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

The electrorheological (ER) behavior of suspensions of oxidized Si particle s in silicone oil was determined with de electric field E-0. The yield stre ss decreased with the thickness of the surface oxide film and was proportio nal 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 t hickness. When the surface film thickness delta=0.05 mu m, the current dens ity 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 conductin g particles on ER response. The ER response of highly conducting particles with a low conductivity coating with ac field is also discussed.