Mesoporous titania-alumina ceramics are interesting as catalysts and catalyst supports. Monolithic wet-gels of 0.2TiO2-0.8Al 2O3, prepared by hydrolysis of metal alkoxides in alcoholic solutions, were dried at 90°C (xerogel), immersed into a surfactant solution before drying (surfactant-modified gel), or the solvent in wet gels was supercritically extracted in one step from CO2 at 60°C and 24Mpa for 2 h (aerogel). Thermal evolution of the microstructure of the gels was evaluated by thermal analyses (TG-DTA), N2 adsorption, scanning electron microscopy, and X-ray diffraction. After calcination at 500°C, the specific surface area of the gels was >400m2 g-1. The average pore radius for the supercritically extracted titania-alumina gel, about 8nm (∼50% of that for alumina aerogels), was 2-4 times larger than that of the surfactant-modified gels and of the xerogel. The specific surface area of the surfactant-modified gels and of the supercritically extracted gels was more than 150m 2g-1 after calcination at 800°C. The pore size and pore volume of these gels minimally decreased after calcination at 800°C, while those values of the xerogel markedly decreased. The thermal stability of the microstructure of mesoporous titania-alumina is improved by surfactant immersion or supercritical extraction.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Condensed Matter Physics
- Materials Chemistry