Always enamoured of the properties of water - there is still so much to learn.
I remember in my flying school days we were learning about microscopic drops of water which, at altitude, would retain their liquid state below 0degC and only freeze when coming into contact with metal or another foreign object. Biggest cause of icing on wings, intakes and carburettors (on piston aircraft). Because the molecules were still in liquid form, radar cannot identify it as an icing hazard...
Pretty much the opposite end of the scale from this article.
We did something like this in high school as part of our chemistry class. We supercooled the distilled water using a salt/ice bath, taking it well below freezing (in a test tube). Then we introduced a "seed" (don't remember if it was a chip of ice, or a bit of sand, or what) - and watched it "freeze" instantly. I'd have to look at my notes to know what the experiment actually was for, how it was conducted, lab notes, etc - because there was a point to it all (not just as a demonstration of super-cooling and freezing)...
That reminds me of a really cool experiment we did in chemistry. You can create anice packs" that are basically a super-saturated solution that precipitates when you snap a little trigger in the corner of the pouch, creating an endothermic reaction. It was really awesome, and I definitely remember a lot more from experiments like that then I do "titrate [x] in to [y] and take notes" experiments.
Has me thinking of the dangers of drinking vodka outdoors in Siberia, in the winter. Of course any ill effect of the vodka might be considered mercy, in such conditions.
I wonder if the forced phase-change the confinement causes applies to other contexts? Could we use a similar trick to force superconductive materials into their low-temperature superconductive phase at higher temperatures?
(Repost of the same comment from the other thread about the same paper)
I'm by no means an expert, and I may be wrong, but I personally don't think that it's possible to achieve superconductivity at room temperature and normal pressure using this approach at the current state of the art.
If you take a look at the phase diagram of the water [1] you could notice that the pressure required to crystallize water at temperature near 105°C is something near p_freeze = 2.5⋅10^9 Pa. However, the water is inside of the nanotubes of radius r = 0.5⋅10^(-9) m (the article says about the tubes being of diameter 1.05 nm). Such small radius creates significant surface tension (the same force that allows soap bubbles to exist) which is expressed by equation [2] as Δp = γ/r. According to
[3] the surface tension coefficient for water at 105°C is γ = 58⋅10^(-3) N/m, so Δp ≈ 1.2⋅10^8 Pa. The required for crystallization and the actual pressures differ in just one order of magnitude.
But the reasoning above used the macroscopic physical laws, and of course one could expect deviations from them when thinking about diameters as small as 4 water molecule diameters. Of course there is still no theoretical model that describes this configuration and calculates exact values of p_freeze and Δp precisely for it. But such model don't have to change the orders of magnitude in the problem, just estimate factors of order of 1, and we could use rough intuition gained previously about the process even without such model.
So if you try to apply these intuitions to the superconductivity you immediately meet difficulties because all known superconductors are in solid state, not liquid. It could be overcome by putting it to the nanotubes in liquid state and then letting it crystallize. Let's assume that this is possible. Evidence [4] suggests that to get a superconductor at high temperatures it requires to have pressure of order 10^11-10^12 Pa. This pressure is two orders of magnitude higher than the one required to freeze water at 100°C. That means that surface tension coefficient in such material should be two orders of magnitude higher than in liquid H2O to create pressure of order of magnitude required for phase transition to superconducting state.
I wasn't able to find data about surface tension in superconducting materials like like H2S mentioned in [4], but I doubt that it is 100 larger than surface tension in water. And it is impossible to significantly increase pressure by decreasing radius of tubes because this radius is already of order of molecules size. So I don't think that it is possible to get high temperature superconductors at normal pressure and room temperature using nanotubes and already known superconducting materials.
Space elevators are limited in tension not buckling
Solid core things are not considerably stronger in buckling than hollow (there is some increase but not staggering huge like orders of magnitude)
Also with the exception of giant single crystals, the microstructure usually doesn't relate very closely to macrostructure. The best human scale I beam material does not resemble I beams at microscopic scale, for example the microstructure of steel is very important to its properties but has nothing to do with its behavior in an I beam. The best buckling material, if buckling even mattered which it doesn't, would probably not be microscopically tubular.
Space elevators are engineer-annoying in that it requires no basic research and not much engineering work to build a low-G one like on the moon, we have everything we need, yet one for the earth is at least one or two or three fundamental research steps away. Assuming you mean boring passive mostly inherently stable designs. If you want to make launch loops and rotor-vators then all bets are off and if you can handle the dynamic stability problems (and the massive cost) we can make those today. Note I'm talking about the engineering... we have industrial scale capacity to build a lunar elevator with materials that have been proven space rated, in comparison people insist on comparing them to earth elevator designs where at best we have theoretical calculations of theoretical compounds that might be almost good enough if they can be made at all, then made in massive industrial quantities and if they can be space rated. Spectra fishing line is good enough for a toy scale lunar space elevator, technically it would work but you'd get much higher payload with fancier stuff.
In my infinite spare time in my retirement or something I'm going to make a small scale launch loop capable of flinging snowballs or model airplanes or similar, or possibly never get around to doing it, or possibly end up a Darwin award winner. I can't even imagine what the FAA would think of a loop that I've calculated is technically within my ability to build and finance. Of course if the wire snapped I'd be in a substantial amount of trouble especially if it finally impacted a foreign country or something. In theory using relatively boring materials a large nation-state level effort could easily replace first and probably second rocket stages with a loop. One interesting solution to the reusable first stage problem is to not have one to begin with.
how big a loop do you think would be feasable to build, by a person such as yourself?
I assume you've looked at the equations (I have not), so how does a smaller loop affect the necessary speed of the rotor? does it increase or decrease?
Just spitballing, I'm no materials scientist, but the property of water which makes it so well suited to hydraulics is its lack of compressability. If these tubes can be crammed full of the stuff then it might increase rigidity to the point where it strengthens the tube's structural characteristics.
As a non-physicist I was thinking the molecules become jammed, immobilised upon expansion; for want of a better analogy a swollen foot in a shoe, no more wiggle room. But the article says that the solid water does melt at even higher temperatures.
> Moreover the difference between 1.05 and 1.06 nm drastically affected freezing point.
I think the author might have misread something. The Van der Waals radius of a carbon atom is only 0.17 nm, so the radius of a single tube can't vary in steps of 0.01 nm. Maybe this just referred to the average tube radius?
Hmm. A tube is composed of many carbon atoms in a ring. Add one more atom, you increase the circumference by 0.34nm but the radius only by 0.34/2pi=0.054nm. So still looks infeasible.
"electrical and thermal properties of ice while remaining stable at room temperature"
This sounds pretty amazing. My first thought was there has to be some sort of application toward air conditioning. However, then I started thinking that an even better place to start would be to find ways to utilize this in clean energy. The scale / complexity of production could probably be a non-starter, but (just as an example) if I can put ice into a body of water and more or less guarantee it will never return to water form, at a large enough scale it probably could have hydro-electric applications.
Forgive me if the idea appears somewhat naive. Please correct me if I'm wrong about this but, given that the "frozen" water exhibits thermal properties of ice, in theory couldn't a closed system be built to generate electricity given the constant displacement of water running through the system. By taking advantage of the constant cycle of temperature variations within the system?
EDIT: Just looked it up, it appears difference in weight between 4 deg C and 21 deg C (1 ft^3 of water) is a little more than 1/10th of 1 lb.
Don't get me wrong. I agree with the laws of thermodynamics :) , but just like we exploit a "closed loop" / "seemingly perpetual" system between the moon and the oceans, or flowing rivers, couldn't there exist other "closed loop" systems? After all, on the scale of a human life that closed loop system (between moon and oceans) is, for all practical purposes, perpetual.
The quote "thermal properties of ice" is part of the line:
> And the finding might lead to new applications — such as, essentially, ice-filled wires — that take advantage of the unique electrical and thermal properties of ice while remaining stable at room temperature.
This tidbit of Science Journalism reads like a whimsical fantasy of the writer of the article after a cursory read of the abstract, rather than a statement of fact by the authors of the paper. It's important to differentiate these types of phrases when reading this sort of article.
The "thermal properties" here do not seem to actually include the temperature; they're heating it up to measure the melting point of the ice they form. There's no indication that it spontaneously changes temperature when exposed to this physical phenomenon, nor that the ice remains solid when returned to the liquid water, nor that the process generates a constant flow. If these things happened, I would definitely expect the paper to focus on that application.
More generally, any idea which would violate the laws of thermodynamics should probably be dismissed as a misunderstanding of the system. It's good to be curious, but you should also be skeptical.
Microfuidics have a lot of interesting potential applications; $SPOUSE works on using them for point-of-care diagnostics, also in the MIT ChemE department.
I remember in my flying school days we were learning about microscopic drops of water which, at altitude, would retain their liquid state below 0degC and only freeze when coming into contact with metal or another foreign object. Biggest cause of icing on wings, intakes and carburettors (on piston aircraft). Because the molecules were still in liquid form, radar cannot identify it as an icing hazard...
Pretty much the opposite end of the scale from this article.