The Study of the Effects of Power Processing on the Character- ization of Magnesia Derived from Alkoxides

• Main Authors: Mu Tsuan Tsai, 蔡木村
• Other Authors: H.C.Shih
• Format: Others
• Language: zh-TW
• Published: 1993
• Online Access: http://ndltd.ncl.edu.tw/handle/14479219466285911315

博士 === 國立清華大學 === 材料科學(工程)研究所 === 81 === Magnesia powders prepared from alkoxide sol-gel process and alkoxide-hydrolysis process have been demonstrated in this study. Gel-derived powders exhibit porous aggregates and extensive hard agglomerates, which are regarded as an intrinsic nature of gel powders; the morphology of the powders obtained from hydrolysis-precipitate route is a function of water content and retains highly agglomerated particles, suggesting that localized microgels are formed during processing. However, a simple modified sol-gel approach is also proposed to synthesize fine-sized powders with a narrower size-distribution and with less hard agglomerates that is shown to be feasible. The thermal behaviors and crystallinities of as-prepared powders are similar in all cases, however, there exists a significant difference in particle morphology. It was found that the starting powder morphologies, especially the state of hard agglomeration, strongly affect the uniformity and microstructural evolution during forming and densification. However, a uniform, high-strength, dense (98-99%) and translucent magnesia can be achieved by sintering the modified powder compacts at temperatures much lower than those required for conventional magnesia powders. The obtained powders were characterized and compared. Their compaction and sintering behaviors would also be discussed.