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Physicists Have Identified a Metal That Conducts Electricity But Not Heat (2017)
- NikolaeVarius 7y agoIt conducts heat, just much less than expected
- emerongi 7y agoIs it possible to have a material that doesn't conduct heat?
- saagarjha 7y agoThe lack of a material, e.g. a perfect vacuum, as long as radiation doesn't get involved.
- duckymcduckface 7y agoRadiation becomes the dominant heat transfer mode in that case though, usually gets really small at day to day temperatures though.
- Dylan16807 7y agoIt's not that small. Blackbody radiation at room temperature is 450 watts per square meter. And it only takes an extra 15C to get 100 net watts transferred per square meter.
- katmannthree 7y agoRadiation is always involved, even at very low temperatures.
- opportune 7y agoNo, that would essentially mean that it doesn’t interact with neighboring matter (eg air bouncing off of it) since heat is really an emergent property of all the particles in a material bouncing/vibrating amongst each other. There are things that don’t conduct heat but they aren’t regular matter.
- klyrs 7y agoSuperconductors come pretty close.
- jacquesm 7y agoNo, but you can get surprisingly close with aerogels: https://www.youtube.com/watch?v=PmKt_6EhA24 https://www.youtube.com/watch?v=PmKt_6EhA24
- liopleurodon 7y agoApparently it's transparent. I'll have to remember this the next time I need to build a whale tank
- twic 7y ago> But a team in the US showed this isn't the case for metallic vanadium dioxide (VO2) - a material that's already well known for its strange ability to switch from a see-through insulator to a conductive metal at the temperature of 67 degrees Celsius (152 degrees Fahrenheit). The next time you need to do whale sous-vide, i think.
- the8472 7y agoThe transition temperature can be tuned with dopants[0]. And the switching happens from transparent at low temperatures to reflective at higher temperatures. 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-whale-tank.pdf?sequence=1&isAllowed=y https://dr.ntu.edu.sg/bitstream/handle/10220/25845/for-your-...
- ianai 7y agoIs that a Star Trek movie reference?
- robinduckett 7y agoFrom 2017
- dbcurtis 7y ago> which basically states that good conductors of electricity will also be proportionally good conductors of heat, which is why things like motors and appliances get so hot when you use them regularly. NOOOOO!!!!!...... How can science reporting be so bad???
- randyrand 7y agoIt is why they feel hot to human touch though :)
- MobileVet 7y agoBecause reporters aren’t scientists. The article links directly to a page on the law so maybe a little grace could be given? https://en.wikipedia.org/wiki/Wiedemann%E2%80%93Franz_law https://en.wikipedia.org/wiki/Wiedemann%E2%80%93Franz_law
- Ensorceled 7y agoMaking relatable analogies is hard.
- BubRoss 7y agoThat's not an analogy, it isn't explaining something in terms of something else.
- duckqlz 7y agoAnalogy : a comparison of one thing to another for the purpose of explanation. https://www.lexico.com/en/definition/analogy https://www.lexico.com/en/definition/analogy
- coldtea 7y agoThat's exactly what your parent said. 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".
- choonway 7y agoThe interior of a cathode ray tube?
- unnouinceput 7y agoQuote: "The metal, found in 2017..." Erm, say what again? Here's wiki for vanadium, you might wanna check that year : https://en.wikipedia.org/wiki/Vanadium https://en.wikipedia.org/wiki/Vanadium
- ImminentFate 7y agoThey’re talking about vanadium dioxide’s transition, but it’s still a poorly worded phrase
- unnouinceput 7y agoForm wiki: 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?
- narag 7y agoMaybe he meant that "elemental metal" is redundant? In other words: can we call "metal" anything not in the periodic table?
- klyrs 7y agoAlloys of various elemental metals are also metals, but aren't elemental.
- Armisael16 7y ago‘Elemental metal’ means the element not bonded to other elements (ie mostly pure vanadium). There’s no reason an element can’t be common but the pure element be rare. 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).
- sbhn 7y agoVanadium expands/contracts with temperature which means you can extract energy from it.
- Iv 7y agoThat article is weirdly written and it is not clear how the title relates to the content. 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?
- neltnerb 7y agoThe way they work is by having a bimetallic junction where a temperature difference between that junction and the other side of the wire pair is connected causes a voltage difference. 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-flows-in-vanadium-dioxide/ 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.
- ianai 7y agoLooks like his stuff has been known about for some time. What’s kept it from being used before now?
- neltnerb 7y ago$14/kg for unprocessed V2O5, presumably VO2 is brittle. 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.
- the8472 7y agoOne application is a thin window coating, you wouldn't need much of it. The manufacturing process is probably more expensive than the raw material.
- lightedman 7y agoThis would likely not work well in desert areas over an appreciable period of time, since most vanadium compounds are pretty soft, and desert winds tend to contain very hard particles of silica.
- neltnerb 7y agoI agree that the window application probably won't work (it's not like it's less thermally conductive than glass anyway), but why wouldn't they just coat the inside of the pane if they're worried about abrasive damage? 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.
- the8472 7y agoIt's not about thermal conductivity, it's about IR transmissivity. Above a certain temperature it would reduce the IR transmitted to the inside, thus keeping things cooler in the summer while still allowing the inside to be warmed by the sun during winter. 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.
- zwsxedcrfvtgb 7y agoIs VO_{2}, a metal oxide, really a metal? 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?
- neltnerb 7y agoThe formal definition of a metal is just that it has overlapping conduction and valence bands. https://en.wikipedia.org/wiki/Valence_and_conduction_bands 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...
- brennanpeterson 7y agoElectrical conductivity is electron motion, and if you have electrons to carry charge, you also get thermal conductivity. So metals (in the general sense) are good electrical and thermal conductors. 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.
- achr2 7y agoFrom a quick google, Vanadium also exhibits interesting properties for superconducting. I wonder if studying these higher temperature electron effects could impact that field..
- perlgeek 7y ago> The metal, found in 2017, contradicts something called the Wiedemann-Franz Law, which basically states that good conductors of electricity will also be proportionally good conductors of heat, which is why things like motors and appliances get so hot when you use them regularly. 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?
- dreamcompiler 7y agoCame here to post this. Motors and appliances heat up because of friction and because they are less-than-perfect conductors of electricity. Their good heat conductivity is why they don't get even hotter. 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.
- wwarner 7y agoYou have to be patient and read past the inaccuracies and hyperbole in these physics reports. This is the first I've heard of VO2 and this surprising behavior and I think it's an amazing advance.