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CAS Number 12007-25-9
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Linear Formula MgB2
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Molecular Weight 45.93
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EC Number 234-501-2
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MDL number MFCD00049752
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PubChem Substance ID 329758102
Magnesium diboride (MgB2) is a simple ionic binary compound that has proven to be an inexpensive and useful superconducting
material.
Detailed description
Thermal conductivity[edit]
MgB2 is
a multi-band superconductor, that is each Fermi surface has different
superconducting energy gap. For MgB2, sigma bond of boron is strong,
and it induces large s-wave superconducting gap, and pi bond is weak and
induces small s-wave gap.[17] The quasiparticle
states of the vortices of large gap are highly confined to the vortex core. On
the other hand, the quasiparticle states of small gap are loosely bound to the
vortex core. Thus they can be delocalized and overlap easily between adjacent
vortices.[18] Such delocalization
can strongly contribute to the thermal conductivity, which shows abrupt
increase above Hc1.[17]
Possible applications
Superconductors
Superconducting properties and low cost make
magnesium diboride attractive for a variety of applications.[19] For those
applications, MgB2 powder
is compressed with silver metal (or 316 stainless steel) into wire and
sometimes tape via the PIT process
In 2006 a 0.5 tesla open MRI superconducting magnet system was built
using 18 km of MgB2 wires.
This MRI used a closed-loop cryocooler, without requiring
externally supplied cryogenic liquids for cooling.[20][21]
"...the next generation MRI instruments must be
made of MgB2 coils
instead of NbTi coils, operating in
the 20–25 K range without liquid helium for cooling. ... Besides the magnet
applications MgB2 conductors
have potential uses in superconducting transformers, rotors and transmission
cables at temperatures of around 25 K, at fields of 1 T."[19]
Thin coatings can be used in superconducting radio
frequency cavities to minimize energy loss and reduce the inefficiency of
liquid helium cooled niobium cavities.
Because of the low cost of its constituent elements,
MgB2 has promise for
use in superconducting low to medium field magnets, electric motors and
generators, fault current limiters and current leads.[citation needed]
Propellants, explosives, pyrotechnics
Unlike elemental boron whose combustion is
incomplete through the glassy oxide layered impeding oxygen diffusion,
magnesium diboride burns completely when ignited in oxygen or in mixtures with
oxidizers.[23] Thus magnesium
boride has been proposed as fuel in ram jets,.[24] In addition the use
of MgB2 in
blast-enhanced explosives [25] and propellants has
been proposed for the same reasons. Most recently it could be shown that decoy flares containing magnesium
diboride/Teflon/Viton display 30–60%
increased spectral efficiency, Eλ (J
g−1sr−1), compared to classical Magnesium/Teflon/Viton(MTV) payloads.
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