Carbon Nanotube B 74

8/8/2019 Carbon Nanotube B 74

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Engineering CHEMISTRY

TERM PAPER ON

CARBON NANOTUBES

SUBMITTED BY: Adil

Hussain Lone

SUBMITTED TO: Nidhi Sethi

SECTION: G5001

ROLL NO: B-74

REGD NO: 11013757

Acknowledgement


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It is my profound pleasure to express my sincerest gratitude to my esteemed supervisor,Ms

Nidhi Sethi,Lecturer ,department of chemistry Lovely Professional University ,Phagwara[

Punjab], for her inspiring guidance for all the times. It is both encouraging and

informative .i feel it is my pleasure to work under her expert guidance and supervision.

I feel highly obliged to my teacher for her keen interest and valuable suggestions .

I owe my gratitude to my dear parents and would like to say special thanks to my brother

for their help ,support ,and motivation. Above all, I thank Almighty God for all this

grace,blessings and strength throughout the journey of this term paper.

ADIL HUSSAIN LONE .

Table Contents


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1 Types of carbon nanotubes.

o 1.1 Single-walled

o 1.2 Multi-walledo 1.3 Torus

o 1.4 Nanobud

o 1.5 Cup stacked carbon nanotubes

o 1.6 Extreme carbon nanotubes

2 Properties

o 2.1 Strength

o 2.2 Hardness

o 2.3 Kinetic

o 2.4 Electrical

o 2.5 Thermal

o 2.6 Defects

o 2.7 One-dimensional transport

o 2.8 Toxicity

3 Synthesis

o 3.1 Arc discharge

o 3.2 Laser ablation

o 3.3 Chemical vapor deposition (CVD)

3.3.1 Super-growth CVD

o 3.4 Natural, incidental, and controlled flame environmentso 3.5 Application related issues

4 Potential applications

o 4.1 Structural

o 4.2 In electrical circuits

o 4.3 As paper batteries

o 4.4 Current applications

o 4.5 Solar cells

o 4.6 Ultracapacitors

o 4.7 Other applications

5 Discovery

6 B00ks

7 References
http://en.wikipedia.org/wiki/Carbon_nanotube#Single-walledhttp://en.wikipedia.org/wiki/Carbon_nanotube#Multi-walledhttp://en.wikipedia.org/wiki/Carbon_nanotube#Torushttp://en.wikipedia.org/wiki/Carbon_nanotube#Nanobudhttp://en.wikipedia.org/wiki/Carbon_nanotube#Cup_stacked_carbon_nanotubeshttp://en.wikipedia.org/wiki/Carbon_nanotube#Extreme_carbon_nanotubeshttp://en.wikipedia.org/wiki/Carbon_nanotube#Propertieshttp://en.wikipedia.org/wiki/Carbon_nanotube#Strengthhttp://en.wikipedia.org/wiki/Carbon_nanotube#Hardnesshttp://en.wikipedia.org/wiki/Carbon_nanotube#Kinetichttp://en.wikipedia.org/wiki/Carbon_nanotube#Electricalhttp://en.wikipedia.org/wiki/Carbon_nanotube#Thermalhttp://en.wikipedia.org/wiki/Carbon_nanotube#Defectshttp://en.wikipedia.org/wiki/Carbon_nanotube#One-dimensional_transporthttp://en.wikipedia.org/wiki/Carbon_nanotube#Toxicityhttp://en.wikipedia.org/wiki/Carbon_nanotube#Synthesishttp://en.wikipedia.org/wiki/Carbon_nanotube#Arc_dischargehttp://en.wikipedia.org/wiki/Carbon_nanotube#Laser_ablationhttp://en.wikipedia.org/wiki/Carbon_nanotube#Chemical_vapor_deposition_.28CVD.29http://en.wikipedia.org/wiki/Carbon_nanotube#Super-growth_CVDhttp://en.wikipedia.org/wiki/Carbon_nanotube#Natural.2C_incidental.2C_and_controlled_flame_environmentshttp://en.wikipedia.org/wiki/Carbon_nanotube#Application_related_issueshttp://en.wikipedia.org/wiki/Carbon_nanotube#Potential_applicationshttp://en.wikipedia.org/wiki/Carbon_nanotube#Structuralhttp://en.wikipedia.org/wiki/Carbon_nanotube#In_electrical_circuitshttp://en.wikipedia.org/wiki/Carbon_nanotube#As_paper_batterieshttp://en.wikipedia.org/wiki/Carbon_nanotube#Current_applicationshttp://en.wikipedia.org/wiki/Carbon_nanotube#Solar_cellshttp://en.wikipedia.org/wiki/Carbon_nanotube#Ultracapacitorshttp://en.wikipedia.org/wiki/Carbon_nanotube#Other_applicationshttp://en.wikipedia.org/wiki/Carbon_nanotube#Discoveryhttp://en.wikipedia.org/wiki/Carbon_nanotube#Referenceshttp://en.wikipedia.org/wiki/Carbon_nanotube#Referenceshttp://en.wikipedia.org/wiki/Carbon_nanotube#Multi-walledhttp://en.wikipedia.org/wiki/Carbon_nanotube#Torushttp://en.wikipedia.org/wiki/Carbon_nanotube#Nanobudhttp://en.wikipedia.org/wiki/Carbon_nanotube#Cup_stacked_carbon_nanotubeshttp://en.wikipedia.org/wiki/Carbon_nanotube#Extreme_carbon_nanotubeshttp://en.wikipedia.org/wiki/Carbon_nanotube#Propertieshttp://en.wikipedia.org/wiki/Carbon_nanotube#Strengthhttp://en.wikipedia.org/wiki/Carbon_nanotube#Hardnesshttp://en.wikipedia.org/wiki/Carbon_nanotube#Kinetichttp://en.wikipedia.org/wiki/Carbon_nanotube#Electricalhttp://en.wikipedia.org/wiki/Carbon_nanotube#Thermalhttp://en.wikipedia.org/wiki/Carbon_nanotube#Defectshttp://en.wikipedia.org/wiki/Carbon_nanotube#One-dimensional_transporthttp://en.wikipedia.org/wiki/Carbon_nanotube#Toxicityhttp://en.wikipedia.org/wiki/Carbon_nanotube#Synthesishttp://en.wikipedia.org/wiki/Carbon_nanotube#Arc_dischargehttp://en.wikipedia.org/wiki/Carbon_nanotube#Laser_ablationhttp://en.wikipedia.org/wiki/Carbon_nanotube#Chemical_vapor_deposition_.28CVD.29http://en.wikipedia.org/wiki/Carbon_nanotube#Super-growth_CVDhttp://en.wikipedia.org/wiki/Carbon_nanotube#Natural.2C_incidental.2C_and_controlled_flame_environmentshttp://en.wikipedia.org/wiki/Carbon_nanotube#Application_related_issueshttp://en.wikipedia.org/wiki/Carbon_nanotube#Potential_applicationshttp://en.wikipedia.org/wiki/Carbon_nanotube#Structuralhttp://en.wikipedia.org/wiki/Carbon_nanotube#In_electrical_circuitshttp://en.wikipedia.org/wiki/Carbon_nanotube#As_paper_batterieshttp://en.wikipedia.org/wiki/Carbon_nanotube#Current_applicationshttp://en.wikipedia.org/wiki/Carbon_nanotube#Solar_cellshttp://en.wikipedia.org/wiki/Carbon_nanotube#Ultracapacitorshttp://en.wikipedia.org/wiki/Carbon_nanotube#Other_applicationshttp://en.wikipedia.org/wiki/Carbon_nanotube#Discoveryhttp://en.wikipedia.org/wiki/Carbon_nanotube#Referenceshttp://en.wikipedia.org/wiki/Carbon_nanotube#Referenceshttp://en.wikipedia.org/wiki/Carbon_nanotube#Single-walled


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Carbon nanotube

Carbon nanotubes (CNTs; also known as buckytubes) are allotropes of carbon with a cylindrical nanostructure. Nanotubes have been constructed with length-to-diameter ratio of up to132,000,000:1, which is significantly larger than any other material. These cylindrical carbonmolecules have novelpropertieswhich make them potentially useful in many applications innanotechnology, electronics, optics, and other fields ofmaterials science, as well as potential uses in

architecturalfields. They may also have applications in the construction ofbody armor. Theyexhibit extraordinary strength and unique electrical properties, and are efficient thermal conductors.

Nan tubes are members of the fullerene structural family, which also includes the sphericalbuckyballs. The ends of a nanotube may 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 fewnanometers (approximately 1/50,000th of the width of a human hair), while they can be up to 18centimeters in length (as of 2010). Nanotubes are categorized as single-walled nanotubes (SWNTs)andmulti-walled nanotubes (MWNTs).

Chemical bonding in nanotubes is described by applied quantum chemistry, specifically,orbital

hybridization. The chemical bonding of nanotubes is composed entirely ofsp2

bonds, similar tothose ofgraphite. These bonds, which are stronger than thesp3bonds found in diamonds, providenanotubues with their unique strength. Moreover, nanotubes naturally align themselves into "ropes"held together by Vander Waals forces.
http://en.wikipedia.org/wiki/Allotropes_of_carbonhttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Moleculehttp://en.wikipedia.org/wiki/Chemical_propertyhttp://en.wikipedia.org/wiki/Chemical_propertyhttp://en.wikipedia.org/wiki/Nanotechnologyhttp://en.wikipedia.org/wiki/Electronicshttp://en.wikipedia.org/wiki/Opticshttp://en.wikipedia.org/wiki/Materials_sciencehttp://en.wikipedia.org/wiki/Architecturehttp://en.wikipedia.org/wiki/Architecturehttp://en.wikipedia.org/wiki/Body_armorhttp://en.wikipedia.org/wiki/Body_armorhttp://en.wikipedia.org/wiki/Electricityhttp://en.wikipedia.org/wiki/Conduction_(heat)http://en.wikipedia.org/wiki/Fullerenehttp://en.wikipedia.org/wiki/Fullerene#.22Buckyball.22http://en.wikipedia.org/wiki/Fullerene#.22Buckyball.22http://en.wikipedia.org/wiki/Carbon_nanotube#Single-walledhttp://en.wikipedia.org/wiki/Carbon_nanotube#Multi-walledhttp://en.wikipedia.org/wiki/Carbon_nanotube#Multi-walledhttp://en.wikipedia.org/wiki/Quantum_chemistryhttp://en.wikipedia.org/wiki/Quantum_chemistryhttp://en.wikipedia.org/wiki/Orbital_hybridizationhttp://en.wikipedia.org/wiki/Orbital_hybridizationhttp://en.wikipedia.org/wiki/Orbital_hybridizationhttp://en.wikipedia.org/wiki/Orbital_hybridizationhttp://en.wikipedia.org/wiki/Chemical_bondinghttp://en.wikipedia.org/wiki/Orbital_hybridisation#sp2_hybridshttp://en.wikipedia.org/wiki/Orbital_hybridisation#sp2_hybridshttp://en.wikipedia.org/wiki/Orbital_hybridisation#sp2_hybridshttp://en.wikipedia.org/wiki/Orbital_hybridisation#sp2_hybridshttp://en.wikipedia.org/wiki/Orbital_hybridisation#sp2_hybridshttp://en.wikipedia.org/wiki/Orbital_hybridisation#sp2_hybridshttp://en.wikipedia.org/wiki/Orbital_hybridisation#sp2_hybridshttp://en.wikipedia.org/wiki/Graphitehttp://en.wikipedia.org/wiki/Graphitehttp://en.wikipedia.org/wiki/Orbital_hybridisation#sp3_hybridshttp://en.wikipedia.org/wiki/Orbital_hybridisation#sp3_hybridshttp://en.wikipedia.org/wiki/Orbital_hybridisation#sp3_hybridshttp://en.wikipedia.org/wiki/Orbital_hybridisation#sp3_hybridshttp://en.wikipedia.org/wiki/Orbital_hybridisation#sp3_hybridshttp://en.wikipedia.org/wiki/Diamondhttp://en.wikipedia.org/wiki/Van_der_Waals_forcehttp://en.wikipedia.org/wiki/Allotropes_of_carbonhttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Moleculehttp://en.wikipedia.org/wiki/Chemical_propertyhttp://en.wikipedia.org/wiki/Nanotechnologyhttp://en.wikipedia.org/wiki/Electronicshttp://en.wikipedia.org/wiki/Opticshttp://en.wikipedia.org/wiki/Materials_sciencehttp://en.wikipedia.org/wiki/Architecturehttp://en.wikipedia.org/wiki/Body_armorhttp://en.wikipedia.org/wiki/Electricityhttp://en.wikipedia.org/wiki/Conduction_(heat)http://en.wikipedia.org/wiki/Fullerenehttp://en.wikipedia.org/wiki/Fullerene#.22Buckyball.22http://en.wikipedia.org/wiki/Carbon_nanotube#Single-walledhttp://en.wikipedia.org/wiki/Carbon_nanotube#Multi-walledhttp://en.wikipedia.org/wiki/Quantum_chemistryhttp://en.wikipedia.org/wiki/Orbital_hybridizationhttp://en.wikipedia.org/wiki/Orbital_hybridizationhttp://en.wikipedia.org/wiki/Chemical_bondinghttp://en.wikipedia.org/wiki/Orbital_hybridisation#sp2_hybridshttp://en.wikipedia.org/wiki/Graphitehttp://en.wikipedia.org/wiki/Orbital_hybridisation#sp3_hybridshttp://en.wikipedia.org/wiki/Diamondhttp://en.wikipedia.org/wiki/Van_der_Waals_force


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Types of carbon nanotubes

Single-walled

Armchair(n,n)

The chiral vector is bent,while the translation vectorstays straight

Graphene nanoribbonThe chiral vector is bent, whilethe translation vector staysstraight

Zigzag (n,0)Chiral (n,m)n and m can be countedat the end of the tube

Graphene nanoribbon

The (n,m) nanotube naming scheme can be thought of as a vector (Ch) in an infinite graphenesheet that describes how to "roll up" the graphene sheet to make the nanotube. T denotes the tubeaxis, and a1 and a2 are the unit vectors of graphene in real space.

An STM image of single-walled carbon nanotube

Transmission electron microscopy image showing a single-walled carbon nanotube

Most single-walled nanotubes (SWNT) have a diameter of close to 1 nanometer, with a tubelength that can be many millions of times longer. The structure of a SWNT can beconceptualized by wrapping a one-atom-thick layer of graphite called graphene into a seamlesscylinder. The way the graphene sheet is wrapped is represented by a pair of indices (n,m) calledthe chiral vector. The integers n and m denote the number of unitvectorsalong two directions inthe honeycomb crystal lattice of graphene. Ifm = 0, the nanotubes are called "zigzag". Ifn = m,the nanotubes are called "armchair". Otherwise, they are called "chiral". The diameter of ananotube can be calculated from its (n,m) indices as follows

where a = 0.246 nm.

Single-walled nanotubes are an important variety of carbon nanotube because they exhibitelectric properties that are not shared by the multi-walled carbon nanotube (MWNT) variants. Inparticular, theirband gap can vary from zero to about 2 eV and their electrical conductivity canshow metallic or semiconducting behavior, whereas MWNTs are zero-gap metals. Single-wallednanotubes are the most likely candidate for miniaturizing electronics beyond the micro

electromechanical scale currently used in electronics. The most basic building block of thesesystems is the electric wire, and SWNTs can be excellent conductors. One useful application ofSWNTs is in the development of the first intramolecularfield effect transistors(FET).
http://en.wikipedia.org/wiki/Scanning_tunneling_microscopehttp://en.wikipedia.org/wiki/Vector_(geometric)http://en.wikipedia.org/wiki/Vector_(geometric)http://en.wikipedia.org/wiki/Vector_(geometric)http://en.wikipedia.org/wiki/Crystal_latticehttp://en.wikipedia.org/wiki/Band_gaphttp://en.wikipedia.org/wiki/Field_effect_transistorshttp://en.wikipedia.org/wiki/Field_effect_transistorshttp://en.wikipedia.org/wiki/Field_effect_transistorshttp://en.wikipedia.org/wiki/File:CntHAADF.jpghttp://en.wikipedia.org/wiki/File:Chiraltube.gifhttp://en.wikipedia.org/wiki/Scanning_tunneling_microscopehttp://en.wikipedia.org/wiki/Vector_(geometric)http://en.wikipedia.org/wiki/Crystal_latticehttp://en.wikipedia.org/wiki/Band_gaphttp://en.wikipedia.org/wiki/Field_effect_transistors


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Production of the first intramolecularlogic gate using SWNT FETs has recently become possibleas well. To create a logic gate you must have both a p-FET and an n-FET. Because SWNTs app-FETs when exposed to oxygen and n-FETs otherwise, it is possible to protect half of an SWNTfrom oxygen exposure, while exposing the other half to oxygen. This results in a single SWNTthat acts as a NOT logic gate with both p and n-type FETs within the same molecule.

Single-walled nanotubes are dropping precipitously in price, from around $1500 per gram as of

2000 to retail prices of around $50 per gram of as-produced 4060% by weight SWNTs as ofMarch 2010.

Multi-walled

SEM image of carbon nanotubes bundles.

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. IntheRussian Dollmodel, sheets of graphite are arranged in concentric cylinders, e.g. a (0,8)single-walled nanotube (SWNT) within a larger (0,17) single-walled nanotube. In theParchmentmodel, a single sheet of graphite is rolled in around itself, resembling a scroll of parchment or arolled newspaper. The interlayer distance in multi-walled nanotubes is close to the distancebetween graphene layers in graphite, approximately 3.4 .

The special place of double-walled carbon nanotubes (DWNT) must be emphasized here becausetheir morphology and properties are similar to SWNT but their resistance to chemicals issignificantly improved. This is especially important when functionalizationis required (thismeans grafting of chemical functions at the surface of the nanotubes) to add new properties tothe CNT. In the case of SWNT, covalent functionalization will break some C=C double bonds,leaving "holes" in the structure on the nanotube and thus modifying both its mechanical andelectrical properties. In the case of DWNT, only the outer wall is modified. DWNT synthesis onthe gram-scale was first proposed in 2003 by the CCVD technique, from the selective reductionof oxide solutions in methane and hydrogen.

TORUS
http://en.wikipedia.org/wiki/Logic_gatehttp://en.wikipedia.org/wiki/Scanning_electron_microscopehttp://en.wikipedia.org/wiki/Matryoshka_dollhttp://en.wikipedia.org/wiki/Scroll_(parchment)http://en.wikipedia.org/wiki/Surface_functionalizationhttp://en.wikipedia.org/wiki/Surface_functionalizationhttp://en.wikipedia.org/wiki/Double_bondhttp://en.wikipedia.org/wiki/File:CNTSEM.JPGhttp://en.wikipedia.org/wiki/Logic_gatehttp://en.wikipedia.org/wiki/Scanning_electron_microscopehttp://en.wikipedia.org/wiki/Matryoshka_dollhttp://en.wikipedia.org/wiki/Scroll_(parchment)http://en.wikipedia.org/wiki/Surface_functionalizationhttp://en.wikipedia.org/wiki/Double_bond


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A stable nanobud structure

A nanotorus is theoretically described as carbon nanotube bent into a torus(doughnut shape).Nanotori are predicted to have many unique properties, such as magnetic moments 1000 timeslarger than previously expected for certain specific radii. Properties such asmagnetic moment,thermal stability, etc. vary widely depending on radius of the torus and radius of the tube.

Nanobud

Carbon nanobuds are a newly created material combining two previously discovered allotropes

of carbon: carbon nanotubes and fullerenes. In this new material, fullerene-like "buds" arecovalently bonded to the outer sidewalls of the underlying carbon nanotube. This hybrid materialhas useful properties of both fullerenes and carbon nanotubes. In particular, they have beenfound to be exceptionally good field emitters. In composite materials, the attached fullerenemolecules may function as molecular anchors preventing slipping of the nanotubes, thusimproving the composites mechanical properties.

Cup stacked carbon nanotubes

Cup-stacked carbon nanotubes (CSCNTs) differ from other quasi-1D carbon structures thatnormally behave as a metallic conductor of electrons. CSCNTs exhibit semiconducting behaviors

due to the stacking microstructure of graphene layers.

Extreme carbon nanotubes

Cycloparaphenylene

The observation of the longestcarbon nanotubes (18.5 cm long) was reported in 2009. Theywere grown on Si substrates using an improved chemical vapor deposition(CVD) method andrepresent electrically uniform arrays of single-walled carbon nanotubes. Theshortestcarbonnanotube is the organic compound cycloparaphenylene which was synthesized in early 2009.The thinnestcarbon nanotube is armchair (2,2) CNT with a diameter of 3 . This nanotube wasgrown inside a multi-walled carbon nanotube. Assigning of carbon nanotube type was done bycombination ofhigh-resolution transmission electron microscopy (HRTEM),Ramanspectroscopy and density functional theory (DFT) calculations.

The thinnest freestandingsingle-walled carbon nanotube is about 4.3 in diameter. Researcherssuggested that it can be either (5,1) or (4,2) SWCNT, but exact type of carbon nanotube remainsquestionable. (3,3), (4,3) and (5,1) carbon nanotubes (all about 4 in diameter) wereunambiguously identified using more precise aberration-corrected high-resolution transmissionelectron microscopy. However, they were found inside of double-walled carbon nanotubes.
http://en.wikipedia.org/wiki/Carbon_nanobudhttp://en.wikipedia.org/wiki/Torushttp://en.wikipedia.org/wiki/Torushttp://en.wikipedia.org/wiki/Magnetic_momenthttp://en.wikipedia.org/wiki/Magnetic_momenthttp://en.wikipedia.org/wiki/Carbon_nanobudhttp://en.wikipedia.org/wiki/Chemical_vapor_depositionhttp://en.wikipedia.org/wiki/Chemical_vapor_depositionhttp://en.wikipedia.org/wiki/High-resolution_transmission_electron_microscopyhttp://en.wikipedia.org/wiki/Raman_spectroscopyhttp://en.wikipedia.org/wiki/Raman_spectroscopyhttp://en.wikipedia.org/wiki/Raman_spectroscopyhttp://en.wikipedia.org/wiki/Density_functional_theoryhttp://en.wikipedia.org/wiki/High-resolution_transmission_electron_microscopyhttp://en.wikipedia.org/wiki/High-resolution_transmission_electron_microscopyhttp://en.wikipedia.org/wiki/File:NanoBud.JPGhttp://en.wikipedia.org/wiki/Carbon_nanobudhttp://en.wikipedia.org/wiki/Torushttp://en.wikipedia.org/wiki/Magnetic_momenthttp://en.wikipedia.org/wiki/Carbon_nanobudhttp://en.wikipedia.org/wiki/Chemical_vapor_depositionhttp://en.wikipedia.org/wiki/High-resolution_transmission_electron_microscopyhttp://en.wikipedia.org/wiki/Raman_spectroscopyhttp://en.wikipedia.org/wiki/Raman_spectroscopyhttp://en.wikipedia.org/wiki/Density_functional_theoryhttp://en.wikipedia.org/wiki/High-resolution_transmission_electron_microscopyhttp://en.wikipedia.org/wiki/High-resolution_transmission_electron_microscopy


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Properties

Strength

Carbon nanotubes are the strongest and stiffest materials yet discovered in terms oftensilestrength and elastic modulus respectively. This strength results from the covalent sp bondsformed between the individual carbon atoms. In 2000, a multi-walled carbon nanotube wastested to have a tensile strength of 63 gigapascals (GPa). (This, for illustration, translates into theability to endure tension of a weight equivalent to 6422 kg on a cable with cross-section of 1mm2.) Since carbon nanotubes have a low density for a solid of 1.3 to 1.4 gcm3, its specificstrength of up to 48,000 kNmkg1 is the best of known materials, compared to high-carbonsteel's 154 kNmkg1.

Under excessive tensile strain, the tubes will undergoplastic deformation , which means thedeformation is permanent. This deformation begins at strains of approximately 5% and canincrease the maximum strain the tubes undergo before fracture by releasing strain energy.

CNTs are not nearly as strong under compression. Because of their hollow structure and highaspect ratio, they tend to undergobuckling when placed under compressive, torsional or bendingstress.

Comparison of mechanical properties

MaterialYoung's modulus

(TPa)

Tensile strength

(GPa)

Elongation at break

(%)

SWNT ~1 (from 1 to 5) 1353E 16

Armchair

SWNT

0.94T 126.2T 23.1

ZigzagSWNT

0.94T 94.5T 15.617.5

ChiralSWNT

0.92

MWNT 0.27E0.8E0.95E 11E63E150E

Stainlesssteel

0.186E0.214E 0.38E1.55E 1550

Kevlar

29&149 0.06

E

0.18

E

3.6

E

3.8

E

~2

Experimental observation; Theoretical prediction

The above discussion referred to axial properties of the nanotube, whereas simple geometricalconsiderations suggest that carbon nanotubes should be much softer in the radial direction thanalong the tube axis. Indeed, TEMobservation of radial elasticity suggested that even the van derWaals forces can deform two adjacent nanotubes. Nanoindentation experiments, performed by
http://en.wikipedia.org/wiki/Tensile_strengthhttp://en.wikipedia.org/wiki/Tensile_strengthhttp://en.wikipedia.org/wiki/Elastic_modulushttp://en.wikipedia.org/wiki/Pascal_(unit)http://en.wikipedia.org/wiki/Millimetrehttp://en.wikipedia.org/wiki/Specific_strengthhttp://en.wikipedia.org/wiki/Specific_strengthhttp://en.wikipedia.org/wiki/Deformation_(engineering)#Plastic_deformationhttp://en.wikipedia.org/wiki/Bucklinghttp://en.wikipedia.org/wiki/Young's_modulushttp://en.wikipedia.org/wiki/Tensile_strengthhttp://en.wikipedia.org/wiki/Stainless_steelhttp://en.wikipedia.org/wiki/Stainless_steelhttp://en.wikipedia.org/wiki/Kevlarhttp://en.wikipedia.org/wiki/Transmission_electron_microscopyhttp://en.wikipedia.org/wiki/Transmission_electron_microscopyhttp://en.wikipedia.org/wiki/Tensile_strengthhttp://en.wikipedia.org/wiki/Tensile_strengthhttp://en.wikipedia.org/wiki/Elastic_modulushttp://en.wikipedia.org/wiki/Pascal_(unit)http://en.wikipedia.org/wiki/Millimetrehttp://en.wikipedia.org/wiki/Specific_strengthhttp://en.wikipedia.org/wiki/Specific_strengthhttp://en.wikipedia.org/wiki/Deformation_(engineering)#Plastic_deformationhttp://en.wikipedia.org/wiki/Bucklinghttp://en.wikipedia.org/wiki/Young's_modulushttp://en.wikipedia.org/wiki/Tensile_strengthhttp://en.wikipedia.org/wiki/Stainless_steelhttp://en.wikipedia.org/wiki/Stainless_steelhttp://en.wikipedia.org/wiki/Kevlarhttp://en.wikipedia.org/wiki/Transmission_electron_microscopy


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several groups on multiwalled carbon nanotubes, indicated Young's modulus of the order ofseveral GPa confirming that CNTs are indeed rather soft in the radial direction.

Hardness

Diamond is considered to be the hardest material. Under conditions of high temperature and highpressure, graphite transforms into diamond. One study succeeded in the synthesis of a super-hard

material by compressing SWNTs to above 24 GPa at room temperature. The hardness of thismaterial was measured with ananoindenteras 62152 GPa. The hardness of reference diamondandboron nitride samples was 150 and 62 GPa, respectively. Thebulk modulusof compressedSWNTs was 462546 GPa, surpassing the value of 420 GPa for diamond

Kinetic

Multi-walled nanotubes are multiple concentric nanotubes precisely nested within one another.These exhibit a striking telescoping property whereby an inner nanotube core may slide, almostwithout friction, within its outer nanotube shell, thus creating an atomically perfect linear orrotational bearing. This is one of the first true examples ofmolecular nanotechnology, the precisepositioning of atoms to create useful machines. Already, this property has been utilized to createthe world's smallest rotational motor. Future applications such as a gigahertz mechanicaloscillator are also envisage

Electrical

Band structures computed using tight binding approximation for (6,0) CNT (zigzag, metallic)(10,2) CNT (semiconducting) and (10,10) CNT (armchair, metallic).

Because of the symmetry and unique electronic structure of graphene, the structure of a nanotubestrongly affects its electrical properties. For a given (n,m) nanotube, ifn = m, the nanotube ismetallic; ifn m is a multiple of 3, then the nanotube is semiconducting with a very small band
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gap, otherwise the nanotube is a moderatesemiconductor. Thus all armchair (n = m) nanotubesare metallic, and nanotubes (6,4), (9,1), etc. are semiconducting

However, this rule has exceptions, because curvature effects in small diameter carbon nanotubescan influence strongly electrical properties. Thus, a (5,0) SWCNT that should be semiconductingin fact is metallic according to the calculations. Likewise, vice versa-- zigzag and chiral

SWCNTs with small diameters that should be metallic have finite gap (armchair nanotubesremain metallic). In theory, metallic nanotubes can carry an electric current density of 4 109

A/cm2 which is more than 1,000 times greater than metals such as copper.

Multiwalled carbon nanotubes with interconnected inner shells show superconductivitywith arelatively high transition temperature Tc = 12K. In contrast, the Tc value is an order ofmagnitude lower for ropes of single-walled carbon nanotubes or for MWNTs with usual, non-interconnected shells.

Thermal

All nanotubes are expected to be very good thermal conductors along the tube, exhibiting aproperty known as "ballistic conduction", but good insulators laterally to the tube axis.Measurements show that a SWNT has a room-temperature thermal conductivity along its axis ofabout 3500 Wm1K1compare this to copper, a metal well-known for its good thermalconductivity, which transmits 385 Wm1K1. A SWNT has a room-temperature thermalconductivity across its axis of about 1.52 Wm1K1, which is about as thermally conductive assoil. The temperature stability of carbon nanotubes is estimated to be up to 2800 C invacuumand about 750 C in air.

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 thetensile strength by up to 85%. Another form of carbon nanotube defect is theStone Wales defect,which creates a pentagon and heptagon pair by rearrangement of the bonds. Because of the verysmall structure of CNTs, the tensile strength of the tube is dependent on its weakest segment in asimilar manner to a chain, where the strength of the weakest link becomes the maximum strengthof the chain.

Crystallographic defects also affect the tube's electrical properties. A common result is loweredconductivity through the defective region of the tube. A defect in armchair-type tubes (whichcanconduct electricity) can cause the surrounding region to become semiconducting, and single

monoatomic vacancies induce magnetic properties.

Crystallographic defects strongly affect the tube's thermal properties. Such defects lead tophonon scattering, which in turn increases the relaxation rate of the phonons. This reduces themean free pathand reduces the thermal conductivity of nanotube structures. Phonon transportsimulations indicate that substitutional defects such as nitrogen or boron will primarily lead toscattering of high-frequency optical phonons. However, larger-scale defects such as Stone Walesdefects cause phonon scattering over a wide range of frequencies, leading to a greater reductionin thermal conductivity.
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One-dimensional transport

Because of the nanoscale dimensions, electrons propagate only along the tube's axis and electrontransport involves many quantum effects. Because of this, carbon nanotubes are frequentlyreferred to as one-dimensional.

Toxicity

Determining the toxicity of carbon nanotubes has been one of the most pressing questions innanotechnology. Unfortunately, such research has only just begun. Thus, the data are stillfragmentary and subject to criticism. Preliminary results highlight the difficulties in evaluatingthe toxicity of this heterogeneous material. Parameters such as structure, size distribution,surface area, surface chemistry,surface charge, andagglomeration state as well as purity of the

samples, have considerable impact on the reactivity of carbon nanotubes. However, availabledata clearly show that, under some conditions, nanotubes can cross membrane barriers, whichsuggests that if raw materials reach the organs they can induce harmful effects such asinflammatory and fibrotic reactions.

A study led by Alexandra Porter from the University of Cambridge shows that CNTs can enterhuman cells and accumulate in thecytoplasm, causing cell death.

Results of rodent studies collectively show that regardless of the process by which CNTs weresynthesized and the types and amounts of metals they contained, CNTs were capable ofproducing inflammation,epithelioid granulomas (microscopic nodules),fibrosis, and

biochemical/toxicological changes in the lungs. Comparative toxicity studies in which mice weregiven equal weights of test materials showed that SWCNTs were more toxic thanquartz, whichis considered a serious occupational health hazard when chronically inhaled. As a control,ultrafine carbon blackwas shown to produce minimal lung responses.

The needle-like fiber shape of CNTs, similar to asbestos fibers, raises fears that widespread useof carbon nanotubes may lead to mesothelioma, cancer of the lining of the lungs often caused byexposure to asbestos. A recently-published pilot study supports this prediction. Scientistsexposed the mesotheliallining of the body cavity of mice, as a surrogate for the mesotheliallining of the chest cavity, to long multiwalled carbon nanotubes and observed asbestos-like,

length-dependent, pathogenic behavior which included inflammation and formation of lesionsknown as granulomas. Authors of the study conclude:

"This is of considerable importance, because research and business communities continueto invest heavily in carbon nanotubes for a wide range of products under the assumptionthat they are no more hazardous than graphite. Our results suggest the need for furtherresearch and great caution before introducing such products into the market if long-termharm is to be avoided."

According to co-author Dr. Andrew Maynard:
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"This study is exactly the kind of strategic, highly focused research needed to ensure thesafe and responsible development of nanotechnology. It looks at a specific nanoscalematerial expected to have widespread commercial applications and asks specificquestions about a specific health hazard. Even though scientists have been raisingconcerns about the safety of long, thin carbon nanotubes for over a decade, none of theresearch needs in the current U.S. federal nanotechnology environment, health and safetyrisk research strategy address this question."

Although further research is required, results presented today clearly demonstrate that, undercertain conditions, especially those involving chronic exposure, carbon nanotubes can pose aserious risk to human health.

Synthesis

Powder of carbon nanotubes

Techniques have been developed to produce nanotubes in sizeable quantities, includingarcdischarge, laser ablation, high pressure carbon monoxide (HiPco), andchemical vapor deposition(CVD). Most of these processes take place in vacuum or with process gases. CVD growth ofCNTs can occur in vacuum or at atmospheric pressure. Large quantities of nanotubes can besynthesized by these methods; advances in catalysis and continuous growth processes are makingCNTs more commercially viable.

Arc discharge

Nan tubes were observed in 1991 in the carbon soot of graphite electrodes during an arcdischarge, by using a current of 100 amps, that was intended to produce fullerenes. However thefirst macroscopic production of carbon nanotubes was made in 1992 by two researchers atNEC'sFundamental Research Laboratory.

The method used was the same as in 1991. During this process, the carbon contained in thenegative electrode sublimates because of the high discharge temperatures. Because nanotubes
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were initially discovered using this technique, it has been the most widely-used method ofnanotube 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.

Laser ablation

In the laser ablation process, apulsed laservaporizes a graphite target in a high-temperaturereactor while an inert gasis bled into the chamber. Nan tubes develop on the cooler surfaces ofthe reactor as the vaporized carbon condenses. A water-cooled surface may be included in thesystem to collect the nanotubes.

This process was developed by Dr. Richard Smalleyand co-workers at Rice University, who atthe time of the discovery of carbon nanotubes, were blasting metals with a laser to producevarious metal molecules. When they heard of the existence of nanotubes they replaced the metalswith graphite to create multi-walled carbon nanotubes Later that year the team used a compositeof graphite and metal catalyst particles (the best yield was from a cobaltandnickel mixture) tosynthesize single-walled carbon nanotubes.

The laser ablation method yields around 70% and produces primarily single-walled carbonnanotubes with a controllable diameter determined by the reaction temperature. However, it ismore expensive than either arc discharge or chemical vapor deposition.

Chemical vapor deposition (CVD)

Nan tubes being grown by plasma enhanced chemical vapor deposition

The catalytic vapor phase deposition of carbon was first reported in 1959, but it was not until1993 that carbon nanotubes were formed by this process. In 2007, researchers at the Universityof Cincinnati (UC) developed a process to grow aligned carbon nanotube arrays of 18 mm lengthon a FirstNano ET3000 carbon nanotube growth system
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During CVD, a substrate is prepared with a layer of metal catalyst particles, most commonlynickel, cobalt, iron, or a combination. The metal nanoparticles can also be produced by otherways, including reduction of oxides or oxides solid solutions. The diameters of the nanotubesthat are to be grown are related to the size of the metal particles. This can be controlled bypatterned (or masked) deposition of the metal, annealing, or by plasma etching of a metal layer.The substrate is heated to approximately 700C. To initiate the growth of nanotubes, two gasesare bled into the reactor: a process gas (such asammonia,nitrogenorhydrogen) and a carbon-

containing gas (such as acetylene, ethylene,ethanol ormethane). Nan tubes grow at the sites ofthe 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. Thismechanism is still being studied. The catalyst particles can stay at the tips of the growingnanotube during the growth process, or remain at the nanotube base, depending on the adhesionbetween the catalyst particle and the substrate. Thermal catalytic decomposition of hydrocarbonhas become an active area of research and can be a promising route for the bulk production ofCNTs. Fluidised bed reactor is the most widely used reactor for CNT preparation. Scale-up ofthe reactor is the major challange.

CVD is a common method for the commercial production of carbon nanotubes. For this purpose,

the metal nanoparticles are mixed with a catalyst support such as MgO or Al2O3 to increase thesurface area for higher yield of the catalytic reaction of the carbon feedstock with the metalparticles. One issue in this synthesis route is the removal of the catalyst support via an acidtreatment, which sometimes could destroy the original structure of the carbon nanotubes.However, alternative catalyst supports that are soluble in water have proven effective fornanotube growth.

If aplasma is generated by the application of a strong electric field during the growth process(plasma enhanced chemical vapor deposition*), then the nanotube growth will follow thedirection of the electric field. By adjusting the geometry of the reactor it is possible to synthesizevertically aligned carbon nanotubes (i.e., perpendicular to the substrate), a morphology that has

been of interest to researchers interested in the electron emission from nanotubes. Without theplasma, the resulting nanotubes are often randomly oriented. Under certain reaction conditions,even in the absence of a plasma, closely spaced nanotubes will maintain a vertical growthdirection resulting in a dense array of tubes resembling a carpet or forest.

Of the various means for nanotube synthesis, CVD shows the most promise for industrial-scaledeposition, because of its price/unit ratio, and because CVD is capable of growing nanotubesdirectly on a desired substrate, whereas the nanotubes must be collected in the other growthtechniques. The growth sites are controllable by careful deposition of the catalyst. In 2007, ateam from Meijo University demonstrated a high-efficiency CVD technique for growing carbonnanotubes from camphor. Researchers at Rice University, until recently led by the lateRichard

Smalley, have concentrated upon finding methods to produce large, pure amounts of particulartypes of nanotubes. Their approach grows long fibers from many small seeds cut from a singlenanotube; all of the resulting fibers were found to be of the same diameter as the originalnanotube and are expected to be of the same type as the original nanotubes

Super-growth CVD
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SEM photo of SWNT forests produced by super-growth

A small SWNT sample produced by super-growth

Super-growth CVD (water-assisted chemical vapour deposition) process was developed by KenjiHata, Sumio Iijima and co-workers atAIST, Japan. In this process, the activity and lifetime ofthe catalyst are enhanced by addition of water into the CVD reactor. Dense millimeter-tallnanotube "forests", aligned normal to the substrate, were produced.

Their specific surface exceeds 1,000 m2/g (capped) or 2,200 m2/g (uncapped), surpassing thevalue of 4001,000 m2/g for HiPco samples. The synthesis efficiency is about 100 times higherthan for the laser ablation method. The time required to make SWNT forests of the height of

2.5 mm by this method was 10 minutes in 2004. Those SWNT forests can be easily separatedfrom the catalyst, yielding clean SWNT material (purity >99.98%) without further purification.For comparison, the as-grown HiPco CNTs contain about 5-35% of metal impurities; it istherefore purified through dispersion and centrifugation that damages the nanotubes. The super-growth process avoids this problem. Patterned highly organized single-walled nanotubestructures were successfully fabricated using the super-growth technique.

The mass densityof super-growth CNTs is about 0.037 g/cm3. It is much lower than that ofconventional CNT powders (~1.34 g/cm3), probably because the latter contain metals andamorphous carbon.

The super-growth method is basically a variation of CVD. Therefore, it is possible to growmaterial containing SWNT, DWNTs and MWNTs, and to alter their ratios by tuning the growthconditions. Their ratios change by the thinness of the catalyst. Many MWNTs are included sothat the diameter of the tube is wide.

The vertically aligned nanotube forests originate from a "zipping effect" when they are immersedin a solvent and dried. The zipping effect is caused by the surface tension of the solvent and thevan der Waals forces between the carbon nanotubes. It aligns the nanotubes into a densematerial, which can be formed in various shapes, such as sheets and bars, by applying weak
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compression during the process. Densification increases the Vickers hardnessby about 70 timesand density is 0.55 g/cm3. The packed carbon nanotubes are more than 1 mm long and have a

carbon purity of 99.9% or higher; they also retain the desirable alignment properties of thenanotubes forest.

Natural, incidental, and controlled flame environments

Fullerenes and carbon nanotubes are not necessarily products of high-tech laboratories; they arecommonly formed in such mundane places as ordinary flames, produced by burning methane,ethylene and benzene, and they have been found in soot from both indoor and outdoorairHowever, these naturally occurring varieties can be highly irregular in size and qualitybecause the environment in which they are produced is often highly uncontrolled. Thus, althoughthey can be used in some applications, they can lack in the high degree of uniformity necessaryto satisfy the many needs of both research and industry. Recent efforts have focused onproducing more uniform carbon nanotubes in controlled flame environments. Such methods havepromise for large-scale, low-cost nanotube synthesis, though they must compete with rapidlydeveloping large scale CVD production.

Application related issues

Centrifuge tube with a solution of carbon nanotubes, which were sorted by diameter usingdensity-gradient ultracentrifugation.

Many electronic applications of carbon nanotubes crucially rely on techniques of selectivelyproducing either semiconducting or metallic CNTs, preferably of a certain chirality. Severalmethods of separating semiconducting and metallic CNTs are known, but most of them are notyet suitable for large-scale technological processes. The most efficient method relies on density-gradient ultracentrifugation which separates surfactant-wrapped nanotubes by the minutedifference in their density. This density difference often translates into difference in the nanotubediameter and (semi)conducting properties. Another method of separation uses a sequence of

freezing, thawing, and compression of SWNTs embedded in agarose gel. This process results ina solution containing 70% metallic SWNTs and leaves a gel containing 95% semiconductingSWNTs. The diluted solutions separated by this method show various colors. Moreover, SWNTs
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can be separated by the column chromatography method. Yield is 95% in semiconductor typeSWNT and 90% in metallic type SWNT.

In addition to separation of semiconducting and metallic SWNTs, it is possible to sort SWNTsby length, diameter, and chirality. The highest resolution length sorting, with length variation of


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For perspective, outstanding breakthroughs have already been made. Pioneering work led by RayH. Baughman at the NanoTech Institute has shown that single and multi-walled nanotubes canproduce materials with toughness unmatched in the man-made and natural worlds.

In electrical circuits

Nanotube based transistorshave been made that operate at room temperature and that are capable

of digital switching using a single electron. However, one major obstacle to realization ofnanotubes has been the lack of technology for mass production. In 2001 IBM researchersdemonstrated how metallic nanotubes can be destroyed, leaving semiconducting ones behind foruse as transistors. Their process is called "constructive destruction" which includes the automaticdestruction of defective nanotubes on thewafer. This process, however, only gives control overthe electrical properties on a statistical scale.

The potential of carbon nanotubes was demonstrated in 2003 when room-temperature ballistictransistors with ohmic metal contacts and high-k gatedielectric were reported, showing 2030xhigher ON current than state-of-the-art Si MOSFETs. This presented an important advance in thefield as CNT was shown to potentially outperform Si. At the time, a major challenge was ohmic

metal contact formation. In this regard,palladium, which is a highwork functionmetal wasshown to exhibit Schottky barrier-free contacts to semiconducting nanotubes with diameters>1.7 nm.

The first nanotube integrated memory circuit was made in 2004. One of the main challenges hasbeen regulating the conductivity of nanotubes. Depending on subtle surface features a nanotubemay act as a plain conductoror as a semiconductor. A fully automated method has however beendeveloped to remove non-semiconductor tubes.

Another way to make carbon nanotube transistors has been to use random networks of them. Bydoing so one averages all of their electrical differences and one can produce devices in large

scale at the wafer level. This approach was first patented by Nanomix Inc (date of originalapplication June 2002 ). It was first published in the academic literature by theUnited StatesNaval Research Laboratory in 2003 through independent research work. This approach alsoenabled Nanomix to make the first transistor on a flexible and transparent substrate.

Large structures of carbon nanotubes can be used for thermal management of electronic circuits.An approximately 1 mmthick carbon nanotube layer was used as a special material to fabricatecoolers, this materials has very low density, ~20 times lower weight than a similar copperstructure, while the cooling properties are similar for the two materials.

Overall, incorporating carbon nanotubes as transistors into logic-gate circuits with densitiescomparable to modern CMOS technology has not yet been demonstrated.

As paper batteries

Apaper battery is abatteryengineered to use a paper-thin sheet ofcellulose (which is the majorconstituent of regular paper, among other things) infused with aligned carbon nanotubes. Thenanotubes act as electrodes; allowing the storage devices to conduct electricity. The battery,which functions as both a lithium-ion battery and asupercapacitor, can provide a long, steady
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power output comparable to a conventional battery, as well as a supercapacitors quick burst ofhigh energyand while a conventional battery contains a number of separate components, thepaper battery integrates all of the battery components in a single structure, making it more energyefficient.

Current applications

Current use and application of nanotubes has mostly been limited to the use of bulk nanotubes,which is a mass of rather unorganized fragments of nanotubes. Bulk nanotube materials maynever achieve a tensile strength similar to that of individual tubes, but such composites maynevertheless yield strengths sufficient for many applications. Bulk carbon nanotubes havealready been used as composite fibers inpolymers to improve the mechanical, thermal andelectrical properties of the bulk product.

Easton-Bell Sports, Inc. have been in partnership withZyvex Performance Materials, using CNT

technology in a number of theirbicyclecomponentsincluding flat and riser handlebars, cranks,forks, seatposts, stems and aero bars.

Zyvex Performance Materials has also built a 54' maritime vessel, thePiranha UnmannedSurface Vessel, as a technology demonstrator for what is possible using CNT technology. CNTshelp improve the structural performance of the vessel, resulting in a lightweight 8,000lb boat.

Solar cells

Solar cells developed at theNew Jersey Institute of Technologyuse a carbon nanotube complex,formed by a mixture of carbon nanotubes and carbonbuckyballs (known as fullerenes) to form

snake-like structures. Buckyballs trap electrons, although they can't make electrons flow. Addsunlight to excite thepolymers, and the buckyballs will grab the electrons. Nan tubes, behavinglike copper wires, will then be able to make the electrons or current flow.

Ultracapacitors

MIT Laboratory for Electromagnetic and Electronic Systems uses nanotubes to improveultracapacitors. The activated charcoal used in conventional ultracapacitors has many smallhollow spaces of various size, which create together a large surface to store electric charge. Butas charge is quantized into elementary charges, i.e. electrons, and each such elementary chargeneeds a minimum space, a significant fraction of the electrode surface is not available for storage

because the hollow spaces are not compatible with the charge's requirements. With a nanotubeelectrode the spaces may be tailored to sizefew too large or too smalland consequently thecapacity should be increased considerably.

Other applications
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Aligned nanotubes are preferred for many applications.

Carbon nanotubes have been implemented in nanoelectromechanical systems, includingmechanical memory elements (NRAMbeing developed byNantero Inc.) and nanoscale electricmotors (seeNanomotor).

In May 2005, Nanomix Inc placed on the market a hydrogen sensor which integrated carbonnanotubes on a silicon platform. Since then Nanomix has been patenting many such sensorapplications such as in the field of carbon dioxide, nitrous oxide, glucose, DNA detection, etc.

Eikos Inc ofFranklin,Massachusetts and Unidym Inc. ofSilicon Valley, California aredeveloping transparent, electrically conductive films of carbon nanotubes to replaceindium tinoxide (ITO). Carbon nanotube films are substantially more mechanically robust than ITO films,making them ideal for high-reliability touchscreensand flexible displays. Printable water-basedinks of carbon nanotubes are desired to enable the production of these films to replace ITO.[111]

Nanotube films show promise for use in displays for computers, cell phones, PDAs, and ATMs.

A nanoradio, a radio receiver consisting of a single nanotube, was demonstrated in 2007. In 2008it was shown that a sheet of nanotubes can operate as a loudspeaker if an alternating current isapplied. The sound is not produced through vibration butthermoacoustically.[112]

Because of the high mechanical strength of carbon nanotubes, research is being made intoweaving them into clothes to create stab-proof and bulletproof clothing. The nanotubes wouldeffectively stop the bullet from penetrating the body, although the bullet's kinetic energy wouldlikely cause broken bones and internal bleeding.

A flywheel made of carbon nanotubes could be spun at extremely high velocity on a floatingmagnetic axis in a vacuum, and potentially store energy at adensityapproaching that ofconventional fossil fuels. Since energy can be added to and removed from flywheels veryefficiently in the form of electricity, this might offer a way ofstoring electricity, making theelectrical grid more efficient and variable power suppliers (like wind turbines) more useful in

meeting energy needs. The practicality of this depends heavily upon the cost of making massive,unbroken nanotube structures, and their failure rate under stress. Ultra-short SWNTs (US-tubes)have been used as nanoscaled capsules for delivering MRI contrast agents in vivo.

Nitrogen-doped carbon nanotubes may replaceplatinumcatalysts used to reduce oxygen infuelcells. A forest of vertically-aligned nanotubes can reduce oxygen in alkaline solution moreeffectively than platinum, which has been used in such applications since the 1960s. Thenanotubes have the added benefit of not being subject to carbon monoxide poisoning.
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Discovery

A 2006 editorial written by Marc Monthioux and Vladimir Kuznetsov in the journal Carbondescribed the interesting and often misstated origin of the carbon nanotube. A large percentageof academic and popular literature attributes the discovery of hollow, nanometer-size tubescomposed of graphitic carbon to Sumio IijimaofNECin 1991

In 1952 L. V. Radushkevich and V. M. Lukyanovich published clear images of 50 nanometerdiameter tubes made of carbon in the SovietJournal of Physical Chemistry. This discovery waslargely unnoticed, as the article was published in the Russian language, and Western scientists'access to Soviet press was limited during the Cold War. It is likely that carbon nanotubes wereproduced before this date, but the invention of thetransmission electron microscope(TEM)allowed direct visualization of these structures.

Carbon nanotubes have been produced and observed under a variety of conditions prior to 1991.A piiiiiaper by Oberlin, Endo, and Koyama published in 1976 clearly showed hollow carbonfibers with nanometer-scale diameters using a vapor-growth technique. Additionally, the authorsshow a TEM image of a nanotube consisting of a single wall of graphene. Later, Endo has

referred to this image as a single-walled nanotube.

In 1979 John Abrahamson presented evidence of carbon nanotubes at the 14th BiennialConference of Carbon at Pennsylvania State University. The conference paper described carbonnanotubes as carbon fibers which were produced on carbon anodes during arc discharge. Acharacterization of these fibers was given as well as hypotheses for their growth in a nitrogenatmosphere at low pressures

In 1981 a group of Soviet scientists published the results of chemical and structuralcharacterization of carbon nanoparticles produced by a thermocatalytical disproportionation ofcarbon monoxide. Using TEM images and XRDpatterns, the authors suggested that their

carbon multi-layer tubular crystals were formed by rolling graphene layers into cylinders.They speculated that by rolling graphene layers into a cylinder, many different arrangements ofgraphene hexagonal nets are possible. They suggested two possibilities of such arrangements:circular arrangement (armchair nanotube) and a spiral, helical arrangement (chiral tube).

In 1987, Howard G. Tennett of Hyperion Catalysis was issued a U.S. patent for the production of"cylindrical discrete carbon fibrils" with a "constant diameter between about 3.5 and about70 nanometers..., length 102 times the diameter, and an outer region of multiple essentiallycontinuous layers of ordered carbon atoms and a distinct inner core...."

Iijima's discovery of multi-walled carbon nanotubes in the insoluble material of arc-burned

graphite rods in 1991 and Mintmire, Dunlap, and White's independent prediction that if single-walled carbon nanotubes could be made, then they would exhibit remarkable conductingproperties helped create the initial buzz that is now associated with carbon nanotubes. Nanotuberesearch accelerated greatly following the independent discoveries by Bethune at IBM and Iijimaat NEC ofsingle-walledcarbon nanotubes and methods to specifically produce them by addingtransition-metal catalysts to the carbon in an arc discharge. The arc discharge technique waswell-known to produce the famed Buckminster fullerene on a preparative scale, and these resultsappeared to extend the run of accidental discoveries relating to fullerenes. The originalobservation of fullerenes in mass spectrometry was not anticipated, and the first mass-production
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technique by Krtschmer and Huffman was used for several years before realizing that itproduced fullerenes.

The discovery of nanotubes remains a contentious issue. Many believe that Iijima's report in1991 is of particular importance because it brought carbon nanotubes into the awareness of thescientific community as a whole.

Books

Carbon Nanotube Science, by P.J.F. Harris, Cambridge University Press, 2009. Book : Carbon Nanotube - Multifunctional Material, Edited by Prakash R. Somani and

M. Umeno, Applied Science Innovations Pvt. Ltd., India. The Application of Carbon Nan tubes and Graphene to Electronics .

References

1. ^ abc Wang, X.; Li, Q.; Xie, J.; Jin, Z.; Wang, J.; Li, Y.; Jiang, K.; Fan, S. (2009). "Fabrication ofUltralong and Electrically Uniform Single-Walled Carbon Nan tubes on Clean Substrates".NanoLetters9 (9): 31373141. doi:10.1021/nl901260b. PMID19650638.

2. ^ Mintmire, J.W.; Dunlap, BI; White, CT (3 February 1992). "Are Fullerene Tubules Metallic?".Physical Review Letters68 (5): 631634. doi:10.1103/PhysRevLett.68.631. PMID10045950.

3. ^ Dekker, Cees (1999). "Carbon nanotubes as molecular quantum wires"(PDF).Physics Today52: 2228. doi:10.1063/1.882658.http://www.physicstoday.org/vol-56/iss-2/pdf/vol52no5p22-28.pdf.

4. ^ Martel, R.; Derycke, V.; Lavoie, C.; Appenzeller, J.; Chan, K. K.; Tersoff, J.; Avouris, Ph.(2001). "Ambipolar Electrical Transport in Semiconducting Single-Wall Carbon Nan tubes".Physical Review Letters87: 256805. doi:10.1103/PhysRevLett.87.256805.

5. ^ "Carbon Solutions, Inc.".http://www.carbonsolution.com.6. ^ "CarboLex".http://carbolex.com.7. ^ Flahaut, E.; Bacsa, R; Peigney, A; Laurent, C (2003). "Gram-Scale CCVD Synthesis of

Double-Walled Carbon Nan tubes". Chemical Communications12 (12): 14421443.doi:10.1039/b301514a.PMID12841282.

8. ^ ab Liu, Lei; Guo, G. Y.; Jayanthi, C. S.; Wu, S. Y. (2002). "Colossal Paramagnetic Moments inMetallic Carbon Nanotori".Physical Review Letters88: 217206.doi:10.1103/PhysRevLett.88.217206.

9. ^ Huhtala, Maria (2002)."Carbon nanotube structures: molecular dynamics simulation at realisticlimit"(PDF). Computer Physics Communications146: 30. doi:10.1016/S0010-4655(02)00432-0.http://www.princeton.edu/~msammalk/publications/cpc146_02.pdf.

10.^ Liu, Q; Ren, W; Chen, Z; Yin, L; Li, F; Cong, H; Cheng, H (2009). "Semiconducting propertiesof cup-stacked carbon nanotubes". Carbon47: 731. doi:10.1016/j.carbon.2008.11.005.http://carbon.imr.ac.cn/file/Journal/2009/1249016438117.pdf.

11.^ "A Better Way to Make Nanotubes". Berkeley Lab.. January 5, 2009.

http://newscenter.lbl.gov/feature-stories/2009/01/05/better-way-to-make-nanotubes/.12.^ "Carbon Nanohoops: Shortest Segment of a Carbon Nanotube Synthesized". Berkeley Lab..

http://www.lbl.gov/msd/assets/docs/highlights/09-Bertozzi.pdf.13.^ "Synthetic organic chemistry".A centre of chemistry excellence. Nature. October 7, 2009.

http://www.nature.com/naturejobs/2009/091008/full/nj0264.html#a-centre-of-chemistry-excellence.

14.^ Zhao, X.; Liu, Y.; Inoue, S.; Suzuki, T.; Jones, R. O.; Andol, Y. (2004). "Smallest CarbonNanotube is 3 in Diameter".Physical Review Letters92 (12): 125502.doi:10.1103/PhysRevLett.92.125502.PMID15089683.
http://www.cup.cam.ac.uk/catalogue/catalogue.asp?isbn=9780521828956http://www.applied-science-innovations.com/http://www.applied-science-innovations.com/http://www.printedelectronicsworld.com/articles/the_application_of_carbon_nanotubes_and_graphene_to_electronics_00001499.asphttp://en.wikipedia.org/wiki/Carbon_nanotube#cite_ref-Longest_0-0http://en.wikipedia.org/wiki/Carbon_nanotube#cite_ref-Longest_0-1http://en.wikipedia.org/wiki/Carbon_nanotube#cite_ref-Longest_0-2http://en.wikipedia.org/wiki/Digital_object_identifierhttp://en.wikipedia.org/wiki/Digital_object_identifierhttp://dx.doi.org/10.1021%2Fnl901260bhttp://en.wikipedia.org/wiki/PubMed_Identifierhttp://en.wikipedia.org/wiki/PubMed_Identifierhttp://www.ncbi.nlm.nih.gov/pubmed/19650638http://en.wikipedia.org/wiki/Carbon_nanotube#cite_ref-1http://en.wikipedia.org/wiki/Digital_object_identifierhttp://dx.doi.org/10.1103%2FPhysRevLett.68.631http://en.wikipedia.org/wiki/PubMed_Identifierhttp://www.ncbi.nlm.nih.gov/pubmed/10045950http://www.ncbi.nlm.nih.gov/pubmed/10045950http://www.ncbi.nlm.nih.gov/pubmed/10045950http://en.wikipedia.org/wiki/Carbon_nanotube#cite_ref-2http://www.physicstoday.org/vol-56/iss-2/pdf/vol52no5p22-28.pdfhttp://www.physicstoday.org/vol-56/iss-2/pdf/vol52no5p22-28.pdfhttp://en.wikipedia.org/wiki/Digital_object_identifierhttp://dx.doi.org/10.1063%2F1.882658http://www.physicstoday.org/vol-56/iss-2/pdf/vol52no5p22-28.pdfhttp://www.physicstoday.org/vol-56/iss-2/pdf/vol52no5p22-28.pdfhttp://www.physicstoday.org/vol-56/iss-2/pdf/vol52no5p22-28.pdfhttp://www.physicstoday.org/vol-56/iss-2/pdf/vol52no5p22-28.pdfhttp://en.wikipedia.org/wiki/Carbon_nanotube#cite_ref-3http://en.wikipedia.org/wiki/Digital_object_identifierhttp://dx.doi.org/10.1103%2FPhysRevLett.87.256805http://en.wikipedia.org/wiki/Carbon_nanotube#cite_ref-4http://www.carbonsolution.com/http://www.carbonsolution.com/http://www.carbonsolution.com/http://en.wikipedia.org/wiki/Carbon_nanotube#cite_ref-5http://carbolex.com/http://carbolex.com/http://carbolex.com/http://carbolex.com/http://en.wikipedia.org/wiki/Carbon_nanotube#cite_ref-6http://en.wikipedia.org/wiki/Digital_object_identifierhttp://dx.doi.org/10.1039%2Fb301514ahttp://dx.doi.org/10.1039%2Fb301514ahttp://en.wikipedia.org/wiki/PubMed_Identifierhttp://en.wikipedia.org/wiki/PubMed_Identifierhttp://www.ncbi.nlm.nih.gov/pubmed/12841282http://en.wikipedia.org/wiki/Carbon_nanotube#cite_ref-nanotori_7-0http://en.wikipedia.org/wiki/Carbon_nanotube#cite_ref-nanotori_7-1http://en.wikipedia.org/wiki/Digital_object_identifierhttp://dx.doi.org/10.1103%2FPhysRevLett.88.217206http://dx.doi.org/10.1103%2FPhysRevLett.88.217206http://en.wikipedia.org/wiki/Carbon_nanotube#cite_ref-8http://www.princeton.edu/~msammalk/publications/cpc146_02.pdfhttp://www.princeton.edu/~msammalk/publications/cpc146_02.pdfhttp://www.princeton.edu/~msammalk/publications/cpc146_02.pdfhttp://www.princeton.edu/~msammalk/publications/cpc146_02.pdfhttp://en.wikipedia.org/wiki/Digital_object_identifierhttp://en.wikipedia.org/wiki/Digital_object_identifierhttp://dx.doi.org/10.1016%2FS0010-4655(02)00432-0http://www.princeton.edu/~msammalk/publications/cpc146_02.pdfhttp://en.wikipedia.org/wiki/Carbon_nanotube#cite_ref-9http://carbon.imr.ac.cn/file/Journal/2009/1249016438117.pdfhttp://carbon.imr.ac.cn/file/Journal/2009/1249016438117.pdfhttp://en.wikipedia.org/wiki/Digital_object_identifierhttp://dx.doi.org/10.1016%2Fj.carbon.2008.11.005http://carbon.imr.ac.cn/file/Journal/2009/1249016438117.pdfhttp://en.wikipedia.org/wiki/Carbon_nanotube#cite_ref-10http://newscenter.lbl.gov/feature-stories/2009/01/05/better-way-to-make-nanotubes/http://newscenter.lbl.gov/feature-stories/2009/01/05/better-way-to-make-nanotubes/http://newscenter.lbl.gov/feature-stories/2009/01/05/better-way-to-make-nanotubes/http://en.wikipedia.org/wiki/Carbon_nanotube#cite_ref-11http://www.lbl.gov/msd/assets/docs/highlights/09-Bertozzi.pdfhttp://www.lbl.gov/msd/assets/docs/highlights/09-Bertozzi.pdfhttp://en.wikipedia.org/wiki/Carbon_nanotube#cite_ref-12http://www.nature.com/naturejobs/2009/091008/full/nj0264.html#a-centre-of-chemistry-excellencehttp://www.nature.com/naturejobs/2009/091008/full/nj0264.html#a-centre-of-chemistry-excellencehttp://www.nature.com/naturejobs/2009/091008/full/nj0264.html#a-centre-of-chemistry-excellencehttp://www.nature.com/naturejobs/2009/091008/full/nj0264.html#a-centre-of-chemistry-excellencehttp://en.wikipedia.org/wiki/Carbon_nanotube#cite_ref-Smallest_at_MWCNT_13-0http://en.wikipedia.org/wiki/Digital_object_identifierhttp://dx.doi.org/10.1103%2FPhysRevLett.92.125502http://dx.doi.org/10.1103%2FPhysRevLett.92.125502http://en.wikipedia.org/wiki/PubMed_Identifierhttp://en.wikipedia.org/wiki/PubMed_Identifierhttp://www.ncbi.nlm.nih.gov/pubmed/15089683http://www.cup.cam.ac.uk/catalogue/catalogue.asp?isbn=9780521828956http://www.applied-science-innovations.com/http://www.applied-science-innovations.com/http://www.printedelectronicsworld.com/articles/the_application_of_carbon_nano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