Yasuo Kaga

Influence of cell configuration on measuring interfacial impedances between a solid electrolyte and an electrode

For AC impedance spectroscopy to measure interfacial impedances between an electrolyte and a working electrode in solid electrolyte cells with three electrodes, the experimental error that is caused by the cell configuration is analyzed using a numerical model. To simulate AC impedance spectra, potential and current distributions in the disk type cells are calculated for various frequencies, and the impedance between the reference electrode and the working electrode is estimated. From the calculation, it is clarified that the difference in the size between the working electrode and the counter electrode can cause the experimental error and the deformation of the impedance spectra from a simple semicircle. The influences of the material properties and the cell configuration on the error and the deformation of the impedance spectrum are discussed.

Measurement of MHD combustion-gas temperatures and potassium number densities in the presence of cold boundary layers

Abstract The wing-reversal method is useful, with small influence by self-resonant absorption, for the measurement of MHD combustion-gas temperatures in the presence of cold boundary layers. We show how the errors caused by self-absorption in the wing-reversal method are obtained by using correction factors for temperature and potassium atom density in boundary layers, without numerical integration of the radiative transfer equation. The radiative transfer equation and the absorption coefficient of potassium may be simplified when the optical thickness is appreciably smaller than unity. We have used this method on MHD combustion gases. The measured main flow temperature agrees with the thermal equilibrium temperature within 1%, while the measured main flow potassium atom density is about 65% of the equilibrium density.

Relationships between the gas permeabilities and the microstructures of plasma sprayed oxide layers

Abstract The performance and reliability of a solid oxide fuel cell depends upon the characteristics of the cell components. In particular, the gas permeabilities of the electrodes affect the fuel utilization and efficiency of the cell, and the gas tightness of the electrolyte layer has an important influence on life and reliability of the cell. In this paper, the gas permeabilities of the electrode layers are shown to be viscous flow and those of the electrolyte to be molecular flow.

A new ceramics coating technique for sofc using the etl laser spraying process

Abstract A new ceramic coating technique using a CO 2 laser has been developed to make high temperature solid oxide fuel cells. A high power density laser beam is passed near the substrate. Coating material is supplied by an extra-high accuracy powder supply device and passes across the laser beam. The coating material is melted in the laser beam and deposited on the substrate surface. A YSZ (yttria-stabilized zirconia) layer was made in test experiments. The cyrstal structure of the coated layer was the same as that of the original coating material.

Reply to the note on the flow behaviour of combustion gas in the boundary layer of an MHD generator

Abstract The temperature profile in Fig. 3 of Ref. 1 is better approximated by a relation for a turbulent boundary layer than a laminar boundary layer. The critical Reynolds number is expected to be lowered in the flow train of MHD combustion gas because of large turbulence in the combustor and by roughness along the duct.