Waxberry-like hierarchical Ni@C microspheres with high-performance microwave absorption†
The rational design of the microstructure of magnetic carbon-based composites has become a popular strategy to enhance their microwave absorption properties. Herein, with Ni-containing metal–organic framework as the self-sacrificing precursor, we have successfully prepared waxberry-like Ni@C microspheres as novel microwave absorbing materials, which artfully integrated the advantages of core–shell configuration and hierarchical architecture. The effects of the pyrolysis temperature on the microstruture, carbon content, relative graphitization degree, magnetic properties, and electromagnetic parameters were carefully investigated. The composite that was pyrolyzed at 700 °C (Ni@C-700) exhibited desirable microwave absorption performance, including a strong reflection loss intensity of −73.2 dB and a broad qualified bandwidth of 4.8 GHz with an applied thickness of 1.8 mm. The electromagnetic analysis revealed that such good performance of Ni@C-700 was benefited from both the well-matched impedance and decent attenuation ability. The superiority of this unique microstruture was also validated by comparing it with some homologous composites and isolated core–shell Ni@C nanoparticles. It is believed that these results may provide a new pathway to promote the electromagnetic applications of conventional magnetic carbon-based composites by optimizing their microstructure.