and 6 GPa) and the number of rotations (n = 1 and 5). The ECAP and HPT samples were studied by synchrotron radiation at DESY-Petra III GEMS line. On the ECAP samples, textures were thus determined while for both ECAP and HPT samples the measurements were further analyzed by MAUD. Domain sizes and phase volume fractions were determined as a function of the radial direction of the samples. Alpha and Omega phases were detected in different amounts depending mostly on hydrostatic pressure and shear deformation. These transition phases can be pressure-induced during HPT processing and the results of Vickers microhardness measurements were related to the processing parameters and to the amounts of these phases.

  4. High-pressure Phase Equilibria for Binary Ethanol System Containing Supercriticai CO2

    Institute of Scientific and Technical Information of China (English)

    朱虎刚; 田宜灵; 陈丽; 秦颖; 冯季军

    2001-01-01

    High-pressure phase behavior of supercritical (SC) CO2+ethanol system was investigated at 333.2 K,348.2K, 353.2K, 368.2K, 413.2K and 453.2K and pressure from 2.0MPa to 14.3MPa. The measurement was carried out in a cylindrical autoclave with a moveable piston and a window for adjustment and observation of phase equilibria at given T and p. The samples were taken from two coexisting phases and were analyzed to obtain their compositions. It is shown that the solubility of SC CO2 in ethanol increases drastically with pressures at the given temperature, but the content of ethanol in CO2-rich phase increase faintly.

  5. High-pressure Phase Equilibria for Binary Ethanol System Containing Supercritical CO2

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    High-pressure phase behavior of supercritical (SC) CO2+ethanol system was investigated at 333.2 K, 348.2 K, 353.2 K, 368.2 K, 413.2 K and 453.2 K and pressure from 2.0 MPa to 14.3 MPa. The measurement was carried out in a cylindrical autoclave with a moveable piston and a window for adjustment and observation of phase equilibria at given T and p. The samples were taken from two coexisting phases and were analyzed to obtain their compositions. It is shown that the solubility of SC CO2 in ethanol increases drastically with pressures at the given temperature, but the content of ethanol in CO2-rich phase increase faintly.

  6. Phase transition and superconductivity of SrFe2As2 under high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Uhoya, Walter [University of Alabama, Birmingham; Montgomery, Jeffrey M [University of Alabama, Birmingham; Tsoi, Georgiy [University of Alabama, Birmingham; Vohra, Yogesh [University of Alabama, Birmingham; McGuire, Michael A [ORNL; Sefat, A. S. [Oak Ridge National Laboratory (ORNL); Sales, Brian C [ORNL; Weir, S. T. [Lawrence Livermore National Laboratory (LLNL)

    2011-01-01

    High pressure x-ray diffraction and electrical resistance measurements have been carried out on SrFe{sub 2}As{sub 2} to a pressure of 23 GPa and temperature of 10 K using a synchrotron source and designer diamond anvils. At ambient temperature, a phase transition from the tetragonal phase to a collapsed tetragonal (CT) phase is observed at 10 GPa under non-hydrostatic conditions. The experimental relation that T-CT transition pressure for 122 Fe-based superconductors is dependent on ambient pressure volume is affirmed. The superconducting transition temperature is observed at 32 K at 1.3 GPa and decreases rapidly with a further increase of pressure in the region where the T-CT transition occurs. Our results suggest that T{sub C} falls below 10 K in the pressure range of 10-18 GPa where the CT phase is expected to be stable.

  7. High-pressure phase transition and properties of spinel ZnMn2O4

    DEFF Research Database (Denmark)

    Åbrink, S.; Waskowska, A.; Gerward, Leif;

    1999-01-01

    -pressure behavior of ZnMn2O4 was investigated up to 52 GPa using the energy-dispersive x-ray diffraction technique and synchrotron radiation. The structural first-order phase transition from the body-centered to primitive-tetragonal cell takes place at P-c = 23 GPa. The high-pressure phase is metastable down......X-ray photoelectron spectroscopy, magnetic measurements, and a single-crystal x-ray structure determination at normal pressure have shown that Jahn-Teller active manganese ions in ZnMn2O4 are present in one valence state (III) on the octahedral sites of the spinel structure. The high...... coordinated Mn3+ is either in the d(z)(2) orbital or in the d(x2-y2). In the first configuration the MnO6 octahedron will be elongated and this is the case at normal pressure, while the second configuration gives the flattened octahedron. In the high-pressure phase some proportion of the e(g) electrons...

  8. Phase Behavior at High Pressure of the Ternary System: CO2, Ionic Liquid and Disperse Dye

    Directory of Open Access Journals (Sweden)

    Helen R. Mazzer

    2012-01-01

    Full Text Available High pressure phase behavior experimental data have been measured for the systems carbon dioxide (CO2 + 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim] [PF6] and carbon dioxide (CO2 + 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim] [PF6] + 1-amino-2-phenoxy-4-hydroxyanthraquinone (C.I. Disperse Red 60. Measurements were performed in the pressure up to 18 MPa and at the temperature (323 to 353 K. As reported in the literature, at higher concentrations of carbon dioxide the phase transition pressure increased very steeply. The experimental data for the binary and ternary systems were correlated with good agreement using the Peng-Robinson equation of state. The amount of water in phase behavior of the systems was evaluated.

  9. Phase stability of TiH{sub 2} under high pressure and temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Selva Vennila, R.; Durygin, A.; Saxena, S.K. [Center for Study of Matter at Extreme Conditions (CeSMEC), Florida International University, VH-150, University Park, Miami, FL 33199 (United States); Merlini, Marco [European Synchrotron Radiation Facility (ESRF), Grenoble 38043 (France); Wang, Zhongwu [Cornell High Energy Synchrotron Source (CHESS), Wilson Laboratory, Cornell University, Ithaca, NY 14853 (United States)

    2008-11-15

    Phase stability of titanium hydride (TiH{sub 2}) was studied at high pressure-high temperature conditions using synchrotron radiation under non-hydrostatic conditions. Resistive heating method was used to heat the sample to a maximum temperature of 873 K in a diamond anvil cell (DAC) under pressure up to 12 GPa. Pressure-temperature behavior was studied by varying the temperature upto 823 K in steps of 50 K with pressure variations within 3 GPa. Structural phase transformation from tetragonal (I4/mmm) to cubic (Fm-3 m) was observed with increase in temperature. Tetragonal phase was found to be stabilized when the sample was subjected to pressure and temperature cycle. (author)

  10. The high-pressure phase behavior and compressibility of 2,4,6-trinitrotoluene

    Energy Technology Data Exchange (ETDEWEB)

    Stevens, Lewis L.; Velisavljevic, Nenad; Hooks, Daniel E.; Dattelbaum, Dana M. (LANL)

    2008-10-24

    The phase stability and isothermal compression behavior of 2,4,6-trinitrotoluene (TNT) have been established to 26.5 GPa using angle-dispersive x-ray diffraction. P-V isotherms derived from the high-pressure x-ray spectra displayed a slight density hysteresis around 4.0 GPa and a sharp discontinuity at - 20.0 GPa. The latter transition is ascribed to a monoclinic-to-orthorhombic first-order phase transition in TNT. The conversion of the isothermal P-V data to the shock velocity-particle velocity plane revealed a deviation from linearity at low u{sub p}, a cusp associated with the phase transition at high u{sub p}, and general agreement with the wealth of unreacted Hugoniot data on TNT.

  11. Nanosecond Ultrasonics to Study Phase Transitions in Solid and Liquid Systems at High Pressure and Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Bonner, B P; Berge, P A; Carlson, S C; Farber, D L; Akella, J

    2007-03-21

    This report describes the development of a high-frequency ultrasonic measurement capability for application to the study of phase transitions at elevated pressure and temperature. We combined expertise in various aspects of static high-pressure technique with recent advances in wave propagation modeling, ultrasonic transducer development, electronic methods and broadband instrumentation to accomplish the goals of this project. The transduction and electronic systems have a demonstrated bandwidth of 400 MHz, allowing investigations of phenomena with characteristic times as short as 2.5 nS. A compact, pneumatically driven moissanite anvil cell was developed and constructed for this project. This device generates a high-pressure environment for mm dimension samples to pressures of 3 GPa. Ultrasonic measurements were conducted in the moissanite cell, an LLNL multi-anvil device and in a modified piston cylinder device. Measurements for water, and elemental tantalum, tin and cerium demonstrate the success of the methods. The {gamma}-{alpha} phase transition in cerium was clearly detected at {approx}0.7 GPa with 75 MHz longitudinal waves. These results have direct application to important problems in LLNL programs, as well as seismology and planetary science.

  12. Nanosecond Ultrasonics to Study Phase Transitions in Solid and Liquid Systems at High Pressure and Temperature

    International Nuclear Information System (INIS)

    This report describes the development of a high-frequency ultrasonic measurement capability for application to the study of phase transitions at elevated pressure and temperature. We combined expertise in various aspects of static high-pressure technique with recent advances in wave propagation modeling, ultrasonic transducer development, electronic methods and broadband instrumentation to accomplish the goals of this project. The transduction and electronic systems have a demonstrated bandwidth of 400 MHz, allowing investigations of phenomena with characteristic times as short as 2.5 nS. A compact, pneumatically driven moissanite anvil cell was developed and constructed for this project. This device generates a high-pressure environment for mm dimension samples to pressures of 3 GPa. Ultrasonic measurements were conducted in the moissanite cell, an LLNL multi-anvil device and in a modified piston cylinder device. Measurements for water, and elemental tantalum, tin and cerium demonstrate the success of the methods. The γ-α phase transition in cerium was clearly detected at ∼0.7 GPa with 75 MHz longitudinal waves. These results have direct application to important problems in LLNL programs, as well as seismology and planetary science

  13. Phase relations in the Fe-FeSi system at high pressures and temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, Rebecca A.; Campbell, Andrew J.; Reaman, Daniel M.; Miller, Noah A.; Heinz, Dion L.; Dera, Przymyslaw; Prakapenka, Vitali B. (UC); (Maryland)

    2016-07-29

    The Earth's core is comprised mostly of iron and nickel, but it also contains several weight percent of one or more unknown light elements, which may include silicon. Therefore it is important to understand the high pressure, high temperature properties and behavior of alloys in the Fe–FeSi system, such as their phase diagrams. We determined melting temperatures and subsolidus phase relations of Fe–9 wt% Si and stoichiometric FeSi using synchrotron X-ray diffraction at high pressures and temperatures, up to ~200 GPa and ~145 GPa, respectively. Combining this data with that of previous studies, we generated phase diagrams in pressure–temperature, temperature–composition, and pressure–composition space. We find the B2 crystal structure in Fe–9Si where previous studies reported the less ordered bcc structure, and a shallower slope for the hcp+B2 to fcc+B2 boundary than previously reported. In stoichiometric FeSi, we report a wide B2+B20 two-phase field, with complete conversion to the B2 structure at ~42 GPa. The minimum temperature of an Fe–Si outer core is 4380 K, based on the eutectic melting point of Fe–9Si, and silicon is shown to be less efficient at depressing the melting point of iron at core conditions than oxygen or sulfur. At the highest pressures reached, only the hcp and B2 structures are seen in the Fe–FeSi system. We predict that alloys containing more than ~4–8 wt% silicon will convert to an hcp+B2 mixture and later to the hcp structure with increasing pressure, and that an iron–silicon alloy in the Earth's inner core would most likely be a mixture of hcp and B2 phases.

  14. High-pressure phase transitions of CaRhO3 perovskite

    Science.gov (United States)

    Shirako, Yuichi; Kojitani, Hiroshi; Akaogi, Masaki; Yamaura, Kazunari; Takayama-Muromachi, Eiji

    2009-09-01

    High-pressure phase transitions of CaRhO3 perovskite were examined at pressures of 6-27 GPa and temperatures of 1,000-1,930°C, using a multi-anvil apparatus. The results indicate that CaRhO3 perovskite successively transforms to two new high-pressure phases with increasing pressure. Rietveld analysis of powder X-ray diffraction data indicated that, in the two new phases, the phase stable at higher pressure possesses the CaIrO3-type post-perovskite structure (space group Cmcm) with lattice parameters: a = 3.1013(1) Å, b = 9.8555(2) Å, c = 7.2643(1) Å, V m = 33.43(1) cm3/mol. The Rietveld analysis also indicated that CaRhO3 perovskite has the GdFeO3-type structure (space group Pnma) with lattice parameters: a = 5.5631(1) Å, b = 7.6308(1) Å, c = 5.3267(1) Å, V m = 34.04(1) cm3/mol. The third phase stable in the intermediate P, T conditions between perovskite and post-perovskite has monoclinic symmetry with the cell parameters: a = 12.490(3) Å, b = 3.1233(3) Å, c = 8.8630(7) Å, β = 103.96(1)°, V m = 33.66(1) cm3/mol ( Z = 6). Molar volume changes from perovskite to the intermediate phase and from the intermediate phase to post-perovskite are -1.1 and -0.7%, respectively. The equilibrium phase relations determined indicate that the boundary slopes are large positive values: 29 ± 2 MPa/K for the perovskite—intermediate phase transition and 62 ± 6 MPa/K for the intermediate phase—post-perovskite transition. The structural features of the CaRhO3 intermediate phase suggest that the phase has edge-sharing RhO6 octahedra and may have an intermediate structure between perovskite and post-perovskite.

  15. Turbulence modelling of high-pressure convective boiling two-phase flows

    International Nuclear Information System (INIS)

    This article is a contribution to the modelling of multidimensional high-pressure convective boiling two-phase flows relative to PWR's thermal hydraulics conditions. Postulating that the turbulence is one possible physical mechanism for heat removal from the wall towards the two-phase flow core, this work focuses on modelling turbulent transport terms in the momentum and energy balance equations. Using the pioneering work of Sato et al., the momentum and the energy balance equations are derived for a two-phase mixture. Such a system can be expressed as a combination of parameters, which include the local void fraction as well as the fluid velocity profile, the wall shear stress and the eddy diffusivity. By specifying a closure relation for this last parameter, a numerical solution can be obtained. As a preliminary step towards a numerical solution, the turbulent structure of the two-phase flow is expressed as a linear superposition of an inherent liquid turbulence and an additional one due to the bubble agitation. On the basis of this theory, the mixture velocity and temperature profiles can be predicted provided that the local void fraction and the wall shear stress are known. The model is then tested against the experimental data bank DEBORA (Garnier et al.,) which is devoted to the study of high pressure boiling flows. The first results are encouraging for the mechanical part but some discrepancies are observed on temperature profiles for boiling tests. This work should be continued in order to (i) improve the model especially for the thermal aspects and (ii) identify the key parameters responsible for the heat flux limitation (DNB). (author)

  16. Phase stability and magnetic behavior of hexagonal phase of N2-O2 system with kagome lattice under high pressure and low temperature

    Science.gov (United States)

    Akahama, Y.; Ishihara, D.; Yamashita, H.; Fujihisa, H.; Hirao, N.; Ohishi, Y.

    2016-08-01

    The pressure-temperature (P -T ) phase diagram of N2-O2 mixture with a composition of N2-48 mol % O2 has been investigated using x-ray diffraction and the phase stability of a hexagonal phase (space group: P 6 /mmm), with the kagome lattice examined under high-pressure and low-temperature conditions. While the phase appears as a low-temperature phase of the cubic phase (P m 3 n ) with the structure of γ -O2 or δ -N2 and is stable in a wide range of pressures and temperatures, it transforms to lower symmetry monoclinic or orthorhombic phases at lower temperature, accompanied with a distortion of the kagome lattice. Based on Rietveld refinements, the monoclinic and orthorhombic phases are found to be in the P 21/a and Cmmm space groups, respectively. In magnetization measurements, a magnetic transition is observed with a relatively large drop of magnetization, corresponding to the cubic-to-hexagonal phase transition. This suggests that the hexagonal phase has a certain magnetic ordered state that arises from the molecular magnetic moment of O2.

  17. Novel high-pressure phases of AlP from first principles

    Science.gov (United States)

    Liu, Chao; Hu, Meng; Luo, Kun; Yu, Dongli; Zhao, Zhisheng; He, Julong

    2016-05-01

    By utilizing a crystal structure prediction software via particle swarm optimization, this study proposes three new high-pressure phases of aluminum phosphide (AlP) with high density and high hardness, in addition to previously proposed phases (wz-, zb-, rs-, NiAs-, β-Sn-, CsCl-, and Cmcm-AlP). These new phases are as follows: (1) an I 4 ¯ 3d symmetric structure (cI24-AlP) at 55.2 GPa, (2) an R 3 ¯ m symmetric structure (hR18-AlP) at 9.9 GPa, and (3) a C222 symmetric structure (oC12-AlP) at 20.6 GPa. Based on first-principle calculations, these phases have higher energetic advantage than CsCl- and β-Sn-AlP at ambient pressure. The independent elastic constants and phonon dispersion spectra are calculated to check the mechanical and dynamic stabilities of these phases. According to mechanical property studies, these new AlP phases have higher hardness than NiAs-AlP, and oC12-AlP has the highest hardness of 7.9 GPa. Electronic band structure calculations indicate that NiAs- and hR18-AlP have electrical conductivity. Additionally, wz-, zb-, and oC12-AlP possess semiconductive properties with indirect bandgaps, and cI24-AlP has a semiconductive property with a direct bandgap.

  18. Structure determination of the high-pressure phase of CdSe

    International Nuclear Information System (INIS)

    Structural phase transition sequence of CdSe has been investigated at pressures up to 60 GPa under quasi-hydrostatic conditions using synchrotron X-ray diffraction. A phase transition from the wurtzite type (B4) to the NaCl-type (B1) structure has been observed, followed by another phase transition to an orthorhombic structure at 27 GPa, in agreement with previous reports. We show that this high-pressure orthorhombic phase has a Pnma symmetry rather than being a Cmcm-symmetric structure as previously suggested. From our observations, the appearance of the new reflections and reflection splitting with increasing pressure is due to the change of atomic relative positions in crystal lattice and the difference in the compression ratio of lattice parameters for the Pnma structure, and we find no evidence for the third phase transition reported previously. The pressure-induced phase transition of CdSe has been further confirmed by the density-functional theory calculations.

  19. Phase transition and equation of state of paratellurite (TeO2) under high pressure

    Science.gov (United States)

    Liu, Xun; Mashimo, Tsutomu; Kawai, Nobuaki; Sekine, Toshimori; Zeng, Zhaoyi; Zhou, Xianming

    2016-07-01

    The Hugoniot data for TeO2 single crystals were obtained for pressures up to ∼85 GPa along both the (a-axis) and (c-axis) directions using a velocity interferometer system for any reflector and inclined-mirror method combined with a powder gun or two-stage light gas gun. The Hugoniot-elastic limit of TeO2 was determined to be 3.3–4.3 GPa along the c-axes. The shock velocity (U s) versus particle velocity (U p) relation for TeO2 shows a kink around U p = 1.0 km s‑1, which suggests a phase transition completes at ∼26 ± 2 GPa. The Hugoniot relations of the low and high pressure phase are given by U s = 3.13(5) + 1.10(6)U p for U p 1.0 km s‑1, respectively. First-principles geometry optimizations based on the generalized gradient approximation after Perdew, Burke and Ernzerhof method were also performed on TeO2. It suggested that a continuous structure distortion occurs up to 22 GPa, and the lattice parameters b and c abruptly increase and decrease at 22 GPa, respectively, indicating a first-order phase transition to the cotunnite structure phase. The equation of state of the cotunnite phase TeO2 is discussed based on the experimental and simulation results.

  20. Synthesis of Novel Extended Phases of Molecular Solids at High Pressures and Temperatures

    International Nuclear Information System (INIS)

    This study is for in-situ investigation of chemical bonding and molecular structure of low z-elements and simple molecular solids at high pressures and temperatures using 3rd-generation synchrotron x-ray diffraction. To understand the contribution of the empty d-electron orbital of Mg in relation to the formation of molecular solids like MgO, which is one of the important Earth lower mantle materials and MgB2, which has recently been the focus of intense superconducting material research, we have performed double-sided laser heating experiments using a diamond anvil cell (DAC). Understanding the structural stability and the formation of the above Mg-compounds requires studying Mg itself as well as the relevant compounds. BL10XU at the Spring-8 was used to study phase stability and make accurate equation of state (EOS) determinations of Mg coupled with external heating and the double-sided laser heating technique. Monochromatic x-ray at 30 keV (0.4135 (angstrom)) was focused to about 40 (micro)m at the sample and the diffracted x-ray were recorded using a high-resolution image plate (3000 x 3000 pixels with a 0.1 mm resolution per pixel). EOS parameters for hcp and bcc Mg were determined by fitting to a Birch-Murnaghan equation. An isothermal compression of Mg at 300 K up to 100 GPa provides EOS parameters (B0, B0(prime), and V0) comparable for both hcp and bcc phases, which is similar to the cases for hcp and fcc phases measured in cobalt and xenon. Similar EOS parameters for both low and high pressure phases with a very small or no measurable volume discontinuity at the phase transition pressure suggests that the hcp-bcc structural transition of Mg may be driven by a stacking fault due to a shear instability as seen in xenon and cobalt. Compared to the recent estimation determined using a large volume press [1], our B0 is smaller by more than 10% suggesting that the difference may be due to non-hydrostatic conditions. The phase boundary of Mg up to 650 K was

  1. Phase Behaviour of the System Propene/Polypropene at High Pressure

    Directory of Open Access Journals (Sweden)

    Oliver Ruhl

    2011-01-01

    Full Text Available The phase behaviour of mixtures of supercritical propene and a number of polypropenes, which have a similar density but significantly different molecular weights and tacticities, was investigated in a broad range of polymer weight fractions and temperatures at high pressures. The cloud-point pressures were measured optically, using a view cell which was equipped with two windows made of synthetic sapphire and a metal bellows to accurately adjust the pressure. The cloud-point pressures were found in the range from 29 to 37 MPa decreasing with increasing polymer weight fraction and increasing with increasing temperature and polymer molecular weight. The critical weight fraction was found below 2 to 6 wt.-%. Whereas the cloud-point pressures of atactic and syndiotactic samples were high and very similar, the isotactic species exhibit distinctly lower values. The results, extrapolated to lower temperatures, show good agreement with the literature data.

  2. High pressure induced phase transition and superdiffusion in anomalous fluid confined in flexible nanopores

    Energy Technology Data Exchange (ETDEWEB)

    Bordin, José Rafael, E-mail: josebordin@unipampa.edu.br [Campus Caçapava do Sul, Universidade Federal do Pampa, Caixa Postal 15051, CEP 96570-000, Caçapava do Sul, RS (Brazil); Krott, Leandro B., E-mail: leandro.krott@ufrgs.br; Barbosa, Marcia C., E-mail: marcia.barbosa@ufrgs.br [Instituto de Física, Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, CEP 91501-970, Porto Alegre, RS (Brazil)

    2014-10-14

    The behavior of a confined spherical symmetric anomalous fluid under high external pressure was studied with Molecular Dynamics simulations. The fluid is modeled by a core-softened potential with two characteristic length scales, which in bulk reproduces the dynamical, thermodynamical, and structural anomalous behavior observed for water and other anomalous fluids. Our findings show that this system has a superdiffusion regime for sufficient high pressure and low temperature. As well, our results indicate that this superdiffusive regime is strongly related with the fluid structural properties and the superdiffusion to diffusion transition is a first order phase transition. We show how the simulation time and statistics are important to obtain the correct dynamical behavior of the confined fluid. Our results are discussed on the basis of the two length scales.

  3. High-Pressure Phase Behavior of Polycaprolactone, Carbon Dioxide, and Dichloromethane Ternary Mixture Systems

    Energy Technology Data Exchange (ETDEWEB)

    Gwon, JungMin; Kim, Hwayong [Seoul National University, Seoul (Korea, Republic of); Shin, Hun Yong [Seoul National University of Science and Technology, Seoul (Korea, Republic of); Kim, Soo Hyun [Korea Institute of Science and Technology, Seoul (Korea, Republic of)

    2015-04-15

    The high-pressure phase behavior of a polycaprolactone (Mw=56,145 g/mol, polydispersity 1.2), dichloromethane, and carbon dioxide ternary system was measured using a variable-volume view cell. The experimental temperatures and pressures ranged from 313.15 K to 353.15 K and up to 300 bar as functions of the CO{sub 2}/dichloromethane mass ratio and temperature, at poly(D-lactic acid) weight fractions of 1.0, 2.0, and 3.0%. The correlation results were obtained from the hybrid equation of state (Peng-Robinson equation of state + SAFT equation of state) for the CO{sub 2}-polymer system using the van der Waals one-fluid mixing rule. The three binary interaction parameters were optimized by the simplex method algorithm.

  4. A dynamic study of the warm-up phase of a high-pressure mercury lamp

    International Nuclear Information System (INIS)

    A time-dependent two-dimensional computational fluid model has been adopted to investigate the dynamic behavior of the high-pressure mercury lamp during the last phase of the warm-up period. The model solves the combined momentum, continuity, energy, and electric field equations for the plasma and the energy equation for the wall. Two models have been compared. The first takes convection into account and is called ''convection model.'' The second, which neglects this term, is termed ''convectionless model.'' Good agreement between the predictions and experimental data from literature has been obtained. It is found that the convection affects the lamp performance by increasing the mercury losses behind the electrodes and the mercury-evaporation time.

  5. High-pressure light scattering apparatus to study pressure-induced phase separation in polymer solutions

    Science.gov (United States)

    Xiong, Yan; Kiran, Erdogan

    1998-03-01

    A new high-pressure time- and angle-resolved light scattering apparatus has been developed to study the kinetics of phase separation in polymer solutions and other fluid mixtures under pressure at near- and supercritical conditions. The system consists of a high-pressure polymer loading chamber, a solvent charge line, a variable-volume scattering cell (with a built-in movable piston connected to a pressure generator, and an expansion rod driven by an air-actuated diaphragm), and a recirculation pump which are all housed in a temperature-controlled oven. The system is operable at pressures up to 70 MPa, and temperatures up to 473 K. The scattering cell is a short path-length cell made of two flat sapphire windows that are separated by 250 μm. It is designed to permit measurements of transmitted and scattered light intensities over an angle range from 0° to 30°. A linear image sensor with 256 elements is used to monitor the time evolution of the scattered light intensities at different angles. With this sensor, the angle range from 2° to 13° is scanned at a sampling rate of 3.2 ms/scan. The pressure quenches are achieved by movement of the air-actuated movable expansion rod, or by the movement of the piston with the aid of the pressure generator to bring about either rapid (at rates approaching 2000 MPa/s) or slow pressure changes in the system. Quench depth is also adjustable, and very deep (70 MPa) or very shallow (as low as 0.1 MPa) pressure quenches are readily achievable. The temperature and the pressure of the solution in the scattering cell, and the transmitted and scattered light intensities at different angles are recorded in real time through a computerized data acquisition system before and during phase separation. The experimental system is especially suited to follow the kinetics of phase separation in polymer solutions and to assess the metastable and unstable regions where phase separation proceeds by the nucleation and growth, and the spinodal

  6. Hexagonal ice transforms at high pressures and compression rates directly into "doubly metastable" ice phases.

    Science.gov (United States)

    Bauer, Marion; Winkel, Katrin; Toebbens, Daniel M; Mayer, Erwin; Loerting, Thomas

    2009-12-14

    We report compression and decompression experiments of hexagonal ice in a piston cylinder setup in the temperature range of 170-220 K up to pressures of 1.6 GPa. The main focus is on establishing the effect that an increase in compression rate up to 4000 MPa/min has on the phase changes incurred at high pressures. While at low compression rates, a phase change to stable ice II takes place (in agreement with earlier comprehensive studies), we find that at higher compression rates, increasing fractions and even pure ice III forms from hexagonal ice. We show that the critical compression rate, above which mainly the metastable ice III polymorph is produced, decreases by a factor of 30 when decreasing the temperature from 220 to 170 K. At the highest rate capable with our equipment, we even find formation of an ice V fraction in the mixture, which is metastable with respect to ice II and also metastable with respect to ice III. This indicates that at increasing compression rates, progressively more metastable phases of ice grow from hexagonal ice. Since ices II, III, and V differ very much in, e.g., strength and rheological properties, we have prepared solids of very different mechanical properties just by variation in compression rate. In addition, these metastable phases have stability regions in the phase diagrams only at much higher pressures and temperatures. Therefore, we anticipate that the method of isothermal compression at low temperatures and high compression rates is a tool for the academic and industrial polymorph search with great potential. PMID:20001064

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

    Science.gov (United States)

    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 . PMID:26457868

  8. Review of high pressure phases of calcium by first-principles calculations

    Science.gov (United States)

    Ishikawa, T.; Nagara, H.; Suzuki, N.; Tsuchiya, J.; Tsuchiya, T.

    2010-03-01

    We review high pressure phases of calcium which have obtained by recent experimental and first-principles studies. In this study, we investigated the face-centered cubic (fcc) structure, the body-centered cubic (bcc) structure, the simple cubic (sc) structure, a tetragonal P43212 [Ishikawa T et al. 2008 Phys. Rev. B 77 020101(R)], an orthorhombic Cmca [Ishikawa T et al. 2008 Phys. Rev. B 77 020101(R)], an orthorhombic Cmcm [Teweldeberhan A M and Bonev S A 2008 Phys. Rev. B 78 140101(R)], an orthorhombic Pnma [Yao Y et al. 2008 Phys. Rev. B 78 054506] and a tetragonal I4/mcm(00) [Arapan S et al. 2008 Proc. Natl. Acad. Sci. USA 105 20627]. We compared the enthalpies among the structures up to 200 GPa and theoretically determined the phase diagram of calcium. The sequence of the structural transitions is fcc (0- 3.5 GPa) → bcc (3.5 - 35.7 GPa) → Cmcm (35.7- 52GPa) → P43212 (52-109 GPa) → Cmca (109-117.4GPa) → Pnma (117.4-134.6GPa) → I4/mcm(00) (134.6 GPa -). The sc phase is experimentally observed in the pressure range from 32 to 113 GPa but, in our calculation, there is no pressure region where the sc phase is the most stable. In addition, we found that the enthalpy of the hexagonal close-packed (hcp) structure is lower than that of I4/mcm(00) above 495 GPa.

  9. Phase equilibrium data and thermodynamic modeling of the system (CO2 + biodiesel + methanol) at high pressures

    International Nuclear Information System (INIS)

    Highlights: → We measured phase behavior for the system involving {CO2 + biodiesel + methanol}. → The saturation pressures were obtained using a variable-volume view cell. → The experimental data were modeled using PR-vdW2 and PR-WS equations of state. - Abstract: The main objective of this work was to investigate the high pressure phase behavior of the binary systems {CO2(1) + methanol(2)} and {CO2(1) + soybean methyl esters (biodiesel)(2)} and the ternary system {CO2(1) + biodiesel(2) + methanol(3)} were determined. Biodiesel was produced from soybean oil, purified, characterized and used in this work. The static synthetic method, using a variable-volume view cell, was employed to obtain the experimental data in the temperature range of (303.15 to 343.15) K and pressures up to 21 MPa. The mole fractions of carbon dioxide were varied according to the systems as follows: (0.2383 to 0.8666) for the binary system {CO2(1) + methanol(2)}; (0.4201 to 0.9931) for the binary system {CO2(1) + biodiesel(2)}; (0.4864 to 0.9767) for the ternary system {CO2(1) + biodiesel(2) + methanol(3)} with a biodiesel to methanol molar ratio of (1:3); and (0.3732 to 0.9630) for the system {CO2 + biodiesel + methanol} with a biodiesel to methanol molar ratio of (8:1). For these systems, (vapor + liquid), (liquid + liquid), (vapor + liquid + liquid) transitions were observed. The phase equilibrium data obtained for the systems were modeled using the Peng-Robinson equation of state with the classical van der Waals (PR-vdW2) and Wong-Sandler (PR-WS) mixing rules. Both thermodynamic models were able to satisfactorily correlate the phase behavior of the systems investigated and the PR-WS presented the best performance.

  10. High pressure monoclinic phases of Sb{sub 2}Te{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Souza, S.M.; Poffo, C.M.; Triches, D.M. [Departamento de Engenharia Mecanica, Universidade Federal de Santa Catarina, Campus Universitario Trindade, S/N, C.P. 476, 88040-900 Florianopolis, Santa Catarina (Brazil); Lima, J.C. de, E-mail: fsc1jcd@fisica.ufsc.br [Departamento de Fisica, Universidade Federal de Santa Catarina, Campus Universitario Trindade, S/N, C.P. 476, 88040-900 Florianopolis, Santa Catarina (Brazil); Grandi, T.A. [Departamento de Fisica, Universidade Federal de Santa Catarina, Campus Universitario Trindade, S/N, C.P. 476, 88040-900 Florianopolis, Santa Catarina (Brazil); Polian, A.; Gauthier, M. [Physique des Milieux Denses, IMPMC, CNRS-UMR 7590, Universite Pierre et Marie Curie-Paris 6, 4 Place Jussieu, 75252 Paris Cedex 05 (France)

    2012-09-15

    The effect of pressure on nanostructured rhombohedral {alpha}-Sb{sub 2}Te{sub 3} (phase I) was investigated using X-ray diffraction (XRD) and Raman spectroscopy (RS) up to 19.2 and 25.5 GPa, respectively. XRD patterns showed two new high pressure phases (named phases II and III). From a Rietveld refinement of XRD patterns of {alpha}-Sb{sub 2}Te{sub 3}, the unit cell volume as a function of pressure was obtained and the values were fitted to a Birch-Murnaghan equation of state (BM-EOS). The best fit was obtained for bulk modulus B{sub 0}=36.1{+-}0.9 GPa and its derivative B{sub 0}{sup Prime }=6.2{+-}0.4 (not fixed). Using the refined structural data for {alpha}-Sb{sub 2}Te{sub 3}, for pressures up to 9.8 GPa, changes in the angle of succession [Te-Sb-Te-Sb-Te], in the interaromic distances of Sb and Te atoms belonging to this angle of succession and in the interatomic distances of atoms located on the c axis were examined. This analysis revealed an electronic topological transition (ETT) along the a and c axes at close to 3.7 GPa. From the RS spectra, the full widths at half maximum (FWHM) of the Raman active modes of {alpha}-Sb{sub 2}Te{sub 3} were plotted as functions of pressure and showed an ETT along the a and c axes at close to 3.2 GPa. The XRD patterns of phases II and III were well reproduced assuming {beta}-Bi{sub 2}Te{sub 3} and {gamma}-Bi{sub 2}Te{sub 3} structures similar to those reported in the literature for {alpha}-Bi{sub 2}Te{sub 3}.

  11. The role of equilibrium volume and magnetism on the stability of iron phases at high pressures.

    Science.gov (United States)

    Alnemrat, S; Hooper, J P; Vasiliev, I; Kiefer, B

    2014-01-29

    The present study provides new insights into the pressure dependence of magnetism by tracking the hybridization between crystal orbitals for pressures up to 600 GPa in the known hcp, bcc and fcc iron. The Birch-Murnaghan equation of state parameters are; bcc: V0 = 11.759 A(3)/atom, K0 = 177.72 GPa; hcp: V0 = 10.525 A(3)/atom, K0 = 295.16 GPa; and fcc: V0 = 10.682 A(3)/atom, K0 = 274.57 GPa. These parameters compare favorably with previous studies. Consistent with previous studies we find that the close-packed hcp and fcc phases are non-magnetic at pressures above 50 GPa and 60 GPa, respectively. The principal features of magnetism in iron are predicted to be invariant, at least up to ∼6% overextension of the equilibrium volume. Our results predict that magnetism for overextended fcc iron disappears via an intermediate spin state. This feature suggests that overextended lattices can be used to stabilize particular magnetic states. The analysis of the orbital hybridization shows that the magnetic bcc structure at high pressures is stabilized by splitting the majority and minority spin bands. The bcc phase is found to be magnetic at least up to 600 GPa; however, magnetism is insufficient to stabilize the bcc phase itself, at least at low temperatures. Finally, the analysis of the orbital contributions to the total energy provides evidence that non-magnetic hcp and fcc phases are likely more stable than bcc at core earth pressures.

  12. Synthesis of Dense BC3 Phases under High-Pressure and High-Temperature

    Science.gov (United States)

    Zinin, P.; Ming, L.; Acosta, T.; Jia, R.; Hellebrand, E.; Ishii, H.

    2010-12-01

    The finding of the new diamond-like B-C phases is of fundamental importance. These phases are potential high-temperature superconductors and their development is important for understanding the nature of high-temperature superconductivity (Moussa, Cohen, Phys. Rev. B, 77, 064518 2008). They will shed light on the nature of the bonding of the boron atoms in a diamond-like structure. Recently, theoretical simulations of pressure- and temperature-induced phase transition in the B-C system demonstrated that the incorporation of B atoms into a diamond structure should not lead to a drastic distortion of the cubic cell of a diamond (Lowther, J. Phys. Condense Matter. 17, 3221, 2005). In this report we present data on the synthesis of new dense phases cubic BC3 (c-BC3) phase from graphitic BC3 phase (g-BC3) phase under high pressure and high temperature. Two graphitic polycrystalline BCx samples were compressed in a diamond-anvil cell to about 24 GPa and 45 GPa, respectively, and then were laser-heated to ~2000 K. After quenching, each sample was decompressed gradually stepwise to the atmospheric pressure. Synchrotron-based X-ray diffraction patterns were taken before and after the laser-heating, and also at each pressure step-down. The experimental data showed that two new phases were synthesized: (a) an orthorhombic phase with a0 = 3.74 Å, b0 = 3.24 Å, c0=4.25 Å; and (b) a cubic phase with a0 = 3.587Å recovered from 24 GPa and 44 GPa, respectively. The zero-pressure lattice parameter of the cubic phase obtained in this study is larger than that of diamond (i.e., a0=3.5667 Å, ASTM # 6-0675), which is consistent with theoretical prediction The micro-Raman measurements were directly performed on the new phases. The Raman spectra excited by a green (Nd-YAG, 532-nm) laser were taken with a confocal Raman system (WiTec alpha300). The Raman spectrum of the c-BC3 phase is similar to that of diamond-like BC3 phase (Zinin et al., J. Raman Spectrosc., 38, 1362, 2007) with a

  13. Development and testing of a new apparatus for the measurement of high-pressure low-temperature phase equilibria

    DEFF Research Database (Denmark)

    Fonseca, José M.S.; von Solms, Nicolas

    2012-01-01

    A new apparatus for the study of high-pressure phase equilibria at low temperatures using an analytical method was designed, assembled and tested. The apparatus was specially developed for the study of multi-phase equilibria in systems containing hydrocarbons, water and hydrate inhibitors, at tem...

  14. Extraction of Lipids from Chlorella saccharophila Using High-Pressure Homogenization Followed by Three Phase Partitioning.

    Science.gov (United States)

    Mulchandani, Ketan; Kar, Jayaranjan R; Singhal, Rekha S

    2015-07-01

    Commercial exploitation of microalgae for biofuel and food ingredients is hindered due to laborious extraction protocols and use of hazardous chemicals. Production of lipids in the microalga grown in modified BG11 medium was evaluated to arrive at the appropriate harvesting conditions. The use of three phase partitioning (TPP) as a green approach for extraction of lipids from Chlorella saccharophila was investigated. Cells disrupted by probe sonication were used for separation of lipids by TPP. The TPP-optimized conditions of 30 % ammonium sulfate, using slurry/t-butanol of 1:0.75 for 60 min at 25 to 35 °C, showed a lipid recovery of 69.05 ± 3.12 % (w/w) as against 100 % (w/w) by using chloroform-methanol extraction. Subsequently, parameters of high-pressure homogenization for cell disruption were optimized for maximum recovery of lipids by TPP. A final recovery of 89.91 ± 3.69 % (w/w) lipids was obtained along with ∼1.26 % w/w carotenoids of dry biomass in the t-butanol layer and protein content of ∼12 % w/w of dry biomass in the middle protein layer due to ammonium sulfate precipitation, after performing TPP under the optimized conditions.

  15. Traction and nonequilibrium phase behavior of confined sheared liquids at high pressure

    Science.gov (United States)

    Gattinoni, Chiara; Heyes, David M.; Lorenz, Christian D.; Dini, Daniele

    2013-11-01

    Nonequilibrium molecular dynamics simulations of confined model liquids under pressure and sheared by the relative sliding of the boundary walls have been carried out. The relationship between the time-dependent traction coefficient, μ(t), and the state of internal structure of the film is followed from commencement of shear for various control parameters, such as applied load, global shear rate, and solid-liquid atom interaction parameters. Phase diagrams, velocity and temperature profiles, and traction coefficient diagrams are analyzed for pure Lennard-Jones (LJ) liquids and a binary LJ mixture. A single component LJ liquid is found to form semicrystalline arrangements with high-traction coefficients, and stick-slip behavior is observed for high pressures and low-shear velocities, which is shown to involve periodic deformation and stress release of the wall atoms and slip in the solid-liquid boundary region. A binary mixture, which discourages crystallization, gives a more classical tribological response with the larger atoms preferentially adsorbing commensurate with the wall. The results obtained are analyzed in the context of tribology: the binary mixture behaves like a typical lubricant, whereas the monatomic system behaves like a traction fluid. It is discussed how this type of simulation can give insights on the tribological behavior of realistic systems.

  16. High-pressure electron-resonance studies of electronic, magnetic, and structural phase transitions. Progress report

    International Nuclear Information System (INIS)

    Research is described in development of a high-pressure electron-resonance probe capable of operating down to 1.50K temperatures. The apparatus has been used to measure the EPR of a sample of DPPH at room temperature and zero pressure. EPR has been used to measure valence field instabilities in alloy systems. Studies have been done on metal-insulator transitions at high pressure, and are briefly described

  17. Prediction of new high pressure phase of TaB{sub 3}: First-principles

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xiaozheng [College of Science, Inner Mongolia University of Technology, Hohhot 010051 (China); State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Zhao, Erjun, E-mail: ejzhao@yahoo.com [College of Science, Inner Mongolia University of Technology, Hohhot 010051 (China); Wu, Zhijian, E-mail: zjwu@ciac.ac.cn [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China)

    2015-05-25

    Highlights: • Crystal structure of TaB{sub 3} is predicted using the evolutionary algorithm USPEX code. • The structural and mechanical properties of tantalum borides are investigated by DFT. • The stable phases are found by enthalpy-pressure relationship and convex hull. • oC16–TaB{sub 3} has a estimated hardness (41.2 GPa) and indentation strength (22.8 GPa). • High pressure is advantageous to syntheses of ruthenium Triborides oC16–TaB{sub 3}. - Abstract: The phase stability, elastic, mechanical, dynamical and electronic properties of tantalum borides, i.e., Ta{sub 2}B, TaB, Ta{sub 3}B{sub 4}, Ta{sub 5}B{sub 6}, TaB{sub 2} and TaB{sub 3}, have been investigated by first-principles. The calculated convex hull indicates that at ambient conditions, the ground state phases are tI12–Ta{sub 2}B, oC8–TaB, oC22–Ta{sub 5}B{sub 6}, oI14–Ta{sub 3}B{sub 4}, and hP3–TaB{sub 2}; while at 75 GPa, they are tI12–Ta{sub 2}B, oC8–TaB, oC22–Ta{sub 5}B{sub 6}, oI14–Ta{sub 3}B{sub 4}, hP3–TaB{sub 2} and oC16–TaB{sub 3}; oC8–TaB, oC22–Ta{sub 5}B{sub 6}, oI14–Ta{sub 3}B{sub 4}, oC16–TaB{sub 3} are the most stable phases at 120 GPa. The enthalpy-pressure relationship reveals that the hP3–TaB{sub 2} is the most stable below 75 GPa, while the predicted oC16–TaB{sub 3} becomes the most stable above 75 GPa. Combining the estimated hardness (41.2 GPa) and indentation strength (22.8 GPa) for oC16–TaB{sub 3}, it is suggested that oC16–TaB{sub 3} is hard or potential superhard. Since it is not available experimentally, further experimental synthesis could be rewarding.

  18. Melting phase relations in the system H2O - NH3 at high pressure

    Science.gov (United States)

    Sugimura, E.; Hirose, K.; Komabayashi, T.; Ohishi, Y.; Hirao, N.; Dubrovinsky, L. S.

    2012-12-01

    The density models of Uranus and Neptune constrained by their gravitational moments from Voyager mission suggest that mantles of these planets may be predominantly comprised of water (H2O), methane (CH4), and ammonia (NH3). The impurities in pure water would greatly influence the phase relations in the water-rich system expected in the icy mantle, which must be known to construct a plausible planetary model. One of important effects of the impurity is on the liquidus temperature (Tliq), since it decides the actual presence of solid phase within the icy mantle. In order to determine Tliq in H2O-rich region of the H2O - CH4 - NH3 ternary system, the melting phase relations in the H2O - CH4 and H2O - NH3 systems must be accurately known. However, previous melting experiments on each binary system were limited to several gigapascals, thus need to be explored to higher P-T conditions for application in interiors of Uranus and Neptune. We have investigated high-pressure (P) and -temperature (T) melting phase relations in the H2O - NH3 system based on a combination of visual observation and angle-dispersive x-ray diffraction (XRD) measurements at BL10XU, SPring-8. High-P-T conditions were generated in an externally-resistive heated diamond anvil cell (DAC). Starting material was 20wt% NH3 aqueous solution whose composition was checked via Tliq of the solution measured in a DAC at near atmospheric pressure. The aqueous solution was loaded into a gold-lined hole in a preindented rhenium gasket in order to insulate the sample from rhenium. Pressure was determined from the unit-cell volume of gold liner. Melting and freezing of the sample were detected by monitoring disappearance/appearance of diffraction peaks of solid and diffuse scattering of liquids, as well as observing melting/crystallization of crystal grains under microscope. Up to 20 GPa at room temperature, in addition to ice VII, diffraction peaks of bcc-like phase, which is most likely to be the reported phase VI

  19. Collapsed tetragonal phase and superconductivity of BaFe[subscript 2]As[subscript 2] under high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Uhoya, Walter; Stemshorn, Andrew; Tsoi, Georgiy; Vohra, Yogesh K.; Sefat, Athena S.; Sales, Brian C.; Hope, Kevin M.; Weir, Samuel T. (UAB); (ORNL); (LLNL); (Montevallo)

    2010-11-12

    High pressure x-ray diffraction and electrical resistance measurements have been carried out on BaFe{sub 2}As{sub 2} to a pressure of 35 GPa and temperature of 10 K using a synchrotron source and designer diamond anvils. At ambient temperature, a phase transition from the tetragonal phase to a collapsed tetragonal (CT) phase is observed at 17 GPa under nonhydrostatic conditions as compared to 22 GPa under hydrostatic conditions. The superconducting transition temperature increases rapidly with pressure up to 34 K at 1 GPa and decreases gradually with a further increase in pressure. Our results suggest that T{sub C} falls below 10 K in the pressure range of 16-30 GPa, where CT phase is expected to be stable under high-pressure and low-temperature conditions.

  20. Mechanical behaviors and phase transition of Ho{sub 2}O{sub 3} nanocrystals under high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Xiaozhi [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China); Center for High Pressure Science and Technology Advanced Research (HPSTAR), 1690 Cailun Rd., Pudong, Shanghai 201203 (China); Ren, Xiangting [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China); He, Duanwei, E-mail: duanweihe@scu.edu.cn, E-mail: yangwg@hpstar.ac.cn [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China); Institute of Fluid Physics and National Key Laboratory of Shockwave and Detonation Physic, China Academy of Engineering Physics, Mianyang 621900 (China); Chen, Bin [Center for High Pressure Science and Technology Advanced Research (HPSTAR), 1690 Cailun Rd., Pudong, Shanghai 201203 (China); Yang, Wenge, E-mail: duanweihe@scu.edu.cn, E-mail: yangwg@hpstar.ac.cn [Center for High Pressure Science and Technology Advanced Research (HPSTAR), 1690 Cailun Rd., Pudong, Shanghai 201203 (China); High Pressure Synergetic Consortium (HPSynC), Geophysical Laboratory, Carnegie Institution of Washington, 9700 S Cass Avenue, Argonne, Illinois 60439 (United States)

    2014-07-21

    Mechanical properties and phase transition often show quite large crystal size dependent behavior, especially at nanoscale under high pressure. Here, we have investigated Ho{sub 2}O{sub 3} nanocrystals with in-situ x-ray diffraction and Raman spectroscopy under high pressure up to 33.5 GPa. When compared to the structural transition routine cubic -> monoclinic -> hexagonal phase in bulk Ho{sub 2}O{sub 3} under high pressure, the nano-sized Ho{sub 2}O{sub 3} shows a much higher onset transition pressure from cubic to monoclinic structure and followed by a pressure-induced-amorphization under compression. The detailed analysis on the Q (Q = 2π/d) dependent bulk moduli reveals the nanosized Ho{sub 2}O{sub 3} particles consist of a clear higher compressible shell and a less compressible core. Insight into these phenomena shed lights on micro-mechanism studies of the mechanical behavior and phase evolution for nanomaterials under high pressure, in general.

  1. The High-Pressure Phase of MgB2C2

    NARCIS (Netherlands)

    Woerle, Michael; Fischbach, Urs; Widmer, Daniel; Krumeich, Frank; Nesper, Reinhard; Evers, Juergen; Stalder, Roland; Ulmer, Peter

    2010-01-01

    A high-pressure modification of MgB2C2 was synthesized and structurally characterized. The compound crystallizes in the orthorhombic space group Pnnm, with the lattice parameters a = 7.19633(3) angstrom, b = 4.61791(13) angstrom and c = 2.77714(8) angstrom. The compound contains heterographene B-C n

  2. A new phase of ThC at high pressure predicted from a first-principles study

    Science.gov (United States)

    Guo, Yongliang; Qiu, Wujie; Ke, Xuezhi; Huai, Ping; Cheng, Cheng; Han, Han; Ren, Cuilan; Zhu, Zhiyuan

    2015-08-01

    The phase transition of thorium monocarbide (ThC) at high pressure has been studied by means of density functional theory. Through structure search, a new phase with space group P 4 / nmm has been predicted. The calculated phonons demonstrate that this new phase and the previous B2 phase are dynamically stable as the external pressure is greater than 60 GPa and 120 GPa, respectively. The transformation from B1 to P 4 / nmm is predicted to be a first-order transition, while that from P 4 / nmm to B2 is found to be a second-order transition.

  3. Study of film thickness on fuel rod under high pressure and high temperature steam-water two phase flow

    International Nuclear Information System (INIS)

    The liquid film thickness on the fuel rod is measured by ultrasonic echo technique under high temperature and high pressure steam-water two phase flow. As quality is increased, film thickness is decreased. The film thickness is about 0.2 mm at 9% of quality under 1 MPa. It was found from test data that disturbance wave is not measured clearly and change of film is small. (author)

  4. Ergot alkaloids in rye flour determined by solid phase cation-exchange and high pressure liquid chromatography with fluorescence detection

    OpenAIRE

    Storm, Ida Drejer; Have Rasmussen, Peter; Strobel, Bjarne W.; Hansen, Hans Christian Bruun

    2008-01-01

    Abstract Ergot alkaloids (EAs) are mycotoxins which are unavoidable contaminants of cereal products, particularly rye. A method was compiled employing clean-up by cation-exchange solid phase extraction, separation by high-pressure liquid chromatography under alkaline conditions and fluorescence detection. It is capable of separating and quantifying both C8-isomers of ergocornine, a-ergocryptine, ergocristine, ergonovine, and ergotamine. The average recovery was 61?10 % with limits ...

  5. High-Pressure Torsion of Ti: Synchrotron characterization of phase volume fraction and domain sizes

    OpenAIRE

    Bolmaro, Raúl E; Sordi, Vitor L.; Ferrante, Maurizio; Brokmeier, Heinz-Günter; Kawasaki, Megumi; Terence G. Langdon

    2014-01-01

    Rods of grade 2 Ti were processed by Equal-Channel Angular Pressing (ECAP) (phi = 120° at 573 K) employing 2, 4 and 6 passes. The same billets were further deformed by High- Pressure Torsion (HPT) at room temperature, varying both the hydrostatic pressure (1 and 6 GPa) and the number of rotations (n = 1 and 5). The ECAP and HPT samples were studied by synchrotron radiation at DESY-Petra III GEMS line. On the ECAP samples, textures were thus determined while for both ECAP and HPT samples the m...

  6. Stability of rhombohedral phases in vanadium at high-pressure and high-temperature: first-principles investigations

    CERN Document Server

    Wang, Yi X; Chen, Xiang R; Geng, Hua Y

    2016-01-01

    The pressure-induced transition of vanadium from BCC to rhombohedral structures is unique and intriguing among transition metals. In this work, the stability of these phases is revisited by using density functional theory. At finite temperatures, a novel transition of rhombohedral phases back to BCC phase induced by thermal electrons is discovered. This reentrant transition is found not driven by phonons, instead it is the electronic entropy that stabilizes the latter phase, which is totally out of expectation. Parallel to this transition, we find a peculiar and strong increase of the shear modulus C44 with increasing temperature. It is counter-intuitive in the sense that it suggests an unusual harding mechanism of vanadium by temperature. With these stability analyses, the high-pressure and finite-temperature phase diagram of vanadium is proposed. Furthermore, the dependence of the stability of RH phases on the Fermi energy and chemical environment is investigated. The results demonstrate that the position o...

  7. The piston-cylinder apparatus for in-situ structural investigations of high-pressure phases of gas hydrates with the use of synchrotron radiation

    CERN Document Server

    Mirinski, D S; Larionova, E G; Kurnosov, A V; Ancharov, A I; Dyadin, Y A; Tolochko, B P; Sheromov, M A

    2001-01-01

    The piston-cylinder apparatus for the investigation of high-pressure gas hydrate phases by the powder diffraction method is presented. The first results concerning the nature of the high-pressure gas hydrate phase in the sulfur hexafluoride-water system are reported.

  8. The stability of Al,Fe-bearing phase H and a new pyrite-type hydroxide at high pressures

    Science.gov (United States)

    Nishi, M.; Kuwayama, Y.; Tsuchiya, J.; Irifune, T.

    2015-12-01

    Water plays an important role in the structure, dynamics, and evolution of planets because hydrogen can affect the physical properties and stabilities of constituent minerals in the planets. Since alumimous phase H (MgSiO4H2-AlOOH) is stable over the entire pressure range of the lower mantle, the hydrated subducting plate may deliver a certain amount of water into the bottom of the Earth's mantle (Tsuchiya 2013, Nishi et al. 2013, Ohira et al. 2014, Walter et al. 2015). Compositional analysis of phase H grains synthesized from natural serpentine shows the presence of the Fe component in this phase (Nishi et al., 2015). This result suggests that phase H would also form solid solutions with ɛ-FeOOH, since ɛ-FeOOH is isostructural to phase H and δ-AlOOH. Moreover, an ab initio calculation has recently predicted that the new high pressure form of AlOOH, which has pyrite-type structure, would be stabilized at pressures above 170 GPa (Tsuchiya and Tsuchiya, 2011). Although this pyrite-type hydroxide has been found in InOOH, this structure in AlOOH has not been reported by experimental studies. Here we examine the composition and stability of Al,Fe-bearing phase H using a multi-anvil apparatus combined with sintered diamond anvils. Results show that large amounts of Fe and Al are partitioned into phase H relative to bridgmanite. Fe likely affects the stability of phase H in the lower mantle. Also, we conducted high pressure experiments on pure δ-AlOOH by using laser-heated diamond anvil cell (DAC) techniques up to 200 GPa and 2,500 K. In-situ X-ray diffraction (XRD) measurements indicated that the transition from the δ-AlOOH to the pyrite-type structure occurs at high pressures above 190 GPa. Our experimental results exhibited a density reduction of 2.6 wt.% through the structural transition, and both experimental data plots and theoretical calculations showed similar compressibilities of δ-AlOOH and pyrite-type AlOOH. In recent years, hundreds of extra

  9. A new experimental setup for the liquid-solid phase transition determination in crude oils under high pressure conditions

    Energy Technology Data Exchange (ETDEWEB)

    A. Rizzo; H. Carrier; J. Castillo; S. Acevedo; J. Pauly [UNEXPO - Vicerectorado Barquisimeto (Venezuela). Departamento de Ingeniera Quimica

    2007-08-15

    A high pressure apparatus based on two sapphire windows high pressure cell coupled with a detection system of the reflected and refracted light intensities coming from a laser beam was designed to determine the phase transitions by the measurement of the light intensity change. The setup was used to measure the wax disappearance temperature under pressure up to 100 MPa in pure component, synthetic complex mixtures made up of distributions of n-paraffins ranging from n-C{sub 20} to n-C{sub 42}. Finally a real stabilized condensate was successfully investigated and the sensitivity of the detection system was demonstrated on a dark crude oil. 30 refs., 10 figs., 1 tab.

  10. Structural and magnetic phase transitions in gadolinium under high pressures and low temperatures

    Science.gov (United States)

    Samudrala, Gopi K.; Tsoi, Georgiy M.; Weir, Samuel T.; Vohra, Yogesh K.

    2014-10-01

    High pressure structural transition studies have been carried out on rare earth metal gadolinium in a diamond anvil cell at room temperature to 169 GPa. Gadolinium has been compressed to 38% of its initial volume at this pressure. With increasing pressure, a crystal structure sequence of hcp → Sm-type → dhcp → fcc → dfcc → monoclinic has been observed in our studies on gadolinium. The measured equation of state of gadolinium is presented to 169 GPa at ambient temperature. Magnetic ordering temperature of gadolinium has been studied using designer diamond anvils to a pressure of 25 GPa and a temperature of 10 K. The magnetic ordering temperature has been determined from the four-point electrical resistivity measurements carried out on gadolinium. Our experiments show that the magnetic transition temperature decreases with increasing pressure to 19 GPa and then increases when gadolinium is subjected to higher pressures.

  11. A first principles study of phase stability, bonding, electronic and lattice dynamical properties of beryllium chalcogenides at high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Dabhi, Shweta [Department of Physics, Maharaja Krishnakumarsinhji Bhavnagar University, Bhavnagar 364001 (India); Mankad, Venu [Central Institute of Plastic Engineering and Technology, Ahmedabad (India); Jha, Prafulla K., E-mail: prafullaj@yahoo.com [Department of Physics, Faculty of Science, The M.S. University of Baroda, Vadodara 390002 (India)

    2014-12-25

    Highlights: • First principles calculations are performed for BeS, BeSe and BeTe in B3, B8 and B1 phases. • They are indirect wide band gap semiconductors stable in B3 phase at ambient condition. • Phonon calculations at ambient and high pressure are reported. • The NiAs phase is dynamically stable at high pressure. - Abstract: The present paper reports a detailed and systematic theoretical study of structural, mechanical, electronic, vibrational and thermodynamical properties of three beryllium chalcogenides BeS, BeSe and BeTe in zinc blende, NiAs and rock salt phases by performing ab initio calculations based on density-functional theory. The calculated value of lattice constants and bulk modulus are compared with the available experimental and other theoretical data and found to agree reasonably well. These compounds are indirect wide band gap semiconductors with a partially ionic contribution in all considered three phases. The zinc blende phase of these chalcogenides is found stable at ambient condition and phase transition from zinc blende to NiAs structure is found to occur. The bulk modulus, its pressure derivative, anisotropic factor, Poission’s ratio, Young’s modulus for these are also calculated and discussed. The phonon dispersion curves of these beryllium chalcogenides in zinc blende phase depict their dynamical stability in this phase at ambient condition. We have also estimated the temperature variation of specific heat at constant volume, entropy and Debye temperature for these compounds in zinc blende phase. The variation of lattice-specific heat with temperature obeys the classical Dulong–Petit’s law at high temperature, while at low-temperature it obeys the Debye’s T{sup 3} law.

  12. Two-phase convection in the high-pressure ice layer of the large icy moons: geodynamical implications

    Science.gov (United States)

    Kalousova, K.; Sotin, C.; Tobie, G.; Choblet, G.; Grasset, O.

    2015-12-01

    The H2O layers of large icy satellites such as Ganymede, Callisto, or Titan probably include a liquid water ocean sandwiched between the deep high-pressure ice layer and the outer ice I shell [1]. It has been recently suggested that the high-pressure ice layer could be decoupled from the silicate core by a salty liquid water layer [2]. However, it is not clear whether accumulation of liquids at the bottom of the high-pressure layer is possible due to positive buoyancy of water with respect to high-pressure ice. Numerical simulation of this two-phase (i.e. ice and water) problem is challenging, which explains why very few studies have self-consistently handled the presence and transport of liquids within the solid ice [e.g. 3]. While using a simplified description of water production and transport, it was recently showed in [4] that (i) a significant fraction of the high-pressure layer reaches the melting point and (ii) the melt generation and its extraction to the overlying ocean significantly influence the global thermal evolution and interior structure of the large icy moons.Here, we treat the high-pressure ice layer as a compressible mixture of solid ice and liquid water [5]. Several aspects are investigated: (i) the effect of the water formation on the vigor of solid-state convection and its influence on the amount of heat that is transferred from the silicate mantle to the ocean; (ii) the fate of liquids within the upper thermal boundary layer - whether they freeze or reach the ocean; and (iii) the effect of salts and volatile compounds (potentially released from the rocky core) on the melting/freezing processes. Investigation of these aspects will allow us to address the thermo-chemical evolution of the internal ocean which is crucial to evaluate the astrobiological potential of large icy moons. This work has been performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA. [1] Hussmann et al. (2007), Treatise of

  13. Thermal expansion study on high-pressure phases of SmS

    International Nuclear Information System (INIS)

    We have measured the thermal expansion coefficient αL(T) of SmS under pressure up to 21.6kbar. In the golden phase, an excitation gap Δ inferred from αL(T) decreases with increasing pressure. When the system enters the metallic phase from the golden phase, Δ collapses suddenly to zero, and simultaneously, a huge sharp anomaly appears in the αL(T) curve, reflecting the magnetic phase transition

  14. Ambient-condition growth of high-pressure phase centrosymmetric crystalline KDP microstructures for optical second harmonic generation.

    Science.gov (United States)

    Ren, Yan; Zhao, Xian; Hagley, Edward W; Deng, Lu

    2016-08-01

    Noncentrosymmetric potassium dihydrogen phosphate (KH2PO4 or KDP) in the tetragonal crystal phase is arguably the most extensively studied nonlinear optical crystal in history. It has prolific applications ranging from simple laser pointers to laser inertial confinement fusion systems. Recently, type IV high-pressure KDP crystal sheets with a monoclinic crystal phase having centrosymmetric properties have been observed. However, it was found that this new crystal phase is highly unstable under ambient conditions. We report ambient-condition growth of one-dimensional, self-assembled, single-crystalline KDP hexagonal hollow/solid-core microstructures that have a molecular structure and symmetry identical to the type IV KDP monoclinic crystal that was previously found to exist only at extremely high pressures (>1.6 GPa). Furthermore, we report highly efficient bulk optical second harmonic generation (SHG) from these ambient condition-grown single-crystalline microstructures, even though they have a highly centrosymmetric crystal phase. However, fundamental physics dictates that a bulk optical medium with a significant second-order nonlinear susceptibility supporting SHG must have noncentrosymmetric properties. Laue diffraction analysis reveals a weak symmetry-breaking twin-crystal lattice that, in conjunction with tight confinement of the light field by the tubular structure, is attributed to the significant SHG even with sample volumes <0.001 mm(3). A robust polarization-preserving effect is also observed, raising the possibility of advanced optical technological applications. PMID:27574703

  15. High-pressure structural phase transitions in chromium-doped BaFe[subscript 2]As[subscript 2

    Energy Technology Data Exchange (ETDEWEB)

    Uhoya, W.O.; Montgomery, J.M.; Samudrala, G.K.; Tsoi, G.M.; Vohra, Y.K.; Weir, S.T.; Sefat, A.S. (UAB); (LLNL); (ORNL)

    2012-10-23

    We report on the results from high pressure x-ray powder diffraction and electrical resistance measurements for hole doped BaFe{sub 2-x}Cr{sub x}As{sub 2} (x = 0, 0.05, 0.15, 0.4, 0.61) up to 81 GPa and down to 10 K using a synchrotron source and diamond anvil cell (DAC). At ambient temperature, an isostructural phase transition from a tetragonal (T) phase (I4/mmm) to a collapsed tetragonal (CT) phase is observed at 17 GPa. This transition is found to be dependent on ambient pressure unit cell volume and is slightly shifted to higher pressure upon increase in the Cr-doping. Unlike BaFe{sub 2}As{sub 2} which superconduct under high pressure, we have not detected any evidence of pressure induced superconductivity in chromium doped samples in the pressure and temperature range of this study. The measured equation of state parameters are presented for both the tetragonal and collapsed tetragonal phases for x = 0.05, 0.15, 0.40 and 0.61.

  16. Structural phase transitions of ionic layered PbFX (X = Cl−or Br–) compounds under high pressure

    International Nuclear Information System (INIS)

    The PbFX (X = Cl–or Br–) compounds crystallize in tetragonal structure with space group P4/nmm. High pressure X-ray diffraction studies carried out on PbFCl compound reveals that it undergoes pressure induced structural transitions at ∼18 GPa and ∼38 GPa to orthorhombic and monoclinic (P21/m) phases respectively. Like PbFCl, a similar phase transition from tetragonal to orthorhombic phase is observed in PbFBr at intermediate pressure. These phase transitions seem to be similar to the transitions involving other matlockite structure compounds such as BaFX (X = Cl–, Br–or I–). PbFCl has a larger structural stability range compared to BaFCl and is attributed to the large anisotropic coordination of the Pb2+ and Cl–ions

  17. Formation of metastable phases in magnesium–titanium system by high-pressure torsion and their hydrogen storage performance

    International Nuclear Information System (INIS)

    No binary phases exist in the Mg–Ti binary equilibrium phase diagram and the two elements are totally immiscible even in liquid form. This study shows that four metastable phases (two with the bcc and fcc structures and two with the hcp structures) are formed in the Mg–Ti system by severe plastic deformation (SPD) through the process of high-pressure torsion (HPT). Investigation of hydrogenation properties reveals that these metastable phases are decomposed to pure Mg and Ti during heating before they can absorb the hydrogen in the form of ternary Mg–Ti hydrides. First-principles calculations show that the hydrogenation reaction should occur thermodynamically, and ternary Mg–Ti hydrides with the cubic structure should form at low temperature. However, the slow kinetics for this reaction appears to be the limiting step. Calculations show that the binding energy of hydrogen increases and the thermodynamic stability of hydrides undesirably increases by addition of Ti to Mg

  18. Structure of intermediate phase II of LiNH2 under high pressure.

    Science.gov (United States)

    Yamawaki, Hiroshi; Fujihisa, Hiroshi; Gotoh, Yoshito; Nakano, Satoshi

    2014-08-21

    A new intermediate phase (phase II) was found between phases I and III in LiNH2 in the pressure range of 10 to 13 GPa through the analysis of infrared and powder X-ray diffraction measurements to 25 GPa at room temperature. This result agreed with the prediction of a stable phase between phases I and III through theoretical calculations. Powder X-ray diffraction measurement and DFT calculation showed that this phase has a monoclinic structure with space group C2/c (Z = 8), which is the same structure as that of a slightly tilted crystal lattice of the Fddd structural model. The enthalpy of the C2/c structure was also found to be almost the same as that of the Fddd structure.

  19. Modelling three-phase releases of carbon dioxide from high-pressure pipelines

    OpenAIRE

    Martynov, S.; S. Brown; Mahgerefteh, H.; Sundara, V.; Chen, S.; Zhang, Y.

    2014-01-01

    This paper describes the development and experimental validation of a three-phase flow model for predicting the transient outflow following the failure of pressurised CO2 pipelines and vessels. The choked flow parameters at the rupture plane, spanning the dense-phase and saturated conditions to below the triple point, are modelled by maximisation of the mass flowrate with respect to pressure and solids mass fraction at the triple point. The pertinent solid/vapour/liquid phase equilibrium data...

  20. High-pressure phase of the cubic spinel NiMn2O4

    DEFF Research Database (Denmark)

    Åsbrink, S.; Waskowska, A.; Olsen, J. Staun;

    1998-01-01

    It has been observed that the fee spinel NiMn2O4 transforms to a tetragonal structure at about 12 GPa. The tetragonal phase does not revert to the cubic phase upon decompression and its unit-cell constants at ambient pressure are a(0)=8.65(8) and c(0)=7.88(15) Angstrom (distorted fee). Within thr......). The bulk modulus of the cubic phase is 206(4) GPa....

  1. High-pressure high-temperature synthesis of novel binary and ternary nitride phases of group 4 and 14 elements

    OpenAIRE

    Dzivenko, D. A.; Horvath-Bordon, E.; Zerr, A.; Miehe, G.; Kroll, P.; Boehler, R.; McMillan, P.F.; Riedel, R.

    2008-01-01

    Our recent experiments on high-pressure high-temperature synthesis of novel ternary nitrides of group 4 and 14 elements are presented. Dense carbon nitride imide, C2N2(NH), was synthesized for the first time in a laser heated diamond anvil cell (LH-DAC) at pressures above 27 GPa and temperatures around 2000 K. Based on results of the electron diffraction-, EELS-and SIMS-measurements combined with theoretical calculations the structure of this new C-N-H phase was suggested to be of the defect-...

  2. Structural phase transition and elastic properties of thorium pnictides at high pressure

    Indian Academy of Sciences (India)

    Kuldeep Kholiya; B R K Gupta

    2007-04-01

    In the present paper we have pointed out the weaknesses of the approach by Aynyas et al [1] to study the structural phase transition and elastic properties of thorium pnictides. The calculated values of phase transition pressure and other elastic properties using the realistic and actual approach are also given and compared with the experimental and previous theoretical work.

  3. Stability of the high-pressure body-centered-cubic phase of helium

    NARCIS (Netherlands)

    Frenkel, D.

    1986-01-01

    This paper report absolute free-energy calculations of the fluid, body-centered-cubic, and face-centered-cubic phases of helium at T=327.04 K. We find that at and around this temperature the model potential proposed by Aziz et al. doe not yield a stable bcc phase. Quantum corrections do not alter th

  4. High pressure Laue diffraction and its application to study microstructural changes during the α → β phase transition in Si

    Energy Technology Data Exchange (ETDEWEB)

    Popov, D., E-mail: dpopov@carnegiescience.edu; Park, C.; Kenney-Benson, C.; Shen, G. [High Pressure Collaborative Access Team, Geophysical Laboratory, Carnegie Institution of Washington, Argonne, Illinois 60439 (United States)

    2015-07-15

    An approach using polychromatic x-ray Laue diffraction is described for studying pressure induced microstructural changes of materials under pressure. The advantages of this approach with respect to application of monochromatic x-ray diffraction and other techniques are discussed. Experiments to demonstrate the applications of the method have been performed on the α → β phase transition in Si at high pressures using a diamond anvil cell. We present the characterization of microstructures across the α–β phase transition, such as morphology of both the parent and product phases, relative orientation of single-crystals, and deviatoric strains. Subtle inhomogeneous strain of the single-crystal sample caused by lattice rotations becomes detectable with the approach.

  5. Structural and electronic properties of high pressure phases of lead chalcogenides

    Science.gov (United States)

    Petersen, John; Scolfaro, Luisa; Myers, Thomas

    2012-10-01

    Lead chalcogenides, most notably PbTe and PbSe, have become an active area of research due to their thermoelectric properties. The high figure of merit (ZT) of these materials has brought much attention to them, due to their ability to convert waste heat into electricity. Variation in synthesis conditions gives rise to a need for analysis of structural and thermoelectric properties of these materials at different pressures. In addition to the NaCl structure at ambient conditions, lead chalcogenides have a dynamic orthorhombic (Pnma) intermediate phase and a higher pressure yet stable CsCl phase. By altering the lattice constant, we simulate the application of external pressure; this has notable effects on ground state total energy, band gap, and structural phase. Using the General Gradient Approximation (GGA) in Density Functional Theory (DFT), we calculate the phase transition pressures by finding the differences in enthalpy from total energy calculations. For each phase, elastic constants, bulk modulus, shear modulus, Young's modulus, and hardness are calculated, using two different approaches. In addition to structural properties, we analyze the band structure and density of states at varying pressures, paying special note to thermoelectric implications.

  6. High-pressure phase behaviour of poly(D-lactic acid), trichloromethane, and carbon dioxide ternary mixture systems

    International Nuclear Information System (INIS)

    Highlights: • The high pressure phase behaviour of poly(D-lactic acid), trichloromethane and carbon dioxide ternary mixtures was measured. • The experimental data shows the characteristics of the LCST behaviour of (polymer + solvent + gas) systems. • The hybrid equation of state for the (polymer + carbon dioxide) system was used to correlate the experimental data. - Abstract: The high pressure phase behaviour of poly(D-lactic acid) (Mw = 359,000), trichloromethane, and carbon dioxide ternary mixture systems is presented in this study. Cloud and bubble point pressures were measured using a variable volume view cell at temperatures (313.15 to 363.15) K and pressures up to 33.6 MPa. The hybrid equation of state for the polymer-carbon dioxide system was used to correlate the experimental results. The van der Waals one-fluid mixing rule with three adjustable binary interaction parameters was used for all correlations. The binary parameters were optimised using the simplex method algorithm

  7. A route to possible civil engineering materials: the case of high-pressure phases of lime

    OpenAIRE

    A. Bouibes; Zaoui, A.

    2015-01-01

    Lime system has a chemical composition CaO, which is known as thermodynamically stable. The purpose here is to explore further possible phases under pressure, by means of variable-composition ab initio evolutionary algorithm. The present investigation shows surprisingly new stable compounds of lime. At ambient pressure we predict, in addition to CaO, CaO2 as new thermodynamically stable compound. The latter goes through two phases transition from C2/c space group structure to Pna21 at 1.5 GPa...

  8. Compressibility of the high-pressure rocksalt phase of ZnO

    DEFF Research Database (Denmark)

    Recio, J.M.; Blanco, M.A.; Luana, V.;

    1998-01-01

    We report the results of a combined experimental and theoretical investigation on the stability and the volume behavior under hydrostatic pressure of the rocksalt (B1) phase of ZnO. Synchrotron-radiation x-ray powder-diffraction data are obtained from 0 to 30 GPa. Static simulations of the ZnO B1...... in the range of 160-194 GPa. For its zero-pressure first derivative, the experimental and theoretical data yield a value of 4.4+/-1.0. Overall, our results show that the ZnO B1 phase is slightly more compressible than previously reported. [S0163-1829(98)07537-7]....

  9. Stability of rhombohedral phases in vanadium at high-pressure and high-temperature: first-principles investigations

    Science.gov (United States)

    Wang, Yi X.; Wu, Q.; Chen, Xiang R.; Geng, Hua Y.

    2016-09-01

    The pressure-induced transition of vanadium from BCC to rhombohedral structures is unique and intriguing among transition metals. In this work, the stability of these phases is revisited by using density functional theory. At finite temperatures, a novel transition of rhombohedral phases back to BCC phase induced by thermal electrons is discovered. This reentrant transition is found not driven by phonons, instead it is the electronic entropy that stabilizes the latter phase, which is totally out of expectation. Parallel to this transition, we find a peculiar and strong increase of the shear modulus C44 with increasing temperature. It is counter-intuitive in the sense that it suggests an unusual harding mechanism of vanadium by temperature. With these stability analyses, the high-pressure and finite-temperature phase diagram of vanadium is proposed. Furthermore, the dependence of the stability of RH phases on the Fermi energy and chemical environment is investigated. The results demonstrate that the position of the Fermi level has a significant impact on the phase stability, and follows the band-filling argument. Besides the Fermi surface nesting, we find that the localization/delocalization of the d orbitals also contributes to the instability of rhombohedral distortions in vanadium.

  10. Phase relation of CaSO4 at high pressure and temperature up to 90 GPa and 2300 K

    Science.gov (United States)

    Fujii, Taku; Ohfuji, Hiroaki; Inoue, Toru

    2016-05-01

    Calcium sulfate (CaSO4), one of the major sulfate minerals in the Earth's crust, is expected to play a major role in sulfur recycling into the deep mantle. Here, we investigated the crystal structure and phase relation of CaSO4 up to ~90 GPa and 2300 K through a series of high-pressure experiments combined with in situ X-ray diffraction. CaSO4 forms three thermodynamically stable polymorphs: anhydrite (stable below 3 GPa), monazite-type phase (stable between 3 and ~13 GPa) and barite-type phase (stable up to at least 93 GPa). Anhydrite to monazite-type phase transition is induced by pressure even at room temperature, while monazite- to barite-type transition requires heating at least to 1500 K at ~20 GPa. The barite-type phase cannot always be quenched from high temperature and is distorted to metastable AgMnO4-type structure or another modified barite structure depending on pressure. We obtained the pressure-volume data and density of anhydrite, monazite- and barite-type phases and found that their densities are lower than those calculated from the PREM model in the studied P-T conditions. This suggests that CaSO4 is gravitationally unstable in the mantle and fluid/melt phase into which sulfur dissolves and/or sulfate-sulfide speciation may play a major role in the sulfur recycling into the deep Earth.

  11. Beryl-II, a high-pressure phase of beryl: Raman and luminescence spectroscopy to 16.4 GPa

    Science.gov (United States)

    O'Bannon, Earl; Williams, Quentin

    2016-10-01

    The Raman and Cr3+ and V2+ luminescence spectra of beryl and emerald have been characterized up to 15.0 and 16.4 GPa, respectively. The Raman spectra show that an E 1g symmetry mode at 138 cm-1 shifts negatively by -4.57 (±0.55) cm-1/GPa, and an extrapolation of the pressure dependence of this mode indicates that a soft-mode transition should occur near 12 GPa. Such a transition is in accord with prior theoretical results. Dramatic changes in Raman mode intensities and positions occur between 11.2 and 15.0 GPa. These changes are indicative of a phase transition that primarily involves tilting and mild distortion of the Si6O18 rings. New Raman modes are not observed in the high-pressure phase, which indicates that the local bonding environment is not altered dramatically across the transition (e.g., changes in coordination do not occur). Both sharp line and broadband luminescence are observed for both Cr3+ and V2+ in emerald under compression to 16.4 GPa. The R-lines of both Cr3+ and V2+ shift to lower energy (longer wavelength) under compression. Both R-lines of Cr3+ split at ~13.7 GPa, and the V2+ R1 slope changes at this pressure and shifts more rapidly up to ~16.4 GPa. The Cr3+ R-line splitting and FWHM show more complex behavior, but also shift in behavior at ~13.7 GPa. These changes in the pressure dependency of the Cr3+ and V2+ R-lines and the changes in R-line splitting and FWHM at ~13.7 GPa further demonstrate that a phase transition occurs at this pressure, in good agreement with our Raman results. The high-pressure phase of beryl appears to have two Al sites that become more regular under compression. Hysteresis is not observed in our Raman or luminescence spectra on decompression, suggesting that this transition is second order in nature: The occurrence of a second-order transition near this pressure is also in accord with prior theoretical results. We speculate that the high-pressure phase (beryl-II) might be a mildly modulated structure, and/or that

  12. Beryl-II, a high-pressure phase of beryl: Raman and luminescence spectroscopy to 16.4 GPa

    Science.gov (United States)

    O'Bannon, Earl; Williams, Quentin

    2016-08-01

    The Raman and Cr3+ and V2+ luminescence spectra of beryl and emerald have been characterized up to 15.0 and 16.4 GPa, respectively. The Raman spectra show that an E 1g symmetry mode at 138 cm-1 shifts negatively by -4.57 (±0.55) cm-1/GPa, and an extrapolation of the pressure dependence of this mode indicates that a soft-mode transition should occur near 12 GPa. Such a transition is in accord with prior theoretical results. Dramatic changes in Raman mode intensities and positions occur between 11.2 and 15.0 GPa. These changes are indicative of a phase transition that primarily involves tilting and mild distortion of the Si6O18 rings. New Raman modes are not observed in the high-pressure phase, which indicates that the local bonding environment is not altered dramatically across the transition (e.g., changes in coordination do not occur). Both sharp line and broadband luminescence are observed for both Cr3+ and V2+ in emerald under compression to 16.4 GPa. The R-lines of both Cr3+ and V2+ shift to lower energy (longer wavelength) under compression. Both R-lines of Cr3+ split at ~13.7 GPa, and the V2+ R1 slope changes at this pressure and shifts more rapidly up to ~16.4 GPa. The Cr3+ R-line splitting and FWHM show more complex behavior, but also shift in behavior at ~13.7 GPa. These changes in the pressure dependency of the Cr3+ and V2+ R-lines and the changes in R-line splitting and FWHM at ~13.7 GPa further demonstrate that a phase transition occurs at this pressure, in good agreement with our Raman results. The high-pressure phase of beryl appears to have two Al sites that become more regular under compression. Hysteresis is not observed in our Raman or luminescence spectra on decompression, suggesting that this transition is second order in nature: The occurrence of a second-order transition near this pressure is also in accord with prior theoretical results. We speculate that the high-pressure phase (beryl-II) might be a mildly modulated structure, and/or that

  13. Equilibrium Between Phases of Matter: Supplemental Text for Materials Science and High-Pressure Geophysics

    NARCIS (Netherlands)

    Jacobs, M.H.G.; Oonk, H.A.J.

    2012-01-01

    The Second Volume of Equilibrium between Phases of Matter, when compared with the First Volume, by H.A.J. Oonk and M.T. Calvet, published in 2008, amounts to an extension of subjects, and a deepening of understanding. In the first three sections of the text an extension is given of the theory on iso

  14. Structural phase transitions in IrO2 at high pressures

    International Nuclear Information System (INIS)

    Structural transformations in iridium dioxide (IrO2) were investigated using first-principles calculations up to a pressure of 50 GPa at 0 K. The phase transformation from the rutile-type to the pyrite-type structure was confirmed at 8-15 GPa. Although structures of the CaCl2-type and α-PbO2-type are observed in other metal dioxides, such as SiO2, GeO2, and SnO2, our calculations indicated that these structures are metastable in IrO2. Our calculations explain experimental observations which show the direct transformation from the rutile-type to the pyrite-type structures in IrO2. The bulk modulus of the pyrite-type phase calculated in this study is in good agreement with the experimental value. The non-magnetic state is stable relative to the ferromagnetic and antiferromagnetic states in all IrO2 phases. The calculated electronic density of states suggests that the pyrite-type phase is metallic

  15. Neutron diffraction and electrical transport studies on the incommensurate magnetic phase transition in holmium at high pressures

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, Sarah [University of Alabama, Birmingham; Uhoya, Walter [University of Alabama, Birmingham; Tsoi, Georgiy [University of Alabama, Birmingham; Wenger, Lowell E [University of Alabama, Birmingham; Vohra, Yogesh [University of Alabama, Birmingham; Chesnut, Gary Neal [University of Alabama, Birmingham; Weir, S. T. [Lawrence Livermore National Laboratory (LLNL); Tulk, Christopher A [ORNL; Moreira Dos Santos, Antonio F [ORNL

    2012-01-01

    Neutron diffraction and electrical transport measurements have been made on the heavy rare earth metal holmium at high pressures and low temperatures in order to elucidate its transition from a paramagnetic (PM) to a helical antiferromagnetic (AFM) ordered phase as a function of pressure. The electrical resistance measurements show a change in the resistance slope as the temperature is lowered through the antiferromagnetic Neel temperature. The temperature of this antiferromagnetic transition decreases from approximately 122 K at ambient pressure at a rate of -4.9 K GPa(-1) up to a pressure of 9 GPa, whereupon the PM-to-AFM transition vanishes for higher pressures. Neutron diffraction measurements as a function of pressure at 89 and 110 K confirm the incommensurate nature of the phase transition associated with the antiferromagnetic ordering of the magnetic moments in a helical arrangement and that the ordering occurs at similar pressures as determined from the resistance results for these temperatures.

  16. Formation of collapsed tetragonal phase in EuCo2As2 under high pressure

    International Nuclear Information System (INIS)

    The structural properties of EuCo2As2 have been studied up to 35 GPa, through the use of x-ray diffraction in a diamond anvil cell at a synchrotron source. At ambient conditions, EuCo2As2 (I4/mmm) has a tetragonal lattice structure with a bulk modulus of 48 ± 4 GPa. With the application of pressure, the a axis exhibits negative compressibility with a concurrent sharp decrease in c-axis length. The anomalous compressibility of the a axis continues until 4.7 GPa, at which point the structure undergoes a second-order phase transition to a collapsed tetragonal (CT) state with a bulk modulus of 111 ± 2 GPa. We found a strong correlation between the ambient pressure volume of 122 parents of superconductors and the corresponding tetragonal to collapsed tetragonal phase transition pressures.

  17. First-principles calculations of structure and high pressure phase transition in gallium nitride

    Institute of Scientific and Technical Information of China (English)

    Tan Li-Na; Hu Cui-E; Yu Bai-Ru; Chen Xiang-Rong

    2007-01-01

    The phase transitions of semiconductor GaN from the Wurtzite (WZ) structure and the zinc-blende (ZB) structure to the rocksalt (RS) structure are investigated by using the first-principles plane-wave pseudopotential density functional method combined with the ultrasoft pseudopotential scheme in the generalized gradient approximation (GGA)correction. It is found that the phase transitions from the WZ structure and the ZB structure to the RS structure occur at pressures of 46.1 GPa and 45.2 GPa, respectively. The lattice parameters, bulk moduli and their pressure derivatives of these structures of GaN are also calculated. Our results are consistent with available experimental and other theoretical results. The dependence of the normalized formula-unit volume V/Vo on pressure P is also successfully obtained.

  18. Phase Equilibria of the Carbon Dioxide + 1-Decanol System at High Pressures.

    Science.gov (United States)

    Ioniţă, Simona; Feroiu, Viorel; Geană, Dan

    2013-11-14

    In this work experimental vapor-liquid equilibrium (VLE) data and three-phase vapor-liquid-liquid equilibrium (VLLE) data are presented for the carbon dioxide + 1-decanol system. The VLE data were measured at five temperatures, (303.2, 308.2, 323.2, 333.2, and 343.2) K, and pressures up to 16 MPa. The VLLE data cover pressure-temperature (P-T) values from 289 K and 5 MPa to the upper critical end point (UCEP). We have used two models to represent the complex fluid phase behavior (P-T critical curve, VLLE line, and VLE isotherms) of the carbon dioxide + 1-decanol system: the cubic general equation of state (GEOS) and Peng-Robinson (PR) equation in conjunction with van der Waals two parameters conventional mixing rules (2PCMR). A correlation method involving temperature-dependent interaction parameters and a semipredictive approach with independent temperature interaction parameters have been used. Comparisons with experimental data reported in this work and available in the literature indicate that the topology of fluid phase behavior is satisfactorily given by the semipredictive procedure both for the critical line and in subcritical region, considering the relative simple used cubic equations of state.

  19. High pressure phase transformation in yttrium sulfide(YS): A first principle study

    International Nuclear Information System (INIS)

    First principles calculations have been carried out to analyze structural, elastic and dynamic stability, of YS under hydrostatic compression. The comparison of enthalpies of rocksalt type (B1) and CsCl type cubic (B2) structures determined as a function of compression suggests the B1→B2 transition at ∼ 49 GPa. Various physical quantities such as zero pressure equilibrium volume, bulk modulus, and pressure derivative of bulk modulus have been derived from the theoretically determined equation of state. The single crystal elastic constants derived from the energy strain method agree well with the experimental values. The activation barrier between B1 and B2 phases calculated at transition point is ∼ 17/mRy/formula unit. Our lattice dynamic calculations show that at ambient condition, the B1 phase is lattice dynamically stable and frequencies of phonon modes in different high symmetry directions of Brillouin zone agrees well with experimental values. The B2 phase also is dynamical stable at ambient condition as well as at ∼ 49 GPa, supporting our static lattice calculation

  20. A molecular dynamics study of ambient and high pressure phases of silica: Structure and enthalpy variation with molar volume

    Science.gov (United States)

    Rajappa, Chitra; Sringeri, S. Bhuvaneshwari; Subramanian, Yashonath; Gopalakrishnan, J.

    2014-06-01

    Extensive molecular dynamics studies of 13 different silica polymorphs are reported in the isothermal-isobaric ensemble with the Parrinello-Rahman variable shape simulation cell. The van Beest-Kramer-van Santen (BKS) potential is shown to predict lattice parameters for most phases within 2%-3% accuracy, as well as the relative stabilities of different polymorphs in agreement with experiment. Enthalpies of high-density polymorphs - CaCl2-type, α-PbO2-type, and pyrite-type - for which no experimental data are available as yet, are predicted here. Further, the calculated enthalpies exhibit two distinct regimes as a function of molar volume—for low and medium-density polymorphs, it is almost independent of volume, while for high-pressure phases a steep dependence is seen. A detailed analysis indicates that the increased short-range contributions to enthalpy in the high-density phases arise not only from an increased coordination number of silicon but also shorter Si-O bond lengths. Our results indicate that amorphous phases of silica exhibit better optimization of short-range interactions than crystalline phases at the same density while the magnitude of Coulombic contributions is lower in the amorphous phase.

  1. A molecular dynamics study of ambient and high pressure phases of silica: structure and enthalpy variation with molar volume.

    Science.gov (United States)

    Rajappa, Chitra; Sringeri, S Bhuvaneshwari; Subramanian, Yashonath; Gopalakrishnan, J

    2014-06-28

    Extensive molecular dynamics studies of 13 different silica polymorphs are reported in the isothermal-isobaric ensemble with the Parrinello-Rahman variable shape simulation cell. The van Beest-Kramer-van Santen (BKS) potential is shown to predict lattice parameters for most phases within 2%-3% accuracy, as well as the relative stabilities of different polymorphs in agreement with experiment. Enthalpies of high-density polymorphs - CaCl2-type, α-PbO2-type, and pyrite-type - for which no experimental data are available as yet, are predicted here. Further, the calculated enthalpies exhibit two distinct regimes as a function of molar volume-for low and medium-density polymorphs, it is almost independent of volume, while for high-pressure phases a steep dependence is seen. A detailed analysis indicates that the increased short-range contributions to enthalpy in the high-density phases arise not only from an increased coordination number of silicon but also shorter Si-O bond lengths. Our results indicate that amorphous phases of silica exhibit better optimization of short-range interactions than crystalline phases at the same density while the magnitude of Coulombic contributions is lower in the amorphous phase. PMID:24985659

  2. A molecular dynamics study of ambient and high pressure phases of silica: structure and enthalpy variation with molar volume.

    Science.gov (United States)

    Rajappa, Chitra; Sringeri, S Bhuvaneshwari; Subramanian, Yashonath; Gopalakrishnan, J

    2014-06-28

    Extensive molecular dynamics studies of 13 different silica polymorphs are reported in the isothermal-isobaric ensemble with the Parrinello-Rahman variable shape simulation cell. The van Beest-Kramer-van Santen (BKS) potential is shown to predict lattice parameters for most phases within 2%-3% accuracy, as well as the relative stabilities of different polymorphs in agreement with experiment. Enthalpies of high-density polymorphs - CaCl2-type, α-PbO2-type, and pyrite-type - for which no experimental data are available as yet, are predicted here. Further, the calculated enthalpies exhibit two distinct regimes as a function of molar volume-for low and medium-density polymorphs, it is almost independent of volume, while for high-pressure phases a steep dependence is seen. A detailed analysis indicates that the increased short-range contributions to enthalpy in the high-density phases arise not only from an increased coordination number of silicon but also shorter Si-O bond lengths. Our results indicate that amorphous phases of silica exhibit better optimization of short-range interactions than crystalline phases at the same density while the magnitude of Coulombic contributions is lower in the amorphous phase.

  3. Recycling of water of high pressure cleaning of pipes. Phase 1. Quality demands and economical aspects

    International Nuclear Information System (INIS)

    According to the regulation 6.1 in the current licence Surface Water Pollution Law (WVO, abbreviated in Dutch) of October 10, 1997, ECN carried out the first phase of a study on the title subject with respect to pipes applied in oil and gas exploration. In the present situation water of the so-called pipe-cleaner is transported via a seapipe after precipitation and membrane filtration. Next to the quality demands and economical aspects attention is paid to a number of environmental aspects

  4. A route to possible civil engineering materials: the case of high-pressure phases of lime

    Science.gov (United States)

    Bouibes, A.; Zaoui, A.

    2015-07-01

    Lime system has a chemical composition CaO, which is known as thermodynamically stable. The purpose here is to explore further possible phases under pressure, by means of variable-composition ab initio evolutionary algorithm. The present investigation shows surprisingly new stable compounds of lime. At ambient pressure we predict, in addition to CaO, CaO2 as new thermodynamically stable compound. The latter goes through two phases transition from C2/c space group structure to Pna21 at 1.5 GPa, and Pna21 space group structure to I4/mcm at 23.4 GPa. Under increasing pressure, further compounds such as CaO3 become the most stable and stabilize in P-421m space group structure above 65 GPa. For the necessary knowledge of the new predicted compounds, we have computed their mechanical and electronic properties in order to show and to explain the main reasons leading to the structural changes.

  5. In-situ Phase Transformation and Deformation of Iron at High Pressure andTemperature

    Energy Technology Data Exchange (ETDEWEB)

    Miyagi, Lowell; Kunz, Martin; Knight, Jason; Nasiatka, James; Voltolini, Marco; Wenk, Hans-Rudolf

    2008-07-01

    With a membrane based mechanism to allow for pressure change of a sample in aradial diffraction diamond anvil cell (rDAC) and simultaneous infra-red laser heating, itis now possible to investigate texture changes during deformation and phasetransformations over a wide range of temperature-pressure conditions. The device isused to study bcc (alpha), fcc (gamma) and hcp (epislon) iron. In bcc iron, room temperature compression generates a texture characterized by (100) and (111) poles parallel to the compression direction. During the deformation induced phase transformation to hcp iron, a subset of orientations are favored to transform to the hcp structure first and generate a texture of (01-10) at high angles to the compression direction. Upon further deformation, the remaining grains transform, resulting in a texture that obeys the Burgers relationship of (110)bcc // (0001)hcp. This is in contrast to high temperature results that indicate that texture is developed through dominant pyramidal {2-1-12}<2-1-13> and basal (0001)-{2-1-10} slip based on polycrystal plasticity modeling. We also observe that the high temperature fcc phase develops a 110 texture typical for fcc metals deformed in compression.

  6. A route to possible civil engineering materials: the case of high-pressure phases of lime.

    Science.gov (United States)

    Bouibes, A; Zaoui, A

    2015-07-23

    Lime system has a chemical composition CaO, which is known as thermodynamically stable. The purpose here is to explore further possible phases under pressure, by means of variable-composition ab initio evolutionary algorithm. The present investigation shows surprisingly new stable compounds of lime. At ambient pressure we predict, in addition to CaO, CaO2 as new thermodynamically stable compound. The latter goes through two phases transition from C2/c space group structure to Pna21 at 1.5 GPa, and Pna21 space group structure to I4/mcm at 23.4 GPa. Under increasing pressure, further compounds such as CaO3 become the most stable and stabilize in P-421m space group structure above 65 GPa. For the necessary knowledge of the new predicted compounds, we have computed their mechanical and electronic properties in order to show and to explain the main reasons leading to the structural changes.

  7. High-pressure phase transition makes B4.3C boron carbide a wide-gap semiconductor

    Science.gov (United States)

    Hushur, Anwar; Manghnani, Murli H.; Werheit, Helmut; Dera, Przemyslaw; Williams, Quentin

    2016-02-01

    Single-crystal B4.3C boron carbide is investigated through the pressure-dependence and inter-relation of atomic distances, optical properties and Raman-active phonons up to ~70 GPa. The anomalous pressure evolution of the gap width to higher energies is striking. This is obtained from observations of transparency, which most rapidly increases around 55 GPa. Full visible optical transparency is approached at pressures of  >60 GPa indicating that the band gap reaches ~3.5 eV at high pressure, boron carbide is a wide-gap semiconductor. The reason is that the high concentration of structural defects controlling the electronic properties of boron carbide at ambient conditions initially decreases and finally vanishes at high pressures. The structural parameters and Raman-active phonons indicate a pressure-dependent phase transition in single-crystal natB4.3C boron carbide near 40 GPa, likely related to structural changes in the C-B-C chains, while the basic icosahedral structure appears to be less affected.

  8. Structural variety beyond appearance: high-pressure phases of CrB4 in comparison with FeB4.

    Science.gov (United States)

    Zhang, Yunkun; Wu, Lailei; Wan, Biao; Zhao, Yan; Gao, Rui; Li, Zhiping; Zhang, Jingwu; Gou, Huiyang; Mao, Ho-kwang

    2016-01-28

    Employing particle swarm optimization (PSO) combined with first-principles calculations, we systemically studied high-pressure behaviors of hard CrB4. Our predictions reveal a distinct structural evolution under pressure for CrB4 despite having the same initial structure as FeB4. CrB4 is found to adopt a new P2/m structure above 196 GPa, another Pm structure at a pressure range of 261-294 GPa and then a Pmma structure beyond 294 GPa. Instead of puckering boron sheets in the initial structure, the high-pressure phases have planar boron sheets with different motifs upon compression. Comparatively, FeB4 prefers an I41/acd structure over 48 GPa with tetrahedron B4 units and a P213 structure above 231 GPa having equilateral triangle B3 units. Significantly, CrB4 exhibits persistent metallic behavior in contrast with the semiconducting features of FeB4 upon compression. The varied pressure response of hard tetraborides studied here is of importance for understanding boron-rich compounds and designing new materials with superlative properties. PMID:26692374

  9. High-pressure phase transition makes B4.3C boron carbide a wide-gap semiconductor.

    Science.gov (United States)

    Hushur, Anwar; Manghnani, Murli H; Werheit, Helmut; Dera, Przemyslaw; Williams, Quentin

    2016-02-01

    Single-crystal B4.3C boron carbide is investigated through the pressure-dependence and inter-relation of atomic distances, optical properties and Raman-active phonons up to ~70 GPa. The anomalous pressure evolution of the gap width to higher energies is striking. This is obtained from observations of transparency, which most rapidly increases around 55 GPa. Full visible optical transparency is approached at pressures of  >60 GPa indicating that the band gap reaches ~3.5 eV; at high pressure, boron carbide is a wide-gap semiconductor. The reason is that the high concentration of structural defects controlling the electronic properties of boron carbide at ambient conditions initially decreases and finally vanishes at high pressures. The structural parameters and Raman-active phonons indicate a pressure-dependent phase transition in single-crystal (nat)B4.3C boron carbide near 40 GPa, likely related to structural changes in the C-B-C chains, while the basic icosahedral structure appears to be less affected.

  10. High volumetric hydrogen density phases of magnesium borohydride at high-pressure: A first-principles study

    Institute of Scientific and Technical Information of China (English)

    Fan Jing; Bao Kuo; Duan De-Fang; Wang Lian-Cheng; Liu Bing-Bing; Cui Tian

    2012-01-01

    The previously proposed theoretical and experimental structures,bond characterization,and compressibility of Mg(BH4)2 in a pressure range from 0 to 10 GPa are studied by ab initio density-functional calculations.It is found that the ambient pressure phases of meta-stable I41/amd and unstable P-3ml proposed recently are extra stable and cannot decompose under high pressure.Enthalpy calculation indicates that the ground state of F222 structure proposed by Zhou et al.[2009 Phys.Rev.B 79 212102]will transfer to I41/amd at 0.7 GPa,and then to a P-3m1 structure at 6.3 GPa.The experimental P6122 structure (α-phase) transfers to I41/amd at 1.2 GPa.Furthermore,both I41/amd and P-3m1 can exist as high volumetric hydrogen density phases at low pressure.Their theoretical volumetric hydrogen densities reach 146.351 g H2/L and 134.028 g H2/L at ambient pressure,respectively.The calculated phonon dispersion curve shows that the I41/amd phase is dynamically stable in a pressure range from 0 to 4 GPa and the P-3ml phase is stable at pressures higher than 1 GPa.So the I41/amd phase may be synthesized under high pressure and retained to ambient pressure.Energy band structures show that they are both always ionic crystalline and insulating with a band-gap of about 5 eV in this pressure range.In addition,they each have an anisotropic compressibility.The c axis of these structures is easy to compress.Especially,the c axis and volume of P-3m1 phase are extraordinarily compressible,showing that compression along the c axis can increase the volumetric hydrogen content for both I41/amd and P-3m1 structures.

  11. THE GENERALIZED MAXIMUM LIKELIHOOD METHOD APPLIED TO HIGH PRESSURE PHASE EQUILIBRIUM

    Directory of Open Access Journals (Sweden)

    Lúcio CARDOZO-FILHO

    1997-12-01

    Full Text Available The generalized maximum likelihood method was used to determine binary interaction parameters between carbon dioxide and components of orange essential oil. Vapor-liquid equilibrium was modeled with Peng-Robinson and Soave-Redlich-Kwong equations, using a methodology proposed in 1979 by Asselineau, Bogdanic and Vidal. Experimental vapor-liquid equilibrium data on binary mixtures formed with carbon dioxide and compounds usually found in orange essential oil were used to test the model. These systems were chosen to demonstrate that the maximum likelihood method produces binary interaction parameters for cubic equations of state capable of satisfactorily describing phase equilibrium, even for a binary such as ethanol/CO2. Results corroborate that the Peng-Robinson, as well as the Soave-Redlich-Kwong, equation can be used to describe phase equilibrium for the following systems: components of essential oil of orange/CO2.Foi empregado o método da máxima verossimilhança generalizado para determinação de parâmetros de interação binária entre os componentes do óleo essencial de laranja e dióxido de carbono. Foram usados dados experimentais de equilíbrio líquido-vapor de misturas binárias de dióxido de carbono e componentes do óleo essencial de laranja. O equilíbrio líquido-vapor foi modelado com as equações de Peng-Robinson e de Soave-Redlich-Kwong usando a metodologia proposta em 1979 por Asselineau, Bogdanic e Vidal. A escolha destes sistemas teve como objetivo demonstrar que o método da máxima verosimilhança produz parâmetros de interação binária, para equações cúbicas de estado capazes de descrever satisfatoriamente até mesmo o equilíbrio para o binário etanol/CO2. Os resultados comprovam que tanto a equação de Peng-Robinson quanto a de Soave-Redlich-Kwong podem ser empregadas para descrever o equilíbrio de fases para o sistemas: componentes do óleo essencial de laranja/CO2.

  12. Theoretical predictions of novel superconducting phases of BaGe3 stable at atmospheric and high pressures.

    Science.gov (United States)

    Zurek, Eva; Yao, Yansun

    2015-03-16

    A series of new superconducting binary silicides and germanides have recently been synthesized under high-pressure high-temperature conditions. A representative member of this group, BaGe3, was theoretically investigated using evolutionary structure searches coupled with structural analogies in the pressure range from 1 atm to 250 GPa, where three new phases were discovered. At 1 atm, in addition to the synthesized P63/mmc phase, we predicted two new phases, I4/mmm and Amm2, to be dynamically stable. The Amm2 structure comprises Ge clusters and triangular prisms intercalated with Ba and Ge atoms, a unique structural motif unknown to this group. The I4/mmm structure has been previously synthesized in binary silicides and is calculated to be thermodynamically stable in BaGe3 between 15.6 and 35.4 GPa. Above 35.4 GPa, two new phases of P6̅m2 and R3̅m symmetry become the global minima and remain so up to the highest pressure considered. These two phases have very similar enthalpies, and both feature layers of double Kagome nets of Ge intercalated with Ba-Ge layers. The predicted phases are suggested to be metallic with itinerant electrons and to be potentially superconducting from the considerable electron-phonon coupling strength. Density functional perturbation calculations combined with the Allen-Dynes-modified McMillan formula were used to estimate the superconducting critical temperatures (Tc) for these new phases, which, with slight pressure variations, are comparable to the experimental Tc measured for the P63/mmc phase.

  13. Hydrostatic Compression Behavior and High-Pressure Stabilized β-Phase in γ-Based Titanium Aluminide Intermetallics

    Directory of Open Access Journals (Sweden)

    Klaus-Dieter Liss

    2016-07-01

    Full Text Available Titanium aluminides find application in modern light-weight, high-temperature turbines, such as aircraft engines, but suffer from poor plasticity during manufacturing and processing. Huge forging presses enable materials processing in the 10-GPa range, and hence, it is necessary to investigate the phase diagrams of candidate materials under these extreme conditions. Here, we report on an in situ synchrotron X-ray diffraction study in a large-volume press of a modern (α2 + γ two-phase material, Ti-45Al-7.5Nb-0.25C, under pressures up to 9.6 GPa and temperatures up to 1686 K. At room temperature, the volume response to pressure is accommodated by the transformation γ → α2, rather than volumetric strain, expressed by the apparently high bulk moduli of both constituent phases. Crystallographic aspects, specifically lattice strain and atomic order, are discussed in detail. It is interesting to note that this transformation takes place despite an increase in atomic volume, which is due to the high ordering energy of γ. Upon heating under high pressure, both the eutectoid and γ-solvus transition temperatures are elevated, and a third, cubic β-phase is stabilized above 1350 K. Earlier research has shown that this β-phase is very ductile during plastic deformation, essential in near-conventional forging processes. Here, we were able to identify an ideal processing window for near-conventional forging, while the presence of the detrimental β-phase is not present under operating conditions. Novel processing routes can be defined from these findings.

  14. High-temperature- and high-pressure-induced formation of the Laves-phase compound XeS2

    Science.gov (United States)

    Yan, Xiaozhen; Chen, Yangmei; Xiang, Shikai; Kuang, Xiaoyu; Bi, Yan; Chen, Haiyan

    2016-06-01

    We explore the reactivity of xenon with sulfur under high pressure, using unbiased structure searching techniques combined with first-principles calculations, which identify a stable XeS2 compound crystallized in a Laves phase with hypercoordinated (16-fold) Xe at 191 GPa and 0 K. Taking the thermal effects into account, we find that increasing the temperature could further stabilize it. The formation of XeS2 is a consequence of pressure-induced charge transfer from Xe to S atoms and the delocalization of Xe 5 p and S 3 p electrons. Meanwhile, the stabilization into a Laves phase of XeS2 is the result of delocalized chemical bonding and the need for optimum structure packing. The present discussion of the formation mechanism in XeS2 is general, and conclusions can be used to understand the formation of other Laves-phase compounds and the Xe chemistry that allows closed-shell Xe to participate in chemical reactions.

  15. Phase behavior for the poly(alkyl methacrylate)+supercritical CO{sub 2}+DME mixture at high pressures

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Yong-Seok; Chio, Sang-Won; Byun, Hun-Soo [Chonnam National University, Yeosu (Korea, Republic of)

    2016-01-15

    The phase behavior curves of binary and ternary system were measured for poly(alkyl methacrylate) in supercritical CO{sub 2}, as well as for the poly(alkyl methacrylate)+dimethyl ether (DME) (or 1-butene) in CO{sub 2}. The solubility curves are reported for the poly(alkyl methacrylate)+DME in supercritical CO{sub 2} at temperature from (300 to 465) K and a pressure from (3.66 to 248) MPa. Also, The high-pressure static-type apparatus of cloud-point curve was tested by comparing the measured phase behavior data of the poly(methyl methacrylate) [PMMA]+CO{sub 2}+20.0 and 30.4 wt% methyl methacrylate (MMA) system with literature data of 10.4, 28.8 and 48.4 wt% MMA concentration. The phase behavior data for the poly(alkyl methacrylate)+CO{sub 2}+DME mixture were measured in changes of the pressure-temperature (p, T) slope and with DME concentrations. Also, the cloud-point pressure for the poly(alkyl methacrylate)+1- butene solution containing supercritical CO{sub 2} shows from upper critical solution temperature (UCST) region to lower critical solution temperature (LCST) region at concentration range from (0.0 to 95) wt% 1-butene at below 455 K and at below 245MPa.

  16. Phase diagram of ZrZn2 at high pressure: Low-temperature features and elusive superconductivity

    International Nuclear Information System (INIS)

    Studies of the AC magnetic susceptibility and electrical resistivity of polycrystalline samples of ZrZn2, synthesized at high pressure, were performed at pressures up to 4.5 GPa and temperatures down to 0.4 K. The evolution with pressure of the line of ferromagnetic phase transformations qualitatively agrees with numerous previous data, though the transition temperature is highly sensitive to the quality and history of samples. Upon approaching zero temperature, the transition line bends toward the pressure axis as dictated by the Nernst theorem. An additional feature of the phase diagram was discovered in the samples with the highest Curie temperature (25-26 K). The electrical resistance of these samples drastically decreases near 1.4-1.8 K at ambient pressure. The temperature of this resistive transition does not change much with pressure and crosses the Curie line at a pressure near 1.2 GPa, seemingly forming some sort of tetracritical point. Application of magnetic fields up to 2 T suppresses the transition that one may expect if superconductivity is involved. However, heat capacity measurements do not show any anomaly at the transition, which resembles the case described by Pfliederer et al. [Nature (2001) 58

  17. Developing a platform for high-resolution phase contrast imaging of high pressure shock waves in matter

    Science.gov (United States)

    Schropp, Andreas; Patommel, Jens; Seiboth, Frank; Arnold, Brice; Galtier, Eric C.; Lee, Hae Ja; Nagler, Bob; Hastings, Jerome B.; Schroer, Christian G.

    2012-10-01

    Current and upcoming X-ray sources, such as the Linac Coherent Light Source (LCLS) at the Stanford Linear Accelerator Center (SLAC, USA), the SPring-8 Angstrom Compact Free Electron Laser (SACLA, Japan), or the X-ray Free Electron Laser (XFEL, Germany) will provide X-ray beams with outstanding properties.1, 2 Short and intense X-ray pulses of about 50 fs time duration and even shorter will push X-ray science to new frontiers such as, e. g., in high-resolution X-ray imaging, high-energy-density physics or in dynamical studies based on pump-probe techniques. Fast processes in matter often require high-resolution imaging capabilities either by magnified imaging in direct space or diffractive imaging in reciprocal space. In both cases highest resolutions require focusing the X-ray beam.3, 4 In order to further develop high-resolution imaging at free-electron laser sources we are planning a platform to carry out high-resolution phase contrast imaging experiments based on Beryllium compound refractive X-ray lenses (Be-CRLs) at the Matter in Extreme Conditions (MEC) endstation of the LCLS. The instrument provides all necessary equipment to induce high pressure shock waves by optical lasers. The propagation of a shock wave is then monitored with an X-ray Free Electron Laser (FEL) pulse by magnified phase contrast imaging. With the CRL optics, X-ray beam sizes in the sub-100nm range are expected, leading to a similar spatial resolution in the direct coherent projection image. The experiment combines different state-of-the art scientific techniques that are currently available at the LCLS. In this proceedings paper we describe the technical developments carried out at the LCLS in order to implement magnified X-ray phase contrast imaging at the MEC endstation.

  18. Characterization of boron nitride phase transformations in the Li–B–N system under high pressure and high temperature

    Energy Technology Data Exchange (ETDEWEB)

    Guo, W., E-mail: guowei1982cry@163.com [College of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan 030024 (China); National Key Lab of Superhard Materials, Jilin University, Changchun 130012 (China); Shi, Y. [College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024 (China); Yang, P. [College of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan 030024 (China); Ma, H.A.; Jia, X. [National Key Lab of Superhard Materials, Jilin University, Changchun 130012 (China); Wang, S., E-mail: wangshuang@tyut.edu.cn [College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024 (China)

    2015-09-25

    Highlights: • The characterization of cBN phase transformation in Li{sub 3}N melt is revealed under HPHT. • A simultaneous precipitation and dissolution of cBN in Li{sub 3}BN{sub 2} melt is proved. • The BN phase transition behaviors of Li{sub 3}N–hBN and Li{sub 3}N–cBN system is not equivalent. • The results provide a clue for further improvement of the quality of direct sintering of cubic boron nitride. - Abstract: The possible phase transformations of boron nitride in the Li–B–N system have been discussed by the chemical reactions of Li{sub 3}N, hBN and cBN at the conditions of 5.0 GPa and 1300–1500 °C. The results of the reaction between Li{sub 3}N and hBN shows that certain Li–B–N eutectic compound(s) which were produced in the thermodynamical stable region of cBN have no catalytic effect for cBN growth. It indicates that a certain irreversible BN precipitation/dissolution process takes place in Li{sub 3}N melt. However, the reaction between Li{sub 3}N and hBN is preferential when Li{sub 3}N, hBN and cBN coexist in Li–B–N system, and the regrowth of cBN is observed, namely the morphology of cBN changing from irregular to fine shape crystals with well-facetted (1 1 1) surface. Furthermore, the estimated sizes of regrown cBN are almost same as those of the raw cBN. This indicates a simultaneous cBN dissolution and precipitation process in Li{sub 3}N + hBN/cBN system under high pressure and high temperature.

  19. Crystal structure of SrGeO3 in the high-pressure perovskite-type phase

    Directory of Open Access Journals (Sweden)

    Akihiko Nakatsuka

    2015-05-01

    Full Text Available Single crystals of the SrGeO3 (strontium germanium trioxide high-pressure phase have been synthesized successfully at 6 GPa and 1223 K. The compound crystallizes with the ideal cubic perovskite-type structure (space group Pm-3m, which consists of a network of corner-linked regular GeO6 octahedra (point-group symmetry m-3m, with the larger Sr atoms located at the centers of cavities in the form of SrO12 cuboctahedra (point-group symmetry m-3m in the network. The degrees of covalencies included in the Sr—O and the Ge—O bonds calculated from bond valences are 20.4 and 48.9%, respectively. Thus, the Ge—O bond of the GeO6 octahedron in the SrGeO3 perovskite has a strong covalency, comparable to those of the Si—O bonds of the SiO4 tetrahedra in silicates with about 50% covalency. The thermal vibrations of the O atoms in the title compound are remarkably suppressed in the directions of the Ge—O bonds. This anisotropy ranks among the largest observed in stoichiometric cubic perovskites.

  20. Application of phase-modulated dispersion interferometry to electron-density diagnostics of high-pressure plasma

    International Nuclear Information System (INIS)

    Phase-modulated dispersion interferometry (PMDI) is a technique for measuring the electron density in plasmas that was first developed for large fusion reactors. In this paper, we demonstrate the potential of PMDI for the diagnostics of microplasma generated at high pressures. PMDI can eliminate the effect of nondispersive components in the refractive-index variation on the measurement; therefore, most of the variation of the refractive index induced by the variation of gas density is eliminated by signal processing, contributing to accurate electron-density determination in microplasmas. The measurement results for a pulsed-dc microplasma in an atmospheric-pressure helium gas flow revealed that the electron density of the microplasma was in the range between 4 × 1013 and 1.4 × 1014 cm−3, and our PMDI system had a temporal resolution of 110µs and a sensitivity of the line-integrated electron density of 7 × 1011 cm−2. (fast track communication)

  1. Electronic, mechanical, phase transition, and thermo-physical properties of TMC (TM = V, Nb, and Ta): high pressure ab initio study

    Science.gov (United States)

    Chauhan, Mamta; Gupta, Dinesh C.

    2015-12-01

    The structural, electronic, mechanical, phase transition, and thermo-physical properties of refractory carbides, viz. VC, NbC, and TaC have been computed in stable B1 and high pressure B2 phases by means of two different ab initio calculations using pseudo- and full-potential schemes. These materials have mixed covalent-, metallic-, and ionic-type bonding. The calculations of elastic constants show the mechanical stability of these materials in B1 phase only. The brittle nature and anisotropy is observed in these materials in B1 phase. Non-central forces are present in both the phases. Elastic wave velocities and Debye temperature have also been calculated. The present results on structural, phase transition, elastic, and other properties are in reasonably good agreement with the available experimental and theoretical data. The calculations in high pressure phase need experimental verification.

  2. High-pressure high-temperature synthesis of novel binary and ternary nitride phases of group 4 and 14 elements

    Energy Technology Data Exchange (ETDEWEB)

    Dzivenko, D A; Horvath-Bordon, E; Miehe, G; Riedel, R [FB Materialwissenschaft, TU Darmstadt, Petersenstrasse 23, 64287 Darmstadt (Germany); Zerr, A [LPMTM-CNRS, Universite Paris Nord, 99 Av. J.B. Clement, 93430 Villetaneuse (France); Kroll, P [Department of Chemistry, UTA, Arlington, Texas 760019-0065 (United States); Boehler, R [Hochdruckgruppe, MPI fuer Chemie, J.-J.-Becher-Weg 27, 55128 Mainz (Germany); McMillan, P F [Department of Chemistry, UCL, 20 Gordon Street, London WC1 H0AJ (United Kingdom)], E-mail: dzivenko@materials.tu-darmstadt.de

    2008-07-15

    Our recent experiments on high-pressure high-temperature synthesis of novel ternary nitrides of group 4 and 14 elements are presented. Dense carbon nitride imide, C{sub 2}N{sub 2}(NH), was synthesized for the first time in a laser heated diamond anvil cell (LH-DAC) at pressures above 27 GPa and temperatures around 2000 K. Based on results of the electron diffraction-, EELS-and SIMS-measurements combined with theoretical calculations the structure of this new C-N-H phase was suggested to be of the defect-wurtzite type. Farther, macroscopic amounts of a new oxynitride of zirconium having cubic Th{sub 3}P{sub 4}-type structure, c-Zr{sub 2.86}(N{sub 0.88}O{sub 0.12}){sub 4}, were synthesized at high pressures and temperatures using a multi-anvil apparatus. Earlier this structure was observed for binary nitrides of zirconium(IV) and hafnium(IV) synthesized in microscopic amounts in a LH-DAC. The lattice parameter of c-Zr{sub 2.86}(N{sub 0.88}O{sub 0.12}){sub 4} was found to be a{sub 0} = 6.7549(1) A which is slightly larger than that of c-Zr{sub 3}N{sub 4}. Isotropic bulk and shear moduli of c-Zr{sub 2.86}(N{sub 0.88}O{sub 0.12}){sub 4} of B{sub 0} = 219 GPa and G{sub 0} = 96 GPa, respectively, were determined from the compression and nanoindentation measurements. The Vickers microhardness, H{sub V}(1), of the porous (about 30 vol. %) sample of c-Zr{sub 2.86}(N{sub 0.88}O{sub 0.12}){sub 4} was measured to be 12 GPa, similar to that of single crystal {delta}-ZrN.

  3. Effects of gasket on coupled plastic flow and strain-induced phase transformations under high pressure and large torsion in a rotational diamond anvil cell

    Science.gov (United States)

    Feng, Biao; Levitas, Valery I.

    2016-01-01

    Combined plastic flow and strain-induced phase transformations (PTs) under high pressure in a sample within a gasket subjected to three dimensional compression and torsion in a rotational diamond anvil cell (RDAC) are studied using a finite element approach. The results are obtained for the weaker, equal-strength, and stronger high-pressure phases in comparison with low-pressure phases. It is found that, due to the strong gasket, the pressure in the sample is relatively homogenous and the geometry of the transformed zones is mostly determined by heterogeneity in plastic flow. For the equal-strength phases, the PT rate is higher than for the weaker and stronger high-pressure phases. For the weaker high-pressure phase, transformation softening induces material instability and leads to strain and PT localization. For the stronger high-pressure phase, the PT is suppressed by strain hardening during PT. The effect of the kinetic parameter k that scales the PT rate in the strain-controlled kinetic equation is also examined. In comparison with a traditional diamond anvil cell without torsion, the PT progress is much faster in RDAC under the same maximum pressure in the sample. Finally, the gasket size and strength effects are discussed. For a shorter and weaker gasket, faster plastic flow in radial and thickness directions leads to faster PT kinetics in comparison with a longer and stronger gasket. The rates of PT and plastic flows are not very sensitive to the modest change in a gasket thickness. Multiple experimental results are reproduced and interpreted. Obtained results allow one to design the desired pressure-plastic strain loading program in the experiments for searching new phases, reducing PT pressure by plastic shear, extracting kinetic properties from experiments with heterogeneous fields, and controlling homogeneity of all fields and kinetics of PTs.

  4. High Pressure Biomass Gasification

    Energy Technology Data Exchange (ETDEWEB)

    Agrawal, Pradeep K

    2016-07-29

    According to the Billion Ton Report, the U.S. has a large supply of biomass available that can supplement fossil fuels for producing chemicals and transportation fuels. Agricultural waste, forest residue, and energy crops offer potential benefits: renewable feedstock, zero to low CO2 emissions depending on the specific source, and domestic supply availability. Biomass can be converted into chemicals and fuels using one of several approaches: (i) biological platform converts corn into ethanol by using depolymerization of cellulose to form sugars followed by fermentation, (ii) low-temperature pyrolysis to obtain bio-oils which must be treated to reduce oxygen content via HDO hydrodeoxygenation), and (iii) high temperature pyrolysis to produce syngas (CO + H2). This last approach consists of producing syngas using the thermal platform which can be used to produce a variety of chemicals and fuels. The goal of this project was to develop an improved understanding of the gasification of biomass at high pressure conditions and how various gasification parameters might affect the gasification behavior. Since most downstream applications of synags conversion (e.g., alcohol synthesis, Fischer-Tropsch synthesis etc) involve utilizing high pressure catalytic processes, there is an interest in carrying out the biomass gasification at high pressure which can potentially reduce the gasifier size and subsequent downstream cleaning processes. It is traditionally accepted that high pressure should increase the gasification rates (kinetic effect). There is also precedence from coal gasification literature from the 1970s that high pressure gasification would be a beneficial route to consider. Traditional approach of using thermogravimetric analyzer (TGA) or high-pressure themogravimetric analyzer (PTGA) worked well in understanding the gasification kinetics of coal gasification which was useful in designing high pressure coal gasification processes. However, similar approach for

  5. High Pressure Biomass Gasification

    Energy Technology Data Exchange (ETDEWEB)

    Agrawal, Pradeep K [Georgia Tech Research Corporation, Atlanta, GA (United States)

    2016-07-29

    According to the Billion Ton Report, the U.S. has a large supply of biomass available that can supplement fossil fuels for producing chemicals and transportation fuels. Agricultural waste, forest residue, and energy crops offer potential benefits: renewable feedstock, zero to low CO2 emissions depending on the specific source, and domestic supply availability. Biomass can be converted into chemicals and fuels using one of several approaches: (i) biological platform converts corn into ethanol by using depolymerization of cellulose to form sugars followed by fermentation, (ii) low-temperature pyrolysis to obtain bio-oils which must be treated to reduce oxygen content via HDO hydrodeoxygenation), and (iii) high temperature pyrolysis to produce syngas (CO + H2). This last approach consists of producing syngas using the thermal platform which can be used to produce a variety of chemicals and fuels. The goal of this project was to develop an improved understanding of the gasification of biomass at high pressure conditions and how various gasification parameters might affect the gasification behavior. Since most downstream applications of synags conversion (e.g., alcohol synthesis, Fischer-Tropsch synthesis etc) involve utilizing high pressure catalytic processes, there is an interest in carrying out the biomass gasification at high pressure which can potentially reduce the gasifier size and subsequent downstream cleaning processes. It is traditionally accepted that high pressure should increase the gasification rates (kinetic effect). There is also precedence from coal gasification literature from the 1970s that high pressure gasification would be a beneficial route to consider. Traditional approach of using thermogravimetric analyzer (TGA) or high-pressure themogravimetric analyzer (PTGA) worked well in understanding the gasification kinetics of coal gasification which was useful in designing high pressure coal gasification processes. However

  6. High-Temperature Phase Transitions in CsH2PO4 Under Ambient and High-Pressure Conditions: A Synchrotron X-ray Diffraction Study

    Energy Technology Data Exchange (ETDEWEB)

    Botez,C.; Hermosillo, J.; Zhang, J.; Qian, J.; Zhao, Y.; Majzlan, J.; Chianelli, R.; Pantea, C.

    2007-01-01

    To clarify the microscopic origin of the temperature-induced three-order-of-magnitude jump in the proton conductivity of CsH2PO4 (superprotonic behavior), we have investigated its crystal structure modifications within the 25-300 C temperature range under both ambient- and high-pressure conditions using synchrotron x-ray diffraction. Our high-pressure data show no indication of the thermal decomposition/polymerization at the crystal surface recently proposed as the origin of the enhanced proton conductivity. Instead, we found direct evidence that the superprotonic behavior of the title material is associated with a polymorphic structural transition to a high-temperature cubic phase. Our results are in excellent agreement with previous high-pressure ac impedance measurements.

  7. The local phase transitions of the solvent in the neighborhood of a solvophobic polymer at high pressures

    Energy Technology Data Exchange (ETDEWEB)

    Budkov, Yu. A., E-mail: urabudkov@rambler.ru [G.A. Krestov Institute of Solution Chemistry of the Russian Academy of Sciences, Ivanovo (Russian Federation); National Research University Higher School of Economics, Moscow (Russian Federation); Department of Chemistry, Lomonosov Moscow State University, Moscow (Russian Federation); Vyalov, I. I. [Istituto Italiano di Tecnologia, via Morego 30, Genova 16163 (Italy); Kolesnikov, A. L. [Ivanovo State University, Ivanovo (Russian Federation); Institut für Nichtklassische Chemie e.V., Universitat Leipzig, Leipzig (Germany); Georgi, N., E-mail: bancocker@mail.ru [Max Planck Institute for Mathematics in the Sciences, Leipzig (Germany); Chuev, G. N. [Max Planck Institute for the Physics of Complex Systems, Dresden (Germany); Institute of Theoretical and Experimental Biophysics, Russian Academy of Science, Pushchino, Moscow Region (Russian Federation); Kiselev, M. G. [G.A. Krestov Institute of Solution Chemistry of the Russian Academy of Sciences, Ivanovo (Russian Federation); Department of Chemistry, Lomonosov Moscow State University, Moscow (Russian Federation)

    2014-11-28

    We investigate local phase transitions of the solvent in the neighborhood of a solvophobic polymer chain which is induced by a change of the polymer-solvent repulsion and the solvent pressure in the bulk solution. We describe the polymer in solution by the Edwards model, where the conditional partition function of the polymer chain at a fixed radius of gyration is described by a mean-field theory. The contributions of the polymer-solvent and the solvent-solvent interactions to the total free energy are described within the mean-field approximation. We obtain the total free energy of the solution as a function of the radius of gyration and the average solvent number density within the gyration volume. The resulting system of coupled equations is solved varying the polymer-solvent repulsion strength at high solvent pressure in the bulk. We show that the coil-globule (globule-coil) transition occurs accompanied by a local solvent evaporation (condensation) within the gyration volume.

  8. Synchrotron X-ray diffraction studies of phase transitions and mechanical properties of nanocrystalline materials at high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Prilliman, Gerald Stephen

    2003-09-01

    The behavior of nanocrystals under extreme pressure was investigated using synchrotron x-ray diffraction. A major part of this investigation was the testing of a prototype synchrotron endstation on a bend magnet beamline at the Advanced Light Source for high pressure work using a diamond anvil cell. The experiments conducted and documented here helped to determine issues of efficiency and accuracy that had to be resolved before the construction of a dedicated ''super-bend'' beamline and endstation. The major conclusions were the need for a cryo-cooled monochromator and a fully remote-controllable pressurization system which would decrease the time to change pressure and greatly reduce the error created by the re-placement of the diamond anvil cell after each pressure change. Two very different types of nanocrystal systems were studied, colloidal iron oxide (Fe{sub 2}O{sub 3}) and thin film TiN/BN. Iron oxide nanocrystals were found to have a transition from the {gamma} to the {alpha} structure at a pressure strongly dependent on the size of the nanocrystals, ranging from 26 GPa for 7.2 nm nanocrystals to 37 GPa for 3.6 nm nanocrystals. All nanocrystals were found to remain in the {alpha} structure even after release of pressure. The transition pressure was also found, for a constant size (5.7 nm) to be strongly dependent on the degree of aggregation of the nanocrystals, increasing from 30 GPa for completely dissolved nanocrystals to 45 GPa for strongly aggregated nanocrystals. Furthermore, the x-ray diffraction pattern of the pressure induced {alpha} phase demonstrated a decrease in intensity for certain select peaks. Together, these observations were used to make a complete picture of the phase transition in nanocrystalline systems. The size dependence of the transition was interpreted as resulting from the extremely high surface energy of the {alpha} phase which would increase the thermodynamic offset and thereby increase the kinetic barrier

  9. Synchrotron X-ray diffraction studies of phase transitions and mechanical properties of nanocrystalline materials at high pressure

    International Nuclear Information System (INIS)

    The behavior of nanocrystals under extreme pressure was investigated using synchrotron x-ray diffraction. A major part of this investigation was the testing of a prototype synchrotron endstation on a bend magnet beamline at the Advanced Light Source for high pressure work using a diamond anvil cell. The experiments conducted and documented here helped to determine issues of efficiency and accuracy that had to be resolved before the construction of a dedicated ''super-bend'' beamline and endstation. The major conclusions were the need for a cryo-cooled monochromator and a fully remote-controllable pressurization system which would decrease the time to change pressure and greatly reduce the error created by the re-placement of the diamond anvil cell after each pressure change. Two very different types of nanocrystal systems were studied, colloidal iron oxide (Fe2O3) and thin film TiN/BN. Iron oxide nanocrystals were found to have a transition from the γ to the α structure at a pressure strongly dependent on the size of the nanocrystals, ranging from 26 GPa for 7.2 nm nanocrystals to 37 GPa for 3.6 nm nanocrystals. All nanocrystals were found to remain in the α structure even after release of pressure. The transition pressure was also found, for a constant size (5.7 nm) to be strongly dependent on the degree of aggregation of the nanocrystals, increasing from 30 GPa for completely dissolved nanocrystals to 45 GPa for strongly aggregated nanocrystals. Furthermore, the x-ray diffraction pattern of the pressure induced α phase demonstrated a decrease in intensity for certain select peaks. Together, these observations were used to make a complete picture of the phase transition in nanocrystalline systems. The size dependence of the transition was interpreted as resulting from the extremely high surface energy of the α phase which would increase the thermodynamic offset and thereby increase the kinetic barrier to transition that must be overridden with pressure. The

  10. Laser-driven phase transitions in aqueous colloidal gold nanoparticles under high pressure: picosecond pump-probe study.

    Science.gov (United States)

    Hashimoto, Shuichi; Katayama, Tetsuro; Setoura, Kenji; Strasser, Michael; Uwada, Takayuki; Miyasaka, Hiroshi

    2016-02-14

    Pump-probe transient extinction spectroscopy was used to analyze 355 nm picosecond laser heating-induced phenomena in 60 nm-diameter aqueous gold nanoparticles (AuNPs) under a high pressure of 60 MPa. Kinetic spectroscopy revealed that a supercritical layer surrounding the AuNP nucleated with a lifetime of approximately 1 ns during its dynamic expansion and decay for a fluence of 19.6 mJ cm(-2). Moreover, in the post-mortem transmission electron micrographs we observed a number of fragments, a small percentage of size-reduced cores, and erupted particles among the intact particles after 60 shots, suggesting that evaporation occurred under laser illumination. The particle temperature calculation indicated that evaporation begins with a liquid droplet AuNP surrounded by a supercritical layer at temperatures below the boiling point of gold. By applying high pressure, we obtained a clear picture of the evaporation event, which was not possible at ambient pressure because bubble formation caused particle temperatures to rise uncontrollably. In this study, we shed light on the critical role of the supercritical layer formed around the AuNP under high pressure during laser-induced evaporation. PMID:26812175

  11. First-principles study on the phase transition, elastic properties and electronic structure of Pt{sub 3}Al alloys under high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yanjun [Key Laboratory of Oil and Gas Equipment of Ministry of Education, Southwest Petroleum University, Chengdu, Sichuan 610500 (China); Huang, Huawei [National Key Laboratory for Nuclear Fuel and Materials, Nuclear Power of China, Chengdu, Sichuan 610041 (China); Pan, Yong, E-mail: yongpanyn@163.com [State Key Laboratory of Advanced Technologies for Comprehensive Utilization of Platinum Metals, Kunming 650106 (China); Zhao, Guanghui; Liang, Zheng [Key Laboratory of Oil and Gas Equipment of Ministry of Education, Southwest Petroleum University, Chengdu, Sichuan 610500 (China)

    2014-06-01

    Highlights: • The phase transition of Pt{sub 3}Al alloys occurs at 60 GPa. • The elastic modulus of Pt{sub 3}Al alloys increase with increasing pressure. • The cubic structure has good resistance to volume deformation under high pressure. • The pressure enhances the hybridization between Pt atom and Al atom. - Abstract: The phase transition, formation enthalpies, elastic properties and electronic structure of Pt{sub 3}Al alloys are studied using first-principle approach. The calculated results show that the pressure leads to phase transition from tetragonal structure to cubic structure at 60 GPa. With increasing pressure, the elastic constants, bulk modulus and shear modulus of these Pt{sub 3}Al alloys increase linearly and the bond lengths of Pt–Al metallic bonds and the peak at E{sub F} decrease. The cubic Pt{sub 3}Al alloy has excellent resistance to volume deformation under high pressure. We suggest that the phase transition is derived from the hybridization between Pt and Al atoms for cubic structure is stronger than that of tetragonal structure and forms the strong Pt–Al metallic bonds under high pressure.

  12. Two-Phase Critical Discharge of Initially Saturated or Subcooled Water Flowing in Sharp-Edgred Tubes at High Pressure

    Institute of Scientific and Technical Information of China (English)

    1995-01-01

    The transient critical flow experiment with sharp-deged tubes as the break geometries is conducted in high pressure convective circulation test loop of Xi'an Jiantong University.The initial Steady operation pressure is up to 22.0MPa.An empirical correlation was made to obtain the critical mass flow rates,the critical pressure ratio and the thermal nonequilibrium number were correlated as the functions of the tube length to tube diameter ratio L/D.The predicted critical mass flow rate gets a higher accureacy for short tubes with L/D 12.

  13. A density functional study of the high-pressure chemistry of MSiN2(M = Be, Mg, Ca): prediction of high-pressure phases and examination of pressure-induced decomposition

    Science.gov (United States)

    Rebecca Römer, S.; Kroll, Peter; Schnick, Wolfgang

    2009-07-01

    Normal pressure modifications and tentative high-pressure phases of the nitridosilicates MSiN2 with M = Be, Mg, or Ca have been thoroughly studied by density functional methods. At ambient pressure, BeSiN2 and MgSiN2 exhibit an ordered wurtzite variant derived from idealized filled β-cristobalite by a C1-type distortion. At ambient pressure, the structure of CaSiN2 can also be derived from idealized filled β-cristobalite by a different type of distortion (D1-type). Energy-volume calculations for all three compounds reveal transition into an NaCl superstructure under pressure, affording sixfold coordination for Si. At 76 GPa BeSiN2 forms an LiFeO2-type structure, corresponding to the stable ambient-pressure modification of LiFeO2, while MgSiN2 and CaSiN2 adopt an LiFeO2-type structure, corresponding to a metastable modification (24 and 60 GPa, respectively). For both BeSiN2 and CaSiN2 intermediate phases appear (for BeSiN2 a chalcopyrite-type structure and for CaSiN2 a CaGeN2-type structure). These two tetragonal intermediate structures are closely related, differing mainly in their c/a ratio. As a consequence, chalcopyrite-type structures exhibit tetrahedral coordination for both cations (M and Si), whereas in CaGeN2-type structures one cation is tetrahedrally (Si) and one bisdisphenoidally (M) coordinated. Both structure types, chalcopyrite and CaGeN2, can also be derived from idealized filled β-cristobalite through a B1-type distortion. The group-subgroup relation of the BeSiN2/MgSiN2, the CaSiN2, the chalcopyrite, the CaGeN2 and the idealized filled β-cristobalite structure is discussed and the displacive phase transformation pathways are illustrated. The zero-pressure bulk moduli were calculated for all phases and have been found to be comparable to compounds such as α- Si3N4, CaIrO3 and Al4C3. Furthermore, the thermodynamic stability of BeSiN2, MgSiN2 and CaSiN2 against phase agglomerates of the binary nitrides M3N2 and Si3N4 under pressure are examined.

  14. Study of cements silicate phases hydrated under high pressure and high temperature; Etude des phases silicatees du ciment hydrate sous haute pression et haute temperature

    Energy Technology Data Exchange (ETDEWEB)

    Meducin, F.

    2001-10-01

    This study concerns the durability of oil-well cementing. Indeed, in oil well cementing a cement slurry is pumped down the steel casing of the well up the annular space between it and the surrounding rock to support and protect the casing. The setting conditions of pressure and temperature may be very high (up to 1000 bar and 250 deg C at the bottom of the oil-well). In this research, the hydration of the main constituent of cement, synthetic tri-calcium silicate Ca{sub 3}SiO{sub 2}, often called C{sub 3}S (C = CaO; S = SiO{sub 2} and H H{sub 2}O), is studied. Calcium Silicate hydrates are prepared in high-pressure cells to complete their phase diagram (P,T) and obtain the stability conditions for each species. Indeed, the phases formed in these conditions are unknown and the study consists in the hydration of C{sub 3}S at different temperatures, pressures, and during different times to simulate the oil-well conditions. In a first step (until 120 deg C at ambient pressure) the C-S-H, a not well crystallized and non-stoichiometric phase, is synthesized: it brings adhesion and mechanical properties., Then, when pressure and temperature increase, crystallized phases appear such as jaffeite (Ca{sub 6}(Si{sub 2}O{sub 7})(OH){sub 6}) and hillebrandite (Ca{sub 2}(SiO{sub 3})(OH){sub 2}). Silicon {sup 29}Si Nuclear Magnetic Resonance (using standard sequences MAS, CPMAS) allow us to identify all the silicates hydrates formed. Indeed, {sup 29}Si NMR is a valuable tool to determine the structure of crystallized or not-well crystallized phases of cement. The characterization of the hydrated samples is completed by other techniques: X- Ray Diffraction and Scanning Electron Microscopy. The following results are found: jaffeite is the most stable phase at C/S=3. To simulate the hydration of real cement, hydration of C{sub 3}S with ground quartz and with or without super-plasticizers is done. In those cases, new phases appear: kilchoanite mainly, and xonotlite. A large amount of

  15. Supercooling of aqueous dimethylsulfoxide solution at normal and high pressures: Evidence for the coexistence of phase-separated aqueous dimethylsulfoxide solutions of different water structures

    Science.gov (United States)

    Kanno, H.; Kajiwara, K.; Miyata, K.

    2010-05-01

    Supercooling behavior of aqueous dimethylsulfoxide (DMSO) solution was investigated as a function of DMSO concentration and at high pressures. A linear relationship was observed for TH (homogeneous ice nucleation temperature) and Tm (melting temperature) for the supercooling of aqueous DMSO solution at normal pressure. Analysis of the DTA (differential thermal analysis) traces for homogeneous ice crystallization in the bottom region of the TH curve for a DMSO solution of R =20 (R: moles of water/moles of DMSO) at high pressures supported the contention that the second critical point (SCP) of liquid water should exist at Pc2=˜200 MPa and at Tc2<-100 °C (Pc2: pressure of SCP, Tc2: temperature of SCP). The presence of two TH peaks for DMSO solutions (R =15, 12, and 10) suggests that phase separation occurs in aqueous DMSO solution (R ≤15) at high pressures and low temperatures (<-90 °C). The pressure dependence of the two TH curves for DMSO solutions of R =10 and 12 indicates that the two phase-separated components in the DMSO solution of R =10 have different liquid water structures [LDL-like and HDL-like structures (LDL: low-density liquid water, HDL: high-density liquid water)] in the pressure range of 120-230 MPa.

  16. High-pressure-high-temperature phase relations of MgGeO3 : First-principles calculations

    Science.gov (United States)

    Tsuchiya, Taku; Tsuchiya, Jun

    2007-09-01

    The high-pressure-high-temperature behavior of MgGeO3 has been investigated by first-principles computations. It is found that at 300K , the first transformation from ilmenite to orthorhombic perovskite at 24-38GPa is followed by the second one to the CaIrO3 structure at 51-56GPa . Quasiharmonic free energy calculations suggest that the first transformation has a negative Clapeyron slope ( -9.3MPa/K at 1000K ), whereas the second one has a less temperature-sensitive positive Clapeyron slope ( +7.8MPa/K at 1000K ). It is also confirmed that the LiNbO3 structure does not have its own stability P,T conditions. Pressure dependence of the Goldschmidt tolerance factor indicates a clear correlation between distortion of the perovskite structure and relative stability of perovskite and postperovskite structures.

  17. Structural phase transition of edge-sharing copper oxide Ca0.85CuO2 under high pressure

    Institute of Scientific and Technical Information of China (English)

    MAI Wenjie; ZHANG Gongmu; QIN Xiaomei; CHEN Liangchen; LI Fengying; YU Richeng; LIU Jing; JIN Changqing

    2004-01-01

    The perovskite-like structure compound Ca0.85- CuO2 has interesting structural properties: it has infinite one-dimensional edge-sharing copper-oxygen chains as well as partial occupancy of the Ca sites resulting in an incommensurate superstructure. In situ high-pressure energy dispersive X-ray diffraction measurements on polycrystalline powder Ca0.85CuO2 have been performed by using diamond anvil cell (DAC) instrument with synchrotron radiation. The results for the first time show that edge-sharing copper oxide Ca0.85CuO2 undergoes a structural transition at 14.5 GPa, and furthermore the structural transition is reversible.

  18. High-pressure phases in shock-induced melt of the unique highly shocked LL6 chondrite Northwest Africa 757

    Science.gov (United States)

    Hu, Jinping; Sharp, Thomas G.

    2016-07-01

    Northwest Africa 757 is unique in the LL chondrite group because of its abundant shock-induced melt and high-pressure minerals. Olivine fragments entrained in the melt transform partially and completely into ringwoodite. Plagioclase and Ca-phosphate transform to maskelynite, lingunite, and tuite. Two distinct shock-melt crystallization assemblages were studied by FIB-TEM analysis. The first melt assemblage, which includes majoritic garnet, ringwoodite plus magnetite-magnesiowüstite, crystallized at pressures of 20-25 GPa. The other melt assemblage, which consists of clinopyroxene and wadsleyite, solidified at ~15 GPa, suggesting a second veining event under lower pressure conditions. These shock features are similar to those in S6 L chondrites and indicate that NWA 757 experienced an intense impact event, comparable to the impact event that disrupted the L chondrite parent body at 470 Ma.

  19. High pressure investigations on hydrous magnesium silicate-phase A using first principles calculations: H---H repulsion and changes in hydrogen bond geometry with compression

    Science.gov (United States)

    Poswal, H. K.; Sharma, Surinder; Sikka, S. K.

    2009-09-01

    We have carried out first principles structural relaxation calculations on the hydrous magnesium silicate Phase A (Mg7Si2O8(OH)6) under high pressures. Our results show that phase A does not undergo any phase transition upto ~ 45 GPa. We find that non-bonded H--H distance reaches a limiting value of 1.85 angstrom at about 45 GPa. The H--H repulsive strain releasing mechanism in Phase A is found to be dramatically different from the hydrogen bond bending one that was proposed by Hofmeister et al1 for Phase B. It is based on the reduction of one of the O-H bond distances with compression.

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

    Science.gov (United States)

    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 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.

  1. High Pressure and high temperature phase transition in FeTiO3: implications for the deep interior of giant planet

    Science.gov (United States)

    Hamane, D.; Zhang, M.; Yagi, T.; Yanming, M.

    2011-12-01

    The discovery of the structural phase transition of perovskite into a CaIrO3-type phase at high pressures invites the investigation of further phase transitions in order to understand the deep interior of giant planet. Recent experimental studies for FeTiO3 have detected a new dissociation to a dense compound assemblage rather than the CaIrO3-type phase at high pressures. Since the phase relation of FeTiO3 is expected to be significant for estimating the ultrahigh-pressure behavior of ABX3 compounds such as MgSiO3, we investigated the phase transition in FeTiO3 up to 80 GPa and 2600K by synchrotron X-ray diffraction using a laser-heated diamond anvil cell and analytical transmission electron microscopy observations. We conclude that FeTiO3 ilmenite transforms into the following phase(s) with increasing pressure: FeTiO3 (perovskite) at 18-30 GPa, 1/2 Fe2TiO4 (Ca2TiO4-type) + TiO2 (OI-type) at 30-45 GPa and high temperature, FeO (wüstite) + TiO2 (OI) at 30-45 GPa and low temperature, and 2/3 FeO (wüstite) + 1/3 FeTi3O7 (orthorhombic phase) above 45 GPa. We also estimates the structural model of FeTi3O7 phase by using the particle swarm optimization simulation, and Rietveld refinement based on this model structure gave an excellent fit with the experimentally obtained X-ray diffraction pattern. This new high-density FeTi3O7 structure consists of the polyhedra for monocapped prisms FeO7, bicapped prisms TiO8, and tricapped prisms TiO9 with Imm2 symmetry. The dense compound assemblage found in FeTiO3 is promising for investigating the behavior of ABX3 compounds under ultrahigh pressures, and our experimental results suggest that the AB3X7 type oxide instead of cotunnite SiO2 may produce the denser assemblage even in the silicate system at ultra high pressure. This new model has not yet been proposed as a candidate, but our suggestion will be important for predicting the mineral assemblage in the deep interiors of giant planets.

  2. Physical properties and phase diagram of the magnetic compound Cr0.26NbS1.74 at high pressures

    Science.gov (United States)

    Sidorov, V. A.; Petrova, A. E.; Pinyagin, A. N.; Kolesnikov, N. N.; Khasanov, S. S.; Stishov, S. M.

    2016-06-01

    We report the results of a study of magnetic, electrical, and thermodynamic properties of a single crystal of the magnetic compound Cr0.26NbS1.74 at ambient and high pressures. Results of the measurements of magnetization as a function of temperature reveal the existence of a ferromagnetic phase transition in Cr0.26NbS1.74. The effective number of Bohr magnetons per Cr atom in the paramagnetic phase of Cr0.26NbS1.74 is µeff ≈ 4.6µB, which matches the literature data for Cr1/3NbS2. Similarly, the effective number of Bohr magnetons per Cr atom in the saturation fields is rather close in both substances and corresponds to the number of magnetons in the Cr+3 ion. In contrast to the stoichiometric compound, Cr0.26NbS1.74 does not show a metamagnetic transition, that indicates the lack of a magnetic soliton. A high-pressure phase diagram of the compound reveals the quantum phase transition at T = 0 and P ≈ 4.2 GPa and the triple point situated at T ≈ 20 K and P ≈ 4.2 GPa.

  3. Compressibility and phase transformations of AgInSe{sub 2} from high-pressure X-ray diffraction studies

    Energy Technology Data Exchange (ETDEWEB)

    Orlova, N.S.; Turtsevich, G.A.; Bodnar, I.V. [Institute of Solid State and Semiconductor Physics, Minsk (Belarus)

    1994-06-01

    The compound AgInSe{sub 2} is one of the A{sup I}B{sup III}C{sup VI}{sub 2} ternary semiconductors, which exhibit unique optical properties and are highly promising materials for use in nonlinear optics and semiconductor engineering. Their elastic properties are of great importance and yet, unlike other characteristics, remain inadequately studied. In particular, the elastic constants were determined only for AgGaS{sub 2} and AgGaSe{sub 2}. The compressibilities were measured for a number of CuB{sup III}C{sup VI}{sub 2} compounds and for three Ag compounds AgGaS{sub 2}, AgGaSe{sub 2}, and AgGaTe{sub 2}. No data on the compressiblity of AgInC{sup VI}{sub 2} compounds is available in the literature. The compressibilities along the major directions of AgInS{sub 2} crystals with the chalcopyrite structure were reported. In this work, we studied the compressibility of AgInSe{sub 2} using high-pressure X-ray diffraction analysis.

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

    Science.gov (United States)

    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.

  5. Effects of grinding-induced grain boundary and interfaces on electrical transportation and structure phase transition in ZnSe under high pressure

    Science.gov (United States)

    Jie, Yang; Pei, Wang; Guo-Zhao, Zhang; Xiao-Xue, Zhou; Jing, Li; Cai-Long, Liu

    2016-06-01

    Interface and scale effects are the two most important factors which strongly affect the structure and the properties of nano-/micro-crystals under pressure. We conduct an experiment under high pressure in situ alternating current impedance to elucidate the effects of interface on the structure and electrical transport behavior of two ZnSe samples with different sizes obtained by physical grinding. The results show that (i) two different-sized ZnSe samples undergo the same phase transitions from zinc blend to cinnabar-type phase and then to rock salt phase; (ii) the structural transition pressure of the 859-nm ZnSe sample is higher than that of the sample of 478 nm, which indicates the strong scale effect. The pressure induced boundary resistance change is obtained by fitting the impedance spectrum, which shows that the boundary conduction dominates the electrical transport behavior of ZnSe in the whole experimental pressure range. By comparing the impedance spectra of two different-sized ZnSe samples at high pressure, we find that the resistance of the 478-nm ZnSe sample is lower than that of the 859-nm sample, which illustrates that the sample with smaller particle size has more defects which are due to physical grinding. Project supported by the National Natural Science Foundation of China (Grant Nos. 11404133 and 11374121) and the Program of Science and Technology Development Plan of Jilin Province, China (Grant No. 20140520105JH).

  6. The effect of morphology and confinement on the high-pressure phase transition in ZnO nanostructure

    Energy Technology Data Exchange (ETDEWEB)

    Kotmool, Komsilp; Bovornratanaraks, Thiti, E-mail: thiti.b@chula.ac.th [Center of Excellence in Forum for Theoretical Science, Department of Physics, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand); Chakraborty, Sudip [Condensed Matter Theory Group, Department of Physics, University of Uppsala, Box 530, SE 75121 Uppsala (Sweden); Ahuja, Rajeev [Condensed Matter Theory Group, Department of Physics, University of Uppsala, Box 530, SE 75121 Uppsala (Sweden); Applied Materials Physics, Department of Materials and Engineering, Royal Institute of Technology (KTH), S-100 44 Stockholm (Sweden)

    2015-03-21

    The transition pressure (P{sub t}) of the B4-to-B1 phase transformation of zinc oxide nanoparticle (n-ZnO) structures was investigated in terms of their size and morphology. Nanorods, nanopencils, nanopyramids, nanowires, and nanotubes of the B4 phase in various sizes were directly built up by accounting for the atomic basis of the core and surface regions. The previously proposed transformation path was performed for constructing shapes and sizes compatible with B1 phases. Using systematic density functional theory, the surfaces were cleaved from the optimized crystal structures at different pressures in both the B4 and B1 phases. A method for calculating the surface energy at different pressures is proposed using an asymmetric slab model. Using the proposed model, the transition pressure of n-ZnO structures was found to significantly depend on their morphology and size, which is in good agreement with the available experimental reports.

  7. Phase transitions and equation of state of CsI under high pressure and the development of a focusing system for x-rays

    International Nuclear Information System (INIS)

    The phase transitions and equation of state of ionic solid cesium iodide were studied under high pressure and room temperature in a diamond anvil cell. The studies were carried out using both energy dispersive and angular dispersive diffraction methods on synchrotron radiation sources over the pressure range from atmospheric pressure to over 300 gigapascals (3 million atmospheres). CsI undergoes a distinct phase transition at about 40 GPa, a pressure that is much lower than the reported insulator-metal transition at 110 GPa, from the atmospheric pressure B2(CsCl) structure to an orthorhombic structure. At higher pressures, a continuous distortion in the structure was observed with a final structure similar to a hcp lattice under ultra high pressure. No volume discontinuity was observed at the insulator-metal transition. The newly found transition sequence is different from the result of previous static compression studies. The current structure has a smaller unit cell volume than the previous assignment. This has resolved a long existing controversy among the previous static compression studies, the dynamic compression studies, and the theoretical studies. The current results also explain the apparent discrepancy between the present study and the previous static studies. We also present the development of a focusing system for high energy x-rays (> 12 keV) that is particularly suited for high pressure diffraction studies. This system uses a pair of multilayer coated spherical mirrors in a Kirkpatrick-Baez geometry. A focused beam size less than 10 micron in diameter can be readily achieved with sufficient intensity to perform diffraction studies. 93 refs., 46 figs., 15 tabs

  8. Theoretical investigations on phase stability, elastic constants and electronic structures of D0{sub 22}- and L1{sub 2}-Al{sub 3}Ti under high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jian, E-mail: lijian@xsyu.edu.cn [School of Materials Science and Engineering, Xi’an Shiyou University, Xi’an 710065 (China); School of Materials, Northwestern Polytechnical University, Xi’an 710072 (China); Zhang, Ming [School of Petroleum Engineering, Xi’an Shiyou University, Xi’an 710065 (China); Luo, Xian [School of Materials, Northwestern Polytechnical University, Xi’an 710072 (China)

    2013-04-15

    Highlights: ► High pressure stability of D0{sub 22}, L1{sub 2}-Al{sub 3}Ti are studied using first-principles method. ► Structural, energetic and thermodynamic properties are calculated under 0–40 GPa. ► L1{sub 2}-Al{sub 3}Ti is more stable than D0{sub 22}-Al{sub 3}Ti when pressure is above 20–30 GPa. ► The dependence of elastic, anisotropy and Debye temperature are investigated. ► Ti-3d and Al-3p electron interaction is strengthened under high pressure. -- Abstract: Phase stability, elastic and thermodynamic properties, and electronic structure of titanium trialuminide (Al{sub 3}Ti) with Ll{sub 2} and D0{sub 22} structures under pressure up to 40 GPa have been investigated using first-principles calculations. The equilibrium structure and formation energy show that L1{sub 2}-Al{sub 3}Ti is stable when the pressure is higher enough, approximately above than 20–30 GPa. The elastic constants, anisotropy index and Debye temperature of both phases increase with the pressure going up, and L1{sub 2}-Al{sub 3}Ti has better ductility, smaller anisotropy and lower Debye temperature than D0{sub 22}-A1{sub 3}Ti. The pressure-induced Ti-3d delocalization can strengthen its orbital hybridization with Al(s,p), which leads to stronger atomic bonding, and subsequently makes the L1{sub 2}-Al{sub 3}Ti more stable under high pressure.

  9. Phase behaviour and thermodynamic modelling for the system (grape seed oil + carbon dioxide + ethanol) at high pressures

    International Nuclear Information System (INIS)

    This short communication reports phase equilibrium data (cloud points), employing the synthetic static method, for the system {grape seed oil (GSO) + carbon dioxide (CO2) + ethanol} up to T = 343.15 K and 22.53 MPa. Experimental results were modelled using the Peng-Robinson equation of state with the classical van der Waals quadratic mixing rule (PR-vdW2). It is shown that the thermodynamic model is able to represent satisfactorily the phase behaviour of the system investigated

  10. Polymorphism of iron at high pressure: A 3D phase-field model for displacive transitions with finite elastoplastic deformations

    Science.gov (United States)

    Vattré, A.; Denoual, C.

    2016-07-01

    A thermodynamically consistent framework for combining nonlinear elastoplasticity and multivariant phase-field theory is formulated at large strains. In accordance with the Clausius-Duhem inequality, the Helmholtz free energy and time-dependent constitutive relations give rise to displacive driving forces for pressure-induced martensitic phase transitions in materials. Inelastic forces are obtained by using a representation of the energy landscape that involves the concept of reaction pathways with respect to the point group symmetry operations of crystal lattices. On the other hand, additional elastic forces are derived for the most general case of large strains and rotations, as well as nonlinear, anisotropic, and different elastic pressure-dependent properties of phases. The phase-field formalism coupled with finite elastoplastic deformations is implemented into a three-dimensional Lagrangian finite element approach and is applied to analyze the iron body-centered cubic (α-Fe) into hexagonal close-packed (ɛ-Fe) phase transitions under high hydrostatic compression. The simulations exhibit the major role played by the plastic deformation in the morphological and microstructure evolution processes. Due to the strong long-range elastic interactions between variants without plasticity, a forward α → ɛ transition is energetically unfavorable and remains incomplete. However, plastic dissipation releases considerably the stored strain energy, leading to the α ↔ ɛ ↔α‧ (forward and reverse) polymorphic phase transformations with an unexpected selection of variants.

  11. Multi-Length Scale Modeling of High-Pressure-Induced Phase Transformations in Soda-Lime Glass

    Science.gov (United States)

    Grujicic, M.; Bell, W. C.; Glomski, P. S.; Pandurangan, B.; Cheeseman, B. A.; Fountzoulas, C.; Patel, P.

    2011-10-01

    Molecular-level modeling and simulations are employed to study room-temperature micro-structural and mechanical response of soda-lime glass when subjected to high (i.e., several giga-Pascal) uniaxial-strain stresses/pressure. The results obtained revealed the occurrence of an irreversible phase-transformation at ca. 4 GPa which was associated with a (permanent) 3-7% volume reduction. Close examination of molecular-level topology revealed that the pressure-induced phase transformation in question is associated with an increase in the average coordination number of the silicon atoms, and the creation of two- to fourfold (smaller, high packing-density) Si-O rings. The associated loading and unloading axial-stress versus specific-volume isotherms were next converted into the corresponding loading Hugoniot and unloading isentrope axial-stress versus specific-volume relations. These were subsequently used to analyze the role of the pressure-induced phase-transformation/irreversible-densification in mitigating the effects of blast and ballistic impact loading onto a prototypical glass plate used in monolithic and laminated transparent armor applications. The results of this part of the study revealed that pressure-induced phase-transformation can provide several beneficial effects such as lowering of the loading/unloading stress-rates and stresses, shock/release-wave dispersion, and energy absorption associated with the study of phase-transformation.

  12. The nonlinear anomalous lattice elasticity associated with the high-pressure phase transition in spodumene: A high precission static compression study

    CERN Document Server

    Ullrich, A; Miletich, R; 10.1007/s00269-009-0300-8

    2010-01-01

    The high-pressure behavior of the lattice elasticity of spodumene, LiAlSi2O6, was studied by static compression in a diamond-anvil cell up to 9.3 GPa. Investigations by means of single-crystal XRD and Raman spectroscopy within the hydrostatic limits of the pressure medium focus on the pressure ranges around similar to 3.2 and similar to 7.7 GPa, which have been reported previously to comprise two independent structural phase transitions. While our measurements confirm the well-established first-order C2/c-P2(1)/c transformation at 3.19 GPa (with 1.2% volume discontinuity and a hysteresis between 0.02 and 0.06 GPa), both unit-cell dimensions and the spectral changes observed in high-pressure Raman spectra give no evidence for structural changes related to a second phase transition. Monoclinic lattice parameters and unit-cell volumes at in total 59 different pressure points have been used to re-calculate the lattice-related properties of spontaneous strain, volume strain, and the bulk moduli as a function of pr...

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

    Science.gov (United States)

    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.

  14. Evidence for a High-Pressure Phase Transition of ε-2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (CL-20) Using Vibrational Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ciezak, J.; Jenkins, T; Liu, Z

    2007-01-01

    The high-pressure response of {epsilon}-2,4,6,8,10,12-hexanitrohexaazaisowurtizane (CL-20) has been examined to 27 GPa in diamond anvil cells using vibrational spectroscopy. The results reveal evidence of an {epsilon}{yields}{Upsilon} pressure-induced phase transition between 4.1 and 6.4 GPa and suggest the existence of a {Upsilon}{yields}{zeta} transition near 18.7 GPa. Several Raman and infrared frequencies were found to decrease in intensity as the phase boundaries are approached. An anomalous intensity increase was noted in the C-N-C infrared mode that is believed to result from an increase in the Raman cross-section due to a stronger interlayer coupling under pressure.

  15. The disproportionation reaction phase transition, mechanical, and lattice dynamical properties of the lanthanum dihydrides under high pressure: A first principles study

    Science.gov (United States)

    Yang, Jin-Wen; Gao, Tao; Gong, Yan-Rong

    2014-06-01

    The pressure-induced disproportionation reaction phase transition, mechanical, and dynamical properties of LaH2 with fluorite structure under high pressure are investigated by performing first-principles calculations using the projector augmented wave (PAW) method. The phase transition of 2LaH2 → LaH + LaH3 obtained from the usual condition of equal enthalpies occurs at the pressure of 10.38 GPa for Perdew-Wang (PW91) functional and 6.05 GPa for Ceperly-Adler (CA) functional, respectively. The result shows that the PW91 functional calculations agree excellently with the experimental finding of 11 GPa of synchrotron radiation (SR) X-ray diffraction (XRD) of Machida et al. and 10 GPa of their PBE functional theoretical result. Three independent single-crystal elastic constants, polycrystalline bulk modulus, shear modulus, Young's modulus, elastic anisotropy, Poisson's ratio, the brittle/ductile characteristics and elastic wave velocities over different directions dependences on pressure are also successfully obtained. Especially, the phonon dispersion curves and corresponding phonon density of states of LaH2 under high pressure are determined systematically using a linear-response approach to density functional perturbation theory (DFPT). Our results demonstrate that LaH2 in fluorite phase can be stable energetically up to 10.38 GPa, stabilized mechanically up to 17.98 GPa, and stabilized dynamically up to 29 GPa, so it may remain a metastable phase above 10.38 GPa up to 29 GPa, these calculated results accord with the recent X-Ray diffraction experimental finding and theoretical predictions of Machida et al.

  16. Shock Induced Emission from Sapphire in High-Pressure Phase of Rh2O3 (Ⅱ) Structure

    Institute of Scientific and Technical Information of China (English)

    ZHANG Dai-Yu; LIU Fu-Sheng; HAO Gao-Yu; SUN Yu-Huai

    2007-01-01

    @@ A distinct optical emission from the Rh2 O3 (Ⅱ) structural sapphire is observed under shock compression of 125,132, and 143 Gpa. The emission intensity continuously increases with the thickness of shocked sapphire. The colour temperature is determined to be about 4000K, which is obviously smaller than the reported value of the alpha phase alumina at the pressures below 80 Gpa. The present results suggest that the structural transformation will cause an obvious change of optical property in sapphire.

  17. High-pressure apparatus

    NARCIS (Netherlands)

    Schepdael, van L.J.M.; Bartels, P.V.; Berg, van den R.W.

    1999-01-01

    The invention relates to a high-pressure device (1) having a cylindrical high-pressure vessel (3) and prestressing means in order to exert an axial pressure on the vessel. The vessel (3) can have been formed from a number of layers of composite material, such as glass, carbon or aramide fibers which

  18. Dynamic mechanical behavior and high pressure phase stability of a zirconium-based bulk metallic glass and its composite with tungsten

    Science.gov (United States)

    Martin, Morgana

    2008-10-01

    The research involved performing controlled impact experiments on BMG composites consisting of amorphous Zr57Nb5Cu 15:4Ni12:6Al10 (LM106 or Vitreloy106) with crystalline tungsten reinforcement particles. Monolithic LM106 was also examined to aid in the understanding of the composite. The mechanical behavior of the composite was investigated over a range of strain rates (10-3 s -1 to 106 s-1), stress states (compression, compression-shear, tension), and temperatures (RT to 600°C) to determine the dependence of mechanical properties and deformation and failure modes (i.e., homogeneous deformation vs. inhomogeneous shear banding) on these parameters. Mechanical testing in the quasi-static to intermediate strain-rate regimes was performed using an Instron, Drop Weight Tower, and Split Hopkinson Pressure Bar, respectively. High-strain-rate mechanical properties of the BMG-matrix composite and monolithic BMG were investigated using dynamic compression (reverse Taylor) and dynamic tension (spall) impact experiments performed using a gas gun instrumented with velocity interferometry and high-speed digital photography. These experiments provided information about dynamic strength and deformation modes, and allowed for validation of constitutive models via comparison of experimental and simulated transient deformation profiles and free surface velocity traces. Hugoniot equation of state measurements were performed on the monolithic BMG to investigate the high pressure phase stability of the glass and the possible implications of a high pressure phase transformation on mechanical properties. Specimens were recovered for post-impact microstructural and thermal analysis to gain information about the mechanisms of dynamic deformation and fracture, and to examine for possible shock-induced phase transformations of the amorphous phase. For the composite, mechanical testing revealed positive strain-rate sensitivity of its yield stress and negative strain-rate sensitivity of its

  19. Phase stability, physical properties of rhenium diboride under high pressure and the effect of metallic bonding on its hardness

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Ming-Min [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China); Kuang, Xiao-Yu, E-mail: scu_kxy@163.com [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China); Wang, Zhen-Hua; Shao, Peng; Ding, Li-Ping [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China); Huang, Xiao-Fen [Physics Department, Sichuan Normal University, Chengdu 610068 (China)

    2013-12-25

    Highlights: •The transition pressure P{sub t} between the ReB{sub 2}–ReB{sub 2} and MoB{sub 2}–ReB{sub 2} phases is firstly determinate. •The single-bonded B–B feather remains in ReB{sub 2} compounds. •A semiempirical method to evaluate the hardness of crystals with partial metallic bond is presented. •The large hardness (39.1 GPa) of ReB{sub 2}–ReB{sub 2} indicate that it is a superhard material. •The zigzag interconnected B–Re and B–B covalent bonds underlie the ultraincompressibilities. -- Abstract: Using first-principles calculations, the elastic constants, thermodynamic property and structural phase transition of rhenium diboride under pressure are investigated by means of the pseudopotential plane-waves method, as well as the effect of metallic bond on its hardness. Eight candidate structures of known transition-metal compounds are chosen to probe for rhenium diboride ReB{sub 2}. The calculated lattice parameters are consistent with the experimental and theoretical values. Based on the third order Birch–Murnaghan equation of states, the transition pressure P{sub t} between the ReB{sub 2}–ReB{sub 2} and MoB{sub 2}–ReB{sub 2} phases is firstly determinate. Elastic constants, shear modulus, Young’s modulus, Poisson’s ratio and Debye temperature are derived. The single-bonded B–B feather remains in ReB{sub 2} compounds. Furthermore, according to Mulliken overlap population analysis, a semiempirical method to evaluate the hardness of multicomponent crystals with partial metallic bond is presented. Both strong covalency and a zigzag topology of interconnected bonds underlie the ultraincompressibilities. In addition, the superior performance and large hardness (39.1 GPa) of ReB{sub 2}–ReB{sub 2} indicate that it is a superhard material.

  20. High-pressure structural phase transitions in TiO sub 2 and synthesis of the hardest known oxide

    CERN Document Server

    Ahuja, R

    2002-01-01

    Despite great technological importance and many investigations, a material with a measured hardness comparable to that of diamond or cubic boron nitride has yet to be identified. Our combined theoretical and experimental investigations led to the discovery of a new polymorph of titanium dioxide, where titanium is ninefold coordinated to oxygen in the cotunnite (PbCl sub 2) structure. Hardness measurements on this phase, synthesized at pressures above 60 GPa and temperatures above 1000 K, reveal that this material is the hardest oxide yet discovered. Furthermore, it is one of the least compressible (with a measured bulk modulus of 431 GPa) and hardest (with a microhardness of 38 GPa) polycrystalline materials studied so far.

  1. High-pressure phase behavior of MnTiO3: decomposition of perovskite into MnO and MnTi2O5

    Science.gov (United States)

    Okada, Taku; Yagi, Takehiko; Nishio-Hamane, Daisuke

    2011-04-01

    The phase relations and compression behavior of MnTiO3 perovskite were examined using a laser-heated diamond-anvil cell, X-ray diffraction, and analytical transmission electron microscopy. The results show that MnTiO3 perovskite becomes unstable and decomposes into MnO and orthorhombic MnTi2O5 phases at above 38 GPa and high temperature. This is the first example of ABO3 perovskite decomposing into AO + AB2O5 phases at high pressure. The compression behavior of volume, axes, and the tilting angle of TiO6 octahedron of MnTiO3 perovskite are consistent with those of other A2+B4+O3 perovskites, although no such decomposition was observed in other perovskites. FeTiO3 is also known to decompose into two phases, instead of transforming into the CaIrO3-type post-perovskite phase and we argue that one of the reasons for the peculiar behavior of titanate is the weak covalency of the Ti-O chemical bonds.

  2. High pressure phase transitions in Mg{sub 1-x}Ca{sub x}O: Theory

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, Anurag; Chauhan, Mamta [Advanced Material Research Lab, Indian Institute of Information Technology and Management, Gwalior (India); Singh, R.K. [Department of Physics, ITM University, Gurgaon (India); Padegaonker, Rishikesh [Indian Embassy School, Sana (Yemen)

    2011-08-15

    We have analysed a B1 {yields} B2 structural phase transitions in Mg{sub 1-x}Ca{sub x}O solid solutions and their ground state properties by using first principle density functional theory and charge transfer interaction potential (CTIP) approach. The effects of exchange-correlation interactions are handled by the generalized gradient approximation with Perdew-Burke-Ernzerhof type parameterization. CTIP approach includes the long range modified Coulomb with charge transfer interactions and short range part of this model includes the van der Waals as well as Hafemeister Flygare type overlap repulsive interactions. The study observes a linear variation of calculated transition pressure, bulk modulus and lattice parameter of Mg{sub 1-x}Ca{sub x}O as a function of Ca composition. The observed results for the end point members are in agreement to their experimental counterparts and the deviations have been discussed. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. Construction of a Direct Water-Injected Two-Stroke Engine for Phased Direct Fuel Injection-High Pressure Charging Investigations

    Science.gov (United States)

    Somsel, James P.

    1998-01-01

    The development of a water injected Orbital Combustion Process (OCP) engine was conducted to assess the viability of using the powerplant for high altitude NASA aircraft and General Aviation (GA) applications. An OCP direct fuel injected, 1.2 liter, three cylinder, two-stroke engine has been enhanced to independently inject water directly into the combustion chamber. The engine currently demonstrates low brake specific fuel consumption capability and an excellent power to weight ratio. With direct water injection, significant improvements can be made to engine power, to knock limits/ignition advance timing, and to engine NO(x) emissions. The principal aim of the testing was to validate a cyclic model developed by the Systems Analysis Branch at NASA Ames Research Center. The work is a continuation of Ames' investigations into a Phased Direct Fuel Injection Engine with High Pressure Charging (PDFI-ITPC).

  4. High Pressure Structural Phase Transition and Electronic Properties of NdX (X = P, As, Sb) Compounds : A First Principles Study

    Science.gov (United States)

    Kumar Singh, Sanjay; Singh, Rajeshwar; Singh, R. P.

    2015-06-01

    The structural and phase transition properties of NdX (X = P, As, Sb) under high pressure have been investigated using an ab-initiofull potential linear augmented plane wave plus local orbitals approach within the framework of density functional theory as implanted in the WIEN2k package. In this approach the generalized gradient approximation is chosen for the exchange-correlation functional energy optimization for calculating the total energy. At ambient conditions NdX stabilize in NaCl (B1 phase) structure. Under compression, it undergoes first-order structural transition from Fm-3m to P4/mmm (body centre tetragonal) phase at 30.0, 24.06 and 15.1 GPa which is found to be in good agreement with the available experimental data 30.0, 24.2 and 15.0 GPa respectively. The structural properties viz., equilibrium lattice constants, bulk modulus and its pressure derivative and volume collapse are also calculated and compared with previous calculations and available experimental data. The local spin-density approximation along with Hubbard-U corrections and spin-orbit coupling has been used for correct prediction of electronic properties.

  5. On the Chemical Evolution of Upper Mantle of the Early Earth—An Experimental Study on Melting of the Silicate Phase in Jilin Chondrite at High Pressures

    Institute of Scientific and Technical Information of China (English)

    谢鸿森; 方虹; 等

    1989-01-01

    Relatively old ages of chondrites(normally around 4.5Ga)suggest that their parent bodies did not experience any mely-fractionation under high temperature and high pressure conditions pertaining to the interior of terrestrial plaets.Therefore,it is reasonable to take chondrites as starting materials in the study of the chemical evolution of the early earth.The sillicate phase in the Jilin chondrite (H5)was chosen for this purpose because it possesses a chemical composition similar to that of the primitive mantle.The melting experiment was carried out at 20-30 k bar and has rsulted in a product which contains1-5% melts in addition to solid cryustal phase.The chemical composition of the melt phases and the partitioning of various elements between the coexisting silicate melts are geochemically similar to those of anatectic rocks on the earth.This can thus serve as the basis for discussing the chemical evolution of the early upper mantle.

  6. Elastic Constants at High Pressure, Solid-Liquid Phase Boundaries and Equations of State for Solid and Liquid Copper and 316-Stainless Steel

    Science.gov (United States)

    Hayes, Dennis

    1999-06-01

    Prior accurate measurements of sound speed on the Hugoniot for copper and 316-SS are used to construct complete equations of state for solid and liquid phases. Differences between calculated bulk and observed elastic sound-speed in the solid are used to infer high-pressure elastic constants. At higher pressures, where the shocked state is entirely liquid, data are sufficient to construct the EOS including an accurate estimate for Grüneisen's ratio. The liquid EOS also reasonably describes some low-pressure, high-temperature properties, including density, sound speed, variation of sound speed with temperature, and thermal expansion, lending confidence to its accuracy. Results are comparable for each metal: the shear modulus increases along the Hugoniot and then drops precipitously toward zero as the pressure nears the liquid-phase boundary. In the liquid, Grüneisen's ratio is observed to be constant and agrees with the value measured for the liquid at zero pressure. The state below which this constancy holds is identified as the smallest pressure on the Hugoniot at which melting is complete. The gap between pure solid and pure liquid is identified as the mixed-phase region and in the case of copper, its size and location are in reasonable agreement with published ab initio calculations of Moriarty. Confidence in calculated temperature and entropy is less then that in pressure, volume and energy owing to uncertainties in specific heats.

  7. High pressure annular two-phase flow in a narrow duct. Part 1: Local measurements in the droplet field, and Part 2: Three-field modeling

    Energy Technology Data Exchange (ETDEWEB)

    Trabold, T.A.; Kumar, R. [Lockheed Martin Corp., Schenectady, NY (United States)

    1999-07-01

    In Part 1, detailed measurements were made in a high pressure, adiabatic (boiled at the inlet) annular flow in a narrow, high aspect ratio duct using a gamma densitometer, hot-film anemometer and high-speed video photography. Measurements of void fraction, droplet frequency, velocity, drop size, and interfacial area concentration have been made to support the three field computational capability. An important aspect of this testing is the use of a modeling fluid (R-134a) in a vertical duct which permits visual access in annular flow. This modeling fluid accurately simulates the low liquid-to-vapor density ratio of steam-water flows at high pressures. These measurements have been taken in a narrow duct of hydraulic diameter 4.85 mm, and a cross-section aspect ratio of 22.5. However, the flow displays profiles of various shapes not only in the narrow dimension, but also in the width dimension. In particular, the shape of the droplet profiles depends on the entrained droplet flux from the edges in the vapor core. The average diameter from these profiles compare well with the models developed in the literature. Interfacial area concentration for these low density ratio flows is higher than the highest concentration reported for air-water flows. Video records show that along with the bow-shaped waves, three-dimensional {lambda}-shaped waves appear in annular flows for high flow rates. Part 2 outlines the development of a three-field modeling approach in annular flow and the predictive capability of an analysis code. Models have been developed here or adapted from the literature for the thin film near the wall as well as the droplets in the vapor core, and have been locally applied in a fully developed, two-phase adiabatic boiling annular flow in a duct heated at the inlet at high pressure. Numerical results have been obtained using these models that are required for the closure of the continuity and momentum equations. The two-dimensional predictions are compared with

  8. Experimental study of simulating high pressure steam-water two-phase flow with sulfur hexafluoride gas and ethyl alcohol liquid (droplets behavior of downward mist flow)

    International Nuclear Information System (INIS)

    The full text follows. Mist flow appears in various industrial plants and machines; nuclear power plants, chemical plants, heat exchangers, steam turbines, and so on. Behaviors of droplet have effects on heat and mass transfer process on them. As for nuclear power plants, droplet diameters of downward mist flow have an important effect on peak-clad-temperature (PCT) at loss of coolant accidents (LOCA). Reliability of two-fluid model computer codes to predict gas-liquid two-phase flow relies on the experimental database. We simulated actual pressure steam-water two-phase flow using Sulfur Hexafluoride gas and ethyl alcohol liquid two-phase flow at low pressures. The specific objectives of this study are to: (1) simulate easily a high pressure and high temperature steam-water system by using alternative fluids; (2) clarify the diameter of droplet which does not break up any more (stable droplet diameter) in the blow down phenomenon of LOCA; (3) extend the downward mist flow database to lower liquid-to-gas density ratio. We carried out the experiment of downward mist flow with two kinds of fluids: Sulfur Hexafluoride (SF6) and ethyl alcohol (C2H5OH) as gas and liquid phase, respectively. Those fluids can simulate a high pressure and temperature steam-water system of 6 MPa, and 550 K at the condition of the lower pressure and atmospheric temperature (0.5 MPa and 300 K, respectively). The physical properties of SF6 and C2H5OH are as same as steam-water system. The density ratio and surface tension, which affect on the diameter of droplet, of SF6 / C2H5OH at 0.5 MPa and 300 K is about 30 and 2.1 10-2 N/m, respectively. SF6 is widely used in electronic equipment as insulating gas. It stays in the same chemical state under the condition of atmospheric temperature and chemical decomposition due to thermal energy is not developed below 770 K. Experimental conditions of superficial gas and liquid velocities were 1.5 m/s-10 m/s and 0.01 m/s-0.03 m/s, respectively. The system

  9. Spin-phonon coupling, high-pressure phase transitions, and thermal expansion of multiferroic GaFeO3: A combined first principles and inelastic neutron scattering study

    Science.gov (United States)

    Gupta, Mayanak Kumar; Mittal, Ranjan; Zbiri, Mohamed; Singh, Ripandeep; Rols, Stephane; Schober, Helmut; Chaplot, Samrath Lal

    2014-10-01

    We have carried out an extensive phonon study on multiferroic GaFeO3 to elucidate its dynamical behavior. Inelastic neutron scattering measurements are performed over a wide temperature range, 150 to 1198 K. First principles lattice dynamical calculations are done for the sake of the analysis and interpretation of the observations. The comparison of the phonon spectra from magnetic and nonmagnetic calculations highlights pronounced differences. The energy range of the vibrational atomistic contributions of the Fe and O ions are found to differ significantly in the two calculation types. Therefore, magnetism induced by the active spin degrees of freedom of Fe cations plays a key role in stabilizing the structure and dynamics of GaFeO3. Moreover, the computed enthalpy in various phases of GaFeO3 is used to gain deeper insights into the high-pressure phase stability of this material. Further, the volume dependence of the phonon spectra is used to determine its thermal expansion behavior.

  10. An experimental study of two-phase critical flow with non-condensable gas in a small-diameter pipe at high pressure and normal temperature

    International Nuclear Information System (INIS)

    An experimental study is performed on two-phase critical flow with non-condensable gas in a small diameter pipe at high pressure and normal temperature. T2GDM, which is a test section for measuring void fraction inside, is used on KAREI non-condensable gas two-phase critical flow test facility which has the existing test section T2. The gamma densitometer for void fraction measurement is composed of a sealed gamma ray source, a shielding equipment, a radiation detector, a signal processing unit and a traversing system. The measurement results show that a lot of void is generated while passing through the test section. Experimental data of critical flow rates are generated using two test section of T2 and T2GDM. The results show that the critical flow rates decrease rapidly with the increase of the volumetric gas fraction. The experiments are simulated with the MARS2.1 code. The simulation results show that the modified Henry-Fauske model in the MARS2.1 code predicts well the measured critical flow rates when the non-condensable gas is not injected, while it over-predicts the flow rates when the non-condensable gas is injected

  11. High-pressure phase behaviors of ZnTiO3: ilmenite-perovskite transition, decomposition of perovskite into constituent oxides, and perovskite-lithium niobate transition

    Science.gov (United States)

    Akaogi, M.; Abe, K.; Yusa, H.; Kojitani, H.; Mori, D.; Inaguma, Y.

    2015-06-01

    High-pressure high-temperature phase transitions of ZnTiO3 ilmenite were examined using multianvil apparatus up to 25.5 GPa and 1,500 °C and diamond anvil cell to 26.5 GPa and about 2,000 °C. Combined results of the multianvil quench experiments and in situ diamond anvil cell experiments indicated that at about 10 GPa and 1,200 °C ZnTiO3 ilmenite transforms to orthorhombic perovskite which is converted to lithium niobate phase on release of pressure. The boundary of the ilmenite-provskite transition is expressed by P(GPa) = 15.9 - 0.005 T (°C). The high-pressure experiments also indicated that at 20-24 GPa and 1,000-1,400 °C ZnTiO3 orthorhombic perovskite dissociates into rocksalt-type ZnO + baddeleyite-type TiO2 which are recovered, respectively, as wurtzite-type ZnO and α-PbO2-type TiO2 at 1 atm. The boundary of the perovskite dissociation is expressed by P(GPa) = 8.7 + 0.011 T (°C). Molar volume changes of ZnTiO3 at ambient conditions were estimated as -4.7 % for the ilmenite-perovskite transition and -3.5 % for the perovskite decomposition into the oxides. The absence of CaIrO3-type postperovskite in ZnTiO3 is consistent with that dissociation of ZnTiO3 perovskite into the oxides has the larger molar volume change than -1 to -2 % of the perovskite-postperovskite transition in various ABO3 compounds and with previous data that ABO3 perovskites with relatively ionic B-O bonds do not transform to the postperovskite. The transition behaviors of ZnTiO3 are similar to those of MnTiO3 and FeTiO3, but ZnTiO3 perovskite dissociates into the constituent oxides.

  12. Infrared Spectra of High Pressure Carbon Monoxide

    Energy Technology Data Exchange (ETDEWEB)

    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.

  13. High-pressure high-temperature phase relations in FeTiO3 up to 35 GPa and 1600 °C

    Science.gov (United States)

    Akaogi, M.; Abe, K.; Yusa, H.; Ishii, T.; Tajima, T.; Kojitani, H.; Mori, D.; Inaguma, Y.

    2016-08-01

    Phase relations in FeTiO3 were precisely determined at 25-35 GPa and 600-1600 °C using multianvil high-pressure experiments with tungsten carbide anvils. Pressure generation up to about 36 GPa at 1600 °C was evaluated using Al2O3 solubility in MgSiO3 perovskite (Pv) in the system MgSiO3-Al2O3. At about 28 GPa, FeTiO3 Pv dissociates into an assemblage of calcium titanate (CT)-type Fe2TiO4 + orthorhombic-I (OI)-type TiO2 below 1200 °C. However, above 1200 °C at 28 GPa, FeTiO3 Pv decomposes into a new, denser phase assemblage of CT-type Fe2TiO4 + a new compound of FeTi2O5. The new phase FeTi2O5 was recovered as an amorphous phase at 1 atm. In situ X-ray diffraction experiments at 35.1 GPa indicated that the new phase (N-p) FeTi2O5 has orthorhombic symmetry with cell parameters a = 8.567(2) Å, b = 5.753(1) Å and c = 5.257(1) Å. In addition, the assemblage of CT-type Fe2TiO4 + OI-type TiO2 changes to FeO wüstite (Wu) + OI-type TiO2 at about 33 GPa below 1000 °C. The phase assemblages in FeTiO3 are denser in the order: FeTiO3 (Pv) → 1/2Fe2TiO4 (CT) + 1/2TiO2 (OI) → 1/3Fe2TiO4 (CT) + 1/3FeTi2O5 (N-p) → FeO (Wu) + TiO2 (OI). Our results indicate that the upper stability limit of FeTiO3 Pv is about 28 GPa at 600-1600 °C. This puts a constraint on peak shock pressure for formation of naturally discovered lithium niobate-type FeTiO3 which was interpreted to be retrograde transition product of FeTiO3 Pv on release of shock pressure.

  14. High pressure furnace

    Science.gov (United States)

    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.

  15. High pressure oxygen furnace

    Science.gov (United States)

    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.

  16. Deuterium High Pressure Target

    CERN Document Server

    Perevozchikov, V; Vinogradov, Yu I; Vikharev, M D; Ganchuk, N S; Golubkov, A N; Grishenchkin, S K; Demin, A M; Demin, D L; Zinov, V G; Kononenko, A A; Lobanov, V N; Malkov, I L; Yukhimchuk, S A

    2001-01-01

    The design of the deuterium high-pressure target is presented. The target having volume of 76 cm^3 serves to provide the experimental research of muon catalyzed fusion reactions in ultra-pure deuterium in the temperature range 80-800 K under pressures of up to 150 MPa. The operation of the main systems of the target is described: generation and purification of deuterium gas, refrigeration, heating, evacuation, automated control system and data collection system.

  17. Deuterium high pressure target

    International Nuclear Information System (INIS)

    The design of the deuterium high-pressure target is presented. The target having volume of 76 cm3 serves to provide the experimental research of muon catalyzed fusion reactions in ultra-pure deuterium in the temperature range 80-800 K under pressures of up to 150 MPa. The operation of the main systems of the target is described: generation and purification of deuterium gas, refrigeration, heating, evacuation, automated control system and data collection system

  18. Determination of six microcystins and nodularin in surface and drinking waters by on-line solid phase extraction-ultra high pressure liquid chromatography tandem mass spectrometry.

    Science.gov (United States)

    Beltrán, Eduardo; Ibáñez, María; Sancho, Juan Vicente; Hernández, Félix

    2012-11-30

    Microcystins and nodularin are cyclic peptides hepatotoxins produced by cyanobacterial genera (blue-green algae). Toxic cyanobacterial blooms are a worldwide problem, as reported in several countries, like China, Australia, or the United States. Therefore, it is necessary to develop sensitive and reliable analytical methodology to determine this type of toxins in water at parts per billion levels, or even lower. In this work, the potential of solid-phase extraction coupled on-line to ultra-high-pressure liquid chromatography/electrospray tandem mass spectrometry (SPE-UHPLC-MS/MS) has been investigated for the efficient quantification and confirmation of microcystins LR, RR, YR, LY, LW, LF and nodularin in surface and drinking water samples, at sub-ppb levels. The method developed involves the injection of only 1 mL of water sample into the on-line SPE-UHPLC-MS/MS system and allows the rapid determination of the compounds selected (8 min of chromatographic run), avoiding laborious sample treatment. The method was validated in surface and drinking water by means of recovery experiments at 0.25 and 1 μg L(-1). Average recoveries (n=5) ranged from 71 to 116%, with relative standard deviations (RSDs) lower than 15%. For microcystins LR, RR, YR and nodularin, a third level was also assayed (0.1 μg L(-1)) obtaining satisfactory data too. Limits of detection between 0.002 and 0.0405 μg L(-1) were estimated (0.0005 μg L(-1) for nodularin). The developed method was applied to the analysis of water samples collected in the province of Castellón (Spain). The acquisition of three MS/MS transitions for each compound allowed the unequivocal confirmation of positive samples, which was supported by the accomplishment of ion intensity ratios and retention time when compared with reference standards. PMID:23107121

  19. Phase transitions and photoinduced transformations at high pressure in the molecular donor-acceptor fullerene complex {Cd(dedtc)2}2 · C60

    Science.gov (United States)

    Meletov, K. P.; Konarev, D. V.; Tolstikova, A. O.

    2015-06-01

    The Raman spectra of crystals of C60 fullerene-cadmium diethyldithiocarbamate molecular donor-acceptor complexes {Cd(dedtc)2}2 · C60 were measured at pressures of up to 17 GPa, and the crystal lattice parameters of these complexes were determined at pressures of up to 6 GPa. An increase in pressure up to ˜2 GPa leads to changes in the Raman spectra, which are manifested by splitting of the intramolecular H g (1)- H g (8) phonon modes and by softening of the A g (2) mode of the C60 molecule. A further increase in pressure up to 17 GPa does not induce significant new changes to the Raman spectra, while a decrease is accompanied by the reverse transformation at a pressure of about 2 GPa. The pressure dependence of the lattice parameters also exhibits a reversible feature at 2 GPa related to a jumplike decrease in compressibility. All these data are indicative of a phase transition in the vicinity of 2 GPa related to the formation of covalent bonds between C60 molecules and, probably, the appearance of C120 dimers in fullerene layers. It was also found that, in the pressure interval from 2 to 6.3 GPa, the Raman spectra of complexes exhibit photoinduced transformations under prolonged exposure to laser radiation with a wavelength of λ = 532 nm and power density up to 5000 W/cm2. These changes are manifested by splitting and softening of the A g (2) mode and resemble analogous changes accompanying the photopolymerization of C60 fullerene. The intensity of new bands exhibits exponential growth with increasing exposure time. The photopolymer yield depends on both the laser radiation power and external pressure. The A g (2) mode splitting under irradiation can be related to the formation of photo-oligomers with various numbers of intermolecular covalent bonds per C60 molecule.

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

    Science.gov (United States)

    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

  1. Phase transitions and photoinduced transformations at high pressure in the molecular donor-acceptor fullerene complex (Cd(dedtc){sub 2}){sub 2} · C{sub 60}

    Energy Technology Data Exchange (ETDEWEB)

    Meletov, K. P., E-mail: mele@issp.ac.ru [Russian Academy of Sciences, Institute of Solid State Physics (Russian Federation); Konarev, D. V. [Russian Academy of Sciences, Institute of Problems of Chemical Physics (Russian Federation); Tolstikova, A. O. [Russian Academy of Sciences, Institute of Solid State Physics (Russian Federation)

    2015-06-15

    The Raman spectra of crystals of C{sub 60} fullerene-cadmium diethyldithiocarbamate molecular donor-acceptor complexes (Cd(dedtc){sub 2}){sub 2} · C{sub 60} were measured at pressures of up to 17 GPa, and the crystal lattice parameters of these complexes were determined at pressures of up to 6 GPa. An increase in pressure up to ∼2 GPa leads to changes in the Raman spectra, which are manifested by splitting of the intramolecular H{sub g}(1)-H{sub g}(8) phonon modes and by softening of the A{sub g}(2) mode of the C{sub 60} molecule. A further increase in pressure up to 17 GPa does not induce significant new changes to the Raman spectra, while a decrease is accompanied by the reverse transformation at a pressure of about 2 GPa. The pressure dependence of the lattice parameters also exhibits a reversible feature at 2 GPa related to a jumplike decrease in compressibility. All these data are indicative of a phase transition in the vicinity of 2 GPa related to the formation of covalent bonds between C{sub 60} molecules and, probably, the appearance of C{sub 120} dimers in fullerene layers. It was also found that, in the pressure interval from 2 to 6.3 GPa, the Raman spectra of complexes exhibit photoinduced transformations under prolonged exposure to laser radiation with a wavelength of λ = 532 nm and power density up to 5000 W/cm{sup 2}. These changes are manifested by splitting and softening of the A{sub g}(2) mode and resemble analogous changes accompanying the photopolymerization of C{sub 60} fullerene. The intensity of new bands exhibits exponential growth with increasing exposure time. The photopolymer yield depends on both the laser radiation power and external pressure. The A{sub g}(2) mode splitting under irradiation can be related to the formation of photo-oligomers with various numbers of intermolecular covalent bonds per C{sub 60} molecule.

  2. Intermolecular Interactions at high pressure

    DEFF Research Database (Denmark)

    Eikeland, Espen Zink

    2016-01-01

    . High-pressure crystallography is the perfect method for studying intermolecular interactions, by forcing the molecules closer together. In all three studied hydroquinone clathrates, new pressure induced phase transitions have been discovered using a mixture of pentane and isopentane as the pressure...... transformation is therefore most likely kinetically hindered when surrounded by solidified silicone oil. The calculated intermolecular energies in all three hydroquinone clathrates show the anticipated strong interactions in the host framework and the weaker host-guest interactions. As the pressure is raised...... illustrates how important it is to quantify all intermolecular interactions in structures. This enables researchers to see a more complete picture and not focus only on a few interactions deemed particularly important....

  3. Theory of high pressure hydrogen, made simple

    CERN Document Server

    Magdau, Ioan B; Ackland, Graeme J

    2015-01-01

    Phase I of hydrogen has several peculiarities. Despite having a close-packed crystal structure, it is less dense than either the low temperature Phase II or the liquid phase. At high pressure, it transforms into either phase III or IV, depending on the temperature. Moreover, spectroscopy suggests that the quantum rotor behaviour disappears with pressurisation, without any apparent phase transition. Here we present a simple thermodynamic model for this behaviour based on packing atoms and molecules and discuss the thermodynamics of the phase boundaries. We also report first principles molecular dynamics calculations for a more detailed look at the same phase transitions.

  4. Combined Theoretical and in Situ Scattering Strategies for Optimized Discovery and Recovery of High-Pressure Phases: A Case Study of the GaN–Nb 2 O 5 System

    Energy Technology Data Exchange (ETDEWEB)

    Woerner, William R.; Qian, Guang-Rui; Oganov, Artem R.; Stephens, Peter W.; Dharmagunawardhane, H. A. Naveen; Sinclair, Alexandra; Parise, John B.

    2016-04-04

    The application of pressure in solid-state synthesis provides a route for the creation of new and exciting materials. However, the onerous nature of high-pressure techniques limits their utility in materials discovery. The systematic search for novel oxynitrides—semiconductors for photocatalytic overall water splitting—is a representative case where quench high-pressure synthesis is useful and necessary in order to obtain target compounds. We utilize state of the art crystal structure prediction theory (USPEX) and in situ synchrotron-based X-ray scattering to speed up the discovery and optimization of novel compounds using high-pressure synthesis. Using this approach, two novel oxynitride phases were discovered in the GaN–Nb2O5 system. The (Nb2O5)0.84:(NbO2)0.32:(GaN)0.82 rutile structured phase was formed at 1 GPa and 900 °C and gradually transformed to a α-PbO2-related structure above 2.8 GPa and 1000 °C. The low-pressure rutile type phase was found to have a direct optical band gap of 0.84 eV and an indirect gap of 0.51 eV.

  5. Coexistence of weak ferromagnetism and ferroelectricity in the high pressure LiNbO{sub 3}-type phase of FeTiO{sub 3}.

    Energy Technology Data Exchange (ETDEWEB)

    Varga, T.; Kumar, A.; Vlahos, E.; Denev, S.; Park, M.; Hong, S.; Sanehira, T.; Wang, Y.; Fennie, C. J.; Streiffer, S. K.; Ke, X.; Schiffer, P.; Gopalan, V.; Mitchell, J. F.; Pennsylvania State Univ.; Univ. of Chicago; Cornell Univ.

    2009-01-01

    We report the magnetic and electrical characteristics of polycrystalline FeTiO{sub 3} synthesized at high pressure that is isostructural with acentric LiNbO{sub 3} (LBO). Piezoresponse force microscopy, optical second harmonic generation, and magnetometry demonstrate ferroelectricity at and below room temperature and weak ferromagnetism below {approx} 120 K. These results validate symmetry-based criteria and first-principles calculations of the coexistence of ferroelectricity and weak ferromagnetism in a series of transition metal titanates crystallizing in the LBO structure.

  6. Structural relaxation accompanied by photo-induced chromatic phase transition of polydiacetylenes with butylene-N-difluorophenyl carbamate side chains

    Energy Technology Data Exchange (ETDEWEB)

    Maekawa, Yuuki; Sakamoto, Naoya; Kokado, Ryousuke; Kajimoto, Naoshi; Izumi, Yuuichiro [Department of Materials Science and Chemistry, Wakayama University, 930 Sakaedani, Wakayama (Japan); Itoh, Chihiro, E-mail: citoh@sys.wakayama-u.ac.jp [Department of Materials Science and Chemistry, Wakayama University, 930 Sakaedani, Wakayama (Japan)

    2013-01-15

    We have studied the phase transition of poly-5,7-dodecadiyne-1,12-diol bis[2,4-difluorophenyl carbamate] (PDA-2,4-DFPC) and poly-5,7-dodecadiyne-1,12-diol bis[3,4-difluorophenyl carbamate] (PDA-3,4-DFPC) by visible reflection spectroscopy and mid-infrared absorption spectroscopy. Both PDA-2,4-DFPC and PDA-3,4-DFPC show the reflection spectra characterized by a sharp peak at around 1.9 eV at room temperature. While PDA-3,4-DFPC shows thermochromic phase transition to the phase showing the reflection spectrum with a peak around 2.2 eV above 120 Degree-Sign C, PDA-2,4-DFPC shows no abrupt change of the reflection spectrum. However, PDA-2,4-DFPC shows drastic change of the reflection spectrum under 532-nm CW-laser excitation. Based on these results, we can draw the following two conclusions. First, the phase transition behavior of PDA can be controlled by modifying the side-chain structure. Second, we demonstrate that thermally inaccessible phase of PDA is induced by the photo-excitation. By measuring mid-infrared absorption of PDAs, we elucidated that conformational change of side chains is accompanied with the phase transition. Based on the results, we discussed the role of the side chain in the phase transition. - Highlights: Black-Right-Pointing-Pointer We have synthesized polydiacetylene (PDA) with difluorophenyl carbamate side chain. Black-Right-Pointing-Pointer PDAs show distinct phase transition (PT) depending on the side-chain structure. Black-Right-Pointing-Pointer PDA with 3,4-difluorophenyl carbamate shows PT by thermal stimulation. Black-Right-Pointing-Pointer However, PDA with 2,4-difluorophenyl carbamate shows PT only under photo-excitation.

  7. High pressure engineering and technology

    International Nuclear Information System (INIS)

    This book contains 10 papers. Some of the titles are: Control of vibration in high pressure piping systems; Hazards and safeguards of high pressure hydraulic fatigue testing; Load, stress and fatigue analysis of threaded end closures; Application of fatigue crack growth to an isostatic press; and Time dependent failure in high strength steels for autoclave service

  8. Observation of a re-entrant phase transition in the molecular complex tris(μ2-3,5-diisopropyl-1,2,4-triazolato-κ2N1:N2trigold(I under high pressure

    Directory of Open Access Journals (Sweden)

    Christopher H. Woodall

    2016-09-01

    Full Text Available We report a molecular crystal that exhibits four successive phase transitions under hydrostatic pressure, driven by aurophilic interactions, with the ground-state structure re-emerging at high pressure. The effect of pressure on two polytypes of tris(μ2-3,5-diisopropyl-1,2,4-triazolato-κ2N1:N2trigold(I (denoted Form-I and Form-II has been analysed using luminescence spectroscopy, single-crystal X-ray diffraction and first-principles computation. A unique phase behaviour was observed in Form-I, with a complex sequence of phase transitions between 1 and 3.5 GPa. The ambient C2/c mother cell transforms to a P21/n phase above 1 GPa, followed by a P21/a phase above 2 GPa and a large-volume C2/c supercell at 2.70 GPa, with the previously observed P21/n phase then reappearing at higher pressure. The observation of crystallographically identical low- and high-pressure P21/n phases makes this a rare example of a re-entrant phase transformation. The phase behaviour has been characterized using detailed crystallographic theory and modelling, and rationalized in terms of molecular structural distortions. The dramatic changes in conformation are correlated with shifts of the luminescence maxima, from a band maximum at 14040 cm−1 at 2.40 GPa, decreasing steeply to 13550 cm−1 at 3 GPa. A similar study of Form-II displays more conventional crystallographic behaviour, indicating that the complex behaviour observed in Form-I is likely to be a direct consequence of the differences in crystal packing between the two polytypes.

  9. Psychosocial Accompaniment

    OpenAIRE

    Mary Watkins

    2015-01-01

    This essay advocates for a paradigm shift in psychology toward the activity and ethics of accompaniment. Accompaniment requires a reorientation of the subjectivity, interpersonal practices, and critical understanding of the accompanier so that (s)he can stand alongside others who desire listening, witnessing, advocacy, space to develop critical inquiry and research, and joint imagination and action to address desired and needed changes. The idea of “accompaniment” emerged in liberation theolo...

  10. High pressure diffraction at ISIS

    International Nuclear Information System (INIS)

    The development of the high pressure diffraction programme at ISIS is reviewed. Along with general accounts of the technique and the pressure cells used, examples of science carried out in this field are given. (author)

  11. A numerical study of the gas-liquid, two-phase flow maldistribution in the anode of a high pressure PEM water electrolysis cell

    DEFF Research Database (Denmark)

    Olesen, Anders Christian; Rømer, Carsten; Kær, Søren Knudsen

    2016-01-01

    -phase flow model for establishing the effect of geometry and a two-phase flow model for studying the effect of dispersed gas bubbles. Both models account for turbulence and heat transport. By means of the developed models, it is elucidated that the circular-planar shape of the interdigitated flow field...... causes maldistribution, if land areas of equal width are applied. Moreover, below a water stoichiometry of 350, and at a current density of 1 A/cm2, flow and temperature maldistribution is adversely affected by the presence of the gas phase; particularly gas hold-up near outlet channels can cause...

  12. Advanced Diagnostics for High Pressure Spray Combustion.

    Energy Technology Data Exchange (ETDEWEB)

    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.

  13. 晶体化学新领域——高压相变晶体化学%New Special Field of Crystal Chemistry: High-Pressure Phase Transition Crystal Chemistry

    Institute of Scientific and Technical Information of China (English)

    施倪承; 李国武; 马喆生; 熊明

    2011-01-01

    用X射线衍射的方法衡量原子及离子的尺寸并测定其晶体结构是人类进入微观世界最为关键的一步.在通常的温度和压力下各种原子及离子的结合方式及排布规则已在晶体化学中得到详尽的阐述.笔者着重探讨了在高压下离子化合物及矿物的晶体化学特点.在高压下随着压力的增加,氧化物及硅酸盐中阳离子会发生从低配位数多面体向高配位数的多面体的迁移.这种迁移是由于阴阳离子半径比值改变所致.计算了不同的SiO2多形中氧和硅的离子半径,表明氧离子半径随压力增加而不断缩小,硅离子半径却随着压力的增加及相变的发生而逐渐增大,这种现象可能是由于离子化合物向金属相转变的结果.%The method which use X ray diffraction to measure the size of atom and ion and determine crystal structure is most important step for mankind get into microscopic view world. At usual temperature and pressure, the connection pattern and the arrangement rule of various atom and ion have already elaborated in the crystal chemistry in detail. In this paper, the study on the crystal chemistry characteristics of ionic compounds and minerals was emphasized under high pressure. Under high pressure when the pressure increases, the cations of silicon in oxide or silicate minerals occurred migration from low coordination number polyhedra to high coordination number polyhedra. This migration is due to the change with radius ratio of cations to anions. Under high pressure the ionic radii of oxygen and silicon have been calculated for different SiO2 polymorphs. It is indicated that the ionic radius of oxygen is decreasing gradually with the increase of pressure, but the cation radius of silicon is increasing with the increase of pressure and the occurrence of phase transitions. This kind of phenomenon may be due to the transition from ionic compounds to metallic phases under high pressure.

  14. Microscopic Experimental Approaches to High Pressure Chemistry

    OpenAIRE

    Russell, T.; ALLEN, T.; Rice, J.; Gupta, Y.

    1995-01-01

    The experimental study of the chemistry related to the deflagration/detonation of energetic materials is extremely challenging due to the high pressure, high temperature, and time domain under which the chemical reactions occur. In addition, non equilibrium pressure and temperature conditions temporally effect the reaction pathways and rates during the reaction process. The multiple phases of material present (i.e. the heterogeneous nature of the problem), the multiple reaction pathways (both...

  15. High Pressure Multicomponent Adsorption in Porous Media

    DEFF Research Database (Denmark)

    Shapiro, Alexander; Stenby, Erling Halfdan

    1999-01-01

    We analyse adsorption of a multicomponent mixture at high pressure on the basis of the potential theory of adsorption. The adsorbate is considered as a segregated mixture in the external field produced by a solid adsorbent. we derive an analytical equation for the thickness of a multicomponent film...... close to a dew point. This equation (asymptotic adsorption equation, AAE) is a first order approximation with regard to the distance from a phase envelope....

  16. Ergot alkaloids in rye flour determined by solid-phase cation-exchange and high-pressure liquid chromatography with fluorescence detection

    DEFF Research Database (Denmark)

    Storm, Ida Marie Lindhardt Drejer; Rasmussen, Peter Have; Strobel, B.W.;

    2008-01-01

    Ergot alkaloids are mycotoxins that are undesirable contaminants of cereal products, particularly rye. A method was developed employing clean-up by cation-exchange solid-phase extraction, separation by high-performance liquid chromatography under alkaline conditions and fluorescence detection...

  17. Modification of Sako-Wu-Prausnitz equation of state for fluid phase equilibria in polyethylene-ethylene systems at high pressures

    Directory of Open Access Journals (Sweden)

    F. Gharagheizi

    2006-09-01

    Full Text Available In order to model phase equilibria at all pressures, it is necessary to have an equation of state. We have chosen the Sako-Wu-Prausnitz cubic equation of state, which had shown some promising results. However, in order to satisfy our demands, we had to modify it slightly and fit new pure component parameters. New pure component parameters have been determined for ethylene and the n-alkane series, using vapor pressure data, saturated liquid volume and one-phase PVT-data. For higher n-alkanes, where vapor pressure data are poor or not available, determination of the pure component parameters was made in part by extrapolation and in part by fitting to one-phase PVT-data. Using one-fluid van der Waals mixing rules, with one adjustable interaction parameter, good correlation of binary hydrocarbon system was obtained, except for the critical region. The extension of the equation of state to polyethylene systems is covered in this work. Using the determined parameters, flash and cloud point calculations were performed, and treating the polymer as polydisperse. The results fit data well.

  18. B1 B2 structural phase transition and elastic properties of UX (X = S, Se, and Te) compounds at high pressure

    Science.gov (United States)

    Varshney, Dinesh; Kaurav, N.; Kinge, R.; Singh, R. K.

    2007-06-01

    Pressure induced structural phase transformation and mechanical properties of NaCl-type (B1) to CsCl-type (B2) structure in uranium monochalcogenides (UX; X = S, Se, and Te) are presented. An effective interionic interaction potential is constructed, consisting of the long-range Coulomb and the Hafemeister and Flygare type short-range overlap repulsion extended up to the second-neighbour ions and the van der Waals (vdW) interaction. Particular attention is devoted to evaluate the vdW coefficients following the Slater-Kirkwood variational method, as both the ions are polarizable. Our calculated results have revealed reasonably good agreement with the available experimental data on the phase transition pressures (Pt = 81, 21, 13 GPa) and the elastic properties of UX (X = S, Se, and Te). The equation of state curves (plotted between V (P)/V (0) and pressure) for both the NaCl-type (B1) and CsCl-type (B2) structures obtained by us are in fairly good agreement with the experimental results. The calculated values of the volume collapses (ΔV (P)/V (0)) are also closer to their observed data. The variations of the second- and third-order elastic constants with pressure have followed systematic trends, which are almost identical to those exhibited by the measured and observed data in other compounds of the NaCl-type structure family.

  19. High-pressure structural study of phase-A, Mg sub 7 Si sub 2 H sub 6 O sub 1 sub 4 using synchrotron radiation

    CERN Document Server

    Kudoh, Y; Kagi, H; Sasaki, S; Tanaka, M

    2002-01-01

    The specimen used in this study was a single crystal of phase-A Mg sub 6 sub . sub 9 sub 9 Si sub 1 sub . sub 9 sub 9 H sub 6 sub . sub 0 sub 6 O sub 1 sub 4 synthesized using a multi-anvil apparatus at conditions of 1000 deg. C and 10 GPa. Sets of x-ray diffraction intensities were measured with a single crystal of 60 x 50 x 30 mu m using synchrotron radiation up to 9.4 GPa. The unit-cell parameters observed gave K sub 0 = 105 GPa (assuming that K' = 4). With increasing pressure, significant decreases of O-O distances for hydrogen bonds were observed.

  20. High pressure neon arc lamp

    Science.gov (United States)

    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.

  1. LLL dynamic high pressure experiments

    Energy Technology Data Exchange (ETDEWEB)

    Nellis, W.J.

    1979-01-01

    The Lawrence Livermore Laboratory has several experimental facilities to measure material properties at dynamic high pressures. These include an isobaric expansion experiment, a two-stage light-gas gun, and a high-power laser facility (Janus). Each of these are briefly described.

  2. Magnetic and Superconducting Materials at High Pressures

    Energy Technology Data Exchange (ETDEWEB)

    Struzhkin, Viktor V. [Carnegie Inst. of Washington, Washington, DC (United States)

    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

  3. High pressure studies of potassium perchlorate

    Science.gov (United States)

    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.

  4. Measurement of high-pressure steam jet from crack area at practical FBR

    International Nuclear Information System (INIS)

    One of the design basis accidents in sodium-cooled fast reactor is sodium-water reaction at steam generator (SG). In case of a defect occurred on a heat transfer tube, the high-pressure water/vapor will spout into the low-pressure sodium surrounding outside the tube. As sodium is ordinarily quite reactive with water, this will initiate sodium-water reactions accompanied by high chemical heat generation. The liquid droplet in the reaction steam outflow would impinge on neighboring tubes to cause erosion, while the chemical reaction will cause corrosion, eventually may lead to secondary tube failure. Focusing on the erosion part, this study is to evaluate the liquid droplet impingement erosion (LDIE) rate on neighboring tubes caused by SG heat transfer tube rupture. In this paper, as a basic study, the pressure and temperature distribution of high-pressure two-phase free jet into the air is measured. (author)

  5. High Pressure - High Temperature Polymorphism in Ta: Resolving an Ongoing Experimental Controversy

    Energy Technology Data Exchange (ETDEWEB)

    Burkovsky, L; Chen, S P; Preston, D L; Belonoshko, A B; Rosengren, A; Mikhaylushkin, A S; Simak, S I; Moriarty, J A

    2010-04-07

    Phase diagrams of refractory metals remain essentially unknown. Moreover, there is an ongoing controversy over the high pressure (P) melting temperatures of these metals: results of diamond anvil cell (DAC) and shock wave experiments differ by at least a factor of two. From an extensive ab initio study on tantalum we discovered that the body-centered cubic phase, its physical phase at ambient conditions, transforms to another solid phase, possibly hexagonal omega phase, at high temperature (T). Hence the sample motion observed in DAC experiments is not due to melting but internal stresses accompanying a solid-solid transformation, as explained in more detail in our work. In view of our results on tantalum and previous work on molybdenum, as well as other published data, it is highly plausible that high-PT polymorphism is a general feature of Groups V and VI refractory metals.

  6. High pressure rinsing parameters measurements

    Energy Technology Data Exchange (ETDEWEB)

    Cavaliere, E. [INFN Milano - LASA, Via F.lli Cervi 201, I-20090 Segrate (MI) (Italy); Fusetti, M. [INFN Milano - LASA, Via F.lli Cervi 201, I-20090 Segrate (MI) (Italy); Michelato, P. [INFN Milano - LASA, Via F.lli Cervi 201, I-20090 Segrate (MI) (Italy); Pagani, C. [INFN Milano - LASA, Via F.lli Cervi 201, I-20090 Segrate (MI) (Italy)]. E-mail: carlo.pagani@mi.infn.it; Pierini, P. [INFN Milano - LASA, Via F.lli Cervi 201, I-20090 Segrate (MI) (Italy); Paulon, R. [INFN Milano - LASA, Via F.lli Cervi 201, I-20090 Segrate (MI) (Italy); Sertore, D. [INFN Milano - LASA, Via F.lli Cervi 201, I-20090 Segrate (MI) (Italy)

    2006-07-15

    High pressure rinsing with ultra pure water jet is an essential step in the high field superconducting cavity production process. In this paper, we illustrate the experimental characterization of a HPR system, in terms of specific power and energy deposition on the cavity surfaces and on the damage threshold for niobium. These measurements are used to tentatively derive general rules for the optimization of the free process parameters (nozzle geometry, speeds and water pressure)

  7. Neutron scattering at high pressure

    OpenAIRE

    Mcwhan, D.B.

    1984-01-01

    The techniques to do elastic and inelastic neutron scattering at steady-state and pulsed sources are reviewed. The pressure cells available at most neutron scattering centres are capable of reaching pressures of the order of 5 GPa (50 kbar), and attempts to reach 10 GPa have been made. For elastic scattering, a comparison is made between neutron scattering and X-ray scattering at high pressure using rotating anode or synchrotron sources.

  8. High pressure rinsing system comparison

    Energy Technology Data Exchange (ETDEWEB)

    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

  9. High pressure gas vessels for neutron scattering experiments

    CERN Document Server

    Done, R; Evans, B E; Bowden, Z A

    2010-01-01

    The combination of high pressure techniques with neutron scattering proves to be a powerful tool for studying the phase transitions and physical properties of solids in terms of inter-atomic distances. In our report we are going to review a high pressure technique based on a gas medium compression. This technique covers the pressure range up to ~0.7GPa (in special cases 1.4GPa) and typically uses compressed helium gas as the pressure medium. We are going to look briefly at scientific areas where high pressure gas vessels are intensively used in neutron scattering experiments. After that we are going to describe the current situation in high pressure gas technology; specifically looking at materials of construction, designs of seals and pressure vessels and the equipment used for generating high pressure gas.

  10. High Pressure Hydrogen from First Principles

    Science.gov (United States)

    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.

  11. High pressure gas metering project

    International Nuclear Information System (INIS)

    The initial research and development of a system that uses high pressure helium gas to pressurize vessels over a wide range of pressurization rates, vessel volumes, and maximum test pressures are described. A method of controlling the mass flow rate in a test vessel was developed by using the pressure difference across a capillary tube. The mass flow rate is related to the pressurization rate through a real gas equation of state. The resulting mass flow equation is then used in a control algorithm. Plots of two typical pressurization tests run on a manually operated system are included

  12. High-pressure investigations of lanthanoid oxoarsenates. I. Single crystals of scheelite-type Ln[AsO{sub 4}] phases with Ln = La-Nd from monazite-type precursors

    Energy Technology Data Exchange (ETDEWEB)

    Metzger, Sebastian J.; Ledderboge, Florian; Schleid, Thomas [Stuttgart Univ. (Germany). Inst. fuer Anorganische Chemie; Heymann, Gunter; Huppertz, Hubert [Innsbruck Univ. (Austria). Inst. fuer Allgemeine, Anorganische und Theoretische Chemie

    2016-08-01

    Transparent single crystals of the scheelite-type Ln[AsO{sub 4}] phases with Ln = La-Nd are obtained by the pressure-induced monazite-to-scheelite type phase transition in a Walker-type module under high-pressure and high-temperature conditions of 11 GPa at 1100-1300 C. Coinciding with this transition, there is an increase in density and a reduction in molar volume of about 4.5 % for the scheelite-type phases (tetragonal, I4{sub 1}/a) for La[AsO{sub 4}] (a = 516.92(4), c = 1186.1(9) pm), Ce[AsO{sub 4}] (a = 514.60(1), c = 1175.44(2) pm), Pr[AsO{sub 4}] (a = 512.63(4), c = 1168.25(9) pm), and Nd[AsO{sub 4}] (a = 510.46(4), c = 1160.32(11) pm) as compared to the well-known monazite-type phases (monoclinic, P2{sub 1}/n). Surprisingly enough, the scheelite-type oxoarsenates(V) exhibit a lower coordination number for the Ln{sup 3+} cations (CN = 8 versus CN = 8 + 1), whereas the isolated tetrahedral [AsO{sub 4}]{sup 3-} anions (d(As-O) = 168.9-169.3 pm for the scheelites as compared to d(As-O) = 167.1-169.9 pm for the monazites) remain almost unchanged. So the densification must occur because of the loss of two edge-connections of the involved [LnO{sub 8+1}]{sup 15-} polyhedra with the [AsO{sub 4}]{sup 3-} tetrahedra in the monazite- resulting in exclusively vertex connected [LnO{sub 8}]{sup 13-} and [AsO{sub 4}]{sup 3-} units in the scheelite-type structure.

  13. Materials response under static and dynamic high pressures

    International Nuclear Information System (INIS)

    Studies on equation of state and phase transitions at high pressures have significantly contributed to our basic understanding of condensed matter physics. High-pressure data on materials also find important applications in applied sciences. The developments in first principle theories and experimental techniques are listed. The similarities and differences in behaviour of materials under static and dynamic pressures are discussed. The article also describes the current interplay between theoretical and experimental high-pressure research with illustrations from our own studies and emphasis on future scope. (author). 135 refs., 10 figs., 2 tabs

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

    Energy Technology Data Exchange (ETDEWEB)

    Ovsyannikov, Sergey V., E-mail: sergey.ovsyannikov@uni-bayreuth.de, E-mail: sergey2503@gmail.com; Wenz, Michelle D.; Pakhomova, Anna S.; Dubrovinsky, Leonid [Bayerisches Geoinstitut, Universität Bayreuth, Universitätsstrasse 30, Bayreuth D-95447 (Germany); Bykova, Elena; Bykov, Maxim [Bayerisches Geoinstitut, Universität Bayreuth, Universitätsstrasse 30, Bayreuth D-95447 (Germany); Laboratory of Crystallography, Universität Bayreuth, Universitätsstrasse 30, D-95447 Bayreuth (Germany); Glazyrin, Konstantin; Liermann, Hanns-Peter [Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, D-22603 Hamburg (Germany)

    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.

  15. Research status and development trend of pulverized coal transportation by dense phase conveying system under high pressure%煤粉加压密相输送系统研究现状及发展方向

    Institute of Scientific and Technical Information of China (English)

    李君; 卢洪; 郭屹; 李轩

    2015-01-01

    In order to optimize the dense phase conveying system in dry coal gasification process, the dense phase pneumatic conveying technology under high pressure and solid conveying pump based on the theory of solid mechanics of granular media were introduced. The characteristics and critical process of the two methods were summarized.The development trend of solid conveying pump under high pressure was introduced.The fundamental research about granular media statics and dynamics, the function relationship between coal types,moisture,particles size and friction coefficient were the focus of the research.The maximum delivery pressure of Stamet Pump and PWR which provided for the coal types in China was researched.Concerning the bottleneck of XTL industrial scale-up,we also put forward the solutions.%为优化干法煤气化的煤粉密相输送系统,介绍了加压密相气力输送技术和基于散体力学理论的固体输送泵技术2种典型的煤粉加压密相输送技术,分析了2种典型技术的技术特征及气体加压密相输送技术中的关键问题,提出了干粉加压固体输送泵的发展方向。固体输送泵技术是未来煤粉密相输送的发展趋势。未来应加强国内散体力学的相关理论、数值及试验研究,包括散体静力学,散体动力学的相关基础研究;研究煤种、水分、粒径等参数与摩擦系数之间的函数关系,确定Stamet Pump及PWR针对国内煤种所能提供的最大输出压力;确定典型的Stamep Pump、PWR的XTL技术工业放大的瓶颈所在,提出切实可行的放大解决方案。

  16. High-pressure structural properties of tetramethylsilane

    Science.gov (United States)

    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).

  17. Polyurethane interpenetrating networks synthesized under high pressure

    International Nuclear Information System (INIS)

    Using time resolved and real time small angle x-ray scattering on Beamline I-IV at SSRL, the phase separation behavior in a series of linear mixtures, semi-interpenetrating (SIPN) and interpenetrating polymer networks (IPN) was investigated as a function of temperature and composition. Polystyrene (PS) and polyurethane (PU) are polymers that at room temperature and pressure are incompatible over the entire composition range. Preparation of the mixed polymers under high pressure forces the two to be miscible. Crosslinking either one or both of the components can prohibit phase separation of the two components when the pressure is released and the ''mixture'' is heated to temperatures in access of the glass transition temperatures of the two polymers

  18. High pressure processing of meat

    DEFF Research Database (Denmark)

    Grossi, Alberto; Christensen, Mette; Ertbjerg, Per;

    Abstract Background: The research of high pressure (HP) processing of meat based foods needs to address how pressure affects protein interactions, aggregation and/or gelation. The understanding of the gel forming properties of myofibrillar components is fundamental for the development of muscle......–PAGE gels of myofibrillar protein extract from HP treated meat showed that myofibrillar proteins form high molecular weight aggregates after HP treatment. Myofibrillar protein aggregates were stable in a reducing environment, suggesting that disulfide bonds are not the main molecular interactions...... the rheological properties of pork meat batters by inducing formation of protein gels. HP induced protein gels are suggested to be formed by high molecular weight myofibrillar protein aggregates and by peptides formed by lysosomal enzyme-induced cleavage of myofibrillar proteins. Perspectives: The data presented...

  19. Steam Oxidation at High Pressure

    Energy Technology Data Exchange (ETDEWEB)

    Holcomb, Gordon R. [NETL; Carney, Casey [URS

    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.

  20. A fully automated method for simultaneous determination of aflatoxins and ochratoxin A in dried fruits by pressurized liquid extraction and online solid-phase extraction cleanup coupled to ultra-high-pressure liquid chromatography-tandem mass spectrometry.

    Science.gov (United States)

    Campone, Luca; Piccinelli, Anna Lisa; Celano, Rita; Russo, Mariateresa; Valdés, Alberto; Ibáñez, Clara; Rastrelli, Luca

    2015-04-01

    According to current demands and future perspectives in food safety, this study reports a fast and fully automated analytical method for the simultaneous analysis of the mycotoxins with high toxicity and wide spread, aflatoxins (AFs) and ochratoxin A (OTA) in dried fruits, a high-risk foodstuff. The method is based on pressurized liquid extraction (PLE), with aqueous methanol (30%) at 110 °C, of the slurried dried fruit and online solid-phase extraction (online SPE) cleanup of the PLE extracts with a C18 cartridge. The purified sample was directly analysed by ultra-high-pressure liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) for sensitive and selective determination of AFs and OTA. The proposed analytical procedure was validated for different dried fruits (vine fruit, fig and apricot), providing method detection and quantification limits much lower than the AFs and OTA maximum levels imposed by EU regulation in dried fruit for direct human consumption. Also, recoveries (83-103%) and repeatability (RSD < 8, n = 3) meet the performance criteria required by EU regulation for the determination of the levels of mycotoxins in foodstuffs. The main advantage of the proposed method is full automation of the whole analytical procedure that reduces the time and cost of the analysis, sample manipulation and solvent consumption, enabling high-throughput analysis and highly accurate and precise results.

  1. Phase equilibrium at high pressure of heavy oil fraction in propane and n-butane; Equilibrio de fases em alta pressao de fracoes pesadas do petroleo em propano e n-butano

    Energy Technology Data Exchange (ETDEWEB)

    Canziani, Daniel B.; Ndiaye, Papa M. [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil); Oliveira, Jose V. de; Corazza, Marcos L. [Universidade Regional Integrada, Erechim, RS (Brazil)

    2008-07-01

    One of the biggest challenge of the oil industry is the preparation and adequacy of existing refineries for processing of heavy oil in large quantities. Specifically aims of this work is to measure phase equilibria date at high-pressure with systems involving GOP (Heavy Gasoil), RAT (Atmospheric Residue) and Marlim (crude oil) in n-butane and propane, using the static-synthetic method. The influence of the addition of methanol on the transition pressure is also investigated. With regard to tests made with the use of methanol as a co-solvent, those with higher levels of methanol (5% in mass fraction) had presented transition pressures a little higher than systems with 1% of methanol and systems without methanol. The systems without methanol showed similar pressures. All systems are PT diagrams of the type Lower Critical Solution Temperature (LCST). Among the solvents used the n-butane shown to be the most soluble for all solutes, in particular for the RAT. With the n-butane were observed only liquid-vapour equilibria, and with propane the liquid-liquid, liquid-liquid-vapour and liquid-liquid-fluid equilibria could be observed. The system Propane-5%Methanol-GOP presented liquid-liquid-vapour transitions, indicates be a diagram of the type V (according to the classification of van Konynenburg and Scott). (author)

  2. Proteomic analysis of oil body membrane proteins accompanying the onset of desiccation phase during sunflower seed development.

    Science.gov (United States)

    Thakur, Anita; Bhatla, Satish C

    2015-01-01

    A noteworthy metabolic signature accompanying oil body (OB) biogenesis during oilseed development is associated with the modulation of the oil body membranes proteins. Present work focuses on 2-dimensional polyacrylamide gel electrophoresis (2-D PAGE)-based analysis of the temporal changes in the OB membrane proteins analyzed by LC-MS/MS accompanying the onset of desiccation (20-30 d after anthesis; DAA) in the developing seeds of sunflower (Helianthus annuus L.). Protein spots unique to 20-30 DAA stages were picked up from 2-D gels for identification and the identified proteins were categorized into 7 functional classes. These include proteins involved in energy metabolism, reactive oxygen scavenging, proteolysis and protein turnover, signaling, oleosin and oil body biogenesis-associated proteins, desiccation and cytoskeleton. At 30 DAA stage, exclusive expressions of enzymes belonging to energy metabolism, desiccation and cytoskeleton were evident which indicated an increase in the metabolic and enzymatic activity in the cells at this stage of seed development (seed filling). Increased expression of cruciferina-like protein and dehydrin at 30 DAA stage marks the onset of desiccation. The data has been analyzed and discussed to highlight desiccation stage-associated metabolic events during oilseed development.

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

    Science.gov (United States)

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

    1987-09-01

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

  4. High-Pressure Lightweight Thrusters

    Science.gov (United States)

    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

  5. Investigation of Methacrylic Acid at High Pressure Using Neutron Diffraction

    DEFF Research Database (Denmark)

    Marshall, William G.; Urquhart, Andrew; Oswald, Iain D. H.

    2015-01-01

    This article shows that pressure can be a low-intensity route to the synthesis of polymethacrylic acid. The exploration of perdeuterated methacrylic acid at high pressure using neutron diffraction reveals that methacrylic acid exhibits two polymorphic phase transformations at relatively low press...

  6. Investigation of Acrylic Acid at High Pressure using Neutron Diffraction

    DEFF Research Database (Denmark)

    Johnston, Blair F.; Marshall, William G.; Parsons, Simon;

    2014-01-01

    This article details the exploration of perdeuterated acrylic acid at high pressure using neutron diffraction. The structural changes that occur in acrylic acid-d4 are followed via diffraction and rationalised using the Pixel method. Acrylic acid undergoes a reconstructive phase transition to a n...

  7. High-pressure protein crystallography of hen egg-white lysozyme

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, Hiroyuki; Nagae, Takayuki [Nagoya University, Chikusa, Nagoya, Aichi 464-8603 (Japan); Watanabe, Nobuhisa, E-mail: nobuhisa@nagoya-u.jp [Nagoya University, Chikusa, Nagoya, Aichi 464-8603 (Japan); Nagoya University, Chikusa, Nagoya, Aichi 464-8603 (Japan)

    2015-04-01

    The crystal structure of hen egg-white lysozyme (HEWL) was analyzed under pressures of up to 950 MPa. The high pressure modified the conformation of the molecule and induced a novel phase transition in the tetragonal crystal of HEWL. Crystal structures of hen egg-white lysozyme (HEWL) determined under pressures ranging from ambient pressure to 950 MPa are presented. From 0.1 to 710 MPa, the molecular and internal cavity volumes are monotonically compressed. However, from 710 to 890 MPa the internal cavity volume remains almost constant. Moreover, as the pressure increases to 950 MPa, the tetragonal crystal of HEWL undergoes a phase transition from P4{sub 3}2{sub 1}2 to P4{sub 3}. Under high pressure, the crystal structure of the enzyme undergoes several local and global changes accompanied by changes in hydration structure. For example, water molecules penetrate into an internal cavity neighbouring the active site and induce an alternate conformation of one of the catalytic residues, Glu35. These phenomena have not been detected by conventional X-ray crystal structure analysis and might play an important role in the catalytic activity of HEWL.

  8. High pressure and multiferroics materials: a happy marriage.

    Science.gov (United States)

    Gilioli, Edmondo; Ehm, Lars

    2014-11-01

    The community of material scientists is strongly committed to the research area of multiferroic materials, both for the understanding of the complex mechanisms supporting the multiferroism and for the fabrication of new compounds, potentially suitable for technological applications. The use of high pressure is a powerful tool in synthesizing new multiferroic, in particular magneto-electric phases, where the pressure stabilization of otherwise unstable perovskite-based structural distortions may lead to promising novel metastable compounds. The in situ investigation of the high-pressure behavior of multiferroic materials has provided insight into the complex interplay between magnetic and electronic properties and the coupling to structural instabilities.

  9. High pressure and multiferroics materials: a happy marriage

    Directory of Open Access Journals (Sweden)

    Edmondo Gilioli

    2014-11-01

    Full Text Available The community of material scientists is strongly committed to the research area of multiferroic materials, both for the understanding of the complex mechanisms supporting the multiferroism and for the fabrication of new compounds, potentially suitable for technological applications. The use of high pressure is a powerful tool in synthesizing new multiferroic, in particular magneto-electric phases, where the pressure stabilization of otherwise unstable perovskite-based structural distortions may lead to promising novel metastable compounds. The in situ investigation of the high-pressure behavior of multiferroic materials has provided insight into the complex interplay between magnetic and electronic properties and the coupling to structural instabilities.

  10. High-pressure test loop design and application

    International Nuclear Information System (INIS)

    A high-pressure test loop (HPTL) has been constructed for the purpose of performing a number of chemistry experiments at simulated HTGR conditions of temperature, pressure, flow, and impurity content. The HPTL can be used to develop, modify, and verify computer codes for a variety of chemical processes involving gas phase transport in the reactor. Processes such as graphite oxidation, fission product transport, fuel reactions, purification systems, and dust entrainment can be studied at high pressure, which would largely eliminate difficulties in correlating existing laboratory data and reactor conditions

  11. High pressure effects on fruits and vegetables

    NARCIS (Netherlands)

    Timmermans, R.A.H.; Matser, A.M.

    2016-01-01

    The chapter provides an overview on different high pressure based treatments (high pressure pasteurization, blanching, pressure-assisted thermal processing, pressure-shift freezing and thawing) available for the preservation of fruits and vegetable products and extending their shelf life. Pressure t

  12. A decline in transcript abundance for Heterodera glycines homologs of Caenorhabditis elegans uncoordinated genes accompanies its sedentary parasitic phase

    Directory of Open Access Journals (Sweden)

    Overall Christopher C

    2007-04-01

    Full Text Available Abstract Background Heterodera glycines (soybean cyst nematode [SCN], the major pathogen of Glycine max (soybean, undergoes muscle degradation (sarcopenia as it becomes sedentary inside the root. Many genes encoding muscular and neuromuscular components belong to the uncoordinated (unc family of genes originally identified in Caenorhabditis elegans. Previously, we reported a substantial decrease in transcript abundance for Hg-unc-87, the H. glycines homolog of unc-87 (calponin during the adult sedentary phase of SCN. These observations implied that changes in the expression of specific muscle genes occurred during sarcopenia. Results We developed a bioinformatics database that compares expressed sequence tag (est and genomic data of C. elegans and H. glycines (CeHg database. We identify H. glycines homologs of C. elegans unc genes whose protein products are involved in muscle composition and regulation. RT-PCR reveals the transcript abundance of H. glycines unc homologs at mobile and sedentary stages of its lifecycle. A prominent reduction in transcript abundance occurs in samples from sedentary nematodes for homologs of actin, unc-60B (cofilin, unc-89, unc-15 (paromyosin, unc-27 (troponin I, unc-54 (myosin, and the potassium channel unc-110 (twk-18. Less reduction is observed for the focal adhesion complex gene Hg-unc-97. Conclusion The CeHg bioinformatics database is shown to be useful in identifying homologs of genes whose protein products perform roles in specific aspects of H. glycines muscle biology. Our bioinformatics comparison of C. elegans and H. glycines genomic data and our Hg-unc-87 expression experiments demonstrate that the transcript abundance of specific H. glycines homologs of muscle gene decreases as the nematode becomes sedentary inside the root during its parasitic feeding stages.

  13. Numerical Simulation on Pneumatic Conveying of Dense Phase Pulverized Coal in Horizontal Pipe at High Pressure%水平管段高压超浓相煤粉输送特性的数值模拟

    Institute of Scientific and Technical Information of China (English)

    胥宇鹏; 熊源泉; 周海军; 贺春辉; 陈先梅; 沈湘林

    2012-01-01

    The numerical simulation on the pneumatic transmission of ultra-high-pressure dense phase pulverized coal with CO2 as the medium was performed by the modified κ~ε turbulence mod-el. In the model, the turbulence interaction between gas and solid particle is considered for the pneumatic conveying of the pulverized coal whose particulate phase concentration is up to 25%. The model was applied to simulate the pneumatic transmission in an integration pipe including a vertical pipe, an elbow pipe, and a horizontal pipe. The velocity and concentration distributions of different size particles on cross sections in a horizontal pipe, and the radial concentration distri-bution of solid particles at different superficial gas velocities in a horizontal pipe were obtained. The simulation results show that the pulverized coal with larger particle size will deposit more easily in the horizontal pipe under the same transport conditions. The concentration distribution in the sedimentary area is smaller at the same size particle and the greater superficial gas velocity. The simulation results are in reasonably good agreement with the experimental data achieved by ECT imaging.%在充分考虑气固两相相互作用的基础上,利用修正后的κ-ε湍流模型对以CO2为输送介质的高压超浓相煤粉气力输送进行了数值模拟.对于固相体积分数高达25%的高压超浓相煤粉气力输送,采用该模型模拟一体化管道(垂直管、弯管、水平管连接在一起),获得了水平管段中不同粒径的颗粒在截面上的速度分布、浓度分布,以及不同表观气速下水平管段中固相的径向浓度分布.模拟结果表明,在相同的输送条件下,大粒径煤粉的速度较低,更容易在水平管道沉积;煤粉粒径相同时,表观气速较大的颗粒在沉积区的浓度分布较小.将模拟结果与相同试验条件下的水平管电容层析成像(ECT)结果进行了对比,验证了本文模拟结果的正确性.

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

    Science.gov (United States)

    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. Deformation Twinning of a Silver Nanocrystal under High Pressure

    Energy Technology Data Exchange (ETDEWEB)

    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.

  16. Revealing properties of single-walled carbon nanotubes under high pressure

    CERN Document Server

    Tang Jie; Sasaki, T; Yudasaka, M; Matsushita, A; Iijima, S

    2002-01-01

    It was found by the x-ray diffraction experiment under hydrostatic pressure that the carbon nanotubes are compressed easily with a high volume compressibility of 0.024 GPa sup - sup 1. The single-walled carbon nanotubes are polygonized when they form bundles of hexagonal close-packed structure and the inter-tubular gap is smaller than the equilibrium spacing of graphite. Under high pressure, further polygonization occurs to accommodate the extra amount of volume reduction. The ratio of the short and the long diagonals in the hexagonalized cross section is found to have changed from 0.991 at zero pressure to 0.982 at 1.5 GPa pressure, when the Bragg reflection from the nanotube lattice diminished. Accompanying polygonization, a discontinuous change in electrical resistivity was observed at 1.5 GPa pressure, suggesting a phase transition had occurred.

  17. Stable magnesium peroxide at high pressure.

    Science.gov (United States)

    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.

  18. Stable magnesium peroxide at high pressure

    Science.gov (United States)

    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.

  19. Stable magnesium peroxide at high pressure.

    Science.gov (United States)

    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

  20. Application of High Pressure in Food Processing

    Directory of Open Access Journals (Sweden)

    Herceg, Z.

    2011-01-01

    Full Text Available In high pressure processing, foods are subjected to pressures generally in the range of 100 – 800 (1200 MPa. The processing temperature during pressure treatments can be adjusted from below 0 °C to above 100 °C, with exposure times ranging from a few seconds to 20 minutes and even longer, depending on process conditions. The effects of high pressure are system volume reduction and acceleration of reactions that lead to volume reduction. The main areas of interest regarding high-pressure processing of food include: inactivation of microorganisms, modification of biopolymers, quality retention (especially in terms of flavour and colour, and changes in product functionality. Food components responsible for the nutritive value and sensory properties of food remain unaffected by high pressure. Based on the theoretical background of high-pressure processing and taking into account its advantages and limitations, this paper aims to show its possible application in food processing. The paper gives an outline of the special equipment used in highpressure processing. Typical high pressure equipment in which pressure can be generated either by direct or indirect compression are presented together with three major types of high pressure food processing: the conventional (batch system, semicontinuous and continuous systems. In addition to looking at this technology’s ability to inactivate microorganisms at room temperature, which makes it the ultimate alternative to thermal treatments, this paper also explores its application in dairy, meat, fruit and vegetable processing. Here presented are the effects of high-pressure treatment in milk and dairy processing on the inactivation of microorganisms and the modification of milk protein, which has a major impact on rennet coagulation and curd formation properties of treated milk. The possible application of this treatment in controlling cheese manufacture, ripening and safety is discussed. The opportunities

  1. High pressure differential conductance measurements of (Pb,Sn)Se

    Science.gov (United States)

    Paul, Tiffany; Vangennep, Derrick; Jackson, Daniel; Biswas, Amlan; Hamlin, James

    Topological transitions have been recognized as a new type of quantum phase transition. Recently, a number of papers have reported scanning tunneling microscope (STM) measurements of the Landau level spectra of topologically non-trivial materials. Such measurements can offer substantial insight into the nature of the transition between topologically distinct phases. Although applied pressure represents an attractive means to drive a topological quantum phase transition, STM measurements can not be performed under high pressure conditions. In this talk, I will discuss our recent attempts to observe Landau level spectra in compressed (Pb,Sn)Se using differential conductance measurements. Acknowledgements: TAP supported by REU NSF DMR-1461019. Pressure cell development and measurements at high magnetic fields supported by the National High Magnetic Field Laboratory User Collaboration Grants Program. Synthesis, characterization, and high pressure measurements supported by NSF DMR-1453752.

  2. Nickel-graphite composites of variable architecture by graphitization-accompanied spark plasma sintering and hot pressing and their response to phase separation

    Directory of Open Access Journals (Sweden)

    Dudina D.V.

    2015-01-01

    Full Text Available We report the formation and phase separation response of nickel-graphite composites with variable-architecture phases by graphitization-accompanied consolidation via Spark Plasma Sintering and hot pressing. It was shown that the application of pressure during consolidation is crucial for the occurrence of graphitization and formation of 3D graphite structures. We evaluated the suitability of the synthesized composites as precursors for making porous structures. Nickel behaved as a space holder with the particle size and spatial distribution changing during consolidation with the temperature and determining the structure of porous graphite formed by phase separation by dissolution in HCl. The response of the consolidated Ni-Cgr to separation of carbon by its burnout in air was studied. The result of the carbon removal was either the formation of a dense and continuous NiO film on the surface of the compacts or oxidation through the compact thickness. The choice between these two options depended on the density of the compacts and on the presence of carbon dissolved in nickel. It was found that during the burnout of graphite from Ni-Cgr composites, sintering, rather than formation of pores, dominated.

  3. Cagelike diamondoid nitrogen at high pressures.

    Science.gov (United States)

    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

  4. High-pressure study on some superconductors

    CERN Document Server

    Li, K Q; Yao, Y S; Che, G C; Zhao, Z X

    2002-01-01

    High-pressure study has played an important role in the investigation of conventional superconductors. Since the discovery of cuprate superconductors, high-pressure study has become even more important, especially as regards high-pressure synthesis and the effect of pressure. In this report, the new materials Ca-doped Pr-123, (Fe, Cu)-1212, and MgB sub 2 - a very new and interesting system synthesized under high pressure with good quality - will be discussed. Chemical inner pressure has been thought to explain the high T sub c of Ca-doped Pr-123. As another possibility, the replacement of the physical pressure effect by a chemical effect will be discussed.

  5. High pressure processing for food safety.

    Science.gov (United States)

    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.

  6. High pressure effects on fruits and vegetables

    OpenAIRE

    Timmermans, R.A.H.; Matser, A.M.

    2016-01-01

    The chapter provides an overview on different high pressure based treatments (high pressure pasteurization, blanching, pressure-assisted thermal processing, pressure-shift freezing and thawing) available for the preservation of fruits and vegetable products and extending their shelf life. Pressure treatment can be used for product modification through pressure gelatinization of starch and pressure denaturation of proteins. Key pressure–thermal treatment effects on vitamin, enzymes, flavor, co...

  7. Energy efficiency of high pressure pneumatic systems

    OpenAIRE

    Trujillo, José A.

    2015-01-01

    The energy efficiency assessment of high-pressure pneumatic circuits is the aim of this dissertation. From a historical perspective the past and cur- rent activities with regards to the energy saving conservation in pneumatic technology were examined, and it could be concluded that high pressure pneumatic circuits have been repeatedly used for years in several industrial applications but to date no studies on that specific field are known. After a systematic review of studies concerning e...

  8. High pressure elasticity and thermal properties of depleted uranium

    Science.gov (United States)

    Jacobsen, M. K.; Velisavljevic, N.

    2016-04-01

    Studies of the phase diagram of uranium have revealed a wealth of high pressure and temperature phases. Under ambient conditions the crystal structure is well defined up to 100 gigapascals (GPa), but very little information on thermal conduction or elasticity is available over this same range. This work has applied ultrasonic interferometry to determine the elasticity, mechanical, and thermal properties of depleted uranium to 4.5 GPa. Results show general strengthening with applied load, including an overall increase in acoustic thermal conductivity. Further implications are discussed within. This work presents the first high pressure studies of the elasticity and thermal properties of depleted uranium metal and the first real-world application of a previously developed containment system for making such measurements.

  9. Temperature control for high pressure processes up to 1400 MPa

    Energy Technology Data Exchange (ETDEWEB)

    Reineke, K; Mathys, A; Knorr, D [Berlin University of Technology, Department of Food Biotechnology and Food Process Engineering, Koenigin-Luise-Str. 22, D-14195 Berlin (Germany); Heinz, V [German Institute of Food Technology, p. o. box: 1165, D-49601, Quackenbrueck (Germany)], E-mail: alexander.mathys@tu-berlin.de

    2008-07-15

    Pressure- assisted sterilisation is an emerging technology. Hydrostatic high pressure can reduce the thermal load of the product and this allows quality retention in food products. To guarantee the safety of the sterilisation process it is necessary to investigate inactivation kinetics especially of bacterial spores. A significant roll during the inactivation of microorganisms under high pressure has the thermodynamic effect of the adiabatic heating. To analyse the individual effect of pressure and temperature on microorganism inactivation an exact temperature control of the sample to reach ideal adiabatic conditions and isothermal dwell times is necessary. Hence a heating/cooling block for a high pressure unit (Stansted Mini-Food-lab; high pressure capillary with 300 {mu}L sample volume) was constructed. Without temperature control the sample would be cooled down during pressure built up, because of the non-adiabatic heating of the steel made vessel. The heating/cooling block allows an ideal adiabatic heat up and cooling of the pressure vessel during compression and decompression. The high pressure unit has a pressure build-up rate up to 250 MPa s{sup -1} and a maximum pressure of 1400 MPa. Sebacate acid was chosen as pressure transmitting medium because it had no phase shift over the investigate pressure and temperature range. To eliminate the temperature difference between sample and vessel during compression and decompression phase, the mathematical model of the adiabatic heating/cooling of water and sebacate acid was implemented into a computational routine, written in Test Point. The calculated temperature is the setpoint of the PID controller for the heating/cooling block. This software allows an online measurement of the pressure and temperature in the vessel and the temperature at the outer wall of the vessel. The accurate temperature control, including the model of the adiabatic heating opens up the possibility to realise an ideal adiabatic heating and

  10. Temperature control for high pressure processes up to 1400 MPa

    Science.gov (United States)

    Reineke, K.; Mathys, A.; Heinz, V.; Knorr, D.

    2008-07-01

    Pressure- assisted sterilisation is an emerging technology. Hydrostatic high pressure can reduce the thermal load of the product and this allows quality retention in food products. To guarantee the safety of the sterilisation process it is necessary to investigate inactivation kinetics especially of bacterial spores. A significant roll during the inactivation of microorganisms under high pressure has the thermodynamic effect of the adiabatic heating. To analyse the individual effect of pressure and temperature on microorganism inactivation an exact temperature control of the sample to reach ideal adiabatic conditions and isothermal dwell times is necessary. Hence a heating/cooling block for a high pressure unit (Stansted Mini-Food-lab; high pressure capillary with 300 μL sample volume) was constructed. Without temperature control the sample would be cooled down during pressure built up, because of the non-adiabatic heating of the steel made vessel. The heating/cooling block allows an ideal adiabatic heat up and cooling of the pressure vessel during compression and decompression. The high pressure unit has a pressure build-up rate up to 250 MPa s-1 and a maximum pressure of 1400 MPa. Sebacate acid was chosen as pressure transmitting medium because it had no phase shift over the investigate pressure and temperature range. To eliminate the temperature difference between sample and vessel during compression and decompression phase, the mathematical model of the adiabatic heating/cooling of water and sebacate acid was implemented into a computational routine, written in Test Point. The calculated temperature is the setpoint of the PID controller for the heating/cooling block. This software allows an online measurement of the pressure and temperature in the vessel and the temperature at the outer wall of the vessel. The accurate temperature control, including the model of the adiabatic heating opens up the possibility to realise an ideal adiabatic heating and cooling as

  11. 超高压联合高密度 CO2处理钝化对虾多酚氧化酶%Inactivation of polyphenol oxidase from Litopenaeus vannamei treated by ultra high pressure combined dense phase carbon dioxide

    Institute of Scientific and Technical Information of China (English)

    邓倩琳; 刘书成; 刘蒙娜; 刘媛; 郭明慧; 吉宏武; 李承勇; 高静

    2016-01-01

    Ultra high pressure (UHP) and dense phase carbon dioxide (DPCD) processes are effective non-thermal pasteurization methods that have gained increasing attention in inactivation of undesired enzymes and microorganisms in food industry. The advantage of UHP is to process foods that are already packaged and therefore are not liable to post-process contamination. Although UHP effectively eliminates microorganisms, it does not inactivate some key enzymes that reduce the product quality. For example, UHP may increase the activities of polyphenol oxidase (PPO) at lower pressure. As a continuous operation, DPCD needs aseptic filling to containers, but can inactivate enzymes. Therefore it is logical to combine these technologies to benefit from their individual advantages. The presence of carbon dioxide (CO2) in the sample medium might create a more acidic environment and synergistically interact with pressure to damage or alter the structures of enzymes and microbial cells. In order to make up for the disadvantage of UHP in inactivating PPO and use the advantage of DPCD in inactivating PPO, the inactivation effect of PPO from Litopenaeus vannamei treated by UHP combined with CO2 (UHP+CO2) was studied, and the feasibility of developing new shrimp products by UHP+CO2 was explored. The crude PPO extracts of 2 mL were treated with 2% CO2 (v/v) package alone, or UHP alone, or UHP + 2% CO2 (v/v). The treatment temperature was 30±2 ℃. The treatment pressure was 100, 200, 300, 400 and 500 MPa, respectively. The treatment time was 5, 10, 15, 20, 25 and 30 min, respectively. The results showed that: The PPO was inactivated more effectively by UHP+CO2 than CO2 treatment and UHP treatment alone. Treated at 100 MPa for 30 min by UHP+CO2, PPO activity dropped to 18.92%±1.52%. At 200 MPa for 10 min by UHP+CO2, PPO activity dropped to 10.91%±1.08%. At 300 MPa for 10 min by UHP+CO2, 95% PPO was inactivated. At 400 MPa for 5 min by UHP+CO2, the residual activity of PPO was less than 3

  12. Some recent investigations of materials under high pressures

    Indian Academy of Sciences (India)

    Surinder M Sharma

    2006-07-01

    By subjecting materials to high pressures one can significantly reduce inter-atomic and intermolecular distances. This causes drastic changes in the nature of electronic and vibrational states and also in bonding, bringing about several unusual structural, electronic and magnetic phase transitions. In addition, these studies provide a very useful data about the equation of state of the materials of interest. Several examples from our work are presented which elucidate the richness of physics under these conditions.

  13. Modelling of two-phase friction from isothermal spreading experiments with gas fed from the bottom and application to spreading accompanied by solidification

    Energy Technology Data Exchange (ETDEWEB)

    Veteau, J. M.; Spindler, B. [Commissariat a l' Energie Atomique, Grenoble (France); Daum, G. [Ecole Centrale de Lyon, Lyon (France)

    2003-07-01

    In the framework of R and D on Severe Accidents on PWR, an estimation of the spreading extent of Corium is needed in the case of a vessel melt-through. With several test series chosen to favor particular phenomena affecting the spreading process, the CORINE experimental program provided a data base and helps assessment of spreading codes. Hence, pure hydrodynamics, effect of bottom and top crust, as well as bulk freezing were successively investigated and allowed the assessment of the THEMA spreading code developed at CEA in France. Spreading with gas fed from the bottom was also experimentally studied, in connection with gas released by the decomposition of concrete in the reactor case. In order to model this particular effect, the THEMA code, which solves fluid mechanics balance equations averaged over the depth of the fluid, considers the concept of two-phase friction multiplier, already worked out for two-phase flows in pipes. A set of correlations for two-phase friction multipliers proposed in the literature for pipes according to the liquid-to-fluid viscosity ratio was implemented in the code, just replacing the constant pipe diameter by the local and time dependent hydraulic diameter of the spreading sheet. The model was assessed on 20 isothermal spreading tests conducted on the CORINE facility, and depicts very satisfactorily the complex effect of gas versus fluid viscosity found experimentally. Application to prediction of spreading accompanied by solidification in 5 tests conducted with a non eutectic Bismuth-Lead alloy on the CORINE facility gave also good results.

  14. Reinvestigation of high pressure polymorphism in hafnium metal

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, K. K., E-mail: kkpandey@barc.gov.in; Sharma, Surinder M. [High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, Mumbai-400 085 (India); Gyanchandani, Jyoti; Dey, G. K. [Materials Science Division, Bhabha Atomic Research Centre, Mumbai-400 085 (India); Somayazulu, M. [Geophysical Laboratory, Carnegie Institution of Washington, Washington, D.C. 20015 (United States); Sikka, S. K. [Indian National Science Academy, New Delhi-110 002 (India)

    2014-06-21

    There has been a recent controversy about the high pressure polymorphism of Hafnium (Hf). Unlike, the earlier known α→ω structural transition at 38 ± 8 GPa, at ambient temperature, Hrubiak et al. [J. Appl. Phys. 111, 112612 (2012)] did not observe it till 51 GPa. They observed this transition only at elevated temperatures. We have reinvestigated the room temperature phase diagram of Hf, employing x-ray diffraction (XRD) and DFT based first principles calculations. Experimental investigations have been carried out on several pure and impure Hf samples and also with different pressure transmitting media. Besides demonstrating the significant role of impurity levels on the high pressure phase diagram of Hf, our studies re-establish room temperature α→ω transition at high pressures, even in quasi-hydrostatic environment. We observed this transition in pure Hf with equilibrium transition pressure P{sub o} = 44.5 GPa; however, with large hysteresis. The structural sequence, transition pressures, the lattice parameters, the c/a ratio and its variation with compression for the α and ω phases as predicted by our ab-initio scalar relativistic (SR) calculations are found to be in good agreement with our experimental results of pure Hf.

  15. Structures of Liquid Aluminium under High Pressure

    Institute of Scientific and Technical Information of China (English)

    LI Hui; WANG Guang-Hou; BIAN Xiu-Fang; ZHANG Lin

    2001-01-01

    Molecular dynamics simulation has been carried out for melt A1 under constant temperature and constant pressure. The interaction between atoms is described by tight-binding many-body potentials based on the second moment approximation to the electronic density of states. The pair correlation function and the pair analysis technique are used to reveal the structural features of liquid Al under normal and high pressure. High pressure is favourable to the existence of bcc clusters 1661 and 1441, but has no effect on the fcc cluster 1421. The bond pair 1551 and 1541 with fivefold symmetry exists at high pressure. The microstructure of liquid is more similar to the non-crystalline structure than to the crystalline structure. The simulation results are supported by thex-ray experimental results.

  16. Curved and conformal high-pressure vessel

    Energy Technology Data Exchange (ETDEWEB)

    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.

  17. Techniques in high pressure neutron scattering

    CERN Document Server

    Klotz, Stefan

    2013-01-01

    Drawing on the author's practical work from the last 20 years, Techniques in High Pressure Neutron Scattering is one of the first books to gather recent methods that allow neutron scattering well beyond 10 GPa. The author shows how neutron scattering has to be adapted to the pressure range and type of measurement.Suitable for both newcomers and experienced high pressure scientists and engineers, the book describes various solutions spanning two to three orders of magnitude in pressure that have emerged in the past three decades. Many engineering concepts are illustrated through examples of rea

  18. Experimental study of lower mantle materials by high pressure in situ x-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Yagi, Takehiko [Tokyo Univ. (Japan). Inst. for Solid State Physics

    1999-10-01

    A new experimental system was constructed to make high pressure and temperature in situ X-ray diffraction study under lower mantle conditions. Behavior of silicates and oxides were studied using the new system, which consists of laser-heated diamond anvil cell combined with synchrotron radiation. It became clear that the behavior of garnet is very complicated and the high pressure phase(s) varices depending on the pressure, temperature, and compositions. Several new unquenchable high pressure phases were found through the present study. (author)

  19. High pressure and synchrotron radiation satellite workshop

    Energy Technology Data Exchange (ETDEWEB)

    Bass, J.; Guignot, N.; Morard, G.; Mezouar, M.; Andrault, D.; Bolfan-Casanova, N.; Sturhahn, W.; Daniel, I.; Reynard, B.; Simionovici, A.; Sanchez Valle, C.; Martinez, I.; Kantor, I.; Dubrovinsky, I.; Mccammon, C.; Dubrovinskaia, N.; Kurnosiv, A.; Kuznetsov, A.; Goncharenko, I.; Loubeyre, P.; Desgreniers, S.; Weck, G.; Yoo, C.S.; Iota, V.; Park, J.; Cynn, H.; Gorelli, F.; Toulemonde, P.; Machon, D.; Merlen, A.; San Miguel, A.; Amboage, M.; Aquilanti, G.; Mathon, O.; Pascarelli, S.; Itie, J.P.; Mcmillan, P.F.; Trapananti, A.; Di Cicco, A.; Panfilis, S. de; Filipponi, A.; Kreisel, J.; Bouvier, P.; Dkhil, B.; Chaabane, B.; Rosner, H.; Koudela, D.; Schwarz, U.; Handestein, A.; Hanfland, M.; Opahle, I.; Koepernik, K.; Kuzmin, M.; Mueller, K.H.; Mydosh, J.; Richter, M.; Hejny, C.; Falconi, S.; Lundegaard, L.F.; Mcmahon, M.I; Loa, I.; Syassen, K.; Wang, X.; Roth, H.; Lorenz, T.; Farber Daniel, I.; Antonangeli Daniele, I.; Krisch, M.; Badro, J.; Fiquet, G.; Occelli, F.; Mao, W.L.; Mao, H.K.; Eng, P.; Kao, C.C.; Shu, J.F.; Hemley, R.J.; Tse, J.S.; Yao, Y.; Deen, P.P.; Paolasini, I.; Braithwaite, D.; Kernavanois, N.; Lapertot, G.; Rupprecht, K.; Leupold, O.; Ponkratz, U.; Wortmann, G.; Beraud, A.; Krisch, M.; Farber, D.; Antonangeli, D.; Aracne, C.; Zarestky, J.L.; Mcqueeney, R.; Mathon, O.; Baudelet, F.; Decremps, F.; Itie, J.P.; Nataf, I.; Pascarelli, S.; Polian, A

    2006-07-01

    The workshop is dedicated to recent advances on science at high pressure at third generation synchrotron sources. A variety of experiments using synchrotron radiation techniques including X-ray diffraction, EXAFS (extended X-ray absorption fine structure), inelastic X-ray scattering, Compton scattering and Moessbauer spectroscopy of crystalline, liquid or amorphous samples, are reported. This document gathers the abstracts of the presentations.

  20. High pressure and synchrotron radiation satellite workshop

    International Nuclear Information System (INIS)

    The workshop is dedicated to recent advances on science at high pressure at third generation synchrotron sources. A variety of experiments using synchrotron radiation techniques including X-ray diffraction, EXAFS (extended X-ray absorption fine structure), inelastic X-ray scattering, Compton scattering and Moessbauer spectroscopy of crystalline, liquid or amorphous samples, are reported. This document gathers the abstracts of the presentations

  1. High pressure synthesis of bismuth disulfide

    DEFF Research Database (Denmark)

    Søndergaard-Pedersen, Simone; Nielsen, Morten Bormann; Bremholm, Martin

    In this research the BiS2 compound was synthesized by a high pressure and high temperature method using a multi-anvil large volume press and the structure was solved by single crystal diffraction. The structure contains Bi atoms in distorted square-based pyramidal coordination to five surrounding...

  2. High Pressure Inactivation of HAV within Mussels

    Science.gov (United States)

    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...

  3. High pressure studies on nanometer sized clusters: Structural, optical, and cooperative properties

    Energy Technology Data Exchange (ETDEWEB)

    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.

  4. Hydrogen bond effects on compressional behavior of isotypic minerals: high-pressure polymorphism of cristobalite-like Be(OH)2

    Science.gov (United States)

    Shelton, Hannah; Barkley, Madison C.; Downs, Robert T.; Miletich, Ronald; Dera, Przemyslaw

    2016-09-01

    Three isotypic crystals, SiO2 (α-cristobalite), ɛ-Zn(OH)2 (wülfingite), and Be(OH)2 (β-behoite), with topologically identical frameworks of corner-connected tetrahedra, undergo displacive compression-driven phase transitions at similar pressures (1.5-2.0 GPa), but each transition is characterized by a different mechanism resulting in different structural modifications. In this study, we report the crystal structure of the high-pressure γ-phase of beryllium hydroxide and compare it with the high-pressure structures of the other two minerals. In Be(OH)2, the transition from the ambient β-behoite phase with the orthorhombic space group P212121 and ambient unit cell parameters a = 4.5403(4) Å, b = 4.6253(5) Å, c = 7.0599(7) Å, to the high-pressure orthorhombic γ-polymorph with space group Fdd2 and unit cell parameters (at 5.3(1) GPa) a = 5.738(2) Å, b = 6.260(3) Å, c = 7.200(4) Å takes place between 1.7 and 3.6 GPa. This transition is essentially second order, is accompanied by a negligible volume discontinuity, and exhibits both displacive and reversible character. The mechanism of the phase transition results in a change to the hydrogen bond connectivities and rotation of the BeO4 tetrahedra.

  5. Measurement of gas-liquid two-phase flow around horizontal tube bundle using SF6-water. Simulating high-pressure high-temperature gas-liquid two-phase flow of PWR/SG secondary coolant side at normal pressure

    International Nuclear Information System (INIS)

    In order to improve prediction accuracy of analysis code used for design and development of industrial products, technology had been developed to create and evaluate constitutive equation incorporated in analysis code. The experimental facility for PWR/SG U tubes part was manufactured to measure local void fraction and gas-liquid interfacial velocity with forming gas-liquid upward two-phase flow simulating high-pressure high-temperature secondary coolant (water-steam) rising vertically around horizontal tube bundle. The experimental facility could reproduce flow field having gas-liquid density ratio equivalent to real system with no heating using SF6 (Sulfur Hexafluoride) gas at normal temperature and pressure less than 1 MPa, because gas-liquid density ratio, surface tension and gas-liquid viscosity ratio were important parameters to determine state of gas-liquid two-phase flow and gas-liquid density ratio was most influential. Void fraction was measured by two different methods of bi-optical probe and conductivity type probe. Test results of gas-liquid interfacial velocity vs. apparent velocity were in good agreement with existing empirical equation within 10% error, which could confirm integrity of experimental facility and appropriateness of measuring method so as to set up original constitutive equation in the future. (T. Tanaka)

  6. 'Weird' crystal structures of elements at high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Kolobyanina, Tat' yana N [L.F. Vereshchagin Institute of High Pressure Physics, Russian Academy of Sciences, Troitsk, Moscow region (Russian Federation)

    2002-12-31

    New crystal structures, in particular incommensurate composite crystals, discovered in the high-pressure phases of Group I, II, IV, and V elements are described, and their intermetallic and other binary structural analogs are discussed. (reviews of topical problems)

  7. High-pressure oxidation of methane

    DEFF Research Database (Denmark)

    Hashemi, Hamid; Christensen, Jakob Munkholt; Gersen, Sander;

    2016-01-01

    Methane oxidation at high pressures and intermediate temperatures was investigated in a laminar flow reactor and in a rapid compression machine (RCM). The flow-reactor experiments were conducted at 700–900 K and 100 bar for fuel-air equivalence ratios (Φ) ranging from 0.06 to 19.7, all highly......–456 bar) and flame speeds (1–10 bar) from literature. The model yielded satisfactory predictions for the onset temperature as well as for most major species upon ignition in the flow reactor, but the concentration of particularly CH3OH was severely underpredicted, indicating that further work is desirable...... on reactions of CH3O and CH3OO. Measured ignition delay times from the RCM tests were reproduced well by the model for high pressures, but underpredicted at 15 bar. For the shock tube and flame conditions, predictions were mostly within the experimental uncertainty. Prompt dissociation of HCO increased...

  8. Inspection technology for high pressure pipes

    International Nuclear Information System (INIS)

    Various kinds of defects are likely to be occurred in the welds of high pressure pipes in nuclear power plants. Considering the recent accident of Zuruga nuclear power plant in Japan, reasonable policy is strongly requested for the high pressure pipe integrity. In this study, we developed the technologies to inspect pipe welds automatically. After development of scanning robot prototype in the first research year, we developed and implemented the algorithm of automatic tracking of the scanning robot along the weld line of the pipes. We use laser slit beam on weld area and capture the image using digital camera. Through processing of the captures image, we finally determine the weld line automatically. In addition, we investigated a new technology on micro systems for developing micro scanning robotic inspection of the pipe welds. The technology developed in this study is being transferred to the industry. (author)

  9. High pressure hydrogen time projection chamber

    International Nuclear Information System (INIS)

    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 H2 with 2 kV/cm drift field and 7 kV on the 35μ sense wires, the drift velocity is about 0.5 cm/μsec and the spatial resolution +-200μ

  10. High pressure synthesis of BiS2

    DEFF Research Database (Denmark)

    Søndergaard-Pedersen, Simone; Nielsen, Morten Bormann; Bremholm, Martin

    crystal structures and electrical properties.1,2 Up until now, the most sulfur rich phase in the Bi-S phase diagram was Bi2S3.3 For BiS2 the Bi atoms have anisotropic charge distribution and more complex structures are expected when comparing the layered structures of transition metal dichalcogenides....... The possibilities of using high pressure synthesis to discover new phases in the Bi-S binary system were investigated as early as the 1960’s.4 The research led to discovery of a compound with BiS2 stoichiometry, but no structure solution of BiS2 was reported. A reason behind making this new phase is to study...... the physical properties since the related compound Bi2S3 is known to be a thermoelectric material.5 In this research the BiS2 compound was synthesized by a high pressure and high temperature method using a multi-anvil large volume press and the structure was solved by single crystal diffraction. The structure...

  11. High pressure effects on allergen food proteins.

    Science.gov (United States)

    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).

  12. Simulation and Optimal Design of High-Pressure-Differential and High-Solid-Phase Relief Valves%高压差高固含量减压阀的仿真优化设计

    Institute of Scientific and Technical Information of China (English)

    王新昶; 孙方宏; 孙乐申; 丁庆华; 彭东辉

    2011-01-01

    Relief valves used in the coal liquefaction equipment are running in an extremely harsh environment with extraordinarily high pressure differential and intensely slurry flow erosion.Based on the finite volume method(FVM),the pressure and flow distributions of relief valves were analyzed,with K-ε turbulence and Mixture multiphase model.Moreover,for the new-style relief valves,variations of pressure drops with valve apertures and turbulence intensities with depths of valve seat hole were studied.Considering the fluid-erosion theory,optimal design was accomplished and the easy-wearing positions of the relief valves were accurately predicted to provide theoretical basis for the choice of wear resistant materials.The application results show that the easy-wearing positions are coincide with the predictions.Moreover,the working lifetime is largely elongated up to 1 200 hours and suitable for the practical application.%基于有限容积法,采用K-ε双方程湍流模型和Mixture多相流模型,对高压差高固态浓度流体冲蚀极端工况条件下工作的煤液化减压阀阀体内的压力分布和流场状态进行了计算流体动力学分析,研究了新型结构减压阀在不同开度下压降的变化情况,以及不同阀座孔深度下湍流强度的变化情况.结合流体冲蚀理论,完成了对其结构的优化改进,并对易磨损部位做出了精确预测,为关键部位耐磨材料的筛选提供了理论依据.实际应用实验结果表明,该新型减压阀使用过程中易磨损部位与仿真预测一致,使用寿命超过了1 200 h,满足实际应用需求.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Science.gov (United States)

    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.

  15. Determining complex crystal structures from high pressure single-crystal diffraction data collected on synchrotron sources

    Science.gov (United States)

    McMahon, M. I.; Loa, I.; Stinton, G. W.; Lundegaard, L. F.

    2013-08-01

    As part of a Long Term Project, single-crystal diffraction techniques have been developed for use at the high pressure beamlines ID09 and ID27 at the European Synchrotron Radiation Facility, and have been utilised to determine the crystal structures of various high pressure phases, including those with incommensurate structures, at both high and low temperatures. The same techniques have also been used to determine the structures of high pressure phases at the SRS, Diamond and Petra-III synchrotron sources. In this paper, we describe technical details of the methods developed, and describe some of the considerations necessary for planning experiments and collecting and processing the data. We then illustrate the quality of data that can be obtained, and the complexity of the structures that can be refined, using recent results obtained from complex high pressure phases of N2 and Ba.

  16. High-pressure study of substrate material ScAlMgO4

    OpenAIRE

    Errandonea, D.; R. S. Kumar; Ruiz-Fuertes, J.; Segura, A.; Haussuehl, E.

    2011-01-01

    We report on the structural properties of ScAlMgO4 studied under quasi-hydrostatic pressure using synchrotron high-pressure x-ray diffraction up to 40 GPa. We also report on single-crystal studies of ScAlMgO4 performed at 300 K and 100 K. We found that the low-pressure phase remains stable up to 24 GPa. At 28 GPa, we detected a reversible phase transformation. The high-pressure phase is assigned to a monoclinic distortion of the low-pressure phase. No additional phase transition is observed u...

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

    Science.gov (United States)

    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

  18. High pressure as a tool to study electron localization

    Energy Technology Data Exchange (ETDEWEB)

    Hill, R.J.A.; Itskevich, I.E.; Stoddart, S.T.; Murphy, H.M.; Thornton, A.S.G.; Main, P.C.; Eaves, L.; Henini, M. [Nottingham Univ. (United Kingdom). School of Physics and Astronomy; Maude, D.K.; Portal, J.C. [LCMI-CNRS, Grenoble (France); INSA-CNRS, Toulouse (France)

    2001-01-01

    We have used high pressure to investigate resonant tunnelling in a single-barrier, n-i-n GaAs/AlAs/GaAs diode with an embedded layer of InAs self-assembled quantum dots (SAQD). We have obtained convincing evidence for resonant tunnelling through individual {gamma}-valley-related electron states that we associate with the SAQD. The tunnel current through a SAQD was used as a local probe of a localized phase of a two-dimensional electron system in the accumulation layer of the diode. We have found evidence that at low densities, the localized electrons form relatively large, high-density clusters. (orig.)

  19. High-Pressure Hydrogen from First-Principles

    Science.gov (United States)

    Morales, Miguel A.

    2014-03-01

    The main approximations typically employed in first-principles simulations of high-pressure hydrogen are 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. MAM 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.

  20. Structural properties of BeO at high pressure

    Indian Academy of Sciences (India)

    Umesh Kumar Sakalle; Anita Singh; Ekta Sharma

    2014-10-01

    In the present paper, we have investigated the phase transition and elastic properties of BeO at high pressure using three-body potential model (TBPM). The present interaction potential consists of longrange coulomb and three-body interactions and short-range overlap repulsion effective up to second neighbour ions. We have studied the phase transition from wurtzite (4) to rock salt (1) for BeO. The phase transition pressure (t) obtained from this approach shows a respectably good agreement with experimental and other theoretical data. We have also computed the collapse of relative volume changes ( (t)/(0)). Three-body potential model has also been used to derive the correct expressions for third-order elastic constants and pressure derivatives of second-order elastic constants for BeO.

  1. HIGH PRESSURE COAL COMBUSTON KINETICS PROJECT

    Energy Technology Data Exchange (ETDEWEB)

    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

  2. High-pressure liquid chromatographic gradient mixer

    Science.gov (United States)

    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.

  3. High pressure liquid chromatographic gradient mixer

    Science.gov (United States)

    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".

  4. High pressure water jet injuries of the hand: Case report and review of the literature

    Directory of Open Access Journals (Sweden)

    Bilgen Can

    2013-12-01

    Full Text Available Internal and external injuries after high pressure water jet injuries are dispropotional. This situation refers to a misjudgement of vital injuries. Because of there is no approved treatment algorithm to evaluate this type of injuries, treatment and diagnosis are controversial. In our study we presented a patient with a high pressure water jet injury of 4th digit, to take attention of the general properties of this type of injuries with accompanied literature review. [Hand Microsurg 2013; 2(3.000: 125-127

  5. High pressure structural behavior of YGa{sub 2}: A combined experimental and theoretical study

    Energy Technology Data Exchange (ETDEWEB)

    Sekar, M., E-mail: sekarm@igcar.gov.in [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam-603102, Tamil Nadu (India); Shekar, N.V. Chandra [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam-603102, Tamil Nadu (India); Babu, R. [Chemical Group@, Indira Gandhi Centre for Atomic Research, Kalpakkam-603102, Tamil Nadu (India); Sahu, P. Ch. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam-603102, Tamil Nadu (India); Sinha, A.K.; Upadhyay, Anuj; Singh, M.N. [Indus Synchrotron Utilization Division, Raja Ramanna Center for Advanced Technology, Indore-452013 (India); Babu, K. Ramesh; Appalakondaiah, S.; Vaitheeswaran, G. [Advanced Centre for Research in High Energy Materials, University of Hyderabad, Gachibowli, Hyderabad-500046, Telangana (India); Kanchana, V. [Department of Physics, Indian Institute of Technology Hyderabad, Ordnance Factory Estate, Yeddumailaram-502 205, Telangana (India)

    2015-03-15

    High pressure structural stability studies were carried out on YGa{sub 2} (AlB{sub 2} type structure at NTP, space group P6/mmm) up to a pressure of ~35 GPa using both laboratory based rotating anode and synchrotron X-ray sources. An isostructural transition with reduced c/a ratio, was observed at ~6 GPa and above ~17.5 GPa, the compound transformed to orthorhombic structure. Bulk modulus B{sub 0} for the parent and high pressure phases were estimated using Birch–Murnaghan and modified Birch–Murnaghan equation of state. Electronic structure calculations based on projector augmented wave method confirms the experimentally observed two high pressure structural transitions. The calculations also reveal that the ‘Ga’ networks remains as two dimensional in the high pressure isostructural phase, whereas the orthorhombic phase involves three dimensional networks of ‘Ga’ atoms interconnected by strong covalent bonds. - Graphical abstract: High pressure X-ray diffraction patterns of YGa{sub 2} up to ~35 GPa shows an isostructural phase transition at ~5 GPa and transition to an orthorhombic structure ~14 GPa. - Highlights: • High pressure structural stability studies were carried out on YGa{sub 2} up to 35 GPa. • An isostructural transition with reduced c/a ratio was observed above 6 GPa. • Above 17.5 GPa, the compound transformed to orthorhombic structure. • PAW based electronic structure calculations have been carried out. • Calculations confirm the experimentally observed structural transitions.

  6. Simulation of High-Pressure Methane Hydrate Combustion

    Science.gov (United States)

    Popov, Pavel; Sirignano, William

    2015-11-01

    With its prevalence in ocean floor deposits, methane hydrate has recently attracted considerable attention in the combustion community. We present a new scheme for the simulation of methane hydrate combustion at high, near critical pressures. This process features a combination of solid, liquid and gas phases, wherein the solid methane hydrate melts into a bubbly liquid, which then evaporates into a gas phase; methane-air combustion occurs in the gas phase. In addition to its multiphase nature, this problem features the additional challenge of modelling the gas/liquid phase transition at near-critical pressures. A new computational procedure has been developed to simulate this problem, using a detailed chemical mechanism for the simulation of reaction in the gas phase, and featuring a volume-of-fluid (VOF) approach for the simulation of the liquid phase with gas bubbles - a low Stokes number is assumed. This procedure is applied to a laminar shear flow methane hydrate combustion problem. Particular attention is directed to the effects on simulation results of the high-pressure equation of state, liquid/gas phase transition modelling, and the bubbly liquid phase modelling. Simulation results are compared to experimental observations. Supported by AFOSR grant FA9550-12-1-0156, AFOSR scientific manager: Dr. Mitat Birkan.

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

    Science.gov (United States)

    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.

  8. Low temperature amorphization and superconductivity in FeSe single crystals at high pressures

    Energy Technology Data Exchange (ETDEWEB)

    Stemshorn, Andrew K.; Tsoi, Georgiy; Vohra, Yogesh K.; Sinogeiken, Stanislav; Wu, Phillip M.; Huang, Yilin; Rao, Sistla M.; Wu, Maw-Kuen; Yeh, Kuo W.; Weir, Samuel T. (IP-Taiwan); (UAB); (Duke); (LLNL)

    2010-08-04

    In this study, we report low temperature x-ray diffraction studies combined with electrical resistance measurements on single crystals of iron-based layered superconductor FeSe to a temperature of 10 K and a pressure of 44 GPa. The low temperature high pressure x-ray diffraction studies were performed using a synchrotron source and superconductivity at high pressure was studied using designer diamond anvils. At ambient temperature, the FeSe sample shows a phase transformation from a PbO-type tetragonal phase to a NiAs-type hexagonal phase at 10 {+-} 2 GPa. On cooling, a structural distortion from a PbO-type tetragonal phase to an orthorhombic Cmma phase is observed below 100 K. At a low temperature of 10 K, compression of the orthorhombic Cmma phase results in a gradual transformation to an amorphous phase above 15 GPa. The transformation to the amorphous phase is completed by 40 GPa at 10 K. A loss of superconductivity is observed in the amorphous phase and a dramatic change in the temperature behavior of electrical resistance indicates formation of a semiconducting state at high pressures and low temperatures. The formation of the amorphous phase is attributed to a kinetic hindrance to the growth of a hexagonal NiAs phase under high pressures and low temperatures.

  9. Stable Calcium Nitrides at Ambient and High Pressures.

    Science.gov (United States)

    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

  10. (Ultra high pressure homogenization for continuous high pressure sterilization of pumpable foods - a review

    Directory of Open Access Journals (Sweden)

    Erika eGeorget

    2014-08-01

    Full Text Available Bacterial spores have a strong resistance to both chemical and physical hurdles and create a risk for food industry which has been tackled by applying high thermal intensity treatments to sterilize food. These strong thermal treatments lead to reduction of the organoleptic and nutritional properties of food and alternative 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 (UHPH 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.

  11. New developments in high pressure x-ray spectroscopy beamline at High Pressure Collaborative Access Team

    International Nuclear Information System (INIS)

    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

  12. A new and improved strategy combining a dispersive-solid phase extraction-based multiclass method with ultra high pressure liquid chromatography for analysis of low molecular weight polyphenols in vegetables.

    Science.gov (United States)

    Silva, Catarina L; Haesen, Nathaly; Câmara, José S

    2012-10-19

    This paper reports on the development and optimization of a modified Quick, Easy, Cheap Effective, Rugged and Safe (QuEChERS) based extraction technique coupled with a clean-up dispersive-solid phase extraction (dSPE) as a new, reliable and powerful strategy to enhance the extraction efficiency of free low molecular-weight polyphenols in selected species of dietary vegetables. The process involves two simple steps. First, the homogenized samples are extracted and partitioned using an organic solvent and salt solution. Then, the supernatant is further extracted and cleaned using a dSPE technique. Final clear extracts of vegetables were concentrated under vacuum to near dryness and taken up into initial mobile phase (0.1% formic acid and 20% methanol). The separation and quantification of free low molecular weight polyphenols from the vegetable extracts was achieved by ultrahigh pressure liquid chromatography (UHPLC) equipped with a phodiode array (PDA) detection system and a Trifunctional High Strength Silica capillary analytical column (HSS T3), specially designed for polar compounds. The performance of the method was assessed by studying the selectivity, linear dynamic range, the limit of detection (LOD) and limit of quantification (LOQ), precision, trueness, and matrix effects. The validation parameters of the method showed satisfactory figures of merit. Good linearity (Rvalues2>0.954; (+)-catechin in carrot samples) was achieved at the studied concentration range. Reproducibility was better than 3%. Consistent recoveries of polyphenols ranging from 78.4 to 99.9% were observed when all target vegetable samples were spiked at two concentration levels, with relative standard deviations (RSDs, n=5) lower than 2.9%. The LODs and the LOQs ranged from 0.005 μg mL(-1) (trans-resveratrol, carrot) to 0.62 μg mL(-1) (syringic acid, garlic) and from 0.016 μg mL(-1) (trans-resveratrol, carrot) to 0.87 μg mL(-1) ((+)-catechin, carrot) depending on the compound. The method

  13. 常压及高压凝固Al-Mg及Al-Mg-Zn合金中Al相的固溶体结构%Solid solution structure of Al phase in Al-Mg and Al-Mg-Zn alloys solidifying under normal pressure and high pressure

    Institute of Scientific and Technical Information of China (English)

    王振玲; 张涛; 李莉; 周月波; 王宏伟; 魏尊杰

    2012-01-01

    采用X射线衍射仪、能谱仪和透射电镜分别对Al-9.6%Mg合金、Al- 11Mg-4.5Zn合金和Al- 17Zn- 1.5Mg合金常压及6 GPa高压凝固后Al相的固溶体结构进行研究.结果表明:6GPa高压凝固后,Al-9.6%Mg合金中Mg在Al相中的固溶度显著增大:在Al-11Mg-4.5Zn合金和Al- 17Zn- 1.5Mg合金中,Mg、Zn溶质在Al相中的固溶度均增大,但Zn比Mg固溶的比例要大得多.在常压凝固条件下,与纯铝相比,3种合金中Al相的晶格常数均增大.与常压凝固相比,高压凝固Al-9.6Mg合金和Al-11Mg-4.5Zn中Al相晶格常数分别增大了1.178%和0.220%;在Al- 17Zn- 1.5Mg合金中,Al相晶格常数变化很小.此外,在Al-Mg-Zn合金中,原子半径较大的Mg固溶到Al相中,导致其晶格常数增大,原子半径较小的Zn固溶到Al相中,导致其晶格常数减小,且高压凝固后,溶质的原子半径越小,在Al相中固溶的比例越大.%The solid solution structures of Al phases in Al-9.6%Mg, Al-llMg-4.5Zn andAl-17Zn-1.5Mg alloys solidified under normal pressure and high pressure were investigated using XRD, EDS and TEM. The results show that the solid solubility of Mg in Al phase in Al-9.6%Mg alloy increases remarkably, and those of Mg and Zn in Al phase in Al-llMg-4.5Zn and Al-17Zn-1.5Mg alloys increase, however, the proportion of Zn saturating in Al phase is much more than that of Mg. Under the condition of normal pressure solidification, the lattice constants of Al phases in three alloys have an increment comparing with that of pure Al. In contrast to normal pressure solidification, the lattice constants of Al phases in Al-9.6Mg alloy and AI-llMg-4.5Zn alloy solidifying at 6 GPa high pressure increase up to 1.178% and 0.220%, respectively. And the lattice constant of Al phase in AI-17Zn-1.5Mg alloy changes little. Furthermore, Mg with larger atomic radius saturating in Al phase leads to the increment of the lattice constant in Al-Mg-Zn alloy, and that of Zn with smaller atomic radium causes

  14. Theoretical design of diamondlike superhard structures at high pressure

    Science.gov (United States)

    Quan, Li; Wei-Tao, Zheng

    2016-07-01

    Diamond, as the hardest known material, has been widely used in industrial applications as abrasives, coatings, and cutting and polishing tools, but it is restricted by several shortcomings, e.g., its low thermal and chemical stability. Considerable efforts have been devoted to designing or synthesizing the diamond-like B-C-N-O compounds, which exhibit excellent mechanical property. In this paper, we review the recent theoretical design of diamond-like superhard structures at high pressure. In particular, the recently designed high symmetric phase of low-energy cubic BC3 meets the experimental observation, and clarifies the actual existence of cubic symmetric phase for the compounds formed by B-C-N-O system, besides the classical example of cubic boron nitride. Project supported by the National Natural Science Foundation of China (Grant Nos. 51202084, 11474125, and 51372095).

  15. High pressure research using muons at the Paul Scherrer Institute

    Science.gov (United States)

    Khasanov, R.; Guguchia, Z.; Maisuradze, A.; Andreica, D.; Elender, M.; Raselli, A.; Shermadini, Z.; Goko, T.; Knecht, F.; Morenzoni, E.; Amato, A.

    2016-04-01

    Pressure, together with temperature and magnetic field, is an important thermodynamical parameter in physics. Investigating the response of a compound or of a material to pressure allows to elucidate ground states, investigate their interplay and interactions and determine microscopic parameters. Pressure tuning is used to establish phase diagrams, study phase transitions and identify critical points. Muon spin rotation/relaxation (μSR) is now a standard technique making increasing significant contribution in condensed matter physics, material science research and other fields. In this review, we will discuss specific requirements and challenges to perform μSR experiments under pressure, introduce the high pressure muon facility at the Paul Scherrer Institute (PSI, Switzerland) and present selected results obtained by combining the sensitivity of the μSR technique with pressure.

  16. Theoretical design of diamondlike superhard structures at high pressure

    Institute of Scientific and Technical Information of China (English)

    李全; 郑伟涛

    2016-01-01

    Diamond, as the hardest known material, has been widely used in industrial applications as abrasives, coatings, and cutting and polishing tools, but it is restricted by several shortcomings, e.g., its low thermal and chemical stability. Con-siderable efforts have been devoted to designing or synthesizing the diamond-like B–C–N–O compounds, which exhibit excellent mechanical property. In this paper, we review the recent theoretical design of diamond-like superhard structures at high pressure. In particular, the recently designed high symmetric phase of low-energy cubic BC3 meets the experimental observation, and clarifies the actual existence of cubic symmetric phase for the compounds formed by B–C–N–O system, besides the classical example of cubic boron nitride.

  17. Synthesis of sodium polyhydrides at high pressures.

    Science.gov (United States)

    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

  18. Synthesis of sodium polyhydrides at high pressures

    Science.gov (United States)

    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.

  19. Synthesis of sodium polyhydrides at high pressures.

    Science.gov (United States)

    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.

  20. Urea and deuterium mixtures at high pressures

    Energy Technology Data Exchange (ETDEWEB)

    Donnelly, M., E-mail: m.donnelly-2@sms.ed.ac.uk; Husband, R. J.; Frantzana, A. D.; Loveday, J. S. [Centre for Science at Extreme Conditions and School of Physics and Astronomy, The University of Edinburgh, Erskine Williamson Building, Peter Guthrie Tait Road, The King’s Buildings, Edinburgh EH9 3FD (United Kingdom); Bull, C. L. [ISIS, Rutherford Appleton Laboratory, Oxford Harwell, Didcot OX11 0QX (United Kingdom); Klotz, S. [IMPMC, CNRS UMR 7590, Université P and M Curie, 4 Place Jussieu, 75252 Paris (France)

    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.

  1. High-pressure coal fuel processor development

    Energy Technology Data Exchange (ETDEWEB)

    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.

  2. Temperature-controlled ionic liquid dispersive liquid phase microextraction combined with ultra-high-pressure liquid chromatography for the rapid determination of triclosan,triclocarban and methyl-triclosan in aqueous samples

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    As extraction solvents,ionic liquids have green characteristics.In this study,an environmentally benign analytical method termed temperature-controlled ionic liquid dispersive liquid phase microextraction (TIL-DLME) combined with ultra-highpressure liquid chromatography (UHPLC)-tunable ultraviolet detection (TUV) was developed for the pre-concentration and determination of triclosan (TCS),triclocarban (TCC) and methyl-triclosan (M-TCS) in water samples.Significant parameters that may affect extraction efficiencies were examined and optimized,including the types and amount of ionic liquids,volume of the diluent,heating temperature,cooling time,salt effect and pH value.Under the optimum conditions,linearity of the method was observed in the ranges of 0.0100-100 μgL-1 for TCS and M-TCS,and 0.00500-50.0 μgL-1 for TCC with correlation coefficients (r2) > 0.9903.The limits of detection (LODs) ranged from 1.15 to 5.33 ngL-1.TCS in domestic water and TCC in reclaimed water were detected at the concentrations of 1.01 and 0.126 μgL-1,respectively.The spiked recoveries of the three target compounds in reclaimed water,irrigating water,waste water and domestic water samples were obtained in the ranges of 68.4%-71.9%,61.6%-87.8%,58.9%-74.9% and 64.9%-92.4%,respectively.Compared with the previous dispersive liquid-liquid microextraction method (DLLME) about the determination of TCS,TCC and M-TCS,this method is not only more environmentally friendly but also more sensitive.

  3. Novel and sensitive reversed-phase high-pressure liquid chromatography method with electrochemical detection for the simultaneous and fast determination of eight biogenic amines and metabolites in human brain tissue.

    Science.gov (United States)

    Van Dam, Debby; Vermeiren, Yannick; Aerts, Tony; De Deyn, Peter Paul

    2014-08-01

    A fast and simple RP-HPLC method with electrochemical detection (ECD) and ion pair chromatography was developed, optimized and validated in order to simultaneously determine eight different biogenic amines and metabolites in post-mortem human brain tissue in a single-run analytical approach. The compounds of interest are the indolamine serotonin (5-hydroxytryptamine, 5-HT), the catecholamines dopamine (DA) and (nor)epinephrine ((N)E), as well as their respective metabolites, i.e. 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), 5-hydroxy-3-indoleacetic acid (5-HIAA) and 3-methoxy-4-hydroxyphenylglycol (MHPG). A two-level fractional factorial experimental design was applied to study the effect of five experimental factors (i.e. the ion-pair counter concentration, the level of organic modifier, the pH of the mobile phase, the temperature of the column, and the voltage setting of the detector) on the chromatographic behaviour. The cross effect between the five quantitative factors and the capacity and separation factors of the analytes were then analysed using a Standard Least Squares model. The optimized method was fully validated according to the requirements of SFSTP (Société Française des Sciences et Techniques Pharmaceutiques). Our human brain tissue sample preparation procedure is straightforward and relatively short, which allows samples to be loaded onto the HPLC system within approximately 4h. Additionally, a high sample throughput was achieved after optimization due to a total runtime of maximally 40min per sample. The conditions and settings of the HPLC system were found to be accurate with high intra and inter-assay repeatability, recovery and accuracy rates. The robust analytical method results in very low detection limits and good separation for all of the eight biogenic amines and metabolites in this complex mixture of biological analytes. PMID:24857034

  4. High-pressure transformation in the cobalt spinel ferrites

    Energy Technology Data Exchange (ETDEWEB)

    Blasco, J., E-mail: jbc@posta.unizar.es [Instituto de Ciencia de Materiales de Aragón and Departamento de Física de la Materia Condensada, Consejo Superior de Investigaciones Científicas y Universidad de Zaragoza, 50009 Zaragoza (Spain); Subías, G.; García, J. [Instituto de Ciencia de Materiales de Aragón and Departamento de Física de la Materia Condensada, Consejo Superior de Investigaciones Científicas y Universidad de Zaragoza, 50009 Zaragoza (Spain); Popescu, C. [CELLS-ALBA Synchrotron Light Facility, Ctra. BP1413 km 3.3, 08290 Cerdanyola del Vallès, Barcelona (Spain); Cuartero, V. [European Synchrotron Radiation Facility, F-38043 Grenoble Cedex 9 (France)

    2015-01-15

    We report high pressure angle-dispersive x-ray diffraction measurements on Co{sub x}Fe{sub 3−x}O{sub 4} (x=1, 1.5, 1.75) spinels at room temperature up to 34 GPa. The three samples show a similar structural phase transformation from the cubic spinel structure to an analogous post-spinel phase at around 20 GPa. Spinel and post-spinel phases coexist in a wide pressure range (∼20–25 GPa) and the transformation is irreversible. The equation of state of the three cubic spinel ferrites was determined and our results agree with the data obtained in related oxide spinels showing the role of the pressure-transmitting medium for the accurate determination of the equation of state. Measurements releasing pressure revealed that the post-spinel phase is stable down to 4 GPa when it decomposes yielding a new phase with poor crystallinity. Later compression does not recover either the spinel or the post-spinel phases. This phase transformation induced by pressure explains the irreversible lost of the ferrimagnetic behavior reported in these spinels. - Graphical abstract: Pressure dependence of the unit cell volume per formula unit for Co{sub 1.5}Fe{sub 1.5}O{sub 4} spinel. Circles and squares stand for spinel and postspinel phases, respectively. Dark (open) symbols: determination upon compression (decompression). - Highlights: • The pressure induces similar phase transformation in Co{sub 3−x}Fe{sub x}O{sub 4} spinels (1≤x≤2). • The postspinel phases decompose after releasing pressure. • The irreversibility of this phase transformation explains the disappearance of magnetism in these spinels after applying pressure. • Accurate equation of state can be obtained up to 10 GPa using an alcohol mixture as pressure transmitting medium. • The equation of state suggests similar elastic properties for these spinels in this composition range.

  5. Novel High Pressure Pump-on-a-Chip Technology Project

    Data.gov (United States)

    National Aeronautics and Space Administration — HJ Science & Technology, Inc. proposes to develop a novel high pressure "pump-on-a-chip" (HPPOC) technology capable of generating high pressure and flow rate on...

  6. High-pressure stainless steel active membrane microvalves

    Science.gov (United States)

    Sharma, G.; Svensson, S.; Ogden, S.; Klintberg, L.; Hjort, K.

    2011-07-01

    In this work, high-pressure membrane microvalves have been designed, manufactured and evaluated. The valves were able to withstand back-pressures of 200 bar with a response time of less than 0.6 s. These stainless steel valves, manufactured with back-end batch production, utilize the large volume expansion coupled to the solid-liquid phase transition in paraffin wax. When membrane materials were evaluated, parylene coated stainless steel was found to be the best choice as compared to polydimethylsiloxane and polyimide. Also, the influence of the orifice placement and diameter is included in this work. If the orifice is placed too close to the rim of the membrane, the valve can stay sealed even after turning the power off, and the valve will not open until the pressure in the system is released. The developed steel valves, evaluated for both water and air, provide excellent properties in terms of mechanical stability, ease of fabrication, and low cost. Possible applications include sampling at high pressures, chemical microreactors, high performance liquid chromatography, pneumatics, and hydraulics.

  7. The Characteristics and Structure of High Pressure (1-42 bars) Gas Tungsten Arcs

    OpenAIRE

    Allum, C. J.

    1982-01-01

    The last decade has seen a considerable growth in the exploitation of deep sea mineral reserves. Accompanying these developments has come the need for suitable underwater repair and uainten-nce techniques. one such technique involves the use of fusion welding processes in localised dry high pressure environments created around weldments. Pressure chambers at Cranfield have been employed to simulate this sitiu. ation. These have been used to investigate the influence of ambie...

  8. Molecular effects of high-pressure processing on food studied by resonance Raman.

    Science.gov (United States)

    Tintchev, Filip; Wackerbarth, Hainer; Kuhlmann, Uwe; Toepfl, Stefan; Knorr, Dietrich; Hildebrandt, Peter; Heinz, Volker

    2010-02-01

    Pressurization may cause unwanted side effects including color or texture changes of fish and meat. The color changes of poultry, pork, and smoked salmon were studied by CIE L*, a*, b* system, and resonance Raman (RR). High-pressure processing (HPP) of pork and chicken meat resulted in significant color modification at pressures higher than 270 and 280 MPa, respectively. RR spectra were taken after a high-pressure treatment of pork meat. According to the RR-data, deoxymyoglobin is the dominating myoglobin species in pork meat. High-pressure treatment causes conformational changes resulting in a stabile nonnative ferrous myoglobin species while the ferrous myoglobin state is maintained. High-pressure treatment causes a decrease of the relative RR intensities of astaxanthin by salmon as probed with 514 nm. RR spectra excited at 413 nm revealed a heterogeneous broadening of astaxanthin bands accompanied by the formation of deoxymyoglobin or deoxyhemoglobin. The broadening is interpreted as the degradation products of astaxanthin. Obviously, the high-pressure treatment of smoked salmon triggers redox processes of astaxanthin and the heme protein.

  9. Reliability of BWR high pressure core cooling

    International Nuclear Information System (INIS)

    The high pressure coolant injection system (HPCI), and the reactor core isolation cooling system (RCIC) are steam turbine driven systems that can inject water into a boiling water reactor at full operating pressure. Their purpose is to supply water during any failure that allows water to be lost while the reactor is at pressure and temperature. A large number of BWR plants are not meeting HPCI and RCIC performance goals for core cooling. NSAC considers concurrent failure of NPCI and RCIC to be the most probable potential cause of low reactor water level and possibly fuel damage in a boiling water reactor. Between January 1978 and May 1981, 169 licensee event reports were filed where HPCI or RCIC was inoperable or was declared inoperable. The present effort has shown that at least 40% of NPCI and RCIC problems might be averted by a high quality preventive maintenance program. About half of the plants do not perform cold quick-start surveillance testing of HPCI and RCIC. They do perform routine startup tests, but the equipment is first preheated and the startup is relatively gentle. However, emergency start-ups are abrupt and from the cold condition. Therefore, cold quick-start testing is the only way to assure that all components, control systems, and instruments are functioning correctly for automatic safety initiation. (author)

  10. The high-pressure behavior of bloedite

    DEFF Research Database (Denmark)

    Comodi, Paola; Nazzareni, Sabrina; Balic Zunic, Tonci;

    2014-01-01

    High-pressure single-crystal synchrotron X‑ray diffraction was carried out on a single crystal of bloedite [Na2Mg(SO4)24H2O] compressed in a diamond-anvil cell. The volume-pressure data, collected up to 11.2 GPa, were fitted by a second- and a third-order Birch-Murnaghan equation of state (EOS......), yielding V0 = 495.6(7) Å3 with K0 = 39.9(6) GPa, and V0 = 496.9(7) Å3, with K0 = 36(1) GPa and K′ = 5.1 (4) GPa-1, respectively. The axial moduli were calculated using a Birch-Murnaghan EOS truncated at the second order, fixing K′ equal to 4, for a and b axes and a third-order Birch-Murnaghan EOS for c...... axis. The results were a0 = 11.08(1) and K0 = 56(3) GPa, b0 = 8.20(2) and K0 = 43(3) GPa, and c0 = 5.528(5), K0 = 40(2) GPa, K′ = 1.7(3) GPa-1. The values of the compressibility for a, b, and c axes are ba = 0.0060(3) GPa-1, bb = 0.0078(5) GPa-1, bc = 0.0083(4) GPa-1 with an anisotropic ratio of ba...

  11. Recent progress in high-pressure studies on organic conductors

    Directory of Open Access Journals (Sweden)

    Syuma Yasuzuka and Keizo Murata

    2009-01-01

    Full Text Available Recent high-pressure studies of organic conductors and superconductors are reviewed. The discovery of the highest Tc superconductivity among organics under high pressure has triggered the further progress of the high-pressure research. Owing to this finding, various organic conductors with the strong electron correlation were investigated under high pressures. This review includes the pressure techniques using the cubic anvil apparatus, as well as high-pressure studies of the organic conductors up to 10 GPa showing extraordinary temperature and pressure dependent transport phenomena.

  12. HIGH PRESSURE PHASE EQUILIBRIUM: PREDICTION OF ESSENTIAL OIL SOLUBILITY

    Directory of Open Access Journals (Sweden)

    Lúcio CARDOZO-FILHO

    1997-12-01

    Full Text Available This work describes a method to predict the solubility of essential oils in supercritical carbon dioxide. The method is based on the formulation proposed in 1979 by Asselineau, Bogdanic and Vidal. The Peng-Robinson and Soave-Redlich-Kwong cubic equations of state were used with the van der Waals mixing rules with two interaction parameters. Method validation was accomplished calculating orange essential oil solubility in pressurized carbon dioxide. The solubility of orange essential oil in carbon dioxide calculated at 308.15 K for pressures of 50 to 70 bar varied from 1.7± 0.1 to 3.6± 0.1 mg/g. For same the range of conditions, experimental solubility varied from 1.7± 0.1 to 3.6± 0.1 mg/g. Predicted values were not very sensitive to initial oil composition.Este trabalho descreve uma metodologia para o cálculo da solubilidade de óleos essenciais em dióxido de carbono a altas pressões baseada na formulação proposta em 1979 por Asselineau, Bogdanic e Vidal. Foram utilizadas as equações cúbicas de estado de Peng-Robinson e Soave-Redlich-Kwong com regras de mistura de van der Waals com dois parâmetros de interação. O cálculo da solubilidade do óleo essencial de laranja em dióxido de carbono pressurizado foi usado para validação do método. A solubilidade calculada a 308,15 K para pressões entre 50 e 70 bar variou entre 1,5 e 4,1 mg/g. Valores experimentais para as mesmas condições variam entre 1,7± 0.1 a 3,6± 0.1 mg/g. Os valores preditos não são muito sensíveis à composição inicial do óleo essencial.

  13. Microstructure and mechanical properties of an Al–Mg alloy solidified under high pressures

    International Nuclear Information System (INIS)

    Highlights: •Al–42.2Mg alloy was solidified under pressures of 1, 2, and 3 GPa and the microstructure analyzed. •A thermodynamic calculation of the Al–Mg phase diagram at high pressures was performed. •The phase content changes from predominantly γ-Al12Mg17 at 1 GPa to FCC solid solution at 3 GPa. •The β-Al3Mg2 is predicted to remain stable at low temperatures but is not observed. •The alloy solidified at high pressure has remarkably enhanced ultimate tensile strength. -- Abstract: Phase formation, the microstructure and its evolution, and the mechanical properties of an Al–42.2 at.% Mg alloy solidified under high pressures were investigated. After solidification at pressures of 1 GPa and 2 GPa, the main phase is the γ phase, richer in Al than in equilibrium condition. When the pressure is further increased to 3 GPa, the main phase is the supersaturated Al(Mg) solid solution with Mg solubility up to 41.6 at.%. Unlike in similar alloys solidified at ambient pressure, the β phase does not appear. Calculated high-pressure phase diagrams of the Al–Mg system show that although the stability range of the β phase is diminished with pressure, it is still thermodynamically stable at room temperature. Hence, the disappearance of the β phase is interpreted as kinetic suppression, due to the slow diffusion rate at high pressures, which inhibits solid–solid reactions. The Al–42.2 at.% Mg alloy solidified under 3 GPa has remarkably enhanced ultimate tensile strength compared to the alloy solidified under normal atmospheric pressure

  14. High pressure, high current, low inductance, high reliability sealed terminals

    Science.gov (United States)

    Hsu, John S [Oak Ridge, TN; McKeever, John W [Oak Ridge, TN

    2010-03-23

    The invention is a terminal assembly having a casing with at least one delivery tapered-cone conductor and at least one return tapered-cone conductor routed there-through. The delivery and return tapered-cone conductors are electrically isolated from each other and positioned in the annuluses of ordered concentric cones at an off-normal angle. The tapered cone conductor service can be AC phase conductors and DC link conductors. The center core has at least one service conduit of gate signal leads, diagnostic signal wires, and refrigerant tubing routed there-through. A seal material is in direct contact with the casing inner surface, the tapered-cone conductors, and the service conduits thereby hermetically filling the interstitial space in the casing interior core and center core. The assembly provides simultaneous high-current, high-pressure, low-inductance, and high-reliability service.

  15. In situ viscosity measurements of albite melt under high pressure

    CERN Document Server

    Funakoshi, K I; Terasaki, H

    2002-01-01

    The viscosities of albite (NaAlSi sub 3 O sub 8) melt under high pressures have been measured using an x-ray radiography falling sphere method with synchrotron radiation. This method has enabled us to determine the precise sinking velocity directly. Recent experiments of albite melt showed the presence of a viscosity minimum around 5 GPa (Poe et al 1997 Science 276 1245, Mori et al 2000 Earth Planet. Sci. Lett. 175 87). We present the results for albite melt up to 5.2 GPa at 1600 and 1700 deg. C. The viscosity minimum is clearly observed to be around 4.5 GPa, and it might be explained not by the change of the compression mechanism in albite melt but by change of the phase itself.

  16. Compaction and High-Pressure Response of Granular Tantalum Oxide

    Science.gov (United States)

    Vogler, Tracy; Root, Seth; Knudson, Marcus; Thornhill, Tom; Reinhart, William

    2015-06-01

    The dynamic behavior of nearly fully-dense and porous tantalum oxide (Ta2O5) is studied. Two particle morphologies are used to obtain two distinct initial tap densities, which correspond to approximately 40% and 15% of crystalline density. The response is characterized from low pressures, which result in incomplete compaction, to very high pressures where the thermal component of the EOS dominates. Issues related to a possible phase transformation along the Hugoniot and to establishing reasonable error bars on the experimental data will be discussed. The suitability of continuum and mesoscale models to capture the experimental results will be examined. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  17. High pressure/high temperature thermogravimetric apparatus. Final report

    Energy Technology Data Exchange (ETDEWEB)

    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.

  18. Cobalt ferrite nanoparticles under high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Saccone, F. D.; Ferrari, S.; Grinblat, F.; Bilovol, V. [Instituto de Tecnologías y Ciencias de la Ingeniería, “Ing. H. Fernández Long,” Av. Paseo Colón 850 (1063), Buenos Aires (Argentina); Errandonea, D., E-mail: daniel.errandonea@uv.es [Departamento de Fisica Aplicada, Institut Universitari de Ciència dels Materials, Universitat de Valencia, c/ Doctor Moliner 50, E-46100 Burjassot, Valencia (Spain); Agouram, S. [Departamento de Física Aplicada y Electromagnetismo, Universitat de València, 46100 Burjassot, Valencia (Spain)

    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.

  19. Experimental investigations of melting at ultra-high pressures and temperatures

    Science.gov (United States)

    Kavner, Abby

    The laser-heated diamond anvil cell is an important experimental tool used to access the high pressures and temperatures existing in the interior of the Earth and other planets. The ability to measure a temperature at high pressures is established, and the melting curves of elemental platinum and a complex aggregate, Allende meteorite, are determined. The melting curve of platinum was determined using a laser-heated diamond anvil cell in the pressure range of 12 to 70 GPa. The melting temperature at a given pressure is bracketed by a combination of visual observations and corresponding temperature measurements. The complete melting curve is built up from a series of melting experiments as a function of pressure, performed under different experimental conditions in the diamond cell; however, the placement of the phase boundary is inherently uncertain, due to an experimental "region of indifference" as the phase boundary is approached. To quantify the uncertainties, a statistical method using the logistic model is presented to provide best-fit phase boundaries to the platinum melting data, and can be generalized to fit phase boundary data of any sort. The high-pressure high-temperature phase diagram of Allende meteorite, a chondritic meteorite serving as a model of a primordial terrestrial planet, was investigated in the pressure and temperature ranges of 15 to 70 GPa and 1000 to 4000 K. The melting curve determined here overlaps and is in excellent agreement with previous piston-cylinder and multi-anvil measurements on the same material (Agee, et al., 1995). X-ray diffraction analysis of phases quenched from high pressure and temperature, and high pressure phases both before and after heating, are in good agreement with previous work. The phase diagram of Allende meteorite can be used to constrain events in the early geological evolution of the terrestrial planets.

  20. Stability of rutile-type TiO sub 2 under high pressure

    CERN Document Server

    Sasaki, T

    2002-01-01

    The high-pressure phases of TiO sub 2 have been investigated theoretically on the basis of first-principles density functional theory. Both the equation of states of the low-pressure phase and the structural phase transitions (the rutile-to-alpha-PbO sub 2 -type and alpha-PbO sub 2 -to-baddeleyite transitions) were successfully explained in agreement with previous experiments. The calculation suggests the possibility that the high-pressure phase next to the baddeleyite phase does not have the brookite structure, which has been observed in ZrO sub 2 and HfO sub 2. Furthermore, the stability of the low-pressure phases in TiO sub 2 was discussed on the basis of the atomic electronic structure.

  1. Performance of Structured Packing in High Pressure Distillation

    Institute of Scientific and Technical Information of China (English)

    张鹏; 刘春江; 等

    2002-01-01

    Performance of Mellapak 250Y and 350Y corrugated structured packing in distillation applications at pressures ranging from 0.3 to 2.0MPa is analysed by using HTU-NTU method.These data are obtained in distillation column with 0.15m diameter operated with n-butane/n-pentane system at total reflux.In considering the axial backmixing effects.the height of an overall gas phase transfer unit,HTUOG,is divided into two parts.One part represents the height of an overall gas phase transfer unit,without backmixing, designated as HUTOG,and the other part,designated as the height of a backmixing unit(HBUO),accounts for the backmixing effects.The HTUOG is evaluated from the measured concentration profile of n-butane in liquid phase.The HBUO obtained experimentally is correlated in terms of the properties of the materials being separated and the equivalent diameter of the structured packing.Our result shows that HBUO varies from 0.12 to 0.34m as pressure increases from 1.0 to 1.9MPa.It indicates that the overall efficiency of the structured packing decreas gradually at high pressure,as a result of the vapor backmixing.

  2. Dome-shaped magnetic order competing with high-temperature superconductivity at high pressures in FeSe.

    Science.gov (United States)

    Sun, J P; Matsuura, K; Ye, G Z; Mizukami, Y; Shimozawa, M; Matsubayashi, K; Yamashita, M; Watashige, T; Kasahara, S; Matsuda, Y; Yan, J-Q; Sales, B C; Uwatoko, Y; Cheng, J-G; Shibauchi, T

    2016-01-01

    The coexistence and competition between superconductivity and electronic orders, such as spin or charge density waves, have been a central issue in high transition-temperature (Tc) superconductors. Unlike other iron-based superconductors, FeSe exhibits nematic ordering without magnetism whose relationship with its superconductivity remains unclear. Moreover, a pressure-induced fourfold increase of Tc has been reported, which poses a profound mystery. Here we report high-pressure magnetotransport measurements in FeSe up to ∼15 GPa, which uncover the dome shape of magnetic phase superseding the nematic order. Above ∼6 GPa the sudden enhancement of superconductivity (Tc≤38.3 K) accompanies a suppression of magnetic order, demonstrating their competing nature with very similar energy scales. Above the magnetic dome, we find anomalous transport properties suggesting a possible pseudogap formation, whereas linear-in-temperature resistivity is observed in the normal states of the high-Tc phase above 6 GPa. The obtained phase diagram highlights unique features of FeSe among iron-based superconductors, but bears some resemblance to that of high-Tc cuprates. PMID:27431724

  3. Effects of high pressure on the microstructure and hardness of a Cu-Zn alloy

    Institute of Scientific and Technical Information of China (English)

    ZHAO Jun; LIU Lin; YANG Jingru; PENG Guirong; LIU Jianhua; ZHANG Ruijun; XING Guangzhong

    2008-01-01

    The microstructure of a Cu-Zn alloy treated under different high pressures was investigated by means of metallographic,scanning electron microscope (SEM),energy dispersive spectrometer (EDS),and X-ray diffraction (XRD),and the hardness of the Cu-Zn alloy was also measured.The results show that the a phase with a smaller grain size,different shapes,and random distribution appears in the Cu-Zn alloy during the solid-state phase transformation generation in the temperature range of 25-750℃ and the pressure range of 0-6 GPa.The amount of residual α phase in the microstructure decreases and then increases with increasing pressure.Under a high pressure of 3 GPa,the least volume fraction of residual α phase was obtained,and under a high pressure of 6 GPa,the changes of the microstructure of the Cu-Zn alloy were not obvious.In addition,high pressure can increase the hardness of the Cu-Zn alloy,but it cannot generate any new phase.

  4. In-situ high-pressure x-ray diffraction study of zinc ferrite nanoparticles

    Science.gov (United States)

    Ferrari, S.; Kumar, R. S.; Grinblat, F.; Aphesteguy, J. C.; Saccone, F. D.; Errandonea, D.

    2016-06-01

    We have studied the high-pressure structural behavior of zinc ferrite (ZnFe2O4) nanoparticles by powder X-ray diffraction measurements up to 47 GPa. We found that the cubic spinel structure of ZnFe2O4 remains up to 33 GPa and a phase transition is induced beyond this pressure. The high-pressure phase is indexed to an orthorhombic CaMn2O4-type structure. Upon decompression the low- and high-pressure phases coexist. The compressibility of both structures was also investigated. We have observed that the lattice parameters of the high-pressure phase behave anisotropically upon compression. Further, we predict possible phase transition around 55 GPa. For comparison, we also studied the compression behavior of magnetite (Fe3O4) nanoparticles by X-ray diffraction up to 23 GPa. Spinel-type ZnFe2O4 and Fe3O4 nanoparticles have a bulk modulus of 172 (20) GPa and 152 (9) GPa, respectively. This indicates that in both cases the nanoparticles do not undergo a Hall-Petch strengthening.

  5. Cyclic High Pressure Torsion of Nickel and Armco Iron

    OpenAIRE

    Wetscher, Florian; Pippan, Reinhard

    2006-01-01

    Abstract Cyclic high pressure torsion, a modified version of High Pressure Torsion, is applied to Armco-iron and nickel. The results in terms of microstructure and flow stress are compared to samples deformed by conventional high pressure torsion. For both processes and both materials, a saturation in the decrease of the structure size and the increase in the flow stress is observed. The minimum size of the structural elements which is obtainable is smallest for the conventionally ...

  6. Functional Sub-states by High-pressure Macromolecular Crystallography.

    Science.gov (United States)

    Dhaussy, Anne-Claire; Girard, Eric

    2015-01-01

    At the molecular level, high-pressure perturbation is of particular interest for biological studies as it allows trapping conformational substates. Moreover, within the context of high-pressure adaptation of deep-sea organisms, it allows to decipher the molecular determinants of piezophily. To provide an accurate description of structural changes produced by pressure in a macromolecular system, developments have been made to adapt macromolecular crystallography to high-pressure studies. The present chapter is an overview of results obtained so far using high-pressure macromolecular techniques, from nucleic acids to virus capsid through monomeric as well as multimeric proteins.

  7. Nanocomposite Thermolectric Materials by High Pressure Powder Consolidation Manufacturing Project

    Data.gov (United States)

    National Aeronautics and Space Administration — In response to NASA's need to develop advanced nanostructured thermolectric materials, UTRON is proposing an innovative high pressure powder consolidation...

  8. Stability of very-high pressure arc discharges against perturbations of the electron temperature

    Energy Technology Data Exchange (ETDEWEB)

    Benilov, M. S. [Departamento de Fisica, Ciencias Exactas e Engenharia, Universidade da Madeira, Largo do Municipio, Funchal 9000 (Portugal); Hechtfischer, U. [Philips Lighting, BU Automotive Lamps, Technology, Philipsstrasse 8, Aachen 52068 (Germany)

    2012-04-01

    We study the stability of the energy balance of the electron gas in very high-pressure plasmas against longitudinal perturbations, using a local dispersion analysis. After deriving a dispersion equation, we apply the model to a very high-pressure (100 bar) xenon plasma and find instability for electron temperatures, T{sub e}, in a window between 2400 K and 5500-7000 K x 10{sup 3} K, depending on the current density (10{sup 6}-10{sup 8} A/m{sup 2}). The instability can be traced back to the Joule heating of the electron gas being a growing function of T{sub e}, which is due to a rising dependence of the electron-atom collision frequency on T{sub e}. We then analyze the T{sub e} range occurring in very high-pressure xenon lamps and conclude that only the near-anode region exhibits T{sub e} sufficiently low for this instability to occur. Indeed, previous experiments have revealed that such lamps develop, under certain conditions, voltage oscillations accompanied by electromagnetic interference, and this instability has been pinned down to the plasma-anode interaction. A relation between the mechanisms of the considered instability and multiple anodic attachments of high-pressure arcs is discussed.

  9. Metal additive manufacturing of a high-pressure micro-pump

    NARCIS (Netherlands)

    Wits, Wessel W.; Weitkamp, Sander J.; Es, van J.

    2013-01-01

    For the thermal control of future space applications pumped two-phase loops are an essential part to handle the increasing thermal power densities. This study investigates the design of a reliable, leak tight, low-weight and high-pressure micro-pump for small satellite applications. The developed mi

  10. Progress in high pressure EDXD system and research at Beijing Synchrotron Radiation Facility

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The synchrotron radiation from a new wiggler of BEPC has been used to high pressure research. Upgraded DAC apparatus and EDXD system have been operated to determine the pressure-induced phase transition of materials at BSRF since June 1998. The improved performance of the system and the preliminary results of the research were described.

  11. Shock Effects and High Pressure Polymorphs in Polymict Eucrite Northwest Africa 10658

    Science.gov (United States)

    Fudge, C.; Wittmann, A.; Garvie, L. A. J.; Sharp, T. G.

    2016-08-01

    We report the presence of coesite in polymict eucrite NWA 10658. High pressure silica phases have previously been described to coexist with silica glass in the Béréba eucrite. We will present data from transmission electron microscope investigations.

  12. The Working Principle and Use of High Pressures in the Food Industry

    OpenAIRE

    Karlović, S.; Brnčić, M.; Ježek, D.; Tripalo, B.; Bosiljkov, T.

    2010-01-01

    High pressure in the food industry, as a new non-thermal method, is applied in many phases of food processing. This new non-thermal technology was developed in the 1990s. The main advantages of high-pressure processing are in the short time of processing which is between a few seconds and 30 minutes. Processing of solid or liquid food products with or without packaginghappens in the temperature interval 5 – 90 °C, and pressures 50 – 1000 MPa. The driving pressure is distributed uniformly thro...

  13. Synthesis and high-pressure electrical resistivity studies of Ti{sub 3}Al

    Energy Technology Data Exchange (ETDEWEB)

    Vennila, R. Selva [Department of Physics, Anna University, Chennai 600025 (India)]. E-mail: rsvennila@yahoo.co.in; Porchelvi, E. Elamurugu [Department of Physics, Anna University, Chennai 600025 (India); Joy, K.M. Freny [Department of Physics, Anna University, Chennai 600025 (India); Arun, T.K. Jaya [Department of Physics, Anna University, Chennai 600025 (India); Jaya, N. Victor [Department of Physics, Anna University, Chennai 600025 (India)

    2005-04-19

    Titanium aluminide (Ti{sub 3}Al) has been synthesized by a powder metallurgical method. X-ray diffraction studies show the formation of a single phase with hexagonal structure. Electrical resistivity studies were carried out by a four-probe technique both at high pressure and high temperature using a Bridgman Opposed Anvil High Pressure Device (OAHPD). The sample was studied up to a pressure and temperature of 10 GPa and 250 deg. C, respectively. The electrical resistivity is found to decrease with increasing pressure. The temperature effect causes an upward shift in the electrical resistivity in the range of pressure considered.

  14. High-pressure-induced structural changes, amorphization and molecule penetration in MFI microporous materials: a review.

    Science.gov (United States)

    Vezzalini, Giovanna; Arletti, Rossella; Quartieri, Simona

    2014-06-01

    This is a comparative study on the high-pressure behavior of microporous materials with an MFI framework type (i.e. natural mutinaite, ZSM-5 and the all-silica phase silicalite-1), based on in-situ experiments in which penetrating and non-penetrating pressure-transmitting media were used. Different pressure-induced phenomena and deformation mechanisms (e.g. pressure-induced over-hydration, pressure-induced amorphization) are discussed. The influence of framework and extra-framework composition and of the presence of silanol defects on the response to the high pressure of MFI-type zeolites is discussed. PMID:24892591

  15. Asymptotic analysis soot model for a high pressure common rail diesel engine

    Energy Technology Data Exchange (ETDEWEB)

    Qiu, Tao; Qi, Zhiquan; Yin, Wenhui; Liu, Yongfeng

    2010-07-01

    Polycyclic hydrocarbons (PAHs) are mainly responsible for the formation of soot but a more accurate model is needed. The aim of this paper is to present a temperature phase model to optimize calculation for high pressure common rail diesel engine. This new model was developed and implemented in KIVA code and then tested through simulations. Results showed that this new model better matches measured data than the original one increasing the accuracy by up to 50%. The model developed was proved to be an improvement compare to the original KIVA-3V model and it can be used to optimize calculations for high pressure common rail diesel engines.

  16. High-pressure processing for preservation of blood products

    NARCIS (Netherlands)

    Matser, A.M.; Ven, van der C.; Gouwerok, C.W.N.; Korte, de D.

    2005-01-01

    The possibilities of high pressure as a preservation method for human blood products were evaluated by examining the functional properties of blood fractions, after high-pressure processing at conditions which potentially inactivate micro-organisms and viruses. Blood platelets, red blood cells and b

  17. 76 FR 38697 - High Pressure Steel Cylinders From China

    Science.gov (United States)

    2011-07-01

    ..., 2011 (76 FR 28807). The conference was held in Washington, DC, on June 1, 2011, and all persons who... COMMISSION High Pressure Steel Cylinders From China Determinations On the basis of the record \\1\\ developed... injured by reason of imports from China of high pressure steel cylinders, provided for in subheading...

  18. 77 FR 37712 - High Pressure Steel Cylinders From China

    Science.gov (United States)

    2012-06-22

    ... Commission, Washington, DC, and by publishing the notice in the Federal Register on January 23, 2012 (77 FR... COMMISSION High Pressure Steel Cylinders From China Determinations On the basis of the record \\1\\ developed... imports of high pressure steel cylinders from China, provided for in subheading 7311.00.00 of...

  19. Determination of Vanillin from Tincture and Extract Products of Vanilla by Using Reversed Phase High Pressure Liquid Chromatography%反相高效液相色谱法检测香草兰豆酊、浸膏中香兰素

    Institute of Scientific and Technical Information of China (English)

    卢少芳; 初众; 赵建平

    2009-01-01

    采用反相高效液相色谱法测定香草兰豆酊、浸膏中香兰素含量,色谱柱为C_(18)柱,甲醇/0.5%冰乙酸水溶液(20/80.v/v)为流动相,等浓度洗脱,测定波长为280 nm,外标法定量.该方法相对标准偏差分别为0.28%和0.24%.加标回收率为97.89%~100.71%.本方法具有操作简便,结果准确等优点,特别适用于香草兰豆酊、浸膏等精深加工产品中香兰素含量的检测分析.%A simple, rapid and accurate method was developed for determination of vanillin by Reversed Phase High Pressure Liquid Chromatography. In this method chromatographic column was C18, mobile phase methanol/0.5% acetic acid (20/80, v/v), elution isocratic, wavelength 280nm, External Standard for quantification. With this method the relative standard deviation was 0.28% for detection of the samples of vanilla tincture and 0.24% for detection of the samples of vanilla extract, and the spike recovery rate ranged from 98.89% to 100.71%. This method is good for determination of vanillin from the well-processed vanilla tincture and the vanilla extract.

  20. Tertiary plate tectonics and high-pressure metamorphism in New Caledonia

    Science.gov (United States)

    Brothers, R.N.; Blake, M.C., Jr.

    1973-01-01

    The sialic basement of New Caledonia is a Permian-Jurassic greywacke sequence which was folded and metamorphosed to prehnite-pumpellyite or low-grade greenschist facies by the Late Jurassic. Succeeding Cretaceous-Eocene sediments unconformably overlie this basement and extend outwards onto oceanic crust. Tertiary tectonism occurred in three distinct phases. 1. (1) During the Late Eocene a nappe of peridotite was obducted onto southern New Caledonia from northeast to southwest, but without causing significant metamorphism in the underlying sialic rocks. 2. (2) Oligocene compressive thrust tectonics in the northern part of the island accompanied a major east-west subduction zone, at least 30 km wide, which is identified by an imbricate system of tectonically intruded melanges and by development of lawsonite-bearing assemblages in adjacent country rocks; this high-pressure mineralogy constituted a primary metamorphism for the Cretaceous-Eocene sedimentary pile, but was overprinted on the Mesozoic prehnite-pumpellyite metagreywackes. 3. (3) Post-Oligocene transcurrent faulting along a northwest-southeast line (the sillon) parallel to the west coast caused at least 150 km of dextral offset of the southwest frontal margin of the Eocene ultramafic nappe. At the present time, the tectonics of the southwest Pacific are related to a series of opposite facing subduction (Benioff) zones connected by transform faults extending from New Britain-Solomon Islands south through the New Hebrides to New Zealand and marking the boundary between the Australian and Pacific plates. Available geologic data from this region suggest that a similar geometry existed during the Tertiary and that the microcontinents of New Guinea, New Caledonia and New Zealand all lay along the former plate boundary which has since migrated north and east by a complex process of sea-floor spreading behind the active island arcs. ?? 1973.

  1. High-Pressure Oxygen Generation for Outpost EVA Study

    Science.gov (United States)

    Jeng, Frank F.; Conger, Bruce; Ewert, Michael K.; Anderson, Molly S.

    2009-01-01

    The amount of oxygen consumption for crew extravehicular activity (EVA) in future lunar exploration missions will be significant. Eight technologies to provide high pressure EVA O2 were investigated. They are: high pressure O2 storage, liquid oxygen (LOX) storage followed by vaporization, scavenging LOX from Lander followed by vaporization, LOX delivery followed by sorption compression, water electrolysis followed by compression, stand-alone high pressure water electrolyzer, Environmental Control and Life Support System (ECLSS) and Power Elements sharing a high pressure water electrolyzer, and ECLSS and In-Situ Resource Utilization (ISRU) Elements sharing a high pressure electrolyzer. A trade analysis was conducted comparing launch mass and equivalent system mass (ESM) of the eight technologies in open and closed ECLSS architectures. Technologies considered appropriate for the two architectures were selected and suggested for development.

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

    Science.gov (United States)

    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.

  3. Elasticity of stishovite at high pressure

    Science.gov (United States)

    Li, Baosheng; Rigden, Sally M.; Liebermann, Robert C.

    1996-08-01

    The elastic-wave velocities of stishovite, the rutile-structured polymorph of SiO 2, were measured to 3 GPa at room temperature in a piston cylinder apparatus using ultrasonic interferometry on polycrystalline samples. These polycrystalline samples (2-3 mm in length and diameter) were hot-pressed at 14 GPa and 1050°C in a 2000 ton uniaxial split-sphere apparatus (USSA-2000) using fused silica rods as starting material. They were characterized as low porosity (less than 1%), single phase, fine grained, free of cracks and preferred orientation, and acoustically isotropic by using density measurement, X-ray diffraction, scanning electron microscopy, and bench-top velocity measurements. On the basis of subsequent in situ X-ray diffraction study at high P and T on peak broadening on similar specimens, it is evident that the single crystal grains within these polycrystalline aggregates are well equilibrated and that these specimens are free of residual strain. P- and S-wave velocities measured at 1 atm are within 1.5% of the Hashin-Shtrikman bounds calculated from single-crystal elastic moduli. Measured pressure derivatives of the bulk and shear moduli, K' 0 = 5.3 ± 0.1 and G' 0 = 1.8 ± 0.1, are not unusual compared with values measured for other transition zone phases such as silicate spinel and majorite garnet. Isothermal compression curves calculated with the measured values of K0 and K' 0 agree well with experimental P-V data to 16 GPa. The experimental value of dG /dP is in excellent agreement with predictions based on elasticity systematics. Theoretical models are not yet able to replicate the measured values of K' 0 and G' 0.

  4. High-pressure studies on Tc and crystal structure of iron chalcogenide superconductors

    Directory of Open Access Journals (Sweden)

    Hiroki Takahashi, Takahiro Tomita, Hiroyuki Takahashi, Yoshikazu Mizuguchi, Yoshihiko Takano, Satoshi Nakano, Kazuyuki Matsubayashi and Yoshiya Uwatoko

    2012-01-01

    Full Text Available The superconducting transition temperature, Tc, in iron-based solids can be enhanced by applied pressure: Tc increases from 8 to 37 K for the 11-type FeSe when the pressure is raised from 0 to 4 GPa. High-pressure studies can elucidate the mechanism of superconductivity in such novel materials. In this paper, we present a high-pressure study of Fe(Se1−xTex and Fe(Se1−xSx. In the case of Fe(Se1−xTex, the maximum Tc under high pressure did not exceed the Tc of FeSe, which can be attributed to the structural transition to the monoclinic phase. For Fe(Se1−xSx (0 < x < 0.3, Tc exhibited a significant increase with pressure; however, the maximum Tc under high pressure did not exceed the Tc of FeSe. This may be due to the disorder induced by substituting S for Se, which is similar to the pressure effect on Tc for the 1111-type superconductor Ca(Fe1−xCoxAsF. The Tc of Fe(Se1−xSx showed a complex behavior below 1 GPa, first decreasing and then increasing with increasing pressure. From high-pressure x-ray diffraction measurements, the Tc (P curve was correlated with the local structural parameter.

  5. High-pressure powder x-ray diffraction study of EuVO{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Garg, Alka B. [High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, Maharashtra (India); Errandonea, D., E-mail: daniel.errandonea@uv.es [Departamento de Física Aplicada—ICMUV, MALTA Consolider Team, Universidad de Valencia, Edificio de Investigación, C/Dr. Moliner 50, Burjassot, 46100 Valencia (Spain)

    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.

  6. Metabolic Activity of Bacteria at High Pressure

    Science.gov (United States)

    Picard, A.; Daniel, I.; Oger, P.

    2008-12-01

    Over the last 20 years, there has been increasing evidence for the presence of a large number of microbes in the oceanic subsurface. Such a habitat has a very low energy input because it is deprived of light. A few meters below the sediment surface, conditions are already anoxic in most cases, sulfate reduction and/or methanogenesis becoming thus the primary respiratory reactions of organic matter. Neither the fate of methanogenesis, nor the fate of Dissimilatory Metal-Reduction (DMR) has been investigated so far as a function of pressure. For this reason, we measured experimentally the pressure limits of microbial anaerobic energetic metabolism. In practice, we measured in situ the kinetics of selenite respiration by the bacterial model Shewanella oneidensis MR-1 under high hydrostatic pressure (HHP) between 0 and 150 MPa at 30°C. MR-1 stationary-phase cells were used in Luria-Bertani (LB) medium amended with lactate as an additional electron donor and sodium selenite as an electron acceptor. In situ measurements were performed by X- ray Absorption Near-Edge Structure (XANES) spectroscopy in both a diamond-anvil cell and an autoclave. A red precipitate of amorphous Se(0) was virtually observed at any pressure to 150 MPa. A progressive reduction of selenite Se(IV) into selenium Se(0) was also observed in the evolution of XANES spectra with time. All kinetics between 0.1 and 150 MPa can be adjusted to a first order kinetic law. MR-1 respires all available selenite up to 60 MPa. Above 60 MPa, the respiration yield decreases linearly as a function of pressure and reaches 0 at 155 ±5 MPa. This indicates that selenite respiration by Shewanella oneidensis MR-1 stops at about 155 MPa, whereas its growth is arrested at 50 MPa. Hence, the present results show that the respiration of selenium by the strain MR-1 occurs efficiently up to 60 MPa and 30°C, i.e. from the surface of a continental sediment to an equivalent depth of about 2 km, or beneath a 5-km water column and

  7. High-Pressure Polymorph of NaBiO3.

    Science.gov (United States)

    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

  8. Production of nanograined intermetallics using high-pressure torsion

    Energy Technology Data Exchange (ETDEWEB)

    Alhamidi, Ali; Edalati, Kaveh; Horita, Zenji, E-mail: horita@zaiko.kyushu-u.ac.jp [Department of Materials Science and Engineering, Faculty of Engineering, Kyushu University, Fukuoka (Japan)

    2013-11-01

    Formation of intermetallics is generally feasible at high temperatures when the lattice diffusion is fast enough to form the ordered phases. This study shows that nanograined intermetallics are formed at a low temperature as 573 K in Al- 25 mol% Ni, Al- 50 mol.% Ni and Al- 50 mol% Ti powder mixtures through powder consolidation using high-pressure torsion (HPT). For the three compositions, the hardness gradually increases with straining but saturates to the levels as high as 550-920 Hv. In addition to the high hardness, the TiAl material exhibits high yield strength as {approx}3 GPa with good ductility as {approx}23%, when they are examined by micropillar compression tests. X-ray diffraction analysis and high-resolution transmission electron microscopy reveal that the significant increase in hardness and strength is due to the formation of nanograined intermetallics such as Al{sub 3}Ni, Al{sub 3}Ni{sub 2}, TiAl{sub 3}, TiAl{sub 2} and TiAl with average grain sizes of 20-40 nm (author)

  9. Synthesis of metal-nitrides using high pressures and temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Guillaume, C; Serghiou, G [University of Edinburgh, School of Engineering and Electronics, Kings Buildings, Mayfield Road, EH9 3JL UK (United Kingdom); Morniroli, J P [Laboratoire de Metallurgie Physique et Genie des Materiaux, UMR CNRS 8517, Universite des Sciences et Technologies de Lille et Ecole Nationale Superieure de Chimie de Lille, Cite Scientifique, 59655 Villeneuve d' Ascq Cedex (France); Frost, D J [Bayerisches Geoinstitut, Universitat Bayreuth, D-95440, Bayreuth (Germany)], E-mail: george.serghiou@ed.ac.uk

    2008-07-15

    Technologically, high density nitrides are showing promise for both ceramic and electronic applications. In a laser-heated diamond cell we prepare high density metal-nitrides by reaction of the nitrogen pressure medium with an elemental substrate. Two of our objectives are to develop criteria governing whether denser than ambient nitride phases will form, and to in particular establish the parameters required for synthesis in a multianvil press using elemental starting materials. We have already synthesized transition metal nitrides in a multianvil press using elemental starting materials, including hexagonal nickel nitride and alkali rhenium nitrides. Unlike previous metals, we also report that Cu does not form a nitride after heating with NaN{sub 3} at 2000 K and 20 GPa. Notably, Cu{sub 3}N is a semiconductor exhibiting weak directional bonds, whereas the immediately adjacent lower atomic number systems are metallic interstitial nitrides. We also briefly mention our work on processing high pressure and temperature recovered reaction products with focused ion beam methods for tailored characterization using electron microscopy.

  10. High-pressure transformations in sulfuric acid hydrates

    International Nuclear Information System (INIS)

    The Galilean moons of Jupiter; Io, Europa, Ganymede and Callisto, have surfaces that are composed of very different materials to the silicates that make up our Earth. For Europa and Ganymede, two moons under intense investigation from past and future space missions, their surfaces are made up of ice and hydrates. Despite the apparent ‘simplicity’ of these materials, we still observe very complex geological formations on these moons – including subduction. This means we need to understand the transformations of candidate surface materials under a range of pressure/temperature conditions in order to accurately explain the formations on these icy surfaces. One hydrate candidate material for the surfaces of these moons are sulfuric acid hydrates, formed from radolytic sulfur (from Io) reacting with the surface ice. Sulfuric acid hydrates have already been established to have a complex phase diagram with composition. We have now used the Mito cell at the PLANET instrument to undertake the first investigation of the high-pressure behavior of the water rich sulfuric acid hydrates. Compressing at 100 K and 180 K we see that the hemitriskaidekahydrate becomes the stable water-rich hydrate and observe some interesting relaxation behaviour in this material at pressure, which could have significant consequences for the interiors of Ganymede.

  11. High pressure behavior of 3d transition metal carbonates

    Science.gov (United States)

    Farfan, G. A.; Wang, S.; Boulard, E.; Mao, W. L.

    2012-12-01

    Understanding the behavior of carbon-rich phases in Earth's lower mantle is critical for modeling the global carbon cycle since the lower mantle may be the major repository for carbon in our planet. We were interested in the behavior of carbonates containing 3d transition metals, which can exhibit unusual properties at extreme conditions. Thus, we studied siderite (FeCO3) and rhodochrosite (MnCO3) at high pressure using a diamond anvil cell coupled with Raman spectroscopy, X-ray diffraction (XRD) and X-ray emission spectroscopy. In siderite we observed a high to low spin transition and associated volume collapse at approximately 46 GPa which is consistent with previous reports. Our Raman data show that the C-O bonds soften when the Fe2+ volume collapses (Farfan et al, 2012). In contrast, our XES results indicate that the Mn2+ in rhodochrosite does not undergo a spin transition like siderite up to 50 GPa. We observed a new Raman peak emerging above 48 GPa, which is a similar pressure at which a new structure was found in a previous XRD study.

  12. Experimental Survey of Microbial Survival at High Pressure

    Science.gov (United States)

    Griffin, P.; Kish, A.

    2008-12-01

    The magnitude and onset of lethal pressure effects varies widely even among closely related organisms. This variability complicates the prediction of a species' piezotolerance based on cellular physiology and native stress resistance. In this study several non-piezophilic species were cultured at optimal conditions to both mid log and stationary phases, exposed to elevated pressure for ten minutes, and plated upon return to ambient conditions to determine survival via colony count. The archaeal halophile Halobacterium strain NRC-1 exhibited almost full survival up to pressures of 400 MPa. Model organism Escherichia coli was used to establish a baseline for bacterial organisms but also displayed a bifurcated pressure response, with pressure-sensitive and -tolerant substrains residing within a single population . Pressure exposure proved slightly more lethal to the bacterial halophile Chromohalobacter salexigens than for E. coli up to a critical point of 300 MPa beyond which modest increases in pressure (~ 25 MPa) decreased survival by orders of magnitude. These survival data combined with a comparison of cellular physiology and native stress resistance provide some insight into which aspects of cellular function contribute to high pressure survival.

  13. Safety analysis of high pressure gasous fuel container punctures

    Energy Technology Data Exchange (ETDEWEB)

    Swain, M.R. [Univ. of Miami, Coral Gables, FL (United States)

    1995-09-01

    The following report is divided into two sections. The first section describes the results of ignitability tests of high pressure hydrogen and natural gas leaks. The volume of ignitable gases formed by leaking hydrogen or natural gas were measured. Leaking high pressure hydrogen produced a cone of ignitable gases with 28{degrees} included angle. Leaking high pressure methane produced a cone of ignitable gases with 20{degrees} included angle. Ignition of hydrogen produced larger overpressures than did natural gas. The largest overpressures produced by hydrogen were the same as overpressures produced by inflating a 11 inch child`s balloon until it burst.

  14. High-pressure compressibility and thermal expansion of aragonite

    Science.gov (United States)

    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

  15. Rapid identification of micro-constituents in monoammonium glycyrrhizinate raw materials by high-pressure solid phase extraction-high performance liquid chromatography-mass spectrometry%高压固相萃取-高效液相色谱-质谱法快速鉴定甘草酸单铵原料中的微量成分

    Institute of Scientific and Technical Information of China (English)

    杨学东; 唐绪岩; 桑琳

    2012-01-01

    Objective:To establish a method for rapid identification of micro-constituents in monoammonium glycyrrhizinate by high-pressure solid phase extraction-high performance liquid chromatography-mass spectrometry. Method; HPLC preparative chromato-graph was adopted for determining the optimal method for high-pressure solid phase extraction under optimal conditions. 5C18MS-II column (20. 0 mm x20. 0 mm) was used as the extraction column, with 35% acetonitrile-acetic acid solution (pH 2. 20) as eluent at the speed of 16 mL min~ . The sample size was 0. 5 mL, and the extraction cycle was 4. 5 min. Then, extract liquid was analyzed by high performance liquid chromatography-mass spectrometry ( HPLC-MS) after being concentrated by 100 times. Result: Under the optimal condition of high-pressure solid phase extraction-high performance liquid chromatography-mass spectrometry, 10 components were rapidly identified from monoammonium glycyrrhizinate raw materials. Among them, the chemical structures of six micro-constituents were identified as 3-O-[β-D-glucuronopyranosyl-β-D)-glucuronopyranosyl ] -30-O-β-D-apiopyranosylglycynhetic/3-O-[β-D)-glucuroriopy-ranosyl-β-D-glueuronopyranosyl] -30-O-β-D-arabinopyranosylglycyrrhetic, glycyrrhizic saponin F3 , 22-hydroxyglyeyrrhizin/18α-glycyr-rhizic saponin G2, 3-0-[β-D-rhamnopyranosyl]-24-hydroxyglycyrrhizin, glycyrrhizic saponin J2, and glycyrrhizic saponin B2 by MS" spectra analysis and reference to literatures. Four main chemical components were identified as glycyrrhizic saponin G2, 18β-glycyrrhi-zic acid, uralglycyrrhizic saponin B and 18α-glycyrrhizic acid by liquid chromatography, MSn and ultraviolet spectra information and comparison with reference substances. Conclusion: The method can be used to identify chemical constituents in monoammonium glycyrrhizinate quickly and effectively, without any reference substance, which provides basis for quality control and safe application of monoammonium glycyrrhizinate

  16. Studies on synthesis of diamond at high pressure and temperature

    Science.gov (United States)

    Kailath, Ansu J.

    chapter is a general introduction incorporating the information regarding diamond together with a brief history of diamond synthesis. It also includes the details of the high pressure synthesis of diamond, the uses of diamond grits, the advantages of the synthetic diamond grit over natural grit and an outline to elucidate the reasons which prompted to undertake the present work. The details of the technique used in the present studies for synthesis of diamond grits by high-pressure high-temperature process are included in chapter II. The hydraulic press used for synthesis, the details of the reactant materials, stacking of the high pressure cell and the details of synthesis run have been described together with the separation procedure to isolate diamond grits from the frozen slug. Different analytical and characterization techniques used in the present studies for the analysis and characterization of the reactant materials, synthesized diamonds and the crystallization medium have been illustrated in chapter III. The effect of different synthesizing parameters on synthesized diamond crystals were studied. This study includes: (a) dependence of yield of diamond on temperature and pressure, (b) dependence of crystal size on cook length, (c) effect of variation of the relative amounts of carbonaceous material and catalyst on synthesis, (d) morphological variation and (e) effect of pressure pulse on synthesized crystals. Various observations made during this study and the results obtained have been compiled in chapter IV. The synthesized diamond crystals were characterized by X-ray Powder Diffraction (XRD), Raman Spectroscopy, Scanning Electron Microscopy (SEM) and Optical Microscopy. The results obtained have been compiled in chapter V. In addition to these, the results obtained from the Infrared Spectra and the Electron Paramagnetic Spectra have also been included. Studies of crystallization medium and inclusions in the synthesized diamonds were carried out. This include

  17. High-pressure studies on molecular crystals-relations between structure and high-pressure behavior

    Energy Technology Data Exchange (ETDEWEB)

    Orgzall, Ingo [Institut fuer Duennschichttechnologie und Mikrosensorik e.V., Kantstrasse 55, D-14513 Teltow (Germany); Emmerling, Franziska [Bundesanstalt fuer Materialforschung und -pruefung, Richard-Willstaetter-Strasse 11, D-12489 Berlin (Germany); Schulz, Burkhard [Institut fuer Physik, Universitaet Potsdam, Am Neuen Palais 10, D-14469 Potsdam (Germany); Franco, Olga [Heinrich-Heine-Universitaet Duesseldorf, Institut fuer Physikalische Chemie II, Universitaetsstrasse 1, Gebaeude 26.42.02, D-40225 Duesseldorf (Germany)], E-mail: orgzall@uni-potsdam.de, E-mail: franziska.emmerling@bam.de, E-mail: buschu@uni-potsdam.de, E-mail: olga.franco@uni-duesseldorf.de

    2008-07-23

    This paper summarizes attempts to understand structure-property relationships for a large class of aromatic diphenyl-1,3,4-oxadiazole molecules. Starting from the investigation of the crystal structure several common packing motifs as well as characteristic differences are derived. Many different molecules show a rather planar conformation in the solid state. A stronger intermolecular twist is only observed for compounds with substituents occupying the ortho-positions of the phenyl rings. Most crystal structures are characterized by the formation of stacks leading to intense {pi}-{pi} acceptor-donor interactions between oxadiazole and phenyl rings. High-pressure investigations result in a soft compression behavior typical for organic molecular crystals. The bulk behavior may be described by the Murnaghan equation of state with similar coefficients (bulk modulus and its pressure derivative) for nearly all investigated compounds but also for related substances. The compression shows a strong anisotropy resulting from the specific features and packing motifs of the crystal structure. This is clearly indicated by a corresponding strain analysis. Additionally to the crystal structure the Raman spectrum was also investigated under increasing pressure. The different pressure behavior of external and internal modes reflects the difference between intra- and intermolecular interactions.

  18. High-pressure studies on molecular crystals-relations between structure and high-pressure behavior

    International Nuclear Information System (INIS)

    This paper summarizes attempts to understand structure-property relationships for a large class of aromatic diphenyl-1,3,4-oxadiazole molecules. Starting from the investigation of the crystal structure several common packing motifs as well as characteristic differences are derived. Many different molecules show a rather planar conformation in the solid state. A stronger intermolecular twist is only observed for compounds with substituents occupying the ortho-positions of the phenyl rings. Most crystal structures are characterized by the formation of stacks leading to intense π-π acceptor-donor interactions between oxadiazole and phenyl rings. High-pressure investigations result in a soft compression behavior typical for organic molecular crystals. The bulk behavior may be described by the Murnaghan equation of state with similar coefficients (bulk modulus and its pressure derivative) for nearly all investigated compounds but also for related substances. The compression shows a strong anisotropy resulting from the specific features and packing motifs of the crystal structure. This is clearly indicated by a corresponding strain analysis. Additionally to the crystal structure the Raman spectrum was also investigated under increasing pressure. The different pressure behavior of external and internal modes reflects the difference between intra- and intermolecular interactions

  19. Crystallographic and magnetic structure of HAVAR under high-pressure using diamond anvil cell (DAC)

    Energy Technology Data Exchange (ETDEWEB)

    Halevy, Itzhak, E-mail: halevyi@caltech.edu [Nuclear Research Center-Negev (Israel); Haroush, Shlomo [Soreq NRC, NRC Negev (Israel); Eisen, Yosef; Silberman, Ido; Moreno, Dany [Soreq NRC (Israel); Hen, Amir [Ben Gurion Univ., Department of Nuclear Engineering (Israel); Winterrose, Mike L. [Department of Materials Science California Institute of Technology (United States); Ghose, Sanjit; Chen Zhiqiang [Brookhaven National Laboratory, NSLS (United States)

    2010-04-15

    Annealed (H1) and cold-rolled (H2) HAVAR has been studied using high-pressure synchrotron X-ray diffraction. A structural phase transformation was discovered at {approx}13 GPa at ambient temperature, transforming from m - 3 m (S.G. 225) to P 63/m m c (S.G. 194) symmetry. The transition was not reversible on pressure release. The low-pressure cubic phase was found to be more compressible than the high-pressure hexagonal phase. Conventional Moessbauer and NFS shows that the HAVAR is not magnetic at room temperature and no splitting is observed. The SQUID indicates a huge difference in the temperature dependence of the magnetic susceptibility between the cold Rolled HAVAR compared to the annealed HAVAR.

  20. High-pressure vapor-liquid equilibrium data for CO2-orange peel oil

    Directory of Open Access Journals (Sweden)

    G.R. Stuart

    2000-06-01

    Full Text Available Recently, there has been a growing interest in fractionating orange peel oil by the use of supercritical carbon dioxide (SCCO2. However, progress in this area has been hindered by the lack of more comprehensive work concerning the phase equilibrium behavior of the SCCO2-orange peel oil system. In this context, the aim of this work is to provide new phase equilibrium data for this system over a wide range of temperatures and pressures, permitting the construction of coexistence PT-xy curves as well as the P-T diagram. The experiments were performed in a high-pressure variable-volume view cell in the temperature range of 50-70ºC from 70 to 135 atm and in the CO2 mass fraction composition range of 0.35-0.98. Based on the experimental phase equilibrium results, appropriate operating conditions can be set for high-pressure fractionation purposes.

  1. A high pressure distorted α-uranium ( Pnma) structure in plutonium

    Science.gov (United States)

    Sikka, S. K.

    2005-01-01

    Under pressure many rare earths and actinide metals transform to α-U type structure or its lower symmetry distorted forms. We have reinterpreted the diffraction data of Dabos et al. for Pu [S. Dabos et al. J. Alloys Compd. 190 (1993) 237] and find that an Am IV type distorted α-U structure in Pnma space group can explain its high pressure phase. The structures of both the high pressure Am IV type phase and α-Pu, the 0.1 MPa phase, are shown to have a distorted hcp topology. The upturn in the atomic volume of Pu at 0.1 MPa can also be rationalized on the basis of this proposal.

  2. Metallization and Hall-effect of Mg{sub 2}Ge under high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yuqiang [State Key Laboratory of Superhard Materials, Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012 (China); Tianjin Key Laboratory of Advanced Electrical Engineering and Energy Technology, School of Electrical Engineering and Automation, Tianjin Polytechnic University, Tianjin 300387 (China); Department of Mechanical Engineering, Texas Tech University, Lubbock, Texas 79409 (United States); Gao, Yang [State Key Laboratory of Superhard Materials, Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012 (China); Department of Mechanical Engineering, Texas Tech University, Lubbock, Texas 79409 (United States); Han, Yonghao, E-mail: hanyh@jlu.edu.cn; Liu, Cailong; Peng, Gang; Ke, Feng; Gao, Chunxiao [State Key Laboratory of Superhard Materials, Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012 (China); Wang, Qinglin [State Key Laboratory of Superhard Materials, Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012 (China); Center for High Pressure Science and Technology Advanced Research, Changchun 130012 (China); Ma, Yanzhang [Department of Mechanical Engineering, Texas Tech University, Lubbock, Texas 79409 (United States)

    2015-10-05

    The electrical transport properties of Mg{sub 2}Ge under high pressure were studied with the in situ temperature-dependent resistivity and Hall-effect measurements. The theoretically predicted metallization of Mg{sub 2}Ge was definitely found around 7.4 GPa by the temperature-dependent resistivity measurement. Other two pressure-induced structural phase transitions were also reflected by the measurements. Hall-effect measurement showed that the dominant charge carrier in the metallic Mg{sub 2}Ge was hole, indicating the “bad metal” nature of Mg{sub 2}Ge. The Hall mobility and charge carrier concentration results pointed out that the electrical transport behavior in the antifluorite phase was controlled by the increase quantity of drifting electrons under high pressure, but in both anticotunnite and Ni{sub 2}In-type phases it was governed by the Hall mobility.

  3. The high pressure gas Cerenkov counter at the Omega Facility.

    CERN Multimedia

    1975-01-01

    The high-pressure gas Cerenkov was used to measure reactions as pion (or kaon)- hydrogen --> forward proton - X. It was built by the Ecole Polytechnique (Palaiseu). Here Peter Sonderegger and Patrick Fleury,

  4. Novel High Pressure Pump-on-a-Chip Technology Project

    Data.gov (United States)

    National Aeronautics and Space Administration — HJ Science & Technology, Inc proposes to develop a novel high pressure "pump-on-a-chip" and "valve-on-a-chip" microfluidic technology for NASA planetary science...

  5. Development of high pressure gas cells at ISIS

    Science.gov (United States)

    Kirichek, O.; Done, R.; Goodway, C. M.; Kibble, M. G.; Evans, B.; Bowden, Z. A.

    2012-02-01

    High-pressure research is one of the fastest-growing areas of natural science, and one that attracts as diverse communities as those of physics, bio-physics, chemistry, materials science and earth science. In condensed matter physics there are a number of highly topical areas, such as quantum criticality, pressure-induced superconductivity or non-Fermi liquid behaviour, where pressure is a fundamental parameter. Reliable, safe and user-friendly high pressure gas handling systems with gas pressures up to 1GPa should make a significant impact on the range of science possible. The ISIS facility is participating in the NMI3 FP7 sample environment project supported by the European Commission which includes high pressure gas cell development. In this paper the progress in designing, manufacturing and testing a new generation of high pressure gas cells for neutron scattering experiments is discussed.

  6. High pressure processing reaches the U.S. market

    International Nuclear Information System (INIS)

    The first food product commercially produced by a U.S. company using high-pressure processing has had successful test market results. High-pressure processing permits food to be preserved by subjecting it to pressures in the range of 60,000-100,000 psi for a short time instead of exposing the food to heat, freezing, chemicals, or irradiation. To produce Classic Guacamole, Avomex of Keller, Texas, uses a batch isostatic press to deactivate the enzymes in the avocado and to kill bacteria, obtaining a refrigerated shelf life of over 30 days. The guacamole is then vacuum packed and processed again. The product undergoes no heat treatment and does not contain preservatives, and the high pressure does not affect its texture, color, or taste. Meanwhile, a continuous system for high-pressure processing of pumpable foods is currently being developed by Flow International of Kent, Washington, and will be used for testing and applications work at Oregon State University

  7. Beam steering effects in turbulent high pressure flames

    Energy Technology Data Exchange (ETDEWEB)

    Hemmerling, B.; Kaeppeli, B. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-06-01

    The propagation of a laser beam through a flame is influenced by variations of the optical density. Especially in turbulent high pressure flames this may seriously limit the use of laser diagnostic methods. (author) 1 fig., 2 refs.

  8. High pressure structures of "111" type iron-based superconductors predicted from first-principles.

    Science.gov (United States)

    Zhang, Xinxin; Wang, Yanchao; Ma, Yanming

    2012-11-21

    The high-pressure crystal structures of the "111" type iron-based superconductors: NaFeAs, LiFeP and LiFeAs have been systematically explored by using particle-swarm structural searches. It was found that though these iron-based superconductors are chemically similar, they adopted distinct structural phase transitions: P4/nmm→Cmcm→P3m1 for NaFeAs, P4/nmm→Cmcm→I4mm for LiFeP, and P4/nmm→P3m1 →I4mm→P6(3)/mmc for LiFeAs under high pressure. The high pressure orthorhombic Cmcm phase preserved the structural features of FeX(4)(X = As, P) tetrahedral layers present in the ambient-pressure P4/nmm structure. However, the FeX(4) tetrahedrons in the Cmcm phase were clearly distorted, leading to changes in the electronic behavior around the Fermi level. Under higher pressures, the FeX(4) layered structural features were no longer persistent and three-dimensional crystal structures were stabilized in other P3m1, I4mm, and P6(3)/mmc phases, which featured FeAs(5)/FeAs(6) hexahedron and octahedrons, FeX(5) tetragonal pyramids, and FeAs(6) octahedrons, respectively. Analysis of the electronic density of states suggests that most of the high pressure phases are metallic except for the tetragonal I4mm phase, which possesses a narrow band gap. This semiconducting state might relate to the tetragonal pyramid structure formed by FeX(5) unit, which might be favorable for charge localization.

  9. The Working Principle and Use of High Pressures in the Food Industry

    Directory of Open Access Journals (Sweden)

    Karlović, S.

    2010-11-01

    Full Text Available High pressure in the food industry, as a new non-thermal method, is applied in many phases of food processing. This new non-thermal technology was developed in the 1990s. The main advantages of high-pressure processing are in the short time of processing which is between a few seconds and 30 minutes. Processing of solid or liquid food products with or without packaginghappens in the temperature interval 5 – 90 °C, and pressures 50 – 1000 MPa. The driving pressure is distributed uniformly through the whole product independently of its quantity and shape. These processing characteristics combined with improved food microbiological safety, less energy expenditure, low concentration of waste products and longer shelf life make high-pressure processing a very promising novel food technology. Combined with lower cost of treatment (but unfortunately higher initial cost of equipment compared to traditional processing technologies, it is also economically profitable. The main purpose of such treated food products are in preservation of sensory, nutritive and textural properties. As the temperature increase is very low, there are no significant changes in sensory properties, in contrast to conventional thermal processing (sterilization, pasteurization. However, with the combination of heating or cooling and high pressure, modification of existing and creation of new food products is possible. Today, high pressure is used for the treatment of meat products (inactivation of microorganisms, freezing and defrosting of foodstuffs, production of fruit juices (pasteurization, processing of oysters, modificationof milk characteristics (foaming etc. The main purpose of this work is to present the working principle and application of high pressure in the food industry.

  10. Highly crystallized poly (lactic acid) under high pressure

    OpenAIRE

    Jin Zhang; Ding-Xiang Yan; Jia-Zhuang Xu; Hua-Dong Huang; Jun Lei; Zhong-Ming Li

    2012-01-01

    Biodegradable poly (lactic acid) (PLA) usually has a crystallinity less than 10% due to its poor crystallization ability. In this work, we found high pressure could significantly facilitate formation of crystallites of PLA, resulting in a crystallinity high up to 66.3% at pressure and temperature of 300 MPa and 185 ºC. High-pressure induced crystalline reorganization and lamellar thickening led to two melting temperatures in the highly crystallized PLA but without cold crystallization compare...

  11. A Generalized Equation of State for High-Pressure Liquids

    Institute of Scientific and Technical Information of China (English)

    LIANG Yan-bo; TONG Jing-shan

    2005-01-01

    An equation of state (EOS) for high-pressure liquids, I.e., Tait EOS, is deduced according to isothermal compressibility KT=-1/V·((а)V/(а)p)T·.Based on the equation, a generalized EOS for high pressure-liquids is established by using the reduced state principle and introducing a characteristic parameter-configuration factorξ.Reasonably satisfactory P-V-T data for many organic compounds, including some polar components, were calculated by using the equation.

  12. High pressure dielectric studies on the structural and orientational glass

    Science.gov (United States)

    Kaminska, E.; Tarnacka, M.; Jurkiewicz, K.; Kaminski, K.; Paluch, M.

    2016-02-01

    High pressure dielectric studies on the H-bonded liquid d-glucose and Orientationally Disordered Crystal (ODIC) 1,6-anhydro-d-glucose (levoglucosan) were carried out. It was shown that in both compounds, the structural relaxation is weakly sensitive to compression. It is well reflected in the low pressure coefficient of the glass transition and orientational glass transition temperatures which is equal to 60 K/GPa for both d-glucose and 1,6-anhydro-d-glucose. Although it should be noted that ∂ Tg 0 / ∂ p evaluated for the latter compound seems to be enormously high with respect to other systems forming ODIC phase. We also found that the shape of the α-loss peak stays constant for the given relaxation time independently on the thermodynamic condition. Consequently, the Time Temperature Pressure (TTP) rule is satisfied. This experimental finding seems to be quite intriguing since the TTP rule was shown to work well in the van der Waals liquids, while in the strongly associating compounds, it is very often violated. We have also demonstrated that the sensitivity of the structural relaxation process to the temperature change measured by the steepness index (mp) drops with pressure. Interestingly, this change is much more significant in the case of d-glucose with respect to levoglucosan, where the fragility changes only slightly with compression. Finally, kinetics of ODIC-crystal phase transition was studied at high compression. It is worth mentioning that in the recent paper, Tombari and Johari [J. Chem. Phys. 142, 104501 (2015)] have shown that ODIC phase in 1,6-anhydro-d-glucose is stable in the wide range of temperatures and there is no tendency to form more ordered phase at ambient pressure. On the other hand, our isochronal measurements performed at varying thermodynamic conditions indicated unquestionably that the application of pressure favors solid (ODIC)-solid (crystal) transition in 1,6-anhydro-d-glucose. This result mimics the impact of pressure on the

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

    Science.gov (United States)

    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.

  14. Advances and synergy of high pressure sciences at synchrotron sources

    International Nuclear Information System (INIS)

    Introductory overview to the special issue papers on high-pressure sciences and synchrotron radiation. High-pressure research in geosciences, materials science and condensed matter physics at synchrotron sources is experiencing growth and development through synergistic efforts around the world. A series of high-pressure science workshops were organized in 2008 to highlight these developments. One of these workshops, on 'Advances in high-pressure science using synchrotron X-rays', was held at the National Synchrotron Light Source (NSLS), Brookhaven National Laboratory, USA, on 4 October 2008. This workshop was organized in honour of Drs Jingzhu Hu and Quanzhong Guo in celebration of their retirement after up to 18 years of dedicated service to the high-pressure community as beamline scientists at X17 of NSLS. Following this celebration of the often unheralded role of the beamline scientist, a special issue of the Journal of Synchrotron Radiation on Advances and Synergy of High-Pressure Sciences at Synchrotron Sources was proposed, and we were pleased to invite contributions from colleagues who participated in the workshop as well as others who are making similar efforts at synchrotron sources worldwide.

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

    Science.gov (United States)

    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

  16. High-pressure crystallography of periodic and aperiodic crystals

    Directory of Open Access Journals (Sweden)

    Clivia Hejny

    2015-03-01

    Full Text Available 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.

  17. A new high-pressure research facility at the Australian Synchrotron

    Science.gov (United States)

    Clark, S.; Rushmer, T. A.; Glover, C.; Turner, S.; Garrett, R.; Wang, Y.

    2012-12-01

    The development of large volume, multi-anvil experimental techniques in the United States and their use with synchrotron sources has brought new technology to the experimental community. These facilities have allowed us to significantly improve our understanding of the physical properties of Earth and planetary materials under high pressures and temperatures. In 2011-2012, this technology is being brought to the Australian Synchrotron, and will provide the Australian scientific community an opportunity to significantly improve understanding of materials under extreme conditions. The high-pressure deformation system located at the Australian Synchrotron is comprised of a D-DIA deformation apparatus and a 250T hydraulic press together with the necessary x-ray definition and detection systems. The development of a synchrotron-based, high-pressure and temperature deformation facility is an exciting new opportunity and a major advance in experimental capability for Australia. We will build into the facility a unique addition, the accompanying AC conductivity system that will allow conductivity measurements at the same time as x-ray diffraction and imaging. This is important for the projects where interconnectivity of fluids is being investigated; as it will provide us with an in-situ measure of melt connectivity. In this presentation we will describe the new facility, include details of installation and commissioning progress and outline the initial science program.

  18. Potassium-Rich Ices at High Pressures and Temperatures

    Science.gov (United States)

    Frank, M. R.; Scott, H. P.; Aarestad, E.; Prakapenka, V.

    2014-12-01

    Accurate modeling of planetary interiors requires that the pressure-volume-temperature properties of phases present within the body be well understood. The high-pressure polymorphs of H2O have been studied extensively, due to the abundance of ice phases in icy moons and likely vast number of extra-solar planetary bodies, with only select studies evaluating impurity-laden ices. In this study, ice formed from a 1.6 mole percent KCl-bearing aqueous solution was studied up to 33 GPa and 650 K, and the incorporation of K+ and Cl- into the ice VII structure was documented. The compression data at 300 K were fit with a third order Birch-Murnaghan equation of state and yielded K, K/, and V0 of 24.7±0.9 GPa, 4.44±0.09, and 39.17±0.15 Å3, respectively. Thermal expansion coefficients were also determined for several isothermal compression curves at elevated temperatures, and a P-V-T equation of state will be presented. The melting of ice VII with incorporated K+ and Cl- was determined up to 625 K and 10.6 GPa and was fit by using a Simon-Glatzel equation. The melting curve is systematically depressed relative to the melting curve of pure H2O by approximately 45 K and 80 K at 4 and 11 GPa, respectively. Interestingly, a portion of the K+ and Cl- contained within the ice VII structure was observed to exsolve with increasing temperature and pressure. This suggests that an internal differentiating process could concentrate a K-rich phase deep within H2O-rich planets, and we speculate that this could supply an additional source of heat through the radioactive decay of 40K. Birch (1951; JGR, 56, 107-126) has estimated that 40K contributes 2.7 μcal/g.year for each wt.% of K, and our results suggest at least 3.33 wt.% can be incorporated into the structure of ice VII, thus making it a source of heat rather than just a conductive layer. In conclusion, our data illustrate a mechanism that may concentrate K at depth and impact the supposed pressure and temperature within moderate

  19. Novel high pressure structures and superconductivity of niobium disulfide

    International Nuclear Information System (INIS)

    Highlights: • At 26 GPa, NbS2 transits from the 2H structure to the novel I4/mmm structure. • The Nb and S atoms forms a new [NbS8] hexahedron unit in the I4/mmm-NbS2. • The I4/mmm-NbS2 exhibits a higher Tc than 2H-NbS2. • The higher Tc is resulted from the stronger electron–phonon coupling coefficients. - Abstract: We have investigated the pressure-induced phase transition and superconducting properties of niobium disulfide (NbS2) based on the density functional theory. The structures of NbS2 at pressures from 0 to 200 GPa were predicted using the multi-algorithm collaborative (MAC) structure prediction technique. The previously known 1T-, 2H-, and 3R-NbS2 were successfully reproduced. In addition, many metastable structures which are potential to be synthesized were also discovered. Based on the enthalpy calculations, we found that at 26 GPa NbS2 transits from the double-hexagonal (2H) structure to the tetragonal I4/mmm structure with a 10.6% volume reduction. The calculated elastic constants and phonon dispersion curves of I4/mmm-NbS2 confirm its mechanical and dynamical stability at high pressure. More interestingly, the coordination number of Nb in I4/mmm structure is eight which is larger than that in the traditional metal dichalcogenides, indicating a new type of bondings of Nb and S atoms. In the new Nb–S bondings, one Nb atom and neighboring eight S atoms form a [NbS8] hexahedron unit. Furthermore, I4/mmm-NbS2 exhibits a higher superconducting critical temperature than 2H-NbS2, as is resulted from the stronger electron–phonon coupling coefficients

  20. Effect of high pressure on microstructure of crystallizing amorphous Nd9Fe85B6 alloy

    Institute of Scientific and Technical Information of China (English)

    WU Wei; LI Hui; XIE Yanwu; ZHANG Xiangyi

    2008-01-01

    The effect of high pressure on the microstructure of annealed amorphous NdgFegsB6 alloy was studied. It was found that applica- tion of high pressure made the microstructure of the crystallized alloy much more homogeneous. The average grain size of the Nd2Fe14B phase decreased with the increase of pressure, whereas, the size of the α-Fe first increased when a pressure of 1 Gpa was applied and then decreased with further increase of pressure. Pressure-induced (410) texture of the Nd2Fe14B phase was also observed. The present study sug-gested an effective route for controlling the microstructure in a nanoscale solid.

  1. Operational life improvement of SSME high-pressure turbopumps. [Space Shuttle Main Engine

    Science.gov (United States)

    Hale, J. R.; Wood, B. K.

    1985-01-01

    The current Space Shuttle Main Engine (SSME) Phase I engine demonstrated excellent flight performance but showed limited operational life of the high-pressure fuel turbopumps (HPFTP). Design improvements, supporting analyses, and test results of the SSME Phase II development program are presented. The HPFTP improvements include reduction of turbine operating temperature by 110 to 130 R by reconstructing the seals and the flow contours; modifications of the first- and second-stage turbine blades by recontouring the shank, shotpeening the shank surface, and applying a multilayered, plasma-spray coating to the shank on the downstream side to reduce the effect of the disk coolant; and reduction of the tendency for thermal cracks in the turbine by changing weld configuration to avoid the concentration of stresses in local areas. The high-pressure oxidizer turbopump has been also modified to improve bearing life and to eliminate subsynchronous whirl.

  2. High-pressure synthesis of mesoporous stishovite: potential applications in mineral physics

    Science.gov (United States)

    Stagno, Vincenzo; Mandal, Manik; Landskron, Kai; Fei, Yingwei

    2015-06-01

    Recently, we have described a successful synthesis route to obtain mesoporous quartz and its high-pressure polymorph coesite by nanocasting at high pressure using periodic mesostructured precursors, such as SBA-16 and FDU-12/carbon composite as starting materials. Periodic mesoporous high-pressure silica polymorphs are of particular interest as they combine transport properties and physical properties such as hardness that potentially enable the industrial use of these materials. In addition, synthesis of mesoporous crystalline silica phases can allow more detailed geology-related studies such as water/mineral interaction, dissolution/crystallization rate and the surface contribution to the associated thermodynamic stability (free energy and enthalpy) of the various polymorphs and their crossover. Here, we present results of synthesis of mesoporous stishovite from cubic large-pore periodic mesoporous silica LP-FDU-12/C composite as precursor with an fcc lattice. We describe the synthesis procedure using multi-anvil apparatus at 9 GPa (about 90,000 atm) and temperature of 500 °C. The synthetic mesoporous stishovite is, then, characterized by wide and small-angle X-ray diffraction, scanning/transmission electron microscopy and gas adsorption. Results show that this new material is characterized by accessible mesopores with wide pore size distribution, surface area of ~45 m2/g and volume of pores of ~0.15 cm3/g. Results from gas adsorption indicate that both porosity and permeability are retained at the high pressures of synthesis but with weak periodic order of the pores.

  3. Prediction of superconducting iron-bismuth intermetallic compounds at high pressure

    CERN Document Server

    Amsler, Maximilian; Wolverton, Chris

    2016-01-01

    The synthesis of materials in high-pressure experiments has recently attracted increasing attention, especially since the discovery of record breaking superconducting temperatures in the sulfur-hydrogen and other hydrogen-rich systems. Commonly, the initial precursor in a high pressure experiment contains constituent elements that are known to form compounds at ambient conditions, however the discovery of high-pressure phases in systems immiscible under ambient conditions poses an additional materials design challenge. We performed an extensive multi component $ab\\,initio$ structural search in the immiscible Fe--Bi system at high pressure and report on the surprising discovery of two stable compounds at pressures above $\\approx36$ GPa, FeBi$_2$ and FeBi$_3$. According to our predictions, FeBi$_2$ is a metal at the border of magnetism with a conventional electron-phonon mediated superconducting transition temperature of $T_{\\rm c}=1.3$ K at 40 GPa. In analogy to other iron-based materials, FeBi$_2$ is possibly...

  4. X-ray imaging for studying behavior of liquids at high pressures and high temperatures using Paris-Edinburgh press

    International Nuclear Information System (INIS)

    Several X-ray techniques for studying structure, elastic properties, viscosity, and immiscibility of liquids at high pressures have been integrated using a Paris-Edinburgh press at the 16-BM-B beamline of the Advanced Photon Source. Here, we report the development of X-ray imaging techniques suitable for studying behavior of liquids at high pressures and high temperatures. White X-ray radiography allows for imaging phase separation and immiscibility of melts at high pressures, identified not only by density contrast but also by phase contrast imaging in particular for low density contrast liquids such as silicate and carbonate melts. In addition, ultrafast X-ray imaging, at frame rates up to ∼105 frames/second (fps) in air and up to ∼104 fps in Paris-Edinburgh press, enables us to investigate dynamics of liquids at high pressures. Very low viscosities of melts similar to that of water can be reliably measured. These high-pressure X-ray imaging techniques provide useful tools for understanding behavior of liquids or melts at high pressures and high temperatures

  5. X-ray imaging for studying behavior of liquids at high pressures and high temperatures using Paris-Edinburgh press

    Energy Technology Data Exchange (ETDEWEB)

    Kono, Yoshio; Kenney-Benson, Curtis; Park, Changyong; Shen, Guoyin [HPCAT, Geophysical Laboratory, Carnegie Institution of Washington, 9700 S. Cass Ave., Argonne, Illinois 60439 (United States); Shibazaki, Yuki [Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Aramaki aza Aoba 6-3, Aoba-ku, Sendai 980-8578 (Japan); Wang, Yanbin [GeoSoilEnviroCARS, Center for Advanced Radiation Sources, The University of Chicago, 5640 S. Ellis Avenue, Chicago, Illinois 60637 (United States)

    2015-07-15

    Several X-ray techniques for studying structure, elastic properties, viscosity, and immiscibility of liquids at high pressures have been integrated using a Paris-Edinburgh press at the 16-BM-B beamline of the Advanced Photon Source. Here, we report the development of X-ray imaging techniques suitable for studying behavior of liquids at high pressures and high temperatures. White X-ray radiography allows for imaging phase separation and immiscibility of melts at high pressures, identified not only by density contrast but also by phase contrast imaging in particular for low density contrast liquids such as silicate and carbonate melts. In addition, ultrafast X-ray imaging, at frame rates up to ∼10{sup 5} frames/second (fps) in air and up to ∼10{sup 4} fps in Paris-Edinburgh press, enables us to investigate dynamics of liquids at high pressures. Very low viscosities of melts similar to that of water can be reliably measured. These high-pressure X-ray imaging techniques provide useful tools for understanding behavior of liquids or melts at high pressures and high temperatures.

  6. Some Aspects of the Crystal Chemistry of Perovskites under High Pressures

    OpenAIRE

    Wang, Di

    2012-01-01

    This thesis makes contributions to the methodology of quantitative description of the tilting systems of perovskite structures and theoretical analysis of high-pressure phase transitions of representative perovskites. Chapter 1 and 2 introduce the perovskite structures, tilting classification and descriptions. The structures in each of the 15 tilt systems have been decomposed in to the amplitudes of symmetry-adapted modes in order to provide a clear and unambiguous definition of the tilt ...

  7. Transportable, small high-pressure preservation vessel for cells

    Energy Technology Data Exchange (ETDEWEB)

    Kamimura, N; Sotome, S; Shimizu, A [Department of Environmental Engineering for Symbiosis, Soka University, 1-236 Tangi-cho, Hachioji, Tokyo 192-8577 (Japan); Nakajima, K [Department of Bioinformatics, Soka University, 1-326 Tangi-cho, Hachioji, Tokyo 192-8577 (Japan); Yoshimura, Y, E-mail: mf_kamimura@yahoo.co.j [Department of Applied Chemistry, National Defence Academy, 1-10-20 Hashirimizu, Yokosuka, Kanagawa 239-8686 (Japan)

    2010-03-01

    We have previously reported that the survival rate of astrocytes increases under high-pressure conditions at 4{sup 0}C. However, pressure vessels generally have numerous problems for use in cell preservation and transportation: (1) they cannot be readily separated from the pressurizing pump in the pressurized state; (2) they are typically heavy and expensive due the use of materials such as stainless steel; and (3) it is difficult to regulate pressurization rate with hand pumps. Therefore, we developed a transportable high-pressure system suitable for cell preservation under high-pressure conditions. This high-pressure vessel has the following characteristics: (1) it can be easily separated from the pressurizing pump due to the use of a cock-type stop valve; (2) it is small and compact, is made of PEEK and weighs less than 200 g; and (3) pressurization rate is regulated by an electric pump instead of a hand pump. Using this transportable high-pressure vessel for cell preservation, we found that astrocytes can survive for 4 days at 1.6 MPa and 4{sup 0}C.

  8. High pressure x-ray diffraction studies on U-Al systems

    International Nuclear Information System (INIS)

    In this paper, high pressure x-ray diffraction studies of the three U-Al compounds, namely, UAl2, UAl3 and UAl4 are presented. The experiments are carried out using a unique diamond anvil high pressure x-ray diffraction system in the Guinier geometry up to a maximum pressure of ∼ 35 GPa. The compressibility behaviour of UAl2 is consistent with its itinerant 5f states, whereas that of UAl3 and UAl4 indicate more towards their localized nature. Among these three compounds, a structural phase transition in UAl2 has been observed at ∼ 11 GPa and the structure of the high pressure phase has been identified to be of MgNi2 type with space group P63/mmc. The structure of UAl2 at NTP is of MgCu2 type with space group Fd3m. From the electron to atom ratio (e/α) consideration, another structural phase transition, namely, MgNi2-MgCu2 at a higher pressure is proposed. Further, on a similar consideration, a new pressure induced structural sequence, namely, MgCu2-MgNi2 (or MgZn2-MgCu2) in the AB2 type compounds of the f electron based systems is suggested. (author)

  9. High pressure synthesis of amorphous TiO{sub 2} nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Li, Quanjun; Liu, Ran; Wang, Tianyi; Xu, Ke; Dong, Qing; Liu, Bo; Liu, Bingbing, E-mail: liubb@jlu.edu.cn [State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China); Liu, Jing [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China)

    2015-09-15

    Amorphous TiO{sub 2} nanotubes with diameters of 8-10 nm and length of several nanometers were synthesized by high pressure treatment of anatase TiO{sub 2} nanotubes. The structural phase transitions of anatase TiO{sub 2} nanotubes were investigated by using in-situ high-pressure synchrotron X-ray diffraction (XRD) method. The starting anatase structure is stable up to ∼20GPa, and transforms into a high-density amorphous (HDA) form at higher pressure. Pressure-modified high- to low-density transition was observed in the amorphous form upon decompression. The pressure-induced amorphization and polyamorphism are in good agreement with the previous results in ultrafine TiO{sub 2} nanoparticles and nanoribbons. The relationship between the LDA form and α-PbO{sub 2} phase was revealed by high-resolution transmission electron microscopy (HRTEM) study. In addition, the bulk modulus (B{sub 0} = 158 GPa) of the anatase TiO{sub 2} nanotubes is smaller than those of the corresponding bulks and nanoparticles (180-240 GPa). We suggest that the unique open-ended nanotube morphology and nanosize play important roles in the high pressure phase transition of TiO{sub 2} nanotubes.

  10. Diagnostics and modeling of high pressure streamer induced discharges

    International Nuclear Information System (INIS)

    A great variety of diagnostic has been applied to gain information on basic parameter governing high pressure nonthermal filamentary plasmas (and namely streamer induced filamentary discharges). Apart from electrical diagnostics, gas discharge, in contrast with solid state physics, can greatly benefit from all optical techniques owing to its ''transparent'' state. Emission and absorption spectroscopy, as well as LIF or CARS (talk are given during this meeting on these two techniques) are among such specific possibilities. The figures gained from these diagnostic measurements has generally no meaning by itself. They must be worked out, by means of calibrated former results, and/or by using them as input in high pressure plasma modeling. Mixing experimental and modeling approach is necessary for reaching relevant physical knowledge of the high pressure filamentary discharges processes. It is shown that diffusion, and thermal space and time distribution, must fully be taken into account

  11. Enhanced MgB2 Superconductivity Under High Pressure

    Institute of Scientific and Technical Information of China (English)

    刘振兴; 靳常青; 游江洋; 李绍春; 朱嘉林; 禹日成; 李风英; 苏少奎

    2002-01-01

    We report on in situ high-pressure studies up to 1.0 GPa on the MgB2 superconductor which was high-pressure synthesized. The as-prepared sample is of high quality in terms of sharp superconducting transition (Tc) at 39K from the magnetic measurements. The in situ high-pressure measurements were carried out using a Be-Cu piston-cylinder-type instrument with mixed oil as the pressure transmitting medium which warrants a quasihydrostatic pressure environment at low temperature. The superconducting transitions were measured using the electrical conductance method. It is found that Tc increases by more than 1 K with pressure in the low-pressure range, before the Tc value decreases with the further increase of the pressure.

  12. High pressure common rail injection system modeling and control.

    Science.gov (United States)

    Wang, H P; Zheng, D; Tian, Y

    2016-07-01

    In this paper modeling and common-rail pressure control of high pressure common rail injection system (HPCRIS) is presented. The proposed mathematical model of high pressure common rail injection system which contains three sub-systems: high pressure pump sub-model, common rail sub-model and injector sub-model is a relative complicated nonlinear system. The mathematical model is validated by the software Matlab and a virtual detailed simulation environment. For the considered HPCRIS, an effective model free controller which is called Extended State Observer - based intelligent Proportional Integral (ESO-based iPI) controller is designed. And this proposed method is composed mainly of the referred ESO observer, and a time delay estimation based iPI controller. Finally, to demonstrate the performances of the proposed controller, the proposed ESO-based iPI controller is compared with a conventional PID controller and ADRC. PMID:27012440

  13. Confinement of hydrogen at high pressure in carbon nanotubes

    Science.gov (United States)

    Lassila, David H.; Bonner, Brian P.

    2011-12-13

    A high pressure hydrogen confinement apparatus according to one embodiment includes carbon nanotubes capped at one or both ends thereof with a hydrogen-permeable membrane to enable the high pressure confinement of hydrogen and release of the hydrogen therethrough. A hydrogen confinement apparatus according to another embodiment includes an array of multi-walled carbon nanotubes each having first and second ends, the second ends being capped with palladium (Pd) to enable the high pressure confinement of hydrogen and release of the hydrogen therethrough as a function of palladium temperature, wherein the array of carbon nanotubes is capable of storing hydrogen gas at a pressure of at least 1 GPa for greater than 24 hours. Additional apparatuses and methods are also presented.

  14. High Pressure Processing Technology and Equipment Evolution: A Review

    Directory of Open Access Journals (Sweden)

    Wael M. Elamin

    2015-12-01

    Full Text Available High pressure processing (HPP is an interesting non-thermal technology that involves the sterilization of food by the mean of ultra-high pressures, which lead to extending the shelf life of processed food, as well as maintaining nutritional value and quality of food products. The consumers’ increasing demand for this new products graped the interest of several already-existing high pressure equipment manufacturers around the globe. The successful of this technology encouraged them to enter the field of food processing and adjust their existing technologies to adapt to the new process. This review spots the major discoveries in HPP equipment history, describes the current applications of HHP in processing and provides comprehensive information about HPP equipment technology used in commercial and research applications. In addition, this paper presents the major manufacturers in HPP equipment industry around the world.

  15. Experiment on Wear Behavior of High Pressure Gas Seal Faces

    Institute of Scientific and Technical Information of China (English)

    XU Jing; PENG Xudong; BAI Shaoxian; MENG Xiangkai; LI Jiyun

    2014-01-01

    Current researches show that mechanical deformation of seal ring face makes fluid film clearance decrease at high pressure side, thus a divergent clearance is formed and face wear occurs more seriously at the high pressure side than that on the low pressure side. However, there is still lack of published experimental works enough to prove the theoretical results. In this paper, a spiral groove dry gas seal at high pressures is experimentally investigated so as to prove the face wear happened at the high pressure side of seal faces due to the face mechanical deformation, and the wear behavior affected by seal ring structure is also studied. The experimental results show that face wear would occur at the high pressure side of seal faces due to the deformation, thus the leakage and face temperature increase, which all satisfies the theoretical predictions. When sealed pressure is not less than 5 MPa, the pressure can provide enough opening force to separate the seal faces. The seal ring sizes have obvious influence on face wear. Face wear, leakage and face temperature of a dry gas seal with the smaller cross sectional area of seal ring are less than that of a dry gas seal with bigger one, and the difference of leakage rate between these two sizes of seal face width is in the range of 24%–25%. Compared with the effect of seal ring sizes, the effect of secondary O-ring seal position on face deformation and face wear is less. The differences between these two types of dry gas seals with different secondary O-ring seal positions are less than 5.9% when the rotational speed varies from 0 to 600 r/min. By linking face wear and sealing performance changes to the shift in mechanical deformation of seal ring, this research presents an important experimental method to study face deformation of a dry gas seal at high pressures.

  16. High-pressure-low-temperature x-ray power diffractometer.

    Science.gov (United States)

    Syassen, K; Holzapfel, W B

    1978-08-01

    A high-pressure technique for x-ray diffraction studies at low temperatures is described. The system consists of a Bridgman anvil type high-pressure device with either tungsten carbide or boron carbide anvils, a liquid He cryostat, and x-ray diffractometer operating in Debye-Scherrer geometry. The newly developed boron carbide anvil cell is capable of containing a liquid pressure transmitting medium. The precision of the lattice parameter determination is discussed and the effect of nonisostatic stress components on the diffraction pattern is examined.

  17. Novel High Pressure Multi-Component Diffusion Cell

    OpenAIRE

    Muthia Elma; Paul Massarotto; Victor Rudolph

    2012-01-01

    A novel high pressure multi-component diffusion cell (HPMCDC) apparatus has been designed and built to measure single and binary gas diffusion, including co-current and counter-diffusion, from low to high pressures. The apparatus incorporates capability to investigate scale effects in solid coal specimens, up to 25 mm in diameter and 25 mm in thickness. Future experiments will be conducted to measure diffusion and counter-diffusion of CH4 and CO2 gases in solid coal, at various temperatures, ...

  18. Equation of state of liquid Indium under high pressure

    International Nuclear Information System (INIS)

    We apply an equation of state of a power law form to liquid Indium to study its thermodynamic properties under high temperature and high pressure. Molar volume of molten indium is calculated along the isothermal line at 710K within good precision as compared with the experimental data in an externally heated diamond anvil cell. Bulk modulus, thermal expansion and internal pressure are obtained for isothermal compression. Other thermodynamic properties are also calculated along the fitted high pressure melting line. While our results suggest that the power law form may be a better choice for the equation of state of liquids, these detailed predictions are yet to be confirmed by further experiment

  19. On some hydrogen bond correlations at high pressures

    Science.gov (United States)

    Sikka, S. K.

    2007-09-01

    In situ high pressure neutron diffraction measured lengths of O H and H O pairs in hydrogen bonds in substances are shown to follow the correlation between them established from 0.1 MPa data on different chemical compounds. In particular, the conclusion by Nelmes et al that their high pressure data on ice VIII differ from it is not supported. For compounds in which the O H stretching frequencies red shift under pressure, it is shown that wherever structural data is available, they follow the stretching frequency versus H O (or O O) distance correlation. For compounds displaying blue shifts with pressure an analogy appears to exist with improper hydrogen bonds.

  20. Equation of state of liquid Indium under high pressure

    Science.gov (United States)

    Li, Huaming; Sun, Yongli; Li, Mo

    2015-09-01

    We apply an equation of state of a power law form to liquid Indium to study its thermodynamic properties under high temperature and high pressure. Molar volume of molten indium is calculated along the isothermal line at 710K within good precision as compared with the experimental data in an externally heated diamond anvil cell. Bulk modulus, thermal expansion and internal pressure are obtained for isothermal compression. Other thermodynamic properties are also calculated along the fitted high pressure melting line. While our results suggest that the power law form may be a better choice for the equation of state of liquids, these detailed predictions are yet to be confirmed by further experiment.

  1. Equation of state of liquid Indium under high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Li, Huaming, E-mail: huamingli@gatech.edu, E-mail: mo.li@gatech.edu; Li, Mo, E-mail: huamingli@gatech.edu, E-mail: mo.li@gatech.edu [College of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan 030024 (China); School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332 (United States); Sun, Yongli [College of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan 030024 (China)

    2015-09-15

    We apply an equation of state of a power law form to liquid Indium to study its thermodynamic properties under high temperature and high pressure. Molar volume of molten indium is calculated along the isothermal line at 710K within good precision as compared with the experimental data in an externally heated diamond anvil cell. Bulk modulus, thermal expansion and internal pressure are obtained for isothermal compression. Other thermodynamic properties are also calculated along the fitted high pressure melting line. While our results suggest that the power law form may be a better choice for the equation of state of liquids, these detailed predictions are yet to be confirmed by further experiment.

  2. High pressure torsion of Cu-based metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Hobor, S; Kovacs, Zs; Revesz, A [Department of Materials Physics, Eoetvoes University, Budapest, H-1518, P.O.B. 32, Budapest (Hungary); Zhilyaev, A P [Centro Nacional de Investigaciones Metalurgicas, 28040 Madrid, Spain and Institute for Metals Superplasticity Problems, RAS, 450001 Ufa (Russian Federation); Varga, L K [Research Institute for Solid state Physics and Optics, Hungarian Academy of Sciences. H-1525 Budapest, P.O.B. 49 (Hungary); Szabo, P J, E-mail: hobors@metal.elte.h [Deparment of Materials Science and Engineering, University of Technology and Economy, Budapest, H-1111 (Hungary)

    2010-07-01

    Cu-Zr-Ti metallic glass was subjected to high pressure torsion applying different revolution times (180s, 120s, 60s). Both deformation and deformation rate dependent microstructural and thermal properties were characterized by scanning electron microscopy, X-ray diffraction and calorimetry, respectively. In order to estimate the temperature rise in the metallic glass during high pressure torsion, quasi three-dimensional heat conduction equation with a source term was considered. Solutions indicate that the saturation temperature strongly depends on the revolution time, i. e. on the deformation rate.

  3. High-Pressure Minerals in Meteorites: Constraints on Shock Conditions and Duration

    Science.gov (United States)

    Sharp, Thomas G.

    2004-01-01

    The objective of this research was to better understand the conditions and duration of shock metamorphism in meteorites through microstructural and microanalytical characterization of high-pressure minerals. A) Continue to investigate the mineralogy and microstructures of melt-veins in a suite of chondritic samples ranging from shock grades S3 through S6 to determine how the mineral assemblages that crystallize at high-pressure and are related to shock grade. B) Investigate the chemical, mineralogical, and microstructural heterogeneities that occur across melt veins to interpret crystallization histories. C) Use static high-pressure experiments to simulate crystallization of melt veins for mineralogical and textural comparisons with the melt veins of naturally shocked samples. D) Characterize the compositions and defect microstructures of polycrystalline ringwoodite, wadsleyite, majorite, (Mg,Fe)Si03-ilmenite and (Mg,Fe)SiO3-perovskite in S6 samples to understand the mechanisms of phase transformations that occur during shock. These results will combined with kinetic data to constrain the time scales of kinetic processes. E) Investigate the transformations of metastable high-pressure minerals back to low- pressure forms to constrain post-shock temperatures and estimates of the peak shock pressure. Of these objectives, we have obtained publishable data on A, B and D. I am currently doing difficult high-pressure melting and quench experiments on an L chondrite known as Mbale. These experiments will provide additional constraints on the mineral assemblages that are produced during rapid quench of an L chondrite at pressures of 16 to 25 GPa. Results from published or nearly published research is presented below. Lists of theses, dissertations and publications are given below.

  4. High-pressure X-ray diffraction study of bulk- and nanocrystalline GaN

    DEFF Research Database (Denmark)

    Jorgensen, J.E.; Jakobsen, J.M.; Jiang, Jianzhong;

    2003-01-01

    Bulk- and nanocrystalline GaN have been studied by high-pressure energy-dispersive X-ray diffraction. Pressure-induced structural phase transitions from the wurtzite to the NaCl phase were observed in both materials. The transition pressure was found to be 40 GPa for the bulk-crystalline GaN, while...... the wurtzite phase was retained up to 60 GPa in the case of nanocrystalline GaN. The bulk moduli for the wurtzite phases were determined to be 187 ( 7) and 319 ( 10) GPa for the bulk- and nanocrystalline phases, respectively, while the respective NaCl phases were found to have very similar bulk moduli [ 208...

  5. A high-pressure study of PbCO3 by XRD and Raman spectroscopy

    Science.gov (United States)

    Zhang, Yu-Feng; Liu, Jing; Qin, Zhen-Xing; Lin, Chuan-Long; Xiong, Lun; Li, Rui; Bai, Li-Gang

    2013-03-01

    The pressure-induced phase transitions of PbCO3 are studied using synchrotron radiation in a diamond anvil cell at room temperature. The XRD measurement indicates that PbCO3 with an initial phase of aragonite-type structure undergoes two phase transitions at ~7.8 GPa and ~15.7 GPa, respectively. The higher-pressure phase appearing at ~15.7 GPa is stable up to 51.8 GPa. The two phase transitions are further confirmed by Raman scattering up to 23.3 GPa. During the decompression process, the high-pressure phases of PbCO3 are gradually recovered to the starting aragonite-type structure, but exhibit some hysteresis. The bulk modulus B0 of the aragonite-type structure is obtained to be 63±(3) GPa by fitting the volume-pressure data to the Birch—Murnaghan equation of states with B'0 fixed to 4.

  6. Pyrolysis oil upgrading by high pressure thermal treatment

    NARCIS (Netherlands)

    Miguel Mercader, de F.; Groeneveld, M.J.; Kersten, S.R.A.; Venderbosch, R.H.; Hogendoorn, J.A.

    2010-01-01

    High pressure thermal treatment (HPTT) is a new process developed by BTG and University of Twente with the potential to economically reduce the oxygen and water content of oil obtained by fast pyrolysis (pyrolysis oil), properties that currently complicate its co-processing in standard refineries. D

  7. A high-pressure MWPC detector for crystallography

    DEFF Research Database (Denmark)

    Ortuno-Prados, F.; Bazzano, A.; Berry, A.;

    1999-01-01

    The application of the Multi-Wire Proportional Counter (MWPC) as a potential detector for protein crystallography and other wide-angle diffraction experiments is presented. Electrostatic problems found with our large area MWPC when operated at high pressure are discussed. We suggest that a solution...

  8. A high pressure sample facility for neutron scattering

    International Nuclear Information System (INIS)

    Commissioning tests involving deformation studies and tests to destruction as well as neutron diffraction measurements of a standard sample have been carried out on the SERC high pressure sample facility for neutron scattering studies. A detailed description of the pressurising equipment is given. (author)

  9. Effect of high pressure on physicochemical properties of meat.

    Science.gov (United States)

    Buckow, Roman; Sikes, Anita; Tume, Ron

    2013-01-01

    The application of high pressure offers some interesting opportunities in the processing of muscle-based food products. It is well known that high-pressure processing can prolong the shelf life of meat products in addition to chilling but the pressure-labile nature of protein systems limits the commercial range of applications. High pressure can affect the texture and gel-forming properties of myofibrillar proteins and, hence, has been suggested as a physical and additive-free alternative to tenderize and soften or restructure meat and fish products. However, the rate and magnitude at which pressure and temperature effects take place in muscles are variable and depend on a number of circumstances and conditions that are still not precisely known. This review provides an overview of the current knowledge of the effects of high pressure on muscle tissue over a range of temperatures as it relates to meat texture, microstructure, color, enzymes, lipid oxidation, and pressure-induced gelation of myofibrillar proteins.

  10. Temperature effects for high pressure processing of Picornaviruses

    Science.gov (United States)

    Investigation of the effects of pre-pressurization temperature on the high pressure inactivation for single strains of aichivirus (AiV), coxsackievirus A9 (CAV9) and B5 (CBV5) viruses, as well as human parechovirus -1 (HPeV), was performed. For CAV9, an average 1.99 log10 greater inactivation was ...

  11. Advantages of high pressure sterilisation on quality of food products

    NARCIS (Netherlands)

    Matser, A.M.; Krebbers, B.; Berg, van den R.W.; Bartels, P.V.

    2004-01-01

    High pressure processing can be used for sterilisation of food products if applied at elevated temperatures and using the temperature increase due to adiabatic compression. By choosing the appropriate process conditions, it is possible to completely inactivate both vegetative cells and microbial spo

  12. DRILLING CHARACTERISTICS OF COMBINATIONS OF DIFFERENT HIGH PRESSURE JET NOZZLES

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yu-ying; LIU Yong-wang; XU Yi-ji; REN Jian-hua

    2011-01-01

    The high speed fluid jet for directly or indirectly breaking rock is one of the most effective ways to improve the deep penetration rate. In order to maximize the efficiency of energy use, the flow characteristics of different combinations of high pressure jet nozzles are analyzed through numerical simulations. According to the velocity vectors at the bottom and the bottom hole pressure diagram, the effects of the high pressure nozzle combinations on the flow structure and the penetration rate are analyzed. It is shown that the combination of three vertical edge nozzles is very efficient, but inefficient in cleaning the bottom hole and eroding the wall.The jet velocity is 400 m/s and the radius is 5 mm, with a center nozzle added, the problem can be solved, but the high-pressure fluid displacement would increase. The center nozzle's jet velocity is 200 m/s and the radius is 8 mm, the combination of two vertical edge nozzles and a center tilt nozzle or that of a vertical edge nozzle and a center tilt nozzle would provide a flow structure favorable for drilling. The angle of inclination is 10°. To take advantage of high pressure jet energy to improve the efficiency of drilling, it is important to select a suitable nozzle combination according real conditions.

  13. Pneumomediastinum following high pressure air injection to the hand.

    LENUS (Irish Health Repository)

    Kennedy, J

    2010-04-01

    We present the case of a patient who developed pneumomediastinum after high pressure air injection to the hand. To our knowledge this is the first reported case of pneumomediastinum where the gas injection site was the thenar eminence. Fortunately the patient recovered with conservative management.

  14. Pneumomediastinum following high pressure air injection to the hand.

    LENUS (Irish Health Repository)

    Kennedy, J

    2012-02-01

    We present the case of a patient who developed pneumomediastinum after high pressure air injection to the hand. To our knowledge this is the first reported case of pneumomediastinum where the gas injection site was the thenar eminence. Fortunately the patient recovered with conservative management.

  15. Inapplicability of high pressure spray injection for chelate administration

    International Nuclear Information System (INIS)

    A high-pressure spray injector was tested for use in injecting chelating agents around radionuclides in wounds. It was difficult to employ because of the force required for proper injection, and it did not improve the effectiveness of the injected chelate in removing intramuscularly injected 238Pu. (U.S.)

  16. High-pressure applications in medicine and pharmacology

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Jerson L; Foguel, Debora; Suarez, Marisa; Gomes, Andre M O; Oliveira, Andrea C [Centro Nacional de Ressonancia Magnetica Nuclear, Departamento de Bioquimica Medica, Instituto de Ciencias Biomedicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ 21941-590 (Brazil)

    2004-04-14

    High pressure has emerged as an important tool to tackle several problems in medicine and biotechnology. Misfolded proteins, aggregates and amyloids have been studied, which point toward the understanding of the protein misfolding diseases. High hydrostatic pressure (HHP) has also been used to dissociate non-amyloid aggregates and inclusion bodies. The diverse range of diseases that result from protein misfolding has made this theme an important research focus for pharmaceutical and biotech companies. The use of high pressure promises to contribute to identifying the mechanisms behind these defects and creating therapies against these diseases. High pressure has also been used to study viruses and other infectious agents for the purpose of sterilization and in the development of vaccines. Using pressure, we have detected the presence of a ribonucleoprotein intermediate, where the coat protein is partially unfolded but bound to RNA. These intermediates are potential targets for antiviral compounds. The ability of pressure to inactivate viruses, prions and bacteria has been evaluated with a view toward the applications of vaccine development and virus sterilization. Recent studies demonstrate that pressure causes virus inactivation while preserving the immunogenic properties. There is increasing evidence that a high-pressure cycle traps a virus in the 'fusion intermediate state', not infectious but highly immunogenic.

  17. Synthesis of novel Ru2C under high pressure-high temperature conditions.

    Science.gov (United States)

    Sanjay Kumar, N R; Chandra Shekar, N V; Chandra, Sharat; Basu, Joysurya; Divakar, R; Sahu, P Ch

    2012-09-12

    We report here, for the first time, synthesis of the Fe(2)N type hexagonal phase of ruthenium carbide by a high pressure-high temperature technique using a laser heated diamond anvil cell (LHDAC). The synthesis is carried out by laser heating a mixture of pure elements, Ru and C, at very low 'pressure' of 5 GPa and T ~ 2000 K. The structure of the temperature quenched high pressure phase is characterized by in situ high pressure x-ray diffraction (HPXRD) and is corroborated by ex situ TEM imaging and diffraction, carried out for the first time on the retrieved sample synthesized by LHDAC. The lattice parameters of Ru(2)C at ambient pressure are found to be a = 2.534 Å and c = 4.147 Å. In situ HPXRD studies up to 14.2 GPa yield a bulk modulus of 178(4) GPa. Electronic structure calculations reveal the system to be metallic in nature with a degree of covalence along the Ru-C bond. As ruthenium is isoelectronic to osmium, this result for Ru(2)C has significant implications in the synthesis and study of osmium carbides. PMID:22906879

  18. Surface characterization of TiNi deformed by high-pressure torsion

    Energy Technology Data Exchange (ETDEWEB)

    Awang Shri, Dayangku Noorfazidah [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8577 (Japan); Structural Materials Unit, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047 (Japan); Tsuchiya, Koichi, E-mail: tsuchiya.koichi@nims.go.jp [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8577 (Japan); Structural Materials Unit, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047 (Japan); Yamamoto, Akiko [Biomaterials Unit, International Center for Material Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044 (Japan)

    2014-01-15

    Effect of grain refinements and amorphization by high-pressure torsion (HPT) on surface chemistry was investigated on TiNi. X-ray diffraction and micro-Vickers tests were used to check the phase changes and hardness before and after HPT. X-ray photoelectron spectroscopy was used to observe the changes in the natural passive film formation on the surface. Phase analysis reveals the change of crystalline TiNi to nanostructured one with increased hardness with straining by HPT. Grain refinement and amorphization caused by HPT reduce the amount of metallic Ni in the passive films and also increase the thickness of the film.

  19. High-pressure behavior of solid nitrobenzene: Combined Raman spectroscopy and DFT-D calculations study

    Science.gov (United States)

    Wang, Wen-Peng; Liu, Fu-Sheng; Liu, Qi-Jun; Zhang, Lin-Ji; Wang, Yi-Gao; Liu, Zheng-Tang

    2016-09-01

    Nitrobenzene (NB), a simplest structure of the aromatic nitro compounds, was investigated as a model for understanding structural properties in nitro derivatives of benzene and anilines. Using the Raman spectroscopic technique, the vibrational modes of solid NB were examined under hydrostatic compression up to 10 GPa. The Raman spectra indicated that a subtle phase transition occurred around 5 GPa. Also, the dispersion corrected density functional theory (DFT-D) calculations were performed to provide further insight into pressure effects on the molecular geometry. The calculated data suggested that NB molecules were distorted, and molecular conformation was readjusted when the phase transition with vibrational changes took place under high-pressure.

  20. High-pressure structural study of solid mercury up to 200 GPa

    International Nuclear Information System (INIS)

    High-pressure powder x-ray diffraction experiments have been carried out on solid mercury up to 196 GPa at room temperature. The hexagonal-close-packed δ phase, which exists above 36 GPa, is found to remain stable up to the highest pressure investigated. The c/a axial ratio monotonously decreases under pressure in a manner similar to that of zinc and cadmium. There is no anomaly in the pressure dependence of the c/a axial ratio. We present complete structural data of β, γ, and δ phases of solid mercury, which constrain the PV equation of state at 300 K. (paper)

  1. Effects of cavitation on high-pressure atomization

    Science.gov (United States)

    Dabiri Satari, Sadegh

    2009-12-01

    Although disintegration and breakup of a liquid jet emerging from a nozzle has been studied for a long time, the effects of nozzle internal flow and specifically cavitation on the breakup of liquid jets have not been well understood. In the orifice of liquid injectors at high pressure, cavitation occurs behind the sharp corners, where a strong pressure drop is present due to quick change in the flow direction. In addition, a high level of shear stress is present inside the boundary layer. Therefore, it is important to understand the influence of the shear on the cavitation. There are two main questions to be answered: What is the effect of the shear stress on the cavitation inception? And, how does the shear stress influence the cavitation bubble dynamics? In order to answer the above questions, the laminar flow of a liquid through the orifice of an atomizer is studied by means of numerical solution of Navier-Stokes equations. The total-stress criterion for cavitation is applied to find the regions where cavitation is likely to occur and compared with those of the traditional pressure criterion. Results show that the viscous stress has significant effects on cavitation inception. Cavitation bubble dynamics is also affected by the presence of shear strain or normal strain in the flow. Interaction between a single cavitation bubble and strained flow is considered in the next part. As a result of interaction between the shear flow and the bubble, two re-entrant jets are observed on two sides of the bubble during the collapse phase. Re-entrant jets with enough strength could breakup the bubble into smaller bubbles. Finally, four sources of disturbances are proposed that could be responsible for the improvement of atomization due to cavitation. Three of these sources are monopoles, quadrupoles and the vorticity generated during the bubble growth and collapse. It is shown that the monopole sources have the strongest contribution to the disturbances at the orifice exit

  2. Calorimetry at high-pressure using high-frequency Joule-heating

    Science.gov (United States)

    Geballe, Zachary; Struzhkin, Viktor

    2015-03-01

    Calorimetric measurements of materials at 1 to 100 GPa of pressure would provide intriguing tests of condensed matter theories, sensitive probes of chemical reactions during high-pressure synthesis, and useful inputs for models of the Earth's interior. We present the design and first results of quantitative heat capacity measurements at >10 GPa of pressure. High-frequency AC voltage heats a small metal strip pressed between diamond anvils, creating temperature oscillations whose amplitudes are determined from the higher harmonics of voltage. Thermal models show that frequencies >100 kHz are required to contain heat in the ng-mass samples, while electrical models show that frequencies >100 MHz are not practical. Our experimental results show that the heat capacity of iron and nickel can indeed be measured at high frequencies in diamond anvil cells, paving the way for studies of the energetics of a wide-variety of entropy-driven phase changes at high pressure.

  3. The Simulation of High Pressure Nucleation Experiments in Diffusion Cloud Chamber

    CERN Document Server

    Fisenko, Sergey P

    2007-01-01

    For high- pressure nucleation experiments in upward diffusion cloud chamber, there is the great deviation of predictions of classical nucleation theory from experimental results; the discrepancy is more than 10 orders of magnitude of nucleation rate. Experimental data for 1-propanol vapor are under investigation in this paper. It was shown that mathematical model of a single droplet growth and motion semi- quantitatively explained all experimentally discovered regularities. For explanations low nucleation rate versus high supersaturation, the coalescence mechanism in gaseous phase has been proposed. As result of coalescence the vast majority of newly formed clusters evaporate and restore vapor density and temperature profile in DCC. The observed picture with low nucleation rate is result of diffusion interaction between small clusters and droplets in nucleation zone for high- pressure nucleation experiments.

  4. High-pressure structural study of yttrium monochalcogenides from experiment and theory

    DEFF Research Database (Denmark)

    Vaitheeswaran, G.; Kanchana, V.; Svane, A.;

    2011-01-01

    High-pressure powder x-ray diffraction experiments using synchrotron radiation are performed on the yttrium monochalcogenides YS, YSe, and YTe up to a maximum pressure of 23 GPa. The ambient NaCl structure is stable throughout the pressure range covered. The bulk moduli are determined to be 93, 82......, and 67 GPa for YS, YSe, and YTe, respectively. First-principles total energy calculations are carried out using the full-potential linear muffin-tin orbital method. The calculated and measured lattice constants and bulk moduli are in good agrement. Under applied pressure, the yttrium monochalcogenides...... are predicted to undergo a structural transition. Assuming that the high-pressure phase corresponds to the CsCl crystal structure, transition pressures of 53, 36, and 14 GPa are found for YS, YSe, and YTe, respectively....

  5. Application backwards characteristics analysis method to dynamic response of metals under high pressure

    Directory of Open Access Journals (Sweden)

    Pan Hao

    2015-01-01

    Full Text Available Dynamic yield strength of metals/alloys depends on loading pressure and rates sensitively. With the development of laser interferometer measurement system, extracting strength information from window/free surface velocity profiles in shock and ramp loading experiments is becoming an important method to investigate materials’ dynamic response under high pressure and high strain rates. Backwards characteristics analysis method (BCAM can analyze the velocity profiles more reasonable because it accounts for bending of the incoming characteristics due to impedance mismatch between the sample and window. Synthetic analyses of reverse impact experiment and graded-density impactor loading-releasing experiment suggest that BCAM can give more accurate results including sound speed-particle velocity and yield strength at high pressure than incremental impedance matching method. We use BCAM to analyze velocity profiles of Sn in shock-release experiments and obtain its shear modulus and yield strength at different shock pressure and investigate its phase transition and dynamic unloading response.

  6. High pressure behaviour of uranium dicarbide (UC2): Ab-initio study

    Science.gov (United States)

    Sahoo, B. D.; Mukherjee, D.; Joshi, K. D.; Kaushik, T. C.

    2016-08-01

    The structural stability of uranium dicarbide has been examined under hydrostatic compression employing evolutionary structure search algorithm implemented in the universal structure predictor: evolutionary Xtallography (USPEX) code in conjunction with ab-initio electronic band structure calculation method. The ab-initio total energy calculations involved for this purpose have been carried out within both generalized gradient approximations (GGA) and GGA + U approximations. Our calculations under GGA approximation predict the high pressure structural sequence of tetragonal → monoclinic → orthorhombic for this material with transition pressures of ˜8 GPa and 42 GPa, respectively. The same transition sequence is predicted by calculations within GGA + U also with transition pressures placed at ˜24 GPa and ˜50 GPa, respectively. Further, on the basis of comparison of zero pressure equilibrium volume and equation of state with available experimental data, we find that GGA + U approximation with U = 2.5 eV describes this material better than the simple GGA approximation. The theoretically predicted high pressure structural phase transitions are in disagreement with the only high experimental study by Dancausse et al. [J. Alloys. Compd. 191, 309 (1993)] on this compound which reports a tetragonal to hexagonal phase transition at a pressure of ˜17.6 GPa. Interestingly, during lowest enthalpy structure search using USPEX, we do not see any hexagonal phase to be closer to the predicted monoclinic phase even within 0.2 eV/f. unit. More experiments with varying carbon contents in UC2 sample are required to resolve this discrepancy. The existence of these high pressure phases predicted by static lattice calculations has been further substantiated by analyzing the elastic and lattice dynamic stability of these structures in the pressure regimes of their structural stability. Additionally, various thermo-physical quantities such as equilibrium volume, bulk modulus, Debye

  7. High pressure study of a highly energetic nitrogen-rich carbon nitride, cyanuric triazide

    Energy Technology Data Exchange (ETDEWEB)

    Laniel, Dominique; Desgreniers, Serge [Laboratoire de physique des solides denses, University of Ottawa, Ottawa, Ontario K1N 6N5 (Canada); Downie, Laura E. [Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia B3H 4R2 (Canada); Smith, Jesse S. [High Pressure Collaborative Access Team, Carnegie Institution of Washington, Argonne, Illinois 60439 (United States); Savard, Didier; Murugesu, Muralee [Department of Chemistry, University of Ottawa, Ottawa, Ontario K1N 6N5 (Canada)

    2014-12-21

    Cyanuric triazide (CTA), a nitrogen-rich energetic material, was compressed in a diamond anvil cell up to 63.2 GPa. Samples were characterized by x-ray diffraction, Raman, and infrared spectroscopy. A phase transition occurring between 29.8 and 30.7 GPa was found by all three techniques. The bulk modulus and its pressure derivative of the low pressure phase were determined by fitting the 300 K isothermal compression data to the Birch-Murnaghan equation of state. Due to the strong photosensitivity of CTA, synchrotron generated x-rays and visible laser radiation both lead to the progressive conversion of CTA into a two dimensional amorphous C=N network, starting from 9.2 GPa. As a result of the conversion, increasingly weak and broad x-ray diffraction lines were recorded from crystalline CTA as a function of pressure. Hence, a definite structure could not be obtained for the high pressure phase of CTA. Results from infrared spectroscopy carried out to 40.5 GPa suggest the high pressure formation of a lattice built of tri-tetrazole molecular units. The decompression study showed stability of the high pressure phase down to 13.9 GPa. Finally, two CTA samples, one loaded with neon and the other with nitrogen, used as pressure transmitting media, were laser-heated to approximately 1100 K and 1500 K while compressed at 37.7 GPa and 42.0 GPa, respectively. In both cases CTA decomposed resulting in amorphous compounds, as recovered at ambient conditions.

  8. High pressure study of a highly energetic nitrogen-rich carbon nitride, cyanuric triazide

    International Nuclear Information System (INIS)

    Cyanuric triazide (CTA), a nitrogen-rich energetic material, was compressed in a diamond anvil cell up to 63.2 GPa. Samples were characterized by x-ray diffraction, Raman, and infrared spectroscopy. A phase transition occurring between 29.8 and 30.7 GPa was found by all three techniques. The bulk modulus and its pressure derivative of the low pressure phase were determined by fitting the 300 K isothermal compression data to the Birch-Murnaghan equation of state. Due to the strong photosensitivity of CTA, synchrotron generated x-rays and visible laser radiation both lead to the progressive conversion of CTA into a two dimensional amorphous C=N network, starting from 9.2 GPa. As a result of the conversion, increasingly weak and broad x-ray diffraction lines were recorded from crystalline CTA as a function of pressure. Hence, a definite structure could not be obtained for the high pressure phase of CTA. Results from infrared spectroscopy carried out to 40.5 GPa suggest the high pressure formation of a lattice built of tri-tetrazole molecular units. The decompression study showed stability of the high pressure phase down to 13.9 GPa. Finally, two CTA samples, one loaded with neon and the other with nitrogen, used as pressure transmitting media, were laser-heated to approximately 1100 K and 1500 K while compressed at 37.7 GPa and 42.0 GPa, respectively. In both cases CTA decomposed resulting in amorphous compounds, as recovered at ambient conditions

  9. High pressure study of a highly energetic nitrogen-rich carbon nitride, cyanuric triazide.

    Science.gov (United States)

    Laniel, Dominique; Downie, Laura E; Smith, Jesse S; Savard, Didier; Murugesu, Muralee; Desgreniers, Serge

    2014-12-21

    Cyanuric triazide (CTA), a nitrogen-rich energetic material, was compressed in a diamond anvil cell up to 63.2 GPa. Samples were characterized by x-ray diffraction, Raman, and infrared spectroscopy. A phase transition occurring between 29.8 and 30.7 GPa was found by all three techniques. The bulk modulus and its pressure derivative of the low pressure phase were determined by fitting the 300 K isothermal compression data to the Birch-Murnaghan equation of state. Due to the strong photosensitivity of CTA, synchrotron generated x-rays and visible laser radiation both lead to the progressive conversion of CTA into a two dimensional amorphous C=N network, starting from 9.2 GPa. As a result of the conversion, increasingly weak and broad x-ray diffraction lines were recorded from crystalline CTA as a function of pressure. Hence, a definite structure could not be obtained for the high pressure phase of CTA. Results from infrared spectroscopy carried out to 40.5 GPa suggest the high pressure formation of a lattice built of tri-tetrazole molecular units. The decompression study showed stability of the high pressure phase down to 13.9 GPa. Finally, two CTA samples, one loaded with neon and the other with nitrogen, used as pressure transmitting media, were laser-heated to approximately 1100 K and 1500 K while compressed at 37.7 GPa and 42.0 GPa, respectively. In both cases CTA decomposed resulting in amorphous compounds, as recovered at ambient conditions. PMID:25527947

  10. 1,1-Diamino-2,2-dinitroethylene under high pressure-temperature.

    Science.gov (United States)

    Bishop, Matthew M; Chellappa, Raja S; Pravica, Michael; Coe, Josh; Liu, Zhenxian; Dattlebaum, Dana; Vohra, Yogesh; Velisavljevic, Nenad

    2012-11-01

    The structural phase stability of 1,1-diamino-2,2-dinitroethylene (FOX-7) has been studied up to 10 GPa through isothermal compression at 100 °C and 200 °C using synchrotron mid- and far-infrared spectroscopy. During isothermal compression at 100 °C changes are observed in vibrational spectra with increase in pressure that are indicative of significant distortion to monoclinic α phase or a possible structural transformation to a high pressure α(') phase at 2.2 GPa and α(") phase at 6.1 GPa. At 200 °C, for the far- and mid-IR regimes, the similar changes were observed at 2.1 (2.0) GPa and 5.3 (5.5) GPa, respectively. The observed change is nearly isobaric, consistent with previously reported high pressure and room temperature values, up to the highest temperature of 200 °C reached in our experiments. Over the total P-T range investigated, up to ∼10 GPa and 200 °C, we observed no evidence of sample decomposition. The observed changes are partially reversible with only slight evidence of the high pressure distortion remaining upon complete decompression. Additional isobaric heating at 1.07 GPa was performed in the mid-IR regime, which clearly revealed an onset of decomposition at 360 °C. Further x-ray or neutron diffraction, which are needed to fully resolve the cause of observed changes above 2 and 5 GPa, are ongoing. PMID:23145728

  11. High pressure study of a highly energetic nitrogen-rich carbon nitride, cyanuric triazide

    Science.gov (United States)

    Laniel, Dominique; Downie, Laura E.; Smith, Jesse S.; Savard, Didier; Murugesu, Muralee; Desgreniers, Serge

    2014-12-01

    Cyanuric triazide (CTA), a nitrogen-rich energetic material, was compressed in a diamond anvil cell up to 63.2 GPa. Samples were characterized by x-ray diffraction, Raman, and infrared spectroscopy. A phase transition occurring between 29.8 and 30.7 GPa was found by all three techniques. The bulk modulus and its pressure derivative of the low pressure phase were determined by fitting the 300 K isothermal compression data to the Birch-Murnaghan equation of state. Due to the strong photosensitivity of CTA, synchrotron generated x-rays and visible laser radiation both lead to the progressive conversion of CTA into a two dimensional amorphous C=N network, starting from 9.2 GPa. As a result of the conversion, increasingly weak and broad x-ray diffraction lines were recorded from crystalline CTA as a function of pressure. Hence, a definite structure could not be obtained for the high pressure phase of CTA. Results from infrared spectroscopy carried out to 40.5 GPa suggest the high pressure formation of a lattice built of tri-tetrazole molecular units. The decompression study showed stability of the high pressure phase down to 13.9 GPa. Finally, two CTA samples, one loaded with neon and the other with nitrogen, used as pressure transmitting media, were laser-heated to approximately 1100 K and 1500 K while compressed at 37.7 GPa and 42.0 GPa, respectively. In both cases CTA decomposed resulting in amorphous compounds, as recovered at ambient conditions.

  12. Germination of vegetable seeds exposed to very high pressure

    International Nuclear Information System (INIS)

    Effects of high hydrostatic pressure were investigated on vegetable seeds in the GPa range to examine the potentialities of breed improvement by high-pressure processing. Specimens of several seeds of broccoli (Brassica oleracea var. italica), Turnip leaf (Brassica rapa var. perviridis) and Potherb Mustard (Brassica rapa var. nipposinica) were put in a teflon capsule with liquid high pressure medium, fluorinate, and inserted into a pyrophillite cube. By using a cubic anvil press a hydrostatic pressure of 5.5 GP a was applied to these seeds for 15 minutes. After being brought back to ambient pressure, they were seeded on humid soil in a plant pot. Many of these vegetable seeds began to germinate within 6 days after seeded.

  13. Novel High Pressure Multi-Component Diffusion Cell

    Directory of Open Access Journals (Sweden)

    Muthia Elma

    2012-01-01

    Full Text Available A novel high pressure multi-component diffusion cell (HPMCDC apparatus has been designed and built to measure single and binary gas diffusion, including co-current and counter-diffusion, from low to high pressures. The apparatus incorporates capability to investigate scale effects in solid coal specimens, up to 25 mm in diameter and 25 mm in thickness. Future experiments will be conducted to measure diffusion and counter-diffusion of CH4 and CO2 gases in solid coal, at various temperatures, pressures and for three distinct ranks of coal. The experiments will also address the frequent and controversial literature conclusions that the apparent-diffusion of CH4, inconsistent with gas diffusion theory.

  14. A decade of railgun development for high pressure research

    Energy Technology Data Exchange (ETDEWEB)

    Hawke, R.S.

    1988-07-20

    This paper summarizes a decade of effort towards development of railguns into useful high pressure tools. In 1942 the first successful railgun accelerated a 10-g projectile to about 1 km/s, and in the 1960's velocities approaching 10 km/s were achieved, but without verification of projectile integrity. Later work at the Australian National University showed the potential of railguns to launch intact projectiles. About 10 years ago efforts began to develop railguns for a variety of purposes, including high pressure shock wave equation-of-state (EOS) research. Problems and their causes in this research are now more clearly understood and efforts are being made to develop the railgun into a hypervelocity EOS tool.

  15. Is high-pressure water the cradle of life?

    Energy Technology Data Exchange (ETDEWEB)

    Bassez, Marie-Paule [Universite de Strasbourg-3, Departement Chimie, 72 route du Rhin, 67400 Illkirch (France)

    2003-06-25

    Several theories have been proposed for the synthesis of prebiotic molecules. This letter shows that the structure of supercritical water, or high-pressure water, could trigger prebiotic synthesis and the origin of life deep in the oceans, in hydrothermal vent systems. Dimer geometries of high-pressure water may have a point of symmetry and a zero dipole moment. Consequently, simple apolar molecules found in submarine hydrothermal vent systems will dissolve in the apolar environment provided by the apolar form of the water dimer. Apolar water could be the medium which helps precursor molecules to concentrate and react more efficiently. The formation of prebiotic molecules could thus be linked to the structure of the water inside chimney nanochannels and cavities where hydrothermal piezochemistry and shock wave chemistry could occur. (letter to the editor)

  16. JT8D high pressure compressor performance improvement

    Energy Technology Data Exchange (ETDEWEB)

    Gaffin, W.O.

    1981-11-01

    An improved performance high pressure compressor with potential application to all models of the JT8D engine was designed. The concept consisted of a trenched abradable rubstrip which mates with the blade tips for each of the even rotor stages. This feature allows tip clearances to be set so blade tips run at or near the optimum radius relative to the flowpath wall, without the danger of damaging the blades during transients and maneuvers. The improved compressor demonstrated thrust-specific fuel consumption and exhaust gas temperature improvements of 1.0% and at least 10/sup 0/C over the takeoff and climb power range at sea level static conditions, compared to a bill-of-material high pressure compressor. Surge margin also improved 4 percentage points over the high power operating range. A thrust-specific fuel consumption improvement of 0.7% at typical cruise conditions was calculated based on the sea level test results.

  17. JT8D high pressure compressor performance improvement

    Science.gov (United States)

    Gaffin, W. O.

    1981-01-01

    An improved performance high pressure compressor with potential application to all models of the JT8D engine was designed. The concept consisted of a trenched abradable rubstrip which mates with the blade tips for each of the even rotor stages. This feature allows tip clearances to be set so blade tips run at or near the optimum radius relative to the flowpath wall, without the danger of damaging the blades during transients and maneuvers. The improved compressor demonstrated thrust specific fuel consumption and exhaust gas temperature improvements of 1.0 percent and at least 10 C over the takeoff and climb power range at sea level static conditions, compared to a bill-of-material high pressure compressor. Surge margin also improved 4 percentage points over the high power operating range. A thrust specific fuel consumption improvement of 0.7 percent at typical cruise conditions was calculated based on the sea level test results.

  18. Measurements of plasma potential in high-pressure microwave plasmas

    International Nuclear Information System (INIS)

    Plasma potential of a high-pressure (∼1 Torr) microwave-generated argon plasma is measured using a Langmuir probe and a cold emissive probe. The operation of a hot emissive probe in a high-pressure plasma has been very difficult due to frequent burn-outs and significantly reduced lifetime of the probe filament, which, in turn, limits the possibility of collecting a wide range of data. The I-V characteristics from both Langmuir and emissive probes are interpreted using the collisionless probe theory since the collision correction factor is not very significant. The plasma potential determined from both Langmuir and cold emissive probe characteristics agrees well with one another and is observed to be dependent on the operating gas pressure but relatively unchanged as a function of the microwave power. An average plasma potential determined over the operating range of microwave powers varies nonlinearly with the gas pressure.

  19. High pressure ratio cryocooler with integral expander and heat exchanger

    Science.gov (United States)

    Crunkleton, J. A.; Smith, J. L., Jr.; Iwasa, Y.

    A new 1 W, 4.2 K cryocooler is under development that is intended to miniaturize helium temperature refrigeration systems using a high-pressure-ratio Collins-type cycle. The configuration resulted from optimization studies of a saturated vapor compression (SCV) cycle that employs miniature parallel-plate heat exchangers. The basic configuration is a long displacer in a close-fitting, thin-walled cylinder. The displacer-to-cylinder gap is the high-pressure passage of the heat exchanger, and the low-pressure passage is formed by a thin tube over the OD of the cylinder. A solenoid-operated inlet valve admits 40 atm helium to the displacer-to-cylinder gap at room temperature, while the solenoid-operated exhaust valve operates at 4 atm. The single-stage cryocooler produces 1 W of refrigeration at 40 K without precooling and at 20 K with liquid nitrogen precooling.

  20. Landmine Detection and Discrimination Using High-Pressure Waterjets

    Directory of Open Access Journals (Sweden)

    Daryl G. Beetner

    2004-10-01

    Full Text Available Methods of locating and identifying buried landmines using high-pressure waterjets were investigated. Methods were based on the sound produced when the waterjet strikes a buried object. Three classification techniques were studied, based on temporal, spectral, and a combination of temporal and spectral approaches using weighted density distribution functions, a maximum likelihood approach, and hidden Markov models, respectively. Methods were tested with laboratory data from low-metal content simulants and with field data from inert real landmines. Results show that the sound made when the waterjet hit a buried object could be classified with a 90% detection rate and an 18% false alarm rate. In a blind field test using 3 types of harmless objects and 7 types of landmines, buried objects could be accurately classified as harmful or harmless 60%–90% of the time. High-pressure waterjets may serve as a useful companion to conventional detection and classification methods.

  1. Equation of state of liquid Indium under high pressure

    Directory of Open Access Journals (Sweden)

    Huaming Li

    2015-09-01

    Full Text Available We apply an equation of state of a power law form to liquid Indium to study its thermodynamic properties under high temperature and high pressure. Molar volume of molten indium is calculated along the isothermal line at 710K within good precision as compared with the experimental data in an externally heated diamond anvil cell. Bulk modulus, thermal expansion and internal pressure are obtained for isothermal compression. Other thermodynamic properties are also calculated along the fitted high pressure melting line. While our results suggest that the power law form may be a better choice for the equation of state of liquids, these detailed predictions are yet to be confirmed by further experiment.

  2. ICAR ATRP of Acrylonitrile under Ambient and High Pressure

    Directory of Open Access Journals (Sweden)

    Zhicheng Huang

    2016-03-01

    Full Text Available It is well known that well-defined polyacrylonitrile (PAN with high molecular weight (Mw > 106 g·mol−1 is an excellent precursor for high performance carbon fiber. In this work, a strategy for initiators for a continuous activator regeneration atom transfer radical polymerization (ICAR ATRP system for acrylonitrile (AN was firstly established by using CuCl2·2H2O as the catalyst and 2,2′-azobis(2-methylpropionitrile (AIBN as the thermal initiator in the presence of ppm level catalyst under ambient and high pressure (5 kbar. The effect of catalyst concentration and polymerization temperature on the polymerization behaviors was investigated. It is important that PAN with ultrahigh viscosity and average molecular weight (Mη = 1,034,500 g·mol−1 could be synthesized within 2 h under high pressure.

  3. High pressure extraction of phenolic compounds from citrus peels†

    Science.gov (United States)

    Casquete, R.; Castro, S. M.; Villalobos, M. C.; Serradilla, M. J.; Queirós, R. P.; Saraiva, J. A.; Córdoba, M. G.; Teixeira, P.

    2014-10-01

    This study evaluated the effect of high pressure processing on the recovery of high added value compounds from citrus peels. Overall, the total phenolic content in orange peel was significantly (P antioxidant activity than orange peel. Pressure-treated samples (300 MPa, 10 min; 500 MPa, 3 min) demonstrated higher phenolic content and antioxidant activity comparatively to the control samples. For more severe treatments (500 MPa, 10 min), the phenolic content and antioxidant activity decreased in both lemon and orange peels. This paper was presented at the 8th International Conference on High Pressure Bioscience & Biotechnology (HPBB 2014), in Nantes (France), 15-18 July 2014.

  4. The effect of high pressure on nitrogen compounds of milk

    International Nuclear Information System (INIS)

    The effect of pressurization at different pressures (from 200 to 1000 MPa, at 200 MPa intervals, tconst. = 15 min) and periods of time (from 15 to 35 min, at 10 min intervals, pconst. = 800 MPa) on the changes of proteins and nitrogen compounds of skimmed milk was studied. The pressurization caused an increase in the amount of soluble casein and denaturation of whey proteins. The level of nonprotein nitrogen compounds and proteoso-peptone nitrogen compounds increased as a result of the high-pressure treatment. These changes increased with an increase in pressure and exposure time. High-pressure treatment considerably affected the changes in the conformation of milk proteins, which was reflected in the changes in the content of proteins sedimenting and an increase in their degree of hydration

  5. Is high-pressure water the cradle of life?

    International Nuclear Information System (INIS)

    Several theories have been proposed for the synthesis of prebiotic molecules. This letter shows that the structure of supercritical water, or high-pressure water, could trigger prebiotic synthesis and the origin of life deep in the oceans, in hydrothermal vent systems. Dimer geometries of high-pressure water may have a point of symmetry and a zero dipole moment. Consequently, simple apolar molecules found in submarine hydrothermal vent systems will dissolve in the apolar environment provided by the apolar form of the water dimer. Apolar water could be the medium which helps precursor molecules to concentrate and react more efficiently. The formation of prebiotic molecules could thus be linked to the structure of the water inside chimney nanochannels and cavities where hydrothermal piezochemistry and shock wave chemistry could occur. (letter to the editor)

  6. Monte Carlo Study of High Pressure Ion Chamber Energy Response

    Institute of Scientific and Technical Information of China (English)

    GAO; Fei; XIAO; Xue-fu; ZHANG; Li; NI; Ning; HOU; Jin-bing

    2012-01-01

    <正>High pressure gas ionization chamber (HPIC) is the most popular instrument for environmental radiation measurement because of low inherent background, good stability, better directional response and high precision. The energy response of HIPC is not good because its wall is not made of air effective material, and the response of 100 keV photons is about 60% higher than normal. The energy response of

  7. Cosmic Rays Response of High-pressure Ionization Chamber

    Institute of Scientific and Technical Information of China (English)

    GAO; Fei; XIAO; Xue-fu; NI; Ning; ZHANG; Xi; HOU; Jin-bing; SONG; Ming-zhe; WANG; Hong-yu

    2013-01-01

    In order to study cosmic rays response characteristics of self-designed HPIC(high pressure ionization chamber),model JLZ-Ⅲ,the JLZ-Ⅲwas placed on a boat which is 3 meters much deeper and at least 1 kilometer away from land to measure air kerma rate in the open water in Miyun Reservoir(geomagnetic latitude 29°N,altitude 160 m),Beijing.The result was compared with the measurement

  8. Discrete Approaches for Optimal Routing of High Pressure Pipes

    OpenAIRE

    Schelbert, Jakob

    2015-01-01

    The planning of a whole power plant involves diversivied specializations in engineering and can take up to several years. Within the planning procedure the routing of the high pressure pipes transporting the hot steam from the main boiler to the steam turbines exerts a strong influence on efficiency of the power plant. The design of pipe routing is usually done by a specially trained and experienced engineer with the aid of CAE software. The starting point of the problem is given by...

  9. Conventional superconductivity at 190 K at high pressures

    OpenAIRE

    Drozdov, A. P.; Eremets, M. I.; Troyan, I. A.

    2014-01-01

    The highest critical temperature of superconductivity Tc has been achieved in cuprates: 133 K at ambient pressure and 164 K at high pressures. As the nature of superconductivity in these materials is still not disclosed, the prospects for a higher Tc are not clear. In contrast the Bardeen-Cooper-Schrieffer (BCS) theory gives a clear guide for achieving high Tc: it should be a favorable combination of high frequency phonons, strong coupling between electrons and phonons, and high density of st...

  10. Equation of state of liquid Indium under high pressure

    OpenAIRE

    Huaming Li; Yongli Sun; Mo Li

    2015-01-01

    We apply an equation of state of a power law form to liquid Indium to study its thermodynamic properties under high temperature and high pressure. Molar volume of molten indium is calculated along the isothermal line at 710K within good precision as compared with the experimental data in an externally heated diamond anvil cell. Bulk modulus, thermal expansion and internal pressure are obtained for isothermal compression. Other thermodynamic properties are also calculated along the fitted high...

  11. High Pressure Hydrogen Storage on Carbon Materials for Mobile Applications

    OpenAIRE

    Blackman, James Michael

    2005-01-01

    Recognising the difficulties encountered in measuring the adsorption of hydrogen at high pressure, a reliable volumetric differential pressure method of high accuracy and good repeatability has been developed for measurement up to ca 100 bar. The apparatus used has two identical limbs, a sample and a blank limb, between which a high accuracy differential pressure cell measures changes in pressure. By simultaneously expanding the two limbs and closely controlling the temperature of the entir...

  12. High-pressure biotechnology in medicine and pharmaceutical science

    OpenAIRE

    Masson Patrick; Tonello Carole; Balny Claude

    2001-01-01

    High-pressure (HP) biotechnology is an emerging technique initially applied for food processing and more recently in pharmaceutical and medical sciences. Pressure can stabilize enzymes and modulate both their activity and specificity. HP engineering of proteins may be used for enzyme-catalyzed synthesis of fine chemicals, pharmaceuticals, and production of modified proteins of medical or pharmaceutical interest. HP inactivation of biological agents is expected to be applicable to sterilizatio...

  13. High-Pressure Valve With Controlled Seating Force

    Science.gov (United States)

    Bradley, R. H.

    1987-01-01

    Poppet and seat less likely to be damaged by faulty operation. Improvements in widely-used high-pressure valve increase accuracy of preloading of poppet. Redesigned valve prevents metal shavings and other debris from developing during operation, installation, or removal. New features include secondary seal in cap. Belleville washers create precise value of seating force. If installer attempts to exceed force, torque limiter gives tactile and aural warning and makes further force increases difficult.

  14. High pressure-sensitive gene expression in Lactobacillus sanfranciscensis

    Directory of Open Access Journals (Sweden)

    Vogel R.F.

    2005-01-01

    Full Text Available Lactobacillus sanfranciscensis is a Gram-positive lactic acid bacterium used in food biotechnology. It is necessary to investigate many aspects of a model organism to elucidate mechanisms of stress response, to facilitate preparation, application and performance in food fermentation, to understand mechanisms of inactivation, and to identify novel tools for high pressure biotechnology. To investigate the mechanisms of the complex bacterial response to high pressure we have analyzed changes in the proteome and transcriptome by 2-D electrophoresis, and by microarrays and real time PCR, respectively. More than 16 proteins were found to be differentially expressed upon high pressure stress and were compared to those sensitive to other stresses. Except for one apparently high pressure-specific stress protein, no pressure-specific stress proteins were found, and the proteome response to pressure was found to differ from that induced by other stresses. Selected pressure-sensitive proteins were partially sequenced and their genes were identified by reverse genetics. In a transcriptome analysis of a redundancy cleared shot gun library, about 7% of the genes investigated were found to be affected. Most of them appeared to be up-regulated 2- to 4-fold and these results were confirmed by real time PCR. Gene induction was shown for some genes up-regulated at the proteome level (clpL/groEL/rbsK, while the response of others to high hydrostatic pressure at the transcriptome level seemed to differ from that observed at the proteome level. The up-regulation of selected genes supports the view that the cell tries to compensate for pressure-induced impairment of translation and membrane transport.

  15. NUMERICAL INVESTIGATION OF STRESS GENERATED IN HIGH PRESSURE HEAT EXCHANGER

    OpenAIRE

    Sandeep S. Samane*, Sudhakar S. Umale

    2016-01-01

    Heat Exchangers are used to transfer heat effectively from one medium to another medium. There are several aspects to study the performance of heat exchanger. This paper is concerned with thermo-mechanical issues i.e. thermal expansion due to high temperature and high pressure conditions of U-tube heat exchanger. Tubesheet is very complex part of heat exchanger which expands at high temperature. Due to high temperature difference between shell side and channel side fluids thermal stress are g...

  16. High-pressure highly reduced nitrides and oxides from chromitite of a Tibetan ophiolite

    Science.gov (United States)

    Dobrzhinetskaya, Larissa F.; Wirth, Richard; Yang, Jingsui; Hutcheon, Ian D.; Weber, Peter K.; Green, Harry W.

    2009-01-01

    The deepest rocks known from within Earth are fragments of normal mantle (≈400 km) and metamorphosed sediments (≈350 km), both found exhumed in continental collision terranes. Here, we report fragments of a highly reduced deep mantle environment from at least 300 km, perhaps very much more, extracted from chromite of a Tibetan ophiolite. The sample consists, in part, of diamond, coesite-after-stishovite, the high-pressure form of TiO2, native iron, high-pressure nitrides with a deep mantle isotopic signature, and associated SiC. This appears to be a natural example of the recently discovered disproportionation of Fe2+ at very high pressure and consequent low oxygen fugacity (fO2) in deep Earth. Encapsulation within chromitite enclosed within upwelling solid mantle rock appears to be the only vehicle capable of transporting these phases and preserving their low-fO2 environment at the very high temperatures of oceanic spreading centers. PMID:19880742

  17. XRD and XAS structural study of CuAlO2 under high pressure.

    Science.gov (United States)

    Pellicer-Porres, J; Segura, A; Ferrer-Roca, Ch; Polian, A; Munsch, P; Kim, D

    2013-03-20

    We present the results of x-ray diffraction and x-ray absorption spectroscopy experiments in CuAlO(2) under high pressure. We discuss the polarization dependence of the x-ray absorption near-edge structure at the Cu K-edge. XRD under high pressure evidences anisotropic compression, the a-axis being more compressible than the c-axis. EXAFS yields the copper-oxygen bond length, from which the only internal parameter of the delafossite structure is deduced. The combination of anisotropic compression and the internal parameter decrease results in a regularization of the AlO(6) octahedra. The anisotropic compression is related to the chemical trends observed in the lattice parameters when Al is substituted by other trivalent cations. Both experiments evidence the existence of an irreversible phase transition that clearly manifests at 35 ± 2 GPa. The structure of the high-pressure polymorph could not be determined, but it implies a change of the Cu environment, which remains anisotropic. Precursor effects are observed from the lowest pressures, which are possibly related to crystal breaking at a submicroscopic scale with partial reorientation of the crystallites. PMID:23423689

  18. High-pressure structural and elastic properties of Tl₂O₃

    Energy Technology Data Exchange (ETDEWEB)

    Gomis, O., E-mail: osgohi@fis.upv.es; Vilaplana, R. [Centro de Tecnologías Físicas, MALTA Consolider Team, Universitat Politècnica de València, 46022 València (Spain); Santamaría-Pérez, D. [Departamento de Física Aplicada-ICMUV, MALTA Consolider Team, Universidad de Valencia, Edificio de Investigación, C/Dr. Moliner 50, 46100 Burjassot (Spain); Earth Sciences Department, University College London, Gower Street, WC1E 6BT London (United Kingdom); Ruiz-Fuertes, J. [Departamento de Física Aplicada-ICMUV, MALTA Consolider Team, Universidad de Valencia, Edificio de Investigación, C/Dr. Moliner 50, 46100 Burjassot (Spain); Geowissenschaften, Goethe-Universität, Altenhöferallee 1, 60438 Frankfurt am Main (Germany); Sans, J. A.; Manjón, F. J.; Mollar, M. [Instituto de Diseño para la Fabricación y Producción Automatizada, MALTA Consolider Team, Universitat Politècnica de València, 46022 València (Spain); and others

    2014-10-07

    The structural properties of Thallium (III) oxide (Tl₂O₃) have been studied both experimentally and theoretically under compression at room temperature. X-ray powder diffraction measurements up to 37.7 GPa have been complemented with ab initio total-energy calculations. The equation of state of Tl₂O₃ has been determined and compared to related compounds. It has been found experimentally that Tl₂O₃ remains in its initial cubic bixbyite-type structure up to 22.0 GPa. At this pressure, the onset of amorphization is observed, being the sample fully amorphous at 25.2 GPa. The sample retains the amorphous state after pressure release. To understand the pressure-induced amorphization process, we have studied theoretically the possible high-pressure phases of Tl₂O₃. Although a phase transition is theoretically predicted at 5.8 GPa to the orthorhombic Rh₂O₂-II-type structure and at 24.2 GPa to the orthorhombic α-Gd₂S₃-type structure, neither of these phases were observed experimentally, probably due to the hindrance of the pressure-driven phase transitions at room temperature. The theoretical study of the elastic behavior of the cubic bixbyite-type structure at high-pressure shows that amorphization above 22 GPa at room temperature might be caused by the mechanical instability of the cubic bixbyite-type structure which is theoretically predicted above 23.5 GPa.

  19. Terahertz time-domain spectroscopy of high-pressure flames

    Institute of Scientific and Technical Information of China (English)

    Jason BASSI; Mark STRINGER; Bob MILES; Yang ZHANG

    2009-01-01

    Laser spectroscopy in the visible and near infrared is widely used as a diagnostic tool for combustion devices, but this approach is difficult at high pressures within a sooty flame itself. High soot concentrations render flames opaque to visible light, but they remain transparent to far-infrared or terahertz (THz) radiation. The first far-infrared absorption spectra, to the best of our knowledge, of sooty, non-premixed, ethylene high-pressure flames covering the region of 0.2-2.5 THz is presented. A specially designed high-pressure burner which is optically accessible to THz radiation has been built allowing flame transmission measurements up to pressures of 1.6 MPa. Calculations of the theoretical combustion species absorption spectra in the 0.2-3 THz range have shown that almost all the observable features arise from H2O. A few OH (1.84 and 2.51 THz), CH (2.58 THz), and NH3 (1.77 and 2.95 THz) absorption lines are also observable in principle. A large number of H2O absorption lines are observed in the ground vibrational in a laminar non-premixed, sooty flame (ethylene) at pressures up to 1.6 MPa.

  20. Boundary Layer Ventilation Processes During a High Pressure Event

    Science.gov (United States)

    Gray, S. L.; Dacre, H. F.; Belcher, S. E.

    2006-12-01

    It is often assumed that ventilation of the atmospheric boundary layer is weak during high pressure events. But is this always true? Here we investigate the processes responsible for ventilation of the atmospheric boundary layer during a high pressure event that occured on the 9 May 2005 using the UK Met Office Unifed Model. Pollution sources are represented by the constant emission of a passive tracer everywhere over land. The ventilation processes observed include a sea breeze circulation, turbulent mixing across the top of the boundary layer followed by large-scale ascent, and shallow convection. Vertical distributions of tracer are validated with AMPEP (Aircraft Measurement of chemical Processing Export fluxes of Pollutants over the UK) CO aircraft measurements and are shown to agree impressively well. Budget calculations of tracers are performed in order to determine the relative importance of these ventilation processes. The sea breeze circulation was found to ventilate 26% of the boundary layer tracer by sunset of which 2% was above 2km. A combination of the sea breeze circulation and turbulent mixing ventilated 46% of the boundary layer tracer, of which 10% was above 2km. Finally, the sea breeze circulation, turbulent mixing and shallow convection processes together ventilated 52% of the tracer into the free troposphere, of which 26% was above 2km. Hence this study shows that signicant ventilation of the boundary layer can occur during high pressure events; turbulent mixing and convection processes can double the amount of pollution ventilated from the boundary layer.