No limit yet for carbon nanotube fibers
Lab makes case for high-performance carbon nanotube fibers for industry


Date:
August 17, 2020
Source:
Rice University
Summary:
Researchers report advances in their quest to make the best carbon
nanotube fibers for industry.



FULL STORY ========================================================================== Carbon nanotube fibers made at Rice University are now stronger than
Kevlar and are inching up on the conductivity of copper.


==========================================================================
The Rice lab of chemical and biomolecular engineer Matteo Pasquali
reported in Carbon it has developed its strongest and most conductive
fibers yet, made of long carbon nanotubes through a wet spinning process.

In the new study led by Rice graduate students Lauren Taylor and Oliver
Dewey, the researchers noted that wet-spun carbon nanotube fibers,
which could lead to breakthroughs in a host of medical and materials applications, have doubled in strength and conductivity every three years,
a trend that spans almost two decades.

While that may never mimic Moore's Law, which set a benchmark for computer
chip advances for decades, Pasquali and his team are doing their part
to advance the method they pioneered to make carbon nanotube fibers.

The lab's threadlike fibers, with tens of millions of nanotubes in cross section, are being studied for use as bridges to repair damaged hearts,
as electrical interfaces with the brain, for use in cochlear implants,
as flexible antennas and for automotive and aerospace applications.

They are also part of the Carbon Hub, a multiuniversity research
initiative launched in 2019 by Rice with support from Shell, Prysmian
and Mitsubishi to create a zero-emissions future.



========================================================================== "Carbon nanotube fibers have long been touted for their potential
superior properties," Pasquali said. "Two decades of research at
Rice and elsewhere have made this potential a reality. Now we need a
worldwide effort to increase production efficiency so these materials
could be made with zero carbon dioxide emissions and potentially with concurrent production of clean hydrogen." "The goal of this paper is
to put forth the record properties of the fibers produced in our lab,"
Taylor said. "These improvements mean we're now surpassing Kevlar in
terms of strength, which for us is a really big achievement. With just
another doubling, we would surpass the strongest fibers on the market."
The flexible Rice fibers have a tensile strength of 4.2 gigapascals (GPa), compared to 3.6 GPa for Kevlar fibers. The fibers require long nanotubes
with high crystallinity; that is, regular arrays of carbon-atom rings
with few defects. The acidic solution used in the Rice process also helps reduce impurities that can interfere with fiber strength and enhances
the nanotubes' metallic properties through residual doping, Dewey said.

"The length, or aspect ratio, of the nanotubes is the defining
characteristic that drives the properties in our fibers," he said,
noting the surface area of the 12-micrometer nanotubes used in Rice
fiber facilitates better van der Waals bonds. "It also helps that the collaborators who grow our nanotubes optimize for solution processing
by controlling the number of metallic impurities from the catalyst and
what we call amorphous carbon impurities." The researchers said the
fibers' conductivity has improved to 10.9 megasiemens (million siemens)
per meter. "This is the first time a carbon nanotube fiber has passed
the 10 megasiemens threshold, so we've achieved a new order of magnitude
for nanotube fibers," Dewey said. Normalized for weight, he said the
Rice fibers achieve about 80% of the conductivity of copper.



==========================================================================
"But we're surpassing platinum wire, which is a big achievement for
us," Taylor said, "and the fiber thermal conductivity is better than
any metal and any synthetic fibers, except for pitch graphite fibers."
The lab's goal is to make the production of superior fibers efficient
and inexpensive enough to be incorporated by industry on a large scale,
Dewey said.

Solution processing is common in the production of other kinds of fibers, including Kevlar, so factories could use familiar processes without
major retooling.

"The benefit of our method is that it's essentially plug-and-play,"
he said.

"It's inherently scalable and fits in with the way synthetic fibers are
already made." "There's a notion that carbon nanotubes are never going
to be able to obtain all the properties that people have been hyping
now for decades," Taylor said.

"But we're making good gains year over year. It's not easy, but
we still do believe this technology is going to change the world."
Co-authors of the paper are Rice alumnus Robert Headrick; graduate
students Natsumi Komatsu and Nicolas Marquez Peraca; Geoff Wehmeyer,
an assistant professor of mechanical engineering; and Junichiro Kono,
the Karl F. Hasselmann Professor in Engineering and a professor of
electrical and computer engineering, of physics and astronomy, and of
materials science and nanoengineering. Pasquali is the A.J. Hartsook
Professor of Chemical and Biomolecular engineering, of chemistry and of materials science and nanoengineering.

The U.S. Air Force Office of Scientific Research, the Robert A. Welch Foundation, the Department of Energy's Advanced Manufacturing Office
and the Advanced Research Projects Agency-Energy supported the research.


========================================================================== Story Source: Materials provided by Rice_University. Note: Content may
be edited for style and length.


========================================================================== Journal Reference:
1. Lauren W. Taylor, Oliver S. Dewey, Robert J. Headrick, Natsumi
Komatsu,
Nicolas Marquez Peraca, Geoff Wehmeyer, Junichiro Kono, Matteo
Pasquali.

Improved Properties, Increased Production, and the Path to Broad
Adoption of Carbon Nanotube Fibers. Carbon, 2020; DOI: 10.1016/
j.carbon.2020.07.058 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200817150447.htm

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