New Horizons in Carbon Chemistry and Materials Science
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MRS BULLETIN/NOVEMBER 1994
of cyanopolyynes that had been synthesized in the laboratory.2 Much has been written about the discovery of C 6o and many aspects of the discovery have been probed—even books on the subject are scheduled to appear.5 This new allotrope of carbon, however, also has a prehistory. In 1970 the first suggestion of the existence of Cm was published by Osawa6 and the following year a more detailed discussion of the molecule was published in a book with Yoshida.7 Bochvar and Gal'pern then published the first Huckel calculation,8 and in 1980 Davidson9 published a group theoretical treatment that reduced the problem of calculating the Huckel energy levels so that they could be done on a hand calculator. Concurrently, Chapman was developing synthetic strate-
gies with the aim of producing C m directly in the laboratory.10 About the same time as the experimental discovery, Haymet also published calculations.11 A conjecture predating all these studies was published by Jones1213 in 1966 under the pseudonym of Daedalus (in the New Scientist). Jones proposed that hollow-cage molecules might be synthesized by modifying the hightemperature graphite production process in such a way that pentagonal defects (disclinations) might be introduced into the graphene network. The fact that the molecule existed in the minds of some prescient scientists prior to its discovery in 1985 is interesting because it bears on the real surprise of the C ® story. The real surprise is not that Cm exists— after all Osawa had noted in 1970 that it should be stable if it could be formed—but that the molecule forms spontaneously in a chaotic carbon plasma. At the time of the molecule's discovery it was guessed that perhaps one part in 106 of the available carbon might have found its way into C 6o molecules. When, in 1990, Kratschmer, Lamb, Fostiropoulos, and Huffman14 made the breakthrough which led to the production of C 6o in high yields (about 10%), we were forced to completely reappraise our ideas of the structure of graphite in particular and of carbon in general. How, one might ask, could it be that conventional wisdom had caused us to accept that the spontaneous creation of closed cages would be a rare event when, in fact, under certain circumstances closure appears to be essentially quantitative. Since the Kratschmer et al. breakthrough,14 our knowledge has advanced to a staggering degree as new fields of carbon chemistry, physics, and materials science1516 are being planted and are blossoming rapidly and excitingly.
Figure 1. Schematic diagrams for carbon black particles (taken from Heydenreich, Hess, and Ban17). The diagrams depict a hypothetical model for the infrastructure of a spheroidal graphitic particle, (a) Schematic drawing of the assumed structure of a graphite crystallite (the c spacing is 3.5-3.7 A, the c and a0dimensions are 11-15 and 15-20 A, respectively, and there is rotational disorder about the c axis), (b) A perspective schematic drawing of the way crystallites (a) were assumed to aggregate, as a way to
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