Material characterization in support of the development of an anode substrate for solid oxide fuel cells
- PDF / 572,470 Bytes
- 11 Pages / 612 x 792 pts (letter) Page_size
- 60 Downloads / 221 Views
MATERIALS RESEARCH
Welcome
Comments
Help
Material characterization in support of the development of an anode substrate for solid oxide fuel cells D. Simwonis Department of Chemical Engineering, National Technical University of Athens, Athens GR-15773, Greece
A. Naoumidis, F. J. Dias, and J. Linke Institute for Materials in Energy Systems (IWE), Forschungszentrum J¨ulich GmbH, J¨ulich D-52425, Germany
A. Moropoulou Department of Chemical Engineering, National Technical University of Athens, Athens GR-15773, Greece (Received 21 March 1996: accepted 23 January 1997)
A new design for solid oxide fuel cells (SOFC’s) was developed aiming at the reduction of the total electrical resistance of the cell. The thickness of the electrolyte was decreased, while the anode took on the role of the substrate. The pore structure with respect to gas permeability of this component has to be optimized for the proper operation of this design. Anode substrates, consisting of a cermet (yttrium-stabilized ZrO2 and metallic Ni) and produced by two different processes, coat mix and tape casting, were characterized with respect to pore structure (shape and mean radius), porosity (total, open and permeable), pore size distribution and air permeability. The following methods were used: (i) optical and electron scanning microscopy in combination with image analysis, (ii) mercury porosity, and (iii) air permeability. Correlations between air permeability and porosity and also the percentage of permeable pores in anodes show the superiority of coat mix samples to tape-cast ones. It has been observed that the coat mix process can produce anode substrates with interconnecting porosity, while tape casting, as used in this study, needs some modifications in order to be appropriate for this purpose. I. INTRODUCTION
Solid oxide fuel cells (SOFC’s) are currently being developed because of the superiority of this energy conversion device regarding high efficiency and low pollution.1 It consists of an electrolyte (8 mol % Y2 O3 -stabilized ZrO2 : YSZ) with two electrodes, the anode, a CERMET NiyYSZ, and the cathode, a perovskite on the basis of LaMnO3 . Fuel (hydrogen or various hydrocarbons) is oxidized on the anode, while the oxidant (oxygen or air) is reduced on the cathode. The electrons move by an external circuit from the anode to the cathode, while the electrolyte conducts ions from the cathode to the anode. The voltage of a single SOFC depends on the difference in oxygen partial pressure on both sides of the electrolyte and the temperature. It is expected that the working voltage will be about 0.7 V for a current density of 0.5–1 A cm22 . For that reason, more than one unit has to be connected by a component called interconnect (doped LaCrO3 or metallic alloys) in electrochemical series (stacks) to form a serviceable voltage. At present two SOFC stack configurations have been developed: (i) the tubular design (in the USA and Japan)2 and (ii) the flat design (favored in Europe). Developments at Forschungszentrum J¨ulich GmbH are 1508
http:/
Data Loading...
