Microstructure of mesophase pitch-based carbon fiber and its control Optical micrograph Scanning electron micrograph 0.5 um Transmission electron micrograph( Bright field image) Transmission electron micrograph(Dark field image) d Fig. 6. OM. SEM, TEM-BF. and TEM-DF images of the longitudinal sections in F-C. (a) OM photograph. (b)SEM photograph. (c) TEM-BF image (d) TEM-DF image ion, although Oberlin's photograph suggests its pres- 4. DISCUSSION ence [22] 4.1 Micro-structural units in the transverse section 3.3 Some properties of the mesophase pitch The present study clarified the microscopic and based carbon fibers and their relations to the macroscopic structures of mesophase pitch-based microstructures graphitized fibers Table 3 summarized some properties of the meso- The fiber basically consists of clusters, micro phase pitch-based carbon fibers used in this study. domains, domains and isochromatic areas ll fibers showed similar values of the Lc(002 ), the Particularly, the present authors claim the existence height of crystallite stacking, and the degree of pre- of micro-domains as a basic unit in the mesophase ferred orientation(DO). Among them, F-A showed pitch-based carbon fiber. The size, shape and distribu the highest values of Lc(002)and DO, whereas its tion of domains, which are assembled units of micro ensile strength and Youngs modulus were lowest. domains, appear to influence the mechanical proper F-C fiber with typical random transverse alignment ties of the mesophase pitch-based carbon fiber as th lowed excellent values of tensile strength, and units of mechanical responses, as suggested by Gerald Young,s modulus in spite of its inferiority of Lc(002) et al. [18]. It is of value to discuss how the size and and DO. Particularly, higher compressive strength of arrangement of the domains are defined to form the F-C compared to other fibers was very suggestive of trans the relationships between the mechanical properties carbon fiber. and microstructures of the mesophase pitch-based Mesophase pitch exhibits the liquid crystalline nature during spinning where mesogen moleculesMicrostructure of mesophase pitch-based carbon fiber and its control 951 Optical micrograph Scanning electron micrograph , 0.5 pm , Transmission electron micrograph (Bright field image) Transmission electron micrograph (Dark field image) 0.5 pm t I 0.5 pm t I Fig. 6. OM, SEM, TEM-BF, and TEM-DF images of the longitudinal sections in F-C. (a) OM photograph. (b) SEM photograph. (c) TEM-BF image. (d) TEM-DF image. tion, although Oberlin’s photograph suggests its pres￾ence. [22] 3.3 Some properties of the mesophase pitch￾based carbon$bers and their relations to the Table 3 summarized some properties of the meso￾microstructures phase pitch-based carbon fibers used in this study. All fibers showed similar values of the Lc(OO2), the height of crystallite stacking, and the degree of pre￾ferred orientation (DO). Among them, F-A showed the highest values of Lc(OO2) and DO, whereas its tensile strength and Young’s modulus were lowest. F-C fiber with typical random transverse alignment showed excellent values of tensile strength, and Young’s modulus in spite of its inferiority of Lc(OO2) and DO. Particularly, higher compressive strength of F-C compared to other fibers was very suggestive of the relationships between the mechanical properties and microstructures of the mesophase pitch-based carbon fibers. 4. DISCUSSION 4.1 Micro-structural units in the transverse section The present study clarified the microscopic and macroscopic structures of mesophase pitch-based graphitized fibers. The fiber basically consists of clusters, micro￾domains, domains and isochromatic areas. Particularly, the present authors claim the existence of micro-domains as a basic unit in the mesophase pitch-based carbon fiber. The size, shape and distribu￾tion of domains, which are assembled units of micro￾domains, appear to influence the mechanical proper￾ties of the mesophase pitch-based carbon fiber as the units of mechanical responses, as suggested by Gerald et al. [IS]. It is of value to discuss how the size and arrangement of the domains are defined to form the transverse texture of particular features in the carbon fiber. Mesophase pitch exhibits the liquid crystalline nature during spinning where mesogen molecules