A typical coal tar Pitch used in manufacturing of graphite electrodes was individually modified with various silicon-bearing additives yielding mixtures that were pyrolyzed (carbonized) stepwise at increased temperatures up to 1650 degreesC. Three commercially available additives such as the elemental Si, silica SiO2, and poly(carbosilane) {-CH2-SiH(CH3)-}(n) as well as reference silicon carbide SiC were used. The resulting intermediate and final materials were studied with the XRD and Si-29 MAS NMR methods. For two additives, i.e., elemental Si and poly(carbosilane), the beginning of their conversion to SiC was detected at 1300 degreesC while for SiO2 higher temperatures were required under applied conditions. (C) 2002 Elsevier Science B.V. All rights reserved.