Sealing arrangement for high-temperature fuel cell stack

摘要

Disclosed is a sealing assembly for metal components, wherein the sealing assembly has an electrical insulating effect, and wherein the sealing assembly comprises a ceramic layer and a base brazing material disposed thereon, to which germanium is added. The addition of germanium advantageously ranges from 0.1 to 5.0 mol %, and preferably between 0.5 and 2.5 mol %. A particular embodiment provides for the use of a brazing material which additionally comprises silicon in the range of >0 to 2.5 mol %, and preferably between 0.1 and 0.9 mol %. Furthermore, a brazing material having a further addition of 10 to 40% by volume of Al2TiO5, and preferably between 20 and 30% by volume of Al2TiO5, has proven to be particularly suited for the sealing assembly. The use of the special brazing material composition inside the sealing assembly generally results in reproducibly tight and insulating joints having the following properties: a) escape of brazing material is prevented and running of brazing material is reduced, b) the porosity of the brazing material (primarily individual pores or narrow pore lines) is markedly reduced, c) the brazed joints have sufficient electrical resistance, and d) the brazed joints are generally sufficiently gas-tight (leakage rate during He leakage test <10−3 mbar*1*s−1).

主权项

1. A sealing assembly for metal components, the sealing assembly having an electrical insulating property by which said metal components are electrically insulated from each other by the sealing assembly, the sealing assembly configured as a gas-tight seal between said metal components at temperatures above 400 degrees Celsius, the sealing assembly comprising:
a ceramic layer which is an electrical insulator, the ceramic layer having pores and grain boundaries; a brazing material disposed on and in contact with the ceramic layer without a barrier layer between the ceramic layer and the brazing material; the brazing material having a composition configured to reduce infiltration of the brazing material into the ceramic layer at pores and grain boundaries of the ceramic layer; said brazing material composition comprising:
a base brazing material;germanium at an amount that reduces pore formation in the brazing material; andsilicon at an amount that reduces capillarity of the base brazing material,wherein the amount of germanium is in the range of 0.1 to 5.0 mol %; andwherein the amount of silicon is greater than 0 and up to 2.5 mol %.