Non-Newtonian power-law behavior of TiO2/SAE 50 nano-lubricant: An experimental report and new correlation

In the present study rheological behavior of SAE 50w Engine Oil containing TiO2 nanoparticles of 30 nm is empirically investigated. Various samples of nano-lubricant were made by adding nanoparticles in 0%, 0.125%, 0.25%, 0.5%, 0.75%, 1% and 1.5% solid volume fractions. Dynamic viscosity of the samples was measured in temperature ranges of 25 to 50 °C and in various shear rates. The results clearly showed that the nano-lubricant as well as the base oil was non-Newtonian fluids behaving as power-law equation. From the values of power law index it was revealed that the nano-lubricant exhibited shear thinning behavior, though in high solid volume fractions it tends to Newtonian behavior. With using viscosity data, a new correlation is proposed in terms of temperature and solid volume fraction which has R-squared values of 0.9751. Margins of deviation for experimental data prediction were < 1.52%. Nano-lubricant was studied to determine its sensitivity to adding a specific extra amount of nanoparticles. It was revealed by the results that the nano-lubricant is more sensitive to solid volume fraction variations than variations of temperature; the sample with 1% solid volume fraction had the maximum sensitivity at 25 °C.