Electromagnetic and microwave absorption properties of carbonyl iron and carbon fiber filled epoxy/silicone resin coatings

The microwave electromagnetic properties of carbonyl-iron particles as magnetic absorber and carbon fiber as conductive absorber filled insulating epoxy/silicone resin coatings were investigated. The complex permittivity of the coatings increased while the complex permeability remained almost constant in the frequency range of 2-18 GHz, when the carbon fiber content was increased and the carbonyl-iron content kept constant. The minimum reflection loss of the coatings shifted to the lower frequency region by increasing the carbon fiber content or coating thickness. When the content of carbonyl iron was 65 wt% and carbon fiber was 2 wt%, the reflection loss below -10 dB can obtain in the frequency range of 8-18 GHz with coating thickness being 1 mm.