Unfolding the origin of superlubricity at macroscale with graphene-nanodiamond ensembles
by
DrAnirudha Sumant
(CNM/ANL)
→
US/Central
Conf. Rm. D-172 (Bldg. 241)
Conf. Rm. D-172
Bldg. 241
Description
Minimizing friction and wear-related mechanical failures across all length-scales remains as one of the greatest challenge in today’s moving mechanical systems. The search for new materials that can reduce friction and wear related energy losses has lately intensified and the understanding of those mechanisms that control friction from nano to macro-scales has been viewed as essential in managing energy dissipation that could ultimately translate into energy savings. Our research work at Argonne is focused on understanding graphene’s exceptional materials properties [1-4] and how these properties could be manipulated at atomic scales to achieve superlow friction and improved wear performance at macroscopic levels. To this end, we have recently shown that the wear-life of even a one atom thick sheet of graphene can be significantly enhanced in hydrogen atmosphere [5]. In this case, we have shown that hydrogen passivates carbon dangling bonds of a ruptured graphene that do not allow graphene layer to break-apart during high contact pressure sliding conditions. In another recent study, we demonstrated that how superlubricity (or near zero friction) can be achieved by combined uses of graphene and nanodiamonds on sliding surfaces. In this work, we experimentally demonstrated that superlubricity can be realized at macroscales with sliding a diamond-like carbon (DLC) surface against graphene mixed with nanodiamonds [6]. We showed that during sliding, graphene patches wrap around nanodiamonds reducing the contact area and DLC provides a perfect incommensurate surface to achieve superlubric state for extended time periods. We performed detailed large-scale molecular dynamics simulations which closely elucidated the mesoscopic link that bridges the nanoscale mechanics and macroscopic experimental observations, thus introducing a new mechanism to explain our experimental results. Our discovery brings a paradigm shift in understanding frictional behavior of 2D materials and offers a direct pathway for designing energy efficient frictionless tribological systems as well as provides a fundamental basis for developing universal friction mechanism that could further predict frictional behavior of these materials systems.
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