A study on rheological characteristics of hybrid nano-lubricants containing MWCNT-TiO2 nanoparticles

In the present study, dynamic viscosity of four nano-lubricant with different combinations of carbon nanotube (CNTs) and Titania (TiO2) nanoparticles (10%–90% and 55%–45%) in 10w40 engine oil has been investigated. These nanofluids were prepared in solid volume fraction range of 0.25%–1% and have been tested at temperature ranging from 15 °C to 55 °C. Another investigated variable was the fluid shear rate that has been taken into consideration in order to study the rheological behavior of nanofluids. Increase and decrease of the viscosity are the effects of particle volume fraction and temperature on the nanofluid, respectively. In all types of nanofluids, it is occurred about 80% reduction in the viscosity with increasing of the temperature, of which the used nanoparticle has no significant effect on this value. Moreover, the nanofluids containing MWCNTs at the solid volume fraction of 0.75%, is faced with an increase of 100% in the viscosity. The experimental results also indicate that increasing in the percentage of carbon nanotube in the nanofluid has a considerable effect on the non-Newtonian behavior of the fluid and this increase enhances the shear-thinning behavior of suspensions.