NSF NIRT Grant 0609115

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NSF NIRT Grant 0609115 Hierarchical
Nanomanufacturing of Carbon Nanotube Sheets and
Yarns and their Applications for Active
Nano-Materials Systems PIs Ray H. Baughman,1
Karen Lozano,2 Anvar Zakhidov,1 and Mei Zhang1, 3
1. University of Texas at Dallas, 2. University
of Texas - Pan American, and 3. Florida State
University

• Results
• The measured thermal conductivity (3? method) of
  yarns (26 W/mK) and yarns (50 W/mK) is not high.
• The strong observed dependence (Fig. 2) of
  thermal conductivity on nanotube bundling
  provides the explanation.
• Inter-tube connections are relatively
  unimportant for limiting both phonon and
  electronic transport, since individual bundle and
  bulk measurements (normalized to density) differ
  little.
• Network models indicate thermal and electrical
  transport on all walls of 8 wall, hundred ?m long
  nanotubes.
• Experiment and theory show mechanical stress
  transfer is low between outer and inner MWNT
  walls for above long nanotubes.
• Individual MWNTs break, rather than slide out,
  when pulled from a twisted 10 ?m diameter yarn
  made of 8 wall, hundred ?m long nanotubes.
• Thermal expansion is negative at RT for twisted
  yarns (about -3.4X10-6/ºC).
• Filtration-produced nanotube sheet shows abrupt
  switch in the sign of Poissons ratio vs MWNT
  weight percent.

• III. Demonstrate Sheet and Yarn Applications
• for Active Nano-Materials Systems
• Fig. 4 (Left) MRI imaging of a 3 mm mouse brain
  and 250 ?m blood vessel using carbon nanotube
  antenna, in collaborative work with Tursiop
  International (UTD licensee). (Right)
  Self-supporting 50 nm thick, transparent nanotube
  sheets mounted in metal frames for electron
  stripping in an ion beam accelerator.
• Results
• Demonstrated two new applications for MWNT
  sheets (Fig. 4),
• MRI antennas and transparent grids for electron
  stripping.
• Demonstrated that twist-spun MWNT yarns provide
  high actuator strokes (up to 0.5) at high loads
  (30 MPa, versus the 0.3 MPa stress generation
  capability of natural muscles) and low creep even
  at these high loads.
• IV. Demonstrate First Synthesis Route to Carbon
  Nanotubes of One Predetermined Type

• I. Obtain and Deploy Deep Understanding
• of Sheet and Yarn Fabrication processes
• Fig. 1 (A) SEM image from movie showing the
  transformation of 300 ?m high nanotube forest
  (left) to nanotube sheet (right).
• B Picture of the continuous draw of a nanotube
  sheet and the wrapping of this sheet on a
  rotating mandrel.
• Problem Very few types of nanotube forests are
  drawable to make yarns and sheets, and minor
  changes in reaction conditions causes a
  transition from drawable forests to undrawable
  forests.
• Results
• The number of nanotubes per forest area must be
  in a narrow range in order to obtain the degree
  of intermittent bundling needed for sheet or yarn
  draw.
• Using movies of the drawing process taken in a
  SEM (Fig. 1A), a model explaining the
  transition from vertically aligned nanotubes in
  forests to horizontally aligned nanotubes in
  nanotube yarns and sheets was derived.

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B