CNT Fibers Cables Made from Lightweight Carbon Nanotubes

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Researchers at the IMDEA Materials Institute in Madrid have developed the first CNT fibers with electrical conductivity comparable to that of copper and aluminium cables. The advantage: they are much lighter and could replace heavy copper cables.

At the IMDEA Materials Institute, a scalable manufacturing process for carbon nanotube fibers (CNT fibers) with electrical conductivity comparable to that of copper and aluminum was presented for the first time. These fibers are considered ideal building blocks for electrical conductors due to their unique combination of low density and electrical, thermal and mechanical properties.

So far, however, they have not offered the necessary electrical conductivity to provide a realistic alternative to conventional materials, particularly copper, on an industrial scale. "This is the first time we have obtained results with CNT fibers that show sufficient performance in this respect to offer a realistic industrial alternative to conventional conductive materials," said Dr. Juan José Vilatela, lead researcher at IMDEA Materials.

Specifically, the researchers were able to produce gas-phase intercalated CNT fibers with a conductivity of up to 24.5 MS/m at room temperature—almost half the conductivity of copper, but six times lighter.

The Secret Lies in the Tetrachloroaluminate

The key to the high conductivity was the introduction of tetrachloroaluminate (AlCl₄) for intercalation into the CNT fibers. AlCl₄ acts as a dopant that does not interfere with the CNT fiber structure. By maintaining the original structure of the CNT bundles, the doping process increases conductivity while preserving their mechanical properties. "In addition, AlCl₄- offers a strong doping effect compared to other dopants we have studied, without increasing the weight excessively," explained IMDEA materials researcher Ana Inés de Isidro Gómez.

Specifically, the researchers showed that by doping the highly aligned CNT fibers with AlCl₄, they were able to achieve a more than 17-fold increase in the electrical conductivity of the fibers. This resulted in an average specific conductivity that exceeded that of copper, with the highest measured value exceeding that of aluminum.

Prospect of Even Higher Electrical Conductivity

"This is particularly important in the electrification of means of transport, be it electric vehicles, drones or aircraft, which require a large number of cables with the lowest possible weight," said Dr. Vilatela. "It is also promising for overhead power lines, which are often constrained by their own weight."

"We have clearly demonstrated that intercalation in the gas phase can increase the conductivity of commercial CNT fibers well beyond their previous upper limit. This provides both record-breaking electrical conductivity and the prospect of further increases," concluded de Isidro Gómez.

The results were published in the journal "Science" and represent a breakthrough for the future of electrification in aerospace, electric vehicles (EVs), drones and related applications that require lightweight and high-strength electrical conductors. This publication is the result of a collaboration with the Nanoscopy on Low Dimensional Materials (NLDM) group at the Institute of Nanoscience and Materials of Aragon (INMA), a joint center of the Spanish National Research Council (CSIC) and the University of Zaragoza (Unizar), led by Dr. Raúl Arenal (Araid researcher). The research was also carried out in collaboration with the Technical University of Madrid (UPM) and researchers from the University of Zaragoza at INMA (CSIC-Unizar).

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