Atomic-scale interfacial instability of hydrogenated amorphous carbon film at elevated temperature

Tribochemical reactions can modify the surface structure and chemical properties of amorphous carbon films during sliding, thereby altering their tribological behavior. Understanding the effects of temperature on the reaction process is important for the widespread application of amorphous carbon films, particularly at elevated temperatures. Upon sliding at temperatures higher than 373 K, the a-C:H film with 40 at.% H demonstrated atomic interfacial instability, disrupting the interfacial ordered structures with increased friction and wear. Reactive molecular dynamics (MD) simulations further revealed that the interfacial material transfer of hydro-carbon clusters in the a-C:H film with 40 at.% H at elevated temperatures was triggered by mechanochemical exfoliation of graphitic rings, leading to significant wear of the interfacial structures. When the hydrogen content decreased to 10 at.% H, more carbon chains were mechanochemically fragmented between the sliding surfaces to trap the interfacial atoms, resulting in stabilized, ordered structures and a low friction state.