Claims
- 1. Process for making a fused quartz glass tube capable of forming an outer layer of uniformly fine crystalline silica when heated to a temperature at which such crystalline silica forms which comprises forming a first tube from fused quartz glass containing a crystallization promoting nuclei whose rate of diffusion in quartz glass is less than that of sodium at elevated temperatures, inserting a second, snugly fitting fused quartz glass tube into said first tube and thereafter fusing said first and second tubes together at a temperature of at least 1200.degree. C wherein the fused quartz glass recrystallizes.
- 2. Process of claim 1 wherein said diffusion process is carried out at a temperature of at least 1300.degree. C.
- 3. A process according to claim 1 wherein the crystallization promoting nuclei is an element of Group IV of the Periodic Table, boron, aluminum, phosphorus, antimony, zinc, magnesium, calcium, gallium, or an oxide, carbide or nitride thereof.
- 4. A process according to claim 3 wherein said nuclei are present in an amount of from 4 to about 800 ppm.
- 5. A process according to claim 4 wherein the concentration of nuclei at the outer surface of the quartz glass tube is less than about 5.multidot.10.sup.17 nuclei per sq. cm.
- 6. A process according to claim 5 wherein the surface concentration of said nuclei is from about 1.multidot.10.sup.14 to about 5.multidot.10.sup.17 nuclei per sq. cm.
- 7. Process for making a fused quartz glass tube capable of forming an outer layer of uniformly fine crystalline silica when heated to a temperature at which such crystalline silica forms which comprises grinding into a powder a composition consisting essentially of fused quartz glass containing from about 4 to about 800 ppm of crystallization promoting nuclei having a rate of diffusion in fused quartz glass less than that of sodium at elevated temperatures, applying said powder to the outser surface of a fused quartz glass cylinder and thereafter heating and drawing said cylinder into a tube and heating said tube at a temperature of at least 1200.degree. C.
- 8. A process according to claim 7 wherein said cyrstallization promoting nuclei is an element of Group IV of the Periodic Table, boron, aluminum, phosphorus, antimony, zinc, magnesium, calcium, gallium, or an oxide, carbide or nitride thereof.
- 9. A process according to claim 8 wherein the concentration of nuclei at the outer surface of the quartz glass tube is less than about 5.multidot.10.sup.17 nuclei per sq. cm.
- 10. A process according to claim 9 wherein the surface concentration of said nuclei is from about 1.multidot.10.sup.14 to about 5.multidot.10.sup.17 nuclei per sq. cm.
Priority Claims (3)
Number |
Date |
Country |
Kind |
1696061 |
Feb 1968 |
DE |
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1771077 |
Mar 1968 |
DE |
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1988697 |
Mar 1968 |
DE |
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RELATED APPLICATIONS
This is a division of application Ser. No. 383,432 filed July 27, 1973, now U.S. Pat. No. 3,927,697 issued Dec. 23, 1975, which is, in turn, a division of Ser. No. 166,844 filed July 28, 1971, Now U.S. Pat. No. 3,776,809 issued Dec. 4, 1973, which is, in turn, a continuation of Ser. No. 793,755 filed Jan. 24, 1969, and Ser. No. 810,713 filed Mar. 26, 1969, both now abandoned.
US Referenced Citations (12)
Non-Patent Literature Citations (1)
Entry |
"Handbook of Glass Manufacture," vol. II, Fay V. Tooley - Ogden Pub. Co., New York, 1960, pp. 192-199. |
Related Publications (1)
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Number |
Date |
Country |
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810713 |
Mar 1969 |
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Divisions (2)
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Number |
Date |
Country |
Parent |
383432 |
Jul 1973 |
|
Parent |
166844 |
Jul 1971 |
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Continuations (1)
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Number |
Date |
Country |
Parent |
793755 |
Jan 1969 |
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