Octahedral shaped magnetite nanoparticle added carbonyl iron suspension and its magnetorheology

Magnetorheological (MR) fluids, magnetic particles such as carbonyl iron (CI) and magnetite dispersed in a nonmagnetic liquid, change tunably and reversibly from a liquid-like to a solid-like state under applied magnetic field strengths, thus possessing huge engineering applications. Among the many magnetic particles available, CI microspheres have been widely used as magnetizable particles for MR fluids due to their high magnetic permeability, soft magnetic property and common availability. However, their high density causes serious sedimentation drawback and abrasion within equipment of application . A range of strategies including the introduction of additives or coating technologies to the particles have been reported to prevent the CI particles from caking or decreasing the particle density, thereby reducing the sedimentation rate . Three major methods have been applied to improve the sedimentation stability of MR fluids . These include adding surfactants, adding nanoparticles or using nanomagnetizable particles or coating magnetizable particles with polymer. In this study, we used octahedral shaped Fe₃O₄ nanoparticles as an additive for the CI based MR fluids to solve the sedimentation problem . MR properties of two MR fluid systems with and without the octahedral shaped Fe₃O₄ nanoparticles were examined using a rotational rheometer with magnetic field supply device .