A facile process to optimize performance of regenerated Nd-Fe-B sintered magnets:Chemo-selective dissolution washing

In this work,the recycled Nd-Fe-B powders and regenerated Nd-Fe-B sintered magnets with low impurity content were successfully prepared from Nd-Fe-B magnet sludge via reduction diffusion(RD)method followed by a chemo-selective dissolution washing proc ess.The chemo-selective dissolution effect of various solution(deionized water,dilute acetic acid solution,NH_(4)Cl-methanol solution) was evaluated by impurity content and magnetic properties of the recycled Nd-Fe-B powder.The NH_(4)Cl-methanol solution can selectively remove impurities with minimal damage to the magnetic phase.Besides,the optimal NH_(4)Cl concentration and liquid-to-solid ratio were investigated.As a consequence,the contents of Ca,O,and H after optimal washing process are reduced to 0.07 wt%,0.31 wt% and 0.22 wt%,respectively.Hence,M_(3) Tis increased to 146.72 emu/g,which is 33% higher than that of the initial sludge.Then,the regenerated Nd-Fe-B sintered magnets with properties of B_(r)=11.66 kG,H_(cj)=16.49 kOe,and(BH)_(m)=31.78 MGOe were successfully prepared by mixing with 40 wt% Nd4Fe14B alloy powders.Compared with the corresponding regenerated magnets washed with deionized water,the remanence and coercivity are increased by 18% and 59%,respectively.

Short-process recycling of Nd-Fe-B sintered magnet sludge wastes:Challenges and approaches

Nd-Fe-B sintered magnet sludge wastes are one kind of typical commodity of recyclable rare-earth permanent magnet resources,and recycling such kind of wastes with economical and environmentally friendly techniques is crucial to the sustainable rare-earth industry.However,the current multistage wet process recycling technique for the sludge wastes involves high fabrication cost,excessive energy consumption,and heavy environmental burden.Therefore,short-process recycling techniques for Nd-Fe-B sintered magnet wastes have drawn increasing attention in the past decades.In this paper,we review recent efforts into short-process recycling Nd-Fe-B sintered magnet sludge wastes with emphasis on in-situ recycling techniques.