A room-temperature superconductor? New developments

Post by rajamaka » Tue, Aug 01, 2023, 9:07 PM UTC

csteubs wrote: post #417

nwiswell wrote: post #317

Earlier quoted context omitted.

It would be sub-10%* gold content. We're talking about gold doping, specifically substitution in the Pb(1) site, not an alloy. ETA: I was off by an order of magnitude (originally I said sub-1%) because the doping is extensive, and the mass of the lead/gold is a dominant fraction of the total. The formula given in the paper is (subscripts in brackets): Pb[10−x]Cu[x](PO4)[6]O with 0.9 Similarly for Au we would have Pb[…

Having to handle lead for a practically unretrievable amount of gold would (I hope) be enough of a deterrent for the vast majority of "citizen scrappers". Worst case, I think a Pb/Au scrap grey-market would look something like the current catalytic converter market, where raw materials are purchased at set rate by an intermediary and then sold for further processing. Most people know there's gold in their computer pa…

Post by whimsicalism » Tue, Aug 01, 2023, 9:07 PM UTC

dingnuts wrote: post #429

whimsicalism wrote: post #346

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> it's seriously underachieving not only compared to US, but even compared to the rest of the developed world. This statement would have been viewed as absolutely obvious and ridiculous 2 decades ago. The fact that it even needs to be said now is indicating how fast they are advancing.

No, it's evidence of how fast they advanced under Deng. It is unclear that the advancement is continuing / has continued into Xi's reign, especially since the beginning of his third term.

Post by philwelch » Tue, Aug 01, 2023, 9:08 PM UTC

hosh wrote: post #378

ASalazarMX wrote: post #305

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The force of tradition is amazing. Imagine centuries knowing how to make something that explodes violently, and using it for entertainment instead of weapons. Just like how Mesoamerican civilizations invented the wheel, but only used it on children toys and not for transportation. There were no draft animals in the region, but they didn't even make wheelbarrows. https://www.mexicolore.co.uk/aztecs/home/the-concept-of…

Keep in mind, the Chinese were using bombs, granades, and rockets in warfare. Cannons were slowly being incorporated during the Ming. It’s just that, the Chinese also had standardized crossbows capable of punching through armor, and allowed for long range sniping, centuries before gunpowder. The Manchus who founded the Qing dynasty valued archery, and were slower to adopt firearms. The mid and late Qing period saw fi…

Post by pizzalife » Tue, Aug 01, 2023, 9:09 PM UTC

missedthecue wrote: post #464

evgen wrote: post #376

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1.2 billion _old_ people. While quantity has a quality all its own, in this case the demographics are not what you want to see if you are predicting long-term Chinese growth just based on population.

Median age China, 2022: 38.5 Median age USA, 2022: 38.9

Post by fallingknife » Tue, Aug 01, 2023, 9:10 PM UTC

jacquesm wrote: post #478

derefr wrote: post #432

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Resistance is what makes things hot, and heat is what makes dumping huge amounts of charge current into batteries a bad idea. No resistance → no heat → no need to charge with low current†. Another way to say it is that, with a superconducting wire, you can make the wire as thin as you want and still pass the same amount of current through it, without melting the wire. Picture using a USB-C cable to charge your car. †…

> you can make the wire as thin as you want No, superconductors have a specific current above which they stop superconducting so you will want to stay away from that limit. This particular superconductor has been presented with a very low Ic (150 mA in the original paper0 which would not make it particularly useful in such applications but future iterations (assuming it is all true) may improve on that (they should o…