High purity transparent silica glass
US6133178A · kind A · utility
Assignees
Inventors
Key dates
| Filing date | Dec 3, 1998 |
| Grant date | Oct 17, 2000 |
| Priority date | — |
| Expiry date | Dec 3, 2018 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC03C2203/10
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
A high-purity transparent silica glass containing Fe, Na and K impurities each in an amount of 0.01-0.3 ppm, and an OH group in an amount of 0-3 ppm; among the Fe impurities, the content of metallic Fe having a valency of +0 being not larger than 0.1 ppm. This transparent silica glass exhibits, even when it is maintained at 900-1,400.degree. C. for at least 20 hours, an extinction coefficient of not larger than 0.009 at a wavelength of 400 nm, and does not become colored as visually examined. The silica glass is made by a process wherein powdery silica filled in a mold cavity is melted at 1,700.degree. C. or higher, characterized in that the melting is conducted in a graphite mold having a porous high-purity graphite layer provided on the mold inner surface so that the filled silica is not contacted with the mold; said porous layer having a bulk density of 0.1-1.5 g/cm.sup.3, and the content of each of Fe, Na and K impurities in the porous layer being not larger than 1 ppm.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.