Transcript Carbon Nanotube Synthesis – Presentation Here

Synthesis of CNT
Presented by : Varun Doshi
Roll no - 29
What is Nanotechnology?
• Nanotechnology is the ability to control or
manipulate materials on the atomic scale to
create structures that have novel properties and
functions because of their size, shape or
composition.
• These structures are typically less than 100
nanometers in size.
Understanding the
Nanodimension
What Are Carbon
Nanotubes?
• CNT can be described as a
sheet of graphite rolled into
a cylinder
• Constructed from hexagonal
rings of carbon
• Can have one layer or
multiple layers
• Can have caps at the ends
making them look like pills
Carbon nanotube properties

One dimensional sheets of hexagonal network of carbon rolled
to form tubes

~1 nm in diameter & can be microns long in length

Varieties include single-wall and multi-wall nanotubes, ropes,
bundles, arrays

Strongest and stiffest materials yet discovered in terms of
tensile strength and elastic modulus

Multi-walled nanotubes 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
CNT properTies …CONTD
• 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.
• Multiwalled carbon nanotubes with interconnected
inner shells show superconductivity with a relatively
high transition temperature
Methods of synthesis
of CNT
• Arc discharge
• Laser ablation
• Chemical vapor deposition (CVD)
Arc Discharge
• Nanotubes were initially discovered using this technique so it
is the most widely-used method of nanotube synthesis
• Carbon contained in the negative electrode sublimates
because of the high discharge temperatures forming
Nanotubes
• Yield for this method is up to 30 percent by weight
• Produces both single- and multi-walled nanotubes with
lengths of up to 50 micrometers with few structural defects
Diagrammatic representation
of Arc Discharge
Laser ablation
• Developed by Dr. Richard Smalley and co-workers at Rice University
• Pulsed laser vaporizes a graphite target in a high-temperature reactor
which has inert gas
• Nanotubes develop on the cooler surfaces of the reactor as the
vaporized carbon condenses
• 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
• More expensive than either arc discharge or chemical vapor deposition
Diagrammatic representation
of Laser ablation
Chemical vapor deposition
(CVD)
• Commercial method for production of carbon nanotubes
• Substrate is prepared with a layer of metal catalyst particles(commonly
nickel, cobalt, iron, or a combination)
• Diameters of the nanotubes depends on the size of the metal particles
• 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)
• This can be controlled by patterned (or masked) deposition of the metal,
annealing, or by plasma etching of a metal layer
• Substrate is now heated to ~ 700°C which initiate the growth of nanotubes
CVD . . . contd
• Nanotubes grow at the sites of the metal catalyst; the carboncontaining 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.
• Catalyst particles can stay at the tips of the growing nanotube during
the growth process, or remain at the nanotube base, depending on
the adhesion between the catalyst particle and the substrate
• One issue in this synthesis route is the removal of the catalyst
support via an acid treatment, which sometimes could destroy the
original structure of the carbon nanotubes. However, alternative
catalyst supports that are soluble in water have proven effective for
nanotube growth
Diagrammatic representation
of CVD
CNT application in
nanomedicine
• Multipurpose innovative carriers for drug
delivery and diagnostic applications
• Biosensors, composite materials, molecular
electronics
• Delivery of drugs, antigens and genes
• Functionalized CNTs with high solubility and
low toxicity as drug carriers
• High loading capacity of drug in double
functionalized carbon nanotube
Bibliography
• Available at URL:
http://www.fy.chalmers.se/atom/research/nanotubes/experimental.xml
• Available at URL:
http://ipn2.epfl.ch/CHBU/NTproduction2.htm
• Available at URL:
http://www.ifwdresden.de/institutes/iff/research/Cabon/CNT/laser-ablation
• Available at URL:
http://www.fy.chalmers.se/atom/research/nanotubes/experimental.xml