Shear-induced lamellar ordering and interfacial sliding in amorphous carbon films: A superlow friction regime

A shear-induced phase transition from disorder to lamellar ordering in amorphous carbon films are investigated by molecular dynamics simulations. Formation of well-separated graphene-like interfacial layers is observed with large interlayer distances, diminishing and ultimately vanishing interlayer bonds, which provides a near-frictionless sliding plane. The steady-state velocity accommodation mode after the running-in stage is interfacial sliding between the graphene-like layers, which explains the experimentally observed graphitization and formation of carbon-rich transfer layers. A superlow friction or superlubricity regime with friction coefficient of approximately 0.01 originates from the extremely large repulsive and low shear interactions across the sliding interface.