Enhanced microwave absorption capacity of hierarchical structural MnO2@NiMoO4 composites
Hierarchical hybrid nanostructures are desirable materials for microwave absorption (MA) capacity. However, how to obtain this kind of versatile structural materials still remains a great challenge. In this work, a novel MA composite of MnO2@NiMoO4 was synthesized via two-step hydrothermal processes combined with a simple annealing process. As confirmed by X-ray diffraction, scanning electron microscopy, energy-dispersive spectrometry, and transmission electron microscopy analysis, the well-defined NiMoO4 nanosheets could uniformly cover the surface of the MnO2 nanorods. Compared with pure MnO2 nanorods, these hierarchical composite structures could provide a higher superficial area, and more effective components, which will favor the penetration of microwaves into the absorber effectively instead of reflecting it, and then translate it into thermal energy. The minimum reflection loss (RL) value of MnO2@NiMoO4 composites was −31.4 dB at 11.2 GHz with a thickness of 3 mm, and the band of reflection loss was below −10 dB when frequency was in the range from 9.6 to 14.1 GHz. However, the minimum RL value of MnO2 was only −12.5 dB at 10.4 GHz with a thickness of 3 mm. The significantly enhanced microwave absorption of MnO2@NiMoO4 composites is mainly attributed to the hierarchical hybrid nanostructures, multi-effective components, good impedance matching, and interfacial polarization between MnO2 and NiMoO4. Meanwhile, the surface attached NiMoO4 is useful to increase the multiple reflection of electromagneticwaves. It is believed that these MnO2@NiMoO4 composites could serve as an excellent microwave absorber in practical applications.
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