Morphology controllable urchin-shaped bimetallic nickel-cobalt oxide/carbon composites with enhanced electromagnetic wave absorption performance

The microscopic morphology of electromagnetic wave absorbers influences the multiple reflections of electromagnetic waves and impedance matching, determining the absorption properties. Herein, the urchin-shaped bimetallic nickel-cobalt oxide/carbon (NiCo2O4/C) composites are prepared via a hy-drothermal route, whose absorption properties are investigated by different morphologies regulated by changing calcination temperature. A minimum reflection loss (RLmin) of-75.26 dB is achieved at a match-ing thickness of 1.5 mm, and the effective absorption bandwidth (EAB) of 8.96 GHz is achieved at 2 mm. Multi-advantages of the synthesized NiCo2O4/C composites contribute to satisfactory absorption proper-ties. First, the interweaving of the needle-like structures increases the opportunities for scattering and multiple reflections of incident electromagnetic waves, and builds up a conductive network to facilitate the enhancement of conductive losses. Second, the carbon component in the NiCo2O4/C composites en-hances the interfacial polarization and reduces the density of the absorber. Besides, generous oxygen va-cancy defects are introduced into the NiCo2O4/C composites, which induces defect polarization and dipole polarization. In summary, the ternary coordination of components, defects and morphology led to out-standing electromagnetic wave absorption, which lightened the path for improving the electromagnetic wave absorption property and enriching the family of NiCo2O4 absorbers with excellent performance.(c) 2023 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.