Tag Archives: Yeshayahu Talmon

Detangling carbon nanotubes (CNTs)

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An April 27, 2022 news item on ScienceDaily announces research into a solution to a vexing problem associated with the production of carbon nanotubes (CNTs),

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 in Science 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.

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An April 22, 2022 Rice University news release (received via email and also published on April 27, 2022 on EurekAlert), which originated the news item, delves further into how the research has environmental benefits and into its technical aspects (Note Links have been removed),

“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.

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Here’s a link to and a citation for the paper,

Versatile acid solvents for pristine carbon nanotube assembly by 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. Science Advances • 27 Apr 2022 • Vol 8, Issue 17 • DOI: 10.1126/sciadv.abm3285

This paper is open access.

Soap and water for creating 2D nanoflakes (hexagonal boron nitride [hBN] sheets)

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Rice University (Texas, US) has a pretty image illustrating the process of making 2D nanoflakes,

Caption: The image displays the exfoliation of hexagonal boron nitride into atomically thin nanosheets aided by surfactants, a process refined by chemists at Rice University. Credit: Ella Maru Studio

A January 27, 2021 news item on Nanowerk announces the Rice University news,

Just a little soap helps clean up the challenging process of preparing two-dimensional hexagonal boron nitride (hBN).

Rice University chemists have found a way to get the maximum amount [number] of quality 2D hBN nanosheets from its natural bulk form by processing it with surfactant (aka soap) and water. The surfactant surrounds and stabilizes the microscopic flakes, preserving their properties.

Experiments by the lab of Rice chemist Angel Martí identified the “sweet spot” for making stable dispersions of hBN, which can be processed into very thin antibacterial films that handle temperatures up to 900 degrees Celsius (1,652 degrees Fahrenheit).

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A brief grammatical moment: I can see where someone might view it as arguable (see second paragraph of the above excerpt) but for me ‘amount’ is for something like ‘flour’ for an ‘amount of flour’. ‘Number’ is for something like a ‘number of sheets’. The difference lies in your ability to count the items. Generally speaking, you can’t count the number of flour, therefore, it’s the amount of flour, but you can count the number of sheets. Can count these hexagonal boron nitride (hBN) sheets? If not, is what makes this arguable.

A January 27, 2021 Rice University news release (also on EurekAlert), which originated the news item, delves into details,

The work led by Martí, alumna Ashleigh Smith McWilliams and graduate student Cecilia Martínez-Jiménez is detailed in the American Chemical Society journal ACS Applied Nano Materials.

“Boron nitride materials are interesting, particularly because they are extremely resistant to heat,” Martí said. “They are as light as graphene and carbon nanotubes, but you can put hBN in a flame and nothing happens to it.”

He said bulk hBN is cheap and easy to obtain, but processing it into microscopic building blocks has been a challenge. “The first step is to be able to exfoliate and disperse them, but research on how to do that has been scattered,” Martí said. “When we decided to set a benchmark, we found the processes that have been extremely useful for graphene and nanotubes don’t work as well for boron nitride.”

Sonicating bulk hBN in water successfully exfoliated the material and made it soluble. “That surprised us, because nanotubes or graphene just float on top,” Martí said. “The hBN dispersed throughout, though they weren’t particularly stable.

“It turned out the borders of boron nitride crystals are made of amine and nitric oxide groups and boric acid, and all of these groups are polar (with positive or negative charge),” he said. “So when you exfoliate them, the edges are full of these functional groups that really like water. That never happens with graphene.”

Experiments with nine surfactants helped them find just the right type and amount to keep 2D hBN from clumping without cutting individual flakes too much during sonication. The researchers used 1% by weight of each surfactant in water, added 20 milligrams of bulk hBN, then stirred and sonicated the mix.

Spinning the resulting solutions at low and high rates showed the greatest yield came with the surfactant known as PF88 under 100-gravity centrifugation, but the highest-quality nanosheets came from all the ionic surfactants under 8,000 g centrifugation, with the greatest stability from common ionic surfactants SDS and CTAC.

DTAB — short for dodecyltrimethylammonium bromide — under high centrifugation proved best at balancing the yield and quality of 2D hBN. The researchers also produced a transparent film from hBN nanosheets dispersed in SDS and water to demonstrate how they can be processed into useful products.

“We describe the steps you need to do to produce high-quality hBN flakes,” Martí said. “All of the steps are important, and we were able to bring to light the consequences of each one.”

Understanding the Exfoliation and Dispersion of Hexagonal Boron Nitride Nanosheets by Surfactants: Implications for Antibacterial and Thermally Resistant Coatings by Ashleigh D. Smith McWilliams, Cecilia Martínez-Jiménez, Asia Matatyaho Ya’akobi, Cedric J. Ginestra, Yeshayahu Talmon, Matteo Pasquali, and Angel A. Martí. ACS Appl. Nano Mater. 2021, 4, 1, 142–151 DOI: https://doi.org/10.1021/acsanm.0c02437 Publication Date: January 7, 2021 Copyright © 2021 American Chemical Society

This paper is behind a paywall.

Prima donna of nanomaterials (carbon nanotubes) tamed by scientists at Rice University (Texas, US), Teijin Armid (Dutch/Japanese company), and Technion Institute (based in Israel)

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The big news is that a multinational team has managed to spin carbon nanotubes (after 10 years of work) into threads that look like black cotton and display both the properties of metal wires and of carbon fibers. Here’s more from the Jan. 10, 2013 news item on ScienceDaily,

“We finally have a nanotube fiber with properties that don’t exist in any other material,” said lead researcher Matteo Pasquali, professor of chemical and biomolecular engineering and chemistry at Rice. “It looks like black cotton thread but behaves like both metal wires and strong carbon fibers.”

The research team includes academic, government and industrial scientists from Rice; Teijin Aramid’s headquarters in Arnhem, the Netherlands; the Technion-Israel Institute of Technology in Haifa, Israel; and the Air Force Research Laboratory (AFRL) in Dayton, Ohio.

The Jan. 10, 2013 Rice University news release on EurekAlert, which originated the news item, describes some of the problems presented when trying to produce carbon nanotube fiber at an industrial scale,

The phenomenal properties of carbon nanotubes have enthralled scientists from the moment of their discovery in 1991. The hollow tubes of pure carbon, which are nearly as wide as a strand of DNA, are about 100 times stronger than steel at one-sixth the weight. Nanotubes’ conductive properties — for both electricity and heat — rival the best metal conductors. They also can serve as light-activated semiconductors, drug-delivery devices and even sponges to soak up oil.

Unfortunately, carbon nanotubes are also the prima donna of nanomaterials [emphasis mine]; they are difficult to work with, despite their exquisite potential. For starters, finding the means to produce bulk quantities of nanotubes took almost a decade. Scientists also learned early on that there were several dozen types of nanotubes — each with unique material and electrical properties; and engineers have yet to find a way to produce just one type. Instead, all production methods yield a hodgepodge of types, often in hairball-like clumps.

Creating large-scale objects from these clumps of nanotubes has been a challenge. A threadlike fiber that is less than one-quarter the thickness of a human hair will contain tens of millions of nanotubes packed side by side. Ideally, these nanotubes will be perfectly aligned — like pencils in a box — and tightly packed. Some labs have explored means of growing such fibers whole, but the production rates for these “solid-state” fibers have proven quite slow compared with fiber-production methods that rely on a chemical process called “wet spinning.” In this process, clumps of raw nanotubes are dissolved in a liquid and squirted through tiny holes to form long strands.

Thank you to the writer of the Rice University news release for giving me the phrase “prima donna of nanomaterials.”

The news release goes on to describe the years of work and collaboration needed to arrive at this point,

Shortly after arriving at Rice in 2000, Pasquali began studying CNT wet-spinning methods with the late Richard Smalley, a nanotechnology pioneer and the namesake of Rice’s Smalley Institute for Nanoscale Science and Technology. In 2003, two years before his untimely death, Smalley worked with Pasquali and colleagues to create the first pure nanotube fibers. The work established an industrially relevant wet-spinning process for nanotubes that was analogous to the methods used to create high-performance aramid fibers — like Teijin’s Twaron — which are used in bulletproof vests and other products. But the process needed to be refined. The fibers weren’t very strong or conductive, due partly to gaps and misalignment of the millions of nanotubes inside them.

“Achieving very high packing and alignment of the carbon nanotubes in the fibers is critical,” said study co-author Yeshayahu Talmon, director of Technion’s Russell Berrie Nanotechnology Institute, who began collaborating with Pasquali about five years ago.

The next big breakthrough came in 2009, when Talmon, Pasquali and colleagues discovered the first true solvent for nanotubes — chlorosulfonic acid. For the first time, scientists had a way to create highly concentrated solutions of nanotubes, a development that led to improved alignment and packing.

“Until that time, no one thought that spinning out of chlorosulfonic acid was possible because it reacts with water,” Pasquali said. “A graduate student in my lab, Natnael Bahabtu, found simple ways to show that CNT fibers could be spun from chlorosulfonic acid solutions. That was critical for this new process.”

Pasquali said other labs had found that the strength and conductivity of spun fibers could also be improved if the starting material — the clumps of raw nanotubes — contained long nanotubes with few atomic defects. In 2010, Pasquali and Talmon began experimenting with nanotubes from different suppliers and working with AFRL scientists to measure the precise electrical and thermal properties of the improved fibers.

During the same period, Otto [Marcin Otto, Business Development Manager at Teijin Aramid] was evaluating methods that different research centers had proposed for making CNT fibers. He envisaged combining Pasquali’s discoveries, Teijin Aramid’s know-how and the use of long CNTs to further the development of high performance CNT fibers. In 2010, Teijin Aramid set up and funded a project with Rice, and the company’s fiber-spinning experts have collaborated with Rice scientists throughout the project.

“The Teijin scientific and technical help led to immediate improvements in strength and conductivity,” Pasquali said.

Study co-author Junichiro Kono, a Rice professor of electrical and computer engineering, said, “The research showed that the electrical conductivity of the fibers could be tuned and optimized with techniques that were applied after initial production. This led to the highest conductivity ever reported for a macroscopic CNT fiber.”

The fibers reported in Science have about 10 times the tensile strength and electrical and thermal conductivity of the best previously reported wet-spun CNT fibers, Pasquali said. The specific electrical conductivity of the new fibers is on par with copper, gold and aluminum wires, but the new material has advantages over metal wires.

Here’s an explanatory video the researchers have provided,

A more commercial perspective is covered in the Teijin Armid Jan. 11, 2013 news release (Note: A link has been removed),

“Our carbon nanotube fibers combine high thermal and electrical conductivity, like that seen in metals, with the flexibility, robust handling and strength of textile fibers”, explained Marcin Otto, Business Development Manager at Teijin Aramid. “With that novel combination of properties it is possible to use CNT fibers in many applications in the aerospace, automotive, medical and (smart) clothing industries.”

Teijin’s cooperation and involvement was crucial to the project. Twaron technology enabled improved performance, and an industrially scalable production method. That makes it possible to find applications for CNT fibers in a range of commercial or industrial products. “This research and ongoing tests offer us a glimpse into the potential future possibilities of this new fiber. For example, we have been very excited by the interest of innovative medical doctors and scientists exploring the possibilities to use CNT fiber in surgical operations and other applications in the medical field”, says Marcin Otto. Teijin Aramid expects to replace the copper in data cables and light power cables used in the aerospace and automotive industries, to make aircraft and high end cars lighter and more robust at the same time. Other applications could include integrating light weight electronic components, such as antennas, into composites, or replacing cooling systems in electronics where the high thermal conductivity of carbon nanotube fiber can help to dissipate heat.

Teijin Aramid is currently trialing samples of CNT fiber on a small scale with the most active prospective customers. Building up a robust supply chain is high on the project team’s list of priorities. As well as their carbon fiber, aramid fiber and polyethylene tape, this new carbon nanotube fiber is expected to allow Teijin to offer customers an even broader portfolio of high performance materials.

Teijin Group (which is headquartered in Japan) has been mentioned here before notably in a July 19, 2010 posting about a textile inspired by a butterfly’s wing (Morphotex) which, sadly, is no longer being produced as noted in a more recent April 12, 2012 posting about Teijin’s then new fiber ‘Nanofront™’ for use in sports socks.