Fabrication of NiO/NiCo(2)O(4) Mixtures as Excellent Microwave Absorbers

The NiO/NiCo(2)O(4) mixtures with unique yolk-shell structure were synthesized by a simple hydrothermal route and subsequent thermal treatment. The elemental distribution, composition, and microstructure of the samples were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and scanning electron microscope (SEM), respectively. The microwave absorption property was investigated by using vector network analysis (VNA). The results indicated that the excellent electromagnetic wave absorption property of the NiO/NiCo(2)O(4) mixtures was achieved due to the unique yolk-shell structure. In detail, the maximum reflection loss (RL) value of the sample reached up to − 37.0 dB at 12.2 GHz and the absorption bandwidth with RL below − 10 dB was 4.0 GHz with a 2.0-mm-thick absorber. In addition, the NiO/NiCo(2)O(4) mixtures prepared at high temperature, exhibited excellent thermal stability. Possible mechanisms were investigated for improving the microwave absorption properties of the samples. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s11671-019-2988-9) contains supplementary material, which is available to authorized users.