Sm2Fe17合金的氮化处理及其相关影响

从SmFeN稀土永磁材料的晶体结构和磁性特点出发,对Sm2Fe17Nx氮化的基本原理和处理工艺进行了总结,同时详细介绍了影响氮化的各种因素,最后对未来SmFeN的研制提出了展望.     

Sm12.8Fe87.2合金氮化前后高能球磨的研究

用破碎法制备了Sm12.8Fe87.2合金及其氮化物,对比研究了高能球磨工艺对母合金及其氮化物粉末的形貌、组织结构 及磁性能的影响。研究发现,高能球磨细化Sm12.8Fe87.2合金粉末或Sm12.8Fe87.2Nx氮化物粉末的过程均由大粉末颗粒→压延或 断裂成层片状→断裂成小颗粒3个阶段循环组成,并均在球磨一定时间后使粉末中的Sm2Fe17型相完全非晶化,α-Fe含量增 高且没有完全非晶化。球磨细化同粒度氮化物粉末的速度比母合金粉末的快。氮化过程不改变Sm12.8Fe87.2合金粉末球磨后 的相结构。氮化物的非晶化过程应当为:Sm2Fe17Nx(晶态)→SmFeN(非晶)+α-Fe。经两种高能球磨方式得到的氮化物粉末 的矫顽力随着球磨时间的延长而降低,而剩磁与磁化强度值在球磨时间短时降低,延长时间又增高,到球磨到主相非晶化 后又降低。     

Sm掺杂对Ca_(0.4)Sr_(0.6)Bi_4Ti_4O_(15)铁电薄膜性能的影响

利用溶胶凝胶工艺在Pt/TiO_2 /SiO_2 /Si衬底上制备了Ca_0.4Sr_0.6Sm_xBi_4-xTi_4O_(15)铁电薄膜.研究了不同钐掺量对薄膜的显微结构、晶粒取向及铁电性能的影响.结果表明:钐掺杂对钙锶铋钛铁电薄膜既有抑制氧空位所导致的畴钉扎作用,也有抑制晶粒生长发育的作用.当钐掺量x=0.05时薄膜样品晶粒发育较良好,沿a轴择优取向,I_((200))/I_((119))=0.869;样品铁电性能优良,剩余极化强度P_r=10.2 μC/cm~2,矫顽场强度E_c=120 kV/cm.     

微量稀土Sm对AZ91D显微组织和腐蚀性能的影响

利用扫描电镜 (SEM) 结合能谱分析 (EDS)、X射线衍射 (XRD)、腐蚀失重实验、电化学极化曲线等方法,研究了0.1%,0.4%,0.7%和1.0%的Sm对AZ91D合金的微观组织和腐蚀性能的影响,并对其腐蚀机理进行分析。结果表明：随着Sm含量的增加,合金中粗大的枝状第二相 (β-Mg₁₇Al₁₂) 逐渐断裂变小,其体积分数下降,因为Sm会结合Al形成颗粒状的Al₂Sm和杆状的Al₃Sm,从而减少晶界处第二相的数量,使第二相呈不连续分布;AZ91D的耐腐蚀性随着Sm加入量的增多,先增加后降低;当Sm加入量为1.0%时,合金的耐腐蚀性与不添加Sm的AZ91D接近;Sm的最佳添加量为0.4%。     

Influences of Annealing Temperature and Doping Concentration on Microstructural and Optical Properties of CeO2:Sm3+ Nanocrystals

Nanocrystals of CeO₂ with different doping concentrations of Sm³⁺ were synthesized by a novel and cost-effective method. The crystal structure, morphology and particle size were systematically investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Effects of the annealing temperature and doping concentrations on the microstructural properties of the crystals were studied. X-ray diffraction analysis indicates that the cubic structure of the CeO₂ is not affected by the doping of Sm³⁺ up to a doping concentration of 20%. Different structural parameters such as lattice constant, surface area, bulk density and porosity of the crystal were determined and discussed. Microscopic images of the CeO₂:Sm³⁺ suggest that the thermal decomposition of oxalate precursor is a suitable synthesis pathway to produce uniform-sized microparticles and nanoparticles. The influences of annealing temperature and doping concentration of Sm³⁺ on the optical properties of the nanocrystals were also discussed. The photoluminescence excitation spectra reveal that the charge transfer band is redshifted with increasing annealing temperatures. Emission attains its maximum intensity for Sm³⁺ concentration of 1%, and higher concentrations lead to emission quenching.     

Sm、Ti复合变质对AM60合金显微组织和力学性能的影响

采用XRD、OM和SEM等手段研究AM60合金中加入Sm和Ti后的组织和性能,并分别分析Sm和Ti对合金组织和性能的影响.结果表明,适量加入Sm和Ti都可以使合金组织得到极大地细化,减少了β相的析出,加入Ti后合金有少量的Al3Ti生成;Sm、Ti的复合加入则形成颗粒状Al2Sm、Mg41Sm5相和晕圈状球形化合物Al18Ti2Mg3,Ti的变质作用和适当的T6处理使合金中的杆状相钝化或者消失,粗大颗粒相变得圆整细小.复合添加比单独添加得到更优的力学性能,同时加入1.0％Sm和0.4％Ti,合金室温抗拉强度和伸长率分别达到226 MPa和6.7％,比母合金分别提高了34.5％和39.6％; 200℃高温抗拉强度和伸长率分别达到170 MPa和10.4％,比母合金分别提高53.2％和82.5％.T6处理可以进一步提高该合金的力学性能.     

Sm,Pr双掺CeO2基固体电解质的合成及性能研究

利用溶胶-凝胶法合成固体电解质Ce_0.8Sm_0.2-xPr_xO_1.9 (x=0.02～0.08),通过用X射线衍射（XRD）、原子力显微镜（AFM）、拉曼光谱（Raman）和交流阻抗谱对固溶体的微结构和电性能进行了表征。XRD分析结果表明：经800℃烧结2h后样品均为单相立方萤石结构,平均晶粒尺寸为35-46nm之间。AFM图像表明,样品晶粒近似球形,分布较均匀,Pr离子掺入后,空洞明显减小,当掺杂量x=0.08时,晶界有小颗粒生成,晶粒尺寸为2～8μm之间。Raman结果表明：Ce_0.8Sm_0.2-xPr_xO_1.9是具有氧空位的立方萤石结构,镨离子的掺杂有利于氧空位的形成。交流阻抗测试表明,随着Pr离子的掺杂量的增加Ce_0.8Sm_0.2-xPr_xO_1.9的电导率逐渐提高,活化能降低。     

A comparative study of differently prepared rare earths-modified ceria-supported gold catalysts for preferential oxidation of CO

The preferential oxidation of CO in H₂-rich gas was studied over gold catalysts supported on ceria modified by rare earths (RE = La, Sm, Gd and Y). The ceria supports were prepared by mechanochemical activation or co-precipitation. The amount of RE₂O₃ was 10 wt%. Gold (2 wt%) was added by the deposition-precipitation method. The samples were characterized using XRD, HRTEM, HAADF, TPR, and Raman spectroscopy. It was established that catalysts prepared by co-precipitation were more active than samples made by mechanochemical activation. A gold catalyst on yttrium-modified ceria, prepared by co-precipitation, exhibited the highest catalytic activity and selectivity, and high stability. No substantial differences in the size distribution and average size of the nanogold particles in the studied catalysts were observed. The main reason for the differences in PROX activity of these gold catalysts was searched into the role of the ceria supports, depending on the preparation method, and the nature of the modifier.     

Structure and electrochemical hydrogen storage characteristics of the as-cast and annealed La0.8-xSmxMg0.2Ni3.15Co0.2Al0.1Si0.05 （x=0-0.4） alloys

In order to ameliorate the electrochemical cycle stability of the RE-Mg-Ni based A2B7-type electrode alloys, the Mg content in the alloy was reduced and La in the alloy was partially substituted by Sm. The La0.8-xSmxMg0.2Ni3.15Co0.2Al0.1Si0.05 (x=0, 0.1, 0.2, 0.3, 0.4) elec-trode alloys were fabricated by casting and annealing. The microstructures of the as-cast and annealed alloys were characterized by XRD and SEM. The electrochemical hydrogen storage characteristics of the as-cast and annealed alloys were measured. The results revealed that all of the experimental alloys mainly consisted of two phases: (La,Mg)2Ni7 phase with the hexagonal Ce2Ni7-type structure and LaNi5 phase with the hexagonal CaCu5-type structure. As Sm content grew from 0 to 0.4, the discharge capacity and the high rate discharge ability (HRD) first in-creased and then decreased for the as-cast and annealed alloys, whereas the capacity retaining rate (S100) after 100 cycles increased continuously.