Microstructure study of the rare-earth intermetallic compounds R<sub>5sub>(Si_xGe>1-xsub>)>4sub> and R<sub>5sub>(Si_xGe>1-xsub>)>3sub>

Energy Technology Data Exchange (ETDEWEB)

Cao, Qing [Iowa State Univ., Ames, IA (United States)

2012-01-01

The unique combination of magnetic properties and structural transitions exhibited by many members of the R<sub>5sub>(Si_xGe>1-xsub>)>4sub> family (R = rare earths, 0 ≤ x ≤ 1) presents numerous opportunities for these materials in advanced energy transformation applications. Past research has proven that the crystal structure and magnetic ordering of the R<sub>5sub>(Si_xGe>1-xsub>)>4sub> compounds can be altered by temperature, magnetic field, pressure and the Si/Ge ratio. Results of this thesis study on the crystal structure of the Er<sub>5sub>Si>4sub> compound have for the first time shown that the application of mechanical forces (i.e. shear stress introduced during the mechanical grinding) can also result in a structural transition from Gd<sub>5sub>Si>4sub>-type orthorhombic to Gd<sub>5sub>Si>2sub>Ge>2sub>-type monoclinic. This structural transition is reversible, moving in the opposite direction when the material is subjected to low-temperature annealing at 500 °C.

Mass-radius relations and core-envelope decompositions of super-Earths and sub-Neptunes

Energy Technology Data Exchange (ETDEWEB)

Howe, Alex R.; Burrows, Adam [Department of Astrophysical Sciences, Princeton University, Peyton Hall, Princeton, NJ 08544 (United States); Verne, Wesley, E-mail: arhowe@astro.princeton.edu, E-mail: burrows@astro.princeton.edu [Department of Computer Science, Princeton University, Princeton, NJ 08544 (United States)

2014-06-01

Many exoplanets have been discovered with radii of 1-4 R {sub ⊕}, between that of Earth and Neptune. A number of these are known to have densities consistent with solid compositions, while others are 'sub-Neptunes' likely to have significant H{sub 2}-He envelopes. Future surveys will no doubt significantly expand these populations. In order to understand how the measured masses and radii of such planets can inform their structures and compositions, we construct models both for solid layered planets and for planets with solid cores and gaseous envelopes, exploring a range of core masses, H{sub 2}-He envelope masses, and associated envelope entropies. For planets in the super-Earth/sub-Neptune regime for which both radius and mass are measured, we estimate how each is partitioned into a solid core and gaseous envelope, associating a specific core mass and envelope mass with a given exoplanet. We perform this decomposition for both ''Earth-like'' rock-iron cores and pure ice cores, and find that the necessary gaseous envelope masses for this important sub-class of exoplanets must range very widely from zero to many Earth masses, even for a given core mass. This result bears importantly on exoplanet formation and envelope evaporation processes.

Effect of rare-earth additions on the structure and dielectric energy storage properties of Ba{sub x}Sr{sub 1-x}TiO{sub 3}-based barium boronaluminosilicate glass-ceramics

Energy Technology Data Exchange (ETDEWEB)

Xiu, Shaomei; Xiao, Shi; Zhang, Wenqin; Xue, Shuangxi; Shen, Bo, E-mail: shenbo@tongji.edu.cn; Zhai, Jiwei, E-mail: apzhai@tongji.edu.cn

2016-06-15

Ba{sub x}Sr{sub 1-x}TiO{sub 3}-based barium boroaluminosilicate (BST-BBAS) glass-ceramics added with La{sub 2}O{sub 3}, Gd{sub 2}O{sub 3} and Yb{sub 2}O{sub 3} were fabricated through the melting method followed by controlled crystallization, respectively. The X-ray diffraction and the field emission scanning electron microscopy were investigated the phase composition and microstructure for the BST-BBAS glass-ceramics added with rare-earth additions, then the temperature-dependent dielectric properties and the voltage-withstand measurements were applied to study the effect of rare-earth additions on the dielectric energy storage density. These results show that the certain content of rare-earth additions can optimize the microstructure and phase structure effectively. And with the decrease of ionic radiuses of rare-earth elements, the microstructure of the glass-ceramics become more uniform. When added with 0.5 mol% Yb{sup 3+}, the theoretical energy storage density of the BST-BBAS glass-ceramics gets the largest value of 3.5 J/cm{sup 3} which is about 1.8 times compared to the undoped one. - Highlights: • A certain content of Yb{sub 2}O{sub 3} can restrain the formation of BaSi{sub 2}O{sub 5}and SiO{sub 2} phases. • The addition of rare earth can optimize the microstructure. • With 0.5 mol% Yb{sup 3+}, the dielectric energy storage density got the largest value of 3.5 J/cm{sup 3}.

Quantum algebra U{sub qp}(u{sub 2}) and application to the rotational collective dynamics of the nuclei; Algebre quantique U{sub qp}(u{sub 2}) et application a la dynamique collective de rotation dans les noyaux

Energy Technology Data Exchange (ETDEWEB)

Barbier, R

1995-09-22

This thesis concerns some aspects of new symmetries in Nuclear Physics. It comprises three parts. The first one is devoted to the study of the quantum algebra U{sub qp}(u{sub 2}). More precisely, we develop its Hopf algebraic structure and we study its co-product structure. The bases of the representation theory of U{sub qp}(u{sub 2}) are introduced. On one hand, we construct the finite-dimensional irreducible representations of U{sub qp}(u{sub 2}). On the other hand, we calculate the Clebsch-Gordan coefficients with the projection operator method. To complete our study, we construct some deformed boson mappings of the quantum algebras U{sub qp}(u{sub 2}), U{sub q{sup 2}}(su{sub 2}) and U{sub qp}(u{sub 1,1}). The second part deals with the construction of a new phenomenological model of the non rigid rotator. This model is based on the quantum algebra U{sub qp}(u{sub 2}). The rotational energy and the E2 reduced transition probabilities are obtained. They depend on the two deformation parameters q and p of the quantum algebra. We show how the use of the two-parameter deformation of the algebra U{sub qp}(u{sub 2}) leads to a generalization of the U{sub q}(su{sub 2})-rotator model. We also introduce a new model of the anharmonic oscillator on the basis of the quantum algebra U{sub qp}(u{sub 2}). We show that the system of the U{sub q}(su{sub 2})-rotator and of the anharmonic oscillator can be coupled with the use of the deformation parameters of U{sub qp}(u{sub 2}). A ro-vibration energy formula and expansion `a la` Dunham are obtained. The aim of the last part is to apply our non rigid rotator model to the rotational collective dynamics of the superdeformed nuclei of the A{approx}130 - 150 and A{approx}190 mass regions and deformed nuclei of the actinide and rare earth series. We adjust the free parameters of our model and compare our results with those from four other models of the non rigid rotator. A comparative analysis is given in terms of transition energies.

Effect of rare-earth ion size on local electron structure in RBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (R = Tm, Dy, Gd, Eu, Nd and Y) superconductors: A positron study

Energy Technology Data Exchange (ETDEWEB)

Chen Zhenping [Department of Technology and Physics, Zhengzhou University of Light Industry, 5 Dongfeng Road, Zhengzhou, Henan 450002 (China)]. E-mail: czhping@zzuli.edu.cn; Zhang Jincang [Department of Physics, Shanghai University, Shanghai 200436 (China); Su Yuling [Department of Technology and Physics, Zhengzhou University of Light Industry, 5 Dongfeng Road, Zhengzhou, Henan 450002 (China); Xue Yuncai [Department of Technology and Physics, Zhengzhou University of Light Industry, 5 Dongfeng Road, Zhengzhou, Henan 450002 (China); Cao Shixun [Department of Physics, Shanghai University, Shanghai 200436 (China)

2006-02-15

The effects of rare-earth ionic size on the local electron structure, lattice parameters and superconductivity have been investigated by positron annihilation technique (PAT) and related experiments for RBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (R = Tm, Dy, Gd, Eu, Nd and Y) superconductors. The local electron density n {sub e} is evaluated as a function of the rare-earth radius. The results show that both the bulk-lifetime {tau} {sub B} and the defect lifetime {tau} {sub 2} increase with increasing rare-earth ionic radius, while the local electron density n {sub e} decrease with increasing rare-earth ionic radius. These results prove that the changes of n {sub e}, the degree of orthorhombic distortion and the coupling between the Cu-O chains and the CuO{sub 2} planes all have an effect on the superconductivity of RBa{sub 2}Cu{sub 3}O{sub 7-{delta}} systems.

Elasticity of Relativistic Rigid Bodies?

Science.gov (United States)

Smarandache, Florentin

2013-10-01

In the classical Twin Paradox, according to the Special Theory of Relativity, when the traveling twin blasts off from the Earth to a relative velocity v =√{/3 } 2 c with respect to the Earth, his measuring stick and other physical objects in the direction of relative motion shrink to half their lengths. How is that possible in the real physical world to have let's say a rigid rocket shrinking to half and then later elongated back to normal as an elastic material when it stops? What is the explanation for the traveler's measuring stick and other physical objects, in effect, return to the same length to their original length in the Stay-At-Home, but there is no record of their having shrunk? If it's a rigid (not elastic) object, how can it shrink and then elongate back to normal? It might get broken in such situation.

Temperature-induced spin reorientation and magnetization jump of rare-earth orthoferrite Ho{sub 0.5}Pr{sub 0.5}FeO{sub 3} single crystal

Energy Technology Data Exchange (ETDEWEB)

Wang, Guohua; Zhao, Weiyao; Cao, Yiming; Kang, Baojuan [Department of Physics, and International Center of Quantum and Molecular Structures, Shanghai University, Shanghai 200444 (China); Zhang, Jincang [Department of Physics, and International Center of Quantum and Molecular Structures, Shanghai University, Shanghai 200444 (China); Materials Genome Institute, Shanghai University, Shanghai 200444 (China); Shanghai Key Laboratory of High Temperature Superconductors, Shanghai University, Shanghai 200444 (China); Ren, Wei, E-mail: renwei@shu.edu.cn [Department of Physics, and International Center of Quantum and Molecular Structures, Shanghai University, Shanghai 200444 (China); Materials Genome Institute, Shanghai University, Shanghai 200444 (China); Shanghai Key Laboratory of High Temperature Superconductors, Shanghai University, Shanghai 200444 (China); Cao, Shixun, E-mail: sxcao@shu.edu.cn [Department of Physics, and International Center of Quantum and Molecular Structures, Shanghai University, Shanghai 200444 (China); Materials Genome Institute, Shanghai University, Shanghai 200444 (China); Shanghai Key Laboratory of High Temperature Superconductors, Shanghai University, Shanghai 200444 (China)

2016-07-25

We report temperature-induced spin reorientation and magnetization jump effects in the rare earth (RE) orthoferrite Ho{sub 0.5}Pr{sub 0.5}FeO{sub 3} single crystal. The single crystal of about 6 mm in diameter and 50 mm in length was successfully grown by optical floating zone method. Both X-ray diffraction and Laue photograph confirmed the homogeneity and high quality of the crystal. Magnetic properties of Ho{sub 0.5}Pr{sub 0.5}FeO{sub 3} single crystal are studied over a wide temperature range from 2 to 300 K. Spin reorientation transition from Γ{sub 2} to Γ{sub 4} phase is observed in the temperature range of 75–90 K. At lower temperature, the Ho{sub 0.5}Pr{sub 0.5}FeO{sub 3} shows an abrupt jump of magnetization along the a-axis, which occurs only in the field-cooling process, and is sensitive to external applied magnetic field. By analyzing the jump temperature and magnitude of the magnetization, we conclude that it is caused by the spin reversal of the rare earth ions. The isothermal magnetization versus field hysteresis loop measurements along a axis explain the spin configuration variation from 3 K to 60 K. - Highlights: • Ho{sub 0.5}Pr{sub 0.5}FeO{sub 3} single crystal was grown by optical floating zone method. • It shows an abrupt jump of magnetization along a axis at low temperature. • The jump height and temperature is sensitive to external applied magnetic field. • It is attributed to the spin reversal of the rare earth ions.

Enstatite, Mg/sub 2/Si/sub 2/O/sub 6/: A neutron diffraction refinement of the crystal structure and a rigid-body analysis of the thermal vibration

Energy Technology Data Exchange (ETDEWEB)

Ghose, S.; Schomaker, V.; McMullan, R.K.

1986-01-01

Synthetic enstatite, Mg/sub 2/Si/sub 2/O/sub 6/, is orthorhombic, space group Pbca, with eight formula units per cell and lattice parameters a = 18.235(3), b = 8.818(1), c = 5.179(1) A at 23/sup 0/C. A least-squares structure refinement based on 1790 neutron intensity data converged with an agreement factor R(F/sup 2/) = 0.032, yielding Mg-O and Si-O bond lengths with standard deviations of 0.0007 and 0.0008 A, respectively. The variations observed in the Si-O bond lengths within the silicate tetrahedra A and B are caused by the differences in primary coordination of the oxygen atoms and the proximity of the magnesium ions to the silicon atoms. The latter effect is most pronounced for the bridging bonds of tetrahedron. A. The smallest O-Si-O angle is the result of edge-sharing by the Mg(2) octahedron and the A tetrahedron. An analysis of rigid-body thermal vibrations of the two crystallographically independent (SiO/sub 4/) tetrahedra indicates considerable librational motion, leading to a thermal correction of apparent Si-O bond lengths as large as +0.002 A at room temperature.

Thermochemistry of rare earth doped uranium oxides Ln{sub x}U{sub 1−x}O{sub 2−0.5x+y} (Ln = La, Y, Nd)

Energy Technology Data Exchange (ETDEWEB)

Zhang, Lei; Navrotsky, Alexandra, E-mail: anavrotsky@ucdavis.edu

2015-10-15

Lanthanum, yttrium, and neodymium doped uranium dioxide samples in the fluorite structure have been synthesized, characterized in terms of metal ratio and oxygen content, and their enthalpies of formation measured by high temperature oxide melt solution calorimetry. For oxides doped with 10–50 mol % rare earth (Ln) cations, the formation enthalpies from constituent oxides (LnO{sub 1.5}, UO{sub 2} and UO{sub 3} in a reaction not involving oxidation or reduction) become increasingly exothermic with increasing rare earth content, while showing no significant dependence on the varying uranium oxidation state. The oxidation enthalpy of Ln{sub x}U{sub 1−x}O{sub 2−0.5x+y} is similar to that of UO{sub 2} to UO{sub 3} for all three rare earth doped systems. Though this may suggest that the oxidized uranium in these systems is energetically similar to that in the hexavalent state, thermochemical data alone can not constrain whether the uranium is present as U{sup 5+}, U{sup 6+}, or a mixture of oxidation states. The formation enthalpies from elements calculated from the calorimetric data are generally consistent with those from free energy measurements. - Highlights: • We synthesize, characterize Ln{sub x}U{sub 1−x}O{sub 2−0.5x+y} solid solutions (Ln = La, Y, Nd). • Formation enthalpies become more exothermic with increasing rare earth content. • Oxidation enthalpy of Ln{sub x}U{sub 1−x}O{sub 2−0.5x+y} is similar to that of UO{sub 2} to UO{sub 3}. • Direct calorimetric measurements are in good agreement with free energy data.

A basic study on capture and solidification of rare earth nuclide (Nd) in LiCl-KCl eutectic salt using an inorganic composite with Li{sub 2}OAl{sub 2}O{sub 3}- SiO{sub 2}-B{sub 2}O{sub 3} systems

Energy Technology Data Exchange (ETDEWEB)

Kim, Na Young; Eum, Hee Chul; Park, Hwan Seo; Ahn, Do Hee [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2017-03-15

The pyroprocessing of spent nuclear fuel generates LiCl-KCl eutectic waste salt containing radioactive rare earth nuclides. It is necessary to develop a simple process for the treatment of LiCl-KCl eutectic waste in a hot-cell facility. In this study, capture and solidification of a rare earth nuclide (Nd) in LiCl-KCl eutectic salt using an inorganic composite with a Li{sub 2}OAl{sub 2}O{sub 3}- SiO{sub 2}-B{sub 2}O{sub 3} system was conducted to simplify the existing separation and solidification process of rare earth nuclides in LiCl-KCl eutectic waste salt from the pyroprocessing of spent nuclear fuel. More than 98wt% of Nd in LiCl-KCl eutectic salt was captured when the mass ratio of the composite was 0.67 over NdCl3 in the eutectic salt. The content of Nd{sub 2}O{sub 3} in the Nd captured-composite reached about 50wt%, and this composite was directly fabricated into a homogeneous and chemical resistant glass waste in a monolithic form. These results will be utilized in designing a process to simplify the existing separation and solidification process.

Structure, electronic properties, luminescence and chromaticity investigations of rare earth doped KMgBO{sub 3} phosphors

Energy Technology Data Exchange (ETDEWEB)

Zheng, Jianghui; Cheng, Qijin [School of Energy Research, Xiamen University, Xiamen 361005 (China); Wu, Shunqing [Department of Physics, Xiamen University, Xiamen, 361005 (China); Zhuang, Yixi [College of Materials, Xiamen University, Xiamen 361005 (China); Guo, Ziquan; Lu, Yijun [Department of Electronic Science, Fujian Engineering Research Center for Solid-state Lighting, Xiamen University, Xiamen 361005 (China); Chen, Chao, E-mail: cchen@xmu.edu.cn [School of Energy Research, Xiamen University, Xiamen 361005 (China); Department of Physics, Xiamen University, Xiamen, 361005 (China); Department of Electronic Science, Fujian Engineering Research Center for Solid-state Lighting, Xiamen University, Xiamen 361005 (China)

2015-09-01

In this work, the optimization of the geometry and the electronic properties of the host matrix KMgBO{sub 3} were investigated using density functional theory, and the comprehensive photoluminescence and chromaticity properties on five rare earth ion-doped (RE = Ce{sup 3+}, Tm{sup 3+}, Tb{sup 3+}, Eu{sup 3+}, Dy{sup 3+}) KMgBO{sub 3} phosphors were also studied. By introducing RE ions into the KMgBO{sub 3} host, excellent purple, blue, green, red and white emitting light could be obtained under the near-ultraviolet light excitation. The results suggest that rare earth doped KMgBO{sub 3} phosphors are potential luminescence materials for the application in the near-ultraviolet white light-emitting diodes. - Highlights: • The electronic properties of the host matrix KMgBO{sub 3} were investigated. • The PL properties on rare earth ions doped KMgBO{sub 3} phosphors were studied. • The chromaticity properties on rare earth ions doped KMgBO{sub 3} samples were studied. • Tm{sup 3+} and Eu{sup 3+} doped KMgBO{sub 3} samples show higher color purity than commercial phosphors.

Synthesis and crystal structure of the rare earth borogermanate EuGeBO{sub 5}

Energy Technology Data Exchange (ETDEWEB)

Chi, Yang; Zhuang, Yan; Guo, Sheng-Ping [Yangzhou Univ., Jiangsu (China). College of Chemistry and Chemical Engineering

2017-03-01

The synthesis and crystal structure of the rare earth borogermanate EuGeBO{sub 5} are reported. It is synthesized by high-temperature solid-state reaction and crystallizes in the monoclinic space group P2{sub 1}/c (no. 14) with the unit cell parameters a=4.8860(5), b=7.5229(8), c=9.9587(10) Aa, and β=91.709(3) . Its crystal structure features a polyanion-type layer (GeBO{sub 5}){sup 3-} constructed by BO{sub 4} and GeO{sub 4} tetrahedra connected alternatingly. Eu{sup 3+} ions are located in cavities and are coordinated by eight O atoms. Various structures of the related compounds REMM'O{sub 5} (RE=rare earth metal; M=Si, Ge, and Sn; M'=B, Al, and Ga) are also discussed.

Magnetic properties and structural transitions of fluorite-related rare earth osmates Ln{sub 3}OsO{sub 7} (Ln=Pr, Tb)

Energy Technology Data Exchange (ETDEWEB)

Hinatsu, Yukio, E-mail: hinatsu@sci.hokudai.ac.jp [Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo 060-0810 (Japan); Doi, Yoshihiro [Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo 060-0810 (Japan)

2013-02-15

Ternary rare-earth osmates Ln{sub 3}OsO{sub 7} (Ln=Pr, Tb) have been prepared. They crystallize in an ortho-rhombic superstructure of cubic fluorite with space group Cmcm. Both of these compounds undergo a structural phase transition at 130 K (Ln=Pr) and 580 K (Ln=Tb). These compounds show complex magnetic behavior at low temperatures. Pr{sub 3}OsO{sub 7} exhibits magnetic transitions at 8 and 73 K, and Tb{sub 3}OsO{sub 7} magnetically orders at 8 and 60 K. The Os moments become one-dimensionally ordered, and when the temperature is furthermore decreased, it provokes the ordering in the Ln{sup 3+} sublattice that simultaneously becomes three-dimensionally ordered with the Os sublattice. - Graphical abstract: Ternary rare-earth osmates Ln{sub 3}OsO{sub 7} (Ln=Pr, Tb) have been prepared. They crystallize in an orthorhombic superstructure of cubic fluorite with space group Cmcm. Both of these compounds undergo a structural phase transition at 130 K (Ln=Pr) and 580 K (Ln=Tb). These compounds show complex magnetic behavior at low temperatures. Pr{sub 3}OsO{sub 7} exhibits magnetic transitions at 8 and 73 K, and Tb{sub 3}OsO{sub 7} magnetically orders at 8 and 60 K. Highlights: Black-Right-Pointing-Pointer Ternary rare-earth osmates Ln{sub 3}OsO{sub 7} (Ln=Pr, Tb) with an ordered defect-fluorite structure have been prepared. Black-Right-Pointing-Pointer Both of these compounds undergo a structural phase transition at 130 K (Ln=Pr) and 580 K (Ln=Tb). Black-Right-Pointing-Pointer These compounds show complex magnetic behavior at low temperatures due to magnetic ordering of Ln and Os.

Enhanced NH{sub 3} gas sensing performance based on electrospun alkaline-earth metals composited SnO{sub 2} nanofibers

Energy Technology Data Exchange (ETDEWEB)

Xu, Shuang [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, Key Laboratory of Physical Chemistry, School of Chemistry and Material Science, Heilongjiang University, Harbin 150080 (China); Kan, Kan [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, Key Laboratory of Physical Chemistry, School of Chemistry and Material Science, Heilongjiang University, Harbin 150080 (China); Daqing Branch, Heilongjiang Academy of Sciences, Daqing 163319 (China); Yang, Ying; Jiang, Chao [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, Key Laboratory of Physical Chemistry, School of Chemistry and Material Science, Heilongjiang University, Harbin 150080 (China); Gao, Jun [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, Key Laboratory of Physical Chemistry, School of Chemistry and Material Science, Heilongjiang University, Harbin 150080 (China); Department of Chemistry, Harbin Normal University, Harbin 150025 (China); Jing, Liqiang [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, Key Laboratory of Physical Chemistry, School of Chemistry and Material Science, Heilongjiang University, Harbin 150080 (China); Shen, Peikang [Department of Physics and Engineering Sun Yat-sen University, Guangzhou 510275 (China); Li, Li, E-mail: llwjjhlju@sina.cn [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, Key Laboratory of Physical Chemistry, School of Chemistry and Material Science, Heilongjiang University, Harbin 150080 (China); Key Laboratory of Chemical Engineering Process and Technology for High-efficiency Conversion, School of Chemistry and Material Science, Heilongjiang University, Harbin 150080 (China); and others

2015-01-05

Highlights: • The small-sized SnO{sub 2} (5–7 nm) were obtained by adding the alkaline-earth. • Sr-composited SnO{sub 2} nanofibers showed uniform nanotubes structure (Sr/SnO{sub 2}). • Sr/SnO{sub 2} showed an excellent sensing performance to NH{sub 3} at room temperature. - Abstract: One-dimensional alkaline-earth metals composited SnO{sub 2} (Ae/SnO{sub 2}) nanofibres were fabricated via electrospinning technique, followed by thermal treatment at 600 °C for 5 h. Transmission electron microscopy (TEM) studies showed that the nanoparticles size of Ae/SnO{sub 2} was 5–7 nm, which was smaller than the pristine SnO{sub 2} nanorods attached by 20 nm nanoparticles. Moreover, Sr/SnO{sub 2} nanocomposites showed uniform nanotubes structure with the wall thickness of about 30 nm, in which all the nanoparticles were connected to their neighbors by necks. The Sr/SnO{sub 2} nanotubes exhibited an excellent sensing response toward NH{sub 3} gas at room temperature, lower detection limit (10 ppm), faster response time (6 s towards 2000 ppm∼16 s towards 10 ppm) and better reversibility compared to the pristine SnO{sub 2} nanorods. The enhanced sensor performances were attributed to the higher conductivity of the Sr/SnO{sub 2}. Mott–Schottky plots (M–S) and electrochemical impedance spectroscopy (EIS) measurements indicated that the carrier density of Sr/SnO{sub 2} nanotubes was 3 fold of that pristine SnO{sub 2}.

Synthesis, characterization, and chemical bonding analysis of the lithium alkaline-earth metal gallide nitrides Li{sub 2}(Ca{sub 3}N){sub 2}[Ga{sub 4}] and Li{sub 2}(Sr{sub 3}N){sub 2}[Ga{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Pathak, Manisha; Bobnar, Matej; Ormeci, Alim; Hoehn, Peter [Chemische Metallkunde, Max-Planck-Institut fuer Chemische Physik fester Stoffe, Dresden (Germany); Stoiber, Dominik; Niewa, Rainer [Institut fuer Anorganische Chemie, Universitaet Stuttgart (Germany); Ovchinnikov, Alexander [Chemische Metallkunde, Max-Planck-Institut fuer Chemische Physik fester Stoffe, Dresden (Germany); Department of Chemistry and Biochemistry, University of Delaware, Newark, DE (United States)

2017-11-17

Large single crystals of Li{sub 2}(Ca{sub 3}N){sub 2}[Ga{sub 4}] and Li{sub 2}(Sr{sub 3}N){sub 2}[Ga{sub 4}] up to several mm in size were grown from mixtures of the respective elements and binary alkaline-earth metal nitrides in reactive lithium melts employing a modified high-temperature centrifugation-aided filtration (HTCAF) technique. The main structural features of these isotypic phases are stella quadrangula building units [Ga{sub 4}]Li{sub 4/2} and octahedra (Nae{sub 6/2}), which form two independent interpenetrating networks. The phases crystallize in the η-carbide structure and represent diamagnetic small bandgap semiconductors. Real-space chemical bonding analysis indicates predominantly ionic bonding. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

A Study on Electrochemical Reduction of Rare Earth Oxides in Molten LiCl-Li{sub 2}O Salt

Energy Technology Data Exchange (ETDEWEB)

Lee, Min Woo; Jeong, Sang Mun; Lee, See Hoon [Chungbook National University, Chungju (Korea, Republic of); Sohn, Jung Min [Chonbuk National University, Jeonju (Korea, Republic of)

2016-05-15

In this study, the electrochemical reduction of RE{sub 2}O{sub 3} (RE = Nd or Ce) has been conducted via co-reduction NiO to increase the reduction degree of the rare earth oxides in molten molten LiCl containing 1wt% Li{sub 2}O. The electrochemical reduction behavior of the mixed RE{sub 2}O{sub 3}-NiO oxide has been investigated and the reduction path of RE{sub 2}O{sub 3} has been proposed. An electorchemical spent fuel processing technology, pyroprocessing, has been developed for recycling of spent fuel to be applied to a sodium-cooled fast reactor. The spent fuel is reduced in the oxide reduction process. It is well known that the rare earth oxides are hardly reduced due to their electrochemical and thermodynamic stability. The rare earth oxides unreduced in the reduction process can cause problems via reaction with UCl{sub 3} in the electrorefiner. To tackle those problems, the electrochemical reduction of rare earth oxide has been conducted via co-reduction of NiO in LiCl molten salt containing 1 wt% Li{sub 2}O. The reduction of the oxide mixture starts from the reduction of NiO to Ni, followed by that of RE{sub 2}O{sub 3} on the produced Ni to form intermetallic RENi{sub 5}. The mixed oxide pellets were successfully reduced to the RENi5 alloy by constant electrolysis at 3.0 V at 650 .deg. C. The crucial aspect to these results is that the thermodynamically stable rare-earth oxide, Nd{sub 2}O{sub 3} was successfully converted to the metal in the presence of NiO.

Structural flexibility in magnetocaloric RE<sub>5sub>T>4sub> (RE=rare-earth; T=Si,Ge,Ga) materials: Effect of chemical substitution on structure, bonding and properties

Energy Technology Data Exchange (ETDEWEB)

Misra, Sumohan [Iowa State Univ., Ames, IA (United States)

2008-01-01

The binary, ternary and multicomponent intermetallic compounds of rare-earth metals (RE) with group 14 elements (Tt) at the RE<sub>5sub>Tt>4sub> stoichiometry have been known for over 30 years, but only in the past decade have these materials become a gold mine for solid-state chemistry, materials science and condensed matter physics. It all started with the discovery of a giant magnetocaloric effect in Gd<sub>5sub>Si>2sub>Ge>2sub>, along with other extraordinary magnetic properties, such as a colossal magnetostriction and giant magnetoresistance. The distinctiveness of this series is in the remarkable flexibility of the chemical bonding between well-defined, subnanometer-thick slabs and the resultant magnetic, transport, and thermodynamic properties of these materials. This can be controlled by varying either or both RE and Tt elements, including mixed rare-earth elements on the RE sites and different group 14 (or T = group 13 or 15) elements occupying the Tt sites. In addition to chemical means, the interslab interactions are also tunable by temperature, pressure, and magnetic field. Thus, this system provides a splendid 'playground' to investigate the interrelationships among composition, structure, physical properties, and chemical bonding. The work presented in this dissertation involving RE<sub>5sub>T>4sub> materials has resulted in the successful synthesis, characterization, property measurements, and theoretical analyses of various new intermetallic compounds. The results provide significant insight into the fundamental magnetic and structural behavior of these materials and help us better understand the complex link between a compound's composition, its observed structure, and its properties.

Mass-radius relations and core-envelope decompositions of super-Earths and sub-Neptunes

International Nuclear Information System (INIS)

Howe, Alex R.; Burrows, Adam; Verne, Wesley

2014-01-01

Many exoplanets have been discovered with radii of 1-4 R ⊕ , between that of Earth and Neptune. A number of these are known to have densities consistent with solid compositions, while others are 'sub-Neptunes' likely to have significant H 2 -He envelopes. Future surveys will no doubt significantly expand these populations. In order to understand how the measured masses and radii of such planets can inform their structures and compositions, we construct models both for solid layered planets and for planets with solid cores and gaseous envelopes, exploring a range of core masses, H 2 -He envelope masses, and associated envelope entropies. For planets in the super-Earth/sub-Neptune regime for which both radius and mass are measured, we estimate how each is partitioned into a solid core and gaseous envelope, associating a specific core mass and envelope mass with a given exoplanet. We perform this decomposition for both ''Earth-like'' rock-iron cores and pure ice cores, and find that the necessary gaseous envelope masses for this important sub-class of exoplanets must range very widely from zero to many Earth masses, even for a given core mass. This result bears importantly on exoplanet formation and envelope evaporation processes.

Lattice-dynamical estimation of atomic thermal parameters for silicates: Forsterite. alpha. -Mg sub 2 SiO sub 4

Energy Technology Data Exchange (ETDEWEB)

Pilati, T.; Bianchi, R. (Consiglio Nazionale delle Ricerche, Milan (Italy). Centro per lo Studio delle Relazioni tra Struttura e Reattivita' Chimica); Gramaccioli, C.M. (Milan Univ. (Italy). Dipt. di Scienze della Terra)

1990-06-01

As an example of extending harmonic lattice-dynamical procedures to silicates, the atomic thermal parameters for forsterite Mg{sub 2}SiO{sub 4}, an important constituent of earth's crust, have been calculated on this basis. For this purpose, Iishi's rigid-ion model was used, with slight modifications. Although such potentials were derived exclusively from fitting IR and Raman-active frequencies, the reproduction of the phonon-dispersion curves is good, and the calculation of thermodynamic functions such as entropy provides values which are near to calorimetric estimates. The calculated atomic thermal parameters are in good agreement with the experimental values reported by most authors. The calculations at various temperatures show the effect of zero-point motion very clearly: its contribution to temperature factors is about half of the total at room temperature. Bond-length corrections for thermal libration can be applied using the general-case formula: these amount to 0.003 A for the Si-O bonds at room temperature. Although the thermal parameters in the SiO{sub 4} group fit a rigid-body model, the correction obtained using the Schomaker-Trueblood procedure gives a significantly different result: this is essentially due to the weak librational character of the motion of silicate groups in the structure. (orig.).

Effect of local perturbations of the geomagnetic field on cosmic ray cutoff rigidities at Jungfraujoch and Kiel

International Nuclear Information System (INIS)

Flueckiger, E.O.; Smart, D.F.; Shea, M.A.

1983-01-01

We have investigated the effect of local perturbations of the geomagnetic field on the vertical cosmic ray cutoff rigidities at Jungfraujoch and Kiel as representative mid-latitude neutron monitor stations. The main, effective, and Stoermer vertical cutoff rigidities and their changes were determined by utilizing the trajectory-tracing technique in a magnetic field which is modeled as a simple dipole field to which the disturbance field is superposed. It was found that the cosmic ray cutoff rigidities are most sensitive to variations of the z component of the geomagnetic field at geomagnetic latitudes -20 0 0 and at longitudes within 90 0 to the east of these northern hemisphere stations. Furthermore, cutoff rigidity variations at Kiel are predominantly due to changes of the geomagnetic field within geocentric distances 2.5R/sub E/< r<6R/sub E/, whereas at Jungfraujoch changes in cutoff rigidities are caused almost exclusively by magnetic disturbances within 1R/sub E/< r<4.5R/sub E/. For both locations the dependence of the main, effective, and Stoermer vertical cutoff rigidities on the radial, latitudinal and longitudinal structure of the magnetic perturbations is given explicitly. The results are discussed with respect to the theory by Treiman (1953) describing the effect of a ring current on cosmic ray cutoff rigidities. It is also shown that for the analysis of the characteristic properties of the correlation between cutoff rigidity variations and specific geomagnetic perturbations the rigidity corresponding to the first ''discontinuity band'' of the rigidity spectrum is an extremely useful parameter

Substitution disorder and photoluminescent property of a new rare-earth borate: K{sub 3}TbB{sub 6}O{sub 12}

Energy Technology Data Exchange (ETDEWEB)

Zhao, Dan; Ma, Fa-Xue; Huang, Min; Chen, Peng-Fei; Zhang, Rong-Hua [Henan Polytechnic Univ., Jiaozuo (China). College of Chemistry and Chemical Engineering; Zhang, Rui-Juan [Henan Polytechnic University, Jiaozuo (China). Academic Affairs Office; Wei, Wei [Capital Normal Univ., Beijing (China). Dept. of Chemistry

2016-11-01

A new rare-earth borate K{sub 3}TbB{sub 6}O{sub 12} has been prepared using the high temperature molten salt method and was structurally determined by single crystal X-ray diffraction analyses. The structure features a three-dimensional (3D) framework which is composed of isolated B{sub 5}O{sub 10}, KO{sub 6}, KO{sub 8} and TbO{sub 6} groups. An atom site in the 3{sub 2} screw axis is shared by K and Tb atoms with the molar ratio of 1:1. The self-activated photoluminescence (PL) property of K{sub 3}TbB{sub 6}O{sub 12} was studied. Under the excitation of 378 nm, the emission spectrum exhibits an intense green emission centered at 543-548 nm with the chromaticity coordinates (0.342, 0.590), which can be assigned to the {sup 5}D{sub 4} → {sup 7}F{sub 5} transition of Tb{sup 3+}. The excitation spectra cover a wide range from 330 to 385 nm, which suggests that the K{sub 3}TbB{sub 6}O{sub 12} phosphors can be effectively excited by a near-UV light source. One may expect that compound K{sub 3}TbB{sub 6}O{sub 12} can be used as a green phosphor pumped by near-UV LED chips.

Rigid'' skeleton dynamics of Li sub 3 In sub 2 (PO sub 4 ) sub 3 superionic conductor

Energy Technology Data Exchange (ETDEWEB)

Naganovsky, Y K; Sigaryov, S E [Inst. of Crystallography, Academy of Sciences, Moscow (USSR)

1992-01-01

The effect studied is made by the thermal prehistory of the Li{sub 3}In{sub 2}(PO{sub 4}){sub 3} ceramics on their structural and electrophysical characteristics. Annealing at T>1290 K is shown to result in a monoclinic (HT) and at T<1230 K, rhombohedral (LT) modifications of the crystal structure of Li{sub 3}In{sub 2}(PO{sub 4}){sub 3}. At the same temperature the ionic conductivity ({sigma}) of the HT-modification is found to be higher than that of LT-modification. Annealing of LT-ceramics at {proportional to}985 K leads to a decrease of {sigma} by as much as two order of magnitude seems due to Li{sup +}-ions redistribution in the (In{sub 2}P{sub 3}O{sub 12}){sub 3{infinity}}{sup 3-} skeleton cavities. In the 290-650 K temperature range phase transitions both in LT- and HT-Li{sub 3}In{sub 2}(PO{sub 4}){sub 3} are observed. (orig.).

Cluster model calculation for X-ray magnetic circular dichroism at rare-earth (R) L sub 2 sub , sub 3 absorption edges in R sub 2 Fe sub 1 sub 4 B

CERN Document Server

Asakura, K; Harada, I; Ogasawara, H; Fukui, K; Kotani, A

2002-01-01

X-ray magnetic circular dichroism (MCD) at the L sub 2 sub , sub 3 absorption edges for the entire series of rare-earth (RE) elements in R sub 2 Fe sub 1 sub 4 B (R=RE) is studied based on a cluster model including 10 RE and 16 Fe atoms. The cluster model takes into account band effects of RE 5d states, to which the electric dipole transition occurs from the core 2p states, as well as spin polarization of the 5d states due to the interatomic hybridization with the spin polarized Fe 3d states. We also take into account spin and orbital polarization of the 5d states due to the 5d-4f intra-atomic exchange interaction, and the 2p to 4f quadrupole transition. The calculated results are in satisfactory agreement with experimental ones, suggesting that the cluster model calculation provides a new method to calculate quantitatively MCD spectra of RE systems with complicated atomic arrangements. (author)

Calculations of the magnetic properties of R{sub 2}M{sub 14}B intermetallic compounds (R=rare earth, M=Fe, Co)

Energy Technology Data Exchange (ETDEWEB)

Ito, Masaaki, E-mail: masaaki.ito@neel.cnrs.fr [CNRS, Institut Néel, 25 rue des Martyrs, BP166, 38042 Grenoble (France); University Grenoble Alpes, Institut Néel, 38042 Grenoble (France); Advanced Material Engineering Division, Toyota Motor Corporation, Susono 410-1193 (Japan); Yano, Masao [Advanced Material Engineering Division, Toyota Motor Corporation, Susono 410-1193 (Japan); Dempsey, Nora M. [CNRS, Institut Néel, 25 rue des Martyrs, BP166, 38042 Grenoble (France); University Grenoble Alpes, Institut Néel, 38042 Grenoble (France); Givord, Dominique [CNRS, Institut Néel, 25 rue des Martyrs, BP166, 38042 Grenoble (France); University Grenoble Alpes, Institut Néel, 38042 Grenoble (France); Instituto de Fisica, Universidade Federal do Rio de Janeiro, Rio de Janeiro (Brazil)

2016-02-15

The hard magnetic properties of “R–M–B” (R=rare earth, M=mainly Fe) magnets derive from the specific intrinsic magnetic properties encountered in Fe-rich R{sub 2}M{sub 14}B compounds. Exchange interactions are dominated by the 3d elements, Fe and Co, and may be modeled at the macroscopic scale with good accuracy. Based on classical formulae that relate the anisotropy coefficients to the crystalline electric field parameters and exchange interactions, a simple numerical approach is used to derive the temperature dependence of anisotropy in various R{sub 2}Fe{sub 14}B compounds (R=Pr, Nd, Dy). Remarkably, a unique set of crystal field parameters give fair agreement with the experimentally measured properties of all compounds. This implies reciprocally that the properties of compounds that incorporate a mixture of different rare-earth elements may be predicted accurately. This is of special interest for material optimization that often involves the partial replacement of Nd with another R element and also the substitution of Co for Fe. - Highlights: • Anisotropy constants derived from CEF parameters of R{sub 2}M{sub 14}B compounds (M=Fe, Co). • Anisotropy constants of all R{sub 2}Fe{sub 14}B compounds using unique set of CEF parameters. • Moment non-collinearity in magnetization processes under B{sub app} along hard axis.

Comparative study of rare earth hexaborides using high resolution angle-resolved photoemission

Energy Technology Data Exchange (ETDEWEB)

Ramankutty, S.V., E-mail: s.v.ramankutty@uva.nl [Van der Waals-Zeeman Institute, Institute of Physics (IoP), University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); Jong, N. de; Huang, Y.K.; Zwartsenberg, B. [Van der Waals-Zeeman Institute, Institute of Physics (IoP), University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); Massee, F. [Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, NY 14853 (United States); Bay, T.V. [Van der Waals-Zeeman Institute, Institute of Physics (IoP), University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); Golden, M.S., E-mail: m.s.golden@uva.nl [Van der Waals-Zeeman Institute, Institute of Physics (IoP), University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); Frantzeskakis, E., E-mail: e.frantzeskakis@uva.nl [Van der Waals-Zeeman Institute, Institute of Physics (IoP), University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands)

2016-04-15

Highlights: • ARPES electronic structure study of rare-earth (RE) hexaborides SmB{sub 6}, CeB{sub 6} and YbB{sub 6}. • Increasing RE valence Yb[II], Sm[II/III], Ce[III] increases d-band occupancy. • YbB{sub 6} and SmB{sub 6} posses 2D states at E{sub F}, whereas the Fermi surface of CeB{sub 6} is 3D. • ARPES, LEED and STM data prove structural relaxation of the SmB{sub 6}(001) surface. - Abstract: Strong electron correlations in rare earth hexaborides can give rise to a variety of interesting phenomena like ferromagnetism, Kondo hybridization, mixed valence, superconductivity and possibly topological characteristics. The theoretical prediction of topological properties in SmB{sub 6} and YbB{sub 6} has rekindled the scientific interest in the rare earth hexaborides, and high-resolution ARPES has been playing a major role in the debate. The electronic band structure of the hexaborides contains the key to understand the origin of the different phenomena observed, and much can be learned by comparing the experimental data from different rare earth hexaborides. We have performed high-resolution ARPES on the (001) surfaces of YbB{sub 6}, CeB{sub 6} and SmB{sub 6}. On the most basic level, the data show that the differences in the valence of the rare earth element are reflected in the experimental electronic band structure primarily as a rigid shift of the energy position of the metal 5d states with respect to the Fermi level. Although the overall shape of the d-derived Fermi surface contours remains the same, we report differences in the dimensionality of these states between the compounds studied. Moreover, the spectroscopic fingerprint of the 4f states also reveals considerable differences that are related to their coherence and the strength of the d–f hybridization. For the SmB{sub 6} case, we use ARPES in combination with STM imaging and electron diffraction to reveal time dependent changes in the structural symmetry of the highly debated SmB{sub 6

Luminescence of rare-earth ions in Mg[sub 2]SiO[sub 4

Energy Technology Data Exchange (ETDEWEB)

Van der Voort, D; Maat-Gersdorf, I de; Blasse, G [Rijksuniversiteit Utrecht (Netherlands)

1992-01-01

The luminescence of the rare-earth ions Eu[sup 3+], Tb[sup 3+] and Ce[sup 3+] in Mg[sub 2]SiO[sub 4] is reported. The Tb[sup 3+] ion shows a change in emission colour from blue to green depending on the charge compensator. This is ascribed to a difference in coupling of the Tb[sup 3+] ion to the vibrational lattice modes. The Eu[sup 3+] ion has an average quantum efficiency under charge-transfer excitation of 60% at 4.2 and 20% at 300 K. The Ce[sup 3+] emission is situated in the blue and shows a Stokes shift of 3 500 cm[sup -1]. The relaxation of these ions in the excited state is discussed in terms of their positive effective charge and the stiffness of their surroundings.

Pressure dependence of magnetic ordering temperatures of rare earth-Sn/sub 3/ compounds

Energy Technology Data Exchange (ETDEWEB)

Foner, S [Massachusetts Inst. of Tech., Cambridge (USA). Francis Bitter National Magnet Lab.

1979-12-01

Measurements of the hydrostatic pressure dependence of the Neel temperatures, Tsub(N), are reported for PrSn/sub 3/, NdSn/sub 3/, GdSn/sub 3/ and CeIn/sub 3/. Tsub(N) is found to increase with applied pressure for PrSn/sub 3/ and NdSn/sub 3/, whereas Tsub(N) is pressure independent within experimental error for GdSn/sub 3/ and CeIn/sub 3/. Slightly Sn-deficient RESn/sub 3/ (RE = rare earth) compounds are found consistently to be weakly ferromagnetic. The physical properties of the RESn/sub 3/ compounds exhibit analogies with the corresponding properties of dilute superconducting (LaRE)Sn/sub 3/ alloys. The high pressure data for PrSn/sub 3/ and CeIn/sub 3/ are qualitatively consistent with a 'Kondo necklace' model for magnetically ordered RE compounds with unstable 4f shells.

Pressure dependence of magnetic ordering temperatures of rare earth - Sn/sub 3/ compounds

Energy Technology Data Exchange (ETDEWEB)

DeLong, L E [Virginia Univ., Charlottesville (USA). Dept. of Physics; Guertin, R P; Foner, S

1979-12-01

Measurements of the hydrostatic pressure dependence of the Neel temperatures, Tsub(N), are reported for PrSn/sub 3/, NdSn/sub 3/, GdSn/sub 3/ and CeIn/sub 3/. Tsub(N) is found to increase with applied pressure for PrSn/sub 3/ and NdSn/sub 3/, whereas Tsub(N) is pressure independent within experimental error for GdSn/sub 3/ and CeIn/sub 3/. Slightly Sn-deficient RESn/sub 3/ (RE=rare earth) compounds are found consistently to be weakly ferromagnetic. The physical properties of the RESn/sub 3/ compounds exhibit analogies with the corresponding properties of dilute superconducting (LaRE)Sn/sub 3/ alloys. The high pressure data for PrSn/sub 3/ and CeIn/sub 3/ are qualitatively consistent with a 'Kondo necklace' model for magnetically ordered RE compounds with unstable 4f shells.

Synthesis of three-dimensional rare-earth ions doped CNTs-GO-Fe{sub 3}O{sub 4} hybrid structures using one-pot hydrothermal method

Energy Technology Data Exchange (ETDEWEB)

Gao, Guo, E-mail: guogao@sjtu.edu.cn [Institute of Nano Biomedicine and Engineering, Department of Instrument Science and Technology, Key Laboratory for Thin Film and Microfabrication Technology of Ministry of Education, School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Zhang, Qiang; Cheng, Xin-Bing [Beijing Key Laboratory of Green Chemical Reaction Engineering and Technology, Department of Chemical Engineering, Tsinghua University, Beijing 100084 (China); Sun, Rongjin [Institute of Nano Biomedicine and Engineering, Department of Instrument Science and Technology, Key Laboratory for Thin Film and Microfabrication Technology of Ministry of Education, School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Shapter, Joseph G., E-mail: joe.shapter@flinders.edu.au [School of Chemical and Physical Sciences, Flinders University, Bedford Park, Adelaide 5042 (Australia); Yin, Ting [Institute of Nano Biomedicine and Engineering, Department of Instrument Science and Technology, Key Laboratory for Thin Film and Microfabrication Technology of Ministry of Education, School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Cui, Daxiang, E-mail: dxcui@sjtu.edu.cn [Institute of Nano Biomedicine and Engineering, Department of Instrument Science and Technology, Key Laboratory for Thin Film and Microfabrication Technology of Ministry of Education, School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China)

2015-11-15

Rechargeable lithium ion batteries (LIBs) are currently the dominant power source for all sorts of electronic devices due to their low cost and high energy density. The cycling stability of LIBs is significantly compromised due to the broad satellite peak for many anode materials. Herein, we develop a facile hydrothermal process for preparing rare-earth (Er, Tm) ions doped three-dimensional (3D) transition metal oxides/carbon hybrid nanocomposites, namely CNTs-GO-Fe{sub 3}O{sub 4}, CNTs-GO-Fe{sub 3}O{sub 4}-Er and CNTs-GO-Fe{sub 3}O{sub 4}-Tm. The GO sheets and CNTs are interlinked by ultrafine Fe{sub 3}O{sub 4} nanoparticles forming three-dimensional (3D) architectures. When evaluated as anode materials for LIBs, the CNTs-GO-Fe{sub 3}O{sub 4} hybrid composites have a bigger broad satellite peak. As for the CNTs-GO-Fe{sub 3}O{sub 4}-Er and CNTs-GO-Fe{sub 3}O{sub 4}-Tm hybrid composites, the broad satellite peak can be completely eliminated. When the current density changes from 5 C back to 0.1 C, the capacity of CNTs-GO-Fe{sub 3}O{sub 4}-Tm hybrid composites can recover to 1023.9 mAhg{sup −1}, indicating an acceptable rate capability. EIS tests show that the charge transfer resistance does not change significantly after 500 cycles, demonstrating that the cycling stability of CNTs-GO-Fe{sub 3}O{sub 4}-Tm hybrid composites are superior to CNTs-GO-Fe{sub 3}O{sub 4} and CNTs-GO-Fe{sub 3}O{sub 4}-Er hybrid structures. - Graphical abstract: One-pot hydrothermal method for synthesis of rare-earth ions doped CNTs-GO-Fe{sub 3}O{sub 4} hybrid structures as anode materials of LIBs have been reported. - Highlights: • We report the synthesis of rare-earth ions doped CNTs-GO-Fe{sub 3}O{sub 4} hybrid structures. • The hybrid structures can improve the cycling stability of lithium storage. • As for anode materials, the broad satellite peak can be completely eliminated. • When the rate return back to 0.1 C, the capacity can recover to 1023.9 mAhg{sup −1}. • After 500

Computer modelling of defect structure and rare earth doping in LiCaAlF sub 6 and LiSrAlF sub 6

CERN Document Server

Amaral, J B; Valerio, M E G; Jackson, R A

2003-01-01

This paper describes a computational study of the mixed metal fluorides LiCaAlF sub 6 and LiSrAlF sub 6 , which have potential technological applications when doped with a range of elements, especially those from the rare earth series. Potentials are derived to represent the structure and properties of the undoped materials, then defect properties are calculated, and finally solution energies for rare earth elements are calculated, enabling preferred dopant sites and charge compensation mechanisms to be predicted.

Rare earth oxide reinforced Al{sub 2}O{sub 3}-TiO{sub 2} ceramics for inert coating of metallic parts for petroleum extraction

Energy Technology Data Exchange (ETDEWEB)

Yadava, Yoggendra Prasad; Rego, Sheila Alves Bezerra da Costa; Ferreira, Ricardo Artur Sanguinetti [Universidade Federal de Pernambuco (UFPE), Recife (Brazil)

2012-07-01

Recent findings of largest known pre-salt petroleum reservoir in Brazil have created an intense demand for new materials capable of withstanding direct contact with the crude petroleum as it is a highly corrosive and chemically reactive fluid. Petroleum drilling equipment, storage tanks and transportation systems suffer from constant physical stress caused by chemical attack of crude petroleum on its structure. Ceramics are materials with high chemical stability in hostile environment and therefore can be used as an inert coating material to resolve such problems. To date, ceramics based on alumina are most widely used in practice where there is demand for high mechanical strength and high fracture toughness. However intrinsic fragility of ceramics is still a fatal factor for their use in mechanical structures. To improve these characteristics, usually ceramics are reinforced with one or more ceramic additives. Mechanical properties of alumina based ceramics improve considerably with the addition of TiO{sub 2}, TiN, ZrO{sub 2} etc. ceramic additives. Nucleation and propagation of cracks is a major problem for ceramic coating applications. Initial studies show that addition of small percentages of rare earth oxides can increase the toughness of the alumina based ceramics. In the present work, we have produced rare-earth oxide (CeO{sub 2}) reinforced Al{sub 2}O{sub 3}-TiO{sub 2} ceramics in proportions of 5-20 wt% TiO{sub 2} and 2%wt% CeO{sub 2} through thermomechanical processing and sintering techniques and studied there microstructural characteristics and mechanical properties. To evaluate the potential of these ceramics as inert coatings for crude petroleum extraction, storage and transportation systems, we have studied the physic-chemical and mechanical stability of these ceramics in crude petroleum environment. Our studies presented satisfactory results in terms of physic-chemical and mechanical stability of these materials for the use of 2wt% of CeO{sub 2

Self-propagating high temperature synthesis, structural morphology and magnetic interactions in rare earth Ho{sup 3+} doped CoFe{sub 2}O{sub 4} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Lohar, K.S. [Materials Research Laboratory, Srikrishna Mahavidyalaya Gunjoti, Omerga, Osmanabad 413 613, MS (India); Pachpinde, A.M.; Langade, M.M. [Department of Chemistry, Jawahar Art Science and Commerce College Andur, Osmanabad, MS (India); Kadam, R.H. [Materials Research Laboratory, Srikrishna Mahavidyalaya Gunjoti, Omerga, Osmanabad 413 613, MS (India); Shirsath, Sagar E., E-mail: shirsathsagar@hotmail.com [Spin Device Technology Center, Department of Information Engineering, Shinshu University, Nagano 380-8553 (Japan)

2014-08-01

Highlights: • Rare earth Ho{sup 3+} substituted CoFe{sub 2}O{sub 4.} • XRD and IR spectra reveal the spinel structure. • Magnetization and coercivity increased with Ho{sup 3+} substitution. - Abstract: Substitution effect of rare earth trivalent Ho{sup 3+} ions on the composition, Ho{sub x}CoFe{sub 2−x}O{sub 4}, with x varying from 0.0 to 0.1 in steps of 0.025 using sol–gel auto combustion route has been investigated. Examination of X-ray diffraction (XRD) patterns shows that all the samples consisted of ferrite phases of typical spinel cubic structure, and when Ho{sup 3+} ion content was x ⩾ 0.075, orthoferrite–HoFeO{sub 3} phase was detected. The micro and nanostructure of the synthesized Ho doped CoFe{sub 2}O{sub 4} ferrites were investigated by scanning and transmission electron microscopy respectively. With increasing doping content of Ho{sup 3+} ions, the lattice constant, particle size and bulk density increased, and after an increase to its maximum value, the sample particle size and density dropped down. Cation distribution estimated from XRD patter revealed that the Co{sup 2+} and Ho{sup 3+} ions prefer to occupy octahedral B-site whereas Fe{sup 3+} ions are distributed over tetra- and octa-hedral site. Oxygen positional parameter shows larger values than its ideal value. The analysis of magnetic properties revealed that the saturation magnetization and coercivity of CoFe{sub 2}O{sub 4} increased with the rare earth Ho{sup 3+} substitution.

Structural, optical and spectroscopical investigations into rare-earths perowskites RGaO{sub 3} (R=La, Pr, Nd) and NdBa-2Cu{sub 3}O{sub 7-{delta}}; Strukturelle, optische und spektroskopische Untersuchungen von Seltenen-Erd-Perowskiten RGaO{sub 3} (R=La, Pr, Nd) und NdBa{sub 2}Cu{sub 3}O{sub 7-{delta}}

Energy Technology Data Exchange (ETDEWEB)

Marti, W. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

1995-07-01

In this work I was engaged in rare-earth perovskites. Primarily I investigated the structure of the rare-earth gallates RGaO{sub 3} (R=La, Pr, Nd) as a function of the temperature by means of neutron diffraction and x-ray diffraction. As the high-T{sub c} superconductors these compounds belong to the family of the perovskites, they are ferroelastic and centro-symmetric. Because of the lanthanide-contraction all lattice constants and distortion parameters change systematically. The rare-earth-gallates RGaO{sub 3} (R=La, Pr, Nd) are promising substrates for epitaxy of high-T{sub c} superconductors like RBa{sub 2}Cu{sub 3}OO{sub 7-{delta}} because of their structure parameters and expansion coefficients. I succeeded in producing plane-parallel single-domain crystals by means of uniaxial stress. The first order phase transition was observable only in LaGaO{sub 3}. A structurally phase transition from orthorhombic to rhombohedral symmetry (high-temperature phase) occurs at 423 K. The hysteresis of the phase transition temperature of about 1.5 K was measured with single-domain crystals by means of neutron diffraction and polarized light microscopy. In NdGaO{sub 3} we determined the long-range, three-dimensional, antiferromagnetic ordering of the Nd{sup 3+}-ions below the ordering temperature at T{sub N}=0.97 K by means of magnetic neutron diffraction. The spin configuration could be described by a (--c{sub z})-mode. Measurements of the magnetic susceptibility confirm the easy direction of magnetization to be the c-axis. Below 300mK an additional nuclear spin polarization due to the hyperfine-interaction appears parallel to the electronic spins, which amounts to 70% at 10mK. Further I investigated the optical properties of the rare-earth gallates. The birefringence of plane-parallel, polished single-domain crystals with thickness up to 300 {mu}m was measured by means of orthoscopy and conoscopy. (author) figs., tabs., refs.

Syntheses, crystal structures and photoluminescence properties of two rare-earth molybdates CsLn(MoO{sub 4}){sub 2} (Ln=Eu, Tb)

Energy Technology Data Exchange (ETDEWEB)

Zhao, Dan; Ma, Fa-Xue; Liu, Bao-Zhong; Fan, Yun-Chang; Han, Xue-Feng; Zhang, Lei; Nie, Cong-Kui [Henan Polytechnic Univ. (China). College of Chemistry and Chemical Engineering

2018-04-01

Single crystals of two cesium rare-earth molybdates CsLn(MoO{sub 4}){sub 2} (Ln=Eu, Tb) have been prepared using the high temperature molten salt (flux) method. Single-crystal X-ray diffraction analyses reveal that they crystallize in the orthorhombic space group Pccm (No. 49) and features a 2D layer structure that is composed of [Ln(MoO{sub 4}){sub 2}]{sub ∞} and [Cs]{sub ∞} layers. Under near-UV light excitation, emission spectrum of CsEu(MoO{sub 4}){sub 2} consists of several sharp lines due to the characteristic electronic transitions of Eu{sup 3+} ions, whereas CsTb(MoO{sub 4}){sub 2} exhibits characteristic green emission of Tb{sup 3+} ions.

CeNi{sub 3}-type rare earth compounds: crystal structure of R{sub 3}Co{sub 7}Al{sub 2} (R=Y, Gd–Tm) and magnetic properties of {Gd–Er}{sub 3}Co{sub 7}Al{sub 2}, {Tb, Dy}{sub 3}Ni{sub 8}Si and Dy{sub 3}Co{sub 7.68}Si{sub 1.32}

Energy Technology Data Exchange (ETDEWEB)

Morozkin, A.V., E-mail: morozkin@tech.chem.msu.ru [Department of Chemistry, Moscow State University, Leninskie Gory, House 1, Building 3, GSP-1, Moscow 119991 (Russian Federation); Yapaskurt, V.O. [Department of Petrology, Geological Faculty Moscow State University, Leninskie Gory, Moscow 119991 (Russian Federation); Nirmala, R. [Indian Institute of Technology Madras, Chennai 600 036 (India); Quezado, S.; Malik, S.K. [Departamento de Física Teórica e Experimental, Universidade Federal do Rio Grande do Norte, Natal 59082-970 (Brazil)

2017-03-15

The crystal structure of new CeNi{sub 3}-type {Y, Gd–Tm}{sub 3}Co{sub 7}Al{sub 2} (P63/mmc. N 194, hP24) compounds has been established using powder X-ray diffraction studies. The magnetism of Tb{sub 3}Ni{sub 8}Si and Dy{sub 3}Ni{sub 8}Si is dominated by rare earth sublattice and the magnetic properties of R{sub 3}Co{sub 7}Al{sub 2} (R =Gd–Er) and Dy{sub 3}Co{sub 7.68}Si{sub 1.32} are determined by both rare earth and cobalt sublattices. Magnetization data indicate ferromagnetic ordering of {Tb, Dy}{sub 3}Ni{sub 8}Si at 32 K and 21 K, respectively. Gd{sub 3}Co{sub 7}Al{sub 2} and Tb{sub 3}Co{sub 7}Al{sub 2} exhibit ferromagnetic ordering at 309 K and 209 K, respectively, whereas Dy{sub 3}Co{sub 7}Al{sub 2}, Ho{sub 3}Co{sub 7}Al{sub 2}, Er{sub 3}Co{sub 7}Al{sub 2} and Dy{sub 3}Co{sub 7.68}Si{sub 1.32} show a field dependent ferromagnetic-like ordering at 166 K, 124 K, 84 K and 226 K, respectively followed by a low temperature transition at 34 K for Dy{sub 3}Co{sub 7}Al{sub 2}, 18 K for Ho{sub 3}Co{sub 7}Al{sub 2}, 56 K for Er{sub 3}Co{sub 7}Al{sub 2}, 155 K and 42 K for Dy{sub 3}Co{sub 7.68}Si{sub 1.32}. Among these compounds, Dy{sub 3}Ni{sub 8}Si shows largest magnetocaloric effect (isothermal magnetic entropy change) of −11.6 J/kg·K at 18 K in field change of 50 kOe, whereas Tb{sub 3}Co{sub 7}Al{sub 2}, Dy{sub 3}Co{sub 7}Al{sub 2} and Dy{sub 3}Co{sub 7.68}Si{sub 1.32} exhibit best permanent magnet properties in the temperature range of 2–5 K with remanent magnetization of 11.95 μ{sub B}/fu, 12.86 μ{sub B}/fu and 14.4 μ{sub B}/fu, respectively and coercive field of 3.0 kOe, 1.9 kOe and 4.4 kOe, respectively. - Highlights: • {Y, Gd–Tm}{sub 3}Co{sub 7}Al{sub 2} compounds crystallize in the CeNi{sub 3}-type structure. • {Gd-Er}{sub 3}Co{sub 7}Al{sub 2} show ferrimagnetic ordering at 309 K, 209 K, 166 K, 124 K and 84 K. • Dy{sub 3}Co{sub 7.68}Si{sub 1.32} exhibits magnetic transitions at 226 K, 155 K and 42 K. • {Tb-Er}{sub 3}Co{sub 7}Al{sub 2

Synthesis, structures, and luminescent properties of sodium rare-earth metal(III) chloride oxotellurates(IV), Na{sub 2}Ln{sub 3}Cl{sub 3}[TeO{sub 3}]{sub 4} (Ln = Sm, Eu, Gd, Tb, Dy, and Ho)

Energy Technology Data Exchange (ETDEWEB)

Charkin, Dmitri O.; Dorofeev, Sergey G.; Berdonosov, Peter S.; Dolgikh, Valery A. [Department of Chemistry, Lomonosov Moscow State University (Russian Federation); Zitzer, Sabine; Greiner, Stefan; Schleid, Thomas [Institut fuer Anorganische Chemie, Universitaet Stuttgart (Germany); Olenev, Andrei V. [Department of Chemistry, Lomonosov Moscow State University (Russian Federation); Sine Theta Ltd., Moscow (Russian Federation)

2017-11-17

Six sodium rare-earth metal(III) chloride oxotellurates(IV), Na{sub 2}Ln{sub 3}Cl{sub 3}[TeO{sub 3}]{sub 4}, isostructural to Na{sub 2}Y{sub 3}Cl{sub 3}[TeO{sub 3}]{sub 4}, were synthesized by flux techniques and characterized by single-crystal XRD. The compounds crystallize in the monoclinic space group C2/c with lattice constants a = 23.967(1), b = 5.6342(3), c = 16.952(1) Aa, β = 134.456(5) for Ln = Sm, a = 23.932(2), b = 5.6044(5), c = 17.134(1) Aa, β = 135.151(6) for Ln = Eu, a = 23.928(1), b = 5.5928(1), c = 17.1133(8) Aa, β = 135.366(3) for Ln = Gd, a = 23.907(1), b = 5.569(3), c = 16.745(1) Aa, β = 134.205(3) for Ln = Tb, a = 23.870(1), b = 5.547(3), c = 16.665(1) Aa, β = 134.102(3) for Ln = Dy, and a = 23.814(1), b = 5.526(3), c = 16.626(1) Aa, β = 134.016(3) for Ln = Ho and Z = 4. Their crystal structure can be considered as a framework built of intergrowing Ln-O and Na-(O,Cl) slabs with channel walls decorated by tellurium atoms of [TeO{sub 3}]{sup 2-} groups. The luminescent properties of the new compounds due to the Ln{sup 3+} cations are described and discussed. We also discuss the crystal chemistry of various alkali-metal rare-earth metal(III) halide oxochalcogenates(IV). (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Conditions for oceans on Earth-like planets orbiting within the habitable zone: importance of volcanic CO{sub 2} degassing

Energy Technology Data Exchange (ETDEWEB)

Kadoya, S. [Department of Earth and Planetary Science, The University of Tokyo, Kiban Bldg. 408, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan); Tajika, E., E-mail: kadoya@astrobio.k.u-tokyo.ac.jp, E-mail: tajika@astrobio.k.u-tokyo.ac.jp [Department of Complexity Science and Engineering, The University of Tokyo, Kiban Bldg. 409, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan)

2014-08-01

Earth-like planets in the habitable zone (HZ) have been considered to have warm climates and liquid water on their surfaces if the carbonate-silicate geochemical cycle is working as on Earth. However, it is known that even the present Earth may be globally ice-covered when the rate of CO{sub 2} degassing via volcanism becomes low. Here we discuss the climates of Earth-like planets in which the carbonate-silicate geochemical cycle is working, with focusing particularly on insolation and the CO{sub 2} degassing rate. The climate of Earth-like planets within the HZ can be classified into three climate modes (hot, warm, and snowball climate modes). We found that the conditions for the existence of liquid water should be largely restricted even when the planet is orbiting within the HZ and the carbonate-silicate geochemical cycle is working. We show that these conditions should depend strongly on the rate of CO{sub 2} degassing via volcanism. It is, therefore, suggested that thermal evolution of the planetary interiors will be a controlling factor for Earth-like planets to have liquid water on their surface.

Magnetic sublattices in Np{sub 2}Co{sub 17} and Np{sub 2}Ni{sub 17}

Energy Technology Data Exchange (ETDEWEB)

Colineau, E., E-mail: eric.colineau@ec.europa.eu; Hen, A. [Institute for Transuranium Elements (ITU), European Commission, Joint Research Centre (JRC) (Germany); Sanchez, J.-P. [CEA, INAC-SPSMS (France); Griveau, J.-C.; Magnani, N.; Eloirdi, R. [Institute for Transuranium Elements (ITU), European Commission, Joint Research Centre (JRC) (Germany); Halevy, I. [Ben Gurion University, Nuclear Engineering Department (Israel); Gaczyński, P. [Institute for Transuranium Elements (ITU), European Commission, Joint Research Centre (JRC) (Germany); Orion, I. [Ben Gurion University, Nuclear Engineering Department (Israel); Shick, A. B. [Institute of Physics, ASCR (Czech Republic); Caciuffo, R. [Institute for Transuranium Elements (ITU), European Commission, Joint Research Centre (JRC) (Germany)

2016-12-15

Rare-earth-based compounds R{sub 2}T{sub 17} (R=Rare earth; T=Transition metal) have been extensively studied and developed for applications as permanent magnets. The actinide-based analogues, however, are much less documented and we report here about the magnetic properties of Np{sub 2}Co{sub 17} and Np{sub 2}Ni{sub 17}, as inferred from {sup 237}Np Mössbauer spectroscopy, the best resonance in actinides, and specific heat.

Influence of the terrestrial magnetic field geometry on the cutoff rigidity of cosmic ray particles

International Nuclear Information System (INIS)

Herbst, K.; Kopp, A.; Heber, B.

2013-01-01

Studies of the propagation of charged energetic particles in the Earth's magnetic field go back to Carl Stoermer. In the end, his investigations finally lead to the definition of the so-called cutoff rigidity RC; that is, the minimum momentum per charge a particle must have in order to reach a certain geographical location. Employing Monte Carlo simulations with the PLANETOCOSMICS code we investigate the correlation between the geomagnetic field structure and the cutoff rigidity. We show that the geometry of the magnetic field has a considerable influence on the resulting cutoff rigidity distribution. Furthermore, we will present a simple geometry-based parameter, δB, which is able to reflect the location-dependent cutoff rigidity. We show that this correlation is also visible in the temporal evolution of the Earth's magnetic field, at least over the last 100 yr. Using latitude scans with neutron monitors, changes of the relative counting rates at different positions are calculated, showing small variations for, e.g., Kiel and Moscow, while large ones occur at Mexico City as well as on the British Virgin Islands.

Activity of RE/sub 2/O/sub 3/ in liquid La/sub 2/O/sub 3/-Al/sub 2/O/sub 3/-CaF/sub 2/ and Ce/sub 2/O/sub 3/-CaO-CaF/sub 2/ slags

International Nuclear Information System (INIS)

Changzhen, W.; Shuqing, Y.; Qieng, D.

1985-01-01

In the course of electro-slag refining, if the slag contains rare earth oxides, the amount of rare earth introduced to the steel depends on the composition of the slag and other conditions. The main aim of this investigation is to study the activity of RE/sub 2/O/sub 3/ in the electro-slags of various compositions. One is the La/sub 2/O/sub 3/-CaO-CaF/sub 2/ ternary slag system and the other is the Ce/sub 2/O/sub 3/-CaO-CaF/sub 2/ slag system. The iso-activity diagram for RE/sub 2/O/sub 3/ and the liquid boundary for slags system were estimated

Photoluminescence of trivalent rare earths in perovskite stacking polytypes Ba/sub 2/Lasub(2-x)REsub(x)/sup 3 +/MgW/sub 2/vacantO/sub 12/, Ba/sub 6/Ysub(2-x)REsub(x)/sup 3 +/W/sub 3/vacantO/sub 18/, and Sr/sub 8/SrGdsub(2-x)REsub(x)/sup 3 +/W/sub 4/vacantO/sub 24/

Energy Technology Data Exchange (ETDEWEB)

Kemmler-Sack, S [Tuebingen Univ. (Germany, F.R.). Lehrstuhl fuer Anorganische Chemie 2

1981-12-01

Rhombohedral 12 L staking polytypes Ba/sub 2/Lasub(2-x)REsub(x)/sup 3 +/MgW/sub 2/vacantO/sub 12/ show with RE/sup 3 +/ = Pr, Sm, Eu, Tb, Dy, Ho, Er, Tm; the 18 L stacking polytypes Ba/sub 6/Ysub(2-x)REsub(x)/sup 3 +/W/sub 3/vacantO/sub 18/ and the polymorphic perovskites Sr/sub 8/SrGdsub(2-x)REsub(x)/sup 3 +/W/sub 4/vacantO/sub 24/ with RE/sup 3 +/ = Sm, Eu, Dy, Ho, Er visible photoluminescence. The concentration dependence and the influence of the coordination number of the rare earth are reported.

Low-temperature SCR of NO with NH{sub 3} over activated semi-coke composite-supported rare earth oxides

Energy Technology Data Exchange (ETDEWEB)

Wang, Jinping; Yan, Zheng; Liu, Lili; Zhang, Yingyi; Zhang, Zuotai; Wang, Xidong, E-mail: xidong@pku.edu.cn

2014-08-01

The catalysts with different rare earth oxides (La, Ce, Pr and Nd) loaded onto activated semi-coke (ASC) via hydrothermal method are prepared for the selective catalytic reduction (SCR) of NO with NH{sub 3} at low temperature (150–300 °C). It is evidenced that CeO{sub 2} loaded catalysts present the best performance, and the optimum loading amount of CeO{sub 2} is about 10 wt%. Composite catalysts by doping La, Pr and Nd into CeO{sub 2} are prepared to obtain further improved catalytic properties. The SCR mechanism is investigated through various characterizations, including XRD, Raman, XPS and FT-IR, the results of which indicate that the oxygen defect plays an important role in SCR process and the doped rare earth elements effectively serve as promoters to increase the concentration of oxygen vacancies. It is also found that the oxygen vacancies in high concentration are favored for the adsorption of O{sub 2} and further oxidation of NO, which facilitates a rapid progressing of the following reduction reactions. The SCR process of NO with NH{sub 3} at low temperature over the catalysts of ASC composite-supported rare earth oxides mainly follows the Langmuir–Hinshlwood mechanism.

Unusual pressure dependence of the crystallographic structure in RNiO{sub 3} perovskites (R = rare earth)

Energy Technology Data Exchange (ETDEWEB)

Medarde, M.; Mesot, J.; Rosenkranz, S. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Lacorre, P. [Lab. Fluorures, Le Mans (France); Marshall, W.; Loveday, J.S. [Edinburgh Univ. (United Kingdom); Klotz, S.; Hamel, G. [Paris-6 Univ., 75 (France)

1997-09-01

We report the first experimental observation of a pressure-induced structural phase transition in the RNiO{sub 3} series (R = rare earth). At {approx_equal} 40 kbar, the space group of NdNiO{sub 3} changes from Pbnm(orthorhombic) to the PrNiO{sub 3} indicating that the symmetry of the structure increases with pressure. (author) 1 fig., 7 refs.

Studies on the Ln/sub 2/O/sub 3/ (Ln: rare-earth elements)-SrO-V/sub 2/O/sub 3/ system, 1. Phase diagrams at 1400/sup 0/C

Energy Technology Data Exchange (ETDEWEB)

Shin-ike, T [Osaka Dental Coll., Hirakata (Japan); Adachi, G; Shiokawa, J

1980-11-01

Rare-earth oxides Ln/sub 2/O/sub 3/ (Ln : Nd, Eu or Er), strontium oxide SrO and vanadium oxide V/sub 2/O/sub 3/ were mixed in a given molecular ratio, heated at 1400/sup 0/C in vacuum. The products were examined by an x-ray diffraction method to study the phase relations of the ternary systems. On heating, part of the trivalent vanadium was oxidized to the tetravalent state by atmospheric oxygen. In this experimental condition, the following ternary-phase solid solutions were identified: perovskite type Nd sub(1-x)Sr sub(x)VO sub(3-0.1x) (x > 0.3. cubic, x < 0.3: orthorhombic) and Eu sub(1-x)Sr sub(x)VO sub(3-0.1x) (x > 0.4: cubic, x < 0.4: orthorhombic), K/sub 2/NiF/sub 4/ type SrO.Nd sub(1-x)Sr sub(x)VO sub(3-0.1x) (x > 0.3) and SrO.Eu sub(1-x)Sr sub(x)VO sub(3-0.1x) (x > 0.4) and Eu/sub 3/Ti/sub 2/O/sub 7/ type SrO.2Nd sub(1-x)Sr sub(x)VO sub(3-0.1x) (x > 0.3) and SrO.2Eu sub(1-x)Sr sub(x)VO sub(3-0.1x) (x > 0.4). For the Er/sub 2/O/sub 3/-SrO-V/sub 2/O/sub 3/ system, only a mixture of Er/sub 2/O/sub 3/, SrVO sub(2.9), ErVO/sub 3/, SrO and V/sub 2/O/sub 3/ was obtained.

Angle-resolved photoemission spectroscopy of rare earth LaSb{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Michiardi, Matteo; Arnold, Fabian; Faerch Fisher, Karl Frederik; Svane, Axel; Bianchi, Marco; Brummerstedt Iversen, Bo; Hofmann, Philip [Aarhus University (Denmark); Shwetha, G.; Kanchana, V. [IIT-Hyderabad (India); Ganapathy, Vaitheeswaran [University of Hyderabad (India)

2016-07-01

Several rare earth diantimonides have been found to exhibit intriguing electronic properties such as anisotropic linear and non-saturating magnetoresistance. Among these materials, LaSb{sub 2} is not only considered for application in magnetoresistive devices but it is also found to be superconducting at low temperatures and it is investigated as candidate material to host charge density wave phases. Despite the several studies on its transport properties, the electronic structure of LaSb{sub 2} is still largely unknown. Here we present an angle-resolved photoemission spectroscopy and ab-initio calculation study of LaSb{sub 2}(001). The observed band structure is found to be in good agreement with theoretical predictions. Our results reveal that LaSb{sub 2} is a semimetal with a strongly nested two-dimensional Fermi surface. The low energy spectrum is characterized by four massive hole pockets and by four shallow, strongly directional, electron pockets that exhibit Dirac-like dispersion. We speculate on the possibility that this peculiar electronic structure drives the magnetoresistance to its quantum limit, explaining its unconventional behavior.

Optimization of L1{sub 0} FePt/Fe{sub 45}Co{sub 55} thin films for rare earth free permanent magnet applications

Energy Technology Data Exchange (ETDEWEB)

Giannopoulos, G., E-mail: g.giannopoulos@inn.demokritos.gr; Psycharis, V.; Niarchos, D. [INN, NCSR Demokritos, Athens 15310 (Greece); Reichel, L. [IFW Dresden, P.O. Box 270116, 01171 Dresden (Germany); TU Dresden, Institute for Materials Science, 01062 Dresden (Germany); Markou, A.; Panagiotopoulos, I. [Department of Materials Science and Engineering, University of Ioannina, Ioannina 45110 (Greece); Damm, C.; Fähler, S. [IFW Dresden, P.O. Box 270116, 01171 Dresden (Germany); Khan, Imran; Hong, Jisang [Department of Physics, Pukyong National University, Busan 608-737 (Korea, Republic of)

2015-06-14

The magnetic properties of magnetron sputtered bilayers consisting of Fe{sub 45}Co{sub 55} ultrathin layers on top of L1{sub 0} FePt films epitaxially grown on MgO substrates are studied in view of their possible application as rare earth free permanent magnets. It is found that FePt layers induce a tetragonal distortion to the Fe-Co layers which leads to increased anisotropy. This allows to take advantage of the Fe-Co high magnetic moment with less significant loss of the coercivity compared to a typical hard/soft exchange spring system. A maximum energy product approaching 50 MGOe is obtained for a FePt(7 ML)/FeCo/(5 ML) sample. The results are in accordance with first-principles computational methods, which predict that even higher energy products are possible for micromagnetically optimized microstructures.

Effects of Majorana physics on the UHE ν{sub τ} flux traversing the Earth

Energy Technology Data Exchange (ETDEWEB)

Duarte, Lucia [Universidad de la Republica, Instituto de Fisica, Facultad de Ingenieria, Montevideo (Uruguay); Romero, Ismael; Zapata, Gabriel; Sampayo, Oscar A. [Universidad Nacional de Mar del Plata, Instituto de Investigaciones Fisicas de Mar del Plata (IFIMAR), CONICET, UNMDP, Departamento de Fisica, Mar del Plata (Argentina)

2017-02-15

We study the effects produced by sterile Majorana neutrinos on the ν{sub τ} flux traversing the Earth, considering the interaction between the Majorana neutrinos and the standard matter as modeled by an effective theory. The surviving tau-neutrino flux is calculated using transport equations including Majorana neutrino production and decay. We compare our results with the pure Standard Model interactions, computing the surviving flux for different values of the effective lagrangian couplings, considering the detected flux by IceCube for an operation time of 10 years, and Majorana neutrinos with mass m{sub N} ∝ m{sub τ}. (orig.)

Rare-earths influence in the thermoluminescent response of monoclinic ZrO{sub 2}; Influencia de tierras raras en la respuesta termoluminiscente de ZrO{sub 2} monoclinico

Energy Technology Data Exchange (ETDEWEB)

Mendoza A, D.; Gonzalez M, P.R. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico); Vasquez L, M.J.; Rubio R, E. [Centro Universitario de Vinculacion, BUAP, 72000 Puebla (Mexico)

2005-07-01

Zirconium oxide (ZrO{sub 2}) with rare-earths (Nd, Dy, Eu and Y) as dopant were prepared by sol gel method and irradiated with gamma radiation. The thermoluminescent (TL) signal was studied as function of the impurities present for temperatures from 50 to 350 C. Pure ZrO{sub 2} produces a strong TL signal induced by gamma radiation, with a maximum located at 150 C, while ZrO{sub 2} doped with Nd, Dy and Y showed a TL signal with minor intensity, but with a maximum like to pure ZrO{sub 2}. However, when Eu is present as impurity the TL signal is much smaller than pure ZrO{sub 2}, with a maximum very enlarged. These results indicate that exits a strong influence of the rare-earths presents in the TL response and opens the possibility to control the TL signal in a wide range of dosages allowing to use these systems as a wide range dosimeter. Details of the thermoluminescent behavior of pure and doped ZrO{sub 2} will be discussed. (Author)

Solar tri-diurnal variation of cosmic rays in a wide range of rigidity

Science.gov (United States)

Mori, S.; Ueno, H.; Fujii, Z.; Morishita, I.; Nagashima, K.

1985-01-01

Solar tri-diurnal variations of cosmic rays have been analyzed in a wide range of rigidity, using data from neutron monitors, and the surface and underground muon telescopes for the period 1978-1983. The rigidity spectrum of the anisotropy in space is assumed to be of power-exponential type as (P/gamma P sub o) to the gamma exp (gamma-P/P sub o). By means of the best-fit method between the observed and the expected variations, it is obtained that the spectrum has a peak at P (=gamma P sub o) approx = 90 GV, where gamma=approx 3.0 and P sub o approx. 30 GV. The phase in space of the tri-diurnal variation is also obtained as 7.0 hr (15 hr and 23 hr LT), which is quite different from that of approx. 1 hr. arising from the axisymmetric distribution of cosmic rays with respect to the IMF.

Spectroscopic and dielectric properties of titanium doped MgO-Al{sub 2}O{sub 3}-B{sub 2}O{sub 3} glass system

Energy Technology Data Exchange (ETDEWEB)

Raju, G Naga; Ramesh, N Ch; Naresh, P; Krishna, T L; Srinivasulu, K; Sudhkar, K S V; Rao, P Venkateswara, E-mail: gnag_9@rediffmail.com [Department of Physics, Acharya Nagarjuna University-Nuzvid Campus, Nuzvid - 521 201 (India)

2009-07-15

In this paper we have reported the influence of titanium ions on different spectroscopic and dielectric properties of MgO-Al{sub 2}O{sub 3}-B{sub 2}O{sub 3} glasses. The analysis of result of all these studies has indicated that as the concentration of TiO{sub 2} increased in the glass matrix, there is a gradual transformation of titanium ions from octahedral position to tetrahedral positions and cause to increase the rigidity of glass network.

Impact of larger rare earth Pr{sup 3+} ions on the physical properties of chemically derived Pr{sub x}CoFe{sub 2−x}O{sub 4} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Pachpinde, A.M.; Langade, M.M. [Department of Chemistry, Jawahar Art Science and Commerce College Andur, Osmanabad, MS (India); Lohar, K.S.; Patange, S.M. [Materials Research Laboratory, Srikrishna Mahavidyalaya Gunjoti, Omerga, Osmanabad 413 613, MS (India); Shirsath, Sagar E., E-mail: shirsathsagar@hotmail.com [Spin Device Technology Center, Department of Information Engineering, Shinshu University, Nagano 380 8553 (Japan)

2014-01-31

Highlights: • Rare earth Pr{sup 3+} substituted CoFe{sub 2}O{sub 4}. • Sol–gel auto combustion synthesis. • XRD and IR spectra reveal the spinel structure. • Magnetization and coercivity increased with Pr{sup 3+} substitution. - Abstract: Rare earth Pr{sup 3+} ions with its larger ionic radii substituted CoFe{sub 2}O{sub 4} nanoparticles with x ranging from 0.0 to 0.1 were synthesized by sol–gel auto-combustion chemical method. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (IR) and vibrating sample magnetometer (VSM) were employed to characterize the physical properties of these ferrite nanoparticles. XRD pattern reveals the formation of cubic spinel ferrite with the signature of PrFeO{sub 3} phases for x ⩾ 0.05. SEM images show that the synthesized samples are in good homogeneity with uniformly distributed grain. The results of IR spectroscopy analysis indicated that the functional groups of cobalt spinel ferrite were formed during the sol–gel process. The cations distribution between the tetrahedral (A-site) and octahedral sites (B-site) has been estimated by XRD analysis. Room temperature magnetic measurement shows saturation magnetization and coercivity increased from 54.7 to 64.2 emu/g and 644 to 1013 Oe, respectively with the increasing Pr{sup 3+} substitution.

The first quinary rare earth thiophosphates. Cs{sub 5}Ln{sub 3}X{sub 3}(P{sub 2}S{sub 6}){sub 2}(PS{sub 4}) (Ln = La, Ce, X = Br, Cl) and the quasi-quaternary Cs{sub 10}Y{sub 4}Cl{sub 10}(P{sub 2}S{sub 6}){sub 3}

Energy Technology Data Exchange (ETDEWEB)

Schoop, Leslie Mareike; Eger, Roland; Nuss, Juergen; Pielnhofer, Florian [Max Planck Institute for Solid State Research, Stuttgart (Germany); Lotsch, Bettina Valeska [Max Planck Institute for Solid State Research, Stuttgart (Germany); Nanosystems Initiative Munich (NIM) and Center for Nanoscience, Muenchen (Germany)

2017-12-13

We report the first examples of quinary rare earth thiophosphates with a fully ordered cation and anion distribution, Cs{sub 5}Ln{sub 3}X{sub 3}(P{sub 2}S{sub 6}){sub 2}(PS{sub 4}), (Ln = La, Ce and X = Br, Cl) as well as the quasi-quaternary Cs{sub 10}Y{sub 4}Cl{sub 10}(P{sub 2}S{sub 6}){sub 3}. These four new compounds crystallize in three different, unknown structure types. The yellowish, transparent, brittle Cs{sub 5}Ce{sub 3}Br{sub 3}(P{sub 2}S{sub 6}){sub 2}(PS{sub 4}) crystallizes in the orthorhombic space group Pnma (no. 62) with a = 13.276(3), b = 14.891(3), c = 19.593(4) Aa, and V = 3873(1) Aa{sup 3} in a novel structure type. Colorless crystals of Cs{sub 5}La{sub 3}Br{sub 3}(P{sub 2}S{sub 6}){sub 2}(PS{sub 4}) and Cs{sub 5}La{sub 3}Cl{sub 3}(P{sub 2}S{sub 6}){sub 2}(PS{sub 4}) are isotypic and were obtained in the monoclinic space group P2{sub 1}/m (no. 11) with a = 9.715(2), b = 14.310(3), c = 13.685(3) Aa, β = 100.16(3) and V = 1873(1) Aa{sup 3} and a = 9.513(2), b = 14.182(3), c = 13.699(3) Aa, β = 99.39(3) and V = 1823(1) Aa{sup 3}, respectively. Both structures contain isolated hexathiohypodiphosphate(IV) [P{sub 2}S{sub 6}]{sup 4-} and thiophosphate [PS{sub 4}]{sup 3-} units that are arranged alternately in layers. Cs{sub 10}Y{sub 4}Cl{sub 10}(P{sub 2}S{sub 6}){sub 3} crystallizes in colorless transparent platelets in the orthorhombic space group Pnnm (no. 58) with a = 13.153(3), b = 28.964(6), c = 7.780(2) Aa, and V = 2964(1) Aa{sup 3}. The structure is composed of isolated [P{sub 4/2}S{sub 6}]{sup 4-} octahedra containing four half occupied P positions surrounded octahedrally by sulfur. We show with Raman scattering that this disordered thiophosphate anion shows a Raman spectrum that is distinct from spectra published for other literature-known thiophosphate anions. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Diurnal and Sub-Diurnal Terms of Nutation

National Research Council Canada - National Science Library

Brzezinski, Aleksander

2000-01-01

.... Based on the available rigid-Earth amplitudes, he estimates this lunisolar effect in polar motion for an elastic Earth with liquid core, and compares it to the oceanic and atmospheric perturbations...

The Dopants and Doping Level Dependence of the Structure and Magnetic Properties of the Eu (BA<sub>1-xsub>LR_x)>2sub>Cu>3sub>O>7+δsub>

Energy Technology Data Exchange (ETDEWEB)

Lin, Yu [Iowa State Univ., Ames, IA (United States)

2002-12-31

Eu(Ba<sub>1-xsub>LR_x)>2sub>Cu>3sub>O>7+δsub> were systematically studied in order to understand how the valence of the rear earth elements, ionic sizes and magnetic moment affect the crystal structure and magnetic and electrical properties. Differential thermal analyses were carried out to check the phase purity, X-ray data were least-squares fitted to determine the lattice parameters, and DC-SQUID magnetometry was used to characterize the superconducting properties. These results showed that the crystallography is consistent with other EuLR123ss series, LR = La, Pr, Eu. The lattice parameters vary with the ionic radii of the rare earth ions. Unlike the uniform change in lattice parameter, the superconducting transition did not vary systematically with the ionic size of the dopants. Although the general trend was for T<sub>c> to decrease with decreasing ionic size of the dopant, for the same doping level, Pr was anomalous, depressing T<sub>c> faster. Although the exact mechanism is not clear, this result is consistent with the depression of T<sub>c> for Pr substitution for the rare earth in R123. The critical current J<sub>c> was determined using the Bean model from magnetization versus field measurements as a function of temperature and field. The effect of the dopants on J<sub>c> with the increasing of temperature or applied field was determined. For T < 77 K and small values of x, the value of J<sub>c> was increased over that of the x = 0 sample. In addition, the smaller the substituting atom, the higher the J<sub>c> becomes. For instance, at x = 0.025, Eu123 < EuLa.025 < EuPr.025 < EuNd.025 < EuEu.025. The enhancement of J<sub>c> disappears for x > 0.05 and T > 0.5T<sub>c>.

Superconductivity in alkaline earth-substituted La2CuO/sub 4-y/

International Nuclear Information System (INIS)

Bednorz, J.G.; Mueller, K.A.; Takashige, M.

1987-01-01

La 2 CuO/sub 4-y/ ceramics containing a few percent of Ca 2+ , Sr 2+ , and Ba 2+ ions have been prepared. Resistivity and susceptibility measurements exhibit superconductive onsets (as in earlier Ba 2+ -containing samples). The onset temperature La 2 CuO/sub 4-y/ with Sr 2+ is higher and its superconductivity-induced diamagnetism larger than that found with Ba 2+ and Ca 2+ . This is proof that the electronic change resulting from alkaline earth-doping, rather than the size effect, is responsible for superconductivity. The ionic radius of Sr 2+ is close to that of La 3+ for which it presumably substitutes

Rare earth-rich cadmium compounds RE{sub 10}TCd{sub 3} (RE = Y, Tb, Dy, Ho, Er, Tm, Lu; T = Rh, Pd, Ir, Pt) with an ordered Co{sub 2}Al{sub 5}-type structure

Energy Technology Data Exchange (ETDEWEB)

Block, Theresa; Klenner, Steffen; Heletta, Lukas; Poettgen, Rainer [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie

2018-04-01

Eighteen new rare earth-rich intermetallic phases RE{sub 10}TCd{sub 3} (RE = Y, Tb, Dy, Ho, Er, Tm, Lu; T = Rh, Pd, Ir, Pt) were obtained by induction melting of the elements in sealed niobium ampoules followed by annealing in muffle furnaces. All samples were characterized by X-ray powder diffraction. The structures of four representatives were refined from single-crystal X-ray diffractometer data: ordered Co{sub 2}Al{sub 5} type, P6{sub 3}/mmc, a = 951.2(1), c = 962.9(2) pm, wR = 0.0460, 595 F{sup 2} values, 20 parameters for Er{sub 10}RhCd{sub 3}; a = 945.17(4), c = 943.33(4), wR = 0.0395, 582 F{sup 2} values, 21 parameters for Lu{sub 9.89}PdCd{sub 3.11}; a = 964.16(6), c = 974.93(6) pm, wR = 0.0463, 614 F{sup 2} values, 21 parameters for Y{sub 10}Ir{sub 1.09}Cd{sub 2.91}; a = 955.33(3), c = 974.56(3) pm, wR = 0.0508, 607 F{sup 2} values, 22 refined parameters for Dy{sub 9.92}IrCd{sub 3.08}. Refinements of the occupancy parameters revealed small homogeneity ranges resulting from RE/Cd, respectively T/Cd mixing. The basic building units of the RE{sub 10}TCd{sub 3} phases are transition metal-centered RE{sub 6} trigonal prisms (TP) that are condensed with double-pairs of empty RE{sub 6} octahedra via common triangular faces. A second type of rods is formed by slightly distorted RE3 rate at Cd{sub 6}RE{sub 6} icosahedra which are condensed via Cd{sub 3} triangular faces. The shortest interatomic distances occur for RE-T, compatible with strong covalent bonding interactions. Temperature dependent magnetic susceptibility measurements were performed for RE{sub 10}RhCd{sub 3} (RE = Dy-Tm, Lu), RE{sub 10}IrCd{sub 3} (RE = Er, Tm, Lu) and RE{sub 10}PtCd{sub 3} (RE = Y, Lu). While Y{sub 10}PtCd{sub 3} and Lu{sub 10}TCd{sub 3} (T = Rh, Ir, Pt) show Pauli paramagnetic behavior, the compounds containing paramagnetic rare earth elements show Curie-Weiss behavior (the experimental magnetic moments indicate stable trivalent RE{sup 3+}) and magnetic ordering at low temperatures

KEPLER-21b: A 1.6 R{sub Earth} PLANET TRANSITING THE BRIGHT OSCILLATING F SUBGIANT STAR HD 179070

Energy Technology Data Exchange (ETDEWEB)

Howell, Steve B. [National Optical Astronomy Observatory, Tucson, AZ 85719 (United States); Rowe, Jason F.; Bryson, Stephen T. [NASA Ames Research Center, Moffett Field, CA 94035 (United States); Quinn, Samuel N. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Marcy, Geoffrey W.; Isaacson, Howard [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Ciardi, David R. [NASA Exoplanet Science Institute/Caltech, Pasadena, CA 91125 (United States); Chaplin, William J.; Elsworth, Yvonne [School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Metcalfe, Travis S. [High Altitude Observatory and Scientific Computing Division, National Center for Atmospheric Research, Boulder, CO 80307 (United States); Monteiro, Mario J. P. F. G. [Centro de Astrofisica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Appourchaux, Thierry [Institut d' Astrophysique Spatiale, Universite Paris XI-CNRS (UMR8617), Batiment 121, 91405 Orsay Cedex (France); Basu, Sarbani [Department of Astronomy, Yale University, New Haven, CT 06520-8101 (United States); Creevey, Orlagh L. [Departamento de Astrofisica, Universidad de La Laguna, E-38206 La Laguna, Tenerife (Spain); Gilliland, Ronald L. [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Quirion, Pierre-Olivier [Canadian Space Agency, 6767 Boulevard de l' Aeroport, Saint-Hubert, QC, J3Y 8Y9 (Canada); Stello, Denis [Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney, NSW 2006 (Australia); Kjeldsen, Hans; Christensen-Dalsgaard, Joergen [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Garcia, Rafael A. [Laboratoire AIM, CEA/DSM-CNRS-Universite Paris Diderot-IRFU/SAp, 91191 Gif-sur-Yvette Cedex (France); and others

2012-02-20

We present Kepler observations of the bright (V = 8.3), oscillating star HD 179070. The observations show transit-like events which reveal that the star is orbited every 2.8 days by a small, 1.6 R{sub Earth} object. Seismic studies of HD 179070 using short cadence Kepler observations show that HD 179070 has a frequency-power spectrum consistent with solar-like oscillations that are acoustic p-modes. Asteroseismic analysis provides robust values for the mass and radius of HD 179070, 1.34 {+-} 0.06 M{sub Sun} and 1.86 {+-} 0.04 R{sub Sun }, respectively, as well as yielding an age of 2.84 {+-} 0.34 Gyr for this F5 subgiant. Together with ground-based follow-up observations, analysis of the Kepler light curves and image data, and blend scenario models, we conservatively show at the >99.7% confidence level (3{sigma}) that the transit event is caused by a 1.64 {+-} 0.04 R{sub Earth} exoplanet in a 2.785755 {+-} 0.000032 day orbit. The exoplanet is only 0.04 AU away from the star and our spectroscopic observations provide an upper limit to its mass of {approx}10 M{sub Earth} (2{sigma}). HD 179070 is the brightest exoplanet host star yet discovered by Kepler.

CsSc{sub 3}F{sub 6}[SeO{sub 3}]{sub 2}. A new rare-earth metal(III) fluoride oxoselenate(IV) with sections of the ReO{sub 3}-type structure

Energy Technology Data Exchange (ETDEWEB)

Greiner, Stefan; Schleid, Thomas [Institut fuer Anorganische Chemie, Universitaet Stuttgart (Germany)

2017-09-04

A new representative of rare-earth metal(III) fluoride oxoselenates(IV) derivatized with alkali metals could be synthesized via solid-state reactions. Colorless single crystals of CsSc{sub 3}F{sub 6}[SeO{sub 3}]{sub 2} were obtained through the reaction of Sc{sub 2}O{sub 3}, ScF{sub 3}, and SeO{sub 2} (molar ratio 1:1:3) with CsBr as reactant and fluxing agent. For this purpose, corundum crucibles embedded as liners into evacuated silica ampoules were applied as containers for these reactions at 700 C for seven days. The new quintenary compound crystallizes in the trigonal space group P3m1 with a = 565.34(4) and c = 1069.87(8) pm (c/a = 1.892) for Z = 1. The crystal structure of CsSc{sub 3}F{sub 6}[SeO{sub 3}]{sub 2} contains two crystallographically different Sc{sup 3+} cations. Each (Sc1){sup 3+} is surrounded by six fluoride anions as octahedron, while the octahedra about (Sc2){sup 3+} are formed by three fluoride anions and three oxygen atoms from three terminal [SeO{sub 3}]{sup 2-} anions. The [(Sc1)F{sub 6}]{sup 3-} octahedra link via common F{sup -} vertices to six fac-[(Sc2)F{sub 3}O{sub 3}]{sup 6-} octahedra forming {sup 2}{sub ∞}{[Sc_3F_6O_6]"9"-} layers parallel to (001). These layers are separated by oxygen-coordinated Cs{sup +} cations (C.N. = 12), arranging for the charge compensation, while Se{sup 4+} cations within the layers surrounded by three oxygen atoms as ψ{sup 1}-tetrahedral [SeO{sub 3}]{sup 2-} units complete the structure. EDX measurements confirmed the composition of the title compound and single-crystal Raman studies showed the typical vibrational modes of isolated [SeO{sub 3}]{sup 2-} anions with ideal C{sub 3v} symmetry. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Effect of rare-earth composition on microstructure and pinning properties of Zr-doped (Gd, Y)Ba{sub 2}Cu{sub 3}O{subx} superconducting tapes.

Energy Technology Data Exchange (ETDEWEB)

Selvamanickam, V.; Chen, Y.; Zhang, Y.; Guevara, A.; Shi, T.; Yao, Y.; Majkic, G.; Lei, C.; Galtsyan, E.; Miller, D. J. (Materials Science Division); (Univ. Houston); (SuperPower Inc.)

2012-01-01

The effect of changing Gd + Y content from 1.2 to 1.6 in the precursor of (Gd,Y)Ba{sub 2}Cu{sub 3}O{sub 7} superconducting thin film tapes made by metal organic chemical vapor deposition (MOCVD) at a constant Gd:Y ratio and a fixed Zr content of 7.5% has been studied. The influence of changing the Gd:Y ratio from Gd = 0 to Y= 0 in 0.2 mol steps at a constant Gd + Y content of 1.2 in the precursor has also been investigated at a fixed Zr content of 7.5%. The critical current of these films is found to vary significantly as a function of rare-earth content as well as a function of rare-earth type. Even for a fixed Zr content, it is found that the critical current in the orientation of magnetic field parallel to the a-b plane and that in the orientation of field perpendicular to the a-b plane can be systematically varied with changing Gd + Y content as well as with changing Gd:Y ratio. The nanoscale defect structures along the a-b plane and along the c-axis are found to be sensitive to these changes in rare-earth content and type.

Modeling impacts of NH{sub 3} on uptake of H{sub 2}SO{sub 4} by charged nucleating nanoparticles in the Earth's atmosphere

Energy Technology Data Exchange (ETDEWEB)

Nadykto, A. B., E-mail: anadykto@gmail.com [Atmospheric Science Research Center, State University of New York at Albany, 251 Fuller Road, Albany, NY 12203 (United States); Department of Applied Mathematics, Moscow State University of Technology “STANKIN”, Vadkovsky per. 1, Moscow 127055 (Russian Federation); Nazarenko, K. M.; Markov, P. N. [Department of Applied Mathematics, Moscow State University of Technology “STANKIN”, Vadkovsky per. 1, Moscow 127055 (Russian Federation); Yu, F. [Atmospheric Science Research Center, State University of New York at Albany, 251 Fuller Road, Albany, NY 12203 (United States)

2016-06-08

The understanding of the role of ammonia, a well-known stabilizer of binary sulfuric acid-water clusters, in the gas-to-nanoparticle conversion in the Earth atmosphere is critically important for the assessment of aerosol radiative forcing associated with the climate changes. The sulfuric acid H{sub 2}SO{sub 4} is present in the atmosphere in the form of the gas-phase hydrates (H{sub 2}SO{sub 4})(H{sub 2}O){sub n}, whose interaction with NH{sub 3} leads to the formation of more stable bisulfate clusters (NH{sub 3})(H{sub 2}SO{sub 4})(H{sub 2}O){sub n}. Although the impact of NH{sub 3} on the thermochemical stability of binary clusters nucleating homogeneously has been studied in some detail in the past, the effect of ammonia on other microphysical properties relevant to nucleation remains insufficiently well understood. In the present study, the effect of ammonia on the electrical dipole moment controlling the nucleation of airborne ions via the dipole-charge interaction has been investigated using the Density Functional Theory (DFT), ab initio MP2 and model chemistry G3 methods. The presence of ammonia in (H{sub 2}SO{sub 4})(H{sub 2}O){sub n} is found to lead to very large enhancement in the dipole moment, which exceeds 2.0-2.5 Debyes (∼60-80%), 3.7-5.0 Debyes (∼90-180%), 1.4-4.5 Debyes (∼50-150%) and 2.1-5.5 Debyes (∼60-700%) for n = 0, n = 1, n = 2 and n = 3, respectively. The implications of this include the significantly increased uptake of the sulfuric acid, the key atmospheric nucleation precursor, by airborne ions and neutrals (due to dipole-dipole interaction), enhanced nucleation rates and the elevated production of ultrafine particles, which cause adverse health impacts.

Orbital energies and structural non-rigidity of complex hydrides according to data on ab initio calculations

Energy Technology Data Exchange (ETDEWEB)

Boldyrev, A I; Sukhanov, L P; Charkin, O P [AN SSSR, Moscow. Inst. Novykh Khimicheskikh Problem

1982-01-01

In approximation by the Hartree-Fock-Routine method using several Gauss type bases ionization potentials of complex hydrides LiBeH/sub 3/, NaBeH/sub 3/, LiMgH/sub 3/, LiBH/sub 4/, NaBH/sub 4/ and LiAlH/sub 4/ have been calculated. A problem of the show of structural non-rigidity of complex molecules L(MX/sub 4/) with tetrahedral anions (MX/sub 4/)/sup -/ in photoelectron spectra is considered.

A cesium rare-earth silicate Cs{sub 3}RESi{sub 6}O{sub 15} (RE = Dy-Lu, Y, In). The parent of an unusual structural class featuring a remarkable 57 Aa unit cell axis

Energy Technology Data Exchange (ETDEWEB)

Terry, Rylan; Vinton, Daniel; McMillen, Colin D.; Kolis, Joseph W. [Department of Chemistry and Center for Optical Materials Science and Engineering Technologies (COMSET), Clemson University, H.L. Hunter Laboratories (United States)

2018-02-19

The structure of Cs{sub 3}RESi{sub 6}O{sub 15}, where RE = Dy-Lu, Y, In, is unusual in that it contains octahedrally coordinated rare-earth ions; their relative orientation dictates the structure, as they rotate about the c-axis supported by the cyclic Si{sub 6}O{sub 15} framework. The repeat unit of the rotation is eight units generating a very long (ca. 57 Aa) unit cell axis. This unusual repeat unit is created by the structural flexibility of the hexasilicate ring, which is in turn affected by the size of the rare earth ion as well as the size of alkali ion residing within the silicate layers. Previous work showed for the smaller Sc{sup 3+} ion, the rotation of the octahedra is not sufficient to achieve closure at an integral repeat unit and an incommensurate structure results. The products are prepared as large, high quality single crystals using a high-temperature (650 C) hydrothermal method with CsOH and F{sup -} mineralizers. The presence of fluoride is essential to the formation of the product. (copyright 2018 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

Fluorine-ion conductivity of different technological forms of solid electrolytes R{sub 1–y}M{sub y}F{sub 3–y} (LaF{sub 3} Type ) (M = Ca, Sr, Ba; R Are Rare Earth Elements)

Energy Technology Data Exchange (ETDEWEB)

Sorokin, N. I., E-mail: nsorokin1@yandex.ru; Sobolev, B. P. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

2016-05-15

We have investigated the conductivity of some representatives of different technological forms of fluoride-conducting solid electrolytes R{sub 1–y}M{sub y}F{sub 3–y} (M = Ca, Sr, Ba; R are rare earth elements) with an LaF{sub 3} structure: single crystals, cold- and hot-pressing ceramics based on a charge prepared in different ways (mechanochemical synthesis, solid-phase synthesis, and fragmentation of single crystals), polycrystalline alloys, etc. It is shown (by impedance spectroscopy), that different technological forms of identical chemical composition (R, M, y) exhibit different electrical characteristics. The maximum conductivity is observed for the single-crystal form of R{sub 1–y}M{sub y}F{sub 3–y} tysonite phases, which provides (in contrast to other technological forms) the formation of true volume ion-conducting characteristics.

The quaternary arsenide oxides Ce{sub 9}Au{sub 5-x}As{sub 8}O{sub 6} and Pr{sub 9}Au{sub 5-x}As{sub 8}O{sub 6}

Energy Technology Data Exchange (ETDEWEB)

Bartsch, Timo; Hoffmann, Rolf-Dieter; Poettgen, Rainer [Univ. Muenster (Germany). Inst. fuer Anorganische und Analytische Chemie

2016-07-01

The quaternary gold arsenide oxides Ce{sub 9}Au{sub 5-x}As{sub 8}O{sub 6} and Pr{sub 9}Au{sub 5-x}As{sub 8}O{sub 6} were synthesized from the rare earth elements (RE), rare earth oxides, arsenic and gold powder at maximum annealing temperatures of 1173 K. The structures were refined from single crystal X-ray diffractometer data: Pnnm, a=1321.64(6) pm, b=4073.0(3), c=423.96(2), wR2=0.0842, 3106 F{sup 2} values, 160 variables for Ce{sub 9}Au{sub 4.91(4)}As{sub 8}O{sub 6} and Pnnm, a=1315.01(4), b=4052.87(8), c=420.68(1) pm, wR2=0.0865, 5313 F{sup 2} values, 160 variables for Pr{sub 9}Au{sub 4.75(1)}As{sub 8}O{sub 6}. They represent a new structure type and show a further extension of pnictide oxide crystal chemistry. A complex polyanionic gold arsenide network [Au{sub 5}As{sub 8}]{sup 15-} (with some disorder in the gold substructure) is charge compensated with polycationic strands of condensed edge-sharing O rate at RE{sub 4/4} and O rate at RE{sub 4/3} tetrahedra ([RE{sub 4}O{sub 3}]{sub 2}{sup 12+}) as well as RE{sup 3+} cations in cavities.

Accuracy limit of rigid 3-point water models

Science.gov (United States)

Izadi, Saeed; Onufriev, Alexey V.

2016-08-01

Classical 3-point rigid water models are most widely used due to their computational efficiency. Recently, we introduced a new approach to constructing classical rigid water models [S. Izadi et al., J. Phys. Chem. Lett. 5, 3863 (2014)], which permits a virtually exhaustive search for globally optimal model parameters in the sub-space that is most relevant to the electrostatic properties of the water molecule in liquid phase. Here we apply the approach to develop a 3-point Optimal Point Charge (OPC3) water model. OPC3 is significantly more accurate than the commonly used water models of same class (TIP3P and SPCE) in reproducing a comprehensive set of liquid bulk properties, over a wide range of temperatures. Beyond bulk properties, we show that OPC3 predicts the intrinsic charge hydration asymmetry (CHA) of water — a characteristic dependence of hydration free energy on the sign of the solute charge — in very close agreement with experiment. Two other recent 3-point rigid water models, TIP3PFB and H2ODC, each developed by its own, completely different optimization method, approach the global accuracy optimum represented by OPC3 in both the parameter space and accuracy of bulk properties. Thus, we argue that an accuracy limit of practical 3-point rigid non-polarizable models has effectively been reached; remaining accuracy issues are discussed.

Anomalous Pd substitution effects in the thermoelectric oxide NaCo sub 2 sub - sub x Pd sub x O sub 4

CERN Document Server

Kitawaki, R

2002-01-01

We prepared a set of polycrystalline samples of the thermoelectric oxide NaCo sub 2 sub - sub x Pd sub x O sub 4 (x = 0, 0.05, 0.1, and 0.2), and investigated the Pd substitution effects on transport phenomena. The effects are so drastic that just 5-10% Pd ions reduce the resistivity and the Seebeck coefficient to one third of the values for x = 0, and increase the magnitude of the Hall coefficient by three times. A semi-quantitative analysis has revealed that the x = 0.2 sample has much smaller effective mass and carrier concentration than the x = 0.05 sample. This is difficult to explain within a rigid-band picture, and is qualitatively consistent with a strong-correlation picture applied to the Ce-based heavy-fermion systems.

Superconductivity of Ta{sub 34}Nb{sub 33}Hf{sub 8}Zr{sub 14}Ti{sub 11} high entropy alloy from first principles calculations

Energy Technology Data Exchange (ETDEWEB)

Jasiewicz, K.; Wiendlocha, B.; Korben, P.; Kaprzyk, S.; Tobola, J. [AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, Al. Mickiewicza 30, 30-059, Krakow (Poland)

2016-05-15

The Korringa-Kohn-Rostoker method with the coherent potential approximation (KKR-CPA) is applied to study the first superconducting high entropy alloy (HEA) Ta{sub 34}Nb{sub 33}Hf{sub 8}Zr{sub 14}Ti{sub 11} (discovered in 2014 with T{sub c}=7.3 K), focusing on estimations of the electron-phonon coupling constant λ. The electronic part of λ has been calculated using the rigid muffin-tin approximation (RMTA), while the phonon part has been approximated using average atomic mass and experimental Debye temperature. The estimated λ=1.16 is close to the value determined from specific heat measurements, λ=0.98, and suggests rather strong electron-phonon coupling in this material. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Effect of Tb and Al substitution within the rare earth and cobalt sublattices on magnetothermal properties of Dy{sub 0.5}Ho{sub 0.5}Co{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Chzhan, V.B., E-mail: lemuriform@gmail.com [Baikov Institute of Metallurgy and Material Sciences, Russian Academy of Sciences, Moscow 119334 (Russian Federation); National University of Science and Technology “MISIS”, Moscow 119049 (Russian Federation); Tereshina, E.A. [Institute of Physics CAS, Prague 18221 (Czech Republic); Mikhailova, A.B. [Baikov Institute of Metallurgy and Material Sciences, Russian Academy of Sciences, Moscow 119334 (Russian Federation); Politova, G.A. [Baikov Institute of Metallurgy and Material Sciences, Russian Academy of Sciences, Moscow 119334 (Russian Federation); International Laboratory of High Magnetic Fields and Low Temperatures, Wroclaw 53-421 (Poland); Tereshina, I.S. [Baikov Institute of Metallurgy and Material Sciences, Russian Academy of Sciences, Moscow 119334 (Russian Federation); Faculty of Physics, Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Kozlov, V.I. [Faculty of Physics, Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Ćwik, J. [International Laboratory of High Magnetic Fields and Low Temperatures, Wroclaw 53-421 (Poland); Nenkov, K. [IFW Dresden, P.O. Box 270116, 01171 Dresden (Germany); Alekseeva, O.A.; Filimonov, A.V. [Peter the Great St. Petersburg Polytechnic University, St. Petersburg 195251 (Russian Federation)

2017-06-15

Highlights: • Single-phase (Tb,Dy,Ho)(Co,Al){sub 2} alloys synthesized using high-purity metals. • Temperature dependence of lattice parameters measured in a wide temperature range. • Tb and Al substitution increase the Curie temperature in Dy{sub 0.5}Ho{sub 0.5}Co{sub 2.} • The MCE measured by direct and indirect methods. • Materials with ‘table-like’ MCE are found. - Abstract: The effect of Tb and Al substitution within the rare earth and cobalt sublattices on structural and magnetothermal properties of Dy{sub 0.5}Ho{sub 0.5}Co{sub 2} has been studied. Multicomponent Laves phase alloys Tb{sub x}(Dy{sub 0.5}Ho{sub 0.5}){sub 1−x}Co{sub 2−y}Al{sub y} (x = 0, 0.3, 0.4, 0.5; y = 0, 0.25) synthesized using high-purity metals have been studied using X-ray diffraction analysis, heat capacity and magnetocaloric measurements. Dy{sub 0.5}Ho{sub 0.5}Co{sub 2} has a first order phase transition at the Curie temperature T{sub C} ≈ 110 K. Both Tb and Al substitution leads to increase of the T{sub C}. The increasing Tb content leads to the decreases slightly the MCE and all the transitions near the Curie temperature are of the first order. As for the Al-containing compounds, MCE measurements show that the phase transition type changes from the first to the second-order. The advantage of Tb{sub x}(Dy{sub 0.5}Ho{sub 0.5}){sub 1−x}Co{sub 1.75}Al{sub 0.25} as compared with Al-free alloys is ‘table-like’ behavior of MCE.

Motion and magnetic field structure of the Earth's magnetic tail near 30 R/sub E/

International Nuclear Information System (INIS)

Bowling, S.B.

1975-01-01

The analysis of data taken by the NASA-GSFC magnetometer experiment on the Explorer 34 spacecraft has shown that the diurnal wobble of the geomagnetic dipole axis measurably influences the position of the magnetotail near 30 R/sub E/ (earth radii). Viewed in the solar-ecliptic coordinate system, the dipole wobble resolves into components of motion perpendicular and parallel to the earth-sun line. The perpendicular component exerts a torque on the magnetotail and causes the neutral sheet (the midplane of the magnetotail) to pivot about an axis approximately parallel to the solar-wind flow direction. The parallel component encourages the neutral sheet to move above and below the solar-magnetospheric equatorial plane with an amplitude of 1 R/sub E/, as if the neutral sheet were hinged at a geocentric distance of 5.25 R/sub E/. The motion of the neutral sheet is also characterized by a random flapping in the solar-ecliptic Z-direction at a velocity of 100 km/sec and an amplitude of +- 2 R/sub E/. Results suggest the existence of a layer of nearly uniform cross-tail electric current that is about 2.3 R/sub E/ thick and envelops the neutral sheet. The magnetic field, whose average geometry resembles a flattened and extended dipole, gradually reverses direction within this current layer. The field is perpendicular to the neutral sheet where it has a value of 2 γ (1γ = 10 -5 Gauss). The analysis does not suggest a strong dependence of the magnetic-field configuration on the geomagnetic index Kp, although the field may intermittently disrupt into localized and short-lived magnetic loops during periods of enhanced geomagnetic activity

The temperature dependence studies of rare-earth (Dy.sup.3+./sup., Sm.sup.3+./sup., Eu.sup.3+./sup. and Tb.sup.3+./sup.) activated Gd.sub.3./sub.Ga.sub.3./sub.Al.sub.2./sub.O.sub.12./sub. garnet single crystals

Czech Academy of Sciences Publication Activity Database

Bartosiewicz, Karol; Babin, Vladimir; Beitlerová, Alena; Boháček, Pavel; Jurek, Karel; Nikl, Martin

2017-01-01

Roč. 189, Sep (2017), s. 126-139 ISSN 0022-2313 R&D Projects: GA ČR GA16-15569S EU Projects: European Commission(XE) 316906 - LUMINET Institutional support: RVO:68378271 Keywords : Gd3Ga3Al2O12 * rare earth dopants * energy transfer * thermal quenching * single crystal Sub ject RIV: BH - Optics, Masers, Lasers OBOR OECD: Optics (including laser optics and quantum optics) Impact factor: 2.686, year: 2016

Rigid multibody system dynamics with uncertain rigid bodies

Energy Technology Data Exchange (ETDEWEB)

Batou, A., E-mail: anas.batou@univ-paris-est.fr; Soize, C., E-mail: christian.soize@univ-paris-est.fr [Universite Paris-Est, Laboratoire Modelisation et Simulation Multi Echelle, MSME UMR 8208 CNRS (France)

2012-03-15

This paper is devoted to the construction of a probabilistic model of uncertain rigid bodies for multibody system dynamics. We first construct a stochastic model of an uncertain rigid body by replacing the mass, the center of mass, and the tensor of inertia by random variables. The prior probability distributions of the stochastic model are constructed using the maximum entropy principle under the constraints defined by the available information. The generators of independent realizations corresponding to the prior probability distribution of these random quantities are further developed. Then several uncertain rigid bodies can be linked to each other in order to calculate the random response of a multibody dynamical system. An application is proposed to illustrate the theoretical development.

Crystal growth and structure of KLnP/sub 4/O/sub 12/

International Nuclear Information System (INIS)

Guangyan, H.; Shuzhen, L.; Shuying, Y.; Mingyu, C.

1985-01-01

Potassium rare earth tetraphosphates KLnP/sub 4/O/sub 12/ are a kind of polyphosphates of rare earths with unique properties and structures. KNdP/sub 4/O/sub 12/ is a high-Nd-concentration laser material with a non-centrosymmetric space group P2, yielding linear and nonlinear optical properties. α-KErP/sub 4/O/sub 12/ might be used as a material for engineering device purpose. KTbP/sub 4/O/sub 12/ can emit strong green fluorescence, it might be a kind of a new crystal material for laser or luminescence. In order to search for new crystal materials and to study the correlations among the composition, structures and the properties of rare earth compounds, the crystal growth of KLnP/sub 4/O/sub 12/ and their structures are studied in this paper

Automated protocols for spaceborne sub-meter resolution "Big Data" products for Earth Science

Science.gov (United States)

Neigh, C. S. R.; Carroll, M.; Montesano, P.; Slayback, D. A.; Wooten, M.; Lyapustin, A.; Shean, D. E.; Alexandrov, O.; Macander, M. J.; Tucker, C. J.

2017-12-01

The volume of available remotely sensed data has grown exceeding Petabytes per year and the cost for data, storage systems and compute power have both dropped exponentially. This has opened the door for "Big Data" processing systems with high-end computing (HEC) such as the Google Earth Engine, NASA Earth Exchange (NEX), and NASA Center for Climate Simulation (NCCS). At the same time, commercial very high-resolution (VHR) satellites have grown into a constellation with global repeat coverage that can support existing NASA Earth observing missions with stereo and super-spectral capabilities. Through agreements with the National Geospatial-Intelligence Agency NASA-Goddard Space Flight Center is acquiring Petabytes of global sub-meter to 4 meter resolution imagery from WorldView-1,2,3 Quickbird-2, GeoEye-1 and IKONOS-2 satellites. These data are a valuable no-direct cost for the enhancement of Earth observation research that supports US government interests. We are currently developing automated protocols for generating VHR products to support NASA's Earth observing missions. These include two primary foci: 1) on demand VHR 1/2° ortho mosaics - process VHR to surface reflectance, orthorectify and co-register multi-temporal 2 m multispectral imagery compiled as user defined regional mosaics. This will provide an easy access dataset to investigate biodiversity, tree canopy closure, surface water fraction, and cropped area for smallholder agriculture; and 2) on demand VHR digital elevation models (DEMs) - process stereo VHR to extract VHR DEMs with the NASA Ames stereo pipeline. This will benefit Earth surface studies on the cryosphere (glacier mass balance, flow rates and snow depth), hydrology (lake/water body levels, landslides, subsidence) and biosphere (forest structure, canopy height/cover) among others. Recent examples of products used in NASA Earth Science projects will be provided. This HEC API could foster surmounting prior spatial-temporal limitations while

New 3-D coordination polymers based on semi-rigid V-shape tetracarboxylates

Energy Technology Data Exchange (ETDEWEB)

Huang, Jing-Jing; Xu, Wei; Wang, Yan-Ning [College of Chemistry, Jilin University, Jiefang Road 2519, Changchun 130023, Jilin (China); State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University, Qianjin Road 2699, Changchun 130012, Jilin (China); Yu, Jie-Hui, E-mail: jhyu@jlu.edu.cn [College of Chemistry, Jilin University, Jiefang Road 2519, Changchun 130023, Jilin (China); State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University, Qianjin Road 2699, Changchun 130012, Jilin (China); Zhang, Ping, E-mail: zhangping@jlu.edu.cn [College of Chemistry, Jilin University, Jiefang Road 2519, Changchun 130023, Jilin (China); Xu, Ji-Qing [College of Chemistry, Jilin University, Jiefang Road 2519, Changchun 130023, Jilin (China); State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University, Qianjin Road 2699, Changchun 130012, Jilin (China)

2015-03-15

Under the hydrothermal conditions, the reactions of transition-metal salts, tetracarboxylic acids and N,N′-donor ligands yielded three new coordination polymers as [Cu{sub 4}(fph){sub 2}(bpe){sub 3}(H{sub 2}O){sub 2}]·2H{sub 2}O (fph=4,4′-(hexafluoroisopropylidene)diphthalate, bpe=1,2-bis(pyridyl)ethylene) 1, [Co{sub 2}(fph)(bpa){sub 2}(H{sub 2}O){sub 2}]·3H{sub 2}O (bpa=1,2-bis(pyridyl)ethylane) 2, and [Ni(H{sub 2}O)(H{sub 2}oph)(bpa)] (oph=4,4′-oxydiphthalate) 3. X-ray single-crystal diffraction analysis revealed that the title three compounds all possess the three-dimensional (3-D) network structures. For compound 1, the fph molecules first link the Cu{sup 2+} ions into a two-dimensional (2-D) wave-like layer with a (4,4) topology. The bpe molecules act as the second linkers, extending the 2-D layers into a 3-D network. For compound 2, the fph molecules still serve as the first connectors, linking the Co{sup 2+} ions into a one-dimensional (1-D) tube-like chain. Then the bpa molecules propagate the chains into a 3-D (4,4,4)-connected network. In the formation of the 3-D network of compound 3, the oph molecule does not play a role. The bpa molecules as well as the water molecules act as a mixed bridge. Only a kind of 4-connected metal node is observed in compound 3. The magnetic properties of compounds 1–3 were investigated and all exhibit the predominant antiferromegnetic magnetic behaviors. - Graphical abstract: Structures of three semi-rigid V-shape tetracarboxylate-based coordination polymers were reported, and their magnetic properties were investigated. - Highlights: • Structures of three tetracarboxylate-based coordination polymers were reported. • Role of organic bases in metal–tetracarboxylate compounds was discussed. • Characters of V-shape and semi-rigidity for tetracarboxylate play a key role in crystal growth. • Their magnetic properties were investigated.

Journal of Earth System Science | Indian Academy of Sciences

Indian Academy of Sciences (India)

Home; Journals; Journal of Earth System Science. Santimoy Kundu. Articles written in Journal of Earth System Science. Volume 124 Issue 1 February 2015 pp 161-170. Influence of rigid boundary on the propagation of torsional surface wave in an inhomogeneous layer · Shishir Gupta Rehena Sultana Santimoy Kundu.

Journal of Earth System Science | Indian Academy of Sciences

Indian Academy of Sciences (India)

Home; Journals; Journal of Earth System Science. Rehena Sultana. Articles written in Journal of Earth System Science. Volume 124 Issue 1 February 2015 pp 161-170. Influence of rigid boundary on the propagation of torsional surface wave in an inhomogeneous layer · Shishir Gupta Rehena Sultana Santimoy Kundu.

R<sub>5sub>T>4sub> compounds - unique multifunctional intermetallics for basic research and applications

Energy Technology Data Exchange (ETDEWEB)

Mudryk, Yaroslav

2016-10-01

The unique properties of the rare-earth elements and their alloys have brought them from relative obscurity to high profile use in common high-tech applications. The broad technological impact of these remarkable materials may have never been known by the general public if not for the supply concerns that placed the rare-earth materials on the front page of newspapers and magazines. Neodymium and dysprosium, two essential components of Nd<sub>2sub>Fe>14sub>B-based high-performance permanent magnets, have drawn much attention and have been deemed critical materials for many energy-related applications. Ironically, the notoriety of rare-earth elements and their alloys is the result of a global movement to reduce their use in industrial applications and, thus, ease concerns about their supply and ultimately to reduce their position in high-tech supply chains. Research into the applications of lanthanide alloys has been de-emphasized recently due to the perception that industry is moving away from the use of rare-earth elements in new products. While lanthanide supply challenges justify efforts to diversify the supply chain, a strategy to completely replace the materials overlooks the reasons rare earths became important in the first place -- their unique properties are too beneficial to ignore. Rare-earth alloys and compounds possess truly exciting potential for basic science exploration and application development such as solid-state caloric cooling. In this brief review, we touch upon several promising systems containing lanthanide elements that show important and interesting magnetism-related phenomena.

Crystal structure, magnetization, {sup 125}Te NMR, and Seebeck coefficient of Ge{sub 49}Te{sub 50}R{sub 1} (R = La, Pr, Gd, Dy, and Yb)

Energy Technology Data Exchange (ETDEWEB)

Levin, E.M., E-mail: levin@iastate.edu [Division of Materials Sciences and Engineering, US Department of Energy Ames Laboratory, Ames, IA 50011 (United States); Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States); Cooling, C. [Division of Materials Sciences and Engineering, US Department of Energy Ames Laboratory, Ames, IA 50011 (United States); Bud’ko, S.L. [Division of Materials Sciences and Engineering, US Department of Energy Ames Laboratory, Ames, IA 50011 (United States); Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States); Straszheim, W.E. [Division of Materials Sciences and Engineering, US Department of Energy Ames Laboratory, Ames, IA 50011 (United States); Lograsso, T.A. [Division of Materials Sciences and Engineering, US Department of Energy Ames Laboratory, Ames, IA 50011 (United States); Department of Materials Sciences and Engineering, Iowa State University, Ames, IA 50011 (United States)

2017-05-01

GeTe, a self-doping semiconductor, is a well-known base compound for thermoelectric and phase-change materials. It is known, that replacement of Ge in Ag{sub 6.5}Sb{sub 6.5}Ge{sub 37}Te{sub 50} (TAGS-85) material by rare earth Dy significantly enhances both the power factor and thermoelectric figure of merit. Here we demonstrate how replacement of Ge in GeTe by rare earths with different atomic size and localized magnetic moments affect XRD patterns, magnetization, {sup 125}Te NMR spectra and spin-lattice relaxation, and the Seebeck coefficient of the alloys with a nominal composition of Ge{sub 49}Te{sub 50}R{sub 1} (R = La, Pr, Gd, Dy, and Yb). SEM, EDS and WDS data show that rare earth atoms in the matrix are present at smaller extent compared to a nominal composition, whereas rare earth also is present in inclusions. Rare earths affect the Seebeck coefficient, which is a result of interplay between the reduction due to higher carrier concentration and enhancement due to magnetic contribution. The effect of replacement of Ge in GeTe by Dy on the Seebeck coefficient is smaller than that observed in Ag{sub 6.5}Sb{sub 6.5}Ge{sub 36} Te{sub 50}Dy{sub 1}. This can be explained by larger amount of rare earth, which can be embedded into the lattice of materials containing [Ag + Sb] atomic pairs and possible effect from these pairs. - Highlights: • The effects of rare earth in Ge{sub 49}Te{sub 50}R{sub 1} (R = La, Pr, Gd, Dy, and Yb) are studied. • Rare earth atoms in the matrix are present at smaller extent compared to a nominal composition. • The effect on the Seebeck coefficient is a result from carrier concentration and magnetic contribution.

Exploration of R<sub>2sub>XM>2sub> (R=Sc, Y, Ti, Zr, Hf, rare earth; X=main group element; M=transition metal, Si, Ge): Structural Motifs, the novel Compound Gd<sub>2sub>AlGe>2sub> and Analysis of the U<sub>3sub>Si>2sub> and Zr<sub>3sub>Al>2 sub>Structure Types

Energy Technology Data Exchange (ETDEWEB)

McWhorter, Sean William [Iowa State Univ., Ames, IA (United States)

2006-01-01

In the process of exploring and understanding the influence of crystal structure on the system of compounds with the composition Gd<sub>5sub>(Si_xGe>1-xsub>)>4sub> several new compounds were synthesized with different crystal structures, but similar structural features. In Gd<sub>5sub>(Si_xGe>1-xsub>)>4sub>, the main feature of interest is the magnetocaloric effect (MCE), which allows the material to be useful in magnetic refrigeration applications. The MCE is based on the magnetic interactions of the Gd atoms in the crystal structure, which varies with x (the amount of Si in the compound). The crystal structure of Gd<sub>5sub>(Si_xGe>1-xsub>)>4sub> can be thought of as being formed from two 3²434 nets of Gd atoms, with additional Gd atoms in the cubic voids and Si/Ge atoms in the trigonal prismatic voids. Attempts were made to substitute nonmagnetic atoms for magnetic Gd using In, Mg and Al. Gd<sub>2sub>MgGe>2sub> and Gd<sub>2sub>InGe>2sub> both possess the same 3²434 nets of Gd atoms as Gd<sub>5sub>(Si_xGe>1-xsub>)>4sub>, but these nets are connected differently, forming the Mo<sub>2sub>FeB>2sub> crystal structure. A search of the literature revealed that compounds with the composition R<sub>2sub>XM>2sub> (R=Sc, Y, Ti, Zr, Hf, rare earth; X=main group element; M=transition metal, Si, Ge) crystallize in one of four crystal structures: the Mo<sub>2sub>FeB>2sub>, Zr<sub>3sub>Al>2sub>, Mn<sub>2sub>AlB>2sub> and W<sub>2sub>CoB>2sub> crystal structures. These crystal structures are described, and the relationships between them are highlighted. Gd<sub>2sub>AlGe>2sub> forms an entirely new crystal structure, and the details of its synthesis and characterization are given. Electronic structure calculations are performed to understand the nature of bonding in this compound and how

Rare earth chalcogels NaLnSnS{sub 4} (Ln = Y, Gd, Tb) for selective adsorption of volatile hydrocarbons and gases

Energy Technology Data Exchange (ETDEWEB)

Edhaim, Fatimah; Rothenberger, Alexander [Physical Science and Engineering Division, King Abdullah University of Science and Technology, Thuwal (Saudi Arabia)

2017-08-16

The synthesis and characterization of the rare earth chalcogenide aerogels NaYSnS{sub 4}, NaGdSnS{sub 4}, and NaTbSnS{sub 4} is reported. Rare earth metal ions like Y{sup 3+}, Gd{sup 3+}, and Tb{sup 3+} react with the chalcogenide clusters [SnS{sub 4}]{sup 4-} in aqueous formamide solution forming extended polymeric networks by gelation. Aerogels obtained after supercritical drying have BET surface areas of 649 m{sup 2}.g{sup -1} (NaYSnS{sub 4}), 479 m{sup 2}.g{sup -1} (NaGdSnS{sub 4}), and 354 m{sup 2}.g{sup -1} (NaTbSnS{sub 4}). Electron microscopy and physisorption studies reveal that the new materials have pores in the macro (above 50 nm) and meso (2-50 nm) regions. These aerogels show higher adsorption of toluene vapor over cyclohexane vapor and CO{sub 2} over CH{sub 4} or H{sub 2}. The notable adsorption capacity for toluene (NaYSnS{sub 4}: 1108 mg.g{sup -1}; NaGdSnS{sub 4}: 921 mg.g{sup -1}; and NaTbSnS4: 645 mg.g{sup -1}) and high selectivity for gases (CO{sub 2}/H{sub 2}: 172 and CO{sub 2}/CH{sub 4}: 50 for NaYSnS{sub 4}, CO{sub 2}/H{sub 2}: 155 and CO{sub 2}/CH{sub 4}: 37 for NaGdSnS{sub 4}, and CO{sub 2}/H{sub 2}: 75 and CO{sub 2}/CH{sub 4}: 28 for NaTbSnS{sub 4}) indicate potential future use of chalcogels in adsorption-based gas or hydrocarbon separation processes. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Breathing mode distortion and magnetic order in rare-earth nickelates RNiO{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Hampel, Alexander; Ederer, Claude [Materials Theory, ETH Zuerich (Switzerland)

2016-07-01

Rare-earth nickelate perovskites display a rich and not yet fully understood phase diagram, where all RNiO{sub 3} compounds with R from Sm to Lu undergo a non-magnetic metal-insulator transition (MIT). This transition is connected to a lattice distortion, which can be described as breathing mode of the oxygen octahedra surrounding the Ni cations. Between 100-250 K the RNiO{sub 3} compounds undergo a magnetic transition to an antiferromagnetic (AFM) state, with a wave-vector k= [(1)/(4) (1)/(4) (1)/(4)] relative to the underlying simple cubic perovskite structure. Here, we use density functional theory and its extensions (DFT+U, DFT+DMFT) together with distortion mode analysis to explore the interplay between lattice distortions, magnetic order, and the strength of the local Coulomb interaction U in rare earth nickelates. Our results show a strong dependency of the breathing mode amplitude on the magnetic order, with a much larger breathing mode obtained for the AFM state compared to the ferromagnetic case. Furthermore, we demonstrate that DFT+U is able to capture the correct trends of the lattice distortions across the nickelate series.

Latitudinal variation rate of geomagnetic cutoff rigidity in the active Chilean convergent margin

Science.gov (United States)

Cordaro, Enrique G.; Venegas, Patricio; Laroze, David

2018-03-01

We present a different view of secular variation of the Earth's magnetic field, through the variations in the threshold rigidity known as the variation rate of geomagnetic cutoff rigidity (VRc). As the geomagnetic cutoff rigidity (Rc) lets us differentiate between charged particle trajectories arriving at the Earth and the Earth's magnetic field, we used the VRc to look for internal variations in the latter, close to the 70° south meridian. Due to the fact that the empirical data of total magnetic field BF and vertical magnetic field Bz obtained at Putre (OP) and Los Cerrillos (OLC) stations are consistent with the displacement of the South Atlantic magnetic anomaly (SAMA), we detected that the VRc does not fully correlate to SAMA in central Chile. Besides, the lower section of VRc seems to correlate perfectly with important geological features, like the flat slab in the active Chilean convergent margin. Based on this, we next focused our attention on the empirical variations of the vertical component of the magnetic field Bz, recorded in OP prior to the Maule earthquake in 2010, which occurred in the middle of the Chilean flat slab. We found a jump in Bz values and main frequencies from 3.510 to 5.860 µHz, in the second derivative of Bz, which corresponds to similar magnetic behavior found by other research groups, but at lower frequency ranges. Then, we extended this analysis to other relevant subduction seismic events, like Sumatra in 2004 and Tohoku in 2011, using data from the Guam station. Similar records and the main frequencies before each event were found. Thus, these results seem to show that magnetic anomalies recorded on different timescales, as VRc (decades) and Bz (days), may correlate with some geological events, as the lithosphere-atmosphere-ionosphere coupling (LAIC).

Magnetic properties of compounds Ba/sub 3/Fesub(2-x)Msub(x)UO/sub 9/ with M=Y, Sc, In and rare earth

Energy Technology Data Exchange (ETDEWEB)

Grenet, J C; Berthon, J [Paris-11 Univ., 91 - Orsay (France); Poix, P [Ecole Nationale Superieure de Chimie, 67 - Strasbourg (France)

1979-01-01

The compounds Ba/sub 3/Fesub(2-x)Msub(x)UO/sub 9/ crystallize in the perovskite type system. The magnetic behavior of these compounds is different when M/sup 3 +/ is dia- or paramagnetic. When M/sup 3 +/ is diamagnetic, the magnetic exchange interaction between A and B sublattices is strongly antiferromagnetic, the (UO/sub 6/)/sup 6 -/ clusters having a special effect. When M/sup 3 +/ is paramagnetic, the perovskite compounds have three magnetic sublattices. In the third one are placed rare earth ions M/sup 3 +/; in this case the A-B exchange interactions are antiferromagnetic but the interactions with the third sublattice are probably slightly ferromagnetic. This special feature and the fact that a temperature of compensation is missing differentiate these perovskites from the garnets.

Cluster-spin dynamics in a GaMo{sub 4}S{sub 8}-type compound: {sup 27}Al nuclear magnetic resonance study of AlMo{sub 4}S{sub 8}

Energy Technology Data Exchange (ETDEWEB)

Ikeno, R; Nakamura, H; Kohara, T [Graduate School of Material Science, University of Hyogo, Kamigori, Ako-gun, Hyogo 678-1297 (Japan)

2007-01-31

The cluster-spin dynamics of the tetrahedral Mo{sub 4} cluster, involved in AlMo{sub 4}S{sub 8} with a cubic GaMo{sub 4}S{sub 8} type structure, was investigated by NMR of the nonmagnetic {sup 27}Al site located outside the cluster. The nuclear spin-lattice relaxation is described well by the conventional local moment model assuming the presence of S=1/2 at each cluster, indicating that each Mo{sub 4} cluster behaves like a local spin with rigid magnitude. This behaviour is in contrast to the in-cluster relaxation, which reflects the spin-density fluctuations inside the cluster as a small unit of metal.

Seismic passive earth resistance using modified pseudo-dynamic method

Science.gov (United States)

Pain, Anindya; Choudhury, Deepankar; Bhattacharyya, S. K.

2017-04-01

In earthquake prone areas, understanding of the seismic passive earth resistance is very important for the design of different geotechnical earth retaining structures. In this study, the limit equilibrium method is used for estimation of critical seismic passive earth resistance for an inclined wall supporting horizontal cohesionless backfill. A composite failure surface is considered in the present analysis. Seismic forces are computed assuming the backfill soil as a viscoelastic material overlying a rigid stratum and the rigid stratum is subjected to a harmonic shaking. The present method satisfies the boundary conditions. The amplification of acceleration depends on the properties of the backfill soil and on the characteristics of the input motion. The acceleration distribution along the depth of the backfill is found to be nonlinear in nature. The present study shows that the horizontal and vertical acceleration distribution in the backfill soil is not always in-phase for the critical value of the seismic passive earth pressure coefficient. The effect of different parameters on the seismic passive earth pressure is studied in detail. A comparison of the present method with other theories is also presented, which shows the merits of the present study.

Relative recoilless F-factors in REFeO{sub 3} (RE = rare-earth La, Pr, Nd and Sm) orthoferrites synthesized by self-combustion method

Energy Technology Data Exchange (ETDEWEB)

Morales, L.A; Sierra-Gallego, G. [Departamento de Materiales y Minerales, Facultad de Minas, Universidad Nacional de Colombia, Calle 75 # 79A-51, Bloque M17, Medellín (Colombia); Barrero, C.A. [Grupo de Estado Sólido, Instituto de Física, Universidad de Antioquia, Calle 70 No. 52-21, A.A. 1226, Medellín (Colombia); Arnache, O., E-mail: oscar.arnache@udea.edu.co [Grupo de Estado Sólido, Instituto de Física, Universidad de Antioquia, Calle 70 No. 52-21, A.A. 1226, Medellín (Colombia)

2016-09-15

Highlights: • Rare-earth orthoferrites were successfully synthesized by the self-combustion method. • The relative recoilless F-factors for REFeO{sub 3} with respect to α-Fe were calculated. • Magnetic hyperfine fields, cell volumes and Fe−O−Fe bond angles are correlated. - Abstract: In this work, rare-earth orthoferrites polycrystalline compounds REFeO{sub 3} (REFO) with RE = rare-earth La, Pr, Nd and Sm were synthesized by the self-combustion method. A direct correlation between the magnitude of the magnetic hyperfine field and the Fe−O{sub 1}−Fe bond angles was observed. From transmission Mössbauer spectra recorded at room-temperature, relative recoilless F-factors for these REFO compounds were estimated. The method applied to perform this calculation was based on the determination of two subspectral areas present in a mixture of known amounts of the compound under study and a standard sample (α-Fe). For that purpose spectra were thickness-corrected and fitted using lorentzian lines. The so obtained factors were F-{sub REFeO3} (RE = rare-earth La, Pr, Nd and Sm): 1.30 ± 0.02, 1.08 ± 0.04, 1.15 ± 0.05, 1.18 ± 0.08 respectively. The absolute recoilless factors obtained by this method had an average relative error around 11% in comparison with the values predicted by the Debye model.

Synthesis and characterization of BaAl{sub 2}O{sub 4}:Eu{sup 2+} co-doped with different rare earth ions

Energy Technology Data Exchange (ETDEWEB)

Lephoto, M.A. [Department of Physics, University of the Free State, Private bag X 13, Phuthaditjaba 9866, P.O. Box 339, Bloemfontein, ZA 9300 (South Africa); Ntwaeaborwa, O.M., E-mail: ntwaeab@ufs.ac.za [Department of Physics, University of the Free State, Private bag X 13, Phuthaditjaba 9866, P.O. Box 339, Bloemfontein, ZA 9300 (South Africa); Pitale, Shreyas S.; Swart, H.C. [Department of Physics, University of the Free State, Private bag X 13, Phuthaditjaba 9866, P.O. Box 339, Bloemfontein, ZA 9300 (South Africa); Botha, J.R. [Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth, ZA 6031 (South Africa); Mothudi, B.M. [Department of Physics, University of South Africa, P.O Box 392, Pretoria, ZA 6031 (South Africa)

2012-05-15

Combustion method was used in this study to prepare BaAl{sub 2}O{sub 4}:Eu{sup 2+} phosphors co-doped with different trivalent rare-earths (Re{sup 3+}=Dy{sup 3+}, Nd{sup 3+}, Gd{sup 3+}, Sm{sup 3+}, Ce{sup 3+}, Er{sup 3+}, Pr{sup 3+} and Tb{sup 3+}) ions at an initiating temperature of 600 Degree-Sign C. The phosphors were annealed at 1000 Degree-Sign C for 3 h. As confirmed from the X-ray diffraction (XRD) data, both as prepared and post annealed samples crystallized in the well known hexagonal structure of BaAl{sub 2}O{sub 4}. All samples exhibited bluish-green emission associated with the 4f{sup 6}5d{sup 1}{yields}4f{sup 7} transitions of Eu{sup 2+} at {approx}500 nm. Although the highest intensity was observed from Er{sup 3+} co-doping, the longest afterglow (due to trapping and detrapping of charge carriers) was observed from Nd{sup 3+} followed by Dy{sup 3+} co-doping. The traps responsible for the long afterglow were studied using thermoluminescence (TL) spectroscopy.

The O{sub 2} A-Band in the Fluxes and Polarization of Starlight Reflected by Earth-Like Exoplanets

Energy Technology Data Exchange (ETDEWEB)

Fauchez, Thomas [Laboratoire d’Optique Atmosphèrique (LOA), UMR 8518, Université Lille 1, Villeneuve d’Ascq (France); Rossi, Loic; Stam, Daphne M. [Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft (Netherlands)

2017-06-10

Earth-like, potentially habitable exoplanets are prime targets in the search for extraterrestrial life. Information about their atmospheres and surfaces can be derived by analyzing the light of the parent star reflected by the planet. We investigate the influence of the surface albedo A {sub s}, the optical thickness b {sub cloud}, the altitude of water clouds, and the mixing ratio of biosignature O{sub 2} on the strength of the O{sub 2} A-band (around 760 nm) in the flux and polarization spectra of starlight reflected by Earth-like exoplanets. Our computations for horizontally homogeneous planets show that small mixing ratios ( η < 0.4) will yield moderately deep bands in flux and moderate-to-small band strengths in polarization, and that clouds will usually decrease the band depth in flux and the band strength in polarization. However, cloud influence will be strongly dependent on properties such as optical thickness, top altitude, particle phase, coverage fraction, and horizontal distribution. Depending on the surface albedo and cloud properties, different O{sub 2} mixing ratios η can give similar absorption-band depths in flux and band strengths in polarization, especially if the clouds have moderate-to-high optical thicknesses. Measuring both the flux and the polarization is essential to reduce the degeneracies, although it will not solve them, especially not for horizontally inhomogeneous planets. Observations at a wide range of phase angles and with a high temporal resolution could help to derive cloud properties and, once those are known, the mixing ratio of O{sub 2} or any other absorbing gas.

TWO NEARBY SUB-EARTH-SIZED EXOPLANET CANDIDATES IN THE GJ 436 SYSTEM

International Nuclear Information System (INIS)

Stevenson, Kevin B.; Harrington, Joseph; Lust, Nate B.; Blecic, Jasmina; Hardy, Ryan A.; Cubillos, Patricio; Campo, Christopher J.; Lewis, Nikole K.; Montagnier, Guillaume; Moses, Julianne I.; Visscher, Channon

2012-01-01

We report the detection of UCF-1.01, a strong exoplanet candidate with a radius 0.66 ± 0.04 times that of Earth (R ⊕ ). This sub-Earth-sized planet transits the nearby M-dwarf star GJ 436 with a period of 1.365862 ± 8 × 10 –6 days. We also report evidence of a 0.65 ± 0.06 R ⊕ exoplanet candidate (labeled UCF-1.02) orbiting the same star with an undetermined period. Using the Spitzer Space Telescope, we measure the dimming of light as the planets pass in front of their parent star to assess their sizes and orbital parameters. If confirmed today, UCF-1.01 and UCF-1.02 would be designated GJ 436c and GJ 436d, respectively, and would be part of the first multiple-transiting-planet system outside of the Kepler field. Assuming Earth-like densities of 5.515 g cm –3 , we predict both candidates to have similar masses (∼0.28 Earth-masses, M ⊕ , 2.6 Mars-masses) and surface gravities of ∼0.65 g (where g is the gravity on Earth). UCF-1.01's equilibrium temperature (T eq , where emitted and absorbed radiation balance for an equivalent blackbody) is 860 K, making the planet unlikely to harbor life as on Earth. Its weak gravitational field and close proximity to its host star imply that UCF-1.01 is unlikely to have retained its original atmosphere; however, a transient atmosphere is possible if recent impacts or tidal heating were to supply volatiles to the surface. We also present additional observations of GJ 436b during secondary eclipse. The 3.6 μm light curve shows indications of stellar activity, making a reliable secondary eclipse measurement impossible. A second non-detection at 4.5 μm supports our previous work in which we find a methane-deficient and carbon monoxide-rich dayside atmosphere.

Two nearby Sub-Earth-sized Exoplanet Candidates in the GJ 436 System

Science.gov (United States)

Stevenson, Kevin B.; Harrington, Joseph; Lust, Nate B.; Lewis, Nikole K.; Montagnier, Guillaume; Moses, Julianne I.; Visscher, Channon; Blecic, Jasmina; Hardy, Ryan A.; Cubillos, Patricio; Campo, Christopher J.

2012-08-01

We report the detection of UCF-1.01, a strong exoplanet candidate with a radius 0.66 ± 0.04 times that of Earth (R ⊕). This sub-Earth-sized planet transits the nearby M-dwarf star GJ 436 with a period of 1.365862 ± 8 × 10-6 days. We also report evidence of a 0.65 ± 0.06 R ⊕ exoplanet candidate (labeled UCF-1.02) orbiting the same star with an undetermined period. Using the Spitzer Space Telescope, we measure the dimming of light as the planets pass in front of their parent star to assess their sizes and orbital parameters. If confirmed today, UCF-1.01 and UCF-1.02 would be designated GJ 436c and GJ 436d, respectively, and would be part of the first multiple-transiting-planet system outside of the Kepler field. Assuming Earth-like densities of 5.515 g cm-3, we predict both candidates to have similar masses (~0.28 Earth-masses, M ⊕, 2.6 Mars-masses) and surface gravities of ~0.65 g (where g is the gravity on Earth). UCF-1.01's equilibrium temperature (T eq, where emitted and absorbed radiation balance for an equivalent blackbody) is 860 K, making the planet unlikely to harbor life as on Earth. Its weak gravitational field and close proximity to its host star imply that UCF-1.01 is unlikely to have retained its original atmosphere; however, a transient atmosphere is possible if recent impacts or tidal heating were to supply volatiles to the surface. We also present additional observations of GJ 436b during secondary eclipse. The 3.6 μm light curve shows indications of stellar activity, making a reliable secondary eclipse measurement impossible. A second non-detection at 4.5 μm supports our previous work in which we find a methane-deficient and carbon monoxide-rich dayside atmosphere.

Thermoluminescent analysis of CaSO{sub 4} composites activated with rare earths; Analise termoluminescente de compositos de CaSO{sub 4} ativado com terras raras

Energy Technology Data Exchange (ETDEWEB)

Junot, D.O.; Chagas, M.A.P.; Souza, D.N., E-mail: danilo.junot@hotmail.com, E-mail: mchagasfisica@gmail.com, E-mail: divanizi@ufs.br [Universidade Federal de Sergipe (UFS), Sao Cristovao, SE (Brazil). Departamento de Fisica

2013-07-01

Since the thermoluminescence started to be applied to the dosimetry of ionizing radiation in 1940 different materials detectors have been proposed, and one of the most common is CaSO{sub 4}. The motivation of this work was to produce crystals of CaSO{sub 4} doped with rare earth elements such as europium (Eu), neodymium (Nd) and thulium (Tm). It was also produced crystals of CaSO{sub 4}:Ag. The interest in the production of these materials was to investigate other methods of production of thermoluminescent materials. The results show that the CaSO{sub 4}:Tm is more suitable for use in the thermoluminescent dosimetry. Although not the most intense peak, the peak at 170 °C could be a dosimetric peak. Analyses showed that all samples have a TL response proportional to the dose absorbed. (author)

Reaction kinetics of H{sub 2}, O{sub 2}, and H{sub 2}O with rare earths (Y, La, Ce, Pr, Nd, Gd, Tb, Dy, and Er) at 298 K

Energy Technology Data Exchange (ETDEWEB)

Enomoto, M.; Ohata, Y. [Course of Applied Science, Graduate School of Engineering, Tokai University, 4-1-1 Kita-Kaname, Hiratsuka, Kanagawa 259-1292 (Japan); Uchida, H., E-mail: huchida@keyaki.cc.u-tokai.ac.jp [Course of Applied Science, Graduate School of Engineering, Tokai University, 4-1-1 Kita-Kaname, Hiratsuka, Kanagawa 259-1292 (Japan)

2013-12-15

Highlights: ► H{sub 2} molecules react with a clean surface of each RE sample at the highest reactivity even at 298 K. ► The H{sub 2} reactivity becomes reduced by the formation of dihydrides of each RE sample. ► The RE with a clean surface adsorb O{sub 2} more than one monolayer of O{sub 2} even at 298 K. ► The quantitative reactivity of the H atoms dissociated from H{sub 2}O was calculated. -- Abstract: High reactivity of rare earths (RE) with H{sub 2}, O{sub 2} and H{sub 2}O is well known even at room temperature. The formation of stable surface oxides/hydroxides on the surface is the one of serious problems in the production and use of materials containing RE. We have investigated the quantitative reactivities of H{sub 2}, O{sub 2}, and H{sub 2}O with the surface of Y, La, Ce, Pr, Nd, Gd, Tb, Dy, and Er under ultra high vacuum condition. The H{sub 2}, O{sub 2} and H{sub 2}O gases exhibited the highest reactivity on the clean surface of the RE at 298 K. This means that all gas molecules impinging the surface dissociate and chemisorbed. The O atoms dissociated from O{sub 2} adsorb to for oxides layers of the metals. The H atoms dissociated from H{sub 2} diffuse into the metals to form hydrides which were found to decrease the H{sub 2} reactivity. The H atoms dissociated form H{sub 2}O diffuse into the metals or form hydroxides of the metals. With increasing coverage of each gas molecules, the reactivity of each gas was decreased by several orders of magnitude.

Organic Aerosols in the Presence of CO{sub 2} in the Early Earth and Exoplanets: UV–Vis Refractive Indices of Oxidized Tholins

Energy Technology Data Exchange (ETDEWEB)

Gavilan, Lisseth; Carrasco, Nathalie; Vettier, Ludovic [LATMOS, Université Versailles St Quentin, UPMC Université Paris 06, CNRS, 11 blvd d’Alembert, F-78280 Guyancourt (France); Broch, Laurent [LCP-A2MC, Institut Jean Barriol, Université de Lorraine, Metz (France); Fleury, Benjamin, E-mail: lisseth.gavilan@latmos.ipsl.fr [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

2017-10-10

In this experimental study we investigate the role of atmospheric CO{sub 2} on the optical properties of organic photochemical aerosols. To this end, we add CO{sub 2} to a N{sub 2}:CH{sub 4} gas mixture used in a plasma typically used for Titan studies. We produce organic thin films (tholins) in plasmas where the CO{sub 2}/CH{sub 4} ratio is increased from 0 to 4. We measure these films via spectrometric ellipsometry and apply a Tauc–Lorentz model, used for optically transparent materials, to obtain the thickness of the thin film, its optical band gap, and the refractive indices in the UV–visible (270–600 nm). All samples present a significant absorption band in the UV. According to the Tauc–Lorentz model, as the CO{sub 2}/CH{sub 4} ratio is quadrupled, the position of the UV band is shifted from ∼177 nm to 264 nm while its strength is quadrupled. Consequently, we infer that oxidized organic aerosols absorb more efficiently at longer UV wavelengths than reduced aerosols. Our laboratory wavelength-tabulated UV–vis refractive indices provide new constraints to atmospheric models of the early Earth and Earth-like exoplanets including photochemical hazes formed under increasingly oxidizing conditions.

Some thermoelectric properties of the light rare earth sesquiselenides (R2Se/sub 3-x/)

International Nuclear Information System (INIS)

Takeshita, T.; Beaudry, B.J.; Gschneidner, K.A. Jr.

1981-01-01

Rare earth sesquiselenides of the Th 3 P 4 structure show variable electric properties over their homogeneity range, i.e., ranging from metallic (R 3 Se 4 ) to semimetallic (R 2 Se/sub 3-x/, where 0.14 > x > 0) to semiconducting (R 2 Se 3 ). The composition change is due to the formation of metal vacancies in the Th 3 P 4 structure with no vacancies at R 3 Se 4 and 4.75 at. % vacancies at R 2 Se 3 . The rare earth sesquiselenides are also refractory materials and therefore are of interest for high temperature thermoelectric applications. Preliminary results of thermoelectric power and electrical resistivity measurements on the light lanthanide sesquiselenides (La through Sm) are presented

Structural modulation and luminescent properties of four Cd{sup II} coordination architectures based on 3-(pyridin-4-yl)-5-(pyrazin-2-yl)-1H-1,2,4-triazole and flexible/rigid dicarboxylate ligands

Energy Technology Data Exchange (ETDEWEB)

Xia, Liang; Dong, Wen-Wen, E-mail: dongww1@126.com; Ye, Xiao; Zhao, Jun; Li, Dong-Sheng, E-mail: lidongsheng1@126.com

2016-10-15

To systematically investigate the influence of the flexible or rigid auxiliary ligands on the structures and properties of transition metal compounds, we synthesized four new d{sup 10} coordination polymers (CPs) from 3-(pyridin-4-yl)-5-(pyrazin-2-yl)-1H-1,2,4-triazole (4-Hpzpt) and flexible/rigid dicarboxylate ligands, [Cd(4-pzpt){sub 2}]{sub n} (1), [Cd{sub 3}(4-pzpt){sub 2}(suc){sub 2}]{sub n} (2), [Cd{sub 2}(4-Hpzpt)(nbc){sub 2}(H{sub 2}O)]{sub n} (3) and ([Cd{sub 2}(4-pzpt){sub 2}(tfbdc)(H{sub 2}O){sub 4}]·H{sub 2}O){sub n} (4) (H{sub 2}suc=1,2-ethanedicarboxylic acid, H{sub 2}nbc=hthalene-1,4-dicarboxylic acid, H{sub 2}tfbdc =2,3,5,6-tetrafluoroterephthalic acid). Single crystal X-ray analysis indicates that compound 1 shows a 4{sup 4}-sql layer, which is extended to a 3D network via nonclassical C–H{sup …}N hydrogen bonds. Compound 2 possesses a 6-connected pcu-4{sup 12}0.6{sup 3} net composed of trinuclear Cd{sup II}-clusters. Compound 3 represents a rare 3D (3,4,4,5)-connected topology with a Schläfli symbol of (4·6·7)(4·5{sup 3}·7{sup 2})(5{sup 3}·6·7·9)(4{sup 2}·5{sup 5}·6·7{sup 2}). Compound 4 exhibits a 2D+2D→2D parallel interpenetrated 6{sup 3}-hcb network. The adjacent 2D networks are interdigitated with each other to form the resulting 3D supramolecular architecture through classical O–H{sup …}N and O–H{sup …}O hydrogen bonds. Structural diversities indicate that the nature of flexible/rigid-dicarboxlates plays crucial roles in modulating structures of these compounds. Moreover, the luminescent properties of them have been briefly investigated. - Graphical abstract: Four new Cd{sup II} coordination architectures constructed from the primary ligand 4-Hpzpt and flexible/rigid dicarboxylate coligands. Structural diversities indicate that the nature of flexible/rigid-dicarboxlates plays crucial roles in modulating structures of these compounds. And more, the thermal stability and luminescence are discussed. - Highlights: �

Squeezing clathrate cages to host trivalent rare-earth guests

Energy Technology Data Exchange (ETDEWEB)

Wang, Jian [Iowa State Univ., Ames, IA (United States). Department of Chemistry; Ames Lab., Ames, IA (United States); He, Yuping [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Mordvinova, Natalia E. [Laboratoire CRISMAT, ENSICAEN, CNRS UMR (France); Lebedev, Oleg [Laboratoire CRISMAT, ENSICAEN, CNRS UMR (France); Kovnir, Kirill [Iowa State Univ., Ames, IA (United States). Department of Chemistry; Ames Lab., Ames, IA (United States)

2017-11-01

Strike difference of the trivalent rare-earth cations from their alkali and alkaline-earth peers is in the presence of localized 4f-electrons and strong spin-orbit coupling. Placing trivalent rare-earth cations inside the fullerene molecules or in between the blocks of itinerant magnetic intermetallics gave rise to plethora of fascinating properties and materials. A long-time missing but hardly desired piece is the semiconducting or metallic compound where rare-earth cations are situated inside the oversized polyhedral cages of three-dimensional framework. In this work we present a synthesis of such compounds, rare-earth containing clathrates Ba<sub>8-xsub>R_xCu>16sub>P>30sub>. The unambiguous proofs of their composition and crystal structure were achieved by a combination of synchrotron powder diffraction, time-of-flight neutron powder diffraction, scanning-transmission electron microscopy, and electron energy-loss spectroscopy. Our quantum-mechanical calculations and experimental characterizations show that the incorporation of the rare-earth cations significantly enhances the hole mobility and concentration which results in the drastic increase in the thermoelectric performance.

Electronic and magnetic structure of RENi{sub 2}Mn{sub x}-compounds (RE = rare earth, x = 0, 0.25, 0.5, 0.75, 1, 1.25) with respect to ErNi{sub 2}Mn{sub x}

Energy Technology Data Exchange (ETDEWEB)

Balinski, Kamil; Kuepper, Karsten [Department of Physics, Osnabrueck University (Germany); Chrobak, Artur [Department of Physics, University of Silesia in Katowice (Poland); Kuznetzsova, T.V.; Mushnikov, N.V.; Marchenkov, V.V. [Institute of Metal Physics, 620990 Ekaterinburg (Russian Federation)

2015-07-01

Rare earth (RE) and transition metal (T) compounds are research field since the 1960s. Because of huge magnetocalorical effect and giant magnetostriction the RE-T-compounds are excellent for applications like magnetic cooling or hydrogen storage devices. Besides of that RE-Ni{sub 2}-type of alloys are, due to the relatively simple crystal structure and the fact that Ni{sub 2} does not indicate any %behavior with result in an magnetic moment, excellent candidates for studies of magnetic behavior of RE's and their binding partners. The electronic structure of ErNi{sub 2}Mn{sub x} (x = 0, 0.25, 0.5, 0.75, 1, 1.25) is characterized by XPS and ResPES, the magnetic structure is investigated by SQUID and PPMS techniques, and resistivity measurements are made. Variation in Mn concentration revealed the position of Mn 3d-states at 1.7 eV. The XPS intensity at 1.7 eV can be correlated with the behavior of the Curie temperature and the resistivity. While similar RENi{sub 2}Mn{sub x}-systems, where RE had been replaced by Gd and Tb, highest resistivity, Curie temperature and the highest Mn 3d-valence band state intensity were observed at x = 0.5. ErNi{sub 2}Mn{sub x}-system behave different and show the mentioned maxima at x = 1.25.

The Nature of the Distinctive Microscopic Features in R<sub>5sub>(Si_xGe>1-xsub>)>4sub> Magnetic Refrigeration Materials

Energy Technology Data Exchange (ETDEWEB)

Ugurlu, Ozan [Iowa State Univ., Ames, IA (United States)

2006-01-01

Magnetic refrigeration is a promising technology that offers a potential for high energy efficiency. The giant magnetocaloric effect of the R<sub>5sub>(Si<sub>x>, Ge<sub>1-xsub>)>4sub> alloys (where R=rare-earth and O ≤ x ≤ 1), which was discovered in 1997, make them perfect candidates for magnetic refrigeration applications. In this study the microstructures of Gd<sub>5sub>(Six>, Ge<sub>1-xsub>)>4sub> alloys have been characterized using electron microscopy techniques, with the focus being on distinctive linear features first examined in 1999. These linear features have been observed in R<sub>5sub>(Six>, Ge<sub>1-xsub>)>4sub> alloys prepared from different rare-earths (Gd, Tb, Dy and Er) with different crystal structures (Gd<sub>5sub>Si>4sub>-type orthorhombic, monoclinic and Gd<sub>5sub>Ge>4sub>-type orthorhombic). Systematic scanning electron microscope studies revealed that these linear features are actually thin-plates, which grow along specific directions in the matrix material. The crystal structure of the thin-plates has been determined as hexagonal with lattice parameters a=b=8.53 Å and c=6.40 Å using selected area diffraction (SAD). Energy dispersive spectroscopy analysis, carried out in both scanning and transmission electron microscopes, showed that the features have a composition approximating to R<sub>5sub>Six,Ge>1-xsub>)>3sub>.phase. Orientation relationship between the matrix and the thin-plates has been calculated as [- 1010](1-211)<sub>p>//[010](10-2)<sub>m>. The growth direction of the thin plates are calculated as (22 0 19) and (-22 0 19) by applying the Ag approach of Zhang and Purdy to the SAD patterns of this system. High Resolution TEM images of the Gd_{5sub>Ge>4sub> were used to study the crystallographic relationship. A terrace-ledge structure was observed at the interface and a 7° rotation of the reciprocal lattices}

Luminescent phosphors, based on rare earth substituted oxyfluorides in the A(1){sub 3-x} A(2){sub x}MO{sub 4}F family with A(1)/A(2)=Sr, Ca, Ba and M=Al, Ga

Energy Technology Data Exchange (ETDEWEB)

Park, Sangmoon, E-mail: spark@silla.ac.k [Department of Engineering in Energy and Applied Chemistry, Silla University, Busan 617-736 (Korea, Republic of); Vogt, Thomas [NanoCenter and Department of Chemistry and Biochemistry, University of South Carolina, Columbia 29208, SC (United States)

2009-09-15

A new family of UV-activated phosphors made by substituting rare-earth activators such as trivalent Eu, Tb, Tm and Er into A(1){sub 3-x}A(2){sub x}MO{sub 4}F host lattices (A(1)/A(2)=Sr, Ca, Ba; M=Al, Ga) are introduced and their activation and emission spectra as well as their CIE values reported. The Tm-substituted system can be activated using light with a wavelength of 360 nm. Relative intensities of a family of Tb-substituted green phosphors activated at 254 nm and with emissions centered near 548 nm are discussed.

Superstructure formation in PrNi{sub 2}Al{sub 3} and ErPd{sub 2}Al{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Eustermann, Fabian; Hoffmann, Rolf-Dieter [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie; Janka, Oliver [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie; Oldenburg Univ. (Germany). Inst. fuer Chemie

2017-09-01

The intermetallic phase ErPd{sub 2}Al{sub 3} was obtained by arc-melting of the elements and subsequent annealing for crystal growth. The sample was studied by X-ray diffraction on powders and single crystals. The structure of ErPd{sub 2}Al{sub 3} was refined from X-ray diffraction data and revealed a superstructure of PrNi{sub 2}Al{sub 3} - a CaCu{sub 5} derivative (P6/m, a=1414.3(1), c=418.87(3) pm wR=0.0820, 1060 F{sup 2} values, 48 variables). The same superstructure was subsequently found for PrNi{sub 2}Al{sub 3} (P6/m, a=1407.87(4), c=406.19(2) pm, wR=0.0499, 904 F{sup 2} values, 47 variables). In the crystal structure, the aluminium and transition metal atoms form a polyanionic network according to [T{sub 2}Al{sub 3}]{sup δ-}, while rare earth atoms fill cavities within the networks. They are coordinated by six transition metal and twelve aluminum atoms. In contrast to the PrNi{sub 2}Al{sub 3} type structure reported so far, two crystallographic independent rare-earth sites are found of which one (1b) is shifted by 1/2 z, causing a distortion in the structure along with a recoloring of the T and Al atoms in the network.

Formation of Self-Assembled Ba<sub>2sub>YNbO>6sub> Nanocolumns and their Contribution to Flux-Pinning and J<sub>c> in Nb-doped YBa<sub>2sub>Cu>3sub>O>7- sub> Films

Energy Technology Data Exchange (ETDEWEB)

Wee, Sung Hun [ORNL; Goyal, Amit [ORNL; Zuev, Yuri L [ORNL; Cantoni, Claudia [ORNL; Selvamanickam, V. [SuperPower Incorporated, Schenectady, New York; Specht, Eliot D [ORNL

2010-01-01

Ba{sub 2}RENbO{sub 6} (RE = rare earth elements including Y) compounds are considered new additives for superior flux-pinning in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) films due to their excellent chemical inertness to and large lattice mismatches with YBCO. Simultaneous laser ablation of a YBCO target and a Nb metal foil attached to the surface of the target resulted in epitaxial growth of YBCO films having columnar defects comprised of self-aligned Ba{sub 2}YNbO{sub 6} (BYNO) nanorods parallel to the c-axis of the film. Compared to pure YBCO, YBCO+BYNO films exhibited no T{sub c} reduction as well as superior J{sub c} performance with higher self- and in-field J{sub c} by a factor of 1.5-7 and also exhibited a strong J{sub c} peak for H {parallel} c indicative of strong c-axis correlated flux-pinning.

Cosmic ray access to earth satellites from below-horizon directions

International Nuclear Information System (INIS)

Humble, J.E.; Smart, D.F.; Shea, M.A.

1982-01-01

The traditional description of cosmic ray access to a given point, by use of main and Stormer cut-off rigidities, is not appropriate to describe the behaviour of charged particles approaching an earth satellite from all possible directions below the optical horizon. From certain azimuths, particles of high rigidity are unable to reach the spacecraft whilst particles at lower rigidity, having smaller local radii of curvature in the geomagnetic field, can reach it. In such cases no main cut-off, in the normal sense of that term, can exist. Examples of this behaviour are shown and appropriate new cut-off definitions are provided

Can deformation of a polymer film with a rigid coating model geophysical processes?

Science.gov (United States)

Volynskii, A. L.; Bazhenov, S. L.

2007-12-01

The structural and mechanical behavior of polymer films with a thin rigid coating is analyzed. The behavior of such systems under applied stress is accompanied by the formation of a regular wavy surface relief and by regular fragmentation of the coating. The above phenomena are shown to be universal. Both phenomena (stress-induced development of a regular wavy surface relief and regular fragmentation of the coating) are provided by the specific features of mechanical stress transfer from a compliant soft support to a rigid thin coating. The above phenomena are associated with a specific structure of the system, which is referred to as “a rigid coating on a soft substratum” system (RCSS). Surface microrelief in RCSS systems is similar to the ocean floor relief in the vicinity of mid-oceanic ridges. Thus, the complex system composed of a young oceanic crust and upper Earth's mantle may be considered as typically “a solid coating on a soft substratum” system. Specific features of the ocean floor relief are analyzed in terms of the approach advanced for the description of the structural mechanical behavior of polymer films with a rigid coating. This analysis allowed to estimate the strength of an ocean floor.

IMPACT OF η{sub Earth} ON THE CAPABILITIES OF AFFORDABLE SPACE MISSIONS TO DETECT BIOSIGNATURES ON EXTRASOLAR PLANETS

Energy Technology Data Exchange (ETDEWEB)

Léger, Alain [IAS, Univ. Paris-Sud, Orsay (France); Defrère, Denis [Steward Observatory, Department of Astronomy, University of Arizona, 933 N. Cherry Ave, Tucson, AZ 85721 (United States); Malbet, Fabien [UJF-Grenoble 1/CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), UMR 5274, BP 53, F-38041 Grenoble cedex 9 (France); Labadie, Lucas [I. Physikalisches Institut der Universität zu Köln, Zülpicher Str. 77, D-50937 Cologne (Germany); Absil, Olivier, E-mail: Alain.Leger@ias.u-psud.fr [Département d’Astrophysique, Géophysique and Océanographie, Université de Liège, 17 Allée du Six Août, B-4000 Liège (Belgium)

2015-08-01

We present an analytic model to estimate the capabilities of space missions dedicated to the search for biosignatures in the atmosphere of rocky planets located in the habitable zone of nearby stars. Relations between performance and mission parameters, such as mirror diameter, distance to targets, and radius of planets, are obtained. Two types of instruments are considered: coronagraphs observing in the visible, and nulling interferometers in the thermal infrared. Missions considered are: single-pupil coronagraphs with a 2.4 m primary mirror, and formation-flying interferometers with 4 × 0.75 m collecting mirrors. The numbers of accessible planets are calculated as a function of η{sub Earth}. When Kepler gives its final estimation for η{sub Earth}, the model will permit a precise assessment of the potential of each instrument. Based on current estimations, η{sub Earth} = 10% around FGK stars and 50% around M stars, the coronagraph could study in spectroscopy only ∼1.5 relevant planets, and the interferometer ∼14.0. These numbers are obtained under the major hypothesis that the exozodiacal light around the target stars is low enough for each instrument. In both cases, a prior detection of planets is assumed and a target list established. For the long-term future, building both types of spectroscopic instruments, and using them on the same targets, will be the optimal solution because they provide complementary information. But as a first affordable space mission, the interferometer looks the more promising in terms of biosignature harvest.

Bang-Bang Practical Stabilization of Rigid Bodies

Science.gov (United States)

Serpelloni, Edoardo

In this thesis, we study the problem of designing a practical stabilizer for a rigid body equipped with a set of actuators generating only constant thrust. Our motivation stems from the fact that modern space missions are required to accurately control the position and orientation of spacecraft actuated by constant-thrust jet-thrusters. To comply with the performance limitations of modern thrusters, we design a feedback controller that does not induce high-frequency switching of the actuators. The proposed controller is hybrid and it asymptotically stabilizes an arbitrarily small compact neighborhood of the target position and orientation of the rigid body. The controller is characterized by a hierarchical structure comprising of two control layers. At the low level of the hierarchy, an attitude controller stabilizes the target orientation of the rigid body. At the high level, after the attitude controller has steered the rigid body sufficiently close to its desired orientation, a position controller stabilizes the desired position. The size of the neighborhood being stabilized by the controller can be adjusted via a proper selection of the controller parameters. This allows us to stabilize the rigid body to virtually any degree of accuracy. It is shown that the controller, even in the presence of measurement noise, does not induce high-frequency switching of the actuators. The key component in the design of the controller is a hybrid stabilizer for the origin of double-integrators affected by bounded external perturbations. Specifically, both the position and the attitude stabilizers consist of multiple copies of such a double-integrator controller. The proposed controller is applied to two realistic spacecraft control problems. First, we apply the position controller to the problem of stabilizing the relative position between two spacecraft flying in formation in the vicinity of the L2 libration point of the Sun-Earth system as a part of a large space telescope

Rare earth ion controlled crystallization of mica glass-ceramics

Energy Technology Data Exchange (ETDEWEB)

Garai, Mrinmoy; Karmakar, Basudeb, E-mail: basudebk@cgcri.res.in

2016-09-05

In understanding the effects of rare earth ions to control the crystallization and microstructure of alkaline boroaluminosilicate system, the CeO{sub 2}, Nd{sub 2}O{sub 3}, Sm{sub 2}O{sub 3} and Gd{sub 2}O{sub 3} doped K{sub 2}O−MgO−B{sub 2}O{sub 3}−Al{sub 2}O{sub 3}−SiO{sub 2}−F glasses were synthesized by melt-quenching at 1550 °C. Higher density (2.82–3.06 g cm{sup −3}) and thermal stability (glass phase) is experiential on addition of rare earth content, which also affects in increasing the glass transition temperature (T{sub g}) and crystallization temperature (T{sub c}). Decrease of thermal expansion in glasses with rare earth ion content is maintained by the stabilization of glass matrix owing to their large cationic field strength. A significant change in the non-isothermal DSC thermogram observed at 750–1050 °C is attributed to fluorophlogopite crystallization. Opaque glass-ceramics were prepared from such glasses by single step heat-treatment at 1050 °C; and the predominant crystalline phases are identified as fluorophlogopite mica, KMg{sub 3}(AlSi{sub 3}O{sub 10})F{sub 2} by XRD and EDX analysis. The compact glass-ceramic microstructure by the agglomeration of fluorophlogopite mica crystallites (crystal size ∼ 100–500 nm, FESEM) is achieved in attendance of rare earth ion; and such microstructure controlled the variation of density, thermal expansion and microhardness value. Higher thermal expansion (11.11–14.08 × 10{sup −6}/K at 50–800 °C and 50–900 °C) of such glass-ceramics approve that these rare earth containing glasses can be useful for high temperature vacuum sealing application with metal or solid electrolyte. The increase of Vickers microhardness (5.27–5.61 GPa) in attendance of rare earth ions is attributed to the compact crystallinity of fluorophlogopite mica glass-ceramic microstructure. - Highlights: • Synthesis of rare earth oxide doped alkaline boroaluminosilicate glasses. • Development of opaque

Low beta rigid mode stability criterion for an arbitrary Larmor radius plasma

International Nuclear Information System (INIS)

Berk, H.L.; Wong, H.V.

1987-05-01

The low beta flute interchange dispersion relation for rigid displacement perturbation of axisymmetric plasma equilibria with arbitrary Larmor radius particles and field line curvature, large compared to the plasma radius, is derived. The equilibrium particle orbits are characterized by two constants of motion, energy and angular momentum, and a third adiabatic invariant derived from the rapid radial motion. The Vlasov equation is integrated, assuming that the mode frequency, axial ''bounce'' frequency, and particle drift frequency are small compared to the cyclotron frequency, and it is demonstrated that the plasma response to a rigid perturbation has a universal character independent of Larmor radius. As a result the interchange instability is the same as that predicted from conventional MHD theory. However, a new prediction, more optimistic than earlier work, is found for the low density threshold of systems like Migma, which are disc-shaped, that is, the axial extent Δz is less than the radial extent r 0 . For Δz/sub r 0 / much less than 1, the stability criterion is determined by the total particle number. Whereas the older theory (Δz/sub r 0 / much greater than 1) predicted instability at about the densities achieved in actual Migma experiments, the present theory (Δz/sub r 0 / much less than 1) indicates that the experimental results were for plasmas with particle number below the interchange threshold

The two-body problem of a pseudo-rigid body and a rigid sphere

DEFF Research Database (Denmark)

Kristiansen, Kristian Uldall; Vereshchagin, M.; Gózdziewski, K.

2012-01-01

n this paper we consider the two-body problem of a spherical pseudo-rigid body and a rigid sphere. Due to the rotational and "re-labelling" symmetries, the system is shown to possess conservation of angular momentum and circulation. We follow a reduction procedure similar to that undertaken...... in the study of the two-body problem of a rigid body and a sphere so that the computed reduced non-canonical Hamiltonian takes a similar form. We then consider relative equilibria and show that the notions of locally central and planar equilibria coincide. Finally, we show that Riemann's theorem on pseudo......-rigid bodies has an extension to this system for planar relative equilibria....

Rigid Body Sampling and Individual Time Stepping for Rigid-Fluid Coupling of Fluid Simulation

Directory of Open Access Journals (Sweden)

Xiaokun Wang

2017-01-01

Full Text Available In this paper, we propose an efficient and simple rigid-fluid coupling scheme with scientific programming algorithms for particle-based fluid simulation and three-dimensional visualization. Our approach samples the surface of rigid bodies with boundary particles that interact with fluids. It contains two procedures, that is, surface sampling and sampling relaxation, which insures uniform distribution of particles with less iterations. Furthermore, we present a rigid-fluid coupling scheme integrating individual time stepping to rigid-fluid coupling, which gains an obvious speedup compared to previous method. The experimental results demonstrate the effectiveness of our approach.

Electrical resistivity of YbRh{sub 2}Si{sub 2} and EuT{sub 2}Ge{sub 2} (T=Co,Cu) at extreme conditions of pressure and temperature

Energy Technology Data Exchange (ETDEWEB)

Dionicio, G.A.

2006-07-01

This investigation addresses the effect that pressure, p, and temperature, T, have on 4f states of the rare-earth elements in the isostructural YbRh{sub 2}Si{sub 2}, EuCo{sub 2}Ge{sub 2}, and EuCu{sub 2}Ge{sub 2} compounds. Upon applying pressure the volume of the unit cell reduces, enforcing either the enhancement of the hybridization of the 4f localized electrons with the ligand or a change in the valence state of the rare-earth ions. Here, we probe the effect of a pressure-induced lattice contraction on these system by means of electrical-resistivity measurements, {rho}(T), from room temperature down to 100 mK. (orig.)

Rotational modes of a simple Earth model

Science.gov (United States)

Seyed-Mahmoud, B.; Rochester, M. G.; Rogister, Y. J. G.

2017-12-01

We study the tilt-over mode (TOM), the spin-over mode (SOM), the free core nutation (FCN), and their relationships to each other using a simple Earth model with a homogeneous and incompressible liquid core and a rigid mantle. Analytical solutions for the periods of these modes as well as that of the Chandler wobble is found for the Earth model. We show that the FCN is the same mode as the SOM of a wobbling Earth. The reduced pressure, in terms of which the vector momentum equation is known to reduce to a scalar second order differential equation (the so called Poincaŕe equation), is used as the independent variable. Analytical solutions are then found for the displacement eigenfucntions in a meridional plane of the liquid core for the aforementioned modes. We show that the magnitude of motion in the mantle during the FCN is comparable to that in the liquid core, hence very small. The displacement eigenfunctions for these aforementioned modes as well as those for the free inner core nutation (FICN), computed numerically, are also given for a three layer Earth model which also includes a rigid but capable of wobbling inner core. We will discuss the slow convergence of the period of the FICN in terms of the characteristic surfaces of the Poincare equation.

Enhanced pinning in mixed rare earth-123 films

Science.gov (United States)

Driscoll, Judith L [Los Alamos, NM; Foltyn, Stephen R [Los Alamos, NM

2009-06-16

An superconductive article and method of forming such an article is disclosed, the article including a substrate and a layer of a rare earth barium cuprate film upon the substrate, the rare earth barium cuprate film including two or more rare earth metals capable of yielding a superconductive composition where ion size variance between the two or more rare earth metals is characterized as greater than zero and less than about 10.times.10.sup.-4, and the rare earth barium cuprate film including two or more rare earth metals is further characterized as having an enhanced critical current density in comparison to a standard YBa.sub.2Cu.sub.3O.sub.y composition under identical testing conditions.

Synthesis, crystal structure, and magnetic properties of novel 2D kagome materials RE{sub 3}Sb{sub 3}Mg{sub 2}O{sub 14} (RE = La, Pr, Sm, Eu, Tb, Ho): Comparison to RE{sub 3}Sb{sub 3}Zn{sub 2}O{sub 14} family

Energy Technology Data Exchange (ETDEWEB)

Sanders, M.B.; Baroudi, K.M.; Krizan, J.W.; Mukadam, O.A.; Cava, R.J. [Department of Chemistry, Princeton University, Princeton, NJ (United States)

2016-10-15

The crystal structures and magnetic properties of RE{sub 3}Sb{sub 3}Mg{sub 2}O{sub 14} (RE = La, Pr, Sm, Eu, Tb, Ho) with a perfect kagome lattice are presented and compared to RE{sub 3}Sb{sub 3}Zn{sub 2}O{sub 14}. Rietveld structure refinements were performed using X-ray diffraction data, indicating that the layered compounds are fully structurally ordered. The compounds crystallize in a rhombohedral supercell of the cubic pyrochlore structure, in the space group R-3m. Magnetic susceptibility measurements show no signs of magnetic ordering above 2 K. The RE{sub 3}Sb{sub 3}Mg{sub 2}O{sub 14} family is similar to that of RE{sub 3}Sb{sub 3}Zn{sub 2}O{sub 14}; however, the series reported here features a fully ordered distribution of cations in both the nonmagnetic antimony and magnetic rare earth kagome lattices. Unlike the offsite disorder that Zn{sup 2+} experiences in RE{sub 3}Sb{sub 3}Zn{sub 2}O{sub 14}, the magnesium sites in RE{sub 3}Sb{sub 3}Mg{sub 2}O{sub 14} are completely ordered. Here we compare the magnetic properties in both series of kagome compounds to determine how significant Zn{sup 2+}'s positional ordering is within this structure type. The compounds reported here appear to be relatively defect-free and are therefore model systems for investigating magnetic frustration on an ideal 2D rare earth kagome lattice. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Rigidly foldable origami gadgets and tessellations

Science.gov (United States)

Evans, Thomas A.; Lang, Robert J.; Magleby, Spencer P.; Howell, Larry L.

2015-01-01

Rigidly foldable origami allows for motion where all deflection occurs at the crease lines and facilitates the application of origami in materials other than paper. In this paper, we use a recently discovered method for determining rigid foldability to identify existing flat-foldable rigidly foldable tessellations, which are also categorized. We introduce rigidly foldable origami gadgets which may be used to modify existing tessellations or to create new tessellations. Several modified and new rigidly foldable tessellations are presented. PMID:26473037

Structural influence of aluminium, gallium and indium metal oxides by means of dielectric and spectroscopic properties of CaO-Sb{sub 2}O{sub 3}-B{sub 2}O{sub 3} glass system

Energy Technology Data Exchange (ETDEWEB)

Srinivasa Reddy, M. [Department of Physics, Acharya Nagarjuna University P.G. Centre, Nuzvid 521 201, AP (India); Naga Raju, G. [Department of Physics, Acharya Nagarjuna University P.G. Centre, Nuzvid 521 201, AP (India); Nagarjuna, G. [Department of Chemistry, Acharya Nagarjuna University, Nagarjunanagar, AP (India); Veeraiah, N. [Department of Physics, Acharya Nagarjuna University P.G. Centre, Nuzvid 521 201, AP (India)]. E-mail: nvr8@rediffmail.com

2007-07-12

Dielectric constant ({epsilon}'), loss (tan {delta}), ac conductivity ({sigma}) of CaO-Sb{sub 2}O{sub 3}-B{sub 2}O{sub 3}:M{sub 2}O{sub 3} (Al{sub 2}O{sub 3}, Ga{sub 2}O{sub 3} and In{sub 2}O{sub 3}) glasses with varying concentrations of M{sub 2}O{sub 3} (0-5 mol%), were measured as a function of frequency and temperature over moderately wide ranges. The analysis of results of these studies along with IR, Raman and optical absorption spectra and also DTA studies indicated that in the concentration ranges, 0 {<=} Al{sub 2}O{sub 3} {<=} 4, 0 {<=} Ga{sub 2}O{sub 3} {<=} 2 and 1 {<=} In{sub 2}O{sub 3} {<=} 5, Al{sup 3+}, Ga{sup 3+} ions occupy tetrahedral positions whereas In{sup 3+} ions take up octahedral substitutional positions, cross-link with the other structural units in the glass network and increase the rigidity of the glass network.

Properties of the histogram location approach and the extent and change of downward nominal wage rigidity in the EU

Directory of Open Access Journals (Sweden)

Andreas Behr

2006-06-01

Full Text Available The histogram location approach has been proposed by Kahn (1997 to estimate the fraction of wage cuts prevented by downward nominal wage rigidity. In this paper, we analyze the validity of the approach by means of a simulation study which yielded evidence of unbiasedness but also of potential underestimation of rigidity parameter uncertainty and therefore of potential anticonservative inference. We apply the histogram location approach to estimate the extent of downward nominal wage rigidity across the EU for 1995-2001. Our data base is the User Data Base (UDB of the European Community Household Panel (ECHP. The results show wide variation in the fraction of wage cuts prevented by nominal wage rigidity across the EU. The lowest rigidity parameters are found for the UK, Spain and Ireland, the largest for Portugal and Italy. Analyzing the change of rigidity between sub periods 1995-1997 and 1999-2001 even shows an widening of the differences in nominal wage rigidity. Due to the finding of large differences across the EU, the results imply that the costs of low inflation policies across the EU differ substantially.

Study of CeO{sub x}, PrO{sub x}, and Ce{sub x}Pr{sub 1-x}O{sub 2-{delta}} films on Si(111) by means of high-energetic X-ray photoelectron spectroscopy; Untersuchung von CeO{sub x}-, PrO{sub x}- und Ce{sub x}Pr{sub 1-x}O{sub 2-{delta}}- Filmen auf Si (111) mittels hochenergetischer Roentgen-Photoelektronenspektroskopie

Energy Technology Data Exchange (ETDEWEB)

Allahgholi, Aschkan

2013-03-15

The intention of this work is to shed light on two much discussed topics in the study of rare earth oxides (REO) by hard x-ray photoelectron spectroscopy (HAXPES): (i) Due to the complex spectral shape of the Ce3d region, there have been many discussions on proper approaches to determine the concentration of Ce{sup 3+} and Ce{sup 4+} species in CeO{sub x} over the last decades. (ii) Recently, the true electron structure of rare earth oxides gained new attention, since ab initio calculations showed the necessity of considering additional inter atomic charge transfer to Ce5d levels. Using HAXPES and resonant HAXPES, the question of the true electronic structure of rare earth oxides is approached from the experimental side. As a third topic, the obtained results for cerium oxide and praseodymium oxide are applied in order to investigate the plasma oxidized mixed oxide Ce{sub x}Pr{sub 1-x}O{sub 2-{delta}} grown on Si(111) during thermal reduction. (orig.)

Apparent molar volumes and apparent molar heat capacities of Pr(NO{sub 3}){sub 3}(aq), Gd(NO{sub 3}){sub 3}(aq), Ho(NO{sub 3}){sub 3}(aq), and Y(NO{sub 3}){sub 3}(aq) at T (288.15, 298.15, 313.15, and 328.15) K and p = 0.1 MPa

Energy Technology Data Exchange (ETDEWEB)

Hakin, Andrew W. [Department of Chemistry and Biochemistry, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta, T1K 3M4 (Canada)]. E-mail: hakin@uleth.ca; Liu Jinlian [Department of Chemistry and Biochemistry, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta, T1K 3M4 (Canada); Erickson, Kristy [Department of Chemistry and Biochemistry, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta, T1K 3M4 (Canada); Munoz, Julie-Vanessa [Department of Chemistry and Biochemistry, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta, T1K 3M4 (Canada); Rard, Joseph A. [Energy and Environment Directorate, Lawrence Livermore National Laboratory, University of California, Livermore, CA 94550 (United States)

2005-02-01

Relative densities and relative massic heat capacities have been measured for acidified solutions of Y(NO{sub 3}){sub 3}(aq), Pr(NO{sub 3}){sub 3}(aq), and Gd(NO{sub 3}){sub 3}(aq) at T = (288.15, 298.15, 313.15, and 328.15) K and p = 0.1 MPa. In addition, relative densities and massic heat capacities have been measured at the same temperatures and pressure for Y(NO{sub 3}){sub 3}(aq) and Ho(NO{sub 3}){sub 3}(aq) solutions without excess acid (n.b. measurements at T = 328.15 K for Ho(NO{sub 3}){sub 3}(aq) were not performed due to the limited volume of solution available). Apparent molar volumes and apparent molar heat capacities for the aqueous salt solutions have been calculated from the experimental apparent molar properties of the acidified solutions using Young's rule, whereas the apparent molar properties of the solutions without excess acid were calculated directly from the measured densities and massic heat capacities. The two sets of data for the Y(NO{sub 3}){sub 3}(aq) systems provide a check of the internal consistency of the Young's rule approach we have utilised. The concentration dependences of the apparent molar volumes and heat capacities of the aqueous salt solutions have been modelled at each investigated temperature using the Pitzer ion interaction equations to yield apparent molar properties at infinite dilution. Complex formation within the aqueous rare earth nitrate systems is discussed qualitatively by probing the concentration dependence of apparent molar volumes and heat capacities. In spite of the complex formation in the aqueous rare earth nitrate systems, there is a high degree of self-consistency between the apparent molar volumes and heat capacities at infinite dilution reported in this manuscript and those previously reported for aqueous rare earth perchlorates.

Stabilisation of ZrO/sub 2/ with rare-earth oxides with atomic numbers from 58 to 71

Energy Technology Data Exchange (ETDEWEB)

Tcheivili, L; Passarino de Marques, M N [Instituto Nacional de Tecnologia Industrial, Buenos Aires (Argentina)

1978-01-01

In the present work, the stabilisation of ZrO/sub 2/ with 14 rare earths (58 to 71) was investigated. The aim was to carry out the experiments at a temperature of 1550/sup 0/C, at which many oxides do not exist in the cubic form and the others, such as PrO/sub 2/ and Lu/sub 2/O/sub 3/, have not yet been studied. All the experiments of the series were carried out under constant conditions, in order to determine if there was any difference in principle between them. All the oxides stabilise ZrO/sub 2/, but those with the lower atomic numbers (58, 59, 60) show some deviation. The minimum and maximum mol% limits were ascertained, between which ZrO/sub 2/ is fully stabilised, and the phases are given which occur with the various mol% proportions. In conclusion, an experiment was carried out with all oxides having di- tri- and quadri-valent cations, which belong to the cubic system. In view of their difference in ionic radius to the Zr/sup 4 +/ ion, the conclusion can be drawn that all oxides which can stabilise ZrO/sub 2/ have larger cation radii than that of the Zr/sup 4 +/ ion.

Generation of H{sub 2} and CO by solar thermochemical splitting of H{sub 2}O and CO{sub 2} by employing metal oxides

Energy Technology Data Exchange (ETDEWEB)

Rao, C.N.R., E-mail: cnrrao@jncasr.ac.in; Dey, Sunita

2016-10-15

Generation of H{sub 2} and CO by splitting H{sub 2}O and CO{sub 2} respectively constitutes an important aspect of the present-day concerns with energy and environment. The solar thermochemical route making use of metal oxides is a viable means of accomplishing these reduction reactions. The method essentially involves reducing a metal oxide by heating and passing H{sub 2}O or CO{sub 2} over the nonstoichiometric oxide to cause reverse oxidation by abstracting oxygen from H{sub 2}O or CO{sub 2}. While ceria, perovskites and other oxides have been investigated for this purpose, recent studies have demonstrated the superior performance of perovskites of the type Ln{sub 1−x}A{sub x}Mn{sub 1−y}M{sub y}O{sub 3} (Ln=rare earth, A=alkaline earth, M=various +2 and +3 metal ions), in the thermochemical generation of H{sub 2} and CO. We present the important results obtained hitherto to point out how the alkaine earth and the Ln ions, specially the radius of the latter, determine the performance of the perovskites. The encouraging results obtained are exemplefied by Y{sub 0.5}Sr{sub 0.5}MnO{sub 3} which releases 483 µmol/g of O{sub 2} at 1673 K and produces 757 µmol/g of CO from CO{sub 2} at 1173 K. The production of H{sub 2} from H{sub 2}O is also quite appreciable. Modification of the B site ion of the perovskite also affects the performance. In addition to perovskites, we present the generation of H{sub 2} based on the Mn{sub 3}O{sub 4}/NaMnO{sub 2} cycle briefly. - Graphical abstract: Ln{sub 0.5}A{sub 0.5}Mn{sub 1−x}M{sub x}O{sub 3} (Ln=lanthanide; A=Ca, Sr; M=Al, Ga, Sc, Mg, Cr, Fe, Co) perovskites are employed for the two step thermochemical splitting of CO{sub 2} and H{sub 2}O for the generation of CO and H{sub 2}. - Highlights: • Perovskite oxides based on Mn are ideal for the two-step thermochemical splitting of CO{sub 2} and H{sub 2}O. • In Ln{sub 1−x}A{sub x}MnO{sub 3} perovskite (Ln=rare earth, A=alkaline earth) both Ln and A ions play major roles

Tetracyanidoborates with triply charged rare earth metal cations and their optical properties

Energy Technology Data Exchange (ETDEWEB)

Hackbarth, Liisa

2015-11-24

The aim of this thesis is the description of the synthesis and characterization of a new group of tetracyanidoborates: tetracyanidoborates with trivalent rare earth metal cations. Their optical properties in the ultraviolet and visible range are also discussed. Common synthetic routes for tetracyanidoborates are adapted and applied to the preparation of the rare earth tetracyanidoborate hydrates. They are accessible with high yields and high purity through a reaction between the tetracyanidoboronic acid and rare earth hydroxides. It is shown that the rare earth tetracyanidoborates form isostructural groups, like the [LRE(H{sub 2}O){sub 5}][B(CN){sub 4}]{sub 3}.0.5 H{sub 2}O, where LRE{sup 3+} is La, Ce, Pr, Nd, Sm, Eu and Gd, the [HRE(H{sub 2}O){sub 7}][B(CN){sub 4}]{sub 3} and the [HRE(H{sub 2}O){sub 8}][B(CN){sub 4}]{sub 3}.3 H{sub 2}O, where HRE{sup 3+} is Tb, Dy, Ho, Er, Tm, Yb, Lu and Y. Furthermore, the coordination number 9 is noticed to be common among the light rare earth cations, whereas the minor coordination number 8 is prevalent for the heavy rare earth cations in their tetracyanidoborates. This different construction of the coordination spheres between light and heavy rare earth cations leads to different structures depending on the energetic efficiency of the structural arrangement. Generally, the rare earth tetracyanidoborate hydrates are found to crystallize in the monoclinic crystal system. Moreover, other different crystal structures are observed depending on the crystallization temperature and the type of coordinated ligands and co-crystallized solvent molecules. The tetracyanidoborate hydrates with triply charged rare earth cations are characterized comprehensively by X-ray diffraction, vibrational spectroscopy, NMR-spectroscopy as well as by thermal analysis. Furthermore, the optical properties of some dehydrated rare earth tetracyanidoborates are investigated by UV-spectroscopy and luminescence measurements. The results of the optical

Rare Earth Garnet Selective Emitter

Science.gov (United States)

Lowe, Roland A.; Chubb, Donald L.; Farmer, Serene C.; Good, Brian S.

1994-01-01

Thin film Ho-YAG and Er-YAG emitters with a platinum substrate exhibit high spectral emittance in the emission band (epsilon(sub lambda) approx. = 0.75, sup 4)|(sub 15/2) - (sup 4)|(sub 13/2),for Er-YAG and epsilon(sub lambda) approx. = 0.65, (sup 5)|(sub 7) - (sup 5)|(sub 8) for Ho-YAG) at 1500 K. In addition, low out-of-band spectral emittance, epsilon(sub lambda) less than 0.2, suggest these materials would be excellent candidates for high efficiency selective emitters in thermophotovoltaic (TPV) systems operating at moderate temperatures (1200-1500 K). Spectral emittance measurements of the thin films were made (1.2 less than lambda less than 3.0 microns) and compared to the theoretical emittances calculated using measured values of the spectral extinction coefficient. In this paper we present the results for a new class of rare earth ion selective emitters. These emitters are thin sections (less than 1 mm) of yttrium aluminum garnet (YAG) single crystal with a rare earth substitutional impurity. Selective emitters in the near IR are of special interest for thermophotovoltaic (TPV) energy conversion. The most promising solid selective emitters for use in a TPV system are rare earth oxides. Early spectral emittance work on rare earth oxides showed strong emission bands in the infrared (0.9 - 3 microns). However, the emittance outside the emission band was also significant and the efficiency of these emitters was low. Recent improvements in efficiency have been made with emitters fabricated from fine (5 - 10 microns) rare earth oxide fibers similar to the Welsbach mantle used in gas lanterns. However, the rare earth garnet emitters are more rugged than the mantle type emitters. A thin film selective emitter on a low emissivity substrate such as gold, platinum etc., is rugged and easily adapted to a wide variety of thermal sources. The garnet structure and its many subgroups have been successfully used as hosts for rare earth ions, introduced as substitutional

Rare earth-transition metal indides with Lu{sub 5}Ni{sub 2}In{sub 4}-type structure

Energy Technology Data Exchange (ETDEWEB)

Zaremba, Roman; Hermes, Wilfried; Eul, Matthias; Poettgen, Rainer [Inst. fuer Anorganische und Analytische Chemie, Univ. Muenster (Germany)

2008-12-15

New intermetallic compounds RE{sub 5}T{sub 2}In{sub 4} (RE = Sc, Y, La-Nd, Sm, Gd-Tm, Lu; T = Rh, Ir) were synthesized by arc-melting of the elements or by induction melting of the elements in tantalum crucibles under flowing argon. The samples were characterized by X-ray powder diffraction. They crystallize with the orthorhombic Lu{sub 5}Ni{sub 2}In{sub 4}-type structure, space group Pbam, Z = 2, a 2: 1 intergrowth variant of CsCl and AlB{sub 2} related slabs of compositions InRE{sub 8} (distorted cubes) and RhRE{sub 6} (distorted trigonal prisms). Susceptibility measurements of Ce{sub 5}Ir{sub 2}In{sub 4} have revealed modified Curie-Weiss behavior above 70 K with an experimental magnetic moment of 2.45(1) {mu}{sub B} / Ce atom. The cerium magnetic moments order ferri- or ferromagnetically at T{sub C} = 7.1(2) K. (orig.)

Earth Rotation

Science.gov (United States)

Dickey, Jean O.

1995-01-01

The study of the Earth's rotation in space (encompassing Universal Time (UT1), length of day, polar motion, and the phenomena of precession and nutation) addresses the complex nature of Earth orientation changes, the mechanisms of excitation of these changes and their geophysical implications in a broad variety of areas. In the absence of internal sources of energy or interactions with astronomical objects, the Earth would move as a rigid body with its various parts (the crust, mantle, inner and outer cores, atmosphere and oceans) rotating together at a constant fixed rate. In reality, the world is considerably more complicated, as is schematically illustrated. The rotation rate of the Earth's crust is not constant, but exhibits complicated fluctuations in speed amounting to several parts in 10(exp 8) [corresponding to a variation of several milliseconds (ms) in the Length Of the Day (LOD) and about one part in 10(exp 6) in the orientation of the rotation axis relative to the solid Earth's axis of figure (polar motion). These changes occur over a broad spectrum of time scales, ranging from hours to centuries and longer, reflecting the fact that they are produced by a wide variety of geophysical and astronomical processes. Geodetic observations of Earth rotation changes thus provide insights into the geophysical processes illustrated, which are often difficult to obtain by other means. In addition, these measurements are required for engineering purposes. Theoretical studies of Earth rotation variations are based on the application of Euler's dynamical equations to the problem of finding the response of slightly deformable solid Earth to variety of surface and internal stresses.

Tile-based rigidization surface parametric design study

Science.gov (United States)

Giner Munoz, Laura; Luntz, Jonathan; Brei, Diann; Kim, Wonhee

2018-03-01

Inflatable technologies have proven useful in consumer goods as well as in more recent applications including civil structures, aerospace, medical, and robotics. However, inflatable technologies are typically lacking in their ability to provide rigid structural support. Particle jamming improves upon this by providing structures which are normally flexible and moldable but become rigid when air is removed. Because these are based on an airtight bladder filled with loose particles, they always occupy the full volume of its rigid state, even when not rigidized. More recent developments in layer jamming have created thin, compact rigidizing surfaces replacing the loose volume of particles with thinly layered surface materials. Work in this area has been applied to several specific applications with positive results but have not generally provided the broader understanding of the rigidization performance as a function of design parameters required for directly adapting layer rigidization technology to other applications. This paper presents a parametric design study of a new layer jamming vacuum rigidization architecture: tile-based vacuum rigidization. This form of rigidization is based on layers of tiles contained within a thin vacuum bladder which can be bent, rolled, or otherwise compactly stowed, but when deployed flat, can be vacuumed and form a large, flat, rigid plate capable of supporting large forces both localized and distributed over the surface. The general architecture and operation detailing rigidization and compliance mechanisms is introduced. To quantitatively characterize the rigidization behavior, prototypes rigidization surfaces are fabricated and an experimental technique is developed based on a 3-point bending test. Performance evaluation metrics are developed to describe the stiffness, load-bearing capacity, and internal slippage of tested prototypes. A set of experimental parametric studies are performed to better understand the impact of

Synthesis, crystal structure, and physical properties of the Gd{sub 3}BiO{sub 3} and Gd{sub 8}Bi{sub 3}O{sub 8} phases

Energy Technology Data Exchange (ETDEWEB)

Forbes, Scott; Yuan, Fang [Department of Chemistry and Chemical Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4M1 (Canada); Kosuda, Kosuke; Kolodiazhnyi, Taras [Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Mozharivskyj, Yurij, E-mail: mozhar@mcmaster.ca [Department of Chemistry and Chemical Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4M1 (Canada)

2016-01-15

The second and third known rare-earth bismuthide oxides, Gd{sub 3}BiO{sub 3} and Gd{sub 8}Bi{sub 3}O{sub 8}, have been discovered via high temperature reactions at 1300 °C. Like its Gd–Sb–O counterparts, the Gd{sub 3}BiO{sub 3} and Gd{sub 8}Bi{sub 3}O{sub 8} phases crystallize in the monoclinic C2/m space group, with the latter containing disordered Bi atoms along the b direction of the unit cell. Unlike the RE{sub 8}Sb{sub 3}O{sub 8} series, the formation of the Gd{sub 3}BiO{sub 3} phase does not necessarily precede the formation of Gd{sub 8}Bi{sub 3}O{sub 8}, which is likely due to the difficulty of accommodating bismuth in the RE–O framework due to its larger size. Physical property measurements performed on a pure Gd{sub 8}Bi{sub 3}O{sub 8} sample reveal semiconducting behavior. Although electronic structure calculations predict metallic behavior due to an unbalanced electron count, the semiconducting behavior originates from the Anderson localization of the Bi p states near the Fermi level as a result of atomic disorder. - Graphical abstract: Reaction of GdBi and Gd{sub 2}O{sub 3} at high temperatures yields Gd–Bi–O phases. - Highlights: • Gd{sub 3}BiO{sub 3} and Gd{sub 8}Bi{sub 3}O{sub 8}, the second and third rare-earth bismuthide oxides, have been discovered. • Gd{sub 3}BiO{sub 3} and Gd{sub 8}Bi{sub 3}O{sub 8} are isostructural with RE{sub 3}SbO{sub 3} and RE{sub 8}Sb{sub 3}O{sub 8}. • Gd{sub 8}Bi{sub 3}O{sub 8} displays semiconducting behavior despite an unbalanced electron count. • Anderson localization of Bi p states results in semiconducting behavior in Gd{sub 8}Bi{sub 3}O{sub 8}.

Crystal structures and thermal decomposition of permanganates AE[MnO{sub 4}]{sub 2} . n H{sub 2}O with the heavy alkaline earth elements (AE=Ca, Sr and Ba)

Energy Technology Data Exchange (ETDEWEB)

Henning, Harald; Bauchert, Joerg M.; Conrad, Maurice; Schleid, Thomas [Stuttgart Univ. (Germany). Inst. fuer Anorganische Chemie

2017-10-01

Reexamination of the syntheses and crystal structures as well as studies of the thermal decomposition of the heavy alkaline earth metal permanganates Ca[MnO{sub 4}]{sub 2} . 4 H{sub 2}O, Sr[MnO{sub 4}]{sub 2} . 3 H{sub 2}O and Ba[MnO{sub 4}]{sub 2} are the focus of this work. As an alternative to the very inelegant Muthmann method, established for the synthesis of Ba[MnO{sub 4}]{sub 2} a long time ago, we employed a cation-exchange column loaded with Ba{sup 2+} cations and passed through an aqueous potassium-permanganate solution. We later used this alternative also with strontium- and calcium-loaded columns and all the compounds synthesized this way were indistinguishable from the products of the established methods. Ca[MnO{sub 4}]{sub 2} . 4 H{sub 2}O exhibiting [CaO{sub 8}] polyhedra crystallizes in the orthorhombic space group Pccn with the lattice parameters a=1397.15(9), b=554.06(4) and c=1338.97(9) pm with Z=4, whereas Sr[MnO{sub 4}]{sub 2} . 3 H{sub 2}O with [SrO{sub 10}] polyhedra adopts the cubic space group P2{sub 1}3 with a=964.19(7) pm and Z=4. So the harder the AE{sup 2+} cation, the higher its demand for hydration in aqueous solution. Consequently, the crystal structure of Ba[MnO{sub 4}]{sub 2} in the orthorhombic space group Fddd with a=742.36(5), b=1191.23(7) and c=1477.14(9) pm with Z=8 lacks any crystal water, but contains [BaO{sub 12}] polyhedra. During the thermal decomposition of Ca[MnO{sub 4}]{sub 2} . 4 H{sub 2}O, the compound expels up to two water molecules of hydration, before the crystal structure collapses after the loss of the third H{sub 2}O molecule at 157 C. The crystal structure of Sr[MnO{sub 4}]{sub 2} . 3 H{sub 2}O breaks down after the expulsion of the third water molecule as well, but this already occurs at 148 C. For both the calcium and the strontium permanganate samples, orthobixbyite-type α-Mn{sub 2}O{sub 3} and the oxomanganates(III,IV) AEMn{sub 3}O{sub 6} (AE=Ca and Sr) remain as final decomposition products at 800 C

Earth's structure and evolution inferred from topography, gravity, and seismicity.

Science.gov (United States)

Watkinson, A. J.; Menard, J.; Patton, R. L.

2016-12-01

Earth's wavelength-dependent response to loading, reflected in observed topography, gravity, and seismicity, can be interpreted in terms of a stack of layers under the assumption of transverse isotropy. The theory of plate tectonics holds that the outermost layers of this stack are mobile, produced at oceanic ridges, and consumed at subduction zones. Their toroidal motions are generally consistent with those of several rigid bodies, except in the world's active mountain belts where strains are partitioned and preserved in tectonite fabrics. Even portions of the oceanic lithosphere exhibit non-rigid behavior. Earth's gravity-topography cross-spectrum exhibits notable variations in signal amplitude and character at spherical harmonic degrees l=13, 116, 416, and 1389. Corresponding Cartesian wavelengths are approximately equal to the respective thicknesses of Earth's mantle, continental mantle lithosphere, oceanic thermal lithosphere, and continental crust, all known from seismology. Regional variations in seismic moment release with depth, derived from the global Centroid Moment Tensor catalog, are also evident in the crust and mantle lithosphere. Combined, these observations provide powerful constraints for the structure and evolution of the crust, mantle lithosphere, and mantle as a whole. All that is required is a dynamically consistent mechanism relating wavelength to layer thickness and shear-strain localization. A statistically-invariant 'diharmonic' relation exhibiting these properties appears as the leading order approximation to toroidal motions on a self-gravitating body of differential grade-2 material. We use this relation, specifically its predictions of weakness and rigidity, and of folding and shear banding response as a function of wavelength-to-thickness ratio, to interpret Earth's gravity, topography, and seismicity in four-dimensions. We find the mantle lithosphere to be about 255-km thick beneath the Himalaya and the Andes, and the long

Development of AL{sub 2}O{sub 3} - ZrO{sub 2} ceramic composite reinforced with rare earth oxides (Y{sub 2}O)3) for inert coating of storage and transport systems of crude petroleum; Desenvolvimento de composito ceramico Al{sub 2}O{sub 3} - ZrO{sub 2} reforcada com oxido de terra rara para sistema de armazenamento e transporte de petroleo cru

Energy Technology Data Exchange (ETDEWEB)

Silva, J.C.; Yadava, Y.P.; Sanguinetti Ferreira, R.A.; Albuquerque, L.T., E-mail: juliana.carvalhosilva@ufpe.br [Universidade Federal de Pernambuco (UFPE), Jaboatao de Guararapes, PE (Brazil). Centro de Tecnologia. Departamento de Engenharia Mecanica

2014-07-01

The advancement of the oil sector has generated the need for the use of materials resistant to aggressive environments to oil. Although ceramics have high melting point and high hardness is, on the other hand, more fragile and less tough, which can cause damage to the metal structure. The Al{sub 2}O{sub 3} based ceramics reinforced with rare earth oxide can improve tenaciousness and makes the ceramic material more resistant. This article aims to present the production of composite Al{sub 2}O{sub 3} - Y{sub 2}O{sub 3} stabilized ZrO{sub 2} by uniaxial pressing, following sintering (1200-1350 deg C). Structural and microstructural characterizations as XRD (X-Ray Diffraction) and SEM (Scanning Electron Microscopy) and mechanical tests as Vickers hardness, % absorption and % linear shrinkage were conducted to evaluate the feasibility of using the composite and ceramic coating for storage and transportation of oil tanks. The results indicate that the proportions of 5%, 10% and 30% ZrO{sub 2} make it suitable as a good composite suitable coating. (author)

Impact of hydrogen absorption on crystal structure and magnetic properties of RE{sub 2}T{sub 2}X compounds

Energy Technology Data Exchange (ETDEWEB)

Mašková, S., E-mail: maskova@mag.mff.cuni.cz [Department of Condensed Matter Physics, Charles University, Prague 2 (Czech Republic); Kolomiets, A. [Department of Condensed Matter Physics, Charles University, Prague 2 (Czech Republic); Department of Physics, Lviv Polytechnic National University, Lviv (Ukraine); Havela, L. [Department of Condensed Matter Physics, Charles University, Prague 2 (Czech Republic); Andreev, A.V. [Institute of Physics, AVCR, Prague 8 (Czech Republic); Svoboda, P. [Department of Condensed Matter Physics, Charles University, Prague 2 (Czech Republic)

2015-10-05

Highlights: • RE{sub 2}Pd{sub 2}In(Sn) compounds absorb, depending on RE, different amounts of hydrogen. • Compounds with the light rare earths become amorphous upon the hydrogenation. • Compounds with the heavy rare earths preserve the original tetragonal structure. • Magnetic ordering temperatures of RE{sub 2}Pd{sub 2}In compounds are reduced by the hydrogenation. - Abstract: RE{sub 2}Pd{sub 2}In, RE{sub 2}Pd{sub 2}Sn compounds (RE = rare earth) absorb, depending on the rare earth (RE) element, different amounts of hydrogen. The parent compounds RE{sub 2}Pd{sub 2}In show the linear decrease of both lattice parameters and the unit cell volume with the increasing atomic number of RE, attributed to the lanthanide contraction. All the compounds absorb at least 2 H/f.u.; the tetragonal structure is merely expanded. The expansion is anisotropic (Δc/c > Δa/a), and for RE = Tb, Dy, Ho, and Er the lattice even contracts along the a-axis (Δa/a < 0), whereas Δc/c still weakly increases. A higher H concentration can be achieved in the compounds with light rare earths (La, Nd, both for In and Sn), which then become amorphous. The magnetic ordering temperatures of all studied RE{sub 2}Pd{sub 2}In compounds are dramatically reduced by the hydrogenation, typically to the temperature range below 1.8 K.

Characterization of the electronic and magnetic structure of multifunctional NaREF{sub 4} (RE = rare earth) core-shell nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Schneider, Lilli; Kuepper, Karsten [Physics Department, University of Osnabrueck (Germany); Rinkel, Thorben; Haase, Markus [Institute of Chemistry, University of Osnabrueck (Germany); Chrobak, Artur [Institute of Physics, University of Silesia (Poland)

2014-07-01

Rare earth (RE) based nanoparticles of type NaREF{sub 4} have attracted lot of attention in the last few years due to their upconverting luminescence. Here, we want to concentrate on electronic and magnetic properties of NaREF{sub 4}/NaGdF{sub 4} nanocrystals, since the magnetic behaviour of these fluorescent nanoparticles are of utmost importance from fundamental and applicative point of view as well. Hexagonal β-phase nanocrystals (3-22 nm) were prepared and characterized by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). A detailed study of the electronic structure and magnetic coupling phenomena of the different core-shell nanoparticles is performed using X-ray photoelectron spectroscopy (XPS), magnetometry (SQUID) and X-ray magnetic circular dichroism (XMCD). First SQUID measurements of NaEuF{sub 4}/NaGdF{sub 4} core-shell nanoparticles show butterfly shaped hysteresis loops at low temperature (2 K) in contrast to superparamagnetic behaviour observed for the corresponding ''pure'' NaEuF{sub 4} and NaGdF{sub 4} nanoparticles.

Magnetism and superconductivity in Eu(Ho)Mo/sub 6/S/sub 8/

Energy Technology Data Exchange (ETDEWEB)

Capone, D.W. II; Lai Fook, M.S.; Guertin, R.P.; Hinks, D.G.; Dunlap, B.D.; Foner, S.; Abou-Aly, A.I.; Brooks, J.S.

1984-10-01

A variety of ambient and high pressure experimental results reveal the interplay between magnetism and superconductivity in Ho doped samples of the pressure induced superconductor, EuMo/sub 6/S/sub 8/. Ho concentrations up to 50 atomic percent of the rare earth ions were used. High resolution magnetic measurements are consistent with the crystalline electric field ground state for the Ho/sup 3 +/ ions being a magnetic doublet consisting largely of J/sub z/ = 18. The results of high pressure magnetization experiments reveal negligible effects of reduced lattice constant on the rare earth-rare earth interactions. Resistivity in a 10 atomic percent sample for P = 10 kbar shows the suppression of a P = 0 structural transition, metallic conductivity down to low temperatures, and finally superconductivity at 8 K. The upper critical field, H/sub c2/(T), for this sample was measured for P = 7, 10 and 12 kbar and showed strong reentrant behavior (dH/sub c2/(T)/dT > 0 as T ..-->.. 0 K). A minimum with field in the resistivity above H/sub c2/ was also observed at lowest temperatures. The H/sub c2/(T) data are compared with those of EuMo/sub 6/S/sub 8/ at high pressure, which shows positive curvature, and HoMo/sub 6/S/sub 8/, in which superconductivity is quenched by ferromagnetism at low temperatures. 14 references, 4 figures.

Recovery of UO[sub 2]/PuO[sub 2] in IFR electrorefining process

Science.gov (United States)

Tomczuk, Z.; Miller, W.E.

1994-10-18

A process is described for converting PuO[sub 2] and UO[sub 2] present in an electrorefiner to the chlorides, by contacting the PuO[sub 2] and UO[sub 2] with Li metal in the presence of an alkali metal chloride salt substantially free of rare earth and actinide chlorides for a time and at a temperature sufficient to convert the UO[sub 2] and PuO[sub 2] to metals while converting Li metal to Li[sub 2]O. Li[sub 2]O is removed either by reducing with rare earth metals or by providing an oxygen electrode for transporting O[sub 2] out of the electrorefiner and a cathode, and thereafter applying an emf to the electrorefiner electrodes sufficient to cause the Li[sub 2]O to disassociate to O[sub 2] and Li metal but insufficient to decompose the alkali metal chloride salt. The U and Pu and excess lithium are then converted to chlorides by reaction with CdCl[sub 2].

Structural features of layered iron pnictide oxides (Fe{sub 2}As{sub 2})(Sr{sub 4}M{sub 2}O{sub 6})

Energy Technology Data Exchange (ETDEWEB)

Ogino, H., E-mail: tuogino@mail.ecc.u-tokyo.ac.j [Department of Applied Chemistry, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); JST-TRIP, Sanban-cho, Chiyoda-ku, Tokyo 102-0075 (Japan); Sato, S.; Matsumura, Y.; Kawaguchi, N.; Ushiyama, K. [Department of Applied Chemistry, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); JST-TRIP, Sanban-cho, Chiyoda-ku, Tokyo 102-0075 (Japan); Katsura, Y. [Magnetic Materials Laboratory, RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198 (Japan); Horii, S. [JST-TRIP, Sanban-cho, Chiyoda-ku, Tokyo 102-0075 (Japan); Kochi University of Technology, Kami, Kochi 782-8502 (Japan); Kishio, K.; Shimoyama, J. [Department of Applied Chemistry, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); JST-TRIP, Sanban-cho, Chiyoda-ku, Tokyo 102-0075 (Japan)

2010-12-15

Structural features of newly found perovskite-based iron pnictide oxide system have been studied. Compared to REFePnO system, perovskite-based system tend to have smaller Pn-Fe-Pn angle and higher pnictogen height owing to low electronegativity of alkaline earth metal and small repulsive force between pnictogen and oxigen atoms. As-Fe-As angles of (Fe{sub 2}As{sub 2})(Sr{sub 4}Cr{sub 2}O{sub 6}), (Fe{sub 2}As{sub 2})(Sr{sub 4}V{sub 2}O{sub 6}) and (Fe{sub 2}Pn{sub 2})(Sr{sub 4}MgTiO{sub 6}) are close to ideal tetrahedron and those pnictogen heights of about 1.40 A are close to NdFeAsO with optimized carrier concentration. These structural features of this system may lead to realization of high-T{sub c} superconductivity in this system.

Magnetic structures of Er{sub 6}Mn{sub 23} and Dy{sub 6}Mn{sub 23}

Energy Technology Data Exchange (ETDEWEB)

Ouladdiaf, B. [Institut Max von Laue - Paul Langevin, 38 - Grenoble (France); Deportes, J. [Laboratoire de Magnetisme L. Neel, C.N.R.S., BP 166, 38042 Grenoble Cedex 9 (France); Rodriguez-Carvajal, J. [Institut Max von Laue - Paul Langevin, 38 - Grenoble (France)]|[Laboratoire Leon Brillouin (CEA-CNRS), Centre d`Etudes de Saclay, Gif sur Yvette (France)

1995-08-01

The R{sub 6}Mn{sub 23} (R=rare earth) compounds crystallize in the cubic Th{sub 6}Mn{sub 23}-type structure with space group Fm3m. Powder neutron-diffraction experiments were performed on Dy{sub 6}Mn{sub 23} and Er{sub 6}Mn{sub 23}. The magnetic unit cell coincides with the chemical one. The R moments have a ferromagnetic non-collinear arrangement, whereas the Mn moments are parallel to the [1 1 1] direction. The magnetic structures belong to the three-dimensional {Gamma}{sub 5g} irreducible representation of Fm3m associated with the wave vector K=[0 0 0]. The spin configurations in both compounds result from the competition between the R-R, R-Mn magnetic interactions and the crystal electric field on the R ions. (orig.).

Adsorption of alkali, alkaline-earth, simple and 3d transition metal, and nonmetal atoms on monolayer MoS{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Li, X. D.; Fang, Y. M.; Wu, S. Q., E-mail: zzhu@xmu.edu.cn, E-mail: wsq@xmu.edu.cn [Department of Physics and Institute of Theoretical Physics and Astrophysics, Xiamen University, Xiamen 361005 (China); Zhu, Z. Z., E-mail: zzhu@xmu.edu.cn, E-mail: wsq@xmu.edu.cn [Department of Physics and Institute of Theoretical Physics and Astrophysics, Xiamen University, Xiamen 361005 (China); Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, Xiamen 361005 (China)

2015-05-15

Single adsorption of different atoms on pristine two-dimensional monolayer MoS{sub 2} have been systematically investigated by using density functional calculations with van der Waals correction. The adatoms cover alkali metals, alkaline earth metals, main group metal, 3d-transition metals, coinage metal and nonmetal atoms. Depending on the adatom type, metallic, semimetallic or semiconducting behavior can be found in direct bandgap monolayer MoS{sub 2}. Additionally, local or long-range magnetic moments of two-dimensional MoS{sub 2} sheet can also attained through the adsorption. The detailed atomic-scale knowledge of single adsorption on MoS{sub 2} monolayer is important not only for the sake of a theoretical understanding, but also device level deposition technological application.

Coagulation calculations of icy planet formation around 0.1-0.5 M {sub ☉} stars: Super-Earths from large planetesimals

Energy Technology Data Exchange (ETDEWEB)

Kenyon, Scott J. [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States); Bromley, Benjamin C., E-mail: skenyon@cfa.harvard.edu, E-mail: bromley@physics.utah.edu [Department of Physics, University of Utah, 201 JFB, Salt Lake City, UT 84112 (United States)

2014-01-01

We investigate formation mechanisms for icy super-Earth-mass planets orbiting at 2-20 AU around 0.1-0.5 M {sub ☉} stars. A large ensemble of coagulation calculations demonstrates a new formation channel: disks composed of large planetesimals with radii of 30-300 km form super-Earths on timescales of ∼1 Gyr. In other gas-poor disks, a collisional cascade grinds planetesimals to dust before the largest planets reach super-Earth masses. Once icy Earth-mass planets form, they migrate through the leftover swarm of planetesimals at rates of 0.01-1 AU Myr{sup –1}. On timescales of 10 Myr to 1 Gyr, many of these planets migrate through the disk of leftover planetesimals from semimajor axes of 5-10 AU to 1-2 AU. A few percent of super-Earths might migrate to semimajor axes of 0.1-0.2 AU. When the disk has an initial mass comparable with the minimum-mass solar nebula, scaled to the mass of the central star, the predicted frequency of super-Earths matches the observed frequency.

Synthesis and luminescent properties of trivalent rare-earth (Eu{sup 3+}, Tb{sup 3+}) ions doped nanocrystalline AgLa(PO{sub 3}){sub 4} polyphosphates

Energy Technology Data Exchange (ETDEWEB)

Krishna Bharat, L.; Jeon, Yong Il; Yu, Jae Su, E-mail: jsyu@khu.ac.kr

2014-11-25

Highlights: • AgLa(PO{sub 3}){sub 4}:Eu{sup 3+}, Tb{sup 3+} nanocrystalline phosphors were prepared by a sol–gel process. • The luminescent properties were studies by near-UV excitation. • The intense MD transition indicates the presence of high inversion symmetry site. • These results suggest that the compound is a good candidate for optical applications. - Abstract: The AgLa(PO{sub 3}){sub 4} phosphors activated with trivalent rare-earth (Eu{sup 3+}, Tb{sup 3+}) ions were prepared by a sol–gel synthesis method. The crystal structure of the compound was studied by X-ray diffraction patterns and found to be crystallized in the monoclinic system with a space group P2{sub 1}/c, indicating the calculated lattice parameters of a = 10.08 Å, b = 13.12 Å, and c = 7.314 Å. The Fourier-transform infrared spectrum, photoluminescence excitation/emission spectra, and decay curves were examined to study the optical properties. The analysis of the Eu{sup 3+} ions related emission spectrum revealed the presence of highly symmetric sites for the activator ions. The Tb{sup 3+} ions related emission spectrum exhibited a {sup 5}D{sub 3} emission due to the prolonged calcination at high temperatures, which reduces the residual hydroxyl ions. The optical properties show that this host material is suitable for phosphor materials and laser crystals.

On real structures on rigid surfaces

Energy Technology Data Exchange (ETDEWEB)

Kulikov, Vik S [Steklov Mathematical Institute, Russian Academy of Sciences (Russian Federation); Kharlamov, V M [Institut de Recherche Matematique Avanee Universite Louis Pasteur et CNRS 7 rue Rene Descartes (France)

2002-02-28

We construct examples of rigid surfaces (that is, surfaces whose deformation class consists of a unique surface) with a particular behaviour with respect to real structures. In one example the surface has no real structure. In another it has a unique real structure, which is not maximal with respect to the Smith-Thom inequality. These examples give negative answers to the following problems: the existence of real surfaces in each deformation class of complex surfaces, and the existence of maximal real surfaces in every complex deformation class that contains real surfaces. Moreover, we prove that there are no real surfaces among surfaces of general type with p{sub g}=q=0 and K{sup 2}=9. These surfaces also provide new counterexamples to the 'Dif = Def' problem.

Rigidity and symmetry

CERN Document Server

Weiss, Asia; Whiteley, Walter

2014-01-01

This book contains recent contributions to the fields of rigidity and symmetry with two primary focuses: to present the mathematically rigorous treatment of rigidity of structures, and to explore the interaction of geometry, algebra, and combinatorics. Overall, the book shows how researchers from diverse backgrounds explore connections among the various discrete structures with symmetry as the unifying theme.  Contributions present recent trends and advances in discrete geometry, particularly in the theory of polytopes. The rapid development of abstract polytope theory has resulted in a rich theory featuring an attractive interplay of methods and tools from discrete geometry, group theory, classical geometry, hyperbolic geometry and topology.  The volume will also be a valuable source as an introduction to the ideas of both combinatorial and geometric rigidity theory and its applications, incorporating the surprising impact of symmetry. It will appeal to students at both the advanced undergraduate and gradu...

Band gaps and photocurrent responses of two novel alkaline earth metal(II) complexes based on 4,5-di(4′-carboxylphenyl)benzene

Energy Technology Data Exchange (ETDEWEB)

Meng, Jiang Ping; Yan, Zhi Shuo; Long, Ji Ying [Department of Applied Chemistry, College of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400030 (China); Gong, Yun, E-mail: gongyun7211@cqu.edu.cn [Department of Applied Chemistry, College of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400030 (China); Lin, Jian Hua, E-mail: jhlin@pku.edu.cn [Department of Applied Chemistry, College of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400030 (China); State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China)

2017-01-15

By using a rigid dicarboxylate ligand, 4,5-di(4′-carboxylphenyl)benzene (H{sub 2}L), two complexes formulated as SrL(DMF)(H{sub 2}O)·(CH{sub 3}CN) (DMF=N,N′-dimethylformamide) (1) and BaL(H{sub 2}O){sub 2} (2) were solvothermally synthesized and structurally characterized by single-crystal X-ray diffraction. Complexes 1 and 2 display two-dimensional (2D) layer structures. The two complexes exhibit different electrochemical and photoelectrochemical properties. Their thermal stabilities, cyclic voltammograms, UV–vis absorption and diffuse reflectance spectra and photoluminescence properties have been investigated. The band structures, the total density of states (TDOS) and partial density of states (PDOS) of the two complexes were calculated by CASTEP program. Complex 2 exhibits much higher photocurrent density than complex 1. The Mott–Schottky plots reveal that complexes 1 and 2 both are p-type semiconductors, which are in agreement with their band structure calculations. - Graphical abstract: Two alkaline earth metal(II) complexes with 2D layer structures are p-type semiconductors, they possess different band structures and density of states. And the Ba(II) complex 2 exhibits much higher photocurrent density than the Sr(II) complex 1.

Synthesis, structural and optical properties of pure and rare-earth ion doped TiO{sub 2} nanowire arrays by a facile hydrothermal technique

Energy Technology Data Exchange (ETDEWEB)

Bandi, Vengala Rao; Raghavan, Chinnambedu Murugesan; Grandhe, Bhaskar kumar; Kim, Sang Su [Department of Physics, Changwon National University, Changwon 641-773 (Korea, Republic of); Jang, Kiwan, E-mail: kwjang@changwon.ac.kr [Department of Physics, Changwon National University, Changwon 641-773 (Korea, Republic of); Shin, Dong-Soo [Department of Chemistry, Changwon National University, Changwon 641-773 (Korea, Republic of); Yi, Soung-Soo [Department of Photonics, Silla University, Busan 617-736 (Korea, Republic of); Jeong, Jung-Hyun [Department of Physics, Pukyong National University, Busan 608-737 (Korea, Republic of)

2013-11-29

Single crystalline pure and rare-earth metal ions (Eu{sup 3+} and Ce{sup 3+}) doped TiO{sub 2} nanowire arrays were prepared on conductive fluorine doped indium tin oxide substrates by a facile hydrothermal method. Initially the conditions and parameters were optimized to prepare the high quality TiO{sub 2} nanowire arrays in the absence of organic additives. The average diameter and length of the TiO{sub 2} nanowire were found to be ∼ 30–50 nm and ∼ 0.5–1.5 μm, respectively. The formations of rutile phase structure in all the samples were confirmed by x-ray diffractometric analysis while the transmission electron microscopy confirms the single crystallinity and the maximum orientation of growth direction along [001] for the as-grown TiO{sub 2} nanowire. The optical properties of all the samples were analyzed using photoluminescence spectroscopy. The photocatalytic properties of the pure and doped TiO{sub 2} were investigated for the decomposition of organic toludine blue-O dye under ultraviolet irradiation. The result demonstrates that the Ce{sup 3+}: TiO{sub 2} decomposed almost 90% of the organic dye within 80 min. - Highlights: • Rare-earth (RE) doped TiO{sub 2} nanowire arrays were prepared by hydrothermal method • RE doping enhanced the growth rate of TiO{sub 2} nanowire arrays • The catalysts used to check their photocatalytic activity by toludine blue-O dye • RE doped TiO2 act as unprecedented photocatalyst for organic dye decomposition.

Birationally rigid varieties

CERN Document Server

Pukhlikov, Aleksandr

2013-01-01

Birational rigidity is a striking and mysterious phenomenon in higher-dimensional algebraic geometry. It turns out that certain natural families of algebraic varieties (for example, three-dimensional quartics) belong to the same classification type as the projective space but have radically different birational geometric properties. In particular, they admit no non-trivial birational self-maps and cannot be fibred into rational varieties by a rational map. The origins of the theory of birational rigidity are in the work of Max Noether and Fano; however, it was only in 1970 that Iskovskikh and Manin proved birational superrigidity of quartic three-folds. This book gives a systematic exposition of, and a comprehensive introduction to, the theory of birational rigidity, presenting in a uniform way, ideas, techniques, and results that so far could only be found in journal papers. The recent rapid progress in birational geometry and the widening interaction with the neighboring areas generate the growing interest ...

Ternary silicides ScIr{sub 4}Si{sub 2} and RERh{sub 4}Si{sub 2} (RE = Sc, Y, Tb-Lu) and quaternary derivatives RERh{sub 4}Si{sub 2-x}Sn{sub x} (RE = Y, Nd, Sm, Gd-Lu) - structure, chemical bonding, and solid state NMR spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Vosswinkel, Daniel; Benndorf, Christopher; Poettgen, Rainer [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie; Eckert, Hellmut [Muenster Univ. (Germany). Inst. fuer Physikalische Chemie; Sao Paulo Univ., Sao Carlos (Brazil). Inst. of Physics; Matar, Samir F. [Bordeaux Univ., CNRS, ICMCB, UPR 9048, Pessac (France)

2016-11-01

The silicides ScIr{sub 4}Si{sub 2} and RERh{sub 4}Si{sub 2} (RE = Sc, Y, Tb-Lu) and silicide stannides RERh{sub 4}Si{sub 2-x}Sn{sub x}(RE = Y, Nd, Sm, Gd-Lu) were synthesized from the elements by arc-melting and subsequent annealing. The new compounds crystallize with the orthorhombic YRh{sub 4}Ge{sub 2} type structure, space group Pnma. They were characterized by X-ray powder patterns and several structures were refined from single crystal X-ray diffractometer data. The main structural motifs of this series of silicides are tricapped trigonal prisms formed by the transition metal and rare earth atoms. One of the two crystallographically independent silicon sites allows for formation of solid solutions with tin, exemplarily studied for ErRh{sub 4}Si{sub 2-x}Sn{sub x}. Electronic structure calculations reveal strong covalent Rh-Si bonding as the main stability factor. Multinuclear ({sup 29}Si, {sup 45}Sc, and {sup 89}Y) magic-angle spinning (MAS) NMR spectra of the structure representatives with diamagnetic rare-earth elements (Sc, Y, Lu) are found to be consistent with the crystallographic data and specifically confirm the selective substitution of Sn in the Si2 sites in the quaternary compounds YRh{sub 4}SiSn and LuRh{sub 4}SiSn.

Structural/surface characterization and catalytic evaluation of rare-earth (Y, Sm and La) doped ceria composite oxides for CH{sub 3}SH catalytic decomposition

Energy Technology Data Exchange (ETDEWEB)

He, Dedong; Chen, Dingkai; Hao, Husheng; Yu, Jie; Liu, Jiangping; Lu, Jichang; Liu, Feng [Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500 (China); Wan, Gengping [Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500 (China); Research Center for Analysis and Measurement, Hainan University, Haikou, 570228 (China); He, Sufang [Research Center for Analysis and Measurement, Kunming University of Science and Technology, Kunming, 650093 (China); Luo, Yongming, E-mail: environcatalysis222@yahoo.com [Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500 (China)

2016-12-30

Highlights: • Ce{sub 0.75}RE{sub 0.25}O{sub 2-δ} (RE = Y, Sm and La) were synthesized by citrate complexation method. • Ce{sub 0.75}Y{sub 0.25}O{sub 2-δ} exhibited the best stability for the decomposition of CH{sub 3}SH. • Cation radius played a key role in determining structure and surface characteristics. • Catalytic behavior depended on synergistic role of oxygen vacancies and basic sites. • Ce{sub 2}S{sub 3} accumulation on the surface was responsible for the deactivation of catalyst. - Abstract: A series of rare earth (Y, Sm and La) doped ceria composite oxides and pure CeO{sub 2} were synthesized and evaluated by conducting CH{sub 3}SH catalytic decomposition test. Several characterization studies, including XRD, BET, Raman, H{sub 2}-TPR, XPS, FT-IR, CO{sub 2}-TPD and CH{sub 3}SH-TPD, were undertaken to correlate structural and surface properties of the obtained ceria-based catalysts with their catalytic performance for CH{sub 3}SH decomposition. More oxygen vacancies and increased basic sites exhibited in the rare earth doped ceria catalysts. Y doped ceria sample (Ce{sub 0.75}Y{sub 0.25}O{sub 2-δ}), with a moderate increase in basic sites, contained more oxygen vacancies. More structural defects and active sites could be provided, and a relatively small amount of sulfur would accumulate, which resulted in better catalytic performance. The developed catalyst presented good catalytic behavior with stability very similar to that of typical zeolite-based catalysts reported previously. However, La doped ceria catalyst (Ce{sub 0.75}La{sub 0.25}O{sub 2-δ}) with the highest alkalinity was not the most active one. More sulfur species would be adsorbed and a large amount of cerium sulfide species (Ce{sub 2}S{sub 3}) would accumulate, which caused deactivation of the catalysts. The combined effect of increased oxygen vacancies and alkalinity led to the catalytic stability of Ce{sub 0.75}Sm{sub 0.25}O{sub 2-δ} sample was comparable to that of pure CeO{sub

High temperature properties of rare-earth tungstates RE{sub 2}W{sub 2}O{sub 9}

Energy Technology Data Exchange (ETDEWEB)

Marrero-López, D., E-mail: damarre@uma.es [Dpto. de Física Aplicada I, Universidad de Málaga, 29071-Málaga (Spain); Canales-Vázquez, J. [Renewable Energy Research Institute, University of Castilla-La Mancha, 02071-Albacete (Spain); Ruiz-Morales, J.C.; Núñez, P. [Dpto. de Química, U.D. Química Inorgánica, Universidad de la Laguna, 38206-Tenerife (Spain)

2015-02-15

Highlights: • RE{sub 2}W{sub 2}O{sub 9} (RE = Nd, Pr, Sm, Eu and Gd) are prepared by freeze-drying precursor. • The samples crystallize in the monoclinic s.g. P2{sub 1}/c. • A first order phase transition was detected between 330 and 590 °C. • These materials exhibit low ionic conductivity of 10{sup -5} S cm{sup -1} at 800 °C. - Abstract: RE{sub 2}W{sub 2}O{sub 9} (RE = Ce, Nd, Pr, Sm, Eu, Gd and Tb) compounds have been prepared by a freeze-drying precursor method in order to explore their high temperature thermal properties by different techniques. Samples with Nd, Pr, Sm, Eu and Gd crystallize in the same monoclinic structure with space group P2{sub 1}/c. The thermal, X-ray diffraction, and electrical analysis reveal the existence of a reversible first order phase transition, which is accompanied by a sudden decrease of the unit cell volume and conductivity. A large thermal hysteresis of about 250 °C is also observed during the heating and cooling processes. These materials exhibit low electrical conductivity of the order of 10{sup -5} S cm{sup -1} at 800 °C.

Electronic phase separation in the rare-earth manganates (La sub 1 sub - sub x Ln sub x) sub 0 sub . sub 7 Ca sub 0 sub . sub 3 MnO sub 3 (Ln = Nd, Gd and Y)

CERN Document Server

Sudheendra, L

2003-01-01

Electron transport and magnetic properties of three series of manganates of the formula (La sub 1 sub - sub x Ln sub x) sub 0 sub . sub 7 Ca sub 0 sub . sub 3 MnO sub 3 with Ln = Nd, Gd and Y, wherein only the average A-site cation radius (r sub A ) and associated disorder vary, without affecting the Mn sup 4 sup + /Mn sup 3 sup + ratio, have been investigated in an effort to understand the nature of phase separation. All three series of manganates show saturation magnetization characteristic of ferromagnetism, with the ferromagnetic T sub c decreasing with increasing x up to a critical value of x, x sub c (x sub c = 0.6, 0.3, 0.2 respectively for Nd, Gd, Y). For x > x sub c , the magnetic moments are considerably smaller, showing a small increase around T sub M , the value of T sub M decreasing slightly with increase in x or decrease in (r sub A ). The ferromagnetic compositions (x x sub c are insulating. The magnetic and electrical resistivity behaviour of these manganates is consistent with the occurrence...

Alkaline earth filled nickel skutterudite antimonide thermoelectrics

Science.gov (United States)

Singh, David Joseph

2013-07-16

A thermoelectric material including a body centered cubic filled skutterudite having the formula A.sub.xFe.sub.yNi.sub.zSb.sub.12, where A is an alkaline earth element, x is no more than approximately 1.0, and the sum of y and z is approximately equal to 4.0. The alkaline earth element includes guest atoms selected from the group consisting of Be, Mb, Ca, Sr, Ba, Ra and combinations thereof. The filled skutterudite is shown to have properties suitable for a wide variety of thermoelectric applications.

Characterisation of an optimised high current MgO/Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8.21} composite conductor using pulsed transport currents with pulsed magnetic fields

Energy Technology Data Exchange (ETDEWEB)

Glowacki, B A; Gilewski, A; Rogacki, K; Kursumovic, A; Evetts, J E; Jones, H; Henson, R; Tsukamoto, O

2003-01-15

High temperature superconducting conductors are already used in hybrid magnets to produce fields that enhance the performance of conventional magnets made from A-15 type low temperature superconducting wires. For such applications it is vital that the interdependence of the critical parameters such as critical current versus magnetic field can be mapped under high field and high current conditions. However these superconductors have high critical currents even at fields over 20 T, making accurate measurements difficult due to the thermal and mechanical problems. In this paper, we compare measurements on the fully optimised Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8.21} flat rigid conductors using an innovative pulsed high transport current and pulsed high field technique. We show how analysis of the voltage signal from Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8.21} tape in pulsed conditions may be used to extract the critical current under quasi-stationary conditions.

Thermochemistry of rare-earth trifluorides

International Nuclear Information System (INIS)

Kim, K.Y.; Johnson, C.E.

1981-01-01

Using the most recent crystallographic data, the Born-Lande equation was employed to calculate lattice energies of the rare-earth trifluorides. The excellent agreement ( 0 sub(f)(MX 3 ,c,298.15K) can be estimated. The magnitude of the monotonic change of ΔH 0 sub(f)(MX 3 ) for the rare-earth trihalides series (14 4f electrons) is comparable to the energy change between Sc and Ti in which only one 3d electron is added. This energy change is consistent with the chemical evidence that the electrons in the f-orbitals of rare earths contribute negligibly to the bonding. (author)

Rigidity of Glasses and Macromolecules

Science.gov (United States)

Thorpe, M. F.

1998-03-01

The simple yet powerful ideas of percolation theory have found their way into many different areas of research. In this talk we show how RIGIDITY PERCOLATION can be studied at a similar level of sophistication, using a powerful new program THE PEBBLE GAME (D. J. Jacobs and M. F. Thorpe, Phys. Rev. E) 53, 3682 (1996). that uses an integer algorithm. This program can analyse the rigidity of two and three dimensional networks containing more than one million bars and joints. We find the total number of floppy modes, and find the critical behavior as the network goes from floppy to rigid as more bars are added. We discuss the relevance of this work to network glasses, and how it relates to experiments that involve the mechanical properties like hardness and elasticity of covalent glassy networks like Ge_xAs_ySe_1-x-y and dicuss recent experiments that suggest that the rigidity transition may be first order (Xingwei Feng, W. J.Bresser and P. Boolchand, Phys. Rev. Lett 78), 4422 (1997).. This approach is also useful in macromolecules and proteins, where detailed information about the rigid domain structure can be obtained.

Rare-Earth Transition-Metal Intermetallics: Structure-bonding-Property Relationships

Energy Technology Data Exchange (ETDEWEB)

Han, Mi-Kyung [Iowa State Univ., Ames, IA (United States)

2006-01-01

Our explorations of rare-earth, transition metal intermetallics have resulted in the synthesis and characterization, and electronic structure investigation, as well as understanding the structure-bonding-property relationships. Our work has presented the following results: (1) Understanding the relationship between compositions and properties in LaFe<sub>13-xsub>Si<sub>x> system: A detailed structural and theoretical investigation provided the understanding of the role of a third element on stabilizing the structure and controlling the transformation of cubic NaZn<sub>13sub>-type structures to the tetragonal derivative, as well as the relationship between the structures and properties. (2) Synthesis of new ternary rare-earth iron silicides RE<sub>2-xsub>Fe>4sub>Si>14-ysub> and proposed superstructure: This compound offers complex structural challenges such as fractional occupancies and their ordering in superstructure. (3) Electronic structure calculation of FeSi<sub>2sub>: This shows that the metal-semiconductor phase transition depends on the structure. The mechanism of band gap opening is described in terms of bonding and structural distortion. This result shows that the electronic structure calculations are an essential tool for understanding the relationship between structure and chemical bonding in these compounds. (4) Synthesis of new ternary rare-earth Zinc aluminides Tb<sub>3sub>Zn>3.6sub>Al>7.4sub>: Partially ordered structure of Tb<sub>3.6sub>Zn>13-xsub>Al>7.4sub> compound provides new insights into the formation, composition and structure of rare-earth transition-metal intermetallics. Electronic structure calculations attribute the observed composition to optimizing metal-metal bonding in the electronegative (Zn, Al) framework, while the specific ordering is strongly influenced by specific orbital interactions. (5) Synthesis of new structure type of Zn_{39sub>(CrxAl>1-xsub>)}

Rigidity-tuning conductive elastomer

Science.gov (United States)

Shan, Wanliang; Diller, Stuart; Tutcuoglu, Abbas; Majidi, Carmel

2015-06-01

We introduce a conductive propylene-based elastomer (cPBE) that rapidly and reversibly changes its mechanical rigidity when powered with electrical current. The elastomer is rigid in its natural state, with an elastic (Young’s) modulus of 175.5 MPa, and softens when electrically activated. By embedding the cPBE in an electrically insulating sheet of polydimethylsiloxane (PDMS), we create a cPBE-PDMS composite that can reversibly change its tensile modulus between 37 and 1.5 MPa. The rigidity change takes ˜6 s and is initiated when a 100 V voltage drop is applied across the two ends of the cPBE film. This magnitude of change in elastic rigidity is similar to that observed in natural skeletal muscle and catch connective tissue. We characterize the tunable load-bearing capability of the cPBE-PDMS composite with a motorized tensile test and deadweight experiment. Lastly, we demonstrate the ability to control the routing of internal forces by embedding several cPBE-PDMS ‘active tendons’ into a soft robotic pneumatic bending actuator. Selectively activating the artificial tendons controls the neutral axis and direction of bending during inflation.

Rigidity-tuning conductive elastomer

International Nuclear Information System (INIS)

Shan, Wanliang; Diller, Stuart; Tutcuoglu, Abbas; Majidi, Carmel

2015-01-01

We introduce a conductive propylene-based elastomer (cPBE) that rapidly and reversibly changes its mechanical rigidity when powered with electrical current. The elastomer is rigid in its natural state, with an elastic (Young’s) modulus of 175.5 MPa, and softens when electrically activated. By embedding the cPBE in an electrically insulating sheet of polydimethylsiloxane (PDMS), we create a cPBE–PDMS composite that can reversibly change its tensile modulus between 37 and 1.5 MPa. The rigidity change takes ∼6 s and is initiated when a 100 V voltage drop is applied across the two ends of the cPBE film. This magnitude of change in elastic rigidity is similar to that observed in natural skeletal muscle and catch connective tissue. We characterize the tunable load-bearing capability of the cPBE–PDMS composite with a motorized tensile test and deadweight experiment. Lastly, we demonstrate the ability to control the routing of internal forces by embedding several cPBE–PDMS ‘active tendons’ into a soft robotic pneumatic bending actuator. Selectively activating the artificial tendons controls the neutral axis and direction of bending during inflation. (paper)

Rare-earth transition-metal intermetallics: Structure-bonding-property relationships

Energy Technology Data Exchange (ETDEWEB)

Han, M. K. [Iowa State Univ., Ames, IA (United States)

2006-01-01

The explorations of rare-earth, transition metal intermetallics have resulted in the synthesis and characterization, and electronic structure investigation, as well as understanding the structure-bonding property relationships. The work has presented the following results: (1) Understanding the relationship between compositions and properties in LaFe<sub>13-xsub>Si<sub>x> system: A detailed structural and theoretical investigation provided the understanding of the role of a third element on stabilizing the structure and controlling the transformation of cubic NaZn{sub 13}-type structures to the tetragonal derivative, as well as the relationship between the structures and properties. (2) Synthesis of new ternary rare-earth iron silicides Re<sub>2-xsub>Fe>4sub>Si>14-ysub> and proposed superstructure: This compound offers complex structural challenges such as fractional occupancies and their ordering in superstructure. (3) Electronic structure calculation of FeSi<sub>2sub>: This shows that the metal-semiconductor phase transition depends on the structure. The mechanism of band gap opening is described in terms of bonding and structural distortion. This result shows that the electronic structure calculations are an essential tool for understanding the relationship between structure and chemical bonding in these compounds. (4) Synthesis of new ternary rare-earth Zinc aluminides Tb<sub>3sub>Zn>3.6sub>Al>7.4sub>: Partially ordered structure of Tb<sub>3sub>Zn>3.6sub>Al>7.4sub> compound provides new insights into the formation, composition and structure of rare-earth transition-metal intermetallics. Electronic structure calculations attribute the observed composition to optimizing metal-metal bonding in the electronegative (Zn, Al) framework, while the specific ordering is strongly influenced by specific orbital interactions. (5) Synthesis of new structure type of Zn_{39sub>(CrxAl>1-xsub>)>81sub}

The formation of crystals in glasses containing rare earth oxides

Energy Technology Data Exchange (ETDEWEB)

Fadzil, Syazwani Mohd [Pohang University of Science and Technology (POSTECH), Pohang (Korea, Republic of); Hrma, Pavel [Pohang University of Science and Technology (POSTECH), Pohang, South Korea and Pacific Northwest National Laboratory, Richland, Washington (United States); Crum, Jarrod [Pacific Northwest National Laboratory, Richland, Washington (United States); Siong, Khoo Kok; Ngatiman, Mohammad Fadzlee; Said, Riduan Mt [National University of Malaysia, Bandar Baru Bangi, Selangor (Malaysia)

2014-02-12

Korean spent nuclear fuel will reach the capacity of the available temporary storage by 2016. Pyroprocessing and direct disposal seems to be an alternative way to manage and reuse spent nuclear fuel while avoiding the wet reprocessing technology. Pyroprocessing produces several wastes streams, including metals, salts, and rare earths, which must be converted into stabilized form. A suitable form for rare earth immobilization is borosilicate glass. The borosilicate glass form exhibits excellent durability, allows a high waste loading, and is easy to process. In this work, we combined the rare earths waste of composition (in wt%) 39.2Nd{sub 2}O{sub 3}–22.7CeO{sub 2}–11.7La{sub 2}O{sub 3}–10.9PrO{sub 2}–1.3Eu{sub 2}O{sub 3}–1.3Gd{sub 2}O{sub 3}–8.1Sm{sub 2}O{sub 3}–4.8Y{sub 2}O{sub 3} with a baseline glass of composition 60.2SiO{sub 2}–16.0B{sub 2}O{sub 3}–12.6Na{sub 2}O–3.8Al{sub 2}O{sub 3}–5.7CaO–1.7ZrO{sub 2}. Crystallization in waste glasses occurs as the waste loading increases. It may produce complicate glass processing and affect the product quality. To study crystal formation, we initially made glasses containing 5%, 10% and 15% of La{sub 2}O{sub 3} and then glasses with 5%, 10% and 15% of the complete rare earth mix. Samples were heat-treated for 24 hours at temperatures 800°C to 1150°C in 50°C increments. Quenched samples were analyzed using an optical microscope, scanning electron microscope with energy dispersive spectroscopy, and x-ray diffraction. Stillwellite (LaBSiO{sub 5}) and oxyapatite (Ca{sub 2}La{sub 8}Si{sub 6}O{sub 26}) were found in glasses containing La{sub 2}O{sub 3}, while oxyapatite (Ca{sub 2}La{sub 8}Si{sub 6}O{sub 26} and NaNd{sub 9}Si{sub 6}O{sub 26}) precipitated in glasses with additions of mixed rare earths. The liquidus temperature (T{sub L}) of the glasses containing 5%, 10% and 15% La{sub 2}O{sub 3} were 800°C, 959°C and 986°C, respectively; while T{sub L} was 825°C, 1059°C and 1267°C for glasses

On flexible and rigid nouns

DEFF Research Database (Denmark)

Rijkhoff, Jan

2010-01-01

classes. Finally this article wants to claim that the distinction between rigid and flexible noun categories (a) adds a new dimension to current classifications of parts of speech systems, (b) correlates with certain grammatical phenomena (e.g. so-called number discord), and (c) helps to explain the parts......This article argues that in addition to the major flexible lexical categories in Hengeveld’s classification of parts of speech systems (Contentive, Non-Verb, Modifier), there are also flexible word classes within the rigid lexical category Noun (Set Noun, Sort Noun, General Noun). Members...... by the flexible item in the external world. I will then argue that flexible word classes constitute a proper category (i.e. they are not the result of a merger of some rigid word classes) in that members of flexible word categories display the same properties regarding category membership as members of rigid word...

A highly triflated rare-earth ion in [Eu(O{sub 3}SCF{sub 3}){sub 8}]{sup 5-}

Energy Technology Data Exchange (ETDEWEB)

Bruns, Joern; Kluener, Thorsten; Kraeuter, Jessica; Wickleder, Mathias S. [Carl von Ossietzky Universitaet Oldenburg, Institut fuer Chemie (Germany); Krueger, Sascha; Adlung, Matthias; Wickleder, Claudia [Universitaet Siegen, Institut fuer Anorganische Chemie (Germany); Niehaus, Oliver; Poettgen, Rainer [Westfaelische Wilhelms Universitaet Muenster, Institut fuer Anorganische und Analytische Chemie (Germany)

2015-08-24

The reaction of Eu{sub 2}O{sub 3} with fuming nitric acid, trifluormethanesulfonic acid, and its anhydride in torch-sealed glass ampoules at 120 C gave the europium compound (NO){sub 5}[Eu(O{sub 3}SCF{sub 3}){sub 8}] (orthorhombic, Fddd, Z=16, a=1932.69(4), b=2878.44(7), c=2955.12(7) pm, V=16439.7(7) Aa{sup 3}). The compound exhibits the [Eu(O{sub 3}SCF{sub 3}){sub 8}]{sup 5-} anion showing for the first time a lanthanide ion that is exclusively coordinated by eight triflate anions. The anion has been further investigated by DFT calculations, which also allowed clear assignment of the vibrational spectra. Moreover, magnetochemical and luminescence measurements gave additional insight into the properties of this complex. The luminescence spectra revealed that the Eu{sup 3+} ions are in a pseudo D{sub 4d} symmetric environment. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

The calculated magnetic, electronic and thermodynamic properties of Ce{sub 3}Co{sub 29}Si{sub 4}B{sub 10} compound

Energy Technology Data Exchange (ETDEWEB)

Huo, Jin-Rong [Institute of Applied Physics, Beijing University of Science and Technology, Beijing 100083 (China); Wang, Xiao-Xu [Institute of Applied Physics, Beijing University of Science and Technology, Beijing 100083 (China); Cloud Computing Department, Beijing Computing Center, Beijing 100084 (China); Hu, Yao-Wen [Department of Physics, Tsinghua University, Beijing 100084 (China); Zhang, Guo-Hua; Cheng, Hai-Xia; Li, Lu [Institute of Applied Physics, Beijing University of Science and Technology, Beijing 100083 (China); Qian, Ping, E-mail: qianping@ustb.edu.cn [Institute of Applied Physics, Beijing University of Science and Technology, Beijing 100083 (China)

2016-05-15

The magnetic moment, lattice parameter and atom fraction coordinates for Ce{sub 3}Co{sub 29}Si{sub 4}B{sub 10} are calculated by the first-principles GGA+U method, and the results indicate that the calculated and experimental values are basically accordant when U=2.6 eV. We study the interaction effect and orbital hybridization between Co and Ce atoms. The projected density of states at U=2.6 eV which provided by Co-2c, Ce-2b and Ce-4d sites are contrasted with else U values. Meanwhile the electron density of states for different sites and the distance between various atoms are exhibited. In addition, the thermodynamic properties of Ce{sub 3}Co{sub 29}Si{sub 4}B{sub 10} are evaluated by using a series of interatomic pair potentials. - Graphical abstract: Change of the total magnetic moment for Ce{sub 3}Co{sub 29}Si{sub 4}B{sub 10} along with the value of U. There is a sharply decline of the curve at U=2.6 eV and, at the moment, the total magnetic moment of the compound have a good agreement with the experimental data. - Highlights: • We research of quaternary rare earth and transition metal compounds. • We perform the calculation of magnetic moment and electronic structure by GGA+U method. • The orbital hybridization between Co and Ce atoms is displayed and analyzed. • Show the plot of projected density of states for different sites more clearly. • Calculate the thermodynamic property of rare-earth transition metal compound.

Structural and Magnetothermal Properties of Compounds: Yb<sub>5sub>Si_xGe>4-xsub>,Sm>5sub>Si_xGe>4-xsub>, EuO, and Eu<sub>3sub>O>4sub>

Energy Technology Data Exchange (ETDEWEB)

Ahn, Kyunghan [Iowa State Univ., Ames, IA (United States)

2007-01-01

The family of R<sub>5sub>Si_xGe>4-xsub> alloys demonstrates a variety of unique physical phenomena related to magneto-structural transitions associated with reversible breaking and reforming of specific bonds that can be controlled by numerous external parameters such as chemical composition, magnetic field, temperature, and pressure. Therefore, R<sub>5sub>Si_xGe>4-xsub> systems have been extensively studied to uncover the mechanism of the extraordinary magneto-responsive properties including the giant magnetoresistance (GMR) and colossal magnetostriction, as well as giant magnetocaloric effect (GMCE). Until now, more than a half of possible R<sub>5sub>Si_xGe>4-xsub> pseudobinary systems have been completely or partially investigated with respect to their crystallography and phase relationships (R = La, Pr, Nd, Gd, Tb, Dy, Er, Lu, Y). Still, there are other R<sub>5sub>Si_xGe>4-xsub> systems (R = Ce, Sm, Ho, Tm, and Yb) that are not studied yet. Here, we report on phase relationships and structural, magnetic, and thermodynamic properties in the Yb<sub>5sub>Si_xGe>4-xsub>and Sm<sub>5sub>Si_xGe>4-xsub> pseudobinary systems, which may exhibit mixed valence states. The crystallography, phase relationships, and physical properties of Yb<sub>5sub>Si_xGe>4-xsub> alloys with 0 ≤ x ≤ 4 have been examined by using single crystal and powder x-ray diffraction at room temperature, and dc magnetization and heat capacity measurements between 1.8 K and 400 K in magnetic fields ranging from 0 to 7 T. Unlike the majority of R<sub>5sub>Si_xGe>4-xsub> systems studied to date, where R is the rare earth metal, all Yb-based germanide-silicides with the 5:4 stoichiometry crystallize in the same Gd<sub>5sub>Si>4sub>-type structure. The magnetic properties of Yb<sub>5sub>Si_xGe>4-xsub> materials are nearly composition

Indides RE{sub 3}T{sub 2}In{sub 4} (RE = Y, Gd-Tm, Lu; T = Ni, Ru, Rh) with a ZrNiAl superstructure

Energy Technology Data Exchange (ETDEWEB)

Heying, Birgit; Niehaus, Oliver; Rodewald, Ute C.; Poettgen, Rainer [Univ. Muenster (Germany). Inst. fuer Anorganische und Analytische Chemie

2016-07-01

Three series of rare earth-transition metal-indides RE{sub 3}T{sub 2}In{sub 4} (RE=Y, Gd-Tm, Lu; T=Ni, Ru, Rh) were synthesized from arc-melted RE{sub 3}T{sub 2} precursor compounds and indium tear shot in sealed niobium ampoules using different annealing sequences. The new indides crystallize with the hexagonal Lu{sub 3}Co{sub 2}In{sub 4}-type structure, space group P anti 6. All samples were characterized on the basis of Guinier powder patterns and six structures were refined from single crystal X-ray diffractometer data. The RE{sub 3}T{sub 2}In{sub 4} structures are derived from the ZrNiAl type through RE/In ordering, paralleled by a symmetry reduction from P anti 62m to P anti 6. This induces twinning for some of the investigated crystals. The main crystal chemical motifs of the RE{sub 3}T{sub 2}In{sub 4} structures are trigonal prisms of rare earth, respectively indium atoms that are filled by the transition metals.

Polarity of translation boundaries in antiferroelectric PbZrO{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Wei, Xian-Kui, E-mail: xiankui.wei@epfl.ch [Ceramics Laboratory, EPFL–Swiss Federal Institute of Technology, Lausanne 1015 (Switzerland); Peter Grünberg Institute and Ernst Ruska Center for Microscopy and Spectroscopy with Electrons, Research Center Jülich, 52425 Jülich (Germany); Jia, Chun-Lin [Peter Grünberg Institute and Ernst Ruska Center for Microscopy and Spectroscopy with Electrons, Research Center Jülich, 52425 Jülich (Germany); International Centre of Dielectric Research, The School of Electronic and Information Engineering, Xi’an Jiaotong University, Xi’an 710049 (China); Roleder, Krystian [Institute of Physics, University of Silesia, Katowice 40007 (Poland); Setter, Nava [Ceramics Laboratory, EPFL–Swiss Federal Institute of Technology, Lausanne 1015 (Switzerland)

2015-02-15

Graphical abstract: Strain-free rigid model and aberration-corrected transmission electron microscopes are used to investigate the polarity of translation boundaries in antiferroelectric PbZrO{sub 3}. - Highlights: • Domain boundaries in antiferroelectric PbZrO{sub 3} show polar and antipolar property. • The antiphase boundary can split into “sub-domains”. • Polarization reversal possibly exists inside the translation boundaries. • Thermal treatment can alter morphology and density of the translation boundaries. - Abstract: The polarity of translation boundaries (TBs) in antiferroelectric PbZrO{sub 3} is investigated. We show that previous experimentally reported polar property of R{sub III-1} type TB can be well approximated by a strain-free rigid model. Based on this, the modeling investigation suggests that there are two additional polar TBs, three antipolar-like TBs and one antipolar antiphase boundary. High-resolution scanning-transmission-electron-microscopy study reveals that the straight R{sub III-1} type TB can split into “sub-domains” with possible polarization reversal, suggesting the occurrence of ferroic orders at the TBs. In addition, dependence of morphology and density of the TBs on thermal treatments is discussed according to our results.

MOA-2011-BLG-262Lb: A sub-Earth-mass moon orbiting a gas giant primary or a high velocity planetary system in the galactic Bulge

Energy Technology Data Exchange (ETDEWEB)

Bennett, D. P. [Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556 (United States); Batista, V. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Bond, I. A.; Ling, C. H. [Institute of Natural and Mathematical Sciences, Massey University, Auckland 0745 (New Zealand); Bennett, C. S. [Department of Physics, Massachussets Institute of Technology, Cambridge, MA 02139 (United States); Suzuki, D.; Koshimoto, N. [Department of Earth and Space Science, Osaka University, Osaka 560-0043 (Japan); Beaulieu, J.-P. [UPMC-CNRS, UMR 7095, Institut d' Astrophysique de Paris, 98bis Boulevard Arago, F-75014 Paris (France); Udalski, A. [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland); Donatowicz, J. [Technische Universität Wien, Wieder Hauptst. 8-10, A-1040 Vienna (Austria); Bozza, V. [Dipartimento di Fisica, Università di Salerno, Via Ponte Don Melillo 132, I-84084 Fisciano (Italy); Abe, F.; Fukunaga, D.; Itow, Y.; Masuda, K.; Matsubara, Y.; Muraki, Y. [Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya 464-8601 (Japan); Botzler, C. S.; Freeman, M. [Department of Physics, University of Auckland, Private Bag 92-019, Auckland 1001 (New Zealand); Fukui, A., E-mail: bennett@nd.edu [Okayama Astrophysical Observatory, National Astronomical Observatory of Japan, Okayama 719-0232 (Japan); Collaboration: MOA Collaboration; PLANET Collaboration; μFUN Collaboration; OGLE Collaboration; RoboNet Collaboration; and others

2014-04-20

We present the first microlensing candidate for a free-floating exoplanet-exomoon system, MOA-2011-BLG-262, with a primary lens mass of M {sub host} ∼ 4 Jupiter masses hosting a sub-Earth mass moon. The argument for an exomoon hinges on the system being relatively close to the Sun. The data constrain the product M{sub L} π{sub rel} where M{sub L} is the lens system mass and π{sub rel} is the lens-source relative parallax. If the lens system is nearby (large π{sub rel}), then M{sub L} is small (a few Jupiter masses) and the companion is a sub-Earth-mass exomoon. The best-fit solution has a large lens-source relative proper motion, μ{sub rel} = 19.6 ± 1.6 mas yr{sup –1}, which would rule out a distant lens system unless the source star has an unusually high proper motion. However, data from the OGLE collaboration nearly rule out a high source proper motion, so the exoplanet+exomoon model is the favored interpretation for the best fit model. However, there is an alternate solution that has a lower proper motion and fits the data almost as well. This solution is compatible with a distant (so stellar) host. A Bayesian analysis does not favor the exoplanet+exomoon interpretation, so Occam's razor favors a lens system in the bulge with host and companion masses of M{sub host}=0.12{sub −0.06}{sup +0.19} M{sub ⊙} and m{sub comp}=18{sub −10}{sup +28} M{sub ⊕}, at a projected separation of a{sub ⊥}=0.84{sub −0.14}{sup +0.25} AU. The existence of this degeneracy is an unlucky accident, so current microlensing experiments are in principle sensitive to exomoons. In some circumstances, it will be possible to definitively establish the mass of such lens systems through the microlensing parallax effect. Future experiments will be sensitive to less extreme exomoons.

A single crystal study of RE{sub 14}Co{sub 3}In{sub 3} (RE = Y, Tb, Dy, Ho, Er)

Energy Technology Data Exchange (ETDEWEB)

Zaremba, V.I.; Kalychak, Y.M.; Dzevenko, M.V. [Inorganic Chemistry Dept., Ivan Franko National Univ. of Lviv (Ukraine); Rodewald, U.Ch.; Heying, B.; Poettgen, R. [Inst. fuer Anorganische und Analytische Chemie, Westfaelische Wilhelms-Univ. Muenster (Germany)

2006-01-01

The rare earth-cobalt-indides RE{sub 14}Co{sub 3}In{sub 3} (RE = Y, Tb, Dy, Ho, Er) were prepared in polycrystalline form from the elements by arc-melting. Small single crystals were grown through a special annealing sequence. The compounds were investigated on the basis of X-ray powder and single crystal data: Lu{sub 14}Co{sub 2}In{sub 3} (Gd{sub 14}Co{sub 3}In{sub 2.7}) type, P4{sub 2}/nmc, Z = 4, a = 959.0(1), c = 2319.1(5) pm, wR2 = 0.055, 2289 F{sup 2} values, 65 variables for Y{sub 13.90}Co{sub 2.99}In{sub 3.02}, a = 953.8(1), c = 2315.8(5) pm, wR2 = 0.108, 2357 F{sup 2} values, 65 variables for Tb{sub 13.92}Co{sub 3.01}In{sub 2.92}, a = 949.24(3), c = 2296.5(1) pm, wR2 = 0.129, 2518 F{sup 2} values, 65 variables for Dy{sub 13.90}Co{sub 2.97}In{sub 2.95}, a = 946.3(1), c = 2289.0(5) pm, wR2 = 0.099, 2297 F{sup 2} values, 64 variables for Ho{sub 14}Co{sub 2.80}In{sub 2.89}, and a = 941.0(1), c = 2274.2(5) pm, wR2 = 0.140, 2450 F{sup 2} values, 65 variables for Er{sub 13.83}Co{sub 2.88}In{sub 3.10}. All RE{sub 14}Co{sub 3}In{sub 3} indides show a small degree of In/Co mixing (between 7 and 16% Co) on the 4c In1 site and defects on the 8g Co1 positions (between 84 and 95% Co). Except for the holmium compound, the RE{sub 14}Co{sub 3}In{sub 3} intermetallics also reveal RE/In mixing on the 4c RE1 sites, leading to the refined compositions. The seven crystallographically independent RE sites have between 9 and 10 nearest RE neighbors. The RE{sub 14}Co{sub 3}In{sub 3} structures consist of a complex intergrowth of rare earth based polyhedra. Both cobalt sites have a distorted trigonal-prismatic rare earth coordination. An interesting feature is the In2-In2 dumb-bell with an In2-In2 distance of 300 pm (for Ho{sub 14}Co{sub 2.80}In{sub 2.89}). The crystal chemistry of the RE{sub 14}Co{sub 3}In{sub 3} indides is discussed. (orig.)

CT-3DRA registration for radiosurgery treatments: a comparison among rigid, affine and non rigid approaches

International Nuclear Information System (INIS)

Stancanello, J.; Loeckx, D.; Francescon, P.; Calvedon, C.; Avanzo, M.; Cora, S.; Scalchi, P.; Cerveri, P.; Ferrigno, G.

2004-01-01

This work aims at comparing rigid, affine and Local Non Rigid (LNR) CT-3D Rotational Angiography (CT-3DRA) registrations based on mutual information. 10 cranial and 1 spinal cases have been registered by rigid and affine transformations; while LNR has been applied to the cases where residual deformation must be corrected. An example of CT-3DRA registration without regularization term and an example of LNR using the similarity criterion and the regularization term as well as 3D superposition of the 3DRA before and after the registration without the regularization term are presented. All the registrations performed by rigid transformation converged to an acceptable solution. The results about the robustness test in axial direction are reported. Conclusions: For cranial cases, affine transformation endowed with threshold-segmentation pre-processing can be considered the most favourable solution for almost all registrations; for some cases, LNR provides more accurate results. For the spinal case rigid transformation is the most suitable when immobilizing patient during examinations; in this case the increase of accuracy by using LNR registrations seems to be not significant

The RMgSn{sub 2} series of compounds (R = rare earth metal). Synthesis, crystal structure, and magnetic measurements

Energy Technology Data Exchange (ETDEWEB)

Solokha, Pavlo; Minetti, Riccardo; De Negri, Serena; Saccone, Adriana [Dipartimento di Chimica e Chimica Industriale, Universita di Genova (Italy); Pereira, Laura Cristina J.; Goncalves, Antonio P. [Centro de Ciencias e Tecnologias Nucleares, Instituto Superior Tecnico, EN 10, Universidade de Lisboa, Bobadela (Portugal)

2017-06-30

The novel isostructural series of phases RMgSn{sub 2} (R = Y, La-Nd, Sm, Gd-Tm, Lu) is presented. They were prepared by direct synthesis in an induction furnace and subsequently annealed at 500 C. Their crystal structures were determined through single-crystal X-ray diffraction analysis of the Ce representative [I anti 42m, tI32-LaMgSn{sub 2}, Z = 8, a = 0.82863(3) nm, c = 1.23129(5) nm] and confirmed by powder X-ray diffraction analysis of the other members of the series. Rietveld refinements were also performed on the homologues with R = Pr, Tm, and Y. The title phases show a unique space distribution of atoms, characterized by the presence of a Sn-Sn dumbbell distanced at around 0.29 nm. Their structures are related to those of a few binary AeTt{sub 3} (Ae = alkaline earth; Tt = Si, Ge; I4/mmm, tI32-YbSi{sub 3}) compounds that are stable at high pressure, characterized by a more complex 3D covalently bonded Tt network. Compounds CeMgSn{sub 2} and TbMgSn{sub 2} were magnetically characterized; they show paramagnetic behavior with the presence of ferromagnetic interactions, more pronounced in the case of TbMgSn{sub 2}, as suggested by the Curie-Weiss temperatures, determined in the high-temperature range, of 0.96 and 27.6 K for CeMgSn{sub 2} and TbMgSn{sub 2}, respectively. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Torsional Rigidity of Minimal Submanifolds

DEFF Research Database (Denmark)

Markvorsen, Steen; Palmer, Vicente

2006-01-01

We prove explicit upper bounds for the torsional rigidity of extrinsic domains of minimal submanifolds $P^m$ in ambient Riemannian manifolds $N^n$ with a pole $p$. The upper bounds are given in terms of the torsional rigidities of corresponding Schwarz symmetrizations of the domains in warped...

Flexible and rigid cystoscopy in women.

Science.gov (United States)

Gee, Jason R; Waterman, Bradley J; Jarrard, David F; Hedican, Sean P; Bruskewitz, Reginald C; Nakada, Stephen Y

2009-01-01

Previous studies have evaluated the tolerability of rigid versus flexible cystoscopy in men. Similar studies, however, have not been performed in women. We sought to determine whether office-based flexible cystoscopy was better tolerated than rigid cystoscopy in women. Following full IRB approval, women were prospectively randomized in a single-blind manner. Patients were randomized to flexible or rigid cystoscopy and draped in the lithotomy position to maintain blinding of the study. Questionnaires evaluated discomfort before, during, and after cystoscopy. Thirty-six women were randomized to flexible (18) or rigid (18) cystoscopy. Indications were surveillance (16), hematuria (15), recurrent UTIs (2), voiding dysfunction (1), and other (2). All questionnaires were returned by 31/36 women. Using a 10-point visual analog scale (VAS), median discomfort during the procedure for flexible and rigid cystoscopy were 1.4 and 1.8, respectively, in patients perceiving pain. Median recalled pain 1 week later was similar at 0.8 and 1.15, respectively. None of these differences were statistically significant. Flexible and rigid cystoscopy are well tolerated in women. Discomfort during and after the procedure is minimal in both groups. Urologists should perform either procedure in women based on their preference and skill level.

Magnetic properties of RT<sub>2sub>Zn>20sub>; R = rare earth, T = Fe, Co, Ru, Os and Ir

Energy Technology Data Exchange (ETDEWEB)

Jia, Shuang [Ames Lab. and Iowa State Univ., Ames, IA (United States)

2008-01-01

It is well known that rare earth intermetallic compounds have versatile, magnetic properties associated with the 4f electrons: a local moment associated with the Hund's rule ground state is formed in general, but a strongly correlated, hybridized state may also appear for specific 4f electronic configuration (eg. for rare earth elements such as Ce or Yb). On the other hand, the conduction electrons in rare earth intermetallic compounds, certainly ones associated with non hybridizing rare earths, usually manifest non-magnetic behavior and can be treated as a normal, non-interacted Fermi liquid, except for some 3d-transition metal rich binary or ternary systems which often manifest strong, itinerant, d electron dominant magnetic behavior. Of particular interest are examples in which the band filling of the conduction electrons puts the system in the vicinity of a Stoner transition: such systems, characterized as nearly or weakly ferromagnet, manifest strongly correlated electronic properties [Moriya, 1985]. For rare earth intermetallic compounds, such systems provide an additional versatility and allow for the study of the behaviors of local moments and hybridized moments which are associated with 4f electron in a correlated conduction electron background.

The bottom of the universe: Flat earth science in the Age of Encounter.

Science.gov (United States)

Allegro, James J

2017-03-01

This essay challenges the dominance of the spherical earth model in fifteenth- and early-sixteenth-century Western European thought. It examines parallel strains of Latin and vernacular writing that cast doubt on the existence of the southern hemisphere. Three factors shaped the alternate accounts of the earth as a plane and disk put forward by these sources: (1) the unsettling effects of maritime expansion on scientific thought; (2) the revival of interest in early Christian criticism of the spherical earth; and (3) a rigid empirical stance toward entities too large to observe in their entirety, including the earth. Criticism of the spherical earth model faded in the decades after Magellan's crew returned from circuiting the earth in 1522.

Hydrothermal synthesis and characterization of the praseodymium borate-nitrate Pr[B{sub 5}O{sub 8}(OH)(H{sub 2}O){sub 0.87}]NO{sub 3}.2H{sub 2}O

Energy Technology Data Exchange (ETDEWEB)

Ortner, Teresa S.; Huppertz, Hubert [Innsbruck Univ. (Austria). Inst. fuer Allgemeine, Anorganische und Theoretische Chemie

2017-10-01

The praseodymium borate-nitrate Pr[B{sub 5}O{sub 8}(OH)(H{sub 2}O){sub 0.87}]NO{sub 3}.2H{sub 2}O was obtained in a hydrothermal synthesis. It crystallizes monoclinically in the space group P2{sub 1}/n (no. 14) with four formula units (Z=4) and unit cell parameters of a=641.9(3), b=1551.8(7), c=1068.4(5) pm, with β=90.54(2) yielding V=1.0643(8) nm{sup 3}. The defect variant constitutes the missing member in the series of isostructural, early rare earth borate-nitrates of the composition RE[B{sub 5}O{sub 8}(OH)(H{sub 2}O){sub x}]NO{sub 3}.2H{sub 2}O [RE=La (x=0; 1), Ce (x=1), Nd (x=0.85), Sm (x=0)]. In addition to powder and single-crystal X-ray diffraction data, the novel borate-nitrate was characterized through IR and Raman spectroscopy.

Rare-earth metal transition metal borocarbide and nitridoborate superconductors

Energy Technology Data Exchange (ETDEWEB)

Niewa, Rainer; Shlyk, Larysa; Blaschkowski, Bjoern [Stuttgart Univ. (Germany). Inst. fuer Anorganische Chemie

2011-07-01

Few years after the discovery of superconductivity in high-T{sub c} cuprates, borocarbides and shortly after nitridoborates with reasonably high T{sub c}s up to about 23 K attracted considerable attention. Particularly for the rare-earth metal series with composition RNi{sub 2}[B{sub 2}C] it turned out, that several members exhibit superconductivity next to magnetic order with both T{sub c} above or below the magnetic ordering temperature. Therefore, these compounds have been regarded as ideal materials to study the interplay and coexistence of superconductivity and long range magnetic order, due to their comparably high ordering temperatures and similar magnetic and superconducting condensation energies. This review gathers information on the series RNi{sub 2}[B{sub 2}C] and isostructural compounds with different transition metals substituting Ni as well as related series like RM[BC], RM[BN], AM[BN] and R{sub 3}M{sub 2}[BN]{sub 2}N (all with R = rare-earth metal, A = alkaline-earth metal, M = transition metal) with special focus on synthesis, crystal structures and structural trends in correspondence to physical properties. (orig.)

Influence of Rare Earth Elements on Microstructure and Mechanical Properties of Mg{sub 97}Zn{sub 1}Y{sub 1}RE{sub 1} Alloys

Energy Technology Data Exchange (ETDEWEB)

Kim, Jonghyun, E-mail: joindoc@kumamoto-u.ac.jp [Department of Material Science, Magnesium Research Center (MRC), Kumamoto University, Kumamoto, 860-8555 (Japan); Kawamura, Y. [Department of Material Science, Magnesium Research Center (MRC), Kumamoto University, Kumamoto, 860-8555 (Japan)

2013-06-20

Mg{sub 97}Zn{sub 1}Y{sub 1}RE{sub 1} (RE=La, Ce, Nd and Sm, at. %) alloys were prepared by high-frequency induction melting in an Ar atmosphere. Rods were extruded at 623 K and a ram speed of 2.5 mm·s{sup −1} using a circular die with an extrusion ratio of 10. The microstructure and mechanical properties of the extruded alloys were investigated. The Mg{sub 97}Zn{sub 1}Y{sub 1}Nd{sub 1} and Mg{sub 97}Zn{sub 1}Y{sub 1}Sm{sub 1} alloys consisted of only two phases: α-Mg and a Mg-RE intermetallic compound. The Mg{sub 97}Zn{sub 1}Y{sub 1}La{sub 1} and Mg{sub 97}Zn{sub 1}Y{sub 1}Ce{sub 1} alloys consisted of three phases: α-Mg, a Mg-RE intermetallic compound, and a Mg{sub 12}ZnY phase with a long-period stacking ordered (LPSO) phase. Additionally, after extrusion, the three-phase Mg{sub 97}Zn{sub 1}Y{sub 1}RE{sub 1} alloys, i.e., those with an LPSO phase, had a stratified microstructure and exhibited better mechanical properties than those without an LPSO. At room temperature, the yield strength and ultimate tensile strength of the three-phase Mg{sub 97}Zn{sub 1}Y{sub 1}La{sub 1} and Mg{sub 97}Zn{sub 1}Y{sub 1}Ce{sub 1} alloys were 381–384 MPa and 427–429 MPa, respectively, and yield strengths greater than 280 MPa were observed at the elevated temperature of 523 K.

Analysis of Switched-Rigid Floating Oscillator

Directory of Open Access Journals (Sweden)

Prabhakar R. Marur

2009-01-01

Full Text Available In explicit finite element simulations, a technique called deformable-to-rigid (D2R switching is used routinely to reduce the computation time. Using the D2R option, the deformable parts in the model can be switched to rigid and reverted back to deformable when needed during the analysis. The time of activation of D2R however influences the overall dynamics of the system being analyzed. In this paper, a theoretical basis for the selection of time of rigid switching based on system energy is established. A floating oscillator problem is investigated for this purpose and closed-form analytical expressions are derived for different phases in rigid switching. The analytical expressions are validated by comparing the theoretical results with numerical computations.

Isomerization of butene-1 on rare earth oxides. [Rare earths: La, Nd, Dy

Energy Technology Data Exchange (ETDEWEB)

Khodakov, Yu S; Nesterov, V K; Minachev, Kh M [AN SSSR, Moscow. Inst. Organicheskoj Khimii

1975-09-01

A study has been made into the isomerization of butene-1 on oxides of rare-earth elements. The dependence of the reaction rate at 20/sup 0/C on the baking temperature of La and Nd oxides have the maximum at 700/sup 0/C. A decrease in the activity of these oxides after bakinq at 800/sup 0/C is observed, as well as during experiments at -30 deq C. In the case of Dy/sub 2/O/sub 3/, the activity at 20/sup 0/C increases gradually with Tsub(bak)=500 to 800/sup 0/C Zeolite 0.57LaNaY exhibits maximum activity at Tsub(bak)=500/sup 0/C Similar data as to the effect of the baking temperature on the catalyst activity were obtained earlier for hydrogenation of ethylene. According to their maximum activity, oxides of rare-earth elements, in the isomerization as well as hydrogenation reactions, can be arranged as follows: La/sub 2/O/sub 3/>Nd/sub 2/O/sub 3/sub 2/O/sub 3/. LaNaY has a lower activity, with respect to La/sup 3 +/ cation, than La/sub 2/O/sub 3/. The Na-form of zeolite Y was not active. The regularities of variation in the catalytic activity of La, Nd, Dy oxides and zeolite 0.57LaNaY in the reactions of double bond shift in butenes and hydroqenation of ethylene are similar.

Magnetic susceptibility of the rare earth tungsten oxide bronzes of the defected perovskite-type structure (Rsub(x)WO/sub 3/)

Energy Technology Data Exchange (ETDEWEB)

Gesicki, A; Polaczek, A [Warsaw Univ. (Poland)

1975-01-01

Magnetic susceptibility of rare earth tungsten bronzes Rsub(x)WO/sub 3/ of cubic symmetry was measured in the 80-293 K range with the Gouy method. In disagreement with the data reported by other authors it was stated that the Curie-Weiss law with negative Weiss parameter was fulfilled in each case. Possible coupling mechanisms are briefly discussed.

Synthesis, crystal structures, and luminescent properties of Cd(II) coordination polymers assembled from semi-rigid multi-dentate N-containing ligand

Energy Technology Data Exchange (ETDEWEB)

Yuan, Gang; Shao, Kui-Zhan; Chen, Lei; Liu, Xin-Xin [Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University, Changchun 130024, Jilin (China); Su, Zhong-Min, E-mail: zmsu@nenu.edu.cn [Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University, Changchun 130024, Jilin (China); Ma, Jian-Fang [Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University, Changchun 130024, Jilin (China)

2012-12-15

Three new polymers, [Cd(L){sub 2}(H{sub 2}O){sub 2}]{sub n} (1), [Cd{sub 3}(L){sub 2}({mu}{sub 3}-OH){sub 2}({mu}{sub 2}-Cl){sub 2}(H{sub 2}O){sub 2}]{sub n} (2), {l_brace}[Cd{sub 2}(L){sub 2}(nic){sub 2}(H{sub 2}O){sub 2}]{center_dot}H{sub 2}O{r_brace}{sub n} (3) (HL=5-(4-((1H-1,2,4-triazol-1-yl)methyl)phenyl)-1H-tetrazole, Hnic=nicotinic acid) have been prepared and structurally characterized. Compounds 1 and 2 display 2D monomolecular layers built by the inter-linking single helical chains and L{sup -} ligands connecting chain-like [Cd({mu}{sub 3}-OH)({mu}{sub 2}-Cl)]{sub n} secondary building units, respectively. Compound 3 is constructed from the mixed ligands and possesses a (3,4)-connected framework with (4{center_dot}8{sup 2})(4{center_dot}8{sup 2}{center_dot}10{sup 3}) topology. Moreover, the fluorescent properties of HL ligand and compounds 1-3 are also been investigated. - Graphical abstract: Three new coordination polymers based on the semi-rigid multidentate N-donor ligand have been successfully synthesized by hydrothermal reaction. Complexes 1 and 2 exhibit the 2D layers formed by inter-linking single helices and L{sup -} anions bridging 1D chain-like SBUs, respectively. Complex 3 is buit by L{sup -} and assistant nic{sup -} ligands connecting metal centers and possesses a (3,4)-connected framework with (4 Multiplication-Sign 8{sup 2})(4 Multiplication-Sign 8{sup 2} Multiplication-Sign 10{sup 3}) topology. Moreover, these complexes display fluorescent properties indicating that they may have potential applications as optical materials. Highlights: Black-Right-Pointing-Pointer Three Cd-compounds were prepared from semi-rigid HL ligand with different N-containing groups. Black-Right-Pointing-Pointer They exhibit diverse structures from 2D monomolecular layer to 3D covalent framework. Black-Right-Pointing-Pointer The HL ligands displayed various coordination modes under different reaction conditions. Black-Right-Pointing-Pointer These compounds exhibit

Exchange-bias-like effect in Pr{sub 0.75}Tb{sub 0.25}Al{sub 2} and Pr{sub 0.7}Tb{sub 0.3}Al{sub 2} samples

Energy Technology Data Exchange (ETDEWEB)

Tedesco, J.C.G., E-mail: tedesco.jcg@gmail.com [Instituto de Física “Gleb Wataghin”, Universidade Estadual de Campinas—UNICAMP, 13083-859 Campinas, SP (Brazil); Pires, M.J.M. [Instituto de Ciência e Tecnologia—ICT, Universidade Federal dos Vales do Jequitinhonha e Mucuri—UFVJM, 39100-000 Diamantina, MG (Brazil); Carvalho, A. Magnus G. [Divisão de Metrologia de Materiais (DIMAT), INMETRO, 25250-020 Duque de Caxias, RJ (Brazil); Sousa, V.S.R. de [Instituto de Física “Armando Dias Tavares”, Universidade do Estado do Rio de Janeiro—UERJ, 20550-013 Rio de Janeiro, RJ (Brazil); Cardoso, L.P.; Coelho, A.A. [Instituto de Física “Gleb Wataghin”, Universidade Estadual de Campinas—UNICAMP, 13083-859 Campinas, SP (Brazil)

2013-08-15

The magnetic behavior of pseudobinary Pr{sub 0.7}Tb{sub 0.3}Al{sub 2} and Pr{sub 0.75}Tb{sub 0.25}Al{sub 2} compounds was studied, and a predominant ferrimagnetic ordering was observed. Noteworthy characteristics such as negative magnetization, compensation points and exchange-bias-like (EB-like) effect were found. This EB-like effect was observed at temperatures below the compensation points. The effect is somewhat different from the one already studied in similar systems combining light and heavy rare earths. The results indicate that the EB-like effect characteristics are related to the conduction electron magnetic polarization and an induced unidirectional anisotropy present in these compounds. - Highlights: ► Ferrimagnetic behavior is observed in Pr{sub 0.7}Tb{sub 0.3}Al{sub 2} and Pr{sub 0.75}Tb{sub 0.25}Al{sub 2} materials. ► Magnetic data indicate a strong unidirectional anisotropy in studied materials. ► Studied materials present the exchange-bias-like effect. ► Exchange-bias-like effect explained in analogy with the known mechanism of thin films.

Torsional rigidity, isospectrality and quantum graphs

International Nuclear Information System (INIS)

Colladay, Don; McDonald, Patrick; Kaganovskiy, Leon

2017-01-01

We study torsional rigidity for graph and quantum graph analogs of well-known pairs of isospectral non-isometric planar domains. We prove that such isospectral pairs are distinguished by torsional rigidity. (paper)

Photoemission study of the skutterudite compounds CoSb sub 3 and RhSb sub 3

CERN Document Server

Ishii, H; Fujimori, A; Nagamoto, Y; Koyanagi, T; Sofo, J O

2002-01-01

We have studied the electronic structure of the skutterudite compounds CoSb sub 3 and Co(Sb sub 0 sub . sub 9 sub 6 Te sub 0 sub . sub 0 sub 4) sub 3 by photoemission spectroscopy. Valence-band spectra revealed that a significant amount Sb 5p states are present near the Fermi level and are hybridized with Co 3d states just below it. The spectra are well reproduced by the band-structure calculation, suggesting that the effect of electron correlations is not important. When Te is substituted for Sb and n-type carriers are doped into CoSb sub 3 , the spectra are shifted to higher binding energies as described by the rigid-band model. From this shift and the free-electron model for the conduction and valence bands, we have estimated the band gap of CoSb sub 3 to be 0.03-0.04 eV, consistent with transport measurements. Photoemission spectra of RhSb sub 3 have also been measured and revealed expected similarities to and differences from those of CoSb sub 3. Unusual temperature dependence has been observed for the s...

Theoretical study of phase forming of NaZn sub 1 sub 3 -type rare-earth intermetallics

CERN Document Server

Chang Hong; Liang Jing Kui; Rao Guang Hui

2003-01-01

By using the interatomic pair potential obtained with the lattice inversion method, the stability of RT sub 1 sub 3 sub - sub x M sub x (R = La, Ce, Pr and Nd; T=Co and Fe; M=Si, Al, Cr, V and Ti) of the NaZn sub 1 sub 3 type and its derivative structure are studied. The structural transition of LaT sub 1 sub 3 sub - sub x Si sub x (T=Co and Fe) between the cubic one with the space group Fm3c and the tetragonal one with I4/mcm is imitated from the viewpoint of energy. As for the function of the third elements, Al and Si are beneficial to the phase stability of RT sub 1 sub 3 sub - sub x M sub x , whereas Cr, Ti and V are unfavourable to the stability. In the calculation, the range of x, with which RT sub 1 sub 3 sub - sub x M sub x could crystallize in the cubic or tetragonal structures, agrees with the experiments very well. The calculated crystallographic parameters coincide with the experimental observation. In the cubic structure, Si and Al prefer the 96i site, and in the tetragonal structure Si first occ...

Perovskite phases in the systems AO-SE/sub 2/O/sub 3/-UO/sub 2,x/ with A=alkaline earth metal and SE=rare earths, La, and Y. VII. The systems Ba/sub 2/CaUO/sub 6/-Ba/sub 2/Gd/sub 0. 67/UO/sub 6/ and Ba/sub 2/CaUO/sub 6/-Ba/sub 2/Y/sub 0. 67/UO/sub 6/

Energy Technology Data Exchange (ETDEWEB)

Kemmler-Sack, S; Seemann, I; Schittenhelm, H J [Tuebingen Univ. (F.R. Germany). Institut fuer Anorganische Chemie

1976-05-01

The ordered perovskite Ba/sub 2/CaUO/sub 6/ forms a solid solution series with Ba/sub 2/Gdsub(0.67)UO/sub 6/ and Ba/sub 2/Ysub(0.67)UO/sub 6/, respectively. The deviations from the ideal behaviour are studied by X-ray, diffuse reflectance and vibrational methods.

Perovskite phases in the systems AO-SE/sub 2/O/sub 3/-UO/sub 2,x/ with A=alkaline earth metal and SE=rare earths, La, and Y. IX. The systems Ba/sub 2/SrUO/sub 6/-Ba/sub 2/Gd/sub 0. 67/UO/sub 6/ and Ba/sub 2/SrUO/sub 6/-Ba/sub 2/Y/sub 0. 67/UO/sub 6/

Energy Technology Data Exchange (ETDEWEB)

Kemmler-Sack, S; Seemann, I [Tuebingen Univ. (F.R. Germany). Inst. fuer Anorganische Chemie I

1976-07-01

The ordered perovskite Ba/sub 2/SrUO/sub 6/ forms a solid solution series with Ba/sub 2/Gdsub(0.67)UO/sub 6/ and Ba/sub 2/Ysub(0.67)UO/sub 6/ respectively. The deviations from the ideal behaviour are studied by X-ray, diffuse reflectance and vibrational methods.

Rigidity of monodromies for Appell's hypergeometric functions

Directory of Open Access Journals (Sweden)

Yoshishige Haraoka

2015-01-01

Full Text Available For monodromy representations of holonomic systems, the rigidity can be defined. We examine the rigidity of the monodromy representations for Appell's hypergeometric functions, and get the representations explicitly. The results show how the topology of the singular locus and the spectral types of the local monodromies work for the study of the rigidity.

Synthesis, microstructure and EPR of CaMnO{sub 3} and Eu{sub x}Ca{sub 1-x}MnO{sub 3} manganite, obtained by coprecipitation

Energy Technology Data Exchange (ETDEWEB)

Santiago T, M.; Hernandez C, L.; Legorreta G, F. [Universidad Autonoma del Estado de Hidalgo, AACTyM, Carretera Pachuca-Tulancingo Km 4.5, 42074 Pachuca, Hidalgo (Mexico); Montiel S, H. [UNAM, Centro de Ciencias Aplicadas y Desarrollo Tecnologico, Departamento de Tecnociencias, Ciudad Universitaria, 04510 Mexico D. F. (Mexico); Alvarez L, G. [IPN, Escuela Superior de Fisica y Matematicas, Departamento de Fisica, U. P. Adolfo Lopez Mateos, Edif. 9, Col. Lindavista, 07738 Mexico D. F. (Mexico); Flores G, M. A., E-mail: mar200878@hotmail.com [Universidad Politecnica de Pachuca, Laboratorio de Nanotecnologia y Bioelectromagnetismo Aplicado, Carretera Pachuca-Cd. Sahagun Km 20, Ex-Hacienda de Santa Barbara, 43830 Zempoala, Hidalgo (Mexico)

2011-07-01

The synthesis of CaMnO{sub 3} and Eu{sub x}Ca{sub 1-x}MnO{sub 3} obtained by coprecipitation method is showed. The synthesized samples were characterized by X-ray diffraction and scanning electronic microscopy, the powders showed orthorhombic structure and pnma space group. When it was doped with Europium, their morphology tendency was spherical. Measurements were carried out on electron paramagnetic resonance (EPR) with constant frequency = 9.4 GHz (band X) and dc magnetic field (H dc) 0-0.8 T, measurements were at 300 K and 77 K. EPR spectra showed significant differences between both samples, indicating that the substitution of divalent alkaline earth cations by trivalent rare earth ions, allowing the formation of a mixed valence state of manganese, Mn{sup 3+} and Mn{sup 4+}. A 77 K, the manganite of concentration x = 0.30 had a magnetic ordering, noted by the presence of hysteresis. (Author)

PHOTOCHEMISTRY IN TERRESTRIAL EXOPLANET ATMOSPHERES. II. H{sub 2}S AND SO{sub 2} PHOTOCHEMISTRY IN ANOXIC ATMOSPHERES

Energy Technology Data Exchange (ETDEWEB)

Hu Renyu; Seager, Sara; Bains, William, E-mail: hury@mit.edu [Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)

2013-05-20

Sulfur gases are common components in the volcanic and biological emission on Earth, and are expected to be important input gases for atmospheres on terrestrial exoplanets. We study the atmospheric composition and the spectra of terrestrial exoplanets with sulfur compounds (i.e., H{sub 2}S and SO{sub 2}) emitted from their surfaces. We use a comprehensive one-dimensional photochemistry model and radiative transfer model to investigate the sulfur chemistry in atmospheres ranging from reducing to oxidizing. The most important finding is that both H{sub 2}S and SO{sub 2} are chemically short-lived in virtually all types of atmospheres on terrestrial exoplanets, based on models of H{sub 2}, N{sub 2}, and CO{sub 2} atmospheres. This implies that direct detection of surface sulfur emission is unlikely, as their surface emission rates need to be extremely high (>1000 times Earth's volcanic sulfur emission) for these gases to build up to a detectable level. We also find that sulfur compounds emitted from the surface lead to photochemical formation of elemental sulfur and sulfuric acid in the atmosphere, which would condense to form aerosols if saturated. For terrestrial exoplanets in the habitable zone of Sun-like stars or M stars, Earth-like sulfur emission rates result in optically thick haze composed of elemental sulfur in reducing H{sub 2}-dominated atmospheres for a wide range of particle diameters (0.1-1 {mu}m), which is assumed as a free parameter in our simulations. In oxidized atmospheres composed of N{sub 2} and CO{sub 2}, optically thick haze, composed of elemental sulfur aerosols (S{sub 8}) or sulfuric acid aerosols (H{sub 2}SO{sub 4}), will form if the surface sulfur emission is two orders of magnitude more than the volcanic sulfur emission of Earth. Although direct detection of H{sub 2}S and SO{sub 2} by their spectral features is unlikely, their emission might be inferred by observing aerosol-related features in reflected light with future generation

Production of thermoluminescent dosemeters based on MgB{sub 4}O{sub 7}: Dy and MgB{sub 4}O{sub 7}: Tm; Producao de dosimetros termoluminescentes a base de MgB{sub 4}O{sub 7}: Dy e MgB{sub 4}O{sub 7}: Tm

Energy Technology Data Exchange (ETDEWEB)

Souza, Luiza Freire de; Souza, Divanizia N., E-mail: luizaf25@hotmail.com, E-mail: divanizi@ufs.br [Universidade Federal de Sergipe (UFS), Sao Cristovao, SE (Brazil). Programa de Pos-Graduacao em Fisica

2013-07-01

The thermoluminescent dosimetry (TL) is a well-established technique for the detection of ionizing radiation in hospitals, clinics, and industrial establishments where there is the need to quantify the radiation. For this practice is require the use phosphors which are sensitive to radiation. Some phosphors are already commonly used in this practice, for example, TLD-100 (LiF: Mg, Ti), CaSO{sub 4}:Tm and CaSO{sub 4}:Dy. A compound that was most recently introduced in dosimetry and has many advantageous features to detect neutrons, electrons and gamma is the magnesium tetraborate (MgB{sub 4}O{sub 7}), but the undoped material is not good for dosimetry, since signal does not show satisfactory thermoluminescence. The present work presents the analysis of the compound MgB{sub 4}O{sub 7} when doped with rare earth elements, thulium (Tm) and dysprosium (Dy). The production of MgB{sub 4}O{sub 7}: Dy and MgB{sub 4}O{sub 7}: Tm occurred under acidic conditions. Following the process of crystal growth, several tests were made on phosphors produced to verify the quality of materials as TL dosimeter. Initially, was made the identification of the crystalline phases found in the material, using the technique of X-ray diffractometry, and then were evaluated and compared the TL emission curves of the crystals with two different types of dopants, to this, the samples were irradiated with different radiation sources: {sup 137}Cs (0,66 MeV), {sup 60}Co (1.25 MeV) and X-rays (0.41 MeV) and based on the results was evaluated the energy dependence of phosphors. Another characteristic analyzed, was the decay of TL signal for the material (fading). The results show that the material can be an excellent TL dosimeter when doped with rare earth elements Dy and Tm. (author)

Nd{sub 2}Fe{sub 14}B and Pr{sub 2}Fe{sub 14}B magnets characterisation and modelling for cryogenic permanent magnet undulator applications

Energy Technology Data Exchange (ETDEWEB)

Benabderrahmane, C., E-mail: chamseddine.benabderrahmane@synchrotron-soleil.fr [Synchrotron SOLEIL, St Aubin (France); Berteaud, P.; Valleau, M.; Kitegi, C.; Tavakoli, K.; Bechu, N.; Mary, A.; Filhol, J.M.; Couprie, M.E. [Synchrotron SOLEIL, St Aubin (France)

2012-03-21

Cryogenic permanent magnet undulators take benefit from improved magnetic properties of RE{sub 2}Fe{sub 14}B (Rare Earth based magnets) at cryogenic temperatures for achieving short period high magnetic field. In particular, using Praseodymium instead of Neodymium generally employed for insertion devices avoids limitation due to Spin Reorientation Transition phenomenon. Magnetic properties of magnet samples (Nd{sub 2}Fe{sub 14}B and Pr{sub 2}Fe{sub 14}B) versus temperature have been investigated and applied to a 20 mm period Nd{sub 2}Fe{sub 14}B (BH50) and to a 18 mm period Pr{sub 2}Fe{sub 14}B (CR53) systems. Four period undulators have been built, characterised and compared to the models.

Magnetic properties of a Ho.sub.2./sub.Fe.sub.14./sub.Si.sub.3./sub. single crystal

Czech Academy of Sciences Publication Activity Database

Andreev, Alexander V.; Gorbunov, Denis; Skourski, Y.; Kuz'min, M.D.; Tereshina, Evgeniya; Henriques, Margarida Isabel Sousa

2017-01-01

Roč. 694, Feb (2017), s. 761-766 ISSN 0925-8388 R&D Projects: GA ČR GA16-03593S Institutional support: RVO:68378271 Keywords : rare-earth intermetallics * ferrimagnetism * magnetic anisotropy * high magnetic fields * feld-induced transitions Sub ject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 3.133, year: 2016

Thermoelectric transport in rare-earth compounds

Energy Technology Data Exchange (ETDEWEB)

Koehler, Ulrike

2007-07-01

This work focuses on the thermoelectric transport in rare-earth compounds. The measurements of the thermal conductivity, thermopower, and Nernst coefficient are supplemented by investigations of other quantities as magnetic susceptibility and specific heat. Chapter 2 provides an introduction to the relevant physical concepts. Section 1 of that chapter summarizes the characteristic properties of rare-earth systems; section 2 gives an overview on thermoelectric transport processes in magnetic fields. The applied experimental techniques as well as the new experimental setup are described in detail in Chapter 3. The experimental results are presented in Chapter 4-6, of which each concentrates on a different subject. In Chapter 4, various Eu clathrates and the skutterudite-like Ce{sub 3}Rh{sub 4}Sn{sub 13} are presented, which have been investigated as potential thermoelectric materials for applications. Chapter 5 focusses on the study of the energy scales in the heavy-fermion series Lu{sub 1-x}Yb{sub x}Rh{sub 2}Si{sub 2} and Ce{sub x}La{sub 1-x}Ni{sub 2}Ge{sub 2} by means of thermopower investigations. Chapter 6 is dedicated to the thermoelectric transport properties of the correlated semimetal CeNiSn with special emphasis on the Nernst coefficient of this compound. (orig.)

The Effect of Displacement Mode of Rigid Retaining Walls on Shearing Bands by Active Earth Pressure

Directory of Open Access Journals (Sweden)

A. Sekkel

2013-10-01

Full Text Available This work treats the physical modeling of failure mechanisms by active earth pressure. This last is developed by retaining wall movement. A lot of research showed that wall displacement has a significant effect on active earth pressure. A good comprehension of active earth pressure phenomenon and its failure mechanisms help us to better conceive retaining walls. The conception of a small-scale model allowed the realization of active earth pressure tests, while displacing the mobile wall toward the outside of the massif. The studied material is that of Schneebeli; light two-dimensional material made of cylindrical plastic rollers, simulating granular non-cohesive soil. The evolution of shearing zones under continuous and discontinuous displacement modes of mobile walls by correlation pictures allows the investigation of the localization of deformations and failure mechanisms.

Microstructural, magnetic and transport properties of La{sub 0.5}Pr{sub 0.2}Pb{sub 0.3-x}Sr{sub x}MnO{sub 3} manganites

Energy Technology Data Exchange (ETDEWEB)

Craus, M.-L., E-mail: kraus@nf.jinr.ru [Joint Institute for Nuclear Research, Dubna (Russian Federation); National Institute of Research and Development for Technical Physics, Iasi (Romania); Islamov, A.Kh., E-mail: islamov@nf.jinr.ru [Joint Institute for Nuclear Research, Dubna (Russian Federation); Laboratory of Advanced Research of Membrane Proteins, Moscow Institute of Physics and Technology, Dolgoprudniy (Russian Federation); Anitas, E.M., E-mail: anitas@theor.jinr.ru [Joint Institute for Nuclear Research, Dubna (Russian Federation); Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest-Magurele (Romania); Cornei, N., E-mail: ncornei@uaic.ro [“Al. I. Cuza” University, Chemistry Department, Iasi (Romania); Luca, D., E-mail: dluca@tuiasi.ro [“Gh. Asachi” Technical University, Faculty of Materials Science and Engineering, Iasi (Romania)

2014-04-01

Highlights: • We synthesized a series of pure La{sub 0.5}Pr{sub 0.2}Pb{sub 0.3−x}Sr{sub x}MnO{sub 3} manganites using ceramic technology. • The crystalline structure depends on the Sr concentration. • Small-angle neutron scattering reveals the presence of magnetic nanodomains at temperatures higher than Curie temperature. • The crystalline structure, the shape and the concentration of magnetic nanodomains are correlated with transport phenomena. - Abstract: The most interesting and studied materials for practical applications of colossal magnetorsistance effect are rare earth manganites with general formula RMnO{sub 3} (where R is a rare/alkaline earth element). The coexisting of competing phases in manganites, such as metallic ferromagnetic, charge ordered, antiferromagnetic insulating and ferromagnetic insulating phases, determines an important change of magnetic and transport properties with the microstructure. In this paper, we report on the correlations between microstructural, magnetic and transport properties at temperatures ranging from 263 to 343 K of La{sub 0.5}Pr{sub 0.2}Pb{sub 0.3-x}Sr{sub x}MnO{sub 3} manganites synthesized by ceramic technology. The microstructure is studied using X-ray diffraction (XRD), small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) at Sr concentrations x=0.00,0.05,0.15 and 0.20. SAXS and SANS data show the formation of magnetic nanodomains in the mosaic blocks, at temperatures higher than Curie temperature T{sub C}. SANS data reveal the shape and concentration of magnetic nanodomains, and their dependency on temperature. The La{sub 0.5}Pr{sub 0.2}Pb{sub 0.3-x}Sr{sub x}MnO{sub 3} manganites crystallize as cubic structure Pm3{sup ¯}m (x=0.00 and x=0.05) or as rhombohedral structure R3{sup ¯}c (x=0.15 and x=0.20). We found that transport phenomena at temperatures higher than T{sub C} are greatly influenced by nanodomains concentration and their shape. We show that about room temperature

REAuAl{sub 4}Ge{sub 2} and REAuAl{sub 4}(Au{sub x}Ge{sub 1-x}){sub 2} (RE=rare earth element): Quaternary intermetallics grown in liquid aluminum

Energy Technology Data Exchange (ETDEWEB)

Xiuni, Wu [Department of Chemistry, Michigan State University, East Lansing, Michigan 48824 (United States); Kanatzidis, Mercouri G [Department of Chemistry, Michigan State University, East Lansing, Michigan 48824 (United States)

2005-11-15

The two families of intermetallic phases REAuAl{sub 4}Ge{sub 2} (1) (RE=Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Tm and Yb) and REAuAl{sub 4}(Au{sub x}Ge{sub 1-x}){sub 2} (2) (x=0.4) (RE=Ce and Eu) were obtained by the reactive combination of RE, Au and Ge in liquid aluminum. The structure of (1) adopts the space group R-3m (CeAuAl{sub 4}Ge{sub 2}, a=4.2384(7)A, c=31.613(7)A; NdAuAl{sub 4}Ge{sub 2}, a=4.2258(4)A, c=31.359(5)A; GdAuAl{sub 4}Ge{sub 2}, a=4.2123(6)A, c=30.994(6)A; ErAuAl{sub 4}Ge{sub 2}, a=4.2074(4)A, c=30.717(5)A). The structure of (2) adopts the tetragonal space group P4/mmm with lattice parameters: a=4.3134(8)A, c=8.371(3)A for EuAuAl{sub 4}(Au{sub x}Ge{sub 1-x}){sub 2} (x=0.4). Both structure types present slabs of ''AuAl{sub 4}Ge{sub 2}'' or ''AuAl{sub 4}(Au{sub x}Ge{sub 1-x}){sub 2}'' stacking along the c-axis with layers of RE atoms in between. Magnetic susceptibility measurements indicate that the RE atoms (except for Ce and Eu) possess magnetic moments consistent with +3 species. The Ce atoms in CeAuAl{sub 4}Ge{sub 2} and CeAuAl{sub 4}(Au{sub x}Ge{sub 1-x}){sub 2} (x=0.4) appear to be in a mixed +3/+4 valence state; DyAuAl{sub 4}Ge{sub 2} undergoes an antiferromagnetic transition at 11K and below this temperature exhibits metamagnetic behavior. The Eu atoms in EuAuAl{sub 4}(Au{sub x}Ge{sub 1-x}){sub 2} (x=0.4) appear to be in a 2+ oxidation state.

SEPARATION OF TRANSURANIC ELEMENTS FROM RARE EARTH COMPOUNDS

Science.gov (United States)

Kohman, T.P.

1961-11-21

A process of separating neptunium and plutonium values from rare earths and alkaline earth fission products present on a solid mixed actinide carrier (Th or U(IV) oxalate or fluoride) --fission product carrier (LaF/sub 3/, CeF/sub 3/, SrF/sub 2/, CaF/sub 2/, YF/sub 3/, La oxalate, cerous oxalate, Sr oxalate, Ca oxalate or Y oxalate) by extraction of the actinides at elevated temperature with a solution of ammonium fluoride and/or ammonium oxalate is described. Separation of the fission-product-containing carriers from the actinide solution formed and precipitation of the neptunium and plutonium from the solution with mineral acid are also accomplished. (AEC)

Theoretical study of negative thermal expansion mechanism of ZnF{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Wang, Lei [Center for Clean Energy and Quantum Structures, Zhengzhou University, Zhengzhou 450001 (China); Yuan, Peng-Fei; Wang, Fei; Sun, Qiang [Center for Clean Energy and Quantum Structures, Zhengzhou University, Zhengzhou 450001 (China); School of Physics and Engineering, Zhengzhou University, Zhengzhou 450052 (China); Liang, Er-Jun, E-mail: ejliang@zzu.edu.cn [Center for Clean Energy and Quantum Structures, Zhengzhou University, Zhengzhou 450001 (China); School of Physics and Engineering, Zhengzhou University, Zhengzhou 450052 (China); Jia, Yu, E-mail: jiay@zzu.edu.cn [Center for Clean Energy and Quantum Structures, Zhengzhou University, Zhengzhou 450001 (China); School of Physics and Engineering, Zhengzhou University, Zhengzhou 450052 (China)

2012-05-15

Graphical abstract: ZnF{sub 2} owns open-framework structure and its negative thermal expansion (NTE) properties have been confirmed using a first-principles calculation. According to the phonon eigenvectors and group theory analysis, the lowest frequency (48.9 cm{sup -1}, B{sub 1g} mode) rigid unit mode (RUM) of ZnF{sub 6} causes a rotary coupling between two adjacent octahedrons and makes the Zn-Zn distance shorter, which is considered to be most responsible for the NTE properties of ZnF{sub 2}. Highlights: Black-Right-Pointing-Pointer The NTE properties of ZnF{sub 2} are confirmed using a first-principles calculation. Black-Right-Pointing-Pointer Phonon mode classification and Grueneisen parameters are systematically presented. Black-Right-Pointing-Pointer The rigid unit mode causes a rotary coupling and makes the Zn-Zn distance shorter. Black-Right-Pointing-Pointer The optical branch with the lowest frequency is most responsible for the NTE. -- Abstract: ZnF{sub 2} is reported to exhibit negative thermal expansion (NTE) at lower temperatures very recently. In this article, we present the electronic and NTE properties of ZnF{sub 2} using a first-principles calculation. Our results show that ZnF{sub 2} is an insulator with a direct band gap and a strong hybridization occurs between Zn-3p, 4s and F-2p states. The related calculations on NTE properties are obtained within the quasi-harmonic approximation. The resulting relationship between volume and temperature confirms the NTE properties. Besides, we discuss the NTE mechanism in accordance to phonon vibrational modes. The phonon vibrational modes contributing to the NTE are singled out by Grueneisen parameters and all these modes are low-frequency optical phonons. The lowest frequency rigid unit mode (RUM) of ZnF{sub 6} causes a rotary coupling between two adjacent octahedrons and makes the Zn-Zn distance shorter, which is most responsible for the NTE properties of ZnF{sub 2}.

Volatilisation of alkali and alkaline earth metallic species during the gasification of a Victorian brown coal in CO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Quyn, Dimple Mody; Li, Chun-Zhu [CRC for Clean Power from Lignite, Department of Chemical Engineering, PO Box 36, Monash University, Victoria 3800 (Australia); Hayashi, Jun-ichiro [Centre for Advanced Research of Energy Conversion Materials, Hokkaido University, N13-W8, Kita-ku, Sapporo 060-8628 (Japan)

2005-08-25

A Victorian brown coal was gasified in a bench-scale quartz fluidised-bed/fixed-bed reactor in order to study the volatilisation of Na, Ca, and Mg during devolatilisation and gasification and their roles in the reactivity of chars. It was found that the majority of Na was volatilised at 900 {sup o}C under all conditions and that a Na retention limit was achieved in the char with the progress of CO{sub 2} gasification. In some cases, the presence of CO{sub 2} during devolatilisation enhanced the Na retention in the char. In contrast, the retention of Ca (and Mg) was unaffected by CO{sub 2} during devolatilisation at 900C but decreased drastically upon nascent char gasification. The fundamental differences in volatilisation between the alkali and alkaline earth metallic species are discussed in this paper.

Unveiling the Structural Evolution of Ag<sub>1.2sub>Mn>8sub>O>16sub> under Coulombically Controlled (De)Lithiation

Energy Technology Data Exchange (ETDEWEB)

Huang, Jianping [Department; Hu, Xiaobing [Energy; Brady, Alexander B. [Department; Wu, Lijun [Energy; Zhu, Yimei [Energy; Takeuchi, Esther S. [Department; Energy; Department; Marschilok, Amy C. [Department; Department; Takeuchi, Kenneth J. [Department; Department

2018-01-02

MnO<sub>2sub> materials are considered promising cathode materials for rechargeable lithium, sodium, and magnesium batteries due to their earth abundance and environmental friendliness. One polymorph of MnO<sub>2sub>, α-MnO<sub>2sub>, has 2 × 2 tunnels (4.6 Å × 4.6 Å) in its structural framework, which provide facile diffusion pathways for guest ions. In this work, a silver-ion-containing α-MnO<sub>2sub> (Ag<sub>1.2sub>Mn>8sub>O>16sub>) is examined as a candidate cathode material for Li based batteries. Electrochemical stability of Ag<sub>1.2sub>Mn>8sub>O>16sub> is investigated through Coulombically controlled reduction under 2 or 4 molar electron equivalents (e.e.). Terminal discharge voltage remains almost constant under 2 e.e. of cycling, whereas it continuously decreases under repetitive reduction by 4 e.e. Thus, detailed structural analyses were utilized to investigate the structural evolution upon lithiation. Significant increases in lattice a (17.7%) and atomic distances (~4.8%) are observed when x in Li<sub>xAg>1.2sub>Mn>8sub>O>16sub> is >4. Ag metal forms at this level of lithiation concomitant with a large structural distortion to the Mn–O framework. In contrast, lattice a only expands by 2.2% and Mn–O/Mn-Mn distances show minor changes (~1.4%) at x < 2. The structural deformation (tunnel breakage) at x > 4 inhibits the recovery of the original structure, leading to poor cycle stability at high lithiation levels. This report establishes the correlation among local structure changes, amorphization processes, formation of Ag⁰, and long-term cycle stability for this silver-containing α-MnO<sub>2sub> type material at both low and high lithiation levels.

Investigation into the magnetic properties of pyrochlore-type rare-earth hafnates

Energy Technology Data Exchange (ETDEWEB)

Chun, Jung Hwan; Kremer, Reinhard K.; Lin, Chengtian [MPI for Solid State Research, Stuttgart (Germany)

2015-07-01

Cubic rare-earths transition metal pyrochlores with composition R{sub 2}TM{sub 2}O{sub 7} have attracted broad attention because of their unusual magnetic ground state properties related to geometrical frustration of the pyrochlores lattice. So far, the investigation focused mainly on 3d and 4d transition metal systems. The magnetic properties of rare-earths 5d TM pyrochlores are comparatively less well studied. Here we report on the single-crystal growth and the magnetic properties of some rare-earth hafnates (R =Nd, Gd, Dy; TM = Hf) of composition R{sub 2}Hf{sub 2}O{sub 7}. Nd{sub 2}Hf{sub 2}O{sub 7} and Gd{sub 2}Hf{sub 2}O{sub 7} crystallize with the cubic pyrochlores structure whereas diverging reports on the structure of Dy{sub 2}Hf{sub 2}O{sub 7} are available in literature. Crystals of R{sub 2}Hf{sub 2}O{sub 7} have been grown and their structural and magnetic properties have been investigated. Our investigations confirm Nd{sub 2}Hf{sub 2}O{sub 7} and Gd{sub 2}Hf{sub 2}O{sub 7} to crystallize in the cubic pyrochlores structure. Antiferromagnetic ordering below ∝0.5 K has been observed by magnetic susceptibility and heat capacity measurements for both compounds.

From Wage Rigidities to Labour Market Rigidities: A Turning-Point in Explaining Equilibrium Unemployment?

OpenAIRE

Marco Guerrazzi; Nicola Meccheri

2009-01-01

This paper offers a critical discussion of the concept of labour market rigidity relevant to explaining unemployment. Starting from Keynes’s own view, we discuss how the concept of labour market flexibility has changed over time, involving nominal or real wage flexibility, contract flexibility or labour market institution flexibility. We also provide a critical assessment of the factors that lead the search framework highlighting labour market rigidities (frictions) to challenge the more wide...

Anisotropic magnetic properties of Dy{sub 6}Cr{sub 4}Al{sub 43} single crystal

Energy Technology Data Exchange (ETDEWEB)

Maurya, Arvind, E-mail: arvindmaurya@tifr.res.in; Thamizhavel, A., E-mail: arvindmaurya@tifr.res.in; Dhar, S. K., E-mail: arvindmaurya@tifr.res.in [Department of Condensed Matter Physics and Material Science, Tata Institute of Fundamental Research, Mumbai-400005 (India)

2014-04-24

We have studied the anisotropic magnetic behavior of the rare earth intermetallic compound Dy{sub 6}Cr{sub 4}Al{sub 43}. This compound crystallizes in the hexagonal symmetry and orders ferromagnetically at 8.3 K as confirmed by the magnetic susceptibility and heat capacity measurements. A significant anisotropy in the magnetization is observed between the c axis and the ab-plane. The easy axis liesin theab-plane at low temperatures; however it orients itselfalong the c-axis above 170 K as inferred from the susceptibility data.

Synthesis, crystal and electronic structures, and magnetic properties of LiLn{sub 9}Mo{sub 16}O{sub 35} (Ln=La, Ce, Pr, and Nd) compounds containing the original cluster Mo{sub 16}O{sub 36}

Energy Technology Data Exchange (ETDEWEB)

Gougeon, Patrick; Gall, Philippe [UMR CNRS 6226 - ' ' Sciences Chimiques de Rennes' ' , Universite de Rennes 1 - INSA (France); Cuny, Jerome; Gautier, Regis; Le Polles, Laurent [UMR CNRS 6226 - ' ' Sciences Chimiques de Rennes' ' , Ecole Nationale Superieure de Chimie de Rennes (France); Delevoye, Laurent; Trebosc, Julien [UMR CNRS 8181 - UCCS, ENSCL, Universite Lille Nord de France, Villeneuve d' Ascq (France)

2011-12-02

The new compounds LiLn{sub 9}Mo{sub 16}O{sub 35} (Ln=La, Ce, Pr, and Nd) were synthesized from stoichiometric mixtures of Li{sub 2}MoO{sub 4}, Ln{sub 2}O{sub 3}, Pr{sub 6}O{sub 11} or CeO{sub 2}, MoO{sub 3}, and Mo heated at 1600 C for 48 h in a molybdenum crucible sealed under a low argon pressure. The crystal structure, determined from a single crystal of the Nd member, showed that the main building block is the Mo{sub 16}O{sub 36} unit, the Mo{sub 16} core of which is totally new and results from the fusion of two bioctahedral Mo{sub 10} clusters. It can also be viewed as a fragment of an infinite twin chain of edge-sharing Mo{sub 6} octahedra. The Mo{sub 16}O{sub 36} cluster units share some oxygen atoms to form infinite chains running parallel to the b axis, which are separated by the rare-earth and lithium cations. {sup 7}Li-NMR experiments, carried out at high field on the nonmagnetic LiLa{sub 9}Mo{sub 16}O{sub 35}, provided insights into the local environment of the lithium ions. Magnetic susceptibility measurements confirmed the trivalent oxidation state of the magnetic rare-earth cations and indicated the absence of localized moments on the Mo{sub 16} clusters. The electronic structure of the LiLn{sub 9}Mo{sub 16}O{sub 35} compounds was analyzed using molecular and periodic quantum calculations. The study of the molecular orbital diagrams of isolated Mo{sub 16}O{sub 36} models allowed the understanding of this unique metallic architecture. Periodic density functional theory calculations demonstrated that few interactions occur between the Mo{sub 16} clusters, and predicted semiconducting properties for LiLn{sub 9}Mo{sub 16}O{sub 35} as a band gap of 0.57 eV was computed for the lanthanum phase. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Identifying Floppy and Rigid Regions in Proteins

Science.gov (United States)

Jacobs, D. J.; Thorpe, M. F.; Kuhn, L. A.

1998-03-01

In proteins it is possible to separate hard covalent forces involving bond lengths and bond angles from other weak forces. We model the microstructure of the protein as a generic bar-joint truss framework, where the hard covalent forces and strong hydrogen bonds are regarded as rigid bar constraints. We study the mechanical stability of proteins using FIRST (Floppy Inclusions and Rigid Substructure Topography) based on a recently developed combinatorial constraint counting algorithm (the 3D Pebble Game), which is a generalization of the 2D pebble game (D. J. Jacobs and M. F. Thorpe, ``Generic Rigidity: The Pebble Game'', Phys. Rev. Lett.) 75, 4051-4054 (1995) for the special class of bond-bending networks (D. J. Jacobs, "Generic Rigidity in Three Dimensional Bond-bending Networks", Preprint Aug (1997)). This approach is useful in identifying rigid motifs and flexible linkages in proteins, and thereby determines the essential degrees of freedom. We will show some preliminary results from the FIRST analysis on the myohemerythrin and lyozyme proteins.

Neutron spectroscopic study of the crystal field interaction in Pr{sub 1-x}La{sub x}NiO{sub 3} (0{<=}x{<=}0.7)

Energy Technology Data Exchange (ETDEWEB)

Rosenkranz, S.; Medarde, M.; Mesot, J.; Zolliker, M.; Furrer, A. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Lacorre, P. [LeMans, Univ. (France)

1997-09-01

The crystal field interaction at the rare earth site in Pr{sub 1-x}La{sub x}NiO{sub 3} has been studied using inelastic neutron scattering. A parametrization consistent over the whole series is obtained and discussed within the point-charge model. (author) 2 figs., 3 refs.

Exchange interactions and the state of iron atoms in Bi{sub 3}Nb{sub 1−x}Fe{sub x}O{sub 7−δ}

Energy Technology Data Exchange (ETDEWEB)

Chezhina, N.V., E-mail: chezhina@nc2490.spb.edu [St. Petersburg State University, 7/9 Universitetskaya Nab., 199034 (Russian Federation); Korolev, D.A. [St. Petersburg State University, 7/9 Universitetskaya Nab., 199034 (Russian Federation); Zhuk, N.A. [Syktyvkar State University (Russian Federation); Lutoev, V.P.; Makeev, B.A. [Institute of Geology Komi Scientific Center of Ural branch of Russian Academy of Sciences, Syktyvkar (Russian Federation)

2017-03-15

On the basis of the results of magnetic susceptibility and ESR studies of the Bi{sub 3}Nb{sub 1−x}Fe{sub x}O{sub 7−δ} solid solutions iron atoms in the solid solutions of cubic modification of bismuth niobate were found to exist as Fe(III) monomers and exchange bound Fe(III)-O-Fe(III) dimers with antiferro- and ferromagnetic type of superexchange. The exchange parameters and the distribution of monomers and dimers in the solid solutions were calculated as a function of paramagnetic atom content. - Graphical abstract: The study of the Bi{sub 3}Nb{sub 1−x}Fe{sub x}O{sub 7−δ} solid solutions showed that the introduction of iron atoms into the structure of Bi{sub 3}NbO{sub 7} stabilizes the cubic structure of bismuth niobate making the phase transition tetragonal ↔ cubic structure irreversible. In the Bi{sub 3}Nb{sub 1−x}Fe{sub x}O{sub 7−δ} solid solutions we observe the formation of dimers with antiferro- and ferromagnetic exchange. Such clusters are partially retained even at the infinite dilution of the solid solution, which testifies for their rigidity. A sufficiently high parameter of ferromagnetic exchange in a dimer (+53 cm{sup −1}) seems to result from iron atoms being located in the vicinity of oxygen vacancy. - Highlights: • The reversible transition cubic – tetragonal modifications in Bi{sub 3}NbO{sub 7} becomes irreversible. • Only cubic modification of Bi{sub 3}Nb{sub 1-x}Fe{sub x}O{sub 7-δ} is stable due to clusters of Fe atoms. • These clusters are sufficiently strong and retained even at the infinite dilution. • The calculations of magnetic susceptibility give the distribution of the clusters and single atoms.

Spectroscopy features of Pr{sup 3+} and Er{sup 3+} ions in Li{sub 2}O-ZrO{sub 2}-SiO{sub 2} glass matrices mixed with some sesquioxides

Energy Technology Data Exchange (ETDEWEB)

Srinivasa Rao, Ch. [Department of Physics, Acharya Nagarjuna University - Nuzvid Campus, Nuzvid-521201, A.P. (India); Kityk, I.V., E-mail: iwank74@gmail.com [Electrical Engineering Department, Technical University of Czestochowa, Aleja Armii, Krajowej 17/19, PL-42-201 Czestochowa (Poland); Srikumar, T.; Naga Raju, G.; Ravi Kumar, V.; Gandhi, Y.; Veeraiah, N. [Department of Physics, Acharya Nagarjuna University - Nuzvid Campus, Nuzvid-521201, A.P. (India)

2011-09-15

Highlights: > Optical spectra of Pr{sup 3+} and Er{sup 3+} ions in Li{sub 2}O-ZrO{sub 2}-SiO{sub 2}: Pr{sub 2}O{sub 3}/Er{sub 2}O{sub 3} with sesquioxides (viz., Al{sub 2}O{sub 3}, Sc{sub 2}O{sub 3}, Y{sub 2}O{sub 3}) studied. > The highest branching ratios {beta}{sub r} and quantum efficiencies of {sup 3}P{sub 0} {yields} {sup 3}H{sub 4} (Pr{sup 3+}) and {sup 4}S{sub 3/2} {yields} {sup 4}I{sub 15/2} (Er{sup 3+}) emissions have shown principal role of Y{sub 2}O{sub 3}. > Principal role of disorder around rare earth is established. - Abstract: The glasses of the composition Li{sub 2}O-ZrO{sub 2}-SiO{sub 2}: Pr{sub 2}O{sub 3}/Er{sub 2}O{sub 3} mixed with three interesting sesquioxides (viz., Al{sub 2}O{sub 3}, Sc{sub 2}O{sub 3}, Y{sub 2}O{sub 3}) were synthesized. Optical absorption and fluorescence spectra (in the spectral range 350-2100 nm were studied at ambient temperature. The Judd-Ofelt theory was applied to characterize the absorption and luminescence spectra of Pr{sup 3+} and Er{sup 3+} ions in these glasses. Following the luminescence spectra, various radiative properties like transition probability A, branching ratio {beta} and the radiative life time {tau} for different emission levels of two rare earth ions have been evaluated. The radiative life times for the upper levels {sup 3}P{sub 0} (Pr{sup 3+}) and {sup 4}S{sub 3/2} (Er{sup 3+}) have also been measured and quantum efficiencies were estimated. The variations observed in these parameters were discussed in the light of changing environment of rare earth ions due to mixing of different sesquioxides in the glass network.

Failure evolution in granular material retained by rigid wall in active mode

Science.gov (United States)

Pietrzak, Magdalena; Leśniewska, Danuta

2012-10-01

This paper presents a detailed study of a selected small scale model test, performed on a sample of surrogate granular material, retained by a rigid wall (typical geotechnical problem of earth thrust on a retaining wall). The experimental data presented in this paper show that the deformation of granular sample behind retaining wall can undergo some cyclic changes. The nature of these cycles is not clear - it is probably related to some micromechanical features of granular materials, which are recently extensively studied in many research centers in the world. Employing very precise DIC (PIV) method can help to relate micro and macro-scale behavior of granular materials.

High-pressure synthesis and crystal structure of In{sub 3}B{sub 5}O{sub 12}

Energy Technology Data Exchange (ETDEWEB)

Vitzthum, Daniela; Schauperl, Michael; Liedl, Klaus R.; Huppertz, Hubert [Univ. Innsbruck (Austria). Inst. fuer Allgemeine, Anorganische und Theoretische Chemie

2017-03-01

Orthorhombic In{sub 3}B{sub 5}O{sub 12} was synthesized in a Walker-type multianvil apparatus under high-pressure/high-temperature conditions of 12.2 GPa and 1500 C. Its structure is isotypic to the rare earth analogs RE{sub 3}B{sub 5}O{sub 12} (RE=Sc, Er-Lu). In the field of indium borate chemistry, In{sub 3}B{sub 5}O{sub 12} is the third known ternary indium borate besides InBO{sub 3} and InB{sub 5}O{sub 9}. The crystal structure of In{sub 3}B{sub 5}O{sub 12} has been determined via single-crystal X-ray diffraction data collected at room temperature. It crystallizes in the orthorhombic space group Pmna with the lattice parameters a=12.570(2), b=4.5141(4), c=12.397(2) Aa, and V=703.4(2) Aa{sup 3}. IR and Raman bands of In{sub 3}B{sub 5}O{sub 12} were theoretically determined and assigned to experimentally recorded spectra.

Quaternary equilibrium diagrams ZrO{sub 2}-Al{sub 2}O{sub 3}-SiO{sub 2}-(CaO, MgO, TiO{sub 2}). A powerful tool for the development of new materials by reaction sintering; Diagramas de equilibrio cuaternarios ZrO{sub 2}-Al{sub 2}O{sub 3}-SiO{sub 2}- (CaO, MgO, TiO{sub 2}). Una poderosa herramienta para el desarrollo de nuevos materiales por sinterizacion reactiva

Energy Technology Data Exchange (ETDEWEB)

Moya, J. S.; Bartolome, J. F.; Pena, P.

2011-07-01

In this paper we set out, discuss and evaluate the work on Mullite-zirconia composites obtained by reaction sintering led and inspired by Salvador de Aza on the basis of ZrO{sub 2}-Al{sub 2}O{sub 3}-SiO{sub 2}-(CaO, MgO, TiO{sub 2}) multicomponent phase equilibrium diagrams. We analyze their impact on different areas of ceramic science and technology such as refractory grogs, aluminum industry, etc. The possible fields of future applications such as dental prosthesis replacing partially stabilized zirconia materials with rare earths are also reported. (Author) 42 refs.

Theoretical investigation of elementary reaction of complexing LiH+BeH/sub 2/. -->. LiBeH/sub 3/

Energy Technology Data Exchange (ETDEWEB)

Charkin, O P; Boldyrev, A I; Sukhanov, L P [AN SSSR, Chernogolovka. Inst. Novykh Khimicheskikh Problem

1979-01-01

In the framework of non-empirical Hartree-Fock-Roothaan method on the basis of gauss functions of Roos and Siegbahn made are calculations of different sections of potential surface elementary reaction of complexing LiH+BeH/sub 2/ ..-->.. LiBeH/sub 3/. Charts of potential surface are presented. Questions of the elementary mechanism of elementary processes of complexing and effect of mutual orientation of the reagents upon the reaction mechanism are considered. Stability of LiBeH/sub 3/ molecule to different dissociation channels and different aspects of structural non-rigidity of the L(MXsub(k+1)) complexes at super barrier excitation are discussed.

The low temperature specific heat and electrical transport, magnetic properties of Pr{sub 0.65}Ca{sub 0.35}MnO{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Han, Zhiyong, E-mail: zyhan@cauc.edu.cn

2017-02-01

The magnetic properties, electrical transport properties, and low temperature specific heat of polycrystalline perovskite manganese oxide Pr{sub 0.65}Ca{sub 0.35}MnO{sub 3} have been investigated experimentally. It is found that there exists cluster glass state in the sample at low temperature besides the antiferromagnetic insulating state. With the increase of magnetic field, antiferromagnetic insulating state converts to ferromagnetic metal state and the Debye temperature decreases gradually. In addition, the low temperature electron specific heat in zero magnetic field is obviously larger than that of ordinary rare-earth manganites oxide and this phenomenon is related to the itinerant electrons in ferromagnetic cluster state and the disorder in Pr{sub 0.65}Ca{sub 0.35}MnO{sub 3}. - Highlights: • There exists cluster glass state in the sample at low temperature besides the antiferromagnetic insulating state. • With the increase of magnetic field, antiferromagnetic insulating state converts to ferromagnetic metal state. • Low temperature electron specific heat in zero magnetic field is larger than that of ordinary rare-earth manganites oxide.

Theoretical investigations on magnetocaloric effect in Er{sub 1−y}Tb{sub y}Al{sub 2} series

Energy Technology Data Exchange (ETDEWEB)

Ribeiro, P.O., E-mail: paula.ribeiro@gmail.com [Instituto de Física, Universidade do Estado do Rio de Janeiro – UERJ, Rua São Francisco Xavier, 524, 20550-013 RJ (Brazil); Alho, B.P.; Alvarenga, T.S.T.; Nóbrega, E.P.; Sousa, V.S.R. de [Instituto de Física, Universidade do Estado do Rio de Janeiro – UERJ, Rua São Francisco Xavier, 524, 20550-013 RJ (Brazil); Carvalho, A. Magnus G. [Laboratório Nacional de Luz Síncrotron, CNPEM, 13083-970 Campinas, SP (Brazil); Caldas, A. [Sociedade Unificada de Ensino Superior e Cultura, SUESC, 20211-351 Rio de Janeiro, RJ (Brazil); Oliveira, N.A. de; Ranke, P.J. von [Instituto de Física, Universidade do Estado do Rio de Janeiro – UERJ, Rua São Francisco Xavier, 524, 20550-013 RJ (Brazil)

2015-04-01

We report on the magnetic and magnetocaloric effect calculations in rare earth Er{sub 1−y}Tb{sub y}Al{sub 2} compounds (y=0.00, 0.25, 0.5, 0.75 and 1.00). Our model Hamiltonian has contributions of the crystalline electrical field anisotropy in both Er and Tb magnetic sublattices, disorder in exchange interactions among Er–Er, Tb–Tb and Er–Tb magnetic ions and the Zeeman effect. The magnetization, the isothermal entropy change (ΔS{sub T}) and the adiabatic temperature change (ΔT{sub ad}) dependence on temperature were simulated and, compared with the experimental data available. - Highlights: • Modeling Er{sub (1−y)}Tb{sub y}Al{sub 2} intermetallic compounds. • Magnetic entropy changes in Er{sub (1−y)}Tb{sub y}Al{sub 2}. • Adiabatic temperature changes in Er{sub 0.75}Tb{sub 0.25}Al{sub 2} and Er{sub 0.65}Tb{sub 0.35}Al{sub 2} compounds.

Zintl-phases with layer anions: preparation and crystal structures of the isotypic compounds SrSn sub 2 As sub 2 and Sr sub 0. 87 Ba sub 0. 13 Sn sub 2 As sub 2 and a single crystal structure determination of KSnSb. Zintl-Phasen mit Schichtanionen: Darstellung und Kristallstrukturen der isotypen Verbindungen SrSn sub 2 As sub 2 und Sr sub 0,87 Ba sub 0,13 Sn sub 2 As sub 2 sowie eine Einkristallstrukturbestimmung von KSnSb

Energy Technology Data Exchange (ETDEWEB)

Eisenmann, B; Klein, J [Abt. 2 fuer Anorganische Chemie, Technische Hochschule Darmstadt (Germany)

1991-06-01

The metallic reflecting compounds SrSn{sub 2}As{sub 2} and Sr{sub 0.87}Ba{sub 0.13}Sn{sub 2}As{sub 2} were prepared from the melt, they crystallize in the trigonal rhombohedral system (space group R3m, Z = 3) with lattice constants see ''Inhaltsuebersicht''. In the crystal structure of the isotypic compounds threebonded Sn atoms and threebonded As atoms together form puckered layers which are isostructural to grey As. The mean values of the bond lengths Sn -- As are 277.6 pm (SrSn{sub 2}As{sub 2}) and 279.1 pm (Sr{sub 0.87}Ba{sub 0.13}Sn{sub 2}As{sub 2}) resp. Along (001) the alkaline earth atoms occupy the octahedral interstices of As atoms between each second SnAs layer. The single crystal structure determination of KSnSb confirms the results of the X-ray powder analysis, but leads to slightly different values for the bond lengths.

Soft soils reinforced by rigid vertical inclusions

Directory of Open Access Journals (Sweden)

Iulia-Victoria NEAGOE

2013-12-01

Full Text Available Reinforcement of soft soils by rigid vertical inclusions is an increasingly used technique over the last few years. The system consists of rigid or semi-rigid vertical inclusions and a granular platform for the loads transfer from the structure to the inclusions. This technique aims to reduce the differential settlements both at ground level as below the structure. Reinforcement by rigid inclusions is mainly used for foundation works for large commercial and industrial platforms, storage tanks, wastewater treatment plants, wind farms, bridges, roads, railway embankments. The subject is one of interest as it proves the recently concerns at international level in research and design; however, most studies deal more with the static behavior and less with the dynamic one.

Rare earth-ruthenium-magnesium intermetallics

Energy Technology Data Exchange (ETDEWEB)

Stein, Sebastian; Kersting, Marcel; Heletta, Lukas; Poettgen, Rainer [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie

2017-07-01

Eight new intermetallic rare earth-ruthenium-magnesium compounds have been synthesized from the elements in sealed niobium ampoules using different annealing sequences in muffle furnaces. The compounds have been characterized by powder and single crystal X-ray diffraction. Sm{sub 9.2}Ru{sub 6}Mg{sub 17.8} (a=939.6(2), c=1779(1) pm), Gd{sub 11}Ru{sub 6}Mg{sub 16} (a=951.9(2), c=1756.8(8) pm), and Tb{sub 10.5}Ru{sub 6}Mg{sub 16.5} (a=942.5(1), c=1758.3(4) pm) crystallize with the tetragonal Nd{sub 9.34}Ru{sub 6}Mg{sub 17.66} type structure, space group I4/mmm. This structure exhibits a complex condensation pattern of square-prisms and square-antiprisms around the magnesium and ruthenium atoms, respectively. Y{sub 2}RuMg{sub 2} (a=344.0(1), c=2019(1) pm) and Tb{sub 2}RuMg{sub 2} (a=341.43(6), c=2054.2(7) pm) adopt the Er{sub 2}RuMg{sub 2} structure and Tm{sub 3}Ru{sub 2}Mg (a=337.72(9), c=1129.8(4) pm) is isotypic with Sc{sub 3}Ru{sub 2}Mg. Tm{sub 3}Ru{sub 2}Mg{sub 2} (a=337.35(9), c=2671(1) pm) and Lu{sub 3}Ru{sub 2}Mg{sub 2} (a=335.83(5), c=2652.2(5) pm) are the first ternary ordered variants of the Ti{sub 3}Cu{sub 4} type, space group I4/mmm. These five compounds belong to a large family of intermetallics which are completely ordered superstructures of the bcc subcell. The group-subgroup scheme for Lu{sub 3}Ru{sub 2}Mg{sub 2} is presented. The common structural motif of all three structure types are ruthenium-centered rare earth cubes reminicent of the CsCl type. Magnetic susceptibility measurements of Y{sub 2}RuMg{sub 2} and Lu{sub 3}Ru{sub 2}Mg{sub 2} samples revealed Pauli paramagnetism of the conduction electrons.

Numerical evidence for quadrupolar-octopolar order in RETM{sub 2}(Al,Zi){sub 20}

Energy Technology Data Exchange (ETDEWEB)

Attig, Jan [Institute for Theoretical Physics, University of Cologne (Germany); Tse, Darrell; Lee, Eric Kin-Ho; Paramekanti, Arun; Kim, Yong Baek [Department of Physics, University of Toronto, ON (Canada)

2016-07-01

Motivated by recent experiments on materials of the type RETM{sub 2}(Al,Zi){sub 20} (where RE is a rare earth and TM a transition metal element) we investigate a minimal model for the pseudo-spin degrees of freedom of the rare earth ions. The model is described by J1-J2 pseudo-spin interactions in three-dimensions where the XY part models quadrupolar order and the Ising part models octopolar order. We use various computational methods such as simulating annealing to find the zero temperature phase digram and investigate further by using single-spin flip Monte Carlo simulations for finite temperature. One notable finding is the existence of non-coplanar spiral ordering of pseudo-spins, which may explain some of the experimental data on the electronic ordering in RETM{sub 2}(Al,Zi){sub 20}.

Luminescent and magnetic properties of Fe{sub 3}O{sub 4}@SiO{sub 2}:phen:Eu{sup 3+}

Energy Technology Data Exchange (ETDEWEB)

Silva, Raphael Lucas de Sousa; Figueiredo, Alberthmeiry Teixeira de; Barrado, Cristiano Morita, E-mail: alberth@ufg.br [Universidade Federal de Goiás (UFG), Catalão, GO (Brazil). Departamento de Química; Sousa, Marcelo Henrique [Universidade de Brasília (UnB), DF (Brazil). Faculdade de Ceilândia

2017-10-15

Magnetite was doped with rare earth ions (europium) to produce core-shell materials with both magnetic and luminescent properties, i.e., a magnetic Fe{sub 3}O{sub 4} oxide core and a SiO{sub 2} :phen:Eu{sup 3+} shell. The resulting material was analyzed by X-ray powder diffraction and transmission electron microscopy, and subjected to magnetic and luminescence emission measurements. All the synthesized materials exhibited superparamagnetic behavior and luminescence emission. The magnetic behavior of Fe{sub 3}O{sub 4} and luminescence emission of SiO{sub 2} :phen:Eu{sup 3+} of the materials were compared to precursors. (author)

Determination of rare earth impurities in thorium by spectrographic methods

Energy Technology Data Exchange (ETDEWEB)

Wray, L W

1957-08-15

A method for determining rare earth impurities in thorium in the fractional ppm range is described. Before spectrographic examination is possible, the impurities must be freed from the thorium matrix. This is accomplished by removing the bulk of the thorium by extraction with TBP-CCl{sub 4} and the remainder by extraction with TTA-C{sub 6}H{sub 6}. This results in a consistent recovery of rare earths of about 85% with an average sensitivity of 0.2 ppm. The experimental error is within 10%. Details of the procedure are given together with working curves for the major neutron absorbing rare earths; i.e. dysprosium, europium, gadolinium and samarium. (author)

Synthesis and photoluminescence properties of Sm{sup 3+}substituted glaserite-type orthovanadates K{sub 3}Y[VO{sub 4}]{sub 2} with monoclinic structure

Energy Technology Data Exchange (ETDEWEB)

Duke John David, A., E-mail: dukejohndavid02@gmail.com [Voorhees College, Vellore, Tamil Nadu (India); Muhammad, G. Shakil [Islamiah College, Vaniyambadi, Tamil Nadu (India); Sivakumar, V. [National Institute of Technology (NIT), Rourkela (India)

2016-09-15

A novel phosphor of Glaserite type Orthovanadate K{sub 3}Y[VO{sub 4}]{sub 2} substituted with the trivalent rare-earth Sm{sup 3+} ions were synthesized by the conventional high temperature solid-state reaction method, their structural characterization and photoluminescent properties were investigated by X-ray diffraction and spectrofluorimetry. The phase-purity of glaserite structure in the synthesized compound was verified by XRD study. The morphology was measured by FESEM. Host lattice emits broad-band green color and it is originated from the [VO{sub 4}]{sup 3−}. Photoluminescence studies of Sm{sup 3+} activated samples show orange red emission. The charge transfer behaviours from [VO{sub 4}]{sup 3−} to Sm{sup 3+} ions (host to activator) in K{sub 3}Y{sub (1−x)}[VO{sub 4}]{sub 2}: {sub x}Sm{sup 3+} phosphors have been confirmed by photoluminescence and PL decay life time measurement. No concentration quenching was observed even for higher concentration of the dopant Sm{sup 3+} ions. The CIE chromaticity color coordinate values were calculated and it is very much closer to the NTSC standards. All the results clearly indicate that self-activated K{sub 3}Y{sub 1−x}[VO{sub 4}]{sub 2} with the rare earth {sub x}Sm{sup 3+} activated phosphors show great potential as a phosphor material for near-UV based white LEDs.

Formation of Y{sub x}Nd{sub 1-x}Ba{sub 2}Cu{sub 3}O{sub 7-{delta}} (0{<=}x{<=}0.9) superconductors from an undercooled melt via aero-acoustic levitation

Energy Technology Data Exchange (ETDEWEB)

Gustafson, D.E.; Hofmeister, W.H.; Bayuzick, R.J.; Nagashio, K.; Kuribayashi, K

2003-01-20

This paper presents the results of rapid solidification experiments performed on the copper oxide superconductors Y{sub x}Nd{sub 1-x}Ba{sub 2}Cu{sub 3}O{sub 7-{delta}} (0{<=}x{<=}0.9). Spherical rare earth (RE) 123 specimens were levitated in O{sub 2} using aero-acoustic levitation (AAL), melted with a laser, undercooled, and solidified. The peritectic transformation temperature for the reaction RE{sub 2}BaCuO{sub 5}+liquid{yields}REBa{sub 2}Cu{sub 3}O{sub 7-{delta}} corresponding to the maximum recalescence temperature during solidification was determined. RE123 was formed directly from the melt for Y-Nd binary alloy compositions with Nd concentration greater than 20% (Y concentration less than 80%). A minimum in the peritectic transformation temperature for the Nd/Y123 system corresponding to a composition Y{sub 0.3}Nd{sub 0.7}123 was determined at 66 deg. C below the peritectic of pure Nd123.

Synthesis, structure and chemical bonding of CaFe{sub 2−x}Rh{sub x}Si{sub 2} (x=0, 1.32, and 2) and SrCo{sub 2}Si{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Hlukhyy, Viktor, E-mail: viktor.hlukhyy@lrz.tu-muenchen.de; Hoffmann, Andrea V.; Fässler, Thomas F.

2013-07-15

The finding of superconductivity in Ba{sub 0.6}K{sub 0.4}Fe{sub 2}As{sub 2} put the attention on the investigation of compounds that crystallize with ThCr{sub 2}Si{sub 2} structure type such as AT{sub 2}X{sub 2} (A=alkali/alkaline earth/rare earth element; T=transition metal and X=element of the 13–15th group). In this context the silicides CaFe{sub 2}Si{sub 2}, CaFe{sub 0.68(6)}Rh{sub 1.32(6)}Si{sub 2}, CaRh{sub 2}Si{sub 2} and SrCo{sub 2}Si{sub 2} have been synthesized by reaction of the elements under an argon atmosphere. Single crystals were obtained by special heat treatment in welded niobium/tantalum ampoules. The compounds were investigated by means of powder and single crystal X-ray diffraction. All compounds crystallize in the ThCr{sub 2}Si{sub 2}-type structure with space group I4/mmm (No. 139): a=3.939(1) Å, c=10.185(1) Å, R{sub 1}=0.045, 85 F{sup 2} values, 8 variable parameters for CaFe{sub 2}Si{sub 2}; a=4.0590(2) Å, c=9.9390(8) Å, R{sub 1}=0.030, 90 F{sup 2} values, 10 variable parameters for CaFe{sub 0.68(6)}Rh{sub 1.32(6)}Si{sub 2}; a=4.0695(1) Å, c=9.9841(3) Å, R{sub 1}=0.031, 114 F{sup 2} values, 9 variable parameters for CaRh{sub 2}Si{sub 2}; and a=3.974(1) Å, c=10.395(1) Å, R{sub 1}=0.036, 95 F{sup 2} values, 8 variable parameters for SrCo{sub 2}Si{sub 2}. The structure of SrCo{sub 2}Si{sub 2} contains isolated [Co{sub 2}Si{sub 2}]{sup 2−} 2D-layers in the ab-plane whereas in CaFe{sub 2−x}Rh{sub x}Si{sub 2} the [T{sub 2}Si{sub 2}] layers (T=Fe and Rh) are interconnected along the c-axis via Si3Si bonds resulting in a three-dimentional (3D) [T{sub 2}Si{sub 2}]{sup 2−} polyanions and therefore belong to the so-called collapsed form of the ThCr{sub 2}Si{sub 2}-type structure. The SrCo{sub 2}Si{sub 2} and CaRh{sub 2}Si{sub 2} are isoelectronic to the parent 122 iron–pnictide superconductors AeFe{sub 2}As{sub 2} (Ae=alkaline earth elements), whereas CaFe{sub 2}Si{sub 2} is a full substituted variant (As/Si) of CaFe{sub 2}As{sub 2

Earth-ionosphere cavity

International Nuclear Information System (INIS)

Tran, A.; Polk, C.

1976-01-01

To analyze ELF wave propagation in the earth-ionosphere cavity, a flat earth approximation may be derived from the exact equations, which are applicable to the spherical cavity, by introducing a second-order or Debye approximation for the spherical Hankel functions. In the frequency range 3 to 30 Hz, however, the assumed conditions for the Debye approximation are not satisfied. For this reason an exact evaluation of the spherical Hankel functions is used to study the effects of the flat earth approximation on various propagation and resonance parameters. By comparing the resonance equation for a spherical cavity with its flat earth counterpart and by assuming that the surface impedance Z/sub i/ at the upper cavity boundary is known, the relation between the eigenvalue ν and S/sub v/, the sine of the complex angle of incidence at the lower ionosphere boundary, is established as ν(ν + 1) = (kaS/sub v/) 2 . It is also shown that the approximation ν(ν + 1) approximately equals (ν + 1/2) 2 which was used by some authors is not adequate below 30 Hz. Numerical results for both spherical and planar stratification show that (1) planar stratification is adequate for the computation of the lowest three ELF resonance frequencies to within 0.1 Hz; (2) planar stratification will lead to errors in cavity Q and wave attenuation which increase with frequency; (3) computation of resonance frequencies to within 0.1 Hz requires the extension of the lower boundary of the ionosphere to a height where the ratio of conduction current to displacement current, (sigma/ωepsilon 0 ), is less than 0.3; (4) atmospheric conductivity should be considered down to ground level in computing cavity Q and wave attenuation

Precipitation of the rare earth double sodium and rare earths from the sulfuric liquor and the conversion into rare earth hydroxides through meta ethic reaction; Precipitacao do sulfato duplo de terras raras e sodio a partir de licor sulfurico e sua conversao em hidroxido de terras raras mediante reacao metatetica

Energy Technology Data Exchange (ETDEWEB)

Abreu, Renata D.; Oliveira, Ester F.; Brito, Walter de; Morais, Carlos A. [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)]. E-mails: rda@cdtn.br; esterfo@cdtn.br; britow@cdtn.br; cmorais@cdtn.br

2007-07-01

This work presents the purification study of the rare earths through precipitation of rare earth and sodium (Na TR (SO{sub 4}){sub 2}. x H{sub 2}O)) double sulfate and his conversion to rare earths hydroxide TR(OH){sub 3} by meta ethic reaction through the addition of sodium hydroxide solution to the solid double sulfate. The study used the sulfuric liquor as rare earth sample, generated in the chemical processing of the monazite with sulfuric acid by the Industrias Nucleares do Brasil - INB, Brazil, after the thorium and uranium extraction. The work investigated the influence of the main variables involved in the precipitation of Na TR(SO{sub 4}){sub 2}.xH{sub 2}O and in the conversion for the TR(OH){sub 3}, as follows: type and excess of the precipitation agent, temperature and time reaction. The obtained solid composites were characterized by X-ray diffraction, infrared and chemical analysis. The double sulfate diffractogram indicated the Na TR(SO{sub 4}){sub 2} mono-hydrated. The characterization of the metatese products has shown that, for obtaining the complete conversion of NaTR(SO{sub 4}){sub 2}.H{sub 2}O into TR(OH){sub 3}, the reaction must be hot processed ({approx}70 deg C) and with small excess of Na OH ({<=} 5 percent). (author)

Neutron scattering study on R{sub 2}PdSi{sub 3} (R=Ho,Er,Tm) compounds

Energy Technology Data Exchange (ETDEWEB)

Tang, Fei

2010-12-14

Previous studies on the family of inter-metallic rare-earth compounds R{sub 2}PdSi{sub 3} revealed multifaceted magnetic properties, for instance, spin-glass like behavior. Experimental observations include: Signs of a crystallographic superstructure, complicated magnetic structures both in zero field and in applied magnetic fields as well as a generic phase in applied fields for compounds in the series with the heavy rare-earths R=Gd, Tb, Dy, Ho, Er and Tm. This thesis expands the studies on the magnetic properties of R{sub 2}PdSi{sub 3} employing mainly neutron scattering on single crystals with the focus on the compounds with R=Ho, Er and Tm. A detailed analysis of the crystallographic superstructure using modulation wave approach and group theory is presented. The resulting structure implies the existence of two different rare-earth sites with reduced symmetry and an arrangement of the different sites according to sequences as determined by the superstructure. It is shown that the reduced symmetry of the rare-earth sites is explicitly observed in the energy spectra of inelastic neutron scattering. The results on the magnetic structures and excitations are shown and discussed in the framework of the superstructure model. Specifically the generic phase in applied fields is interpreted as a direct consequence of the crystallographic superstructure. It is rather unusual that a crystallographic superstructure is playing such a decisive, and through the field dependence also tunable role in determining the magnetic properties as observed in R{sub 2}PdSi{sub 3}. The mediating interactions between the crystallographic part and the magnetic part of the system are discussed. (orig.)

Oligomeric rare-earth metal cluster complexes with endohedral transition metal atoms

Energy Technology Data Exchange (ETDEWEB)

Steinberg, Simon; Zimmermann, Sina; Brühmann, Matthias; Meyer, Eva; Rustige, Christian; Wolberg, Marike; Daub, Kathrin; Bell, Thomas; Meyer, Gerd, E-mail: gerd.meyer@uni-koeln.de

2014-11-15

Comproportionation reactions of rare-earth metal trihalides (RX{sub 3}) with the respective rare-earth metals (R) and transition metals (T) led to the formation of 22 oligomeric R cluster halides encapsulating T, in 19 cases for the first time. The structures of these compounds were determined by single-crystal X-ray diffraction and are composed of trimers ((T{sub 3}R{sub 11})X{sub 15}-type, P6{sub 3}/m), tetramers ((T{sub 4}R{sub 16})X{sub 28}(R{sub 4}) (P-43m), (T{sub 4}R{sub 16})X{sub 20} (P4{sub 2}/nnm), (T{sub 4}R{sub 16})X{sub 24}(RX{sub 3}){sub 4} (I4{sub 1}/a) and (T{sub 4}R{sub 16})X{sub 23} (C2/m) types of structure) and pentamers ((Ru{sub 5}La{sub 14}){sub 2}Br{sub 39}, Cc) of (TR{sub r}){sub n} (n=2–5) clusters. These oligomers are further enveloped by inner (X{sup i}) as well as outer (X{sup a}) halido ligands, which possess diverse functionalities and interconnect like oligomers through i–i, i–a and/or a–i bridges. The general features of the crystal structures for these new compounds are discussed and compared to literature entries as well as different structure types with oligomeric T centered R clusters. Dimers and tetramers originating from the aggregation of (TR{sub 6}) octahedra via common edges are more frequent than trimers and pentamers, in which the (TR{sub r}) clusters share common faces. - Graphical abstract: Rare earth-metal cluster complexes with endohedral transition metal atoms (TR{sub 6}) may connect via common edges or faces to form dimers, trimers, tetramers and pentamers of which the tetramers are the most prolific. Packing effects and electron counts play an important role. - Highlights: • Rare-earth metal cluster complexes encapsulate transition metal atoms. • Oligomers are built via connection of octahedral clusters via common edges or faces. • Dimers through pentamers with closed structures are known. • Tetramers including a tetrahedron of endohedral atoms are the most prolific.

Photoluminescence of rare-earth-doped Ca{sub 4}Ga{sub 2}S{sub 7}; Fotolyuminestsentsiya Ca{sub 4}Ga{sub 2}S{sub 7}:RZEh

Energy Technology Data Exchange (ETDEWEB)

Tagiev, B G; Tagiev, O B; Dzhabbarov, R B; Musaeva, N N; Kasumov, U F [Inst. Fiziki im. G.M. Abdullaeva AN Azerbajdzhana, Baku (Azerbaijan)

2001-12-01

One obtained Ca{sub 4}Ga{sub 2}S{sub 7}:REM crystals and studied their photoluminescent (PL) properties. One used Nd, Ce, Pr and Tb as promoters. It is shown that in all investigated crystals one observed PL intensity maximums at {lambda} 543 nm that result from intracentre transitions of Nd{sup 3+} ions. The excitation energy is effectively transferred nonradiatingly from Ce{sup 3+}, Pr{sup 3+}, Tb{sup 3+} ions to Nd{sup 3+} ion. In the case, Ce{sup 3+}, Pr{sup 3+}, Tb{sup 3+} are the effective ions-sensitizers.

On ternary intermetallic aurides. CaAu{sub 2}Al{sub 2}, SrAu{sub 2-x}Al{sub 2+x} and Ba{sub 3}Au{sub 5+x}Al{sub 6-x}

Energy Technology Data Exchange (ETDEWEB)

Stegemann, Frank [Institut fuer Anorganische und Analytische Chemie, Westfaelische Wilhelms-Universitaet Muenster (Germany); Benndorf, Christopher [Institut fuer Anorganische und Analytische Chemie, Westfaelische Wilhelms-Universitaet Muenster (Germany); Institut fuer Physikalische Chemie, Westfaelische Wilhelms-Universitaet Muenster (Germany); Institut fuer Mineralogie, Kristallographie und Materialwissenschaften, Universitaet Leipzig (Germany); Zhang, Yuemei; Fokwa, Boniface P.T. [Department of Chemistry, University of California, Riverside, CA (United States); Bartsch, Manfred; Zacharias, Helmut [Physikalisches Institut, Westfaelische Wilhelms-Universitaet Muenster (Germany); Eckert, Hellmut [Institut fuer Physikalische Chemie, Westfaelische Wilhelms-Universitaet Muenster (Germany); Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo, Sao Carlos, SP (Brazil); Janka, Oliver [Institut fuer Anorganische und Analytische Chemie, Westfaelische Wilhelms-Universitaet Muenster (Germany); Institut fuer Chemie, Carl von Ossietzky Universitaet Oldenburg (Germany)

2017-11-17

The intermetallic compound CaAu{sub 2}Al{sub 2}, and the members of the solid solutions SrAu{sub 2-x}Al{sub 2+x} (0 ≤ x ≤ 0.33) and Ba{sub 3}Au{sub 5+x}Al{sub 6-x} (x = 0, 0.14, 0.49) were synthesized from the elements in sealed tantalum ampoules. The Ca compound crystallizes with the orthorhombic ThRu{sub 2}P{sub 2} type structure, whereas the targeted SrAu{sub 2}Al{sub 2} was found to form a solid solution according to SrAu{sub 2-x}Al{sub 2+x}. For the Ba system no ''BaAu{sub 2}Al{sub 2}'' was found, however, Ba{sub 3}Au{sub 5+x}Al{sub 6-x} was discovered to crystallize in the monoclinic space group C2/c with its own structure type. The samples were investigated by powder X-ray diffraction and their crystal structures were refined on the basis of single-crystal X-ray diffraction data. All compounds were characterized furthermore by susceptibility measurements. The crystallographic aluminum sites of CaAu{sub 2}Al{sub 2} and Ba{sub 3}Au{sub 5}Al{sub 6} can be differentiated by {sup 27}Al solid state NMR spectra on the basis of their different electric field gradients, in agreement with theoretical calculations. The electron transfer from the alkaline earth metals and the aluminum atoms onto the gold atoms was investigated by X-ray photoelectron spectroscopy (XPS) classifying these intermetallics as aurides, in full agreement with the calculated Bader charges. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Studies of valence of selected rare earth silicides determined using Si K and Pd/Rh L{sub 2,3} XANES and LAPW numerical studies

Energy Technology Data Exchange (ETDEWEB)

Zajdel, P., E-mail: pawel.zajdel@us.edu.pl [Institute of Physics, University of Silesia, ul. Uniwersytecka 4, 40-007 Katowice (Poland); Kisiel, A., E-mail: andrzej.kisiel@uj.edu.pl [M. Smoluchowski Institute of Physics, Jagiellonian University, ul. Lojasiewicza 11, 30-348 Kraków (Poland); Szytuła, A., E-mail: andrzej.szytula@uj.edu.pl [M. Smoluchowski Institute of Physics, Jagiellonian University, ul. Lojasiewicza 11, 30-348 Kraków (Poland); Goraus, J., E-mail: jerzy.goraus@us.edu.pl [Institute of Physics, University of Silesia, ul. Uniwersytecka 4, 40-007 Katowice (Poland); Balerna, A., E-mail: antonella.balerna@lnf.infn.it [Laboratori Nazionali di Frascati, INFN, Lab DAPHINE-Light, Via E. Fermi 40, I-00044 Frascati (Italy); Banaś, A., E-mail: slsba@nus.edu.sg [Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore 117603 (Singapore); Starowicz, P., E-mail: pawel.starowicz@uj.edu.pl [M. Smoluchowski Institute of Physics, Jagiellonian University, ul. Lojasiewicza 11, 30-348 Kraków (Poland); Konior, J., E-mail: jerzy.konior@uj.edu.pl [M. Smoluchowski Institute of Physics, Jagiellonian University, ul. Lojasiewicza 11, 30-348 Kraków (Poland); Cinque, G., E-mail: gianfelice.cinque@diamond.ac.uk [Diamond Light Source, Harwell Campus, OX11 0DE Chilton-Didcot (United Kingdom); Grilli, A., E-mail: antonio.grilli@lnf.infn.it [Laboratori Nazionali di Frascati, INFN, Lab DAPHINE-Light, Via E. Fermi 40, I-00044 Frascati (Italy)

2015-12-01

Highlights: • The Si K and Pd L{sub 3} edges of R{sub 2}PdSi{sub 3} (R = Ce, Nd, Tb, Dy, Ho, Er) and HoRh{sub 2−x}Pd{sub x}Si{sub 2} are reported. • The R–Si bonds possess polar and 4d5s bands of Pd and Rh metallic characters. • There is no indication of Ce having a different valence than the other rare earths. • The positions and features of the calculated edges exhibit a fair agreement up to ≈10 eV. • The supercell used for Ho{sub 2}PdSi{sub 3} is good enough to reproduce the Si K edge. - Abstract: We report on the investigation of Si and Pd/Rh chemical environments using X-ray Absorption Near Edge Spectroscopy in two different families of rare earth silicides R{sub 2}PdSi{sub 3} (R = Ce, Nd, Tb, Dy, Ho, Er) and HoRh{sub 2−x}Pd{sub x}Si{sub 2} (x = 0, 0.5, 0.75, 1.0, 1.5, 1.8, 2.0). The Si K, Pd L{sub 3} and Rh L{sub 3} absorption edges were recorded in order to follow their changes upon the variation of 4f and 4d5s electron numbers. In both cases it was found that the Si K edge was shifted ≈0.5 eV toward lower energies, relative to pure silicon. In the first family, the shift decreases with increasing number of f-electrons, while the Si K edge remains constant upon rhodium–palladium substitution. In all cases the Pd L{sub 3} edge was shifted to higher energies relative to metallic Pd. No visible change in the Pd L{sub 3} position was observed either with a varying 4f electron count or upon Pd/Rh substitution. Also, the Rh L{sub 3} edge did not change. For two selected members, Ho{sub 2}PdSi{sub 3} and HoPd{sub 2}Si{sub 2}, the Wien2K’09 (LDA + U) package was used to calculate the electronic structure and the absorption edges. Si K edges were reproduced well for both compounds, while Pd L{sub 3} only exhibited a fair agreement for the second compound. This discrepancy between the Pd L{sub 3} theory and experiment for the Ho{sub 2}PdSi{sub 3} sample can be attributed to the specific ordered superstructure used in the numerical calculations

Coupled effects of atmospheric N/sub 2/O and O/sub 3/ on the earth's climate

Energy Technology Data Exchange (ETDEWEB)

Wang, W C; Sze, N D

1980-08-07

Increased application of nitrogen fertilizer could perturb the atmospheric nitrogen cycle and might lead to a possible increase in atmospheric N/sub 2/O. N/sub 2/O plays an important role in stratospheric chemistry as well as in the global radiation budget. Recent studies suggest that perturbation of local ozone could also significantly affect the global climate. Here we show that a doubling in the present day N/sub 2/O level might significantly perturb the distribution of O/sub 3/ and HNO/sub 3/, and that the associated climatic feedbacks from O/sub 3/ and HNO/sub 3/ perturbations could contribute as much as 0.23 K warming of the surface temperature, in addition to 0.44 K directly caused by N/sub 2/O doubling.

Phase transition and conduction mechanism in Pb{sub 2}Na{sub 0.8}R{sub 0.2}Nb{sub 4.8}Fe{sub 0.2}O{sub 15} material (R=rare earth)

Energy Technology Data Exchange (ETDEWEB)

Bouziane, M. [Laboratoire de Chimie du Solide Appliquée, Faculté des Sciences, Université Mohammed V-Agdal, Avenue Ibn Batouta, BP 1014 Rabat (Morocco); Taibi, M., E-mail: taibiens@yahoo.fr [Laboratoire de Physico-Chimie des Matériaux (LAF 502), Ecole Normale Supérieure, Université Mohammed V-Agdal, BP 5118 Rabat (Morocco); Boukhari, A. [Laboratoire de Chimie du Solide Appliquée, Faculté des Sciences, Université Mohammed V-Agdal, Avenue Ibn Batouta, BP 1014 Rabat (Morocco)

2013-11-15

Electrical properties of Pb{sub 2}Na{sub 0.8}Eu{sub 0.2}Nb{sub 4.8}Fe{sub 0.2}O{sub 15} tungsten bronze compound were investigated. Ferroelectric phase transition of diffuse type is observed at 395 °C. Conductivity study as a function of temperature (RT-600 °C) and at three different frequencies (10, 100 and 1000 kHz) suggests the existence of dominant ionic conduction. The rise of ac conductivity on increasing temperature supports the NTCR (negative temperature coefficient of resistance) behaviour of the material. The activation energies have been evaluated from ac conductivity using Arrhenius equation and discussed. Different conduction mechanisms were identified. For comparison, the conducting properties of Pb{sub 2}Na{sub 0.8}R{sub 0.2}Nb{sub 4.8}Fe{sub 0.2}O{sub 15} (R=Dy, Nd, La) were also investigated. - Graphical abstract: Thermal evolution of lnσ{sub ac} of Pb{sub 2}Na{sub 0.8}Eu{sub 0.2}Nb{sub 4.8}Fe{sub 0.2}O{sub 15} at selected frequencies. Display Omitted - Highlights: • We found that TB compounds exhibit a diffuse type of first- order transition. • A negative temperature coefficient of resistance (NTCR) behaviour is observed. • Three conduction mechanisms were identified: n-and/or p-type at low temperatures. • The conduction mechanism in the studied compounds is very complex.

The association of coronal mass ejections with their effects near the Earth

Directory of Open Access Journals (Sweden)

R. Schwenn

2005-03-01

Full Text Available To this day, the prediction of space weather effects near the Earth suffers from a fundamental problem: The radial propagation speed of "halo" CMEs (i.e. CMEs pointed along the Sun-Earth-line that are known to be the main drivers of space weather disturbances towards the Earth cannot be measured directly because of the unfavorable geometry. From inspecting many limb CMEs observed by the LASCO coronagraphs on SOHO we found that there is usually a good correlation between the radial speed and the lateral expansion speed V<sub>exp> of CME clouds. This latter quantity can also be determined for earthward-pointed halo CMEs. Thus, V<sub>exp> may serve as a proxy for the otherwise inaccessible radial speed of halo CMEs. We studied this connection using data from both ends: solar data and interplanetary data obtained near the Earth, for a period from January 1997 to 15 April 2001. The data were primarily provided by the LASCO coronagraphs, plus additional information from the EIT instrument on SOHO. Solar wind data from the plasma instruments on the SOHO, ACE and Wind spacecraft were used to identify the arrivals of ICME signatures. Here, we use "ICME" as a generic term for all CME effects in interplanetary space, thus comprising not only ejecta themselves but also shocks as well. Among 181 front side or limb full or partial halo CMEs recorded by LASCO, on the one hand, and 187 ICME events registered near the Earth, on the other hand, we found 91 cases where CMEs were uniquely associated with ICME signatures in front of the Earth. Eighty ICMEs were associated with a shock, and for 75 of them both the halo expansion speed V<sub>exp> and the travel time T<sub>tr> of the shock could be determined. The function T<sub>tr>=203-20.77*ln (V<sub>exp> fits the data best. This empirical formula can be used for predicting further ICME arrivals, with a 95% error margin of about one day. Note, though, that in 15% of comparable cases, a

Radiation curing of {gamma}-Al{sub 2}O{sub 3} filled epoxy resin

Energy Technology Data Exchange (ETDEWEB)

Kang, Phil Hyun; Kim, Dong Jin; Nho, Young Chang [KAERI, Taejon (Korea, Republic of)

2003-10-01

Epoxy resins are widely utilized as high performance thermosetting resins for many industrial applications but characterized by a relatively low toughness. Recently, the incorporation with rigid inorganic was suggested to improve the mechanical properties of epoxy resins. In the present work, an attempt has been taken to disperse nano-sized {gamma}- Al{sub 2}O{sub 3} particles into diglycidyl ether of bisphenol-A (DGEBA) epoxy resins for improvement of the mechanical properties. These hybrid epoxy-alumina composites were prepared using by the {gamma}-ray curing technique that was conducted with 100kGy under nitrogen at room temperature. The composites were characterized by determining gel content, UTM (Instron model 4443), SEM, FT-IR studies.

Phase transition of the orthorhombic fluorite-related compounds Ln{sub 3}IrO{sub 7} (Ln = Pr, Nd, Sm, Eu)

Energy Technology Data Exchange (ETDEWEB)

Hinatsu, Yukio, E-mail: hinatsu@sci.hokudai.ac.j [Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo 060-0810 (Japan); Doi, Yoshihiro; Nishimine, Hiroaki; Wakeshima, Makoto [Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo 060-0810 (Japan); Sato, Mineo [Department of Chemistry and Chemical Engineering, Faculty of Engineering, Niigata University, 8050 Ikarashi 2-nocho, Niigata 950-2181 (Japan)

2009-12-04

Rare earth iridium oxides Ln{sub 3}IrO{sub 7} (Ln = Pr, Nd, Sm, and Eu) were prepared and their structures were determined by X-ray diffraction measurements. At room temperature, Pr{sub 3}IrO{sub 7} crystallized in an orthorhombic superstructure of cubic fluorite with space group Cmcm. The differential thermal analysis (DTA) and specific heat measurements for Ln{sub 3}IrO{sub 7} (Ln = Pr, Nd, Sm, and Eu) showed a phase transition at 262, 342, 420, and 485 K, respectively. At low temperatures, Ln{sub 3}IrO{sub 7} crystallized in a monoclinic structure with the space group P2{sub 1}/n. The transition temperatures increased with decreasing the ionic radius of rare earths, which indicates that the transition is stress-induced and occurs with the lattice contraction on cooling. These results for Ln{sub 3}IrO{sub 7} were compared with the phase transitions observed for Ln{sub 3}MoO{sub 7}, Ln{sub 3}RuO{sub 7}, Ln{sub 3}ReO{sub 7}, and Ln{sub 3}OsO{sub 7}.

Determination of rare earth oxides in Li{sub 2}CO{sub 3} by x-ray fluorescence analysis

Energy Technology Data Exchange (ETDEWEB)

Mengfu, Wei; Xinmian, Xu [Sichuan Inst. of Material and Technology (China)

1994-07-01

The mechanism of light elements incoherent scatter has been studied. By combining the incoherent scatter intensity with character line intensity to calculate the appearance concentration, the Lucas-Tooth and Pyne intensity correction model is corrected. By using this model and least-square method of regression of linear equations, the x-ray fluorescence analysis method is used for determining Sc{sub 2}O{sub 3}, Y{sub 2}O{sub 3}, La{sub 2}O{sub 3}, Tm{sub 2}O{sub 3} and Lu{sub 2}O{sub 3} in Li{sub 2}CO{sub 3} which are standard samples in the laboratory. The precision of the method is better than 4.0%, and the best is up to 1.4%. Advantages of the method are accurate, easy to control, fast and various elements can be simultaneously determined.

Growth and Characterization of Ce- Substituted Nd<sub>2sub>Fe>14sub>¹¹B Single Crystals

Energy Technology Data Exchange (ETDEWEB)

Susner, M. A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division; Conner, B. S. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division; Saparov, B. I. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division; McGuire, M. A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division; Crumlin, E. J. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source; Veith, G. M. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source; Cao, H. B. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Quantum Condensed Matter Division; Shanavas, K. V. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division; Parker, D. S. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division; Chakoumakos, B. C. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Quantum Condensed Matter Division; Sales, B. C. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division

2015-08-31

Single crystals of (Nd<sub>1-xsub>Ce_x)>2sub>Fe>14sub>B are grown out of Fe-(Nd,Ce) flux. Chemical and structural analysis of the crystals indicates that (Nd<sub>1-xsub>Ce_x)>2sub>Fe>14sub>B forms a solid solution until at least x = 0.38 with a Vegard-like variation of the lattice constants with x. Refinements of single crystal neutron diffraction data indicate that Ce has a slight site preference (7:3) for the 4g rare earth site over the 4f site. Furthermore, magnetization measurements show that for x = 0.38 the saturation magnetization at 400 K, a temperature important to applications, falls from 29.8 for the parent Nd<sub>2sub>Fe>14sub>B to 27.6 μ<sub>B>/f.u., the anisotropy field decreases from 5.5 T to 4.7 T, and the Curie temperature decreases from 586 to 543 K. First principles calculations carried out within density functional theory are used to explain the decrease in magnetic properties due to Ce substitution. Although the presence of the lower-cost and more abundant Ce slightly affects these important magnetic characteristics, this decrease is not large enough to affect a multitude of applications. Ce-substituted Nd<sub>2sub>Fe>14sub>B is therefore a potential high-performance permanent magnet material with substantially reduced Nd content.

Synchrotron Diffraction Studies of Spontaneous Magnetostriction in Rare Earth Transition Metal Compounds

Energy Technology Data Exchange (ETDEWEB)

Yang, Ning [Iowa State Univ., Ames, IA (United States)

2004-12-19

Thermal expansion anomalies of R<sub>2sub>Fe>14sub>B and R<sub>2sub>Fe>17sub>C_x> (x = 0,2) (R = Y, Nd, Gd, Tb, Er) stoichiometric compounds are studied with high-energy synchrotron X-ray powder diffraction using Debye-Schemer geometry in temperature range 10K to 1000K. Large spontaneous magnetostriction up to their Curie temperatures (T<sub>c>) is observed. The a-axes show relatively larger invar effects than c-axes in the R<sub>2sub>Fe>14sub>B compounds whereas the R<sub>2sub>Fe>17sub>C_x> show the contrary anisotropies. The iron sub-lattice is shown to dominate the spontaneous magnetostriction of the compounds. The contribution of the rare earth sublattice is roughly proportional to the spin magnetic moment of the rare earth in the R<sub>2sub>Fe>14sub>B compounds but in R<sub>2sub>Fe>17sub>C_x>, the rare earth sub-lattice contribution appears more likely to be dominated by the local bonding. The calculation of spontaneous magnetostrain of bonds shows that the bonds associated with Fe(j2) sites in R<sub>2sub>Fe>14sub>B and the dumbbell sites in R<sub>2sub>Fe>17sub>C_x> have larger values, which is strongly related to their largest magnetic moment and Wigner-Seitz atomic cell volume. The roles of the carbon atoms in increasing the Curie temperatures of the R<sub>2sub>Fe>17sub> compounds are attributed to the increased separation of Fe hexagons. The R<sub>2sub>Fe>17sub> and R<sub>2sub>Fe>14sub>B phases with magnetic rare earth ions also show anisotropies of thermal expansion above<sub> csub>. For R<sub>2sub>Fe>17sub> and R<sub>2sub>Fe>14sub>B the a<sub> asub>/a> csub> > 1 whereas the anisotropy is reversed with the interstitial carbon in R<sub>2sub>Fe>17sub>. The average bond magnetostrain is shown to be a possible predictor of the magnetic moment of Fe sites in the compounds. Both of the theoretical and

Structural studies of type N superconductive compounds: R{sub 2-x}Ce{sub x}CuO{sub 4{+-}{delta}} (R = Gd, Eu, Sm, Nd, Pr); influences of chemical treatments on physical properties; Etudes structurales des composes supraconducteurs de type N: R{sub 2-x}Ce{sub x}CuO{sub 4{+-}{delta}} (R = Gd, Eu, Sm, Nd, Pr); influences des traitements chimiques sur les proprietes physiques

Energy Technology Data Exchange (ETDEWEB)

Vigoureux, P

1995-06-01

Different chemical treatments of R{sub 2-x}Ce{sub x}CuO{sub 4{+-}{delta}} compounds monocrystals (gadolinium, europium, samarium, neodymium and praseodymium cuprates) modify their physical properties especially their superconductive properties. The presented chemical treatments are: the substitution of the trivalent rare earth element R by an other trivalent lanthanide, its substitution by tetravalent cerium, and heat treatment under low oxygen pressure. After these chemical treatments, structural modifications are observed by neutrons and X-rays diffraction, and allow to precise their actions: size effect of the rare earth element on the deformation of the CuO{sub 2} planes, links between deformation and superconductivity and magnetic properties. (A.B.). 394 refs/.

The stabilization of the highest oxidation states of transition metals under oxygen pressures: TlNiO sub 3 , a new Ni(III) perovskite - comparison of the electronic properties with those of TNiO sub 3 (T = rare earth and Y)

CERN Document Server

Kim, S J; Presniakov, I

2002-01-01

The crystal structure and the magnetic properties of TlNiO sub 3 have been characterized and compared with those of TNiO sub 3 (T = rare earth and Y). The electronic structure of Ni(III) has been investigated by Moessbauer spectroscopy. Through these analyses, the effects of the A-site ion on structural distortion, magnetic behaviour and electronic structure of Ni(III) in a perovskite have been discussed.

Anti-bombing insensitivity life of molybdenum cathode doped with La{sub 2}O{sub 3} and Y{sub 2}O{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Wang Jinshu [School of Materials Science and Engineering, Beijing University of Technology, Beijing 100022 (China)]. E-mail: wangjsh@bjut.edu.cn; Wang Yiman [School of Materials Science and Engineering, Beijing University of Technology, Beijing 100022 (China); Zhou Meiling [School of Materials Science and Engineering, Beijing University of Technology, Beijing 100022 (China)

2006-03-15

Anti-bombing insensitivity of La{sub 2}O{sub 3}-Y{sub 2}O{sub 3}-Mo secondary emitter has been studied in this paper. The variation of maximum secondary emission coefficient {delta} {sub max} with time was measured. The cathode after life experiment was analyzed by means of HRM, SEM, EDS and XRD. The results showed that {delta} {sub max} of La{sub 2}O{sub 3}-Y{sub 2}O{sub 3}-Mo cathode operating at 1100 deg. C under continuous electron bombardment of 300 W/cm{sup 2} was still about 2.5 after 1000 h operation, indicating that this kind of cathode had good anti-bombing insensitivity. In the internal part of the cathode, RE{sub 2}O{sub 3} (rare earth oxide) and molybdenum grains distributed alternately and there existed a certain relationship between crystallographic orientation of RE{sub 2}O{sub 3} and that of molybdenum. It was found that a RE{sub 2}O{sub 3} layer was formed on the surface after operation. The high {delta} {sub max} of La{sub 2}O{sub 3}-Y{sub 2}O{sub 3}-Mo cathode was related to the RE{sub 2}O{sub 3} layer on the surface and the amount of nanosized La{sub 2}O{sub 3} particles on the Y{sub 2}O{sub 3} layer.

Quaternary chalcogenides La{sub 3}Sn{sub 0.5}InS{sub 7} and La{sub 3}Sn{sub 0.5}InSe{sub 7}

Energy Technology Data Exchange (ETDEWEB)

Iyer, Abishek K.; Lee, Emma J.; Bernard, Guy M.; Michaelis, Vladimir K.; Mar, Arthur [Department of Chemistry, University of Alberta, Edmonton, AB (Canada); Yin, Wenlong [Department of Chemistry, University of Alberta, Edmonton, AB (Canada); Institute of Chemical Materials, China Academy of Engineering Physics, Mianyang (China)

2017-12-13

The quaternary chalcogenides La{sub 3}Sn{sub 0.5}InS{sub 7} and La{sub 3}Sn{sub 0.5}InSe{sub 7} were prepared by reactions of the elements at 1050 C and 950 C, respectively. They adopt noncentrosymmetric structures [hexagonal, space group P6{sub 3}, Z = 2; a = 10.2993(11) Aa, c = 6.0921(6) Aa for La{sub 3}Sn{sub 0.5}InS{sub 7}; a = 10.6533(7) Aa, c = 6.4245(4) Aa for La{sub 3}Sn{sub 0.5}InSe{sub 7}] in which the half-occupancy of Sn atoms within octahedral sites classifies them as belonging to the La{sub 3}Mn{sub 0.5}SiS{sub 7}-type branch of the large family of quaternary rare-earth chalcogenides RE{sub 3}M{sub 1-x}M{sup '}Ch{sub 7}. The site distribution in La{sub 3}Sn{sub 0.5}InCh{sub 7}, with higher-valent Sn atoms occupying octahedral instead of tetrahedral sites, is reversed from the typical situation observed in other RE{sub 3}M{sub 1-x}M{sup '}Ch{sub 7} compounds. The ordered distribution of Sn atoms in octahedral sites and In atoms in tetrahedral sites was evaluated by bond valence sum analyses. Moreover, {sup 119}Sn solid-state nuclear magnetic resonance (NMR) spectroscopy confirms the occupation of Sn{sup 4+} species exclusively within octahedral sites. An optical bandgap of 1.45 eV was found for La{sub 3}Sn{sub 0.5}InS{sub 7}. Band structure calculations on an ordered superstructure model of La{sub 3}Sn{sub 0.5}InS{sub 7} reveal that avoidance of strongly Sn-S antibonding levels is an important driving force for the Sn deficiency. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Determination of free boron in rare earth hexaborides

Energy Technology Data Exchange (ETDEWEB)

Kugai, L N; Nazarchuk, T N [AN Ukrainskoj SSR, Kiev. Inst. Problem Materialovedeniya

1975-06-01

The method of N.I. Timofeeva et al. (1968) for the determination of free B in rare earth hexaborides was modified by replacing the 1:10 HNO/sub 3/ by nonoxidizing 2:1 or 3:1 H/sub 2/SO/sub 4/ to dissolve the hexaborides and leave free B in the residue. A sample of 0.5-1.0 g rare earth hexaboride was heated in 50-80 ml 3:1 H/sub 2/SO/sub 4/ at 210/sup 0/ for 2 hr, and the cool solution was diluted. The residue containing free B and B/sub 4/C was filtered, rinsed, and heated in dilute HNO/sub 3/ at mild temperature for 15-20 min. The filtrate was separated from insoluble B/sub 4/C, neutralized with 10% NaOH, and H/sub 3/BO/sub 3/ was titrated with NaOH in the presence of inverted sugar vs. phenophthalein. The free B content was underestimated by less than or equal to 4.3% in nearly all cases. The proposed technique is applicalbe to hexaborides of La, Y, Ce, Pr, Nd, Sm, Gd, and Eu.

Reaction of xenon difluoride with certain rare earth fluorocomplexes of Cs/sub 3/MF/sub 6/ composition

Energy Technology Data Exchange (ETDEWEB)

Kiselev, Yu.M.; Goryachenkov, S.A.; Martynenko, L.I. (Moskovskij Gosudarstvennyj Univ. (USSR))

1983-05-01

By thermographic method in a specially manufactured nickel cell for thermal analysis the reaction of XeF/sub 2/ with Cs/sub 3/M/sup 3/F/sub 6/ (M=Ce, Pr, Tb, Nd, Dy, Er) is studied. Temperatures of thermal effects (Ts) corresponding to Cs/sub 3/M/sup 4/F/sub 7/ formation regularly increase in the series Ce-Tb-Pr-Dy-Nd (115-382 deg C). Cs/sub 3/M/sup 4/F/sub 7/ compounds are characterized by the methods of chemical analysis, X-ray diffraction and oscillating spectroscopy (IR and CS spectroscopy). Experimental data are best of all interpreted on assumption of the presence in Cs/sub 3/M/sup 4/F/sub 7/ crystals statistically oriented MF/sub 7/ fragments of the Dsub(5h) symmetry.

An approach based on genetic algorithms and DFT for studying clusters: (H{sub 2}O) {sub n} (2 {<=} n {<=} 13) cluster analysis

Energy Technology Data Exchange (ETDEWEB)

Sabato de Abreu e Silva, Elcio [Departamento de Quimica - ICEx, Universidade Federal de Minas Gerais, Av. Antonio Carlos 6627, Pampulha (31.270-901) Belo Horizonte, Minas Gerias (Brazil); Anderson Duarte, Helio [Departamento de Quimica - ICEx, Universidade Federal de Minas Gerais, Av. Antonio Carlos 6627, Pampulha (31.270-901) Belo Horizonte, Minas Gerias (Brazil); Belchior, Jadson Claudio [Departamento de Quimica - ICEx, Universidade Federal de Minas Gerais, Av. Antonio Carlos 6627, Pampulha (31.270-901) Belo Horizonte, Minas Gerias (Brazil)], E-mail: jadson@ufmg.br

2006-04-21

The present work proposes the application of a genetic algorithm (GA) for determining global minima to be used as seeds for a higher level ab initio method analysis such as density function theory (DFT). Water clusters ((H{sub 2}O) {sub n} (2 {<=} n {<=} 13)) are used as a test case and for the initial guesses four empirical potentials (TIP3P, TIP4P, TIP5P and ST2) were considered for the GA calculations. Two types of analysis were performed namely rigid (DFT{sub R}M) and non rigid (DFT{sub N}RM) molecules for the corresponding structures and energies. For the DFT analysis, the PBE exchange correlation functional and the large basis set A-PVTZ have been used. All structures and their respective energies calculated through the GA method, DFT{sub R}M and DFT{sub N}RM are compared and discussed. The proposed methodology showed to be very efficient in order to have quasi accurate global minima on the level of ab initio calculations and the data are discussed in the light of previously published results with particular attention to ((H{sub 2}O) {sub n} (2 {<=} n {<=} 13)) clusters. The results suggest that the stabilization energy error for the empirical potentials used are additive with respect to the cluster size, roughly 0.5 kcal mol{sup -1} per water molecule after ZPE correction. Finally, the approach of using GA/empirical potential structures as starting point for ab initio optimization methods showed to be a computationally manageable strategy to explore the potential energy surface of large systems at quantum level. In conclusion, this work proposes an alternative approach to accurately study properties of larger systems in a very efficient manner.

CO{sub 2} geothermal heat probe - Phase 2; CO{sub 2}-Erdwaermesonde - Phase 2

Energy Technology Data Exchange (ETDEWEB)

Grueniger, A.; Wellig, B.

2009-12-15

In this project the fluid dynamics and thermodynamics inside a CO{sub 2} geothermal heat probe have been investigated. The functionality of such a probe, which works like a thermosyphon, was analyzed by means of a simulation model in MATLAB. The model couples the behaviour inside the heat probe with the heat conduction in the earth. A parameter study revealed that the self-circulation character of such a probe leads to flattening of the vertical earth temperature profile near the probe and, hence, leads to more uniform heat removal along the probe. The circulation of CO{sub 2} even goes on when the heat pump is off. This might be advantageous for the regeneration phase. The heat transfer resistance of the evaporating CO{sub 2} film flowing down the probe wall is very small compared to the conduction resistance of the earth. Therefore, no difference has been found between the performances of a conventional heat pipe and a configuration where the liquid phase injection is distributed on different height stages along the probe. It is estimated that the seasonal performance factor of heat pumps can be improved by 15-25% with a CO{sub 2} geothermal heat probe. The main advantage is that the heat transfer to the evaporator of the heat pump (condensation of CO{sub 2} / evaporation of refrigerant) is much more efficient than in a conventional brine probe without phase change. Furthermore, no circulation pump is needed. (authors)

Rare earth elements recycling from waste phosphor by dual hydrochloric acid dissolution

Energy Technology Data Exchange (ETDEWEB)

Liu, Hu [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Zhang, Shengen, E-mail: zhangshengen@mater.ustb.edu.cn [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Pan, Dean; Tian, Jianjun; Yang, Min; Wu, Maolin [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Volinsky, Alex A. [Department of Mechanical Engineering, University of South Florida, Tampa, FL 33620 (United States)

2014-05-01

Highlights: • The article provides a new method for recycling rare earth (RE) from waste phosphor. • When compared with the traditional methods, leach rate was much higher. • Y–Eu concentrate and Tb–Ce concentrate were obtained successively. • It would reduce the burden of later extraction, separation and purification. - Abstract: This paper is a comparative study of recycling rare earth elements from waste phosphor, which focuses on the leaching rate and the technical principle. The traditional and dual dissolution by hydrochloric acid (DHA) methods were compared. The method of dual dissolution by hydrochloric acid has been developed. The Red rare earth phosphor (Y{sub 0.95}Eu{sub 0.05}){sub 2}O{sub 3} in waste phosphor is dissolved during the first step of acid leaching, while the Green phosphor (Ce{sub 0.67}Tb{sub 0.33}MgAl{sub 11}O{sub 19}) and the Blue phosphor (Ba{sub 0.9}Eu{sub 0.1}MgAl{sub 10}O{sub 17}) mixed with caustic soda are obtained by alkali sintering. The excess caustic soda and NaAlO{sub 2} are removed by washing. The insoluble matter is leached by the hydrochloric acid, followed by solvent extraction and precipitation (the DHA method). In comparison, the total leaching rate of the rare earth elements was 94.6% by DHA, which is much higher than 42.08% achieved by the traditional method. The leaching rate of Y, Eu, Ce and Tb reached 94.6%, 99.05%, 71.45%, and 76.22%, respectively. DHA can decrease the consumption of chemicals and energy. The suggested DHA method is feasible for industrial applications.

Characterization of Nd{sub 2}AlO{sub 3}N and Sm{sub 2}AlO{sub 3}N oxynitrides synthesized by carbothermal reduction and nitridation

Energy Technology Data Exchange (ETDEWEB)

Chevire, Francois, E-mail: francois.chevire@univ-rennes1.fr [UMR CNRS 6226 ' Sciences Chimiques de Rennes' , Equipe Verres et Ceramiques, Groupe Materiaux Azotes et Ceramiques, Universite de Rennes 1, 35042 Rennes Cedex (France); Pallu, Arthur; Ray, Erwan; Tessier, Franck [UMR CNRS 6226 ' Sciences Chimiques de Rennes' , Equipe Verres et Ceramiques, Groupe Materiaux Azotes et Ceramiques, Universite de Rennes 1, 35042 Rennes Cedex (France)

2011-05-12

Research highlights: > Carbothermal reduction and nitridation leads to rare earth aluminum oxynitride starting from oxide mixture. > Absorption shifts towards visible in Nd{sub 2}AlO{sub 3}N (orange) and Sm{sub 2}AlO{sub 3}N (yellow). > Oxynitrides are stable up to 600 deg. C in air. > The so-called 'intermediate phase' phenomenon is evidenced in Sm{sub 2}AlO{sub 3}N. - Abstract: The Nd{sub 2}AlO{sub 3}N and Sm{sub 2}AlO{sub 3}N oxynitrides with the K{sub 2}NiF{sub 4}-type structure have been prepared from oxide mixture at 1250 deg. C using the carbothermal reduction and nitridation route (CRN). Optimization of the process is discussed to prevent surface oxidation of the oxynitrides during the synthesis. The absorption of Nd{sub 2}AlO{sub 3}N and Sm{sub 2}AlO{sub 3}N, orange and yellow respectively, has been characterized by diffuse reflectance as well as their thermal stability versus oxidation by thermogravimetric analyses.

Thermostability in rubredoxin and its relationship to mechanical rigidity

Science.gov (United States)

Rader, A. J.

2010-03-01

The source of increased stability in proteins from organisms that thrive in extreme thermal environments is not well understood. Previous experimental and theoretical studies have suggested many different features possibly responsible for such thermostability. Many of these thermostabilizing mechanisms can be accounted for in terms of structural rigidity. Thus a plausible hypothesis accounting for this remarkable stability in thermophilic enzymes states that these enzymes have enhanced conformational rigidity at temperatures below their native, functioning temperature. Experimental evidence exists to both support and contradict this supposition. We computationally investigate the relationship between thermostability and rigidity using rubredoxin as a case study. The mechanical rigidity is calculated using atomic models of homologous rubredoxin structures from the hyperthermophile Pyrococcus furiosus and mesophile Clostridium pasteurianum using the FIRST software. A global increase in structural rigidity (equivalently a decrease in flexibility) corresponds to an increase in thermostability. Locally, rigidity differences (between mesophilic and thermophilic structures) agree with differences in protection factors.

Thermostability in rubredoxin and its relationship to mechanical rigidity

International Nuclear Information System (INIS)

Rader, A J

2010-01-01

The source of increased stability in proteins from organisms that thrive in extreme thermal environments is not well understood. Previous experimental and theoretical studies have suggested many different features possibly responsible for such thermostability. Many of these thermostabilizing mechanisms can be accounted for in terms of structural rigidity. Thus a plausible hypothesis accounting for this remarkable stability in thermophilic enzymes states that these enzymes have enhanced conformational rigidity at temperatures below their native, functioning temperature. Experimental evidence exists to both support and contradict this supposition. We computationally investigate the relationship between thermostability and rigidity using rubredoxin as a case study. The mechanical rigidity is calculated using atomic models of homologous rubredoxin structures from the hyperthermophile Pyrococcus furiosus and mesophile Clostridium pasteurianum using the FIRST software. A global increase in structural rigidity (equivalently a decrease in flexibility) corresponds to an increase in thermostability. Locally, rigidity differences (between mesophilic and thermophilic structures) agree with differences in protection factors

Cubic rare-earth compounds: variants of the three-state Potts model

International Nuclear Information System (INIS)

Kim, D.; Levy, P.M.; Uffer, L.F.

1975-01-01

In appropriate cubic fields, rare-earth ions have sixfold degenerate ground states. When the angular momentum of the rare earth is large, the six levels are characterized by states that are directed along the cube edges. Within these states the angular momentum operators J/sub x/, J/sub y/, and J/sub z/ have particularly simple matrix representations. The projection of an isotropic pair coupling between the rare earths onto these sixfold degenerate states leads to an interaction Hamiltonian H = -I Σ/sub (ij)/ sigma/sub i/sigma/sub j/delta/sub l/sub i/sub l/sub j//, where sigma takes on the values +-1 and l the values x, y, and z. This interaction is a variant of the three-state Potts model. Magnetic and quadrupolar anisotropy field terms are added to the Hamiltonian and the symmetry properties of the phase diagram associated with this model are determined. For nonzero quadrupolar anisotropy fields, the model is shown to have the thermodynamic behavior of an Ising model. However, for zero fields a new symmetry appears and in the mean-field approximation the model has tricritical-like exponents. This simple model is able to account for the large specific-heat critical exponent α' = 1 / 2 which has been observed for holmium antimonide in zero external fields. To the extent that the mean-field approximation is an accurate guide, we predict there are many cubic rare-earth compounds which exhibit tricritical-like behavior in zero field. In addition, for pure quadrupole coupling between rare earths in the sixfold degenerate states, the interaction Hamiltonian is exactly the three-state Potts model. In the mean-field approximation this system has a first-order phase transition. However, a small quadrupolar anisotropy field is sufficient to drive the system to a wing critical point. The specific heat has a critical exponent of α = 2 / 3 or 1 depending on the path taken to approach this critical point. (auth)

49 CFR 587.18 - Dimensions of fixed rigid barrier.

Science.gov (United States)

2010-10-01

... TRAFFIC SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) DEFORMABLE BARRIERS Offset Deformable Barrier § 587.18 Dimensions of fixed rigid barrier. (a) The fixed rigid barrier has a mass of not... 49 Transportation 7 2010-10-01 2010-10-01 false Dimensions of fixed rigid barrier. 587.18 Section...

RIGIDITY, SENSITIVITY AND QUALITY OF ATTACHMENT - THE ROLE OF MATERNAL RIGIDITY IN THE EARLY SOCIOEMOTIONAL DEVELOPMENT OF PREMATURE-INFANTS

NARCIS (Netherlands)

BUTCHER, PR; KALVERBOER, A; MINDERAA, RB; VANDOORMAAL, EF; TENWOLDE, Y

1993-01-01

The associations between a mother's rigidity, her sensitivity in early (3 month) interaction and the quality of her premature infant's attachment at 13 months were investigated. Rigidity as a personality characteristic was not found to be significantly associated with sensitivity or quality of

EPR study of the low-spin state of Ru{sup 3+}in the YAl{sub 3}(BO{sub 3}){sub 4} and EuAl{sub 3}(BO{sub 3}){sub 4} aluminum borates

Energy Technology Data Exchange (ETDEWEB)

Prokhorov, A.A., E-mail: andaprokhorov@gmail.com [Institute of Physics AS CR, Na Slovance 2, Praha 8 18221 (Czech Republic); Chernush, L.F. [A.A. Galkin Donetsk Physico-Technical Institute, 72, R. Luxembourg Str., Donetsk 83114 (Ukraine); Dyakonov, V.P.; Szymczak, H. [Institute of Physics, PAS, al. Lotników 32/46, Warsaw 02-668 (Poland); Prokhorov, A.D. [A.A. Galkin Donetsk Physico-Technical Institute, 72, R. Luxembourg Str., Donetsk 83114 (Ukraine)

2016-12-15

New data on the ground state of impurity Ru{sup 3+} ions in the crystals of YAl{sub 3}(BO{sub 3}){sub 4} and EuAl{sub 3}(BO{sub 3}){sub 4} aluminum borates were obtained. It was shown that Ru{sup 3+} ion replaces trivalent rare-earth ions without breaking the symmetry of the site. The crystal field acting on 4d{sup 5} ions forms an EPR spectrum, which is described by the spin Hamiltonian with S=1/2. The spin-Hamiltonian parameters determined are equal to g{sub II}=1.963, g{sub ⊥}=3.796, A{sub II}=43.03*10{sup −4} cm{sup −1}, A{sub ⊥}=84.86*10{sup −4} cm{sup −1} in the YAl{sub 3}(BO{sub 3}){sub 4} crystal (at T=15 K) and g{sub II}=2.016, g{sub ⊥}=3.796 in the EuAl{sub 3}(BO{sub 3}){sub 4} crystal (at T=15 K). It is found that the value of ∆g=g{sub II}-g{sub ⊥} is an indicator of distortions of nearest environment of Ru{sup 3+} ion. The angle between the C{sub 3} axis and the direction into nearest oxygen ion was determined. The EPR linewidth of Ru{sup 3+} ion increases with increasing temperature due to the dipole-dipole and exchange interactions with the excited states of the host lattice Ru{sup 3+} ion.

Thermodynamic and neutron diffraction studies on multiferroic NdMn{sub 2}O{sub 5}

Energy Technology Data Exchange (ETDEWEB)

Chattopadhyay, S.; Balédent, V.; Auban-Senzier, P.; Pasquier, C.; Doubrovsky, C. [Laboratoire de Physique des Solides, Université Paris-Sud, CNRS-UMR 8502, 91405 Orsay (France); Greenblatt, M. [Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, NJ 08854 (United States); Foury-Leylekian, P., E-mail: pascale.foury@u-psud.fr [Laboratoire de Physique des Solides, Université Paris-Sud, CNRS-UMR 8502, 91405 Orsay (France)

2015-03-01

Magnetically frustrated RMn{sub 2}O{sub 5} oxides have attracted considerable attention in recent years, because most of the members of this family show spin ordering induced dielectric polarization along with strong magneto-electric coupling. Although the true origin of the ferroelectricity is still a matter of debate, it has been observed that the magneto-electric phase diagram can be substantially tuned with the variation of rare earth elements. In this work, we have chosen NdMn{sub 2}O{sub 5} as the compound of our interest since it lies exactly in between the ferroelectric and non-ferroelectric members of this family and also, because there are few investigations performed on RMn{sub 2}O{sub 5} systems with large rare earth atoms . With the combination of heat capacity, magnetic susceptibility, dielectric permittivity, powder X-ray diffraction, and powder neutron diffraction measurements, it has been found that NdMn{sub 2}O{sub 5} undergoes an incommensurate magnetic ordering around 30 K followed by a possible ferroelectric-like transition at ∼26 K. Another lock-in kind of magnetic transition appears when the temperature is decreased to ∼15 K. With further lowering of temperature, an antiferromagnetic ordering, which is presumably associated with the Nd{sup 3+}, is achieved near 4 K. This study thus sheds light on a new compound of the RMn{sub 2}O{sub 5} series presenting different multiferroic properties.

Preparation, patterning and luminescent properties of oxyapatite La sub 9 sub . sub 3 sub 3 (SiO sub 6) sub 4 O sub 2 :A(A = Eu sup 3 sup + , Tb sup 3 sup + , Ce sup 3 sup +) phosphor films by sol-gel soft lithography

CERN Document Server

Han, X M; Xing, R B; Fu, J; Wang, S B; Han, Y C

2003-01-01

Silicate oxyapatite La sub 9 sub . sub 3 sub 3 (SiO sub 6) sub 4 O sub 2 :A (A = Eu sup 3 sup + , Tb sup 3 sup + and/or Ce sup 3 sup +) phosphor films and their patterning were fabricated by a sol-gel process combined with soft lithography. X-ray diffraction(XRD), Fourier transform infrared spectroscopy, atomic force microscopy, optical microscopy and photoluminescence spectra, as well as lifetimes, were used to characterize the resulting films. The results of XRD indicated that the films began to crystallize at 800 deg. C and the crystallinity increased with the increase in annealing temperatures. Transparent nonpatterned phosphor films were uniform and crack-free, which mainly consisted of rodlike grains with a size between 150 and 210 nm. Patterned thin films with different bandwidths(20, 50 mu m) were obtained by the micromoulding in capillaries technique. The doped rare earth ions(Eu sup 3 sup + , Tb sup 3 sup + and Ce sup 3 sup +) showed their characteristic emission in crystalline La sub 9 sub . sub 3 ...

Synthesis, crystal structure, and magnetism of A{sub 2}Co{sub 12}As{sub 7} (A=Ca, Y, Ce–Yb)

Energy Technology Data Exchange (ETDEWEB)

Tan, Xiaoyan [Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306 (United States); Ovidiu Garlea, V. [Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Chai, Ping [Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306 (United States); Geondzhian, Andrey Y. [National Research Nuclear University “Moscow Engineering Physics Institute”, 115409 Moscow (Russian Federation); Yaroslavtsev, Alexander A. [National Research Nuclear University “Moscow Engineering Physics Institute”, 115409 Moscow (Russian Federation); European XFEL GmbH, 22761 Hamburg (Germany); Xin, Yan [National High Magnetic Field Laboratory, Tallahassee, FL 32310 (United States); Menushenkov, Alexey P. [National Research Nuclear University “Moscow Engineering Physics Institute”, 115409 Moscow (Russian Federation); Chernikov, Roman V. [DESY Photon Science, 22603 Hamburg (Germany); Shatruk, Michael, E-mail: shatruk@chem.fsu.edu [Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306 (United States)

2016-04-15

Ternary intermetallics, A{sub 2}Co{sub 12}As{sub 7} (A=Ca, Y, Ce–Yb), have been synthesized by annealing mixtures of elements in molten Bi at 1223 K. The materials obtained crystallize in the P6{sub 3}/m variant of the Zr{sub 2}Fe{sub 12}P{sub 7} structure type. The unit cell volume shows a monotonic decrease with the increasing atomic number of the rare-earth metal, with the exception of Ce-, Eu-, and Yb-containing compounds. An examination of these outliers with X-ray absorption near edge structures (XANES) spectroscopy revealed mixed valence of Ce, Eu, and Yb, with the average oxidation states of +3.20(1), +2.47(5), and +2.91(1), respectively, at room temperature. Magnetic behavior of A{sub 2}Co{sub 12}As{sub 7} is generally characterized by ferromagnetic ordering of Co 3d moments at 100–140 K, followed by low-temperature ordering of rare-earth 4f moments. The 3d-4f magnetic coupling changes from antiferromagnetic for A=Pr–Sm to ferromagnetic for A=Ce and Eu–Yb. Polarized neutron scattering experiments were performed to support the postulated ferro- and ferrimagnetic ground states for Ce{sub 2}Co{sub 12}As{sub 7} and Nd{sub 2}Co{sub 12}As{sub 7}, respectively. - Graphical abstract: Title arsenides were synthesized by Bi‐flux method. They exhibit mixed valence for A = Ce, Eu, Yb, ferrimagnetism for A = Ca, Y, Pr–Sm, and ferromagnetism for A = Eu–Tm. - Highlights: • A2Co12As7 (A=Ca, Y, Ce–Yb) were synthesized in Bi flux. • Ce, Eu, Yb exhibit mixed valence in the corresponding structures. • The character of 3d‐4f magnetic coupling changes at the half‐filled f shell. • Materials behave as ferrimagnets for A=Ca, Y, Pr–Sm and as ferromagnets for A=Eu–Yb.

Structural and photoluminescence study of Er-Yb codoped nanocrystalline ZrO{sub 2}-B{sub 2}O{sub 3} solid solution

Energy Technology Data Exchange (ETDEWEB)

Salas, P. [Centro de Fisica Aplicada y Tecnologia Avanzada, Universidad Nacional Autonoma de Mexico, A.P. 1-1010, Queretaro 76000 (Mexico); Borja-Urby, R. [Grupo de Espectroscopia de Materiales Avanzados y nanoestructurados (EMANA), Centro de Investigaciones en Optica, A. C., Loma del Bosque 115, Col. Lomas del Campestre, C.P. 37150 Leon, Gto. (Mexico); Diaz-Torres, L.A., E-mail: ditlacio@cio.mx [Grupo de Espectroscopia de Materiales Avanzados y nanoestructurados (EMANA), Centro de Investigaciones en Optica, A. C., Loma del Bosque 115, Col. Lomas del Campestre, C.P. 37150 Leon, Gto. (Mexico); Rodriguez, G. [Centro de Fisica Aplicada y Tecnologia Avanzada, Universidad Nacional Autonoma de Mexico, A.P. 1-1010, Queretaro 76000 (Mexico); Vega, M. [Centro de Geociencias, Universidad Nacional Autonoma de Mexico, A.P. 1-1010, Queretaro 76000 (Mexico); Angeles-Chavez, C. [Instituto Mexicano del Petroleo, Programa de Ingenieria Molecular, Eje Central Lazaro Cardenas 152, A.P. 14-805, 07730 Mexico, DF (Mexico)

2012-09-20

Codoped Er{sup 3+} and Yb{sup 3+} nanocrystalline ZrO{sub 2}-B{sub 2}O{sub 3} phosphor obtained by a modified sol-gel method is demonstrated. The addition of up to 2.5 mol% B{sub 2}O{sub 3} to nanocrystalline ZrO{sub 2}:Yb(2%), Er(1%) keep the tetragonal rare-earth stabilized ZrO{sub 2} phase; whereas higher B{sub 2}O{sub 3} content destabilize the tetragonal phase, leading to the tetragonal to monoclinic transition with no tetragonal ZrO{sub 2} phase segregation. Visible upconversion of the luminescent active ions, Er{sup 3+} and Yb{sup 3+}, depend strongly on B{sub 2}O{sub 3} content. The PL intensity is strongly quenched for high B{sub 2}O{sub 3} content due to increasing multiphonon relaxation processes related to B-O and B-O-B vibronic modes.

Quaternary rare-earth sulfides RE{sub 3}M{sub 0.5}GeS{sub 7} (RE=La–Nd, Sm; M=Co, Ni) and Y{sub 3}Pd{sub 0.5}SiS{sub 7}

Energy Technology Data Exchange (ETDEWEB)

Iyer, Abishek K. [Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2 (Canada); Yin, Wenlong [Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2 (Canada); Institute of Chemical Materials, China Academy of Engineering Physics, Mianyang 621900 (China); Lee, Emma J. [Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2 (Canada); Lin, Xinsong [Centre for Oil Sands Sustainability, Northern Alberta Institute of Technology, Edmonton, Alberta, Canada T6N 1E5 (Canada); Mar, Arthur, E-mail: arthur.mar@ualberta.ca [Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2 (Canada)

2017-06-15

The two metal-deficient series of quaternary Ge-containing sulfides RE{sub 3}M{sub 0.5}GeS{sub 7} (RE = La–Nd, Sm; M = Co, Ni), as well as the related Si-containing sulfide Y{sub 3}Pd{sub 0.5}SiS{sub 7}, were prepared by reactions of the elements at 1050 °C. Single-crystal X-ray diffraction analysis performed on all compounds confirmed noncentrosymmetric hexagonal structures (space group P6{sub 3}, Z =2) with cell parameters in the ranges of a =10.0–10.3 Å and c =5.7–5.8 Å for RE{sub 3}Co{sub 0.5}GeS{sub 7} and RE{sub 3}Ni{sub 0.5}GeS{sub 7}, or a =9.7891(3) Å and c =5.6840(4) Å for Y{sub 3}Pd{sub 0.5}SiS{sub 7}. They are classified as La{sub 3}Mn{sub 0.5}SiS{sub 7}-type structures, with M atoms centred within octahedra (in contrast to La{sub 3}CuSiS{sub 7}-type structures in which M atoms occupy trigonal planar sites) and Ge atoms centred within tetrahedra, both types of polyhedra being arranged in one-dimensional stacks aligned along the c-direction. Charge balance requirements dictate half-occupancy of the M sites. However, bond valence sum arguments indicated that the M atoms are somewhat underbonded within these octahedral sites, so that there is evidence that in some compounds, they can also enter the trigonal planar site at low occupancy (~5%). Magnetic measurements on RE{sub 3}Co{sub 0.5}GeS{sub 7} (RE = Ce, Pr, Sm) revealed paramagnetic behaviour for the Ce and Pr members and apparent antiferromagnetic ordering (T{sub N} =14 K) for the Sm member; fitting to the Curie-Weiss law gave effective magnetic moments consistent with the presence of RE{sup 3+} and Co{sup 2+} species. Band structure calculations on ordered models of La{sub 3}M{sub 0.5}GeS{sub 7} (M = Co, Ni) showed that the Fermi level cuts through M 3d states in the DOS curve and supported the presence of strong M–S and Ge–S bonding interactions. - Graphical abstract: RE{sub 3}M{sub 0.5}GeS{sub 7} (M = Co, Ni) and Y{sub 3}Pd{sub 0.5}SiS{sub 7} contain M atoms partially occupying

Greenhouse impact of CH{sub 4}, N{sub 2}O and CFC emissions in Finland and its control potential

Energy Technology Data Exchange (ETDEWEB)

Pipatti, R.; Savolainen, I.; Sinisalo, J. [VTT Energy, Espoo (Finland)

1995-12-31

Methane (CH{sub 4}), nitrous oxide (N{sub 2}O) and chlorofluorocarbon (CFC) emissions contribute considerably to the anthropogenic enhancement of Earth`s greenhouse effect. The limitation of atmospheric concentrations of CH{sub 4} and N{sub 2}O is considered important also in the Climate Convention. Chlorine released from the CFCs in the stratosphere destroys ozone (O{sub 3}) and the emissions are therefore regulated with the Montreal Protocol. The greenhouse impact of CFCs might be, at least to some extent, compensated by the depletion of O{sub 3} which is also a greenhouse gas. The objective of the presentation is to assess the role of anthropogenic CH{sub 4}, N{sub 2}O, and CFC emissions in the total direct greenhouse impact due to human activities in Finland. The emission estimates for the gases are presented, as well as scenarios for emission history, future development and control potential. The greenhouse impact of the gases is compared with that of carbon dioxide (CO{sub 2}) emissions in Finland. (author)

Greenhouse impact of CH{sub 4}, N{sub 2}O and CFC emissions in Finland and its control potential

Energy Technology Data Exchange (ETDEWEB)

Pipatti, R; Savolainen, I; Sinisalo, J [VTT Energy, Espoo (Finland)

1996-12-31

Methane (CH{sub 4}), nitrous oxide (N{sub 2}O) and chlorofluorocarbon (CFC) emissions contribute considerably to the anthropogenic enhancement of Earth`s greenhouse effect. The limitation of atmospheric concentrations of CH{sub 4} and N{sub 2}O is considered important also in the Climate Convention. Chlorine released from the CFCs in the stratosphere destroys ozone (O{sub 3}) and the emissions are therefore regulated with the Montreal Protocol. The greenhouse impact of CFCs might be, at least to some extent, compensated by the depletion of O{sub 3} which is also a greenhouse gas. The objective of the presentation is to assess the role of anthropogenic CH{sub 4}, N{sub 2}O, and CFC emissions in the total direct greenhouse impact due to human activities in Finland. The emission estimates for the gases are presented, as well as scenarios for emission history, future development and control potential. The greenhouse impact of the gases is compared with that of carbon dioxide (CO{sub 2}) emissions in Finland. (author)

Alkaline earth metal doped tin oxide as a novel oxygen storage material

Energy Technology Data Exchange (ETDEWEB)

Dong, Qiang, E-mail: dong@tagen.tohoku.ac.jp [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku Sendai 980-8577 (Japan); Yin, Shu; Yoshida, Mizuki; Wu, Xiaoyong; Liu, Bin [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku Sendai 980-8577 (Japan); Miura, Akira; Takei, Takahiro; Kumada, Nobuhiro [Department of Research Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Miyamae cho-7, Kofu 400-8511 (Japan); Sato, Tsugio [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku Sendai 980-8577 (Japan)

2015-09-15

Alkaline earth metal doped tin oxide (SnO{sub 2}) hollow nanospheres with a diameter of 50 nm have been synthesized successfully via a facial solvothermal route in a very simple system composed of only ethanol, acetic acid, SnCl{sub 4}·5H{sub 2}O and A(NO{sub 3}){sub 2}·xH{sub 2}O (A = Mg, Ca, Sr, Ba). The synthesized undoped SnO{sub 2} and A-doped SnO{sub 2} hollow nanospheres were characterized by the oxygen storage capacity (OSC), X-ray diffraction, transmission electron microscopy and the Brunauer–Emmet–Teller (BET) technique. The OSC values of all samples were measured using thermogravimetric-differential thermal analysis. The incorporation of alkaline earth metal ion into tin oxide greatly enhanced the thermal stability and OSC. Especially, Ba-doped SnO{sub 2} hollow nanospheres calcined at 1000 °C for 20 h with a BET surface area of 61 m{sup 2} g{sup −1} exhibited the considerably high OSC of 457 μmol-O g{sup −1} and good thermal stability. Alkaline earth metal doped tin oxide has the potential to be a novel oxygen storage material.

Screening novel candidates and exploring design strategies for organic dye sensitizers with rigid π-linker: A theoretical study

Energy Technology Data Exchange (ETDEWEB)

Zhu, Kai-Li [Gansu Key Laboratory of Polymer Materials, College of Chemistry and Chemical Engineering, Key Laboratory of Eco-environment-related Polymer Materials, Ministry of Education, Northwest Normal University, Lanzhou, 730070 Gansu (China); College of Chemistry and Life Science, Gansu Normal University for Nationalities, Hezuo, 747000 Gansu (China); Liu, Le-Yan [College of Chemistry and Life Science, Gansu Normal University for Nationalities, Hezuo, 747000 Gansu (China); Geng, Zhi-Yuan, E-mail: zhiyuangeng@126.com [Gansu Key Laboratory of Polymer Materials, College of Chemistry and Chemical Engineering, Key Laboratory of Eco-environment-related Polymer Materials, Ministry of Education, Northwest Normal University, Lanzhou, 730070 Gansu (China); Yan, Pen-Ji; Lu, Yan-Hong; Liu, Rui-Rui [Gansu Key Laboratory of Polymer Materials, College of Chemistry and Chemical Engineering, Key Laboratory of Eco-environment-related Polymer Materials, Ministry of Education, Northwest Normal University, Lanzhou, 730070 Gansu (China)

2015-07-15

Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations have been carried out to explore the underlying origin of merits for rigid π-spacer based on reference dyes C255 and C254. The results demonstrate that higher short-circuit current density (J{sub SC}) of C255 is primarily ascribed to the lower EBE, while the biggish short-circuit current density (V{sub OC}) mainly originates from the larger μ{sub normal} compared to C254. Besides, a novel index integral of overlap between hole and electron (S) is firstly introduced to quantitatively estimate the facility of intramolecular charge transfer (ICT) and preliminarily confirmed to be effective for the research target of this work. Furthermore, three series of dyes (C-series, A-series, AC-series) have been designed and characterized to screen promising sensitizer candidates and design strategies, while delightful results have been achieved including 6 promising candidates, design stratagem on efficiently reducing the charge recombination and combinational tactics on screening new dyes with excellent spectral properties or outstanding DSSC performance. - Graphical abstract: Display Omitted - Highlights: • Novel S index was introduced in and confirmed to be effective to estimate ICT. • The merits of rigid π bridge have been theoretically revealed. • Six promising candidates have been screened out. • New strategy on reduce charge recombination was reported. • Novel combinational tactics were acquired and justified to be feasible.

Investigation on thermophysical properties of RE{sub 6}UO{sub 12}(s) (RE = La, Pr, Nd, Sm)

Energy Technology Data Exchange (ETDEWEB)

Sahu, Manjulata, E-mail: manju@barc.gov.in [Radioanalytical Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Krishnan, K. [Fuel Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Jain, Dheeraj [Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Saxena, M.K. [Radioanalytical Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Dash, Smruti [Product development Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)

2016-08-10

Highlights: • Synthesis of RE{sub 6}UO{sub 12}(s)(RE = La, Pr, Nd, Sm) was performed by combustion method and characterization by XRD. • Thermal expansion measurements were carried out on RE{sub 6}UO{sub 12}(s)(RE = Pr, and Sm) using HT-XRD. • Heat capacity of RE{sub 6}UO{sub 12}(s)(RE = La, Pr, Nd, Sm) was measured in the temperature range 300–870 K. • The nonstoichiometry in RE{sub 6}UO{sub 12}(s) was checked using TG, XPS, chemical analysis and electrical conductivity measurement. - Abstract: RE{sub 6}UO{sub 12}(s) (RE = La, Pr, Nd, Sm) was synthesized by citrate-nitrate combustion method. The synthesis condition for Pr{sub 6}UO{sub 12}(s) was optimized. Nonstoichiometry in these rare earth uranates in argon atmosphere was analysed using various techniques like thermogravimetry (TG), X-ray photo electron spectroscopy (XPS), chemical analysis and electrical conductivity measurements. Thermal expansions of RE{sub 6}UO{sub 12}(s) (RE = Pr and Sm) was studied in the temperature range 298–1273 K by high temperature X-ray powder diffractometry and compared with that of similar rare earth compounds reported in the literature. Heat capacity of RE{sub 6}UO{sub 12}(s) (RE = La, Pr, Nd, Sm) was measured by differential scanning calorimetry in the temperature range 300–870 K. Enthalpy, entropy and Gibbs energy functions of these compounds were computed from the measured heat capacity data.

Activation analysis of rare-earth elements in opium and cannabis samples. [Neutron reactions

Energy Technology Data Exchange (ETDEWEB)

Henke, G [Muenster Univ. (Germany, F.R.). Inst. fuer Pharmazeutische Chemie

1977-01-01

Rare-earth concentrations in 65 Opium, Cannabis and Cannabis resin samples seized from various parts of the world were determined by destructive NAA. Because of the greater concentrations of Ca, P, K, Fe, Na and Si in plant materials, rare-earth elements were isolated after neutron irradiation and determined by gamma-spectrometry. The main steps of the method are: Preashing of 1 g Cannabis resin, 2.5 g Cannabis, or 7.5 g Opium, respectively, in quartz ampoules (5 h, 500 deg C). Neutron irradiation, 24 h at 5x10/sup 13/n cm/sup -2/sec/sup -1/. Cooling period 2-3 days. After addition of 0.1 ..mu..Ci /sup 139/Ce and rare-earth carriers wet ashing of irradiated samples with H/sub 2/SO/sub 4//HNO/sub 3/, followed by alternate addition of HNO/sub 3/ and H/sub 2/O/sub 2/ (30%). Precipitation and removal of silicates, precipitation of fluorides, precipitation of hydroxides. Dissolution of hydroxides in HCl. Extraction with di-(2-ethylhexyl)phosphate (DEHP)/toluene and twice back-extraction of rare earths, gamma-spectrometry of HCl phase. Due to sample activity and half-life of nuclides, three measurements were made on each sample: 2 days (for La, Sm, Gd, Ho, Er, Yb); 14 days (for Nd, Lu) and 30 days after irradiation (for Ce, Eu, Tb). Great variations in absolute element concentrations, but only small significant differences of rare earth concentration ratios were found, indicating inconsiderable biogeochemical fractionation. The mean values of these ratios correspond to the relative abundances of the rare earths in the upper continental earth's crust.

Structures and magnetic properties of rare earth double perovskites containing antimony or bismuth Ba{sub 2}LnMO{sub 6} (Ln=rare earths; M=Sb, Bi)

Energy Technology Data Exchange (ETDEWEB)

Otsuka, Shumpei, E-mail: m-nis-s-o@ec.hokudai.ac.jp; Hinatsu, Yukio

2015-07-15

A series of double perovskite-type oxides Ba{sub 2}LnMO{sub 6} (Ln=lanthanides; M=Sb, Bi) were synthesized and their structures were studied. The Ln and M are structurally ordered in the rock-salt type at the B-site of the perovskite ABO{sub 3}. For Ba{sub 2}PrBiO{sub 6} and Ba{sub 2}TbBiO{sub 6}, it has been found that the disordering between Ln ion and Bi ion occurs at the B-site of the double perovskite and both the Pr (Tb) and Bi exist in two oxidation state in the same compound from the analysis of the X-ray diffraction and magnetic susceptibility data. Magnetic susceptibility measurements show that all these compounds are paramagnetic and have no magnetic ordering down to 1.8 K. - Graphical abstract: Tolerance factor for Ba{sub 2}LnMO{sub 6} (M=Sb, Bi) plotted against the ionic radius of Ln{sup 3+}. We have found that there is a clear relation between crystal structures and tolerance factors. - Highlights: • The Ln and M ions are structurally ordered in the rock-salt type at the B-site. • The disordering between Pr (Tb) ion and Bi ion occurs at the B-site. • Ba{sub 2}LnMO{sub 6} (M=Sb, Bi) have no magnetic ordering down to 1.8 K.

A reactive distillation process for the treatment of LiCl-KCl eutectic waste salt containing rare earth chlorides

Energy Technology Data Exchange (ETDEWEB)

Eun, H.C., E-mail: ehc2004@kaeri.re.kr; Choi, J.H.; Kim, N.Y.; Lee, T.K.; Han, S.Y.; Lee, K.R.; Park, H.S.; Ahn, D.H.

2016-11-15

The pyrochemical process, which recovers useful resources (U/TRU metals) from used nuclear fuel using an electrochemical method, generates LiCl-KCl eutectic waste salt containing radioactive rare earth chlorides (RECl{sub 3}). It is necessary to develop a simple process for the treatment of LiCl-KCl eutectic waste salt in a hot-cell facility. For this reason, a reactive distillation process using a chemical agent was achieved as a method to separate rare earths from the LiCl-KCl waste salt. Before conducting the reactive distillation, thermodynamic equilibrium behaviors of the reactions between rare earth (Nd, La, Ce, Pr) chlorides and the chemical agent (K{sub 2}CO{sub 3}) were predicted using software. The addition of the chemical agent was determined to separate the rare earth chlorides into an oxide form using these equilibrium results. In the reactive distillation test, the rare earth chlorides in LiCl-KCl eutectic salt were decontaminated at a decontamination factor (DF) of more than 5000, and were mainly converted into oxide (Nd{sub 2}O{sub 3}, CeO{sub 2}, La{sub 2}O{sub 3}, Pr{sub 2}O{sub 3}) or oxychloride (LaOCl, PrOCl) forms. The LiCl-KCl was purified into a form with a very low concentration (<1 ppm) for the rare earth chlorides.

Polymorphism of perovskite compounds Ba/sub 2/SEsub(0. 67)Wsup(VI)O/sub 6/. 2. The systems Ba/sub 2/Ndsub(0. 67(1-x))Ysub(0. 67x)WO/sub 6/ and Ba/sub 2/Ndsub(0. 67)Wsub(1-x)Usub(x)O/sub 6/

Energy Technology Data Exchange (ETDEWEB)

Schnittenhelm, H J; Kemmler-Sack, S [Tuebingen Univ. (Germany, F.R.). Inst. fuer Chemie

1977-06-01

In the system Ba/sub 2/Ndsub(0.67(1-x))Ysub(0.67x)WO/sub 6/ the formation of a continuous series of mixed crystals with cubic 1:1 ordered perovskite structure is observed. The existence of a hexagonal modification is confined to the Y-rich side (x => 0.9). In the Ba/sub 2/Ndsub(0.67)Wsub(1-x)Usub(x)O/sub 6/ series only for x =< 0.25 homogeneous cubic perovskites are obtained. In contrast to systems with other rare earths the Nd series show uncommon optical properties.

Antiperovskite nitridophosphate oxide Ho{sub 3}[PN{sub 4}]O by high-pressure metathesis

Energy Technology Data Exchange (ETDEWEB)

Kloss, Simon D.; Weidmann, Niels; Schnick, Wolfgang [Department of Chemistry, University of Munich (LMU), Butenandtstrasse 5-13, 81377, Munich (Germany)

2017-04-03

Rare-earth nitridophosphates are a recently discovered class of materials, which are accessible by high-pressure metathesis. Antiperovskite-type Ho{sub 3}[PN{sub 4}]O was synthesized from HoF{sub 3}, LiPN{sub 2}, Li{sub 3}N, and Li{sub 2}O at 5 GPa and ca. 1025 C by this method and the multianvil technique. Ho{sub 3}[PN{sub 4}]O contains rarely observed isolated PN{sub 4} tetrahedra and can be derived by the hierarchical substitution of the ABX{sub 3} perovskite, in which Ho occupies the X positions, O occupies the B position, and the PN{sub 4} tetrahedra occupy the A position. The structure was refined on the basis of powder diffraction data [I4/mcm, a = 6.36112(3), c = 10.5571(1) Aa, Z = 4, R{sub wp} = 0.04, R{sub Bragg} = 0.01, χ{sup 2} = 2.275] starting from the structural model of isotypic Gd{sub 3}[SiN{sub 3}O]O. To characterize Ho{sub 3}[PN{sub 4}]O, elemental analyses were performed through energy-dispersive X-ray spectroscopy (EDX) and inductively coupled plasma optical emission spectroscopy (ICP-OES). Ho{sub 3}[PN{sub 4}]O is paramagnetic down to low temperatures with μ{sub eff} = 10.43(1) μ{sub B} and a Curie temperature (Θ) of 0.11(4) K. It shows the optical characteristics of Ho{sup 3+} ions and vibrations corresponding to isolated PN{sub 4} tetrahedra. On the basis of DFT calculations [generalized gradient approximation (GGA)], Ho{sub 3}[PN{sub 4}]O has an indirect band gap of 1.87 eV. We demonstrate the versatility of high-pressure metathesis by attaining the low end of the P/N atomic ratio κ = 1/4. This confirms the previous assumption that rare-earth nitridophosphates with κ = 1/2 to 1/4 are feasible by this method. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Synthesis of Eu{sub x}Si{sub 6-z}Al{sub z}O{sub z}N{sub 8-z} green phosphor and its luminescent properties

Energy Technology Data Exchange (ETDEWEB)

Ryu, Jeong Ho; Won, Hyong Sik; Park, Youn-Gon; Kim, Sang Hyun; Song, Won Young; Suzuki, Hideo; Yoon, Chulsoo [Samsung Electro-Mechanics Co., LTD, Corporate R and D Institute, Suwon, Gyunggi-Do (Korea)

2009-06-15

Rare-earth-doped oxynitride or nitride compounds have been reported to be photoluminescent and may then serve as new phosphors because of their good thermal and chemical stabilities. In this work, Eu{sup 2+}-doped {beta}-SiAlON phosphor with a composition of Eu{sub x}Si{sub 6-z}Al{sub z}O{sub z}N{sub 8-z} (x=0.018,z=0.23) was prepared by gas-pressured solid state reaction. The crystallinity and particle morphology of the prepared phosphor were characterized. The Stokes shift and zero-phonon line were calculated mathematically and estimated from the spectral data. The temperature dependence of photoluminescence was measured from 25 to 250 C. The prepared Eu{sup 2+}-doped {beta}-SiAlON green phosphor showed superior thermal quenching property compared to silicate (SrBaSiO{sub 4}:Eu{sup 2+}) green phosphor. The white light-emitting diode (LED) back-lighting unit (BLU) using the prepared {beta}-SiAlON:Eu{sup 2+} green phosphor exhibited higher color gamut than a commercial silicate phosphor. (orig.)

Radon Sub-slab Suctioning System Integrated in Insulating Layer

DEFF Research Database (Denmark)

Rasmussen, Torben Valdbjørn

2013-01-01

This poster presents a new radon sub-slab suctioning system. This system makes use of a grid of horizontal pressurised air ducts located within the lower part of the rigid insulation layer of the ground floor slab. For this purpose a new system of prefabricated lightweight elements is introduced...

Novel precursors for the deposition of rare earth oxides; Neuartige Precursor zur Abscheidung von Selten-Erd-Oxiden

Energy Technology Data Exchange (ETDEWEB)

Ahlers, Mareike

2010-02-22

During this work rare earth solvates with nitrate and perchlorate anions have been investigated. All compounds have been structurally characterized and analyzed using thermal gravimetric analysis. The decomposition residues were analyzed using powder diffraction methods. Almost all compounds showed a characteristically intense exothermic decomposition step during the thermal decomposition, most likely caused by an intramolecular redox reaction between the nitrate or perchlorate anion respectively and the organic solvent molecules. The nitrates RE(NO{sub 3}){sub 3}(CH(OCH{sub 3}){sub 3}){sub 2} (RE = Sm, Eu) were isolated and characterized for the first time as the intermediate of the dehydration reaction with trimethyl orthoformate. The known compound group of dimethoxyethane solvates was then expanded with RE(NO{sub 3}){sub 3}(O{sub 2}C{sub 4}H{sub 10}) (RE = La, Sm, Eu). Considering the possible use as precursor material the already described neodymium compound is also discussed. The thermal decomposition of these compounds yields the respective cubic rare earth oxide and shows the typical intense exothermic decomposition reaction. A variety of different precursor system based on nitrate solvates for the deposition of rare earth oxide layers on a silicon surface was developed and investigated in collaboration with the group of Prof. Dr. Al-Shamery (Univ. Oldenburg). Ultra thin films on a H-Si(111) surface were obtained via the deposition of the precursor, which was dissolved in organic solvents. An oxide layer was detected after the heating of the sample. The film thickness was measured as < 10 nm, whereas the thickness of the film was controlled by the concentration of the precursor solution. Sm(ClO{sub 4}){sub 3}(CH(OCH{sub 3}){sub 3}){sub 3} was isolated and characterized for the first time as the intermediate of the dehydration reaction with trimethyl orthoformate. Eu(ClO{sub 4}){sub 3}(CH(OCH{sub 3}){sub 3}){sub 2}(MeOH){sub 2} was obtained without

Temperature dependence of the coercive field of gas atomized Fe{sub 73.5}Si{sub 13.5}B{sub 9}Nb{sub 3}Cu{sub 1}

Energy Technology Data Exchange (ETDEWEB)

Garcia-Escorial, A., E-mail: age@cenim.csic.es [CENIM-CSIC, Avda, Gregorio del Amo, 8, 28040 Madrid (Spain); Lieblich, M. [CENIM-CSIC, Avda, Gregorio del Amo, 8, 28040 Madrid (Spain); Hernando, A.; Aragon, A.; Marin, P. [Instituto de Magnetismo Aplicado, IMA, P.O. Box 155, 28230 Madrid (Spain)

2012-09-25