The problem of the present invention is to provide a carbon fiber manufacturing device in which fiber to be carbonized is irradiated with microwaves and thereby heated, wherein the carbon fiber manufacturing device is compact and capable of performing carbonization at atmospheric pressure without requiring an electromagnetic wave absorber or other additives or preliminary carbonization through external heating. This carbon fiber manufacturing device (200) includes: a cylindrical furnace (27) comprising a cylindrical waveguide in which one end is closed, a fiber outlet (27b) being formed in the one end of the cylindrical waveguide and a fiber inlet (27a) being formed in the other end of the cylindrical waveguide; a microwave oscillator (21) for introducing microwaves into the cylindrical furnace (27); and a connection waveguide (22) having one end connected to the microwave oscillator (21) side and the other end connected to one end of the cylindrical furnace (27).

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.

A carbon-fiber-precursor acrylic fiber bundle which can smoothly pass through a flame-resistance impartation step and a carbonization step. The carbon-fiber-precursor acrylic fiber bundle has a high-density part as a portion thereof, wherein the high-density part satisfies the following requirements (A) and (B). Requirement A: The high-density part has a maximum fiber density ρ.sub.max of 1.33 g/cm.sup.3 or higher. Requirement B: The portion extending between an intermediate-density point and a maximum-density-region arrival point has an increase in fiber density of 1.3×10.sup.−2 g/cm.sup.3 or less per 10 mm of the fiber bundle length.

An oxidation furnace for the oxidative treatment of fibers having a housing which is gas-tight, apart from passage openings for the fibers, inter alia. A process chamber is located in the interior of the housing. Deflecting rollers guide the fibers through the process chamber in a serpentine manner so that the fibers lie next to one another as a fiber carpet which spans a plane between opposite deflecting rollers. An atmosphere-generating device can generate a hot working atmosphere and includes a blowing device with at least one outlet window through which a hot working atmosphere can be blown into the process chamber between two adjacent planes of the fiber carpet (22a). The working atmosphere is guided into the process chamber by a flow guiding system. The flow guiding system includes exchangeable flow guiding elements with flow passages which can be detachably and/or movably mounted on the blowing device, before the outlet window.

An oxidation furnace for the oxidative treatment of fibers having a housing which is gas-tight, apart from passage openings for the fibers, inter alia. A process chamber is located in the interior of the housing. Deflecting rollers guide the fibers through the process chamber in a serpentine manner so that the fibers lie next to one another as a fiber carpet which spans a plane between opposite deflecting rollers. An atmosphere-generating device can generate a hot working atmosphere and includes a blowing device with at least one outlet window through which a hot working atmosphere can be blown into the process chamber between two adjacent planes of the fiber carpet (22a). The working atmosphere is guided into the process chamber by a flow guiding system. The flow guiding system includes exchangeable flow guiding elements with flow passages which can be detachably and/or movably mounted on the blowing device, before the outlet window.

An object of the present invention is to provide a method for a carbon nanofiber composite, which can obtain a carbon nanofiber composite with high productivity and high activity, and which does not require removal of fluidizing materials or dispersing materials. The present invention also provides a carbon nanofiber composite having improved dispersibility. The method for producing the carbon nanofiber composite includes bringing at least one catalyst and at least one particulate carbon material into contact with at least one gas containing at least one gaseous carbon-containing compound while mechanically stirring the catalyst and the particulate carbon material in a reactor. The carbon nanofiber composite includes carbon nanofibers and at least one particulate carbon material, wherein the particulate carbon material has 70% by volume or more of particles with a particle diameter of 1 μm or less, and/or a median diameter D50 by volume of 1 μm or less.

An object of the present invention is to provide a method for a carbon nanofiber composite, which can obtain a carbon nanofiber composite with high productivity and high activity, and which does not require removal of fluidizing materials or dispersing materials. The present invention also provides a carbon nanofiber composite having improved dispersibility. The method for producing the carbon nanofiber composite includes bringing at least one catalyst and at least one particulate carbon material into contact with at least one gas containing at least one gaseous carbon-containing compound while mechanically stirring the catalyst and the particulate carbon material in a reactor. The carbon nanofiber composite includes carbon nanofibers and at least one particulate carbon material, wherein the particulate carbon material has 70% by volume or more of particles with a particle diameter of 1 μm or less, and/or a median diameter D50 by volume of 1 μm or less.

A method of producing a precursor fiber for carbon fiber includes extruding a polyacrylonitrile copolymer solution from a spinneret into the air, immersing it in a coagulation bath liquid stored in a coagulation bath, redirecting traveling of the coagulating fiber bundle by a first guide immersed in the coagulation bath disposed below the spinneret, and pulling it out of the coagulation bath liquid into the air to prepare a coagulated fiber bundle, which is then subjected to at least a washing step in water, stretching step, oil agent applying step, and drying step, wherein the depth-directional coagulation bath immersion length, which means a distance between the starting point of the immersion of the spinning dope solution in the coagulation bath liquid and the first guide immersed in the coagulation bath where traveling of the coagulating fiber bundle is redirected, is 3 to 40 cm.

A method includes a freezing process in which a solution or gel containing cellulose nanofibers is frozen to obtain a frozen component, a drying process in which the frozen component is dried in a vacuum to obtain a dry component, and a carbonizing process in which the dry component is heated and carbonized in a non-combustible atmosphere, and in the carbonizing process, the dry component is heated together with a reducing catalyst and also a material that generates a reducing gas by thermal decomposition.