Structure of electrorheological fluids: a dielectric study of chain formation.
A dielectric measurement method has been proposed to apply to the study of the microstructure of electrorheological (ER) fluids. To test our measurement method the dielectric permittivity increment caused by pair and chain formation was measured in dilute Brownian ER fluids composed of silicone oil and nanosized silica particles. The critical values of the electric field required to induce structure formation were experimentally determined from the electric field dependence of the measured permittivity increment. From the electric field induced time evolution of the relative permittivity of ER fluids, the characteristic times of the pair and chain formation were calculated. Our experimental results for the time constants are in good agreement with the corresponding theoretical data obtained from the Eyring theory.
Institute of Physics and Mechatronics, University of Pannonia, PO Box 158, 8201 Veszprém, Hungary. bhorvath@almos.uni-pannon.hu
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