Effect of ball milling and moderate surface oxidization on the microwave absorption properties of FeSiAl composites

•We improve the microwave absorbing properties of FeSiAl composite via moderate surface oxidation.•The FeSiAl composite possesses inferior permittivity and superior permeability.•The minimum RL and peak frequency are −39.67 dB and 1.40 GHz at the thickness of 4 mm.•The FeSiAl composite can be applied in the low frequency (L and S band).

Commercially available irregular FeSiAl alloys were used as raw materials. The microwave absorption properties of FeSiAl/paraffin composites were improved by ball milling the alloys and moderately oxidizing their surfaces. Permittivity and permeability of the as-milled composites distinctly increased compared with those before milling. Moderate surface oxidization significantly reduced permittivity whereas permeability almost maintained its initial value compared with those of as-milled composites. Consequently, the microwave absorption properties were significantly improved. The minimum reflection loss (RL) of the absorber with 35 vol% surface-oxidated flake reached −39.67 dB at 1.40 GHz at a thickness of 4 mm. Effective microwave absorption (RL < −10 dB) was achieved within the range of 0.73–3.94 GHz at the thickness of 2–5 mm, which may be applied to the L- and S-bands.