Double-layer microwave absorber based on nanocrystalline Zn0.5Ni0.5Fe2O4/α-Fe microfibers

The microwave absorption properties of the nanocrystalline NiZn ferrite (Zn0.5Ni0.5Fe2O4) and iron (alpha-Fe) microfibers with single-layer and double-layer structures were investigated in the frequency range of 2-18 GHz. The double-layer absorbers have much better microwave absorption properties than the single-layer absorbers, and the microwave absorption properties of the double-layer structure are influenced by the coupling interactions between the absorbing layer and matching layer. With the absorbing layer thickness 0.7 mm of alpha-Fe microfibers-wax composite and the matching layer thickness 1.5 mm of Zn0.5Ni0.5Fe2O4 microfibers-wax composite, the minimum reflection loss (RL) reaches about -71 dB at 16.2 GHz and the absorption band width is about 9.2 GHz ranging from 8.8 to 18 GHz with the RL value exceeding -10 dB. While, when the absorbing layer is the Zn0.5Ni0.5Fe2O4 microfibers-wax composite with thickness 1.8 mm and the matching layer is the alpha-Fe microfibers-wax composite with thickness 0.2 mm, the RL value achieves the minimum about -73 dB at 13.8 GHz and the absorption band width is about 10.2 GHz ranging from 7.8 to 18 GHz with the RL value exceeding -10 dB, which covers the whole X-band (8.2-12.4 GHz) and K-u-band (12.4-18 GHz). (C) 2011 Elsevier Ltd. All rights reserved.