Abstract
A new reduction–diffusion method for preparing submicron-sized Sm2Fe17N3 was developed. First, submicron-sized α-Fe/Sm2O3 composite precursors with good dispersibility were prepared directly by ultrasonic spray pyrolysis and hydrogen reduction (USP-HR). Then, the precursor was successfully converted into Sm2Fe17N3 powder by Ca reduction–diffusion and nitridation. The results displayed that the precursor prepared by USP-HR was a monodisperse homogeneous composite of spherical particles of α-Fe and Sm2O3. α-Fe and Sm2O3 exist in an intercalated structure in the composite spherical particles. This creates conditions for the preparation of ultrafine Sm2Fe17N3 particles with uniform sizes and dispersity. The results show that Sm2Fe17N3 is a single-phase, composed of submicron-sized particles with no other impurity phases. The physical property measurement system shows that the coercivity of 0.616 ± 0.347 µm particles reaches 14.7 kOe.
Highlights
In recent years, the miniaturization and light weight nature of electronic devices along with the rapid development of new energy vehicles require higher working temperatures and magnetic performances for permanent magnets
The results displayed that the precursor prepared by ultrasonic spray pyrolysis and hydrogen reduction (USP-HR) was a monodisperse homogeneous composite of spherical particles of α-Fe and Sm2O3. α-Fe and Sm2O3 exist in an intercalated structure in the composite spherical particles
The scanning electron microscopy (SEM) image revealed that ultrasonic spray pyrolysis led to the formation of the spherical particles, and the particles are monodisperse without agglomeration
Summary
The miniaturization and light weight nature of electronic devices along with the rapid development of new energy vehicles require higher working temperatures and magnetic performances for permanent magnets. Curie temperature (748 K, about 160 K higher than Nd2Fe14B) and exhibits higher saturation magnetization (1.54–1.57 T, comparable to Nd2Fe14B) and a large anisotropy field (21–26 T, about 3 times higher than Nd2Fe14B), in addition to the superior anti-oxidation properties and corrosion resistance compared to Nd2Fe14B. The particle size of the alloy powder obtained by this method is coarse and needs to be refined by ball milling. It is necessary to develop a method for directly preparing the ultrafine Sm2Fe17 alloy without subsequent ball milling. Okada et al reported a submicron-sized Sm2Fe17 powder, which was produced by the reduction–diffusion of a precursor prepared by a direct coprecipitation technique.. Okada et al reported a submicron-sized Sm2Fe17 powder, which was produced by the reduction–diffusion of a precursor prepared by a direct coprecipitation technique.9 They developed a nitridation process and post-processing method for submicron-sized powders. The powder has submicron particle size (0.616 ± 0.347 μm) and the coercivity of the submicron particles reaches 14.7 kOe without dehydrogenation
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