
German Scientists Create Aerographite, the Lightest Material in the World - japaget
http://www.sciencespacerobots.com/blog/71720122
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rejuvenile
I used to make aerogels (a related class of materials) in high school; allow
me to give a (hopefully accurate) layperson's overview.

Aerogels formerly held the record for least dense solid. They're not gels, but
they're called aerogels because they're made from gels. As the name "aero"
implies, they're mostly air, giving them incredible strength-to-weight ratios
and insulating properties. Silica aerogels are translucent and quite amazing
to hold; it's like holding a cloud.

Aerogels are made from colloids (a.k.a. gels), which are long chains of
polymers formed in water. Free-floating around in the water, they form very
long, intricate, 3-D maze-like structures. If you've ever made JELL-O, you've
made (and eaten) a colloid. It’s the intricate structure of the colloid which
keeps the suspended water from spilling out.

Silica aerogels are formed by removing the water from a silica gel, leaving
only the maze like structure behind. This structure is very delicate, and if
you attempt to evaporate the water out near room temperature/pressure, the
capillary action of water will collapse the structure like a dried out
jellyfish. However, if you heat and pressurize the system past the critical
point, the water becomes a supercritical liquid and it can be removed without
pulling the rest of the material inwards.

It appears that what they’ve done here is similar, except they use a multi-
step process to deposit carbon on the colloid, then remove the colloid
completely, leaving nothing but a carbon maze. I presume they can't make
colloids out of carbon directly, hence the multistep process.

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fusiongyro
What an awesome hobby that must be! I'd be inclined to try it if I weren't
sure I'd kill myself with chemistry.

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Ralith
I am certain it's easier than you are imagining. Try it!

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beambot
That's pretty cool. But I'm a bit confused... FTA, _the aerographite density
is 0.2 mg/cm3._

From Wikipedia on Aerogel (another very lightweight solid) [1], _The lowest-
density aerogel is a silica nanofoam at 1 mg/cm3, which is the evacuated
version of the record-aerogel of 1.9 mg/cm3. The density of air is 1.2 mg/cm3
(at 20 °C and 1 atm). Only the recently manufactured metallic microlattices
have a lower density at 0.9 mg/cm3._

How are they computing the density of the aerographite such that it doesn't
float away (having 1/6 the density of air)? Are they only considering the mass
of the carbon and not the internal air?!

[1] <http://en.wikipedia.org/wiki/Aerogel>

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ehsanu1
It's probably "evacuated" as well, ie there's no internal air. You can get the
weight inside a vacuum so it doesn't float away.

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Ralith
If you RTFA, you see there's a video of them sitting on a table in regular
atmosphere. You'll also see that it's just basically a very fine carbon
hairball. They're obviously measuring the density of the thing itself, and not
the air that happens to be drifting through the gaps.

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SilasX
Which is to say, they're counting the air passing through the gaps for
purposes of _volume_ but not _mass_ in the density calculation.

So, could I claim to have the lightest material if I made a hollow, porous,
giant hairball?

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sigkill
As someone who has worked with metal foams, you are technically correct.

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Arjuna
Here is the press release with further information, video and images:

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

Interesting potential for batteries (quoted from above link):

 _"Due to its unique material characteristics, Aerographite could fit onto the
electrodes of Li-ion batteries. In that case, only a minimal amount of battery
electrolyte would be necessary, which then would lead to an important
reduction in the battery's weight. This purpose was sketched by the authors in
a recently published article. Areas of application for these small batteries
might be electronic cars or e-bikes. Thus, the material contributes to the
development of green means of transportation."_

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stephengillie
<https://en.wikipedia.org/wiki/Aerographite>

_Owing to its interconnected tubular network structure, aerographite resists
tensile forces much better than other carbon foams as well as silica aerogels.
It has a very low Poisson ratio, as demonstrated by a complete shape recovery
of a 3-mm-tall sample after it was compressed down to 0.1 mm. Its ultimate
tensile strength (UTS) depends on material density..._

How soon will we see this used instead of metal frameworks or latex foam? In
aircraft wings, car seats, etc?

Even more interesting: _Upon external compression, the conductivity increases,
along with material density_. Pressure-sensitive aircraft wings? Car seats
that know what their occupants weigh?

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Ralith
> Pressure-sensitive aircraft wings? Car seats that know what their occupants
> weigh?

Both of these things are pretty easy and cheap to do with existing technology.

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btipling
The research on light and strong materials is key to one day developing space
elevators.

<http://en.wikipedia.org/wiki/Space_elevator#Cable>

I don't know what the strength of this material is or its breaking length (a
breaking length of 5,000 km is required for a space elevator), the abstract
doesn't say so, but research like this is really exciting.

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ZoFreX
I don't understand geeks' obsessions with space elevators. It's not like
materials are the only obstacle holding us back - they would be continually
bombarded by meteors, and travelling up them would involve extremely long
exposure to the high radiation band of the atmosphere.

Now launch loops, that I could get excited about.

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ajays
Aerogel (aka "solid smoke") was the lightest so far, at 1mg/cc[1] .

The density of air is 1.2 mg/cc.

FTA: "The substance weighs just 0.2 milligrams per cubic centimeter"

So why doesn't this thing just fly away, if its density is 0.2 mg/cc ?

[1] <http://en.wikipedia.org/wiki/Aerogel>

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jws
I suspect it is 0.2mg/cc when weighed in a vacuum.

It does point out a blurry line between substance and structure. At some
point, the voids in the material get large enough that you would call it a
structure, for instance, if you outlined a soccer ball in fine copper wire and
removed the soccer ball it would certainly be even lighter than this, but you
wouldn't call it a substance.

~~~
ars
> It does point out a blurry line between substance and structure.

It's not new.

What is the density of a boat? The density of the boat as a whole is lower
than water - so it floats.

But if you could only the materials it's made of they are all heavier.

So you have to know what you are describing.

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ChuckMcM
Exactly and a boat only 'floats' because it holds out the water and thus
establishes a pressure differential. If you could put one of these things in a
vacuum chamber, then put a seal around the outside of it, and then take it
out, it would float. Except what it would really do is compress. And from the
article it looks like it would compress to a size which put it into the 3 - 5
mg/cc range if not higher.

That said, in Neal Stephenson's diamond age they used vacuum balloons as a
floatation device. something that I hope we can build at some point.

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jere
>Think of the Aerographite as an ivy-web, which winds itself around a tree.
And than take away the tree.

I would totally expect this stuff to be transparent based on the description.
Shows what I know.

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tbrownaw
The structure is on approximately the same scale as the wavelength of visible
light. I think that's in common with other recent ultra-black materials, it's
either that there's just a huge amount of surface area or some sort of
quantum-mechanics effect.

~~~
rejuvenile
Aerogels can have a surface area of ~2,500 m2 g-1, which is incredibly high.

I wonder if this material, being made of carbon and likely having a similarly
high surface area, would make a good capacitor.

~~~
Someone
[https://en.wikipedia.org/wiki/Aerographite#Potential_applica...](https://en.wikipedia.org/wiki/Aerographite#Potential_applications)
claims 1.25Wh/kg. I hope that isn't for the lightest variant; in Wh/m^3, that
wouldn't be that good.

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gmack
IANAP, but if this material is "jet black", i.e. absorbs most light, and also
highly conductive, wouldn't it also be a great component for organic solar
cells? Graphene is apparently already an interesting candidate for this
application, promising lower costs of manufacture (if not higher efficiency).

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uncomfytruths
If they could turn it into a thread imagine what it could do for the fashion
industry. Amazing dresses that flow in the wind even when there is no wind.
I'd be worried about strength though.

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padobson
Plus one for the least geeky application, and the most marketable I've seen so
far in this post.

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unreal37
I had a dream last week that scientists would someday be able to remove the
Higgs Boson from atoms to make truly weightless materials. I should patent
that.

As far as "flying away", from the video embedded in the linked article, you
can see the aerographite is barely able to sit still on the table before the
rod is introduced - one of them is about to fly away just sitting there. It
just "looks" extremely light.

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Locke1689
The Higgs boson doesn't provide mass to anything, the Higgs field does. The
Higgs field also provides a negligible fraction of the mass of baryons.

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InclinedPlane
Indeed! The Higgs field provides rest mass to electrons and other fundamental
particles. However, most of the mass of, say, a human body comes from the mass
of protons and neutrons, and that mass is almost entirely from the kinetic
energy of quarks and other nucleon constituents.

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Locke1689
Actually, no. The kinetic energy is a property of the particles (thermal
energy, actually), but it does not supply their rest mass. 99% of the rest
mass of baryons is due to the strong nuclear force.

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jhuckestein
Think about this for a second. If you wear a tracksuit made of this you'll be
able to jump higher than when you're naked.

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jhuckestein
Why is this being downvoted? I'm not a physicist but to me this sounds
plausible. I think that's pretty mind-boggling.

~~~
archangel_one
Same concept as the full-body suits that competitive swimmers wore for a few
years (IIRC they are now banned) which made them more buoyant than they would
have been without.

