In-situ construction of Cu@C3N4 for oil lubrication

In this study, a series of graphitic carbon nitride (g-C3N4) decorated with Cu nanoparticle hybrids (CNx/Cuy) were prepared by one pot calcination method. The chemical composition of hybrids were determined by XRD, FTIR and XPS analysis. And the synthesized CNx/Cuy hybrid presented different morphologies with the different x/y ration. Then CNx/Cuy were added to liquid paraffin as lubricant additive, and the tribological properties of lubricant oils for steel/steel friction pairs were evaluated using a ball-on-disk tribometer. The results showed that friction processes lubricated with oil containing CN3/Cu1 shows better tribological properties. And oil containing 0.2 wt % CN3/Cu1 could achieve 57.3 % and 53.8 % reduction in the friction coefficient, respectively, compared to pure liquid paraffin and liquid paraffin containing pure g-C3N4. Based on the analysis of the worn surface topography and chemical composition, the excellent lubrication performance resulted from the formation of tribochemistry-induced tribo-film. The average thickness of tribo-film was about 100 nm, and it was composed of carbonization resulting from g-C3N4, Cu, Fe and self-lubricating Fe2O3. The formation of Fe2O3 and carbonization in the tribo-film indicating the interaction between CN3/Cu1 with steel surfaces enhanced the stability and strength of tribo-film. Thereby the metal surface was further protected from friction and wear.