COMPARISONS BETWEEN FULLERENE AND FORMS OF WELL-KNOWN CARBONS

The sublimation process and heterogeneous reactions of three batches of C60 fullerene, in argon, helium, air, or hydrogen, have been investigated at 25-1000-degrees-C under non-isothermal heating of 5-degrees-C/min. The results are compared against those obtained with well characterized carbons; Saran char (a highly reactive disordered carbon) and SP-1 graphite (less reactive, well-ordered carbon). Dependence of reaction rates on temperature and values of activation energies for the sublimation and hydrogenation processes are reported. In argon or helium, fullerene sublimes leaving behind a non-volatile carbon residue weighing 5-17% of the starting weight, depending on sample origin and aging. In air, the C60 first chemisorbs oxygen to a limit corresponding, on the average, to 1.5 oxygen atoms/C60 molecule. The carbon then gasifies to CO and CO2 at a rapid rate; higher than the rate of Saran or SP-1 gasification. In hydrogen, while the rates of SP-1 and Saran gasification up to 1000-degrees-C are insignificant, the volatile part of fullerene particles completely gasifies/sublimes at 500-800-degrees-C, leaving behind the non-volatile carbon residue (soot). The surface areas and porosity of one fullerene batch have been determined by gas adsorption techniques (Kr, N2, O2, at -196-degrees-C, and CO2 at 25-degrees-C). The sample has constricted micropores whose internal surface area and apparent average micropore width, determined by CO2 adsorption, are 131.9 m2/g and 1.19-1.26 nm, respectively. Selected potential applications of C60 in the areas of carbon composites are outlined.