Mechanical strengths and thermal properties of titania-doped alumina aerogels and the application as high-temperature thermal insulator

Alumina (Al₂O₃)-based diphasic aerogels have better physical properties than those of pure Al₂O₃ aerogel according to previous studies. In the present research, we focused on an alumina–titania (Al₂O₃-TiO₂) diphasic aerogel. A series of Al₂O₃ aerogels were synthesized and studied with and without minor TiO₂ dopants (up to 10 mol%). We found that the pure Al₂O₃ aerogel, which had the fiber-like particles, was stronger than those with TiO₂ dopants that possessed the sphere-like particles. However, the sphere-like particles make the TiO₂-doped Al₂O₃ aerogel (with 3 mol% TiO₂) possessing the largest specific surface area (SSA) of 650 m²/g, much larger than that of the pure Al₂O₃ aerogel (326 m²/g). This work proved that fiber-like particles enhance strength but reduce SSA of Al₂O₃ aerogel. At last, ceramic fibers reinforced Al₂O₃ aerogel composites with the sizes of 20 cm width × 20 cm length × 1 cm thickness were fabricated. The aerogel composites possessed a thermal conductivity of 0.136 W/m K at 1000 °C, better than those of the ceramic fiber blankets itself (0.30 W/m K), indicating potential application as high-temperature thermal insulator.