Tangle no more, nanotubes
Solvent simplifies industrial 3D, roll-to-roll carbon nanotube printing
and more

Date:
April 27, 2022
Source:
Rice University
Summary:
Scientists have developed an acid-based solvent that simplifies
carbon nanotube processing in a way that's less toxic and easy to
scale up for industrial applications.



FULL STORY ========================================================================== Carbon nanotubes that are prone to tangle like spaghetti can use a little special sauce to realize their full potential.


==========================================================================
Rice University scientists have come up with just the sauce, an acid-based solvent that simplifies carbon nanotube processing in a way that's easier
to scale up for industrial applications.

The Rice lab of Matteo Pasquali reported inScience Advances on its
discovery of a unique combination of acids that helps separate nanotubes
in a solution and turn them into films, fibers or other materials with excellent electrical and mechanical properties.

The study co-led by graduate alumnus Robert Headrick and graduate student Steven Williams reports the solvent is compatible with conventional manufacturing processes. That should help it find a place in the
production of advanced materials for many applications.

"There's a growing realization that it's probably not a good idea to
increase the mining of copper and aluminum and nickel," said Pasquali,
Rice's A.J.

Hartsook Professor and a professor of chemical and biomolecular
engineering, chemistry and materials science and nanoengineering. He is
also director of the Rice-based Carbon Hub, which promotes the development
of advanced carbon materials to benefit the environment.

"But there is this giant opportunity to use hydrocarbons as our ore,"
he said.

"In that light, we need to broaden as much as possible the range in which
we can use carbon materials, especially where it can displace metals
with a product that can be manufactured sustainably from a feedstock
like hydrocarbons." Pasquali noted these manufacturing processes produce
clean hydrogen as well.



========================================================================== "Carbon is plentiful, we control the supply chains and we know how to
get it out in an environmentally responsible way," he said.

A better way to process carbon will help. The solvent is based on methanesulfonic (MSA), p-toluenesulfonic (pToS)and oleum acids that,
when combined, are less corrosive than those currently used to process nanotubes in a solution. Separating nanotubes (which researchers refer
to as dissolving) is a necessary step before they can be extruded through
a needle or other device where shear forces help turn them into familiar
fibers or sheets.

Oleum and chlorosulfonic acids have long been used to dissolve nanotubes without modifying their structures, but both are highly corrosive. By
combining oleum with two weaker acids, the team developed a broadly
applicable process that enables new manufacturing for nanotubes products.

"The oleum surrounds each individual nanotube and gives it a very
localized positive charge," said Headrick, now a research scientist at
Shell. "That charge makes them repel each other." After detangling,
the milder acids further separate the nanotubes. They found MSA is best
for fiber spinning and roll-to-roll film production, while pToS, a solid
that melts at 40 degrees Celsius (104 degrees Fahrenheit), is particularly useful for 3D printing applications because it allows nanotube solutions
to be processed at a moderate temperature and then solidified by cooling.



==========================================================================
The researchers used these stable liquid crystalline solutions to make
things in both modern and traditional ways, 3D printing carbon nanotube aerogels and silk screen printing patterns onto a variety of surfaces, including glass.

The solutions also enabled roll-to-roll production of transparent films
that can be used as electrodes. "Honestly, it was a little surprising
how well that worked," Headrick said. "It came out pretty flawless on
the very first try." The researchers noted oleum still requires careful handling, but once diluted with the other acids, the solution is much
less aggressive to other materials.

"The acids we're using are so much gentler that you can use them with
common plastics," Headrick said. "That opens the door to a lot of
materials processing and printing techniques that are already in place
in manufacturing facilities.

"It's also really important for integrating carbon nanotubes into other devices, depositing them as one step in a device-manufacturing process,"
he said.

They reported the less-corrosive solutions did not give off harmful fumes
and were easier to clean up after production. MSA and pToS can also be
recycled after processing nanotubes, lowering their environmental impact
and energy and processing costs.

Williams said the next step is to fine-tune the solvent for applications,
and to determine how factors like chirality and size affect nanotube processing.

"It's really important that we have high-quality, clean, large diameter
tubes," he said.

Co-authors of the paper are alumna Lauren Taylor and graduate students
Oliver Dewey and Cedric Ginestra of Rice; graduate student Crystal Owens
and professors Gareth McKinley and A. John Hart at the Massachusetts
Institute of Technology; alumna Lucy Liberman, graduate student Asia
Matatyaho Ya'akobi and Yeshayahu Talmon, a professor emeritus of chemical engineering, at the Technion-Israel Institute of Technology, Haifa,
Israel; and Benji Maruyama, autonomous materials lead in the Materials
and Manufacturing Directorate, Air Force Research Laboratory.

The research was supported by the Air Force Office of Scientific Research (FA9550-12-1-0035, FA9550-15-1-0370, FA9550-19-1-7045), the Robert
A. Welch Foundation (C-1668), the Department of Energy (DE-EE0007865, DE-AR0001015), the NASA Space Technology Research Institute (NNX17AJ32G),
a NASA Space Technology Research Fellowship (NNX14AL71H), a National
Defense Science and Engineering Graduate Research Fellowship and the
United States-Israel Binational Science Foundation (2016161).


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


========================================================================== Journal Reference:
1. Robert J. Headrick, Steven M. Williams, Crystal E. Owens, Lauren W.

Taylor, Oliver S. Dewey, Cedric J. Ginestra, Lucy Liberman,
Asia Matatyaho Ya'akobi, Yeshayahu Talmon, Benji Maruyama, Gareth
H. McKinley, A. John Hart, Matteo Pasquali. Versatile acid solvents
for pristine carbon nanotube assembly. Science Advances, 2022; 8
(17) DOI: 10.1126/ sciadv.abm3285 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/04/220427140621.htm

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