French scientists have developed a way to
spin into fibres one of the new wonder
materials of modern chemistry.
Carbon nanotubes, which measure just a few
billionths of a metre across, have extraordinary
electrical and mechanical properties - in
particular, outstanding strength. They are
likely to find applications in many hi-tech
areas, from tiny electric devices to
extra-resistant coatings.
But the tubes are
difficult to produce in
bulk and order in a way
that would allow
researchers to tap their
undoubted potential.
Now, Scientists from
the Paul Pascal
Research Centre at the
University of Bordeaux, and colleagues, have
devised a method to fabricate "indefinitely
long" ribbons and fibres from literally trillions of
individual nanotubes. These ribbons and fibres
will bend without breaking and can even be
tied into knots.
The work brings the industrial production of
materials based on carbon nanotubes one step
nearer.
Flowing stream
Carbon nanotubes are essentially sheets of
graphite, a single atom deep, that have been
folded back on themselves.
Their discovery in 1991
followed quickly that of
buckminsterfullerene,
the spherical cage of
carbon atoms that
looks like a soccer ball.
The tubes can be
single-walled, or
multi-walled with one
"skin" of atoms siting
neatly inside another.
To make buckyballs
and tubes, scientists
vaporise carbon in the
presence of a catalyst.
But, not only is it an
expensive process, the
individual molecules are
difficult to organise.
The French work
tackled the ordering
problem. The team
dispersed a raw
nanotube soot into a
surfactant, or
detergent, solution, which was then injected
into a flowing steam of a polymer solution.
This caused the nanotubes to recondense into
a mesh, and the flow aligned the mesh into
ribbons. When dried, the ribbons collapsed into
narrower fibres.
Fibres could eventually make super-strong textiles
(Scale bar: 1mm)
The fibres made by the French team were
between 10 and 100 millionths of a metre in
diameter.
"The main point of this work is that we have
processed the nanotubes into a form that is of
practical use," co-researcher Dr Philippe Poulin
told BBC News Online. "And we very pleased
because we think the method is simple enough
to be scalable to an industrial level."
Dr Ray Baughman, a material scientist with
Honeywell International, said long and
ultra-strong nanotube fibres could be used in a
variety of future applications, from artificial
muscles to hydrogen storage.
Commenting on the French study, he said: "By
building on their discoveries, it will be possible
to devise an economically viable process for
spinning strong nanotube fibres.
"However, at the current price of purified
single-walled nanotubes (about $1,000 per
gram), single-walled carbon nanotube fibres
are only attractive for devices requiring little
material.
But, if this price fell, as expected, large-scale,
commercially viable applications would also be
possible, he said.
The French research is published in the journal
Science.
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