Tesla’s investor day on 1 March started with a rambling, detailed discourse on power and the setting earlier than transitioning right into a sequence 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 components in any respect,” declared Colin Campbell, Tesla’s director of power-train engineering.
It was a shocking disclosure that left most specialists 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 could possibly 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 unsure it’s attainable 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 latest 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 then again, the corporate—and particularly, its CEO—has a historical past of constructing 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 route. 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 referred to as 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 a long time in the past, magnetic energy may be enormously improved by including to the crystalline lattice atoms with unpaired electrons within the 4f orbital—notably the rare-earth components 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, may be exploited to attain excessive coercivity, the important property that lets a everlasting magnet keep magnetized. Additionally, by way of a number of complicated 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.
Because the Nineteen Eighties, a everlasting magnet based mostly on a compound of neodymium, iron, and boron (NdFeB), has dominated high-performance purposes, together with motors, smartphones, loudspeakers, and wind-turbine mills. A 2019 research by Roskill Data Companies, in London, discovered that greater than 90 p.c 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 specialists 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 specialists 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 p.c of the permanent-magnet market.
There are greater than a rating of everlasting magnets that use no rare-earth components, or don’t use a lot of them. However none of those have made an influence exterior the laboratory.
Ferrite magnets, based mostly on a type of iron oxide, are low cost and account for practically 30 p.c 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 power product, measured in megagauss-oersteds (MGOe). It displays each the energy of a magnet in addition to its coercivity. For the kind of NdFeB generally utilized in automotive traction motors, this worth is mostly round 35 MGOe. For the perfect ferrite magnets, it’s round 4.
“Even for those who get the best-performance ferrite magnet, you should have efficiency about 5 to 10 instances beneath neodymium-iron-boron,” says Daniel Salazar Jaramillo, a magnetics researcher on the Basque Middle for Supplies, Functions, and Nanostructures, in Spain. So in comparison with a synchronous motor constructed with NdFeB magnets, one based mostly on ferrite magnets will likely be a lot bigger and heavier, a lot weaker, or some mixture of the 2.
To make certain, there are greater than a rating of different everlasting magnets that use no rare-earth components or don’t use a lot of them. However none of those have made an influence exterior the laboratory. The checklist of attributes wanted for a commercially profitable everlasting magnet consists of excessive discipline energy, excessive coercivity, tolerance of excessive temperatures, good mechanical energy, ease of producing, and lack of reliance on components which are scarce, poisonous, or problematic for another motive. All the candidates at this time fail to tick a number of of those bins.
Iron-nitride magnets, comparable 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 components.Niron Magnetics
However give it a number of extra years, say some researchers, and one or two of those may very effectively break by way of. Among the many most promising: iron nitride, Fe16N2. A Minneapolis startup, Niron Magnetics, is now commercializing expertise 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 government vice chairman, Andy Blackburn, informed Spectrum that the corporate intends to introduce its first product late in 2024. Blackburn says it is going to be a everlasting magnet with an power product above 10 MGOe, for which he anticipates purposes in loudspeakers and sensors, amongst others. If it succeeds, it is going to 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 perfect ferrite kind, 60 years in the past.
Niron’s first providing will likely be adopted in 2025 by a magnet with an power product above 30 MGOe, in line with Blackburn. For this he makes a somewhat daring prediction: “It’ll have pretty much 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 might be very effectively suited to use within the traction motors of electrical autos.
There will likely be extra to return, Blackburn declares. “All these new nanoscale-engineering capabilities have allowed us to create supplies that may have been unattainable to make 20 years in the past,” he says.
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