
Room Temperature Superconductivity Found in Graphite Grains - ZoFreX
http://www.technologyreview.com/view/429203/room-temperature-superconductivity-found-in/?nlid=nldly&nld=2012-09-13
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joshuahedlund
I'm gathering from the article and comments here and there that "room
temperature superconductivity" would be an awesome breakthrough that would
lead to lots of awesome things, but I'm not familiar with this sort of thing.
Can you guys give some examples of _why_ this would be so awesome?

~~~
saulrh
One simple answer: lossless power transmission over long distance. A
measurable percentage of our electrical generation is lost in powerlines or
transformers without doing any useful work.

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thirdhaf
Zero loss is only true for DC transmission. It's true, loss is lower than
copper at 50-60Hz AC but radiative losses don't magically disappear. You're
also limited in how much current you can carry since superconductivity breaks
down in sufficiently high magnetic fields. For all that room temperature
superconductors are revolutionary because of the jump in power density in
things like motors and yes power lines.

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andrewflnr
But didn't we only use AC because it was more efficient? So we switch back,
and turn it back into AC for our houses, until we can switch over completely.

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mercuryrising
AC becomes less efficient (financially and electrically) at more than 1
Megavolt. The big big transmission lines in the United States actually use DC
because the AC transformers would have to be so large, and the losses at that
high of a voltage are huge (and that 1 MV generators get to be fairly
expensive).

NPR made a really awesome visualization of the United States grid
([http://www.npr.org/templates/story/story.php?storyId=1109973...](http://www.npr.org/templates/story/story.php?storyId=110997398))
that shows the lines used to transmit power from generating sources.

~~~
dhughes
Adding to that high voltage more than anything is the benefit of AC.

The weight of the conductor is a big problem for long runs of power lines so
if you double the AC voltage the weight of the conductor can decrease by 25%.
DC over 1500 V isn't really possible/efficient (some limit of generators) but
AC can be many hundreds of thousands of volts.

It appears some of my electronics training is sinking in, I put it to good
use!

~~~
mercuryrising
What do you mean by doubling the AC voltage to decrease the weight by 25%? If
I continue doubling, will I eventually not need a conductor?

The true power of AC is the fact that the energy is transmitted through the
electric and magnetic fields (Poynting vector). DC needs to push everything
down a little copper tube. When you start oscillating things though, the
effective area of your conductor increases greatly (you start using the air as
a transmission medium). This is why you can do things like this
([http://hacknmod.com/hack/field-of-fluorescent-tubes-
powered-...](http://hacknmod.com/hack/field-of-fluorescent-tubes-powered-by-
ambient-current/)).

~~~
dhughes
I'm just going by my textbook, I'm still new to this.

I understand what you're saying about AC creating an emf and pushing itself
through a conductor via magnetism and frequency. The skin effect would play a
big role in this too. As I say I'm still new to this, I know enough to be
dangerous.

Here's the exact quote in case you are interested:

 _"The weight of a conductor required to transmit a given amount of power a
given distance with a fixed loss varies inversely as the square of the
transmission voltage."_

~~~
mercuryrising
Ah ha! That's actually kind of cool.

Power's given as: P = V^2 * R R is given as: R = rho _L/(pi_ r^2)
Substituting: and clumping constants: P = (V^2 / r^2) * (rho*L/pi) Weight is
proportional to r^2, we can see that voltage and weight are inverses of one
another, and increasing the voltage for a fixed amount of power decreases the
radius necessary to transmit it, decreasing the weight.

I really wish I still had my lecture notes about the energy flow through free
space, this is the best I could find online -
<http://amasci.com/elect/poynt/poynt.html>.

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greenmountin
Doug Natelson at Nanoscale Views is a physicist who works with nano stuff, and
I expected him to comment[1] on this. Basically he said it looks interesting
but isn't really proof. Which fits with my viewpoint, where I discount
anything reported in Technology Review or that starts with "MIT/Harvard
Scientists". When it's real, it'll be in Nature.

[1] [http://nanoscale.blogspot.com/2012/09/room-temperature-
super...](http://nanoscale.blogspot.com/2012/09/room-temperature-
superconductivity.html)

~~~
sp332
It was published in Advanced Materials, a peer-reviewed journal.
[http://onlinelibrary.wiley.com/doi/10.1002/adma.201202219/ab...](http://onlinelibrary.wiley.com/doi/10.1002/adma.201202219/abstract)
Here's the pre-print PDF <http://arxiv.org/pdf/1209.1938v1>

~~~
nirvana
Hacker News is "peer reviewed", but that doesn't mean every top voted story is
correct.

I worked in a major lab in this exact area (high temperature
superconductivity) and had papers published in much more prestigious journals,
and getting published was often a question of politics more than science- if
your results undermine a theory that one of your "peers" built his career on,
you may not be getting published in that journal, no matter how scientifically
correct.

And back in those days things were a lot less political than they are now.

Don't presume that "peer review" means anything. It really doesn't. It doesn't
mean the peers have reproduced the results, and it doesn't mean the peers are
even up to speed specifically enough to be able to authoritatively say the
results are correct.

It is about as equivalent as the fact-checkers at the New York Times, and you
know how often they print retractions. At the time, quality was slipping too
and it was getting more political.

I'm skeptical about this claim, but it has been awhile since I worked in that
area, so I won't say either way.

But don't take "peer review" as meaning anything significant.

It's like saying Obama is telling the truth because democratic "truth squads"
blessed his opinion.

~~~
sp332
_Don't presume that "peer review" means anything. It really doesn't. It
doesn't mean the peers have reproduced the results, and it doesn't mean the
peers are even up to speed specifically enough to be able to authoritatively
say the results are correct._

I know what peer review means, and I know that it's none of those things. But
getting a paper published in a peer-reviewed journal means you passed a sniff
test, which is better than being written up in your Alma Mater's pop-news
magazine.

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orangeduck
If this becomes verified then it is very exciting - give me my hover board.

Even if it is entirely impractical in use, the thought that a room temperature
superconductor may exist in one form or other is just more evidence that
little stops the march of science :)

~~~
ZoFreX
Absolutely! I really liked that this article didn't over-hype it and made the
limitations and caveats very clear. While it's extremely far from usable, if
we know of even one instance where this phenomenon occurs, we can try to
figure out _why_ , and then replicate on a wider scale.

Obviously it's not going to be in our living rooms anytime soon, but when we
do crack this it's going to have a rather radical impact.

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th0ma5
One could do this at home right with a pencil, a small glass of water, and
some time?

~~~
46Bit
The first issue you'll run into is that the graphite grains they are using
"several tens of micrometers grain size graphite powder" [1]. It might not be
straightforward to make that from a pencil, but you could buy the powder
online.

I've not read the full paper so there might be more significant barriers to
trying this at home, but it looks plausible. Good luck!

[1] <http://arxiv.org/pdf/1209.1938v1.pdf> (end of page 1)

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eykanal
This is an attention-grabbing headline, at best. As described in the article,
the scientists found highly transient evidence of superconductive behavior in
a tiny subset of graphite grains. While that is incredible, it's not the same
as "room temperature superconductivity found!!!".

~~~
ZoFreX
I think it is the same, if (and correct me if I'm wrong here) this is the
first time we've observed room temperature superconductivity of any kind?

It would mean that a hypothesized phenomenon has been confirmed as possible,
and more importantly would mean we could start to understand the conditions
under which it occurs and see if we can apply that to anything on a slightly
larger scale.

~~~
jcfrei
_The overall results indicate that room temperature superconductivity appears
to be reachable_

The paper goes into more detail:

 _The observed magnetic characteristics as a function of temperature, magnetic
field and time, provide evidence for weakly coupled grains through Josephson
interaction, revealing the existence of superconducting vortices._ [0]

My layman interpretation is that they've observed a property of
superconduction, however their graphite flakes didn't demonstrate any actual
superconductivity.

[0] <http://arxiv.org/ftp/arxiv/papers/1209/1209.1938.pdf>

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jpdoctor
1\. Thanks for the arxiv link, (OP: it belongs at the top)

2\. Magnetic characteristics of perfect diamagnetism are indeed "actual
superconductivity." If there were some residual resistance, the magnetic field
would not be completely expelled from that part of the material.

Wikipedia's entry serves as a nice intro to diamagnetism, which is the
underlying principle for the measurement.
<http://en.wikipedia.org/wiki/Diamagnetism>

~~~
jcfrei
thanks for clearing that up for me!

