Superelastic Graphene‐Based Composite Aerogel for Thermal and Electromagnetic Protection in Extreme Temperature Environments

Abstract The aerogel materials stacked with nanomaterials usually have good thermal insulation and electromagnetic wave (EMW) absorption properties due to their porous properties. However, consecutive mechanical loading cycles under extreme temperature environments cause irreversible structural and mechanical damage. Furthermore, there is an inherent contradiction between the characteristics of multiple interfaces and their anti‐fatigue performance. In this study, polyimide (PI) fibers are dispersed in graphene aerogel, and the composite aerogel (G‐PI@F ₂₀ /CNT _x ) can be formed by in situ welding. The hierarchical porous structure endows aerogel with excellent superelasticity, thermal insulation, and EMW absorption properties. The aerogel endures 90% strain compression cycles over a temperature range of −196 to 160 °C, with deformation loss remaining below 5%. This hierarchical porous structure hinders phonon conduction, resulting in low thermal conductivity (0.0313 W m ⁻¹ K ⁻¹ ). The aerogel with a thickness of 4.1 mm achieves an effective absorption bandwidth (EAB) of 12.48 GHz. By increasing the thickness to 20.3 mm, ultra‐broadband absorption of 15.24 GHz and an optimal reflection loss (RL _min ) of −43.49 dB are attained. These findings provide crucial insights into the design of multifunctional EMW absorbing materials and offer a general strategy for synthesizing superelastic aerogels.