ICMCTF2007 Session TS2P: TS3 Poster Session
Thursday, April 26, 2007 5:00 PM in Room Town & Country
Thursday Afternoon
Time Period ThP Sessions | Topic TS2 Sessions | Time Periods | Topics | ICMCTF2007 Schedule
|
TS2P-1 Electrically Conductive Amorphous Carbon Film Coating on Metal Bipolar Plate for the PEFC
Y. Show (Tokai University, Japan) Metal bipolar plate for fuel cell (FC) has advantages of high manufacturability and mechanical strength. The fuel cell using metal bipolar plates generally shows lower output power than that of carbon bipolar plates, because oxidized layer, which is high electrical resistivity, exists on metal surface and it increases contact resistance between bipolar plate and membrane electrode assembly (MEA) in fuel cell. In this study, amorphous carbon (a-C) film was coated on Ti bipolar plate to prevent the formation of oxides layer. The a-C coated metal bipolar plate achieves the Fuel Cell with high power. Ti electrode was used as metal bipolar plate. Oxidized layer on Ti bipolar plate was removed by hydrofluoric acid. The a-C film was grown on the Ti bipolar plate by using plasma CVD equipment. Ethylene gas was used as source gas. Growth temperature was 600°C. Growth time was fixed at 3 hours. The fuel cell using the bare Ti bipolar plates showed maximum output power of 1.3W. Ti bipolar plate coated with a-C film at 600°C showed the maximum output power of 1.8W. Impedance analyzer measurement for these FCs indicated that the amorphous carbon coating decreased the contact resistance between the bipolar plate and the MEA. Therefore, the FC fabricated with the metal bipolar plate, which is coated with a-C film at high temperature, shows high output power. |
|
TS2P-2 Microstructure and Performance of Anode Supported SOFC Single Cells with Anode/Electrolyte and Cathode/Electrolyte Interlayers
H.K. Yang, J.H. Moon, H.W. Choi, K.H. Kim, H.H. Yoon, J.S. Kim, S.J. Park (Kyungwon University, Korea) For the years, several attempts have been made to lower the operating temperature of Solid Oxide Fuel Cells(SOFCs) by using thin film electrolytes. Though thin film electrolyte enables to lower the operating temperature, drawbacks such as activation polarization are prevalent. Recently, application of thin film composite interlayers is introduced as a means to improve charge transfer reaction in the electrode/electrolyte interface. Although there have been a few reports on the benefit of using interlayer in SOFC, further studies are required to understand the effect of interlayers on the SOFC performances. In this study, anode-supported SOFC single cells with electrode interlayer were fabricated and the effect of microstructures of the cell on the SOFC performance was evaluated. The electrochemical performances of SOFC single cells were evaluated by polarization curves and impedance spectra. The characterization of microstructure of the cells were performed by AFM, SEM, FIB (Focused Ion Beam) Systems, and XRD measurements. In reality, the insertion of interlayer, a denser YSZ electrolyte layer could be prepared and the electrochemical performance of SOFC could be enhanced significantly. |
|
TS2P-3 Electrical Properties of Ceria and Samaria Doped Ceria Thin Films
C. Mansilla (Instituto de Ciencia de Materiales de Sevilla, CSIC-USE, Spain); J.P. Holgado, J.P. Espinós (Instituto de Ciencia de Materiales de Sevilla, Spain); F. Yubero (ICMSE (CSIC-Univ. Sevilla), Spain); A.R. González-Elipe (Insituto de Ciencia de Materiales de Sevilla, Spain) The performance of intermediate temperature solid oxide fuel cells is strongly affected by the microstructure, thickness and electrical properties of the electrodes, ionic conductor and other intermediate layers used in the final design of the fuel cell. Cerium-based oxides present a notable technological interest as electrolyte due to their high electrical conductivity at relatively low temperatures. These compounds may be considered as very promising candidates to work as buffer layer either between anode and metallic supports or YSZ - Manganites cathode systems, acting in both cases as a prominent diffusion barrier. In this context, ceria and samaria doped ceria thin films have been prepared by ion beam assisted deposition (IBAD). The samaria doped ceria films were grown using a multilayer strategy, alternating deposition of ceria and samaria layers. Two different temperatures of substrate were used (200 and 500°C), together with ion assistance, as preparation parameters in order to obtain thin films with controlled microstructure. XRD, SEM and UV-Vis absorption have been used to study the evolution of the microstructure, morphology and density in the films. The electrical conductivity of the thin films has been studied in pure O2 atmosphere as a function of temperature by DC measurements. For ceria films, the highest electrical conductivity was achieved for samples prepared at 200°C under Ar+ assistance. Samaria doped ceria films showed the highest conductivity when prepared at 500°C under Ar+ bombardment and doped with 15% of Sm. The electrical properties of the films (activation energy and conductivity) exhibit clear grain size dependence, and can be correlated with the presence of both ionic and electronic contributions on the films. |
|
TS2P-4 Deposition of La0.8√sub 0.2Cr0.97V0.03O3 and MnCr2O4 Thin Films on Ferritic Alloy for Solid Oxide Fuel Cell Application
L. Mikkelsen, P.V. Hendriksen, N. Pryds, K. Rodrigo (Risoe National Laboratory, Denmark) Ferritic alloys forming a chromia oxide scale are investigated as interconnect material for solid oxide fuel cell (SOFC) stacks. Problems when using chromia-forming alloys as interconnects are the increasing electrical resistance across the oxide scale formed during use and evaporation of chromium containing oxides and oxy-hydroxides on the air side of the interconnect during operation. Such evaporation leads to deposition of chromium-containing oxides at the cathode-electrolyte interface, which leads to degradation of the SOFC cathode. This phenomenon is known as "chromium poisoning". In order to reduce the growth rate of the oxide scale and stop the chromium poisoning from the alloy coatings are applied on alloys. Dense coatings rather than porous ones are particularly interesting, since it will probably be easier with such coatings to hinder chromium poisoning. Thin films of La0.8√sub 0.2Cr0.97V0.03O3 and MnCr2O4 were deposited on a commercially available Fe22Cr alloy (Crofer 22APU) by large area pulsed laser deposition. The surface morphology and the structural information of the as-deposited films were investigated by scanning electron microscopy (SEM) and X-ray diffraction, respectively. Alloys deposited with thin films were subsequently oxidized at 1173 K for 1000 h in air. The effects of the deposited thin films on the oxidation behaviour were investigated by weight gain measurements as well as by SEM. Finally, the overall oxidation resistance and oxidation growth mechanism of the coated samples are discussed. |