Application of graphene derivatives and their nanocomposites in tribology and lubrication: a review.

Reducing friction and increasing lubrication are the goals that every tribologist pursues. Accordingly, layered graphene materials have attracted great research interest in tribology due to their anti-friction, anti-wear and excellent self-lubricating properties. However, recent studies have found that other forms of graphene derivatives not only perform better in tribological and lubricating applications, but also solve the problem of graphene being prone to agglomeration. Based on a large number of reports, herein, we review the research progress on graphene derivatives and their nanocomposites in tribology and lubrication. In the introduction, the topic of the article is introduced by highlighting the hazards and economic losses caused by frictional wear and the excellent performance of graphene materials in the field of lubrication. Then, by studying the classification of graphene materials, the research status of their applications in tribology and lubrication is introduced. The second chapter introduces the application of graphene derivatives in improving tribological properties. The main types of graphene are graphene oxide (GO), doped graphene (doped elements such as nitrogen, boron, phosphorus, and fluorine), graphene-based films, and graphene-based fibers. The third chapter summarizes the application of graphene-based nanocomposites in improving friction and anti-wear and lubrication properties. According to the different functional modifiers, they can be divided into three categories: graphene-inorganic nanocomposites (sulfides, metal oxides, nitrides, metal nanoparticles, and carbon-containing inorganic nanoparticles), graphene-organic nanocomposites (alkylation, amine functionalization, ionic liquids, and surface modifiers), and graphene-polymer nanocomposites (carbon chain polymers and heterochain polymers). Graphene not only exhibits an excellent performance in traditional processing and lubrication applications, but the fourth chapter proves that it has a good application prospect in the field of ultra-low friction and superlubricity. In the application part of the fifth chapter, the lubrication mechanism proposed by graphene as a nano-lubricant is introduced first; then, the main application research status is summarized, including micro-tribology applications, bio-tribology applications, and liquid lubrication additive applications. The last part is based on the following contents. Firstly, the advantages of graphene-based nanocomposites as lubricants and their current shortcomings are summarized. The challenges and prospects of the commercial applications of graphene-based nanocomposites in tribology and lubrication are further described.