Accelerated creep in solid oxide fuel cell anode supports during reduction

Henrik Lund Frandsen, Malgorzata Grazyna Makowska, Fabio Greco, Christodoulos Chatzichristodoulou, De Wei Ni, Declan Curran, M. Strobl, Luise Theil Kuhn, Peter Vang Hendriksen

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Abstract

To evaluate the reliability of solid oxide fuel cell (SOFC) stacks during operation, the stress field in the stack must be known. During operation the stress field will depend on time as creep processes relax stresses. The creep of reduced Ni-YSZ anode support at operating conditions has been studied previously. In this work a newly discovered creep phenomenon taking place during the reduction is reported. This relaxes stresses at a much higher rate (∼ x104) than creep during operation. The phenomenon was studied both in three-point bending and uniaxial tension. Differences between the two measurements could be explained by newly observed stress promoted reduction. Finally, samples exposed to a small tensile stress (∼ 0.004 MPa) were observed to expand during reduction, which is in contradiction to previous literature. These observations suggest that release of internal residual stresses between the NiO and the YSZ phases occurs during reduction. The accelerated creep should practically eliminate any residual stress in the anode support in an SOFC stack, as has previously been indirectly observed. This phenomenon has to be taken into account both in the production of stacks and in the simulation of the stress field in a stack based on anode supported SOFCs. (C) 2016 Elsevier B.V. All rights reserved.
Original languageEnglish
JournalJournal of Power Sources
Volume323
Pages (from-to)78-89
Number of pages12
ISSN0378-7753
DOIs
Publication statusPublished - 2016

Keywords

  • Creep
  • Reduction
  • SOFC
  • SOEC
  • Ni-YSZ
  • Chemo-mechanical coupling

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