OAK
RIDGE, Tenn., April 3, 2006 — Oak Ridge National
Laboratory researchers have demonstrated a way to
sustain high supercurrents in wires in the presence
of a large applied magnetic field -- a step which
could greatly expand practical applications of superconductors.
By creating columns of self-aligned, non-superconductive "nanodots" within
the superconductor, the ORNL team has produced a
high-temperature superconductor that works even in
a powerful magnetic field.
The ORNL work, reported in the current issue of
Science, increases the plausibility of high-temperature
superconductors in motors, generators, air defense
systems and other applications once limited by the
negative effects of applied magnetic fields.
Lead author for the Science paper is Sukill Kang,
a post-doctoral fellow in the Materials Sciences
and Technology Division at ORNL.
Kang's mentor, Amit Goyal, is an ORNL distinguished
scientist and the project's technical leader who
also co-developed the rolling-assisted-biaxially-textured
substrates (RABiTS) process which deposits brittle,
ceramic-like high temperature superconducting materials
onto a substrate, or template, that gives the wires
the texture, flexibility and mechanical strength
of metal.
Superconductors carry large amounts of current when
cooled, offering much more efficient energy transmission
for a wide range of uses. Advances in achieving supercurrent
at higher temperatures with liquid nitrogen, which
is more practical than liquid helium needed to cool
older superconductors at lower temperatures, have
made the technology more applicable.
However, magnetic fields have remained an obstacle
to many superconductor applications, Goyal said.
The problem is that naturally occurring vortices
-- whirling cylindrical forces between the atoms
of the superconducting material -- begin to move
about under applied magnetic fields, creating electrical
resistance and power dissipation. Large scale supercurrents
can flow only if these vortices remain firmly locked
in place, or "pinned."
ORNL's answer was to incorporate "misfit" nanodots
of non-conductive material throughout the entire
thickness of the superconductor and effectively pin
the vortices and prevent their movement, enabling
high supercurrents even in the presence of high applied
magnetic fields.
"Most applications of superconductors require the
superconductor to be in large applied magnetic fields," Goyal
said. "Thus, to truly sustain very high current in
strong magnetic fields, you must prevent the vortices
from moving.
"One way to do that is to have non-superconducting
regions which "pin" or prevent these vortices from
moving. They provide a barrier. To get adequate,
effective, non-superconducting regions to do this
work for us, they had to be of the nanoscale dimensions.
"This is a nice combination of the use of nanotechnology
and superconductivity. With continued advances in
nanotechnology, maybe even more interesting things
are possible in the future.
Bob Hawsey, manager of ORNL's superconductivity
program, said the work, sponsored by the Department
of Energy's Office of Electricity Delivery and Energy
Reliability, may lead to even more developments in
superconductivity.
"These results demonstrate the potential for the
'second generation' high-temperature superconductors
to have broad applicability in the electric power
sector of our economy" Hawsey said. "Our team is
working with three U.S. companies to learn how to
apply these innovative, short-sample laboratory results
to industrial processes."
UT-Battelle manages Oak Ridge National Laboratory
for the Department of Energy.
Media Contact: Mike
Bradley
Communications and External Relations
865.576.9553
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