Multilayer Polyimide/MXene/Ni Aerogels with Controlled Alignment for Broadband Electromagnetic Absorption and Multifunctional Protection.

Rationally coupling nanoscale material design with macroscopic architecture is crucial for achieving lightweight absorbers with broadband and strong electromagnetic (EM) wave attenuation. Herein, multiscale-engineered polyimide (PI)/MXene/Ni aerogels integrating magnetic Ni nanochains, dielectric MXene sheets, and anisotropic porous architectures are reported. Ni nanochains with controlled morphology were synthesized via NaOH-assisted hydrazine reduction, while directional freezing enabled the fabrication of random, parallel, and normal aerogel architectures. The normal-aligned PI/MXene/Ni aerogel exhibits a remarkable minimum reflection loss (RLmin) of -72.42 dB at 2.8 mm. Guided by a genetic-algorithm optimization, tri-layer assemblies further expand the effective absorption bandwidth (EAB) to 8.4 GHz while maintaining an outstanding RLmin of -61.69 dB. The superior absorption originates from synergistic dielectric-magnetic-structural losses, including interfacial polarization, ohmic/eddy-current dissipation, and gradient impedance matching enabled by the layered porous framework. Beyond EM attenuation, the aerogels feature ultralow density, high compressive strength, enhanced hydrophobicity, intrinsic flame retardancy, and low thermal conductivity, providing effective infrared stealth and thermal protection. This work demonstrates a multiscale design strategy to create multifunctional, broadband EM absorbers for demanding electronic and aerospace environments.