To clarify how particle size distribution affects temperature rise and mechanical behavior during the compaction of PBX-3 molding powder, a three-dimensional multi-particle finite element model (MPFEM) was developed under different particle size distribution conditions. The model was used to simulate the densification, particle deformation, contact evolution, and temperature variation of the particle system during uniaxial compaction. The effects of plastic deformation and interparticle friction on energy dissipation and temperature rise were also considered. The results show that the temperature evolution during compaction exhibits distinct stage-dependent characteristics, with a pronounced increase associated with enhanced plastic and frictional dissipation. Particle size distribution significantly affects particle rearrangement, deformation behavior, contact conditions, and the resulting temperature rise. An increase in the friction coefficient further enhances frictional dissipation and consequently promotes temperature increase. Under the particle size ranges and compaction conditions considered in this study, the most pronounced temperature rise occurs for particles within the 0.06-0.14 mm size range. This behavior is mainly attributed to the regulation of particle contact structures and plastic deformation by particle size distribution, which in turn governs energy dissipation and thermal evolution during compaction. These findings provide a numerical basis for understanding and controlling thermal effects during PBX powder compaction.
Conventional solid combustion catalysts improve the combustion performance of composite solid propellants (CSPs) but degrade mechanical properties due to increased solid content and poor interfacial bonding. To resolve this, we propose a copper-based multivalent synergistic catalysis strategy. Ammonium perchlorate (AP) was embedded into carboxymethyl chitosan copper (CMC-Cu) organic framework via droplet-solution contact assembly, yielding a multifunctional AP/CMC-Cu composite. During thermal decomposition, CMC-Cu generates in-situ Cu/CuO/Cu2O multivalent active species that act as catalytic intermediates, accelerating electron transfer from ClO4- and reducing AP's high-temperature decomposition peak to 318.4 degrees C with a 39.4% decrease in activation energy. Meanwhile, abundant -NH2 and -OH groups in CMC-Cu covalently cross-link with toluene diisocyanate (TDI) in the binder, greatly enhancing AP-binder interfacial adhesion. Propellants with CMC-Cu show a 41-ms shorter ignition delay, 36.8% higher burning rate, tensile strength of 0.54 MPa, and adhesion index reduced to 1.24, effectively suppressing dewetting. This work offers new insights into multivalent copper catalyst design and provides a low-cost route to AP-based propellants with simultaneously improved combustion efficiency and mechanical performance.
To improve the ignition and combustion performance of aluminum, this study prepared Al-Mg-Li ternary alloys using the centrifugal atomization method, and based on this, prepared-Mg-Li/RDX composites with different mass ratios. The combustion behavior of the Al-Mg-Li/RDX composites was systematically studied, monitoring their combustion state, combustion, pressure, and pressure rise rate. Results demonstrated that lithium incorporation effectively disrupts the dense oxide layer on aluminum particles, significantly enhancing combustion reactivity. The addition of RDX accelerated more vigorous oxidation reactions in the Al-Mg-Li alloy, leading to more complete combustion of the powder. As RDX content increased, combustion duration shortened progressively while peak pressure and pressure rise rates continued to rise. Especially under the condition of 30% RDX content, the heat of combustion, peak pressure, and pressure rise rate of the Al-Mg-Li/RDX sample all superior to those of the Al/RDX and Al-Mg/RDX samples with the same ratio, exhibiting more concentrated exothermic characteristics and a shorter combustion duration. Furthermore, comprehensive characterization using SEM, EDS, XRD, and XPS techniques was conducted to elucidate the combustion mechanism of the Al-Mg-Li/RDX system. This research provides both theoretical foundations and experimental evidence for developing next-generation high-performance aluminum-based alloy fuels.
This study used a novel fluorine-containing melt casting carrier explosive, DFDNTN (5-fluoro-3-methyl-2,4-dinitrophenylamine), and a typical melt casting carrier explosive, TNAZ, to form a low eutectic. When TNAZ:DFDNTN = 6:4, a low eutectic with a melting point of 88 degrees C can be formed; it also has a high decomposition temperature. This eutectic has good compatibility with high-energy explosives RDX and HMX. The difference in the values of the high temperature of the low-eutectic material with RDX and HMX is less than 2 degrees C and its constant-temperature experimental weight loss rate at 100 degrees C for 360 min can be significantly improved compared with that of single component TNAZ. At 100 degrees C for 360 min, the weight loss rate of DFDNTN is 15%, and the weight loss rate of TNAZ reaches 93%, almost completely losing weight. For TNAZ:DFDNTN = 6:4, the weight loss rate is 53 %. Its safety indexes are FS >= 324 and IS>20, and the theoretically calculated detonation velocity is v D = 8196 m s(-1). Crystal cross-section tests demonstrate that, compared with conventional TNT carrier explosive, the eutectic features a denser packing structure and more uniform grain size, which is beneficial to the compactness and mechanical properties of explosives; its higher viscosity relative to TNT may account for its superior molding performance.
Increasing environmental regulations are driving the development of green solid propellants with reduced toxicity and lower life-cycle environmental impact. The binder plays a critical role in solid propellants, with hydroxyl-terminated polybutadiene (HTPB) being the most widely used despite its petroleum origin, environmental concerns, and restricted availability. This study evaluates castor oil (CO), a renewable, biodegradable, and low-toxicity resource, as a sustainable alternative binder. A CO-based polyurethane prepolymer containing 30% (w/w) toluene diisocyanate was synthesized and characterized by Fourier transform infrared spectroscopy (FT-IR), rheology, particle distribution, hardness tests, and scanning electron microscopy (SEM). The results showed 20% faster curing and hardness comparable to HTPB, highlighting the potential of CO as a viable and sustainable binder for solid propellant applications. Additionally, SEM analysis comparing the top and bottom regions of two CO-based samples produced by different synthesis using ammonium perchlorate (AP) as filler demonstrated a more homogeneous AP distribution in the sample #2 (a prepolymer it was first synthesized by reacting CO with 30% of the TDI needed for complete curing).
