Science and Technology

Atmanirbhar magnets

M Ramesh | Updated on August 01, 2021

How to make new magnets that depend less on Chinese rare earths

As the world moves towards electric mobility, one unseen hurdle is ‘magnet’. EVs need better motors, and this calls for better magnets. As of today, the best magnets are produced with ‘rare earth metals’ — 17 in all — whose extraction is extremely difficult.

Guess which country controls the supply of magnets to the world? China. It is beside the point whether China has emerged as the world’s supplier of rare earths because of lax labour and environment laws. And it is known to put the squeeze on supplies when it is displeased. Ask Japan!

This is a challenge and an opportunity for India. In this regard, work at the government-owned International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI) in developing new magnets, which can not only make India self-reliant but also supply to the world, appears significant. Scientist R Gopalan, who heads ARCI in Chennai, is an expert in magnets.

One of Gopalan’s works relates to the discovery of a new process for making neodymium-iron-boron magnets, hailed as the ‘champion of magnets’. NIB is an excellent alloy for making magnets, but it starts losing magnetism when heated. Motors, particularly in EVs, generate a lot of heat. To overcome this problem, NIB magnets are doped with another rare metal, dysprosium. China controls dysprosium supply. Today’s NIB magnets contain 15-20 per cent dysprosium, but Gopalan has developed a different process (called ‘grain boundary diffusion’) to produce equally good magnets with less than 1 per cent dysprosium. “The world is keen on this technology,” Gopalan tells Quantum.

Now, even this bit of dysprosium becomes critical when you are talking of millions of motors in EVs and elsewhere. Gopalan has produced such a dysprosium-free NIB alloy “on a lab scale”; talks are on with a few industries to put up a pilot plant using this “ultimate rare earth magnet technology”.

ARCI has next trained its sights on ‘rare-earth-free’ magnets, with work on a manganese-bismuth alloy. The beauty of this alloy is that, unlike others, it becomes a better magnet when heated (due to ‘high coercivity’). However, there are “metallurgical challenges” in making this alloy in such a way that it is also easy to magnetise. Gopalan suggests that until this process is perfected, a combination of NIB and manganese-bismuth could serve industry well.

ARCI is also working on magnets based on a rare earth that India has plenty of — Samarium. “Samarium-iron nitride is a good candidate to replace NIB,” Gopalan says. Thus, there are three magnet technologies cooking in ARCI that promise less dependence on China.

Gopalan’s team has also succeeded in improving conventional magnets. Last year it developed an iron-phosphorus alloy that can replace conventional silicon steel magnets and is 20 per cent cheaper. ARCI has also developed a new process of producing strontium ferrite hard magnets with coercivity of 6.6 oersteds, compared with the 5 oersteds of the conventional strontium ferrite magnets. The better the magnets, the fewer you need — then they weigh less and occupy less space.

Magnets are low-value, small components, but without them there can be no motors, no industry. Control over magnets is therefore critical, says Gopalan.

Published on August 01, 2021

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