Hollow and solid combined double-shell nitrogen-doped carbon-Fe3C-Fe nanospheres with tunable shell thickness and magnetic component for enhanced electromagnetic wave absorption

Previous research has fully demonstrated that the core-shell spherical structure can facilitate multiple reflection within the cavity and provide polarization relaxation at the heterogeneous interfaces. In this study, double-shell nitrogen-doped carbon-Fe3C-Fe (NC-Fe3C-Fe, referred to as CFF) nanospheres composed of hollow NC-Fe3C and solid NC-Fe3C/Fe nanospheres are synthesized in an interconnected three-dimensional structure. The doubleshell is composed of nitrogen-doped carbon outer shells and Fe3C inner shells, derived from the carbonization of polydopamine (PDA) and controllable etching of the Fe nanotemplates in the PDA@Fe. In this strategy, the carbon shells provide dielectric loss, and the Fe3C and Fe contribute to magnetic loss, bringing about a magneticelectric synergistic effect on effective electromagnetic wave absorption (EMA). By adjusting the thickness of the carbon shells and the etching time of the Fe, the CFF achieves a minimum reflection loss of -74.00 dB at a thickness of 1.91 mm, with an effective absorption bandwidth of 5.04 GHz. In addition, by the radar cross-section (RCS) scattering simulation, the RCS value at a scattering angle of 0 degrees decreased by 32.06 dBm2, confirming an excellent EMA capability in practical far-field applications. This study provides an effective strategy for the application of core-shell and double-shell structures in the EMA materials.