Seong-Hwa Hong

Pore structure analysis of activated carbon fiber by microdomain-based model

The pore structures of commercial pitch and PAN-based activated carbon fibers (ACFs) were investigated. The pore size and pore size distribution of pitch-based ACFs were measured by nitrogen adsorption isotherms and 129Xe NMR spectroscopy and compared with each other. Scanning tunneling microscopy showed that the ACFs were composed of spherical microdomain units the size of a few nanometers. The activation mechanism of ACFs was considered and explained by novel hypothesis; the concept of microdomain structure of ACFs was considered and explained to overcome limitation of the conventional fractal hypothesis. Whereas micropores were generated on each microdomain, the origin of mesopores was interdomain pores, resulting from the microdomain hypothesis.

Transverse Sphere and Texture of Carbon Fibers Prepared through Cross Shaped Nozzles of Different Lobe Dimensions

Methylnaphthalene <bived mesophase pitch was spun through Y- and cross- shaped nozzles of different lobe dimensions in temperature range of 280 to 295°C by fixing the spinning rate to evaluate die-swelling phenomena which defonned cross-sectional shape and domain alignment of the carbon fiber. The higher temperature of spinning enhanced the refonnation through the lower viscosity. The thinner lobe emphasized the die-swelling through the larger shear rate, which reduces the viscosity, although the nozzles of the present study had the same cross-sectional area. Shape factors of the nozzle and fiber rescribe the extents of cause and results of die-swelling, respectively. Die-swelling is found to change the radial type alignment of the constituent domains to random order. The degrees of preferred orientation along the fiber axis were slightly influenced by die-swelling. The pressure in spinning and the nozzle shape were correlated to the reformation extent of the resultant fiber.