| 摘要 |
PROBLEM TO BE SOLVED: To obtain synthetic silica glass powder by hydrolyzing an alkoxysilane wherein the system is cooled to enough low temperatures to prevent evaporated components from condensation/gelation, and by baking the resultant gel so as to suppress the development of black foreign matter and reduce bubbling in the molding process for the silica glass powder in a molten state. SOLUTION: This synthetic silica glass powder is obtained by the following process: a high-purity alkoxysilane such as tetramethoxysilane is hydrolyzed with about 1-10 equivalent times of pure water to form a sol which is then gelatinized at normal or higher temperatures; the resulting silica gel is ground and dried at about 50-200 deg.C into powder about 5-30 wt.% in liquid content and about 10-1,000μm in particle size; the dried silica gel powder is subsequently heat-treated pref. at 300-500 deg.C or so and then baked at about 1,000-1,300 deg.C; wherein during the hydrolysis process, spots where evaporated components may condensate are cooled to <=10 deg.C (pref. <=5 deg.C or so); thereby affording the aimed synthetic silica glass powder free from any black foreign matter. The other objective silica glass molded form with extremely low bubble generation is obtained by molding the above synthetic silica glass powder in a molten state.
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