What is the mysterious tesla magnet?

Tesla Investor Day It began on March 1 with a detailed and rambling speech on energy and the environment before moving into a series of mostly predictable announcements and brags. And then, out of nowhere, an absolute bomb appeared: “We’ve designed the following drive unit, which uses a permanent magnet motor, to use no rare earth elements at all,” he announced. Colin Campbelldirector of power train engineering at Tesla.

It was a startling revelation that left most experts in permanent magnetism wary and baffled. Alexander Gabay “I am skeptical that any non-rare-earth permanent magnets can be used in a synchronous traction motor in the near future,” says one University of Delaware researcher emphatically. and at Uppsala University in Sweden, Alina Vishinaa physicist, “I’m not sure it’s possible to use only rare-earth-free materials to make a powerful and efficient engine.”

The problem here is physics, which not even Tesla can change.

And at the recent magnet conference ping liu, a professor at the University of Texas at Arlington, asked other researchers what they thought of Tesla’s ad. “Nobody quite understands this,” he says. (Tesla did not respond to an email seeking clarification for Campbell’s comment.)

Tesla’s technical prowess should not be underestimated. But on the other hand, the company — and in particular, its CEO — has a history of making the business fitfully The endless sensational claims (We’re still waiting for that $35,000 Model 3For example).

The problem here is physics, which not even Tesla can change. Permanent magnetism occurs in some crystalline materials when the electron spins of some atoms in the crystal are forced to point in the same direction. And the more these alignment turns, the stronger the magnetism. For this, ideal atoms are those that contain unpaired electrons that gather around the nucleus in what is known as an electron 3D orbits. The peaks are iron, with four unpaired 3d electrons, and cobalt, with three.

But 3D electrons alone are not enough to make super strong magnets. As researchers discovered decades ago, magnetic strength can be greatly improved by adding unpaired electrons to the atoms of the crystal lattice in the 4f orbital – in particular the rare earth elements neodymium, samarium and dysprosium. These 4f electrons enhance a property of the crystal lattice called ferromagnetism anisotropy– In fact, the magnetic moments of the atoms reinforce the adhesion to the given directions in the crystal lattice. This, in turn, can be exploited to achieve success coercive force, the primary property that allows permanent magnets to remain magnetised. Also, through several complex physical mechanisms, the 4f unpaired electrons can amplify the magnetism of the crystal by coordinating and stabilizing the spin alignment of the 3d electrons in the lattice.

Since the 1980s, permanent magnets have been composite-based neodymium iron boron (NdFeB)Take control of high-performance applications, including motors, smartphones, amplifiers, generators and wind turbines. A 2019 study by Roskill Information Services in London found that more than 90 percent One of the permanent magnets used in automobile traction motors was NdFeB.

If the rare-earth permanent magnet isn’t for Tesla’s next motor, what type is it? Of the experts willing to speculate, the choice was unanimous: ferrite magnets. Of the non-rare-earth permanent magnets that have been invented to date, only two are in large-scale production: ferrite and another type called Alnico (aluminum nickel cobalt). Tesla will not use Alnico, six experts called Domain insist on. These magnets are weak, and more importantly, the global supply of cobalt charged too that they make less than 2 percent of the permanent magnet market.

There is more than one grade of permanent magnets that do or do not use a lot of rare earth elements. But none of them had an effect outside of the laboratory.

Ferrite magnets, which are based on a form of iron oxide, are inexpensive and account for nearly 30 percent of the permanent magnet market by sales. But it’s also weak (one of its main uses is closing refrigerator doors). One of the key performance indicators for permanent magnets is their maximum power product which is measured in megaGauss Oersteds (MGOe). It reflects the strength of the magnet as well as conquering it. For the NdFeB type commonly used in automobile traction motors, this value is generally around 35 MGOe. For the best ferrite magnets, it is about 4.

“Even if you get the best-performing ferrite magnet, you’ll have about five to ten times less performance than neodymium-iron-boron,” he says. Daniel Salazar Jaramilloa magnet researcher at Basque Center for Materials, Applications and Nanostructures, In Spain. Compared to a synchronous motor built with NdFeB magnets, a motor based on ferrite magnets will be much larger and heavier, much weaker, or a combination of the two.

There are certainly more than one class of other permanent magnets that don’t or don’t use a lot of rare earth elements. But none of them had an effect outside of the laboratory. The list of attributes necessary for a commercially successful permanent magnet includes high field strength, high strength, high temperature tolerance, good mechanical strength, ease of manufacture, and no dependence on rare, toxic, or otherwise problematic elements. All candidates today fail to check one or more of these boxes.

Silver dial on a black background.

Iron nitride magnets, like this one from startup Niron Magnetics, are among the most promising crop of permanent magnets that don’t use rare earth elements.Nero magnet

But if you give it a few more years, say some researchers, one or two of them could be a huge hit. Among the most promising: Iron nitride, Fe16n2. a startup in Minneapolis, Nero magnetis now commercializing groundbreaking technology with funding from ARPA-E by Jianping Wang at the University of Minnesota in the early 2000s, having previously worked for Hitachi. said Neron’s executive vice president, Andy Blackburn Domain The company plans to introduce its first product in late 2024. Blackburn says it will be a permanent magnet with an energy product higher than 10 MGOe, which foresees applications in amplifiers and sensors, among other things. If successful, it would be the first new commercial permanent magnet since NdFeB, 40 years ago, and the first commercial non-rare-earth permanent magnet since strontium-ferrite, the best type of ferrite, 60 years ago.

Niron’s first offering will be followed in 2025 by a magnet with an energy product above 30 MGOe, according to Blackburn. That is why he made a rather bold prediction: “It will have as good or better flux than neodymium. It will have the strength of ferrite, and it will have samarium cobalt temperature coefficients ”- better than NdFeB. If the magnet really manages to combine all these traits (if it is large ), then it will be very suitable for use in electric vehicle traction motors.

And Blackburn declares that there will be more to come. “All these new nano-engineering capabilities have allowed us to create materials that would have been impossible to make 20 years ago,” he says.

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