Synthesis and Viscoelastic Behavior of Non-Stoichiometric Spinel Ferrite Particle Suspension

Magnetorheological (MR) fluid with tunable and reversible phase transition is one of the most promising smart materials for engineering applications. In this paper, to improve the MR performance of ferrites, non-stoichiometric Zn-doped spinel ferrite (Zn0.417Fe2.583O4) nanoparticles with a high saturation magnetization and a truncated octahedron-like shape were synthesized using a thermal decomposition process. The crystallographic structure was analyzed using X-ray diffraction and field emission transmission electron microscope image. The Zn0.417Fe2.583O4 had a high saturation magnetization value of 101 A . m(2)/kg at 933 kA/m, showing higher saturation magnetization than other ferrites. The MR characteristics of the Zn0.417Fe2.583O4 particles suspended in silicone oil were studied using a rotation rheometer under various magnetic field strengths. This MR fluid exhibited typical MR characteristics, and its flow curves were fit well with the Herschel-Bulkley model.