Enhanced magnetorheological characteristics of hollow magnetite nanoparticle-carbonyl iron microsphere suspension

Highly magnetic Fe3O4 nanoparticles with a hollow spherical shape were fabricated via a solvothermal technique and were introduced into soft-magnetic carbonyl iron (CI)-based magnetorheological (MR) fluid to enhance the stability and its MR properties. The structural behaviors and magnetic characteristics of hollow Fe3O4, pure CI, and the hollow Fe3O4/CI mixture were demonstrated by scanning electron microscope, transmission electron microscope, and vibrating sample magnetometry. The MR properties of the systems with and without the hollow Fe3O4 additive were examined by controlled shear rate and oscillatory tests using a rotation-rheometer. The Herschel-Bulkley equation provided an adequate fit for the flow curve, and all of the yield stresses followed the universal scaling equation. The suspension characteristics of the two MR systems were further examined using a Turbiscan device. The CI-based MR fluid with hollow Fe3O4 additive was observed to exhibit higher yield stress as well as improved dispersion than does the pristine CI-based MR fluid, demonstrating that the performance of CI-based MR fluids can be further optimized by using additives.