Tribological assessment of a water-based nanofluid containing CeO2 nanoparticles supported on multiwalled carbon nanotubes

This work reports the tribological assessment of ceria (CeO2) nanoparticles supported on multiwalled carbon nanotubes as water-based lubricant additives. Crystalline multiwalled carbon nanotubes (MWCNTs) were obtained by a spray pyrolysis method using alpha-pinene, a renewable feedstock, as carbon source and ferrocene as catalyst. CeO2 nanoparticles with an average diameter of similar to 1.7 nm homogenously distributed on the MWCNTs were synthetized using a microwave-assisted method. MWCNTs at 0.10 wt% and CeO2/MWCNTs composite at 0.10, 0.05 and 0.01 wt% concentrations were completely dispersed in water. Tribological tests were carried out in a commercial pin-on-disk tribometer at an operating load of 10 N for 1 h in steel-steel contacts. The results indicate that CeO2/MWCNTs composite can reduce friction and wear at the proper concentration. The lowest coefficient of friction (similar to 0.11) was observed at 0.10 wt%, which represents a 74.4% reduction with respect to pure water. A 39.8% wear reduction was obtained at a 0.05 wt% concentration. The synergistic effect of CeO2 nanoparticles and MWCNTs promotes the formation of a tribofilm consisting of highly aligned graphene layer inside the wear tracks.