Fabrication of DDP-functionalized carbon nitride nanosheets via thiol-ene “click” reaction as lubricant additives

Herein, the functionalized graphite carbon nitride (DDP@g-C₃N₄) nanosheets were successfully prepared via the surface self-assembly method combined with “click” reaction. Firstly, the 3-(trimethoxysilyl) propyl acrylate (TOPA) was self-assembled onto the g-C₃N₄ surface to obtain TOPA@g-C₃N₄, then the dialkyl dithiophosphate (DDP) was grafted onto TOPA@g-C₃N₄ via thiol-ene “click” reaction formation of DDP@g-C₃N₄. The load-carrying capacity of PAO10 is increased to 900 N from 200 N with 1.5 wt% DDP@g-C₃N₄ addition, and the average COF decreased from 0.17 to 0.10, accompanied by a 96.7 % decrease in wear volume. This improved lubricating performance is attributed to the formation of a continuous protective film including iron oxides, iron sulfide, and iron phosphate via tribochemical reactions, which prevent direct contact and seizure between friction pairs.