Fast reaction of AlNPs promoted by oxide shell

【摘要】：Combustion of Aluminum nanoparticles(AlNPs) has long been investigated experimentally because of its use in various energetic formulations for propellants and explosives. But the limited spatio-temporal resolution in experiments in particular makes it challenging to explore the microstructural evolution of AlNPs oxidation and associated mechanisms. Here we perform large-scale reactive molecular dynamics simulations to study the structural evolution of AlNPs with 2-4 nm thick oxide shell in oxygen environment. We find the temporal hollowing processes of AlNPs for both symmetrical and asymmetrical oxidations, in which the morphological evolution can be understood by discrepant electric field and temperature distributions for different system. In the early time, core Aluminum atoms experience a fast reaction with oxide shell. Environmental oxygen does not react with AlNPs until the surface O/Al ratio decreases to ～1.2. Moreover, based on our simulation results, previous experimental data agree well with the proposed model, which can well describe the relationship between combustion efficiency and oxide shell thickness, reveling that oxide shell promotes other than hinders combustion of AlNPs. The molecular insights obtained here would be significant for understanding the underlying mechanism and further modelling of AlNPs combustion