Innenbeschichtung poröser Körper mittels Atomlagenabscheidung zur Redoxstabilisierung anodengestützter Festoxidbrennstoffzellen

Keuter, Thomas

Dissertation / PhD Thesis/Book

FZJ-2015-05029

Innenbeschichtung poröser Körper mittels Atomlagenabscheidung zur Redoxstabilisierung anodengestützter Festoxidbrennstoffzellen

Keuter, T. (Corresponding author)FZJ*

2015
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich
ISBN: 978-3-95806-069-2

Jülich : Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag, Schriften des Forschungszentrums Jülich Reihe Energie & Umwelt / Energy & Environment 273, XII, 133 S. (2015) = Universität Bochum, Diss., 2015

Please use a persistent id in citations: http://hdl.handle.net/2128/9033

Abstract: Fuel cells convert directly the chemical energy of fuels into electrical energy with a high efficiency and are flexible in use due to their modular design. Anode-supported Solid Oxide Fuel Cells (SOFCs) consist of a nickel/8YSZ substrate (8YSZ ˆ= with 8 mol-% yttria stabilized zirconia), a nickel/8YSZ anode, an 8YSZ electrolyte, and a cathode. In case of reoxidation of the nickel in the substrate, the substrate expands in lateral direction and creates tensile stresses and cracks in the electrolyte, resulting in a decrease of the cell performance or a complete cell failure. The aim of this work is the stabilization of anode-supported SOFCs with respect to reoxidation by coating the inner surface of the porous substrate, using the process of atomic layer deposition (ALD). The deposited layer protects the nickel in the substrate against oxidation and prevents in this way a crack formation in the electrolyte and a cell failure. More generally, the inner surface coating of porous media using ALD is investigated experimentally and described theoretically by a model. Atomic layer deposition of zirconia using the precursors TEMAZ and O$_{2}$ was developed in the in-house ALD machine, because this process is not described in literature. In order to model atomic layer deposition, Knudsen diffusion and second-order surface reaction kinetics of the precursors were combined and the thickness of the deposited layer within the porous medium was predicted. The inner surface coating of Ni/8YSZ substrates was proven by a conformal coating of the grains and the ALD model was verified. The zirconia layer protected the coated parts of the substrate for at least 17 redox cycles. It was not possible to coat the entire inner surface of the substrate and consequently, reoxidation of the substrate led to cracks in the electrolyte. The zirconia layer did not influence the electrochemical performance of the SOFC leading to the conclusion that a complete coating of the substrate can solve the problem of reoxidation. Additionally, the combination of a thin electrolyte and a low operating temperature is promising, too.

Note: Universität Bochum, Diss., 2015

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