金属材料分析方法的选择和施行第六讲金属材料中稀土元素的测定(续)

钇的离子半径介于镝与钬之间,因此它的性质更接近于重稀元素。当元素的价态发生变化时,离子半径也发生变化。例如三价铕离子的半径为1.13,而二价铕的半径就增加到1.2~1.3,这就与锶的离子半径(1.27)接近了。因此,二价铕离子的性质与碱土金属离子比较相似,因而,就有可能用硫酸锶来共沉淀铕,以富集微量的铕。表6-3中还列出了稀土元素三价离子的颜色,可作为鉴别的参考。1.4镧系元素的化学性质在1.2及1.3节中简要地提到了镧系元素的电子结构和价态的关系以及镧系收缩和原子半径,离子半径的递变规律。这些元素的上述性质和现象对它们的化学性质也…     

镧系元素+3价离子颜色对称性规律的理论研究

本文根据德布罗意关系式和洪特规则,分析了镧系元素+3价离子能量与波长之间的关系,从理论上初步论证和解释了镧系元素+3价离子颜色以钆为中心具有对称性的规律。采用量子化学计算软件——密度泛函理论计算程序ADF,对镧系离子 4f轨道和 5d轨道的能级差进行计算,验证了推论的正确性。     

离子质电比和相差异因子对离子半径的的综合标度

依据已建立的离子质电比和相差异因子对离子半径的标度方法,系统性地研究了非稳定构型阳离子的相差异因子,采用回归分析法,改进了非稳定构型阳离子半径的计算公式。将稳定构型阳离子半径公式推广到等电子阳离子半径系统,计算了ⅡA(B)-ⅦA族52种离子半径数据;用改进的非稳定构型阳离子半径公式计算了四到七周期过渡元素(包括镧系和錒系),+1到+8各价态阳离子半径373个,其中预测了较为合理的271种阳离子半径数据。与前文中稳定构型阳离子半径合在一起,共108种元素508种离子半径,这些数据随周期数、族数以及价态等变化十分规律,是一套较好的、较为完整的单原子离子半径数据。     

离子交换法分离镍、钴的改进

在高校无机专业化学实验中,通常都用阳离子交换树脂分离镍、钴。虽然这两种金属离子与树脂结合的亲合能力不同,但由于Ni2+、Co2+离子半径接近,价数相同,因此需进一步用柠檬酸铵缓冲液淋洗。经过多次吸附—解吸,才使它们先后从树脂上洗脱下来,以达到分离目的。现在改用阴离子交换树脂,速度快、方法简便,分离效果好。     

镧系元素对Pd/Al2O3的修饰及其与丙烯腈气相加氢的关联

用浸渍法制备了镧系元素(Ce,La,Sm)修饰的低负载Pd(0.05 w.t%)/A l2O3催化剂,并应用于丙烯腈选择性加氢反应,实验结果表明:这种方法制备的催化剂对丙烯腈具有很好的选择性,镧系元素的添加大大促进了催化剂的活性和稳定性。XRD的测试结果表明稀土元素铈的添加减弱了Pd和载体A l2O3之间的相互作用,从而导致了Pd从载体表面游离出来。从TEM照片上可以看出催化剂颗粒尺寸的变化。XPS的测试结果表明用镧系元素修饰的Pd的结合能向较高能级发生了转移,从而使得钯被还原为零价。     

堆积图——堆积模型在镧系元素萃取中的应用

目前,在萃取化学中,配位数饱和原理的应用较普遍.但是,由于它只考虑配位电子数而忽略了配体的空间因素,这一原理在 f -电子组(镧、锕系)的应用就受到了很大限制.十分关键的一个问题是:“饱和配位数”对于镧系本身就没有严格定义.在已经测定的结构中,镧系元素配合物的配位数自3变化至12,人们很难从中选一配位数作为判别依据.研究配位体对中心     

湖南湘潭市的城市地质环境调查

从地质环境、水文环境、大气环境和地球化学环境阐述了湘潭市区的城市环境,提出进一步开展城市生态地球化学研究,对环境状态未来的变化进行预测,加强环境保护,使经济发展与自然环境和谐一致。     

地球化学模拟在高放废物地质处置中的应用与发展

随着核能事业的发展,高放废物的处理和处置问题日益突出.其中,研究高放废物在环境介质中的吸附、扩散和迁移行为是获取放射性核素对周围环境和人群健康影响的基础参数的最重要和最直接的途径.近年来,人们利用已有的实验数据及核素的基础热力学和动力学数据,附以相应的数学模型,建立了一些地球化学模拟软件,用于分析核素在地质介质中可能发生的连续性和长期性变化.目前,国内外常用的地球化学模拟软件有十多种.本文从热力学平衡计算原理、种态分布计算方法和表面配位模型假设等几个方面对地球化学模拟软件进行了简要介绍,对近年来地球化学模拟软件在核素种态分布计算和表面配位模型模拟两方面的应用进行了举例分析,并以Ca-U-CO3配合物为例,说明完备的热力学数据对地球化学模拟软件发展的重要性,以期促进我国地球化学模型的应用和发展.     

中国稀土科技文献索引(1988)

地质与选矿007008009010,几2 fJ4‘且‘l月1 dl心心心心‘015016刃17习18 五台山地区前寒武纪变质岩石的稀土元素地质化学,吴素珍,地球化学,1988,(2),118. 辽宁中元古代~中生代泥质岩稀土元素地球化学,和政军,地球化学,1988,(2),129. 碱性岩中磷灰石,相石和错石的稀土元素地球化学特征,周玲棣等,地球地学,1988,(3),224. 忆铝石榴石晶体高压相变研究,熊大和等,地质科学,1988,(3),239、 白云鄂博辉长石,胡辅佑等,地质科学,1988,(3),259. 江西省石英脉石型钨矿床黑钨矿中稀土元素的组成特点,林伟圣,地质与勘探,1988,24(2),17. 钟腾复式花岗岩…     

Ce1-xM′xCa0.2O1.8-0.4x (M=Y,La和Gd)

采用水热法合成了系列双掺杂的萤石结构Ce1-xLnxCa0.2O1.8-0.4x固溶体, 并研究了3种稀土离子对固溶体导电性的影响, 发现掺杂离子半径接近Ce4+时, 体系电导率增大而活化能降低. 同时发现水热合成的Ce1-xLnxCa0.2O1.8-0.4x样品的平均粒度按着掺入离子Y3+, Gd3+, La3+的顺序逐渐减小, 分别为32, 20和15 nm. 这种变化是由于Y3+半径比La3+和Gd3+更接近Ce4+, 因而在水热合成过程中, 掺Y3+的体系更有利于晶粒的生长, 得到的晶体粒度较大.     

Electrokinetic transport through the nanopores in cell membrane during electroporation

In electroporation, applied electric field creates hydrophilic nanopores in a cell membrane that can serve as a pathway for inserting biological samples to the cell. It is highly desirable to understand the ionic transfer and fluid flow through the nanopores in order to control and improve the cell transfection. Because of submicron dimensions, conventional theories of electrokinetics may lose their applicability in such nanopores. In the current study, the Poisson-Nernst-Planck equations along with modified Navier-Stokes equations and the continuity equation are solved in order to find electric potential, fluid flow, and ionic concentration through the nanopores. The results show that the electric potential, velocity field, and ionic concentration vary with the size of the nanopores and are different through the nanopores located at the front and backside of the cell membrane. However, on a given side of the cell membrane, angular position of nanopores has fewer influences on liquid flow and ionic transfer. By increasing the radius of the nanopores, the averaged velocity and ionic concentration through the nanopores are increased. It is also shown that, in the presence of electric pulse, electrokinetic effects (electroosmosis and electrophoresis) have significant influences on ionic mass transfer through the nanopores, while the effect of diffusion on ionic mass flux is negligible in comparison with electrokinetics. Increasing the radius of the nanopores intensifies the effect of convection (electroosmosis) in comparison with electrophoresis on ionic flux.     

Multielement analysis by sequential instrumental and radiochemical neutron activation

We measured 37 elements in six USGS geological camples and one NBS biological orchard leaf (OL) sample, using sequential INAA and radiochemical group separation coupled with high resolution, high efficiency Ge(Li), and a Ge(Li) with anticoincidence shields. The elemental concentrations in these samples vary over three orders of magnitude. Our results agree very well with the reported values. The rare earth values in PCC-1 are 2–4 times lower than the reported values. Precise REE patterns are defined in USGS samples, which are characteristic of the total rock types. The REE pattern in OL is identical to the mineral apatite. In addition to the possibility that OL may be contaminated by local soil, it is also possible that the uptake of REE trace elements by plants from soil is perhaps dominated by accessory mineral such as apatite, or plants take up the REE from bulk soil in a preferential manner as a smooth function of the REE ionic radii.     

Applicability of capillary electrophoresis to the analysis of trace rare earth elements in geological samples.

This study developed a methodology to analyze trace rare earth elements (REEs) in geological materials by capillary electrophoresis (CE). Changed from dilute HNO3 into a water medium by heating, REE ions are detectable at approximately 2 ng mL(-1). In the presence of coexisting elements from geological samples, REE separations were carried out. After sample fusion with Na2O2 and interference separation with ammonium pyrrolidinedithiocarbamate chelate, REE analytes were coprecipitated with Mg(OH)2 at pH 8.5, and then prepared into a water medium for CE determination. Using the standard addition method, this protocol was validated by analyses with better than 5% precision. This method was applied to geological materials; the REE results are in consistence with their certified values. With electrokinetic injection, internal standard (IS) selected among lanthanides is a prerequisite of high-quality REE data. An approach was proposed to derive the IS content for further correcting its contribution from unknown samples.     

Tuning of the structure and emission spectra of upconversion nanocrystals by alkali ion doping

Recently, lanthanide based nanocrystals with upconversion fluorescence emission have attracted a lot of interest and the nanocrystals have been used for bioimaging, biodetection, and therapeutic applications. Use of the nanocrystals for multiplexed detection has also been explored; however, nanocrystals with multicolor emission are required. Some efforts have been made to tune the emission spectra of the nanocrystals based on manipulation of upconverting lanthanide ions doped in the crystals or creation of core/shell structures. In this work, alkali ions with an ionic radius slightly larger or smaller than Na such as Li and K were doped into NaYF(4):Yb,Er nanocrystals and their effect on the crystal structure and subsequently the upconversion emission spectra were studied. It was found that the phase transition occurs in the nanocrystals when a different amount of Li and K was doped. Furthermore, the intensity ratios between the blue, green, and red emission peaks changed accordingly, and make it possible to tune the upconversion fluorescence of the nanocrystals by Li and K doping.     

煤可溶烃中一种特殊的稀土元素地球化学现象 ——以渭北中熟煤为例

用数理统计方法研究了渭北中熟煤中稀土元素（REE）在可溶烃和无机矿物中的赋存规律。结果表明,REE在可溶烃和矿物质之间有明显的互补关系,其中,轻稀土（LREE）和重稀土（HREE）又各呈现出不同的分布和赋存特征。但无论是LREE还是HREE,这种赋存分布规律都决定于其离子半径及内部的电子构型变化规律。LREE随着原子序数增大,其在有机的可溶烃和无机矿物中赋存规律性减弱,而HREE随着原子序数的增大,其在可溶烃和无机矿物中赋存规律性增强。这种“互补”和同步消长的关系在可溶烃各族组分之间也存在,并对煤成烃有一定的潜在作用。这是作者以前发现的“稀土元素煤地化效应”的另一种表现形式。     

Determination of Fibre Pore Structure: Influence of Salt,pH and Conventional Wet Strength Resins

It has been shown, in the present investigation, that the two methods used to investigate the pore size distribution of unbleached chemical pulps, i.e. inverse size exclusion chromatography (ISEC) and nuclear magnetic resonance (NMR), give different average pore radius for the pores inside the fibre wall. This is due to the way in which these experiments are performed and the sensitivity of the methods to different types of pores in the cell wall. It was also shown that the two methods gave different results when changing the pH and the ionic strength of the pulp suspension. The pore radius, as detected with ISEC, decreased with both increasing ionic strength and decreasing pH, indicating a loose structure of the exterior of the fibrillar network. However, the pore radius as detected with NMR, was virtually unaffected when increasing the ionic strength, indicating a very rigid structure of the interior of the fibre wall. Decreasing pH though, lead to a decrease in pore radius indicating that upon protonation of the carboxylic groups in the fibre wall, the electrostatic repulsion is diminished and the average pore radius decreases. The NMR technique was also used to study wet strength aid penetration into the fibre wall. It was shown that wet strength aids with a small molecular weight, penetrated the fibre wall, as detected by a decrease in pore radius. It was also shown that addition of different wet strength aids increased the tensile index of the sheet and decreased the fibre strength, measured as zero span-strength of the sheets.     

甲醇处理煤的微孔性质及反应性研究

在低于临界温度下,用甲醇处理了三种不同变质程度的煤,以研究其比表面积及微孔容积等表面特性的变化。结果表明,用甲醇处理后煤的微孔性质发生了较大变化,其变化的大小顺序是:沈北褐煤>大同烟煤>晋城无烟煤。随甲醇处理温度或干馏温度升高,煤及半焦的孔径均向小的方向偏移。煤的平均孔径为8.2—8.6A;半焦的平均孔径为6.3—7.5A。煤经甲醇处理后其半焦的反应性均比未处理的高。     

镧系收缩效应对稀土-煤相互作用的影响及煤中有机态稀土的赋存形式研究

通过酸洗脱灰及腐殖酸提取等方法对伊敏褐煤进行处理,并应用ICP-MS对处理前后的样品进行了稀土元素测定。在对脱灰前后稀土元素与灰分和C、H、O等有机组成元素的相关性以及稀土元素在腐殖酸中的赋存特征分析的基础上,认为煤中稀土元素-有机质相互作用受煤化作用过程中的脱氧、脱氢和增碳作用控制。稀土与煤中各类官能团相互作用形成四类有机态稀土元素复合物,第一类是与被烷基侧链高度取代的芳香结构单元形成的复合物;第二类是与氢化芳香结构单元形成的复合物;第三类是与低取代度的芳香结构单元形成的复合物;第四类是与含氧官能团作用形成的复合物,后两类的稳定性差。这些有机态稀土元素复合物的稳定性在总体受镧系收缩效应控制的基础上,还受稀土元素化学价态的影响;重稀土与有机质形成的有机态稀土元素复合物的稳定性大于轻稀土。轻稀土在原煤中和腐殖酸的结合不稳定,且具有与镧系收缩相反的效应;轻稀土在脱灰煤中和腐殖酸的结合,与中稀土、重稀土在原煤和脱灰煤中腐殖酸结合规律相同,都体现了良好的镧系收缩效应。     

Extraction of rare earth elements with phosphoryl-containing lariat crown ether in the presence of ionic liquids

Interfacial distribution of rare earth elements (REE) La, Ce, Pr, Nd, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y between aqueous solutions of their nitrates and solutions of the lariat crown ether 1,4,10,13-tetraoxa-7,16-diaza(diphenylphosphinylmethyl)cyclooctadecane in dichloroethane was studied in the presence of the ionic liquids 1-butyl-3-methylimidazolium hexafluorophosphate and 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide. The stoichiometry of extracted complexes was determined; the effect of HNO₃ concentration in the aqueous phase and the nature of extractant and ionic liquid on the extraction efficiency of REE(III) was considered.     

Neutron activation analysis of the rare earth elements in rocks from the earth's upper mantle and deep crust

Three techniques for analyzing rare earth elements (REE) in geological materials are described, i.e. instrumental neutron activation analysis (INAA), neutron activation analysis with pre-irradiation chemical REE separation (PCS-NAA) and radiochemical neutron activation analysis (RNAA). The knowledge of REE concentrations in eclogites, peridotites and minerals from the earth's lower crust and upper mantle is very useful in constraining their petrogenetic history.