The demand for energy, such as electricity, around the world is increasing, with much of this demand being met through the use of fossil fuel resources. Of course, the use of fossil fuels for energy production leads to the emissions of greenhouse gases to the atmosphere that are linked to climate change. Moving away from fossil fuels requires the development and deployment of clean energy technologies such as wind turbines and electric vehicles (EVs). (1) These technologies are often reliant on high-performance rare earth permanent magnets (REPMs). The past two decades witnessed a surge in REPMs with them reaching a market value of $14.4 billion in 2020 (representing about 70% of the global permanent magnet market value), compared to a 35% market share in early 2000s. (2,3) Currently, around 90% of the rare earth supplies come from China. (4) The near-monopolization of the rare earth element supply and processing makes the supply chain volatile. For example, when China cut the export quota of rare earth elements by 40% in 2010, some rare earth material prices increased by two, three, or even ten times in 2011 over their previous levels. (5,6) The U.S. Department of Energy (DOE) examined and analyzed the criticality of rare earth elements and 00other key strategic materials, and concluded that neodymium and dysprosium are the most critical rare earth metals with respect to clean energy technologies. (7) Moreover, the pandemic made things worse, as hundreds of mines were partially, if not wholly, closed. While the effects of the pandemic on metal markets seem to be ebbing, the prices of such materials as neodymium and dysprosium are likely to remain subject to substantial supply risk moving forward due to soaring demand and competition for constrained material supplies. (4,8)

Given the supply risk associated with rare earth elements and associated price volatility, a number of strategies are being pursued globally to limit the risk, e.g., finding new sources for these critical materials and developing material alternatives. One strategy that seems to offer promise with respect to REPMs is to recover magnets from end-of-life (EOL) products and capture magnet waste during sintered magnet processing. It is envisioned that such reclaimed materials could be used to fashion “new” magnets and, thus, temper the demand for virgin resources. A comparative life cycle assessment of producing magnets from virgin materials and through magnet-to-magnet recycling showed that recycling is an environmentally preferable choice. (9) Furthermore, recycling is also preferred with respect to magnet performance since it enables the adaptation to newly discovered methods that improve magnet strength and ductility. (10)

...There are three methods to produce NdFeB magnets: sintering, bonding, and hot deformation. (11) Only the first two methods have been successfully commercialized. (12) The manufacturing of sintered NdFeB magnets starts with strip casting where the alloy is melted in a furnace at around 1000 °C and then processed and quenched in a strip caster into sheets. (13,14) Strip casting avoids the unwanted α-Fe phase through rapid cooling. (15) The cast alloy sheets are then rolled and pulverized into a fine powder. The powder is pressed into a green compact in the presence of a magnetic field. The green compact then goes through the thermal process of sintering, followed by finishing with machining, magnetizing, and coating to prevent corrosion. A sintered NdFeB magnet has a maximum energy product (BHmax) of around 200–400 kJ m^–3, making it the highest available magnetic performance from NdFeB. However, the brittleness of sintered magnets requires careful handling and limits the magnets to simple geometries. (16) Further machining sintered magnets to produce complex shapes will produce a lot of magnet wastages...

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A bonded magnet contains a mixture of magnetic powder and nonmagnetic polymer or rubber binder. (17) There are four methods to manufacture bonded magnets: compression bonding, injection molding, extrusion, and calendaring. The end products of compression and injection molding are rigid magnets, which provide good magnetic performance and are not excessively brittle; these processes are generally economically competitive. Calendaring can produce only flexible magnets. Both flexible and rigid magnets can be produced using extrusion...

...Manufacturing magnets through compression bonding starts with melt spinning, which melts NdFeB ingots. The molten alloy is poured into a tundish and directed onto the surface of a quench rim to form a ribbon through the nozzle at the bottom of the tundish. To get a finer grade of the powder (less than150 μm), the ribbon is crushed and annealed in an inert atmosphere. Then, the crushed powder is encapsulated or blended with the bonding resin. After that, the epoxy encapsulated powder is compacted into a green compact of the desired shape...

...While there are many studies focusing on the improvement of magnet properties and manufacturing processes, few have examined the economics and environmental impact of industrial magnet production. This is especially the case for the newly developed BAAM process. BAAM has been reported to have produced magnets with comparable or even better performance than IM magnets. (21) A recent life-cycle assessment comparison of BAAM and IM indicated that BAAM has a smaller environmental impact; however, an economic comparison has yet to be reported; this is the focus of this paper. Moreover, a comparative techno-economic analysis may shed light on the industrial feasibility of these processes...

...The comparative TEA results show that producing NdFeB magnets using the BAAM method has better economic performance than IM (profit is 10% higher). Although the BAAM equipment is more expensive than the IM equipment, the increased capital cost for BAAM is more than made up through energy and material savings. That being said, owing to the fact that BAAM is a new technology, the price of BAAM equipment may rise in the years ahead. An increase in the price of BAAM equipment by more than a factor of 1.4 will cause the BAAM method to lose its economic advantage over IM. Both the environmental impact and economic analyses indicate that BAAM is superior to IM....