Atomistic Origin of the Complex Morphological Evolution of Aluminum Nanoparticles during Oxidation: A Chain-like Oxide Nucleation and Growth Mechanism.

Metal nanoparticles usually show different oxidation dynamics from bulk metals, which results in various oxide nanostructures because of their size-related surface effects. In this work, we have found and investigated the chain-like nucleation and growth of oxides on the aluminum nanoparticle (ANP) surface, using molecular dynamics simulations with the reactive force-field (ReaxFF). After nucleation, the chain-like oxide nuclei could stay on the ANP surface and continue growing into an oxide shell, extend outward from the surface to form longer oxide chains, or detach from the ANP to generate independent oxide clusters, which is highly dependent on the oxygen content, temperature, and nanoparticle size. Our results emphasize the complicated interplay between the surface structure of nanoparticles and the environmental conditions in determining the formation of oxides, which provides insights into the atomic-scale oxidation mechanism of metal nanoparticles.