Low melting temperature silver braze alloy

Abstract

A brazing alloy comprising elemental silver alloyed with elemental silicon in a silver/silicon ratio between about 95/5 and 99/1, preferably about 97/3. Small amounts of silicon alloyed with silver depress the alloy liquidus curve significantly, the liquidus temperature of a silver and silicon eutectic alloy being about 837° C. Brazing alloys in accordance with the invention are useful in bonding ceramics to ceramics, ceramics to metals, and metals to metals. Copper, vanadium, or other oxygen-reactive surface bonding elements may also be included. Silver/silicon alloys are useful in applications such as assembly of components of solid oxide fuel cells. A variety of silver/silicon alloy brazes can be used within the same fuel cell so that subsequent brazing can be performed without reliquifying a previous braze. A brazing alloy comprising elemental silver and ruthenium in a silver/ruthenium ratio between 97/3 and 99/1 is also included.

1 - 8 . (canceled)  
   
   
       9 . A fuel cell assembly comprising a first component and a second component wherein said first and second components are bonded by a brazing alloy consisting essentially of silver and silicon, wherein said alloy has a liquidus temperature of less than 962° C.  
   
   
       10 . A fuel cell assembly in accordance with  claim 9  wherein the weight percent ratio of said silver to said silicon is between about 99/1 and about 95/5.  
   
   
       11 . A fuel cell assembly in accordance with  claim 23  wherein the weight percent ratio of said silver to said ruthenium is between about 99/1 and about 97/3.  
   
   
       12 . A fuel cell assembly in accordance with  claim 9  wherein at least one of said first and second components is a ceramic component.  
   
   
       13 . A fuel cell assembly in accordance with  claim 9  wherein at least one of said first and second components is a metal component.  
   
   
       14 . A fuel cell assembly in accordance with  claim 9  wherein said brazing alloy is a first brazing alloy, said fuel assembly further comprising an additional element wherein said additional element is bonded to one of said first element, second element and another element by a second brazing alloy having a liquidus temperature less than said liquidus temperature of said first brazing compound.  
   
   
       15 . A fuel cell assembly in accordance with  claim 9  wherein said assembly comprises a solid oxide fuel cell.  
   
   
       16 - 18 . (canceled)  
   
   
       19 - 21 . (not entered)  
   
   
       22 . A fuel cell assembly in accordance with  claim 10  wherein said liquidus temperature is about 835° C.  
   
   
       23 . A fuel cell assembly comprising a first component and a second component wherein said first and second components are bonded by a brazing alloy consisting essentially of silver and ruthenium, wherein said alloy has a liquidus temperature of less than 962° C.  
   
   
       24 . A fuel cell assembly in accordance with  claim 23  wherein at least one of said first and second components is a ceramic component.  
   
   
       25 . A fuel cell assembly in accordance with  claim 23  wherein at least one of said first and second components is a metal component.  
   
   
       26 . A fuel cell assembly in accordance with  claim 23  wherein said brazing alloy is a first brazing alloy, said fuel assembly further comprising an additional element wherein said additional element is bonded to one of said first element, second element and another element by a second brazing alloy having a liquidus temperature less than said liquidus temperature of said first brazing compound.  
   
   
       27 . A fuel cell assembly in accordance with  claim 23  wherein said assembly comprises a solid oxide fuel cell.  
   
   
       28 . A fuel cell assembly in accordance with  claim 11  wherein said liquidus temperature is about 920° C.  
   
   
       29 . A fuel cell assembly comprising a first component and a second component wherein said first and second components are bonded by a brazing alloy consisting essentially of silver, silicon, and a third elemental component selected from the group consisting of copper and vanadium, and wherein said alloy has a liquidus temperature of less than 962° C.