Active braze techniques on beta-alumina

1. A method of sealing a portion of beta-alumina electrolyte, insulated collar and metal rings of a sodium-based thermal battery, comprising:

a) introducing a braze alloy composition between a first component and a second component to be joined, wherein the first component is comprised of beta-alumina and the second component is comprised of a ceramic insulator;

b) introducing the braze alloy composition between the second component and a third component to be joined, wherein the third component is comprised of metal or metal alloy; and

c) heating the components to form an active braze seal (joint) between the first component and the second component and between the second component and the third component.

2. The method according to claim 1 , wherein said ceramic insulator is selected from alpha-alumina, spinel, zirconia and yttria, and combinations thereof.

3. The method according to claim 2 , wherein said ceramic insulator is alpha-alumina.

4. The method according to claim 1 , wherein said braze alloy composition comprises nickel and an active metal element, and further comprises a) germanium, b) niobium and chromium, or c) silicon and boron; or wherein said braze alloy composition comprises copper, nickel and an active metal element.

5. The method according to claim 1 , wherein the heating is carried out at a brazing temperature, wherein said brazing temperature is equal to or greater than the liquidus temperature of the braze alloy composition and less than the melting temperatures of the components to be joined.

6. The method according to claim 4 , wherein the heating is carried out at a brazing temperature, wherein said brazing temperature is equal to or greater than the liquidus temperature of the braze alloy composition and less than the melting temperatures of the components to be joined.

7. The method according to claim 6 , wherein the heating comprises holding the brazing temperature constant for about 1 minute to about 30 minutes after the braze alloy becomes substantially liquid.

8. The method according to claim 7 , wherein the heating comprises holding the brazing temperature constant in a range of about 1050 to about 1100 degrees Celsius for about 15 minutes, then holding the brazing temperature constant at a temperature in a range of about 1150 to about 1250 degrees Celsius for about 15 minutes.

9. The method according to claim 1 , wherein the heating is carried out in an ultra high pure argon atmosphere or 1%-5% hydrogen (balanced by argon) or ultra high pure helium or vacuum.

10. The method according to claim 1 , wherein the third component comprises nickel or a nickel based alloy.

11. The method according to claim 4 , wherein the active metal element is selected from titanium, zirconium, hafnium, vanadium, and combinations thereof.

12. The method according to claim 11 , wherein the active metal element is titanium.

13. A method of joining a ceramic insulator and beta-alumina by active brazing, comprising:

a) introducing a braze alloy composition between the ceramic insulator and the beta-alumina to be joined; and

b) heating the components to form an active braze seal (joint) between the ceramic insulator and the beta-alumina;

wherein said braze alloy composition comprises nickel and an active metal element, and further comprises a) germanium, b) niobium and chromium, or c) silicon and boron; or wherein said braze alloy composition comprises copper, nickel and an active metal element; and wherein

the heating step is carried out at a brazing temperature that is equal to or greater than the liquidus temperature of the braze alloy composition; and less than the melting temperatures of the components to be joined; comprising the step of holding the brazing temperature constant in a range of about 1050 to about 1100 degrees Celsius for about 15 minutes, then holding the brazing temperature constant at a temperature in a range of about 1150 to about 1250 degrees Celsius for about 15 minutes.

14. The method according to claim 13 , wherein said ceramic insulator is selected from alpha-alumina, spinel, zirconia and yttria, and combinations thereof.

15. The method according to claim 14 , wherein said ceramic insulator is alpha-alumina.

16. The method according to claim 13 , wherein the heating is carried out in an ultra high pure argon atmosphere, or 1%-5% hydrogen (balanced by argon) or ultra high pure helium or vacuum.

17. The method according to claim 13 , wherein the active metal element is selected from titanium, zirconium, hafnium, vanadium, and combinations thereof.

18. The method according to claim 17 , wherein the active metal element is titanium.

19. The method according to claim 1 , wherein the sodium-based thermal battery is a sodium metal halide battery.