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

Shear thickening fluids (STFs) are a class of non-Newtonian fluids that exhibit an increase in viscosity under applied shear stress, particularly when the shear rate surpasses a critical value termed the critical shear rate. The shear thickening phenomenon is reversible, implying that shear-thickened fluids return to their low-viscosity flowable state from a high-viscosity thickened state when the 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 using the ultrasonic homogenization technique. The influence of particle size, viscosity of dispersion medium, and test temperature on the steady shear rheology of nanosilica dispersions was studied. From the experimental studies, it was observed that with the decrease in particle size, the severity of shear thickening enhanced, while the onset of shear thickening got delayed by high shear rates. Temperature was also found to drastically influence the thickening intensity. As the test temperature increased, the severity of shear thickening was measured in terms of the highest viscosity attained after the onset of the shear thickening phenomenon.