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Applied materials Victoria Riabicheva Olexandra Tupalo English supervisor- Ekaterina Kuznetsova Science supervisor- Oleg Uzlov THE DISCOVERY, STRUCTURE, PROPERTIES AND APPLICATION OF CARBON NANOTUBES ВІДКРИТТЯ, СТРУКТУРА, ВЛАСТИВОСТІ ТА ЗАСТОСУВАННЯ ВУГЛЕЦЕВИХ НАНОТРУБОК У даній роботі розглядаються визначення, структура, синтез та застосування вуглецевих нанотрубок, як важливої частини сучасного ринку виготовлення матеріалів. In the following work the definition, structure, synthesis and application of carbon nanotubes, being an important part of the modern material producing market, are considered. Keywords: carbon nanotubes, fullerene, graphene, multi-walled, superhard phasenanotubes. Carbon nanotubes are molecular-scale tubes of graphitic carbon with outstanding properties. They are among the stiffest and strongest fibres known, and have remarkable electronic properties and many other unique characteristics. For these reasons they have attracted huge academic and industrial interest. History The discovery that carbon could form stable, ordered structures other than graphite and diamond stimulated researchers worldwide to search for other new forms of carbon. It was shown in 1990 that C60 could be produced in a simple arc-evaporation apparatus readily available in all laboratories. It was using such an evaporator that the Japanese scientist Sumio Iijima discovered fullerene-related carbon nanotubes in 1991. Structure The bonding in carbon nanotubes is sp², with each atom joined to three neighbours, as in graphite. The tubes can therefore be considered as rolled-up graphene sheets (graphene is an individual graphite layer). There are three distinct ways in which a graphene sheet can be rolled into a tube. The first two of these, known as “armchair” and “zig-zag” have a high degree of symmetry. The terms "armchair" and "zig-zag" refer to the arrangement of hexagons around the circumference. The third class of tube is known as chiral, meaning that it can exist in two mirror-related forms.[1] Synthesis The arc-evaporation method, which produces the best quality nanotubes, involves passing a current of about 50 amps between two graphite electrodes in an atmosphere of helium. This causes the graphite to vaporise, some of it condensing on the walls of the reaction vessel and some of it on the cathode. It is the deposit on the cathode which contains the carbon nanotubes. Single-walled nanotubes are produced when Co and Ni or some other metal is added to the anode. It has been known since the 1950s, if not earlier, that carbon nanotubes can also be made by passing a carbon-containing gas, such as a hydrocarbon, over a catalyst. The catalyst consists of nano-sized particles of metal, usually Fe, Co or Ni. These particles catalyse the breakdown of the gaseous molecules into carbon, and a tube then begins to grow with a metal particle at the tip. The big advantage of catalytic synthesis over arcevaporation is that it can be scaled up for volume production. The third important method for making carbon nanotubes involves using a powerful laser to vaporise a metal-graphite target. This can be used to produce single-walled tubes with high yield. Properties The strength of the material results from the covalent sp² bonds formed between the individual carbon atoms. In 2000, a multi-walled carbon nanotube was tested to have a tensile strength of 63 gigapascals (GPa) Standard single walled carbon nanotubes can withstand a pressure up to 24GPa without deformation. Maximum pressures measured using current experimental techniques are around 55GPa. Because of 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 n = m, the nanotube is metallic; if n − m is a multiple of 3, then the nanotube is semiconducting with a very small band gap, otherwise the nanotube is a moderate semiconductor. [3] Potential uses include: Textiles - can make waterproof and/or tear-resistant fabrics Concrete - CNTs in concrete increase its tensile strength, and halt crack propagation. Polyethylene - Adding CNT to polyethylene can increase the polymer's elastic modulus by 30%. Sports equipment - Stronger and lighter tennis rackets, bicycle parts, etc. Space elevator - CNTs are under investigation as possible components of the tether up which a space elevator can climb. Synthetic muscles - CNTs are ideal for synthetic muscle. Bridges - CNTs may be able to replace steel in suspension and other bridges. Fire protection - Thin layers of buckypaper can significantly improve fire resistance due to the efficient reflection of heat by the dense, compact layer of CNT or carbon fibers. Air pollution filter - CNT membranes can filter carbon dioxide from power plant emissions. Water filter - CNT can purportedly reduce desalination costs by 75%. [2] Defects As with any material, the existence of a crystallographic defect affects the material properties. Defects can occur in the form of atomic vacancies. High levels of such defects can lower the tensile strength by up to 85%. Another form of carbon nanotube defect is the Stone Wales defect, which creates a pentagon and heptagon pair by rearrangement of the bonds. Because of the very small structure of CNTs, the tensile strength of the tube is dependent on its weakest segment in a similar manner to a chain, where the strength of the weakest link becomes the maximum strength of the chain. Determining the toxicity of carbon nanotubes has been one of the most pressing questions in nanotechnology. Available data clearly show that, under some conditions, nanotubes can cross membrane barriers, which suggests that if raw materials reach the organs they can induce harmful effects such as inflammatory and fibro tic reactions. REFERENCES: 1. ЗОЛОТУХИН И.В. «УГЛЕРОДНЫЕ НАНОТРУБКИ». ФИЗИКА. 1999 2. HTTP://NANOTRUBKI.NAROD.RU 3. HTTP://EN.WIKIPEDIA.ORG