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Electroviscous effect of moderately concentrated colloidal suspensions

Abstract:

The electroviscous effect of a colloidal suspension is considered. The disagreement between the different existing theories and the experimental results is pointed out. A new development, based upon a cell model concept, is proposed. This new approach is valid for Newtonian fluids and disordered systems, which impose the condition of low shear rate, corresponding to the low Newtonian plateau in general flow curves of colloidal suspensions. The theory is valid for moderately concentrated suspensions and thin double layers. The numerical results are analyzed, resulting in a dependence of the electroviscous effect with the particle concentration. A maximum of the electroviscous coefficient with the ζ-potential for every particle concentration and electrokinetic radius is found, although the very high ζ value where the maximum appears makes it inaccessible for experimental tests. The theoretical pbkp_redictions are compared with a few experimental results. A better agreement in the region of validity of the theory is found.