Identifying the effects of cobalt addition in copper-graphene nanoplatelet composites towards improved tribological performance

Abstract Obtaining good affinity between graphene and copper in copper-graphene composites is the key to make full use of the good anti-wear ability of graphene. Copper-graphene nanoplatelets (Cu-GNPs) composites were prepared by ball-milling and hot pressed sintering with the addition of a small amount of cobalt to form intact graphene/cobalt/copper interfaces. The microstructural characterization shows that the GNPs are uniformly distributed on the grain boundaries of copper grains. The cobalt here acts as “binder”, bringing graphene and copper together efficiently. Benefiting from the unique structural design, Cu-GNPs composite doped with 0.25 wt % cobalt exhibits improved anti-wear performance with a stable friction coefficient of 0.246 and a small volume wear rate of 8.3 × 10−5 mm3/(N·m) (20% of that of pure copper composite). Excessive cobalt causes a significant increase of the structural defects in graphene and the formation of amorphous carbon, resulting in degradation of friction properties.