| 摘要 |
PURPOSE: A manufacturing method of silica glass by sol-gel process is provided to reduce drying time largely and form cracks rarely after drying by a sequential subdivided drying process of gel. CONSTITUTION: The method comprises the steps of: (i)mixing silica, dispersant such as tetramethyl ammonium hydroxide(TMAH) and tetraethyl ammonium hydroxide, binder such as polyethyloxazoline and polyvinyl acetate, gelation agent such as methyl formate, methyl lactate and ethyl lactate, plasticizer such as glycerin, ethylene glycol, 2-methylpropane-1,2,3-triol and deionized water; (ii)molding sol and gelling; (iii)demolding gel; (iv)drying as the following steps: the primary drying, a constant rate period(CRP), at 25-40°C and 65-80% of relative humidity for 60-72hrs.; the secondary drying, reaching at a critical point(CP), at 15-25°C and 40-60% of relative humidity for 72-96hrs.; the tertiary drying at 30-80°C for 25-48hrs. (iv)thermal-treating as the following steps: heating at 10-50°C/hr to 300-600°C for the elimination of remaining organics of gel; at 100°C/hr to 500-100°C for an effective time to separate gel and eliminate remaining OH ions in a Cl2 gas atmosphere; at 100°C/hr to 1100-1400°C for about 5hrs. in He gas atmosphere.
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