METHOD OF AND APPARATUS FOR INTRODUCING AN IMPREGNATING FLUID INTO A POROUS SUBSTRATE REGION

摘要

A method for making an impregnated fuel cell edge seal utilizing specialized tooling and modifying the exemplary carbon/graphite impregnant dispersion, which might include, for example, 66 % carbon or graphite by weight, by adding to it a minor amount (e.g., 7 %) of a concentrated solution of ammonium hydroxide (e.g., about 58 % by weight of the NH4OH in water, equivalent to about 28-30 % by weight of NH3 gas added to water to make the solution) to the dispersion, increasing the pH of the impregnant up to a level of about of 10.5 to 11.5, improving the flow characteristics of the dispersion and decreasing the tendency of such a dispersion to solidify during the impregnation process. The modified impregnant is forced into the edge area of the electrode substrate (E.S.) of the fuel cell, producing an integral edge seal, using a specialized tool (10 or 10') having a rigid die (12) or a resiliently yieldable die (12') with a cooperating substantially rigid plunger (11 or 11'), which define between them an elongated chamber or channel (13 or 13') for the impregnant (30; see figs. 1-3 or 5). Such a tool (10 or 10') overcomes the effects of thixotropy, as the volume of the impregnant (30) is constrained by the volume of the chamber (13 or 13'), producing a seal which is uniform in density and dimensionally controlled by the shape of the channel (13), eliminating the varying shear forces of the prior art. The specialized tooling (10 or 10') can also be used to impregnate wetproofing material, particularly a fluorocarbon, into an electrode substrate to form corrosion resistant seals.