Effect of gelation initiators on microstructure and thermal stability of Y₂O₃-SiO₂ composite aerogels

Abstract This study employed tetraethyl orthosilicate (TEOS) and Y(NO 3 ) 3 ·6H 2 O as precursors to synthesize Y 2 O 3 -SiO 2 composite aerogels via sol-gel combined with ethanol supercritical drying technology. The influence of ammonia (NH 4 OH) and propylene oxide (PO) as gelation initiators on the structure and properties of Y 2 O 3 -SiO 2 composite aerogels was investigated. Following calcination at 1100 °C, the specific surface areas of Y 2 O 3 -SiO 2 composite aerogels prepared with ammonia and propylene oxide as gelation initiators were found to be 128.84 m 2 /g and 25.33 m 2 /g, respectively. Notably, aerogels prepared using ammonia as the gelation initiator exhibited enhanced high-temperature phase and structural stability. To overcome the brittleness and low strength associated with aerogels, mullite fibers were incorporated into Y 2 O 3 -SiO 2 aerogels using a vacuum impregnation process, resulting in Y 2 O 3 -SiO 2 aerogel fiber composites. The thermal conductivity of the Y 2 O 3 -SiO 2 aerogel composites was as low as 0.092 W/m −1 ·K −1 at 1000 °C, significantly lower than that of 0.135 W/m −1 ·K −1 for the SiO 2 aerogel fiber composites. Due to the high specific surface area and thermal stability, Y 2 O 3 -SiO 2 aerogel fiber composites demonstrate promising potential as thermal insulation materials suitable for diverse applications in the aerospace industry.