Abstract

Ultra-low friction of amorphous carbon (a-C) film can be achieved by binding to hydrogen atoms or texturing conformations. However, it remains unclear how selective surface hydrogenation affects the friction behavior of textured a-C film. In particular, the corresponding transformation of interfacial structure and the movement of hydrogen atoms have not yet been reported because of the limitation of in-situ experimental characterization. Here, textured a-C films with selective hydrogenated surfaces were prepared, and the corresponding friction response and the transformation of interfacial structure were investigated systematically using reactive molecular dynamics simulation. Results showed that introducing hydrogen atoms to the selective bump sites of textured a-C surfaces significantly reduced the friction coefficient; however, its efficiency was closely sensitive to the hydrogen content, which was related to the interfacial passivation and the repulsion effect induced by H atoms. Most importantly, the separation of –CH clusters from textured a-C surface during sliding process and their re-bonding with the naked mating a-C surface played a key role in further enhancing the repulsive effect between contacted a-C surfaces, thereby improving the anti-friction behavior, which has not been mentioned in previous studies. These results suggest a new approach to develop the high-efficient a-C friction system for applications.