To perform a flame-resistant treatment on a precursor fiber strand by sending hot air to a heat treatment chamber (2) through a hot air blowing nozzle (4) in a direction parallel to a running direction of a precursor fiber strand (10). The hot air blowing from the hot air blowing nozzle (4) passes through a porous plate and a rectifying member that satisfy the following conditions (1) to (4), wherein the conditions are set as follows: (1) A/B≧4.0; (2) 0.15≦α≦0.35; (3) 0≦B−d≦20; and (4) 80% or more of an area of one opening of the porous plate when causing facing surfaces of the porous plate and the rectifying member to overlap each other is included in one opening of the rectifying member, A indicating a hot air passage distance (mm) of the rectifying member, B indicating a horizontal maximum distance (mm) of one opening of the rectifying member, α indicating a rate of hole area of the porous plate, and d indicating an equivalent diameter (mm) of the porous plate. Accordingly, it is possible to provide a parallel stream type flame-resistant heat treatment furnace having exhibiting the uniform heat transfer performance throughout the inside of the heat treatment chamber by preventing the blockage of the nozzle caused by a silicone compound generated inside the heat treatment chamber even in the hot air blowing nozzle having a simple structure.

To perform a flame-resistant treatment on a precursor fiber strand by sending hot air to a heat treatment chamber (2) through a hot air blowing nozzle (4) in a direction parallel to a running direction of a precursor fiber strand (10). The hot air blowing from the hot air blowing nozzle (4) passes through a porous plate and a rectifying member that satisfy the following conditions (1) to (4), wherein the conditions are set as follows: (1) A/B≧4.0; (2) 0.15≦α≦0.35; (3) 0≦B−d≦20; and (4) 80% or more of an area of one opening of the porous plate when causing facing surfaces of the porous plate and the rectifying member to overlap each other is included in one opening of the rectifying member, A indicating a hot air passage distance (mm) of the rectifying member, B indicating a horizontal maximum distance (mm) of one opening of the rectifying member, α indicating a rate of hole area of the porous plate, and d indicating an equivalent diameter (mm) of the porous plate. Accordingly, it is possible to provide a parallel stream type flame-resistant heat treatment furnace having exhibiting the uniform heat transfer performance throughout the inside of the heat treatment chamber by preventing the blockage of the nozzle caused by a silicone compound generated inside the heat treatment chamber even in the hot air blowing nozzle having a simple structure.

Provided is a carbon-fiber nonwoven cloth with low resistance to gases or liquids passing through, and low resistance in the thickness direction to heat or electricity, which is particularly appropriate for a gas diffusion electrode of a polymer electrolyte fuel cell; the cloth having an air gap with a diameter of at least 20 μm, at least some of the carbon fibers being continuous from one surface to the other surface, and the apparent density being 0.2-1.0 g/cm.sup.3, or, having an air gap with a diameter of at least 20 μm and at least some of the carbon fibers being mutually interlaced, and further, at least some of the carbon fibers being oriented toward the thickness direction and the apparent density being 0.2-1.0 g/cm.sup.3.

Provided is a carbon-fiber nonwoven cloth with low resistance to gases or liquids passing through, and low resistance in the thickness direction to heat or electricity, which is particularly appropriate for a gas diffusion electrode of a polymer electrolyte fuel cell; the cloth having an air gap with a diameter of at least 20 μm, at least some of the carbon fibers being continuous from one surface to the other surface, and the apparent density being 0.2-1.0 g/cm.sup.3, or, having an air gap with a diameter of at least 20 μm and at least some of the carbon fibers being mutually interlaced, and further, at least some of the carbon fibers being oriented toward the thickness direction and the apparent density being 0.2-1.0 g/cm.sup.3.

Methods for the preparation of carbon fiber from polyolefin fiber precursor, wherein the polyolefin fiber precursor is partially sulfonated and then carbonized to produce carbon fiber. Methods for producing hollow carbon fibers, wherein the hollow core is circular- or complex-shaped, are also described. Methods for producing carbon fibers possessing a circular- or complex-shaped outer surface, which may be solid or hollow, are also described.

Provided is a method of producing an integral 3D humic acid-carbon hybrid foam, comprising: (A) forming a solid shape of humic acid-polymer particle mixture; and (B) pyrolyzing the solid shape of humic acid-polymer particle mixture to thermally reduce humic acid into reduced humic acid sheets and thermally convert polymer into pores and carbon or graphite that bonds the reduced humic acid sheets to form the integral 3D humic acid-carbon hybrid foam.

Provided is a method of producing an integral 3D humic acid-carbon hybrid foam, comprising: (A) forming a solid shape of humic acid-polymer particle mixture; and (B) pyrolyzing the solid shape of humic acid-polymer particle mixture to thermally reduce humic acid into reduced humic acid sheets and thermally convert polymer into pores and carbon or graphite that bonds the reduced humic acid sheets to form the integral 3D humic acid-carbon hybrid foam.

A carbonization method of carbonizing precursor fibers that are being conveyed includes carbonization performed using a plurality of carbonization furnaces for heating fibers arranged in the direction in which the fibers are conveyed. The plurality of carbonization furnaces include at least one carbonization furnace that heats the fibers using plasma when the fibers are passing through the inside of the at least one carbonization furnace. A carbon fiber production method includes a carbonization process of carbonizing precursor fibers that are being conveyed. The carbonization process is performed with the above carbonization method.

A carbonization method of carbonizing precursor fibers that are being conveyed includes carbonization performed using a plurality of carbonization furnaces for heating fibers arranged in the direction in which the fibers are conveyed. The plurality of carbonization furnaces include at least one carbonization furnace that heats the fibers using plasma when the fibers are passing through the inside of the at least one carbonization furnace. A carbon fiber production method includes a carbonization process of carbonizing precursor fibers that are being conveyed. The carbonization process is performed with the above carbonization method.

This invention innovates a low cost method to synthesize carbon fibers through graphene composites, which are fabricated through chemical treatment of graphite. This invention also is related to the applications of thereof carbon fibers in different fields. Several examples of such fields would be to use carbon fibers to manufacture carbon fiber tubes, pipes or risers, or car/airplane/computer parts, bicycles, and sports supplies and many additional applications.