Atomic perspectives revealing the evolution behavior of aluminum nanoparticles in energetic materials

Abstract Aluminum nanoparticles (ANP) are important components of modern energetic systems because of their excellent combustion performance. However, the underlying mechanism of ANP in energetic materials during ignition is unclear. Based on the ReaxFF-lg method, the oxidation mechanism of ANP in pentaerythritol tetranitrate (PETN) was analyzed from an atomic perspective, and the evolution of ANP from single and multi-particle models during ignition were studied. Adding ANP increases the heat release and accelerates the decomposition of PETN. ANP inhibits CO2 emissions and increases H2O yields. Both particle size and passivated layer influence the oxidation mechanisms due to different surface effects. The oxidation mechanism of smaller ANP is dominated by Al atom diffusion, but the larger ANP involves O inward diffusion and Al outward diffusion at both solid and melting states. An important behavior of chained C/Al clusters accumulation was observed during the later combustion, which agrees with the earlier experiments. The lattice diffusion aggregation of ANP and the aggregations of O/Al and C/Al cluster were revealed during the reaction. The calculated temperature distribution revealed that the hot spots in aluminized PETN originate from the oxidation heat release of ANP. This work provides an atomic perspective demonstration on the diffusion oxidation mechanism of ANP in energetic materials.