Abstract: An object of the present invention is to provide a pitch carbon fiber having a decreased occurrence of cracking along the direction of the fiber axis of the pitch carbon fiber, which has conventionally occurred in a melt blowing method, and having high thermal conductivity. The invention is directed to a pitch carbon fiber having a melt mark recognized in the fiber corresponding to 60 to less than 100% of the cross-section of the fiber, and having a lattice spacing (d 002 value) of 0.3362 nm or less in the graphite layer and a crystallite size (Lc) of 60 nm or more derived from the thicknesswise direction, as determined by X-ray diffractometry. The pitch carbon fiber can be produced under specific conditions for spinning and infusibilization.

Abstract: Pitch-based graphitized short fibers formed from mesophase pitch as a raw material, having an average fiber diameter of 5 to 20 ?m, a percentage (CV value) of a variance of a fiber diameter with respect to the average fiber diameter of 8 to 15%, a number average fiber length of 20 to 500 ?m, and a crystallite size (La) derived from a growth direction of a hexagonal net plane of 30 nm or more, having graphene sheets that are closed upon observation of an end surface of a filler with a transmission electron microscope, and a substantially flat surface observed with a scanning electron microscope, and having an R value, which is a relative intensity ratio (ID/IG) of an intensity (ID) of a Raman band in the vicinity of 1,360 cm?1 to an intensity (IG) of a Raman band in the vicinity of 1,580 cm?1 measured by laser Raman spectroscopy, in a range of 0.01 to 0.07. The short fibers can be filled in a rubber composition at a high density without inhibition of curing of the rubber composition.

Abstract: A nonwoven fabric which contains pitch-based carbon fibers having a high elongation and a high elastic modulus which are not attained in the prior art and is obtained by improving the tensile elongation of carbon fibers derived from mesophase pitch, a felt obtained from the nonwoven fabric, and production processes therefore. The nonwoven fabric contains pitch-based carbon fibers, wherein the pitch-based carbon fibers have (i) an average fiber diameter (D1) measured by an optical microscope of more than 2 ?m and 20 ?m or less, (ii) a percentage of the degree of fiber diameter distribution (S1) to average fiber diameter (D1) measured by an optical microscope of 3 to 20%, (iii) a tensile elastic modulus of 80 to 300 GPa and (iv) a tensile elongation of 1.4 to 2.5%.

Abstract: A carbon fiber composite sheet obtained by combining a carbon fiber aggregate with a thermosetting resin component selected from the group consisting of thermosetting silicone-based gel components, thermosetting epoxy resin components and thermosetting silicone resin components, and then curing the thermosetting resin component, the carbon fiber composite sheet having crystallite sizes of at least 5 nm in the direction of growth of the hexagonal mesh surface of the carbon fibers composing the carbon fiber aggregate, and the carbon fiber composite sheet having a thermal conductivity of at least 2 W/(m·K).

Abstract: A carbon fiber composite sheet obtained by combining a carbon fiber aggregate with a thermosetting resin component selected from the group consisting of thermosetting silicone-based gel components, thermosetting epoxy resin components and thermosetting silicone resin components, and then curing the thermosetting resin component, the carbon fiber composite sheet having crystallite sizes of at least 5 nm in the direction of growth of the hexagonal mesh surface of the carbon fibers composing the carbon fiber aggregate, and the carbon fiber composite sheet having a thermal conductivity of at least 2 W/(m·K).