Nanostructure Design and Heterojunction Regulation of NiCo ₂ O ₄ /ZnO Composites for Microwave Absorption

To address challenges in complex electromagnetic environments, the development of high-efficiency microwave absorbers has become a major research direction in electromagnetic protection. In this study, NiCo2O4/ZnO heterostructure nanocomposites were synthesized via a two-step hydrothermal method, in which ZnO nanoparticles were anchored on the needle-like surface of NiCo2O4. Compared with pure urchin-like NiCo2O4, NiCo2O4/ZnO heterostructure composites exhibited lower reflection loss and a broader effective absorption bandwidth. These improvements arise from nanoscale heterointerfaces between NiCo2O4 and ZnO, abundant oxygen vacancies, and synergistic loss mechanisms, all of which promote multiple reflections and scattering of electromagnetic waves. Specifically, NiCo2O4/ZnO-25% nano heterostructure composites achieved an RLmin of −59.45 dB at 17.14 GHz, with an extended effective absorption bandwidth of 3.8 GHz, owing to the optimized impedance matching. Furthermore, tuning the ZnO content in the NiCo2O4/ZnO heterostructure composites enables controllable frequency shifting of the microwave absorption peak across the C-, X-, and Ku-bands. This work offers a feasible strategy and experimental support for designing lightweight, high-performance microwave absorbers, and broadens the application prospects of multicomponent oxide nanocomposites in electromagnetic protection and stealth technologies.