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.
I want to emphasize how strange a piece of aerogel is to hold. The aerogel fragments I've seen were cylindrical, and looked exactly like bits of hot glue sticks. However, it feels nothing like a hot glue stick. Touching this particular aerogel was like touching a lighter, fluffier, finer grained version of styrofoam, almost like the cotton candy to styrofoam's unleavened bread. The aerogel is also ridiculously low-mass, so it seems to require no effort to hold or move around. It's something that must be experienced.
that reminds me of the (thankfully!) small hydrogen explosion I set off in my parents' basement when I was in High School. I was trying to make a hydrogen-powered bunsen burner. I blew up my prototype but no other damage (the prototype was powered by a magnesium-vinegar hydrogen gas generator).
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?!
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.
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."
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?
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.
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.
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.
maybe, though I do wonder how it compares with belly-button fluff in terms of lightness and strength. joke aside how durable is it as by definition it will be extreemly brittle andthe video does seem to indicate that with bits breaking off. If they made round ablls then structurely it would be a little bit more robust.
I do wonder what use it could actualy be though. Not very strong, ok it's light but it's not much stronger than air going by that video. I do wonder if you could make a static drawn bellows with this to move air, but thats me being geek.
Anybody know what uses this could have beyond coffins for ants sent via beemail! Anybody know a use?
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.
LoL. I had the exact same thought [1], but you managed to finish your comment while I was still away reading about aerogel. ;-)
Incidentally, there was a "carbon nanotube aerogel" that (AFAIK) has the exact same composition as this one and is listed at 1.5 mg/cc [2]. Weighing in a vacuum would seem a bit sensationalistic IMO.
In the video (from the article), they wafted up and down between the static-magnetic pull of a wand and the pull of gravity. But they don't stay in the air for long.
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.
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).
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.
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.
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.
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.
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.
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.