Synergism lubrication of graphene and carbon nanotube in polymeric composites under drying sliding condition

The internal lubrication of polyimide (PI) with added graphene oxides (GOs) and carbon nanotubes (MWCNTs), as well as their binary hybrid nano-additives (GCNTs), were contrastively investigated under dry sliding conditions. The friction coefficient of neat PI or its nanocomposites decreases as a stepwise increase of the load fitting a negative exponential equation while growing linearly as a stepwise increase of the velocity. Micromorphological and physicochemical variations occurring at friction interfaces have been analyzed using X-ray photoelectron spectroscopy, Raman spectroscopy, and high-resolution transmission electron microscopy results. Given the structural discrepancy between GOs and MWCNTs, the obtaining results showed that the different microcosmic tribological mechanisms for GCNTs enable to produce a synergistic lubricating effect, resulting in facilitating the complicating interface sliding between nanocomposites and steel balls.