Book	FZJ-2013-06513

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Entwicklung protonenleitender Werkstoffe und Membranen auf Basis von Lanthan-Wolframat für die Wasserstoffabtrennung aus Gasgemischen

Seeger, J. (Corresponding author)FZJ*

2013
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich
ISBN: 978-3-89336-903-4

Please use a persistent id in citations: http://hdl.handle.net/2128/5714

Abstract: Lanthanum tungstate La$_{6-x}$WO$_{12-\delta}$ (named LWO) is a ceramic material with mixed protonic electronic conductivity. Thereby it is a good candidate membrane material for hydrogen separation from synthesis gas in a fossil pre-combustion power plant. This work shows a material optimization by substitution targeted to clearly enhance the mixed conductivity and thereby the hydrogen flow through the LWO membrane. The first part of the work shows the synthesis and characterization of unsubstituted LWO. It points out that monophase LWO powder can be reproducibly synthesized. The La/W-ratio has to be considerably smaller than the nominal ratio of La/W = 6.0. It also depends on the used sintering conditions. Different relevant properties of LWO like stability in conditions close to application, thermal expansion, sintering behavior or microstructure were determined. Furthermore, the electrical conductivity of the material was investigated. LWO exhibits a prevailing protonic conductivity up to 750 °C in wet atmospheres. Under dry atmospheres n-type conductivity was dominating. Oxygen ion and n-type conductivity dominated in wet and dry atmospheres above 750 °C. The main part of the work is concerned with the development of new LWO based materials by substitutions. The aim is to achieve an improved mixed protonic electronic conductivity. Substitution elements for lanthanum side were Mg, Ca, Sr, Ba, Ce, Nd, Tb, Y and Al, while for the tungsten side Mo, Re and Ir were used. The total conductivity of the developed materials was investigated and compared to that of the unsubstituted LWO. The substitution of lanthanum led to no appreciable enhancement of the conductivity whereas the substitution of tungsten with 20 mol% molybdenum or 20 mol% rhenium clearly improved it. This caused a hydrogen flow about seven times higher for 20 mol% molybdenum- and about ten times higher for 20 mol% rhenium-substituted LWO in comparison with the unsubstituted LWO at 700 °C. In the last part of the work first asymmetric membranes consisting of a thin functional layer and a supporting substrate to enhance the hydrogen flow by reducing the membrane thickness were developed. It succeeded in manufacturing gastight samples. However the samples became highly curved during the sintering. Therefore, further intensive component development will be required.

Note: Universität Bochum, Diss., 2013

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Contributing Institute(s):

1. Werkstoffsynthese und Herstellungsverfahren (IEK-1)

Research Program(s):

1. 122 - Power Plants (POF2-122) (POF2-122)

Appears in the scientific report 2013

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Database coverage:

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