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Abstract:

Abstract:Hydroxylammonium nitrate （HAN） aqueous solution is strongly acidic and highly oxidative. To address these characteristics， three sorbitol acetal-based low-molecular-weight gelators （D₁， D₂， D₃） were designed and synthesized， and the rapid gelation of HAN aqueous solution was successfully achieved. The gelation ability of the three gelators， as well as the rheological and thermodynamic properties of the HAN gel propellants， were systematically investigated. The results showed that all three gelators were structurally stable in acidic media and cooperatively constructed a three-dimensional network through non-covalent interactions， including hydrogen bonding， π-π stacking and halogen bonding. With only 1.0% gelator， 70% HAN aqueous solution could be gelled within 90-120 s. Rheological tests indicated that all three HAN gel propellants exhibited pronounced shear-thinning behavior， and their viscosities at high shear rate approached that of pure HAN solution， with a viscosity of 95.9 mPa·s at 1000 s^-1. The thixotropic recovery rate reached as high as 87.5%， and the critical strain was 23.7%， demonstrating excellent mechanical stability. Thermodynamic analysis showed that the gel-sol transition temperatures ranged from 55-75 ℃. After storage at -25 ℃ for 30 min， no crystal precipitation or liquid exudation was observed， indicating suitable phase-transition reversibility and low-temperature stability. The gelators reduced the freezing point of HAN aqueous solution to below -25 ℃ and promoted the exothermic decomposition of HAN. The peak decomposition temperature decreased by 26.4 ℃， and the decomposition enthalpy increased to 526.3 J‧g^-1. This study provides new low-molecular-weight gelator materials for the gelation of high-energy liquid propellants with strong acidity and oxidizing properties.

Abstract:To address the rapid heat dissipation， difficulty in sustaining combustion， and unstable energy release of energetic films under the strong cooling effect of water， Ti/poly（vinylidene fluoride） （Ti/PVDF） composite energetic films with different Ti contents were prepared by solution blending followed by freeze-drying. Their structural characteristics， wettability， thermal behavior， and ignition/combustion performance in air and underwater environments were systematically investigated. The results show that Ti particles were effectively incorporated into the PVDF matrix， while the characteristic crystalline structure of metallic Ti and the fluoropolymer structure of PVDF were retained， providing the structural basis for exothermic reactions between Ti and fluorinated decomposition products. Compared with air， the rapid heat transfer and strong cooling effect of water markedly increased the ignition difficulty and strongly influenced combustion propagation and energy release. At low Ti contents， the heat generated by the system was insufficient to compensate for heat loss to the surrounding water， making effective ignition difficult. As the Ti content increased， the apparent heat release increased and the underwater ignition and sustained reaction capability were enhanced. Meanwhile， the continuous film-forming and encapsulation effects of PVDF weakened， resulting in reduced hydrophobicity and more pronounced water contact and cooling of the reaction zone. Under the combined influence of enhanced heat release and intensified water cooling， the film containing 50 wt.% Ti exhibited better combustion sustainability， whereas the 60 and 70 wt.% Ti films reacted more rapidly and generated pronounced bubbles and surface disturbances. Overall， the 50 wt.% Ti film is more suitable for applications requiring sustained and stable combustion， while the 60 wt.% Ti film is more favorable for rapid and concentrated energy release.

Abstract:To comprehensively evaluate the thermal safety of energetic plasticizer/binder composite systems， a multiscale thermal analysis strategy was applied to N-butyl-N-（2-nitroxyethyl）nitramine （BuNENA）， poly（3，3-bis（azidomethyl）oxetane-co-tetrahydrofuran） （PBT）， and a BuNENA/PBT composite system with a mass ratio of 1∶1. Differential scanning calorimetry （DSC）， non-isothermal kinetic analysis， slow cook-off tests， 5 s explosion point tests， and self-accelerating decomposition temperature （T_SADT） calculations based on the Semenov model were used to investigate their thermal decomposition behavior and thermal safety characteristics. The DSC results showed that BuNENA mainly underwent exothermic decomposition at 180-240 ℃， whereas PBT decomposed in a higher temperature range of 220-300 ℃. The BuNENA/PBT composite exhibited two exothermic peaks， and the first exothermic peak shifted to a higher temperature with a reduced low-temperature exothermic intensity， indicating that PBT could suppress the concentrated heat release of BuNENA at relatively low temperatures. Kinetic analysis further showed that the apparent activation energy of the first decomposition stage of BuNENA/PBT increased compared with that of pure BuNENA， suggesting an enhanced thermal decomposition barrier. In the slow cook-off test， the initial reaction temperature increased from 151.6 ℃ for BuNENA to 162.5 ℃ for BuNENA/PBT. The 5 s explosion point increased from 261.5 ℃ to 290.2 ℃. For a 25 kg package， the no-return temperature （T_NR） and SADT of BuNENA/PBT were 134.7 ℃ and 128.1 ℃， respectively， which were higher than those of BuNENA. These results indicate that compounding BuNENA with PBT can reduce low-temperature concentrated exothermicity and improve the thermal safety margin of BuNENA-based energetic composite systems under slow heating， transient thermal stimulation， and storage-related thermal conditions.

Abstract:Accurate characterization of the internal residual stress field in polymer-bonded explosives （PBX） is crucial for evaluating structural integrity and service safety. However， traditional inversion methods struggle to reconstruct this distribution efficiently and with high precision. A novel residual stress inversion method integrating distributed optical fiber sensing with physics-informed neural networks （PINNs） was proposed. TATB-based PBX cylindrical specimens measuring ϕ110×120 mm served as the research objects. Strain release data during the layer-removal test were acquired in real time using optical frequency-domain reflectometry （OFDR） technology. A PINNs inversion model was constructed using Gaussian temperature-field parameters as intermediate variables. Physical constraints， including static equilibrium equations and boundary conditions， were embedded into the loss function. This approach achieved an efficient mapping from limited surface strain data to the internal stress field. Results indicate that the model achieves a coefficient of determination of 0.954. The inverted results strictly satisfy fundamental solid mechanics constraints. Compared with traditional finite element optimization-based inversion methods， the PINNs model requires only about 5 min for a single inference after offline training. The reconstructed internal stress field exhibits a typical “tension inside， compression outside” distribution pattern. The maximum tensile stress reaches 1.03 MPa at the core， while the maximum compressive stress reaches -0.77 MPa at the middle of the lateral surface. This distribution pattern aligns perfectly with the physical mechanism of residual stress generation caused by non-uniform shrinkage during the cooling process of thermal pressing.

Abstract:ReaxFF molecular dynamics simulations were performed to clarify the reactivity and thermal safety risks of metallic aluminum during the disposal of failed propellants using high-pressure water jets. A nano-aluminum/water impact model was constructed. Water molecules were assigned impact velocities of 150-400 m·s^-1 to represent different water-jet loading intensities. The temperature response， energy evolution， cluster morphology， radial distribution function， coordination number， bond formation， and reaction product generation were analyzed. The results show that impact velocity plays a dominant role in triggering the Al-water reaction. As the impact velocity increases， the peak temperature of the system increases from 2563 K significantly. The rapid temperature rise indicates efficient conversion of impact kinetic energy into internal energy and interfacial reaction heat. Structural analysis shows that the Al─Al metallic bonding network undergoes local rupture and rearrangement under impact loading. The peak value of the radial distribution function and the average coordination number decrease sharply at approximately 5 ps. This change indicates a rapid transition of the aluminum cluster from an initially dense packing state to a highly dispersed state. The dispersed structure exposes more reactive aluminum sites and increases the Al-water interfacial contact area. Chemical analysis shows that water adsorption and dissociation are accelerated after structural dispersion. Al─O and Al─H intermediates form during the early reaction stage， accompanied by the generation of H₂ and H₃O⁺. Large-scale simulations further show that sufficient water supply strengthens the coupling among impact loading， structural dispersion， and chemical heat release. These findings provide atomic-scale dynamic support for optimizing water-jet disposal processes for decommissioned aluminum-containing solid propellants and for predicting on-site thermal safety risks.

Abstract:To accurately predict the blast parameters of various typical explosives under low-temperature and low-pressure conditions， a comprehensive dataset was established by integrating dimensional analysis with numerical simulations using the AUTODYN software. Based on the dataset， a machine learning model employing the random forest regression algorithm was developed for blast parameter prediction， and its performance was systematically evaluated. The importance of characteristic variables was further quantified using the Shapley Additive Explanations. Results indicate that the proposed model requires only relevant properties of the explosives and air as inputs to accurately predict the blast parameters—including peak overpressure， impulse， arrival time， and duration—across a wide range of conditions， encompassing normal temperature and pressure， low-temperature， low-pressure， and high-altitude environments. The model achieves an average relative error of less than 15%， indicating strong predictive accuracy and generalization capability. Notably， the model eliminates the need for TNT equivalent conversion， and avoids discrepancies associated with different TNT equivalency models. Sensitivity analysis identifies dimensionless distance as the most influential parameter governing blast behavior. Under high-altitude conditions， reduced atmospheric pressure leads to decreased peak overpressure and impulse， earlier arrival times， and prolonged durations. In contrast， lower ambient temperatures result in increased impulse， as well as extended arrival times and durations， while exerting a negligible effect on peak overpressure.

Abstract:To rapidly calibrate the Lee-Tarver three-term ignition and growth model parameters for DNAN-based explosives， a barrier test simulation model was established with HMX as the donor explosive and DNAN/RDX-based aluminized explosive as the receptor charge. The influence of model parameters on the shock initiation response of the explosive was investigated. Based on the response characteristics at the critical barrier thickness for detonation， the 15 parameters of the ignition and growth model were classified into coefficient parameters， exponent parameters， and threshold parameters. Quantitative relationships between each parameter and the explosive reaction rate were obtained through classified adjustment， and parameter sensitivity analysis was completed. The results indicate that the critical barrier thickness for complete detonation of DNAN-based explosives is 7.5-8.0 mm， and the critical barrier thickness for low-velocity detonation is 25.0-25.5 mm. Parameters I， G₁， G₂， F_igmax， and F_GRmax exhibit a positive correlation with the explosive reaction rate， while parameters y， e， g， z， a， and F_GRmin exhibit a negative correlation with the explosive reaction rate. Parameters G₁， y， a， and F_GRmax are identified as the key sensitive parameters affecting the reaction degree. The findings provide a basis for parameter adjustment in the rapid calibration of the Lee-Tarver three-term ignition and growth model.

Abstract:Melt-cast carrier explosives are fundamental low-melting-point constituents for melt-cast explosive formulations， and their properties are critical to the engineering practicability of melt-cast explosives. To address the inherent drawbacks of the traditional melt-cast carrier explosive 2，4，6-trinitrotoluene （TNT）， energetic eutectic mixtures have emerged as a popular research focus， benefiting from their tunable thermochemical properties， energy and safety performances. Methods for constructing T-X and H-X phase diagrams of energetic eutectic mixtures are elaborated， alongside approaches to determine their compositions， melting points and phase distribution rules. Additionally， the state-of-the-art studies on energetic eutectic mixtures based on 1，3，3-trinitroazetidine （TNAZ）， 3，4-dinitrofurzanfuroxan （DNTF）， 1-methyl-3，4，5-trinitropyrazole （MTNP） are discussed. On the basis of current research situation， the development potential and core research directions of energetic eutectic mixtures are proposed. This work intends to facilitate the design and formula optimization of novel low-sensitivity， high-energy melt-cast explosives.

Abstract:As an efficient process analytical technology， near-infrared spectroscopy （NIRS） holds significant application value in the field of energetic materials. To meet the demands of component analysis and process monitoring for energetic materials in complex production environments， this review systematically summarizes the research progress of NIRS in this field over the past five years， with a particular focus on its applications in determining the component contents of gun propellants， solid propellants， and explosives. It further reviews the effectiveness of this technology in predicting key performance parameters， assessing stability， and monitoring manufacturing processes. In response to the key challenges encountered in practical applications， this review discusses future development directions from the perspectives of analytical method innovation， multi-technology integration， and the construction of standardized spectral libraries， aiming to provide valuable references for the continued in-depth research and engineering application of this technology.