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1

Surfaces of complex intermetallic compounds: insights from density functional calculations.  

PubMed

Conspectus Complex intermetallic compounds are a class of ordered alloys consisting of quasicrystals and other ordered compounds with large unit cells; many of them are approximant phases to quasicrystals. Quasicrystals are the limiting case where the unit cell becomes infinitely large; approximants are series of periodic structures converging to the quasicrystal. While the unique properties of quasicrystals have inspired many investigations of their surfaces, relatively little attention has been devoted to the surface properties of the approximants. In general, complex intermetallic compounds display rather irregular, often strongly corrugated surfaces, making the determination of their atomic structure a very complex and challenging task. During recent years, scanning tunneling microscopy (STM) has been used to study the surfaces of several complex intermetallic compounds. If atomic resolution can be achieved, STM permits visualization of the local atomistic surface structure. However, the interpretation of the STM images is often ambiguous and sometimes even impossible without a realistic model of the structure of the surface and the distribution of the electronic density above the surface. Here we demonstrate that ab initio density functional theory (DFT) can be used to determine the energetics and the geometric and electronic structures of the stable surfaces of complex intermetallic compounds. Calculations for surfaces with different chemical compositions can be performed in the grand canonical ensemble. Simulated cleavage experiments permit us to determine the formation of the cleavage planes requiring the lowest energy. The investigation of the adsorption of molecular species permits a comparison with temperature-programmed thermal desorption experiments. Calculated surface electronic densities of state can be compared with the results of photoelectron spectroscopy. Simulations of detailed STM images can be directly confronted with the experimental results. Detailed results are presented for two intermetallic compounds that have recently attracted much attention as active and highly selective catalysts for the semihydrogenation of alkynes to alkenes, but the identification of the catalytically active surfaces was found to be very difficult. The crystal structure of B20-type GaPd can be interpreted as the lowest order approximant of icosahedral Al-Pd-Mn quasicrystals. Among the low-index surfaces, the {100} surface shows 2-fold symmetry and the {210} surface pseudo-5-fold symmetry; for both the surface stoichiometry is identical to that of the bulk. Because the structure lacks inversion symmetry, the {111} surfaces have polar character and permit terminations of widely different chemical composition. Results for all three surfaces are presented and compared with the available experiments. The crystal structure of orthorhombic Al13Co4 is built by pentagonal clusters similar to those found in decagonal Al-Co and Al-Ni-Co quasicrystals. A simulated cleavage experiment shows that the constituent clusters remain intact upon cleavage, resulting in the formation of a highly corrugated (100) surface. The calculated STM images are found to be in very good agreement with experiment and permit in addition identification of possible surface modifications by the desorption of individual atoms. Pentagonal motifs on the {210} surface of GaPd and on the (100) surface of Al13Co4 consisting of simple- and transition-metal atoms have been identified as the catalytically active centers for the semihydrogenation of acetylene to ethylene. PMID:24741993

Hafner, Jürgen; Kraj?í, Marian

2014-11-18

2

Structural and Electronic Investigations of Complex Intermetallic Compounds  

SciTech Connect

In solid state chemistry, numerous investigations have been attempted to address the relationships between chemical structure and physical properties. Such questions include: (1) How can we understand the driving forces of the atomic arrangements in complex solids that exhibit interesting chemical and physical properties? (2) How do different elements distribute themselves in a solid-state structure? (3) Can we develop a chemical understanding to predict the effects of valence electron concentration on the structures and magnetic ordering of systems by both experimental and theoretical means? Although these issues are relevant to various compound classes, intermetallic compounds are especially interesting and well suited for a joint experimental and theoretical effort. For intermetallic compounds, the questions listed above are difficult to answer since many of the constituent atoms simply do not crystallize in the same manner as in their separate, elemental structures. Also, theoretical studies suggest that the energy differences between various structural alternatives are small. For example, Al and Ga both belong in the same group on the Periodic Table of Elements and share many similar chemical properties. Al crystallizes in the fcc lattice with 4 atoms per unit cell and Ga crystallizes in an orthorhombic unit cell lattice with 8 atoms per unit cell, which are both fairly simple structures (Figure 1). However, when combined with Mn, which itself has a very complex cubic crystal structure with 58 atoms per unit cell, the resulting intermetallic compounds crystallize in a completely different fashion. At the 1:1 stoichiometry, MnAl forms a very simple tetragonal lattice with two atoms per primitive unit cell, while MnGa crystallizes in a complicated rhombohedral unit cell with 26 atoms within the primitive unit cell. The mechanisms influencing the arrangements of atoms in numerous crystal structures have been studied theoretically by calculating electronic structures of these and related materials. Such calculations allow us to examine various interactions at the atomic scale, interactions which include orbital overlap, two-electron interactions, and Madelung terms. Moreover, these electronic studies also provide links between the angstrom-scale atomic interactions and the macro-scale physical properties, such as magnetism. Over the past few decades, there have been many significant developments toward understanding structure-bonding-property relationships in extended solids in terms of variables including atomic size, valence electron concentration, and electronegativity. However, many simple approaches based on electron counting, e.g., the octet rule, the 18-electron rule, or Wade's rules for boranes, cannot be applied adequately or universally to many of the more complex intermetallic compounds. For intermetallic phases that include late transition metals and post transition main group elements as their constituents, one classification scheme has been developed and effectively applied by using their valence electron count per atom (vec). These compounds are known as Hume-Rothery electron phases, and they have a variety of structure types with vec < 2.0 as shown in Table 1.

Hyunjin Ko

2008-08-18

3

Intermetallic Compounds  

NASA Astrophysics Data System (ADS)

We have focused on the binary narrow-bandgap intermetallic compounds FeGa3 and RuGa3 as thermoelectric materials. Their crystal structure is FeGa3-type (tetragonal, P42/ mnm) with 16 atoms per unit cell. Despite their simple crystal structure, their room temperature thermal conductivity is in the range 4-5-W-m-1-K-1. Both compounds have narrow-bandgaps of approximately 0.3-eV near the Fermi level. Because their Seebeck coefficients are quite large negative values in the range 350-<-| S 373K|-<-550- ?V-K-1 for undoped samples, it should be possible to obtain highly efficient thermoelectric materials both by adjusting the carrier concentration and by reducing the thermal conductivity. Here, we report the effects of doping on the thermoelectric properties of FeGa3 and RuGa3 as n and p-type materials. The dimensionless figure of merit, ZT, was significantly improved by substitution of Sn for Ga in FeGa3 (electron-doping) and by substitution of Zn for Ga in RuGa3 (hole-doping), mainly as a result of optimization of the electronic part, S 2 ?.

Takagiwa, Y.; Matsuura, Y.; Kimura, K.

2014-06-01

4

Metastable Cd4Sb3: a complex structured intermetallic compound with semiconductor properties.  

PubMed

The metastable binary intermetallic compound Cd4Sb3 was obtained as polycrystalline ingot by quenching stoichiometric Cd-Sb melts and as mm-sized crystals by employing Bi or Sn fluxes. The compound crystallizes in the monoclinic space group Pn with a = 11.4975(5) A, b = 26.126(1) A, c = 26.122(1) A, beta = 100.77(1) degrees, and V = 7708.2(5) A(3). The actual formula unit of Cd4Sb3 is Cd13Sb10 and the unit cell contains 156 Cd and 120 Sb atoms (Z = 12). Cd4Sb3 displays a reversible order-disorder transition at 373 K and decomposes exothermically into a mixture of elemental Cd and CdSb at around 520 K. Disordered beta-Cd4Sb3 is rhombohedral (space group R3c, a approximately = 13.04 A, c approximately = 13.03 A) with a framework isostructural to beta-Zn4Sb3. The structure of monoclinic alpha-Cd4Sb3 bears resemblance to the low-temperature modifications of Zn4Sb3, alpha- and alpha'-Zn4Sb3, in that randomly distributed vacancies and interstitial atoms of the high-temperature modification aggregate and order into distinct arrays. However, the nature of aggregation and distribution of aggregates is different in the two systems. Cd4Sb3 displays the properties of a narrow gap semiconductor. Between 10 and 350 K the resistivity of melt-quenched samples first increases with increasing temperature until a maximum value at 250 K and then decreases again. The resistivity maximum is accompanied with a discontinuity in the thermopower, which is positive and increasing from 10 to 350 K. The room temperature values of the resistivity and thermopower are about 25 mohms cm and 160 microV/K, respectively. Flux synthesized samples show altered properties due to the incorporation of small amounts of Bi or Sn (less than 1 at. %). Thermopower and resistivity appear drastically increased for Sn doped samples. Characteristic for Cd4Sb3 samples is their low thermal conductivity, which drops below 1 W/mK above 130 K and attains values around 0.75 W/mK at room temperature, which is comparable to vitreous materials. PMID:19006411

Tengå, Andreas; Lidin, Sven; Belieres, Jean-Philippe; Newman, N; Wu, Yang; Häussermann, Ulrich

2008-11-19

5

Studies on drilling processes of intermetallic compounds  

Microsoft Academic Search

Intermetallic compounds have high-specific strength, good creep resistance and excellent oxidation and corrosion resistance at high temperatures. Those good mechanical properties make intermetallic compounds very promising structure materials in industries. Ni3Al and Fe3Al are two typical intermetallic compounds. This paper focuses on machinability and tool wear mechanism of PVD TiAlN coated cemented carbide tool in drilling of Ni3Al and Fe3Al.

L. Liu; H. Shao; L. X. Huang

2009-01-01

6

Lithium reactions with intermetallic-compound electrodes.  

SciTech Connect

Intermetallic compounds are under investigation as possible anode materials in lithium batteries. The compounds on which the Argonne National Laboratory group has primarily focused were selected on the basis of structural compatibility between host and product (lithiated) phases. In this presentation, we discuss the additional insights into the behavior of intermetallic-compound anodes that are available from materials modeling.

Benedek, R.; Thackeray, M. M.; Chemical Engineering

2002-08-22

7

New twisted intermetallic compound superconductor: A concept  

NASA Technical Reports Server (NTRS)

Method for processing Nb3Sn and other intermetallic compound superconductors produces a twisted, stabilized wire or tube which can be used to wind electromagnetics, armatures, rotors, and field windings for motors and generators as well as other magnetic devices.

Coles, W. D.; Brown, G. V.; Laurence, J. C.

1972-01-01

8

Magnetic Properties of Intermetallic Uranium Compounds.  

National Technical Information Service (NTIS)

Magnetic properties of intermetallic uranium compounds have been investigated. The magnetic properties were studied at zero pressure in fields up to 35T. Their pressure dependences were investigated at pressures up to 8kbar in fields up to 10T. Specific h...

P. H. Frings

1984-01-01

9

Driving Magnetostructural Transitions in Layered Intermetallic Compounds  

NASA Astrophysics Data System (ADS)

We report the dramatic effect of applied pressure and magnetic field on the layered intermetallic compound Pr0.5Y0.5Mn2Ge2. In the absence of pressure or magnetic field this compound displays interplanar ferromagnetism at room temperature and undergoes an isostructural first order magnetic transition (FOMT) to an antiferromagnetic state below 158 K, followed by another FOMT at 50 K due to the reemergence of ferromagnetism as praseodymium orders (TCPr). The application of a magnetic field drives these two transitions towards each other, whereas the application of pressure drives them apart. Pressure also produces a giant magnetocaloric effect such that a threefold increase of the entropy change associated with the lower FOMT (at TCPr) is seen under a pressure of 7.5 kbar. First principles calculations, using density functional theory, show that this remarkable magnetic behavior derives from the strong magnetoelastic coupling of the manganese layers in this compound.

Wang, J. L.; Caron, L.; Campbell, S. J.; Kennedy, S. J.; Hofmann, M.; Cheng, Z. X.; Md Din, M. F.; Studer, A. J.; Brück, E.; Dou, S. X.

2013-05-01

10

First-principles studies of Ni-Ta intermetallic compounds  

SciTech Connect

The structural properties, heats of formation, elastic properties, and electronic structures of Ni-Ta intermetallic compounds are investigated in detail based on density functional theory. Our results indicate that all Ni-Ta intermetallic compounds calculated here are mechanically stable except for P21/m-Ni{sub 3}Ta and hc-NiTa{sub 2}. Furthermore, we found that Pmmn-Ni{sub 3}Ta is the ground state stable phase of Ni{sub 3}Ta polymorphs. The polycrystalline elastic modulus has been deduced by using the Voigt-Reuss-Hill approximation. All Ni-Ta intermetallic compounds in our study, except for NiTa, are ductile materials by corresponding G/K values and poisson's ratio. The calculated heats of formation demonstrated that Ni{sub 2}Ta are thermodynamically unstable. Our results also indicated that all Ni-Ta intermetallic compounds analyzed here are conductors. The density of state demonstrated the structure stability increases with the Ta concentration. - Graphical abstract: Mechanical properties and formation heats of Ni-Ta intermetallic compounds are discussed in detail in this paper. Highlights: Black-Right-Pointing-Pointer Ni-Ta intermetallic compounds are investigated by first principle calculations. Black-Right-Pointing-Pointer P21/m-Ni{sub 3}Ta and hc-NiTa{sub 2} are mechanically unstable phases. Black-Right-Pointing-Pointer Pmmn-Ni{sub 3}Ta is ground stable phase of Ni{sub 3}Ta polymorphs. Black-Right-Pointing-Pointer All Ni-Ta intermetallic compounds are conducting materials.

Zhou Yi [Department of Materials Science and Engineering, College of Materials, and Research Center of Materials Design and Applications, Xiamen University, Xiamen 361005 (China); Wen Bin, E-mail: wenbin@ysu.edu.cn [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Ma Yunqing [Department of Materials Science and Engineering, College of Materials, and Research Center of Materials Design and Applications, Xiamen University, Xiamen 361005 (China); Melnik, Roderick [M2NeT Lab, Wilfrid Laurier University, Waterloo,75 University Ave. West, Ontario, N2L 3C5 (Canada); MIT Department, University of Jyvaeskylae, Jyvaeskylae (Finland); Liu Xingjun, E-mail: lxj@xmu.edu.cn [Department of Materials Science and Engineering, College of Materials, and Research Center of Materials Design and Applications, Xiamen University, Xiamen 361005 (China)

2012-03-15

11

Synthesis and characterization of nanocrystalline binary and ternary intermetallic compounds  

E-print Network

nanocrystalline powders. Using this process, I was able to access several binary and ternary intermetallics, including two new phases: AuCuSn2 and AuNiSn2. These compounds were isolated as nanocrystals using low temperature solution synthesis techniques, which had...

Leonard, Brian Matthew

2009-05-15

12

Development of New Cryocooler Regenerator Materials--Ductile Intermetallic Compounds.  

National Technical Information Service (NTIS)

The volumetric heat capacities of a number of binary and ternary Er- and Tm-based intermetallic compounds, which exhibited substantial ductilities, were measured from (approx)3 to (approx)350 K. They have the RM stoichiometry (where R = Er or Tm, and M is...

K. A. Gschneidner, A. O. Pecharsky, V. K. Pecharsky

2004-01-01

13

Hyperfine Fields in Thulium, Gadolinium and Dysprosium Intermetallic Compounds  

Microsoft Academic Search

This thesis is concerned with the study of hyperfine interactions at both the rare earth and non-rare earth nuclei in a number of intermetallic compounds, with particular emphasis on the cubic Laves structure. It is shown how the observed hyperfine data can be interpreted in terms of quite simple ionic Hamiltonians incorporating both magnetic exchange and crystal field effects at

John Michael Cadogan

1983-01-01

14

AN INVESTIGATION OF INTERMETALLIC COMPOUNDS FOR VERY HIGH TEMPERATURE APPLICATIONS  

Microsoft Academic Search

The preparation, fabrication, and properties of intermetallic compcunds ; under development for service at 2300 to 3000 tained F are described. ; The compounds, principally beryllides, have exhibited strengths, as measured by ; the modulus-of-rupture test, of 40,000 psi at 2700 tained F and ; resistance to oxidation for 100 hours at 2800 tained F and have ; indicated good

R. M. Paine; A. J. Stonehouse; W. W. Beaver

1959-01-01

15

Intermediate valence in Yb Intermetallic compounds Jon Lawrence  

E-print Network

ion model: Two nearly-degenerate localized configurations form hybridized w.f.: a [4f13(5d6s)3> + b [4 configurations: conduction electrons hop on and off the 4f impurity orbital. Hybridization strength = V2 where1 Intermediate valence in Yb Intermetallic compounds Jon Lawrence University of California, Irvine

Lawrence, Jon

16

Enthalpies of formation of the Al–Nb intermetallic compounds  

Microsoft Academic Search

The enthalpies of formation of the intermetallic compounds of the Al–Nb system were measured by direct reaction calorimetry at high temperatures. Results were compared with the available experimental values based on calorimetric and vapor pressure measurements and computed values based on the semiempirical model of Miedema. X-ray Powder Diffraction and Electron Microprobe Analysis techniques were used to verify the crystal

Kamal Mahdouk; Jean-Claude Gachon; Lahcen Bouirden

1998-01-01

17

Unique intermetallic compounds prepared by shock wave synthesis  

NASA Technical Reports Server (NTRS)

Technique compresses fine ground metallic powder mixture beyond crystal fusion point. Absence of vapor pressure voids and elimination of incongruous effects permit application of technique to large scale fabrication of intermetallic compounds with specific characteristics, e.g., semiconduction, superconduction, or magnetic properties.

Otto, G.; Reece, O. Y.; Roy, U.

1971-01-01

18

Explosive reaction pressing of intermetallic compounds from stoichiometric powder mixtures  

SciTech Connect

Intermetallic NiAl, TiAl, and TiAl{sub 3} were synthesized by shock compression experiments from stoichiometric powder mixtures of nickel and aluminium as well as of titanium and aluminium. Good consolidation and complete intermetallic reaction were achieved by the direct method of explosive compaction. For each powder mixture, a certain individual threshold pressure has to be exceeded in order to initiate intermetallic reaction. The reacting compounds melted completely with subsequent rapid solidification during the passage of the shock wave. The new material shows high hardness. Pores are formed by gaseous reaction products in the NiAl and TiAl{sub 3} compacts. The TiAl structure is fully-dense and dendritic.

Kochsiek, D.; Pruemmer, R.; Brunold, A. [Ernst-Mach-Institut of the Fraunhofer Research Association, Freiburg (Germany)

1995-09-01

19

Enthalpies of formation of the Al–Ni intermetallic compounds  

Microsoft Academic Search

The Al–Ni system has been investigated by direct reaction calorimetry at high temperatures. Enthalpies of formation of the intermetallic compounds AlNi3, AlNi, Al3Ni2, and Al3Ni were determined and compared with the available experimental values based on calorimetric and emf measurements and with the calculated values from theoretical models. X-ray powder diffraction (XRD) and electron probe microanalysis (EPMA) were used to

F. Z Chrifi-Alaoui; M Nassik; K Mahdouk; J. C Gachon

2004-01-01

20

Magnetic field controlled FZ single crystal growth of intermetallic compounds  

NASA Astrophysics Data System (ADS)

Intermetallic rare-earth-transition-metal compounds with their coexistence of magnetic ordering and superconductivity are still of great scientific interest. The crystal growth of bulk single crystals is very often unsuccessful due to an unfavorable solid-liquid interface geometry enclosing concave fringes. The aim of the work is the contactless control of heat and material transport during floating-zone single crystal growth of intermetallic compounds. This control is provided by a tailored design of the electromagnetic field and the resulting electromagnetically driven convection. Numerical simulations for the determination of the electromagnetic field configuration induced by the RF heater coil and the solution of the coupled heat and hydrodynamic equations were done for the model substance Ni with and without additional magnetic field. As a result, an innovative magnetic two-phase stirrer system has been developed which enables the controlled influence on the melt ranging from intensive inwards/outwards flows to flows almost at rest. The selection of parameters necessary for the desired fluid flow is determined from numerical simulation. The basis for the calculations are the process-related fluid flow conditions which are determined by the mode of heating, heat radiation at the free surface and material parameters. This treatment of the problem leads to the customised magnetic field for the special intermetallic compound. The application of the new magnetic system leads to a distinct improvement of the solid-liquid interface validated on experiments with the model substance Nickel.

Hermann, R.; Behr, G.; Gerbeth, G.; Priede, J.; Uhlemann, H.-J.; Fischer, F.; Schultz, L.

2005-02-01

21

Isomerization of diacetoxybutenes on intermetallic compounds of palladium and rhodium  

SciTech Connect

A study has been made of the isomerization of cis- and trans-1,4-diacetoxybut-2-enes and 3,4-diacetoxybut-1-ene, catalysed by intermetallic compounds of palladium and rhodium. During geometric isomerization, two mechanisms are realized: the traditional triplet (biradical) mechanism and an exchange mechanism. Skeletal-structural isomerization is the intermediate link during Z,E-transformation of diacetoxybutenes. The predominant formation of one of the geometric isomers is determined by the nature of the platinoid atom in the catalytic system. 8 refs., 2 figs., 3 tabs.

Devekki, A.V.; Yakushkin, M.I.; Kul`chitskaya, T.Yu.; Trushova, N.V. [All-Union Scientific Research Inst. of Petrochemical Processes, St. Petersburg (Russian Federation)

1992-12-31

22

Statistically based assessment of formation enthalpy for intermetallic compounds  

NASA Astrophysics Data System (ADS)

A simplified composition-independent atomic size difference factor is proposed to account for the statistical deviation of original Miedema's model for formation enthalpies of binary intermetallic compounds from experimental data. We demonstrate that with the incorporation of this new factor, one can achieve a high level of correlation with respect to available experimental data. Using this statistically refined model, we propose a methodology for assessing where the next level of statistical refinement is needed, utilizing a data-mapping framework of ‘critical descriptors’. This provides a way to identify the search space where needs further experimental work to be performed.

Zhang, R. F.; Rajan, K.

2014-09-01

23

Intermetallic compounds at aluminum-to-copper and copper-to-tin electrical interfaces  

Microsoft Academic Search

The effects of intermetallic compounds on the electrical and mechanical properties of bimetallic friction welded Al-Cu joints and tin-plated copper wire conductors are studied. The formation and growth of intermetallic compounds are studied in the temperature range 200-525°C for the Al-Cu system, and 80°-200°C for the Cu-Sn system. The formation and growth of intermetallic phases exert a pronounced effect on

M. Braunovic; N. Aleksandrov

1992-01-01

24

Development of New Cryocooler Regenerator Materials-Ductile Intermetallic Compounds  

SciTech Connect

The volumetric heat capacities of a number of binary and ternary Er- and Tm-based intermetallic compounds, which exhibited substantial ductilities, were measured from {approx}3 to {approx}350 K. They have the RM stoichiometry (where R = Er or Tm, and M is a main group or transition metal) and crystallize in the CsCl-type structure. The heat capacities of the Tm-based compounds are in general larger than the corresponding Er-based materials. Many of them have heat capacities which are significantly larger than those of the low temperature (<15 K) prototype cryocooler regenerator materials HoCu{sub 2}, Er{sub 3}Ni and ErNi. Utilization of the new materials as regenerators in the various cryocoolers should improve the performance of these refrigeration units for cooling below 15 K.

K.A. Gschneidner; A.O. Pecharsky; V.K. Pecharsky

2004-09-30

25

Intermetallic compounds as negative electrodes of Ni/MH batteries  

NASA Astrophysics Data System (ADS)

This review is devoted to the main families of thermodynamically stable intermetallic compounds (AB5-, AB2- and AB-type alloys) that have been researched in the last thirty years as materials for negative electrodes in nickel-metal hydride batteries. The crystal structure of these compounds and their hydrides is widely described. Their solid-gas hydrogenation properties and, particularly, the related desorption isotherm curves are examined as a useful criterion for the selection of suitable battery materials. The electrochemical performances obtained with these alloys are reported and the given solutions to common problems such as corrosion, passivation, decrepitation and short cycle life are discussed. Only AB5-based compounds have achieved, up to now, enough development for being widely present on the market, and exhibit improved battery performances in comparison with the polluting Ni/Cd batteries. The high capacity of AB2-based compounds and the remarkable electrochemical activity of some AB-based alloys make, however, further research on all the reviewed families still valuable.

Cuevas, F.; Joubert, J.-M.; Latroche, M.; Percheron-Guégan, A.

2001-04-01

26

X (X: Al, Mo, Ti, Pt, Si, Nb, V, and Zr) intermetallic compounds  

NASA Astrophysics Data System (ADS)

In the present study, the ground-state properties of Ni3X intermetallic compounds were analyzed by means of the first-principles pseudo-potential method using the Cambridge serial total energy package code. The calculated lattice parameters of Ni3X intermetallic compounds are in good agreement with the experimental and other theoretical data. The single-crystal elastic constants were calculated; the hardness, ductile, and plasticity of materials were analyzed. The calculated enthalpies of formation showed that all of intermetallic compounds were thermodynamically stable; Debye temperature and heat capacity are calculated and discussed. Moreover, the chemical bonding in these intermetallic compounds was interpreted by calculating the density of states, electron density difference distribution, and Mulliken analysis; magnetism properties were briefly analyzed.

Chen, Qiang; Huang, Zhiwei; Zhao, Zude; Hu, Chuankai

2014-09-01

27

Refinement of the lamellar structure in TiAl-based intermetallic compound by addition of carbon  

SciTech Connect

Intermetallic compounds based on TiAl are under extensive studies for structural materials in aerospace applications. Recently the effects of interstitial elements on the mechanical properties have been reported, which can be summarized as the enhancement of tensile strength and creep resistance. Appel reported that the creep resistance of TiAl alloy could be increased by carbon addition. Considering the important effect of carbon on the creep resistance of TiAl, it is important to gather more information on the basic role of carbon on the microstructure. In ingot alloys, there is an indication that the details of the fully lamellar structure were affected by carbon or nitrogen. This effect, however, has not been addressed in the intermetallic compound processed by powder metallurgical method. In this respect, the TiAl compound made by EPM (Elemental Powder Method) is of particular interest since this process is a potential alternative to ingot metallurgy for fabricating parts of complex shape. Recently the authors reported that a TiAl-Mn-Mo alloy could be successfully produced by EPM. In the present study, therefore, it was intended to study the effect of carbon on the phase transformation of this alloy of a FL (Fully Lamellar) microstructure.

Park, H.S.; Nam, S.W.; Kim, N.J.; Hwang, S.K.

1999-11-05

28

New Interest in Intermetallic Compound ZnSb  

NASA Astrophysics Data System (ADS)

The intermetallic compound ZnSb has been known since the 1830s. It has semiconductor properties, but its mechanical, thermal, and chemical properties are very close to those of a metallic alloy. When thermoelectrics based on (BiSb)2(TeSe)3 solid solutions were created, interest in ZnSb subsided. However, the current situation is different, as tellurium has become expensive and rare. Moreover, its compounds are too toxic, and it is too difficult to produce such materials and devices from these solid solutions. Recently, n-type material based on Mg2(SnSi) solid solution was proposed in the Laboratory of Physics for Thermoelements of the Ioffe Physical-Technical Institute. This material together with ZnSb may form a promising couple for creating various thermoelectric modules. In this paper, various properties (Hall and Seebeck coefficients, electrical and thermal conductivities) are reported in the temperature range from 80 K to 797 K. Different acceptor impurities have been tested. The Hall concentration at room temperature varied from 1.5 × 1018 cm-3 to 2.7 × 1019 cm-3. Some features have been discovered in the behavior of the thermoelectric parameters of double-doped ZnSb samples at temperatures above 500 K. Their nature points to a temperature-dependent increase of the Hall concentration. The existence of two temperature ranges with additional doping is revealed by Hall coefficient and electrical conductivity measurements in the range from 80 K to 797 K. The experimental data are discussed based on a model of the energy spectrum with impurity and native defect states localized in the energy gap. It is shown that the dimensionless thermoelectric figure of merit of ZnSb: Cd, Ag, Sn is not less than 1.0 at 600 K.

Fedorov, M. I.; Prokof'eva, L. V.; Pshenay-Severin, D. A.; Shabaldin, A. A.; Konstantinov, P. P.

2014-06-01

29

Surface integrity on grinding of gamma titanium aluminide intermetallic compounds  

NASA Astrophysics Data System (ADS)

Gamma-TiAl is an ordered intermetallic compound characterized by high strength to density ratio, good oxidation resistance, and good creep properties at elevated temperatures. However, it is intrinsically brittle at room temperature. This thesis investigates the potential for the use of grinding to process TiAl into useful shapes. Grinding is far from completely understood, and many aspects of the individual mechanical interactions of the abrasive grit with the material and their effect on surface integrity are unknown. The development of new synthetic diamond superabrasives in which shape and size can be controlled raises the question of the influence of those variables on the surface integrity. The goal of this work is to better understand the fundamentals of the abrasive grit/material interaction in grinding operations. Experimental, analytical, and numerical work was done to characterize and predict the resultant deformation and surface integrity on ground lamellar gamma-TiAl. Grinding tests were carried out, by analyzing the effects of grit size and shape, workpiece speed, wheel depth of cut, and wear on the subsurface plastic deformation depth (PDD). A practical method to assess the PDD is introduced based on the measurement of the lateral material flow by 3D non-contact surface profilometry. This method combines the quantitative capabilities of the microhardness measurement with the sensitivity of Nomarski microscopy. The scope and limitations of this technique are analyzed. Mechanical properties were obtained by quasi-static and split Hopkinson bar compression tests. Residual stress plots were obtained by x-ray, and surface roughness and cracking were evaluated. The abrasive grit/material interaction was accounted by modeling the force per abrasive grit for different grinding conditions, and studying its correlation to the PDD. Numerical models of this interaction were used to analyze boundary conditions, and abrasive size effects on the PDD. An explicit 2D triple planar slip crystal plasticity model of single point scratching was used to analyze the effects of lamellae orientation, material anisotropy, and grain boundaries on the deformation.

Murtagian, Gregorio Roberto

30

New Rare-Earth Transition-Metal Intermetallic Compounds and Metastable Phases for Permanent Magnetic Materials  

Microsoft Academic Search

After three generations of the discovery of rare-earth permanent magnets, based on SmCo5, Sm2Co17 and Nd2Fe14B Compounds, a great effort has been made on researching new rare-earth transition-metal (R-T) intermetallic Compounds in\\u000a permanent magnetic materials. The aim is to have a better understanding of structural and magnetic properties of the intermetallics\\u000a and to find new R-T Compounds possessing good intrinsic

Z. D. Zhang

31

Intermetallic compounds containing lanthanides (studies of magnetic anisotropy)  

Microsoft Academic Search

The powerful permanent magnetism of certain rare earth intermetallics (e.g., SmCo5) is a consequence of the strong magnetic anisotropy in these materials. Both sublattices contribute to magnetic anisotropy. Usually the contribution of the rare earth predominates over that of its chemical partner, a d-transition element in systems of practical interest. The rare earth anisotropy has been treated by quantum mechanics

W. E. Wallace

1977-01-01

32

Solid state intermetallic compound layer growth between copper and hot dipped indium coatings  

Microsoft Academic Search

Solid state growth of intermetallic compound layers that form between hot dipped indium coatings and copper was investigated in diffusion couples aged at temperatures of 70, 100 and 135 °C and time periods of up to 300 days. At an annealing temperature of 70 °C, the metastable composition, Cu36In64, was observed at the interface. Ageing at 100 °C caused a

P. T. Vianco; A. C. Kilgo; R. Grant

1995-01-01

33

An Investigation Into the Fabrication and Electrical Properties of NiAl Intermetallic Compound Thin Films  

Microsoft Academic Search

Ni-Al intermetallic compounds nanocrystalline thin films were deposited by direct current magnetron co-sputtering from elemental Ni and Al targets. The integrity of the thin films and their elemental compositions were assessed using a scanning electron microscope (SEM) equipped with an energy dispersive spectroscope analyzer. The morphologies of thin alloy films are density and smoothing characterized by atomic force microscope and

Jicheng Zhou; Jinbo Zhu; Jianwu Yan

2008-01-01

34

C15 intermetallic compounds HfV{sub 2}+Nb  

SciTech Connect

Phase fields and equilibria in the Hf-V-Nb system were determined using a combination-of SEM, EDS and x-ray diffraction. The structural stability of the C15 HfV{sub 2+}Nb was studied by x-ray diffraction and specific heat measurements. The elastic constants of C15 HfV{sub 2+}Nb were measured by the resonant ultrasound spectroscopy technique. First-principle quantum mechanical calculations based on the local-density-functional theory have been employed to study the total energy and electronic structure of C15 HfV{sub 2}, which can be used to understand the physical and metallurgical properties of the C15 intermetallics HfV{sub 2+}Nb.

Chu, F.; Chen, S.P.; Mitchell, T.E. [Los Alamos National Lab., NM (United States); Pope, D.P. [Pennsylvania Univ., Philadelphia, PA (United States). Dept. of Materials Science and Engineering; Liu, C.T. [Oak Ridge National Lab., TN (United States)

1994-12-31

35

Structural building principles of complex face-centered cubic intermetallics.  

PubMed

Fundamental structural building principles are discussed for all 56 known intermetallic phases with approximately 400 or more atoms per unit cell and space-group symmetry F43m, Fd3m, Fd3, Fm3m or Fm3c. Despite fundamental differences in chemical composition, bonding and electronic band structure, their complex crystal structures show striking similarities indicating common building principles. We demonstrate that the structure-determining elements are flat and puckered atomic {110} layers stacked with periodicities 2p. The atoms on this set of layers, which intersect each other, form pentagon face-sharing endohedral fullerene-like clusters arranged in a face-centered cubic packing (f.c.c.). Due to their topological layer structure, all these crystal structures can be described as (p × p × p) = p(3)-fold superstructures of a common basic structure of the double-diamond type. The parameter p, with p = 3, 4, 7 or 11, is determined by the number of layers per repeat unit and the type of cluster packing, which in turn are controlled by chemical composition. PMID:21775807

Dshemuchadse, Julia; Jung, Daniel Y; Steurer, Walter

2011-08-01

36

Optical properties of Group X-XII intermetallic compounds studied by HR-EELS.  

PubMed

Electronic structure of d orbital states in transition metals is a key factor for their physical properties and chemical functions. Copper and intermetallic compound PdZn have good catalysis function for the methanol steam reforming reaction. Tsai et al. showed that from results of XPS measurements the d electronic structure of PdZn was similar with that of copper, and the catalysis function should be related to the d electron states [1]. This similarity of d electronic states leads to another view point of the mechanism for coloring the intermetallic compounds. It is well-known that the characteristic red color of copper is caused by interband transition from the d electrons. Therefore, PdZn and Group X-XII intermetallic compounds are expected to be colored and the optical properties should depend on the d electronic states. In this study, the relations between optical properties and d electron states of Group X-XII intermetallic compounds were investigated by using high energy-resolution electron energy-loss spectroscopy (HR-EELS) based on transmission electron microscopy (TEM). From the relation between optical properties and d electronic states, the mechanism of colored intermetallic compounds will be discussed.Figure shows the optical reflectivity of NiZn, PdZn and PtZn, which were derived from EELS spectra by Kramers-Kronig analysis. Intensity drops (arrows) of the reflectivity were observed in visible energy region. These are caused by the interband transitions from d electronic states. The energy positions of the reflectivity drops have tendency of shifting to higher energy side with increasing atomic number of Group X elements (Ni ? Pd ? Pt). This indicates that the transition energies of d electrons become larger with the atomic number of the elements. First principle calculations (WIEN2k) confirmed that the interband transitions of d electronic states were excitations from bonding d states to hybrid states of anti-bonding s, p, and d states of Group X elements. The bonding anti-bonding energy split increase with the atomic numbers because of increasing crossover of wave function. This implies the intermetallic compounds should be colored and the color should be changed gradually depending on the atomic number of Group X elements. PMID:25359811

Sato, Yohei; Terauchi, Masami; Kameoka, Satoshi; Tsai, An-Pang

2014-11-01

37

Microscopic evidence for magnetic-phase coexistence in the intermetallic compound Nd7Rh3  

NASA Astrophysics Data System (ADS)

The intermetallic compound Nd7Rh3, which shows two magnetic transitions, one at 32 K and another around 16 K, has been known to exhibit a magnetic-field induced first-order magnetic phase transition (FOPT) at low temperatures. Using neutron diffraction we tracked the evolution of the magnetic features as a function of temperature and external magnetic field across the two transition temperatures. We provide evidence for the existence of both antiferromagnetism and ferromagnetism below 20 K. Notably the results reveal concrete evidence for the partial persistence of the high-field magnetic state at 2 K after cycling through the magnetic-field-induced magnetic transition, thereby offering microscopic evidence for magnetic coexistence phenomenon in this intermetallic compound.

Rayaprol, S.; Siruguri, V.; Hoser, A.; Ritter, C.; Sampathkumaran, E. V.

2014-10-01

38

Intermetallic compound layer growth kinetics in non-lead bearing solders  

SciTech Connect

The introduction of alternative, non-lead bearing solders into electronic assemblies requires a thorough investigation of product manufacturability and reliability. Both of these attributes can be impacted by the excessive growth of intermetallic compound (IMC) layers at the solder/substrate interface. An extensive study has documented the stoichiometry and solid state growth kinetics of IMC layers formed between copper and the lead-free solders: 96.5Sn-3.5Ag (wt.%), 95Sn-5Sb, 100Sn, and 58Bi-42Sn. Aging temperatures were 70--205 C for the Sn-based solders and 55--120 C for the Bi-rich solder. Time periods were 1--400 days for all of the alloys. The Sn/Cu, Sn-Ag/Cu, and Sn-Sb/Cu IMC layers exhibited sub-layers of Cu{sub 6}Sn{sub 5} and Cu{sub 3}Sn; the latter composition was present only following prolonged aging times or higher temperatures. The total layer growth exhibited a time exponent of n = 0.5 at low temperatures and a value of n = 0.42 at higher temperatures in each of the solder/Cu systems. Similar growth kinetics were observed with the low temperature 58Bi-42Sn solder; however, a considerably more complex sub-layer structure was observed. The kinetic data will be discussed with respect to predicting IMC layer growth based upon solder composition.

Vianco, P.T.; Kilgo, A.C.; Grant, R.

1995-04-01

39

Magnetism in Rare-Earth Metals and Rare-Earth Intermetallic Compounds  

Microsoft Academic Search

Some of our recent local spin density electronic structure calculations for a number of ferromagnetic rare-earth systems are reviewed. A simplified model of the level densities for rare-earth (R) transition metal (M) intermetallic compounds, RmMn, is used to describe in a simple way the main features of their basic electronic structure. Explicit calculations for LuFe2 and RFe2 (R = Gd-Yb)

Börje Johansson; Lars Nordström; Olle Eriksson; M. S. S. Brooks

1991-01-01

40

Multiphase Field Simulations of Intermetallic Compound Growth During Lead-Free Soldering  

Microsoft Academic Search

A multiphase field simulation of the morphological evolution of the intermetallic compounds (IMCs) formed during the reaction\\u000a between liquid Sn-based solder and a copper substrate is presented. The Cu-substrate, Cu3Sn (? phase), and Cu6Sn5 (? phase) layers (or grains), as well as the Sn-liquid phase are considered. Interfaces are defined by the presence of more\\u000a than one phase at a

M. S. Park; R. Arróyave

2009-01-01

41

Some regularities of melting points of AB-type intermetallic compounds  

Microsoft Academic Search

A modified cellular model is proposed for the investigation of melting point regularities of AB-type intermetallic compounds. By this model, five parameters of constituent elements: electronegativity difference, ?X; valence electron density difference, ?(ZR3); electron-atom ratio, ea; metallic radius ratio, RARB; and the average melting point of constituent elements, Tavg, are used to find a mathematical model for the melting point

L. Chonghe; Guo Jin; Qin Pei; Chen Ruiliang; Chen Nianyi

1996-01-01

42

Massive spalling of intermetallic compounds in solder-substrate reactions due to limited supply of the active element  

SciTech Connect

Massive spalling of intermetallic compounds has been reported in the literature for several solder/substrate systems, including SnAgCu soldered on Ni substrate, SnZn on Cu, high-Pb PbSn on Cu, and high-Pb PbSn on Ni. In this work, a unified thermodynamic argument is proposed to explain this rather unusual phenomenon. According to this argument, two necessary conditions must be met. The number one condition is that at least one of the reactive constituents of the solder must be present in a limited amount, and the second condition is that the soldering reaction has to be very sensitive to its concentration. With the growth of intermetallic, more and more atoms of this constituent are extracted out of the solder and incorporated into the intermetallic. As the concentration of this constituent decreases, the original intermetallic at the interface becomes a nonequilibrium phase, and the spalling of the original intermetallic occurs.

Yang, S. C.; Ho, C. E.; Chang, C. W.; Kao, C. R. [Department of Chemical and Materials Engineering, National Central University, Jhongli City, Taiwan (China); Department of Materials Science and Engineering, National Taiwan University, Taipei, Taiwan (China)

2007-04-15

43

Low temperature properties of some Er-rich intermetallic compounds  

SciTech Connect

The low temperature volumetric heat capacity ({approx}3.5 to 350 K) and magnetic susceptibility ({approx}4 to 320 K) of Er{sub 3}Rh, Er{sub 3}Ir, Er{sub 3}Pt, Er{sub 2}Al, and Er{sub 2}Sn have been measured. All of the compounds order antiferromagnetically (or ferrimagnetically), and most exhibit more than one magnetic ordering transition. The volumetric heat capacities in general are smaller than those of the prototype magnetic regenerator materials, except for Er{sub 3}Ir in the 12 to 14 K temperature range.

K.A. Gshneidner,jr; A.O. Pecharsky; L.Hale; V.K. Pecharsky

2004-09-30

44

Long-Term Behavior of the Tritides Formed by Nickel-Based Intermetallic Compounds  

SciTech Connect

Some properties of the tritide phases formed by the intermetallic compounds Mg2Ni, ZrNi, and LaNi5 have been studied. Whereas ZrNiT3 will retain its stoichiometry indefinitely when sufficient gaseous tritium is available, the stoichiometries of Mg2NiT4 and LaNi5T6.9 decrease with time. Although all three intermetallic tritides can retain large quantities of the helium-3 tritium decay daughter product in the solid phase, irreversible release of helium begins after several hundred days for ZrNiTx and Mg2NiTx. However, LaNi5Tx retains all of the helium generated in the solid for at least 2400 days. NMR measurements for ZrNiTx and Mg2NiTx imply that helium is retained in microscopic bubbles as previously observed in several binary metal tritides.

Bowman, Jr., R. C.; Steinmeyer, R. H.; Matson, L. K.; Attalla, A.; Craft, B. D.

1985-04-01

45

The use of high magnetic fields at the study of magnetism and superconductivity in intermetallic compounds  

SciTech Connect

Magnetic fields have a large impact on the magnetic and superconducting properties of solids. High magnetic fields are required to reach magnetic saturation along a hard magnetic direction in a variety of rare-earth intermetallics, to break the ferrimagnetic moment configuration in specific 3d-4f intermetallics, to quench the strongly correlated electron states in heavy fermion compounds, to reach the upper critical fields in several classes of superconductors, to study flux-pinning phenomena in the high-{Tc} superconductors, etc. In the present review, the attention is focused to the field interval 20--50 tesla. Experiments in this field range are the privilege of specialized high magnetic field laboratories. There is a lively activity in this area of research with the number of participating institutes continuously growing.

Franse, J.J.M.; Boer, F.R. de; Frings, P.H.; Visser, A. de [Univ. of Amsterdam (Netherlands). Van der Waals-Zeeman Lab.] [Univ. of Amsterdam (Netherlands). Van der Waals-Zeeman Lab.

1994-03-01

46

Optical properties of intermetallic compounds from first principles calculations: a search for the ideal plasmonic material.  

PubMed

First principles calculations have been used to predict the optical properties for a range of intermetallic compounds for which little or no experimental optical data are currently available. Density functional theory combined with the random phase approximation is used to calculate the dielectric functions for these compounds. The aim of this work is to investigate how the band edge and plasma frequency vary with composition in order to identify materials with promising plasmonic properties. Towards this end the intermetallic compounds chosen are composed of elements which on their own have reasonable optical properties for plasmonic applications. The position of the band edge relative to the plasma frequency is most favourable in the simple binary compounds formed from the alkali plus noble metals NaAu, KAu and KAg. In particular, for KAu the band edge and plasma frequency occur at almost the same frequency, and hence the imaginary part of the dielectric function is practically zero for frequencies below the plasma frequency. In addition, the plasma frequency in this compound is at relatively low frequency, promising a material with strong plasmon response in the infrared. PMID:21825328

Blaber, M G; Arnold, M D; Ford, M J

2009-04-01

47

Degradation behavior of Ca-Mg-Zn intermetallic compounds for use as biodegradable implant materials.  

PubMed

With the goal of developing new biodegradable implant materials, we have investigated the degradation behavior of (Ca, Mg)-based intermetallic compounds. The degradation behavior of the compounds within the Ca-Mg-Zn system was roughly classified into four groups, and their behaviors were strongly influenced by the compositions of the compounds. For example, the Ca3MgxZn(15-x) compound exhibited a large solubility region with varying the Mg/Zn ratio, and the Ca3Mg12Zn3 phase alloy with the lowest Zn content was rapidly broken apart within 6h of immersion. Alternatively, the Ca3Mg4.6Zn10.4 phase alloy with the highest Zn content retained the bulk shape even after 250h of immersion. These varying degradation behaviors were ascribed to the difference in the formability of Zn oxide as a protective layer against corrosion on the specimen surfaces, depending on the Zn content. The gained results suggest that there is a feasibility on developing new biodegradable materials based on intermetallic compounds in which the degradation rate can be controlled by their compositions. PMID:25280708

Hagihara, Koji; Shakudo, Shuhei; Fujii, Kenta; Nakano, Takayoshi

2014-11-01

48

Structural plasticity: how intermetallics deform themselves in response to chemical pressure, and the complex structures that result.  

PubMed

Interfaces between periodic domains play a crucial role in the properties of metallic materials, as is vividly illustrated by the way in which the familiar malleability of many metals arises from the formation and migration of dislocations. In complex intermetallics, such interfaces can occur as an integral part of the ground-state crystal structure, rather than as defects, resulting in such marvels as the NaCd2 structure (whose giant cubic unit cell contains more than 1000 atoms). However, the sources of the periodic interfaces in intermetallics remain mysterious, unlike the dislocations in simple metals, which can be associated with the exertion of physical stresses. In this Article, we propose and explore the concept of structural plasticity, the hypothesis that interfaces in complex intermetallic structures similarly result from stresses, but ones that are inherent in a defect-free parent structure, rather than being externally applied. Using DFT-chemical pressure analysis, we show how the complex structures of Ca2Ag7 (Yb2Ag7 type), Ca14Cd51 (Gd14Ag51 type), and the 1/1 Tsai-type quasicrystal approximant CaCd6 (YCd6 type) can all be traced to large negative pressures around the Ca atoms of a common progenitor structure, the CaCu5 type with its simple hexagonal 6-atom unit cell. Two structural paths are found by which the compounds provide relief to the Ca atoms' negative pressures: a Ca-rich pathway, where lower coordination numbers are achieved through defects eliminating transition metal (TM) atoms from the structure; and a TM-rich path, along which the addition of spacer Cd atoms provides the Ca coordination environments greater independence from each other as they contract. The common origins of these structures in the presence of stresses within a single parent structure highlights the diverse paths by which intermetallics can cope with competing interactions, and the role that structural plasticity may play in navigating this diversity. PMID:25238606

Berns, Veronica M; Fredrickson, Daniel C

2014-10-01

49

Magnetic properties and magnetocaloric effects in Er3-xGdxCo intermetallic compounds  

NASA Astrophysics Data System (ADS)

A series of intermetallic Er3-xGdxCo (x = 0.5-3) compounds were synthesized and their magnetic properties and magnetocaloric effects were investigated. The Neél temperature (TN) could be tuned from 28 to 129 K by partially replacement of Gd with Er. For a field change of 5 T, the Er1.5Gd1.5Co exhibited a minimum -?SM of 9.8 J/kg K and maximum refrigerant capacity power (RCP) value of 629 J/kg which originated from an enlarged temperature span of magnetic entropy change in the compound. Results demonstrate that it is a feasible way to search for a large RCP material from the compounds with two magnetic transitions and controlled temperature region.

Mo, Zhao-Jun; Shen, Jun; Yan, Li-Qin; Wu, Jian-Feng; Tang, Cheng-Chun; Shen, Bao-Gen

2013-01-01

50

Multiconfigurational nature of 5f orbitals in uranium and plutonium and their intermetallic compounds  

NASA Astrophysics Data System (ADS)

The structural, electronic, and magnetic properties of U and Pu elements and intermetallics remain poorly understood despite decades of effort, and currently represent an important scientific frontier toward understanding matter. The last decade has seen great progress both due to the discovery of superconductivity in PuCoGa5 and advances in theory that finally can explain fundamental ground state properties in elemental plutonium, such as the phonon dispersion curve, the non-magnetic ground state, and the volume difference between the ? and ? phases. A new feature of the recent calculations is the presence not only of intermediate valence of the Pu 5f electrons, but of multiconfigurational ground states, where the different properties of the ? and ? phases are primarily governed by the different relative weights of the 5f^4, 5f^5, and 5f^6 electronic configurations. The usual method for measuring multiconfigurational states in the lanthanides is to measure the lanthanide LIII-edge x-ray absorption near-edge structure (XANES), a method that is severely limited for the actinides because the spectroscopic features are not well enough separated. Advances in resonant x-ray emission spectroscopy (RXES) have now allowed for spectra with sufficient resolution to resolve individual resonances associated with the various actinide valence states. Utilizing a new spectrometer at the Stanford Synchrotron Radiation Lightsource (SSRL), RXES data have been collected that show, for the first time, spectroscopic signatures of each of these configurations and their relative changes in various uranium and plutonium intermetallic compounds. In combination with conventional XANES spectra on related compounds, these data indicate such states may be ubiquitous in uranium and plutonium intermetallics, providing a new framework toward understanding properties ranging from heavy fermion behavior, superconductivity, and intermediate valence to mechanical and fundamental bonding behavior in these materials.

Booth, Corwin

2013-03-01

51

Complex Compound Chemical Heat Pumps  

E-print Network

Complex-compound solid-vapor fluid pairs can be used in heat of reaction heat pumps for temperature amplifier (TA) as well as heat amplifier (HA) cycle configurations. This report describes the conceptual hardware design for complex compound...

Rockenfeller, U.; Langeliers, J.; Horn, G.

52

Superplasticity and solid state bonding of the TiAl intermetallic compound with micro- and submicrocrystalline structure  

SciTech Connect

The use of superplastic phenomenon makes it possible to reduce considerably the temperature of solid state bonding of the TiAl intermetallic compound as compared with conventional diffusion bonding. At decreasing the superplastic deformation temperature due to the reduction of the grain size an adequate decrease of the temperature threshold of solid state weldability of the TiAl intermetallic compound was observed. In the TiAl intermetallic compound with submicrocrystalline grain size the formation of a sound solid state joint occurs in the process of deformation at the temperature t = 850 C and strain {var_epsilon} = 10%. Since the temperature-strain-rate conditions of solid state bonding and those of superplasticity coincide, it is assumed that the mechanism controlling the bonding process is grain boundary sliding, the main deformation mechanism of superplasticity.

Lutfullin, R.Ya.; Imayev, R.M.; Kaibyshev, O.A.; Hismatullin, F.N.; Imayev, V.M. [Russian Academy of Sciences, Ufa (Russian Federation). Inst. for Metals Superplasticity Problems] [Russian Academy of Sciences, Ufa (Russian Federation). Inst. for Metals Superplasticity Problems

1995-11-01

53

Characterization of second-phase plates in a Gd5Ge3 intermetallic compound  

SciTech Connect

Rare-earth compounds based on the stoichiometry R5(SixGe1?x)4 (R = rare-earth elements) exhibit many unusual features, including possessing R5(SixGe1?x)3 thin plates which always precipitate from the matrix despite efforts to suppress their formation. In an effort to better understand the unique relationship between these two intermetallic alloy systems, the bulk microstructure of the compound Gd5Ge3 was examined using scanning (SEM) and transmission electron microscopy (TEM) and optical microscopy. Surprisingly, SEM examination revealed a series of thin plates present in the Gd5Ge3 matrix similar to what is seen in Gd5Ge4. TEM observation revealed that a role reversal had occurred, with the thin plates possessing the orthorhombic structure and composition of Gd5Ge4. The orientation relationship between Gd5Ge4 thin plates and the Gd5Ge3 matrix was determined to be Graphic the same relationship reported for Gd5Ge3 plates precipitating from a Gd5Ge4 matrix. However, by exchanging the respective roles of the phases as regards matrix vs. precipitate, the total number of precipitation variants seen can be increased from two to six. The persistence with which these two intermetallic systems co-exist is truly unique. However, understanding exactly the kinetic and thermodynamic conditions that lead to their unique relationship is hampered by the high formation temperatures at which the observed reaction occurs.

Cao, Qing [Ames Laboratory; Chumbley, Leonard S. [Ames Laboratory

2013-05-16

54

The corrosion behavior of the T1 (Al2CuLi) intermetallic compound in aqueous environments  

NASA Technical Reports Server (NTRS)

The intermetallic compound T1 (Al2CuLi) is suspected to play an important role in the localized corrosion at subgrain boundaries in Al-Li-Cu alloys. The intermetallic was synthesized for characterization of its corrosion behavior. Experiments performed included open circuit potential measurements, potentiodynamic polarization, and corrosion rate vs. pH in solutions whose pH was varied over the range of 3 to 11. Subgrain boundary pitting and continuous subgrain boundary corrosion are discussed in terms of the data obtained. Evidence suggesting the dealloying of copper from this compound is also presented.

Buchheit, R. G.; Stoner, G. E.

1989-01-01

55

Composition dependence of atomic mobility in single phase {gamma} TiAl intermetallic compounds  

SciTech Connect

Pure, single phase TiAl intermetallic compounds, with a low oxygen concentration, were investigated as a function of aluminum content. Their structural state was characterized by residual electrical resistivity measurements. In the alloys with 50 to 54.5 at% Al, reversible resistivity variations, consistent with small changes of the degree of long-range order, were detected during thermal treatments at increasing then decreasing temperatures (in the range 820--1020 K for the stoichiometric alloy). From these variations, two main conclusions concerning the atomic mobility in these alloys can be derived: (1) atomic mobility is composition dependent -- it increases significantly as the deviation from stoichiometry increases, i.e. for higher aluminum contents; and (2) the comparison of stoichiometric Ni{sub 3}Al and TiAl shows that atomic mobility is smaller in the latter compound.

Dimitrov, C.; Martin, N.; Fekkar, H.; Dimitrov, O. [CECM-CNRS, Vitry-sur-Seine (France)] [CECM-CNRS, Vitry-sur-Seine (France)

1996-05-01

56

First principles calculations of the optical and plasmonic response of Au alloys and intermetallic compounds  

NASA Astrophysics Data System (ADS)

Pure Au is widely used in plasmonic applications even though its use is compromised by significant losses due to damping. There are some elements that are less lossy than Au (e.g. Ag or Al) but they will normally oxidize or corrode under ambient conditions. Here we examine whether alloying Au with a second element would be beneficial for plasmonic applications. In order to evaluate potential alternatives to pure Au, the density of states (DOS), dielectric function and plasmon quality factor have been calculated for alloys and compounds of Au with Al, Cd, Mg, Pd, Pt, Sn, Ti, Zn and Zr. Substitutional alloying of Au with Al, Cd, Mg and Zn was found to slightly improve the plasmonic response. Of the large number of intermetallic compounds studied, only AuAl2, Au3Cd, AuMg, AuCd and AuZn were found to be suitable for plasmonic applications.

Keast, V. J.; Barnett, R. L.; Cortie, M. B.

2014-07-01

57

Crystal structure and chemical bonding of novel Li-containing polar intermetallic compound La11Li12Ge16  

NASA Astrophysics Data System (ADS)

A novel Li-containing polar intermetallic compound La11Li12Ge16 has been synthesized using the high-temperature reaction method and characterized by both powder and single-crystal X-ray diffractions. The title compound crystallized in the orthorhombic crystal system (space group Immm, Z=2, Pearson symbol oI78) with fifteen crystallographically unique atomic positions in the asymmetric unit, and the lattice parameters are refined as a=4.5244(4) Å, b=6.9932(6) Å, and c=53.043(5) Å. The complex crystal structure of the title compound can be described as a 2:1 intergrowth of two closely related compounds: La2Li2Ge3 (Ce2Li2Ge3-type) and La3Li4Ge4 (Zr3Cu4Si4-type) acting like "building-blocks" along the c-axis. Six La sites are categorized into three distinct types based on the local coordination environment showing the coordination numbers of 12-14. Three unique Li sites are placed in the centers of local tetrahedra formed by four Ge atoms which eventually construct Ge2 dimers or 1-dimensional cis-/trans-Ge chains. Theoretical investigations using the tight-binding linear muffin-tin orbital (LMTO) method provide rationales for an improved structural stability and for unique local coordination geometries established by anionic elements including [LiGe4] tetrahedra, cis-/trans-Ge chain and Ge2 dimers.

Jung, Yaho; Nam, Gnu; Jeon, Jieun; Kim, Youngjo; You, Tae-Soo

2012-12-01

58

Hyperfine interactions in intermetallic rare earth-gallium compounds studied by 111 Cd PAC  

NASA Astrophysics Data System (ADS)

Magnetic and electric hyperfine interaction of the nuclear probe 111In/111Cd in intermetallic compounds of the rare earth-gallium system have been investigated by perturbed angular correlation (PAC) spectroscopy. The PAC measurements, supported by X-ray diffraction, provide evidence for a marked phase preference of 111In for hexagonal RGa2 over orthorhombic RGa and of RGa3 with the L12 structure over RGa2. In the case of SmGa2, the magnetic hyperfine field Bhf, the electric quadrupole interaction and the angle ? between Bhf and the symmetry axis of the electric field gradient have been determined as a function of temperature. The angle ? = 0 is consistent with the results of previous magnetization studies. Up to T ? 17 K the magnetic hyperfine field has a constant value of Bhf = 3.0(2) T. The rapid decrease at higher T gives the impression of a first-order transition with an order temperature of TN = 19.5 K. In the RKKY model of indirect 4 f interaction the ratio TC/Bhf(0) is a measure of the coupling constant. For 111Cd:SmGa2 (TC/Bhf(0)~6.5 K/T) this ratio is significantly smaller than for the same probe in other R intermetallics (SmAl2 ~9.5 K/T, Sm2In ~13.5 K/T).

Cavalcante, F. H. M.; Pereira, L. F. D.; Saitovitch, H.; Mestnik-Filho, J.; Pasquevich, A. F.; Forker, M.

2013-05-01

59

Structural analysis of the intermetallic surface compound CePt5/Pt (111 )  

NASA Astrophysics Data System (ADS)

We report on a detailed low-energy electron diffraction (LEED) and low-temperature scanning tunneling microscopy (STM) study of the intermetallic surface compound CePt5 on Pt(111). Depending on the thickness we observe various diffraction patterns and superstructures. In the low-thickness regime a slightly compressed (2 ×2 ) superstructure is aligned along the <1 1 ¯0 > direction of the Pt(111) substrate. STM reveals another, much larger superstructure with a periodicity of (9.02 ±0.45 ) nm presumably responsible for the strongly broadened LEED spots. At about 3 unit cells (u.c.) the surface is dominated by a (3 ?{3 }×3 ?{3 }) R 30? pattern as revealed by LEED satellites and Fourier-transformed high-resolution STM images. It is interpreted as a moiré pattern between the film and the substrate. We precisely determine the superstructure of the intermetallic film to (10/9 ?{3 }×10/9 ?{3 }) R 30? with respect to the Pt(111) substrate. Above 3 u.c. the satellites progressively disappear. A model is developed that consistently describes this thickness-dependent transition. For CePt5 films with a thickness between 6 and 11 u.c. the lattice of the compressed (2 ×2 ) superstructure rotates back into the substrate's <1 1 ¯0 > directions.

Kemmer, Jeannette; Praetorius, Christian; Krönlein, Andreas; Hsu, Pin-Jui; Fauth, Kai; Bode, Matthias

2014-11-01

60

Photoemission Study of the Rare Earth Intermetallic Compounds: RNi2Ge2 (R=Eu, Gd)  

SciTech Connect

EuNi{sub 2}Ge{sub 2} and GdNi{sub 2}Ge{sub 2} are two members of the RT{sub 2}X{sub 2} (R = rare earth, T = transition metal and X = Si, Ge) family of intermetallic compounds, which has been studied since the early 1980s. These ternary rare-earth intermetallic compounds with the tetragonal ThCr{sub 2}Si{sub 2} structure are known for their wide variety of magnetic properties, Extensive studies of the RT{sub 2}X{sub 2} series can be found in Refs [ 1,2,3]. The magnetic properties of the rare-earth nickel germanides RNi{sub 2}Ge{sub 2} were recently studied in more detail [4]. The purpose of this dissertation is to investigate the electronic structure (both valence band and shallow core levels) of single crystals of EuNi{sub 2}Ge{sub 2} and GdNi{sub 2}Ge{sub 2} and to check the assumptions that the f electrons are non-interacting and, consequently, the rigid-band model for these crystals would work [11], using synchrotron radiation because, to the best of our knowledge, no photoemission measurements on those have been reported. Photoemission spectroscopy has been widely used to study the detailed electronic structure of metals and alloys, and especially angle-resolved photoemission spectroscopy (ARPES) has proven to be a powerful technique for investigating Fermi surfaces (FSs) of single-crystal compounds.

Jongik Park

2004-12-19

61

Gas atomization synthesis of refractory or intermetallic compounds and supersaturated solid solutions  

DOEpatents

A metallic melt is atomized using a high pressure atomizing gas wherein the temperature of the melt and the composition of the atomizing gas are selected such that the gas and melt react in the atomization spray zone to form a refractory or intermetallic compound in the as-atomized powder particles. A metallic melt is also atomized using a high pressure atomizing gas mixture gas wherein the temperature of the melt and the ratio of a reactive gas to a carrier gas are selected to form powder particles comprising a supersaturated solid solution of the atomic species of the reactive gas in the particles. The powder particles are then heat treated to precipitate dispersoids in-situ therein to form a dispersion strengthened material. 9 figures.

Anderson, I.E.; Lograsso, B.K.; Ellis, T.W.

1994-11-29

62

Gas atomization synthesis of refractory or intermetallic compounds and supersaturated solid solutions  

DOEpatents

A metallic melt is atomized using a high pressure atomizing gas wherein the temperature of the melt and the composition of the atomizing gas are selected such that the gas and melt react in the atomization spray zone to form a refractory or intermetallic compound in the as-atomized powder particles. A metallic melt is also atomized using a high pressure atomizing gas mixture gas wherein the temperature of the melt and the ratio of a reactive gas to a carrier gas are selected to form powder particles comprising a supersaturated solid solution of the atomic species of the reactive gas in the particles. The powder particles are then heat treated to precipitate dispersoids in-situ therein to form a dispersion strengthened material.

Anderson, Iver E. (Ames, IA); Lograsso, Barbara K. (Ames, IA); Ellis, Timothy W. (Ames, IA)

1994-01-01

63

The effect of crystal structure stability on the mobility of gas bubbles in intermetallic uranium compounds  

SciTech Connect

Irradiation experiments with certain low-enrichment, high-density, uranium-base intermetallic alloys that are candidate reactor fuel materials, such as U/sub 3/Si and U/sub 6/Fe, have revealed extraordinarily large voids at low and medium fuel burnup. This phenomenon of breakaway swelling does not occur in other fuel types, such as U/sub 3/Si/sub 2/ and UAl/sub 3/, where a distribution of relatively small and stable fission gas bubbles forms. In situ transmission electron microscope observations of ion radiation-induced rapid swelling of intermetallic materials are consistent with growth by plastic flow. Large radiation enhancement of plastic flow in amorphous materials has been observed in several independent experiments and is thought to be a general materials phenomenon. The basis for a microscopic theory of fission gas bubble behavior in irradiated amorphous compounds has been formulated. The assumption underlying the overall theory is that the evolution of the porosity from that observed in the crystalline material to that observed in irradiated amorphous U/sub 3/Si as a function of fluence is due to a softening of the irradiated amorphous material. Bubble growth in the low-viscosity material has been approximated by an effective enhanced diffusivity. Mechanisms are included for the radiation-induced softening of the amorphous material, and for a relation between gas atom mobilities and radiation-induced (defect-generated) changes in the material. Results of the analysis indicate that the observed rapid swelling in U/sub 3/Si arises directly from enhanced bubble migration and coalescence due to plastic flow. 34 refs., 11 figs.

Rest, J.; Hofman, G.L.; Birtcher, R.C.

1988-01-01

64

Growth of a Au-Ni-Sn intermetallic compound on the solder-substrate interface after aging  

SciTech Connect

Au/Ni metallization has become increasingly common in microelectronic packaging when Cu pads are joined with Pb-Sn solder. The outermost Au layer serves to protect the pad from corrosion and oxidation and the Ni layer provides a diffusion barrier to inhibit detrimental growth of Cu-Sn intermetallics. As a result of reflowing eutectic Pb-Sn on top of Au/Ni metallization, the as-solidified joints have AuSn{sub 4} precipitates distributed throughout the bulk of the solder joint, and Ni{sub 3}Sn{sub 4} intermetallics at the interface. Recent work has shown that the Au-Sn redeposits onto the interface during aging, compromising the strength of the joint. The present work shows that the redeposited intermetallic layer is a ternary compound with stoichiometry Au{sub 0.5}Ni{sub 0.5}Sn{sub 4}. The growth of this intermetallic layer was investigated, and results show that the ternary compound is observed to grow after as little as 3 hours at 150 C and after 3 weeks at 150 C has grown to a thickness of 10 {micro}m. Additionally, methods for inhibiting the growth of the ternary layer were investigated and it was determined that multiple reflows, both with and without additional aging can substantially limit the thickness of the ternary layer.

Minor, Andrew M.; Morris, J.W., Jr.

1999-12-16

65

Near-net shape processing of TiAl intermetallic compounds by pseudo HIP-SHS  

SciTech Connect

In this study, the authors present a new fabrication route based on a combination of Pseudo-HIP and SHS (self-propagating high-temperature synthesis) for producing TiAl intermetallic compounds. Near-net shape products with nearly full density were produced by the utilization of heat release and transient liquid phase involved in SHS under mechanical pressure by Pseudo-HIP. Microstructural control was conducted by subsequent heat treatment after the SHS. The fine grains obtained, consisting of equiaxed gamma and alpha2 by PseudoHIP-SHS, resulted in an improvement in the deformability of Ti-rich TiAl at high temperatures. Reactive bonding of TiAl can also be achieved by using the PseudoHIP-SHS process. Two elemental metal powder compacts set in Pseudo-HIP were bonded at the time of the reactive sintering of the compacts. Insert materials of elemental metal mixtures can be used for the bonding of TiAl compounds using Pseudo-HIP or uniaxial press.

Taguchi, K.; Ayada, M. [NHK Spring R and D Center, Inc., Yokohama (Japan); Ishihara, K.N.; Shingu, P.H. [Kyoto Univ. (Japan). Dept. of Energy Science and Engineering

1995-12-31

66

Magnetic field controlled floating-zone single crystal growth of intermetallic compounds  

NASA Astrophysics Data System (ADS)

Radio-frequency (RF) floating zone single crystal growth is an important technique for the preparation of single bulk crystals. The advantage of the floating-zone method is the crucible-free growth of single crystals of reactive materials with high melting points. The strong heat diffusion on the surface, as well as the melt convection in the molten zone due to induction heating, often leads to an undesired solid-liquid interface geometry with a concave (towards the solid phase) outer rim. These concave parts aggravate the single crystal growth over the full cross-section. A two-phase stirrer was developed at IFW Dresden in order to avoid the problems connected with these concave parts. It acts as a magnetic field pump and changes the typical double vortex structure to a single roll structure, thus pushing hot melt into the regions where the concave parts may arise. The current in the secondary coil is induced by the primary coil, and the capacitor and the resistance of the secondary circuit are adjusted to get a stable 90 degree phase-shift between the coil currents. Single crystal growth of industrial relevant RuAl and TiAl intermetallic compounds was performed based on the material parameters and using the adjusted two-phase stirrer. Very recently, the magnetic system was applied to the crystal growth of biocompatible TiNb alloys and antiferromagnetic Heusler MnSi compounds.

Hermann, R.; Gerbeth, G.; Priede, J.

2013-03-01

67

Effect of surface finish metallurgy on intermetallic compounds during soldering with tin-silver-copper solders  

Microsoft Academic Search

Solder joint reliability is dependent on both thickness and morphology of the intermetallics that form and grow at the solder joint interface during soldering and subsequent thermal ageing and examining the morphology of these intermetallics is of great importance. The focus of this paper is to present experimental results of a comprehensive study of the interfacial reactions during soldering of

A. Ourdjini; M. A. Azmah Hanim; I. Siti Rabiatull Aisha; Y. T. Chin

2008-01-01

68

Influence of notch shape and geometry during creep crack growth testing of TiAl intermetallic compounds  

Microsoft Academic Search

In order to establish the optimum pre-crack shape and geometry for creep crack growth (CCG) testing of high-temperature brittle materials, several shapes of starter notches were evaluated experimentally on TiAl intermetallic compound. Fatigue pre-cracks are frequently inappropriate in these materials because they tend to promote out-of-plane crack growth in the lamellar structured TiAl materials. Based on the experimental results with

Akio Fuji; Masaaki Tabuchi; A. Toshimitsu Yokobori; Takeo Yokobori

1999-01-01

69

Computational investigation of intermetallic compounds (Cu 6Sn 5 and Cu 3Sn) growth during solid-state aging process  

Microsoft Academic Search

Computational investigations of the morphological evolution and growth kinetics for intermetallic compounds (IMCs, Cu6Sn5 and Cu3Sn) formed during reaction and aging between Sn-based solder and a copper substrate are presented. Cu-substrate, Cu3Sn (? phase) and Cu6 Sn5 (? phase) layers (or grains), as well as the Sn-liquid phase (or Sn-solid phase) are considered during the soldering (solid-state aging) process. In

M. S. Park; R. Arróyave

2011-01-01

70

Model-based predictions of solid state intermetallic compound layer growth in hybrid microelectronic circuits  

SciTech Connect

A mathematical model was developed to quantitatively describe the intermetallic compound (IMC) layer growth that takes place between a Sn-based solder and a noble metal thick film conductor material used in hybrid microcircuit (HMC) assemblies. The model combined the reaction kinetics of the solder/substrate interaction, as determined from ancillary isothermal aging experiments, with a 2-D finite element mesh that took account of the porous morphology of the thick film coating. The effect of the porous morphology on the IMC layer growth when compared to the traditional 1-D computations was significant. The previous 1-D calculations under-predicted the nominal IMC layer thickness relative to the 2-D case. The 2-D model showed greater substrate consumption by IMC growth and lesser solder consumption that was determined with the 1-D computation. The new 2-D model allows the design engineer to better predict circuit aging and hence, the reliability of HMC hardware that is placed in the field.

Vianco, P.T.; Erickson, K.L.; Hopkins, P.L.

1997-12-31

71

Transition of Roughness Evolution in Cu-In Alloy Films by the Formation of Intermetallic Compounds  

NASA Astrophysics Data System (ADS)

The evolution of the surface morphology of Cu-In alloy film has been studied using an atomic force microscope. Samples of Cu-In were prepared by sequential vacuum deposition: copper was deposited to 10-40 nm thick first on a glass substrate, followed by the deposition of various amounts of indium to make the indium composition in the range of 0-75 at.%. Samples were prepared under three different conditions: A) deposited at room temperature (RT); B) deposited at RT and annealed at 120°C in vacuo; and C) deposited at 120°C. Samples formed by A and B (series A and B) showed a growth with a dynamical exponent ? of ˜0.3 while the atomic ratio In/Cu was less than 2. The formation of CuIn2 intermetallic compound was observed by X-ray diffraction as the atomic ratio approached 2. After that, ? suddenly increased to ˜0.7, which was attributed to the segregation of excess indium atoms to form cap-shaped islands. For samples grown by C (series C), the roughness initially increased more rapidly with ?˜ 0.7 and decreased above In/Cu˜ 1. It showed a minimum at In/Cu=2 and finally increased again with ?˜ 0.7 by forming indium islands, as in series A and B.

Nakano, Takeo; Mizuhashi, Hiroshi; Baba, Shigeru

2005-04-01

72

The oxidation resistance of a sputtered, microcrystalline TiAl-intermetallic-compound film  

SciTech Connect

The oxidation behavior of a cast TiAl intermetallic compound and its sputtered microcrystalline film was investigated at 700-900{degrees}C in static air. At 700{degrees}C, both the cast alloy and its sputtered microcrystalline film exhibited excellent oxidation resistance. No scale spallation was observed. However, at 800-900{degrees}C, the oxidation kinetics for the cast TiAl alloy followed approximately a linear rate law, which indicates that it has poor oxidation resistance over this temperature range. The poor oxidation resistance of TiAl was due to the formation of an Al{sub 2}O{sub 3}+TiO{sub 2} scale which spalled extensively during cooling. Nevertheless, the sputtered, TiAl-microcrystalline film exhibited very good oxidation resistance. The oxidation kinetics followed approximately the parabolic rate law at all temperatures. Although the composition of the scales was the same as that of scales formed on the cast alloy, the scales formed on the sputtered microcrystalline-TiAl film are adherent strongly to the substrate. No scale spallation was found at 700-850{degrees}C, while a small amount of spallation was observed only at 900{degrees}c. This indicates that microcrystallization can improve the oxidation resistance of the TiAl alloy.

Fuhui Wang; Hanyi Lou; Weitao Wu [Corrosion Science Lab., Shenyang (China)

1995-06-01

73

Investigation of the Growth of Intermetallic Compounds Between Cu Pillars and Solder Caps  

NASA Astrophysics Data System (ADS)

In flip chip applications, Cu pillars with solder caps are regarded as next-generation electronic interconnection technology, because of high input/output density. However, because of diffusion and reaction of Sn and Cu during the high-temperature reflow process, intermetallic compounds (IMC) are formed, and grow, at the interface between the cap and the pillar. Understanding the growth behavior of interfacial IMC is critical in the design of solder interconnections, because excessive growth of IMC can reduce the reliability of connections. In this study, the growth of IMC during thermal cycling, an accelerated method of testing the service environment of electronic devices, was studied by use of focused ion beam-scanning electron microscopy. Under alternating high and low-temperature extremes, growth of Cu6Sn5 ( ?-phase) and Cu3Sn ( ?-phase) IMC was imaged and measured as a function of the number of cycles. The total IMC layer grew significantly thicker but became more uniform during thermal cycling. The Cu3Sn layer was initially thinner than the Cu6Sn5 layer but outgrew the Cu6Sn5 layer after 1000 cycles. It was found that, with limited Cu and Sn diffusion, consumption of Cu6Sn5 for growth of the Cu3Sn layer can result in a thinner Cu6Sn5 layer after thermal cycling.

Lin, Jui-Ching; Qin, Yi; Woertink, Julia

2014-11-01

74

Reactivity of plasma-sintered beryllium-titanium intermetallic compounds with water vapor  

NASA Astrophysics Data System (ADS)

Beryllium-titanium intermetallic compounds (beryllides) are candidates for advanced neutron multipliers in water-cooled solid breeder demonstration (DEMO) reactor. In contrast to beryllium, which is highly reactive with water vapor above 873 K, the beryllide is considerably more stable with much lower hydrogen-gas-generation rates. To investigate the effect of phase compositions on the reactivity with water vapor, the beryllides were plasma-sintered for different times to produce different phase compositions. They were examined by thermogravimetric analysis and the H2-generation rate was measured at 1273 and 1473 K for 24 h under Ar gas containing 1% H2O. The resulting weight gain of the beryllides under 1% H2O was in good agreement with previous results showing that with an increase in the area fraction of Be, the oxidation resistance under Ar gas containing 1% H2O decreases. The result of the H2-generation rate at 1273 K demonstrates that the larger the fraction of Be, the higher the H2-generation rate. It is clear that the Be phase in the plasma-sintered beryllides attributes to an increase in H2-gas generation. We report here on the effect of phase compositions on reactivity with water vapor of the plasma-sintered beryllides.

Kim, Jae-Hwan; Nakamichi, Masaru

2014-12-01

75

Charge transfer on the metallic atom-pair bond, and the crystal structures adopted by intermetallic compounds.  

PubMed

It has been argued in our recent papers that the heat of formation of intermetallic compounds is mostly concentrated in the nearest neighbor unlike atom-pair bonds, and that the positive term in Miedema's equation is associated with charge transfer on the bond to maintain electroneutrality. In this paper, taking examples of some well populated crystal-structure types such as MgCu(2), AsNa(3), AuCu(3), MoSi(2) and SiCr(3) types, the effect of such charge transfer on the crystal structures adopted by intermetallic compounds is examined. It is shown that the correlation between the observed size changes of atoms on alloying and their electronegativity differences is supportive of the idea of charge transfer between atoms. It is argued that the electronegativity and valence differences need to be of the required magnitude and direction to alter, through charge transfer, the elemental radius ratios R(A)/R(B) to the internal radius ratios r(A)/r(B) allowed by the structure types. Since the size change of atoms on alloying is highly correlated to how different R(A)/R(B) is from the ideal radius ratio for a structure type, the lattice parameters of intermetallic compounds can be predicted with excellent accuracy knowing R(A)/R(B). A practical application of the approach developed in our recent papers to superalloy design is presented. PMID:22186292

Rajasekharan, T; Seshubai, V

2012-01-01

76

Highly efficient aerobic oxidation of various amines using Pd3Pb intermetallic compounds as catalysts.  

PubMed

Intermetallic Pd3Pb supported on Al2O3 can act as a highly efficient heterogeneous catalyst for the oxidation of various amines including primary, secondary, aromatic, aliphatic, and cyclic amines. PMID:24525669

Furukawa, Shinya; Suga, Akifusa; Komatsu, Takayuki

2014-03-28

77

Interaction of Oxygen and Carbon Monoxide with Cerium and Lanthanum Intermetallic Compounds  

NASA Astrophysics Data System (ADS)

In intermetallic compounds of Ce, the hybridization of the Ce 4f states and the conduction electron states generally results in an increase of the density of states at the Fermi level and has a profound effect on the transport, thermal, magnetic, and other physical properties of these compounds. In an attempt to determine whether these modifications are reflected in the catalytic properties, Auger electron spectroscopy (AES) and temperature programmed desorption (TPD) have been employed for an investigation of the interaction of O_2 and CO with CeIr _2 and its isostructural counterpart LaIr _2. Results from CeIr_2 and LaIr_2 show the following differences: (1) oxygen and carbon penetrate into CeIr _2<=ss deeply than LaIr _2; (2) O_2 and CO exhibit high temperature peaks (at 610 K for O _2 and at 740 and 900 K for CO) in the TPD spectra from the CeIr_2 sample not present in those from the LaIr_2 sample; (3) when the compounds are predosed with CO, substantial thermal desorption of CO_2 occurs from LaIr_2, but none from CeIr _2. Considering that La and Ce are chemically almost identical and the CeIr_2 and LaIr_2 bulk compounds are isostructural, the above differences suggest that the intermediate valence of CeIr_2 affects the interaction with gases. However, no direct relation has been established between the large density of states at the Fermi level and the differences in the interactions, due to the complications related to the presence of CeO _2. Unusual properties discussed are the formation of surface and near-surface oxide species upon exposure to O_2 or CO, the dissociative adsorption of CO and recombination of CO, the production of CO _2, thermal segregation, and subsurface "reservoir" of C and O. Surface and subsurface processes, such as adsorption and penetration, or thermal segregation, recombination, and desorption, are strongly coupled together. A consistent interpretation of the AES data requires consideration of the C and O concentrations occurring in the surface-subsurface region. A procedure for the conversion of AES data into concentrations is developed employing piecewise fitting with exponential decay functions. When LaIr_2 is dosed with CO, oxidation occurs, but TPD studies reveal that the sample remains chemically active, desorbing the equivalent of more than a monolayer of CO and CO_2. This suggests the presence of a certain kinetic mechanism that allows the preservation of the catalytic activity under oxidation, implying the potential for poison-resistance application.

Wu, Ming

78

Formation of Intermetallic Compounds Between Liquid Sn and Various CuNi x Metallizations  

NASA Astrophysics Data System (ADS)

Interfacial reactions between liquid Sn and various Cu-Ni alloy metallizations as well as the subsequent phase transformations during the cooling were investigated with an emphasis on the microstructures of the reaction zones. It was found that the extent of the microstructurally complex reaction layer (during reflow at 240°C) does not depend linearly on the Ni content of the alloy metallization. On the contrary, when Cu is alloyed with Ni, the rate of thickness change of the total reaction layer first increases and reaches a maximum at a composition of about 10 at.% Ni. The reaction layer is composed of a relatively uniform continuous (Cu,Ni)6Sn5 reaction layer (a uniphase layer) next to the NiCu metallizations and is followed by the two-phase solidification structures between the single-phase layer and Sn matrix. The thickness of the two-phase layer, where the intermetallic tubes and fibers have grown from the continuous interfacial (Cu,Ni)6Sn5 layer, varies with the Ni-to-Cu ratio of the alloy metallization. In order to explain the formation mechanism of the reaction layers and their observed kinetics, the phase equilibria in the Sn-rich side of the SnCuNi system at 240°C were evaluated thermodynamically utilizing the available data, and the results of the Sn/Cu x Ni1- x diffusion couple experiments. With the help of the assessed data, one can also evaluate the minimum Cu content of Sn-(Ag)-Cu solder, at which (Ni,Cu)3Sn4 transforms into (Cu,Ni)6Sn5, as a function of temperature and the composition of the liquid solders.

Vuorinen, V.; Yu, H.; Laurila, T.; Kivilahti, J. K.

2008-06-01

79

The effect of microstructures on mechanical behaviors of Ti2AlNb intermetallic compounds  

SciTech Connect

Ti2AlNb intermetallics are presently heat-treated and subjected to compressive loading at various temperatures, in order to ascertain microstructure-mechanical behavior relationships. Heat-treated and oil-quenched samples exhibit beta phase; the 'O' phase transformation was restrained by quenching. The O phase increased with rising heat-treatment temperature. 10 refs.

Wang, Liming; Yao, Mei; Zou, Dunxu; Zhu, Dong; Cai, Qigong (Harbin Institute of Technology, (China) Central Iron and Steel Research Institute, Beijing, (China))

1992-03-01

80

Study on ion-irradiation-induced ferromagnetism in FeRh intermetallic compound by means of magnetic Compton scattering  

SciTech Connect

The magnetic Compton profiles of Fe-50 at. % Rh intermetallic compound were measured to study the ferromagnetism induced by 200 MeV Xe ion irradiation. The magnetic effect at 50 K increases with increasing the ion-fluence. The analysis of the experimental result revealed that the values of spin moment induced by the irradiation were close to the values of magnetization obtained by a superconducting quantum interference device magnetometer, suggesting that the ion irradiation mainly induces the spin magnetic moment. The difference in magnetic Compton profiles between the irradiation-induced ferromagnetism and the intrinsic ferromagnetism in pure Fe is also discussed.

Kosugi, S.; Matsui, T.; Aikoh, K.; Shimizu, K.; Tahara, Y.; Hori, F.; Iwase, A. [Department of Materials Science, Osaka Prefecture University, Sakai, Osaka 599-8531 (Japan); Ishikawa, N. [Japan Atomic Energy Agency(JAEA-Tokai), Tokai, Ibaraki, 319-1195 (Japan); Itou, M.; Sakurai, Y. [Japan Synchrotron Radiation Research Institute(JASRI), Spring-8, Sayo, Hyogo 679-5198 (Japan)

2011-04-01

81

Stability of molybdenum nanoparticles in Sn-3.8Ag-0.7Cu solder during multiple reflow and their influence on interfacial intermetallic compounds  

SciTech Connect

This work investigates the effects of molybdenum nanoparticles on the growth of interfacial intermetallic compound between Sn-3.8Ag-0.7Cu solder and copper substrate during multiple reflow. Molybdenum nanoparticles were mixed with Sn-3.8Ag-0.7Cu solder paste by manual mixing. Solder samples were reflowed on a copper substrate in a 250 Degree-Sign C reflow oven up to six times. The molybdenum content of the bulk solder was determined by inductive coupled plasma-optical emission spectrometry. It is found that upon the addition of molybdenum nanoparticles to Sn-3.8Ag-0.7Cu solder, the interfacial intermetallic compound thickness and scallop diameter decreases under all reflow conditions. Molybdenum nanoparticles do not appear to dissolve or react with the solder. They tend to adsorb preferentially at the interface between solder and the intermetallic compound scallops. It is suggested that molybdenum nanoparticles impart their influence on the interfacial intermetallic compound as discrete particles. The intact, discrete nanoparticles, by absorbing preferentially at the interface, hinder the diffusion flux of the substrate and thereby suppress the intermetallic compound growth. - Highlights: Black-Right-Pointing-Pointer Mo nanoparticles do not dissolve or react with the SAC solder during reflow. Black-Right-Pointing-Pointer Addition of Mo nanoparticles results smaller IMC thickness and scallop diameter. Black-Right-Pointing-Pointer Mo nanoparticles influence the interfacial IMC through discrete particle effect.

Haseeb, A.S.M.A., E-mail: haseeb@um.edu.my; Arafat, M.M., E-mail: arafat_mahmood@yahoo.com; Johan, Mohd Rafie, E-mail: mrafiej@um.edu.my

2012-02-15

82

Formation and Growth of Intermetallic Compound Cu6Sn5 at Early Stages in Lead-Free Soldering  

NASA Astrophysics Data System (ADS)

In this work, the early stages of the formation and growth of the intermetallic compound Cu6Sn5 during soldering reactions between a Cu substrate and liquid Sn are examined through phase-field simulations. The liquid Sn-based solder (L phase) and the copper substrate (? phase) are considered to be under metastable equilibrium conditions that eventually lead to nucleation of the Cu6Sn5 intermetallic compound (IMC) (? phase) at the solid/liquid interface. Nucleation is incorporated into the model through a classical treatment considering that individual nucleation events follow a Poisson distribution function. The driving forces for the nucleation and phase transformations are obtained by coupling the phase-field simulations to CALPHAD models. In the phase-field simulations, physical properties such as liquid surface as well as IMC interfacial energies are treated parametrically to probe the behavior of the system under various growth conditions. The simulations are compared with previous works and are shown to have good (qualitative) agreement with recent detailed studies on the early stages of the interaction between Cu and liquid Sn.

Park, M. S.; Arroyave, R.

2010-12-01

83

Phase transitions as a function of material constants and temperature in intermetallic compounds of the terfenol-D type  

NASA Astrophysics Data System (ADS)

A model of magnetic and magnetoelastic properties of intermetallic compounds has been considered with the inclusion of the influence of the “giant” magnetoelastic coupling and the biquadratic exchange interaction. The phase transitions as a function of material constants and temperature have been investigated in the framework of the proposed model. It has been demonstrated that the ferromagnetic and quadrupole phases can be formed in the system under consideration. In this case, the phase transition between these phases is a first-order transition and occurs through the intermediate, i.e., quadrupole-ferromagnetic, state. The dependences of the phase transition temperature on the Heisenberg and biquadratic exchange interaction constants have been obtained for compounds of the terfenol-D type.

Fridman, Yu. A.; Klevets, F. N.; Vo?tenko, A. P.

2010-07-01

84

Surface composition of ordered intermetallic compounds PtBi and PtPb  

NASA Astrophysics Data System (ADS)

The surface composition of bulk electrodes made from the ordered intermetallic phases PtBi and PtPb has been studied by ex-situ X-ray photoelectron spectroscopy (XPS) after being subjected to various electrochemical treatments. Analysis of the freshly polished surfaces showed that in the surface and near surface regions the less-noble metals; Bi and Pb are oxidized to a significant extent (28% and 41%, respectively). Upon cycling to increasingly positive potentials, the fraction of oxidized to metallic forms of Bi and Pb decreased gradually to reach the minimal values of 7% and 6% at +400 mV vs. Ag/AgCl (saturated KCl). The observed decrements are due to leaching of surface oxides; Bi 2O 3 on PtBi and PbCO 3 or Pb(OH) 2 on PtPb. When the potential sweep was extended to more positive values, there was a linear decrease in the surface concentration of the less-noble metal, along with a slight increase in the amount of the species in their oxidized state (Bi 2O 3 for PtBi and PbSO 4 for PtPb). Leaching of Bi from the electrode surface occurs in accordance to the Pourbaix diagram for elemental bismuth, indicating no significant increase in stability arising from the formation of an intermetallic phase with platinum. In the case of PtPb, however, the Pb starts to dissolve away at potentials significantly more positive (+800 mV) than what was anticipated from the Pourbaix diagram. The results obtained here are in accord with our previous observations on the effects of electrochemical pre-treatment on these intermetallic phases for the electrocatalytic oxidation of formic acid and other potential fuel cell fuels.

Blasini, D. R.; Rochefort, D.; Fachini, E.; Alden, L. R.; DiSalvo, F. J.; Cabrera, C. R.; Abruña, H. D.

2006-07-01

85

Influence of the structural-phase state on the strength and plasticity of the pressure-synthesized intermetallic compound Ni 3 Al  

Microsoft Academic Search

878 The strength of hightemperature nickel alloys con? taining up to 70% disperse ?'?phase particles based on the intermetallic compound Ni3Al is largely determined by the strength and plasticity of the intermetallicphase par? ticles, which, in turn, depend on their structural-phase state. If we understand the influence of the structural- phase state on the plasticity and strength of the interme?

V. E. Ovcharenko; O. B. Perevalova; E. N. Boyangin

2010-01-01

86

NMR study of YCo/sub 12/B/sub 6/ and GdCo/sub 12/B/sub 6/ intermetallic compounds  

SciTech Connect

Spin-echo nuclear magnetic resonance was used to study /sup 59/Co hyperfine fields in the intermetallic compounds RCo/sub 12/B/sub 6/ with R = Y and Gd. Two groups of signals were obtained and interpreted in terms of anisotropic orbital contributions to the hyperfine field in the domain walls and domains.

Erdmann, K.; Rosenberg, M.; Buschow, K.H.J.

1988-04-15

87

JOURNAL DE PHYSIQUE Colloque C4, supplment au n" 4, Tome 40, avril 1979, page C4-142 Magnetic neutron scattering on intermetallic uranium compounds (*)  

E-print Network

neutron scattering on intermetallic uranium compounds (*) M. Loewenhaupt (f ), S. Horn (**), F. Steglich.- Abstract. -- We report on inelastic neutron scattering experiments performed in the temperature range 5 K quasielastic line. Using thermal neutrons, no inelastic contributions to the magnetic scattering could

Paris-Sud XI, Université de

88

Elastic, Electronic and Thermodynamic Properties of Rh3X(X = Zr, Nb and Ta) Intermetallic Compounds  

NASA Astrophysics Data System (ADS)

Structural, electronic, elastic and thermodynamic properties of Rh3X(X = Zr, Nb, Ta) intermetallic compounds are investigated in the framework of density functional theory (DFT). The exchange-correlation (XC) potential is treated with the generalized gradient approximation (GGA) and local density approximation (LDA). The computed ground state properties agree well with the available theoretical and experimental values. The elastic constants are obtained by calculating the total energy versus volume conserving strains using Mehl model. The electronic and bonding properties are discussed from the calculations of band structures (BSs), densities of states and electron charge densities. The volume and bulk modulus at high pressure and temperature are investigated. Additionally, thermodynamic properties such as the heat capacity, thermal expansion and Debye temperature at high pressures and temperatures are also analyzed.

Ould Kada, M.; Seddik, T.; Sayede, A.; Khenata, R.; Bouhemadou, A.; Deligoz, E.; Alahmed, Z. A.; Bin Omran, S.; Rached, D.

2014-11-01

89

Intermetallic compound layer formation between copper and hot-dipped 100In, 50In50Sn, 100Sn, and 63Sn37Pb coatings  

Microsoft Academic Search

The growth kinetics of intermetallic compound layers formed between four hot-dipped solder coatings and copper by solid state,\\u000a thermal aging were examined. The solders were l00Sn, 50In-50Sn, 100In, and 63Sn-37Pb (wt.%); the substrate material was oxygen-free,\\u000a high conductivity Cu. The total intermetallic layer of the 100Sn\\/Cu system exhibited a combination of parabolic growth at\\u000a lower aging temperatures and t0.42 growth

Paul T. Vianco; Paul F. Hlava; Alice C. Kilgo

1994-01-01

90

The Influence of Sn Orientation on Intermetallic Compound Evolution in Idealized Sn-Ag-Cu 305 Interconnects: an Electron Backscatter Diffraction Study of Electromigration  

NASA Astrophysics Data System (ADS)

Previous research showed the relationship between Sn grain orientation and the intermetallic growth rate in Sn-Ag-Cu (SAC)305 interconnects. Samples with the Sn c-axis aligned parallel to the current flow have an intermetallic compound growth rate significantly faster than samples with the c-axis perpendicular to the current flow. This study continues the previous research by investigating intermetallic growth in polygranular joints and in joints that have a thin Ni layer at the cathodic or anodic interface of the interconnect. Planar SAC305 interconnects were sandwiched between two Cu pads (sometimes incorporating a thin Ni layer at the interface) and subjected to uniaxial current. The crystallographic orientation of Sn in these samples was characterized with electron backscatter diffraction before and after electromigration testing. The results show that polycrystalline joints have relatively slow intermetallic growth rates, close to those found in single-crystal joints with the c-axis perpendicular to the current. When a Ni layer was present on the anode side, the intermetallic grew at a rate comparable to that in samples without a Ni layer. However, when the Ni layer was on the cathode side, the intermetallic growth was significantly retarded. The measured growth rates of the intermetallic, combined with literature values for the diffusion of Cu in Sn, were used to calculate values for the effective charge, z *, which is significantly smaller for samples with current parallel to the c-axis than for either polycrystalline samples or samples with the c-axis perpendicular to the electron flow.

Linares, Xioranny; Kinney, Chris; Lee, Kyu-Oh; Morris, J. W.

2014-01-01

91

Phase stability and elasticity of C15 transition-metal intermetallic compounds  

SciTech Connect

First-principle quantum mechanical calculations based on the local-density-functional theory have been performed to study the electronic, physical and metallurgical properties of C15 intermetallics MV{sub 2} (M = Zr, Hf, or Ta). The elastic constants of C15 HfV{sub 2} + Nb were measured by the resonant ultrasound spectroscopy technique. The phase stability of C15 HfV{sub 2} + Nb was studied by specific heat measurements and by transmission electron microscopy in a low temperature specimen holder. The total energies and their lattice volume dependence were used to obtain the equilibrium lattice constants and bulk modulus. The band structures at the X-point near the Fermi level were employed to understand the anomalous temperature dependence of shear modulus of the C15 intermetallics. It was found that the double degeneracy with a linear dispersion relation of electronic levels at the X-point near the Fermi surface is mainly responsible for the C15 anomalous elasticity. The density of states at the Fermi level, N(E{sub F}), and the Fermi surface geometry were obtained to understand the low temperature phase instability of C15 HfV{sub 2} and ZrV{sub 2} and the stability of C15 TaV{sub 2}. It was proposed that the large N(E{sub F}) and Fermi surface nesting are the physical reasons for the structural instability of the C15 HfV{sub 2} and ZrV{sub 2} at low temperatures. The relation between anomalous elasticity and structural instability of C15 HfV{sub 2} and ZrV{sub 2} is also discussed.

Chu, F.; Mitchell, T.E.; Chen, S.P. [Los Alamos National Lab., NM (United States); Sob, M.; Siegl, R.; Pope, D.P. [Pennsylvania Univ., Philadelphia, PA (United States). Dept. of Materials Science and Engineering

1995-03-01

92

Ba{sub 5}Ti{sub 12}Sb{sub 19+x}, a polar intermetallic compound with a stuffed gamma-brass structure  

SciTech Connect

The polar intermetallic compound Ba{sub 5}Ti{sub 12}Sb{sub 19+x} (x<=0.2) has been synthesized by reaction of the elements. Single-crystal X-ray diffraction analysis revealed that it adopts a new structure type (Ba{sub 5}Ti{sub 12}Sb{sub 19.102(6)}, space group P43-barm, Z=2, a=12.4223(11) A, V=1916.9(3) A{sup 3}). The set of Ba and Sb sites corresponds to the structure of Cu{sub 9}Al{sub 4}, a gamma-brass type with a primitive cell. A complex three-dimensional framework of Ti atoms, in the form of linked planar Ti{sub 9} clusters, is stuffed within the gamma-brass-type Ba-Sb substructure. Notwithstanding its relationship to the gamma-brass structure, the compound does not appear to conform to the Hume-Rothery electron concentration rules. Band structure calculations on an idealized Ba{sub 5}Ti{sub 12}Sb{sub 19} model suggest that the availability of bonding states above the Fermi level is responsible for the partial occupation, but only to a limited degree, of an additional Sb site within the structure. Magnetic measurements indicated Pauli paramagnetic behaviour. - A gamma-brass substructure built up of Ba-Sb clusters is stuffed with planar Ti{sub 9} clusters.

Bie Haiying [Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2 (Canada); Mar, Arthur, E-mail: arthur.mar@ualberta.c [Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2 (Canada)

2009-11-15

93

Effects of Bonding Wires and Epoxy Molding Compound on Gold and Copper Ball Bonds Intermetallic Growth Kinetics in Electronic Packaging  

NASA Astrophysics Data System (ADS)

This paper discusses the influence of bonding wires and epoxy mold compounds (EMC) on intermetallic compound (IMC) diffusion kinetics and apparent activation energies ( E aa) of CuAl and AuAl IMCs in a fineline ball grid array package. The objective of this study is to study the CuAl and AuAl IMC growth rates with different epoxy mold compounds and to determine the apparent activation energies of different combination of package bills of materials. IMC thickness measurement has been carried out to estimate the coefficient of diffusion ( D o) and E aa various aging conditions of different EMCs and bonding wires. Apparent activation energies ( E aa) of both wire types were investigated after high temperature storage life tests (HTSL) for both molding compounds. Au bonds were identified to have faster IMC formation, compared to slower IMC growth of Cu. The E aa obtained for CuAl IMC diffusion kinetics are 1.08 and 1.04 eV with EMC A and EMC B, respectively. For AuAl IMC diffusion kinetics, the E aa obtained are 1.04 and 0.98 eV, respectively, on EMC A and EMC B. These values are close to previous HTSL studies conducted on Au and Cu ball bonds and are in agreement to the theory of HTSL performance of Au and Cu bonding wires.Overall, EMC B shows slightly lower apparent activation energy ( E aa) valueas in CuAl and AuAl IMCs. This proves that the different types of epoxy mold compounds have some influence on IMC growth rates.

Gan, C. L.; Classe, F. C.; Chan, B. L.; Hashim, U.

2014-04-01

94

Intermetallic compound layer formation between copper and hot-dipped 100In, 50In-50Sn, 100Sn, and 63Sn-37Pb coatings  

NASA Astrophysics Data System (ADS)

The growth kinetics of intermetallic compound layers formed between four hot-dipped solder coatings and copper by solid state, thermal aging were examined. The solders were l00Sn, 50In-50Sn, 100In, and 63Sn-37Pb (wt.%); the substrate material was oxygen-free, high conductivity Cu. The total intermetallic layer of the 100Sn/Cu system exhibited a combination of parabolic growth at lower aging temperatures and t0.42 growth at the higher temperatures. The combined apparent activation energy was 66 kJ/mol. These results are compared to the total layer growth observed with the 63Sn-37Pb/Cu system which showed parabolic kinetics at similar temperatures and an apparent activation energy of 45 kJ/mol. Both 100Sn and 63Sn-37Pb diffusion couples showed a composite intermetallic layer comprised of Cu3Sn and Cu6Sn5. The intermetallic compound layer formed between In and Cu changed from a CuIn2 stoichiometry at short annealing times to a Cu57In43 composition at longer periods. The growth kinetics were parabolic with an apparent activation energy of 20 kJ/mol. The intermetallic layer growth of the 50In-50Sn/Cu system exhibited extreme variations in the layer thicknesses which prohibited a quantitative assessment of the growth kinetics. The layer was comprised of two compounds: Cu26Sn13In8 which was the dominant phase and a thin layer of Cu17Sn9In24 adjacent to the solder.

Vianco, Paul T.; Hlava, Paul F.; Kilgo, Alice C.

1994-07-01

95

Multiscale Study of Interfacial Intermetallic Compounds in a Dissimilar Al 6082-T6/Cu Friction-Stir Weld  

NASA Astrophysics Data System (ADS)

The objective of this work was to characterize the Al x Cu y intermetallic compounds (IMCs) formed at the abutting interface during solid-state friction-stir welding (FSW) of 6082 aluminum alloy and pure copper. As IMCs are potential sources of flaws in case of mechanical loading of welds, their study is essential at various scale lengths. In the present case, they have been identified by neutron diffraction, electron backscattered diffraction, and transmission electron microscopy. Neutron diffraction analyses have shown that a shift of the tool from the interface, in particular towards the Cu part, generates an increase of the IMCs' volume fraction. In accordance with an exacerbation of its kinetics of formation by FSW, a 4- ?m-thick layer has precipitated at the interface despite the shortness of the thermal cycle. This layer is composed of two sublayers with the Al4Cu9 and Al2Cu stoichiometry, respectively. Convergent beam electron diffraction analyses have, however, disclosed that the crystallography of the current Al2Cu compound does not comply with the usual tetragonal symmetry of this phase. The Al2Cu phase formation results from both the local chemical composition and thermodynamics, whereas the development of Al4Cu9 is rather due to both the local chemical composition and the shortness of the local FSW thermal cycle.

Avettand-Fenoël, M. N.; Taillard, R.; Ji, G.; Goran, D.

2012-12-01

96

The oxidation resistance, hardness and constitution of some intermetallic compounds containing zinc  

Microsoft Academic Search

The majority of the binary compounds of zinc with the metals from titanium to copper inclusive has been prepared, hardness\\u000a tested and oxidized in air at successively higher temperatures. A zinc-ruthenium and some zinc-gadolinium compounds have also\\u000a been tested. From the oxidation results, the temperature corresponding to a weight change of 1 mg cm?2 over 4h was determined by interpolation.

H. E. N. Stone

1976-01-01

97

The oxidation resistance, hardness and constitution of some intermetallic compounds containing zinc  

Microsoft Academic Search

The majority of the binary compounds of zinc with the metals from titanium to copper inclusive has been prepared, hardness tested and oxidized in air at successively higher temperatures. A zinc-ruthenium and some zinc-gadolinium compounds have also been tested. From the oxidation results, the temperature corresponding to a weight change of 1 mg cm-2 over 4h was determined by interpolation.

H. E. N. Stone

1976-01-01

98

Interdependent Intermetallic Compound Growth in an Electroless Ni-P/Sn-3.5Ag Reaction Couple  

NASA Astrophysics Data System (ADS)

The interfacial microstructure of electroless Ni-P/Sn-3.5Ag solder joints was investigated after reflow and high-temperature solid-state aging to understand its interdependent growth mechanism and related kinetics of intermetallic compounds (IMCs) at the interface. The reflow and aging results showed that mainly three IMC layers, Ni3Sn4, Ni2SnP, and Ni3P, formed during the soldering reaction. It was found that the Ni3Sn4 and Ni3P layers grow predominantly as long as the electroless Ni-P layer is present; however, once the Ni-P layer is fully consumed, the Ni2SnP layer grows rapidly at the expense of the Ni3P layer. A transition in the Ni3Sn4 morphology from needle and chunky shape to scallop shape was observed after the solid-state aging of reflowed samples. The kinetics data obtained from the growth of compound layers in the aged samples revealed that initially the growth of the Ni2SnP layer is controlled by diffusion, and subsequently by the rate of reaction after the Ni-P metallization is fully consumed. It was found that complete transformation of the electroless Ni-P layer into a Ni3P layer results in the rapid growth of the Ni2SnP layer due to the dominating reaction of Sn with Ni3P. The apparent activation energies for the growth of Ni3Sn4, Ni2SnP, and Ni3P compound layers were found to be 98.9 kJ/mol, 42.2 kJ/mol, and 94.3 kJ/mol, respectively.

Kumar, Aditya; Chen, Zhong

2011-02-01

99

Intermetallic compound layer development during the solid state thermal aging of 63Sn37Pb solder\\/Au-Pt-Pd thick film couples  

Microsoft Academic Search

A study was performed which examined the solid state, intermetallic compound layer growth kinetics between 63Sn-37Pb solder and a 76Au-21Pt-3Pd (wt.%) thick film conductor on 96% alumina substrates. A linear, multivariable regression analysis was used to assess the experimental data according to the following empirical relationship: x-x0=Atn exp(-?H\\/RT). A time exponent of n=0.78±0.08 was observed, suggesting that a combination of

Paul T. Vianco; John J. Stephens; Jerome A. Rejent

1997-01-01

100

Effect of Stress State on Growth of Interfacial Intermetallic Compounds Between Sn-Ag-Cu Solder and Cu Substrates Coated with Electroless Ni Immersion Au  

Microsoft Academic Search

Excessive intermetallic compound (IMC) growth in solder joints will significantly decrease the reliability of the joints.\\u000a IMC growth is known to be influenced by numerous factors during the component fabrication process and in service. It is reported\\u000a that, other than temperature and holding time, stress can also influence the IMC growth behavior. However, no existing method\\u000a can be used to

S. L. Ngoh; W. Zhou; J. H. L. Pang

2008-01-01

101

Ferromagnetic-to-antiferromagnetic transition in (Hf1-xTix)Fe2 intermetallic compounds induced by geometrical frustration of the Fe(2a) sites  

Microsoft Academic Search

The ferromagnetic-to-antiferromagnetic transition in the hexagonal (Hf1-xTix)Fe2 (0<=x<=1) intermetallic compounds has been investigated by 57Fe Mössbauer spectroscopy. At 10 K, the transition occurs within rather narrow concentration limits, around x=0.55 0.65. We found that the key factor governing the unexpected quick change of the magnetic structure is the magnetic frustration of the Fe(2a) sites. The magnetic frustration is caused by

N. N. Delyagin; A. L. Erzinkyan; V. P. Parfenova; I. N. Rozantsev; G. K. Ryasny

2008-01-01

102

Ferromagnetic-to-antiferromagnetic transition in (Hf 1? x Ti x )Fe 2 intermetallic compounds induced by geometrical frustration of the Fe(2a) sites  

Microsoft Academic Search

The ferromagnetic-to-antiferromagnetic transition in the hexagonal (Hf1?xTix)Fe2 (0?x?1) intermetallic compounds has been investigated by 57Fe Mössbauer spectroscopy. At 10K, the transition occurs within rather narrow concentration limits, around x=0.55–0.65. We found that the key factor governing the unexpected quick change of the magnetic structure is the magnetic frustration of the Fe(2a) sites. The magnetic frustration is caused by the noncollinearity

N. N. Delyagin; A. L. Erzinkyan; V. P. Parfenova; I. N. Rozantsev; G. K. Ryasny

2008-01-01

103

Icosahedral quasicrystals of intermetallic compounds are icosahedral twins of cubic crystals of three kinds, consisting of large (about 5000 atoms) icosahedral complexes in either a cubic body-centered or a cubic face-centered arrangement or smaller (about 1350 atoms) icosahedral complexes in the ?-tungsten arrangement  

PubMed Central

The twofold-axis electron-diffraction photographs of icosahedral quasicrystals are of three kinds, reflecting three different structures of the cubic crystals that by icosahedral twinning form the quasicrystals. The first kind, represented by Al13Cu4Fe3, contains two very large icosahedral complexes, each of about 4680 atoms, in the body-centered arrangement, with six smaller icosahedral complexes (104 atoms each) in the principal interstices. The second kind, represented by Al5Mn, contains four of the very large complexes in the face-centered arrangement (cubic close packing), with four of the smaller clusters in the interstices. The third kind, represented by Al6CuLi3, contains eight icosahedral complexes, each of about 1350 atoms, in the ?-W arrangement. The supporting evidence for these cubic structures is discussed as well as other evidence showing that the simple quasicrystal theory, which states that quasicrystals do not involve any translational identity operations, has to be modified. Images PMID:16594078

Pauling, Linus

1989-01-01

104

In situ study on the effect of thermomigration on intermetallic compounds growth in liquid-solid interfacial reaction  

NASA Astrophysics Data System (ADS)

Synchrotron radiation real-time imaging technology was carried out in situ to observe and characterize the effect of thermomigration on the growth behavior of interfacial intermetallic compounds (IMCs) in Cu/Sn/Cu solder joint during soldering. The thermomigration resulted in asymmetrical formation and growth of the interfacial IMCs. Cu6Sn5 and Cu3Sn IMCs formed at the cold end and grew rapidly during the whole soldering process. However, only Cu6Sn5 IMC formed at the hot end and remained relatively thin until solidification. The IMCs at the cold end were nearly seven times thicker than that at the hot end after solidification. The Cu dissolution at the cold end was significantly restrained, while that at the hot end was promoted, which supplied Cu atoms to diffuse toward the cold end under thermomigration to feed the rapid IMC growth. Moreover, the thermomigration also caused asymmetrical morphology of the interfacial IMCs at the cooling stage, i.e., the Cu6Sn5 IMC at the cold end transformed into facet structure, while that at the hot end remained scallop-type. The asymmetrical growth behavior of the interfacial IMCs was analyzed from the view point of kinetics.

Qu, Lin; Zhao, Ning; Ma, Haitao; Zhao, Huijing; Huang, Mingliang

2014-05-01

105

Atomistic simulation of radiation-induced amorphization of the B2 ordered intermetallic compound NiTi  

SciTech Connect

Amorphization of the B2 intermetallic compound NiTi under electron irradiation has been investigated using molecular dynamics. The effect of irradiation was simulated using two processes: (1) Ni and Ti atoms were exchanged, resulting in chemical disorder, and (2) Frenkel pairs were introduced, leading to the formation of stable point defects and also chemical disorder upon mutual recombination of interstitials and vacancies. After {approximately}0.4 exchanges per atom, the first process resulted in an energy increase of approximately 0.11 eV/atom and a volume increase of 1.91%. On the other hand, after introducing {approximately}0.5 Frenkel pairs per atom, the second process led to smaller increases of 0.092 eV/atom in energy and 1.43% in volume. The calculated radial distribution functions (RDFs) were essentially identical to each other and to the calculated RDF of a quenched liquid. The structure factor, however, showed that long-range order was still present after atom exchanges, while the introduction of Frenkel pairs resulted in the loss of long-range order. It was concluded that point defects are necessary for amorphization to occur in NiTi, although chemical disorder alone is capable of storing enough energy to make the transition possible. 18 refs., 3 figs.

Sabochick, M.J. (Air Force Inst. of Tech., Wright-Patterson AFB, OH (USA). Dept. of Engineering Physics); Lam, N.Q. (Argonne National Lab., IL (USA))

1990-12-01

106

Low-temperature solution synthesis of alloys and intermetallic compounds as nanocrystals  

E-print Network

were synthesized via solution techniques where metal compounds are reduced by NaBH4 or n-butyllithium at temperatures below 300°C. To form hollow particles, metal nanoparticles of Co, Ni, Pb were synthesized via reduction by NaBH4 in water and reacted...

Vasquez, Yolanda

2009-05-15

107

Environmental effects in niobium-base alloys and other selected intermetallic compounds. Final report, 1 Jan 87-31 Oct 90  

SciTech Connect

Niobium aluminides and silicides as well as other intermetallic compounds have potential for use in advanced gas turbines where increased operating temperatures are necessary to obtain the targeted performance goals. These materials will be subjected to a variety of environments over a range of temperatures. Two of the principal reactants in these environments are oxygen and hydrogen. This program has been concerned with the effects of oxygen and hydrogen on niobium alloys and other selected intermetallic compounds. The investigations involving oxygen examined the mechanisms by which intermetallic compounds are degraded in oxidizing environments. Emphasis was placed upon the conditions which must be achieved in order to obtain sufficient oxidation resistance for use at temperatures above about 1100 deg C. Oxidation was investigated at temperatures between 500 and 1400 C in oxygen and in air. Investigations involving hydrogen have emphasized brittle fracture, crack growth and the behavior of hydrides in Ti-24Al-11Nb (at. %). Some work of this type was also performed on TiAl. The mechanical properties of these alloys were determined after exposure to hydrogen. Mechanical tests included simple tensile and compression tests, and notched bend and precracked compact tension specimens. Properties such as yield strength and ultimate strength, tensile strength, ductility, and fracture toughness have been determined as a function of both hydrogen (hydride) content and temperature.

Meier, G.H.; Thompson, A.W.

1991-04-30

108

Effect of Laser Processing Parameters on the Formation of Intermetallic Compounds in Fe-Al Dissimilar Welding  

NASA Astrophysics Data System (ADS)

Fusion welding of steel to aluminum is difficult due to formation of different types of Fe-Al intermetallics (IMs). In this work, 2 mm-thick steel was joined to 6 mm aluminum in overlap configuration using a 8 kW CW fiber laser. A defocused laser beam was used to control the energy input and allow melting of the aluminum alone and form the bond by wetting of the steel substrate. Experimentally, the process energy was varied by changing the power density (PD) and interaction time separately to understand the influence of each of these parameters on the IM formation. It was observed that the IM formation is a complex function of PD and interaction time. It was also found that the mechanical strength of such joint could not be simply correlated to the IM layer thickness but also depends on the area of wetting of the steel substrate by molten aluminum. In order to form a viable joint, PD needs to be over a threshold value where although IM growth will increase, the strength will be better due to increased wetting. Any increase in interaction time, with PD over the threshold, will have negative effect on the bond strength.

Meco, Sonia; Ganguly, Supriyo; Williams, Stewart; McPherson, Norman

2014-09-01

109

The Electronic Structure of GOLD-GALLIUM(,2) and GOLD-INDIUM(,2) Intermetallic Compounds  

NASA Astrophysics Data System (ADS)

The (111) and (001) surfaces of gold gallium (AuGa(,2)) and the (111) surface of gold indium (AuIn(,2)) were characterized using Auger electron spectroscopy (AES), low-energy electron diffraction (LEED), and electron energy loss spectroscopy (EELS). In all three systems, AES was used to study the surface chemistry, while LEED was used to determine the size and orientation of the surface net. The EELS spectra revealed surface and bulk plasmon loss features as well as transitions from the Au 5d portion of the valence band and either the Ga 3d or In 4d core levels. The (001) surfaces of both compounds were studied using synchrotron radiation excited angle-resolved photoemission (ARPES). Spectra collected for photoelectron emission normal to the surfaces were used to map the E(k) versus k dispersion relation along the (DELTA) symmetry line of the bulk Brillouin Zone (BZ). In addition, off-normal -emission ARPES spectra were used to map the E(k) versus k(,11) dispersion relation of the surface state which was found on both systems. Finally, the off-normal-emission data was also used to examine the band structure along (SIGMA) and (LAMDA) in the bulk BZ of both compounds.

Nelson, Jeffrey Glenn

110

Ultrarapid formation of homogeneous Cu6Sn5 and Cu3Sn intermetallic compound joints at room temperature using ultrasonic waves.  

PubMed

Homogeneous intermetallic compound joints are demanded by the semiconductor industry because of their high melting point. In the present work, ultrasonic vibration was applied to Cu/Sn foil/Cu interconnection system at room temperature to form homogeneous Cu6Sn5 and Cu3Sn joints. Compared with other studies based on transient-liquid-phase soldering, the processing time of our method was dramatically reduced from several hours to several seconds. This ultrarapid intermetallic phase formation process resulted from accelerated interdiffusion kinetics, which can be attributed to the sonochemical effects of acoustic cavitation at the interface between the liquid Sn and the solid Cu during the ultrasonic bonding process. PMID:24279981

Li, Zhuolin; Li, Mingyu; Xiao, Yong; Wang, Chunqing

2014-05-01

111

Electrocatalytic Formation and Inactivation of Intermetallic Compounds in Electrorefining of Silicon  

NASA Astrophysics Data System (ADS)

Silicon for solar cell purposes is today produced by an energy intensive process exhibiting high irreversible thermodynamic energy losses. The purity of the product; 99,9999999 pct (9N), far exceeds what is generally accepted to be the requirements for photovoltaic purposes (4-6N). According to thermodynamics, all elements except boron may be removed from silicon by three layer electrochemical refining above the melting point of Si. Boron, on the other hand, shows higher affinity to specific transition metals compared to silicon. This may be exploited by applying two principles in parallel; electrochemical refining and electrocatalyzed reaction-precipitation of transition metal borides as heavy, stable particles. In this study we report on the formation of such compounds at the cathode-electrolyte interface during electrochemical refining. The trends and mechanisms observed in the laboratory scale investigation indicate that high purity silicon may be produced in industrial scale reactors at low cost- and energy intensity.

Olsen, Espen; Rolseth, Sverre; Thonstad, Jomar

2010-08-01

112

Hydrogenation-induced insulating state in the intermetallic compound LaMg2Ni.  

PubMed

Hydrogenation-induced metal-semiconductor transitions usually occur in simple systems based on rare earths and/or magnesium, accompanied by major reconstructions of the metal host (atom shifts >2 A). We report on the first such transition in a quaternary system based on a transition element. Metallic LaMg2Ni absorbs hydrogen near ambient conditions, forming the nonmetallic hydride LaMg2NiH7 which has a nearly unchanged metal host structure (atom shifts <0.7 A). The transition is induced by a charge transfer of conduction electrons into tetrahedral [NiH4]4- complexes having closed-shell electron configurations. PMID:15783759

Yvon, K; Renaudin, G; Wei, C M; Chou, M Y

2005-02-18

113

Polarity effect of electromigration on intermetallic compound (IMC) formation in lead-free solder V-groove samples  

NASA Astrophysics Data System (ADS)

With the trend of further miniaturization of very-large-scale-integration (VLSI) of circuits, electromigration becomes a reliability concern in solder alloys. The polarity effect of electromigration on intermetallic compound (IMC) formation at the anode and the cathode in solder V-groove samples has been investigated. The V-groove solder line samples, with width of about 100 mum and length of 500--700 mum, were used to study the change in thickness and morphology of interfacial IMC at anode and cathode in the SnAg 3.8Cu0.7/Cu system under different current density and temperature settings. The current densities were in the range of 103 to 104A/ cm2 and the temperature settings were 120° C, 150°C and 180°C. The samples were formed by flowing molten lead-free solder SnAg 3.8Cu0.7 into V-grooves etched on (001) silicon wafers, and two copper wires were used as electrodes. We observed that IMC transformed from initial scallop-type into layer-type morphology with or without applying current. Due to the polarity of electric current and the local current crowding, IMC transformed from scallop-type into layer-type morphology differently from cathode to anode. We also found that the same IMCs of Cu6Sn 5 and Cu3Sn formed at solder/Cu interfaces with or without the passage of electric current. The growth of IMC has been enhanced by electric current at the anode and inhibited at the cathode, comparing with samples without applying current. A kinetic theory is derived, based on the Cu mass flux transport in the sample, to model the growth rate of IMC at anode and cathode.

Gan, Hua

114

Solid state phase equilibria and intermetallic compounds of the Al-Cr-Ho system  

SciTech Connect

The solid state phase equilibria of the Al-Cr-Ho ternary system at 500 Degree-Sign C were experimentally investigated. The phase relations at 500 Degree-Sign C are governed by 14 three-phase regions, 29 two-phase regions and 15 single-phase regions. The existences of 10 binary compounds and 2 ternary phases have been confirmed. Al{sub 11}Cr{sub 2}, Al{sub 11}Cr{sub 4} and Al{sub 17}Ho{sub 2} were not found at 500 Degree-Sign C. Crystal structures of Al{sub 9}Cr{sub 4} and Al{sub 8}Cr{sub 4}Ho were determined by the Rietveld X-ray powder data refinement. Al{sub 9}Cr{sub 4} was found to exhibit cubic structure with space group I4-bar 3m (no. 217) and lattice parameters a=0.9107(5) nm. Al{sub 8}Cr{sub 4}Ho crystallizes in ThMn{sub 12} structure type with space group I4/mmm (no. 139) and lattice parameters a=0.8909(4) nm, c=0.5120(5) nm. It is concluded that the obtained Al{sub 4}Cr phase in this work should be {mu}-Al{sub 4}Cr by comparing with XRD pattern of the hexagonal {mu}-Al{sub 4}Mn compound. - Graphical abstract: The solid state phase equilibria of the Al-Cr-Ho ternary system at 500 Degree-Sign C. Highlights: Black-Right-Pointing-Pointer Al-Cr-Ho system has been investigated. Black-Right-Pointing-Pointer Al{sub 9}Cr{sub 4} has cubic structure with space group I4-bar 3m. Black-Right-Pointing-Pointer Al{sub 8}Cr{sub 4}Ho crystallizes in ThMn{sub 12} type with space group I4/mmm. Black-Right-Pointing-Pointer Al{sub 4}Cr phase is {mu}-type at 500 Degree-Sign C.

Pang, Mingjun [Laboratory of Nonferrous Metal Materials and New Processing Technology, Ministry of Education, Guangxi University, Nanning, Guangxi 530004 (China) [Laboratory of Nonferrous Metal Materials and New Processing Technology, Ministry of Education, Guangxi University, Nanning, Guangxi 530004 (China); SAIC-GM-Wuling Automobile Co., Ltd., Liuzhou, Guangxi 545007 (China); Zhan, Yongzhong, E-mail: zyzmatres@yahoo.com.cn [Laboratory of Nonferrous Metal Materials and New Processing Technology, Ministry of Education, Guangxi University, Nanning, Guangxi 530004 (China)] [Laboratory of Nonferrous Metal Materials and New Processing Technology, Ministry of Education, Guangxi University, Nanning, Guangxi 530004 (China); Du, Yong [State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China)] [State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China)

2013-02-15

115

GMR in intermetallics  

SciTech Connect

Typical examples of giant magnetoresistance (GMR) effects observed in intermetallic compounds at various conditions are reviewed and some comparisons with the GMR magnetic multilayer systems are shown. Possibilities of tuning material parameters desired for applications are discussed in context of present understanding of the mechanisms responsible for GMR in this class of materials. 18 refs.

Sechowsky, V.; Havela, L. [Charles Univ., Prague (Czech Republic). Dept. of Metal Physics; Nakotte, H. [Los Alamos National Lab., NM (United States); Brueck, E. [Amsterdam Univ. (Netherlands). Van der Waals-Zeeman Inst.

1996-04-01

116

The intermetallic compound Ni 3 Au and gold-nickel solid solutions in metalliferous sediments of the triassic chert formation in Sikhote-Alin in the Far East  

Microsoft Academic Search

The intermetallic compound Ni3Au and Au-Ni solid solutions (native nickel Au and Au-bearing native Ni) were found in the contact metamorphosed metalliferous\\u000a sediments of the Triassic chert formation in Sikhote-Alin. The metalliferous rocks are characterized by high contents of Au,\\u000a Ag, and PGE, as well as the presence of diverse minerals of precious metals. Nickel gold (Au0.91-0.88 Ni0.09-0.12) is found

N. V. Miroshnichenko; Ye. V. Perevoznikova

2010-01-01

117

Surface structures of In-Pd intermetallic compounds. I. Experimental study of In thin films on Pd(111) and alloy formation.  

PubMed

A combination of experimental methods was used to study the structure of In thin films deposited on the Pd(111) surface and the alloying behavior. X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED), and scanning tunneling microscopy results indicate that surface alloying takes place at room temperature. Below 2 monolayer equivalents (MLEs), the LEED patterns show the formation of three rotational domains of InPd(110) of poor structural quality on top of the Pd(111) substrate. Both core-levels and valence band XPS spectra show that the surface alloy does not yet exhibit the electronic structure characteristic of the 1:1 intermetallic compound under these conditions. Annealing the 1 MLE thin film up to 690 K yields to a transition from a multilayer InPd near-surface intermetallic phase to a monolayer-like surface alloy exhibiting a well ordered (?3×?3) R30(?) superstructure and an estimated composition close to In2Pd3. Annealing above 690 K leads to further In depletion and a (1 × 1) pattern is recovered. The (?3×?3) R30(?) superstructure is not observed for thicker films. Successive annealing of the 2 MLE thin film leads the progressive disappearance of the InPd diffraction spots till a sharp (1 × 1) pattern is recovered above 690 K. In the high coverage regime (from 4 to 35 MLE), the formation of three rotational domains of a bcc-In7Pd3 compound with (110) orientation is observed. This In-rich phase probably grows on top of interfacial InPd(110) domains and is metastable. It transforms into a pure InPd(110) near-surface intermetallic phase in a temperature range between 500 and 600?K depending on the initial coverage. At this stage, the surface alloy exhibits core-level chemical shifts and valence band (VB) spectra identical to those of the 1:1 InPd intermetallic compound and resembling Cu-like density of states. Annealing at higher temperatures yields to a decrease of the In concentration in the near-surface region to about 20 at.% and a (1 × 1) LEED pattern is recovered. PMID:25173025

McGuirk, G M; Ledieu, J; Gaudry, É; de Weerd, M-C; Fournée, V

2014-08-28

118

Surface structures of In-Pd intermetallic compounds. I. Experimental study of In thin films on Pd(111) and alloy formation  

NASA Astrophysics Data System (ADS)

A combination of experimental methods was used to study the structure of In thin films deposited on the Pd(111) surface and the alloying behavior. X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED), and scanning tunneling microscopy results indicate that surface alloying takes place at room temperature. Below 2 monolayer equivalents (MLEs), the LEED patterns show the formation of three rotational domains of InPd(110) of poor structural quality on top of the Pd(111) substrate. Both core-levels and valence band XPS spectra show that the surface alloy does not yet exhibit the electronic structure characteristic of the 1:1 intermetallic compound under these conditions. Annealing the 1 MLE thin film up to 690 K yields to a transition from a multilayer InPd near-surface intermetallic phase to a monolayer-like surface alloy exhibiting a well ordered (?{3}× &sqrt{3}); {R30}° superstructure and an estimated composition close to In2Pd3. Annealing above 690 K leads to further In depletion and a (1 × 1) pattern is recovered. The (?{3}× ?{3}) {R30}° superstructure is not observed for thicker films. Successive annealing of the 2 MLE thin film leads the progressive disappearance of the InPd diffraction spots till a sharp (1 × 1) pattern is recovered above 690 K. In the high coverage regime (from 4 to 35 MLE), the formation of three rotational domains of a bcc-In7Pd3 compound with (110) orientation is observed. This In-rich phase probably grows on top of interfacial InPd(110) domains and is metastable. It transforms into a pure InPd(110) near-surface intermetallic phase in a temperature range between 500 and 600 K depending on the initial coverage. At this stage, the surface alloy exhibits core-level chemical shifts and valence band (VB) spectra identical to those of the 1:1 InPd intermetallic compound and resembling Cu-like density of states. Annealing at higher temperatures yields to a decrease of the In concentration in the near-surface region to about 20 at.% and a (1 × 1) LEED pattern is recovered.

McGuirk, G. M.; Ledieu, J.; Gaudry, É.; de Weerd, M.-C.; Fournée, V.

2014-08-01

119

Reorganizations of complex networks: Compounding and reducing  

NASA Astrophysics Data System (ADS)

Real networks interact with each other by different kinds of topological connections, which are usually demonstrated by linking nodes of different networks. Simple connection, such as one-to-one corresponding, random connection and similar connection are adopted for studying the interacted networks. Practical interrelations established between the two networks are ignored. In this study, a generalized framework of multi-subnet composited complex network that allowed us to investigate interrelations among several subnets is developed. Based on that, reorganizations of networks: compounding (compound subnets into a "bigger" one) and reducing (obtain a "smaller" network from a "bigger" one) are proposed. As an empirical evidence, influence of compounding on traffic dynamics is discussed. And the properties of nodes linking two networks are also considered. Onset of compounding between two networks is revealed. Numerical simulations on artificial networks as well as real bus and tube networks of Qingdao in China agree well with our analysis, which show validity of our model.

Shao, Fengjing; Sui, Yi

2014-12-01

120

First-principles characterization of the anisotropy of theoretical strength and the stress-strain relation for a TiAl intermetallic compound.  

PubMed

We perform first-principles computational tensile and compressive tests (FPCTT and FPCCT) to investigate the intrinsic bonding and mechanical properties of a ?-TiAl intermetallic compound (L 1(0) structure) using a first-principles total energy method. We found that the stress-strain relations and the corresponding theoretical tensile strengths exhibit strong anisotropy in the [001], [100] and [110] crystalline directions, originating from the structural anisotropy of ?-TiAl. Thus, ?-TiAl is a representative intermetallic compound that includes three totally different stress-strain modes. We demonstrate that all the structure transitions in the FPCTT and FPCCT result from the breakage or formation of bonds, and this can be generalized to all the structural transitions. Furthermore, based on the calculations we qualitatively show that the Ti-Al bond should be stronger than the Ti-Ti bond in ?-TiAl. Our results provide a useful reference for understanding the intrinsic bonding and mechanical properties of ?-TiAl as a high-temperature structural material. PMID:21825422

Zhou, Hong-Bo; Zhang, Ying; Liu, Yue-Lin; Kohyama, Masanori; Yin, Peng-Gang; Lu, Guang-Hong

2009-04-29

121

Interfacial reaction of intermetallic compounds of ultrasonic-assisted brazed joints between dissimilar alloys of Ti6Al4V and Al4Cu1Mg.  

PubMed

Ultrasonic-assisted brazing of Al4Cu1Mg and Ti6Al4V using Zn-based filler metal (without and with Si) has been investigated. Before brazing, the Ti6Al4V samples were pre-treated by hot-dip aluminizing and ultrasonic dipping in a molten filler metal bath in order to control the formation of intermetallic compounds between the Ti6Al4V samples and the filler metal. The results show that the TiAl(3) phase was formed in the interface between the Ti6Al4V substrate and the aluminized coating. For the Zn-based filler metal without Si, the Ti6Al4V interfacial area of the brazed joint did not change under the effect of the ultrasonic wave, and only consisted of the TiAl(3) phase. For the Zn-based filler metal with Si, the TiAl(3) phase disappeared and a Ti(7)Al(5)Si(12) phase was formed at the interfacial area of the brazed joints under the effect of the ultrasonic wave. Due to the TiAl(3) phase completely changing to a Ti(7)Al(5)Si(12) phase, the morphology of the intermetallic compounds changed from a block-like shape into a lamellar-like structure. The highest shear strength of 138MPa was obtained from the brazed joint free of the block-like TiAl(3) phase. PMID:21489846

Ma, Zhipeng; Zhao, Weiwei; Yan, Jiuchun; Li, Dacheng

2011-09-01

122

Possible complex organic compounds on Mars.  

PubMed

It is suggested that primitive Mars had somehow similar environments as primitive Earth. If life was born on the primitive earth using organic compounds which were produced from the early Earth environment, the same types of organic compounds were also formed on primitive Mars. Such organic compounds might have been preserved on Mars still now. We are studying possible organic formation on primitive and present Mars. A gaseous mixture of CO2, CO, N2 and H2O with various mixing ratios were irradiated with high energy protons (major components of cosmic rays). Hydrogen cyanide and formaldehyde were detected among volatile products, and yellow-brown-colored water-soluble non-volatile substances were produced, which gave amino acids after acid-hydrolysis. Major part of "amino acid precursors" were not simple molecules like aminonitriles, but complex compounds which eluted earlier than free amino acids in cation-exchange HPLC. These organic compounds should be major targets in the future Mars mission. Strategy for the detection of the complex organics on Mars will be discussed. PMID:11541335

Kobayashi, K; Sato, T; Kajishima, S; Kaneko, T; Ishikawa, Y; Saito, T

1997-01-01

123

Possible complex organic compounds on Mars  

NASA Astrophysics Data System (ADS)

It is suggested that primitive Mars had somehow similar environments as primitive Earth. If life was born on the primitive earth using organic compounds which were produced from the early Earth environment, the same types of organic compounds were also formed on primitive Mars. Such organic compounds might have been preserved on Mars still now. We are studying possible organic formation on primitive and present Mars. A gaseous mixture of CO_2, CO, N_2 and H_2O with various mixing ratios were irradiated with high energy protons (major components of cosmic rays). Hydrogen cyanide and formaldehyde were detected among volatile products, and yellow-brown-colored water-soluble non-volatile substances were produced, which gave amino acids after acid-hydrolysis. Major part of ``amino acid precursors'' were not simple molecules like aminonitriles, but complex compounds which eluted earlier than free amino acids in cation-exchange HPLC. These organic compounds should be major targets in the future Mars mission. Strategy for the detection of the complex organics on Mars will be discussed.

Kobayashi, K.; Sato, T.; Kajishima, S.; Kaneko, T.; Ishikawa, Y.; Saito, T.

1997-05-01

124

Superconductivity in the C32 intermetallic compounds AAl 2- xSi x, with A=Ca and Sr; and 0.6< x<1.2  

NASA Astrophysics Data System (ADS)

The intermetallic compounds AAl 2- xSi x, where A=Ca, Sr or Ba, crystallize in the C32 structure, same as the recently discovered MgB 2 with a high superconducting transition temperature of 39 K. For x=1, superconductivity has been observed in AAlSi with A=Ca and Sr, but not with A=Ba. The transition temperatures are 7.8 and 5.1 K, respectively for CaAlSi and SrAlSi. The CaAl 2- xSi x compound system display a Tc-peak at x=1, a possible x-induced electronic transition at x?0.75 and a possible miscibility gap near x?1.1 which results in a very broad superconducting transition. The Seebeck coefficients of AAlSi indicate that their carriers are predominantly electrons in nature, in contrast to the holes in MgB 2.

Lorenz, B.; Lenzi, J.; Cmaidalka, J.; Meng, R. L.; Sun, Y. Y.; Xue, Y. Y.; Chu, C. W.

2002-12-01

125

Revealing Fe magnetism in lanthanide-iron intermetallic compounds by tuning the rare-earth L{sub 2,3}-edge x-ray absorption edges  

SciTech Connect

We present a systematic x-ray magnetic circular dichroism (XMCD) study performed at the rare-earth L{sub 2,3} edges in R(Al{sub 1-x}Fe{sub x}){sub 2} Laves phase compounds. The progressive substitution of Al by Fe reveals the existence of a non-negligible contribution of Fe to the rare-earth XMCD spectra. This contribution has been isolated and shown to be similar to the dichroic spectrum recorded at the Fe K edge. These results open the possibility of monitoring the Fe magnetism in lanthanides-iron intermetallic compounds by probing the rare-earth L{sub 2,3}-edge x-ray absorption edges.

Laguna-Marco, M.A. [CITIMAC, Universidad de Cantabria, Avda. de los Castros s/n, 39005 Santander (Spain); Chaboy, J.; Piquer, C. [Instituto de Ciencia de Materiales de Aragon, CSIC-Universidad de Zaragoza, 50009 Zaragoza (Spain); Maruyama, H.; Ishimatsu, N. [Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526 (Japan); Kawamura, N.; Takagaki, M.; Suzuki, M. [Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Mikazuki, Sayo, Hyogo 679-5148 (Japan)

2005-08-01

126

Icosahedral and decagonal quasicrystals of intermetallic compounds are multiple twins of cubic or orthorhombic crystals composed of very large atomic complexes with icosahedral point-group symmetry in cubic close packing or body-centered packing: Structure of decagonal Al6Pd  

PubMed Central

A doubly icosahedral complex involves roughly spherical clusters of atoms with icosahedral point-group symmetry, which are themselves, in parallel orientation, icosahedrally packed. These complexes may form cubic crystallites; three structures of this sort have been identified. Analysis of electron diffraction photographs of the decagonal quasicrystal Al6Pd has led to its description as involving pentagonal twinning of an orthorhombic crystal with a = 51.6 Å, b = 37.6 Å, and c = 33.24 Å, with about 4202 atoms in the unit, comprising two 1980-atom doubly icosahedral complexes, each involving icosahedral packing of 45 44-atom icosahedral complexes (at 0 0 0 and 1/2 1/2 1/2) and 242 interstitial atoms. The complexes and clusters are oriented with one of their fivefold axes in the c-axis direction. Images PMID:16594092

Pauling, Linus

1989-01-01

127

Synthesis and study of binary actinide and lanthanide compounds. IX. Thermal breakdown of the intermetallics: Pt/sub 5/Sm, Pt/sub 5/Gd, and Pt/sub 5/Am  

SciTech Connect

The thermal breakdown of Pt/sub 5/Sm, Pt/sub 5/Gd, and Pt/sub 5/Am intermetallics under vacuum was studied. The compounds had high thermal resistance up to their melting points and quickly dissociated in the liquid state. Their high melting points hindered preparation of lanthanide and actinide metals by such dissociation.

Ryabinin, M.A.; Radchenko, V.M.; Seleznev, A.G.; Levedeva, L.S.; Shushakov, V.D.; Vasil'ev, V.Ya.

1987-01-01

128

Magnetic and magnetocaloric properties of rare earth intermetallic compounds HoCo2-xNix (x=0.75 and 1.25)  

NASA Astrophysics Data System (ADS)

Magnetic and magnetocaloric properties of polycrystalline rare earth intermetallic compounds HoCo2-xNix (x=0.75 and 1.25) have been investigated. Both HoCo1.25Ni0.75 and HoCo0.75Ni1.25 compounds crystallize in MgCu2 type, cubic Laves phase structure (space group Fd3barm, no. 227) and order ferromagnetically at ~40 K and ~36 K (TC) respectively. Field dependent magnetization at 5 K shows soft ferromagnetic behavior. The saturation magnetization value is about 8.5 ?B/f.u. for both compounds. Magnetocaloric effect in HoCo2-xNix (x=0.75 and 1.25) compounds has been evaluated in terms of isothermal magnetic entropy change (?Sm) that peaks around TC with maximum values of about -16.7 J/kg K and -15.2 J/kg K, respectively, for a field change of 70 kOe. Substitution of Ni at the Co-site of HoCo2 broadens the magnetic transition and enhances relative cooling power which makes these materials suitable for low temperature magnetic refrigeration applications.

Mondal, Rajib; Nirmala, R.; Arout Chelvane, J.; Nigam, A. K.

2014-09-01

129

Anomalous temperature dependence of the yield strength in IVa-VIII intermetallic compounds with B2 structure  

Microsoft Academic Search

The mechanical properties of the binary compound CoHf, and the pseudo-binary compounds CoTi-CoZr and CoTi-NiTi with B2 structure were measured as functions of testing temperature, composition and strain rate. In all of investigated compounds, the anomalous (positive) temperature dependence of the yield strength was observed at intermediate temperatures. The yield strength of CoHf compounds was dependent on composition through the

T. Takasugi; O. Izumi; M. Yoshida

1991-01-01

130

Influence of deviation from stoichiometry on the plasticity and mechanism of fracture of the boron-alloyed intermetallic compound Ni3Al obtained by self-propagating high-temperature synthesis  

Microsoft Academic Search

We have studied the effect that deviation of the composition of an ally from stoichiometry has on the plasticity delta, strength sigmaB, and the fracture mechanism of the intermetallic compound Ni3Al obtained by self-propagating high-temperature synthesis. The variation of the tensile strength, plasticity, type of fracture, and the cohesive strength sigmacoh of grains have been show to be correlated. The

G. P. Bakach; E. F. Dudarev; V. E. Ovcharenko; V. P. Lyubivoi; T. Yu. Chubenko; E. G. Barmina

1994-01-01

131

Influence of deviation from stoichiometry on the plasticity and mechanism of fracture of the boron-alloyed intermetallic compound Ni 3 Al obtained by self-propagating high-temperature synthesis  

Microsoft Academic Search

We have studied the effect that deviation of the composition of an ally from stoichiometry has on the plasticity d, strength sB, and the fracture mechanism of the intermetallic compound Ni3Al obtained by self-propagating high-temperature synthesis. The variation of the tensile strength, plasticity, type of fracture, and the cohesive strength scoh of grains have been show to be correlated. The

G. P. Bakach; E. F. Dudarev; V. E. Ovcharenko; V. P. Lyubivoi; T. Yu. Chubenko; E. G. Barmina

1994-01-01

132

Experimental and theoretical studies on the C15 intermetallic compounds MV{sub 2} (M = Zr, Hf and Ta): Elasticity and phase stability  

SciTech Connect

The phase stability of C15 HfV{sub 2} was studied by specific heat measurements. The elastic constants of C15 HfV{sub 2} were measured by the resonant ultrasound spectroscopy. Total energy and electronic structure of C15 intermetallic compounds MV{sub 2} (M = Zr, Hf and Ta) were calculated using the linear muffin tin orbital (LMTO) method. The band structures at X-point near the Fermi level were used to understand the anomalous shear moduli of the C15 HfV{sub 2} and ZrV{sub 2}. It was found that the double degeneracy with a linear dispersion relation of electronic levels at the x-point near the Fermi surface is mainly responsible for the C15 anomalous elasticity at high temperatures. The densities of states at Fermi level and the geometry of the Fermi surface were used to explain the low temperature phase instability of C15 HfV{sub 2} and ZrV{sub 2} and the stability of C15 TaV{sub 2}. The relationship between the anomalous elasticity and structural instability of C15 HfV{sub 2} and ZrV{sub 2} were also studied.

Chu, F.; Mitchell, T.E.; Chen, S.P. [Los Alamos National Lab., NM (United States); Sob, M.; Siegl, R.; Pope, D.P. [Univ. of Pennsylvania, Philadelphia, PA (United States). Dept. of Materials Science and Engineering

1994-12-01

133

Electron diffraction study on the crystal structure of a ternary intermetallic compound Co{sub 3}AlC{sub x}  

SciTech Connect

Intermetallic compound Co{sub 3}AlC{sub x}, or called {kappa}-phase, has been reported to assume the E2{sub 1}, or Perovskite structure. In the present work its crystal structure is critically reinvestigated in the two-phase alloys containing {kappa}-phase in the Co primary solid solution matrix, {alpha}(Co), using conventional electron diffraction. It is shown that the crystal structure of {kappa}-phase is a derivative of E2{sub 1} being a cubic structure composed of eight E2{sub 1} sub-unit cells in a half of which the body center sites are not occupied by carbon atoms. As a result, its space group is Fm3m and the chemical formula should be Co{sub 3}AlC{sub 0.5}. It is also found that the lattice parameter of the phase is about twice as large as that of {alpha}(Co). Orientation relationship of the {kappa}-phase with the matrix {alpha}(Co) is found to be similar to the case for the {gamma}{prime} phase with the fcc {gamma} matrix in a Ni-base superalloy since three orthogonal axes of {kappa}-phase are parallel to those of {alpha}(Co). Lattice misfit under this orientation relationship between the two phases is found to be about 2.5%.

Mishima, Yoshinao; Hwang, K.Y.; Wei, F.G.

1999-07-01

134

Control of beta phase in an EPM-processed intermetallic compound based on Ti-Al-Mn-Mo  

SciTech Connect

Gamma TiAl alloys have been under considerable research in recent years because of their good specific strength and the high resistance to creep and oxidation at elevated temperatures. Since the first report on their promising high temperature properties the gamma alloys have been continuously improved and their merits are highly valued now. Among the methods to produce the gamma alloys, EPM (Elemental Powder Metallurgy) method drew attention due to its amenability to the cost-effective near-net shape processing. In the EPM method alloying reaction is basically the exothermic reactions between elemental powders. A practical drawback of using this reaction as a sole method of alloying is the Kirkendall pores generated by the difference in the diffusivities of each alloying element. Therefore high temperature deformation process is added to seal the pores and consolidate the alloying reaction. In the previous attempt, the authors used hot extrusion to consolidate the TiAl compound containing Mn and Mo for improved mechanical properties. The Mo addition and the inherent characteristics of EPM, however, raised a question about the presence of {beta} phase that may cause undesirable effect on high temperature mechanical properties. In the present work, the authors attempted to answer this question from the stand point of finding a practical control method of {beta} phase and optimizing the microstructure.

Lee, T.K.; Hwang, S.K. [Inha Univ., Inchon (Korea, Republic of). Dept. of Metallurgical Engineering] [Inha Univ., Inchon (Korea, Republic of). Dept. of Metallurgical Engineering; Nam, S.W. [Korea Advanced Inst. of Science and Technology, Taejon (Korea, Republic of). Dept. of Materials Science and Engineering] [Korea Advanced Inst. of Science and Technology, Taejon (Korea, Republic of). Dept. of Materials Science and Engineering; Kim, N.J. [Pohang Univ. of Science and Technology, Pohang (Korea, Republic of). Center for the Advanced Aerospace Materials] [Pohang Univ. of Science and Technology, Pohang (Korea, Republic of). Center for the Advanced Aerospace Materials

1997-06-01

135

Identification of major metal complexing compounds in Blepharis aspera  

Microsoft Academic Search

Verbascoside and isoverbascoside, present at 0.7% and 0.2% (w\\/w dryweight), were identified to be major compounds that could contribute to the metal complexation in Blepharis aspera collected in Botswana, Africa. The metallophyte B. aspera has high ability to cope with a high level of metal accumulation. The presence of metal complexing compounds and\\/or antioxidants can prevent oxidative reactions in lipids,

Edward Eddie Mmatli; Helle Malerød; Steven Ray Wilson; Berhanu Abegaz; Tyge Greibrokk; Elsa Lundanes; Karl E. Malterud; Dirk Petersen; Frode Rise

2007-01-01

136

Defect complexes in III V compounds  

NASA Astrophysics Data System (ADS)

Some technically important examples of defect complexes in III-V semi-conductors will be briefly discussed in this paper. It is now clear that the midgap donor level in GaAs, often referred to as EL2, is not as previously assumed due to substitutional oxygen on an As site, but is a defect complex involving a Ga vacancy. This defect makes it possible to grow undoped semi-insulating GaAs for the production of integrated circuits. Defect reactions can be monitored by studying the luminescence from ZnO pairs, which are used to obtain red light from GaP LED's. The A and B levels often present in liquid phase GaAs are identified as the GaAs antisite. A normally unwanted but frequent contaminant in III-V semiconductors is Cu. We now know that the two copper-related levels which may appear in all large bandgap III-V's are not two levels of the same defect. At least one of the defects therefore has to be a complex. Studies in series of alloys demonstrate that the copper-related levels have the same defect origin in GaP, InP, GaAs and AlAs.

Ledebo, Lars-Åke

137

Processing of Complex Compound Semiconductors in Space  

NASA Technical Reports Server (NTRS)

The purpose of this first year ground based research effort was to develop growth and characterization facilities for bulk single crystals of compound semiconductor alloys. As a system of 2-6 alloy crystal growth, C sub x Mn sub (1-x)Te was chosen since it has a relatively narrow solidus-liquidus separation serving as a suitable first model for zone melting and solution growth. Also, it allows, in principle, perfect lattice matching to Cd sub x Hg sub(1-x)Te that needs to be studied as a model for the investigation of heteroepitaxial growth from Te-solutions. A vertical zone melting furnace was built and used in the synthesis of Cd sub x Mn sub(1-x)Te from the elements and crystal growth in carbon coated fused silica crucibles of Bridgman growth geometry. Photoluminescence spectra of the crystals reveal band to band recombination at energies that agree with the reported literature data. In addition, deep luminescence is present at energies corresponding to proportional shifts from the 1.4 eV deep emission observed for bulk single crystals of CdTe.

Bachmann, K.

1985-01-01

138

Complex compound polyvinyl alcohol-titanic acid/titanium dioxide  

NASA Astrophysics Data System (ADS)

A complex compound polyvinyl alcohol-titanic acid has been produced and investigated by means of IR and Raman spectroscopy, X-ray diffraction, and synchronous thermal analysis. It is claimed that it represents an interpolymeric complex of polyvinyl alcohol and hydrated titanium oxide.

Prosanov, I. Yu.

2013-02-01

139

Synthesis, Crystal Chemistry, and Physical Properties of Ternary Intermetallic Compounds An 2 T 2 X( An=Pu, Am; X=ln, Sn; T=Co, Ir, Ni, Pd, Pt, Rh)  

Microsoft Academic Search

The synthesis, structural, and physical characterization of nine new ternary intermetallic compounds belonging to the isostructuralAn2T2Xfamily with the transuranium Pu and Am elements, namely, Pu2Ni2In, Pu2Pd2In, Pu2Pt2In, Pu2Rh2In, Pu2Ni2Sn, Pu2Pd2Sn, Pu2Pt2Sn, Am2Ni2Sn, and Am2Pd2Sn, are reported. From these compounds only Pu2Rh2In, Am2Ni2Sn, and Am2Pd2Sn melt incongruently. All of these compounds crystallize in a tetragonal U3Si2-type structure, with the space groupP4\\/mbm,

L. C. J. Pereira; F. Wastin; J. M. Winand; B. Kanellakopoulos; J. Rebizant; J. C. Spirlet; M. Almeida

1997-01-01

140

Considerable rise in the stability of combined superconductors doped by intermetallic compounds with an extremely high low-temperature specific heat  

Microsoft Academic Search

The influence of doping intermetallics based on rare-earth elements and ceramics with an extremely high low-temperature specific heat on the stability of combined NbTi superconductors against electromagnetic disturbances is studied experimentally and theoretically. The objects of investigation are standard NbTi conductors (0.85 mm in diameter) in a copper matrix that are soldered to copper wires containing high-specific-heat dopants. CeCu6, HoCu2,

V. E. Keilin; P. A. Alekseev; I. A. Kovalev; S. L. Kruglov; V. N. Lazukov; M. I. Medvedev; D. I. Shutova

2007-01-01

141

Compound complex curves: the authentic geometry of esthetic dentistry.  

PubMed

Observers are drawn to the intricate and unpredictable way light reflects off the compound complex curved surfaces seen in nature, art, and industry. Teeth are no exception, containing as they do such detail in their gross anatomy, fine anatomic detail, and surface texture. Compound complex curves are particularly important when engineered materials are used to mimic naturally occurring objects, including prosthetic teeth, and they can provide both authenticity and beauty. The purpose of this article was to describe the nature of compound complex curves, their historical context, and their importance in creating natural-looking prostheses. Classically, such curves have been described by using descriptive qualitative methods or quantitative mathematical methods; now these approaches merge. Natural tooth anatomy contains interlinked features at different levels of scale from gross to fine surface texture detail. These curves should be created appropriately for individual restorative treatments. PMID:24589121

Scoble, Han O; White, Shane N

2014-06-01

142

Structure and luminescence properties of tellurium(IV) complex compounds  

NASA Astrophysics Data System (ADS)

Using the tellurium(IV) complex compounds as an example, we study the interrelation between the geometric structure and spectral luminescence properties. We find that, in the series of compounds of Te(IV), which are characterized by the island octahedral coordination of Te(IV) ions, the luminescence intensity depends on the degree of distortion of the Te(IV) coordination polyhedron, the Stokes shift, and the energy of the luminescence transition. We revealed that the considered series of Te(IV) compounds possess reversible thermochromic properties.

Sedakova, T. V.; Mirochnik, A. G.; Karasev, V. E.

2011-05-01

143

Vibrational spectroscopy and structural analysis of complex uranium compounds (review)  

SciTech Connect

The paper reports on the combined application of experimental and theoretical methods of vibrational spectroscopy together with low-temperature luminescence data to determine the characteristic features of the formation and structure of complex systems, not only containing ligands directly coordinated to the CA uranium, but also associated with the extraspherical polyatomic electrically charged particles: organic cations. These include uranyl complexes and heterocyclical amines. Studied here were compounds of tetra-halouranylates with pyridine and its derivates, as well as dipyridyl, quinoline and phenanthroline. Structural schemes are also proposed for other uranyl complexes with protonated heterocyclical amines with a more complicated composition, which correctly reflect their spectroscopic properties.

Umreiko, D.S.; Nikanovich, M.V.

1985-06-01

144

Considerable rise in the stability of combined superconductors doped by intermetallic compounds with an extremely high low-temperature specific heat  

Microsoft Academic Search

The influence of doping intermetallics based on rare-earth elements and ceramics with an extremely high low-temperature specific\\u000a heat on the stability of combined NbTi superconductors against electromagnetic disturbances is studied experimentally and\\u000a theoretically. The objects of investigation are standard NbTi conductors (0.85 mm in diameter) in a copper matrix that are\\u000a soldered to copper wires containing high-specific-heat dopants. CeCu6, HoCu2,

V. E. Keilin; P. A. Alekseev; I. A. Kovalev; S. L. Kruglov; V. N. Lazukov; M. I. Medvedev; D. I. Shutova

2007-01-01

145

Removal of cyanides by complexation with ferrous compounds  

SciTech Connect

Alkaline chlorination, an oxidation process with chlorine (Cl{sub 2}) or hypochlorite (ClO{sup {minus}}), is the most widely accepted method of cyanide treatment. However, removal of cyanide from wastewater to the extent required by the effluent limits imposed by Federal and State regulatory authorities is practically impossible, especially when the majority of the cyanide is present as an iron-cyanide complex. One potential treatment method being further investigated uses ferrous (Fe{sup 2+}) compounds to react with free and complex cyanide ions and produce insoluble iron-cyanide complexes. However, sludges generated by this treatment method contain cyanide wastes which may be considered a hazardous waste by the US Environmental Protection Agency (US EPA). The studies reported in this paper demonstrate that ferrous (Fe{sup 2+}) precipitation can remove cyanide ions (both free and complex) to a concentration within the range of 1 to 2 mg/L. The wastewaters utilized in these tests were collected from a coke plant facility. Synthetic cyanide solutions were used in the studied as well. Ferrous compounds used in the studies included commercial-grade ferrous sulfate, commercial-grade ferrous chloride, and spent pickle liquor (containing ferrous ion). The desired effluent quality was successfully attained in the treatment of the above-mentioned wastewaters by using ferrous compounds as well as spent pickle liquor.

Varuntanya, C.P.; Zabban, W. [Chester Environmental, Moon Township, PA (United States)

1995-12-31

146

Microstructure Changes and Physical Properties of the Intermetallic Compounds Formed at the Interface Between Sn-Cu Solders and a Cu Substrate Due to a Minor Addition of Ni  

NASA Astrophysics Data System (ADS)

The influence of Cu content and added Ni on the morphology of the intermetallic compound (IMC) layer formed at the interface between liquid Sn-Cu-based solders and a Cu substrate and on the strength of simulated solder joints was investigated. The reaction of a Sn-0.7Cu alloy with the substrate led to the formation of a thin layer of Cu6Sn5 ( ?-phase) with typical scallop morphology that did not grow with longer reaction times. Higher Cu content such as in the Sn-1.4Cu alloy led to extensive growth with increased reaction time; at long reaction times, Cu3Sn ( ?-phase) was observed at the interface between the Cu substrate and the Cu6Sn5 layer. A small nickel addition to the Sn-0.7Cu alloy significantly changed the IMC morphology, accelerated its growth kinetics, prevented formation of the Cu3Sn layer, and reduced the rate of substrate dissolution.

Harcuba, Petr; Jane?ek, Miloš

2010-12-01

147

Integrating giant microwave absorption with magnetic refrigeration in one multifunctional intermetallic compound of LaFe11.6Si1.4C0.2H1.7  

PubMed Central

Both microwave absorption and magnetocaloric effect (MCE) are two essential performances of magnetic materials. We observe that LaFe11.6Si1.4C0.2H1.7 intermetallic compound exhibits the advantages of both giant microwave absorption exceeding ?42?dB and magnetic entropy change of ?20?Jkg?1K?1. The excellent electromagnetic wave absorption results from the large magnetic loss and dielectric loss as well as the efficient complementarity between relative permittivity and permeability. The giant MCE effect in this material provides an ideal technique for cooling the MAMs to avoid temperature increase and infrared radiation during microwave absorption. Our finding suggests that we can integrate the giant microwave absorption with magnetic refrigeration in one multifunctional material. This integration not only advances our understanding of the correlation between microwave absorption and MCE, but also can open a new avenue to exploit microwave devices and electromagnetic stealth. PMID:23887357

Song, Ning-Ning; Ke, Ya-Jiao; Yang, Hai-Tao; Zhang, Hu; Zhang, Xiang-Qun; Shen, Bao-Gen; Cheng, Zhao-Hua

2013-01-01

148

Complex Dynamics of Compound Vesicles in Linear Flow  

NASA Astrophysics Data System (ADS)

We report first experimental observations of dynamics of compound vesicles in linear flow realized in a microfluidic four-roll mill. We show that while a compound vesicle undergoes the same main tank-treading, trembling (TR), and tumbling regimes, its dynamics are far richer and more complex than that of unilamellar vesicles. A new swinging motion of the inner vesicle is found in TR in accord with simulations. The inner and outer vesicles can exist simultaneously in different dynamical regimes and can undergo either synchronized or unsynchronized motions depending on the filling factor. A compound vesicle can be used as a physical model to study white blood cell dynamics in flow similar to a unilamellar vesicle used successfully to model anucleate cells.

Levant, Michael; Steinberg, Victor

2014-04-01

149

Complex conductivity of UTX compounds in high magnetic fields  

SciTech Connect

We have performed rf-skin depth (complex-conductivity) and magnetoresistance measurements of anti ferromagnetic UTX compounds (T=Ni and X=Al, Ga, Ge) in applied magnetic fields up to 60 T applied parallel to the easy directions. The rf penetration depth was measured by coupling the sample to the inductive element of a resonant tank circuit and then, measuring the shifts in the resonant frequency {Delta}f of the circuit. Shifts in the resonant frequency {Delta}f are known to be proportional to the skin depth of the sample and we find a direct correspondence between the features in {Delta}f and magnetoresistance. Several first-order metamagnetic transitions, which are accompanied by a drastic change in {Delta}f, were observed in these compounds. In general, the complex-conductivity results are consistent with magnetoresistance data.

Mielke, Charles H [Los Alamos National Laboratory; Mcdonald, Ross D [Los Alamos National Laboratory; Zapf, Vivien [Los Alamos National Laboratory; Altarawneh, M M [Los Alamos National Laboratory; Lacerda, A [Los Alamos National Laboratory; Alsmadi, A M [HASHEMITE UNIV; Alyones, S [HASHEMITE UNIV; Chang, S [NIST; Adak, S [NMSU; Kothapalli, K [NMSU; Nakotte, H [NMSU

2009-01-01

150

Complex conductivity of UTX compounds in high magnetic fields  

SciTech Connect

We have performed Resonance Frequency (RF) skin depth (complex-conductivity) and magnetoresistance measurements of antiferromagnetic UTX compounds (T Ni, and X := AI, Ga, Ge) in applied magnetic fields up to 60 T applied parallel to the easy directions. The RF penetration depth was measured by coupling the sample to the inductive element of a resonant tank circuit and then, measuring the shifts in the resonant frequency {Delta}f of the circuit. Shifts in the resonant frequency {Delta}f are known to be proportional to the skin depth of the sample and we find a direct correspondence between the features in {Delta}f and magnetoresistance. Several first-order metamagnetic transitions, which are accompanied by a drastic change in {Delta}f, were observed in these compounds. In general, the complex-conductivity results are consistent with magnetoresistance data.

Lacerda, Alex Hugo [Los Alamos National Laboratory; Mielke, Charles H [Los Alamos National Laboratory; Mc Donald, Ross D [Los Alamos National Laboratory

2008-01-01

151

SrZn{sub 2}Sn{sub 2} and Ca{sub 2}Zn{sub 3}Sn{sub 6} - two new Ae-Zn-Sn polar intermetallic compounds (Ae: alkaline earth metal)  

SciTech Connect

SrZn{sub 2}Sn{sub 2} and Ca{sub 2}Zn{sub 3}Sn{sub 6}, two closely related new polar intermetallic compounds, were obtained by high temperature reactions of the elements. Their crystal structures were determined with single crystal XRD methods, and their electronic structures were analyzed by means of DFT calculations. The Zn-Sn structure part of SrZn{sub 2}Sn{sub 2} comprises (anti-)PbO-like {l_brace}ZnSn{sub 4/4}{r_brace} and {l_brace}SnZn{sub 4/4}{r_brace} layers. Ca{sub 2}Zn{sub 3}Sn{sub 6} shows similar {l_brace}ZnSn{sub 4/4}{r_brace} layers and {l_brace}Sn{sub 4}Zn{r_brace} slabs constructed of a covalently bonded Sn scaffold capped by Zn atoms. For both phases, the two types of layers are alternatingly stacked and interconnected via Zn-Sn bonds. SrZn{sub 2}Sn{sub 2} adopts the SrPd{sub 2}Bi{sub 2} structure type, and Ca{sub 2}Zn{sub 3}Sn{sub 6} is isotypic to the R{sub 2}Zn{sub 3}Ge{sub 6} compounds (R=La, Ce, Pr, Nd). Band structure calculations indicate that both SrZn{sub 2}Sn{sub 2} and Ca{sub 2}Zn{sub 3}Sn{sub 6} are metallic. Analyses of the chemical bonding with the electron localization function (ELF) show lone pair like basins at Sn atoms and Zn-Sn bonding interactions between the layers for both title phases, and covalent Sn-Sn bonding within the {l_brace}Sn{sub 4}Zn{r_brace} layers of Ca{sub 2}Zn{sub 3}Sn{sub 6}. - Graphical abstract: Crystal structures of the new Ae-Zn-Sn polar intermetallic phases SrZn{sub 2}Sn{sub 2} and Ca{sub 2}Zn{sub 3}Sn{sub 6}. Highlights: Black-Right-Pointing-Pointer New polar intermetallic phases SrZn{sub 2}Sn{sub 2} and Ca{sub 2}Zn{sub 3}Sn{sub 6}. Black-Right-Pointing-Pointer Obtained by high temperature reactions of the elements. Black-Right-Pointing-Pointer Single crystal XRD structure determination and DFT electronic structure calculations. Black-Right-Pointing-Pointer Closely related crystal and electronic structures. Black-Right-Pointing-Pointer Metallic conductivity coexisting with lone pairs and covalent bonding features.

Stegmaier, Saskia [Department Chemie, Technische Universitaet Muenchen, Lichtenbergstrasse 4, 85747 Garching (Germany); Faessler, Thomas F., E-mail: Thomas.Faessler@lrz.tum.de [Department Chemie, Technische Universitaet Muenchen, Lichtenbergstrasse 4, 85747 Garching (Germany)

2012-08-15

152

Reactivity of bromine atom complexes with organic compounds  

SciTech Connect

Complexes of bromine atoms with bromo compounds (C{sub 2}H{sub 5}Br{center dot}Br, CH{sub 2}Br{sub 2}{center dot}Br, CHBr{sub 3}{center dot}Br, and CBr{sub 4}{center dot}Br) were produced by pulse radiolysis of the corresponding bromoalkane dissolved in cyclohexane. With benzene as solvent, the complex C{sub 6}H{sub 6}{center dot}Br was produced. These complexes oxidized phenols to phenoxyl radicals and abstract reactive hydrogens from various compounds. Absolute rate constants for these reactions were determined by following the decay of the Br atom complexes (at 370, 390, 425, 480 and 540 nm, respectively) as a function of substrate concentration. The rate constants varied from 10{sup 5} to 10{sup 10} M{sup {minus}1} s{sup {minus}1} and were strongly dependent on the nature of the Br atom complex and of the organic substrate.

Shoute, L.C.T.; Neta, P. (National Institute of Standards and Technology, Gaithersburg, MD (USA))

1990-09-06

153

Considerable rise in the stability of combined superconductors doped by intermetallic compounds with an extremely high low-temperature specific heat  

NASA Astrophysics Data System (ADS)

The influence of doping intermetallics based on rare-earth elements and ceramics with an extremely high low-temperature specific heat on the stability of combined NbTi superconductors against electromagnetic disturbances is studied experimentally and theoretically. The objects of investigation are standard NbTi conductors (0.85 mm in diameter) in a copper matrix that are soldered to copper wires containing high-specific-heat dopants. CeCu6, HoCu2, CeAl2, and PrB6 intermetallics (at 4.2 K, their specific heat is on average 150 times that of copper) or Cd2O2S ceramics (at 4.2 K, its specific heat is higher than that of copper by 600 times) are introduced into combined superconductor samples in the form of fine powder. The powder is placed into the copper wire either as one thick (0.6 mm in diameter) strand or as 19 thin (0.1 mm in diameter) strands. An undoped reference sample contains a solid conductor. Samples with a transport current placed in an external transverse magnetic field are subjected to longitudinal magnetic disturbances causing pulsed heating of the samples by eddy currents. The disturbance time is varied in a wide range: from 50 ?s to 1.2 ms. To compare the critical energy densities of the disturbances in differently shaped samples, a mathematical technique is developed that is based on analytical solution of the equation of electromagnetic diffusion into the sample. It is found that the critical energy density of doped samples is much higher (by several times) than that of the reference sample. Upon direct cooling of the samples by liquid helium in a vertical channel (the most intense heat removal under steady-state conditions), the effect of stability improvement for the doped samples persists. Moreover, it is shown that the high-specific-heat dopants, raising the heat needed to warm the sample, restrict the heat flux into the liquid and thereby increase the energy removed by the coolant during unsteady heat transfer.

Keilin, V. E.; Alekseev, P. A.; Kovalev, I. A.; Kruglov, S. L.; Lazukov, V. N.; Medvedev, M. I.; Shutova, D. I.

2007-09-01

154

Microstructure study of the rare-earth intermetallic compounds R5(SixGe1-x)4 and R5(SixGe1-x)3  

SciTech Connect

The unique combination of magnetic properties and structural transitions exhibited by many members of the R{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} 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 5(Si{sub x}Ge{sub 1-x}){sub 4} 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 5}Si{sub 4} 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 5}Si{sub 4}-type orthorhombic to Gd{sub 5}Si{sub 2}Ge{sub 2}-type monoclinic. This structural transition is reversible, moving in the opposite direction when the material is subjected to low-temperature annealing at 500 ?C. Successful future utilization of the R{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} family in novel devices depends on a fundamental understanding of the structure-property interplay on the nanoscale level, which makes a complete understanding of the microstructure of this family especially important. Past scanning electron microscopy (SEM) observation has shown that nanometer-thin plates exist in every R{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} (“5:4”) phase studied, independent of initial parent crystal structure and composition. A comprehensive electron microscopy study including SEM, energy dispersive spectroscopy (EDS), selected area diffraction (SAD), and high resolution transmission electron microscopy (HRTEM) of a selected complex 5:4 compound based on Er rather than Gd, (Er{sub 0.9Lu{sub 0.1}){sub 5}Si{sub 4}, has produced data supporting the assumption that all the platelet-like features present in the R{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} family are hexagonal R{sub 5}(Si{sub x}Ge{sub 1-x}){sub 3} (“5:3”) phase and possess the same reported orientation relationship that exists for the Gd{sub 5}Ge{sub 4} and Gd{sub 5}Si{sub 2}Ge{sub 2} compounds, i.e. [010](102?){sub m} || [101?0](12?11){sub p}. Additionally, the phase identification in (Er{sub 0.9}Lu{sub 0.1}){sub 5}Si{sub 4} carried out using X-ray powder diffraction (XRD) techniques revealed that the low amount of 5:3 phase is undetectable in a conventional laboratory Cu K? diffractometer due to detection limitations, but that extremely low amounts of the 5:3 phase can be detected using high resolution powder diffraction (HRPD) employing a synchrotron source. These results suggest that use of synchrotron radiation for the study of R{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} compounds should be favored over conventional XRD for future investigations. The phase stability of the thin 5:3 plates in a Gd{sub 5}Ge{sub 4} sample was examined by performing long-term annealing at very high temperature. The experimental results indicate the plates are thermally unstable above 1200?C. While phase transformation of 5:3 to 5:4 occurs during the annealing, the phase transition is still fairly sluggish, being incomplete even after 24 hours annealing at this elevated temperature. Additional experiments using laser surface melting performed on the surface of a Ho{sub 5}(Si{sub 0.8}Ge{sub 0.}2){sub 4} sample showed that rapid cooling will suppress the precipitation of 5:3 plates. Bulk microstructure studies of polycrystalline and monocrystalline Gd{sub 5}Ge{sub 3} compounds examined using optical microscopy, SEM and TEM also show a series of linear features present in the Gd{sub 5}Ge{sub 3} matrix, similar in appearance in many ways to the 5:3 plates observed in R{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} compounds. A systematic microscopy analysis of these linear features revealed they also are thin plates with a stoichiometric composition of Gd{sub 5}Ge{sub 4} with an orthorhombic structure. The orientation relationship between the 5:3 matrix and the precipitate 5:4 thin plates was determined as [101?0] (12?11){s

Cao, Qing

2012-07-26

155

Exposure profiling of reactive compounds in complex mixtures.  

PubMed

Humans are constantly exposed to mixtures, such as tobacco smoke, exhaust from diesel, gasoline or new bio-fuels, containing several 1000 compounds, including many known human carcinogens. Covalent binding of reactive compounds or their metabolites to DNA and formation of stable adducts is believed to be the causal link between exposure and carcinogenesis. DNA and protein adducts are well established biomarkers for the internal dose of reactive compounds or their metabolites and are an integral part of science-based risk assessment. However, technical limitations have prevented comprehensive detection of a broad spectrum of adducts simultaneously. Therefore, most studies have focused on measurement of abundant individual adducts. These studies have produced valuable insight into the metabolism of individual carcinogens, but they are insufficient for risk assessment of exposure to complex mixtures. To overcome this limitation, we present herein proof-of-principle for comprehensive exposure assessment, using N-terminal valine adduct profiles as a biomarker. The reported method is based on our previously established immunoaffinity liquid chromatography-tandem mass spectrometry (LC-MS/MS) method with modification to enrich all N-terminal valine alkylated peptides. The method was evaluated using alkylated peptide standards and globin reacted in vitro with alkylating agents (1,2-epoxy-3-butene, 1,2:3,4-diepoxybutane, propylene oxide, styrene oxide, N-ethyl-N-nitrosourea and methyl methanesulfonate), known to form N-terminal valine adducts. To demonstrate proof-of-principle, the method was successfully applied to globin from mice treated with four model compounds. The results suggest that this novel approach might be suitable for in vivo biomonitoring. PMID:23219592

Goel, Shilpi; Evans-Johnson, Julie A; Georgieva, Nadia I; Boysen, Gunnar

2013-11-16

156

CCMR: Characterization of ordered intermetallics as catalysts for fuel cell applications  

NSDL National Science Digital Library

Characterization of new intermetallic compounds for fuel cell anodes was carried out in fuels such as formic acid (FA), methanol, and ethanol using cyclic voltammetry. A significant number of these ordered intermetallic phases exhibited enhanced electrocatalytic activity when compared to bulk platinum (Pt), in terms of both oxidation onset potential and current density. The Pt3Ta, Pt2Ta, Pt3Ti, PtZr, and Pt3Nb ordered intermetallic phases were the most promising electrocatalysts tested for fuel cell applications.

Cruz Quiã±ones, Miguel

2005-08-17

157

Fabrication of near net-shaped Al-based intermetallics matrix composites  

Microsoft Academic Search

Intermetallic compounds based on aluminium with Ni, Fe or Ti offer new opportunities for developing superior\\/advanced structural alloys for applications as diversified as biomedical and aerospace-aircraft industries. Aluminides have the attractive characteristics of low density, high strength, good corrosion and oxidation resistance, non-strategic elements and relatively low cost.There are several techniques for synthesizing the intermetallics and intermetallic matrix composites (IMCs),

M. R Ghomashchi

2001-01-01

158

Magnetic properties and structure of R{sub 2}Co{sub 17{minus}x}Ti{sub x} intermetallic compounds (R=Pr or Nd)  

SciTech Connect

The effect of substitution of Ti for Co in compounds R{sub 2}Co{sub 17{minus}x}Ti{sub x} (R=Pr or Nd, and x=0.0{endash}2.0) on the structure and the magnetic properties has been investigated. It is found that the solubility of Ti in the compounds R{sub 2}Co{sub 17{minus}x}Ti{sub x} (R=Pr or Nd) is around 1.0. The R{sub 2}Co{sub 16}Ti (R=Pr or Nd) are isostructures to their parent compounds (rhombohedral), and its unit cell is expanded. The spontaneous magnetization {mu}{sub s} and Curie temperature T{sub C} decrease with increasing Ti content, owing to the magnetic dilution and the reduction of the moment of Co sublattice caused by Ti substitution. Moreover, an anomaly in the M-T curves of Pr{sub 2}Co{sub 16}Ti and Nd{sub 2}Co{sub 17{minus}x}Ti{sub x} compounds with x=0.5 and 1.0 may be attributed to a spin reorientation. This transition may originate from the change of crystal electron field due to the preferential occupation of Ti atoms on specific crystallographic sites. {copyright} {ital 1997 American Institute of Physics.}

Tang, H. [Institute of Metal Research, Academia Sinica, 72 Wenhua Road, 110015 Shenyang, Peoples Republic of (China)] [Institute of Metal Research, Academia Sinica, 72 Wenhua Road, 110015 Shenyang, Peoples Republic of (China); Shen, B.G. [Institute of Physics, Academia Sinica, P.O. Box 603, 100080 Beijing, Peoples Republic of (China)] [Institute of Physics, Academia Sinica, P.O. Box 603, 100080 Beijing, Peoples Republic of (China); Buschow, K.H.; de Boer, F.R. [Van der Waals--Zeeman Laboratory, University of Amsterdam, Valckenierstraat, 1018 XE Amsterdam (The Netherlands)] [Van der Waals--Zeeman Laboratory, University of Amsterdam, Valckenierstraat, 1018 XE Amsterdam (The Netherlands); Wang, Y.Z.; Qiao, G.W. [Institute of Metal Research, Academia Sinica, 72 Wenhua Road, 110015 Shenyang, Peoples Republic of (China)] [Institute of Metal Research, Academia Sinica, 72 Wenhua Road, 110015 Shenyang, Peoples Republic of (China)

1997-04-01

159

High-temperature structural intermetallics  

SciTech Connect

In the last one and a half decades, a great deal of fundamental and developmental research has been made on high-temperature structural intermetallics aiming at the implementation of these intermetallics in aerospace, automotive and land-based applications. These intermetallics include aluminides formed with either titanium, nickel or iron and silicides formed with transition metals. Of these high-temperature intermetallics, TiAl-based alloys with great potential in both aerospace and automotive applications have been attracting particular attention. Recently TiAl turbocharger wheels have finally started being used for turbochargers for commercial passenger cars of a special type. The current status of the research and development of these high-temperature intermetallics is summarized and a perspective on what directions future research and development of high-temperature intermetallics should take is provided.

Yamaguchi, M.; Inui, H.; Ito, K.

2000-01-01

160

Complex Hydride Compounds with Enhanced Hydrogen Storage Capacity  

SciTech Connect

The United Technologies Research Center (UTRC), in collaboration with major partners Albemarle Corporation (Albemarle) and the Savannah River National Laboratory (SRNL), conducted research to discover new hydride materials for the storage of hydrogen having on-board reversibility and a target gravimetric capacity of ? 7.5 weight percent (wt %). When integrated into a system with a reasonable efficiency of 60% (mass of hydride / total mass), this target material would produce a system gravimetric capacity of ? 4.5 wt %, consistent with the DOE 2007 target. The approach established for the project combined first principles modeling (FPM - UTRC) with multiple synthesis methods: Solid State Processing (SSP - UTRC), Solution Based Processing (SBP - Albemarle) and Molten State Processing (MSP - SRNL). In the search for novel compounds, each of these methods has advantages and disadvantages; by combining them, the potential for success was increased. During the project, UTRC refined its FPM framework which includes ground state (0 Kelvin) structural determinations, elevated temperature thermodynamic predictions and thermodynamic / phase diagram calculations. This modeling was used both to precede synthesis in a virtual search for new compounds and after initial synthesis to examine reaction details and options for modifications including co-reactant additions. The SSP synthesis method involved high energy ball milling which was simple, efficient for small batches and has proven effective for other storage material compositions. The SBP method produced very homogeneous chemical reactions, some of which cannot be performed via solid state routes, and would be the preferred approach for large scale production. The MSP technique is similar to the SSP method, but involves higher temperature and hydrogen pressure conditions to achieve greater species mobility. During the initial phases of the project, the focus was on higher order alanate complexes in the phase space between alkaline metal hydrides (AmH), Alkaline earth metal hydrides (AeH2), alane (AlH3), transition metal (Tm) hydrides (TmHz, where z=1-3) and molecular hydrogen (H2). The effort started first with variations of known alanates and subsequently extended the search to unknown compounds. In this stage, the FPM techniques were developed and validated on known alanate materials such as NaAlH4 and Na2LiAlH6. The coupled predictive methodologies were used to survey over 200 proposed phases in six quaternary spaces, formed from various combinations of Na, Li Mg and/or Ti with Al and H. A wide range of alanate compounds was examined using SSP having additions of Ti, Cr, Co, Ni and Fe. A number of compositions and reaction paths were identified having H weight fractions up to 5.6 wt %, but none meeting the 7.5 wt%H reversible goal. Similarly, MSP of alanates produced a number of interesting compounds and general conclusions regarding reaction behavior of mixtures during processing, but no alanate based candidates meeting the 7.5 wt% goal. A novel alanate, LiMg(AlH4)3, was synthesized using SBP that demonstrated a 7.0 wt% capacity with a desorption temperature of 150°C. The deuteride form was synthesized and characterized by the Institute for Energy (IFE) in Norway to determine its crystalline structure for related FPM studies. However, the reaction exhibited exothermicity and therefore was not reversible under acceptable hydrogen gas pressures for on-board recharging. After the extensive studies of alanates, the material class of emphasis was shifted to borohydrides. Through SBP, several ligand-stabilized Mg(BH4)2 complexes were synthesized. The Mg(BH4)2*2NH3 complex was found to change behavior with slightly different synthesis conditions and/or aging. One of the two mechanisms was an amine-borane (NH3BH3) like dissociation reaction which released up to 16 wt %H and more conservatively 9 wt%H when not including H2 released from the NH3. From FPM, the stability of the Mg(BH4)2*2NH3 compound was found to increase with the inclusion of NH3 groups in the inner-Mg coordination

Mosher, Daniel A.; Opalka, Susanne M.; Tang, Xia; Laube, Bruce L.; Brown, Ronald J.; Vanderspurt, Thomas H.; Arsenault, Sarah; Wu, Robert; Strickler, Jamie; Anton, Donald L.; Zidan, Ragaiy; Berseth, Polly

2008-02-18

161

Synthesis, structures and bonding of superconducting barium vanadium sulfide and intermetallic solid state compounds of group 2, 3, 13, 14 and transition elements  

Microsoft Academic Search

Superconducting transition is well known for the Chevrel phases M xMo6S8 and MxMo6Se 8 where M is dopant metal such as Pb, In, Tl and La. Not many ternary group 5 transition metal chalcogenides of similar composition, however, are known to be superconductors. The synthesis and observation of superconducting transition of the Ba doped compound BaxV6S8 (x = 0.45--0.48) is

Kim Carl Lobring

2001-01-01

162

Recent advances in ordered intermetallics  

SciTech Connect

This paper briefly summarizes recent advances in intermetallic research and development. Ordered intermetallics based on aluminides and silicides possess attractive properties for structural applications at elevated temperatures in hostile environments; however, brittle fracture and poor fracture resistance limit their use as engineering materials in many cases. In recent years, considerable efforts have been devoted to the study of the brittle fracture behavior of intermetallic alloys; as a result, both intrinsic and extrinsic factors governing brittle fracture have been identified. Recent advances in first-principles calculations and atomistic simulations further help us in understanding atomic bonding, dislocation configuration, and alloying effects in intermetallics. The basic understanding has led to the development of nickel, iron, and titanium aluminide alloys with improved mechanical and metallurgical properties for structural use. Industrial interest in ductile intermetallic alloys is high, and several examples of industrial involvement are mentioned.

Liu, C.T.

1992-12-31

163

Anisotropic physical properties of the Al13Fe4 complex intermetallic and its ternary derivative Al13(Fe,Ni)4  

NASA Astrophysics Data System (ADS)

We have investigated the magnetic susceptibility, the electrical resistivity, the specific heat, the thermoelectric power, the Hall coefficient, and the thermal conductivity of the Al13Fe4 and Al13(Fe,Ni)4 monoclinic approximants to the decagonal quasicrystal. While the Al13Fe4 crystals are structurally well ordered, the ternary derivative Al13(Fe,Ni)4 contains substitutional disorder and is considered as a disordered version of the Al13Fe4 . The crystallographic-direction-dependent measurements were performed along the a? , b , and c directions of the monoclinic unit cell, where the (a?,c) atomic planes are stacked along the b direction. The electronic transport and the magnetic properties exhibit significant anisotropy. The stacking b direction is the most conducting direction for the electricity and heat. The effect of substitutional disorder in Al13(Fe,Ni)4 is manifested in the large residual resistivity ?(T?0) and significantly reduced thermal conductivity of this compound, as compared to the ordered Al13Fe4 . Specific-heat measurements reveal that the electronic density of states at the Fermi level of both compounds is high. The anisotropic Hall coefficient RH reflects complex structure of the anisotropic Fermi surface that contains electronlike and holelike contributions. Depending on the combination of directions of the current and the magnetic field, electronlike (RH<0) or holelike (RH>0) contributions may dominate, or the two contributions compensate each other (RH?0) . Similar complicated anisotropic behavior was observed also in the thermopower. The anisotropic Fermi surface was calculated ab initio using the atomic parameters of the refined Al13Fe4 structural model that is also presented in this work.

Pop?evi?, P.; Smontara, A.; Ivkov, J.; Wencka, M.; Komelj, M.; Jegli?, P.; Vrtnik, S.; Bobnar, M.; Jagli?i?, Z.; Bauer, B.; Gille, P.; Borrmann, H.; Burkhardt, U.; Grin, Yu.; Dolinšek, J.

2010-05-01

164

Magnetic Studies of New Cerium Intermetallics: Screening for Mixed Valence  

Microsoft Academic Search

We have been searching for new cerium compounds to explore their potential for thermoelectric applications. The figure of merit of a thermoelectric material depends on the square of the thermopower, S, and the product of the resistivity and thermal conductivity as S^2\\/ rhokappa. In the class of intermetallics called \\

Robert Allan Gordon

1996-01-01

165

A compilation of corrosion potentials reported for intermetallic phases in aluminum alloys  

SciTech Connect

A compilation of corrosion potentials reported for Al-based intermetallic compounds is presented. The range of corrosion potentials for dilute aluminum binary alloys is also given. This compilation is intended to serve as an aid in establishing galvanic relationships among discrete microstructural elements in aluminum alloys. This compilation is based primarily on data reported in the corrosion literature with a focus on corrosion potentials for intermetallic compound particles found in commercial alloys.

Buchheit, R.G. [Sandia National Labs., Albuquerque, NM (United States). Mechanical Metallurgy and Corrosion Dept.

1995-11-01

166

Synthesis and microstructural characterization of Ti–Al 3Ti metal–intermetallic laminate (MIL) composites  

Microsoft Academic Search

Ti–Al3Ti laminated composites have been fabricated through reactive sintering in vacuum using Ti and Al foils with different initial thicknesses. The aluminum layer is consumed by forming a titanium aluminide intermetallic compound. Thus, the final microstructure consists of alternating layers of intermetallic compound and unreacted Ti metal. Microstructural characterization by scanning electron microscopy (SEM), X-ray diffractometry (XRD) and energy dispersive

L. M. Peng; J. H. Wang; H. Li; J. H. Zhao; L. H. He

2005-01-01

167

Humic acid complexation of basic and neutral polycyclic aromatic compounds  

E-print Network

anthropogenic sources including the combustion of fossil fuels, chemical manufacturing, pe- troleum refining in revised form 22 April 2002; accepted 30 April 2002 Abstract Complexation by humic acid (HA) of basic mechanism (i.e., a dark complex is formed) when the protonated form is adsorbed via ion exchange to HA

Chorover, Jon

168

The thermodynamic properties of calcium intermetallic compounds  

Microsoft Academic Search

The thermodynamic properties of calcium alloys have been measured by emf (an original pin-point method) and calorimetry in recent years. A review of experimental results obtained for 15 binary (Ca,M) systems is presented (with M ? Ni, Pd, Pt, Cu, Ag, Au, Mg, Al, Ga, Si, Ge, Sn, Pb, Sb, Bi), and numerical optimization is performed for some of them.

M. Notin; J. Mejbar; A. Bouhajib; J. Charles; J. Hertz

1995-01-01

169

A ring-distortion strategy to construct stereochemically complex and structurally diverse compounds from natural products.  

PubMed

High-throughput screening is the dominant method used to identify lead compounds in drug discovery. As such, the makeup of screening libraries largely dictates the biological targets that can be modulated and the therapeutics that can be developed. Unfortunately, most compound-screening collections consist principally of planar molecules with little structural or stereochemical complexity, compounds that do not offer the arrangement of chemical functionality necessary for the modulation of many drug targets. Here we describe a novel, general and facile strategy for the creation of diverse compounds with high structural and stereochemical complexity using readily available natural products as synthetic starting points. We show through the evaluation of chemical properties (which include fraction of sp(3) carbons, ClogP and the number of stereogenic centres) that these compounds are significantly more complex and diverse than those in standard screening collections, and we give guidelines for the application of this strategy to any suitable natural product. PMID:23422561

Huigens, Robert W; Morrison, Karen C; Hicklin, Robert W; Flood, Timothy A; Richter, Michelle F; Hergenrother, Paul J

2013-03-01

170

A Ring Distortion Strategy to Construct Stereochemically Complex and Structurally Diverse Compounds from Natural Products  

PubMed Central

High-throughput screening is the dominant method to identify lead compounds in drug discovery. As such, the makeup of screening libraries will largely dictate the biological targets that can be modulated and the therapeutics that can be developed. Unfortunately, most compound screening collections consist principally of planar molecules with little structural or stereochemical complexity, compounds that do not offer the arrangement of chemical functionality necessary for modulation of many drug targets. Here we describe a novel, general, and facile strategy for the creation of diverse compounds with high structural and stereochemical complexity using readily available natural products as synthetic starting points. We show, through evaluation of chemical properties including fraction of sp3 carbons, ClogP, and the number of stereogenic centers, that these compounds are significantly more complex and diverse than those in standard screening collections, and guidelines are given for the application of this strategy to any suitable natural product. PMID:23422561

Huigens, Robert W.; Morrison, Karen C.; Hicklin, Robert W.; Flood, Timothy A.; Richter, Michelle F.; Hergenrother, Paul J.

2014-01-01

171

Intermetallic insertion anodes for lithium batteries.  

SciTech Connect

Binary intermetallic compounds containing lithium, or lithium alloys, such as Li{sub x}Al, Li{sub x}Si and Li{sub x}Sn have been investigated in detail in the past as negative electrode materials for rechargeable lithium batteries. It is generally acknowledged that the major limitation of these systems is the large volumetric expansion that occurs when lithium reacts with the host metal. Such large increases in volume limit the practical use of lithium-tin electrodes in electrochemical cells. It is generally recognized that metal oxide electrodes, MO{sub y}, in lithium-ion cells operate during charge and discharge by means of a reversible lithium insertion/extraction process, and that the cells offer excellent cycling behavior when the crystallographic changes to the unit cell parameters and unit cell volume of the Li{sub x}MO{sub y} electrode are kept to a minimum. An excellent example of such an electrode is the spinel Li{sub 4}Ti{sub 5}O{sub 12}, which maintains its cubic symmetry without any significant change to the lattice parameter (and hence unit cell volume) during lithium insertion to the rock-salt composition Li{sub 7}Ti{sub 5}O{sub 12}. This spinel electrode is an example of a ternary Li{sub x}MO{sub y} system in which a binary MO{sub y} framework provides a stable host structure for lithium. With this approach, the authors have turned their attention to exploring ternary intermetallic systems Li{sub x}MM{prime} in the hope of finding a system that is not subject to the high volumetric expansion that typifies many binary systems. In this paper, the authors present recent data of their investigations of lithium-copper-tin and lithium-indium-antimonide electrodes in lithium cells. The data show that lithium can be inserted reversibly into selected intermetallic compounds with relatively small expansion of the lithiated intermetallic structures.

Thackeray, M. M.; Vaughey, J.; Johnson, C. S.; Kepler, K. D.

1999-11-12

172

[Influence of natural complex compounds with hipolipidemic activity on expression of bacteria virulence factors].  

PubMed

Natural complex compounds with hipolipidemic activity, having considerable inhibitory effect on expression of bacteria virulence factors were isolated. Inhibitory properties of the compounds with respect to pyocyanine and protease formation, as well as their influence on the quorum sensing mechanism in Chromobacterium violacium were shown. PMID:22359861

Gotovtseva, V Iu; Grammatikova, N É; Bibikova, M V; Katlinski?, A V

2011-01-01

173

Direct conjugate addition of alkynes with ?,?-unsaturated carbonyl compounds catalyzed by NCN-pincer Ru complexes.  

PubMed

NCN-pincer Ru-complexes containing bis(oxazolinyl)phenyl ligands serve as suitable catalysts in the direct conjugate additions of ?,?-unsaturated carbonyl compounds, including ketones, esters, and amides, as well as vinylphosphonates, giving various ?-alkynyl carbonyl and phosphonate compounds. A bis(oxazolinyl)phenyl (phebox)-Ru complex also catalyzes the asymmetric conjugate addition of an alkyne with a ?-substituted, ?,?-unsaturated ketone to produce a chiral ?-alkynyl ketone. PMID:23180508

Ito, Jun-ichi; Fujii, Kohei; Nishiyama, Hisao

2013-01-01

174

Thermodynamics of the sorption of cerium complex compounds on anionite  

NASA Astrophysics Data System (ADS)

Sorption of cerium in the form of complexes with Trilon B (EDTA) from acid media at pH 3 using weakly basic anionite D-403 in nitrate, chloride, or sulfate forms is studied. The equation of the mass action law is linearized for ion exchange reactions, allowing us to calculate the limiting sorption of ethylenediaminetetraacetate cerate (EDTA cerate) ions on anionite and the constants of the exchange of complex cerium ions by chloride, nitrate, and sulfate ions. The limiting sorption of EDTA cerate ions in the anionite phase transitioning to the sulfate form is lower than that of ions on nitrate or chloride anionite, due to the high ionic potential of the sulfate ions. A sorption series of EDTA cerate ions on anionite D-403 in different ion exchange forms is presented according to the Gibbs energy of the ion exchange equilibrium.

Cheremisina, O. V.; Chirkst, D. E.; Ponomareva, M. A.

2013-09-01

175

Synergistic effect of some pharmaceutical compounds on cobalt-60 complexes.  

PubMed

Synergism in the extraction of cobalt from acetate 0.1 M aqueous medium, pH = 5.3 has been investigated using a mixture of thenoyl-trifluoro acetone and antipyrine, 4-iodoantipyrine or 4-aminopyrine (AAPy), synergism was observed in all the cases. The maximum synergistic effect was observed in the case of 4-(AAPy). The nature of the extracted species has been determined and the equilibrium constants for the adducts have been evaluated. The thermodynamic parameters of these reactions have been calculated to elucidate the mechanism of formation of the extracted species. These compounds were found to be good donors capable in strength to other alkyl phosphorus donors. PMID:1667314

Farah, K; el-Shaboury, G; Kandil, A

1991-01-01

176

A computational method for planning complex compound distributions under container, liquid handler, and assay constraints.  

PubMed

A systematic method for assembling and solving complex compound distribution problems is presented in detail. The method is based on a model problem that enumerates the mathematical equations and constraints describing a source container, liquid handler, and three types of destination containers involved in a set of compound distributions. One source container and one liquid handler are permitted in any given problem formulation, although any number of compound distributions may be specified. The relative importance of all distributions is expressed by assigning weights, which are factored into the final mathematical problem specification. A computer program was created that automatically assembles and solves a complete compound distribution problem given the parameters that describe the source container, liquid handler, and any number and type of compound distributions. Business rules are accommodated by adjusting weighting factors assigned to each distribution. An example problem, presented and explored in detail, demonstrates complex and nonintuitive solution behavior. PMID:23603752

Russo, Mark F; Wild, Daniel; Hoffman, Steve; Paulson, James; Neil, William; Nirschl, David S

2013-10-01

177

A Study on Removing Basic Nitrogen Compounds From Diesel Oil by Ferric Chloride Complexing Agent  

Microsoft Academic Search

Removal of the basic nitrogen compounds from diesel oil by using ferric chloride as complexing agent was studied. The influence of affect factors on treating conditions was investigated, and orthogonal tests were done to conform the optimum process condition. The results showed that the optimum condition was that of the volume ratio of complexing agent to oil was 1.0, stirring

H. Yu; Z. Hu

2012-01-01

178

Role of Ag in the formation of interfacial intermetallic phases in Sn-Zn soldering  

NASA Astrophysics Data System (ADS)

This study explored the effect of Ag as the substrate or alloying element of solders on the interfacial reaction in Sn-Zn soldering. Results show that instead of Ag-Sn compounds, ?-AgZn and ?-Ag5Zn8 form at the Sn-Zn/Ag interface. The addition of Ag in Sn-Zn solders leads to the precipitation of ?-AgZn3 from the liquid solder on preformed interfacial intermetallics. The morphology of this additional AgZn3 is closely related to the solidification process of Ag-Zn intermetallics and the under intermetallic layer.

Song, Jenn-Ming; Liu, Pei-Chi; Shih, Chia-Ling; Lin, Kwang-Lung

2005-09-01

179

CCMR: Pt hexafluoroacetlyacetonate as a Precursor for Pt Intermetallic Nanoparticle Synthesis  

NSDL National Science Digital Library

This research sought to investigate a better precursor for platinum (Pt) intermetallic nanoparticles that can be utilized as anode electrocatalysts in fuel cells. The compound Pt hexafluoroacetylacetonate can be used as a Pt intermetallic precursor for making PtPb nanoparticles when using appropriate washes (methanol usage and hexane avoidance). Modifying the standard procedures for the synthesis of PtPb nanoparticle synthesis may be useful in future work where organic ligands must be avoided in order to achieve room temperature particle crystallization.

Weiss, Marilyn

2007-08-29

180

Microlaminated high temperature intermetallic composites  

Microsoft Academic Search

The thrust to weight ratio of aircraft engines is limited by the density and elevated temperature capability of high temperature turbine materials. Single crystal superalloys, which are the current state-of-the-art in high temperature turbine blade materials, have limited potential for further increases in temperature capability. High temperature intermetallics offer the advantage of higher specific strength and higher temperature capability, but

R. G. Rowe; D. W. Skelly; M. Larsen; J. Heathcote; G. R. Odette; G. E. Lucas

1994-01-01

181

Crystal structure of the intermetallics produced by a calcium hydride method  

NASA Astrophysics Data System (ADS)

Practically important intermetallics TiNi, NiAl, Ni3Al, TiAl, and Zr3Al2 (St 101 alloy for gas absorbers) produced by the calcium hydride method are comprehensively studied. The total content of impurities in these intermetallic powders does not exceed 1 wt %, and the fraction of the main phase in compounds with a narrow homogeneity region is at least 93-96 vol %. The main phases in all powders under study have a defectless crystal lattice, and their lattice parameters point to a low content of dissolved impurities in all intermetallics except for Zr3Al2. A high degree of homogeneity of the phase compositions of the intermetallic powders is supported by a scanning electron microscopy investigation.

Kasimtsev, A. V.; Sviridova, T. A.

2012-05-01

182

To distinguish between complex compounds such as coffee aromas, researchers use a  

E-print Network

To distinguish between complex compounds such as coffee aromas, researchers use a printed array the Coffee « All 2010 News « News « College of Liberal Arts & Sciences « University of Illinois CHEMISTRY Wake Up and Smell the Coffee Artificial nose can detect problems in coffee batches. Advertisers have

Suslick, Kenneth S.

183

Ambient volatile organic compound (VOC) concentrations around a petrochemical complex and a petroleum refinery  

Microsoft Academic Search

Air samples were collected between September 2000 and September 2001 in Izmir, Turkey at three sampling sites located around a petrochemical complex and an oil refinery to measure ambient volatile organic compound (VOC) concentrations. VOC concentrations were 4–20-fold higher than those measured at a suburban site in Izmir, Turkey. Ethylene dichloride, a leaded gasoline additive used in petroleum refining and

Eylem Cetin; Mustafa Odabasi; Remzi Seyfioglu

2003-01-01

184

Redox potentials and HPLC behavior of cobalt and iron complexes with pyridylazo compounds.  

PubMed

The redox potentials of cobalt and iron complexes with ten pyridylazo compounds, E(0)(ML2) (ML(2)(+/0); M: Co(III/II), Fe(III/II); L(-): pyridylazo compounds), have been determined in order to explore the difference in their reversed-phase HPLC behavior. The redox potentials of Co complexes were in the range of -0.62 - 0.03 V, while those of Fe complexes were -0.06 - 0.59 V relative to 0.20 V for ferricinium/ferrocene. The redox potentials of both the Co and Fe complexes were linearly correlated to the basicities of the ligands. The correlation was quantitatively explained by a difference in dependence of the stabilities of M(III) and M(II) complexes on the ligand basicities. The complex of [Co(III)L(2)](+) or [Fe(II)L(2)] with any compound injected in the reversed-phase HPLC system was detected without any change in the composition. When [Co(II)L(2)] was injected, only those complexes having the highest potentials of E(0)(CoL2) congruent with 0.0 V were detected as [Co(II)L(2)], while other complexes having lower potentials gave a peak of [Co(III)L(2)](+). When [Fe(III)L(2)](+) was injected, only complexes having the lowest potentials of E(0)(FeL2) congruent with 0.0 V were detected as [Fe(III)L(2)](+), while others having higher potentials gave a peak of [Fe(II)L(2)]. PMID:19075467

Yasui, Takashi; Nunome, Yoko; Ohnishi, Takashi; Yamaguchi, Masayo; Tamamura, Saki; Yamada, Hiromichi; Yuchi, Akio

2008-12-01

185

Charge-transfer complexes of pyrimidine Schiff bases with aromatic nitro compounds  

NASA Astrophysics Data System (ADS)

Charge-transfer (CT) complexes of pyrimidine Schiff bases, derived from condensation of 2-aminopyrimidine and substituted benzaldehydes, with some aromatic polynitro compounds were prepared and investigated using IR, UV, visible and 1H NMR spectroscopy. For all solid complexes, the main interaction between the donor and acceptor molecules takes place through the ?-?* interaction. Strong and some weak acidic acceptors, in addition interact through proton transfer from the acceptor molecule to the basic centre of the electron donor. Also, an n-?* transition was detected in some complexes.

Issa, Yousry M.; El Ansary, A. L.; Sherif, O. E.; Hassib, H. B.

2011-08-01

186

Separating complex compound patient motion tracking data using independent component analysis  

NASA Astrophysics Data System (ADS)

In SPECT imaging, motion from respiration and body motion can reduce image quality by introducing motion-related artifacts. A minimally-invasive way to track patient motion is to attach external markers to the patient's body and record their location throughout the imaging study. If a patient exhibits multiple movements simultaneously, such as respiration and body-movement, each marker location data will contain a mixture of these motions. Decomposing this complex compound motion into separate simplified motions can have the benefit of applying a more robust motion correction to the specific type of motion. Most motion tracking and correction techniques target a single type of motion and either ignore compound motion or treat it as noise. Few methods account for compound motion exist, but they fail to disambiguate super-position in the compound motion (i.e. inspiration in addition to body movement in the positive anterior/posterior direction). We propose a new method for decomposing the complex compound patient motion using an unsupervised learning technique called Independent Component Analysis (ICA). Our method can automatically detect and separate different motions while preserving nuanced features of the motion without the drawbacks of previous methods. Our main contributions are the development of a method for addressing multiple compound motions, the novel use of ICA in detecting and separating mixed independent motions, and generating motion transform with 12 DOFs to account for twisting and shearing. We show that our method works with clinical datasets and can be employed to improve motion correction in single photon emission computed tomography (SPECT) images.

Lindsay, C.; Johnson, K.; King, M. A.

2014-03-01

187

Superplasticity in metals, ceramics, and intermetallics  

SciTech Connect

This volume represent the proceedings of the Symposium on Superplasticity in metals, Ceramics, and intermetallics, part of the materials Research Society 1990 Spring Meeting. Topics covered include: fundamentals and theory, superplastic microstructure synthesis and uses, superplastic forming and diffusion bonding, intermetallic superplasticity, metallurgical superplasticity, ceramic superplasticity, and superplastic alloys.

Mayo, M.J. (Pennsylvania State Univ., University Park, PA (United States)); Kobayashi, M. (Nagaoka Technical Coll., Niigata (Japan)); Wadsworth, J. (Lockheed Research and Development Division, Palo Alto, CA (US))

1990-01-01

188

Stereoselective hydrogenation of model compounds and preparation of tailor-made glycerides with chromium tricarbonyl complexes  

Microsoft Academic Search

Studies on the mechanism of stereoselectivity of chromium tricarbonyl catalysts with model compounds provided the basis for\\u000a the preparation of simulated fats. These synthetic fats were prepared by taking advantage of the unique property of chromium\\u000a carbonyl complexes to catalyze hydrogenation of polyunsaturates tocis-monounsaturates. Oils simulating the composition of peanut oil were produced by hydrogenating soybean oil stereoselectively\\u000a to an

E. N. Frankel; F. L. Thomas; J. C. Cowan

1970-01-01

189

Controlling Magnetism of a Complex Metallic System Using Atomic Individualism  

NASA Astrophysics Data System (ADS)

When the complexity of a metallic compound reaches a certain level, a specific location in the structure may be critically responsible for a given fundamental property of a material while other locations may not play as much of a role in determining such a property. The first-principles theory has pinpointed a critical location in the framework of a complex intermetallic compound—Gd5Ge4—that resulted in a controlled alteration of the magnetism of this compound using precise chemical tools.

Mudryk, Y.; Paudyal, D.; Pecharsky, V. K.; Gschneidner, K. A., Jr.; Misra, S.; Miller, G. J.

2010-08-01

190

Volatile compounds in cryptic species of the Aneura pinguis complex and Aneura maxima (Marchantiophyta, Metzgeriidae).  

PubMed

Aneura pinguis is one of the liverwort species complexes that consist of several cryptic species. Ten samples collected from different regions in Poland are in the focus of our research. Eight of the A. pinguis complex belonging to four cryptic species (A, B, C, E) and two samples of closely related species Aneura maxima were tested for the composition of volatile compounds. The HS-SPME technique coupled to GC/FID and GC/MS analysis has been applied. The fiber coated with DVB/CAR/PDMS has been used. The results of the present study, revealed the qualitative and quantitative differences in the composition of the volatile compounds between the studied species. Mainly they are from the group of sesquiterpenoids, oxygenated sesquiterpenoids and aliphatic hydrocarbons. The statistical methods (CA and PCA) showed that detected volatile compounds allow to distinguish cryptic species of A. pinguis. All examined cryptic species of the A. pinguis complex differ from A. maxima. Species A and E of A. pinguis, in CA and PCA, form separate clusters remote from two remaining cryptic species of A. pinguis (B and C) and A. maxima. Relationship between the cryptic species appeared from the chemical studies are in accordance with that revealed on the basis of DNA sequences. PMID:25034615

Wawrzyniak, Rafa?; Wasiak, Wies?aw; B?czkiewicz, Alina; Buczkowska, Katarzyna

2014-09-01

191

High-temperature ordered intermetallic alloys II; Proceedings of the Second Symposium, Boston, MA, Dec. 2-4, 1986  

NASA Technical Reports Server (NTRS)

The papers presented in this volume provide on overview of recent theoretical and experimental research in the field of high-temperature ordered intermetallic alloys. The papers are gouped under the following headings: ordering behavior and theory, microstructures, mechanical behavior, alloy design and microstructural control, and metallurgical properties. Specific topics discussed include antiphase domains, disordered films and the ductility of ordered alloys based on Ni3Al; kinetics and mechanics of formation of Al-Ni intermetallics; deformability improvements of L1(2)-type intermetallic compounds; B2 aluminides for high-temperature applications; and rapidly solidified binary TiAl alloys.

Stoloff, N. S. (editor); Koch, C. C. (editor); Liu, C. T. (editor); Izumi, O. (editor)

1987-01-01

192

Microstructural Characteristics of Accumulative Roll-Bonded Ni-Al-Based Metal-Intermetallic Laminate Composite  

NASA Astrophysics Data System (ADS)

The present investigation is an attempt to develop metal-intermetallic laminate composites based on Ni-Al system. In this study, Ni sheets and Al foils have been used for the development of Ni-Al laminate using accumulative roll-bonding technique at 773 K. The laminate composites were then subjected to the controlled annealing to affect reactive diffusion at the Ni/Al interface leading to intermetallic compound formation. The accumulative roll-bonded laminates showed good bonding of layers. Annealing treatment at 773 K led to formation of reaction product and maintained the interface integrity. A qualitative compositional analysis at the interfaces reflected the formation of Al-Ni compounds, and a gradual compositional gradient also across the interface. This process seems to be of promise so far as the continuous production of large scale metal-intermetallic laminate composites is concerned.

Srivastava, V. C.; Singh, T.; Ghosh Chowdhury, S.; Jindal, V.

2012-09-01

193

Morphology of molecular complexes of=20 poly(ethylene oxide) and disubstituted benzenic compounds.  

NASA Astrophysics Data System (ADS)

Oligomers of ethylene oxide (EO) crystallize from the melt as lamellar crystals with an integral number of folds (n or with an extended chain conformation. Poly(ethylene oxide) (PEO) forms various crystalline molecular complexes with organic compounds such as urea, thiourea, p-dihalagenobenzenes (PDCL), resorcinol (RES), hydroquinone (HYD), p-nitrophenol (PNP), 2-methyl resorcinol (MRES), 5-methyl resorcinol,... The stoichiometry and the crystal structure of these molecular complexes were determined by differential scanning calorimetry and X-ray diffraction, respectively. For molecular weights ranging between 2000 and 10000, the following complexes PEO-PDCL, PEO-RES, PEO-HYD, PEO-MRES crystallize from the melt as integral folded chains (IFC) crystals. At high crystallization temperatures, these molecular complexes crystallize as extended chains (EC) lamellar crystals. Mixtures of EC and 1-IFC crystals are obtained at lower crystallization temperatures. Time-resolved SAXS study of the crystallization of these molecular complexes indicate that non-integral folded chain (NIFC) crystals are present in the early stages of crystallization. These NIFC crystals are metastable and transform into EC or IFC lamellar crystals by a thickening or a thinning process. On the other hand, the PEO-PNP molecular complex crystallizes as stable NIFC lamellar crystals. Explanations related to the crystal structure of these complexes and to their mode of growth are invoked to explain these two different lamellar morphology.

Dosi=E8re, M.

1997-03-01

194

Aromatization of ethane over Pt,Ga\\/HZSM-5 catalyst and the effect of intermetallic hydrogen acceptor on the reaction  

Microsoft Academic Search

The effect of the hydride-forming intermetallic compound Zr2Fe on the aromatization of ethane over Pt,Ga\\/HZSM-5 catalyst has been studied under different reaction conditions (temperature, GHSV, ethane dilution with Ar). In the presence of intermetallic hydrogen acceptor aromatics yield from ethane at 500°C was 6-fold higher and reached 61 wt.-% as a result of releasing hydrogen elimination, selectivity to aromatics being

O. V. Chetina; T. V. Vasina; V. V. Lunin

1995-01-01

195

Prediction of intermetallics formation during metal ion implantation into Al at elevated temperature  

NASA Astrophysics Data System (ADS)

The model of effective heat of formation in metal-Al binary system proposed by Pretorius et al. was developed based on characteristics of the solid-state reaction at interface to predict the formation of intermetallics during metal ion implantation into Al substrate at elevated temperature. For the Fe, Hf, Mo, Nb, Ni, Ta and Zr ion implantation with the ion energy of 50-140 keV under the ion current density of 10-60 ?A/cm 2 into Al substrate to the implantation dose of 10 17-10 18 ions/cm 2 at the elevated temperature ranging from 300 °C to 600 °C, the model of effective heat of formation predicted the formation of intermetallics Al 13Fe 4, HfAl 3, MoAl 12, NbAl 3, NiAl 3, TaAl 3 and ZrAl 3, which were consistent with the experimental results. Taking the kinetic factors and the limitation of thermodynamic data into account, the model of effective heat of formation explained the formation of metastable intermetallics Cr 14Al 86 at the lower temperature of 400 °C and of the stable intermetallics Cr 2Al 13 at the higher temperature of 510 °C, and the formation of simple intermetallics VAl 3 relative to complex intermetallics V 4Al 23, VAl 7, and VAl 10, for the Cr and V ion implantation into Al substrate, respectively, at the elevated temperature up to 510 °C.

Chen, T.; Chang, H. W.; Lei, M. K.

2005-11-01

196

Submicellar complexes may initiate the fungicidal effects of cationic amphiphilic compounds on Candida albicans.  

PubMed Central

The killing of Candida albicans by a series of amphiphilic quaternary ammonium compounds (QACs) with different hydrocarbon chain lengths was closely related to the binding of the compounds to the cells and damage of the cell membranes. The membrane damage was measured as the level of release of the UV-absorbing material into the medium in which the cells were suspended and as the level of uptake of propidium iodide in individual cells by flow cytometry. It was shown that of the compounds tested, hexadecyltrimethylammonium bromide (cetyltrimethylammonium bromide [CTAB]) bound most efficiently. Tetradecyl betainate chloride (B14), tetradecanoylcholine bromide (C14), tetradecyltrimethylammonium bromide (TTAB), and dodecyltrimethylammonium bromide (DTAB) followed and had declining degrees of binding efficiency. The proportion of CTAB bound was almost total at concentrations up to the critical micelle concentration (CMC) of the compound, whereas that of B14 was somewhat smaller. For the two remaining tetradecyl compounds (C14 and TTAB), still smaller proportions were bound at low concentrations, but the proportions rose disproportionally at increasing concentrations to a distinct maximum at concentrations of 0.2 to 0.5 times the CMC. We propose that interfacial micelle-like aggregates are formed at the cell surface as a step in the binding process. An analogous, but less conspicuous, maximum was seen for DTAB. Thus, great differences in the binding affinity of QACs with different hydrocarbon chains at different concentrations to C. albicans were observed. These differences were related to the CMC of the compound. In contrast, the binding of TTAB to Salmonella typhimurium 395 MS was almost total at low as well as high concentrations until saturation was attained, indicating fundamental differences between binding to the yeast and binding to gram-negative bacteria. The importance of lipid-type complexes or aggregates to the antifungal effect of membrane-active substances are discussed. PMID:9055990

Ahlstrom, B; Chelminska-Bertilsson, M; Thompson, R A; Edebo, L

1997-01-01

197

Synthesis and Hydride Transfer Reactions of Cobalt and Nickel Hydride Complexes to BX3 Compounds  

SciTech Connect

Hydrides of numerous transition metal complexes can be generated by the heterolytic cleavage of H{sub 2} gas such that they offer alternatives to using main group hydrides in the regeneration of ammonia borane, a compound that has been intensely studied for hydrogen storage applications. Previously, we reported that HRh(dmpe){sub 2}, dmpe = 1,2-bis(dimethylphosphinoethane) was capable of reducing a variety of BX{sub 3} compounds having hydride affinity (HA) greater than or equal to HA of BEt{sub 3}. This study examines the reactivity of less expensive cobalt and nickel hydride complexes, (HCo(dmpe){sub 2} and [HNi(dmpe){sub 2}]{sup +}), to form B-H bonds. The hydride donor abilities ({Delta}G{sub H{sup -}}{sup o}) of HCo(dmpe){sub 2} and [HNi(dmpe){sub 2}]{sup +} were positioned on a previously established scale in acetonitrile that is cross-referenced with calculated HAs of BX{sub 3} compounds. The collective data guided our selection of BX{sub 3} compounds to investigate and aided our analysis of factors that determine favorability of hydride transfer. HCo(dmpe){sub 2} was observed to transfer H{sup -} to BX{sub 3} compounds with X = H, OC{sub 6}F{sub 5} and SPh. The reaction with B(SPh){sub 3} is accompanied by formation of (BH{sub 3}){sub 2}-dmpe and (BH{sub 2}SPh){sub 2}-dmpe products that follow from reduction of multiple BSPh bonds and loss of a dmpe ligand from Co. Reactions between HCo(dmpe){sub 2} and B(SPh){sub 3} in the presence of triethylamine result in formation of Et{sub 3}N-BH{sub 2}SPh and Et{sub 3}N-BH{sub 3} with no loss of dmpe ligand. Reactions of the cationic complex [HNi(dmpe){sub 2}]{sup +} with B(SPh){sub 3} under analogous conditions give Et{sub 3}N-BH{sub 2}SPh as the final product along with the nickel-thiolate complex [Ni(dmpe){sub 2}(SPh)]{sup +}. The synthesis and characterization of HCo(dedpe){sub 2} (dedpe = diethyldiphenyl(phosphino)ethane) from H{sub 2} and a base is also discussed; including the formation of an uncommon trans dihydride species, trans-[(H{sub 2})Co(dedpe){sub 2}][BF{sub 4}].

Mock, Michael T.; Potter, Robert G.; O'Hagan, Molly J.; Camaioni, Donald M.; Dougherty, William G.; Kassel, W. S.; DuBois, Daniel L.

2011-12-05

198

Probing Complex Free-Radical Reaction Pathways of Fuel Model Compounds  

SciTech Connect

Fossil (e.g. coal) and renewable (e.g. woody biomass) organic energy resources have received considerable attention as possible sources of liquid transportation fuels and commodity chemicals. Knowledge of the reactivity of these complex materials has been advanced through fundamental studies of organic compounds that model constituent substructures. In particular, an improved understanding of thermochemical reaction pathways involving free-radical intermediates has arisen from detailed experimental kinetic studies and, more recently, advanced computational investigations. In this presentation, we will discuss our recent investigations of the fundamental pyrolysis pathways of model compounds that represent key substructures in the lignin component of woody biomass with a focus on molecules representative of the dominant beta-O-4 aryl ether linkages. Additional mechanistic insights gleaned from DFT calculations on the kinetics of key elementary reaction steps will also be presented, as well as a few thoughts on the significant contributions of Jim Franz to this area of free radical chemistry.

Buchanan III, A C [ORNL; Kidder, Michelle [ORNL; Beste, Ariana [ORNL; Britt, Phillip F [ORNL

2012-01-01

199

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

SciTech Connect

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-x}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-x}Fe{sub 4}Si{sub 14-y} 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 2}: 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 3}Zn{sub 3.6}Al{sub 7.4}: Partially ordered structure of Tb{sub 3}Zn{sub 3.6}Al{sub 7.4} 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{sub 39}(Cr{sub x}Al{sub 1-x}){sub 81}: These layered structures are similar to icosahedral Mn-Al quasicrystalline compounds. Therefore, this compound may provide new insights into the formation, composition and structure of quasicrystalline materials.

Han, M.K.

2006-05-06

200

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

SciTech Connect

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-x}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-x}Fe{sub 4}Si{sub 14-y} 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 2}: 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 3}Zn{sub 3.6}Al{sub 7.4}: Partially ordered structure of Tb{sub 3}Zn{sub 3.6}Al{sub 7.4} 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{sub 39}(Cr{sub x}Al{sub 1-x}){sub 81}: These layered structures are similar to icosahedral Mn-Al quasicrystalline compounds. Therefore, this compound may provide new insights into the formation, composition and structure of quasicrystalline materials.

Mi-Kyung Han

2006-05-01

201

Method of making sintered ductile intermetallic-bonded ceramic composites  

DOEpatents

A method of making an intermetallic-bonded ceramic composite involves combining a particulate brittle intermetallic precursor with a particulate reactant metal and a particulate ceramic to form a mixture and heating the mixture in a non-oxidizing atmosphere at a sufficient temperature and for a sufficient time to react the brittle intermetallic precursor and the reactant metal to form a ductile intermetallic and sinter the mixture to form a ductile intermetallic-bonded ceramic composite.

Plucknett, Kevin (Sharnbrook, GB); Tiegs, Terry N. (Lenoir City, TN); Becher, Paul F. (Oak Ridge, TN)

1999-01-01

202

Compound  

NASA Astrophysics Data System (ADS)

We have prepared Ce-doped polycrystalline AgSbTe2.01 compounds from high-purity elements by a melt-quench technique followed by spark plasma sintering, and their thermoelectric transport properties have been investigated in the temperature range of 300 K to 625 K. The actual concentration of Ce was much less than the initial composition, but roughly proportional to it. Small additions of Ce shifted the composition of the homogeneity range from the nearly ideal atomic ratio Ag:Sb:Te = 0.98:1.02:2.01 toward Sb rich (Ag poor), and led to the reemergence of Ag2Te impurity in AgSbTe2 compound. The Ce-doped samples possessed lower electrical conductivity compared with the undoped AgSbTe2.01 compound at room temperature, but the carrier mobility and effective mass were essentially constant, indicating intact band structure near the covalent band maximum upon Ce substitution for Sb. Due to the decrease of lattice vibration anharmonicity resulting from Ce substitution for Sb, the lattice conductivity of the Ce-doped samples was about 0.1 W m-1 K-1 higher than that of the AgSbTe2.01 sample, and the magnitude spanned the range from 0.30 W m-1 K-1 to 0.55 W m-1 K-1. A ZT of 1.20 was achieved at about 615 K for the AgSb0.99Ce0.01Te2.01 sample.

Du, B.; Li, H.; Tang, X.

2014-06-01

203

High Density Hydrogen Storage System Demonstration Using NaAlH4 Based Complex Compound Hydrides  

SciTech Connect

This final report describes the motivations, activities and results of the hydrogen storage independent project "High Density Hydrogen Storage System Demonstration Using NaAlH4 Based Complex Compound Hydrides" performed by the United Technologies Research Center under the Department of Energy Hydrogen Program, contract # DE-FC36-02AL67610. The objectives of the project were to identify and address the key systems technologies associated with applying complex hydride materials, particularly ones which differ from those for conventional metal hydride based storage. This involved the design, fabrication and testing of two prototype systems based on the hydrogen storage material NaAlH4. Safety testing, catalysis studies, heat exchanger optimization, reaction kinetics modeling, thermochemical finite element analysis, powder densification development and material neutralization were elements included in the effort.

Daniel A. Mosher; Xia Tang; Ronald J. Brown; Sarah Arsenault; Salvatore Saitta; Bruce L. Laube; Robert H. Dold; Donald L. Anton

2007-07-27

204

Large compound vesicles from amphiphilic block copolymer/rigid-rod conjugated polymer complexes.  

PubMed

Morphology evolution in complexes of amphiphilic block copolymers poly(styrene)-b-poly(acrylic acid) (PS-b-PAA) and poly(styrene)-b-poly(ethylene oxide) (PS-b-PEO) in the presence of polyaniline (PANI) in aqueous solution is reported. Transmission electron microscopy, atomic force microscopy, and dynamic light scattering techniques were used to study the morphologies at various PANI contents [aniline]/[acrylic acid] ([ANI]/[AA]) ranging from 0.1 to 0.7. The interpolyelectrolyte complex formed between PAA and PANI plays a key role in the morphology transformation. Spherical micelles formed from pure block copolymers were transformed into large compound vesicles upon increasing PANI concentration due to internal block copolymer segregation. In addition to varying PANI content, the kinetic pathway of nanoparticle formation was controlled through different water addition methods and was critical in the formation of multigeometry nanoparticles. PMID:25310873

Palanisamy, Anbazhagan; Guo, Qipeng

2014-11-01

205

Cannabis, a complex plant: different compounds and different effects on individuals  

PubMed Central

Cannabis is a complex plant, with major compounds such as delta-9-tetrahydrocannabinol and cannabidiol, which have opposing effects. The discovery of its compounds has led to the further discovery of an important neurotransmitter system called the endocannabinoid system. This system is widely distributed in the brain and in the body, and is considered to be responsible for numerous significant functions. There has been a recent and consistent worldwide increase in cannabis potency, with increasing associated health concerns. A number of epidemiological research projects have shown links between dose-related cannabis use and an increased risk of development of an enduring psychotic illness. However, it is also known that not everyone who uses cannabis is affected adversely in the same way. What makes someone more susceptible to its negative effects is not yet known, however there are some emerging vulnerability factors, ranging from certain genes to personality characteristics. In this article we first provide an overview of the biochemical basis of cannabis research by examining the different effects of the two main compounds of the plant and the endocannabinoid system, and then go on to review available information on the possible factors explaining variation of its effects upon different individuals. PMID:23983983

2012-01-01

206

Cannabis, a complex plant: different compounds and different effects on individuals.  

PubMed

Cannabis is a complex plant, with major compounds such as delta-9-tetrahydrocannabinol and cannabidiol, which have opposing effects. The discovery of its compounds has led to the further discovery of an important neurotransmitter system called the endocannabinoid system. This system is widely distributed in the brain and in the body, and is considered to be responsible for numerous significant functions. There has been a recent and consistent worldwide increase in cannabis potency, with increasing associated health concerns. A number of epidemiological research projects have shown links between dose-related cannabis use and an increased risk of development of an enduring psychotic illness. However, it is also known that not everyone who uses cannabis is affected adversely in the same way. What makes someone more susceptible to its negative effects is not yet known, however there are some emerging vulnerability factors, ranging from certain genes to personality characteristics. In this article we first provide an overview of the biochemical basis of cannabis research by examining the different effects of the two main compounds of the plant and the endocannabinoid system, and then go on to review available information on the possible factors explaining variation of its effects upon different individuals. PMID:23983983

Atakan, Zerrin

2012-12-01

207

compounds  

NASA Astrophysics Data System (ADS)

Size is the key factor of nanostructured materials, since all the structural, transport, electrical, magnetic and other physical properties can be tuned by this factor of materials. Only the condition is to choose appropriate inexpensive scale-processing method for material synthesis which offers good control over the stoichiometry, morphology and particle size distribution. Present communication deals with the studies on the sol-gel grown Y0.95Ca0.05MnO3 (YCMO) nanostructured compounds for their size-induced tuning of dielectric behavior. Structural studies reveal the single phasic nature with improved crystallite size with sintering temperature. Dielectric constant (real and imaginary) is found to increase with temperature and crystallite size/sintering temperature. High dielectric loss has been observed in the present system. Size dependent activation energy ( E a), obtained from modulus measurement, showing the increase in E a with crystallite size. The variation in various dielectric parameters and E a has been discussed in the light of crystallite size, crystallite boundaries, oxygen vacancies and charge carrier hopping.

Shah, N. A.

2014-10-01

208

Assessing the Geochemical Reactivity of Fe-DOM Complexes in Lacustrine Sediments Using Nitroaromatic Probe Compounds  

NASA Astrophysics Data System (ADS)

The complexation environment of Fe in anoxic sediment porefluids is important for understanding its role in biogeochemical reactions in these systems. These include the microbial dissolution of iron-bearing sediments and the degradation of hydrophobic pesticides. We studied the effect of naturally occurring Fe-DOM complexes on the reduction of two nitroaromatic compounds (NACs) as a surrogate for probing electron-transfer kinetics, and monitored the geochemical parameters affecting reactivity. We found that Fe(II) was necessary for rapid NAC reduction (< 24 hr), and observed faster reduction with increased pH. NAC reduction in `pH-adjusted' porefluids (acidified to pH 2.5 after porefluid extraction and raised to the native pH (between 6.5 to 7.8) prior to reaction) was similar to that observed in model systems containing Fe(II) and aquatic fulvic acids. Conversely, NAC reduction in fresh, unaltered porefluids was slower than that observed in `pH-adjusted' porefluids, indicating that the natural metal redox speciation differs between fresh and `pH-adjusted' samples. Electrochemical scans demonstrate a vertical gradient in concentrations of Fe(III), Fe(II), and Mn(II) from 0 to 30 cm depth. Furthermore, the electrochemical data indicate that ferric iron in these systems is predominantly complexed with organic ligands, with a half-cell potential of -0.45 V. The magnitude of this ferric-organic peak decreases when porefluids are pH- adjusted for short durations (acidified to pH 2.5 and re-raised to circumneutral levels) and disappears completely when the acidified porefluid is allowed to equilibrate overnight. These data show that pH-adjustment of porefluids presumably alters both their complexation chemistry and reactivity towards NACs, and shows how small changes in Fe complexation chemistry potentially affects electron transfer reactions in anoxic environments.

Hakala, J.; Fimmen, R. L.; Chin, Y.; Agrawal, S. G.; Ward, C. P.

2007-12-01

209

Organic compounds as indicators for transport in an urban characterized complex karst system  

NASA Astrophysics Data System (ADS)

In northern Hesse (Germany), sediments of the Upper Permian (Zechstein-Formations) are outcropping in a coastal facies along the western rim of the Rhenish Massif. The geologic section is characterized by a sequence of carbonate rocks (carbonates of the Werra-, Staßfurt- and Leine-Formations) and predominantly fine clastic sediments. The carbonate aquifers of the Werra-Formation and the Leine-Formation are used for drinking water abstraction of a provincial town and surrounding communities. Concurrently, the urban area is characterized by industrial and commercial uses. The groundwater flow system is composed of three potential karst aquifers, aquitards and aquicludes within a complex tectonically faulted area. The study area is divided into three spring catchment areas. However, the locations of the subsurface water divides are unknown. Traditional methods to determine the catchment areas (e.g. artificial tracer tests) are difficult to apply, due to a lack of adequate injection points. The presented work deals with the use of organic compounds as indicators for subsurface flow paths. Medical drugs, pesticides, corrosion inhibitors and such typical waste water compounds as caffeine (NÖDLER ET AL. 2010) are observed in approximately fifty groundwater observation points by regular sampling. The seasonal variability of the distribution pattern of organic compounds is low. The most common compounds are atrazine and its metabolites desethylatrazine and desisopropylatrazine, as well as the corrosion inhibitor 1H-benzotriazole. Since these substances are applied in different regions different input functions can be assumed. However, the highest concentrations are detected along a North-orientated axis, which also exhibits the greatest compound variety. This distribution pattern indicates preferential flow and transport pathways in the subsurface. The absence of organic compounds in other parts of the investigation area implies the existence of a water divide between these areas. The occurence of atrazine in groundwater samples denotes the existence of a water component with a transit time of more than 20 years because the use of atrazine as a pesticide has been banned in Germany since 1991. Furthermore, since atrazine and 1H-benzotriazole are found in all investigated aquifers, the presence of hydraulic connections between the aquifers (e.g. associated to faults) is likely. In addition to the long-term flow component, the periodic detection of such antibiotics as erythromycine, after strong recharge events (for example snow-melt events), suggests also the presence of a short-term flow component in the aquifer system. Consequently, the observation of organic compounds is an appropriate method to determine subsurface flow paths within complex aquifer systems. Furthermore, such a method can also be employed in the subsurface to approximate transit times and to identify mixing zones. Lecture NÖDLER, K., LICHA, T., BESTER, B., K. SAUTER, M. (2010): Development of a multi-residue analytical method, based on liquid chromatography-tandem mass spectrometry, for the simultaneous determination of 46 micro-contaminants in aqueous samples.- Journal of Chromatography A, 1217 (2010) 6511-6521.

Reh, R.; Licha, T.; Nödler, K.; Geyer, T.; Sauter, M.

2012-04-01

210

Water oxidation catalysed by manganese compounds: from complexes to 'biomimetic rocks'.  

PubMed

One of the most fundamental processes of the natural photosynthetic reaction sequence is the light-driven oxidation of water to molecular oxygen. In vivo, this reaction takes place in the large protein ensemble Photosystem II, where a ?-oxido-Mn(4)Ca- cluster, the oxygen-evolving-complex (OEC), has been identified as the catalytic site for the four-electron/four-proton redox reaction of water oxidation. This Perspective presents recent progress for three strategies which have been followed to prepare functional synthetic analogues of the OEC: (1) the synthesis of dinuclear manganese complexes designed to act as water-oxidation catalysts in homogeneous solution, (2) heterogeneous catalysts in the form of clay hybrids of such Mn(2)-complexes and (3) the preparation of manganese oxide particles of different compositions and morphologies. We discuss the key observations from the studies of such synthetic manganese systems in order to shed light upon the catalytic mechanism of natural water oxidation. Additionally, it is shown how research in this field has recently been motivated more and more by the prospect of finding efficient, robust and affordable catalysts for light-driven water oxidation, a key reaction of artificial photosynthesis. As manganese is an abundant and non-toxic element, manganese compounds are very promising candidates for the extraction of reduction equivalents from water. These electrons could consecutively be fed into the synthesis of "solar fuels" such as hydrogen or methanol. PMID:22068958

Wiechen, Mathias; Berends, Hans-Martin; Kurz, Philipp

2012-01-01

211

Advanced ordered intermetallic alloy deployment  

SciTech Connect

The need for high-strength, high-temperature, and light-weight materials for structural applications has generated a great deal of interest in ordered intermetallic alloys, particularly in {gamma}-based titanium aluminides {gamma}-based TiAl alloys offer an attractive mix of low density ({approximately}4g/cm{sup 3}), good creep resistance, and high-temperature strength and oxidation resistance. For rotating or high-speed components. TiAl also has a high damping coefficient which minimizes vibrations and noise. These alloys generally contain two phases. {alpha}{sub 2} (DO{sub 19} structure) and {gamma} (L 1{sub 0}), at temperatures below 1120{degrees}C, the euticoid temperature. The mechanical properties of TiAl-based alloys are sensitive to both alloy compositions and microstructure. Depending on heat-treatment and thermomechanical processing, microstructures with near equiaxed {gamma}, a duplex structure (a mix of the {gamma} and {alpha}{sub 2} phases) can be developed in TiAl alloys containing 45 to 50 at. % Al. The major concern for structural use of TiAl alloys is their low ductility and poor fracture resistance at ambient temperatures. The purpose of this project is to improve the fracture toughness of TiAl-based alloys by controlling alloy composition, microstructure and thermomechanical treatment. This work is expected to lead to the development of TiAl alloys with significantly improved fracture toughness and tensile ductility for structural use.

Liu, C.T.; Maziasz, P.J.; Easton, D.S. [Oak Ridge National Lab., TN (United States)

1997-04-01

212

Dislocation sources in ordered intermetallics  

SciTech Connect

An overview on the current understanding of dislocation sources and multiplication mechanisms is made for ordered intermetallic alloys of the L1{sub 2}, B2, and D0{sub 19} structures. In L1{sub 2} alloys, a large disparity of edge/screw segments in their relative mobility reduces the efficiency of a Frank-Read Type multiplication mechanism. In Fe-40%Al of the B2 structure, a variety of dislocation sources are available for <111> slip, including ones resulting from condensation of thermal vacancies. In NiAl with the relatively high APB energy, <100> dislocations may result from the dislocation decomposition reactions, the prismatic punching out from inclusion particles, and/or steps and coated layers of the surface. Internal interfaces often provide sites for dislocation multiplication, e.g., grain boundaries, sub-boundaries in Ni{sub 3}Ga, NiAl and Ti{sub 3}Al, and antiphase domain boundaries in Ti{sub 3}Al. As for the crack tip as a dislocation source, extended SISFs trailed by super-Shockley partials emanating form the cracks in Ni{sub 3}Al and Co{sub 3}Ti are discussed in view of a possible toughening mechanism.

Yoo, M.H. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.; Appel, F.; Wagner, R. [GKSS-Research Centre, Geesthacht (Germany). Inst. for Materials Research; Mecking, H. [Technical Univ. Hamburg-Harburg, Hamburg (Germany)

1996-09-01

213

Polar intermetallic compounds as catalysts for hydrogenation reactions: synthesis, structures, bonding, and catalytic properties of Ca(1-x)Sr(x)Ni4Sn2 (x=0.0, 0.5, 1.0) and catalytic properties of Ni3Sn and Ni3Sn2.  

PubMed

The potential of polar intermetallic compounds to catalyze hydrogenation reactions was evaluated. The novel compounds CaNi4Sn2, SrNi4Sn2, and Ca(0.5)Sr(0.5)Ni(4)Sn(2) were tested as unsupported alloys in the liquid-phase hydrogenation of citral. Depending on the reaction conditions, conversions of up to 21.0 % (253 K and 9.0 MPa hydrogen pressure) were reached. The binary compounds Ni3Sn and Ni3Sn2 were also tested in citral hydrogenation under the same conditions. These materials gave conversions of up to 37.5 %. The product mixtures contained mainly geraniol, nerol, citronellal, and citronellol. The isotypic stannides CaNi4Sn2, Ca(0.5)Sr(0.5)Ni4Sn2, and SrNi4Sn2 were obtained by melting mixtures of the elements in an arc-furnace under an argon atmosphere. Single crystals were synthesized in tantalum ampoules using special temperature modes. The novel structures were established by single-crystal X-ray diffraction. They crystallize in the tetragonal space group I4/mcm with parameters: a=7.6991(7), c=7.8150(8) A, wR2=0.034, 162 F(2) values, 14 variable parameters for CaNi4Sn2; a=7.7936(2), c=7.7816(3) A, wR2=0.052, 193 F(2) values, 15 variable parameters for Ca(0.5)Sr(0.5)Ni4Sn2; and a=7.8916(4), c=7.7485(5) A, wR2=0.071, 208 F(2) values, 14 variable parameters for SrNi4Sn2. The Ca(1-x)Sr(x)Ni(4)Sn(2) (x=0.0, 0.5, 1.0) structures can be represented as a stuffed variant of the CuAl2 type by the formal insertion of one-dimensional infinite Ni-cluster chains [Ni4] into the Ca(Sr)Sn2 substructure. The Ni and Sn atoms form a three-dimensional infinite [Ni4Sn2] network in which the Ca or Sr atoms fill distorted octagonal channels. The densities of states obtained from TB-LMTO-ASA calculations show metallic character for both compounds. PMID:18288652

Hlukhyy, Viktor; Raif, Fabian; Claus, Peter; Fässler, Thomas F

2008-01-01

214

Ion binding compounds, radionuclide complexes, methods of making radionuclide complexes, methods of extracting radionuclides, and methods of delivering radionuclides to target locations  

DOEpatents

The invention pertains to compounds for binding lanthanide ions and actinide ions. The invention further pertains to compounds for binding radionuclides, and to methods of making radionuclide complexes. Also, the invention pertains to methods of extracting radionuclides. Additionally, the invention pertains to methods of delivering radionuclides to target locations. In one aspect, the invention includes a compound comprising: a) a calix[n]arene group, wherein n is an integer greater than 3, the calix[n]arene group comprising an upper rim and a lower rim; b) at least one ionizable group attached to the lower rim; and c) an ion selected from the group consisting of lanthanide and actinide elements bound to the ionizable group. In another aspect, the invention includes a method of extracting a radionuclide, comprising: a) providing a sample comprising a radionuclide; b) providing a calix[n]arene compound in contact with the sample, wherein n is an integer greater than 3; and c) extracting radionuclide from the sample into the calix[n]arene compound. In yet another aspect, the invention includes a method of delivering a radionuclide to a target location, comprising: a) providing a calix[n]arene compound, wherein n is an integer greater than 3, the calix[n]arene compound comprising at least one ionizable group; b) providing a radionuclide bound to the calix[n]arene compound; and c) providing an antibody attached to the calix[n]arene compound, the antibody being specific for a material found at the target location.

Chen, Xiaoyuan (Syracuse, NY); Wai, Chien M. (Moscow, ID); Fisher, Darrell R. (Richland, WA)

2000-01-01

215

Reactivity of thiosemicarbazides with redox active metal ions: controlled formation of coordination complexes versus heterocyclic compounds.  

PubMed

The reactions of 1,1-dimethyl-4-phenylthiosemicarbazide (LH) with Cu(II) and Sn(IV) have been investigated. If THF or methanol is used as solvent with Cu(II), oxidative cyclisation and coupling are observed, yielding a 1,2,4-thiadiazole or a 1,3,4-thiadiazolium salt. SnI(4) is also able to induce oxidative coupling of two thiosemicarbazide ligands, yielding 1,2,4-thiadiazolium or 1,2,4-triazolium salts, with I(3)(-) as the counterion, depending on the reaction conditions. By contrast, reaction of LH with SnI(4) in acetone yields a 1,3-thiazolium salt, with I(-) as counterion. Reaction with Cu(II) salts or SnI(4) in basic media leads to the formation of metal complexes containing two deprotonated thiosemicarbazide ligands. In the reaction of CuCl(2) in water in the presence of acid a complex containing two neutral ligands is obtained. Reactions with SnCl(4) are not able to induce ligand cyclisation, although a coordination compound with two neutral ligands was isolated from methanol. PMID:19180593

López-Torres, Elena; Dilworth, Jonathan R

2009-01-01

216

Spark plasma sintering of titanium aluminide intermetallics and its composites  

NASA Astrophysics Data System (ADS)

Titanium aluminide intermetallics are a distinct class of engineering materials having unique properties over conventional titanium alloys. gamma-TiAl compound possesses competitive physical and mechanical properties at elevated temperature applications compared to Ni-based superalloys. gamma-TiAl composite materials exhibit high melting point, low density, high strength and excellent corrosion resistance. Spark plasma sintering (SPS) is one of the powder metallurgy techniques where powder mixture undergoes simultaneous application of uniaxial pressure and pulsed direct current. Unlike other sintering techniques such as hot iso-static pressing and hot pressing, SPS compacts the materials in shorter time (< 10 min) with a lower temperature and leads to highly dense products. Reactive synthesis of titanium aluminide intermetallics is carried out using SPS. Reactive sintering takes place between liquid aluminum and solid titanium. In this work, reactive sintering through SPS was used to fabricate fully densified gamma-TiAl and titanium aluminide composites starting from elemental powders at different sintering temperatures. It was observed that sintering temperature played significant role in the densification of titanium aluminide composites. gamma-TiAl was the predominate phase at different temperatures. The effect of increasing sintering temperature on microhardness, microstructure, yield strength and wear behavior of titanium aluminide was studied. Addition of graphene nanoplatelets to titanium aluminide matrix resulted in change in microhardness. In Ti-Al-graphene composites, a noticeable decrease in coefficient of friction was observed due to the influence of self-lubrication caused by graphene.

Aldoshan, Abdelhakim Ahmed

217

Microstructural evolution and intermetallic formation in Al-8wt% Si-0.8wt% Fe alloy due to grain refiner and modifier additions  

NASA Astrophysics Data System (ADS)

An alloy of Al-8wt% Si-0.8wt% Fe was cast in a metallic die, and its microstructural changes due to Ti-B refiner and Sr modifier additions were studied. Apart from usual refinement and modification of the microstructure, some mutual influences of the additives took place, and no mutual poisoning effects by these additives, in combined form, were observed. It was noticed that the dimensions of the iron-rich intermetallics were influenced by the additives causing them to become larger. The needle-shaped intermetallics that were obtained from refiner addition became thicker and longer when adding the modifier. It was also found that ?-Al and eutectic silicon phases preferentially nucleate on different types of intermetallic compounds. The more iron content of the intermetallic compounds and the more changes in their dimensions occurred. Formation of the shrinkage porosities was also observed.

Hassani, Amir; Ranjbar, Khalil; Sami, Sattar

2012-08-01

218

cis-trans Germanium chains in the intermetallic compounds ALi 1- xIn xGe 2 and A2(Li 1- xIn x) 2Ge 3 ( A=Sr, Ba, Eu)—experimental and theoreticalstudies  

NASA Astrophysics Data System (ADS)

Two types of strontium-, barium- and europium-containing germanides have been synthesized using high temperature reactions and characterized by single-crystal X-ray diffraction. All reported compounds also contain mixed-occupied Li and In atoms, resulting in quaternary phases with narrow homogeneity ranges. The first type comprises EuLi 0.91(1)In 0.09Ge 2, SrLi 0.95(1)In 0.05Ge 2 and BaLi 0.99(1)In 0.01Ge 2, which crystallize in the orthorhombic space group Pnma (BaLi 0.9Mg 0.1Si 2 structure type, Pearson code oP16). The lattice parameters are a=7.129(4)-7.405(4) Å; b=4.426(3)-4.638(2) Å; and c=11.462(7)-11.872(6) Å. The second type includes Eu 2Li 1.36(1)In 0.64Ge 3 and Sr 2Li 1.45(1)In 0.55Ge 3, which adopt the orthorhombic space group Cmcm (Ce 2Li 2Ge 3 structure type, Pearson code oC28) with lattice parameters a=4.534(2)-4.618(2) Å; b=19.347(8)-19.685(9) Å; and c=7.164(3)-7.260(3) Å. The polyanionic sub-structures in both cases feature one-dimensional Ge chains with alternating Ge-Ge bonds in cis- and trans-conformation. Theoretical studies using the tight-binding linear muffin-tin orbital (LMTO) method provide the rationale for optimizing the overall bonding by diminishing the ?- p delocalization along the Ge chains, accounting for the experimentally confirmed substitution of Li forIn.

You, Tae-Soo; Bobev, Svilen

2010-12-01

219

Characterization of Complex Organic Compounds Formed in Simulated Planetary Atmospheres by the Action of High Energy Particles  

NASA Astrophysics Data System (ADS)

A wide variety of organic compounds, which are not simple organics but also complex organics, have been found in planets and comets. We reported that complex organics was formed in simulated planetary atmospheres by the action of high energy particles. Here we characterized the experimental products by using chromatographic and mass spectrometric techniques. A gaseous mixture of CO, N2 and H2O was irradiated with high energy protons (major components of cosmic rays). Water-soluble non-volatile substances, which gave amino acids after acid-hydrolysis, were characterized by HPLC and mass spectrometry. Major part of the products were complex compounds with molecular weight of several hundreds. Amino acid precursors were produced even when no water was incorporated with the starting materials. It was suggested that complex molecules including amino acid precursors were formed not in solution from simple molecules like HCN, but directly in gaseous phase

Kobayashi, Kensei; Kaneko, Takeo; Saito, Takeshi

1999-01-01

220

Complexation of Amino Compounds by 18C6 Improves Selectivity by IMS-IMS-MS: Application to Petroleum Characterization  

PubMed Central

Complexation of a series of related amino compounds by 18-crown-6 ether (18C6) is studied as a means of improving the resolution of mixtures by combinations of ion mobility spectrometry (IMS) and mass spectrometry (MS) techniques. Mixtures of the isomeric amines n-octylamine (NOA), dibutylamine (DBA), and diisopropylethylamine (DIPEA) were electrosprayed to produce gaseous [M + H]+ ions. These species have overlapping mobilities and are not resolved by IMS. Addition of 18C6 yields [M + 18C6 + H]+ ion complexes that are resolved by IMS. In subsequent experiments, [M + 18C6 + H]+ ion complexes are separated according to their mobilities and specific species are selected and exposed to collisional activation. This analysis yields dissociation voltages that are inversely correlated with the number of separate substitutions on the nitrogen atom of the amino compounds; dissociation voltages of ~40, ~90, and ~150 V are obtained for the tri-, di-, and mono-substituted amino compounds DIPEA, DBA, and NOA, respectively. For these complexes, an inverse correlation is also observed with respect to the gas-phase basicities (GB) of the amino compounds (964, 935, and 895 kJ mol?1, respectively). Studies of 18C6 complexes with a series of n-alkylamines (CnH2n+3N where n=3 to 18, respectively) show that dissociation voltages increase systematically (from ~140 to ~190 V) under the conditions employed. The sensitivity to collision energy provides an additional means of distinguishing between classes of compounds. The approach is extended as a means of separating nitrogen-containing compounds from petroleum. PMID:21472516

Li, Zhiyu; Valentine, Stephen J.; Clemmer, David E.

2013-01-01

221

Complexation of Amino Compounds by 18C6 Improves Selectivity by IMS-IMS-MS: Application to Petroleum Characterization  

NASA Astrophysics Data System (ADS)

Complexation of a series of related amino compounds by 18-crown-6 ether (18C6) is studied as a means of improving the resolution of mixtures by combinations of ion mobility spectrometry (IMS) and mass spectrometry (MS) techniques. Mixtures of the isomeric amines n-octylamine (NOA), dibutylamine (DBA), and diisopropylethylamine (DIPEA) were electrosprayed to produce gaseous [M + H]+ ions. These species have overlapping mobilities and are not resolved by IMS. Addition of 18C6 yields [M + 18C6 + H]+ ion complexes that are resolved by IMS. In subsequent experiments, [M + 18C6 + H]+ ion complexes are separated according to their mobilities and specific species are selected and exposed to collisional activation. This analysis yields dissociation voltages that are inversely correlated with the number of separate substitutions on the nitrogen atom of the amino compounds; dissociation voltages of ~40, ~90, and ~150 V are obtained for the tri-, di-, and mono-substituted amino compounds DIPEA, DBA, and NOA, respectively. For these complexes, an inverse correlation is also observed with respect to the gas-phase basicities (GB) of the amino compounds (964, 935, and 895 kJ mol-1, respectively). Studies of 18C6 complexes with a series of n-alkylamines (C n H2 n+3N where n = 3 to 18, respectively) show that dissociation voltages increase systematically (from ~140 to ~190 V) under the conditions employed. The sensitivity to collision energy provides an additional means of distinguishing between classes of compounds. The approach is extended as a means of separating nitrogen-containing compounds from petroleum.

Li, Zhiyu; Valentine, Stephen J.; Clemmer, David E.

2011-05-01

222

Halogen-Bridged Metal Complexes: Model Compounds for High-Tc Superconductors?  

NASA Astrophysics Data System (ADS)

A simple model for describing the family of quasi-one-dimensional halogen-bridged metal complexes is presented which takes both electron-phonon and electron-electron interactions into account. A competition between chemical bonding and charge disproportionation occurs in these MX chains. The charge-density wave ground state appears to be the rule, but minor modifications, e.g., replacing chlorine by iodine, can strongly change its character from a large amplitude mixed valence limit to that of a small amplitude Peierls distortion. Correspondingly, the polaronic defect states which are very localized in one regime become quite extended in the other. Experimental data for two specific materials are analysed in terms of the two limiting cases. Finally the recently discovered quasi-two-dimensional high-Tc superconductors and the related three-dimensional material BaPb1-xBixO3 are considered as interpenetrating MX chains. It is proposed that in these compounds the oxygen plays a similar role as the halogen in the MX chain in delocalizing the electronic states at the Fermi energy.

Baeriswyl, D.; Bishop, A. R.

1987-01-01

223

Fatigue of titanium alloys and intermetallics  

Microsoft Academic Search

This dissertation represents the results of an investigation of fatigue in titanium alloys and intermetallics. The results of a combined experimental and analytical study of the probabilistic nature of fatigue crack growth in Ti-6Al-4 V are presented. A simple experimental fracture mechanics framework is presented for the determination of statistical fatigue crack growth parameters from two fatigue tests. A probabilistic

Weimin Shen

2002-01-01

224

Surfaces of Intermetallics: Quasicrystals and Beyond  

SciTech Connect

The goal of this work is to characterize surfaces of intermetallics, including quasicrystals. In this work, surface characterization is primarily focused on composition and structure using X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM) performed under ultrahigh vacuum (UHV) conditions.

Yuen, Chad [Ames Laboratory

2012-10-26

225

MD study of primary damage in L10 TiAl structural intermetallics  

NASA Astrophysics Data System (ADS)

Computer modelling by molecular dynamics has been applied to study the radiation damage created in collision cascades in L10 TiAl intermetallic compound. Either Al or Ti primary knock-on atoms (PKA) with energy 5 keV ? EPKA ? 20 keV were introduced in the intermetallic crystals at temperatures ranging from 100 K to 900 K. At least 24 different cascade for each (EPKA, T, PKA type) set were modelled in order to simulate a random spatial and temporal distribution of PKAs and provide statistical reliability of the results. The total yield of more than 760 simulated cascades is the largest yet reported for this binary intermetallic material. A comprehensive treatment of the modelling results has been carried out. The number of Frenkel pairs, fraction of Al and Ti vacancies, self-interstitial atoms and anti-sites as a function of (EPKA, T, PKA type) has been established. Preferred formation of Al self-interstitial atoms has been detected in L10 TiAl structural intermetallics exposed to irradiation.

Voskoboinikov, Roman E.

2013-05-01

226

Alumina as diffusion barrier to intermetallic formation in thermal interface materials made from indium and copper  

NASA Astrophysics Data System (ADS)

Indium and copper react at wide range of temperatures to form intermetallic compounds that have different physical, mechanical and thermal properties. Liquid Phase Sintered indium-copper composite long-term performance as thermal interface material is adversely affected by the evolution of the intermetallic. In this study, i) the effect of intermetallic formation and growth on the performance of Liquid Phase Sintered copper-indium composite, ii) the effect of alumina as diffusion barrier between indium and copper, (iii) thermal stability and wettability between indium and alumina, iv) the indium and quartz wettability, v) indium and tungsten oxide wettability have been studied. Deleterious effect of the intermetallic formation and growth on the thermal and mechanical properties has been observed. 5nm of alumina deposited by Atomic Layer Deposition on flat copper surface has been optimized to prevent diffusion process between indium and copper at 120°C. 15nm of alumina prevented the reaction at 230°C. Instability of indium thin film thermally deposited on sapphire substrate was observed. Also, decrease in the sintering density of indium-alumina composite with increasing temperature was observed. The dewetting contact angle between liquid indium and sapphire was ˜127°. The wetting experiments between indium and different oxides showed that indium wets tungsten oxide and quartz..

Saleh, Ibrahim Khalifa

227

Revisiting a Rare Intermetallic Ternary Nitride, Ni 2Mo 3N: Crystal Structure and Property Measurements  

NASA Astrophysics Data System (ADS)

The intermetallic ternary nitride, Ni 2Mo 3N, has been synthesized by the ammonolysis of a complexed mixed-metal chloride precursor. This compound crystallizes in the cubic space group P4 132 [213] with Z=4 and a lattice parameter of a=6.6340(2) Å, as determined from powder X-ray and neutron diffraction experiments and the Rietveld refinement of the neutron data collected at room temperature. The refinement converged with Rwp=0.032, Rp=0.025, RI=0.059, and ?2=1.48. Ni 2Mo 3N assumes a filled ?-manganese structure, ideally consisting of a lattice of corner-sharing Mo 6N octahedra in a five-membered ring arrangement and an interpenetrating net-like lattice of nickel atoms which occupy the pentagonal holes formed by the molybdenum nitride polyhedral rings. Electrical and magnetic characterization of Ni 2Mo 3N indicate that it is a metallic conductor which antiferromagnetically orders at 14.7 K. Neutron diffraction conducted at 10 K suggests that the size of the magnetic unit cell matches that of the crystallographic unit cell. A version of this nitride phase which is substoichiometric in nitrogen and therefore has a smaller lattice parameter also displays antiferromagnetic ordering, but with a much higher ordering temperature of 68.7 K.

Weil, K. S.; Kumta, P. N.; Grins, J.

1999-08-01

228

Detection and differentiation of neutral organic compounds by 19F NMR with a tungsten calix[4]arene imido complex.  

PubMed

Fluorinated tungsten calix[4]arene imido complexes were synthesized and used as receptors to detect and differentiate neutral organic compounds. It was found that the binding of specific neutral organic molecules to the tungsten centers induces an upfield shift of the fluorine atom appended on the arylimido group, the extent of which is highly dependent on electronic and steric properties. We demonstrate that the specific bonding and size-selectivity of calix[4]arene tungsten-imido complex combined with (19)F NMR spectroscopy is a powerful new method for the analysis of complex mixtures. PMID:24299149

Zhao, Yanchuan; Swager, Timothy M

2013-12-18

229

Processing of permanent magnet materials based on rare earth-transition metal intermetallics  

Microsoft Academic Search

A compact survey is given of the processing of high-performance permanent magnet materials, which are based on the intermetallic compounds SmCo5, Sm2Co17 and Nd2Fe14B. In addition, the present development state of magnets based on the recently discovered Sm2Fe17N3 phase is compiled. Besides the commercial manufacturing technologies, powder metallurgy including sintering and rapid quenching, novel processing routes, i.e. mechanical alloying, hydrogen

C. Kuhrt

1995-01-01

230

Characterisation of high temperature corrosion products on FeAl intermetallics by XPS  

Microsoft Academic Search

FeAl (42 at.% Al) intermetallic compound was exposed to a mixture gas of (95%N2+5%H2) plus 1% H2S at 600°C. The corrosion products on the surface of FeAl specimens were examined by using scanning electron microscopy, energy dispersive spectroscopy and X-ray photoelectron spectroscopy (XPS). The XPS depth profile revealed that the thin scale consists of two layers: a layer of mixture

C.-H Xu; W Gao; M Hyland; H Gong

2001-01-01

231

The development of Nb-based advanced intermetallic alloys for structural applications  

NASA Astrophysics Data System (ADS)

A new generation of refractory material systems with significant increases in temperature capability is required to meet the demands of future aerospace applications. Such materials require a balance of properties such as low-temperature damage tolerance, high-temperature strength, creep resistance, and superior environmental stability for implementation in advanced aerospace systems. Systems incorporating niobium-based beta alloys and intermetallic compounds have the potential for meeting these requirements.

Subramanian, P. R.; Mendiratta, M. G.; Dimiduk, D. M.

1996-01-01

232

Geometrical frustration, heavy fermions, and lattice disorder in uranium and cerium intermetallics  

Microsoft Academic Search

Geometrical frustration may lead to a variety of interesting states of matter such as spin super-solids, spin-ice, or spin-liquids. While frustration has been widely studied in oxides such as the pyrochlores or Mott insulators, the effect of geometrical frustration on the development of the heavy-fermion state or quantum criticality in intermetallic compounds has received much less attention. Samples from two

Y. Jiang; C. H. Booth; P. H. Tobash; E. D. Bauer; J. D. Thompson

2010-01-01

233

The erosion behaviour of NiAl intermetallic coatings produced by high velocity oxy-fuel thermal spraying  

Microsoft Academic Search

This paper examines the erosion behaviour of high velocity oxy-fuel thermal (HVOF) NiAl intermetallic compounds (IMC) coatings over a range of angles and particle velocities, in air at room temperature. Results showed a variation of mass loss with velocity and angle. Maximum erosion was observed at 90° for all velocities, suggestive of classical brittle behaviour. Morphological examination of the coatings'

J. A Hearley; J. A Little; A. J Sturgeon

1999-01-01

234

An inventory of biogenic volatile organic compounds for a subtropical urban-rural complex  

NASA Astrophysics Data System (ADS)

Increases in atmospheric volatile organic compounds (VOC), especially in relation to biogenic VOC (BVOC), and haze days that affect the built-up areas are believed to be closely correlated. The present study aims to provide a spatially and temporally resolved BVOC inventory of a subtropical urban-rural complex, the Greater Hangzhou Area (GHA) in China. Urban green space was subdivided into block green space and linear green space; rural areas were classified into four primary forest types. A field survey was conducted to assess the vegetation composition (species, size) and foliar mass of each tree species. BVOC emission potentials were obtained from measurement and literature. Results showed (1) the emission intensity (annual BVOC emissions per land area) in the entire GHA is 3.37 × 106 g C km-2 yr-1, and rural forest (excluding bamboo forest) exhibits lower average emission intensity (2.74 × 106 g C km-2 yr-1) than that of urban green space (3.13 × 106 g C km-2 yr-1); (2) Within the built-up area, the block green space has higher emission intensity (3.93 × 106 g C km-2 yr-1) than the linear green space (2.63 × 106 g C km-2 yr-1); (3) in Hangzhou city, BVOC emissions of native and exotic trees exhibited no differences; and (4) in rural areas, bamboo forests and coniferous forests were the major contributors of BVOC emissions, whereas the original vegetation type of this region, evergreen broad-leaved forest, possessed lower BVOC emissions. The results suggest that total BVOC emission can be controlled to low levels by planting low-emitting species in built-up areas while restoring original broad-leaved forest vegetation in rural areas.

Chang, Jie; Ren, Yuan; Shi, Yan; Zhu, Yimei; Ge, Ying; Hong, Shengmao; Jiao, Li; Lin, Fengmei; Peng, Changhui; Mochizuki, Tomoki; Tani, Akira; Mu, Ying; Fu, Chengxin

2012-09-01

235

Slater-Pauling behavior within quaternary intermetallic borides of the Ti{sub 3}Co{sub 5}B{sub 2} structure-type  

SciTech Connect

First-principles, density-functional studies of several intermetallic borides of the general type M{sub 2}M'Ru{sub 5-n}Rh{sub n}B{sub 2} (n=0-5; M=Sc, Ti, Nb; M'=Fe, Co) show that the variation in saturation magnetic moment with valence-electron count follows a Slater-Pauling curve, with a maximum moment occurring typically at 66 valence electrons. The magnetic moments in these compounds occur primarily from the 3d electrons of the magnetically active M' sites, with some contribution from the Ru/Rh sites via magnetic polarization. Electronic DOS curves reveal that a rigid-band approach is a reasonable approximation for the estimation of saturation moments and the analysis of orbital interactions in this family of complex borides. COHP analyses of the M'-M' orbital interactions indicate optimized interactions in the minority spin states for Co-containing phases, but strong bonding interactions remaining in Fe-containing phases. - Graphical abstract: Theoretically determined (spin-polarized LMTO-GGA) local magnetic moments as a function of the chemical valence Z for various intermetallic borides.

Burghaus, Jens [Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1, 52062 Aachen (Germany); Dronskowski, Richard, E-mail: drons@HAL9000.ac.rwth-aachen.d [Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1, 52062 Aachen (Germany); Miller, Gordon J. [Department of Chemistry, Iowa State University, Ames, IA 50011 (United States)

2009-10-15

236

Screening for Active Small Molecules in Mitochondrial Complex I Deficient Patient's Fibroblasts, Reveals AICAR as the Most Beneficial Compound  

PubMed Central

Congenital deficiency of the mitochondrial respiratory chain complex I (CI) is a common defect of oxidative phosphorylation (OXPHOS). Despite major advances in the biochemical and molecular diagnostics and the deciphering of CI structure, function assembly and pathomechanism, there is currently no satisfactory cure for patients with mitochondrial complex I defects. Small molecules provide one feasible therapeutic option, however their use has not been systematically evaluated using a standardized experimental system. In order to evaluate potentially therapeutic compounds, we set up a relatively simple system measuring different parameters using only a small amount of patient's fibroblasts, in glucose free medium, where growth is highly OXPOS dependent. Ten different compounds were screened using fibroblasts derived from seven CI patients, harboring different mutations. 5-Aminoimidazole-4-carboxamide ribotide (AICAR) was found to be the most beneficial compound improving growth and ATP content while decreasing ROS production. AICAR also increased mitochondrial biogenesis without altering mitochondrial membrane potential (??). Fluorescence microscopy data supported increased mitochondrial biogenesis and activation of the AMP activated protein kinase (AMPK). Other compounds such as; bezafibrate and oltipraz were rated as favorable while polyphenolic phytochemicals (resverastrol, grape seed extract, genistein and epigallocatechin gallate) were found not significant or detrimental. Although the results have to be verified by more thorough investigation of additional OXPHOS parameters, preliminary rapid screening of potential therapeutic compounds in individual patient's fibroblasts could direct and advance personalized medical treatment. PMID:22046392

Weissman, Sarah; Link, Gabriela; Wikstrom, Jakob D.; Saada, Ann

2011-01-01

237

Use of emanation thermal analysis and evolved gas analysis in thermal study of zinc(II) benzoate complex compounds  

Microsoft Academic Search

Thermal behaviours of three zinc(II) benzoate complex compounds (two new with caffeine and urea), namely Zn(C6H5COO)2, Zn(C6H5COO)2·caf2, Zn(C6H5COO)2·u2, were characterized by using thermogravimetry (TG\\/DTG), differential thermal analysis (DTA), evolved gas analysis (EGA) with\\u000a mass spectrometry (MS) detection and emanation thermal analysis (ETA). Temperature intervals of the stability of the compounds\\u000a as well as the mechanisms of their thermal degradation were

Lenka Findoráková; Katarína Gy?ryová; Eva Ve?erníková; Vladimír Balek

2009-01-01

238

Addressing Machining Issues for the Intermetallic Compound 60-NITINOL  

NASA Technical Reports Server (NTRS)

60-NITINOL (60 wt.% Ni - 40 wt.% Ti) is being studied as a material for advanced aerospace components. Frequent wire breakage during electrical-discharge machining of this material was investigated. The studied material was fabricated from hot isostatically pressed 60-NITINOL powder obtained through a commercial source. Bulk chemical analysis of the material showed that the composition was nominal but had relatively high levels of certain impurities, including Al and O. It was later determined that Al2O3 particles had contaminated the material during the hot isostatic pressing procedure and that these particles were the most likely cause of the wire breakage. The results of this investigation highlight the importance of material cleanliness to its further implementation.

Stanford, Malcolm K.; Wozniak, Walter A.; McCue, Terry R.

2012-01-01

239

Trace elements and the mechanical properties of intermetallic compounds  

SciTech Connect

In this paper the brittleness of grain boundaries in Ni{sub 3}Al is discussed with special emphasis on the effects of B. The effects of alloy stoichiometry, environment (hydrogen), grain boundary character and B levels are described and interpreted in terms of current theories. It is shown that the grain boundaries in Ni{sub 3}Al are intrinsically weaker than the bulk (the weakness is not an impurity effect), the weakness is exacerbated by atmospheric moisture, and that B in the boundaries both increases the intrinsic strength of the boundaries and reduces the deleterious effects of atmospheric moisture. Only low angle boundaries and twin boundaries are intrinsically strong in Ni{sub 3}Al, even in the absence of B.

Lin, Hui; Pope, D.P. [Univ. of Pennsylvania, Philadelphia, PA (United States). Dept. of Materials Science and Engineering; George, E.P. [Oak Ridge National Lab., TN (United States)

1995-02-01

240

Elastic Properties of the Intermetallic Compound ReSi 2  

Microsoft Academic Search

Structural properties are crucial for understanding deformation behavior of a solid, e.g., dislocation slip systems, twinning modes, etc. A knowledge of elastic constants is essential for many practical applications related to the mechanical properties of a solid: load-deflection, thermoelastic stress, internal strain (residual stress), sound velocities, dislocation core structure, and fracture toughness. Further, the elastic properties may provide insight on

A. Misra; F. Chu; T. E. Mitchell

1998-01-01

241

A Study on the Formation of Intermetallics During the Heat Treatment of Explosively Welded Al-Ti Multilayers  

NASA Astrophysics Data System (ADS)

Metallic-intermetallic laminate composites are promising materials for many applications, namely, in the aerospace industry. Ti/TiAl3 laminates are one of the interesting laminate composites, which are mostly used in aerospace applications. In this work, commercially pure aluminum and titanium sheets were explosively joined. The multilayer samples were annealed between 1 and 260 hours at 903 K (630 °C) in ambient atmosphere, and the formation and growth of the intermetallic compound at the Ti/Al interface were monitored. Microstructural investigations were carried out using optical and scanning electron microscopes equipped with energy-dispersive spectroscopy and the X-ray diffraction technique. The microhardness profile of the layers was also determined. The thickness and type of Al-Ti intermetallics were determined. It was found that the only intermetallic phase observed in the interfaces was TiAl3. It was also shown that two mechanisms for TiAl3 growth exist: reaction and diffusion controlled. The growth exponent was equal to 0.94 for the reaction-controlled mechanism (first step) and 0.31 for the diffusion-controlled mechanism (second step). These values were in good agreement with theoretical values (1 and 0.5 for the first and second steps, respectively). Based on the results of this research, a kinetic model for the formation and growth of TiAl3 intermetallic phase was proposed.

Foadian, Farzad; Soltanieh, Mansour; Adeli, Mandana; Etminanbakhsh, Majid

2014-04-01

242

Magnetic Phase Diagram of the Binary Intermetallic GdSi  

NASA Astrophysics Data System (ADS)

The magnetic phase diagram of the binary intermetallic GdSi is investigated via magnetotransport and magnetization measurements along all three principal crystal axes. At zero applied field, two distinct phase transitions are observed at 53 and 54.7 K, corresponding to a spin flip and Neel transition, respectively. An additional ordered antiferromagnetic state appears for magnetic fields applied in the a-c plane, transitioning to a ferromagnetic ground state at H˜20 T. Although Gd ions are well characterized by local spin-only moments, and the magnetic anisotropy is small in this system, the additional antiferromagnetic ordering transition is observed to be considerably softer along c than along a. The interplay between this complex magnetic phase diagram, the band structure, and quantum effects will be discussed.

Silevitch, D. M.; Feng, Yejun; Yan, J.-Q.; Wang, Jiyang; Woo, Nayoon; Rosenbaum, T. F.

2013-03-01

243

Photochemistry of pyrylium compounds: excitation-induced rearrangement of a molecule-solvent complex  

NASA Astrophysics Data System (ADS)

Photochemical rearrangement of the complex pyrylium molecule - solvent is studied in solvents of various polarity and nucleophilicity. Upon photoexcitation two types of transient fluorescent excited-state complexes are formed due to intramolecular charge transfer and geometrical rearrangement of the complex.

Kaliteevskaya, E. N.; Krutyakova, V. P.; Razumova, T. K.; Rochal, A. D.

2002-05-01

244

Electronic structure of complex compounds of uranyl with consideration of the inner orbitals of the uranium atom  

SciTech Connect

The electronic structure and spectra of halo, nitrato, and acetato complexes of uranyl have been calculated by a semiempirical MO method. The valence basis was expanded by taking into account the inner 6p orbitals of the U atom. An analysis of the populations on the atoms was carried out. According to the calculated data, the structure of the uranyl grouping in all the complexes considered remains practically the same, accounting for the similarity in the structure of the electronic absorption and fluorescence spectra of uranyl compounds.

Borkovskii, N.B.; Kovrikov, A.B.; Umreiko, D.S.

1985-09-01

245

Complex model for plasma-enhanced heteroepitaxial deposition of A2B6 semiconductor compounds using MOC  

Microsoft Academic Search

A complex model for low-temperature PEMOCVD of A2B6 semiconductor layers is considered as follows: (i) metal-organic compound (MOC) molecules together with the carrier gas flux arrive at the reaction zone of a horizontal reactor where a gas discharge is maintained by means of an external inductor; (ii) molecular dissociation and convective diffusion of atoms of material to be deposited occur

S. N. Ershov; M. I. Vasilevskiy; T. I. Benushis; B. V. Gurilev; A. B. Ozerov

1992-01-01

246

Optical investigations of alkali metal thiomanganates(II) containing isolated complexes as well as chain and planar compounds.  

PubMed

Tetracoordinated Mn(II) complexes providing different molecular structures were investigated using various spectroscopical procedures. Na(6)MnS(4) contains separate pseudotetrahedral Mn-S complex units, K(2)MnS(2) has chains of edge-shared tetrahedra, and Cs(2)Mn(3)S(4) crystallizes in corresponding layers. Also doped materials, i.e., Cs(2)(Mn(x)Zn(1-x))(3)S(4) with 0.0 < x < 1.0, are considered. Absorption spectra recorded from samples incorporated in polyethylene pellets and excitation spectra taken from pure materials at 15-20 K temperature are assigned on the basis of energy level calculations obtained from the angular overlap model. All compounds exhibit intensive emission in the red, some of them also in the yellow region, which both are investigated in the temperature range from 12.5 to 250 K, in some cases varying the excitation power and excitation wavelength. Decay measurements supply lifetimes and activation energies evaluated from Arrhenius plots. The results support an assignment of both types of emissions to MnS(4) complex entities for all compounds, the red emission from the lowest excited level (Kasha luminescence) and the yellow emission, observed for some of the compounds with increasing intensity at lower temperature, from higher electronic levels. PMID:11849086

Rosellen, Ulrike; Schmidtke, Hans-Herbert

2002-02-25

247

How do nanometer scale dislocation traces evolve in the stress anomaly domain of intermetallics?  

NASA Astrophysics Data System (ADS)

The yield stress of Ni3Al intermetallic compounds exhibits positive temperature dependence. These compounds are used as the reinforcing phase of superalloys for aerospace and aeronautic applications. The proposed models based on cross-slip events from primary octahedral to cube slip planes explain this phenomenon either by dislocation velocity or mobile dislocation density effects. In situ atomic force microscopy observations of Ni3(Al,Hf) single crystals under increasing strain are reported. The fine slip line structure provides a direct evidence of a permanent locking of mobile dislocations in the yield stress anomaly domain.

Coupeau, Christophe; Bonneville, Joël

2007-04-01

248

Separation of compounds with multiple -OH groups from dilute aqueous solutions via complexation with organoboronate  

SciTech Connect

The complexing extractant agent investigated in this work is 3-nitrophenylboronic acid (NPBA) in its anionic form (NPB). NPBA and Aliquat 336 (quaternary amine) is dissolved in 2-ethyl-l-hexanol, and the extractant is contacted with aq. NaOH. Solutes investigated were 1,2-propanediol, glycerol, fructose, sorbitol and lactic acid. Batch extraction experiments were performed at 25{degree}C. Partition coefficients, distribution ratios and loadings are reported for varying concentrations of solute and NPB. All solutes complexed with NPB{sup {minus}}, with all complexes containing only one NPB{sup {minus}} per complex. The 1:1 complexation constants for the solutes glycerol, fructose and sorbitol follow trends similar to complexation with B(OH){sub 4}{sup {minus}} (aq.), i.e. the complexation constants increase with increasing number of {minus}OH groups available for complexation. Assumption of 1:1 complex is not valid for 1, 2-propanediol, which showed overloading (more than one mole of solute complexed to one mole NPB{sup {minus}}) at higher concentrations. The {minus}OH group on the NPB{sup {minus}} which is left uncomplexed after one solute molecule had bound to the other two {minus}OH groups may be responsible for the overloading. Overloading is also observed in extraction of tactic acid, but through a different mechanism. It was found that TOMA{sup +} can extract lactic acid to an extent comparable to the uptake of lactic acid by NPB{sup {minus}}. The complexation is probably through formation of an acid-base ion pair. Losses of NPBA into the aqueous phase could lead to problems, poor economics in industrial separation processes. One way of overcoming this problem would be to incorporate the NPBA onto a solid support.

Chow, Tina Kuo Fung

1992-05-01

249

A NEW MASS SPECTROMETRIC TECHNIQUE FOR IDENTIFYING TRACE-LEVEL ORGANIC COMPOUNDS IN COMPLEX MIXTURES  

EPA Science Inventory

Most organic compounds are not found in mass spectral libraries and cannot be easily identified from low resolution mass spectra. Ion Composition Elucidation (ICE) utilizes selected ion recording with a double focusing mass spectrometer in a new way to determine exact mas...

250

The Complexity of Factors Driving Volatile Organic Compound Emissions by Plants  

Microsoft Academic Search

The emissions of volatile organic compounds, VOC, from plants have strong relevance for plant physiology, plant ecology, and atmospheric chemistry. We report here on the current knowledge of the many internal (genetic and biochemical) and external (abiotic - temperature, light, water availability, wind, ozone, and biotic - animal, plant and microorganisms interactions) factors that control emission rates of different VOC

J. Peñuelas; J. Llusià

2001-01-01

251

Crystal structures of multidrug-resistant HIV-1 protease in complex with two potent anti-malarial compounds.  

PubMed

Two potent inhibitors (compounds 1 and 2) of malarial aspartyl protease, plasmepsin-II, were evaluated against wild type (NL4-3) and multidrug-resistant clinical isolate 769 (MDR) variants of human immunodeficiency virus type-1 (HIV-1) aspartyl protease. Enzyme inhibition assays showed that both 1 and 2 have better potency against NL4-3 than against MDR protease. Crystal structures of MDR protease in complex with 1 and 2 were solved and analyzed. Crystallographic analysis revealed that the MDR protease exhibits a typical wide-open conformation of the flaps (Gly48 to Gly52) causing an overall expansion in the active site cavity, which, in turn caused unstable binding of the inhibitors. Due to the expansion of the active site cavity, both compounds showed loss of direct contacts with the MDR protease compared to the docking models of NL4-3. Multiple water molecules showed a rich network of hydrogen bonds contributing to the stability of the ligand binding in the distorted binding pockets of the MDR protease in both crystal structures. Docking analysis of 1 and 2 showed a decrease in the binding affinity for both compounds against MDR supporting our structure-function studies. Thus, compounds 1 and 2 show promising inhibitory activity against HIV-1 protease variants and hence are good candidates for further development to enhance their potency against NL4-3 as well as MDR HIV-1 protease variants. PMID:22469467

Yedidi, Ravikiran S; Liu, Zhigang; Wang, Yong; Brunzelle, Joseph S; Kovari, Iulia A; Woster, Patrick M; Kovari, Ladislau C; Gupta, Deepak

2012-05-11

252

Crystal structures of multidrug-resistant HIV-1 protease in complex with two potent anti-malarial compounds  

SciTech Connect

Two potent inhibitors (compounds 1 and 2) of malarial aspartyl protease, plasmepsin-II, were evaluated against wild type (NL4-3) and multidrug-resistant clinical isolate 769 (MDR) variants of human immunodeficiency virus type-1 (HIV-1) aspartyl protease. Enzyme inhibition assays showed that both 1 and 2 have better potency against NL4-3 than against MDR protease. Crystal structures of MDR protease in complex with 1 and 2 were solved and analyzed. Crystallographic analysis revealed that the MDR protease exhibits a typical wide-open conformation of the flaps (Gly48 to Gly52) causing an overall expansion in the active site cavity, which, in turn caused unstable binding of the inhibitors. Due to the expansion of the active site cavity, both compounds showed loss of direct contacts with the MDR protease compared to the docking models of NL4-3. Multiple water molecules showed a rich network of hydrogen bonds contributing to the stability of the ligand binding in the distorted binding pockets of the MDR protease in both crystal structures. Docking analysis of 1 and 2 showed a decrease in the binding affinity for both compounds against MDR supporting our structure-function studies. Thus, compounds 1 and 2 show promising inhibitory activity against HIV-1 protease variants and hence are good candidates for further development to enhance their potency against NL4-3 as well as MDR HIV-1 protease variants.

Yedidi, Ravikiran S.; Liu, Zhigang; Wang, Yong; Brunzelle, Joseph S.; Kovari, Iulia A.; Woster, Patrick M.; Kovari, Ladislau C.; Gupta, Deepak (LECOM); (WSI); (NWU); (MUSC); (WSU)

2012-06-19

253

Design and synthesis of novel complexes containing N-phenyl-1H-pyrazole moiety: Ni complex as potential antifungal and antiproliferative compound  

NASA Astrophysics Data System (ADS)

Cu(II) (1), Ni(II) (2), Cr(III) (3) and Fe(III) (4) complexes with 3-acetyl-4-benzoyl-1-phenyl-1H-pyrazole (L1) were prepared and structurally characterized. Usual coordination of L1 was achieved through nitrogen of pyrazole moiety and carbonyl acetyl group. Electronic spectra of the complexes indicate that the geometry of the metal center was six coordinate octahedral. In vitro antimicrobial activity of the ligand and complex compounds was screened in terms of antibacterial effect on Staphylococcus aureus (Gram-positive), Escherichia coli (Gram-negative) and antifungal effect on the fungi Aspergillus flavus and candida albicans using the modified Kirby-Bauer disc diffusion and minimum inhibitory concentrations (MIC) methods. Ni(II) complex (2) exhibited remarkable antifungal inhibition against Candida albicans equal to the standard antifungal agent. To continue our study some structural modifications are formed by adding 4-fluoro-benzoyl moiety to L1 in different forms to produce different ligands, 3-acetyl-4-(4-flourobenzoyl)-1-phenyl-1H-pyrazole (L2) and 3-[(3-acetyl-1-phenyl-1H-4-pyrazolyl)carbonyl]-1-phenyl-4-(4-flourobenzoyl)-1H-pyrazole (L3), Ni complexes (5 and 6) are prepared and comparable in vitro antimicrobial study is evaluated. In vitro cytotoxicity of the Ni(II) complex (2) is studied using MTT assay. The analysis of the cell test showed that (2) displayed quite small cytotoxic response at the higher concentration level which indeed would further enable us for more opportunities in therapeutic and biomedical challenges. Both of the capability as a potent in vitro antifungal agent and the cell test analysis show Ni(II) complex (2) as a promising material in the translation of observed in vitro biological phenomenon into clinical therapies settings.

El-Gamel, Nadia E. A.; Farghaly, Thoraya A.

2013-11-01

254

Implications for complex cognition from the hafting of tools with compound adhesives in the Middle Stone Age, South Africa  

PubMed Central

Compound adhesives made from red ochre mixed with plant gum were used in the Middle Stone Age (MSA), South Africa. Replications reported here suggest that early artisans did not merely color their glues red; they deliberately effected physical transformations involving chemical changes from acidic to less acidic pH, dehydration of the adhesive near wood fires, and changes to mechanical workability and electrostatic forces. Some of the steps required for making compound adhesive seem impossible without multitasking and abstract thought. This ability suggests overlap between the cognitive abilities of modern people and people in the MSA. Our multidisciplinary analysis provides a new way to recognize complex cognition in the MSA without necessarily invoking the concept of symbolism. PMID:19433786

Wadley, Lyn; Hodgskiss, Tamaryn; Grant, Michael

2009-01-01

255

Comparison of Sm complexes with Sn compounds for syntheses of copolymers composed of lactide and ?-caprolactone and their biodegradabilities  

Microsoft Academic Search

The comparison of organolanthanide complexes, (C5Me5)2SmMe(THF) (Sm1) and [(C5Me5)2Sm]2(PhC?C?C?CPh) (Sm2), with tin compounds, Bu2Sn(OMe)2 (Sn1) and Bu2Sn(OCH2CH2CH2O) (Sn2), in the preparation of random and diblock copolymers composed of l-lactide (l-LA) or d,l-LA and ?-caprolactone (CL), and the preparation of triblock copolymers composed of l-LA\\/CL\\/l-LA was studied and the biodegradabilities of the resulting copolymers with proteinase K and a compost were

Hajime Yasuda; Katsuhiro Yamamoto; Yuushou Nakayama; Chikara Tsutsumi; Philippe Lecomte; Robert Jerome; Stephan McCarthy; David Kaplan

2004-01-01

256

Draft genomes of three Antarctic Psychrobacter strains producing antimicrobial compounds against Burkholderia cepacia complex, opportunistic human pathogens.  

PubMed

Herein we present the draft genomes of three Psychrobacter strains isolated from Antarctic sponges and able to inhibit the growth of bacteria belonging to the Burkholderia cepacia complex, responsible for infections of the respiratory system in patients affected by Cystic Fibrosis. The comparative analysis of the annotated genomes of these Psychrobacter strains highlighted their differences in terms of overall genomic content (e.g. shared gene sets) and allowed the identification of gene clusters hypothetically involved in the biosynthesis of antimicrobial compounds. PMID:24401162

Fondi, Marco; Orlandini, Valerio; Perrin, Elena; Maida, Isabel; Bosi, Emanuele; Papaleo, Maria Cristiana; Michaud, Luigi; Lo Giudice, Angelina; de Pascale, Donatella; Tutino, Maria Luisa; Liò, Pietro; Fani, Renato

2014-02-01

257

Microscopic mechanisms of metastable phase formation during ball milling of intermetallic TiAl phases  

SciTech Connect

Powders of the intermetallic equilibrium phases {alpha}{sub 2}-Ti{sub 3}Al, {gamma}-TiAl and TiAl{sub 3} were ball milled in order to investigate the microscopic origins of the energetic destabilization and the transformation into metastable phases during the milling process. It was found that the intermetallic phases were chemically partially disordered on milling followed by the transformation into solid solution phases after long milling. In detail, for the {gamma} phase, the formation of numerous deformation twins, thin h.c.p. lamellae and lamellae of the 9R phase formed by an antitwin operation was observed by TEM. The disordering of the D0{sub 22}-TiAl{sub 3} phase occurred inhomogeneously in the material via the formation of antiphase boundaries on (001) planes, resulting in a f.c.c. solid solution in the final state. In summary, it can be concluded that the formation of the observed metastable phases results from chemical disordering, whereas the excess enthalpy of grain boundaries plays only a minor role for the energetical destabilization of the intermetallic compounds during milling in this case.

Klassen, T.; Oehring, M.; Bormann, R. [GKSS Research Centre, Geesthacht (Germany)] [GKSS Research Centre, Geesthacht (Germany)

1997-09-01

258

A new technology for diffusion bonding intermetallic TiAl to steel with composite barrier layers  

SciTech Connect

In this study, intermetallic TiAl and steel are diffusion bonded successfully by using composite barrier layers of titanium/vanadium/copper. The relationship of the bond parameters and tensile strength of the joints is discussed, and the optimum bond parameters were obtained. The reaction products and the interface structures of the joints were investigated by SEM, EPMA, and XRD. In this case, a dual phase Ti{sub 3}Al+TiAl layer and a Ti solid solution, which enhances the strength of the joint, are obtained at the TiAl/Ti interface. A formation mechanism at the interface of TiAl/Ti was proposed. The whole reaction process can be divided into three stages. In the first stage, Ti (Al{sub ss}) layer is formed at the interface TiAl/titanium. In the second stage, the continuous diffusion of Al atoms from TiAl to titanium leads to the formation of Ti{sub 3}Al, a TiAl+Ti{sub 3}Al layer is formed adjacent to TiAl. In the last stage, the thickness of each reaction layer increases with bonding time according to a parabolic law. The interface of TiAl/titanium/vanadium/copper/steel was free from intermetallic compounds and other brittle phases, and the strength of the joint was as high as 420 MPa, very close to that of the TiAl base. This method provides a reliable bonding method of intermetallic TiAl and steel.

He, P.; Feng, J.C.; Zhang, B.G.; Qian, Y.Y

2003-01-15

259

Crystal Structure of Patatin-17 in Complex with Aged and Non-Aged Organophosphorus Compounds  

PubMed Central

Patatin is a non-specific plant lipase and the eponymous member of a broad class of serine hydrolases termed the patatin-like phospholipase domain containing proteins (PNPLAs). Certain PNPLA family members can be inhibited by organophosphorus (OP) compounds. Currently, no structural data are available on the modes of interaction between the PNPLAs and OP compounds or their native substrates. To this end, we present the crystal structure of patatin-17 (pat17) in its native state as well as following inhibition with methyl arachidonyl fluorophosphonate (MAFP) and inhibition/aging with diisopropylphosphorofluoridate (DFP). The native pat17 structure revealed the existence of two portals (portal1 and portal2) that lead to its active-site chamber. The DFP-inhibited enzyme underwent the aging process with the negatively charged phosphoryl oxygen, resulting from the loss of an isopropyl group, being within hydrogen-binding distance to the oxyanion hole. The MAFP-inhibited pat17 structure showed that MAFP did not age following its interaction with the nucleophilic serine residue (Ser77) of pat17 since its O-methyl group was intact. The MAFP moiety is oriented with its phosphoryl oxygen in close proximity to the oxyanion hole of pat17 and its O-methyl group located farther away from the oxyanion hole of pat17 relative to the DFP-bound state. The orientation of the alkoxy oxygens within the two OP compounds suggests a role for the oxyanion hole in stabilizing the emerging negative charge on the oxygen during the aging reaction. The arachidonic acid side chain of MAFP could be contained within portals 1 or 2. Comparisons of pat17 in the native, inhibited, and aged states showed no significant global conformational changes with respect to their C? backbones, consistent with observations from other ?/? hydrolases such as group VIIA phospholipase A2. PMID:25248161

Wijeyesakere, Sanjeeva J.; Richardson, Rudy J.; Stuckey, Jeanne A.

2014-01-01

260

Preparation and study on the inclusion complexes of two tanshinone compounds with ?-cyclodextrin  

NASA Astrophysics Data System (ADS)

Solid inclusion complexes of two tanshinones (Tans): tanshinone IIA (Tan IIA), tanshinone I (Tan I) with ?-cyclodextrin (?-CD) were synthesized by coprecipitation method. The solid inclusion complexes were characterized by using several analytical techniques: 1H NMR spectra, IR spectra and thermal analysis. Stoichiometry of the inclusion complexes of Tans with ?-CD or HP-?-CD is 1:1 which was investigated in solution. The formation constants of the complexes were determined by UV spectrophotometry. For same kind of CD, the stability was in the order: Tan IIA > Tan I; for same guest, the stability was in the order: HP-?-CD > ?-CD. The effect of temperature on the inclusion interaction was examined and the thermodynamic parameters of inclusion process, ? G, ? H, ? S were determined as well. The experimental results indicate that the inclusion process was an exothermic and enthalpy-driven process accompanied with a negative entropic contribution. The inclusion interaction between CD and Tans satisfied the law of enthalpy-entropy compensation.

Yuexian, Fan; Junfen, Li; Chuan, Dong

2005-01-01

261

Classification Consistency and Accuracy for Complex Assessments under the Compound Multinomial Model  

ERIC Educational Resources Information Center

For a test that consists of dichotomously scored items, several approaches have been reported in the literature for estimating classification consistency and accuracy indices based on a single administration of a test. Classification consistency and accuracy have not been studied much, however, for "complex" assessments--for example, those that…

Lee, Won-Chan; Brennan, Robert L.; Wan, Lei

2009-01-01

262

Acid-Basic and Complexing Properties of Compounds with a C(X)NHP(Y) Fragments  

Microsoft Academic Search

N-(thio)carbonyl(thio)amidophosphates, their open-chain and crown-containing analogues with a C (X) NHP (Y) fragments are NH acids with pKa 8–11 and the effective complexing agents for “soft” ion metals.

Nail Zabirov; Sergej Kashevarov; Rafael Cherkasov

1996-01-01

263

Gene Expression Profiling Identifies Important Genes Affected by R2 Compound Disrupting FAK and P53 Complex.  

PubMed

Focal Adhesion Kinase (FAK) is a non-receptor kinase that plays an important role in many cellular processes: adhesion, proliferation, invasion, angiogenesis, metastasis and survival. Recently, we have shown that Roslin 2 or R2 (1-benzyl-15,3,5,7-tetraazatricyclo[3.3.1.1~3,7~]decane) compound disrupts FAK and p53 proteins, activates p53 transcriptional activity, and blocks tumor growth. In this report we performed a microarray gene expression analysis of R2-treated HCT116 p53+/+ and p53-/- cells and detected 1484 genes that were significantly up- or down-regulated (p < 0.05) in HCT116 p53+/+ cells but not in p53-/- cells. Among up-regulated genes in HCT p53+/+ cells we detected critical p53 targets: Mdm-2, Noxa-1, and RIP1. Among down-regulated genes, Met, PLK2, KIF14, BIRC2 and other genes were identified. In addition, a combination of R2 compound with M13 compound that disrupts FAK and Mmd-2 complex or R2 and Nutlin-1 that disrupts Mdm-2 and p53 decreased clonogenicity of HCT116 p53+/+ colon cancer cells more significantly than each agent alone in a p53-dependent manner. Thus, the report detects gene expression profile in response to R2 treatment and demonstrates that the combination of drugs targeting FAK, Mdm-2, and p53 can be a novel therapy approach. PMID:24452144

Golubovskaya, Vita M; Ho, Baotran; Conroy, Jeffrey; Liu, Song; Wang, Dan; Cance, William G

2014-01-01

264

Photosensitizing action of complex compounds of transition-metal salts with aromatic nitrogen-containing vinyl monomers  

SciTech Connect

Production of photosensitizers degradation of high-pressure polyethylene (HPPE) and its technological wastes is of great importance for solving the problem of development of polymers having controllable life. By introducing chemical additives (sensitizers) into ethylene polymers it is possible to obtain photodegradable films (PDR). After a certain service life PDR disintegrate under atmospheric conditions into small fragments, which are then destroyed by soil microorganisms. This obviates the laborious operation of removal of the films from fields and at the same time solves the urgent problem of environmental protection. In order to extend the range of photosensitizing additives for degradation of HPPE, the authors have studied aromatic nitrogen-containing vinyl monomers and their complexes with iron and cobalt chlorides. The properties of these complexes are given in Table 1. The tests were carried out in comparison with the most effective photosensitizer of polyethylene degradation, ferralin (VIII). It was shown that an iron-containing complex compound of the quinoline series has higher photosensitizing activity than the corresponding cobalt complex.

Garashchenko, Z.M.; Borodulina, M.Z.; Skvortsova, G.G.; Domnina, E.S.; Andriyankov, M.A.; Loginova, V.P.; Zelenkova, T.N.

1987-09-10

265

An exploratory investigation of polar organic compounds in waters from a lead–zinc mine and mill complex  

USGS Publications Warehouse

Surface water samples were collected in 2006 from a lead mine-mill complex in Missouri to investigate possible organic compounds coming from the milling process. Water samples contained relatively high concentrations of dissolved organic carbon (DOC; greater than 20 mg/l) for surface waters but were colorless, implying a lack of naturally occurring aquatic humic or fulvic acids. Samples were extracted by three different types of solid-phase extraction and analyzed by electrospray ionization/mass spectrometry. Because large amounts of xanthate complexation reagents are used in the milling process, techniques were developed to extract and analyze for sodium isopropyl xanthate and sodium ethyl xanthate. Although these xanthate reagents were not found, trace amounts of the degradates, isopropyl xanthyl thiosulfonate and isopropyl xanthyl sulfonate, were found in most locations sampled, including the tailings pond downstream. Dioctyl sulfosuccinate, a surfactant and process filtering aid, was found at concentrations estimated at 350 ?g/l at one mill outlet, but not downstream. Release of these organic compounds downstream from lead-zinc mine and milling areas has not previously been reported. A majority of the DOC remains unidentified.

Rostad, Colleen E.; Schmitt, Christopher J.; Schumacher, John G.; Leiker, Thomas J.

2011-01-01

266

Detecting Complex Organic Compounds Using the SAM Wet Chemistry Experiment on Mars  

NASA Astrophysics Data System (ADS)

The search for organic molecules on Mars can provide important first clues of abiotic chemistry and/or extinct or extant biota on the planet. Gas Chromatography Mass Spectrometry (GC-MS) is currently the most relevant space-compatible analytical tool for the detection of organic compounds. Nevertheless, GC separation is intrinsically restricted to volatile molecules, and many molecules of astrobiological interest are chromatographically refractory or polar. To analyze these organics such as amino acids, nucleobases and carboxylic acids in the Martian regolith, an additional derivatization step is required to transform them into volatile derivatives that are amenable to GC analysis. As part of the Sample Analysis at Mars (SAM) experiment onboard Mars Science Laboratory (MSL) Curiosity rover, a single-step protocol of extraction and chemical derivatization with the silylating reagent N-methyl-N-(tert-butyldimethylsilyl)-trifluoroacetamide (MTBSTFA) has been developed to reach a wide range of astrobiology-relevant refractory organic molecules (Mahaffy et al. 2012; Stalport et al. 2012). Seven cups in the SAM instrument are devoted to MTBSTFA derivatization. However, this chemical reaction adds a protective silyl group in place of each labile hydrogen, which makes the molecule non-identifiable in common mass spectra libraries. Therefore, we have created an extended library of mass spectra of MTBSTFA derivatized compounds of interest, considering their potential occurrence in Mars soils. We then looked specifically for MTBSTFA derivatized compounds using the existing and the newly created library, in various Mars analog soils. To enable a more accurate interpretation of the in situ derivatization GC-MS results that will be obtained by SAM, the lab experiments were performed as close as possible to the SAM flight instrument experimental conditions. Our first derivatization experiments display promising results, the laboratory system permitting an extraction and detection of several proteinogenic amino acids and carboxylic acids from Martian analog materials. Preliminary results show a lack of derivatized organic molecules in hydrated solid samples however, where the MTBSTFA reagent possibly reacts preferentially with the water from hydrated minerals (Stalport et al. 2012). This result shows the importance of a complete understanding of the MTBSTFA reaction depending on the nature of the soil and will help guide the selection of optimal samples for the SAM wet chemistry on Mars.

Freissinet, C.; Buch, A.; Glavin, D. P.; Brault, A.; Eigenbrode, J. L.; Kashyap, S.; Martin, M. G.; Miller, K.; Mahaffy, P. R.; Team, M.

2013-12-01

267

Hydrosilylation of unsaturated (hetero)aromatic aldehydes and related compounds catalyzed by transition metal complexes  

Microsoft Academic Search

[Rh(COD)CI]2 has been found to be a more active catalyst than Ir, Ru, Pt and Pd complexes for the hydrosilylation of unsaturated furan and aromatic aldehydes with HSiEt3. 1,4- and 1,2-addition reactions giving unsaturated silyl ethers in cis- and trans-configurations occurred as well as the hydrogenation reactions which produce the corresponding saturated silyl ethers. The migration of the ethyl group

Irina Iovel; Juris Popelis; Alexander Gaukhman; Edmunds Lukevics

1998-01-01

268

Bacterial metabolism of aromatic compounds and a complex hazardous waste under anaerobic conditions  

SciTech Connect

The biological fate of organic chemicals in the environment depends upon a variety of physical/chemical factors. In the absence of molecular oxygen, the importance of terminal electron acceptors has been often overlooked. Since anaerobic microbial consortia are dependent upon the availability of particular electron acceptors, these conditions can play an important role in influencing the fate of environmental pollutants. In this research, different electron acceptors were evaluated for their effects on the biodegradation of environmental toxicants. Two anaerobic bioassays, the Biochemical Methane Potential (BMP) and the Anaerobic Toxicity Assay (ATA), were used to evaluate a series of phthalic acid esters (PAEs), substituted phenols and a landfill leachate, for their methanogenic biodegradability and toxicity. Many of the PAEs and phenols could be stoichiometrically mineralized. In addition, the landfill leachate was found to be inhibitory at concentrations greater than 10%, and partially mineralized in approximately 50 weeks. Based upon these assays, 6 different functional groups and their isomers were evaluated for their effect on the biodegradability and toxicity of phenol under methanogenic and denitrifying conditions. These results indicated that nitro- and chloro-substituted phenols were persistent under denitrifying conditions. Under methanogenic conditions, these compounds were metabolized to a more reduced intermediate with less toxicity. Conversely, amino-substituted phenols were not readily mineralized under methanogenic conditions, but were metabolized after minimal lag under denitrifying conditions. From active denitrifying phenol degrading cultures, a pure culture was obtained which could grow on phenol and on a variety of other alkyl-substituted aromatic compounds. Additional studies have tentatively identified several alicyclic metabolites including cyclohexanol, 2-cyclohexene-1-ol, cyclohexanone and 2-cyclohexene-1-one from phenol catabolism.

O'Connor, O.A.

1992-01-01

269

Hyperfine interactions in the mixed ligand complexes of phenolic compounds with iron phthalimide  

NASA Astrophysics Data System (ADS)

Six new mixed ligand complexes of iron phthalimide with gallic acid, pyridoxine, sulphosalicylic acid, salicylaldehyde, anisaldehyde, and naphthaldehyde have been prepared and characterised on the basis of conductance, magnetic susceptibility, IR, electronic and Mössbauer spectroscopic studies. The room temperature Mössbauer spectra exhibit a broad and asymmetric doublet which persists down to 50 K. The I. S. and Q. S. values indicate iron to be in +3 and high spin state. The magnetic moment values (˜5.0 BM at 300 K decreasing to ˜ 3.0 BM at 77 K) do not show any magnetic transition.

Sharma, C. L.; Samuel, K. J.; Garg, V. K.; Singh, B. P.

1987-04-01

270

INVESTIGATION OF THE PROCESSES AND OF THE PRODUCTS OF THE INTERACTION OF HIGH-MOLECULAR COMPOUNDS WITH INORGANIC SALTS. I. FORMATION OF POLYACROLEIN COMPLEXES WITH URANYL NITRATE  

Microsoft Academic Search

Modification of polymers, such as polyacrolein, which possess complexing ; groups makes it possible to prepare compounds able to react selectively with ; inorganic salts. Experiments carried out under static conditions on the ; formation of coordination complexes with uranyl nitrate showed that the amount of ; U extracted with pH values ranging from 3 to 4 varies greatly: the

I. V. Andreeva; P. F. Andreev; E. M. Rogozina

1962-01-01

271

Process for recovering niobium and/or tantalum metal compound from such ores further containing complexes of uranium, thorium, titanium and/or rare earth metals  

SciTech Connect

A process for recovering one or more non-radioactive transition metal compounds from an ore containing one or more compounds of said transition metal or metals and further containing at least one complex of a member selected from the group consisting of uranium, thorium, radium, titanium, and rare earth metals, which comprises decomposing said ore in crushed condition by means of an acid so that a portion of the ore is brought into solution in a liquid phase and another portion of the ore remains in a solid phase, said compound or compounds of the transition metal or metals to be recovered passing into only the liquid or into only the solid phase, the uranium in the crushed ore being treated so as to cause substantially all of said uranium to be present in an oxidation state in which it cannot, during the decomposition step, pass into the phase containing the transition metal compound or compounds.

Floeter, W.; Schoening, G.; Schroeer, K.

1984-05-29

272

Theoretical investigation of phosphinidene oxide polypyridine ruthenium(II) complexes: toward the design of a new class of photochromic compounds.  

PubMed

A DFT-based computational study performed in the gas phase and in acetonitrile on polypyridine ruthenium isomer complexes [Ru(tpy)(bpy)(POPh)](2+) and [Ru(tpy)(bpy)(OPPh)](2+) (bpy = 2,2'-bipyridine, tpy = 2,2':6',2?-terpyridine, Ph = phenyl) predicts that they constitute a prototype for a new family of inorganic photochromic systems. The two isomers are found to absorb in different spectral regions to excited states that are connected adiabatically through a thermodynamically and kinetically favorable triplet potential energy profile. Nonadiabatic routes were identified and shown to be preferable over the adiabatic mechanism. The reverse isomerization reaction is found to be achievable only thermally. The current predictive work will be of prime importance to experimentalists for the design of new inorganic phosphorus-based compounds with attractive photochromic properties. PMID:24205941

Vieuxmaire, Olivier P J; Piau, Rémi E; Alary, Fabienne; Heully, Jean-Louis; Sutra, Pierre; Igau, Alain; Boggio-Pasqua, Martial

2013-12-01

273

Saturation fluorimetry of complex organic compounds with a high local concentration of fluorophores (by the example of phytoplankton)  

SciTech Connect

Saturation of fluorescence of complex organic compounds with a high local concentration of fluorescing molecules (fluorophores), when singlet-singlet annihilation makes a noticeable contribution to saturation, is considered. The fluorescence saturation curve is obtained analytically for the case of a rectangular temporal and spatial distribution of photons in a laser pulse. It is shown that the fluorescence saturation curve depends on the parameter {Phi}{sub 0}, which is proportional to the concentration of fluorescing molecules, and on the parameters A, B, and {alpha} describing the influence of singlet-singlet annihilation, bleaching of an optically thin layer, and nonstationarity of excitation, respectively. The fluorescence saturation curves are studied experimentally for compounds with a high local concentration of fluorescing molecules such as molecules of a monoculture of diatomic alga Thalassiosira weissflogii. The experimental fluorescence saturation curves are well described by the obtained analytic expression. The values of the parameter {Phi}{sub 0}, proportional to the concentration of chlorophyll a, and the parameter A (for the first time) are obtained from the alga fluorescence saturation curves. (laser applications and other topics in quantum electronics)

Maslov, D V; Ostroumov, E E; Fadeev, V V [Department of Physics, M.V. Lomonosov Moscow State University, Moscow (Russian Federation)

2006-02-28

274

The formation and growth of intermetallics in composite solder  

Microsoft Academic Search

The formation and growth of intermetallics at the solder\\/substrate interface are factors affecting the solderability and reliability\\u000a of electronic solder joints. This study was performed to better understand the diffusion behavior and microstructural evolution\\u000a of Cu?Sn intermetallics at the composite solder\\/copper substrate interface for eutectic solder and solder alloys containing\\u000a particle additions of Cu, Cu3Sn, Cu6Sn5, Ag, Au, and Ni.

Yujing Wu; Jennifer A. Sees; Cyrus Pouraghabagher; L. Ann Foster; James L. Marshall; Elizabeth G. Jacobs; Russell F. Pinizzotto

1993-01-01

275

The formation and growth of intermetallics in composite solder  

Microsoft Academic Search

The formation and growth of intermetallics at the solder\\/substrate interface are factors affecting the solderability and reliability of electronic solder joints. This study was performed to better understand the diffusion behavior and microstructural evolution of Cu-Sn intermetallics at the composite solder\\/copper substrate interface for eutectic solder and solder alloys containing particle additions of Cu, Cu3Sn, Cu6Sn5, Ag, Au, and Ni.

Yujing Wu; Jennifer A. Sees; Cyrus Pouraghabagher; L. Ann Foster; James L. Marshall; Elizabeth G. Jacobs; Russell F. Pinizzotto

1993-01-01

276

Quasi-one-dimensional magnons in an intermetallic marcasite  

SciTech Connect

We present inelastic neutron scattering measurements and rst principles calculations examining the intermetallic marcasite CrSb2. The observed spin wave dispersion implies that the magnetic interactions are strongly one-dimensional with antiferromagnetic chains parallel to the crystalline c-axis. Such low-dimensional excitations are unexpected in a semiconducting intermetallic system. Moreover this material may be further interesting in that the magnetic anisotropy may enhance thermoelectric properties along particular crystallographic directions.

Stone, Matthew B [ORNL; Lumsden, Mark D [ORNL; Nagler, Stephen E [ORNL; Singh, David J [ORNL; Sales, Brian C [ORNL; Mandrus, David [ORNL

2012-01-01

277

Intermetallic phase formation in thin solid-liquid diffusion couples  

SciTech Connect

Conducting joints with low fabrication temperatures and high thermal stability are useful in modern electronics. This paper discusses the potential use of intermetallic phases in making such joints. Thin interconnection layers that consist entirely of intermetallic phases have been produced by joining planar Cu substrates that are coated with thin films of Sn. Thin layers (1-5 {mu}m) of intermetallic phases are produced at temperatures slightly above the melting temperature of Sn in a process similar to reflow soldering. Metallography and x-ray analysis are used to characterize the formation mechanism of the intermetallic. Cu dissolves into the liquid Sn by diffusion along narrow channels between grains of the growing {eta}-Cu{sub 6}Sn{sub 5} intermetallic phase. tensile tests were used to measure mechanical properties. The joint strength increased with reaction time. The joint fails in a ductile mode as long as unreacted Sn is present, but fractures along interphase boundaries when the joint is completely intermetallic. 6 refs., 5 figs.

Bartels, F.; Morris, J.W. Jr. [Lawrence Berkeley Lab., CA (United States); Dalke, G.; Gust, W. [Max-Planck-Institut fuer Metallforschung, Stuttgart (Germany)

1994-08-01

278

Binding in transition metal complexes: Reduced multireference coupled-cluster study of the MCH2+ (M =Sc to Cu) compounds  

NASA Astrophysics Data System (ADS)

The recently developed reduced multireference coupled-cluster method with singles and doubles (RMR CCSD), which is perturbatively corrected for triples [RMR CCSD(T)], is employed to compute binding energies of nine transition metal ions with CH2. Unlike analogous compounds involving main-group elements, the MCH2+ (M =Sc to Cu) transition metal complexes often exhibit a non-negligible multireference character. The authors thus employ the RMR CCSD(T) method, which represents an extension of the standard single-reference (SR) CCSD(T) method and can account for multireference effects, while employing only small reference spaces. In this way the role of quasidegeneracy effects on the binding energies of these complexes can be assessed at a higher SD(T) level than is possible with the widely used ab initio methods, namely, with the standard SR CCSD(T) approach, and provide a new benchmark for these quantities. The difference between the RMR and the standard CCSD(T) methods becomes particularly evident when considering nonequilibrium geometries.

Li, Xiangzhu; Paldus, Josef

2007-06-01

279

Yttrium and lanthanide complexes of ?-dialdehydes: synthesis, characterization, luminescence and electrochemistry of coordination compounds with the conjugate base of bromomalonaldehyde.  

PubMed

Novel yttrium, europium and terbium coordination compounds having formulae [AsPh4][Ln(BrMA)4] (6LN), Ln(BrMA)3(bipyO2) (7Ln), Ln(NMA)3(phen) (8Ln) and Ln(NMA)3(terpy) (9Ln) (Ln = Y, Eu, Tb; BrMA = conjugate base of bromomalonaldehyde; bipyO2 = 2,2'-bipyridine-N,N'-dioxide; phen = 1,10-phenantroline; terpy = 2,2':6',2''-terpyridine) were synthesized and characterized by using spectroscopic and electrochemical techniques. Uncharged europium and, to a lesser extent, terbium complexes showed appreciable luminescence in the solid state upon excitation with UV light. Polymeric materials and ionic liquids containing BrMA and lanthanides were prepared and photoluminescence measurements were carried out. From an electrochemical point of view, europium(III) BrMA-complexes showed a quasi-reversible one-electron reduction process. The one electron transfer reaction Eu(III) to Eu(II) allowed the photoluminescence tuning of 8Eu deposited on the surface of a glassy carbon electrode. PMID:24819039

Bortoluzzi, Marco; Battistel, Dario; Roppa, Stefania; Daniele, Salvatore; Perosa, Alvise; Enrichi, Francesco

2014-06-28

280

Toxicological significance in the cleavage of esterase-beta-glucuronidase complex in liver microsomes by organophosphorus compounds.  

PubMed

Egasyn is an accessory protein of beta-glucuronidase (beta-G) in the liver microsomes. Liver microsomal beta-G is stabilized within the luminal site of the microsomal vesicles by complexation with egasyn which is one of the carboxylesterase isozymes. We investigated the effects of organophosphorus compounds (OPs) such as insecticides on the dissociation of egasyn-beta-glucuronidase (EG) complex. The EG complex was easily dissociated by administration of OPs, i.e. fenitrothion, EPN, phenthionate, and bis-beta-nitrophenyl phosphate (BNPP), and resulting beta-G dissociated was released into blood, leading to the rapid and transient increase of plasma beta-G level with a concomitant decrease of liver microsomal beta-G level. In a case of phenthionate treatment, less increase in plasma beta-G level was observed, as compared with those of other OPs. This may be explained by the fact that phenthionate was easily hydrolyzed by carboxylesterase. Similarly, carbamate insecticides such as carbaryl caused rapid increase of plasma beta-G level. In contrast, no significant increase of plasma beta-G level was observed when pyrethroid insecticides were administered to rats. This is due to the fact that pyrethroids such as phenthrin and allethrin were easily hydrolyzed by A-esterase as well as carboxylesterase. On the other hand, addition of OPs to the incubation mixture containing liver microsomes caused the release of beta-G from microsomes to the medium. From these in vivo and in vitro data, it is concluded that increase of the plasma beta-G level after OP administration is much more sensitive biomarker than cholinesterase inhibition to acute intoxication of OPs and carbamates. PMID:10421485

Satoh, T; Suzuki, S; Kawai, N; Nakamura, T; Hosokawa, M

1999-05-14

281

Phenolic compounds in virgin olive oils I. Low-wavelength quantitative determination of complex phenols by high-performance liquid chromatography under isocratic elution  

Microsoft Academic Search

An HPLC method that allows the determination of complex phenolic compounds at low ? (225 nm) after solid-phase extraction from virgin olive oils is reported. The separation was achieved on ODS-2, ODS-1 and C8 columns in eluting mixtures 10?3M H2SO4?CH3CN employed with different ratios. The method was employed for the quantitative determination of phenolic compounds in oils. It allows the

Filippo M. Pirisi; Alberto Angioni; Paolo Cabras; Vincenzo L. Garau; Maria Teresa Sanjust di Teulada; Marlene Karim dos Santos; Giovanni Bandino

1997-01-01

282

Exploring the effects of dimensionality on the magnetic properties of intermetallic nanowires  

NASA Astrophysics Data System (ADS)

Correlated electron intermetallic bulk systems exhibit exciting phenomena, such as unconventional superconductivity, heavy fermion behavior, magnetic ordering, and quantum criticality. However, such exciting properties in related systems with reduced dimensionality are rather unexplored and unpredictable. In this work, we explore the routes for synthesizing nanowires of the intermetallic antiferromagnet compound GdIn3 by an innovative method: the metallic-flux nanonucleation (MFNN). This technique allows the simultaneous synthesis of bulk GdIn3 single crystals (TN3D=45 K) and their low-dimensional (LD) analogs, which nucleate with diameter d?200 nm and length l?30 ?m inside pores of an Al2O3 template. Both systems were studied by means of Energy Dispersive Spectroscopy (EDS), magnetic susceptibility, heat capacity and electron spin resonance (ESR) measurements. Interestingly, the metallic nanowires show a drastic suppression of the antiferromagnetic ordering to TNLD=4 K. These observations suggest the presence of LD magnetic frustration in this compound and possibly open a new route to explore the role of low-dimensionality in strongly correlated materials.

Rosa, P. F. S.; de Oliveira, L. A. S.; de Jesus, C. B. R.; Moura, K. O.; Adriano, C.; Iwamoto, W.; Garitezi, T. M.; Granado, E.; Saleta, M. E.; Pirota, K. R.; Pagliuso, P. G.

2014-08-01

283

Process for synthesizing compounds from elemental powders and product  

DOEpatents

A process for synthesizing intermetallic compounds from elemental powders is described. The elemental powders are initially combined in a ratio which approximates the stoichiometric composition of the intermetallic compound. The mixed powders are then formed into a compact which is heat treated at a controlled rate of heating such that an exothermic reaction between the elements is initiated. The heat treatment may be performed under controlled conditions ranging from a vacuum (pressureless sintering) to compression (hot pressing) to produce a desired densification of the intermetallic compound. In a preferred form of the invention, elemental powders of Fe and Al are combined to form aluminide compounds of Fe[sub 3] Al and FeAl. 25 figures.

Rabin, B.H.; Wright, R.N.

1993-12-14

284

Thermal stress effects in intermetallic matrix composites  

NASA Technical Reports Server (NTRS)

Intermetallic matrix composites develop residual stresses from the large thermal expansion mismatch (delta-alpha) between the fibers and matrix. This work was undertaken to: establish improved techniques to measure these thermal stresses in IMC's; determine residual stresses in a variety of IMC systems by experiments and modeling; and, determine the effect of residual stresses on selected mechanical properties of an IMC. X ray diffraction (XRD), neutron diffraction (ND), synchrotron XRD (SXRD), and ultrasonics (US) techniques for measuring thermal stresses in IMC were examined and ND was selected as the most promising technique. ND was demonstrated on a variety of IMC systems encompassing Ti- and Ni-base matrices, SiC, W, and Al2O3 fibers, and different fiber fractions (Vf). Experimental results on these systems agreed with predictions of a concentric cylinder model. In SiC/Ti-base systems, little yielding was found and stresses were controlled primarily by delta-alpha and Vf. In Ni-base matrix systems, yield strength of the matrix and Vf controlled stress levels. The longitudinal residual stresses in SCS-6/Ti-24Al-llNb composite were modified by thermomechanical processing. Increasing residual stress decreased ultimate tensile strength in agreement with model predictions. Fiber pushout strength showed an unexpected inverse correlation with residual stress. In-plane shear yield strength showed no dependence on residual stress. Higher levels of residual tension led to higher fatigue crack growth rates, as suggested by matrix mean stress effects.

Wright, P. K.; Sensmeier, M. D.; Kupperman, D. S.; Wadley, H. N. G.

1993-01-01

285

SCB ignition of pyrotechnics, thermites and intermetallics  

SciTech Connect

We investigated ignition of pyrotechnics, metal-fuel/metal-oxide compositions (thermites), and exothermic alloy compositions (intermetallics) using a semiconductor bridge (SCB). It was shown that these materials could be ignited at low energy levels with an appropriately designed SCB, proper loading density, and good thermal isolation. Materials tested included Al/CuO, B/BaCrO{sub 4}, TiH{sub 1.65}/KClO{sub 4}, Ti/KClO{sub 4}, Zr/BaCrO{sub 4}, Zr/CuO, Zr/Fe{sub 2}O{sub 3}, Zr/KClO{sub 4}, and 100-mesh Al/Pd. Firing set was a capacitor discharge unit with charge capacitors ranging from 3 to 20,000 {mu}F at charge voltages 5-50 V. Devices functioned a few miliseconds after onset of current pulse at input energies as low as 3 mJ. We also report on a thermite torch design.

Bickes, R.W. Jr.; Grubelich, M.C.

1996-09-01

286

Cuticular Compounds Bring New Insight in the Post-Glacial Recolonization of a Pyrenean Area: Deutonura deficiens Deharveng, 1979 Complex, a Case Study  

PubMed Central

Background In most Arthropod groups, the study of systematics and evolution rely mostly on neutral characters, in this context cuticular compounds, as non-neutral characters, represent an underexplored but potentially informative type of characters at the infraspecific level as they have been routinely proven to be involved in sexual attraction. Methods and Findings The collembolan species complex Deutonura deficiens was chosen as a model in order to test the utility of these characters for delineating four infraspecific entities of this group. Specimens were collected for three subspecies (D. d. deficiens, D. d. meridionalis, D. d. sylvatica) and two morphotypes (D. d. sylvatica morphoype A and B) of the complex; an additional species D. monticola was added. Cuticular compounds were extracted and separated by gas chromatography for each individual. Our results demonstrate that cuticular compounds succeeded in separating the different elements of this complex. Those data allowed also the reconstruction of the phylogenetic relationships among them. Conclusions The discriminating power of cuticular compounds is directly related to their involvement in sexual attraction and mate recognition. These findings allowed a discussion on the potential involvement of intrinsic and paleoclimatic factors in the origin and the diversification of this complex in the Pyrenean zone. This character type brings the first advance from pattern to process concerning the origin of this species complex. PMID:21209797

Porco, David; Bedos, Anne; Deharveng, Louis

2010-01-01

287

Multiconfigurational nature of 5f orbitals in uranium and plutonium intermetallics  

PubMed Central

Uranium and plutonium’s 5f electrons are tenuously poised between strongly bonding with ligand spd-states and residing close to the nucleus. The unusual properties of these elements and their compounds (e.g., the six different allotropes of elemental plutonium) are widely believed to depend on the related attributes of f-orbital occupancy and delocalization for which a quantitative measure is lacking. By employing resonant X-ray emission spectroscopy (RXES) and X-ray absorption near-edge structure (XANES) spectroscopy and making comparisons to specific heat measurements, we demonstrate the presence of multiconfigurational f-orbital states in the actinide elements U and Pu and in a wide range of uranium and plutonium intermetallic compounds. These results provide a robust experimental basis for a new framework toward understanding the strongly-correlated behavior of actinide materials. PMID:22706643

Booth, C.H.; Jiang, Yu; Wang, D.L.; Mitchell, J.N.; Tobash, P.H.; Bauer, E.D.; Wall, M.A.; Allen, P.G.; Sokaras, D.; Nordlund, D.; Weng, T.-C.; Torrez, M.A.; Sarrao, J.L.

2012-01-01

288

ION COMPOSITION ELUCIDATION (ICE): A HIGH RESOLUTION MASS SPECTROMETRIC TOOL FOR IDENTIFYING ORGANIC COMPOUNDS IN COMPLEX EXTRACTS OF ENVIRONMENTAL SAMPLES  

EPA Science Inventory

Unidentified Organic Compounds. For target analytes, standards are purchased, extraction and clean-up procedures are optimized, and mass spectra and retention times for the chromatographic separation are obtained for comparison to the target compounds in environmental sample ...

289

Corrosion behavior of binary titanium aluminide intermetallics  

SciTech Connect

The corrosion behavior of arc-melted binary titanium aluminide intermetallics TiAl, Ti{sub 2}Al, and TiAl{sub 3} in aqueous sodium sulfate and sodium chloride solutions was measured and compared to that of pure Ti and Al. Effects of electrolyte composition (e.g., sulfate [0.25 M SO{sub 4}{sup 2}{sup {minus}}], chloride [0.1 to 1.0 M Cl{sup {minus}}], and pH [3 to 10]) were examined. Anodic polarization of titanium aluminides in aqueous SO{sub 4}{sup 2}{sup {minus}} solutions was similar (showing passive behavior), but no pitting or pitting potential (E{sub pit}) was observed. In aqueous NaCl, however, titanium aluminides were susceptible to pitting, and E{sub pit} decreased with increasing Al content (i.e., Ti{sub 3}Al had the highest E{sub pit} and, therefore, a greater resistance to pitting, followed by TiAl and TiAl{sub 3}). For TiAl, E{sub pit} was slightly dependent upon pH or Cl{sup {minus}} concentration. Pit morphology and E{sub pit} values were quite different for TiAl compared to Ti{sub 3}Al. TiAl showed numerous small pits, whereas Ti{sub 3}Al exhibited fewer but larger and deeper pits. The larger pit density for TiAl was associated with Al-rich interdendrite regions. One interesting feature of the anodic polarization curves for Ti{sub 3}Al was a small anodic peak frequently observed at {approximately}1.4 V{sub SCE} to 1.8 V{sub SCE}. Results suggested this peak was associated with pit initiation, since pitting initiated concurrently with the peak or immediately afterward.

Saffarian, H.M.; Gan, Q.; Hadkar, R.; Warren, G.W. [Univ. of Alabama, Tuscaloosa, AL (United States). Dept. of Metallurgical and Materials Engineering

1996-08-01

290

Intermetallic growth and mechanical behavior of low and high melting temperature solder alloys  

Microsoft Academic Search

The presence of an intermetallic is often an indication of good wetting in a solder joint. However, excessive intermetallic\\u000a growth and the brittleness of the intermetallic layer may be detrimental to joint reliability. This study examined the growth\\u000a and mechanical behavior of interfacial intermetallics between copper and six solder alloys commonly used in electronics assembly.\\u000a The solder alloys tested were

D. R. Frear; P. T. Vianco

1994-01-01

291

Intermetallic alloy welding wires and method for fabricating the same  

DOEpatents

Welding wires for welding together intermetallic alloys of nickel aluminides, nickel-iron aluminides, iron aluminides, or titanium aluminides, and preferably including additional alloying constituents are fabricated as two-component, clad structures in which one component contains the primary alloying constituent(s) except for aluminum and the other component contains the aluminum constituent. This two-component approach for fabricating the welding wire overcomes the difficulties associated with mechanically forming welding wires from intermetallic alloys which possess high strength and limited ductilities at elevated temperatures normally employed in conventional metal working processes. The composition of the clad welding wires is readily tailored so that the welding wire composition when melted will form an alloy defined by the weld deposit which substantially corresponds to the composition of the intermetallic alloy being joined. 4 figs.

Santella, M.L.; Sikka, V.K.

1996-06-11

292

Intermetallic alloy welding wires and method for fabricating the same  

DOEpatents

Welding wires for welding together intermetallic alloys of nickel aluminides, nickel-iron aluminides, iron aluminides, or titanium aluminides, and preferably including additional alloying constituents are fabricated as two-component, clad structures in which one component contains the primary alloying constituent(s) except for aluminum and the other component contains the aluminum constituent. This two-component approach for fabricating the welding wire overcomes the difficulties associated with mechanically forming welding wires from intermetallic alloys which possess high strength and limited ductilities at elevated temperatures normally employed in conventional metal working processes. The composition of the clad welding wires is readily tailored so that the welding wire composition when melted will form an alloy defined by the weld deposit which substantially corresponds to the composition of the intermetallic alloy being joined.

Santella, Michael L. (Knoxville, TN); Sikka, Vinod K. (Oak Ridge, TN)

1996-01-01

293

Studies of Intermetallic Growth in Cu-Solder Systems and Wettability at Solid-Liquid Interfaces.  

National Technical Information Service (NTIS)

The metallurgical bond formed between tin-lead solder and the copper substrate is characterized by the formation of an intermetallic layer. The growth of the intermetallic layer is the result of competing mechanisms, growth of the intermetallic at the int...

R. W. Martin

1991-01-01

294

Anisotropy of magnetic and transport properties in actinide intermetallics  

SciTech Connect

The authors have studied the giant magnetic anisotropy, which is a characteristic feature of actinide intermetallics, for uranium ternary intermetallics crystallizing in various structure types. It is shown that the easy magnetization direction is in general oriented perpendicular to the directions of the presumed strongest U-U bonding. Moreover, the coupling of magnetic moments is usually strong and ferromagnetic along this direction(s), whereas in directions perpendicular to it, the authors observe weaker ferro or antiferromagnetic coupling. This situation can be explained supposing the mechanism of the hybridization-induced exchange interaction and the related magnetic anisotropy.

Havela, L.; Sechovsky, V. [Charles Univ., Prague (Czech Republic). Dept. of Metal Physics] [Charles Univ., Prague (Czech Republic). Dept. of Metal Physics; Nakotte, H.; Brueck, E.; Boer, F.R. de [Univ. of Amsterdam (Netherlands). Van der Waals-Zeeman Lab.] [Univ. of Amsterdam (Netherlands). Van der Waals-Zeeman Lab.

1994-03-01

295

Non-covalent interactions of nitrous oxide with aromatic compounds: Spectroscopic and computational evidence for the formation of 1:1 complexes  

NASA Astrophysics Data System (ADS)

We present the first study of intermolecular interactions between nitrous oxide (N2O) and three representative aromatic compounds (ACs): phenol, cresol, and toluene. The infrared spectroscopic experiments were performed in a Ne matrix and were supported by high-level quantum chemical calculations. Comparisons of the calculated and experimental vibrational spectra provide direct identification and characterization of the 1:1 N2O-AC complexes. Our results show that N2O is capable of forming non-covalently bonded complexes with ACs. Complex formation is dominated by dispersion forces, and the interaction energies are relatively low (about -3 kcal mol-1); however, the complexes are clearly detected by frequency shifts of the characteristic bands. These results suggest that N2O can be bound to the amino-acid residues tyrosine or phenylalanine in the form of ? complexes.

Cao, Qian; Gor, Gennady Y.; Krogh-Jespersen, Karsten; Khriachtchev, Leonid

2014-04-01

296

Non-covalent interactions of nitrous oxide with aromatic compounds: spectroscopic and computational evidence for the formation of 1:1 complexes.  

PubMed

We present the first study of intermolecular interactions between nitrous oxide (N2O) and three representative aromatic compounds (ACs): phenol, cresol, and toluene. The infrared spectroscopic experiments were performed in a Ne matrix and were supported by high-level quantum chemical calculations. Comparisons of the calculated and experimental vibrational spectra provide direct identification and characterization of the 1:1 N2O-AC complexes. Our results show that N2O is capable of forming non-covalently bonded complexes with ACs. Complex formation is dominated by dispersion forces, and the interaction energies are relatively low (about -3 kcal mol(-1)); however, the complexes are clearly detected by frequency shifts of the characteristic bands. These results suggest that N2O can be bound to the amino-acid residues tyrosine or phenylalanine in the form of ? complexes. PMID:24735296

Cao, Qian; Gor, Gennady Y; Krogh-Jespersen, Karsten; Khriachtchev, Leonid

2014-04-14

297

Electrical resistivity and Curie temperature studies on (YGdx)(Fe0.7Co0.3)2 intermetallics  

NASA Astrophysics Data System (ADS)

This paper looks at synthesis, electrical resistivity and Mössbauer effect studies on intermetallic compounds (YGdx)(Fe0.7Co0.3)2. Cubic Laves phase of MgCu2-type were observed across the series. The lattice parameters linearly increase with Gd concentration and the lattice parameters of the intermetallics series (YGdx)(Fe0.7Co0.3)2 are compared to data previously observed for the R(FeCox)2 series (R=Y, Dy, Gd) and (YGdx)M2 series (M=Fe, Co). Electrical resistivity for the (YGdx)(Fe0.7Co0.3)2 intermetallic series was measured in the temperature range 15-1100 K. Parameters characterizing the resistivity dependence on temperature were determined. Residual, phonon and magnetic resistivity were separated from the measured electrical resistivity using both the Matthiesen formula and the Bloch-Gruneisen formula. Curie temperatures of the studied series were determined using both electrical resistivity and Mössbauer effect measurements, with the Mössbauer effect measured in the temperature range around the magnetic ordering temperature. The Curie temperature increases with x. The obtained Curie temperatures for the (YGdx)(Fe0.7Co0.3)2 are similar to data known for the R(FeCox)2 series (R=Y, Dy, Gd) and (YGdx)M2 series (M=Fe, Co).

Guzdek, P.; Pszczo?a, J.; Chmist, J.; Stoch, P.; Zachariasz, P.; Onak, M.

2013-01-01

298

Fatigue of titanium alloys and intermetallics  

NASA Astrophysics Data System (ADS)

This dissertation represents the results of an investigation of fatigue in titanium alloys and intermetallics. The results of a combined experimental and analytical study of the probabilistic nature of fatigue crack growth in Ti-6Al-4 V are presented. A simple experimental fracture mechanics framework is presented for the determination of statistical fatigue crack growth parameters from two fatigue tests. A probabilistic framework is introduced for the modeling of fatigue damage in three gamma-based titanium aluminides: Ti-45Al-2Mn-2Nb+0.8vol.%TiB 2, Ti-47Al-2Mn-2Nb+0.8vol.%TiB2 and Ti-48Al-2Cr-2Nb. This includes empirical stress-life and fracture mechanics approaches to the estimation of material reliability or the risk of failure. A combined experimental and analytical study of fatigue crack growth and dwell-fatigue crack growth in forged Ti-6Al-2 Sn-4Zr-2Mo-0.2%Si (Ti-6242) is presented. Following an initial characterization of microstructures and basic mechanical properties, the micro mechanisms of long fatigue crack growth are presented for three microstructures. The fatigue crack growth rates in the near-threshold, Paris and high DeltaK regimes are then characterized with empirical linearized crack growth laws. Finally, the results of dwell-fatigue crack growth experiments are presented for the three microstructures. The underlying mechanisms of dwell crack growth are compared with the mechanisms of fatigue crack growth before discussing the implications of the work for the prediction of dwell or fatigue crack growth in Ti-6242. The effects of different frequencies on dwell fatigue are also explored. The results of an experimental study of fatigue crack nucleation and growth in a Ti-6Al-4V/TiB in-situ whisker-reinforced composite are presented. The onset of crack nucleation is shown to correspond to ˜20% of the total life at a stress range of 480MPa. The long fatigue crack growth rates in the Paris regime in the Ti-6Al-4V/TiB composite are comparable to those of Ti-6Al-4 V processed under nominally identical conditions. However, the fatigue crack growth rates in the composite are faster than those in the matrix alloy at lower DeltaK values. Cyclic deformation of the composite is associated with strain softening, presumably as a result of progressive interfacial decohesion around the TiB whiskers early in the fatigue deformation process.

Shen, Weimin

299

The intermetallic formation and growth kinetics at the interface of near eutectic tin-silver-copper solder alloys and gold/nickel metallization  

NASA Astrophysics Data System (ADS)

The formation of a one micron thick layer of an intermetallic compound between a solder alloy and a metallic substrate generally constitutes a good solder joint in an electronic device. However, if the compound grows too thick, and/or if multiple intermetallic compounds form, poor solder joint reliability may result. Thus significant interest has been focused on intermetallic compound phase selection and growth kinetics at such solder/metal interfaces. The present study focuses on one such specific problem, the formation and growth of intermetallic compounds at near eutectic Sn-Ag-Cu solder alloy/Ni interfaces. Sn-3.0Ag-0.5Cu solder was reflowed on Au/Ni substrates, resulting in the initial formation and growth of (CuNi)6Sn 5 at Sn-3.0Ag-0.5Cu /Ni interfaces. (NiCu)3Sn4 formed between the (CuNi)6Sn5 and the Ni substrate when the concentration of Cu in the liquid SnAgCu solder decreased to a critical value which depended upon temperature: 0.37, 0.31 and 0.3(wt.%) at reflow temperatures of 260°C, 245°C and 230°C respectively. The growth rate of (CuNi)6Sn5 was found to be consistent with extrapolations of a diffusion limited growth model formulated for lower temperature, solid state diffusion couples. The long range diffusion of Cu did not limit growth rates. The spalling of (CuNiAu)6Sn5 from (NiCu)3 Sn4 surfaces during reflow was also examined. When the Cu concentration in the solder decreased to approximately 0.28wt.%, the (Cu,Ni,Au) 6Sn5 was observed to spall. Compressive stress in (CuNiAu) 6Sn5 and weak adhesion between (CuNiAu)6Sn 5 and (NiCu)3Sn4 was found to cause this effect.

Gao, Mao

300

Uptake and fate of phenol and aniline in rainbow trout and daphnids during single-compound and complex-mixture exposures  

SciTech Connect

Studies were conducted of the potential for uptake and mobilization of phenol and aniline when presented as single compounds to the biouptake of these compounds within a complex water-soluble fraction (WSF) of a coal liquid. Estimated bioconcentration factors (BCF) of phenol-only exposures differed from BCFs obtained in the presence of the WSF. Differences in uptake could be due to competitive interactions among similar molecules for uptake and absorption, since phenolic compounds comprised nearly 90% of the soluble components in the complex mixture. Observed differences in unextractable /sup 14/C residues suggested selective binding of phenol or metabolites to trout tissue storage sites. Differences in potential for bioaccumulation of phenol in complex mixtures were not consistent with estimates of BCF as determined by measured octanol/water coefficient values. In contrast to phenol, presence of coal-liquid water solubles did not significantly influence either the uptake or elimination of /sup 14/C aniline by daphnids or trout. Identification of metabolites would provide useful information on potential differences in biotransformation and elimination mechanisms in complex organic mixtures. 15 references, 2 figures, 6 tables.

Dauble, D.D.; Riley, R.G.; Bean, R.M.; Lusty, E.W.; Hanf, R.W. Jr.

1984-10-01

301

Importance of cross-correlated relaxation in the spectra of simple organofluorine compounds: Spectral complexity of A3B3X spin systems compared to ABX spin systems  

NASA Astrophysics Data System (ADS)

In a continuation of our initial investigation of the complex 13C and 19F spectra exhibited by two simple organofluorine compounds, additional organofluorine compounds expected to exhibit a wide range of spectral complexity were studied. Spectral simulations are critical for analyzing the more complex spin systems, in particular, A3B3X and A6B3X. Cross-correlated relaxation is commonly observed; examples of 13Csbnd 19F cross-correlated relaxation are shown with the signals for each nucleus exhibiting unequal relaxation rates. Higher order effects are particularly noticeable in the spectra of perfluoro-t-butyl alcohol because of a large 4JFF value in the (13CF3)(12CF3)212COH isotopomer. The many additional transitions in an A3B3X spin system compared to an ABX spin system result in much more complex 19F (A3 and B3) and 13C (X) spectra, even though only three types of nuclei are involved in each spin system. The corresponding protio compounds typically constitute a much simpler A3M3X spin system because the long-range nJHH coupling (n ? 4) is much smaller than the corresponding long-range nJFF coupling. Spectra previously published for ethane-1-13C (A3B3X) and hexafluoroethane-1-13C (A3M3X) are notable exceptions and are discussed.

Alemany, Lawrence B.; Malloy, Thomas B.; Nunes, Megan M.; Zaibaq, Nicholas G.

2012-09-01

302

The study of new complex compounds of Ni (II) and Co (II) with N- hydroxy-succinimide and their potential applications as sensors  

NASA Astrophysics Data System (ADS)

In this paper, the study of obtaining new coordination compounds of Ni (II) and Co(II) using as ligand, N-hydroxy-succinimide, was presented. Also, the stability constants of these compounds in aqueous medium were determined. The obtaining conditions and the stability of the new compounds were accomplished in aqueous solutions using characteristic methods for coordination compounds: pH-metry, conductometry and UV-VIS absorption spectroscopy. The combination ratios and the stability constants were determined with methods characteristic for studies in solutions. From experimental data resulted that the combination ratio of central metallic atoms with the ligand N-hydroxy-succinimide was: 1:1 and respectively 1:2. In the experiments were used salts of NiCl2.6H2O and CoCl2.6H2O. The optimal domain of pH stability of the studied compounds is limited between 5.74 - 5.86 for Co- N-hydroxy-succinimide (for molar ratio 1:1 and 1:2) and respectively 5.69 - 5.87 for Ni-N-hydroxysuccinimide( for molar ratio 1:1 and 1:2, too). It is important to mention that these compounds were used with very good results in determination of wastewaters from textile, metallurgical, chemical and food industry. Complexion reactions with this ligand are very sensitive for the cations in this paper mentioned. Therefore it is used most often with success in analytical chemistry and also it is posibil to use as sensors. The new complex compounds has electronics transitions at ? = 517 nm for both complexes Co-N-hydroxy-succinimide at molar ratio 1:1 and 1:2 and also at the same ? = 397nm for Ni-N-hydroxysuccinimide at molar ratio 1:1 and 1:2. These complexes compounds was separated and recrystallized from aqueous solution. From the spectrophotometric data it was determined the type and the nature of the electronics transitions by Dq parameters.

Sibiescu, Doina; Tutulea, Mihaela-Dana; Mî??, Carmen; Stan, Corneliu; Ro?ca, Ioan; Vizitiu, Mihaela

2010-11-01

303

Transmission electron microscopy characterization of thermomechanically treated Al?Ti-(8, 10, 15)% Cr intermetallics.  

PubMed

The ordered L1?-type Al?Ti-(8, 10, 15)% Cr intermetallic compounds, namely, Al??Ti??Cr?, Al??Ti??Cr??, and Al??Ti??Cr??, were prepared by induction melting followed by thermomechanical treatment. Their microstructure, compositional variation, and crystal structure were characterized using X-ray diffraction, optical microscopy, and scanning and transmission electron microscopy equipped with energy-dispersive spectroscopy. The Al??Ti??Cr? alloy consisted of the L1?-Al?Ti matrix and precipitates of ??-Ti?Al, D0??-Al?Ti, and ?-TiAl. The Al??Ti??Cr?? and Al??Ti??Cr?? alloys consisted of the L1?-Al?Ti matrix and grains of ?-TiAl and ?-Cr. PMID:23920182

Jang, Ok Jun; Yang, Cheol-Woong; Lee, Dong Bok

2013-08-01

304

Oxidation of high-temperature intermetallics; Proceedings of the Workshop, Cleveland, OH, Sept. 22, 23, 1988  

NASA Technical Reports Server (NTRS)

The present conference on the high-temperature oxidation behavior of aerospace structures-applicable intermetallic compounds discusses the influence of reactive-element additions on the oxidation of Ni3Al base alloys, the effect of Ni3Al oxidation below 850 C on fracture behavior, the oxidation of FeAl + Hf, Zr, and B, the synergistic effect of Al and Si on the oxidation resistance of Fe alloys, and pack cementation coatings of Cr-Al on Fe, Ni, and Co alloys. Also discussed are the formation of alumina on Nb- and Ti-base alloys, the oxidation behavior of titanium aluminide alloys, silicide coatings for refractory metals, the oxidation of chromium disilicide, and the oxidation behavior of nickel beryllides.

Grobstein, Toni (editor); Doychak, Joseph (editor)

1989-01-01

305

Nickel-catalyzed asymmetric arylations of [alpha]-halocarbonyl compounds and studies of boratabenzene-containing transition metal complexes  

E-print Network

Chapter 1 begins with a review of the current literature on cross-coupling methods to generate a-arylcarbonyl compounds, with a special emphasis on asymmetric arylations. The second section of chapter 1 describes the ...

Lundin, Pamela M. (Pamela Marie)

2010-01-01

306

The Rise of Complexity: Cell Signaling Compounds in Pavilion Lake Microbialites and Temperate Zone Microbial Community Ecosystems  

NASA Astrophysics Data System (ADS)

A distinctive assemblage of freshwater calcite microbialites was studied at Pavilion Lake, British Columbia, Canada, using standard microbial methods, morphological observations, PLFA analysis, and biochemical analysis to identify cell-signalling (quorum sensing) compounds.

Turse, C.; Schulze-Makuch, D.; Lim, D.; Laval, B.; Irwin, L.

2010-04-01

307

Influence of lipophilic anionic compounds on the selectivity of ion-selective electrodes based on podands with phosphoryl complexing groups  

Microsoft Academic Search

The dependence of the potentiometric selectivity of ion-selective electrodes (ISEs) based on phosphoryl-containing podands on concentration of the lipophilic compounds (sodium tetraphenylborate or potassium tetrakis-p-Cl-phenylborate) was investigated. It was demonstrated that the selectivity of the Ca- or\\/and Ba-selective electrodes over the alkali metals (AMs) and alkaline-earth metals (AEMs) increases with the lipophilic compound content. In case of AMs the changes

O. M Petrukhin; Ye. V Frakiisky; A. B Kharitonov; Yu. I Urusov; V. Ye Baulin

1999-01-01

308

Wear of iron–aluminide intermetallic-based alloys and composites by hard particles  

SciTech Connect

In this study, the resistance of alloys and composites based on the intermetallic compounds Fe3Al and FeAl to wear by hard particles was assessed and compared to the behavior of selected metals, alloys, other intermetallic compounds and ceramics. Pin abrasion tests were performed on these materials at room temperature. Among other things, it was found that as the Al atomic percent in binary Fe–Al increased, the alloys became more abrasion resistant. In summary, the ranking of the alloys in terms of abrasion resistance from the most resistant to the least resistant proceeds as follows: FeAl > Fe3Al > #1;-Fe alloy with 16 at.% Al > pure Fe > pure Al. These results are discussed in terms of the hardnesses of the respective alloys. The addition between 40 and 70 vol.% of a hard second phase (e.g. TiC or TiB2) decreased the wear rate of the Fe3Al and FeAl composites by an order of magnitude compared to the parent alloy. In addition, solid particle erosion tests were performed on an FeAl alloy, and FeAl + 80 vol.% TiC, FeAl + 80 vol.% WC, FeAl + 80 vol.% TiB2 cermets at 25, 180, 500 and 700?C, and the results were compared to erosion behavior of several conventional alloys and cemented carbides (WC–Co). The ranking of the erosion resistance of the FeAl alloys and composite materials was as follows: (most resistant) FeAl–WC > FeAl–TiB2 > FeAl–TiC > FeAl (least resistant). This behavior was related to both the cermet microstructure and material removal mechanisms.

Alman, David E.; Hawk, Jeffrey A.; Tylczak, Jeffrey H.; Dogan, Cynthia P.; Wilson, Rick D.

2001-10-01

309

A theoretical analysis of the extraction of heterocyclic organic compounds from an organic phase using chemically mediated electrochemically modulated complexation in ion exchange polymer beads  

SciTech Connect

A cyclical electrochemical process for the removal of heterocyclic organic compounds (pollutants) from an organic solvent using an ion-exchange polymer is analyzed. In this analysis, there are three main steps: In the first step, the polymer beads containing the active form of the complexing agent are contacted with the contaminated (feed) hydrocarbon phase. The pollutant diffuses into the beads and binds with the complexing agent which is in the reduced state. It is a fast reversible reaction. For the second step, the beads which contain a pollutant are contacted with a waste (receiving) phase and a chemical mediator is then used to oxidize the complexing agent and to reduce its affinity towards the pollutant so that it can be released. The oxidation of the complexing agent is an irreversible reaction. This is a moving boundary problem with countercurrent diffusion. For each mole of mediator that goes into the bead, one mole of pollutant exits since each complexing agent binds one pollutant. In the third step, the waste hydrocarbon phase is removed and a second chemical mediator is then used to reduce the complexing agent. The reduction of the complexing agent is also an irreversible reaction. Partial differential equations are used to analyze this process. 26 refs., 9 figs.

Ozekin, K.; Noble, R.D.; Koval, C.A.

1991-01-01

310

The significance of ACTH for the process of formation of complex heparin compounds in the blood during immobilization stress  

NASA Technical Reports Server (NTRS)

Adrenocorticotropin (ACTH) was administered to rats at different times following adrenalectomy. Adrenocorticotropin caused a significant increase in the formation of heparin complexes even in the absence of stress factor. When ACTH secretion is blocked, immobilization stress is not accompanied by an increase in the process of complex formation. The effect of ACTH on the formation of heparin complexes was mediated through its stimulation of the adrenal cortex.

Kudryashov, B. A.; Shapiro, F. B.; Lomovskaya, F. B.; Lyapina, L. A.

1979-01-01

311

Separation of compounds with multiple -OH groups from dilute aqueous solutions via complexation with organoboronate. [1,2-propanediol  

SciTech Connect

The complexing extractant agent investigated in this work is 3-nitrophenylboronic acid (NPBA) in its anionic form (NPB). NPBA and Aliquat 336 (quaternary amine) is dissolved in 2-ethyl-l-hexanol, and the extractant is contacted with aq. NaOH. Solutes investigated were 1,2-propanediol, glycerol, fructose, sorbitol and lactic acid. Batch extraction experiments were performed at 25{degree}C. Partition coefficients, distribution ratios and loadings are reported for varying concentrations of solute and NPB. All solutes complexed with NPB{sup {minus}}, with all complexes containing only one NPB{sup {minus}} per complex. The 1:1 complexation constants for the solutes glycerol, fructose and sorbitol follow trends similar to complexation with B(OH){sub 4}{sup {minus}} (aq.), i.e. the complexation constants increase with increasing number of {minus}OH groups available for complexation. Assumption of 1:1 complex is not valid for 1, 2-propanediol, which showed overloading (more than one mole of solute complexed to one mole NPB{sup {minus}}) at higher concentrations. The {minus}OH group on the NPB{sup {minus}} which is left uncomplexed after one solute molecule had bound to the other two {minus}OH groups may be responsible for the overloading. Overloading is also observed in extraction of tactic acid, but through a different mechanism. It was found that TOMA{sup +} can extract lactic acid to an extent comparable to the uptake of lactic acid by NPB{sup {minus}}. The complexation is probably through formation of an acid-base ion pair. Losses of NPBA into the aqueous phase could lead to problems, poor economics in industrial separation processes. One way of overcoming this problem would be to incorporate the NPBA onto a solid support.

Chow, Tina Kuo Fung.

1992-05-01

312

Metal complexes of ONO donor Schiff base ligand as a new class of bioactive compounds; Synthesis, characterization and biological evolution  

NASA Astrophysics Data System (ADS)

Present work reviews that, the synthesis of (E)-N";-((7-hydroxy-4-methyl-2-oxo-2H-chromen-8-yl)methylene)benzohydrazide [L] ligand and their metal complexes. The colored complexes were prepared of type [M2+L]X2, where M2+ = Mn, Co, Ni, Cu, Sr and Cd, L = (7-hydroxy-4-methyl-2-oxo-2H-chromen-8-yl)methylene)benzohydrazide, X = Cl-. Ligand derived from the condensation of 8-formyl-7-hydroxy-4-methylcoumarin and benzohydrazide in the molar ratio 1:1 and in the molar ratio 1:2 for metal complexes have been prepared. The chelation of the ligand to metal ions occurs through the both oxygen groups, as well as the nitrogen atoms of the azomethine group of the ligand. Reactions of the Schiff base ligand with Manganese(II), Cobalt(II), Nickel(II), Copper(II), Strontium(II), and Cadmium(II) afforded the corresponding metal complexes. The structures of the obtained ligand and their respective metal complexes were elucidated by infra-red, elemental analysis, Double beam UV-visible spectra, conductometric measurements, magnetic susceptibility measurements and also thermochemical studies. The metal complex exhibits octahedral coordination geometrical arrangement. Schiff base ligand and their metal complexes were tested against antioxidants, antidiabetic and antimicrobial activities have been studied. The Schiff base metal complexes emerges effective ?-glucosidase inhibitory activity than free Schiff base ligand.

Kumar Naik, K. H.; Selvaraj, S.; Naik, Nagaraja

2014-10-01

313

Bioaccumulation of fossil fuel components during single-compound and complex-mixture exposures of Daphnia magna  

Microsoft Academic Search

The evaluation of potential ecological consequences from introduction of fossil fuel chemicals into aquatic environments is a complicated process that requires information about physical, chemical, and biological properties of many different types of organic compounds. One concern in aquatic hazard evaluation is the bioaccumulation of these organic components by aquatic biota. Two general approaches are usually used to assess the

D. D. Dauble; D. W. Carlile; R. W. Jr. Hanf

1986-01-01

314

Current activated tip sintering of Ni-Ti intermetallics  

NASA Astrophysics Data System (ADS)

This thesis investigated the current activated tip-sintering of reactive mixtures of nickel and titanium to form Ni-Ti intermetallics. The effect of elemental powder composition, heating profile and micro-jet inert gas pressures on the developed macro- and microstructure was investigated. The heating profile brought upon by selective electric current application was found to have a significant effect on whether the reaction is a volumetric combustion or a self-propagating high temperature one. The best results in terms of homogeneity and Ni-Ti intermetallics yield, were obtained for an inert gas pressure of 4 psi under for the nickel rich composition. In addition, surprising results at the higher inert gas pressures show the formation of hollow products, which can give rise future exploration of this technique for combustion synthesizing hollow products of different shapes.

Sharma, Nitin

315

Magnetoelastic properties of substituted Er1-xGdxMn6Sn6 intermetallic system  

NASA Astrophysics Data System (ADS)

The forced magnetostriction of polycrystalline samples of Er1-xGdxMn6Sn6 (0?x?1) intermetallics with hexagonal HfFe6Ge6-type structure is investigated in the temperature range of 77-480 K. Gd substitution has a significant effect on interatomic distances and especially on inter-sublattice R-Mn couplings. The replacement of Er by Gd results in increasing the ordering temperature followed by reinforcement of the R-Mn coupling, as well as decreasing the magnetostriction values owing to the S-state character of Gd3+ ions. The results show that the contribution of Er sublattice to anisotropic magnetoelastic effects is positive, while that of Gd and Mn is negative. All the examined samples exhibit considerable magnetovolume anomalies at the ordering temperature (TC=338, 381, 412 and 434 K for the samples with x=0, 0.2, 0.6 and 1.0, respectively). While the unsubstituted sample exhibits metamagnetic transitions, Gd-contained compounds do not show this behavior, owing to the strong Gd-Mn coupling. The experimental results obtained are discussed in the framework of the two-magnetic sublattice by bearing in mind the lattice parameter dependence of the interlayer Mn-Mn exchange interaction in these layered compounds. From the temperature dependence of magnetostriction values and considering the magnetostriction equation for a hexagonal structure, we attempt to determine the signs of some of the magnetostriction constants for these compounds and the influence of Gd substitution on them.

Tabatabai Yazdi, Sh.; Tajabor, N.; Roknabadi, M. Rezaee; Behdani, M.; Pourarian, F.

2014-06-01

316

From the Cover: Implications for complex cognition from the hafting of tools with compound adhesives in the Middle Stone Age, South Africa.  

PubMed

Compound adhesives made from red ochre mixed with plant gum were used in the Middle Stone Age (MSA), South Africa. Replications reported here suggest that early artisans did not merely color their glues red; they deliberately effected physical transformations involving chemical changes from acidic to less acidic pH, dehydration of the adhesive near wood fires, and changes to mechanical workability and electrostatic forces. Some of the steps required for making compound adhesive seem impossible without multitasking and abstract thought. This ability suggests overlap between the cognitive abilities of modern people and people in the MSA. Our multidisciplinary analysis provides a new way to recognize complex cognition in the MSA without necessarily invoking the concept of symbolism. PMID:19433786

Wadley, Lyn; Hodgskiss, Tamaryn; Grant, Michael

2009-06-16

317

The effect of the amphoteric properties of amino acids in the zwitterionic form on the structure of iodine complex compounds in aqueous solutions  

NASA Astrophysics Data System (ADS)

The donor-acceptor interactions in three model systems: water-glycine (a), water-glycine-KI3 (b), water-glycine-KI3-LiCl-ethanol (c) were investigated by UV-, IR-spectroscopy, and the quantum-chemical DFT-B3PW91/midi method. UV- and IR spectrum data for the considered systems agree well with the results of calculations of the spectral characteristics of glycine cluster that consists of six molecules, and models that simulate the influence of the zwitterionic form of glycine on the structure of complex iodine compounds in the systems (b-c). Localization of a negative and a positive charge at the ends of a zwitterion makes it possible for a cluster of glycine zwitterions to be formed in water. In such cluster glycine molecules are located under each other so that the protonated group is always under (or above) the carboxy group. Glycine fragments are bound by strong hydrogen bonds and also by hydrogen bonding interactions with water molecules. In the water-glycine-KI3-LiCl-ethanol system the cluster of glycine zwitterions splits the iodide ion into I- and I2 (I- reacts with the protonated amino group, and I2 with the carboxy group). This creates conditions for the formation of an iodine complex compound, in which molecular iodine reveals the acceptor properties towards glycine, and the donor properties towards the LiCl-ethanol complex.

Yuldasheva, Gulnara A.; Zhidomirov, Georgii M.; Leszczynski, Jerzy; Ilin, Aleksandr I.

2013-02-01

318

Stability of I3 complexes in III-V compound semiconductors by tight-binding molecular dynamics  

NASA Astrophysics Data System (ADS)

Intrinsic interstitials in GaAs are known to have a large formation energy that makes their concentration almost negligible in as-grown materials. However, interstitials must be explicitly considered in implanted GaAs where collision cascades, induced by the energetic ions, produce a large amount of Frenkel defects: these, indeed, can be considered as a source of interstitials that can migrate and evolve in larger aggregates. Due to the wide relaxation pattern induced by intrinsic interstitials, large supercells are necessary to avoid artifacts that, in practice, make first-principles calculations too computationally demanding, even for complexes involving just three interstitials. Following previous papers on di-interstitials, this paper reports on the structural, stability, and electronic properties of I3 complexes, depending on the topology and the stoichiometry, approached by semiempirical tight-binding molecular dynamics and damped dynamics. I3 complexes reveal a strong tendency to form these structures, and a stability hierarchy is determined between them. All the stable and metastable structures have been studied regarding the electronic structure, the charge distribution through the Mulliken analysis, the localization of the defect related wave function, and the local lattice strain field around the complex. The present study is aimed to define the selection rules that must be considered in order to build up larger In (with n?4 ) self-interstitials complexes in GaAs .

Zollo, G.; Gala, F.

2007-03-01

319

The effects of adrenalectomy and corticsteroid injection on the fibrinolytic activity of complex heparin compounds in the blood during immobilization  

NASA Technical Reports Server (NTRS)

Total non-enzymatic fibrinolytic activity in the blood of rats increased three times in response to stress caused by 30 minute immobilization, and the activity of epinephrine-heparin complex increased nine times. In adrenalectomized animals, which showed a weak response to the same stress, intraperitoneal injection of hydrocortisone 30 minutes prior to immobilization normalized the response. Obtained results indicate that adrenalectomy leads to sharp reduction of heparin complexing with thromogenic proteins and epinephrine, while substitution therapy with hydrocortisone restores anticoagulation system function.

Kudryashov, B. A.; Lomovskaya, E. G.; Shapiro, F. B.; Lyapina, L. Y.

1980-01-01

320

Valence, coordination number, and PAV cells in metallic rare earth compounds F. L. Carter  

E-print Network

Valence, coordination number, and PAV cells in metallic rare earth compounds F. L. Carter Naval, generalized coordination numbers, and Pauling's metallic valences are given for 24 intermetallic rare earth compounds. The results clearly indicate that as much as 33 % rare earth isovalent volume contraction can

Paris-Sud XI, Université de

321

A low-temperature NMR study of the structure of the ionic complexes of phosphoryl compounds with a hydrogen bond  

SciTech Connect

In the present work, low-temperature /sup 1/H NMR spectroscopy was used to study two types of complexes in which the phosphoryl group is part of either the acid or basic part of the molecule. Ionic complexes of trifluoromethylsulfonic acid with phosphoryl bases: (C/sub 8/H/sub 17/)/sub 3/P=O (1), (C/sub 2/H/sub 5/)/sub 2/PON(C/sub 2/H/sub 5/)/sub 2/ (2), and the dioxide (C/sub 2/H/sub 5/)/sub 2/P(O)CH/sub 2/CH/sub 2/P(O)(C/sub 2/H/sub 5/)/sub 2/ (3), and complexes of diethylphosphoric acid with dimethylformamide (4), dimethylsulfoxide (5), THF (6), and other ionic complexes of the type (C/sub 2/H/sub 5/O/sub 2/PO/sub 2/)/sub 2//sup -/HX/sup +/ with a homoconjugated anion, where X = N(C/sub 4/H/sub 9/) or (CD/sub 3/)/sub 3/ /sup 15/NH were studied.

Golubov, N.S.; Denisov, G.S.; Matrosov, E.I.; Kabachnik, M.I.

1982-04-01

322

Design of Lewis acid-base complex: enhancing the stability and first hyperpolarizability of large excess electron compound.  

PubMed

In the present paper, a new type of Lewis acid-base complex BX3...Li@Calix[4]pyrrole (X = H and F) was designed and assembled based on electride molecule Li@calix[4]pyrrole (as a Lewis base) and the electron deficient molecule BX3 (as a Lewis acid) by employing quantum mechanical calculation. The new Lewis acid-base complex offers an interesting push-excess electron-pull (P-e-P) framework to enhance the stability and nonlinear optical (NLO) response. To measure the nonlinear optical response, static first hyperpolarizabilities (? 0) are exhibited. Significantly, point-face assembled Lewis acid-base complex BF3...Li@Calix[4]pyrrole (II) has considerable first hyperpolarizabilities (? 0) value (1.4? × ?106 a.u.), which is about 117 times larger than reported 11,721 a.u. of electride Li@Calix[4]pyrrole. Further investigations show that, in BX3...Li@Calix[4]pyrrole with P-e-P framework, a strong charge-transfer transition from the ground state to the excited state contributes to the enhancement of first hyperpolarizability. Theory calculation of enthalpies of reaction (?rH0) at 298 K demonstrates that it is feasible to synthetize the complexes BX3...Li@Calix[4]pyrrole. In addition, compared with Li@Calix[4]pyrrole, the vertical ionization potential (VIP) and HOMO-LUMO gap of BX3...Li@Calix[4]pyrrole have obviously increased, due to the introduction of the Lewis acid molecule BX3. The novel Lewis acid-base NLO complex possesses not only a large nonlinear optical response but also higher stability. PMID:24022783

Ma, Fang; Miao, Tifang; Zhou, Zhongjun; Sun, Dengming

2013-11-01

323

Synthesis, characterization, and antibacterial activity of structurally complex 2-acylated 2,3,1-benzodiazaborines and related compounds.  

PubMed

A set of 2-acylated 2,3,1-benzodiazaborines and some related boron heterocycles were synthesized, characterized, and tested for antibacterial activity against Escherichia coli and Mycobacterium smegmatis. By high-field solution NMR, the heretofore unknown class of 2-acyl-1-hydroxy-2,3,1-diazaborines has been found to be able to exist in several interconvertable structural forms along a continuum comprised of an open hydrazone a, a monomeric B-hydroxy diazaborine b, and an anhydro dimer c. X-Ray crystallography of one of the anhydro dimers, 17c, revealed it to have an unprecedented structure featuring a double intramolecular O?B chelation. The crystal structure of another compound, 37, showed it to be based on a new pentacyclic B heterocycle framework. Nine compounds were found to possess activities against E. coli, and two others were active against M. smegmatis. The finding that these two contain isoniazid covalently embedded in their structures suggests that they might possibly be acting as prodrugs of this well-known antituberculosis agent in vivo. PMID:25238079

Kanichar, Divya; Roppiyakuda, Lance; Kosmowska, Ewa; Faust, Michelle A; Tran, Kim P; Chow, Felicia; Buglo, Elena; Groziak, Michael P; Sarina, Evan A; Olmstead, Marilyn M; Silva, Isba; Xu, H Howard

2014-09-01

324

Genomic analysis of three sponge-associated Arthrobacter Antarctic strains, inhibiting the growth of Burkholderia cepacia complex bacteria by synthesizing volatile organic compounds.  

PubMed

In this work we analyzed the ability of three Arthrobacter strains (namely TB23, TB26 and CAL618), which were isolated from the Antarctic sponges Haliclonissa verrucosa and Lyssodendrix nobilis, to specifically inhibit the growth of a panel of 40 Burkholderia cepacia complex strains, representing a major cause of infections in patients that are affected by Cystic Fibrosis. The inhibitory activity was due to the synthesis of antimicrobial compounds, very likely volatile organic compounds (VOCs), and was partially dependent on the growth media that were used for Antarctic strains growth. The phylogenetic analysis revealed that two of them (i.e. CAL 618 and TB23) were very close and very likely belonged to the same Arthrobacter species, whereas the strain TB26 was placed in a distant branch. The genome of the strains TB26 and CAL618 was also sequenced and compared with that of the strain TB23. The analysis revealed that TB23 and CAL618 shared more genomic properties (GC content, genome size, number of genes) than with TB26. Since the three strains exhibited very similar inhibition pattern vs Bcc strains, it is quite possible that genes involved in the biosynthesis of antimicrobial compounds very likely belong to the core genome. PMID:24231161

Orlandini, Valerio; Maida, Isabel; Fondi, Marco; Perrin, Elena; Papaleo, Maria Cristiana; Bosi, Emanuele; de Pascale, Donatella; Tutino, Maria Luisa; Michaud, Luigi; Lo Giudice, Angelina; Fani, Renato

2014-01-01

325

Delivery of Exogenous Complex Organic Compounds by Solar System Small Bodies and Space Dusts and Its Relevance to Origins of Life  

NASA Astrophysics Data System (ADS)

A wide variety of organic compounds including amino acid precursors have been detected in such extraterrestrial bodies as carbonaceous chondrites and comets. It was suggested that these organics were formed in quite cold environments. We irradiated frozen mixtures of possible constituents of ice mantles of interstellar dust particles including water, methanol and ammonia with high-energy heavy ions from HIMAC, National Institute of Radiological Science, Japan. Amino acid precursors with complex structures were detected whose molecular weights are up to a few thousands. Such complex amino acid precursors are much stronger than free amino acids against radiation. Such organics could have been incorporated in solar system small bodies after the formation of the solar system and delivered to the primitive Earth. Possible carriers of such organics are meteorites, comets and interplanetary dust particles (IDPs) that were formed from comets and meteorites. It is suggested that IDPs brought much more organics than meteorites and comets. However, nature of organics in IDPs is little known, since they have been collected only in terrestrial biosphere. We are planning a space experiments named Tanpopo, where IDPs would be collected in aerogel equipped on the Exposure Facility of the International Space Station. In addition, amino acids and their relating compounds would be exposed to space environments to see their possible alteration processes in the interplanetary space. We will report some preliminary results for the preparation of the mission including the capture of amino acid-containing particles at high velocity with ultra-low density aerogel.

Kobayashi, Kensei; Fushimi, Hidehiko; Motoyama, Takuya; Kaneko, Takeo; Obayashi, Yumiko; Yoshida, Satoshi; Mita, Hajime; Yabuta, Hikaru; Okudaira, Kyoko; Hashimoto, Hirofumi; Yokobori, Shin-Ichi; Yamagishi, Akihiko

326

Synthesis and Characterization of Metal Complexes to be Employed in the Catalytic Depolymerization of Lignin Model Compounds  

SciTech Connect

Lignin is an earth-abundant biopolymer that is grossly underutilized as a value stream in current biomass conversion technologies because there exist no economic and technically feasible routes for lignin depolymerization and upgrading to fuels and chemicals. The development of new mild and selective catalytic routes to depolymerize this recalcitrant biopolymer is required to more effectively utilize lignin. To that end, our group aims to synthesize and characterize a collection of organometallic catalysts to promote atom-economical catalytic lignin deconstruction. These catalysts have been screened against dimeric lignin model compounds in order to gain mechanistic insights into their modes of action. In addition, experimental efforts have been coupled with quantum mechanical calculations to elucidate solution behavior of the catalysts as well as the mechanisms of lignin depolymerization. Detailed synthetic procedures, as well as spectroscopic and crystallographic characterization and DFT calculations will be presented.

Chmely, S. C.; Kim, S.; Beckham, G. T.

2012-01-01

327

Oxidation and Diffusion in Ti-Al-(Mo, Nb) Intermetallics  

NASA Astrophysics Data System (ADS)

The oxidation resistance of Ti-Al intermetallics is superior to many of their counterparts at high temperatures. High-temperature stability of these intermetallics appears to improve with a ternary alloying addition such as Mo, Nb, etc. A detailed analysis of oxidation of the Ti3Al intermetallics, Ti3Al-2.9 at. pct Mo and Ti3Al-1.1 at. pct Nb, in pure oxygen using crystallographic and microscopic techniques is presented here. The alloy containing 1.1 at. pct Nb did not show an improvement in oxidation resistance over the base alloy but that containing 2.9 at. pct Mo showed marked resistance to oxidation. Activation energies of oxidation for both the alloys were comparable with those reported in the literature for similar compositions. TiO2 and Al2O3 were the major phases present in the oxide scales of the oxidized alloys. The crystal orientations from the X-ray diffraction (XRD) patterns and the morphologies from scanning electron microscopy (SEM) were in good agreement and were helpful in further analysis of the oxidation process. The effective diffusion of oxygen in the oxide layers was calculated using the mole fraction of individual oxide and the diffusivity of oxygen in pure oxide. The activation energy for the effective diffusion of oxygen through the oxide layers was determined to be ~24 kJ/mol. The activation energy for the oxidation process was higher than that of the diffusion of oxygen. Hence, it can be concluded that the oxidation process in both the alloys studied is not diffusion controlled.

Ramachandran, M.; Mantha, D.; Williams, C.; Reddy, R. G.

2011-01-01

328

The formation and growth of intermetallics in composite solder  

NASA Astrophysics Data System (ADS)

The formation and growth of intermetallics at the solder/substrate interface are factors affecting the solderability and reliability of electronic solder joints. This study was performed to better understand the diffusion behavior and microstructural evolution of Cu-Sn intermetallics at the composite solder/copper substrate interface for eutectic solder and solder alloys containing particle additions of Cu, Cu3Sn, Cu6Sn5, Ag, Au, and Ni. Annealing temperatures of 110 to 160°C were used with aging times of 0 to 64 days. The copper-containing composite solders generally formed thinner Cu6Sn5 layers, but thicker Cu3Sn layers than were formed by the eutectic solder alone. These copper-containing additions, therefore, resulted in increased activation energies for Cu6Sn5 formation and decreased activation energies for Cu3Sn formation as compared to the eutectic solder. The activation energy for Cu3Sn formation decreased relative to eutectic solder for silver and gold composite solders even though less Cu3Sn was formed at the substrate interface. Nickel and palladium drastically reduced the Cu3Sn thickness and increased the Cu6Sn5 thickness. However, the Cu6Sn5 contained a substantial volume fraction of voids close to the copper substrate. We propose two mechanisms to explain the effects of the copper-containing and silver particles on the kinetics of intermetallic formation. First, the particles act as tin-sinks which remove tin from the solder and decrease the amount of tin available for reaction at the solder/substrate interface. Second, the particles reduce the cross-sectional area available for tin diffusion, which also reduces the amount of tin available at the interface for reaction.

Wu, Yujing; Sees, Jennifer A.; Pouraghabagher, Cyrus; Foster, L. Ann; Marshall, James L.; Jacobs, Elizabeth G.; Pinizzotto, Russell F.

1993-07-01

329

Conversion of the under bump metallurgy into intermetallics: the impact on flip chip reliability  

Microsoft Academic Search

In high temperature applications, the conversion of the under bump metallurgy (UBM) into UBM-Sn intermetallics can ultimately limit the reliability of flip chip components. Here, an intermetallic growth model characterizing the rate of electrical failure to the rate of UBM consumption is developed which derives a relationship between field reliability and accelerated temperature tests. For a flip chip structure employing

Frank Stepniak

2001-01-01

330

Synthesis and properties of Ti-Al laminated composites with an intermetallic layer  

NASA Astrophysics Data System (ADS)

Metal-intermetallic laminated composites are fabricated upon reaction sintering of titanium and aluminum foils of various thicknesses. The mechanical properties of the composites with various metallic and intermetallic component contents are estimated using static and dynamic tests. The mechanical properties of the laminated composites are found to be anisotropic during static and dynamic loading.

Patselov, A. M.; Rybin, V. V.; Grinberg, B. A.; Ivanov, M. A.; Eremina, O. V.

2011-04-01

331

Synthesis and properties of Ti-Al laminated composites with an intermetallic layer  

Microsoft Academic Search

Metal-intermetallic laminated composites are fabricated upon reaction sintering of titanium and aluminum foils of various thicknesses. The mechanical properties of the composites with various metallic and intermetallic component contents are estimated using static and dynamic tests. The mechanical properties of the laminated composites are found to be anisotropic during static and dynamic loading.

A. M. Patselov; V. V. Rybin; B. A. Grinberg; M. A. Ivanov; O. V. Eremina

2011-01-01

332

(Alloy phase stability and intermetallic research): Foreign trip report, June 12July 11, 1987  

Microsoft Academic Search

I participated in the NATO Advanced Study Institute on ''Alloy Phase Stability'' sponsored by NATO, DOE and the Office of Naval Research (ONR). Three invited lectures on ''Phase Stability and Alloy Design of Ordered Intermetallic Alloys'' were given which summarized current effects on alloy design of ductile ordered intermetallics. The need of theoretical calculations to predict the structural stability in

1987-01-01

333

A survey of combustible metals, thermites, and intermetallics for pyrotechnic applications  

SciTech Connect

Thermite mixtures, intermetallic reactants, and metal fuels have long been used in pyrotechnics. Advantages include high energy density, impact insensitivity, high combustion temperature, and a wide range of gas production. They generally exhibit high temperature stability and possess insensitive ignition properties. This paper reviews the applications, benefits, and characteristics of thermite mixtures, intermetallic reactants, and metal fuels. 50 refs, tables.

Fischer, S.H.; Grubelich, M.C.

1996-08-01

334

Iridium complex catalyzed germylative coupling reaction between alkynes and iodogermanes - a new route to alkynylgermanium and alkynylgermasilicon compounds.  

PubMed

The new reaction of terminal alkynes with iodogermanes proceeding in the presence of an Ir(I)-complex [{Ir(?-Cl)(CO)2}2] () and NEt((i)Pr)2, as a hydrogen iodide acceptor, leads to the formation of functionalized alkynylgermanes. This reaction occurs via direct activation of the Csp-H bond in the starting alkyne. Detailed stoichiometric experiments using [Ir(cod)(CCPh)(PCy3)] () and iodogermane were performed and resulted in a proposal of a reasonable mechanism for the germylative coupling reaction between alkynes and iodogermanes. PMID:25286331

Rzonsowska, Monika; Kownacki, Ireneusz; Dudziec, Beata; Marciniec, Bogdan

2014-10-22

335

Vertebrate pheromones and other semiochemicals: the potential for accommodating complexity in signalling by volatile compounds for vertebrate management  

PubMed Central

The interaction between volatile and non-volatile, e.g. proteinaceous, components of pheromone and other semiochemical-based signalling systems presents a daunting set of problems for exploitation in the management of vertebrates, good or bad. Aggravating this is the complexity of the mixtures involved with pheromones, not only by definition associated with each species, but also with individual members of that species and their positions within their immediate communities. Nonetheless, already in some contexts, particularly where signals are perceived at other trophic levels from those of the vertebrates, e.g. by arthropods, reductionist approaches can be applied whereby the integrity of complex volatile mixtures is maintained, but perturbed by augmentation with individual components. In the present article, this is illustrated for cattle husbandry, fish farming and human health. So far, crude formulations have been used to imitate volatile semiochemical interactions with non-volatile components, but new approaches must be developed to accommodate more sophisticated interactions and not least the activities of the non-volatile, particularly proteinaceous components, currently being deduced. PMID:25109967

Pickett, John A.; Barasa, Stephen; Birkett, Michael A.

2014-01-01

336

Vertebrate pheromones and other semiochemicals: the potential for accommodating complexity in signalling by volatile compounds for vertebrate management.  

PubMed

The interaction between volatile and non-volatile, e.g. proteinaceous, components of pheromone and other semiochemical-based signalling systems presents a daunting set of problems for exploitation in the management of vertebrates, good or bad. Aggravating this is the complexity of the mixtures involved with pheromones, not only by definition associated with each species, but also with individual members of that species and their positions within their immediate communities. Nonetheless, already in some contexts, particularly where signals are perceived at other trophic levels from those of the vertebrates, e.g. by arthropods, reductionist approaches can be applied whereby the integrity of complex volatile mixtures is maintained, but perturbed by augmentation with individual components. In the present article, this is illustrated for cattle husbandry, fish farming and human health. So far, crude formulations have been used to imitate volatile semiochemical interactions with non-volatile components, but new approaches must be developed to accommodate more sophisticated interactions and not least the activities of the non-volatile, particularly proteinaceous components, currently being deduced. PMID:25109967

Pickett, John A; Barasa, Stephen; Birkett, Michael A

2014-08-01

337

Structures of KcsA in complex with symmetrical quaternary ammonium compounds reveal a hydrophobic binding site.  

PubMed

Potassium channels allow for the passive movement of potassium ions across the cell membrane and are instrumental in controlling the membrane potential in all cell types. Quaternary ammonium (QA) compounds block potassium channels and have long been used to study the functional and structural properties of these channels. Here we describe the interaction between three symmetrical hydrophobic QAs and the prokaryotic potassium channel KcsA. The structures demonstrate the presence of a hydrophobic pocket between the inner helices of KcsA and provide insight into the binding site and blocking mechanism of hydrophobic QAs. The structures also reveal a structurally hidden pathway between the central cavity and the outside membrane environment reminiscent of the lateral fenestration observed in sodium channels that can be accessed through small conformational changes in the pore wall. We propose that the hydrophobic binding pocket stabilizes the alkyl chains of long-chain QA molecules and may play a key role in hydrophobic drug binding in general. PMID:25093676

Lenaeus, Michael J; Burdette, Dylan; Wagner, Tobias; Focia, Pamela J; Gross, Adrian

2014-08-19

338

The effect of surface preparation on the oxidation behavior of gamma TiAl-base intermetallic alloys  

SciTech Connect

Titanium aluminides, specifically the intermetallic compound gamma TiAl, are being investigated as potential aerospace and automotive materials due to high specific strength and stiffness. The oxidation behavior of gamma TiAl has been studied extensively. Oxygen exposures tend to produce slow growing alumina rich scales at low temperatures. At higher temperatures (approximately 800 C), the alumina breaks down locally and mixed oxide nodules form. At temperatures at and above 1,000 C, the nodules grow rapidly and merge to form a thick mixed oxide scale. The oxidation behavior in atmospheres containing nitrogen is significantly different. Nitrogen reacts with titanium in the alloy to form titanium nitrides at the scale/alloy interface. It is not possible to form a continuous, protective alumina layer, resulting in rapid oxidation in air. Important initial research also pointed to surface preparation as a potential factor in the oxidation behavior of gamma TiAl alloys. The material used for this study was stoichiometric Ti-50Al (nominal composition in atomic percent), a single phase {gamma} TiAl alloy with large equiaxed grains. In addition, material with a lower aluminum content (Ti-48Al) was also investigated. This alloy is notable because it contains significant amounts of the intermetallic alpha-2 Ti{sub 3}Al dispersed in small lamellar colonies as a second phase.

Rakowski, J.M.; Meier, G.H.; Pettit, F.S. [Univ. of Pittsburgh, PA (United States)] [Univ. of Pittsburgh, PA (United States); Dettenwanger, F.; Schumann, E.; Ruehle, M. [Max Planck Inst. fuer Metallforschung, Stuttgart (Germany)] [Max Planck Inst. fuer Metallforschung, Stuttgart (Germany)

1996-12-15

339

Molecularly Imprinted Polymers for Selective Analysis of Chemical Warfare Surrogate and Nuclear Signature Compounds in Complex Matrices  

SciTech Connect

This paper describes the preparation and evaluation of molecularly imprinted polymers (MIPs) that display specificity toward diisopropyl methylphosphonate (DIMP) and tributyl phosphate (TBP). Polymer activity was assessed by solid-phase extraction and high-performance liquid chromatography experiments. Both DIMP- and TBP-specific MIPs selectively retained their targets relative to a nonimprinted control. Proof-of-principle experiments demonstrated highly selective analysis of the targets from fortified complex matrix samples (diesel fuel, gasoline, and air extract concentrate). The retained MIP fractions gave near quantitative recovery of the target analytes with very low matrix background content. The same fraction from the control sorbent was less pure and recovered only about half of the analyte.

Harvey, Scott D.

2005-08-01

340

Intermetallic and titanium matrix composite materials for hypersonic applications  

SciTech Connect

As part of the French Program of Research and Technology for Advanced Hypersonic Propulsion (PREPHA) which was launched in 1992 between Aerospatiale, Dassault Aviation, ONERA, SNECMA and SEP, an important work is specially devoted to the development of titanium and intermetallic composite materials for large airframe structures. At Dassault Aviation, starting from a long experience in Superplastic Forming - Diffusion Bonding (SPF-DB) of titanium parts, the effort is brought on the manufacturing and characterization of composites made from Timet beta 21S or IMI 834 foils and Textron SCS6 fiber fabrics. At `Aersopatiale Espace & Defence`, associated since a long time about intermetallic composite materials with university research laboratories, the principal effort is brought on plasma technology to develop the gamma titanium aluminide TiAl matrix composite reinforced by protected silicon carbide fibers (BP SM 1240 or TEXTRON SCS6). The objective, is to achieve, after 3 years of time, to elaborate a medium size integrally stiffened panel (300 x 600 sq mm).

Berton, B.; Surdon, G.; Colin, C. [Dassault Aviation, Saint-Cloud (France)]|[Aersopatiale Space & Defence, St Medard en Jalles (France)

1995-09-01

341

Intermetallic superconductors---The state of development in 1991  

SciTech Connect

The commercial fabrication of intermetallic superconductors has reached a high degree of maturity in the past thirty years. The only significant, commercial requirement for superconducting wire is the construction of magnetic resonance imaging (MRI) devices for medical diagnosis. In addition to this demand there are one-time projects such as high energy particle accelerators which often need considerable quantities of superconducting material over the few years of construction. R D projects also provide a fluctuating market for superconducting materials, in the past the projects have included power apparatus such as generators, motors, energy storage and transmission cables, and magnets for experimental fusion reactors. Superconducting magnetically levitated trains have undergone full scale trials in Japan and Germany. This is by no means a comprehensive list of all the possible applications. Virtually all the devices requiring a magnetic field to be produced by superconducting windings have used NbTi wire, but a few experimental Nb{sub 3}Sn high field magnets have been constructed. This report briefly discusses development of intermetallic superconductors.

Forsyth, E.B.

1991-01-01

342

Creep of fully lamellar near {gamma}-TiAl intermetallics  

SciTech Connect

The influence of the fully lamellar morphology and third phase {beta} on the creep properties of near {gamma}-TiAl intermetallics is presented. Specifically, the effect of improved microstructural control obtainable by a stepped cool, involving furnace cooling and air cooling from the {alpha} single phase, on creep resistance is demonstrated for three near {gamma}-TiAl intermetallics: binary Ti-48Al, ternary Ti-48Al-2W and Ti-47Al-2Nb-1Mn-0.5W-0.5Mo-0.2Si. The results indicate that appropriate stepped cooling can be used to reduce the lamellar interface spacing without the formation of Widmanstaetten, feathery {gamma} or {gamma}{sub M} structures, leading to longer creep life and reduced creep strain rates. A second benefit of stepped cooling is prevention of {beta} formation during cooling from the {alpha} phase, allowing controlled {beta} precipitation during aging at 950 C. Creep tests on variously aged Ti-48Al-2W indicate that {beta} precipitation along lamellar grain boundaries improves creep resistance. Development of a uniform fully lamellar structure in Ti-47Al-2Nb-1Mn-0.5W-0.5Mo-0.2Si significantly improves creep resistance. Applying the stepped cool to this alloy allows the precipitation of {beta} and silicides to be controlled during lower temperature aging.

Beddoes, J.; Zhao, L.; Chen, W.R.; Du, X.

1999-07-01

343

SURFACE MODIFICATION OF ZIRCALOY-4 SUBSTRATES WITH NICKEL ZIRCONIUM INTERMETALLICS  

SciTech Connect

Surfaces of Zircaloy-4 (Zr-4) substrates were modified with nickel-zirconium (NiZr) intermetallics to tailor oxidation performance for specialized applications. Surface modification was achieved by electroplating Zr-4 substrates with nickel (Ni) and then performing thermal treatments to fully react the Ni plating with the substrates, which resulted in a coating of NiZr intermetallics on the substrate surfaces. Both plating thickness and thermal treatment were evaluated to determine the effects of these fabrication parameters on oxidation performance and to identify an optimal surface modification process. Isothermal oxidation tests were performed on surface-modified materials at 290°, 330°, and 370°C under a constant partial pressure of oxidant (i.e., 1 kPa D2O in dry Ar at 101 kPa) for 64 days. Test results revealed an enhanced, transient oxidation rate that decreased asymptotically toward the rate of the Zr-4 substrate. Oxidation kinetics were analyzed from isothermal weight gain data, which were correlated with microstructure, hydrogen pickup, strength, and hardness.

Luscher, Walter G.; Gilbert, Edgar R.; Pitman, Stan G.; Love, Edward F.

2013-02-01

344

Activated charcoal-mediated RNA extraction method for Azadirachta indica and plants highly rich in polyphenolics, polysaccharides and other complex secondary compounds  

PubMed Central

Background High quality RNA is a primary requisite for numerous molecular biological applications but is difficult to isolate from several plants rich in polysaccharides, polyphenolics and other secondary metabolites. These compounds either bind with nucleic acids or often co-precipitate at the final step and many times cannot be removed by conventional methods and kits. Addition of vinyl-pyrollidone polymers in extraction buffer efficiently removes polyphenolics to some extent, but, it failed in case of Azadirachta indica and several other medicinal and aromatic plants. Findings Here we report the use of adsorption property of activated charcoal (0.03%–0.1%) in RNA isolation procedures to remove complex secondary metabolites and polyphenolics to yield good quality RNA from Azadirachta indica. We tested and validated our modified RNA isolation method across 21 different plants including Andrographis paniculata, Aloe vera, Rosa damascena, Pelargonium graveolens, Phyllanthus amarus etc. from 13 other different families, many of which are considered as tough system for isolating RNA. The A260/280 ratio of the extracted RNA ranged between 1.8-2.0 and distinct 28S and 18S ribosomal RNA bands were observed in denaturing agarose gel electrophoresis. Analysis using Agilent 2100 Bioanalyzer revealed intact total RNA yield with very good RNA Integrity Number. Conclusions The RNA isolated by our modified method was found to be of high quality and amenable for sensitive downstream molecular applications like subtractive library construction and RT-PCR. This modified RNA isolation procedure would aid and accelerate the biotechnological studies in complex medicinal and aromatic plants which are extremely rich in secondary metabolic compounds. PMID:23537338

2013-01-01

345

Complex Brugada syndrome inheritance in a family harbouring compound SCN5A and CACNA1C mutations.  

PubMed

Brugada syndrome (BrS) is characterized by ST-segment elevation in the right precordial leads and is associated with increased risk of sudden cardiac death. We have recently reported families with BrS and SCN5A mutations where some affected members do not carry the familial mutation. We evaluated the involvement of additional genetic determinants for BrS in an affected family. We identified three distinct gene variants within a family presenting BrS (5 individuals), cardiac conduction defects (CCD, 3 individuals) and shortened QT interval (4 individuals). The first mutation is nonsense, p.Q1695*, lying within the SCN5A gene, which encodes for NaV1.5, the ?-subunit of the cardiac Na(+) channel. The second mutation is missense, p.N300D, and alters the CACNA1C gene, which encodes the ?-subunit CaV1.2 of the L-type cardiac Ca(2+) channel. The SCN5A mutation strictly segregates with CCD. Four out of the 5 BrS patients carry the CACNA1C variant, and three of them present shortened QT interval. One of the BrS patients carries none of these mutations but a rare variant located in the ABCC9 gene as well as his asymptomatic mother. Patch-clamp studies identified a loss-of-function of the mutated CaV1.2 channel. Western-blot experiments showed a global expression defect while increased mobility of CaV1.2 channels on cell surface was revealed by FRAP experiments. Finally, computer simulations of the two mutations recapitulated patient phenotypes. We report a rare CACNA1C mutation as causing BrS and/or shortened QT interval in a family also carrying a SCN5A stop mutation, but which does not segregate with BrS. This study underlies the complexity of BrS inheritance and its pre-symptomatic genetic screening interpretation. PMID:25341504

Béziau, Delphine M; Barc, Julien; O'Hara, Thomas; Le Gloan, Laurianne; Amarouch, Mohamed Yassine; Solnon, Aude; Pavin, Dominique; Lecointe, Simon; Bouillet, Patricia; Gourraud, Jean-Baptiste; Guicheney, Pascale; Denjoy, Isabelle; Redon, Richard; Mabo, Philippe; le Marec, Hervé; Loussouarn, Gildas; Kyndt, Florence; Schott, Jean-Jacques; Probst, Vincent; Baró, Isabelle

2014-11-01

346

Local decomposition induced by dislocation motions inside tetragonal Al2Cu compound: slip system-dependent dynamics  

PubMed Central

Dislocations in a crystal are usually classified into several independent slip systems. Motion of a partial dislocation in monometallic crystals may remove or create stacking fault characterized with a partial of a lattice translation vector. However, it is recently known that motion of partial dislocations in complex structure, such as that inside an intermetallic Al2Cu compound, lead to a local composition deviation from its stoichiometric ratio and the resultant structure collapse. Here we report such a local decomposition behaviors are strongly dependent on slip system of dislocations. Under applied external stress, we have studied dislocation motion behaviors in the three independent slip systems of [001](110), [100]() and [110]() within tetragonal Al2Cu crystal by using molecular dynamics method. We found dislocation motions in all these slip systems result in local decomposition but their physical details differ significantly. PMID:24196169

Chen, D.; Ma, X. L.

2013-01-01

347

Coupling solid-phase microextraction with ambient mass spectrometry using surface coated wooden-tip probe for rapid analysis of ultra trace perfluorinated compounds in complex samples.  

PubMed

Coupling solid-phase microextraction (SPME) with ambient mass spectrometry using surface coated wooden-tip probe was achieved for the first time and applied in the analysis of ultra trace perfluorinated compounds (PFCs) in complex environmental and biological samples. We modified n-octadecyldimethyl[3-(trimethoxysilyl)propyl]ammonium chloride on the surface of sharp wooden tip via silanization to form a novel SPME probe, which was then used for highly selective enrichment of PFCs from complex matrices and applied as a solid substrate to induce electrospray ionization for mass spectrometric analysis. The porous structural surface together with the dual extraction mechanisms (reversed phase adsorption and ion exchange adsorption) demonstrated that the SPME probe has an outstanding enrichment capacity, enhancing sensitivity by approximately 4000-8000 folds for the detection in aqueous samples, and 100-500-fold in whole blood and milk samples. The method showed good linearity, with correlation coefficient values (r(2)) of no less than 0.9931 for eight target PFCs. The limits of detection and qualification of the eight PFCs were 0.06-0.59 and 0.21-1.98 ng/L, respectively. Quantification of real samples was achieved by isotope internal standard calibration curve method or isotope dilution method, and ultratrace levels of PFCs present in lake water, river water, whole blood, and milk samples had been successfully detected and qualified. PMID:25354323

Deng, Jiewei; Yang, Yunyun; Fang, Ling; Lin, Li; Zhou, Haiyun; Luan, Tiangang

2014-11-18

348

Spectroscopic studies of diketoacids-metal interactions. A probing tool for the pharmacophoric intermetallic distance in the HIV-1 integrase active site.  

PubMed

The interactions with divalent cations of 4-phenyl-4-oxo-2-hydroxybuten-2-oic acid (benzoylpyruvic acid (BPA)), the pharmacophore of HIV-1 integrase inhibitors, were investigated using spectroscopic tools. In the absence of the enzyme, a 2:2 metal-ligand complex was characterized with an intermetallic distance of 4-6 A. Molecular modeling allowed us to propose a compatible structure for the metal-ligand complex. BPA does not inhibit the reactions catalyzed by HIV-1 IN, emphasizing the importance of the aromatic ring substitution in the antiviral activity. PMID:15481994

Maurin, Cédric; Bailly, Fabrice; Buisine, Eric; Vezin, Hervé; Mbemba, Gladys; Mouscadet, Jean François; Cotelle, Philippe

2004-10-21

349

Microstructure evolution and hardness change in ordered Ni3V intermetallic alloy by energetic ion irradiation  

NASA Astrophysics Data System (ADS)

Ni3V bulk intermetallic compounds with ordered D022 structure were irradiated with 16 MeV Au ions at room temperature. The irradiation induced phase transformation was examined by means of the transmission electron microscope (TEM), the extended X-ray absorption fine structure measurement (EXAFS) and the X-ray diffraction (XRD). We also measured the Vickers hardness for unirradiated and irradiated specimens. The TEM observation shows that by the Au irradiation, the lamellar microstructures and the super lattice spot in diffraction pattern for the unirradiated specimen disappeared. This TEM result as well as the result of XRD and EXAFS measurements means that the intrinsic D022 structure of Ni3V changes into the A1 (fcc) structure which is the lattice structure just below the melting point in the thermal equilibrium phase diagram. The lattice structure change from D022 to A1 (fcc) accompanies a remarkable decrease in Vickers microhardness. The change in crystal structure was discussed in terms of the thermal spike and the sequential atomic displacements induced by the energetic heavy ion irradiation.

Hashimoto, A.; Kaneno, Y.; Semboshi, S.; Yoshizaki, H.; Saitoh, Y.; Okamoto, Y.; Iwase, A.

2014-11-01

350

Optimized Cu-Sn Wafer-Level Bonding Using Intermetallic Phase Characterization  

NASA Astrophysics Data System (ADS)

The objective of this study is to optimize the Cu/Sn solid-liquid interdiffusion process for wafer-level bonding applications. To optimize the temperature profile of the bonding process, the formation of intermetallic compounds (IMCs) which takes place during the bonding process needs to be well understood and characterized. In this study, a simulation model for the development of IMCs and the unreacted remaining Sn thickness as a function of the bonding temperature profile was developed. With this accurate simulation model, we are able to predict the parameters which are critical for bonding process optimization. The initial characterization focuses on a kinetics model of the Cu3Sn thickness growth and the amount of Sn thickness that reacts with Cu to form IMCs. As-plated Cu/Sn samples were annealed using different temperatures (150°C to 300°C) and durations (0 min to 320 min). The kinetics model is then extracted from the measured thickness of IMCs of the annealed samples.

Luu, Thi-Thuy; Duan, Ani; Aasmundtveit, Knut E.; Hoivik, Nils

2013-12-01

351

Characterization of ceramics and intermetallics fabricated by self-propagating high-temperature synthesis  

NASA Technical Reports Server (NTRS)

Three efforts aimed at investigating the process of self-propagating high temperature synthesis (SHS) for the fabrication of structural ceramics and intermetallics are summarized. Of special interest was the influence of processing variables such as exothermic dopants, gravity, and green state morphology in materials produced by SHS. In the first effort directed toward the fabrication of SiC, exothermic dopants of yttrium and zirconium were added to SiO2 or SiO2 + NiO plus carbon powder mix and processed by SHS. This approach was unsuccessful since it did not produce the desired product of crystalline SiC. In the second effort, the influence of gravity was investigated by examining Ni-Al microstructures which were produced by SHS combustion waves traveling with and opposite the gravity direction. Although final composition and total porosities of the combusted Ni-Al compounds were found to be gravity independent, larger pores were created in those specimens which were combusted opposite to the gravity force direction. Finally, it was found that green microstructure has a significant effect on the appearance of the combusted piece. Severe pressing laminations were observed to arrest the combustion front for TiC samples.

Hurst, Janet B.

1989-01-01

352

Synthesis, Structure and bonding Analysis of the Polar Intermetallic Phase Ca2Pt2Cd  

SciTech Connect

The polar intermetallic phase Ca2Pt2Cd was discovered during explorations of the Ca-Pt-Cd system. The compound was synthesized by high temperature reactions, and its structure refined by single-crystal X-ray diffraction as orthorhombic, Immm, a = 4.4514(5), b = 5.8415(6), c = 8.5976(9) Å, Z = 2. The structure formally contains infinite, planar networks of [Pt2Cd]4– along the ab plane, which can be described as tessellation of six and four-member rings of the anions, with cations stuffed between the anion layers. The infinite condensed platinum chains show a substantial long–short distortion of 0.52 Å, an appreciable difference between Ca2Pt2Cd (26 valence electrons) and the isotypic but regular Ca2Cu2Ga (29 VE). The relatively large cation proportion diminishes the usual dominance of polar (Pt–Cd) and 5d–5d (Pt–Pt) contributions to the total Hamilton populations.

Samal, Saroj L.; Corbett, John D.

2012-08-14

353

Nanocomposite Fe-Al Intermetallic Coating Obtained by Gas Detonation Spraying of Milled Self-Decomposing Powder  

NASA Astrophysics Data System (ADS)

The nanocomposite structure of Fe-Al intermetallic coating, created in situ during gas detonation spraying (GDS) of as-milled self-decomposing powder and containing disordered 8 nm FeAl nanocrystals, was analyzed using scanning electron microscopy (SEM) with energy-dispersive x-ray (EDX) spectroscopy, transmission electron microscopy (TEM), selected-area electron diffraction (SAED), and x-ray diffraction methods. It is found that the Fe-Al coating is characterized by a sublayer morphology consisting of flattened and partially melted splats containing a wide Al range from about 26 to 52 at.%, as well as Al2O3 oxides, created in situ at the internal interfaces of splats during the GDS process. The complex oxide films, identified as amorphous Al2O3, which are formed in the nanocrystalline Fe-Al matrix of the GDS coating behave like a composite reinforcement in the intermetallic Fe-Al coating. The combined presence of nanosized subgrains in the Fe-Al matrix and the Al2O3 nanoceramic dispersoids significantly increases the microhardness of the coating.

Senderowski, Cezary

2014-10-01

354

Effects of additive elements on structural and electronic properties of Sn-based intermetallics by first principles  

NASA Astrophysics Data System (ADS)

First-principles calculations are performed to study the structural and electronic properties of Sn-based intermetallic compounds (IMCs) with substitution elements. Cu atoms preferentially occupy the 2a sites in (Ni1 - x Cu x )3Sn4 structures. With the increase of Cu content, the heats of formation (H f) of (Ni1 - x Cu x )3Sn4 structures become higher. For the Ni3Sn4-based ternary structures with different substitution elements, a simple rule for the H f is obtained. Comparing with the substitution elements in group IB (Cu, Ag, Au), those from group VIIIB (Co, Ni, Pd, Pt) are more helpful for stabilizing the ternary structures. For substitution elements in the same group, the H f of these ternary structures becomes lower with the increase of atomic number. This rule is verified by calculating the H f of Cu6Sn5-based and AuSn4-based ternary structures.

Yu, Chun; Chen, Jieshi; Xu, Jijin; Chen, Junmei; Lu, Hao

2014-04-01

355

Metal- and intermetallic-matrix composites for aerospace propulsion and power systems  

NASA Technical Reports Server (NTRS)

The requirements for high specific strength refractory materials of prospective military, civil, and space propulsion systems are presently addressed in the context of emerging capabilities in metal- and intermetallic-matrix composites. The candidate systems encompass composite matrix compositions of superalloy, Nb-Zr refractory alloy, Cu-base, and Ti-base alloy types, as well as such intermetallics as TiAl, Ti3Al, NiAl, and MoSi2. The brittleness of intermetallic matrices remains a major consideration, as does their general difficulty of fabrication.

Doychak, J.

1992-01-01

356

Negative stiffness of the FeAl intermetallic nanofilm  

NASA Astrophysics Data System (ADS)

Uniaxial tension of the nanofilm of the FeAl intermetallic alloy has been simulated by the molecular dynamics method. It has been found that the nanofilm is elastically deformed by 37%. There is a region in the stress-strain curve, where the strain increases with a decrease in the tensile stress, which indicates the negative stiffness of the nanofilm in this region. The uniform strain with a decrease in the tensile stress is unstable thermodynamically, which leads to the appearance domains with different elastic strains in the nanofilm. The deformation in the unstable region develops due to the domain-wall motion; as a result, the domains with a higher strain grow at the expense of the domains with a lower strain. A similar deformation mechanism was recently described by Savin with coworkers for the DNA molecule.

Bukreeva, K. A.; Babicheva, R. I.; Dmitriev, S. V.; Zhou, K.; Mulyukov, R. R.

2013-09-01

357

Magnetic properties of RNi 5-xCu x intermetallics  

NASA Astrophysics Data System (ADS)

The magnetic properties have been studied for the series of RNi 5-xCu x intermetallics with R=Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Lu; x?2.5. Compositional dependences of magnetic susceptibility for the Pauli paramagnets (R=Y, La, Ce, Lu) and the Curie temperature for ferromagnets (R=Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm) have maximum at x=0.2-0.4 and 1, respectively. The substitution of Cu for Ni is accompanied by decreasing spontaneous magnetic moment and increasing coercive force of all ferromagnetic RNi 5-xCu x but GdNi 5-xCu x. These results are explained in the frame of band magnetism, random local crystal field, and domain wall pinning theories.

Kuchin, A. G.; Ermolenko, A. S.; Kulikov, Yu. A.; Khrabrov, V. I.; Rosenfeld, E. V.; Makarova, G. M.; Lapina, T. P.; Belozerov, Ye. V.

2006-08-01

358

Overview of the development of FeAl intermetallic alloys  

SciTech Connect

B2-phase FeAl ordered intermetallic alloys based on an Fe-36 at.% Al composition are being developed to optimize a combination of properties that includes high-temperature strength, room-temperature ductility, and weldability. Microalloying with boron and proper processing are very important for FeAl properties optimization. These alloys also have the good to outstanding resistance to oxidation, sulfidation, and corrosion in molten salts or chlorides at elevated temperatures, characteristic of FeAl with 30--40 at.% Al. Ingot- and powder-metallurgy (IM and PM, respectively) processing both produce good properties, including strength above 400 MPa up to about 750 C. Technology development to produce FeAl components for industry testing is in progress. In parallel, weld-overlay cladding and powder coating technologies are also being developed to take immediate advantage of the high-temperature corrosion/oxidation and erosion/wear resistance of FeAl.

Maziasz, P.J.; Liu, C.T.; Goodwin, G.M.

1995-09-01

359

Processing Issues for Preliminary Melts of the Intermetallic Compound 60-NITINOL  

NASA Technical Reports Server (NTRS)

The effect of various high temperature heat treatments and cooling rates on the hardness of cast 60-NITINOL (60wt%Ni- 40wt%Ti) was studied. The hardness ranged from approximately 33 HRC for annealed specimens to 63 HRC for water quenched specimens. Aging did not have a further effect on the hardness of the heat-treated and quenched material. The issue of material contamination and its possible effect on quench cracking during heat treatment above 1000 C was explored. The Charpy impact energy of the material was found to be relatively low (ranging from 0.4 to 1.0 J) and comparable to that of cast magnesium. Selection of service environments and applications for this material based on these findings should consider the processing route by which it was produced.

Stanford, Malcolm K.; Thomas, Fransua; DellaCorte, Christopher

2012-01-01

360

Experimental evidence for room-temperature intermetallic compound formation at the Pd/Al interface  

NASA Astrophysics Data System (ADS)

The growth of Pd films on Al and Pd/Al interface formation were studied with use of ultraviolet photoemission spectroscopy (UPS) and low-energy ion scattering. At room temperature, the deposited Pd intermixes with the Al substrate and forms a thin surface alloy about 5 monolayers (ML) thick. Bulklike Pd states start to build up at EF when the Pd coverage exceeds 4 ML. More than 8 ML of Pd are needed to completely cover the Al substrate and to fully develop the Pd metallic valence band. A Pd4d-derived band centered at 4 eV below EF was observed both for monolayer Pd coverage on Al and for thick Al on Pd. It is argued that this deep-lying d band is due to the interaction between Pd and Al through the hybridization of the Pd d and Al s states.

Jiang, L. Q.; Ruckman, M. W.; Strongin, Myron

1989-01-01

361

Elastic properties of the intermetallic compound ReSi{sub 2}  

SciTech Connect

Structural properties are crucial for understanding deformation behavior of a solid, e.g., dislocation slip systems, twinning modes, etc. A knowledge of elastic constants is essential for many practical applications related to the mechanical properties of a solid: load-deflection, thermoelastic stress, internal strain (residual stress), sound velocities, dislocation core structure, and fracture toughness. Further, the elastic properties may provide insight on the atomic bonding and resistance to deformation by shear. In this investigation, the elastic properties of ReSi{sub 2} were evaluated using resonant ultrasound spectroscopy (RUS) and are compared to the elastic properties of other transition metal disilicides.

Misra, A.; Chu, F.; Mitchell, T.E. [Los Alamos National Lab., NM (United States). Materials Science and Technology Div.] [Los Alamos National Lab., NM (United States). Materials Science and Technology Div.

1998-02-13

362

The synthesis of intermetallic compounds under dinamic compression of powder mixture on metal surface  

Microsoft Academic Search

The initial powder mixtures (Fe-Si, Nb-Al, Al-Ni) were shock loaded on the surface of steel plates. The structure investigation of obtained surface layers reveals homogeneous distribution of elements and formation of intermettallides.

A. R. Kutsar; A. V. Kaunov; V. M. Bukin; N. B. Dyakonova; I. A. Korsunskaya; A. F. Sanches-Bolinches

1990-01-01

363

Formation of the Intermetallic Compounds Between Liquid Sn Different Cu-Ni Metalization.  

National Technical Information Service (NTIS)

Interfacial reactions between liquid tin and different Cu-Ni alloy metallizations as well as the subsequent phase transformations during the cooling were investigated with the emphasis on microstructures of the reaction zones. It was found out that the ex...

V. Vuorinen, T. M. Kohonen, J. K. Kivilahti

2001-01-01

364

Oxidation resistance of intermetallic compounds Al 3 Ti and TiAl  

Microsoft Academic Search

The oxidation kinetics and morphological features of Al3Ti and TiAl were investigated. The oxidation resistance of Al3Ti is much better than that of TiAl, for example, by a factor of about 30 at 1000° C for 48 h. The big difference in the oxidation resistance is related to the characteristics of the external oxide scales of a protective Al2O3 or

Y. Umakoshi; M. Yamaguchi; T. Sakagami; T. Yamane

1989-01-01

365

Oxygen scavenging effect of the alpha-2 phase in the TiAl intermetallic compound  

SciTech Connect

The ductility of TiAl can be enhanced by utilizing the lamellar structure of this material; it has been suggested in the past that one of the two mechanisms operating in the enhancement of TiAl ductility is that the alpha-2 phase of the lamellar TiAl structure might enhance ductility by scavenging oxygen from the gamma matrix. In this work, this possibility is investigated experimentally by determining the compositions of alpha-2 and gamma phases of TiAl using an atom-probe field-ion microscope. It is shown that the alpha-2 phase in the lamellar structure of TiAl is much more enriched in oxygen than is the gamma phase, indicating that the alpha-2 phase acts as an oxygen scavenger, decreasing the oxygen content in the gamma phase and improving its ductility. 10 refs.

Uemori, R.; Hanamura, T.; Morikawa, H. (Nippon Steel Corp., Kawasaki, (Japan))

1992-03-01

366

A Resonating-Valence-Bond Theory of Metals and Intermetallic Compounds  

Microsoft Academic Search

The resonating-valence-bond theory of metals discussed in this paper differs from the older theory in making use of all nine stable outer orbitals of the transition metals, for occupancy by unshared electrons and for use in bond formation; the number of valency electrons is consequently considered to be much larger for these metals than has been hitherto accepted. The metallic

L. Pauling

1949-01-01

367

Magnetostriction and thermal expansion of HoFe11-xCoxTi intermetallic compounds  

NASA Astrophysics Data System (ADS)

The thermal expansion and magnetostriction of the HoFe11-xCoxTi (0?x?11) alloys have been investigated, using the strain gauge technique in the temperature range 77-600 K. Both thermal expansion and thermal expansion coefficient exhibit an anomalous behaviour and Invar effect below Curie temperature (TC=516 K) in sample with x=0. The increase of x in HoFe11-xCoxTi system leads to disappearing of the Invar effect and increasing of the average thermal expansion coefficient from 6.370×10-6 K-1 in x=0 to 10.735×10-6 K-1 in x=11 below room temperature. In addition, the spontaneous volume magnetostriction decreases with Co content. The magnetostriction compensation point is observed in the anisotropic magnetostriction curve of all samples. The maximum value of anisotropic magnetostriction (???50×10-6) at room temperature is observed in sample with x=9. The saturation behaviour only appears in samples with x=5, 7 and 9. In samples with x=3, 5 and 7, a noticeable volume magnetostriction (?V/V) is observed in low temperature due to first-order magnetisation process. Moreover, ?V/V exhibits a large anomaly about 45×10-6 and 20×10-6 around room temperature related to spin reorientation transition in samples with x=9 and 11, respectively. The results are discussed based on the local magnetic moment model and irreducible magnetoelastic coupling modes.

Sanavi Khoshnoud, D.; Tajabor, N.; Motevalizadeh, L.; Fruchart, D.

2014-08-01

368

Fermi surface properties of AB (A = Y, La; B = Pb, In, Tl) intermetallic compounds under  

E-print Network

A is a rare earth element or Y, and B is In, Sn, Tl or Pb) crystallizing in the AuCu3 type structure properties, magnetic susceptibility and thermopower, as functions of their valence electron concentration [1 substitution of Sn in LaIn3-xSnx alloy and suggested that this is due to the increase of the lattice parameter

Svane, Axel Torstein

369

Spin reorientation transition and hard magnetic properties of MnBi intermetallic compound  

NASA Astrophysics Data System (ADS)

The effects of mechanical grinding (MG) on the crystallite size, the spin reorientation transition temperature (TSR) and the hard magnetic properties in melt-spun low temperature phase (LTP) MnBi have been investigated in order to understand the origin of magnetic hardening induced by MG. The room-temperature coercive field (?0Hcj) is enhanced dramatically from 0.08 T before MG to 1.5 T after MG for 43.2 ks while TSR is concurrently suppressed from 110 to 38 K. The coercive force exhibits positive temperature dependence approximately 50-60 K above TSR and the lowered TSR after MG could result in magnetic hardening at room temperature. The room-temperature coercive force of LTP-MnBi is highly dependent on the crystallite size (D) and is found to be described phenomenologically by the following relationship: ?0Hcj = ?0Ha(?/D)n, where ?0Ha is ˜ 4 T, the Bloch wall width ? is 7 nm, and the exponent n is approximately 0.7. Our results suggest that the grain refinement is the primary origin of the hardening effect induced by MG with a possible minor hardening effect due to the suppression of the spin reorientation transition temperature.

Suzuki, K.; Wu, X.; Ly, V.; Shoji, T.; Kato, A.; Manabe, A.

2012-04-01

370

Hyperfine interaction studies of local environments of probe atoms in intermetallic compounds  

E-print Network

or absence of nearby point defects. Partial information can be obtained about the point symmetries In probe: · NiAl and FeAl are materials of interest in high-temperature structural applications. Formation:collins@wsu.edu http://defects.physics.wsu.edu/ Interactions of nuclear moments with internal fields in solids lead

Collins, Gary S.

371

Theory and computer simulation of the precipitation of ordered intermetallic compounds in binary and ternary alloys  

NASA Astrophysics Data System (ADS)

The precipitation of L1sb2 ordered Alsb3Li precipitates in Al-Li alloys, and of DOsb{22} ordered Nisb3V and L1sb2 ordered Nisb3Al precipitates in Ni-Al-V alloys has been studied. In addition, the coarsening kinetics of the Alsb3Li precipitates have also been studied. It is found that a critical nucleus consists of fluctuations of both composition and long-range order parameter profiles. It is shown that only when the composition of the initial disordered matrix is near the phase boundary of the disordered phase, are the composition and order parameter values inside the critical nucleus close to those of the equilibrium ordered phase, and that the critical profiles become increasingly diffuse as the composition of the disordered matrix approaches the ordering instability line. Based on the non-classical nucleation theory, the size of critical fluctuations, the critical free energy change and the nucleation rate are estimated for the specific case of the precipitation of metastable deltasp' ordered phase from a disordered matrix in the Al-Li alloy. The morphological evolution and coarsening kinetics of L1sb2 ordered deltasp' (Alsb3Li) precipitates in a disordered Al matrix (alpha) has been investigated using computer simulations based on both stochastic and deterministic microscopic diffusion equations. A projected two-dimensional model of a three-dimensional fcc lattice has been employed. The coalescence or encounters among precipitates as well as the accompanying morphological evolution are automatically taken into account. The coalescence of two in-phase precipitates forms one large particle while encounters between two out-of phase precipitates results in an antiphase domain boundary (APB) wetted by a layer of the disordered phase. Volume fractions ranging from 20 to 65% have been studied. It is found that the cube of the average particle radius varies linearly with time in the scaling regime for all the volume fractions studied. It is shown that the particle-size distribution (PSD)s become increasingly broad and their skewness changes sign from negative to positive with increasing precipitate volume fraction. During coarsening, the volume fraction is not constant, approaching the equilibrium value only asymptotically with time. The kinetics of diffusional phase transformations in the pseudobinary Nisb3Al-Nisb3V system have been studied using a computer simulation technique based on microscopic diffusion equations. The focus is on the atomic ordering and compositional clustering process during the phase transformation of an initially homogeneous disordered Al ternary alloy (Nisb{75}Alsb{25-x}Vsb{x}) into a two-phase mixture of L1sb2 (Nisb3Al) and DOsb{22} (Nisb3V) ordered phases. The computer simulations demonstrate that at small vanadium content, the L1sb2 ordered domains appear first, followed by the nucleation of DOsb{22} ordered domains at the antiphase domain boundaries of L1sb2 phase, whereas at large vanadium content, precipitation of DOsb{22} domains precedes L1sb2 domain formation. The simulation results are discussed employing the thermodynamic stability analysis. The ordering and clustering kinetics predicted from our computer simulation seem to be consistent with recent experimental observations on the alloys. (Abstract shortened by UMI.)

Poduri, Ramakrishna

372

Formation and Porous Anodization of Intermetallic TiAl2 Compound  

NASA Astrophysics Data System (ADS)

Anodization of TiAl2 films, fabricated by annealing of magnetron deposited Al-Ti nanostructured composite films at 600 °C, provides formation of a porous film mostly consisting of straight and smooth tubes of about 60-70 nm in diameter. Whereas anodization of as-deposited films leads to a porous film with a strongly marked grain structure and curved vertical pores.

Lazarouk, S. K.

2013-05-01

373

Fabrication and corrosion resistance of HVOF-sprayed Ni2Si intermetallic compound  

NASA Astrophysics Data System (ADS)

In this study, Ni2Si powders were deposited onto 420 stainless steel substrate using high velocity oxy-fuel (HVOF) process. The coatings were characterized by X-ray diffractometery, optical and scanning electron microscopy and microhardness measurements. Tafel polarization tests and electrochemical impedance spectroscopy (EIS) measurements were employed to study corrosion performance of the coatings in 70% H2SO4 media at room temperature. Here, a dense sintered Ni2Si was used as reference material. The results showed the phase composition of HVOF coating is similar to that of feedstock powders. The corrosion rate of HVOF Ni2Si coatings was much lower than that of 420 stainless steel substrate but slightly higher than that of bulk Ni2Si. Further investigation showed that both thermally sprayed and sintered (reference) Ni2Si alloys exhibited similar anodic polarization behavior including a narrow active section followed by a wide passive region.

Verdian, M. M.; Raeissi, K.; Salehi, M.

2013-05-01

374

Rare-earth iron-based intermetallic compounds and their carbides: Structure and magnetic behaviors  

NASA Astrophysics Data System (ADS)

The structural and magnetic properties of Sm2Fe17-xMox, its out of equilibrium precursor SmFe9-yMoy and their carbides are investigated by means of powder X-ray diffraction, magnetic measurements and high-resolution transmission electron microscopy. The structure of the nanocrystalline Sm1-s(Fe,Mo) alloys are governed by the s Sm vacancy rate and the x amount of Mo. In this work, the Rietveld analysis shows that for s=0.33 the structure is R3¯m of Th2Zn17-type and P6/mmm with the stoichiometry 1/9 for s=0.36. Moreover, it points out a lattice expansion along the c-axis after Mo substitution for Fe and reveals a 6c preferential occupation for Mo atoms in R3¯m structure, and 2e for the out of equilibrium hexagonal precursor. Upon carbon insertion, the lattice expansion favors the Curie temperature increase up to 35% for Sm2Fe16.42Mo0.58C2 and 49% for the metastable SmFe8.7Mo0.3C carbide. The Curie temperature and the coercive field of the 1/9 carbides are higher than those of 2/17 ones. This makes the out of equilibrium hexagonal precursor a competitive candidate for use as permanent magnet.

Khazzan, S.; Mliki, N.; Bessais, L.; Djéga-Mariadassou, C.

2010-01-01

375

Synthesis and characterization of patterned surfaces and catalytically relevant binary nanocrystalline intermetallic compounds  

E-print Network

PtSn2 ? PtSn ? Pt3Sn. Our conversion chemistry occurs in solution at temperatures below 300 °C and within 1 hour, highlighting the high reactivity of our nanocrystalline materials compared to the bulk. Some evidence of the generality for this process...

Cable, Robert E.

2009-05-15

376

Synthesis and characterization of patterned surfaces and catalytically relevant binary nanocrystalline intermetallic compounds  

E-print Network

....................................................................... 107 6.1 Introduction................................................................................... 107 6.2 Experimental details ..................................................................... 109 6.3 Colloidal crystal microarrays...-µm wells. A 5 µL aqueous suspension of 2.8-µm polystyrene spheres covers 12 of the 10 × 10 microwell arrays. Note that the schematic representations show only 4 individual microwells, a small subset of a single microarray, while the photograph...

Cable, Robert E.

2008-10-10

377

Conditions for SHS of intermetallic compounds with selective laser sintering of powdered compositions  

Microsoft Academic Search

The selective laser sintering of powdered mixtures traditionally used in high-temperature synthesis technology is studied.\\u000a It is shown that a controlled exothermic combustion reaction can be set up in the focal spot of a CW Nd-YAG laser. The required\\u000a laser interaction parameters (power, scan rate, and laser beam diameter) and dispersity and composition of the powder composition\\u000a are determined for

I. V. Shishkovskii; A. G. Makarenko; A. L. Petrov

1999-01-01

378

Fatigue Life Prediction of an Intermetallic Matrix Composite at Elevated Temperatures.  

National Technical Information Service (NTIS)

A strain-based fatigue life prediction method is proposed for an intermetallic matrix composite (IMC) under tensile cyclic loadings at elevated temperatures. Styled after the Universal Slopes method, the model utilizes the composite's tensile properties t...

P. A. Bartolotta

1991-01-01

379

Mechanical alloying of FeAl intermetallics in the DO3 composition range  

Microsoft Academic Search

Binary Fe-Al intermetallics with compositions ranging between 10 and 30 at% have been produced by mechanical alloying. The elemental powders were milled together resulting in the dissolution of the Al atoms into the Fe lattice. Subsequent heat treatment of the compacted powder resulted in the formation of the intermetallic. However, complete suppression of the DO3 (Fe3Al) structure in favour of

G. H. Fair; J. V. Wood

1994-01-01

380

Processing, properties, and ballistic performance of titanium-aluminum titanium metal-intermetallic laminate (MIL) composites  

Microsoft Academic Search

A systematic investigation into the processing of Ti-Al3Ti metal-intermetallic laminate (MIL) composites from elemental titanium and aluminum foils in open air by a novel one step technique, and subsequent characterization, physical, mechanical and ballistic testing was carried out. Al3Ti is the only intermetallic phase to form, and no oxides or other phases are formed. Composites with Ti volume fractions of

David John Harach

2000-01-01

381

Synthesis and properties of Ti-Al laminated composites with an intermetallic layer  

Microsoft Academic Search

Metal-intermetallic laminated composites are fabricated upon reaction sintering of titanium and aluminum foils of various\\u000a thicknesses. The mechanical properties of the composites with various metallic and intermetallic component contents are estimated\\u000a using static and dynamic tests. The mechanical properties of the laminated composites are found to be anisotropic during static\\u000a and dynamic loading.

A. M. Patselov; V. V. Rybin; B. A. Grinberg; M. A. Ivanov; O. V. Eremina

2011-01-01

382

Analysis of low-temperature intermetallic growth in copper-tin diffusion couples  

Microsoft Academic Search

A multiphase diffusion model was constructed and used to analyze the growth of the ?- and ?-phase intermetallic layers at a plane Cu-Sn interface in a semi-infinite diffusion couple. Experimental measurements\\u000a of intermetallic layer growth were used to compute the interdiffusivities in the? and? phases and the positions of the interfaces as a function of time. The results suggest that

Z. Mei; A. J. Sunwoo; J. W. Morris

1992-01-01

383

Selection of low cost materials for the sorption of copper and herbicides as single or mixed compounds in increasing complexity matrices.  

PubMed

Low cost materials (sugar beet pulp, corncob, corncob char, perlite, vermiculite, sand, sediment) have been tested for their ability to quickly sorb copper, glyphosate, diuron and 3,4-dichloroaniline (3,4-DCA) as single or mixed compounds. Tests have been performed in increasingly complex liquid matrices: ultra pure water (UPW), runoff water (RW) and sediment extract medium (SEM). Highest sorption levels in UPW are achieved with corncob char for Cu (93%), glyphosate (74%), diuron (98%) and 3,4-DCA (99%). Other ready-to-use adequate sorbents are sugar beet pulp for Cu and sand for glyphosate, diuron and 3,4-DCA. Sorption levels obtained in UPW are significantly altered in SEM as a result of its higher dissolved organic carbon concentration, tenuous changes being obtained with RW. Interactions between herbicides and Cu are pointed out: higher sorption level is observed for glyphosate in mixture with Cu, as it is observed with diuron and 3,4-DCA when mixed with all other pollutants. Langmuir model has been found to better fit the data for copper, whereas Freundlich one has been found more relevant for diuron and 3,4-DCA. Our results stress the need for studying adsorption in different matrices when searching for sorbents to be used in field conditions. PMID:20594640

Huguenot, David; Bois, Paul; Jézéquel, Karine; Cornu, Jean-Yves; Lebeau, Thierry

2010-10-15

384

Increased Survivorship and Altered Cytokine Profile from Treatment of Influenza A H1N1-Infected Mice with Ekybion: A Drug Complex of Natural Extracts and Inorganic Compounds  

PubMed Central

Ekybion is a drug complex of 16 natural extracts and inorganic compounds designed to treat a variety of respiratory pathogens of bacterial and viral origin. It is licensed throughout Europe for the treatment of respiratory tract infections from equine parainfluenza type 3 and equine herpes virus type 1 in equine stables. The purpose of this paper was to test the efficacy of Ekybion on a well-developed animal model of influenza A infection and determine a mode of action. Experiments were performed with Balb/c mice infected with a lethal dose of influenza A/PR/8/34 H1N1 virus and treated with nebulized Ekybion every 8?h in a time-dependant or dose-dependant fashion. These experiments showed that mice treated prior to infection with Ekybion had a higher survival rates (~46%) compared with untreated animals (~0%). Paradoxically, these mice showed no significant difference in lung virus titer or weight loss. There was, however, a decrease in the level of GM-CSF, IL-6, and G-CSF cytokines in the lungs of Ekybion-treated, infected mice. It is possible that decreases in proinflammatory cytokines may have contributed to increased survivorship in Ekybion-treated influenza-infected mice. PMID:20981272

Lupfer, Christopher; Besnouin, Didier; Tepper, Samuel E.; Maselko, Maciej; Patton, Kristin M.; Pastey, Manoj

2011-01-01

385

PILOT STUDY ON INTERNATIONAL EXCHANGE ON DIOXINS AND RELATED COMPOUNDS - SCIENTIFIC BASIS FOR THE DEVELOPMENT OF THE INTERNATIONAL METHOD OF RISK ASSESSMENT FOR COMPLEX MIXTURE OF DIOXINS AND RELATED COMPOUNDS  

EPA Science Inventory

The Pilot Study on International Information Exchange on Dioxins and Related Compounds was initiated to apply the cooperative efforts of several nations to address issues associated with PCDDs, PCDFs, and related compounds. he three-year study was conducted under the CCMS of NATO...

386

LJournal of Alloys and Compounds 326 (2001) 166173 www.elsevier.com/locate/jallcom  

E-print Network

, the hyperfine field B at thehf 57 ¨respective magnetic moments generally order magnetically Fe nuclei a magnetic6 6 moment, the magnetic ordering processes of the R and Fe Intermetallic compounds which contain Independent magnetic ordering of the rare-earth (R) and Fe sublattices in the RFe Ge and RFe Sn series6 6 6 6

Ryan, Dominic

387

JOURNAL DE PHYSIQUE Colloque C5, supplment au n 5, Tome 40, Mai 1979, page C5-286 Hydrogen storage properties and characteristics of rare earth compounds  

E-print Network

storage properties and characteristics of rare earth compounds C. E. Lundin Denver Research Institute. -- The characteristics of rare earth intermetallic compounds that absorb sufficient hydrogen to be of interest for energy. Industrial participation is beginning to emerge and shows good potential for expansion. The rare earth

Paris-Sud XI, Université de

388

Magnetovolume effects of Y–Fe–Co–Ti intermetallics  

Microsoft Academic Search

Thermal expansion and magnetic properties of the YFe11?xCoxTi compounds have been investigated by various experimental methods. A large magnetovolume effect has been clearly observed below TC for the Fe-rich compounds. When the transition metal concentration changes from Fe to Co rich, the invar-like effect becomes less pronounced and almost disappears close to the pure-Co compound. The dependence of the spontaneous

J. L. Wang; M. R. Ibarra; C. Marquina; B. Garc?´a-Landa; O. Tegus; Qunfeng Xiao; F. M. Yang; G. H. Wu

2002-01-01

389

Complementing approaches to demonstrate chlorinated solvent biodegradation in a complex pollution plume: Mass balance, PCR and compound-specific stable isotope analysis  

NASA Astrophysics Data System (ADS)

This work describes the use of different complementing methods (mass balance, polymerase chain reaction assays and compound-specific stable isotope analysis) to demonstrate the existence and effectiveness of biodegradation of chlorinated solvents in an alluvial aquifer. The solvent-contaminated site is an old chemical factory located in an alluvial plain in France. As most of the chlorinated contaminants currently found in the groundwater at this site were produced by local industries at various times in the past, it is not enough to analyze chlorinated solvent concentrations along a flow path to convincingly demonstrate biodegradation. Moreover, only a few data were initially available to characterize the geochemical conditions at this site, which were apparently complex at the source zone due to (i) the presence of a steady oxygen supply to the groundwater by irrigation canal losses and river infiltration and (ii) an alkaline pH higher than 10 due to former underground lime disposal. A demonstration of the existence of biodegradation processes was however required by the regulatory authority within a timeframe that did not allow a full geochemical characterization of such a complex site. Thus a combination of different fast methods was used to obtain a proof of the biodegradation occurrence. First, a mass balance analysis was performed which revealed the existence of a strong natural attenuation process (biodegradation, volatilization or dilution), despite the huge uncertainty on these calculations. Second, a good agreement was found between carbon isotopic measurements and PCR assays (based on 16S RNA gene sequences and functional genes), which clearly indicated reductive dechlorination of different hydrocarbons (Tetrachloroethene—PCE-, Trichloroethene—TCE-, 1,2- cisDichloroethene— cis-1,2-DCE-, 1,2- transDichloroethene— trans-1,2-DCE-, 1,1-Dichloroethene—1,1-DCE-, and Vinyl Chloride—VC) to ethene. According to these carbon isotope measurements, although TCE biodegradation seems to occur only in the upgradient part of the studied zone, DCE and VC dechlorination (originating from the initial TCE dechlorination) occurs along the entire flowpath. TCE reductase was not detected among the Dehalococcoides bacteria identified by quantitative PCR (qPCR), while DCE and VC reductases were present in the majority of the population. Reverse transcriptase PCR assays (rt-PCR) also indicated that bacteria and their DCE and VC reductases were active. Mass balance calculations showed moreover that 1,1-DCE was the predominant DCE isomer produced by TCE dechlorination in the upgradient part of the site. Consequently, coupling rt-PCR assays with isotope measurements removes the uncertainties inherent in a simple mass balance approach, so that when the three methods are used jointly, they allow the identification and quantification of natural biodegradation, even under apparently complex geochemical and hydraulic conditions.

Courbet, Christelle; Rivière, Agnès; Jeannottat, Simon; Rinaldi, Sandro; Hunkeler, Daniel; Bendjoudi, Hocine; de Marsily, Ghislain

2011-11-01

390

Study on the Formation and Characterization of the Intermetallics in Friction Stir Welding of Aluminum Alloy to Coated Steel Sheet Lap Joint  

NASA Astrophysics Data System (ADS)

Multimaterial fabrication such as joining of steel and aluminum is currently prominent in a variety of industries. Friction stir welding is a novel solid-state welding process that causes good joint strength between steel and aluminum. However, the phenomenon contributing significant strength at the interface is not yet clear. In the present study, the interface of the friction stir lap-welded aluminum and coated steel sheet having joint strength maximum (71.4 pct of steel base metal) and minimum, respectively, under two parameter combinations, i.e., 1000 rpm 50 mm min-1 and 500 rpm 100 mm min-1, was exclusively characterized by X-ray diffraction, transmission electron microscopy (TEM), concentration profile, and elemental mapping by electron-probe microanalysis. A TEM-assisted EDS study identifies the morphologies of large size Al13Fe4 and small size Fe3Al-type intermetallic compounds at the interface. The diffusion-induced intermetallic growth (thickness) measured from a backscattered image and concentration profile agreed well with the numerically calculated one. The growth of these two phases at 1000 rpm 50 mm min-1 is attributed to the slower cooling rate (~3.5 K/s) with higher diffusion time (44 seconds) along the interface in comparison to the same for 500 rpm 100 mm min-1 with faster cooling rate (~10 K/s) and less diffusion time (13.6 seconds). The formation of thermodynamically stable and hard intermetallic phase Al13Fe4 at 1000 rpm and travel speed 50 mm min-1 in amounts higher than 500 rpm and a travel speed of 100 mm min-1 results in better joint strength, i.e., 71.4 pct, of the steel base metal.

Das, H.; Ghosh, R. N.; Pal, T. K.

2014-10-01

391

Modeling non-isothermal intermetallic layer growth in the 63Sn-37Pb/Cu system  

SciTech Connect

A model describing diffusion-controlled growth of multiple intermetallic layers and the displacement of the interfaces between layers was developed and implemented in a 1-D computer code based on method-of-lines. The code was applied to analysis of intermetallic layer growth in isothermal solder aging experiments performed with 100 Sn/Cu and 63Sn-37Pb/Cu solder-substrate systems. Analyses indicated that intermetallic layer growth was consistent with a bulk diffusion mechanism involving Cu and/or Sn. In this work, nonisothermal solder-aging experiments were done with the 63Sn- 37Pb/Cu system using two temperature histories (4 cycles/day between 223-443 K, and 72 cycles/day between 223-443 K). Isothermal experiments were also done at 443 K. Thickness of Cu{sub 3}Sn and Cu{sub 6}Sn{sub 5} intermetallic layers were determined vs time for each temperature history. An updated version of the model and code were used to predict the intermetallic layer growth. Arrhenius expressions for diffusion coefficients in both Cu3Sn and Cu6Sn5 layers were determined. Agreement between prediction and experiment was generally good. In some cases, predicted layer growth was less than experiment, but within error. This paper describes the nonisothermal experiments and a comparison of predicted and observed layer growth vs time.

Vianco, P.T.; Hopkins, P.L.; Erickson, K.L.; Frear, D.R.; Davidson, R.

1996-12-31

392

An MHD heat source based on intermetallic reactions  

SciTech Connect

The main objective of this program was the development of an MHD heat source of potential use in Space - Based Multi Megawatt, MHD Power Systems. The approach is based on extension of high temperature chemical/ion release technology developed by the General Sciences, Incorporated (GSI) team and successfully applied in other Space Applications. Solid state reactions have been identified which can deliver energy densities and electrons in excess of those from high energy explosives as well as other conventional fuels. The use of intermetallic reactions can be used to generate hot hydrogen plasma from the reaction, to create a high level of seedant ionization, can be packaged as a cartridge type fuels for discrete pulses. The estimated weight for energizing a (100 MW - 1000 sec) Pulsed MHD Power System can range from 12 to 25 {times} 10{sup 3} kg depending on reaction system and strength of the magnetic field. The program consisted of two major tasks with eight subtasks designed to systematically evaluate these concepts in order to reduce fuel weight requirements. Laboratory measurements on energy release, reaction product identification and levels of ionization were conducted in the first task to screen candidate fuels. The second task addressed the development of a reaction chamber in which conductivity, temperature and pressure were measured. Instrumentation was developed to measure these parameters under high temperature pulsed conditions in addition to computer programs to reduce the raw data. Measurements were conducted at GSI laboratories for fuel weights of up to 120 grams and at the Franklin Research Center* for fuel weights up to 1 kilogram. The results indicate that fuel weight can be scaled using modular packaging. Estimates are presented for fuel weight requirements. 15 refs.

Sadjian, H.; Zavitsanos, P. (General Sciences, Inc., Souderton, PA (United States)); Marston, C.H. (Villanova Univ., PA (United States))

1991-05-06

393

Improvement of sensitivity to platinum compound with siRNA knockdown of upregulated genes in platinum complex-resistant ovarian cancer cells in vitro  

Microsoft Academic Search

It is known that some cancers show platinum complex resistance and that others show platinum complex sensitivity among ovarian cancers. Oxaliplatin (cis-[oxalato[trans-l-1, 2-diamino-cyclohexane] platinum[II

Hironobu Yanagie; Tomoyuki Hisa; Aya Ogata; Ayaka Miyazaki; Yasumasa Nonaka; Teturo Nishihira; Isao Osada; Takayuki Sairennji; Hirotaka Sugiyama; Yoshitaka Furuya; Yosinori Kidani; Shinichi Takamoto; Hiroyuki Takahashi; Masazumi Eriguchi

2009-01-01

394

Improvement of sensitivity to platinum compound with siRNA knockdown of upregulated genes in platinum complex-resistant ovarian cancer cells in vitro.  

PubMed

It is known that some cancers show platinum complex resistance and that others show platinum complex sensitivity among ovarian cancers. Oxaliplatin (cis-[oxalato[trans-l-1, 2-diamino-cyclohexane] platinum[II

Yanagie, Hironobu; Hisa, Tomoyuki; Ogata, Aya; Miyazaki, Ayaka; Nonaka, Yasumasa; Nishihira, Teturo; Osada, Isao; Sairennji, Takayuki; Sugiyama, Hirotaka; Furuya, Yoshitaka; Kidani, Yosinori; Takamoto, Shinichi; Takahashi, Hiroyuki; Eriguchi, Masazumi

2009-09-01

395

Superplasticity and hot rolling of two-phase intermetallic alloy based on TiAl  

SciTech Connect

The recent investigations of superplasticity (SP) in intermetallic alloys indicate that these materials exhibit lower indices of SP (the relative elongation to rupture) at high enough homologous temperatures and low strain rates compared to conventional alloys. This behavior inhibits application of SP effects in intermetallics. The results of two-phase titanium alloys indicate that the combination of a high stable microstructure with a submicron grain size is necessary to realize the effect of SP at relatively high strain rates. The aim of the present work is to examine the SP behavior of a Ti-46at.%Al intermetallic alloy (TiAl + Ti{sub 3}Al) with micro- and submicron grain sizes and to apply obtained results in hot rolling.

Imayev, R.; Shagiev, M.; Salishchev, G.; Imayev, V.; Valitov, V. [Russian Academy of Sciences, Ufa (Russian Federation). Inst. for Metals Superplasticity Problems] [Russian Academy of Sciences, Ufa (Russian Federation). Inst. for Metals Superplasticity Problems

1996-03-15

396

The Effect of In Situ Intermetallic Formation on Al-Sn Foaming Behavior  

NASA Astrophysics Data System (ADS)

The effect of in situ intermetallic formation on the foaming behavior of Al-3 wt pct Sn alloy has been investigated by introducing five different alloying elements—Co, Mg, Mn, Ni, and Ti. The alloying elements were designed, using thermodynamic calculations, to form various intermetallic phases which are (i) stable until final foaming temperature and (ii) dissolved during the foaming process. Thermal analysis using DSC was carried out to characterize the formation and dissolution of intermetallic phases during the foaming process. The foaming tests of the Al-3 wt pct Sn-X alloy were carried out using a mechanical expandometer and the macrostructure of the foam was scanned with an X-ray tomographer. It is found that the foaming behavior and foam stability of Al-3 wt pct Sn alloy can be actively controlled by the alloying elements.

Aguirre-Perales, Lydia Y.; Drew, Robin A. L.; Jung, In-Ho

2014-08-01

397

Method of treating intermetallic alloy hydrogenation/oxidation catalysts for improved impurity poisoning resistance, regeneration and increased activity  

DOEpatents

Alternate, successive high temperature oxidation and reduction treatments, in either order, of intermetallic alloy hydrogenation and intermetallic alloy oxidation catalysts unexpectedly improves the impurity poisoning resistance, regeneration capacity and/or activity of the catalysts. The particular alloy, and the final high temperature treatment given alloy (oxidation or reduction) will be chosen to correspond to the function of the catalyst (oxidation or hydrogenation).

Wright, Randy B. (Idaho Falls, ID)

1992-01-01

398

TEM ANALYSIS OF THE GROWTH OF OXIDE SCALES AT DIFFERENT TEMPERATURES IN FeAl GRADE 3 INTERMETALLIC ALLOY  

E-print Network

TEM ANALYSIS OF THE GROWTH OF OXIDE SCALES AT DIFFERENT TEMPERATURES IN FeAl GRADE 3 INTERMETALLIC)546457272, e-mail: fpedraza@univ-lr.fr Abstract Upon the isothermal oxidation of an ODS FeAl Grade 3 intermetallic alloy, a structured oxide scale is developed between 800 and 950º C. TEM studies have revealed

Paris-Sud XI, Université de

399

Special Features of the Correlation between the Uranium–Oxygen Interatomic Distances and the Frequencies of the Valence Vibrations of the UO 2 2+ Group in Complex Compounds of Uranyl  

Microsoft Academic Search

We considered the factors due to which the dependences between the uranium–oxygen distances R0 and the frequencies of valence vibrations ?as for complex compounds of uranyl are described by two independent expressions generally represented by equations of the type R0 = a + b?as-2\\/3 (b > 0) with the coefficients a and b differing in the regions R0 R0 >

V. V. Syt'ko; E. N. Kabaeva

2002-01-01

400

JOURNAL DE PHYSIQUE Colloque C5, supplment au n 5, Tome 40, Mai 1979, page C5-95 Magnetic structures of rare earth intermetallics  

E-print Network

structures of rare earth intermetallics J. Rossat-Mignod DRF/DN Centre d'Etudes Nucleaires-85X 38041 Grenoble variety of magnetic behaviours of rare earth intermetallics. Introduction. -- The aim of this paper is to give a general view of the magnetic structure work done so far concerning rare earth intermetallic

Paris-Sud XI, Université de

401

Intermetallic insertion electrodes with a zinc blende-type structure for Li batteries : a study of Li{sub x}InSb (0 {le} x {lt} 3).  

SciTech Connect

The intermetallic compound InSb with a zinc blende-type (diamond) structure has been investigated as a host structure for lithium. After one break-in cycle, it appears that lithium can be inserted electrochemically into the structure in a two-step process to the approximate composition Li{sub 2}InSb. X-ray diffraction analysis showed that further lithiation of Li{sub 2}InSb displaces In from the structure to yield a closely related Li{sub 3}Sb-type structure. The electrochemical reaction that occurs between 1.2 and 0.5 V is reversible. The cubic unit cell expands isotropically by only 5.6% upon Li insertion to the end member Li{sub 2+x}In{sub 1-x}Sb at x{approx}0.5. This finding has implications for developing commercially attractive intermetallic insertion electrodes with zinc blende-type structures for lithium-ion batteries.

Vaughey, J. T.; O'Hara, J.; Thackeray, M. M.; Chemical Engineering

2000-01-01

402

High-temperature oxidation of LnCu{sub 2} intermetallics and their catalytic behavior in 4-methyl-2-pentanol decomposition  

SciTech Connect

The air-oxidation of the intermetallic compounds LaCu{sub 2}, CeCu{sub 2}, PrCu{sub 2}, and NdCu{sub 2} was followed by thermogravimetry. The mass uptake occurred over a wide range of temperature (423-1100 K), leading to two stoichiometrics according to the lanthanide; CeCu{sub 2}O{sub 4} and LnCu{sub 2}O{sub 3.5} (Ln = La, Pr, Nd). The characterization by powder X-ray diffraction, scanning electron microscopy/energy dispersive X-ray analysis, and surface area measurements showed that segregation took place with the formation of CuO along with CeO{sub 2} or Ln{sub 2}CuO{sub 4} (Ln = La, Pr, Nd). Therefore, the oxidized intermetallics are better described by the formulas CeO{sub 2}{center_dot}2CuO and Ln{sub 2}CuO{sub 4}{center_dot}3CuO. The oxidation process noticeably increased the surface areas and promoted CuO migration to the surface. These systems exhibited selectivities in 4-methyl-2-pentanol decomposition, which are associated with the lanthanide. 34 refs., 4 figs., 3 tabs.

Ballivet-Tkatchenko, D.; Branco, J. [CNRS, Toulouse (France); Matos, A.P. de [INETI/ICEN, Sacavem (Portugal)

1995-04-13

403

Bonding in tris(. eta. sup 5 -cyclopentadienyl) actinide complexes. 5. A comparison of the bonding in Np, Pu, and transplutonium compounds with that in lanthanide compounds and a transition-metal analogue  

SciTech Connect

Cp{sub 3}An (An = U, Np, Pu, Am, Cm, Bk, Cf) compounds have been investigated via X{alpha}-SW molecular orbital calculations with quasi-relativistic corrections. The 5f-orbital energy drops across the series while the 6d-orbital energy rises. Due to the greater radial extension of the 6d orbitals, the metal 6d orbitals are more important in bonding the Cp ligands than the 5f orbitals. Comparison of the actinide compounds with the lanthanide series reveals some minor differences. The 4f orbitals and 6s orbital of the lanthanides are not as effective at bonding the Cp ligands as the 5f orbitals and 7s orbital of the actinides. Also, the semicore 5p orbitals of the lanthanides have a greater antibonding influence on the Cp ligands than do the 6p orbitals of the actinides. Comparison of the actinide compounds with ({eta}{sup 5}-Cp){sub 3}Zr shows some major differences. The 4d orbitals of zirconium are much more effective at bonding the Cp ligands than the 6d orbitals of the actinides.

Strittmatter, R.J.; Bursten, B.E. (Ohio State Univ., Columbus (USA))

1991-01-16

404

Exploratory Synthesis: The Fascinating and Diverse Chemistry of Polar Intermetallic Phases  

SciTech Connect

Exploratory synthetic adventures regarding the inorganic chemistry of polar intermetallic phases have proven to be especially productive of novel compositions, new and unprecedented structures, and unusual bonding regimes. Reactions of diverse elements with widely different electronegativities allow the definition of two opposed classes of products: polycationic or polyanionic clusters or networks of metals paired with the corresponding monatomic anions or cations. These can be usefully viewed as intermetallic 'salts', redox products of simpler neutral intermetallic systems but with widely different factors governing their stabilities. Thus, combinations of rare-earth metals alone or with late transition metals form a novel variety of polymetal network structures with relatively isolated telluride (or halide) spacer anions. Similarly, extensions of traditional Zintl phases of the alkali or alkaline-earth metals from the later p elements to the earlier triels, Ga-Tl especially, yield many new and elegant polyanionic structures. The substitution or addition of still earlier p or late d metal components produces still electron-poorer and more condensed polar intermetallic phases with increasingly delocalized bonding, higher coordination numbers, and more unusual structures and bonding. These discoveries have also led to new approaches: electronic tuning via band calculations to generate new families of quasicrystals and their crystalline approximants with their characteristic structural regimes and regularities. Gold as a substituent generates particularly novel bonding in arrays of mixed metals or polygold anionic networks.

Corbett, John D.

2009-12-07

405

OXIDATION MECHANISMS OF LOW ENERGY-HIGH FLUX NITRIDED ODS FeAl INTERMETALLIC ALLOY  

E-print Network

an argon atmosphere. Then, an artificial air (80% N2-20% O2) flow was let in the oxidising chamber for 24 h.- INTRODUCTION Upon the high temperature oxidation in air of TiAl intermetallic alloys, nitridation is observed diffusion layer containing AlN and a segregation of - Fe. The high temperature isothermal oxidation

Paris-Sud XI, Université de

406

FIB-SEM investigation of trapped intermetallic particles in anodic oxide films  

E-print Network

FIB-SEM investigation of trapped intermetallic particles in anodic oxide films on AA1050 aluminium. The anodic film subsequently was analyzed using focused ion beam-scanning electron microscopy (FIB-SEM), SEM and Si with two different structures: irregular and round shaped. FIB-SEM cross-sectioned images revealed

Dunin-Borkowski, Rafal E.

407

Crystal and Molecular Structures of a Tricyclic Phosphorus Ester, a Cobalt(III) Macrocyclic Complex and a Trans Coordinated Platinum(II) Compound.  

National Technical Information Service (NTIS)

The reaction chemistry and structurebonding features of some new hypercoordinate and strained non-metal compounds have been investigated. In an effort to create a species containing hypervalent phosphorus, 7-hydroxymethyl-4-phospha-3,5,9-trioxa-tricyclo u...

D. J. Wintergrass

1987-01-01

408

Bio-sensitive activities of coordination compounds containing 1,10-phenanthroline as co-ligand: Synthesis, structural elucidation and DNA binding properties of metal(II) complexes  

NASA Astrophysics Data System (ADS)

Present work reports the DNA binding and cleavage characteristics of a series of mixed-ligand complexes having the composition [M(L)(phen)2]Cl2 (where M = Cu(II), Ni(II), Co(II) and Zn(II) and phen as co-ligand) in detail. Their structural features and other properties have been deduced from their elemental analyses, magnetic susceptibility and molar conductivity as well as from IR, UV-Vis, 1H NMR and EPR spectral studies. The UV-Vis, magnetic susceptibility and EPR spectral data of metal complexes suggest an octahedral geometry. The binding properties of these complexes with calf thymus DNA (CT-DNA) have been explored using electronic absorption spectroscopy, viscosity measurement, cyclic voltammetry and differential pulse voltammetry. The DNA-binding constants for Cu(II), Ni(II), Co(II), and Zn(II) complexes are 6.14 × 105 M-1, 1.8 × 105 M-1, 6.7 × 104 M-1 and 2.5 × 104 M-1 respectively. Detailed analysis reveals that these complexes interact with DNA through intercalation binding. Nuclease activity has also been investigated by gel electrophoresis. Moreover, the synthesized Schiff base and its mixed-ligand complexes have been screened for antibacterial and antifungal activities. The data reveal that the complexes exhibit higher activity than the parent ligand.

Raman, Natarajan; Mahalakshmi, Rajkumar; Mitu, Liviu

2014-10-01

409

Intermetallic and metal-rich phases in the system Li-Ba-In-N  

NASA Astrophysics Data System (ADS)

Three new intermetallic phases, BaLi 2.1In 1.9, BaLi 1.12In 0.98, and BaLi 1.06In 1.16 and two subnitrides Li 35In 45Ba 39N 9 and LiIn 2Ba 3N 0.83 have been synthesized and their crystal structures have been determined. According to single crystal X-ray diffraction data BaLi 2.1In 1.9 and BaLi 1.12In 0.98 crystallize with hexagonal symmetry (BaLi 2.1In 1.9: P6 3/ mmc, a=10.410(2), c=8.364(2) Å, Z=6, V=785.0(2) Å 3) and BaLi 1.12In 0.98: P6/ mmm, a=17.469(1), c=10.6409(7) Å, Z=30, V=2813.5(8) Å 3), while BaLi 1.06In 1.16 has a rhombohedral structure ( R-3 c, a=18.894(3), c=85.289(17) Å, Z=276, V=26368(8) Å 3). BaLi 2.1In 1.9 is isostructural with the known phase BaLi 4. The phase BaLi 1.12In 0.98 is structurally related to Na 8K 23Cd 12In 48, while BaLi 1.06In 1.16 is isostructural with Li 33.3Ba 13.1Ca 3. A sample containing structurally similar BaLi 1.12In 0.98 and BaLi 1.02In 1.16 was also investigated by transmission electron microscopy. Li 35In 45Ba 39N 9 and LiIn 2Ba 3N 0.83 crystallize with tetragonal ( I-42 m, a=15.299(2), c=30.682(6) Å, Z=2, V=7182(2) Å 3) and cubic ( Fd-3 m, a=14.913(2) Å, Z=8, V=3316.7(7) Å 3) symmetry, respectively. While the first-mentioned subnitride belongs to the Li 80Ba 39N 9 structure type, the second extends the structural family of Ba 6In 4.78N 2.72. The structural features of the new compounds are discussed in comparison to the known phases and the results of total energy calculations.

Smetana, Volodymyr; Vajenine, Grigori V.; Kienle, Lorenz; Duppel, Viola; Simon, Arndt

2010-08-01

410

Creep of particle-reinforced NiAl intermetallics: New materials for up to 1400 {degree}C  

SciTech Connect

The intermetallic compound NiAl is a promising high temperature material as it possesses a favorable combination of advantageous properties (high melting point, low density, high thermal conductivity, good oxidation resistance). However its creep resistance is far inferior to that of advanced superalloys. The authors have developed new powder-metallurgical NiAl alloys, where the creep strength is raised by incorporating fine yttria dispersoids. The materials are produced by mechanical alloying and subsequent coarse-grain recrystallization at temperatures close to the solidus temperature. The resulting alloys show exceptional creep strength up to 1,400 C, thereby exceeding the temperature capability of superalloys significantly. The creep properties are in agreement with their recently developed model for ``detachment-controlled creep``, in which the release of dislocations from incoherent particles determines the creep rate. In addition, the brittleness problem at room temperature can be moderately alleviated by incorporating coarse ductile phases such as Mo. While the particles raise the critical stress intensity factor, they do not improve the room temperature tensile ductility.

Arzt, E.; Grahle, P. [Max-Planck-Institut fuer Metallforschung, Stuttgart (Germany); [Univ. of Stuttgart (Germany). Institut fuer Metallkunde

1995-08-01

411

Hydridoborylene complexes and di-, tri-, and tetranuclear borido complexes with hydride ligands.  

PubMed

Mono- and dinuclear hydridoborylene complexes were prepared by intermetallic borylene transfer from Group VI borylene or metalloborylene reagents. The hydride and borylene ligands were found to interact with each other significantly, although the boron ligand retains much of its former borylene character. Zero-valent platinum fragments were successively added to the dinuclear hydridoborylene complexes, resulting in tri- and tetranuclear borido complexes, in which the B-H interaction has been lost, and the hydride ligands now bridge two metal centers. The complexes were studied spectroscopically, crystallographically, and by DFT methods, and the unusual bonding situation in the M-B-H triangles of hydridoborylene complexes were evaluated. PMID:24218369

Bauer, Jürgen; Bertsch, Stefanie; Braunschweig, Holger; Dewhurst, Rian D; Ferkinghoff, Katharina; Hörl, Christian; Kraft, Katharina; Radacki, Krzysztof

2013-12-16

412

Temperature-dependent electron shuffle in molecular group?13/15 intermetallic complexes.  

PubMed

Monovalent RAl (R=HC[C(Me)N(2,6-iPr2 C6 H3 )]2 ) reacts with E2 Et4 (E=Sb, Bi) with insertion into the weak E?E bond and subsequent formation of RAl(EEt2 )2 (E=Sb 1; Bi 2). The analogous reactions of RGa with E2 Et4 yield a temperature-dependent equilibrium between RGa(EEt2 )2 (E=Sb 3; Bi 4) and the starting reagents. RIn does not interact with Sb2 Et4 under various reaction conditions, but formation of RIn(BiEt2 )2 (5) was observed in the reaction with Bi2 Et4 at low temperature. PMID:25196650

Ganesamoorthy, Chelladurai; Bläser, Dieter; Wölper, Christoph; Schulz, Stephan

2014-10-20

413

Proton-ionizable crown compounds. 1. Synthesis, complexation properties, and structural studies of macrocyclic polyether-diester ligands containing a triazole subcyclic unit  

SciTech Connect

A series of macrocyclic polyether-diester ligands containing a proton-ionizable triazole subcyclic unit has been prepared. The crystal structure of one ligand shows that it forms a hydrate with the water molecule located in the macrocyclic cavity. The water is coordinated by hydrogen bonding to two oxygen atoms of the macrocycle and to the NH group of the triazole moiety. These macrocycles also form complexes with amines. These amine complexes are kinetically more stable than complexes formed by the triazole ligands with the corresponding alkylammonium perchlorate salts. The crystal structure of one of these complexes shows that the triazole ring has donated a proton to the amine group. 41 references, 4 figures, 2 tables.

Bradshaw, J.S.; Chamberlin, D.A.; Harrison, P.E.; Wilson, B.E.; Arena, G.; Dalley, N.K.; Lamb, J.D.; Izatt, R.M.; Morin, F.G.; Grant, D.M.

1985-08-23

414

New coordination compounds of some rare-earth metal complexes with sulfur and nitrogen Schiff bases and their in vitro antibacterial and antifungal properties  

Microsoft Academic Search

A series of rare-earth metal complexes with Schiff bases have been prepared by the interactions of hydrated lanthanide(III) chloride with the sodium salts of 1-(2-thienyl)ethanone hydrazinecarbothioamide (LH) and 1-(2-thienyl)ethanonehydrazinecarboxamide (LH) in 1:3 molar ratios and characterized by their elemental analyses, molar conductance and IR, NMR (H and C) electronic and EPR spectral studies. The spectral data suggested that the complexes

Ritu Singh; Krishna Sharma; R. V. Singh

2010-01-01

415

Catalytic O2 evolution from water induced by adsorption of [OH2)(terpy)Mn(mu-O)2Mn(terpy)(OH2)]3+ complex onto clay compounds.  

PubMed

Water oxidation to evolve O2 in photosynthesis is catalyzed by an enzyme whose active site contains a mu-oxo-bridged manganese core. Catalytic O2 evolution has been difficult to establish by manganese-oxo complexes in homogeneous aqueous solutions. The reaction of [(OH2)(terpy)MnIII(mu-O)2MnIV(terpy)(OH2)]3+ (terpy = 2,2':6',2' '-terpyridine) (1) with a CeIV oxidant leads to the decomposition of 1 to the permanganate ion without O2 evolution in an aqueous solution but catalytically produces O2 from water when 1 is adsorbed on clay compounds. 18O-labeling experiments showed that the oxygen atoms in O2 originate exclusively from water. Catalysis of O2 evolution requires cooperation of 2 equiv of 1 adsorbed on clay compounds. PMID:15225027

Yagi, Masayuki; Narita, Komei

2004-07-01

416

Synthesis and characterisation of silver, zinc and cadmium compounds with an N 3O 2 Schiff base macrocycle: the crystal and molecular structures of the silver(I) and cadmium(II) complexes  

Microsoft Academic Search

The metal-templated cyclocondensation of 2,6-diformylpyridine and 1,4-bis(2-aminophenoxy)butane in the presence of silver(I), zinc(II) and cadmium(II) salts gave the following di-imine macrocyclic complexes: [AgL](ClO4) (1), [ZnL](ClO4)2·2H2O (2), [ZnL](NO3)2 (3), [CdL(H2O)2](ClO4)2 (4) and [CdL(NO3)(CH3OH)](NO3) (5) (L=macrocyclic ligand). All compounds have been characterised by microanalysis, IR, conductivity measurements, MS-FAB and 1H NMR spectroscopic studies. Compounds 1, 4 and 5 were also studied by

Laura Valencia; Harry Adams; Rufina Bastida; David E Fenton; Alejandro Mac??as

2001-01-01

417

Compound Interest  

NSDL National Science Digital Library

Albert Einstein called compound interest the 8th wonder of the world. Find out why compound interest and the time value of money are so important. What is Interest Click on the following link to read about the different types of interest. Loans and Interest So why learn about compound interest? Using time and interest to your advantage, you can make more money than you have ever dreamed of. See how the time value of ...

Riches, Ms.

2007-10-16

418

Coordination compounds in medicinal chemistry  

Microsoft Academic Search

In medicinal chemistry metal complexes as pharmaceuticals have received limited attention compared with organic compounds. Much of the attention has been given to Pt(II) complexes that inhibit tumor growth, but a widely applicable target for development of metal complexes as pharmaceuticals has emerged from new perspectives of enzymes in disease processes. In this review we look at work involving the

Chad W. Schwietert; John P. McCue

1999-01-01

419

Reactions of aromatic nitro-compounds. LV. Anionic sigma-complexes of sym-trinitrobenzene with the alkoxides of dihydric alcohols  

SciTech Connect

The reactions of alkoxides of dihydric alcohols with 2,4,6-trinitroanisole and picryl chloride have been studied. The reaction between 2,4,6-trinitroanisole and sodium 2-hydroxyethoxide, 3-hydroxypropoxide, 4-hydroxybutoxide, and 2-methoxyethoxide gives the unsymmetrical 1-methoxy-1-hydroxyalkoxy-2,4,6-trinitrocyclohexa-2,5-dienate sigma-complexes, which are converted on heating into the 1,1-dihydroxyalkoxy-2,4-6-trinitrocyclohexa-2,5-dienate sigma-complexes. In the case of sodium 1-methoxy-1-(..beta..-hydroxyethoxy)-2,4,6-trinitrocyclohexa-2,5-dienate, heating results in intramolecular spirocyclization of the ..beta..-hydroxyethoxy grouping to give sodium 6,8,10-trinitro-1,4-dioxaspiro(4,5)deca-6,9-dienate. The reaction of sodium 3-hydroxy-propoxide, 4-hydroxybutoxide, 2-methoxyethoxide, and diethyleneglycolate with picryl chloride gives the symmetrical 1,1-dihyroxyalkoxy sigma-complexes, while sodium 2-hydroxyethoxide forms a sigma-complex with a 1,3-dioxolane spiro-ring. The composition and structures of the sigma-complexes, isolated as their sodium salts, were established by their elemental analyses and PMR and IR spectroscopy.

Mel'nikov, A.I.; Gitis, S.S.; Kaminskii, A.Ya.

1986-12-20

420

Structural studies on copper(II) complex containing (Z)-2-(2-Aminothiazol-4-yl)- N-(2-hydroxyethyl)-2-(hydroxyimino) acetamide, A model compound for a cephalosporin antibiotic cefdinir  

Microsoft Academic Search

(Z)-2-(2-aminothiazol-4-yl)-N-(2-hydroxyethyl)-2-(hydroxyimino)acetamide (HL) has been employed as a model compound for an orally active cephalosporin antibiotic, Cefdinir (CFDN). A binuclear copper(II) complex Cu2L4 (1) has been obtained from an aqueous solution containing CuCl2 and HL, and its structure determined by means of X-ray crystallography: monoclinic, P2\\/c, a = 11.954(3) A?, b = 10.661(3) A?, c = 16.969(7) A?, ? = 108.13(3)°,

Shuhei Deguchi; Yayoi Shihahara; Marie T. Mooney; Kyoko Yamamoto; Toshiji Tada; Mamoru Fujioka; Yoshihiko Okamoto; Tsutomu Yasuda; Shinnichiro Suzuki

1997-01-01

421

Involvement of 5f-orbitals in the bonding and reactivity of organoactinide compounds: thorium(IV) and uranium(IV) bis (hydrazonato) complexes  

SciTech Connect

Migratory insertion of diphenyldiazomethane into both metal-carbon bonds of the bis(alkyl) and bis(aryl) complexes (C5Me5)2AnR2 yields the first f-element bis(hydrazonato) complexes (C5Me5)2An[2-(N,N')-R-N-NCPh2]2 [An = Th, R = CH3 (18), PhCH2 (15), Ph (16); An = U, R = CH3 (17), PhCH2 (14)], which have been characterized by a combination of spectroscopy, electrochemistry, and X-ray crystallography. The two hydrazonato ligands adopt an 2-coordination mode leading to 20-electron (for Th) and 22-electron (for U) complexes that have no transition-metal analogues. In fact, reaction of (C5H5)2Zr(CH3)2 or (C5Me5)2Hf(CH3)2 with diphenyldiazomethane is limited to the formation of the corresponding mono(hydrazonato) complex (C5R5)2M[2-(N,N')-CH3-N-NCPh2](CH3) (M = Zr, R = H or M = Hf, R = CH3). The difference in the reactivities of the group 4 metal complexes and the actinides was used as a unique platform for investigating in depth the role of 5f orbitals on the reactivity and bonding in actinide organometallic complexes. The electronic structure of the (C5H5)2M[2-(N,N')-CH3-N-NCH2]2 (M = Zr, Th, U) model complexes was studied using density functional theory (DFT) calculations and compared to experimental structural, electrochemical, and spectroscopic results. Whereas transition-metal bis(cyclopentadienyl) complexes are known to stabilize three ligands in the metallocene girdle to form saturated (C5H5)2ML3 species, in a bis(hydrazonato) system, a fourth ligand is coordinated to the metal center to give (C5H5)2ML4. DFT calculations have shown that 5f orbitals in the actinide complexes play a crucial role in stabilizing this fourth ligand by stabilizing both the s and p electrons of the two 2-coordinated hydrazonato ligands. In contrast, the stabilization of the hydrazonato ligands was found to be significantly less effective for the putative bis(hydrazonato) zirconium(IV) complex, yielding a higher energy structure. However, the difference in the reactivities of the group 4 metal and actinide complexes does not arise on thermodynamic grounds but is primarily of kinetic origin. Unfavorable steric factors have been ruled out as the sole influence to explain these different behaviors, and electronic factors were shown to govern the reactivity. For the actinides, both the C5H5 and more realistic C5Me5 ligands have been taken into account in computing the energy surface. The reaction profile for the C5Me5 system differs from that with the C5H5 ligand by a uniform shift of 5 kcal/mol in the relative energies of the transition state and products. The insertion of a second diazoalkane molecule into the sole metal-carbon bond in the mono(hydrazonato) complexes involves a high energy barrier (20 kcal/mol) for the zirconium(IV) system, whereas the actinides can facilitate the approach of the diazoalkane by coordination (formation of an adduct) and its insertion into the An-C bond with a very low barrier on the potential energy surface.

Cantat, Thibault [Los Alamos National Laboratory; Graves, Christopher R [Los Alamos National Laboratory; Morris, David E [Los Alamos National Laboratory; Kiplinger, Jaquel