Could this material be a cost-effective replacement for stainless steel? I'm thinking of applications where the antimicrobial properties of copper would be beneficial.
Iron ore costs $~100/ton, The cost of copper ore is hard to find (possibly because there are so many types, and because it tends to be processed locally AFAICT) but you're looking at ~$5000/ton.
So the raw-material cost should be about 50x, and apparently stainless steel costs ~$2500/ton so even if the processing is free you're already 2x the price.
So, no. Copper is about as rare as lithium, for context. Iron is an amazingly cheap metal.
There’s a reason that people tin-plate the food-contact surfaces of copper cookware.
I do in fact have some brass and alpaca "silverware". Because of the nickel, the alpaca stuff doesn't corrode; the brass stuff does, and if I don't keep the corrosion scrubbed off with steel wool, not only does it look like shit, acidic foods like yogurt taste bad. But I haven't gotten sick from it. It's probably not impossible to get sick that way, but it's challenging because of the short contact time, the low temperature, the small contact area, and the nasty taste.
Boiling tomato sauce down in a copper pot for a couple of hours is a different situation, and I wonder if this may have contributed to the early modern belief that tomatoes were poisonous. But the toxicity of copper acetate from vinegar (verdigris, used as a pigment) was already well-known.
Unplated copper pots have been commonplace for centuries and in use for millennia, and the most common way to get poisoned by them is to neglect to scrub off the blue-green basic copper carbonate that forms eventually from exposing wet copper to air. The carbonate is enormously more reactive to acids than the bare metal. My father-in-law related an incident from his childhood where a girl in his village got in a lot of trouble by poisoning half the village by cooking in unscrubbed copper!
Nobody died, though. Heavy metal poisoning from copper is not the same kind of menace as lead, arsenic, cadmium, and mercury. We can tolerate much higher levels, and it doesn't bioaccumulate.
Sounds impossible if you don't realize the horseshoes weren't steel.
The others I'm not so sure about. I think you'd have corrosion issues with water tanks and bacterial issues there are easily addressed by regulating temperature. And why would heat exchangers require particularly high strength? Since when are those a structural component?
In any case as you said electroplating something cheap is probably the way to go.
As for water tanks, regulating temperature is not always "easy", and a major reason copper is used for water pipes is its great resistance to corrosion. In this case apparently it will be more expensive than the same mass of stainless, but it's apparently also stronger than stainless, so maybe you can use less of it, making it cheaper again.
The heat exchanger point is interesting. However doesn't stainless already lose out to 3D printed aluminum for the sort of applications where the optimization is worth the cost? This material is even heaver than steel and substantially more expensive.
It's tangential but I wonder how amenable to 3D printing this material will prove to be.
High-energy cryogenic ball milling of 10 grams for four hours in a continuous flow of liquid nitrogen under an argon atmosphere with <1ppm oxygen (https://www.science.org/action/downloadSupplement?doi=10.112...) sounds expensive, but maybe they only did it that way because it was a low-risk way to ensure the alloying worked with the lab equipment they had on hand, not because it's the cheapest way to make the material. Hopefully cheaper ways are found.
I'm no expert in heat exchangers, but my calculations suggest 3-D printing is or will be an enormous boost there, and may reverse the gradient of merit for wall material thermal conductivity, favoring good thermal insulators over good thermal conductors like copper and aluminum. As for aluminum, it is only suitable for low temperatures.
I'm curious. What mechanism would lead to an insulator being favored in a heat exchanger?
Fair point about aluminum and temperature. As a layman an engine block is high temperature to me. I guess this would be extremely useful for more exotic stuff.
I could be wrong about this, but I didn't just make it up; I got it from Lingai Luo's book on heat and mass transfer intensification, which hopefully I've understood correctly.
With 3D printing I wonder if you could insert bands of insulator into an otherwise conductive wall? But you're dealing with large (potentially ridiculously so) temperature ranges so I wonder if it would prove difficult to match the thermal properties of the two materials closely enough.
I now have the weirdest desire to play with heat exchanger designs that I have absolutely zero use for. I've been nerd sniped.
When we’re talking about advanced materials, "high strength" means hundreds of MPa and "high temperature" is beyond 500°C (and more depending on the application).
(It would be excellent to be able to clean my silverware by firing it in a kiln, though with a copper alloy I'd probably have to scrub off the verdigris.)
Ok but if you do that then what is the point of the exercise? I thought fancy flatware was thin because of the appearance. If the edges are thick doesn't that defeat the purpose?
The equivalent thickness being something like 5x stronger is of course the benefit here.
I don't think price is an issue for high end home use items. Rich people buy far weirder and more expensive things.
Price is always an issue. Maybe you're willing to pay €100 a spoon, or €1000, or even €10000, but nobody is going to pay €1000000000 per spoon. If there's a good chance the price will drop by a factor of 10 in the next year, many rich people might be unwilling to pay even €100.
The process described sounds like it would currently be able to produce a spoon for a cost on the order of €100k: four PhDs working for a month is maybe €50k, but they're also tying up a lot of rather expensive lab space, and I think they're using analytical-grade fine chemicals rather than metallurgical-grade copper and tantalum. And in this study they made roughly enough for half a spoon. The second spoon would probably cost closer to €1000.
In an adjacent exchange it seemed we both expected the price to be far lower. 10x or even 50x the material cost of a piece of stainless steel flatware seems well within budget for a rich customer.
And I found some studies suggesting that 304 and 316 stainless steel leach very little nickel when in contact with food. It’s the cheaper nickel-containing stainless steel that’s a problem.
But even if suitable - it will be mostly novelty I guess. Still want one.
I'm also not sure how much being in an alloy would impact the antimicrobial effects of copper.
Generally copper does retain its antibacterial properties in alloys where it's a high proportion of the alloy, like this one.
Tantalum is in demand today, yes. Tantalum capacitors are a well known application, but it is used in all sorts of things.
My point was that even if tantalum were free, a material that is 96.5% copper is still not going to be significantly cheaper than copper, which I think is a pretty self-evident outcome.
This new alloy is useful only for high-temperature applications, like turbines and heat exchangers, where its main advantage over the existing alloys (based on nickel or cobalt) is its much higher thermal conductivity.
Moreover, the kinds of stainless steel that have little or no nickel content (e.g. ferritic, martensitic, superferritic, duplex, manganese-austenitic) will always have a price several times lower than any copper alloy.
This copper alloy will be rather expensive due to the high cost of tantalum. However the content in tantalum is small, so the price will remain acceptable for its applications.