Well-crystallized jadeite was successfully synthesized from its glass phase under high pressure and high temperature conditions by simulating the mineralization principle of natural jadeite.Some of the synthetic jadeite samples present highly saturated colors and smooth finish which are the main features of high quality jadeite.The results of X-ray diffraction (XRD) and scanning electron microscopy (SEM) characterization show that the jadeite samples possess a relatively high degree of crystallinity and exhibit a good texture structure with vitreous luster and an appearance exactly like those of natural jadeite.The jade samples were also studied in detail by confocal micro-Raman spectroscopy.It is observed that the sharp Raman bands of synthetic jadeite samples are consistent with those of the natural jadeite.The differential scanning calorimetry (DSC) curve indicates that the thermal stability of synthetic jadeites is the same as natural jadeite.The hardness and density of synthetic jadeite measured are also similar to natural jadeite.In addition, it is found that the temperature plays a quite important role in crystal growth and knitting structure in terms of the synthetic jadeite samples.

The magnetically driven device CQ-4 was used to drive a copper flyer plate to impact a pure iron specimen to achieve one dimensional plane-wave loading, and a high-accurate Doppler pin system was utilized to record the free-surface velocity histories of the flyer and specimen.The results indicate that if the pure iron material experiences α ↔ε phase transition during shock loading and unloading, its spallation strength reaches to 3.4 GPa which is distinctly higher than the reported value of 1.2-1.9 GPa without phase transition.The possible cause of this phenomenon is that a multitude of dislocations in the crystal lattices of the pure iron are formed during the α ↔ε reversible phase transition.Moreover, the free-surface velocity history reveals that the spallation has occurred in the near-surface of the specimen.The formation of the shallow spallation may be related to the rarefaction wave formed at the time of reversal phase transition in the pure iron specimen.Because if only consider the interactions between the rarefaction waves generated by the reflection of plastic wave as well as phase transition wave and rarefaction wave when analyzing the stress wave propagations in the flyer-specimen system, it is impossible to interpret the detected shallow spallation in the experiment.

The pure bulk tungsten and W-TiC alloy were sintered by high-pressure and high-temperature (HPHT) method, and their densification behavior and hardness were systematically investigated.It is found that the pure tungsten sample sintered at the circumstance of 5.0 GPa and 1 500 ℃ for 15 min exhibits unique properties, its relative density and hardness are as high as 99.3% and 6.43 GPa, respectively.Moreover, the values for W-TiC alloy with TiC mass fraction of 1.5% are 99.0% and 7.58 GPa respectively under the same sintering conditions.It is concluded from the experimental results that the HPHT sintering method plays an important role in the aspects of accelerating the densification, improving the sintering efficiency and bringing down the sintering temperature.Furthermore, the relations of the sintering kinetics, microstructures and the evolutions of mechanical properties versus pressure and temperature were all explored for tungsten and W-TiC alloy.

The longitudinal and shear sound velocities (v_p and v_s) of SiC-diamond composite under hydrostatic pressure were measured simultaneously in a multi-anvil apparatus, and the relationship between modulus and pressure was also obtained.v_p and v_s increase with increasing pressure in the pressure range of 0 to 1.4 GPa and keep stable at higher pressure.The variations of sound velocities are attributed to the closing procession of micro voids and cracks during compression.The bulk modulus of SiC-diamond composite is higher than the shear modulus at ambient pressure, whereas the bulk modulus increases faster than the shear modulus with increasing pressure and exceeds the shear modulus at 1.4 GPa.In the pressure range of 1.4 to 4.3 GPa, the bulk and shear modulus of SiC-diamond composite are about 360 and 350 GPa, respectively.

The origin, ignition and growth of hot spot are keys to understand the shock initiation in heterogeneous explosive.An experimental method of shock behavior for millimeter-scale plastic-bonded explosives (PBX) is developed by using an electrical explosion driven low-velocity flyer, a quick-response thermocouple and a high speed and micro-scale camera, in which the camera consists of a microscope, a high speed camera and an image transmission bunch.The dynamic collapse process of the precast cavity with a diameter of 0.5 mm in PBX is captured.The physical image and temperature curve of the precast cavity in PBX are obtained during the dynamic collapse process, which may provide a foundation for the hot spots experiment in PBX.

Traditional two-dimensional (2D) metallographic modeling method is commonly used to evaluate the spatial void distribution in shocked metals.However, its error was not quantified.This paper reports the comparison of 2D method and three-dimensional (3D) high resolution X-ray tomography method on evaluating the spatial void distribution in the shocked ultrapure aluminum with different damage degrees.A regression equation (errors vs.impact velocity) was deduced to quantify the errors and a potential correction can be made based on the equation.Therefore, caution should be exercised when using the results reported by 2D methods in the literature.

The equation groups of one dimensional magnetohydrodynamics code SSS/MHD are given, and a calculation model of magnetically driven isentropic compression on a side-step aluminum sample is established.Based on the calculated values of current and particle velocity at the back interface of sample, according to the ones obtained by the experiment, the change of dynamic inductance of the configuration (sample), the law of magnetic field diffusion, and the distributions of temperature, density, pressure and particle velocity in sample are analyzed, which are important to deeply understand the physical process and improve the experimental design.

In the directional blasting in various engineering area and the numerical simulation of detonation, it is sometimes necessary to estimate the initiation time from the initiation position to a specific point of the explosive.Based on the Huygens' principle, the advancing front technique is introduced in the numerical mesh generation in order to calculate the detonation in the explosive.Furthermore, a computational method is proposed to evaluate the initiation time of the explosive from the initiation position to an arbitrary position of the explosive.Compared with traditional algorithms, this method is suitable for the explosive with complex geometric domain when coping with the initiation time.Several numerical examples are given to verify the effectiveness of this method.

The fragmentation and penetration of the 40Cr steel cylindrical shells preformed by local quenching technology were studied experimentally.Through scanning electron microscopy (SEM) analysis, it is found that the microstructure of hardened layer in the cylindrical shell is predominantly needle and lath type martensite, and it is more refined and brittle than bulk material.Based on the performance difference, the steel cylindrical shell fractures along the designed path during the expansion process.The mass distribution of the preformed fragments is relatively uniform and the penetration also meets the requirement, which can provide reference for design of ammunition.

This paper presents brief results of an experimental investigation on deformation shapes of cylindrical shell filled with soil subjected to lateral explosion loading, and the ultimate deformation shapes are obtained.Based on the experimental results, a corresponding analytical model is undertaken by using the plastic hinge theory.In the analytical model, the cylindrical shell is divided into several end-to-end rigid square bars.The deformation shape of cylindrical shell is described by the translation and rotation process of rigid square bars.The expressions of the spring force, moment and deflection angle between adjacent bars are deduced theoretically in detail.In addition, the blast loading conditions are studied in terms of the covering width of outer layer explosive and the initial velocity of cylindrical shell.Theoretical and experimental results show a good agreement, thus the analytical model can be considered as a valuable tool in understanding the deformation mechanism and predicting the deformation shape of cylindrical shell under lateral contact explosion.The various deformation shapes of cylindrical shell can be achieved by modifying the covering width of outer layer explosive and initial velocity of cylindrical shell.

For the purpose of understanding the law of coal mine gas explosion, gas explosion characteristics under different ambient humidity conditions were experimentally determined, and the inhibition of water vapor on gas explosion is analyzed.The results show that when the premixed gas varies from dry state to saturation state, the upper and lower explosion limits decrease and increase by 0.31% and 0.11% respectively, and the explosion concentration range is reduced; the corresponding maximum explosion pressure and the maximum rate of pressure rise decay from 0.802 MPa and 23.38 MPa/s to 0.746 MPa and 18.59 MPa/s.The vapor components in premixed gas play an effective role in suppression of gas explosion.

The growth theory of natural diamonds and the development history of synthetic diamonds were introduced.The preparation methods of synthetic diamond were discussed from 3 aspects of static-pressure, impact-pressure and low-pressure methods.The ultra-high pressure technologies of synthetic diamonds were reviewed including the belt-type, tetrahedral-type, cubic-type and split-sphere-type high pressure apparatuses.The problems and development trend of synthetic diamond science and technology were also summarized.