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The Amazing Properties of Aerogel
RideMax writes "We all know NASA is using a substance called 'aerogel' in the Stardust spacecraft to catch pieces of the Wild-2 comet. The NYT is running an article about some other amazing aerogel properties. My favorite quote: 'It's the lowest density of any solid, and it has the highest thermoinsulation properties. Though it would be very expensive, you could take a two- or three-bedroom house, insulate it with aerogel, and you could heat the house with a candle. But eventually the house would become too hot.'" We've looked at Aerogel before.
Very good Aerogel FAQ.
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This informative comment was lifted from a comment made the last time aerogels were discussed on slashdot (see the original comment here).
Check it out - this auction on Ebay is selling a 4-6 Cubic inch chunk of Aerogel with a "Buy it Now" price of $160. Considering the auction says it costs about $200 per cubic inch to make, thats a deal. I'm guessing some /.'er with deep pockets will be buying this pretty soon!
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It's interesting that Aerogel is always mentioned as being the insulator on the mars Sojourner Rover (and current mars rovers) but it's almost never mentioned that the heat source inside the insulated electronics boxes is not merely waste resistive heating from the electronic components themselves, but from Plutonium Radioisotope Heater Units of a couple ounces each. Maybe it's a good thing they're kept low profile, the clueless luddites would have a field day.
- "Hear that?! The percolations are imminent! Cease your ingress!"
The pictures are amazing. Wow. http://stardust.jpl.nasa.gov/photo/aerogel.html
"You could take a two or three bedroom house, insulate it with aerogel, and you could heat the house with a candle."
Well, sure, anybody can point out the obvious "if you have a crack in your house" stuff, but the idea is still valid. So, don't go pulling out pivnert from 10th grade chemistry and using that as your basis for second-guessing an illustrative statement.
However, your house would STILL get too hot, even using PV = nRT. V here is constant. R, of course, is the Rieberg constant, the value of which I don't know off-hand. As long as no air leaks out, then as T goes up, P goes up accordingly. But T is on an absolute scale. Kelvins, here. 293.15 K is room temperature, 20 degrees C, and if you heat that up to 30 degrees C, 303.15 K is, in terms of proportionality, not too much of an increase, but hotter than is comfortable, i.e. too hot. Then particles, due to the pressure differential between outside and inside, want to leak out that crack. And what's happened? THE TEMPERATURE HASN'T DECREASED. n in PV = nRT has gone down in order to bring P down to atmospheric pressure outside. Oh, dear, T is higher, and nothing's leaking out! This, silly head, is why it's possible to heat a house in the first place. By your reasoning, a house could never be a different temperature than outside! Which, thank goodness, isn't the case.
And then, of course, "as a matter of fact," the air is exactly what keeps it hot, and any other thermally insulative materials, i.e. fiberglass or aerogel. When you heat up a house, you run air into a furnace, heat it up, and then pump it through the rest of the house. A candle would heat up the air immediately above it (rising products from chemical reaction) and that air diffuses throughout the house, heating it up. Just like your furnace. True, there's radiative heating from the candle as well, but compare the difference in heat when you stick your finger an inch above a candle vs. an inch to the side of it. Radiative heating is universally dispersive. Convective goes straight up. BIG difference between the two there. Oh, well, it looks like a candle COULD heat up the house insulated with aerogel.
Yes, I am a physicist.
From What's an aerogel?:
Vacuum is *not* actually the perfect insulator. It is true that no heat is conducted trough vacuum, but on the other hand vacuum is near perfect in letting heat *radiate*. Now, if you combine vacuum with one or more reflective films to reflect back most of the radiated heat then you have eh, uhm, invented the termos-bottle.
Silicon dioxide is actually very common. Actually it's a form of quartz. Unless I am mistaken it's the same stuff they put in the little white packet that comes with your hard disk to keep condensation from forming in the antistatic bag...
Regardless, the cost of Aerogel is in its manufacture, not its ingredients. Aerogel is actually just a crystalline structure that forms when SiO2 molecules are suspended in ethanol. The trick is figuring out how to get the ethanol out and replace it with air after the lattices form. This process is called supercritical drying and involves pushing liquid CO2 though the structure at very high pressures. Actually the entire process of how to make the stuff can be found here. It's suprisingly simple. Besides the supercritical drying bit, it seems almost like something you could make yourself.
-R
The short answer is that yes it could, but only temporarily.
I believe Aerogel is an open celled matrix, meaning that the eventually the hydrogen (especially hydrogen) would leak out causing a block of the stuff to return to the ground.
I suppose it would be possible to seal a block of aerogel in some sort of polymer making for a structurally solid balloon.
..of ships and shoes and sealing wax, of cabbages and kings.