A power cable made entirely of iodine-doped double-walled carbon nanotubes is just as efficient as traditional power cables at a sixth the weight of copper and silver, according to researchers at Rice University. Image: Yao Zhao/Rice University |
Cables made of carbon nanotubes are inching toward electrical conductivities
seen in metal wires, and that may light up interest among a range of
industries, according to Rice
University researchers.
A Rice laboratory made such a cable from double-walled carbon nanotubes and
powered a fluorescent light bulb at standard line voltage—a true test of the
novel material’s ability to stake a claim in energy systems of the future.
The work appears in Nature.
Highly conductive nanotube-based cables could be just as efficient as
traditional metals at a sixth of the weight, says Enrique Barrera, a Rice
professor of mechanical engineering and materials science. They may find wide
use first in applications where weight is a critical factor, such as airplanes
and automobiles, and in the future could even replace traditional wiring in
homes.
The cables developed in the study are spun from pristine nanotubes and can
be tied together without losing their conductivity. To increase conductivity of
the cables, the team doped them with iodine and the cables remained stable. The
conductivity-to-weight ratio (called specific conductivity) beats metals,
including copper and silver, and is second only to the metal with highest specific
conductivity, sodium.
Yao Zhao, who recently defended his dissertation toward his doctorate at
Rice, is the new paper’s lead author. He built the demo rig that let him toggle
power through the nanocable and replace conventional copper wire in the light-bulb
circuit.
Zhao left the bulb burning for days on end, with no sign of degradation in
the nanotube cable. He’s also reasonably sure the cable is mechanically robust;
tests showed the nanocable to be just as strong and tough as metals it would
replace, and it worked in a wide range of temperatures. Zhao also found that
tying two pieces of the cable together did not hinder their ability to conduct
electricity.
The few centimeters of cable demonstrated in the present study seems short,
but spinning billions of nanotubes (supplied by research partner Tsinghua University) into a cable at all is quite
a feat, Barrera says. The chemical processes used to grow and then align
nanotubes will ultimately be part of a larger process that begins with raw
materials and ends with a steady stream of nanocable, he said. The next stage
would be to make longer, thicker cables that carry higher current while keeping
the wire lightweight. “We really want to go better than what copper or
other metals can offer overall,” he says.