Recycling permanent magnets

The Fraunhofer Institute in Germany has developed a process to recycle permanent magnets. Up until now, extracting rare earth elements from magnets has been both laborious and expensive.

The researchers heat magnets to more than 1000°C to liquefy the material in a melting pot. It is then directed via a nozzle onto a water-cooled copper wheel that rotates at a speed at an equivalent speed up to 80mph.

As soon as the melted droplet comes into contact with the copper, it transfers its heat to the metal within fractions of a second and solidifies. The scientists call the emerging material formations ‘flakes’.

“Instead of trying to regain each individual type of rare earth, we focus on recycling the entire material, the complete magnet,” says Oliver Diehl, a scientist at Fraunhofer. “The demo system can process up to half a kilogram of molten material and is somewhere between a lab and a large-scale plant.”

The researchers are optimising the properties of the recycled magnets by varying the melt spinning process – such as the speed of the copper wheel, for example, or the temperature of the melted material during the rapid solidification process. Both influence the cooling rate and consequentially also the crystalline structure of the solidified material.

In the melt spinning procedure crystallisation is avoided and either an amorphous structure is formed where the atoms are irregularly arranged, or a nanocrystalline structure where the atoms arrange themselves in nanometre-sized grains.

The grain sizes, meaning the areas with the same crystalline structure can be specifically varied. They can be used to change the properties of the permanent magnet. In a further step, the researchers mill the flakes into a powder, which can then be further processed and pressed into its final shape.

Justin Cunningham

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Are there any environmental effects of the processes used in recycling the magnets?

Comment Jaybesteen, 05/09/2016

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