from MSE-HUST

1. Class: Material Science Engineering
Student : Hoang Van Tien -2012
Hanoi

2. DID YOU KNOW?
 Carbon nanotubes, composed of interlocking
carbon atoms, are 1000x thinner than an
average human hair – but can be 200x
stronger than steel.

3. outline
 Definition
 Theory and properties
 Synthesis
 Potential and current applications
 Challenges and future

4. What are carbon nanotubes
CNT: Rolling-up a graphene sheet to form a tube
Schematic STM image
of a CNT of CNT
4

5.  Carbon nanotubes are hexagonally shaped
arrangements of carbon atoms that have
been rolled into tubes.
 These tiny straw-like cylinders of pure carbon
have useful electrical propeties. They have
already been used to make tiny transistor and
one-dimentional copper wire

6. Types of CNTs
 Single Wall CNT (SWCNT)
 Multiple Wall CNT (MWCNT)
 Can be metallic or semiconducting
depending on their geometry.

7. Single- walled
-Most single-walled
nanotubes (SWNTs)
have a diameter of cloes
to 1 nanometer,with a
tube length that can be
many millions of time
longer
-The structure of a
SWNTs can be
conceptualized by
wrapping a one-atom-
thick layer of graphite
called graphene in to a
seamless cylender

8. If:
m=0 , the nanotubes are called zigzag
n=m ,the nanotubes are called armchair
Otherwise ,they are called chiral

9. Multi-walled
 Multi-walled nanotubes (MWNTs) consist of
multiple rolled layer( concentric tubes) of
graphene
Triple-walled
armchair CNTs

10.  In the Russian Doll model, sheets of graphite are
arranged in concentric cylinders, e.g., a (0,8) single-
walled nanotube (SWNT) within a larger (0,17) single-
walled nanotube.
 In the Parchment model, a single sheet of graphite is
rolled in around itself, resembling a scroll of parchment
or a rolled newspaper.
 The interlayer distance in multi-walled nanotubes is
close to the distance between graphene layers in
graphite, approximately 3.4 Å. The Russian Doll structure
is observed more commonly. Its individual shells can be
described as SWNTs, which can be metallic or
semiconducting.

11. compare
 Single –walled CNTs exhibit electric
properties that are not shared by the multi-
walled CNTs variant
 SWNTs is useful in the development of the
first intramolecular field effect transistors
(FET)

12. torus
-Torus is theoretically described
as carbon nanotube bent into a
torus (doughnut shape) .
-Nanotorus are predicted to
have many unique properties
such as :
+magnetic moments
+thermal stability …
-Vary widely depending on
radius of the torus and the
radius of the tube

13. nanobud

14.  In nanotechnology,carbon nanobuds form a
material (discovered and synthesized in 2006) which
combines two previously discovered allotropes of
carbon: carbon nanotubes and spheroidal
fullerences (or, in short, fullerenes)
 fullerenes are covalently bonded to the outer
sidewalls of the underlying nanotube
=>>>> Has useful properties of both fullerenes and
carbon nanotubes

15. Extreme carbon nanotubes
-The observation of the longest carbon
nanotubes (18.5 cm long) was reported in
2009. These nanotubes were grown on Si
substrates using an improved chemical
vapor deposition (CVD) method and
represent electrically uniform arrays of
single-walled carbon nanotubes.
-The shortest carbon nanotube is the
organic compound cycloparaphenylene
-The thinnest carbon nanotube is
armchair (2,2) CNT with a diameter of 3
Å. This nanotube was grown inside a
multi-walled carbon nanotube
-The thinnest freestanding single-walled
carbon nanotube is about 4.3 Å in
diameter

16. PROPERTIES OF
CARBON
NANOTUBES

17. Strength and elasticity
 CNTs are expected to be the
ultimate high-strength filber
 Single wall carbon nanotubes
are stiffer than steel and are
very resistant to damage
from physical forces
 Carbon Nanotubes (CNTs)
very useful as probe tips for
very high-resolution scanning
probe microscopy.

18. elasticity
-The current Young’s modulus value of single walled
carbon nanotubes is about 1 terapascal
-The modulus of the multi walled carbon nanotubes
correlates to the amount of disorder in the carbon nanotube
walls
-when multi walled carbon nanotubes break, the
outermost layers break first

19. Comparison of mechanical properties
Materials Young’modulus(Tpa) Tensile Elongation at
strength(Gpa) break(%)
SWNTE ~1 (from 1 to 5) 13-53 16
Armchair 0.94 126.2 23.1
SWNTT
Zigzag SWNTT 0.94 94.5 15.6-17.5
Chiral SWNT 0.92
MWNTE 0.2-0.8-0.95 11-63-150
Stainless steelE 0.186-0.214 0.38-1.55 15-50
Kevlar-29&149E 0.06-0.18 3.6-3.8 ~2
EExperimental observation; TTheoretical prediction

20. Electrical properties
 For a given (m,n)
nanotubes:
 If n=m(armchair) the
CNTS is metalic
 If n-m is multiple of 3
,the CNTs is
semiconducting with a
small band gap
 Otherwise ,the CNTs is
moderates
semiconductor

21. Thermal property
 All nanotubes are expected to be very good thermal
conductors along the tube, exhibiting a property known
as "ballistic conduction ", but good insulators laterally to
the tube axis.
 SWNT has a room-temperature thermal conductivity
along its axis of about 3500 W·m−1·K−1.
 in copper : 385 W·m−1·K−1
 A SWNT has a room-temperature thermal conductivity
across its axis (in the radial direction) of about 1.52
W·m−1·K−1. (same as oil)

22. defect
 As with any material, the existence of a
crystallographic defect affects the material
properties.
 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.
 Crystallographic defects also affect the tube's
electrical properties and thermal properties.

23. Toxicity .
 Under some conditions ,nanotubes can cross
membrane barriers ,which suggests that if raw
materials reach the organs, they can include
harmful effects such as inflammatory and
fibrotic reactions
 CNTs were capable of
producing inflammation, epithelioid
granulomas (microscopic nodules), fibrosis, and
biochemical/toxicological changes in the lungs
 =>>>carbon nanotubes can pose a serious risk to
human health

24. synthesis
Techniques have
been developed
to produce carbon
nanotubes in
sizeable quanlities
,some of them are:
- Arc discharge
- Laser ablation
- Chemical vapor
deposition(CVD)

25. Arc discharge
 Nanotubes were observed in 1991 in the carbon
soot of graphite electrodes during an arc
discharge, by using a current of 100 amps , that
was intended to produce fullerenes.
 the carbon contained in the negative electrode
sublimates because of the high-discharge
temperatures.
 The yield for this method is up to 30% by weight
and it produces both single- and multi-walled
nanotubes with lengths of up to 50 micrometers
with few structural defects

26. Laser ablation
 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 . However, it is more expensive than either
arc discharge or chemical vapor deposition.

27. Chemical vapor deposition
 a substrate is prepared with a layer of metal catalyst
particles, most commonly nickel, cobalt, iron , or a
combination.
 The substrate is heated to approximately 700°C.
 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.

28. Laser-assisted thermal
chemical vapour deposition

29. the growth mechanism .

30.  Sources of laser:a medium power, continuous
wave CO 2 laser,perpendicularonto a
substrate,
 pyrolyses sensitised mixtures of Fe(CO) 5
vapour and acetylene in a flow reactor.
 Catalyst: Fe (very small iron particles)
 Substrate: sillica.
iron pentacarbonyl
vapour,
single- and
+ethylene multi-walled
+acetylene
carbon
nanotubes

32. Purification
 The main impurities :graphite (wrapped up) sheets,
amorphous carbon, metal catalyst and the smaller
fullerenes…
 Rules :
-separate the SWNTs from the impurities
- give a more homogeneous diameter or size distribution.
 The techniques that will be discussed are oxidation, acid
treatment, annealing, ultrasonication, micro filtration,
ferromagnetic separation, cutting, functionalisation and
chromatography techniques.

33. applications
Nanotubes are rolled-up graphene sheets, and graphene is
one of the stiffest materials when subjected to deformations
parallel to the sheet.
nanotubes show exceptional mechanical properties,
especially a high strength-to-weight ratio.
Applications:
 Field emission
 Nanotube sensors
 Nanotube transistors
 Nanotubes as SPM tips
 Energy Storage
 Conductive Adhesives and Connectors
 Biomedical Applications……….

34. Schematics of a nanotube transistor, with some measurements.

35. Use of a MWNT as AFM tip. VGCF stands for Vapour Grown Carbon Fibre.
At the centre of this fibre the MWNT forms the tip.the VGCG provides a
convenient and robust technique for mounting the MWNT probe for use in
a scanning probe instrustment

36. Space elevator

37. Faster computer chips

38. cancer treatment
 Use carbon nanotubes as drug delivery tools

39. Challenges and potentials
 Potentials :
 the new wonder material, can useful in many types of
industry ,especially in electronics applications
 The field of research for CNTs has become so broad
over the past 20 years that they are being tested for
use in fields .
 Challenges :
 Too expensive (~ $ 200per gram)
 toxicological issues.
 hard to purification and the ability to manipulate
structures at the atomic scale….

40. summary
 Carbon nanotubes have very different properties
compared to the other carbon allotropes
- these unique properties offer huge potential in product
development.
 Nanomaterials, particularly carbon nanotubes (CNTs), hold
great promise for a variety of industrial, consumer, and
biomedical applications, due to their outstanding and novel
properties.

41. sources
1. D.A.Bochvar and E.G.Gal'pern,
Dokl.Akad.Nauk.USSR, 209, (610, 1973 )
2.http://www.ou.edu/engineering/nanotube, 2003
3. http://nanotube.msu.edu/
4.http://www.pa.msu.edu/cmp/csc/nanotube.htm5
5.http://en.wikipedia.org/wiki/Carbon_nanotube
6.http://students.chem.tue.nl/carbonnanotubes/
applications.html
……….