Ultralight, Elastic, Thermally Insulating, and High-Temperature Resistant Al2O3–SiO2–B2O3 Nanofibrous Aerogels Prepared via the Direct Foaming Method

Ceramic nanofibrous aerogels exhibit ultralow density and thermal conductivity, which make them ideal candidates for thermal protection in extreme environments. However, the current limitations in pore-forming techniques hinder their further advancement. In this study, ultralight, highly elastic, and high-temperature-resistant ceramic nanofibrous aerogels were successfully prepared through the direct foaming method using flexible Al2O3–SiO2–B2O3 nanofibers as raw materials and Tween 80 as the foaming agent. Foams generated in the slurry exhibited exceptional stability, facilitating the formation of a porous three-dimensional network structure with nonoriented pores and tightly bonded fiber connections within the green body after the drying process. This porous structure was obtained via sintering and maintained stability at temperatures up to 1000 °C. In addition, the porosity was controlled by adjusting the content of the foaming agent. An increase in the Tween 80 dosage resulted in a higher number of air bubbles per unit volume within the slurry, accompanied by a decrease in their sizes. Consequently, the structure possessed abundant pores with small sizes, promoting gradual deterioration in fiber junctions. As a result, the aerogels demonstrated a decrease in density and elasticity as well as improved thermal insulation properties. These findings provide novel insights for the preparation and performance regulation of ceramic nanofibrous aerogels.