Preparation of La2Zr2O7 composite SiO2 aerogels and their fiber-reinforced materials for thermal insulation applications

Abstract

Lanthanum zirconate (La2Zr2O7) aerogel, with its unique pyrochlore structure, is extensively utilized in thermal insulation owing to its nanopore formation. Nevertheless, the single-phase La2Zr2O7 aerogels have drawbacks of being tough to mold, having a structure that can collapse at high temperatures. This study employed the epoxide sol-gel method to prepare mesoporous aerogels with complete shapes, low densities, and high specific surface areas consisting of La2Zr2O7 composite SiO2 (LZS). Meanwhile, the formed SiO2 amorphous phase can inhibit the growth of pyrochlore crystals and improve the thermal stability of the material. When the amount of SiO2 reached 10 % (LZS10), its density was 0.094+0.006 g/cm3, and the surface area was 88.7 m2/g with 24 % pore volume retention after heat treatment at 1000 °C, showing excellent heat resistance. Quartz fiber reinforced LZS10 aerogel composites (FLZS10) with a thickness of 5 mm were also prepared to study their thermal insulation properties in practical applications. Among them, FLZS10 exhibits a thermal conductivity of 0.057±0.002 W·m−1·K−1 after heat treatment at 1000 °C. When one side of FLZS10 is exposed to a flame at 1000 °C, the temperature of the opposite side is only 284.7 °C, indicating an outstanding thermal insulation performance.