2013 Volume 12 Issue 1 Pages A3-A13
The low friction mechanism of diamond-like carbon (DLC) was investigated by first-principles molecular dynamics and tight-binding quantum chemical molecular dynamics methods. We found that under a load of 1 GPa low friction of H-terminated DLC is realized by hydrogen-hydrogen repulsion. Furthermore, H2 formation reaction occurs at the friction interface and it leads to the further decrement of the friction coefficient. On the other hand, we found that under a high load of 7 GPa C–C bond formation reaction occurs and it significantly increases the friction coefficient. A text book of mechanical engineering states that the friction coefficient does not depend on the load. However, our simulation results show that when chemical reactions occur at the friction interface the friction coefficient depends on the load. This means that our present outcomes rewrite the textbook of mechanical engineering. Furthermore, we also propose that OH-termination of the DLC surface can solve the increment of the friction coefficient under a high load of 7 GPa and it can be realized by tribochemical reactions under methanol environments.
