![]() ![]() One area where their size, structure and conductive properties all come into play is electronics, says Robertson. By controlling the temperature of the deposition process, different diameters can be achieved, while other techniques make it possible to create multi-walled nanotubes, that is nanotubes within nanotubes. In fact, nanotubes can come in a variety of shapes and sizes. This may sound quite short, but with a width of just one nanometre, that represents a length-to-diameter ratio of more than 10m to one. Using this technique it has been possible to grow nanotubes in excess of 10 centimetres long. ![]() As the gas reacts with the catalyst, carbon deposits start to build up, forming increasingly long cylindrical cage-like structures. This involves immersing a metal catalyst, such as gold or nickel cobalt, in a high-temperature vapour made up of a carbon-rich gas, such as acetylene mixed in with a processing gas such as ammonia. "We grow them through chemical vapour deposition," says John Robertson, a professor of solid-state electronics and nanoscale science at the University of Cambridge. So instead they need to be synthesized or, more often than not, grown. However, because in nature they occur in such a wide range of sizes and forms, nanotubes created naturally are of little practical use. That is because they can be found in nature, formed in ordinary flames and present within soot. Others have since argued that multi-walled nanotubes had actually been observed some 40 years earlier by scientists in Russia, but due to it being published in Russian and because of restricted access to Soviet journals by western scientists, this went largely unnoticed.Įither way, the fact is carbon nanotubes have been around long before the advent of the transmission electron microscope allowed us to set eyes on them. This means that both heat and electrons are able to pass through them with the greatest of ease.Ĭarbon nanotubes first captured the world's attention in 1991 when Sumio Iijima, a researcher with NEC, published a paper in Nature describing the synthesis of "needle-like tubes" of carbon. And the lattice-like arrangement of carbon atoms is not only extremely strong, but it gives them a high thermal and electrical conductivity. Their shape – picture a sheet of carbon just a single atom thick, which has been rolled up into a very long cylinder – gives them an extremely high surface area which is useful in a range of applications, such as coatings or batteries. With potential uses in everything from tennis racquets and bulletproof vests to electronic components and energy storage devices, if there's one material that epitomises the scope of nanotechnology it has to be the carbon nanotube. And with equally impressive electrical and thermal properties these hollow tubes of carbon, just one atom thick, are proving to be one of the most versatile materials ever discovered. With a strength-to-weight ratio 117 times greater than steel, carbon nanotubes are the strongest and stiffest material known to man. ![]()
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