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.