Urchin-like Amorphous Nitrogen-Doped Carbon Nanotubes Encapsulated with Transition-Metal-Alloy@Graphene Core@Shell Nanoparticles for Microwave Energy Attenuation

Herein, we report three-dimensional (3D) urchin-like amorphous nitrogen-doped CNT (NCNT) arrays with embedded cobalt-nickel@graphene core@shell nanoparticles (NPs) in the inner parts of NCNTs (CoNi@G@NCNTs) for highly efficient absorption toward microwave (MW). The CoNi NPs are covered with about seven layers of graphene shell, resulting in the formation of CoNi@G core–shell structures. In the meanwhile, the CoNi@G core–shell NPs are further encapsulated within NCNTs. Benefitting from the multiple scattering of the unique 3D structure toward MW, cooperative effect between magnetic loss and dielectric loss, and additional interfacial polarizations, the 3D urchin-like CoNi@G@NCNTs exhibit excellent MW energy attenuation ability with a broad absorption bandwidth of 5.2 GHz with a matching thickness of merely 1.7 mm, outperforming most reported absorbers. Furthermore, the chemical stability of the 3D urchin-like CoNi@G@NCNTs is improved greatly due to the presence of the graphene coating layers and outmost NCNTs, facilitating their practical applications. Our results highlight a novel strategy for fabrication of 3D nanostructures as high-performance MW-absorbing materials.