Construction of hierarchical yolk-shell Fe@SiO2@NC composites with dual impedance matching layers and dual built-in electric fields for efficient electromagnetic wave absorption

Abstract

The composites prepared by combining lightweight carbon materials with magnetic metals have demonstrated excellent dielectric and magnetic properties, indicating potential applications in the field of electromagnetic wave (EMW) absorption. However, the rational microstructure design and component optimization of these composites in regulating their magnetic-dielectric balance to achieve high-performance EMW absorption remains challenging. Herein, hierarchical yolk-shell Fe@SiO₂@NC composites with dual impedance matching layers and dual built-in electric fields were prepared by self-template aggregation and in situ reduction strategies. The introduction of a SiO₂ wave-transparent layer into a conventional dielectric-magnetic system has resulted in the successful realization of nanoscale precise impedance matching regulation in absorbers, thereby enabling effective ultra-wideband EMW absorption. The dual impedance matching layers of the internal void layer and the SiO₂ wave-transparent layer facilitate multiple scattering and reflection of EMWs within the absorbers, and the dual built-in electric fields of Fe/SiO₂ and SiO₂/NC can effectively enhance interfacial polarization effect to attenuate EMWs. The predominantly optimized Fe@SiO₂@NC-2 exhibits an ultra-wide effective absorption bandwidth (EAB) of 7.10 GHz and an impressive minimum reflection loss (RL_min) of −64.83 dB, indicating that optimizing the impedance matching via quantitative design can maximize the EMW absorption performance. This work provides a straightforward yet effective approach for constructing multi-component materials with hierarchical yolk-shell structure, which offers valuable insight into the microstructure design and component optimization of innovative EMW absorption materials.