Quantum dots of graphene oxide as nano-additives trigger macroscale superlubricity with an extremely short running-in period

Abstract

Achievement of macroscale superlubricity with liquid usually requires a long running-in period, which can reach several hours for ceramic materials, leading to severe wear and additional energy loss. In this study, we successfully solve the problem using graphene oxide quantum dots (GOQDs) as nano-additives in ethylene glycol aqueous solution, which can make the coefficient of friction between Si3N4 and sapphire reduce to 0.0068 (superlubricity state) with only a running-in period of 6 s. The running-in period is shortened by 95.7%, and meanwhile, the wear volume is also reduced by 90.0%, comparing to that lubricated by ethylene glycol aqueous solution in the absence of GOQDs. Our study provides direct evidence that the formation of tribofilm consisting of GOQDs is critical for achieving of superlubricity with extremely short running-in period, which can provide boundary lubrication and significantly enhance the load carrying capability of tribofilms. These findings provide insights of the interfacial structural governed superlubrication behaviors, which can aid the development of superlubricity systems with a limited running-in period and reduced wear for industrial applications.