Physicists Have Identified a Metal That Conducts Electricity But Not Heat (2017)
sciencealert.com
sciencealert.com
However if that metal has a good electricity conductivity and a low heat one, wouldn't that make it an ideal candidate for seebeck-effect generators? My understanding was that the efficency of these cells is mostly limited by the heat conducted at the junction. If one of the metals at the junction is a heat insulator, it should work wonders, no?
If you were able to prevent heat from going from the hot side to the cold side through the electrical wiring, yeah, I think the efficiency would go up. I worked on a battery project once where the internals were over 400C, and we needed like 000 gauge wiring which in copper meant our major thermal losses were through our conductors.
But the article is badly written and has a bad title. The actual article is here:
https://newscenter.lbl.gov/2017/01/26/electricity-not-heat-f...
and indeed they specifically mention applications to thermoelectrics. The big takeaway was the 10x lower thermal conductivity than expected for the given electrical conductivity.
Kind of embarrassing that the linked article on sciencealert just copy-pastes random portions into a new article and doesn't even bother with the credits at the bottom.
I'll have to remember this the next time I need to build a whale tank
The next time you need to do whale sous-vide, i think.
That said, its highest transmittance is in the infrared, it's not that great in the visible spectrum.
[0] https://dr.ntu.edu.sg/bitstream/handle/10220/25845/for-your-...
Using mostly his index fingers.
Suck it vim users, your editor has nothing on MOLECULAR DESIGN for System 3.0
Which is just alumna (aluminium oxide, AKA ruby and other gems).
They traded the formula for the glass. The company didn't manufacture transparent aluminum on the spot and give it to them.
It's just a movie. :-)
Now if we only had computers we could talk to. (Without trying to sell us something in the process.)
Erm, no. That's not how it works.
Things become hot due to electrical and mechanical losses; if you run them long enough, the heat moves out no matter how good or bad of a heat conductor you use.
In fact, you usually want a not-too-bad heat conductor, to avoid overheating the active components.
That said, there are still good use cases for such a material, for example when conducting electricity through a heat shield (furnace or freezer).
Do I want to continue reading, after the second paragraph contains such confusing statements?
There's more:
"The electrons were moving in unison with each other, much like a fluid, instead of as individual particles like in normal metals,"
Which describes a superconductor, but that word never appears in the writeup.
Subject is interesting but this article is clearly written by someone not very familiar with the science.
This actually annoys me a bit. Without knowings anything about it: it's a ceramic, almost certainly a semiconductor, and since its a semiconductor it can behave electronically like a metal under certain conditions.
Some semiconductors have poor phonon conduction, others quite good (ability to conduct heat).
Some semiconductors have good oxygen vacancy conductivity and poor electronic and hole conductivity. That gives you a transparent conductor.
And most ceramics are brittle. Is VO_{2} brittle?
In short, is this VO_{2} really a metal, or "just" a cool semiconductor?
https://en.wikipedia.org/wiki/Valence_and_conduction_bands
So it doesn't matter whether it's brittle (superconductors are brittle) or whether it's an oxide or whether it's a ceramic as well (superconductors), or a glass as well (metglass). What matters is that at your temperature of interest the bands overlap so that you have free moving electrons.
But reading some other literature suggests that "metallic" VO2 is indeed a semiconductor (not actual insulator) at lower temperatures and thermal energy makes the electrons energetic enough to jump to the conduction band and become a metal. So I think I'd say it's a "hot" semiconductor.
Ruthenium Oxide, Tungsten Oxide, and Chromium Oxide (at least one of them) are also metallic, with 10-20x worse conductivity than copper. Just a weird fact I had to figure out for a project. Actual metallic, not temperature dependent just phase dependent (CrO2 vs Cr2O3 for instance).
On the other hand, alumina is a great thermal conductor (about 10x worse than copper) but has almost no electrical conductivity, so I'm not so sure about this law relating the two in the first place. I've never heard of it being a law, I've always just treated that as a rule of thumb...
If you have very hard materials, with high phonon conduction, you can get thermal transport via phonons. But, these are almost all poor electrical conductors, as you need very tight binding to get hard materials with high phonon velocity.
The prototypical example of the second case is diamond.
Copper, despite all the news stories and it shooting up in 2011 (to almost $10/kg) is today only $5.70/kg pure.
I like the idea of tuning it to act as a passive way to heat and cool homes but compared to fiberglass insulation?
I buy thermoelectric and nonvolatile memory applications though.
Either way, if I were to pick a technology to improve desert glass insulation it'd be with a coating that allows in light but reflects infrared. Windows are mostly radiative heat transport after all, you can always double pane them for more direct conductive insulation.
Even in a desert the temperature-dependent behavior may be beneficial to cool during the night. But if it is not then yes, a different, harder coating that always reflects IR would be preferable.
NOOOOO!!!!!...... How can science reporting be so bad???
The article links directly to a page on the law so maybe a little grace could be given?
Parent: "That's not an analogie, it isn't explaining something in terms of something else."
You: "Analogy : a comparison of one thing to another for the purpose of explanation."
Well, the parent says this isn't an analogy, as it's not "comparing one thing to another for the purpose of explanation".
So a piece of aluminum will be cooler than a piece of iron. The Al might transfer more heat to my fingers than the steel... or it might not (that depends on many more factors than just the conductivity).
Conductive materials are likely to be good heat conductors because the electrons themselves can conduct heat, and because the crystal structures of conventional metals (e.g. copper) tend to be good for both.
These two effects are entirely unrelated.
Erm, say what again?
Here's wiki for vanadium, you might wanna check that year :
The elemental metal is rarely found in nature, but once isolated artificially, the formation of an oxide layer (passivation) somewhat stabilizes the free metal against further oxidation.
That's literally 2nd phrase there, right at beginning. Tell me, does that strike you as something to be discovered only in 2017? Or the guys who made the discover(y)/(ies) already seen VO2?
Also wiki is wrong since Vanadium is as rare as Copper. Does Copper strikes you as something rare?
In other words: can we call "metal" anything not in the periodic table?
Also the oxide the wiki article is talking about is V2O5, not VO2 (though VO2 was known beforehand - it’s easy to find articles about it from the 50s).