| 摘要 |
PURPOSE: A transparent silica glass composition comprising silica sol, gelling agent, and formamide as a drying aid is provided. The resultant silica glass with good transparency and near theoretical density(2.202g/cm3) is manufactured by sintering silica compacts under vacuum, not air or He atmosphere of conventional method. CONSTITUTION: The method for manufacturing transparent silica glass comprises the steps of: (i) preparing a silica sol by mixing 40-60pts.wt. of silica powder, fumed silica(40-100nm), 1-5pts.wt. of dispersant such as tetramethyl ammonium hydroxide(TMAH) or tetraethyl ammonium hydroxide(TEAH), and 40-60pts.wt. of deionized water; (ii) adding 0.5-5pts.wt. of gelling agents, aliphatic ester compounds such as methyl lactate and ethyl formate, 2-30pts.wt.(based on 100pts.wt. of dispersant) of drying aid such as formamide, and optionally 0.1-3pts.wt. of plasticizers such as glycerin and ethylene glycol; (iii) pouring the silica sol into a mold and gelling; (iv) demolding to get a bulky gel; (v) drying to 30-50deg.C for 48hrs. or more; (vi) thermal treating at 5-50deg.C/hr to 300-600deg.C for removal of organics; (vii) thermal treating at 100deg.C/hr to 500-1000deg.C in Cl2 atmosphere for removal of hydroxide ions and metallic impurities; (viii) sintering at 1200-1700deg.C for 0.1-100hrs. at a vacuum between 10-1 and 10-6torr. The step for removing foams in silica sol is optionally added to the next of step (i).
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