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

The stability of a colloidal system occupies a central position in colloid science. According to the DLVO theory, the interparticle potential admits t wo contributions: the Van der Waals attraction and the electrostatic repuls ion. In this paper, we present a comparison of two methods to study the int eraction 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 thro ugh a mechanical method or through electrical measurements. In the first ca se, a shear force is applied until, by viscous resuspension, the layer brea ks apart. From the critical shear stress at which the layer destruction occ urs, we deduce the cohesive force between the particles. The electrical mea surement consists in inverting the polarity of the applied voltage after th e layer has formed. The attractive forces between particles is then deduced from the tensile voltage, the voltage at which the layer breaks. (C) 2001 Elsevier Science B.V. All rights reserved.