RATE OF DECOMPOSITION OF C-60 AND C-70 HEATED IN AIR AND THE ATTEMPTED CHARACTERIZATION OF THE PRODUCTS

Solid C60 and C70 were decomposed by heating in air at temperatures ranging from 150 to 250-degrees-C and times ranging from 1 to 743 h. The products dissolved increasingly poorly with increasing temperatures and longer times. The rates at which soluble fullerenes were extracted from products decreased also with longer time of heating. Extrapolations of decomposition rates to 25-degrees-C suggested that a fullerene mix containing 15 mole% C70 became totally insoluble in toluene after about 450 y, while that time is about 2,000 y for C60. Analytical techniques for the characterization of products included X-ray diffraction, Raman spectroscopy, infrared spectroscopy, UV-visible spectroscopy, mass-spectrometry, and electron microprobe analysis. The insoluble products contained no detectable amounts of fullerenes. The products were partially soluble in acetone, methanol, and water. The insoluble portions contained a fine-grained, black powder consisting of very small carbon particles. The products contained substances with aromatic bonds, and with C=O, C-C, and carboxylic groups.