Preparation of magnetic cobalt fibres and their microwave properties

A novel method for preparing short magnetic metal fibres is proposed. In th is 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 held is applied to induce the growth of metal fibres. Us ing this method, magnetic cobalt fibres of a diameter down to 1.2 mum were successfully prepared. The prepared cobalt fibres had a narrow diameter dis tribution and a low degree of agglomeration, and their diameters could be e asily controlled by changing the reaction temperature. Using the transmissi on/reflection waveguide method, the complex permeability and permittivity o f 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 pr esent magnetic loss at microwave frequency, and that the microwave permeabi lity and permittivity of cobalt fibres decrease as the diameter increases.