| 摘要 |
PURPOSE:To obtain the titled intermediate product so as to prevent external contamination of impurities and exhaustion of the heating medium, by treating at high temperatures an opaque glass containing closed cells therein prepared by drawing a porous preform to effect transparent vitrification. CONSTITUTION:First, fine glass particles are prepared by hydrolyzing a precursor for making glass (e.g. a metal alkoxide). Thence, a porous preform obtained by collecting the above fine particles is heated followed by drawing to convert into an opaque glass containing closed cells therein. This opaque glass is then treated at high temperatures to effect transparent vitrification. |
