Rheological and tribological behaviour of nanofluids: an experimental evaluation

Abstract Commercially available synthetic engine oils of SAE grades 5W40 were taken as base fluids for preparing nano fluids by blending 0.1% and 0.2% concentration by weight of the functionalized Cu and MoS 2 nanoparticles in them. The base fluids and their blends were characterized using standard ASTM and IS testing methods for their physicochemical and tribo performance behaviours. The rheological studies were performed on a Rheometer while the tribological investigations were performed on tribo-tester. The study reveal that a small improvement in anti- friction behaviour of about 6% and 4% reported for the 0.2 wt% of Cu and MoS 2 nanoparticles respectively in the tested lubricants indicate that finished products have little scope to improve anti-friction properties under the influence of already present additives, however anti-wear properties showed significant enhancement up to 20% for 0.2% MoS 2 and up to 15% for 0.2% nano-Cu indicating better anti-wear properties of MoS 2 and Cu nanoparticle blends. Rheological studies reveal that blending of nanoparticles has marginal influence on the rheological behaviour of the lubricants. The lubricants show shear thinning behaviour at low shear rates. However at higher shear rates, lubricants behave as Newtonian fluids.