Bo-Sung Rhee

Scanning tunnelling microscopy study of activated carbon fibres

Scanning tunnelling microscopy (STM) has been used to study isotropic pitch-based carbon fibres before and after steam activation. The results show that the present carbon fibre precursor exhibits a particulate surface which is very favourable for the formation of activated carbon fibre. After activation, the carbon fibre surface becomes much more porous and rougher, and the mesopores are evidently present on the surface. Because the scale is down to atomic resolution, the STM observations offer direct evidence for the existence of micropores on the surface of the activated carbon fibres. In addition, the surface textures of both fibres are presented and discussed.

A comparison of pressure and reflux in the two-stage production of mesophase

Abstract Pitch-based carbon fibers are formed by melt spinning a liquid crystal, mesophase precursor into fiber form. This fiber is then heat treated to develop its modulus and strength. In the present study, a two-stage heat treatment process was evaluated and found to yield an excellent mesophase precursor for carbon fibers. In one variation of the process, a reflux was applied during an initial heat treatment of the isotropic pitch, and then the pitch was sparged with nitrogen during a final stage of pyrolysis. In the second variation, the isotropic pitch was heat treated under a moderate pressure prior to a final stage where, again, nitrogen was sparged through the pitch during pyrolysis. Both of these two-stage processes produced mesophase which could be readily spun at approximately the same temperature as mesophase produced by solvent extraction. Also, the physical properties of the final heat treated fibers were quite comparable to those of the solvent extraction mesophase fibers.

Surface free energy of carbon fibers with circular and non-circular cross sections coated with silicon carbide

Abstract Mesophase pitch-based carbon fibers with circular and non-circular (ribbon, C-shaped) cross sections were coated with a thin, approximately 100–150 nm SiC-layer, using a CVD technique. The surface free energy of the uncoated and SiC-coated carbon fibers was determined by measuring the contact angle of a variety of liquids with known polar and dispersive components of their total surface free energy. It was shown that the polar and dispersive components of the total surface free energy of the carbon fibers depends strongly on both the SiC-layer as well as on the shape of the cross section.