Frequency Responses of the AC-Impedance of Ground Powders in Dispersion

Abstract

To investigate the method of estimating the degree of dispersion and stability of a dispersed system, the frequency responses of AC-impedance were measured using ground SiO₂, TiO₂ and Al₂O₃ powders.
It was found that the electric equivalent circuit of the dispersed system was a parallel circuit made up of a resister and capacitor. Its AC-impedance was dominated by the concentration of the dissociation ion on the surface layer of the powders.
From the measurement of the AC-impedance and of the concentration of the dissociation ions in the dispersed system with increasing specific surface area of grinding powders, it was found that for the SiO₂-CH₃OH and TiO₂-CH₃OH systems, the AC-impedance and the concentration of the dissociation ions, H⁺ showed an interesting tendency. For the Al₂O₃-CH₃OH systems, the AC-impedance tended to decrease while the concentration of the dissociation ions, OH^- showed an interesting tendency.
The AC-impedance of the dispered system was closely related to the concentration of the dissociation ion on the surface layer of powders.