This document provides an overview of carbon nanotubes, including their properties, types (single-walled vs multi-walled), methods of synthesis (arc discharge, laser ablation, chemical vapor deposition), applications, challenges and future outlook. Carbon nanotubes have extraordinary strength and unique electrical properties. They show promise for applications in electronics, optics, energy storage and more, but challenges remain in controlling their growth and assembly at scale.

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4.  Properties
 Advantages
 Disadvantages
 Applications
 Challenges
 Future
 Conclusion

5. INTRODUCTION
Carbon nanotubes are :-
• Allotropes of carbon with a
cylindrical nanostructure.
• Hexagonally shaped arrangements
of carbon atoms that have been
rolled into tubes.
• Nanotubes have been constructed
with length-to-diameter ratio of up
to 132,000,000:1,significantly
larger for any other material.
• Their name is derived from their
long, hollow structure with the
walls formed by one-atom-thick
sheets of carbon called Graphene.

6. These sheets are rolled at specific and discrete “
chiral “ angles, and the combination of rolling
angle and radius decides the nanotube
properties.
They posses unusual properties, valuable for
nanotechnology, electronics, optics, Mechanical
Engg. and other fields of material science &
Technology.

7. Timeline Of Carbon Nanotubes
1952- L.V Radushkevich published tubes made up of carbon
From Soviet Union.
1976- koyama showed carbon fibers with Nano scale dia.
1979- John Abrahamson presented evidence for CNT.
1981-Soviet scientists chemical structural characterization of
CNTs.
1987- Howard g. had patent for production of cylindrical
discrete carbon fibrils.

8. They were discovered
In 1991 by the Japanese
electron microscopist
SUMIO IIJIMA NEC
Laboratory in Tsukuba-- used
high-resolution transmission
electron microscopy to
observe carbon
nanotubes, And into the
awareness of the scientific
community .

9. Single-walled
Nanotubes
Carbon (SWNTS)
Nanotubes Multi-walled
Nanotubes
(MWNTS)

10. Most single-walled nanotubes
(SWNT) have a diameter of
close to 1 nanometre, with a
tube length that can be many
millions of times longer.
The structure of a SWNT can be
conceptualized by wrapping a
one-atom-thick layer of
graphite called graphene into a
seamless cylinder.

11. The way the graphene sheet is
wrapped is represented by a pair of
indices (n,m) called the chiral
vector.
The integers n and m denote the
number of unit vectors along two
directions in the honeycomb crystal
lattice of graphene.
If m = 0, the nanotubes are called The (n,m) nanotube naming
"zigzag". If n = m, the nanotubes scheme can be thought of as a
vector (Ch) in an infinite
are called "armchair". graphene sheet that describes
Otherwise, they are called "chiral". how to "roll up" the graphene
sheet to make the nanotube. T
denotes the tube axis, and a1
and a2 are the unit vectors of
graphene in real space.

13. Various Types Of SWNT
Armchair (n,n) Zigzag (n,0)

14. Chiral (n,m)

15. 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.
• In the Russian Doll model, sheets
of graphite are arranged in concentric
cylinders.
• In the Parchment model, a single
sheet of graphite is rolled in around
itself, resembling a scroll of parchment
or a rolled newspaper.(The Russian
Doll structure is observed more
commonly).

16. About MWNT
 The telescopic motion ability of inner shells
and their unique mechanical properties will
permit the use of multi-walled nanotubes as
main movable arms in coming Nano
mechanical devices.

17. Other carbon nanotube structures
Torus
carbon nanotube bent into a torus
(doughnut shape). Nanotori
are predicted to have many
unique properties, such as
magnetic moments 1000
times larger than previously
expected for certain specific
radii. Properties such as
magnetic moment, thermal
stability, etc. vary widely
depending on radius of the
torus and radius of the tube.

18.  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" are covalently bonded to the
outer sidewalls of the underlying
carbon.
 They good field emitters. In composite
materials, the attached fullerene
molecules may function as molecular
anchors preventing slipping of the
nanotubes, thus improving the
composite’s mechanical properties.

19.  Graphenated carbon nanotubes (g-CNTs) :-
Graphenated CNTs are a relatively new hybrid that
combines graphitic foliates grown along the sidewalls of
multi walled or bamboo style CNTs use in super capacitor
applications.
 Peapod :-
A Carbon peapod] is a novel hybrid carbon material which
traps fullerene inside a carbon nanotube.
 Cup-stacked carbon nanotubes :-
CSCNTs exhibit semiconducting behaviors due to the
stacking microstructure of graphene layers.

20. Synthesis of Carbon Nanotubes
Techniques have been developed to produce nanotubes
in sizeable quantities.
some of them are:-
Synthesis
Chemical
Arc Laser vapor
discharge Ablation deposition
(CVD)

21. Arc discharge
• CNT production requires 3 elements ,
I. Carbon feed
II. Metal catalyst
III. Heat
a) Two Graphite electrodes placed in an inert Helium
atmosphere .
b) When DC current is passed anode is consumed and
material forms on cathode.
c) For SWNT mixed metal catalyst is inserted into anode
d) Pure iron catalyst + Hydrogen-inert gas mixture gives 20
to 30cm long tube.
e) The nanotubes were initially discovered using this
technique, it has been the most widely-used method of
nanotube synthesis.

22. Laser Ablation
• In the laser ablation process, a pulsed
laser vaporizes a graphite target in a
high-temperature reactor while an inert
gas is 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 with a
controllable diameter determined by the
reaction temperature.
• it is more expensive than either arc
discharge or chemical vapor deposition.

23. Chemical vapor deposition (CVD)
• During CVD, a substrate is prepared with a layer
of metal catalyst articles, 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 700°c.
• To initiate the growth of nanotubes, two gases
are bled into the reactor: a process gas (such as
ammonia, nitrogen or hydrogen) and a carbon-
containing gas (such as
acetylene, ethylene, ethanol or methane).
• 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.

24. Arc Discharge Method Chemical Vapor Deposition Laser Ablation
(Vaporization)
Connect two graphite rods Place substrate in oven, heat Blast graphite with intense
to a power supply, place to 600 C, and slowly add a laser pulses; use the laser
them millimeters apart, and carbon-bearing gas such as pulses rather than electricity
throw switch. At 100 amps, methane. As gas to generate carbon gas from
carbon vaporizes in a hot decomposes it frees up which the NTS form; try
plasma. carbon atoms, which various conditions until hit
recombine in the form of on one that produces
NTS prodigious amounts of
SWNTS
Can produce SWNT and Easiest to scale to industrial Primarily SWNTS, with a
MWNTs with few structural production; long length large diameter range that
defects can be controlled by varying
the reaction temperature
Tubes tend to be short with NTS are usually MWNTS and By far the most costly,
random sizes and directions often riddled with defects because requires expensive
lasers

25. Visual Promo of CNT Synthesis

26. The The shortest The thinnes
observation The thinnest
carbon t
of carbon
nanotube is freestandin
the longest the organic nanotube is
g single-
carbon compound armchair
walled
nanotubes cycloparaphe (2,2) CNT
carbon
(18.5 cm nylene, which with a
was nanotube is
long) was diameter of
synthesized about 4.3 Å
reported in 3 Å.
in early 2009. in diameter.
2009.

27. Properties Of Carbon Nanotubes
 Carbon nanotubes are the strongest, flexible and stiffest
materials yet discovered in terms of tensile strength and
elastic modulus respectively.
 This strength results from the covalent sp2 bonds formed
between the individual carbon atoms(which is stronger than
the sp3 bonds found in Diamond & Alkenes).
 CNTs are not nearly as strong under compression. Because of
their hollow structure and high aspect ratio, they tend to
undergo buckling when placed under compressive, torsional
or bending stress.

28. Hardness :-
• The hardness(152 Gpa) and bulk modulus(462–546) of carbon
nanotubes are greater than diamond, which is considered the
hardest material.(:that of diamond is 150GPa & 420GPa).
Kinetic Property:-
• Multi-walled nanotubes, multiple concentric nanotubes precisely
nested within one another, exhibit a striking telescoping property
whereby an inner nanotube core may slide, almost without
friction, within its outer nanotube shell thus creating an
atomically perfect linear or rotational bearing, the precise
positioning of atoms to create useful machines.

29. Electrical Properties:-
Because of the symmetry and unique electronic
structure of graphene, the structure of a nanotube
strongly affects its electrical properties.-
Very high current carrying capacity.
Thermal Conductivity :-
All nanotubes are expected to be very good thermal
conductors along the tube.( Measurements show that a
SWNT has a room-temperature thermal conductivity more
than copper.)

30. Optical properties:-
EM Wave absorption :-
• current military push for radar absorbing materials (RAM) to
better the stealth characteristics of aircraft and other military
vehicles. (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. (Measurements show that a SWNT has
a room-temperature thermal conductivity along its axis
of about 3500 W·m−1·K−1;] compare this to copper, a
metal well known for its good thermal
conductivity, which transmits 385 W·m−1·K−1.)

31. Comparison of mechanical properties
Material Young's Modulus Tensile Strength Elongation At
(Tpa) (Gpa) Break (%)
SWNT ~1 (from 1 to 5) 13–53 16
Armchair SWNT 0.94 126.2 23.1
Zigzag SWNT 0.94 94.5 15.6-17.5
Chiral SWNT 0.92
MWNT 0.27-0.8--0.95 11-63-150
Stainless steel 0.186-0.214 0.38-1.55 15-50
Kevlar–29&149 0.06-0.18 3.6-3.8 ~2

32. 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.

33. Advantages
• Extremely small and lightweight.
• Resources required to produce them are plentiful, and
many can be made with only a small amount of
material
• Are resistant to temperature changes, meaning they
function almost just as well in extreme cold as they do
in extreme heat
• Improves conductive, mechanical, and flame barrier
properties of plastics and composites.
• Enables clean, bulk micromachining and assembly of
components.
• Improves conductive, mechanical, and flame barrier
properties of plastics and composites.

34. Disadvantages
• Despite all the research, scientists still don't
understand exactly how they work.
• Extremely small, so are difficult to work with.
• Currently, the process is relatively expensive to
produce the nanotubes.
• Would be expensive to implement this new
technology in and replace the older technology in
all the places that we could.
• At the rate our technology has been becoming
obsolete, it may be a gamble to bet on this
technology.

35. • Nano
electronics
• Doping
• Nano balance
• Nano
tweezers
• Data storage
• Magnetic
nanotube
• Nanogear

36. • Nanotube actuator
• Molecular Quantum wires
• Hydrogen Storage
• Noble radioactive gas storage
• Solar storage
• Waste recycling
• Electromagnetic shielding
• Dialysis Filters
• Thermal protection
• Nanotube reinforced composites
• Reinforcement of armour and other materials
• Reinforcement of polymer
• Avionics
• Collision-protection materials
• Fly wheels

37.  Growth mechanism of Fullerene and CNT is still a
mystery
 At present, they are not possible to grow in a
controlled way
 Still not able to select size and helicity during growth
 Making connection between CNTs is uncontrollable
now
 When bulk quantity is needed no manufacturing
techniques are available
 Manipulation of CNTs is another problem

39. References & Links
• www.sciencedaily.com?CNT
• www.En.wikianswers.org/CNT
• www.images.google.com/CNT
• www.youtube.com/CNT
• www.scribd.com
• www.microsoft.com/encarta
• http://www.pa.msu.edu/cmp/csc/ntproperties
• http://en.wikipedia.org/wiki/Nanotubes
• http://www.rdg.ac.uk/%7Escsharip/tubes.htm