M. Choi, J. Jang, A.V. Sumant, J. Kim, Y. Jang, S. Kim
Pusan National University,
Korea
Keywords: graphene oxide, superlubricity, solid lubricants, macroscale friction
Summary:
Solid lubricants are crucial alternatives to liquid lubricants in extreme environments and can also enhance mechanical system performance under ambient conditions at the macroscale. Among them, graphene—a representative two-dimensional nanomaterial—has garnered significant attention due to its exceptional nanoscale tribological properties. Nevertheless, implementing graphene as a solid lubricant in macroscale industrial systems remains challenging. Recent studies suggest that functionalizing graphene, particularly through oxidation, markedly improves its lubricating performance, emphasizing the strong correlation between the tribological behavior of graphene-based materials and their elemental or compositional characteristics. In this study, we demonstrate the versatility of graphene oxide (GO) as a solid lubricant by systematically tailoring its structural and compositional properties. Under ambient conditions, a heterogeneous structure comprising graphene oxide layered on pristine graphene (PG), GO-on-PG, significantly improved the durability more than 100 times compared to that of PG. Under humidity- and oxygen-free conditions, bare GO exhibited an ultralow COF. Notably, in inert gas environments (e.g., argon and nitrogen), graphene oxide achieved superlubricity (COF < 0.01). By elucidating the intrinsic lubrication mechanisms of GO across varied environments, we highlight its potential to serve as a robust solid lubricant in diverse engineering applications. Notably, this work provides the first demonstration of macroscale superlubricity using GO as a single material, underscoring its exceptional promise in bridging fundamental research with industrial relevance.