Soot produced from graphite through are discharge was separated into four f
ractions which were structurally analyzed. The toluene-soluble fraction car
ried C-60, C-70, and C-76-C-120 fullerenes while the toluene-insoluble quin
oline-soluble fraction (ca, 1 wt%) consisted Of larger clusters of C-70 to
C-400 which have a similar framework to C-60 or C-70 fullerenes. Graphitic
substances in the quinoline-insoluble fraction were separated through preci
pitation in acetone. Combustion of the quinoline-insoluble fraction free fr
om graphitic substances (15 wt%) revealed two kinds of carbon framework str
uctures; one is a pentagon-containing system similar to fullerenes (ca. 30
wt%) and the other is a rather graphitic, hexagonal system (ca. 45 wt%). Th
e pentagon-containing system in 'soot' particles burned in air at temperatu
res as low as 400 degrees C and was thermally converted to a hexagonal stru
cture by heat treatment above 800 degrees C, (C) 2000 Elsevier Science Ltd.
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