Multiscale Structural Engineering of Cellulose‐Derived Carbon Aerogel Metamaterials for Broadband Microwave Absorption

Developing broadband microwave absorption materials remains a major challenge due to the causality principle at the resonant thickness. Herein, a multiscale design strategy is developed to fabricate cellulose nanofiber-derived carbon aerogel (VBFA) by incorporating defects at the microscopic level and controlling pore sizes at the mesoscopic level. The VBFA is further architected into a lance-shaped metamaterial (LMA) by modulating its macroscopic structural parameters. Theoretical and experimental investigations reveal that defects predominantly influence the absorption intensity, pore size governs the absorption frequency, and structural parameters determine the bandwidth. The vacancy defects with 1.85 eV potential difference induced by P-atom doping and boundary defects arising from heterogeneous I_D/I_G interfaces synergistically enable VBFA to achieve a RL_min value of -71.1 dB at 15.1 GHz. Both experimental and simulation results further demonstrate that smaller pores effectively facilitate the transfer and dissipation of induced currents generated by lower frequencies. Furthermore, the broadband absorption performance covering 1.2-1.9 GHz and 3.3-18.0 GHz for LMA is achieved by a single-factor optimization program. The E/H-field and Power loss results also confirm the structural advantages of lance shape in optimizing the microwave transmission paths. This multiscale strategy establishes a novel paradigm for the rational design of broadband absorption materials.