3D microstructure effects in Ni-YSZ anodes : prediction of effective transport properties and optimization of redox stability

Pecho, Omar M.; Stenzel, Ole; Iwanschitz, Boris; Gasser, Philippe; Neumann, Matthias; Schmidt, Volker; Prestat, Michel; Hocker, Thomas; Flatt, Robert J.; Holzer, Lorenz

doi:10.3390/ma8095265

Please use this identifier to cite or link to this item: https://doi.org/10.21256/zhaw-1476

Publication type:	Article in scientific journal
Type of review:	Peer review (publication)
Title:	3D microstructure effects in Ni-YSZ anodes : prediction of effective transport properties and optimization of redox stability
Authors:	Pecho, Omar M. Stenzel, Ole Iwanschitz, Boris Gasser, Philippe Neumann, Matthias Schmidt, Volker Prestat, Michel Hocker, Thomas Flatt, Robert J. Holzer, Lorenz
DOI:	10.3390/ma8095265 10.21256/zhaw-1476
Published in:	Materials
Volume(Issue):	8
Issue:	9
Page(s):	5554
Pages to:	5585
Issue Date:	26-Aug-2015
Publisher / Ed. Institution:	MDPI
ISSN:	1996-1944
Language:	English
Subjects:	Electrode; Fuel cell; Map; Microstructure
Subject (DDC):	540: Chemistry 621.3: Electrical, communications, control engineering
Abstract:	This study investigates the influence of microstructure on the effective ionic and electrical conductivities of Ni-YSZ (yttria-stabilized zirconia) anodes. Fine, medium, and coarse microstructures are exposed to redox cycling at 950 ºC. FIB (focused ion beam)-tomography and image analysis are used to quantify the effective (connected) volume fraction (Φeff), constriction factor (β), and tortuosity (τ). The effective conductivity (σeff) is described as the product of intrinsic conductivity (σ0) and the so-called microstructure-factor (M): σeff = σ0 x M. Two different methods are used to evaluate the M-factor: (1) by prediction using a recently established relationship, Mpred = ε β^0.36/τ^5.17, and (2) by numerical simulation that provides conductivity, from which the simulated M-factor can be deduced (Msim). Both methods give complementary and consistent information about the effective transport properties and the redox degradation mechanism. The initial microstructure has a strong influence on effective conductivities and their degradation. Finer anodes have higher initial conductivities but undergo more intensive Ni coarsening. Coarser anodes have a more stable Ni phase but exhibit lower YSZ stability due to lower sintering activity. Consequently, in order to improve redox stability, it is proposed to use mixtures of fine and coarse powders in different proportions for functional anode and current collector layers.
URI:	https://digitalcollection.zhaw.ch/handle/11475/1629
Fulltext version:	Published version
License (according to publishing contract):	CC BY 4.0: Attribution 4.0 International
Departement:	School of Engineering
Organisational Unit:	Institute of Computational Physics (ICP)
Appears in collections:	Publikationen School of Engineering

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Pecho, O. M., Stenzel, O., Iwanschitz, B., Gasser, P., Neumann, M., Schmidt, V., Prestat, M., Hocker, T., Flatt, R. J., & Holzer, L. (2015). 3D microstructure effects in Ni-YSZ anodes : prediction of effective transport properties and optimization of redox stability. Materials, 8(9), 5554–5585. https://doi.org/10.3390/ma8095265

Pecho, O.M. et al. (2015) ‘3D microstructure effects in Ni-YSZ anodes : prediction of effective transport properties and optimization of redox stability’, Materials, 8(9), pp. 5554–5585. Available at: https://doi.org/10.3390/ma8095265.

O. M. Pecho et al., “3D microstructure effects in Ni-YSZ anodes : prediction of effective transport properties and optimization of redox stability,” Materials, vol. 8, no. 9, pp. 5554–5585, Aug. 2015, doi: 10.3390/ma8095265.

PECHO, Omar M., Ole STENZEL, Boris IWANSCHITZ, Philippe GASSER, Matthias NEUMANN, Volker SCHMIDT, Michel PRESTAT, Thomas HOCKER, Robert J. FLATT und Lorenz HOLZER, 2015. 3D microstructure effects in Ni-YSZ anodes : prediction of effective transport properties and optimization of redox stability. Materials. 26 August 2015. Bd. 8, Nr. 9, S. 5554–5585. DOI 10.3390/ma8095265

Pecho, Omar M., Ole Stenzel, Boris Iwanschitz, Philippe Gasser, Matthias Neumann, Volker Schmidt, Michel Prestat, Thomas Hocker, Robert J. Flatt, and Lorenz Holzer. 2015. “3D Microstructure Effects in Ni-YSZ Anodes : Prediction of Effective Transport Properties and Optimization of Redox Stability.” Materials 8 (9): 5554–85. https://doi.org/10.3390/ma8095265.

Pecho, Omar M., et al. “3D Microstructure Effects in Ni-YSZ Anodes : Prediction of Effective Transport Properties and Optimization of Redox Stability.” Materials, vol. 8, no. 9, Aug. 2015, pp. 5554–85, https://doi.org/10.3390/ma8095265.