Abstract: According to the present invention, there is disclosed a carbon fiber having a strand tensile strength of 6,100 MPa or more, a strand tensile modulus of 340 GPa or more and a density of 1.76 g/cm3 or more and possessing, on the surface, striations oriented in a direction parallel to the fiber axis, wherein the distance between striations in a 2×2 ?m area of the carbon fiber surface when observed by a scanning probe microscope is 0.1 to 0.3 ?m, the root mean square surface roughness Rms (5 ?m) in a 5×5 ?m area of the carbon fiber surface when observed by a scanning probe microscope is 20 to 40 nm, and the root mean square surface roughness Rms (0.5 ?m) when measured in a 0.5×0.5 ?m area is 2 to 12 nm.

Abstract: According to the present invention, there is disclosed a carbon fiber having a strand tensile strength of 6,100 MPa or more, a strand tensile modulus of 340 GPa or more and a density of 1.76 g/cm3 or more and possessing, on the surface, striations oriented in a direction parallel to the fiber axis, wherein the distance between striations in a 2×2 ?m area of the carbon fiber surface when observed by a scanning probe microscope is 0.1 to 0.3 ?m, the root mean square surface roughness Rms (5 ?m) in a 5×5 ?m area of the carbon fiber surface when observed by a scanning probe microscope is 20 to 40 nm, and the root mean square surface roughness Rms (0.5 ?m) when measured in a 0.5×0.5 ?m area is 2 to 12 nm.

Abstract: A method for producing mesophase pitch based carbon fibers which enables to produce high strength high modulus carbon fibers at a relatively low temperature with stabilized production manner. This method comprises carbonizing infusibilized fibers, in an inert atmosphere under no tension state or a tension of 1 mg/denier or less in the first stage to give a specified interlayer spacing and a crystallite thickness and then carbonizing under a tension of 50-300 mg/denier at a temperature of 2600.degree. C. or more in the second stage.

Abstract: A method for producing high strength, high modulus carbon fibers having a modulus of elasticity of 75 tonf/mm.sup.2 or more and a tensile strength of 250 kgf/mm.sup.2 or more is provided. This method comprises graphitizing mesophase-pitch-based carbon fibers at a temperature of 2600.degree. C. or more for several seconds or for several minutes while stretching said fibers with a stretching ratio which satisifies specified relations.