Pressure-transmitting Medium Research Articles

A Synchrotron Mössbauer Spectroscopy Study of a Hydrated Iron-Sulfate at High Pressures

Szomolnokite is a monohydrated ferrous iron sulfate mineral, FeSO4·H2O, where the ferrous iron atoms are in octahedral coordination with four corners shared with SO4 and two with H2O groups. While somewhat rare on Earth, szomolnokite has been detected on the surface of Mars along with several other hydrated sulfates and is suggested to occur near the surface of Venus. Previous measurements have characterized the local environment of the iron atoms in szomolnokite using Mössbauer spectroscopy at a range of temperatures and 1 bar. Our study represents a step towards understanding the electronic environment of iron in szomolnokite under compression at 300 K. Using a hydrostatic helium pressure-transmitting medium, we explored the pressure dependence of iron’s site-specific behavior in a synthetic szomolnokite powdered sample up to 95 GPa with time-domain synchrotron Mössbauer spectroscopy. At 1 bar, the Mössbauer spectrum is well described by two Fe2+-like sites and no ferric iron, consistent with select conventional Mössbauer spectra evaluations. At pressures below 19 GPa, steep gradients in the hyperfine parameters are most likely due to a structural phase transition. At 19 GPa, a fourth site is required to explain the time spectrum with increasing fractions of a low quadrupole splitting site, which could indicate the onset of another transition. Above 19 GPa we present three different models, including those with a high- to low-spin transition, that provide reasonable scenarios of electronic environment changes of the iron in szomolnokite with pressure. We summarize the complex range of Fe2+ spin transition characteristics at high-pressures by comparing szomolnokite with previous studies on ferrous-iron bearing phases.

High pressure anomalies in exfoliated MoSe2: resonance Raman and x-ray diffraction studies

Detailed high pressure Resonance Raman (RR) Spectroscopy and x-ray diffraction (XRD) studies are carried out on 3–4 layered MoSe2 obtained by liquid exfoliation. Analysis of ambient XRD pattern and RR spectra indicate the presence of a triclinic phase along with its parent hexagonal phase. Slope change in the linear behavior of reduced pressure (H) with respect to Eulerian strain (fE) is observed at about 13 GPa in hexagonal phase and at about 17 GPa for the triclinic phase. High pressure Raman measurements using two different pressure transmitting media (PTM) show three linear pressure regions, separated by pressure values around which anomalies in the structure are observed. A broad minimum in the FWHM values of mode at about 10–12 GPa indicate to an electron-phonon coupling. Above 33 GPa the sample completely gets converted to the triclinic structure, which indicates the importance of strain in structural as well as electronic properties of two dimensional materials.

Explosive Welding of Thin Aluminum Plate onto Magnesium Alloy Plate Using a Gelatin Layer as a Pressure-Transmitting Medium

Mg alloys are extensively used in various automotive, aerospace, and industrial applications. Their limited corrosion resistance can be enhanced by welding a thin Al plate onto the alloy surface. In this study, we perform the explosive welding of a thin Al plate, accelerated by the detonation of an explosive through a gelatin layer as a pressure-transmitting medium, onto two Mg alloy samples: Mg96Zn2Y2 alloy containing a long-period stacking ordered phase in an α-Mg matrix and commercial AZ31. The bonding interface is characterized using optical microscopy, scanning electron microscopy, X-ray diffraction, and electron probe microanalysis. Under moderate experimental conditions, the thin Al plates are successfully welded onto the Mg alloys, showing typical wavy interfaces without intermediate layers. Due to the decreased energetic condition corresponding to the use of a thin flyer plate and gelatin medium, the resulting bonding quality is better than that obtained using a regular explosive welding technique. Further, based on the well-known window for explosive welding, we estimate that the experimental conditions for successful bonding are close to the lower welding limit for a thin Al plate with the two Mg alloys considered. These findings may contribute to improving the quality of materials welded with explosive welding.

Interaction Between FeOOH and NaCl at Extreme Conditions: Synthesis of Novel Na2FeCl4OHx Compound

Iron(III) oxide-hydroxide, FeOOH, is abundant in the banded iron formations (BIFs). Recent studies indicate that BIFs may carry water down to the lower mantle with subducting slabs. The previous experiments investigating the properties of FeOOH at extreme pressures (P) and temperatures (T) were performed in diamond anvil cells (DACs), where it was compressed inside alkali metal halide pressure-transmitting media (2). Alkali metal halides such as NaCl or KCl are expected to be chemically inert; therefore, they are widely used in DAC experiments. Here, we report the chemical interaction between FeOOH and NaCl pressure medium at 107(2) GPa and 2400(200) K. By means of single-crystal X-ray diffraction (SC-XRD) analysis applied to a multigrain sample, we demonstrate the formation of a Na2FeCl4OHx phase and provide its structural solution and refinement. Our results demonstrate that at high P-T conditions, the alkali metal halides could interact with hydrous phases and thus cannot be used as a pressure transmitting and thermal insulating medium in DAC experiments dedicated to studies of hydroxyl or water-bearing materials at high P-T.

Compressional behavior of strontianite SrCO3 by synchrotron X-ray radiation diffraction: effects of pressure transmitting media

The compressional behavior of strontianite SrCO3 was investigated at ambient temperature and high pressure, using a diamond anvil cell (DAC) with Ne as a pressure transmitting medium. X-ray diffraction patterns were collected to ~52 GPa using in situ angle-dispersive synchrotron-based powder X-ray diffraction (XRD). A phase transition was observed at ~20 GPa, and no indications of further transitions were detected up to ~52 GPa. The pressure-volume (P-V) data within 0.27-17.35 GPa were fitted to a third-order Birch-Murnaghan equation of state (BM3 EoS) to obtain the elastic coefficients including zero-pressure unit-cell volume, isothermal bulk modulus and its pressure derivative: V0 = 258.4(3) Å3, KT0 = 55(2) GPa, and K'T0 = 4.3(3). The V0 and KT0 were obtained as 258.1(2) Å3 and 57.1(6) GPa, when fixed K'T0 = 4. The axial compressional behavior of strontianite was also investigated by fitting the pressure-lattice parameter data to a parameterized form of the BM3 EoS, and the compression of the a-, b-, and c-axis was strongly anisotropic, with Ka0 = 104(6), Kb0 = 52(12), and Kc0 = 31.6(5) GPa. Based on this and previous studies using different pressure transmitting media (PTM), the effects PTM on the compressional behavior of strontianite were discussed.

Intrinsic and Extrinsic Responses of ZIF-8 under High Pressure: A Combined Raman and X-ray Diffraction Investigation

ZIF-8 is a prototypical porous material in the family of zeolitic imidazolate frameworks, and its structural stability is of great significance for a wide range of practical applications. Here, the intrinsic and extrinsic structural and mechanical responses of nanosized ZIF-8 perturbed by high external pressure have been comparatively investigated based on our in situ Raman measurements in different pressure environments, accompanied by synchrotron X-ray diffraction measurements and results from previous reports. An improvement of both the chemical and crystallographic stability of ZIF-8, rather than an intrinsic quick deterioration, can be observed when penetrating guest molecules get into the pores. Spectral evidence demonstrates that the C═C section of the imidazolate ring is an optimal interaction site for the penetrating methanol, water, and nitrogen molecules. We further find that water molecules can cleave Zn–N bonds to bring linker-associated defects to ZIF-8. When compressed in the nonpenetrating silicone oil as a pressure transmitting medium (PTM) or when no PTM is used, irreversibility is observed, while samples show a highly reversible transformation both in the short-range and long-range regions upon decompression from a partially or entirely amorphous state in penetrating PTM. Furthermore, the released samples transform to a dense bulk state in the absence of penetrating PTM instead of preserving the original nanosized particles when penetrating pressure transmitting fluids is present. Moreover, the compressible behavior of ZIF-8 varies and is found to be strongly influenced by the size and polarity of molecules in the pores. The present results indicate that the stability, compressibility, and reversibility of ZIF-8 under pressure are closely related to the pressure environments and the characteristics of the guest molecules in the PTM. Thus, this study sheds light on the available mechanical modifications and selectable applications of ZIF-8 as gas absorbents for the future.

Hot-pressing of Tellurite glass with a sacrificial pressure-transmitting medium

Glass powder of composition 70TeO2-20WO3-10La2O3 (mol%) was sintered to high density within a hot-press using a sacrificial powder as a pressure-transmitting medium. The potassium chloride (KCl) sacrificial power was found to minimize sample friction and adhesion to the die during pressing, facilitated the extraction of the densified sample from the die and was easily removable due to its water solubility. This fabrication process maximizes pressure transference to the green-body and enables sintered parts with optical quality comparable to those obtained by the melt-quench technique.

Metal–organic frameworks under pressure

Metal–organic frameworks (MOFs) are a broad and interesting class of materials known for their mechanical flexibility. As such, their response to pressure is usually extreme and often counterintuitive. This tutorial review surveys the structural response of MOFs to pressure as observed experimentally. It describes the experimental tools exploited in high-pressure crystallographic measurements and highlights some of the experiment design choices that influence the actual physics probed in these measurements. The main focus of the review is a description of the key pressure-driven structural responses exhibited by MOFs: isosymmetric compression, including negative compressibility; symmetry-lowering transitions; changes in connectivity; amorphization; and inclusion of the pressure-transmitting medium within the MOF pores. The review concludes both by highlighting some functional implications of these responses and by flagging some future directions for the field.

Effect of Pressure Treatment on the Specific Surface Area in Kaolin Group Minerals

Pressure can tailor the properties of a material by changing its atomistic arrangements and/or crystal morphology. We have investigated the changes in the adsorption properties of kaolin group minerals as a function of pressure treatment in the gigapascal range. External pressures have been applied using a large volume press (LVP) to kaolinite (Al2Si2O5(OH)4) and halloysite (H4Al2O9Si2·2H2O), which represent natural 2D layered and 1D nanowire structures, respectively. Powdered samples have been compressed up to 3 GPa in 1 GPa steps at room temperature and recovered by up to ca. 0.35 g from each pressure step. Brunauer–Emmett–Teller (BET) measurements were conducted using N2 gas to measure the specific surface area, pore size distribution, and pore volume of the pressure-treated samples. As the treatment pressure increased, kaolinite showed an increase in the adsorption behavior from nonpores to mesopores, whereas halloysite responded in an opposite manner to show a decrease in its adsorption capability. We discuss the contrasting effects of pressure-treatment on the two morphologically distinct kaolin group minerals based on field-emission scanning electron microscope (FE-SEM) images measured on each recovered material. We observed that the layers in kaolinite separate into smaller units upon increasing pressure treatment, whereas the tubes in halloysite become flattened, which led to the contrasting changes in surface area. Further study is in progress to compare this effect to when water is used as the pressure-transmitting medium.

Parallel background subtraction in diamond anvil cells for high pressure X-ray data analysis

ABSTRACTWe present a simple and effective approach to improve X-ray data collected under extreme conditions of pressure and temperature. The X-ray data of the sample and the amorphous, liquid, or crystalline pressure transmitting media (PTM) which surround the sample are collected separately at each pressure and temperature, allowing a satisfactory background subtraction. Using this method, we are able to identify weak diffraction peaks of the low-Z elements Li and Na and amorphous silica under pressure and at cryogenic temperatures. In addition to exploration of phase diagrams of low-Z materials, this method can also be applied to recognize new phases of other unknown materials such as binary hydrides in the high pressure and high-temperature synthesis, and to allow deterministic identification of the onset pressure of structural phase transitions and the presence of mixed phases.

Hydrostaticity of pressure-transmitting media for high pressure infrared spectroscopy

ABSTRACTEnsuring hydrostatic conditions in high pressure experiments is of utmost importance for obtaining reproducible and comparable dataset. Here, we investigate the degree of hydrostaticity of four pressure-transmitting media (PTM), three alkali halides and polyethylene, commonly used in infrared (IR) spectroscopy using multiple rubies as pressure sensors within a diamond anvil cell (DAC) pressure cavity. We demonstrate that the pressure standard deviation is always below 0.3 GPa at pressures below 10 GPa and that sodium chloride (NaCl) provides the best quasi-hydrostatic conditions up to 21 GPa. In the 10–20 GPa pressure range, NaCl, cesium iodide (CsI), and polyethylene perform significantly better than 4:1 ethanol–methanol or silicone oil – widely used PTM in high pressure experiments. These results will enable a more reliable and quantitative comparison between different experiments where the PTM investigated here are used.

Visualization of shockwave behavior in water and gelatin

Explosive welding is a popular method that is utilized to bond different types of metals. In particular, with the use of underwater explosive welding technique, the uniform acceleration of a thin plate over a very short flying distance is possible, which makes the technique suitable for the welding of thin plates onto a base plate to modify various properties of the surface of interest for protection against extreme environments. However, the use of water complicates the setup of the assembly, and therefore, in this study, we attempt to use other pressure-transmitting media, such as gelatin, which exhibits shockwave propagation similar to water. The similarity of shockwave propagation of the two materials is confirmed via optical observations utilizing a high-speed camera for two types of explosives. Thus, our findings confirm the viability of the use of gelatin as a pressure-transmitting medium for explosive welding.

Giant and Reversible Inverse Barocaloric Effects near Room Temperature in Ferromagnetic MnCoGeB0.03.

Hydrostatic pressure represents an inexpensive and practical method of driving caloric effects in brittle magnetocaloric materials, which display first-order magnetostructural phase transitions whose large latent heats are traditionally accessed using applied magnetic fields. Here, moderate changes of hydrostatic pressure are used to drive giant and reversible inverse barocaloric effects near room temperature in the notoriously brittle magnetocaloric material MnCoGeB0.03 . The barocaloric effects compare favorably with those observed in barocaloric materials that are magnetic. The inevitable fragmentation provides a large surface for heat exchange with pressure-transmitting media, permitting good access to barocaloric effects in cooling devices.

Insights into Polymorphism of Lithium Manganese Oxide, Li0.95Mn2.05O4: A Comprehensive Survey of the High-Pressure Properties

Understanding the structural behavior of lithium manganese oxide (LMO) under high pressure, especially under nonhydrostatic pressure conditions, could provide more insights into control of the mechanochemical processes occurring during battery operation and allow predicting new applications for this type of oxides. Here, we report pressure-induced structural changes in Li0.95Mn2.05O4 at two temperatures, 300 and 380 K, investigated in situ through synchrotron X-ray powder diffraction up to 13 GPa in a diamond anvil cell. Compression-induced strain triggers a cascade of local structure deformations, which finally result in the structural phase transition to the high-pressure tetragonal phase. A comparison of bulk moduli at two temperatures reveal that due to the differences in the response of the structure to the strain, Li0.95Mn2.05O4 exhibits the rare property of “warm hardening”. Additionally, a direct correlation between hydrostaticity of the pressure-transmitting medium and structural transformations ...

Ultrahigh pressure equation of state of tantalum to 310 GPa

ABSTRACTThe isothermal compression of transition metal tantalum (Ta) was studied in a diamond anvil cell by X-ray diffraction utilizing rhenium (Re) and gold (Au) as internal X-ray pressure standards. The Re pressure marker was employed during non-hydrostatic compression to pressures up to 310 GPa while the Au pressure marker was used during quasi-hydrostatic compression in a neon pressure-transmitting medium to 80 GPa. Two ultra-high pressure experiments were conducted on Ta and Re mixtures utilizing focused-ion beam machined toroidal diamond anvils with central flats varying from 8 microns to 16 microns in diameter. The Ta metal was observed to be stable in the body-centered-cubic phase to a volume compression V/V0 = 0.581. The measured equations of state (EOS) of Ta using two different calibrations of the Re pressure marker are compared with the ambient temperature isotherm derived from shock compression data. We provide a detailed analysis of EOS fit parameters for Ta under quasi-hydrostatic and non-hydrostatic conditions.

Building of Pressure-Assisted Ultra-High Temperature System and Its Inactivation of Bacterial Spores.

The pressure-assisted ultra-high temperature (PAUHT) system was built by using soybean oil as pressure-transmitting medium, and the multiple regression equation of soybean oil temperature change (ΔTP) during pressurization as a function of initial temperature (Ti) and set pressure (P) was developed: ΔTP = -13.45 + 0.46 Ti + 0.0799 P - 0.0037 - 2.83 × 10-5 P2. The fitted model indicated that the temperature of the system would achieve ≥121°C at 600 MPa when the initial temperature of soybean oil was ≥84°C. The PAUHT system could effectively inactivate spores of Bacillus subtilis 168 and Clostridium sporogenes PA3679 (less than 1 min). Treatment of 600 MPa and 121°C with no holding time resulted in a 6.75 log reductions of B. subtilis 168 spores, while treatment of 700 MPa and 121°C with pressure holding time of 20 s achieved more than 5 log reductions of C. sporogenes PA3679 spores. By comparing the PAUHT treatment with high pressure or thermal treatment alone, and also studying the effect of compression on spore inactivation during PAUHT treatment, the inactivation mechanism was further discussed and could be concluded as follows: both B. subtilis 168 and C. sporogenes PA3679 spores were triggered to germinate firstly by high pressure, which was enhanced by increased temperature, then the germinated spores were inactivated by heat.

Allanite at high pressure: effect of REE on the elastic behaviour of epidote-group minerals

The compressional behaviour of a natural allanite from Lago della Vecchia (upper Cervo valley, Italy) metagranitoids [A1( $$ {\text{Ca}}_{0.69}{\text{Fe}}_{0. 3 1}^{ 2+ } $$ )Σ1.00A2(Ca0.46Ce0.24La0.12Sm0.02Pr0.05Nd0.09Th0.02)Σ1.00M1( $$ {\text{Al}}_{0.65}{\text{Fe}}_{0. 3 4}^{ 3+ } $$ Ti0.02)Σ1.01M2(Al0.99)M3( $$ {\text{Fe}}_{0. 5 4}^{3 + } {\text{Fe}}_{0. 3 6}^{ 2+ } $$ Mg0.06 $$ {\text{Ti}}_{0.0 2}^{ 4+ } $$ Al0.01)Σ0.99Si1,Si2,Si3(Si2.80Al0.20)Σ3.00O11(OH,O)] has been investigated up to 16 GPa (at 298 K) by means of in situ synchrotron single-crystal X-ray diffraction. Experiments have been conducted under hydrostatic conditions, using a diamond anvil cell and the mix methanol:ethanol:water = 16:3:1 (up to 10 GPa) and neon (up to 16 GPa) as pressure-transmitting media. No phase transition has been observed within the pressure-range investigated. Data collected in decompression prove that, at least up to 16 GPa (at 298 K), the deformation mechanisms are fully reversible. A third-order Birch–Murnaghan Equation of State (BM-EoS) was fitted to the P–V data (up to 10 GPa), giving: V0 = 470.2(2) A3, KP0,T0 = 131(4) GPa and K′= 1.9(8). The evolution of the lattice parameters with pressure shows a slight anisotropic compression pattern, with KP0,T0(a):KP0,T0(b):KP0,T0(c) = 1.24:1.52:1. The monoclinic β-angle decreases monotonically with pressure, with: βP(°) = βP0 – 0.0902(4)P (R2 = 0.997, with P in GPa). The main deformation mechanisms at the atomic scale are described based on a series of structure refinements at different pressures. A comparison between the compressional behavior of allanite, epidote and clinozoisite is carried out.

Packing Rearrangements in 4-Hydroxycyanobenzene Under Pressure

4-hydroxycyanobenzene (4HCB) is a dipolar molecule formed of an aromatic substituted benzene ring with the CN and OH functional groups at the 1 and 4 positions. In the crystalline state, it forms spiral chains via hydrogen bonding, which pack together through interactions. The direct stacking of benzene rings down the a- and b-axes and its interactions throughout the structure gives rise to its semiconductor properties. Here, high-pressure studies are conducted on 4HCB in order to investigate how the packing and intermolecular interactions, related to its semiconductor properties, are affected. High-pressure single-crystal X-ray diffraction was performed with helium and neon as the pressure-transmitting mediums up to 26 and 15 GPa, respectively. The pressure-dependent behaviour of 4HCB in He was dominated by the insertion of He into the structure after 2.4 GPa, giving rise to two phase transitions, and alterations in the interactions above 4 GPa. 4HCB compressed in Ne displayed two phase transitions associated with changes in the orientation of the 4HCB molecules, giving rise to twice as many face-to-face packing of the benzene rings down the b-axis, which could allow for greater charge mobility. In the He loading, the hydrogen bonding interactions steadily decrease without any large deviations, while in the Ne loading, the change in 4HCB orientation causes an increase in the hydrogen bonding interaction distance. Our study highlights how the molecular packing and interactions evolve with pressure as well as with He insertion.

Pressure tolerance of Artemia cysts compressed in water medium

ABSTRACTThe high pressure tolerance of cysts of Artemia salina was investigated up to several GPa in water. No survival was observed after exposure to 1.0 GPa for 15 min. After exposure to 2.0 GPa for the same time duration, the hatching rate had recovered to 33%, but decreased to 8% following compression at 7.5 GPa. This contrasts with results using Fluorinert™ as the pressure-transmitting medium where 80–88% recovery was observed. The lower survival rate in water is accompanied by swelling of the eggs, indicating that liquid H2O close to the ice-VI crystallization pressure penetrated inside the eggs. This pressure exceeds the stability limit for proteins and other key biomolecules components within the embryos that could not be resuscitated. Rehydration takes several minutes and so was not completed for all samples compressed to higher pressures, prior to ice-VI formation, resulting in renewed survival. However H2O penetration inside the shell resulted in increased mortality.

The Zinc Story under High Pressure

A historical review is presented on the experimental and theoretical studies on Zn under high pressure. Based on our high-pressure powder x-ray diffraction experiments that have been done for nearly a decade, we describe the structural change of Zn up to 126 GPa at room temperature. Although several experimental and theoretical studies indicated an anomalous change of the c/a axial ratio with pressure, we found no such an anomaly within our experimental uncertainty. Our high-pressure low-temperature experiments up to 18 GPa at 40 K also gave no evidence of the c/a anomaly. We suspect that the pressure-transmitting media played an important role in producing the anomaly. The structural anisotropy of Zn is drastically reduced at high pressures, which would be a general trend for hexagonal close-packed (hcp) metals.