New magnetorheological fluids based on magnetic fibers

In this work, we report the synthesis under the presence of external magnetic fields of two types of magnetic microfibers: (i) cobalt wires; and (ii) rigid filaments of chemically linked iron microspheres. Optical microscopy and scanning electron microscopy (SEM) were used for characterizing their shape and size. The effect of magnetic field intensity, mixing frequency and reagent concentration on the final size of the fibers was investigated. The particles were also characterized by means of energy dispersive X-ray spectroscopy (EDX). The magnetization curves of both the cobalt wires and the iron filaments were obtained and compared with those of cobalt spheres and iron spheres respectively. Finally, these magnetic fibers were used for the preparation of new smart composites by dispersing them in a liquid carrier. Interestingly, the suspensions of cobalt wires show a remarkable increase in the yield stress when compared to conventional (based on spherical particles) magnetorheological fluids.