Abstract: The SiO₂ aerogel exhibits excellent thermal insulation performances, however, its structure tends to sinter and collapse at high temperatures, and it has relatively high brittleness, which limit its widespread application in high-temperature and complex environments. This study employed the sol-gel method and supercritical drying technology, using tetraethyl orthosilicate as the silicon source, to prepare mullite fiber/SiO₂-ZrO₂-Y₂O₃ aerogel composite thermal insulation felts (MF/SZYAs). A systematic investigation was conducted on the microstructure, thermal insulation performance, and high-temperature thermal stability of MF/SZYAs. The results indicate that the prepared MF/SZYAs possess a well-developed nanoscale three-dimensional network pore structure, with zirconium and yttrium elements uniformly distributed within the aerogel matrix. At room temperature, the density of MF/SZYAs is 0.134 5 g·cm^-3, with a compressive strength of 2.26 kPa at 10% strain, a specific surface area of 515.7 m²·g^-1 and a thermal conductivity of 0.035 1 W·m^-1·K^-1. After heat treatment at 1 000 ℃, MF/SZYAs exhibit excellent thermal stability, with a thermal conductivity of 0.045 4 W·m^-1·K^-1 and a specific surface area of 183.1 m²·g^-1. Following heat treatment at 1 200 ℃, although the macroscopic volume of MF/SZYAs remains largely unchanged, significant sintering occurs within the internal three-dimensional nanostructure, resulting in a notable decrease in specific surface area (14.3 m²·g^-1) and an increase in thermal conductivity (0.047 3 W·m^-1·K^-1). Good thermal stability is primarily attributed to the enhanced structural stability and thermal radiation scattering ability of SiO₂ aerogels due to the co-doping of zirconium and yttrium. The research results provide important theoretical support for the development of efficient, lightweight, and thermally stable thermal insulation materials, and the prepared composite thermal insulation materials have wide application prospects in the industrial field.

Key words: SiO₂-ZrO₂-Y₂O₃ aerogel, mullite fiber felt, sol-gel method, thermal stability, nanoporous structure, thermal insulation performance