Simultaneous High Pressure Research Articles

Sound Velocities of Stishovite at Simultaneous High Pressure and High Temperature Suggest an Eclogite‐Rich Layer Beneath the Hawaii Hotspot

AbstractCompressional and shear wave velocities of polycrystalline stishovite (SiO2) have been measured at simultaneous high pressures and temperatures up to 14.5 GPa and 800°C. By fitting velocities to the finite strain equations, the elastic moduli and density were determined to be KS0 = 306.6(46) GPa, KS′ = 4.92(10), ∂KS/∂T = −0.024(1) GPa/K, G0 = 229.0(34) GPa, G′ = 1.07(10), ∂G/∂T = −0.017(1) GPa/K, ρ0 = 4.287(2) g/cm3. Our modeling suggested that, in the eclogite, coesite‐stishovite transition can increase P and S wave velocities by 2.4% and 3.5%, respectively. A comparison between geophysical observations and our model shows that the coesite‐stishovite phase transition in the eclogite can potentially be responsible for the occurrence of the X discontinuity beneath Hawaii. In addition, our current results suggest an eclogite‐rich layer between 340 and 450 km depth beneath Hawaii. The eclogite concentration at the top and bottom of the layer is 41–55 vol% and >77 vol%, respectively.

Sound velocities in lunar mantle aggregates at simultaneous high pressures and temperatures: Implications for the presence of garnet in the deep lunar interior

Recent experimental and theoretical studies on lunar magma ocean crystallisation have suggested the presence of significant proportions of garnet in the deep lunar interior. While phase relation studies indicate a deep lunar mantle consisting of olivine, pyroxene, and garnet, the compatibility of such an assemblage with seismic models of the lunar interior is yet untested. In this study we report compressional and shear wave velocities in an iron-rich assemblage consisting of olivine, orthopyroxene, clinopyroxene, and garnet up to ∼8 GPa and 1300 K, by means of ultrasonic interferometry measurements combined with synchrotron techniques using the multi-anvil press apparatus. Sound velocity and density models of lunar mantle rocks along a selenotherm based on our experimental results find good agreement with the seismic and density profiles at lunar interior depths of 740–1260 km. Further models are constructed, allowing for the variation of chemical composition, phase proportion, and temperature; these suggest that a garnet-rich deep lunar mantle is compatible with present-day lower lunar mantle temperatures of between 1400–1800 K. Our results show that lunar mantle rocks with up to 33 wt.% garnet may provide an explanation for the observed high velocities of the lower lunar mantle. The presence of garnet in the lowermost part of the Moon's mantle has significant implications for the depth and temperature of the Moon's magma ocean as well as the composition, structure and internal dynamics of the solid Moon.

Fast Seismic Anomalies Under Continents Explained by the Delaminated Lower Continental Crust—Implications From High Pressure‐Temperature Elasticity of Jadeite

AbstractSeismic tomography has shown that the shear wave velocities (Vs) under continents, especially under cratons, are extremely fast at 100–200 km depth, which is difficult to explain by low temperatures or high Mg#. Alternatively, delaminated eclogitic lower continental crust has been proposed to account for these fast seismic anomalies. However, the thermoelastic properties of jadeite which constitutes up to 60–80 mol% of clinopyroxene in the potentially delaminated lower continental crust are not well constrained. In this study, we measured the single‐crystal elasticity of jadeite by Brillouin spectroscopy under simultaneous high pressure and temperature conditions for the first time. We found that the temperature dependence of Vs of jadeite is extremely small if not negligible. The seismic velocities of the potentially delaminated lower continental crusts were subsequently modeled and found to match the widely observed fast seismic anomalies under cratons between 100 and 200 km depth.

Risk factors for cerebral edema following aneurysm clipping in patients with aneurysmal subarachnoid hemorrhage.

To investigate the factors that contribute to the development of cerebral edema after aneurysm clipping in individuals with aneurysmal subarachnoid hemorrhage (aSAH). A total of 232 patients with aSAH caused by rupture and treated with aneurysm clipping were included in the retrospective analysis of clinical data. Postoperatively, the participants were categorized into two groups based on the presence or absence of cerebral edema: a complication group (n=33) and a non-complication group (n=199).A comparison was made between the overall data of the 2 groups. In the complication group, there were higher proportions of patients experiencing recurrent bleeding, aneurysm in the posterior circulation, Fisher grade III-IV, World Federation of Neurosurgical Societies (WFNS) grade II, Hunt-Hess grade III-IV, concomitant hypertension, duration from onset to operation ≥12h, and concomitant hematoma compared to the non-complication group (p<0.05). Cerebral edema after aneurysm clipping was associated with several risk factors including repeated bleeding, aneurysm in the back of the brain, Fisher grade III-IV, WFNS grade II, Hunt-Hess grade III-IV, simultaneous high blood pressure and hematoma, and a duration of at least 12 hours from the start of symptoms to the surgical procedure (p<0.05). In patients with aSAH, the risk of cerebral edema after aneurysm clipping is increased by recurrent bleeding, aneurysm in the posterior circulation, Fisher grade III-IV, WFNS grade II, Hunt-Hess grade III-IV, concomitant hypertension and hematoma, and duration of ≥12h from onset to operation.

Enhancing CO2 adsorption capacity of ZIF-8 by synergetic effect of high pressure and temperature

Metal–organic frameworks (MOFs) and zeolitic imidazolate frameworks (ZIFs) are promising porous materials for adsorption and storage of greenhouse gases, especially CO2. In this study, guided by the CO2 phase diagram, we explore the adsorption behavior of solid CO2 loaded with ZIF-8 framework by heating the sample under high pressures, resulting in a drastic improvement in the CO2 uptake. The behavior of CO2 under simultaneous high temperature (T) and pressure (P) conditions is directly monitored by in situ FTIR spectroscopy. The remarkable enhancement in CO2 adsorption capability observed can be attributed to the synergetic effect of high T and P: high temperature greatly enhances the transport property of solid CO2 by facilitating its diffusion into the framework; high pressure effectively modifies the pore size and shape via changing the linker orientation and creating new adsorption sites within ZIF-8. Our study thus provides important new insights into the tunability and enhancement of CO2 adsorptive capability in MOFs/ZIFs using pressure and temperature combined as a synergetic approach.

Study of Elastic Properties of Mantle Solids &amp; Variations of Density (ρ) of Earth with Depth (r)

In the present study, there is now some knowledge on the elastic characteristics of the key rock-forming minerals in the mantle. Gruneisen parameter is reasonably constant from material to material and temperature independent. The majority of measurements are taken under settings that are very different from the pressure and temperature conditions in the deep mantle. This is useful because density fluctuations with temperature, pressure, composition, and phase are pretty well understood. At high temperatures, the elastic characteristics are mostly determined by volume due to thermal expansion. Because the lower mantle is under simultaneous high pressure and high temperature, it is unclear if the standard high-temperature limit simplifications are necessarily accurate.

In-situ ultrasonic calibrations of pressure and temperature in a hinge-type double-stage cubic large volume press

Here, simultaneous in-situ calibration of pressures and temperatures was performed in a hinge-type second-stage cubic large volume press (LVP) up to 15 GPa and 1400 K by an acoustic travel-time approach. Based on the recently reported P–t S and P–T–t P–t S equations for Al2O3 buffer rod, the cell pressures and temperatures in the chamber of LVP were in-situ determined, in comparison with those by conventional off-line (or fixed-points) pressure calibration method and direct thermocouple measurement, respectively. It is found that the cell pressures of the LVP chamber are significantly reduced after annealing at simultaneous high pressures and high temperatures, owing to the stress relaxation as accumulate in the LVP chamber. This acoustic travel-time method is verified to be a good way for precise determination of thermal (cell) pressures at high temperature conditions, and is of great importance and necessity to conduct in-situ physical property measurements under extreme high P–T conditions, especially when the precious synchrotron x-ray/neutron diffraction beams are not available.

Hollow Core Bragg Fiber Integrated With Regenerate Fiber Bragg Grating for Simultaneous High Temperature and gas Pressure Sensing

We have proposed and experimentally demonstrated a novel optical fiber sensor for simultaneous measurement of high temperature and gas pressure based on a Regenerated Fiber Bragg grating (RFBG) cascaded with a homemade hollow core Bragg fiber (HCBF). The HCBF functions as an anti-resonant reflecting waveguide and acts as a pressure and temperature sensing unit. The sample was fabricated and tested in our lab, exhibiting a high linear pressure and temperature sensitivity of −3.747 nm/MPa and 25.925 pm/°C in a large-dynamic range of 2 MPa and 600 °C, respectively. The RFBG, as a temperature monitor, was integrated to compensate the temperature cross-correspondence of the HCBF. By utilizing a 2 × 2 matrix obtained with the experimental results, simultaneous measurement of temperature and gas pressure can be achieved. Besides, compact size, low cost and high sensitivity make the sensor more competitive in harsh environment application.

Thermoelastic properties of tungsten at simultaneous high pressure and temperature

The compressional (P) and shear wave velocities (S) and unit cell volumes (densities) of polycrystalline tungsten (W) have been measured simultaneously up to 10.5 GPa and 1073 K using ultrasonic interferometry in conjunction with x-ray diffraction and x-radiography techniques. Thermoelastic properties of W were derived using different methods. We obtained the isothermal bulk modulus KT0 = 310.3(1.5) GPa, its pressure derivative K′T0 = 4.4(3), its temperature derivative at constant pressure (∂KT/∂T)P=−0.0138(1)GPaK−1 and at constant volume (∂KT/∂T)V=−0.0050GPaK−1, the thermal expansion α(0, T) = 1.02(27) × 10−5 + 7.39(3.2) × 10−9 T (K−1), as well as the pressure derivative of thermal expansion (∂α/∂P)T=−1.44(1)×10−7K−1GPa−1 based on the high-temperature Birch–Murnaghan equation of state (EOS), the Vinet EOS, and thermal pressure approach. Finite strain analysis allowed us to derive the elastic properties and their pressure/temperature derivatives independent of the choice of pressure scale. A least-squares fitting yielded KS0 = 314.5(2.5) GPa, KS0′ = 4.45(9), (∂KS/∂T)P = − 0.0076(6) GPa K−1, G0 = 162.4(9) GPa, G0′ = 1.8(1), (∂G/∂T)P = − 0.0175(9) GPa K−1, and α298K=1.23×10−5K−1. Fitting current data to the Mie–Grüneisen–Debye EOS with derived θ0=383.4K yielded γ0=1.81(6)andq=0.3. The thermoelastic parameters obtained from various approaches are consistent with one another and comparable with previous results within uncertainties. Our current study provides a complete and self-consistent dataset for the thermoelastic properties of tungsten at high P–T conditions, which is important to improve the theoretical modeling of these materials under dynamic conditions.

Viscosity measurement from microscale convection at high pressure and temperature

Measurements of induced thermal convection have been used to study fluid viscosity at simultaneous high pressure and temperature conditions. Direct observations of flow were made by tracking entrained particles in samples melted by laser heating during high-pressure confinement. Finite element models confirmed thermal convection as the origin of the detected motions, and were refined to assess the fluid viscosity. Observations of flow in ethanol partially melted in the laser-heated diamond anvil cell at 2--3 GPa point to a sharply rising viscosity at room temperature above the equilibrium solidification pressure, similar to that seen previously in methanol. The analysis shows that measurement of viscosity from convective flow in laser-heated fluids under static pressure is a promising strategy to determine viscosity at ultrahigh pressures, where high melting temperatures and small samples preclude application of traditional viscometric techniques. The data confirm theoretical predictions of detectable natural convection at ultralow Rayleigh numbers ($\mathrm{Ra}\ensuremath{\ll}1$) in a microscopic system having sufficiently large temperature gradients.

An improved setup for radial diffraction experiments at high pressures and high temperatures in a resistive graphite-heated diamond anvil cell.

We present an improved setup for the experimental study of deformation of solids at simultaneous high pressures and temperatures by radial x-ray diffraction. This technique employs a graphite resistive heated Mao-Bell type diamond anvil cell for radial x-ray diffraction in combination with a water-cooled vacuum chamber. The new chamber has been developed by the sample environment group at PETRA III and implemented at the Extreme Conditions Beamline P02.2 at PETRA III, DESY (Hamburg, Germany). We discuss applications of the new setup to study deformation of a variety of materials, including ferropericlase, calcium perovskite, bridgmanite, and tantalum carbide, at high-pressure/temperature.

Axial Compressibility and Thermal Equation of State of Hcp Fe–5wt% Ni–5wt% Si

Knowledge of the elastic properties and equations of state of iron and iron alloys are of fundamental interest in Earth and planetary sciences as they are the main constituents of telluric planetary cores. Here, we present results of X-ray diffraction measurements on a ternary Fe–Ni–Si alloy with 5 wt% Ni and 5 wt% Si, quasi-hydrostatically compressed at ambient temperature up to 56 GPa, and under simultaneous high pressure and high temperature conditions, up to 74 GPa and 1750 K. The established pressure dependence of the c/a axial ratio at ambient temperature and the pressure–volume–temperature (P–V–T) equation of state are compared with previous work and literature studies. Our results show that Ni addition does not affect the compressibility and axial compressibility of Fe–Si alloys at ambient temperature, but we suggest that ternary Fe–Ni–Si alloys might have a reduced thermal expansion in respect to pure Fe and binary Fe–Si alloys. In particular, once the thermal equations of state are considered together with velocity measurements, we conclude that elements other than Si and Ni have to be present in the Earth’s inner core to account for both density and seismic velocities.

Tantalum strength at extreme strain rates from impact-driven Richtmyer-Meshkov instabilities.

Recently, Richtmyer-Meshkov instability (RMI) experiments driven by high explosives and fielded with perturbations on a free surface have been used to study strength at extreme strain rates and near zero pressure. The RMI experiments reported here used impact loading, which is experimentally simpler, more accurate to analyze, and which also allows the exploration of a wider range of conditions. Three experiments were performed on tantalum at shock stresses from 20 to 34 GPa, with six different perturbation sizes at each shock level, making this the most comprehensive set of strength-focused RMI experiments reported to date on any material. The resulting estimated average strengths of 1200-1400 MPa at strain rates of 10^{7}/s exceeded, by 40% or more, a common power law extrapolation from data at strain rates below 10^{4}/s. Taken together with other data in the literature that show much higher strength at simultaneous high rates and high pressure, these RMI data isolated effects and indicated that, in the range of conditions examined, the pressure effects are more significant than rate effects.

Single-crystal diffractometer coupled with double-sided laser heating system at the Extreme Conditions Beamline P02.2 at PETRAIII.

Combination of in situ laser heating with single-crystal X-ray diffraction (scXRD) in diamond anvil cells (DACs) provides a tool to study crystal structures and/or chemistry of materials at simultaneous high pressures and high temperatures. Here, we describe the first dedicated single-crystal X-ray diffractometer coupled with double-sided laser heating (dsLH) system. The scXRD/dsLH setup was developed for the P02.2 Extreme Conditions Beamline at PETRA III and became available for general users in 2017. It enables the collection of reliable scXRD data at simultaneous high pressure and high temperature. We demonstrate the performance of the setup on example of studies of iron and chromium nitrides.

Rich Polymorphism of a Metal–Organic Framework in Pressure–Temperature Space

We present an in situ powder X-ray diffraction study on the phase stability and polymorphism of the metal–organic framework ZIF-4, Zn(imidazolate)2, at simultaneous high pressure and high temperature, up to 8 GPa and 600 °C. The resulting pressure–temperature phase diagram reveals four, previously unknown, high-pressure–high-temperature ZIF phases. The crystal structures of two new phases—ZIF-4-cp-II and ZIF-hPT-II—were solved by powder diffraction methods. The total energy of ZIF-4-cp-II was evaluated using density functional theory calculations and was found to lie in between that of ZIF-4 and the most thermodynamically stable polymorph, ZIF-zni. ZIF-hPT-II was found to possess a doubly interpenetrated diamondoid topology and is isostructural with previously reported Cd(Imidazolate)2 and Hg(Imidazolate)2 phases. This phase exhibited extreme resistance to both temperature and pressure. The other two new phases could be assigned with a unit cell and space group, although their structures remain unknown. The pressure–temperature phase diagram of ZIF-4 is strikingly complicated when compared with that of the previously investigated, closely related ZIF-62 and demonstrates the ability to traverse complex energy landscapes of metal–organic systems using the combined application of pressure and temperature.

Using thermal analysis technology to assess the thermal stability of 1,3-dimethylimidazolium nitrate

1,3-Dimethylimidazolium nitrate ([Mmim]NO3), an ionic liquid, is a versatile and novel solvent for the petrochemical industry. Nevertheless, under high temperature conditions or thermal upset scenarios, [Mmim]NO3 can be decomposed in a manner that produces an explosion or other serious safety problems. The aim of this research was to investigate the thermal stability of [Mmim]NO3 by simultaneous thermogravimetric analyzer and high pressure differential scanning calorimetry. Isothermal experiments indicated that [Mmim]NO3 would be decomposed at a temperature substantially lower than the onset temperature. A pseudo-zero-order rate expression was applied to characterize the thermal decomposition kinetics of [Mmim]NO3, and related thermokinetic parameters were further obtained. Moreover, the temperature at which the thermal decomposition of ILs reached 10.0% for a given time of 10.0 h (T0.1/10h) was defined to assess the long-term thermal stability, which can be used as the maximum operating temperature of [Mmim]NO3. The results of this study may provide relevant processes for safer control based on the thermal hazard assessment of [Mmim]NO3.

Microstructure evolution, densification behavior and mechanical properties of nano-HfB2 sintered under high pressure

A series of pure HfB2 ceramics have been prepared by sintering nano-grained powder using high-energy ball milling at 700–1600 °C and 5.5 GPa. The HfB2 ceramics are characterized via various techniques for their residual stress, grain size, density, microstructures and defects, hardness, fracture toughness, thermal stability, and oxidation resistance. All properties strongly depend on the treatment temperature, but the exact manner of dependence for each property varies. The results identified that the HfB2 ceramic sintered at a relatively low temperature of 1000 °C and 5.5 GPa – a bulk pure nano-grained composite for the first time – has the best overall performance. It has a relative density of 99.6%, a Vickers hardness of 26 GPa, a fracture toughness of 5.2 MPa m1/2, and excellent thermal stability and oxidation resistance at high temperatures. Additional strengthening and stabilizing effects are provided by microstructures and defects such as large-angle grain boundaries, stacking faults and twinning. Simultaneous high temperature and high pressure is an effective sintering route for HfB2 ceramics with grain-size ranging from nanometer to micron.

A step toward better understanding of behavior of organic materials at simultaneous high pressures and high temperatures

ABSTRACTUsing an external heating system, specifically designed for the lever-type diamond anvil cell, we investigated for the first time the phase relationships in the C2H2O4 system at temperatures exceeding 850°C and pressures up to 6.5 GPa. In situ Raman spectroscopy was applied for the characterization of structural features of observed high-temperature phases, which transformed to the black carbon-rich material upon quenching and decompression. Results of this work give insights on the pressure-induced polymerization process of organic compounds at high temperatures.

Simultaneous high-pressure high-temperature elastic velocity measurement system up to 27 GPa and 1873 K using ultrasonic and synchrotron X-ray techniques.

A new pulse-echo interferometry system has been developed for measurements of sound velocity at simultaneous high pressure and temperature corresponding to those of the Earth's lower mantle, using synchrotron X-ray techniques at SPring-8. A combination of a low-noise high-frequency amplifier and a high-speed solid-state relay system allowed us to clearly detect the ultrasonic echoes of a small sample (<1.0 mm in diameter and length) in multi-anvil apparatus. A new high-pressure cell has also been introduced for precise measurement of the length of the tiny sample by X-ray radiography imaging under very high pressure and temperature. The new system was tested by measuring elastic velocities of α-Al2O3 over wide pressure and temperature ranges of up to 27 GPa and 1873 K, respectively. The resultant adiabatic bulk modulus, shear modulus, and pressure and temperature derivatives of α-Al2O3 are K0S = 251.2 (18) GPa, ∂KS/∂P = 4.21 (10), ∂KS/∂T = -0.025 (1), G = 164.1 (7), ∂G/∂P = 1.59 (3), ∂G/∂T = -0.021 (1). These values are consistent with those previously reported based on experiments at high temperatures at ambient pressure and high pressures at room temperature. The present system allows precise measurements of the elastic velocities of minerals under the pressures and temperatures corresponding to the lower mantle for the first time, which should greatly contribute to our understanding of mineralogy of the whole mantle.

Grüneisen parameter and equations of states for copper – High pressure study

A consistent computational scheme is proposed for calculating various thermophysical properties under simultaneous high temperature and high pressure condition in conjunction with first principles density functional theory, whereas anharmonic contribution is added perturbatively. We have demonstrated that the Grüneisen parameter γth can be calculated from the knowledge of ab initio binding energy, and separate volume dependence of γth is required. Taking copper as a prototype, we have calculated static and dynamic equation of states and some thermodynamic properties along the shock Hugoniot. Present study reveals the importance of anharmonic effect on various thermal properties by examining Grüneisen parameter. Computed high pressure melting curve confirms this assertion and concludes the non-negligible contributions of temperature dependence of Grüneisen parameter.