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/Fe3O4 composites with the Fe3O4 nanoparticles depositing on the surface of Fe polyhedrons. The Fe3O4 content in the Fe/Fe3O4 composites can be easily improved by the decrease of volume ratio of ethanol (95 vol%)/distilled water (Vethanol/Vwater). The electromagnetic parameters of the Fe/Fe3O4 composites (70 wt%)-paraffin mixtures are deeply depended upon the Fe3O4 content. The complex permittivity is gradually decreased and the complex permeability maintain the modest value with the increase of the Fe3O4 content. When the Fe3O4 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 Fe3O4 nanoparticles, the wide-frequency microwave absorption properties of the Fe/Fe3O4 composites at high frequency can be attributed to dipole polarization relaxation loss of the Fe3O4 nanoparticles, interfacial polarization relaxation loss between Fe and Fe3O4 and preferable impedance matching. This result indicates that the Fe/Fe3O4 composites could be a candidate for microwave absorption field.