Gas-Tight Sealing Method for Solid Oxide Fuel Cells
The long-term performance of a solid oxide fuel cell is very dependent on the materials and techniques used to hermetically seal the components of the stack. Researchers at PNNL have developed a method for fabricating durable and thermal-mechanically stable seals for solid oxide fuel cells (SOFC) needing metal-to-metal or metal-to-ceramic joining.Description
Known as the Gas-Tight Sealing Method, the technique employs a surface modification or coating that creates an optimum surface for the seal. Aluminum is applied to the metal component surface and oxidized to form Al2O3 or an oxide film embedded with nodules is thermally grown on the surface of metal substrate. The surface modification changes the surface chemistry and morphology of the metal allowing for better compatibility with other metal parts and sealing materials. The nodules embedded in the metal bonding surface that provides for better adhesion to a sealing layer of glass, metal or a combination of materials.Benefits
- More durable, better performance—chemical reactions between surfaces are mitigated improving long term thermal stability of the seal during thermal cycling
- Reliability built in—the mechanical interlocking that occurs with the nodules and the sealing material results in a stronger, stable seal
- Energy efficiency – the resulting hermetic seal blocks energy from undesirable "escape" from the fuel cell stack.
- Utility and electricity generation
- High temperature electrochemical devices including solid oxide fuel cells, batteries, and sensors
|Title and Abstract||
Gas-tight metal/ceramic or metal/metal seals for applications in high temperature electrochemical devices and method of making
A method of joining metal and metal, or metal and ceramic parts, wherein a first metal part is selected and then processed to form a bond coat that will effectively bond to a sealing material which in turn bonds to a second metal or ceramic part without degrading under the operating conditions of electrochemical devices. Preferred first metal parts include alumina forming alloys from the group consisting of ferritic stainless steels (such as Fecralloys), austinetic stainless steels, and superalloys, and chromia forming alloys formed of ferritic stainless steels. In the case of chromia forming ferritic stainless steels, this bond coat consists of a thin layer of alumina formed on the surface, with a diffusion layer between the first metal part and this thin layer. The bond coat provides a good bonding surface for a sealing layer of glass, braze or combinations thereof, while at the same time the diffusion layer provides a durable bond between the thin alumina layer and the first metal part. In the case of alumina forming alloys, the bond coat consists of cauliflower-like growths of an aluminum oxide nodules embedded in the surface of the alumina forming alloys.
|Pacific Northwest National Laboratory||01/18/2005
|Technology ID||Development Stage||Availability||Published||Last Updated|
|13501-E||Prototype - Reduced to practice||Available - Available for licensing in all fields||09/10/2010||09/10/2010|