Three-layer structure microwave absorbers based on nanocrystalline alpha-Fe, Fe0.2(Co0.2Ni0.8)0.8 and Ni0.5Zn0.5Fe2O4 porous microfibers.

The three-layer structure microwave absorbers with thickness of 2 mm were designed based on nanocrystalline alpha-Fe, Fe0.2(Co0.2Ni0.8)0.8 and Ni0.5Zno.sFe204 porous microfibers with diameters about 2-5 microm. The electromagnetic parameters and microwave absorption properties were investigated by vector network analyzer in the frequency range of 2-18 GHz. The results show that the three-layer structure microwave absorbers display stronger absorption properties in a wide frequency range than the single-layer and double-layer microwave absorber. For the three-layer structure, the microwave absorption properties are mainly influenced by the microfibers layer arrangement order, total thickness and each layer thickness. When the Ni0.5Zn0.5Fe2O4 porous microfibers layer is arranged as the impedance-matching surface layer, with a total thickness of 2 mm consisting of 0.7 mm thick alpha-Fe porous microfibers inner layer, 0.9 mm thick Fe0.2(Co0.2Ni0.8)0.8 porous microfibers medium layer and 0.4 mm thick impedance-matching surface layer, the three-layer structure has a strongest microwave absorption of 45.7 dB at 12.8 GHz, the absorption bandwidth (with RL < -10 dB ) of 10.2 GHz from 7.8 GHz to 18 GHz and bandwidth (with RL < -20 dB) of 4.4 GHz from 11.1 GHz to 15.5 GHz respectively. This three-layer structure is promising microwave absorbers to meet the requirements of thin thickness, light weight and wide band for military and civil applications.