One-pot solvothermal synthesis of Fe/Fe3O4 composites with broadband microwave absorption

Abstract In the present work, we have developed a simple and low-cost solvothermal method for the one-pot construction of the Fe/Fe 3 O 4 composites with the Fe 3 O 4 nanoparticles depositing on the surface of Fe polyhedrons. The Fe 3 O 4 content in the Fe/Fe 3 O 4 composites can be easily improved by the decrease of volume ratio of ethanol (95 vol%)/distilled water (V ethanol /V water ). The electromagnetic parameters of the Fe/Fe 3 O 4 composites (70 wt%)-paraffin mixtures are deeply depended upon the Fe 3 O 4 content. The complex permittivity is gradually decreased and the complex permeability maintain the modest value with the increase of the Fe 3 O 4 content. When the Fe 3 O 4 content is 56 wt%, the minimum reflection loss ( RL) value can reach −33 dB at a matching thickness of 1.5 mm. The optimal RL is −24.6 dB at 2 mm with the absorption bandwidth of 5 GHz and the integrated bandwidth with RL below −10 dB is 14.4 GHz in the frequency range of 3.6–18 GHz with a changeable thickness of 1.4–5 mm. Due to the double-loss characteristics of the Fe 3 O 4 nanoparticles, the wide-frequency microwave absorption properties of the Fe/Fe 3 O 4 composites at high frequency can be attributed to dipole polarization relaxation loss of the Fe 3 O 4 nanoparticles, interfacial polarization relaxation loss between Fe and Fe 3 O 4 and preferable impedance matching. This result indicates that the Fe/Fe 3 O 4 composites could be a candidate for microwave absorption field.