Sm2Fe17和Sm10.5Fe88.5Zr1.0的氮化行为

通过真空电弧炉制备了Sm2Fe17和Sm10.5Fe88．5Zr1．0母合金，铸态Sm2Fe17先经均匀化处理后再氮化．而Sm10.5Fe88．5Zr1．0则不经均匀化退火而直接在高纯氮气中氮化。运用扫描电子显微镜和X射线衍射技术对其氮化行为进行了研究。薄片扩散实验表明氮在Sm2Fe17中的扩散要比在Sm10.5Fe88．5Zr1．0中的扩散快。运用Fick第二定律通过理论计算得出直径为20μm的Sm2Fe17合金和Sm10.5Fe88．5Zr1.0合金球形粉末粒子，实现充分氮化的时间为10h和16h。实际粉末实现完全氮化的时间要比理论计算的时间少。这和粒径分布、颗粒表面状态、氮化过程产生的微裂纹以及实际条件和理想条件的差异有关。对于直径为20μm的粉末，氮化时间为6h时氮化已基本完成，氮化时间过长．Sm2Fe17Nx会发生分解。     

Chemical Interaction between Sm2Fe17 and Ammonia

The interaction between Sm₂Fe₁₇ and ammonia in the presence of NH₄Cl (10 wt % relative to Sm₂Fe₁₇) as an activator is studied at initial NH₃ pressures from 0.6 to 0.8 MPa and temperatures from 150 to 500°C. The results indicate that, depending on the reaction temperature in the Sm₂Fe₁₇–NH₃ system, both hydriding of the parent intermetallic phase and disproportionation resulting in the formation of another hydride phase may occur. The reaction products are found to consist of fine particles. The magnetic properties of the products of Sm₂Fe₁₇ nitriding in ammonia are studied.     

Rapid quenching and nitrogenation of Sm2Fe17 alloys

The production of hard magnetic samarium-iron nitrides by rapid quenching of Sm₂Fe₁₇ alloys followed by a nitrogenation treatment is described and analysed. Rapid quenching of Sm₂Fe₁₇ produces almost pure Sm₂Fe₁₇ phase with 40 to 100 nm grain size. At low temperature (T465°C), the nitrogenation treatment under 1 bar N₂-H₂ (5%) mainly produces the definite compound Sm₂Fe₁₇N_3– and follows reasonably well an Arrhenius law, the reaction rate being limited by diffusion through the Sm₂Fe₁₇N_3– reacted layer. At higher temperatures (T465°C), disproportionation reactions simultaneously take place, which transform the metastable nitride into free iron and tiny SmN crystallites (about 10 nm wide). It is concluded that the nitrogenation treatment should be performed at about 400°C in order to reach a sufficient reaction rate for the nitride formation while (possibly) avoiding disproportionation reactions whose by-products (Fe and SmN) are deleterious for permanent magnet applications.     

Sm2Fe17Nx永磁材料的研究进展

综述了目前Sm2Fe17Nx化合物及Sm2Fe17Nx磁粉的制备方法，以及Sm2Fe17Nx化合物渗氮过程的条件选择．并进一步指出了Sm2Fe17Nx磁粉的发展现状和趋势。     

Structural change in Sm2Fe17 alloys during homogenization and HD processing

The evolution of phase compositions, phase change and microstructure in Sm₂Fe₁₇ alloys during anneal and hydrogenation–disproportionation processing has been studied systematically using X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The results indicate that, after annealing at 1050 °C for 24 h, the main phase in the as-homogenized ingot is Sm₂Fe₁₇ with a rhombohedral Th₂Zn₁₇-type structure, together with a negligible amount of α-Fe phase. A minor phase, SmFe₃/SmFe₂, is barely detectable. The Sm₂Fe₁₇ alloy first absorbs the hydrogen in the hydrogenation atmosphere with a pressure of 0.1 MPa. Disproportionation begins at T ≥ 500 °C, and large amounts of SmH_x and α-Fe phases are formed, partly in microcrystalline or amorphous structures. As the temperature increases, the microcrystals and amorphous structures transform into a fully crystalline structure, the transformation becoming complete at 750 °C. The resultant crystal grain size is about 50–100 nm.     

Hydrogen absorption and desorption characteristics of ferro-titanium alloys

Hydrogen absorption and desorption characteristics of commercially supplied ferrotitaniums with 41 to 51 at% Ti have been studied. The characteristics are similar to those of high purity FeTi although the ferro-titaniums include some impurities. The activation temperatures of the ferro-titaniums are slightly higher than that of the high purity FeTi. Plateaus in the hydrogen absorption and desorption curves are not obvious compared with those of high purity FeTi. It is concluded that the ferro-titaniums are good, low-cost hydrogen storage materials.     

57Fe Mossbauer effect studies of Sm2Fe17 under different heat treatment conditions

Room-temperature 57Fe Mossbauer spectra have been measured in Sm2Fe17 under different heat treatment conditions. The details of fitting these spectra is exhaustively discussed. The spectra of Sm2Fe17 are split into seven inequivalent magnetic sites. An identical result was obtained by using two fitting modes. The following has been indicated from the results for all samples. Firstly for these samples containing α-Fe sextets and paramagnetic doublets, by choosing an appropriate annealing system, the smallest amount of impurities might be obtained, i.e. an approximately single-phase Sm2Fe17 compound was obtained. Secondly the overall weighted average fields were all approximately equal. This was thought to arise because the different heat treatment conditions caused no change in the near-neighbour coordination of iron atoms. Thirdly the 6c site and 18 h site had the largest and the smallest hyperfine fields, respectively. This revised version was published online in November 2006 with corrections to the Cover Date.     

Magnetic anisotropy in Sm2Fe17-xMx (M = Al, Ga) and (Sm1-xTmx)(2)Fe14Al3

1. IntroductionMany illtermetajlic compounds of R-Fe and R-Co(R: rare earths) have some ideal properties as highquality permanent magnet materials where a largemagnetic anisotropy of 4f electrons is coupled withstrong exchange interaction of 3d electrons via the4f-3d illteraction.In 1967 the SmCos magnet was discovered as thefirst rare earth permanent magnet, and in 1973 moreimproved magnet in the form of SmZCo17 was developed, These two compounds were found to have excellellt permanellt m…     

高性能各向异性Sm2Fe17Nx磁粉的制备

本文研究了高性能各向异性Ｓｍ２Ｆｅ１７Ｎｘ磁粉的制备工艺路线与工艺参数。优化了制备与工艺参数。已制备出磁性能达到：Ｂｒ＝１．３９Ｔ，Ｈｃｉ＝８５０ＫＡ／ｍ和（ＢＨ）ｍ＝２３６ＫＪ／ｍ＾３的各向异性Ｓｍ２Ｆｅ１７Ｎ２．８８磁粉，该磁粉的各向异性场ＨＡ达到２０Ｔ。     

合金元素对Sm2Fe17Nx微观结构和性能的影响

综述了合金元素的添加对Sm2Fe17Nx稀土永磁材料的微观结构以及性能的影响。介绍了取代元素的分类，从理论和研究现状等方面分析和总结了合金元素对Sm2Fe17Nx稀土永磁材料的热稳定性、磁性能以及工艺性能的影响规律，并对今后Sm2Fe17Nx稀土永磁材料的研究和开发提出了建议。     

合金元素对Sm2Fe17Nx微观结构和性能的影响

综述了合金元素的添加对Sm2Fe17Nx稀土永磁材料的微观结构以及性能的影响.介绍了取代元素的分类,从理论和研究现状等方面分析和总结了合金元素对Sm2Fe17Nx稀土永磁材料的热稳定性、磁性能以及工艺性能的影响规律,并对今后Sm2Fe17Nx稀土永磁材料的研究和开发提出了建议.     

Crystal structure of compounds Fe17Gd2 and Fe17Tb2

Abstract

Differential thermal analysis and dilatometry investigations of Fe–Gd alloys in the range 5–16·6 at.-% Gd showed the occurrence of a phase transformation at about 1215°C. From X-ray diffraction investigations, it was concluded that this corresponds to an allotropic change in Fe₁₇Gd₂ from the rhombohedral Zn₂Th₂ type at low temperature to the hexagonal Ni₁₇Th₂ type at high temperature. Both these structures were detected in as cast samples of Fe–Gd and Fe–Tb alloys. However, in the Fe₁₇Tb₂ compound, no transformation was detected by differential thermal analysis.

MST/1227     

高性能Sm2Fe17Nx磁粉制备关键技术研究

采用粉末冶金工艺制备了Sm2Fe17Nx永磁粉末,研究了工艺参数对Sm2Fe17合金的显微组织及Sm2Fe17Nx粉末磁特性的影响。结果表明,铸态合金的均匀化、粉末的氮化以及粉碎过程是获得高性能磁粉的关键因素。采用最佳工艺条件制备的磁粉的磁特性为：4πMr=1．24T．iHc=756kA／m,(BH)max=220kJ／m^3。     

制备Sm2Fe17Nx稀土永磁粉的工艺研究现状

综述了制备Sm2Fe17Nx稀土永磁粉的主要方法，指出对现有工艺的深入研究与不断改进，开发新工艺，开创新技术，探索出一条成熟的，经济实用的生产工艺线路，对获得高性能的Sm2Fe17Nx磁体，并使之成为具有竞争力的第四代稀土永磁体，有相当重要的意义，此外还对如何控制工艺中影响Sm2Fe17Nx磁性能的一些主要因素做了简要分析。     

The hydrogenation behaviour of the phases Sm2Co17 and Pr2Co17

The compounds Sm₂Co₁₇ and Pr₂Co₁₇ have been charged with hydrogen and the hydrogen compositions determined between pressures of approximately 2.5×10^–2 and 13 atm at temperatures of 150 and 200° C. Very low rates of hydrogen absorption were observed below 150° C so that solubility measurements have not been obtained below this temperature. The X-ray diffraction studies show that the structure of the metal lattice is unchanged by the hydrogenation process, i.e. the rhombohedral, Th₂Zn₁₇ structure type with space groupR¯3_m is maintained. As a result of the expansion the alloys become cracked and friable on hydrogenation.     

Optical absorption of Nd, Sm and Dy in bismuth borate glasses with large radiative transition probabilities

This paper reports on the optical properties of Nd³⁺, Sm³⁺ and Dy³⁺ in bismuth borate glasses, with Bi₂O₃ content varying from 30 to 60 mol%. The variation of the optical properties with composition plays a dominant role in determining a good laser host material. The variation of the Judd–Ofelt intensity parameters Ω_t (t=2,4,6) and the radiative transition probabilities and the hypersensitive band positions, with composition, have been discussed in detail. The changes in position and intensity parameters of the transitions in the optical absorption spectra are correlated to the structural changes in the host glass matrix. The variation of Ω₂ with Bi₂O₃ content has been attributed to changes in the asymmetry of the ligand field at the rare earth ion site and to the changes in their rare earth–oxygen (R–O) covalency, whereas the variation of Ω₆ strongly depends on nephlauxetic effect. The shift of the hypersensitive band shows that the covalency of the R–O bond increases with increase of Bi₂O₃ content, due to increased interaction between the rare earth ions and the non-bridging oxygens. The radiative transition probabilities of the rare earth ions are large in bismuth borate glasses, suggesting their suitability for laser applications.     

Hydrogen decrepitation as a method of powder preparation of a 2:17-type,Sm(Co,Cu, Fe,Zr)8.92 magnetic alloy

The present work has shown that hydrogen decrepitation of a 2:17-type Sm (Co_0.673 Cu_0.080Fe_0.222Zr_0.025)_8.92 alloy is a very rapid and convenient means of producing powdered material for the production of polymer-bonded permanent magnets. The magnets made from the hydrogen decrepitated powder (average particle size 100m) exhibited improved demagnetization loop shapes, higher intrinsic coercivities and improved elevated temperature stability when compared with the magnets produced from the standard milled powder material (average particle size 40m). These differences in properties have been related to the differences in the character of the powders produced by the two methods of decrepitation.     

单相纳米晶Sm2Co17合金的制备与性能表征

提出了一种制备单相纳米晶Sm2Co17合金块体材料的新方法.利用XRD和TEM分析了制备出的纳米晶Sm2Co17合金的相结构和显微组织.研究表明制备的单相纳米晶Sm2Co17合金在室温下具有密排六方的晶体结构,与传统的菱方晶体结构的粗晶Sm2Co17合金具有不同的结构热稳定性.测定了单相纳米晶Sm2Co17合金的磁性能和力学性能,与同种成分的粗晶材料相比,单相纳米晶Sm2CO17合金的磁性能和力学性能均获得显著提高.