Study Of Preparation Of Stabilized Tetragonal Crystalline Structure Zirconia Aerogel

Zirconia is a kind of transition metal oxide with many fantastic physiochemical properties. Zirconia appears in three crystalline structures: monoclinic, tetragonal and cubic. Only monoclinic zirconia is thermodynamically stable at room temperature. The activity and selectivity of catalyst prepared with zirconia is contact with the crystalline structure of zirconia. Zirconia aerogel with pure tetragonal crystal structure and higher structure stability gained an interesting attention in the recent years, because it offers the possibility of producing a wide variety of unusual materials with interesting properties for applications in heterogeneous catalysis and ceramic materials.In this thesis, zirconia aerogel was prepared by a relatively new and extraordinarily convenient method, heating of alcohol-aqueous solutions followed by supercritical fluid drying. And the thesis was composed of three main parts, namely, the effect of raw materials on the properties of zirconia aerogels, the effect of volume ratio of high alcohol to water on the properties of zirconia aerogel, the way of drying on the properties of zirconia.The methods of N₂ adsorption/desorption, transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to investigate the properties of zirconia.It is discovered that different raw materials lead to different properties of zirconia aerogel. The zirconia aerogel prepared with zirconyl nitrate dihydrate has high specific surface area and pure tetragonal crystalline structure. But the crystalline structure of zirconia aerogel prepared with zirconium nitrate pentahydrate and zirconyl chloride octahydrate are the mixture of tetragonal and monoclinic crystalline structure.And the volume ratio of alcohol to water has an obvious influence on the properties of zirconia aerogel. When the volume ratio of alcohol to water is 30, the specific surface area of zirconia aerogel could reach 637m2-g'1 which is much higher than that of documents so far. After calcining at 700°C, its specific surface area is still 134m2-g''. After calcination at 300 °C, zirconia aerogel entirely existed in the form of pure tetragonal crystalline structure and its kept stable till 700 °C.Both the crystalline structure of zirconia aerogle and zirconia xerogel is tetragonal crystalline structure. But the specific surface area of zirconia aerogel is much higher than that of zirconia xerogel.