Aerogel fibers uniting characteristics of both aerogels (lightweight and porosity) and fibers (flexibility and wearability) exhibit a great potential for the production of the next generation of thermal protection textiles; still, the complex drying procedures and mechanical brittleness remain the main obstacles toward further exploitation. Herein, flexible and robust aramid nanofiber aerogel fibers (ANAFs) are scalably prepared by continuous wet-spinning coupled with fast air-drying. This synthesis involves calcium ions (Ca2⁺) cross-linking and solvent displacement by low surface tension solvents, to enhance skeleton strength and reduce the capillary force during evaporation, respectively, thus minimizing shrinkage to 29.0% and maximizing specific surface area to 225.0 m2 g-1 for ANAF. Surprisingly, the air-dried ANAF showed excellent tensile strength (13.5 MPa) and toughness (7.0 MJ m-3), allowing their easy weaving into the textile without damage. Importantly, the ANAF textile with a skin-core porous structure exhibited low thermal conductivity (≈38.5 mW m-1 K-1) and excellent thermal insulation ability in the wide temperature range (-196 to 400 °C). Besides, the aramid molecular structure, as well as Ca2⁺ cross-linking, endowed the ANAF with high thermal stability and flame retardancy. Consequently, the robust ANAF with a fast-air-drying method is promising for thermal protection in extreme environments, such as in spacesuits.
Keywords: aerogel fiber; ambient drying; aramid nanofiber; high mechanical properties; thermal insulation.
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