Enduring macroscopic lubrication of thin graphene films achieved by pre-gelation with polymer nanofibers

Graphene-based thin-film materials have been regarded as promising solid lubricants for industrial applications. However, to create thin graphene films with high and long-lasting lubricity especially under macroscopic contacts is still challenging. Here a composite thin graphene film capable of achieving a coefficient of friction (CoF) of as low as ∼0.06 for 214110 consecutive reciprocating friction cycles under a relatively high contact normal load and sliding frequency of 7 N and 30 Hz, respectively, all by physical lubrication is fabricated via a “sol-gel-film” transition approach, which has hardly been exploited for constructing thin film-based solid lubricants, using few-layer graphene nanosheets (GNS) and polymer nanofibers that are both of unsatisfactory lubricity as building blocks. Such “two negatives make an affirmative” lubrication mechanism is likely to be a synergistic effect between the heat dissipating capacity of GNS and the robustness of polymer nanofibers. And this also endows the resultant gel film a superb and tunable thermal conductivity and mechanical strength via controlling the in-plane stretching ratio of a hybrid gel precursor for assembling the composite film. We envision that our study may provide a simple and effective solution to the technical challenges of graphene-based lubrication films.