Researchers have found a way to make high- performance magnets without the need for rare earth elements, which are usually found in China.
A team from the University of Cambridge, working with colleagues from Austria, discovered a new way to make a possible replacement for rare-earth magnets.
Extreme methods have been used in the past to make tetrataenite. The addition of a common element could mean that it's possible to make it at scale without any specialized treatment.
The results are published in a journal. Cambridge Enterprise, the University's commercialization arm, has filed a patent application for the technology.
Magnets with rare earth elements are the best for building a zero-carbon economy. Rare earths are abundant in Earth's crust. China has a near monopoly on rare earth production. There are concerns that the rare earth supply could be at risk due to tensions with China.
"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," said Professor Lindsay Greer from Cambridge's Department of Materials Science & Metallurgy. There is an urgent search for alternative materials that don't require rare earths.
One of the most promising alternatives is Tetrataenite, an iron- nickel alloy with an ordered atomic structure. As a meteorite slowly cools, it gives the iron and nickel atoms enough time to order themselves into a particular stacking sequence within the structure, resulting in a material with magnetic properties approaching those of rare earth magnets.
The technique of bombarding iron-nickel alloys with neutrons is not suitable for mass production.
Scientists have been fascinated with getting that ordered structure, but it's always felt far away. Over the years, it has not been possible to make a substance of this magnitude.
An alternative that doesn't require millions of years of cooling or irradiation has been found by a group of people.
The team was studying the mechanical properties of iron-nickel alloys with small amounts of phosphorus. The growth structure called dendrites can be seen in the pattern of phases inside these materials.
"For most people, it would have ended there: nothing interesting to see in the dendrites, but when I looked closer, I saw an ordered atomic structure," said the first author.
The structure expected for iron-nickel alloys, which is a disordered crystal not of interest as a high- performance magnet, looks like the pattern of tetrataenite. It took a closer look by Ivanov to identify it.
The iron and nickel atoms are able to form ordered stacking without waiting for millions of years because of the presence of phosphorus in meteorites. They were able to speed up the formation of tetrataenite by between 11 and 15 orders of magnitude by mixing iron, nickel, and Phosphorus in the right quantities.
We melted the alloy, poured it into a mold, and we had tetrataenite, which was amazing. You would have to wait millions of years for it to form if you did something extreme. This result changes how we view this material.
There is more work that needs to be done to determine if the method for producing tetrataenite will work for high- performance magnets. Major magnet manufacturers are hoping to work on this.
It's possible that the work will force a revision of views on whether the formation of tetrataenite in meteorites actually takes millions of years.
More information: Direct formation of hard-magnetic tetrataenite in bulk alloy castings, Advanced Science (2022). DOI: 10.1002/advs.202204315 Journal information: Advanced Science
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