A molecular dynamics study of the effects of velocity and diameter on the impact behavior of zinc oxide nanoparticles

Molecular dynamics simulations of particle impact have been conducted for a ceramic with mixed ionic-covalent bonding. For these simulations, individual zinc oxide (ZnO) nanoparticles (NPs) were impacted onto a ZnO substrate to observe the effects of impact velocity (1500-3500 m s-1) and particle diameter (10, 20, and 30 nm) on particle deformation and film formation mechanisms that arise during the micro-cold spray process for producing films. The study shows that a critical impact velocity range exists, generally between 1500 and 3000 m s-1, for sticking of the NP to the substrate. Results suggest that solid-state amorphization-induced viscous flow is the primary deformation mechanism present during impact. Decreasing particle diameter and increasing impact velocity results in an increased degree of amorphization and higher local temperatures within the particle. The impact behavior of mixed ionic-covalent bonded ZnO is compared to the behavior of previously studied ionic and covalent materials.