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 suspen sion rheology was modified by various Tiron or sodium tripolyphosphate addi tions. Using a specific procedure for data interpretation, it was shown tha t the global dielectric relaxation phenomenon, in the intermediate frequenc y range, is composed of three or four more-or-less separate dielectric rela xations. The peak positions and intensities vary with the dispersant quanti ty 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 e xistence of active surface sites on particles, which were subject to physic al adsorption or chemical binding for cations and anions from the dispersan t. (C) 2001 Academic Press.