Features of ceramic nanoparticle deformation in aerosol deposition explored by molecular dynamics simulation

Abstract

The deformation and bonding of particles in Aerosol Deposition (AD) is a topic of growing technological interest for solid-state coating and additive manufacturing with ceramic materials. The core feature of the AD process is the unexpected plasticity of ceramics at high strain rates and small length scales, which is also a topic of general interest for understanding the response of intrinsically brittle materials to dynamic deformation. We explore this feature through computational analysis of the impact of ceramic particles – modelled based on a Lennard-Jones description of submicron TiO2-anatase particles in a two-dimensional molecular-dynamics system – onto a substrate at a range of impact velocities (100–800 m/s). The deformation behaviour of the particle for each impact velocity was analysed with respect to the evolution of the stress, strain, and temperature fields. The results reveal indications of dislocation-based plasticity within a certain velocity regime. This velocity regime, which becomes narrower with increasing the particle size, coincides incidentally with bonding of particles to the substrate in AD. The results also show that outside this regime, the impact is associated predominantly with either rebounding (at lower velocities) or particle fracture (at higher velocities). The simulation results are interpreted in view of a phenomenological model of fragmentation, considering the interplay between the material properties, such as the fracture energy, and the kinetic energy of particles upon impact. Based on the simulations and the analytical model, a window of deposition is proposed for AD.