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## Graphene Aerogel Takes World's Lightest Material Crown198

Posted by samzenpus
from the I-don't-feel-a-thing dept.
cylonlover writes "Not even a year after it claimed the title of the world's lightest material, aerographite has been knocked off its crown by a new aerogel made from graphene. Created by a research team from China's Zhejiang University in the Department of Polymer Science and Engineering lab headed by Professor Gao Chao, the ultra-light aerogel has a density of just 0.16 mg/cm3, which is lower than that of helium and just twice that of hydrogen."
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## Graphene Aerogel Takes World's Lightest Material Crown

• #### Density calculation? (Score:4, Interesting)

on Monday March 25, 2013 @09:08AM (#43270321) Journal

I'm assuming that the 'density' figure given is a 'weight of graphene in a given volume' one, rather than one that includes the gasses occupying the pores/cells of the material?

It would be quite shocking indeed if something largely saturated in nitrogen and oxygen were less dense than helium...

• #### Re: (Score:3)

I suspect you're right.

OTOH, how strong is it? Graphene is supposed to be tough stuff. If it could be used to trap hydrogen and keep it from burning it might be very useful (eg. replace all water-ships with airships).

• #### Re: (Score:2)

At the density levels we are talking about here, I'd assume that the surface area is absolutely enormous(particularly per unit weight) so normally-negligible things like gases absorbed onto the surface might become a significant factor, as well as those mechanically trapped within the pores.

• #### Re:Density calculation? (Score:5, Informative)

on Monday March 25, 2013 @10:22AM (#43271213)

OTOH, how strong is it? Graphene is supposed to be tough stuff.

I have no idea how strong graphene areogel is, but I have handled silica aerogel and it is extremely fragile. It it difficult to handle it without accidentally fracturing it. My daughter used a disk of aerogel as in insulator in her school science project last year, and we had to buy three disks (\$30 each) because they kept breaking. I hope graphene aerogel is stonger.

• #### Re: (Score:3)

TFA says it's "very strong and extremely elastic, bouncing back after being compressed". The application they project is swabbing up oil spills, but there have to be lots and lots of other applications out there.

• #### Re: (Score:2)

I have handled silica aerogel and it is extremely fragile. It it difficult to handle it without accidentally fracturing it. ... I hope graphene aerogel is stronger.

Accoring to TFA: The result is a material the team claims is very strong and extremely elastic, bouncing back after being compressed.

So this stuff appears to be much more robust than silica aerogels, which are rigid and brittle, and not elastic in the least. That should give it many more practical applications.

• #### Re: (Score:2)

Now THAT would be fascinating... First "charge" a piece of the graphene aerogel with hydrogen, then bring it out into the air and try to light one corner with a match or small torch. I'll bet that the mechanical structure is delicate enough that the match or torch would trigger the release of some hydrogen, which would then burn. The interesting part would be if that flame triggered a cascade or just died out, and if a cascade were triggered, how fast it would be, and how much the carbon would participat

• #### Re: (Score:2)

Of course, the fact that extremely high surface area carbon and hydrogen gas might have lead to methane formation long before you get to light it is a completely different issue.
• #### Re: (Score:2)

Yeah, interesting material but in no way the lightest. If the holes in the material count to its volume, you can get lower density with a big balloon.

• #### Aerogel vs. M&Ms (Score:3)

on Monday March 25, 2013 @09:09AM (#43270331)

I still remember the first time I learned about aerogel. The picture had a column of Aerogel about the size of a double-height coke can on one side of a balance and 3 M&Ms on the other side that weighed more.

• #### Re:Aerogel vs. M&Ms (Score:5, Informative)

on Monday March 25, 2013 @09:12AM (#43270377) Journal

The insulative properties [wikimedia.org] are also pretty dramatic. There is another picture floating around with some crayons in place of the flower. That little stunt might not work as well with carbon aerogels as it does with silica ones, though...

• #### Re: (Score:2)

It's more impressive when you do it the other way around: http://upload.wikimedia.org/wikipedia/commons/thumb/e/ea/Aerogelbrick.jpg/568px-Aerogelbrick.jpg [wikimedia.org]

• #### Enter the new airship age ... (Score:5, Insightful)

on Monday March 25, 2013 @09:11AM (#43270353)

Make a bag around it. Remove the air. We have an airship with the lift somewhere between H and He.

So how strong is the aerogel? How big a bag can we make and have it support atmospheric pressure on the other side? That will really determine the lift efficiency.

• #### Re: (Score:2, Insightful)

You still have the weather issues that make airships impractical and now your lifting agent costs billions per fill. That is just the first two problems.

• #### Re: (Score:2)

Because cutting edge materials never get cheaper when a valid use is found for them and they start getting produced on industrial, economical scales.

• #### Re: (Score:3)

You still have the weather issues that make airships impractical.

I'm sure all the operators who fly airships daily would be interested to hear why you think it's impractical to do what they are doing.

• #### Re: (Score:2)

Which ones are those?

All the ones I know of are used only for advertising and pleasure cruising due to these limitations.

• #### Re: (Score:2)

And horatio, there are more things on heaven and earth, than you- I- or any one man will ever think of
the best you can hope to do, is appreciate a reasonable smidgeon of one percent

Humans are endlessly variable, and there are a lot of us.

http://en.wikipedia.org/wiki/Zeppelin_NT [wikipedia.org]

"The Zeppelin NT ("Neue Technologie", German for new technology) is a class of helium-filled airships being manufactured since the 1990s by the German company Zeppelin Luftschifftechnik GmbH (ZLT) in Friedrichshafen.[1] The initial mo

• #### Re: (Score:2)

From your article, two salient points:
1. Number built : 4 (since 1997. Not exactly in widespread use then)
2. Capacity: 12 passengers or 1,900 kg (So, only used for advertising and pleasure cruises, as the grandparent said).
• #### Re: (Score:2)

Those are only for advertising and pleasure cruises.

This is because of the inherent stability issues that lighter than air craft all face.

• #### Re: (Score:2)

So how strong is the aerogel?

Probably about 1/1000 as strong as it would have to be to withstand atmospheric pressure. That's *IF* you could remove all the encapsulated air, which of course you couldn't.

• #### Re: (Score:2)

That's *IF* you could remove all the encapsulated air, which of course you couldn't

I believe this is quite possible following the aerogel production process. Once the supercritical compound is "drained" out it, the aerogel would basically be at vacuum.

• #### Re: (Score:2)

You know those storage bags that you suck the air out of with a vacuum so they take up less space? Imagine putting a sponge in one, and sucking out all the air. It would end up flat as a pancake, which is probably the same way a bag of areogel would look under those conditions.

• #### Re: (Score:2)

... except a sponge is not a rigid structure, unlike aerogel.

• #### Re: (Score:3)

When something is described as "extremely elastic, bouncing back after being compressed" then it's unlikely to be all that rigid...

• #### Re: (Score:2)

I am (perhaps incorrectly) under the assumption that aerogels are rigid. [wikipedia.org]

• #### Re: (Score:2)

Just make a bag and remove the air for an airship. I don't see this aerogel contributing to either vacuum or bag stability.
• #### Re: (Score:2)

So how strong is the aerogel? How big a bag can we make and have it support atmospheric pressure on the other side? That will really determine the lift efficiency.

As an ultralight foam, it has strength, but very little. You can order aerogel samples online - I did a year or two ago (glass aerogel, not graphene). It's extremely brittle and has almost no impact strength, but it has sufficient strength to be made useful. You could conceivably do what you suggest and create a bag of it, then isolate it from the exterior surface or any surface that might see impact damage. It could certainly be made to work if you had enough time, money, and talented minds.

The problem is,

• #### Re: (Score:3)

Going to vacuum from either He or H gives very little extra lift. Air at STP is just a little over 1.1kg/m3, while H2 is about 100g and He is about 200g. So you get about 1kg of lift per m3. With vacuum you get, well about 1kg per m3.
• #### Re: (Score:3)

Make a bag around it. Remove the air. We have an airship with the lift somewhere between H and He.

Using a vacuum gives you little additional buoyancy. Air has a density of about 1.2 kg/m^3. Hydrogen has a density of about 0.09 kg/m^3. So a cubic meter of vacuum has a buoyancy of 1.2 kg/m^3, and a cubic meter of H has a buoyancy of 1.11 kg/m^3. So a vacuum will only give you about 8% more lift than using hydrogen, and about 16% more than using helium. The expense and hassle of maintaining a vacuum is unlikely to be worth the gain.

• #### What ever happened to precision of speech? (Score:5, Informative)

on Monday March 25, 2013 @09:11AM (#43270355) Homepage

Obviously not 'lightest', but 'least dense'. Sheesh, editors - do your JOB! The /. title should be "Silly folk at Gizmag confuse mass with density when describing world's least dense solid.'

• #### Re:What ever happened to precision of speech? (Score:4, Funny)

on Monday March 25, 2013 @09:30AM (#43270575)
Obviously the editors are not the least dense.
• #### Re: (Score:2)

Which makes me think...

It might not be appropriate to consider aerogels "solid" in the "3D solid" sense. It might be better to consider aerogels to be a real and physical example of a "factal solid," and I wouldn't care to attempt to assign the fractional dimensionality to such a thing. But aerogels seem to have the essential characteristics of the "space-filling" shapes described in fractal literature.

• #### Re: (Score:2)

Aerogels should be considered structures, like a house.
• #### Re: (Score:2)

Obviously not 'lightest', but 'least dense'.

You've just got to apply a correction factor. Ask yourself whether it is the lightest material per kilogram...

• #### Re: (Score:2)

Lightest per kilogram? A have a feather and a gold brick that are both exactly 1kg/kg.

• #### Density (Score:2, Interesting)

" the ultra-light aerogel has a density of just 0.16 mg/cm3, which is lower than that of helium and just twice that of hydrogen."

Picture in the article shows a chunk of the stuff being supported by a blade of grass. If the density's lower than that of helium, why isn't it floating away instead of sitting there like a thing that's denser than the atmosphere around it?

• #### Re:Density (Score:5, Informative)

on Monday March 25, 2013 @09:21AM (#43270467)

The density is measured including its interior space. In reality the interior space is filled with air and its realtive weight is the carbon structure alone.
To make it float you would have to find a way to seal off the interior structure and remove the air from that.

• #### Re: (Score:2)

The density is measured including its interior space. In reality the interior space is filled with air and its realtive weight is the carbon structure alone. To make it float you would have to find a way to seal off the interior structure and remove the air from that.

I don't understand that. If the inner air "cavities" are connected to the outside and thus have the outside air's vertical pressure gradient, they should exert the same buoyant force / upward "lift" on the carbon structure, or not?

• #### Re: (Score:3, Informative)

If the density's lower than that of helium, why isn't it floating away

being repeated verbatim by an idiot slashdot submitters

then not being deleted by idiot slashdot editors

then being voted up in the firehose by equally stupid readers.

On a "tech" site, with three separate links in the editorial chain, you'd think that it would have been spotted, but nooooooo.

• #### Re: (Score:2)

Because the atmosphere that surrounds it is also inside the gel, between the pores. That still makes it heavier than air, by aforementioned 0.16mg/cm3. A saturated sponge will also sink, despite being 'lighter' than water.
• #### Re: (Score:2)

Because the material is extremely porous, and is saturated with ambient air.

In a vacuum, the material should float.

• #### Re: (Score:2)

In a vacuum, the material should float.

What would it be displacing in a vacuum? Paging @Archimedes.

• #### Re: (Score:3)

Just to clarify, you would need to seal the outer surface, and pull a vacuum on the internal volume of the material. Then, assuming that the sealing coating didn't weigh too much, the stuff should float.

• #### Re: (Score:2)

Yay, you finally said it right!

I am just imagining (like everyone else) 3D printers of this stuff that create rigid blimp sections which are assembled (interlocking) and provide a permanent no-gas lighter-than-air rigid support structure. You only need to maintain vacuum, which is far more easy and desirable than having to lug a fixed amount of compressed buoyant gas around.

• #### 14 psi (Score:2)

You are also assuming that the outside air pressure wouldn't crush it down to a density that would make it sink.

I would be really surprised if you could just evacuate the stuff and make it float. Some day we'll use evacuated carbon nanostructures for lighter than air, but I don't think we're there yet.

• #### Re: (Score:3)

Why would it float in a vacuum?

Now that *WOULD* be magically ground breaking tech ;)

• #### Carbon is awesome (Score:3)

on Monday March 25, 2013 @09:32AM (#43270597)

Can be used to make the hardest or lightest stuff on the planet.

Carbon's reputation is however spoiled by a couple of Oxygen a-holes that like to latch on to it, stupid no good Oxygen.

• #### OK, explain this to me, someone... (Score:2)

This stuff is lighter than helium (presumably at standard pressure and temperature) and yet not buoyant in air. That presumably means it's air-permeable in much the same way that a cellulose sponge is water permeable? In that case, in what sense is it lighter than helium? If you enclosed a volume of this stuff in a gas-tight membrane it would presumably be buoyant in air, but that - it seems to me - would surely be because vacuum is lighter than air?

• #### Re: (Score:2)

Yes. Depending on the actual strength and other factors you may be able to make it lighter than air by sealing it into an air-tight membrane of some sort and removing all of the air. If it retains its structure it would then be lighter than air.

• #### Brief Kings (Score:5, Funny)

on Monday March 25, 2013 @10:00AM (#43270965)

Graphene Aerogel Takes World's Lightest Material Crown

A crown should weigh heavy on a ruler's brow, lest he forget the weight of his responsibility.

• #### I don't quite get it (Score:5, Interesting)

on Monday March 25, 2013 @10:01AM (#43270973) Homepage
What makes this so different from, say, creating a hollow cube with some very fine polymer for the vertices, with the faces and interior remaining empty? If something's full of holes, is its density still measurable in a meaningful way? A battleship is less dense than water in this sense, but the material it's made from isn't.
• #### Re: (Score:2)

What defines solid? There's lots of things that are "solid" but filled with holes; think pumice or a brick. Molecules are mostly empty space, as are atoms themselves. It's not necessarily any sillier to think of aerogel as being solid than it is to think of pumice being solid. If you want to draw the line, it's always going to be arbitrary

• #### Re: (Score:2)

And how do you make one dimensional graphene fibres?

• #### Transparent aluminum? (Score:2)

But it will take years to figure out the dynamics of this matrix.

• #### Dumb question? (Score:2)

Here's my stupid question: if it's less dense than helium, and about 1/10 that of nitrogen (1.6 mg/cm3)...why is it pictured *sitting* on anything? Why doesn't it float away?

If, as I suspect, it's porous and it's being measured as 'less dense' than He only because they are taking the actual mass/OUTER VOLUME...well, that's not actual density is it? If so, then by this method my portable dog kennel (made of STEEL) is only an order of magnitude more dense than oxygen.

• #### Re: (Score:2)

It doesn't float away because it's filled with air. If it were filled with nothing (i.e., a vacuum) it should float away.

It's very reasonable to think about the overall density of something. Think about a boat - a boat floats because it is overall less dense than water it displaces.

• #### Material? (Score:2)

Graphene Aerogel Takes World's Lightest Material Crown

This thing seems to consist mainly of air. Doesn't that stretch the definition of "material" quite a bit? If I create a 10-foot wireframe cube consisting of just 12 thin aluminium stiffeners, and define the whole interior of the thing as part of the "material", that's gonna have a pretty low density too.

• #### "density" .... really? (Score:2)

I can change the density of hydrogen or helium by heating it up, or compressing it.
If I wanted hydrogen to be less dense than whatever aerogel, I just need to move the hydrogen to a bigger bottle.

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