Surfactant-free electrodeposition of reduced graphene oxide/copper composite coatings with enhanced wear resistance

How to uniformly disperse graphene sheets into the electrolyte is one of the main challenges to synthesize graphene enhanced nanocomposites by electrodeposition. A surfactant-free colloidal solution comprised of copper (II)-ethylene diamine tetra acetic acid ([Cu(ll)EDTA](2-)) complexes and graphene oxide (GO) sheets is proposed to electrodeposit reduced graphene oxide/copper (RGO/Cu) composite coatings. Anionic [Cu(ll)EDTA](2-) complexes stably coexist with negatively charged GO sheets due to the electrostatic repulsion between them, facilitating the electrochemical reduction and uniform dispersion of GO sheets into the copper matrix. The RGO/Cu composite coatings are well characterized by XRD, Raman, SEM and XPS. Their tribological behavior as a function of RGO content in composite coatings and normal loads are investigated. Also the chemical composition and topography of the wear tracks for the composite coatings are analyzed to deduce the lubricating and anti-wear mechanism of RGO/Cu composite coatings. (C) 2017 Elsevier B.V. All rights reserved.