Follow Slashdot blog updates by subscribing to our blog RSS feed

 


Forgot your password?
Close
typodupeerror
×
Science

Physicists Have Identified a Metal That Conducts Electricity But Not Heat (sciencealert.com) 83

Posted by msmash from the how-about-that dept.
Researchers have identified a metal that conducts electricity without conducting heat - an incredibly useful property that defies our current understanding of how conductors work. From a report: 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. 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). "This was a totally unexpected finding," said lead researcher Junqiao Wu from Berkeley Lab's Materials Sciences Division back in January 2017. "It shows a drastic breakdown of a textbook law that has been known to be robust for conventional conductors. This discovery is of fundamental importance for understanding the basic electronic behaviour of novel conductors." Not only does this unexpected property change what we know about conductors, it could also be incredibly useful - the metal could one day be used to convert wasted heat from engines and appliances back into electricity, or even create better window coverings that keep buildings cool.
This discussion has been archived. No new comments can be posted.

Physicists Have Identified a Metal That Conducts Electricity But Not Heat More

Physicists Have Identified a Metal That Conducts Electricity But Not Heat

Comments Filter:

  • Where can I buy some?

  • No longer a law.

    • Not the first [Re:Wiedemann-Franz Law] (Score:5, Informative)

      by Geoffrey.landis ( 926948 ) on Monday December 02, 2019 @10:49AM (#59476752) Homepage

      It's only a law for a certain restricted range of materials, ones in which thermal energy of conduction electrons are the main conductor of heat.

      Superconductors are also materials that conduct electricity better than heat (in fact, they conduct electricity infinitely better than heat. Cooper pairs of electrons carry charge but can't carry thermal energy; if you give them thermal energy, it breaks the pairs). So this is not actually the first material found that does so; it's just that it does this at above room temperature, not at cryogenic temperatures.

      The article actually does state this-- the summary is misleading:

        Researchers already knew of a handful of other materials that conduct electricity better than heat, but they only display those properties at temperatures hundreds of degrees below zero, which makes them highly impractical for any real-world applications.

      • old [Re:Not the first [Re:Wiedemann-Franz Law]] (Score:5, Informative)

        by Geoffrey.landis ( 926948 ) on Monday December 02, 2019 @10:52AM (#59476772) Homepage

        ...odd that this two-year-old research result suddenly makes the news, though.
        https://newscenter.lbl.gov/201... [lbl.gov]

      • Re: (Score:1)

        by Anonymous Coward

        "The article actually does state this"

        Sssssssss! You RTFA? Apostate!

      • Copper pairs of electrons carry charge but can't carry thermal energy; if you give them thermal energy, it breaks the pairs).

        Wait what?

        Cooper pairs of electrons carry charge but can't carry thermal energy; if you give them thermal energy, it breaks the pairs).

        God damn it eyes, don't betray me like that

      • Is a metal oxide a metal? or is that another way they headline is misleading.
        super conductors I thought were primarily ceramics so not metal.

      • Re:Not the first [Re:Wiedemann-Franz Law] (Score:4, Interesting)

        by serviscope_minor ( 664417 ) on Monday December 02, 2019 @04:46PM (#59478118) Journal

        Superconductors are also materials that conduct electricity better than heat (in fact, they conduct electricity infinitely better than heat. Cooper pairs of electrons carry charge but can't carry thermal energy; if you give them thermal energy, it breaks the pairs). So this is not actually the first material found that does so; it's just that it does this at above room temperature, not at cryogenic temperatures.

        You also don't have to go that exotic: graphite is a very poor conductor of heat: you can heat one end of a pencil lead to incandescence and can comfortably hold it a few cm away. And it's conductive.

      • It's only a law for a certain restricted range of materials, ones in which thermal energy of conduction electrons are the main conductor of heat.

        A little more clear to state that it's the law for one particular mode of conduction. Some hundred years or so ago we only knew of one conduction mode, or perhaps also ion current, whereas now they seem to be breeding like bunnies.

    • Re: (Score:1)

      by Splot ( 5965912 )

      ...merely a suggestion.

    • VO2 is not really a metal. Perhaps this will clinch this distinction about this ceramic material.

    • No longer a law.

      Physics doesn't have laws, we make those to say "yep, never seen it do that before" in advance.

      • No longer a law.

        Physics doesn't have laws, we make those to say "yep, never seen it do that before" in advance.

        Yeah. They're more like local ordinances.

  • Wiedemann-Franz Law (Score:4, Insightful)

    by cyberchondriac ( 456626 ) on Monday December 02, 2019 @10:48AM (#59476742) Journal

    Capt Jack Sparrow : "It's more of a suggestion, really."

    This is why one should not wield science as absolutes or dogma; sometimes what you hold to be an incontrovertible truth turns out not to be so solid.
    This is not to bash science or scientific method, before those with poor reading comprehension jump on my back, I'm just saying, keep an open mind ( within reason) and acknowledge that some subset of the known and accepted physics of today are possibly subject to change tomorrow.

    • Re: (Score:3)

      by Kjella ( 173770 )

      I've never met a scientist that has a genuinely closed mind to new observations, even though they'll certainly question your data and methods if it contradicts everyone else. Everyone knows that theoretically there's no guarantee any law of nature is applicable tomorrow and practically it's based on observation and our incomplete sampling and understanding of it. However 99.99% of those who question the validity of science don't bring any new observations, they just want to raze it to the ground and say all

    • Except no one "held it to be an incontrovertible truth". Red the actual article; the summary was clearly written by someone who can't physics.

    • Re:Wiedemann-Franz Law (Score:5, Informative)

      by shmlco ( 594907 ) on Monday December 02, 2019 @11:54AM (#59477074) Homepage

      Most "laws" exist within a given domain. For example, engineers can pretty much accept the "laws" of thermodynamics for the majority of common cases. It's only when you start getting very, very small, very, very cold, or extremely hot that the laws start spewing nonsense... an indication that you've reached the edges of your domain and that you're going to need a new set of "laws" to cover those aspects. Quantum mechanics, anyone?

      • The laws of Thermodynamics are however one of those bits of physics that apply under all conditions at all times. Think of them like the speed of light or equivalence principle.

        • The laws of Thermodynamics are however one of those bits of physics that apply under all conditions at all times.

          Nope. The "Laws" of Thermodynamics are macroscopic phenomena that are based on the statistical properties of large numbers of particles. They do not apply at the atomic or quantum scale.

        • Re: (Score:2)

          by Jamu ( 852752 )
          They do not. The laws of thermodynamics are based on statistical physics. With few enough microstates, and enough patience, you'll see violations.

    • Nonsense... lets call a politician and regulate everyones behavior as though this current truth will be the truth tomorrow and hate on everyone else asking you to at least prove it first.

  • because what ? (Score:5, Insightful)

    by bugs2squash ( 1132591 ) on Monday December 02, 2019 @10:48AM (#59476744)
    Motors get hot because they conduct heat - that doesn't sound right. They get hot because there are resistive losses. If the motor components did not conduct heat then it seems to me that somehow that heat woudl get trapped which seems like a bad thing

    • Unless the heat gets converted to electricity instead?

      • Unless the heat gets converted to electricity instead?

        What you're talking about is a thermoelectric generator, which is an entirely different thing than simply not conducting heat very well.

        If an object cannot conduct heat, but it can conduct electricity, then unless it is a superconductor with zero resistance, it will get hotter and hotter. Eventually it will reach a temperature where it will break down (melt, break chemical bonds, whatever).

        I would guess that the usefulness of this is to better control the method in which waste heat is conducted away from th

    • I think they mean that the outer shell of motors (a.k.a the "motor") and appliances get hot to the touch because the heat is conducted from the hot components of the motor components to the outer shell.

    • Re: (Score:2)

      by ganv ( 881057 )
      Yes, the original post is pretty confused. Motors get hot because the coils are not 100% efficient and dissipate some of the electrical energy into heat. High thermal conductivity is essential to motors to allow them to transmit that heat out of the motor. And I don't think there is anything that "does not conduct heat" except a vacuum. If there are molecules, they can collide and transmit their thermal energy. Likely the result is showing that thermal conductivity by electrons is much lower in this m

    • Ding! Give that man a prize. If the motors were wound with superconducting wires they would not get nearly as hot. Of course there are other sources of heat generated in a motor such as friction (from bearings and parts moving in air).

      • Ding! Give that man a prize. If the motors were wound with superconducting wires they would not get nearly as hot.

        And because superconductors can generate a much higher magnetic field strength for the same energy as a conventional motor winding, you can make motors a good deal smaller. Northrup Grumman has built and demonstrated [nextbigfuture.com] a 36.5 MW ceramic superconductor ship propulsion motor for the US Navy that operates at liquid nitrogen temperatures. Older copper motors in that class are 250 tonnes. The newest are still 180 tonnes. The superconducting motor is less than 75 tonnes. The US Navy plans to reduce the weight

    • . They get hot because there are resistive losses. If the motor components did not conduct heat then it seems to me that somehow that heat woudl get trapped which seems like a bad thing.

      The temperature would just rise until the innards melted. Pretty much all motor designs have some losses in the form of heat, these need to be passed to the surroundings. piling energy into any system without limit is not a good idea, unless you are looking for a meltdown or explosion.

    • Motors get hot because they conduct heat - that doesn't sound right.

      Actually that is still correct. If it wasn't then it would be just the motor windings that get hot and there would be absolutely no benefit to cooling them from the outside, something done on most motors.

  • Ignorance (Score:5, Insightful)

    by DeathToBill ( 601486 ) on Monday December 02, 2019 @10:51AM (#59476768) Journal

    "which is why things like motors and appliances get so hot when you use them regularly"

    No. Just no. Someone failed thermodynamics. They get hot because they have resistance. They dissipate that heat to the environment because they're good conductors. If they were poor conductors, they would get hotter through being unable to dissipate the heat.

    • That's one less correction I have to make to an error found on the Internet. . . .

    • And that's the clue that the summary is likely to be completely wrong. And oh look, the author is using a semi-conductor device to write as though materials like that don't exist. And fails to tell us about the actual interesting novel thing, that they found a material that does this at high instead of very low temps.

    • But only if you use them regularly. If you use them at irregular intervals, they don't get hot. It's the Klüles-Zubmytter law.

    • If they were poor conductors, they would get hotter through being unable to dissipate the heat.

      Internally, for sure.

      If the resistance of the windings (and the size of other loss mechanisms, such as magnetic hysteresis and eddy currents), as well as thermal conductivity, stayed the same, the core would heat more but the surface would end up at the same temperature (just take longer getting there, and cooling off later). That's because the surface temperature is the balance between the dissipation adding he

  • Better start being quite friendly with China.

    This is one of those 'Rare earth' metals - not truly uncommon at all, but the cost-per-pound of V05 (Vanadium and 5 oxygens) is around $6 or so per pound according to Google. That might not seem like a lot, but it's highly sensitive to supply and market fluctuations historically.

    A large new demand would by one of those market fluctuations.

    Start large-scale production world wide of circuits with either that engineered as part of the wiring, or as heat gates or mo

    • Suggest further study. It's a relatively light element, no where near the rare earth part of the periodic table. It's a troublesome component of coal and other fossil fuels, where when burned it catalyzes the sulfur dioxide into trioxide and then with water to sulfuric acid, which eats boilers.

      It's not super cheap because there's not enough demand to get to economies of scale, and not being a rare earth element at all means it lacks the big issue with those - always being found with radioactive thorium.

  • This Science "Alert" is nearly three years old. How does this make the the front page?

  • The universe doesn't owe you to behave in any way at all, it just does what it does.
    I wish doctors in their stubborn arrogance would understand that too.

  • Considering it's a metallic oxide, shouldn't it be called a ceramic? Some ceramics can be superconductors and etc...

  • How else would it work?

    Wash me but don't make me wet?

  • which is why things like motors and appliances get so hot when you use them regularly

    No, just no.

  • I would love to see the change to in computer builds if they can use it produce highspeed CPUs and GPUs without the need for cooling?

  • Maybe its not a metal. There are non-metallic conductors. Its sounds to me that the headline should be "Vanadium Dioxide No Longer Considered a Metal"

  • [...] which is why things like motors and appliances get so hot when you use them regularly.

    No, that's because of friction losses! Not because they are good at conducting heat, but because they produce it.

    • Also eddy current losses in the iron. It's why transformer cores aren't solid blocks of iron, and why ferrites are used at higher frequencies, as they don't conduct eddy currents. Most of the heat is, however, I2R losses in the copper due to *lack* of perfect conductivity. So the "just no" isn't even enough to point out the stupid here.

      FWIW, anything less than a perfect insulator of heat would allow all the generated heat to escape - it's only a matter of how hot the inside gets before equilibrium is atta

  • ... for thermoelectric generators and/or Peltier coolers? If less heat leaks across a junction by thermal conduction, more energy might be transferred by the Peltier/Seebeck/Thompson* effect.

    *Have I forgotten anyone?

  • Wiedemann-Franz Law is usually derived by assuming (a) Ohms law and (b) free electron gas. Highly doubt VO2 is well described by the free electron gas.

    This 'Law' is like a chemistry law, it's kinda true. Remarkably true for 'regular' conductors (where free electron gas is a good approximation).

  • Now we'll have stay cool, killer robot overlords.
  • Did they get it from the To The Stars Academy?
  • Sounds like a candidate for a replacement material for a thermal mug.

    WAIT! Forget I said anything. This is MY idea!
    I patented it ;-)

    You heard it from me first!

  • Wat? (Score:2)

    by rthille ( 8526 )

    "which is why things like motors and appliances get so hot when you use them regularly"

    No, that's not why motors and appliances get hot...

Slashdot Top Deals

It is now pitch dark. If you proceed, you will likely fall into a pit.

Close