Facile fabrication of long-chain alkyl functionalized ultrafine reduced graphene oxide nanocomposites for enhanced tribological performance.

Due to their ultrathin 2D laminated structure as well as excellent mechanical and thermal stabilities, ultrafine graphene-based nanoparticles exhibit fascinating advantages as highly-efficient lubricant additives. However, it remains a daunting challenge to achieve good and durable dispersion of these graphene-based nanoparticles in lubricating oils. Herein, we report a facile and efficient integration strategy involving particle size miniaturization, surface grafting with octadecyl alcohol (OA), and partial chemical reduction to prepare a novel long-chain alkyl functionalized ultrafine reduced graphene oxide (RGO--OA) with highly-dispersive capacity and superior tribological performance. The chemical composition and structural characteristics, microstructural morphology, and particle size distribution of RGO--OA were systematically investigated. Combining significantly improved lipophilicity derived from the long-chain alkyl grafting and partial chemical reduction with the small-size effect gave rise to outstanding long-term dispersion stability (as long as one month) of RGO--OA in the finished oil. Moreover, the friction coefficient and wear volume of finished oil with merely 0.005 wt% RGO--OA greatly reduced to 0.065 and 10 316 μm, decreased by 9.7% and 44%, respectively, compared to those of pristine finished oil, demonstrating remarkable friction reduction and anti-wear performances. Consequently, owing to the characteristics of facile fabrication, durable dispersion stability, and superior tribological performance at an extremely low content, this novel nanoadditive shows a promising application potential in the tribology field.