Studies On The Influence Factors For The Formation Of Zirconia Microcrystal Under Hydrothermal Conditions

Zirconia (ZrO₂) is one of the high-tech ceramics having excellent performance for application, such as transformation toughening, high-temperature thermal-stability, thermal insulation, low thermal conductivity etc. Furthermore, the ZrO₂ is used not only as high-tech ceramics, but also as catalyst, catalyst support, sensor and electronic materials.The preparation of ZrO₂ powder is the foundation for high technology ZrO₂ ceramics. There are different methods for the preparation of ZrO₂ nowadays, however, it is difficult to prepare the ultra-fine ZrO₂ particle with controlling morphology and size now. The improvement of preparing methods and chemical technology for ultra-fine ZrO₂ particles needs long-term studying.Hydrothermal preparation is the one of important methods of preparing ZrO₂. The hydrothermal preparation process is generally completed under high-temperature and high-pressure conditions. The product from the hydrothermal preparation is usually pure, uniformity and needn't further crystallization step. The product can meet the requirements of the application for some high technology ceramics. Comparing with the conventional preparation methods, hydrothermal methods have the obvious advantages in preparing high quality ZrO₂ powders.The influence factors during the hydrothermal process, such as fill factor, concentration or pH value of the precursor, time or temperature of the hydrothermal reaction, which have great influence on product from hydrothermal reaction, were considered in this thesis. The results indicated that the fill factor didn't have influence on the size or the content of m-ZrO₂ (Xm) during the hydrothermal reaction. As the concentration of hydrothermal precursor was raised, the content of m-ZrO₂ (Xm) remained constant and the crystalline size of ZrO₂ increased. When the pH value of hydrothermal precursor was about 8.00, the content of m-ZrO₂ (Xm) was the lowest. When the pH value of hydrothermal precursor was about 1.00, 2.00 or 12.00, 13.00, the content of m-ZrO₂ (Xm) was the highest and phase-pure m-ZrO₂ (Xm) formed. The...