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 and oscillatory dynamic model under gradient magnetic field. Flow curves are well fitted to the Hershel-Bulkley model, and dynamic, elastic and static yield stresses were confirmed to follow a universal scaling equation. The dispersion stabilities of MRFs were measured using an optical analyzer of Turbiscan. The CI/nanosphere-based MRF were 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 damping applications in mechanical system. Results shown that the CI/nanosphere-based MRF exhibited improved dispersion stability, magnetorheological and damping performance, which is attributed to the nanosphere filling the free volume among the CI, inducing stiffer chain structures and improved magnetorheological and damping performance.