Tunable defects and interfaces of hierarchical dandelion-like NiCo2O4 via Ostwald ripening process for high-efficiency electromagnetic wave absorption

Micromorphology of absorbent materials has always been one of the important parameters of microwave absorption performance. The adjustment of morphologic and structure can effectively enhance absorbing performance. In this work, hierarchical dandelion-like NiCo2O4(HDNCO) is prepared by solvothermal method and calcination. The effects of Ostwald ripening process on structure, morphology and absorbing performance are studied. The results indicate that structure and morphology of HDNCO have a significant effect on the absorption performance. Due to the special morphology and structure of HDNCO, the impedance matching can be improved. When Ostwald ripening process is 2 h, the reflection loss (RL) value reaches −45.08 dB at 2.1 mm, and the effective absorption bandwidth (EAB) is 3.06 GHz. Moreover, the EAB of HDNCO with Ostwald ripening time of 6 h reaches 3.68 GHz at only 1.0 mm and the EAB of HDNCO with Ostwald ripening time of 9 h is 5.78 GHz at 2.2 mm. The Ostwald ripening process changes the structure and morphology of HDNCO, which leads to improve the absorbing properties. Thus, this work has important guiding significance for the structural design of high-performance microwave absorber.