Simultaneous High Pressure Research Articles

Elasticity and sound velocities of polycrystalline grossular garnet (Ca3Al2Si3O12) at simultaneous high pressures and high temperatures

The elastic wave velocities of a dense polycrystalline specimen (99.7% of theoretical density) of synthetic grossular garnet (Ca3Al2Si3O12) were measured to pressures of ∼10GPa and temperatures of 1000K by transfer-function ultrasonic interferometry in conjunction with energy-dispersive synchrotron X-radiation in a deformation DIA-type cubic-anvil apparatus. The calculated elastic bulk (Ks) and shear (G) moduli data were fitted to functions of Eulerian strain to 3rd order, yielding the zero-pressure values [Ks=171.2 (8)GPa; G=107.4 (2)GPa] and their pressure derivatives [(∂Ks/∂P)T=4.47 (2); (∂G/∂P)T=1.29 (5)]. The temperature dependences of the elastic moduli obtained from linear regression of entire P–T–Ks and P–T–G data are: (∂Ks/∂T)P=−1.38 (3)×10−2 GPa/K and (∂G/∂T)P=−1.28 (2)×10−2GPa/K. These results together with those from previous studies for garnets with varying compositions suggest that most of the thermo-elastic properties of garnet are insensitive to grossular content, with the exception of the shear modulus, which significantly depends on the calcium content.

Thermal equation of state of synthetic orthoferrosilite at lunar pressures and temperatures

Iron-rich orthopyroxene plays an important role in models of the thermal and magmatic evolution of the Moon, but its density at high pressure and high temperature is not well-constrained. We present in situ measurements of the unit-cell volume of a synthetic polycrystalline end-member orthoferrosilite (FeSiO3, fs) at simultaneous high pressures (3.4–4.8 GPa) and high temperatures (1,148–1,448 K), to improve constraints on the density of orthopyroxene in the lunar interior. Unit-cell volumes were determined through in situ energy-dispersive synchrotron X-ray diffraction in a multi-anvil press, using MgO as a pressure marker. Our volume data were fitted to a high-temperature Birch–Murnaghan equation of state (EoS). Experimental data are reproduced accurately, with a \(\varDelta P\) standard deviation of 0.20 GPa. The resulting thermoelastic parameters of fs are: V0 = 875.8 ± 1.4 A3, K0 = 74.4 ± 5.3 GPa, and \(\frac{{\text d}K}{{\text d}T} = -0.032 \pm 0.005\,\hbox{GPa K}^{-1}\), assuming \({K}^{\prime}_{0} = 10 \). We also determined the thermal equation of state of a natural Fe-rich orthopyroxene from Hidra (Norway) to assess the effect of magnesium on the EoS of iron-rich orthopyroxene. Comparison between our two data sets and literature studies shows good agreement for room-temperature, room-pressure unit-cell volumes. Preliminary thermodynamic analyses of orthoferrosilite, FeSiO3, and orthopyroxene solid solutions, (Mg1−xFex) SiO3, using vibrational models show that our volume measurements in pressure–temperature space are consistent with previous heat capacity and one-bar volume–temperature measurements. The isothermal bulk modulus at ambient conditions derived from our measurements is smaller than values presented in the literature. This new simultaneous high-pressure, high-temperature data are specifically useful for calculations of the orthopyroxene density in the Moon.

The Effect of High Pressure Torsion on Structural Refinement and Mechanical Properties of an Austenitic Stainless Steel

In the present study, the high pressure torsion (HPT) was used to refine the grain structure down to the nanometer scale in an austenitic stainless steel. The principles of HPT lay on torsional deformation under simultaneous high pressure of the specimen, which results in substantial reduction in the grain size. Disks of the 316LVM austenitic stainless steel of 10 mm in diameter were subjected to equivalent strains epsilon of 32 at RT and 450 degrees C under the pressure of 4 GPa. Furthermore, two-stage HPT processes, i.e., deformation at room temperature followed by deformation at 450 degrees C, were performed. The resulting microstructures were investigated in TEM observations. The mechanical properties were measured in terms of the microhardness and in tensile tests. HPT performed at two-stage conditions (firstly at RT next at 450 degrees C) gives similar values of microhardness to the ones obtained after deforming only at 450 degrees C but performed to higher values of the overall equivalent strain epsilon. The effect of high pressure torsion on structural refinement and mechanical properties of an austenitic stainless steel was evaluated.

High Pressure Homogenization as a Novel Approach for the Preparation of Co-Crystals

The feasibility of producing pharmaceutical co-crystals by simultaneous high pressure homogenization (HPH) of solid API and co-former has been investigated using as model the co-crystal forming system represented by theophylline (TPL) and saccharin (SAC). First, thermodynamic aspects of this process have been clarified by investigating the ternary system TPL – SAC – water, particularly by constructing its phase diagram and by measuring representative points of its solubility in water at temperatures between 15 and 35 °C. In a second step, the co-crystal TPL:SAC has been produced through simultaneous homogenization of aqueous suspensions of the raw materials TPL and SAC, achieving at the same time a solvent-mediated transformation of the precursors toward the co-crystal TPL:SAC and a comminution of the product particles. After 2 h of processing, corresponding to ca. 34 passes across the homogenizer at a pressure drop of 600 bar, a narrow size distribution with a median x50 of 4.1 μm has been obtained. Finally, the presented concept has been extended to the use of liquid carbon dioxide as operating fluid of the homogenization process. Also in this case, TPL and SAC have been converted successfully into a product consisting largely of the co-crystal TPL:SAC, while achieving at the same time a comminution of particles down to an average size of 5.8 μm. Liquid carbon dioxide is subject to residue-free evaporation upon pressure release, such that the micronized product particles can be directly recovered in form of a dry powder at the end of the process. The presented results open thus new possibilities for a quick and clean manufacturing of pharmaceutical co-crystals whose particle size distribution can be tightly tuned.

Early Left Ventricular Diastolic Function Quantitation Using Directional Impedances

Impedance has been used in vascular biology to characterize the frequency dependent opposition the circulatory system presents to blood flow in response to a pulsatile pressure gradient. It has also been used to characterize diastolic function (DF) via the early, diastolic left ventricular (LV) pressure-flow relation. In a normal LV, early filling volume is accommodated primarily by wall-thinning and ascent of the mitral annulus relative to the spatially fixed apex (longitudinal chamber expansion). Simultaneously, the endocardial (transverse or short axis) dimension also increases while epicardial (transverse) external dimension remains essentially constant. To quantify these directional filling attributes, we compute longitudinal (Z(L)) and transverse (Z(T)) impedances during early rapid-filling (Doppler E-wave). Z(L) and Z(T) were calculated from 578 cardiac cycles of simultaneous transmitral flow and high fidelity LV pressure data in 17 subjects with normal LV function. Average Z(L) was 0.7 ± 0.4 mmHg s/cm(4) and average Z(T) was 238 ± 316 mmHg s/cm(2). Direct comparison, in the same units is achieved by computing Z(T) over the ≈10 cm(2) cross-sectional area of LV (denoted ŽT) revealing that Z(L) is ≈34 times smaller than Ž(T). This quantifies the physiologic preference for longitudinal LV volume accommodation. Lowest Z(L) and Z(T) values occurred in the first harmonic with monotonically increasing values with higher harmonics. We conclude that Z(L) and Z(T) characterize longitudinal and transverse chamber properties of DF and therefore, diastolic dysfunction can be viewed as a state of impedance mismatch.

Elasticity of diamond at high pressures and temperatures

We combine density functional theory within the local density approximation, the quasiharmonic approximation, and vibrational density of states to calculate single crystal elastic constants, and bulk and shear moduli of diamond at simultaneous high pressures and temperatures in the ranges of 0–500 GPa and 0–4800 K. Comparison with experimental values at ambient pressure and high temperature shows an excellent agreement with our first-principles results validating our method. We show that the anisotropy factor of diamond increases to 40% at high pressures and becomes temperature independent.

Influence of mixing on the precipitation of zinc oxide nanoparticles with the miniemulsion technique

Nanoparticles enjoy great popularity in chemical, pharmaceutical, cosmetic and textile industry due to the unique properties related to their small particle size (x<100nm). A promising process to synthesise nanoparticles is the precipitation in emulsion droplets. Submicron emulsion droplets (0.1μm up to several microns) as nanoreactors enable for the control of particle growth. Furthermore a simple scale-up can be achieved by a numbering-up of droplets. The particle precipitation is achieved once an amphiphilic reactant passes the interface into a droplet loaded with the reaction partner. With this contribution we introduce a continuous technical process which allows for a simultaneous high pressure emulsification and an instantaneous mixing (SEM) of the reactant. First we characterised the SEM-process in respect of its mixing quality with the Villermaux Dushmann reaction and CFD simulations. Geometrical as well as experimental parameters proved to influence the mixing quality of this process. Applying the SEM-process for the precipitation of zinc oxide in a miniemulsion, we could show that the resulting particle size is significantly influenced by the mixing efficiency. Nevertheless, once a sufficiently good mixing quality is reached, no further change in particle size can be detected depicting that the transport of reactant is the controlling parameter.

CO2-assisted high pressure homogenization: A solvent-free process for polymeric microspheres and drug–polymer composites

The study explores the enabling role of near-critical CO(2) as a reversible plasticizer in the high pressure homogenization of polymer particles, aiming at their comminution as well as at the formation of drug-polymer composites. First, the effect of near-critical CO(2) on the homogenization of aqueous suspensions of poly lactic-co-glycolic acid (PLGA) was investigated. Applying a pressure drop of 900 bar and up to 150 passes across the homogenizer, it was found that particles processed in the presence of CO(2) were generally of microspherical morphology and at all times significantly smaller than those obtained in the absence of a plasticizer. The smallest particles, exhibiting a median x(50) of 1.3 μm, were obtained by adding a small quantity of ethyl acetate, which exerts on PLGA an additional plasticizing effect during the homogenization step. Further, the study concerns the possibility of forming drug-polymer composites through simultaneous high pressure homogenization of the two relevant solids, and particularly the effect of near-critical CO(2) on this process. Therefore, PLGA was homogenized together with crystalline S-ketoprofen (S-KET), a non-steroidal anti-inflammatory drug, at a drug to polymer ratio of 1:10, a pressure drop of 900 bar and up to 150 passes across the homogenizer. When the process was carried out in the presence of CO(2), an impregnation efficiency of 91% has been reached, corresponding to 8.3 wt.% of S-KET in PLGA; moreover, composite particles were of microspherical morphology and significantly smaller than those obtained in the absence of CO(2). The formation of drug-polymer composites through simultaneous homogenization of the two materials is thus greatly enhanced by the presence of CO(2), which increases the efficiency for both homogenization and impregnation.

Simultaneous sound velocity and density measurements of hcp iron up to 93 GPa and 1100 K: An experimental test of the Birch's law at high temperature

We performed sound velocity and density measurements on polycrystalline hexagonal close-packed (hcp) iron at simultaneous high pressure and high temperature, up to 93GPa and 1100K, by inelastic x-ray scattering and x-ray diffraction. Our experimental results indicate that high-temperature anharmonic corrections are negligible at least up to 1100K and that the aggregate compressional velocity VP scales linearly with density over the pressure and temperature range of the investigation (Birch's law). The new results are compared with literature studies and we discuss the extrapolation schemes commonly used in experimental mineral physics, with specific regard to extrapolations to the Earth's core conditions.

Conductive and ferromagnetic contributions of H in ZnCoO using H2 hot isostatic pressure

For highly H injected ZnCoO achieved by simultaneous high pressure (1000 bar) and annealing using a hot isostatic pressure (HIP), we report electrical and magnetic properties with first-principles calculation results. The HIP process increased the carrier concentration by ∼103 times and restored the conductivity up to that of H injected ZnO. Interestingly, with maintaining high conductivity, the extended HIP processing time significantly enhanced the short-ranged spin orderings of Co-H-Co complexes. Based on the experimental and theoretical results, we proposed the explanation for the relation magnetic characteristics and the behavior of hydrogen triggering spin ordering for spintronic applications.

Characterization of gas–solid flow in conical spouted beds operating with heavy particles

This study presents the results of an experimental investigation of the hydrodynamics of conical spouted beds operating with high density particles. This type of spouted beds is frequently encountered in chemical vapor deposition coating of nuclear fuel elements. Measurements were performed in three 15cm ID full circular (γ=30°, 45°, 60°) and one half circular conical spouted (γ=30°) bed with yttria-stabilized zirconia particles (dp=0.5, 1mm; ρp=6050kg/m3). For the complete characterization of the hydrodynamic regimes, simultaneous high speed camera and bed pressure drop measurements were carried out in a half circular conical spouted bed to visualize the gas–solid flow patterns and match them with the corresponding bed pressure drop values and its spectral characteristics. The results show that the minimum spouting velocity increases with cone angle, particle diameter and static bed height. The average bed pressure drop decreases with cone angle. Minimum spouting velocity values obtained from full and half bed experiments resulted in a maximum 15% difference. The spectral analyses of the bed pressure drop indicated a dominant frequency of 12Hz in the stable spouting region. After the initiation of external spouting, an unstable intermittent spouting region which extends up to approximately 1.2Ums has been identified. The results of this work can be successfully used in the hydrodynamic design of spouted bed nuclear fuel coaters.

In Situ High-Pressure and Low-Temperature Study of Ammonia Borane by Raman Spectroscopy

As a promising hydrogen storage material, ammonia borane was investigated at simultaneous high pressures (up to 15 GPa) in a diamond anvil cell and at low temperatures (down to 80 K) using a cryostat by in situ Raman spectroscopy. When ammonia borane was cooled from room temperature to 220 K at near ambient pressure, an expected phase transformation from I4mm to Pmn21 was observed. Then the sample was compressed to 15 GPa isothermally at 180 K. Three pressure-induced structural transformations were observed as evidenced by the change in the Raman profile as well as the pressure dependence of the major Raman modes. The decompression and warming-up experiments suggest that these pressure–temperature (P–T)-induced transformations are reversible. These observations, together with factor group analysis, allowed us to examine the possible structures of the new high-pressure phases and the nature of phase transitions. Raman measurements from multiple runs covering various P–T paths, when combined with previously...

Anelasticity maps for acoustic dissipation associated with phase transitions in minerals

Acoustic dissipation due to structural phase transitions in minerals could give rise to large seismic attenuation effects superimposed on the high temperature background contribution from dislocations and grain boundaries in the Earth. In addition to the possibility of a sharp peak actually at a transition point for both compressional and shear waves, significant attenuation might arise over wider temperature intervals due to the mobility of transformation twins or other defects associated with the transition. Attenuation due to structural phase transitions in quartz, pyroxenes, perovskites, stishovite and hollandite, or to spin state transitions of Fe2+ in magnesiowustite and perovskite and the hcp/bcc transition in iron–nickel (Fe–Ni) alloy, are reviewed from this perspective. To these can be added possible loss behaviour associated with reconstructive transitions which might occur by a ledge mechanism on topotactic interfaces (orthopyroxene/clinopyroxene, olivine/spinel and perovskite/postperovskite), with impurities (Snoek effect) or with mobility of protons. There are experimental difficulties associated with measuring dissipation effects in situ at simultaneous high pressures and temperatures, so reliance is currently placed on investigation of analogue phases such as LaCoO3 for spin-state behaviour and LaAlO3 for the dynamics of ferroelastic twin walls. Similarly, it is not possible to measure loss dynamics simultaneously at the low stresses and low frequencies that pertain in seismic waves, so reliance must be placed on combining different techniques, such as dynamic mechanical analysis (low frequency, relatively high stress) and resonant ultrasound spectroscopy (high frequency, low stress), to extrapolate acoustic loss behaviour over wide frequency, temperature and stress intervals. In this context ‘anelasticity maps’ provide a convenient means of representing different loss mechanisms. Contouring of the inverse mechanical quality factor, Q−1, can be achieved if the appropriate constitutive laws are known. The overall approach is illustrated using the examples of spin-state transitions of Co3+ in LaCoO3 and twin mobility in single crystals of the rhombohedral phase of LaAlO3. Anelasticity maps of this type should give seismologists a clearer view of the characteristic patterns of seismic velocity and attenuation that could be used to detect (or rule out) the presence of particular phase transitions or loss behaviour in the core and mantle.

Electrical properties of natural and synthetic nano-crystalline MgTiO3 geikielite at mantle pressure and temperature conditions

Electrical resistivity of nanocrystalline (30–40 nm crystallite size) and a crystalline sample of geikielite MgTiO 3 has been measured at simultaneous high pressure and high temperature up to 6 GPa and 800 K, respectively. The temperature dependence of the electrical resistivity of both the and sample obeys the Arrehenius behavior in the temperature range between 3 and 800 K and pressure range up to 6.0 GPa. The activation volume of the electrical conduction coarse crystalline sample of geikielite is almost twice that of the nanocrystalline geikielite indicating the increase of activation volume with the crystallite size. The activation energy the electronic conduction decreases from eV at room pressure to 0.25 eV at 6.0 GPa geikielite, and to 0.225 eV in the same pressure range geikielite. The pressure dependence of the activation energy of geikielite sample is found to obey the following expressions \[{\Delta}\mathit{E} (eV) = 0.39 {-} 0.026(1) \mathit{P} + 0.0036 \mathit{P}^{2} for natural sample, and\] \[{\Delta}\mathit{E} (eV) = 0.68 {-} 0.080 (2) \mathit{P} + 0.0007 \mathit{P}^{2} for synthetic sample,\] where P is pressure in GPa. We observe a crossover from extended state type conduction to hopping conduction at 4.0 GPa and 350 K nano-crystalline geikielite. However, there is no such change of conduction mechanism observed the geikielite at high pressures and high temperatures. The present study reveals the phase stability of nano-crystalline geikielite and geikielite up to mantle pressure and temperature conditions, viz. 6 GPa and 800 K, and no phase transition or decomposition is observed in the sample.

Modeling mass transfer during osmotic dehydration of strawberries under high hydrostatic pressure conditions

Abstract Simultaneous application of high hydrostatic pressure (200–400 MPa) during osmotic dehydration of strawberries was studied in this investigation. The high hydrostatic pressure treatment improved the diffusion coefficients of water and soluble solids compared to atmospheric pressure operation. Effects of process pressure on diffusion coefficients were achieved through an Arrhenius-type equation. Mathematical modeling of mass transfer was performed applying Newton, Henderson–Pabis, Page and Weibull models. Based on statistical results, the Weibull model gave the best goodness of fit on the experimental data under the studies' operative conditions. Industrial relevance: This article deals with the mathematical modeling of mass transfer during simultaneous high hydrostatic pressure treatment and osmotic dehydration of strawberries. Transfer of water and soluble solids during this combined process were satisfactorily simulated with the Weibull model. Results indicated that application of this innovative technology improved strawberries dehydration rates compared to atmospheric pressure operation resulting in a dried fruit with intermediate moisture content ready to be used as input material of further processes.

Equation of state and phase diagram of FeO

Wüstite, Fe 1 − x O, is an important component in the mineralogy of Earth's lower mantle and may also be a component in the core. Therefore the high pressure, high temperature behavior of FeO, including its phase diagram and equation of state, is essential knowledge for understanding the properties and evolution of Earth's deep interior. We performed X-ray diffraction measurements using a laser-heated diamond anvil cell to achieve simultaneous high pressures and temperatures. Wüstite was mixed with iron metal, which served as our pressure standard, under the assumption that negligible oxygen dissolved into the iron. Our data show a positive slope for the subsolidus phase boundary between the B1 and B8 structures, indicating that the B1 phase is stable at the P–T conditions of the lower mantle and core. We have determined the thermal equation of state of B1 FeO to 156 GPa and 3100 K, finding an isothermal bulk modulus K 0 = 149.4 ± 1.0 GPa and its pressure derivative K 0′ = 3.60 ± 0.4. This implies that 7.7 ± 1.1 wt.% oxygen is required in the outer core to match the seismologically-determined density, under the simplifying assumption of a purely Fe–O outer core.

The thermal equation of state of FeTiO3 ilmenite based on in situ X-ray diffraction at high pressures and temperatures

We present in situ measurements of the unit-cell volume of a natural terrestrial ilmenite (Jagersfontein mine, South Africa) and a synthetic reduced ilmenite (FeTiO 3 ) at simultaneous high pressure and high temperature up to 16 GPa and 1273 K. Unit-cell volumes were determined using energy-dispersive synchrotron X-ray diffraction in a multi-anvil press. Mössbauer analyses show that the synthetic sample contained insignificant amounts of Fe 3+ both before and after the experiment. Results were fit to Birch- Murnaghan thermal equations of state, which reproduce the experimental data to within 0.5 and 0.7 GPa for the synthetic and natural samples, respectively. At ambient conditions, the unit-cell volume of the natural sample [V 0 = 314.75 ± 0.23 (1σ) Å 3 ] is significantly smaller than that of the synthetic sample [V 0 = 319.12 ± 0.26 Å 3 ]. The difference can be attributed to the presence of impurities and Fe 3+ in the natural sample. The 1 bar isothermal bulk moduli KT0 for the reduced ilmenite is slightly larger than for the natural ilmenite (181 ± 7 and 165 ± 6 GPa, respectively), with pressure derivatives K 0 ′ = 3 ± 1. Our results, combined with literature data, suggest that the unit-cell volume of reduced ilmenite is significantly larger than that of oxidized ilmenite, whereas their thermoelastic parameters are similar. Our data provide more appropriate input parameters for thermo-chemical models of lunar interior evolution, in which reduced ilmenite plays a critical role.

Dynamic behavior of an aggregate material at simultaneous high pressure and strain rate: SHPB triaxial tests

Low velocity impacts on energetic materials induce plastic deformations and sliding friction which can lead to ignition. If some ignition criteria have been proposed, the remaining difficulty is to characterize the mechanical behavior of the material when submitted to the corresponding solicitations (high pressure and high strain rate). Thus, a technique based on the Split Hopkinson Pressure Bars system is proposed to carry out a triaxial compression test. A cylindrical specimen is placed into a confining ring and is compressed by the system of bars. The ring prevents the radial extension of the specimen and creates a lateral confining pressure. The material and dimensions chosen for the ring maintain a constant radial pressure during the test. Some tests were carried out on an inert aggregate material and proved the validity of this experimental device. The experimental data processing shows the influence of both the pressure and the strain rate. The shear stresses, which contribute to thermal dissipation and then to the ignition threshold, increase according to the pressure.

Equation of state and anharmonicity of carbon dioxide phase I up to 12 GPa and 800 K

We present an extended investigation of phase I of carbon dioxide by x-ray diffraction and spectroscopic techniques at simultaneous high pressure and high temperature, up to 12 GPa and 800 K. Based on the present and literature data, we show that a Mie-Grüneisen-Debye model reproduces within experimental uncertainties the equation of state of CO(2) over the entire range of stability of phase I. Using infrared and Raman spectroscopy, we have determined the frequencies of the zone-center lattice modes as a function of pressure and temperature. We have then extracted the volume and temperature dependencies of the optical lattice mode frequencies and their respective Grüneisen parameters. We find a large difference between the thermodynamic Grüneisen parameter obtained from the P-V-T data and those associated with the optical lattice modes. This suggests, within the quasiharmonic approximation, that acoustic modes have a dominant contribution to the anharmonicity of the system.

Elastic wave velocities of silica glass at high temperatures and high pressures

The elastic compressional (P) and shear (S) wave velocities of silica glass at simultaneous high pressures and high temperatures were measured using a combination of ultrasonic interferometry, in situ synchrotron x-ray diffraction, and radiographic techniques in a large-volume Kawai-type multianvil apparatus. We found no first-order amorphous-amorphous transformation throughout the pressure and temperature conditions between 2 and 5 GPa and up to 1173 K, contrary to previous studies suggested by piston cylinder experiments or molecular dynamics simulations. For each of the 650 and 800 K isothermal runs, the P and S wave velocities initially decreased with increasing pressure, reaching minimum values at around 3–4 GPa, followed by increases with pressure up to 6.1 GPa; on successive decompression to ambient pressure, both velocities changed irreversibly due to permanent densification, and no minima were observed in both velocities. We also found that, in a second compression-decompression cycle at 800 K, the densified silica glass was compressed reversibly (elastically) within errors without further irreversible densification. Using the measured P and S wave velocities in such reversible (elastic) compression regions as a function of pressure, we found the density of silica glass increases with temperature from 300 to 800 K at all the measured pressure range up to 6.1 GPa, providing a direct evidence of a negative thermal expansion of silica glass at high pressures.