Magnetorheological characteristics of carbonyl iron microparticles with different shapes

Two different shapes of spherical- and flake-like soft-magnetic carbonyl iron (CI) microparticles were dispersed in silicone oil to prepare magnetorheological (MR) fluids. The magnetic-field dependent rheological behaviors of the MR fluids were scrutinized focusing on their shape effect. Saturation magnetization of the flake-shaped CI was obtained to be slightly lower than that of spherical-shaped CI. However, rheological properties of shear stress, shear viscosity, and storage modulus of the flake-shaped CI MR fluid surpassed those of the spherical-shaped CI MR suspension under applied magnetic field strengths. The flake-shaped CI based MR fluid also demonstrated superior sedimentation stability compared with the spherical-shaped CI. This was due to large surface area, suggesting that the anisotropy of CI particles plays an important role in their MR performance.