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 AlH3 composite. Perfect AlH3 and surface-passivated AlH3 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 AlH3 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-AlH3 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/AlH3 is much larger than those of the
HMX system. Surface-passivated AlH3 particles only affect the initial decomposition rate of
HMX. In
HMX and AlH3 composites, the strong attraction of Al in AlH3 to O and the activation of the intermediate reaction by H2 cause
HMX to decompose rapidly. The final decomposition products of pure
HMX are H2O, N2, and CO2, and those of
HMX/AlH3 are H2O, N2, and Al-containing clusters dominated by C-Al. The final gas production shows that the specific impulse of
HMX/AlH3 is larger than that of
HMX.