Friction reducing properties of onion-like carbon based lubricant under high contact pressure

In this study, carbon based nanomaterials such as onion-like carbon (OLC), carbon nanotube and buckminsterfullerene (or buckyball) (C₆₀) have been investigated as nanocolloidal additives for liquid lubricants. When tested under a range of contact pressures from 0·51 to 1·10 GPa, OLC provided the best overall friction reducing property in synthetic lubricant, although the friction reducing properties of all nanocarbon materials were dependent on the contact pressure. Detailed transmission electron microscopy revealed that the OLC kept its original structure intact and induced the formation during sliding of a thin 'tribofilm' composed of OLC, nanosized wear debris, amorphous carbon and graphitic layers on the wear debris. This tribofilm seems to be responsible for reduced friction under boundary conditions.