Na₂CO₃ and graphene nanocomposites toward efficient lubrication

Lubrication by graphene from nanoscale to macroscale has attracted increasing interest in recent years. However, the graphene can only withstand load of 2 N (corresponds to Hertzian contact stress of 0.41 GPa) during sliding. In this work, a composite of graphene and sodium carbonate coating shows an improved load-carrying capability during lubricated contacts. Compared to the pure graphene deposited coating, the composite can reduce the friction from 0.6 to 0.16 and wear by one order of magnitude at 1.29 GPa, and can provide an effective lubrication even at the high load of 40 N (corresponds to maximum Hertzian contact stress of 2.06 GPa). The improved lubricating property by the composite of sodium carbonate and graphene results from the stronger adhesion of the composite on the steel surface and the sliding induced soft tribofilm formed at the rubbing interface. Interface observation indicates a high sp fraction of carbon at the top of the tribofilm which contributes to the easy slippery. This study provides a new approach to widen the applications of graphene to lubricated contacts under heavier loads. 2