Rationally selecting the chemical composition of the Nd–Fe–B magnet for high-efficiency grain boundary diffusion of heavy rare earths

Abstract

Higher diffusion efficiency of Tb was found in Nd–Fe–B than in Pr–Nd–Fe–B sintered magnets. This is because the reactive Pr brings more intergranular oxides, which blocks the diffusion channel for Tb and consumes Tb at the triple-junction phase.

Tb–Cu grain boundary diffusion effects on single- and multi-main-phase Nd–Fe–B based magnets

“…For the diffused SMP magnets, with increasing diffusion depth, the squareness remains at a higher value. 21,39 As shown in Fig. 6, the diffusion depth of the diffused MMP magnet is higher than that of the diffused SMP magnet, but the squareness of the diffused MMP magnet decreases seriously unexpectedly.…”

“…The well-studied Tb 70 Cu 30 alloy was chosen as the diffusion source because of its simple preparation and great coercivity enhancement for sintered magnets. [40][41][42] The melt-spun Tb-Cu (Tb 70 Cu 30 , at%) ribbons were crushed into powder with a size of o300 mm and then mixed with alcohol and polyvinyl alcohol (PVA) to prepare the diffusion source in a slurry form. The initial magnets were ultrasonically cleaned with acetone and alcohol for 15 min, and the diffusion source was coated onto the two easy planes (c-planes) of the magnets.…”

“…Various types of diffusion sources, such as inorganic compounds, 17,18 metals, 19 and alloys 20 have been developed. However, the GBD efficiency of HREs is also closely related to the state of the initial magnet, such as the composition 21–23 and grain size, 24 but less attention has been paid to this issue.…”

“…The loop squareness is closely related to the depth of diffusion for the diffused SMP magnets. 21,39 The evolution of the microstructure of MMP magnets during the GBD process and the underlying mechanism are still unclear. In this work, the element diffusion and demagnetization behavior of GBD treated MMP magnets are investigated and compared with those of the SMP magnets.…”

Outstanding anti-corrosion performance in Nd–Fe–B permanent magnets by constructing a hydrophobic triplex surface coating

“…[6][7][8] Once magnetized to saturation, the Nd-Fe-B permanent magnet remains in the magnetized condition throughout the service life, and acts as a fixed source of magnetic flux in high-efficiency electric motors and generators, hence exhibiting an inextricable link to renewable energy application and prime importance for the low-carbon economy. [9][10][11] During the past three decades, continual technological advances along the pathways of grain boundary diffusion [12][13][14] and grain refinement 15,16 have propelled the increased coercivity and enhanced resistance to thermal demagnetization for higher service temperatures above 150 1C. However, the indispensable component Nd forms a low-electrode-potential Nd-rich intergranular phase, which is prone to rapid corrosion as the anode in corrosive environments, while the high-electrode-potential Nd 2 Fe 14 B matrix phase acts as the cathode.…”