1 Introduction

Fullerenes and carbon nanotubes are unique, respectively, in the larger family of carbon-based materials as interrelated prototypes for zero-dimensional quantum dots and one-dimensional quantum wires. The fullerene molecule is the fundamental building block of the crystalline phase, and through doping and chemical reactions, forms the basis of a large family of materials, many having especially interesting properties. Likewise, carbon nanotubes, which are capped at each end by half of a fullerene, have aroused great interest in the research community because of their exotic electrical and mechanical properties. The unique properties of fullerenes and carbon nanotubes described in this chapter are also expected to be of interest for practical applications.

In 1985, the existence of a stable molecule or cluster with 60 carbon atoms (designated as Ceo) was established experimentally by mass spectrographic analysis [1], and it was conjectured that the C6o cluster was a molecule with icosahedral symmetry. The name of "fullerene" was given to the family of closed cage carbon molecules by Kroto and Smalley [1] because of their resemblance to the geodesic domes designed and built by R. Buckminster Fuller [2]. The name "buckminsterfullerene" or simply "buckyball" was given specifically to the C6o molecule. In the early gas phase work, the fullerene molecules were produced by the laser vaporization of carbon from a graphite target in a pulsed jet of helium [1, 3],

In the fall of 1990, a new crystalline form of carbon, based on Ceo, was synthesized for the first time by Kratschmer, Huffman and co-workers [4], Their discovery of a simple method using a carbon arc for preparing gram quantities of Ceo and C70 represented a major advance to the field because previous synthesis techniques could only supply trace quantities [1, 5], The availability of large quantities of C6o and C70 fullerenes provided a great stimulus to this research field. It was soon found [6, 7] that the intercalation of alkali metals into solid Ceo to a stoichiometry M3C60 (where M = K, Rb) could greatly modify the electronic properties of the host fullerene lattice, yielding not only metallic conduction, but also relatively high transition temperature (18 <TC< 40K) superconductors [8], The discovery of relatively high temperature superconductivity [9, 10] in these compounds (see §2.6.2) further spurred research activity in this field of C6o-related materials.

Regarding a historical perspective on carbon nanotubes, very small diameter (less than 10 nm) carbon filaments were observed in the 1970's through synthesis of vapor grown carbon fibers prepared by the decomposition of benzene at 1100°C in the presence of Fe catalyst particles of ~10 nm diameter [11, 12], However, no detailed systematic studies of such very thin filaments were reported in these early years, and it was not until lijima's observation of carbon nanotubes by high resolution transmission electron microscopy (HRTEM) that the carbon nanotube field was seriously launched. A direct stimulus to the systematic study of carbon filaments of very small diameters came from the discovery of fullerenes by Kroto, Smalley, and coworkers [1]. The realization that the terminations of the carbon nanotubes were fullerene-like caps or hemispheres explained why the smallest diameter carbon nanotube observed would be the same as the diameter of the Ceo molecule, though theoretical predictions suggest that nanotubes arc more stable than fullerenes of the same radius [13]. The Iijima observation heralded the entry of many scientists into the field of carbon nanotubes, stimulated especially by the un usual quantum effects predicted for their electronic properties. Independently, Russian workers also reported discovery of carbon nanotubes and nanotube bundles, but generally having much smaller aspect (length to diameter) ratios [14, 15].

This article reviews the structure and properties of fullcrenes, fullerene-based materials and carbon nanotubes in the context of carbon materials for advanced technologies.

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