

Aerographite: six times lighter than air, conductive, and super-strong - razzaj
http://www.extremetech.com/extreme/133056-aerographite-six-times-lighter-than-air-conductive-and-super-strong

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Stratoscope
> six times lighter than air

If it's lighter than air, doesn't it float away? Wouldn't this make it a bit
hard to work with? Why doesn't the article say anything about this obvious
consideration?

OTOH, the piece in the photo with the drop of water does not appear to be
trying to float away - unless it's the water drop holding it down. So maybe it
_isn't_ lighter than air? Or is the piece glued down?

> Non-conductive objects, such as plastics, could be coated with aerographite
> to make them conductive — without gaining weight.

While the material may be very light, I'm certain its weight is nonzero (and
non-negative). This doesn't even make sense.

Fascinating material, dumb article.

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TallGuyShort
Coating plastic in this material would add mass, not weight. You can fill a
balloon with helium, and in a vacuum it would be heavier because it has more
"stuff" in it. But in our atmosphere, it is less dense than the air, so it
floats because the air it displaces is pulled by gravity with greater force.

So the weight is non-zero, but it's actually negative in our atmosphere. It's
mass is positive.

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sageikosa
Buoyancy. The weight is still positive (net force of gravity downward), but
the air pressure is greater. In the case of the balloon, the added weight of
the helium is overpowered by the increased air pressure due to the larger
displacement volume, and the balloon follows the path of least resistance
(lower air pressure, at higher altitude).

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js2
Previous discussion[1] from when the paper was press released[2]:

1\. <http://news.ycombinator.com/item?id=4260778>

2\. [http://www.uni-
kiel.de/aktuell/pm/2012/2012-212-aerographit-...](http://www.uni-
kiel.de/aktuell/pm/2012/2012-212-aerographit-e.shtml)

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wtvanhest
For those that have studied physics in depth:

The article says: "5,000 times less dense than water, and six times lighter
than air"… so what does it mean by lighter than air exactly? I presume in
means that if it were in a vacuum that it would have less mass than whatever
its outside edges of volume would be?

That seems misleading since if you break the material down to the smallest
piece, then compared air volume to that piece it wouldn't actually be lighter
right?

Am I thinking about this correctly?

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jws
We've been down this road before. I think the misleading part is that it
doesn't displace air to any significant extent.

By this logic, a roll of chain link fence is three times lighter than
water[1]. But it still sinks.

EOM

[1] Calculations follow…

50 feet of 6 foot tall 9 gauge chain link fence rolls into an 18" diameter
cylinder 6 feet tall and weighs 216 pounds.
[http://www.homedepot.com/webapp/wcs/stores/servlet/ProductDi...](http://www.homedepot.com/webapp/wcs/stores/servlet/ProductDisplay?productId=202024344&storeId=10051&langId=-1&catalogId=10053&ci_sku=202024344&ci_kw=%7bkeyword%7d&kwd=%7bkeyword%7d&cm_mmc=shopping%2d%5f%2dgoogleads%2d%5f%2dpla%2d%5f%2d202024344&ci_gpa=pla#.UJPECrQ8D8s)

Mr. A. Wolfram says that is a volume a 80 gallons.
[http://www.wolframalpha.com/input/?i=volume+of+a+cylinder+18...](http://www.wolframalpha.com/input/?i=volume+of+a+cylinder+18+inches+in+diameter+and+6+feet+long+in+gallons)

Water is about 8 pounds to the gallon, so the water of equivalent volume would
be 640 pounds.

Steel fencing is one third the density of water! Write the press release!

Sorry about the units, world, at least I didn't break into microfortnights.

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jopt
Great analogy, helped me understand why I felt this whole six times lighter
thing was strange.

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ph0rque
If a piece of aerographite were to be sealed on the outside, and all the air
removed, then yes, it would float. But without this treatment, the air
permeates the microstructure, and it does not float.

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kps
So, the question is — if you take a zeppelin-sized chunk of aerographite, seal
the outside, and evacuate the air, will it hold up to the pressure?

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ph0rque
You don't even need aerographite for that:
<http://www.dangermouse.net/gurps/zeppelin/vacuum.html>

However, you need a material strong enough not to implode due to the outside
pressure of air. Not sure how good material tech is for that.

Even if it were strong enough, you would have constant "leaks" of air into the
vacuum cells. So you would need a vacuum pump working all the time. Still
might be worth it, though.

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alexchamberlain
Can I ask a stupid question... If it's lighter than air, does it float?

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jws
It does not displace a significant volume of air, so no steampunk airships for
you. But I'll bet breezes blow it around.

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windsurfer
I wonder if you could wrap the sponge in a balloon-like thing and then take
away all the air inside. That would likely float, if the material was strong
enough, no?

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pyre
You'd have the weight of the balloon-like thing that you wrapped it in though.

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peeters
And yet Zeppelins still fly.

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pyre
I never said it was impossible, just that it's another consideration. If the
Zeppelin's structure was too heavy it _wouldn't_ fly, no?

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eliben
Nanotechnology is awesome, but most of it seems to be in early research
stages. Any good references for nanotechnology products used commercially
_today_?

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StavrosK
How many times less dense than air is helium?

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regularfry
[http://www.wolframalpha.com/input/?i=density+of+air+divided+...](http://www.wolframalpha.com/input/?i=density+of+air+divided+by+the+density+of+helium)

~~~
StavrosK
Very nice, thank you.

