Lubrication Performance of Hydrogenated Graphene on Diamond-Like Carbon Films Based on Molecular Dynamics Simulation

Graphene is a good candidate for solid lubricants due to its unique atomic structure. Its lubrication properties are sensitive to chemical modifications such as hydrogenations. Here, an investigation on the lubrication behavior of hydrogenated graphene on a substrate of diamond-like carbon films is performed via molecular dynamics simulations. Hydrogenated graphene exhibits excellent lubrication behaviors at low or intermediate normal loads, but loses its lubrication effect at high normal loads. In addition, it is demonstrated that the friction force is unaffected by the asperities with small periodicity around the substrate surface. Moreover, the improved lubrication for multilayer hydrogenated graphene is sensitive to its adhesion interactions with substrate, which is different from previously reported cases. This is because the relative movement of concaves changes as the number of graphene layer increases. Although the rigidity of hydrogenated graphene increases induced by chemical modifications, its larger friction force results from the atomic-level roughness. It is believed that these findings can provide a guideline for the superlubricity design based on the chemically modified graphene.