Microstructure changes of self-mated fullerene-like hydrogenated carbon films from low friction to super-low friction with the increasing normal load

Self-mated fullerene-like hydrogenated carbon films (FL-C:H films) realized the conversion from low friction (similar to 0.012) to super-low friction (similar to 0.006) state due to the increasing normal load. The structure changes in the conversion and the effect of environments (N-2 and humid air) on the structure changes were discussed by the combination of SEM, TEM, Raman and XPS spectra. With the increasing normal load, smaller wear scar area (or contact area) and thicker tribofilm could be observed. At smaller scale (such as nanoscale), not only more perfect graphitic structure can be formed, but newly formed longer graphitic sheets also tended to curve.