Nanotribological Properties of Oxidized Diamond/Silica Interfaces: Insights into the Atomistic Mechanisms of Wear and Friction by Ab Initio Molecular Dynamics Simulations

Controlling friction and wear at silica–diamond
interfaces
is crucial for their relevant applications in tribology such as micro-electromechanical
systems and atomic force microscopes. However, the tribological performance
on diamond surfaces is highly affected by the working environment
where atmospheric gases are present. In this work, we investigate
the effects of adsorbed oxygen on the friction and wear of diamond
surfaces sliding against silica by massive ab initio molecular dynamics
simulations. Different surface orientations, O-coverages, and tribological
conditions are considered. The results suggest that diamond surfaces
with full oxygen passivation are very effective in preventing surface
adhesion, and as a result present extremely low friction and wear.
At low oxygen coverage, Si–O–C bond formation was observed
as well as atomistic wear initiated from C–C bond breaking
at extreme pressure. The analysis of electronic structures of the
configurations resulting from key tribochemical reactions clarifies
the mechanisms of friction reduction and atomistic wear. Overall,
our accurate in silico experiments shed light on the influence of
adsorbed oxygen on the tribological properties and wear mechanisms
of diamond against silica.