| 摘要 |
PURPOSE:To manufacture the titled glass having a very low concn. of OH groups, by pretreating finely powdered starting materials for fluoride glass with HF, F3, BF3, CF4, Cl2, CCl4 or SOCl2 and by melting the pretreated materials with an electric furnace. CONSTITUTION:Finely powdered starting materials 10 for fluoride glass are charged into a platinum crucible 2, and the crucible 2 is mounted on a stage 8. A cover 3 is put on the crucible 2, and a pipe attached to the cover 3 is connected to an exhaust system. A platinum crucible 6 is mounted on a crucible stand 7 below an electric furnace 1, and the stand 7 is moved upward to insert the crucible 6 into the crucible 2. After heating the materials 10 with the furnace 1, a gas for an OH group removing reaction is introduced from a pipe 4 to cause said reaction. HF, F2, BF3, CF4, Cl2, CCl4 or SOCl2 is used as the gas. After finishing the reaction, the materials 10 freed of OH groups are melted by heating with the furnace 1 and allowed to flow in the crucible 6 through holes 11. The resulting molten glass is cast in a casting mold, annealed in the mold, and slowly cooled to manufacture a fluoride glass preform. |
