2019 年 18 巻 2 号 p. 103-104
Diamond-like carbon (DLC) is a class of amorphous carbon materials with excellent friction properties. Graphitization of DLC caused by friction induces wear of DLC. Further, the existence of water molecules decrease the graphitization rate of DLC. In order to reduce the wear caused by graphitization, it is essential to reveal the mechanism by which water molecules decrease graphitization of DLC. Therefore, the friction simulations of DLC in both water and vacuum environment were carried out by reactive molecular dynamics method. We find that terminal-H atoms are removed by friction and dangling bonds are generated in both environments. In water environment, the generated dangling bonds connect with H and OH generated by the dissociation of water molecule, inhibiting the transformation from sp3 to sp2 carbon atoms and the formation of double bonds.We find that these are reasons for the suppression of DLC graphitization and the decrement of DLC wear.