Constructing heterogeneous conductive network with core-shell Ag@Fe3O4 for dual-band effective microwave absorption

The compatibility of effective microwave absorption for low and middle frequency range is still a huge challenge, which restricts the application prospect in the multi-band electromagnetic environment. To tackle the issue, the core-shell structured Ag@Fe3O4 composites are proposed in this work to construct heterogeneous conductive network, suppressing the conductive capacity and improving the interfacial polarization. The dominant contribution of polarization to the permittivity accelerates the decrease of quarter-wavelength thickness with frequency, which induces identical theoretical matching thickness over 2–18 GHz with the integral order of n = 1 to n = 3. Combined with strong magnetic loss and appropriate dielectric loss, the Fe3O4/Ag composites finally reveal excellent absorption properties at both 2–12 GHz and 15–18 GHz bands. By adjusting the core radius and shell thickness, the sample with Fe3O4/Ag molar ratio of 3:1 achieves the broadest absorption bandwidth of 5.08 GHz, covering both 3.5–7.1 GHz and 16.6–18.0 + GHz. The CST simulations further confirm the RCS reduction of Ag@Fe3O4 composites for practical application. The findings open a new avenue to develop competitive absorbers that can cope with multiband electromagnetic waves.