title: Commercial-scale recycling of NdFeB-type magnets with grain boundary modification yields products with 'designer properties' that exceed those of starting materials.
abstract: NdFeB-type magnets dominate the market for high performance magnetic materials, yet production of 'virgin' magnets via mining is environmentally, financially and energetically costly. Hence, interest is growing in 'magnet to magnet' recycling schemes that offer the potential for cheaper, more environmentally-friendly solutions to the world's growing appetite for rare-earth based magnetic materials. Unfortunately, previously described recycling processes only partially capitalise on this potential, because the methods described to date are limited to 'laboratory scale' or operate only under ideal conditions and result in products that fail to recapture the coercivity of the starting, scrap materials. Herein, we report a commercial scale process (120 kg batches) that completely recovers the properties of the starting scrap magnets. Indeed, 'grain boundary modification', via careful addition of a proprietary mix of blended elements, produces magnets with 'designer properties' that can exceed those of the starting materials and can be closely tailored to meet a wide variety of end-user applications, including high-coercivity (>2000 kA/m), sintered magnets suitable for motor applications.
authors.affiliation: Urban Mining Technology Co., Perryville, MD 21903, USA. Electronic address: miha.zakotnik@gmail.com.
authors.forename: M
authors.initials: M
authors.lastname: Zakotnik
authors.affiliation: Urban Mining Technology Co., Perryville, MD 21903, USA.
authors.forename: C O
authors.initials: CO
authors.lastname: Tudor
mesh_terms: D001895:Boron / Q000032:analysis*; D007501:Iron / Q000032:analysis*; D059346:Magnets / Q000032:analysis*; D009354:Neodymium / Q000032:analysis*; D059027:Recycling / Q000379:methods*
chemical_list: D009354:Neodymium; D007501:Iron; D001895:Boron
keywords: Grain boundary modification; High energy recycled permanent magnets; Processing technology; Recycling waste NdFeB-type sintered magnets; Restoration/improvement of magnetic performance; Urban mining; Waste rare earths