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

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.