Tribochemistry of ultra-low friction fullerene-like carbon films in humid air.

• FL-C:H films can exhibit macroscale ultra-low friction in humid air. • The ultra-low friction mechanisms of FL-C:H films in humid air is discussed. • The tribochemistry is interpreted by structure, counterparts and environmental molecules. Hydrogenated fullerene-like carbon (FL-C:H) films can exhibit macroscale superlubricity, which is expected to make energy and material losses in the mechanical motion systems very small and can be used in various applications. However, the mechanism under ambient conditions and internal structure characterization for FL-C:H films need to be understood in depth. Here, we have discussed the tribochemistry of ultra-low friction FL-C:H films in humid air with the help of our previous studies. The ultra-low friction mechanism in open air can be interpreted in terms of their internal structure features, interfacial electron density from sliding counterparts, oxidation from environmental molecules, and friction induced in-situ formation of graphitic nanoparticles. [ABSTRACT FROM AUTHOR]