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The present investigation attempted to optimize the R-D (reduction-diffusion) process for fabricating Sm2Fe17 nanoscale powder from ball-milled powders of samarium oxide and iron oxide using a solid reducing agent of calcium hydrides (CaH2). It was found that the target alloy phase of Sm2Fe17 can be produced by controlling the gas atmosphere in the process of powder preparation to R-D reaction. Powder handling of CaH2 in a protective atmosphere is essential to avoid the formation of Ca(OH)2 which suppresses calcium formation. A switching gas atmosphere of H2 to Ar-H2 during the R-D process at 350oC resulted in a reduction of Fe2O3 and alloying of Sm-Fe, consequently forming nanocrystalline Sm2Fe17.

This study investigated the effect of process temperature on the alloying process during synthesis of Sm 2 Fe 17 powder from ball-milled samarium oxide (Sm 2 O 3) powders and a solid reducing agent of calcium hydrides (CaH 2) using iron nanopowder (n-Fe powder) by a reduction-diffusion (R-D) process. The n-Fe-Sm 2 O 3-CaH 2 mixed powders were subjected to heat treatment at 850~1100℃ in Ar-H 2 for 5 h. It was found that the iron nanopowders in the mixed powders are sintered below 850℃ during the R-D process and the SmH 2 is synthesized by a reduced Sm that combines with H 2 around 850℃. The results showed that SmH 2 is able to separate Sm and H 2 respectively depending on an increase in process temperature, and the formed Sm 2 Fe 17 phase on the surface of the sintered Fe nanopowder agglomerated at temperatures of 950~1100℃ in this study. The formation of the Sm 2 Fe 17 layer is mainly due to the diffusion reaction of Sm atoms into the sintered Fe nanopowder, which agglomerates above 950℃. We concluded that nanoscale Sm 2 Fe 17 powder can be synthesized by controlling the diffusion depth using well-dispersed Fe nanopowders.