Magnetorheology of soft magnetic carbonyl iron suspension with single-walled carbon nanotube additive and its yield stress scaling function

The serious dispersion problem of carbonyl iron (CI) based magnetorheological (MR) fluid, due to the large density mismatch between CI particles and continuous medium, has hampered its MR applications. To resolve this undesirable sedimentation, we introduced fibrous single-walled carbon nanotube (SWNT) into CI suspension as additives. The dynamic yield stress change measured as a function of magnetic field strength was examined by adopting a universal equation which was originally applied for electrorheological (ER) fluids. In addition, the viscoelastic performances of CI/SWNT suspension were compared to investigate the influence of additives on the pristine CI suspension. The sedimentation ratio was also examined to confirm the role of submicron SWNT bundles.