Thermodynamic study of the formation of C-60 and C-70 by combustion or pyrolysis

An assessment of the available thermodynamic data of gaseous and condensed fullerene C-70 is presented. Gibbs energy minimization of the gaseous C-H-O -Ar chemical system, including large polyaromatic hydrocarbons and the full erenes C-60 and C-70, helps to determine under which conditions C-60 and C- 70 molecules are stable. The influence of the addition of halogen atoms in the gas phase on the improvement of the yield of these two fullerenes in di fferent conditions is investigated by minimizing the Gibbs energy of the ga seous C-H-F-O-Ar chemical system. The evolution of the yields of the two fu llerenes, and of the C-70(C-70 + C-60) ratio as a function of temperature, pressure, and C/H ratio in the reactants is illustrated and compared with c orresponding experimental information from a literature review. In the ligh t of these calculations, the possibility of the direct production of fuller ene films containing variable amounts of C-60 and C-70 by a continuous proc ess such as combustion or pyrolysis is discussed. (C) 1999 The Electrochemi cal Society. All rights reserved.