In-Field Heat Treatment Effect on Nitridation of Sm₂Fe₁₇

Abstract

An in-field heat treatment furnace utilized for a magnet with a 50 mm room-temperature bore was made to study magnetic field effect on gas-solid reaction. Using this furnace, nitridation of Sm 2 Fe 17 powder was performed under a 5-T magnetic field and a 0.1-MPa nitrogen gas pressure for the temperature range 623 to 743 K. Applying a magnetic field of 5 T promoted nitridation by approximately 0.6 nitrogen atoms per formula unit compared with zero-field nitridation, and almost fully nitride Sm 2 Fe 17 N 2.9 was obtained at 743 K.

Magnetic Field Effect on Nitrogenation of Sm₂Fe₁₇

“…The M-T curve of Sm 2 Fe 17 N 2.9 showed a single Brillouin-function curve. 15) The determined T C of Sm 2 Fe 17 N 2.9 was 746 K, which is almost the same as that of FN Sm 2 Fe 17 N 3 . 2) Figure 2 shows m S at 10 K for the ZFN (open circles) and IFN-5T (solid circles).…”

“…The thermomagnetization (M-T ) curves of host Sm 2 Fe 17 , Sm 2 Fe 17 N 2.3 (ZFN) and Sm 2 Fe 17 N 2.9 (IFN-5T) in a magnetic field of 1 T were measured in the T range of 10830 K, which was shown in Ref. 15). The M-T curves for 0.6 ¯x ¯2.3 did not show the Brillouin-function like curve but a superposition of two M-T curves, 15) suggesting that the PN and FN phase coexisted in the sample.…”

“…However, the XRD patterns for x = 2.3 and 2.9 did not show clearly the two phase coexistence of the PN and FN phases but a single nitride phase with a very small amount of ¡-Fe phase. 15) The determined lattice parameters for the nitride with x = 2.3 and 2.9 are listed in Table 1. The parameters of the nitride with x = 2.9 are comparable to the data for FN Sm 2 Fe 17 N 3 reported in previous literature.…”

“…15). The M-T curves for 0.6 ¯x ¯2.3 did not show the Brillouin-function like curve but a superposition of two M-T curves, 15) suggesting that the PN and FN phase coexisted in the sample. The M-T curve of Sm 2 Fe 17 N 2.9 showed a single Brillouin-function curve.…”

“…Recently, to clarify the MFE on nitrogenation, we developed an in-field heat treatment furnace utilized for a 5-T cryocooled superconducting magnet with a 50 mm room-temperature bore. 15) In this paper, we describe a review of MFE on the nitrogenation of Sm 2 Fe 17 , which suggests competition between enhancement of phase transformation and suppression of diffusion processes by applying a magnetic field.…”