Sequential Coating of Magnetic Carbonyliron Particles with Polystyrene and Multiwalled Carbon Nanotubes and Its Effect on Their Magnetorheology

A two-step process for the sequential coating of magnetic carbonyliron (CI) particles with polystyrene (PS) and multiwalled carbon nanotubes (MWCNTs) was used to improve the sedimentation stability of micrometer-sized magnetic CI particles for magnetorheological (MR) applications under an applied magnetic field. The CI particles were initially coated with nanosized PS beads using an in situ dispersion polymerization method and then wrapped with a dense MWCNT nest through a solvent-casting method in a water/oil emulsion system. The morphology, MR performance, and sedimentation stability of the synthesized magnetic composite particles were examined. The composite particles showed enhanced MR characteristics and dispersion stability.