Method for fabricating a ribbed electrode substrate

Claim 1

A method for fabricating a porous one piece fuel cell electrode substrate having a flat surface on one side and ribs on the other side thereof, said ribs forming U-shaped channels therebetween extending across said substrate, comprising the steps of: preparing a uniform, dry mixture comprising about 20% phenolic resin, by weight, and about 80% carbon fibers, by weight, the fibers being less than 50 mils in length; loading a predetermined amount of the mixture into a molding die having the mirror image of the rib pattern desired in the substrate by sifting said mixture into said die through a screen, the amount of mixture being just sufficient to provide the finished part with a preselected porosity of at least 75% after pressing, and distributing the mixture uniformly throughout the die; simultaneously pressing the mixture in the die to the desired thickness of the substrate and heating the mixture to above the melt point of the resin but to less than the final cure temperature of the resin and holding the pressure and temperature at least until the resin cures to an extent such that it retains its pressed shape after release of the pessure; fully curing the pressed part; heat treating the fully cured part up to at least 2100° C. in an inert atmosphere to convert the resin to glassy carbon; and impregnating the entire flat surface of the heat treated part with a wetproofing material except at select locations uniformly distributed under the ribs, said impregnating being to a depth of at least about the thickness of the substrate between the ribs.

Claim 2

A method for fabricating a porous one piece fuel cell electrode substrate having a flat surface on one side and ribs on the other side thereof, said ribs forming U-shaped channels therebetween extending across said substrate, comprising the steps of: preparing a uniform, dry mixture comprising about 20% phenolic resin, by weight, and about 80% carbon fibers, by weight, the fibers being less than 50 mils in length; loading a predetermined amount of the mixture into a molding die having the mirror image of the rib pattern desired in the substrate by sifting said mixture into said die through a screen, the amount of mixture being just sufficient to provide the finished part with a preselected porosity of at least 75% after pressing, and distributing the mixture uniformly throughout the die; simultaneously pressing the mixture in the die to the desired thickness of the substrate and heating the mixture to above the melt point of the resin but to less than the final cure temperature of the resin and holding the pressure and temperature at least until the resin cures to an extent such that it retains its pressed shape after release of the pessure; fully curing the pressed part; heat treating the fully cured part up to at least 2100° C. in an inert atmosphere to convert the resin to glassy carbon; and impregnating the entire flat surface of the heat treated part with a wetproofing material except at select locations uniformly distributed under the ribs, said impregnating being to a depth of at least about the thickness of the substrate between the ribs.