Carbon Nanotubes and Polymers:

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Carbon Nanotubes and Polymers Nanocomposites for
spacecraft applications
Shavesha L. Rutledge Lunch Learn November 4,
2004 1130 a.m. - 100 p.m. Building 22, Room 184
NASA Goddard Space Flight Center Code
562 American University, Washington D.C.
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The Discovery of Carbon Nanotubes

• While researching buckyballs, Dr. Sumio Iijima
  discovered Carbon Nanotubes (CNTs) in 1991.
• Buckyballs are nanometer-sized spheres with 60
  carbon atoms in the shape of a soccer ball.
• Dr. Iijima was blasting sheets of graphite loose
  by passing electricity from one graphite rod to
  another in a process called arc-discharge.

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What are Carbon Nanotubes?

• The tubes are rolled up sheets of graphite that
  have amazing stiffness, strength, and resilience.
• These tubular carbon molecules can be classified
  into two groups
• Multi-walled Carbon Nanotubes
• Single-walled Carbon nanotubes

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Multi-walled and Single-walled CNTs

• Multi-walled
• Concentric graphitic layers
• Diameters range from 10 - 50 nm
• Length gt 10 Microns
• Structurally stable
• Contain regions of structural imperfection
• Single-walled
• Discovered in 1993
• Typical diameter 1nm
• Curled rather than straight

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Outstanding Properties

• Can be metallic or semi-conducting
• Composed of sp2 bonds, providing them with their
  unique strength

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Outstanding Properties
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Growth of CNTs

• Arc-discharge method
• Laser Ablation method
• Chemical Vapor Deposition (CVD)
• High Pressure Carbon Monoxide (HiPco) process
• NASA/GSFC Non-catalytic method

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Arc-Discharge Method

• Evaporates carbon atoms by a plasma of helium gas
• The gas is ignited by high currents that pass
  through opposing carbon anodes and cathodes
• The arc discharge is dependent on keeping a 1 mm
  gap between the carbon electrodes

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Laser Ablation Chemical Vaporization Deposition

• Laser Ablation uses a laser to blast a graphite
  target with metal in it. As the plume gets blown
  out of the furnace, different types of high
  quality carbon nanotubes form in a big clump that
  must then be sorted to be useful.
• Chemical Vapor Deposition (CVD) uses metal
  nanoparticles to break down hydrocarbon gas, like
  methane. Since the nanoparticles absorb the
  carbon and precipitate out nanotubes, CVD gives
  the most control over where nanotubes form.

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HiPCO NASA/GSFC Methods
HiPCO process was developed by Dr. Richard
Smalleys group at Rice University. The
nanotubes are produced from gas phase reactions
of iron carbonyl at high pressures in carbon
monoxide. Carbon monoxide is added to iron
pentacarbonyl and is heated to produce SWNTs

• NASA/GSFC method was developed by Dr. Jeannette
  Benavides and group at NASA/GSFC. The process
  uses a helium arc welder that is ignited by a
  current flowing through an anode tube which
  contains a carbon rod. A current is applied and
  carbon nanotubes are deposited on the carbon
  cathode.

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Applications of CNTs
Chemical Genetic Probes A nanotube-tipped AFM
can trace a stand of DNA and identify chemical
markers that reveal which of several possible
variants of a gene is present in the
strand Mechanical Memory A screen of nanotubes
laid on support blocks is used as a binary memory
device with voltages forcing some tubes to
contact the on state and the others to separate
the off state.
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Applications of CNTs
Hydrogen Ion Storage Nanotubes might store
hydrogen in their hallow centers and release it
gradually in efficient and inexpensive fuel
cells. They can also hold lithium ions, which
could lead to longer-lived batteries. Nanotweezers
Two nanotubes attached to electrodes as a glass
rod, can be opened and closed by changing
voltage. The tweezers can be used to pick up nm
size objects. Sharper Scanning Microscope Attache
d to the tip of a scanning probe microscope,
nanotubes can bust the resolution by a factor of
10 or more allowing clearer views of proteins and
other molecules.
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Polymers
Polyethylene
Polystyrene
Polycaprolactone
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Polystyrene

• Advantages of Polystyrene
• Cheap
• Rigid
• Transparent
• Good electrical properties
• Large body of data
• Disadvantages of Polystyrene
• Brittle
• Poor resistance (especially to organics)
• Susceptible to UV degradation

• Applications of Polystyrene
• Light diffusers
• Beakers
• Electronic housings
• Video/Audio Cassette cases

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Polyethylene

• NASA Balloons
• Thin polyethylene material (0.8 mil thick)
• 40 million cubic feet in volume
• 600 feet in diameter
• Taller than a 60 story building
• Consists of a balloon, a parachute, and a payload
• Payload can weigh up to 8,000 pounds

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Polycaprolactone

• Advantages of Polycaprolactone
• Low temperature activation
• Ease of processing
• Good adhesion to difficult substrates
• Flexibility at low temperatures
• Soluble
• High tear strengths
• Nontoxic biodegradable
• Ability to be electrospun into fibers

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Electrospinning
The Process An electrically charged jet of
polymer solution or melt is created by a high
voltage source. When the electrical force at the
surface of a polymer solution or melt overcomes
the surface tension the jet is ejected. As the
intensity of the electric field is increased the
surface of the fluid at the tip of the capillary
tube elongates to form a Taylor cone.

• Parameters that affect the process
• Solution properties (viscosity, conductivity
  surface tension)
• Electric Potential, Flow rate Concentration
• Distance between the capillary and collection
  screen
• Temperature
• Motion of target screen
• Capillary tilt

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Extrusion
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Polystyrene (PS) Results
FTIR of synthesized Polystyrene by an emulsion
process. Pattern of bands in the 3000-cm-1 are
also found in FTIR spectrums of commercial
polystyrene.
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PS Results Continued
Molecular weight determinations Gel Permeation
Chromatography was used to determine the
molecular weight of the Polystyrene sample. The
molecular weight of the sample was 214K g/mole
Figure 2 TGA-DTA of synthesized polystyrene.
Thermal degradation begins around 3000C.
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Carbon Nanotubes for the PS
Raman Spectra The Raman displays a band at
approximately 1320 cm-1 and a band at 1580 cm-1
Theses bands are indicative of multi-walled
carbon nanotubes. The broad peak around 2800
cm-1 indicates the possible presence of amorphous
carbon.
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Carbon Nanotubes for the PS
TGA-DTA of GSFC synthesized carbon nanotubes
Multi-wall carbon nanotubes are confirmed by the
degradation beginning at 5000C in the TGA-DTA
analysis.
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Carbon Nanotubes/PS Results
SEM image of Polystyrene multi-walled carbon
nanotubes
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Polycaprolactone (PCL) Results
PCL film on an aluminum backing and carbon double
sticky tape.
A magnified view of the film to show the PCL
fibers
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Carbon Nanotubes PCL Results
SEM images of the carbon nanotubes produced by
the JSC/HiPCO Process. Images reveal the presence
of raw SWNTs.
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Carbon Nanotubes PCL Results
SEM and STEM images of the JSC/HiPCO produced
SWNTs. The TE detector shows the presence of
iron catalyst particles inside the carbon
nanotubes.
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Carbon Nanotubes PCL Results
SEM image of the PCL/CNT fibers. The fibers are
not as smooth as before.
SEM image of the PCL/CNT film on an aluminum
backing
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Carbon Nanotubes PCL Results
SEM image of the PCL/CNT fibers. The CNTs were
not dispersed before adding them to the PCL
solution
CNTs were dispersed before adding them to the
PCL solution
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The Future

• Add functional groups to the carbon nanotubes or
  the polymer chain in order to create chemical
  bonding as opposed to physical attraction.
• Develop a process for compounding the LDPE.
• Use the extruder to produce nanocomposite rods.
• Complete the characterization of the produced
  nanocomposites by using analytical instruments
  such as TEM, AFM, Raman, etc.

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Summary
Polymers doped with carbon nanotubes to produce
nanocomposites have the potential to deliver
extraordinary lightweight materials with superior
mechanical, thermal and electronic properties.
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References

• 1.      Tokumoto, Hiroshi "Carbon Nanotube AFM
  for Nano-Science and NanoTechnology,
  http//www.es.hokudai.ac.jp/nano/english/nano_c_02
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• 2.      Swan, Thomas Co. Ltd., "Nanomaterials
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  mages.html, October 28, 2004
• 3.      Weizmann Institute of Science,
  "Nanochemistry Group Nanoscale Materials
  Chemistry and Biophysics, http//www.weizmann.ac.
  il/materials/ernesto/projects.html, October 26,
  2004
• 4.      BBC News, "Worlds Smallest Tweezers",
  http//news.bbc.co.uk/1/hi/sci/tech/557388.stm,
  October 26, 2004
• 5.      Woolward, Iain, Smith, Sharon,
  "Nanotechnology Enabled Sensors,
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• 6.      Daenen, Michael, "Wonderous World of
  Carbon Nanotubes, http//students.chem.tue.nl/ifp
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• 7.      Fairbrother, Debbie, "Balloon Program
  Office", http//www.wff.nasa.gov/code820/,
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• 8.      NASA, "SAMPE", http//www.nasatechnology.c
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• CNT Team, Carbon Nanotubes, http//plaza.snu.ac.
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• 10. Canright, Shelly, NASA Student Features,
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  October, 26, 2004