Improvement of thermal stability performance of SiO2 aerogels by MgAl2O4 nano-powder

This study successfully synthesized the bulk MgAl ₂ O ₄ -SiO ₂ aerogels with excellent thermal stability using tetraethyl orthosilicate (TEOS) and MgAl ₂ O ₄ nanopowders as precursors via a sol-gel and supercritical drying process. The incorporation of MgAl ₂ O ₄ powders caused a slight increase in the thermal conductivity, from 0.0312 W/m/K to 0.0322 W/m/K, but the material demonstrated excellent thermal resistance at the temperatures exceeding 800℃. After heat treatment at 1100℃ for 2 h, the MgAl ₂ O ₄ -SiO ₂ aerogels maintained a high specific surface area of 81.949 m ² /g, a large pore volume of 0.575 cm ³ /g and a low thermal conductivity of 0.0584 W/m/K, while the pure SiO ₂ aerogels presented a dense structure due to viscous flow among particles and pore collapse, with a specific surface area of 0.882 m ² /g, a pore volume of 0.002 cm ³ /g and the thermal conductivity of 0.0962 W/m/K. Additionally, the MgAl ₂ O ₄ induced secondary particle aggregation, leading to larger particle sizes and coarser skeletal structures, different from the uniform pore shrinkage in the pure SiO ₂ aerogels. The MgAl ₂ O ₄ significantly inhibited the growth of cristobalite particles during heat treatment at 1200℃ and promoted the formation of micron-scale macroporous, and lamellar structures.