Investigation on Tribological Performance of NanoZnO and Mixed Oxide of Cu-Zn as Additives in Engine Oil

The paper presents the comparative study on the antiwear properties of zinc oxide and Cu-Zn mixed oxide nanoparticles, as additive in SAE20W40 engine oil. The nanoparticles were prepared using precipitation method and characterized using scanning microscopy imaging technique and XRD analysis. The particle size was found to be between 70-80 nm.The stability of the nanosuspension play a vital role in the antiwear performance. Therefore the stability studies were carried out by dispersing varying concentration of nanoparticle between 0.01wt% - 0.05wt% in the engine oil using surface modifiers and sonication. Nanosuspensions above 0.02 wt% of nanoparticles showed sedimentation on long standing for 36h. Based on this, the concentration of nanoparticle in the engine oil was optimized as 0.01 and 0.02wt%.The nanosuspensions with optimized concentration i.e.0.01wt% ZnO, 0.02 wt% ZnO, 0.01wt% Cu-Zn and 0.02 wt% Cu- Zn mixed oxides were tested for antiwear property using four ball tester. The results revealed a reduction in friction and wear in comparison with the base oil. However, the zinc oxide suspensions exhibited highest reduction in CoF, WSD and WSD values. This can be attributed to the smaller particle size and uniform dispersion of zinc oxide nanoparticles in comparison to the mixed oxides of Cu-Zn.