Magnetite/Copolymer Nanosphere Added Soft-Magnetic Carbonyl Iron Based Magnetorheological Fluid and Its Damping Performance

Magnetite/copolymer (Fe3O4/copolymer) nanosphere was synthesized via chemical oxidative polymerization and utilized as an additional ingredient in soft-magnetic carbonyl iron (CI) microsphere-based magnetorheological fluid (MRF) to improve its magnetorheological and damping performance. MRFs with a monodisperse phase (CI-based MRF) and with a bidisperse phase (CI/nanosphere-based MRF) were prepared using polyalphaolefin as an oil medium. Magnetorheological performances of CI-based MRF and CI/nanosphere-based MRF were analyzed by the steady shear model under a gradient magnetic field. Results show that the flow curves are well fit to the Hershel-Bulkley model, and dynamic yield stresses strongly depend on the intensity of the magnetic field. CI/nanosphere-based MRF exhibited improved magnetorheological, which is attributed to the nanosphere filling the free volume among the CI, inducing stiffer chain structures. Owing to its improved magnetorheological properties, the CI/nanosphere-based MRF was further injected into a custom-designed magnetorheological damper (MRD), and its damping force characteristics including damping force as a function of magnetic field, displacement, and velocity, were investigated for vibration reduction applications in mechanical system.