COMPARISON OF HIGH-PURITY H-2 O-2 AND LPG O-2 FLAME-FUSED SILICA GLASSES FROM SOL-GEL SILICA POWDER

High-quality flame-fused silica glasses were obtained from high-purity starting sol-gel silica powders, under H-2/O-2 and liquid propane gas (LPG)/O-2 flames. Neither metallic nor carbon contamination was observed during the fusion process, even by using domestic LPG. The flame-fused sol-gels showed lower impurity levels than silica glasses from natural quartz and of the same order as the commercial synthetic silica glasses (chemical vapor deposition process). By fusion with an LPG/O-2 flame, the aggregation of OH radicals during the fusion process was verified to be about 100 ppm lower with viscosity two times higher than that of silica glasses fused by H-2/O-2. The viscosity of this flame-fused sol-gel silica is lower than the flame-fused silica from rock crystal, but is one order of magnitude higher than that of the synthetic silica glass.