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

Abstract

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.

Understanding Interlayer Contact Conductance in Twisted Bilayer Graphene

“…As illustrated in Figure a–d, three domains (SLG, BLG, and Cu) showing different friction responses in each panel can be clearly distinguished. Friction forces of both SLG and BLG domains are much smaller than that of bare copper substrate since an ideal graphene film is atomically smooth and has no dangling bond, resulting in low shear strength . Friction force of SLG is larger than that of BLG, which is consistent with previous literature .…”

Superlubricity of Graphite Induced by Multiple Transferred Graphene Nanoflakes

“…The superlubricity, a physical regime in which the friction between two sliding surfaces nearly vanishes (or the sliding friction coefficient is in the level of 0.001),2 is one of the most effective approaches to reduce the frictional energy dissipation and meanwhile provide a near‐wearless condition. There are a series of solid lubricants, such as the diamond‐like carbon (DLC) film and 2D or 3D layered materials, including graphene, graphite, boron nitride, and molybdenum disulfide (MoS 2 ), that have been observed to achieve the superlubricity state under certain special conditions 3. For example, Martin et al observed the superlow friction of a MoS 2 coating in the ultrahigh vacuum, where the atomic origin of superlubricity was from the incommensurate contact of MoS 2 basal planes 4.…”

Structural Superlubricity Based on Crystalline Materials

“…Within a generalized Prandtl–Tomlinson model, highly reliable description of the physical processes could be given underlying the measured phenomena . Based on the theoretical and experimental realizations, superlubricity of graphene sliding against graphite with real contact area on nanoscale is found to persist under ultrahigh contact pressure (≈1 GPa).…”

“…Copyright 2008, American Physical Society; 2016 Reproduced with permission . Copyright 2016, AAAS; 2017 Reproduced with permission . Copyright 2017, Macmillan Publishers Ltd; 2018 Reproduced with permission .…”