Enhancing the reaction efficiency and ignition performance of core-shell Al@HMX composites by precise catalysis of graphene-based carbohydrazide complexes

The incomplete combustion of aluminum in solid propellants leads to a low-level energy release. As a promising strategy, fuel/oxidizer interfacial control is proved to be effective for enhancing their reaction efficiency and less environmental dependence. In this paper, in order to investigate the effect of interfacial control on the reaction efficiency of Al and HMX, spherical Al@HMX composites with polydopamine as interfacial layer were prepared via spray-drying technique. The morphology, structure, heat of reaction, thermal stability, condensed/gaseous products, decomposition kinetics as well as the ignition performance of the composites under the catalytic effects of graphene-based carbohydrazide complexes (GO-CHZ-M, M = Co²⁺ or Ni²⁺) were comprehensively investigated. Results showed that the heat of reaction of Al@HMX increased by 220 J g⁻¹ compared to corresponding physical mixture (5655 J g⁻¹), which was further increased to 6210 J g⁻¹ in presence of minor GO-CHZ-Co (1 wt%) as a catalyst. Moreover, the thermal decomposition temperature of HMX was slightly increased in Al@HMX composites. Under the synergy of interfacial control and GO-based catalysts, the enhanced reaction efficiency of Al with HMX was observed and verified by a shorter ignition delay time (reduced from 126 to 71 ms) and the condensed products analysis, with decreasing unreacted Al content and increasing content of submicron-sized particles. Gaseous products investigation illustrated that there were two main decomposition pathways for Al@HMX composites: the C[sbnd]N scission (dominant) and N[sbnd]N scission, where the latter could be enhanced by GO-CHZ-M catalysts.