A carbon fiber production method includes a carbon fiber production step including an oxidation step and a carbonization step; and an exhaust gas processing step including a heat exchange step; an external air mixing step; and a mixed external air supplying step in which the mixed external air is supplied to at least one step that uses heated gas in the steps in the carbon fiber production step; and among the exhaust gases, a high heating value exhaust gas having a heating value of 250 kcal/Nm.sup.3 or higher is supplied to an inlet side of an exhaust gas combustion apparatus and a low heating value exhaust gas having a heating value lower than 150 kcal/Nm.sup.3 is supplied to an outlet side of the exhaust gas combustion apparatus, respectively.

A method of producing carbon fibers includes the step of providing polyacrylonitrile precursor polymer fiber filaments. The polyacrylonitrile precursor filaments include from 87-97 mole % acrylonitrile, and less than 0.5 mole % of accelerant functional groups. The filaments are no more than 3 deniers per filament. The polyacrylonitrile precursor fiber filaments can be arranged into tows of at least 150,000 deniers per inch width. The arranged polyacrylonitrile precursor fiber tows are stabilized by heating the tows in at least one oxidation zone containing oxygen gas and maintained at a first temperature T.sub.1 while stretching the tows at least 10% to yield a stabilized precursor fiber tow. The stabilized precursor fiber tows are carbonized by passing the stabilized precursor fiber tows through a carbonization zone. Carbon fibers produced by the process are also disclosed.

A method for making carbon fiber in which the tensile strength of carbon fiber is increased without dehumidifying the ambient air that enters every oxidation oven in a multiple oxidation oven system. A positive effect on tensile strength is provided when ambient air entering only the first oven in a series of oxidation ovens is dehumidified. In addition, the ambient air entering the last oven is not dehumidified when one or more of the preceding oxidation ovens is operated with dehumidified air.

Systems and methods are provided for fabricating carbon nanostructures by low voltage near-field electromechanical spinning (LV-NFEMS). Processes described herein can produce 2-5 nm carbon nanowires with ultrahigh electrical conductivity using top-down and controlled reductive techniques from a polymer. Configurations are also provided to allow for deposition control and fiber elongation/alignment. One embodiment uses a low voltage near-field electromechanical spinning process to produce a polymer fiber from a polymer solution. Another embodiment of the method uses pyrolysis to convert the produced polymer fiber into a 2-5 nm carbon nanowire. System configurations provide advancements in polymer droplet control and control of a sustained jet of polymer solution with the use low voltages. Systems and processes described herein can include use of an array of polymer precursor nanofibers suspended onto a silicon substrate and converted to carbon nanowires. In another embodiment, ultra-thin carbon fibers can be integrated onto a carbon electrode scaffold.

The invention relates to a method and to a device for stabilizing precursor fibers for the production of carbon fibers. In the method, precursor fibers are first heated to a first temperature and held at the temperature for a predefined duration. Subsequently, the precursor fibers are heated to at least one second temperature, which is higher than the first temperature, and held at said temperature for a predefined duration. During each heating and between the heating steps, the precursor fibers are in a gas atmosphere having a negative pressure in the range between 12 mbar and 300 mbar and having an oxygen partial pressure of 2.5 to 63 mbar. The device has at least one evacuable, elongate vacuum chamber for feeding the precursor fibers through, at least two lock units and at least one heating unit. At least one lock unit is used for the sealed insertion of precursor fibers into the at least one vacuum chamber, while at least one other lock unit is used for the sealed removal of precursor fibers from the at least one vacuum chamber. The heating unit has at least two individually controllable heating elements, which are suitable for heating the at least one vacuum chamber to at least two different temperatures in heating zones which are adjacent in the longitudinal direction.

A manufacturing method and an apparatus enable high productivity. A method for manufacturing an oxidized fiber bundle includes joining an upstream precursor fiber bundle and a downstream precursor fiber bundle together with a joining fiber bundle, and oxidizing the joined precursor fiber bundles by feeding the joined precursor fiber bundles through an oxidization furnace. The joining includes applying an oiling agent to a joint area of a joining target precursor fiber bundle before joining the joining target precursor fiber bundle and the joining fiber bundle together. A quantity of the oiling agent adhering to the joint area is 0.15 to 0.85 wt %.

A method of producing carbon fibers includes the step of providing polyacrylonitrile precursor polymer fiber filaments. The polyacrylonitrile precursor filaments include from 87-97 mole % acrylonitrile, and less than 0.5 mole % of accelerant functional groups. The filaments are no more than 3 deniers per filament. The polyacrylonitrile precursor fiber filaments can be arranged into tows of at least 150,000 deniers per inch width. The arranged polyacrylonitrile precursor fiber tows are stabilized by heating the tows in at least one oxidation zone containing oxygen gas and maintained at a first temperature T.sub.1 while stretching the tows at least 10% to yield a stabilized precursor fiber tow. The stabilized precursor fiber tows are carbonized by passing the stabilized precursor fiber tows through a carbonization zone. Carbon fibers produced by the process are also disclosed.

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.

Proposed is a method of manufacturing a carbon precursor fiber for a gas diffusion layer having excellent tensile properties (e.g., strength and modulus) by controlling the cross-sectional shape of carbon fiber. The method includes preparing a polyacrylonitrile-based copolymer, preparing spinning products by spinning a spinning solution containing the polyacrylonitrile-based copolymer in a coagulation bath, and obtaining a carbon precursor fiber by drawing the spinning products through heat treatment. The coagulation bath includes an amount of about 60% to 90% by volume of methanol and an amount of about 10% to 40% by volume of dimethylformamide based on the total volume of the coagulation bath.

A method for a fiber bundle, including a heating process of Joule-heating the fiber bundle by energization between at least a pair of electrodes. The fiber bundle is carried in contact with the electrodes and has electrical conductivity at least between the electrodes. At least one of the electrodes has an aggregating structure that aggregates the fiber bundle while being in contact with the outer surface of fiber bundle. The aggregating structure has a trench or cylindrical shape with a structural surface that narrows in the depth direction. When the electrodes are each composed of a rotating body, the aggregating structure is a trench provided on the outer surface of the rotating body. The trench has a bottom surface that narrows toward a rotation center side. The trench may have a widened portion on the outer peripheral edge side. The widened portion guides the fiber bundle to the bottom surface.