Atomic Control of the SrTiO3 Crystal Surface

The atomically smooth SrTiO(3) (100) with steps one unit cell in height was obtained by treating the crystal surface with a pH-controlled NH(4)F-HF solution. The homoepitaxy of SrTiO(3) film on the crystal surface proceeds in a perfect layer-by-layer mode as verified by reflection high-energy electron diffraction and atomic force microscopy. Ion scattering spectroscopy revealed that the TiO(2) atomic plane terminated the as-treated clean surface and that the terminating atomic layer could be tuned to the SrO atomic plane by homooepitaxial growth. This technology provides a well-defined substrate surface for atomically regulated epitaxial growth of such perovskite oxide films as YBa(2)Cu(3)O(7-delta).     

History and Present Situation and Developing Tendency of Rare Earth Applied in Agriculture

History of rare earth applied in agriculture Concept of rare earth Rare earth(RE for short)is a general designation of 17 elements,including 15 elements of lanthanum system,they are lanthanum (La),cerium (Ce),praseodymium (Pr),neodymium (Nd),promethium(Pm),samarium(Sm),europium(Eu),gadolinium(Gd),terbium(Tb),dysprosium(Dy),holmium(Ho),erbium(Er),thulium(Tm),ytterbium(Yb),lutetium(Lu)),and 2 elements of the same clan with lanthanum system: scandium (Se)and yttrium (Y) in the periodic table of elements.Rare earth look like earth or soil,and their quantity which may be separated from ore are very rare or few,so scientists call them rare earth elements.     

野生少花龙葵稀土元素的分析

采用微波消解样品,电感耦合等离子体原子发射光谱仪1次进样曝光同时测定野生少花龙葵样品中的15个稀土元素.结果表明,野生少花龙葵检的稀土元素含量较高,稀土氧化物总量为O.7 mg/kg,检出Ce、Gd、La、Nd、Pr、Sm、Y等7种稀土元素,其他稀土元素由于含量较低而未检出.方法具有快速、简便、准确等优点.     

Opaque minerals of the lunar rocks and dust from mare tranquillitatis

The opaque minerals in the lunar rocks 10047, 10050, 10057, 10059, 10068 and in the dust were studied. Rock 10047 contains ilmenite as a main component besides Al-bearing chromian ulv?spinel, a new Ti, Fe, Zr, Y, Ca silicate, troilite, cobaltian alpha Fe, minor hafnian baddeleyite and dysanalyte. Dysanalyte contains Ca, Ti, and Fe as major elements and shows concentrations (rare earth elements together approximately 10 percent) of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Hf, Y, and Zr plus traces of Nb, Ba, and Na. The chemistry of ilmenite in the igneous rocks shows no appreciable variations. A new mineral of the solid solution series MgTi(2)O(5)-FeTi(2)O(5) has also been encountered in the polymict breccias. The microbreccias and the fines contain meteorite debris indicating an impact origin.     

Atomic-scale chemical imaging of composition and bonding by aberration-corrected microscopy

Using a fifth-order aberration-corrected scanning transmission electron microscope, which provides a factor of 100 increase in signal over an uncorrected instrument, we demonstrated two-dimensional elemental and valence-sensitive imaging at atomic resolution by means of electron energy-loss spectroscopy, with acquisition times of well under a minute (for a 4096-pixel image). Applying this method to the study of a La(0.7)Sr(0.3)MnO3/SrTiO3 multilayer, we found an asymmetry between the chemical intermixing on the manganese-titanium and lanthanum-strontium sublattices. The measured changes in the titanium bonding as the local environment changed allowed us to distinguish chemical interdiffusion from imaging artifacts.     

中药牛膝中稀土元素含量分析

[目的]全面分析牛膝干燥根中的稀土元素含量,为中药牛膝的药效机理研究提供支持。[方法]将风干的牛膝根系用粉碎机磨成粉状,应用等离子体质谱仪全面分析牛膝干燥根中的稀土元素含量。[结果]牛膝中含有大量的稀土元素,Ce的含量最多,Lu的含量最少。含量超过100 ng/g(DW)的稀土元素有La、Ce和Nd,分别达到158.270、448.698和129.608 ng/g(DW);稀土元素Pr、Sm和Gd的含量均大于20 ng/g(DW);稀土元素Eu、Tb、Dy、Ho、Er、Yb的含量在2.536~14.522 ng/g(DW);稀土元素Tm和Lu的含量低于1 ng/g(DW),分别为0.918和0.848 ng/g(DW)。[结论]稀土元素La、Ce和Nd可能在牛膝药效的发挥中起重要作用。     

Atomic-resolution imaging of oxygen in perovskite ceramics

Using an imaging mode based on the adjustment of a negative value of the spherical-aberration coefficient of the objective lens of a transmission electron microscope, we successfully imaged all types of atomic columns in the dielectric SrTiO3 and the superconductor YBa2Cu3O7. In particular, we were able to view the oxygen atoms which, due to their low scattering power, were not previously accessible, and this allowed us to detect local nonstoichiometries or the degree of oxygen-vacancy ordering. This technique offers interesting opportunities for research into oxides, minerals, and ceramics. In particular, this holds for the huge group of perovskite-derived electroceramic materials in which the local oxygen content sensitively controls the electronic properties.     

稀土金属离子对蚕豆根尖微核率及对蚕豆早期生长发育的影响

应用蚕豆初生根尖细胞微核技术研究Ｌａ３＋、Ｓｍ３＋、Ｙ３＋、Ｇｄ３＋等稀土金属离子的诱变性,发现稀土金属离子在达到一定剂量时均可引起蚕豆根尖细胞微核率的升高,与对照组相比差异显著（Ｐ＜０．０５,Ｐ＜０．０１）。在早期生长试验中,应用７ｄ生长的蚕豆幼苗干重表征蚕豆的早期生长情况,比较蚕豆的发芽率及幼苗干重,反映稀土金属离子对蚕豆早期生长发育的毒性。结果表明,稀土金属离子在高浓度时对蚕豆的发芽率有一定影响,其中以Ｓｍ３＋、Ｙ３＋、Ｇｄ３＋更为明显;从蚕豆幼苗干重可以看出,稀土离子在低浓度时对蚕豆早期生长具有刺激作用,并具最适浓度,在高浓度时均具有抑制作用,且随着浓度的升高,抑制作用增强。     

X-ray diffraction study of the ultrathin Al2O3 layer on NiAl110

Ultrathin Al2O3 layers on alloys are used as templates for model catalysts, tunneling barriers in electronic devices, or corrosion-resistant layers. The complex atomic structure of well-ordered alumina overlayers on NiAl110 was solved by surface x-ray diffraction. The oxide layer is composed of a double layer of strongly distorted hexagonal oxygen ions that hosts aluminum ions on both octahedral and tetrahedral sites with equal probability. The alumina overlayer exhibits a domain structure that can be related to characteristic growth defects and is generated during the growth of a hexagonally ordered overlayer (Al2O3) on a body-centered cubic (110) substrate (NiAl).     

云烟及其地质环境中的稀土元素

本文研究了云南东部烤烟及其地质环境中的１５个稀土元素，结果表明，烟叶中稀土含量很低（∑ＲＥＥ＝１０ｍｇ／ｋｇ左右），烤烟对稀土的吸收率亦很低（平均吸收率０．０２３），但烟叶中稀土含量与生化组分含量之间存在稳定而显著的相关性．据此认为，稀土元素虽非烤烟生理必需元素，但对烤烟内在品质有重要影响．通过叶面喷施稀土微肥，能有效调控烟叶化学成分，改善其内在品质。     

基于矿物元素指纹技术的‘富士’苹果产地溯源

【目的】探讨‘富士’苹果果皮矿物元素含量的地域特征及产地溯源的可行性，结合多元统计分析，筛选出有效的判别指标，建立‘富士’苹果产地溯源模型，实现‘富士’苹果产地识别。【方法】以我国两大主产区（渤海湾产区和黄土高原产区）的124份‘富士’苹果为研究对象，采用电感耦合等离子质谱技术（ICP-MS）测定果皮中常量元素钠（Na）、镁（Mg）、钾（K）、钙（Ca），微量元素钒（V）、铬（Cr）、锰（Mn）、铁（Fe）、钴（Co）、镍（Ni）、铜（Cu）、锌（Zn）、砷（As）、钼（Mo）、镉（Cd）、锑（Sb）、钡（Ba）、铅（Pb）、铀（U），稀土元素钇（Y）、镧（La）、铯（Ce）、镨（Pr）、钕（Nd）、钐（Sm）、铕（Eu）、钆（Gd）、铽（Tb）、镝（Dy）、钬（Ho）、铒（Er），共31种矿物元素的含量，并结合独立样本T检验、主成分分析、线性判别分析、正交偏最小二乘判别分析进行‘富士’苹果的产地溯源。【结果】渤海湾产区和黄土高原产区的果皮样品中矿物元素Mg、Ca、Na、Fe、Mn、Cu、Ba、Ni、Nd、Pb、V、Ce、Pr、La、Dy、U、Ho和Co含量差异显著（P<0.05）。主成分分析结果表明，提取的12个主成分累计方差贡献率为81%，可对两大产区的样品进行初步聚类。利用线性判别分析，筛选出10种矿物元素（Mg、Ca、Cr、Mn、Fe、Ni、Gd、Tb、Dy、U）作为判别两大产区‘富士’苹果地域来源较好的指标，所建立的判别模型，对原始整体判别率为92%，交叉验证判别率为89.5%。通过正交偏最小二乘判别分析，确定Co、Ba、Ho、Dy、Pr这5种矿物元素在样品分类中起关键作用，模型的产地鉴别准确率可达98%，实现了两个产区‘富士’苹果的产地溯源。【结论】‘富士’苹果果皮可作为一种有效的溯源部位。稀土元素Dy、Ho、Pr、Gd、Tb的含量可作为‘富士’苹果产地溯源的重要指标。本研究结果可为‘富士’苹果产地溯源提供理论依据和技术支撑。     

氨态氮肥和尿素中稀土元素含量比较

[目的]探讨肥料形态对土壤中稀土元素含量的影响。[方法]利用ICP-MS分析硫酸铵和尿素两种氮肥中稀土元素的含量,研究施用不同形态肥料对土壤中稀土元素含量的影响。[结果]硫酸铵中La、Ce、Pr、Nd含量均高于尿素,La、Pr和Nd含量分别是尿素的6.7、9.9和12.8倍。硫酸铵中纯氮含量不到尿素的50%,使用氮肥时铵态氮肥施用量高于尿素。在同时施肥情况下,硫酸铵施入土壤后的稀土元素La、Pr和Nd分别是尿素施入土壤后的13.4、19.8和25.6倍。[结论]铵态氮肥(硫酸铵)的稀土元素含量是尿素的数倍,有利于补充土壤中的稀土元素。     

不同成因型母质发育土壤稀土元素的地球化学特征分析

分析了 1 7种母质发育土壤的稀土元素 (REE)的地球化学特征 ,结果表明 :(1 )基性岩浆岩母质发育土壤的稀土总丰度最高 ,红砂岩者最低 ;(2 )岩浆岩和喷出岩者的 REE科勃尔分布模式仍表现出母岩特征 ,沉积型者则相对平稳 ,但海相沉积型者变异显著 ;(3 )各类母质发育者∑ Ce/∑Y特征值达 3 .5 -4.7,∑ Ce与∑ Y分馏特征明显 ;(4 )砂页岩等 4种母质者δCe正异常 ,火山喷出岩等 3种母质者 δCe相对稳定 ,酸性岩浆岩等 1 0种母质者 δCe负异常 ;紫砂岩母质者 δEu正异常 ,页岩等 3种母质者δEu相对稳定 ,基性岩浆岩等 1 3种母质者 δEu负异常 ;(5 )逐步回归分析表明 ,∑ REE与 Ce、Sm、Dy、Lu,∑ Ce与 Pr、Sm,∑ Y与 Dy、Lu相关显著 ;(6)双重筛选逐步回归分析表明 ,∑ REE、∑ Ce与土壤 Fe2 O3相关极显著 ,∑ Y与土壤 p H值、粉砂粒、物理性粘粒相关显著 ;(7)通过 REE动态聚类分析 ,不同母质土壤可划分为基于岩性背景的三大类     

ICP-MS法测定茶叶中的16种稀土元素含量

[目的]旨在了解茶叶中的稀土元素残留情况,指导茶叶生产,评价茶叶饮用的安全性。[方法]使用HNO3+H2O2混酸体系高压密闭微波前处理样品和ICP-MS等离子体质谱法联合技术,建立测定茶叶样品中l6种(Sc45,Y89,La139,Ce140,Pr141,Sm147,Eu153,Gb157,Tb159,Nd144,Dy163,Ho165,Er166,Tm169,Yb172,Lu175)稀土元素含量的方法。[结果]各曲线呈良好线性关系,仪器检出限为0.002 3~0.692 4μg/L,方法检出限为0.20~35.00μg/kg,加标回收率为93.1%~117.5%(n=7)。[结论]该方法质谱图简单,选择性和灵敏度好,定量准确,且具有精密度和准确度高、操作简单方便、回收率高、重现性好等优点,适合茶叶中稀土元素的检测。     

Orbital reconstruction and covalent bonding at an oxide interface

Orbital reconstructions and covalent bonding must be considered as important factors in the rational design of oxide heterostructures with engineered physical properties. We have investigated the interface between high-temperature superconducting (Y,Ca)Ba(2)Cu3O7 and metallic La(0.67)Ca(0.33)MnO3 by resonant x-ray spectroscopy. A charge of about -0.2 electron is transferred from Mn to Cu ions across the interface and induces a major reconstruction of the orbital occupation and orbital symmetry in the interfacial CuO2 layers. In particular, the Cu d(3z(2)-r(2)) orbital, which is fully occupied and electronically inactive in the bulk, is partially occupied at the interface. Supported by exact-diagonalization calculations, these data indicate the formation of a strong chemical bond between Cu and Mn atoms across the interface. Orbital reconstructions and associated covalent bonding are thus important factors in determining the physical properties of oxide heterostructures.     

Direct imaging of reconstructed atoms on TiO2 (110) surfaces

Determining the atomic structures of oxide surfaces is critical for understanding their physical and chemical properties but also challenging because the breaking of atomic bonds in the formation of the surface termination can involve complex reconstructions. We used advanced transmission electron microscopy to directly observe the atomic structure of reduced titania (TiO2) (110) surfaces from directions parallel to the surface. In our direct atomic-resolution images, reconstructed titanium atoms at the top surface layer are clearly imaged and are found to occupy the interstitial sites of the TiO2 structure. Combining observations from two orthogonal directions, the three-dimensional positioning of the Ti interstitials is identified at atomic dimensions and allows a resolution of two previous models that differ in their oxygen stoichiometries.     

微波消解ICP－MS法结合同时测定香蕉中的16种稀土元素含量

[目的]旨在了解广西香蕉产区施用稀土农用肥的稀土元素残留情况,指导香蕉生产,评价稀土农用肥的安全性。[方法]采用ICP-MS等离子体质谱法和使用HNO3＋H2O2混酸体系高压密闭微波前处理样品联合技术,建立测定香蕉样品中16种稀土元素（Sc45,Y89,La139,Ce140, Pr141,Sm147,Eu153,Gb157,Tb159,Nd144, Dy163,Ho165,Er166,Tm169,Yb172,Lu175）含量的方法。[结果]各曲线呈良好线性关系,仪器检出限为0.002-0.01μg/L,方法检出限为0.1-0.6μg/kg,加标回收率为94.5%-116%,相对标准偏差为2.02%-14.21%。[结论]该方法质谱图简单,选择性和灵敏度好,定量准确,且具有精密度和准确度高、操作简单方便、回收率高、重现性好等优点,适合香蕉等水果中稀土元素的检测,对于指导香蕉生产、有效地种植,具有一定的理论及应用价值。     

ICP-MS测定区域地球化探样品中稀土元素的研究

[目的]为了提高化探样品的分析质量和分析速度.[方法]通过1/5万区域地质矿产调查项目,在青海东部地区发现土壤中含有稀土元素.稀土就是化学元素周期表中镧系元素-镧（La）、铈（Ce）、镨（Pr）、钕（Nd）、钷（Pm）、钐（Sm）、铕（Eu）、钆（Gd）、铽（Tb）、镝（Dy）、钬（Ho）、铒（Er）、铥（Tm）、镱（Yb）、镥（Lu）,以及与镧系的15个元素密切相关的2个元素-钪（Sc）和钇（Y）,共17种元素.采用电感耦合等离子体质谱仪（ICP-MS）,测试化探样品中的稀土元素.[结果]按照该研究分析方法测定稀土15种元素的结果令人满意.[结论]该方法具有操作简便、准确性良好的特点,适用于区域地球化探样品的分析测试.     

KCl肥料中稀土元素含量分析

[目的]确定农业上经常应用的钾肥KCl中的稀土元素,为今后的钾肥肥效试验和农业生产提供基础数据。[方法]应用ICP-MS法详细分析了钾肥KCl中的稀土元素含量。[结果]KCl肥料中含有15种稀土元素,分别是:La、Ce、Pr、Nd、Sm、Eu、Gd、Tb、Dy、Ho、Er、Tm、Yb、Lu和U,它们的含量分别为:61.74、110.73、11.363、2.55、6.452、.89、3.83、0.681、.980、.68、1.11、0.230、.66、0.30和0.73 ng/g。但是没有检测到Th。[结论]市场销售肥料含有多种杂质元素,特别是稀土元素在浓度较低时就会对植物产生明显影响,建议在做肥效试验时应初步了解肥料中稀土元素含量。     

三-(五甲基环戊二烯基)稀土有机配合物中的体积诱导效应

讨论了三-(五甲基环戊二烯基)稀土有机配合物的反应性质,探讨了它们的反应性能与体积效应的关系,发现随着体积效应的增大,三-(五甲基环戊二烯基)稀土有机配合物能发生体积诱导还原反应。