January 27, 2016

Nano-coating makes coaxial cables lighter

Replacing the braided outer conductor in coaxial data cables with a coat of conductive
carbon nanotubes saves significant weight, according to Rice University researchers.
(Credit: Pasquali Lab/Rice University)

(January 27, 2016)  Rice University scientists replace metal with carbon nanotubes for aerospace use

Common coaxial cables could be made 50 percent lighter with a new nanotube-based outer conductor developed by Rice University scientists.

The Rice lab of Professor Matteo Pasquali has developed a coating that could replace the tin-coated copper braid that transmits the signal and shields the cable from electromagnetic interference. The metal braid is the heaviest component in modern coaxial data cables.

The research appears this month in the American Chemical Society journal ACS Applied Materials and Interfaces.

Replacing the outer conductor with Rice’s flexible, high-performance coating would benefit airplanes and spacecraft, in which the weight and strength of data-carrying cables are significant factors in performance.

 A coating of carbon nanotubes, seen through a clear jacket, replaces a braided metal outer
conductor in an otherwise standard coaxial data cable. Rice University scientists designed
the cable to save weight for aerospace applications. (Credit: Jeff Fitlow/Rice University)

Rice research scientist Francesca Mirri, lead author of the paper, made three versions of the new cable by varying the carbon-nanotube thickness of the coating. She found that the thickest, about 90 microns – approximately the width of the average human hair – met military-grade standards for shielding and was also the most robust; it handled 10,000 bending cycles with no detrimental effect on the cable performance.

“Current coaxial cables have to use a thick metal braid to meet the mechanical requirements and appropriate conductance,” Mirri said. “Our cable meets military standards, but we’re able to supply the strength and flexibility without the bulk.”

Coaxial cables consist of four elements: a conductive copper core, an electrically insulating polymer sheath, an outer conductor and a polymer jacket. The Rice lab replaced only the outer conductor by coating sheathed cores with a solution of carbon nanotubes in chlorosulfonic acid. Compared with earlier attempts to use carbon nanotubes in cables, this method yields a more uniform conductor and has higher throughput, Pasquali said. “This is one of the few cases where you can have your cake and eat it, too,” he said. “We obtained better processing and improved performance.”

journal reference >>