Unlocking the secrets behind liquid superlubricity:A state-ofthe-art review on phenomena and mechanisms

作     者：Tianyi HAN Shuowen ZHANG Chenhui ZHANG Tianyi HAN;Shuowen ZHANG;Chenhui ZHANG

作者机构：State Key Laboratory of TribologyTsinghua UniversityBeijing 100084China 

出 版 物：《Friction》 (摩擦（英文版）)

年 卷 期：2022年第10卷第8期

页      面：1137-1165页

核心收录：

学科分类：08[工学] 080203[工学-机械设计及理论] 0802[工学-机械工程] 

基　　金：This work is financially supported by the National Key R&D Program of China(No.2018YFB2002204) the National Natural Science Foundation of China(No.51925506)。 

主　　题：liquid superlubricity hydrodynamic lubrication hydration lubrication surface potential surface forces 

摘      要：Superlubricity,the state of ultralow friction between two sliding surfaces,has become a frontier subject in tribology.Here,a state-of-the-art review of the phenomena and mechanisms of liquid superlubricity are presented based on our ten-year research,to unlock the secrets behind liquid superlubricity,a major approach to achieve superlubricity.An overview of the discovery of liquid superlubricity materials is presented from five different categories,including water and acid-based solutions,hydrated materials,ionic liquids(ILs),two-dimensional(2D)materials as lubricant additives,and oil-based lubricants,to show the hydrodynamic and hydration contributions to liquid superlubricity.The review also discusses four methods to further expand superlubricity by solving the challenge of lubricants that have a high load-carrying capacity with a low shear resistance,including enhancing the hydration contribution by strengthening the hydration strength of lubricants,designing friction surfaces with higher negative surface charge densities,simultaneously combining hydration and hydrodynamic contribution,and using 2D materials(e.g.,graphene and black phosphorus)to separate the contact of asperities.Furthermore,uniform mechanisms of liquid superlubricity have been summarized for different liquid lubricants at the boundary,mixed,and hydrodynamic lubrication regimes.To the best of our knowledge,almost all the immense progresses of the exciting topic,superlubricity,since the first theoretical prediction in the early 1990s,focus on uniform superlubricity mechanisms.This review aims to guide the research direction of liquid superlubricity in the future and to further expand liquid superlubricity,whether in a theoretical research or engineering applications,ultimately enabling a sustainable state of ultra-low friction and ultra-low wear as well as transformative improvements in the efficiency of mechanical systems and human bodies.