Reducing Europe’s reliance on rare earths
Scientists supported by the EU-funded ExtendGlass project may have a found a new way to make the high-performance magnets we need for our low-carbon technologies. Described in a study published in the journal ‘Advanced Science’, this new approach eliminates the need for rare earth elements, for which Europe is currently almost exclusively dependent on China. The best permanent magnets available today contain rare earth elements whose global production is dominated by China. This has led to concerns about continued rare earths supply as geopolitical tensions between China and the West grow. “Rare earth deposits exist elsewhere, but the mining operations are highly disruptive: you have to extract a huge amount of material to get a small volume of rare earths,” explains study senior author Prof. Lindsay Greer of ExtendGlass project host University of Cambridge in a news item posted on the university’s website. “Between the environmental impacts, and the heavy reliance on China, there’s been an urgent search for alternative materials that do not require rare earths.” A very promising replacement for rare earths is an iron-nickel alloy called tetrataenite found in meteorites. Tetrataenite develops naturally over millions of years as a meteorite gradually cools. This gives the iron and nickel atoms time to form a particularly ordered structure that results in a material whose magnetic properties resemble those of rare earth magnets. Since waiting for millions of years was not an option, in the 1960s scientists created tetrataenite artificially by bombarding iron-nickel alloys with neutrons to create the desired atomic structure. However, this method is not replicable on an industrial scale. “Since then, scientists have been fascinated with getting that ordered structure, but it’s always felt like something that was very far away,” observes Prof. Greer.
Beauty in simplicity
That is, it felt very far away until now. The research team has found a potential solution that needs neither millions of years of cooling nor irradiation with neutrons. The discovery was made while investigating the mechanical properties of iron-nickel alloys containing small amounts of phosphorus. As noted in the news item, phosphorus – also found in meteorites – “allows the iron and nickel atoms to move faster, enabling them to form the necessary ordered stacking without waiting for millions of years.” The team mixed iron, nickel and phosphorus in the right quantities to greatly speed up tetrataenite formation so that the material formed in just a few seconds. “What was so astonishing was that no special treatment was needed: we just melted the alloy, poured it into a mould, and we had tetrataenite,” comments Prof. Greer. “The previous view in the field was that you couldn’t get tetrataenite unless you did something extreme, because otherwise, you’d have to wait millions of years for it to form. This result represents a total change in how we think about this material.” While this approach supported by ExtendGlass (Extending the range of the glassy state: Exploring structure and property limits in metallic glasses) may show great promise, more work is needed to see if it is suitable for high-performance magnets. As reported in the news item, the researchers are hoping to collaborate with major magnet manufacturers to test their method. For more information, please see: ExtendGlass project web page
Keywords
ExtendGlass, magnet, rare earth, iron, nickel, phosphorus, tetrataenite, iron-nickel alloy
