Comment by nwiswell | Hacker News Reader

Comment by nwiswell | Hacker News Reader

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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 < x < 1.1.

Similarly for Au we would have Pb[10−x]Au[x](PO4)[6]O. Taking the centerpoint x=1, this becomes Pb[9]Au[1](PO4)[6]O. In other words, there would be one gold atom for every 9 lead atoms.

The "unit cell weight" is 2647.59 g/mol, and the molar mass of gold is 196.97 g/mol, so in fact the hypothetical gold weight content is about 7.44%, not sub-1%.

That said -- presumably superconducting transmission wires would be thinner than the ones we are used to (a function of critical current rather than resistance). So I'm not sure that we'd have a theft problem worse than we already have with copper.

7.44% gold? That's ~$75 per oz of material. And you're talking about lead cable. Its kind of heavy, even if its thin. And it seems really easy to melt and separate. Notably, most power lines are actually aluminum, which is probably where people would really want this. Also chosen for its low weight / density, cause if you're gonna hang lines 100's of feet long, you want 2700 kg/m3, not 9000 kg/m3, and definitely not 11000 kg/m3. Although probably also significant applications in mm, um, and nm scale wiring.

At the end of their comment it notes that because it's a superconductor it would be thinner.

Perhaps assume an aluminum cladding for strength? Depending on how strong of a superconductor it is perhaps it's only 1% superconductor and 99% aluminum on top of the 10% content. So 0.1%?

I dunno, all these metals will be valuable in the future. Just saying, there's another large factor in estimating the gold content (conductivity saturation) that we don't know what it might be.

The superconductor itself would be 7.44% gold, but the wire would probably be much less -- superconducting tape isn't particularly strong so it will probably be wrapped up in layers of insulator and support wires.

I think that's right. There's no indication that it's mechanically strong, so you'd have it wrapped in layers of rubber/epoxy and steel cables in order to suspend it between power poles or transmission pylons.

YBCO tape has a critical current in the 1-10 MA/cm2 range, so if the properties of this RT stuff is anywhere close, the actual superconducting element of the wire could potentially be very thin.

FWIW strip mining operations till materials for ~6 PPM gold.

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 parts, but still opt for the recycling bin/ziploc bag in a junk drawer.

Nah, they'll just drop it in a smelter and sort it using gravity.

It might deter those in wealthy countries, everywhere else would be another story.

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