The influence of tribochemical activity of silica abrasives on the atomic removal of sapphire

The tribochemical mechanism of active abrasives on sapphire was investigated by comparing the scratching behavior of Si and SiO₂ probes through atomic force microscopy (AFM) and ReaxFF molecular dynamics (MD). Experiments revealed that the SiO₂ probe, due to its higher chemical activity, was more sensitive to changes in load and sliding cycles. It exhibited significantly greater increases in wear depth and volume compared to the Si probe. Simulations demonstrated that more Si-O-Al bonds appeared on the contact region of SiO₂ and sapphire, enhancing tribochemical reactions and mechanical force transfer. This revealed the atomic-removal pathway: hydration layer softening, solid-phase chemical reaction, and mechanical stripping. This study provides important insights serving as a valuable guidance to deeply understand the chemical mechanical polishing of sapphire by silica abrasives.