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Abstract: The crystal structure and bonding environment of K2Ca(CO3)2 bütschliite were probed under isothermal compression via Raman spectroscopy to 95 GPa and single crystal and powder X-ray diffraction to 12 and 68 GPa, respectively. A second order Birch-Murnaghan equation of state fit to the X-ray data yields a bulk modulus, $${K}_{0}=46.9$$ K 0 = 46.9 GPa with an imposed value of $${K}_{0}^{\prime}= 4$$ K 0 ′ = 4 for the ambient pressure phase. Compression of bütschliite is highly anisotropic, with contraction along the c-axis accounting for most of the volume change. Bütschliite undergoes a phase transition to a monoclinic C2/m structure at around 6 GPa, mirroring polymorphism within isostructural borates. A fit to the compression data of the monoclinic phase yields $${V}_{0}=322.2$$ V 0 = 322.2  Å3$$,$$ , $${K}_{0}=24.8$$ K 0 = 24.8 GPa and $${K}_{0}^{\prime}=4.0$$ K 0 ′ = 4.0 using a third order fit; the ability to access different compression mechanisms gives rise to a more compressible material than the low-pressure phase. In particular, compression of the C2/m phase involves interlayer displacement and twisting of the [CO3] units, and an increase in coordination number of the K+ ion. Three more phase transitions, at ~ 28, 34, and 37 GPa occur based on the Raman spectra and powder diffraction data: these give rise to new [CO3] bonding environments within the structure.

Elucidating the phase diagram of solid hydrogen is a key objective in condensed matter physics. Several decades ago, it was proposed that at low temperatures and high pressures, solid hydrogen would be a metal with a high superconducting transition temperature. This transition to a metallic state can happen through the closing of the energy gap in the molecular solid or through a transition to an atomic solid. Recent experiments have managed to reach pressures in the range of 400-500 GPa, providing valuable insights. There is strong evidence suggesting that metallization via either of these mechanisms occurs within this pressure range. Computational and experimental studies have identified multiple promising crystal phases, but the limited accuracy of calculations and the limited capabilities of experiments prevent us from determining unequivocally the observed phase or phases. Therefore, it is crucial to investigate the superconducting properties of all the candidate phases. Recently, we reported the superconducting properties of theC2/c-24,Cmca-12,Cmca-4 andI41/amd-2 phases, including anharmonic effects. Here, we report the effects of anisotropy on superconducting properties using Eliashberg theory. Then, we investigate the superconducting properties of deuterium and estimate the size of the isotope effect for each phase. We find that the isotope effect on superconductivity is diminished by anharmonicity in theC2/c-24 andCmca-12 phases and enlarged in theCmca-4 andI41/amd-2 phases. Our anharmonic calculations of theC2/c-24 phase of deuterium agree closely with the most recent experiment by Loubeyreet al(2022Phys. Rev. Lett.29035501), indicating that theC2/c-24 phase remains the leading candidate in this pressure range, and has a strong anharmonic character. These characteristics can serve to distinguish among crystal phases in experiment. Furthermore, expanding our understanding of superconductivity in pure hydrogen holds significance in the study of high-Tchydrides.

Solid solutions Nd 2 MnMn(Mn 4− x Sb x)O 12 , belonging to the A-site columnar-ordered quadruple perovskite subfamily A 2 A′A″B 4 O 12 and prepared by a high-pressure, high-temperature method at about 6 GPa and about 1700 K, were investigated in a compositional range of 0.2 ≤ x ≤ 2.0. Crystal structures were studied using synchrotron powder X-ray diffraction. Two regions with different cation orders in the B sublattice were found: a narrow region of 0.8 ≤ x ≤ 1.0 had a B-site disordered structure with space group P 4 2 / nmc (No. 137), and a wider region of 1.6 ≤ x ≤ 2.0 had a B-site rock-salt-ordered structure with space group P 4 2 / n (No. 86). Small anti-site disorder of Nd and Mn was detected among the A, A′, and A″ sites. In the B-site rock-salt-ordered structures, one B site was solely occupied by Mn, the second B′ site had a mixture of Sb and Mn (for x < 2). The samples showed complex magnetic behavior with two ferrimagnetic transitions. T C1 monotonically increased (from 66 K to 75 K) and T C2 was almost constant (about 6–7 K) for 0.8 ≤ x ≤ 1.0. T C1 monotonically decreased (from 77 K to 63 K) and T C2 monotonically increased (from 19 K to 39 K) for 1.6 ≤ x ≤ 2.0. There was evidence for the third magnetic transition in the 1.7 ≤ x ≤ 2.0 samples, and T C3 increased from 13 K to 20 K with increasing x. [ABSTRACT FROM AUTHOR]

In this study, experimental carry out of liquid–vapor and solid–liquid phase transitions were conducted for the ternary system {CO2 (1) + ethanol (2) + acetaminophen (3)} at different concentrations of paracetamol in ethanol for temperatures from 313 to 333 K and pressures up to 12 MPa. Experimental high pressure phase transition data were obtained using the static method in a variable volume view cell. Experimental data were compared with the literature for systems containing acetaminophen in a saturated solution. The presence of paracetamol in the binary system {CO2 (1) + ethanol (2)} significantly alters the behavior of the phase under the conditions of temperature and concentration studied. It was observed that in the ternary system {CO2 (1) + ethanol (2) + acetaminophen (3)} with a saturated solution at the lowest temperature, 313 K, CO2 acts as a cosolvent for mole fractions lower than 0.6. Thermodynamic simulations employing the Perturbed Chain Statistical Associating Fluid Theory (PC-SAFT) Equations of State (EoS) aligned the experimental results adequately. The observed minimal deviations in pressure and temperature validate the efficacy of the thermodynamic models applied in this study. [ABSTRACT FROM AUTHOR]

A hitherto unknown modification of I2O5 was obtained from high‐pressure/high‐temperature syntheses in a Walker‐type multianvil device at 8 GPa and 250 °C. HP‐I2O5 crystallizes in the monoclinic crystal system with space group P21/c (no. 14) with the unit cell parameters a=12.0612(3) Å, b=4.8613(2) Å, c=6.9585(2) Å, β=100.10(1)° (at 173 K), and four formula units per cell. The single‐crystal structure data are accompanied by powder X‐ray diffraction data at ambient and elevated temperatures. Furthermore, DFT calculations were carried out to investigate the phase transition between the ambient‐pressure polymorph NP‐I2O5 to the newly synthesized high‐pressure phase. [ABSTRACT FROM AUTHOR]

BACKGROUND RESULTS CONCLUSION High‐sodium intake has been proven to bring serious risks to public health. A potential sodium substitute of salt taste‐enhancing hydrolysate (STEH) of protein has been focused on recently. The salt taste‐enhancing activity (STEA) of STEH still needs to be improved. High‐pressure and calcium chloride (CaCl2) pretreatments were reported to affect proteolysis and promote the release of bioactive peptides. Hence, we investigated effects of high‐pressure and CaCl2 pretreatments on hydrolysis and STEA of STEH derived from spent hen.The pretreatments significantly influenced STEA of spent hen meat hydrolysate (SHH), especially 200 MPa pressure and 80 mmol L−1 CaCl2 pretreatments increased 27.1% salt taste intensity of SHH compared to that of blank (without pretreatments) according to sensory evaluation, the SHH umami also increased after pretreatments. In SHH, the proportion of peptides < 1000 Da increased up to 79.37% after the pretreatments compared to 73.68% of the blank. The degree of hydrolysis (DH) increased to 19.45% for moderate high‐pressure (200 MPa) from 18.02% for blank, and the DH decreased after higher high‐pressure and CaCl2 pretreatments, especially for CaCl2 in 80 mmol L−1. The change in particle size distribution of SHH has similar trends to DH.High‐pressure and CaCl2 pretreatments increased STEA of SHH by affecting hydrolysis process. The STEA increase may be related to increased small‐peptide proportion in SHH. Meanwhile, moderate high‐pressure may promote protein unfolding and further increase DH according to particle size distribution of SHH. The combination of proteolysis and pretreatments of high‐pressure and CaCl2 is a promising method to produce STEH. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Developing strategies to systematically increase the critical current, the threshold current below which the superconductivity exists, is an important goal of materials science. Here, the concept of quantum phase transition is employed to enhance the critical current of a kagome superconductor CsV3Sb5, which exhibits a charge density wave (CDW) and superconductivity that are both affected by hydrostatic pressure. As the CDW phase is rapidly suppressed under pressure, a large enhancement in the self‐field critical current (Ic, sf) is recorded. The observation of a peak‐like enhancement of Ic, sf at the zero‐temperature limit (Ic, sf(0)) centered at p* ≈ 20 kbar, the same pressure where the CDW phase transition vanishes, further provides strong evidence of a zero‐temperature quantum anomaly in this class of pressure‐tuned superconductor. Such a peak in Ic, sf(0) resembles the findings in other well‐established quantum‐critical superconductors, hinting at the presence of enhanced quantum fluctuations associated with the CDW phase in CsV3Sb5. [ABSTRACT FROM AUTHOR]

Developing strategies to systematically increase the critical current, the threshold current below which the superconductivity exists, is an important goal of materials science. Here, the concept of quantum phase transition is employed to enhance the critical current of a kagome superconductor CsV3Sb5, which exhibits a charge density wave (CDW) and superconductivity that are both affected by hydrostatic pressure. As the CDW phase is rapidly suppressed under pressure, a large enhancement in the self‐field critical current (Ic, sf) is recorded. The observation of a peak‐like enhancement of Ic, sf at the zero‐temperature limit (Ic, sf(0)) centered at p* ≈ 20 kbar, the same pressure where the CDW phase transition vanishes, further provides strong evidence of a zero‐temperature quantum anomaly in this class of pressure‐tuned superconductor. Such a peak in Ic, sf(0) resembles the findings in other well‐established quantum‐critical superconductors, hinting at the presence of enhanced quantum fluctuations associated with the CDW phase in CsV3Sb5. [ABSTRACT FROM AUTHOR]

Due to its unique properties such as superconductivity and superfluidity, high-pressure properties of hydrogen attract a lot of attention. However, the Liquid–Liquid Transition (LLT) of hydrogen under high-pressure and high-temperature is of particular significance for understanding its metallization. We propose a data-driven machine learning approach based on the density functional theory data to fit the potential energy surface into a deep neural network form. This method overcomes the simulation scale limitations of first-principles approaches to investigate the dissociation behavior of hydrogen molecules under high pressure. Our findings reveal an LLT curve exhibiting a first-order continuous change along with transition zone corresponding to hydrogen molecule dissociation. This study offers valuable insights into the LLT phenomenon and the metallization of hydrogen under high pressure. [ABSTRACT FROM AUTHOR]

Investigating the implications of interlayer coupling on superconductivity is vital for comprehending the intrinsic mechanisms of two-dimensional materials. Van der Waals heterojunctions have attracted extensive research owing to their exotic interlayer coupling. In this study, we investigated the natural heterostructure superconductor featuring 6R-TaS2 via measurements of electrical resistance, the Hall effect, and in-situ synchrotron X-ray diffraction (XRD) under various pressures. The study findings show that the superconducting transition temperature (Tc) of 6R-TaS2 in the range of 0–32.5 GPa exhibits an unusual double-dome behavior as a function of pressure, with the first and second domes in the pressure range of 0–5.3 and 6.8–32.5 GPa, respectively. At 56.6 GPa, a new superconducting phase with a Tc of 2 K was observed. The XRD results show that the singular evolution of the Tc is independent of the structural phase transition. Combining the XRD results, first-principles calculations, and Hall effect measurements, we found that different interlayer coupling effects resulted in double dome superconductivity and the re-emergence of superconducting. Our findings shed light on the pivotal role of interlayer coupling in driving the anomalous alterations in superconducting properties triggered by charge transfer and Fermi surface reconstruction and provide an alternative route for comprehending the mechanisms of superconductivity in transition metal dichalcogenides (TMDs). [ABSTRACT FROM AUTHOR]

This study aims to evaluate homogenization techniques and conditions for producing stable, small droplet‐size water‐in‐oil (W/O) emulsions intended for incorporation into casein hydrolysate–loaded double emulsions. Three commonly used homogenization methods; rotor–stator, ultrasonic, and high‐pressure homogenization were individually optimized utilizing response surface methodology. Instances of over‐processing were observed, particularly with the rotor–stator and ultrasonic homogenizers under specific conditions. Nevertheless, optimal conditions were identified for each technique: 530 s at 17,800 rpm agitation speed for the rotor–stator homogenizer, 139 s at 39% amplitude for the ultrasonic homogenizer, and 520 s at 1475 bar for the high‐pressure homogenizer. Subsequently, the W/O emulsions produced under optimal conditions and their respective W1/O/W2 double emulsions were compared. The rotor–stator and high‐pressure homogenized W/O emulsions exhibited comparable narrow droplet‐size distributions, as indicated by similar Span values. However, high‐pressure homogenization failed to sufficiently minimize droplet size. Ultrasonic homogenization resulted in droplets at the 1‐μm scale but yielded more polydisperse droplet‐size distribution. According to TOPSIS analysis, an emulsion with a viscosity of 93.1 cP (centiPoise), a stability index of 93.8%, a D(90) of 0.67 μm (0th day), and a D(90) of 0.75 μm (30th day) produced using a rotor–stator was selected. Additionally, double emulsions containing primary emulsions prepared with the rotor–stator method demonstrated higher viscosity, narrower droplet‐size distribution, and lower creaming compared to other samples. This investigation sheds light on the influence of homogenization techniques on emulsion properties, providing valuable insights for optimizing double emulsion formulations. [ABSTRACT FROM AUTHOR]

In situ X-ray diffraction and Raman spectroscopy of a synthetic whitlockite, Ca9Mg(PO3OH) (PO4)6, have been conducted at high pressures or high temperatures. The results show that whitlockite is stable up to ~15 GPa at ambient temperature and undergoes a thermally induced dehydrogenation to merrillite above 973 K at ambient pressure. The obtained pressure-volume data were fitted using a third-order Birch-Murnaghan equation of state, yielding an isothermal bulk modulus of K0 = 79(4) GPa with a pressure derivative of K 0 ′ = 4.3(6). When K 0 ′ was fixed at 4, the refined isothermal bulk modulus was 81(1) GPa. The volumetric thermal expansion coefficient (αV) is 4.05(8) × 10-5 K−1, and the axial thermal expansion coefficients (αa and αc) are 1.07(5) × 10−5 K−1 and 1.91(6) × 10−5 K−1. Both compressibility and thermal expansion show an axial anisotropy. The effects of pressure and temperature on the Raman spectra of whitlockite have been quantitatively analyzed. The isothermal and isobaric mode Grüneisen parameters and the intrinsic anharmonic mode parameters of whitlockite were derived. Some amounts of OH−-bearing whitlockite may be preserved in meteorites if whitlockite undergoes a low-temperature process. [ABSTRACT FROM AUTHOR]

The engineering of tunable photoluminescence (PL) in single materials with a full‐spectrum emission represents a highly coveted objective but poses a formidable challenge. In this context, the realization of near‐full‐spectrum PL emission, spanning the visible light range from 424 to 620 nm, in a single‐component two‐dimensional (2D) hybrid lead halide perovskite, (ETA)2PbBr4 (ETA+=(HO)(CH2)2NH3+), is reported, achieved through high‐pressure treatment. A pressure‐induced phase transition occurs upon compression, transforming the crystal structure from an orthorhombic phase under ambient conditions to a monoclinic structure at high pressure. This phase transition driven by the adaptive and dynamic configuration changes of organic amine cations enables an effective and continuous narrowing of the band gap in this halide crystal. The hydrogen bonding interactions between inorganic layers and organic amine cations (N−H⋅⋅⋅Br and O−H⋅⋅⋅Br hydrogen bonds) efficiently modulate the organic amine cations penetration and the octahedral distortion. Consequently, this phenomenon induces a phase transition and results in red‐shifted PL emissions, leading to the near‐full‐spectrum emission. This work opens a possibility for achieving wide PL emissions with coverage across the visible light spectrum by employing high pressure in single halide perovskites. [ABSTRACT FROM AUTHOR]

The cathodic reduction of pressurized CO2 (PrCO2CR) at suitable cathodes can allow to produce various chemicals, such as formic acid/formate (FA) and carbon monoxide or synthesis gas, with high faradic efficiencies (FEs) and productivities. Here, we have performed the conversion of CO2 in an undivided pressurized electrochemical reactor using silver cathode in order to determine the optimal values of CO2 pressure and current density. It was found that the plot FE vs. pressure resulted in a curve with a maximum. Similarly, an optimal value of current density can be selected for the PrCO2CR. The competition between the production of carbon monoxide and formic acid/formate is strongly affected by both the pressure and the current density. Eventually the effect of pressure and current density on the economic figures of the process was evaluated. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of High Pressure Physics is the property of Chinese Journal of High Pressure Physics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We performed electrical resistivity and X-ray diffraction measurements on the BiS2-based compound, EuSr2Bi2S2.5Se1.5F4, under high pressure using cubic and diamond anvil cells, respectively. We have also measured electrical resistivity at low temperatures and ambient pressures. The superconducting transition temperature (T c) was 1.13 K at ambient pressure and EuSr2Bi2S2.5Se1.5F4 was found to behave like a superconductor. Upon the application of increased pressure, T c increased and then decreased again, which was attributed to the structural phase transitions that accompany increased pressure in EuSr2Bi2S2.5Se1.5F4 superconductors. [ABSTRACT FROM AUTHOR]

Besides an elevated intraocular pressure (IOP), advanced age is one of the most crucial risk factors for developing glaucoma. βB1-Connective Tissue Growth Factor (βB1-CTGF) high-pressure glaucoma mice were used in this study to assess whether glaucoma mice display more inflammatory and aging processes than age-matched controls. Therefore, 20-month-old βB1-CTGF and corresponding wildtype (WT) controls were examined. After IOP measurements, retinas were processed for (immuno-)histological and quantitative real-time PCR analyses. A significantly higher IOP and diminished retinal ganglion cell numbers were noted in βB1-CTGF mice compared to WT. An enhanced macrogliosis as well as an increased number of microglia/macrophages and microglia was detected in retinas of old glaucoma mice. Interleukin (IL)-1β, IL-6, tumor necrosis factor-α, and transforming growth factor-β2 were upregulated, suggesting an ongoing inflammation. Moreover, βB1-CTGF retinas displayed an increased senescence-associated β-galactosidase staining accompanied by a downregulation of Lmnb1 (laminin-B1) mRNA levels. Our results provide a deeper insight into the association between inflammation and high-pressure glaucoma and thus might help to develop new therapy strategies. • Older βB1-CTGF mice display high intraocular pressure and signs of glaucoma. • Ganglion cell loss is accompanied by macro- and microgliosis. • These old glaucoma mice show a strong pro-inflammatory response in the retina. • Increased senescent markers are expressed in the retina. [ABSTRACT FROM AUTHOR]

Melting experiments of Fe3C were conducted to 85 GPa in laser‐heated diamond anvil cells with in situ X‐ray diffraction and post‐experiment textural observation. From the determined pressure‐temperature conditions of the melting curve for Fe3C, together with literature data on the melting point of diamond and eutectic point of the system Fe‐Fe3C/Fe7C3 under high pressures, we established a self‐consistent thermodynamic model for high‐pressure melting of the system Fe‐C including the mixing parameters for liquids. The results show that mixing of Fe and C liquids is negatively nonideal from 1 bar to the pressure at the center of the Earth. The departure from ideal mixing becomes progressively larger with increasing pressure, which leads to greatly stabilized liquids under core pressures. The modeled carbon content in eutectic melts under core pressures is 3.3–4.4 wt%. From the Gibbs free energy, we derived an internally consistent parameters for Fe‐C outer cores which included the crystallizing points at their bottoms, isentropic thermal profiles, and densities and longitudinal seismic wave speeds (Vp). While the addition of carbon in excess of the eutectic melt composition effectively reduces the density of iron liquid, the Vp of iron liquid is not greatly changed. Therefore, the low density and high Vp of PREM relative to pure iron cannot be reconciled by an Fe‐C liquid. Therefore, the Earth's core cannot be approximated by the system Fe‐C and should include another light element. Plain Language Summary: The presence or absence of carbon in the Earth's central core has long been discussed in order to account for the observed core density lower than iron because the identification of such light elements in the core will provide critical information about the origin and evolution of the solid Earth. The relevance of carbon in the Earth's core is testable by comparing the density and seismic wave velocities of candidate Fe‐C materials with observations. Here we present a new experiment‐based thermodynamic model for the system Fe‐C. We first determined the melting points of Fe3C to 85 GPa. We then assessed thermodynamic parameters of Fe‐C liquids, from the constrained pressure‐temperature conditions of the melting curve for Fe3C, together with literature data. From the established model, we consistently computed the properties of hypothetical Fe‐C liquid outer cores including the density and longitudinal seismic wave velocity. While a carbon concentration greater than 4 wt% effectively reduces the density of iron liquid, the seismic velocity is not greatly changed, and therefore carbon cannot reconcile the low density and high velocity nature of the Earth's outer core. Therefore, the Earth's core cannot be approximated by the system Fe‐C and should include another light element. Key Points: Melting experiments of Fe3C were conducted to 85 GPa in diamond anvil cells with in situ X‐ray diffraction and textural observationA thermodynamic model for melting of the system Fe‐C which is applicable to the center of the Earth was establishedThe Earth's core cannot be approximated by the system Fe‐C and should include another light element [ABSTRACT FROM AUTHOR]

Compressibility and structural evolution of K-cymrite, hexagonal high-pressure KAlSi3O8·H2O, has been studied up to 18 GPa using synchrotron single crystal X-ray diffraction in Ne pressure medium. K-cymrite retains its original symmetry P6/mmm up to a pressure of 7.3 GPa. As the pressure increases from 7.3 to 8.5 GPa, the weak satellite reflections appear on diffraction patterns and remain up to maximum applied pressure of 18 GPa indicating incommensurate modulation. However, main reflections can be still indexed in hexagonal cell and structure successfully solved in initial P6/mmm group. After pressure release, K-cymrite reverts to initial non-modulated single-crystal state. The parameters of third-order Birch-Murnaghan equation of state for K-cymrite are V0 = 190.45(12) ų, K0 = 56.5(7) GPa and K0’ = 3.2(12), with bulk modulus notably deviating from earlier result (K0 = 45(2) GPa and K0’ = 1.3(10)) obtained in vaseline media. [ABSTRACT FROM AUTHOR]

K-Ca double carbonates recently identified in inclusions in diamonds, as well as associated alkali-carbonate melts can play an important role in the deep carbon cycle. We studied pressure-induced changes in the crystal structure of high-pressure α-K2Ca3(CO3)4 phase up to 20 GPa using synchrotron single-crystal x-ray diffraction in diamond anvil cell. At ~ 7 GPa at room temperature the orthorhombic P212121 phase of α-K2Ca3(CO3)4 undergoes displacive phase transition into monoclinic P1121 phase. Despite the phase transition, PV-curve does not demonstrate any irregularities so that both phases can be described by the same 4th order Birch-Murnaghan equation of state with V0 = 1072.5(3) Å3, K0 = 51.1(8) GPa, K’0=3.7(3), K’’0=0.12(6). [ABSTRACT FROM AUTHOR]

This study developed a fibre-optic laser Doppler velocimetry sensor for use in opaque, high-temperature, and high-pressure fluid flows by inserting the fibre perpendicular to the main flow. The tip of the optical fibre was obliquely polished and chemically etched using a buffered hydrofluoric acid solution, and a reflective mirror was deposited on the surface of the oblique fibre tip. Based on the results of the verification test using the rotating annular open channel, the fabrication conditions of the fibre tip were optimized for measuring the lubricating oil flow. The flow velocity profiles in the engine's oil flow of the lubrication system during engine bench testing were measured. These velocity profiles were influenced by variations in the measurement position, oil temperature, and engine speed. The measurement accuracy of this sensor was compared with the volumetric flow rate obtained by cross-sectional area integration of the flow velocity profile, as measured using a Coriolis flowmeter, and the difference was within 1%. By combining computational simulation for flow and optical attenuation and particle scattering in light transmission through a working fluid, this fibre-optic sensor achieved a measurement volume of 200 microns in length and 200 microns in width at a distance of 900–1000 microns from the sensor. [ABSTRACT FROM AUTHOR]

This paper offers a comprehensive DFT investigation into the structural, mechanical and thermodynamic characteristics of four distinct Mg2C3 crystal structures across a broad pressure spectrum spanning from 0GPa to 100GPa, utilizing the GGA-PBE method. Our rigorous calculations indicate that Mg2C3 undergoes phase transitions from the Pnnm phase to the C2/m phase at PGGA1=1.3GPa, and subsequently to the P21/m phase at PGGA2=35.8GPa. Notably, within the pressure range of approximately 0–20GPa, the enthalpy difference between the Pnnm and Pbca phases shrinks considerably, hinting at the possibility of their coexistence under lower pressure conditions. Furthermore, our analysis delves into the interplay between the mechanical and thermodynamic properties of Mg2C3 and pressure, revealing that the C2/m structure possesses exceptional ductility in Mg2C3 crystals under low to moderate pressure, whereas Mg2C3 exhibits brittleness under high pressure. Additionally, a notable variation in material hardness is observed throughout the phase transition process. [ABSTRACT FROM AUTHOR]

Explorative high‐pressure/high‐temperature syntheses (7 GPa, 800 °C) starting from Er2O3, CdO, and H3BO3 yielded single‐crystals of the hitherto unknown compound ErCd2B7O13(BO(OH)3). This compound crystallizes trigonally in the non‐centrosymmetric space group R3c with the unit cell parameters a=8.8418(2) Å, c=22.4972(8) Å, and six formula units per cell. The crystal structure is composed of corner‐sharing trigonal planar [BO3] and tetrahedral [BO4] groups, forming a complex three‐dimensional framework. In this article, the structural data and characteristics of ErCd2B7O13(BO(OH)3) are presented in detail. Furthermore, the compound's infrared spectrum is discussed. [ABSTRACT FROM AUTHOR]

Alternatives to the conventional thermal processing (TT) of food are an area of research that has grown tremendously in recent decades. The impact of these alternative techniques on the sensory profile of fruit juices has been discussed in the literature but only in a fragmented manner. This review takes a macroscopic approach to discuss the influence of emerging thermal and non-thermal techniques currently used by industries on a commercial scale, like high-pressure processing (HPP), ohmic heating (OH), and pulse electric field processing (PEF), on certain sensory characteristics of fruit juices and beverages. A sensory impression of a product is a result of a complex mixture of several compounds. The sensory profile varies with the type of processing technique due to differences in intensities and the inactivation mechanism for enzymes. Heat plays a role in the generation of flavor and odor-active compounds; hence, a different sensory profile is expected with alternative techniques that operate at ambient temperatures (HPP and PEF) or have short treatment time due to rapid heating (OH). HPP, OH, and PEF positively influence the retention of compounds that contribute to a fresh-like sensory experience. However, enzyme inactivation is often challenging with alternative techniques resulting in higher residual activity, affecting sensory quality during storage. Nevertheless, there is evidence in the literature of products with stable sensory properties during storage after processing with alternative techniques. Additionally, some residual enzyme activity may play a role in flavor enhancement during storage, i.e., the release of aglycones from glycoconjugates by pectolytic enzymes. Multiple factors like fruits' cultivar, way of cultivation, external growth conditions, andmaturity stage at the time of harvest influence its sensory quality and, subsequently, the products derived from them. The review concludes with the impression that there is extensive literature on the effects of HPP on the sensory properties of fruit juices. However, the research is limited in discussing the influence of OH and PEF. Additionally, it is difficult to make a fair and systematic comparison among the different preservation technologies because of the lack of standardization and comprehensive sensory evaluation in the studies in the literature. [ABSTRACT FROM AUTHOR]

The high-pressure behaviour of inderborite [ideally CaMg[B3O3(OH)5]2(H2O)4⋅2H2O, space group C 2/ c with a ≈ 12.14, b ≈ 7.43, c ≈ 19.23 Å and β ≈ 90.3° at room conditions] has been studied by two in situ single-crystal synchrotron X-ray diffraction experiments up to ~10 GPa, using He as pressure-transmitting fluid. Between 8.11(5) and 8.80(5) GPa, inderborite undergoes a first-order phase transition to its high-pressure polymorph, inderborite-II (with a ≈ 11.37, b ≈ 6.96, c ≈ 17.67 Å, β ≈ 96.8° and ΔV ≈ 7.0%, space group unknown). The isothermal bulk modulus (KV0 = β−1P0,T0, where β P0,T0 is the volume compressibility coefficient) of inderborite was found to be KV0 = 41(1) GPa. The destructive nature of the phase transition prevented any structure resolution of inderborite-II or even the continuation of the experiments at pressures higher than 10.10(5) GPa. In the pressure range 0–8.11(5) GPa, the compressional anisotropy of inderborite, indicated by the ratio between the principal components of the Eulerian finite unit-strain ellipsoid, is ɛ1:ɛ2:ɛ3 = 1.4:1.05:1. The deformation mechanisms at the atomic scale in inderborite are here described. Our findings support the hypothesis of a quasi-linear correlation between the total H2O content and P -stability range in hydrated borates, as the pressure at which inderborite undergoes the phase transition falls in line with most of the hydrate borates studied at high-pressure so far. [ABSTRACT FROM AUTHOR]

Diamond anvil cells have garnered significant attention in high‐pressure studies as a valuable tool for investigating material preparation, phase transition dynamics, and ultra‐high‐pressure physical chemistry. Its potential applications span fields such as materials science, condensed matter physics, chemistry, and geology. This study conducts a comprehensive review of the utilization of laser‐heated diamond anvil cell (LH‐DAC) devices in conjunction with in situ optical characterization techniques, such as X‐Ray and Raman scattering. Further, diverse in situ performance measurement methods encompassing electrical, thermal, magnetic, and acoustic analyses are examined. The development and role of the prevailing in situ measurement techniques have been described, along with the current progress in applied research for each technique. This study aims to facilitate the discovery of new structures and properties of materials under high pressure–temperature conditions. [ABSTRACT FROM AUTHOR]

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Hydrogen and helium saturate the 1D pore systems of the high‐silica (Si/Al>30) zeolites Theta‐One (TON), and Mobile‐Twelve (MTW) at high pressure based on x‐ray diffraction, Raman spectroscopy and Monte Carlo simulations. In TON, a strong 22 % volume increase occurs above 5 GPa with a transition from the collapsed P21 to a symmetrical, swelled Cmc21 form linked to an increase in H2 content from 12 H2/unit cell in the pores to 35 H2/unit cell in the pores and in the framework of the material. No transition and continuous collapse of TON is observed in helium indicating that the mechanism of H2 insertion is distinct from other fluids. The insertion of hydrogen in the larger pores of MTW results in a strong 11 % volume increase at 4.3 GPa with partial symmetrization followed by a second volume increase of 4.5 % at 7.5 GPa, corresponding to increases in hydrogen content from 43 to 67 and then to 93 H2/unit cell. Flexible 1D siliceous zeolites have a very high H2 capacity (1.5 and 1.7 H2/SiO2 unit for TON and MTW, respectively) due to H2 insertion in the pores and the framework, in contrast to other atoms and molecules, thereby providing a mechanism for strong swelling. [ABSTRACT FROM AUTHOR]

AlB4O6N, Al0.97Cr0.03B4O6N, and Al0.83Cr0.17B4O6N are the first representatives of the recently established structure‐family of oxonitridoborates containing Al3+. These compounds are isotypic to CrB4O6N and are synthesized in a multi‐anvil press under high‐pressure/high‐temperature conditions of 7.0 GPa/1350 °C. Structural refinement by single‐crystal X‐ray diffraction shows that they crystallize in the space group P63mc (no. 186) with two formula units per cell. Detailed characterization including high‐temperature X‐ray powder diffraction (HT‐XRD), electron probe microanalysis (EPMA), measurements of second harmonic generation (SHG), hardness, photoluminescence properties, vibrational spectroscopy, and band structure calculations reveal intriguing physicochemical properties that strongly resemble the famous material ruby. [ABSTRACT FROM AUTHOR]

This article spotlights the interest in using co-localized infrared (IR)–Raman spectroscopy as an innovative approach for the in situ monitoring of complex gas mixtures, e.g., hydrogen (H2), nitrogen (N2), carbon monoxide (CO), carbon dioxide (CO2), and methane (CH4), at elevated pressures. Thus, by combining the IR and Raman spectra of CH4, we proposed a new methodology for the calibration of the Raman spectra to circumvent the fact that Raman intensities are arbitrary (laser power, instrument response, integration time, and fluorescence). Applying our methodology to scale several consecutive experiments, the concentrations of all gases were determined with a relative uncertainty lower than 10%. These original results highlight the interest in co-localized IR–Raman spectroscopy analysis in a single cell for the quantitative analysis of solutes by Raman spectroscopy without the use of an internal standard. [ABSTRACT FROM AUTHOR]

Physical properties of mantle minerals are essential for comprehensive geodynamic modeling. High-pressure experiments allow measurements of physical properties but fundamental insights into their evolution with pressure are often experimentally inaccessible. Here we report the first in situ experimental determination of the optical refractive index, its wavelength-dispersion, and optical absorption coefficient of ferropericlase up to ~140 GPa at room temperature. All these properties change gradually in dominantly high-spin (below ~50 GPa) and low-spin (above ~80 GPa) ferropericlase. However, in the mixed-spin state (i.e., significant presence of both high- and low-spin iron), the index dispersion and the absorption coefficient decrease by a factor of three and ~30%, respectively. These anomalies suggest that charge transport by small polaron is reduced in mixed-spin ferropericlase, providing fundamental insights into the factor-of-three lower electrical conductivity of ferropericlase at ~50–70 GPa. [ABSTRACT FROM AUTHOR]

Safety and reliability are the major challenges to face for the development and acceptance of hydrogen technology. It is therefore crucial to deeply study material compatibility, in particular for tribological components that are directly in contact with hydrogen. Some of the most critical parts are sealing materials that need increased safety requirements. In this study, the fretting behavior of several elastomer materials were evaluated against 316L stainless steel in an air and hydrogen environment up to 10 MPa. Several grades of cross-linked hydrogenated acrylonitrile butadiene (HNBR), acrylonitrile butadiene (NBR) and ethylene propylene diene monomer rubbers (EPDM) were investigated. Furthermore, aging experiments were conducted for 7 days under static conditions in 100 MPa of hydrogen followed by rapid gas decompression. Fretting tests revealed that the wear of these compounds is significantly affected by the hydrogen environment compared to air, especially with NBR grades. After the aging experiment, the friction response of the HNBR grades is characterized by increased adhesion due to elastic deformation, leading to partial slip. [ABSTRACT FROM AUTHOR]

Abstract Developing strategies to systematically increase the critical current, the threshold current below which the superconductivity exists, is an important goal of materials science. Here, the concept of quantum phase transition is employed to enhance the critical current of a kagome superconductor CsV3Sb5, which exhibits a charge density wave (CDW) and superconductivity that are both affected by hydrostatic pressure. As the CDW phase is rapidly suppressed under pressure, a large enhancement in the self‐field critical current (Ic, sf) is recorded. The observation of a peak‐like enhancement of Ic, sf at the zero‐temperature limit (Ic, sf(0)) centered at p* ≈ 20 kbar, the same pressure where the CDW phase transition vanishes, further provides strong evidence of a zero‐temperature quantum anomaly in this class of pressure‐tuned superconductor. Such a peak in Ic, sf(0) resembles the findings in other well‐established quantum‐critical superconductors, hinting at the presence of enhanced quantum fluctuations associated with the CDW phase in CsV3Sb5.

High-pressure processing (HPP) has been employed in the food and pharmaceutical industries for multiple applications, such as microbial inactivation, shelf life extension, homogenizing/stabilizing emulsions, suspensions, gels, and other colloidal systems, cold extraction of meat in crustaceans, the opening of mollusks, etc. However, high pressure is known to affect the stability and the quality of barosensitive (i.e., sensitivity because of the level of pressure) components of the bioproducts, such as proteins. In general, Le Chatelier's principle dictates the fate of high molecular weight polymeric compounds like proteins under high pressure, suggesting a tendency to degrade into simpler monomers. From a structural analysis point of view, this generally results in increased tendencies for the protein to denature from its native state and possibly affect its ability to renature. Protein crystallization is also affected favorably or unfavorably by pressure, depending on the effect of pressure on nucleation and crystal growth steps for the particular type of protein. Protein refolding is another effect whose kinetics can be optimized by pressure. This work discusses the mechanisms of the impact of pressure on protein structure, crystallization refolding, and unfolding, with examples of the application of these processes in recent literature.

With the development of hydrogen fuel cell vehicles, hydrogen refuelling stations are required to operate at a higher pressure. However, the safety issue of high pressure hydrogen is always considered as the barrier of the wide application of such transportation infrastructures. In this paper, the safety evaluation is performed on a 70 MPa hydrogen dispenser, as one of the most vulnerable equipment to safety events in hydrogen refuelling stations. The numerical simulations are conducted for the hydrogen leakage and combustion for the prototype of the dispenser. The results show the high radiation during the combustion, and the environmental wind can reduce it by promoting the diffusion of hydrogen. Accordingly, the lethal ranges in different cases are manifested by radiation heat flux at the concerned height for the safety of humans. Furthermore, an improved design of the hydrogen dispenser is proposed to cancel the lower ventilation holes based on the analysis. As a result, the radiation heat fluxes due to the hydrogen combustion after leakage is significantly reduced and consequently lead to smaller lethal ranges, indicating the enhanced safety performance of the hydrogen dispenser. • A numerical study is conducted for the hydrogen combustion from a 70 MPa hydrogen dispenser. • The safety distance is evaluated for hydrogen leakage and combustion of dispensers under different wind conditions. • An improved design of the hydrogen dispenser is proposed and proved to be effective in enhancing the safety performance. [ABSTRACT FROM AUTHOR]

GaAs nanowires (NWs) have wide application potential as near-infrared optical devices and the high-pressure strategy has been applied to modulate their crystal and electronic structures. As another typical thermodynamic parameter, temperature can also affect the optical performance of semiconductors. Here we report the excitation-wavelength-dependent photoluminescence (EWDP) in GaAs NWs under high-pressure conditions. The pressure for achieving the maximum photoluminescence (PL) intensity and bandgap transition from direct to indirect of GaAs NWs varies (1.7–2.7 GPa) with the wavelength of the incident lasers (633–473 nm). The Raman peak of GaAs NWs shifts towards higher frequency with increasing excitation wavelengths at the same high-pressure conditions, revealing the stronger heating effect induced by incident laser with the shorter wavelength. The relative temperature difference in GaAs NWs induced by two different lasers can be estimated up to 537 K, and the strong heating effect suppresses the light-emission efficiency in GaAs NWs. With increasing the pressure, the relative temperature difference presents a gradual declining trend and PL intensity presents an opposite trend, which relates to the pressure-induced suppression of nonradiative recombination in GaAs NWs. Our study provides insights into the mechanisms for the EWDP effect and an alternative route to modulate the high-pressure performance of nanodevices. [ABSTRACT FROM AUTHOR]

In this study, we conduct extensive high‐pressure experiments to investigate phase stability in the cobalt‐nitrogen system. Through a combination of synthesis in a laser‐heated diamond anvil cell, first‐principles calculations, Raman spectroscopy, and single‐crystal X‐ray diffraction, we establish the stability fields of known high‐pressure phases, hexagonal NiAs‐type CoN, and marcasite‐type CoN2 within the pressure range of 50–90 GPa. We synthesize and characterize previously unknown nitrides, Co3N2, Pnma‐CoN and two polynitrides, CoN3 and CoN5, within the pressure range of 90–120 GPa. Both polynitrides exhibit novel types of polymeric nitrogen chains and networks. CoN3 feature branched‐type nitrogen trimers (N3) and CoN5 show π‐bonded nitrogen chain. As the nitrogen content in the cobalt nitride increases, the CoN6 polyhedral frameworks transit from face‐sharing (in CoN) to edge‐sharing (in CoN2 and CoN3), and finally to isolated (in CoN5). Our study provides insights into the intricate interplay between structure evolution, bonding arrangements, and high‐pressure synthesis in polynitrides, expanding the knowledge for the development of advanced energy materials [ABSTRACT FROM AUTHOR]

Phosphorus, a group V non-metallic element, exhibits a unique electronic structure along with excellent optical, electrical and mechanical properties, and has a wide range of application prospects. Recent studies have demonstrated that phosphorus and phosphides are easily affected and regulated by external fields and have rich physical and chemical properties under high pressure. In addition, the unique structure and electronic properties of phosphorus and phosphides give them many physical properties that differ from those of traditional materials. Therefore, the use of high pressure to induce structural transformation and superconducting transformation in phosphorus and phosphides has become the focus of high-pressure research. In this paper, the structural, electrical, and optical responses of black phosphorus, germanium phosphide, and arsenic phosphide under high-pressure conditions are reviewed and discussed. Furthermore, we also explore the structure-activity relationships between the structures and physical properties and forecast the future research directions of phosphides under high pressure. [ABSTRACT FROM AUTHOR]

H2S and CO2 are considered two main impurities of natural gas and biogas. These impurities must be removed in order to achieve economic and environmental restrictions. Adsorption is a promising technology studied to achieve this goal. Among alternative adsorbents studied to capture H2S and CO2, porous aromatic frameworks (PAFs) had shown potential application because of suitable selectivity and remarkable adsorption capacity. However, H2S and CO2 adsorption/desorption data on PAF-30 are still scarce in literature. Thus, in this work, H2S (up to 2.5 bar) and CO2 and CH4 (up to 50 bar) adsorption/desorption isotherms on PAF-30 were determined at 293, 303 and 313 K for the first time in literature. PAF-30 was synthesized and characterized by XRD, FTIR, 13C-NMR, Ar and CO2 physisorption, SEM, TEM, TGA and DSC analyzes. Then, adsorption isotherms were determined gravimetrically. Experimental data were modelled with Jensen-Seaton equation. The results indicated that PAF-30 presents adsorption capacities in the order H2S > CO2 > CH4. Adsorption/desorption branches do not match for systems studied, due to a hysteresis effect. Adsorption capacity decreases with temperature, indicating that physisorption is the main phenomenon observed. Experimental data were represented by Jensen-Seaton model. Thermodynamic analysis showed that all systems are exothermic and spontaneous. Working capacities obtained indicate that temperature reduces the performance for gas purification and that H2S systems are affected by hysteresis loop. Moreover, cyclic adsorption results show that PAF-30 has potential to be applied and further studied in PSA simulations for H2S and CO2 capture under high-pressure conditions. [ABSTRACT FROM AUTHOR]

This report presents work on the orthorhombic phases Ln2CdB5O11(OH) (Ln = Tm, Lu). The title compounds were synthesized in a Walker-type multianvil device at 7 GPa and 650 °C, and the resulting samples were thoroughly investigated through single-crystal and powder X-ray diffraction methods. Lu2CdB5O11(OH) crystallizes in the space group Pmna (no. 53) with the unit cell parameters a = 12.772(2), b = 4.6017(7), and c = 12.481(2) Å. Similar unit cell parameters are observed for the isotypic Tm analogue compound. The crystals have a layered crystal structure built up by four-, five-, and eight-membered rings of corner-sharing [BO4] tetrahedra. The structural data are accompanied by attenuated total reflection (ATR) infrared spectra and energy-dispersive X-ray spectroscopy (EDX). [ABSTRACT FROM AUTHOR]

Orthorhombic crystals of the compounds γ-Eu(BO2)3 and γ-Gd(BO2)3 were obtained by high-pressure/high-temperature syntheses at 10.5 GPa and 1100 and 900 °C, respectively. The structures were solved by single-crystal X-ray diffraction methods. The two compounds crystallize with four formula units per cell in the space group Pca21 (no. 29) with the unit cell parameters a = 18.2729(7), b = 4.4076(2), c = 4.2505(1) Å (Ln = Eu), and a = 18.2591(6), b = 4.4055(1), c = 4.2477(1) Å (Ln = Gd). Their infrared spectra and the luminescence spectrum of γ-Eu(BO2)3 are discussed. [ABSTRACT FROM AUTHOR]

The structural properties of NbON oxynitride under high pressure were investigated through in situ synchrotron X-ray diffraction (SXRD) up to 43 GPa. It was found that the bulk modulus of baddeleyite NbON (290 GPa) is larger than that of ZrO2 (150 GPa), indicating that the introduction of highly covalent nitrogen imparts greater stiffness. Furthermore, SXRD patterns reveal the emergence of a peak signaling a new crystalline phase above around 20 GPa. This is in contrast to TaON, where diffraction patterns only show an increase in background beyond 33 GPa. First-principle calculations suggest that the high-pressure phase adopts an orthorhombic cotunnite-type structure, distinguishing it from the oxide counterparts, wherein the ambient pressure phase transforms to a cotunnite structure via an orthorhombic-I structure. [ABSTRACT FROM AUTHOR]

Orthorhombic crystals of the compounds γ-Eu(BO2)3 and γ-Gd(BO2)3 were obtained by high-pressure/high-temperature syntheses at 10.5 GPa and 1100 and 900 °C, respectively. The structures were solved by single-crystal X-ray diffraction methods. The two compounds crystallize with four formula units per cell in the space group Pca21 (no. 29) with the unit cell parameters a = 18.2729(7), b = 4.4076(2), c = 4.2505(1) Å (Ln = Eu), and a = 18.2591(6), b = 4.4055(1), c = 4.2477(1) Å (Ln = Gd). Their infrared spectra and the luminescence spectrum of γ-Eu(BO2)3 are discussed. [ABSTRACT FROM AUTHOR]

During their formation, terrestrial planets underwent a magma ocean phase during which their metallic cores segregated from their silicate mantles and their early atmospheres formed. These planetary formation processes resulted in a redistribution of the abundances of highly volatile elements (HVEs, such as H, C, N, and S) between the planets' metallic cores, silicate mantles, and atmospheres. This review presents the numerous experimental techniques used to simulate the conditions and identify the parameters that influenced the behavior of HVEs during planetary formation. We also review the analytical techniques used to characterize the different types of experimental samples and quantify the distribution of HVEs between metallic and silicate phases, as well as their solubilities in silicate glasses. This exhaustive review targets students and young researchers beginning their work on the subject, or, more generally, scientists seeking a better understanding of this field of research. [ABSTRACT FROM AUTHOR]

With economic development and the burgeoning need for energy, numerous underground gas pipelines have been deployed for operation. Buried gas pipelines often suffer failures as a result of adverse factors, including corrosion, uneven subsidence, and damage caused by third parties. To investigate and predict the diffusion behavior following a natural gas pipeline leakage, Fluent software is utilized to develop a numerical model for the leakage and diffusion of high-pressure natural gas within a confined space. This model incorporates the Soave–Redlich–Kwong equation of state, which is widely recognized for its exceptional precision in characterizing the behavior of natural gas under high-pressure conditions. The study focuses on the analysis of leakage and diffusion behavior as well as the examination of how pipeline operating pressure and leakage diameter have an impact on the dispersion of leaked gas. Further, the prediction model for the diffusion distance of the hazardous area is developed, employing the least-square method and finite element calculations. The results show that, during the leakage process, a vortex and velocity region emerge, extending along the confined space. The farther away from the leakage hole above the pipeline, the higher the overall concentration of the gas. Moreover, the horizontal diffusion distance of gas at the bottom of the pipeline is considerably smaller than that above it. However, gas tends to readily accumulate in a high concentration area at the bottom of the pipeline. Elevating the leakage diameter and the operation pressure leads to a significant rise in gas concentration and the horizontal diffusion of the hazardous area. It is worth noting that the leakage diameter has a more pronounced effect on gas diffusion than does the pressure. The prediction model proposed in this study effectively anticipates the horizontal diffusion of the hazardous area within confined spaces. [ABSTRACT FROM AUTHOR]

Reference liquids can be useful in the new quantitative approach to elastohydrodynamic lubrication calculations only if the properties of these liquids are accurately modeled. The pressures in the contact sometimes exceed the pressures of the available viscometer measurements, requiring extrapolation. The previtreous piezoviscous response is always faster-than-exponential with an apparent divergence pressure. Therefore, any model used for extrapolation must possess these characteristics and up to now published work in EHL, where extrapolation of the viscosity of squalane is performed, has not. To date, the only model that has been shown to accurately extrapolate to high pressure is the Hybrid model. This expression was applied to six reference liquids for use in quantitative investigations in EHL. Viscosity measurements for trioctyl trimellitate were extended to 1.1 GPa. The results obtained with high pressure viscometers are preferable over molecular dynamics results if they are different. Molecular dynamics calculations are not currently capable of reliable results for viscosity at very high pressures. [ABSTRACT FROM AUTHOR]

We report a joint high-pressure experimental and theoretical study of the structural, vibrational, and photoluminescent properties of pure and Eu3+-doped cubic Y2O3 nanoparticles with two very different average particle sizes. We compare the results of synchrotron X-ray diffraction, Raman scattering, and photoluminescence measurements in nanoparticles with ab initio density-functional simulations in bulk material with the aim to understand the influence of the average particle size on the properties of pure and doped Y2O3 nanoparticles under compression. We observe that the high-pressure phase behavior of Y2O3 nanoparticles depends on the average particle size, but in a different way to that previously reported. Nanoparticles with an average particle size of ~37 nm show the same pressure-induced phase transition sequence on upstroke and downstroke as the bulk sample; however, nanoparticles with an average particle size of ~6 nm undergo an irreversible pressure-induced amorphization above 16 GPa that is completed above 24 GPa. On downstroke, 6 nm nanoparticles likely consist of an amorphous phase. [ABSTRACT FROM AUTHOR]

The cold sintering process, a novel technique for low-temperature ceramic processing, effectively removes interparticle pores via dissolution and re-precipitation. However, it often triggers grain growth, especially in nanocrystalline ceramics. To address this issue, the present study proposed an innovative two-step cold sintering process with an initial step at 1.5 GPa/RT (room temperature) for 10 min, followed by a subsequent step at 300 MPa/250 °C for 45 min. This method yields ZnO nanocrystalline ceramics with 97.5 % relative density and a 39 nm average grain size (from 30 nm powder). The initial high-pressure step significantly enhances the pressure gradient and particle solubility, leading to very high supersaturation and the occurrence of homogenous nucleation during pressure release. Subsequently, the formation of the crystal nuclei in the interparticle voids can dramatically improve the density of the compact by the additional pore filling and avoid recrystallization-induced grain growth during the second-step cold sintering process. • We successfully prepared dense ZnO nanocrystalline ceramics for the first time by a two-step cold sintering process. • The initial step at 1.5 GPa/RT for 10 min enables homogenous nucleation and elimination of interparticle pores. • Subsequent sintering at 300 MPa/250 °C for 45 min enhances density and inhibits excessive grain growth. • A relative density of 97.5% and an average grain size of 39 nm were achieved for ZnO ceramic. [ABSTRACT FROM AUTHOR]