Carbon Nanotubes

Carbon Nanotubes - a breakthrough in sciencenanoTUBESCARBON

What are carbon nanotubes?

Carbon nanotubes(CNTs) areallotropes of carbon with acylindricalnanostructure.Nanotubes have been constructed with length-to-diameter ratio of up to 132,000,000:1 .They have unusual properties, which are valuable fornanotechnology,electronics,opticsand other fields of materials scienceand technology.Nanotubes are members of thefullerenestructural family.Thechemical bondingof nanotubes is composed entirely ofsp2bonds, similar to those ofgraphite.

History of the NanotubesThe history of carbon nanotubes is not entirely clear, giving proper credit to the person that invented the carbon nanotube has been the subject of several high tech debates among the scientific communities.The initial history of nanotubes started in the 1970s. A preparation of the planned carbon filaments was completed byMorinobu Endowho was earning his Ph.D. at the University of Orleans, France.In 1991 the true first invention of nanotube was finally made. In 1993 Iijima and Donald Bethune found single walled nanotubes known as buckytubes. This helped the scientific community make more sense out of not only the potential for nanotube research, but the use and existence of fullerenes.With this information, the complete discovery of carbon nanotubes was realized and Iijima and Bethune were ultimately credited with their discovery in their entirety.Roger Bacon is technically the first scientist to discover these hollow tubes of carbon that are changing lives on a daily basis.Since the initial rediscovery of the nanotubes in 1991, who discovered carbon nanotubes is no longer as important as who can come up with the most practical applications.

Types of carbon Nanotubes

Classified mainly in two types: SINGLE WALLED NANOTUBES MULTI WALLED NANOTUBES

OTHER RELATED STRUCTURES: TORUS NANOBUD GRAPHENATED CARBON NANOTUBES (g-CNTS) NITROGEN DOPED CARBON NANOTUBES (N-CNTS) PEAPOD CUP-STACKED CARBON NANOTUBE

SINGLE WALLED NANOTUBESDiameter :- 1 nanometer Band gap :- 0-2ev.SWNTs with diameters of an order of a nanometer can be excellent conductors.Their electrical conductivity can show metallic or semiconducting behaviour.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 of March 2010.SWNTs have been viewed as too expensive for widespread application but are forecast to make a large impact in electronics applications by 2020 according to The Global Market for Carbon Nanotubes report.

Single Walled Carbon Nanotubes

MULTI WALLED NANOTUBESMulti-walled nanotubes (MWNT) consist of multiple rolled layers (concentric tubes) of graphene.Interlayer distance :- 3.4 To describe structure of MWNT there are two models:- 1. Russian doll model 2. Parchment model

MULTI WALLED NANOTUBES

OTHER RELATED STRUCTURESTORUS :-It is a carbon nanotube bent in a torus shape (i.e. doughnut shape)NANOBUD :-Carbon Nanobuds are created combining carbon nanotubes and fullerenesGRAPHENATED CARBON NANOTUBE :-They are new hybrids that combines graphitic foliates grown along the sidewalls of MWNT.NITROGEN DOPED CARBON NANOTUBE :-These are used for enhancing storage capacity of Li-ion batteries. N-doping provides defects in the walls of CNT's allowing for Li ions to diffuse into inter-wall spacePEAPOD :-A carbon peapod is a novel hybrid carbon material which traps fullerene inside a Carbon nanotube.CUP-STACKED CARBON NANOTUBES :- CSCNTs exhibit semiconducting behaviours due to the stacking microstructure of graphene layers.

OTHER RELATED STRUCTURES

TORUS

NANOBUD

GRAPHENATED CNT

NITROGEN DOPED CNT

PEAPOD

CUP STACKED CNT

PROPERTIESSTRENGTH :- Carbon nanotubes are the strongest, flexible and stiffest materials yet discovered in terms of tensile strength and elastic modulus respectively. HARDNESS :- The hardness (152 Gpa) and bulk modulus (462546 Gpa) of carbon nanotubes are greater than diamond, which is considered the hardest material. ELECTRICAL PROPERTIES:- Because of the symmetry and unique electronic structure of graphene, nanotube has a very high current carrying capacity.THERMAL CONDUCTIVITY:- All nanotubes are expected to be very good thermal conductors along the tube, but good insulators laterally to the tube axis.

PROPERTIES (Cont.)EM WAVE ABSORPTION:- There has been some research on filling MWNTs with metals, such as Fe, Ni, Co, etc., to increase the absorption effectiveness of MWNTs in the microwave regime.THERMAL PROPERTIES:- All nanotubes are expected to be very good thermal conductors along the tube, but good insulators laterally to the tube axis. TOXICITY:- 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 fibrotic reactions. CRYSTALLOGRAPHIC DEFECT:- As with any material, the existence of a crystallographic defect affects the material properties. Defects can occur in the form of atomic vacancies.

Mechanical Properties of Engineering FibersFiber materialSpecific DensityYoung's modulus(Tpa)Strength (Gpa)Strain at break(%)Carbon Nanotube 1.3 2110 6010HS Steel 7.80.24.1 300010^6 10^7Copper4006 x 10^7Carbon fiber-Pitch10002 - 8.5 x 10^6Carbon fiber-PAN8 - 1056.5 - 14 x 10^6

SYNTHESISThere are three methods for the synthesis of carbon nanotubes :-ARC DISCHARGE LASER ABLATION CHEMICAL VAPOUR DEPOSITION

ARC DISCHARGE

METHODACTUAL APPARTUS

LASER ABLATIONMETHODACTUAL APPARTUS

CHEMICAL VAPOUR DEPOSITIONMETHODACTUAL APPARTUS

APPLICATIONSBiomedicalResearchers from Rice University and State University of New York have shown that the addition of low weight% of carbon nanotubes can lead to significant improvements in the mechanical properties of biodegradable polymeric nano composites for applications in tissue engineering including bone,cartilage,muscle and nerve tissue.Structural

Electrical circuits

Because of the carbon nanotube's superior mechanical properties, many structures have been proposed ranging from everyday items like clothes and sports gear to combat jackets andspace elevators. However, the space elevator will require further efforts in refining carbon nanotube technology, as the practical tensile strength of carbon nanotubes must be greatly improvedNanotube-basedtransistors, also known ascarbon nanotube field-effect transistors (CNTFETs), have been made that operate at room temperature and that are capable of digital switching using a single electron . However, one major obstacle to realization of nanotubes has been the lack of technology for mass production

APPLICATIONS (Cont.)Electrical cables and wiresWires for carrying electric current may be fabricated from pure nanotubes and nanotube-polymer composites. It has already been demonstrated that carbon nanotube wires can successfully be used for power or data transmission.Solar cellsOne of the promising applications of single-walled carbon nanotubes (SWNTs) is their use in solar panels, due to their strong UV/Vis-NIR absorption characteristics. Research has shown that they can provide a sizable increase in efficiency, even at their current unoptimized stateRadar absorptionRadars work in the microwave frequency range, which can be absorbed by MWNTs. Applying the MWNTs to the aircraft would cause the radar to be absorbed and therefore seem to have a smallerradar cross-section. One such application could be to paint the nanotubes onto the planeSupercapacitorMIT Research Laboratory of Electronics uses nanotubes to improvesupercapacitors. The activated charcoal used in conventional ultracapacitors has many small hollow spaces of various size, which create together a large surface to store electric charge.

APPLICATIONS (Cont.)Optical power detectorsA spray-on mixture of carbon nanotubes and ceramic demonstrates unprecedented ability to resist damage while absorbing laser light. Such coatings that absorb as the energy of high-powered lasers without breaking down are essential for optical power detectors that measure the output of such lasers.AcousticsOne of the promising applications of single-walled carbon nanotubes (SWNTs) is their use in solar panels, due to their strong UV/Vis-NIR absorption characteristics. Research has shown that they can provide a sizable increase in efficiency, even at their current unoptimized stateEnvironmental remediationA CNT nano-structured sponge (nanosponge) containing sulfur and iron is more effective at soaking up water contaminants such as oil, fertilizers, pesticides and pharmaceuticals. Their magnetic properties make them easier to retrieve once the clean-up job is done.Water treatmentIt has been shown that carbon nanotubes exhibit strong adsorption affinities to a wide range of aromatic and aliphatic contaminants in water,due to their large and hydrophobic surface areas. They also showed similar adsorption capacities as activated carbons in the presence of natural organic matter. As a result, they have been suggested as promising adsorbents for removal of contaminant in water and wastewater treatment systems.

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