Team makes case for high performance carbon nanotube fibers for industry

Carbon nanotube fibers made at Rice University are now stronger than Kevlar and are relying on the conductivity of copper.

The Travel lab of chemical and biomolecular engineer Matteo Pasquali reported in Carbon it has developed its strongest and most conductive fibers to date, made from long carbon nanotubes by 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 can lead to breakthroughs in a host of medical and material applications, have doubled in strength every three years. and conductivity, a trend that spans nearly two decades.

While that can never be imitated by Moore’s law, which has been a benchmark for computer chip advances for decades, Pasquali and his team are doing their part to create the method they pioneered to make carbon nanotube fibers.

The lab’s threaded fibers, with tens of millions of nanotubes in cross section, are being investigated 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 multi-university research initiative launched in 2019 by Rice with support from Shell, Prysmian and Mitsubishi to create a future for zero emissions.

“Carbon nanotube fibers are long toute for their potential superior properties,” said Pasquali. “Two decades of research at Rice and elsewhere have made this potentially a reality. Now we need a global effort to increase production efficiency so that these materials can be made with zero carbon dioxide emissions and potentially with simultaneous production of clean hydrogen.”

“The purpose of this paper is to set the record properties of the fibers produced in our lab,” Taylor said. “These improvements mean that we are now surpassing Kevlar in terms of strength, which is a really big achievement for us. With just one more doubling, we would be overtaking the strongest fibers on the market.”

The flexible Travel Fiber has a tensile strength of 4.2 gigapascals (GPa), compared to 3.6 GPa for Kevlar fibers. The fibers require long nanowires with high crystallinity; that is, regular arrays of carbon atom rings with few defects. The acidic solution used in the Travel process also helps reduce impurities that can shrink with glass fiber and can improve the metal properties of the nanoburn by residual doping, Dewey said.

“The length, as an aspect ratio, of the nanoburns is the defining property that drives the properties in our fibers,” he said, noting the surface area of ​​the 12-micrometer nanoburns used in travel fibers facilitates better Van der Waals tires. “It also helps that the collaborators who grow our nanotubes optimize for solution processing by controlling the number of metal impurities from the catalyst and what we call amorphous carbon contaminants.”

The researchers said that the conductivity of the fibers has been improved to 10.9 megahertz (million semen) per meter. “This is the first time that a carbon nanotube fiber has passed the 10-megaseme threshold, so we have reached a new order of reach for nanotube fibers,” said Dewey. Normalized for weight, he said, the travel fibers reach about 80% of the conductivity of copper.

“But we survive platinum wire, which is a great achievement for us,” Taylor said, “and the thermal conductivity of glass fiber is better than any metal and all synthetic fibers except pitch graphite fibers.”

The lab’s goal is to make the production of superior fibers efficient and inexpensive enough to be widely absorbed by industry, Dewey said. Solution solution is common in the production of other types of fibers, including Kevlar, so that factories could use trusted processes without major overhaul.

“The advantage of our method is that it is essentially plug-and-play,” he said. “It’s inherently scalable and fits the way synthetic fibers are already made.”

“There’s an idea that carbon nanotubes are never capable of getting all the properties that people have been hyping for decades now,” Taylor said. “But we make good profits year after year. It’s not easy, but we still believe that this technology will change the world.”

Co-authors of the paper are Rice alumnus Robert Headrick; graduates Natsumi Komatsu and Nicolas Marquez Peraca; Geoff Wehmeyer, an assistant professor of mechanical engineering; and Junichiro Kono, the Karl F. Hasselmann professor of engineering and a professor of electrical and computer engineering, of physics and astronomy, and of materials science and nanoengineering. Pasquali is the AJ Hartsook Professor of Chemical and Biomolecular Engineering, Chemistry and Materials Science and Nanoengineering.