Magnetic crystallite-decorated hollow multi-cavity carbon nanosheet spheres for superior electromagnetic absorption

Abstract

Carbonaceous-magnetic composites have emerged as the most attractive absorbers in recent years, and creating hierarchically porous structures in composites is generally considered an indispensable strategy to enhance overall performance. Herein, we design a series of carbonaceous-magnetic composites with superior electromagnetic absorption performance. Via simple spray-drying of a solution containing metal/carbon precursors and a water-removal salt template (i.e., NaCl), the as-made materials feature a complex hierarchical architecture with a hollow interior and a multi-cavity shell, which is assembled from ultrathin carbon nanosheets decorated with magnetic crystallites. The proposed method is generally applicable and can integrate various magnetic crystallites (e.g., Fe3O4, Ni, FeCo, and CoFe2O4) into hollow multi-cavity carbon spheres. The optimal Fe3O4-based absorber achieves effective absorption bandwidth (7.7–13.4 GHz) covering the entire X band and excellent electromagnetic attenuation capability (−51.1 dB) with a thin thickness of 2.7 mm. Furthermore, a simulation demonstrates that an absorbing coating with the optimal absorber enables remarkably reduced radar cross section lower than −10 dBm2 over the whole measurement range. These results indicate that proposed microwave absorbing materials have practical feasibility in civilian and military stealth applications.