Making Impossible Possible
The ore monazite can contain different rare-earth minerals important in energy applications, like neodymium. Below, a worker sorts magnetic parts containing rare-earth minerals from disassembled hard drives.
Perhaps the most important clash so far over these so-called “rare-earth minerals” opened up on March 13 when the United States, Japan, and the European Union filed a complaint at the World Trade Organization against China, which controls 95 percent of world production.
These obscure 17 elements are called rare, but they are actually common. They are just found scattered in such small amounts that the potential return seldom makes the cost of mining them worthwhile. But they help the modern world run, making cell phones buzz, producing the vivid colors we see on TV, allowing computer hard drives to store data. But what makes rare-earth minerals a strategic resource is that they are a crucial component in new energy technologies, enabling regenerative braking in hybrid cars, more efficient large wind turbines, high-efficiency fluorescent lighting, and photovoltaic thin films.
The U.S. Department of Energy says that deployment of clean energy technology could be slowed in the coming years by supply challenges for at least five rare-earth metals.
The new trade action seeks to force China to loosen export restrictions that other nations argue has kept the price of rare-earth metals artificially high outside the People’s Republic. But while the diplomatic process moves slowly forward, scientists worldwide are prospecting for breakthroughs that might circumvent China and win greater rare-earth metal independence for their countries.
These scientists view their objective as “inventing our way around any critical dependence on rare-earth materials,” says Mark Johnson, program director at the U.S. Advanced Research Projects Agency-Energy (ARPA-E). His agency, set up to fund transformational energy innovation in the United States, is among the participants meeting this week in Tokyo at a trilateral EU-Japan-U.S. conference on research into rare-earth alternatives.
The WTO action this month amounts to an opening salvo in a process that could take months or years. The United States, Europe, and Japan argue that China imposes several unfair export restraints on the critical materials, including duties, quotas, and pricing requirements. Officially, the nations have requested “consultations” with China; if those negotiations fail to achieve a resolution in 60 days, the countries that launched the complaints may request establishment of a WTO dispute settlement panel.
But meanwhile, in the laboratory, scientists are focused intently on the goal of reducing or eliminating rare-earth elements in powerful permanent magnets used in everything from jet engines to electrical generators. Rare-earth minerals are not magnets themselves, but when added to magnetic elements like iron, they create uniquely strong magnets, impossible to move with one’s bare hands. And a little rare-earth metal goes a long way. The strength of these rare-earth-enhanced magnets has helped to miniaturize electronics and to reduce the weight of electric cars.
When a rare-earth element combines with a conventional metallic element like iron, the two form a unique crystal structure that aligns its magnetic orientation in one direction. “Imagine each atom is a bar magnet aligning parallel to one another,” says Frank Johnson, senior engineer at General Electric Global Research in Niskayuna, New York. “As though they’re holding hands, the magnetic fields from each atom sum up to a huge magnetic moment.” The electrons in rare-earth metals have a strong interaction with the atoms next to them, creating a forceful pull in one direction. Ordinary magnetic materials like iron do not have this property and can be easily demagnetized.
University of Delaware Professor George C. Hadjipanayis, who co-invented the strongest rare-earth magnet 30 years ago, now is leading a team of scientists in an ARPA-E project to make magnets that are less dependent on the rare-earth elements. Like the team in George Clooney’s Ocean’s Eleven, where each member had to pull off the feat of a lifetime, each member of the ARPA-E project team is taking on a different outsized challenge. Says Bill McCallum, senior materials scientist at the U.S. Department of Energy’s Ames Laboratory in Iowa: “Each of us has [to have] at least one miracle scenario to be successful.”
Hadjipanayis is trying to make a magnet more than twice the strength of the neodymium iron boron (NdFeB) magnet he invented with 30 percent to 40 percent less rare-earth metal than today’s permanent magnets. How? By mixing a rare-earth metal with a non-rare-earth magnetic metal at nano-scale. The pull between the atoms at less than 20 nanometers apart is especially robust. Because rare-earth elements, especially at nano-scale, oxidize and ignite easily, “it takes some time to learn how to do,” he says.
At the University of Nebraska, Professor David Sellmyer is trying to avoid some of these problems by making the particles in a vacuum. “We make the particles by sputtering them out of a sputtering gun, and they collide with each other and form the structure we want,” he explains.
At Ames Lab, McCallum is taking a different approach. Instead of a rare-earth-free magnet, he’s making a “free rare-earth magnet” with cerium, one of the most abundant rare-earth elements in the world. Unlike Hadjipanayis, he is merely trying to make a magnet that’s stronger than any non-rare-earth magnet. Today, many applications use NdFeB magnets; those without rare-earth metals at all simply aren’t strong enough. But if Ames Lab can make something in between for electric vehicles and wind turbines, cerium can help conserve neodymium.
But cerium is tricky. It has a particular electron that likes to mix with electrons in other metals, demagnetizing the composite at the temperatures at which electric vehicles operate. McCallum is trying to find an element, such as hydrogen or nitrogen, to mix with cerium that will keep cerium’s problematic electron from misbehaving. But stabilizing those gases is a challenge.
Professor Laura Lewis at Northeastern University in Boston may face the highest hurdle of all. Her mission is to make a rare-earth-free magnet, using a compound found only in meteorites. She is trying to replicate the meteorite mix of iron laid on top of nickel on top of another layer of iron. Iron and nickel, both abundant, by themselves are easily demagnetized. But in this special crystal structure, they take on strength that makes them hard to demagnetize. The problem: “They only form naturally by a tenth of a degree per million years,” says Lewis. “So it takes one billion years.” Lewis says she sees “hints” of a time-saving man-made solution.
Meanwhile, GE Global Research is lending its expertise in a separate ARPA-E project to produce rare-earth nanocomposites at scale. “You need to have an understanding [of] what can be scaled to a ton level,” says Steven Duclos, GE Global’s chief scientist of material sustainability. “That’s as much a key to success as any kind of chemistry.”
In the rest of the world, scientists are exploring many avenues, including improvements in today’s NdFeB magnets. One option: To cut the amount of dysprosium, another rare-earth metal used in the magnets. Scientists found that putting dysprosium only at the boundaries between the grains in the magnet is enough to do the trick. The University of Tohoku and Intermetallics Co. Ltd in Japan, as well as companies such as Siemens AG in Germany, are searching for ways to apply dysprosium in just those spots.
As scientists around the world search for a path to independence from rare-earth metals, they each hope for their own magnetic moment. If their efforts hold charge, they’ll be able to power new industries—and maybe even a little world trade peace.
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