Potential Massive Improvement in Superconductors

[djolds1]

http://nextbigfuture.com/2008/09/superc ... gular.html

Superconductors Under a Pile of Regular Metal Could Have Critical Temperatures of 200K instead of 50K


Theorists propose that for certain types of superconductors, contact with a metal layer could greatly increase the transition temperatures of these materials—in some cases by as much as an order of magnitude.

[imaginatium]

There already exists a 200K superconductor http://superconductors.org/200K.htm

The 200K material is believed to have a B212/1212C intergrowth structure, where B=11 and C=copper chain. This structure is shown below left and has the chemical formula Sn6Ba4Ca2Cu10Oy. The general formula for this new family of superconductors is SnxBa4Ca2Cu(x+4)Oy. Within this new family, unit cells with 3 to 6 atoms of tin (x) have been found to superconduct, with 6 atoms of tin producing a new record high Tc near 201K.

Since the 200K material contains only inexpensive and non-toxic elements, a method of refinement to increase its volume fraction is now all that is required for it to become the first commercial superconductor capable of operating at dry ice temperatures.

Synthesis of these materials was by the solid state reaction method. Stoichiometric amounts of the below precursors were mixed, pelletized and sintered for 11 hours at 890C. The pellet was then annealed for 10 hours at 500C in flowing O2.

SnO 99.9% (Alfa Aesar) 5.57 moles
BaCuOx 99.9% (Alfa Aesar) 5.98 moles
CaCO3 99.95% (Alfa Aesar) 1.38 moles
CuO 99.995% (Alfa Aesar) 3.29 moles

Could this be viable for WB100?

I see a couple of possible advantages:
1. it could be cooled with liquid CO2 and water - cutting cooling cost
2. the simpler cooling would reduce the cross section of the coils - reducing lost energy
3. It will probably be relatively inexpensive compared with other superconductive materials

[kcdodd]

Would depend on it's capability with high amps and b-fields.

[icarus]

Looks like they've already taken it up to 212 [K] in Nov. '08.

http://superconductors.org/212K.htm

Somewhere near a recent overnight low in Alaska!

[KitemanSA]

Could this be viable for WB100?
I see a couple of possible advantages:
1. it could be cooled with liquid CO2 and water - cutting cooling cost
2. the simpler cooling would reduce the cross section of the coils - reducing lost energy
3. It will probably be relatively inexpensive compared with other superconductive materials

Sorry, liquid CO2 cannot get you below about 217K, and that is at 5+bar. As the article pointed out, it was above DRY ICE temperatures, about 195K. Weird stuff, CO2!

[imaginatium]

Could this be viable for WB100?
I see a couple of possible advantages:
1. it could be cooled with liquid CO2 and water - cutting cooling cost
2. the simpler cooling would reduce the cross section of the coils - reducing lost energy
3. It will probably be relatively inexpensive compared with other superconductive materials

Sorry, liquid CO2 cannot get you below about 217K, and that is at 5+bar. As the article pointed out, it was above DRY ICE temperatures, about 195K. Weird stuff, CO2!

Ok even if we needed LN2, it still has the advantages I mentioned. Ln2 is much cheaper than LHe, and we would still be able to reduce the cross sectional diameter, from what is needed for LHe cooled MgB2

[MSimon]

Looks like they've already taken it up to 212 [K] in Nov. '08.

http://superconductors.org/212K.htm

Somewhere near a recent overnight low in Alaska!

So far it is not a bulk material. Just a twitch in a Resistance vs Temp Graph.

[D Tibbets]

Assuming a practical superconducter that operates at 200 K or above is achieved, what could be used as a coolant, other than liquid nitrogen. Would liquid amonia, methane, or some compound- like a mixture of methane and an alcohol, etc be possible. I'm guessing things like viscosity, conductivity, chemical reactions (disolving the varnish on the wires, flamability, etc are majer concerns). I'm guessing liquid oxygen would not be good because even at cryogenic temperatures, it probably is to reactive, or is it. They use it in reusable rocket engines like in the Shuttle.


Dan Tibbets

[blaisepascal]

Assuming a practical superconducter that operates at 200 K or above is achieved, what could be used as a coolant, other than liquid nitrogen. Would liquid amonia, methane, or some compound- like a mixture of methane and an alcohol, etc be possible. I'm guessing things like viscosity, conductivity, chemical reactions (disolving the varnish on the wires, flamability, etc are majer concerns). I'm guessing liquid oxygen would not be good because even at cryogenic temperatures, it probably is to reactive, or is it. They use it in reusable rocket engines like in the Shuttle.

Ethanol melts at 159K, but I don't know it's cryogenic properties. I've heard it gets very viscous at low temps.

I suspect that unless we are dealing with some really nasty stuff it'll be relatively easy to deal with chemical reactions. It makes sense to make the coolant loop closed.

LOX wouldn't make a good coolant, at least compared to LN. LOX boils at 90K, LN at 77K. When liquifying air, you get 4 times the LN than you get LOX for not much more work. LOX is a highly concentrated oxydizer -- which is one of the reasons they use it rocket engines -- and will tend to react quickly and spontaneously with organics. Look for YouTube videos of people lighting barbecues with LOX sometime.

What's the problem with LN?

[KitemanSA]

Assuming a practical superconducter that operates at 200 K or above is achieved, what could be used as a coolant, other than liquid nitrogen.

Fluorinert FC-87 gets down to about -115C, but it gets pretty thick.

long url

[kurt9]

Liquid Nitrogen is very cheap (cheaper than milk by volume) and is chemically inert.

It is fairly easy to use in that you simply "top off" your supply as it boils off. If you use a lot of it, you can buy the compressor and other equipment to make it yourself.

[D Tibbets]

Thanks for the responses. Liquid nitrogen is certainly hard to beat. I'm partially motivated by conciderations of "very high" temperature superconductors (if any are ever developed) or even cooled copper wires, say in the region of 250-270 degrees K (~-20 to -40 degrees C). For instance, pumping automobile antifreeze through an electromagnent should handle this temperature, without having to deal with cryogenics, etc. I'm guessing the trade offs favor something like liquid nitrogen on the large scale. But, on the small scale/ demonstration type projects it might be cheeper. Certainly, the magnets will have to be cooled in some way to both achieve super conductivity (or just to reduce the resistivity of copper wire), and to remove any Ohmic heat generated and any external heat from the magnets.

Or, another way of looking at it- is it worthwile to mildly cool an antifreeze/ alcohol, etc to improve the conductivity of copper (say by a facter of two) and pump it through the magnet case instead of just pumping through room temperature water? It might allow you to push up the current in the wires and thus increase the magnetic field strength (or increase the run time) in a system that would be at it's limit with water cooling. Using something that could handle a (mildly) colder temperature, perhaps is less viscous, and perhaps has a greater thermal capacity could push the tests further without costs much greater than simple water cooling.

El cheepo example- Use an old chest freezer filled with enough antifreeze mixture to pump through the magnets for say 5 min at 10 gallons per min. Dump the effluent into a second freezer, repeat. This way you could probably do several tests per day. No closed system, no radiaters, etc.


Dan Tibbets


Dan Tibbets

[MSimon]

My BOE calculations say that to get reasonable fields - .45T continuous - you have to go to LN2.

It is cheap for one shot experiments and can be reliquefied for continuous operation. Or just operated total loss for the first few months to see if further capital investment is warranted.

[imaginatium]

My BOE calculations say that to get reasonable fields - .45T continuous - you have to go to LN2.

It is cheap for one shot experiments and can be reliquefied for continuous operation. Or just operated total loss for the first few months to see if further capital investment is warranted.

So what's the most cost effective superconductor, that can be LN2 cooled?

[MSimon]

My BOE calculations say that to get reasonable fields - .45T continuous - you have to go to LN2.

It is cheap for one shot experiments and can be reliquefied for continuous operation. Or just operated total loss for the first few months to see if further capital investment is warranted.

So what's the most cost effective superconductor, that can be LN2 cooled?

None at this time. 77K superconductivity at reasonable Jc (current density) is not possible in strong magnetic fields. High fields require lower temperatures. For superconductivity electrons have to travel in pairs. Magnetic fields split the pairs. I think the Zeeman effect also describes this in a different domain (photon production from level "jumping").