New strategy for the ultra-short process regeneration of sintered Nd-Fe-B sludge via purification-remixing incorporation

Abstract

The highly efficient and green recycling of sintered Nd-Fe-B sludge has emerged as a pressing concern in light of the escalating production of sludge. In this work, a novel ultra-short process strategy of purification-remixing incorporation is proposed for in-situ regeneration across several types of Nd-Fe-B sludges. The magnetic properties of the regenerated magnets are effectively restored by remixing the purified sludge at 30 wt% into customized high-remanence magnetic powder, followed by the adjustment of rare earth content to 30.5 % using rare earth-rich compounds. For magnets using 48SH sludge, the remanence and coercivity are recovered to 13.8 kG and 22.2 kOe, respectively, with recovery rates of 97 % and 108.3 %, which are almost as high as those of the original magnets. The temperature stability of the magnet is comparable to that of the original magnet as well. The comprehensive analysis attributes the attainment of high-performance to the repair and optimization of the microstructure, particularly focusing on the grain boundary phase.The ultra-short recovery process and the reuse of solvents in the purification phase minimize the total energy consumption and carbon emissions, and show great potential for green recycling for Nd-Fe-B sludge.