Synthesis of CoFe/Al₂O₃ composite nanoparticles as the impedance matching layer of wideband multilayer absorber

CoFe/Al₂O₃ composite nanoparticles were successfully prepared by hydrogen-thermally reducing cobalt aluminum ferrite. Compared with CoFe alloy nanoparticles, the permeability of CoFe/Al₂O₃ composite nanoparticles was remarkably enhanced and an improved impedance characteristic was achieved due to the introduction of insulated Al ₂O₃. A multilayer absorber with CoFe/Al₂O ₃ composite nanoparticles as the impedance matching layer and CoFe nanoflake as the dissipation layer was designed by using genetic algorithm, in which an ultrawide operation frequency bandwidth over 2.5-18 GHz was obtained. The microwave absorption performance in both normal and oblique incident case was evaluated by using electromagnetic simulator. The backward radar cross-section (RCS) was decreased at least 10 dB over a wide frequency range by covering the multilayer absorber on the surface of perfect electrical conductive plate.