EFFECT OF SURFACE MOISTURE ON THE POLARIZATION OF INDIVIDUAL GLASS SPHERES

When glass particles adsorb water from humid environments their low fr equency dielectric properties change drastically. To investigate the p olarization mechanism, variable frequency measurements upon individual glass particles (similar to 50 mu m diameter) suspended in silicone o il were performed with a computer-controlled dielectrophoretic levitat or. The electrical properties of individual particles have been measur ed in the frequency range between 10 Hz and 100 kHz. A relaxation in t he induced dipole moment of moistened glass particles suspended in sil icone oil is clearly evident in measured spectra. Surface moisture cau ses the characteristic relaxation times of soda-lime glass particles t o change by up to 5 orders of magnitude. The relaxation spectra are sa tisfactorily modeled by the Debye equation and a model based on ohmic surface conduction appears to explain the phenomenon. This research ha s potential implications with respect to the controversy surrounding t he influence of moisture on the performance of electrorheological flui ds.