Improvement of magnetorheological greases with superparamagnetic nanoparticles

Abstract

Magnetorheological greases (MRGs) is a viscoelastic suspension comprised of carbonyl iron (CI) particles in a thixotropic medium; grease, which able to solve the instability problem that occurs in oil medium like MRFs. The primary purpose introduction of superparamagnetic nanoparticles γ-Fe2O3 in MRGs suspension is to investigate the effect of additives toward MRGs characteristics. Two types of MRGs suspension with and without nanoparticles γ-Fe2O3 were prepared in the same CI particles concentration for comparison purpose. It was observed that MRGs with incorporated of 1 wt% nanoparticles γ-Fe2O3 showed an increment regarding magnetic properties. In the meantime, the off-state viscosity of MRGs containing nanoparticles γ-Fe2O3 was reduced, however, increased during on-state condition. This fact indicates that the interspaces between CI particles are filled by the nanoparticles γ-Fe2O3. Therefore, the introduction of the nanoparticles indirectly improved the MRGs properties.