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Rice’s Carbon Nanotube Fibers Outperform Copper

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Scanning electron microscope images show typical carbon nanotube fibers created at Rice University and broken into two by high-current-induced Joule heating. Rice researchers broke the fibers in different conditions – air, argon, nitrogen and a vacuum – to see how well they handled high current. The fibers proved overall to be better at carrying electrical current than copper cables of the same mass. (Image Credit: Kono Lab/Rice University)

On a pound-per-pound basis, carbon nanotube-based fibers invented at Rice University have greater capacity to carry electrical current than copper cables of the same mass, according to new research. While individual nanotubes are capable of transmitting nearly 1,000 times more current than copper, the same tubes coalesced into a fiber using other technologies fail long before reaching that capacity. A series of tests at Rice showed the wet-spun carbon nanotube fiber still handily beat copper, carrying up to four times as much current as a copper wire of the same mass. That, said the researchers, makes nanotube-based cables an ideal platform for lightweight power transmission in systems where weight is a significant factor, like aerospace applications. Present-day transmission cables made of copper or aluminum are heavy because their low tensile strength requires steel-core reinforcement. Scientists working with nanoscale materials have long thought there’s a better way to move electricity from here to there. Certain types of carbon nanotubes can carry far more electricity than copper. The ideal cable would be made of long metallic “armchair” nanotubes that would transmit current over great distances with negligible loss, but such a cable is not feasible because it’s not yet possible to manufacture pure armchairs in bulk, Rice professor Matteo Pasquali said. In the meantime, the Pasquali lab has created a method to spin fiber from a mix of nanotube types that still outperforms copper. The cable developed is strong and flexible even though at 20 microns wide, it’s thinner than a human hair.