Unraveling the friction response from selective hydrogenation of textured amorphous carbon surface

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 molec-ular 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.