Fluorinated Graphene: A Promising Macroscale Solid Lubricant under Various Environments

Abstract

Graphene-related materials are promising solid lubricants owing to their easy shear between lattice layers. However, the coefficient of friction (COF) of graphene is not sufficiently low at the macroscale, and the lubrication performance is largely restricted by the external environment. In this study, we fabricated a fluorinated graphene (FG) coating on a stainless-steel substrate by a simple electrophoretic deposition in ethanol. The FG coating exhibited an excellent lubrication performance, which reduced the COF by 54.0 and 66.2% compared to those of pristine graphene and graphene oxide coatings, respectively. The lubrication enhancement of FG coating is attributed to its extremely low surface energy and interlaminar shear strength. The formation of ionic metal–fluorine chemical bonds provided a robust solid tribofilm and transfer layer on the friction pairs, which further increased the lubrication performance of the FG coating. The limited influence of the humidity on the lubrication performance of the FG coating is attributed to the hydrophobicity of the FG nanoflakes, which could prevent the influence of water molecules on the sliding interface. The excellent lubrication performance and better environmental adaptability of the FG make it a promising solid lubricant for mechanical engineering applications.

Role of nanoparticles in achieving macroscale superlubricity of graphene/nano-SiO2 particle composites

“…Moreover, the d spacing of the formed graphene nanoscrolls (0.38 nm) was greater than the interlayer spacing of pure graphene (0.34 nm) [34], which may have been due to the tensile stress in the outer layers. As verified in previous studies, the increase in the interlayer spacing of graphene is favorable to reducing friction to a certain degree [38,39], which could well account for the desired friction-reducing effect of the as formed graphene nanoscrolls. Because the formation of graphene nanoscrolls at an increased load (referring to a high contact stress) is essential for achieving macroscale superlubricity of the as prepared graphene/ nano-SiO 2 particle composite coating, it can be inferred that the superlubricating graphene/nano-SiO 2 particle composite coating could be applicable to instrumental components working under harsh conditions (e.g., high contact pressure).…”

Environmental Molecular Effect on the Macroscale Friction Behaviors of Graphene

“…There are only nitrogen molecules in the nitrogen atmosphere, so the H 2 O molecules may enter into the layers of graphene nanosheets, inducing the d -spacing of layers to increase slightly. The larger d -spacing is advantageous for graphene, enabling a low friction ( Liu et al, 2019 ; Rosenkranz et al, 2020 ). This may be a part of the reason that the friction coefficient of graphene in the air is lower than in nitrogen.…”

Recent Advances in Fluorinated Graphene from Synthesis to Applications: Critical Review on Functional Chemistry and Structure Engineering

“…The specific CF bonds bring about great changes for surface character of FG like low surface energy, which thus expands the applications of FG in relevant fields including lubrication, self-cleaning, and oil-water separation. [46][47][48]50,157,[187][188][189][190][191][192][193][194][195][196][197] FG with a high fluorine content has been considered as an excellent lubricant, including its noumenal film coating and additive in lubricating oil and composites materials. Lei et al prepared high-quality FG nanosheets via the intercalation of raw FGi by N,N-dimethylformamide (DMF) through microwave treatment.…”