High-pressure Properties Research Articles

Anti-inflammatory and intestinal microbiota modulation properties of high hydrostatic pressure treated cyanidin-3-glucoside and blueberry pectin complexes on dextran sodium sulfate-induced ulcerative colitis mice.

This study investigated the anti-inflammatory effects of cyanidin-3-glucoside (C3G) and blueberry pectin (BP) complexes on mice with dextran sodium sulfate (DSS)-induced colitis before and after high hydrostatic pressure (HHP) treatment. Real-time polymerase chain reaction (RT-PCR), western blotting, and 16S rDNA sequencing were used to study the expression of inflammation-related factors, activation of signal pathway-related proteins, and changes in the intestinal flora in ulcerative colitis (UC) mice. The results showed that HHP-treated C3G-BP complexes significantly relieved diarrhea and blood loss in the stool of UC mice and alleviated colon shortening. The potential mechanism of action involved reduction in intestinal oxidative stress mRNA expression of pro-inflammatory factors, improvement in anti-inflammatory factor levels, inhibition of the NF-κB signaling pathway, increased protein levels of Bcl-2/Bax and caspase-3/cleaved caspase-3 genes, and improved gut microbiota composition. Compared with other experimental groups, the HHP-treated C3G-BP complexes group exhibited the best anti-inflammatory effect on DSS-induced UC mice. The results may provide new ideas for using C3G-BP complexes for treating UC and help develop better processing methods.

High-pressure synthesis, crystal structure, and physical properties of NaAlB14 single crystals

Pure NaAlB14 single crystals were successfully synthesized directly from Na, Al, and B at high pressure and high temperature, different from the previously reported method, that is, synthesized from Na2B4O7, Al, and B. The growth of NaAlB14 single crystals was promoted by increasing the reaction temperature. The atomic structures of NaAlB14 single crystal along the [100], [010], [001], and [021] axes were characterized by using a scanning transmission electron microscope. The Raman spectra of NaAlB14 were investigated theoretically and experimentally, and they showed the expected oscillations of the covalent framework. In addition, photoluminescence spectra indicated that NaAlB14 is a semiconductor luminescence material with red (1.68 eV) and near-infrared (1.50 and 1.36 eV) emission characteristics. The band structure revealed that NaAlB14 is an indirect band gap semiconductor with a wide band gap of 2.22 eV.

Study on Phase Transition and Gas Deviation Coefficient of Natural Gas with High Carbon Dioxide Content

It is the basic research subject that analyzes and calculate the law and numerical value of phase change and gas deviation coefficient of natural gas with high-CO2 content in the process of safe and effective development of gas reservoirs, which is obtained by high-pressure physical properties PVT (Pressure-Volume-Temperature) experiments and different calculation methods calculations. Aiming at natural gas with high-CO2 content in the Dongfang gas field, the phase change characteristics and physical parameters of different PVT samples are simulated and tested by Chandler 3000-GL analyzer and PVT SIM software. The experimental data shows that the phase state of natural gas with different content of CO2 has not changed in the study range. At the same time, the deviation coefficient calculated by different calculation methods (DPR, DAK, BB, HY, Gopal) are compared with the experimental data, and the applicable scope of different calculation methods are obtained. The results show that the improved Gopal has high accuracy and is suitable for the calculation of the deviation coefficient of natural gas with high-CO2 content under high temperature and high pressure in the Dongfang gas field.

Influence of microstructure on the high-pressure hydrogen SSRT properties of Cr-Mo steel

In a high pressure hydrogen gas environment, there is a risk of "hydrogen embrittlement (HE)" by hydrogen entered to the steels. Therefore, many experiments of steels in high pressure hydrogen gas have been conducted such as tensile, fatigue and so on. However, there are little knowledge of influence of the material microstructure on HE. There is a possibility of HE susceptibility of steels depending on the material microstructure. Therefore, objective of this development is clarification of the microstructure to excellent HE resistance. As a result of Slow Strain Rate Tensile (SSRT) test under hydrogen environment, tempered martensite structure with finely cementite dispersed was most excellent in HE resistance. The reason for this is considered that the generation of micro voids, which is the initiation of surface cracks affecting ductility of SSRT, was suppressed.

Influence of Lattice Defects on the High Pressure Properties of Ni0.66mn2.33o4 Ceramics

Influence of Lattice Defects on the High Pressure Properties of Ni0.66mn2.33o4 Ceramics

High-Pressure Photoluminescence Properties of Cr3+-Doped LaGaO3 Perovskites Modulated by Pressure-Induced Phase Transition.

The photoluminescence properties of Cr3+-doped LaGaO3 perovskites are investigated by high-pressure spectroscopy. The pressure-induced phase transition from orthorhombic (Pbnm) to rhombohedral (R3̅c) at around 2 GPa is confirmed by Raman spectroscopy. Cr3+-doped LaGaO3 shows deep-red emission peaks around 730 nm due to the zero-phonon line (R-line) and the phonon sidebands, which correspond to Cr3+: 2Eg → 4A2g transitions in the ideal octahedral site and the Cr-Cr pair luminescence (N-line) under ambient condition. Under a high pressure, the R-line shifts to a lower energy at a rate of -13 cm-1/GPa. From the pressure dependence of photoluminescence excitation (PLE) spectra, it is suggested that the redshift of the R-line is caused by the decrease of Racah parameters B and C. Moreover, the N-line luminescence becomes stronger relative to the R-line with increasing pressure and the N-line/R-line can be used to monitor the phase transition pressure. Under a high pressure, the tilt angle of the GaO6 octahedral unit becomes smaller. It implies that the enhanced N-line luminescence is caused by the stronger superexchange interaction between Cr3+ ions due to the increased Cr-O-Cr bond angle closer to 180°.

First-principles calculations of the high-pressure behavior, electronic, magnetic, and elastic properties of praseodymium pnictides: PrX (X = P, As and Bi)

We report ab-initio calculation of the structural, magnetic, elastic, and electronic properties of the PrX (X = P, As and Bi). The structural stability and phase transition of PrX (X = P, As, Bi) compounds in (NaCl-type), (CsCl-type), (Zinc blende-type), WC-Bh (Hexagonal) and L10 (Tetragonal) structures in ferromagnetic state are investigated using the augmented plane wave plus local orbital (APW + lo) method within GGA + U, and mBJ-GGA + U approximations. Careful inspection of electronic properties indicates that most of the compounds exhibit half-metallic behavior. The total magnetic moment of all investigated compounds is obtained to be 2 µB. The mechanical stability test performed on the computed elastic constants Cij demonstrate that investigated compounds are mechanically stable. To elucidate chemical stability, chemical bonds are investigated and found to be mainly characterized by an ionic-covalent mixture. Moreover, elastic anisotropy of all compounds is calculated. Subsequently.

Arctic transmission oil

The tasks of the development of the Far North, the Arctic and the Antarctic require ensuring the operability of equipment units in low temperatures. To solve this problem, it is necessary to develop lubricants using new synthetic oils, a distinctive feature of which are low pour points. On the basis of polyethylsiloxane fluid and petroleum oil, we have developed a gear oil for the Arctic latitudes, which is efficient at temperatures down to -75 ° C (TMarktic). It is shown TMarktic’s antifriction properties are better than those of TSgip helicopter tail gear oil. The combined use of XPS and IR-Fourier methods for the analysis of the friction surface made it possible to conclude that the formation of the boundary film involves both antiwear additive molecules, which are part of the modified oil, due to the P-O, P=O, S=O bonds, so and molecules of polyethylsiloxane liquid due to C-O and Si-O bonds. Secondary surface structures are formed by TMarctic oil on the surface of iron oxide and include hydrocarbon and siloxane fragments. The high antiwear and extreme pressure properties of TMarktic are due to free sulfur and bound in iron sulfide.

NaZnF3 as a low-pressure analog of MgSiO3

Solid-state systems whose properties at high pressure (exceeding 1 GPa) mimic those of MgSiO3 are of large importance in the study of the interior of planets. By means of Density Functional Theory (DFT) calculations we studied the high pressure properties of a MgSiO3 analogue, NaZnF3. We reproduce the phase-transition sequence previously reported for this compound (GdFeO3 -> CaIrO3 -> La2S3), and predict that it should undergo a two-step dissociation: decomposition into a equimolar mixture of Na2ZnF4 and NaZn2F5 at 25.4 GPa, followed by a breakdown into ZnF2 and NaF at 66.8 GPa. These processes are analogous to those predicted for compressed MgSiO3. Moreover, both Na2ZnF4 and NaZn2F5 are isostructural with analogous phases from the Mg-Si-O system. We also find that both these novel compounds are thermodynamically stable at ambient conditions (Na2ZnF4) or at low pressure of 19 GPa (NaZn2F5). Our study indicates that NaZnF3 could serve as a good low-pressure analogue of MgSiO3 exhibiting the same sequence of phase transitions, and pressure induced decomposition, but at pressures an order of magnitude lower.

Assessment of the suitability of a gate design modification compared to the change in pressing velocity considering the distribution of gases in the casting volume

The qualitative properties of high pressure die castings are closely correlated with their internal structure, which is directly conditioned by the gas entrapment in the melt volume during the casting cycle. It is known that the gas entrapment in the volume of the melt and their subsequent distribution into the cast can be reduced by changing the technological parameters of the casting cycle or by the modification of the gating system design. The contribution addresses the issue of which variant of the gas content reduction is more efficient regarding the gas entrapment and the nature of the melt flow in the runners. The experiments are based on a real casting process. The established design solution of the gating system and the technological parameters setting are considered as a referential. Different gating system modifications were designed where the design modification is connected with the cross-section of a gate, in which the final acceleration of the melt flow occurs. The observed melt velocity in the gate is considered as a correlation factor, based on which the modification in the piston velocity is determined. The assessed parameter is the gas entrapment in the cast volume at the end of the filling phase. Assessment of the casting cycle and evaluation of experiments is performed using simulation program Magmasoft. Based on the performed analyses, it can be stated that the gate design modification will affect the filling regime of the die cavity by changing the melt velocity in gate, but the nature of the melt flow in runners remains unchanged. Modification of the piston velocity affects the filling regime of the die cavity, and also the nature of the melt flow as it passes through the runners, thereby promoting the gas entrapment in the melt volume. Therefore, it is necessary to pay an increased attention to the design of the gating system and only after debugging the design to proceed to the optimization of technological parameters.

High-pressure synthesis, crystal structure, and physical properties of NaB13C2 single crystals

A new boron-rich boride carbide of sodium, NaB13C2 single crystals have been successfully synthesized from the elements under high temperature and high pressure. The crystals are reddish black with a metallic luster and show a regular hexagonal prism shape. NaB13C2 crystallizes into an orthorhombic LiB13C2-type structure with a space group of Imma (No. 74) and the lattice constants are a = 10.9417 Å, b = 5.6756 Å, c = 8.0898 Å. The crystal structure is characterized by a covalent framework of B12 icosahedra connected by CBC chains and Na atoms located in the void of the framework. The measured and calculated Raman spectra of NaB13C2 are in good agreement and show expected oscillations of the covalent framework. The electronic band structures reveal that NaB13C2 is a wide band gap semiconductor with a band gap of 3.36 eV. As a novel wide band gap semiconductor, NaB13C2 may have potential applications in semiconductor field.

Effect of the projector augmented wave potentials on the simulation of thermodynamic properties of vanadium

We report significant differences in high-pressure properties of vanadium at zero temperature and finite temperature when different projector augmented wave (PAW) potentials are used in simulations based on density functional theory. When a PAW potential with only five electrons taken as valence electrons is used, the cold pressures in the high-pressure region are seriously underestimated, and an abnormality occurs in the melting curve of vanadium at about 400 GPa. We show that the reason for these discrepancies lies in the differences in the descriptions of the interatomic force, electron dispersion, and anisotropy of electron bonding obtained from different PAW potentials at high pressure, which lead to striking differences in the mechanical stability of the system. We propose a procedure for selecting PAW potentials suitable for simulations at high temperature and high pressure. Our results provide valuable guidance for future simulations of thermodynamic properties under extreme conditions.

Investigations of High-Pressure Properties of MnF2 Based on the First-Principles Method

Investigations of High-Pressure Properties of MnF₂ Based on the First-Principles Method

Turbulent chemical-species mixing in the Venus lower atmosphere at different altitudes: a direct numerical simulation study relevant to understanding species spatial distribution

To evaluate a recent hypothesis of species stratification in the Venus lower atmosphere, a time-dependent, three-dimensional model is proposed for studying turbulent mixing of many species in the Venus lower atmosphere. This model is based on fundamental physics embedding non-equilibrium thermodynamics, the Onsager classical relationship between fluxes and forces, high-pressure transport property calculation and a real-gas equation of state. The conservation equations are self-contained, with no need for coefficients based on parametrizations to match Venus observations. The rationale for solving these equations in relatively small spatial domains at different altitudes in the Venus lower atmosphere is presented. The equations are solved in a temporal mixing layer configuration that is eminently suited to investigate turbulent mixing between two streams of different composition. The adopted simulation method is Direct Numerical Simulation (DNS). A substantial database of DNS realizations is generated for mixtures of two and seven species, with different levels of initial stratification, and at the realistic conditions of pressures and temperatures in the Venus lower atmosphere at three altitudes. High density-gradient magnitude regions (HDGM) are shown to form under initial high stratification conditions, with larger gradient values obtained at low altitudes where supercritical conditions occur. Independent of the altitude lower than 50 km, under low stratification conditions, mixing produces a more uniform spatial distribution of the density than at higher initial stratification. Under low initial stratification conditions, the influence of the minor species on the global behavior of the flow seems to be negligible. At high initial stratification conditions, differences in diffusion of various species play an important role in determining the mixture characteristics. The hypothesis of chemical species separation is discussed in the light of the present results which do not support the existence of stable species separation in the lower Venus atmosphere, independent of the number of species or the altitude.

Fast aging strengthening by hybrid precipitates in high pressure die-cast Al-Si-Cu-Mg-Zn alloy

The improvement on mechanical properties in high pressure die casting (HPDC) Al Si alloys is an important issue for their application. In this present study, it is found that the artificial aging with low-temperature and short-time can remarkably improve the mechanical properties of HPDC Al-Si-Cu-Mg-Zn alloy, which can avoid heat-treatable defect formation of HPDC Al alloy and be applied in industrial production. The experimental results indicate that the as-cast microstructure of HPDC Al-Si-Cu-Mg-Mn-Zn alloy shows uniformly-distributed GB phases, fine grains and fine AlFeMnSi granular phases. Ascribed to the high cooling rate of HPDC, significant refinement of the obtained microstructure can be achieved. In addition, with the increase of aging temperature from 160 to 220 °C, the θ′ nanoscale phase can be sufficiently precipitated which results in the formation of hybrid precipitates, thus providing a better strengthening effect. The short-time artificial aging at 220 °C for 30 min remarkably improves the hardness of alloy from 115 to 145 HV with an increment of 26.1%. It is found that the hybrid precipitates including β″, Q′ and θ′ are believed to be responsible for such high strengthening contribution by superimposed strengthening in Al-matrix. The Cu-containing nano-precipitates are considered to promote the strengthening of short-time artificial aging in the HPDC Al-Si-Cu-Mg-Zn alloy. The present study provides a feasible and high-efficiency method to prepared HPDC alloy with excellent mechanical properties. • Aging-hardening behavior of HPDC Al-Si-Cu-Mg-Zn alloy was investigated. • Precipitation sequence of aging HPDC Al-Si-Cu-Mg-Zn alloy was elucidated. • Significant improvement on hardness (26.1%) was achieved due to hybrid precipitates. • Precipitation hardening effect on aging HPDC Al-Si-Cu-Mg-Zn alloy was revealed.

High-pressure magnetic properties of antiferromagnetic samarium up to 30 GPa using a SQUID-based vibrating coil magnetometer

Samarium (Sm) has antiferromagnetic (AFM) ordering at the hexagonal site at ${T}_{\mathrm{N}}(\text{hex})=106$ K, and at the cubic site at ${T}_{\mathrm{N}}(\text{cub})=14$ K at ambient pressure. The structural transition from the so-called Sm-type structure to the double hexagonal close-packed (dhcp) structure occurs at approximately 6 GPa. According to electrical resistance measurements, the shift of ${T}_{\mathrm{N}}$(hex) toward the low-temperature side occurs simultaneously with the shifting of ${T}_{\mathrm{N}}$(cub) toward the high-temperature side with increasing pressure. We conducted dc magnetic measurements on Sm at high pressure up to 30 GPa using a SQUID-based vibrating-coil-magnetometer to pursue ${T}_{\mathrm{N}}$(cub) at high pressure: The magnetic measurements revealed stepwise anomalies below 2 GPa. A ferromagnetic (FM) anomaly was observed in the dhcp structure, suggesting that spins at both structural sites formed the FM magnetization. In the face-centered cubic (fcc) structure at above 12 GPa, a reduction in the magnetic signal occurred. In the distorted fcc structure at above 20 GPa, sufficient suppression of the FM moment was observed and afterward the diamagnetic signal suggesting the possibility of superconductivity was observed.

Structural, electronic and magnetic properties of TlFeSe2 under high pressure

The high-pressure (HP) properties of TlFeSe2 are investigated based on the first-principles calculations combined with structure-searching method. The low-pressure C2/m phase will transform into the orthorhombic Pnma phase at 2 GPa, with 8% volume collapse, the insulator–metal transition and the bicollinear antiferromagnetic-to-nonmagnetic spin-crossover. At pressure higher than 8 GPa, the HP C2/m phase will become the ground state. Both Pnma phase and HP C2/m phase are constituted by one-dimensional chains of edge-sharing FeSe5 tetragonal pyramids. Pressuring decrease the Se–Se bond length giving rise to the transition from [Se2]3− to [Se2]2−. Negative charge transfer causes the Fe2+ with ∼2 μ B magnetic moment at ambient pressure and the nonmagnetic Fe1.5+ at higher pressure. The Fermi surfaces of HP phases are also discussed.

Experimental Investigation on Enhanced-Oil-Recovery Mechanisms of Using Supercritical Carbon Dioxide as Prefracturing Energized Fluid in Tight Oil Reservoir

SummaryFracturing is the necessary means of tight oil development, and the most common fracturing fluid is slickwater. However, the Loess Plateau of the Ordos Basin in China is seriously short of water resources. Therefore, the tight oil development in this area by hydraulic fracturing is extremely costly and environmentally unfriendly. In this paper, a new method using supercritical carbon dioxide (CO2) (ScCO2) as the prefracturing energized fluid is applied in hydraulic fracturing. This method can give full play to the dual advantages of ScCO2 characteristics and mixed-water fracturing technology while saving water resources at the same time. On the other hand, this method can reduce reservoir damage, change rock microstructure, and significantly increase oil production, which is a development method with broad application potential.In this work, the main mechanism, the system-energy enhancement, and flowback efficiency of ScCO2 as the prefracturing energized fluid were investigated. First, the microscopic mechanism of ScCO2 was studied, and the effects of ScCO2 on pores and rock minerals were analyzed by nuclear-magnetic-resonance (NMR) test, X-ray-diffraction (XRD) analysis, and scanning-electron-microscope (SEM) experiments. Second, the high-pressure chamber-reaction experiment was conducted to study the interaction mechanism between ScCO2 and live oil under formation conditions, and quantitively describe the change of high-pressure physical properties of live oil after ScCO2 injection. Then, the numerical-simulation method was applied to analyze the distribution and existence state of ScCO2, as well as the changes of live-oil density, viscosity, and composition in different stages during the full-cycle fracturing process. Finally, four injection modes of ScCO2-injection core-laboratory experiments were designed to compare the performance of ScCO2 and slickwater in terms of energy enhancement and flowback efficiency, then optimize the optimal CO2-injection mode and the optimal injection amount of CO2 slug.The results show that ScCO2 can dissolve calcite and clay minerals (illite and chlorite) to generate pores with sizes in the range of 0.1 to 10 µm, which is the main reason for the porosity and permeability increases. Besides, the generated secondary clay minerals and dispersion of previously cemented rock particles will block the pores. ScCO2 injection increases the saturation pressure, expansion coefficient, volume coefficient, density, and compressibility of crude oil, which are the main mechanisms of energy increase and oil-production enhancement. After analyzing the four different injection-mode tests, the optimal one is to first inject CO2 and then inject slickwater. The CO2 slug has the optimal value, which is 0.5 pore volume (PV) in this paper.In this paper, the main mechanisms of using ScCO2 as the prefracturing energized fluid are illuminated. Experimental studies have proved the pressure increase, production enhancement, and flowback potential of CO2 prefracturing. The application of this method is of great significance to the protection of water resources and the improvement of the fracturing effect.

Elucidating the structural properties and reversible regional texture effect of GdB6 under high pressure

As hard and refractory materials with high chemical resistance and mechanical strength, lanthanide hexaborides (LnB6) have attracted much attention. Among the family of LnB6, gadolinium hexaboride (GdB6) occupies a special position due to the half-filled 4f shell of Gd. Here, using in situ synchrotron radiation angle-dispersive X-ray diffraction in a diamond anvil cell at room temperature, the structural stability and compression behavior of GdB6 are investigated extensively, GdB6 is observed to be structurally stable up to 73 GPa, and the bulk modulus of 177 GPa is obtained under hydrostatic compression. In this paper, an interesting observation of pressure-induced spotty diffraction rings of GdB6 is reported, its formation mechanism can be well described by the reversible regional texture effect, which highlights the rearrangement of crystal grains under high pressure. The rearrangement mechanism has been well explained by investigating the pressure dependence of full width at half maximum, macro-differential stress and grain size. Collective grain rotation behavior motivated by stress difference is critical for the rearrangement process, the strong isotropy and strong stability of GdB6 structure also provide necessary conditions for high-pressure grain rotation behavior. These results will help to promote the understanding of high-pressure structural properties of GdB6, and provide novel insights on the high-pressure grain behavior in hard materials with strong isotropy and three-dimensional skeleton constituted of strong covalent bonds.

High pressure thermal conductivity of three ethyl esters in the liquid phase

Recently, biodiesel is considered as a biodegradable, renewable and high-potential fuel which could be used directly in tradition internal combustion engines. Fuel’ transport properties in high pressure are required to model the process of fuel spray, atomization and combustion accurately. This work, three ethyl esters’ liquid thermal conductivity (biodiesel compounds) in the liquid phase was measured by an experiment system which is established based on a transient hot-wire method with a bare platinum hot wire. The measurements were conducted at the temperatures ranging from 292 K to 372 K and pressure up to 15 MPa. The combined expanded uncertainty of the measurement was estimated to be ±2.0% (in the 0.95 confidence level). For interpolation, the relationship between measured results with temperature and pressure were correlated as a polynomial function, and the maximum deviation of correlations were less than 0.30%.