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INTRODUCTION Carbon nanotubes ( CNTs ) are allotropes of carbon with a cylindrical nanostructure. A carbon molecules that resembles a cylinder made out of chicken wire .

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Applications of- nanotechnology, electronics, optics, field of materials science, potential uses in architectural fields ,construction of body armor . The remarkable properties, allow drive towards miniaturization at the nanometer scale. Nanotechnology, predicted to spark a series of industrial revolutions in the next two decades. CNT’s conduct electricity better than copper, transmit heat better than diamond, they rank among the strongest materials. Several decades from now we may see integrated circuits with components and wires made from nanotubes.

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CNT’s are unique “1-D" , can be envisioned as rolled single sheets graphene. This rolling can be done at different angles and curvatures resulting in different properties . Length-to-diameter ratio, can be as high as 132,000,000:1. Diameter of CNT’s app.1/50K width of hair. Basically there two types of CNT’s Single-walled nanotubes Multi –walled nanotubes Armchair nanotube Zig-zag nanotube ELECTRONIC STRUCTURE OF CNT

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Typical diameter of a single-wall nanotube was just one or two nanometers. Band gap can vary 0 to 2 eV , their electrical conductivity can show metallic or semiconducting behaviour SWNT’s LED’s , Photo detectors, therapeutic approaches, optoelectronic memory devices Production of the first intramolecular logic gate using SWNT’s FETs Single -wallED nanotubes (SWNTs) Graphene is an atomic-scale honeycomb lattice

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MWNTs are wrapped into multiple layers , parchment scroll or of multiple cylinders, one inside the other. Multi-walled nanotubes Few tens of nanometers across The highest tensile strength of an individual MWNT that has been tested is 63 Gpa . Appln Photo catalytic H2 production from water. -Ni coated MWNTs 1-D magnetic material. -Enhancing anodic performance of Enterobacter fuel cell. - Multi channel MOSFETs

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MORE ON ELECTRONIC PROPERTIES Field emission Unlike conventional conducting polymer, e - can propagate freely MWNTs interactions between adjacent layers is the subject of ongoing research. Combining different CNT, and supplementing them with gate electrodes, there is the potential to make variety of electronic devices, range from quantum wires to FETs Perfect metallic nanotube should be a ballistic conductor. A defect-free carbon nanotube is like an optical fibre Electron microscopy In several areas of industry, includes lighting and displays (low vg) .

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2. Conductance of nanotubes Nanotube Transistors Behave like p-MOSFETs Nanotube rectifier created by the intersection of two tubes such as a metallic tube crossing over a semiconducting tube

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3. Nanotubes as model 1-Dimensional systems e- can travel for long distances without being backscattered. In metals , scattering length from lattice vibrations are typically several nanometers An e- in a 1-D system can only scatter by completely reversing its direction. 4. Nano-electromechanical devices growth on surfaces with micro-fabrication methods, new studies and applications new studies and applications, novel CNT (electronic property retraced) eg Conductance of the tube drops sharply, when tube is deformed , restored into its original value when the deformation is retracted.

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5. Nanotubes for chemical sensors Detect small conc’s of gas molecules with ultra high sensitivity . Sensing applns - environmental monitoring, -control of chemical processes - agriculture and medical areas

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POTENTIAL APPLICATIONS Structura l- Create stab-proof and bulletproof clothing. In electrical circuits (CNFETs) - operate at room temp , capable of dig switching using a e- -2001 IBM researchers -constructive destruction - 1 mm–thick CNTs, used special material to fabricate coolers As paper batteries- cellulose sheet, integrates all of the battery components in a single structure. Solar cells- New Jersey Institute of Technology , use CNTs complex, formed by a mixture of CNTs Ultra capacitors- MIT Laboratory for EES uses nanotubes to improve ultracapacitors

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CURRENT APPLICATIONS Bulk carbon nanotubes have already been used as composite fibers in polymer as s to improve the (MET) properties of the bulk product (no tensile strength) Easton-Bell Sports Inc- CNT technology in a no. of their bicycle comp Zyvex Performance Materials- has also built a maritime vessel Amroy Europe Oy- Hybtonite carbon nanoepoxy resins lightweight 8,000 lb boat that can carry a payload of 15,000 lb over a range of 2,500 miles

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Other current applications include Aligned nanotubes are preferred for many applns In tissue engineering , CNTs act as scaffolding for bone growth. Kanzius cancer therapy , SWNTs around cancerous cells Ideal for high-reliability touch screens and flexible displays. A nanoradio a radio receiver consisting of SWNTs(2007) Sheet of nanotubes can operate as a loudspeaker if an alternating current is applied. Nitrogen-doped carbon nanotubes may replace platinum catalysts(CO poisoning) Ultra-short SWNTs ( US-tubes ) have been used as nanoscaled capsules for delivering MRI contrast agents in vivo.

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An Insight into the Exclusive Applications… ….into the future No signs not compete, these cons will almost surely die with the present. Futuristic technological revolution involving the nanomachines and the assemblers-disassemblers brotherhood , silicon based electronics will surely be a misfit . bird’s view -As the counterpart of the silicon-based electronic devices. -As building blocks of these nanoscale devices. -Fundamental part of the manipulating mechanism in an assembler or a disassembler

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Applications and challenges 1st commercial device that uses MWNT may be a lamp Field emission, eg Samsung, for example, plans to market a flat-panel colour display (MWNTs 2yrs). CNTs used to store hydrogen to power electric vehicles. Techniques, painstaking and utterly inappropriate for mass production . High-quality CNTs, only produced in very limited quantities. Commercial nanotube soot costs 10 times as much as gold! Appear destined to open up a host of new practical applications and improve our understanding nanometre scale. -As a part of observing medium such as in electron microscope .

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Disadvantages Lifetime (degradation- exposed to oxygen ) Reliability Difficulties in mass production, production cost High electric field or temperature gradients. Avalanche breakdow n, CNT (multi ch CNFETs)

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CONCLUSION Carbon nanotubes exhibit a wealth of properties and phenomena. Like any new technology, CNTs will have to outperform current technology to gain a foothold in commercial markets. In the past ten years or so, the remarkable EM properties of carbon nanotubes have captured the attention of researchers worldwide. novel structures, wide range of potential applications , billions of dollars. Turn nanoscience to a technology, need to grow CNTs and fabricate nanometre-sized devices on a large scale. Early efforts to characterize pure samples, difficulty in assembling. Future IC unavoidably rely on some sort of chemical "self-assembly" , quasi-1D systems and their practical applications.

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REFERENCE [1 ] Carbon Nanotube Science, by P.J.F. Harris, Cambridge University Press, 2009 . [2] Book : Carbon Nanotube - Multifunctional Material, Edited by Prakash R. Somani and M. Umeno , Applied Science Innovations Pvt. Ltd., India . [3] The Application of Carbon Nanotubes and Graphene to Electronics . [4] [5] [6]

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