Synthesis of multi-element (F,N,S) doped carbon nanospheres derived from polystyrene as lubricant additives for tribological performance improvement

In this study, the uniform dense polydopamine (PDA) coating was deposited on hyper-cross-linked polystyrene nanospheres (HPSs) through the oxidative polymerization of dopamine with polyethyleneimine (PEI), then which underwent acidification and subsequent anion exchange with LiNTf₂ to obtain HPSs@PDA electrolyte (HPSs@PDA-NTf₂). So, the multi-element-doped carbon nanospheres (F,N,S-PCNs) were synthesized through the carbonization of HPSs@PDA-NTf₂, demonstrating exceptional tribological performance. Compared to 500SN, the mean COF of nanolubricant (500SN + 2.0 wt.% F,N,S-PCNs) decreased from 0.181 to 0.110, and the wear volume reduced by 90.3%. The load-carrying capacity of F,N,S-PCNs as lubricant additives is increased from 150N (500SN) to 450N. The F,N,S-PCNs can infiltrate the contact area and adsorb on the friction pair surface, forming a physical adsorption film that prevents the direct contact of surface. Additionally, the active elements (F,N,S) in F,N,S-PCNs undergo tribochemical reactions with the friction pair under mechanical force and thermal effects to form a chemical protective film. This dual effect significantly enhances the boundary lubrication performance of the lubricating oil. This study presents a novel approach for synthesizing multi-element co-doped carbon nanospheres, significantly enhancing the effectiveness of oil-based lubrication technology in the field.