129-NMR-spektroskopische Untersuchungen an Carbon Black und Graphit
Porous Carbon Blacks with specific surfaces of up to 1475 m²/g were examined and characterized by 129Xe NMR spectroscopy. Graphite is regarded as a not-porous reference. The porosity of Carbon Blacks can be divided in three categories: inter-aggregate, intra-aggregate and intra-particle pores. A reciprocal behavior of the chemical shift to the middle pore radius has been found. Here the pressure and temperature dependence of the chemical shift are to be considered and only with pressures over 8-12 bar a characteristic limit value is reached. The diffusion coefficient of the intra-porous xenon atoms was determined with the help of the PFG NMR spectroscopy and lies with ambient temperature and a pressure from 10 to 12 bar within the range of 3·10-9 to 3·10-8m²/s. The adsorption in micro-porous Carbon Blacks can be described by the pore filling theory of Dubinin and co-workers.