A method of forming carbon fibers having internal cavities. The method includes applying a polymer material to a tooling component to form carbon fiber precursor hollow tubes, oxidizing the carbon fiber precursor hollow tubes, and carbonizing the carbon fiber hollow tubes to form carbon fibers, each having a hollow inner cavity

Disclosed are amorphous carbon nanofibers including copper nanoparticles or copper alloy nanoparticles, copper composite nanoparticles prepared by grinding the amorphous carbon nanofibers and implemented as surfaces of Cu-included particles are partially or wholly coated with amorphous carbons, a dispersed solution including the copper composite nanoparticles, and preparation methods thereof and the amorphous carbon nanofibers include nanoparticles including copper, copper nanoparticles or copper alloy nanoparticles, and, the copper composite nanoparticles are implemented as surfaces of Cu-included particles are partially or wholly coated with amorphous carbons.

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 are: chopped carbon fiber bundles which have high fluidity without decreasing the dispersibility of carbon fibers and the physical properties of a molded product; and a method for producing chopped carbon fiber bundles with high productivity. Chopped carbon fiber bundles, each of which contain a carbon fiber bundle having a total fineness of from 25,000 dtex to 45,000 dtex (inclusive) and a sizing agent in an amount of from 1% by mass to 5% by mass (inclusive) relative to the total mass of the chopped carbon fiber bundle. The length (L) of each chopped carbon fiber bundle along the fiber direction of the carbon fiber bundle is from 1 mm to 50 mm (inclusive); the ratio of the longest diameter (Dmax) to the shortest diameter (Dmin) of a cross section perpendicular to the fiber direction of each chopped carbon fiber bundle, namely Dmax/Dmin is from 6.0 to 18.0 (inclusive); and the orientation parameter of the single fibers present in the surface of each chopped carbon fiber bundle is 4.0 or less.

A carbon nanotube aggregate according to one embodiment of the present invention includes a plurality of carbon nanotubes, in which: the carbon nanotubes each have a plurality of walls; a distribution width of a wall number distribution of the carbon nanotubes is 10 walls or more; a relative frequency of a mode of the wall number distribution is 25% or less; and a length of each of the carbon nanotubes is more than 10 μm. A carbon nanotube aggregate according to another embodiment of the present invention includes a plurality of carbon nanotubes, in which: the carbon nanotubes each have a plurality of walls; a mode of a wall number distribution of the carbon nanotubes is present at a wall number of 10 or less; a relative frequency of the mode is 30% or more; and a length of each of the carbon nanotubes is more than 10 μm.

(Problem) In conventional method for producing artificial graphite, in order to obtain a product having excellent crystallinity, it was necessary to mold a filler and a binder and then repeat impregnation, carbonization and graphitization, and since carbonization and graphitization proceeded by a solid phase reaction, a period of time of as long as 2 to 3 months was required for the production and cost was high and further, a large size structure in the shape of column and cylinder could not be produced. In addition, nanocarbon materials such as carbon nanotube, carbon nanofiber and carbon nanohorn could not be produced. (Means to solve) A properly pre-baked filler is sealed in a graphite vessel and is subsequently subjected to hot isostatic pressing (HIP) treatment, thereby allowing gases such as hydrocarbon and hydrogen to be generated from the filler and precipitating vapor-phase-grown graphite around and inside the filler using the generated gases as a source material, and thereby, an integrated structure of carbide of the filler and the vapor-phase-grown graphite is produced. In addition, nanocarbon materials are produced selectively and efficiently by adding a catalyst or adjusting the HIP treating temperature.

A single-crystal silicon carbide and a single-crystal silicon carbide wafer of good-quality are disclosed that are low in dislocations, micropipes and other crystal defects and enable high yield and high performance when applied to a device, wherein the ratio of doping element concentrations on opposite sides in the direction of crystal growth of the interface between the seed crystal and the grown crystal is 5 or less and the doping element concentration of the grown crystal in the vicinity of the seed crystal is 2×10.sup.19 cm.sup.−3 to 6×10.sup.20 cm.sup.−3.

Provided is an epoxy-amine adduct that offers high reactivity, contributes to better adhesion between a resin and a reinforcing fiber in a fiber-reinforced composite material, and can be easily blended with another component such as a resin. The epoxy-amine adduct has two or more amino groups per molecule and is obtained by a reaction of an epoxy compound (A) having two or more alicyclic epoxy groups per molecule with an amine compound (B) having two or more amino groups per molecule. The epoxy compound (A) is preferably a compound represented by Formula (a): ##STR00001##

There is provided a reinforcing carbon fiber bundle of the present invention is a reinforcing carbon fiber bundle with a sizing agent adhered to surfaces of carbon fibers, and characterized in that the sizing agent is constituted by at least two components, a first component does not melt at 150° C., and a second component in flowable at 150° C., and the reinforcing carbon fiber bundle is improved in impregnation property and openability and is excellent in workability and optimum for a composite.

A carbon fiber bundle from which a carbon fiber composite material having high tensile strength can be obtained has the following configuration. Specifically, the carbon fiber bundle has a strand elastic modulus of 265-300 GPa, strand strength of at least 6.0 GPa, and knot strength of at least 820 N/mm.sup.2, and includes at least 30,000 filaments.