Electrorheology of suspensions of si particles with an oxide film in silicone oil

The electrorheological (ER) behavior of suspensions of oxidized Si particles in silicone oil was determined with de electric field E-0. The yield stress decreased with the thickness of the surface oxide film and was proportional to E-0(1.7) when the surface film thickness delta=0.2 mu m, The current density and the field dependent exponent decreased with the surface film thickness. When the surface film thickness delta=0.05 mu m, the current density was proportional to E-0(1.3). The results are in accord with our recent non-ohmic conduction model for the influence of an oxide film on conducting particles on ER response. The ER response of highly conducting particles with a low conductivity coating with ac field is also discussed.