Integrating Sulfur Doping with a Multi‐Heterointerface Fe₇S₈/NiS@C Composite for Wideband Microwave Absorption

Abstract

Heterointerface engineering is presently considered a valuable strategy for enhancing the microwave absorption (MA) properties of materials via compositional modification and structural design. In this study, a sulfur‐doped multi‐interfacial composite (Fe7S8/NiS@C) coated with NiFe‐layered double hydroxides (LDHs) is successfully prepared using a hydrothermal method and post‐high‐temperature vulcanization. When assembled into twisted surfaces, the NiFe‐LDH nanosheets exhibit porous morphologies, improving impedance matching, and microwave scattering. Sulfur doping in composites generates heterointerfaces, numerous sulfur vacancies, and lattice defects, which facilitate the polarization process to enhance MA. Owing to the controllable heterointerface design, the unique porous structure induced multiple heterointerfaces, numerous vacancies, and defects, endowing the Fe7S8/NiS@C composite with an enhanced MA capability. In particular, the minimum reflection loss (RLmin) value reached −58.1 dB at 15.8 GHz at a thickness of 2.1 mm, and a broad effective absorption bandwidth (EAB) value of 7.3 GHz is achieved at 2.5 mm. Therefore, the Fe7S8/NiS@C composite exhibits remarkable potential as a high‐efficiency MA material owing to the synergistic effects of the polarization processes, multiple scatterings, porous structures, and impedance matching.

In Situ Growth of CoNi Alloy/N-Doped Hollow Carbon Foam for Electromagnetic Wave Absorption

“…The hollow three-dimensional structure can effectively reduce the quality of the sample, and the rich interface composed of the NCF and CoNi alloy promotes multiple reflections and refractions of electromagnetic waves, promoting EMA. The air in these gaps was used to adjust the dielectric constant, thereby achieving better impedance matching . The heterogeneous interface formed by CoNi and NCF led to an uneven distribution of positive and negative space charges, resulting in the formation of macroscopic dipole moments, which could lead to interface polarization losses .…”

“…The air in these gaps was used to adjust the dielectric constant, thereby achieving better impedance matching. 37 The heterogeneous interface formed by CoNi and NCF led to an uneven distribution of positive and negative space charges, resulting in the formation of macroscopic dipole moments, which could lead to interface polarization losses. 38 Under the effect of the applied magnetic field, the composite material generated induced current at better conductivity, which was conducted on the three-dimensional conductive network composed of NCF, thus generating transmission loss, and the doping of N atoms and the presence of defects in the carbon foam were induced to oscillate and generate dipole polarization.…”

Self-Assembled Heterojunction Interfaces between g-C3N4 and rGO Nanosheets for Enhanced Electromagnetic Wave Absorption

“…Freeze-drying is used to build a three-dimensional porous network structure, which increases the scattering and reflection of electromagnetic waves inside the material and enhances the loss mechanism. 54,55 When the filling ratio is 30% and the thickness is 3 mm, the maximum effective absorption bandwidth of C-G-0.5 reaches 8.08 GHz, and the minimum reflection loss is −38.07 dB. Meanwhile, in order to verify that the heterojunction interfaces and the impedance matching properties play a role in the composites, we annealed the material, and the performance of the material decreased after annealing.…”