The Performance of Carbon-Based Nanomaterials in Different Base Oils and an Oil Blend

Different carbon-based nanomaterials (fullerenes, graphene, SWCNTs, and SWCNT-COOH) were tested as additives in a base mineral oil, SN150; rapeseed oil (RSO); and a 50/50 by volume blend of the two using an HFRR (high-frequency reciprocating rig) tester for coefficient of friction (COF) and wear scar diameter (WSD) determinations and a four-ball tester for welding point determinations. The concentrations considered for the HFRR tests were 0.1, 0.5, 1, and 2 wt.%, while the concentration considered for the welding point tests was 0.5 wt.%. The results of the welding point tests showed that the addition of different nanoparticles made it so that welding occurred at much lower pressures compared to the pure oils. This is due to the hardness of the nanoparticles, which increases the local temperature and pressure at the contact points between them and the surfaces, causing welding to occur much sooner. The results of the HFRR tests showed a possible synergistic effect between the fullerenes and SWCNT-COOH and the oil blend, which may be attributed to possible interactions that occurred at a molecular level between the nanoparticles and the different molecules of the oil blend.