Preparation of N, F, P co-doped carbon nanospheres derived from polypyrrole for enhanced tribological performance

In this study, nitrogen-, fluorine-, and phosphorus- co-doped carbon nanospheres (N,F,P-CNs) were successfully prepared by low-temperature carbonization of polypyrrole (PPy) at 400 ℃ under a N₂ atmosphere with the assistance of ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate ([HMIM]PF₆). Benefiting from the successful incorporation of nitrogen, fluorine and phosphorus heteroatoms, together with the partial retention of a lipophilic organic phase, the N,F,P-CNs promote the formation of a robust protective film through their participation in tribochemical reactions. This complex boundary film, composed of carbonitrides, iron oxides and phosphates, significantly enhances lubrication performance of the base oil. Compared with base oil 500SN, lubricant based on N,F,P-CNs-2 significantly reduces the average friction coefficient from 0.169 to 0.112 (a reduction of 33.7%) and lowered the wear volume by 85.6%, while dramatically increasing the maximum load carrying capacity from 150 N to 450 N.