Synergistic dual-gradient Janus aerogels for absorption-dominant EMI shielding and infrared stealth

Advanced electromagnetic protection requires both efficient wave attenuation and reduced reflection to suppress secondary radiation. Here, we report a Janus aerogel composite (J-EMI) consisting of a polyimide (PI)-based dual-gradient absorption layer and a dense Ti 3 C 2 T x MXene reflective layer. The dual-gradient layer (DGL-3) comprises opposing gradients of magnetic Fe 3 O 4 nanoparticles and conductive polypyrrole (PPy), which together improve impedance matching and attenuation capability. Owing to the conductive-magnetic coupling in this structure, DGL-3 shows an attenuation constant of 739 Np m −1 . The resulting J-EMI composite achieves a shielding effectiveness (SE t ) of 67.2 dB at a thickness of 800 μm (±50 μm). The Janus structure reduces front-face reflection and exhibits absorption-dominant shielding behavior with an absorption-to-reflection (A/R) ratio of 1.27 through an absorb-reflect-reabsorb process. In addition, the porous framework provides a low thermal conductivity of 0.02 W m −1 K −1 , enabling infrared stealth and thermal insulation. The composite also supports Joule heating for rapid de-icing within 60 s and retains over 94% of its shielding performance after exposure to thermal shock (−196 to 600 °C) and corrosive chemical environments. This work presents a Janus dual-gradient design that integrates EMI shielding, thermal management, and environmental stability in a lightweight aerogel system.