M. Matsubayashi

In-situ observation of dynamic water behavior in polymer electrolyte fuel cell by combined method of Small-Angle Neutron Scattering and Neutron Radiography

In-situ observation was conducted on an operating polymer electrolyte fuel cell with a combined method of small-angle neutron scattering (SANS) and neutron radiography (NR). The combined measurement system has been recently developed to visualize water in a wide length scale from nano- to millimeter and successfully detected a spatial distribution of the water generated in individual cell elements; NR macroscopically detected the water in a gas diffusion layer and a flow-field, whereas SANS microscopically did in a membrane electrode assembly. In particular SANS was found to be a strong tool to make a rather precise analysis on the water content inside of ion conducting channels of polymer electrolyte membrane.

Development of a Small-Aperture Slit System for a High Collimator Ratio at the Thermal Neutron Radiography Facility in JRR-3

A small-aperture slit system has been developed and installed to enhance the collimator ratio (“L/D”) of the thermal neutron radiography facility (TNRF) in JRR-3. The degree of unsharpness on neutron images is reduced by increasing the L/D. The small-aperture slit system increased the L/D by creating a small aperture size (“D”). Image sharpness improved when the aperture size was reduced to below 10mm by 10mm in the TNRF. On the other hand, there was almost no difference in unsharpness on images obtained above 10mm by 10mm in aperture size. These results indicate that an aperture size of less than 10mm by 10mm should be used for high-spatial-resolution imaging at the TNRF. The beam area of the small-aperture slits was relatively small in comparison with that of a conventional large collimator, though gradually increasing with increasing aperture size. Even with an aperture size of 5mm by 5 mm, the practical beam area for imaging examinations corresponded to around 25mm by 20 mm, which is enough area to carry out high-spatial-resolution imaging.

Visualization and Measurement of Dynamic Water Behavior in PEFC by Neutron Radiography

Hydrogen gas and air are supplied in saturated moist condition to keep a membrane wet in a PEFC. Condensation may occur in the cathode by the FC reaction, since air is saturated moist condition. The condensed water may affect on the fuel cell performance. It is very important for the design to know the water behaviors. In this study, in-situ visualization of an operating PEFC was carried by neutron radiography with the cell voltage measurements. A JARI standard cell was improved for the visualization with the same performance. Water distribution in the fuel cell could be quantitatively measured from visualized images via some image processing methods. The relationships between the water distributions and cell voltage fluctuations were clearly shown from the visualization and measurement results. The difference in water distribution for three types of gas supply channel was clearly shown.Copyright