1. By Vibin Varghese 10CHE6012 SJC(PG)

2. Sumio Iijima( Iijima Sumio , born May 2, 1939) is aJapanese physicist ,often cited as the discoverer ofcarbon nanotubes . 3. Carbon nanotubes( CNTs ; also known asbuckytubes ) areallotropes of carbonwith a cylindrical nanostructure. Nanotubes are members of thefullerenestructural family, which also includes the sphericalbuckyballs .The ends of a nanotube might be capped with a hemisphere of the buckyball structure.Their name is derived from their size, since the diameter of a nanotube is on the order of a few nanometers (approximately 1/50,000th of the width of a human hair), while they can be up to 18 centimeters in length (as of 2010) 4. The nature of the bonding of a nanotube is described by appliedquantum chemistry .Thechemical bondingof nanotubes is composed entirely ofsp 2bonds , similar to those ofgraphite .This bonding structure, which is stronger than thesp 3bondsfound indiamonds , provides the molecules with their unique strength.Nanotubes naturally align themselves into "ropes" held together byVan der Waals forces 5. Types of carbon nanotubesandrelated structures Structure Nanotubes are mainly categorized as: single-walled nanotubes(SWNTs)And multi-walled nanotubes(MWNTs). 6.

A single-wall carbon nanotube can be imagined asgraphene sheetrolled at a certain "chiral" angle with respect to a plane perpendicular to the tube's long axis. (graphene is an individual graphite layer).

Consequently, SWNT can be defined by its diameter and chiral angle.

The chiral angle can range from 0 to 30 degrees.

Let us first understand the basic structure of a single walled CNT 7. More conveniently, a pair of indices ( n , m ) is used .The indices refer to equally longunit vectorsat 60 angles to each other across a single 6-membercarbon ring .Taking the origin as carbon number 1, thea 1unit vector may be considered as the line drawn from carbon 1 to carbon 3, and thea 2unit vector is then the line drawn from carbon 1 to carbon 5 8. There are three distinct ways in which a graphene sheet can be rolled into a tube, as shown below: (n,m)=(5,5) "armchair". (n,m)=9,0) "zigzag" (n,m)=(10,5) chiral 9. To produce a nanotube with the indices say,(6,3) the sheet is rolled up so that the atom labelled (0,0)is superimposed on the one labelled (6,3) 10. Tubes havingn = m(chiral angle = 0) are called "armchair". Those withm =0 (chiral angle = 30) "zigzag". When n and m are any two different positive integral numbers they are called chiral"armchair". "zigzag". chiral 11. 12. The terms "armchair" and "zig-zag" refer to the arrangement of hexagons around the circumference. Chiral means that it can exist in two mirror-related forms. The diameter of a nanotube can be calculated from its (n,m) indices as follows wherea= 0.246 nm. 13.

Most single-walled nanotubes (SWNT) have a diameter of close to 1nanometer, with a tube length that can be many millions of times longer.

The way the graphene sheet is wrapped is represented by a pair of indices ( n , m )

called the chiral vector. The integersnandmdenote the number of unitvectors

along two directions in the honeycombcrystal latticeof graphene.

Ifm= 0, the nanotubes are called "zigzag".

Ifn=m , the nanotubes are called "armchair". Otherwise, they are called "chiral".

14.

Single-walled nanotubes are an important variety of

carbon nanotube

because they exhibit electric properties that are not shared by

the multi-walled carbon nanotube (MWNT) variants.

15. 16. Multi-walled nanotubes (MWNT) Multi-walled nanotubes (MWNT) consist of multiple rolled layers (concentric tubes) of graphite. There are two models which can be used to describe the structures of multi-walled nanotubes 17. There are two types of MWNTs.They are: 1.Russian Dollmodeland2.Parchment model 18. In theRussian Dollmodel, sheets of graphite are arranged in concentric cylinders In theParchmentmodel, a single sheet of graphite is rolled in around itself, resembling a scroll of parchment or a rolled newspaper. Theinterlayer distance - approximately3.4 . 19. The special place ofdouble-walled carbon nanotubes (DWNT) functionalization . In the case of SWNT, covalent functionalization will break some C=Cdouble bonds ,leaving "holes"in the structure on the nanotube and thusmodifying both its mechanical and electrical properties .In the case of DWNT, only the outer wall is modified. 20. A nanotorus is theoretically described as carbon nanotube bent into atorus(doughnut shape).nanotorus High magnetic moments 21. Nanobud In this new material,fullerene-like "buds"are covalently bonded to the outer sidewalls of the underlying carbon nanotube.They have been found to be exceptionallygoodfield emitters . 22. Extreme CNTs longestcarbon nanotubes (18.5cm long) . shortestcarbon nanotubeis the organic compoundcycloparaphenylene Cycloparaphenylene 23. Thethinnest carbon nanotube is armchair (2,2) CNT with a diameter of 3 Thethinnest freestanding single-walled carbon nanotube is about 4.3 in diameter 24. Strength Carbon nanotubes are thestrongest and stiffest materialsyet discovered in terms oftensile strengthandelastic modulusrespectively. covalent sp bonds 63 gigapascals (GPa) .Properties 25. Hardness Diamondis considered to be the hardest material.One study succeeded in the synthesis of a super-hard material by compressing SWNTs to above 24 GPa atroom temperature .Thebulk modulusof compressed SWNTs was462546 GPa , surpassing the value of 420 GPa for diamond 26. Kinetic Multi-walled nanotubes , - perfect linear or rotational bearing Already this property has been utilized to create theworld's smallest rotationalmotor 27. Thermal All nanotubes are expected to be very goodthermal conductorsalong the tube, but good insulators laterally to the tube axis.thermal conductivityalong its axis of about3500 Wm 1 K 1 compare this to copper,which transmits385 Wm 1 K 1 28. Toxicity Unfortunately research has only just begun and the data are still fragmentary andsubject to criticism .CNTs can enter human cells and accumulate in thecytoplasm ,causing cell death . Results ofrodent studiesshows that it can causeinflammation ,epithelioid granulomas(microscopic nodules),fibrosis , and biochemical/toxicological changes in the lungs For those involving chronic exposure, carbon nanotubescan pose a serious risk to human health 29. Techniques have been developed to produce nanotubes in sizeable quantities, including arc discharge ,laser ablation , andchemical vapor deposition(CVD) Synthesis 30. Arc dischargeNanotubes were observed in 1991 in the carbon soot of graphiteelectrodesduring an arc discharge During this process, the carbon contained in the negative electrode sublimates because of the high discharge temperatures. Because nanotubes were initially discovered using this technique, it has been the most widely-used method of nanotube synthesis. The yield for this method is up to 30 percent by weight and it produces both single- and multi-walled nanotubes with lengths of up to 50 micrometers with few structural defects 31. Laser ablation In the laser ablation process, apulsed laservaporizes a graphite target in a high-temperature reactor while aninert gasis bled into the chamber. Nanotubes develop on the cooler surfaces of the reactor as the vaporized carbon condenses.A water-cooled surface may be included in the system to collect the nanotubes. The laser ablation method yields around 70% and produces primarily single-walled carbon nanotubes. 32. Chemical vapor deposition (CVD) During CVD, a substrate is prepared with a layer of metal catalyst particles, most commonly nickel, cobalt,iron , or a combination The diameters of the nanotubes that are to be grown are related to the size of the metal particles.The substrate is heated to approximately 700C.To initiate the growth of nanotubes, two gases are bled into the reactor: a process gas (such asammonia ,nitrogenorhydrogen ) and a carbon-containing gas (such asacetylene ,ethylene ,ethanolormethane ). Nanotubes grow at the sites of the metal catalyst; the carbon-containing gas is broken apart at the surface of the catalyst particle, and the carbon is transported to the edges of the particle, where it forms the nanotubes. 33. Nanotubes being grown bychemical vapor deposition 34. Natural, incidental, and controlledflame environments

Fullerenesand carbon nanotubes ---ordinaryflames , produced by burning methane, ethylene, and benzene,

found insoot

However, these naturally occurring varieties can be highly irregular in size and quality because the environment in which they are produced is often highly uncontrolled

35. Potential applications Structural clothes : combat jackets concrete : polyethylene : sports equipment : 36. synthetic muscles : hightensile strength fibers : bridges : ultrahigh-speedflywheels : fire protection: solar cells : superconductor transistor : 37. loudspeaker : replacingpiezoelectricspeakers ingreeting cards Electroacoustic 38. air pollution filter biotech container :hydrogen storage :water filter Chemical 39. Oscillator : Slick surface thermal radiation : Mechanical 40. diode , used to dissipate heat from tiny computer chips paper batteries Electrical circuits 41. www.nanocyl.com/CNT-Expertise.../ Carbon - Nanotubes http://iopscience.iop.org/1367-2630/5/1/117 en.wikipedia.org/wiki/ Carbon _ nanotube http://physicsworld.com/cws/article/print/1761 www.nanotech-now.com /Introduction www.nanocyl.com/CNT-Expertise.../ Carbon - Nanotubes Carbon nanotubes:preparation and properties-Thomas W. Ebbesen ,1997 Carbon nanotubes: basic concepts and physical properties By Stphanie Reich, Christian Thomsen, Janina Maultzsch 42. Queries????? 43.