Nano-MoS2 and Graphene Additives in Oil for Tribological Applications

Nano-additives have attracted lots of attentions in recent years due to their special performances. A traditional lubricating additive MoS2 with nano-scale and a novel additive graphene were reviewed in this chapter. The synthesis methods, properties, and tribological applications of these two kinds of nano-additives dispersed in media have been reported. Nano-MoS2 has three main nanostructures including nano-ball particles, nano-sheets, and nano-tubes. The wide accepted lubricating mechanisms for the MoS2 nano-balls, nano-sheets, and nano-tubes are nano-bearing effects, slippery roles, and combined actions of rolling and sliding, respectively. Exfoliation and transfer seem to be the main pattern for MoS2 nano-balls. For graphene, the adsorption and tribo-reaction account for its lubricating properties. A synergistic lubricating effect for using graphene and MoS2 together dispersed in oil was found. Graphene was proved to extend the retention of MoS2 on the surfaces and prevent the oxidation of MoS2. Simultaneously, MoS2 prevented the graphene from being ground into small and defective platelets. Both of them help to form a thicker adsorbed and tribo-film which result in a lower friction and wear. Other properties and applications of nano-MoS2 and graphene are also reviewed. It shows that these two nano-additives have diverse functions and great potential for industrial applications.