Carbon surface: Area, porosity, chemistry, and energy

Data from the adsorption of nitrogen at 77 K are interpreted in terms of surface area and porosity, for a range of carbon blacks and two porous carbons, using the BET, alpha(s), and Dubinin-Radushkevich methods. Heat of immersion (Delta H-i) data, for nonpolar (n-heptane) and polar (water) liquids are correlated with surface structure and chemistry, respectively. An average value of Delta H-i approximate to 107 mJ m(-2) is obtained for the dispersion interaction of nonporous carbon blacks by immersion into n-heptane. Where nitrogen adsorption data indicate the presence of microporosity, higher values of Delta H-i are observed which are thought to contain a contribution due to enhanced adsorption forces within pores. Data from samples of one specific black, which had been oxidized to varying levels using an oxygen/ozone fluidized bed apparatus, are presented showing a linear relationship between the surface oxygen levels and their polar interaction with water. (C) 1996 Academic Press, Inc.