Niobium foil-can anyone use it?

[Spasticteapot]

Hello, all!

A while back, I made some extremely thin niobium ribbon for some jewelry. Sadly, I could'nt get it to affix to the silver.

However, I was wondering if anyone else could use some if I were to make more. I can likely get access to a roller for pressing out the niobium into a thin foil; getting it straight would be a bit trickier.

Niobium has a few interesting properties, the most notable of which being that it is a very inert metal, and won't oxidize under almost any circumstances. It is, however, somewhat brittle.

I've got a few bits of niobium wire left; could anyone use these for ribbon drivers?

[auplater]

what size is the wire, how much ya' got, and $$?

auplater

[angsuman]

Well not sure if you can use it in a ribbon should be interesting. My dad did some research with Niobium for a high temperature heat exchanger for a nuclear reacter, apparently the metal is very expensive and very hard and they had trouble cutting it their tools. Should be interesting if anyone cooks something up not sure about any other properties of Niobium.

[grahamprie]

Hi,

I use Niobium where I work - we make very sensitive measuring instruments which depend on the properties of this rather unusual metal.

We use it to wind electro-magnet coils, but when they are cooled down to the temperature of liquid Helium, the Niobium becomes a superconductor, so all the resistance disappears.

We make the coils into a closed loop by welding the ends of the wire together, and by some clever stuff I won't describe, we can trap a current into the coil and make a permanent but adjustable magnet. ( as long as it stays cold )

As far as using the stuff at room temperature is concerned, all I know is that it's a pig to machine, you can't solder to it, and it work-hardens, so if you think it's brittle now, you aint seen nuthin yet... Don't use it for any application where it will see repeated stress - it WILL crack through.

Electrically it's not a lot of use - about 10 times worse a conductor than Copper - unless you have some way to cool it below 9 degrees Kelvin...

It forms an insulating skin when exposed to the Oxygen in air, like Aluminium does, but faster, so it's like anodising for free, and once it's formed, the Oxide coating can be dyed in the same way.

It's too heavy for things like surgical implants - Titanium is better for hip-joints, etc., but as the oxide makes it non-allergenic, it's OK for jewelry, and lighter than stainless steel.

Hope this helps

grahamprie

[Stocker]

http://en.wikipedia.org/wiki/Niobium


can't your company resell the stuff?

[jneutron]

Originally posted by grahamprie

We make the coils into a closed loop by welding the ends of the wire together, and by some clever stuff I won't describe, we can trap a current into the coil and make a permanent but adjustable magnet. ( as long as it stays cold )

Awww, your no fun.

What's so special about persistance switches, anyway?

Cheers, John

[poobah]

Spill it rocket boy... what are persistance switches?

[jneutron]

Originally posted by poobah
Spill it rocket boy... what are persistance switches?

Rocket boy?? who, me??

Ya make a coil using supers.

Ya take da ends, and ya connects em togetha.

Den ya puts da heater on it.

And ya's solder some more leads to the coil leads...

When ya's wanna put current in da coil, ya heats da connection, makin it a resistor. Puts in current to da coilz, coupla hunnert or tousands of amperesands.. When ya'z done, ya toins off da heater. The joint, itsa gonna cool down. When it gets colda again, poof...ya gots ya persistant currents..

Easy..right??



For super magnets, helium is a big cost issue. The leads that come out to room temperature consume a lot, as they have to be very good conductors of current, but that also comes with good heat conduction. Ice forms at the exit points, and it costs a lot of helium.

So, one solution is to short the magnet inside the helium with another piece of superconductor. That way, once there is current in the magnet, it will continue (persist) even with the supply off. Because the shorting piece is superconducting, it has to be made non-superconducting for the time you wish to charge the magnet.. That is done by heating it a bit. Once that is done, a voltage can be put across it, and the magnet will begin to charge..one volt across one henry, one ampere per second..

Once the magnet current is at the desired point, the heater for the shorting piece is turned off. When it becomes a superconductor, you can turn the supply off, and the current will continue to circulate.

Then, you have a mechanical widget that disconnects the leads to the outside world, and now there is no thermal conduction to boil off helium.

There are a several other charging techniques, but this switch is simple, reliable, and is used all over the place. By welding the niobium titanium filaments without the copper cladding, you can even eliminate the small ir drop that happens through the copper cladding. While solder joints can be made that drop into the nano-ohm regime, it is still better to have super to super contact. That way, the field remains constant for a long time, a prerequisite for MRI machines.

Cheers, John

[auplater]

for instance, a strap of superconductor across the magnet terminals... run above Tc by heating to develop a voltage, then the heater is turned off to allow it to superconduct and complete the persistent mode circuit.


auplater

[poobah]

Like this?

The coil is tapped assymmetrically to establish a "majority current".

You kick it with thousand of amps because it's a race to preserve the current until the coil cools down?