Synthesis of chain-like ɑ-Fe/Fe₃O₄ core/shell composites exhibiting enhanced microwave absorption performance in high-frequency under an ultrathin matching thickness

Coaxial heterogeneous chain-like ɑ-Fe/Fe₃O₄ composites were synthesized by a facile two-step solvothermal method. The ɑ-Fe nanochains were first obtained by a simple liquid phase reduction process, and the ɑ-Fe/Fe₃O₄ core/shell composites were prepared by subsequent oxidation process. The electromagnetic properties of ɑ-Fe/Fe₃O₄ core/shell composites were measured with the coaxial reflection/transmission technique at 1.0–18.0 GHz. The ɑ-Fe/Fe₃O₄ core/shell composites have an optimal absorption peak value of about − 25.6 dB at 16.3 GHz and its effective absorption bandwidth lower than − 10 dB reaches 3.6 GHz (from 14.4 to 18.0 GHz). Importantly, the optimal absorption peak matching thickness of the absorber is only 0.8 mm. The enhanced microwave absorption performance is mainly originated from good impedance matching, which is related to low conductivity and magnetic loss of the coaxial heterogeneous chain-like ɑ-Fe/Fe₃O₄ core/shell composites. The reflection loss results indicate that the ɑ-Fe/Fe₃O₄ core/shell composites with thin thickness, wide absorption bandwidth and strong absorption characteristics can be used as excellent microwave absorption material in the high-frequency region.