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The infertile electromagnetic (EM) attenuating behavior of carbon material makes the improvement of its performance remain a significant challenge. Herein, a facile and low‐cost strategy radically distinct from the prevalent approaches by constructing polar covalent bonds between sp2‐hybridized and sp3‐hybridized carbon atoms to introduce strong dipolar polarization is proposed. Through customizing and selectively engineering the N moieties conjugated with carbon rings, the microstructure of the as‐synthesized 2D nanosheet is gradually converted with the partial transition from sp3 carbons to sp2 carbons, where the electric dipoles between them are also tuned. Supported by the DFT calculations, a progressively enhanced sp2─sp3 C─C dipolar polarization is caused by this controllable structure evolution, which is demonstrated to contribute dominantly to the total dielectric loss. By virtue of this unduplicated loss behavior, a remarkable effective absorption bandwidth (EAB) beyond ‐10 dB of 8.28 GHz (2.33 mm) and an ultrawide EAB beyond ‐5 dB of 13.72 GHz (4.93 mm) are delivered, which upgrade the EM performance of carbon material to a higher level. This study not only demonstrates the huge perspective of sp2─sp3‐hybridized carbon in EM elimination but also gives pioneering insights into the carbon–carbon polarization mechanism for guiding the development of advanced EM absorption materials. [ABSTRACT FROM AUTHOR]

Magnetic composites have received increasing attention for electromagnetic wave absorption (EMA) applications. However, the practical EMA performance of the materials is severely hampered by mismatching impedance characteristics and finite electromagnetic attenuation capacity. Controlling the components and building the architecture fabrication is necessary to solve these issues. Herein, a series of Fe3O4, Fe3O4&Fe and Fe microspheres with flower-like hierarchical structures were constructed through a solvothermal method followed by an annealed process. This hierarchical structure and the synergy effect of dielectric dissipation and magnetic loss capacity offer Fe3O4 a perfect impedance matching, providing an excellent EMA performance of an effective absorption bandwidth (EAB) of 4.0 GHz and a reflection loss (RL) of 67.9 dB. Meanwhile, the coordination of the hierarchical structures and the multiple components endow Fe3O4&Fe composites with an EAB as wide as 5.7 GHz (9.0–14.7 GHz) and a RL as strong as 78.7 dB at 1.88 mm, which covers 75% X and 45% Ku bands. Such a remarkable lightweight and broad properties is due to the decent X band impedance matching and appropriate attenuation capacity. Therefore, this work highlights the significant of regulating the hierarchical structure and components to enhance the EMA performances. [ABSTRACT FROM AUTHOR]

To achieve highly efficient electromagnetic wave absorber, elaborately designing magnetic–dielectric Co@TiO2 microspheres with core–shell configuration are successfully constructed through a facile sequential process of liquid phase reduction–sol–gel–annealing. Owing to the core–shell configuration and the synergistic effect among magnetic and dielectric components, the annealed sample shows outstanding electromagnetic wave absorption (EMA) in X and Ku band. Impressively, a maximum reflection loss (RLmax) is reached –56.6 dB at a coating thickness of 2.3 mm with corresponding effective absorption bandwidth (EAB10) of 7.2 GHz (including 65% of Ku band and 82.5% of X band), much stronger than those of as-prepared Co (EAB10 of 1.6 GHz, RLmax of 14.6 dB) and pristine Co@TiO2 (EAB10 of 2.9 GHz, RLmax of 16.3 dB). An EAB10 covering completely the whole X and Ku band could be obtained by controlling the thickness only from 2.0 mm to 2.5 mm. The composites have both outstanding RL and wide EAB10 with the thin coating thickness, reinforcing that fabricating core–shell configuration composites is an efficient strategy to boost the EMA efficiency. [ABSTRACT FROM AUTHOR]