Heterointerface engineering in porous microspheres for magnetic-dielectric balance to boost electromagnetic wave absorption

Heterointerface engineering originated from structure design is a promising approach to develop high-performance electromagnetic (EM) absorption materials but remains challenges in revealing the EM modulation mechanism. In this work, a diffusion-driven self-assemble strategy was proposed to construct porous NiFe2O4 microspheres with rich confined cavities. Followed by an in-situ vapor phase polymerization, conductive polypyrrole (PPy) layers were tightly coated on NiFe2O4 surface, building numerous ferrite-polymer heterointerfaces. Systematic investigation demonstrated that the controllable coating thickness and porous structure were crucial to regulate the component dependency EM properties and the dielectric-magnetic balance. Accordingly, these activated heterointerfaces and lattice defects inevitably produced polarization response to enhance the dielectric loss, and the confined magnetic coupling among hierarchical cavities strengthened the magnetic loss, jointly contributing to the boosted dissipation of incident EM energy. Owing to the synergy merits, optimum core–shell NiFe2O4@PPy microspheres exhibited an impressive broadband EM absorption performance with a wide effective absorption bandwidth covered 6.8 GHz at 2.62 mm. This study provides methodological guidance to design magnetic-dielectric EM absorption materials, and deciphers the mechanism of structure-interface modulated EM properties