Facile synthesis of urchin-like ZnO hollow spheres with enhanced electromagnetic wave absorption properties

Urchin-like ZnO hollow spheres were synthesized by a simple hydrothermal method and their electromagnetic and microwave absorbing properties were investigated. The enlarged SEM image shows that as-prepared ZnO precursor is composed of randomly close-packed porous nanosheets. On the contrary, well-crystallized ZnO spheres are obtained after calcination. The TEM images provide further insight into the detailed structure, showing the typically urchin-like and hollow morphology of ZnO calcined at 500 °C. The SAED pattern clearly demonstrates the single-crystalline feature of urchin-like ZnO hollow spheres. It can be found that the urchin-like ZnO calcined at 500 °C exhibit relatively higher EM wave absorption properties than others. The maximum RL is up to -20 dB at 14.3 GHz and the EM wave absorption shows dual peaks with increasing thickness.