Sorptive properties and small angle neutron scattering from porous carbon

Abstract

The investigated carbons included eight graphitized carbon blacks (A to H), ball milled to give specific surface areas ranging from 5 to 540 m 2g −1, a Koch-Light graphite (nonporous), graphitized (g-FT) and ungraphitized (u-FT) carbons, activated charcoal, and charcoal cloth. Small-angle neutron scattering (SANS) Porod plots (In I versus In Q) showed normal Porod behavior (negative slope = 4.0) with the Koch-Light and u-FT carbons but marked deviations (<3) were evident for activated charcoal and charcoal cloth. The Porod slopes (−3.6 to −2.8) for the samples A to H reflected the extent of ball milling. These deviations from Porod behavior may also reflect the fractal nature of the solids. Lamond n-N′ type plots constructed from nitrogen isotherms at 78 K indicated the presence of ultramicropores ( d < 0.7 nm) only in the cases of activated charcoal and charcoal cloth. Water isotherms (303 K) on graphite H and g-FT showed the hydrophobic nature of these surfaces. With sample H. the sorption of 2,2-dimethyl-propane (spherical) was quite similar to that of n-butane (linear).