Fabrication and phase evolution of Pr2Fe14C-based magnetic nanoparticles prepared by mechanochemical method

A facile mechanochemical method for fabricating Pr₂Fe₁₄C-based magnetic nanoparticles was reported. H and C were introduced by the decomposition of heptane during the high-energy ball milling process and reacted simultaneously with Pr₃Fe₁₄B_x (X = 0–0.2) alloy to form Fe₇C₃, PrH_2+δ and α-Fe phases. Subsequently, the H₂ released from the PrH_2+δ and Pr₂Fe₁₄C-based magnetic materials were obtained during a fast vacuum annealing process. Compared with the traditional heat-treatment which involved time-consuming annealing and multi-steps cooling process, the zero holding time annealing with a fast heating rate will effectively reduce the energy consumption. Addition of small amounts of boron is demonstrated to promote the formation of Pr₂Fe₁₄C and reduce the quantity of magnetically soft Pr₂Fe₁₇ and α-Fe phases. The optimal magnetic properties of M_r = 5.9 kG, _iH_c = 19.8 kOe and (BH)_max = 8.0 MGOe were obtained in Pr₃Fe₁₄B_0.1 sample after ball-milling for 7 h and subsequently annealing. Microstructure morphology analysis of the as-annealed Pr₃Fe₁₄B_0.1 powder reveals that the particles are almost rectangular shapes with an average size of about 117 nm. This bottom-up approach for fabrication of Pr₂Fe₁₄C nanoparticles may provide new thoughts for the preparation of high-performance magnetic materials.