Lec. (7)
Structure of matter
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Graphite – Van der Waals Bonds
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www.scifun.ed.ac.uk/card/flakes.html
Graphite
www.webelements.com
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Graphite
Soft and slippery
Brittle
Electrical conductor
Insoluble in water.
Very high melting point
Many strong covalent bonds holding the structure together
but only in 2 dimensions. The layers are free to slide easily
over one another. Graphite powder is used as a lubricant.
All of the bonds are directional within a layer and stress
across a layer will tend to break them. Graphite rods used for
electrolysis easily break when dropped.
Only three of the valence (outer shell) electrons are used in
sigma bonding. The other electron is in a 'p' orbital which can
overlap laterally with neighbouring 'p' orbitals making giant
molecular pi orbitals that extend over the whole of each layer.
Electrons are free to move within these delocalised pi
orbitals.
There are only very weak Van der Waal's attractions between
the carbon atoms and the water molecules whereas the
carbon atoms are bonded very tightly to one another.
Many strong covalent bonds holding the layers together - it
requires massive amounts of energy to pull it apart
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Diamond
www.webelements.com
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Diamond
Hard
Many strong covalent bonds holding the structure
together.
Brittle
All of the bonds are directional and stress will tend to
break the structure (In a malleable substance, such as
for example a metal, the bonding is non-directional and
can still act if the particles are displaced with respect to
one another).
All of the valence (outer shell) electrons are used in
bonding. The bonds are sigma and the electrons are
located between the two carbon nuclei being bonded
together. None of the electrons are free to move
Insulator
Insoluble in water.
Very high melting point
There are only very weak Van der Waal's attractions
between the carbon atoms and the water molecules
whereas the carbon atoms are bodned very tightly to
one another.
Many strong covalent bonds holding the structure
together - it requires massive amounts of energy to pull
it apart
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Diamond
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www.webelements.com
Nanocarbon
Properties &
Applications
• Electrical
• Mechanical
• Thermal
• Storage
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http://www.youtube.com/watch?v=4yRjYiw_H_s
Fullerenes
Discovered in 1985
Nobel prize Chemistry 1996
Curl, Kroto, and Smalley
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Buckyballs
C60
32 facets
(12 pentagons and 20
hexagons)
C70, C76, and C84
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Bucky Balls
• Symmetric shape
→ lubricant
• Large surface area
→ catalyst
• High temperature (~750oC)
• High pressure
• Hollow
→ caging particles
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Buckyballs
• Forms a crystal by weak van der
Waals force
• Superconductivity
- K3C60: 19.2 K
- RbCs2C60: 33 K
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Kittel, Introduction to Solid State Physics, 7the ed. 1996.
Buckyballs
• Forms a crystal by weak van der
Waals force
• Superconductivity
- K3C60: 19.2 K
- RbCs2C60: 33 K
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http://invsee.asu.edu/nmodules/Carbonmod/crystalline.html
Buckyballs
Soft and slippery
Brittle
Few covalent bonds holding the molecules together but
only weak Vander Waals forces between molecules.
Soft weak crystals typical of covalent substances
Electrical Insulator
No movement of electrons available from one molecule
to the next. The exception could be the formation of
nano-tubes that are capable of conducting electricity
along their length. These are the subject of some
experiments in micro electronics
Insoluble in water.
There are only very weak Van der Waal's attractions
between the carbon atoms and the water molecules
whereas the carbon atoms are bonded very tightly to
one another in the molecules.
Low Melting Point Solids
Typical of covalent crystals where only Van der Waal's
interactions have to be broken for melting.
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Carbon Nanotubes (CNT)
•
•
•
•
Like graphite but all coiled up
Typically 10 Angstroms in diameter
Can be electrically conductive or semiconducting
SWNT and MWNT
– Composites, transistors, hydrogen storage
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Courtesy of and ©Copyright Professor Charles M. Lieber Group
Nanotube
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Armchair
Zigzag
Spiral
The "armchair" type has the characteristics of a metal
The "zigzag" type has properties that change depending on the tube diameter
The "spiral" type has the characteristics of a semiconductor
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Nanotube
High aspect ratio:
Length:
μm to cm
length
 1000
diameter
→ quasi 1D solid
Diameter:
as low as 1 nm
SWCNT – 1.9 nm
18673.
Zheng et al. Nature Materials 3 (2004)
Nanotube Intro Video
• Earth and sky: Properties of Nanotubes
•
http://www.youtube.com/watch?v=zQAK4xxPGfM&mode=related&search=Nanotube
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Introduction
A carbon nanotube (CNT) is
a tubular molecule with
axial symmetry and
diameter in the
nanometer range
(Muller).
It can be considered as a
rolled up graphene sheet.
However, it possesses
many properties that
leave no doubt this is not
just graphene.
http://www.msm.cam.ac.uk/phasetrans/2005/paper/img19.png
http://www.nanotech-now.com/nanotube-buckyball-sites.htm
Types
• Single Walled CNT (SWCNT): one-atom-thick CNTs
• Multi Walled CNT (MWCNT): concentric layers of
CNTs
http://www-ibmc.u-strasbg.fr/ict/images/SWNT_MWNT.jpg
Properties
Among some of the
properties of the CNTs
we can find:
• Electrical: Both metallic and nonmetallic behaviors are observed,
while geometry plays a profound
part in determining the electronic
behavior. (Ebbesen)
http://www.studentsoftheworld.info/sites/family/img/27335_Electricity.jpg
• Elastic: Tensile Young’s module and
torsion shear module comparable to
that of diamond (Lu).
http://www.nanoshel.com/research-center/wp-content/uploads/2009/01/ballistic-impact.jpg
Properties
• Mechanical: Carbon
nanotubes have high
strength plus
extraordinary
flexibility and
resilience. (Salvetat)
• Thermal: Thermal
expansion of carbon
nanotubes will be
essentially isotropic
that is, uniform in all
directions (Ruoff).
http://brent.kearneys.ca/wp-content/uploads/2006/05/carbon_nanotube.jpg
Nanotube Stats
• Current capacity
Carbon nanotube 1 GAmps / cm2
Copper wire
1 MAmps / cm2
• Thermal conductivity
Comparable to pure diamond (3320 W / m.K)
• Temperature stability
Carbon nanotube
750 oC (in air)
Metal wires in microchips 600 – 1000 oC
• Caging
May change electrical properties
→ can be used as a sensor
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Nanotubes
Carbon nanotubes are the strongest known material.
• Young Modulus (stiffness):
Carbon nanotubes
Carbon fibers
High strength steel
1250 GPa
425 GPa (max.)
200 GPa
• Tensile strength (breaking strength)
Carbon nanotubes
11- 63 GPa
Carbon fibers
3.5 - 6 GPa
High strength steel
~ 2 GPa
• Elongation to failure : ~ 20-30 %
• Density:
  E
Carbon nanotube (SW) 1.33 – 1.40 gram / cm3
Aluminium
2.7 gram / cm3
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Synthesis of Carbon Nanotubes
• IFW-Dresden Carbon Nanotubes
•
http://www.youtube.com/watch?v=tgToxaOqF10&mode=related&search=Nanotube
• Synthesis of Carbon nanotube
•
http://www.youtube.com/watch?v=8N79nlhwcgM&mode=related&search=C60%20Ful
lerene%20Fullereno%20Buckyball
• Growth of Carbon nanotube
•
http://www.youtube.com/watch?v=1p8vFdCJRZE&NR=1&feature=fvwp
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Water Resistant Coatings
http://www.youtube.com/watch?v=HIGMB_R3pgI&feature=related
http://www.youtube.com/watch?v=nTbz8w1SB1U&feature=fvw
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Carbon Fiber
A 6 μm diameter carbon filament
(running from bottom left to top
right) compared to a human hair.
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CNT Carbon Nanotube Opti-Flex composite handle technology,
provids maximum handle flex-three times greater than aluminum
Sports Equipment
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Carbon Nanotube/Cement
Composite Systems
In concrete, they increase the tensile strength, and halt crack propagation.
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The Space Elevator
http://www.youtube.com/watch?v=lVV0S9cNLKI&feature=related
www.nanooze.org
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www.enterprisemission.com
Space Elevator
• NOVA space elevator intro
• http://www.youtube.com/watch?v=pnwZmWoymeI&
mode=related&search
• 2 minute space elevator intro
• http://www.youtube.com/watch?v=F2UZDHHDhog
• Space Elevator Competition: USST's
First Place Climb
•
http://www.youtube.com/watch?v=VkdfuQdoW_Q&mode=related&sear
ch=space-elevator%20turbo%20crawler
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CNT light bulb filament:
alternative to tungsten filaments in
incandescent lamps
The average efficiency is 40% higher than that of a tungsten filament at the
same temperature (1400–2300 K).
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Nano Radio
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•http://nsf.gov/news/news_summ.jsp?cntn_id=110566
When a radio wave of a specific frequency impinges on the
nanotube, it begins to vibrate vigorously.
An electric field applied to the nanotube forces electrons to be
emitted from its tip.
This electrical current may be used to detect the mechanical
vibrations of the nanotube, and thus listen to the radio waves.
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•http://nsf.gov/news/news_summ.jsp?cntn_id=110566
Nanotube Radio
• http://www.youtube.com/watch?v=gkQkzvnstkg
• http://www.youtube.com/watch?v=yQz9C7yE1kc
&feature=related
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Carbon Nanotube
Electronics
• Carbon nanotube in microchip
•
http://www.youtube.com/watch?v=74YkJYT7Uj4&mod
e=related&search=Nanotube
• Customized Y-Shaped Nanotubes
•
http://www.youtube.com/watch?v=SGWHBQQKmOs
Transistors – the active component of virtually all electronic devices, are what we
refer to as electronic switching devices. In a transistor, a small electric current can
be used to control the on/off of a larger current.
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Semiconducting CNTs have been used to fabricate field effect transistors (CNTFETs).
The electron mean free path in SWCNTs can exceed 1 micron (this is very large)
therefore it is projected that CNT devices will operate in the frequency range of 42
hundreds of GHz.
Kavli Institute Delft
SEM image of superconducting transistors
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CNT-FED
Professor George Lisensky
http://mrsec.wisc.edu/Edetc/cineplex/nanoquest/applications.html
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CNT-FED
Carbon nanotubes can be electrically conductive and due to their small diameter of
several nanometers, they can be used as field emitters with extremely high efficiency
for field emission displays (FED). The principle of operation resembles that of the45
cathode ray tube, but on a much smaller length scale.
Bucky Paper
A thin sheet made from nanotubes that are 250 times stronger than steel and 10
times lighter that could be used as a heat sink for chipboards, a backlight for LCD
screens or as a faraday cage to protect electrical devices
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Warwick ICAST
http://www.youtube.com/watch?v=i4Ax8sY2U4A&mode=related&search=Nanotube
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Hydrogen Storage
Carbon nanotubes covered in titanium atoms provide a very efficient method for
storing hydrogen.
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'Artificial muscles' made from
nanotubes
"Artificial muscles" have been made from millions of carbon nanotubes. Like natural
muscles, providing an electrical charge causes the individual fibers to expand and
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the whole structure to move.
Bone cells grown on
carbon
nanotubes
Researchers at the University of California, Riverside have published findings
that show, for the first time, that bone cells can grow and proliferate on a scaffold
of carbon nanotubes. Scientists found that the nanotubes, 100,000 times finer
than a human hair, are an excellent scaffold for bone cells to grow on.
http://biosingularity.wordpress.com/2006/03/21/researchers-grow-bone-cells-oncarbon-nanotubes/
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http://neurophilosophy.wordpress.com/2006/03/17/123/
Nano SQUID
A SQUID is a superconducting interferometer device. SQUID devices can be used to
monitor infinitesimally small magnetic fields or currents. The originality of this work, is
to use gate-tunable carbon-nanotubes (CNT) for the Josephson junctions. The device
combines features of single electron transistors with typical properties of a SQUID
interferometer. The gate tunability of the CNT junctions enhance the sensitivity of the
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device which can in principle detect the spin of a single molecule.