Optimization of Fe@Ag core–shell nanowires with improved impedance matching and microwave absorption properties

Abstract

Ag-coated Fe (Fe@Ag) core–shell nanowires (NWs) with enhanced electromagnetic wave absorption were successfully synthesized by the liquid-phase reduction method and the layer-plus-island growth mode. Changing the molar ratio of Fe to Ag controlled the Ag shell thickness to produce different impedance matching and attenuation constants of the Fe@Ag core–shell NWs. The Fe@Ag core–shell NWs with a Fe:Ag ratio of 2:1 significantly improved optimal microwave absorption performance as compared to raw Fe NWs. At a mass fraction of 25%, the minimum reflection loss (RLmin) can reach − 58.69 dB at 7.53 GHz with a matching absorber thickness of 3.36 mm. In addition, the effective absorption bandwidth (EAB, RL ≤ − 10 dB) can be extended to 7.32 GHz, to cover the majority of the C and X bands. Three major aspects contribute to the superior microwave absorption performance: the complementary effect of the polarization of Fe-Ag interface, the impedance matching improvement stems from a proper eddy current, and the small-scale effect caused by a one-dimensional structure. This study demonstrates the promising high-efficiency microwave absorbing capabilities of Fe@Ag core–shell NWs for future use in practical applications.