Peter J. F. Harris

Carbon Nanotubes and Related Structures: New Materials for the Twenty-first Century

1. Introduction 2. Synthesis 3. Structure 4. The physics of nanotubes 5. Nano-capsules and nano-test-tubes 6. The ultimate carbon fibre? 7. Curved crystals, inorganic fullerenes and nanorods 8. Carbon onions and spheroidal carbon 9. Future directions Index.

Carbon nanotube composites

Abstract Carbon nanotubes are molecular-scale tubes of graphitic carbon with outstanding properties. They are among the stiffest and strongest fibres known, with Youngs moduli as high as 1 TPa and tensile strengths of up to 63 GPa. They also have remarkable electronic properties and can be metallic or semiconducting depending on their structure and diameter. There is currently great interest in exploiting these properties by incorporating carbon nanotubes into some form of matrix. A wide range of polymer matrices have been employed, and there is growing interest in nanotube/ceramic and nanotube/metal composites. This review outlines the properties of carbon nanotubes and describes the preparation and properties of carbon nanotube composites. The prospects for commercial exploitation of these materials are discussed.

A self-repairing, supramolecular polymer system: healability as a consequence of donor–acceptor π–π stacking interactions

A novel supramolecular polymer system, in which the terminal pyrenyl groups of a polyamide intercalate into the chain-folds of a polyimide via electronically-complementary pi-pi stacking, shows both enhanced mechanical properties relative to those of its individual components and facile healing characteristics as a result of the thermoreversibility of non-covalent interactions.

Fullerene-related structure of commercial glassy carbons

Glassy carbon is a technologically important material widely used in products such as electrodes and high-temperature crucibles. However, the properties which make glassy carbon so valuable in these applications are poorly understood, since its detailed atomic structure is not known. A model for the structure of glassy carbon put forward many years ago has gained wide acceptance, but appears to suffer from serious shortcomings. In particular, it fails to account for the chemical inertness of the carbon, and for its high proportion of closed porosity. Here I show, using high-resolution transmission electron microscopy, that glassy carbons obtained from commercial suppliers contain a high proportion of fullerene-related structures. On the basis of these observations, models are put forward for the structures of ‘low-temperature’ and ‘high-temperature’ glassy carbons which incorporate non-six-membered rings.Glassy carbon is a technologically important material widely used in products such as electrodes and high-temperature crucibles. However, the properties which make glassy carbon so valuable in these applications are poorly understood, since its detailed atomic structure is not known. A model for the structure of glassy carbon put forward many years ago has gained wide acceptance, but appears to suffer from serious shortcomings. In particular, it fails to account for the chemical inertness of the carbon, and for its high proportion of closed porosity. Here I show, using high-resolution transmission electron microscopy, that glassy carbons obtained from commercial suppliers contain a high proportion of fullerenerelated structures. On the basis of these observations, models are put forward for the structures of ‘low-temperature’ and ‘high-temperature’ glassy carbons which incorporate non-six-membered rings.

New Perspectives on the Structure of Graphitic Carbons

Graphitic forms of carbon are important in a wide variety of applications, ranging from pollution control to composite materials, yet the structure of these carbons at the molecular level is poorly understood. The discovery of fullerenes and fullerene-related structures such as carbon nanotubes has given a new perspective on the structure of solid carbon. This review aims to show how the new knowledge gained as a result of research on fullerene-related carbons can be applied to well-known forms of carbon such as microporous carbon, glassy carbon, carbon fibers, and carbon black.

High-resolution electron microscopy studies of non-graphitizing carbons

Abstract High-resolution electron microscopy is used to study the structure of two typical non-graphitizing carbons before and after heat treatment at temperatures in the range 2100–2600°C. It is found that these heat treatments can result in the formation of closed carbon nanoparticles, which are apparently fullerene-like in structure. This suggests that fullerene-like elements were present in the original carbons and leads us to propose a new model for the structure of non-graphitizing carbons.

Imaging the atomic structure of activated carbon

The precise atomic structure of activated carbon is unknown, despite its huge commercial importance in the purification of air and water. Diffraction methods have been extensively applied to the study of microporous carbons, but cannot provide an unequivocal identification of their structure. Here we show that the structure of a commercial activated carbon can be imaged directly using aberration-corrected transmission electron microscopy. Images are presented both of the as-produced carbon and of the carbon following heat treatment at 2000 °C. In the 2000 °C carbon clear evidence is found for the presence of pentagonal rings, suggesting that the carbons have a fullerene-related structure. Such a structure would help to explain the properties of activated carbon, and would also have important implications for the modelling of adsorption on microporous carbons.

A simple technique for the synthesis of filled carbon nanoparticles

Abstract A new method has been developed for the production of filled carbon nanoparticles, which has many advantages over the usual arc-evaporation technique. The method involves high-temperature heat treatment of a microporous carbon which has been impregnated with a compound of the material to be encapsulated. In this study, this technique is used to synthesise nanoparticles filled with molybdenum, uranium and cobalt.

High-resolution electron microscopy of a microporous carbon

The structure of a microporous carbon prepared by the carbonization of sucrose was examined using high-resolution electron microscopy. It was found to be disordered and isotropic and primarily made up of tightly curved individual carbon layers, enclosing pores typically about 1nm in size. Completely closed carbon particles were also present. These observations suggest that the carbon may have a fullerene-related structure, in which pentagons and heptagons are distributed randomly throughout a hexagonal network, producing continuous curvature.

Self-Assembly of Peptide Nanotubes in an Organic Solvent

The self-assembly of a modified fragment of the amyloid beta peptide, based on sequence Abeta(16-20), KLVFF, extended to give AAKLVFF is studied in methanol. Self-assembly into peptide nanotubes is observed, as confirmed by electron microscopy and small-angle X-ray scattering. The secondary structure of the peptide is probed by FTIR and circular dichroism, and UV/visible spectroscopy provides evidence for the important role of aromatic interactions between phenylalanine residues in driving beta-sheet self-assembly. The beta-sheets wrap helically to form the nanotubes, the nanotube wall comprising four wrapped beta-sheets. At higher concentration, the peptide nanotubes form a nematic phase that exhibits spontaneous flow alignment as observed by small-angle neutron scattering.