Calculo tensorial

Carbon nanotubes and their application in the construction industry

Makar, J.M.; Beaudoin, J.J.

NRCC-46618

A version of this document is published in / Une version de ce document se trouve dans : 1st International Symposium on Nanotechnology in Construction, Paisley, Scotland, June 22-25, 2003, pp. 331-341

http://irc.nrc-cnrc.gc.ca/ircpubs

Proceedings of 1st InternationalSymposium on Nanotechnology in Construction June 23-25, 2003, Paisley, Scotland

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CARBON NANOTUBES AND THEIR APPLICATION IN THE CONSTRUCTION INDUSTRY

J.M. Makar and J.J. Beaudoin Institute for Research in Construction, National Research Council Canada 1200 Montreal Road, Ottawa, Ontario K1A 0R6 Canada

1 INTRODUCTION Carbon nanotubes (CNT) are the subject of one of the most important areas ofresearch in nanotechnology. Their unique properties and potential for valuable commercial applications ranging from electronics to chemical process control have meant that an enormous amount of effort has been undertaken on the investigation of nanotubes in the last five years. Despite this high level of research activity, very little attention has been paid to potential applications in theconstruction industry. This paper seeks to bridge the gap between CNT and construction materials research. It describes carbon nanotubes, including their structure, how they are produced and their properties. Potential applications, both in general and specifically for the construction industry, are presented. The paper concludes by giving the results of initial research at the National ResearchCouncil's Institute for Research in Construction on carbon nanotube/cement composites. 2 TUBE STRUCTURE Carbon nanotubes can be visualized as a modified form of graphite. Graphite is formed from many layers of carbon atoms that are bonded in a hexagonal pattern in flat sheets, with weak bonds between the sheets and strong bonds within them. A CNT can be thought of as a sheet or sheets of graphite thathave been rolled up into a tube structure. CNT can be single walled nanotubes (SWNT), as if a single sheet had been rolled up, or multiwalled (MWNT), similar in appearance to a number of sheets rolled together. Figure 1 shows a schematic of a single walled nanotube. CNT can be produced with different types of chirality (the orientation of the hexagons formed by the carbon atoms with respect to thetube axis). Two tubes with the same diameter may therefore have different structures despite being formed solely of carbon atoms. CNT are described by their chiral vector as (m,n) tubes, where m and n are integer numbers (Figure 2). A (m,0) tube {e.g. (10,0)} is described as an armchair tube since the hexagons in the tube run straight along its length in a manner similar to the arms of an armchair,while a tube with m=n {e.g. (5,5)} is called a zig-zag tube, since the hexagons zig-zag down the length of the tube. The nanotube shown in Figure 1 is also a zig-zag tube. Tubes may also have chirality between these two extremes, such as the (5,4)

Proceedings of 1st International Symposium on Nanotechnology in Construction June 23-25, 2003, Paisley, Scotland

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tube that would be formedby rolling up a tube with the vector shown at the bottom of Figure 2.

Figure 1

Schematic of a Single Walled Nanotube

Figure 2

Nanotube Chiral Vectors and Top Views of Schematic Tubes (The black dots are carbon atoms)

3 SYNTHESIS Three different approaches have been taken to produce CNT.1 The first method to be discovered uses an electric arc-discharge, where a high voltage electricalcurrent is passed through the air (or an inert or reactive gas) into a carbon electrode. The other methods are

Proceedings of 1st International Symposium on Nanotechnology in Construction June 23-25, 2003, Paisley, Scotland

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laser ablation, using a high intensity laser beam directed at a carbon target, and chemical vapour deposition, which uses a carbon based gas such as methane at...