Abstract:Carotenoids， valued for their exceptional free radical scavenging properties and low biological toxicity， were systematically investigated as potential stabilizers for propellants. A comprehensive evaluation strategy， incorporating differential thermal analysis （DTA）， methyl violet test strips， isothermal thermogravimetry， vacuum stability testing， and accelerating rate calorimetry （ARC）， was employed to assess their stabilizing effects. Four representative carotenoids-lycopene， β-carotene， xanthophyll， and astaxanthin， were examined for their stabilization performance in nitrocellulose （NC） and absorptive composition systems. All tested carotenoids demonstrated superior thermal stability compared to conventional stabilizers. Notably， astaxanthin exhibited the most significant enhancement： it prolonged the methyl violet discoloration time of NC by 40 min， reducing mass loss by 17.90%， decreased the maximum adiabatic decomposition temperature rise rate by 0.134 ℃·min^-1， and lowered gas pressure release per unit mass by 12.0 kPa. In absorptive compositions， it extended the methyl violet discoloration time by 34 min while reducing mass loss by 14.18%. Free radical scavenging tests and intermediate structural analyses revealed the underlying stabilization mechanism： carotenoids effectively suppress autocatalytic decomposition via nitrogen-oxygen free radical capture， achieving nearly 90% scavenging efficiency at 8 mmol·L^-1. Additionally， secondary derivatives formed during carotenoid degradation were free of nitrosamine groups， significantly reducing toxicological concerns.

Abstract:The pressure of underwater near-field explosion is high and damping rapidly， which is difficult to test accurately. To investigate the near-field explosion shock wave loading and driving characteristics of aluminized explosives， a model was established to calculate the incident shock wave pressure according to the theory of strong shock wave driving air-backed metal plate . Firstly， the free-field shock wave pressure at 2 R₀-6 R₀ （charge radius） distance of spherical TNT charges and driving law of 3 mm-thick air-backed steel plate were calculated by numerical simulation. Then the shock wave pressure before cavitation was calculated based on the velocity –time history data. Finally， tests of underwater explosion driving 3 mm-thick air-backed steel plate at 5 R₀were conducted on TNT and five different aluminized explosives， which verified the accuracy of the shock wave pressure calculation model. Results also show that for every 5% increase in the content of 2 μm aluminum， the acceleration time of plates increases by 4.4%. With larger particle size of aluminum powder， the acceleration time of plate is longer， but the maximum velocity is smaller. 20 μm and 2 μm aluminum powder absorbs energy in the detonation reaction zone， resulting in a decrease in the detonation velocity and pressure of TNT. While 200 nm aluminum powder may partially participate in the detonation reaction zone and release energy， which positively supports the propagation of detonation waves.

Abstract:The fast-running method based on engineering experience is an important tool to assess the explosion damage inside the building structure. To provide the reference for the selection and subsequent improvement of relevant calculation methods， the full-scale confined explosion tests on three-story masonry-concrete building were carried out under two scenarios. The five fast-running methods developed in recent years （i.e. FIST method， charge weight-standoff graphs method， equivalent dynamic load method， energy method， equivalent method） were used to calculate the damage of the buildings. The evaluation indicator and scoring criteria of 5-dimensional calculation ability were put forward. The characteristics of each fast-running method were compared and analyzed. The reasons for the difference in the ability of each method are discussed. Some suggestions for improvement are given. The results show that the charge weight-standoff graphs method is not suitable for the damage assessment of building structure subjected to confined explosions. The FIST method and equivalent method have high accuracy in calculating the masonry wall. The energy method has high accuracy in calculating the RC slabs， but the computational efficiency is low. The calculation efficiency of equivalent dynamic load method is high， but the calculation accuracy is low. In addition， considering the propagation law of the shock wave in complex building structure， improving the scale of numerical simulation are the main way to improve the computing ability of FIST-like and equivalent-like method.

Abstract:The core-shell structure can effectively suppress the formation of large aluminum （Al） agglomerates in Al-matrix composites， enhance the energy release efficiency of Al powder， and improve its ignition performance and combustion energy release characteristics. Based on the characteristics of core-shell structured Al-matrix composites， an overview of the research progress was summarized. The commonly used preparation methods for core-shell structured Al-matrix composites was discussed， effects of different compositions on the combustion performance， energy release efficiency and stability of these composites were analyzed. Furthermore， the potential applications and future development directions of core-shell structured Al-matrix composites were outlined. Optimizing the preparation techniques for core-shell structures to achieve large-scale production， regulating the composition of the coating materials or constructing functional interlayers at the matrix-coating interface can effectively improve the mass and heat transfer characteristics during the combustion process of Al-matrix composites.

Abstract:To investigate the creep mechanical properties of tri-component hydroxyl-terminated polybutadiene （HTPB） composite solid propellant under different temperatures and stress levels， creep mechanical performance tests were conducted using a self-developed mechanical creep testing equipment， a temperature-humidity environmental chamber， and a high-definition camera. Tests were performed at environmental temperatures of 10 ℃， 25 ℃， 40 ℃ and 55 ℃， covering a stress range of 0.072 to 0.712 MPa . The strain-creep time curves were obtained， along with the variation patterns of typical mechanical property parameters with environmental temperature and stress level. A master curve for the creep rupture time， reflecting the propellant’s failure behavior under broad loading conditions， was established. The results indicate that， as the stress level increases， the characteristics of the propellant’s strain-creep time curve shift from three stages to four stages. Increasing environmental temperature reduces the critical stress level at which the four-stage curve characteristic exhibits， and this stress follows an exponential decay pattern， decreasing from 0.562 MPa at 10 ℃ to 0.262 MPa at 55 ℃ with a reduction ratio of 53.38%. The initial creep compliance increases with rising environmental temperature but remains almost unchanged with increasing stress level. When both environmental temperature and stress level increase， the creep rate increases， creep rupture time shortens， cumulative damage degree increases， and cumulative damage rate accelerates. In contrast， the fracture strain is primarily sensitive to changes in stress level and exhibits a linear increasing trend with increasing stress level. The creep rate under 55 ℃ and 0.412 MPa is approximately 493 times that under the same stress level at 10 ℃， and the creep rupture time is about 2.14% of that under the same stress level at 25 ℃. Finally， based on the double logarithmic test data of creep rupture time versus stress level under different environmental temperatures， and using the environmental temperature-stress level equivalence relationship， a master curve for propellant’s creep rupture time was established. At the same time， exponential mathematical expressions for this master curve and the temperature shift factor were obtained. Calculations using these expressions indicate that， to ensure a vertically stored SRM grain does not experience creep rupture failure within 15 years at 25 ℃， the loading stress level should be lower than 0.2176 MPa.

Abstract:Improving the structural integrity of charge is of great significance for ensuring the working stability of solid rocket motor （SRM）. Multi-angle tensile loading tests were carried out on the HTPB propellant bonded specimens. During the tensile process， binocular cameras combined with three-dimensional digital image correlation （DIC） methods were used to analyze the deformation field of the bonded specimens. According to the mesoscopic structure of the specimen， a mesoscopic cohesive zone model （CZM） was established and further subjected to numerical simulation analysis， based on three types of damage modes including particle dewetting， matrix fracture and debonding of the bonding interface. The damage evolution law， cracking mechanism and failure mode of the specimen under different tensile and shear stress states were explored. The test results show that the bonded specimen are more prone to damage under the tensile-shear mixed stress state. At the same time， the bearing capacity of the specimen decreases and a greater tensile displacement will occur with increasing the tensile angle. The area where the strain of the bonded specimen is relatively large at the critical state is the location where macroscopic cracks initiate. The numerical simulation results show that the first principal stress is the main factor affecting the generation of cracks in solid propellants， and when the value of the first principal stress is greater than 0.548 MPa， it will lead to the initiation of cracks. Furthermore， the smaller the stretching angle is， the easier the deweeting between the particle and matrix in the propellant is to occur. However， it is easier for the propellant/liner interface to de-bond and the crack propagation location is closer to this interface when the stretching angle increases.

Abstract:As an emerging high-energy substance， the development of perovskite energetic materials in both variety and quantity has more urgency. The first perchlorate-based double perovskite energetic material ｛（C₆H₁₄N₂）₂［Na（NH₄）（ClO₄）₆］｝_n （DPE-1） and a single perovskite energetic material ［（C₄H₁₂N₂）K（ClO₄）₃］_n （PAP-2） were synthesized by a solution-based method. The chemical structure， thermal stability， detonation performance， and mechanical sensitivity of both DPE-1 and PAP-2 were systematically investigated. Single-crystal X-ray diffraction analysis shows that DPE-1 crystallizes in a double perovskite structure with space group Pa-3， while PAP-2 crystallizes in a single perovskite structure with space group Pnma. Compared with the previously reported periodate-based double perovskite energetic material DPPE-1， DPE-1 exhibits significant improvements in the thermal decomposition temperature （T_dec=368.9 ℃）， detonation velocity （D=8858 m·s^-1）， detonation pressure （p=38.4 GPa）， impact sensitivity （IS >40 J）， and friction sensitivity （FS=20 N）. These results validate the feasibility of exploring high-performance， green primary explosives within the double perovskite structural framework. PAP-2 demonstrates comparable thermal stability （T_dec>280 ℃） and detonation performance （D >8500 m·s^-1， p >30 GPa） with other single perovskite energetic materials in the same series， but its impact sensitivity is significantly increased and friction sensitivity is significantly reduced.

Abstract:Ultrafine hexanitrostilbene （HNS） is widely used in explosion foil initiators and related applications due to its outstanding thermal stability and excellent high-voltage short-pulse performance. However， its high surface energy during service process leads to solid-phase ripening. Previous studies have explored the effects of temperature， residual solvents， and time on the solid phase ripening of ultrafine HNS， but these investigations primarily focused on isolated or narrowly factors. Currently， no multivariate predictive model has been established. In this study， a predictive model was developed based on previously obtained small angle X-ray scattering （SAXS） data， including specific surface area （SSA） and relative specific surface area （RSSA）， obtained under varying temperatures and residual dimethylformamide （DMF） contents. The model was constructed using machine learning algorithms and optimized empirical models. It comprehensively accounts for time， temperature， and residual DMF content in its predictions. The results show that on the training dataset， the random forest （RF） model achieved an R² of 0.9989 in predictions， while the polynomial regression （PR） model and optimized empirical model attained R² values of 0.9091 and 0.9129， respectively. By comparing the prediction performance of these three models， the most suitable model for predicting the solid phase ripening process of ultrafine HNS was identified. Furthermore， purity tests and scanning electron microscopy （SEM） characterization revealed that particle characteristic variations exert significantly influence on the extent of solid-phase ripening in ultrafine HNS. A predictive method was established for the solid-phase ripening process of ultrafine HNS， laying a foundation for investigating its aging mechanisms and optimizing storage stability.

Abstract:Technological and industrial transformations driven by data science and artificial intelligence are profoundly impacting the field of materials science， presenting both unprecedented opportunities and significant challenges for the innovation of energetic materials. As an emerging technology， machine learning offers novel research paradigm for the molecular design and synthesis of energetic materials. It is expected to solve the long-standing bottlenecks such as low efficiency， high cost， and lengthy development cycles. Although some successful cases have been reported， the application of machine learning across the full research cycle of energetic molecules—design， screening， synthesis， and performance validation—remains in a relatively immature stage compared with the application in other advanced materials domains. This review outlines the current research status of machine learning-assisted development of energetic materials， summarizes its applications in molecular design， single-property prediction， and multi-property simultaneous prediction. Nonetheless， the use of machine learning in design and synthesis of energetic materials with targeted properties remains fraught with challenges. Future efforts should prioritize the control of data quality and the construction of standardization frameworks， the development of interpretable machine learning models， and the establishment of interdisciplinary integration platforms， further promoting the efficient creation of high-performance energetic materials.

Abstract:A testing device for measuring the curing shrinkage rate of solid propellants was developed in this study. In addition， the online monitoring test of curing shrinkage of HTPB/IPDI propellant was carried out. The relationship between curing shrinkage and time during the curing process of solid propellant was obtained. By constructing the relationship between curing shrinkage， curing degree and curing kinetics， the curing degree change law and curing kinetics model of solid propellant during curing process were obtained. The results show that the curing shrinkage of solid propellants changes in a three-stage S-type. The maximum curing shrinkage is about 0.108%， and the maximum curing reaction rate is 7.809×10^-6. During the isothermal curing process， the curing reaction rate curve of HTPB/IPDI propellant shows a bell-shaped curve， so the thermal curing of solid propellant has autocatalytic characteristics. The pre-exponential factor A₀ of the self-catalytic kinetics model for HTPB/IPDI propellant is 379.0871 s^-1. The reaction orders m and n are 0.711 and 1.501. The results provide a new method to test the shrinkage of propellant and clarify the curing reaction characteristics of composite solid propellants.