稀土产品中钍的测定

为解决高含量稀土和钍的分离问题对稀土产品中钍进行测定。该方法对比酒石酸、三乙醇胺的用量，设计分离富集工艺，采用743型大孔树脂分离稀土和钍，使用偶氮胂Ⅲ比色法测定。试样经过碱熔，水浸取加入三乙醇胺，过滤。沉淀用盐酸（4mol／L）溶解，在酒石酸存在下，用盐酸（4mol／L）淋洗杂质，用氯化铵溶液（20％）将树脂转化为铵型后，再用草酸铵溶液（4％）洗脱钍。在盐酸（4mol／L）介质中，用偶氮胂III显色于波长660nm处测定。实验表明该方法操作简便，设备简单，结果稳定，精密度和准确度高。     

广东首个稀土产品交易平台平远挂牌

正广东首个稀土产品交易平台——湖南稀贵金属交易所股份有限公司稀土产品交易中心,1月4日在广东平远正式挂牌成立。该交易中心的成立,将为国内稀土产品的定价、贸易提供一个新的公开、公平、公正的第三方定价及重要的交易平台。广东平远是中国重要的中重稀土储量地区,当前,平远拥有稀土矿开采企业,以及国内稀土分离规模最大、生产能力最强的全分离企业。近年来,随着广东稀土产品检     

赣州市政府筹资18亿元启动钨、稀土产品收储计划

据媒体报道,"世界钨都""稀土王国"——江西赣州日前由政府牵头筹资约18亿元,在全市启动钨、稀土产品收储计划,储备钨精矿及钨加工产品1万吨和稀土原矿及各类稀土分离产品1万吨。此次收储旨在稳定市场价格,帮助企业渡过难关。     

我国的中、重类稀土储备仅能维持15至20年

正目前,全球约90%的稀土产品仍然来自中国。据统计,我国稀土储量仅剩2700万吨,在世界总储量中的占比由过去的70%以上下降至目前的30%。按现有生产速度,我国的中重类稀土储备仅能维持15至20年,未来极可能需要进口。     

土壤样品中锆的测定

本文介绍用偶氮胂Ⅲ作显色剂,以分光光度法测定土壤中锆的方法。Zr(Ⅳ)在酸性介质中与偶氮胂Ⅲ形成蓝紫色络合物,最大吸收波长在660nm。方法的检测限为2ng。土壤样品以Na_2O_2熔融予处理,分离掉多数干扰离子。方法用于标准土壤样品的测定,变异系数<2%,测定值与标准值的相对误差<10%。     

宁波海关首次查获禁止进口的稀土产品废料

11月5日消息：日前,宁波海关成功查获一起稀土产品氧化铈废料违规进口案,共查获氧化铈废料1吨。据悉,这是宁波海关首次在进口货运渠道查获国家禁止进口的稀土产品废料,这批货物将被责令退运。     

环境水样中钍测定不确定度评定

依据GB 11224—89《水中钍的分析测定》的分析方法,对偶氮胂Ⅲ分光光度法测定环境水样中钍含量的不确定度进行评定,分析不确定度来源,测定其分量,合成标准不确定度。水样中钍含量为0.372μg/L时,当包含因子k=2时,给出扩展不确定度为0.032μg/L。     

赣州筹资18亿收储钨和稀土

为稳定市场价格，帮助企业渡过难关，“世界钨都”“稀土王国”——江西赣州日前由政府牵头筹资约18亿元，在全市启动钨、稀土产品收储计划，储备钨精矿及钨加工产品1万t和稀土原矿及各类稀土分离产品1万t。     

稀交所或成为我国争夺稀土产品定价话语权重要推动力

事件： 经过多年的酝酿，包头稀土产品交易所有限公司于2012年8月8日在包头正式揭牌成立，这标志着中国稀土企业自行发起组织的稀土产品现货交易平台组建完成。参与该平台建设的企业包括了中国南北稀土产区的主要企业，根据组建方案，内蒙古包钢稀土（集团）高科技股份有限公司、国储物质调节中心、中国稀有稀土有限公司、     

工信部拟修改稀土政策法规 建产品追溯制度

正我国稀土等原材料出口措施争端案在WTO败诉。为了应对明年稀土出口形势变化,下一阶段,工信部将及时修改完善相关政策法规和管理措施。具体包括:推动稀有金属管理条例早日出台;修改完善稀土指令和稀土管理办法;建立稀土产品的追溯制度;对轻重稀土实行分类管理,在严厉打击稀土违法违规生产,同时,继续调整和相应增加轻稀     

The optical absorption edge of rare earth sesquisulfides and alkaline earth - rare earth sulfides

Optical band gaps were measured by diffuse reflectance spectroscopy on a series of Ln₂S₃ compounds of α, δ, ε and τ structure types and on a series of ternary sulfides MLn₂S₄ (M = Sr, Cd, Mg) of Th₃P₄, CaFe₂O₄ and spinel structure types. Sharp absorption edges are observed with band gaps ranging from 2.2 to 3.5 eV. Systematic changes occur with rare earth radii. Analysis of some of the absorption edges suggests direct forbidden transitions.     

Magnetism of rare earth alloys

The main properties of the rare earth elements are discussed, emphasizing their magnetic properties. However, it is difficult to use these elements in practice, because their Curie points are located below room temperature. In order to take advantage of the properties of these substances, they can be alloyed with iron, cobalt, or nickel. The properties of the rare earth-cobalt alloys are discussed, the phase diagram and the crystal structures are described, and the ferrimagnetic behavior is explained. Alloys of interest for magnet applications are selected.     

Thermodynamics of rare earth sesquioxides

Experimental thermochemical and related data for rare earth sesquioxides, R₂O₃ (R = Sc, Y, La-Lu) are critically reviewed to provide a consistent set of thermodynamic functions covering the temperature range from at least 298 K up to above the melting point taking the polymorphism into account. Discrepancies in the available data are discussed and further studies to resolve them and to fill the gaps in the current knowledge are suggested. The best values for the temperatures of the reversible polymorphic transformations are recommended. Using high-pressure and molar volume data as well as ionic radius of a trivalent rare earth cation as an independent parameter the relative stabilities of different structures (the cubic C-form, the monoclinic B-form, the hexagonal A-form, the hexagonal H-form, and the cubic X-form) are estimated quantitatively for all rare earth sesquioxides. Based on the empirical relationship between the entropy of fusion and the corresponding fractional volume change, the entropies and enthalpies of fusion of the lanthanide sesquioxides are estimated. The reliability of the assessed functions and transition data is tested through the sample calculations of phase diagrams, where R′ and R″ represent different rare earth cations.     

稀土纳米材料的研究进展

稀土纳米材料的研究与应用将有助于发现新性质,开拓新材料,已成为当前的研究热点.本文简述了稀土纳米粉体、稀土纳米薄膜、稀土纳米陶瓷和纳米复合与组装的研究进展,介绍了在磁性材料、发光材料、催化剂、光学材料等领域稀土纳米材料的应用和进展.     

Magnetic relaxation in rare earth garnets

An attempt has been made to review the ferromagnetic resonance and relaxation data on rare earth iron garnets and in the light of it, to analyze the data on Sm and Eu thin films and Gd and Dy bulk polycrystalline samples obtained in our laboratory. A phenomenological approach adopted to explain the temperature and composition dependence of the line width andg _eff appears to explain the complex spectra in most cases.     

Thermoelectric efficiency of rare earth sesquisulfides

Thermo-electric efficiency of several rare earth sesquisulfides is presented and compared with those of commonly known thermo-electric materials. The available data show that at high temperatures dysprosium sesquisulfide has the best thermo-electric efficiency when compared with other well-known materials.     

Binary systems of rare earth oxysulfides

Pseudobinary rare earth oxysulfide systems were studied by X-ray diffraction, high resolution electron microscopy and fluorescence spectroscopy with Eu³⁺ as a probe. The different methods gave consistent results for the composition range and segregation phenomena in the two-phase region of the (LaO)₂S ? (LnO)₂S system (Ln = Y or Lu). The preparative method appeared to be of some importance.     

Resonance modes in rare earth doped microcrystals

Alkaline earth sulfide phosphors doped with Eu²⁺ or Ce³⁺ are good candidates for wavelength conversion in LEDs for general lighting applications. A very broad emission spectrum can be obtained by preparing SrS:Eu-SrS:Ce core-shell particles. These microcrystals are rectangular cuboids and can also be efficiently excited with electrons in a scanning electron microscope. The broad emission spectrum, ranging from 450 nm to 650 nm, consists of the combined emission of Ce³⁺ and Eu²⁺ centers. Using cathodoluminescence (CL) in a scanning electron microscope, evaluation of the emission characteristics of individual cuboids was possible. Sharp peaks in the CL-spectra of individual particles could be observed and described as being resonance modes. The spectral positions and the line widths of resonance modes in these core-shell microcrystals are predicted by an extension of the plane wave model, taking into account the dispersion of the refractive index and the existence of open orbits.