Influence of Al and Al2O3 Nanoparticles on the Thermal Decay of 1,3,5-Trinitro-1,3,5-triazinane (RDX): Reactive Molecular Dynamics Simulations

WZ Hao and LL Niu and RJ Gou and CY Zhang, JOURNAL OF PHYSICAL CHEMISTRY C, 123, 14067-14080 (2019).

DOI: 10.1021/acs.jpcc.9b03575

Metallic additives, Al nanoparticles in particular, have extensively been used in energetic materials (EMs), of which thermal decomposition is one of the most basic properties. Nevertheless, the underlying mechanism for the highly active Al nanoparticles and their oxidized counterparts, the Al2O3 nanoparticles, influencing the thermal decay of aluminized EMs has not fully been understood. Herein, we explore the influence of Al and Al2O3 nanoparticles on the thermal decomposition of 1,3,5-trinitro-1,3,5-triazinane (RDX), one of the most common EMs, based on large-scale reactive force field molecular dynamics simulations within three heating schemes (constant-temperature, programmed, and adiabatic heating). The presence of Al nanoparticles significantly reduces the induction time and energy required to activate the RDX decay and greatly increases energy release. The fundamental reason for these results is that Al changes the primary decay pathway from the unimolecular N-NO2 scission of RDX to bimolecular barrier-free or low- barrier Al-involved reactions and possesses a strong O-extraction capability and a moderate one to react with C/H/N. It is also responsible for the growth of the AI-containing clusters. In addition, Al2O3 nanoparticles can also demonstrate such catalysis capability but contribute less to the enhancement of energy release. Moreover, the detailed evolutions of key thermodynamic properties, intermediate and final gaseous products, and Al-containing products are also presented. Besides, under the programmed heating and adiabatic heating conditions, the catalysis of the Al and Al2O3 nanoparticles becomes more distinct. Therefore, many properties of aluminized EMs are expected to well be understood by our simulation results.

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