title: 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.
authors.affiliation: State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China.
authors.forename: Shu-Wei
authors.initials: SW
authors.lastname: Liu
authors.affiliation: Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Hua-Ping
authors.initials: HP
authors.lastname: Wang
authors.affiliation: School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Xu
authors.affiliation: State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China.
authors.forename: Tian-Bao
authors.initials: TB
authors.lastname: Ma
authors.affiliation: Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Gui
authors.initials: G
authors.lastname: Yu
authors.affiliation: State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China.
authors.forename: Chenhui
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Dechao
authors.initials: D
authors.lastname: Geng
authors.affiliation: State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China.
authors.forename: Zhiwei
authors.initials: Z
authors.lastname: Yu
authors.affiliation: School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China.
authors.forename: Shengguang
authors.initials: S
authors.lastname: Zhang
authors.affiliation: School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China.
authors.forename: Wenzhong
authors.initials: W
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China.
authors.forename: Yuan-Zhong
authors.initials: YZ
authors.lastname: Hu
authors.affiliation: State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China.
authors.forename: Jianbin
authors.initials: J
authors.lastname: Luo