| 摘要 |
PURPOSE:To uniformly increase the water repellency of a substrate and to increase the reliability of a fuel cell by diffusing fluororesin vapor in the pores the substrate and depositing there. CONSTITUTION:A specified amount of fluororesin 31 such as PTFE and a porous carbon substrate 24 are fixed in a sealed container 32. A gas supply hole 33 and a gas exhaust hole 34 are closed and the container 32 is heated under vacuum at 400-900 deg.C to evaporate the resin 31. By keeping this condition for one hour, the resin vapor diffuses in the pores the substrate, and by cooling the container 32 to 100 deg.C or less, resin uniformly deposits on the inner walls of the pores. The inner pressure of the container 32 is returned back to the atmospheric pressure, then the substrate 24 is taken out. The substrate obtained has good phosphoric acid repellency, and a cell using this substrate shows output voltage having low time dependency and also shows high reliability. |
