A nearly pure monoclinic nanocrystalline zirconia |
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Authors: | Gong-Yi Guo Yu-Li Chen |
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Institution: | a Department of Materials Science and Engineering, 540 Division, Shanghai Jiao Tong University, Number 1954, Hua Shan Road, Shanghai 200030, China b College of Chemistry and Chemical Engineering, Shanghai University, Shanghai 200072, China |
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Abstract: | Generally, monoclinic zirconia is considered to be much more difficult to prepare at low temperatures and particularly in a pure state. The present work is the first example that shows that the hydrous zirconia formed by precipitation can yield a nearly pure nanocrystalline monoclinic zirconia at a temperature as low as 320 °C. The crystallite size of the monoclinic zirconia produced in the present work is around 15 nm, and it does not change appreciably as calcination temperature is increased from 320 to or above 400 °C. Such a small monoclinic crystallite arises from some of the chemical and physical factors built into the solution-gelation-xerogel process such as acidic preparation-pH, rapid precipitation, and moderate aging time and drying temperature, which result in a structure different from those of the existing zirconium hydroxides. In addition, the hydrous zirconia exhibits a unique thermal behavior in two respects: first, a sudden weight drop in the region of exothermic peak of the thermogravimetric curve is seen, suggesting that the main decomposition of the hydrous zirconia occurs in this region; second, there is an endothermic peak at high temperature in the differential thermal analysis curve, indicating the presence of coordinated water in the hydrous zirconia. |
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Keywords: | Nanocrystalline zirconia Crystallization Thermal behavior Monoclinic structure |
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