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 10-3,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 ofinterfacial 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 ofgraphene,wear-free sliding is achieved.Our results broaden the scope of superlubricity and promote its wider application in the future.

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

Department of Engineering Mechanics,Tsinghua University,Beijing 100084,China;Center for Nano and Micro Mechanics,Tsinghua University,Beijing 100084,China;Institute of Superlubricity Technology,Research Institute of Tsinghua University in Shenzhen,Shenzhen 518057,China;State Key Laboratory of Tribology,Tsinghua University,Beijing 100084,China;Department of Mechanical Engineering,Tsinghua University,Beijing 100084,China

国家科学评论（英文版）

[1]Deli Peng;Jin Wang;Haiyang Jiang;Shuji Zhao;Zhanghui Wu;Kaiwen Tian;Ming Ma;Quanshui Zheng-.100 km wear-free sliding achieved by microscale superlubric graphite/DLC heterojunctions under ambient conditions)[J].国家科学评论（英文版）,2022(01):12-19

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