Preparation of an α-Fe16N2 Magnet via a Ball Milling and Shock Compaction Approach

alpha ''-Fe16N2 has been suggested as a promising candidate for future rare-earth-free magnets. In this paper, a unique technical route including a ball milling approach and shock compaction is experimentally demonstrated as a promising way to produce an alpha ''-Fe16N2 magnet. Firstly, alpha ''-Fe16N2 powder is prepared by ball milling, in which ammonium nitrate (NH4NO3) is adopted as a solid nitrogen source. The volume ratio of the alpha ''-Fe16N2 phase reaches 70% after 60 h of milling with a ball mill rotation speed of 600 rpm in planetary mode. Its saturation magnetization (M-s) is 210 emu g(-1) and the coercivity is 854 Oe at room temperature. After ball milling, shock compaction is used to compact the milled powder sample into a bulk magnet. Its magnetic properties and crystalline structure are characterized. Overall, the ball milling-based approach can be used to prepare alpha ''-Fe16N2 magnets at an industrial production level.