Study on the relationship between the tribological properties and oxidation degree of graphene derivatives in O/W emulsion

Graphene oxide (GO) underwent a single and double-side modification with octadecylamine (ODA) to MGO1 and MGO2 respectively. MGO1 and MGO2 were incorporated into the O/W base emulsion respectively to change the composition of the boundary layer and the oil phase. It was found that the tribological properties of MGO1-emulsion were better than that of MGO2-emulsion. Chemical composition analysis of the worn surfaces suggests that MGO1 nanosheets might adsorb more easily onto the surface and react better with the bearing steel to produce C–N–O–Fe-containing compounds than do MGO2 nanosheets, and that MGO1 nanosheets were more actively involved in the shear process that occurs in the contact area. SEM and nanoindentation indicated that there was a non-uniform softer MGO1-tribofilm on metal substrate.