Robust, Highly Thermally Stable, Core–Shell Nanostructured Metal Oxide Aerogels as High-Temperature Thermal Superinsulators, Adsorbents, and Catalysts

Abstract

Robust, highly thermally stable, MOx/(MOx–SiO2)/SiO2 core–shell nanostructured metal oxide aerogels with a MOx core and (MOx–SiO2)/SiO2 shell are produced via novel alkoxide chemical liquid deposition techniques. The core–shell nanostructure not only significantly reinforces the nanoparticles but also effectively inhibits the crystal growth and phase transition of metal oxide upon heat treatment, which enhances the heat resistance from approximate 400–800 °C up to 1000–1300 °C. The resultant core–shell nanostructured Al2O3, ZrO2, and TiO2 aerogels can support at least 5800 times their weight and exhibit high surface areas of 139, 186, and 154 m2/g after fired at 1300, 1000, and 1000 °C, respectively, which are the highest surface areas for metal oxide aerogels ever reported. We demonstrate that the core–shell ZrO2 and TiO2 aerogels show enhanced adsorption and photocatalytic performances, respectively, for dye after fired at 1000 °C. The core–shell Al2O3 aerogel/mullite fiber/TiO2 composite possesses ultralow thermal conductivities of 0.058, 0.080, and 0.11 W/mK at 800, 1000, and 1200 °C, respectively, which are the lowest values for inorganic aerogels ever reported. The resulting materials are promising candidates as high-temperature (400–1300 °C) thermal superinsulators, adsorbents, and catalysts.