Researchers at Rice
University have discovered
a method of industrial-scale processing of pure carbon nanotube
fibers. The breakthrough is the result of a nine-year program and the
method builds on the processes that have been used by chemical firms
for decades to produce plastics.
Researcher Matteo Pasquali
from Rice said, "Plastics is a $300 billion U.S. industry
because of the massive throughput that's possible with fluid
processing. The reason grocery stores use plastic bags instead of
paper and the reason polyester shirts are cheaper than cotton is that
polymers can be melted or dissolved and processed as fluids by the
train-car load. Processing nanotubes as fluids opens up all of the
fluid-processing technology that has been developed for
The researchers report that the new process
builds on a discovery made in 2003 at Rice that found a way to
dissolve large amounts of pure nanotubes in strong acetic solvents
like sulfuric acids. The team of researchers found with further
investigation that the nanotubes dissolved in the acidic solutions
aligned themselves like spaghetti in a package to form liquid
crystals that could then be spun into monofilament fibers about as
thick as a human hair.
Researcher Wade Adams said, "That
research established an industrially relevant process for nanotubes
that was analogous to the methods used to create Kevlar from rodlike
polymers, except for the acid not being a true solvent. The current
research shows that we have a true solvent for nanotubes --
chlorosulfonic acid -- which is what we set out to find when we
started this project nine years ago."
To get the proof
that the nanotubes were dissolving spontaneously in the
chlorosulfonic acid the team had to invent new techniques to directly
image the process.
"Ishi Talmon and his colleagues at
Technion did the critical work required to help get direct proof that
nanotubes were dissolving spontaneously in chlorosulfonic acid,"
Pasquali said. "To do this, they had to develop new experimental
techniques for direct imaging of vitrified fast-frozen acid
Ishi Talmon said, "This was a very
difficult study. Matteo's team not only had to pioneer new
experimental techniques to achieve this, they also had to make
significant extensions to the classical theories that were used to
describe solutions of rods. The Technion team had to develop a new
methodology to enable us to produce high-resolution images of the
nanotubes dispersed in chlorosulfonic acid, a very corrosive fluid,
by state-of-the-art electron microscopy at cryogenic
According to the researchers, one major
discovery remains before high-quality carbon nanotubes can be created
and utilized. Current methods produce a myriad of different carbon
nanotubes with different properties, lengths, and diameters.
Researchers are working to find a method of crating only one type of
carbon nanotubes. When batches of metallic conductive nanotubes can
be created the use of nanotubes will boom.