Densification study of solvothermal recycled Nd-Fe-B powders by spark plasma sintering

Abstract The scientific community has been focusing on permanent magnets in the past few years for seeking alternate solutions to the so-called rare-earth crisis. A substantial amount of rare-earth permanent magnets, once consumed, becomes Waste of Electrical and Electronic Equipment (WEEE). This waste represents a valuable secondary resource for rare-earth permanent magnets due to the high recycling potential of scrap magnets. In this study, recycled Nd-Fe-B powders were prepared via a solvothermal treatment technique, involving the treatment of scrap Nd-Fe-B magnets with ethanol. The resulting powder demonstrated coercivity and remanence values of 459.16 kA/m and 0.67 T, respectively. Densification of the recycled powder was subsequently performed using the spark plasma sintering (SPS) technique to examine the effects of SPS parameters on the density, microstructure, and magnetic properties of the sintered samples. Highest magnetic properties were achieved at a sintering temperature of 900°C, yielding coercivity and remanence values corresponding to 70% and 73% of the recycled powder’s initial values.