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A nanotube has a structure similar to a fullerene, but where a fullerene molecule is spherical, a nanotube is cylindrical, with one end typically being capped with half a fullerene molecule. Their name derives from their size; nanotubes are on the order of only a few nanometres wide (on the order of one ten-thousandth the width of a human hair), and their length can be millions of times greater than their width. There are two main types of nanotubes: single-walled nanotubes (SWNT) and multi-walled nanotubes (MWNT).

The structure of a SWNT can be conceptualized by wrapping a one-atom-thick layer of graphite (called graphene) into a seamless cylinder. The way the graphene sheet is wrapped is represented by a pair of indices (n,m) called the chiral vector. The integers n and m denote the number of unit vectors along two directions in the honeycomb lattice of graphene. This is often though of as representing the number of carbon atoms around the circumference of the tube, and the nuber of atoms down the tube axis. If m=0, the nanotubes are called "zigzag". If n=m, the nanotubes are called "armchair". Otherwise, they are called "chiral". Due to the symmetry and unique electronic structure of graphene, the structure of a nanotube strongly affects its electrical properties. For a given (n,m) nanotube, if 2n+m=3q (where q is an integer), then the nanotube is metallic, otherwise the nanotube is a semiconductor. Thus all armchair (n=m) nanotubes are metallic, and nanotubes (5,0), (6,4), (9,1), etc. are semiconducting. An alternative (equivalent) representation of this condition is if (n-m)/3=integer, then the SWNT is metallic. In theory, metallic nanotubes can have an electrical current density more than 1,000 times stronger than metals such as silver and copper. All nanotubes are expected to be very good thermal conductors along the tube, but good insulators laterally to the tube axis.

Nanotubes are composed entirely of sp² bondNotice For a full understanding of this article, it is important to read and understand the article on hybridization. An sp2 bond is any bond which involves an sp2 orbital. sp2 orbitals are the result of the hybridization of an s orbital with two p orbitas, similar to graphite. Stronger than the sp³ bonds found in diamondAlternate meanings: Diamond (disambiguation Diamond is one of the natural allotropes of carbon (the main allotrope being graphite; see also allotropes of carbon). The hardest of naturally occurring materials, diamonds cut into multi-faceted shapes are amo, this bonding structure provides them with their unique strength. Nanotubes naturally align themselves into "ropes" held together by Van der Waals forceIn chemistry, the term van der Waals force originally referred to all forms of intermolecular forces; however, in modern usage it tends to refer only to London forces: those forces which arise from induced rather than permanent dipoles. The forces are nam . Under high pressure, nanotubes can merge together, trading some sp² bonds for sp³ bonds, giving great possibility for producing strong, unlimited-length wires through high-pressure nanotube linking. [1]

While it has long been known that carbon fibres can be produced with a carbon arc, and patents were issued for the process, it was not until 19911991 like 2002, is a palindromic year. It also has the same calendar as 2002, including Easter on March 31. It is a common year starting on Tuesday. Events January January 2 Sharon Pratt Dixon is sworn in as mayor of Washington, DC becoming the first blac that Sumio IijimaSumio Iijima (born May 2, 1939) is a Japanese physicist, best known for discovering carbon nanotubes in 1991. Iijima graduated with a Bachelor of Engineering degree in 1963 from the University of Electro-Communications, Tokyo. He received a Master's degre, a researcher with the NECNEC Corporation is a multi-national information technologies company headquarterd in Minato -ku, Tokyo, Japan. They are an internet solutions business involved in the manufacture and sales of computers, communications equipment, electron devices and softw Laboratory in Tsukuba, Japan, observed that these fibres were hollow. This feature of nanotubes is of great interest to physicists because it permits experiments in one-dimensional quantum physics. Techniques have been developed to produce nanotubes in sizeable quantities, but their cost still prohibits any large scale use of them.

Fullerenes and carbon nanotubes are not necessarily products of high-tech laboratories, and are also formed in such mundane places as candle flames. However, these naturally occurring varieties are highly irregular in size and quality, and the high degree of uniformity necessary to meet the needs of research and industry is impossible in such an uncontrolled environment. There are several methods employed to make nanotubes, such as arc discharge , laser ablation , and chemical vapor deposition (CVD). In general, the CVD method has shown the most promise in being able to produce larger quantities of nanotube (compared to the other methods) at lower cost. This is usually done by reacting a carbon-containing gas (such as acetylene, ethylene, ethanol, etc. with a metal catalyst particle (usually cobalt, nickel, or iron) at temperatures above 600 °C.

Nanotubes can be opened and filled with materials such as biological molecules , raising the possibility of applications in biotechnology. They can be used to dissipate heat from tiny computer chips.

The strength and flexibility of carbon nanotubes makes them of potential use in controlling other nanoscale structures, which suggests they will have an important role in nanotechnology engineering. The highest tensile strength an individual SWNT has been tested to is 63 GPa [2]. In Earth's upper atmosphere, atomic oxygen erodes the carbon nanotubes, but other applications rarely need protection of the carbon nanotube surface. Though it is debatable if nanotube materials can ever be made with a tensile strength approaching that of individual tubes, composites may still yield incredible strengths potentially sufficient to allow the building of such things as space elevators, artificial muscles, ultrahigh-speed flywheels, and more. MIT is working on combat jackets utilizing carbon nanotubes for ultrastrong fibers and for monitoring its wearer's condition.

Carbon nanotubes additionally can also be used to produce nanowires of other chemicals, such as gold or zinc oxide. These nanowires in turn can be used to cast nanotubes of other chemicals, such as gallium nitride. These can have very different properties from CNTs - for example, gallium nitride nanotubes are hydrophilic, while CNTs are hydrophobic, giving them possible uses in organic chemistry that CNTs could not be used for.

One use for nanotubes that has already been developed is as extremely fine electron guns, which could be used as miniature cathode ray tubes in thin high-brightness low-energy low-weight displays. This type of display would consist of a group of many tiny CRTs, each providing the electrons to hit the phosphor of one pixel, instead of having one giant CRT whose electrons are aimed using electric and magnetic fields. These diplays are known as Field Emission Display s (FEDs) A nanotube formed by joining nanotubes of two different diameters end to end can act as a diode, suggesting the possibility of constructing electronic computer circuits entirely out of nanotubes. Nanotubes have been shown to be superconducting at low temperatures.