Silica-Coated N-Doped Porous Carbon Nanospheres as Antiwear and Friction-Reduction Lubricant Additives

In this study, silica-coated nitrogen-doped porous carbon nanospheres (SiO₂@N-MCNs) were successfully prepared in a facile way. Polydopamine was first grafted onto hyper-cross-linked polystyrene nanospheres via oxidative polymerization. Meanwhile, silica could be embedded in a polydopamine layer by the hydrolyzation of tetraethyl orthosilicate. Eventually, SiO₂@N-MCNs were obtained after carbonization. The as-prepared SiO₂@N-MCNs exhibited favorable dispersion stability and improved antiwear and friction-reducing properties when used as lubricant additives. The average friction coefficient (COF) of base oil was reduced to 0.105 from 0.162 after adding 2.0 wt % SiO₂@N-MCNs, the corresponding wear volume was reduced by 97.1%, and particularly the load capacity was increased to 550 N. The excellent antifriction and antiwear properties are attributed to the formation of a successive protective film, including iron oxides, carbonitride, carbon film, and the repairing and filling effect of SiO₂@N-MCNs.