Surface-initiated group transfer polymerization mediated by rare earth metal catalysts

We present the first example of a surface-initiated group transfer polymerization (SI-GTP) mediated by rare earth metal catalysts for polymer brush synthesis. The experimentally facile method allows rapid grafting of polymer brushes with a thickness of >150 nm in <5 min at room temperature. We show the preparation of common poly(methacrylate) brushes and demonstrate that SI-GTP is a versatile route for the preparation of novel polymer brushes. The method gives access to both thermoresponsive and proton-conducting brush layers.     

Determination of rare earth elements in mineral raw materials and rare earth industry products by neutron activation analysis

To determine REE in mineral raw materials, high purity RE metals and their compounds, neutron activation analysis with extraction chromatographic REE separation has been developed. Combination of the developed RE extraction and separation procedures with subsequent -spectrometric analysis of the RE radionuclides allows to determine their content with the lower detection limit –10^–5–10^–8%. The relative standard deviation is 0.2–0.3.     

XRF在稀土分析中的应用与进展

X射线荧光光谱分析技术（XRF）是元素分析的有效工具,其快速、无损、多元素同时测定的特性能满足稀土元素的分析需求,在地质、冶金等多个领域中发挥着十分重要的作用。21世纪以来,稀土产业以及二次资源再利用的发展使得XRF分析方法的同步研发得到重视。本文对近年X射线荧光光谱技术的发展,样品制备方法的完善,稀土分析方法的优化及其在组分、微区与形态的分析中的应用现状进行概述,旨在为XRF技术在稀土分析方面的发展及推广提供参考思路。     

Concentration of all rare earth impurities of cerium sub-group rare earth matrices

The separability of all rare earth impurities from cerium sub-group matrices was investigated. It was found that anion exchange chromatography carried out with aqueous methanol solutions of nitrates provides a useful method for the concentration of all rare earth impurities in neodymium and gadolinium matrices. The concentrate of the impurities can be processed further as required by the method chosen for their analytical determination.     

Precise trace rare earth analysis by radiochemical neutron activation

A rare earth group separation scheme followed by normal Ge(Li), low energy photon detector (LEPD), and Ge(Li)−NaI(Tl) coincidence-noncoincidence spectrometry significantly enhances the detection sensitivity of individual rare earth elements (REE) at or below the ppb level. Based on the selected γ-ray energies, normal Ge(Li) counting is favored for¹⁴⁰La,¹⁷⁰Tb and¹⁶⁹Yb; LEPD is favored for low γ-ray energies of¹⁴⁷Nd,¹⁵³Sm,¹⁶⁶Ho and¹⁶⁹Yb; and noncoincidence counting is favored for¹⁴¹Ce,¹⁴³Ce,¹⁴²Pr,¹⁵³Sm,¹⁷¹Er and¹⁷⁵Yb. The detection of radionuclides^152mEu,¹⁵⁹Gd and¹⁷⁷Lu is equally sensitive by normal Ge(Li) and noncoincidence counting;¹⁵²Eu is equally sensitive by LEPD and normal Ge(Li); and¹⁵³Gd and¹⁷⁰Tm is equally favored by all the counting modes. Overall, noncoincidence counting is favored for most of the REE. Precise measurements of the REE were made in geological and biological standards. Prepared for the U.S. Department of Energy under Contract DE-AC06-76RLO 1830.     

辉光放电质谱法测定稀土矿中的15种稀土元素

利用高纯铜粉与稀土矿石粉末均匀混合压片制样.混合15种高纯稀土氧化物制样建立标准工作曲线,校正15种稀土元素相对灵敏度因子,再进行定量分析.结果 表明,稀土元素工作曲线的线性方程相关系数R2均大于0.996,相对标准偏差(RSD)小于5％,满足定量分析要求.测定结果与电感耦合等离子体质谱法(ICP-MS)和电感耦合等离...     

Neutron activation analysis of rare earth impurities in europium oxide

A neutron activation analysis method for determining Yb, Dy, Ho, Sm and La impurities in europium oxide with sensitivities of 10^?5 to 10^?7% is described. The method is based on a preliminary concentration of the rare earth elements by reducing europium(III) with zinc to europium(II), and separating the trivalent rare earth elements by extraction chromatography. After neutron irradiation, the individual radioisotopes of the rare earth elements are separated by using KU-2 cation exchange resin and ammonium α-hydroxyisobutyrate solution as the eluant.     

Coordination field analysis of rare earth complexes with triangular symmetry

The calculation of the complex matrixes in odd triangular symmetry was accomplished.The configurations of the coordination unit with various triangular symmetries and different ligand numbers were discussed.On the basis of the double-sphere coordination point-charge (DSCPCF) model,the detailed forms of the DSCPCF parameters Bmk and the expressions of the perturbation matrix elements in triangular field (D3,D3h,D3d) were derived.Thereby,the calculation scheme of coordination field perturbation energy of the rare earth complexes with triangular symmetry was constructed After the calculation scheme was programmed,the Stark energies of the crystalline TbAl3(BO3)4 were calculated The results were considerably close to the experimental values     

Neutron activation analysis of rare earth impurities in metallic uranium

A method with a sensitivity of 2·10⁻⁷ to 1·10⁻¹⁰% has been developed for determining Yb, Ho, Dy, Gd, Eu, Sm and La impurities in metallic uranium by means of neutron activation. The method is based on a preliminary chromatographic separation of the total amount of rare earth elements from uranium by passing the solution in sulphuric acid through KU-2 cation exchange resin and eluting the traces of uranium retained by the resin with a solution of ascorbic acid. The rare earth impurities are then eluted from the resin with 4–5N HCl, evaporated, and irradiated for 20 hours with a neutron flux of 1.2·10¹³ n·cm⁻²·sec⁻¹. Subsequently the traces of the rare earth elements are co-precipitated with Fe(OH)₃, dissolved in concentrated HCl and separated from the iron and other impurities by passing the solution through Dowex 1X8 anion exchange resin in the chloride form. The individual rare earth elements are then separated from each other using KU-2 cation exchange resin and a solution of ammonium α-hydroxyisobutyrate as the eluant.     

X-Ray fluorescence analysis of thulium oxide for rare earth impurities

A wavelength dispersive X-ray fluorescence spectrometric method has been developed for the analysis of thulium oxide to determine the neighbouring rare earth impurities. The sample is taken in oxalate form and the analysis is done on a Philips PW 1220 spectrometer with a LiF (200) crystal. The detection limit for holmium, lutetium and yttrium is 0.002%, for dysprosium and erbium 0.005% and for, ytterbium it is 0.01%. The precision at each concentration of the standards and the theoretical detection limits have been calculated. Intensity correction factors for the line overlaps have been determined.     

Studies on rare earth trisoxalatochromates (III), rare earth chromates (V) and rare earth chromites (III)

Rare earth trisoxalatochromates (III), LnCr(C₂O₄)₃·nH₂O (n = 9 for La, and n = 8 for Ce, Pr and Nd) have been isolated and characterized by a number of physicochemical studies. These compounds (except for Ce) serve as precursors for the rare earth chromates (V) and chromites (III). LnCrO₄ may be obtained by heating LnCr(C₂O₄)₃·nH₂O at 520°C for 4 hr and LnCrO₃ at 900°C for a similar period. CeCr(C₂O₄)₃. 8H₂O decomposes to a mixture of CeO₂ and Cr₂O₃. The EPR spectra of LaCrO₄ are consistent with a tetrahedral geometry of the CrO₄ group. Although the unit cell of LaCrO₄ is monoclinic and of NdCrO₄ is tetragonal, compounds of composition La_1−xNd_xCrO₄ show the presence of only monoclinic phase for x up to 0.23. The electronic spectra of LnCrO₃ are compatible with the perovskite structure of these compounds.     

Synthesis of rare earth monoxides

The standard Gibbs energy changes for the formation of an ionic or metallic monoxide from rare earth metal and sesquioxide have been calculated. Under high pressures ionic ytterbium monoxide and lighter rare earth metallic monoxides should be obtained, which is confirmed by experiments in a belt-type apparatus in the range 15–80 kbar and 500-1200°C. For Ln =La, Ce, Pr, Nd, Sm, a face-centered cubic compound is obtained from each reaction. The cell parameters are respectively 5.144, 5.089, 5.031, 4.994, and 4.943 ± 0.005A?. The compounds appear golden yellow with a metallic luster. From chemical analyses and cell parameter consideration it is concluded that these compounds are the rare earth monoxides. For Ln =Gd, Dy, Tm, no reaction is observed at 50 kbar and 1000°C. The rare earth monoxides show a variety of properties: LaO, CeO, PrO, and NdO are metallic with the rare earth in the trivalent state; EuO and YbO are semiconductors with the rare earth in the divalent state; SmO is metallic with samarium in an intermediate valence state close to 3.     

Studies on rare earth trisoxalatoferrate(III) and rare earth ortho ferrite

The preparation and characterization of LaFe(C₂O₄)₃·9H₂O is described but the trisoxalatoferrate(III) of other lanthanides could not be isolated. However, the lanthanum ion in LaFe(C₂O₄)₃·9H₂O can be partly replaced by other lanthanide ions, e.g. with Nd(III) doping to the extent of 0.33 mole fraction of the latter has been accomplished. In the compounds La_1−xNd_xFe(C₂O₄)₃·9H₂O a stron magnetic interaction between Fe³⁺ and Nd³⁺ is observed. From a comparison of the IR and diffuse reflectance spectra and the X-ray diffraction data it is shown that K₃Fe(C₂O₄)₃·9H₂O and LaFe(C₂O₄)₃·9H₂O are not isostructural. Thermal analysis (combined TG, DTA and DTG) of LaFe(C₂O₄)₃·9H₂O establishes that this compound is precursor of LaFeO₃. The LaFeO₃ obtained, has been characterized by its X-ray diffraction pattern, measurement of its magnetic moment, and by its electronic and IR spectra. The thermal behavior of physical mixtures of La₂(C₂O₄)₃·10H₂O and Fe₂(C₂O₄)₃·5H₂O and La₂(C₂O₄)₃·10H₂O and Fe(C₂O₄)·2H₂O has also been investigated and the products of thermal analysis at ∼1000°C in air found to be a mixture of La₂O₃ and αFe₂O₃.     

Distribution characteristics of rare earth elements in plants from a rare earth ore area

The contents of eight rare earth elements (La, Ce, Nd, Sm, Eu, Tb, Yb and Lu) in various plant species taken from a rare earth ore area were determined by instrumental neutron activation analysis. For a given plant, the REE patterns in root, leaf and host soil are different from each other. The REE distribution characteristics in roots of various species are very similar and resemble those in the surface water. The results of this study suggest that there is no significant fractionation between the REEs during their uptake by the plant roots from soil solution. However, the variation of the relative abundance of individual REE occurs in the process of transportation and deposition of REEs in plants.     

X-ray fluorescence spectrometric analysis of erbium oxide for rare earth impurities

An X-ray fluorescence spectrometric method has been developed for the analysis of high purity erbium oxide for the determination of yttrium, terbium, dysprosium, holmium, thulium, ytterbium and lutetium oxide impurities in the concentration range 0.005–0.1%. The sample is taken in oxalate form, mixed with a binder (boric acid) in the weight ratio 31 and made into a double layer pellet. The analysis is done on a Philips PW 1220 X-ray fluorescence spectrometer using a LiF (200) analyzing crystal. The precision at each concentration of the standards and theoretical minimum detection limit for each element has been calculated.     

X-ray-fluorescence analysis of high-purity holmium oxide for common rare earth impurities

Summary An X-ray fluorescence analysis method for determination of Gd, Tb, Dy, Er, Tm and Yb in Holmium oxide is described. Samples are converted to oxalate form and mixed with boric acid in the ratio 31. A double layer pellet is obtained by pressing about 800 mg of this mixture on a boric acid pellet. Selection of experimental parameters and analysis lines are discussed. The estimation limit ranges from 0.005% to 0.5%.

---

Röntgenfluorescenzspektrometrische Analyse von hochreinem Holmiumoxid auf Verunreinigung von Seltenen Erden

Zusammenfassung Die Proben werden in die Oxalatform übergeführt, mit Borsäure vermischt (31) und in Mengen von 800 mg als zweite Schicht auf eine Borsäuretablette gepreßt. Die Auswahl der experimentellen Parameter und der Analysenlinien wird diskutiert. Die Erfassungsgrenzen für Gd, Tb, Dy, Er, Tm und Yo liegen im Bereich von 0,005–0,5%.

     

Radiochemical neutron activation analysis of rare earth elements in peridotitic rocks

The understanding of the geochemistry of basalt petrogenesis and the nature of the upper mantle requires the examination of such rocks as peridotites which in many cases are thought to represent upper mantle material. The mineralogical composition of peridotitic rocks in such that they accommodate large proportions of such trace elements as the transition elements but very small amounts of the rare earths and hygromagmaphile elements. The last two groups are often able to provide a large amount of information leading to petrogenetic models. Owing to the extremely low concentrations of the REE in peridotitic rocks it is necessary to separate them from other elements which will interfere with their precise determination. We have used a radiochemical neutron activation analytical method which is adapted from various published methods. It involves a post-irradiation sample fusion, two separate ion-exchange chromatographic stages and finally a fluoride precipitation. The RNAA procedure is capable of providing very precise REE data for perioditic samples and we have used it for the analysis of such rocks from several geodynamic environments.