An experimental and computational study of high speed two-particle impacts of Ag nanoparticles

Abstract

The laser ablation of the microparticle aerosol process utilizes high velocity (∼1000 m/s) impact of nanoparticles to produce thick films. Transmission electron microscopy was used to study the final morphologies of several particle-to-particle impact events in an effort to understand the film's microstructure and morphology that develop following high-speed impact. A range of particle morphologies and defect structures were observed, even under nominally similar impact conditions. In some instances, grain boundaries were observed within the impacted particles, whereas in other cases, the impacted particles were free of grain boundaries (i.e., epitaxial deposition). To understand the reasons for these ranges in grain morphologies, molecular dynamics simulations were conducted using conditions that were similar to typical experimental conditions. The simulations revealed that the final states of the impacted particles are not only sensitive to impact velocity but that particle crystallographic orientations also strongly influence the final states. The implications of these findings on the ability to control film microstructures are discussed.