Cambridge researchers create tetrataenite rare-earth-free magnets in the laboratory, which could help in the transition to low-carbon technologies.
Photo: Professor Lindsay Greer (middle), Professor of Materials Science, Department of Materials Science & Metallurgy, University of Cambridge with Owain Houghton (left) and Miguel Frausto de Brito Costa (right).
In the transition to low-carbon technologies, rare-earth elements play an important part. Rare earths such as neodymium and samarium are used in the production of high-performance permanent magnets for use within electric motors (notably in electric vehicles) and electric-power generators. Samarium is used in combination with cobalt, which is primarily mined in the Republic of Congo and other parts of Africa that are labeled conflict areas. The extraction of neodymium and samarium carries high environmental impacts and health hazards, as well as geopolitical risks, such as China's near monopoly on global production.
Another material, tetrataenite (L10 Fe-Ni) also offers high-performance permanent-magnet properties. The only problem is that tetrataenite forms over millions of years in iron-nickel meteorites, and is only found in minute quantities within meteorites that land on earth, making extraction unfeasible.
Now a team of researchers in the Department of Materials Science & Metallurgy at the University of Cambridge together with colleagues from the Austrian Academy of Sciences and Montanuniversität in Leoben have found a new way to make tetrataenite in the laboratory, which doesn’t require millions of years of cooling.
Professor Lindsay Greer explains that the discovery came about while researching metallic glass and the mechanical properties of iron-nickel alloys containing small amounts of phosphorus. On closer inspection, Greer and his team noticed an interesting diffraction pattern indicating an ordered atomic structure, similar to that found in meteoritic tetrataenite. “Inside these materials we observed the expected tree-like microstructure called dendrites. In most cases, it would have ended there. But the electron microscope showed an interesting Fe-Ni phase with an ordered atomic structure similar to that found in meteoritic tetrataenite,” said first author Yurii Ivanov, who completed the work while at Cambridge, and is now based at the Italian Institute of Technology in Genoa. Researchers found that phosphorus, which is present 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.
Synthetic tetrataenite offers the potential of rare-earth-free permanent magnets made from elements which are found in abundance in the Earth’s crust and avoid the need to extract a huge amount of material to get a small volume of rare earths.
Greer says that “no special treatment is required, and the end product can be produced within seconds, without having to wait millions of years for tetrataenite to form." Research is still ongoing to determine whether it will be suitable for high-performance magnets.
Currently the global permanent magnets market, valued at USD 19.14 billion in 2021 1 is divided into expensive high-performance magnets, or cheaper ferrite magnets, with few products in the mid-market price sector. Greer explains that synthetic tetrataenite would fill the mid-sector market gap, offering mass-produced high-performance magnets at an affordable cost point.
Previous attempts by a team in France in 1962 to make tetrataenite in the laboratory relied on extreme methods, such as neutron irradiation and not suitable for mass production.
A patent application on the technology has been filed by Cambridge Enterprise, the University’s commercialisation arm, and the Austrian Academy of Sciences.
The research was supported in part by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme and Seventh Framework Programme, and the Austrian Science Fund.
The results are reported in the journal Advanced Science:
The research was conducted with teams at the following institutions:University of Cambridge:Yurii Ivanov (now in Italian Institute of Technology in Genoa)Professor Lindsay GreerDr Nikolaos PanagiotopoulosOwain HoughtonMiguel Frausto de Brito Costa
Austrian Academy of Sciences - Leoben:Dr Baran SaracDr Sergey KetovProfessor Jürgen EckertCranfield University: Dr Konstantinos Georgarakis
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