In-situ growth of core-shell ZnFeO @ porous hollow carbon microspheres as an efficient microwave absorber.

The special structure and composition are the important factors that determine the microwave absorption properties. In this study, the porous hollow carbon microsphere (PHCMS) is synthesized by the self-assembly technology, and ZnFeO particles are synthesized inside the carbon sphere by in-situ preparation with taking advantage of the porous and hollow characteristics of the carbon sphere, which prepares ZnFeO@PHCMS composite material. The composite shows good performance in terms of minimum reflection loss and absorption bandwidth. The results show that the maximum adsorption capacity of the composite is -51.43 dB at 7.2 GHz. When the thickness is 4.8 mm, the effective absorption bandwidth of RL ≤ 10 dB electromagnetic wave is 3.52 GHz. Such enhanced electromagnetic wave absorption properties of ZnFeO@PHCMS are ascribed to the suitable impedance characteristic, the dipole polarization and interfacial polarization, the multiple Debye relaxation process and strong natural resonance, multiple reflection and scattering. This work provides an approach to design effective microwave absorbers having a unique structure to enhance the microwave absorption properties.