Facile solvothermal synthesis of novel hetero-structured CoNi–CuO composites with excellent microwave absorption performance

Hetero-structured functional materials with tailored composition that can provide excellent electromagnetic wave (EMW) absorption with minimal thickness are highly desirable, especially if they can be easily fabricated. Herein, novel hetero-structured CoNi–CuO composite microspheres were fabricated via a facile solvothermal process. The composites with adjusted mass ratios of CuO to CoNi alloy (5/1, 2.5/1 and 1.25/1) were facilely achieved by modulating the quantity of CuCl2·2H2O during the synthesis. It was demonstrated that the enhanced microwave absorption properties could be ascribed to the dielectric CuO, which can favorably increase the interface of the hetero-structure and the impedance matching with CoNi alloyed particles. It was shown that, when the molar ratio was 2.5 : 1, the typical CoNi–CuO composite microspheres presented a promising microwave absorption performance, namely a maximum reflection loss (RL) of −25.1 dB at 13.2 GHz with a thickness of only 2.5 mm, while the effective microwave absorption bandwidth (RL < −10) could reach 3.4 GHz (from 10.0 to 13.4 GHz). As is demonstrated, this kind of newly fabricated CoNi–CuO composite can be regarded as a promising candidate for high-performance microwave absorption materials.