In this study, an Al/Co@RDX composite was meticulously prepared through a combination of planetary high-energy ball-milling and a spray-drying technique. The thermal reactivity of these Al/Co@RDX composites was comprehensively investigated and compared using the TG/DSC technique. It is shown that the initial decomposition temperature of RDX in the DSC curve was decreased by 26.3 °C in the presence of Al/Co, which could be attributed to the nano-sized Co transition metal catalyzing the decomposition reaction of nitrogen oxides in RDX decomposition products. The decomposition peak temperature of RDX and the heat released by the thermal decomposition of RDX in the Al/Co@RDX composite were decreased by 26.3 °C and increased by 74.5 J·g⁻¹, respectively, in comparison with those of pure RDX. The types of major gaseous products released from Al/Co@RDX were found to be identical to those of pure RDX, encompassing N₂O, CH₂O, CO₂ and HCN. However, the concentrations of those gaseous products for Al/Co@RDX were higher than those observed for pure RDX, which may owe to the fact that the Al/Co composite can interact with the –CH₂ and –NO₂ within RDX molecules, which leads to the weakening of the C-N and N-N bonds. In addition, the decomposition of RDX in the Al/Co@RDX composite was observed as a one-step process with an apparent activation energy (E_a) of 115.6 kJ·cm⁻³. The decomposition mechanism of the RDX in the Al/Co@RDX composite was identified to follow the chain scission model (L2), whereas the two-step decomposition physical models observed for pure RDX were found to closely resemble the L2 and autocatalytic models.

This paper investigates the pyrolysis of PODEn (n = 3, 4, 5) using ReaxFF molecular dynamics simulation. A large-scale model, which contains 2000 PODEn molecules, is simulated at 3000 K. The higher frequencies of the initial PODEn decomposition reaction at α or β C-O bond show that the α or β C-O bond in PODEn is not easy to break, which is approximately half the number of the other type of C-O bond dissociation. Furthermore, the bond dissociation energies (BDEs) are calculated using the ReaxFF method. The BDE of α or β C-O bond is higher than that of the other C-O bond, ~3–11 kcal/mol, indicating that BDE is one of the factors causing the different proportions of bonds broken. The evolution of pyrolysis products is also investigated. The results reveal that long-chain pyrolysis products from the initial PODEn decomposition are prone to further reaction, while a large amount of CH3O and CH3 remains in the system. This helps explain the difficulty in α and β C-O bond dissociation reactions. The results of the pyrolysis products are consistent with the result in further chemical kinetic simulation. The C2 species in pyrolysis products is relatively low, especially for C2H4 and C2H3, which is around zero. This supports the ability of PODEn to reduce soot emission.

Laser-induced explosions inside droplets can generate cavitation. This study investigates the transient cavitation process induced by laser-induced shock waves in spherical droplets. Modeling a mixed fluid of water, vapor, and air using a barotropic equation of state. And all phases are compressible. Using an explicit density based solver, 3D (three-dimensional) simulations were conducted for two eccentricity conditions of ε=0.4 and ε=0.6. The results successfully captured the coupling effect between shock waves and two-phase interfaces, as well as the development law of cavitation bubble clouds inside spherical droplets. A prediction of wavefront evolution process was established using ray parameter equations, providing a path diagram for the development of shock/rarefaction waves. Experiments, 3D simulations, and ray parameter equations confirm each other, revealing the core physical mechanism behind the generation of cavitation bubble clouds: the spatial convergence of rarefaction waves within spherical droplets leads to cavitation.