Claims
- 1. A heat insulator disposed between a heating and a non-heating zone in a furnace core tube for insulating and retaining heat in said heating zone, wherein said heat insulator is formed with a porous body of quartz glass having numerous inner microspaces, said porous body comprising a quartz glass foam having an apparent density of 0.1 to 0.8 g/cm.sup.3, a continuous porosity of 60% or less, concentrations of each of Na, K, Li, Cu, Ni, Ca and Ce of 1 ppm or less, a total concentration of metallic impurities of 100 ppm or less, and an OH group content of 100 ppm or less.
- 2. A heat insulator disposed between a heating and a non-heating zone in a furnace core tube for insulating and retaining heat in said heating zone, wherein said heat insulator is formed with a porous body of quartz glass having numerous inner microspaces, said porous body comprising a quartz glass foam having an apparent density of 0.1 to 0.8 g/cm.sup.3, a continuous porosity of 60% or less, concentrations of each of Na, K, Li, Cu, Ni, Ca and Ce of 1 ppm or less, a total concentration of metallic impurities of 100 ppm or less, and an OH group content of 100 ppm or less, and said quartz glass foam containing interior microspaces is obtained by preparing silica glass powder by heat treating high-purity synthetic silica glass powder, which contains 1 ppm or less each of semiconductor-degrading metal impurities, by thermal vapor-phase reaction in an ammonia gas atmosphere at 800.degree. C., and fusing and foaming said silica glass powder in a heat-resistant crucible by heating to 1,700.degree. C. under a reduced pressure atmosphere.
Parent Case Info
This application is a division of application Ser. No. 08/170,164, filed Dec. 23, 1993, now U.S. Pat. No. 5,480,300.
US Referenced Citations (1)
Number |
Name |
Date |
Kind |
5480300 |
Okoshi et al. |
Jan 1996 |
|
Foreign Referenced Citations (1)
Number |
Date |
Country |
64-47020 |
Feb 1989 |
JPX |
Divisions (1)
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Number |
Date |
Country |
Parent |
170164 |
Dec 1993 |
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