Nanomechanical Studies of Superlubricity

We briefly review the nanomechanical studies of ultralow friction in the following carbon hybrid systems: atomic force microscopy (AFM) tip on graphite surface, AFM tip on C60/graphite, graphite on graphite surface, graphite/C60/graphite, and C60 intercalated graphite. For the atomic and flake frictions, frictional force maps are compared between simulations and experiments, which can be explained by stick-slip motion of the tip apex atom and flake. For the graphite/C60/graphite system, superlubricity appears, where the maximum static frictional forces have finite values but denote that dynamical frictional forces are zero within the resolution of the experiment. Furthermore, for the C60 intercalated graphite system, greater superlubricity appears. It is clarified that fullerene intercalated graphite films exhibit ultralow average friction force, and excellent friction coefficients μ < 0.001. Our results propose one of the simple guidelines of designing a practical superlubric system - reduction of the contact area between intercalated C60 and graphite sheet to the point contact. Clearly, the C60 intercalated graphite system will contribute to solving energy and environmental problems in the future.