Tunable dielectric gradient Fe-NC@TiO2 core-shell absorbers: Synergistic interfacial polarization and impedance matching

Porous carbon materials demonstrate significant potential in electromagnetic wave absorption (EMWA). However, precisely tailoring their composition and microstructure remains a major challenge in developing high-performance electromagnetic wave absorbers. Here, a core-shell Fe-NC@TiO 2 nanocomposite with a dielectric gradient structure is presented, designed to effectively regulate dielectric properties and enhance electromagnetic wave absorption. A combined strategy of hydrothermal synthesis and chemical deposition was developed to achieve the in-situ coating of TiO 2 onto MOFs. Subsequently, a pyrolysis strategy was employed to construct core-shell Fe-NC@TiO 2 nanocomposites. Pyrolysis temperature was used to achieve tunable TiO 2 crystallization while maintaining core-shell architecture. The results indicate that the pyrolysis at 800 °C induces a phase transformation of TiO 2 shell from anatase to rutile, resulting in a high dielectric constant. The core-shell structure effectively optimizes the dielectric dispersion characteristics and impedance matching while improving attenuation performance. The Fe-NC@TiO 2 –800 nanocomposites achieved an effective absorption bandwidth (EAB) of 4.93 GHz at 1.47 mm thickness with 30 wt% filler loading, while simultaneously obtained a remarkable minimum reflection loss ( RL min ) of −50.51 dB at 2.05 mm. This work offers novel insights into the structural design of core-shell nanocomposites with tunable electromagnetic properties and has a broad application prospect in the field of EMWA.