In today's podcast, we're going to look at magnesium diboride. Magnesium diboride is an inorganic compound made of two elements, boron, and magnesium that are both abundant in the Earth's crust. It's a water-insoluble, dark gray, solid.

Over the past few years, magnesium diboride has progressed from a remarkable discovery to a promising applied superconductor.

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In today's podcast, we're going to look at magnesium diboride.

Magnesium diboride is an inorganic compound made of two

elements, boron and magnesium.

That are both abundant in the Earth's crust.

It's a water insoluble, dark gray, solid.

Over the past few years, magnesium diboride has progressed from

a remarkable discovery to a promising applied superconductor.

Magnesium diboride is a simple binary compound whose

structure was confirmed in 1953.

It's synthesized via high temperature reactions between

magnesium and boron powders.

However, because magnesium metal melts at 652 degrees centigrade, the reaction

may involve the diffusion of magnesium vapor across boron grain boundaries.

This process can be carried out in situ while the magnesium boron remain in

the tube or ex situ after the magnesium and boron have been formed into a wire.

Hot isostatic pressing at nearly 950 degrees centigrade enhances

the properties of the magnesium diboride wire in both cases.

As for electromagnetic properties of magnesium diboride, it has a very high,

critical temperature of 39 Kelvin, meaning that it can remain superconducting

even at extremely high temperatures.

Magnesium diboride is also a type two superconductor.

Which means it can withstand increasing magnetic fields

without losing superconductivity.

It has an extremely high critical current and finally it has a

relatively high, upper critical field in thin films and fibers.

It exhibits superconductivity up to 74T and 55 T respectively.

Let's look at the thermal conductivity of magnesium diboride a little further.

The electronic structure of magnesium devoid is such that there are two

types of electrons at the Fermi level with very different behavioral

traits; one of which Sigma bonding, is much more strongly superconducting

than the other, Pi bonding.

This contradicts conventional theories of phonon- mediated

superconductivity, which believes that all electrons act in the same way.

Theoretical understanding of magnesium diboride properties has been almost

attained by modeling two energy gaps.

In 2001, it was thought to have behaved very much like a metallic

then a cuprate superconductor.

Magnesium diborate is a multi-band superconductor, which means the

superconducting energy gap varies depending on the Fermi surface.

The Sigma bond of boron in magneisium diboride is strong.

And it induces a large S wave superconducting gap.

Whereas the PI bond is weak and only induces a small S wave gap.

The quasi particles states of the large gap, vertices are tightly

confined to the vortex core.

The quasi particle states of the small gap on the other hand are

connected to the vortex core and can easily delocalize and overlap.

This delocalization significantly contributes to magnesium

diborides thermal conductivity.

As for applications for magnesium diboride, it's a promising material

for fuel in Ram jets and as an ingredient in blast,-enhanced

explosives and propellants.

This is due to its ability to burn completely when ignited in

oxygen or mixtures with oxidizers.

Most recently it has been demonstrated that decoy flares containing magnesium

diboride, teflon viton, exhibit 30 to 60% higher spectral efficiency.

Compared to magnesium, Teflon, viton payloads.

Magnesium diboride has shown promise as a potential fuel for

hybrid rocket propulsion as well.

When mixed with parafin wax, it can improve the fuel grains,

combustion characteristics, and mechanical properties.

The MRI superconducting magnet system was built in 2006, using 18

kilometers of magnesium diboride wires.

The MRI used a closed loop, cryo cooler, which did not require cryogenic

liquids to be supplied externally.

The system was created for medical imaging applications.

Magnesium diboride is also a superconducting material with

significant potential in power applications and electronic devices.

MgB2 based power cables, microwave devices and commercial MRI machines

have all emerged in the last 15 years.

Superconducting radio-frequency or SRF cavities are the next

frontier for magnesium diboride.

SRF cavities are essential for high energy physics research and

are used in particle accelerators.

Finally, magnesium diboride is used in superconducting low to medium

field magnets, electric motors, and generators, fault current limiters,

and current leads due to the low cost of its constituent elements.

And that's all on magnesium diboride today.

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