Abstract: A porous carbon sheet including at least carbon fibers, having a thickness of 30 to 95 ?m, a gas permeation resistance of 0.5 to 8.8 Pa, and a tensile strength of 5 to 50 N/cm, and a gas diffusion electrode substrate including a porous carbon sheet containing at least carbon fibers, at least one surface thereof having a microporous layer containing at least an electric conductive filler, the gas diffusion electrode substrate being dividable in the thickness direction into a smaller pore part and a larger pore part, the larger pore part having a thickness of 3 to 60 ?m.

Abstract: A precursor fiber sheet includes short carbon fibers having an average length of 3 to 10 mm, natural pulp having an ash content of 0.15 mass % or less, and a heat-carbonizable resin, and a porous carbon sheet is obtained by carbonizing the precursor fiber sheet. This enhances gas diffusibility and water removal properties of the porous carbon sheet and has high mechanical strength and few appearance defects even when the bulk density of the porous carbon sheet is lowered.

Abstract: A porous carbon sheet includes a carbon fiber and a binding material, wherein when in a measured surface depth distribution, a ratio of an area of a portion having a depth of 20 ?m or less in a measured area of one surface is a surface layer area ratio X, and a ratio of an area of a portion having a depth of 20 ?m or less in a measured area of another surface is a surface layer area ratio Y, the surface layer area ratio X is larger than the surface layer area ratio Y, and a difference between the surface layer area ratios is 3% or more and 12% or less.

Abstract: A porous carbon sheet contains carbon fiber and a binder, wherein the carbon sheet is characterized in that in a section from a plane having a 50% filling ratio closest to one surface to a plane having a 50% filling ratio closest to the other surface, when letting layer X be a layer with the largest filling ratio close to the one surface, layer Y be a layer with a filling ratio smaller than layer X close to the other surface, and layer Z be the layer positioned between layer X and layer Y for layers obtained by dividing the carbon sheet equally into three in a direction perpendicular to the surfaces, the filling ratio for the layers becomes smaller in order of layer X, layer Y, and layer Z.

Abstract: A porous carbon sheet including at least carbon fibers, having a thickness of 30 to 95 ?m, a gas permeation resistance of 0.5 to 8.8 Pa, and a tensile strength of 5 to 50 N/cm, and a gas diffusion electrode substrate including a porous carbon sheet containing at least carbon fibers, at least one surface thereof having a microporous layer containing at least an electric conductive filler, the gas diffusion electrode substrate being dividable in the thickness direction into a smaller pore part and a larger pore part, the larger pore part having a thickness of 3 to 60 ?m.

Abstract: A precursor fiber sheet includes short carbon fibers having an average length of 3 to 10 mm, natural pulp having an ash content of 0.15 mass % or less, and a heat-carbonizable resin, and a porous carbon sheet is obtained by carbonizing the precursor fiber sheet. This enhances gas diffusibility and water removal properties of the porous carbon sheet and has high mechanical strength and few appearance defects even when the bulk density of the porous carbon sheet is lowered.

Abstract: A porous carbon sheet contains carbon fiber and a binder, wherein the carbon sheet is characterized in that in a section from a plane having a 50% filling ratio closest to one surface to a plane having a 50% filling ratio closest to the other surface, when letting layer X be a layer with the largest filling ratio close to the one surface, layer Y be a layer with a filling ratio smaller than layer X close to the other surface, and layer Z be the layer positioned between layer X and layer Y for layers obtained by dividing the carbon sheet equally into three in a direction perpendicular to the surfaces, the filling ratio for the layers becomes smaller in order of layer X, layer Y, and layer Z.

Abstract: A porous carbon sheet includes a carbon fiber and a binding material, wherein when in a measured surface depth distribution, a ratio of an area of a portion having a depth of 20 ?m or less in a measured area of one surface is a surface layer area ratio X, and a ratio of an area of a portion having a depth of 20 ?m or less in a measured area of another surface is a surface layer area ratio Y, the surface layer area ratio X is larger than the surface layer area ratio Y, and a difference between the surface layer area ratios is 3% or more and 12% or less.

Abstract: A porous carbon sheet obtained by binding separate carbon short fibers with a carbonization product of a resin, wherein the pore mode diameter of the sheet is 45 to 90 ?m and the mean fiber diameter of the carbon short fibers is 5 to 20 ?m. The sheet can be produced by thermoforming a precursor fiber sheet comprising carbon short fibers of 15 to 30 g/m2 in basis weight and a thermosetting resin of 30 to 80 g/m2 in basis weight by hot plates having a certain clearance and carbonizing the thermosetting resin contained in thermoformed precursor fiber sheet.

Abstract: A porous carbon sheet obtained by binding separate carbon short fibers with a carbonization product of a resin, wherein the pore mode diameter of the sheet is 45 to 90 ?m and the mean fiber diameter of the carbon short fibers is 5 to 20 ?m. The sheet can be produced by thermoforming a precursor fiber sheet comprising carbon short fibers of 15 to 30 g/m2 in basis weight and a thermosetting resin of 30 to 80 g/m2 in basis weight by hot plates having a certain clearance and carbonizing the thermosetting resin contained in thermoformed precursor fiber sheet.

Abstract: A porous carbon sheet obtained by binding separate carbon short fibers with a carbonization product of a resin, wherein the pore mode diameter of the sheet is 45 to 90 ?m and the mean fiber diameter of the carbon short fibers is 5 to 20 ?m. The sheet can be produced by thermoforming a precursor fiber sheet comprising carbon short fibers of 15 to 30 g/m2 in basis weight and a thermosetting resin of 30 to 80 g/m2 in basis weight by hot plates having a certain clearance and carbonizing the thermosetting resin contained in thermoformed precursor fiber sheet.

Abstract: A porous carbon sheet obtained by binding separate carbon short fibers with a carbonization product of a resin, wherein the pore mode diameter of the sheet is 45 to 90 ?m and the mean fiber diameter of the carbon short fibers is 5 to 20 ?m. The sheet can be produced by thermoforming a precursor fiber sheet comprising carbon short fibers of 15 to 30 g/m2 in basis weight and a thermosetting resin of 30 to 80 g/m2 in basis weight by hot plates having a certain clearance and carbonizing the thermosetting resin contained in thermoformed precursor fiber sheet.

Abstract: A porous carbon base material includes a sheet containing carbon short fibers dispersed randomly and a carbonized resin, in which the carbon short fibers are bound by the carbonized resin and the volume of pores having a pore diameter of 10 ?m or less is 0.05 to 0.16 cc/g. A method for producing this porous carbon base material includes intermittently transporting a precursor fiber sheet including short carbon fibers dispersed randomly and a resin to a space between heated plates, subjecting the precursor to a heating and pressuring treatment by the heated plates while the transformation stops, carrying out the transportation of the sheet after the treatment, and then carrying out a heat treatment, to thereby carbonize the resin in the sheet.

Abstract: A porous carbon base material includes a sheet containing carbon short fibers dispersed randomly and a carbonized resin, in which the carbon short fibers are bound by the carbonized resin and the volume of pores having a pore diameter of 10 ?m or less is 0.05 to 0.16 cc/g. A method for producing this porous carbon base material includes intermittently transporting a precursor fiber sheet including short carbon fibers dispersed randomly and a resin to a space between heated plates, subjecting the precursor to a heating and pressuring treatment by the heated plates while the transformation stops, carrying out the transportation of the sheet after the treatment, and then carrying out a heat treatment, to thereby carbonize the resin in the sheet.

Abstract: A nonwoven fabric comprising flame-retardant acrylic fibers, characterized in that it has a weight per square-meter of 70 to 190 g/m2, a thickness of 0.1 to 0.3 mm, a density of 0.35 to 0.8 g/cm3; and a nonwoven fabric comprising carbon fibers, characterized in that it has a weight per square-meter of 50 to 150 g/m2, a thickness of 0.1 to 0.25 mm, a density of 0.3 to 0.7 g/cm3, a surface roughness Ra of 30 ?m or less, a tensile strength of 0.2 kgf/cm or more, and a maximum fracture radius being defined in the specification of 20 mm or less. Said carbon fiber nonwoven fabric is produced by subjecting the flame-retardant acrylic fiber nonwoven fabric to a carbonization treatment and can be suitably used as a material for forming an electrode of a fuel cell.

Abstract: A fuel cell-use carbon fiber woven fabric, especially a carbon fiber woven fabric preferably used for the electrode diffusion layer of an electrode element in a fuel cell. The electrode diffusion layer of an electrode element in a fuel cell, requiring conductivity, gas diffusing/permeating features, and strength that withstands handling, is formed from carbon fiber woven fabrics as is widely known. The conventional carbon fiber woven fabric poses such problems that deformation by compression is large, the dimension of a fuel cell is significantly changed by pressurizing, irregularities by weave texture are large, and contact resistance is large. A carbon fiber woven fabric used for a fuel cell-use carbon fiber woven fabric has an average size of warps and wefts constituting the woven fabric of 0.005-0.028 g/m, and a woven density of the warps and/or wefts of 20 pieces/cm.