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Title: New sealing concept for planar solid oxide fuel cells

Abstract

Presented in this paper are results obtained on a new sealing concept for planar solid oxide fuel cells (pSOFCs). By employing a plastically deformable metal membrane as the key sealing element, this design should display a quasi-dynamic response to thermally or mechanically induced stresses. That is, the membrane is designed to readily yield or deform in response to the applied stress and thereby mitigate its transfer to the adjacent ceramic and metal components, while at the same time remaining adherent to both sealing surfaces (non-sliding). Described here are details of the new seal, including a discussion of design issues, initial proof-of-principle results on small test specimens, and a preliminary finite element analyses aimed at scaling the seal to the size and geometry required in a prototypic pSOFC stack.

Authors:
; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
961699
Report Number(s):
PNNL-SA-49419
AA2530000
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Materials Engineering and Performance, 15(4):427-432
Country of Publication:
United States
Language:
English
Subject:
SOFC, sealing, compliant seal

Citation Formats

Weil, K. Scott, Hardy, John S., and Koeppel, Brian J. New sealing concept for planar solid oxide fuel cells. United States: N. p., 2006. Web. doi:10.1361/105994906X117233.
Weil, K. Scott, Hardy, John S., & Koeppel, Brian J. New sealing concept for planar solid oxide fuel cells. United States. doi:10.1361/105994906X117233.
Weil, K. Scott, Hardy, John S., and Koeppel, Brian J. Sat . "New sealing concept for planar solid oxide fuel cells". United States. doi:10.1361/105994906X117233.
@article{osti_961699,
title = {New sealing concept for planar solid oxide fuel cells},
author = {Weil, K. Scott and Hardy, John S. and Koeppel, Brian J.},
abstractNote = {Presented in this paper are results obtained on a new sealing concept for planar solid oxide fuel cells (pSOFCs). By employing a plastically deformable metal membrane as the key sealing element, this design should display a quasi-dynamic response to thermally or mechanically induced stresses. That is, the membrane is designed to readily yield or deform in response to the applied stress and thereby mitigate its transfer to the adjacent ceramic and metal components, while at the same time remaining adherent to both sealing surfaces (non-sliding). Described here are details of the new seal, including a discussion of design issues, initial proof-of-principle results on small test specimens, and a preliminary finite element analyses aimed at scaling the seal to the size and geometry required in a prototypic pSOFC stack.},
doi = {10.1361/105994906X117233},
journal = {Journal of Materials Engineering and Performance, 15(4):427-432},
number = ,
volume = ,
place = {United States},
year = {Sat Apr 08 00:00:00 EDT 2006},
month = {Sat Apr 08 00:00:00 EDT 2006}
}
  • A key element in developing high performance planar solid oxide fuel cell stacks is the hermetic seal between the metal and ceramic components. There are two methods of sealing that are commonly employed: (1) rigid joining or (2) compressive sealing. Each method has its own set of advantages and design constraints. An alternative approach is currently under development that appears to combine some of the advantages of the other two techiques, including hermeticity, mechanical integrity, and minimization of interfacial stresses in either of the joint substrate materials, particulary the ceramic. The new sealing concept relies on a plastically deformable metalmore » seal; one that offers a quasi-dynamic mechanical response in that it is adherent to both sealing surfaces, i.e. non-sliding, but readily yields or deforms under thermally generated stresses, thereby mitigating the development of stresses in the adjacent ceramic and metal components even when a significant difference in thermal expansion exists between the two materials. The pre-experimental design of the seal, initial proof-of-principle results on small test specimens, and finite element analyses aimed at scaling the seal to prototypical sizes and geometries are described herein.« less
  • A key issue in developing commercially viable planar solid oxide fuel cell stacks is appropriate seal design. We are currently developing an alternative approach to rigid and compressive seal designs that conceptually combines advantages of both techiques, including hermeticity, mechanical integrity, and minimization of interfacial stresses in either of the joint substrate materials, particulary the ceramic. The new seal relies on a plastically deformable metal seal; one that offers a quasi-dynamic mechanical response in that it is adherent to both sealing surfaces, i.e. non-sliding, but readily yields or deforms under thermally generated stresses, thereby mitigating the development of stresses inmore » the adjacent ceramic and metal components even when a significant difference in thermal expansion exists between the two materials. Here we employ finite element modeling to assess the potential thermal cycling performance of this design, specifically as it pertains to sealing components with vastly different thermal expansion properties.« less
  • A key element in developing high performance planar solid oxide fuel cell stacks is the hermetic seal between the metal and ceramic components. There are two methods of sealing that are commonly employed: (1) rigid joining or (2) compressive sealing. Each method has its own set of advantages and design constraints. We are currently developing an alternative approach that appears to combine some of the advantages of the other two techiques, including hermeticity, mechanical integrity, and minimization of interfacial stresses in either of the joint substrate materials, particulary the ceramic. The new sealing concept relies on a plastically deformable metalmore » seal; one that offers a quasi-dynamic mechanical response in that it is adherent to both sealing surfaces, i.e. non-sliding, but readily yields or deforms under thermally generated stresses, thereby mitigating the development of stresses in the adjacent ceramic and metal components even when a significant difference in thermal expansion exists between the two materials. Here we described pre-experimental design of the seal, initial proof-of-principle results on small test specimens, and finite element analyses aimed at scaling the seal to prototypical sizes and geometries.« less
  • A novel “refractory” Sr-Ca-Y-B-Si sealing glass (glass-ceramic) was developed for solid oxide fuel cells (SOFCs). The objective was to develop sealing glass with desired thermal properties and minimal interfacial reactions with SOFC components, ceramic electrolyte and metallic interconnect. The current glass was different from conventional sealing glass in that the sealing temperatures were targeted higher (>950 degree C) and hence more refractory. Six glasses were formulated and made by conventional glass-making process. Thermal properties were characterized in the glass state and the sintered (crystallized) state. The effect of formulation on thermal properties was discussed. Candidate glasses were also aged formore » 1000 to 2000 h at elevated temperatures. Thermal expansion measurements showed minimal change after aging. A candidate glass (YSO-1) was used in sealing ceramic electrolyte to a metallic interconnect from 900 degree C to 1050 degree C in air. The interfacial microstructure was characterized and SrCrO4 was identified near the metal interface. Possible reaction mechanism for the chromate formation was discussed.« less
  • One of the keys to developing viable solid oxide fuel cell (SOFC) systems is to first develop reliable and inexpensive stack sealing technology. Three general approaches are currently being pursued, including: rigid bonded sealing, compressive sealing, and compliant bonded sealing. This review highlights the advantages and limitations of each option, discusses some of the leading concepts, and outlines the future steps that need to be taken in their development. Given the number of different SOFC stack designs under development, the variety of potential applications/conditions in which these systems can be used, and the complexities of stack manufacture, it is likelymore » that no one sealing technique will be suitable for all uses. Therefore continued progress in each general area, as well as the development of new concepts, is critical to the eventual success of SOFC technology.« less