Atomistic insights into graphene/fullerene nanoparticles coupled surface topography features in solid–liquid composite lubrication

Graphene and fullerene nanoparticles exhibit remarkable tribological performance in solid-liquid composite lubrication systems. However, the atomic-scale understanding of how surface topography influences their tribological behavior and performance is still limited. Herein, the influence mechanisms of surface topography features (achieved by regulating asperity amplitude and frequency parameters) on system lubrication performance and nanoparticle friction behavior were systematically investigated through friction experiments and molecular simulations. The results indicate that, at the micro-nanoscale, the amplitude parameter predominantly governs the surface roughness features and frictional resistance. This is because an increased amplitude strengthens the boundary lubrication effect, exacerbates stress concentration and structural deformation of graphene, and makes fullerene more likely to fill grooves and difficult to bear normal loads, thereby exacerbating friction and wear (friction coefficient increased by 59%). In contrast, the frequency parameter primarily determines the surface kurtosis features and normal force. At low frequency, low kurtosis features intensify the normal squeezing effect of asperities, inducing the hydrodynamic pressure effect of the base oil, thus enhancing lubrication performance (friction coefficient decreased by 22%). Compared with frequency, the pronounced influence of amplitude on lubrication state and interface contact behavior dominates the tribological properties of the system and the lubrication mechanism of the nanoparticles. Lower surface roughness and kurtosis features are critical for achieving efficient lubrication. This study offers valuable insights into the design of surface topography and the optimization of lubrication performance.