Online ISSN : 2186-2451
Print ISSN : 1344-3542
ISSN-L : 1344-3542
Volume 77 , Issue 5
Showing 1-14 articles out of 14 articles from the selected issue
    2009 Volume 77 Issue 5 Pages 373-378
    Published: May 05, 2009
    Released: March 22, 2012
    The Li storage in mesoporous titania was investigated with varying the framework and porous structure by changing the calcination temperature. By the calcination at 673 K, the amorphous framework was converted into anatase, which is accompanied with the lost of angle X-ray diffraction peak around 2θ=2.4° and with an increase of mesopore diameter. The crystallite size increased while the specific surface area decreased with the increase of calcination temperature. The amorphous framework structure was further analysed by Raman spectroscopy and transmission microscopy. The charge-discharge curves were measured for all mesoporous titanias analysed. The maximum capacity was 225 mAh g−1, which was recorded for 773 K-calcined mesoporous titania. The distinct plateaux appeared in mesoporous anatase and the voltage gap between the plateaux in charge and discharge processes decreased with the calcination temperature. The electrochemical behavior was discussed in relation with the meso- and microscopic structures of the material.
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  • Kazuo TOMIDA, Nagao HISATOME, Tatsuo KABATA, Hiroshi TSUKUDA, Akihiro ...
    2009 Volume 77 Issue 5 Pages 379-387
    Published: May 05, 2009
    Released: March 22, 2012
    In this research, we studied the optimization of a segmented-in-series tubular solid oxide fuel cell using La0.5Sr0.5−xCaxMnO3 system materials for the cathode. La0.5Sr0.25Ca0.25MnO3 (LSCM25) was chosen for the cathode to obtain high electric conductivity and prevent the formation of highly resistive second phases with Y2O3-stabilized ZrO2 (YSZ) electrolyte as a result of X-ray diffraction. To obtain lower resistance at the cathode/electrolyte interface, we studied the optimization of the cathode interlayer by changing the LSCM25-YSZ volume ratio and YSZ particle sizes. As a result, the lowest resistance was obtained at 50 vol.% LSCM25 (particle size: 3 µm)+50 vol.% YSZ (2 µm). The area-specific resistance of a tubular cell stack using the LSCM25 cathode and the LSCM25-YSZ interlayer decreased by 17% compared to a stack using only an LSCM25 cathode. We also conducted power-generation tests under pressurization to measure the cell stack performance integrated with micro gas turbines. Judging from the I-V characteristics, an increase of test pressure brought about not only an increase of open circuit voltage but also a decrease of internal resistances. According to our analysis of the internal resistances using the current interruption method, the electrode polarizations decreased as the operating pressure rose.
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