Ultrafine Sm2Fe17N3 hard magnetic particles synthesized by mechanochemical process

Sm2Fe17N3 compounds have emerged as promising candidates for a new generation of cost-effective permanent magnet materials. In this work, the Sm2Fe17N3 particles were synthesized through a series of steps involving mechanochemical and thermally activated reduction of metal oxides with calcium, followed by nitridation. Our results demonstrate that the mechanochemical milling of precursors significantly reduces the temperature required for the subsequent reduction-diffusion reaction. This enables the synthesis of Sm2Fe17N3 hard magnetic particles at a temperature below the melting point of calcium, which is 250 degrees C lower than those required for conventional reduction-diffusion processes. This reduction in temperature led to a decrease in the Sm2Fe17N3 particle size. Specifically, at a reduction-diffusion temperature of 800 degrees C, ultrafine Sm2Fe17N3 particles with an average diameter of 0.30 mu m, slightly smaller than the theoretically critical single-domain diameter, were obtained. The kinetics of the mechanochemical reactions occurring during ball milling have been extensively investigated. By fitting the proposed theoretical model with the experimental data, the kinetic parameters and quantitative expressions were determined. This work provides an in-depth understanding of environmentally friendly and low-cost mechanochemical processes, offering instructive information for the development of highperformance Sm2Fe17N3 permanent magnetic materials.