Carbonaceous soot dispersion characteristic and mechanism in lubricant with effect of dispersants by molecular dynamics simulation and experimental studies

The effective dispersion of carbonaceous soot has a critical effect on the friction and wear properties and thus decreases energy waste and equipment trouble. Molecular dynamics (MD) simulation and experimental study are performed to unravel the dispersion behavior and mechanism of soot agglomerate in lubricating system with effect of dispersant concentration at various pressures and temperatures. The static, confinement and shear models were created with dispersant polyisobutylsuccinimide polyamine (pib). At static conditions, pib molecules could approach and then self-assemble on soot fragments to disperse soot agglomerate. Under confinement conditions with an external pressure imposed, soot dispersion was better than that under static conditions, and the effect of pressure was not remarkable. The best dispersion characteristic was obtained as dispersant increased to 10 wt% exceeding that the dispersants were excessive and induced their self-aggregation. Under shear conditions, 10 wt% pib molecules showed the best dispersion at both 300 K and 373 K, which is considered as a critical value for soot dispersion from the perspective of MD simulations. Finally, the tribological experiments provided a prime validation for MD simulations. The most effective lubrication occurred in 12.5 wt% sample with friction and wear reduction by 51% and 80% compared to 10 wt% sample, respectively, due to the well soot dispersion and possible friction modification of dispersants.