Macroscale superlubricity of Si-doped diamond-like carbon film enabled by graphene oxide as additives

Carbon-based materials including diamond-like carbon (DLC) and graphene have been demonstrated as extraordinary lubricating materials due to its specific structure and weakness of the interlayer interactions. In this work, the extreme coefficient of friction (COF = 0.002) was achieved on the silicon-doped hydrogenated amorphous carbon (a-C:H:Si) film by lubrication with graphene oxide (GO) nanosheets as additives in ethylene glycol. The tribochemical reactions occurred on the Si3N4 surface and a-C:H:Si film, leading to the formation of the silica colloid layer on both Si3N4 and a-C:H:Si surfaces. In the meantime, the physical adsorption of GO nanosheets on the friction surfaces makes the shear plane transfer from Si3N4/a-C:H:Si interface to GO/GO interface, which results in a further reduction of shear stress. The mechanism and modelling of a-C:H:Si and GO nanosheets synergistic lubrication effect was finally established to reveal the design principle of superlubricity at macroscale.