Morphology and surface properties of carbonizates (C/SiC nanocomposites) obtained via pyrolysis of a coal tar pitch modified with selected silicon-bearing precursors

Morphology of carbon-based composite materials obtained from pyrolysis of a coal tar pitch admixed with selected silicon-bearing additives is discussed based on SEM/EDX observations, mercury porosimetry, BET surface area determinations, and helium density data. The silicon precursors used in the study included elemental silicon Si, silica SiO2, poly(carbomethylsilane) {–CH2–SiH(CH3)–} n , and commercial SiC. Each individual binary mixture, i.e. pitch/silicon additive, was first repeatedly homogenized at 160°C in the liquid medium of the molten pitch followed by carbonization at 500°C. In all cases, one part of the initial 500°C solid carbonizate was further pyrolyzed at 1300°C and another part at 1650°C under an argon flow resulting in nanocomposite products C/SiC. Differences in properties and morphology of the products were linked to specific chemical changes taking place in the reaction systems.