Robust microscale superlubricity under high contact pressure enabled by graphene-coated microsphere

SW Liu and HP Wang and Q Xu and TB Ma and G Yu and CH Zhang and DC Geng and ZW Yu and SG Zhang and WZ Wang and YZ Hu and H Wang and JB Luo, NATURE COMMUNICATIONS, 8, 14029 (2017).

DOI: 10.1038/ncomms14029

Superlubricity of graphite and graphene has aroused increasing interest in recent years. Yet how to obtain a long-lasting superlubricity between graphene layers, under high applied normal load in ambient atmosphere still remains a challenge but is highly desirable. Here, we report a direct measurement of sliding friction between graphene and graphene, and graphene and hexagonal boron nitride (h-BN) under high contact pressures by employing graphene-coated microsphere (GMS) probe prepared by metal-catalyst-free chemical vapour deposition. The exceptionally low and robust friction coefficient of 0.003 is accomplished under local asperity contact pressure up to 1 GPa, at arbitrary relative surface rotation angles, which is insensitive to relative humidity up to 51% RH. This ultralow friction is attributed to the sustainable overall incommensurability due to the multi-asperity contact covered with randomly oriented graphene nanograins. This realization of microscale superlubricity can be extended to the sliding between a variety of two- dimensional (2D) layers.

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