Magnetic‐Dielectric Heterojunctions Regulation in Ni‐MnO/C Microspheres With Tunable Electromagnetic Wave Absorption

Heterojunctions engineering is crucial for optimizing dielectric polarization and electromagnetic (EM) wave absorption, yet precise spatial control over semiconductor components in magnetic-dielectric microspheres remains challenging. Herein, super-dispersed MnO protrusions and Ni particles were confined within a carbon matrix, constructing unique Ni-MnO/C microspheres via a pyrolysis-controlled strategy. Leveraging differences in oxygen affinity, MnO protrusions and Ni particles with tunable dispersity, size, and content were systematically achieved, enabling precise regulation of dielectric behaviors and EM wave absorption. The optimized Ni-MnO/C composite achieved an outstanding minimum reflection loss of -51.49 dB and a maximum effective absorption bandwidth (EAB) of 5.20 GHz. Significantly, by further integrating the composite into metamaterial designs and heat-transfer flexible films, the EAB was dramatically broadened to 12.28 GHz, and thermal insulation was realized. This work introduces a morphological-engineering strategy that not only overcomes the dispersion-control bottleneck in heterojunctions design but also bridges the gap between microstructural tailoring and practical device applications, offering a new idea for high-performance EM wave absorption materials.