Synthesis of NdFeB Magnetic Particles With High (BH)max From Their Optimized Oxide Powders Through Reduction–Diffusion Method

Neodymium–iron–boron (NdFeB) magnetic particles with high ( BH ) _max were obtained using optimized ball-milled (BM) NdFeB oxide powders, instead of unmilled NdFeB oxide powders, through combined chemical processes comprising the spray drying and reduction-diffusion (RD) methods. The NdFeB oxide particles were subjected to the BM process to control their structural properties, including shape and size of the particles. The oxide powders were critical to make the NdFeB magnetic particles with enhanced properties by the RD process. In general, the controlled structural properties of the NdFeB oxide particles have a significant impact on the properties of final NdFeB magnetic particles. This has been explored through the NdFeB magnetic particles synthesized by utilizing BM oxide powders (0, 1, 2, and 4 h) at different time intervals. One-hour BM oxide powders yielded NdFeB magnetic particles with higher magnetic properties: ( BH ) _max of 14.06 MG·Oe, coercivity ( H_C ) of 3.9 kOe, and remanence ( M_R ) of 101 emu/g. This was attributed to minimal shape defects and phase purity with high crystallinity for the optimized BM oxide powders. Thus, NdFeB oxide particles directed the final intermetallic NdFeB magnetic particles structural properties, which strongly affected their magnetic properties. This study on oxide powders BM will be useful for the preparation of other intermetallic alloys with enhanced properties.