Facile synthesis of hierarchical chrysanthemum-like copper cobaltate-copper oxide composites for enhanced microwave absorption performance

Abstract Hierarchical chrysanthemum-like CuCo 2 O 4 -CuO composites were successfully synthesized by a facile one-pot hydrothermal method after calcination at 500 °C. Based on the results of X-ray diffraction (XRD), Raman spectra, thermogravimetric analysis (TGA) and transmission electron microscope (TEM), we found that not only the morphology (from 2 dimensional to 3 dimensional) but also the crystalline structure (Cu 0  + Cu 2 O + CoO x  → CuO + CuCo 2 O 4 ) of the samples could be tuned by the calcination temperature. The existed interfaces of CuCo 2 O 4 -CuCo 2 O 4 , CuCo 2 O 4 -CuO, and CuO-CuO played a key role on the attenuation of electromagnetic waves. The effective absorption frequency bandwidth is up to 4.02 GHz with a matched thickness of 2.8 mm. The CuCo 2 O 4 -CuO/paraffin composites can even exhibit bigger effective frequency bandwidth (from 4.02 to 4.65 GHz) if we turn the incident angle of electromagnetic (EM) wave to a proper value ( i.e. , 45°). We believe that the hierarchical chrysanthemum-like CuCo 2 O 4 -CuO composites can be a good candidate for the high-performance Co-based spinel microwave absorbers.