Carbon nanotubes (CNTs) are cylindrical carbon molecules that have unusual properties that make them potentially useful in many applications in nanotechnology, electronics, optics and other fields. There are two main types of CNTs - single-walled carbon nanotubes (SWNTs) which are made of a single graphene sheet rolled into a seamless cylinder and multi-walled carbon nanotubes (MWNTs) made of multiple graphene sheets in a Russian doll-like structure. CNTs exhibit extraordinary strength and unique electrical properties and can be metallic or semiconducting depending on their structure and chirality. They are synthesized using techniques like arc discharge, laser ablation and chemical vapor deposition and have many

1. CARBON NANO TUBES(CNT)

2. INTRODUCTION
• Carbon has more allotropes than any other element. The most recent additions to this list are
fullerenes (bucky-balls) and nanotubes (bucky-tubes).
• Fullerenes are a class of carbon allotropes, in which molecules composed entirely of carbon, in the
form of a hollow sphere, ellipsoid, or tube. Cylindrical fullerenes are called carbon nanotubes or
bucky-tubes.
• CNT is the most versatile material, with the properties ranging
from optical absorption and emission on one hand to the
mechanical properties of bulk materials such as Young’s modulus,
on the other.
• One can think of a carbon nanotube as a single sheet of graphite
rolled into a tube with bonds at the end of the sheet forming the
bonds that close the tube.

3. The structures of eight
allotropes of carbon
(A) Diamond [3D, network
covalent structure],
(B) Graphite [2D, covalent
plates] (graphene is a single
of graphite),
(C) Lonsdaleite,
(D)C60 [0D, molecules]
(Buckminsterfullerene or
bukyball),
(E) C540 Fullerene,
(F) C70 Fullerene,
(G) Amorphous carbon,
(H)Single-walled carbon
nanotube [1D, tubes]
(buckytube)

4. • Carbon nanotubes (CNTs) are classified as nanomaterials. At the same time, based on the
morphological parameters (length and aspect ratio), CNTs behave as fibers.
• CNT are nanometer-sized diameter and micrometer-sized length (where the length to diameter ratio
exceeds 1000).
• The aspect ratio(the ratio of length to width of a particle) typically encountered is of the order of
100:1.
• In conventional graphite, the sheets of carbon are stacked on top of one another, allowing them to
easily slide past each other. A single sheet of graphite is called graphene.
• When graphene sheets are coiled, they form a cylindrical 1D shape carbon nanotubes.
• A nanotube consists of one or more seamless cylindrical shells of graphitic sheets.
• The nanotube can be closed or open and the length can be several hundred times the width.

5. TYPES OF NANOTUBES
• A nanotube may consist of one tube of graphite (a single-walled nanotube , SWNT)
or a number of concentric tubes, called multi-walled nanotubes (MWNTs).
• When viewed by transmission electron microscopy(TEM) these tubes appear as
planes.
• In SWNTs two planes are observed, representing the edges & in MWNTs more than
two planes are observed, and these can be seen as a series of parallel lines.
• The SWCNTS have typical diameters between 1 and 3 nm, whilst MWCNTs range
from 10 to 200 nm.

6. Structure of SWCNT, DWCNT, and MWCNT in
different imaging techniques:
(A and B) SEM images of MWCNT (high and low
magnification),
(C and D) SEM images of SWCNT (high and low
magnification),
(E) TEM image of a cross-sectional view of a
bundle of SWCNTs
(F)TEM image of a transverse view of a bundle of
SWCNTs
(G) High resolution TEM image of an individual
MWCNT,
(H) SEM image of DWCNT,
(I)TEM image of DWCNT

7. Structure of (a) SWCNT, (b) DWCNT, and (c) MWCNT.
SWCNT-single-walled carbon nanotube; DWCNT-double-walled carbon nanotube;
MWCNT-multi-walled carbon nanotube.

8. • There are different types of SWNTs because the
graphene sheet can be rolled in different ways. The
conventional way to describe this is by looking at the
unrolled sheet and expressing the rolling process by
two vectors namely, Ch and T(translation vector
perpendicular to Ch).
• Ch and T defines a 2D unit cell. This rectangle is
rolled-up in the chiral vector direction.
• Ch is the “chiral vector” that defines the
circumference on the surface of the tube connecting
two equivalent carbon atoms, Ch= nâ1 + mâ2 ,
where â1 and â2 are the two basis vectors of graphite
and n and m are integers.
• n and m are also called indexes and determine the
chiral angle θ = tan–1[√3(m/ (2n + m))].
• The pair of (n,m) indices determines the diameter of
the CNT & chirality of CNT and affects the optical,
mechanical and electronic properties.
The 2D graphene sheet diagram showing a vector
structure classification used to define CNT
structure

9. • The diameter of the nanotube can be expressed as
dt = √3[ac-c(m2 + mn + n2)1/2/π] = |Ch| /π
Where |Ch| is the length of Ch, and ac-c is the C-C bond length (1.42 Å).
• Due to the symmetry of the graphene layer, several tubes, although having different (n,m) notations
are indeed the same. A tube of (0, n) is the same as (n, 0). The tube diameter will increase with an
increase in n and m.
• CNTs with (n−m= 3i, i = 0,1, 2, 3…) are metallic, and those with (n−m = 3i ± 1, i = 1, 2, 3…)are
semiconducting.
• Combining different diameters and chiralities results in several hundred individual nanotubes, each
with its own distinct mechanical, electrical, piezoelectric, and optical properties.
• The structure of the nanotube influences its properties, including conductance, density and lattice
structure. It is known that some nanotubes are metallic, that is, they are conductors, while some are
semiconductors.

10. CLASSIFICATI
ON OF CNT
Single-walled
Carbon
Nanotube
(SWCNT)
Arm Chair
SWCNT
Zig-Zag
SWCNT
Chiral
SWCNT
Multi-walled
Carbon
Nanotube
(MWCNT)
Russian doll
model
Parchment
model

11. The chiral angle is used to separate
single-walled carbon nanotubes into three
classes differentiated by their electronic
properties:
1)armchair (n = m, θ = 30˚)
2)zig-zag (m = 0, n > 0, θ = 0˚)
3)chiral (0 <|m|< n, 0 < θ < 30˚)
The chiral vector C and models of three atomically perfect
SWCNT structures
SINGLE-WALLED CARBON NANOTUBE(SWCNT)

12. • In these nanotubes, the graphene
sheet is rolled up along the chiral
vector smaller than the chiral
angle.
• The armchair carbon nanotubes
are metallic (zero band gap).
• The armchair carbon nanotube
structures have a high degree of
symmetry.
Armchair SWCNT
Rolling up process of a graphene sheet into
an armchair tube(illustration)

13. Zigzag
SWCNT
•In these nanotubes, the
graphene sheet is rolled up
along a vector greater then
the chiral angle.
•Some of Zig-zag nanotubes
can be semiconducting with
a finite band gap.
•The zig-zag carbon
nanotube structures have a
high degree of symmetry.
Rolling up process of a graphene sheet into
a zigzag tube(illustration)

14. •In these nanotubes, the
graphene sheet is rolled
up on the chiral vector.
•Some of chiral
nanotubes can be
semiconducting with a
finite band gap.
•The chiral tube
structure, which in
practice is the most
common, can exist in
two mirror-related
forms.
Chiral
SWCNT
Rolling up process of a graphene sheet
into a chiral tube(illustration)

15. MULTI-WALLED CARBON NANOTUBE (MWCNT)
• Multi walled carbon nanotubes consist of multiple rolled layers (concentric tubes) of graphene layers in a
one dimensional format.
• Two main models can be used to describe the structures of multi-walled nanotubes. They are:
a) Russian doll model and
b) Parchment model/Swiss roll model/Scroll model
• The Russian Doll structure is observed more commonly.
• The Russian doll model consists of sheets of graphite 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.

17. CNT SYNTHESIS METHODS
Main top-down
& bottom-up
techniques of
CNT synthesis
•Electric arc discharge synthesis
•Laser ablation synthesis
•Chemical vapor deposition (CVD)
•Electrolysis
•Diffusion flame synthesis
•High-pressure carbon monoxide (HiPco)
synthesis
•Sonochemical/Hydrothermal method
•Silane solution method
The industrial fabrication of CNTs, both the SWCNT and the MWCNT types, consists of three basic
steps that include the actual CNT synthesis, purification, and functionalization process.

18. • CNT synthesis involves many parameters such as hydrocarbon, catalyst,
temperature, pressure, gas-flow rate, deposition time, reactor geometry.
• Most commonly used CNT precursors are methane, ethylene, acetylene, benzene,
xylene and carbon monoxide.
• Most commonly used metals for synthesizing CNTs are Fe, Co, Ni (Nanometer-size
metal particles are required to enable hydrocarbon decomposition at a lower
temperature than the spontaneous decomposition temperature of the hydrocarbon).
• The same catalyst works differently on different support materials. Commonly
used substrates in CVD are quartz, silicon, silicon carbide, silica, alumina,
alumino-silicate (zeolite), CaCO3, magnesium oxide, etc.

19. Most common CNT synthesis techniques
A.Arc discharge technique
B.Laser ablation technique
C.Chemical vapour deposition technique

20. Growth mechanism of CNT
a) Tip-growth model and
b) Base-growth model/root-growth model/extrusion model
Growth mechanisms of CNT
The most accepted growth mechanisms of
CNT are:
a) Tip-growth and
b) Root growth
c) Structural dependence
on catalyst particle size

21. CARBON NANOTUBE PURIFICATION
• A large problem with CNT application next to large-scale synthesis is the
purification.
• In all the CNT preparation methods, the CNTs come with a number of impurities
whose type and amount depend on the technique used.
• The most common impurities are carbonaceous materials, whereas metals are the
other types of impurities generally observed.
• Purification of carbon nanotubes generally refers to the separation of carbon
nanotubes from other entities.

22. • Depending on technique of carbon nanotube synthesis, there are many different
methods and procedure for purification.
• All purification procedures have the following main steps:
a) preliminary filtration to get rid of large graphite particles and aggregations,
b) dissolution in appropriate solvents to eliminate catalyst particles (concentrated acids as
solvent) and fullerenes (use of organic solvents),
c) Micro-filtration and
d) chromatography (to separate either MWNT and unwanted nanoparticles or SWNT and the
amorphous carbon impurities).

23. FUNCTIONALIZATION OF CNT
• Functionalization or modification of CNTs is performed to introduce changes in the
atomic structure of CNTs through controlled doping or structural reorganization in
order to attain particular properties and functionalities for the desired applications.
• Generally, there are two types of covalent and non-covalent CNT functionalization.
• Functionalization is used for tuning the interfacial properties, increasing the
solubility and preserving the structural properties of CNTs.
• The corresponding dispersion procedures which usually involve ultrasonication,
centrifugation, and filtration are commonly performed by surfactants, polymers, and
biopolymers which provide quick, easy, cheap and efficient modification.

24. DEFECTS AND DISORDER IN CNT
• According to the experimental
observations, the structure of
CNTs is often disordered and
commonly contains a number of
defects namely,
a) Macroscopic defects in CNTs,
b) Atomic scale defects in CNTs &
c) Tailoring CNTs properties by
means of defect introduction.

25. CHARACTERIZATION OF CNT
• There are many production methods for CNTs, each producing material that is slightly different:
different in diameter, length, chirality, purity, catalysts, impurity species, and defects.
Characterization of CNTs to determine the quantity, quality, and properties of the CNTs in the
sample is very important, because its applications will require certification of properties and
function.
• In order to investigate the morphological and structural characterizations of CNTs, a reduced
number of techniques could be used. However, to fully characterize CNTs, there are not so many
techniques available at the individual level such as STM & TEM.
•To obtain qualitative and quantitative information of SWCNT diameter, electronic structure, purity and
crystallinity
•Distinguishes metallic and semi-conducting, chirality (for single SWCNT)
Raman spectroscopy
• The functionalization of the CNTs
X-ray photoelectron spectroscopy
• To obtain 3D images and electronic states of the CNTs
Scanning Tunneling Microscopy
•To obtain some information on the interlayer spacing, the
structural strain and the impurities
X-ray diffraction
• To obtain inter-shell spacing, chiral indices and helicity
Transmission Electron Microscopy
•To determine impurities remaining from synthesis or molecules
capped on the CNT surface
Infrared spectroscopy

26. Electrical Properties:
•The presence of defects on the body of the nanotube can alter the
electronic structure and can make regions of specific electronic
properties, such as metallic and semiconducting.
•CNT synthesis generally results in a mixture of tubes two thirds of
which are semiconducting and one-third metallic.
•In the metallic state the conductivity of the CNT is very high. It is
estimated that they can carry a billion amperes per square
centimeter since they have very few defects to scatter electrons,
and thus a very low resistance.
Mechanical properties:
• The strength of the sp² carbon-carbon bonds gives carbon
nanotubes amazing mechanical properties because they
very strong along their axis, and also very flexible.
• The Young's modulus of the best nanotubes can be as high
as 1000 GPa which is approximately 5 times higher than
steel.
• The tensile strength of nanotubes can be up to 63 GPa,
around 50 times higher than steel.
Physical properties:
•Nanotubes have a high strength-
to-weight ratio (density of 1.8
g/cm3 for MWNTs and 0.8 g/cm3
for SWNTs).
•Nanotubes are highly resistant to
chemical attack. It is difficult to
oxidize them and the onset of
oxidation in nanotubes is 100°C
higher than that of carbon fibers.
As a result, temperature is not a
limitation in practical
applications of nanotubes.
•The surface area of nanotubes is
of the order of 10–20 m2/g, which
is higher than that of graphite.
•Nanotubes also have a very high
thermal conductivity, almost a
factor of 2 more than that of
diamond and the value increases
with decrease in diameter. This
means that they are also very
good conductors of heat.
PROPERTIES OF CNT

27. Some amazing properties of carbon nanotubes.

28. APPLICATIONS OF CNT
• Current use and application of nanotubes has mostly been limited to the use of bulk nanotubes. Bulk
nanotube materials may never achieve a tensile strength similar to that of individual tubes, but such
composites may, nevertheless, yield strengths sufficient for many applications.
• The strength and flexibility of carbon nanotubes makes them of potential use in controlling other
nanoscale structures, which suggests they will have an important role in nanotechnology engineering.
Biomedical
applications
• Artificial
implants
• Tissue
engineering
• Cancer cells
tracing
• Gene and drug
delivery
applications
• Sensor-based
biomedical
applications
Electronic
applications
•CNT based
Diodes, Field-
Effect
Transistors(FET),
and Logic Circuits
•CNT based
Sensors
•Field emission
electron sources
•Transparent
Electrodes
•CNTs as Probes
in Atomic Force
Microscopy
•Bucky-paper
Energy
Storage and
Conversion
Water
Treatment
Space
Elevators
Hydrogen
Storage

29. HEALTH AND SAFETY CONCERNS RELATED TO CNT
• CNTs are considered hazardous when
thinner than 3 µm and longer than ~20
µm, or when no biodegradation in the
lungs by dissolving or breaking is
possible.
• The CNTs induce toxicity, such as
oxidative damage in biological systems
and influence the central nervous
system, trough endothelial cell damage.
• Vascular effects also been induced by
CNTs.
• For safety reasons the exposure limits
and the likelihood of a person to work
with nano-engineered materials need to
be objectively evaluated.

30. REFERENCES
• Aqel, A., El-Nour, K. M. M. A., Ammar, R. A. A., & Al-Warthan, A. (2012). Carbon nanotubes, science and technology part (I) structure, synthesis and
characterisation. Arabian Journal of Chemistry, 5(1), 1–23. DOI: https://doi.org/10.1016/j.arabjc.2010.08.022
• Eatemadi, A., Daraee, H., Karimkhanloo, H. et al. Carbon nanotubes: properties, synthesis, purification, and medical applications. Nanoscale Res Lett 9,
393 (2014). DOI: https://doi.org/10.1186/1556-276X-9-393
• Kumar Jagadeesan, A., Thangavelu, K., & Dhananjeyan, V. (2020). Carbon Nanotubes: Synthesis, Properties and Applications. In 21st Century Surface
Science - a Handbook. IntechOpen. DOI: https://doi.org/10.5772/intechopen.92995
• Rahman, G., Najaf, Z., Mehmood, A., Bilal, S., Shah, A., Mian, S., & Ali, G. (2019). An Overview of the Recent Progress in the Synthesis and
Applications of Carbon Nanotubes. C, 5(1), 3. DOI: https://doi.org/10.3390/c5010003
• Sousa, S. P. B., Peixoto, T., Santos, R. M., Lopes, A., Paiva, M. da C., & Marques, A. T. (2020). Health and Safety Concerns Related to CNT and
Graphene Products, and Related Composites. Journal of Composites Science, 4(3), 106. DOI: https://doi.org/10.3390/jcs4030106
• Ghavamian, A., Rybachuk, M., & Öchsner, A. (2018). Defects in carbon nanotubes. In Defects in Advanced Electronic Materials and Novel Low
Dimensional Structures (pp. 87–136). Elsevier. DOI: https://doi.org/10.1016/b978-0-08-102053-1.00004-1
• Pradeep, T. (2012). Textbook of nanoscience and nanotechnology. McGraw-Hill Education.

31. THANK
YOU