Multiscale Interpenetrated/Interconnected Network Design Confers All‐Carbon Aerogels with Unprecedented Thermomechanical Properties for Thermal Insulation under Extreme Environments

Abstract With ultralight weight, low thermal conductivity, and extraordinary high‐temperature resistance, carbon aerogels hold tremendous potential against severe thermal threats encountered by hypersonic vehicles during the in‐orbit operation and re‐entry process. However, current 3D aerogels are plagued by irreconcilable contradictions between adiabatic and mechanical performance due to monotonicity of the building blocks or uncontrollable assembly behavior. Herein, a spatially confined assembly strategy of multiscale low‐dimensional nanocarbons is reported to decouple the stress and heat transfer. The nanofiber framework, a basis for transferring the loading strain, is covered by a continuous thin‐film‐like layer formed by the aggregation of nanoparticles, which in combination serve as the fundamental structural units for generating an elastic behavior while yielding compartments in aerogels to suppress the gaseous fluid thermal diffusion within distinct partitions. The resulting all‐carbon aerogels with a hierarchical cellular structure and quasi‐closed cell walls achieve the best thermomechanical and insulation trade‐off, exhibiting flyweight density (24 mg cm −3 ), temperature‐constant compressibility (−196–1600 °C), and a low thermal conductivity of 0.04 829 W m −1 K −1 at 300 °C. This strategy provides a remarkable thermal protection material in hostile environments for future aerospace exploration.