Electrorheological effects in carbon, barium titanate, and nickel coated with barium titanate suspensions

Effects of the electric field on the theology, electrorheological (ER) effe cts, are investigated on carbon, barium titanate (BaTiO3) and BaTiO3-coated nickel (BT-Ni) suspensions. Among some electrorheological properties, elec tric field frequency dependence of the induced shear stress (yield stress) observed for three suspensions shows a contrasting behavior. With increase in the electric field frequency, the yield stress decreases above 100 Hz in the carbon suspension, monotonously increases in the BaTiO3 suspension, an d is almost constant in the BT-Ni suspension. The difference in the frequen cy dependence and magnitude of the yield stress is discussed on the basis o f the magnitude and relaxation time of the interfacial polarization and the effect of the particle rotation under the shear flow. (C) 2001 Elsevier Sc ience B.V. All rights reserved.