Core–shell-structured silica-coated magnetic carbonyl iron microbead and its magnetorheology with anti-acidic characteristics

We synthesized silica-coated soft magnetic carbonyl iron (CI) particles through a modified Stöber method, in which the CI particles were pretreated with a grafting agent to enhance the affinity of a precursor of silica. Synthesized magnetic microbeads were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, and anti-acid test in HCl solution. Silica-coated CI shows not only improved wettability to silicone oil with a lower off-state shear viscosity as a better magnetorheological fluid under an applied magnetic field but also enhanced anti-acidic property.