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Mesoporous zirconia aerogels are very interesting materials with important properties used for several applications such as ceramics and catalysis. The textural and structural properties of zirconia aerogel depend on the preparation parameters such as the hydrolysis ratio, the acid and zirconium precursor concentrations, and the gel aging. The extraction of the solvent under its supercritical conditions (high-temperature supercritical conditions) or under the supercritical conditions of CO2 (low-temperature supercritical condition) leads to aerogel zirconia with different properties. In fact, aerogel zirconia dried under high-temperature supercritical conditions is well crystallized and exhibits a large surface area. However, aerogels obtained with low-temperature supercritical conditions are amorphous and present a low surface area. Zirconia aerogels doped by metals, such as platinum, iron, and copper, or ions, in particular sulfate, phosphate, and tungstate anions, exhibit very important catalytic properties in many reactions such as n-alkane isomerization and Fischer–Tropsch synthesis. Doping zirconia with other oxides leads to materials with very interesting properties, allowing its use in fuel cells, thermal barrier coatings, oxygen sensors and many other high-temperature applications. |
