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Mohini FatimaM. Tech (Sem  –III)

Roll No.: 12MTNT 10

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OUTLINES

 INTRODUCTION

 TYPES OF SWNT

 UNIQUE PROPERTIES OF SWNT

 RAMAN CHARACTERIZATION OF SWNT

 APPLICATIONS OF SWNT

 CHALLENGES OF SWNT

 REFERENCES

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INTRODUCTION

Carbon nanotubes (CNT) are among the amazing objects thatscience sometimes creates by accident without meaning to, butthat will likely revolutionize the technological landscapes of thecentury ahead.

Nanotubes are members of the fullerene structural family. Thename is derived from their long hollow structure with the wallsformed by one – atom thick sheets of carbon called Graphene.These sheets are rolled at specific and discrete angles.

The chemical bonding of nanotubes is composed entirely of sp2 bonds, similar to those of graphite.

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INTRODUCTION

CNT are categorized as:

i. Single  – wall Nanotubes (SWNT)

ii. Multi  – wall Nanotubes (MWNT)

SWNT are tubes of graphite that are normally capped at the ends.

SWNT have a single cylindrical wall.

The structure of a SWNT can be visualized as a layer of graphite, a

single atom thick, called graphene, which is rolled into a seamless

cylinder.

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TYPES OF SWNT

An understanding of SWNT structure requires familiarity with the concept of

nanotube chirality.

 Chirality describes both the orientation and diameter to which the sheet is rolled.

Each SWNT on the chirality map is defined by two integers (n, m).

 (n , n) Armchair tubes ϴ = 300

 

(n , 0) Zigzag tubesϴ

 = 00

  (n , m) Chiral tubes 00 < ϴ < 300 

Where, ϴ = angle of helicity

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UNIQUE PROPERTIES OF SWNT

I. Mechanical Properties:

 Young’s modulus ~ 1 TPa Tensile strength ~ 30 GPa Elongation at break ~ 16% High aspect ratio ~1,000 – 10,000

II. Electrical Properties: Electrical conductivity is several orders of magnitude higher than copper For a given (n, m) nanotube

n = m, Nanotube is Metallic

n – 3 = multiple of 3, Nanotube is a small bandgap semiconductor

0.w Nanotube is a moderate semiconductor

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UNIQUE PROPERTIES OF SWNT

III. Thermal Properties:

SWNT are very good thermal conductors along the tube axis, but goodinsulators laterally to the tube axis.

σ ~ 3500 W/m.K along the axis σ ~ 1.52 W/m.K across the axis Temperature stability ~ 28000 C in Vacuum

~ 7500 C in Air 

IV. Optical Properties: SWNT have distinct optical absorption and fluorescence response.Coating of SWNT are transparent in the visible and IR regions of the

spectrum.

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Typical Raman spectrum of SWNT , obtained with 633 nm laser excitation.

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 APPLICATIONS OF SWNT Flat panel displays, conductive plastics, field storage batteries

Micro – electronics / semiconductors

Conducting composites

Controlled drug delivery

 Artificial muscles

Nanolithography

Hydrogen storage

Data storage

Solar storage

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CHALLENGES OF SWNT

 Technical hurdles in the areas of purity, selectivity and dispersibility have so far limited

the widespread application of SWNT.Purity:i. Various manufacturing processes lead to products which are contaminated to

 varying degrees.ii. Secondary processes are necessary to remove these contaminants to provide

product of sufficient purity.

 Selectivity:i. It is desirable to isolate the types of tubes from one another.ii. Laboratory scale methods designed to achieve a high degree of selectivity have

been reported.

 Dispersibility:i. SWNT are difficult to disperse because of their tendency to form ropes or bundles.ii. Exfoliation of bundles can be achieved by sonication of aqueous solution of SWNT

in the presence of surface active molecules.

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REFERENCES

• b 

•b Wang, X.; Li, Qunqing; Xie, Jing; Jin, Zhong; Wang, Jinyong; Li, Yan; Jiang, Kaili; Fan, Shoushan

(2009). "Fabrication of Ultralong and Electrically Uniform Single-Walled Carbon Nanotubes onClean Substrates". Nano Letters 9 (9): 3137 –

3141.Bibcode:2009NanoL...9.3137W. doi:10.1021/nl901260b. PMID 19650638. • Gullapalli, S.; Wong, M.S. (2011). "Nanotechnology: A Guide to Nano-Objects". Chemical

Engineering Progress 107 (5): 28 –32. •Mintmire, J.W.; Dunlap, B.I.; White, C.T. (1992). "Are Fullerene Tubules Metallic?". Phys. Rev.

Lett. 68 (5): 631 –

634. Bibcode:1992PhRvL..68..631M. doi:10.1103/PhysRevLett.68.631.PMID 10045950. •Dekker, C. (1999). "Carbon nanotubes as molecular quantum wires". Physics Today  52 (5): 22 –

28. Bibcode:1999PhT....52e..22D. doi:10.1063/1.882658. •Martel, R.; Derycke, V.; Lavoie, C.; Appenzeller, J.; Chan, K.; Tersoff, J.; Avouris, Ph. (2001).

"Ambipolar Electrical Transport in Semiconducting Single-Wall Carbon Nanotubes". Phys. Rev.

Lett. 87 (25):

256805. Bibcode:2001PhRvL..87y6805M.doi:10.1103/PhysRevLett.87.256805 . PMID 11736597. • Flahaut, E.; Bacsa, Revathi; Peigney, Alain; Laurent, Christophe (2003). "Gram-Scale CCVD

Synthesis of Double-Walled Carbon Nanotubes". Chemical Communications 12 (12): 1442 –

1443. doi:10.1039/b301514a. PMID 12841282. 

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