Synthesis of 3D flower-like ZnO/ZnCo2O4 composites with the heterogeneous interface for excellent electromagnetic wave absorption properties.

Reasonable structure and composition are essential for electromagnetic wave absorption (EMW). Herein, ZnO hollow spheres were prepared with carbon spheres as templates and then synthesized ZnO/ZnCo2O4 composites by the solvothermal method and annealing treatment. The flower-like ZnCo2O4 material was produced by self-assembly of ZnCo2O4 nanosheets. The absorbing material with the complex structure has multiple scattering and reflection, conduction loss, resonance, and eddy current loss characteristics. Furthermore, the addition of ZnO hollow spheres has a significant impact on electromagnetic parameters and absorption properties. As a result, the addition of ZnO hollow spheres can greatly enhance the complex permittivity of the ZnO/ZnCo2O4 composites and obtain excellent EMW absorbing properties. It is worth noting that ZnO/ZnCo2O4 composites show the best EMW absorption properties when the ZnO hollow spheres were added up to 5 mg. The minimum reflection loss is -55.42 dB and a matching thickness of 1.99 mm while the maximum effective absorption bandwidth can also reach 7.44 GHz with a matching thickness of 2.4 mm. Our research can prove that the structure and composition have a significant influence on the properties of the absorbing material, which provides ideas for the development of absorbing materials with high-performance.