Facile Synthesis of Three-Dimensional Porous Co/MnO Composites Derived from Bimetal Oxides for Highly Efficient Electromagnetic Wave Absorption

In this work, we report the synthesis of porous flower-like Co/MnO composite microspheres assembled by plentiful lamellae for microwave absorption applications. Electron microscopy observations indicated that, in the composites, Co nanoparticles with the size of 20-30 nm are uniformly distributed in the MnO matrix. We investigated the electromagnetic (EM) wave absorption properties of the Co/MnO composites with different Co proportions. When the molar ratio between Co and MnO is 2:1, the best electromagnetic wave absorption performance is achieved. Notably, the optimal reflection loss value reaches -64.2 dB at 10.9 GHz corresponding to the thickness of 2.3 mm, and the effective absorption bandwidth (RL < -10 dB) is up to 6.0 GHz with the thickness of 2.1 mm. The prominent absorption performance of the as-prepared Co/MnO composites mainly arises from the superior impedance matching behavior and strong attenuation capacity as a consequence of the synergistic effect between Co and MnO nanoparticles as well as the hierarchical structure which leads to multiple loss pathways.