These electrical properties, however, do not depend on whether the hexagonal lattice is rolled from its back to front or from its front to back and hence are the same for the tube and its mirror image. Ī special group of achiral single-wall carbon nanotubes are metallic, but all the rest are either small or moderate band gap semiconductors. This construction also allows single-wall carbon nanotubes to be labeled by a pair of integers. In addition, most are chiral, meaning the tube and its mirror image cannot be superimposed. Rolling up a hexagonal lattice along different directions to form different infinitely long single-wall carbon nanotubes shows that all of these tubes not only have helical but also translational symmetry along the tube axis and many also have nontrivial rotational symmetry about this axis. These properties are expected to be valuable in many areas of technology, such as electronics, optics, composite materials (replacing or complementing carbon fibers), nanotechnology, and other applications of materials science. In addition, they can be chemically modified. They also have exceptional tensile strength and thermal conductivity because of their nanostructure and strength of the bonds between carbon atoms. Thus, for many purposes, end effects are neglected and the length of carbon nanotubes is assumed infinite.Ĭarbon nanotubes can exhibit remarkable electrical conductivity, while others are semiconductors. The length of a carbon nanotube produced by common production methods is often not reported, but is typically much larger than its diameter. Such tubes were discovered in 1952 by Radushkevich and Lukyanovich. Multi-wall carbon nanotubes are also sometimes used to refer to double- and triple-wall carbon nanotubes.Ĭarbon nanotubes can also refer to tubes with an undetermined carbon-wall structure and diameters less than 100 nanometres. If not identical, these tubes are very similar to Oberlin, Endo, and Koyama's long straight and parallel carbon layers cylindrically arranged around a hollow tube. Multi-wall carbon nanotubes ( MWCNTs) consisting of nested single-wall carbon nanotubes weakly bound together by van der Waals interactions in a tree ring-like structure. In this construction, periodic boundary conditions are imposed over the length of this roll-up vector to yield a helical lattice of seamlessly bonded carbon atoms on the cylinder surface. Although not made this way, single-wall carbon nanotubes can be idealized as cutouts from a two-dimensional hexagonal lattice of carbon atoms rolled up along one of the Bravais lattice vectors of the hexagonal lattice to form a hollow cylinder. Single-wall carbon nanotubes ( SWCNTs) are one of the allotropes of carbon, intermediate between fullerene cages and flat graphene, with diameters in the range of a nanometre. A carbon nanotube ( CNT) is a tube made of carbon with diameters typically measured in nanometers.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. Archives
December 2022
Categories |