TRANSPARENT VITRIFICATION PROCESS OF OPTICAL POROUS GLASS

摘要

PURPOSE:To prolong the life of a furnace core pipe and to secure long term production of high quality transparent glass by vitrifying porous glass to transparent glass using a furnace core pipe comprising a quartz pipe coated with heat stabilizing and devitrification preventing glass. CONSTITUTION:A furnace core pipe 3 to be used for the transparent vitrification of optical porous glass 6 comprises a quartz glass 4 and a glass layer 5 covering the outer peripheral surface of the quartz pipe. The glass layer 5 is constituted of Al2O3-SiO2 having <=ca.100mu thickness to stabilize the quartz pipe 4 against heat and to prevent devitrification of the pipe 4. The furnace core pipe 3 is installed to the inside of a heating furnace 1 having a heating element built therein and an alumina cylindrical pipe 2 to the inside periphery. The porous glass 6 is fed into the furnace core pipe 3 and heated while supplying gaseous mixture of He with Cl2. By this method, the furnace core pipe 3 is stabilized against heat and vitrification can be performed at high temp. Therefore, a product of high quality is obtd.