2, Argonne National Laboratory, Argonne, Illinois, United States
3, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, United States
Tribological systems are an integral part of any moving mechanical assembly, from nanoscale microelectromechanical systems to macroscale automotive and aerospace applications. Minimizing friction and wear-related mechanical failures in order to allow superior performance and long-lasting operation of moving mechanical systems remains the one of today’s greatest challenges. Despite intense research efforts superlubricity, or near zero friction, has seldom been achieved at engineering scales or in practical systems. Much of the difficulty has often been due to the very complex physical, chemical, and mechanical interactions that occur simultaneously at sliding interfaces of mechanical systems.
In this study we evaluate tribological performance of carbon nanomaterials [1-2], and demonstrate realization of superlubricity regime at macroscale in an all-carbon-based ensemble when diamond nanoparticles are mixed with graphene and slide against diamond-like carbon (DLC) surface . We show that during sliding in dry atmosphere, graphene patches wrap around tiny diamond nanoparticles and form nanoscrolls, thus dramatically reducing the contact area with a perfectly incommensurate DLC surface. The coefficient of friction reaches ultralow values (0.004) thus demonstrating the long-lasting superlubric regime. This superlubricity is stable over a range of temperature, load, and sliding velocity conditions. Our large-scale molecular dynamic simulations elucidate the mesoscopic link between nanoscale mechanics and macroscopic experimental observations.
The highlighted carbon-based superlubricity provides a fundamental basis for developing universal friction mechanism and offers a direct pathway for designing smart frictionless tribological systems for practical applications of industrial interest.
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 D. Berman, et al., Science, 348 (2015) 1118-1122