Patent ID: 6946110

Claim:
A process for producing fine carbon fibers comprising: adding vapor-grown fine carbon fibers having a diameter of 1 μm or less to boron or a boron compound; compacting the mixture of fine carbon fibers and boron or a boron compound to obtain a solidified shaped mixture; relieving pressure after completion of shaping; regulating the bulk density of the mixture of fine carbon fibers and boron or a boron compound during compacting such that the solidified mixture has a bulk density of 0.05 g/cm 3 or more after pressure relief; and heat treating said fine carbon fibers to a temperature of 2000° C. or higher while said bulk density is maintained, to produce fine carbon fibers having an interlayer distance d002 between carbon layers as determined by an X-ray diffraction method of 0.335 to 0.342 nm, and satisfying d002<0.3448-0.0028 (blog φ) where φ represents the diameter the carbon fibers and the units of d002 are nm, and a thickness Lc of the crystal in the C axis direction of 40 nm or less.