Superconductivity near room temperature
nature.com
nature.com
> Drozdov et al. observed this isotope effect and found that, compared with the lanthanum hydride samples, the critical temperature in lanthanum deuteride samples is lower by almost exactly the amount predicted by the theory.
So like the article points out:
> From a scientific standpoint, these results suggest that we might be entering a transition from discovering superconductors by empirical rules, intuition or luck to being guided by concrete theoretical predictions.
Whilst this result might require huge pressures, steady progress towards a theory of super-conduction is an exciting thing indeed.
But yah, you can bathe a much more complicated "circuit" in liquid nitrogen a lot easier than compressing it with diamond anvils. Though no commercial superconducting computers have emerged, cmos is just too cost effective currently, and the known examples are still in the 4K range.
But you have to put energy in to compress it, energy that is lost (since you're compressing it isothermally). Since we're talking about 1E6 atm, any appreciable volume would require insane amounts of E to compress.
How much energy it is depends on the volume change as you compress. If your material is completely incompressible, there is no volume change, no work done as the pressure rises, and therefore no energy stored.
In practice, for a material of bulk modulus K by definition you have
-K dV/V = dP.
V = V_0/exp(P/K)
The work done while compressing is the integral of -PdV, which per that first differential equation we can rewrite as the integral of P * V/K * dP (we want to integrate dP because we know what the limits are: it's going from 1atm, or 1e-4 GPa, to 1e6 atm = 1e2 GPa).
Plugging in our expression for V we get the integral, from 1e-4 to 100, of P/K * V_0/exp(P/K) dP. The integral there is:
K * V_0 * (-P/K - 1) * exp(-P/K)
K * V_0 * ((-100/K - 1) * exp(-100/K) + 1)
OK, so let's try an actual material and actual volume. Steel has a bulk modulus of 160 GPa according to <https://en.wikipedia.org/wiki/Bulk_modulus#Selected_values>. So for steel we have:
160 * V_0 * ((-100/160 - 1) * exp(-100/160) + 1) =
160 * V_0 * 0.13 =
21 * V_0
21e9 N/m^2 * 1e-6 m^3 = 2.1e4 J
If your material is more compressible, the numbers are higher, as long as it's not too compressible (in which case it just collapses into a tiny volume quickly and not much more work gets done after that). If we take K = 50 (a typical number for glass from that table), you get:
50 * V_0 * ((-100/50 - 1)*exp(-100/50) + 1) =
50 * V_0 * 0.6 =
30 * V_0
Again, all this assumes pressure-invariant bulk modulus, which seems moderately unlikely when you are dealing with pressures that are on the order of the size of the bulk modulus or even larger, as here.
As the article points out, diamonds naturally form in a high-pressure environment but are stable at standard atmosphere and temperature.
Although I suppose there aren't any theoretical obstructions to indefinitely maintaining low temperatures either.
lanthanum hydride @ 250K at > 1 million atm.
It's still very impressive though.
I'm not raging at ttsda. It is an advance. Of sorts. But not nearly as much as the headline suggests.
Basically, low temperature superconductors (e.g. niobium titanium) are liquid helium cooled.
High temperature superconductors (e.g. YBCO, BSCCO) are everything else, but generally liquid nitrogen cooled.
In the scientific community, High-Tc superconductors typically refer to Type II superconductors, eg cuprates. And the “High-Tc” term means above temperatures relative to the usual elemental superconductor Tc’s, eg about 20K or so.
Materials that can superconduct above 77K are especially sought after since they can be cooled with only liquid nitrogen, much cheaper and abundant than liquid helium.
Even if we could compress anything other than a spec of this stuff, it would still require massive amounts of PV work to achieve the P required.
> The effort to manufacture synthetic diamond provided substantial motivation for the development of high-pressure methods. Today, however, synthetic diamonds are grown using a low-pressure technique called chemical-vapour deposition. Optimistically, it might eventually be possible to use similar low-pressure methods to produce metastable superconducting compounds that are initially discovered at high pressure.
So, no, everybody cares about high temperature superconducors, because the higher the temperature, the strongest magnet you can build out of them.
That would be an exciting development.
The suns central pressure is 2.5*10^11 bar according to nasa.
https://en.m.wikipedia.org/wiki/Sun
https://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html
https://phys.org/news/2019-02-navy-patent-room-temperature-s...
"The application claims that a room-temperature superconductor can be built using a wire with an insulator core and an aluminum PZT (lead zirconate titanate) coating deposited by vacuum evaporation with a thickness of the London penetration depth and polarized after deposition.
An electromagnetic coil is circumferentially positioned around the coating such that when the coil is activated with a pulsed current, a non-linear vibration is induced, enabling room temperature superconductivity.
"This concept enables the transmission of electrical power without any losses and exhibits optimal thermal management (no heat dissipation)," according to the patent document, "which leads to the design and development of novel energy generation and harvesting devices with enormous benefits to civilization.""
That's about -10F, or -23C.
(And it would make a lot more sense to put that in the article. Most of us don't "think" in Kelvin.)
Especially since the article says room temperature. I know a lot of people on HN are interested in superconductors but don't necessarily use K frequently if ever.
Oh - it has to be at 1atm and -20 of course...
One million atmospheres is an important detail to leave out of the title.
What is the level of (in)efficieny for say power lines? And power cords, etc around the office/house?
That is, of the electricity produced, how much is lost due to how it's transported? Does decentralizing production (e.g., solar panels on your own roof) help in any way?
I'd still guess the bulk of the value would be in more local uses, but there are some interesting large-scale possibilities, including power transmission.
https://en.m.wikipedia.org/wiki/Electric_power_transmission#...
> In general, losses are estimated from the discrepancy between power produced (as reported by power plants) and power sold to the end customers
[0] https://en.wikipedia.org/wiki/Electric_power_transmission#Lo...
A superconducor rejects magnetic fields (a bit like a Faraday cage). What if you cranck it up high enough and force the superconductor in place? You lose superconductivity.
For that reason, there is actually a limit to thew current that can be transmitted, though it is much higher than with conventional cables (you still can't power a city with a hair-thin cable, IIRC).
Consider the other losses:
- Thermal (gas turbine) cycle: 40-60% lost (the big one) - Transformer loss: 1-2%. You pay this every time you step up/down, so it adds up. - Capacitive coupling: I dunno, but length dependent. It has to be about the same as Ohmic losses since once it's large you switch to DC lines (and take an Ohmic loss hit from lower V) - You're house's power factor (which, unlike industrial users, you're not charged for).
[0] in the sixties very large V lines were introduced (0.75 - 1.0 MV ??). They work, but it's not considered worthwhile.
Point is, they're kinda useless for transmission.
[0] MRI magnets are superconducting for the efficiency of superconductors, not for the field strength! The strongest magnets are not made of superconductors but out of copper pipes: electrical conductors with coolant pumped through them!