Abstract:Nitrogen-containing compounds， acting as nitrogen donors， directly influence the types of high nitrogen compounds formed under laser irradiation. To understand the impact of various nitrogen-containing compounds on the formation of high-nitrogen compounds， three representative compounds NaN₃， Si₃N₄ and P₃N₅ were ablated using a pulsed Nd： YAG laser in a nitrogen atmosphere. The plasma characteristics and the evolution of the transient intermediates generated by laser sputtering were investigated by transient spectrometer. The findings indicate that the laser ablation of NaN₃ yields the highest number of nitrogen atoms （N Ⅰ）， monovalent nitrogen ions （N Ⅱ）， and trivalent nitrogen ions （N Ⅲ）， with the longest duration of nitrogen plasma. The lifetimes of N Ⅰ， N Ⅱ， and N Ⅲ reached 39，400 ns， 39，400 ns， and 19，450 ns， respectively. Among the three nitrogen donors， the laser ablation of NaN₃ in a nitrogen atmosphere is most likely to result in the formation of high-nitrogen or all-nitrogen compounds.

Abstract:Fluoropolymers such as polyvinylidene fluoride （PVDF） can effectively inhibit the agglomeration of aluminum powder and enhance its reactivity. However， the affinity between fluorinated polymers and the surface of Al particles covered by alumina is poor， and the inhibitory effect of fluorinated polymers directly coating the Al surface on Al aggregation is not ideal. In this study， a microwave-enhanced reaction method was used to obtain hydroxylated modified PVDF-OH. PVDF-OH was coated on the surface of aluminum powder by solvent/non-solvent method for preparation Al@PVDF-OH. Subsequently， the prepared Al@PVDF-OH Composite fuel is used to prepare composite solid propellants. The molecular structure and elemental composition of PVDF-OH were studied using infrared spectroscopy and X-ray diffraction. Using equipment such as scanning electron microscope， differential scanning calorimeter， high-speed camera， and oxygen bomb calorimeter study the microstructure composition and combustion performance of Al@PVDF-OH composite fuels. The results showed that the PVDF-OH prepared by microwave-assisted preparation had a higher hydroxyl content， and the optimal treatment condition was 1 minute at a microwave power of 240 W. The combustion performance of Al@PVDF-OH composite fuel was superior to that of Al@PVDF composite fuel coated with unmodified PVDF and Al@PVDF-OH（H） composite fuel coated with heat-modified PVDF-OH（H）. The optimal PVDF-OH content was found to be 15%. Compared to pure aluminum， the combustion heat value of Al@PVDF-OH composite fuel with 15% PVDF-OH increased from 19140 kJ·kg^-1 to 24912 kJ·kg^-1. Combustion tests with ammonium perchlorate （AP） showed that the ignition delay time of Al@PVDF-OH composite fuel shortened from 77 ms to 70 ms， and the burning rate increased from 195.7 mm·s^-1 to 225.7 mm·s^-1 compared to pure aluminum. Compared to aluminum-based solid propellants， solid propellants based on Al@PVDF-OH composite fuel exhibited an increase in combustion heat value from 13281 kJ·kg^-1 to 14020 kJ·kg^-1， an increase in burning rate from 1.281 mm·s^-1 to 1.915 mm·s^-1， and a reduction in the particle size D90 of condensed phase combustion products from 74.324 μm to 52.749 μm.

Abstract:The condensation and accumulation of Nitroglycerin （NG）-containing volatiles on various solid surfaces during the propellant rolling process， which pose safety hazards， were investigated using molecular dynamics simulation methods. The study was conducted by constructing a hybrid system model consisting of NG volatiles and solid surfaces， examining the effects of solid surface material， surface roughness， and NG content on molecular dynamics characteristic parameters such as radial distribution function， mean square displacement， diffusion coefficient， and relative density distribution of NG volatiles in the hybrid system. The findings demonstrate that as the mass fraction of NG increases， the size of volatile condensate clusters on the solid surface progressively diminishes. Conversely， the condensation ratio of volatiles exhibits a trend of initial increase followed by a decrease， with the maximum condensation ratio occurring at 70% NG， corresponding to a diffusion coefficient of 0.0364. The diffusion coefficient for the condensation of volatiles containing NG on a silica （SiO₂） surface is 2.1228， which is substantially greater than that on surfaces composed of copper （Cu）， calcium oxide （CaO）， and ferrum （Fe）. However， the uniformity of the SiO₂ surface condensate cluster is poor. The introduction of surface roughness factors has opposite effects on the condensation amount of volatiles on the SiO₂ and Fe surfaces. When the SiO₂ surface goes from smooth to roughness of 0.4 nm， the diffusion coefficient increases from 2.1228 to 10.7156， and the condensation amount of volatiles on the surface increases； however， when the Fe surface goes from smooth to roughness of 0.4 nm， the diffusion coefficient decreases from 17.5673 to 1.8462， and the condensation amount of the surface volatiles decreases.

Abstract:In order to study the effects of strain rate and tensile-shear angle on the tensile-shear strength of NEPE propellant， tensile-shear tests of the propellant for 5 tensile-shear angles （0°， 30°， 45°， 60°， 90°） and 5 strain rates （0.0012， 0.0048， 0.024， 0.12， 1 s^-1） were carried out by using tensile-shear fixtures and butterfly test specimens. The variation of tensile-shear strength with tensile-shear angle and strain rate of propellant under combined tensile-shear loading was obtained. Based on the experimental results， the tensile-shear strength limit of propellant was described by the improved circular equation， and the tensile-shear strength criterion of propellant at different strain rates was established by combining the double shear unified strength theory， and the corresponding theoretical limit surface of the unified strength of propellant was drawn. Finally， the established tensile-shear strength criterion was used to predict the tensile-shear strengths of 0.12 s^-1 and 1 s^-1 strain rates for the tensile-shear angles of 15° and 75°. The validity of the established tensile-shear strength criterion was verified by comparing the predicted results with the experimental data. The results show that the tensile-shear strength of NEPE propellant under combined tensile-shear load increases with the increase of tensile-shear angle and strain rate. By fitting and solving the material parameter values， the improved circular equation and unified strength criterion established can well describe the tensile-shear strength of NEPE propellant for different loading angles and strain rates. Based on the established strength criterion， the errors between the predicted values and the experimental values of the tensile strength limits at the strain rates of 0.12 s^-1 and 1 s^-1 for the tensile-shear angles of 15° and 75° are less than the allowable error range of the actual treatment by 15%.

Abstract:To further balance the energy and safety of 5-nitro-3-（trinitromethyl）-1H-1，2，4-triazole， four nitrogen-rich energetic ionic salts were synthesized using 2-（5-amino-1H-1，2，4-triazole-3-yl） acetic acid as a starting material through a silver salt substitution reaction. The structures of all new compounds were characterized using nuclear magnetic resonance， Fourier transform infrared spectroscopy， differential scanning calorimetry， thermogravimetric analysis， and single crystal X-ray diffraction. The results indicate that the ammonium salt， hydrazine salt， and guanidine salt of 5-nitro-3-（trinitromethyl）-1H-1，2，4-triazole exhibit higher initial decomposition temperature than that of the precursor. Moreover， the hydrazine salt and guanidine salt belong to the different crystal systems with distinct crystal packing arrangements and densities. However， they share consistent characteristics in terms of intermolecular weak interactions， with the H…O interaction being the predominant contributor. With the decreasing of the ratios of N…O and O…O interactions， the sensitivity of the nitrogen-rich energetic ionic salts to mechanical stimuli decreases. Finally， the analysis of the distribution of molecular electrostatic potential supplements the explanation for the change in impact sensitivity of 5-nitro-3-（trinitromethyl）-1H-1，2，4-triazole after salt formation. Among the four ionic compounds， the hydrazine salt exhibits outstanding detonation performance （D=8634 m·s^-1， p=30.2 GPa， I_sp=263.5 s） with relative high sensitivity. In contrast， the triaminoguanidine salt demonstrates excellent overall performance. It has a detonation velocity comparable to that of the hydrazine salt （D=8627 m·s^-1）， a heat of formation nearly 1.4 times greater than that of the precursor （ΔH_f=0.644 kJ·g^-1）， and a low mechanical sensitivity （IS=10.3 J， FS=150 N）.

Abstract:3D printing technology has the characteristics of customization， mold free， and flexibility， which can provide an effective approach for the shaping of special structure solid propellant grains in multi-thrust or multi -pulse solid rocket motors. At present， research on 3D printing of solid propellant grain has been conducted both domestically and internationally. This article focuses on the application of typical 3D printing processes such as binder jetting， photopolymerization curing， and material extrusion in the formation of heterogeneous solid propellant grains with contained complex structures， gradients， and multi material integration. It summarizes the key issues that exist in the 3D printing of these three types of solid propellant grains. The future research directions were prospected， and it was emphasized that the future manufacturing of heterogeneous solid propellant grains should focus on low sensitivity specialized solid propellant slurries， printing equipment for large grain forming， and insulation coating printing technology.

Abstract:Energetic materials serve as the energy source for munition damage， directly impacting the strike range and effectiveness of munitions. With the increasing strategic requirements of modern weapon systems for high energy， high efficiency and high security， research on the thermal properties of energetic materials has gained more attention. The thermal properties of energetic materials not only directly affect the energy output， control and regulation of energetic materials， but also are related to the safe transportation， storage and use. In order to provide a reference for the research methods of thermal properties of energetic materials， this paper systematically reviews the thermal performance characterization techniques and theoretical prediction models applied to energetic materials in recent years， involving the analysis of thermal decomposition reaction mechanism， combustion performance test， detonation performance evaluation and safety performance prediction， and analyzes and compares the characteristics and application scope of each characterization technology. Finally， it proposes that the experimental characterization technology in future research should be developed in the direction of high integration， high spatiotemporal resolution， small dose non-contact interference， and real-time monitoring and analysis. In the computational simulation research， it is necessary to co-construction and share the standard database according to the actual production of energetic materials， in order to obtain a high-precision and high-efficiency performance prediction model.

Abstract:In order to investigate the influence and regularities of planar integrated transient voltage suppressor diodes （TVS） on the performance of anti-static integrated semiconductor bridge initiator transducers， capacitor discharge firing experiments were carried out to study the effect of the parallel quantity of planar integrated TVS diodes and breakdown voltage on the electrical explosion performance. Its influence on the static electrostatic reliability performance of semiconductor bridge initiator transducers were also investigated by 500 pF/500 Ω/25 kV static discharge experiments. The results indicate that when the excitation energy approaches the upper limit of the energy absorbed per unit time by a single planar integrated TVS diode， increasing the number of parallel planar integrated TVS diodes will prolong the burst time of the SCB initiator transducer element， and may even affect the normal bursting of the SCB initiator transducer element. Conversely， if the excitation energy is insufficient to bring the energy absorbed per unit time by a single planar integrated TVS diode close to its upper limit， the bursting performance of the SCB initiator transducer element will not change with the number of parallel planar integrated TVS diodes. When the excitation voltage exceeds the breakdown voltage of the planar integrated TVS diodes， the lower the breakdown voltage of the TVS diode， the longer the burst time of the SCB initiator transducers， and the greater the burst energy， and potentially affecting the normal burst of the SCB initiator transducer element. Reducing the breakdown voltage of the planar integrated TVS diodes and increasing the number of parallel diodes can enhance the electrostatic reliability of the SCB initiator transducers. When designing an antistatic integrated semiconductor bridge chip with dimensions of 350 μm（W）×100 μm（L）×2 μm（H）， it is possible to integrate two TVS diodes with breakdown voltages slightly below 14 V， or one with a breakdown voltage slightly above 7 V.

Abstract:To improve the ignition reliability of firearm firing-ignition systems， the Lagrangian-Eulerian fluid-structure coupling method （ALE） was used to establish the ignition model of the firing-ignition systems， and a parametric simulation platform was built. The pressure start time was used as the ignition output performance characteristic parameter to establish the ignition reliability proxy model of the firearm firing-ignition system. The reliability of the firing-ignition systems under the influence of changes in structure and assembly parameters was simulated and studied. At the same time， based on small-caliber rifle firing-ignition system， an ignition system simulation test device was designed， and experimental research on the ignition performance and reliability of the ignition system was carried out to verify the ignition model. The results show that the error between the calculation results of the firearm firing-ignition reliability analysis model and the experimental results is 0.72%， indicating that the model has good accuracy. The influence rule of the average change of each factor on the system reliability is as follows： striking pin protrusion> locking gap> fire table head diameter> primer shell thickness> primer loading depth> firing pin head diameter. The standard deviation change has little impact on system reliability. This study provides theoretical and technical guidance for the reliability design of firearm firing-ignition systems.

Abstract:To develop a high-performance burning rate catalyst for solid propellant， an iron-loaded carbon nanotube material （Fe@CNTs） was synthesized by high-temperature pyrolysis of the caged precursor. The elemental composition， microscopic morphology， phase structure， specific surface area， and catalytic decomposition performance of Fe@CNTs were investigated by scanning electron microscope-energy dispersive spectrometer （SEM-EDS）， transmission electron microscopy （TEM）， X-ray diffraction （XRD）， X-ray photoelectron spectroscopy （XPS）， Fourier transform infrared spectroscopy （FTIR）， nitrogen sorption isotherm measurement （BET）， differential scanning calorimeter （DSC）， and thermogravimetry-mass spectrometry （TG-MS）. The results show that， Fe@CNTs is an iron-loaded carbon nanotube material with a high specific surface area， which can reduce the exothermic peak temperatures of octogen （HMX）， dihydroxylammonium 5，5′-bistetrazole-1，1′-diolate （TKX-50）， 1，1-diamino-2，2-dinitroethylene （FOX-7）， hexogeon （RDX）， and hexanitrohexaazaisowurtzitane （CL-20） by 1.8 ℃， 40.4 ℃， 4.9 ℃， 6 ℃， and 8.8 ℃， respectively， when the addition amount of this material is 6%. The calculations of thermal decomposition kinetics based on the Kissinger-Ozawa model show that the apparent activation energies of 6%Fe@CNTs/HMX and 6%Fe@CNTs/TKX-50 decrease by 96.9-97.1 kJ·mol^-1 and 11.2-11.9 kJ·mol^-1， respectively. Theoretical calculations of thermodynamic and thermal safety parameters indicate that HMX and TKX-50 are still in a thermodynamically stable state after adding Fe@CNTs. Based on the results of TG-MS， the possible catalytic mechanism of Fe@CNTs on HMX and TKX-50 is further proposed.

Abstract:The solidification process of melt-cast explosive is a significant step during its research and manufacture. solidification， and related charge quality play a key role in the detonation performance and safety of explosives. Based on domestic and foreign research works， the development of solidification techniques of the melt-cast explosive is systematically summarized from three aspects： finite element simulation， solidification process and on-line detection methods. The application of the finite element simulation in flow -temperature-stress field simulation during casting and solidification process of the melt-cast explosive is reviewed. The formation of defects during the solidification process and the effects of different techniques on solidification are elucidated. Furthermore， the application of on-line detection of temperature， stress-strain， viscosity， and internal structure in the high-quality precision forming techniques of melt-cast explosive is discussed. The development of numerical simulation， solidification process optimization and on-line detection technique in melt-cast explosive can provide vital theoretical and technical guidance for the design and development of the solidification equipments and the quality improvement of solidified charges. In the future， the improvement of the charge and solidification technique requires further development and application in aspects such as model construction of equipment-material， safety of process equipment， precise control of process conditions， real-time information monitoring， on-line detection and adaptive regulation.

Abstract:In order to explore the propagation patterns and characteristics of methane vapor cloud combustion waves in tunnels， the CE/SE （space-time conservation element and solution element） method in LS-DYNA software was employed to establish a pre-mixed explosion model of methane and air in the tunnel， which was validated through experimental data. In this paper， typical combustion waveforms of methane vapor cloud with a concentration 9.5% in different test positions were demonstrated by numerical simulation. The propagation and evolution law of overpressure and temperature was analyzed. The injury effects of overpressure and thermal radiation on human in tunnel were investigated. It was revealed that the combustion pressure wave along the tunnel can be divided into four stages： free expansion， reflection dissipation， wall acceleration， and Mach propagation. The pressure variation presented three characteristics： wall impact rise， reflective decay， and stable propagation. The pressure wave presented a sort of periodical reflection propagation mode radially， while the intensity was declining according to the consumption of methane. The temperature field evolved symmetrically from the ignition point to the tunnel entrance and the peak temperature decayed rapidly along the path. The temperature field radiated from the ignition point to the bottom of the tunnel， leading to a gradual convergence of in a certain section and decreased slowly over time. For the injury effects caused by a combination of combustion overpressure and thermal radiation， the fatal distance was 13.51m， the severe injury distance was 13.51~23.51m， the moderate injury distance was 23.51-160 m while the concentration of methane vapor cloud was 5%. For the methane vapor cloud with a concentration 6.5%， those distances were 16.46 m， 16.46~45.36 m and 45.36~160 m respectively. As for a concentration 9.5%， the fetal distance was 20.58m and the severe injury distance was 20.58~160m.

Abstract:Herein， we develop a new method to prepare the ammonium dinitramide/pyrazine-1， 4-dioxide （ADN/PDO） cocrystal， which is highly efficient and environmental-friendly due to utilizing the reaction crystallization with pure water as the solvent， and also comprehensively characterized its performance.. The morphology and structure of the cocrystal were characterized by optical microscopy （OP）， powder X-ray diffraction （PXRD）， and single crystal X-ray diffraction （SXRD）， respectively. In detail， the ADN/PDO cocrystal was prismatic and formed by the combination of ADN and PDO molecules at a molar ratio of 2∶1. Moreover， the ADN/PDO cocrystal belongs to the monoclinic crystal system with a space group of P2₁/c， owning a theoretical density of 1.779 g·cm^-3 at room temperature. Furthermore， through the differential scanning calorimetric （DSC） measurement， it turned out that the melting point of the prepared ADN/PDO cocrystal is 113.3 ℃， which is 21.3 ℃ higher than that of ADN， and the decomposition temperature is slightly higher than that of ADN， demonstrating good thermal stability of the prepared ADN/PDO cocrystal. Then， the hygroscopicity of the prepared cocrystal， measured by the weight increment method， is significantly low at only 2.6%， while that of ADN is at 45%. In addition， calculated by the NASA CEA， the theoretical specific impulse of the cocrystal reaches 277.9 s while that of ADN is 197.5 s， demonstrating the high energy performance of the cocrystal. In conclusion， the reported method based on the reaction crystallization successfully enables the efficient production of a high-energy， low-hygroscopic ADN/PDO cocrystal， thereby facilitating the further assessment of its application performance.

Abstract:The pilot-scale energetic material wastewater is a kind of wastewater which is extremely difficult to degrade， containing high concentrations of various nitrogen-containing compounds， such as ammonia nitrogen （NH₃-N）， nitrite （NO₂^-）， nitrate （NO₃^-）， and other organic pollutants . To realize the efficient and directional removal of these nitrogen-containing compounds， boron-doped diamond （BDD） electrodes were prepared by the hot-filament chemical vapor deposition （HFCVD） method and utilized to degrade the wastewater. The effects of electrolyte composition and concentration， modified electrode type， and electrolysis device structure on the degradation efficiency were investigated. It demonstrated that adding 0.1 M sodium chloride （NaCl） electrolyte to energetic material wastewater could improve the selectivity of NH₃-N direct conversion to nitrogen （N₂）. Using Cu/BDD and Ni/BDD cathodes accelerate the conversion process of high-valent nitrogen to NH₃-N. Under the dual electrolysis cell structure system， employing Cu/BDD and Ni/BDD electrodes as anodes improve the degradation rate of NH₃-N conversion to N₂. Therefore， the approach utilizes metal-modified BDD electrodes as anodes， is expected to be a highly effective method in the rapid and selective degradation of energy material wastewater， especially when using 0.1 M NaCl as electrolyte.

Abstract:As an important thermodynamic parameter of explosives， thermal conductivity significantly affects the ignition response characteristics of explosive charge. In order to quickly and effectively obtain the thermal conductivity of explosives without tests， an axisymmetric heat conduction theoretical model of typical cylindrical charge structure is established， and its steady-state analytical solution is derived. Also， a method for calculating the thermal conductivity of explosives is proposed based on the slow cook-off experimental data. The thermal conductivity of a new type of insensitive explosive， GOL-1（HMX/Al/AP/Binder）， is determined. The numerical simulation results of the ignition response of small-size charge structure under typical cook-off conditions shows that the calculated results of the charge center temperature-time curves at different heating rates are basically consistent with the experimental results， and the deviations of ignition temperature at charge center and ignition time between the calculated and experimental results are 2.27% and 1.12% at most， which indicates the effectiveness of the thermal conductivity of the GOL-1 and the feasibility of the numerical simulation method. The established calculation method reveals the thermal conductivity characteristics and rules based on the temperature-time curves of slow cook-off experiments， which is more suitable for calculating the thermal conductivity of explosives compared with volume-weighted method and string or parallel heat conduction model. In the absence of experimental data for determining the thermal conductivity of new explosives， this method is an effective determination method， providing a basic parameter for the design and evaluation of thermal safety of ammunition and promoting the development of digital design and quantitative evaluation of safe ammunition.

Abstract:Two new explosives， C₈H₂₄N₄（ClO₄）₄ and C₈H₂₄N₄（NO₃）₄?2H₂O， were prepared from 1，4，7，10-tetranitrocyclododecane by salt formation with nitric acid and perchloric acid respectively， which are expected to be used as emergency reserve materials of weapons in emergency wartime. The structures， thermal properties， and detonation performances of the target products were studied through single crystal X-ray diffraction， infrared spectroscopy， elemental analysis， differential thermal analysis， thermogravimetric analysis， and EXPLO 5.0 program. The results indicate that C₈H₂₄N₄（ClO₄）₄ crystallizes in the orthogonal crystal system， Pcc2 space group with a crystal density 1.968 g?cm^-3. The crystal of C₈H₂₄N₄（NO₃）₄?2H₂O is a dihydrate with a crystal density of 1.642 g?cm^-3， which belongs to the monoclinic crystal system P2₁/n space group. The thermal decomposition peak temperatures of C₈H₂₄N₄（NO₃）₄?2H₂O and C₈H₂₄N₄（ClO₄）₄ are 293.2 ℃ and 284.1 ℃， and activation energies are 131.76 kJ·mol^-1 and 195.18 kJ·mol^-1， respectively. Compounds C₈H₂₄N₄（NO₃）₄?2H₂O and C₈H₂₄N₄（ClO₄）₄ exhibit excellent detonation properties， showing very promising performance values （C₈H₂₄N₄（NO₃）₄?2H₂O， V=8058 m?s^-1， P=24.0 GPa； C₈H₂₄N₄（ClO₄）₄， V=8680 m?s^-1， P=36.2 GPa）. Moreover， the impact sensitivities of C₈H₂₄N₄（NO₃）₄?2H₂O and C₈H₂₄N₄（ClO₄）₄ are 36 J and 33 J， respectively， and their friction sensitivities are higher than 360 N.

Abstract:To obtain the ignition and growth model parameters of HNS-Ⅳ based polymer bonded explosive （PBX） under shock initiation， the shock wave loading method from explosive plane wave lens was used. The shock waves were attenuated by attenuators and impacted with tested explosives， and the interface particle velocity profiles between tested explosives and LiF （lithium fluoride） windows were measured by photonic Doppler velocimetry. Several explosive pellets with varying thicknesses could be mounted to the attenuator in one shot， by adjusting the thickness of attenuator to change the input pressure， the growth process of interface particle velocity was obtained. Meanwhile， the unreacted shock adiabatic curve of tested explosive was measured by the reverse-impact method， and the cylinder expansion velocity history was acquired by 10 mm diameter cylinder test. Then， the JWL （Jones-Wilkins-Lee） equation of state （EOS） parameters of unreacted explosives and detonation products were fitted with experimental results by genetic algorithm. Finally， the interface particle velocity histories between explosives with varying thicknesses and LiF windows were fitted with the ignition and growth model. The results show that the fitting correlation coefficients of EOS parameter curves for unreacted explosives and detonation products are high enough， and the obtained ignition and growth model parameters well simulate shock initiation experimental results， which can meet the requirement of initiation train design.

Abstract:The planetary motion of impeller in the vertical mixer can effectively promote the dispersed circulation and homogeneous distribution of different material components, which has been employed in the preparation procedure of solid propellant slurry. However, the mixer involves complex interfaces and motions that it is difficult to study the mixing mechanism and rheological property of slurries by traditional methods. Based on the smoothed particle hydrodynamics (SPH), the continuum was discretized into the conserved particles with physical quantities for simulating the interaction between the propellant slurry and blades under laminar flow. A meshless method for the mixing process of propellant slurries in non?Newtonian fluid state was developed by combining the Herschel?Bulkley (HB) constitutive model. The numerical simulations were compared with the experiments to verify the accuracy of the proposed model. The correlations of the blade motion parameters and power consumption were explored. The effects of geometric configurations and rotation modes on the mixing uniformity of slurries and the torque loads of impellers were analyzed. Research findings indicate that the simulation and literature experiment results have a good agreement that the average relative error between them is around 4.98% in the non?Newtonian fluid with shear rate index n = 0.47. The mixing uniformity index of planetary impellers increased by 8.9% and 7.3% respectively than those of central and eccentric impellers after stirring for 2.65 s. The maximum amplification in torque can reach 38.4% within the revolution radius range of 0.11Dw-0.23Dw at Reynolds number Re = 1.

Abstract:To gain a comprehensive understanding of the properties changes of TNT crystals under strong magnetic field radiation， the morphological changes， the lattice constants and the thermal decomposition characteristic were explored using the scanning electron microscope， X-ray diffraction， Raman spectroscopy and differential scanning calorimeter （DSC）， respectively. Moreover， the variations of lattice constants， molecules distributions， mechanical properties and theoretical impact sensitivity of TNT under magnetic field radiation were investigated by molecular dynamics simulations. The experimental results， with the application of 6 T magnetic field， showed that the microscopic morphology was changed from the scale-needle structure to the irregular block structure， and the exothermic peak temperature of thermal decomposition was increased from 289.6 ℃ to 304.1 ℃. However， the crystal phase structure and lattice constants of the TNT remained unchanged. Furthermore， theoretical investigations indicated that the TNT lattice constant not affected by magnetic field radiation， but the magnetic field did change the molecules distribution in the TNT crystal. The 8 T magnetic field radiation significantly improved the ductility of TNT. However， it simultaneously increased the impact sensitivity of TNT by comparing the ratio for the longest trigger bonds.

Abstract:In order to study the potential mechanism of unexpected ignition of confined charge in the process of penetrating multi-layer target， by integrating the designs of multi-layer nested strikers and bidirectional limited structure， a nonlinear amplification experimental method of confined charges under continuous multiple impacts loading was established. The effectiveness of the experimental method， and the intrinsic mechanism of nonlinear response amplification were analyzed. The influence of nonlinear response of charges under multiple impacts loading on ignition behaviors was studied. The results show that the experimental method can implement multiple impacts loading with sub-millisecond pulse width， and 100 MPa-scale peak stress value. When the characterized frequency of loading is close to the intrinsic frequency of confined charges， structural nonlinear response amplification emerges， and the stress amplitude increases gradually. For the same striker velocity and mass， while varying frequency of loading， the PBX-3 charges could be ignited if structural nonlinear response is amplified and could not be ignited if structural nonlinear response is not amplified. It is found that the structural nonlinear response amplification effect is an important factor leading to charge ignition.

Abstract:To investigate the cook-off response characteristics of JEO explosive （NTO/HMX/additives）， an experimental system for multi-point temperature and pressure measurements during the cook-off process of explosive was devised. The cook-off experiments of JEO explosive were conducted at two different heating rates of 5 ℃·min^-1 and 2 ℃·min^-1 to obtain the ignition time， ignition temperature， temperature history at different positions within the explosive， and pressure evolution inside the device. The effect of heating rates on temperature and pressure variations and reaction intensity during the cook-off process of JEO explosive was analyzed. Furthermore， based on the experimental research， a multiphase flow species transport model for explosive cook-off was adopted considering the influence of pressures on the thermal decomposition reaction of explosive， and numerical simulations were conducted to investigate the thermal decomposition process of JEO explosive under different heating rates using Fluent software. The results indicate that the thermal decomposition reaction of JEO explosive proceeds slowly before phase transition， while it accelerates significantly afterwards， leading to a rapid increase in temperature and an exponential growth in pressure until ignition. The ignition temperature of JEO explosive is approximately 220 ℃， and its response level is deflagration under the constraint conditions of this experiment， demonstrating excellent thermal safety. As the heating rate decreases， the ignition time of JEO explosive prolongs， and the ignition location shifts from the edge of the charge towards the center， resulting in an increased intensity of the reaction. During the thermal decomposition process before ignition， only a small portion of the explosive undergoes reaction， with the majority of the reaction occurring during the combustion stage after ignition.

Abstract:The morphology and structure of energetic materials have significant impact on their various properties. In order to improve the inherent performance of existing energetic materials and meet the different application requirements of weapon， the assembly of energetic materials is an effective technology. Based on the relevant works of domestic and foreign scholars， the current methods of energetic materials assembly and the effects on performances were summarized from two perspectives： the directly affecting the structure of single-component energetic materials through assembly and regulating their performance， and the assembly components and composite structure of multi-component composite energetic materials synergistically regulating the performance. The enlightenment of other functional materials assembly for energetic material was elaborated. Currently， the assembly of single-component energetic materials can achieve new crystal morphology， while multi-component assembly can compensate for the inadequacy of available performance control， and achieve synergistic improvement of energy and safety performance. However， the development of energetic material assembly still faces problems such as monotonous assembly methods， difficult process control， unclear assembly mechanisms， and insufficient research on multi-components. Future research may focus on three perspectives： the improvement of crystal assembly theory for energetic materials， the development of mesoscopic characterization techniques， and the exploration of new assembly technologies.

Abstract:To investigate the combustion characteristics of ternary active metal fuels Al/B/Mg （ABM） and Al/B/MgH₂ （ABM-H）， the heat of combustion and minimum ignition energy were studied by using an oxygen bomb calorimeter and a Hartmann tube， respectively. The sub-transient process of flame propagation and the spatiotemporal distribution characteristics of temperature fields were determined by using a high-speed camera system and a high-speed infrared camera system. The results indicate that the calorific values of ABM and ABM-H are 34.1 and 32.2 MJ·kg^-1， respectively， exhibiting increases of 14.4% and 8.1% over pure Al （29.8 MJ·kg^-1）. The minimum ignition energies of ABM， ABM-H， and Al are 160-170， 100-110， and 20-30 mJ， respectively. Compared to pure Al， the combustion duration of ABM and ABM-H increase by 65.5%， 34.5% and the peak flame propagation velocities increase by 12.6%， 23.0%， respectively， at a mass concentration of 625 g·m^-3. At a mass concentration of 500 g·m^-3， ABM-H and ABM exhibit the largest peak flame propagation velocities by 45.05， 38.7 m·s^-1， and the maximum temperatures peak of flame surface by 1856， 1717 ℃， respectively， where ABM-H shows a 7.6% improvement on temperatures peak of flame surface and a faster heating-rate compared to ABM. It suggests that the ABM and ABM-H formulations significantly reduce the explosion risk of the dust/air mixture， and significantly improving the combustion performance. ABM demonstrates superior thermal effects in calorific value and duration of combustion， whereas ABM-H exhibits higher reactivity in terms of minimum ignition energy， flame propagation speed， and temperature rise rate.

Abstract:In order to improve the energy release characteristics of Al powder in composite explosives， combining the advantages of microstructure design and surface modification of Al particles， hexanitrohexaazaisowurtzitane （CL-20）/Al@Co/nitrated bacterial cellulose （NBC） composite with 3D network structure was prepared. Firstly， Al@Co particles were synthesized by coating Al with Co via the replacement reaction. Then， Al@Co and CL-20 particles were deposited into the 3D network structure of NBC to form CL-20/Al@Co/NBC composite with 3D network structure. The transmission electron microscopy （TEM）， scanning electron microscope （SEM）， X-ray diffraction （XRD）， X-ray photoelectron spectroscopy （XPS） and Fourier transform infrared spectroscopy （FT-IR） were used to characterize the morphology and structure of the composites. The properties were analyzed by thermal analysis， sensitivity test and combustion test. The results show that the Al@Co particles are formed by coating Co on the Al surface with a thickness of about 32 nm. The CL-20/Al@Co/NBC composite has a 3D network structure. Compared with the NBC+CL-20+Al mixture and CL-20/Al/NBC composite， the higher thermal decomposition peak temperature of Al in CL-20/Al@Co/NBC composite is elevated by 123.7 ℃ and 99.5 ℃， and the heat release is increased by 5.93 kJ·g^-1 and 4.50 kJ·g^-1， respectively. Moreover， CL-20/Al@Co/NBC has a shorter ignition delay time， faster combustion rate， lower impact sensitivity （30 J） and friction sensitivity （192 N）.

Abstract:Due to contacts with additives or changes of environmental conditions （temperature or pressure）， the polymorphism hexanitrohexaazaisowurtzitane （CL-20） is easy to transform into mixed crystal form in propellant system， which leads to structural damage and performance degradation of the propellant. In order to hinder the contact between the solvent and CL-20， then inhibit the crystal transformation of CL-20， the polyphenol amine （PCHA） film was prepared based on the oxidative self-polymerization of hexamethylenediamine （HMDA） and catechol （CCh）. The surface of CL-20 crystal was modified by water suspension method under mild conditions. The scanning electron microscopy （SEM）， Fourier transform infrared spectroscopy （FT-IR）， Raman spectroscopy （RAMAN）， X-ray diffraction （XRD） and X-ray photoelectron spectroscopy （XPS） were used to study the morphology， coating content， thermal properties， and stability in ethylene glycol solution for the composite particles. The results show that HMDA and CCh can modify the surface of CL-20 crystal under mild conditions and form a dense PCHA coating layer. The content of PCHA is about 1% measured by dissolution weighing method and high performance liquid chromatography （HPLC）. The PCHA coating layer increases the crystal transition and thermal decomposition temperature by 16 ℃ and 7 ℃， respectively. The thermal decomposition activation energy E_a at different heating rates was calculated by Kissinger method. The activation energy of CL-20@PCHA is about 8 kJ·mol^-1 higher than that of CL-20， and the thermal stability is greatly improved. The XRD test results indicate that the PCHA film can effectively prevent the contact between the solvent and CL-20， slow down the dissolution rate of CL-20 in the solvent， and effectively inhibit the crystal transformation of CL-20.

Abstract:In order to study the effect of high pressure from screw pumping and medium deep hole charging on the microstructure and thermal stability of the on-site mixed emulsion explosive matrix， the microstructure， particle size distribution， crystallization content， thermal decomposition process， thermal decomposition reaction activation energy， thermal decomposition mechanism function and rate equation of the matrix under atmospheric and high pressures were studied by optical microscope， laser particle size analyzer， water solubility experiment， thermogravimetry and derivative thermogravimetry （TG-DTG） couple method， Kissinger method and Ozawa method， Coats-Redfern method and ?atava method. The results show that from atmospheric pressure to high pressure， polymerization， demulsification and crystallization of the intra-matrix phase droplets appeared， the particle size increased from 3.717 μm to 4.474 μm， the precipitation amount of ammonium nitrate crystals increased from 0.0530 g to 0.0640 g， and the uniformity of the emulsion system was weakened. The average thermal decomposition onset temperature of the matrix T_onset increased from 157.4 ℃ to 184.0 ℃， the average first-order derivative thermogravimetric peak temperature T_p increased from 262.6 ℃ to 281.8 ℃， the average mass loss rate increased from 0.1454 %·s^-1 to 0.1476 %·s^-1， and the reaction activation energy decreased from 108.49 kJ·mol^-1 to 84.74 kJ·mol^-1. The free water released by evaporative demulsification under high pressure might cause the rise of T_onset and T_p， and the thermal decomposition reaction was more likely to occur. The activation energy calculated by the Ozawa method had a different trend with the increase of conversion rate， and the thermal decomposition reaction mechanism function changed from Valensi equation to inverse Jinder equation and the rate equation also changed. The high pressure promotes the process of droplet polymerization， demulsification and crystallization of the intra-matrix phase， reduces the activation energy of the thermal decomposition reaction， and weakens the homogeneity and thermal stability of the system.

Abstract:In order to study the influence of explosive crystal particle size on mechanical properties and interfacial enhancement of polymer bonded explosive （PBX）， HMX-based PBXs were prepared by using four kinds of HMX with different particle sizes （160 μm，60 μm，25 μm and 150 nm） as main explosive. The fluorine resin and neutral polymeric bonding agent were used as binder and interface enhancement agent， respectively. The compressive stress-strain test and Brazilian test were performed to obtain the compressive and tensile mechanical properties of 8 types of PBXs at room temperature （20 ℃） and high temperature （60 ℃）， respectively. The storage modulus and mechanical loss factor were obtained using the three-point bending mode of dynamic mechanical analysis. The cross-sections of PBXs were characterized by scanning electron microscopy. Results show that both the compressive and tensile mechanical strength of explosive increase with the decreasing of HMX particle size， in which the nano-HMX based PBX （PBX-nano） shows the highest strength. The compressive strength and tensile strength of PBX-nano are 61.3 MPa and 5.7 MPa， increasing by 73.1% and 63.5% from PBX-L， respectively. By adding the bonding agent， the compressive mechanical strength and tensile mechanical strength for all the PBXs are significantly improved， especially the PBX-nano. The tensile strength of PBX-nano-M at 20 ℃ and 60 ℃ are up to 10.4 MPa and 5.8 MPa， which are 82.6% and 101.4% higher than that of PBX-nano， respectively. When the average particle size of HMX decreases from 100 μm to 100 nm， the greater the fracture energy required for interface debonding/damage and even fracture of explosive， the greater the increase in tensile mechanical strength.

Abstract:Ammonium perchlorate （AP） is an important oxidant in solid propellants， and its thermal decomposition performance directly affects the combustion characteristics of solid propellants. The use of combustion catalysts can lower the decomposition temperature and increase the decomposition rate of AP. Different methods for microstructure control of nano-combustion catalysts for AP thermal decomposition were studied and summarized. The effects of microstructure control methods such as crystal planes， defects， and composite interfaces on the catalytic activity and catalytic mechanism of combustion catalysts for AP thermal decomposition reaction were analyzed. Besides， the characteristics of catalysts that can achieve optimal catalytic performance were explored. The results indicate that the catalytic activity of nanometal oxide combustion catalysts can be improved by adjusting the exposed crystal faces， element doping and constructing a composite interface structure. Among them， transition metal oxide nano-catalysts can enhance catalytic activity by exposing designated crystal planes， and element doping enhances catalytic activity by generating defects， while constructing a composite interface structure utilizes interface effects to regulate the activity of catalytic sites， thereby enhancing catalytic activity. Transition metal oxide nano-catalysts showed good catalytic activity in improving the thermal decomposition performance of AP.

Abstract:In order to solve the problems of low density and effective oxygen content of the existing oxidant NH₄ClO₄ （AP） for mixed explosives， the oxidant KClO₄ （KP） with higher density and oxygen content was compounded with AP， and the optimal ratio of AP/KP composite oxidant was determined by Molecular Dynamics. The novel AP/KP composite oxidant with high density and high oxygen release was prepared by physical mixing and solvent evaporation method， respectively， and its elemental composition， morphology， structure， composition and thermal properties were characterized by inductively coupled plasma spectrum generator （ICP）， scanning electron microscope （SEM）， X-ray powder diffractometer （XRD） and thermal analyzer （DSC-TG）. The results show that element and particle size distribution of the AP/KP composite oxidant prepared by solvent evaporation method is reasonable and uniform. The crystal form has not changed， and the crystal form is relatively complete， as proved by XRD. The thermal decomposition peak temperature of AP and KP was decreased by 11.25 ℃ and 13.87 ℃， respectively， which was more conducive to the thermal decomposition process. In addition， the composite oxidants prepared by physical mixing and solvent evaporation method were introduced into typical metal combustible agent Al powder， the ignition and combustion properties of samples prepared by different methods with Al powder were compared and studied. The results show that when the AP/KP composite oxidant prepared by solvent evaporation was mixed with Al powder， the combustion calorific value reached 12.228 MJ·kg^-1， and the pressurization rate reached 5.21 MPa·s^-1. The laser ignition test shows that the shortcomings of slow AP combustion reaction rate and difficult KP ignition were greatly improved.

Abstract:In order to improve the ignition and combustion performance of boron powder， four kinds of micro- and nano B-Fe-Bi₂O₃@AP/PVDF composite were prepared by high-energy ball milling combined with spray drying method. According to their high calorific value and high combustion efficiency， four composite were named as μBHH_c， μBHC_e， nBHH_c， and nBHC_e. Their morphology， thermal reactivity， ignition delay time， mass burning rate and condensed phase combustion products were characterized and analyzed. The results show that the maximum calorific value of μBHH_c and μBHC_e composite in argon is 9.7 kJ·g^-1， and the maximum combustion efficiency in argon is 66.2 %. The maximum calorific value in oxygen is 14.6 kJ·g^-1， the maximum combustion efficiency is in oxygen 93.3%， and the oxidation peak temperature is between 750 ℃ and 760 ℃. The maximum calorific value of nBHH_c and nBHC_e composite in argon is 9.9 kJ·g^-1， and the maximum combustion efficiency is in argon 68.9%. The maximum calorific value in oxygen is 14.8 kJ·g^-1， the maximum combustion efficiency in oxygen is 97.2%， and the oxidation peak temperature is between 595 ℃ and 600 ℃. The highest combustion temperature of all kinds of composite is between 1954 ℃ and 2011 ℃. The ignition delay time of nBHH_c composite is the shortest （26 ms）， while the mass burning rate is the highest （1.84 g·s^-1）. The μBHC_e composite has the longest ignition delay time （39 ms） and the lowest mass burning rate （0.80 g·s^-1）. The condensed phase combustion products of various composites are mainly composed of B₂O₃， B₄C and a small amount of incompletely burned boron. The morphology of condensed phase combustion products includes 5-10 μm spheres and 10-20 μm flakes.

Abstract:The octahedral cyclotrimethylenetrinitramine crystal （O-RDX） with an average particle size of 9.35 μm was prepared through the solvent-antisolvent method in the dimethylsulfoxide （DMSO） -ethylene glycol （EG） system using 1-ethyl-3-methylethimidazole acetate （EmimOAc） as an additive. The effects of crystallization parameters such as solvent system， solution concentration， crystallization temperature， additive and stirring speed on the growth behavior of RDX（cyclotrimethylenetrinitramine） crystals were systematically studied. It was observed that the main factor influencing the growth of RDX crystals was the supersaturation. With the gradual decrease of supersaturation， RDX crystals experienced the changes of rough growth， 2D growth and spiral growth， and the morphology of RDX crystals gradually evolved from dendritic to octahedral crystals. The results of analytical tests revealed that O-RDX crystals were in the α-form which was consistent with the raw RDX， showing high crystal density with few crystal internal defects and an increase of 5 ℃ in decomposition temperature. Moreover， compared to the raw RDX， the impact sensitivity and the friction sensitivity of O-RDX decreased by 60% and 50%， respectively. To further explore the formation mechanism of O-RDX， adhesion energy model and the molecular dynamics method were applied to simulate the crystal morphology of RDX in the presence of EmimOAc. The simulated results demonstrated that there were six main crystal faces of RDX： （1 1 1）， （2 0 0）， （1 0 2）， （0 2 0）， （2 1 0）， and （0 2 1）. The formation of the double-cone octahedral morphology originated from the uniform growth rates of the main crystal faces of RDX under the action of EmimOAc. The theoretical simulations generally agreed well with the experimental phenomena.