陳化處理對ZTA超微粉末特性研究

• Main Author: 歐陽允亮
• Other Authors: 顏富士
• Format: Others
• Language: zh-TW
• Published: 1995
• Online Access: http://ndltd.ncl.edu.tw/handle/16726107471763189876

碩士 === 國立成功大學 === 資源工程學系 === 83 === 　　ZTA powders obtained by chemical coprecipitation method were aged at different temperature (40, 60, 80℃) during colloidal states, by which the properties of the powders can be adjusted. Effects or aging time and temperature on the properties of the powders were investigated. The ZTA gel powders were synthesized at pH=9. Coprecipitation temperature were at room temperature (RT) and above RT (40, 60, 80℃). 　　In this research, the stable phases of aluminum hydroxide were boehmite (> 80℃), and bayerite(RT). The cryctallite phases after aging depend on temperature: below 60℃, it would be bayerite phase; above 60℃, it would exist as boehmite phase. The crystallite phases of aluminum hydroxide at high coprecipitation temperature depend on the coprecipitation temperatures: below 60℃, it would boehmite and bayerite phases; above 60℃, it still exist as boehmite phase. At the same aging temperature, the stable phase is still bayerite as temperature below 60℃. However, as the temperature above 60℃, the transformation sequence would be bayerite→gibbaite→boehmite(stable phase). 　　If the starting phase is bayerite, we could obtain a dense ZTA ceramics at a lower calcination temperature (900℃) under the sintering condition (1550℃/4hr). On the contrast, it needs a higher calcination temperature (≧1000℃) to obtain a dense ceramic for boehmite phase. The calcined powders with BET surface area at 70∼130 m2/g could sinter to dense (≧96% T.D.). ZTA ceramics prepared by RT coprecipitation could find intragranular ZrO2 particles. However, by HT coprecipitation, ZrO2 particles would locate at grain boundary, i.e, intergranular. It is shown that ZrO2 particles can grow properly at a lower calcination temperature by HT coprecipitation and aging process. Therefore, using HT coprecipitation and aging process can shorten aging time to get bayerite phase, and obtain ZTA ceramic with ideal toughening mechanism.