Microstructure degradation of cermet anodes for solid oxide fuel cells : quantification of nickel grain growth in dry and in humid atmospheres

Holzer, Lorenz; Iwanschitz, Boris; Hocker, Thomas; Münch, Beat; Prestat, Michel; Wiedenmann, Daniel; Vogt, Uli; Holtappels, Peter; Sfeir, Josef; Mai, Andreas; Graule, Thomas

doi:10.1016/j.jpowsour.2010.08.017

Publication type:	Article in scientific journal
Type of review:	Peer review (publication)
Title:	Microstructure degradation of cermet anodes for solid oxide fuel cells : quantification of nickel grain growth in dry and in humid atmospheres
Authors:	Holzer, Lorenz Iwanschitz, Boris Hocker, Thomas Münch, Beat Prestat, Michel Wiedenmann, Daniel Vogt, Uli Holtappels, Peter Sfeir, Josef Mai, Andreas Graule, Thomas
DOI:	10.1016/j.jpowsour.2010.08.017
Published in:	Journal of Power Sources
Volume(Issue):	196
Issue:	3
Page(s):	1279
Pages to:	1294
Issue Date:	1-Feb-2011
Publisher / Ed. Institution:	Elsevier
ISSN:	0378-7753 1873-2755
Language:	English
Subjects:	Microstructure analysis; Nickel coarsening; Ostwald ripening; Anode degradation
Subject (DDC):	530: Physics 621.3: Electrical, communications, control engineering
Abstract:	The effects of compositional and environmental parameters on the kinetics of microstructural degradation are investigated for porous Ni/CGO anodes in solid oxide fuel cells (SOFC). Improved methodologies of SEM-imaging, segmentation and object recognition are described which enable a precise quantification of nickel grain growth over time. Due to these methodological improvements the grain growth can be described precisely with a standard deviation of only 5–15 nm for each time step. In humid atmosphere (60 vol.% H2O, 40% N2/H2) the growth rates of nickel are very high (up to 140%/100 h) during the initial period (<200 h). At longer exposure time (>1000 h) the growth rates decrease significantly to nearly 0%/100 h. In contrast, under dry conditions (97 vol.% N2, 3 vol.% H2) the growth rates during the initial period are much lower (ca. 1%/100 h) but they do not decrease over a period of 2000 h. In addition to the humidity factor there are other environmental and compositional parameters which have a strong influence on the kinetics of the microstructural degradation. The nickel coarsening is strongly depending on the gas flow rate. Also the initial microstructures and the anode compositions have a big effect on the degradation kinetics. Thereby small average grain sizes, wide distribution of particle size and high contents of nickel lead to higher coarsening and degradation rates. Whereas the nickel coarsening appears to be the dominant degradation mechanism during the initial period (<200 h) other degradation phenomena become more important during long exposure time (>1000 h) in humidified gas. Thereby the evaporation of volatile nickel species may lead to a local increase of the Ni/CGO ratio. Due to the surface wetting of CGO a continuous layer tends to form on the surface of the nickel grains which prevents further grain growth and evaporation of nickel. These phenomena lead to a microstructural reorganization between 1000 and 2300 h of exposure. This complex pattern of degradation phenomena also leads to a change of the amount of active microstructural sites that are important for catalytic reactions at the pore-nickel interfaces and for electrochemical reactions at the triple phase boundaries (TPB).
URI:	https://digitalcollection.zhaw.ch/handle/11475/1671
Fulltext version:	Published version
License (according to publishing contract):	Licence according to publishing contract
Departement:	School of Engineering
Organisational Unit:	Institute of Computational Physics (ICP)
Appears in collections:	Publikationen School of Engineering

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Holzer, L., Iwanschitz, B., Hocker, T., Münch, B., Prestat, M., Wiedenmann, D., Vogt, U., Holtappels, P., Sfeir, J., Mai, A., & Graule, T. (2011). Microstructure degradation of cermet anodes for solid oxide fuel cells : quantification of nickel grain growth in dry and in humid atmospheres. Journal of Power Sources, 196(3), 1279–1294. https://doi.org/10.1016/j.jpowsour.2010.08.017

Holzer, L. et al. (2011) ‘Microstructure degradation of cermet anodes for solid oxide fuel cells : quantification of nickel grain growth in dry and in humid atmospheres’, Journal of Power Sources, 196(3), pp. 1279–1294. Available at: https://doi.org/10.1016/j.jpowsour.2010.08.017.

L. Holzer et al., “Microstructure degradation of cermet anodes for solid oxide fuel cells : quantification of nickel grain growth in dry and in humid atmospheres,” Journal of Power Sources, vol. 196, no. 3, pp. 1279–1294, Feb. 2011, doi: 10.1016/j.jpowsour.2010.08.017.

HOLZER, Lorenz, Boris IWANSCHITZ, Thomas HOCKER, Beat MÜNCH, Michel PRESTAT, Daniel WIEDENMANN, Uli VOGT, Peter HOLTAPPELS, Josef SFEIR, Andreas MAI und Thomas GRAULE, 2011. Microstructure degradation of cermet anodes for solid oxide fuel cells : quantification of nickel grain growth in dry and in humid atmospheres. Journal of Power Sources. 1 Februar 2011. Bd. 196, Nr. 3, S. 1279–1294. DOI 10.1016/j.jpowsour.2010.08.017

Holzer, Lorenz, Boris Iwanschitz, Thomas Hocker, Beat Münch, Michel Prestat, Daniel Wiedenmann, Uli Vogt, et al. 2011. “Microstructure Degradation of Cermet Anodes for Solid Oxide Fuel Cells : Quantification of Nickel Grain Growth in Dry and in Humid Atmospheres.” Journal of Power Sources 196 (3): 1279–94. https://doi.org/10.1016/j.jpowsour.2010.08.017.

Holzer, Lorenz, et al. “Microstructure Degradation of Cermet Anodes for Solid Oxide Fuel Cells : Quantification of Nickel Grain Growth in Dry and in Humid Atmospheres.” Journal of Power Sources, vol. 196, no. 3, Feb. 2011, pp. 1279–94, https://doi.org/10.1016/j.jpowsour.2010.08.017.