Structure and microwave-absorbing properties of Fe-particle containing alumina prepared by micro-arc discharge oxidation

Alumina films containing Fe particles were produced on aluminum alloy substrates by micro-arc oxidation with additive Fe particles in the electrolyte. The permittivity–frequency and permeability–frequency properties were determined in the microwave frequency regime of 6.5–18 GHz by vector network analysis. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray fluorescence (XRF) were employed to investigate the microstructures and compositions. Our results show that about 16.16 wt.% Fe particles are embedded in the alumina films and the acquired complex permittivity and permeability values match the microwave frequency. When the matching thickness is 2 mm, the minimum RL values are − 10.5 dB at 9.6 GHz and − 9.1 dB at 16.3 GHz. The results suggest a new design of microwave absorbers based on electromagnetic wave-absorbing materials that eliminate the use of a mixture of agglutinants in the preparation.