Meteorite impact events are considered as important influences on the composition of Earth’s early atmosphere, with substantial implications for biological evolution. The physicochemical behavior of sulfur-bearing minerals during such natural impact events is crucial for understanding the role of sulfur in the evolution of Earth’s ocean-atmosphere system. Here, we conducted shock recovery experiments on natural pyrite (FeS₂) under shock pressures of approximately 20 and 55 GPa to investigate its decomposition characteristics under high-velocity impact. The experimental results indicate that pyrite undergoes partially decomposition into pyrrhotite and sulfur at the shock pressure of about 55 GPa, revealing its thermodynamic instability and the release of sulfur vapor. Our results suggest that the desulfurization of pyrite during meteorite impacts may contribute to the release of sulfur gases into oceanic and atmospheric systems. Such environmental changes may be linked to the Permian-Triassic mass extinction event approximately 250 million years ago, providing important insights into the biological crises of that era.

Diamond anvil cell (DAC) is a kind of widely used static-high-pressure device. Benefitting from its wide pressure range, excellent optical applicability and convenience of use, DAC provides a tremendous boost to the development of high-pressure science. However, at high pressures, factors like solidification of pressure transmitting medium may cause destruction of the hydrostatic pressure condition in the DAC sample chamber, leading to the generation of pressure gradients. In this work, a new method of using the technique of picosecond ultrasonics to investigate acoustic signal distribution at various locations within the sample chamber was proposed, which can analyze the pressure distribution via the acoustic observations. Limitations in the continuity of signal acquisition, sample selection, etc. can be overcome in this experimental technique, which could be built and manipulated in an ordinary laboratory. Here, pressure gradient in silicon oil was carried out under compression using this technique, and the results revealed that the pressure gradient in the sample chamber increased from 1.3×10⁻⁴ GPa/μm at 1 GPa to 5.3×10⁻² GPa/μm at 30 GPa. In addition, the anomalous change of standard deviation of the pressure distribution was analyzed by combining it with in-situ Raman spectroscopy, then the possible phase transitions of silicone oil at high pressures were discussed.

To improve the performance of the CO₂ phase change excitation agent, titanium powder with mass fractions of 2%, 4%, 6%, 8%, and 10% was added to the excitation agent. The contents of ammonium oxalate and salicylic acid were controlled to adjust the zero oxygen balance, respectively. The ignition reliability, pressure performance, thermal decomposition characteristics, safety performance and temperature resistance property were investigated by on-site ignition tests, thermogravimetric analysis, temperature resistance performance tests and theoretical calculations. The results show that: all the excitation agents are successfully ignited inside the tube after adding titanium powder with mass fractions of 2%, 4%, 6%, and 8%. The peak pressure is directly associated with the heat release amount of the excitation agent. Within the addition range of this test, the excitation agent with 8% titanium powder has the best pressure performance inside the tube. After adding titanium powder with a mass fraction of 8%, the peak pressures of excitation agent without adjusting the oxygen balance, with adjusting the zero oxygen balance through ammonium oxalate, and with adjusting the zero oxygen balance through salicylic acid increase by 11.81%, 14.27%, and 17.85%, respectively. The apparent activation energies of the three samples decrease by 5.96 kJ/mol, increase by 33.47 and 6.80 kJ/mol, respectively, indicating that adjusting the zero oxygen balance can optimize the thermal stability of the excitation agent. After adding titanium powder with a mass fraction of 8%, the safety of the excitation agent is good, and the temperature index T_s is above 90 ℃.

In order to study the effect of water content on the performance of porous granular ammonium nitrate on-site mixed ammonium amine explosives, five groups of on-site mixed ammonium amine explosives with different water contents were prepared by controlling the water content in the aqueous phase. We used scanning electron microscope to observe the internal microstructure of porous granular ammonium nitrate, and Brinkley-Wilson method to carry out theoretical calculations on the heat of detonation and detonation velocity of the explosives. The solubility of porous granular ammonium nitrate at different water contents was tested, and the viscosity of the ammonium amine explosive matrix, the immersion conductivity and the detonation velocity were tested. The results show that with the increase of water mass fraction from 9% to 17%, the mixing homogeneity of ammonium amine explosive matrix increased, the initial viscosity decreases from 218539 mPa·s to 99443 mPa·s; the conductivity of the explosive immersed in water with different water content for 3 h first decreased from 1.416 mS/cm to 1.234 mS/cm, and then increases to 2.600 mS/cm; the theoretical detonation velocity decreases from 4943 m/s to 4716 m/s; the actual detonation velocity is affected by the content of solid ammonium nitrate, first increasing from 3376 m/s to 3676 m/s, and then decreasing to 3631 m/s. In actual production, the mass fraction of water in on-site mixed ammonium amine explosives should be controlled at approximately 13%. At this water content, the explosives exhibit optimal water resistance, and achieve a relatively high actual detonation velocity.

In order to improve the ultimate pressure bearing capacity and increase the volume of the cavity of the belt type ultra-high pressure die, a structure of winding discrete type large cavity ultra-high pressure die was proposed. This die is mainly composed of discreted cylinder, supporting ring and steel wire winding layers. The circumferential stress of the integral cylinder is eliminated in discrete structure and there is no need to use large size cemented carbide and supporting ring, which can effectively improve the pressure bearing capacity of high pressure die, reduce the difficulty of its manufacturing, and make it easy to obtain large cavity volume. The key parameters of the structure of high pressure die are designed and calculated to determine the optimal size of the geometry. It is found that under the same working internal pressure loading in numerical simulation, the stress of the discrete cylinder is lower, and the stress environment on the inner wall of the cylinder is effectively improved. The pressure bearing capacity of the winding discrete large-cavity ultra-high pressure die is predicted. It is found that the pressure bearing capacity of the die gradually increases with the increase of the number of discrete blocks, but the growth rate is slower and slower. Therefore, it is not feasible to increase the pressure bearing capacity of the cylinder by increasing the number of discrete blocks infinitely. The analysis shows that the winding discreted large cavity ultra-high pressure die has higher pressure bearing capacity, longer life and lower operating cost. It provides a new idea and method for the design of high pressure device with large volume and high pressure bearing capacity.

To elucidate the evolution laws of impact velocity of high-pressure pulse water jet and the breakage characteristics of coal under confining condition, a coupled smoothed particle hydrodynamics-finite element (SPH-FEM) algorithm is adopted. A sinusoidal velocity is applied to the plunger inside the pipeline. The evolution laws of water jet velocity inside and outside the nozzle were obtained, and the temporal damage and breakage characteristics of coal under load and unload conditions impacted by pulse water jet were compared and analyzed. The influence of key parameters such as average velocity, pulse amplitude, and pulse frequency on damage and breakage characteristics of coal was revealed. The results show that the velocity evolution of water jet particles inside and outside the nozzle undergoes four stages: a stationary stage and transient acceleration to a low speed in the pipeline, acceleration inside the convergent section of the nozzle, micro-acceleration inside the straight section of the nozzle, and pulse variation speed following a sinusoidal variation after exiting the nozzle. Under the stress free and two-dimensional stress load conditions, the broken pits of coal specimen exhibit an abnormal development, and undergoes from bowl shape to U-shape, respectively. Two-dimensional stress load has a suppressive effect on the derivation and propagation of internal cracks in coal, reducing the rock-breaking efficiency. Besides, pulse water jet has a higher rock-breaking efficiency on loaded coal specimens than that of continuous water jet. The depth and area of coal fragmentation increase exponentially with the increase of plunger’s average velocity or pulse amplitude, and show a trend of initial increase and subsequent decrease with the increase of pulse frequency, indicating the existence of an optimal pulse frequency for coal fragmentation. The research findings could provide a theoretical guidance for improving the rock-breaking efficiency of high-pressure pulse water jet under confining conditions and optimizing the working parameters.

In order to investigate the dynamic response process, damage characteristics and damage mode of polyurea coated masonry infill walls with built-in tie reinforcement under close-range explosion load, a series of close-range explosion tests were performed on masonry wall with different polyurea coating methods and thicknesses. Additionally, numerical studies were carried out using the LS-DYNA software. Based on the resistance function of the brick wall, steel bar and polyurea coating, an improved equivalent single degree of freedom (ESDOF) theoretical calculation model was established. This model can accurately describe the displacement response of the polyurea coated masonry infill walls with built-in tie reinforcement under close-range explosion load. Three damage modes: surface mortar layer damage, open pit dislocation with back bulge, and penetration damage were identified according to the wall’s out-of-face response characteristics during close-range explosion load. With the increase of the number of tension reinforcement, the anti-explosion performance of the wall improves and the critical penetration damage charge increases.

Taking Shuitun North Road Station of Jinan Rail Transit Line 7 as an example, a numerical simulation study was conducted to investigate the structural damage and failure effects of the metro structure based on the fluid-structure couple and full restart algorithm in LS-DYNA software. This study focused on two scenaries: projectile penetration followed by an explosion from outside to inside, and the inner explosion of a large equivalent TNT charge. Firstly, the accuracy of the numerical simulation and the selection of material model parameters were validated through the penetration followed by explosion test. Then, three cases of two-dimensional numerical model for penetration followed by explosion from outside to inside and three cases of three-dimensional numerical models for internal explosion were established. The damage mode of the metro structure and the damage condition for personnel and auxiliary components were analyzed. The simulation results demonstrate that the failure mode of the metro structure subjected to projectile penetration followed by explosion was localized damage. When the explosion occurs inside the metro structure, the peak of overpressure decays faster in the area close to explosion and slower in the middle and far area of the explosion. The present research results can provide a reference for further studies on the radial and normal shock wave propagation attenuation laws of the metro structure subjected to internal explosion.

In order to explore the influence of injection pressure on the deflagration characteristics of gasoline in the confined space, a 20 L spherical explosion test device was used to examine the changes of characteristic parameters, i.e., the transient flame propagation and temperature of gasoline mist deflagration under different injection pressures. The results showed that the optimum spraying time was 100 ms, and the maximum explosion pressure and maximum explosion pressure rise rate increased linearly with the increase of injection pressure, while explosion duration decreased linearly. The change of injection pressure had a more significant effect on explosion duration, and the combustion efficiency of gasoline increased significantly with the increase of injection pressure. Based on the colorimetric temperature measurement method, the flame temperature field was reconstructed. It was found that the maximum average temperature had a linear relationship with injection pressure, and the maximum average temperature increased with injection pressure. The influence of injection pressure on the deflagration characteristics of gasoline mist was analyzed through the changes of mist morphology and flame temperature during flame propagation. The outcome of this research can provide theoretical reference for the design of turbocharged direct injection internal combustion engine and the improvement of combustion efficiency and economy of gasoline internal combustion engine.