Effect of a hard magnetic particle additive on rheological characteristics of microspherical carbonyl iron-based magnetorheological fluid

Magneto-responsive magnetorheological (MR) characteristics of soft-magnetic carbonyl iron (CI) based MR fluid were examined at four different additive concentrations of hard magnetic γ-Fe2O3 nanoparticles to improve both the dispersion stability and the MR performance. The magnetic stimuli-response of their rheological behavior was determined by examining the flow and dynamic oscillation properties at each additive concentration under a magnetic field using a rotational rheometer. Enhanced yield stresses due to the addition of hard magnetic nanoparticles correlated well using the universal yield stress scaling equation and the parameter critical magnetic field strength. Sedimentation properties of the MR fluid with and without the hard magnetic nanoparticle additive were further tested using a Turbiscan, and showed improved dispersion stability with the additive.