Understanding Wear at the Diamond-Silica Interface - The role of environment and interfacial chemistry

Abstract

Diamond is renowned for its exceptional hardness and wear resistance, yet measurable material loss can occur under nanoscale sliding contact. In this work, the wear of microcrystalline diamond (MCD) sliding against silicon oxide is investigated using an atomic force microscopy (AFM)-based tribological platform. Experiments are performed in a non-repeated sliding configuration, enabling the evolution of friction and wear to be studied while minimizing the influence of prior surface modification.

Diamond wear is quantified through topographical analysis of the wear footprints generated on the silicon oxide counter-surface, allowing nanoscale material removal to be tracked with high sensitivity. A strong environmental dependence is observed, with wear being highest in vacuum and progressively reduced in ambient air and hydrogen-rich atmospheres. Friction exhibits a similar trend during the initial stages of sliding.

The results are consistent with a tribochemical wear mechanism governed by surface passivation. In the absence of passivating species, stress-assisted interfacial bond formation promotes atom-by-atom removal of carbon from the diamond surface. Conversely, hydrogen-, oxygen-, and water-containing species suppress wear by passivating reactive surface sites and reducing interfacial bonding. These findings demonstrate the critical role of environmental chemistry in controlling diamond wear and highlight surface passivation as an effective strategy for improving the durability of diamond-based tribological systems.