Controlled formation of amine-templated mesostructured zirconia with remarkably high thermal stability

Abstract

In order to control the reactivity of the inorganic precursor and the hybrid formation, the evaporation induced self-assembly procedure (EISA) has been applied to direct alkyl amines into zirconia hybrid composites. It is demonstrated that, with controlled water amounts, a mesostructured wormhole-like high-surface-area zirconia can be formed but the mesostructure collapses due to massive crystallisation of the zirconia walls into tetragonal zirconia as the calcination temperature rises to 400 °C. To overcome the lack in thermal stability, zirconia hybrids are treated in aqueous ammonia to protect the primary particles in the zirconia walls against uncontrolled particle growth and crystallisation. The growth of the initially amorphous zirconia particles in the walls is limited by increasing the condensation degree upon ammonia treatment resulting in mesostructured zirconia consisting of nanosized ‘tetragonal’ particles at higher temperatures. It is shown that the alkaline-treated zirconias have a remarkable thermal stability with retention of most physical characteristics such as high surface area, pore volume and mesoporosity up to a temperature of 800 °C.