The effect from adsorbed water on the polarization of individual glass particles suspended in silicone oil (a model electrorheological fluid)

When glass particles adsorb water from humid environments their low frequency dielectric properties change drastically. To investigate the polarization mechanism, variable frequency measurements upon individual glass particles (;Depending on the type of surface treatment, the characteristic relaxation times of soda-lime glass particles can change by more than 5 orders of magnitude. The relaxation time depends strongly on the amount of moisture that is adsorbed but is ultimately determined by the concentration of ions in the surface layer. When salts are introduced on the surface of hydrogen glass particles, a broadening of the relaxation in the DEP spectra is observed. A possible explanation has been offered that attributes the distribution of relaxations to a non-uniform surface conductivity created by the irregular formation of salt crystals on the surface.;This research has potential implications with respect to the controversy surrounding the influence of moisture on the performance of electrorheological (ER) fluids. Experiments are presented which provide evidence that the instability of hydrous electrorheological (ER) fluids is due to the loss of particle surface moisture, which severely degrades the ER effect by altering the particle polarization. In addition to establishing the importance of ions dissociated from the surface of glass particles by adsorbed water, it has been found that the dipole moment is influenced by impurity ions that leach out from the bulk. Interfacial polarization, which enables most ER fluids, is therefore determined in the glass-water-oil system by the interaction between the water and ions both at and near the surfaces of particles.