Fullerenes cylindrical

The field of fullerene chemistry expanded in an unexpected direction in 1991 when Sumio lijima of the NEC Fundamental Research Laboratories in Japan discovered fibrous carbon clusters in one of his fullerene preparations This led within a short time to substances of the type portrayed in Figure 11 7 called single-walled nanotubes The best way to think about this material IS as a stretched fullerene Take a molecule of Ceo cut it in half and place a cylindrical tube of fused six membered carbon rings between the two halves... 

In the theoretical carbon nanotube literature, the focus is on single-wall tubules, cylindrical in shape with caps at each end, such that the two caps can be joined together to form a fullerene. The cylindrical portions of the tubules consist of a single graphene sheet that is shaped to form the cylinder. With the recent discovery of methods to prepare single-w alled nanotubes[4,5), it is now possible to test the predictions of the theoretical calculations. 

The final section of the volume contains three complementary review articles on carbon nanoparticles. The first by Y. Saito reviews the state of knowledge about carbon cages encapsulating metal and carbide phases. The structure of onion-like graphite particles, the spherical analog of the cylindrical carbon nanotubes, is reviewed by D. Ugarte, the dominant researcher in this area. The volume concludes with a review of metal-coated fullerenes by T. P. Martin and co-workers, who pioneered studies on this topic. 

The synthesis of molecular carbon structures in the form of C q and other fullerenes stimulated an intense interest in mesoscopic carbon structures. In this respect, the discovery of carbon nanotubes (CNTs) [1] in the deposit of an arc discharge was a major break through. In the early days, many theoretical efforts have focused on the electronic properties of these novel quasi-one-dimensional structures [2-5]. Like graphite, these mesoscopic systems are essentially sp2 bonded. However, the curvature and the cylindrical symmetry cause important modifications compared with planar graphite. 

To reach the fantastic heights required by a space elevator, new materials are essential. Skyscrapers of today are usually composed of a steel framework, but steel is too heavy to use for the space elevator—the tower must be so high and needs so much material that it could not possibly support its own weight if it was made of steel. One possibility for a new material is related to the fullerenes discussed in the text. Carbon nanotubes are cylindrical fullerenes composed of sheets of graphites rolled into tiny cylinders with a diameter of roughly 0.00000004 inches (0.0000001 cm)—a nanometer. The structure and bonds of carbon nanotubes could potentially be used to create a material with about 50-100 times the strength of steel. A slender ribbon of carbon nanotube could be the key to bringing the dream of a space elevator into reality. 

Five years after the discovery of fullerenes, Iijima reported in 19911 a novel form of organized carbon which consists of hollow cylindrical structures, a few nanometers in diameter and some micrometers long. Although hollow carbon nanofibers had been prepared for several decades, their walls had never been resolved by High-Resolution Transmission Electron Microscopy (HRTEM). These HRTEM images allowed Iijima to conclude that the walls of the so-called multi-walled carbon nanotubes (MWCNTs) are made up of several concentric cylinders, each being formed by a graphene sheet rolled... 

The discoveries of fullerenes and carbon nanotubes have contributed to enriching the variety in the world of carbons, where the new comers have opened a new realm bridging between traditional carbon and nanomaterials. Ball-shaped fullerenes and cylindrical-shaped carbon nanotubes form... 

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