A team of researchers from Rice University, in collaboration with scientists at the Dutch firm Teijin Aramid, have concluded a study that proves on a pound-for-pound basis, carbon nanotube-based fibers have greater capacity for carrying electrical current than copper cables of the same mass.
The group analyzed the materials’ current-carrying capacity, or ampacity, with a custom rig that allowed them to test the nanotubes alongside metal cables of the same diameter. The cables were tested while they were suspended in the air, in a vacuum, and in nitrogen and argon environments.
Based on the group’s different means of approach, carbon nanotube fibers exposed to nitrogen performed best, followed by argon, and finally open air. All three were able to cool via convection.
The fibers in a vacuum had the lowest current carrying capacity, and they were only able to cool by radiation.
The fact that carbon nanotubes are better at carrying electricity than copper is well documented—on average, individual nanotubes can transmit nearly 1,000 times more current than copper. The problem is when those tubes are coalesced into a fiber, they fail before reaching capacity.
In order to overcome this hurdle, the team wet-spun the carbon nanotube fibers and re-ran the tests, discovering that this approach overwhelmingly beat out the copper, so much so that it was able to carry four times as much current as a copper wire of the same mass.
The group believes their nanotube-based cables will be ideal for light-weight power transmission in systems where weight is a factor (like aerospace applications). That’s because today’s transmission cables are made of either copper or aluminum, both of which are very heavy because their low tensile strength requires steel-core reinforcement. For a while, scientists have been looking for better, more efficient and lightweight method of getting electricity from point A to point B. Carbon nanotubes were discovered, but their tendency to fail remained an obstacle for a while.
The ideal cable, in the group’s opinion, would be something made of long metallic “armchair” nanotubes that would transmit current over longer distances with negligible loss. This isn’t doable just yet because manufacturing “armchair” nanotubes in bulk is a process not yet perfected to the point of mass production.
The Rice team was led by professors Junichiro Kono and Matteo Pasquali, the latter of whom explains that one of the things which held this technology back was a disconnect between electrical engineers who study the current carrying capacity of conductors, and material scientists working on the actual development of the carbon nanotubes themselves.
“The outcome is that these fibers have the highest CCC ever reported for any carbon-based fibers,” Kono said. “Copper still has better resistivity by an order of magnitude, but we have the advantage that carbon fiber is light. So if you divide the CCC by the mass, we win.”
The group plans on exploring the fiber’s multifunctional aspects, including flexible optoelectronic device application.
Their paper was published in the journal Advanced Functional Materials.
Story via rice.edu
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