Chemically Functionalized Reduced Graphene Oxide as a Novel Material for Reduction of Friction and Wear

Graphene, a lamellar structured material, easily shears at the contact interfaces and exhibits excellent mechanical strength and conductivity, which promises its potential for tribological applications. However, the dispersion of graphene in lube media is a big challenge. Herein, we developed a chemical approach for selective inclusion of long alkyl chains on the edges and defects sites of reduced graphene oxide sheets through the amide linkage, which facilitates their stable dispersion in the lube oil. Chemical and structural features of site-selective chemically functionalized reduced graphene oxide are monitored by FTIR, XPS, XRD, TG-DTA, FESEM, and HRTEM. Tribological test results showed that the chemically functionalized reduced graphene oxide, as an additive to 10W-40 engine oil, significantly reduced both the friction and the wear of steel balls. The stable dispersion of chemically functionalized reduced graphene oxide provides low resistance in a sheared contact owing to weak van der Waals interaction between their lamellas, thus significantly reducing both the friction and the wear.