Abstract: A specific sizing agent comprising as the main component an adduct of mono- or poly-cyclic phenol with alkylene oxide is applied in a specified amount to the surface of a high-strength and high-elasticity carbon fiber or a precursor fiber thereof and then dried to prepare a reinforcing carbon fiber according to the present invention, which is then preformed into a fiber arrangement, impregnated with a precursor of matrix carbon, and carbonized to produce a high-strength and high-elasticity carbon-carbon composite material.

Abstract: A method for producing high density, high strength carbon-carbon composite material, is provided by using pitch-based carbonaceous fibers carbonized at a temperature lower than 2200.degree. C. or structures, including said carbonaceous fibers as a principal constituent, as a reinforcement material, impregnating said reinforcement material with a carbonaceous material such as pitch or the like and then heat treating said impregnated material.

Abstract: A porous carbon-carbon composite having a porosity of 25-65%, higher strength and higher uniformity can be obtained by using carbon fibers having a fiber diameter of 2.5-32 micron and a fiber length of not longer than 2 mm in an amount of 60% by weight or more.

Abstract: A porous isotropic carbon-carbon composite having a porosity of 25 to 85% and substantially isotropic mechanical strength, and containing 60% by weight or more of aggregate particles having an aspect ratio of 10 or smaller and reinforced in one direction with carbon fiber is provided.

Abstract: A process for producing a high density, high strength carbon-carbon composite which does not require high cost secondary reinforcement treatment. This process comprises impregnating an aggregate such as a bundle of a carbon fiber with a liquid dispersion of a carbonaceous material of specified size of a fine powder or a short fiber of carbonaceous material to form a reinforcement material of a carbon fiber having the fine powder or the short fiber of a carbonaceous material distributed on the surface as well as in the inside of said bundle of a carbon fiber, and impregnating said aggregate of a carbon fiber with one or more liquid carbonaceous material selected from the group consisting of a phenolic resin, a furan resin and a pitch and carbonizing the impregnated bundle of a carbon fiber, and if necessary, graphitizing the carbonized product.

Abstract: High strength, high modulus carbon fibers derived from high mesophase content pitch, having a plurality of sheets formed of planes of hexagonal carbon networks oriented, in the direction of the fiber axis and having a cross-sectional arrangement which does not carbonize to a graphitic structure are characterized by electron and X-ray diffraction pattern wherein the (10) band is not resolved into (100) and (101) lines, by an interlayer spacing greater than 3.38 angstrom and by negative magnetic resistivity when composed to graphitized fibers.