Macroscopic ultra-low friction and wear enabled by carboxylated graphene with glycerol

Reducing wear and even achieving superlubrication in industrial applications using simple yet effective methodologies has been a longstanding research objective. In this study, we propose a convenient approach by employing a combination of carboxylated graphene (Gr-COOH) coating with glycerol as lubricants. Compared to the non-lubricated state, this strategy enabled the achievement of superlubrication with an exceptionally low friction coefficient of 0.002, while simultaneously reducing wear volume of substrate by 4 orders of magnitude, and the wear of the counterpart balls are nearly zero. The transfer of Gr-COOH to the ball surface led to the formation of a low shear resistance interface with the Gr-COOH present on the substrate. Nanoscopic experiments with atomic force microscopy revealed that the substrate surface lubricated by this method exhibited more hydrophilic properties. The formation of a featured hydrophilic interface enables the persistence of glycerol molecules in the contact region for an extended duration, thereby facilitating continuous elastohydrodynamic lubrication. This proposed lubrication methodology holds broad utilization potential as a wear-reduction strategy across various industrial fields.