Dielectric dispersion in the frequency range 1 MHz-1 GHz of concentrated suspensions in relation to rheology

Dielectric measurements were performed on concentrated suspensions of TiO2 (50 vol%) and clay (40 vol%) in the frequency range 1 MHz-1 GHz. The suspension rheology was modified by various Tiron or sodium tripolyphosphate additions. Using a specific procedure for data interpretation, it was shown that the global dielectric relaxation phenomenon, in the intermediate frequency range, is composed of three or four more-or-less separate dielectric relaxations. The peak positions and intensities vary with the dispersant quantity and the suspension rheology. A correlation was found between the aspect of dielectric spectrums and the suspension consistency when the dispersant quantity varied. The dielectric spectrum aspects were also related to the existence of active surface sites on particles, which were subject to physical adsorption or chemical binding for cations and anions from the dispersant. (C) 2001 Academic Press.