Preparation of mesoporous La2Zr2O7 aerogel via non-alkoxide sol-gel process with different solvent systems

Abstract

Mesoporous La2Zr2O7(LZO) aerogels were successfully prepared by combining the epoxide-mediated sol-gel method with non-alkoxide salts. Gelation was controlled by adding propylene oxide to the solution of nitrate. The effect of solvent systems of pure water, pure ethanol, and a mixture of water and ethanol on the sol-gel was investigated. Gels cannot be obtained using either pure water or mixed solvent systems. However, LZO aerogels synthesized with pure ethanol solvent exhibited a mesoporous structure with a surface area of 413.2 m2/g and an average pore size of 12.3 nm. The prepared LZO aerogels had an amorphous structure containing some organic components. After heat treatment, the organics were pyrolyzed and the LZO started to crystallize. At about 1000°C, the LZO transformed from fluorite structure to pyrochlore structure. In addition, LZO still maintains a good skeletal structure after calcined at 1000°C. Above 1200°C, the grains start to stick as well as the grain size increases significantly due to the sintering of nanocrystalline LZO grains. The surface area can be maintained at 149.6 m2/g after heat treatment at 600°C and dropped to 9.3 m2/g after 1400°C for 3h.