Graphitic Carbon\nNitride: Achieving Superlow\nFriction and Wear on Engineering\nSteel

Graphitic carbon nitride (g-C<sub>3</sub>N<sub>4</sub>) is a typical\ntwo-dimensional (2D) material acclaimed for its layered structure\nand electronic properties, showcasing promise across various domains\nsuch as catalysis, CO<sub>2</sub> reduction, and lubrication. In this\nstudy, g-C<sub>3</sub>N<sub>4</sub> is synthesized as an oil-based\nnanoadditive within oleic acid (OA), exhibiting superlow friction\ncoefficient (COF) within steel/steel contacts under high pressure.\nWhen dispersed g-C<sub>3</sub>N<sub>4</sub> in OA at a concentration\nof 0.25 wt %, the COF is reduced from 0.077 to 0.022 compared to the\nbase oil. The amino groups in g-C<sub>3</sub>N<sub>4</sub> promote\nthe formation of continuous friction films, creating a composite tribofilm\nmade of carbon layers, carbon nitride, and iron oxides. This tribofilm\neffectively prevents direct contact between tribopairs, leading to\nsignificant friction reduction and enhanced antiwear properties. These\nfindings offer insights into the design of lubricant additives for\nbase oils and highlight the promising potential of carbon nitride\nin lubrication and tribology applications.