Superconductive Electromagnets

[mach990]

Hi everyone,

I was wondering a little about superconductive electromagnets. Somewhere, I heard that Carbon Nanotubes had special properties, one of which is that they're superconductors (something to do with some quantum effect or another).

Anyways, I was wondering, could you make a superconductive electromagnet out of a CNT? If you can, could you increase the power of the magnet by increasing the amount of electricity that goes through it?

Ultimately, I was just wondering if it would be hypothetically possible to create a hovercraft using carbon nanotube superconductive electromagnets to run on special roads with fixed electromagnets. The steering would be done by tilting the nanotubes on the bottom of the hovercraft.

Just hypothetically, would that be possible? Not taking into account the gigantic expense that would be.

Thanks

 

[Civilized]

Somewhere, I heard that Carbon Nanotubes had special properties, one of which is that they're superconductors (something to do with some quantum effect or another).

That's right, at a temperature around -260 degrees centigrade, carbon nanotubes become superconducting.

Anyways, I was wondering, could you make a superconductive electromagnet out of a CNT?

In theory yes, since any superconducting material is already a superconducting electromagnet, it's just a matter of assembling several tubes together.

If you can, could you increase the power of the magnet by increasing the amount of electricity that goes through it?

Yes that's right, the strength of the magnet will increase as you increase the current through the superconductor. But this will only work up to a point, and once the magnetic field is too strong it will destroy the superconductivity. So even in theory there is a limit to the magnetic field strength.

Ultimately, I was just wondering if it would be hypothetically possible to create a hovercraft using carbon nanotube superconductive electromagnets to run on special roads with fixed electromagnets.

Hypothetically it would be possible, but there is no special reason to use nanotubes for this purpose. Why not just use large ceramic superconducting plates?

The steering would be done by tilting the nanotubes on the bottom of the hovercraft.

OK, but remember that nanotubes are nano-small, so if you are imagining a macroscopic rod being tilted then that is not a nanotube.

 

[mach990]

Yes that's right, the strength of the magnet will increase as you increase the current through the superconductor. But this will only work up to a point, and once the magnetic field is too strong it will destroy the superconductivity. So even in theory there is a limit to the magnetic field strength.

Any idea what that limit is? Would it be powerful enough for lots of the magnets to lift a minivan size thing into the air?

Hypothetically it would be possible, but there is no special reason to use nanotubes for this purpose. Why not just use large ceramic superconducting plates?

Well, I figured that with the nanotubes you'd be able to rotate them a little bit in order to steer the vehicle. Would ceramic plates be able to tilt enough to provide steering? And, would they be more or less energy efficient than nanotubes? That is, do they need to be cooled more than the nanotubes to be superconductive?

OK, but remember that nanotubes are nano-small, so if you are imagining a macroscopic rod being tilted then that is not a nanotube.

I know. I wasn't sure of the physics of it though. It should appear like a flat surface, because there's lots and lots of nanotubes. And then you'd see some ripples on the surface as they rotated in groups.

So.. I don't know.. would billions of nanotubes be more effective than say 6 ceramic plates? They'd have to either tilt, or vary electric current to turn.

I was basically wondering whether it would be hypothetically possible with nanotubes. Thank you very much for your excellent reply, as well.

One other question.. The struction of the carbon nanotube.. Is it capped off like a cylinder, or is it open ended, like a rolled up carpet? Is it the shape of a CNT that makes it superconducting, or just the size?

 

[pallidin]

Well, if you want to do a 6-billion dollar project, most anything is possible.
But is it practical?

 

[mach990]

Well, I doubt it. That's why I said hypothetical. Who knows though? In some ways, it might be practical. But a lot can happen in a while. After all, technology grows exponentially, so it might not cost in the 6 billion dollar range...

But I know, it wouldn't be practical now or soon. I was just wondering about the physics of it.

 

[viola.geek]

Wikipedia has a pretty good article about carbon nanotubes. My supervisor told me to read it before I started work in the lab. I think the properties of carbon nanotubes are because of their structure, but keep in mind that there are different types of CNTs. (Single-walled, multi-walled...and I've read in some papers about bamboo-type CNTs, but I don't know really anything about the bamboo-type.)

It is also still unknown if CNTs are toxic (which is why we take precautions to avoid touching them in any way...gloves, goggles, masks to cover our mouths, etc). They're still a new material to be researched (if this sentence makes sense). Remember asbestos? That was a new material with all these awesome properties, but it turned out to be really dangerous.

CNTs are usually mixed with other conductive materials as well. There's a ton of journal articles involving different "mixtures" with CNTs, especially about battery research with CNTs as part of the electrodes.

In such a project like you're thinking of, something like this would probably be more realistic -- mixing them with a conductive additive or something. Are you thinking of some sort of giant coating with CNTs in it?

 

[mach990]

Ok, I will look at the Wikipedia article on them. I think I glanced at it once, but never thoroughly read it.

Yes, I was sort of thinking of a coating that would be applied to the bottom of the hovercraft, and also a coating to be applied to the roads (Or a structure of CNTs built onto the bottom). I wanted it to be CNTs because it might be possible to rotate them, and thus change the magnetic field so that the car moves in different directions. However, if the same thing could be done with a mixture, then that would probably be even better.