Development of Carbon Skeletons in Pitches

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The formation and growth of carbon skeletons, i.e., mesophase, in pitches which are in liquid state are understood in comparison with polyimides which are carbonized in solid state and vapor-grown carbon fibers which are grown in gas-phase carbonization. The structure and texture of carbons, which are resulted from the development of carbon skeletons, and their importance in carbon science and technology are discussed in the cases of films and fibers.1.Development of carbon skeletonsThe development of carbon skeletons depended strongly on chemical constitution and thermal history of pitches. Some pitches were heterogeneous at a micrometric scale, isotropic phase containing Brooks-Taylor type mesophase spheres and anisotropic domains consisting of basic structural units associated edge-to-edge with a long range statistical orientation. Some pitches were homogneous, consisting of anisotropic domains with a long range statistical orientation.2.Structure development in carbon materialsThe … More heterogeneous and homogeneous textures in pitches were found to be remained even after the spinning to fibers. From the pitch containing large amount of edge-to-edge anisotropic regions, for example, the fibers with radial texture in their cross-section were spinned, and their texture was found to be kept during oxidation, carbonization and subsequent graphitization. In the carbon films prepared from polyimides, the development of graphite structure was found to be strongly governed by the molecular orientation in the precursor polyimide films. The same situation was observed on vapor-grown carbon fibers.3.Textures in carbon materials and their functionsThe effects of texture in carbon materials on their functions were studied by focusing on the development of graphitic structure with high temperature heat treatment, the interaction with polymer matrices and intercalation of sulfuric acid and lithium ions by using carbon fibers with different textures. The mechanical properties of carbon fiber/carbon matrix composites were also studied. Less