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, NiCo 2 O 4 /ZnO heterostructure nanocomposites were synthesized via a two-step hydrothermal method, in which ZnO nanoparticles were anchored on the needle-like surface of NiCo 2 O 4 . Compared with pure urchin-like NiCo 2 O 4, NiCo 2 O 4 /ZnO heterostructure composites exhibited lower reflection loss and a broader effective absorption bandwidth. These improvements arise from nanoscale heterointerfaces between NiCo 2 O 4 and ZnO, abundant oxygen vacancies, and synergistic loss mechanisms, all of which promote multiple reflections and scattering of electromagnetic waves. Specifically, NiCo 2 O 4 /ZnO-25% nano heterostructure composites achieved an RL min 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 NiCo 2 O 4 /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.