Synthesis and magnetorheology of suspensions of cobalt particles with tunable particle size

Different samples of cobalt powder were synthesized. Particle size and shape were characterized by electron microscopy and light scattering. These measures showed that the synthesized powders consisted of monodisperse spheres with average diameters ranging between 63 and 760 nm. These powders were used for the preparation of magnetorheological (MR) fluids by dispersing them in silicone oil. It was found that particle size did not have much influence on the MR response of MR fluids for average particle diameters larger than 100 nm. On the other hand, the MR response decreased appreciably when average particle diameter was diminished below 100 nm.