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Sample records for accompanying high-pressure phase

  1. High-pressure phase transitions of strontianite

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  2. Phase transition and structure of silver azide at high pressure

    NASA Astrophysics Data System (ADS)

    Hou, Dongbin; Zhang, Fuxiang; Ji, Cheng; Hannon, Trevor; Zhu, Hongyang; Wu, Jianzhe; Levitas, Valery I.; Ma, Yanzhang

    2011-07-01

    Silver azide (AgN3) 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° 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, N1 at 4d, and N2 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 KOT = 39 ± 5 GPa with KOT' = 10 ± 7 and KOT = 57 ± 2 GPa with KOT' = 6.6 ± 0.2, respectively.

  3. High-pressure phase transitions in adamantane

    NASA Astrophysics Data System (ADS)

    Vijayakumar, V.; Garg, Alka B.; Godwal, B. K.; Sikka, S. K.

    2000-11-01

    We report angle dispersive X-ray diffraction (ADXRD) measurements on adamantane carried out at SPRING-8 to the pressures of 25 GPa. The tetragonal phase observed at 0.5 GPa remains stable up to 12.5 GPa. In this pressure range the intermolecular hydrogen separation reduces from 2.37 to1.87 Å with relative angle of rotation of the two molecules increasing from 8.5° to 10.5° in agreement with values from energy minimization. At 16 GPa, the diffraction pattern could be indexed either by a tetragonal or a monoclinic cell. Beyond 22 GPa only monoclinic cell indexes the patterns. The present findings corroborate the earlier Raman results.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

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

    SciTech Connect

    Durandurdu, Murat

    2015-10-15

    The high-pressure behavior of the orthorhombic cotunnite type ZrO{sub 2} is explored using an ab initio constant pressure technique. For the first time, a novel hexagonal phase (Ni{sub 2}In type) within P6{sub 3}/mmc symmetry is predicted through the simulation. The Ni{sub 2}In type crystal is the densest high-pressure phase of ZrO{sub 2} proposed so far and has not been observed in other metal dioxides at high pressure before. The phase transformation is accompanied by a small volume drop and likely to occur around 380 GPa in experiment. - Graphical abstract: Post-cotunnite Ni{sub 2}In type hexagonal phase forms in zirconia at high pressure. - Highlights: • A post-cotunnite phase is predicted for ZrO{sub 2} through an ab initio simulation. • Cotunnite ZrO{sub 2} adopts the Ni{sub 2}In type structure at high pressure. • The Ni{sub 2}In type structure is the densest high-pressure phase of ZrO{sub 2} proposed so far. • The preferred mechanism in ZrO{sub 2} differs from the other metal dioxides.

  6. Experimental methods for phase equilibria at high pressures.

    PubMed

    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 transformation in iron under fast compression

    SciTech Connect

    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.

  8. High-pressure phase transitions in rubidium and caesium hydroxides.

    PubMed

    Hermann, Andreas

    2016-06-28

    A computational investigation of the high-pressure phase sequence of the heaviest alkali hydroxides, RbOH and CsOH, shows that the phase diagram of both compounds is richer than hitherto thought. First-principles calculations suggest, based on energetics and comparisons to experimental diffraction and spectroscopy signatures, that the high-pressure phase RbOH-VI, stable above 6 GPa in experiment, should be assigned the KOH-VI structure type, and features localised hydrogen-bonded (OH)4 units. Meanwhile, a new high-pressure phase CsOH-VII is predicted to be stable above 10 GPa in an isosymmetric phase transition that, like RbOH-VI, marks the transition from layered to three-dimensional network structures under increased compression. Both new phases highlight an unexpected flexibility of hydrogen bond network formation in a series of compounds that seemingly only vary in the cation size, and potential consequences for similar systems, such as water-carrying minerals, are discussed briefly. PMID:27271485

  9. Theoretical Predictions of Phase Transitions at Ultra-high Pressures

    NASA Astrophysics Data System (ADS)

    Boates, Brian

    2013-06-01

    We present ab initio calculations of the high-pressure phase diagrams of important planetary materials such as CO2, MgSiO3, and MgO. For CO2, we predict a series of distinct liquid phases over a wide pressure (P) and temperature (T) range, including a first-order transition to a dense polymer liquid. We have computed finite-temperature free energies of liquid and solid CO2 phases to determine the melting curve beyond existing measurements and investigate possible phase separation transitions. The interaction of these phase boundaries with the mantle geotherm will also be discussed. Furthermore, we find evidence for a vast pressure-temperature regime where molten MgSiO3 decomposes into liquid SiO2 and solid MgO, with a volume change of approximately 1.2 percent. The demixing transition is driven by the crystallization of MgO ? the reaction only occurs below the high-pressure MgO melting curve. The predicted transition pressure at 10,000 K is in close proximity to an anomaly reported in recent laser-driven shock experiments of MgSiO3. We also present new results for the high-pressure melting curve of MgO and its B1-B2 solid phase transition, with a triple point near 364 GPa and 12,000 K.

  10. Elasticity of methane hydrate phases at high pressure.

    PubMed

    Beam, Jennifer; Yang, Jing; Liu, Jin; Liu, Chujie; Lin, Jung-Fu

    2016-04-21

    Determination of the full elastic constants (cij) of methane hydrates (MHs) at extreme pressure-temperature environments is essential to our understanding of the elastic, thermodynamic, and mechanical properties of methane in MH reservoirs on Earth and icy satellites in the solar system. Here, we have investigated the elastic properties of singe-crystal cubic MH-sI, hexagonal MH-II, and orthorhombic MH-III phases at high pressures in a diamond anvil cell. Brillouin light scattering measurements, together with complimentary equation of state (pressure-density) results from X-ray diffraction and methane site occupancies in MH from Raman spectroscopy, were used to derive elastic constants of MH-sI, MH-II, and MH-III phases at high pressures. Analysis of the elastic constants for MH-sI and MH-II showed intriguing similarities and differences between the phases' compressional wave velocity anisotropy and shear wave velocity anisotropy. Our results show that these high-pressure MH phases can exhibit distinct elastic, thermodynamic, and mechanical properties at relevant environments of their respective natural reservoirs. These results provide new insight into the determination of how much methane exists in MH reservoirs on Earth and on icy satellites elsewhere in the solar system and put constraints on the pressure and temperature conditions of their environment. PMID:27389226

  11. Elasticity of methane hydrate phases at high pressure

    NASA Astrophysics Data System (ADS)

    Beam, Jennifer; Yang, Jing; Liu, Jin; Liu, Chujie; Lin, Jung-Fu

    2016-04-01

    Determination of the full elastic constants (cij) of methane hydrates (MHs) at extreme pressure-temperature environments is essential to our understanding of the elastic, thermodynamic, and mechanical properties of methane in MH reservoirs on Earth and icy satellites in the solar system. Here, we have investigated the elastic properties of singe-crystal cubic MH-sI, hexagonal MH-II, and orthorhombic MH-III phases at high pressures in a diamond anvil cell. Brillouin light scattering measurements, together with complimentary equation of state (pressure-density) results from X-ray diffraction and methane site occupancies in MH from Raman spectroscopy, were used to derive elastic constants of MH-sI, MH-II, and MH-III phases at high pressures. Analysis of the elastic constants for MH-sI and MH-II showed intriguing similarities and differences between the phases' compressional wave velocity anisotropy and shear wave velocity anisotropy. Our results show that these high-pressure MH phases can exhibit distinct elastic, thermodynamic, and mechanical properties at relevant environments of their respective natural reservoirs. These results provide new insight into the determination of how much methane exists in MH reservoirs on Earth and on icy satellites elsewhere in the solar system and put constraints on the pressure and temperature conditions of their environment.

  12. High pressure phase transition in Pr-monopnictides

    SciTech Connect

    Raypuria, Gajendra Singh E-mail: gsraypuria@gmail.com; Gupta, Dinesh Chandra

    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.

  13. High pressure structural phase transitions of PbPo

    NASA Astrophysics Data System (ADS)

    Bencherif, Y.; Boukra, A.; Zaoui, A.; Ferhat, M.

    2012-09-01

    First-principles calculations have been performed to investigate the high pressure phase transitions and dynamical properties of the less known lead polonium compound. The calculated ground state parameters for the NaCl phase show good agreement with the experimental data. The obtained results show that the intermediate phase transition for this compound is the orthorhombic Pnma phase. The PbPo undergoes from the rocksalt to Pnma phase at 4.20 GPa. Further structural phase transition from intermediate to CsCl phase has been found at 8.5 GPa. In addition, phonon dispersion spectra were derived from linear-response to density functional theory. In particular, we show that the dynamical properties of PbPo exhibit some peculiar features compared to other III-V compounds. Finally, thermodynamics properties have been also addressed from quasiharmonic approximation.

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

    SciTech Connect

    Yoo, C

    2004-05-26

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

  15. A novel phase of beryllium fluoride at high pressure.

    PubMed

    Rakitin, Maksim S; Oganov, Artem R; Niu, Haiyang; Esfahani, M Mahdi Davari; Zhou, Xiang-Feng; Qian, Guang-Rui; Solozhenko, Vladimir L

    2015-10-21

    A previously unknown thermodynamically stable high-pressure phase of BeF2 has been predicted using the evolutionary algorithm USPEX. This phase occurs in the pressure range 18-27 GPa. Its structure has C2/c space group symmetry and contains 18 atoms in the primitive unit cell. Given the analogy between BeF2 and SiO2, silica phases have been investigated as well, but the new phase has not been observed to be thermodynamically stable for this system. However, it is found to be metastable and to have comparable energy to the known metastable phases of SiO2, suggesting a possibility of its synthesis. PMID:26388165

  16. High-pressure Raman spectroscopy of phase change materials

    SciTech Connect

    Hsieh, Wen-Pin Mao, Wendy L.; Zalden, Peter; Wuttig, Matthias; Lindenberg, Aaron M.

    2013-11-04

    We used high-pressure Raman spectroscopy to study the evolution of vibrational frequencies of the phase change materials (PCMs) Ge{sub 2}Sb{sub 2}Te{sub 5}, GeSb{sub 2}Te{sub 4}, and SnSb{sub 2}Te{sub 4}. We found that the critical pressure for triggering amorphization in the PCMs decreases with increasing vacancy concentration, demonstrating that the presence of vacancies, rather than differences in the atomic covalent radii, is crucial for pressure-induced amorphization in PCMs. Compared to the as-deposited amorphous phase, the pressure-induced amorphous phase has a similar vibrational spectrum but requires much lower laser power to transform into the crystalline phase, suggesting different kinetics of crystallization, which may have implications for applications of PCMs in non-volatile data storage.

  17. Phase transitions and hydrogen bonding in deuterated calcium hydroxide: High-pressure and high-temperature neutron diffraction measurements

    SciTech Connect

    Iizuka, Riko; Komatsu, Kazuki; Kagi, Hiroyuki; Nagai, Takaya; Sano-Furukawa, Asami; Hattori, Takanori; Gotou, Hirotada; Yagi, Takehiko

    2014-10-15

    In situ neutron diffraction measurements combined with the pulsed neutron source at the Japan Proton Accelerator Research Complex (J-PARC) were conducted on high-pressure polymorphs of deuterated portlandite (Ca(OD){sub 2}) using a Paris–Edinburgh cell and a multi-anvil press. The atomic positions including hydrogen for the unquenchable high-pressure phase at room temperature (phase II′) were first clarified. The bent hydrogen bonds under high pressure were consistent with results from Raman spectroscopy. The structure of the high-pressure and high-temperature phase (Phase II) was concordant with that observed previously by another group for a recovered sample. The observations elucidate the phase transition mechanism among the polymorphs, which involves the sliding of CaO polyhedral layers, position modulations of Ca atoms, and recombination of Ca–O bonds accompanied by the reorientation of hydrogen to form more stable hydrogen bonds. - Graphical abstract: Crystal structures of high-pressure polymorphs of Ca(OD){sub 2}, (a) at room temperature (phase II′) and (b) at high temperature (phase II), were obtained from in situ neutron diffraction measurements. - Highlights: • We measured in situ neutron diffraction of high-pressure polymorphs of Ca(OD){sub 2}. • Hydrogen positions of the high-pressure phase are first determined. • The obtained hydrogen bonds reasonably explain Raman peaks of OH stretching modes. • A phase transition mechanism among the polymorphs is proposed.

  18. The phase diagram of high-pressure superionic ice

    PubMed Central

    Sun, Jiming; Clark, Bryan K.; Torquato, Salvatore; Car, Roberto

    2015-01-01

    Superionic ice is a special group of ice phases at high temperature and pressure, which may exist in ice-rich planets and exoplanets. In superionic ice liquid hydrogen coexists with a crystalline oxygen sublattice. At high pressures, the properties of superionic ice are largely unknown. Here we report evidence that from 280 GPa to 1.3 TPa, there are several competing phases within the close-packed oxygen sublattice. At even higher pressure, the close-packed structure of the oxygen sublattice becomes unstable to a new unusual superionic phase in which the oxygen sublattice takes the P21/c symmetry. We also discover that higher pressure phases have lower transition temperatures. The diffusive hydrogen in the P21/c superionic phase shows strong anisotropic behaviour and forms a quasi-two-dimensional liquid. The ionic conductivity changes abruptly in the solid to close-packed superionic phase transition, but continuously in the solid to P21/c superionic phase transition. PMID:26315260

  19. High-pressure behavior of fcc phase FeHx

    NASA Astrophysics Data System (ADS)

    Thompson, E. C.; Chidester, B.; Fischer, R. A.; Prakapenka, V.; Bi, W.; Alp, E. E.; Campbell, A. J.

    2015-12-01

    Earth's core is composed of iron with the inclusion of light elements to compensate for the difference between seismically obtained densities and the density of pure Fe at relevant pressure and temperature conditions. As the most abundant and lightest element in the solar system, hydrogen is a plausible contributor to this core density deficit. Nearly stoichiometric iron hydride (FeHx) has been shown to result from the reaction of Fe and hydrous silicates, and is stable up to at least 80 GPa [1]. Iron hydride formation at Earth's surface is unlikely because the equilibrium hydrogen solubility in iron at atmospheric conditions is prohibitively low, yet as hydrogen solubility increases with pressure, so does the likelihood of FeHx formation within the Earth's interior [2]. Recent experimental and ab initio attempts disagree on the equation of state parameters needed to describe the compressional behavior of FeHx [3-5]. The work presented here combines synchrotron x-ray diffraction of laser-heated diamond anvil cell compressed samples with high-pressure, ambient temperature nuclear resonant inelastic scattering (NRIXS) and synchrotron Mössbauer spectroscopy (SMS) to better constrain the behavior of the fcc phase of FeHx at elevated pressures and temperatures. By pairing P-V-T data for iron hydride with the sound velocity information available through high-pressure NRIXS studies, we can better understand the degree to which hydrogen may contribute to the density deficit of Earth's iron core. [1] Antonov et al. (1998) J. Alloys Compd. 264, 214-222 [2] Fukai and Akimoto (1983) Proc. Japan Acad. 59, 158-162 [3] Pépin et al. (2014) Phys. Rev. Lett. 265504, 1-5 [4] Hirao (2004) Geophys. Res. Lett. 31, L06616 [5] Badding et al. (1991) Science. 253, 421-424

  20. Phase diagram of methane at high pressures and temperatures

    NASA Astrophysics Data System (ADS)

    Goncharov, A. F.; Chen, X.; Lobanov, S.; Chen, P.; Litasov, K. D.; Mao, H.

    2012-12-01

    We report the results of Raman spectroscopy measurements and visual observations of methane at high pressures (up to 80 GPa) and high temperatures (up to 2000 K). The experiments have been performed in resistive and laser heated diamond anvil cell (RHDAC and LHDAC, respectively) combined with confocal Raman microscope. The melting line has been determined by visual observations of the phase equilibrium and by Raman spectroscopy (in RHDAC). The results show an increase in slope of the melting line at 24 GPa and 800 K related to the presence of a triple point between the melt and two solid phases: orientationally disordered below 24 GPa and orientationally ordered above 24 GPa. Methane melts congruently to at least 26 GPa. The LHDAC experiments show that above 1100 K methane chemically reacts to form carbon and molecular hydrogen. At T>1350 K in the whole studied pressure range, there is a formation of longer alkanes, and at T>2000 double bonded hydrocarbons such as alkenes have been detected. These results evidence that hydrocarbons constitute an important part of the reduced C-O-H fluid under geothermal conditions.

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

    SciTech Connect

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

    1992-06-25

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

  2. High-pressure phase equilibria with compressed gases.

    PubMed

    Ren, Wei; Scurto, Aaron M

    2007-12-01

    An apparatus is described that is capable of determining high-pressure vapor-liquid equilibrium, liquid-liquid equilibrium, solid-liquid-vapor equilibrium, vapor-liquid-liquid equilibrium, and mixture critical points and transitions. The device is capable of temperatures to 150 degrees C and pressures to 300 bars (higher with slight modifications). The construction and operation are described in detail and do not require the use of mercury. This method requires very low sample volumes and no analytical equipment nor system-specific calibration. The apparatus was verified by comparison with literature data for the decane-CO(2) mixture and CO(2)-ionic liquid [1-hexyl-3-methyl-imidazolium bis(trifyl)imide)] systems. The experimental data have excellent agreement with the literature data that used different experimental methods. A rigorous error analysis of the system is also presented.

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

    SciTech Connect

    Yoo, C S

    1999-07-22

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

  4. Collective spin 1 singlet phase in high-pressure oxygen

    PubMed Central

    Crespo, Yanier; Fabrizio, Michele; Scandolo, Sandro; Tosatti, Erio

    2014-01-01

    Oxygen, one of the most common and important elements in nature, has an exceedingly well-explored phase diagram under pressure, up to and beyond 100 GPa. At low temperatures, the low-pressure antiferromagnetic phases below 8 GPa where O2 molecules have spin S = 1 are followed by the broad apparently nonmagnetic ε phase from about 8 to 96 GPa. In this phase, which is our focus, molecules group structurally together to form quartets while switching, as believed by most, to spin S = 0. Here we present theoretical results strongly connecting with existing vibrational and optical evidence, showing that this is true only above 20 GPa, whereas the S = 1 molecular state survives up to about 20 GPa. The ε phase thus breaks up into two: a spinless ε0 (20−96 GPa), and another ε1 (8−20 GPa) where the molecules have S = 1 but possess only short-range antiferromagnetic correlations. A local spin liquid-like singlet ground state akin to some earlier proposals, and whose optical signature we identify in existing data, is proposed for this phase. Our proposed phase diagram thus has a first-order phase transition just above 20 GPa, extending at finite temperature and most likely terminating into a crossover with a critical point near 30 GPa and 200 K. PMID:25002513

  5. Phase transition of solid bismuth under high pressure

    NASA Astrophysics Data System (ADS)

    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).

  6. High pressure structural phase transition in uranium monochalcogenides

    NASA Astrophysics Data System (ADS)

    Srivastava, A. K.; Kumari, Samiksha; Gupta, B. R. K.

    2010-01-01

    The pressure induced phase transition in uranium monochalcogenides, UX (X = S, Se, and Te) is studied by two-body potential approach. It is found that US, USe and UTe undergo a structural phase transition from NaCl (B1) type to CsCl (B2) type at 78.5, 21 and 9.5 GPa, respectively, which is in good agreement with the recent experimental data. In addition, second-order elastic constants (SOECs) (C 11, C 12 and C 14) have been calculated which can be used to establish the nature of the forces in these materials. The present study shows that the considered two-body potential model can be used to predict the phase transition pressure in UX compounds provided the strength and hardness parameters in B1 and B2 phases are different.

  7. New Phase Transition of Solid Bromine under High Pressure

    SciTech Connect

    San-Miguel, A.; Libotte, H.; Gaspard, J.-P.; Gauthier, M.; Aquilanti, G.; Pascarelli, S.

    2007-07-06

    Solid bromine has been studied by x-ray absorption spectroscopy experiments up to a maximum pressure of 75 GPa. The data analysis of the extended fine structure reveals that the intramolecular distance first increases, reaching its maximum value at 25{+-}5 GPa. From this value the intramolecular distance abruptly begins to decrease evidencing a nonpreviously observed phase transformation taking place at 25{+-}5 GPa. A maximum variation of 0.08 A ring is observed at 65{+-}5 GPa where again a phase transition occurs. This last transformation could correspond with the recently observed change to an incommensurate modulated phase. We discuss the possible generalization of the observed new phase transition at 25{+-}5 GPa to the case of the other halogens.

  8. Phase diagram of Mo at high pressure and temperature

    SciTech Connect

    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.

  9. High pressure phase transition and elastic properties of americium telluride

    NASA Astrophysics Data System (ADS)

    Aynyas, Mahendra; Rukmangad, Aditi; Arya, B. S.; Sanyal, S. P.

    2013-06-01

    The structural and elastic properties of Americium Telluride (AmTe) have been investigated by using a modified inter-ionic potential theory (MIPT). This theory is capable of explaining first order phase transition with a crystallographic change NaCl to CsCl structure for this compound. The values of optimized lattice constant, phase transition pressure, zero pressure bulk modulus and second order elastic constants (C11, C44) agree well with their corresponding experimental data. Debye temperature (θD) is also calculated for this compound for the first time.

  10. Kinetics of Solid Phase Reactions at High Pressure and Temperature

    SciTech Connect

    Zaug, J M; Farber, D L; Saw, C K; Weeks, B L

    2002-02-11

    We report on the subject of temperature and/or pressure induced solid-solid phase transitions of energetic molecular crystals. Over the last three years we have applied experimental techniques that when used simultaneously provide insight into some of the complexities that govern reaction rate processes. After more than 55 years of study a global kinetics model describing the P-T phase space transition kinetics of such materials as HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) is not only missing, but from a formal perspective is perhaps as many years away from completion. The essence of this report describes what material parameters affect first-order reaction rates of the CHNO moiety of molecular crystals and introduces the application of new experimental tools thus permitting quantifiable studies of important rate limiting mechanisms.

  11. High pressure phase transition in group III nitrides compounds

    NASA Astrophysics Data System (ADS)

    Soni, Shubhangi; Verma, S.; Kaurav, Netram; Choudhary, K. K.

    2016-05-01

    Using an effective interionic interaction potential (EIOP), the pressure induced structural phase transformation from ZnS-type (B3) to NaCl-type (B1) structure in group III Post-Transition Metal Nitrides [TMN; TM=Ga and Tl] were investigated. The long range Coulomb, van der Waals (vdW) interaction and the short-range repulsive interaction upto second-neighbor ions within the Hafemeister and Flygare approach with modified ionic charge are properly incorporated in the EIOP. The vdW coefficients are computed following the Slater-Kirkwood variational method, as both the ions are polarizable. The estimated value of the phase transition pressure (Pt) and the magnitude of the discontinuity in volume at the transition pressure are consistent as compared to the reported data.

  12. High pressure phase diagram of MgO

    NASA Astrophysics Data System (ADS)

    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.

  13. Phase relations and hardness trends of ZrO[subscript 2] phases at high pressure

    SciTech Connect

    Al-Khatatbeh, Yahya; Lee, Kanani K.M.; Kiefer, Boris

    2010-07-23

    We use high-resolution synchrotron x-ray powder diffraction and density-functional theory (DFT) to investigate the phase stability, equations of state (EOSs), and mechanical hardness of zirconia (ZrO{sub 2}) up to {approx}54 and 160 GPa, respectively. For the equilibrium phase at ambient conditions (MI), we provide an experimental EOS that is comparable to results obtained from room-pressure Brillouin scattering experiments and bulk modulus-volume systematics but different from previous high-pressure experiments. The experimental second-order Birch-Murnaghan EOS parameters of MI-ZrO{sub 2} are: ambient-pressure volume (V{sub 0}) of 35.15({+-}0.03) {angstrom}{sup 3}/f.u. with an ambient-pressure bulk modulus K{sub 0} of 210({+-}28) GPa. For the high-pressure OI phase, we find that the K{sub 0} = 290({+-}11) GPa, which is 19%-32% higher than previously determined, and V{sub 0} = 33.65({+-}0.07) {angstrom}{sup 3}/f.u. The small volume decrease of 3.4% across the MI {yields} OI transition at {approx}10 GPa is associated with a 38% increase in the bulk modulus consistent with our DFT calculations that predict a {approx}36% and 39% increase in K{sub 0} for the generalized gradient and local density approximations, respectively. In contrast to the EOS of MI and OI, we find that our experimental EOS for the high-pressure OII phase is in good agreement with previous measurements. The large volume decrease across the OI {yields} OII phase transition as obtained from both our experiments and calculations is {approx}10%. Our estimates, using scaling relations, indicate that this phase, while dense and quenchable, may have a comparatively low mechanical hardness of {approx} 10 GPa.

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

    NASA Astrophysics Data System (ADS)

    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

  15. High-Pressure Induced New Phases and Properties in Typical Molecular Systems

    NASA Astrophysics Data System (ADS)

    Cui, Tian

    2013-06-01

    High pressure introduces new phases by the rearrangement of atoms and reconfigurations of electronic states in materials, often with new physical and chemical phenomena. Study of the new phases in typical molecular systems under high pressure is an interesting subject, such as energy storage materials of solid hydrogen and polymeric nitrogen, hydrogen-rich compound with high-Tc superconductivity under high pressure, high pressure induced metallization of hydrogen, etc. High-pressure structures and pressure-induced phase transitions in the typical molecular solids, such as solid iodine, CHBr3, N2/CN, HBr/HCl, hydrogen-rich compounds (H2S, ZrH2, AsH3, BaReH9, etc.), and group IVA hydrides (Si2H6, Ge2H6, Sn2H6, etc.) are investigated extensively by means of first-principles density functional theory and extensive prediction strategies (molecular dynamics simulation, simulated annealing, soft mode phase transition, random structure-searching method and evolutionary methodology etc.). The new structures and new properties derived from pressure-induced phase transitions in these typical molecular systems have been observed. It is showed that high pressure provides a path for producing new materials with new properties.

  16. High pressure structural phase transitions of TiO2 nanomaterials

    NASA Astrophysics Data System (ADS)

    Quan-Jun, Li; Bing-Bing, Liu

    2016-07-01

    Recently, the high pressure study on the TiO2 nanomaterials has attracted considerable attention due to the typical crystal structure and the fascinating properties of TiO2 with nanoscale sizes. In this paper, we briefly review the recent progress in the high pressure phase transitions of TiO2 nanomaterials. We discuss the size effects and morphology effects on the high pressure phase transitions of TiO2 nanomaterials with different particle sizes, morphologies, and microstructures. Several typical pressure-induced structural phase transitions in TiO2 nanomaterials are presented, including size-dependent phase transition selectivity in nanoparticles, morphology-tuned phase transition in nanowires, nanosheets, and nanoporous materials, and pressure-induced amorphization (PIA) and polyamorphism in ultrafine nanoparticles and TiO2-B nanoribbons. Various TiO2 nanostructural materials with high pressure structures are prepared successfully by high pressure treatment of the corresponding crystal nanomaterials, such as amorphous TiO2 nanoribbons, α-PbO2-type TiO2 nanowires, nanosheets, and nanoporous materials. These studies suggest that the high pressure phase transitions of TiO2 nanomaterials depend on the nanosize, morphology, interface energy, and microstructure. The diversity of high pressure behaviors of TiO2 nanomaterials provides a new insight into the properties of nanomaterials, and paves a way for preparing new nanomaterials with novel high pressure structures and properties for various applications. Project supported by the National Basic Research Program of China (Grant No. 2011CB808200), the National Natural Science Foundation of China (Grant Nos. 11374120, 11004075, 10979001, 51025206, 51032001, and 21073071), and the Cheung Kong Scholars Programme of China.

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

    NASA Astrophysics Data System (ADS)

    Palanivel, B.; Rao, R. S.; Godwal, B. K.; Sikka, S. K.

    2000-10-01

    High-pressure electronic properties of Be have been investigated theoretically by means of ab initio electronic structure calculations. The calculations have been carried out by the semi-relativistic full-potential, linear muffin-tin orbital (FPLMTO) method, within the local density approximation. The crystal structure stability among the hcp, bcc and orthorhombic (distorted hcp) phases has been studied as a function of compression. The bcc structure is found to be energetically stable at pressures above 180 GPa. From the results of our calculations, the orthorhombic phase cannot occur as an intermediate phase between the ambient pressure hcp phase and the high-pressure bcc structure. Our work thus suggests the need for more accurate high-pressure x-ray data.

  18. Pressure and Temperature effects on the High Pressure Phase Transformation in Zirconium

    SciTech Connect

    Escobedo-Diaz, Juan P.; Cerreta, Ellen K.; Brown, Donald W.; Trujillo, Carl P.; Rigg, Paulo A.; Bronkhorst, Curt A.; Addessio, Francis L.; Lookman, Turab

    2012-06-20

    At high pressure zirconium is known to undergo a phase transformation from the hexagonal close packed (HCP) alpha phase ({alpha}) to the simple hexagonal omega phase ({omega}). Under conditions of shock loading, the high-pressure omega phase is retained upon release. However, the hysteresis in this transformation is not well represented by equilibrium phase diagrams. For this reason, the influence of peak shock pressure and temperature on the retention of omega phase in Zr is explored in this study. In situ VISAR measurements along with post-mortem metallographic and neutron diffraction characterization of soft recovered specimens have been utilized to quantify the volume fraction of retained omega phase, morphology of the shocked alpha and omega phases, and qualitatively understand the kinetics of this transformation. This understanding of the role of peak shock stress will be utilized to address physics to be encoded in our present macro-scale models.

  19. Structural control on displacive phase transitions in minerals at high pressures

    NASA Astrophysics Data System (ADS)

    Miletich, Ronald

    2010-05-01

    High-pressure phase transformations resemble discontinuous thermodynamic and structural changes of materials, which can be assigned to configurational instabilities and lattice-related boundary conditions. In particular transformations, which are predominantely displacive in character, reveal structural control across the critical transition pressures through the structures of the polymorphs involved. Three examples of high-pressure phase transitions will be presented, which have been subject to a series of experimental studies at high pressures using diamond-anvil cells. The first example deals with clinopyroxenes, their static elasticities and elastic anomalies associated with occuring first-order transition. The example of spodumene will demonstrate in particular the structural role of the silicate-chain units, and exemplifies the pronounced deviation from conventional equation-of-state behaviour in the proximity of the critical transition pressure. The second example deals with the high-pressure phase transition of behoite and the structural control of hydrogen bridging on first-order transformations in simple (hydr)oxide phases. The third example will present the second-order transition in the silicate mineral benitoite, which has been chosen to demonstrate the need for high-precision single-crystal techniques in order to track down subtle structural changes related to high-pressure transitions.

  20. High pressure phase transformations in α-AlPO4: an x-ray diffraction investigation

    NASA Astrophysics Data System (ADS)

    Sharma, Surinder M.; Garg, Nandini; Sikka, S. K.

    2000-07-01

    We have re-investigated the high pressure behaviour of berlinite AlPO4 (α-AlPO4) with x-ray diffraction using a powerful synchrotron x-ray source SPring-8. Our results show that it transforms to a crystalline phase beyond ~13 GPa. Our data seem to be consistent with a CrVO4 type of structure in the Cmcm space group, similar to the high pressure phase observed in some isostructural phosphate compounds. The persistence of the diffraction pattern up to 40 GPa establishes that the previously accepted amorphization of AlPO4 around 12-18 GPa is incorrect. Experimental results suggest that the so-called memory glass effect observed earlier may in fact be the reversibility of the α-phase←⇔crystalline phase transformation. Comparisons of our experimental and theoretical results raise serious doubts about the theoretical understanding of the high pressure behaviour of α-AlPO4.

  1. Theoretical confirmation of a high-pressure rhombohedral phase in vanadium metal

    SciTech Connect

    Lee, B; Rudd, R E; Klepeis, J; Soderlind, P; Landa, A

    2007-02-27

    Recent diamond-anvil-cell (DAC) experiments revealed a new phase in vanadium metal at high pressure. Here we present results from first-principles electronic-structure calculations confirming the existence of such phase. The new phase is due to a rhombohedral distortion of the body-centered-cubic (bcc) ambient-pressure phase. The calculated transition pressure of 0.84 Mbar and density compare favorably with the measured data. Interestingly, a re-entrant bcc phase is discovered at an ultra high pressure, close to the limit of DAC experimental capabilities, of about 2.8 Mbar. We show, extending prior work, that the phase transitions in vanadium are driven by subtle electronic-structure effects.

  2. Vibrational Spectroscopy at High Pressure in CF4: Implications to the Phase Diagram

    SciTech Connect

    Lorenzana, H E; Magnus, J L; Evans, W J; Hemmi, N

    2000-08-15

    The molecular analogue of methane, CF{sub 4} is the most fundamental saturated perfluorocarbon, exhibiting complex optical behavior that is highly unusual for such a simple molecular system. We present Raman measurements in solid CF{sub 4} over a wide range in pressure from 1.6 to over 30 GPa at room temperature. The Raman spectra exhibit polarization-dependent intensity variations and history-dependent absence or presence of high pressure modes. Our results compellingly demonstrate that previously identified phase transitions in CF{sub 4} based on Raman signatures need to be reconsidered. Though our data suggest possible new high-pressure transitions, we do not identify new phases because of spectral complexity. Finally, we used the measured longitudinal and transverse optical mode splitting to estimate the dipole moment derivative at high pressures and find it close to that of gaseous CF{sub 4}.

  3. Phase transition induced strain in ZnO under high pressure.

    PubMed

    Yan, Xiaozhi; Dong, Haini; Li, Yanchun; Lin, Chuanlong; Park, Changyong; He, Duanwei; Yang, Wenge

    2016-01-01

    Under high pressure, the phase transition mechanism and mechanical property of material are supposed to be largely associated with the transformation induced elastic strain. However, the experimental evidences for such strain are scanty. The elastic and plastic properties of ZnO, a leading material for applications in chemical sensor, catalyst, and optical thin coatings, were determined using in situ high pressure synchrotron axial and radial x-ray diffraction. The abnormal elastic behaviors of selected lattice planes of ZnO during phase transition revealed the existence of internal elastic strain, which arise from the lattice misfit between wurtzite and rocksalt phase. Furthermore, the strength decrease of ZnO during phase transition under non-hydrostatic pressure was observed and could be attributed to such internal elastic strain, unveiling the relationship between pressure induced internal strain and mechanical property of material. These findings are of fundamental importance to understanding the mechanism of phase transition and the properties of materials under pressure.

  4. Phase transition induced strain in ZnO under high pressure

    NASA Astrophysics Data System (ADS)

    Yan, Xiaozhi; Dong, Haini; Li, Yanchun; Lin, Chuanlong; Park, Changyong; He, Duanwei; Yang, Wenge

    2016-05-01

    Under high pressure, the phase transition mechanism and mechanical property of material are supposed to be largely associated with the transformation induced elastic strain. However, the experimental evidences for such strain are scanty. The elastic and plastic properties of ZnO, a leading material for applications in chemical sensor, catalyst, and optical thin coatings, were determined using in situ high pressure synchrotron axial and radial x-ray diffraction. The abnormal elastic behaviors of selected lattice planes of ZnO during phase transition revealed the existence of internal elastic strain, which arise from the lattice misfit between wurtzite and rocksalt phase. Furthermore, the strength decrease of ZnO during phase transition under non-hydrostatic pressure was observed and could be attributed to such internal elastic strain, unveiling the relationship between pressure induced internal strain and mechanical property of material. These findings are of fundamental importance to understanding the mechanism of phase transition and the properties of materials under pressure.

  5. High pressure phase transitions in scheelite structured fluoride: ErLiF{sub 4}

    SciTech Connect

    Garg, Nandini; Mishra, A.K.; Poswal, H.K.; Tyagi, A.K.; Sharma, Surinder M

    2015-09-15

    Our synchrotron based angle dispersive x-ray diffraction studies on scheelite structured ErLiF{sub 4} show that it undergoes two phase transitions, at ~11.5 and ~15.5 GPa to lower symmetry monoclinic phases, before becoming (irreversibly) amorphous at ~28 GPa. The first high pressure phase transformation to the fergusonite structure (space group I2/a) is found to be of thermodynamically second order. The second high pressure phase could be fitted to the P2/c space group, but detailed analysis rules out the wolframite structure (P2/c space group), common to many scheelite compounds under high pressures. We also suggest that despite the ionic character of the LiF{sub 4} tetrahedra, the compressibility of LnLiF{sub 4} (Ln=Eu–Lu) kind of scheelites is more affected by the LnF{sub 8} dodecahedra than the LiF{sub 4} tetrahedra. - Graphical abstract: Volume per formula unit of the scheelite and high pressure phases of ErLiF{sub 4} as a function of pressure. - Highlights: • ErLiF{sub 4} transforms to fergusonite and P2/c phase at high pressure. • Polyhedra of LnF{sub 8} affects compressibility of LnLiF{sub 4} (Ln=Eu–Lu) more than LiF{sub 4}. • Amorphization pressure varies inversely in LnLiF{sub 4} with ionic size of Ln cation. • In ErLiF{sub 4}a/c ratio reduces with pressure in contrast to reported increase in YLiF{sub 4}.

  6. ANALYSIS OF SELECTED PYRETHROID PESTICIDES USING REVERSE PHASE HIGH PRESSURE LIQUID CHROMATOGRAPHY/UV

    EPA Science Inventory

    This research was conducted in cooperation with EPA Region 4 in Athens, GA to develop a method to analyze selected pyrethroid pesticides using Reverse Phase-High Pressure Liquid Chromatography (HPLC). This HPLC method will aid researchers in separating and identifying these py...

  7. High pressure phase-transformation induced texture evolution and strengthening in zirconium metal: Experiment and modeling

    DOE PAGES

    Yu, Xiaohui; Zhang, Ruifeng; Weldon, David; Vogel, Sven C.; Zhang, Jianzhong; Brown, Donald W.; Wang, Yanbin; Reiche, Helmut M.; Wang, Shanmin; Du, Shiyu; et al

    2015-07-28

    We studied the phase-transition induced texture changes and strengthening mechanism for zirconium metal under quasi-hydrostatic compression and uni-axial deformation under confined high pressure using the deformation-DIA (D-DIA) apparatus. It is shown that the experimentally obtained texture for ω-phase Zr can be qualitatively described by combining a subset of orientation variants previously proposed in two different models. The determined flow stress for the high-pressure ω-phase is 0.5–1.2 GPa, more than three times higher than that of the α-phase. Using first-principles calculations, we investigated the mechanical and electronic properties of the two Zr polymorphs. We find that the observed strengthening can bemore » attributed to the relatively strong directional bonding in the ω phase, which significantly increases its shear plastic resistance over the α-phase Zr. The present findings provide an alternate route for Zr metal strengthening by high-pressure phase transformation.« less

  8. Phase changes of filled ice Ih methane hydrate under low temperature and high pressure.

    PubMed

    Tanaka, Takehiko; Hirai, Hisako; Matsuoka, Takahiro; Ohishi, Yasuo; Yagi, Takehiko; Ohtake, Michika; Yamamoto, Yoshitaka; Nakano, Satoshi; Irifune, Tetsuo

    2013-09-14

    Low-temperature and high-pressure experiments were performed with filled ice Ih structure of methane hydrate under 2.0-77.0 GPa and 30-300 K using diamond anvil cells and a helium-refrigeration cryostat. In situ X-ray diffractometry revealed distinct changes in the compressibility of the axial ratios of the host framework with pressure. Raman spectroscopy showed a split in the C-H vibration modes of the guest methane molecules, which was previously explained by the orientational ordering of the guest molecules. The pressure and temperature conditions at the split of the vibration modes agreed well with those of the compressibility change. The results indicate the following: (i) the orientational ordering of the guest methane molecules from an orientationally disordered state occurred at high pressures and low temperatures; and (ii) this guest ordering led to anisotropic contraction in the host framework. Such guest orientational ordering and subsequent anisotropic contraction of the host framework were similar to that reported previously for filled ice Ic hydrogen hydrate. Since phases with different guest-ordering manners were regarded as different phases, existing regions of the guest disordered-phase and the guest ordered-phase were roughly estimated by the X-ray study. In addition, above the pressure of the guest-ordered phase, another high-pressure phase developed in the low-temperature region. The deuterated-water host samples were also examined, and the influence of isotopic effects on guest ordering and phase transformation was observed.

  9. High pressure phase-transformation induced texture evolution and strengthening in zirconium metal: Experiment and modeling

    SciTech Connect

    Yu, Xiaohui; Zhang, Ruifeng; Weldon, David; Vogel, Sven C.; Zhang, Jianzhong; Brown, Donald W.; Wang, Yanbin; Reiche, Helmut M.; Wang, Shanmin; Du, Shiyu; Jin, Changqing; Zhao, Yusheng

    2015-07-28

    We studied the phase-transition induced texture changes and strengthening mechanism for zirconium metal under quasi-hydrostatic compression and uni-axial deformation under confined high pressure using the deformation-DIA (D-DIA) apparatus. It is shown that the experimentally obtained texture for ω-phase Zr can be qualitatively described by combining a subset of orientation variants previously proposed in two different models. The determined flow stress for the high-pressure ω-phase is 0.5–1.2 GPa, more than three times higher than that of the α-phase. Using first-principles calculations, we investigated the mechanical and electronic properties of the two Zr polymorphs. We find that the observed strengthening can be attributed to the relatively strong directional bonding in the ω phase, which significantly increases its shear plastic resistance over the α-phase Zr. The present findings provide an alternate route for Zr metal strengthening by high-pressure phase transformation.

  10. Theoretical and experimental evidence for the post-cotunnite phase transition in zirconia at high pressure

    NASA Astrophysics Data System (ADS)

    Nishio-Hamane, Daisuke; Dekura, Haruhiko; Seto, Yusuke; Yagi, Takehiko

    2015-05-01

    A post-cotunnite phase transition in zirconia (ZrO2) at high pressure was investigated by synchrotron X-ray diffraction measurements and ab initio calculations based on density functional theory. This study successfully demonstrated a cotunnite- to Fe2P-type phase transition. Static enthalpy difference (Δ H) calculations predicted the appearance of the Fe2P phase at 124 GPa (LDA) and 143 GPa (GGA), and experimental trials demonstrated the coexistence of the Fe2P and cotunnite phases at 175 GPa after heating to 3,000 K. Both phases were quenchable to ambient conditions. The volume of the Fe2P phase was slightly less (~Δ 0.6 %) than that of the cotunnite phase over the experimental pressure range, indicating that the Fe2P phase is the higher pressure phase. The coexistence of both phases in this study may be attributed to the slow kinetics of the phase transition resulting from the close structural relationship of the two phases. An Fe2P-type structural model can be derived by applying a simple operation to the cotunnite-type structure, consisting of a 1/2 shift of several zirconium arrangements parallel to the b-axis of the cotunnite-type unit cell. It is concluded that the high-pressure cotunnite-to-Fe2P phase transition may be a common trend in many dioxides.

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

    NASA Astrophysics Data System (ADS)

    Zhang, Jin S.; Bass, Jay D.

    2016-08-01

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

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

    NASA Astrophysics Data System (ADS)

    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.

  13. Revealing an unusual transparent phase of superhard iron tetraboride under high pressure

    PubMed Central

    Kotmool, Komsilp; Kaewmaraya, Thanayut; Chakraborty, Sudip; Anversa, Jonas; Bovornratanaraks, Thiti; Luo, Wei; Gou, Huiyang; Piquini, Paulo Cesar; Kang, Tae Won; Mao, Ho-kwang; Ahuja, Rajeev

    2014-01-01

    First principles–based electronic structure calculations of superhard iron tetraboride (FeB4) under high pressure have been undertaken in this study. Starting with a “conventional” superconducting phase of this material under high pressure leads to an unexpected phase transition toward a semiconducting one. This transition occurred at 53.7 GPa, and this pressure acts as a demarcation between two distinct crystal symmetries, metallic orthorhombic and semiconducting tetragonal phases, with Pnnm and I41/acd space groups, respectively. In this work, the electron–phonon coupling-derived superconducting Tc has been determined up to 60 GPa and along with optical band gap variation with increasing pressure up to 300 GPa. The dynamic stability has been confirmed by phonon dispersion calculations throughout this study. PMID:25404295

  14. Magnetic and structural phase transitions in erbium at low temperatures and high pressures

    SciTech Connect

    Thomas, Sarah A.; Tsoi, Georgiy M.; Wenger, Lowell E.; Vohra, Yogesh K.

    2012-02-07

    Electrical resistance and crystal structure measurements have been carried out on polycrystalline erbium (Er) at temperatures down to 10 K and pressures up to 20 GPa. An abrupt change in the slope of the resistance is observed with decreasing temperature below 84 K, which is associated with the c-axis modulated (CAM) antiferromagnetic (AFM) ordering of the Er moments. With increasing pressure the temperature of the resistance slope change and the corresponding AFM ordering temperature decrease until vanishing above 10.6 GPa. The disappearance of the slope change in the resistance occurs at similar pressures where the hcp structural phase of Er is transformed to a nine-layer {alpha}-Sm structural phase, as confirmed by our high-pressure synchrotron x-ray diffraction studies. These results suggest that the disappearance in the AFM ordering of Er moments is strongly correlated to the structural phase transition at high pressures and low temperatures.

  15. Revealing an unusual transparent phase of superhard iron tetraboride under high pressure.

    PubMed

    Kotmool, Komsilp; Kaewmaraya, Thanayut; Chakraborty, Sudip; Anversa, Jonas; Bovornratanaraks, Thiti; Luo, Wei; Gou, Huiyang; Piquini, Paulo Cesar; Kang, Tae Won; Mao, Ho-kwang; Ahuja, Rajeev

    2014-12-01

    First principles-based electronic structure calculations of superhard iron tetraboride (FeB4) under high pressure have been undertaken in this study. Starting with a "conventional" superconducting phase of this material under high pressure leads to an unexpected phase transition toward a semiconducting one. This transition occurred at 53.7 GPa, and this pressure acts as a demarcation between two distinct crystal symmetries, metallic orthorhombic and semiconducting tetragonal phases, with Pnnm and I4₁/acd space groups, respectively. In this work, the electron-phonon coupling-derived superconducting T(c) has been determined up to 60 GPa and along with optical band gap variation with increasing pressure up to 300 GPa. The dynamic stability has been confirmed by phonon dispersion calculations throughout this study.

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

    NASA Astrophysics Data System (ADS)

    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.

  17. Phase stability of {epsilon} and {gamma} HNIW (CL-20) at high-pressure and temperature

    SciTech Connect

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

    2007-12-12

    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 ({alpha}, {beta}, {gamma}, {epsilon}, {zeta}). 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 deg. 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 deg. C then underwent a transition to the gamma phase above 125 deg. C and then thermal decomposition occurred above 150 deg. C. Upon compression, the gamma phase underwent a phase transition at both ambient temperature and 140 deg. C. Pressure--volume data for the epsilon and gamma phase at ambient temperature and the epsilon phase at 75 deg. C were fit to the Birch-Murnaghan formalism to obtain isothermal equations of state.

  18. Phase transition and metallization of FeO at high pressures and temperatures

    SciTech Connect

    Fischer, Rebecca A.; Campbell, Andrew J.; Lord, Oliver T.; Shofner, Gregory A.; Dera, Przemyslaw; Prakapenka, Vitali B.

    2012-05-10

    Wuestite, Fe{sub 1-x}O, is an important component in the mineralogy of Earth's lower mantle and may also be a component of the core. Therefore its high pressure-temperature behavior, including its electronic structure, is essential to understanding the nature and evolution of Earth's deep interior. We performed X-ray diffraction and radiometric measurements on wuestite in a laser-heated diamond anvil cell, finding an insulator-metal transition at high pressures and temperatures. Our data show a negative slope for this apparently isostructural phase boundary, which is characterized by a volume decrease and emissivity increase. The metallic phase of FeO is stable at conditions of the lower mantle and core, which has implications for the high P-T character of Fe-O bonds, magnetic field propagation, and lower mantle conductivity.

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

    PubMed

    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

  20. High-pressure and high-temperature study of the phase transition in anhydrite

    NASA Astrophysics Data System (ADS)

    Ma, Y. M.; Zhou, Q.; He, Z.; Li, F. F.; Yang, K. F.; Cui, Q. L.; Zou, G. T.

    2007-10-01

    The high-pressure and high-temperature behaviors of anhydrite (CaSO4) are studied up to 53.5 GPa and 1800 K using double-sided laser heating Raman spectroscopy and x-ray diffraction in diamond anvil cells. The evidence of phase transition from an anhydrite structure to the monazite type was observed at about 2 GPa under cold compression. Another phase transition and a change in color of the sample from transparent to black have been also observed at a pressure of 33.2 GPa after laser heating. The new phase after laser heating persists to 53.5 GPa and 1800 K.

  1. Pyroxenes and olivines: Structural implications of shock-wave data for high pressure phases

    NASA Technical Reports Server (NTRS)

    Jeanloz, R.; Ahrens, T. J.

    1975-01-01

    The nature of the shock-induced, high-pressure phases of olivine and pyroxene rocks is examined in the light of data for the densities of a new class of perovskite-related silicate structures. Also examined are some new Hugoniot and release adiabat data for bronzite. Reexamining available shock data for magnesian pyroxenes and olivines leads to the conclusion that they define a mixed phase (or disequilibrium) region to about the 100 GPa range, related to the kinetics of phase transformation in these silicates. By recognizing this point, certain discrepancies in previous interpretations of shock data can be explained. A set of theoretical Hugonoits for pyroxene and olivine stoichiometry, perovskite-bearing assemblages was constructed based on their properties deduced from high-pressure work, showing that the shock data is compatible with transformations to perovskites in the 45-7GPa region. Finally, the shock data indicate very similar properties for olivine and pyroxene at high pressures making them both equally likely candidates for the lower mantle.

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

    NASA Astrophysics Data System (ADS)

    Smith, Spencer; Montgomery, Jeffrey; Vohra, Yogesh

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

  3. Structural phase transitions in Bi2Se3 under high pressure

    DOE PAGES

    Yu, Zhenhai; Gu, Genda; Wang, Lin; Hu, Qingyang; Zhao, Jinggeng; Yan, Shuai; Yang, Ke; Sinogeikin, Stanislav; Mao, Ho -kwang

    2015-11-02

    Raman spectroscopy and angle dispersive X-ray diffraction (XRD) experiments of bismuth selenide (Bi2Se3) have been carried out to pressures of 35.6 and 81.2 GPa, respectively, to explore its pressure-induced phase transformation. The experiments indicate that a progressive structural evolution occurs from an ambient rhombohedra phase (Space group (SG): R-3m) to monoclinic phase (SG: C2/m) and eventually to a high pressure body-centered tetragonal phase (SG: I4/mmm). Evidenced by our XRD data up to 81.2 GPa, the Bi2Se3 crystallizes into body-centered tetragonal structures rather than the recently reported disordered body-centered cubic (BCC) phase. Furthermore, first principles theoretical calculations favor the viewpoint thatmore » the I4/mmm phase Bi2Se3 can be stabilized under high pressure (>30 GPa). Remarkably, the Raman spectra of Bi2Se3 from this work (two independent runs) are still Raman active up to ~35 GPa. Furthermore, it is worthy to note that the disordered BCC phase at 27.8 GPa is not observed here. The remarkable difference in atomic radii of Bi and Se in Bi2Se3 may explain why Bi2Se3 shows different structural behavior than isocompounds Bi2Te3 and Sb2Te3.« less

  4. Phase transformation of Ho[subscript 2]O[subscript 3] at high pressure

    SciTech Connect

    Jiang, Sheng; Liu, Jing; Li, Xiaodong; Bai, Ligang; Xiao, Wansheng; Zhang, Yufeng; Lin, Chuanlong; Li, Yanchun; Tang, Lingyun

    2012-01-20

    The structural stability of cubic Ho{sub 2}O{sub 3} under high pressure has been investigated by angle-dispersive x-ray diffraction (ADXD) in a diamond anvil cell up to 63.0 GPa at room temperature. The diffraction data reveal two structural transformations on compression. The structural transformation from a cubic to a monoclinic structure starts at 8.9 GPa and is complete at 16.3 GPa with an {approx}8.1% volume collapse. A hexagonal phase begins to appear at {approx}14.8 GPa and becomes dominant at 26.4 GPa. This high-pressure hexagonal phase with a small amount of retained monoclinic phase is stable up to the highest pressure of 63.0 GPa in this study. After release of pressure, the hexagonal phase transforms to a monoclinic structure. A third-order Birch-Murnaghan fit yields zero pressure bulk moduli (B{sub 0}) of 206(3), 200(7) and 204(19) GPa and their pressure derivatives (B'{sub 0}) of 4.8(4), 2.1(4), 3.8(5) for the cubic, monoclinic and hexagonal phases, respectively. Comparing with other rare-earth sesquioxides, it is suggested that the transition pressure from cubic to monoclinic phase, as well as the bulk modulus of the cubic phase, increases with the decreasing of the cation radius of rare-earth sesquioxides.

  5. Structural phase transitions in Bi2Se3 under high pressure

    PubMed Central

    Yu, Zhenhai; Wang, Lin; Hu, Qingyang; Zhao, Jinggeng; Yan, Shuai; Yang, Ke; Sinogeikin, Stanislav; Gu, Genda; Mao, Ho-kwang

    2015-01-01

    Raman spectroscopy and angle dispersive X-ray diffraction (XRD) experiments of bismuth selenide (Bi2Se3) have been carried out to pressures of 35.6 and 81.2 GPa, respectively, to explore its pressure-induced phase transformation. The experiments indicate that a progressive structural evolution occurs from an ambient rhombohedra phase (Space group (SG): R-3m) to monoclinic phase (SG: C2/m) and eventually to a high pressure body-centered tetragonal phase (SG: I4/mmm). Evidenced by our XRD data up to 81.2 GPa, the Bi2Se3 crystallizes into body-centered tetragonal structures rather than the recently reported disordered body-centered cubic (BCC) phase. Furthermore, first principles theoretical calculations favor the viewpoint that the I4/mmm phase Bi2Se3 can be stabilized under high pressure (>30 GPa). Remarkably, the Raman spectra of Bi2Se3 from this work (two independent runs) are still Raman active up to ~35 GPa. It is worthy to note that the disordered BCC phase at 27.8 GPa is not observed here. The remarkable difference in atomic radii of Bi and Se in Bi2Se3 may explain why Bi2Se3 shows different structural behavior than isocompounds Bi2Te3 and Sb2Te3. PMID:26522818

  6. High pressure structural, electronic, and optical properties of polymorphic InVO4 phases

    NASA Astrophysics Data System (ADS)

    Mondal, S.; Appalakondaiah, S.; Vaitheeswaran, G.

    2016-02-01

    In the present work, we report a detailed density functional theory calculation on polymorphic InVO4 phases by means of projector augmented wave method. The computed first-order structural phase transformation from orthorhombic (Cmcm) to monoclinic (P2/c) structure is found to occur around 5.6 GPa along with a large volume collapse of 16.6%, which is consistent with previously reported experimental data. This transformation also leads to an increase in the coordination number of vanadium atom from 4 to 6. The computed equilibrium and high pressure structural properties of both InVO4 phases, including unit cell parameters, equation of state, and bulk moduli, are in good agreement with the available experimental data. In addition, compressibility is found to be highly anisotropic and the b-axis being more compressible than the other for both the structures. Electronic band structures for both the phases were calculated, and the band gaps for orthorhombic and monoclinic InVO4 are found to be 4.02 and 1.67 eV, respectively, within the Tran-Blaha Modified Becke-Johnson potential as implemented in linearized augmented planewave method. We further examined the optical properties such as dielectric function, refractive index, and absorption spectra for both the structures. From the implications of these results, it can be proposed that the high pressure InVO4 phase can be more useful than orthorhombic phase for photo catalytic applications.

  7. Superconducting H5S2 phase in sulfur-hydrogen system under high-pressure

    PubMed Central

    Ishikawa, Takahiro; Nakanishi, Akitaka; Shimizu, Katsuya; Katayama-Yoshida, Hiroshi; Oda, Tatsuki; Suzuki, Naoshi

    2016-01-01

    Recently, hydrogen sulfide was experimentally found to show the high superconducting critical temperature (Tc) under high-pressure. The superconducting Tc shows 30–70 K in pressure range of 100–170 GPa (low-Tc phase) and increases to 203 K, which sets a record for the highest Tc in all materials, for the samples annealed by heating it to room temperature at pressures above 150 GPa (high-Tc phase). Here we present a solid H5S2 phase predicted as the low-Tc phase by the application of the genetic algorithm technique for crystal structure searching and first-principles calculations to sulfur-hydrogen system under high-pressure. The H5S2 phase is thermodynamically stabilized at 110 GPa, in which asymmetric hydrogen bonds are formed between H2S and H3S molecules. Calculated Tc values show 50–70 K in pressure range of 100–150 GPa within the harmonic approximation, which can reproduce the experimentally observed low-Tc phase. These findings give a new aspect of the excellent superconductivity in compressed sulfur-hydrogen system. PMID:26983593

  8. High-pressure phases of a hydrogen-rich compound: Tetramethylgermane

    NASA Astrophysics Data System (ADS)

    Qin, Zhen-Xing; Zhang, Chao; Tang, Ling-Yun; Zhong, Guo-Hua; Lin, Hai-Qing; Chen, Xiao-Jia

    2012-11-01

    The vibrational and structural properties of a hydrogen-rich group IVa hydride, Ge(CH3)4, are studied by combining Raman spectroscopy and synchrotron x-ray diffraction measurements at room temperature and at pressures up to 30.2 GPa. Both techniques allow the obtaining of complementary information on the high-pressure behaviors and yield consistent phase transitions at 1.4 GPa for the liquid to solid and 3.0, 5.4, and 20.3 GPa for the solid to solid. The four high-pressure solid phases are identified to have the cubic, orthorhombic, monoclinic, and monoclinic crystal structures with space groups of Pa-3 for phase I, Pnma for phase II, P21/c for phase III, and P21 for phase IV, respectively. These transitions are suggested to result from the changes in the inter- and intramolecular bonding of this compound. The softening of some Raman modes on CH3 groups and their sudden disappearance indicate that Ge(CH3)4 might be an ideal compound to realize metallization and even high-temperature superconductivity at modest static pressure for laboratory capability.

  9. Superconducting H5S2 phase in sulfur-hydrogen system under high-pressure

    NASA Astrophysics Data System (ADS)

    Ishikawa, Takahiro; Nakanishi, Akitaka; Shimizu, Katsuya; Katayama-Yoshida, Hiroshi; Oda, Tatsuki; Suzuki, Naoshi

    2016-03-01

    Recently, hydrogen sulfide was experimentally found to show the high superconducting critical temperature (Tc) under high-pressure. The superconducting Tc shows 30–70 K in pressure range of 100–170 GPa (low-Tc phase) and increases to 203 K, which sets a record for the highest Tc in all materials, for the samples annealed by heating it to room temperature at pressures above 150 GPa (high-Tc phase). Here we present a solid H5S2 phase predicted as the low-Tc phase by the application of the genetic algorithm technique for crystal structure searching and first-principles calculations to sulfur-hydrogen system under high-pressure. The H5S2 phase is thermodynamically stabilized at 110 GPa, in which asymmetric hydrogen bonds are formed between H2S and H3S molecules. Calculated Tc values show 50–70 K in pressure range of 100–150 GPa within the harmonic approximation, which can reproduce the experimentally observed low-Tc phase. These findings give a new aspect of the excellent superconductivity in compressed sulfur-hydrogen system.

  10. Effect of high pressure homogenization on aqueous phase solvent extraction of lipids from Nannochloris Oculata microalgae

    SciTech Connect

    Samarasinghe, Nalin; Fernando, Sandun; Faulkner, William B.

    2012-12-01

    The ability to extract lipids from high-moisture Nannochloris Oculata algal biomass disrupted with high pressure homogenization was investigated. During the first phase, the effect of high pressure homogenization (system pressure and number of passes) on disrupting aqueous algae (of different concentrations and degree of stress) was investigated. Secondly, the effect of degree of cell wall disruption on the amount of lipids extracted with three solvents, namely: hexane, dichloromethane and chloroform, were compared. Studies reveled that high pressure homogenization is effective on cell disruption while the amount of system pressure being the most significant factor affecting the degree of cell breakage. Although the number of passes had some impact, the level of disruption seemed to level-off after a certain number of passes. The study revealed that slightly polar solvents (such as chloroform and dichloromethane) performed better in aqueous-phase lipid extractions as compared to hexane. Also, it was revealed that it was not necessary to disrupt the algal cells completely to achieve appreciable levels of lipid yields. In fact, conditions that exerted only 20% of the cells to completely disrupt, allowed sufficient damage to liberate most of the lipids contained in the remainder of the cells.

  11. Effect of high pressure homogenization on aqueous phase solvent extraction of lipids from Nannochloris Oculata microalgae

    DOE PAGES

    Samarasinghe, Nalin; Fernando, Sandun; Faulkner, William B.

    2012-12-01

    The ability to extract lipids from high-moisture Nannochloris Oculata algal biomass disrupted with high pressure homogenization was investigated. During the first phase, the effect of high pressure homogenization (system pressure and number of passes) on disrupting aqueous algae (of different concentrations and degree of stress) was investigated. Secondly, the effect of degree of cell wall disruption on the amount of lipids extracted with three solvents, namely: hexane, dichloromethane and chloroform, were compared. Studies reveled that high pressure homogenization is effective on cell disruption while the amount of system pressure being the most significant factor affecting the degree of cell breakage.more » Although the number of passes had some impact, the level of disruption seemed to level-off after a certain number of passes. The study revealed that slightly polar solvents (such as chloroform and dichloromethane) performed better in aqueous-phase lipid extractions as compared to hexane. Also, it was revealed that it was not necessary to disrupt the algal cells completely to achieve appreciable levels of lipid yields. In fact, conditions that exerted only 20% of the cells to completely disrupt, allowed sufficient damage to liberate most of the lipids contained in the remainder of the cells.« less

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    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.

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

    NASA Technical Reports Server (NTRS)

    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.

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

    NASA Astrophysics Data System (ADS)

    Gump, Jared

    2007-06-01

    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, and 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. Theoretical calculations have been performed for a variety of explosive ingredients including CL-20, but it was noted that no experimental measurements existed for comparison with the theoretical bulk modulus calculated for CL-20. Therefore, the phase stabilities of epsilon and gamma 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 5GPa and 175^oC, respectively. No phase change (from the starting epsilon phase) was observed under hydrostatic compression up to 6.3 GPa at ambient temperature. Under ambient pressure the epsilon phase was determined to be stable to a temperature of 120^oC. When heating above 125^oC the gamma phase appeared and it remained stable until thermal decomposition occurred above 150^oC. The gamma phase exhibits a phase change upon compression at both ambient temperature and 140^oC. Pressure -- volume data for the epsilon and gamma phase at ambient temperature and the epsilon phase at 75^oC were fit to the Birch-Murnaghan formalism to obtain isothermal equations of state.

  15. High-pressure and high-temperature stability field of hydrous phase delta-AlOOH

    NASA Astrophysics Data System (ADS)

    Sano, A.; Ohtani, E.; Kondo, T.; Hirao, N.; Sone, T.; Kikegawa, T.; Sata, N.; Ohishi, Y.

    2005-12-01

    Stability field of hydrous phases is a key for understanding water concentration in the earth's mantle. δ-AlOOH is a high-pressure polymorph of diaspore (α-AlOOH) and boehmite (γ-AlOOH). The space group of this phase is Pnn2 and it is similar to CaCl2-type SiO2 which is a high-pressure polymorph of stishovite; edge-sharing Al-O octahedra make single-chain along c-axis. Although it has a large stability field in pressure range from 18 GPa to 32 GPa and temperature of up to 1473 K, the high-pressure stability limits has not yet clarified. In this study, we investigated the stability field of δ-AlOOH up to 130 GPa. The high-pressure experiments were performed using a laser-heated diamond-anvil cell. Starting material was gibbsite (Al(OH)3) powder mixed with platinum black as a laser absorber. The sample was sandwiched by pure gibbsite layers and loaded into a rhenium gasket. Pressures were measured with ruby-fluorescence technique before and after heating. The sample was heated from both sides by a Nd:YAG laser operated in multimode. After experiment, stable phase in each condition was determined using the X-ray diffraction and Raman spectroscopy method. We also conducted in-situ X-ray diffraction experiments under high-pressure and temperature conditions together with the X-ray diffraction of the recovered samples both at BL10XU in SPring-8 and BL-13A in Photon Factory. In these runs, pressures were also calculated using the equation of state of platinum. The experimental conditions were in the pressures between 50-130 GPa and temperatures to 1800 K. X-ray analysis shows the sample recovered from the pressure and temperature range from 40 GPa and 1577 K to 130 GPa and 1800 K consists of δ-AlOOH. In the in-situ experiments, crystallization of δ-AlOOH was observed at 65 GPa and 1300 K and it was stable up to 1700 K. δ-AlOOH is stable in the large pressure range with a dehydration temperature around 1800K. It can be a water reservoir in subducting slabs in the

  16. Five-dimensional visualization of phase transition in BiNiO3 under high pressure

    PubMed Central

    Liu, Yijin; Wang, Junyue; Azuma, Masaki; Mao, Wendy L.; Yang, Wenge

    2014-01-01

    Colossal negative thermal expansion was recently discovered in BiNiO3 associated with a low density to high density phase transition under high pressure. The varying proportion of co-existing phases plays a key role in the macroscopic behavior of this material. Here, we utilize a recently developed X-ray Absorption Near Edge Spectroscopy Tomography method and resolve the mixture of high/low pressure phases as a function of pressure at tens of nanometer resolution taking advantage of the charge transfer during the transition. This five-dimensional (X, Y, Z, energy, and pressure) visualization of the phase boundary provides a high resolution method to study the interface dynamics of high/low pressure phase. PMID:24753622

  17. Phase stability of some actinides with brannerite structure at high pressures

    SciTech Connect

    Zhang, F.X.; Lang, M.; Liu Zhenxian; Ewing, R.C.

    2011-11-15

    Structure behavior of actinide brannerites ThTi{sub 2}O{sub 6}, Y{sub 0.5}U{sub 0.5}Ti{sub 1.5}Nb{sub 0.5}O{sub 6} and their analog oxide CeTi{sub 2}O{sub 6} was studied at high pressure by using in situ x-ray diffraction, Raman scattering and infra-red absorption techniques, respectively. Brannerite structure was found to be not stable and started to become amorphous at pressures above 20 GPa. Some minor crystalline phase(s) due to phase decomposition was observed in all the three samples during pressurization. In addition, the observed bulk modulus indicated that the actinide-bearing brannerites are more compressible than their analog compound CeTi{sub 2}O{sub 6}, which may be related to the asymmetric 5f electron orbits of actinide elements. - Graphical abstract: Actinide-bearing compounds with brannerite structure and their analog CeTi{sub 2}O{sub 6} are not stable at high pressure. They were amorphized after {approx}20 GPa and a minor pressure-induced phase transition or decomposition process was always observed before amorphization. Highlights: > Phase stability of three brannerites CeTi{sub 2}O{sub 6}, ThTi{sub 2}O{sub 6}, and (U,Y)(Ti,Nb){sub 2}O{sub 6} at high pressures. > Brannerite structure was not stable and became amorphous after {approx}20 GPa. > Actinide-bearing brannerites are easier compressed than their analog compound CeTi{sub 2}O{sub 6}.

  18. Phase transition induced strain in ZnO under high pressure

    DOE PAGES

    Yan, Xiaozhi; Dong, Haini; Li, Yanchun; Lin, Chuanlong; Park, Changyong; He, Duanwei; Yang, Wenge

    2016-05-13

    Under high pressure, the phase transition mechanism and mechanical property of material are supposed to be largely associated with the transformation induced elastic strain. However, the experimental evidences for such strain are scanty. The elastic and plastic properties of ZnO, a leading material for applications in chemical sensor, catalyst, and optical thin coatings, were determined using in situ high pressure synchrotron axial and radial x-ray diffraction. The abnormal elastic behaviors of selected lattice planes of ZnO during phase transition revealed the existence of internal elastic strain, which arise from the lattice misfit between wurtzite and rocksalt phase. Furthermore, the strengthmore » decrease of ZnO during phase transition under non-hydrostatic pressure was observed and could be attributed to such internal elastic strain, unveiling the relationship between pressure induced internal strain and mechanical property of material. Ultimately, these findings are of fundamental importance to understanding the mechanism of phase transition and the properties of materials under pressure.« less

  19. Phase transition induced strain in ZnO under high pressure.

    PubMed

    Yan, Xiaozhi; Dong, Haini; Li, Yanchun; Lin, Chuanlong; Park, Changyong; He, Duanwei; Yang, Wenge

    2016-01-01

    Under high pressure, the phase transition mechanism and mechanical property of material are supposed to be largely associated with the transformation induced elastic strain. However, the experimental evidences for such strain are scanty. The elastic and plastic properties of ZnO, a leading material for applications in chemical sensor, catalyst, and optical thin coatings, were determined using in situ high pressure synchrotron axial and radial x-ray diffraction. The abnormal elastic behaviors of selected lattice planes of ZnO during phase transition revealed the existence of internal elastic strain, which arise from the lattice misfit between wurtzite and rocksalt phase. Furthermore, the strength decrease of ZnO during phase transition under non-hydrostatic pressure was observed and could be attributed to such internal elastic strain, unveiling the relationship between pressure induced internal strain and mechanical property of material. These findings are of fundamental importance to understanding the mechanism of phase transition and the properties of materials under pressure. PMID:27173609

  20. Phase transition induced strain in ZnO under high pressure

    PubMed Central

    Yan, Xiaozhi; Dong, Haini; Li, Yanchun; Lin, Chuanlong; Park, Changyong; He, Duanwei; Yang, Wenge

    2016-01-01

    Under high pressure, the phase transition mechanism and mechanical property of material are supposed to be largely associated with the transformation induced elastic strain. However, the experimental evidences for such strain are scanty. The elastic and plastic properties of ZnO, a leading material for applications in chemical sensor, catalyst, and optical thin coatings, were determined using in situ high pressure synchrotron axial and radial x-ray diffraction. The abnormal elastic behaviors of selected lattice planes of ZnO during phase transition revealed the existence of internal elastic strain, which arise from the lattice misfit between wurtzite and rocksalt phase. Furthermore, the strength decrease of ZnO during phase transition under non-hydrostatic pressure was observed and could be attributed to such internal elastic strain, unveiling the relationship between pressure induced internal strain and mechanical property of material. These findings are of fundamental importance to understanding the mechanism of phase transition and the properties of materials under pressure. PMID:27173609

  1. The dynamic response of high pressure phase of Si using phase contrast imaging and X-ray diffraction

    NASA Astrophysics Data System (ADS)

    Lee, H. J.; Galtier, E.; Xing, Z.; Gleason, A.; Granados, E.; Tavella, F.; Schropp, A.; Seiboth, F.; Schroer, C.; Higginbotham, A.; Brown, S.; Arnold, B.; Curiel, R.; Peterswright, D.; Fry, A.; Nagler, B.

    2015-11-01

    Static compression studies have revealed that crystalline silicon undergoes phase transitions from a cubic diamond structure to a variety of phases including body-centered tetragonal phase, an orthorhombic phase, and a hexagonal primitive phase. However, the dynamic response of silicon at high pressure is not well understood. Phase contrast imaging has proven to be a powerful tool for probing density changes caused by the shock propagation into a material. With respect to the elastic and plastic compression, we image shock waves in Si with high spatial resolution using the LCLS X-ray free electron laser and Matter in Extreme Conditions instrument. In this study, the long pulse optical laser with pseudoflat top shape creates high pressures up to 60 GPa. We also measure the crystal structure by observing the X-ray diffraction orthogonal to the shock propagation direction over a range of pressure. In this talk, we will present the capability of simultaneously performing phase contrast imaging and in situ X-ray diffraction during shock loading and will discuss the dynamic response of Si in high pressure phases

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

    NASA Astrophysics Data System (ADS)

    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.

  3. Successive disorder to disorder phase transitions in ionic liquid [HMIM][BF4] under high pressure

    NASA Astrophysics Data System (ADS)

    Zhu, Xiang; Yuan, Chaosheng; Li, Haining; Zhu, Pinwen; Su, Lei; Yang, Kun; Wu, Jie; Yang, Guoqiang; Liu, Jing

    2016-02-01

    In situ high-pressure Raman spectroscopy and synchrotron X-ray diffraction have been employed to investigate the phase behavior of ionic liquid, 1-hexyl-3-methylimidazolium tetrafluoroborate ([HMIM][BF4]) under high pressure up to 20 GPa at room temperature. With increasing pressure, some characteristic bands of [HMIM][BF4] disappear, and some characteristic bands of [HMIM][BF4] display non-monotonic pressure-induced frequency shift and non-monotonic variation of full width at half-maximum. Two successive phase transitions at ˜1.7 GPa and 7.3 GPa have been corroborated by the results above. The glass transition pressure (Pg) of [HMIM][BF4] at ˜7.3 GPa has been obtained by ruby R1 line broadening measurements and analysis of synchrotron X-ray diffraction patterns, and its glass transition mechanism is also analyzed in detail. These facts are suggestive of two successive disorder to disorder phase transitions induced by compression, that is, [HMIM][BF4] serves as a superpressurized glass under the pressure above 7.3 GPa, which is similar to the glassy state at low temperature, and a compression-induced liquid to liquid phase transition in [HMIM][BF4] occurs at ˜1.7 GPa. Besides, the conformational equilibrium of the GAAA conformer and AAAA conformer was converted easily in liquid [HMIM][BF4], while it was difficult to be influenced in glassy state.

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

    NASA Astrophysics Data System (ADS)

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

    2012-07-01

    We report on the results from high pressure x-ray powder diffraction and electrical resistance measurements for hole doped BaFe2-xCrxAs2 (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 BaFe2As2 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.

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

    NASA Astrophysics Data System (ADS)

    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.

  6. Nuclear quantum and electronic exchange-correlation effects on the high pressure phase diagram of lithium

    NASA Astrophysics Data System (ADS)

    Clay, Raymond; Morales, Miguel; Bonev, Stanimir

    Lithium at ambient conditions is the simplest alkali metal and exhibits textbook nearly-free electron character. However, increased core/valence electron overlap under compression leads to surprisingly complex behavior. Dense lithium is known to posses a maximum in the melting line, a metal to semiconductor phase transition around 80GPa, reemergent metallicity around 120GPa, and low coordination solid and liquid phases. In addition to its complex electronic structure at high pressure, the atomic mass of lithium is low enough that nuclear quantum effects could have a nontrivial impact on its phase diagram. Through a combination of density functional theory based path-integral and classical molecular dynamics simulations, we have investigated the impact of both nuclear quantum effects and anharmonicity on the melting line and solid phase boundaries. Additionally, we have determined the robustness of previously predicted tetrahedral clustering in the dense liquid to the inclusion of nuclear quantum effects and approximate treatment of electronic exchange-correlation effects.

  7. Synthesis and equation of state of high pressure phase of chromium-bearing spinel

    NASA Astrophysics Data System (ADS)

    Shieh, S. R.; Khan, T.; Prescher, C.; Prakapenka, V.; MI, Z.

    2015-12-01

    Chromium-bearing spinel (Mg,Fe)Cr2O4 can be found in the Earth's crust, upper mantle, and even in meteorites. Mantle derived chromium-bearing spinel suggests that its high pressure phase may be existing at deep mantle but however its high pressure elastic property is not well understood yet. In situ synchrotron X-ray diffraction studies of magnesiochromite and chromite using the laser-heated diamond anvil cell were performed at GSECARS, Advanced Photon Source, to explore their high pressure phases and elastic property. Our results on magnesiochromite showed dissociation of MgCr2O4 to Cr2O3+MgO at ~15 GPa and to modified Ludwigite (mLd)-type Mg2Cr2O5+Cr2O3 below and above ~1500 K, respectively. At above 20 GPa, only a single phase CaTi2O4-type structure of MgCr2O4 was observed at 1400-2000 K. Pressure-volume data of CaTi2O4 type structure of MgCr2O4 fitted to Birch-Murnaghan equation of state yield zero-pressure volume (V0) = 264.4(8) Å3, bulk modulus (K0) = 185.4(4) GPa, and pressure derivative (K0') = 4; and mLd-type Mg2Cr2O5 yields: V0 = 338.9(8) Å3, K0 = 186.5(6) GPa, K0' = 4. For CaTi2O4 type structure of natural chromite, our fitted P-V data show V0 = 261(1) Å3, K0 = 175.4(2) GPa, and K0' = 4.

  8. a Steinberg-Guinan Model for High-Pressure Carbon: Diamond Phase

    NASA Astrophysics Data System (ADS)

    Orlikowski, Daniel; Correa, Alfredo A.; Schwegler, Eric; Klepeis, John E.

    2007-12-01

    Since the diamond phase of carbon has such a high yield strength, dynamic simulations must account for strength even for strong shock waves (˜3 Mbar). We have determined an initial parametrization of two strength models: Steinberg-Guinan (SG) and a modified or improved SG(ISG), that captures the high pressure dependence of the calculated shear modulus up to 10 Mbar. The models are based upon available experimental data and on calculated elastic moduli using robust density functional theory. Additionally, we have evaluated these models using hydrodynamic simulations of planar shocks experiments.

  9. A Steinberg-Guinan model for High-Pressure Carbon, Diamond Phase

    SciTech Connect

    Orlikowski, D; Correa, A; Schwegler, E; Klepeis, J

    2007-07-27

    Since the carbon, diamond phase has such a high yield strength, dynamic simulations must account for strength even for strong shock waves ({approx} 3 Mbar). We have determined an initial parametrization of two strength models: Steinberg-Guinan (SG) and a modified or improved SG, that captures the high pressure dependence of the calculated shear modulus up to 10 Mbar. The models are based upon available experimental data and on calculated elastic moduli using robust density functional theory. Additionally, we have evaluated these models using hydrodynamic simulations of planar shocks experiments.

  10. Superconductivity of high-pressure phases of S and Se to 230 GPa

    NASA Astrophysics Data System (ADS)

    Struzhkin, Viktor; Gregoryanz, Eugene; Timofeev, Yuri; Eremets, Mikhail; Mao, Ho-Kwang; Hemley, Russell

    2000-03-01

    We have investigated in detail the superconducting state of sulfur in its β-Po phase from 160 to 230 GPa. The superconducting Tc is close to 17 K from 160 to 200 GPa, and drops to 15 K at 230 GPa. Similar behavior was predicted recently [1] from ab initio LDA calculations. The high value of Tc in the β-Po phase is consistent with electon-phonon coupling mechanism with reasonably strong electron-phonon coupling (λ=0.76), and with the standard value of the Morel-Anderson pseudopotential μ^*=0.11 [1]. Our measurements in Se at high pressures indicate superconductivity from 17 to 23 GPa, which apparently has not been previously reported. We relate this behavior to the occurence of new metastable phase in Se which can be observed on decompression from 30 GPa at low temperatures. The results for Tc in Se at higher pressures will be also presented. We will also discuss the similiarities in high-pressure induced superconductivity of chalcogen family members: S, Se, and Te. ^1 Sven P. Rudin and Amy Y. Liu, Phys. Rev. Lett. 83, 3049 (1999).

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

    PubMed

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

    2009-09-23

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

  12. Equation of state and phase diagram of ammonia at high pressures from ab initio simulations

    NASA Astrophysics Data System (ADS)

    Bethkenhagen, Mandy; French, Martin; Redmer, Ronald

    2013-06-01

    We present an equation of state as well as a phase diagram of ammonia at high pressures and high temperatures derived from ab initio molecular dynamics simulations. The predicted phases of ammonia are characterized by analyzing diffusion coefficients and structural properties. Both the phase diagram and the subsequently computed Hugoniot curves are compared to experimental results. Furthermore, we discuss two methods that allow us to take into account nuclear quantum effects, which are of considerable importance in molecular fluids. Our data cover pressures up to 330 GPa and a temperature range from 500 K to 10 000 K. This regime is of great interest for interior models of the giant planets Uranus and Neptune, which contain, besides water and methane, significant amounts of ammonia.

  13. High pressure phase transformation in thorium carbide: A first principle study

    NASA Astrophysics Data System (ADS)

    Sahoo, B. D.; Joshi, K. D.; Gupta, Satish C.

    2013-06-01

    First principles calculations using full potential linearized augmented plane wave (FP-LAPW) method have been carried out to analyze structural, electronic and elastic properties of ThC under hydrostatic compression. Our calculations carried out within the generalized gradient approximation (GGA) predict a structural phase transition from rocksalt type (B1) phase to CsCl type cubic (B2) structure at ˜ 45 GPa. The same transition is predicted to occur at ˜ 35 GPa by the calculations performed within local density approximation (LDA). Various physical quantities such as equilibrium volume, bulk modulus, pressure derivative of bulk modulus and elastic constants determined for both the phases at zero pressure are compared with data available in literature. We find that at zero pressure the B2 structure is unstable elastically also. However, it emerges as elastically stable structure before it stabilizes energetically at high pressure. Further, the activation barrier between these structures has been calculated at various pressures.

  14. Phase transformations in amorphous fullerite C60 under high pressure and high temperature

    NASA Astrophysics Data System (ADS)

    Borisova, P. A.; Blanter, M. S.; Brazhkin, V. V.; Somenkov, V. A.; Filonenko, V. P.

    2015-08-01

    First phase transformations of amorphous fullerite C60 at high temperatures (up to 1800 K) and high pressures (up to 8 GPa) have been investigated and compared with the previous studies on the crystalline fullerite. The study was conducted using neutron diffraction and Raman spectroscopy. The amorphous fullerite was obtained by ball-milling. We have shown that under thermobaric treatment no crystallization of amorphous fullerite into С60 molecular modification is observed, and it transforms into amorphous-like or crystalline graphite. A kinetic diagram of phase transformation of amorphous fullerite in temperature-pressure coordinates was constructed for the first time. Unlike in crystalline fullerite, no crystalline polymerized phases were formed under thermobaric treatment on amorphous fullerite. We found that amorphous fullerite turned out to be less resistant to thermobaric treatment, and amorphous-like or crystalline graphite were formed at lower temperatures than in crystalline fullerite.

  15. Modeling high-pressure and high-temperature phase changes in bulk carbon

    SciTech Connect

    Glosi, J N; Ree, F H

    1999-07-01

    The phase diagram of carbon is not experimentally well known at high pressure and/or high temperature. We have determined the phase diagram of carbon by means of Monte Carlo and molecular dynamics simulations methods using the Brenner bond order potential. The melting line of diamond was found to have a positive slope with the graphite-diamond-liquid triple point in agreement with an estimated value based on experiment. The present calculation predicts a first-order phase transition in liquid carbon terminated by a critical point and by a triple point on the graphite melting line. The low-density liquid is predominantly sp bonded with little sp{sup 3} character. The high-density liquid is mostly sp{sup 3} bonded with little sp character.

  16. Equation of state and phase diagram of ammonia at high pressures from ab initio simulations.

    PubMed

    Bethkenhagen, Mandy; French, Martin; Redmer, Ronald

    2013-06-21

    We present an equation of state as well as a phase diagram of ammonia at high pressures and high temperatures derived from ab initio molecular dynamics simulations. The predicted phases of ammonia are characterized by analyzing diffusion coefficients and structural properties. Both the phase diagram and the subsequently computed Hugoniot curves are compared to experimental results. Furthermore, we discuss two methods that allow us to take into account nuclear quantum effects, which are of considerable importance in molecular fluids. Our data cover pressures up to 330 GPa and a temperature range from 500 K to 10,000 K. This regime is of great interest for interior models of the giant planets Uranus and Neptune, which contain, besides water and methane, significant amounts of ammonia. PMID:23802968

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

    SciTech Connect

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

    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.

  18. The high-pressure phase stability of 2,4,6-trinitrotoluene (TNT)

    NASA Astrophysics Data System (ADS)

    Bowden, P. R.; Chellappa, R. S.; Dattelbaum, D. M.; Manner, V. W.; Mack, N. H.; Liu, Z.

    2014-05-01

    2,4,6-trinitrotoluene (TNT) is a widely used explosive that is relatively insensitive to initiation by shock loading. While the detonation properties of TNT have been extensively reported, the high pressure-temperature (P-T) stability of TNT has not been investigated in detail. At ambient conditions, TNT crystallizes in a monoclinic lattice (space group P21/a), and our previous X-ray diffraction (XRD) measurements at room temperature suggested a phase transition to orthorhombic (space group Pca21) at ~20 GPa. In this work, we have performed in-situ synchrotron XRD and vibrational spectroscopy measurements along the room temperature isotherm to investigate phase stabilities up to 18 GPa. While our Raman spectroscopy measurements indicate spectral changes at ~2 GPa, careful XRD measurements reveal that the monoclinic phase persists up to 10 GPa.

  19. Equation of state and phase diagram of ammonia at high pressures from ab initio simulations.

    PubMed

    Bethkenhagen, Mandy; French, Martin; Redmer, Ronald

    2013-06-21

    We present an equation of state as well as a phase diagram of ammonia at high pressures and high temperatures derived from ab initio molecular dynamics simulations. The predicted phases of ammonia are characterized by analyzing diffusion coefficients and structural properties. Both the phase diagram and the subsequently computed Hugoniot curves are compared to experimental results. Furthermore, we discuss two methods that allow us to take into account nuclear quantum effects, which are of considerable importance in molecular fluids. Our data cover pressures up to 330 GPa and a temperature range from 500 K to 10,000 K. This regime is of great interest for interior models of the giant planets Uranus and Neptune, which contain, besides water and methane, significant amounts of ammonia.

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

    SciTech Connect

    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.

  1. Liquidus Phases of the Richardson H5 Chondrite at High Pressures and Temperatures

    NASA Technical Reports Server (NTRS)

    Channon, M.; Garber, J.; Danielson, L. R.; Righter, K.

    2007-01-01

    Part of early mantle evolution may include a magma ocean, where core formation began before the proto-Earth reached half of its present radius. Temperatures were high and bombardment and accretion were still occurring, suggesting that the proto-Earth consisted of a core and an at least partially liquid mantle, the magma ocean. As the Earth accreted, pressure near the core increased and the magma ocean decreased in volume and became shallower as it began to cool and solidify. As crystals settled, or floated, the composition of the magma ocean could change significantly and begin to crystallize different minerals from the residual liquid. Therefore, the mantle may be stratified following the P-T phase diagram for the bulk silicate Earth. To understand mantle evolution, it is necessary to know liquidus phase relations at high pressures and temperatures. In order to model the evolution of the magma ocean, high pressure and temperature experiments have been conducted to simulate the crystallization process using a range of materials that most likely resemble the bulk composition of the early Earth.

  2. Elasticity and phase transitions of stishovite and sodium chloride at high pressure

    NASA Astrophysics Data System (ADS)

    Lakshtanov, Dmitry Leonidovich

    2007-12-01

    Knowledge of elastic properties of the phases constituting the Earth's mantle are of extreme importance for determination of Earth's chemical composition, the distribution of phases and the processes that result in such distribution. Data on elasticity of these constituent phases are critical not only for interpreting seismic observations, but are also essential for geochemical and geodynamical modeling. This dissertation is mainly devoted to determination of the elasticity and stability of stishovite, the high-pressure silica polymorph, as a major constituent of the MORB layer of subducting lithospheric slabs. These thin (˜10km thick) layers subducted into the Earth mantle create regions of thermal, compositional and, hence, rheological heterogeneity. Being a key component of the mantle convection system, subducting slabs may counteract compositional stratification of the Earth by acting to remix differentiated lithospheric material. In addition, there has recently been great interest in subducting slabs as possible carriers of volatiles - mainly water - back to the lower mantle. Stishovite is likely the primary water-bearing phase. The elastic properties and thermodynamic stability of water-bearing stishovite, and the effect of other impurities on these properties, is the main focus of this work. An important related issue I addressed is the establishment of a self-consistent (absolute) equation of state for the B2 phase of sodium chloride (NaCl). NaCl is a commonly-used pressure transmitting medium in high-pressure devices. Accurate knowledge of the NaCl equation of state therefore reduces errors in pressure determination resulting from the use of the secondary pressure calibrants. In order to perform these tasks I used Brillouin scattering and Raman spectroscopy, combined with synchrotron x-ray diffraction at standard conditions, and at high pressures and temperatures in the diamond anvil cell. Experiments were performed in Merrill-Bassett and piston

  3. Correlated structural and electronic phase transformations in transition metal chalcogenide under high pressure

    NASA Astrophysics Data System (ADS)

    Li, Chunyu; Ke, Feng; Hu, Qingyang; Yu, Zhenhai; Zhao, Jinggeng; Chen, Zhiqiang; Yan, Hao

    2016-04-01

    Here, we report comprehensive studies on the high-pressure structural and electrical transport properties of the layered transition metal chalcogenide (Cr2S3) up to 36.3 GPa. A structural phase transition was observed in the rhombohedral Cr2S3 near 16.5 GPa by the synchrotron angle dispersive X-ray diffraction measurement using a diamond anvil cell. Through in situ resistance measurement, the electric resistance value was detected to decrease by an order of three over the pressure range of 7-15 GPa coincided with the structural phase transition. Measurements on the temperature dependence of resistivity indicate that it is a semiconductor-to-metal transition in nature. The results were also confirmed by the electronic energy band calculations. Above results may shed a light on optimizing the performance of Cr2S3 based applications under extreme conditions.

  4. Observations of a high-pressure phase creation in oleic acid

    NASA Astrophysics Data System (ADS)

    Kościesza, R.; Kulisiewicz, L.; Delgado, A.

    2010-03-01

    Oleic acid is one of the unsaturated fatty acids which frequently appears in food products such as edible fats and oils. A molecule of oleic acid possesses a double carbon bond, C=C, which is responsible for a transition to a new phase when pressure is applied. This work presents the results of optical observations of such a transition. The observations were made in two cases, the first being static p-T conditions under 60 MPa at 20°C and the other the dynamic application of the pressure up to 350 MPa. The obtained visualization reveals differences in the creation of the phase and in its further appearance. Some crystal forms may be recognized. These results tend to be of interest for food engineers due to increasing interest in high-pressure food preservation among nutritionists and medical scientists concerned with fatty acids.

  5. Successive disorder to disorder phase transitions in ionic liquid [HMIM][BF4] under high pressure

    NASA Astrophysics Data System (ADS)

    Zhu, Xiang; Yuan, Chaosheng; Li, Haining; Zhu, Pinwen; Su, Lei; Yang, Kun; Wu, Jie; Yang, Guoqiang; Liu, Jing

    2016-02-01

    In situ high-pressure Raman spectroscopy and synchrotron X-ray diffraction have been employed to investigate the phase behavior of ionic liquid, 1-hexyl-3-methylimidazolium tetrafluoroborate ([HMIM][BF4]) under high pressure up to 20 GPa at room temperature. With increasing pressure, some characteristic bands of [HMIM][BF4] disappear, and some characteristic bands of [HMIM][BF4] display non-monotonic pressure-induced frequency shift and non-monotonic variation of full width at half-maximum. Two successive phase transitions at ∼1.7 GPa and 7.3 GPa have been corroborated by the results above. The glass transition pressure (Pg) of [HMIM][BF4] at ∼7.3 GPa has been obtained by ruby R1 line broadening measurements and analysis of synchrotron X-ray diffraction patterns, and its glass transition mechanism is also analyzed in detail. These facts are suggestive of two successive disorder to disorder phase transitions induced by compression, that is, [HMIM][BF4] serves as a superpressurized glass under the pressure above 7.3 GPa, which is similar to the glassy state at low temperature, and a compression-induced liquid to liquid phase transition in [HMIM][BF4] occurs at ∼1.7 GPa. Besides, the conformational equilibrium of the GAAA conformer and AAAA conformer was converted easily in liquid [HMIM][BF4], while it was difficult to be influenced in glassy state.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    SciTech Connect

    Li, Yanchun E-mail: liuj@ihep.ac.cn; Lin, Chuanlong; Li, Xiaodong; Liu, Jing E-mail: liuj@ihep.ac.cn; Li, Gong; Xu, Jian

    2014-06-14

    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.

  9. The high pressure-temperature phase behavior of 2,4,6-trinitrotoluene (TNT)

    NASA Astrophysics Data System (ADS)

    Bowden, Patrick; Chellappa, Raja; Dattelbaum, Dana; Manner, Virginia; Mack, Nathan; Liu, Zhenxian

    2013-06-01

    2,4,6-trinitrotoluene (TNT) is a widely used explosive that is relatively insensitive to initiation by shock loading. While the detonation properties of TNT have been extensively reported, the high pressure-temperature (P - T) stability of TNT has not been investigated in detail. In addition, there are no studies that have determined the effects of pressure on the stability of the liquid phase. At ambient conditions, TNT crystallizes in a monoclinic lattice (space group P21 / a) , and our previous x-ray diffraction (XRD) measurements at room temperature suggested a phase transition to orthorhombic (space group Pca21) at ~20 GPa. In this work, we have performed in situ synchrotron XRD and vibrational spectroscopy measurements at various P - T conditions along isothermal and isobaric pathways to confirm previously reported phase transitions, and investigate phase stabilities up to 30 GPa and 500°C. Using all the available data, we have established the first comprehensive high P - T phase diagram of TNT, including the melting line as a function of pressure. While our synchrotron IR and Raman spectroscopy measurements indicate spectral changes at ~2 GPa, careful XRD measurements (hydrostatic, He medium and non-hydrostatic) reveal that the monoclinic phase is likely stable up to 20 GPa. We will present a self-consistent P - V - T equation of state derived from the reported structural and vibrational data.

  10. Exploring the Phase Diagram SiO2-CO2 at High Pressures and Temperatures

    NASA Astrophysics Data System (ADS)

    Kavner, A.

    2015-12-01

    CO2 is an important volatile system relevant for planetary sciences and fundamental chemistry. Molecular CO2 has doubly bonded O=C=O units but high pressure-high temperature (HP-HT) studies have recently shown its transformation into a three-dimensional network of corner-linked [CO4] units analogous to the silica mineral polymorphs, through intermediate non-molecular phases. Here, we report P-V-T data on CO2-IV ice from time-of-flight neutron diffraction experiments, which allow determining the compressibility and thermal expansivity of this intermediate molecular-to-non-molecular phase.1 Aditionally, we have explored the SiO2-CO2 phase diagram and the potential formation of silicon carbonate compounds. New data obtained by laser-heating diamond-anvil experiments in CO2-filled microporous silica polymorphs will be shown. In particular, these HP-HT experiments explore the existence of potential CO2/SiO2 compounds with tetrahedrally-coordinated C/Si atoms by oxygens, which are predicted to be stable (or metastable) by state-of-the-art ab initio simulations.2,3 These theoretical predictions were supported by a recent study that reports the formation of a cristobalite-type Si0.4C0.6O2 solid solution at high-pressures and temperatures, which can be retained as a metastable solid down to ambient conditions.4 Entirely new families of structures could exist based on [CO4]4- units in various degrees of polymerisation, giving rise to a range of chain, sheet and framework solids like those found in silicate chemistry. References[1] S. Palaich et al., Am. Mineral. Submitted (2015) [2] A. Morales-Garcia et al., Theor. Chem. Acc. 132, 1308 (2013) [3] R. Zhou et al., Phys. Rev. X, 4, 011030 (2014) [4] M. Santoro et al. Nature Commun. 5, 3761 (2014)

  11. High-pressure phase behavior of binary mixtures of octacosane and carbon dioxide

    SciTech Connect

    McHugh, M.A.; Seckner, A.J.; Yogan, T.J.

    1984-11-01

    The high-pressure fluid phase behavior of binary mixtures of octacosane and CO/sub 2/ is experimentally investigated. Solubilities of octacosane in supercritical CO/sub 2/ and mixture molar volumes are determined for isotherms of 34.7, 45.4, 50.2, and 52.0/sup 0/C over a range of pressures from 80 to 325 atm. The solubility data are obtained by two different experimental techniques. The pressure-temperature projection of the two branches of the three-phase solid-liquid-gas freezing point depression curve is also determined. The octacosane-CO/sub 2/ LCEP is determined as 32.2/sup 0/ C and 72.6 atm. The UCEP, which is at a pressure greater than 650 atm, could not be determined due to the pressure limitation of the experimental apparatus. Phase diagram constructions are used qualitatively to explain the observed phase behavior and to provide information on the expected phase behavior of the octacosane-CO/sub 2/ system at pressures higher than those experimentally investigated.

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

    SciTech Connect

    Yoo, C; Evans, W; Cynn, H

    2004-03-30

    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 MgB{sub 2}, 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 (B{sub 0}, B{sub 0}{prime}, and V{sub 0}) 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 B{sub 0} is smaller by more than 10% suggesting that the difference may be due to non-hydrostatic conditions. The phase

  13. Superconductivity in metastable phases of phosphorus-hydride compounds under high pressure

    NASA Astrophysics Data System (ADS)

    Flores-Livas, José A.; Amsler, Maximilian; Heil, Christoph; Sanna, Antonio; Boeri, Lilia; Profeta, Gianni; Wolverton, Chris; Goedecker, Stefan; Gross, E. K. U.

    2016-01-01

    Hydrogen-rich compounds have been extensively studied both theoretically and experimentally in the quest for novel high-temperature superconductors. Reports on sulfur hydride attaining metallicity under pressure and exhibiting superconductivity at temperatures as high as 200 K have spurred an intense search for room-temperature superconductors in hydride materials. Recently, compressed phosphine was reported to metallize at pressures above 45 GPa, reaching a superconducting transition temperature (TC) of 100 K at 200 GPa. However, neither the exact composition nor the crystal structure of the superconducting phase have been conclusively determined. In this work, the phase diagram of PHn (n =1 ,2 ,3 ,4 ,5 ,6 ) was extensively explored by means of ab initio crystal structure predictions using the minima hopping method (MHM). The results do not support the existence of thermodynamically stable PHn compounds, which exhibit a tendency for elemental decomposition at high pressure even when vibrational contributions to the free energies are taken into account. Although the lowest energy phases of PH1 ,2 ,3 display TC's comparable to experiments, it remains uncertain if the measured values of TC can be fully attributed to a phase-pure compound of PHn.

  14. Atomic ordering in cubic bismuth telluride alloy phases at high pressure

    NASA Astrophysics Data System (ADS)

    Loa, I.; Bos, J.-W. G.; Downie, R. A.; Syassen, K.

    2016-06-01

    Pressure-induced transitions from ordered intermetallic phases to substitutional alloys to semi-ordered phases were studied in a series of bismuth tellurides. By using angle-dispersive x-ray diffraction, the compounds Bi4Te5 , BiTe, and Bi2Te were observed to form alloys with the disordered body-centered cubic (bcc) crystal structure upon compression to above 14-19 GPa at room temperature. The BiTe and Bi2Te alloys and the previously discovered high-pressure alloys of Bi2Te3 and Bi4Te3 were all found to show atomic ordering after gentle annealing at very moderate temperatures of ˜100 ∘C . Upon annealing, BiTe transforms from bcc to the B2 (CsCl) crystal-structure type, and the other phases adopt semi-disordered variants thereof, featuring substitutional disorder on one of the two crystallographic sites. The transition pressures and atomic volumes of the alloy phases show systematic variations across the BimTen series including the end members Bi and Te. First-principles calculations were performed to characterize the electronic structure and chemical bonding properties of B2-type BiTe and to identify the driving forces of the ordering transition. The calculated Fermi surface of B2-type BiTe has an intricate structure and is predicted to undergo three topological changes between 20 and 60 GPa.

  15. Phase transition of iron doped MgO under high pressure by first-principles study

    NASA Astrophysics Data System (ADS)

    Yang, K. S.; Li, S. L.; Zhang, J.; Zeng, Z.; Qin, X. Y.; Zhou, X. M.

    2015-07-01

    The (Mg, Fe)O solid solution is one of the major lower mantle minerals, and studying its properties and structures under high pressure is a fundamental step toward understanding Earth's deep interior. Here within the framework of density functional theory, we first discuss the relationship between the total energy and iron doped positions of (Mg, Fe)O, and find that the doped iron favors to be dispersive. Then the pressure-induced phase transitions of (Mg, Fe)O from NaCl-type (B1) to CsCl-type (B2) are probed. It is found that the phase transition pressure of (Mg, Fe)O decreases with damped oscillation, as the increase of iron concentration. This phenomenon is essentially determined by the iron concentration as well as iron doped positions. The electronic structures of MgO and (Mg0.75Fe0.25)O at 436 GPa are calculated, and the results show that the doped irons play a crucial role in the metallicity of (Mg0.75Fe0.25)O. Our results are in agreement with the experimental counterparts. This study would provide some useful information for understanding the behavior of pressure-induced phase transition and geoscience.

  16. Baddeleyite-type high-pressure phase of TIO2 and its stable P-T region

    NASA Astrophysics Data System (ADS)

    Endo, Shoichi; Sato, Hiromasa; Tang, Jie; Nakamoto, Yuki; Kikegawa, Takumi; Shimomura, Osamu; Kusaba, Keiji

    In-situ X-ray diffraction experiment has been carried out for powdered rutile under high pressure and temperature generated with sintered diamond multianvils. New diffraction lines of the high pressure phase began to appear at ˜12 GPa at room temperature, and the single phase was formed by heating at 770°C under 20.3 GPa. The high pressure phase has the baddeleyite-type structure: baddeleyite is the stable phase of ZrO2 at ambient conditions. The coordination number of Ti increases from six to seven through the transition and the volume is reduced by ˜9%. The stable P-T region of the baddeleyite phase is tentatively presented.

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

    NASA Astrophysics Data System (ADS)

    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 <100> (a-axis) and <001> (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 and U s = 2.73(9) + 1.49(5)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.

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

    PubMed

    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

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

    NASA Astrophysics Data System (ADS)

    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 <100> (a-axis) and <001> (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 and U s = 2.73(9) + 1.49(5)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. Kinematics and thermodynamics of a growing rim of high-pressure phase

    NASA Astrophysics Data System (ADS)

    Morris, S. J. S.

    2014-03-01

    We have reanalysed the problem of growth of a dense product rim on a sphere of parent phase. To decouple the problem of calculating deformation from rheology, we assume spherical symmetry, and incompressible phases. Within the product, the radial deviatoric strain and its time-derivative prove to be of opposite sign: strain is compressive, but the strain rate is tensile. Further, the radial deviatoric strain in the new product adjacent to the interface is invariant in time. Propagation of the phase interface is determined by a competition between two mechanisms: as an element of material is transformed, its shear strain energy is increased; and the core pressure performs work compressing it. For elastic phases, this competition results in metastability. Within a certain pressure range, either phase can occur alone, but the two phases can not coexist. Because this result is inconsistent with experiments by Kawazoe et al. (2010) in which a rim of high-pressure phase (wadsleyite) coexists with a central core of low-pressure phase (olivine), we then incorporate plastic flow. Assuming perfect plasticity, we show that for a given applied pressure exceeding the coexistence pressure, a rim of product can now nucleate if the excess pressure Δp exceeds a critical value depending on yield stress. Increasing Δp above this value allows product to grow into the parent phase. There are now two possibilities, depending on the value of Δp. Growth may eventually cease to produce a state in which the product rim is in equilibrium with a parent core; or growth may follow a more complicated path: within a range of excess pressures, the growth rate can decrease strongly from its initial value to produce a quasi-equilibrium state, before increasing again to a rate similar to that at which transformation began. We interpret these results to mean that if Δp is increased slowly in a series of experiments with constant yield stress, the sample passes through a series of equilibria until

  1. Titanium-scaffolded organic-monolithic stationary phases for ultra-high-pressure liquid chromatography.

    PubMed

    Vonk, Rudy J; Vaast, Axel; Eeltink, Sebastiaan; Schoenmakers, Peter J

    2014-09-12

    Organic-polymer monoliths with overall dimensions larger than one millimetre are prone to rupture - either within the monolith itself or between the monoliths and the containing wall - due to the inevitable shrinkage accompanying the formation of a cross-linked polymeric network. This problem has been addressed by creating titanium-scaffolded poly(styrene-co-divinylbenzene) (S-co-DVB) monoliths. Titanium-scaffolded monoliths were successfully used in liquid chromatography at very high pressures (up to 80MPa) and using gradients spanning the full range of water-acetonitrile compositions (0 to 100%). The kinetic-performance of (50-mm long) titanium-scaffolded monoliths was compared to that of similar monolith created in 1-mm i.d. glass-lined tubing at pressures up to 50MPa. The peak capacities obtained with the titanium-scaffolded column was about 30% lower. An increased Eddy-diffusion, due to the pillar-structure, and a decreased permeability are thought to be the main reasons for this reduced kinetic-performance. No decrease in performance was observed when the titanium-scaffolded columns were operated at pressures of 80MPa for up to 12h. The column-to-column repeatability (n=5) was acceptable in terms of observed peak widths at half heights (RSD ca. 10%) The run-to-run repeatability (n=135) in terms of retention times and peak widths at half height were found to be good. Titanium-scaffolded columns coupled in series up to a combined length of (200mm) were used for the analyses of a complex Escherichia coli protein sample. Our experiments demonstrate that columns based on titanium-scaffolded organic-polymer monolith can be operated under strenuous conditions without loss in performance. The titanium-scaffolded approach makes it feasible to create organic-polymer monoliths in wide-bore columns with accurate temperature control.

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

    PubMed

    Faria, Luiz F O; Ribeiro, Mauro C C

    2015-11-01

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

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

    PubMed

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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

  6. Elastic Softening of Peridotite Due to the Presence of Melt Phases at High Pressure

    SciTech Connect

    Li, L.; Wang, L; Vaughan, M

    2008-01-01

    Here we report an observation of softening of Young's modulus of a sample of KLB-1 peridotite as a metallic Ni melt intruded into it at 2.5 GPa and about 1500 C. A uniaxial oscillation of stress was applied to the sample with frequency of 0.01-0.02 Hz and an amplitude up to 500 MPa. The Young's modulus is measured as the amplitude ratio between the sample and a reference material, while the attenuation is determined by the phase angle delays. The Ni intrusion was captured by in situ X-ray radiography. A planar intrusion occurred gradually, but advanced only during the extension; eventually, the Ni melt dissected the sample on a plane normal to the extension axis. Accompanied softening of Young's modulus was observed after the Ni intrusion was completed. This study suggests that percolation of a liquid metallic phase is possible within a partially melted mantle rock in the presence of a differential stress field.

  7. Structural, electronic and phase transition properties of ytterbium monopnictides under high pressure: A LSDA +U study

    NASA Astrophysics Data System (ADS)

    Kumar Singh, Sanjay; Rana, P.; Verma, U.

    2013-06-01

    In present paper, we have investigated the structural, electronic properties of ytterbium monopnictides (YbX = N, P) and its phase transition behaviour under high pressure by using the full potential linear augmented plane wave plus local orbitals approach within the framework of density functional theory. In the study the generalized gradient approximation (GGA) is chosen for the exchange-correlation functional energy. The equilibrium properties viz., equilibrium lattice constants, bulk modulus, its pressure derivative and total energy are calculated in four different phases i . e . B1, B2, B3 (zinc blende), and BCT phases 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. The LSDA + U strategy shows significant impact on the energy levels of the occupied and unoccupied 4 fstates in the electronic structure of both the compounds. The calculation shows YbX to be semi-metallic. The LSDA + U method provides better description of crystal properties of present system. At ambient conditions YbX (X = N, P) stabilize in NaCl (B1) structure characterized by the space group Fm-3m. Under compression, both YbN and YbP undergo first-order structural transition from Fm-3m (B1) to Pm-3m (B2) at 164.0 and 31.0 GPa, respectively. The One of the authors (UPV) acknowledges the financial assistance provided by UGC, New Delhi F. no. 36-124/2008(SR), India.

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

    PubMed

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  10. Mirrored continuum and molecular scale simulations of the ignition of high-pressure phases of RDX

    NASA Astrophysics Data System (ADS)

    Lee, Kibaek; Joshi, Kaushik; Chaudhuri, Santanu; Stewart, D. Scott

    2016-05-01

    We present a mirrored atomistic and continuum framework that is used to describe the ignition of energetic materials, and a high-pressure phase of RDX in particular. The continuum formulation uses meaningful averages of thermodynamic properties obtained from the atomistic simulation and a simplification of enormously complex reaction kinetics. In particular, components are identified based on molecular weight bin averages and our methodology assumes that both the averaged atomistic and continuum simulations are represented on the same time and length scales. The atomistic simulations of thermally initiated ignition of RDX are performed using reactive molecular dynamics (RMD). The continuum model is based on multi-component thermodynamics and uses a kinetics scheme that describes observed chemical changes of the averaged atomistic simulations. Thus the mirrored continuum simulations mimic the rapid change in pressure, temperature, and average molecular weight of species in the reactive mixture. This mirroring enables a new technique to simplify the chemistry obtained from reactive MD simulations while retaining the observed features and spatial and temporal scales from both the RMD and continuum model. The primary benefit of this approach is a potentially powerful, but familiar way to interpret the atomistic simulations and understand the chemical events and reaction rates. The approach is quite general and thus can provide a way to model chemistry based on atomistic simulations and extend the reach of those simulations.

  11. Strength and structural phase transitions of gadolinium at high pressure from radial X-ray diffraction

    SciTech Connect

    Xiong, Lun Liu, Jing; Bai, Ligang; Li, Xiaodong; Lin, Chuanlong; Lin, Jung-Fu

    2014-12-28

    Lattice strength and structural phase transitions of gadolinium (Gd) were determined under nonhydrostatic compression up to 55 GPa using an angle-dispersive radial x-ray diffraction technique in a diamond-anvil cell at room temperature. Three new phases of fcc structure, dfcc structure, and new monoclinic structure were observed at 25 GPa, 34 GPa, and 53 GPa, respectively. The radial x-ray diffraction data yield a bulk modulus K{sub 0} = 36(1) GPa with its pressure derivate K{sub 0}′ = 3.8(1) at the azimuthal angle between the diamond cell loading axis and the diffraction plane normal and diffraction plane ψ = 54.7°. With K{sub 0}′ fixed at 4, the derived K{sub 0} is 34(1) GPa. In addition, analysis of diffraction data with lattice strain theory indicates that the ratio of differential stress to shear modulus (t/G) ranges from 0.011 to 0.014 at pressures of 12–55 GPa. Together with estimated high-pressure shear moduli, our results show that Gd can support a maximum differential stress of 0.41 GPa, while it starts to yield to plastic deformation at 16 GPa under uniaxial compression. The yield strength of Gd remains approximately a constant with increasing pressure, and reaches 0.46 GPa at 55 GPa.

  12. High-pressure phase relations and thermodynamic properties of CaAl 4Si 2O 11 CAS phase

    NASA Astrophysics Data System (ADS)

    Akaogi, M.; Haraguchi, M.; Yaguchi, M.; Kojitani, H.

    2009-03-01

    Phase relations in CaAl4Si2O11 were examined at 12-23 GPa and 1000-1800 °C by multianvil experiments. A three-phase mixture of grossular, kyanite and corundum is stable below about 13 GPa at 1000-1800 °C. At higher pressure and at temperature below about 1200 °C, a mixture of grossular, stishovite and corundum is stable, indicating the decomposition of kyanite. Above about 1200 °C, CaAl4Si2O11 CAS phase is stable at pressure higher than about 13 GPa. The triple point is placed at 14.7 GPa and 1280 °C. The equilibrium boundary of formation of CAS phase from the mixture of grossular, kyanite and corundum has a small negative slope, and that from the mixture of grossular, stishovite and corundum has a strongly negative slope, while the decomposition boundary of kyanite has a small positive slope. Enthalpies of the transitions were measured by high-temperature drop-solution calorimetry. The enthalpy of formation of CaAl4Si2O11 CAS phase from the mixture of grossular, kyanite and corundum was 139.5 ± 15.6 kJ/mol, and that from the mixture of grossular, stishovite and corundum was 94.2 ± 15.4 kJ/mol. The transition boundaries calculated using the measured enthalpy data were consistent with those determined by the high-pressure experiments. The boundaries in this study are placed about 3 GPa higher in pressure and about 200 °C lower in temperature than those by Zhai and Ito [Zhai, S., Ito, E., 2008. Phase relations of CaAl4Si2O11 at high-pressure and high-temperature with implications for subducted continental crust into the deep mantle. Phys. Earth Planet. Inter. 167, 161-167]. Combining the thermodynamic data measured in this study with those in the literature, dissociation boundary of CAS phase into a mixture of Ca-perovskite, corundum and stishovite and that of grossular into Ca-perovskite plus corundum were calculated to further constrain the stability field of CAS phase. The result suggests that the stability of CAS phase would be limited at the bottom of

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

    NASA Astrophysics Data System (ADS)

    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

  14. Effect of pressure on the selectivity of polymeric C18 and C30 stationary phases in reversed-phase liquid chromatography. Increased separation of isomeric fatty acid methyl esters, triacylglycerols, and tocopherols at high pressure.

    PubMed

    Okusa, Kensuke; Iwasaki, Yuki; Kuroda, Ikuma; Miwa, Shohei; Ohira, Masayoshi; Nagai, Toshiharu; Mizobe, Hoyo; Gotoh, Naohiro; Ikegami, Tohru; McCalley, David V; Tanaka, Nobuo

    2014-04-25

    A high-density, polymeric C18 stationary phase (Inertsil ODS-P) or a polymeric C30 phase (Inertsil C30) provided improved resolution of the isomeric fatty acids (FAs), FA methyl esters (FAMEs), triacylglycerols (TAGs), and tocopherols with an increase in pressure of 20-70MPa in reversed-phase HPLC. With respect to isomeric C18 FAMEs with one cis-double bond, ODS-P phase was effective for recognizing the position of a double bond among petroselinic (methyl 6Z-octadecenoate), oleic (methyl 9Z-octadecenoate), and cis-vaccenic (methyl 11Z-octadecenoate), especially at high pressure, but the differentiation between oleic and cis-vaccenic was not achieved by C30 phase regardless of the pressure. A monomeric C18 phase (InertSustain C18) was not effective for recognizing the position of the double bond in monounsaturated FAME, while the separation of cis- and trans-isomers was achieved by any of the stationary phases. The ODS-P and C30 phases provided increased separation for TAGs and β- and γ-tocopherols at high pressure. The transfer of FA, FAME, or TAG molecules from the mobile phase to the ODS-P stationary phase was accompanied by large volume reduction (-30∼-90mL/mol) resulting in a large increase in retention (up to 100% for an increase of 50MPa) and improved isomer separation at high pressure. For some isomer pairs, the ODS-P and C30 provided the opposite elution order, and in each case higher pressure improved the separation. The two stationary phases showed selectivity for the isomers having rigid structures, but only the ODS-P was effective for differentiating the position of a double bond in monounsaturated FAMEs. The results indicate that the improved isomer separation was provided by the increased dispersion interactions between the solute and the binding site of the stationary phase at high pressure.

  15. First Principles Study of High Pressure Phase Transitions in ThN and UN

    NASA Astrophysics Data System (ADS)

    Modak, P.; Verma, Ashok K.

    2011-07-01

    We have carried out high pressure structural investigations of UN and ThN using ab initio total energy calculations. We have predicted that UN undergoes a structural transition from NaCl to R-3m structure at around 10 GPa pressure whereas that for ThN is absent. However at higher pressure (at 63 GPa) ThN transformed to CsCl structure. Our detailed analysis showed that NaCl structure becomes mechanically unstable at high pressure for UN but remains metastable for ThN.

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

    SciTech Connect

    Yan, Xiaozhi; Ren, Xiangting; He, Duanwei E-mail: yangwg@hpstar.ac.cn; Chen, Bin; Yang, Wenge E-mail: yangwg@hpstar.ac.cn

    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.

  17. Quenching ilmenite with a high-temperature and high-pressure phase using super-high-energy ball milling.

    PubMed

    Hashishin, Takeshi; Tan, Zhenquan; Yamamoto, Kazuhiro; Qiu, Nan; Kim, Jungeum; Numako, Chiya; Naka, Takashi; Valmalette, Jean Christophe; Ohara, Satoshi

    2014-04-25

    The mass production of highly dense oxides with high-temperature and high-pressure phases allows us to discover functional properties that have never been developed. To date, the quenching of highly dense materials at the gramme-level at ambient atmosphere has never been achieved. Here, we provide evidence of the formation of orthorhombic Fe2TiO4 from trigonal FeTiO3 as a result of the high-temperature (>1250 K) and high-pressure (>23 GPa) condition induced by the high collision energy of 150 gravity generated between steel balls. Ilmenite was steeply quenched by the surrounding atmosphere, when iron-rich ilmenite (Fe2TiO4) with a high-temperature and high-pressure phase was formed by planetary collisions and was released from the collision points between the balls. Our finding allows us to infer that such intense planetary collisions induced by high-energy ball milling contribute to the mass production of a high-temperature and high-pressure phase.

  18. Quenching ilmenite with a high-temperature and high-pressure phase using super-high-energy ball milling

    NASA Astrophysics Data System (ADS)

    Hashishin, Takeshi; Tan, Zhenquan; Yamamoto, Kazuhiro; Qiu, Nan; Kim, Jungeum; Numako, Chiya; Naka, Takashi; Valmalette, Jean Christophe; Ohara, Satoshi

    2014-04-01

    The mass production of highly dense oxides with high-temperature and high-pressure phases allows us to discover functional properties that have never been developed. To date, the quenching of highly dense materials at the gramme-level at ambient atmosphere has never been achieved. Here, we provide evidence of the formation of orthorhombic Fe2TiO4 from trigonal FeTiO3 as a result of the high-temperature (>1250 K) and high-pressure (>23 GPa) condition induced by the high collision energy of 150 gravity generated between steel balls. Ilmenite was steeply quenched by the surrounding atmosphere, when iron-rich ilmenite (Fe2TiO4) with a high-temperature and high-pressure phase was formed by planetary collisions and was released from the collision points between the balls. Our finding allows us to infer that such intense planetary collisions induced by high-energy ball milling contribute to the mass production of a high-temperature and high-pressure phase.

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

    NASA Astrophysics Data System (ADS)

    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.

  20. In Situ Observations of Thermoreversible Gelation and Phase Separation of Agarose and Methylcellulose Solutions under High Pressure.

    PubMed

    Kometani, Noritsugu; Tanabe, Masahiro; Su, Lei; Yang, Kun; Nishinari, Katsuyoshi

    2015-06-01

    Thermoreversible sol-gel transitions of agarose and methylcellulose (MC) aqueous solutions on isobaric cooling or heating under high pressure up to 400 MPa have been investigated by in situ observations of optical transmittance and falling-ball experiments. For agarose, which undergoes the gelation on cooling, the application of pressure caused a gradual rise in the cloud-point temperature over the whole pressure range examined, which is almost consistent with the pressure dependence of gelling temperature estimated by falling-ball experiments, suggesting that agarose gel is stabilized by compression and that the gelation occurs nearly in parallel with phase separation under ambient and high-pressure conditions. For MC, which undergoes the gelation on heating, the cloud-point temperature showed a slight rise with an initial elevation of pressure up to ∼150 MPa, whereas it showed a marked depression above 200 MPa. In contrast, the gelling temperature of MC, which is nearly identical to the cloud-point temperature at ambient pressure, showed a monotonous rise with increasing pressure up to 350 MPa, which means that MC undergoes phase separation prior to gelation on heating under high pressure above 200 MPa. Similar results were obtained for the melting process of MC gel on cooling. The unique behavior of the sol-gel transition of MC under high pressure has been interpreted in terms of the destruction of hydrophobic hydration by compression.

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

    NASA Astrophysics Data System (ADS)

    Huang, Hu; Yan, Jiwang

    2016-04-01

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

  2. High-pressure matrix isolation of heterogeneous condensed phase chemical reactions under extreme conditions

    NASA Astrophysics Data System (ADS)

    Rice, Jane K.; Russell, T. P.

    1995-03-01

    A new technique which combines high-pressure and thermal-shock conditions with low-temperature matrix isolation in a gem anvil cell is presented. This serves to partially quench or arrest the reaction sequence of an energetic material. New chemical species are observed which indicate that intermediates are trapped in addition to final products. This combination of high pressure and low temperature helps elucidate the complicated reaction pathways in the deflagration to detonation regime. We have applied this technique to hexanitrohexaazaisowurtzitane (HNIW, chemical name: 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetracyclo[5.5.0.0 5,9.0 3,11]dodecane). Products are identified using infrared spectroscopy and comparisons are made to previously reported data taken under thermal, ambient pressure conditions.

  3. CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: The Phase Transition of Eu2O3 under High Pressures

    NASA Astrophysics Data System (ADS)

    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

    2009-07-01

    Pressure-induced phase transition of cubic Eu2O3 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.

  4. High pressure phase transformations of cubic boron nitride from amorphous boron nitride using magnesium boron nitride as the catalyst

    NASA Astrophysics Data System (ADS)

    Singh, B. P.; Nover, G.; Will, G.

    1995-07-01

    Results are described of high pressure phase transformations of amorphous boron nitride (aBN) to cubic boron nitride (cBN) using magnesium boron nitride (Mg 3B 2N 4) as a catalyst-solvent. It was observed that amorphous boron nitride undergoes various structural modifications under high pressures and high temperatures leading to the formation of hexagonal, cubic and wurtzitic phases of boron nitride. The minimum pressure at which aBN starts transforming into cBN was found to be 25 kbar at 1800°C. This is the lowest pressure for cBN formation employing the catalyst-solvent process and is reported here for the first time.

  5. Thermodynamics of the ferromagnetic phase transition in nearly half metallic CoS2 at high pressures

    SciTech Connect

    Elkin, F. S.; Zibrov, I. P.; Novikov, A. P.; Khasanov, S. S.; Sidorov, V. A.; Petrova, A. E.; Lograsso, Thomas A.; Thompson, J. D.; Stishov, S. M.

    2013-12-06

    The volume change and heat capacity at the ferromagnetic phase transition in COS2 were measured at high pressures using X-rays generated by the Argonne synchrotron light source and by ac-calorimetry, respectively. The transition entropy, calculated on the basis of these experimental data, drops along the transition line due to quantum degradation, as required by Nernst's law. The volume change increases strongly along the transition line, which is explained by specifics of the compressibility difference of coexisting phases that results from nearly half metallic nature of the ferromagnetic phase of COS2. (C) 2013 Elsevier Ltd. All rights reserved.

  6. Development and testing of a high-pressure downhole pump for jet-assist drilling. Topical report, Phase II

    SciTech Connect

    1997-10-01

    The goal of jet-assisted drilling is to increase the rate of penetration (ROP) in deeper gas and oil wells, where the rocks become harder and more difficult to drill. Increasing the ROP can result in fewer drilling days, and therefore, lower drilling cost. In late 1993, FlowDril and the Gas Research Institute (GRI) began a three-year development of a down hole pump (DHP{reg_sign}) capable of producing 30,000 psi out pressure to provide the high-pressure flow for high-pressure jet-assist of the drill bit. The U.S. Department of Energy (DOE) through its Morgantown, WV (DOE-Morgantown) field office, joined with GRI and FlowDril to develop and test a second prototype designed for drilling in 7-7/8 inch holes. This project, {open_quotes}Development and Testing of a High-Pressure Down Hole Pump for Jet-Assist Drilling,{close_quotes} is for the development and testing of the second prototype. It was planned in two phases. Phase I included an update of a market analysis, a design, fabrication, and an initial laboratory test of the second prototype. Phase II is continued iterative laboratory and field developmental testing. This report summarizes the results of Phase II. In the downhole pump approach shown in the following figure, conventional drill pipe and drill collars are used, with the DHP as the last component of the bottom hole assembly next to the bit. The DHP is a reciprocating double ended, intensifier style positive displacement, high-pressure pump. The drive fluid and the high-pressure output fluid are both derived from the same source, the abrasive drilling mud pumped downhole through the drill string. Approximately seven percent of the stream is pressurized to 30,000 psi and directed through a high-pressure nozzle on the drill bit to produce the high speed jet and assist the mechanical action of the bit to make it drill faster.

  7. High pressure phase transition in metallic LaB 6: Raman and X-ray diffraction studies

    NASA Astrophysics Data System (ADS)

    Teredesai, Pallavi; Muthu, D. V. S.; Chandrabhas, N.; Meenakshi, S.; Vijayakumar, V.; Modak, P.; Rao, R. S.; Godwal, B. K.; Sikka, S. K.; Sood, A. K.

    2004-03-01

    High pressure Raman and angle dispersive X-ray diffraction (ADXRD) measurements on the metallic hexaboride LaB 6 have been carried out upto the pressures of about 20 GPa. The subtle phase transition around 10 GPa indicated in Raman measurements is confirmed by ADXRD experiments to be a structural change from cubic to orthorhombic phase. Ab-initio electronic band structure calculations using full potential linear augmented plane wave method carried out as a function of pressure show that this transition is driven by the interception of Fermi level by electronic band minimum around the transition pressure.

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

    NASA Astrophysics Data System (ADS)

    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. Series of Phase Transitions in Cesium Azide Under High Pressure Studied by in situ X-ray Diffraction

    SciTech Connect

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

    2011-12-31

    In situ x-ray diffraction measurements of cesium azide (CsN{sub 3}) were performed at high pressures of up to 55.4 GPa at room temperature. Three phase transitions were revealed as follows: tetragonal (I4/mcm, Phase II) {yields} monoclinic (C2/m, Phase III) {yields} monoclinic (P2{sub 1}/m or P2{sub 1}, Phase IV) {yields} triclinic (P1 or P1{sup -}, Phase V), at 0.5, 4.4, and 15.4 GPa, respectively. During the II-III phase transition, CsN{sub 3} keeps its layered structure and the azide anions rotate obviously. The compressibility of Phase II is dominated by the repulsions between azide anions. The deformation of unit cell is isotropic in Phases II and IV and anisotropic in Phase III. With increasing pressures, the monoclinic angle increases in Phase III and then becomes stable in Phase IV. The bulk moduli of Phases II, III, IV, and V are determined to be 18 {+-} 4, 20 {+-} 1, 27 {+-} 1 and 34 {+-} 1 GPa, respectively. The ionic character of alkali azides is found to play a key role in their pressure-induced phase transitions.

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

    SciTech Connect

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

    2014-11-07

    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 → Smtype→ 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 GP and a temperature of 10 K. The magnetic ordering temperature has been determined from the four-point electrical resistivity measurements carried out on gadolinium. Furthermore, 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. Structural and magnetic phase transitions in gadolinium under high pressures and low temperatures

    DOE PAGES

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

    2014-11-07

    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 → Smtype→ 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 GP and a temperaturemore » of 10 K. The magnetic ordering temperature has been determined from the four-point electrical resistivity measurements carried out on gadolinium. Furthermore, 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.« less

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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

  14. Stability of γ and δ phases in Ti at high pressures

    NASA Astrophysics Data System (ADS)

    Joshi, K. D.; Jyoti, G.; Gupta, Satish C.; Sikka, S. K.

    2002-02-01

    Recently, Vohra and Spencer [Phys. Rev. Lett. 86, 3068 (2001)] reported that titanium metal undergoes a transition from a hexagonal phase (ω) to an orthorhombic phase (distorted hcp, γ phase) under a pressure of 116+/-4 GPa, from energy dispersive x-ray-diffraction measurements. Subsequent to this, very recently, Akahama et al. [Phys. Rev. Lett. 87, 275503 (2001)] also reported that titanium undergoes a transition to a γ phase from an ω phase, contrary to their earlier investigations showing a ω-->β (bcc) transition in Ti at 140 GPa. Additionally, they reported another transition in Ti, a γ-->δ (distorted bcc) transition around 140 GPa. This is unexpected, as the group-IVB elements are expected to undergo s-to-d electron transfer under pressure and thus mimic the transformation sequence α(hcp)-->ω-->β shown by these elements with increasing numbers of d electrons on alloying with d-electron-rich neighbors. This structural sequence under pressure is well established for Zr and Hf. In the present work, we carry out total energy calculations employing the full-potential linear-augmented-plane wave method to examine the stability of the γ and δ phases with respect to the ω and β structures. Our analysis predicts at 0 K the ω phase transforms to a β phase via an intermediate γ phase, whereas at 300 K the ω phase transforms to a β structure directly and the γ phase becomes the most competitive metastable structure in the pressure range of the β-phase stability. The δ phase, however, is not at all stable at any compression. This suggests that the γ phase observed in the experiments is a metastable phase that could be formed due to the shear stresses present in the experiments, and that the ω-->γ structural transition does not represent the phenomenon expected under hydrostatic conditions.

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

    PubMed

    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

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

    PubMed Central

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

    2016-01-01

    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 mm3. A robust polarization-preserving effect is also observed, raising the possibility of advanced optical technological applications. PMID:27574703

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

    PubMed

    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.

  18. Structural phase transitions in Bi2Se3 under high pressure

    SciTech Connect

    Yu, Zhenhai; Gu, Genda; Wang, Lin; Hu, Qingyang; Zhao, Jinggeng; Yan, Shuai; Yang, Ke; Sinogeikin, Stanislav; Mao, Ho -kwang

    2015-11-02

    Raman spectroscopy and angle dispersive X-ray diffraction (XRD) experiments of bismuth selenide (Bi2Se3) have been carried out to pressures of 35.6 and 81.2 GPa, respectively, to explore its pressure-induced phase transformation. The experiments indicate that a progressive structural evolution occurs from an ambient rhombohedra phase (Space group (SG): R-3m) to monoclinic phase (SG: C2/m) and eventually to a high pressure body-centered tetragonal phase (SG: I4/mmm). Evidenced by our XRD data up to 81.2 GPa, the Bi2Se3 crystallizes into body-centered tetragonal structures rather than the recently reported disordered body-centered cubic (BCC) phase. Furthermore, first principles theoretical calculations favor the viewpoint that the I4/mmm phase Bi2Se3 can be stabilized under high pressure (>30 GPa). Remarkably, the Raman spectra of Bi2Se3 from this work (two independent runs) are still Raman active up to ~35 GPa. Furthermore, it is worthy to note that the disordered BCC phase at 27.8 GPa is not observed here. The remarkable difference in atomic radii of Bi and Se in Bi2Se3 may explain why Bi2Se3 shows different structural behavior than isocompounds Bi2Te3 and Sb2Te3.

  19. Real-Time Optical Monitoring of Flow Kinetics and Gas Phase Reactions Under High-Pressure OMCVD Conditions

    NASA Technical Reports Server (NTRS)

    Dietz, N.; McCall, S.; Bachmann, K. J.

    2001-01-01

    This contribution addresses the real-time optical characterization of gas flow and gas phase reactions as they play a crucial role for chemical vapor phase depositions utilizing elevated and high pressure chemical vapor deposition (HPCVD) conditions. The objectives of these experiments are to validate on the basis of results on real-time optical diagnostics process models simulation codes, and provide input parameter sets needed for analysis and control of chemical vapor deposition at elevated pressures. Access to microgravity is required to retain high pressure conditions of laminar flow, which is essential for successful acquisition and interpretation of the optical data. In this contribution, we describe the design and construction of the HPCVD system, which include access ports for various optical methods of real-time process monitoring and to analyze the initial stages of heteroepitaxy and steady-state growth in the different pressure ranges. To analyze the onset of turbulence, provisions are made for implementation of experimental methods for in-situ characterization of the nature of flow. This knowledge will be the basis for the design definition of experiments under microgravity, where gas flow conditions, gas phase and surface chemistry, might be analyzed by remote controlled real-time diagnostics tools, developed in this research project.

  20. Phase diagram of ammonium perchlorate: Raman spectroscopic constrains at high pressures and temperatures

    NASA Astrophysics Data System (ADS)

    Dunuwille, Mihindra; Yoo, Choong-Shik

    2016-06-01

    We present the pressure-temperature (PT) induced physical and chemical transformations in ammonium perchlorates (APs) up to 50 GPa and 450 °C, using diamond anvil cells and confocal micro-Raman spectroscopy, which provide new constraints for the phase diagram of AP. The results show spectral evidences for three new polymorphs (III, IV, and VI) of AP, in addition to two previously known phases (I and II), at various PT conditions with varying degrees of hydrogen bonding and lack of strong spectral evidence for previously known high-temperature cubic phase (phase V). Upon further heating, AP chemically decomposes to N2, N2O, and H2O. The present phase diagram is, therefore, in sharp contrast to the previous one, underscoring a rich polymorphism, a large stability field for solids, and a replacement of the melt with a decomposition line.

  1. A two-dimensional modeling of the warm-up phase of a high-pressure mercury discharge lamp

    SciTech Connect

    Araoud, Z.; Ben Ahmed, R.; Ben Hamida, M. B.; Charrada, K.; Franke, St.; Stambouli, M.; Zissis, G.

    2010-06-15

    The main objective of this work is to provide a better understanding of the warm-up phase of high-intensity discharge lamps. As an example of application, we chose the high-pressure mercury lamp. Based on two-dimensional fluid model parameters, such as the electric current, the length and the diameter of the burner are modified and the effect of the convective transport is studied. This allows us to obtain a thorough understanding of the physics of these lamps in their transitory phase. The simulation of the warm-up phase is a must for the proper predictions of the lamp behavior and can be conducted by solving the energy balance, momentum, and Laplace's equations for the plasma, using the frame of the local thermodynamic equilibrium coupled with the energy balance of the wall.

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

    SciTech Connect

    Popov, D. Park, C.; Kenney-Benson, C.; Shen, G.

    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.

  3. A study of the high pressure phase transition of diacylglycerol oil by means of light transmission and scattering

    NASA Astrophysics Data System (ADS)

    Kościesza, R.; Tefelski, D. B.; Ptasznik, S.; Rostocki, A. J.; Malanowski, A.; Siegoczyński, R. M.

    2012-06-01

    A sample of diacylglycerol (DAG) oil, being a mixture of DAGs and triacylglycerols with a ratio of 82% and 18%, respectively, and with a vestigial content of monoacylglycerols and free fatty acids, has been researched in high pressure conditions. As a result of dynamically applied pressure, a discontinuous (first-order) phase transition of the DAG sample has been observed. After the threshold value of the pressure for the phase change was determined, a number of further measurements were performed. The aim of the measurements was to pressurise the DAG sample with different rates of compression. During the measurements, the following parameters were recorded: the intensities of beams both transmitted and scattered at the angle of 90°, and the temperature of the sample. The obtained data may prove useful for an introductory description of the phase change kinetics induced by dynamically applied pressure.

  4. Synthesis of new Diamond-like B-C Phases under High Pressure and Temperatures

    SciTech Connect

    Ming, L. C.; Zinin, P. V.; Sharma, S. K.

    2014-04-22

    A cubic BC3 (c-BC3) phase was synthesized by direct transformation from graphitic phases at a pressure of 39 GPa and temperature of 2200 K in a laser-heated diamond anvil cell (DAC). A combination of x-ray diffraction (XRD), electron diffraction (ED), transmission electron microscopy (TEM) imaging, and electron energy loss spectroscopy (EELS) measurements lead us to conclude that the obtained phase is hetero-nano-diamond, c-BC3. The EELS measurements show that the atoms inside the cubic structure are bonded by sp3 bonds.

  5. Superconducting Phase in λ-(BEDT-STF)2GaCl4 at High Pressures

    NASA Astrophysics Data System (ADS)

    Minamidate, Takaaki; Oka, Yuki; Shindo, Hironori; Yamazaki, Toshitaka; Matsunaga, Noriaki; Nomura, Kazushige; Kawamoto, Atsushi

    2015-06-01

    Electrical resistivity measurements under pressure were conducted on the organic conductor λ-(BEDT-STF)2GaCl4, which is situated between λ-(ET)2GaCl4 and λ-(BETS)2GaCl4. Magnetic susceptibility was also measured at ambient pressure. A drop in resistivity, which is associated with the superconducting transition, was observed at Tc ≈ 5 K above 1.22 GPa. The superconducting phase was confirmed by pair-breaking under a magnetic field. This is the first observation of superconductivity in λ-(BEDT-STF)2GaCl4. The temperature dependence of spin susceptibility suggests a two-dimensional antiferromagnetic spin system without any magnetic ordering. The phase adjacent to the superconducting phase in λ-type systems is not the antiferromagnetic phase, unlike the case for κ-(ET)2X.

  6. In situ observations of a high-pressure phase of H2O ice

    USGS Publications Warehouse

    Chou, I.-Ming; Blank, J.G.; Goncharov, A.F.; Mao, Ho-kwang; Hemley, R.J.

    1998-01-01

    A previously unknown solid phase of H2O has been identified by its peculiar growth patterns, distinct pressure-temperature melting relations, and vibrational Raman spectra. Morphologies of ice crystals and their pressure-temperature melting relations were directly observed in a hydrothermal diamond-anvil cell for H2O bulk densities between 1203 and 1257 kilograms per cubic meter at temperatures between -10??and 50??C. Under these conditions, four different ice forms were observed to melt: two stable phases, ice V and ice VI, and two metastable phases, ice IV and the new ice phase. The Raman spectra and crystal morphology are consistent with a disordered anisotropic structure with some similarities to ice VI.

  7. Residuum upgrading by high pressure slurry phase technology: Technical, economic and environmental aspects

    SciTech Connect

    Kretschmar, K.; Wenzel, F.

    1994-12-31

    The technology of petroleum residue upgrading in slurry-phase reactors under high hydrogen partial pressure is based on the Bergius-Pier technology for coal liquefaction commercialized in Germany since the mid-1930`s. The paper describes the principle of slurry phase hydrogenation (SPH), reactivity and yield distribution in SPH, the operating pressure of SPH, integrated hydrotreating, processing of liquid and solid wastes, and economics of conversion projects.

  8. Determination of vapor-phase carbonyls by high-pressure liquid chromatography

    SciTech Connect

    Maskarinec, M.P.; Manning, D.L.; Oldham, P.

    1981-01-01

    Methods have been developed for the trapping and quantitative analysis of low molecular weight carbonyls in complex gas phase mixtures. Formaldehyde, acetaldehyde, acrolein, and acetone are separated as the 2-4-dinitrophenylhydrazones with a sensitivity of less than 10 ppB. The separation can be done on a variety of commercial C/sub 18/ reverse-phase columns. 4 figures, 1 table.

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

    NASA Astrophysics Data System (ADS)

    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.

  10. Structural phase stability in group IV metals under static high pressure

    SciTech Connect

    Velisavljevic, Nenad; Chesnut, Garry N; Dattelbaum, Dana M; Vohra, Yogesh K; Stemshorn, Andrew

    2009-01-01

    In group IV metals (Ti, Zr, and Hf) room temperature compression leads to a martensitic transformation from a ductile {alpha} to a brittle {omega} phase. {alpha} {yields} {omega} phase boundary decreases to lower pressure at high temperature and can limit the use of group IV metals in industrial applications. There is a large discrepancy in the transition pressure reported in literature, with some of the variation attributed to experimental conditions (i.e. hydrostatic vs. non-hydrostatic). Shear deformation in non-hydrostatic experiments drives {alpha} {yields} {omega} transition and decreases transition pressure. Impurities can also aid or suppress {alpha} {yields} {omega} transition. By performing x-ray diffraction experiments on samples in a diamond anvil cell we show that interstitial impurities, such as C, N, and O can obstruct {alpha} {yields} {omega} transition and stabilize {alpha} phase to higher pressure. We also show that reduction in grain size can also influence {alpha} {yields} {omega} phase boundary and help stabilize {alpha} phase to higher pressure under non-hydrostatic conditions.

  11. Phase Diagram and Physical Properties of H[subscript 2]O at High Pressures and temperatures: Applications to Planetary Interiors

    SciTech Connect

    Lin, Jung-Fu; Schwegler, Eric; Yoo, Choong-Shik

    2007-02-22

    Here we discuss the phase diagram and physical properties of H{sub 2}O under pressure-temperature conditions relevant to planetary interiors. Recent studies show that the melting curve of H{sub 2}O increases rapidly above a recently discovered triple point at approximately 35 to 47 GPa and 1000 K, indicating a large increase in {Delta}V/{Delta}S (volume versus entropy change) and associated changes in the physical properties of H{sub 2}O at high pressures and temperatures. Existence of the triple point is thought to be associated with the formation of a superionic phase, dynamically-disordered ice VII, or extension of the ice VII-ice X phase boundary; although the precise pressure and temperature of the triple point, curvature of the melting line, and nature of the solid-solid transition below the triple point all remain to be further explored. The steep increase in the melting curve of H{sub 2}O at high pressures and temperatures has important implications on our understanding of planetary interiors. Depending on its curvature, the melting line of H{sub 2}O may intersect the isentropes of Neptune and Uranus as well as the geotherm of Earth's lower mantle. Furthermore, if the triple point is due to the occurrence of the theoretically predicted superionic phase, besides leading to significant ionic conductivity, fast proton diffusion would cause enhanced chemical reactivity and formation of complex compounds in these planets. For example, reaction of H{sub 2}O with iron and other metals to form metal hydrides such as FeH{sub x} could provide a mechanism for incorporation of hydrogen as a light element into Earth's core. The equation of state of water is also presented as it pertains to the properties of hydrous fluid and melt phases in the mantle.

  12. Synthesis of dense BC[subscript x] phases under high-pressure and high-temperature

    SciTech Connect

    Ming, L.C.; Zinin, P.V.; Liu, X.R.; Nakamoto, Y.; Jia, R.

    2010-05-24

    We synthesized a new phase from the B-C system, cubic BC{sub 4} (c-BC{sub 4}), by direct transformation from graphitic phases at a pressure of 44 GPa and a temperature 2020 K in a laser-heated diamond anvil cell (DAC). Both x-ray diffraction and Raman spectroscopy confirm the presence of cubic BC{sub 4} from the sample recovered at ambient conditions. The zero-pressure lattice parameter of the c-BC{sub 4} calculated from diffraction peaks was found to be 3.587 {angstrom}. The composition of the new phase is determined from electron microprobe (EMP) measurements. The value of the C/B ratio is around 4 (3.91 {+-} 0.26).

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

    PubMed Central

    Wang, Yi X.; Wu, Q.; 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 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. PMID:27581551

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    Wang, Yi X; Wu, Q; 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 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. PMID:27581551

  17. Experimental and Theoretical Investigations on Structural and Vibrational Properties of Melilite-Type Sr2ZnGe2O7 at High Pressure and Delineation of a High-Pressure Monoclinic Phase.

    PubMed

    Achary, S Nagabhusan; Errandonea, Daniel; Santamaria-Perez, David; Gomis, Oscar; Patwe, Sadiqua J; Manjón, Francisco Javier; Hernandez, Placida Rodríguez; Muñoz, Alfonso; Tyagi, Avesh Kumar

    2015-07-01

    We report a combined experimental and theoretical study of melilite-type germanate, Sr2ZnGe2O7, under compression. In situ high-pressure X-ray diffraction and Raman scattering measurements up to 22 GPa were complemented with first-principles theoretical calculations of structural and lattice dynamics properties. Our experiments show that the tetragonal structure of Sr2ZnGe2O7 at ambient conditions transforms reversibly to a monoclinic phase above 12.2 GPa with ∼1% volume drop at the phase transition pressure. Density functional calculations indicate the transition pressure at ∼13 GPa, which agrees well with the experimental value. The structure of the high-pressure monoclinic phase is closely related to the ambient pressure phase and results from a displacive-type phase transition. Equations of state of both tetragonal and monoclinic phases are reported. Both of the phases show anisotropic compressibility with a larger compressibility in the direction perpendicular to the [ZnGe2O7](2-) sheets than along the sheets. Raman-active phonons of both the tetragonal and monoclinic phases and their pressure dependences were also determined. Tentative assignments of the Raman modes of the tetragonal phase were discussed in the light of lattice dynamics calculations. A possible irreversible second phase transition to a highly disordered or amorphous state is detected in Raman scattering measurements above 21 GPa.

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

    NASA Astrophysics Data System (ADS)

    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

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

    NASA Astrophysics Data System (ADS)

    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

  20. High Pressure Dielectric Studies of a Substance with the Smectic A1 Phase

    NASA Astrophysics Data System (ADS)

    Urban, Stanisław; Würflinger, Albert

    1999-09-01

    The results of dielectric studies of 5-n-hexyl-2-(4'-isothiocyanato)-l,3-dioxane (6DBT) in the smectic A, phase at pressures up to 150 MPa and temperatures up to 340 K are presented. The low frequen-cy relaxation time τ|| (p, T) yields the activation volume Δ# V|| = RT(∂|| In τ||/p)T and activation enthalpy Δ# H|| = R(∂In τ||/∂T-1)p. The calculated values of these parameters are compared with those ob-tained recently for n-octyl-cyanobiphenyl (8CB) forming the smectic Ad phase. In the case of 6DBT both these quantities are practically constant, whereas those for 8CB decrease, when going away from the phase transitions isotropic -smectic A1 (6DBT) or nematic -smectic Ad (8CB). These differences support our earlier conclusion that increase of pressure leads to a breaking of the antiparallel associa-tions of cyanobiphenyl molecules in the smectic as well as in the nematic phases.

  1. Ice phases under ambient and high pressure: Insights from density functional theory

    NASA Astrophysics Data System (ADS)

    Fang, Yuan; Xiao, Bing; Tao, Jianmin; Sun, Jianwei; Perdew, John P.

    2013-06-01

    Water is common and plays a crucial role in biological, chemical, and physical processes, but its crystalline or ice state has a complicated structure. In this work, we study the lattice mismatch challenge for ice nucleation on silver iodide, the sublimation energy for different ice phases, and the structural phase-transition pressures of ice, with various density functionals. Our calculations show that the recently developed meta-generalized gradient approximation made simple (MGGA_MS) yields a lattice mismatch (3%) of hexagonal ice (ice Ih) with β-AgI in good agreement with experiment (2%), significantly better than the Perdew-Burke-Ernzerhof (PBE) GGA mismatch (6%). MGGA_MS is a computationally efficient semilocal functional that incorporates intermediate-range van der Waals (vdW) interaction, which, overall, performs well for ice and may be expected to improve upon PBE for liquid water. While MGGA_MS predicts the most realistic volumes and volume changes in the phase transitions of ice Ih to trigonal ice (ice II) and tetragonal ice (ice VIII), a more accurate description of some other properties of the higher-pressure phases (ice II and ice VIII) is provided by some functionals that include long-range vdW corrections (e.g., revised Tao-Perdew-Staroverov-Scuseria+vdW for sublimation energy and optB88-vdW for transition pressure).

  2. Theoretical prediction of high pressure phase transition in ScC and YC: Ab initio calculations

    NASA Astrophysics Data System (ADS)

    Sahoo, B. D.; Joshi, K. D.; Gupta, Satish C.

    2013-08-01

    The structural stability of ScC and YC has been analyzed under hydrostatic compression employing the first-principles calculations using the plane-wave pseudopotential method. The comparison of theoretically calculated enthalpies of rocksalt type (B1), primitive orthorhombic (Pmmn), and CsCl type (B2) structures as a function of pressure suggests that the B1 structure transforms to Pmmn phase instead of transforming to B2 phase that predicted by Soni et al. [J. Phys. Chem. Solids 72, 810 (2011)]. The pressure for B1 to Pmmn transition predicted for ScC and YC are ˜80 GPa and ˜30 GPa, respectively. To further substantiate the outcomes of our static lattice calculations, we have performed lattice dynamic calculations also. Our lattice dynamic calculations correctly demonstrate that the B1 phase is dynamically stable structure at ambient condition. Further, for both the carbides, we find that the Pmmn structure becomes dynamically stable around the transition pressure whereas the B2 structure remains unstable, supporting the B1 to Pmmn phase transition predicted by our static lattice calculations.

  3. Monte Carlo simulations of high-pressure phase equilibria of CO2-H2O mixtures.

    PubMed

    Liu, Yang; Panagiotopoulos, Athanassios Z; Debenedetti, Pablo G

    2011-05-26

    Histogram-reweighting grand canonical Monte Carlo simulations were used to obtain the phase behavior of CO(2)-H(2)O mixtures over a broad temperature and pressure range (50 °C ≤ T ≤ 350 °C, 0 ≤ P ≤ 1000 bar). We performed a comprehensive test of several existing water (SPC, TIP4P, TIP4P2005, and exponential-6) and carbon dioxide (EPM2, TraPPE, and exponential-6) models using conventional Lorentz-Berthelot combining rules for the unlike-pair parameters. None of the models we studied reproduce adequately experimental data over the entire temperature and pressure range, but critical assessments were made on the range of T and P where particular model pairs perform better. Away from the critical region (T ≤ 250 °C), the exponential-6 model combination yields the best predictions for the CO(2)-rich phase, whereas the TraPPE/TIP4P2005 model combination provides the most accurate coexistence composition and pressure for the H(2)O-rich phase. Near the critical region (250 °C < T ≤ 350 °C), the critical points are not accurately estimated by any of the models studied, but the exponential-6 models are able to qualitatively capture the critical loci and the shape of the phase envelopes. Local improvements can be achieved at specific temperatures by introducing modification factors to the Lorentz-Berthelot combining rules, but the modified combining rule is still not able to achieve global improvements over the entire temperature and pressure range. Our work points to the challenge and importance of improving current atomistic models so as to accurately predict the phase behavior of this important binary mixture.

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

    SciTech Connect

    Thomas, Sarah; Uhoya, Walter; Tsoi, Georgiy; Wenger, Lowell E; Vohra, Yogesh; Chesnut, Gary Neal; Weir, S. T.; Tulk, Christopher A; Moreira Dos Santos, Antonio F

    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.

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

    PubMed

    Thomas, Sarah A; Uhoya, Walter O; Tsoi, Georgiy M; Wenger, Lowell E; Vohra, Yogesh K; Chesnut, Gary N; Weir, Samuel T; Tulk, Christopher A; dos Santos, Antonio M

    2012-05-30

    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 Néel 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.

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

    NASA Astrophysics Data System (ADS)

    Thomas, Sarah A.; Uhoya, Walter O.; Tsoi, Georgiy M.; Wenger, Lowell E.; Vohra, Yogesh K.; Chesnut, Gary N.; Weir, Samuel T.; Tulk, Christopher A.; dos Santos, Antonio M.

    2012-05-01

    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 Néel 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.

  7. Some aspects of two-phase flow, heat transfer and dynamic instabilities in medium and high pressure steam generators

    NASA Astrophysics Data System (ADS)

    Unal, H. C.

    1981-03-01

    Experimental data for void fraction, incipient point of boiling, initial point of net vapor generation, bubble dynamics, dryout, two-phase flow pressure drop and density-wave oscillations were obtained in long, sodium heated steam generator tubes of different geometries for a wide range of operating conditions and at medium and high pressures. These data and data from literature taken in sodium and electrically heated steam generator tubes were correlated. Aspects of two-phase flow, heat transfer and density-wave oscillations in these steam generators disclosed include the distribution factor in small- and medium-size diameter steam generator tubes, the characteristic of the transitions at the incipient point of boiling and initial point of net vapor generation, bubble growth during subcooled nucleate flow boiling, the importance of the equivalent length for dryout in non-uniformly heated steam generator tubes and the mechanisms of density-wave oscillations in once-through steam generator tubes.

  8. High-pressure superconducting phase diagram of 6Li: Isotope effects in dense lithium

    PubMed Central

    Schaeffer, Anne Marie; Temple, Scott R.; Bishop, Jasmine K.; Deemyad, Shanti

    2015-01-01

    We measured the superconducting transition temperature of 6Li between 16 and 26 GPa, and report the lightest system to exhibit superconductivity to date. The superconducting phase diagram of 6Li is compared with that of 7Li through simultaneous measurement in a diamond anvil cell (DAC). Below 21 GPa, Li exhibits a direct (the superconducting coefficient, α, Tc∝M−α, is positive), but unusually large isotope effect, whereas between 21 and 26 GPa, lithium shows an inverse superconducting isotope effect. The unusual dependence of the superconducting phase diagram of lithium on its atomic mass opens up the question of whether the lattice quantum dynamic effects dominate the low-temperature properties of dense lithium. PMID:25538300

  9. First principles simulation of a superionic phase of hydrogen fluoride (HF) at high pressures and temperatures

    SciTech Connect

    Goldman, N; Fried, L E

    2006-04-10

    The authors have conducted Ab initio molecular dynamics simulations of hydrogen fluoride (HF) at pressures of 5-66 GPa along the 900 K isotherm. They predict a superionic phase at 33 GPa, where the fluorine atoms are fixed in a bcc lattice while the hydrogen atoms diffuse rapidly with a diffusion constant of between 2 x 10{sup -5} and 5 x 10{sup -5} cm{sup 2}/s. They find that a transformation from asymmetric to symmetric hydrogen bonding occurs in HF at 66 GPa and 900 K. With superionic HF they have discovered a model system where symmetric hydrogen bonding occurs at experimentally achievable conditions. Given previous results on superionic H{sub 2}O[1,2,3] and NH{sub 3}[1], they conclude that high P,T superionic phases of electronegative element hydrides could be common.

  10. High-pressure superconducting phase diagram of 6Li: isotope effects in dense lithium.

    PubMed

    Schaeffer, Anne Marie; Temple, Scott R; Bishop, Jasmine K; Deemyad, Shanti

    2015-01-01

    We measured the superconducting transition temperature of (6)Li between 16 and 26 GPa, and report the lightest system to exhibit superconductivity to date. The superconducting phase diagram of (6)Li is compared with that of (7)Li through simultaneous measurement in a diamond anvil cell (DAC). Below 21 GPa, Li exhibits a direct (the superconducting coefficient, α, T(c) proportional M(-α), is positive), but unusually large isotope effect, whereas between 21 and 26 GPa, lithium shows an inverse superconducting isotope effect. The unusual dependence of the superconducting phase diagram of lithium on its atomic mass opens up the question of whether the lattice quantum dynamic effects dominate the low-temperature properties of dense lithium.

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

    SciTech Connect

    Sahoo, B. D. Joshi, K. D. Gupta, Satish C.

    2014-04-24

    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.

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

    PubMed

    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. PMID:24249919

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

    PubMed

    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.

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

    PubMed

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  18. Phase relations in Fe-Ni-C system at high pressures and temperatures

    SciTech Connect

    Narygina, O; Dubrovinsky, L S; Miyajima, N; McCammon, C A; Kantor, I Yu; Mezouar, M; Prakapenka, V B; Dubrovinskaia, N A; Dmitriev, V

    2012-10-23

    We performed comparative study of phase relations in Fe1-x Nix (0.10 ≤ x ≤ 0.22 atomic fraction) and Fe0.90Ni0.10-x Cx (0.1 ≤ x ≤ 0.5 atomic fraction) systems at pressures to 45 GPa and temperatures to 2,600 K using laser-heated diamond anvil cell and large-volume press (LVP) techniques. We show that laser heating of Fe,Ni alloys in DAC even to relatively low temperatures can lead to the contamination of the sample with the carbon coming from diamond anvils, which results in the decomposition of the alloy into iron- and nickel-rich phases. Based on the results of LVP experiments with Fe-Ni-C system (at pressures up to 20 GPa and temperatures to 2,300 K) we demonstrate decrease of carbon solubility in Fe,Ni alloy with pressure.

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

    PubMed Central

    Bouibes, A.; 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, 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. PMID:26202342

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

    SciTech Connect

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

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

    PubMed

    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

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

    PubMed

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  5. New high-pressure phase of Fe3S predicted from first-principles calculation

    NASA Astrophysics Data System (ADS)

    Ishikawa, T.; Tsuchiya, T.

    2010-12-01

    It has long been recognized that the Earth's outer core must contain a significant amount of light elements, candidates for which have included hydrogen, carbon, silicon, sulfur and oxygen. High-P,T experiments (Jephcoat and Olson, 1987; Mao et al., 1998; Fiquet et al., 2001;Uchida et al., 2001) extended this argument to the inner core on the basis of the equation of state analysis of the hexagonal-closed-pack (hcp) form of pure iron, which concluded that it still has 4-5% excess density compared to the inner core values, although significant extrapolations were usually applied. At present, one of the most popular light-element candidates is sulfur. Therefore, it is crucial to determine the melting behavior of the Fe-FeS binary under core conditions, before models of core formation can be developed. The Fe-FeS binary was known to form a eutectic at low pressures (Usselman, 1975). Sherman (1995), however, suggested the stabilization of an intermediate iron sulfide compound Fe3S with AuCu3 form theoretically, and then Fei et al. (1997) found in the high-P,T experiments that Fe3S2 forms over 14 GPa, and Fe3S and Fe2S further form over 21 GPa (Fei et al., 2000). Fe3S, which is the most iron-rich sulfide compound known to exist, has a tetragonal cell isostructural with the Fe3P structure (space group No.82, Z = 8) and no phase transition has so far been identified up to 80 GPa (Seagle et al., 2006) and even at over 200 GPa (Kuwayama private comm.). These are supportive of an ab initio investigation (Martin et al., 2004), which found that the Fe3P structure is the most stable among fcc, LaF3, YF3 and Fe3P postulations. In this study, we explored higher-pressure phases of Fe3S using first-principles calculations. Comparing enthalpies among candidate structures, we found a new structure which is more stable than the Fe3P structure at the inner core pressures. In our presentation, we will make a detailed report with respect to the new stable structure and discuss phase

  6. Laser-driven formation of a high-pressure phase in amorphous silica

    SciTech Connect

    Salleo, Alberto; Taylor, Seth T.; Martin, Michael C.; Panero, Wendy R.; Jeanloz, Raymond; Genin, Francois Y.; Sands, Timothy

    2002-05-31

    A combination of electron diffraction and infrared reflectance measurements shows that synthetic silica transforms partially into stishovite under high-intensity (GW/cm2) laser irradiation, probably by the formation of a dense ionized plasma above the silica surface. During the transformation the silicon coordination changes from four-fold to six-fold and the silicon-oxygen bond changes from mostly covalent to mostly ionic, such that optical properties of the transformed material differ significantly from those of the original glass. This phase transformation offers one suitable mechanism by which laser-induced damage grows catastrophically once initiated, thereby dramatically shortening the service lifetime of optics used for high-power photonics applications such as inertial confinement fusion.

  7. High-pressure high-temperature phase diagram of gadolinium studied using a boron-doped heater anvil

    NASA Astrophysics Data System (ADS)

    Montgomery, J. M.; Samudrala, G. K.; Velisavljevic, N.; Vohra, Y. K.

    2016-04-01

    A boron-doped designer heater anvil is used in conjunction with powder x-ray diffraction to collect structural information on a sample of quasi-hydrostatically loaded gadolinium metal up to pressures above 8 GPa and 600 K. The heater anvil consists of a natural diamond anvil that has been surface modified with a homoepitaxially grown chemical-vapor-deposited layer of conducting boron-doped diamond, and is used as a DC heating element. Internally insulating both diamond anvils with sapphire support seats allows for heating and cooling of the high-pressure area on the order of a few tens of seconds. This device is then used to scan the phase diagram of the sample by oscillating the temperature while continuously increasing the externally applied pressure and collecting in situ time-resolved powder diffraction images. In the pressure-temperature range covered in this experiment, the gadolinium sample is observed in its hcp, αSm, and dhcp phases. Under this temperature cycling, the hcp → αSm transition proceeds in discontinuous steps at points along the expected phase boundary. From these measurements (representing only one hour of synchrotron x-ray collection time), a single-experiment equation of state and phase diagram of each phase of gadolinium is presented for the range of 0-10 GPa and 300-650 K.

  8. Low-pressure clino- to high-pressure clino-enstatite phase transition: a phonon related mechanism

    NASA Astrophysics Data System (ADS)

    Yu, Y.; Wentzcovitch, R.

    2008-12-01

    We have investigated by first principles the compressional behavior of low-pressure (LP) and high-pressure (HP) MgSiO3 clinoenstatite. We have carefully examined cell shapes, chain angles, and polyhedral volume responses, such as angle variances and quasi-elongations, under pressure at room temperature. We have observed opposite behavior of the tetrahedra in the S-rotated and O-rotated chains with pressure in the LP phase, with a slight increase (decrease) in angle variance and quasi-elongation in the former (latter). Inspection of zone center modes of both phases under pressure reveals a transition path that converts the S- rotated chain in the LP phase into the O-rotated chain in the HP phase. This conversion is related to a slight softening of an Ag "metastable" Raman mode under pressure. The thermodynamics of the transformation was also investigated. As in other polymorphic transitions in silicates, phase boundaries determined by the GGA and LDA functionals bracket experimentally measured boundaries with the GGA (LDA) overestimating (underestimating) the same trend that the transition pressure. The calculated Clapeyron slopes are similar and in close agreement with the experimentally determined values. Research supported by NSF/EAR 0635990 and NSF/ITR 0428774 (VLab). Computations were performed at the Minnesota Supercomputing Institute.

  9. Seismic signature of ultra-high pressure hydrous phases in subduction zones and constrains on water recycling

    NASA Astrophysics Data System (ADS)

    Rosa, A. D.; Sanchez-Valle, C.

    2012-12-01

    Seismic anomalies in deep slabs including low velocity zones and seismic anisotropies have often been attributed to the presence of hydrated regions. Superhydrous phase B and phase D which can respectively contain up to 5.8 wt.% and 10 wt.% of water are considered as important water carriers in cold slabs. Phase equilibrium studies have also shown that these phases can represent up to 50 vol.% in water saturated peridotites [1]. Recent Brillouin scattering experiments performed at ambient conditions have revealed the potential for both phases to be responsible for the observed negative velocity anomalies [2]. In addition, due to their layered structure both phases may easily align in a stress field and therefore significantly contribute to observed seismic anisotropies. The detailed knowledge of their seismic properties at high pressure is therefore essential to infer the hydration state of deep subducted slabs. Here, we report the single-crystal elastic properties of superhydrous phase B (chemical composition Mg10.4Si3.1H2.7O18) using Brillouin scattering in the diamond anvil cell. The results on the elasticity studies are combined with previous plasticity studies on phase D [3] and most plausible slip systems of superhydrous B to evaluate the velocity contrast between hydrous and anhydrous peridotites and the contribution of these phases to seismic anisotropy in deep subducted slabs. The results will be discussed in the light of seismic observations to draw a better picture of water recycling via subduction beyond 410 km depth. [1] Iwamori, H. (2004), Earth Planet. Sc. Lett. 227, 57-71. [2] Rosa, A.D., C. Sanchez-Valle and S. Ghosh (2012) Geophys. Res. Lett., 39, L06304. [3] Rosa A.D., et al. (2011) Abstract DI44A-03 Fall AGU Meeting 2011.

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

    SciTech Connect

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

    2011-01-01

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

  11. Evidence for plasma phase transition in high pressure hydrogen from ab-initio simulations

    SciTech Connect

    Morales, M; Pierleoni, C; Schwegler, E; Ceperley, D

    2010-02-08

    We have performed a detailed study of molecular dissociation in liquid hydrogen using both Born-Oppenheimer molecular dynamics with Density Functional Theory and Coupled Electron-Ion Monte Carlo simulations. We observe a range of densities where (dP/d{rho}){sub T} = 0 that coincides with sharp discontinuities in the electronic conductivity, which is clear evidence of the plasma phase transition for temperatures 600K {le} T {le} 1500K. Both levels of theory exhibit the transition, although Quantum Monte Carlo predicts higher transition pressures. Based on the temperature dependence of the discontinuity in the electronic conductivity, we estimate the critical point of the transition at temperatures slightly below 2000 K. We examine the influence of proton zero point motion by using Path Integral Molecular Dynamics with Density Functional Theory; the main effect is to shift the transition to lower pressures. Furthermore, we calculate the melting curve of molecular hydrogen up to pressures of 200 GPa, finding a reentrant melting line in good agreement with previous calculations. The melting line crosses the metalization line at 700 K and 220 GPa using density functional energetics and at 550 K and 290 GPa using Quantum Monte Carlo energetics.

  12. Synthesis, structural characterization and high pressure phase transitions of monolithium hydronium sulfate

    NASA Astrophysics Data System (ADS)

    Banerjee, Debasis; Plonka, Anna M.; Kim, Sun Jin; Xu, Wenqian; Parise, John B.

    2013-01-01

    A three dimensional lithium hydronium sulfate LiSO4·H3O [1], [space group Pna21a=8.7785(12) Å, b=9.1297(12) Å, c=5.2799(7) Å, V=423.16(10) Å3] was synthesized via solvothermal methods using 1,5-naphthalenedisulfonic acid (1,5-NSA) as the source of sulfate ions. The structure of [1], determined by single crystal X-ray diffraction techniques, consists of corner sharing LiO4 and SO4 tetrahedra, forming an anionic 3-D open framework that is charge balanced by hydronium ions positioned within channels running along [001] and forming strong H-bonding with the framework oxygen atoms. Compound [1] undergoes two reversible phase transitions, involving reorientation of SO42- ions at pressures of approximately 2.5 and 5 GPa at room temperature, as evident from characteristic discontinuous frequency drops in the ν1 mode of the Raman spectra. Additionally, compound [1] forms dense β-lithium sulfate at 300 °C, as evident from temperature dependent powder XRD and combined reversible TGA-DSC experiments.

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

    PubMed

    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.

  14. High pressure synthesis of a new phase of YbAg2: Structure, valence of Yb and properties

    DOE PAGES

    Tsvyashchenko, A. V.; Menushenkov, A. P.; Sidorov, V. A.; Petrova, A. E.; Fomicheva, L. N.; Chernysheva, O. V.; Lebed, Yu. B.; Axenov, S. N.; Bud’ko, S. L.; Sun, Liling; et al

    2015-08-05

    The new phase of YbAg2 was obtained using high-pressure and high-temperature reaction. YbAg2 crystallizes in the MgZn2 structure (the space group P63/mmc space group, No 194) with a = 5.68153(3) Å and c = 9.31995(7) Å and the unit cell volume V = 260.54(3) Å3. The XANES analysis showed that the valence state of Yb is +2.8. The low-temperature dependences of the electrical resistivity and magnetic susceptibility can be adequately described by a T2 term that supports the Fermi-liquid picture. Furthermore, the Kadowaki–Woods relation gives a low value of the degeneracy (N = 2).

  15. High pressure synthesis of a new phase of YbAg2: Structure, valence of Yb and properties

    SciTech Connect

    Tsvyashchenko, A. V.; Menushenkov, A. P.; Sidorov, V. A.; Petrova, A. E.; Fomicheva, L. N.; Chernysheva, O. V.; Lebed, Yu. B.; Axenov, S. N.; Bud’ko, S. L.; Sun, Liling; Zhao, Zhongxian

    2015-08-05

    The new phase of YbAg2 was obtained using high-pressure and high-temperature reaction. YbAg2 crystallizes in the MgZn2 structure (the space group P63/mmc space group, No 194) with a = 5.68153(3) Å and c = 9.31995(7) Å and the unit cell volume V = 260.54(3) Å3. The XANES analysis showed that the valence state of Yb is +2.8. The low-temperature dependences of the electrical resistivity and magnetic susceptibility can be adequately described by a T2 term that supports the Fermi-liquid picture. Furthermore, the Kadowaki–Woods relation gives a low value of the degeneracy (N = 2).

  16. Connecting the Water Phase Diagram to the Metastable Domain: High-Pressure Studies in the Supercooled Regime.

    PubMed

    Fanetti, Samuele; Pagliai, Marco; Citroni, Margherita; Lapini, Andrea; Scandolo, Sandro; Righini, Roberto; Bini, Roberto

    2014-11-01

    Pressure is extremely efficient to tune intermolecular interactions, allowing the study of the mechanisms regulating, at the molecular level, the structure and dynamics of condensed phases. Among the simplest molecules, water represents in many respects a mystery despite its primary role in ruling most of the biological, physical, and chemical processes occurring in nature. Here we report a careful characterization of the dynamic regime change associated with low-density and high-density forms of liquid water by measuring the line shape of the OD stretching mode of HOD in liquid water along different isotherms as a function of pressure. Remarkably, the high-pressure studies have been here extended down to 240 K, well inside the supercooled regime. Supported by molecular dynamics simulations, a correlation among amorphous and crystalline solids and the two different liquid water forms is attempted to provide a unified picture of the metastable and thermodynamic regimes of water. PMID:26278751

  17. High-pressure high-temperature phase diagram of gadolinium studied using a boron-doped heater anvil

    DOE PAGES

    Montgomery, J. M.; Samudrala, G. K.; Velisavljevic, N.; Vohra, Y. K.

    2016-04-07

    A boron-doped designer heater anvil is used in conjunction with powder x-ray diffraction to collect structural information on a sample of quasi-hydrostatically loaded gadolinium metal up to pressures above 8GPa and 600K. The heater anvil consists of a natural diamond anvil that has been surface modified with a homoepitaxially grown chemical-vapor-deposited layer of conducting boron-doped diamond, and is used as a DC heating element. Internally insulating both diamond anvils with sapphire support seats allows for heating and cooling of the high-pressure area on the order of a few tens of seconds. This device is then used to scan the phasemore » diagram of the sample by oscillating the temperature while continuously increasing the externally applied pressure and collecting in situ time-resolved powder diffraction images. In the pressure-temperature range covered in this experiment, the gadolinium sample is observed in its hcp, αSm, and dhcp phases. Under this temperature cycling, the hcp → αSm transition proceeds in discontinuous steps at points along the expected phase boundary. From these measurements (representing only one hour of synchrotron x-ray collection time), a single-experiment equation of state and phase diagram of each phase of gadolinium is presented for the range of 0–10GPa and 300–650K« less

  18. [In situ experimental study of phase transition of calcite by Raman spectroscopy at high temperature and high pressure].

    PubMed

    Liu, Chuan-jiang; Zheng, Hai-fei

    2012-02-01

    The phase transitions of calcite at high temperature and high pressure were investigated by using hydrothermal diamond anvil cell combined with Raman spectroscopy. The result showed that the Raman peak of 155 cm(-1) disappeared, the peak of 1 087 cm(-1) splited into 1083 and 1 090 cm(-1) peaks and the peak of 282 cm(-1) abruptly reduced to 231 cm(-1) at ambient temperature when the system pressure increased to 1 666 and 2 127 MPa respectively, which proved that calcite transformed to calcite-II and calcite-III. In the heating process at the initial pressure of 2 761 MPa and below 171 degrees C, there was no change in Raman characteristic peaks of calcite-III. As the temperature increased to 171 degrees C, the color of calcite crystal became opaque completely and the symmetric stretching vibration peak of 1 087 cm(-1), in-plane bending vibration peak of 713 cm(-1) and lattice vibration peaks of 155 and 282 cm(-1) began to mutate, showing that the calcite-III transformed to a new phase of calcium carbonate at the moment. When the temperature dropped to room temperature, this new phase remained stable all along. It also indicated that the process of phase transformation from calcite to the new phase of calcium carbonate was irreversible. The equation of phase transition between calcite-III and new phase of calcium carbonate can be determined by P(MPa) = 9.09T x (degrees C) +1 880. The slopes of the Raman peak (v1 087) of symmetrical stretching vibration depending on pressure and temperature are dv/dP = 5.1 (cm(-1) x GPa(-1)) and dv/dT = -0.055 3(cm(-1) x degrees C(-1)), respectively. PMID:22512172

  19. High-pressure and high-temperature phase diagram for Fe0.9Ni0.1-H alloy

    NASA Astrophysics Data System (ADS)

    Shibazaki, Yuki; Terasaki, Hidenori; Ohtani, Eiji; Tateyama, Ryuji; Nishida, Keisuke; Funakoshi, Ken-ichi; Higo, Yuji

    2014-03-01

    Planetary cores are considered to consist of an iron-nickel (Fe-Ni) alloy and light elements and hydrogen is one of plausible light elements in the core. Here we have performed in situ X-ray diffraction experiments on an Fe0.9Ni0.1-H system up to 15.1 GPa and 1673 K, and investigated the effect of Ni on phase relations of FeHx under high pressure and high temperature. The experimental system in the present work was oversaturated with hydrogen. We found a face-center-cubic (fcc) phase (with hydrogen concentration up to x∼1) and a body-center-cubic (bcc) phase (x < 0.1) as stable phases. The partial melting was observed below 6 GPa. We could not observe a double-hexagonal-close-packed (dhcp) phase because of limitations in pressure and temperature conditions. The stability field of each phase of Fe0.9Ni0.1Hx was almost same as that of FeHx. The solidus of Fe0.9Ni0.1Hx was 500-700 K lower than the melting curve of Fe and its liquidus was 400-600 K lower than that of Fe in the pressure range of this study. Both the solidus and liquidus of Fe0.9Ni0.1Hx were depressed at around 3.5 GPa, as was the solidus of FeHx. The hydrogen contents in fcc-Fe0.9Ni0.1Hx just below solidus were slightly lower than those of fcc-FeHx, which suggests that nickel is likely to prevent dissolution of hydrogen into iron. Due to the lower hydrogen solubilities in Fe0.9Ni0.1 compared to Fe, the solidus of Fe0.9Ni0.1Hx is about 100-150 K higher than that of FeHx.

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

    NASA Astrophysics Data System (ADS)

    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.

  1. Phase diagram of the itinerant helical magnet MnSi at high pressures and strong magnetic fields

    NASA Astrophysics Data System (ADS)

    Stishov, Sergei

    We performed a series of resistivity, heat capacity and ultrasound speed measurements of a MnSi single crystal at high pressures and strong magnetic fields [1-3]. Two notable features of the phase transition in MnSi that disappear on pressure increasin are a sharp peak marking the first order phase transition and a shallow maximum, situated slightly above the critical temperature and pointing to the domain of prominent helical fluctuations. The longitudinal and transverse ultrasound speeds and attenuation were measured in a MnSi single crystal in the temperature range of 2-40 K and magnetic fields to 7 Tesla. The magnetic phase transition in MnSi in zero magnetic field is signified by a quasi-discontinuity in the c11 elastic constant, which almost vanishes at the skyrmion - paramagnetic transition at high magnetic fields. The powerful fluctuations at the minima of c11 make the mentioned crossing point of the minima and the phase transition lines similar to a critical end point, where a second order phase transition meets a first order one.

  2. Structures of two intermediate phases between the B1 and B2 phases of PbS under high pressure

    SciTech Connect

    Li, Yanchun E-mail: liuj@ihep.ac.cn; Lin, Chuanlong; Li, Xiaodong; Liu, Jing E-mail: liuj@ihep.ac.cn; Xu, Jian; Li, Gong

    2014-12-15

    The structural transitions of PbS were investigated at pressures up to 50 GPa using synchrotron powder and single crystal X-ray diffraction (XRD) methods in diamond anvil cells. We found two intermediate phases between the B1 phase under atmospheric pressure and the B2 phase at 21.1 GPa, which is different to previous reports. The structures of these two intermediate phases were indexed as B27 and B33, respectively. Their structural parameters were investigated using density functional theory (DFT) calculations. Our results provide a new insight into understanding the transition pathway between the B1 and B2 phases in PbS.

  3. Strong bioresorbable Ca phosphate-PLA nanocomposites with uniform phase distribution by attrition milling and high pressure consolidation.

    PubMed

    Rakovsky, Artoum; Gotman, Irena; Rabkin, Eugen; Gutmanas, Elazar Y

    2013-02-01

    Highly dense bioresorbable Ca-deficient HA-PLA (CDHA-PLA) and β-TCP-PLA nanocomposite materials with high (up to 80 vol%) contents of the calcium phosphate (CaP) phase and homogeneous phase distribution were prepared via attrition milling followed by high pressure consolidation at ambient temperature. The microstructure and mechanical properties of the materials obtained were studied as a function of milling time and PLA amount. Attrition milling resulted in disintegration of β-TCP powder agglomerates down to 50-150 nm, disintegration of CDHA agglomerates and refinement of 15 × 150 nm(2) CDHA nanoparticles to a size of 8 × 20 nm(2), and in a uniform distribution of the polymer component. Very high compressive strengths up to 400 MPa and high bending strengths up to 70 MPa were obtained. For both β-TCP and CDHA-based nanocomposites, the strength characteristics increased with milling time and decreased with increasing PLA content. For CDHA-based nanocomposites, attrition milling resulted in decrease of ductility while for β-TCP-40 vol% PLA the ductility increased. The observed behavior may be a result of formation of homogeneous, relatively thick (tens of nanometers), ductile PLA layers in β-TCP-PLA nanocomposites, but very thin (several nanometers) PLA layers in attrition milled CDHA-PLA nanocomposites. Degradation of compressive and bending strength in aqueous solutions was observed for all the studied CaP-PLA nanocomposites.

  4. High-Efficiency, Ultra-High Pressure Electrolysis With Direct Linkage to PV Arrays - Phase II SBIR Final Report

    SciTech Connect

    Martin A Shimko

    2009-08-08

    In this Phase II SBIR, Avalence LLC met all proposed objectives. Because the original Phase III partner pulled out of the project, several alternative sites/partners were used to achieve the goals. The on-site operation and PV measurements were performed on a smaller unit at General Motors proving grounds in Milford, MI. The actual equipment targeted for AC Transit will be delivered to Robins Air Force Base in September of 2009 to support the fueling of a fuel cell powered fork lift and 'Bobcat'. In addition the Transit Agency Site Requirements and Constraints were performed for the Greater New Haven Transit District (GNHTD) for the Hamden, CT Public Works building that will be the site for a similar fueling station to be delivered in the Spring of 2010. The Detailed Design Package was also based on the Design for the GNHTD unit. The work on this project successfuly demonstrated the potential of Avalence's high pressure technology to address the need for renewably produced hydrogen fuel for transportation applications. Several follow-on projects in a numerber of related applications are now underway as a result of this SBIR project.

  5. Timing and conditions of high-pressure metamorphism in the western Grenville Province: Constraints from accessory mineral composition and phase equilibrium modeling

    NASA Astrophysics Data System (ADS)

    Marsh, Jeffrey H.; Culshaw, Nicholas G.

    2014-07-01

    Previous geochronological analyses of high pressure (HP) metamorphic rocks in the western Grenville Province, Ontario, Canada have yielded precise U-Pb zircon ages; however, uncertainty has remained as to whether these ages represent the timing of HP metamorphism or the granulite/amphibolite facies overprint accompanying exhumation to a hot middle orogenic crust. Detailed study of these HP rocks, involving garnet, rutile, and zircon trace element analysis, phase equilibrium modeling, and zircon U-Pb geochronology, has yielded much improved constraints on the timing and conditions of HP metamorphism. Zircon from five of the six HP samples yield anchored discordia upper intercept and 207Pb/206Pb weighted average ages between 1097 and 1085 Ma, and typically have trace element compositions consistent with growth in a garnet-rich, plagioclase-poor eclogite-type assemblage (i.e. no negative Eu anomaly and flat HREE trends). Titanium-in-zircon and Zr-in-rutile thermometry indicates that the range of zircon crystallization temperatures for most samples (643-767 °C) is close to that of rutile inclusions in garnet (668-753 °C) and matrix rutile (690-772 °C). Phase relations in a pseudosection calculated for the sample that best preserves the HP assemblage indicate that: (1) the stability field for the inclusions observed in garnet and kyanite is between 11.5 < P < 14 kbar and 600 < T < 700 °C, and (2) zircon and rutile crystallization temperatures intersect the inferred HP assemblage field (Grt + Cpx + Ky + Rt + Hbl + Qtz) and garnet and kyanite modal isopleths at P > ~ 15 kbar, indicating that the ca. 1090 Ma zircon ages date metamorphism at eclogite facies conditions. Thus, the deep burial of mafic lower crust that resulted in HP metamorphism in the western CGB occurred just prior to the main "Ottawan" phase of continental collision in the western Grenville Province (ca. 1080-1040 Ma).

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

    NASA Astrophysics Data System (ADS)

    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.

  7. Pressure-induced structural phase transition, elastic and thermodynamic properties of ReC under high pressure

    NASA Astrophysics Data System (ADS)

    Lei, Hui-Ru; Zhu, Jun; Hao, Yan-Jun; Zhang, Lin; Zhao, Yu-Xin; Zhan, Guo-Fu

    2015-10-01

    The pressure-induced structural phase transition of rhenium monocarbon (ReC) is investigated via the projector augmented wave (PAW) method with the generalized gradient approximation (GGA). Using the first-principles calculations, the equilibrium structural parameters of ReC in rocksalt (NaCl), cesium chloride (CsCl), zinc blende (ZB), wurtzite (WZ), nickel arsenide (NiAs) and tungsten carbide (WC) types are successfully obtained, and the results are well consistent with other theoretical data. It is firstly noted that WC-ReC translates into CsCl-ReC at 510.50 GPa by analyzing the enthalpy difference versus pressure. From the calculated elastic constants, the aggregate elastic modulus (B, G, E), the Poisson's ratio (σ) and the Debye temperature ΘD of WC-type are also derived. It is observed that all the data of WC-ReC obtained increase monotonically with increasing pressure. Meanwhile, the thermodynamic properties of WC-ReC under high temperature and high pressure are investigated applying nonempirical Debye model in the quasi-harmonic approximation.

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

    NASA Astrophysics Data System (ADS)

    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.

  9. High-pressure structural configuration and phase transition in celsian, BaAl2Si2O8

    NASA Astrophysics Data System (ADS)

    Curetti, Nadia; Benna, Piera; Bruno, Emiliano

    2016-10-01

    In situ high-pressure X-ray diffraction study was performed on celsian (Cls97Or3) from Jakobsberg, Sweden. A single crystal of celsian was loaded in an ETH-type diamond anvil cell, and unit-cell parameters were measured at 20 different pressures up to 6.0 GPa at room T. The evolution of the unit-cell parameters and volume as a function of pressure shows a discontinuity at P ~ 5.7 GPa indicating a displacive first-order phase transition. The P-V data were fitted by a second-order Birch-Murnaghan EoS only up to 2.55 GPa, because at higher pressures a slight change in the compressional behavior of the unit-cell volume is observed, indicating a pre-transition volume softening. The resulting EoS coefficients are V 0 = 1461.4(1) Å3 and K T0 = 88.1(6) GPa. A second crystal of celsian was loaded in the DAC cell, and single-crystal in situ HP X-ray diffraction was performed at P = 0.0001, 2.1, 4.2, 5.5, 5.9, 6.5 and 7.8 GPa. The data collections between 0 and 5.5 GPa show only a- and b-type reflections confirming the I2/c space group. The appearance of c and d-type reflections at 5.9, 6.5 and 7.8 GPa, the analysis of the systematic absence and the structural refinements define the HP phase transition as an I2/c-P21/c transition. The most significant changes with compression in celsian are the deformation in the Ba polyhedra and the variation in the T-O-T angles.

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

    NASA Astrophysics Data System (ADS)

    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.

  11. CH3OH in High-Pressure Phases of H2O: Implications for Ice-Rich Planets

    NASA Astrophysics Data System (ADS)

    Aarestad, B.; Frank, M. R.; Scott, H. P.; Maglio, S.; Prakapenka, V.

    2007-12-01

    A significant body of research exists on the structure, lattice parameters, and density of high-pressure ice polymorphs, namely Ice VI and Ice VII, as these ices may make up a considerable part of the interior of large icy satellites and select extra solar planets; though most research thus far has been constrained to the pure H2O system. Salty subsurface oceans are also believed to exist within some of these icy bodies which may have prolonged interaction with the Ice VII phase present, incorporating foreign ions or molecules into the lattice of high-pressure ices. Recent research concerning the effects that charged ions have on Ice VII has shown that the presence of these ions notably affects the structure, increasing the Ice VII molar density at any given pressure relative to pure Ice VII (Frank et al., 2006, PEPI, 155, 152-162). This study focused on the incorporation of CH3OH into Ice VII to determine if the change in density was predominantly a result of charge-induced partial ordering of the hydrogen in Ice VII (as outlined in Frank et al., 2006) or if it was controlled solely by the addition of large foreign molecules into the lattice structure. Solutions of 1.60, 5.00 and 10.0 mol% CH3OH in H2O were loaded into a diamond anvil cell. The experiments were performed at GSECARS 13-BM-D at the Advanced Photon Source at Argonne National Laboratory. The unit cell parameters were measured using monochromatic X-ray radiation, 0.3344 Å, and a MAR 345 online imaging system. Powder diffraction patterns were collected in ~1 GPa increments up to ~31, ~48, and ~35 GPa, respectively. The volume-pressure relations (at 300 K) were used to determine an equation of state (EOS) for select compositions in the CH3OH - H2O system. Diffraction data indicate that the unit cell volume of Ice VII formed from a 1.60 mol% CH3OH aqueous solution did not deviate significantly from that of Ice VII formed from pure H2O. Conversely, the volumes of Ice VII formed from 5.00 and 10.0 mol

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

    PubMed

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

    2009-01-21

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

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

    PubMed

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

    2009-01-21

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

  14. Synchrotron-based x-ray-diffraction study of the intermediate-high-pressure phase in the alloy In0.25Sn0.75

    NASA Astrophysics Data System (ADS)

    Meenakshi, S.; Vijayakumar, V.; Godwal, B. K.; Sikka, S. K.

    2001-12-01

    In0.25Sn0.75 alloy stabilized in the primitive hexagonal phase at ambient conditions is studied in a diamond anvil cell at high pressures with angle-dispersive x-ray diffraction using the synchrotron radiation at ELETTRA. The ambient primitive hexagonal phase was found to undergo a reversible transformation to a mixture of body-centered-tetragonal and hexagonal-close-packed phases above 11.6 GPa and not to the Cmca structure assigned in Si and Ge. The occurrence of the bct phase shows similarity to the high-pressure behavior of Sn. A transformation mechanism from the ph to hcp phase via the bct structure is also described.

  15. Ammonia-water mixtures at high pressures - Melting curves of ammonia dihydrate and ammonia monohydrate and a revised high-pressure phase diagram for the water-rich region. [in primordial solar system ices

    NASA Technical Reports Server (NTRS)

    Boone, S.; Nicol, M. F.

    1991-01-01

    The phase relations of some mixtures of ammonia and water are investigated to create a phase diagram in pressure-temperature-composition space relevant to the geophysical study of bodies in the outer solar system. The mixtures of NH3(x)H2O(1-x), where x is greater than 0.30 but less than 0.51, are examined at pressures and temperatures ranging from 0-6.5 GPa and 125-400 K, respectively. The ruby luminescence technique monitors the pressure and a diamond-anvil cell compresses the samples, and the phases are identified by means of normal- and polarized-light optical microscopy. The melting curve for NH3H2O(2) is described by the equation T = 176 + 60P - 8.5P squared for the ranges of 0.06-1.4 GPa and 179-243 K. The equation for NH3H2O is T = 194 + 37P - P squared, which represents a minor correction of a previous description by Johnson et al. (1985). Observed phase transitions are consistent with the high-pressure stability limit of NH3H2O(2), and the transition boundary is found to be linear.

  16. High pressure homogenization and two-phased anaerobic digestion for enhanced biogas conversion from municipal waste sludge.

    PubMed

    Wahidunnabi, Abdullahil K; Eskicioglu, Cigdem

    2014-12-01

    This study compared advanced anaerobic digestion combining two-phased anaerobic digestion (2PAD) with high pressure homogenization (HPH) pretreatment to conventional anaerobic digestion of municipal sludge at laboratory scale. The study began with examination of thickened waste activated sludge (TWAS) solubilization due to HPH pretreatment at different pressure (0-12,000 psi) and chemical dose (0.009-0.036 g NaOH/g total solids). Homogenizing pressure was found as the most significant factor (p-value < 0.05) for increasing solubilization of particulate chemical oxygen demand (COD) and biopolymers in TWAS. Based on the preliminary results, a pretreatment with chemical dose of 0.009 g NaOH/g total solids and pressure of 12,000 psi was selected for digester studies. Upon acclimation of anaerobic inocula to pretreatments, a total number of twelve lab-scale digesters were operated under scenarios including single-stage (control), 2PAD, and HPH coupled with 2PAD (HPH + 2PAD) at sludge retention times (SRTs) of 20, 14 and 7 days. Between mesophilic and thermophilic temperatures, mesophilic digestion was found to benefit more from pretreatments. Relative (to control) improvements in methane yield and volatile solids (VS) removals increased noticeably as SRT was shortened from 20 to 14 and 7 days. HPH + 2PAD system was found to achieve the maximum methane production (0.61-1.32 L CH4/Ldigester-d) and VS removals (43-64%). Thermophilic control, 2PAD and HPH + 2PAD systems resulted in significant pathogen removals meeting Class A biosolids requirements according to Organic Matter Recycling Regulations (OMRR) of British Columbia (BC) at 20 d SRT. Energy analysis indicated that all the digestion scenarios attained positive energy balance with 2PAD system operated at 20 d SRT producing the maximum net energy of 4.76 GJ/tonne CODadded.

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

    SciTech Connect

    Budkov, Yu. A.; Vyalov, I. I.; Kolesnikov, A. L.; Georgi, N.; Chuev, G. N.; Kiselev, M. G.

    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.

  18. High pressure synthesis gas fermentation

    SciTech Connect

    Not Available

    1992-01-01

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

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

    SciTech Connect

    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 to transition that

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

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

    PubMed

    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

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

    NASA Astrophysics Data System (ADS)

    Mookherjee, Mainak; Tsuchiya, Jun; Hariharan, Anant

    2016-02-01

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

  3. Determination of the phase boundary of the omega to beta transition in Zr using in situ high-pressure and high-temperature X-ray diffraction

    SciTech Connect

    Ono, Shigeaki; Kikegawa, Takumi

    2015-05-15

    The high-pressure behavior of zirconium has been examined using the synchrotron X-ray diffraction technique to a pressure of 38 GPa and a temperature of 800 K employing a hydrothermal diamond anvil cell technique. The structural transition from the ω to the β phase was observed. This transition has a negative dP/dT gradient, which is in general agreement with those reported in previous studies. The transition boundary was determined to be, P (GPa)=41.2–0.025×T (K). The negative slope of the transition, dP/dT, determined in our study using the diamond anvil cell technique was less than half that estimated by the previous study using a large press apparatus. - Graphical abstract: Experimental results and phase boundary of the ω–β transition in Zr. - Highlights: • X-ray diffraction patterns of zirconium were measured by the synchrotron experiments. • High-pressure experiments were performed by an external-heated diamond anvil cell. • Phase diagram of zirconium was determined at high pressures and high temperatures. • Phase boundary between omega and beta transition has a negative dP/dT slope.

  4. High pressure phase transition and superconductivity in transition metal nitride HfN and ZrN: An ab-initio study

    NASA Astrophysics Data System (ADS)

    Asvini Meenaatci, A. T.; prabha, S. Kanaga; palanichamy, R. Rajeswara; Iyakutti, K.

    2012-06-01

    The high pressure structural investigations of HfN and ZrN have been studies using ab initio calculations. It is predicted that ZrN undergoes a structural phase transition from NaCl to ZB structure at around 90.17GPa whereas there is no phase transition for HfN. However at higher pressure (at 108.67GPa) HfN undergo a phase transition from ZB to WC structure. Apart from this, the ground state properties, elastic constants and superconducting transition temperature are calculated and compared with the available results.

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

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

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

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    Kanno, H; Kajiwara, K; Miyata, K

    2010-05-21

    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 T(H) (homogeneous ice nucleation temperature) and T(m) (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 T(H) 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 P(c2)= approximately 200 MPa and at T(c2)<-100 degrees C (P(c2): pressure of SCP, T(c2): temperature of SCP). The presence of two T(H) peaks for DMSO solutions (R=15, 12, and 10) suggests that phase separation occurs in aqueous DMSO solution (Rhigh pressures and low temperatures (<-90 degrees C). The pressure dependence of the two T(H) 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.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

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

    NASA Astrophysics Data System (ADS)

    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.

  12. Equation of state of a high-pressure phase of Gd3Ga5O12

    SciTech Connect

    Mao, Z. Q.; Dorfman, S. M.; Shieh, S.; Lin, Jung-Fu; Prakapenka, Vitali B.; Meng, Yue; Duffy, T. S.

    2011-02-24

    Gd3 Ga5 O12 (GGG), which crystallizes in the garnet structure at ambient conditions, was observed to transform to a high-pressure phase at 88 GPa after laser heating at 1500 K. This new phase is stable at least up to 180 GPa, and can be preserved on decompression to 50 GPa. This phase is cubic and consistent with a perovskite structure of stoichiometry (Gd0.75Ga0.25)GaO3. The zero-pressure bulk modulus, K0, obtained from fitting to a Birch-Murnaghan equation of state is 373(5) GPa with a fixed pressure derivative K' 0 =4. At 170 GPa, the bulk modulus of perovskite-type GGG is 979(15) GPa, which is comparable to that of diamond at the same pressure [956(21) GPa] and consistent with recently reported shock-compression data for Gd3 Ga5 O12. The new high-pressure phase of Gd3 Ga5 O12 is thus highly incompressible.

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

    SciTech Connect

    Sorb, Y.A. Sornadurai, D.

    2015-05-15

    The PbFX (X = Cl{sup –}or Br{sup –}) 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 (P2{sub 1}/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{sup –}, Br{sup –}or I{sup –}). PbFCl has a larger structural stability range compared to BaFCl and is attributed to the large anisotropic coordination of the Pb{sup 2+} and Cl{sup –}ions.

  14. The particle image velocimetry method in the study of the dynamics of phase transitions induced by high pressures in triolein and oleic acid

    NASA Astrophysics Data System (ADS)

    Tefelski, D. B.; Kulisiewicz, L.; Wierschem, A.; Delgado, A.; Rostocki, A. J.; Siegoczyński, R. M.

    2011-03-01

    Particle image velocimetry (PIV) is an optical measurement method capable of providing visualisation of velocity field of particle flow in fluids. After analysis of data acquired in the form of an image sequence, it is possible to retrieve information about flow parameters as mean values of velocity, vorticity, shear and normal strain. This paper presents the results of high pressure experiments using this method applied to triolein and oleic acid samples in their phase transition region. A high pressure optical chamber, He-Ne laser and light-sheet optics together with a digital camera and image acquisition computer allow us to study the motion of particles in high pressure conditions. The set-up was similar to that presented in Özmutlu et al. [Momentum and energy transfer during phase change of water under high hydrostatic pressure, Innov. Food Sci. Emerg. Technol. 7(3) (2006), pp. 161-168] and Kulisiewicz et al. [Visualization of pressure-shift freezing and thawing of concentrated aqueous sucrose solutions, High Press. Res. 27(2) (2007), pp. 291-297]. The analysis of phase transition dynamics in triolein and oleic acid is an extension to the work presented in Tefelski et al. [The investigation of the dynamics of the phase transformation in triolein and oleic acid under pressure, J. Phys.: Conf. Ser. 121(142004) (2008), pp. 1-6]. Oleic acid is a monounsaturated fatty acid and has a bent rod shape. Triolein is a triglyceride and has a "chair"-like shape. It is the base particle of many vegetable oils, especially olive oil. Triolein consists of three chains of oleic acid bound by a glycerol part. Information obtained by the study of phase transitions dynamics is important for food science and food technology processes which involve high pressure treatment. The PIV method shows differences in the solidification process of both substances in time, the existence of inhomogeneities (layers of different densities in the observed flow) and allows us to calculate the

  15. The antagonistic effect of an inhalation anesthetic and high pressure on the phase diagram of mixed dipalmitoyl-dimyristoylphosphatidylcholine bilayers.

    PubMed Central

    Trudell, J R; Payan, D G; Chin, J H; Cohen, E N

    1975-01-01

    Several workers have shown that phase transition-related changes in membrane lipids have a profound effect on membrane-solvated protein function. This phase transition temperature dependence has been explained as resulting from the formation of lateral phase separations within the membrane bilayer. The present study demonstrates that a clinical concentration of an inhalation anesthetic produces changes in both the phase transition temperature of pure lipid bilayers and the lateral phase separation temperature of mixed dipalmitoyl- and dimyristoylphosphatidylcholine bilayers of a magnitude sufficient to influence protein function. It is further shown that pressure is able to antagonize the effect of the anesthetic on these transition temperatures. It is proposed that anesthetic action within nerve membranes may be the result of changes in the lateral phase separation-controlled environment of the membrane-solvated proteins essential to nerve function. PMID:164016

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

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

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

    NASA Astrophysics Data System (ADS)

    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).

  18. Quantum simulation of thermally-driven phase transition and oxygen K-edge x-ray absorption of high-pressure ice.

    PubMed

    Kang, Dongdong; Dai, Jiayu; Sun, Huayang; Hou, Yong; Yuan, Jianmin

    2013-11-20

    The structure and phase transition of high-pressure ice are of long-standing interest and challenge, and there is still a huge gap between theoretical and experimental understanding. The quantum nature of protons such as delocalization, quantum tunneling and zero-point motion is crucial to the comprehension of the properties of high-pressure ice. Here we investigated the temperature-induced phase transition and oxygen K-edge x-ray absorption spectra of ice VII, VIII and X using ab initio path-integral molecular dynamics simulations. The tremendous difference between experiments and the previous theoretical predictions is closed for the phase diagram of ice below 300 K at pressures up to 110 GPa. Proton tunneling assists the proton-ordered ice VIII to transform into proton-disordered ice VII where only thermal activated proton-transfer cannot occur. The oxygen K edge with its shift is sensitive to the order-disorder transition, and therefore can be applied to diagnose the dynamics of ice structures.

  19. Quantum simulation of thermally-driven phase transition and oxygen K-edge x-ray absorption of high-pressure ice

    PubMed Central

    Kang, Dongdong; Dai, Jiayu; Sun, Huayang; Hou, Yong; Yuan, Jianmin

    2013-01-01

    The structure and phase transition of high-pressure ice are of long-standing interest and challenge, and there is still a huge gap between theoretical and experimental understanding. The quantum nature of protons such as delocalization, quantum tunneling and zero-point motion is crucial to the comprehension of the properties of high-pressure ice. Here we investigated the temperature-induced phase transition and oxygen K-edge x-ray absorption spectra of ice VII, VIII and X using ab initio path-integral molecular dynamics simulations. The tremendous difference between experiments and the previous theoretical predictions is closed for the phase diagram of ice below 300 K at pressures up to 110 GPa. Proton tunneling assists the proton-ordered ice VIII to transform into proton-disordered ice VII where only thermal activated proton-transfer cannot occur. The oxygen K edge with its shift is sensitive to the order-disorder transition, and therefore can be applied to diagnose the dynamics of ice structures. PMID:24253589

  20. High-pressure differential thermal analysis (DTA) of the phase behaviors of didodecyl-dimethylammoniumbromide (DDAB) and ditetradecyl-dimethylammoniumbromide (DTAB)

    NASA Astrophysics Data System (ADS)

    Hamann, F.; Reuter, John; Wuerflinger, A.; Godlewska, Malgorzata; Dynarowicz, Patrycja

    1998-01-01

    Dialkyldimethylammonium halides are known for their applications as commercial detergents and for their membrane-mimetic properties. They display both thermotropic and lyotropic liquid crystalline properties. In this work we establish the T(p)-phase diagrams of two representatives, namely didodecyl- and ditetradecyl-ammonium bromides. The transitions between crystal, smectic Ii and smectic I phases were recorded using a high-pressure differential thermal analysis device. For both compounds the stable range of smectic II phase is pressure-limited, resulting in a triple point crystal/smectic II/smectic I. Enthalpy changes at ambient pressure have been determined with the aid of a commercial heat flux differential scanning calorimeter. Volume changes were calculated from the slopes of the transitions lines, employing the Clausius Clapeyron equation.

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

    SciTech Connect

    Kotmool, Komsilp; Bovornratanaraks, Thiti; Chakraborty, Sudip; Ahuja, Rajeev

    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.

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

    SciTech Connect

    Wu, Yan.

    1990-11-01

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  4. High-temperature high-pressure phases of lithium from electron force field (eFF) quantum electron dynamics simulations

    PubMed Central

    Kim, Hyungjun; Su, Julius T.; Goddard, William A.

    2011-01-01

    We recently developed the electron force field (eFF) method for practical nonadiabatic electron dynamics simulations of materials under extreme conditions and showed that it gave an excellent description of the shock thermodynamics of hydrogen from molecules to atoms to plasma, as well as the electron dynamics of the Auger decay in diamondoids following core electron ionization. Here we apply eFF to the shock thermodynamics of lithium metal, where we find two distinct consecutive phase changes that manifest themselves as a kink in the shock Hugoniot, previously observed experimentally, but not explained. Analyzing the atomic distribution functions, we establish that the first phase transition corresponds to (i) an fcc-to-cI16 phase transition that was observed previously in diamond anvil cell experiments at low temperature and (ii) a second phase transition that corresponds to the formation of a new amorphous phase (amor) of lithium that is distinct from normal molten lithium. The amorphous phase has enhanced valence electron-nucleus interactions due to localization of electrons into interstitial locations, along with a random connectivity distribution function. This indicates that eFF can characterize and compute the relative stability of states of matter under extreme conditions (e.g., warm dense matter). PMID:21873210

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

    NASA Astrophysics Data System (ADS)

    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.

  6. High Pressure-Temperature Phase Diagram of 1,1-Diamino-2,2-dinitroethylene (FOX-7).

    PubMed

    Bishop, Matthew M; Velisavljevic, Nenad; Chellappa, Raja; Vohra, Yogesh K

    2015-09-17

    The pressure-temperature (P-T) phase diagram of 1,1-diamino-2,2-dinitroethylene (FOX-7) was determined by in situ synchrotron infrared radiation spectroscopy with the resistively heated diamond anvil cell (DAC) technique. The stability of high-P-T FOX-7 polymorphs is established from ambient pressure up to 10 GPa and temperatures until decomposition. The phase diagram indicates two near isobaric phase boundaries at ∼2 GPa (α → I) and ∼5 GPa (I → II) that persists from 25 °C until the onset of decomposition at ∼300 °C. In addition, the ambient pressure, high-temperature α → β phase transition (∼111 °C) lies along a steep boundary (∼100 °C/GPa) with a α-β-δ triple point at ∼1 GPa and 300 °C. A 0.9 GPa isobaric temperature ramping measurement indicates a limited stability range for the γ-phase between 0.5 and 0.9 GPa and 180 and 260 °C, terminating in a β-γ-δ triple point. With increasing pressure, the δ-phase exhibited a small negative dT/dP slope (up to ∼0.2 GPa) before turning over to a positive 70 °C/GPa slope, at higher pressures. The decomposition boundary (∼55 °C/GPa) was identified through the emergence of spectroscopic signatures of the characteristic decomposition products as well as trapped inclusions within the solid KBr pressure media. PMID:26317366

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

  9. Mass spectrometric elucidation of triacylglycerol content of Brevoortia tyrannus (menhaden) oil using non-aqueous reversed-phase liquid chromatography under ultra high pressure conditions.

    PubMed

    Dugo, Paola; Beccaria, Marco; Fawzy, Nermeen; Donato, Paola; Cacciola, Francesco; Mondello, Luigi

    2012-10-12

    A non-aqueous reversed phase high performance liquid chromatography method was developed, and optimized for triacylglycerol analysis in a Brevoortia tyrannus (menhaden) oil sample. Four columns were serially coupled to tackle such a task, for a total length of 60 cm of shell-packed stationary phase, and operated under ultra high pressure conditions. As detection, positive-ion atmospheric pressure chemical ionization mass spectrometry was used to attain identification of the analyzed sample components. A number of 137 triacylglycerols containing up to 19 fatty acids, with 14-22 carbon atom alkyl chain length and 0-6 double bonds, were positively identified in the complex lipidic sample. This is the first work that reports an extensive characterization of the triacylglycerol fraction of menhaden oil. PMID:22503927

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

    SciTech Connect

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  12. High pressure synthesis gas fermentation

    SciTech Connect

    Not Available

    1991-01-01

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

  13. Kinetics of the wurtzite-to-rock-salt phase transformation in ZnO at high pressure.

    PubMed

    Solozhenko, Vladimir L; Kurakevych, Oleksandr O; Sokolov, Petr S; Baranov, Andrey N

    2011-05-01

    Kinetics of the wurtzite-to-rock-salt transformation in ZnO has been studied in the 5-7 GPa pressure range at temperatures below the activation of diffusion processes. The detailed analysis of non-isothermal experimental data using the general evolution equation describing the kinetics of direct phase transformations in solids allowed us to study the kinetic particularities of both nucleation and growth of the rock-salt phase in parent wurtzite ZnO. The main rate-limiting processes are thermally activated nucleation (E(N) = 383 kJ mol(-1) at 6.9 GPa) and thermally nonactivated (most probably quasi-martensitic) growth (k(G) = 0.833 min(-1) at 6.9 GPa). The high impact of thermal deactivation of nucleation places has been evidenced in the case of slow heating, which indirectly indicates that the rs-ZnO nucleation places are mainly produced by pressure-induced stresses in the parent phase. PMID:21488624

  14. Structural study of the high-pressure antiferroelectric phase of CsH/sub 2/PO/sub 4/

    SciTech Connect

    Schuele, P.J.; Thomas, R.

    1985-01-01

    A three-dimensional neutron diffraction study has been carried out on the pressure-induced antiferroelectric phase of CsH/sub 2/PO/sub 4/. At 100.7/sup 0/K and a hydrostatic pressure of 3.6 kbar, the unit cell parameters are a = 15.625(9), b = 6.254(2), c = 4.886(1) A, ..beta.. = 108.08(3)/sup 0/ and Z = 4. Atomic parameters were determined using full-matrix least-squares methods which yield final agreement indices: R(F/sup 2/) = 0.0715, R/sub w/(F/sup 2/) = 0.0807 and S = 2.13. The structure is nearly consistent with the monoclinic space group P2/sub 1//a but refinement in P2/sub 1/ yields a slightly better fit. The structure is markedly different from those of the paraelectric and ferroelectric phases with large relative displacements (nearly 1 A) of Cs/sup +1/ and PO/sub 4//sup -3/ groups in the x-z plane. Hydrogens bonding in b-chains, which are disordered in the paraelectric phase, show antiferroelectric order.

  15. High resolution reversed phase analysis of recombinant monoclonal antibodies by ultra-high pressure liquid chromatography column coupling.

    PubMed

    Fekete, Szabolcs; Dong, Michael W; Zhang, Taylor; Guillarme, Davy

    2013-09-01

    Monoclonal antibodies (mAbs) represent one of the fastest growing areas of new drug development. However, their analytical characterization is complex and generally requires an array of orthogonal analytical techniques. Reversed phase liquid chromatography is a valuable strategy due to its high resolving power and straightforward compatibility to mass spectrometry. The present study demonstrates that high peak capacity can be attained with intact mAb of ~150 kDa, reduced mAb fragments of ~25-50 kDa and also digested mAb generating numerous peptides of ~0.5-3 kDa. Several long columns packed with fully porous wide-pore sub-2 μm particles were coupled in series to evaluate the effect of column length on peak capacity. By using three columns of 150 mm length, a mobile phase temperature of 80 °C and a gradient time of around 20 min, peak capacities of 117 and 128 were obtained for a commercial intact mAb and its reduced mAb fragments, respectively. On the other hand, when peptide mapping was performed at 50 °C, with a gradient time of 270 min and a column length of 450 mm, a peak capacity of more than 700 was achieved.

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

    NASA Astrophysics Data System (ADS)

    Kim, Moojin; Jin, GuangHai

    2009-04-01

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

  17. The high-pressure phase diagram of Fe(0.94)O - A possible constituent of the earth's core

    NASA Technical Reports Server (NTRS)

    Knittle, Elise; Jeanloz, Raymond

    1991-01-01

    Electrical resistivity measurements to pressures of 83 GPa and temperatures ranging from 300 K to 4300 K confirm the presence of both crystalline and liquid metallic phases of FeO at pressures above 60-70 GPa and temperatures above 1000 K. By experimentally determinig the melting temperature of FeO to 100 GPa and of a model-core composition at 83 GPa, it is found that the solid-melt equilibria can be described by complete solid solution across the Fe-FeO system at pressures above 70 GPa. The results indicate that oxygen is a viable and likely candidate for the major light alloying element of the earth's liquid outer core. The data suggest that the temperature at the core-mantle boundary is close to 4800 K and that heat lost out of the core accounts for more than 20 percent of the heat flux observed at the surface.

  18. High-pressure Powder X-ray Diffraction Study of Cu5Si and Pressure-driven Isostructural Phase Transition

    SciTech Connect

    Li, C.; Yu, Z.; Liu, H.; Lu, T.

    2012-12-03

    The structural behaviour of Cu5Si under high-pressure (HP) has been studied by angular dispersive X-ray diffraction up to 49.9 GPa. The experimental results suggest that a pressure-induced isostructural phase transition occurs around 13.5 GPa as revealed by a discontinuity in volume as a function of pressure. The lattice parameter decreases with the pressure increasing for both low-pressure (LP) and HP phases of Cu5Si. However, a plot of the lattice parameter vs. pressure shows the existence of a plateau between 11.7 and 15.3 GPa. The bulk moduli, derived from the fitting of Birch–Murnaghan equation of state, are 150(2) GPa and 210(3) GPa for the LP phase and the HP phase of Cu5Si, respectively. A change in the electronic state of the copper is assumed to govern the observed structural phase transition.

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

    SciTech Connect

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

    2014-04-07

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

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

    NASA Technical Reports Server (NTRS)

    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).

  1. Thermodynamic data of the high-pressure phase Mg5Al5Si6O21(OH)7 (Mg-sursassite)

    NASA Astrophysics Data System (ADS)

    Grevel, K.-D.; Navrotsky, A.; Kahl, W. A.; Fasshauer, D. W.; Majzlan, J.

    Calorimetric and P-V-T data for the high-pressure phase Mg5Al5Si6O21(OH)7 (Mg-sursassite) have been obtained. The enthalpy of drop solution of three different samples was measured by high-temperature oxide melt calorimetry in two laboratories (UC Davis, California, and Ruhr University Bochum, Germany) using lead borate (2PbO.B2O3) at T=700∘C as solvent. The resulting values were used to calculate the enthalpy of formation from different thermodynamic datasets; they range from -221.1 to -259.4kJmol-1 (formation from the oxides) respectively -13892.2 to -13927.9kJmol-1 (formation from the elements). The heat capacity of Mg5Al5Si6O21(OH)7 has been measured from T=50 ∘C to T=500 ∘C by differential scanning calorimetry in step-scanning mode. A Berman and Brown (1985)-type four-term equation represents the heat capacity over the entire temperature range to within the experimental uncertainty: CP (Mg-sursassite) =(1571.104 -10560.89×T-0.5-26217890.0 ×T-2+1798861000.0×T-3) J K-1 mol-1 (T in K). The PVT behaviour of Mg-sursassite has been determined under high pressures and high temperatures up to 8GPa and 800∘C using a MAX 80 cubic anvil high-pressure apparatus. The samples were mixed with Vaseline to ensure hydrostatic pressure-transmitting conditions, NaCl served as an internal standard for pressure calibration. By fitting a Birch-Murnaghan EOS to the data, the bulk modulus was determined as 116.0+/-1.3GPa, (K'=4), VT,0=446.49 3 exp[∫(0.33+/-0.05) × 10-4 + (0.65+/-0.85)×10-8T dT], (KT/T)P=-0.011+/- 0.004GPaK-1. The thermodynamic data obtained for Mg-sursassite are consistent with phase equilibrium data reported recently (Fockenberg 1998); the best agreement was obtained with ΔfH0298 (Mg-sursassite)= -13901.33kJmol-1, and S0298 (Mg-sursassite)= 614.61JK-1mol-1.

  2. The nonlinear anomalous lattice elasticity associated with the high-pressure phase transition in spodumene: a high-precision static compression study

    NASA Astrophysics Data System (ADS)

    Ullrich, Angela; Schranz, Wilfried; Miletich, Ronald

    2009-12-01

    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 ~3.2 and ~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- P21/ 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 pressure across the transition. A modified Landau free energy expansion in terms of a one component order parameter has been developed and tested against these experimentally determined data. The Landau solution provides a much better reproduction of the observed anomalies than any equation-of-state fit to data sets truncated below and above P tr, thus giving Landau parameters of K 0 = 138.3(2) GPa, K' = 7.46(5), λ V = 33.6(2) GPa, a = 0.486(3), b = -29.4(6) GPa and c = 551(11) GPa.

  3. Phase relation of C-Mg-Fe-Si-O system under various oxygen fugacity conditions at high pressure and high temperature

    NASA Astrophysics Data System (ADS)

    Takahashi, S.; Ohtani, E.; Terasaki, H.; Ito, Y.; Shibazaki, Y.; Ishii, M.; Funakoshi, K.; Higo, Y.

    2010-12-01

    Many exoplanets have been found recently based on the spectroscopic observation. A carbon-rich circumstellar gas was reported to exist around “beta-Pictoris”, which has an exoplanet (Roberge et al., 2006). In such gas, carbon-enriched planet, “carbon-planet” may be formed. Carbon-bearing phase, such as carbide, carbonate, graphite and diamond are likely to compose the carbon-planet interior. Therefore, it is important to investigate phase relations of carbon-rich systems under high pressure conditions. In this study, C-enriched Mg-Si-Fe-O-C system was investigated at high pressure and temperature in order to understand the internal structure of the carbon-planet. Phase relations were studied based on 2 series of experiments; (I)textural observation and chemical analysis of the recovered sample from 4 GPa and 1873K and (II)in situ X-ray diffraction experiments under high pressure and temperature. For the starting materials, we used several different mineral assemblages, as shown below: (i) MgCO3 + Fe + Si + C, (ii) (Mg1.8,Fe0.2)SiO4 + Fe + SiO2 + C, (iii) (Mg1.8,Fe0.2)SiO4 + Fe + Si + C, (iv) MgO + Fe + SiO2 + C, (v) MgO + Fe + Si + C. Oxygen fugacity (fO2) of the sample vaies dependign on these assembleges due to different O amount in the starting materials. The sample was enclosed in graphite or MgO capsule. MgO capsule enables us to estimate fO2 in the sample based on the FeO content of the capsule contacting with the samples. Chemical analyses of the recovered samples were performed using electron microprobe. In situ X-ray diffraction experiments were conducted at 4 GPa and up to 1873 K at BL04B1 beamline, SPring-8 synchrotron facility. Different mineral assemblages and their compositions were observed in the recovered samples depending on the redox condition of the sample. The compositions of metallic melt phases changes from Fe-C composition (C = 6.9~8.2 wt.%) in oxidizing conditions (ΔIW = -2.4 ~ -1.7) to Fe-Si composition (Si = 18 wt.%) in the more

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

    NASA Astrophysics Data System (ADS)

    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

  5. Elastic behaviour and high-pressure phase transition of the P21/n LiAlGe2O6pyroxene

    NASA Astrophysics Data System (ADS)

    Artac, Andreas; Miletich-Pawliczek, Ronald; Nestola, Fabrizio; Redhammer, Günther J.; Secco, Luciano

    2014-05-01

    In a recent work by Redhammer et al. (2012), investigating a synthetic pyroxene sample with composition LiAlGe2O6, a new space group for the big family of pyroxenes has been surprisingly discovered renewing the interest for Li-bearing pyroxene compounds. Actually, the authors of that work intended to investigate the effect of the Si-Ge substitution on the high-pressure behaviour and possibly on the phase transition with respect to spodumene, LiAlSi2O6, investigated by Arlt and Angel in 2000. Spodumene in fact, not only shows a strong first order phase transition at 3.19 GPa from C2/c to P21/c but the low symmetry C2/c shows the greatest bulk modulus never found in pyroxenes (i.e. 144.2 GPa with the first pressure derivative fixed to 4). Redhammer et al. (2012) discovered that substituting Si for Ge in the spodumene structure the effect is dramatic in terms of symmetry change at room conditions with the Ge-spodumene showing a P21/n space group, first discovery of such symmetry in the big family of pyroxene. In this work we loaded one crystal of LiAlGe2O6 in a diamond-anvil cell and investigated the elastic behaviour and its possible high-pressure phase transition by single-crystal X-ray diffraction. In detail, we measured the unit-cell parameters using a Huber four-circle diffractometer equipped with a point detector up to about 9 GPa. The crystal structure was measured at different pressures loading simultaneously two fragments of the same crystal with a different orientation in the same diamond-anvil cell in order to cover a wider portion of the reciprocal space. The intensity data were measured on a STADI IV four-circle diffractometer equipped with a CCD using a diamond-backing plate cell, which gives better structural results with respect to a beryllium backing plate one (i.e. Periotto et al. 2011). The first important result of our work is that we found at about 5.2 GPa a very strong first-order phase transformation from P21/n to P21/c and this is the first

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    SciTech Connect

    Trabold, T.A.; Kumar, R.

    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

  9. High pressure synthesis gas conversion

    SciTech Connect

    Not Available

    1992-01-01

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

  10. High-pressure microfluidics

    NASA Astrophysics Data System (ADS)

    Hjort, K.

    2015-03-01

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

  11. High pressure melt ejection

    SciTech Connect

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

    1983-01-01

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

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

    NASA Astrophysics Data System (ADS)

    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.

  13. Physicochemical and thermodynamic characterization of the encapsulation of methyl jasmonate by natural and modified cyclodextrins using reversed-phase high-pressure liquid chromatography.

    PubMed

    López-Nicolás, José Manuel; Escorial Camps, Marta; Pérez-Sánchez, Horacio; García-Carmona, Francisco

    2013-11-27

    Although the combinations of methyl jasmonate (MeJA) and cyclodextrins (CDs) have been used by different authors to stimulate the production of several metabolites, no study has been published about the possible formation of MeJA-CD complexes when these two molecules are added together to the reaction medium as elicitors. For this reason and because knowledge of the possible complexation process of MeJA with CD under different physicochemical conditions is essential if these two molecules are to be used in cell cultures, this paper looks at the complexation of MeJA with natural and modified CDs using a reversed-phase high-pressure liquid chromatography (RP-HPLC) system. The interaction of MeJA with β-CD was more efficient than with α- and γ-CDs. However, a modified CD, HP-β-CD, was the most effective of all of the CDs tested. Moreover, MeJA formed complexes with CD with a 1:1 stoichiometry, and the formation constants of these complexes were strongly dependent upon the temperature of the mobile phase used but not the pH. To obtain information about the mechanism of the affinity of MeJA for CD, the thermodynamic parameters ΔG°, ΔH°, and ΔS° were calculated. Finally, molecular modeling studies were carried out to propose which molecular interactions are established in the complexation process.

  14. Analysis of eight free progestogens in eggs by matrix solid-phase dispersion extraction and very high pressure liquid chromatography with tandem mass spectrometry.

    PubMed

    Yang, Yi; Shao, Bing; Zhang, Jing; Wu, Yongning; Ying, Jie

    2008-07-15

    A rapid method to identify and quantify unconjugated progestogens in eggs is presented. Samples were prepared based on matrix solid-phase dispersion (MSPD) using C18 as dispersant, followed by a clean-up step with graphitized carbon black (GCB) solid-phase extraction (SPE) cartridges. The analytes were separated by very high pressure LC on a BEH C18 column for a period of 5 min. Electrospray ionization tandem mass spectrometry (ESI-MS/MS) was operated in the positive time-scheduled multi-reaction monitoring mode. Recovery studies were performed at two fortification levels. Average recoveries of the target compounds varied from 83.8% to 111.2% and relative standard deviations ranged from 10.5% to 23.7%. The limits of detection (LODs) and limits of quantitation (LOQs) were in the range of 0.2-2.0 microg kg(-1) and 0.6-5.0 microg kg(-1), respectively. Investigation of real samples indicated that the range of progesterone in eggs was 9.9-40.0 microg kg(-1).

  15. In vivo biosynthesis of L-(/sup 35/S)Cys-arginine vasopressin, -oxytocin, and -somatostatin: rapid estimation using reversed phase high pressure liquid chromatography. [Rats

    SciTech Connect

    Franco-Bourland, R.E.; Fernstrom, J.D.

    1981-01-01

    L(/sup 35/S)Cys-arginine vasopressin, -oxytocin, and -somatostatin were purified from hypothalami and neurohypophyses 4 h after rats received L(/sup 35/S)Cys via the third ventricle. After acetic acid extraction, Sephadex G-25 filtration, and chemoadsorption to C18-silica (Sep-Pak cartridges), the labeled peptides were rapidly separated by gradient elution, reversed phase, high pressure liquid chromatography (HPLC). The identity and isotopic purity of the labeled peptides were determined by several reversed phase HPLC procedures in conjunction with chemical modification. The labeled peptide fractions were at least 50% radiochemically pure. Using this HPLC isolation procedure, incorporation of L-(/sup 35/S)Cys into each peptide was determined in hydrated and dehydrated rats. Label incorporation into arginine vasopressin and oxytocin in the hypothalamus and the neurohypophysis of dehydrated rats was 2-3 times greater than that in hydrated rats. Incorporation of label into hypothalamic and neurohypophyseal somatostatin was unaffected by the hydration state of the animal. This procedure thus provides a very rapid, but sensitive, set of techniques for studying the control of small peptide biosynthesis in the brain.

  16. Structure and phase diagram of an adhesive colloidal dispersion under high pressure: A small angle neutron scattering, diffusing wave spectroscopy, and light scattering study

    NASA Astrophysics Data System (ADS)

    Vavrin, R.; Kohlbrecher, J.; Wilk, A.; Ratajczyk, M.; Lettinga, M. P.; Buitenhuis, J.; Meier, G.

    2009-04-01

    We have applied small angle neutron scattering (SANS), diffusing wave spectroscopy (DWS), and dynamic light scattering (DLS) to investigate the phase diagram of a sterically stabilized colloidal system consisting of octadecyl grafted silica particles dispersed in toluene. This system is known to exhibit gas-liquid phase separation and percolation, depending on temperature T, pressure P, and concentration φ. We have determined by DLS the pressure dependence of the coexistence temperature and the spinodal temperature to be dP /dT=77 bar/K. The gel line or percolation limit was measured by DWS under high pressure using the condition that the system became nonergodic when crossing it and we determined the coexistence line at higher volume fractions from the DWS limit of turbid samples. From SANS measurements we determined the stickiness parameter τB(P,T,φ) of the Baxter model, characterizing a polydisperse adhesive hard sphere, using a global fit routine on all curves in the homogenous regime at various temperatures, pressures, and concentrations. The phase coexistence and percolation line as predicted from τB(P,T,φ) correspond with the determinations by DWS and were used to construct an experimental phase diagram for a polydisperse sticky hard sphere model system. A comparison with theory shows good agreement especially concerning the predictions for the percolation threshold. From the analysis of the forward scattering we find a critical scaling law for the susceptibility corresponding to mean field behavior. This finding is also supported by the critical scaling properties of the collective diffusion.

  17. The effect of pressure and mobile phase velocity on the retention properties of small analytes and large biomolecules in ultra-high pressure liquid chromatography.

    PubMed

    Fekete, Szabolcs; Veuthey, Jean-Luc; McCalley, David V; Guillarme, Davy

    2012-12-28

    A possible complication of ultra-high pressure liquid chromatography (UHPLC) is related to the effect of pressure and mobile phase velocity on the retention properties of the analytes. In the present work, numerous model compounds have been selected including small molecules, peptides, and proteins (such as monoclonal antibodies). Two instrumental setups were considered to attain elevated pressure drops, firstly the use of a post-column restrictor capillary at low mobile phase flow rate (pure effect of pressure) and secondly the increase of mobile phase flow rate without restrictor (i.e. a combined effect of pressure and frictional heating). In both conditions, the goal was to assess differences in retention behaviour, depending on the type or character of the analyte. An important conclusion is that the effect of pressure and mobile phase velocity on retention varied in proportion with the size of the molecule and in some cases showed very different behaviour. In isocratic mode, the pure effect of pressure (experiments with a post-column restrictor capillary) induces an increase in retention by 25-100% on small molecules (MW<300 g/mol), 150% for peptides (~1.3 kDa), 800% for insulin (~6 kDa) and up to >3000% for myoglobin (~17 kDa) for an increase in pressure from 100 bar up to 1100 bar. The important effect observed for the isocratic elution of proteins is probably related to conformational changes of the protein in addition to the effect of molecular size. Working in gradient elution mode, the pressure related effects on retention were found to be less pronounced but still present (an increase of apparent retention factor between 0.2 and 2.5 was observed).

  18. Infrared spectroscopic characterization of dehydration and accompanying phase transition behaviors in NAT-topology zeolites

    SciTech Connect

    Wang, Hsiu-Wen; Bishop, David

    2012-01-01

    Relative humidity (PH2O, partial pressure of water)-dependent dehydration and accompanying phase transitions in NAT-topology zeolites (natrolite, scolecite, and mesolite) were studied under controlled temperature and known PH2O conditions by in situ diffuse-reflectance infrared Fourier transform spectroscopy and parallel X-ray powder diffraction. Dehydration was characterized by the disappearance of internal H2O vibrational modes. The loss of H2O molecules caused a sequence of structural transitions in which the host framework transformation path was coupled primarily via the thermal motion of guest Na?/Ca2? cations and H2O molecules. The observation of different interactions of H2O molecules and Na?/Ca2? cations with host aluminosilicate frameworks under highand low-PH2O conditions indicated the development of different local strain fields, arising from cation H2O interactions in NAT-type channels. These strain fields influence the Si O/Al O bond strength and tilting angles within and between tetrahedra as the dehydration temperature is approached. The newly observed infrared bands (at 2,139 cm-1 in natrolite, 2,276 cm-1 in scolecite, and 2,176 and 2,259 cm-1 in mesolite) result from strong cation H2O Al Si framework interactions in NAT-type channels, and these bands can be used to evaluate the energetic evolution of Na?/Ca2? cations before and after phase transitions, especially for scolecite and mesolite. The 2,176 and 2,259 cm-1 absorption bands in mesolite also appear to be related to Na?/Ca2? order disorder that occur when mesolite loses its Ow4 H2O molecules.

  19. Infrared Spectra of High Pressure Carbon Monoxide

    SciTech Connect

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

    2001-09-21

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

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

    NASA Astrophysics Data System (ADS)

    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.

  1. High pressure in situ x-ray absorption spectroscopy cell for studying simultaneously the liquid phase and the solid-liquid interface

    SciTech Connect

    Grunwaldt, Jan-Dierk; Ramin, Michael; Rohr, Markus; Michailovski, Alexej; Patzke, Greta R.; Baiker, Alfons

    2005-05-15

    A high pressure in situ x-ray absorption spectroscopy cell with two different path lengths and path positions is presented for studying element-specifically both the liquid phase and the solid-liquid interface at pressures up to 250 bar and temperatures up to 220 deg. C. For this purpose, one x-ray path probes the bottom, while the other x-ray path penetrates through the middle of the in situ cell. The basic design of the cell resembles a 10 ml volume batch reactor, which is equipped with in- and outlet lines to dose compressed gases and liquids as well as a stirrer for good mixing. Due to the use of a polyetheretherketone inset it is also suitable for measurements under corrosive conditions. The characteristic features of the cell are illustrated using case studies from catalysis and solid state chemistry: (a) the ruthenium-catalyzed formylation of an amine in 'supercritical' carbon dioxide in the presence of hydrogen; (b) the cycloaddition of carbon dioxide to propylene oxide in the presence of a solid Zn-based catalyst, and (c) the solvothermal synthesis of MoO{sub 3} nanorods from MoO{sub 3}-2H{sub 2}O.

  2. High pressure furnace

    DOEpatents

    Morris, D.E.

    1993-09-14

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

  3. High pressure furnace

    DOEpatents

    Morris, Donald E.

    1993-01-01

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

  4. High pressure oxygen furnace

    DOEpatents

    Morris, D.E.

    1992-07-14

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

  5. High pressure oxygen furnace

    DOEpatents

    Morris, Donald E.

    1992-01-01

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

  6. High pressure ratio turbocharger

    SciTech Connect

    Woollenweber, W.E.

    1991-06-25

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

  7. High-Pressure Research in Mineral Physics

    NASA Astrophysics Data System (ADS)

    Hazen, Robert M.

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

  8. 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.

    PubMed

    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

  9. High pressure atomization

    NASA Astrophysics Data System (ADS)

    Bracco, F. V.

    1982-03-01

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

  10. HIGH PRESSURE DIES

    DOEpatents

    Wilson, W.B.

    1960-05-31

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

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

    SciTech Connect

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

    2007-04-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  13. Multicomponent fuel vaporization at high pressures.

    SciTech Connect

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

    2002-01-01

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

  14. HIGH PRESSURE GAS REGULATOR

    DOEpatents

    Ramage, R.W.

    1962-05-01

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

  15. High pressure mechanical seal

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  16. High pressure mechanical seal

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

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

  17. Real-Time Optical Monitoring and Simulations of Gas Phase Kinetics in InN Vapor Phase Epitaxy at High Pressure

    NASA Technical Reports Server (NTRS)

    Dietz, Nikolaus; Woods, Vincent; McCall, Sonya D.; Bachmann, Klaus J.

    2003-01-01

    Understanding the kinetics of nucleation and coalescence of heteroepitaxial thin films is a crucial step in controlling a chemical vapor deposition process, since it defines the perfection of the heteroepitaxial film both in terms of extended defect formation and chemical integrity of the interface. The initial nucleation process also defines the film quality during the later stages of film growth. The growth of emerging new materials heterostructures such as InN or In-rich Ga(x)In(1-x)N require deposition methods operating at higher vapor densities due to the high thermal decomposition pressure in these materials. High nitrogen pressure has been demonstrated to suppress thermal decomposition of InN, but has not been applied yet in chemical vapor deposition or etching experiments. Because of the difficulty with maintaining stochiometry at elevated temperature, current knowledge regarding thermodynamic data for InN, e.g., its melting point, temperature-dependent heat capacity, heat and entropy of formation are known with far less accuracy than for InP, InAs and InSb. Also, no information exists regarding the partial pressures of nitrogen and phosphorus along the liquidus surfaces of mixed-anion alloys of InN, of which the InN(x)P(1-x) system is the most interesting option. A miscibility gap is expected for InN(x)P(1-x) pseudobinary solidus compositions, but its extent is not established at this point by experimental studies under near equilibrium conditions. The extension of chemical vapor deposition to elevated pressure is also necessary for retaining stoichiometric single phase surface composition for materials that are characterized by large thermal decomposition pressures at optimum processing temperatures.

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

    SciTech Connect

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

    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.

  19. [High Pressure Gas Tanks

    NASA Technical Reports Server (NTRS)

    Quintana, Rolando

    2002-01-01

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

  20. High pressure capillary connector

    DOEpatents

    Renzi, Ronald F.

    2005-08-09

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

  1. Supersolid phase accompanied by a quantum critical point in the intermediate coupling regime of the Holstein model.

    PubMed

    Murakami, Yuta; Werner, Philipp; Tsuji, Naoto; Aoki, Hideo

    2014-12-31

    We reveal that electron-phonon systems described by the Holstein model on a bipartite lattice exhibit, away from half filling, a supersolid (SS) phase characterized by coexisting charge order (CO) and superconductivity (SC), and an accompanying quantum critical point (QCP). The SS phase, demonstrated by the dynamical mean-field theory with a quantum Monte Carlo impurity solver, emerges in the intermediate-coupling regime, where the peak of the Tc dome is located and the metal-insulator crossover occurs. On the other hand, in the weak- and strong-coupling regimes the CO-SC boundary is of first order with no intervening SS phases. The QCP is associated with the continuous transition from SS to SC and characterized by a reentrant behavior of the SS around it. We further show that the SS-SC transition is hallmarked by diverging charge fluctuations and a kink (peak) in the superfluid density. PMID:25615362

  2. Urea-temperature phase diagrams capture the thermodynamics of denatured state expansion that accompany protein unfolding.

    PubMed

    Tischer, Alexander; Auton, Matthew

    2013-09-01

    We have analyzed the thermodynamic properties of the von Willebrand factor (VWF) A3 domain using urea-induced unfolding at variable temperature and thermal unfolding at variable urea concentrations to generate a phase diagram that quantitatively describes the equilibrium between native and denatured states. From this analysis, we were able to determine consistent thermodynamic parameters with various spectroscopic and calorimetric methods that define the urea-temperature parameter plane from cold denaturation to heat denaturation. Urea and thermal denaturation are experimentally reversible and independent of the thermal scan rate indicating that all transitions are at equilibrium and the van't Hoff and calorimetric enthalpies obtained from analysis of individual thermal transitions are equivalent demonstrating two-state character. Global analysis of the urea-temperature phase diagram results in a significantly higher enthalpy of unfolding than obtained from analysis of individual thermal transitions and significant cross correlations describing the urea dependence of ΔH0 and ΔCP0 that define a complex temperature dependence of the m-value. Circular dichroism (CD) spectroscopy illustrates a large increase in secondary structure content of the urea-denatured state as temperature increases and a loss of secondary structure in the thermally denatured state upon addition of urea. These structural changes in the denatured ensemble make up ∼40% of the total ellipticity change indicating a highly compact thermally denatured state. The difference between the thermodynamic parameters obtained from phase diagram analysis and those obtained from analysis of individual thermal transitions illustrates that phase diagrams capture both contributions to unfolding and denatured state expansion and by comparison are able to decipher these contributions.

  3. Unusual electronic and mechanical properties of sodium chlorides at high pressures

    NASA Astrophysics Data System (ADS)

    Bu, Hongxia; Zhao, Mingwen; Zhou, Hongcai; Du, Yanling

    2016-04-01

    Using first-principles calculations, we performed systematic investigation on the electronic and mechanical properties of sodium chlorides with different stoichiometries at high pressures. It was found that most of the phases are metallic except the Pnma-NaCl3 with a gap of 2.155 eV. The extended Cl (or Na) sublattice at Cl-rich (or Na-rich) conditions contributes to the metallization. Accompanied by metallization, the NamCln crystals exhibit good ductility in contrast to the brittle NaCl crystal, due to the changes of binding features induced by high pressure. These results are expected to be useful for understanding the exotic properties of NaCl at high pressures.

  4. Infrared spectroscopic and modeling studies of H2/CH4 microwave plasma gas phase from low to high pressure and power

    NASA Astrophysics Data System (ADS)

    Rond, C.; Hamann, S.; Wartel, M.; Lombardi, G.; Gicquel, A.; Röpcke, J.

    2014-09-01

    InfraRed Tunable Diode Laser Absorption Spectroscopy technique has been implemented in a H2/CH4 Micro-Wave (MW frequency f = 2.45 GHz) plasma reactor dedicated to diamond deposition under high pressure and high power conditions. Parametric studies such as a function of MW power, pressure, and admixtures of methane have been carried out on a wide range of experimental conditions: the pressure up to 270 mbar and the MW power up to 4 kW. These conditions allow high purity Chemical Vapor Deposition diamond deposition at high growth rates. Line integrated absorption measurements have been performed in order to monitor hydrocarbon species, i.e., CH3, CH4, C2H2, C2H4, and C2H6. The densities of the stable detected species were found to vary in the range of 1012-1017 molecules cm-3, while the methyl radical CH3 (precursor of diamond growth under these conditions) measured into the plasma bulk was found up to 1014 molecules cm-3. The experimental densities have been compared to those provided by 1D-radial thermochemical model for low power and low pressure conditions (up to 100 mbar/2 kW). These densities have been axially integrated. Experimental measurements under high pressure and power conditions confirm a strong increase of the degree of dissociation of the precursor, CH4, associated to an increase of the C2H2 density, the most abundant reaction product in the plasma.

  5. Fuel droplet burning rates at high pressures.

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

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

  6. High-pressure neutron diffraction

    SciTech Connect

    Xu, Hongwu

    2011-01-10

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

  7. High pressure ices

    PubMed Central

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

    2012-01-01

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

  8. Infrared spectroscopic and modeling studies of H{sub 2}/CH{sub 4} microwave plasma gas phase from low to high pressure and power

    SciTech Connect

    Rond, C. Lombardi, G.; Gicquel, A.; Hamann, S.; Röpcke, J.; Wartel, M.

    2014-09-07

    InfraRed Tunable Diode Laser Absorption Spectroscopy technique has been implemented in a H{sub 2}/CH{sub 4} Micro-Wave (MW frequency f = 2.45 GHz) plasma reactor dedicated to diamond deposition under high pressure and high power conditions. Parametric studies such as a function of MW power, pressure, and admixtures of methane have been carried out on a wide range of experimental conditions: the pressure up to 270 mbar and the MW power up to 4 kW. These conditions allow high purity Chemical Vapor Deposition diamond deposition at high growth rates. Line integrated absorption measurements have been performed in order to monitor hydrocarbon species, i.e., CH{sub 3}, CH{sub 4}, C{sub 2}H{sub 2}, C{sub 2}H{sub 4}, and C{sub 2}H{sub 6}. The densities of the stable detected species were found to vary in the range of 10{sup 12}–10{sup 17} molecules cm{sup −3}, while the methyl radical CH{sub 3} (precursor of diamond growth under these conditions) measured into the plasma bulk was found up to 10{sup 14} molecules cm{sup −3}. The experimental densities have been compared to those provided by 1D-radial thermochemical model for low power and low pressure conditions (up to 100 mbar/2 kW). These densities have been axially integrated. Experimental measurements under high pressure and power conditions confirm a strong increase of the degree of dissociation of the precursor, CH{sub 4}, associated to an increase of the C{sub 2}H{sub 2} density, the most abundant reaction product in the plasma.

  9. Electrokinetically pumped high pressure sprays

    DOEpatents

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

    2005-11-01

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

  10. Electrokinetically pumped high pressure sprays

    SciTech Connect

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

    2002-01-01

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

  11. Grain size dependence of elastic anomalies accompanying the α β phase transition in polycrystalline quartz

    NASA Astrophysics Data System (ADS)

    McKnight, Ruth E. A.; Moxon, T.; Buckley, A.; Taylor, P. A.; Darling, T. W.; Carpenter, M. A.

    2008-02-01

    The effects of grain size on the elastic properties of quartz through the α-β phase transition have been investigated by resonant ultrasound spectroscopy. It is found that there are three regimes, dependent on grain size, within which elastic properties show different evolutions with temperature. In the large grain size regime, as represented by a quartzite sample with ~100-300 µm grains, microcracking is believed to occur in the vicinity of the transition point, allowing grains to pull apart. In the intermediate grain size regime, as represented by novaculite (1-5 µm grain size) and Ethiebeaton agate (~120 nm grain size), bulk and shear moduli through the transition follow closely the values expected from averages of single crystal data. The novaculite sample, however, has a transition temperature ~7 °C higher than that of single crystal quartz. This is assumed to be due to the development of internal pressure arising from anisotropic thermal expansion. In the small grain size region, agates from Mexico (~65 nm) and Brazil (~50 nm) show significant reductions in the amount of softening of the bulk modulus as the transition point is approached from below. This is consistent with a tendency for the transition to become more second order in character. The apparent changes towards second order character do not match quantitative predictions for samples with homogeneous strain across elastically clamped nanocrystals, however. Some of the elastic variations are also due to the presence of moganite in these samples. True 'nanobehaviour' for quartz in ceramic samples thus appears to be restricted to grain sizes of less than ~50 nm.

  12. High-Pressure Orthorhombic Ferromagnesite as a Potential Deep-Mantle Carbon Carrier

    PubMed Central

    Liu, Jin; Lin, Jung-Fu; Prakapenka, Vitali B.

    2015-01-01

    Knowledge of the physical and chemical properties of candidate deep-carbon carriers such as ferromagnesite [(Mg,Fe)CO3] at high pressure and temperature of the deep mantle is necessary for our understanding of deep-carbon storage as well as the global carbon cycle of the planet. Previous studies have reported very different scenarios for the (Mg,Fe)CO3 system at deep-mantle conditions including the chemical dissociation to (Mg,Fe)O+CO2, the occurrence of the tetrahedrally-coordinated carbonates based on CO4 structural units, and various high-pressure phase transitions. Here we have studied the phase stability and compressional behavior of (Mg,Fe)CO3 carbonates up to relevant lower-mantle conditions of approximately 120 GPa and 2400 K. Our experimental results show that the rhombohedral siderite (Phase I) transforms to an orthorhombic phase (Phase II with Pmm2 space group) at approximately 50 GPa and 1400 K. The structural transition is likely driven by the spin transition of iron accompanied by a volume collapse in the Fe-rich (Mg,Fe)CO3 phases; the spin transition stabilizes the high-pressure phase II at much lower pressure conditions than its Mg-rich counterpart. It is conceivable that the low-spin ferromagnesite phase II becomes a major deep-carbon carrier at the deeper parts of the lower mantle below 1900 km in depth. PMID:25560542

  13. High-pressure orthorhombic ferromagnesite as a potential deep-mantle carbon carrier.

    PubMed

    Liu, Jin; Lin, Jung-Fu; Prakapenka, Vitali B

    2015-01-01

    Knowledge of the physical and chemical properties of candidate deep-carbon carriers such as ferromagnesite [(Mg,Fe)CO₃] at high pressure and temperature of the deep mantle is necessary for our understanding of deep-carbon storage as well as the global carbon cycle of the planet. Previous studies have reported very different scenarios for the (Mg,Fe)CO₃ system at deep-mantle conditions including the chemical dissociation to (Mg,Fe)O+CO₂, the occurrence of the tetrahedrally-coordinated carbonates based on CO₄ structural units, and various high-pressure phase transitions. Here we have studied the phase stability and compressional behavior of (Mg,Fe)CO₃ carbonates up to relevant lower-mantle conditions of approximately 120 GPa and 2400 K. Our experimental results show that the rhombohedral siderite (Phase I) transforms to an orthorhombic phase (Phase II with Pmm2 space group) at approximately 50 GPa and 1400 K. The structural transition is likely driven by the spin transition of iron accompanied by a volume collapse in the Fe-rich (Mg,Fe)CO₃ phases; the spin transition stabilizes the high-pressure phase II at much lower pressure conditions than its Mg-rich counterpart. It is conceivable that the low-spin ferromagnesite phase II becomes a major deep-carbon carrier at the deeper parts of the lower mantle below 1900 km in depth. PMID:25560542

  14. High-pressure orthorhombic ferromagnesite as a potential deep-mantle carbon carrier

    DOE PAGES

    Liu, Jin; Lin, Jung -Fu; Prakapenka, Vitali B.

    2015-01-06

    In this study, knowledge of the physical and chemical properties of candidate deep-carbon carriers such as ferromagnesite [(Mg,Fe)CO3] at high pressure and temperature of the deep mantle is necessary for our understanding of deep-carbon storage as well as the global carbon cycle of the planet. Previous studies have reported very different scenarios for the (Mg,Fe)CO3 system at deep-mantle conditions including the chemical dissociation to (Mg,Fe)O+CO2, the occurrence of the tetrahedrally-coordinated carbonates based on CO4 structural units, and various high-pressure phase transitions. Here we have studied the phase stability and compressional behavior of (Mg,Fe)CO3 carbonates up to relevant lower-mantle conditions ofmore » approximately 120 GPa and 2400 K. Our experimental results show that the rhombohedral siderite (Phase I) transforms to an orthorhombic phase (Phase II with Pmm2 space group) at approximately 50 GPa and 1400 K. The structural transition is likely driven by the spin transition of iron accompanied by a volume collapse in the Fe-rich (Mg,Fe)CO3 phases; the spin transition stabilizes the high-pressure phase II at much lower pressure conditions than its Mg-rich counterpart. It is conceivable that the low-spin ferromagnesite phase II becomes a major deep-carbon carrier at the deeper parts of the lower mantle below 1900 km in depth.« less

  15. Laser techniques in high-pressure geophysics

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  16. Experimental Investigation of Magnetic Superconducting and other Phase Transitions in Novel f-Electron Materials at Ultra-high Pressures using Designer Diamond Anvils

    SciTech Connect

    Maple, M. Brian; Jeffries, Jason R.; Ho, Pei-Chun; Butch, Nicholas P.

    2004-09-01

    Pressure is often used as a controlled parameter for the investigation of condensed matter systems. In particular, pressure experiments can provide valuable information into the nature of superconductivity, magnetism, and the coexistence of these two phenomena. Some f-electron, heavy-fermion materials display interesting and novel behavior at moderately low pressures achievable with conventional experimental techniques; however, a growing number of condensed matter systems require ultrahigh pressure techniques, techniques that generate significantly higher pressures than conventional methods, to sufficiently explore their important properties. To that end, we have been funded to develop an ultrahigh pressure diamond anvil cell facility at the University of California, San Diego (UCSD) in order to investigate superconductivity, magnetism, non-Fermi liquid behavior, and other phenomena. Our goals for the first year of this grant were as follows: (a) set up and test a suitable refrigerator; (b) set up a laser and spectrometer fluorescence system to determine the pressure within the diamond anvil cell; (c) perform initial resistivity measurements at moderate pressures from room temperature to liquid helium temperatures ({approx}1K); (d) investigate f-electron materials within our current pressure capabilities to find candidate materials for high-pressure studies. During the past year, we have ordered almost all the components required to set up a diamond anvil cell facility at UCSD, we have received and implemented many of the components that have been ordered, we have performed low pressure research on several materials, and we have engaged in a collaborative effort with Sam Weir at Lawrence Livermore National Lab (LLNL) to investigate Au4V under ultrahigh pressure in a designer diamond anvil cell (dDAC). This report serves to highlight the progress we have made towards developing an ultrahigh pressure research facility at UCSD, the research performed in the past year

  17. Experimental Investigation of Magnetic Superconducting, and other Phase Transitions in Novel f-Electron Materials at Ultra-high Pressures Using Designer Diamond Anvils

    SciTech Connect

    Maple, M. Brian

    2005-09-13

    Pressure is a powerful control parameter, owing to its ability to affect crystal and electronic structure without introducing defects, for the investigation of condensed matter systems. Some f-electron, heavy-fermion materials display interesting and novel behavior when exposed to pressures achievable with conventional experimental techniques; however, a growing number of condensed matter systems require extreme conditions such as ultrahigh pressures, high magnetic fields, and ultralow temperatures to sufficiently explore the important properties. To that end, we have been funded to develop an ultrahigh pressure facility at the University of California, San Diego (UCSD) in order to investigate superconductivity, magnetism, non-Fermi liquid behavior, and other phenomena under extreme conditions. Our goals for the second year of this grant were as follows: (a) perform electrical resistivity measurements on novel samples at a myriad of pressures using conventional piston-cylinder techniques, Bridgman anvil techniques, and diamond anvil cell technology; (b) install, commission, and operate an Oxford Kelvinox MX-100 dilution refrigerator for access to ultralow temperatures and high magnetic fields. (c) continue the development of diamond anvil cell (DAC) technology. During the past year, we have successfully installed the Oxford Kelvinox MX-100 dilution refrigerator and verified its operability down to 12 mK. We have begun an experimental program to systematically investigate the f-electron compound URu2Si2 under pressure and in the presence of magnetic fields. We have also continued our collaborative work with Sam Weir at Lawrence Livermore National Laboratory (LLNL) on Au4V and implemented a new corollary study on Au1-xVx using ultrahigh pressures. We have continued developing our DAC facility by designing and constructing an apparatus for in situ pressure measurement as well as designing high pressure cells. This report serves to highlight the progress we have made

  18. On the room-temperature phase diagram of high pressure hydrogen: An ab initio molecular dynamics perspective and a diffusion Monte Carlo study

    SciTech Connect

    Chen, Ji; Ren, Xinguo; Li, Xin-Zheng; Alfè, Dario; Wang, Enge

    2014-07-14

    The finite-temperature phase diagram of hydrogen in the region of phase IV and its neighborhood was studied using the ab initio molecular dynamics (MD) and the ab initio path-integral molecular dynamics (PIMD). The electronic structures were analyzed using the density-functional theory (DFT), the random-phase approximation, and the diffusion Monte Carlo (DMC) methods. Taking the state-of-the-art DMC results as benchmark, comparisons of the energy differences between structures generated from the MD and PIMD simulations, with molecular and dissociated hydrogens, respectively, in the weak molecular layers of phase IV, indicate that standard functionals in DFT tend to underestimate the dissociation barrier of the weak molecular layers in this mixed phase. Because of this underestimation, inclusion of the quantum nuclear effects (QNEs) in PIMD using electronic structures generated with these functionals leads to artificially dissociated hydrogen layers in phase IV and an error compensation between the neglect of QNEs and the deficiencies of these functionals in standard ab initio MD simulations exists. This analysis partly rationalizes why earlier ab initio MD simulations complement so well the experimental observations. The temperature and pressure dependencies for the stability of phase IV were also studied in the end and compared with earlier results.

  19. Phase Transformation in Sm{sub 2}O{sub 3} at High Pressure: in Situ Synchrotron X-Ray Diffraction Study And Ab Initio DFT Calculation

    SciTech Connect

    Guo, Q.X.; Zhao, Y.S.; Jiang, C.; Mao, W.L.; Wang, Z.W.; /Cornell U., CHESS

    2009-06-09

    Sm{sub 2}O{sub 3} was compressed at room temperature up to 44.0 GPa and then decompressed back to ambient pressure. In situ X-ray diffraction was used to monitor the structural changes in the sample. A cubic to hexagonal phase transformation was observed in Sm{sub 2}O{sub 3} for the first time. After decompression back to ambient pressure, the hexagonal phase was not quenchable and transformed to a monoclinic phase. Ab initio Density-Functional-Theory (DFT) calculations were performed to obtain theoretical data for comparison with the experimental results and elucidation of the transformation mechanism. A possible phase transformation mechanism that is consistent with the experimental results and theoretical calculations is proposed.

  20. High temperature and high pressure oxidation behavior of Zr-2.5Nb pressure tube material - Effect of β phase composition and surface machining

    NASA Astrophysics Data System (ADS)

    Nouduru, S. K.; Kumar, M. Kiran; Kain, Vivekanand; Khanna, A. S.; Saibaba, N.; Dey, G. K.

    2016-03-01

    Pressure tube material, Zr-2.5Nb, of pressurized heavy water reactors was given selective heat-treatments. The objective was to generate microstructures with different compositions of the second phase β namely, Νb depleted βZr phase and Nb rich βNb phase. The material with βZr was then subjected to surface machining. The presence of phases after different heat-treatments was confirmed by X-ray diffraction and the resultant microstructures were characterized by transmission electron microscopy and electron back scattered diffraction. The Nb content in the β phase after heat-treatments and residual stresses before and after surface machining were measured using X-ray diffraction. Oxidation was carried out in steam at 400 °C and 10 MPa up to 30 days and the oxides were characterized by Raman spectroscopy. It is shown that the presence of Nb rich βNb in the microstructure and faster diffusion of Nb into β phase brought about by surface machining resulted in an enhanced oxidation resistance.

  1. Advanced Diagnostics for High Pressure Spray Combustion.

    SciTech Connect

    Skeen, Scott A.; Manin, Julien Luc; Pickett, Lyle M.

    2014-06-01

    The development of accurate predictive engine simulations requires experimental data to both inform and validate the models, but very limited information is presently available about the chemical structure of high pressure spray flames under engine- relevant conditions. Probing such flames for chemical information using non- intrusive optical methods or intrusive sampling techniques, however, is challenging because of the physical and optical harshness of the environment. This work details two new diagnostics that have been developed and deployed to obtain quantitative species concentrations and soot volume fractions from a high-pressure combusting spray. A high-speed, high-pressure sampling system was developed to extract gaseous species (including soot precursor species) from within the flame for offline analysis by time-of-flight mass spectrometry. A high-speed multi-wavelength optical extinction diagnostic was also developed to quantify transient and quasi-steady soot processes. High-pressure sampling and offline characterization of gas-phase species formed following the pre-burn event was accomplished as well as characterization of gas-phase species present in the lift-off region of a high-pressure n-dodecane spray flame. For the initial samples discussed in this work several species were identified, including polycyclic aromatic hydrocarbons (PAH); however, quantitative mole fractions were not determined. Nevertheless, the diagnostic developed here does have this capability. Quantitative, time-resolved measurements of soot extinction were also accomplished and the novel use of multiple incident wavelengths proved valuable toward characterizing changes in soot optical properties within different regions of the spray flame.

  2. Combustion of liquid sprays at high pressures

    NASA Technical Reports Server (NTRS)

    Shearer, A. J.; Faeth, G. M.

    1977-01-01

    The combustion of pressure atomized fuel sprays in high pressure stagnant air was studied. Measurements were made of flame and spray boundaries at pressures in the range 0.1-9 MPa for methanol and n-pentane. At the higher test pressure levels, critical phenomena are important. The experiments are compared with theoretical predictions based on a locally homogeneous two-phase flow model. The theory correctly predicted the trends of the data, but underestimates flame and spray boundaries by 30-50 percent, indicating that slip is still important for the present experiments (Sauter mean diameters of 30 microns at atmospheric pressure under cold flow conditions). Since the sprays are shorter at high pressures, slip effects are still important even though the density ratio of the phases approach one another as the droplets heat up. The model indicates the presence of a region where condensed water is present within the spray and provides a convenient means of treating supercritical phenomena.

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

    SciTech Connect

    Not Available

    1993-05-01

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

  4. ATOMIC AND MOLECULAR PHYSICS: Synthesizing Metastable Rocksalt-Type MgTe Based on High-Pressure Solid-State Phase Transition: A First-Principles Study

    NASA Astrophysics Data System (ADS)

    Cai, Ying-Xiang; Xu, Rui

    2009-11-01

    The controllability of pressure-induced structural transformation in the hexagonal wurtzite-type MgTe is studied by a first-principles pseudopotential method within the generalized gradient approximation (GGA). Based on the transitional mechanisms of the wurtzite→—NiAs and the wurtzite→—rocksalt, a special method of loading biaxial pressure on the (010) and (001) planes of an orthorhombic cell is designed. At equal biaxial pressure of 2.75 GPa, an abrupt volume collapse is found and the WZ phase transforms into an orthorhombic phase with a tiny distortion. While the pressure decreases to zero, three lattice parameters a, b and c become equal and a metastable rocksalt-type MgTe is obtained.

  5. Electrokinetic high pressure hydraulic system

    DOEpatents

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

    2003-06-03

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

  6. Electrokinetic high pressure hydraulic system

    DOEpatents

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

    2001-01-01

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

  7. High pressure liquid level monitor

    DOEpatents

    Bean, Vern E.; Long, Frederick G.

    1984-01-01

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

  8. Characterization of free thiol variants of an IgG1 by reversed phase ultra high pressure liquid chromatography coupled with mass spectrometry.

    PubMed

    Liu, Hongbin; Jeong, Justin; Kao, Yung-Hsiang; Zhang, Yonghua Taylor

    2015-05-10

    RP-HPLC has been demonstrated as a powerful tool to study antibody free thiol and disulfide variants. Recently, the introduction of UHPLC columns with wide pore size (300Å) and small particle size (1.7μm) offered the opportunity to further improve the separation of such variants. This paper describes a systematic evaluation of stationary phases, operating parameters, and mobile phases for a UHPLC based method to separate free thiol variants of a recombinant monoclonal antibody (referred as mAb A), targeting high resolution, high throughput and improved recovery. Among the four different stationary phases evaluated, UHPLC diphenyl columns were found to provide the best separation. Using an optimized UHPLC method, free thiol variants of mAb A were separated in 5min. Importantly, the UHPLC method revealed minor variants that had coeluted in an HPLC based method, and the UHPLC method is also applicable as a platform method for characterization of other mAbs as well. Furthermore, an on-line UHPLC-MS method was developed to characterize the separated variants, and this method can streamline the characterization of fully assembled monoclonal and bispecific therapeutic antibodies.

  9. Electrokinetic high pressure hydraulic system

    DOEpatents

    Paul, Phillip H.; Rakestraw, David J.

    2000-01-01

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

  10. High-pressure phase transitions and compressibilities of aragonite-structure carbonates: SrCO3 and BaCO3

    NASA Astrophysics Data System (ADS)

    Wang, Meili; Liu, Qiong; Nie, Shufang; Li, Baosheng; Wu, Ye; Gao, Jing; Wei, Xiaozhuo; Wu, Xiang

    2015-06-01

    The aragonite-structure carbonates—strontianite (SrCO3) and witherite (BaCO3)—were investigated by synchrotron X-ray diffraction combined with diamond anvil cells up to 30 and 15 GPa at room temperature, respectively. Phase transitions in SrCO3 ( Pmcn to P21212) and BaCO3 ( Pmcn to Pmmn) were observed at 22.2-26.9 and 9.8-11.2 GPa, respectively. Both strontianite and witherite display anisotropic linear compression under pressure, with the c-axis 2-3 times more compressible than the a-axis and b-axis. The obtained second-order Birch-Murnaghan equation of state parameters for strontianite and witherite are V 0 = 258.4(3) Å3, K 0 = 62(1) GPa; and V 0 = 304.8(3) Å3, K 0 = 48(1) GPa, respectively. Based on the current results for strontianite and witherite and previous data for aragonite (CaCO3) and cerussite (PbCO3), the bulk moduli of the aragonite-structure carbonates exhibit a linear correlation with ambient molar volume [ K T0 (GPa) = 138 (5) - 2.0 (3) × V 0], with V 0 in cm3/mol, and the aragonite-structure to post-aragonite-structure phase transition pressures increase with decreasing ionic radius of the cations.

  11. Preparation and kinetic performance assessment of thick film 10-20 μm open tubular silica capillaries in normal phase high pressure liquid chromatography.

    PubMed

    Forster, Simon; Kolmar, Harald; Altmaier, Stephan

    2013-11-01

    It is well-known that the open tubular column design basically can offer very high plate numbers. Experimental realization has however not kept pace with theoretical considerations, lacking efficient methods for the deposition of a thick film porous layer within a microbore capillary. A previously published sol-gel synthesis method was extended from 20 μm to 10 μm inner diameter fused silica capillaries and the resulting columns were compared to a monolithic reference capillary in terms of kinetic performance at pressure maximum. Column permeability was investigated and pressure/flow-diagrams were obtained with a 400-fold permeability gain for the open tubes. Structural characterizations regarding layer thickness and surface porosity were carried out and displayed via scanning electron microscopy and nitrogen sorption analysis. Chromatographic results in normal phase mode at elevated mobile phase flow rate reveal the intrinsic performance potential of this column format when it comes to kinetic performance limitation plots, which were constructed for all columns prepared and compared to the monolithic silica reference capillary.

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

    NASA Astrophysics Data System (ADS)

    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.

  13. The solubility of carbon monoxide in silicate melts at high pressures and its effect on silicate phase relations. [in terrestrial and other planetary interiors

    NASA Technical Reports Server (NTRS)

    Eggler, D. H.; Mysen, B. O.; Hoering, T. C.; Holloway, J. R.

    1979-01-01

    Autoradiographic analysis and gas chromatography were used to measure the solubility in silicate melts of CO-CO2 vapors (30 to 40% CO by thermodynamic calculation) in equilibrium with graphite at temperatures up to 1700 deg C and pressures to 30 kbar. At near-liquidus temperatures CO-CO2 vapors were found to be slightly more soluble than CO2 alone. As a result of the apparently negative temperature dependence of CO solubility, the solubility of CO-CO2 at superliquidus temperatures is less than that of CO2. Melting points of two silicates were depressed more by CO than by CO2. Phase boundary orientations suggest that CO/CO + CO2 is greater in the liquid than in the vapor. The effect of the presence of CO on periodotite phase relations was investigated, and it was found that melts containing both CO and CO2 are nearly as polymerized as those containing only CO2. These results suggest that crystallization processes in planetary interiors can be expected to be about the same, whether the melts contain CO2 alone or CO2 and CO.

  14. Experimental Investigation of Magnetic, Superconducting, and other Phase Transitions in novel F-Electron Materials at Ultra-high Pressures - Final Progress Report

    SciTech Connect

    Maple, Brian; Jeffires, Jason

    2006-07-28

    This grant, entitled “Experimental investigation of magnetic, superconducting and other phase transitions in novel f-electron materials at ultrahigh pressures,” spanned the funding period from May 1st, 2003 until April 30th, 2006. The major goal of this grant was to develop and utilize an ultrahigh pressure facility—capable of achieving very low temperatures, high magnetic fields, and extreme pressures as well as providing electrical resistivity, ac susceptibility, and magnetization measurement capabilities under pressure—for the exploration of magnetic, electronic, and structural phases and any corresponding interactions between these states in novel f-electron materials. Realizing this goal required the acquisition, development, fabrication, and implementation of essential equipment, apparatuses, and techniques. The following sections of this report detail the establishment of an ultrahigh pressure facility (Section 1) and measurements performed during the funding period (Section 2), as well as summarize the research project (Section 3), project participants and their levels of support (Section 4), and publications and presentations (Section 5).

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

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

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

  16. Evidence of the existence of the high-density and low-density phases in deeply-cooled confined heavy water under high pressures

    SciTech Connect

    Wang, Zhe; Chen, Sow-Hsin; Liu, Kao-Hsiang; Harriger, Leland; Leão, Juscelino B.

    2014-07-07

    The average density of D{sub 2}O confined in a nanoporous silica matrix (MCM-41-S) is studied with neutron scattering. We find that below ∼210 K, the pressure-temperature plane of the system can be divided into two regions. The average density of the confined D{sub 2}O in the higher-pressure region is about 16% larger than that in the lower-pressure region. These two regions could represent the so-called “low-density liquid” and “high-density liquid” phases. The dividing line of these two regions, which could represent the associated 1st order liquid-liquid transition line, is also determined.

  17. High pressure neon arc lamp

    DOEpatents

    Sze, Robert C.; Bigio, Irving J.

    2003-07-15

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

  18. High-pressure well design

    SciTech Connect

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

    1991-12-01

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

  19. High-pressure water facility

    NASA Technical Reports Server (NTRS)

    2006-01-01

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

  20. Magnetic and Superconducting Materials at High Pressures

    SciTech Connect

    Struzhkin, Viktor V.

    2015-03-24

    The work concentrates on few important tasks in enabling techniques for search of superconducting compressed hydrogen compounds and pure hydrogen, investigation of mechanisms of high-Tc superconductivity, and exploring new superconducting materials. Along that route we performed several challenging tasks, including discovery of new forms of polyhydrides of alkali metal Na at very high pressures. These experiments help us to establish the experimental environment that will provide important information on the high-pressure properties of hydrogen-rich compounds. Our recent progress in RIXS measurements opens a whole field of strongly correlated 3d materials. We have developed a systematic approach to measure major electronic parameters, like Hubbard energy U, and charge transfer energy Δ, as function of pressure. This technique will enable also RIXS studies of magnetic excitations in iridates and other 5d materials at the L edge, which attract a lot of interest recently. We have developed new magnetic sensing technique based on optically detected magnetic resonance from NV centers in diamond. The technique can be applied to study superconductivity in high-TC materials, to search for magnetic transitions in strongly correlated and itinerant magnetic materials under pressure. Summary of Project Activities; development of high-pressure experimentation platform for exploration of new potential superconductors, metal polyhydrides (including newly discovered alkali metal polyhydrides), and already known superconductors at the limit of static high-pressure techniques; investigation of special classes of superconducting compounds (high-Tc superconductors, new superconducting materials), that may provide new fundamental knowledge and may prove important for application as high-temperature/high-critical parameter superconductors; investigation of the pressure dependence of superconductivity and magnetic/phase transformations in 3d transition metal compounds, including

  1. High pressure studies of potassium perchlorate

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  2. Three-Dimensional Unsteady Simulation of a Modern High Pressure Turbine Stage Using Phase Lag Periodicity: Analysis of Flow and Heat Transfer

    NASA Technical Reports Server (NTRS)

    Shyam, Vikram; Ameri, Ali; Luk, Daniel F.; Chen, Jen-Ping

    2010-01-01

    Unsteady three-dimensional RANS simulations have been performed on a highly loaded transonic turbine stage and results are compared to steady calculations as well as experiment. A low Reynolds number k- turbulence model is employed to provide closure for the RANS system. A phase-lag boundary condition is used in the periodic direction. This allows the unsteady simulation to be performed by using only one blade from each of the two rows. The objective of this paper is to study the effect of unsteadiness on rotor heat transfer and to glean any insight into unsteady flow physics. The role of the stator wake passing on the pressure distribution at the leading edge is also studied. The simulated heat transfer and pressure results agreed favorably with experiment. The time-averaged heat transfer predicted by the unsteady simulation is higher than the heat transfer predicted by the steady simulation everywhere except at the leading edge. The shock structure formed due to stator-rotor interaction was analyzed. Heat transfer and pressure at the hub and casing were also studied. Thermal segregation was observed that leads to the heat transfer patterns predicted by steady and unsteady simulations to be different.

  3. Raman spectroscopy of triolein under high pressures

    NASA Astrophysics Data System (ADS)

    Tefelski, D. B.; Jastrzębski, C.; Wierzbicki, M.; Siegoczyński, R. M.; Rostocki, A. J.; Wieja, K.; Kościesza, R.

    2010-03-01

    This article presents results of the high pressure Raman spectroscopy of triolein. Triolein, a triacylglyceride (TAG) of oleic acid, is an unsaturated fat, present in natural oils such as olive oil. As a basic food component and an energy storage molecule, it has considerable importance for food and fuel industries. To generate pressure in the experiment, we used a high-pressure cylindrical chamber with sapphire windows, presented in (R.M. Siegoczyński, R. Kościesza, D.B. Tefelski, and A. Kos, Molecular collapse - modification of the liquid structure induced by pressure in oleic acid, High Press. Res. 29 (2009), pp. 61-66). Pressure up to 750 MPa was applied. A Raman spectrometer in "macro"-configuration was employed. Raman spectroscopy provides information on changes of vibrational modes related to structural changes of triolein under pressure. Interesting changes in the triglyceride C‒H stretching region at 2650-3100 cm-1 were observed under high-pressures. Changes were also observed in the ester carbonyl (C˭ O) stretching region 1700-1780 cm-1 and the C‒C stretching region at 1050-1150 cm-1. The overall luminescence of the sample decreased under pressure, making it possible to set longer spectrum acquisition time and obtain more details of the spectrum. The registered changes suggest that the high-pressure solid phase of triolein is organized as β-polymorphic, as was reported in (C. Akita, T. Kawaguchi, and F. Kaneko, Structural study on polymorphism of cis-unsaturated triacylglycerol: Triolein, J. Phys. Chem. B 110 (2006), pp. 4346-4353; E. Da Silva and D. Rousseau, Molecular order and thermodynamics of the solid-liquid transition in triglycerides via Raman spectroscopy, Phys. Chem. Chem. Phys. 10 (2008), pp. 4606-4613) (with temperature-induced phase transitions). The research has shown that Raman spectroscopy in TAGs under pressure reveals useful information about its structural changes.

  4. Investigation of Phase Transformations in High-Alloy Austenitic TRIP Steel Under High Pressure (up to 18 GPa) by In Situ Synchrotron X-ray Diffraction and Scanning Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Ackermann, Stephanie; Martin, Stefan; Schwarz, Marcus R.; Schimpf, Christian; Kulawinski, Dirk; Lathe, Christian; Henkel, Sebastian; Rafaja, David; Biermann, Horst; Weidner, Anja

    2016-01-01

    In order to clarify the difference between the deformation-induced ɛ-martensite ( ɛ 1) and the pressure-induced ɛ-iron ( ɛ 2), high-pressure quasi-hydrostatic experiments were performed on a low-carbon, high-alloy metastable austenitic steel. In situ synchrotron X-ray diffraction measurements as well as post-mortem investigations of the microstructure by electron backscatter diffraction were carried out to study the microstructural transformations. Three processes were observed during compression experiments: first, the formation of deformation-induced hexagonal ɛ 1-martensite, as well as small nuclei of deformation-induced bcc α'-martensite ( α 1') within the fcc γ-matrix due to non-hydrostaticity in the experiments; second, the onset of the phase transformation from the metastable fcc γ-austenite into the hexagonal pressure-induced ɛ 2-iron phase occurred at around 6 GPa; third, during decompression, the hexagonal pressure-induced ɛ 2-iron transformed partially into bcc α'-martensite ( α 2'). Completely different characteristics with regard to habitus as well as to orientation relationships were observed between the pressure-induced phases ( ɛ 2-iron phase and α 2'-martensite) and the deformation-induced martensites ( ɛ 1- and α 1'-martensite).

  5. Structural behaviour of niobium oxynitride under high pressure

    SciTech Connect

    Sharma, Bharat Bhooshan Poswal, H. K. Pandey, K. K. Sharma, Surinder M.; Yakhmi, J. V.; Ohashi, Y.; Kikkawa, S.

    2014-04-24

    High pressure investigation of niobium oxynitrides (NbN{sub 0.98}O{sub 0.02}) employing synchrotron based angle dispersive x-ray diffraction experiments was carried out in very fine pressure steps using membrane driven diamond anvil cell. Ambient cubic phase was found to be stable up to ∼18 GPa. At further high pressure cubic phase showed rhombohedral distortion.

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

    SciTech Connect

    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.

  7. High-pressure, high-temperature deformation of CaGeO3 (perovskite)±MgO aggregates: Elasto-ViscoPlastic Self-Consistent modeling and implications for multi-phase rheology of the lower mantle

    NASA Astrophysics Data System (ADS)

    Hilairet, N.; Tomé, C.; Wang, H.; Merkel, S.; Wang, Y.; Nishiyama, N.

    2014-12-01

    As the largest rocky layer in the Earth, the lower mantle plays a critical role in controlling convective patterns in our planet. Current mineralogical mantle models suggest that the lower mantle is dominated by (Mg,Fe)SiO3 perovskite (SiPv; about 70 - 90% in volume fraction) and (Mg,Fe)O ferropericlase (Fp). Knowledge of rheological properties of the major constituent minerals and stress/strain partitioning among these phases during deformation is critical in understanding dynamic processes of the deep Earth. For the lower mantle, the strength contrast between SiPv and Fp has been estimated [1], the former being much stronger than the latter. However fundamental issues of stress-strain interactions among the major phases still remain to be properly addressed. Here we examine rheological properties of a two-phase polycrystal consisting of CaGeO3 perovskite (GePv) and MgO, deformed in the D-DIA at controlled speed ~1 - 3×10-5 s-1 at high pressures and temperatures (between 3 to 10 GPa and 300 to 1200 K), with bulk axial strains up to ~20% [2]. We use Elasto-ViscoPlastic Self-Consistent modeling (EVPSC) [3] to reproduce lattice strains and textures measured in-situ with synchrotron X-ray diffraction. We compare the results to those on an identical deformation experiment with a single phase (GePv) polycrystal. We will discuss stress distributions between the two phases in the composite, textural developments, relationships with active slip systems, and finally the potential implications for rheological properties of the lower mantle. [1] Yamazaki, D., and S. Karato (2002), Fabric development in (Mg,Fe)O during large strain, shear deformation: implications for seismic anisotropy in Earth's lower mantle, Physics of the Earth and Planetary Interiors, 131(3-4), 251-267. [2] Wang, Y., N. Hilairet, N. Nishiyama, N. Yahata, T. Tsuchiya, G. Morard, and G. Fiquet (2013), High-pressure, high-temperature deformation of CaGeO3 (perovskite)+/- MgO aggregates: Implications for

  8. High pressure rinsing system comparison

    SciTech Connect

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

    2007-06-01

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

  9. Exotic stable cesium polynitrides at high pressure

    DOE PAGES

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

    2015-11-19

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

  10. Exotic stable cesium polynitrides at high pressure

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  11. Exotic stable cesium polynitrides at high pressure

    PubMed Central

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

    2015-01-01

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

  12. Electronic phenomena at high pressure

    SciTech Connect

    Drickamer, H.G.

    1981-01-01

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

  13. Very high-pressure orogenic garnet peridotites

    PubMed Central

    Liou, J. G.; Zhang, R. Y.; Ernst, W. G.

    2007-01-01

    Mantle-derived garnet peridotites are a minor component in many very high-pressure metamorphic terranes that formed during continental subduction and collision. Some of these mantle rocks contain trace amounts of zircon and micrometer-sized inclusions. The constituent minerals exhibit pre- and postsubduction microstructures, including polymorphic transformation and mineral exsolution. Experimental, mineralogical, petrochemical, and geochronological characterizations using novel techniques with high spatial, temporal, and energy resolutions are resulting in unexpected discoveries of new phases, providing better constraints on deep mantle processes. PMID:17519341

  14. Spin-phonon coupling and high-pressure phase transitions of RMnO3 (R=Ca and Pr): An inelastic neutron scattering and first-principles study

    DOE PAGES

    Mishra, S. K.; Gupta, M. K.; Mittal, R.; Kolesnikov, Alexander I.; Chaplot, S. L.

    2016-06-22

    Here, we report inelastic neutron scattering measurements over 7–1251 K in CaMnO3 covering various phase transitions, and over 6–150 K in PrMnO3 covering the magnetic transition. The excitations around 20 meV in CaMnO3 and at 17 meV in PrMnO3 at low temperatures are found to be associated with magnetic origin. We observe coherent magnetic neutron scattering in localized regions in reciprocal space and show it to arise from long-range correlated magnetic spin-waves below the magnetic transition temperature (TN) and short-range stochastic spin-spin fluctuations above TN. In spite of the similarity of the structure of the two compounds, the neutron inelasticmore » spectrum of PrMnO3 exhibits broad features at 150 K unlike well-defined peaks in the spectrum of CaMnO3. This might result from the difference in the nature of interactions in the two compounds (magnetic and Jahn-Teller distortion). Ab initio phonon calculations have been used to interpret the observed phonon spectra. The ab initio calculations at high pressures show that the variations of Mn-O distances are isotropic for CaMnO3 and highly anisotropic for PrMnO3. The calculation in PrMnO3 shows the suppression of Jahn-Teller distortion and simultaneous insulator-to-metal transition. It appears that this transition may not be associated with the occurrence of the tetragonal phase above 20 GPa as reported in the literature, since the tetragonal phase is found to be dynamically unstable, although it is found to be energetically favored over the orthorhombic phase above 20 GPa. CaMnO3 does not show any phase transition up to 60 GPa.« less

  15. High Pressure Hydrogen from First Principles

    NASA Astrophysics Data System (ADS)

    Morales, M. A.

    2014-12-01

    Typical approximations employed in first-principles simulations of high-pressure hydrogen involve the neglect of nuclear quantum effects (NQE) and the approximate treatment of electronic exchange and correlation, typically through a density functional theory (DFT) formulation. In this talk I'll present a detailed analysis of the influence of these approximations on the phase diagram of high-pressure hydrogen, with the goal of identifying the predictive capabilities of current methods and, at the same time, making accurate predictions in this important regime. We use a path integral formulation combined with density functional theory, which allows us to incorporate NQEs in a direct and controllable way. In addition, we use state-of-the-art quantum Monte Carlo calculations to benchmark the accuracy of more approximate mean-field electronic structure calculations based on DFT, and we use GW and hybrid DFT to calculate the optical properties of the solid and liquid phases near metallization. We present accurate predictions of the metal-insulator transition on the solid, including structural and optical properties of the molecular phase. This work was supported by the U.S. Department of Energy at the Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and by LDRD Grant No. 13-LW-004.

  16. High-pressure orthorhombic ferromagnesite as a potential deep-mantle carbon carrier

    SciTech Connect

    Liu, Jin; Lin, Jung -Fu; Prakapenka, Vitali B.

    2015-01-06

    In this study, knowledge of the physical and chemical properties of candidate deep-carbon carriers such as ferromagnesite [(Mg,Fe)CO3] at high pressure and temperature of the deep mantle is necessary for our understanding of deep-carbon storage as well as the global carbon cycle of the planet. Previous studies have reported very different scenarios for the (Mg,Fe)CO3 system at deep-mantle conditions including the chemical dissociation to (Mg,Fe)O+CO2, the occurrence of the tetrahedrally-coordinated carbonates based on CO4 structural units, and various high-pressure phase transitions. Here we have studied the phase stability and compressional behavior of (Mg,Fe)CO3 carbonates up to relevant lower-mantle conditions of approximately 120 GPa and 2400 K. Our experimental results show that the rhombohedral siderite (Phase I) transforms to an orthorhombic phase (Phase II with Pmm2 space group) at approximately 50 GPa and 1400 K. The structural transition is likely driven by the spin transition of iron accompanied by a volume collapse in the Fe-rich (Mg,Fe)CO3 phases; the spin transition stabilizes the high-pressure phase II at much lower pressure conditions than its Mg-rich counterpart. It is conceivable that the low-spin ferromagnesite phase II becomes a major deep-carbon carrier at the deeper parts of the lower mantle below 1900 km in depth.

  17. High pressure study of acetophenone azine

    NASA Astrophysics Data System (ADS)

    Tang, X. D.; Ding, Z. J.; Zhang, Z. M.

    2009-02-01

    High pressure Raman spectra of acetophenone azine (APA) have been measured up to 17.7 GPa with a diamond anvil cell. Two crystalline-to-crystalline phase transformations are found at pressures about 3.6 and 5.8 GPa. A disappearance of external modes and the C-H vibration at pressures higher than 8.7 GPa suggests that the sample undergoes a phase transition to amorphous or orientationally disordered (plastic) state, and the amorphization was completed at about 12.1 GPa. The disordered state is unstable and, then, a polymerization transformation reaction occurs with a further pressure increase. After the pressure has been released, the polymerization state can remain at the ambient condition, indicating that the virgin crystalline state is not recovered. The results show that the phenomenon underlying the pressure induced phase transition of APA may involve profound changes in the coordination environments of the symmetric aromatic azine.

  18. Electrokinetic high pressure hydraulic system

    SciTech Connect

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

    2000-01-11

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

  19. Brillouin scattering at high pressures

    SciTech Connect

    Grimsditch, M.; Polian, A.

    1988-02-01

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

  20. Spray patternation at high pressure

    NASA Astrophysics Data System (ADS)

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

    1989-07-01

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

  1. Electokinetic high pressure hydraulic system

    DOEpatents

    Paul, Phillip H.; Rakestraw, David J.

    2000-01-01

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

  2. Improved high pressure turbine shroud

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

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

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

    SciTech Connect

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

    2015-10-28

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

  4. High pressure xenon ionization detector

    DOEpatents

    Markey, J.K.

    1989-11-14

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

  5. High pressure xenon ionization detector

    DOEpatents

    Markey, John K.

    1989-01-01

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

  6. Stable Lithium Argon compounds under high pressure

    PubMed Central

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

    2015-01-01

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

  7. Amorphous boron nitride at high pressure

    NASA Astrophysics Data System (ADS)

    Durandurdu, Murat

    2016-06-01

    The pressure-induced phase transformation in hexagonal boron nitrite and amorphous boron nitrite is studied using ab initio molecular dynamics simulations. The hexagonal-to-wurtzite phase transformation is successfully reproduced in the simulation with a transformation mechanism similar to one suggested in experiment. Amorphous boron nitrite, on the other hand, gradually transforms to a high-density amorphous phase with the application of pressure. This phase transformation is irreversible because a densified amorphous state having both sp3 and sp2 bonds is recovered upon pressure release. The high-density amorphous state mainly consists of sp3 bonds and its local structure is quite similar to recently proposed intermediate boron nitrite phases, in particular tetragonal structure (P42/mnm), rather than the known the wurtzite or cubic boron nitrite due to the existence of four membered rings and edge sharing connectivity. On the basis of this finding we propose that amorphous boron nitrite might be best candidate as a starting structure to synthesize the intermediate phase(s) at high pressure and temperature (probably below 800 °C) conditions.

  8. High-pressure structural properties of tetramethylsilane

    NASA Astrophysics Data System (ADS)

    Zhen-Xing, Qin; Xiao-Jia, Chen

    2016-02-01

    High-pressure structural properties of tetramethylsilane are investigated by synchrotron powder x-ray diffraction at pressures up to 31.1 GPa and room temperature. A phase with the space group of Pnma is found to appear at 4.2 GPa. Upon compression, the compound transforms to two following phases: the phase with space groups of P21/c at 9.9 GPa and the phase with P2/m at 18.2 GPa successively via a transitional phase. The unique structural character of P21/c supports the phase stability of tetramethylsilane without possible decomposition upon heavy compression. The appearance of the P2/m phase suggests the possible realization of metallization for this material at higher pressure. Project supported by the Cultivation Fund of the Key Scientific and Technical Innovation Project from Ministry of Education of China (Grant No. 708070), the Fundamental Research Funds for the Central Universities, South China University of Technology (Grant No. 2014ZZ0069), the National Natural Science Foundation of China (Grant No. 51502189), and the Doctoral Project of Taiyuan University of Science and Technology, China (Grant No. 20132010).

  9. High pressure volumetric measurements in dipalmitoylphosphatidylcholine bilayers.

    PubMed

    Tosh, R E; Collings, P J

    1986-07-10

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

  10. High pressure chemistry of substituted acetylenes

    SciTech Connect

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

    2011-01-25

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

  11. Steam Oxidation at High Pressure

    SciTech Connect

    Holcomb, Gordon R.; Carney, Casey

    2013-07-19

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

  12. High pressure hollow electrode discharges

    SciTech Connect

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

    1997-12-31

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

  13. Exotic stable cesium polynitrides at high pressure

    SciTech Connect

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

    2015-11-19

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

  14. 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.

    PubMed

    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.

  15. 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.

    PubMed

    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. PMID:25694147

  16. Electrical Transport Experiments at High Pressure

    SciTech Connect

    Weir, S

    2009-02-11

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

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

    PubMed

    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.

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

    PubMed

    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. PMID:26786011

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

    PubMed Central

    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. PMID:26786011

  20. The high-pressure C2/ c P21/ c phase transition along the LiAlSi2O6 LiGaSi2O6 solid solution

    NASA Astrophysics Data System (ADS)

    Nestola, Fabrizio; Ballaran, Tiziana Boffa; Ohashi, Haruo

    2008-09-01

    Two synthetic single-crystals with composition Li(Al0.53Ga0.47)Si2O6 and LiGaSi2O6 and space group C2/ c at room conditions have been studied under pressure by means of X-ray diffraction using a diamond anvil cell. The unit-cell parameters were determined at 12 and 10 different pressures up to P = 8.849 and P = 7.320 GPa for Li(Al0.53Ga0.47)Si2O6 and LiGaSi2O6, respectively. The sample with mixed composition shows a C2/c to P21/ c phase transformation between 1.814 and 2.156 GPa, first-order in character. The transition is characterised by a large and discontinuous decrease in the unit-cell volume and by the appearance of the b-type reflections ( h + k = odd) typical of the primitive symmetry. The Ga end-member shows the same C2/c to P21/ c transformation at a pressure between 0.0001 and 0.39 GPa. The low-pressure value at which the transition occurred did not allow collecting any data in the C2/ c pressure stability field except that on room pressure. Our results compared with those relative to spodumene (LiAlSi2O6, Arlt and Angel 2000a) indicate that the substitution of Al for Ga at the M1 site of Li-clinopyroxenes strongly affects the transition pressure causing a decrease from 3.17 GPa (spodumene) to less than 0.39 GPa (LiGaSi2O6) and decreases the volume discontinuity at the transition. As already found for other compounds, the C2 /c low-pressure phases are more rigid than the P21 /c high-pressure ones. Moreover, the increase of the M1 cation radius causes a decrease in the bulk modulus K T0. The axial compressibility among the Li-bearing clinopyroxenes indicates that the c axis is the most rigid for the C2 /c phases while it becomes the most compressible for the P21 /c phases.

  1. High Pressure Electrolyzer System Evaluation

    NASA Technical Reports Server (NTRS)

    Prokopius, Kevin; Coloza, Anthony

    2010-01-01

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

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

    NASA Astrophysics Data System (ADS)

    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.

  3. Rapid and automated analysis of aflatoxin M1 in milk and dairy products by online solid phase extraction coupled to ultra-high-pressure-liquid-chromatography tandem mass spectrometry.

    PubMed

    Campone, Luca; Piccinelli, Anna Lisa; Celano, Rita; Pagano, Imma; Russo, Mariateresa; Rastrelli, Luca

    2016-01-01

    This study reports a fast and automated analytical procedure for the analysis of aflatoxin M1 (AFM1) in milk and dairy products. The method is based on the simultaneous protein precipitation and AFM1 extraction, by salt-induced liquid-liquid extraction (SI-LLE), followed by an online solid-phase extraction (online SPE) coupled to ultra-high-pressure-liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) analysis to the automatic pre-concentration, clean up and sensitive and selective determination of AFM1. The main parameters affecting the extraction efficiency and accuracy of the analytical method were studied in detail. In the optimal conditions, acetonitrile and NaCl were used as extraction/denaturant solvent and salting-out agent in SI-LLE, respectively. After centrifugation, the organic phase (acetonitrile) was diluted with water (1:9 v/v) and purified (1mL) by online C18 cartridge coupled with an UHPLC column. Finally, selected reaction monitoring (SRM) acquisition mode was applied to the detection of AFM1. Validation studies were carried out on different dairy products (whole and skimmed cow milk, yogurt, goat milk, and powder infant formula), providing method quantification limits about 25 times lower than AFM1 maximum levels permitted by EU regulation 1881/2006 in milk and dairy products for direct human consumption. Recoveries (86-102%) and repeatability (RSD<3, n=6) meet the performance criteria required by EU regulation N. 401/2006 for the determination of the levels of mycotoxins in foodstuffs. Moreover, no matrix effects were observed in the different milk and dairy products studied. The proposed method improves the performance of AFM1 analysis in milk samples as AFM1 determination is performed with a degree of accuracy higher than the conventional methods. Other advantages are the reduction of sample preparation procedure, time and cost of the analysis, enabling high sample throughput that meet the current concerns of food safety and the public

  4. Rapid and automated analysis of aflatoxin M1 in milk and dairy products by online solid phase extraction coupled to ultra-high-pressure-liquid-chromatography tandem mass spectrometry.

    PubMed

    Campone, Luca; Piccinelli, Anna Lisa; Celano, Rita; Pagano, Imma; Russo, Mariateresa; Rastrelli, Luca

    2016-01-01

    This study reports a fast and automated analytical procedure for the analysis of aflatoxin M1 (AFM1) in milk and dairy products. The method is based on the simultaneous protein precipitation and AFM1 extraction, by salt-induced liquid-liquid extraction (SI-LLE), followed by an online solid-phase extraction (online SPE) coupled to ultra-high-pressure-liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) analysis to the automatic pre-concentration, clean up and sensitive and selective determination of AFM1. The main parameters affecting the extraction efficiency and accuracy of the analytical method were studied in detail. In the optimal conditions, acetonitrile and NaCl were used as extraction/denaturant solvent and salting-out agent in SI-LLE, respectively. After centrifugation, the organic phase (acetonitrile) was diluted with water (1:9 v/v) and purified (1mL) by online C18 cartridge coupled with an UHPLC column. Finally, selected reaction monitoring (SRM) acquisition mode was applied to the detection of AFM1. Validation studies were carried out on different dairy products (whole and skimmed cow milk, yogurt, goat milk, and powder infant formula), providing method quantification limits about 25 times lower than AFM1 maximum levels permitted by EU regulation 1881/2006 in milk and dairy products for direct human consumption. Recoveries (86-102%) and repeatability (RSD<3, n=6) meet the performance criteria required by EU regulation N. 401/2006 for the determination of the levels of mycotoxins in foodstuffs. Moreover, no matrix effects were observed in the different milk and dairy products studied. The proposed method improves the performance of AFM1 analysis in milk samples as AFM1 determination is performed with a degree of accuracy higher than the conventional methods. Other advantages are the reduction of sample preparation procedure, time and cost of the analysis, enabling high sample throughput that meet the current concerns of food safety and the public

  5. Behavior of silver molybdate at high-pressure

    SciTech Connect

    Arora, A.K.; Nithya, R.; Misra, Sunasira; Yagi, Takehiko

    2012-12-15

    Behavior of cubic spinel phase of Ag{sub 2}MoO{sub 4} is investigated at high pressure using X-ray diffraction and Raman spectroscopy. The P-V data are fitted to a third order Birch-Murnaghan equation of state using a value of B{sub 0}=113 GPa and B Prime {sub 0}=4. The compound is also found to exhibit a phase transition around 5 GPa to a tetragonal structure and the two phases are found to coexist over a range of pressures. Raman spectra exhibit dramatic changes across the phase transition. Increase of X-ray background scattering and broadening of the Raman peaks associated with MoO{sub 4} tetrahedral ions in the high pressure phase suggest evolution of positional disorder. However, no evidence of pressure-induced amorphization was found up to 47 GPa. - Graphical abstract: Evolution of the integrated intensity of all the diffraction peaks between 12 and 18 degree 2{theta} as a function of pressure. The rapid decrease of the intensity suggests evolution of positional disorder in the high-pressure tetragonal phase. Highlights: Black-Right-Pointing-Pointer First in-situ X-ray diffraction and Raman study of cubic silver molybdate at high pressure. Black-Right-Pointing-Pointer Commencement of a structural transition to a tetragonal phase is found at 2.3 GPa. Black-Right-Pointing-Pointer The high-pressure phase is found to have positional disorder. Black-Right-Pointing-Pointer A bulk modulus of 113 GPa is obtained from the equation of state.

  6. High-Pressure Lightweight Thrusters

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

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

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

    SciTech Connect

    Yamada, Hiroyuki; Nagae, Takayuki; Watanabe, Nobuhisa

    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

    SciTech Connect

    Gilioli, Edmondo; Ehm, Lars

    2014-10-31

    We found that 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. Moreover, 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.

    PubMed

    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.

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

    PubMed

    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. PMID:25485138

  11. NETL- High-Pressure Combustion Research Facility

    ScienceCinema

    None

    2016-07-12

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

  12. NETL- High-Pressure Combustion Research Facility

    SciTech Connect

    2013-07-08

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

  13. Experimental determination of phase equilibria of a basalt from Piton de la Fournaise (La Réunion island): 1 atm data and high pressure results in presence of volatiles.

    NASA Astrophysics Data System (ADS)

    Brugier, Yann-Aurélien; Pichavant, Michel; di Muro, Andréa

    2015-04-01

    To understand the petrogenetic relations between the 4 groups of lavas erupted at Piton de la Fournaise (PdF), constrain the structure of the feeding system and the magma storage conditions, experimental phase equilibria have been determined, both at 1 atm and high pressures (HP), on a lava representative of Steady State Basalts (SSB). The lava (SiO2=49.2 wt%, MgO=7.8 wt%, CaO/Al2O3= 0.81) was fused at 1400°C, 1 atm in air. The resulting glass was crushed and the powder directly used as starting material. The 1atm experiments were performed with the wire-loop method in a vertical CO-CO2 gas mixing furnace. To minimize Fe-loss from the charge, experiments were repeated under constant T-fO2 conditions to progressively saturate the suspension wire with Fe. Intermediate charges were dissolved in HF and the charge from the last cycle retained for detailed study. Analyses of experimental products are in progress. The HP experiments were carried out in an internally heated pressure vessel, at 50MPa and 400MPa, between 1100-1200°C and under fluid-present conditions. Glass (30-50 mg) plus 10% in mass of volatiles (H2O or H2O+CO2) were loaded in Au80Pd20 capsules. Distilled water and Ag2C2O4 (CO2 source) were weighted to give charges with xH2O initial (molar H2O / (H2O+CO2)) ranging from 1 to 0. Run durations lasted for 2-14h. Redox conditions were controlled by loading a given proportion of H2 gas in the vessel (3 bar H2 for 50MPa, 5 bar H2 for 400MPa). Experimental fH2 were determined by solid Pd-Co sensors, leading to fO2 conditions approaching NNO-1. All experiments were rapidly drop quenched and products analyzed by SEM, EMPA and µ-FTIR Spectroscopy. To overcome Fe-loss, both capsule Fe pre-saturation and charge Fe pre-enrichment were tested. The first method was shown to be time-consuming and fraught with difficulties while the second is still being developed. Consequently, the experimental data presented here were obtained with no attempt to circumvent Fe loss

  14. Deformation Twinning of a Silver Nanocrystal under High Pressure

    SciTech Connect

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

    2015-11-01

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

  15. High pressure cosmochemistry applied to major planetary interiors: Experimental studies

    NASA Technical Reports Server (NTRS)

    Nicol, M. F.; Johnson, M.; Boone, S.

    1985-01-01

    The measurement of equilibria in binary fluid-solid systems in diamond anvil cells, represents a major advance of the art of high-pressure experimentation. Vibrational spectroscopy, direct visual observations, and X-ray diffraction crystallography of materials confined in externally heated cells are the primary experimental probes being used. Adiabats in these systems are being measured in order to constrain models of heat flow in these bodies and to detect phase transitions by thermal anomalies. Other studies are directed toward interpreting high pressure reactions in these systems that are suggested by shockwave measurements, and developing methods for reaching high temperatures and high pressures of planetary interest in diamond cells. The overall objective of this project is to determine the properties of the H2-He-H2O-HN3-CH4 system and related small-molecule systems that are needed to constrain theoretical models of the interiors of the major planets.

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

    PubMed

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

    2015-11-11

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

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

    PubMed Central

    Yamada, Hiroyuki; Nagae, Takayuki; Watanabe, Nobuhisa

    2015-01-01

    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 P43212 to P43. 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. PMID:25849385

  18. Stable magnesium peroxide at high pressure.

    PubMed

    Lobanov, Sergey S; Zhu, Qiang; Holtgrewe, Nicholas; Prescher, Clemens; Prakapenka, Vitali B; Oganov, Artem R; Goncharov, Alexander F

    2015-09-01

    Rocky planets are thought to comprise compounds of Mg and O as these are among the most abundant elements, but knowledge of their stable phases may be incomplete. MgO is known to be remarkably stable to very high pressure and chemically inert under reduced condition of the Earth's lower mantle. However, in exoplanets oxygen may be a more abundant constituent. Here, using synchrotron x-ray diffraction in laser-heated diamond anvil cells, we show that MgO and oxygen react at pressures above 96 GPa and T = 2150 K with the formation of I4/mcm MgO2. Raman spectroscopy detects the presence of a peroxide ion (O2(2-)) in the synthesized material as well as in the recovered specimen. Likewise, energy-dispersive x-ray spectroscopy confirms that the recovered sample has higher oxygen content than pure MgO. Our finding suggests that MgO2 may be present together or instead of MgO in rocky mantles and rocky planetary cores under highly oxidized conditions.

  19. Stable magnesium peroxide at high pressure

    NASA Astrophysics Data System (ADS)

    Lobanov, Sergey S.; Zhu, Qiang; Holtgrewe, Nicholas; Prescher, Clemens; Prakapenka, Vitali B.; Oganov, Artem R.; Goncharov, Alexander F.

    2015-09-01

    Rocky planets are thought to comprise compounds of Mg and O as these are among the most abundant elements, but knowledge of their stable phases may be incomplete. MgO is known to be remarkably stable to very high pressure and chemically inert under reduced condition of the Earth’s lower mantle. However, in exoplanets oxygen may be a more abundant constituent. Here, using synchrotron x-ray diffraction in laser-heated diamond anvil cells, we show that MgO and oxygen react at pressures above 96 GPa and T = 2150 K with the formation of I4/mcm MgO2. Raman spectroscopy detects the presence of a peroxide ion (O22-) in the synthesized material as well as in the recovered specimen. Likewise, energy-dispersive x-ray spectroscopy confirms that the recovered sample has higher oxygen content than pure MgO. Our finding suggests that MgO2 may be present together or instead of MgO in rocky mantles and rocky planetary cores under highly oxidized conditions.

  20. Dissociation of methane under high pressure

    NASA Astrophysics Data System (ADS)

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

    2010-10-01

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

  1. Dissociation of methane under high pressure.

    PubMed

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

    2010-10-14

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

  2. Stable magnesium peroxide at high pressure.

    PubMed

    Lobanov, Sergey S; Zhu, Qiang; Holtgrewe, Nicholas; Prescher, Clemens; Prakapenka, Vitali B; Oganov, Artem R; Goncharov, Alexander F

    2015-01-01

    Rocky planets are thought to comprise compounds of Mg and O as these are among the most abundant elements, but knowledge of their stable phases may be incomplete. MgO is known to be remarkably stable to very high pressure and chemically inert under reduced condition of the Earth's lower mantle. However, in exoplanets oxygen may be a more abundant constituent. Here, using synchrotron x-ray diffraction in laser-heated diamond anvil cells, we show that MgO and oxygen react at pressures above 96 GPa and T = 2150 K with the formation of I4/mcm MgO2. Raman spectroscopy detects the presence of a peroxide ion (O2(2-)) in the synthesized material as well as in the recovered specimen. Likewise, energy-dispersive x-ray spectroscopy confirms that the recovered sample has higher oxygen content than pure MgO. Our finding suggests that MgO2 may be present together or instead of MgO in rocky mantles and rocky planetary cores under highly oxidized conditions. PMID:26323635

  3. Stable magnesium peroxide at high pressure

    PubMed Central

    Lobanov, Sergey S.; Zhu, Qiang; Holtgrewe, Nicholas; Prescher, Clemens; Prakapenka, Vitali B.; Oganov, Artem R.; Goncharov, Alexander F.

    2015-01-01

    Rocky planets are thought to comprise compounds of Mg and O as these are among the most abundant elements, but knowledge of their stable phases may be incomplete. MgO is known to be remarkably stable to very high pressure and chemically inert under reduced condition of the Earth’s lower mantle. However, in exoplanets oxygen may be a more abundant constituent. Here, using synchrotron x-ray diffraction in laser-heated diamond anvil cells, we show that MgO and oxygen react at pressures above 96 GPa and T = 2150 K with the formation of I4/mcm MgO2. Raman spectroscopy detects the presence of a peroxide ion (O22−) in the synthesized material as well as in the recovered specimen. Likewise, energy-dispersive x-ray spectroscopy confirms that the recovered sample has higher oxygen content than pure MgO. Our finding suggests that MgO2 may be present together or instead of MgO in rocky mantles and rocky planetary cores under highly oxidized conditions. PMID:26323635

  4. Dissociation of methane under high pressure.

    PubMed

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

    2010-10-14

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

  5. Method of producing a high pressure gas

    DOEpatents

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

    2006-07-18

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

  6. High Pressure Electrochemistry: Application to silver halides

    NASA Astrophysics Data System (ADS)

    Havens, K.; Kavner, A.

    2007-12-01

    constrain thermodynamic models of pressure-dependent electrochemical behavior of materials, which may then be applied to the high temperature, high pressure mineral phases of the deep Earth and planets.

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

    NASA Astrophysics Data System (ADS)

    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.

  8. Design of high pressure waterjet nozzles

    NASA Technical Reports Server (NTRS)

    Mazzoleni, Andre P.

    1994-01-01

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

  9. Design of high pressure waterjet nozzles

    NASA Astrophysics Data System (ADS)

    Mazzoleni, Andre P.

    1994-10-01

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

  10. Cagelike diamondoid nitrogen at high pressures.

    PubMed

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

    2012-10-26

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

  11. Cagelike diamondoid nitrogen at high pressures.

    PubMed

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

    2012-10-26

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

  12. High pressure processing for food safety.

    PubMed

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

    2005-01-01

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

  13. Manufacturing Diamond Under Very High Pressure

    NASA Technical Reports Server (NTRS)

    Voronov, Oleg

    2007-01-01

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

  14. Exploration of the pyrazinamide polymorphism at high pressure.

    PubMed

    Tan, Xiao; Wang, Kai; Li, Shourui; Yuan, Hongsheng; Yan, Tingting; Liu, Jing; Yang, Ke; Liu, Bingbing; Zou, Guangtian; Zou, Bo

    2012-12-13

    We report the high-pressure response of three forms (α, δ, and γ) of pyrazinamide (C(5)H(5)N(3)O, PZA) by in situ Raman spectroscopy and synchrotron X-ray diffraction techniques with a pressure of about 14 GPa. These different forms are characterized by various intermolecular bonding schemes. High-pressure experimental results show that the γ phase undergoes phase transition to the β phase at a pressure of about 4 GPa, whereas the other two forms retain their original structures at a high pressure. We propose that the stabilities of the α and δ forms upon compression are due to the special dimer connection that these forms possess. On the other hand, the γ form, which does not have this connection, prefers to transform to the closely related β form when pressure is applied. The detailed mechanism of the phase transition together with the stability of the three polymorphs is discussed by taking molecular stacking into account. PMID:23176640

  15. Preparation of macroporous zirconia monoliths from ionic precursors via an epoxide-mediated sol-gel process accompanied by phase separation

    NASA Astrophysics Data System (ADS)

    Guo, Xingzhong; Song, Jie; Lvlin, Yixiu; Nakanishi, Kazuki; Kanamori, Kazuyoshi; Yang, Hui

    2015-04-01

    Monolithic macroporous zirconia (ZrO2) derived from ionic precursors has been successfully fabricated via the epoxide-mediated sol-gel route accompanied by phase separation in the presence of propylene oxide (PO) and poly(ethylene oxide) (PEO). The addition of PO used as an acid scavenger mediates the gelation, whereas PEO enhances the polymerization-induced phase separation. The appropriate choice of the starting compositions allows the production of a macroporous zirconia monolith with a porosity of 52.9% and a Brunauer-Emmett-Teller (BET) surface area of 171.9 m2 · g-1. The resultant dried gel is amorphous, whereas tetragonal ZrO2 and monoclinic ZrO2 are precipitated at 400 and 600 °C, respectively, without spoiling the macroporous morphology. After solvothermal treatment with an ethanol solution of ammonia, tetragonal ZrO2 monoliths with smooth skeletons and well-defined mesopores can be obtained, and the BET surface area is enhanced to 583.8 m2 · g-1.

  16. A simplified model of high pressure spray combustion

    NASA Technical Reports Server (NTRS)

    Mao, C.-P.; Wakamatsu, Y.; Faeth, G. M.

    1981-01-01

    A simplified model of high-pressure spray combustion is examined. The analysis relies on a kappa-epsilon-g turbulence model in conjunction with the locally homogeneous flow (LHF) approximation of two-phase flow, which implies infinitely fast transport rates between the phases. High-pressure phenomena near the thermodynamic critical point are treated using the Redlich-Kwong equation of state. Predictions are compared with existing measurements of spray boundaries in a pressure-atomized n-pentane spray (Sauter mean diameter, approximately 30 microns) burning in stagnant air at 3, 6, and 9 MPa. The LHF model overestimates the rate of development of the flow, yielding spray lengths roughly 20% shorter than measured. Calibrated drop-life-history calculations suggest that finite interphase transport rates are the primary cause of the discrepancy.

  17. Chemical Vapor Deposition at High Pressure in a Microgravity Environment

    NASA Technical Reports Server (NTRS)

    McCall, Sonya; Bachmann, Klaus; LeSure, Stacie; Sukidi, Nkadi; Wang, Fuchao

    1999-01-01

    In this paper we present an evaluation of critical requirements of organometallic chemical vapor deposition (OMCVD) at elevated pressure for a channel flow reactor in a microgravity environment. The objective of using high pressure is to maintain single-phase surface composition for materials that have high thermal decomposition pressure at their optimum growth temperature. Access to microgravity is needed to maintain conditions of laminar flow, which is essential for process analysis. Based on ground based observations we present an optimized reactor design for OMCVD at high pressure and reduced gravity. Also, we discuss non-intrusive real-time optical monitoring of flow dynamics coupled to homogeneous gas phase reactions, transport and surface processes. While suborbital flights may suffice for studies of initial stages of heteroepitaxy experiments in space are essential for a complete evaluation of steady-state growth.

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

  19. High pressure structural studies on nanophase praseodymium oxide

    NASA Astrophysics Data System (ADS)

    Saranya, L.; Chandra Shekar, N. V.; Amirthapandian, S.; Hussain, Shamima; Arulraj, A.; Sahu, P. Ch.

    2014-09-01

    The phase stability of nanocrystalline Pr2O3 has been investigated under pressure by in-situ high pressure X-ray diffraction using Mao-Bell type diamond anvil cell. The ambient structure and phase of the praseodymium oxide have been resolved unambiguously using x-ray diffraction, SEM and TEM techniques. Under the action of pressure the cubic phase of the system is retained up to 15 GPa. This is unusual as other isostructural rare earth oxides show structural transformations even at lower pressures. From the best fit to the P-V data with the Murnaghan equation of state yields a bulk modulus of 171 GPa.

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

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

    NASA Astrophysics Data System (ADS)

    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

  2. Synthetic chemistry with periodic mesostructures at high pressure.

    PubMed

    Mandal, Manik; Landskron, Kai

    2013-11-19

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

  3. High-Pressure, Solid-State Experiments for NIF

    SciTech Connect

    Remington, B; Belak, J; Colvin, J; Edwards, J; Kalantar, D; Lasinski, B; Pollaine, S; Shay, H; Weber, S; Wolfer, B

    2001-02-15

    In this report, we summarize our plan for using NIF for measuring solid-state deformation physics at very high pressures, P >> 1 Mbar. There are several key uncertainties, the strength and phase being two of them. The deformation mechanisms at high pressure and high strain rate are also uncertain. The state, as well as strength, of a material that has first been melted, then dynamically refrozen by high-pressure compression is very uncertain. There is no single facility that can address all of these issues at all parameter regimes of interest. Rather, a coordinated plan involving multiple laboratories and universities and multiple facilities will ultimately be needed. We present here our first thoughts for the NIF component of this effort. In Sec. I, we motivate the physics of this regime, and point out the uncertainties, then describe in Sec. II the development work that we have done over the last 5 years in this area. In Sec. III, we describe several NIF designs we have developed to probe solid-state deformation physics at very high pressures.

  4. Nonmetallization and band inversion in beryllium dicarbide at high pressure

    NASA Astrophysics Data System (ADS)

    Du, Henan; Feng, Wanxiang; Li, Fei; Wang, Dashuai; Zhou, Dan; Liu, Yanhui

    2016-05-01

    Carbides have attracted much attention owing to their interesting physical and chemical properties. Here, we systematically investigated global energetically stable structures of BeC2 in the pressure range of 0–100 GPa using a first-principles structural search. A transition from the ambient-pressure α-phase to the high-pressure β-phase was theoretically predicted. Chemical bonding analysis revealed that the predicted phase transition is associated with the transformation from sp2 to sp3 C-C hybridization. The electrical conductivity of the high-pressure phase changed from a metal (α-phase) to a narrow bandgap semiconductor (β-phase), and the β-phase had an inverted band structure with positive pressure dependence. Interestingly, the β-phase was a topological insulator with the metallic surface states protected by the time-reversal symmetry of the crystal. The results indicate that pressure modulates the electronic band structure of BeC2, which is an important finding for fundamental physics and for a wide range of potential applications in electronic devices.

  5. Nonmetallization and band inversion in beryllium dicarbide at high pressure

    PubMed Central

    Du, Henan; Feng, Wanxiang; Li, Fei; Wang, Dashuai; Zhou, Dan; Liu, Yanhui

    2016-01-01

    Carbides have attracted much attention owing to their interesting physical and chemical properties. Here, we systematically investigated global energetically stable structures of BeC2 in the pressure range of 0–100 GPa using a first-principles structural search. A transition from the ambient-pressure α-phase to the high-pressure β-phase was theoretically predicted. Chemical bonding analysis revealed that the predicted phase transition is associated with the transformation from sp2 to sp3 C-C hybridization. The electrical conductivity of the high-pressure phase changed from a metal (α-phase) to a narrow bandgap semiconductor (β-phase), and the β-phase had an inverted band structure with positive pressure dependence. Interestingly, the β-phase was a topological insulator with the metallic surface states protected by the time-reversal symmetry of the crystal. The results indicate that pressure modulates the electronic band structure of BeC2, which is an important finding for fundamental physics and for a wide range of potential applications in electronic devices. PMID:27198492

  6. Nonmetallization and band inversion in beryllium dicarbide at high pressure.

    PubMed

    Du, Henan; Feng, Wanxiang; Li, Fei; Wang, Dashuai; Zhou, Dan; Liu, Yanhui

    2016-01-01

    Carbides have attracted much attention owing to their interesting physical and chemical properties. Here, we systematically investigated global energetically stable structures of BeC2 in the pressure range of 0-100 GPa using a first-principles structural search. A transition from the ambient-pressure α-phase to the high-pressure β-phase was theoretically predicted. Chemical bonding analysis revealed that the predicted phase transition is associated with the transformation from sp(2) to sp(3) C-C hybridization. The electrical conductivity of the high-pressure phase changed from a metal (α-phase) to a narrow bandgap semiconductor (β-phase), and the β-phase had an inverted band structure with positive pressure dependence. Interestingly, the β-phase was a topological insulator with the metallic surface states protected by the time-reversal symmetry of the crystal. The results indicate that pressure modulates the electronic band structure of BeC2, which is an important finding for fundamental physics and for a wide range of potential applications in electronic devices. PMID:27198492

  7. High pressure synthesis gas conversion. Task 1, System construction

    SciTech Connect

    Not Available

    1992-01-01

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

  8. Formation Process of High-Pressure Silica Polymorphs in Lunar Meteorites of the NWA 773 Clan

    NASA Astrophysics Data System (ADS)

    Kayama, M.; Tomioka, N.; Seto, Y.; Ohtani, E.; Nagaoka, H.; Fagan, T. J.; Ozawa, S.; Sekine, T.; Miyahara, M.; Miyake, A.; Tomeoka, K.

    2016-08-01

    Recent studies of lunar samples discovered high-pressure phases of silica in Asuka-881757, NWA 4734 and Apollo 15299. Here, we first discovered high-pressure silica from lunar meteorite NWA 773 clan, constraining the shock-pressure and temperature.

  9. Reinvestigation of high pressure polymorphism in hafnium metal

    SciTech Connect

    Pandey, K. K. Sharma, Surinder M.; Gyanchandani, Jyoti; Dey, G. K.; Somayazulu, M.; Sikka, S. K.

    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.

  10. Reinvestigation of high pressure polymorphism in hafnium metal

    NASA Astrophysics Data System (ADS)

    Pandey, K. K.; Gyanchandani, Jyoti; Somayazulu, M.; Dey, G. K.; Sharma, Surinder M.; Sikka, S. K.

    2014-06-01

    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 Po = 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.

  11. Curved and conformal high-pressure vessel

    DOEpatents

    Croteau, Paul F.; Kuczek, Andrzej E.; Zhao, Wenping

    2016-10-25

    A high-pressure vessel is provided. The high-pressure vessel may comprise a first chamber defined at least partially by a first wall, and a second chamber defined at least partially by the first wall. The first chamber and the second chamber may form a curved contour of the high-pressure vessel. A modular tank assembly is also provided, and may comprise a first mid tube having a convex geometry. The first mid tube may be defined by a first inner wall, a curved wall extending from the first inner wall, and a second inner wall extending from the curved wall. The first inner wall may be disposed at an angle relative to the second inner wall. The first mid tube may further be defined by a short curved wall opposite the curved wall and extending from the second inner wall to the first inner wall.

  12. High pressure electrical insulated feed thru connector

    DOEpatents

    Oeschger, Joseph E.; Berkeland, James E.

    1979-11-13

    A feed-thru type hermetic electrical connector including at least one connector pin feeding through an insulator block within the metallic body of the connector shell. A compression stop arrangement coaxially disposed about the insulator body is brazed to the shell, and the shoulder on the insulator block bears against this top in a compression mode, the high pressure or internal connector being at the opposite end of the shell. Seals between the pin and an internal bore at the high pressure end of the insulator block and between the insulator block and the metallic shell at the high pressure end are hermetically brazed in place, the first of these also functioning to transfer the axial compressive load without permitting appreciable shear action between the pin and insulator block.

  13. High-pressure distillation is different

    SciTech Connect

    Brierley, R.J.P.

    1994-07-01

    Many fluid systems perform differently at higher pressures than at lower ones. This makes high-pressure distillation different, too. But it also offers significant opportunities to engineers, both those deciding on the types of equipment to specify at the design stage, and those responsible for making high-pressure columns work, getting the best out of them, and assessing whether they can be uprated. Indeed, in a number of cases, it has been possible to uprate columns substantially (in one case by 70%) by redesign of the trays, and by replacement of trays with packing. This article provides practical guidance, based on the author's 20 years of experience as a distillation specialist, on how to get the best out of high-pressure distillation.

  14. Layered polymeric nitrogen in RbN3 at high pressures

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoli; Li, Jianfu; Xu, Ning; Zhu, Hongyang; Hu, Ziyu; Chen, Li

    2015-11-01

    The structural evolutionary behaviors of nitrogen in RbN3 have been studied up to 300 GPa using a particle swarm optimization structure searching method combined with density functional calculations. Three stable new phases with P-1, P6/mmm and C2/m structure at pressure of 30, 50 and 200 GPa are identified for the first time. The analysis of the crystal structures of three new predicated phases reveals that the transition of N3- ions goes from linear molecules to polymeric chains, benzene-like rings and then to polymeric layers induced by pressure. The electronic structures of three predicted phases reveal that the structural changes are accompanied and driven by the change of orbital hybridization of N atoms from sp to sp2 and finally to partial sp3. Most interestingly, the Rb atoms show obvious transition metal-like properties through the occupation of 4d orbitals in high-pressure phases. Moreover, the Rb atoms are characterized by strong hybridization between 4d orbitals of Rb and 2p orbitals of N in C2/m structure. Our studies complete the structural evolution of RbN3 under pressure and reveal for the first time that the Rb atoms in rubidium nitride possess transition element-like properties under pressure.

  15. Layered polymeric nitrogen in RbN3 at high pressures.

    PubMed

    Wang, Xiaoli; Li, Jianfu; Xu, Ning; Zhu, Hongyang; Hu, Ziyu; Chen, Li

    2015-01-01

    The structural evolutionary behaviors of nitrogen in RbN3 have been studied up to 300 GPa using a particle swarm optimization structure searching method combined with density functional calculations. Three stable new phases with P-1, P6/mmm and C2/m structure at pressure of 30, 50 and 200 GPa are identified for the first time. The analysis of the crystal structures of three new predicated phases reveals that the transition of N3- ions goes from linear molecules to polymeric chains, benzene-like rings and then to polymeric layers induced by pressure. The electronic structures of three predicted phases reveal that the structural changes are accompanied and driven by the change of orbital hybridization of N atoms from sp to sp(2) and finally to partial sp(3). Most interestingly, the Rb atoms show obvious transition metal-like properties through the occupation of 4d orbitals in high-pressure phases. Moreover, the Rb atoms are characterized by strong hybridization between 4d orbitals of Rb and 2p orbitals of N in C2/m structure. Our studies complete the structural evolution of RbN3 under pressure and reveal for the first time that the Rb atoms in rubidium nitride possess transition element-like properties under pressure. PMID:26564812

  16. Layered polymeric nitrogen in RbN3 at high pressures

    PubMed Central

    Wang, Xiaoli; Li, Jianfu; Xu, Ning; Zhu, Hongyang; Hu, Ziyu; Chen, Li

    2015-01-01

    The structural evolutionary behaviors of nitrogen in RbN3 have been studied up to 300 GPa using a particle swarm optimization structure searching method combined with density functional calculations. Three stable new phases with P-1, P6/mmm and C2/m structure at pressure of 30, 50 and 200 GPa are identified for the first time. The analysis of the crystal structures of three new predicated phases reveals that the transition of N3− ions goes from linear molecules to polymeric chains, benzene-like rings and then to polymeric layers induced by pressure. The electronic structures of three predicted phases reveal that the structural changes are accompanied and driven by the change of orbital hybridization of N atoms from sp to sp2 and finally to partial sp3. Most interestingly, the Rb atoms show obvious transition metal-like properties through the occupation of 4d orbitals in high-pressure phases. Moreover, the Rb atoms are characterized by strong hybridization between 4d orbitals of Rb and 2p orbitals of N in C2/m structure. Our studies complete the structural evolution of RbN3 under pressure and reveal for the first time that the Rb atoms in rubidium nitride possess transition element-like properties under pressure. PMID:26564812

  17. High pressure water jet mining machine

    DOEpatents

    Barker, Clark R.

    1981-05-05

    A high pressure water jet mining machine for the longwall mining of coal is described. The machine is generally in the shape of a plowshare and is advanced in the direction in which the coal is cut. The machine has mounted thereon a plurality of nozzle modules each containing a high pressure water jet nozzle disposed to oscillate in a particular plane. The nozzle modules are oriented to cut in vertical and horizontal planes on the leading edge of the machine and the coal so cut is cleaved off by the wedge-shaped body.

  18. High pressure water jet cutting and stripping

    NASA Technical Reports Server (NTRS)

    Hoppe, David T.; Babai, Majid K.

    1991-01-01

    High pressure water cutting techniques have a wide range of applications to the American space effort. Hydroblasting techniques are commonly used during the refurbishment of the reusable solid rocket motors. The process can be controlled to strip a thermal protective ablator without incurring any damage to the painted surface underneath by using a variation of possible parameters. Hydroblasting is a technique which is easily automated. Automation removes personnel from the hostile environment of the high pressure water. Computer controlled robots can perform the same task in a fraction of the time that would be required by manual operation.

  19. Superelastic carbon spheres under high pressure

    NASA Astrophysics Data System (ADS)

    Li, Meifen; Guo, Junjie; Xu, Bingshe

    2013-03-01

    We report a superelastic deformation behavior of carbon spheres by the in situ Raman spectroscopy in a high-pressure diamond anvil cell. The carbon spheres produced by arc discharging in toluene have a mean diameter of 200 nm and an onion-like multilayer graphitic structure. We find that the elastic coefficients, during both the compression and decompression processes, remain a constant up to 10 GPa, indicating a superior high-pressure structural stability. Such superelastic behavior is related to the isotropic and concentric configuration of carbon spheres and provides additional insight into improving the microscopic mechanical properties of small-scale particles.

  20. High pressure freon decontamination of remote equipment

    SciTech Connect

    Wilson, C.E.

    1987-01-01

    A series of decontamination tests using high pressure FREON 113 was conducted in the 200 Area of the Hanford site. The intent of these tests was to evaluate the effectiveness of FREON 113 in decontamination of manipulator components, tools, and equipment items contaminated with mixed fission products. The test results indicated that high pressure FREON 113 is very effective in removing fissile material from a variety of objects and can reduce both the quantity and the volume of the radioactive waste material presently being buried.

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

    PubMed

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

    2015-09-10

    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 pressures. The first is observed at 0.39 GPa, where both phases were observed simultaneously and confirm our previous observations. This transition is followed by a second transition at 1.2 GPa to a new polymorph that is characterized for the first time. On increasing pressure, the diffraction pattern of phase III deteriorates significantly. On decompression phase III persists to 0.54 GPa before transformation to the ambient pressure phase. There is significant loss of signal after decompression, signifying that there has been a loss of material through polymerization. The orientation of the molecules in phase III provides insight into the possible polymerization reaction. PMID:26289930

  2. Vanadium and V-Ti alloys at high pressure

    NASA Astrophysics Data System (ADS)

    Jenei, Zsolt; Cynn, Hyunchae; Evans, William J.; MacLeod, Simon; Sinogeikin, Stanislav; Meng, Yue

    2013-03-01

    Experimental studies of vanadium found that during compression it undergoes a phase transition from the low pressure body centered cubic crystal structure to a rhombohedral phase at 65 GPa when compressed under quasihydrostatic conditions (PRB 83, 054101). Theoretical studies are in reasonable agreement with the transition pressure and predict that upon further compression above 200 GPa the bcc phase becomes stable again. The latest study (PRL 103, 235501) predicts that alloying vanadium with small amounts of the neighboring elements can increase or decrease the stability of the bcc phase relative to the rhombohedral phase. We performed powder x-ray diffraction experiments in diamond anvil cell of pure vanadium and V-Ti alloys at ambient temperature to very high pressures. We will discuss our results, including the equation of state and the stability of the rhombohedral phase at high pressures. This work performed under the auspices of the US DOE by LLNL under Contract DE-AC52-07NA27344. HPCAT use is supported by DOE-BES, DOE-NNSA, NSF, and the W.M. Keck Foundation. APS is supported by DOE-BES, under Contract No. DE-AC02-06CH11357.

  3. Small, high-pressure liquid hydrogen turbopump

    NASA Technical Reports Server (NTRS)

    Csomor, A.; Sutton, R.

    1977-01-01

    A high pressure, liquid hydrogen turbopump was designed, fabricated, and tested to a maximum speed of 9739 rad/s and a maximum pump discharge pressure of 2861 N/sq. cm. The approaches used in the analysis and design of the turbopump are described, and fabrication methods are discussed. Data obtained from gas generator tests, turbine performance calibration, and turbopump testing are presented.

  4. High Pressure Solution Kinetics of Metal Complexes.

    ERIC Educational Resources Information Center

    Suvachittanont, Surapong

    1983-01-01

    Describes use of activation volumes derived from the effect of pressure reaction rates in aiding the understanding of reaction mechanism. Topics discussed include determination and interpretation of activation volumes, high pressure equipment/techniques, and application of activation volumes in mechanistic elucidation of several inorganic…

  5. High-pressure differential scanning microcalorimeter.

    PubMed

    Senin, A A; Dzhavadov, L N; Potekhin, S A

    2016-03-01

    A differential scanning microcalorimeter for studying thermotropic conformational transitions of biopolymers at high pressure has been designed. The calorimeter allows taking measurements of partial heat capacity of biopolymer solutions vs. temperature at pressures up to 3000 atm. The principles of operation of the device, methods of its calibration, as well as possible applications are discussed. PMID:27036806

  6. High Pressure Inactivation of HAV within Mussels

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The potential of hepatitis A virus (HAV) to be inactivated within Mediterranean mussels (Mytilus galloprovincialis) and blue mussels (Mytilus edulis) by high pressure processing was evaluated. HAV was bioaccumulated within mussels to approximately 6-log10 PFU by exposure of mussels to HAV-contamina...

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

    SciTech Connect

    Tolbert, S.H.

    1995-05-01

    High-pressure Se EXAFS is used to study pressure-induced structural transformations in CdSe nanocrystals. The transformation is wurtzite to rock salt, at a pressure much higher than in bulk. High-pressure XRD is used to confirm the EXAFS results. Diffraction peak widths indicate that nanocrystals do not fragment upon transformation. Optical absorption correlates with structural transformations and is used to measure transition pressures; transformation pressure increases smoothly as nanocrystal size decreases. Thermodynamics of transformation is modeled using an elevated surface energy in the high-pressure phase. High-pressure study of Si nanocrystals show large increases in transformation pressure in crystallites to 500{angstrom} diameter, and an overall change in crystallite shape upon transformation is seen from XRD line widths. C{sub 60} single crystals were studied using Raman scattering; results provide information about the clusters` rotational state. Optical properties of high-pressure phase CdSe clusters were studied.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  10. Investigation of Acrylic Acid at High Pressure Using Neutron Diffraction

    PubMed Central

    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 rationalized using the Pixel method. Acrylic acid undergoes a reconstructive phase transition to a new phase at ∼0.8 GPa and remains molecular to 7.2 GPa before polymerizing on decompression to ambient pressure. The resulting product is analyzed via Raman and FT-IR spectroscopy and differential scanning calorimetry and found to possess a different molecular structure compared with polymers produced via traditional routes. PMID:24650085

  11. High pressure and high temperature behaviour of ZnO

    SciTech Connect

    Thakar, Nilesh A.; Bhatt, Apoorva D.; Pandya, Tushar C.

    2014-04-24

    The thermodynamic properties with the wurtzite (B4) and rocksalt (B1) phases of ZnO under high pressures and high temperatures have been investigated using Tait's Equation of state (EOS). The effects of pressures and temperatures on thermodynamic properties such as bulk modulus, thermal expansivity and thermal pressure are explored for both two structures. It is found that ZnO material gradually softens with increase of temperature while it hardens with the increment of the pressure. Our predicted results of thermodynamics properties for both the phases of ZnO are in overall agreement with the available data in the literature.

  12. Structural Behaviour of Uranium Sulfide under High Pressure

    SciTech Connect

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

    2011-07-15

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

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

    PubMed

    Kloss, Simon David; Schnick, Wolfgang

    2015-09-14

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

  14. High-pressure synthesis and compressive behavior of tantalum nitrides

    SciTech Connect

    Yusa, Hitoshi Kawamura, Fumio; Taniguchi, Takashi; Hirao, Naohisa; Ohishi, Yasuo; Kikegawa, Takumi

    2014-03-14

    WC- and NaCl-type tantalum mononitrides and hexagonal Ta{sub 5}N{sub 6} were prepared at high pressure and temperature, and their compressive behaviors were examined using in situ high-pressure X-ray diffraction. Comparison of the formula volumes of the tantalum mononitrides indicated that the NaCl type was the densest phase. The P–V data showed that the WC-type structure had the highest bulk modulus value (K{sub 0} = 351(1) GPa). An analysis of the compression properties in terms of the crystallographic characteristics of the structures indicated that a prismatic polyhedral array with face-sharing connectivity was responsible for the incompressible nature of these tantalum nitrides.

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

    PubMed

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

    2011-01-01

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

  16. High-pressure combinatorial process integrating hot isostatic pressing.

    PubMed

    Fujimoto, Kenjiro; Morita, Hiroki; Goshima, Yuji; Ito, Shigeru

    2013-12-01

    A high-pressure combinatorial process integrating hot isostatic pressing (HIP) was developed by providing a reaction vessel with a high-pressure tightness based on a commercial flange. The reaction vessel can be used up to 200 MPa and 500 °C under HIP processing condition. Preparation of spinel-type MgAl2O4 from Mg(OH)2, Al(OH)3 and AlOOH was performed using the reaction vessel under 200 MPa and 500 °C as demonstration. The entire powder library was characterized using powder X-ray diffraction patterns, and the single phase of spinel-type MgAl2O4 was obtained from Mg(OH)2+Al(OH)3. These assessments corresponded with previously published data. PMID:24168067

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

    PubMed

    Kloss, Simon David; Schnick, Wolfgang

    2015-09-14

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

  18. High pressure and Multiferroics materials. A happy marriage

    DOE PAGES

    Gilioli, Edmondo; Ehm, Lars

    2014-10-31

    We found that 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. Moreover, the in situ investigation of the high-pressure behavior of multiferroic materials has provided insight into the complex interplay between magnetic and electronic properties andmore » the coupling to structural instabilities.« less

  19. High-pressure liquid chromatography of caffeine in coffee.

    PubMed

    Madison, B L; Kozarek, W J; Damo, C P

    1976-11-01

    A new method is described for the determination of caffeine in coffee, based on high-pressure liquid chromatography. The caffeine is extracted from the sample with water and/or methylene chloride, and then separated from interfering materials by passing an aliquot of the extract through a high-pressure column containing sulfonated cation exchange resin, using 0.01M nitric acid as the mobile phase. An ultraviolet detector measures the absorption of the solution directly. The method is rapid and eliminates the lengthy separations common to other methods. The procedure was applied successfully to decaffeinated and non-decaffeinated green, roasted, and instant coffees. This method gives a more accurate measure of the caffeine content in decaffeinated coffee samples than the micro Bailey-Andrew and modified Levine methods, with equal or better precision. This method gives results equal to those obtained by the official methods for non-decaffeinated samples. PMID:993180

  20. Stability and properties of liquid CO2 at high pressure and high temperature: Implications for electrical conductivities in Earth's lower mantle

    NASA Astrophysics Data System (ADS)

    Wu, Min; Tse, John S.; Pan, Yuanming

    2015-07-01

    Carbon dioxide (CO2), one of the most important planetary materials, has been the subject of extensive experimental and theoretical studies. However, the stabilities and properties of CO2 at high pressures and temperatures relevant to Earth's mantle and core remain controversial. We have studied the molten structures of CO2-V with first-principles molecular dynamic calculations at 60 GPa and different temperatures. The formation of oxygen molecules in the melt is consistent with experimental observations. In particular, the melting transition is accompanying by metallization. The metallic behavior is shown to originate from electron delocalization between oxygen via the overlap of the π orbitals from the dissociated oxygen-rich species. Metallic molten CO2 is a potential candidate to explain the high conductivities of the Earth's lower mantle. Furthermore, theoretical results do not support the existence of the proposed ionic solid phase of CO2 at high temperature and high pressure.

  1. High pressure synthesis gas fermentation. [Quarterly status] report, October 15, 1991--January 14, 1992

    SciTech Connect

    Not Available

    1992-09-01

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

  2. Role of structural barriers for carotenoid bioaccessibility upon high pressure homogenization.

    PubMed

    Palmero, Paola; Panozzo, Agnese; Colle, Ines; Chigwedere, Claire; Hendrickx, Marc; Van Loey, Ann

    2016-05-15

    A specific approach to investigate the effect of high pressure homogenization on the carotenoid bioaccessibility in tomato-based products was developed. Six different tomato-based model systems were reconstituted in order to target the specific role of the natural structural barriers (chromoplast substructure/cell wall) and of the phases (soluble/insoluble) in determining the carotenoid bioaccessibility and viscosity changes upon high pressure homogenization. Results indicated that in the absence of natural structural barriers (carotenoid enriched oil), the soluble and insoluble phases determined the carotenoid bioaccessibility upon processing whereas, in their presence, these barriers governed the bioaccessibility. Furthermore, it was shown that the increment of the viscosity upon high pressure homogenization is determined by the presence of insoluble phase, however, this result was related to the initial ratio of the soluble:insoluble phases in the system. In addition, no relationship between the changes in viscosity and carotenoid bioaccessibility upon high pressure homogenization was found.

  3. On the atomic line profiles in high pressure plasmas

    SciTech Connect

    Janssen, J. F. J.; Gnybida, M.; Rijke, A. J.; Dijk, J. van; Suijker, J. L. G.

    2013-11-14

    In a previous contribution to this journal [H. P. Stormberg, J. Appl. Phys. 51(4), 1963 (1980)], Stormberg presented an analytical expression for the convolution of Lorentz and Levy line profiles, which models atomic radiative transitions in high pressure plasmas. Unfortunately, the derivations are flawed with errors and the final expression, while correct, is accompanied by misguiding comments about the meaning of the symbols used therein, in particular the “complex error function.” In this paper, we discuss the broadening mechanisms that give rise to Stormberg's model and present a correct derivation of his final result. We will also provide an alternative expression, based on the Faddeeva function, which has decisive computational advantages and emphasizes the real-valuedness of the result. The MATLAB/Octave scripts of our implementation have been made available on the publisher's website for future reference.

  4. On the atomic line profiles in high pressure plasmas

    NASA Astrophysics Data System (ADS)

    Janssen, J. F. J.; Gnybida, M.; Suijker, J. L. G.; Rijke, A. J.; van Dijk, J.

    2013-11-01

    In a previous contribution to this journal [H. P. Stormberg, J. Appl. Phys. 51(4), 1963 (1980)], Stormberg presented an analytical expression for the convolution of Lorentz and Levy line profiles, which models atomic radiative transitions in high pressure plasmas. Unfortunately, the derivations are flawed with errors and the final expression, while correct, is accompanied by misguiding comments about the meaning of the symbols used therein, in particular the "complex error function." In this paper, we discuss the broadening mechanisms that give rise to Stormberg's model and present a correct derivation of his final result. We will also provide an alternative expression, based on the Faddeeva function, which has decisive computational advantages and emphasizes the real-valuedness of the result. The MATLAB/Octave scripts of our implementation have been made available on the publisher's website for future reference.

  5. Optical calibration of pressure sensors for high pressures and temperatures

    SciTech Connect

    Goncharov, A F; Gregoryanz, E; Zaug, J M; Crowhurst, J C

    2004-10-04

    We present the results of Raman scattering measurements of diamond ({sup 12}C) and of cubic boron nitride (cBN), and fluorescence measurements of ruby, Sm:YAG, and SrB{sub 4}O{sub 7}:Sm{sup 2+} in the diamond anvil cell (DAC) at high pressures and temperatures. These measurements were accompanied by synchrotron x-ray diffraction measurements on gold. We have extended the room-temperature calibration of Sm:YAG in a quasihydrostatic regime up to 100 GPa. The ruby scale is shown to systematically underestimate pressure at high pressures and temperatures compared with all other sensors. On this basis, we propose a new high-temperature ruby pressure scale that should be valid to at least 100 GPa and 850 K. Historically, the accurate determination of pressure at high temperature and ultrahigh pressure has been extremely difficult. In fact, the lack of a general pressure scale nullifies, to a significant extent, the great innovations that have been made in recent years in DAC experimental techniques [1]. Now, more than ever a scale is required whose accuracy is comparable with that of the experimental data. Since pressure in the DAC is dependent on temperature (due to thermal pressure and also to changes in the properties of the materials that constitute the DAC) such a scale requires quantitative, and separate measurements of pressure and temperature.

  6. First-principles calculations of high-pressure phase transition of TiO2 during decompression: From baddeleyite-type TiO2 to α-PbO2-type TiO2

    NASA Astrophysics Data System (ADS)

    Murata, Hidenobu; Taniguchi, Takashi; Tanaka, Isao

    2016-10-01

    First-principles calculations were used to investigate the phase transition from baddeleyite-type to α-PbO2-type TiO2 during decompression. An intermediate structure was found, and its space group is Pbc21, which is polarized along [001]. The phase transition was mainly caused by oxygen diffusion, which has low activation energy for the phase transition. The activation energy increased as the pressure decreased. These results suggest that rapid decompression and preventing oxygen diffusion would be an effective way of recovering baddeleyite-type TiO2.

  7. Sample injector for high pressure liquid chromatography

    DOEpatents

    Paul, Phillip H.; Arnold, Don W.; Neyer, David W.

    2001-01-01

    Apparatus and method for driving a sample, having a well-defined volume, under pressure into a chromatography column. A conventional high pressure sampling valve is replaced by a sample injector composed of a pair of injector components connected in series to a common junction. The injector components are containers of porous dielectric material constructed so as to provide for electroosmotic flow of a sample into the junction. At an appropriate time, a pressure pulse from a high pressure source, that can be an electrokinetic pump, connected to the common junction, drives a portion of the sample, whose size is determined by the dead volume of the common junction, into the chromatographic column for subsequent separation and analysis. The apparatus can be fabricated on a substrate for microanalytical applications.

  8. Design guide for high pressure oxygen systems

    NASA Technical Reports Server (NTRS)

    Bond, A. C.; Pohl, H. O.; Chaffee, N. H.; Guy, W. W.; Allton, C. S.; Johnston, R. L.; Castner, W. L.; Stradling, J. S.

    1983-01-01

    A repository for critical and important detailed design data and information, hitherto unpublished, along with significant data on oxygen reactivity phenomena with metallic and nonmetallic materials in moderate to very high pressure environments is documented. This data and information provide a ready and easy to use reference for the guidance of designers of propulsion, power, and life support systems for use in space flight. The document is also applicable to designs for industrial and civilian uses of high pressure oxygen systems. The information presented herein are derived from data and design practices involving oxygen usage at pressures ranging from about 20 psia to 8000 psia equal with thermal conditions ranging from room temperatures up to 500 F.

  9. Wound cleansing by high pressure irrigation.

    PubMed

    Rodeheaver, G T; Pettry, D; Thacker, J G; Edgerton, M T; Edlich, R F

    1975-09-01

    All traumatic wounds are contaminated to some degree by both soil and bacteria. Specific infection potentiating factors in soil impair the defenses of the tissue and invite infection. These factors are small in size and resist removal by low pressure irrigation. The efficiency of wound irrigation is markedly improved by delivering the irrigant to the wound under continuous high pressure. Irrigation of the wound with saline solution delivered at 15 pounds per square inch removed 84.8 per cent of the soil infection potentiating factors from the wound. The residual infection potentiating factors remaining in the wound did not significantly impair tissue defenses. On the basis of these experimental studies, clinical studies are now being initiated to test the therapeutic value of high pressure irrigation in traumatic wounds in humans.

  10. High pressure hydrogen time projection chamber

    SciTech Connect

    Goulianos, K.

    1983-01-01

    We describe a high pressure hydrogen gas time projection chamber which consists of two cylindrical drift regions each 45 cm in diameter and 75 cm long. Typically, at 15 atm of H/sub 2/ with 2 kV/cm drift field and 7 kV on the 35..mu.. sense wires, the drift velocity is about 0.5 cm/..mu..sec and the spatial resolution +-200..mu...

  11. High-pressure mechanical instability in rocks

    USGS Publications Warehouse

    Byerlee, J.D.; Brace, W.F.

    1969-01-01

    At a confining pressure of a few kilobars, deformation of many sedimentary rocks, altered mafic rocks, porous volcanic rocks, and sand is ductile, in that instabilities leading to audible elastic shocks are absent. At pressures of 7 to 10 kilobars, however, unstable faulting and stick-slip in certain of these rocks was observed. This high pressure-low temperature instability might be responsible for earthquakes in deeply buried sedimentary or volcanic sequences.

  12. Small, high pressure liquid hydrogen turbopump

    NASA Technical Reports Server (NTRS)

    Csomor, A.; Warren, D. J.

    1980-01-01

    A high pressure, low capacity, liquid hydrogen turbopump was designed, fabricated, and tested. The design configuration of the turbopump is summarized and the results of the analytical and test efforts are presented. Approaches used to pin point the cause of poor suction performance with the original design are described and performance data are included with an axial inlet design which results in excellent suction capability.

  13. (High-pressure structural studies of promethium)

    SciTech Connect

    Haire, R.G.

    1988-11-15

    The primary object of the foreign travel was to carry out collaborative high-pressure structural studies at the European Institute for Transuranium Elements (EITU), Karlsruhe, Federal Republic of Germany. These studies reestablished previous collaborative investigations by ORNL and EITU that have been very productive scientifically during the past few years. The study during the present travel period was limited to a structural study of promethium metal under pressure.

  14. High-pressure mechanical instability in rocks.

    PubMed

    Byerlee, J D; Brace, W F

    1969-05-01

    At a confining pressure of a few kilobars, deformation of many sedimentary rocks, altered mafic rocks, porous volcanic rocks, and sand is ductile, in that instabilities leading to audible elastic shocks are absent. At pressures of 7 to 10 kilobars, however, unstable faulting and stick-slip in certain of these rocks was observed. This high pressure-low temperature instability might be responsible for earthquakes in deeply buried sedimentary or volcanic sequences.

  15. High-pressure Raman study of fully deuterated methane hydrate

    NASA Astrophysics Data System (ADS)

    Yabashi, Ryo; Yoshida, Masashi; Kume, Tetsuji; Sasaki, Shigeo

    2013-06-01

    Methane hydrate (MH: CH4- nH2O) crystallizes in a cubic structure I (sI) which consists of hydrogen-bonded water cages which enclathrate methane molecules as guests. With increasing pressure, the initial sI of MH transforms to a hexagonal structure H (sH) at 0.9 GPa, and eventually to an orthorhombic cage-less structure O at 1.9 GPa. The sH consists of three small S1, two small S2, and one large LL water cages in a hexagonal unit cell. The previous high-pressure Raman measurements for C-H stretching vibration of MH-sH indicated that the capacity of methane molecules in the large LL cage abruptly increased at 1.3 GPa, and its occupation number of methane molecule was about 2.5 above 1.3 GPa. However, this result disagrees with the previous high-pressure neutron diffraction experiments for sH of fully deutarated methane hydrate (FDMH: CD4- nD2O). To solve this discrepancy, we have carried out the high pressure Raman measurements for C-D stretching vibration in the sI and sH phases of FDMH. As a result, we have obtained the different Raman spectral patterns between FDMH and MH, which suggests that the occupancy of CD4 in water cages is somewhat different from CH4.

  16. High-pressure structural study of MnF2

    DOE PAGES

    Stavrou, Elissaios; Yao, Yansun; Goncharov, Alexander F.; Konopkova, Zuzana; Raptis, Constantine

    2015-02-01

    In this study, manganese fluoride (MnF2) with the tetragonal rutile-type structure has been studied using a synchrotron angle-dispersive powder x-ray diffraction and Raman spectroscopy in a diamond anvil cell up to 60 GPa at room temperature combined with first-principles density functional calculations. The experimental data reveal two pressure-induced structural phase transitions with the following sequence: rutile → SrI2 type (3 GPa)→ α–PbCl2 type (13 GPa). Complete structural information, including interatomic distances, has been determined in the case of MnF2 including the exact structure of the debated first high-pressure phase. First-principles density functional calculations confirm this phase transition sequence, and themore » two calculated transition pressures are in excellent agreement with the experiment. Lattice dynamics calculations also reproduce the experimental Raman spectra measured for the ambient and high-pressure phases. The results are discussed in line with the possible practical use of rutile-type fluorides in general and specifically MnF2 as a model compound to reveal the HP structural behavior of rutile-type SiO2 (Stishovite).« less

  17. High-pressure structural study of MnF2

    NASA Astrophysics Data System (ADS)

    Stavrou, Elissaios; Yao, Yansun; Goncharov, Alexander F.; Konôpková, Zuzana; Raptis, Constantine

    2016-02-01

    Manganese fluoride (MnF2) with the tetragonal rutile-type structure has been studied using a synchrotron angle-dispersive powder x-ray diffraction and Raman spectroscopy in a diamond anvil cell up to 60 GPa at room temperature combined with first-principles density functional calculations. The experimental data reveal two pressure-induced structural phase transitions with the following sequence: rutile → SrI2 type (3 GPa)→ α -PbCl2 type (13 GPa). Complete structural information, including interatomic distances, has been determined in the case of MnF2 including the exact structure of the debated first high-pressure phase. First-principles density functional calculations confirm this phase transition sequence, and the two calculated transition pressures are in excellent agreement with the experiment. Lattice dynamics calculations also reproduce the experimental Raman spectra measured for the ambient and high-pressure phases. The results are discussed in line with the possible practical use of rutile-type fluorides in general and specifically MnF2 as a model compound to reveal the HP structural behavior of rutile-type SiO2 (Stishovite).

  18. Electrical Resistivity of natural Marcasite at High-pressures

    NASA Astrophysics Data System (ADS)

    Parthasarathy, Gopalakrishnarao

    2013-06-01

    Marcasite is considered to be a common iron sulfide in reducing Martian sediments and may enclose microbial remains during growth and hence study of marcasite may have significance in the search for fossil life on Mars. The high-pressure phase stability investigations of marcasite are useful in understanding the sulfide mineralogy of Martian surface, affected by meteorite impacts. The sulfides were characterized by electron microprobe micro analyses (EPMA), powder X-ray diffraction, DTA, and FTIR spectroscopic measurements. The samples were powdered using a porcelain mortar and pestle. The chemical composition of the sample was determined by an electron probe micro-analyzer (EPMA). High-pressure electrical resistivity measurements were carried out on natural marcasite, and marcasite rich samples (Marcasite 95 mol % pyrite 5 mol %) up to 7 GPa. Marcasite sample shows a discontinuous decrease in the electrical resistivity at 5. 2 (+/- 0.5) GPa indicating a first order phase transition. The Differential thermal analyses and the Fourier transform infrared spectroscopic measurements on the pressure quenched sample shows the characteristics of pyrite, indicating the pressure induced marcasite-to -pyrite transition of the natural marcasite at 5. 2 (+/- 0.5) GPa. The observation of marcasite to pyrite phase transition may be useful in estimating the pressure experienced by shock events on the Martian surface as well as the meteorites where marcasite- pyrite phases coexist. Financial support from CSIR-SHORE-PSC0205.

  19. High-pressure layered structure of carbon disulfide

    NASA Astrophysics Data System (ADS)

    Naghavi, S. Shahab; Crespo, Yanier; MartoÅák, Roman; Tosatti, Erio

    2015-06-01

    Solid CS2 is superficially similar to CO2, with the same C m c a molecular crystal structure at low pressures, which has suggested similar phases also at high pressures. We carried out an extensive first-principles evolutionary search in order to identify the zero-temperature lowest-enthalpy structures of CS2 for increasing pressure up to 200 GPa. Surprisingly, the molecular C m c a phase does not evolve into β -cristobalite as in CO2 but transforms instead into phases HP2 and HP1, both recently described in high-pressure SiS2. HP1 in particular, with a wide stability range, is a layered P 21/c structure characterized by pairs of edge-sharing tetrahedra and is theoretically more robust than all other CS2 phases discussed so far. Its predicted Raman spectrum and pair correlation function agree with experiment better than those of β -cristobalite, and further differences are predicted between their respective IR spectra. The band gap of HP1-CS2 is calculated to close under pressure, yielding an insulator-metal transition near 50 GPa, in agreement with experimental observations. However, the metallic density of states remains modest above this pressure, suggesting a different origin for the reported superconductivity.

  20. Ionic high-pressure form of elemental boron.

    PubMed

    Oganov, Artem R; Chen, Jiuhua; Gatti, Carlo; Ma, Yanzhang; Ma, Yanming; Glass, Colin W; Liu, Zhenxian; Yu, Tony; Kurakevych, Oleksandr O; Solozhenko, Vladimir L

    2009-02-12

    Boron is an element of fascinating chemical complexity. Controversies have shrouded this element since its discovery was announced in 1808: the new 'element' turned out to be a compound containing less than 60-70% of boron, and it was not until 1909 that 99% pure boron was obtained. And although we now know of at least 16 polymorphs, the stable phase of boron is not yet experimentally established even at ambient conditions. Boron's complexities arise from frustration: situated between metals and insulators in the periodic table, boron has only three valence electrons, which would favour metallicity, but they are sufficiently localized that insulating states emerge. However, this subtle balance between metallic and insulating states is easily shifted by pressure, temperature and impurities. Here we report the results of high-pressure experiments and ab initio evolutionary crystal structure predictions that explore the structural stability of boron under pressure and, strikingly, reveal a partially ionic high-pressure boron phase. This new phase is stable between 19 and 89 GPa, can be quenched to ambient conditions, and has a hitherto unknown structure (space group Pnnm, 28 atoms in the unit cell) consisting of icosahedral B(12) clusters and B(2) pairs in a NaCl-type arrangement. We find that the ionicity of the phase affects its electronic bandgap, infrared adsorption and dielectric constants, and that it arises from the different electronic properties of the B(2) pairs and B(12) clusters and the resultant charge transfer between them.