Extrusion compression molded critical rare earth free bonded permanent magnets

Abstract

Samarium iron nitride (Sm-Fe-N) bonded magnets have emerged as promising candidates for various industrial applications due to their exceptional magnetic properties. Compounds with magnetic material 95 wt fraction (wt.%) (∼74 vol%) and 97 wt.% (∼81 vol%) of SmFeN in a polyamide (PA12) polymer binder are manufactured using a batch mixer followed by compression molding. A maximum energy product (BH)_max of 186.21 kJ.m^-3 (23.4 MGOe) is achieved in the 95 wt.% bonded magnets; 97 wt.% magnets had a (BH)_max of 165.52 kJ.m^-3 (20.8 MGOe). It is found that the degree of alignment (DoA) of 99 % is achieved in the 95 wt.% magnets, whereas the 97 wt.% magnets are limited to a DoA of 90 % respectively. The high DoA can be attributed to low particle-particle interaction during the post-magnetic field alignment process. This research provides a useful insight of binder-particle interactions at very high magnet weight fractions and their effect on magnetic strength and performance.