Nitrogen
and phosphorus doping have been proven to be effective
strategies for improving the tribological properties of carbon-based
materials when used as lubricating oil additives. Herein, an efficient
strategy is demonstrated for the preparation of nitrogen and phosphorus
codoped organic carbon nanospheres (denote as N, P@CN) via a template-free
interfacial copolymerization combined with ammonium hypophosphite-assisted
carbonization. The N and P are found to be homogeneously distributed
through the entire carbon shell. The tribological properties of as-prepared
materials as base oil additives under different test conditions were
evaluated. The as-prepared N, P@CNs exhibit good dispersibility and
stability in base oil due to the presence of many organic functional
groups. Moreover, they are considered to be thermal stable at elevated
temperatures, and the existing robust structure makes them favorable
as lubricant additives. The experiment results show that the friction
reduction and wear resistance abilities of N, P@CNs were superior
to that of pure base oil, because N, P@CNs can induce tribo-chemical
reactions to form a protective film on the interfaces due to the combined
effect of nitrogen and phosphorus. The obtained N, P@CNs could increase
the load carrying capacity of base oil from 250 N to 1050 N. The coefficient
of friction can be reduced to 0.08, and the corresponding wear volume
loss can be decreased by 90%. These findings open up a possibility
to prepare environmentally friendly lubricant additives, such as carbon
nanospheres doped with other elements, to achieve excellent antiwear
and friction-reducing characteristics.