Hierarchical Nanomanufacturing of Carbon Nanotube Sheets and ...

Hierarchical Nanomanufacturing of Carbon Nanotube Sheets and ...

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 Zhang3
1. University of Texas at Dallas, 2. University of Texas - Pan American, and 3. Florida State University
Results:

I. Obtain and Deploy Deep Understanding
of Sheet and Yarn Fabrication processes
A

A

B

B

Fig. 1 (A) SEM image from movie showing the transformation of
300 m high nanotube forest (left) to nanotube sheet (right).
(B) Schematic model of the fundamental process for the
transformation of a nanotube forest (left) to a nanotube sheet,
showing the critical role of nanotubes that migrate between
bundles.

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.

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/C).
Filtration-produced nanotube sheet shows abrupt switch in
the sign of Poissons ratio vs. MWNT weight percent.

II. Determine and Understand Sheet and Yarn
Properties
Thermal conductivity (W/ mK)
Thermal conductivity, W/mK

700

L=10 m, d=10 nm, R=560 k, _=56 k/m

T = 295 K

T=295K

600
500
400

100 W/mK for
our 100 MWNT
bundles

300
200
100
0

0

20

40

60

80

100

Number of MWNT in bundle

Number of MWNTs in Bundle

120

Fig. 2. Thermal conductivity
measurements on individual
nanotube bundles show that
bundling decreases thermal
conductivity.

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) Selfsupporting 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 charge injection based carbon nanotube
artificial muscles that operate between near 0 K and above 1900
K to provide over 3 X strokes in width and thickness directions,
and over 104 %/s stroke rates

Results:
Using movies of the drawing process taken in a SEM
(Fig. 1A), a predictive model (Fig. 1B) explaining the transition
from vertically aligned nanotubes in forests to horizontally
aligned nanotubes in nanotube yarns and sheets was derived.
The nanotube bundle areal density and the linear density of
inter-nanotube connections via migrant nanotubes were
confirmed experimentally and theoretically to be key parameters
needed for sheet or yarn drawability.
Increased nanotube length in spinable forests nearly ten fold,
from 0.3 mm to 2.7 mm, by increasing nanotube diameter.
Synthesized nanotube forests having improved topology that
enabled sheet draw at 120 m/minute and increased the width of
drawable transparent sheets from 5 to 10 cm..
Demonstrated that false-twist and liquid-based densification
provide comparable yarn strengths to those for twist-based
spinning, and increased yarn strength to 1.2 GPa.

III. Demonstrate Sheet and Yarn Applications
for Active Nano-Materials Systems

IV. Demonstrate First Synthesis Route to Carbon
Nanotubes of One Predetermined Type
A

Fig. 3 (A) Measured in-plane Poissons ratio (black) and
density-normalized Youngs modulus (blue) vs. MWNT content
in SWNT/MWNT sheets. The insert illustrates the effect of
Poissons ratio sign on transverse curvature for a bent sheet
strip. (B) Measured density-normalized tensile strength (black)
and density (blue) vs. MWNT content in sheets. (C) Model for
nanotube sheets, where meandering nanotubes are
represented by zigzag chains. (D) The relationships between
in-plane and thickness-direction Poissons ratios for SWNT
(black) and MWNT (red) sheets having the force constant
ratios R that yield the measured Poissons ratios (closed
circles). The Poissons ratio changes result from varying the
indicated average angle between the nanotubes and the sheet
plane. Poissons ratios to the right of the blue line provide
negative linear compressibilities. (Science 320, 504 (2008)).

B

C

D

Fig. 5. A proposed synthesis route to carbon nanotubes of one
type. Solid-state 1,4-addition polymerization reaction (A) converts
linear stacks of cyclic tetradiyne molecules [-(CH2)4CC-CC-]4
(B) into a hydrocarbon nanotube (C), which is the proposed
precursor to the (4,4) nanotube (D).

Results
Two polymerizable tetramer phases were found, one with the
tetramer rings skewered on an array of chloroforms.
Crystal structure determined (J. Reibenspies) for trimer phases
and two tetramer phases - reactivity is consistent with theory.
When polymerizable, the expected Raman spectra and
diffraction data for the hydrocarbon nanotube was obtained.
Conversion of the hydrocarbon nanotubes to nanotubes of one
type has not yet been successful.

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