Structure and Magnetic Properties of Sm2Fe17Nx Sintering Magnets Prepared by Spark Plasma Sintering

Bulk Sm2Fe17Nx sintering magnet was fabricated by spark plasma sintering(SPS) technique. The effects of sintering pressure and sintering temperature on the magnetic properties of the Sm2Fe17Nx magnet were investigated. As a result, the density of the magnet is obviously improved with the increase of sintering pressure, but the coercivity drops since Sm2Fe17Nx has decomposed into SmN, α-Fe and N2. When sintering temperature was only above 200 ℃ under 1 GPa sintering pressure, the coercivity even begins to decrease, which indicates that high pressure promotes the decomposition of the Sm2Fe17Nx at lower temperature. The decomposition is also proved by the decrease of nitrogen and increase of α-Fe in the magnets.     

Preparation of Sm_2Fe_(17)Alloys in Ca-Sm_2O_3-Fe System

Sm2Fe17alloyisanimportantprecursorforthe preparationofSm2Fe17Nxmagnet.Sincethenitrogen containedSm2Fe17(Sm2Fe17Nx)alloy,asapermanent magnetmaterial,possessesahigherCurietempera ture,largeranisotropyfield,betterresistancetooxi dationandthermalstability,and…     

还原扩散法制备Sm2Fe17化合物的工艺研究

研究了还原扩散法制备Sm2Fe17化合物工艺中Sm2O3，Ca，CaCl2的配入量对Sm2Fe17合金均相性的影响，并用XRD对产物进行物相分析。结果表明：当反应温度为1423K，反应时间为5h，Sm2O3，Ca，CaCl2的配入量分别为121％，225％，8％时，还原扩散反应比较充分，能得到均相单一的Sm2Fe17化合物。     

A comparative study on nano La2O3 suspension treated by ultrasonic and ball milling

This paper presented a scientific study of the effects of four dispersion methods on the dispersion capability of nano La2O3 suspensions, which are ball milling, ultrasonic, ultrasonic followed by ball milling and ball milling followed by ultrasonic. For the purposes of comparing their dispersion capability, sedimentation test, Zeta-potential measurement test, particles size measurement test and transmission electron microscopy (TEM) test were carried out. Suspension ability coefficient was also defined with expectation to estimate the stability of nano La2O3 suspension through granularity size, and their relationship curve was worked out. The results showed that ultrasonic followed by ball milling enjoyed an excellent capability of dispersion for nano La2O3 suspension. Its mechanism was discussed, and breakage models of nano La2O3 particles were developed. The study results indicated that ultrasonic followed by ball milling could break through both the limits of ultrasonic dispersion size range and thermo-effect, and thus was able to overcome the problem of the secondary aggregation of nanoparticles. Moreover, aggregations could be further de-agglomerated. As a result, dispersion capability of nano La2O3 suspension could be improved more greatly by ultrasonic followed by ball milling. And its suspension stability was the best with the highest suspension ability coefficient of the nanoparticles. It was found in the experiment that there was almost no obvious phenomenon of stratification for the suspension with a little sediment after being deposited for 8 d.     

Crystal structure and magnetic properties of SmCo6.6Nb0.4 nanoflakes prepared by surfactant-assisted ball milling

SmCo6.6Nb0.4 nanoflakes with TbCu7 structure were successfully prepared by surfactant-assisted high energy ball milling （SA-HEBM） with heptane and oleic acid as milling medium. The microstructure, crystal structure and magnetic properties were stud- ied by scanning electron microscopy, X-ray diffraction, and vibrating sample magnetometer, respectively. The effects of ball milling time on the c-axis crystallographic alignment and coercivity of the nanoflakes were systematically investigated. The research showed that the nanoflakes had an average thickness of 100 nm, an average diameter of 1 μm, with an aspect ratio as high as 100. As the ball milling time increased from 2 to 8 h, the reflection peaks intensity ratio I（002y/I（10l）, which indicated the degree of c-axis crystal texture of the SmCo6.6Nbo.4 phase, increased first, reached a peak at 4 h, and then decreased. Meanwhile, the coercivity of the nanoflakes also increased first, reached a peak at 13.86 kOe for 4 h, and then decreased.     

Sm2(Fe,M)17Nx稀土永磁材料的研究进展

综述了Sm2(Fe，M)17Nx永磁材料的最新研究进展，介绍了Sm2(Fe，M)17Nx磁粉及磁体的制备技术，说明用其他元素替换Sm或Fe对材料性能的影响，以及粉末颗粒具有最佳的尺寸和形貌的重要性。并指出放电等离子烧结技术(SPS)有望成为制备Sm2(Fe，M)17Nx致密磁体的一个有效方法。     

气流磨工艺对Sm(Co,Cu,Fe,Zr)7.5合金粉末特性及磁性能的影响

采用气流磨工艺制备Sm(Co,Cu,Fe,Zr)7.5合金粉末,研究了转速对合金粉末特性的影响及研磨不同阶段的粉末粒度变化,分析了合金磁性能与转速的关系.结果表明,增加转速将细化粉末粒度,提高粉末粒度的均匀性;研磨前阶段粉末粒度明显大于研磨中、后阶段;在转速为3 500 r/min时,所制备的粉末平均粒度约为5 μm,离散度最小,得到合金磁性能最佳,剩磁Br=1.081 T,最大磁能积(BH)max=226 kJ/m3,内禀矫顽力Hcj=2 240 kA/m.     

添加不同钐含量的Sm2Fe17型合金及其氮化物的研究

通过采用粉末冶金法及密封氮化的方法，对添加不同钐含量的Sm2Fe17型合金及其氮化物的组织形貌、物相组成与结构及磁性能进行了研究。结果发现，多补偿添加25％钐可以使Sm2Fe17型合金退火态的α—Fe含量小于2％。Sm-Fe合金冶炼后的主相均表现为菱方Th2zn17型结构，但快冷时优先沿{300}和{220}面长大。氮化后Sm2Fe17晶格膨胀形成Sm2Fe17N，主相，而α—Fe的X射线特征峰未见明显移动。Sm14．2FeB58合金晶胞膨胀相对较小，而Sm12.8Fe87.2晶胞膨胀较大，在氮化20h时有最大△V／V=8．36％：氮化增加合金中的α—Fe含量。Sm14．2Fes5．8N，的剩磁最高为59．5Am^2／kg，S1l0．5Fe89.5Nx磁化强度最高值为193．6Am^2／kg，Sm12．8Fe87．2Nx合金的所有磁性能值基本分布在Sm14．2Fe85．8Nx和Sm10．5Fe89．5Nx的值之间。     

Luminescence Properties of Sm^3＋ doped Bi2ZnB2O7

The phosphors of （Bi1- x Smx ） 2ZnB2O7 （ x = 0. 01, 0. 03, 0. 05, 0. 07, and 0. 09） were synthesized by conventional solid state reaction. The purity of all samples was checked by X-ray powder diffraction （XRD）. XRD analysis shows that all these compounds are of a single phase of Bi2ZnB2O7, indicating that the Bi^3＋ in Bi2ZnB2O7 can be partly replaced by the Sm^3＋ without the change of crystal structure. The excitation and emission spectra at room temperature show the typical 4f-4f transitions of Sm^3＋ . The dominant excitation line is around 404 nm due to ^6H5/2→^4K11/2 and the emission spectrum consists of a series of lines at 563, 599, 646, and 704 nm due to ^4G5/2→^6H5/2, ^6H7/2, ^6H9/2, and ^6H11/2, respectively. The optimal concentration of Sm^3＋ in Bi2ZnB2O7 is about 3mol% （relative to lmol Bi^3＋ ） and the critical distance Rc was calculated as 2.1 nm. The temperature dependence of the emission intensity of Bi1.94Sm0.06ZnB2O7 was examined in the temperature range between 100 and 450 K. The quenching temperature where the intensity has dropped to half of the initial intensity is 280 K. The lifetime for Sm^3＋ in Bi1.94Sm0.06ZnB2O7 is fitted as a value of 0.29 and 1.03 ms.     

Synthesis mechanism of Sm₂Fe₁₇ alloy produced in reduction-diffusion process

Sm2Fe17 alloy was the precursor of Sm2Fe17Nx magnetic materials.Reduction-diffusion(R/D) method was a new preparation process for the Sm2Fe17 alloy,and had been widely employed as a new preparation method for rare earth-transition metal intermetallic compounds.In this text,thermodynamics and kinetics for the synthesis of the Sm2Fe17 alloy by reduction-diffusion(R/D) method in the Ca-Sm2O3-Fe system were analyzed.The related synthesis mechanism of this reaction was investigated in detail by means of scanning electron microscope(SEM).The results showed that the thickness of the Sm2Fe17 alloy layer versus the reaction time could be fit by the parabola law,and its growth model was determined to be:(L0-L)2=43.848 t,the diffusion of Sm into Fe proceeded with the formation of the Sm2Fe17 phase from the very beginning of the reaction,and rich samarium phases,such as SmFe2 and SmFe3,were not formed,and the rate-determining step of the R/D reaction was found to be the peritectic reaction between liquid samarium and solid iron.     

粉末特性对Sm2(Co,Cu,Fe,Zr)17永磁材料及性能的影响

在粉末冶金工艺生产Sm2(Co,Cu,Fe,Zr)17的过程中,粉末特性对材料的性能存在较大影响.本研究对气流磨和滚动球磨两种工艺所制备的粉末进行比较,通过粒度分析及显微镜观察,研究了粉末的粒径与形状对材料性能的影响.分析结果表明,气流磨所制备的粉末平均粒径为4.53μm,尺寸分布范围较窄,粉末颗粒成近似球状,所得材料磁性能参数中Br,(BH)max优于滚动球磨.     

Optimization of microstructures and magnetic properties of Sm(CobalFe0.227Cu0.07Zr0.023)7.6 magnets by sintering treatment

Magnetic properties and microstructures of Sm(Co_(bal)Fe_(0.227)Cu_(0.07)Zr_(0.023_)_(7.6) sintered magnets were optimized by sintering treatment. Results show that the knee-point magnetic field, Hknee, is twofold up and the intrinsic coercivity Hcjincreases by 40%, ranging from 21.64 to 30.39 kOe at the cost of a little decrease of Brfrom 10.84 to 10.31 kGs with sintering temperature decreasing from 1488 to 1473 K. And the average domain width is narrower and more uniform for the specimen sintered at 1473 K than that of the specimen sintered at 1488 K. It is impressive that the density of lamellar phase increases from ~0.050 to ~0.058 nm~(-1) with the sintering temperature decreasing from 1488 to 1473 K. Moreover, the average cellular size is about ~84 nm for the magnets sintered at 1473 K, which is 80% of that of the magnets sintered at 1488 K(~97 nm). And the cell boundary width of the magnets sintered at 1473 K(~7 nm) is only half average width of the magnets sintered at 1488 K(~14 nm). It is found that the Cu content in the cell boundaries is much higher(~17 at%) in the magnets sintered at 1473 K compared to that of the magnets sintered at 1488 K(~10 at%). It can be concluded that smaller cells and narrower cell boundaries together with higher gradient of Cu content are key points for obtaining the optimum Hkneeand Hcj.     

Magnetic Microstructures of 2:17 Type Sm(Co,Fe,Cu,Zr)z Magnets Detected by Magnetic Force Microscopy

The magnetic microstructures of 2:17 type Sm(Co,Fe,Cu,Zr)z magnets were detected by magnetic force microscopy.Comparing the microstructures of the specimens coated with and without Ta thin film before and after heat-treatment, it is found that: (a) as a protection layer, Ta coating layer about 20 nm thick can effectively restrain Sm volatilization under high temperature;(b) the stress built in the 2:17 type Sm-Co magnets during specimen preparation only affects some local parts of the domain structures;(c) the magnetic microstructures vary largely for specimens heat-treated at high temperature without Ta film coating due to Sm volatilization.In addition, by comparing with high coercivity Fe-Pt point tips, it is found that the Co-Cr thin-film tips are not suitable for detecting the magnetic microstructures of strong permanent magnets.     

Preparation of CaS:Eu2+, Sm3+ by Solid Reaction Method and Its Photostimulated Luminescence

The CaS:Eu2 , Sm3 powders were prepared by high-temperature solid method in a reducing atmosphere. The influences of temperature and fired-time on properties of samples were studied. XRD analysis shows that crystal structure of CaS has formed at 700 ℃. Spectrum analysis results show that the samples which were stimulated by 980 nm laser after excited by ultraviolet lamp emit red luminescence peaking at 649 nm.     

Characterization of SPEEK/Y2O3 proton exchange membrane treated with high magnetic field

The membranes of sulfonated poly(etheretherketone) of 48.3% sulfonation degree doped with Y2O3 were prepared, and then treated with parallel high magnetic field of 6 and 12 T at 120 oC for 4 h, respectively. The small-angle X-ray scattering revealed that the struc- ture of the composite membranes would be changed by high magnetic field treatment. The cross-section morphology of the composite membranes by a scanning electron microscope showed that the Y2O3 could be dispersed evenly in the composite membranes which were relatively smooth and compact but formed small conglomeration with increasing Y2O3 content and treating high magnetic field. The water uptake of membranes would be reduced with Y2O3 content increasing, but not be modified by the treatment of high magnetic field. The proton conductivity of membranes would be increased with temperature rising from 20 to 60 oC, and improved under high magnetic field, which could all exceed 10-2 S/cm at 75% relative humidity, but decrease with doping content of Y2O3 from 2 wt.% to 8 wt.%. The methanol permeability of the composite membranes would be decreased with Y2O3 content increasing and slightly reduced after high magnetic field treatment.     

Behavior of leaching and precipitation of weathering crust ion-absorbed type by magnetic field

With weathering crust Ion-Absorbed Type Rare Earth （IATRE） ores in southern Jiangxi as an example, rare earth percolation leaching and leaching solution precipitation process research were carried out under conditions of magnetic field. The effect on the rare earth leaching process such as magnetic field strength, magnetization time, magnetization manner, and other factors were discussed. The effect on the mother rare earth liquor sedimentation rate, purity, and crystallization behavior such as magnetic field strength, magnetization time, and magnetization manner were investigated. Leaching and precipitation mechanism of magnetization on IATRE were analyzed. The results showed that the magnetic treatment can improve leaching rate of weathering crust IATRE and the sedimentation rate, and reduce consumption of reagents.     

Influence of Non—Magnetic Substitutional Atoms on Spontaneous Moment and Curie Temperature of Ce2Co17Compounds

The structure and magnetic properties of Ce2Co17-xMx(M=Ga,Al and Si)compounds for Mcomcentrations up to x=5 were studied by means of X-ray diffraction and magnetic measurements,The experimental results show that the Curie temperatures and Co spontaneous magnetization decrease significantly with increasing the addition of non-magnetic substitutional atoms,and that Si which has a minimum solid solubility ic Ce2Co17causes a largest reduction of Curie temperature,spontaneous magnetization and moment perCo atom compared with Ga and Al.     

烧结温度对高矫顽力Sm2(Co,Fe,Cu,Zr)17永磁体磁性能的影响

为深入了解高矫顽力Sm2(Co,Fe,Cu,Zr)17永磁体烧结温度与磁体磁性能的关系，设计了6种不同烧结温度，分别测试了各温度下烧结试样的密度和磁性能。试验结果表明：高矫顽力Sm2(Co,Fe,Cu,Zr)17磁体的密度随着烧结温度的升高而升高，在1210－1220℃达到最大值；磁体在1205－1210℃烧结时有较高的磁性能，内禀矫顽力超过1910kA/m，最大磁能积达到210kJ/m^3，温度过高或过低都使磁本性能下降；剩磁Br随磁体密度的升高而上升，矫顽力Hci的变化是密度和晶粒大小及胞状尺寸综合作用的结果。