| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2016) | |
| Thin Films | Wednesday Sessions |
| Session TF-WeP |
| Session: | Thin Films Posters Session II |
| Presenter: | Miho Nakamura, Tohoku University, Japan |
| Authors: | M. Nakamura, Tohoku University, Japan S. Sato, Tohoku University Y. Ootani, Tohoku University, Japan Y. Higuchi, Tohoku University, Japan N. Ozawa, Tohoku University, Japan K. Adachi, Tohoku University, Japan M. Kubo, Tohoku University, Japan |
| Correspondent: | Click to Email |
Recently, carbon nitride (CNx) has gained much attention as solid lubricant in automotive engines, aerospace instruments, etc. Experimentally, one of the authors, Adachi, discovered that CNx gives super-low friction coefficient. However, the super-low friction mechanism of CNx has not been clarified experimentally. It is experimentally pointed out that CNx shows lower friction coefficient than diamond-like carbon under specific condition. It means that the role of nitrogen in CNx is very important. However, the function of nitrogen in CNx has not been elucidated. Therefore, the theoretical approach is desired to reveal the role of nitrogen in CNx. In the present study, we employed our original tribochemical reaction simulator based on the tight-binding quantum chemical molecular dynamics method [1-3]. The friction dynamics of H-terminated CNx is simulated under 1 GPa pressure. The simulation result shows low friction coefficient of 0.05. We found that hydrogen-hydrogen repulsion is source of the super-low friction. However, this reason is same with that of H-terminated diamond like carbon films. It means that the role of nitrogen has not been clarified. Then, we investigate the effect of water molecules on the friction dynamic of H-terminated CNx. It is very interesting to see the generation and evaporation of NH3 molecules by the tribochemical reaction of CNx and water. The generation and evaporation of NH3 molecules give low density diamond-like carbon thin films. Therefore, we propose that low density diamond-like carbon generated by the tribochemical reactions of CNx and water gives super-low friction coefficient.
[1] K. Hayashi, M. Kubo et al., J. Phys. Chem. C, 115 (2011) 22981.
[2] K. Hayashi, M. Kubo et al., Faraday Discuss., 156 (2012) 137.
[3] S. Bai, M. Kubo et al., RSC Adv., 4 (2014) 33739.