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Topic Name: Researchers Discovered Fundamental State of Matter will Helpful to Transform Materials Research, Electronics Design
Category: Bioelectronics
Research persons: Valerii Vinokur, Tatyana Baturina
Location: Argonne National Laboratory, U.S. Department of Energy, United States
Details
Superinsulation may sound like a marketing gimmick for a
drafty attic or winter coat. But it is actually a newly discovered fundamental
state of matter created by scientists at the
U.S. Department of Energy's
Argonne National Laboratory in
collaboration with several European institutions. This discovery opens new
directions of inquiry in condensed matter physics and breaks ground for a new
generation of microelectronics.
Led by Argonne senior scientist Valerii Vinokur and Russian
scientist Tatyana Baturina, an international team of scientists from Argonne,
Germany, Russia and Belgium fashioned a thin film of titanium nitride which they
then chilled to near absolute zero. When they tried to pass a current through
the material, the researchers noticed that its resistance suddenly increased by
a factor of 100,000 once the temperature dropped below a certain threshold. The
same sudden change also occurred when the researchers decreased the external
magnetic field.
Like superconductors, which have applications in many different areas of
physics, from accelerators to magnetic-levitation (maglev) trains to MRI
machines, superinsulators could eventually find their way into a number of
products, including circuits, sensors and battery shields.
If, for example, a battery is left exposed to the air, the charge will
eventually drain from it in a matter of days or weeks because the air is not a
perfect insulator, according to Vinokur. "If you pass a current through a
superconductor, then it will carry the current forever; conversely, if you have
a superinsulator, then it will hold a charge forever," he said.
"Titanium nitride films, as well as films prepared from some other materials,
can be either superconductors or insulators depending on the thickness of the
film," Vinokur said. "If you take the film which is just on the insulating side
of the transition and decrease the temperature or magnetic field, then the film
all of a sudden becomes a superinsulator."
Scientists could eventually form superinsulators that would encapsulate
superconducting wires, creating an optimally efficient electrical pathway with
almost no energy lost as heat. A miniature version of these superinsulated
superconducting wires could find their way into more efficient electrical
circuits.
Titanium nitride's sudden transition to a superinsulator occurs because the
electrons in the material join together in twosomes called Cooper pairs. When
these Cooper pairs of electrons join together in long chains, they enable the
unrestricted motion of electrons and the easy flow of current, creating a
superconductor. In superinsulators, however, the Cooper pairs stay separate from
each other, forming self-locking roadblocks.
"In superinsulators, Cooper pairs avoid each other, creating enormous electric
forces that oppose penetration of the current into the material," Vinokur said.
"It's exactly the opposite of the superconductor," he added.
The theory behind the experiment stemmed from Argonne's Materials Theory
Institute, which Vinokur organized six years ago in the laboratory's Materials
Science Division. The MTI hosts a handful of visiting scholars from around the
world to perform cutting-edge research on the most pressing questions in
condensed matter physics. Upon completion of their tenure at Argonne, these
scientists return to their home institutions but continue to collaborate on the
joint projects. The MTI attracts the world's best condensed matter scientists,
including Russian "experimental star" Tatyana Baturina, who, according to
Vinokur, "became a driving force in our work on superinsulators."
Scientists from the Institute of Semiconductor Physics in Novosibirsk, Russia,
Regensburg and Bochum universities in Germany and Interuniversity
Microelectronics Centre in Leuven, Belgium, also participated in the research.
Note for Superinsulation
Superinsulation is an approach to building design, construction, and
retrofitting. A superinsulated house is intended to be heated predominantly by
intrinsic heat sources (waste heat generated by appliances and the body heat of
the occupants), without using passive solar building design techniques or large
amounts of thermal mass, and with very small amounts of backup heat. This has
been demonstrated to work in very cold climates but requires close attention to
construction details in addition to the insulation.
Some may consider that superinsulation is an alternative to passive solar design
(although many building designs include features of both with special attention
to preventing summer overheating). Superinsulation is one of the ancestors of
the passive house approach. A related approach to efficient building design is
zero energy building.
There is no set definition of superinsulation, but superinsulated buildings
typically include:
Very thick insulation (typically R40 walls and R60 roof)
Detailed insulation where walls meet roofs, foundations, and other walls
Airtight construction, especially around doors and windows
a heat recovery ventilator to provide fresh air
No large windows facing any particular direction (unlike passive solar, which
uses large windows facing the sun and fewer/smaller windows facing other
directions).
No large amounts of thermal mass
No active or passive solar heat (but may have solar water heating and/or hot
water heat recycling)
No conventional heating system, just a small backup heater
It is possible to retrofit superinsulation to an existing older house. The
easiest way is to build new exterior walls that allow more space for insulation.
A vapor barrier can be installed on the outside of the original framing. Care
should be exercised when adding a vapor barrier at a location other than on the
"warm-side in winter" to prevent condensation and consequent mold and mildew.
This may cause health problems for the occupants and damage existing structure.
Many builders in northern Canada use a 1/3 to 2/3 approach, placing the vapor
barrier no further out than 1/3 of the R-value of the insulated portion of the
wall. This way, the vapor barrier will usually not fall below the dew point, and
will minimize the possibility of condensation problems. With an internal room
temperature of 20°C (68°F), the vapor barrier will then only reach the dew point
for outside temperatures below −18°C (-1°F). An approved application of a
building wrap on the outside of the insulation underneath the exterior siding
helps keep the wind out, yet allows the insulation to breathe. Tar paper and
other products are available for this purpose.
Interior retrofits are possible where the owner wants to preserve the old
exterior siding, or where setback requirements don't leave space for an exterior
retrofit. Sealing the vapor barrier is more difficult and the house is left with
less interior space. Another approach is to use the 1/3 to 2/3 method mentioned
above, that is to vapor barrier the inside of the existing wall (if it isn't
done already) and add insulation and support structure to the inside. This way,
utilities (power, telephone, cable, and plumbing) can be added in this new wall
space without penetrating the vapor barrier. Again, care must be exercised to
prevent any area of the vapor barrier from becoming a condensation surface.
Adding a second vapor barrier may trap moisture because the dead-space so
created will not breathe. If in doubt, partial removal of existing wall
surfacing might be desirable.
In new construction, the cost of the extra insulation and wall framing is offset
by not requiring a dedicated central heating system. The cost of a
superinsulation retrofit may need to be balanced against the future cost of
heating fuel (which can be expected to fluctuate from year to year due to supply
problems, natural disasters or geopolitical events).
A superinsulated house takes longer to cool in the event of an extended power
failure during cold weather, for example after a severe ice storm disrupts
electric transmission. Adverse weather may hamper efforts to restore power,
leading to outages lasting a week or more. When deprived of their continuous
supply of electricity (either for heat directly, or to operate gas-fired
furnaces), conventional houses cool more rapidly during cold weather, and may be
at greater risk of costly damage due to freezing water pipes. Residents who use
supplemental heating methods without proper care during such episodes, or at any
other time, may subject themselves to risk of fire or carbon monoxide poisoning.
Note for Titanium Nitride
Titanium nitride (TiN) (sometimes known as Tinite or TiNite) is an extremely
hard ceramic material, often used as a coating on titanium alloy, steel,
carbide, and aluminium components to improve the substrate's surface properties.
Applied as a thin coating, TiN is used to harden and protect cutting and sliding
surfaces, for decorative purposes, and as a non-toxic exterior for medical
implants.
The hardness of TiN coatings is difficult to measure as the coatings are
exceptionally hard and the thinness of the coating causes conventional hardness
tests to penetrate into the substrate. Microhardness tests are required for
accurate readings. The hardness of TiN is estimated as ~85 on the Rockwell C
Hardness (~2500 Vickers Hardness or 24.5 gigapascals). The Rockwell C scale is
regarded as crude for readings this high. Special techniques have been developed
to measure TiN hardness.
TiN has excellent infrared (IR) reflectivity properties, reflecting in a
spectrum similar to elemental gold (Au). Depending on the substrate material and
surface finish, TiN will have a coefficient of friction ranging from 0.4 to 0.9
versus itself (non-lubricated). Typical formation has a crystal structure of
NaCl-type with a roughly 1:1 stoichiometry; however TiNx compounds with x
ranging from 0.6 to 1.2 are thermodynamically stable. TiN will oxidize at 600 °C
(~1100 °F) at normal atmosphere, and has a melting point of 2930 °C.
most common use for TiN coating is for edge retention and corrosion resistance
on machine tooling, such as drill bits and milling cutters, often improving
their lifetime by a factor of three or more.
Because of TiN's metallic gold color, it is used to coat costume jewelry and
automotive trim for decorative purposes. TiN is also widely used as a top-layer
coating, usually with nickel (Ni) or chromium (Cr) plated substrates, on
consumer plumbing fixtures and door hardware. TiN is non-toxic, meets FDA
guidelines and has seen use in medical devices and bio-implants, as well as
aerospace and military applications.
Such coatings have also been used in implanted prostheses (especially hip
replacement implants). Such films are usually applied by either reactive growth
(for example, annealing a piece of titanium in nitrogen) or physical vapor
deposition (PVD), with a depth of about 3 micrometers. Its high Young's modulus
(600 gigapascals) relative to titanium alloys (100 GPa) means that thick
coatings tend to flake away, making them much less durable than thin ones.
As a coating it is also used to protect the sliding surfaces of suspension forks
of bicycles and motorcycles as well as the shock shafts of radio controlled
cars.
Though less visible, thin films of TiN are also used in the semiconductor
industry. In copper-based chips, such films find use as a conductive barrier
between a silicon device and the metal contacts used to operate it. While the
film blocks diffusion of metal into the silicon, it is conductive enough (30–70
μΩ·cm) to allow a good electrical connection. In this context, TiN is classified
as a "barrier metal", even though it is clearly a ceramic from the perspective
of chemistry or mechanical behavior.
Led by Argonne senior scientist Valerii Vinokur and Russian scientist Tatyana
Baturina, an international team of scientists from Argonne, Germany, Russia and
Belgium fashioned a thin film of titanium nitride which they then chilled to
near absolute zero. This converts the material to a superinsulator, with
resistance suddenly increased by a factor of 100,000. Newly discovered 'superinsulators'
promise to transform materials research.
Note for Magnetic Levitation
Magnetic levitation, maglev, or magnetic suspension is a method by which an
object is suspended with no support other than magnetic fields. The
electromagnetic force is used to counteract the effects of the gravitational
force.
Earnshaw's theorem proved conclusively that it is not possible to levitate
stably using only static, macroscopic, "classical" electromagnetic fields. The
forces acting on an object in any combination of gravitational, electrostatic,
and magnetostatic fields will make the object's position unstable. However,
several possibilities exist to make levitation viable, for example, the use of
electronic stabilization or diamagnetic materials. Neodymium magnets are some of
the most used magnets for the maglev system.
A substance which is diamagnetic repels a magnetic field. Earnshaw's theorem
does not apply to diamagnets; they behave in the opposite manner of a typical
magnet due to their relative permeability of μr < 1. All materials have
diamagnetic properties, but the effect is very weak, and usually overcome by the
object's paramagnetic or ferromagnetic properties, which act in the opposite
manner. Any material in which the diamagnetic component is strongest will be
repelled by a magnet, though this force is not usually very large. Diamagnetic
levitation can be used to levitate very light pieces of pyrolytic graphite or
bismuth above a moderately strong permanent magnet. As water is predominantly
diamagnetic, this technique has been used to levitate water droplets and even
live animals, such as a grasshopper and a frog; however, the magnetic fields
required for this are very high, typically in the range of 16 teslas, and
therefore create significant problems if ferromagnetic materials are nearby.
Argonne National Laboratory brings the world's brightest scientists and
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for the U.S. Department of Energy's Office of Science.
In figure 1, Argonne scientist Valerii Vinokur and Russian
collaborator Tatyana Baturina examine a graph of the resistance of the
insulating film plotted against the applied magnetic field.
In figure 2, To perform the experiment, the researchers used a dilution
refrigerator, a device in which the temperature can be lowered to several
millikelvin, just above absolute zero. The thin superinsulating films are then
placed in the camera of the dilution fridge.
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