Dissertation / PhD Thesis/Book

PreJuSER-37417

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Herstellung und Charakterisierung von dünnen Elektrolytschichten auf mikrostrukturell modifizierten Anodensubstraten für die Hochtemperatur-Brennstoffzelle

Wanzenberg,Elke (Corresponding author)FZJ*

2003
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich

Please use a persistent id in citations: http://hdl.handle.net/2128/294

Report No.: Juel-4027

Abstract: The operating temperature of solid oxide fuel cells can be lowered by the use of very thin electrolyte membranes. In this work two methods were tested to deposit thin yttriastabilised zirconia membranes onto the anode substrates of the fuel cells: the reactive DC sputtering process and the electrochemical vapour deposition (EVD). An influence of the anodes' microstructure an the quality of the electrolyte membrane was expected. Therefore the microstructure of the substrates was modified by sintering at temperatures between 1300 and 1400 °C. Subsequently the porosity, pore size and electrical conductivity of the anodes were tested. Thin electrolyte membranes were deposited and the influence of the modified microstructure of the anode an microstructure, gas-tightness and ionic conductivity of the membranes were investigated. A following annealing step was supposed to increase the gas-tightness of the electrolyte membranes further. After optimising the processing parameters, several electrolyte membranes were coated with cathode films and these fuel cells were electrochemically tested. It was shown that the EVD process is not suitable for the deposition of YSZ onto the anode substrates, because of removal of the nickel oxide out of the anode due to the chloride precursors leading to the formation of volatile nickel chloride. Electrolyte membranes with a thickness of about 7 $\mu$m were deposited onto the anode substrates by the sputtering process. The following annealing step increased the gas-tightness of the membranes as long as the annealing temperature was chosen to be not muck higher than the sintering temperature of the anode itself. It was shown that the modified microstructure of the anode substrates had no influence an the quality of the electrolyte membranes. Instead, an influence of the modified microstructure of the anode an the performance of the fuel cells was observed. Best power densities were achieved with fuel cells which anodes were sintered at low temperatures (1300 °C). The reason of the better performance is presumably the finer microstructure of the anode and thus the more extended catalytically active Interface. The microstructure and ionic conductivity of the electrolyte membrane did not influence the power density of the fuel cells. Even at operating temperatures of about 600 °C the resistance of the electrolyte was small compared to the total cell resistance caused by electrolyte; electrodes and contacts. These results Show that at first the overpotential occurring at the electrodes should be lowered e.g. by a finer microstructure of the anode. However, sintering of the anode at temperatures below 1300 °C is not recommendable because the electronic conductivity of such anodes decreases strongly due to a decreasing continuity of the network of metallic nickel.

Note: Record converted from VDB: 12.11.2012
Note: Aachen, Techn. Hochsch., Diss., 2003

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Contributing Institute(s):

1. Werkstoffsynthese und Herstellungsverfahren (IWV-1)

Research Program(s):

1. Brennstoffzelle (E01)

Appears in the scientific report 2003
Notes: Nachtrag

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