Sintering Rate and Mechanism of TiO₂ Nanoparticles by Molecular Dynamics

Titania is the dominant white pigment and photocatalytic material, a key component of sunscreens and has promising applications in photovoltaics and sensors of organic vapors. The growth of TiO₂ nanoparticles by sintering, the critical step during their large scale manufacture and processing, is elucidated and quantified by molecular dynamics. Highly mobile ions from the particle surface fill in the initially concave space between nanoparticles (surface diffusion) forming the final, fully-coalesced, spherical-like particle with minimal displacement of inner Ti and O ions (grain boundary diffusion) revealing also the significance and sequence of these two sintering mechanisms of TiO₂. A sintering rate for TiO₂ nanoparticles is extracted that is much faster than that in the literature but nicely converges to it for increasing particle size.