Glass ceramic seals to inconel

• US 4,414,282 A
• Filed: 04/19/1982
• Issued: 11/08/1983
• Est. Priority Date: 04/19/1982
• Status: Expired due to Term

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: United States Department of Energy (Government of the United States of America)
• Inventors: Reed, Scott T., McCollister, Howard L.
• Primary Examiner(s): Kellogg, Arthur D.
• Application Number:
  US06/369,965
• Time in Patent Office: 568 Days
• Field of Search: 65/59.22, 65/43, 65/33, 501/4, 501/7, 501/5, 428/433
• US Class Current: 428/433
• CPC Class Codes: C03C 10/00 Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition
• CPC Class Codes: C03C 27/046 of metals, metal oxides or metal salts only

Abstract

A glass ceramic composition prepared by subjecting a glass composition comprising, by weight, 65-80% SiO₂, 8-16%, Li₂ O, 2-8% , Al₂ O₃, 1-8% K₂ O, 1-5% P₂ O₅ and 1.5-7% B₂ O₃, to the following processing steps of heating the glass composition to a temperature sufficient to crystallize lithium metasilicate therein, holding the glass composition at a temperature and for a time period sufficient to dissolve the lithium metasilicate therein thereby creating cristobalite nucleii, cooling the glass composition and maintaining the composition at a temperature and for a time period sufficient to recrystallize lithium metasilicate therein, and thermally treating the glass composition at a temperature and for a time period sufficient to cause growth of cristobalite and further crystallization of lithium metasilicate producing a glass ceramic composition having a specific thermal expansion coefficient and products containing said composition.

Claims

1. A glass ceramic composition prepared by subjecting a glass composition comprising, by weight, 65-80% SiO₂, 8-16% Li₂ O, 2-8% Al₂ O₃, 1-8% K₂ O, 1-5% P₂ O₅ and 1.5-7% B₂ O₃, to the following processing steps:

a. heating the glass composition to a temperature sufficient to crystallize lithium metasilicate therein;

b. holding the glass composition at a temperature and for a time period sufficient to dissolve the lithium metasilicate therein thereby creating cristobalite nucleii;

c. cooling the glass composition and maintaining the composition at a temperature and for a time period sufficient to recrystallize lithium metasilicate therein; and

d. thermally treating the glass composition at a temperature and for a time period sufficient to cause growth of cristobalite and further crystallization of lithium metasilicate producing a glass ceramic composition having a specific thermal expansion coefficient.

2. The glass ceramic composition as recited in claim 1, having a thermal expansion coefficient α

of 120-160×

10^-7 /°

C.

3. The glass ceramic composition as recited in claim 1, in which the composition of the sealing glass is, by weight, 70-75% SiO₂, 10-14% Li₂ O, 4-6% Al₂ O₃, 3-6% K₂ O, 2-4% P₂ O₅ and 2-5% B₂ O₃.

4. The glass ceramic composition as recited in claim 1, in which the composition of the sealing glass is, by weight, 71.7% SiO₂, 12.6% Li₂ O, 5.1% Al₂ O₃, 4.9% K₂ O, 2.5% P₂ O₅ and 3.2% B₂ O₅.

5. The glass ceramic composition as recited in claim 1, wherein the heating of step (a) is conducted at a temerature up to about 1000°

C., the holding temperature of step (b) is 950°

to 1050°

C. and the holding time is 5 to 60 minutes, the composition is cooled to a temperature of 600°

to 700°

C. and held at said temperature for 10 to 120 minutes in step (c) and wherein the thermal treatment of step (d) is conducted at 775°

to 850°

C. for a time of 10 to 120 minutes.

6. The glass ceramic composition as recited in claim 5, in which the composition of the sealing glass is, by weight, 70-75% SiO₂, 10-14% Li₂ O, 4-6% Al₂ O₃, 3-6% K₂ O, 2-4% P₂ O₅ and 2-5% B₂ O₃.

7. The glass ceramic composition as recited in claim 5, in which the composition of the sealing glass is, by weight, 71.7% SiO₂, 12.6% Li₂ O, 5.1% Al₂ O₃, 4.9% K₂ O, 2.5% P₂ O₅ and 3.2% B₂ O₃.

8. A process for forming a seal between a glass having a thermal expansion coefficient α

of 120-160×

10^-7 /°

C. and a nickel base alloy having substantially the same thermal expansion coefficient, comprising the steps of;

1. applying a glass having a composition, by weight, of 65-80% SiO₂, 8-16% Li₂ O, 2-8% Al₂ O₃, 1-8% K₂ O, 1-5% P₂ O₅ and 1.5-7% B₂ O₃ to the nickel base alloy, and subjecting the glass to the following processing steps;

a. heating the glass composition to a temperature sufficient to crystallize lithium metasilicate therein;

b. holding the glass composition at a temperature and for a time period sufficient to dissolve the lithium metasilicate therein thereby creating cristobalite nucleii;

c. cooling the glass composition and maintaining the composition at a temperature and for a time period sufficient to recrystallize lithium metasilicate therein; and

d. thermally treating the glass composition at a temperature and for a time period sufficient to cause growth of cristobalite and further crystallization of lithium metasilicate producing a glass ceramic composition having a specific thermal expansion coefficient.

9. The process as recited in claim 8, in which the composition of the molten glass is, by weight, 70-75% SiO₂, 10-14% Li₂ O, 4-6% Al₂ O₃, 3-6% K₂ O, 2-4% P₂ O₅ and 2-5% B₂ O₃.

10. The process as recited in claim 8, in which the composition of the molten glass is, by weight, 70-75% SiO₂, 12.6% Li₂ O, 5.1% Al₂ O₃, 4.9% K₂ O, 2.5% P₂ O₅ and 3.2% B₂ O₃.

11. A product produced by the process of claim 8.

12. A product produced by the process of claim 9.

13. A product produced by the process of claim 10.

14. An electrical header produced by the process of claim 8.

15. An electrical header produced by the process of claim 9.

16. An electrical header produced by the process of claim 10.

17. The process as recited in claim 8 wherein the heating of step (a) is conducted at a temperature up to about 1000°

C., the holding temperature of step (b) is 950°

to 1050°

C. and the holding time is 5 to 60 minutes, the composition is cooled to a temperature of 600°

to 700°

C. and held at said temperature for 10 to 120 minutes in step (c) and wherein the thermal treatment of step (d) is conducted at 775°

to 850°

C. for a time of 10 to 120 minutes.

18. The process as recited in claim 17, in which the composition of the molten glass is, by weight, 70-75% SiO₂, 10-14% Li₂ O, 4-6% Al₂ O₃, 3-6% K₂ O, 2-4% P₂ O₅ and 2-5% B₂ O₃.

19. The process as recited in claim 17, in which the composition of the molten glass is, by weight, 71.7% SiO₂, 12.6% Li₂ O, 5.1% Al₂ O₃, 4.9% K₂ O, 2.5% P₂ O₅ and 3.2% B₂ O₃.

20. A product produced by the process recited by claim 17.

21. A product produced by the process recited by claim 18.

22. A product produced by the process recited by claim 19.