CONICAL, HELICALLY WOUND, GRAPHITE WHISKERS - A LIMITING MEMBER OF THE FULLERENES

Conically structured columnar graphite crystals have been studied by electron microscopy and electron diffraction and a formation mechanism is proposed explaining their shape and unusual diffraction effects consisting in periodically interrupted circular ring patterns. A growth mechanism is proposed whereby the initial graphite layer adopts a slitted dome shaped configuration by introducing a fivefold carbon ring in the sixfold carbon network. Successive sheets are rotated with respect to the previous one over a constant angle, thus realizing a helical cone around a "disclination" with a fivefold carbon ring core. This model explains the morphological features and the particular diffraction effects observed on these reproducibly prepared columnar graphite crystals. The growth mechanism has a direct relationship to the formation of the fullerene "bucky ball" molecules.