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Nano
Research...Nano-Forschung
Nano Onderzoek
www.nano-Tsunami.com
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NANOTECH
ADVANCE MAKES CARBON NANOTUBES MORE USEFUL
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UCSD
researchers exploited the strong alignment of nanotube
growth with the direction of electric field lines
to create tailor-made bends.
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San
Diego, CA, April 11, 2005 -- Researchers at UCSD have
made carbon nanotubes bent in sharp predetermined
angles, a technical advance that could lead to use
of the long, thin cylinders of carbon as tiny springs,
tips for atomic force microscopes, smaller electrical
connectors in integrated circuits, and in many other
nanotechnology applications. In a paper published
in the April 7, 2005, issue of the Journal of Physical
Chemistry B, Sungho Jin, a professor of materials
science at UCSD’s Jacobs School of Engineering, reported
a technique to create bent nanotubes by manipulating
the electric field during their growth and adjusting
other conditions.
"Controlling nanotube
geometry is necessary to realize the many promised
applications of these materials," said Jin, a
professor in the Jacobs School’s Department of Mechanical
and Aerospace Engineering. “Our new results show that
we have taken a step toward understanding how to shape
nanotubes to our specifications, an achievement that
could greatly enhance their value to society.”
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Graduate
student Joseph AuBuchon, left, and professor of materials
science Sungho Jin. |
| Joseph
AuBuchon, a graduate student in Jin’s group, exploited
the strong alignment of nanotube growth with the direction
of electric field lines. After growing an aligned array
of straight nanotubes, AuBuchon switched the orientation
of electric field lines 90 degrees to make L-shaped
tubes. He then made more orientation changes to make
zigzags. AuBuchon won a Gold Graduate Student Award
and Best Poster Award for presenting details of his
nanotube research at the spring 2005 meeting of the
Materials Research Society, which was held March 28-April
1 in San Francisco.
Carbon nanotubes hold great promise because of their
exceptionally strong mechanical properties, their
ability to efficiently carry high densities of electric
current, and other unique electrical and chemical
properties. AuBuchon used a plasma enhanced chemical
vapor deposition technique to grow about 2 billion
nanotubes per square centimeter on silicon wafers
seeded with nickel catalyst nanoparticles.
Nanotubes, which are roughly 10,000 times smaller
than a human hair, can be made almost perfectly straight
in special chambers of gas plasma. Successfully shaping
nanotubes has been a goal of materials scientists
since a Japanese researcher discovered them in 1991.
However, the creation of sharp bends is difficult
because once a growth phase of nanotubes is interrupted,
the catalyst particles at the tips of the growing
nanotubes become encased with carbon, blocking future
growth. A key to Jin and AuBuchon’s successful growth
of bent nanotubes involved the discovery of a technique
to prevent the unwanted carbon from encasing the catalyst
between growth steps.
“It’s hard to imagine all the
possible uses for bent nanotubes, but we think one
of them might be to improve the performance of atomic
force microscopy,” said Jin. Atomic force microscopy
uses a mechanical probe to magnify rigid materials
at the atomic scale to produce 3-D images of the surface.
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Nanotube
connectors as thin as 1.2 nanometers are theoretically
capable of supplying sufficiently large electric
currents to integrated circuits.
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also noted that nanotubes may be used as replacements
for conventional electrical connectors made of metal
wires in ever smaller integrated circuits. Such wires
are roughly 70 nanometers wide, but nanotube connectors
as thin as 1.2 nanometers are theoretically capable
of supplying sufficiently large electric currents to
integrated circuits.
In
addition, Jin said the interconnections between microcircuit
devices are often made with metal alloy solders. Unfortunately,
these solders expand and contract at rates different
than those of the microcircuit device, and cycles
of heating and cooling cause fatigue cracking at interconnections.
“If these interconnections were made with electrically
conducting nanotube zigzags, which also act as springs,
not only would we need much less space to make these
interconnections, but the thermal-expansion mismatch
also wouldn’t matter because the interconnections
are flexible,” says Jin. “We call it the compliant
nano-interconnect.”
Using
a modification of the approach to make zigzag nanotubes,
Jin and AuBuchon also produced parallel arrays of
T- and Y-shaped nanotubes that could be used to make
fuel cells more efficient. These arrays of parallel,
branched nanotubes could act as a 3-D scaffolding
for platinum catalyst particles. High densities of
platinum catalyst-tipped nanotubes could enable fuel
cells produce electricity more efficiently.
Joseph
F. AuBuchon, Li-Han Chen, and Sungho Jin, "Control
of Carbon Capping for Regrowth of Aligned Carbon Nanotubes"
(2005). Journal of Physical Chemistry B. 109, pp 6044-6048.
RELATED
LINKS:
Department of Mechanical and Aerospace Engineering
MEDIA
CONTACT:
Rex Graham, Jacobs School of Engineering -- 858-822-3075,
rgraham@soe.ucsd.edu
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This
story has been adapted from a news release -
Diese Meldung basiert auf einer Pressemitteilung -
Deze
tekst is gebaseerd op een nieuwsbericht - |
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