Rheological Study of the Gelation of Particulate Silica Sols

Small amplitude oscillatory shear measurements are useful for studying the gelation of aqueous particulate silica sols, because these dynamic tests do not alter the structure and kinetics of gelation. The dynamic storage modulus of the sol increases with time as the colloid clusters grow and shows a sharp transition at the onset of gelation. Upon shearing, the particulate gel reverses to a sol. The gelation kinetics of the resheared sample is slower than that of the fresh sample. The rheology of the particulate systems is compared with that of an alkoxide silica sol where the dynamic storage modulus does nor change until the onset of gelation. Freeze fracture microscopy was also used to monitor structural changes in the sol-gel system.