Carbon spheres@MnO₂ core-shell nanocomposites with enhanced dielectric properties for electromagnetic shielding

Carbon spheres (CS)@MnO₂ core-shell nanocomposites, with MnO₂ nanoflakes uniformly coating at the surface of CS cores, were successfully synthesized by a facile water-bathing method. MnO₂ amounts is estimated to be 24.7 wt% in CS@MnO₂ nanocomposites. A high dielectric loss value and an electromagnetic shielding effectiveness of 16‒23 dB were observed for the CS@MnO₂ in the frequency range of 8‒18 GHz, which is mainly attributed to the enhanced absorption loss. The incorporation of the CS with MnO₂ improves the electrical conductivity. Meanwhile, the electromagnetic impendence matching has been significantly ameliorated. Moreover, the increasing interfaces between the CS and MnO₂ facilitate the microwave attenuation as well. Thus, the electromagnetic shielding performances were greatly enhanced. Our findings provide an effective methodology for the synthesis of the CS@MnO₂ core-shell nanocomposite for potential electromagnetic applications.