Abstract: Radiative heat transfer significantly impacts the high-temperature thermal insulation performance of Al₂O₃-SiO₂ aerogel composite materials. To reduce their high-temperature thermal conductivity, this study introduces an infrared opacifier via a liquid-phase precursor route. Using aluminum sec-butoxide, tetraethyl orthosilicate, and chromium nitrate nonahydrate as precursors, Cr₂O₃ with excellent infrared shielding capability was incorporated into Al₂O₃-SiO₂ aerogel thermal insulation composites (ASF) through Sol-Gel method followed by ethanol supercritical drying. This approach successfully fabricated Al₂O₃-SiO₂-Cr₂O₃ aerogel thermal insulation composites (ASCF) with excellent high-temperature resistance and thermal insulation performance. The influences of heat treatment temperature on the microstructure, phase composition, thermal stability, and thermal insulation properties of ASCF were systematically investigated. The results indicate that the introduction of Cr₂O₃ enables ASCF to maintain good high-temperature resistance while achieving significantly lower high-temperature thermal conductivity. At 1100 ℃, the thermal conductivity of ASCF is only 0.050 W/(m·K), representing a substantial reduction of 30.6% compared to that of ASF (0.072 W/(m·K)). After heat treatment at 800-1100 ℃, the high-temperature thermal conductivity of ASCF remains largely stable (ranging from 0.052 to 0.055 W/(m·K) at 1100 ℃), indicating outstanding thermal insulation stability. After 7 cycles of infrared radiation heating at 1000 °C for 3300 s using a quartz lamp, the temperature rise curves on the sample's cold surface nearly overlapped. At the end of each cycle, the cold surface temperature remains within a range of 326-358 ℃. Furthermore, the sample maintains its macroscopic integrity, with no visible deformation, cracking, or shrinkage, demonstrating excellent reusability. The liquid-phase precursor approach for introducing infrared absorbers offers a novel strategy for achieving low thermal conductivity in aerogel thermal insulation composites.

Key words: high temperature resistance, thermal insulation, Al₂O₃-SiO₂-Cr₂O₃ aerogel composite, infrared opacifier