Flexible design of composite electromagnetic wave absorber made of aluminum and sendust particles dispersed in polystyrene resin

For the purpose of designing electromagnetic wave absorbers 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 the 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, The effects of the magnetic resonance caused by sendust and magnetic moments caused by sendust and aluminum on the frequency dependence of μ_r* were observed in the composite made of both sendust and aluminum. Thus, it was found that the frequency dependence of μ_r* for the composite made of sendust can be changed by adding aluminum particles in the composite made of sendust. Moreover, when each volume mixture ratio of sendust and aluminum was varied without changing the total volume mixture ratio of sendust and aluminum, the frequency dependence of μ_r* was different despite the value of ε_r*was almost the same, This result leads to a flexible design of an absorber with good absorption characteristics because the frequency dependence of μ_r* can be controlled by selecting suitable volume mixture ratio of sendust and aluminum without changing the vale of ε_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, Furthermore, the reduction in weight of an absorber could be also possible since the aluminum is low mass density.