Effect of magnetic dipolar interactions and size dispersity on the origin of steady state magnetomechanical response in bidisperse Mn–Zn ferrite spherical particle based magnetorheological fluids
Magnetorheological fluids have tunable magneto-mechanical strength. We report the magneto-mechanical (steady-state shear) response of magnetorheological fluids (MRFs) containing bi-disperse Mn–Zn ferrite (Mn0.7Zn0.3Fe2O4) spherical particles synthesized by a solvothermal method. Using a model of magnetic dipolar interactions between the particles, we have explained the origin of the magneto-mechanical response of the MRFs. The observed yield strength values of our MRFs increase with the applied magnetic field strength and the concentration of the ferrite particles in the fluid due to the formation of strong columnar structures which resist the shear. Moreover, the yield strength of the MRFs was found to depend strongly on the particle size, size distribution and the magnetic nature (saturation) of the particles. We have demonstrated that a bi-disperse size distribution of particles in the fluid imparts superior yield strength to the MRF compared to that of the mono-disperse particles. Unlike conventional metallic iron particles, which lead to dispersion instability and are prone to corrosion and thermo-oxidative failures, the low-density corrosion-resistant soft-ferrimagnetic Mn–Zn ferrite particles make our MRF system dependable for various technological applications demanding shock absorption and vibration isolation.