Macroscale Superlubricity on Engineering Steel in the Presence of Black Phosphorus

Friction and wear are the main reasons for decreasing the lifetime of moving mechanical components and causing energy loss. It is desirable to achieve macroscale superlubricity on industrial materials for minimizing friction. Herein, the two-dimensional material black phosphorus (BP) is prepared as an oil-based nanoadditive in oleic acid (OA) and shown to produce macroscale superlubricity at the steel/steel contact under high pressure. Experiments and molecular dynamics simulation reveal that BP quickly captures the carboxylic group and, as a result of the high contact pressure and heat, OA decomposes to release passivating species and recombines to form amorphous carbon giving rise to a composite solid tribofilm with BP. The OA and passivating groups adsorb onto the solid tribofilm to produce the passivating layer, thus resulting in macroscale superlubricity. The findings provide fundamental insight into the nature of tribochemical mechanisms and suggest a new approach to achieve macroscale superlubricity of industrial materials.