S-H. Hong et al. /Carbon 37(1999)917-930 began to show a very periphery. The connection of and random arrangement of such microdomains, showing raight microdomain 60-100 length exhibited very that the skin and core were homogeneous at the magnifica- sharp angles forming tion of 50 000(Fig. lk carbon fiber(Fig. I). The size of the microdomain in the Fig. 2 shows HR-sEM photographs under high magni- as-spun fiber was maintained basically the same after the fication for a series of the transverse cross-sectional heat treatment as well as the extraction. The whole cross- surface of as-spun, stabilized and carbon fibers heat-treated sectional surface exhibited the random transverse texture at 300 to 2400C, which were spun at 310.C, showing 1 danm SPUN 15KU 3200, 00e 400 15kU28 b SKU x2 s15k0×20598 688 15KU x20 Fig. 2. HR-SEM photographs of transverse cross-section of the mesophase pitch-based (a) n,(b) stabilized, and carbon fibers heat-treated at(c)300,d)400,(e)500,()600,(g)700,(h)1000,()1200,0)1500,(k)2000(l)2400: spinning temperature3l0°CS.-H. Hong et al. / Carbon 37 (1999) 917 –930 921 began to show a very straight periphery. The connection of and random arrangement of such microdomains, showing straight microdomains of ca. 50–100 length exhibited very that the skin and core were homogeneous at the magnifica￾sharp angles forming straight domains in the graphitized tion of 50 000 (Fig. 1k). carbon fiber (Fig. 1l). The size of the microdomain in the Fig. 2 shows HR–SEM photographs under high magni￾as-spun fiber was maintained basically the same after the fication for a series of the transverse cross-sectional heat treatment as well as the extraction. The whole cross- surface of as-spun, stabilized and carbon fibers heat-treated sectional surface exhibited the random transverse texture at 300 to 24008C, which were spun at 3108C, showing Fig. 2. HR–SEM photographs of transverse cross-section of the mesophase pitch-based (a) as-spun, (b) stabilized, and carbon fibers heat-treated at (c) 300, (d) 400, (e) 500, (f) 600, (g) 700, (h) 1000, (i) 1200, (j) 1500, (k) 2000, (l) 2400: spinning temperature 3108C