new copper composite

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samitch26
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new copper composite

Postby samitch26 » Tue Aug 13, 2013 12:25 am

check out this article

http://www.nature.com/ncomms/2013/13072 ... s3202.html

it says that a copper and nanotube composite has 100x the ampacity of regular copper

imagine the elcetromagnet with this copper

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Re: new copper composite

Postby mvanwink5 » Tue Aug 13, 2013 10:10 am

When can it be bought for magnet wire and what is the projected cost. :)
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Re: new copper composite

Postby DeltaV » Tue Aug 13, 2013 3:28 pm

Nice find.

I'd like to see that conductivity vs. ampacity plot for various materials (Fig. 1c) in 3D, with temperature as the vertical axis (including liquid nitrogen).

D Tibbets
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Re: new copper composite

Postby D Tibbets » Fri Sep 13, 2013 9:51 pm

To error is human... and I'm very human.

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Re: new copper composite

Postby mvanwink5 » Fri Sep 13, 2013 10:57 pm

Dan,
re: "With similar overall conuctivity, the current induced heating would be similar."
Are you assuming the carbon-copper conductor with 100 times the current carrying capacity has the same resistance as the copper? Really, the heat conductance is not the same as current conductance, no? The point would be for the same size coil and coolant flow you would have 100 times the amp turns, or 20 times the performance of copper cooled with LN.
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Near term, cheap, dark horse fusion hits the air waves, GF - TED, LM - Announcement. The race is on.

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Re: new copper composite

Postby D Tibbets » Tue Sep 17, 2013 10:18 am

According to the quote from the article, the conductivity is the same as copper. Thus via Ohm's law reisistive heating at the same wire cross sectional area would be the same. Conductivity is the inverse of resistance. Assuming the copper and composite wires generate the same heat with the same current, then the improved current carrying capacity can only be due to the elimination of choke points- impurities/ inclusions in the copper wire that is the actual practical limiter on the copper wire ratings. Either that or the composite can tolerate much higher temperatures, thus cooling efficiency can be greater due to the increased delta T. This could perhaps allow for engineering advantages. Otherwise I am at a loss why this material could handle 100 times the resistive heating. I might add that DC resistance appears to be the same from my reading. I suppose induction heating may be different, they didn't say. If this material has different magnetic field / current properties, it may have advantages in AC current transmission, though I'm uncertain what the effects would be in transformers, motors etc. that are dependant on the magnetic effects.

Also, the quote may be misleading. Perhaps they meant the conductivity was 100 times better but it was confused in the article.

Dan Tibbets
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mvanwink5
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Re: new copper composite

Postby mvanwink5 » Tue Sep 17, 2013 10:34 am

Dan, are you sure they weren't talking about heat conductivity being the same and not current conductivity?
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Re: new copper composite

Postby Nanos » Tue Sep 24, 2013 10:43 pm

I'm reminded of reading someplace about someone saying that old used copper cable was different in some manner to new copper cable and was better for the task they had in mind, could using copper cable change it over time like this ?

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Re: new copper composite

Postby Tyler Jordan » Tue Jun 30, 2015 1:33 pm

A Phys.org article with more details on the composite.

http://phys.org/wire-news/159784107/car ... -carr.html
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Re: new copper composite

Postby D Tibbets » Thu Jul 02, 2015 12:07 am

OK, now I understand it perfectly well, almost perfectly, sort of...

This composite material has some differences from copper in current carrying capacity. The actual electrical conductance is similar to copper at similar temperatures, except at high temperatures the electrical conductance is mildly better. This may be similar to the difference between copper and tungsten? The article seems to stress the limit of copper for carrying current before the resistivity (one/ electrical conductance) starts increasing exponentially. This occurs at a few million Amps/ cm cross section in copper and a few hundred million amps in this composite. On the large scale, like household wiring or electromagnet wire, this is almost meaningless unless the current you are pushing is over ~ 10,000 Amps or more. But at the micro scale like traces in computer chips where diameters may be measured in a few dozen nanometers or less. This current carrying capacity before resistive run away is more critical as the diameter of the wires/ traces may be ~ 0.000001 X 0.000001 cm or ~ 10^-12 cm^2. At a capacity for ~2 million Amps / cm^2 in copper, the corresponding usable current carrying capacity in this tiny wire would be about 2 micro amps. This may be fine for running a few tiny transistors, but when you are talking about millions or even much more transisters on a integrated circuit, the current needed to operate all of these circuits may be be millions of times this. Example microprocessors may run at ~ 1 to 200 Watts, which at 5 volts would be about 0.2 to 40 Amps.

I don't know if this improved conductivity without run away resistivity increase is needed for individual traces, but for the power leads into major assemblies within a computer chip, I can envision this limit being reached. Avoiding it would have some design advantages in overall die size and the number of transistors per unit of area you could support.

The down side , which may be irrelevant, is how small this composite can be and retain its properties. Can it be one nanotube wide? Is a bundle of 100 nanotubes necessary for the cumulative properties?

In short, this material may have some design/ engineering advantages on the nano scale, but in the realm of electromagnets like that used in a Polywell or Tokamak, the issue is moot.

My limited understanding is that superconductors can carry up to ~ 10,000 Amps per cm^2 cross section of wire. I wasn't sure what copper's capacity was. It seams it is up to several million Amps per cm^2 (if you can keep it cool) WB6 operated at up to a few thousand amps through it's electromagnet wires. I don't know the cross section of the wire used, but I suspect it was in the region of ~ 0.02 to 0.05 cm^2. This would equate to a current capacity of about 20,000-50,000 Amps. This is ~ 10X that used in WB6, so I suspect the extra capacity would not be needed. The engineering of wire resistivity , cross sectional area, cooling requirements in terms of flow rate and thermal conductivity from the wires would not change. There would not be any advantage to this composite.

The exception may be at higher operating temperatures. Above ~ 80 degrees C this composite material does have some improved electrical conductivity relative to copper, so the necessary cooling may be reduced mildly. The opposite is the case below 80 degrees C (see the chart in the paper).

This all assumes that superconductors for the electromagnets are not an essential requirement. If they can design a practical combination of carbon (or boron?) nanotubes and /or 2 D graphene sheets rolled up in a copper matrix or other substance that has significant (like 10-100X) improved electrical conductance (less Ohmic heating) than copper at similar temperatures the attractiveness goes up considerably.

This engineering consideration of electromagnet windings, superconductors versus good or excellent non superconductor materials is a complex issue. A working superconductor is the obvious winner. But, this assumes the superconductor can operate and survive long enough in the severe B fields, X-ray, and possibly neutron environment. The shielding, low molecular weight (like water)shielding and cooling elements required for superconductors may eliminate much of the size considerations for a superconducting versus non superconducting magrid. The superconductor has an obvious advantage when considering the energy budget, but considerations of heat energy recovery through a water or CO2 steam cycle mitigates this somewhat.

Dan Tibbets
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Re: new copper composite

Postby Tyler Jordan » Thu Jul 02, 2015 3:28 am

I don't think I'm getting this. For whatever strength magnetic field we aim for, we need a certain amount of amp-turns. If this composite wire can carry 100x more current (amps), then we should be able to get by with a lot less copper. So space for cooling can increase, EVEN while overall size of rings can decrease ...

but, being a noob, I'm probably missing something.

given my concerns here: avoiding SC's seems like a plus if possible to do so, but maybe my concerns with regard to quenching are wrong as well.
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Re: new copper composite

Postby D Tibbets » Fri Jul 03, 2015 1:03 am

To error is human... and I'm very human.

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Re: new copper composite

Postby Tyler Jordan » Fri Jul 03, 2015 6:27 am

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kunkmiester
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Re: new copper composite

Postby kunkmiester » Fri Jul 03, 2015 9:38 pm

Resistance of materials generally goes up when you heat it. This limits the capacity.

This composite doesn't resist as much as higher temperatures, and in fact is a hundred times better.

So, the wire in your walls won't care, it doesn't carry enough current to get hot enough to matter.

The teeny tiny wires in a microchip can hit the currents expected, so it might be useful there, since it'd be one less thing to fail due to heat, potentially letting you run the chip hotter, which would be good because you'd be able to worry less about overheating.

For a polywell, it'd also be good, because you have a similar size limitation with large currents. With the expectation of running hotter, you'd be able to use a smaller wire that lets you put more turns in the same space. How does the stuff compare with the liquid nitrogen level superconductors we'd be expecting to use instead?
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Re: new copper composite

Postby Tyler Jordan » Sat Jul 04, 2015 1:33 am

I don't think the size of the wire matters for generating a high magnetic field at least with regular copper. It is amp-turns that gives us a high magnetic field - so high amperage and low turns equals lower amperage and high turns. With normal copper the thicker the wire the more amps you can run through it, so for long-term durability/performance, going with the thickest possible conductor -- something that perhaps looks like a bitter magnet (using plates instead of wire) but isn't a bitter magnet as we're not trying to compress the magnetic field in the center. hence we can run enormous current, not have to worry about insulation problems, space between wires is eliminated (so reducing overall size), cooling is probably easier too, and above all the strength of the conductor is greatly improved reducing deformation.

if we are cooling such a magnet with liquid Nitrogen ... our resistance is low, so cost of running the magnet is much improved (although we would have to factor in cooling cost). We don't have to worry about quenching at all, so we can push magnets right up to whatever we level we desire.

given that scenario, I don't see the advantage of the copper composite unless it can handle a lot more current under such a scenario? - my take-away so far is that it cannot, and, at least for a test machine, I think pure copper looks better than superconductors. As we can push copper magnets under pulsed conditions to super high magnetic fields, if desirable, and it might be.

one thing - the composite has a lower density. if it's thermal conductivity is still relatively the same as pure copper (a big if?), then this should translate as being easier to cool.

.... then again, I may be totally wrong about any number of things here :wink:
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