Magneto-stimuli rheological response of hierarchical Fe₃O₄ submicron spheres for high performance magnetorheological fluid

Uniform Fe₃O₄ submicron spheres assembled by tiny nanocrystals were fabricated via a facile one-step solvothermal strategy. The morphology, crystal structure, mesoporous characteristics, elemental composition and magnetic properties of the resultant magnetic particles were investigated extensively through various characterization techniques. The resulting Fe₃O₄ submicron spheres were nearly monodisperse with an average diameter of 508 nm and demonstrated typical mesoporous structures and superparamagnetic behavior. The rheological responses of magnetorheological (MR) suspension composed of Fe₃O₄ submicron spheres to different intensity of magnetic fields were investigated and the sedimentation stability tests were conducted and compared with that of carbonyl iron particles. The formed MR fluid behaved as Newtonian fluid without an external magnetic field and turned into Bingham behavior under the action of magnetic field. In addition, no significant settlement was observed in the recording period, showing an excellent sedimentation stability for the developed MR fluid.