Glass-ceramic sealants for solid oxide fuel cells: Part I. Physical properties
- PDF / 152,715 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 57 Downloads / 200 Views
MATERIALS RESEARCH
Welcome
Comments
Help
Glass-ceramic sealants for solid oxide fuel cells: Part I. Physical properties K. L. Ley,a) M. Krumpelt, R. Kumar, J. H. Meiser,b) and I. Bloomc) Electrochemical Technology Program, Chemical Technology Division, Argonne National Laboratory, Argonne, Illinois 60439-4837 (Received 10 October 1995; accepted 8 January 1996)
A family of sealant materials has been developed for use in the solid oxide fuel cell (SOFC) and in other applications in the temperature range of 800–1000 ±C. These materials are based on glasses and glass-ceramics in the SrO–La2 O3 –Al2 O3 –B2 O3 –SiO2 system. The coefficients of thermal expansion (CTE) for these materials are in the range of 8–13 3 1026y±C, a good match with those of the SOFC components. These sealant materials bond well with the ceramics of the SOFC and, more importantly, form bonds that can be thermally cycled without failure. At the fuel cell operating temperature, the sealants have viscosities in the range of 104 –106 Pa-s, which allow them to tolerate a CTE mismatch of about 20% among the bonded substrates. The gas tightness of a sample seal was demonstrated in a simple zirconia-based oxygen concentration cell.
I. INTRODUCTION
Solid oxide fuel cells convert the chemical energy of a fuel such as hydrogen into electricity by electrochemical oxidation of the fuel at 800–1000 ±C. Such fuel cells consist of three electrochemically active ceramics: a porous, strontium-doped lanthanum manganite (LSM) cathode; a dense, yttria-stabilized zirconia (YSZ) electrolyte; and a porous, nickel-YSZ cermet (NZC) anode. Several such cells are stacked in series. To build planar solid oxide fuel cell (SOFC) stacks, the cells are separated from one another by fuel and oxidant flow fields and bipolar plates of dense strontium- or calciumdoped lanthanum chromite (LC) or corrosion-resistant metal alloy. In such planar SOFC’s, gas-tight seals must be formed along the edges of each cell and between the fuel cell stack and the gas manifolds. Because of the high temperatures and the highly reducing and oxidizing gases present in the cells, conventional sealants and cements do not work well, and new sealants must be developed. An effective sealant must form gas-tight seals to the cell and stack components, and it must hold the cell and stack together during thermal cycling. Within the fuel cell stack, the sealant must be compatible with the thermal expansion behavior of the fuel cell ceramics; i.e., it must have a CTE value in the range of 10 –13 3 1026y±C. At the stack-to-manifold junction, the much longer sealing distances require a compliant sealant that a)Present
address, Department of Chemistry, Illinois Institute of Technology, Chicago, Illinois 60616. b)Present address, Department of Chemistry, Ball State University, Muncie, Indiana 47306. c) Author to whom correspondence should be addressed.
can tolerate a relatively large mismatch in CTE’s. For example, if the gas manifold material is alumina (CTE 8 3 1026y±C), the sealant must accommodate a 20%
Data Loading...
