Tesla’s investor day on 1 March started with a rambling, detailed discourse on vitality and the surroundings earlier than transitioning right into a collection of largely predictable bulletins and boasts. After which, out of nowhere, got here an absolute bombshell: “We now have designed our subsequent drive unit, which makes use of a permanent-magnet motor, to not use any rare-earth parts in any respect,” declared Colin Campbell, Tesla’s director of power-train engineering.
It was a shocking disclosure that left most consultants in everlasting magnetism cautious and perplexed. Alexander Gabay, a researcher on the College of Delaware, states flatly: “I’m skeptical that any non-rare-earth everlasting magnet might be utilized in a synchronous traction motor within the close to future.” And at Uppsala College, in Sweden, Alena Vishina, a physicist, elaborates, “I’m undecided it’s potential to make use of solely rare-earth-free supplies to make a robust and environment friendly motor.”
The issue right here is physics, which not even Tesla can alter.
And at a current magnetics convention Ping Liu, a professor on the College of Texas, in Arlington, requested different researchers what they considered Tesla’s announcement. “Nobody absolutely understands this,” he reviews. (Tesla didn’t reply to an e-mail asking for elaboration of Campbell’s remark.)
Tesla’s technical prowess ought to by no means be underestimated. However alternatively, the corporate—and specifically, its CEO—has a historical past of creating sporadic sensational claims that don’t pan out (we’re nonetheless ready for that US $35,000 Mannequin 3, for instance).
The issue right here is physics, which not even Tesla can alter. Everlasting magnetism happens in sure crystalline supplies when the spins of electrons of a number of the atoms within the crystal are pressured to level in the identical path. The extra of those aligned spins, the stronger the magnetism. For this, the best atoms are ones which have unpaired electrons swarming across the nucleus in what are often called 3d orbitals. Tops are iron, with 4 unpaired 3d electrons, and cobalt, with three.
However 3d electrons alone should not sufficient to make superstrong magnets. As researchers found many years in the past, magnetic power could be vastly improved by including to the crystalline lattice atoms with unpaired electrons within the 4f orbital—notably the rare-earth parts neodymium, samarium, and dysprosium. These 4f electrons improve a attribute of the crystalline lattice known as magnetic anisotropy—in impact, they promote adherence of the magnetic moments of the atoms to the particular instructions within the crystal lattice. That, in flip, could be exploited to attain excessive coercivity, the important property that lets a everlasting magnet keep magnetized. Additionally, by a number of advanced bodily mechanisms, the unpaired 4f electrons can amplify the magnetism of the crystal by coordinating and stabilizing the spin alignment of the 3d electrons within the lattice.
For the reason that Nineteen Eighties, a everlasting magnet primarily based on a compound of neodymium, iron, and boron (NdFeB), has dominated high-performance functions, together with motors, smartphones, loudspeakers, and wind-turbine mills. A 2019 research by Roskill Data Providers, in London, discovered that greater than 90 % of the everlasting magnets utilized in automotive traction motors had been NdFeB.
So if not rare-earth everlasting magnets for Tesla’s subsequent motor, then what variety? Amongst consultants keen to take a position, the selection was unanimous: ferrite magnets. Among the many non-rare-earth everlasting magnets invented to this point, solely two are in large-scale manufacturing: ferrites and one other kind known as Alnico (aluminum nickel cobalt). Tesla isn’t going to make use of Alnico, a half-dozen consultants contacted by IEEESpectrum insisted. These magnets are weak and, extra essential, the world provide of cobalt is so fraught that they make up lower than 2 % of the permanent-magnet market.
There are greater than a rating of everlasting magnets that use no rare-earth parts, or don’t use a lot of them. However none of those have made an influence outdoors the laboratory.
Ferrite magnets, primarily based on a type of iron oxide, are low cost and account for practically 30 % of the permanent-magnet market by gross sales. However they, too, are weak (one main use is holding fridge doorways shut). A key efficiency indicator of a everlasting magnet is its most vitality product, measured in megagauss-oersteds (MGOe). It displays each the power of a magnet in addition to its coercivity. For the kind of NdFeB generally utilized in automotive traction motors, this worth is usually round 35 MGOe. For the very best ferrite magnets, it’s round 4.
“Even if you happen to get the best-performance ferrite magnet, you should have efficiency about 5 to 10 instances under neodymium-iron-boron,” says Daniel Salazar Jaramillo, a magnetics researcher on the Basque Heart for Supplies, Purposes, and Nanostructures, in Spain. So in comparison with a synchronous motor constructed with NdFeB magnets, one primarily based on ferrite magnets might be a lot bigger and heavier, a lot weaker, or some mixture of the 2.
To make sure, there are greater than a rating of different everlasting magnets that use no rare-earth parts or don’t use a lot of them. However none of those have made an influence outdoors the laboratory. The checklist of attributes wanted for a commercially profitable everlasting magnet contains excessive discipline power, excessive coercivity, tolerance of excessive temperatures, good mechanical power, ease of producing, and lack of reliance on parts which can be scarce, poisonous, or problematic for another cause. All the candidates immediately fail to tick a number of of those containers.
Iron-nitride magnets, equivalent to this one from startup Niron Magnetics, are among the many most promising of an rising crop of everlasting magnets that don’t use rare-earth parts.Niron Magnetics
However give it a number of extra years, say some researchers, and one or two of those might very effectively break by. Among the many most promising: iron nitride, Fe16N2. A Minneapolis startup, Niron Magnetics, is now commercializing know-how that was pioneered with funding from ARPA-E by Jian Ping Wang on the College of Minnesota within the early 2000s, after earlier work at Hitachi. Niron’s govt vp, Andy Blackburn, instructed Spectrum that the corporate intends to introduce its first product late in 2024. Blackburn says will probably be a everlasting magnet with an vitality product above 10 MGOe, for which he anticipates functions in loudspeakers and sensors, amongst others. If it succeeds, will probably be the primary new industrial everlasting magnet since NdFeB, 40 years in the past, and the primary industrial non-rare-earth everlasting magnet since strontium ferrite, the very best ferrite kind, 60 years in the past.
Niron’s first providing might be adopted in 2025 by a magnet with an vitality product above 30 MGOe, in keeping with Blackburn. For this he makes a moderately daring prediction: “It’ll have nearly as good or higher flux than neodymium. It’ll have the coercivity of a ferrite, and it’ll have the temperature coefficients of samarium cobalt”—higher than NdFeB. If the magnet actually manages to mix all these attributes (a giant if), it could be very effectively suited to use within the traction motors of electrical automobiles.
There might be extra to come back, Blackburn declares. “All these new nanoscale-engineering capabilities have allowed us to create supplies that will have been unattainable to make 20 years in the past,” he says.
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