Thermal Decomposition Mechanism of 1,3,5,7-Tetranitro-1,3,5,7-tetrazocane Accelerated by Nano-Aluminum Hydride (AlH₃): ReaxFF-Lg Molecular Dynamics Simulation

Abstract

ReaxFF-low-gradient reactive force field with CHONAl parameters is used to simulate thermal decomposition of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) and AlH 3 composite. Perfect AlH 3 and surface-passivated AlH 3 particles were constructed to mix with HMX. The simulation results indicate HMX is adsorbed on the surface of particles to form O–Al and N–Al bonds. The decomposition of HMX and AlH 3 composite is an exothermic reaction without energy barrier, but the decomposition of pure HMX needs to overcome the energy barrier of 133.57 kcal/mol. Active nano-AlH 3 causes HMX to decompose rapidly at low temperature, and the primary decomposition pathway is the rupture of N–O and C–N bonds. Adiabatic simulation shows that the energy release and temperature increase of HMX/AlH 3 is much larger than those of the HMX system. Surface-passivated AlH 3 particles only affect the initial decomposition rate of HMX. In HMX and AlH 3 composites, the strong attraction of Al in AlH 3 to O and the activation of the intermediate reaction by H 2 cause HMX to decompose rapidly. The final decomposition products of pure HMX are H 2 O, N 2 , and CO 2 , and those of HMX/AlH 3 are H 2 O, N 2 , and Al-containing clusters dominated by C–Al. The final gas production shows that the specific impulse of HMX/AlH 3 is larger than that of HMX.

Recent ReaxFF MD studies on pyrolysis and combustion mechanisms of aviation/aerospace fuels and energetic additives

“…Meanwhile, it is found that the initial reaction path of HMX nanocrystals at low temperature is the breaking of the C-H bond, and the product at low temperature is the same as that at high temperature. Zhao et al 98 studied the pyrolysis process of nano-AlH 3 and HMX composites. The results show that HMX adsorbs on the particle surface by forming Al-O and Al-N bonds.…”

Coupling Effect of Non-Ignition Impact and Heat on the Decay of FOX-7

“…Relatively few studies on decay details of FOX-7, concerning the coupling effect of heat stimulation and low-velocity impact, have been published yet. ReaxFF molecular dynamics simulations (RMD) have been shown to reveal the decomposition mechanism of energetic materials [ 27 , 28 , 29 ]. Herein, the RMD is employed to investigate the effect of heat coupled with compression in different directions on the decomposition reaction network, the final products, and the reaction kinetic parameters of the FOX-7 decomposition.…”