Tunable, Wide‐Temperature, and Macroscale Superlubricity Enabled by Nanoscale Van Der Waals Heterojunction‐to‐Homojunction Transformation

Abstract

Achieving macroscale superlubricity of van der Waals (vdW) nanopowders is particularly challenging, due to the difficulty in forming ordered junctions before friction and the friction‐induced complex contact restructuration among multiple nanometer‐sized junctions. Here, a facile way is reported to achieve vdW nanopowder‐to‐heterojunction conversion by graphene edge‐oxygen (GEO) incorporation. The GEO effectively weakens the out‐of‐plane edge–edge and in‐plane plane–edge states of the vdW nanopowder, leading to a coexistent structure of nanoscale homojunctions and heterojunctions on the grinding balls. When sliding on diamond‐like carbon surfaces, the ball‐supported structure governs macroscale superlubricity by heterojunction‐to‐homojunction transformation among the countless nanoscale junctions. Furthermore, the transformation guides the tunable design of superlubricity, achieving superlubricity (µ ≈ 0.005) at wide ranges of load, velocity, and temperature (−200 to 300 °C). Atomistic simulations reveal the GEO‐enhanced conversion of vdW nanopowder to heterojunctions and demonstrate the heterojunction‐to‐homojunction transformation superlubricity mechanism. The findings are of significance for the macroscopic scale‐up and engineering application of structural superlubricity.

Structural Superlubricity of Two-Dimensional Materials: Mechanisms, Properties, Influencing Factors, and Applications

“…In addition, Yang et al transformed multiple nanoheterojunctions into homogeneous structures by doping graphene edges with oxygen, which effectively suppresses the edge effect. The structure exhibits ultra-low friction (with a COF of approximately 0.005) across a wide range of loads, speeds, and temperatures (from −200 to 300 • C) [125].…”