Construction of ZnO/Ni@C hollow microspheres as efficient electromagnetic wave absorbers with thin thickness and broad bandwidth

Ingenious microstructure design and rational composition collocation have been proved to be an effective strategy for developing efficient electromagnetic wave (EMW) absorbers. It would be promising to fabricate a hollow structured composite integrating multiple loss mechanisms (conduction, magnetic, and polarization losses) for excellent EMW absorption. Herein, a novel dielectric-magnetic compound of ZnO/Ni@C hollow microsphere was prepared through hydrothermal reactions followed by an in-situ chemical vapor deposition (CVD). In this ternary composite, abundant ZnO/Ni heterostructures formed the hollow microsphere skeletons and provided unique Schottky junctions, which endowed the composite with improved impedance matching and strong polarization loss. Meanwhile, the amorphous-polycrystalline carbon layer deposited on the surface of each microsphere enhanced the conduction and interfacial polarization losses. In addition, the magnetic Ni nanoparticles induced magnetic loss. Benefiting from the synergistic effect of the hollow structure and multiple loss mechanisms, the ternary composite exhibits an effective absorption bandwidth as wide as 6.55 GHz at a thickness of only 1.85 mm, accompanied by a minimum reflection loss of –39.8 dB. Besides, the radar cross-section and the electromagnetic field simulation further verify the superior EMW absorption performance of the composites. Our work provides a new reference for the fabrication of dielectric-magnetic ternary hollow microspheres as EMW absorbers with thin thickness and broad bandwidth.