Dispersion Stability And Tribological Properties of Covalently Modified Graphene As A Lubricating Oil Additive

Abstract

Graphene has excellent mechanical properties with a low coefficient of friction and wear resistance and has a wide range of tribological applications. However, the stable dispersion of graphene in lubricating media is challenging. In this study, graphene is processed via covalent modification. A mild oxidation method selectively grafts carboxyl groups on the edge of the graphene sheet, before connecting tertiary alkyl primary amines through amide bonds. The alkyl chain allows graphene to be stably dispersed in hydrocarbon solvents.. FT-IR, XPS, Raman, XRD, SEM, etc. are used to characterize the covalently modified graphene (MG). Dispersion stability experiments showed that MG exhibited stable dispersion in 500N base oil and 15w-40 commercial lubricants, with stability for over 2 months. Tribological test results show that MG in 500N and 15w-40 significantly reduces the friction and wear of steel-steel friction pairs. The stable dispersion of MG in lubricating oil enables the formation of a stable chemical reaction film and graphene physical deposition film during the friction, protects the worn surface, and reduces direct contact, thereby significantly reducing friction and wear.

Experimental investigation of the effect of tribological performance of reduced graphene oxide additive added into engine oil on gasoline engine wear

“…Tribological test results show that MG in 500N and 15W‐40 significantly reduces the friction and wear of steel‐steel friction pairs, which supports our work. The stable dispersion of MG in lubricating oil enables the formation of a stable chemical reaction film and graphene physical deposition film during the friction, which protects the worn surface, and reduces direct contact, thereby significantly reducing friction and wear 11 …”

“…The stable dispersion of chemically functionalized reduced graphene and reduces direct contact, thereby significantly reducing friction and wear. 11 The high mechanical strength, good conductivity and lamellar structure of graphene exhibit its potential for tribological applications. Supporting our work, Mungse, H.P.…”

“…The agglomeration of graphene leads not only to precipitation, but also to the loss of wear resistance and anti‐friction ability 10 . Preventing agglomeration is particularly important for graphene applications because their unique properties are associated with individual sheets 11 …”

“…10 Preventing agglomeration is particularly important for graphene applications because their unique properties are associated with individual sheets. 11 In recent years, the search for novel lubricant materials even coatings have gained increasing importance to face the massive economic and environmental costs related to friction and wear. Graphene chemisorbs on the iron surface and its binding is enhanced by reactive dangling bonds, as those present in pristine graphene flakes used in the colloidal lubricant.…”