Robust and elastic composite aerogel fiber constructed from three-dimensional embedding of silica aerogel particles in nanoporous agarose

Aerogel fibers inherit the advantages of the aerogel and fiber materials, such as good flexibility, low density, and high porosity, and are promising for producing wearable thermal insulation textiles for harsh environments. Nevertheless, the practical application of the three-dimensional (3D) network structures of aerogel fibers is hindered by their poor mechanical properties owing to the nanoporous structure. In this work, we produced composite aerogel fibers (CAFs) by combining SiO 2 gel slurry derived from coal fly ash with agarose and polyurea using wet-spinning and supercritical-drying technologies. In the CAFs, small SiO 2 aerogel particles existed in agarose nanofiber network to form an embedded structure. The synergic effects between the fragile SiO 2 gel skeleton and soft agarose nanofiber gel skeleton endow the CAFs with excellent elasticity, showing considerable of elastic recovery even after radial compression under 40 % strain, thus also helping to overcome some limitations of fragile SiO 2 aerogels and soft agarose nanofiber aerogels in practical applications. Surface modification of aerogel fiber with polyurea not only endows it with ideal hydrophobicity (water contact angle: 130°), but also enhances its tensile resistance (∼2.5 MPa). Furthermore, the aerogel fibers exhibit high specific surface area (∼182 m 2 /g) and low thermal conductivity (0.027 W m −1  K −1 ). Hence, this study constructs the microstructure of silica embedded in the agarose fiber network to obtain SiO 2 /agarose/polyurea CAFs (SAP-CAFs) with excellent performance, which will promote their application in the field of clothing fabrics in extreme temperature and humid environments.