| 摘要 |
PURPOSE:To prepare a porous preform having precise composition, at a high rate of production, without using an electronic thermostatic chamber, by supplying a liquid mixture of two or more glass-forming raw materials to a fine glass powder synthesizing torch furnished with a vaporizing chamber heated above the highest boiling point of the raw materials. CONSTITUTION:A liquid mixture composed of e.g. 90mol% of SiCl4 and 10mol% of GeCl4 stored in a liquid reservoir 14 is introduced into the vaporizing chamber 13 of a fine glass powder synthesizing torch 11 through a liquid pump 15 and a pipe 16. The vaporizing chamber 13 and the center nozzle 17 are heated at 120 deg.C (higher than the boiling point of SiCl4 and GeCl4, i.e. 57.6 deg.C and 84 deg.C) with a heater 12. The liquid mixture is evaporated instantaneously, blown off through the center nozzle 17 to form a flame 18 together with Ar gas, H2 gas and O2 gas, and decomposed to fine glass powder by flame hydrolysis reaction forming a porous preform on the starting member. Since the raw materials are mixed homogeneously together in advance, the fluctuation of the composition is eliminated, and a porous preform can be prepared at a high rate without using an expensive electronic thermostatic chamber. |
