This document provides information about carbon nanotubes. It begins with an acknowledgement and introduction section describing carbon nanotubes. It then discusses the history, chemistry, types (single-walled and multi-walled), methods of preparation (arc evaporation, laser vaporization, chemical vapor deposition), electrical and thermal properties, defects, and applications (water filtration, strengthening materials, capacitors, bone repair, displays, energy storage). It also notes potential health hazards from inhalation of short carbon nanotubes.

1. BARKHATULLAH UNIVERSITY
, BHOPAL
PRESENTATION- CARBON NANOTUBES

2. ACKNOWLEDGEMENT
 I would like to express my special thanks of
gratitude to my teacher MISS Sonalika as well as
our H.O.D Mr.Prabhat jain sir_who gave me the
golden opportunity to do this wonderful project on
the topic “ CARBON NANOTUBES “ which also
helped me in doing a lot of Research and i came
to know about so many new things. I am really
thankful to them. Secondly I would also like to
thank my friends who helped me a lot in finishing
this project within the limited time. I am making this
project not only for marks but to also increase my
knowledge . THANKS AGAIN TO ALL WHO HELPED
ME

3. introduction
Carbon nanotubes (CNTs) are
allotropes of carbon. These
cylindrical carbon molecules
have interesting properties
that make them potentially
useful in many applications in
nanotechnology, electronics,
optics and other fields of
materials science, as well as
potential uses in architectural
fields. They exhibit
extraordinary strength and
unique electrical properties,
and are efficient conductors of
heat.

4. History
In 1985, a molecule called buckminsterfullerene was discovered
by a group of researchers at Rice University. This molecule
consisted of 60 carbon atoms in sp 2 hybridized bonds arranged
in a surprisingly symmetric fashion. The Nobel Prize was awarded
to Richard Smalley, Robert Curl, and Harry Kroto for their
discovery of this new allotrope of carbon. This discovery was
groundbreaking for the now vibrant field of carbon
nanotechnology. Carbon nanotubes, discovered in 1991 by
Sumio Iijima, are members of the fullerene family. Their
morphology is considered equivalent to a graphene sheet
rolled into a seamless tube capped on both ends

5. Chemistry of CNT
Carbon is the most versatile element in the periodic table, owing
to the type, strength, and number of bonds it can form with many
different elements. The diversity of bonds and their corresponding
geometries enable the existence of structural isomers, geometric
isomers, and enantiomers.
Graphite
( Ambient conditions)
sp2 hybridization : planar
Diamond
(High temperature and pressure)
sp3 hybridization: tetrahedral
Nanotube/Fullerene
(certain growth conditions)
sp2 + sp3 character: cylindrical

6. Finite size of graphene layer has dangling bonds. These dangling
bonds correspond to high energy states.
Eliminates dangling bonds Increases Strain Energy
Total Energy decreases
+
Nanotube formation

7. CNT are rolled graphene sheets

8. Types of CNTs
 Single Wall CNT
(SWCNT)
 Multiple Wall CNT
(MWCNT)

9. SWCNT
 a single-walled carbon nanotube (SWCNT) is
a structure rolled from a sheet of graphene. It
can be divided into three kinds, such as
armchair, zigzag and chiral type, according
to its structure. However, it can also be
divided into three categories, including
metal, narrow-gap semiconductor and
moderate-gap semiconductor for its
electronic property, according to its rolling
direction. The helix of a SWNT causes the six
rings of a SWNT’s wall distorted, and makes
unsaturated double-bonds on the rings of a
SWNT to provide resistance while electrons
being conducted. Hence, differences in the
electronic property of a SWNT occur

10. Armchair (n,m) = (5,5)
= 30
Chiral (n,m) = (10,5)
0 < < 30
The graphene sheet labeled with the integers (n, m). The
diameter, chiral angle, and type can be determined by knowing
the integers (n, m).
The chiral angle is used to seprate carbon nanotubes in three classes differentiated by
their electronic properties: armchair (n = m, θ= 30 ˚), zig-zag (m = 0, n > 0, θ = 0 ˚), and
chiral (0 < |m| < n, 0 < θ < 30 ˚)

11. MWCNT
Multi-wall nanotubes can appear either in
the form of a coaxial assembly of SWNT
similar to a coaxial cable, or as a single
sheet of graphite rolled into the shape of a
scroll.
The diameters of MWNT are typically in the
range of 5 nm to 50 nm. The interlayer
distance in MWNT is close to the distance
between graphene layers in graphite.
MWNT are easier to produce in high volume
quantities than SWNT. However, the
structure of MWNT is less well understood
because of its greater complexity and
variety. Regions of structural imperfection
may diminish its desirable material
properties.

12. METHODS FOR PREPRATION OF CNTs
Arc-Evaporation
Arc-evaporation synthesis, also known as electric arc discharge, has long been
known as the best method for synthesizing fullerenes, and it also generates the
highest quality carbon nanotubes.
Arc-evaporation apparatus consists of two graphite electrodes under helium. A
current of around 50A is passed between the electrodes, causing some of the
graphite from the anode to evaporate and condense on the cathode - this
deposit contains the carbon nanotubes.
Arc-evaporation with pure graphite electrodes produces mainly multi-wall
nanotubes, although single-wall nanotubes can be made by this method by
doping the anode with a metal catalyst such as cobalt or nickel.
Whilst the nanotubes produced by arc discharge are of a very high
quality, they are mixed with a large amount of amorphous carbon, which
makes this technique difficult to scale up.

13. Laser Vaporization
The laser vaporization (or laser ablation) method was developed in
1995. A pulsed laser is fired at a graphite target in an inert
environment, at high temperature and pressure. The target is usually
placed at one end of a 50cm quartz tube - the nanotubes are
collected at the opposite end.
The shape and structure of the nanotubes produced by laser
vaporization are more easily controllable, as they are only affected
by a small number of parameters. The yield of carbon nanotubes is
also much higher, with very little amorphous carbon produced, but
the overall amount generated is very small. This combined with the
high operating temperature and pressure make this method highly
inefficient for producing large amounts of carbon nanotubes.

14. Chemical Vapour Deposition (CVD)
Chemical vapour deposition is the method with the most promise for mass
production of carbon nanotubes. It operates at much lower
temperatures, and produces nanotubes in greater quantities than arc
discharge or laser vaporization.
CVD uses a carbon-rich gas feedstock, such as acetylene or ethylene (IUPAC
ethyne, ethene). The gas is passed over a metal nanoparticle catalyst
(typically iron, nickel, or molybdenum) which has been deposited on a porous
substrate (e.g. silica, alumina). Carbon atoms dissociate from the gas
molecules as they pass over the catalyst, rearranging on the surface to form
nanotubes and fullerenes. This allows nanotubes to be synthesized
continuously, making the technique ideal for scaling up to large
manufacturing volumes.

15. Other Synthetic Methods
Several other methods for producing carbon nanotubes
have been reported, which are mostly at an early stage
of research. Some of these may have the potential to be
good mass-production methods, with further
development.
•Diffusion flame synthesis, with a variety of metal
and metal oxide catalysts and support geometries
•Electrolysis of graphite in molten lithium chloride
under an inert atmosphere
•Ball milling and annealing of graphite, catalyzed by
iron contamination from the steel milling balls
•Heat treatment of polyesters formed from citric acid
and ethylene glycol, at 400C in air
•Hydrothermal treatment of polyethylene with a
nickel catalyst under high pressure
•Explosive decomposition of picric acid, in the
presence of cobalt acetate and paraffin, produces a high
yield of relatively homogeneous, "bamboo-shaped"
carbon nanotubes.

16. Electrical Properties
If the nanotube structure is armchair then the electrical
properties are metallic
If the nanotube structure is chiral then the electrical properties
can be either semiconducting with a very small band gap,
otherwise the nanotube is a moderate semiconductor
In theory, metallic nanotubes can carry an electrical current
density of 4×109 A/cm2 which is more than 1,000 times greater
than metals such as copper

17. Thermal Properties
All nanotubes are expected to be very good thermal conductors
along the tube, but good insulators laterally to the tube axis.
It is predicted that carbon nanotubes will be able to transmit up to
6000 watts per meter per Kelvin at room temperature; compare
this to copper, a metal well-known for its good thermal
conductivity, which transmits 385 watts per meter per K.
The temperature stability of carbon nanotubes is estimated to be
up to 2800 C in vacuum and about 750 C in air.

18. Defects
Defects can occur in the form of atomic vacancies. High
levels of such defects can lower the tensile strength by up to
85%.
Because of the very small structure of CNTs, the tensile strength
of the tube is dependent on its weakest segment in a similar
manner to a chain, where the strength of the weakest link
becomes the maximum strength of the chain

19. applications
Carbon nanotubes, miniscule pipes of rolled up carbon
atoms, have amazing properties that have taken the world by
storm. They are currently being integrated into hundreds of different
applications, from green tech to clothing and medicine. Here’s a
peak at some uses for this wonder material.
Its size, surface area (500 square meter per gram), and
adsorption properties make carbon nanotubes an ideal
membrane for filtering toxic chemicals, dissolved salts and
biological contaminants from water.

20. Carbon nanotubes have been added to strengthen materials for
sports equipment, body armor, vehicles, rockets, and building
materials.
Using carbon nanotubes as the electrodes in capacitors
provides more current and better electrical and mechanical
stability than other leading materials
Carbon nanotubes are perfect for allowing damaged bone to
restructure itself: they’re strong, lightweight, and can be
modified for compatibility with any part of the body.

21. From flat screens, to LEDs to flexible displays, nanotubes will
increase your viewing pleasure and portability. These tiny
pipes of carbon make excellent field emitters or conductive
surfaces.
They’re strong, they’re elastic, and they have amazing
electrical properties. Researchers have created a carbon
nanotube aerogel that expands and contracts as it
converts electricity into chemical energy.

22. Health Hazards
According to scientists at the National Institute of Standards and
Technology, carbon nanotubes shorter than about 200
nanometers readily enter into human lung cells similar to the way
asbestos does, and may pose an increased risk to health.
Carbon nanotubes along with the majority of
nanotechnology, are an unexplored matter, and many of the
possible health hazards are still unknown.