Friction and wear behavior of alumina-based graphene and CNFs composites

Alumina - carbon nanofibers (CNF) and alumina - graphene oxide (GO) composites were prepared by spark plasma sintering using freeze-dried powders prepared from optimized suspensions of the mixtures. The tribological behavior was studied using the ball-on-disk technique in dry sliding at ambient conditions and compared to a monolithic alumina used as a reference. At low loads there was little difference between friction and wear behavior, whereas at moderate loads the composites showed a noticeable reduction in wear rate over monolithic alumina, five and 2.5 times for the GO and the CNF composite respectively; the friction coefficient slightly decreased for the alumina - GO material. This behavior is related to the presence of a carbon-rich protecting tribofilm. The film present in the alumina - GO showed better tribological performance due to the absence of coalescence of cracks that led to delamination events in the case of the alumina - CNF composite.