Ignition and Oxidation of Core–Shell Al/Al₂O₃ Nanoparticles in an Oxygen Atmosphere: Insights from Molecular Dynamics Simulation

Abstract

This study employed the reactive force field molecular dynamics to capture atomic-level heat and mass transfer and reaction processes of an aluminum nanoparticle (ANP) oxidizing in a high temperature and pressure oxygen atmosphere, revealing detailed mechanisms for oxidation of ANPs. Temporal variations of temperature, density, mean square displacement, atom consumption rate and heat release rate of ANP have been systematically examined. In addition, the effects of environment on ANP oxidation were also evaluated. The results show that ANP undergoes four stages of preheating, melting, fast Al core and moderate shell oxidations during the whole oxidation process. The Al core starts to melt from core-shell interface with outward diffusion of core Al atoms into the shell. Intense reaction occurs between shell O and core Al atoms around interface at the end of melting, leading to fast Al core oxidation. After complete oxidation of Al core, the oxide shell continues to react with ambient O atoms. Both the initial environmental temperature and the equivalent pressure significantly influence the preheating. Oppositely, the melting stage seems almost independent any of them. While the fast Al core oxidation presents more sensitivity to the ambient equivalent pressure.

Effect of Oxide Shell on Aluminium Nanoparticle Oxidation Using Molecular Dynamics Simulation

“…In sANP, O atoms in the environment continue to diffuse into the core, and the shell does not break. This result is in line with the finding of Zhang et al [18]. Whereas, in nsANP, after the shell has been formed, it maintains its position.…”

“…In this simulation, a canonical ensemble with the Nose/Hoover thermostat method is used [15]. OVITO [18] is used as a post-processing software and visualization tool for simulation results. Figure 1 presents the ANP simulation model.…”

Molecular dynamics simulations of the mechanical behavior of alumina coated aluminum nanowires under tension and compression

“…6 Zhang et al 7 investigated the chain-like nucleation and growth of oxides on aluminum nanoparticle surfaces which was shown to be highly dependent on the oxygen content, temperature, and nanoparticle size. Recently, core-shell Al/Al 2 O 3 nanoparticles in an oxygen atmosphere under high temperature were studied by Chu et al 8 revealing four stages of preheating, melting, fast Al core, and moderate shell oxidations during the oxidation process. The thermal stability of aluminum oxide nanoparticles was recently investigated showing that partial oxidation reduces the nanoparticle melting temperature.…”

Crack Mechanism of Al@Al2O3 Nanoparticles in Hot Energetic Materials

“…The morphology of ANP in a vacuum is basically unchanged at 300 K, while at 3000 K, the atomic migration occurs between a core and shell (Figure 4d), in agreement with the atomic migration observed under O-free conditions, which was thought to be induced by the electric field-induced effect. 18,31,32 Next, we focus on the morphologic changes of the oxides under various conditions. As illustrated in Figure 5, the O atoms of the oxide shell in different models diffuse and migrate inward to various degrees when heated for 20 ps.…”