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I always enjoy seeing one of my videos on HN! Let me know if you have questions.

So what happened with the startup, Niron? [1] They've been trying to commercialize this for years.

[1] https://www.nironmagnetics.com/

I love this guy. Totally living out my physicist-tinker dreams.

He's like the old "Amateur Scientist" column from Scientific American magazine come to YouTube.

It would be interesting to compare the iron nitride magnet sample with an just epoxy + iron filings. I would expect iron to have some area between the curves because iiuc iron is able to hold a magnetic charge.

good luck getting ammonium nitrate without being visited by the police (at least here in Europe)

My bookmark from May 28 says:

https://www.youtube.com/watch?v=M6XIgdS1rzs #Applied-Science #video on #bootstrapping “insanely powerful” planetary ball mill grinder to make α'' iron nitride filled epoxy for magnets, which did work somewhat; he tested it in a 1.6-tesla vibrating sample magnetometer he built using a lock-in amplifier to plot its B–H curve.

Hopefully this summary is useful to others.

On the topic of alternatives to rare-earth magnets, their most important use is probably electrical machines (motors/generators, and switched reluctance electrical machines can supposedly have power densities comparable to rare-earth-magnet permanent-magnet electrical machines, and you can build them out of just punched electrical steel, copper or aluminum wire, and insulator, just like a line-frequency power transformer. (I suspect Metglas would work better than electrical steel, without requiring any strategic materials, but might be impractically expensive.) Some relevant bookmarks from September 22:

https://www.youtube.com/watch?v=TAhF45AtsgA #video by #Akio showing his Arduino-driven switched reluctance motor #electronics control board and working motor #hardware

https://www.youtube.com/watch?v=vvw6k4ppUZU #video about "SynRM" switched reluctance motors made out of sheets with slots punched out to follow field lines. Low-quality AI voiceover from #Lesics.

(You can actually build SRMs out of non-laminated mild steel and speaker wire or whatever, but I think they won't be efficient.)

Another related bookmark from today:

https://www.youtube.com/watch?v=RAQexymmt64 lecture #video from 02012 (? or 02019?) by JR Hendershot about #switched-reluctance motors (“reluctance synchronous motors”) mentioning ABB’s new #SynRM product line (17–350kW), mentioning higher torque density than induction motors (which use the exact same stator design) and lower cost than permanent-magnet electrical machines as key advantages. Cites a price spike in neodymium as a key reason for interest in the area, which makes me think it’s from 02012 rather than 02019, when it was uploaded to YouTube. It actually says that “reluctance synchronous” motors are different from “switched reluctance” motors. Shows little webs in the stamping to hold the flux carriers together in the transversely laminated anisotropy rotor. Shows ABB’s plot of efficiency over its product line, ranging from 88% at 1kW rated power up to 97.5% at 700kW, because of the missing ohmic losses in the rotor relative to an induction motor. Boglietti and Pastorelli’s paper from 02008 reports 17% higher torque for an SRM (RSM) version of an existing induction motor. Shows some asterisk-shaped switched-reluctance rotors (using higher frequencies) and contrasts with RSMs’ trippy rotor design (using the same inverters as for an induction motor). Also has some nice electronics schematics. “The key to the improvements in efficiency and power factor lies in the inductance ratio or the saliency ratio in the d [direct] & q [quadrature] axes.”