MESOPHASE POWDERS (CARBONIZATION AND GRAPHITIZATION)

Four mesophase powders, A, B, C, and D, are studied. A is petroleum de rived, B, C, and D are commercialized powders and are coal-tar derived . No additives are recognized in A, which is almost devoid of cross-li nking oxygen. In B, a thin deposit (approximately 100 nm) of a phase, which appears isotropic in transmission electron microscope (TEM), sur rounds the spheres and the primary quinoline insoluble (QI). C and D a re increasingly altered. The altered areas of C surround a core of res idual mesophase sphere with a thickness up to 1 mum. D, the powder ric her in oxygen, is entirely altered. By aging, B becomes similar to C, whereas C is transformed in a matrix of alteration, including relics o f spheres. After carbonization and heat treatment (HT) at 2800-degrees -C, A is entirely lamellar and strongly graphitized. B, C, and D conta in a decreasing amount of lamellae and an increasing amount of pores o f decreasing size. They have a decreasing ability to graphitize. The i ncreasing alteration is assumed to be due to the occurrence of adsorbe d heavy solvents. They act as dispersing agents on the basic structura l units (BSU). Correspondingly, mesophase spheres regress down to loca l molecular orientations (LMO), which decrease in size as solvent alte ration progresses.