High-temperature behavior of aluminum core–shell nanoparticles with metal or nonmetal coatings: a molecular dynamics study

Abstract

The effects of carbon (C), magnesium (Mg), and aluminum oxide (Al₂O₃) coatings on the thermal stability, oxidation, and ignition behavior of aluminum core–shell nanoparticles were investigated using reactive molecular dynamics (ReaxFF-MD) simulations. Models consisting of a 6 nm Al core and a 1 nm coating were subjected to three types of simulations: thermal stability from 300 to 1300 K, isothermal oxidation at 800 K, and temperature-programmed ignition from 300 to 2700 K. Analyses included lattice structure, bond evolution, atomic diffusion, potential energy, and morphological changes. Among the three coatings, Al₂O₃ exhibited the best thermal and oxidation stability, acting as a dense inert barrier. Carbon coatings provided strong protection due to their high inertness and the formation of interfacial Al–C bonds. However, during isothermal oxidation at 800 K, the carbon shell shrank, inducing lattice distortion in the Al core and reducing its face-centered cubic (FCC) fraction. In contrast, Mg coatings failed rapidly at moderate to high temperatures because of their low melting and ignition points and high reactivity. Ignition simulations further revealed that Mg coatings lowered the ignition temperature and accelerated combustion, while Al₂O₃ delayed ignition. Carbon coatings produced the longest ignition delay and the mildest combustion. Collectively, these results establish an atomic‑scale structure–performance relationship for coated aluminum nanoparticles, providing guidance for designing core–shell fuels in high-performance propellants.