ULTRAMICROPORES IN MICROPOROUS CARBON-FIBERS EVIDENCED BY HELIUM ADSORPTION AT 4.2 K

The adsorption isotherms of He on activated carbon fibres at 4.2 k have been determined gravimetrically. The He adsorption isotherms were of typical type I and were analysed by the Dubinin-Radushkevich plots, giving the micropore volumes which are greater than those obtained from the N2 adsorption isotherm at 77 k by 20-50%. The excess amount of He adsorption was ascribed to the presence of ultramicropores which cannot be assessed by N2 molecules.