Surface morphology of thermal, furnace and pyrolytic carbon blacks by nitrogen adsorption - Relation to the electrical conductivity

The surface morphology of various carbon blacks was studied by low-pressure nitrogen adsorption. The shape of their low-pressure nitrogen isotherm depends on the concentration of surface defects. This defect concentration on the surface is different for thermal blacks, even for those of the same grade. Different surface morphologies were also observed for carbon blacks obtained by pyrolysis of truck tires. The concentration of defects increased with pyrolysis pressure. For the various furnace blacks, however, similar surface morphologies were observed. The electrical conductivity of thermal and pyrolytic carbon blacks decreases with increasing defect concentration. However, in spite of a similar surface morphology, different conductivities were observed for furnace blacks. The carbon black surface morphology is therefore not a determining factor for the electrical conductivity. Furthermore, the graphitic character of the carbon black surface was studied by secondary ion mass spectroscopy (SIMS). For thermal, furnace and pyrolytic carbon blacks, the conductivity increased with increasing graphitic character of the carbon black surface, thus underlining the importance of this parameter.