TY - JOUR
T1 - Accelerated creep in solid oxide fuel cell anode supports during reduction
AU - Frandsen, Henrik Lund
AU - Makowska, Malgorzata Grazyna
AU - Greco, Fabio
AU - Chatzichristodoulou, Christodoulos
AU - Ni, De Wei
AU - Curran, Declan
AU - Strobl, M.
AU - Kuhn, Luise Theil
AU - Hendriksen, Peter Vang
PY - 2016
Y1 - 2016
N2 - 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.
AB - 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.
KW - Creep
KW - Reduction
KW - SOFC
KW - SOEC
KW - Ni-YSZ
KW - Chemo-mechanical coupling
U2 - 10.1016/j.jpowsour.2016.04.097
DO - 10.1016/j.jpowsour.2016.04.097
M3 - Journal article
VL - 323
SP - 78
EP - 89
JO - Journal of Power Sources
JF - Journal of Power Sources
SN - 0378-7753
ER -