Multi-Stage Anisotropic Cellulose-Based Aerogels via “Foam-Flake-Fiber” Interweaving for Versatile Microwave Absorbers

Controllable ice crystallization allows casting of isotropic or anisotropic porous aerogels to tailor versatile electromagnetic wave (EMW) absorbers. In this paper, a multivariate assembly-assisted bidirectional differ-speed freezing technique is developed to prepare the sandwiched nitrogen-doped carbon micro-foam/MXene/cellulose nanofiber aerogel (NCMF/MXene/CNF Aerogel, NCMCA). The NCMF, MXene, and CNF are assembled by alternating “foam-flake-fiber” through attractive interactions, and then undergo directional alignment under bi-directional cross-squeezing of ice crystals, forming a multi-stage anisotropic structure containing integrated periodic grid-like surface and honeycomb-like channels. The high porosity results in ultra-light density (6.2 mg cm −3 ) and thermal insulation (Δ T max = 140 °C). Silane deposition gives NCMCA a large water contact angle (≈133.6°) for anti-icing. Multi-component filling and compressive strain synergistically regulate electron transport and charge polarization for photothermal conversion, piezoresistive sensing, and microwave absorption. In particular, compression-driven dielectric coupling facilitates dynamic modulation of EMW absorption. In addition, NCMCA is capable of efficiently absorbing EMW under far-field conditions, thereby minimizing the radar scattering cross section. This work provides a novel structural design route for composite aerogels to achieve versatility, as well as new insights into the microstructural regulation mechanism of EMW absorption.