Dispersion stability and rheological properties of silica suspensions in aqueous solutions

This historical perspective overviews the dispersion stability and rheological properties of fumed and colloidal silica suspensions in aqueous solutions as a function of the volume fraction of silica (ϕ) (where ϕ is ≤0.1). The silica suspensions exist in a gel state at lower ϕ in acidic conditions than at alkaline pH. The steady-state shear viscosities of silica suspensions at acid conditions exhibit shear thinning behavior at lower ϕ than in alkaline conditions; the magnitudes of the dynamic moduli of the silica suspensions at acidic pH are larger than those at alkaline pH. Changes in the dispersion stability and rheological behavior of the silica suspensions may be attributable to the addition of salt, which decreases electrostatic repulsion. Furthermore, the effects of polymer adsorption on the dispersion stability and rheological behavior of hydrophilic or hydrophobic silica suspensions are discussed.