Electromagnetic microwave absorption of Fe-Si flakes with different mixtures

Flakes of Fe-Si alloy were fabricated to get a relatively high permeability. Additives of graphene, TiO2 and ZnO were mixed with the Fe-Si flakes. The magnetic properties of the Fe-Si alloy flakes were slightly affected by mixing, causing little decrease of the complex permeability. But the complex permittivity was significantly reduced due to the enhanced interfacial resistivity after mixing with graphene, TiO2 or ZnO, resulting in a better electromagnetic impedance matching. The best microwave absorption performance was achieved by mixing TiO2: for an absorber thickness of 1.5 mm, a minimum reflection loss (RL) of −14.1 dB was obtained at 7.1 GHz with a large width of 3.6 GHz in which the RL is lower than −10 dB; with the absorber thickness of 2.4 mm, the minimum RL reaches −35.3 dB at 4.2 GHz. The different effects among graphene, TiO2 and ZnO additives on the electromagnetic properties are mainly related to the morphology of the additives rather than their intrinsic characteristics.