Carbon layer encapsulation strategy for designing multifunctional core-shell nanorod aerogels as high-temperature thermal superinsulators

Aerogels have been considered as attractive candidates for spacecraft thermal protection systems. However, constructing lightweight aerogels with better mechanical strength, higher temperature resistance and lower high-temperature thermal conductivity, whether based on nanoparticles or nanofibers, is still a great challenge. Moreover, to avoid performance degradation caused by moisture absorption, insulating aerogels usually suffer from complex post-processing to obtain superhydrophobicity, which also cannot be guaranteed once the surface breaks down. Herein, a carbon layer encapsulation (CLE) strategy is proposed to resolve the above-mentioned conundrums in a simple way. Thanks to the collaboration of structural design and theoretical simulations, the tailored Al₂O₃-carbon core–shell nanorod aerogels demonstrate excellent comprehensive properties of low density (as low as 0.086 g·cm⁻³), outstanding stiffness (a specific compressive strength of 69.83 kN·m·kg⁻¹), bionic abrasion-durable superhydrophobicity (WCA 156° after 1000 abrasion cycles), ultra-high thermal stability (over 1500 °C in argon and over 1400 °C in air) and high-temperature thermal superinsulating performance (0.065 W·m⁻¹·K⁻¹ at 1200 ℃). The synergy of ultrafine Al₂O₃ nanorods and carbon layers with suitable thickness not only forms a robust lotus leaf-like structure, but also enables the obtained aerogels to exhibit much superior thermal insulation properties than reported Al₂O₃-based aerogels. The significant increase in temperature resistance induced by lattice distortion is also an interesting phenomenon that has been investigated in detail. This novel strategy provides a fresh perspective for the preparation of multifunctional thermal high-temperature superinsulators applicable to spacecraft thermal protection systems.