Exfoliated fluorinated carbons with a low and stable friction coefficient

Abstract

Exfoliation appears as a promising way to decrease the friction coefficient of carbon materials. Although there is massive defluorination during exfoliation, the friction coefficient is not increased and an exfoliated structure facilitates the formation of a homogeneous and stable tribofilm. The weakening of the interparticle interactions due to the exfoliation process is the main explanation for the excellent tribological properties. Three representative examples are studied to evidence the efficiency of the thermal shock to prepare solid lubricants or additives for lubricating oils, high temperature graphite fluorides, fluorinated carbon nanofibers and fluorinated nanodiscs. An opened (graphite fluoride) or defect structure (nanofibers) allows the gases formed during the exfoliation to be evolved; the exfoliation is then successful regardless of the C–F bonding. Exfoliation and defluorination occur simultaneously resulting in samples with a low F/C atomic ratio. On the contrary for the case of fluorinated nanodiscs, the exfoliation fails because of cracks and edges as well as the low diameter of the discs.