Graphene Grown by Chemical Vapour Deposition on Steel Substrates: Friction Behaviour

Graphene was grown by low-pressure chemical vapour deposition on polished steel samples using ethanol as a precursor at different pressures: 200 and 400 mTorr. The samples were characterized by Raman spectroscopy, and the Raman maps clearly show the formation of an inhomogeneous graphene coating with surface regions covered with single-layer, bilayer, and multilayer graphene, the last one covering most of the surface area of the sample when the sample was prepared at 400 mTorr. Scanning electron microscopy revealed the partial coverage of the sample surface when the graphene coating was prepared at a pressure of 200 mTorr. Friction measurements were taken using a micro-tribometer in a ball-on-flat contact geometry with a stainless steel ball as the counterbody. An important reduction in the coefficient of friction was verified even with partial coverage of the steel surface, and it was attributed to the formation of nanographitic structures in the wear track region and partially transferred to the counterbody.