Abstract: A method comprising adding a multi-walled carbon nanotube synthesized by the vapor phase process to a nitric acid aqueous solution of not lower than 0.2 mol/L so as to dissolve a catalyst metal present in the multi-walled carbon nanotube, performing solid-liquid separation to isolate solid matter, and subjecting the isolated solid matter to heat treatment at a temperature higher than 150° C. gives a purified multi-walled carbon nanotube in which the amount of a metallic element left in the multi-walled carbon nanotube originating the catalyst metal is not smaller than 1000 ppm and not larger than 8000 ppm determined by ICP optical emission spectrometry and the amount of an anion left in the multi-walled carbon nanotube originating in the acid is smaller than 20 ppm determined by ion chromatography analysis.

Abstract: Disclosed is a composition containing carbon nanotubes which meets all of the following conditions (1) to (4). (1) When observed via transmission electron microscopy, at least 50 out of every 100 carbon nanotubes are double-walled carbon nanotubes. (2) The carbon nanotubes have an average outer diameter in the range of 1.0 to 3.0 nm. (3) During thermogravimetric analysis under atmosphere at a temperature increase rate of 10° C./minute, a high temperature combustion peak is at 700 to 850° C., and the relationship between low temperature weight loss (TG(L)) and high temperature weight loss (TG(H)) is TG(H)/(TG(L)+TG(H))?0.75. (4) The composition containing carbon nanotubes has a volume resistance value between 1.0×10?2 ?·cm and 1.0×10?4 ?·cm, inclusive. The disclosed composition containing carbon nanotubes primarily has double-walled carbon nanotubes with high electrical conductivity and high heat resistance.

Abstract: A method of producing carbon fibers, in which the producing method comprises allowing a supported type catalyst and a carbon atom-containing compound to come in contact with each other in a heating zone, wherein the supported type catalyst is prepared by a method comprising impregnation of a powdery carrier with colloid containing catalyst to support particles of the catalyst on the powdery carrier having a specifically developed crystal plane such as a powdery carrier being 4 or more in the ratio (I1/I2) of the intensity I1 of the strongest peak to the intensity I2 of the second strongest peak observed in X-ray diffraction, or a powdery carrier having the ratio (I1/I2) of the intensity I1 of the strongest peak to the intensity I2 of the second strongest peak observed in X-ray diffraction of 1.5 times or more the ratio (I1s/I2s) of the intensity I1s of the strongest peak to the intensity I2s of the second strongest peak described in JCPDS.

Abstract: A polymer composite composed of a polymerized mixture of functionalized carbon nanotubes and monomer which chemically reacts with the functionalized nanotubes. The carbon nanotubes are functionalized by reacting with oxidizing or other chemical media through chemical reactions or physical adsorption. The reacted surface carbons of the nanotubes are further functionalized with chemical moieties that react with the surface carbons and selected monomers. The functionalized nanotubes are first dispersed in an appropriate medium such as water, alcohol or a liquefied monomer and then the mixture is polymerized. The polymerization results in polymer chains of increasing weight bound to the surface carbons of the nanotubes. The composite may consists of some polymer chains imbedded in the composite without attachment to the nanotubes.

Abstract: Compositions and methods related to carbon nanotubes are provided. More particularly, imaging agents comprising carbon nanotubes internally loaded with a contrast agent and associated methods are provided. One example of a method may involve a method for imaging comprising: providing an imaging agent comprising a carbon nanotube loaded with contrast agent; introducing the imaging agent into a cell; and imaging the cell to detect the presence of the imaging agent.

Abstract: The present invention is directed to carbon nanostructures, e.g., carbon nanotubes, methods of covalently functionalizing carbon nanostructures, and methods of separating and isolating covalently functionalized carbon. In some embodiments, carbon nanotubes are reacted with alkylating agents to provide water soluble covalently functionalized carbon nanotubes. In other embodiments, carbon nanotubes are reacted with a thermally-responsive agent and exposed to light in order to separate carbon nanotubes of a specific chirality from a mixture of carbon nanotubes.

Abstract: A polymer composite composed of a polymerized mixture of functionalized carbon nanotubes and monomer which chemically reacts with the functionalized nanotubes. The carbon nanotubes are functionalized by reacting with oxidizing or other chemical media through chemical reactions or physical adsorption. The reacted surface carbons of the nanotubes are further functionalized with chemical moieties that react with the surface carbons and selected monomers. The functionalized nanotubes are first dispersed in an appropriate medium such as water, alcohol or a liquefied monomer and then the mixture is polymerized. The polymerization results in polymer chains of increasing weight bound to the surface carbons of the nanotubes. The composite may consists of some polymer chains imbedded in the composite without attachment to the nanotubes.

Abstract: Systems and methods for the formation of carbon-based nanostructures are generally described. In some embodiments, the nanostructures may be formed on a nanopositor. The nanopositor can comprise, in some embodiments, at least one of metal atoms in a non-zero oxidation state and metalloid atoms in a non-zero oxidation state. For example, the nanopositor may comprise a metal oxide, a metalloid oxide, a metal chalcogenide, a metalloid chalcogenide, and the like. The carbon-based nanostructures may be grown by exposing the nanopositor, in the presence or absence of a growth substrate, to a set of conditions selected to cause formation of carbon-based nanostructures on the nanopositor. In some embodiments, metal or metalloid atoms in a non-zero oxidation state are not reduced to a zero oxidation state during the formation of the carbon-based nanostructures. In some cases, metal or metalloid atoms in a non-zero oxidation state do not form a carbide during the formation of the carbon-based nanostructures.

Abstract: Electromagnetic irradiation of functionalized fullerenes in an oxygen-free environment induces conversion of the functionalized fullerenes to carbon nanotubes, carbon nanohorns, carbon onions, diamonds and/or carbon schwarzites. The carbon nanotubes can be multi-wall carbon nanotubes. Advantageously, the subject invention can be used for in-situ synthesis of carbon nanostructures within a matrix to form a carbon nanostructure composite, where positioning of the carbon nanostructures is controlled by the manner of dispersion of the functionalized fullerenes in the matrix. Carbon nanotube comprising features, such as electrical connects, can be formed on a surface by irradiating a portion of a functionalized fullerene coating with a laser beam.

Abstract: The present invention discloses a graphene fiber and a method of manufacturing the same. The graphene fiber is manufactured by oxidizing graphite, dispersing, spinning, drying and heat treatment, and has a diameter less than 100 ?m, a ratio of length to diameter greater than 10, and a ratio of carbon to oxygen greater than 5. The graphene fiber is formed of a plurality of graphene sheets, which envelop an axis and are coaxially stacked one by one from the axis. The thickness of the graphene sheet is less than 3 nm, and chemical bonds are formed to tightly bond the graphene sheets to exhibit excellent mechanical and thermally/electrically conductive properties. The method of the present invention is implemented by simple steps so as to greatly reduce poisonous chemicals possibly generated in the manufacturing environment, thereby improving the safety of manufacturing and reducing the whole processing time and cost.

Abstract: A method for dispersing nanotubes, comprising forming a nanocomposite solution with associated nanotubes and nanoplatelets, mixing a surfactant to the nanocomposite solution, separating the nanocomposite in solution, wherein the nanotubes remain suspended in the surfactant solution, and isolating the nanotubes in solution. In certain instances, the method further comprises functionalizing the nanotubes in solution.

Abstract: A method for preparing a carbon nanotube, including: a) preparing an LPAN solution, stirring the LPAN solution at between 100 and 200° C. for between 100 and 200 hours to yield a cyclized LPAN solution; b) heating the cyclized LPAN solution at between 200 and 300° C. for between 1 and 10 hours to yield an OPAN; c) grinding, screening, and drying at room temperature the OPAN to yield a thermal oxidative precursor; d) calcining the thermal oxidative precursor at between 400 and 1000° C. for between 1 and 24 h in the presence of inert gas having a flow rate of between 10 and 500 mL/min to yield a carbonated precursor; and e) calcining the carbonated precursor at between 1000 and 1500° C. for between 1 and 10 hours in the presence of the inert gas having a flow rate of between 10 and 500 mL/min to yield a carbon nanotube material.

Abstract: In one aspect, the present invention provides nanosized systems for generating electrical energy based on the use of a chemically reactive composition to generate a thermoelectric wave. For example, the system can include at least one nanostructure (e.g., a carbon nanotube) extending along an axial direction between a proximal end and a distal end. A chemically reactive composition is dispersed along at least a portion of the nanostructure, e.g., along its axial direction, so as to provide thermal coupling with the nanostructure. The chemical composition can undergo an exothermic chemical reaction to generate heat. The system can further include an ignition mechanism adapted to activate the chemical composition so as to generate a thermal wave that propagates along the axial direction of the nanostructure, where the thermal wave is accompanied by an electrical energy wave propagating along the axial direction.

Abstract: The present invention provides a high surface area porous carbon material and a process for making this material. In particular, the carbon material is derived from biomass and has large mesopore and micropore surfaces that promote improved adsorption of materials and gas storage capabilities.

Abstract: The present invention is directed to methods of making nanofiber yarns. In some embodiments, the nanotube yarns comprise carbon nanotubes. Particularly, such carbon nanotube yarns of the present invention provide unique properties and property combinations such as extreme toughness, resistance to failure at knots, high electrical and thermal conductivities, high absorption of energy that occurs reversibly, up to 13% strain-to-failure compared with the few percent strain-to-failure of other fibers with similar toughness, very high resistance to creep, retention of strength even when heated in air at 450° C. for one hour, and very high radiation and UV resistance, even when irradiated in air.

Abstract: A method for preparing resin-impregnated graphite articles, including providing a sheet of compressed particles of exfoliated graphite having two major surfaces; impregnating the sheet with a first resin system to form a resin-impregnated sheet; surface treating the resin-impregnated sheet to form at least one structure on at least one of the major surfaces of the sheet to form a surface treated sheet; and treating the sheet with a second resin system.

Abstract: Methods and compositions for the formation of dispersions of nanotubes are provided using solution comprising an aromatic hydrocarbon and an electron donor group. Also provided are methods for isolating carbon nanotubes from the composition, and use of carbon nanotube products.

Abstract: An industrial process and an apparatus for fabricating carbon nanotubes (CNTs) is provided, comprising synthesis of the carbon nanotubes by decomposing a carbon source brought into contact, in a fluidized-bed reactor, whereby the carbon nanotubes synthesized in the reactor and fixed onto the grains of catalytic substrate in the form of an entangled three-dimensional network, forming agglomerates constituting the CNT powder, are recovered sequentially by discharging them while hot, that is to say at the reaction temperature for synthesizing the CNTs, at the foot of the reactor, the sequence in which the discharges are carried out corresponding to the frequency of filling of the reactor.

Abstract: A method for making a carbon nanotube film is provided. In the method, a carbon nanotube array is grown on a substrate, and a rigid drawing device is provided. The carbon nanotube array is adhered to the rigid drawing device via an planar adhesive region of the rigid drawing device. The rigid drawing device is pulled at a speed along a direction away from the substrate, thereby pulling out a continuous carbon nanotube film. The carbon nanotube array includes a plurality of carbon nanotubes. The planar adhesive region have a linear border, wherein the linear border of the planar adhesive region is the closest border of the planar adhesive region to a surface of the substrate. The carbon nanotubes in the carbon nanotube array are adhered via the planar adhesive region.

Abstract: Broad-area synthesis of aligned and densely-packed carbon nanotubes (CNT) is disclosed. CNT are repeatedly synthesized and then drawn together to locally and globally achieve increased packing densities. The process synthesizes an aligned, relatively sparse forest of CNT on a catalyzed sacrificial substrate. The catalyst is removed, thereby releasing the CNT but leaving them in place on the substrate. A liquid-induced collapse produces regions of more densely packed CNT and regions where no CNT remain. A fresh catalyst is deposited on the exposed regions of the substrate and a sparse forest of aligned CNT is regrown in these regions. The CNT also may form on the tops of the densified regions of CNT. The top-growth CNT may be removed or incorporated into the solid such that the solid is expanded axially. This process, e.g., growth then densification, is repeated to form a near-continuous solid of aligned and densely packed CNT.

Abstract: The invention provides a high module carbon fiber and a fabrication method thereof. The high module carbon fiber includes the product fabricated by the following steps: subjecting a pre-oxidized carbon fiber to a microwave assisted graphitization process, wherein the pre-oxidized carbon fiber is heated to a graphitization temperature of 1000-3000° C. for 1-30 min. Further, the high module carbon fiber has a tensile strength of between 2.0-6.5 GPa and a module of between 200-650 GPa.

Abstract: A method for forming graphene nanoribbons includes: (a) dispersing carbon nanotubes in a solvent to obtain a nanotube-dispersing solution; (b) adding an oxidant into the nanotube-dispersing solution to obtain a reaction solution; and (c) microwave heating the reaction solution and longitudinally unzipping the carbon nanotubes to form graphene nanoribbons.

Abstract: An apparatus for manufacturing a carbon nanotube heat sink includes a board, and a number of first and second carbon nanotubes formed on the board. The first carbon nanotubes and the second nanotubes are grown along a substantially same direction from the board. A height difference exists between a common free end of the first carbon nanotubes and a common free end of the second carbon nanotubes.

Abstract: A method for dispersing nanotubes, comprising forming a nanocomposite solution with associated nanotubes and nanoplatelets, mixing a surfactant to the nanocomposite solution, separating the nanocomposite in solution, wherein the nanotubes remain suspended in the surfactant solution, and isolating the nanotubes in solution. In certain instances, the method further comprises functionalizing the nanotubes in solution.

Abstract: Disclosed are a method and an apparatus for separating metallic CNT and semiconducting CNT, comprising treating with a physical separation means of centrifugation, freezing-thawing-squeezing, diffusion, permeation or the like using a gel containing CNT as a dispersed and isolated state (CNT-containing gel), to thereby make semiconducting CNT exist in gel and make metallic CNT exist in solution.

Abstract: An in-situ method and system of collecting, in a liquid, non-agglomerated fullerenic material from a gaseous suspension is provided. The method and system collects non-agglomerated fullerenic material by contacting a gaseous suspension comprising fullerenic material with a suspension liquid, so as to capture the fullerenic material in the suspension liquid; and collecting the liquid suspension as a suspension liquid containing the fullerenic material. This method and system may be particularly useful for collecting fullerenes or nanotubes and maintaining them in solution in non-agglomerated states.

Abstract: In one embodiment of the disclosure, a composite raw material and a method for forming the same are provided. The method includes sulfonating a polycyclic aromatic compound to form a polycyclic aromatic carbon sulfonate (PCAS); and mixing the polycyclic aromatic carbon sulfonate and a polyacrylonitrile (PAN) to form a composite raw material. In another embodiment of the disclosure, a carbon fiber containing the composite raw material described above and a method for forming the same are provided.

Abstract: An apparatus for producing high yields of carbon nanostructures is disclosed. The apparatus includes an electric arc furnace and a feeder that directs solid carbon dioxide into an electrical arc generated by the electric arc furnace.

Abstract: Systems and methods for the formation of carbon-based nanostructures are generally described. In some embodiments, the nanostructures may be formed on a nanopositor. The nanopositor can comprise, in some embodiments, at least one of metal atoms in a non-zero oxidation state and metalloid atoms in a non-zero oxidation state. For example, the nanopositor may comprise a metal oxide, a metalloid oxide, a metal chalcogenide, a metalloid chalcogenide, and the like. The carbon-based nanostructures may be grown by exposing the nanopositor, in the presence or absence of a growth substrate, to a set of conditions selected to cause formation of carbon-based nanostructures on the nanopositor. In some embodiments, metal or metalloid atoms in a non-zero oxidation state are not reduced to a zero oxidation state during the formation of the carbon-based nanostructures. In some cases, metal or metalloid atoms in a non-zero oxidation state do not form a carbide during the formation of the carbon-based nanostructures.

Abstract: A process for making multi-walled carbon nanotubes includes contacting a hydrocarbon-containing gas with an electron beam-treated fly ash catalyst. The electron beam-treated fly ash catalyst contains a total amount of iron oxide and vanadium oxide of up to 5 wt. %. The multi-walled carbon nanotubes may be formed in a low pressure chemical vapor deposition apparatus.

Abstract: A process for multistage thermal treatment of rubber waste, in particular scrap tires, is proposed. The process comprises several steps of transferring a product granulate of rubber waste into three different sequencing heating zones of a reactor (10). In the heating zones (11a, 11b, 11c) the product granulate is heated at a first temperature between 100° to 200° C., preferably 150° to 180° C., then at a second temperature between 200° to 350° C. and at a third temperature between 300° to 600° C. The temperature is maintained until such time that no further oil is emitted within the respective heating zone. As a final step, the product granulate is removed from the reactor (10) and the desirable solid materials are separated.

Abstract: A method of enriching specific species of carbon nanotubes by exposing a composition of carbon nanotubes to an azo compound is provided. The method includes a) mixing the azo compound with a suspension comprising the composition of carbon nanotubes to form a mixture; b) incubating the mixture to react the azo compound with the carbon nanotubes; and c) separating a supernatant and a precipitate formed in the mixture. An electrode and a field-effect transistor comprising a single-walled carbon nanotube species enriched using the method are also provided.

Abstract: There is provided a high-purity carbon nanotube, which can be produced with simple purification by causing graphite to be hardly contained in crude soot obtained immediately after being synthesized by arc-discharge, and a method for producing the same. Soot containing carbon nanotubes produced by arc-discharge using an anode which contains amorphous carbon as a main component is heated at a temperature of not lower than 350° C. to be burned and oxidized, immersed in an acid, heated at a temperature, which is not lower than the heating temperature in the previous burning and oxidation and which is not lower than 500° C., to be burned and oxidized, and immersed in an acid again.

Abstract: A new method for recovering a catalytic metal and carbon nanotubes from a supported catalyst is provided. The carbon nanotube, including carbon nanotube structures, may serve as the support for the catalytic metal. The valence state of the catalytic metal, if not already in the positive state, is raised to a positive state by contacting the supported catalyst with a mild oxidizing agent under conditions which does not destroy the carbon nanotube. The supported catalyst is simultaneously or subsequently contacted with an acid solution to dissolve the catalytic metal without dissolving the carbon nanotube.

Abstract: A method of manufacturing a ferrous oxide nanoparticle includes a water removing step raising temperature of a solution containing an iron oxide, an organic acid dissolving the iron oxide, and a first solvent to a first temperature and removing water in the solution, a second temperature maintaining step raising the first temperature to a second temperature and maintaining the second temperature, and a particle extracting step extracting the ferrous oxide nanoparticle from the solution after the second temperature maintaining step.

Abstract: A manufacturing method of a light transmissive film includes the following steps. A film is provided, and the film includes a plurality of nano-units and has a reference direction. In addition, a plurality of first stripes parallel to each other is formed on the film by an energy beam, and the first stripes are neither perpendicular nor parallel to the reference direction.

Abstract: An active material of the present invention has fine pores formed in the interlayer of a carbon material capable of exhibiting electrochemical double layer capacitance. The fine pores are formed by forming an oxidized graphite structure combined with oxygen in the interlayer of a part or whole of the carbon material containing soft carbon and then removing a part or whole of oxygen in the interlayer. A method for producing an energy storage active material for use in an electrochemical double layer capacitor comprises pre-treating a carbon material through heat treatment and oxidizing the pre-treated carbon material using an oxidant. The method further comprises reducing the oxidized carbon material through heat treatment. The interlayer distances of an active material for respective steps, measured by a powder X-ray diffraction method, are 0.33˜0.36 nm in the pre-treatment step, 0.5˜2.1 nm in the oxidation step, and 0.34˜0.5 nm in the reduction step.

Abstract: A method for making a carbon nanotube film includes the steps of: (a) adding a plurality of carbon nanotubes into a solvent containing metallic ions, and flocculating the carbon nanotubes to get a floccule structure with the metallic ions therein; (b) reducing the metallic ions into metallic atoms, thereby the metallic atoms being attached onto outer surfaces of the carbon nanotubes to form a floccule structure of carbon nanotubes compounded with metal atoms; and (c) separating the floccule structure compounded with metal atoms from the solvent; and (d) shaping the floccule structure compounded with metal atoms to obtain/get the carbon nanotube film.

Abstract: A method of manufacturing a polyacrylonitrile fiber includes a spinning process in which a spinning dope including polyacrylonitrile is spun; a first drawing process; a drying process; and a second hot drawing process in this order.

Abstract: A method for producing carbon nanotubes having specific lengths, said method comprising: producing carbon nanotubes having at least two types of zones along their lengths, wherein each zone type has a characteristic structure that confers specific properties; and processing said carbon nanotubes to selectively attack one zone type more aggressively than another zone type.

Abstract: This invention relates to poly(acrylonitrile) homo- or co-polymer having a number average molecular weight (Mn) of at least 200,000 g/mol and a dispersity () of less than 1.

Abstract: A carbon nanohorn carried material for producing a carbon nanotube by a chemical vapor deposition (CVD) method, including a catalytic metal or a compound thereof contained inside carbon nanohorns or supported on exterior walls of the carbon nanohorns is provided. A carbon nanotube is produced by a CVD reaction using the carbon nanohorn carried material. A novel technical means for producing a carbon nanotube which does not use any noncarbon type carrier, can easily collect and purify the carbon nanotube and can control the length of the carbon nanotube can be provided.

Abstract: A novel fine carbon fiber is produced by vapor growth, in which a graphite-net plane consisting of carbon atoms alone forms a temple-bell-shaped structural unit comprising closed head-top part and body-part with open lower-end, where an angle ? formed by a generatrix of the body-part and a fiber axis is less than 15°, 2 to 30 of the temple-bell-shaped structural units are stacked sharing a central axis to form an aggregate, and the aggregates are connected in head-to-tail style with a distance, thereby forming a fiber. Furthermore, a fine short carbon fibers with excellent dispersibility can be obtained by shortening the fine carbon fiber.

Abstract: An integrated method and apparatus to continuously produce purified Single Wall Carbon Nanotubes (SWNT) from a continuous supply of solid carbon powder fed to an induction plasma torch. The apparatus includes a reactor body disposed to maintain laminar flow of gases with the torch body and coupled to a quenching body where temperature and residence time is controlled. Conveniently, functionalization may take place in the quenching body. The torch is operated with an argon carrier gas, an argon stabilizing gas and a helium sheath gas. Solid carbon reactants are preferably mixed with at least two metal catalysts containing nickel and cobalt with additional metal oxides of yttrium and cerium being desirable.

Abstract: Provided is an aggregate of carbon nanotubes satisfying (1) there is a 2? peak at 24°±2° by X-ray powder diffraction analysis; (2) a height ratio (G/D ratio) of G band to D band by Raman spectroscopic analysis of wavelength 532 nm is 30 or more; and (3) a combustion peak temperature is from 550° C. to 700° C. The present invention provides an aggregate of carbon nanotubes excellent in dispersibility while high quality, giving a film, molded article, membrane or the like having excellent characteristics.

Abstract: In some embodiments, the present disclosure pertains to methods of forming a solution of single-walled carbon nanotube polyelectrolytes in a liquid crystalline phase. In some embodiments, such methods comprise: (a) providing single-walled carbon nanotube polyelectrolytes; and (b) mixing the single-walled polyelectrolytes with a polar aprotic solvent to form a mixture, where the mixing results in the formation of single-walled carbon nanotubes in the liquid crystalline phase. In some embodiments, the polar aprotic solvent comprises crown ether. In some embodiments, the present disclosure pertains to a method of making single-walled carbon nanotube fibers. Further embodiments of the present disclosure pertain to a method of making a single walled carbon nanotube composite. In some embodiments, the present disclosure pertains to an article comprising neat aligned carbon nanotubes.

Abstract: A carbon nanotube film includes a plurality of carbon nanotube strings and one or more carbon nanotubes. The plurality of carbon nanotube strings are separately arranged and located side by side. Distances between adjacent carbon nanotube strings are changed when a force is applied. One or more carbon nanotubes are located between adjacent carbon nanotube strings.

Abstract: Provided is a carbon fiber manufacturing method including a surface treatment step of ejecting an ozone solution in which ozone is dissolved in solvent from a fluid ejecting port toward a carbon fiber bundle and causing the ozone solution to pass between single fibers of the carbon fiber bundle so as to contact surfaces of the single fibers so that the surfaces of carbon fibers are treated by the ozone solution. Also, provided is a carbon fiber subjected to a surface treatment by the carbon fiber manufacturing method.

Abstract: Methods and systems for producing coiled nanotubes. At least one exemplary method of producing coiled carbon nanotubes of the present disclosure comprises the steps of reacting a carbon feedstock and a catalyst within a reaction vessel to produce a reaction product comprising at least about 5% coiled carbon nanotubes, wherein the carbon feedstock comprises either (i) a mixture of a hydrocarbon and water or (ii) an alcohol, and wherein the catalyst comprises at least one Group VIB or VIIIB transition metal.

Abstract: Provided are: a polyacrylonitrile-based precursor fiber for the production of a carbon fiber having a large single-fiber fineness, said precursor fiber ensuring high heat stability of a spinning dope and excellent productivity; and a copolymer suitable for the production of said precursor fiber. Also provided are: high-quality carbon fiber bundles which have a large single-fiber fineness and excellent productivity; a process for producing the same; and a process for producing flameproofed fiber bundles suitable for the production of the carbon fiber bundles. A polyacrylonitrile-based copolymer which comprises 93.0 to 99.4 mol % of acrylonitrile units, 0.5 to 4.0 mol % of (meth)acrylamide-based units, and 0.1 to 3.