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carbon nanotube
A cylindrical structure made only from carbon atoms that are about 1 nanometer (one billionth of a meter) in diameter and 1-100 microns in length. In a graphite sheet, carbon atoms arrange themselves in a two-dimensional hexagonal lattice. Carbon nanotubes can be thought of as a strip of graphite sheet that is rolled up to form a cylinder. There are many different ways to cut up a piece of graphite and roll it up to form a tube. The tubes can have different diameters and different chiralities. The chirality is the twist of the rows of atoms along the length of the tube. Sometimes the atom rows are parallel to the axis of the tube and sometimes the rows form a helix that winds along the tube. When one or more tubes grow inside another carbon nanotube, it is called a multiwalled nanotube. Carbon nanotubes are very strong – about 5 times as strong as steel for the same wieght. The electrical properties of carbon nanotubes depend on their diameter and their chirality. Some tubes are metallic, others are semiconductors.
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• MATERIALS AND MATERIALS SCIENCE
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