Atomic Infusion Induced Reconstruction Enhancing Multifunctional Thermally Conductive Films with Robust Low‐Frequency Electromagnetic Absorption

Deterministic fabrication of highly thermally conductive composite film with satisfying low‐frequency electromagnetic (EM) absorption performance exhibits great potential in advancing the application of 5G smart electric devices but persists challenge. Herein, a multifunctional flexible film combined with hetero‐structured Fe6W6C‐FeWO4@C (FWC‐O@C) as the absorber and aramid nanofibers (ANFs) as the matrix was prepared. Driven by an atomic gradient infusion reduction strategy, the carbon atoms of absorbers can be precisely relocated from carbon shell to core oxometallate lattice and trigger in‐situ carbothermic reduction for customizing unique oxometallate‐carbide heterojunctions and deforming the surface geometrical structure. Such an atoms reconstruction process effectively regulates interface electronic structure and magnetic configuration, resulting in enhanced polarization loss from abundant heterointerfaces and crystal defects and magnetic loss from hierarchical structure endowed magnetic coupling interaction, which jointly contributes to the efficient low‐frequency EM absorption performance. Eventually, optimized FWC‐O@C microplate exhibits a broad absorption bandwidth surpassed the entire C band, and the assembled Fe6W6C‐FeWO4@C/ANF composite film also performs a high thermal conductivity over 2500% higher than that of the pure ANF. These findings provide a new insight into the atomic reconstruction affected EM properties and a generalized methodological guidance for preparing multifunctional thermally conductive composite films.