Enhanced magnetorheological characteristics of hollow magnetite nanoparticle-carbonyl iron microsphere suspension
Wen Jiao Han, Ji Su An, Hyoung Jin Choi
Abstract
Abstract Highly magnetic Fe 3 O 4 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 Fe 3 O 4 , pure CI, and the hollow Fe 3 O 4 /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 Fe 3 O 4 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 Fe 3 O 4 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.