Studies on commercial carbon black by radial distribution function and rietveld refinement

Abstract

The x-ray scattering was measured using a Philips diffractometer, the step-scanning method, molybdenum and copper radiation and a graphite monochromator.The structural models of graphite- and diamond-type have been tested to describe the type of short-range order in three types of commercial carbon black (CARBEX-330, SAKAP-6, SAPEX-20). The Rietveld refinement was used to fit the experimental diffraction pattern of the carbon black to structural data of those crystalline models. Assuming that the "crystallite" size in the carbon black is comparable with the size of the unit cell of corresponding crystalline model, the line broadening in the Rietveld refinement was modelled. The DBWS-9006PC program was used for calculations of lattice constants and atom positions in unit cell. The best fit was obtained for the graphite-type model.The radial distribution analysis was made to compare the results with values of atomic distances obtained by the Rietveld method for the graphite-type model. After the background correction (Ib), effects of the polarization (P), the absorption (A), the fluorescence (IF) and the Compton correction (IC) we may describe the diffusion x-ray scattering [ID(k)] as:ID(k) = (Iexp − Ib − IF − Ic)PAThe calculating of radial distribution function (RDF) and pair distribution function P(r) for the carbon black were performed using a computer program on an IBM At computer. The radii of coordinate spheres for the carbon black were determined by the analysis of peak positions of the pair distribution function.