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

Abstract

Wear-free sliding between two contacted solid surfaces is the ultimate goal towards extending the lifetime of mechanical devices, especially for inventing new types of MEMS (micro-electromechanical system) 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 distance over 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 ultralow COFs are also demonstrated for microscale graphite flake sliding on other six kinds of non-vdW-layered materials with sub-nm roughness. With a synergistic analysis approach, we reveal the underlain 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 ultralow 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.

Robust microscale structural superlubricity between graphite and nanostructured surface

“…) is also orders larger than the typical value for graphite ake sliding on other surfaces showing SSL, which is on the order of 0.1 15 . To understand the phenomenon of the large friction between the graphite ake and the atomic-level at silicon surface in Fig.…”

“…) 11 , 293m/s SSL has attracted wide-ranging interest in not only academic studies 12 , but also practical applications, such as superlubric generators (SLGs) 13,14 and superlubric resonators 11 . More recently, SSL was realized between microscale graphite and many non-van der Waals materials such as diamond-like-carbon (DLC), Si, SiO 2 , Al 3 O 2 , Si 3 N 4 , etc 15 . It greatly broadens the application range of SSL technology.…”

Recent Progress on Carbon Nanomaterials for Resisting the Wear Damages

“…Fullerenes. Superlubricity was an emerging research focus for realizing energy conservation and extending the lifetime of the mechanical components [152,153]. So far, superlubricity with exceptionally low energy dissipation has been observed in experimental and simulation works at both the micro-scale and macroscale under various friction conditions, in which the studied systems were mainly based on carbon materials.…”

Robust Structural Superlubricity under Gigapascal Pressures

“…SSL can be constructed through contacts with only one of the surfaces from the vdW-layered materials with (0001) basal plane (vdW contacts) 23 . The asymmetric SSL contact is expected to be less pressure-resistant.…”

“…However, recent experimental evidence of SSL demonstrates a wear-free behavior over the 100 km sliding distance, which suggests that the gradual wear model might fail for SSL systems 11,23 . It should be noted that the pressure investigated in this study is on the order of several megapascals, much lower than the extreme conditions in applications that could be up to the gigapascal level.…”