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