By analyzing experimental data, we put forward the concept of the limit compression volume ratio and the general design principles of centimeter magnitude sample chamber for two-stage 6-8 type static high pressure apparatus.Based on the limit compression volume ratio, we designed an assembly of 36/20 (Octahedral edge-length 36 mm/anvil truncation edge-length 20 mm) with high pressure generating efficiency.Pressure calibration at room temperature for the 36/20 assembly was performed using the phase transitions of Bi (Ⅲ-Ⅴ, 7.7 GPa), ZnTe (Ⅰ-Ⅱ, 5 GPa; Ⅱ-Ⅲ, 8.9-9.5 GPa; semiconductor-metal, 11.5-13.0 GPa)and ZnS (semiconductor-metal, 15.6 GPa).The experimental results show that the pressure of sample chamber exceeds 15 GPa and the sample diameter reaches 1 cm.The improvements of two-stage 6-8 type static high pressure apparatus have great potential applications in high-pressure experimental research and industrial production.

To study the pressure-specific volume (p-v) reference line and equation of state from the stress-strain curve of material at high pressure, the viscous dissipation due to loading strain rate and thermal dissipation due to irreversible heat conduction in quasi-isentropic compression experiment (ICE) were discussed and analyzed.A backward integration and forward integration method was used to analyze the data in laser driving and magnetic pressure driving ICE with different strain rates.For viscous dissipation, the sound speed, stress-strain curve, temperature and entropy production during loading were obtained, and the relations between high strain rate and these physical quantities were discussed.For thermal dissipation, through the calculation of the thermal conduction and SCG constitutive model, the variation of temperature and the corresponding yield strength, shear module and sound speed were presented.The results show that:in the laser driving ICE with a high strain rate of 10⁸ s^-1), the temperature variation caused by high strain rate is about 180 K, and the entropy production due to heat conduction is about 250 J/(kg·K); and in the magnetic pressure driving with a relatively low strain rate of 10⁵ s^-1, the entropy production is less than 8 J/(kg·K).

B₆O/TiB₂ composites were produced from B-TiO₂ mixtures using "one step reactive sintering method" at high pressures between 4 and 5 GPa.The highest Vicker's hardness is 29 GPa for samples consisting of amorphous B and TiO₂ (molar ratio:14.0:0.8).For samples consisting of crystal B and TiO₂ (molar ratio:14.0:0.8) sintered at the condition of 5 GPa and 1 200 ℃ for 30 min, the highest Vicker's hardness is 32 GPa, and the ratio of densification is up to 99%.High pressure restrains the formation of large crystalline grains and promotes the synthesis of B₆O, and reduces the sintering temperature comparing to that at atmospheric pressure.On the other hand, generated additional TiB₂ and superfluous boron can improve the fracture toughness of the sintered samples.

A laval nozzle with a throat diameter of 2 mm and working current 100 mA was introduced, and on the basis of 2D rotational symmetry model, numerical simulation was taken for the plasma flow in and outside the plasma torch.By adoptting the magnetic vector potential magnetohydrodynamic (MHD) model for the internal nozzle, we avoided the complex integral calculation of self-induction magnetic field intensity, obtained the nozzle internal field coupling and external jet flow state.The impact of nozzle internal electromagnetic field on plasma acceleration and the jet development process were analyzed.The results show that the plasma experiences a 3-stage processes from subsonic to transonic, and to supersonic (2.3Ma).It provides a theoretical basis for the industrial application of supersonic plasma torch.

The dynamic evolution process and velocity field of two elliptic heavy-gas (SF₆) cylinders accelerated by a planar shock wave are studied by laser-sheet high-speed photograph and PIV (particle image velocimetry) diagnostics techniques, respectively.The minor axes (b) of the elliptic cross-sections are aligned perpendicular to the shock direction.While the cylinder dimensions are fixed, we adjust the center-to-center separation (d) between the cylinders.The flow morphologies are visualized and the interaction effect between cylinders is analyzed.When d/b equals 4.0 or 3.0, the two elliptical cylinders roll up into 2 counter-rotating vortex pairs and the interaction is weak.The maximal velocity appears at 2 positions and its magnitude is close to 30 m/s, while the minimal velocity is close to zero and arises at 4 positions.Whend/b decreases to 2.0 or 1.2, due to the strong interaction of the two inner vortices, the inner structure completely disappears and the flow morphology evolves into a counter-vortex pair.The maximal velocity occurs at 4 locations, while the minimal velocity only appears at 2 positions.For the d/b =2.0 case, the evolving images assemble those of the single circular cylinder except for the small gap in the middle.Compared with the d/b =2.0 case, larger amount of baroclinic vorticity is produced in the d/b =1.2 case, and the morphology is similar to the single elliptic cylinder case, with a second vortex phenomenon and bifurcation structure occurring at later times.Actually, we observe a nonlinear, threshold-type behavior of inner vortex formation when d/b varies from 2.0 to 3.0.Finally, we outline and discuss 4 possible mechanisms which may lead to the obvious weakening phenomenon of inner vortices.

The phenomenon of gouging on the surface of the rail in the process of electromagnetic railgun launching was studied.For its launching characteristics, we proposed a formation mechanism of gouging due to oblique impact of small angle based on the actual structure and load characteristics of railguns, and numercal simulation was carried out with the finite element software LS-DYNA under variable parameters.The results show that the depth of gouging decreases with the enlargement of the front end chamfering.The moving backward of the barycentric position of armature increases the threshold speed of gouging, but it also increases the depth of gouging.And the impact of these factors on the depth of gouging is not linear.The new formation mechanism and numerical method provide a new effective way for the anti-gouging research.

To research the laws of spherical, cylindrical, and regular prismatic preformed fragments initiating uncovered explosives, we adopted Mathcad software and the u²d criterion of Held to do the theoretical calculation and analysis.Influences of the preformed fragments' quality, density, shape, length to diameter ratio, and the number of edges were intercompared emphatically and were compared with the simulation results of AUTODYN.The results show that, for spherical fragments, when the diameter is certained, the initiating ability enhances as the density (or mass) of fragments increases; for spherical fragments and cylindrical fragments with a length to diameter ratio of 1, with the same material and diameter, the initiating ability of cylindrical fragments is better than that of spherical ones; for cylindrical and prismatic fragments of the same density and quality, as the length to diameter ratio increases, the fragments' initiating ability decreases; as the number of edges of regular prism fragment increases, the initiating ability decreases, when the edge number approaches infinite, its initiating ability converges with that of the corresponding cylindrical fragment.

In this study, the dispersion, cloud forming process and combustion explosion properties of diesel, combustion retardant diesel and explosion suppression diesel were investigated.A high-speed video camera system was employed to record the process of cloud forming, and an infrared thermal imaging system to record the fireball evolution process.The results show that under the driving force of shock wave from the center initiation explosive, the diesel droplets mix with air rapidly to form cloud.The size of cloud decreases as the kinematic viscosity of diesel increases.Afterwards, fireball appears after the secondary initiation.The highest fireball temperature of combustion retardant diesel decreases 35% compared with diesel, and that of explosion suppression diesel decreases 23% compared with combustion retardant diesel.The maximum fireball diameter and height of combustion retardant diesel reduce 54% and 42% respectively compared with diesel, and those of explosion suppression diesel reduce 46% and 55% respectively compared with combustion retardant diesel.The fireball duration of combustion retardant diesel shortens 38% compared with diesel and that of explosion suppression diesel shortens 47% compared with combustion retardant diesel.Therefore, explosion suppression diesel is better than combustion retardant diesel and combustion retardant diesel is better than diesel in preventing temperature and size growth of fireballs.

Thermoelectric materials Ag_1-xPb₁₈SbTe₂₀ (x=0, 0.3, 0.6) were synthesized by high pressure method.The composition dependent electrical properties were studied from room temperature to 500 ℃.The result of X-ray diffraction indicates that Ag_1-xPb₁₈SbTe₂₀ samples have the structure of NaCl crystal.As Ag content decreases, the lattice constant decreases.The measurement results of electrical properties show that the electrical conductivity of Ag_1-xPb₁₈SbTe₂₀ samples synthesized by high pressure is much higher than that of other preparing methods.The electrical conductivity increases with x, and its maximum value reaches 1 598.4 S/cm at room temperature for the Ag_0.4Pb₁₈SbTe₂₀ sample.As the temperature rises, Seebeck coefficient increases and electrical conductivity decreases.The maximum power factor reaches 1.97 mW/(m·K²) at 300 ℃ for the Ag_0.4Pb₁₈SbTe₂₀ sample.

In this study, we choose different confining pressure materials, pressure transmitting WC-Co platforms and WC-Co wafers, to calibrate pressure of 10/4 (The edge length of octahedral transmitting pressure medium is 10 mm/the truncated angle edge length of WC-Co cemented carbide anvil is 4 mm) assembly of two-stage 6-8 type hydrostatic high-pressure apparatus based on the hinge-type cubic-anvil 6×8 MN press at room temperature, using phase transition of ZnTe under high pressure.The experimental results show that the pyrophyllite is a relatively ideal confining pressure material, but it can not pressurize obviously because of the strength limitations of platforms and wafers.By combining simplified mechanics model of 2 kinds of presses, we also find out that the large-area gasket, formed by pre-gasket and initial confining pressure material together, consumes most of the loading, and the gap is oversized between the first anvils.Therefore, we did not observe any improvement of the 10/4 assembly pressure limit in our experiments.

Using density functional theory (DFT), the reaction of chlorine trifluoride oxide (ClF₃O) with propylene oxide (C₃H₆O) was studied.At the B3PW91/6-31++G(d, p) level, geometries of all species (reactants, transition states and products) were optimized, and the vibrational frequencies and zero point vibrational energies (ZPVE) were calculated.The energies of all species were refined with CCSD(T)/6-31++G(d, p)//B3PW91/6-31++G(d, p) method and ZPVE correction.The calculated results suggest that the initial reaction has various pathways to yield the main products of C₃H₅O and ClOF₂ radicals, and C₃H₆O₂ and ClF₃ molecules.The reactions of C₃H₅O and ClOF₂ radicals have different pathways to yield the main products of C₃H₄O, ClOF and HF molecules.The main reaction channel is C₃H₆O+ClF₃O→TS12→P4 (C₃H₅O+HF+ClOF₂)→P12 (CH₂CHCHO+2HF+ClOF).P4 is produced by C₃H₆O and ClF₃O via TS12 with a low barrier of 15.63 kJ/mol, and P12 can be formed from P4 through a barrierless process.