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Comment by ortusdux | Hacker News Reader

"Alternatively, iron oxide can be mixed with ammonium nitrate in a planetary ball mill; after a few days of milling at 600 rpm, the stainless steel balls decompose the ammonium nitrate into elemental nitrogen, which diffuses into the iron nanoparticles. The resulting α”-Fe16N2 is then separated by magnet and can be formed into solid shapes."

Literally just rust and fertilizer.

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Glad to see Rust being used here, it's a much safer choice than C.

Indeed, we wouldn't want magnets to become a potential source of global warming if they oxidize.

That too... I was thinking more CN (cyanide).

You do have to be very careful if you start piling up ammonium nitrate on an industrial scale:

https://en.wikipedia.org/wiki/List_of_ammonium_nitrate_disas...

I'm not sure I'd want to stand next to a ball mill grinding up ammonium nitrate, myself.

AN is actually quite stable. It clumps when wet, and people back in the day would use dynamite to break mounds of it apart. It takes the addition of fuel to make it slightly unstable, but even then it takes a a high explosive to trigger it. The Beruit explosion was only possible because they stored AN, car tires, and fireworks in one location. And even then, best estimates are that only 5% of the AN combusted.

> And even then, best estimates are that only 5% of the AN combusted.

You say that as though it is a good thing. The way I read it is that it could have been much, much worse if the conditions had been a bit different.

I think the parent's point is that it was stable enough that ~20x as much AN as exploded in Beruit survived being next to an enormous explosion and didn't itself go off. A convoluted argument, to be sure.

From a chemist's standpoint, pointing out the level of inefficiency is straightforward: it sucks compared to X at blowing stuff up! But from a safety engineering PoV ... robots. More robots.

In fairness, the big question about the current sourcing of rare-earth materials is whether it'll cause similar problems at some point. At least in this method the explosions mostly happen at the site of production, as opposed to, say, in the Taiwan Strait.

The scariest bit to me is that if it detonates, the main product of that is nitrous oxide, which is rather… burny, and is its own source of oxygen.

Plus the iron powder which I am pretty sure would start burning too...

Hmm... maybe. It would depend on what stage of the process. Sounds like it starts with iron oxide, which wouldn't burn per se. But it also sounds like the iron oxide is reduced to iron nanoparticles with dissolved nitrogen in the process. Those would probably burn well, and even if they didn't, you might wind up with a bunch of molten iron, thermite-style. That wouldn't be good, either.

I would imagine mining rare earths isn't exactly safe either, so it just needs to beat the safety record of that

Where does all the oxygen from the iron oxide and the nitrate go? How is the iron oxide reduced to iron during the milling?

Water most likely. NH4NO3 + FeO -> FeN + 4 H2O

That equation doesn't balance.

https://www.chemicalaid.com/tools/equationbalancer.php?equat...

The page you are trying to view cannot be shown because the authenticity of the received data could not be verified. Please contact the website owners to inform them of this problem.

I think that's a outdated / misconfigured SSL issue on your side; I'm seeing a valid chain: ISRG X1 -> Let's Encrypt R3 -> chemicalaid.com. Qualys SSL Labs gives it an A+ on both IPv4 [1] and IPv6 [2].

[1]: https://www.ssllabs.com/ssltest/analyze.html?d=www.chemicala...

[2]: https://www.ssllabs.com/ssltest/analyze.html?d=www.chemicala...

My high school chemistry is kind of rusty, so I'd like to be educated on how this works. I thought that O would bind more strongly to Fe than N. If so, then how would they get the N in the ammonium nitrate to displace the O?

Indeed from the physorg article illustration (cited up top) and their description, the N doesn't seem to form a molecular bond with F, but to diffuse into the iron crystal; with F binding to F and N being trapped but not bound. Fe16N2 is then a description of the crystal ratios, not a description of a molecule that can create a crystal.

My chemistry is prob as weak as yours though, so don't trust this too much.

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