| 摘要 |
PURPOSE:To obtain a formed glass having high purity and high density, particularly a formed quartz glass by calcining purified silica having a specified particle size obtd. by a reaction of an aq. soln. of alkali-metal silicate with an acid, crushing the calcined product to a specified particle size, forming the crushed product, and calcining the formed product. CONSTITUTION:Silica having 20mu-1mm mean particle size is obtd. by allowing the aq. soln. of alkali-metal silicate to react with the acid. If the particle size is <20mu, washing and dehydration in a purifying stage becomes difficult. If it exceeds 1mm, extraction of impurities in the purifying stage is difficult. Obtd. silica is then purified by a conventional process such as washing with an aq. soln. of a mineral acid, etc. The purified silica is then calcined, and calcined silica is crushed. Thus, fine silica particles having <20mu mean particle size and having <=10ppm alkali-metal content are obtd. The fine silica particles are then formed, and calcined, again. |
