Preparation and characterization of bonded NdFeB permanent magnet

Preparation and characterization of bonded NdFeB permanent magnets have been performed. NdFeB powder was milled by using the High Energy Milling (HEM) for 3 and 10 hours. The bonded magnets were prepared by NdFeB powder (50–200 mesh) and adhesive epoxy resin with composition variation of 93:7, 95:5, 90:10, 80:20, 70:30, 60:40, and 50:50 (% wt.), respectively. The mix powder was molded using a pressure of 100 kg/cm2 and then annealed at 150 °C for 4 hours. The result of particle size analysis by using PSA showed that the average particle size of NdFeB powder after milling time for 10 hours was 0.37 μm. Based on the differential thermal analysis (DTA) result, it was obtained that the optimal annealing temperature of the mixtures is at 150 °C. The result of the phase analysis by using XRD showed that the major phase is Nd2Fe14B and the minor phase is Fe. The surface morphology was observed by using SEM. The results of SEM showed that the particle shape disordered with the particle size within a range of 0.1–20 μm and some agglomeration occurred. We concluded that the bonded NdFeB permanent magnet with 97 wt% NdFeB and 3 wt% epoxy resin is the best composition. The bonded magnet had a bulk density of 5.06 g/cm3, remanence of 5.32 kG, coercivity of 7.94 kOe and energy product maximum of 5.75 MGOe.