Macro superlubricity of two-dimensional disulphide/amorphous carbon heterogeneous via tribochemistry

Superlubricity is a revolutionary step for tribology, which will endow mechanical systems with energy-saving and long-life servicing. However, it is challenging to realize structural superlubricity and reveal its mechanism under mm-scale on steel. Here, we proposed a new strategy to realize macroscale superlubricity (friction coefficient low to 0.003) by sliding amorphous MoS2 (WS2) against hydrogenated amorphous carbon films. Due to tribo-chemistry induced by friction heating and shear force, the amorphous MoS2 was transformed into two-dimensional crystal MoS2, where the layers were flat without wrinkles. Thus, macroscale (submillimeter range) crystalline/amorphous heterogeneous were formed where friction occurs. Based on the nanoscale analyses and the density functional theory calculations, the superlubricity be attributed to the formation of incommensurate contact between crystalline and hydrogenated amorphous carbon structures accompanied with extremely weak interfacialinteraction are the immediate root of superlubricity.