Parametric Study on the Steady Shear Rheology of Fumed Nanosilica Colloidal Dispersions

Shear thickening fluids (STFs) are a type of non-Newtonian fluids which display sudden increase in viscosity under the applied shear stress, particularly when the shear rate surpasses a critical value termed as the critical shear rate. The phenomenon of shear thickening is reversible implying that shear thickening fluids return to their low viscosity flowable state from a high viscosity thickened state when the applied shear stress is removed. This unique property of STFs is used to develop products for use in shock, vibration, and impact mitigation applications. In this study, various fumed silica (FS)-based shear thickening fluids (STFs) were synthesized by ultrasonic homogenization technique. The influence of specific surface area of fumed silica, viscosity of dispersion medium, and temperature was studied on the rheological properties of nanosilica dispersions. From the experimental studies, it was observed that with the reduction in particle size, the severity of shear thickening enhanced, while the onset of shear thickening got delayed to high shear rates. Temperature was also found to drastically influence the shear thickening intensity. As the temperature increased, the quantum of shear thickening decreased. The severity of shear thickening was generally quantified in terms of the highest viscosity obtained after the onset of shear thickening phenomenon.