Graphitic Carbon Nitride: Achieving Superlow Friction and Wear on Engineering Steel

Graphitic carbon nitride (g-C3N4) is a typical two-dimensional (2D) material acclaimed for its layered structure and electronic properties, showcasing promise across various domains such as catalysis, CO2 reduction, and lubrication. In this study, g-C3N4 is synthesized as an oil-based nanoadditive within oleic acid (OA), exhibiting superlow friction coefficient (COF) within steel/steel contacts under high pressure. When dispersed g-C3N4 in OA at a concentration of 0.25 wt %, the COF is reduced from 0.077 to 0.022 compared to the base oil. The amino groups in g-C3N4 promote the formation of continuous friction films, creating a composite tribofilm made of carbon layers, carbon nitride, and iron oxides. This tribofilm effectively prevents direct contact between tribopairs, leading to significant friction reduction and enhanced antiwear properties. These findings offer insights into the design of lubricant additives for base oils and highlight the promising potential of carbon nitride in lubrication and tribology applications.