To obtain carbon fibers having excellent rigidity, bending strength and adhesiveness to a resin without inducing inflation of a cost and lowering of processability and suitable for a reinforced composite material, etc., by making an acrylic precursor to be fire resistant and carbonizing under a specific condition.
This carbon fiber has a tensile Young's modulus YM (GPa) and a nitrogen content NC(%) satisfying formulae I and II and crystal orientation π002(%) and crystal size Lc () both calculated from X-ray diffraction satisfying formulae III and IV, 1.01-1.25 a surface area ratio and 20-40 spreading index, and is obtained by making an acrylic precursor having fine particles comprising an organic-based compound or a silicon-based compound on the fiber surface to be fire resistant at 0.85-1.0 draw ratio so as to have 0.05-5 % solubility in formic acid and previously carbonizing in an inert atmosphere at 300-800°C and 1.0-1.5 draw ratio, and further carbonizing in an inert atmosphere at 800-1,600°C.
KOBAYASHI MAKOTO
ISHIDA TOMIHIRO
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