100 km wear-free sliding achieved by microscale superlubric graphite/DLC heterojunctions under ambient conditions

Deli Peng; Jin Wang; Haiyang Jiang; Shuji Zhao; Zhanghui Wu; Kaiwen Tian; Ming Ma; Quanshui Zheng

doi:10.1093/nsr/nwab109

100 km wear-free sliding achieved by microscale superlubric graphite/DLC heterojunctions under ambient conditions

Natl Sci Rev. 2021 Jun 24;9(1):nwab109. doi: 10.1093/nsr/nwab109. eCollection 2022 Jan.

Authors

Deli Peng¹, Jin Wang¹, Haiyang Jiang², Shuji Zhao³, Zhanghui Wu¹, Kaiwen Tian², Ming Ma³, Quanshui Zheng¹

Affiliations

¹ Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China.
² Institute of Superlubricity Technology, Research Institute of Tsinghua University in Shenzhen, Shenzhen 518057, China.
³ Center for Nano and Micro Mechanics, Tsinghua University, Beijing 100084, China.

Abstract

Wear-free sliding between two contacted solid surfaces is the ultimate goal in the effort to extend the lifetime of mechanical devices, especially when it comes to inventing new types of micro-electromechanical systems where wear is often a major obstacle. Here we report experimental observations of wear-free sliding for a micrometer-sized graphite flake on a diamond-like-carbon (DLC) surface under ambient conditions with speeds up to 2.5 m/s, and over a distance of 100 km. The coefficient of friction (COF) between the microscale graphite flake, a van der Waals (vdW) layered material and DLC, a non-vdW-layered material, is measured to be of the order of [Formula: see text], which belongs to the superlubric regime. Such ultra-low COFs are also demonstrated for a microscale graphite flake sliding on six other kinds of non-vdW-layered materials with sub-nanometer roughness. With a synergistic analysis approach, we reveal the underlying mechanism to be the combination of interfacial vdW interaction, atomic-smooth interfaces and the low normal stiffness of the graphite flake. These features guarantee a persistent full contact of the interface with weak interaction, which contributes to the ultra-low COFs. Together with the extremely high in-plane strength of graphene, wear-free sliding is achieved. Our results broaden the scope of superlubricity and promote its wider application in the future.

Keywords: DLC; graphite; microscale; structural superlubricity; wear-free.