Tribochemistry of Graphene Oxide/Graphene Confined between Iron Oxide Substrates: Implications for Graphene-Based Lubricants

Abstract

Graphene has been widely tested as a lubricant material for steel sliding contact in engineering applications. The structural and chemical evolutions on friction surfaces are critical to understand the improvement of tribology performance in experiments. Here, we used the reactive molecular dynamics (ReaxFF-MD) simulations to study the friction and wear behaviors of a monolayer graphene oxide or graphene (GO/Gr) flake confined between two amorphous iron oxide substrates. The results show that when under lower loads (<4 GPa), the sliding shear between two substrates is accomplished by folding and unfolding behaviors of the confined GO/Gr flakes. When under relatively higher loads (≥4 GPa), the intensively formed interfacial C–Fe bonds promote the breakage and decomposition of the GO/Gr flakes and also the gradual damaging of the iron oxide surfaces, resulting in partial direct contacts between two substrates. We also found that the presence of functional groups on the GO flakes will affect the formation of interfacial C–Fe bonds, while the detached functional groups could passivate the iron oxide surfaces, thus having a remarkable influence on the tribological properties of steel sliding contacts. These atomistic insights into structural and chemical evolutions during friction can help to promote the usage of GO/Gr flakes as lubricant materials in engineering applications.

Dissipation Mechanisms and Superlubricity in Solid Lubrication by Wet-Transferred Solution-Processed Graphene Flakes: Implications for Micro Electromechanical Devices

“… 67 Hence, our study elucidates key concepts of relevance for different contact junctions—lubricated either by liquid dispersions of graphene or by other wet-transferred 2D flakes 2 , 68 , 69 —that are operated under nominally wearless sliding conditions or do involve more complex tribochemistry and third-body-effects. 8 , 70 …”

Two-dimensional iron oxide/graphene-based nanocomposites as high-performance solid lubricants

“…One theoretical study showed that the barrier energy and shear strength for graphene/metal oxide interface is much lower than that of the chemisorbed interface between graphene and metal (without oxide formation) [49]. Another possible contributing factor is the folding and unfolding of rGO flakes within the 2D nanocomposites during friction, as predicted by a recent simulation study [50]. It may also be related to the elimination of atomic interlock and the block of chemical interactions between neighboring layers.…”

Investigation of Tribological Behavior and Lubrication Mechanisms of Zinc Oxide under Poly α-olefin Lubrication Enhanced by the Electric Field

“…ReaxFF MD simulations can describe the breaking and formation of interatomic bonds and thus can be used to explain the occurrence of tribochemical reactions in materials. − According to ReaxFF MD simulations, Yu et al revealed the significance of shear stress in a tribo-oxidation reaction. Wang et al . found that the formation of interfacial C–Fe bonds has a remarkable influence on the tribological performances of steel sliding contacts.…”