CHAPTER 7: Coated Magnetorheological Composite Particles: Fabrication and Rheology

Recent research on fabrication of magnetic composite magnetorheological (MR) particles as well as their magnetic and rheological characterization are discussed in this chapter. The fabrication of coated magnetic particles is designed to reduce the density mismatch between the suspended magnetic particles and the carrier medium sequentially improving the settling stability of the MR fluid. Coated carbonyl iron (CI) particles with either polymeric or inorganic materials, such as poly(methyl methacrylic acid), polyaniline, silica, and zirconia not only demonstrate much reduced density, but also exhibit enhanced chemical stability and longer lifetime. A range of methodologies for their fabrication, such as in situ polymerization and solvent casting, are developed to prepare micron-sized magnetic composite particles containing CI or Fe₃O₄ as the magnoto-active part, followed by a demonstration of their corresponding morphologies as well as their magnetic and MR properties. Both the magnetic properties of the composite particles and the MR performance of the MR fluid are strongly influenced by the incorporation of non-magnetic materials.