| 摘要 |
PURPOSE:To produce the title opaque glass preform reed of impurities, contg. closed cells, and easy to handle at a low cost by heating a porous glass preform in a furnace core tube to reduce its volume. CONSTITUTION:A sol is formed as a glass forming precursor by hydrolyzing a metal alkoxide, and the sol is dried to obtain fine glass particles. The fine glass particles are collected to obtain a porous glass preform. The porous glass preform 4 is heat-treated, as required, in a dehydrating gas atmosphere, then placed in the quartz furnace core tube 2 through a carrier 6, and heated by a heating furnace 1. The heating is preferably carried out in the atmosphere of the gaseous He or halogen-contg. dehydrating gas introduced from an opening 3. By this method, the volume of the porous glass preform 4 can be reduced at a relatively low temp. without damaging the furnace core tube 2, and an opaque glass preform 5 contg. closed cells and difficult to break is formed. |
