Macroscale superlubricity achieved via hydroxylated hexagonal boron nitride nanosheets with ionic liquid at steel/steel interface

Abstract

Macroscale superlubricity is a prospective strategy in modern tribology to dramatically reduce friction and wear of mechanical equipment; however, it is mainly studied for point-to-surface contact or special friction pairs in experiments. In this study, a robust macroscale superlubricity for point-to-point contact on a steel interface was achieved for the first time by using hydroxylated modified boron nitride nanosheets with proton-type ionic liquids (ILs) as additives in ethylene glycol aqueous (EGaq). The detailed superlubricity process and mechanism were revealed by theoretical calculations and segmented experiments. The results indicate that hydration originating from hydrated ions can significantly reduce the shear stress of EGaq, which plays an essential role in achieving superlubricity. Moreover, the IL induces a tribochemical reaction to form a friction-protective film. Hydroxylated boron nitride nanosheets (HO-BNNs) function as a polishing and self-repairing agent to disperse the contact stress between friction pairs. Superlubricity involves the change in lubrication state from boundary lubrication to mixed lubrication. This finding can remarkably extend the application of superlubricity for point-to-point contact on steel surfaces for engineering applications.

A mucus-inspired solvent-free carbon dot-based nanofluid triggers significant tribological synergy for sulfonated h-BN reinforced epoxy composites

“…9c shows that the nanostructure is composed of five elements B, C, N, O and S, respectively, and these five elements are distributed almost evenly across the nanostructure, implying that the F-CDs and h-BN nano-sheets are hybridized together. 54 Fig. 9d shows the cross-sectional TEM image of the tribo-film formed on the worn counter surface (the steel ball) for h-BN@PSDA/EPs lubricated by 40 wt% F-CDs in PEG 400.…”

Progress in Superlubricity Across Different Media and Material Systems—A Review

“…In reality, liquid lubricants that can exhibit superlubric performance in multifarious applications and over a range of operating conditions are yet to be realized. Among the available liquid media, polar and ionic liquids have been found to be most amenable for achieving superlubricity (Zheng et al, 2021). Glycerol and glycol are canonical examples that have shown promising superlubricity performance.…”

Macroscale Superlubricity with Ultralow Wear and Ultrashort Running-In Period (∼1 s) through Phytic Acid-Based Complex Green Liquid Lubricants

“…Currently, the reported liquid superlubricating materials are divided into pure water, , acid-based solutions, − polyol aqueous solutions, − ionic liquids, − and oil-based lubricants. ,, However, a long running-in period (the time taken for the friction coefficient to decrease to <0.01) is inevitable for almost all liquid superlubricants, which leads to severe wear of the friction pairs before achieving the superlubricating state. , Moreover, the wear caused by long running-in period will also increase the contact area between the friction pairs, resulting in the fact that the final average contact pressure after achieving superlubrication is much smaller than its initial Hertz contact pressure. This reflects that the load-carrying capacity of these liquid superlubricants is also low, that is, the state of superlubrication can only be achieved at a lower contact pressure. , Designing suitable lubricants to combine the advantages of both high load capacity and ultralow friction has always been a major challenge in the field of super lubrication.…”