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

Abstract

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 double-shell 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 magnetic-electric 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° 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.