Lubrication properties of chemically aged reduced graphene-oxide additives

Functionalized graphene is a hydrophilic material that could be an important lubricating additive due to the unique chemical and crystallographic properties. Functionalized aged reduced graphene oxide (A-rGO) additives dispersed in polyethylene glycol (PEG200) significantly improved the lubrication properties of steel-steel contact which is promising for useful application. Aging in humid condition transformed the single phase oxygen functionalized reduced graphene oxide (rGO) into a diphase material where lattice spacing of graphene sheet increased and rGO coexist with the nanocrystalline graphite phase. The evidence of adsorbed graphite tribo-species in the wear track is observed by X-ray photoelectron spectroscopy (XPS) and micro Raman spectroscopy. This acts as a high strength boundary and low shear strength tribofilm for enhancing the antiwear and antifriction properties.