Graphene Nanosheets as Lubricant Additives: Effects of Nature and Size on Lubricating Performance

Graphene has been widely investigated as an additive in lubricating oils to enhance their tribological performance. Here, the effects of the nature and size of the graphene nanosheets on the tribological performance were investigated with the hydrogenated hydroxyl-terminated polybutadiene dioctoate (O-HHTPB-O) as a model base oil after alkylation of the graphene oxide (GO) of different sizes with 1-dodecylamine (DA) and reduction. The 1-dodecylamine-modified graphene oxide (DA-GO) showed better dispersibility in the O-HHTPB-O base oil and subsequently better tribological performance than the reduced one (DA-rGO) for both the larger graphene oxide nanosheets (GO_L) and the smaller graphene oxide nanosheets (GO_S). The DA-GO_S exhibited better wear-reduction performance than the DA-GO_L, owing to its smaller size and higher polarity. Although the DA-GO_L could be ground during the friction, the friction and wear in the original period affected the complete period lubricating performance.