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

Abstract

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.