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.
A (dry) sponge is much lighter than water, but it might not float; when you put it in water, the holes fill up with water, and the question becomes whether the rest of the sponge is light enough to float.
It's the same thing here. When they say it's lighter than air, they're counting the whole structure's volume, with all its holes in it. When you put it in air, and the holes fill up with air, the question then becomes whether the rest of it is lighter than air on its own. (Probably not)
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.
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).
Specific to the water drop: that's a huge drop of water for that piece. Weigh that volume of air and compare it to a drop of water that size - there's no way it's even close. So even if it does float, the water would be more than sufficient to keep it down.
Simply: Buoyancy is the result of a difference in weight when one less dense material displaces another.
What is the displacement of the aerographite samples? The article doesn't say, but the samples are small enough that I'd guess the forces of moving air (breathing near the sample) is more problematic than forces of buoyancy.
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?
What's the smallest piece? A carbon atom? The only reasonable way to compare densities is to take a sizeable chuck of the material and compare it to the same volume of a different material.
If you break it down to the smallest piece, you're talking about Carbon atoms with an atomic mass of roughly 12 versus (mostly) Nitrogen and Oxygen with approximate masses of 14 and 16. So it's lighter as atoms but not by six times.
Most of the Oxygen in our atmosphere is O2, so there's a bond and space between the atoms as well as space between the molecules and others. In the same way, perhaps the carbon is more like closed cell foam that has voids that exclude other atoms. These voids have no mass but contribute to the effective volume.
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.
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.
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?
In the limit, that is zero. Area goes as O(N^2), volume as O(N^3), so if you make it big enough, you could wrap it in a meter of solid steel, and it would still float (guesstimate: a liter of this would lift about a gram of steel, so a cubic kilometer would lift about 10^12 grams or 10^6 tons of steel. You would need 6*10^6 square meters of cover, so you could use 160 kg steel per square meter => you will need something much bigger than a cubic kilometer to get at a meter of steel)
Your real problem is keeping the fabric from being pushed in. It does not matter much, but for that, you may not need to fill the whole thing with stuff.
Nanotechnology is awesome, but most of it seems to be in early research stages. Any good references for nanotechnology products used commercially today?
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.