M.J. Kramer, A. Palasyuk, I.Z. Hlova, J. Cui, I.C. Nlebedim
Ames Lab,
United States
Keywords: magnetic properties, microstructure, permanent magnets, rare earth metals
Summary:
Reducing the criticality of the supply chain for electrification of the transportation sector and in efficient wind generation requires improvements across the supply chain for rare earth elements (REE) for permanent magnets (PM). The highest efficacies in traction motors are based on PMs, particularly those with some content of heavy REE (HREE) due to the need to operate at higher temperatures. REE demand is projected to outstrip supply by 2030. While new mines are being brought on-line, there are still environmental concerns for current separations technologies and metal production. Mitigation of criticality must be multipronged: substitutions for the most critical HREEs, better utilization of the more abundant Ce and La, reduction of REE though new alloys or substitutions in existing compounds and recycling. The Critical Materials Innovation (CMI) Hub is taking an all the above approaches. One of the more promising research avenues to improving Nd2Fe14B based alloys is engineering better grain boundary phases without HREE while reducing the grain size. This work was a 2023 R&D 100 Award winner and received a special recognition in Green Technology, Bronze Award for our work on a continuous hot-roll process to manufacture nanograin Neo magnets. We are also taking a new approach to forming dense monolithic Sm-Fe-N magnets which can replace HREE-based magnets in the most demanding applications. We have produced high-purity (98%) Sm2Fe17N3 powders that on sintering resulted in a bulk magnet with a (BH)max = 16.5 MGOe and 86% relative density. Keeping in mind that more than 91% of the market value REE is in PM, many of these applications do not require a BHmax > 40 MGOe. These ‘gap magnet’ applications can use the more abundant La and Ce, making current mines more profitable. CMI’s research efforts were also awarded another 2023 R&D 100 Award for Critical Rare Earth Free Cerium Gap Magnets, Critical Materials Institute with BUNTING-DuBois.