Macroscale Superlubricity Enabled by the Synergy Effect of Graphene-Oxide Nanoflakes and Ethanediol.

Graphene has been recognized as an excellent lubrication material owing to its two-dimensional structure and weak interlayer interactions. However, most extant works concerning superlubricity involving graphene oxide have been limited to nanoscale or microscale dimensions (of the order of 1-10 μm). In present work, realization of a robust macroscale superlubricity state (μ = 0.0037), by taking advantage of the synergy effect of graphene-oxide nanoflakes (GONFs) and ethanediol (EDO) at Si3N4-SiO2 interfaces is reported. GONFs have been observed as being adsorbed on friction surfaces, thereby preventing direct contact between surface asperities. The extremely low shear stresses developed between these asperities contribute toward enhanced superlubricity and the resulting super-low wear. Meanwhile, the formation of partial-slip hydrodynamic boundary condition at the GONFs-EDO interface along with the formation of hydrated GONFs-EDO networks through hydrogen-bond interactions contribute to the generation of extremely low shear stresses of the liquid lubricating film. Such macroscale superlubricity provides a new approach toward realization of extremely low friction in GONFs through the synergy effect with liquids.