Catalytically tuned Bi 2 Fe 4 O 9 –polypyrrole heterostructures: multifunctional electromagnetic wave absorbers with enhanced stealth and thermal camouflage

Abstract The rational design of composition and microstructure is a proven strategy for developing multifunctional high‐performance electromagnetic wave (EMW) absorbers. In this study, a sandwich‐structured multilayer nanoplate‐like Bi 2 Fe 4 O 9 @Polypyrrole (BFO@PPy) heterostructure was successfully designed and fabricated using an efficient microwave hydrothermal method and an in situ polymerization process. Specifically, Bi 2 Fe 4 O 9 enhances the chemical activity of ammonium persulfate, which in turn initiates the polymerization of pyrrole monomers, resulting in the formation of BFO@PPy heterostructures. The thickness of the PPy coating layer in the BFO@PPy composite can be precisely controlled at the nanoscale, optimizing electromagnetic parameters, conduction losses and interface polarization loss. The fabricated BFO@PPy composite achieves a minimum reflection loss (RL min ) of −57.8 dB at a thickness of 2.5 mm and an effective absorption bandwidth (EAB) of 6.96 GHz. Furthermore, the EMW absorption performance and mechanism were systematically validated through theoretical calculations, radar cross‐sectional simulations (RCS), and first‐principles analysis. Notably, the RCS simulation of a 1:1 scale F‐22 Raptor fighter model provides a realistic evaluation of the composite’s EMW absorption potential in military applications. The efficient fabrication method and superior electromagnetic absorption performance make BFO@PPy a promising candidate for use in complex electromagnetic environments and military domains. Additionally, the BFO@PPy composite exhibits rapid electrothermal conversion at a low voltage (3 V), achieving active infrared camouflage within a controllable temperature range, further highlighting its multifunctional properties.