Preparation and thermal insulation performance of Al2O3[sbnd]Y2O3[sbnd]SiO2 ternary composite aerogels with high specific surface area and low density.

• Crack-free monolithic Al 2 O 3 Y 2 O 3 SiO 2 ternary aerogel was successfully synthesized by synchronous sol-gel method. • Al 2 O 3 Y 2 O 3 SiO 2 aerogel exhibited low density of 0.071 g/cm3 and high specific area up to 675.7 m²/g. • Mullite fiber reinforced Al 2 O 3 Y 2 O 3 SiO 2 aerogel showed excellent thermal insulation performance, the thermal conductivity at 1000 °C is only 0.079 W·m−1·K−1. Against the background of global energy shortages and the need for long-term flight safety of aerospace vehicles, traditional silica aerogels have the problems of insufficient temperature resistance and poor thermal insulation at high-temperatures, and are no longer able to meet the demand. In this study, a series of monolithic Al 2 O 3 Y 2 O 3 SiO 2 ternary aerogels were successfully synthesized via synchronous sol–gel and ethanol supercritical drying. Both the prepared aerogels and the calcined samples at 1000 °C exhibited a complete three-dimensional network structure and a high specific surface area (up to 675.7 m2/g and 214.4 m2/g), which was attributed to the supporting effect of the Al 2 O 3 component on the overall skeleton and the inhibiting effect of the Y 2 O 3 component on the crystal transformation. Mullite fiber reinforced Al 2 O 3 Y 2 O 3 SiO 2 aerogel composites were synthesized by vacuum impregnation using mullite fiber felt as a matrix. The prepared sample exhibit very low thermal conductivity (as low as 0.079 W⋅m−1·K−1 at 1000 °C). In summary, the good structural stability and high temperature thermal insulation performance make Al 2 O 3 Y 2 O 3 SiO 2 ternary aerogel have the potential of efficient service in more application scenarios. This study provides a product optimization reference idea for the thermal insulation material industry. [ABSTRACT FROM AUTHOR]