Iron nanoparticles-based magnetorheological fluids: A balance between MR effect and sedimentation stability

It is a great challenge to make a balance between magnetorheological (MR) effect and sedimentation stability for magnetorheological (MR) fluids. Iron nanoparticle would be a good candidate to achieve this balance, but it lacks efficient preparation method. In this study, a DC arc discharge method was used to prepare iron nanoparticles. Their morphology, magnetic properties, crystal structures and surfaces chemical composition were examined, which confirmed their nano size (similar to 40 nm), high saturation magnetization (similar to 146 emu/g), and high purity. The iron nanoparticles and commercial carbonyl iron micro-sized particles were used as the dispersing phase to prepare MR fluids, respectively. Their magnetorheological effect and sedimentation stability were measured for comparison. The results indicate that the iron nanoparticles-based MR fluids present a slight lower MR effect, but much better sedimentation stability with respect to the MR fluids with carbonyl iron micro-sized particles.