THE STRUCTURAL-CHANGE OF GRAPHITIZATION-CONTROLLED MICROPOROUS CARBON UPON ADSORPTION OF H2O AND N2

The partial graphitization of activated carbon fibers (ACFs) was controlled by heating at 1773-3173 K in Ar. The growth of graphitic crystallites was examined by high-resolution transmission electron microscopy and X-ray diffraction. The adsorption processes of H2O and N2 On the graphitization-controlled ACFs were investigated by use of the in situ X-ray diffraction. The adsorption of H2O at 303 K and N2 at 165 K led to shrinkage of the interlayer spacing, d002, between the graphitic carbon layers. The shrinkage of more graphitized ACF is less remarkable than that of as-received ACF. The d002 value decreased hardly until 40% of the fractional filling of H2O, then it lowered markedly with the fractional filling. On the other hand, only less than 5% of the fractional filling decreased seriously the d002 value in the case of N2 adsorption. The relationship between the molecular adsorption and the graphitic structural change was discussed on the basis of the adsorption process; N2 molecules are at first adsorbed in the deep sites of the distorted slit-shaped micropores, while H2O molecules are firstly adsorbed near the entrance of the micropore with hydrophilic functional groups.