Chemistry of inorganic compounds – Carbon or compound thereof – Elemental carbon
Patent
1991-04-17
1993-08-17
Skapars, Anthony
Chemistry of inorganic compounds
Carbon or compound thereof
Elemental carbon
429 44, D01F 912
Patent
active
052366871
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention concerns a flat plate-like ribbed carbon material of great strength containing carbon fibers and improved with electric conductivity and thermal conductivity along the direction of the thickness that can be used advantageously as an electrode substrate for a fuel cell, as well as a manufacturing method therefor.
2. Background Art
As an electrode substrate for a fuel cell of low electric resistance, there has been known an electrode plate for a fuel cell constituted with a material mainly comprising carbon fibers and having a plurality of gas diffusing pores, in which a thin-walled portion formed as a plate-like member functions as a flow channel for a fuel and an oxidizing gas while a thick-walled portion functions as a collector portion, wherein the carbon fibers constituting the collector portion comprise mono-filaments dependent on each other with the fiber axis thereof substantially oriented along the direction of the thickness of the thick-walled portion (Japanese Patent Laid Open No. Sho 57-210571). As an example for the manufacturing method thereof, the following method is disclosed. An aqueous dispersion containing carbon fibers having a length longer than the thickness of the collector portion properly dispersed therein is prepared, which is subjected to filtering operation by way of filters made of a stainless steel metal wire gauze of about 150 mesh and the carbon fibers are settled on the filters to form a mat-like carbon fibers. Upon filtering operation, if the filtering speed is increased by using a vacuum pump, the carbon fibers settled in a mat-like shape on the filters are oriented along the direction of filtration. The mat-like carbon fibers are impregnated with a binder, for example, a phenol resin, are formed with gas flow channels by hot pressing and, subsequently, they are calcined for carbonizing the binder.
In this method, however, the mat-like carbon fibers are liable to become inhomogenous and it is extremely difficult to manufacture an electrode plate of uniform physical property. This results in a serious problem, in particular, for manufacturing a substrate of large size In addition, the strength of the electrode plate of such a structure is low at the boundary between the thick-walled portion and the thin-walled portion and it is easily broken.
As a method of fabricating a ribbed porous carbon material, there has been known a method of supplying a dry mixture comprising 20 to 50% by weight of a thermosetting resin and 80 to 50% by weight of carbon fibers in such a predetermined amount as to provide a desired porosity into a molding die in a mirror image relationship with the rib pattern desired in the substrate, press molding and then calcining the same (U.S. Pat. No. 4,165,349). Further, there has also been known a method of manufacturing an electrode substrate for a fuel cell having a large porosity and a pore diameter with a sharp distribution, by mixing carbon fibers, a binder and an organic particulate material, press molding them by pressing or rolling, followed by calcination (Japanese Patent Laid Open No. Sho 58-117649).
In this method, however, the starting material tends to be supplied unevenly to the molding die or the roll thus tending to make the physical property of the resultant substrate not uniform.
Furthermore, there has also been known a method of manufacturing an electrode substrate having a uniform physical property by extruding a starting mixture comprising short carbon fibers, a phenolic resin and a molding aid, press molding the same by means of rolling or stamping and then calcining the same (Japanese Patent Laid Open No. Sho 63-21753).
However, even the porous carbon material manufactured by such a method can not completely satisfy the physical property such as electric resistance, heat conductivity and strength required in the field of the fuel cell and a further improvement has been demanded.
It is required for the ribbed porous electrode substrate for used in a fuel cell that the electric conduc
REFERENCES:
patent: 4165349 (1979-08-01), Sandelli
patent: 4490447 (1984-12-01), Battersby
patent: 4506028 (1985-03-01), Fukuda
patent: 4738872 (1988-04-01), Lee
patent: 4814307 (1989-03-01), Funabashi
Abe Hikonori
Fukuda Hiroyuki
Funabashi Masayuki
Kureha Kagaku Kogyo Kabushiki Kaisha
Skapars Anthony
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