Preparation of magnetic cobalt fibres and their microwave properties

Abstract

A novel method for preparing short magnetic metal fibres is proposed. In this method, compounds of magnetic metal are reduced in a hot liquid polyol, and the reducing agent is the polyol itself. As the reaction takes place, a constant magnetic field is applied to induce the growth of metal fibres. Using this method, magnetic cobalt fibres of a diameter down to 1.2 µm were successfully prepared. The prepared cobalt fibres had a narrow diameter distribution and a low degree of agglomeration, and their diameters could be easily controlled by changing the reaction temperature. Using the transmission/reflection waveguide method, the complex permeability and permittivity of cobalt fibre-epoxy resin composites were measured in the frequency range of 8.2-12.4 GHz. The results of the measurements show that cobalt fibres present magnetic loss at microwave frequency, and that the microwave permeability and permittivity of cobalt fibres decrease as the diameter increases.