Alkyl-functionalized black phosphorus nanosheets triggers macroscale superlubricity on diamond-like carbon film

Abstract

The mechanical components’ friction and wear are the main factors to reduce the lifetime and cause the energy loss of machine. In this work, the alkyl-functionalized black phosphorus (BP) nanosheets were synthetized and used as lubricating additives in poly alpha olefins (PAO), which could trigger macroscale superlubricity on the silicon doped diamond-like carbon (Si-DLC) film deposited on the engineering steel surfaces. The COF of the PAO with the alkyl-functionalized BP additives could reduce down to 0.006, which reduced by more than 90% in comparison to that in the absence of functionalized BP. It shows that the high contact pressure and shear action in the running-in process make PAO and functionalized BP recombine to form a composite tribofilm. This composite tribofilm mainly contained the phosphorus oxides and silicon oxides, providing an extremely low shear strength and thereby resulting in a superlubricity state. These findings provide a novel method to achieve oil-based superlubricity on the engineering steel surfaces through the synergistic lubrication effect between the BP and Si-DLC.