Ternary ε-Fe_3-xM_xN_1+δ (M=Co, Ni) were synthesized as spherical bulk materials with variable components through composite high-pressure solid-state metathesis (HPSSM) reactions under 5GPa and at 1673K, employing diversity binary metal oxides (Fe₂O₃, CoO, NiO) and hBN as the reaction precursors.The structural characterizations of the as-prepared iron-based metal nitrides were determined by X-ray powder diffraction (XPD), field-emission scanning electronic microscopy (FE-SEM) and high-resolution transmission electron microscope (HRTEM), etc.First-principles calculations were used to explore the effect of pressure on the reaction enthalpy ΔH in HPSSM.Our results show that the high-pressure confinement environment is favorable for the synthesis of high-quality metal nitrides, and the HPSSM reaction is an effective synthetic route to the bulk iron-based metal nitrides.

We investigated the effects of the roasting course on behaviors of the pyrophyllite gasket under high pressures using Bridgman anvils.The results show that high roasting temperature is beneficial to increase the critical thickness and enlarge the area of the elastic central region of pyrophyllite gaskets, which helps to effectively enlarge the size of the sample chamber.The pressure calibration was carried out using the high-temperature (maximum 900℃) roasted pyrophyllite gasket.And based on this calibration, we measured the temperature at the center of the sample cavity with the improved internal heating assembly under ambient and high pressures respectively.The improved internal heating assembly expanded the heating range up to 1300℃ under 4.0GPa, which provides a much greater variety of conditions for the preparation of bulk metastable materials in the Bridgman anvils.

The research of shaped-charge penetrating concrete target focuses on the material and the structure of the shaped-charge, penetration depth and penetration aperture size, but seldom involves the destruction of a concrete target board.However, the determination of whose overall damage behavior plays a significant role in the penetration effectiveness evaluation of the shaped-charge on the concrete.In the present work, to make up for this defect, we carried out experiments of the heavy-caliber shaped-charges penetrating a large-size concrete target.After the experiment, we cut the concrete target to assess its damage under the shaped-charge loading.We evaluated the concrete target damage at different locations from inside the target and measured the hole diameters at different locations.Cube concrete specimens with a side length of 10cm were also obtained in the same damaged section across the hole center.The strength test results show that the reflective stretching damage radius is about 110cm; the concrete damage is severe within a 100cm radius, and the compressive strength of the concrete specimen at the border within this radius range is about 30MPa, which is about 40% of the original compressive strength; the compressive strengths of the concrete specimens within the scope of the radius 100-140cm are similar and are all around 46MPa, which is about 72% of the original compressive strength; when the radius is larger than 140 cm, the concrete damage is negligible.

In order to find out about the static electric field energy-storaging characteristics of lead zirconate stannate titanate ceramics doped with lanthanum, PbLa(Zr, Sn, Ti)O₃ (PLZST) ceramics with different Sn/Zr ratios were fabricated using the conventional solid-state reaction of oxide method.The compositions of samples are all close to phase bound of ferroelectric (FE) and antiferroelectric (AFE).The energy-storaging characteristics of PLZST ceramics were investigated experimentally through hydrostatic pressure induced discharging.The results show polarized PLZST ceramics in the DC field are in a meta-stable FE state.Phase transitions from FE to AFE occur under the influence of the pressure, and the static electric field energy stored via polarization is released instantly, which leads to high-power current pulses.PLZST ceramics are totally depolarized after the discharging.The largest discharge current density and the largest electric field density are 5.0nA/cm² and 9.45J/cm³ respectively.PLZST ceramics are ideal materials for explosive energy converter's power supply.

Punching shear plays a very important role in assessing the load carrying capacities of connections between slabs and columns or slabs loaded by flat-faced punches, especially in the safety calculation and assessment of containment structures in nuclear power plants.For many years this has been examined by researchers and the influences of the span-to-depth ratio on punching shear strengths are often neglected, and all the equations employed in the current codes are dimensionally inconsistent.We proposed a dimensionless new empirical equation to predict the punching shear strengths of reinforced concrete circular slabs without shear reinforcement which are loaded quasi-statically by flat-faced circular indentors.In the present formulation, we took into consideration various effects such as rebar quantity, rebar spacing and span-to-depth ratio.It is shown that the present equation is in good correlation with available experimental results.It is also shown that the present equation is applicable to square punches as well as square slabs.

Building constitutive models that include damage is the foundation for the research of dynamic mechanical responses of explosives.Based on the viscoelastic character on macroscale and the crack directions on mesoscale, we established a viscoelastic statistical crack mechanics including anisotropic damage, and then obtained the simplified constitutive model under uniaxial loading.By using a numerical program, and taking PBX9501 as an example, we analyzed the extension rules of cracks with various directions, and the strength-difference and strain-rate dependence of failure strength and critical strain of explosives.Furthermore, we discussed the sensitivity of 4 main parameters, the crack number density, the initial crack size, the friction coefficient between crack surfaces and the fracture surface energy.The result demonstrates that the 4 parameters greatly affect the extension and evolvement of cracks, which causes the different mechanical responses of explosives.

By using the dynamic finite element software LS-DYNA, we simulated the working process of a novel emulsion explosive pressure desensitization device, and investigated the characteristics of its flow field distribution and the influence of its structural design on the experimental results.The comparison of simulation and experiment results shows that the row spacing is the critical factor that determines the degree of accuracy in experiment.For the novel dynamic pressure desensitization equipment, when the radius of the emulsion explosive is 2cm and the weight of RDX is 10g, the smallest row spacing, which minimizes the effect of the emulsion explosive in the front row on that in the back row, is determined as 20cm.Therefore, in order to decrease the experiment error, we can decide on the smallest row spacing through numerical simulation before the dynamic desensitization experiments take place.Our work can serve as a reference for the further research.

In the present work we investigated the ablation behavior of the Cu/diamond composite material under the current ranging from 100 to 300kA and the preload ranging from 0.4 to 2.0kN in the initial stage of the electromagnetic rail launch.The analysis reveals that, due to the dual function of the joule heat and electric arc heat, the mass loss and the ablation depth of Cu/diamond composite increase with the increase of the current and decrease with the increase of the preload; in the main ablation area, uneven topography is formed, and the exfoliation of the second phase particles causes a certain number of micro-pores, and thermal stress cracks are produced due to the strong alternating temperature field; micro-bulges and splash at the edge of the main ablation area are attributed to the molten liquid metal affected by the strong eddy current electromagnetic field; in the electrical sliding contact area, micro-scratches are formed due to the friction between the micro-bulges on the armature and the rail, and its wear mechanism is the abrasive wear; in the cross section of the ablation area of Cu/diamond composite, different scales of grains are formed corresponding to the different cooling rates resulting from the rails large length-height ratio, and the surface hardness of Cu/diamond composite undergoes a considerable decrease.

It is a big challenge for measuring the rapidly-increasing ejecta from the melted metal sample under intense shock loading.In this work, we experimentally investigated the ejecta mass, density and velocity distributions on a melted Sn target by adopting the Asay-F-window technique, and focused on the influence of the surface machined states on the ejecta properties.Our results show that the surface perturbation plays a dominate role in the amount, velocity and spatial distribution of the ejected particles, and these quantities tend to increase with the increasing of the surface roughness when the Sn is melted on shock or release.Our research is expected to contribute a lot to better understanding the ejecta behavior and constructing the physical ejecta source model for melted metal upon shock or release.

The nozzle is the core component of a hydraulic horizontal drilling equipment, and optimizing its structure is crucial for helping to improve the construction efficiency of exploiting low permeability oil and gas resources.Based on the computational fluid dynamics (CFD) approach, we studied the effects of the structural parameters of the tail flow (evenly distributed on the end of the nozzle) on the jet flow field.The results show that:when the number of the tail flow (N) is 6, with an angle (α) between 15° and 30° and a diameter (D) of 1.4mm, the nozzle exhibits good performance on the rock fragmentation and discharge; the reasonable design of N and D contributes to implementing the nozzle propulsion and the rock destruction by jet; the reasonable design of the jet nozzle angle α contributes to effectively reducing the abrasion of the jet nozzle and extending its service life.

The plasma jet ignition technology has wide applications in aerospace, weapons and civilian industry.To explore the ignition properties of the plasma jet, we have conducted numerical simulation to study the characteristics of the near field of the transient plasma jet propagation in air, and have obtained the distribution properties of pressure, velocity, temperature and the evolution characteristics of the plasma-air interface.The results indicate that, as the plasma jet propagates, the Mach disk is formed gradually at the near field, and this is accompanied by the phenomenon that the plasma jet ramifies and converges.The parameters of the normal shock upstream do not vary with time, while the parameters downstream do.The calculated displacement of the front of the plasma jet matched well with the measured value.

The quasi-isentropic compression technique of the liner in the Z-pinch can be used to study high pressure state equations of materials.In this research, we designed the quasi-isentropic compression load for PTS shot37 load currents through the MDSC magnetohydrodynamic code, with Al being the load material.The results show that it is impossible to find an appropriate liner for quasi-isentropic compression under the original current pulse, but it is possible under the shaped currents.When the current increasing time is 303ns, the liner with a radius of 2.5mm and a thickness of 0.6mm gets the maximal pressure (63GPa) and implosion speed (15km/s) when the current reaches its maximum, while the remaining solid liner is 0.12mm thick.