Preparation of Sm-Fe-N by High-Pressure N2 Nitridation and Sm2Fe17 by a Diffusion Process

A direct diffusion method starting from Fe powders and Sm was developed for large-scale synthesis of high-purity Sm2Fe17. This method is different from the traditional process in that it is a low-cost, simple, one-step process with well-controlled stoichiometry. High-performance Sm2Fe17Nx powders were obtained by nitriding Sm2Fe17 under N2 with gas pressures up to 40 MPa and subsequent surfactant-assisted ball milling. High-pressure nitrogenation suppressed the decomposition of Sm2Fe17Nx while enhancing the nitrogen absorption rate, which is necessary for high-quality Sm2Fe17Nx synthesis. The coercivity of the Sm2Fe17Nx powders increased significantly with increasing milling time, making the surfactant-assisted ball milling effective in producing high-performance Sm2Fe17Nx powders.