Electronic Theoretical Study of the Interaction between Rare Earth Elements and Impurities at Grain Boundaries in Steel

The model of dislocations was used to construct the model of grain boundary (GB) with pure rare earths, and rare earth elements and impurities. The influence of the interaction between rare earth elements and impurities on the cohesive properties of 5.3° low angle GB of Fe was investigated by the recursion method. The calculated results of environment sensitive embeding energy( E ESE ) show that the preferential segregation of rare earth elements towards GBs exists. Calculations of bond order integrals (BOI) show that rare earth elements increase the cohesive strength of low angle GB, and impurities such as S, P weaken the intergranular cohesion of the GB. So rare earth element of proper quantity added in steel not only cleanses other harmful impurities off the GBs, but also enhances the intergranular cohesion. This elucidates the action mechanism of rare earth elements in steel from electronic level and offers theoretical evidence for applications of rare earth elements in steels.

Mechanism of interaction relation between the rare-earth element Ce and impurity elements Pb and Bi in Ag-based filler metal

The mechanism of interaction relation between the rare-earth element Ce and elements Pb and Bi in Ag-based filler metal has been studied. The results show that the compounds CePb and CeBi with high melting point can be easily produced between these three elements in the filler metal, which greatly limited the formation of the isolated phase Pb or Bi and also eliminated the bad effect of impurity elements Pb and Bi on the spreading property of Ag-based filler metal. The metallurgical and quantum-mechanical bond formation analysis show that a strong chemical affinity was existed between the rare-earth element Ce and impurity elements Pb and Bi, which was proved by the XRD analysis results.

Interaction Rule between Rare Earths and LowMelting Point Elements in Fe-,Cu-,AI-,Ni-Base Liquid Solutions

Interaction rule between representative RE and Sn, Sb, Pb, Cu, S, P low melting point elements respectively in Fe , Cu , Al , Ni base liquid solutions including totally 34 ternary and quarternary systems was investigated. For each system some thermodynamic properties were obtained, such as the standard free energies of equilibrium reactions, activity interaction coefficients etc ..

Simultaneous Determination of Trace Rare Earth Elements and Other Elements in High Purity Terbium Oxide (Tb_4O_7) by ICP-AES After HPLC Separation Using P507 Resin

This article describes a new method for the simultaneous determination of trace rare earth elements (REEs) and non rare earth elements (NREEs) in high purity terbium oxide by ICP-AES after HPLC separation using P507 resin. The chromatographic separation of the analytes from the matrix using dilute nitric acid as mobile phase was studied. The experimental results showed that a favorable separation of trace metals (Cu and Gd) from the matrix (Tb) can easily be achieved by elution with dilute nitric acid within 25 min. The proposed method was applied to the determination of trace metals (Ca, Cu, Mg, Mn, Ni, Si, La, Ce, Pr, Nd, Sm, Eu and Gd) in high purity terbium oxide. The detection limits (DLs) for the analytes ranged from 0.4-4.0 μg\5g -1, and the recoveries are from 78%-105%.

Rare earth element geochemistry of groundwater from a deep seated sandstone aquifer,northern Anhui province,China

Deep coal mines in northern Anhui province,China,provide opportunities for tracing the distribution and fractionation of rare earth elements(REEs) in deep seated environments.Major ions,as well as REE concentrations were measured in groundwater from a sandstone aquifer located between-400 and-280 m.Our results indicate that this groundwater consists of Cl HCO3-Na or Cl CO3-Na water types with warm temperature(30.1-31.4 °C),circumneutral pH(7.27-8.61) and high levels of total dissolved solids(TDS = 1306-2165 mg/L).Concentrations of REEs in groundwater are high as expressed by their Nd concentrations(0.0086-0.018 lg/L).Except for weak heavy REEs(HREE) enrichment relative to light REEs(LREE),the similarity of REE distribution patterns between groundwater and aquifer rock indicate that enrichment of REEs is considered to be controlled by aquifer rock,as well as by their minerals,whereas the fractionation of REEs is controlled by HREE enriched minerals and,to a lesser extent,by inorganic REE complexes.Ce anomalies normalized to Post Archean Average Shale(PAAS) and aquifer rock are weak,which probably reflect the contribution of reduced conditions in combination with pH,rather than a signature of aquifer rock.

Geochronology,Geochemistry,Fluid Inclusion and C,O Isotope Compositions of Calcite Veins in the Paleogene of the Jiangling Basin,South China:Implications for Fluid Evolution and Brine Potash Mineralization

Deep-seated potassium-rich brines were identified in the Jiangling Basin,South China.Although magmatichydrothermal sources have been proposed,the relationship between brine-type potash mineralization and volcanism remains unclear.In this study,U-Pb geochronology,geochemistry,fluid inclusion and C-O isotopic compositions of hydrothermal vein minerals in the Jiangling Basin are examined.Laser ablation U-Pb dating of calcite veins indicates that the ages are slightly younger than the formation age of the Balingshan basalt.Fluid inclusions in hydrothermal minerals show medium–low homogenization temperatures(160–220℃)and low salinities(0.14 to 4.9 wt%NaCl eqv.)and densities(0.882–0.944 g/cm^(3)).The liquid compositions of fluid inclusions in calcite veins from sedimentary strata have higher contents of potassium,compared with those from basalt.The coupled negativeδ^(13)CPDB(-10.3‰to-8.0‰)and positiveδ^(18)OSMOW(17.4‰to 20.7‰)values imply that calcite precipitation resulted from CO_(2)degassing of the basaltic magmatic fluids,as indicated by the gas composition of these inclusions in hydrothermal minerals.Rare earth element patterns indicate that water-rock interaction between hydrothermal fluids and sedimentary wall rocks contributed to the calcite precipitation in sedimentary strata.It is proposed that high-temperature water-rock interaction between magmatic fluids and sedimentary strata resulted in the potassium enrichment in fluids,interpreted as one of the sources of potassium-rich brines in the Jiangling Basin.

Geochemistry of rare earth elements in groundwater from deep seated limestone aquifer in Renlou Coal Mine,Anhui Province,China

Rare earth element (REE) concentrations were measured by ICP-MS for groundwater collected from deep seated Taiyuan Fm limestone aquifer (from-400 to-530 m) in Renlou Coal Mine,northern Anhui Province,China.It can be concluded that the groundwater is warm (34.0-37.2 °C) Cl-Ca,Na type water with circum-neutral pH (7.35-8.28) and high total dissolved solids (TDS,1 746-2 849 mg/L).The groundwater exhibits heavy REEs enrichment relative to light REEs compared with Post Archean Average Shale (PAAS),as well as their aquifer rocks (limestone).The enrichment of REEs is considered to be controlled by terrigeneous materials (e.g.zircon) in aquifer rocks,whereas the fractionation of REEs is controlled by marine derived materials (e.g.calcite),to a less extent,terrigeneous materials and inorganic complexation.The Ce anomalies normalized to PAAS and aquifer rocks are weak,which probably reflects the signature of the aquifer rock rather than redox conditions or pH.The similarities of REE patterns between groundwater and aquifer rocks imply that aquifer rocks play important roles in controlling the REE characteristics of groundwater,and then provide a probability for discrimination of groundwater sources by using REEs.

Magnetic property improvement of niobium doped with rare earth elements

A new idea is proposed by the PKU group to improve the magnetic properties of the Type-Ⅱ superconductor niobium. Rare earth elements like scandium and yttrium are doped into ingot niobium during the smelting processes. A series of experiments have been done since 2010. The preliminary testing results show that the magnetic properties of niobium materials have changed with different doping elements and proportions while the superconductive transition temperature does not change very much. This method may increase the superheating magnetic field of niobium so as to improve the performance of the niobium cavity, which is a key component of SRF accelerators. A Tesla-type single-cell cavity made of scandium-doped niobium is being fabricated.

漳江口溶解态稀土元素的地球化学特征及影响因素

河口区域稀土元素(Rare earth elements, REEs)的地球化学行为对理解海洋中REEs的循环具有重要意义。本文通过现场调查对2018年9月(暴雨时期)、2019年12月(旱季)及2020年8月(湿季)溶解态REEs在漳江口的分布特征、REEs的主要影响因素及人为稀土元素钆(Gd)污染进行研究。结果表明:漳江口溶解态REEs在不同时期的分布及分异存在显著差异,溶解态REEs含量暴雨时期>旱季>湿季。暴雨时期溶解态REEs主要呈现轻/中稀土相对富集及Ce正异常现象,而旱季及湿季溶解态REEs主要呈现重稀土相对富集及Ce负异常现象,颗粒物-水作用是不同时期溶解态REEs含量及分异存在差异的主要原因。Gd在不同时期均呈现正异常,暴雨时期、旱季及湿季人为Gd占比分别为18%~29%、26%~69%及22%~60%,推测Gd污染可能受河口上游医院核磁共振造影剂使用的影响。以上研究表明暴雨导致的颗粒物释放对河口溶解态REEs具有显著的贡献,今后研究需要重视特殊事件(如暴雨)对河口溶解态REEs来源和收支的影响。漳江口上游的人口密度相比全国其他地区较低但存在较为严重的人为Gd污染,说明我国其他河口人为稀土污染及来源也应引起广泛的重视。

三重四极杆电感耦合等离子体质谱(ICP-MS)法测定氧化铕中13种稀土杂质元素

稀土杂质元素直接影响高纯单金属稀土材料的整体性能,是高科技领域许多材料的重要组成部分。通过考察消解酸量、温度、时间,氧气反应气流量,稀释气流量,建立了基于三重四极杆电感耦合等离子体质谱(ICP-MS/MS)法直接测定氧化铕中13种稀土杂质元素的分析方法。采用0.1%基体直接进样,可以很大程度提高前处理分析效率。利用碰撞模式测定氧化铕稀土中的Y、La、Pr、Nd、Sm、Gd、Tb、Dy、Ho、Er、Yb、Lu元素,氧气质量转移模式测定氧化铕中的Tm,两种模式结合可以有效去除多原子干扰,实现氧化铕的稳定测试。通过对氧化铕标准物质(GBW02902)直接测定,结果表明,在碰撞和氧气质量转移模式下,各元素线性相关系数(r)均大于0.9999,方法检出限为0.001~0.023 mg/kg,测试精密度优于2.0%,13种元素的测定值都在认定值的不确定度范围之内。方法操作简单、测定稳定、效率高,为实验室进行氧化铕材料中REE杂质的准确测定提供思路和借鉴。

Geochemistry of Thermal Waters of Continental Margin of Far East of Russia

Studied waters belong to warm （T=30-50℃）, alkaline （pH=8.9-9.3）, low mineralized （TDS〈235 mg/l） Na-HCO3 or Na-SO4-HCO3 thermal waters with high content of SiO2 （up to 81 mg/1） and F （up to 3.9 mg/l）, occur on modern volcano-tectonic rejuvenated areas of Eastern Sikhote-Alin orogenic belt. Low 3He concentration as well as N2/O2 and N2/Ar ratios exclude influence of deep mantle fluid. New rare earth element data constrain our understanding of water-rock interaction occurring in the water source region. Meteoric origin of waters is proved by stable isotope values varying from -71%o to -136.1‰ and from -10.8‰ to -18.8%o for δ^2H and δ^18O respectively. REE patterns reflect high pH, resultfing from water-rock interaction and oxidative conditions. Calculations of deep aquifer temperature using Na-K and quartz geothermometers show 116.8-131.1℃ and 82.2-125.8℃ respectively. Presence of deep faults both with abnormal thermal gradient （-45- 50 K/km） define unique geochemical shape of thermal waters of Sikhote-Alin, area, where no present volcanic activity is registered.

贵德盆地高氟地下水稀土元素特征及其指示意义

高氟地下水是我国乃至国际社会面临的最严重的环境地质问题之一。尽管众多的研究学者已对高氟地下水形成机理开展了广泛的研究,但高氟地下水中稀土元素的分异特征和迁移规律能否指示地下水中氟的富集过程尚不完全清楚。本研究聚焦高氟地下水广泛分布的贵德盆地,通过野外调查取样、室内测试和综合分析以及水文地球化学模拟相结合的技术手段,探究了含水层中氟和稀土元素的分布特征和迁移规律。研究发现贵德盆地地下水中氟的平均浓度为2.67 mg·L^(-1),75%的地下水样品中氟浓度高于1.5 mg·L^(-1),且沿地下水流程呈现出上升趋势。PHREEQC计算结果表明,地下水中氟主要以自由态F-的形式存在(浓度99.5%)。XRD和SEM-EDS的结果表明含水层沉积物中的主要矿物为石英(含量52.9%~56.5%)和斜长石(含量19.8%~21.8%),且斜长石已发生化学风化作用。贵德盆地地下水中稀土元素浓度较低(0.052~0.267μg·L^(-1)),且主要以LnCO^(+)_(3)和Ln(CO_(3))^(-)_(2)的无机络合形态存在(含量>99%,Ln代表稀土元素)。地下水稀土元素北美页岩归一化模式表现为轻稀土元素相对于重稀土元素富集,且具有轻微的Ce负异常和显著的Eu正异常特征。地下水中氟和稀土元素的迁移均受到含水层中铁氧化物矿物的还原性溶解和长石类矿物的非全等水解过程的影响,且地下水中稀土元素的富集过程在一定程度上可以指示地下水中氟的富集过程。研究成果拓展了稀土元素在高氟地下水研究中的应用,可以为识别和揭示高氟地下水的分布和富集机理提供依据。

Controls of interactions between iron hydroxide colloid and water on REE fractionations in surface waters:Experimental study on pH-controlling mechanism

The influence of pH on the partitioning behavior of REE at the water/particulate interface has been studied experimentally. At the beginning of colloid formation the adsorption of REE on iron hydroxide colloids is dominant, followed by REE desorption. Finally adsorption and desorption tend to reach equilibration. The capability of iron hydroxide colloids to adsorb the HREE is greater than that to adsorb the LREE. With increasing pH, LREE/HREE fractionations will take place between iron hydroxide colloids and water, leading to the reduction of their partition coefficient ratio (DLREE/DHREE). The DREE distribution patterns show Y anomalies (DY/DHo <1), with obvious REE tetrad effects appearing under low pH conditions. Experimental results have shown that there do exist REE tetrad effects in nature. In addition to pH, the chemical type of surface water and ion intensity are also the important factors controlling REE tetrad effects and leading to fractionations between particulate-adsorbed REE and dissolved REE.

河流稀土元素地球化学研究进展

河流系统中 ,稀土元素 ( REE)受区域地质背景、风化作用、溶液化学以及水与颗粒物相互作用等因素的影响发生分异。河流悬浮物显示轻稀土 ( LREE)适度富集 ;河水显示重稀土 ( HREE)富集 ,或在 HREE富集的基础上又有适度的中稀土 ( MREE)富集 ;与其它微量元素相比 ,REE在河水与颗粒物之间有较小的分配系数 ( K≈ 1 0 -6) ;河流沉积物多显示平坦的 REE配分模式。

高纯金属镱中杂质元素的电感耦合等离子体质谱法测定

利用电感耦合等离子体质谱仪 (ICP -MS)直接测定了金属镱中除Tm、Lu外其他稀土及非稀土杂质元素 ;通过P507 萃淋树脂色层柱 ,分离绝大部分Yb基体 ,避免了基体元素对Tm、Lu的测定干扰。定量加入内标元素Sc、Cs,有效克服了基体效应所带来的偏差。稀土杂质元素的检出限0.010～0.032μg/g,非稀土杂质元素的检出限为0.12～5.0μg/g。加标回收率为83 %～105 %。方法适用于纯度为99.99 %～99.999

钢中晶界区稀土稀土元素与杂质交互作用的电子理论研究

利用位错模型构造纯净的和稀土及杂质偏聚的晶界模型 ,用Recursion方法研究了稀土与杂质的交互作用对Fe 5 .3°小角度晶界的结合性质的影响。环境敏感镶嵌能和键级积分 (BOI)的计算结果表明 :钢中同时存在稀土和杂质时 ,稀土首先偏聚于晶界。稀土偏聚于晶界时 ,起到加强晶界的作用 ;杂质偏聚于晶界时却起到脆化的作用。钢中加入适量的稀土 ,既净化晶界 ,又提高钢的强度。这一结果从电子层次解释了稀土在钢中的作用机制 。

电感耦合等离子体质谱法测定高纯稀土样品中多种非稀土杂质

研究建立了高纯稀土样品中24种非稀土杂质元素的电感耦合等离子质谱法（ICP-MS）测定方法。考察了几类典型金属样品分析中的基体效应,引入内标元素铟,有效补偿了基体效应引起的非质谱干扰。对几种在分析过程中存在质谱干扰的样品,通过分离基体进行测定。方法测定下限为1.8-390 ng·g^-1,RSD为2.9%-5.4%,加标回收率为92%-107%。

藏南隆子地区恰嘎流纹质次火山岩稀土元素类似四分组效应

恰嘎次火山岩侵位于特提斯喜马拉雅沉积岩系的东南部,雅拉香波片麻岩穹隆与藏南拆离系之间的地区。通过镜下鉴定和对岩石的主量元素、微量元素组成的测试和分析,确定为流纹质次火山岩。该岩体以富SiO2、Al2O3、K2O、Na2O,贫MgO、CaO、TFeO为特征,里特曼指数σ介于1.07-2.37之间,指示其属于钙碱性系列岩石。微量元素的测试结果表明,稀土元素总量较低,其配分图上产生类似于四分组的＂膝折＂效应;富集LILE、亏损HFSE,K/Rb和Rb/Cs比值低于一般酸性岩浆侵入岩体,Y/Ho、Nb/Ta和Zr/Hf的比值均偏离球粒陨石值。结合前人对稀土元素四分组效应的研究,认为富挥发分的流体作用于高度演化的酸性过铝质岩浆后,其稀土元素配分模式也能形成类似四分组的＂膝折＂配分模式,元素Gd显示正异常。

稀土对紫杂铜精炼效果的研究

研究了不同稀土元素对紫杂铜精炼效果的影响。结果表明,添加适量的稀土元素Y、La、Ce有利于提高紫杂铜的导电性能和力学性能,作用效果以Y为佳,其次为La、Ce。当稀土添加量超过0 15%时,其电导率和伸长率随添加量的增加而降低。