Core-Shell Structured Polystyrene Coated Carbonyl Iron Microspheres and their Magnetorheology

Soft magnetic carbonyl iron (CI) microparticle, possessing high magnetic saturation with less magnetic hysteresis, was mostly applied as an active material in magnetorheological (MR) fluids. However, pure CI suspension is known to have poor dispersion stability in the MR fluid system. To overcome this problem, we fabricated polystyrene (PS)-coated CI particles through a simple coating method of dispersion polymerization. Surface morphology of synthesized PS coated CI was observed using scanning electron microscopy. Performance of this MR fluid dispersed in silicone oil, including shear stress and shear viscosity, was measured using a rotational parallel disk rheometer in a steady shear flow and suspension stability was examined by a Turbiscan apparatus. The PS-coated CI suspension was found to improve settling of the CI particles without much deterioration of MR performance.