Dynamic Response of Polyindole Coated Zinc Ferrite Particle Suspension under an Electric Field.

ZnFe2O4 particles initially synthesized through a simple solvothermal method were coated using polyindole (PIn) to prepare an actively controllable core-shell typed hybrid material under both electric and magnetic fields. An advantage of this process is not needing to add the stabilizers or surfactants commonly used for uniform coating when synthesizing core or shell-structured particles. The synthesized ZnFe2O4/PIn particles have a lower density than conventional magnetic particles and have suitable properties as electrorheological (ER) particles. The expected spherical shape of the particles was proven using both scanning electron microscopy and transmission electron microscopy. The chemical characterization was performed using Fourier-transform infrared spectroscopy and X-ray diffraction analysis. To analyze the rheological properties, a ZnFe2O4/PIn based suspension was prepared, and dynamic rheological measurements were performed for different electric field strengths using a rotary rheometer. Both dynamic and elastic yield stresses of the ER fluid had a slope of 1.5, corresponding to the conductivity model. Excellent ER effect was confirmed through rheological analysis, and the prepared ER fluid had a reversible and immediate response to repeated electric fields.