Abstract:To investigate the effect of iron on the ignition and combustion behavior of boron particles in air， B@Fe and B/Fe composite fuels with different iron contents were prepared by chemical in-situ coating method and mechanical mixing method， respectively. The thermal oxidation properties and ignition combustion characteristics of samples in air were studied through thermogravimetry-differential scanning calorimetry （TG-DSC） analysis and laser ignition combustion experiments. The results show that B@Fe composite fuel exhibits better ignition and combustion performance in air atmosphere， compared with boron fuel and B/Fe composite fuel. As the iron content increases from 0% to 9%， the ignition temperature and exothermic peak temperature of B@Fe composite fuel decrease by 234.3 K and 321.6 K， respectively. When the iron content is ≥6%， B@Fe composite fuel also exhibits secondary oxidation behavior in air. Specifically， the total heat release during the thermal oxidation process of B@Fe-9 increases by 48.7% compared to boron powder. B@Fe composite fuel generates a large amount of gas during laser ignition， which promotes the dispersion of combustion products. The flame height rising rate of B@Fe composite fuel with 9% iron content is 4.7 times that of boron， and the ignition delay time is reduced by about 27.5% compared with boron. Comparing the thermal oxidation and ignition combustion processes of B， B@Fe and B/Fe， an ignition and combustion mechanism of B@Fe composite fuel is proposed.

Abstract:To address the issues of incomplete aluminum powder combustion， slow energy release efficiency and prolonged ignition delay， nAl@PVDF@CL-20 composite energetic microspheres were fabricated via electrostatic spray technique. The morphological structure and particle size distribution were optimized by adjusting parameters， including eolvent type， lectric field intensity and sand binder content. Experimental results demonstrated that the uniform microspheres with size distribution of 2.37-2.67 μm and homogeneous component dispersion were achieved using a dimethylformamide/ethyl acetate （DMF/EAC） mixed solvent at the volume ratio of 2∶1， with the PVDF content fixed at 5% and electrode voltage maintained at 14 kV. Concurrently， a crystal phase transition of CL-20 from ɛ-CL-20 to β-CL-20 occurred during atomization and deposition processes due to recrystallization. Furthermore， the adoption of nAl significantly enhanced the energy release efficiency and combustion performance of microspheres. The optimal performance was attained at 40% nAl loading， achieving a maximum equilibrium pressure of 1.17 MPa and a peak pressure rise rate of 6.99×10³ kPa·ms^-1.

Abstract:To study the structure and performance of NC/GAP printed samples， nitrocellulose （NC） and glycidyl azide polymer （GAP） were used as raw materials to prepare NC/GAP printed samples with GAP mass fractions ranging from 0% to 30% via 3D printing. The structure， thermal stability， combustion performance and mechanical properties of NC/GAP composites were characterized by field-emission scanning electron microscopy （FE-SEM）， fourier transform infrared spectroscopy （FT-IR）， differential scanning calorimetry （DSC）， high-speed camera， oxygen bomb calorimeter and universal tensile testing instrument. Results show that the NC/GAP printed samples have regular morphologies， with no obvious interface between the internal layers. With the increasing of GAP content， the thermal stability gradually enhances， the compatibility between NC and GAP gradually deteriorates， the tensile strength gradually decreases， and the combustion rate shows a trend of first increasing and then decreasing. When the mass fraction of GAP is 10%， the maximum combustion rate reaches 25.6 mm·s^-1， which is 46% higher than that of NC. When the mass fraction of GAP increases from 0% to 30%， the heat of combustion in air and argon increase from 2843.2 J·g^-1 to 5260.1 J·g^-1 and 1065.7 J·g^-1 to 1938.7 J·g^-1， increasing by 85% and 82%， respectively.

Abstract:To explore the gel mechanism of hydroxylamine nitrate-based gel propellant， the molecular dynamics （MD） simulations were employed to investigate the microscopic behavior， final crosslinking configuration， and the hydrogen bonding distribution that influences the stability of the hydroxylammonium nitrate/polyacrylamide （PAM）/methanol/water propellant gel system of PAM molecules. Results show that PAM molecules primarily form interaction nodes through intermolecular hydrogen bonding interactions， further promoting the expansion of molecular chains and the construction of a three-dimensional network framework. As the mass fraction of PAM increases from 2.7% to 10.7%， the number of hydrogen bonds formed between PAM molecules increases from 11.98 to 109. Both Van der Waals force interactions and hydrogen bonding jointly drive a self-accelerating crosslinking process of PAM molecules. The radial distribution of hydroxylammonium groups and nitrate ions in hydroxylammonium nitrate shows a bimodal characteristic. The introduction of PAM weakens the intensity of the first peak， as it reduces local interaction and energy density by forming crosslinking "domains"， thereby enhancing the stability of the propellant.

Abstract:To enhance the understanding of safety of multi-chamber mixing processes， a multiphase flow CFD numerical model based on the Eulerian method was established for the continuous mixing of multi-component materials in a multi-chamber kneader， taking a cast polymer bonded explosive （PBX） as the object. Experimental verification was conducted to confirm the reliability of the model. Based on the model， the influence laws of key process and structural parameters including blade rotation speed， kneading clearance and blade profile on the mixing safety stimulus were studied. The results show that the pressure level gradually decreased from the feeding chamber to the discharging chamber. Increasing the blade rotation speed was beneficial for reducing the pressure in the chambers， but the shear stimulus significantly increased. As the blade rotation speed increased from 15 r·min^-1 to 75 r·min^-1， the peak pressure in the kneader decreased from 402966 Pa to 258107 Pa， and the peak shear stress increased from 6268.5 Pa to 16607.9 Pa. Increasing the kneading clearance significantly reduced the pressure and shear stress in the chambers. As the kneading clearance increased from 1 mm to 5 mm， the peak pressure in the kneader decreased from 391094 Pa to 284478 Pa， and the peak shear stress decreases from 8320.5 Pa to 3982.6 Pa. Compared with the two-wing-two-wing blades， four-wing-two-wing blades produced stronger shear stimulus due to more kneading sites， but the blade profile had a smaller impact on the kneading pressure. When the four-wing-two-wing blades and two-wing-two-wing blades were used in chambers 1-7， the peak shear stresses in the kneader were 7481.3 Pa and 4518.1 Pa， respectively.

Abstract:In the process of single screw extrusion molding， the materials are easily affected by process conditions， which leads to self-degradation and heat release， thereby posing potential safety hazards. So quantifying the decomposition heat release of materials during the extrusion process has practical significance. The experimental and simulation methods were combined to investigate the thermal decomposition phenomenon of energetic materials during extrusion process based on the self-developed finite element secondary development subroutine. Combining the thermal decomposition kinetics model of materials， a thermochemical coupling method was proposed to calculate the thermal decomposition degree， temperature rise and the maximum temperature difference between inlet and outlet of energetic materials during extrusion. The influence of process conditions on the thermal decomposition degree of materials was also examined. Additionally， a material thermal decomposition experimental apparatus was built to validate the feasibility of the proposed thermal-chemical coupling method. The results show that under the condition of a screw speed of 10 r·min^-1， compared with ignoring material thermal decomposition， the highest temperature during the screw extrusion process considering the decomposition heat release of materials increased by 0.91 K， and the highest pressure decreased by 8.2%. The decomposition degree of materials is the combined effect of material temperature increase and residence time. Compared to increasing the rotational speed， raising the temperature of barrel presents a greater effect on the thermal decomposition of materials.

Abstract:To enhance the photothermal response of hexanitrostilbene （HNS） under laser initiation， a core-shell composite（HNS@PDI） was prepared by a combining strategy of molecular structure regulation and self-assembly surface deposition method， and the influence of the molecular structure of PDI on its photothermal conversion efficiency and the laser ignition performance of HNS@PDI were systematically studied. The perylene imide （PDI-C12） modified with a dodecyl chain can easily assemble into a J-stacking structure that is conducive to non-radiative exciton transitions. Under 1064 nm laser irradiation， the composite modified with PDI-C12 exhibits a photothermal conversion efficiency of 69.3%， which is 110% higher than that of the short-chain analog PDI-C2（32.9%）. When the PDI loading was optimized to 5%， the laser ignition delay time was reduced to 22 ms at a laser power of 10 W and energy density of 80 W·cm^-2. The PDI shell also significantly improves the safety performance of this composite. The critical impact energy of the composite increases from 5 J to 30 J， and the critical friction force is above 360 N. In addition， the PDI layer effectively inhibits photodecomposition. This study effectively improved the laser ignition performance of HNS， while enhanced the safety and photostability， providing new ideas for the development of high-performance laser ignition agents and photosensitizers.

Abstract:Aiming at the reliability evaluation of the energy transfer interface of pyrotechnic sequence， a reliability evaluation method based on fiducial inference method was proposed. This method fully considered the randomness characteristics of the energy transfer interface data. By constructing the probability distribution model of the performance parameters， the prior knowledge was organically combined with the test data， and the accurate evaluation and randomness quantification of the interface reliability were realized. Firstly， the reliability model of the energy transfer interface of pyrotechnic sequence was established. On this basis， the reliability evaluation algorithm framework based on fiducial inference was designed. In order to verify the effectiveness of the proposed method， the evaluation results of the quantile correction method and the Monte Carlo method were compared and analyzed. The results show that when the sample size is 3 to 70， the deviation between the evaluation results based on the fiducial inference method and the true value is the smallest， demonstrating good convergence and stability. Especially when the sample size is less than or equal to 10， this method shows significant advantages， which effectively overcomes the dependence of traditional methods on sample amount， and provides a new method for the reliability evaluation of the energy transfer interface of pyrotechnic sequences.

Abstract:In order to meet the dual constraint requirements of safety current and anti-electromagnetic radiation power of semiconductor bridge initiating explosive devices， based on GJB 344A-2020'' General specification for insensitive electric initiators''： Non-fire test standard， the electro-magnetic-thermal multi-physical field coupling model was constructed on COMSOL Multiphysics platform by numerical simulation method. By integrating the parallel shunt mechanism of negative temperature coefficient （NTC） thermistor， the loop resistance was monitored in real time and the current input was dynamically compensated. The effects of thermal safety under three working conditions of constant current 1A， constant power 1 W and double constraints 1A1W were compared and analyzed. The results show that the power of 1 A constant current condition is only 0.78 W， which deviates from the standard by 22% because the loop resistance is reduced to 0.78 Ω. The initial current of 1W constant power condition is 0.91 A， which is lower than the safety threshold. The dynamic adjustment strategy realizes the coordinated stability of current and power through closed-loop control. The heat balance temperature of the bridge area is controlled at 449.06 K， and the shunt rate is increased from 29% to 41.26% compared with the 1A constant current condition， and the shunt rate is increased by 0.6% compared with the 1 W constant power condition.

Abstract:The combustion process of energetic materials （EMs） is a complex multi-stage process. By studying their thermal decomposition and combustion reactions， establishing precise combustion reaction kinetics models enables effective prediction of the thermal behavior of EMs， which is of significant importance for their synthesis， production， transportation， storage， and practical application in modern weaponry and equipment. Compared to traditional EMs， third-generation EMs exhibit higher energy density， which imposes more stringent requirements on their thermal stability. This review summarizes recent advances in thermal properties and combustion research of third-generation EMs， including both ionic and covalent types. The current research status on thermal properties and combustion reactions of typical third-generation EMs is expounded from three perspectives： thermal decomposition profiles， decomposition pathways/mechanism， and combustion performance. It identifies the shortcomings of the current research and proposes the research direction of the thermal behavior of the third-generation energetic materials. It is proposed to construct a multi-scale coupled research system： high-precision measurement of combustion parameters via novel experimental apparatus， accurate diagnosis of combustion intermediates， and cross-scale modeling combining quantum chemistry-machine learning-fluid mechanics to achieve full-chain analysis from free-radical mechanisms to macroscopic flame propagation.

Abstract:The explosive spherulites， characterized by their unique micro-nano multi-level structure， multiple grain boundaries， and macroscopic isotropy， present exceptionally advantages in terms of safety， mechanical properties， and energy release， making them a key focus in the morphological control of explosive crystals. This review introduces the concept， connotation， and morphological characteristics of spherulites， and summarizes the preparation methods， characteristics， and performances of the twelve reported explosive spherulites. Preparation techniques include solvent anti-solvent method， cooling method， melting method， membrane emulsification， microchannel technology， and solvent-thermal coupling reaction crystallization， among them the solvent anti-solvent method being the most prevalent. The formation process， morphological traits， and critical preparation factors of different spherulites are analyzed， while the interaction mechanisms among crystal structures， modifiers， and non-crystallographic branches are discussed. It also highlights the changes in safety， combustion performance， and mechanical properties， exploring the underlying reasons for these variations. In response to the current challenges in the development of explosive spherulites， relevant suggestions are proposed from six aspects： formation mechanism， characterization method， scale-up preparation， quality control， structure-activity relationship， and data modeling.