Mechanical stresses of a layer of colloidal particles aggregated by means of an electric field

Abstract

The stability of a colloidal system occupies a central position in colloid science. According to the DLVO theory, the interparticle potential admits two contributions: the Van der Waals attraction and the electrostatic repulsion. In this paper, we present a comparison of two methods to study the interaction forces between particles when their distance of separation varies. The distance between particles is controlled through the application of a DC electric field which is responsible for the formation of a concentrated layer of particles. The cohesion inside the layer is determined either through a mechanical method or through electrical measurements. In the first case, a shear force is applied until, by viscous resuspension, the layer breaks apart. From the critical shear stress at which the layer destruction occurs, we deduce the cohesive force between the particles. The electrical measurement consists in inverting the polarity of the applied voltage after the layer has formed. The attractive forces between particles is then deduced from the tensile voltage, the voltage at which the layer breaks.