ELECTRORHEOLOGICAL PROPERTIES OF BARIUM-TITANATE SUSPENSIONS UNDER OSCILLATORY SHEAR

The electrorheology of suspensions composed of barium titanate particles, silane coupling agent, water, and silicone oil was studied by the use of an oscillating plate rheometer. The magnitude of the complex viscosity, \eta*\, rapidly increases on the application of electric fields and the suspensions change from viscous liquids to solid-like pastes. Significant flow occurs only after a yield stress is exceeded. Because the addition of water contributes to the development of yield stress and the silane coupling agent leads to a decrease of \eta*\ in the absence of electric fields, the electrorheological performance characterized by the balance between the yield stress under electric fields and the zero-field viscosity is markedly improved by a superposition effect of additives. The rapid response can be directly related to the increase in particle-particle attraction, rather than the migration and structural formation of particles. The polarization of adsorbed substances may be primarily responsible for the electrorheological effect.