Study of shear thickening behavior in colloidal suspensions

We studied the shear thickening behavior of the nano silica suspension (silica nanoparticles 12 nm in size suspended in ethylene glycol) under steady shear. The critical shear rate for transition into shear thickening phase was determined at different concentrations and temperatures. The effect of temperature and concentration was studied on the shear thickening behavior. In silica suspension، it was observed that all the samples had a transition into shear thickening phase and also by increasing the temperature، critical shear rate increased and viscosity decreased. Our observations showed that movement in silica suspension was Brownian and temperature could cause a delay in transition into shear thickening phase. Yet، we observed that increasing the concentration would decrease critical shear rate and increase viscosity. Increasing temperature increased Brownian forces and increasing concentration increased hydrodynamic forces، confirming the contrast between these two forces for transition into shear thickening phase for the suspensions containing nano particles.