Effect of octahedral typed iron oxide particles on magnetorheological behavior of carbonyl iron dispersion

Abstract To enhance suspension stability and magnetorheological (MR) effect of carbonyl iron (CI)-based MR fluids, octahedral-shaped magnetite particles were synthesized by a hydrothermal method in an autoclave and then adopted as an additive for soft-magnetic CI-based MR suspensions. Two different MR suspensions comprised of the same CI particles with a 70% weight fraction were prepared; one contained an additional 1 wt% octahedral magnetite according to the carrier fluid weight. The MR characteristics of the two MR suspensions with and without the octahedral-typed magnetite nanoparticles were tested using a rotation-typed rheometer attached with a magnetic field strength generator. The sedimentation profile of the MR suspension with and without the additive was also analyzed. The shear viscosity, shear stress, yield stress, and storage modulus from rheological tests were enhanced by the magnetic additive.