Composite electromagnetic wave absorber made of both sendust and aluminum particles dispersed in polystyrene resin

To design an electromagnetic wave absorber with good absorption properties at frequencies above 1 GHz, the frequency dependences of the relative complex permeability μ_r*, the relative complex permittivity ε_r*, and return loss were investigated for the composite made of both sendust (an alloy of Al 5%, Si 10%, and Fe 85%) and aluminum particles dispersed in polystyrene resin. It was found that the frequency dependence of μ_r* for this composite can be changed by adjusting the particle size of aluminum and the volume mixture ratio of sendust and aluminum. Therefore, a flexible design of an absorber with good absorption characteristics was proposed based on the ability to control μ_r*. The composite made of both sendust and aluminum was found to exhibit a return loss of less than -20 dB in the frequency range of not only several GHz but also around 20 GHz if appropriate volume mixture ratio and particle size were selected.