Life Cycle Assessment of Rare Earth Elements-Free Permanent Magnet Alternatives: Sintered Ferrite and Mn-Al-C

Grain alignment in hexaferrite permanent magnets by compaction at room and elevated temperatures

Shape-controlled precursors enable grain alignment without using an applied magnetic field in the permanent magnet material strontium hexaferrite. The effect is investigated by conducting four series of experiments using different compaction methods: two cold and two hot compactions. The hypothesis is that magnetic short-circuiting will diminish the grain alignment (texture) in cold compacted samples. The two cold compactions were performed below the Curie temperature, one being a simple cold-pressing (CP) and the other being a cold-pressing followed by sintering (CPS). The CP samples showed a relatively weak texture and low remanent magnetisation, while the CPS method yielded a slightly sharpened texture and improved remanent magnetisation compared with CP. In the two hot compactions, the pressing was done above the Curie temperature, using spark plasma sintering (SPS) and induction pressing (IP). SPS and IP samples both showed remarkably sharper textures than the cold-pressed pellets, with roughly doubled texture strength, and consequently better remanent magnetisation. The bulk density of the hot compacted samples increased almost twofold compared with that of the cold compactions. Hot compaction outperforms cold compaction with regard to density, sharpness of texture and remanent magnetisation. This is explained by inter-particle magnetic short-circuiting during cold pressing, which hinders the alignment process and reduces the bulk density.

A Review of the Occurrence and Recovery of Rare Earth Elements from Electronic Waste

Electronic waste (e-waste) contains valuable rare earth elements (REEs) essential for various high-tech applications, making their recovery crucial for sustainable resource management. This review provides an overview of the occurrence of REEs in e-waste and discusses both conventional and emerging green technologies for their recovery. Conventional methods include physical separation, hydrometallurgy, and pyrometallurgy, while innovative approaches such as bioleaching, supercritical fluid extraction, ionic liquid extraction, and lanmodulin-derived peptides offer improved environmental sustainability and efficiency. The article presents case studies on the extraction of REEs from waste permanent magnets and fluorescent powders, highlighting the specific processes involved. Future research should focus on developing eco-friendly leaching agents, separation materials, and process optimization to enhance the overall sustainability and efficiency of REE recovery from e-waste, addressing both resource recovery and environmental concerns effectively.

Towards Production of Cost-Effective Modification of SmCo5-Type Alloys Suitable for Permanent Magnets

SmCo5 constitutes one of the strongest classes of permanent magnets, which exhibit magnetocrystalline anisotropy with uniaxial character and enormous energy and possess high Curie temperature. However, the performance of SmCo5 permanent magnets is hindered by a limited energy product and relatively high supply risk. Sm is a moderately expensive element within the lanthanide group, while Co is a more expensive material than Fe, making SmCo5-based permanent magnets among the most expensive materials in the group. Subsequently, the need for new materials with less content in critical and thus expensive resources is obvious. A promising path of producing new compounds that meet these requirements is the chemical modification of established materials used in PM towards the reduction of expensive resources, for example, reducing Co content with transition metals (like Fe, Ni) or using as substitutes raw rare earth materials with greater abundance than global demand, like Ce and La. Important instruments to achieve these goals are theoretical calculations, such as ab initio methods and especially DFT-based calculations, in predicting possible stable RE-TM intermetallic compounds and their magnetic properties. This review aims to present the progress of recent years in the production of improved SmCo5-type magnets.