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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, Jrgen; Kraj?, Marian

2014-11-18

2

Hydrides of intermetallic compounds  

Microsoft Academic Search

sAspects of the progress over the recent years on hydrides of intermetallic compounds are reviewed with emphasis on structure,\\u000a stability, solid-state properties, catalysis, and kinetics. Some new routes to an understanding of hydride phenomenology are\\u000a indicated. Generally speaking hydrides represent but one special aspect of intermetallic compounds. They are, however, unique\\u000a as model systems for questions concerning the stability of

H. Oesterreicher

1981-01-01

3

Making NiTi intermetallic compound coating using laser plasma complex spraying  

SciTech Connect

To improve the erosion resistance of the Ti-alloys, surface modification technique using complex spraying system coupled with a high power CO{sub 2} laser and a DC plasma gun was applied. The laser plasma complex spraying system (LPCS) was constructed with 5kW CO{sub 2} laser and low pressure DC plasma spraying unit. In this system, the plasma spray coated layer was remelted and rapidly solidified by the CO{sub 2} laser irradiation. So, it is possible to synthesize intermetallic compound coatings from the simply mixed powder. NiTi intermetallic compound is known as a high cavitation erosion resistant material. In a case of only plasma spraying process, Ti and Ni layer were separated mutually in the coatings, but by the laser plasma complex spraying, NiTi, NiTi{sub 2}, and Ni{sub 3}Ti intermetallic compounds were formed in the coatings. And the coatings were joined metallurgically with substrate and contained few defect. The ratio of phases such as NiTi, NiTi{sub 2}, and Ni{sub 3}Ti was varied with the laser irradiation conditions and powder mixed ratio. To evaluate the erosion resistance of the coatings, vibratory cavitation erosion tests were carried out. The cavitation erosion resistance of the coatings were about 20 times as much as Ti6Al4V substrate due to NiTi phase.

Hiraga, Hitoshi; Inoue, Takashi [Applied Laser Engineering Research Institute, Niigata (Japan); Matsunawa, Akira [Osaka Univ. (Japan)

1996-12-31

4

Exploring the structural complexity of intermetallic compounds by an adaptive genetic algorithm.  

PubMed

Solving the crystal structures of novel phases with nanoscale dimensions resulting from rapid quenching is difficult due to disorder and competing polymorphic phases. Advances in computer speed and algorithm sophistication have now made it feasible to predict the crystal structure of an unknown phase without any assumptions on the Bravais lattice type, atom basis, or unit cell dimensions, providing a novel approach to aid experiments in exploring complex materials with nanoscale grains. This approach is demonstrated by solving a long-standing puzzle in the complex crystal structures of the orthorhombic, rhombohedral, and hexagonal polymorphs close to the Zr2Co11 intermetallic compound. From our calculations, we identified the hard magnetic phase and the origin of high coercivity in this compound, thus guiding further development of these materials for use as high performance permanent magnets without rare-earth elements. PMID:24580466

Zhao, X; Nguyen, M C; Zhang, W Y; Wang, C Z; Kramer, M J; Sellmyer, D J; Li, X Z; Zhang, F; Ke, L Q; Antropov, V P; Ho, K M

2014-01-31

5

Intermetallic rare-earth compounds  

Microsoft Academic Search

The physical properties of many of the rare-earth intermetallic compounds have been collected together. They are discussed in terms of the role that the magnetic exchange and crystal field interactions play in determining these properties. It is pointed out that in this vast number of materials there is an ideal chance of establishing which of several second-order terms are effective

K. N. R. Taylor; K. N. R

1971-01-01

6

NUCLEAR ORIENTATION EXPERIMENTS ON CERIUM INTERMETALLIC COMPOUNDS  

E-print Network

L-63 NUCLEAR ORIENTATION EXPERIMENTS ON CERIUM INTERMETALLIC COMPOUNDS A. BENOIT, J. FLOUQUET, M.O. experiments in other Ce intermetallic compounds in order to deter- mine at very low temperatures by melting a small amount of radioactive LaCe alloys with the constituents of the intermetallic compound

Paris-Sud XI, Université de

7

Some statistics on intermetallic compounds.  

PubMed

It is still largely unknown why intermetallic phases show such a large variety of crystal structures, with unit cell sizes varying between 1 and more than 20?000 atoms. The goal of our study was, therefore, to get a general overview of the symmetries, unit cell sizes, stoichiometries, most frequent structure types, and their stability fields based on the Mendeleev numbers as ordering parameters. A total of 20829 structures crystallizing in 2166 structure types have been studied for this purpose. Thereby, the focus was on a subset of 6441 binary intermetallic compounds, which crystallize in 943 structure types. PMID:25470110

Dshemuchadse, Julia; Steurer, Walter

2015-02-01

8

Electrochemical synthesis of intermetallic compounds and complex carbides based on molybdenum (tungsten) and cobalt (nickel)  

Microsoft Academic Search

Systems for the joint electrodeposition of molybdenum (tungsten) and nickel(cobalt) from ionic melts have been identified. Conditions for depositing the intermetallics molybdenum(tungsten)-nickel(cobalt) and double carbides based on these were ascertained. It is shown that the process of electrochemical synthesis is determined, on the whole, by the ratio of partial currents of reacting components, energies of interaction between them, and the

I. A. Novoselova; V. V. Malyshev; Kh. B. Kushkhov; V. I. Shapoval

1996-01-01

9

Aberration-corrected electron microscopy of nanoparticles and intermetallic compounds  

E-print Network

Aberration-corrected electron microscopy of nanoparticles and intermetallic compounds M. Heggen for applications in energy-related catalysis, as well as novel intermetallic compounds, will be presented

Dunin-Borkowski, Rafal E.

10

Structure determination of intermetallic compounds using electron crystallography methods  

E-print Network

Structure determination of intermetallic compounds using electron crystallography methods Louisa and minerals were solved using PED technique. Until today structure of intermetallic compounds was never solved oxides, since #12;for intermetallics no strict constrains on coordination polyhedra, interatomic

Vardi, Amichay

11

New method for computer analysis of complex intermetallic compounds and nanocluster model of the samson phase Cd{sub 3}Cu{sub 4}  

SciTech Connect

A new method is proposed for the computer analysis of crystal structures of complex intermetallic compounds (with more than 1000 atoms per unit cell) using a developed algorithm of the complete decomposition of the 3D graph of the structure into nanocluster substructures. This method has been implemented in the TOPOS software package and approved successfully in an analysis of the complex Cu{sub 3}Cd{sub 4} structure (Samson phase). Cu{sub 3}Cd{sub 4} structure models were used to establish a structural relationship between nanoclusters in this intermetallic compound and nanoclusters in other complex crystal structures: ZrZn{sub 22}, Ru{sub 7}Mg{sub 44}, NaCd{sub 2}, and Mg{sub 2}Al{sub 3}.

Blatov, V. A., E-mail: blatov@ssu.samara.ru [Samara State University (Russian Federation); Ilyushin, G. D., E-mail: ilyushin@ns.crys.ras.ru [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

2010-12-15

12

Anisotropies in Quaternary Intermetallic Compounds  

NASA Astrophysics Data System (ADS)

From the high-temperature series expansion of magnetic susceptibilities and the anisotropic Weiss temperatures, the first Steven's parameter, B2^0 , and the magnetic exchange interaction constant Jex^ll of each R^=3 ions magnetic sublattice in quaternary intermetallic compounds, RNi2B2C B(R= Tm, Er, Ho, Dy, and Tb) were obtained. The R =Dy system shows the biggest B2^0 value and the R = Tb system does the smallest one. Also we have measured and analyzed the anisotropic M(H) isotherms as a function of applied magnetic fields for H perpendicular and parallel to the c-axis for each compounds to check out our crystalline electric field (CEF) results obtained from the previous mentioned method by using the anisotropic Weiss temperatures. It turned out that most of the temperature dependence of magnetization curve M (T) for H perpendicular the c-axis at low temperature comes from the temperature dependent population of the singlet ground state in group L among groups L(low-lying levels of ground states), H(high levels of ground states), and M(first excited states).

Lee, W. C.

2008-03-01

13

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

14

Crystal structure analysis of intermetallic compounds  

NASA Technical Reports Server (NTRS)

Study concerns crystal structures and lattice parameters for a number of new intermetallic compounds. Crystal structure data have been collected on equiatomic compounds, formed between an element of the Sc, Ti, V, or Cr group and an element of the Co or Ni group. The data, obtained by conventional methods, are presented in an easily usable tabular form.

Conner, R. A., Jr.; Downey, J. W.; Dwight, A. E.

1968-01-01

15

Oxygen stabilized zirconium vanadium intermetallic compound  

DOEpatents

An oxygen stabilized intermetallic compound having the formula Zr.sub.x OV.sub.y where x=0.7 to 2.0 and y=0.18 to 0.33. The compound is capable of reversibly sorbing hydrogen at temperatures from -196.degree. C. to 450.degree. C. at pressures down to 10.sup.-6 Torr. The compound is also capable of selectively sorbing hydrogen from gaseous mixtures in the presence of CO and CO.sub.2.

Mendelsohn, Marshall H. (Woodridge, IL); Gruen, Dieter M. (Downers Grove, IL)

1982-01-01

16

THERMAL EXPANSION OF SEVERAL Sn-BASED INTERMETALLIC COMPOUNDS  

Microsoft Academic Search

When two metals are joined by solder, the joining interface undergoes a reaction to yield one or more intermetallic layers. Intermetallic compounds can also grow at the interface of the solder and the substrate during storage (1) at ambient temperatures. While the presence of intermetallic compounds is an indication that a good metallurgical bond has formed, these compounds are often

Nan Jiang; J. A. Clum; R. R. Chromik; E. J. Cotts

1997-01-01

17

Growth of New Intermetallic Compounds from Aluminum Flux  

E-print Network

Growth of New Intermetallic Compounds from Aluminum Flux Susan E. Latturner Department of Chemistry;Intermetallic Compounds Combination of two or more metallic or semimetallic elements -- a range of materials Michigan State University Intermetallics Molten metals as solvents for crystal growth RE[AuAl2]nAl2(AuxSi1

Kanatzidis, Mercouri G

18

SYNTHESIS AND CHARACTERIZATION OF NEW INTERMETALLIC COMPOUNDS  

SciTech Connect

This six-month work is focused mainly on the properties of novel magnetic intermetallics. In the first project, we synthesized several 2:17 intermetallic compounds, namely Nd{sub 2}Fe{sub 15}Si{sub 2}, Nd{sub 2}Fe{sub 15}Al{sub 2}2, Nd{sub 2}Fe{sub 15}SiAl and Nd{sub 2}Fe{sub 15}SiMn, as well as several 1:12 intermetallic compounds, such as NdFe{sub 10}Si{sub 2}, NdFe{sub 10}Al{sub 2}, NdFe{sub 10}SiAl and NdFe{sub 10}MnAl. In the second project, seven compositions of Nd{sub x}Fe{sub 100-x-y}B{sub y} ribbons were prepared by a melt spinning method with Nd and B content increasing from 7.3 and 3.6 to 11 and 6, respectively. The alloys were annealed under optimized conditions to obtain a composite material consisting of the hard magnetic Nd{sub 2}Fe{sub 14}B and soft magnetic {alpha}-Fe phases, typical of a spring magnet structure. In the third project, intermetallic compounds of the type Zr{sub 1}Cr{sub 1}Fe{sub 1}T{sub 0.8} with T=Al, Co and Fe were subjected to hydrogenation. In the fourth project, we performed three crucial experiments. In the first experiment, we subjected a mixture of Fe{sub 3}O{sub 4} and Fe(80-20 wt%) to mechanochemical activation by high-energy ball milling, for time periods ranging from 0.5 to 14 hours. In the second experiment, we ball-milled Fe{sub 3}O{sub 4}:Co{sup 2+} (x=0.1) for time intervals between 2.5 and 17.5 hours. Finally, we exposed a mixture of Fe{sub 3}O{sub 4} and Co(80-20 wt%) to mechanochemical activation for time periods ranging from 0.5 to 10 hours. In all cases, the structural and magnetic properties of the systems involved were elucidated by X-ray diffraction (XRD), Moessbauer spectroscopy and hysteresis loop measurements. The four projects resulted in four papers, which are currently being considered for publication in Intermetallics, IEEE Transactions on Magnetics, Journal of Materials Science Letters and Journal of Materials Science. The contributions reveal for the first time in literature the effect of substitutions on the hyperfine magnetic field of neodymium-based intermetallics, the correlation between structure and magnetic properties in spring magnets, the unique effects induced by hydrogenation on the hyperfine parameters of iron-rich intermetallics and the characteristics of the ball milling process in systems containing magnetite.

Professor Monica Sorescu

2003-05-07

19

Mechanism of Diffusion in Intermetallic Compounds  

NASA Astrophysics Data System (ADS)

In a previous paper appearing in this journal (Tiwari and Mehrotra, Metall. Mater. Trans. A, vol. 43A, 2012, pp. 3654-62), the present authors advanced the hypothesis that the six-jump vacancy cycle, triple-defect mechanism, and antistructure bridge mechanism cannot explain the incidence of Kirkendall effect in B2 intermetallic compounds and hence their suitability as the operative mode of diffusion in these systems rests on dubious foundation. In the preceding contribution, Belova and Murch (BM) contested our hypothesis. This article is a reply to the BM's critique of our paper.

Tiwari, G. P.; Mehrotra, R. S.

2013-10-01

20

Intermetallic compound layer growth by solid state reactions between 58Bi42Sn solder and copper  

Microsoft Academic Search

Solid state intermetallic compound layer growth was examined following ther-mal aging of the 58Bi-42Sn\\/Cu couple for a temperature\\u000a range of 55 to 120C and time periods of from 1 to 400 days. The intermetallic compound layer was comprised of sublayers that\\u000a included the traditional Cu6Sn5 stoichiometry as well as one or more complex Cu-Sn-Bi chemistries. The number of sublayers increased

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

1995-01-01

21

Driving magnetostructural transitions in layered intermetallic compounds.  

PubMed

We report the dramatic effect of applied pressure and magnetic field on the layered intermetallic compound Pr(0.5)Y(0.5)Mn(2)Ge(2). 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 (T(C)(Pr)). 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 T(C)(Pr)) 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. PMID:23745927

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

2013-05-24

22

Interplay between bulk atomic clusters and surface structure in complex intermetallic compounds: The case study of the Al5Co2 (001 ) surface  

NASA Astrophysics Data System (ADS)

The Al5Co2 crystal is a complex intermetallic compound, whose structure can be described by a stacking of chemically bonded atomic motifs. It is a potentially new catalytic material for heterogeneous hydrogenation. A single crystal of this phase has been grown by the Czochralski technique in order to study the influence of the three-dimensional bulk substructure on the two-dimensional surface using both experimental ultrahigh vacuum surface techniques and ab initio methods based on the density functional theory. Some bulk properties are first presented, focusing on chemical bond strengths, the determination of the Al and Co chemical potentials in Al5Co2 , the vibrational properties, and the specific heat. Then, the combination of experimental and computational approaches allows the identification of the surface structure, which was found to depend on the surface preparation conditions. In all cases, the surface terminates at specific bulk layers (Al-rich puckered layers) where various fractions of specific sets of Al atoms are missing, identified as Al3 atoms left at the surface resulting from cluster truncation. Finally, electron density of states calculations and spectroscopic measurements were compared and indicate a strong s p -d hybridization of the topmost pure Al layer with subsurface Co atoms. This could influence the surface reactivity and the catalytic performances of this material.

Meier, M.; Ledieu, J.; De Weerd, M.-C.; Huang, Ying-Tzu; Abreu, G. J. P.; Pussi, K.; Diehl, R. D.; Mazet, T.; Fourne, V.; Gaudry, .

2015-02-01

23

Friction welding of TiAl intermetallic compound  

Microsoft Academic Search

Recent years have seen TiAl intermetallic alloy attracting research interest as a high specific strength intermetallic compound. Practical applications of TiAl, however, are complicated by the fact that the material shows little ductility at temperatures below 1000 K, features poor plastic workability even at temperatures above 1200 K, to say nothing of its performance at normal temperature, and cannot be

T. Shinoda; K. Ito; C. Hayashi

1997-01-01

24

First-principles studies of Al-Ni intermetallic compounds  

SciTech Connect

The structural properties, heats of formation, elastic properties, and electronic structures of Al-Ni intermetallic compounds are analyzed here in detail by using density functional theory. Higher calculated absolute values of heats of formation indicate a very strong chemical interaction between Al and Ni for all Al-Ni intermetallic compounds. According to the computational single crystal elastic constants, all the Al-Ni intermetallic compounds considered here are mechanically stable. The polycrystalline elastic modulus and Poisson's ratio have been deduced by using Voigt, Reuss, and Hill (VRH) approximations, and the calculated ratio of shear modulus to bulk modulus indicated that AlNi, Al{sub 3}Ni, AlNi{sub 3} and Al{sub 3}Ni{sub 5} compounds are ductile materials, but Al{sub 4}Ni{sub 3} and Al{sub 3}Ni{sub 2} are brittle materials. With increasing Ni concentration, the bulk modulus of Al-Ni intermetallic compounds increases in a linear manner. The electronic energy band structures confirm that all Al-Ni intermetallic compounds are conductors. - Graphical abstract: Calculated bulk modulus compared to experimental and other theoretical values for the Al-Ni intermetallic compounds.

Shi Dongmin [School of Materials Science and Engineering, Dalian University of Technology, Dalian 116023 (China); Wen Bin, E-mail: wenbin@dlut.edu.c [School of Materials Science and Engineering, Dalian University of Technology, Dalian 116023 (China); Melnik, Roderick [M2NeT Lab, Wilfrid Laurier University, Waterloo, 75 University Ave. West, Ontario, N2L 3C5 (Canada); Yao Shan; Li Tingju [School of Materials Science and Engineering, Dalian University of Technology, Dalian 116023 (China)

2009-10-15

25

Magnetic field controlled FZ single crystal growth of intermetallic compounds  

Microsoft Academic Search

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 solidliquid 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.

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

2005-01-01

26

Containerless automated processing of intermetallic compounds and composites  

NASA Technical Reports Server (NTRS)

An automated containerless processing system has been developed to directionally solidify high temperature materials, intermetallic compounds, and intermetallic/metallic composites. The system incorporates a wide range of ultra-high purity chemical processing conditions. The utilization of image processing for automated control negates the need for temperature measurements for process control. The list of recent systems that have been processed includes Cr, Mo, Mn, Nb, Ni, Ti, V, and Zr containing aluminides. Possible uses of the system, process control approaches, and properties and structures of recently processed intermetallics are reviewed.

Johnson, D. R.; Joslin, S. M.; Reviere, R. D.; Oliver, B. F.; Noebe, R. D.

1993-01-01

27

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

28

PAC Studies on Zr-Based Intermetallic Compounds  

NASA Astrophysics Data System (ADS)

The Zr2Al, Zr3Al2 and Zr6NiAl2 intermetallic compounds were characterized by means of time differential perturbed angular correlation (TDPAC) and X-ray diffraction. Our interest in these Zr(Hf) aluminides comes from crystallization studies of Zr(Hf)-based bulk metallic glasses which have a wide supercooled liquid region.

Damonte, L. C.; Mendoza-Zlis, L. A.

2004-11-01

29

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

30

First-principles studies of NiTa intermetallic compounds , Bin Wen b,n  

E-print Network

First-principles studies of Ni­Ta intermetallic compounds Yi Zhou a , Bin Wen b,n , Yunqing Ma properties, and electronic structures of Ni­Ta intermetallic compounds are investigated in detail based on density functional theory. Our results indicate that all Ni­Ta intermetallic compounds calculated here

Melnik, Roderick

31

MERLINERLIN a versatile optimization environment applied to the design of metallic alloys and intermetallic compounds  

E-print Network

and intermetallic compounds D.G. Papageorgiou a,*, I.E. Lagaris b , N.I. Papanicolaou c , G. Petsos d , H An important step in the design of alloys and intermetallic compounds using semi-empirical potentials is to de://merlin.cs.uoi.gr/. This was applied to study a particular class of intermetallic compounds and alloys, which are very interesting

Lagaris, Isaac

32

Structural and physical properties of the new intermetallic compound P. Solokha a  

E-print Network

Structural and physical properties of the new intermetallic compound Yb3Pd2Sn2 P. Solokha a , I t The crystal structure of the ternary intermetallic compound Yb3Pd2Sn2 has been determined ab initio from between this structure and those of Eu3Pd2Sn2 and Ca3Pd2Sn2, other novel polar intermetallic compounds

Ryan, Dominic

33

Prediction of stable insulating intermetallic compounds  

NASA Astrophysics Data System (ADS)

We explore the stability of structures exhibiting hybridization gaps across a broad range of binary and ternary intermetallic compositions by means of band structure and total energy calculations. This search reveals previously unknown metal-based insulators, some with large gaps exceeding 1 eV, such as Al2Fe and Al4IrRe. We confirm large gaps using a hybrid density functional including exact exchange, and predict a gap of 2.2 eV for AlMnSi in the Pearson type tP6 structure, which is a chemically ordered ternary variant of the prototype MoSi2 (Pearson type tI6) structure.

Mihalkovi?, M.; Kraj?, M.; Widom, M.

2013-03-01

34

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

35

Theory of the thermoelectricity of intermetallic compounds with Ce or Yb ions and R. Monnier2  

E-print Network

Theory of the thermoelectricity of intermetallic compounds with Ce or Yb ions V. Zlati1 and R received 19 January 2005; published 14 April 2005 The thermoelectric properties of intermetallic compounds and Yb intermetallics. Calculating the effect of pressure on various characteristic energy scales

Freericks, Jim

36

Oxygen-stabilized zirconium-vanadium intermetallic compound  

DOEpatents

An oxygen stabilized intermetallic compound having the formula Zr/sub x/OV/sub y/ where x = 0.7 to 2.0 and y = 0.18 to 0.33 is described. The compound is capable of reversibly sorbing hydrogen at temperatures from - 196/sup 0/C to 450/sup 0/C at pressures down to 10/sup -6/ Torr. The compound is also capable of selectively sorbing hydrogen from gaseous mixtures in the presence of CO and CO/sub 2/.

Mendelsohn, M.H.; Gruen, D.M.

1981-10-06

37

A review of rapid solidification studies of intermetallic compounds  

NASA Technical Reports Server (NTRS)

A review of rapid solidification studies of high-temperature ordered intermetallic compounds is presented. Emphasis is on the nickel - and iron- aluminides which are of potential interest as structural materials. The nickel-base aluminides which have been rapidly solidified exhibit changes in grain size, compositional segregation, and degree of long range order (as reflected in APB size and distribution) which markedly affect mechanical properties. Some experiments indicate the formation of a metastable L1(2) phase in rapidly solidified Fe-(Ni,Mn)-Al-C alloys, while other work observes only a metastable fcc phase in the same composition range. The metastable phases and/or microstructures in both nickel and iron aluminides are destroyed by annealing at temperatures above 750 K, with subsequent degradation of mechanical properties. Rapid solidification studies of several other intermetallic compounds are briefly noted.

Koch, C. C.

1985-01-01

38

Magnetism and superconductivity of uranium and intermetallic compounds  

SciTech Connect

Heat capacity, resistivity, and phonon density of states have been measured on uranium and reported already. Many of the results are on single crystals of purity that has been unavailable before. Some intermetallic compounds have been measured that are in the class of so-called heavy-fermion materials. We present here the latest results along with a discussion of the occurrence of superconductivity or magnetism in these materials.

Cooley, J. C. (Jason C.); Gay, E. C. (Eddie C.); Hanrahan, R. J. (Robert J.); Hults, W. L. (William L.); Lashley, J. C. (Jason C.); Manley, M. E. (Michael E.); McPheeters, C. C. (Charles C.); Schmiedeshoff, G. M. (George M.); Thoma, D. J. (Dan J.); Touton, S. (Sharon); Smith, J. L. (James L.)

2001-01-01

39

High-strength, high-temperature intermetallic compounds  

Microsoft Academic Search

Materials that are solid at high temperatures are in demand for high-temperature structural applications, and materials that have high values of strength-to-weight and stiffness-to-weight are desired for aircraft and space applications. Basic properties that are insensitive to processing history can be used to provide a preliminary ranking of single-phase substances. A compilation is presented of 293 intermetallic compounds (or metal-metalloid

R. L. Fleischer

1987-01-01

40

New crystal structure maps for intermetallic compounds  

NASA Astrophysics Data System (ADS)

New crystal structure maps have been proposed on the basis of the 0953-8984/9/38/008/img6 molecular orbital calculations of electronic structures. Two electronic parameters have been introduced and employed as new parameters for the classification of crystal structures. One is the bond order and the other is the d-orbital energy level of elements. Both of them change following the position of elements in the periodic table. With these parameters crystal structure maps have been constructed for aluminides, silicides, and some transition-metal-based compounds. There is a clear separation of the crystal structures on the maps. These maps are found to be applicable to the prediction of crystal structures not only for binary compounds but also for ternary compounds. The possibilities of structural modification of 0953-8984/9/38/008/img7 and 0953-8984/9/38/008/img8 by alloying are also discussed with the aid of these maps.

Harada, Yoshihisa; Morinaga, Masahiko; Saito, Jun-ichi; Takagi, Yasuharu

1997-09-01

41

Quantum criticality in selected uranium intermetallic and organometallic compounds  

NASA Astrophysics Data System (ADS)

My thesis presents the studies of the bulk properties of materials that exhibit unusual low-temperature properties due to the proximity of a quantum-critical point (QCP), for which long-range magnetic order can be suppressed to 0 K as a consequence of quantum fluctuations. A material can be tuned to the QCP by variation of a non-thermal control parameter such as hydrostatic pressure, magnetic field and chemical pressure/doping. Most of my experimental studies were performed at extreme conditions, such as high magnetic fields, low temperatures and/or high pressures. Two classes of materials were studied, namely uranium intermetallics and organometallics. The investigations on uranium intermetallics were done on compounds close to the edge of magnetism, i.e. the UCu4+xAl 8-x, UCuxAl5-x and UFe1-xNixAl compounds. Several of those compounds exhibit deviations from traditional Fermi-liquid theory and show non-Fermi liquid (NFL) scaling at low temperatures. Field-induced magnetic transitions were studied for some selected uranium compounds (UNiAl, UNiGa, UNiGe and UIrGe) as well. Furthermore, a study of organometallic quantum magnet (DTN: NiCl2-4SC(NH 2)2), which exhibits field-induced quantum criticality, is presented. In DTN, the magnetic-field induced polarization shows magneto-electric couplings between the antiferromagnetic Ni spins and the soft organic lattice.

Nasreen, Farzana

42

Nano-size particles of palladium intermetallic compounds as catalysts for oxidative acetoxylation  

Microsoft Academic Search

Fine particles of palladium containing intermetallic compounds (IMCs) were prepared on the surface of silica gel and their catalytic properties for the oxidative acetoxylation of toluene and 1,3-butadiene (BD) were investigated. Intermetallic compounds were prepared on silica by the successive impregnation using aqueous solutions of palladium dichloride and a compound of the second metal. Through the reduction in hydrogen at

Takayuki Komatsu; Koichiro Inaba; Tomoyuki Uezono; Ayumu Onda; Tatsuaki Yashima

2003-01-01

43

Hydrogen absorption characteristics of oxygen-stabilized rare-earth iron intermetallic compounds  

E-print Network

Hydrogen absorption characteristics of oxygen-stabilized rare-earth iron intermetallic compounds M decade to the study of the hydrogenation characte- ristics of a variety of intermetallic compounds, our by means TGA-DTA techniques. The results were compared to those obtained on binary RFe2 and RFe3 compounds

Paris-Sud XI, Université de

44

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

45

Structural properties of intermetallic Li-Be compound  

NASA Astrophysics Data System (ADS)

We present the structural properties of binary intermetallic compound Li-Be crystallizing in the space group P21/m. We have performed first-principles calculations employing both generalized gradient approximation (GGA) and local density approximation (LDA) within Density Functional Theory (DFT). The calculations are performed using CRYSTAL98 code. Here we obtain the zero-temperature bulk modulus, lattice constant and pressure derivative of bulk modulus by fitting the Murnaghan equation of state. We also present structure factors at a few (hkl) values using both GGA and LDA.

Galav, K. L.; Paliwal, U.; Joshi, K. B.

2012-06-01

46

Structural and physical properties of the new intermetallic compound Yb 3Pd 2Sn 2  

Microsoft Academic Search

The crystal structure of the ternary intermetallic compound Yb3Pd2Sn2 has been determined ab initio from powder X-ray diffraction data. The compound crystallizes as a new structure type in the orthorhombic space group Pbcm and lattice constants a=0.58262(3), b=1.68393(8), c=1.38735(7)nm. Yb3Pd2Sn2 is composed of a complex ?[Pd2Sn2]?? polyanionic network in which the Yb ions are embedded. A comparison between this structure

P. Solokha; I. ?urlik; M. Giovannini; N. R. Lee-Hone; M. Reiffers; D. H. Ryan; A. Saccone

2011-01-01

47

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

48

Synthesis and characterization of nanocrystalline binary and ternary intermetallic compounds  

E-print Network

electron diffraction SEM Scanning electron microscope SQUID Superconducting quantum interference device TEG Tetraethylene glycol TEM Transmission electron microscope XRD X-ray diffraction vii TABLE OF CONTENTS Page ABSTRACT... of intermetallic AuCu bulk powder (500 mg) and its corresponding powder XRD pattern; (j) SEM micrograph of sintered dense submicrometer powder of intermetallic AuCu; (k) intermetallic AuCu nanomesh; (l) intermetallic AuCu colloidal crystal replica...

Leonard, Brian Matthew

2009-05-15

49

First-principle studies of CaX (X=Si,Ge,Sn,Pb) intermetallic compounds Zhiwen Yang a  

E-print Network

First-principle studies of Ca­X (X=Si,Ge,Sn,Pb) intermetallic compounds Zhiwen Yang a , Dongmin Shi structures, and densities of states of 20 intermetallic compounds in the Ca­X (X=Si, Ge, Sn, Pb) systems have indicated that with increasing atomic weight of X, the bulk modulus of Ca­X intermetallic compounds

Melnik, Roderick

50

CRYSTALLINE-TO-AMORPHOUS TRANSFORMATION OF INTERMETALLIC COMPOUNDS IN THE ZR-FE-M SYSTEM INDUCED BY IRRADIATION  

E-print Network

CRYSTALLINE-TO-AMORPHOUS TRANSFORMATION OF INTERMETALLIC COMPOUNDS IN THE ZR-FE-M SYSTEM INDUCED, the damage accumulation mechanisms in the intermetallic compound, and the annealing mechanisms available, Argonne National Laboratory, Argonne, IL 60439, USA. ABSTRACT The binary and ternary intermetallic

Motta, Arthur T.

51

Effective ?-surfaces in {111} plane in FCC Ni and L12 Ni3Al intermetallic compound  

NASA Astrophysics Data System (ADS)

The well-known concept of ? surfaces originally suggested by Prof. Vitek is extended to the case of a shift of one part of a crystal with respect to the other part in two adjacent {111} planes of a stacking fault. The proposed approach is used to construct the effective ? surfaces in the {111} plane in fcc Ni and L12 Ni3Al of intermetallic compound. It is shown that Ni3Al can have five metastable stacking faults in this plane, namely, an intrinsic superlattice stacking fault, an extrinsic superlattice stacking fault, a complex stacking fault, an antiphase boundary, and a complex extrinsic stacking fault. The existence of the latter in the {111} plane in the L12 Ni3Al intermetallic compound has not been reported previously. The shift of the crystal in two close-packed planes in fcc Ni makes it possible to avoid the formation of a high-energy stacking fault which arises when constructing an ordinary ?-surface, as well as to self-consistently include the extrinsic stacking fault into consideration.

Voskoboinikov, R. E.

2013-07-01

52

Control of intermetallic compound layers at interface between steel and aluminum by diffusion-treatment  

Microsoft Academic Search

The toughening of FeAl intermetallic compound coating formed by aluminizing of carbon steel was investigated. The growth mechanism, morphology and mechanical properties of FeAl intermetallic compound layers on the surface of carbon steel were systematically evaluated for specimens diffused at temperatures ranging from 873 to 1323 K after hot dip aluminizing. Fe2Al5 was mainly formed on the specimen surfaces at

Shigeaki Kobayashi; Takao Yakou

2002-01-01

53

Aging studies of Cu-Sn intermetallic compounds in annealed surface mount solder joints  

Microsoft Academic Search

This is the second in a series of investigations aimed at studying the effect of Cu-Sn intermetallic compound on the reliability of surface mount solder joints. Our previous investigation revealed the formation kinetics and characteristics of Cu-Sn intermetallic compounds in LCCC surface mount solder joints during IR-reflow soldering. The present study focuses on the solid state growth of the interfacial

Alex C. K. So; Y. C. Chan

1996-01-01

54

Intermetallic compound formation at Cu-Al wire bond interface  

NASA Astrophysics Data System (ADS)

Intermetallic compound (IMC) formation and evolution at Cu-Al wire bond interface were studied using focused ion beam /scanning electron microscopy, transmission electron microscopy (TEM)/energy dispersive x-ray spectroscopy (EDS), nano beam electron diffraction (NBED) and structure factor (SF) calculation. It was found that discrete IMC patches were formed at the Cu/Al interface in as-packaged state and they grew toward Al pad after high temperature storage (HTS) environment at 150 C. TEM/EDS and NBED results combined with SF calculation revealed the evidence of metastable ?'-CuAl2 IMC phase (tetragonal, space group: I4m2, a = 0.404 nm, c = 0.580 nm) formed at Cu/Al interfaces in both of the as-packaged and the post-HTS samples. Two feasible mechanisms for the formation of the metastable ?'-CuAl2 phase are discussed based on (1) non-equilibrium cooling of wire bond that is attributed to highly short bonding process time and (2) the epitaxial relationships between Cu and ?'-CuAl2, which can minimize lattice mismatch for ?'-CuAl2 to grow on Cu.

Bae, In-Tae; Young Jung, Dae; Chen, William T.; Du, Yong

2012-12-01

55

Intermetallic compound formation at Cu-Al wire bond interface  

SciTech Connect

Intermetallic compound (IMC) formation and evolution at Cu-Al wire bond interface were studied using focused ion beam /scanning electron microscopy, transmission electron microscopy (TEM)/energy dispersive x-ray spectroscopy (EDS), nano beam electron diffraction (NBED) and structure factor (SF) calculation. It was found that discrete IMC patches were formed at the Cu/Al interface in as-packaged state and they grew toward Al pad after high temperature storage (HTS) environment at 150 Degree-Sign C. TEM/EDS and NBED results combined with SF calculation revealed the evidence of metastable {theta} Prime -CuAl{sub 2} IMC phase (tetragonal, space group: I4m2, a = 0.404 nm, c= 0.580 nm) formed at Cu/Al interfaces in both of the as-packaged and the post-HTS samples. Two feasible mechanisms for the formation of the metastable {theta} Prime -CuAl{sub 2} phase are discussed based on (1) non-equilibrium cooling of wire bond that is attributed to highly short bonding process time and (2) the epitaxial relationships between Cu and {theta} Prime -CuAl{sub 2}, which can minimize lattice mismatch for {theta} Prime -CuAl{sub 2} to grow on Cu.

Bae, In-Tae; Young Jung, Dae [Small Scale Systems Integration and Packaging Center, State University of New York at Binghamton, Binghamton, New York 13902 (United States); Chen, William T.; Du Yong [Advanced Semiconductor Engineering Inc., 1255 E Arques Ave, Sunnyvale, California 94085 (United States)

2012-12-15

56

Identification and control of grinding processes for intermetallic compounds  

NASA Astrophysics Data System (ADS)

An intermetallic compound (IMC) is a combination of two or more metals with a particular atomic formula by having either ionic and covalent bonds, or metallic bonds with specific crystal structures. They may be thought of as the intermediate between metals and ceramics. These new materials may combine the best of each class: the ductility, heat and electric conductivity of metals with the strength and oxidation resistance of ceramics. Previous study has proposed that the depth of plastic deformation can be used as a parameter to describe the influence of grinding conditions on other physical properties of subsurface layers. Accordingly, the indentation model has been developed to correlate the depth of plastic deformation with the normal component of grinding force. It has been reported that the under certain grinding conditions the depth of plastic deformation does not follow the indentation model. The primary objective of this research is to explain such deviations and to demonstrate that this model can be used to control and predict the depth of plastic deformation. Elements of this research include the development of an open architecture platform to study grinding process, a signal processing algorithm for gap elimination, introducing and implementation of model reference unfalsification and learning concept, development of a mathematical model for grinding gamma-TiAl, a comparison between conventional and superabrasive grinding, control and prediction of the depth of plastic deformation, and initiation of one of the first databases for grinding gamma-TiAl. This work not only serves as a step toward the use of IMCs in future technology but also serves as a step toward autonomous machining systems using intelligent control and advanced monitoring which is a feature of the future abrasive technology.

Razavi, Hosein Ali

2000-10-01

57

Synthesis and characterization of patterned surfaces and catalytically relevant binary nanocrystalline intermetallic compounds  

E-print Network

synthetic routes to alloy and intermetallic nanomaterials are necessary to efficiently produce them on a large scale for use in new, smaller devices. Drastically reducing the particle sizes of elemental precursors to nanometer length scales can lower... magnetism, 64 shape-memory effects, 65-67 and tunable surface plasmon resonance (SPR) in colloids. 1 Several strategies have been developed for preparing nanoscale zinc/transition metal alloys and intermetallic compounds, such as ball-milling, 68...

Cable, Robert E.

2008-10-10

58

Microwave assisted combustion synthesis of non-equilibrium intermetallic compounds.  

PubMed

A simplified model of the microwave-assisted combustion synthesis of Ni and Al metal powders to form the NiAl intermetallic on titanium and steel substrates is presented. The simulation couples an electro-thermal model with a chemical model, accounting for local heat generation due to the highly exothermic nature of the reactions between the powders. Numerical results, validated by experimental values, show that the capability of microwaves to convey energy, and not heat, can be used to alter the temperature profiles during and after the combustion synthesis, leading to unique intermetallic microstructures. This phenomenon is ascribed to the extended existence of high temperature liquid intermetallic phases, which react with the metallic substrates at the interface. Moreover, microwave heating selectivity allows to maintain the bulk of the substrate metallic materials to a much lower temperature, compared to combustion synthesis in conventionally heated furnaces, thus reducing possible unwanted transformations like phase change or oxidation. PMID:21721328

Veronesi, Paolo; Rosa, Roberto; Colombini, Elena; Leonelli, Cristina; Poli, Giorgio; Casagrande, Angelo

2010-01-01

59

The role of intermetallic compounds in lead-free soldering  

Microsoft Academic Search

The role of intermetallics in soldered joints is ambivalent. They are an essential part of joints to common basis materials and at low levels they have a strengthening effect on solder alloys. At higher levels, however, it is well known that they can cause joint embrittlement. In this paper three aspects of their role have been studied: the microstructure of

Paul G. Harris; Kaldev S. Chaggar

1998-01-01

60

Intermetallic compound layer growth between solid iron and molten aluminium  

Microsoft Academic Search

The interaction between solid iron and liquid aluminium is studied by immersion tests. At first, the intermetallic layers formed at the solidliquid interface and their growth mechanisms are characterized. The Fe2Al5 and FeAl3 phases are identified in the temperature range from 700 to 900C, and their growth is found to be mainly controlled by a diffusion regime. Then, a theoretical

K. Bouch; F. Barbier; A. Coulet

1998-01-01

61

Development of CuSn intermetallic compound at Pb-free solder\\/Cu joint interface  

Microsoft Academic Search

The development of CuSn intermetallic compound (IMC) at the solder\\/Cu joint interface had been studied using two Pb-free solders, Sn3.8Ag0.7Cu and Sn2Ag0.8Cu0.6Sb alloys. Meanwhile, 100Sn\\/Cu joint was applied for comparison. Both Pb-free solder joints were found with thinner CuSn IMC layers at as-soldered state due to the slower dissolution rate of intermetallic compound into the liquid Pb-free solders during reflow

Xin Ma; Fengjiang Wang; Yiyu Qian; Fusahito Yoshida

2003-01-01

62

Highly enantioselective adsorption of small prochiral molecules on a chiral intermetallic compound.  

PubMed

Intrinsically chiral surfaces of intermetallic compounds are shown to be novel materials for enantioselective processes. Their advantage is the significantly higher thermal and chemical stability, and therefore their extended application range for catalyzed chiral reactions compared to surfaces templated with chiral molecular modifiers or auxiliaries. On the Pd1 -terminated PdGa(111) surface, room-temperature adsorption of a small prochiral molecule (9-ethynylphenanthrene) leads to exceptionally high enantiomeric excess ratios of up to 98?%. Our findings highlight the great potential of intrinsically chiral intermetallic compounds for the development of novel, enantioselective catalysts that can be operated at high temperatures and potentially also in harsh chemical environments. PMID:25655521

Prinz, Jan; Grning, Oliver; Brune, Harald; Widmer, Roland

2015-03-23

63

Influence of interfacial intermetallic compound on fracture behavior of solder joints  

Microsoft Academic Search

This paper studies the solder joints of an SnAg lead-free solder system with pure copper wires. The study focuses upon the interrelationships, which exist between the adhesive strength of the joint, its shear strength, the formation of interfacial intermetallic compounds (IMC) and the fractographic morphology. Additionally, the paper determines how these characteristics, and the relationships between them, are influenced by

Hwa-Teng Lee; Ming-Hung Chen; Huei-Mei Jao; Tain-Long Liao

2003-01-01

64

Rapid formation of intermetallic compounds interdiffusion in the Cu?Sn and Ni?Sn systems  

Microsoft Academic Search

Fundamental investigations were carried out to examine a new interconnection technology which is based on the rapid formation of intermetallic compounds composed of a high melting component (e.g. Cu or Ni) and a low melting component (e.g. Sn) between two layers of the high melting component at temperature just above the melting point of Sn. This reaction is known as

S. Bader; W. Gust; H. Hieber

1995-01-01

65

Manufacturing concerns of the electronic industry regarding intermetallic compound formation during the soldering stage  

Microsoft Academic Search

The intermetallic compound (IMC) formed at the interface between the solder and substrate is an inevitable result of the soldering process. It is an indication of good metallurgical bonding. But if it grows too thick, either during soldering or subsequent solid stage aging, it can have a deleterious effect on the strength of a joint or on the subsequent solderability

Howard D. Blair; Tsung-Yu Pan; John M. Nicholson; Ronald P. Cooper; Sung-Won Oh; A. R. Farah

1996-01-01

66

Resonant ultrasound spectroscopy: Elastic properties of some intermetallic compounds  

SciTech Connect

A novel nondestructive evaluation method, resonant ultrasound spectroscopy (RUS), is reviewed with an emphasis upon defining the elastic properties of intermetallic phases. The applications and advantages of RUS as compared to other conventional elastic constant measurement methods are explained. RUS has been employed to measure the elastic properties of single crystal and/or polycrystalline intermetallics, such as Laves phases (C15 HfV{sub 2} and NbCr{sub 2}), Nb-modified titanium aluminides, and transition metal disilicides (C11{sub b} MoSi{sub 2}, C40 NbSi{sub 2} and TaSi{sub 2}). For Laves phases, the elastic properties of HfV{sub 2}-based C15 phases show various anomalies and those of C15 NbCr{sub 2} do not. For Nb-modified titanium aluminides, the elastic properties of O-phase alloys are investigated as a function of alloying content. For transition metal disilicides, single crystal elastic constants of MoSi{sub 2}, NbSi{sub 2}, and TaSi{sub 2} are obtained and compared. Based on the experimentally determined elastic properties, the characteristics of interatomic bonding in these materials are examined and the possible impact of the elastic properties on mechanical behavior is discussed.

Chu, F.; Thoma, D.J.; He, Y.; Maloy, S.A.; Mitchell, T.E. [Los Alamos National Lab., NM (United States). Materials Science Technology Div.

1996-09-01

67

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

68

First-principle studies of Ca-X (X=Si,Ge,Sn,Pb) intermetallic compounds  

SciTech Connect

The structural properties, elastic properties, heats of formation, electronic structures, and densities of states of 20 intermetallic compounds in the Ca-X (X=Si, Ge, Sn, Pb) systems have been systematically investigated by using first-principle calculations. Our computational results indicated that with increasing atomic weight of X, the bulk modulus of Ca-X intermetallic compounds decreases gradually. It was also found that Ca{sub 36}Sn{sub 23} and CaPb are mechanically unstable phases. Results on the electronic energy band and densities of states also indicated that Ca{sub 3}Si{sub 4} is an indirect band gap semiconductor with a band gap of 0.598 eV, and Ca{sub 2}Si, Ca{sub 2}Ge, Ca{sub 2}Sn, and Ca{sub 2}Pb are direct band gap semiconductors with band gaps of 0.324, 0.265, 0.06, and 0.07 eV, respectively. In addition, it is found that the absolute values of heats of formation for all Ca-X intermetallics are larger than 30 kJ/mol atom. - Graphical abstract: Calculated (a) bulk moduli and (b) shear moduli of Ca-X system intermetallic compounds.

Yang Zhiwen; Shi Dongmin [School of Materials Science and Engineering, Dalian University of Technology, Dalian 116023 (China); Wen Bin, E-mail: wenbin@dlut.edu.c [School of Materials Science and Engineering, Dalian University of Technology, Dalian 116023 (China); Melnik, Roderick [M2NeT Lab, Wilfrid Laurier University, Waterloo, 75 University Ave. West, Ontario, N2L3C5 (Canada); Yao Shan; Li Tingju [School of Materials Science and Engineering, Dalian University of Technology, Dalian 116023 (China)

2010-01-15

69

Tracer diffusion of 63Ni in Ni 3(Al,Ge) ternary intermetallic compound  

Microsoft Academic Search

Radio-tracer diffusion measurements of 63Ni have been performed in Ni75AlxGe25?x ternary intermetallic compounds at various temperatures. The tracer diffusivity was found to depend exponentially on the Ge content of the alloy. These compounds are ordered with the L12 structure, where the Ni atom diffusion proceeds mainly via Ni sublattice site jumps. The change of the diffusivity can be attributed to

C. Cserhti; I. A. Szab; Zs. Mrton; G. Erdlyi

2002-01-01

70

Study of the Electronic Structure and Physical Properties of the Iridium Based Intermetallic Compounds Under Pressure  

Microsoft Academic Search

The electronic structure of the Iridium based L12 intermetallic compounds (A3B) such as Ir3Ti, Ir3Zr, Ir3Hf, Ir3V, Ir3Nb and Ir3Ta, which have wide applications as high temperature structural materials are studied by means of Self-Consistent Tight Binding Linear Muffin Tin Orbital (TB-LMTO) method. These compounds are found to crystallize in the Cu3Au type structure. The total energies are calculated as

M. Sundareswari; M. Rajagopalan

2005-01-01

71

Crystallization behavior of iron-containing intermetallic compounds in 319 aluminum alloy  

Microsoft Academic Search

The crystallization behavior of iron-containing intermetallic compounds in industrial grade 319 aluminum alloy has been investigated\\u000a by means of thermal analysis and metallography. In the absence of manganese, the iron compound crystallizes in the? phase, at all cooling rates ranging from 0.1 C\\/s to 20 C\\/s under normal casting temperatures (750 C). However, when the\\u000a melt is superheated to a

L. Anantha Narayanan; F. H. Samuel; J. E. Gruzleski

1994-01-01

72

Ba 5Ti 12Sb 19+x, a polar intermetallic compound with a stuffed ?-brass structure  

NASA Astrophysics Data System (ADS)

The polar intermetallic compound Ba 5Ti 12Sb 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 5Ti 12Sb 19.102(6), space group P43m, Z=2, a=12.4223(11) , V=1916.9(3) 3). The set of Ba and Sb sites corresponds to the structure of Cu 9Al 4, a ?-brass type with a primitive cell. A complex three-dimensional framework of Ti atoms, in the form of linked planar Ti 9 clusters, is stuffed within the ?-brass-type Ba-Sb substructure. Notwithstanding its relationship to the ?-brass structure, the compound does not appear to conform to the Hume-Rothery electron concentration rules. Band structure calculations on an idealized Ba 5Ti 12Sb 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.

Bie, Haiying; Mar, Arthur

2009-11-01

73

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

74

Catalytic properties of intermetallic compounds Ln(NiM)/sub 5/ and their hydrides in hydrogenation reactions  

SciTech Connect

The catalytic (hydrogenation of propylene), asymmetric (enantioselective hydrogenation of ethyl acetoacetate), and magnetic properties of intermetallic compounds with the composition Ln(NiM)/sub 5/(IMC), where Ln = La, Sm, Gd; M = Ti, V, Cr, Mn, Cu, and of their hydrides have been studied. The data obtained indicate that the catalytic activity of the above compounds in both reactions is due to structural peculiarities of IMC and to the affinity of IMC to H/sub 2/. The observed changes in the total and the optical yield of the product of hydrogenation in the presence of IMC hydrides, modified with R,R-(+) tartaric acid, as functions of the nature of d-metals and their combinations, in the initial complex catalyst lead to the assumption that different metal tartrate complexes are formed on the hydride surface which act as centers of enantioselective hydrogenation.

Konenko, I.R.; Starodubtseva, E.V.; Urazbaeva, K.A.; Fedorovskaya, E.A.; Klabunovskii, E.I.; Slinkin, A.A.; Mordovin, V.P.

1989-02-01

75

TiNiSn: A gateway to the (1,1,1) intermetallic compounds  

SciTech Connect

Recent awareness of the transport properties of Skutterudite pnictides has stimulated an interest in numerous other intermetallic compounds having a gap in the density of states at the Fermi level including the MNiSn compounds where M = (Ti, Zr, Hf). These intermetallic half-Heusler compounds are characterized by high Seebeck coefficients ({minus}150 to {minus}300 {micro}V/deg.) and reasonable carrier mobilities (30 to 50 cm{sup 2}/V-s) at room temperature which make them attractive candidates for intermediate temperature thermoelectric applications. Samples of TiNiSn were prepared by arc melting and homogenized by heat treatment. The temperature dependence of the electrical resistivity, Seebeck coefficient, and thermal diffusivity of these samples was characterized between 22 C and 900 C. The electrical resistivity and thermopower both decrease with temperature although the resistivity decreases at a faster rate. Electrical power factors in excess of 25 {micro}W/cm-C{sup 2} were observed in nearly single phase alloys within a 300 to 600 C temperature range. A brief survey of other selected ternary intermetallic compounds is also presented.

Cook, B.A.; Harringa, J.L. [Ames Lab., IA (United States); Tan, Z.S.; Jesser, W.A. [Univ. of Virginia, Charlottesville, VA (United States). Dept. of Materials Science and Engineering

1996-06-01

76

Preferential site occupation in Y and La substituted Pr 2Fe 14B intermetallic compounds  

NASA Astrophysics Data System (ADS)

The crystal structure of Y and La substituted Pr 2Fe 14B intermetallic compounds has been determined by high resolution neutron time-of-flight powder diffraction. A model which takes into account the rare-earth site occupancies and the measured magnetic anisotropy in Pr 2Fe 14B and Nd 2Fe 14B indicates that the contribution of the 4f site anisotropy to the total axial anisotropy is larger than that of the 4g site in Nd 2Fe 14B compounds. In Pr 2Fe 14B compounds, however, the 4f and 4g site anisotropies are equal.

Moze, O.; Pareti, L.; Marusi, G.; Solzi, M.; David, W. I. F.

1989-01-01

77

Intermetallic compound layer growth at the interface between SnCuNi solder and Cu substrate  

Microsoft Academic Search

Phase analysis and growth kinetics of intermetallic compound (IMC) layers formed between low cost SnCuNi solder for wave soldering and Cu substrate by solid state isothermal aging were examined at temperatures between 80 and 150C for 0 to 60 days. The IMC layer was composed of two phases; Cu6Sn5 (also (Cu,Ni)6Sn5) adjacent to the solder, Cu3Sn adjacent to the copper.

Jeong-Won Yoon; Young-Ho Lee; Dae-Gon Kim; Han-Byul Kang; Su-Jeong Suh; Cheol-Woong Yang; Chang-Bae Lee; Jong-Man Jung; Choong-Sik Yoo; Seung-Boo Jung

2004-01-01

78

The quadrupole interaction of 100 Rh in various intermetallic compounds of palladium  

Microsoft Academic Search

The nuclear quadrupole interaction of the 75 keV excited state of100Rh in the ordered intermetallic compounds PdHg, PdPb2 PdSb and PdTe was measured. Using an estimate for the nuclear quadrupole moment of the 75 keV state in100Rh and point ion lattice sums for the lattice electric field gradient (EFG) at the Rh site, the electronic contributionVzzel to the total EFG

R. Vianden; E. N. Kaufmann; R. A. Naumann; G. Schmidt

1979-01-01

79

The quadrupole interaction of100Rh in various intermetallic compounds of palladium  

Microsoft Academic Search

The nuclear quadrupole interaction of the 75 keV excited state of100Rh in the ordered intermetallic compounds PdHg, PdPb2 PdSb and PdTe was measured. Using an estimate for the nuclear quadrupole moment of the 75 keV state in100Rh and point ion lattice sums for the lattice electric field gradient (EFG) at the Rh site, the electronic contribution V {zz\\/el} to the

R. Vianden; E. N. Kaufmann; R. A. Naumann; G. Schmidt

1979-01-01

80

Morphology and growth mechanisms of SAC305-xNi\\/pad joints intermetallic compounds  

Microsoft Academic Search

The formation and growth of intermetallic compounds (IMC) is a key factor to the reliability of soldering joints in modern electronic mounting and packaging industry. In this paper, by means of Olympus, scanning electron microscope (SEM) and Energy Dispersive X-ray (EDX) analysis methods, the morphology and growth mechanisms of IMCs between SAC305-xNi and Cu joint during soldering as well as

Lifeng Wang; Jia Wang; Xue Liu; Xiaojing Liu

2010-01-01

81

Alloy formation processes at electrochemical intercalation of lithium into intermetallic compounds of magnesium with zinc  

Microsoft Academic Search

A comparative study of alloy formation processes that occur during the electrochemical intercalation of lithium from lithium\\u000a chloride solutions in dimethylformamide into intermetallic compounds of magnesium with zinc (MgZn2, Mg2Zn3) and the corresponding individual metals is studied by chronopotentiometric and voltammetric methods. Lithium-containing\\u000a phases are formed in all samples studied; moreover, for MgZn2 and Mg2Zn3 electrodes, the phases formed are

V. V. Ozeryanskaya; V. E. Guterman

2007-01-01

82

Magnetic recording on FePt and FePtB intermetallic compound media  

Microsoft Academic Search

Near-contact recording on high-coercivity FePt intermetallic compound media using a high Bsat write element was investigated. Untextured FePt media were prepared by magnetron sputtering on ZrO2 disks at a substrate temperature of 450C, with postannealing at 450C for 8 h. Both multilayer and cosputtered precursors produced the ordered tetragonal L10 phase with high coercivity between 5 and 12 kOe. To

Ning Li; Bruce M. Lairson

1999-01-01

83

Effect of La on the CuSn intermetallic compound (IMC) growth and solder joint reliability  

Microsoft Academic Search

By adding a small amount of the rare earth element La (only 0.05 wt.%) into the traditional Sn60Pb40 solder alloy, the growth of the CuSn intermetallic compound (IMC) at the interface of solder joints has been depressed. Furthermore, the thermal fatigue life of simulated surface mount solder joints was increased by a factor of 3. Thermodynamic analysis showed that, since

Xin Ma; Yiyu Qian; F Yoshida

2002-01-01

84

Effects of Cu\\/Al intermetallic compound (IMC) on copper wire and aluminum pad bondability  

Microsoft Academic Search

Copper wire bonding is an alternative interconnection technology that serves as a viable, and cost saving alternative to gold wire bonding. Its excellent mechanical and electrical characteristics attract the high-speed, power management devices and fine-pitch applications. Copper wire bonding can be a potentially alternative interconnection technology along with flip chip interconnection. However, the growth of Cu\\/Al intermetallic compound (IMC) at

Hyoung-Joon Kim; Joo Yeon Lee; Kyung-Wook Paik; Kwang-Won Koh; J. Won; Sihyun Choe; Jin Lee; Jung-Tak Moon; Yong-Jin Park

2003-01-01

85

Effect of intermetallic compounds on the shear fatigue of Cu\\/63Sn37Pb solder joints  

Microsoft Academic Search

The effect of Cu-Sn intermetallic compounds (IMC) on the fatigue failure of solder joints has been studied by means of shear cycling. The samples consist of leadless ceramic chip carriers (LCCC) soldered onto FR-4 printed circuit boards (PCB), and are prepared by conventional reflow soldering using a 63Sn-37Pb solder paste and then aged at 150C for 1, 4, 9, 16,

Y. C. Chan; P. L. Tu; A. C. K. So; J. K. L. Lai

1997-01-01

86

Effect of intermetallic compounds on vibration fatigue of ?BGA solder joint  

Microsoft Academic Search

This paper studies the vibration fatigue failure of ?BGA solder-joints reflowed with different temperature profiles, and aging at 120 C for 1, 4, 9, 16, 25, 36 days. The effect of the Ni3Sn4 and Cu-Sn intermetallic compound (IMC) on the fatigue lifetime is also reported. During the vibration fatigue test, in order to identify the failure of ?BGA solder joint,

P. L. Tu; Y. C. Chan; Joseph K. L. Lai

2001-01-01

87

Growth rate of intermetallic compounds in Al\\/Cu bimetal produced by cold roll welding process  

Microsoft Academic Search

The aim of this article is to study the growth rate of intermetallic compounds at the interface of cold roll bonded Al\\/Cu bimetal at 250C and compare the results with a similar study performed on friction welding of Al to Cu. Samples of tri-layered CuAlCu composite were produced by the cold roll welding process and heat treated at constant temperature

M. Abbasi; A. Karimi Taheri; M. T. Salehi

2001-01-01

88

Influence of intermetallic compounds on the adhesive strength of solder joints  

Microsoft Academic Search

This study investigates the influence of intermetallic compound (IMC) growth on the adhesive strength of solder joints. 100Sn and 60Sn40Pb solders were used to solder electrolytic copper wires end to end. Soldered samples were then subjected to high temperature storage testing. The resulting interfacial IMCs in both solders were composed of Cu6Sn5 and Cu3Sn. IMC in the 100Sn solder joint

Hwa-Teng Lee; Ming-Hung Chen

2002-01-01

89

Aging studies of Cu-Sn intermetallic compounds in annealed surface mount solder joints  

Microsoft Academic Search

Our previous investigation (1995), revealed the formation kinetics and characteristics of copper-tin (Cu-Sn) intermetallic compounds (IMC) in leadless ceramic chip carrier (LCCC) surface mount solder joints during infrared (IR)-reflow soldering. The present study focuses on the solid state growth of the interfacial Cu-Sn IMC in LCCC surface mount solder joints under prolonged annealing at elevated temperature. A thick Cu-Sn IMC

Alex C. K. So; Yan C. Chan; J. K. L. Lai

1997-01-01

90

Interfacial reactions and growth kinetics for intermetallic compound layer between In48Sn solder and bare Cu substrate  

Microsoft Academic Search

The growth kinetics of intermetallic compound layer formed between In48Sn solder and bare Cu substrate were investigated at temperatures between 70 and 100C for 060 days. In the solder joint between the In48Sn solder and bare Cu substrate, the intermetallic compound layer was composed of two phases: Cu(In,Sn)2 adjacent to the solder and Cu6(In,Sn)5 which was the dominant phase. A

Dae-Gon Kim; Seung-Boo Jung

2005-01-01

91

Effects of Gas Pressure of Cold Spray on the Formation of Al-Based Intermetallic Compound  

NASA Astrophysics Data System (ADS)

In this paper, postannealing of cold-sprayed (CDGS) coatings for intermetallic compounds (IMC) in the matrix at low temperature and dependences of types and dispersion characteristics of intermetallic compounds on spraying pressure condition were investigated. The pressure prior to entering the gas heater was fixed at 0.7, 1.5, and 2.5 MPa. The relatively soft Al has been coated at low gas pressure condition (0.7 MPa) with severe plastic deformation owing to large peening effect. On the contrary, the Al particles coated at the higher pressure (1.5, 2.5 MPa) were not severely deformed. It was concluded that the pressure-controlled peening effects could alter the main route of Al consumption during annealing: eutectic or compounding of intermetallics. The thin and continuous IMC layer was formed at the interface with low pressure condition (0.7 MPa). On the other hand, the thick and discontinuous IMC layer was observed at the higher pressure condition (1.5, 2.5 MPa). Also, many eutectic pores were found in the Al-Ni composite coatings with lower gas pressure condition (0.7 MPa), but far less were found with high pressure environment.

Lee, H.; Shin, H.; Ko, K.

2010-01-01

92

Crystal electric field in RAgSb{sub 2} (R = Ho, Er, Tm) intermetallic compounds  

SciTech Connect

The magnetic scattering spectra of RAgSb{sub 2} (R = Ho, Er, Tm) intermetallic compounds are measured and their crystal electric field parameters are determined using inelastic neutron scattering. It is revealed that the ground state is a nonmagnetic singlet for the HoAgSb{sub 2} compound, a Kramers doublet with a strongly anisotropic g factor for the ErAgSb{sub 2} compound, and a quasi-doublet (random doublet) characterized by an extremely anisotropic g factor for the TmAgSb{sub 2} compound. The exchange interaction is estimated in the molecular field approximation. The magnetic properties of the RAgSb{sub 2} compounds are analyzed in terms of the energy level schemes and eigenfunctions determined in this study. The calculated anisotropic magnetic susceptibilities for all compounds are in good agreement with the experimental data obtained for single crystals.

Sashin, I. L., E-mail: sashin@nf.jinr.ru; Goremychkin, E. A. [Joint Institute for Nuclear Research (Russian Federation); Szytula, A. [Jagiellonian University, Smoluchowski Institute of Physics (Poland); Clementyev, E. S. [Technical University of Munich (Germany)

2007-05-15

93

Magnetic properties of NpX 2 intermetallic compounds  

NASA Astrophysics Data System (ADS)

The magnetic and electronic properties of NpX 2 (X = Ga, Si) were studied by Mssbauer and ac-dc magnetization techniques. Both order ferromagnetically below TC = 55(2) and 48(2) K respectively. A comparison of our data with the results for other NpX 2 (X = Al, As, Sb, Te) compounds indicates that NpGa 2 is a highly localized 5f electron system, whereas in NpSi 2 the 5f electrons are partially delocalized. The magnetic properties of NpX 2 compounds can neither be consistently explained within the conventional crystal electric field picture (CEF) nor by taking into account hybridization dressing or local spin density models.

Yaar, I.; Gal, J.; Potzel, W.; Kalvius, G. M.; Will, G.; Schfer, W.

1992-02-01

94

Magnetic circular x-ray dichroism in Ce intermetallic compounds  

NASA Astrophysics Data System (ADS)

Magnetic circular x-ray dichroism (MCXD) studies at L2,3 absorption edges in intermediate-valence (IV) compounds CeFe2, Ce(Fe0.8Co0.2)2, CeCo5, Ce2Co17, and trivalent 4f1 systems (CeRu2Ge2, Ce3Al11, CePd, CeFe2H3.8) at the Ce L2,3 edges are presented. The comparison with reference compounds (La, Lu, Hf, Gd) confirms the existence, in such IV systems, of an ordered 5d magnetic moment on the Ce site antiferromagnetically coupled with the 3d Fe (Co) moment. Moreover, this study suggests, provided the 4f orbital moment is almost quenched, the existence of a simple proportionality between the MCXD intensity and the magnetic moment of the probed atom. For instance the MCXD method leads to a Ce 5d magnetic moment in CeFe2 of about 0.35?B antiferromagnetically coupled with the 3d Fe moment, in good agreement with band-structure calculations. The MCXD applications in Ce(Fe,Co)2 and CeFe2Hx permit us to define precisely the electronic structure of Ce in such compounds. Particularly we will show that MCXD experiments at the L2,3 absorption edges of Ce are able to yield valuable information on the degree of hybridization of the 4f electrons in the ground state. Indeed, systematic comparison between the MCXD signals of IV and normal trivalent Ce compounds reveals the extreme sensitivity of the L2,3 MCXD experiments to the degree of localization of the 4f electrons.

Giorgetti, C.; Pizzini, S.; Dartyge, E.; Fontaine, A.; Baudelet, F.; Brouder, C.; Bauer, Ph.; Krill, G.; Miraglia, S.; Fruchart, D.; Kappler, J. P.

1993-11-01

95

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

96

A new method to estimate the atomic volume of ternary intermetallic compounds  

SciTech Connect

The atomic volume of an A{sub x}B{sub y}C{sub z} ternary intermetallic compound can be calculated starting from volumes of some proper A-B, A-C and B-C binary phases. The three methods by Colinet, Muggianu and Kohler, originally used to estimate thermodynamic quantities, and a new method here proposed, were tested to derive volume data in eight systems containing 91 ternary phases with the known structure. The comparison between experimental and calculated volume values shows the best agreement both for the Kohler method and for the new proposed procedure. -- Graphical abstract: Synopsys: the volume of a ternary intermetallic compound can be calculated starting from volumes of some binary phases, selected by the methods of Colinet, Muggianu, Kohler and a new method proposed here. The so obtained values are compared with the experimental ones for eight ternary systems. Display Omitted Research highlights: {yields} The application of some thermodinamic methods to a crystallochemical problem. {yields} The prevision of the average atomic volume of ternary intermetallic phases. {yields} The proposal of a new procedure to select the proper starting set of binary phases.

Pani, M., E-mail: marcella@chimica.unige.i [Department of Chemistry and Industrial Chemistry, University of Genoa, Via Dodecaneso 31, 16146 Genova (Italy); Merlo, F. [Department of Chemistry and Industrial Chemistry, University of Genoa, Via Dodecaneso 31, 16146 Genova (Italy)

2011-05-15

97

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

98

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 250 h 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

99

JOURNAL DE PHYSIQUE Colloque C6, supplment au no 12, Tome 35, Dcembre 1974,page C6-533 INVESTIGATION OF MIXED INTERMETALLIC COMPOUNDS  

E-print Network

-533 INVESTIGATION OF MIXED INTERMETALLIC COMPOUNDS 1. VINCZE (*), M. C. CADEVILLE (**), R. JESSER (***), L. TAKACS results of Mossbauer measurements on the intermetallic compounds (Fei-,Coz)2B (O -,Mn,)Bez. The comparison with the average magnetizationfor the(Fe1-,Coz)~Band(Fe1-,Mn,)Bez compounds suggestsan important

Paris-Sud XI, Université de

100

Brittle intermetallic compound makes ultrastrong low-density steel with large ductility.  

PubMed

Although steel has been the workhorse of the automotive industry since the 1920s, the share by weight of steel and iron in an average light vehicle is now gradually decreasing, from 68.1 per cent in 1995 to 60.1 per cent in 2011 (refs 1, 2). This has been driven by the low strength-to-weight ratio (specific strength) of iron and steel, and the desire to improve such mechanical properties with other materials. Recently, high-aluminium low-density steels have been actively studied as a means of increasing the specific strength of an alloy by reducing its density. But with increasing aluminium content a problem is encountered: brittle intermetallic compounds can form in the resulting alloys, leading to poor ductility. Here we show that an FeAl-type brittle but hard intermetallic compound (B2) can be effectively used as a strengthening second phase in high-aluminium low-density steel, while alleviating its harmful effect on ductility by controlling its morphology and dispersion. The specific tensile strength and ductility of the developed steel improve on those of the lightest and strongest metallic materials known, titanium alloys. We found that alloying of nickel catalyses the precipitation of nanometre-sized B2 particles in the face-centred cubic matrix of high-aluminium low-density steel during heat treatment of cold-rolled sheet steel. Our results demonstrate how intermetallic compounds can be harnessed in the alloy design of lightweight steels for structural applications and others. PMID:25652998

Kim, Sang-Heon; Kim, Hansoo; Kim, Nack J

2015-02-01

101

Confinement Effects on Evolution of Intermetallic Compounds During Metallurgical Joint Formation  

NASA Astrophysics Data System (ADS)

In this work, we compare the microstructural evolution of Sn/Cu/Sn and Cu/Sn/Cu `sandwich' configurations under metallurgical bonding conditions. These simulations are relevant in explaining experimental observations that suggest that the resulting dominant intermetallic compound in Cu-Sn systems depends on the relative supply of Cu and Sn. Through the analysis of morphological evolution and growth rate, it is shown that the Cu6Sn5 layer becomes dominant in the Sn/Cu/Sn structure, while the Cu/Sn/Cu structure is dominated by Cu3Sn after extended reaction periods.

Park, M. S.; Gibbons, S. L.; Arryave, R.

2014-07-01

102

Intermetallic compounds formed during the reflow of In49Sn solder ball-grid array packages  

Microsoft Academic Search

The intermetallic compounds formed at the interfaces between In-49Sn solder balls and Au\\/Ni\\/Cu pads during the reflow of In-49Sn\\u000a solder, ball-grid array (BGA) packages are investigated. Various temperature profiles with peak temperatures ranging from\\u000a 140C to 220C and melting times ranging from 45 sec to 170 sec are plotted for the reflow processes. At peak temperatures\\u000a below 170C, a continuous

T. H. Chuang; S. Y. Chang; L. C. Tsao; W. P. Weng; H. M. Wu

2003-01-01

103

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

104

High-field magnetic properties in Nd-Fe intermetallic compound  

NASA Astrophysics Data System (ADS)

On the basis of the molecular field theory, an improved two-sublattice model is applied to analyze the magnetic properties in Nd2Fe17Hx (x=0, 3 and 4.9) under high magnetic fields. As is known, two types of magnetic ions exist in Nd-Fe intermetallic compound. Here, the exchange interactions of Nd-Nd, Nd-Fe and Fe-Fe are taken into account. And, as to the ferromagnetic compounds, we define the effective exchange field Hex=??effHe, where ? the molecular field coefficient, ?eff the effective magnetic susceptibility, and He the external magnetic field. Meanwhile, the field-dependence characteristics of magnetization at different temperatures are discussed. Also, the parameters ?A and ?B, associated with v and ?eff, are defined, and the field-dependence, temperature-dependence characteristics are analyzed. Additionally, it is confirmed that the hydrogen content shows great influence on the magnetic properties in Nd2Fe17Hx compound.

Wang, Wei; Xu, Haijun; Xu, Xiaomiao; Zhang, Yajun; Li, Feng

2013-04-01

105

Structures and Magnetic Properties of Europium-Transition Metal-Gallium Ternary Intermetallic Compounds with 1:3 Type  

NASA Astrophysics Data System (ADS)

The crystal structures and magnetic properties of novel EuTrGa3?r (T=Pd, Ir, Rh) intermetallic compounds are investigated by using powder x-ray diffraction and magnetic measurements. EuTrGa3?r crystallizes in orthorhombic structure with space group of Cmcm and Z = 4. There are four kinds of nonequivalent 4c crystal positions in EuTrGa3?r unit cell, which are occupied by 4Eu, 4GaI, 4(GaII, T) and 4GaIII, respectively. EuTrGa3?r exhibits the complex magnetic states in low-temperature regime, with the three-, two- and one-antiferromagnetic transitions occurring for T=Ir, T=Rh and T=Pd, respectively. It might be due to the Kondo effect: a localized antiferromagnetic interaction of the isolated impurity spins with the surrounding conduction electrons at low-temperature regime.

He, Qiang; Guo, Yong-Quan

2015-01-01

106

Extreme Poisson's ratios and their electronic origin in B2 CsCl-type AB intermetallic compounds  

NASA Astrophysics Data System (ADS)

Negative Poisson's ratios have been observed in a variety of metals and alloys. However, the electronic origin of this effect remains unclear, as is evident by our limited knowledge about intermetallics showing this behavior. In an effort to clarify the electronic origin of a negative Poisson's ratio, we have performed a systematic and comprehensive study of extreme (both positive and negative) Poisson's ratios behavior in the B2 CsCl-type AB intermetallic family (including 14 common intermetallics and 128 rare-earth-metal transition or main-group-metal intermetallics) by way of density functional theory calculations. We found a pronounced correlation between the extreme Poisson's ratios and the elastic anisotropy, with approximately 70% of the B2 intermetallics showing intrinsic auxetic behavior. We went on to examine the topology and geometry of the electron charge density and found that the extreme Poisson's ratios are attributable to the directionality of the bonds of the material. Auxetic materials were found to have nondirectional bonds, and nonauxetic compounds had directional bonds. Our findings provide an essential electronic perspective to forecast the auxetic behavior, and suggest a new application for intermetallic compounds.

Wang, X. F.; Jones, Travis E.; Li, W.; Zhou, Y. C.

2012-04-01

107

Characterization of second-phase plates in a Gd?Ge? intermetallic compound.  

PubMed

Rare-earth compounds based on the stoichiometry R?(Si(x)Ge(1-x))? (R = rare-earth elements) exhibit many unusual features, including possessing R?(Si(x)Ge(1-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 Gd?Ge? 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 Gd?Ge? matrix similar to what is seen in Gd?Ge?. TEM observation revealed that a role reversal had occurred, with the thin plates possessing the orthorhombic structure and composition of Gd?Ge?. The orientation relationship between Gd?Ge? thin plates and the Gd?Ge? matrix was determined to be [1 0 1 0 ](1 2 1 1)(m)||[0 1 0](1 0 2)(p), the same relationship reported for Gd?Ge? plates precipitating from a Gd?Ge? 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. PMID:23687353

Cao, Q; Chumbley, L S

2013-12-01

108

Surface structures of In-Pd intermetallic compounds. II. A theoretical study.  

PubMed

The (110) surface of the InPd intermetallic compound and the In-Pd surface alloy properties are investigated in the framework of the density functional theory, within the projector augmented plane-wave method. Surface segregation is calculated to be energetically unfavorable at stoichiometric InPd(110) surfaces, while indium antisites are shown to segregate to the surface in off-stoichiometric InPd(110) systems. Concerning surface alloys obtained by burying In-doped Pd layers in Pd(111), we demonstrated that the most stable ones are those presenting atomic indium concentrations below 50 at. % (11 at. %, 25 at. %, 33 at. %). According to our calculations, the In-doped Pd layers with concentration above or equal to 50% lead to In-doped Pd multilayers, each presenting an atomic indium concentration below 50 at. %. Alloying and segregation effects in InPd intermetallic compound and In-Pd surface alloys clearly agree with the larger bonding strength of In-Pd (-0.44 eV) compared to In-In (-0.29 eV) and Pd-Pd (-0.31 eV). PMID:25173026

Gaudry, ; McGuirk, G M; Ledieu, J; Fourne, V

2014-08-28

109

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

110

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

111

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

112

Lattice dynamics of the mixed-conducting intermetallic compound,. beta. -LiAl  

SciTech Connect

The intermetallic compound, ..beta..-LiAl, that crystallizes in the uncommon Zintl structure is a mixed-conducting electrode and has many unusual properties pointing to the existence of unusual bonding in the semi-metallic compound. In order to elucidate the nature of the bonding in LiAl, we have studied the lattice dynamics of ..beta..-LiAl by inelastic neutron scattering. Results for the phonon dispersion curves have been obtained for the principal symmetry directions. A force constant fit to the results indicates that the Al-Al force constants are unusually large. Pair potentials were constructed by conventional pseudopotential calculations. The pair interactions favoring the Zintl structure were used to compute phonon dispersion curves. Good agreement between theory and experiment can be obtained for the acoustic branches.

Brun, T.O.; Robinson, J.E.; Susman, S.; Mildner, D.F.R.; Dejus, R.; Skoeld K.

1983-04-01

113

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

PubMed

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. PMID:25001413

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

2014-07-30

114

Cohesive Properties, Electronic Structure and Phase Stability of High-Temperature Ordered Intermetallic Compounds  

NASA Astrophysics Data System (ADS)

The unusual high temperature properties of the ordered intermetallic compounds have made them highly desirable potential candidates for structural materials in the aerospace industry. However, the lack of ductility at ambient temperature in most of these intermetallic compounds has been the major obstacle in their applications. Very little is known about the cause of their brittleness and possible mechanisms of ductility enhancement. The first principles quantum mechanical methods employed in this study can provide crucial understanding on the properties of these compounds. The linear muffin -tin orbital and the full potential linearized augmented plane wave methods based on density functional theory were used. These self-consistent calculations allow the investigation of the formation and physical properties of these compounds from a microscopic point of view. The calculated results are generally in good agreement with available experimental observations. Stabilizing the compound in a high symmetry structure increases its slip systems and ductility. In (Ni, Co, Fe)_3V, the stable structure is shown to be associated with the fill-up of the bonding states. Corresponding to experiments, the ductile high -symmetry cubic L1_2 phase is found to be the most stable phase in an electron concentration region of 7.75-8.0. Activation of the <111 > slip is expected to be effective in increasing ductility of B2 structured compounds. The {1over 2}<111 >{110 } anti-phase boundary energy of RuAl is found to be only 65% that of NiAl. Unlike RuAl, the charge density near E_{rm F} in NiAl reveals a directional charge distribution along the <111> direction which may hamper its dislocation movement. Deformation by Martensitic transformation is probed in the off-stoichiometry NiAl and NiAl with ternary additions. It is found that in Ni-rich NiAl and NiAl with Fe, Co, Cu on the Al site, the Martensitic L1_0 phase is promoted. It is shown that ternary additions reduce the stability of the B2 phase and significantly affect the Ni-Al bonding. The L2_{1} Heusler phase compounds Ni_2XAl (X = IVA, VA elements) were found to increase the creep strength of NiAl. The calculated cohesive properties of these compounds were found to be in good agreement with experiments. It is also found that the strong Ni-d and X-d hybridization contributes the most to their good phase stability.

Lin, Wayne Wei

115

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

116

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 moir 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; Krnlein, Andreas; Hsu, Pin-Jui; Fauth, Kai; Bode, Matthias

2014-11-01

117

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

118

Enhanced iron magnetic moment in the ThFe11C2 intermetallic compound D. Benea,1,a)  

E-print Network

Enhanced iron magnetic moment in the ThFe11C2 intermetallic compound D. Benea,1,a) O. Isnard,2,3 J moment is observed on certain Fe positions, coexisting with much lower magnetic moments on other iron positions of the lattice. Band structure calculations indeed show that the Fe magnetic moments depend

Paris-Sud XI, Universit de

119

Growth behavior of Cu\\/Al intermetallic compounds and cracks in copper ball bonds during isothermal aging  

Microsoft Academic Search

Copper wires are increasingly used in place of gold wires for making bonded interconnections in microelectronics. There are many potential benefits for use of copper in these applications, including better electrical and mechanical properties, and lower cost. Usually, wires are bonded to aluminum contact pads. However, the growth of Cu\\/Al intermetallic compounds (IMC) at the wire\\/pad interfaces is poorly understood,

C. J. Hang; C. Q. Wang; M. Mayer; Y. H. Tian; Y. Zhou; H. H. Wang

2008-01-01

120

Synthesis of the NiZr 2 intermetallic compound nanophase materials  

NASA Astrophysics Data System (ADS)

The NiZr 2 intermetallic compound nanocrystalline materials were synthesized by completely crystallizing an amorphous NiZr 2 alloy under proper annealing conditions. The microstructure of the NiZr 2 nanophase was characterized by means of transmission electron microscopy (TEM), high resolution electron microscopy (HREM), and X-ray diffraction (XRD), respectively. It was found that the NiZr 2 nanophase sample consists of ultrafine lamellae with thicknesses of a few nanometers and there are well-defined twin boundaries between the neighboring lamellae. The dependence of the annealing temperature on the mean grain size was determined. The formation process of the NiZr 2 nanophase during a polymorphous crystallization of the amorphous phase was monitored by a differential scanning calorimeter (DSC) and its kinetics was analyzed.

K., Lu; D. Liu, X.; H. Yuan, F.

1996-02-01

121

Characterization of Ni-RICH Intermetallic Compound Ni3Al Films with Slow Positron Beam  

NASA Astrophysics Data System (ADS)

Ni-rich intermetallic compound Ni3Al films were deposited using the dual-target magnetron co-sputtering method. The grain-boundary and grain-size characteristics of the as-deposited and post-annealed Ni3Al films were investigated using a slow positron beam. The results demonstrate a distinct change of S-parameter and positron effective diffusion length Leff values as samples were annealed at different ambient atmospheres and temperatures. It shows that the positron trapping center is mainly associated with intergranular vacancies, and changes to either the vacancy cluster size or the grain size have been invoked to explain the changes of the values of the S-parameter and Leff. Ni-rich oxygen-Ni3Al films were also studied. All films were identified using X-ray diffraction and the results confirm the conclusion obtained by the slow positron beam.

Liu, Jiandang; Weng, Huimin; Chen, Xianglei; Du, Huaijiang; Ye, Bangjiao; Li, Wenjuan; Zhou, Jicheng

122

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

123

The surface composition and initial oxidation of zirconium-nickel intermetallic compounds at room temperature  

NASA Astrophysics Data System (ADS)

The surface compositions of five sputter-cleaned zirconium-nickel intermetallic compounds (ZrNi 5, Zr 2Ni 7, ZrNi 3, ZrNi, and Zr 2Ni) have been estimated by quantitative Auger analysis. The quantitative analysis was calibrated using Auger intensities measured on UHV fracture exposed alloy surfaces. The five sputter-cleaned alloys are slightly enriched in surface Zr relative to their bulk compositions. Their initial oxidation at room temperature is accompanied by the preferential surface accumulation of oxidized Zr. We have previously shown that the oxidation of Zr 2Ni 7, ZrNi 3, and ZrNi at 673 K results in the preferential surface accumulation of oxidized Ni. This variation with temperature of the surface compositional stratification and preferential oxidation characteristics of Zr-Ni alloys can have a significant influence on their stability in oxidizing environments.

Deibert, Max C.; Wright, Randy B.

1988-10-01

124

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

125

Free energy of melts and intermetallic compounds of binary alloys determined by a molecular dynamics approach.  

PubMed

We present an atomistic approach aimed at determining the free energy g(liq) of binary alloy liquids, a quantity which governs the thermodynamics of phase transformations and whose evaluation has long been a challenge to modeling methods. Our approach, illustrated here for a metallic system model NiZr, combines two methods: the quasiharmonic approximation, applied for some existing (real or hypothetical) intermetallic compounds, and the liquid-solid coexistence conditions. The underlying equations for g(liq) are solved by means of a subregular-solution approximation. We demonstrate the high reliability of our calculated free energies in determining the phase diagram of a binary system and describing quantitatively the growth kinetics. The latter issue is illustrated by linking molecular dynamics simulations to phase-field modeling with regard to directional solidification and melting in a two-phase system [Ni(x)Zr(1-x)](liq)-Zr(cryst) out of chemical equilibrium. PMID:25353606

Guerdane, M

2014-02-01

126

In situ surface characterization of the intermetallic compound PdGa - A highly selective hydrogenation catalyst  

NASA Astrophysics Data System (ADS)

The structurally well-defined intermetallic compound PdGa - a highly selective catalyst for the semi-hydrogenation of acetylene - was characterized by Fourier transform infrared spectroscopy (FTIR) in situ X-ray photoelectron spectroscopy and in situ prompt gamma activation analysis. A strong modification of the electronic states in PdGa compared to elemental Pd was revealed as well as the complete isolation of the Pd atoms on the surface of PdGa. In situ investigations proved the high stability of the surface, thus excluding segregation phenomena (common for alloys) or sub-surface chemistry involving C and/or H atoms (known for elemental Pd). By suppressing the sub-surface chemistry, the electronic modification as well as the site isolation lead to the high selectivity and long-term stability of PdGa in the semi-hydrogenation of acetylene.

Kovnir, K.; Armbrster, M.; Teschner, D.; Venkov, T. V.; Szentmiklsi, L.; Jentoft, F. C.; Knop-Gericke, A.; Grin, Yu.; Schlgl, R.

2009-06-01

127

Intermetallic Compound Formation Mechanisms for Cu-Sn Solid-Liquid Interdiffusion Bonding  

NASA Astrophysics Data System (ADS)

Cu-Sn solid-liquid interdiffusion (SLID) bonding is an evolving technique for wafer-level packaging which features robust, fine pitch and high temperature tolerance. The mechanisms of Cu-Sn SLID bonding for wafer-level bonding and three-dimensional (3-D) packaging applications have been studied by analyzing the microstructure evolution of Cu-Sn intermetallic compounds (IMCs) at elevated temperature up to 400C. The bonding time required to achieve a single IMC phase (Cu3Sn) in the final interconnects was estimated according to the parabolic growth law with consideration of defect-induced deviation. The effect of predominantly Cu metal grain size on the Cu-Sn interdiffusion rate is discussed. The temperature versus time profile (ramp rate) is critical to control the morphology of scallops in the IMC. A low temperature ramp rate before reaching the bonding temperature is believed to be favorable in a SLID wafer-level bonding process.

Liu, H.; Wang, K.; Aasmundtveit, K. E.; Hoivik, N.

2012-09-01

128

First principle study on structural, mechanical and electronic properties of REAg (RE-Y, La, Pr and Er) intermetallic compounds  

NASA Astrophysics Data System (ADS)

The structural, electronic and mechanical properties of binary B2 - type CsCl structured intermetallic compounds of Ag (ReAg, Re= Y, La, Pr and Er) have been studies systematically by means of first principles density functional theory within generalized gradient approximation. Ground state properties such as lattice constant (a0), bulk modulus (B) and its pressure derivative (B') are obtained. The present results are in good agreement with the experimental and other theoretical calculation available. Amongst all the Intermetallics is found ErAg to be most ductile due to the presence of strong metallic bonding.

Sahu, A.; Makode, Chandrabhan; Pataiya, J.; Sanyal, Sankar P.

2013-02-01

129

High temperature oxidation of beryllium modified intermetallic compounds of the niobium-chromium system  

SciTech Connect

Intermetallic compounds based on the Laves phases NbCr2 and TiCr2 are of interest for high temperature applications. At temperatures where the high temperature strength and creep resistance of these compounds are excellent, their oxidation resistance is relatively poor. Beryllide compounds in the 3-Be, Ti-Be and Nb-Be systems (CrBe2, TiBel2, TiBez, NbBel2) on the other hand, exhibit excellent oxidation resistance even at temperaturets in excess of 1200' C, due to the formation of protective Be0 scales. The pure beryllides have relatively poor mechanical properties however. Therefore we have attempted to improve the oxidation resishnce of the Nb-Cr-Ti based Laves phases using alloying additions of beryllium. Alloys investigated include CrBe2, NbBe2 and NbCr2 with 10,25, and 33 atomic percent beryllium substituted for Cr. We have determined that there is a significant solubility of Be in NbCr2, Beryllium modified NbCr2 exhibits protective oxidation, with the growth of scales containing principally Cr2O3, and BeO.

Hanrahan, R. J. (Robert J.), Peters, M. I. (Maria I.); Cooley, J. C. (Jason C.); Hults, W. L. (William L.); Thoma, D. J. (Dan J.); Chen, K. C. (Katherine C.)

2001-01-01

130

Observation of superconductivity in the intermetallic compound ?-IrSn4.  

PubMed

Low-temperature dc-magnetization, ac electrical resistivity and specific heat measurements were performed on single crystals of the intermetallic compound ?-IrSn4. The compound crystallizes in the tetragonal MoSn4-type structure (space group I41/acd) and exhibits superconductivity below Tc = 0.9 0.05 K. Further, the magnitude of the ratios ?Cp/(?nkBTc) = 1.29, 2?/(kBTc) = 3.55 and of the electron-phonon coupling ?[overline](e-ph) = 0.5 imply that superconductivity in ?-IrSn4 can be ascribed to a s-wave weak coupling regime. We determined crucial thermodynamic characteristics of the superconducting state. It turned out that depending on the assumption of either a spherical or non-spherical Fermi surface, the superconductivity can be ascribed to either a type-I and type-II/1 or type-II in clean limit, respectively. However, the behavior of the upper critical field and the anisotropic crystalline structure of the studied compound provide strong support to the type-II superconductivity. In the normal state the resistivity exhibits a prominent quadratic temperature dependence, which together with a large Kadowaki-Woods ratio and with the enhanced effective mass indicate that the electrons in ?-IrSn4 are strongly correlated. PMID:23529025

Tran, Vinh Hung; Bukowski, Zbigniew; Wi?niewski, Piotr; Tran, Lan Maria; Zaleski, Andrzej J

2013-04-17

131

Targeted crystal growth of rare Earth intermetallics with synergistic magnetic and electrical properties: structural complexity to simplicity.  

PubMed

The single-crystal growth of extended solids is an active area of solid-state chemistry driven by the discovery of new physical phenomena. Although many solid-state compounds have been discovered over the last several decades, single-crystal growth of these materials in particular enables the determination of physical properties with respect to crystallographic orientation and the determination of properties without possible secondary inclusions. The synthesis and discovery of new classes of materials is necessary to drive the science forward, in particular materials properties such as superconductivity, magnetism, thermoelectrics, and magnetocalorics. Our research is focused on structural characterization and determination of physical properties of intermetallics, culminating in an understanding of the structure-property relationships of single-crystalline phases. We have prepared and studied compounds with layered motifs, three-dimensional magnetic compounds exhibiting anisotropic magnetic and transport behavior, and complex crystal structures leading to intrinsically low lattice thermal conductivity. In this Account, we present the structural characteristics and properties that are important for understanding the magnetic properties of rare earth transition metal intermetallics grown with group 13 and 14 metals. We present phases adopting the HoCoGa5 structure type and the homologous series. We also discuss the insertion of transition metals into the cuboctahedra of the AuCu3 structure type, leading to the synthetic strategy of selecting binaries to relate to ternary intermetallics adopting the Y4PdGa12 structure type. We provide examples of compounds adopting the ThMn12, NaZn13, SmZn11, CeCr2Al20, Ho6Mo4Al43, CeRu2Al10, and CeRu4Al16-x structure types grown with main-group-rich self-flux methods. We also discuss the phase stability of three related crystal structures containing atoms in similar chemical environments: ThMn12, CaCr2Al10, and YbFe2Al10. In addition to dimensionality and chemical environment, complexity is also important in materials design. From relatively common and well-studied intermetallic structure types, we present our motivation to work with complex stannides adopting the Dy117Co57Sn112 structure type for thermoelectric applications and describe a strategy for the design of new magnetic intermetallics with low lattice thermal conductivity. Our quest to grow single crystals of rare-earth-rich complex stannides possessing low lattice thermal conductivity led us to discover the new structure type Ln30Ru4+xSn31-y (Ln = Gd, Dy), thus allowing the correlation of primitive volumes with lattice thermal conductivities. We highlight the observation that Ln30Ru4+xSn31-y gives rise to highly anisotropic magnetic and transport behavior, which is unexpected, illustrating the need to measure properties on single crystals. PMID:25730512

Schmitt, Devin C; Drake, Brenton L; McCandless, Gregory T; Chan, Julia Y

2015-03-17

132

Crystal structure and chemical bonding of novel Li-containing polar intermetallic compound La{sub 11}Li{sub 12}Ge{sub 16}  

SciTech Connect

A novel Li-containing polar intermetallic compound La{sub 11}Li{sub 12}Ge{sub 16} 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) A, b=6.9932(6) A, and c=53.043(5) A. The complex crystal structure of the title compound can be described as a 2:1 intergrowth of two closely related compounds: La{sub 2}Li{sub 2}Ge{sub 3} (Ce{sub 2}Li{sub 2}Ge{sub 3}-type) and La{sub 3}Li{sub 4}Ge{sub 4} (Zr{sub 3}Cu{sub 4}Si{sub 4}-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 Ge{sub 2} 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 [LiGe{sub 4}] tetrahedra, cis-/trans-Ge chain and Ge{sub 2} dimers. - Graphical abstract: Reported is a novel ternary Li-containing polar intermetallic compound La{sub 11}Li{sub 12}Ge{sub 16}. The complex crystal structure can be viewed as a simple combination of two closely related known compounds acting as 'building-blocks', La{sub 2}Li{sub 2}G{sub 3} and La{sub 3}Li{sub 4}Ge{sub 4}, in a 2:1 stoichiometric ratio. Highlights: Black-Right-Pointing-Pointer A novel Li-containing polar intermetallic compound La{sub 11}Li{sub 12}Ge{sub 16} was synthesized. Black-Right-Pointing-Pointer The complex crystal structure was easily explained as a combination of two known compounds. Black-Right-Pointing-Pointer Theoretical calculations indicated that the Fermi level was located near the pseudogap.

Jung, Yaho; Nam, Gnu; Jeon, Jieun; Kim, Youngjo [Department of Chemistry, Chungbuk National University, Cheongju, 410 Seungbong-ro Heungduk-gu Chungbuk 361-763 (Korea, Republic of)] [Department of Chemistry, Chungbuk National University, Cheongju, 410 Seungbong-ro Heungduk-gu Chungbuk 361-763 (Korea, Republic of); You, Tae-Soo, E-mail: tsyou@chungbuk.ac.kr [Department of Chemistry, Chungbuk National University, Cheongju, 410 Seungbong-ro Heungduk-gu Chungbuk 361-763 (Korea, Republic of)] [Department of Chemistry, Chungbuk National University, Cheongju, 410 Seungbong-ro Heungduk-gu Chungbuk 361-763 (Korea, Republic of)

2012-12-15

133

On the site preferences of ternary additions to triple defect B2 intermetallic compounds  

SciTech Connect

Knowledge of the site preference of ternary solute additions is essential to developing an understanding of how these solutes affect the properties of B2 intermetallic compounds. A quasichemical model will be presented which is able to predict the site preferences of dilute solute additions to triple defect B2 compounds. The only parameters required are enthalpies of formation at the stoichiometric composition. General equations are developed which can be used to determine site occupations and defect concentrations for dilute as well as non-dilute solute additions. These equations use atom pair bond enthalpies as the parameters. It is found that the site preferences of dilute additions are not always in agreement with predictions based on the solubility lobes in ternary Gibbs isotherms, Predictions for dilute additions to NiAl and FeAl are compared to experimental results found in the literature. Satisfactory correlation is found between the model and the experimental results. In addition, the predictions from the model on vacancy concentrations in Fe doped NiAl are compared to recent experimental results by the authors.

Pike, L.M.; Chen, S.L.; Chang, Y.A. [Univ. of Wisconsin, Madison, WI (United States)] [and others

1995-12-31

134

Possibility of Mg- and Ca-based intermetallic compounds as new biodegradable implant materials.  

PubMed

Mg- or Ca-based intermetallic compounds of Mg2Ca, Mg2Si, Ca2Si and CaMgSi are investigated as possible new candidates for biodegradable implant materials, attempting to improve the degradation behavior compared to Mg and Ca alloys. The reactivity of Ca can be indeed reduced by the formation of compounds with Mg and Si, but its reactivity is still high for applications as an implant material. In contrast, Mg2Si shows a higher corrosion resistance than conventional Mg alloys while retaining biodegradability. In cytotoxicity tests under the severe condition conducted in this study, both pure Mg and Mg2Si showed relatively high cytotoxicity on preosteoblast MC3T3-E1. However, the cell viability cultured in the Mg2Si extract medium was confirmed to be better than that in a pure Mg extract medium in all the conditions investigated with the exception of the 10% extract medium, because of the lower corrosion rate of Mg2Si. The cytotoxicity derived from the Si ion was not significantly detected in the Mg2Si extract medium in the concentration level of ~70 mg/l measured in the present study. For aiming the practical application of Mg2Si as an implant material, however, its brittle nature must be improved. PMID:23910320

Hagihara, Koji; Fujii, Kenta; Matsugaki, Aira; Nakano, Takayoshi

2013-10-01

135

Physical properties and magnetic structure of the intermetallic CeCuBi2 compound  

NASA Astrophysics Data System (ADS)

In this work we combine magnetization, pressure dependent electrical resistivity, heat capacity, 63Cu nuclear magnetic resonance (NMR), and x-ray resonant magnetic scattering experiments to investigate the physical properties of the intermetallic CeCuBi2 compound. Our single crystals show an antiferromagnetic ordering at TN?16 K and the magnetic properties indicate that this compound is an Ising antiferromagnet. In particular, the low temperature magnetization data revealed a spin-flop transition at T =5 K when magnetic fields of about 5.5 T are applied along the c axis. Moreover, the x-ray magnetic diffraction data below TN revealed a commensurate antiferromagnetic structure with propagation wave vector (00 1/2 ) with the Ce3 + moments oriented along the c axis. Furthermore, our heat capacity, pressure dependent resistivity, and temperature dependent 63Cu NMR data suggest that CeCuBi2 exhibits a weak heavy fermion behavior with strongly localized Ce3 + 4 f electrons. We thus discuss a scenario in which both the anisotropic magnetic interactions between the Ce3 + ions and the tetragonal crystalline electric field effects are taking into account in CeCuBi2.

Adriano, C.; Rosa, P. F. S.; Jesus, C. B. R.; Mardegan, J. R. L.; Garitezi, T. M.; Grant, T.; Fisk, Z.; Garcia, D. J.; Reyes, A. P.; Kuhns, P. L.; Urbano, R. R.; Giles, C.; Pagliuso, P. G.

2014-12-01

136

Complex Compound Chemical Heat Pumps  

E-print Network

to adsorbate. Barium chloride, for instance, can complex up to 8 moles of ammonia in Complex compound solid-vapor fluid pairs can one coordination step. be used in heat of reaction heat pumps for temperature amplifier (TA) as well as heat BaC1 2 ? n NH 3... ~ BaCl 2 + n NH 3 amplifier (HA) cycle configurations. (1) This report describes the conceptual hardware with 0 ~ n ~ 8 design for complex compound industrial heat pumps. The main emphasis was directed towards a SOLID-VAroR HEAT OF REACTIOO...

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

137

Effect of Sn particle size on the intermetallic compound formations of cold sprayed Sn-Ni coatings  

NASA Astrophysics Data System (ADS)

Comparative studies on the intermetallic compound (IMC) formations of small (aggregated) and large Sn (irregular) with Ni and Cu in cold gas dynamic sprayed coatings were carried out. The Sn with high purity were selected and prepared as raw materials mixture in order to be sprayed onto Ni and Cu plate-shape substrates. The small particles of Sn (<1 ?m) were successfully coated under conventional coating parameters when they are mixed with larger powder materials. And microstructural observation regards to compound formation similarly worked out for both small and large Sn mixture. However, the intermetallic formation behavior was turned out to be different. After post-annealing, the larger Sn particles in the composite coating formed larger amount of IMC with Ni than small Sn although, owing to larger interfacial area, more intensive reactivities were expected. Also, there were significant differences in the size and distribution of eutectic pores as well.

Ko, K. H.; Lee, H.; Choi, J. O.

2011-01-01

138

Electrochemical behavior and the rate of general corrosion of NiAl intermetallic compound in the unbuffered sodium chloride solutions  

Microsoft Academic Search

Highly reproducible Tafel anodic and cathodic plots were obtained on NiAl intermetallic compound in the neutral and nearly neutral unbuffered NaCl solutions. The corrosion potentials and corrosion current densities were determined by the Tafel extrapolation technique at various pH values and concentrations of NaCl. The corrosion current density and Tafel slopes were determined by fitting the equation for the corrosion

K. V. Rybalka; L. A. Beketaeva; N. G. Bukhanko; A. D. Davydov

2011-01-01

139

The formation and growth of intermetallic compounds and shear strength at Sn-Zn solder\\/Au-Ni-Cu interfaces  

Microsoft Academic Search

The microstructures and shear strength of the interface between SnZn lead-free solders and Au\\/Ni\\/Cu interface under thermal aging conditions was investigated. The intermetallic compounds (IMCs) at the interface between SnZn solders and Au\\/Ni\\/Cu interface were analyzed by field emission scanning electron microscopy and transmission electron microscopy. The results showed the decrease in the shear strength of the interface with aging

K. S. Kim; K. W. Ryu; C. H. Yu; J. M. Kim

2005-01-01

140

Solid state intermetallic compound growth between copper and high temperature, tin-rich solderspart II: Modeling  

Microsoft Academic Search

The solder\\/base metal interfacial chemistry characterizing solder joints impacts the manufacturability and reliability of\\u000a electronic components. A model was developed to predict the long-term diffusion-controlled growth of interfacial intermetallic\\u000a compound layers using short-term experimental data. The model included terms for both constant and variable diffusion coefficients.\\u000a Application of the model was demonstrated using parameter values for 100Sn\\/Cu system and comparing

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

1994-01-01

141

Intermetallic compounds formed during interfacial reactions between liquid Sn8Zn3Bi solders and Ni substrates  

Microsoft Academic Search

The morphology and growth kinetics of intermetallic compounds (IMCs) formed at the interfaces between liquid Sn-8Zn-3Bi solders\\u000a and nickel substrates in the temperature range from 225C to 400C are investigated for the applications in bonding recycled\\u000a sputtering targets to their backing plates. The results show that a continuous single layer of Ni5Zn21 IMC appears at temperatures below 325C, while a

M. Y. Chiu; S. S. Wang; T. H. Chuang

2002-01-01

142

Effect of Cu stud microstructure and electroplating process on intermetallic compounds growth and reliability of flip-chip solder bump  

Microsoft Academic Search

In electroplating-based flip-chip technology, the Cu stud and solder deposition processes are two of the most important factors affecting the reliability of solder joints. The growth of Cu-Sn intermetallic compounds (IMC) also plays a critical role. In this paper, the effect of Cu stud surface roughness and microstructures on the reliability of solder joint was studied. The surface roughness of

Guo-Wei Xiao; Philip C. H. Chan; Annette Teng; Jian Cai; Matthew M. F. Yuen

2001-01-01

143

Structural intermetallics  

Microsoft Academic Search

The intent of the symposium was to provide a detailed and in-depth perspective of the approaches, results and progress toward the structural application of intermetallic compounds and their composites. Longer and insightful presentations which focused on real progress and trends rather than recent results, and extended discussion periods formed the centerpiece of this symposium to achieve these goals. Emphasis was

R. Darolia; J. J. Lewandowski; C. T. Liu; P. L. Martin; D. B. Miracle; M. V. Nathal

1993-01-01

144

Superconductivity in the quaternary intermetallic compounds LnNi2B2C  

Microsoft Academic Search

THE attainment of unprecedentedly high transition temperatures (Tcs) in the copper oxide superconductors illustrates how working with more complex chemical systems allows greater opportunity to balance opposing forces within a single chemical compound, leading to a better optimization of physical properties. For many desired properties, materials with optimal chemical complexity have undoubtedly not yet been found. This appears to be

R. J. Cava; H. Takagi; H. W. Zandbergen; J. J. Krajewski; W. F. Peck; T. Siegrist; B. Batlogg; R. B. van Dover; R. J. Felder; K. Mizuhashi; J. O. Lee; H. Eisaki; S. Uchida

1994-01-01

145

Discovery and characterization of magnetism in sigma-phase intermetallic Fe-Re compounds  

NASA Astrophysics Data System (ADS)

Systematic experimental studies (vibrating sample magnetometry) supported by theoretical calculations (electronic structure by spin self-consistent Korringa-Kohn-Rostoker Green's function method) were performed on a series of intermetallic sigma-phase Fe100-xRex (x = 43-53) compounds. All investigated samples exhibit magnetism with an ordering temperature ranging between 65 K for x = 43 and 23 K for x = 53. The magnetism was revealed to be itinerant and identified as a spin-glass (SG) possibly having a re-entrant character. The SG was found to be heterogeneous, viz., two regimes could be distinguished as far as irreversibility in temperature dependence of magnetization is concerned: (1) of a weak irreversibility and (2) of a strong one. According to the theoretical calculations, the main contribution to the magnetism comes from Fe atoms occupying all five sub lattices, while Re atoms have rather small magnetic moments. However, the calculated average magnetic moments highly (ferromagnetic ordering model) or moderately (antiparallel ordering model) overestimate the experimental data.

Cie?lak, J.; Dubiel, S. M.; Reissner, M.; Tobola, J.

2014-11-01

146

Machinability of Intermetallic Compound Fe3Al from the Viewpoint of Tool Wear  

NASA Astrophysics Data System (ADS)

The intermetallic compound Fe3Al was processed by a reactive sintering process, and its machinability from the viewpoint of tool wear was investigated using dry turning. In cutting Fe3Al with a cemented carbide tool, the tool life was approximately one tenth that of cutting carbon tool steel SK3 because of intense flank wear. The tool life for cutting Fe3Al using the cemented carbide P20(WC-TiC-TaC-Co) tool was longer than for cemented carbide K10(WC-Co). In addition, a cermet tool reached its tool life limit by chipping for the whole cutting speed range measured. The roughness of the machined surface of Fe3Al cut using a cemented carbide tool was much smaller than for SK3. However, for cutting using the cermet tool, the roughness showed a sharp rise due to chipping. It was found that the wear rate of the WC particles in the tool material is larger than TiC particles. The results of the study suggest that the cemented carbide P20 is suitable for cutting Fe3Al.

Sasaki, Tomohiro; Yakou, Takao

147

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

148

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

149

Moessbauer Study of the Ball Milling Disordering Process of FeAl Intermetallic Compounds  

SciTech Connect

Structural changes during ball milling of ordered Fe50Al50 intermetallic compounds were studied. X-Ray diffraction allowed the computation of a Long Range Order parameter (LRO) which dropped to zero after a short milling time. The initial B2 ordered structure gradually transforms into a disordered BCC structure, with a final crystallite size of about 25 nm. Moessbauer spectroscopy was used for obtaining a Chemical Short Range Order parameter (CSRO). Using a semiempirical n-body noncentral potential a model of the partially disordered B2 structure was built allowing computing the distribution of Quadrupole Splitting during the disordering process. Comparison between experimental and simulated Moessbauer spectra shows a maximum of disorder in the system for 5h milling, related to the highest value of the lattice spacing and the broader quadrupole hyperfine distribution. However, after milling for times longer than 5h, there is a change on the behavior of the experimental data that cannot be explained by the simple disordering process.

Oleszak, Dariusz [Faculty of Materials Science and Engineering, Warsaw University of Technology, Woloska 141, 02-507 Warsaw (Poland); Bruna, Pere; Crespo, Daniel [Departament de Fisica Aplicada, Escola Politecnica Superior de Castelldefels, Universitat Politecnica de Catalunya, Avda. del Canal Olimpic s/n, 08860-Castelldefels (Spain); Pradell, Trinitat [Departament de Fisica i Enginyeria Nuclear, ESAB, Universitat Politecnica de Catalunya, Urgell 187, 08036-Barcelona (Spain)

2005-04-26

150

Oxidation behavior of plasma sintered beryllium-titanium intermetallic compounds as an advanced neutron multiplier  

NASA Astrophysics Data System (ADS)

Beryllium intermetallic compounds (beryllides) such as Be12Ti are very promising candidates for advanced neutron multiplier materials in a demonstration fusion power reactor (DEMO). However, beryllides are too brittle to be fabricated either into pebble-type or rod-type shapes via conventional methods (i.e. arc melting and hot isostatic pressing). We have proposed a plasma sintering technique as a new method for beryllide fabrication, and our studies on the properties of plasma sintered beryllides are ongoing. In the present work, the oxidation properties of plasma sintered beryllides were investigated at 1273 K for 24 h in a dry air atmosphere to evaluate the high temperature properties of this material. Thermal gravimetry measurements indicate that specimens with larger fractions of Be12Ti phase corresponding to samples that have been sintered for longer time periods, exhibit superior oxidation properties. Our evaluation of the oxidation behavior of each phase in our beryllide samples is as follows: Be12Ti and Be17Ti2 both have good oxidation resistance, owing to the formation of dense and protective scales, while the Be and Be2Ti phases are mainly responsible for thermal-gravimetry (TG) weight gains, which is indicative of severe oxidation. We attribute the degradation in oxidation resistance specifically to Be2Ti that transforms into TiO2, and also find this phase to be the cause of deterioration in the mechanical properties of samples, owing to cracks near Be2Ti phase conglomerates.

Kim, Jae-Hwan; Nakamichi, Masaru

2013-07-01

151

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

152

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

153

Effect of Thermal Cycle on the Formation of Intermetallic Compounds in Laser Welding of Aluminum-Steel Overlap Joints  

NASA Astrophysics Data System (ADS)

The intermetallic compound (IMC) (or intermetallic phase layer) has a significant influence on the mechanical properties ofjoints between dissimilar metals obtained by thermal processes such as laser welding. Its formation is basically affected by thermal cycles in the joining or contact zone, where the IMC is formed. Within this study, the influence of the thermal cycle on the formation of the IMC during laser welding of an aluminum-steel (Al99.5-DC01) overlap joint was investigated. The temperature was measured directly by a thermocouple, and the weld seam was analyzed by scanning electron microscope (SEM). The influence of peak temperature, cooling time and the integral of the thermal cycle on the thickness of the IMC was identified and discussed. It was identified that cooling time has the biggest influence on the thickness of the IMC.

Fan, J.; Thomy, C.; Vollertsen, F.

154

Studies on Ni-Sn intermetallic compound and P-rich Ni layer at the electroless nickel UBM-solder interface and their effects on flip chip solder joint reliability  

Microsoft Academic Search

The electroless deposited Ni-P (Phosphorus) under bump metallurgy (UBM) layer was fabricated for Sn containing solder bumps. The amount of P in the electroless Ni film was optimized by controlling complexing agents and the pH of plating solution. The interfacial reaction at the electroless Ni UBM\\/solder interface was investigated in this work. The intermetallic compound (IMC) formed at the interface

Young-Doo Jeon; Kyung-Wook Paik; Kyoung-Soon Bok; Woo-Suk Choi; Chul-Lae Cho

2001-01-01

155

Mictomagnetic, ferromagnetic, and antiferromagnetic transitions in La(FexAl1-x)13 intermetallic compounds  

NASA Astrophysics Data System (ADS)

Cubic La(FexAl1-x)13 intermetallic compounds can be stabilized with iron concentration x between 0.46 and 0.92 in the NaZn13-type structure (D23) with Fm3c (O6h) space-group symmetry. Here the Fe-Fe coordination number can increase up to 12. At low x values, a mictomagnetic regime occurs with distinct cusps in the ac susceptibility. With the increase of the iron concentration, a soft ferromagnetic phase is found which at lower temperatures shows anisotropy effects related to reentrant mictomagnetic behavior. Finally, for x>0.86, antiferromagnetic order appears along with a sharp metamagnetic transition in external fields of a few teslas. The saturation magnetic moment increases linearly with x from 1.4?B/Fe to 2.1?B/Fe throughout the ferromagnetic and antiferromagnetic regime. The breakdown of long-range ferromagnetic order at high x values can be explained by modifications of the iron moment and their coupling at a large Fe-Fe coordination number. However, with application of a magnetic field, the ferromagnetic state can be fully recovered. The room-temperature resistivity decreases with increasing x from 200 to 160 ?? cm. The low-temperature slope d?/dT is related to the magnetic order, being negative in the antiferromagnetic state and positive in the ferromagnetic state. The metamagnetic transition causes a decrease of the resistivity of about 20% and a sign change in d?/dT. This behavior is discussed in terms of the two-current model. The thermal expansion exhibits a strong Invar character and is described by a combined band and local-moment model which allows calculations of corresponding magnetovolume coupling constants. The metamagnetic transition causes a large magnetic striction.

Palstra, T. T. M.; Nieuwenhuys, G. J.; Mydosh, J. A.; Buschow, K. H. J.

1985-04-01

156

New observations on intermetallic compound formation in gold ball bonds: general growth patterns and identification of two forms of Au4Al  

Microsoft Academic Search

Relatively little information is available on the growth patterns and metallurgy of AuAl intermetallics in fine-pitch (FP) and ultra-fine pitch (UFP) ball bonding. This paper presents a study of the growth pattern and chemistry of intermetallic compounds formed between a 25 ?m 4 N gold wire and aluminium pad metallization after isothermal ageing in air at 175 C. The data

C. D. Breach; F. Wulff

2004-01-01

157

Hillock and Whisker Growth on Sn and SnCu Electrodeposits on a Substrate Not Forming Interfacial Intermetallic Compounds  

NASA Astrophysics Data System (ADS)

Intermetallic compound (IMC) formation at the interface between the tin (Sn) plating and the copper (Cu) substrate of electronic components has been thought to produce compressive stress in Sn electrodeposits and cause the growth of Sn whiskers. To determine if interfacial IMC is a requirement for whisker growth, bright Sn and a Sn-Cu alloy were electroplated on a tungsten (W) substrate that does not form interfacial IMC with the Sn or Cu. At room temperature, conical Sn hillocks grew on the pure Sn deposits and Sn whiskers grew from the Sn-Cu alloy electrodeposits. These results demonstrate that interfacial IMC is not required for initial whisker growth.

Williams, M. E.; Moon, K.-W.; Boettinger, W. J.; Josell, D.; Deal, A. D.

2007-03-01

158

Asymmetric properties of hydrides of intermetallic compounds based on rare-earth metals, Ni, and Co modified by (+)-tartaric acid  

SciTech Connect

It has been shown that the hydrides of intermetallic compounds with the general formula LnNi/sub 5-x/Co/sub x/ (Ln = La, Sm, Gd; 0 less than or equal to x less than or equal to 5) are active catalysts in the enantioselective hydrogenation of ethyl acetoacetate (EAA). The influence of the pH of the modifying solution on the asymmetric properties of the catalysts at pH 2-14 has been investigated. The stability of the operation of catalysts under the conditions of the modification step and the hydrogenation of EAA has been studied with the aid of a magnetic method.

Starodubtseva, E.V.; Konenko, I.R.; Fedorovskaya, E.A.; Klabunovskii, E.I.; Mordovin, V.P.

1987-03-10

159

Enthalpies of formation of CdPr intermetallic compounds and thermodynamic assessment of the CdPr system  

PubMed Central

In the present study standard enthalpies of formation were measured by reaction and solution calorimetry at stoichiometric compositions of Cd2Pr, Cd3Pr, Cd58Pr13 and Cd6Pr. The corresponding values were determined to be ?46.0, ?38.8, ?35.2 and ?24.7kJ/mol(at), respectively. These data together with thermodynamic data and phase diagram information from literature served as input data for a CALPHAD-type optimization of the CdPr phase diagram. The complete composition range could be described precisely with the present models, both with respect to phase equilibria as well as to thermodynamic input data. The thermodynamic parameters of all intermetallic compounds were modelled following NeumannKopp rule. Temperature dependent contributions to the individual Gibbs energies were used for all compounds. Extended solid solubilities are well described for the low- and high-temperature modifications of Pr and also for the intermetallic compound CdPr. A quite good agreement with all viable data available from literature was found and is presented. PMID:25540475

Reichmann, Thomas L.; Richter, Klaus W.; Delsante, Simona; Borzone, Gabriella; Ipser, Herbert

2014-01-01

160

Electronic and high pressure elastic properties of RECd and REHg (RE=Sc, La and Yb) intermetallic compounds  

NASA Astrophysics Data System (ADS)

Structural, electronic, elastic and mechanical properties of Cd and Hg based rare earth intermetallics (RECd and REHg; RE=Sc, La and Yb) have been investigated using the full-potential linearized augmented plane-wave (FP-LAPW) method within the density-functional theory (DFT). The ground state properties such as lattice constant (a0), bulk modulus (B) and its pressure derivative (B?) have been obtained using optimization method and are found in good agreement with the available experimental results. The calculated enthalpy of formation shows that LaHg has the strongest alloying ability and structural stability. The electronic band structures and density of states reveal the metallic character of these compounds. The structural stability mechanism is also explained through the electronic structures of these compounds. The chemical bonding between rare earth atoms and Cd, Hg is interpreted by the charge density plots along (1 1 0) direction. The elastic constants are predicted from which all the related mechanical properties like Poisson's ratio (?), Young's modulus (E), shear modulus (GH) and anisotropy factor (A) are calculated. The ductility/brittleness of these intermetallics is predicted. Chen's method has been used to predict the Vicker's hardness of RECd and REHg compounds. The pressure variation of the elastic constants is also reported in their B2 phase.

Devi, Hansa; Pagare, Gitanjali; Chouhan, Sunil S.; Sanyal, Sankar P.

2015-01-01

161

Hyperfine interactions at Ta impurities in cobalt and cobalt-hafnium intermetallic compounds  

NASA Astrophysics Data System (ADS)

The magnetic and electric hyperfine interaction of 181Ta impurities on substitutional sites of cobalt metal has been investigated by ?? perturbed angular correlations (PAC) in samples prepared by melting and ion implantation of 181Hf. In molten samples the saturation value of the magnetic hyperfine field of Ta is HHF(Ta:Co(hcp); 9 K)=-40.7(6) T for hexagonal Co and ||HHF(181Ta:Co(fcc) 9 K)||=36.3(5) T for cubic Co. In ion-implanted samples radiation damage causes a slight reduction of the hyperfine field. The magnetic hyperfine field of 181Ta has also been determined in Fe: ||HHF(181Ta:Fe 9 K)||=61.7(9) T for a polycrystalline sample prepared by 181Hf implantation. The temperature dependence of HHF in Co has been measured between 9 and 1410 K. HHF(T) in the hexagonal phase (T<700 K) suggests a Curie temperature for hcp Co of TC(hcp)=975(50) K. In the cubic phase, HHF(T) of 181Ta is close to the magnetization curve of the host with TC(fcc)=1398(5) K, in contrast to the anomalous temperature dependence of HHF of most other impurities in Co investigated up to now. The electric-field gradient of 181Ta on substitutional sites of hexagonal Co is ||Vzz(181Ta:Co 9 K)||=1.23(4)1017 V/cm2. The PAC spectra reflect the transformation of the solid solution of 0.2 at. % of Hf in elemental Co into the Co-Hf intermetallic compounds Hf2Co7 and Hf6Co23 in the temperature range 900<=T<=1320 K. Upon cooling from 1400 K, elemental Co starts to transform into Hf6Co23 at about 1320 K and into Hf2Co7 at about 1220 K. At 1100 K the evolution of the phase equilibrium between the solid solution and Hf2Co7 was observed to occur with a half-life of T1/2=5.5(4) h. The temperature dependence of the hyperfine-interaction parameters suggests magnetic-ordering temperatures of 450 K and 750 K for Hf2Co7 and Hf6Co23, respectively.

Bedi, S. C.; Forker, M.

1993-06-01

162

Morphology of intermetallic compounds formed between lead-free Sn-Zn based solders and Cu substrates  

Microsoft Academic Search

The morphologies of intermetallic compounds formed between Sn-Zn based solders and Cu substrates were investigated in this\\u000a study. The investigated solders were Sn-9Zn, Sn-8.55Zn-0.45Al, and Sn-8.55Zn-0.45Al-0.5Ag. The experimental results indicated\\u000a that the Sn-9Zn solder formed Cu5Zn8 and CuZn5 compounds on the Cu substrate, while the Al-containing solders formed the Al4.2Cu3.2Zn0.7 compound. The addition of Ag to the Sn-8.55Zn-0.45Al solder resulted

Chia-Wei Huang; Kwang-Lung Lin

2006-01-01

163

Morphology of intermetallic compounds formed between lead-free Sn-Zn based solders and Cu substrates  

NASA Astrophysics Data System (ADS)

The morphologies of intermetallic compounds formed between Sn-Zn based solders and Cu substrates were investigated in this study. The investigated solders were Sn-9Zn, Sn-8.55Zn-0.45Al, and Sn-8.55Zn-0.45Al-0.5Ag. The experimental results indicated that the Sn-9Zn solder formed Cu5Zn8 and CuZn5 compounds on the Cu substrate, while the Al-containing solders formed the Al4.2Cu3.2Zn0.7 compound. The addition of Ag to the Sn-8.55Zn-0.45Al solder resulted in the formation of the AgZn3 compound at the interface between the Al4.2Cu3.2Zn0.7 compound and the solder. Furthermore, it was found that the cooling rate of the specimen after soldering had an effect on the quantity of AgZn3 compound formed at the interface. The AgZn3 compound formed with an air-cooling condition exhibited a rougher surface and larger size than with a water-quenched condition. It was believed that the formation of the AgZn3 compound at the interface occurs through heterogenous nucleation during solidification.

Huang, Chia-Wei; Lin, Kwang-Lung

2006-12-01

164

Growth behavior of intermetallic compounds during reactive diffusion between aluminum alloy 1060 and magnesium at 573-673 K  

NASA Astrophysics Data System (ADS)

A potential new research reactor fuel design proposes to use U-Mo fuel in a Mg matrix clad with Al. Interdiffusion between the Mg containing fuel core and Al cladding can result in the formation of intermetallic compounds that can be detrimental to fuel element performance. The kinetics of the reactive diffusion in the binary Al-Mg system was experimentally studied. Layers of the intermetallic compounds, ? (Al3Mg2) and ? (Al12Mg17) phases, were formed between the Al alloy 1060 and Mg during annealing. The ? layer was observed to grow faster than the ? phase. The thickness of each layer can be expressed by a power function of the annealing time with the exponent n close to 0.5 for the ? phase and less than 0.5 for the ? phase. The results suggest that the growth of ? phase is controlled by lattice diffusion and that of the ? phase by grain boundary and lattice diffusion. Metallographic examination showed the grain boundary diffusion in the form of columnar growth of ? phase during annealing. Based on the reactive diffusion equation developed in this work, in the absence of irradiation effects, it will take more than 110 h to consume a half thickness of 400 ?m of the cladding.

Xiao, Lin; Wang, Ning

2015-01-01

165

Emerging applications of intermetallics  

Microsoft Academic Search

Many intermetallic compounds display an attractive combination of physical and mechanical properties, including high melting point, low density and good oxidation or corrosion resistance. This has led to their utilization in many non-structural applications, but success in structural applications has, to date, been limited. This paper reviews the current status of intermetallic applications, with emphasis on new uses that are

N. S Stoloff; C. T Liu; S. C Deevi

2000-01-01

166

Native metals and intermetallic compounds in heavy concentrate halos of the Ol'khovaya-1 River, Kamchatsky Mys Peninsula, eastern Kamchatka  

NASA Astrophysics Data System (ADS)

Various native metals (Pb, Sn, Bi, and Cu) and intermetallic compounds (Au-Pb), (Au-Ag-Pb-Sb), (Pb-Sb), (Pb-Sn), and (Au-Ag-Pb-Sn) have been revealed in placer gold deposits in the Ol'khovaya-1 River and heavy concentrate halos on the Kamchatsky Mys Peninsula, eastern Kamchatka. Interrelations (intergrowths and inclusions) of these metals and intermetallic compounds with gold and host rocks show that they are of natural origin and genetically related to the hydrothermal metasomatic alteration of the Kamchatsky Mys ultramafic massif.

Sandimirova, E. I.; Sidorov, E. G.; Chubarov, V. M.; Ibragimova, E. K.; Antonov, A. V.

2014-12-01

167

Intermetallic compounds formation and interfacial adhesion strength of Sn9Zn0.5Ag solder alloy hot-dipped on Cu substrate  

Microsoft Academic Search

The intermetallic compounds formation and interfacial adhesion strength of the Sn9Zn0.5Ag lead-free solder alloy hot-dipped on Cu substrate have been investigated by pull-off test, X-ray diffractometry, optical microscopy, scanning electron microscopy, transmission electron microscopy and energy dispersive spectrometry. The intermetallic compounds of Ag3Sn, Cu6Sn5 and Cu5Zn8 were identified for Sn9Zn0.5Ag solder alloyCu, in which the thickness of Cu6Sn5 increased from

Tao-Chih Chang; Min-Hsiung Hon; Moo-Chin Wang

2003-01-01

168

High pressure and high temperature investigations on intermetallic compounds using energy-dispersive X-ray powder diffraction  

NASA Astrophysics Data System (ADS)

The intermetallic compounds Mg2Si, MoSi2, WSi2, CrSi2, NbSi2, Ti5Si3, TiSi2, ZrSi2 and Al3Nb were investigated in a pressure range up to 70 kbar and a temperature range up to 1500C in order to determine previously unknown elastic constants and possible phase transformations. The experiments were carried out using the multi-anvil-X-ray apparatus MAX-80 and synchrotron radiation at HASYLAB. A complete phase transition of cubic Mg2Si to a hexagonal phase was observed at 70 kbar and 450C. The high-pressure/high-temperature phase was quenched and recovered for further investigations. All the other compounds remained stable in the mentioned pressure and temperature range. The bulk moduli covered the range from 436 (10) (Mg2Si) to 3350 (190) (WSi2) kbar.

Peun, T.; Lauterjung, J.; Hinze, E.

1995-05-01

169

On the formation of Al{sub 3}Ni{sub 2} intermetallic compound by aluminothermic reduction of nickel oxide  

SciTech Connect

Simultaneous reduction of NiO and formation of Al{sub 3}Ni{sub 2} intermetallic compound at 880, 940 and 1000 deg. C were investigated by means of the thermal reduction method. The optimal Ni contents for the starting samples were determined at different times and temperatures through the compositional analysis. The microstructure of the metallic quenched samples was observed by scanning electron microscope. Moreover, the X-ray diffraction analysis and energy disperse spectrometry were applied to characterize the formation of the phases. The results showed that the metallic samples consisted of Al{sub 3}Ni{sub 2}, Al{sub 3}Ni and Al phases and that there was no trace of Ni, NiO and Al{sub 2}O{sub 3}. It was found that after 10 min at the applied temperatures, the reaction completed. For the longer time, the dispersed Al{sub 3}Ni{sub 2} nuclei were grown and its continuous network formed. By increasing the temperature, the thickness of the Al{sub 3}Ni precipitation around Al{sub 3}Ni{sub 2} phase is enhanced in the samples with the same Ni content. A model was proposed for these reactions. - Research Highlights: {yields} Simultaneous reduction of NiO, and Al{sub 3}Ni{sub 2} intermetallics formation at temperatures lower than Ni melting point. {yields} Presently a mechanism for such a process. {yields} Parametric study of microstructure and formed phases.

Parsa, M.R.; Soltanieh, M., E-mail: mansour_soltanieh@iust.ac.ir

2011-07-15

170

Wear Properties of Intermetallic Compound Reinforced Functionally Graded Materials Fabricated by Centrifugal Solid-particle and In-Situ Methods  

NASA Astrophysics Data System (ADS)

One of the functionally graded material (FGM) fabrication methods is a centrifugal method, which is an application of the centrifugal casting technique. The centrifugal force applied to a homogeneous molten composite assists the formation of the desired gradation. In this paper, the wear properties of two kinds of Al base FGMs, namely Al-Al3Ti FGM and Al-Al3Ni FGM, are reported. The former and the latter hold the oriented intermetallic compound platelets and the particle size gradient, respectively. Here, volume fraction, size, shape and orientation of the reinforcements in the composite play an important role in improving the mechanical properties of the materials, whereby FGMs with oriented platelets or particle size gradient may have special mechanical properties such as increased wear resistance. Based on the experimental results, the origin of anisotropic wear resistance and the effect of particle size on the wear properties are discussed.

Watanabe, Yoshimi; Sato, Hisashi; Fukui, Yasuyoshi

171

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

172

Hydrogen ordering in rare-earth intermetallic (Er, Tb)Fe2 compounds with giant spontaneous magnetostriction  

NASA Astrophysics Data System (ADS)

X-ray diffraction studies of rare-earth intermetallic Er1 - x Tb x Fe2 compounds (with 0 ? x ? 0.6) and their hydrides were performed at room temperature. As the terbium content ( x) in Er1 - x Tb x Fe2 increases, the sign of the magnetostriction constant ?111 was shown to alternate from positive to negative. The lattice parameters, amount of incorporated hydrogen, and sizes of interstices were found to increase with increasing terbium content. The sizes of interstices accessible for occupation with hydrogen atoms were calculated for all alloys and their hydrides. Spontaneous anisotropic magnetostriction related to the rare-earth atoms was found to make no determining contribution to the resulting crystal lattice distortion caused by the incorporation of hydrogen atoms.

Stashkova, L. A.; Gaviko, V. S.; Mushnikov, N. V.; Terent'ev, P. B.

2013-12-01

173

Electronic structure, magnetic, and optical properties of the intermetallic compounds R2Fe17 (R=Pr,Gd)  

NASA Astrophysics Data System (ADS)

In this paper we report comprehensive experimental and theoretical investigation of magnetic and electronic properties of the intermetallic compounds Pr2Fe17 and Gd2Fe17 . Electronic structure of these two systems was probed by optical measurements in the spectral range of 0.22-15?m . On top of that, charge-carrier parameters (plasma frequency ? and relaxation frequency ? ) and optical conductivity ?(?) were determined. Self-consistent spin-resolved band-structure calculations within the conventional LSDA+U method were performed. Theoretical interpretation of the experimental ?(?) dispersions indicates transitions between 3d and 4p states of Fe ions to be the biggest ones. Qualitatively the line shape of the theoretical optical conductivity coincides well with our experimental data. Calculated by the LSDA+U method magnetic moments per formula unit are found to be in good agreement with observed experimental values of saturation magnetization.

Knyazev, Yu. V.; Lukoyanov, A. V.; Kuz'Min, Yu. I.; Kuchin, A. G.; Nekrasov, I. A.

2006-03-01

174

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

175

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

176

Structural determination of NaAl 2Ga 2 intermetallic compound having the ThCr 2Si 2 type structure  

Microsoft Academic Search

NaAl2Ga2 intermetallic compound has been synthesized by direct combination of the elements in the atomic ratio Na:Ga:Al=1:2:2. GuinierHgg X-ray and neutron powder diffraction determined a ThCr2Si2 type structure for the new compound with tetragonal unit cell axis a=4.1817(5) and c=11.388(2).

K. Kadir; D. Norus

2009-01-01

177

Kinetics of intermetallic compound growth between nickel, electroless, NiP, electroless NiB and tin at 453 to 493 K  

Microsoft Academic Search

The growth kinetics, crystal structure, and morphology of the intermetallic compounds formed between nickel, electroless Ni-P and electroless Ni-B coatings with tin at 453 to 493 K for times up to 506 h have been determined by microscopical and X-ray diffraction techniques. The compound Ni3Sn4 was formed. All kinetics followed as parabolic law with activation energies of 128.0, 130.4, and

W. J. Tomlinson; H. G. Rhodes

1987-01-01

178

Ab initio calculations on elastic properties in L12 structure Al3X and X3Al-type (X=transition or main group metal) intermetallic compounds  

NASA Astrophysics Data System (ADS)

As high-temperature structural materials, L12 intermetallic compounds have attracted the strong interest from both fundamental and industrial aspects. Understanding of elastic property is a basis for the complete investigations of mechanical behavior of L12 alloys. In an effort to explore the electronic origin of elastic properties of L12 intermetallics, we have performed a systematic study on elastic constants for single crystals, and Young's modulus, shear modulus, bulk modulus and Poisson's ratio for poly-crystals of 22 known Al3X and X3Al-type (X=transition or main group metal) intermetallics using the ab initio calculations. Based on the calculations of elastic constants and extreme (both positive and negative) Poisson's ratios, we found a pronounced correlation between the extreme Poisson's ratio and the elastic anisotropy, i.e., approximate 40% of the investigated L12 intermetallics exhibit intrinsic auxetic behavior. Furthermore, based on the distribution of bonding charge densities, we revealed that the ductility and extreme Poisson's ratios were attributable to the directionality of bonds of these alloys. Our findings provide a new method to predict mechanical behavior of intermetallics.

Tian, T.; Wang, X. F.; Li, W.

2013-03-01

179

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

180

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

181

Permanent magnetism of intermetallic compounds between light and heavy transition-metal elements.  

PubMed

First-principle calculations are used to investigate the intrinsic magnetic properties of intermetallic alloys of the type XMn, where X is a 4d or 5d element and M is Fe or Co. Emphasis is on the hexagonal C14 Laves-phase 1:2 and 1:5 alloys, the latter crystallizing in the CaCu5 structure. These series are of interest in permanent magnetism from fundamental and practical viewpoints, respectively. In the former, the unit cells form a prototypical motif where a heavy atom with high spin-orbit coupling and magnetocrystalline anisotropy is surrounded by many somewhat smaller M atoms with high magnetization, and the latter are Laves-phase derivatives of renewed interest in permanent magnetism. Our DFT calculations predict magnetic moments, magnetizations and anisotropies, as well as formation energies. The results are analyzed across the 4d and 5d series, especially with respect to hybridization effects between 3d and 4d/5d bands. PMID:24469225

Kumar, P; Kashyap, A; Balamurugan, B; Shield, J E; Sellmyer, D J; Skomski, R

2014-02-12

182

Calculation of the electronic structure of the intermetallic compounds ErNi5 - x Al x ( x = 0, 1, 2)  

NASA Astrophysics Data System (ADS)

The evolution of the electronic structure of the intermetallic compounds ErNi5 - x Al x ( x = 0, 1, 2) with different positions of the substitution of aluminum atoms for nickel atoms has been investigated. For this purpose, spin-polarized calculations of the energy band spectra of these compounds have been performed using the LSDA + U method, which in the local spin density approximation takes into account strong electron correlations in the 4 f shell of the erbium ion. Variants of the substitution of aluminum atoms for nickel atoms in different crystallographic positions in the 3 d sublattice have been considered. An analysis of the band structure has demonstrated that substitutional aluminum impurities lead to the formation of nonmagnetic nickel 3 d states and to a significant decrease in the electron density of states at the Fermi level. A comparison of the total energies of the substitutional configurations has revealed that the occupation of the 3 g positions by aluminum atoms is more energetically favorable.

Lukoyanov, A. V.; Knyazev, Yu. V.

2015-01-01

183

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

2012-12-01

184

The Electrochemical Formation of Ni-Tb Intermetallic Compounds on a Nickel Electrode in the LiCl-KCl Eutectic Melts  

NASA Astrophysics Data System (ADS)

The work presents an electrochemical study on the formation of Ni-Tb intermetallic compounds in the LiCl-KCl-TbCl3 melts on tungsten and nickel electrodes at 773 K (500 C) by electrochemical techniques. For a tungsten electrode, cyclic voltammetry and square-wave voltammetry showed that the electrochemical reduction of Tb(III) proceeded in a one-step process involving three electrons at -2.06 V ( vs Ag/AgCl). For a nickel electrode, the reduction potential of Tb(III)/Tb was observed at more positive values than those on W electrode by cyclic voltammetry, due to the formation of Ni-Tb intermetallic compounds. Square-wave voltammetry and open-circuit chronopotentiometry put into evidence the formation of intermetallic compounds at around -1.27, -1.63, and -1.88 V, respectively. Three alloy samples were obtained by potentiostatic electrolysis on a Ni electrode at various potentials and analyzed by X-ray diffraction, scanning electron micrograph, and energy-dispersive spectrometry. The analysis results confirmed the formation of Ni17Tb2, Ni5Tb, and Ni2Tb alloy compounds.

Han, Wei; Sheng, Qingnan; Zhang, Milin; Li, Mei; Sun, Tingting; Liu, Yaochen; Ye, Ke; Yan, Yongde; Wang, Yingcai

2014-06-01

185

Synthesis and characterization of patterned surfaces and catalytically relevant binary nanocrystalline intermetallic compounds  

E-print Network

As devices and new technologies continue to shrink, nanocrystalline multi-metal compounds are becoming increasingly important for high efficiency and multifunctionality. However, synthetic methods to make desirable nanocrystalline multi...

Cable, Robert E.

2009-05-15

186

Magnetic structure and magnetic entropy change in the intermetallic compound DyCoAl  

Microsoft Academic Search

Magnetic and magnetocaloric properties of polycrystalline DyCoAl compound have been studied in fields up to 9 T. This compound orders ferromagnetically at ~37 K (TC). A maximum magnetic entropy change of ~-18 J\\/kg\\/K is obtained for a field change of 9 T near TC which is reasonably large. Low temperature neutron powder diffraction data indicate collinear ferromagnetic structure where Dy

J. Arout Chelvane; Tilak Das; Rabindra Nath Mahato; A. V. Morozkin; Jagat Lamsal; W. B. Yelon; R. Nirmala; S. K. Malik

2010-01-01

187

Band gap and stability in the ternary intermetallic compounds NiSnM (M=Ti,Zr,Hf): A first-principles study  

Microsoft Academic Search

The structural stability and electronic properties of the ternary intermetallic compounds NiSnM (M=Ti,Zr,Hf) and the closely related Heusler compounds Ni2SnM are discussed using the results of ab initio pseudopotential total-energy and band-structure calculations performed with a plane-wave basis set using the conjugate gradients algorithm. The results characterize the lowest-energy phase of NiSnM compounds, with a SnM rocksalt structure sublattice, as

Serdar gt; Karin M. Rabe

1995-01-01

188

A Study on the Effect of Ageing and Intermetallic Compound Growth on the Shear Strength of Surface Mount Technology Solder Joints  

NASA Astrophysics Data System (ADS)

The effect of ageing and intermetallic compound formation on the surface mount solder joints and its shear strength behavior under extreme mechanical and thermal conditions have been discussed in this paper. The specimens used are solder paste (Sn3.8Ag0.7Cu), bench marker II printed circuit boards (PCB), resistors 1206 and the fabrication of solder joints makes use of conventional surface mount technology (SMT). Reflow process was carried out at a peak temperature of 250 C and the test samples were exposed to isothermal ageing at a constant temperature of 150 C for a period of 600 h. Shear test was conducted on the PCB's. The shear strength of the solder joints rapidly increased during isothermal ageing to a certain time period and then started decreasing. Field emission scanning electron microscopy (FESEM) micrograph of the solder joint and energy dispersive X-ray (EDX) was performed on the solder sample to verify the formation of intermetallic compounds.

Nath, Jyotishman; Mallik, Sabuj; Borah, Anil

2015-04-01

189

Interfaces in lead-free solder alloys: Enthalpy of formation of binary AgSn, CuSn and NiSn intermetallic compounds  

Microsoft Academic Search

Standard enthalpies of formation were determined for a number of binary intermetallic compounds in the systems AgSn, CuSn, and NiSn by means of solution calorimetry in liquid Sn in a Calvet-type microcalorimeter. For the pure elements Ag, Cu, and Ni, the limiting partial enthalpies of mixing as well as the enthalpies of solution at infinite dilution in Sn were measured

H. Flandorfer; U. Saeed; C. Luef; A. Sabbar; H. Ipser

2007-01-01

190

Intermetallic compound growth on Ni, Au\\/Ni, and Pd\\/Ni substrates with Sn\\/Pb, Sn\\/Ag, and Sn solders [PWBs  

Microsoft Academic Search

The growth mechanism of the Ni3Sn4 intermetallic compound (IMC) during aging was studied with three different solders (100Sn, Sn-3.5Ag, and Sn-37Pb) on three different substrates (Ni, Ni\\/Au, and Ni\\/Pd), at the temperatures of 75, 100, 125, and 160C from 1 to 36 days. The growth rates of Ni3Sn 4 with Sn on Ni and Ni\\/Au substrates were similar, growing to

Howard D. Blair; Tsung-Yu Pan; John M. Nicholson

1998-01-01

191

Strong interplay between structure and magnetism in the giant magnetocaloric intermetallic compound LaFe11.4Si1.6: a neutron diffraction study  

Microsoft Academic Search

Crystallographic and magnetic structures of the cubic NaZn13-type intermetallic compound LaFe11.4Si1.6 have been studied by means of powder neutron diffraction. Rietveld analysis indicates that Si atoms substitute for Fe atoms randomly on two different Fe sites. All spins in the unit cell are aligned ferromagnetically with the FeI (8b) moment smaller than the FeII (96i) one. The long-range ferromagnetic ordering

Fangwei Wang; Guang-jun Wang; Feng-xia Hu; A. Kurbakov; Bao-gen Shen; Zhao-hua Cheng

2003-01-01

192

Nanoclusters based on pentagondodecahedra with shells in the form of D32, D42, and D50 deltahedra in crystal structures of intermetallic compounds  

SciTech Connect

The TOPOS software package has been used to form a database of intermetallic compounds containing pentagondodecahedral d clusters (528 crystal structures of intermetallic compounds, 111 topological types, and 47 space symmetry groups). On the whole, 606 atomic d configurations have been selected which are described by 14 point symmetry groups. Examples of nanoclusters are presented which are precursors of the crystal structures of intermetallic compounds with the outer shell in the form of deltahedra D, which are formed above dodecahedra. These nanoclusters are identified in the automatic mode of structural data processing: D32 (K{sub 8}In{sub 6}Ge{sub 40}, Cs{sub 30}Na{sub 3}Sn{sub 162}), D{sub 42} (Ru{sub 3}Be{sub 17}, Y{sub 3}Cd{sub 18}, Ca{sub 3}(Cd{sub 17}Al)), and D{sub 50} (Yb{sub 3}Zn{sub 18}, Ce{sub 3}(Au{sub 14}Sn{sub 3}), Pr{sub 3}Cd{sub 18}, Eu{sub 4}Cd{sub 25}), where 32, 42, and 50 are the numbers of atoms in the shell. Similar deltahedra were found previously in icosahedral nanoclusters (precursors of intermetallic compounds). Structures with the dodecahedral nanocluster precursors containing D42 and D50 deltahedra are approximants of MCd{sub 5.7} (M = Yb or Ca) quasicrystals and belong to the family of MCd{sub 6} (M = Ce, Pr, Nd, Sm, Eu, Gd, Dy, Yb, Y, or Ca).

Pankova, A. A. [Samara State University (Russian Federation); Ilyushin, G. D., E-mail: ilyushin@mail.ru [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Blatov, V. A. [Samara State University (Russian Federation)

2012-01-15

193

The nanoindentation characteristics of Cu 6 Sn 5 , Cu 3 Sn, and Ni 3 Sn 4 intermetallic compounds in the solder bump  

Microsoft Academic Search

In general, formation and growth of intermetallic compounds (IMCs) play a major role in the reliability of the solder joint\\u000a in electronics packaging and assembly. The formation of Cu-Sn or Ni-Sn IMCs have been observed at the interface of Sn-rich\\u000a solders reacted with Cu or Ni substrates. In this study, a nanoindentation technique was employed to investigate nanohardness\\u000a and reduced

Guh-Yaw Jang; Jyh-Wei Lee; Jeng-Gong Duh

2004-01-01

194

Evidence for Cu ion formation by dissolution and dealloying the AlCuMg intermetallic compound in rotating ring-disk collection experiments  

Microsoft Academic Search

Rotating ring-disk collection experiments and stripping voltammetry have been used to detect Cu ions generated by dissolution of the AlCuMg intermetallic compound in aqueous chloride solutions. Cu ions are generated under open-circuit conditions (open-circuit potential -0.930 V{sub SCE}), or by slight anodic or cathodic polarization ({+-}0.050 V from the open-circuit potential). In all cases, Cu ion generation occurs even though

R. G. Buchheit; M. A. Martinez; L. P. Montes

2000-01-01

195

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=0.780.08 was observed, suggesting that a combination of

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

1997-01-01

196

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

197

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

SciTech Connect

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. Cu{sub 6}Sn{sub 5} and Cu{sub 3}Sn IMCs formed at the cold end and grew rapidly during the whole soldering process. However, only Cu{sub 6}Sn{sub 5} 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 Cu{sub 6}Sn{sub 5} 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, E-mail: htma@dlut.edu.cn; Zhao, Huijing; Huang, Mingliang [School of Materials Science and Engineering, Dalian University of Technology, Dalian 116085 (China)

2014-05-28

198

Electrical and thermal transport properties of intermetallic RCoGe2 (R=Ce and La) compounds.  

PubMed

To investigate the electronic structure of the intermetallic compound CeCoGe2, we performed electrical resistivity (?), Seebeck coefficient (S), and thermal conductivity (?) measurements in a temperature range of 10-300?K. For comparison, the non-magnetic counterpart LaCoGe2 is also studied. It is found that CeCoGe2 exhibits a broad maximum in the S(T) near 75?K, at which the sudden drop in the ?(T) is observed. Temperature-dependent electrical resistivity and the Seebeck coefficient of CeCoGe2 can be described well by a two-band model, which reveals the signature of Kondo scattering in CeCoGe2. On the other hand, a typical metallic-like behavior is seen in the non-magnetic LaCoGe2 from the ?(T) and S(T) studies. Analysis of the thermal conductivity indicates that the electronic contribution dominates thermal transport above 100?K in both CeCoGe2 and LaCoGe2. In addition, it is found that the variation in low-temperature lattice thermal conductivity of CeCoGe2 as compared to that of LaCoGe2 is most likely due to the phonon-point-defect scattering. PMID:24861445

Ramachandran, B; Chang, P C; Kuo, Y K; Lue, C S

2014-06-25

199

Synthesis, crystal structure, and magnetic properties of novel intermetallic compounds R2Co2SiC (R = Pr, Nd).  

PubMed

The intermetallic compounds R2Co2SiC (R = Pr, Nd) were prepared from the reaction of silicon and carbon in either Pr/Co or Nd/Co eutectic flux. These phases crystallize with a new stuffed variant of the W2CoB2 structure type in orthorhombic space group Immm with unit cell parameters a = 3.978(4) , b = 6.094(5) , c = 8.903(8) (Z = 2; R1 = 0.0302) for Nd2Co2SiC. Silicon, cobalt, and carbon atoms form two-dimensional flat sheets, which are separated by puckered layers of rare-earth cations. Magnetic susceptibility measurements indicate that the rare earth cations in both analogues order ferromagnetically at low temperature (TC ? 12 K for Nd2Co2SiC and TC ? 20 K for Pr2Co2SiC). Single-crystal neutron diffraction data for Nd2Co2SiC indicate that Nd moments initially align ferromagnetically along the c axis around ?12 K, but below 11 K, they tilt slightly away from the c axis, in the ac plane. Electronic structure calculations confirm the lack of spin polarization for Co 3d moments. PMID:24898034

Zhou, Sixuan; Mishra, Trinath; Wang, Man; Shatruk, Michael; Cao, Huibo; Latturner, Susan E

2014-06-16

200

Micromagnetic analysis of the hardening mechanisms of nanocrystalline MnBi and nanopatterned FePt intermetallic compounds.  

PubMed

The uniaxial intermetallic compounds of L10-FePt and the low temperature NiAs structure of MnBi are suitable alloys for application as high-density recording materials or as high-coercivity permanent magnets. Single domain particles of these materials are characterized by coercive fields above 1 T over a large temperature range. In particular MnBi shows a coercive field of 2 T at 450 K. Its extraordinary magnetic properties in the temperature range up to 600 K are due to an increase of the magnetocrystalline anisotropy constant from 1.2 MJ m(-3) at 300 K to 2.4 MJ m(-3) at 450 K. In spite of the large coercivities obtained for both type of materials their experimental values deviate considerably from the theoretical values Hc = 2K1/Js valid for a homogeneous rotation process in spherical particles. As is well known these discrepancies are due to the deteriorating effects of the microstructure. For an analysis of the coercive fields the Stoner-Wohlfarth theory has to be expanded with respect to higher anisotropy constants and to microstructural effects such as misaligned grains and grain surfaces with reduced anisotropy constants. It is shown that the temperature dependence and the angular dependence of Hc for FePt as well as MnBi can be quantitatively interpreted by taking into account the above mentioned intrinsic and microstructural effects. PMID:24469256

Kronmller, H; Yang, J B; Goll, D

2014-02-12

201

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

202

Effect of heating rate on the combustion synthesis of Ti-Al intermetallic compounds  

Microsoft Academic Search

Titanium aluminide compounds were synthesized by the thermal explosion mode of self-propagating high-temperature synthesis (SHS). The effects of heating rate on the combustion characteristics and the microstructures of the products were studied. It was found that the low density of the reacted sample was due to the outgassing of water vapour and other gases, which were released by dissociation of

H. C. Yi; A. Petric; J. J. Moore

1992-01-01

203

Electronic-structure effects on the intermetallic compounds Al3Ti with the addition of the alloying elements Cr or Mn  

NASA Astrophysics Data System (ADS)

By use of the self-consistent field X? scattered-wave method, the electronic structure was calculated for two models of the Ti6Al12X (X=Al, Cr, or Mn) cluster for the tetragonal DO22 crystal strcuture as well as the Ti4Al14X (X=Al, Cr, or Mn) cluster for the cubic L12 crystal structure in Al3Ti-base intermetallic compounds for contrast. The results are presented for density of states and one-electron properties, such as the relative binding tendency between the atom and the model cluster and the hybrid bonding tendency between the atoms introduced by us. Comparisons are made among the three models of the Ti6Al12X cluster, among those of the Ti4Al14X cluster, and between Ti6Al12X and Ti4Al14X clusters. The effect of the Cr or Mn atom on the physical properties of Al3Ti-base intermetallic compounds is analyzed. The calculations indicate that the addition of the Cr or Mn atom weakens the relative binding tendency between the Ti2 atom and the Ti6Al12X cluster and intensifies that between the Ti1 atom and the Ti4Al14X cluster. Thus the addition of the Cr or Mn atom may promote crystal structure transformation from DO22 to L12 in Al3Ti-base intermetallic compounds. Comparison of the density of states between the Ti6Al12X and Ti4Al14X clusters shows that the stable crystal structure for a given compound is the one in which the Fermi level EF lies in or comes near a minimum in the density of states. The calculation also shows that the Cr or Mn atom strengthens the hybrid bonding tendency between the central atom and the host atoms for the Ti6Al12X and Ti4Al14X clusters and thereby may lead to the constriction of the lattice constant of Al3Ti-base intermetallic compounds. The results also show that the addition of the Cr or Mn atom provides more d electrons to strengthen the p-d and d-d directional bondings for the Ti6Al12X and the Ti4Al14X clusters. Thus, Al3Ti-base intermetallic compounds with the addition of the Cr or Mn atom still remain brittle.

Liu, Senying; Hu, Rongze; Wang, Chongyu

1993-09-01

204

Semiconducting and non-metallic electronic properties of aluminum intermetallic compounds  

Microsoft Academic Search

A study of the electronic properties of crystalline alloys of Alsb2Ru, Alsb3Mn, Alsb{13}Fesb4 and Alsb{13}Cosb4 systems is presented. These compounds, consisting of conventional metals, exhibit strong nonmetallic electronic behavior. Analysis of conductivity and magnetoresistivity experiments on Alsb2Ru indicate that it is truly a semiconducting system. The obtained experimental gap value is 0.2 eV. It is noted that the low temperature

Pavel Volkov

1997-01-01

205

Crystal structure and physical properties of a new intermetallic compound URu 2Al 10  

Microsoft Academic Search

We report on the existence in the URuAl system of a novel compound, URu2Al10, crystallizing in the orthorhombic YbFe2Al10-type structure, where the uranium atoms are caged in RuAl polyhedra, forming a clathrate-like structure. Results of the magnetic susceptibility, electrical resistivity in zero and in magnetic fields up to 8T, thermopower and specific heat, performed in a wide temperature range, are

R. Tro?; M. Pasturel; O. Tougait; M. Potel; H. Nol

2011-01-01

206

Growth kinetic studies of CuSn intermetallic compound and its effect on shear strength of LCCC SMT solder joints  

Microsoft Academic Search

Growth kinetics of interfacial CuSn intermetallic (IMC) layer and its effect on the shear strength on practical LCCC surface mount solder joints were studied for isothermal aging at 70, 120, 155 and 170C. Only normal Cu6Sn5 (?-phase) intermetallic was found in the interfacial IMC layer of as-soldered solder joint, whereas the duplex structure of both ?-phase and ?-phase Cu3Sn existed

Y. C. Chan; Alex C. K. So; J. K. L. Lai

1998-01-01

207

Crystal structure of the intermetallic compound SrCdPt  

PubMed Central

The crystal structure of the title compound, strontium cadmium platinum, adopts the TiNiSi structure type with the Sr atoms on the Ti, the Cd atoms on the Ni and the Pt atoms on the Si positions, respectively. The Pt atoms form cadmium-centred tetrahedra that are condensed into a three-dimensional network with channels parallel to the b-axis direction in which the Sr atoms are located. The latter are bonded to each other in the form of six-membered rings with chair conformations. All atoms in the SrCdPt structure are situated on a mirror plane. PMID:25553000

Gulo, Fakhili; Khler, Jrgen

2014-01-01

208

Polar intermetallic compounds of the silicon and arsenic family elements and their ternary hydrides and fluorides  

SciTech Connect

An investigation has been made on the effects of hydrogen and fluoride in the solid state chemistry of alkaline-earth and divalent rare-earth metal pnictide (Pn) and tetrelide (Tt) phases A{sub 5}(Pn,Tt,){sub 3}Z{sub x}, where A = Ca, Sr, Ba, Sm, Eu, Yb; Pn = As, Sb, Bi; Tt = Si, Ge, Sn, Pb and Z = H, F. Several trivalent rare-earth-metal pnictides, RE{sub 5}Pn{sub 3} (RE = Y, La, Gd, Tb, Dy, Ho, Er, Tm) and alkaline-earth-metal trielides, A{sub 5}Tr{sub 3}Z{sub x} (Tr = Ga, In, Tl) have been included in an effort to complete observed structural trends. Two main experimental techniques were followed throughout this work, (a) reactions in absence of hydrogen or under continuous high vacuum, and (b) reactions with binary metal hydrides, AH{sub x}, in closed containers. The results demonstrate that all the phases reported with the {beta}-Yb{sub 5}Sb{sub 3}-type structure in the A{sub 5}Pn{sub 3} systems are hydrogen-stabilized compounds. Reactions in absence of hydrogen lead to compounds with the Mn{sub 5}Si{sub 3}-type structure. The structure type {beta}-Yb{sub 5}Sb{sub 3} (= Ca{sub 5}SB{sub 3}F) was found to be characteristic of ternary systems and inaccurately associated with phases that form in the Y{sub 5}Bi{sub 3}-type. A new series of isomorphous Zintl compounds with the Ca{sub 16}Sb{sub 11}-type structure were prepared and studied as well. All the alkaline-earth-metal tetrelides, A{sub 5}Tt{sub 3}, that crystallize in the Cr{sub 5}B{sub 3}-type structure can be interstitially derivatized by hydrogen or fluoride. Binary and ternary compounds were characterized by Guinier powder patterns, single crystal X-ray and powder neutron diffraction techniques. In an effort to establish property-structure relationships, electrical resistivity and magnetic measurements were performed on selected systems, and the results were explained in terms of the Zintl concepts, aided by extended Hueckel band calculations.

Leon-Escamilla, E.A.

1996-10-17

209

Crystal structure of the inter-metallic compound SrCdPt.  

PubMed

The crystal structure of the title compound, strontium cadmium platinum, adopts the TiNiSi structure type with the Sr atoms on the Ti, the Cd atoms on the Ni and the Pt atoms on the Si positions, respectively. The Pt atoms form cadmium-centred tetra-hedra that are condensed into a three-dimensional network with channels parallel to the b-axis direction in which the Sr atoms are located. The latter are bonded to each other in the form of six-membered rings with chair conformations. All atoms in the SrCdPt structure are situated on a mirror plane. PMID:25553000

Gulo, Fakhili; Khler, Jrgen

2014-12-01

210

Formation of NiAl Intermetallic Compound by Cold Spraying of Ball-Milled Ni/Al Alloy Powder Through Postannealing Treatment  

NASA Astrophysics Data System (ADS)

Ni/Al alloy powders were synthesized by ball milling of nickel-aluminum powder mixture with a Ni/Al atomic ratio of 1:1. Ni/Al alloy coating was deposited by cold spraying using N2 as accelerating gas. NiAl intermetallic compound was evolved in situ through postspray annealing treatment of cold-sprayed Ni/Al alloy coating. The effect of annealing temperature on the phase transformation behavior from Ni/Al mechanical alloy to intermetallics was investigated. The microstructure of the mechanically alloying Ni/Al powder and NiAl coatings was characterized by scanning electron microscopy and x-ray diffraction analysis. The results show that a dense Ni/Al alloy coating can be successfully deposited by cold spraying using the mechanically alloyed powder as feedstocks. The as-sprayed alloy coating exhibited a laminated microstructure retained from the mechanically alloying powder. The annealing of the subsequent Ni/Al alloy coating at a temperature higher than 850 C leads to complete transformation from Ni/Al alloy to NiAl intermetallic compound.

Zhang, Qiang; Li, Chang-Jiu; Wang, Xiu-Ru; Ren, Zhi-Liang; Li, Cheng-Xin; Yang, Guan-Jun

2008-12-01

211

Magnetic behaviour of Er1-xZrxFe2 intermetallic compounds.  

PubMed

In this work, the structural and magnetic properties of Er1-xZrxFe2 (0.1?x?0.4) were investigated. These compounds crystallize in the cubic MgCu2 (C15) structure, the lattice parameters decreasing with Zr content. Electronic structure calculations were performed, showing a good agreement between theory and experiment. All of the samples are ferrimagnetically ordered, presenting compensation points in the M(T) plots. The compensation point values decrease, while the Curie temperatures increase with Zr content. The experimental Fe moments at 5K decrease with Zr content from 1.70 ?B/atom for x=0.1 to 1.55?B/atom for x=0.4. A non-collinear orientation of the magnetic moments was evidenced in these compounds. The magnetocaloric effect was also studied. A modest magnetocaloric effect was found for all of the samples, spreading across a wide temperature range. A maximum |?SM| value of 1.19Jkg(-1)K(-1) was found for the sample with x=0.1 for an applied field change of 0-4T. Large RCP(?S) values were obtained for all of the samples, mainly due to the wide ?TFWHM values of the ?SM(T) curves. PMID:24141058

Mican, S; Benea, D; Mankovsky, S; Polesya, S; Gnsc?, O; Tetean, R

2013-11-20

212

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

213

Covalent bonding and bandgap formation in intermetallic compounds: a case study for Al3V  

NASA Astrophysics Data System (ADS)

We demonstrate that a special hybridization between the Al(s, p) and V(d) orbitals which is responsible for forming of a deep pseudogap near the Fermi level in the Al3V compound is also associated with the formation of covalent bonds. We analyse the charge distribution in the elementary cell and find an enhanced charge density along the Al-V bonds and certain Al-Al bonds which is characteristic for covalent bonding. The role of the point-group symmetry and the character of the hybrid orbitals forming the covalent bonds are investigated. It is demonstrated that the deep pseudogap close to the Fermi level arises from the bonding-antibonding of the hybrid orbitals.

Krajc, M.; Hafner, J.

2002-03-01

214

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

215

Semiconducting and non-metallic electronic properties of aluminum intermetallic compounds  

NASA Astrophysics Data System (ADS)

A study of the electronic properties of crystalline alloys of Alsb2Ru, Alsb3Mn, Alsb{13}Fesb4 and Alsb{13}Cosb4 systems is presented. These compounds, consisting of conventional metals, exhibit strong nonmetallic electronic behavior. Analysis of conductivity and magnetoresistivity experiments on Alsb2Ru indicate that it is truly a semiconducting system. The obtained experimental gap value is 0.2 eV. It is noted that the low temperature conductivity sigma(4.2\\ K)<1\\ (Omega cm)sp{-1} and the free-carrier density n(T<150\\ K)<10sp{16} cmsp{-3} are comparable to those for doped semiconductors in the vicinity of the metal-insulator transition. Our experimental results are in a good agreement with optical-conductivity experiments and theoretical bandstructure calculations based on the Al-sp and Ru-d states hybridization effects. While Al-Ru system exhibits isotropic electronic properties, Alsb3Mn, Alsb{13}Fesb4 and orthorhombic modification of Alsb{13}Cosb4 show strongly anisotropic transport behavior. Monoclinic Alsb{13}Fesb4 and orthorhombic Alsb{13}Cosb4 display anisotropic rho(T) dependence with metallic behavior along the b-axis and non-metallic resistivity in perpendicular planes. The degree of anisotropy varies from dozens in the Al-Co system to several hundreds for Al-Fe. In contrast, Alsb3Mn system is found to have non-metallic electronic properties along all directions with the degree of anisotropy of 100 at 0.5 K. The observed anomalous electronic properties are discussed in light of electronic-structure effects.

Volkov, Pavel

216

Electronic packing frustration in complex intermetallic structures: the role of chemical pressure in Ca2Ag7.  

PubMed

The assignment of distinct roles to electronics and sterics has a long history in our rationalization of chemical phenomena. Exploratory synthesis in the field of intermetallic compounds challenges this dichotomy with a growing list of phases whose structural chemistry points to an interplay between atomic size effects and orbital interactions. In this paper, we begin with a simple model for how this interdependence may arise in the dense atomic packing of intermetallics: correlations between interatomic distances lead to the inability of a phase to optimize bonds without simultaneously shortening electronically under-supported contacts, a conflict we term electronic packing frustration (EPF). An anticipated consequence of this frustration is the emergence of chemical pressures (CPs) acting on the affected atoms. We develop a theoretical method based on DFT-calibrated ?(2)-Hckel calculations for probing these CP effects. Applying this method to the Ca(2)Ag(7) structure, a variant of the CaCu(5) type with defect planes, reveals its formation is EPF-driven. The defect planes resolve severe CPs surrounding the Ca atoms in a hypothetical CaCu(5)-type CaAg(5) phase. CP analysis also points to a rationale for these results in terms of a CP analogue of the pressure-distance paradox and predicts that the impetus for defect plane insertion is tunable via variations in the electron count. PMID:21619054

Fredrickson, Daniel C

2011-07-01

217

Positron annihilation study of the influence of doping on the 3 d electron states in the Ni3Al intermetallic compound  

NASA Astrophysics Data System (ADS)

The 3 d electron states in Ni3Al single crystals doped with Fe, Co, and Nb have been investigated using angular correlation of annihilation radiation (ACAR). The ACAR spectra contain information on the momentum distribution of valence electrons and strongly bound 3 d electrons of the intermetallic compound. It has been established that the positrons in the Ni3Al crystals predominantly annihilate in the nickel sublattice from delocalized states. The doping of the compound by the third element leads to a variation in the momentum distribution of Ni 3 d electrons due to the change in the character of interatomic bonds. An analysis of the momentum distribution has demonstrated that the niobium atoms increase the covalent component of the chemical bond as compared to the binary compound due to the d Nb- d Ni hybridization. The doping with cobalt atoms also enhances the tendency toward the formation of the covalent bond. At the same time, iron atoms have a weak effect on the electronic structure of the intermetallic compound.

Druzhkov, A. P.; Perminov, D. A.; Stepanova, N. N.

2010-10-01

218

Fragmentation of the fluorite type in Fe8Al(17.4)Si(7.6): structural complexity in intermetallics dictated by the 18 electron rule.  

PubMed

This Article presents the synthesis, structure determination, and bonding analysis of Fe(8)Al(17.4)Si(7.6). Fe(8)Al(17.4)Si(7.6) crystallizes in a new monoclinic structure type based on columns of the fluorite (CaF(2)) structure type. As such, the compound can be seen as part of a structural series in which the fluorite structure-adopted by several transition metal disilicides (TMSi(2))-is fragmented by the incorporation of Al. Electronic structure analysis using density functional theory (DFT) and DFT-calibrated Hckel calculations indicates that the fluorite-type TMSi(2) phases (TM = Co, Ni) exhibit density of states (DOS) pseudogaps near their Fermi energies. An analogous pseudogap occurs for Fe(8)Al(17.4)Si(7.6), revealing that its complex structure serves to preserve this stabilizing feature of the electronic structure. Pursuing the origins of these pseudogaps leads to a simple picture: the DOS minimum in the TMSi(2) structures arises via a bonding scheme analogous to those of 18 electron transition metal complexes. Replacement of Si with Al leads to the necessity of increasing the (Si/Al):TM ratio to maintain this valence electron concentration. The excess Si/Al atoms are accommodated through the fragmentation of the fluorite type. The resulting picture highlights how the elucidating power of bonding concepts from transition metal complexes can extend into the intermetallic realm. PMID:22984870

Fredrickson, Rie T; Fredrickson, Daniel C

2012-10-01

219

Evolution and Stability of a Nanocrystalline Cu3Ge Intermetallic Compound Fabricated by Means of High Energy Ball Milling and Annealing Processes  

NASA Astrophysics Data System (ADS)

In this study, the structural evolution of two nanostructured Cu-22 wt pct Ge (Cu-20 at. pct Ge) and Cu-26 wt pct Ge (Cu-24 at. pct Ge) alloys upon mechanical alloying (MA) with subsequent heat treatment was investigated, and the phase transitions were monitored by means of various characterization methods. The findings indicated that, when the MA process continued for some time, a nanocrystalline ?-Cu(Ge) solid solution was formed, which partially transformed into an amorphous phase. Further MA processing for 20 hours led to the formation of a disordered nanometric ?-Cu3Ge intermetallic compound with a monoclinic crystal structure. Increased milling time subsequently led to the diminishing of the content of the amorphous phase which transformed into ?-Cu3Ge nanocrystals. Clearly, a nanocrystallization transformation occurred upon ball milling principally on account of the accumulated energy due to the heavy mechanical deformation. Crystallization was also seen to occur at 473 K (200 C) after annealing the MA-ed powders, leading to the formation of an ordered ? 1-Cu3Ge intermetallic phase with an orthorhombic structure. The crystallographic relationships between the two disordered and ordered intermetallic phases were also discussed.

Nazarian-Samani, Mahboobeh; Kamali, Ali Reza; Nazarian-Samani, Masoud; Kashani-Bozorg, Seyed Farshid

2015-01-01

220

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

SciTech Connect

Ni/Au metallization layers are used with increasing frequency to protect Cu substrates in ball grid array microelectronic packaging. The external Au layer provides oxidation and corrosion resistance during storage prior to assembly, while the intermediate Ni layer acts as a diffusion barrier that inhibits the formation of a thick Cu-Sn intermetallic layer during aging. During soldering with eutectic Pb-Sn, the Au dissolves into the molten solder and forms fine, needle-shaped AuSn{sub 4} intermetallic precipitates that are retained in a dense distribution in the bulk of the solder joint after it has solidified. However, recent research by Mei et al. has revealed a new and potentially problematic phenomenon that seems to be peculiar to the Ni/au metallization. They found that after extensive aging (150 C for 2 weeks in their case), the Au-Sn intermetallic redeposited onto the solder-substrate interface. The reconstituted interface was significantly weakened and failed by brittle fracture along the surface between the redeposited Au-Sn and the Ni{sub 3}Sn{sub 4} layer that formed during reflow. While the interfacial redeposition of Au-Sn intermetallics has been observed previously, the mechanism remains unknown. The present work was undertaken to identify the mechanism of this phenomenon and explore methods for controlling it.

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

2000-03-01

221

The polarity effect of electromigration on intermetallic compound formation and back stress in v-groove solder lines  

NASA Astrophysics Data System (ADS)

The trend of the miniaturization of VLSI and electronic packaging toward higher input/output density, smaller feature size and greater performance makes electromigration a serious reliability concern in flip chip technology. As an integral part of the joint, intermetallic compound (IMC) formation is very important to achieve good joint strength. However, the effect of electromigration on the IMC formation is a subject in which still very little is known. We utilize solder v-groove samples etched on (001) Si wafer with 100 mum opening to study the polarity effect of electromigration on IMC formation in solder joints. We focus on the interaction between chemical and electrical forces, and the influence of interface morphology on the IMC dissolution. The current densities used are from 103 to 104 A/cm2 and the temperature settings are in the range of 120C to 180C. We have found in both 95.5Sn3.8Ag0.7Cu/Cu and 96.5Sn3.5Ag systems the growth of the IMC has been enhanced by electric current at the anode and inhibited at the cathode. For Ni-Sn compound, kinetic analysis using the motion of the two interfaces gives the general formula of the growth rate as dXdt=aX + b. We have introduced the concept of mean-field theory and the classic model of Zener's precipitation growth into the discussion of the Cu-Sn compound growth under electromigration. A parabolic dependence of the IMC growth on time at the anode is derived as x 2 ? (Cm-Ce)2 (Cs-Ce)2 Dt. The interaction between chemical and electrical forces brings a dynamic equilibrium in IMC dissolution at the cathode. This has been proved theoretically and experimentally. A new critical product has been derived from this dynamic equilibrium, which can provide us a critical IMC thickness before voids formation at a given current density. Our study shows the dissolution rate of Cu with current density 5x103 A/cm2 at 150C is about 0.076 mum/hr. We also notice that the interface morphology plays an important role in the IMC dissolution. When the current density reaches 105 A/cm2, a planar interface will become unstable. Furthermore, this morphological instability can induce phase change in the flip chip solder joint, which finally causes a failure at the cathode. Efforts are also made in the study of back stress in solder joints since the existence of back stress can resist or prevent electromigration from occurring. A multi-solder-segment v-groove sample structure has been developed to obtain the critical products of eutectic SnPb, Sn3.5Ag and Sn3.8Ag0.7Cu solders.

Ou, Shengquan

2005-07-01

222

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, ; de Weerd, M-C; Fourne, V

2014-08-28

223

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, .; de Weerd, M.-C.; Fourne, V.

2014-08-01

224

Microscopic nature of the extremely high specific heat of rare earth intermetallic compounds at low temperatures and the possibility of its application in technical superconductivity  

SciTech Connect

The presence of an unfilled f-electron shell in rare earth intermetallic compounds under conditions of strong electron correlation between localized and delocalized electrons is responsible for the formation of local magnetic moments. According to the data of neutron, synchrotron, and other investigations of a number of such systems, the interaction of these moments with the local crystalline environment, hybridization with conduction electrons, f-f correlations (i.e., both one-site and cooperative phenomena), and combinations of these main effects form the physical base for the reconstruction of the excitation spectrum of an f-electron system and appearance of pronounced specific features of thermodynamic characteristics. The range of characteristic temperatures of these anomalies is determined by the interaction energy, which generally corresponds to the range 1-100 K. For some intermetallic compounds, the additional component of the specific heat (of electron origin) may greatly (by two to three orders of magnitude) exceed the specific heat of conventional structural materials. This feature makes it possible to consider such systems as promising functional materials (a kind of thermodynamic dampers) capable of compensating for various thermal perturbations in low-temperature super-conducting magnetic systems.

Alekseev, P. A.; Znamenskii, N. V.; Lazukov, V. N.; Keilin, V. E.; Kovalev, I. A.; Kruglov, S. L.; Nefedova, E. V.; Sadikov, I. P. [Russian Research Centre Kurchatov Institute (Russian Federation)

2006-12-15

225

Effect of AL Content on Microstructure and Properties of AN Intermetallic Ni-Ti (Al) COMPOUND/Ni Graded Coating Deposited on Copper Substrate  

NASA Astrophysics Data System (ADS)

Copper and its alloys with high electrical and thermal conductivity are a group of widely used engineering materials in numerous applications. In order to improve the tribological properties of copper substrate, an electroplating nickel layer was firstly deposited on copper substrate, subsequently these electroplated specimens were treated by slurry pack cementation process at 900C for 12 h using a slurry mixture composed of TiO2 as titanizing source, pure Al powder as aluminzing source and also a reducer for titanizing, an activator of NH4Cl and albumen (egg white) as cohesive agent. The effect of Al content on the microstructure and the properties of the coating has been studied. The results showed that an intermetallic Ni-Ti (Al) compound/Ni graded layer was formed on copper substrate after slurry pack cementation process. With the rise of Al content in slurry mixture, the microhardness of the graded coating increased and the friction coefficient decreased from 0.35 to 0.18, at the same time, the slurry pack process gradually transited from the titanizing process to an aluminizing one. Correspondingly the main phases of the coating were changed from Ni-Ti intermetallic compounds into Ni-Al ones.

Wang, Hongxing; Chu, Chenglin; Sheng, Xiaobo; Lin, Pinhua; Dong, Yinsheng

226

Growth Of A Au-ni-sn Intermetallic Compound On The Solder-substrate Interface After Aging  

Microsoft Academic Search

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

Andrew M. Minor; Morris J. W. Jr

1999-01-01

227

The early stage dissolution of Ni and the nucleation of Ni-Sn intermetallic compound at the interface during the soldering of Sn-3.5Ag on a Ni substrate  

NASA Astrophysics Data System (ADS)

The early stage soldering reaction, reflow for 5 s at 250 C followed by a liquid nitrogen quench, of Sn-3.5Ag on an electroplated Ni substrate gives rise to a Ni dissolution zone, an amorphous Ni-Sn diffusion zone, and nuclei of NiSn intermetallic compound within the interfacial region. The nucleation of NiSn takes place at the interface between the dissolution zone and the amorphous diffusion zone as well as within the amorphous Ni-Sn diffusion zone, producing 10 nm nanocrystallites. High resolution transmission electron microscope observations indicate that NiSn is the preliminary intermetallic compound that forms during the soldering reaction.

Lin, Yu-Wei; Lin, Kwang-Lung

2010-09-01

228

Study of hyperfine interactions in the intermetallic compound CePd2Si2 using PAC technique with 111Cd as probe nuclei  

NASA Astrophysics Data System (ADS)

Perturbed ?-? angular correlation spectroscopy (PAC) has been used to investigate the hyperfine interactions in the intermetallic compound CePd2Si2 using 111In? 111Cd probe nuclei. Samples of CePd2Si2 were prepared by melting constituent elements in an arc furnace under pure argon atmosphere. Carrier-free 111In nuclei were introduced into the samples by thermal diffusion at 800C in vacuum during 12 h. The measurements were performed in the temperature range of 4.2-300 K. Above the magnetic transition temperature (T N =10 K), the results show two distinct and well defined quadrupole interactions that were assigned to probe nuclei occupying Ce and Si sites in the compound. The quadrupole frequencies were found to decrease linearly with increasing temperature. The PAC spectra taken below 10 K were analyzed with a model including combined electric quadrupole plus magnetic dipole interactions, from which the hyperfine magnetic field was determined.

Cabrera-Pasca, G. A.; Saxena, R. N.; Carbonari, A. W.

229

Study of hyperfine interactions in the intermetallic compound CePd2Si2 using PAC technique with 111Cd as probe nuclei  

NASA Astrophysics Data System (ADS)

Perturbed ? - ? angular correlation spectroscopy (PAC) has been used to investigate the hyperfine interactions in the intermetallic compound CePd2Si2 using 111In?111Cd probe nuclei. Samples of CePd2Si2 were prepared by melting constituent elements in an arc furnace under pure argon atmosphere. Carrier-free 111In nuclei were introduced into the samples by thermal diffusion at 800C in vacuum during 12 h. The measurements were performed in the temperature range of 4.2 300 K. Above the magnetic transition temperature ( T N = 10 K), the results show two distinct and well defined quadrupole interactions that were assigned to probe nuclei occupying Ce and Si sites in the compound. The quadrupole frequencies were found to decrease linearly with increasing temperature. The PAC spectra taken below 10 K were analyzed with a model including combined electric quadrupole plus magnetic dipole interactions, from which the hyperfine magnetic field was determined.

Cabrera-Pasca, G. A.; Saxena, R. N.; Carbonari, A. W.

2007-04-01

230

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  

Microsoft Academic Search

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

Linus Pauling

1989-01-01

231

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 Al(6)Pd.  

PubMed

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 Al(6)Pd has led to its description as involving pentagonal twinning of an orthorhombic crystal with a = 51.6 A, b = 37.6 A, and c = 33.24 A, 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. PMID:16594092

Pauling, L

1989-12-01

232

On the Chemical Bonding in the Intermetallic B32-Type Compounds LiMe (Me = Al, Zn, Ga, Cd, and In)  

NASA Astrophysics Data System (ADS)

The electronic charge distributions in the binary intermetallic B 32 phases LiMe with Me = Zn, Cd. AI, Ga and In have been calculated by the relativistic augmented plane wave method. It is found that the character of the contribution from the various electron bands to the chemical bond is different for the lower valence bands and for the higher valence-conduction bands. The lower valence bands are occupied by two electrons per formula unit LiMe and are predominantly of covalent s-p-type, formed by the diamond-like sublattice of the Me atoms. For all compounds the percentage p-like character is smaller than for the sp3 hybrid within the molecular orbital picture. The valence bands above the covalent bands are s-p-like bands with enhanced metallic character. Besides a large covalent contribution to the chemical bond in the intermetallic B32-type phases, a charge transfer from the lithium atoms to the lib and Ilia elements is found. The amount of charge transfer is distinctly smaller than one electron per formula unit LiMe. It is shown that the charge transfer is correlated to the differences in the electronegativities of the corresponding atoms.

Schmidt, P. C.

1985-04-01

233

Comparison of Sn-Ag-Cu Solder Alloy Intermetallic Compound Growth Under Different Thermal Excursions for Fine-Pitch Flip-Chip Assemblies  

NASA Astrophysics Data System (ADS)

The intermetallic compound (IMC) evolution in Cu pad/Sn-Ag-Cu solder interface and Sn-Ag-Cu solder/Ni pad interface was investigated using thermal shock experiments with 100- ?m-pitch flip-chip assemblies. The experiments show that low standoff height of solder joints and high thermomechanical stress play a great role in the interfacial IMC microstructure evolution under thermal shock, and strong cross-reaction of pad metallurgies is evident in the intermetallic growth. Furthermore, by comparing the IMC growth during thermal aging and thermal shock, it was found that thermal shock accelerates IMC growth and that kinetic models based on thermal aging experiments underpredict IMC growth in thermal shock experiments. Therefore, new diffusion kinetic parameters were determined for the growth of (Cu,Ni)6Sn5 using thermal shock experiments, and the Cu diffusion coefficient through the IMC layer was calculated to be 0.2028 ?m2/h under thermal shock. Finite-element models also show that the solder stresses are higher under thermal shock, which could explain why the IMC growth is faster and greater under thermal shock cycling as opposed to thermal aging.

Tian, Ye; Liu, Xi; Chow, Justin; Wu, Yi Ping; Sitaraman, Suresh K.

2013-08-01

234

M-Al-M groups trapped in cages of Al13M4 (M=Co,Fe,Ni,Ru) complex intermetallic phases as seen via NMR  

NASA Astrophysics Data System (ADS)

The crystallographic structures of decagonal quasicrystals and their periodic approximants are traditionally described as a periodic stacking of atomic planes. By performing a A27l NMR spectroscopic study of the Al13M4 ( M=transition metal) family of four-layer decagonal approximants, including the orthorhombic o-Al13Co4 , the monoclinic Al13Fe4 , its ternary derivative Al13(Fe,Ni)4 , and the monoclinic Al13Ru4 , we show that all these phases contain structural detail of a nearly linear M-Al-M atomic group trapped inside an elongated cage, resembling the three-dimensional (3D) cage-compound structure of the intermetallic clathrates. We determined the electric-field-gradient- (EFG) and the magnetic-shielding tensors at the Al site of the M-Al-M groups. The asymmetry parameter of the EFG tensor was estimated theoretically by a point-charge model, taking into account the charges of both the M-Al-M atoms and the surrounding cage atoms. The calculations support ionic bonding of the M-Al-M group to the cage atoms and the existence of a 3D chemical bonding network in the Al13M4 phases. The above results show that the traditional description of the Al13M4 decagonal approximant phases in terms of two-dimensional (2D) atomic layers stacked along the pseudotenfold crystallographic direction is a convenient geometrical approach to describe their complex structures but is not appropriate for the description of their physical properties, which should be analyzed by taking into account the full 3D nature of the chemical bonding framework. This favors the 3D cage-compound structural description of the Al13M4 phases over the pseudo-2D stacked-layer description.

Jegli?, P.; Vrtnik, S.; Bobnar, M.; Klanjek, M.; Bauer, B.; Gille, P.; Grin, Yu.; Haarmann, F.; Dolinek, J.

2010-09-01

235

Intermetallic compounds formed at the interface between Cu substrate and an Sn-9Zn-0.5Ag lead-free solder  

SciTech Connect

The intermetallic compounds (IMCs) formed at the interface between Cu substrate and an Sn-9Zn-0.5Ag lead-free solder alloy have been investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and electron diffraction (ED). The XRD patterns show that the main IMCs formed at the interface of Sn-9Zn-0.5Ag/Cu are {gamma}-Cu{sub 5}Zn{sub 8} and {eta}'-Cu{sub 6}Sn{sub 5}. The Ag{sub 3}Sn IMC with orthorhombic structure was also observed at the Sn-9Zn-0.5Ag/Cu interface by TEM and ED analyses. The interfacial adhesion strength between the Cu substrate and Sn-9Zn-0.5Ag lead-free solder alloy is higher than that of the Sn-9Zn alloy due to the formation of Ag{sub 3}Sn IMC at the interface.

Chang, T.-C.; Hon, M.-H.; Wang, M.-C

2003-04-30

236

LaAu2 and CeAu2 surface intermetallic compounds grown by high-temperature deposition on Au(111)  

NASA Astrophysics Data System (ADS)

We report on the crystal structure and electronic bands of LaAu2 and CeAu2 surface intermetallic compounds grown by high-temperature deposition on Au(111). By scanning-tunneling microscopy we study the formation of different alloy phases as a function of growth temperature and lanthanide coverage. We determine the specific growth conditions to achieve monolayers and bilayers of LaAu2 and CeAu2 with high crystalline quality. Due to lattice mismatch with the underlying Au substrate, both LaAu2 and CeAu2 exhibit long-range moir patterns, which can serve as templates for further nanostructure growth. By angle-resolved photoemission we map the two-dimensional band structure of these surface alloys, discussing the nature of the different spectral features in the light of first-principles calculations.

Ormaza, M.; Fernndez, L.; Lafuente, S.; Corso, M.; Schiller, F.; Xu, B.; Diakhate, M.; Verstraete, M. J.; Ortega, J. E.

2013-09-01

237

Electronic band structures and magnetism of intermetallic Cu 2Sb-type manganese compounds MnAlGe and MnGaGe  

NASA Astrophysics Data System (ADS)

Electronic band structures of intermetallic manganese compounds, MnAlGe and MnGaGe, having the Cu 2Sb-type crystal structure are calculated for both the non-magnetic and ferromagnetic states by a self-consistent augmented-plane-wave (APW) method. The gross features of the dispersion curve and the density of states of MnAlGe are similar to those of MnGaGe, Mn-3d states are hybridized with Al-3p or Ga-4p states and Ge-4p states. A strong two-dimensional character has been found in the Fermi surfaces obtained for the non-magnetic and ferromagnetic bands. The calculated magnetic moments in the ferromagnetic state are in good agreement with the observed results.

Motizuki, K.; Korenari, T.; Shirai, M.

1992-02-01

238

Solid-state intermetallic compound layer growth between copper and 95.5Sn3.9Ag0.6Cu solder  

Microsoft Academic Search

Long-term, solid-state intermetallic compound (IMC) layer growth was examined in 95.5Sn-3.9Ag-0.6Cu (wt.%)\\/copper (Cu) couples.\\u000a Aging temperatures and times ranged from 70C to 205C and from 1 day to 400 days, respectively. The IMC layer thicknesses\\u000a and compositions were compared to those investigated in 96.5Sn-3.5Ag\\/Cu, 95.5Sn-0.5Ag-4.0Cu\\/Cu, and 100Sn\\/Cu couples. The\\u000a nominal Cu3Sn and Cu6Sn5 stoichiometries were observed. The Cu3Sn layer accounted

Paul T. Vianco; Jerome A. Rejent; Paul F. Hlava

2004-01-01

239

Electric Field Gradient at Nb Site in the Intermetallic Compounds Nb3X (X = AI, In, Si, Ge, Sn) Measured by PAC  

NASA Astrophysics Data System (ADS)

The electric field gradient (efg) at the Nb site in the intermetallic compounds Nb3X (X = Al, In, Si, Ge, Sn) was measured by the Perturbed Angular Correlation (PAC) method using the well-known gamma-gamma cascade of 133 -482 keV in 181Ta from the ?- decay of 181Hf, substituting approximately 0.1 atom percent of Nb. The PAC results show that Vzz drops by nearly 40% when X changes from Al to In, and by about 25% when X changes from Si to Ge and Sn. This behavior is most probably related to the change in the degree of sp hybridization in these compounds. The Vzz values of the studied compounds do not follow the well known universal correlation for the efg's in non-cubic metals but the observed trend is well reproduced by results of ab-initio electronic structure calculations. In the case of Nb3 Al a linear temperature dependence of the quadrupole frequencies was observed in the temperature range of 6.5 to 1210 K.

Junqueira, A. C.; Carbonari, A. W.; Filho, J. Mestnik; Saxena, R. N.

2000-02-01

240

Investigation of modification of hydrogenation and structural properties of LaNi 5 intermetallic compound induced by substitution of Ni by Pd  

NASA Astrophysics Data System (ADS)

The hydrogenation properties of the LaNi 5 (CaCu 5 type, hP6, P6/ mmm) and Pd substituted derivatives LaNi 5 -xPd x compounds have been studied in the whole homogeneity range of the solid solution (0.25? x?1.5). The pressure versus hydrogen content isotherms show several plateaus and an increase of the plateau pressure as a function of palladium concentration. The volume increase of the Pd substituted alloys should have resulted in a lowering, and not an increase, of the plateau pressure, according to the conventional models based on the size effect. In order to elucidate the origin of this anomalous behavior, both an experimental and a theoretical ab initio electronic structure investigation have been carried out. Experimentally, the nature and the structural properties of the hydrides have been studied by both in situ and ex situ neutron diffraction. The crystal structures of the three hydride phases are reported (LaNi 3.5Pd 1.5D 1.96, filled-up CaCu 5 type, P6/ mmm; LaNi 4PdD 2.72, LaNi 2(Ni 0.75Pt 0.25) 3H 2.61 type, oI128, Ibam; LaNi 4.75Pd 0.25D 5.67, partly ordered CaCu 5 type, P6 mm). In addition, the phase diagram of LaNi 5- xPd x-H system has been investigated. The electronic and thermodynamic properties of both intermetallic compounds and the hydrides have been studied by ab initio electronic structure calculations. The theoretical results are in good agreement with our experimental data, and show that electronic interactions play a major role in the hydrogenation behavior of these Pd substituted intermetallic compounds, and that these effects cannot be accounted for by a simplistic model based on the size effect alone.

Prigent, J.; Joubert, J.-M.; Gupta, M.

2011-01-01

241

Electrical, magnetic, and thermal properties of the ?-FeZn10 complex intermetallic phase  

NASA Astrophysics Data System (ADS)

We report the electrical, magnetic, and thermal properties of the ?-FeZn10 phase in the zinc-rich domain of the Fe-Zn system. The ?-FeZn10 phase possesses high structural complexity typical of complex metallic alloys: a giant unit cell comprising 556 atoms, polyhedral atomic order with icosahedrally coordinated environments, fractionally occupied lattice sites, and statistically disordered atomic clusters that introduce intrinsic disorder into the structure. Structural disorder results in suppression of the electrical and heat transport phenomena, making ?-FeZn10 a poor electrical and thermal conductor. Structural complexity results in a complex electronic structure that is reflected in the opposite signs of the thermoelectric power and the Hall coefficient. The ?-FeZn10 phase is paramagnetic down to the lowest investigated temperature of 2 K with a significant interspin coupling of antiferromagnetic type. Specific heat indicates the formation of short-range-ordered spin clusters at low temperatures, very likely a precursor of a phase transition to a collective magnetic state that would take place below 2 K. The magnetoresistance of ?-FeZn10 is sizeable, amounting to 1.5% at 2 K in a 9-T field. The electrical resistivity exhibits a maximum at about 220 K, and its temperature dependence could be explained by the theory of slow charge carriers, applicable to metallic systems with weak dispersion of the electronic bands, where the electron motion changes from ballistic to diffusive upon heating.

Jazbec, S.; Koelj, P.; Vrtnik, S.; Jagli?i?, Z.; Pop?evi?, P.; Ivkov, J.; Stani?, D.; Smontara, A.; Feuerbacher, M.; Dolinek, J.

2012-08-01

242

Peculiarities of the formation of intermetallic coatings based on platinum and zirconium  

NASA Astrophysics Data System (ADS)

We have studied the relationship between the method of production and properties of a multicomponent antiemission coating. A method of obtaining a complex coating with the formation of intermetallic compounds based on platinum and zirconium is proposed. A technology of Pt3Zr intermetallide synthesis that ensures the formation of a uniform coating with stable composition is developed.

Bystrov, Yu. A.; Vetrov, N. Z.; Lisenkov, A. A.

2014-12-01

243

The early stage dissolution of Ni and the nucleation of Ni-Sn intermetallic compound at the interface during the soldering of Sn3.5Ag on a Ni substrate  

Microsoft Academic Search

The early stage soldering reaction, reflow for 5 s at 250 C followed by a liquid nitrogen quench, of Sn-3.5Ag on an electroplated Ni substrate gives rise to a Ni dissolution zone, an amorphous Ni-Sn diffusion zone, and nuclei of NiSn intermetallic compound within the interfacial region. The nucleation of NiSn takes place at the interface between the dissolution zone

Yu-Wei Lin; Kwang-Lung Lin

2010-01-01

244

Electric quadrupole and magnetic dipole interactions at 181Ta impurity in Zr2Ni7 intermetallic compound: Experiment and first-principles calculations  

NASA Astrophysics Data System (ADS)

Electric quadrupole interactions at 181Ta impurity in the intermetallic compound Zr2Ni7 have been studied by perturbed angular correlation technique. It has been found that there are two electric field gradients (EFG) at the 181Ta site due to two different crystalline configurations in Zr2Ni7, while contradictory results were reported from previous investigations. The values of EFG at room temperature have been found to be Vzz=7.91017 V/cm2 and 7.11017 V/cm2 corresponding to present experimental values of quadrupole frequencies and asymmetry parameters for the two sites: ?Q1=70.7(1) Mrad/s, ?=0.28(1), ?=0.8(2)% (site fraction 84%) and ?Q2=63(1) Mrad/s, ?=0.35(5), ??0 (site fraction 9%). Electric field gradients and asymmetry parameters have been computed from the complementary first-principles density functional theory (DFT) to compare with present experimental results. Our calculated values of EFG are found to be in close agreement with the experimental results. No magnetic interactions in Zr2Ni7 have been observed at 298 and 77 K which implies that there is no ferromagnetic ordering in this material down to 77 K. This observation is corroborated by theoretical calculations, wherein no magnetic moment or hyperfine field is found at any atomic site.

Dey, C. C.; Srivastava, S. K.

2013-10-01

245

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

246

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

247

The formation and growth of intermetallic compounds in Sn-Zn and Sn-Zn-Al solder with Ni/Au surface finish bond pad  

NASA Astrophysics Data System (ADS)

In this study, we used microstructure evolution and electron microprobe analysis (EPMA) to investigate the interfacial reactions in Sn-Zn and Sn-Zn-Al solder balls with Au/Ni surface finish ball-grid-array (BGA) bond pad over a period of isothermal aging at 150C. During reflow, Au dissolved into the solder balls and reacted with Zn to form ?-Au3Zn7 and ?2-AuZn3. As aging progressed, ? and ?2 transformed into ?3-AuZn4. Finally, Zn precipitated out next to ?3-AuZn4. The Zn reacted with the Ni layer to form Ni5Zn21. A thin layer (Al, Au, Zn) intermetallic compound (IMC) formed at the interface of the Sn-Zn-Al solder balls, inhibiting the reaction of Ni with Zn. Even after 50 days of aging, no Ni5Zn21 was observed. Instead, fine (Al, Au, Zn) particles similar to Al2 (Au, Zn) in composition formed and remained stable in the solder. The lower ball shear strength corresponded with the brittle fracture morphology in Sn-Zn-Al solder ball samples.

Chang, Shih-Chang; Lin, Sheng-Chih; Hsieh, Ker-Chang

2006-03-01

248

Hyperfine field at Mn in the intermetallic compound LaMnSi2 measured by PAC using 111Cd nuclear probe  

NASA Astrophysics Data System (ADS)

Magnetic hyperfine field at Mn site has been measured in the orthorhombic intermetallic compound LaMnSi2 with PAC spectroscopy using radioactive 111In- 111Cd nuclear probe. Samples of LaMnSi2 were prepared by melting pure metallic components in stoichiometric proportion in an arc furnace under argon atmosphere. The samples were sealed in a quartz tube under helium atmosphere, annealed at 1000 C for 60 h and quenched in water. Samples were analyzed with X-ray diffraction method. 111In was introduced in the samples by thermal diffusion at 1000 C for 60 h. PAC measurements were carried out with a six BaF2 detector spectrometer at several temperatures between 50 K and 410 K. Results show well defined quadrupole and magnetic interactions at all temperatures. The magnetic hyperfine field (Bhf) measured at 50 K is 7.1(1) T. The temperature dependence of Bhf follows the normal Brillouin-like behavior expected for a simple ferromagnetic ordering. The ferromagnetic transition temperature (Tc) was determined to be 401(1) K.

Domienikan, C.; Bosch-Santos, B.; Cabrera Pasca, G. A.; Saxena, R. N.; Carbonari, A. W.

2015-01-01

249

Huge positive hyperfine fields for Sn impurity atoms on R sites of R T intermetallic compounds (R=rare-earth, T=Fe, Co)  

NASA Astrophysics Data System (ADS)

The magnetic hyperfine field Bhf of the 119Sn impurity atom on the R site of the RFe 2 (R=Sm, Tb, Tm), TbCo 2, RCo 5 (R=Dy, Ho, Er), GdCo 3 and Gd 2Co 7 intermetallic compounds has been investigated by Mssbauer spectroscopy technique. At 5 K, very large hyperfine fields equal to 46-56 T were observed. The B values are several times larger than commonly observed for Sn in 3d-based magnetic hosts. The hyperfine fields are positive (that is parallel to the 3d magnetic moments direction). The results can be interpreted qualitatively in terms of the theory proposed for the impurity atoms in homogeneous ferromagnetic hosts [J. Kanamori, H. Katayama-Yoshida, K. Terakura, Hyperfine Interact. 8 (1981) 573; J. Kanamori, H. Katayama-Yoshida, K. Terakura, Hyperfine Interact. 9 (1981) 363; M. Akai, H. Akai, J. Kanamori, J. Phys. Soc. Jpn. 54 (1985) 4246; S. Blgel, H. Akai, R. Zeller, P.H. Dederichs, Phys. Rev. B 35 (1987) 3271], when it is considered that the splitting between bonding and antibonding hybrid states is strongly dependent on the interatomic distance. As the distance between the probe atom and neighboring magnetic atoms increases, the population of the antibonding states grows and, as a consequence, the corresponding positive contribution to the B increases sharply. For Sn atom the positive contribution to the B dominates when the interatomic distance exceeds 0.28-0.29 nm.

Krylov, V. I.; Delyagin, N. N.

2006-10-01

250

Intermetallic-matrix compositesa review  

Microsoft Academic Search

With properties lying between those of metals and ceramics, intermetallic compounds are particularly attractive for high temperature structural applications. Considerable progress has been made in improving the ductility of these rather brittle materials, especially with the titanium aluminides Ti3Al (alpha-2) and TiAl (gamma). But monolithic intermetallic compounds are unlikely to have the right combination of ambient temperature ductility and high

C. M. Ward-Close; R. Minor; P. J. Doorbar

1996-01-01

251

Fermi surface properties of AB3 (A = Y, La; B = Pb, In, Tl) intermetallic compounds under pressure.  

PubMed

The electronic structures, densities of states, Fermi surfaces and elastic properties of AB3 (A =La, Y; B =Pb, In, Tl) compounds are studied under pressure using the full-potential linear augmented plane wave (FP-LAPW) method within the local density approximation for the exchange-correlation functional and including spin-orbit coupling. Fermi surface topology changes are found for all the isostructural AB3 compounds under compression (at V/V0 = 0.90 for LaPb3 (pressure = 8 GPa), at V/V0 = 0.98 for AIn3 (pressure = 1.5 GPa), at V/V0 = 0.80 for ATl3 (pressure in excess of 18 GPa)) apart from YPb3, although its electronic structure at zero pressure is very similar to that of LaPb3. For LaPb3 a softening of the C44 elastic constant under pressure (equivalent to 8 GPa) may be related to the appearance of a new hole pocket around the X point. From the calculated elastic properties and other mechanical properties, all the compounds investigated are found to be ductile in nature with elastic anisotropy. The states at the Fermi level (EF) are dominated by B p states with significant contributions from the A d states. For the La compounds, small hybridizations of the La f states also occur around EF. PMID:23528988

Ram, Swetarekha; Kanchana, V; Svane, A; Dugdale, S B; Christensen, N E

2013-04-17

252

Ab initio investigation of structural, electronic, mechanical, and thermodynamic properties of AlSc2 intermetallic compound under pressure  

NASA Astrophysics Data System (ADS)

The dependences of the structural, electronic, mechanical, and thermodynamic properties of AlSc2 compound on pressure were investigated for the first time by means of the first-principles method based on the density functional theory with generalized gradient approximation and local density approximation. It was found that the pressure has significant effects on the equilibrium volume, mechanical properties, electronic properties and the heat capacity. Our calculated structural data are in good agreement with the previous experimental and theoretical data results. The calculated elastic constants indicate that the AlSc2 compound is mechanically stable in the pressure range of 0-50 GPa. The Zener ratio A and linear compressibility coefficients kc/ka are used to estimate anisotropic elasticity. The isotropic bulk modulus B, shear modulus G, Young's modulus E, and Poisson's ratio ? of polycrystalline AlSc2 compound were determined using the Voigt-Reuss-Hill averaging scheme. The B/G, Poisson's ratio and microhardness parameter are calculated. The band structure and density of states are also discussed. The Debye temperature can be obtained from the elastic constants and the sound velocities and the pressure has little influence. The temperature-dependent behavior of thermodynamical properties (internal energy, entropy, free energy, and heat capacity) at 0, 20, and 40 GPa have been obtained from phonon density of states.

Pang, Mingjun; Zhan, Yongzhong; Wang, Haizhou; Jiang, Wenping; Du, Yong

2011-08-01

253

New Intermetallic Compounds in the Ternary System Yb-T-Al (T=Ag, Au, Pd, Pt)  

NASA Astrophysics Data System (ADS)

Structural characteristics of a number of ternary rare earth/transition metal/aluminium compounds are hexagonal nets of the AlB2-type, Kagom nets and tetragonal pyramides. Crystal structures of the new compounds in the ternary Yb-T-Al systems contain units and sections of them. Kagom nets stacked in an ..ABAB.. sequence are observed in YbAg1.5Al0.5 (MgZn2-type). The crystal structure of Yb8Ag21Al45 is related to the BaHg11-type. YbAu0.8Al3.2 (CaZn2Al2-type) contains tetragonal pyramides which are connected by common edges. Fragments of the AlB2- and BaAl4-type structure are present in Yb5Au15Al16. YbPdAl2 and YbPtAl2 (YbPdAl2-type) contain pentagonal prisms as the characteristic structural elements.

Cordier, G.; Henseleit, R.

254

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

NASA Astrophysics Data System (ADS)

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 discussed. The electronic structure was analyzed using the tight-binding extended Huckel method. Results of Raman-scattering experiments are also discussed. BaGa4 possesses the most popular structure type in solid state chemistry. More than 600 compounds crystallize in this structure. Many compounds of this family exhibit interesting physical properties such as superconductivity, unusual magnetic behavior, valence fluctuation and heavy fermion phenomena. However, little had been reported about the physical properties of BaGa 4 itself. The single crystal growth, structural characterization, computational his, conductivity and AC susceptibility of crystalline BaGa4 is described. V-Ga binary system is of great interest because some compounds in this family are superconductors exhibiting high critical currents and fields. V 2Ga5 has been reported to show a superconducting transition from 2.1 K to 4.2 K,2,6 depending on the preparation procedure and sample quality. However, no single-crystal X-ray structure determination has been reported for this compound, and the full characterization of its superconducting transition has yet to be completed. The single crystal growth, structural determination, and computational study of Ga5V 2 are discussed. Resistivity and magnetization measurement results are also presented. Ternary intermetallic solid-state compounds of lanthanum, transition metal, and germanium have a wide range of technological applications (i.e., rechargeable cells) because of their interesting physical properties. Many compounds of this type with the stoichiometry LnxTyGe z (Ln = lanthanide, T = transition metal) have been synthesized. A few of them crystallize in orthorhombic lattices in which a transition metal forms a square lattice with capping germanium atoms on the square hollows. This structural motif is found in one of the most populous families, the ThCr 2Si2 series that has more than 600 members. LaNiGe2 , is similar in structure with capped square nets. However, there is one very important difference. In this structure, it is the more electronegative element Ge that builds the square lattice. The main structural motif is the NiGe4 pyramid. With computational analysis as the means of exploration, the electronic charge distribution resulting from such a structural arrangement and the changes that occur to this electronic charge distribution when a partial substitution of Si is made to the Ge in the square lattice are described. Two partially substituted compounds with different levels of Si substitution were synthesized. Their synthesis and magnetic susceptibility measurements are also discussed.

Lobring, Kim Carl

255

J. Am. Chem. SOC.1993, 115, 2357-2362 2357 Metal-Metal Bonding in Engel-Brewer Intermetallics  

E-print Network

cluster ZrPt,, as a representative model of Engel-Brewer compounds. Such intermetallic compounds are known-resistant protective coatings. Engel-Brewer intermetallic compounds show potential to serveas such materials. Engel structures of metals and their intermetallic compounds are determined by the number of valence s and p

Carter, Emily A.

256

SOME COMPLEX COMPOUNDS OF NEPTUNIUM(IV) AND RELATED IONS  

Microsoft Academic Search

The phenylarsonate, oxalnte, mandelate, and ethylenediaminetetraacetate ; of neptunium(IV) were radiochemically surveyed by the solvent extraction ; technique. An equation given by Schubert as well as another one evolved by ; Ishimori for the composition of complex compounds, were applied to the measured ; distribution ratios in a di-(2-ethylhexyl)-phosphoric acid-hydrochloric acid ; system containing a complexing agent. The determined molar

T. Ishimori; E. Nakamura

1962-01-01

257

Behavior of carboxylic acids upon complexation with beryllium compounds.  

PubMed

A significant acidity enhancement and changes on aromaticity were previously observed in squaric acid and its derivatives when beryllium bonds are present in those systems. In order to know if these changes on the chemical properties could be considered a general behavior of carboxylic acids upon complexation with beryllium compounds, complexes between a set of representative carboxylic acids RCOOH (formic acid, acetic acid, propanoic acid, benzoic acid, and oxalic acid) and beryllium compounds BeX2 (X = H, F, Cl) were studied by means of density functional theory calculations. Complexes that contain a dihydrogen bond or a OHX interaction are the most stable in comparison with other possible BeX2 complexation patterns in which no other weak interactions are involved apart from the beryllium bond. Formic, acetic, propanoic, benzoic, and oxalic acid complexes with BeX2 are much stronger acids than their related free forms. The analysis of the topology of the electron density helps to clarify the reasons behind this acidity enhancement. Importantly, when the halogen atom is replaced by hydrogen in the beryllium compound, the dihydrogen bond complex spontaneously generates a new neutral complex [RCOO:BeH] in which a hydrogen molecule is lost. This seems to be a trend for carboxylic acids on complexing BeX2 compounds. PMID:25010490

Mykolayivna-Lemishko, Kateryna; Montero-Campillo, M Merced; M, Otilia; Yez, Manuel

2014-07-31

258

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

259

Complex intermetallic phase in multicrystalline silicon doped with transition metals Matthias Heuer,1 Tonio Buonassisi,1 Matthew A. Marcus,2 Andrei A. Istratov,1 Matthew D. Pickett,1 Tomohiro Shibata,3  

E-print Network

Complex intermetallic phase in multicrystalline silicon doped with transition metals Matthias Heuer of the transition metals of the precipitates and a synthetic reference material with composition of Ni0.82Fe0.21Cu0 and Cu on the Si site. This observation provides evidence that transition metals interact during

260

Point defect energetics in the ZrNi and Zr2Ni intermetallics C.S. Moura a,b  

E-print Network

of point defects has been conducted in the ZrNi and Zr2Ni intermetallic compounds using molecular dynamics recent interest in the ir- radiation response of intermetallic compounds, especially in regards defects in the ordered compound. In an eort to understand the dynamic recovery of these intermetallic

Motta, Arthur T.

261

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

262

Effect of aluminium additions on wettability and intermetallic compound (IMC) growth of lead free Sn (2 wt. % Ag, 5 wt. % Bi) soldered joints  

NASA Astrophysics Data System (ADS)

The effect of a trace Al addition (0, 0.01, 0.05 and 0.1 wt. %) in the Sn-2Ag-5Bi solder alloy on wettability and intermetallic compound (IMC) formation of the alloy was investigated. The interface between the solder and a Cu(17 ?m)/Ni(4 ?m)/Au (0.02 ?m) under bump metallized (UBM) substrate was studied. The microstructure of the bulk solder and the interface of the soldered joints was observed in a scanning electron microscope (SEM), and the thickness of the interface reaction layers was estimated. Various IMC phases were identified by energy dispersive spectroscopy (EDS) and by the electron probe micro analyzer (EPMA). The experimental results indicated that the addition of 0.01 wt. % Al in the Sn-2Ag-5Bi solder alloy significantly improved the wettability of the solder more than the other Al additions did. The IMC layer between the bulk Sn-2Ag5Bi-0.01Al solder and the Cu/Ni/Au UBM substrate was almost uniform and thinner than those between the solders containing 0, 0.05, and 0.1 wt. % Al and their respective Cu/Ni/Au UBM substrates. Furthermore, the growth rate of the IMC layer between the Sn-2Ag-5Bi-0.01Al solder and Cu/Ni/Au UBM after 1 to 10 reflow times was lower than that of the IMC layer between the Sn-2Ag-5Bi solder and Cu/Ni/Au UBM. The IMCs in the solder joint interface (e.g., Ni3Sn4) of the Sn-2Ag-5Bi-0.01Al solder were well distributed near the Bi and fine Ag3Sn. The addition of 0.01 wt. % Al in the Sn-2Ag-5Bi solder yielded the best wetting properties for the solder and the minimum growth rate of the IMCs because it increased the nucleation rate of Ag3Sn and uniformly segregated the Bi phase.

Lee, Hee Yul; Sharma, Ashutosh; Kee, Se Ho; Lee, Young Woo; Moon, Jung Tak; Jung, Jae Pil

2014-09-01

263

REFRACTORY CERAMICS AND INTERMETALLIC COMPOUNDS  

Microsoft Academic Search

Possible aerospace applications of refractory nonmetallics are described ; briefly. The available data on the properties of carbides, borides, and ; beryllides are summarized in tables. The probable applications and future trends ; are discussed. (D.L.C.);

W. G. Ramke; J. D. Latva

1963-01-01

264

JOURNAL DE PHYSIQUE Colloque C5, supplment au n 5, Tome 40, Mai 1979, page C5-114 Low temperature heat capacity studies on intermetallic and semimetallic  

E-print Network

heat capacity studies on intermetallic and semimetallic rare earth compounds K. A. Gschneidner, Jr of normal metals, alloys and intermetallic compounds yield information about the integrated density. Hydride forming intermetallic compounds. -- The heat capacity of the several R(T5_XM;|.) compounds, where

Boyer, Edmond

265

Electromigration enhanced kinetics of copper-tin intermetallic compounds in lead-free solder joints and copper low-k dual damascene processing using step and flash imprint lithography  

NASA Astrophysics Data System (ADS)

This dissertation constitutes two major sections. In the first major section, a kinetic analysis was established to investigate the electromigration (EM), enhanced intermetallic compound (IMC) growth and void formation for Sn-based Pb-free solder joints to Cu under bump metallization (UBM). The model takes into account the interfacial intermetallic reaction, Cu-Sn interdiffusion, and current stressing. A new approach was developed to derive atomic diffusivities and effective charge numbers based on Simulated Annealing (SA) in conjunction with the kinetic model. The finite difference (FD) kinetic model based on this approach accurately predicted the intermetallic compound growth when compared to empirical observation. The ultimate electromigration failure of the solder joints was caused by extensive void formation at the intermetallic interface. The void formation mechanism was analyzed by modeling the vacancy transport under electromigration. The effects of current density and Cu diffusivity in Sn solder were also investigated with the kinetic model. The second major section describes the integration of Step and Flash Imprint Lithography (S-FILRTM) into an industry standard Cu/low-k dual damascene process. The yield on a Back End Of the Line (BEOL) test vehicle that contains standard test structures such as via chains with 120 nm vias was established by electrical tests. S-FIL shows promise as a cost effective solution to patterning sub 45 nm features and is capable of simultaneously patterning two levels of interconnect structures, which provides a low cost BEOL process. The critical processing step in the integration is the reactive ion etching (RIE) process that transfers the multilevel patterns to the inter-level dielectrics (ILD). An in-situ, multistep etch process was developed that gives excellent pattern structures in two industry standard Chemical Vapor Deposited (CVD) low-k dielectrics. The etch process showed excellent pattern fidelity and a wide process window. Electrical testing was conducted on the test vehicle to show that this process renders high yield and consistent via resistance. Discussions of the failure behaviors that are characteristic to the use of S-FIL are provided.

Chao, Huang-Lin

266

FIB-SEM investigation of trapped intermetallic particles in anodic oxide films  

E-print Network

, Anodizing, AA1050, Intermetallic particle, FIB-SEM, Oxides, Organometallic compounds Paper type ResearchFIB-SEM investigation of trapped intermetallic particles in anodic oxide films on AA1050 aluminium of this investigation is to understand the structure of trapped intermetallics particles and localized composition

Dunin-Borkowski, Rafal E.

267

Structural transformations in R3Cu4Sn4 (R Ho, Er, Tm) intermetallic J.M. Cadogan a, *  

E-print Network

Structural transformations in R3Cu4Sn4 (R ¼ Ho, Er, Tm) intermetallic compounds J.M. Cadogan a chemistry F. Diffraction/scaterring a b s t r a c t The family of ternary intermetallic compounds R3T4X4 (R 2014 Available online Keywords: A. Rare-earth intermetallics B. Phase transformation B. Crystal

Ryan, Dominic

268

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

269

Reaction synthesis of intermetallics  

SciTech Connect

Exothermicity associated with the synthesis of aluminides was utilized to obtain nickel, iron, and cobalt aluminides. Combustion synthesis, extrusion, and hot pressing were utilized to obtain intermetallics and their composites. Extrusion conditions, reduction ratios, and hot-pressing conditions of the intermetallics and their composites are discussed.

Deevi, S.C.; Sikka, V.K.

1994-12-31

270

Waste-Heat-Driven Cooling Using Complex Compound Sorbents  

NASA Technical Reports Server (NTRS)

Improved complex-compound sorption pumps are undergoing development for use as prime movers in heat-pump systems for cooling and dehumidification of habitats for humans on the Moon and for residential and commercial cooling on Earth. Among the advantages of sorption heat-pump systems are that they contain no moving parts except for check valves and they can be driven by heat from diverse sources: examples include waste heat from generation of electric power, solar heat, or heat from combustion of natural gas. The use of complex compound sorbents in cooling cycles is not new in itself: Marketing of residential refrigerators using SrCl2 was attempted in the 1920s and 30s and was abandoned because heat- and mass-transfer rates of the sorbents were too low. Addressing the issue that gave rise to the prior abandonment of complex compound sorption heat pumps, the primary accomplishment of the present development program thus far has been the characterization of many candidate sorption media, leading to large increases in achievable heat- and mass-transfer rates. In particular, two complex compounds (called "CC260-1260" and "CC260-2000") were found to be capable of functioning over the temperature range of interest for the lunar-habitat application and to offer heat- and mass-transfer rates and a temperature-lift capability adequate for that application. Regarding the temperature range: A heat pump based on either of these compounds is capable of providing a 95-K lift from a habitable temperature to a heat-rejection (radiator) temperature when driven by waste heat at an input temperature .500 K. Regarding the heat- and mass-transfer rates or, more precisely, the power densities made possible by these rates: Power densities observed in tests were 0.3 kilowatt of cooling per kilogram of sorbent and 2 kilowatts of heating per kilogram of sorbent. A prototype 1-kilowatt heat pump based on CC260-2000 has been built and demonstrated to function successfully.

Rocketfeller, Uwe; Kirol, Lance; Khalili, Kaveh

2004-01-01

271

First principles studies on the structural, elastic, electronic properties and heats of formation of MgeAE (AE Ca, Sr, Ba) intermetallics  

E-print Network

of states of eight MgeAE (AE ¼ Ca, Sr, Ba) intermetallic compounds. The ob- tained results indicate ¼ Ca, Sr, Ba) systems intermetallic compounds have generated significant interests over the past fewe9] for the eight Mg intermetallic compounds. Moreover, investigations focused on the elastic

Melnik, Roderick

272

Atomistic simulations of point defects in ZrNi intermetallic C.S. Moura a,b,*, A.T. Motta b  

E-print Network

Atomistic simulations of point defects in ZrNi intermetallic compounds C.S. Moura a,b,*, A.T. Motta energies, and migration mechanisms, in the ZrNi and Zr2Ni intermetallic compounds were simulated using the properties of vacancies and interstitials in the intermetallic compounds ZrNi and Zr2Ni for which realistic

Motta, Arthur T.

273

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

274

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

275

Discontinuous coarsening behavior of Ni(2)MnAl intermetallic compound during isothermal aging treatment of Fe-Mn-Ni-Al alloys.  

PubMed

The discontinuous reaction of the Ni(2)MnAl intermetallic phase was investigated during the aging of a solution-treated Fe-8.3Mn-8.2Ni-4.2Al alloy. During aging, Ni(2)MnAl lamellae formed at the prior austenite grain boundaries and twin boundaries and grew into the neighboring grains. The presence of continuously precipitated fine Ni(2)MnAl particles before the growth of the discontinuously precipitated lamellae was confirmed by dark-field transmission electron microscopy, and it was concluded that the present reaction is a type of discontinuous coarsening process, alpha' + Ni(2)MnAl (continuous precipitation) --> alpha + Ni(2)MnAl (discontinuous coarsening). The chemical driving force and the reduction of the total coherent strain energy were suggested to be the driving force for the discontinuous coarsening reaction. PMID:20551447

Heo, Yoon-Uk; Takeguchi, Masaki; Furuya, Kazuo; Lee, Hu-Chul

2010-08-01

276

Effects of Intermetallics on the Reliability of Tin Coated Cu, Ag, and Ni Parts  

Microsoft Academic Search

The temperature dependence of the growth rates of intermetallic compounds in the Cu-Sn, Ag-Sn and Ni-Sn systems was determined between 100C and 213C for Sn-dipped and Sn-plated samples. Below 175C the fastest growing intermetallic compound was Ag3Sn. The Ni-Sn compoknd, Ni3Sn, was the slowest growing phase below 150C, but the fastest growing phase above 175C. The two Cu-Sn intermetallic phases,

Dennis Olsen; Richard Wright; Howard Berg

1975-01-01

277

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

278

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

279

Novel Hard Magnets J. F. Herbst, Chairman New rare-earth intermetallic phases 3(Fe,M)29X,,: (R=Ce, Pr, Nd, Sm, Gd;  

E-print Network

interest in the structural and magnetic properties of rare-earth (R), iron- rich intermetallic compounds.' Two families of intermetallics, the rhombohe- dral R,(Fe,M)r7 and tetragonal R(Fe,M),, compounds, haveNovel Hard Magnets J. F. Herbst, Chairman New rare-earth intermetallic phases 3(Fe,M)29X,,: (R

Ryan, Dominic

280

High-temperature structural intermetallics  

Microsoft Academic Search

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

M. Yamaguchi; H. Inui; K. Ito

2000-01-01

281

Ductile ordered intermetallic alloys.  

PubMed

Many ordered intermetallic alloys have attractive high-temperature properties; however, low ductility and brittle fracture limit their use for structural applications. The embrittlement in these alloys is mainly caused by an insufficient number of slip systems (bulk brittleness) and poor grain-boundary cohesion. Recent studies have shown that the ductility and fabricability of ordered intermetallics can be substantially improved by alloying processes and control of microstructural features through rapid solidification and thermomechanical treatments. These results demonstrate that the brittleness problem associated with ordered intermetallics can be overcome by using physical metallurgical principles. Application of these principles will be illustrated by results on Ni(3)Al and Ni(3)V-Co(3)V-Fe(3)V. The potential for developing these alloys as a new class of high-temperature structural materials is discussed. PMID:17774926

Liu, C T; Stiegler, J O

1984-11-01

282

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 150C. 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

283

Electronic structure, phase stability, and vibrational properties of Ir-based intermetallic compound IrX (X=Al, Sc, and Ga)  

NASA Astrophysics Data System (ADS)

The phase stability and mechanical properties of B2 type IrX (X=Al, Sc and Ga) compounds are investigated. Self-consistenttotal-energy calculations in the framework of density functional theory using the Generalized Gradient Approximation (GGA) to determine the equations of state and the elastic constants of IrX (X=Al, Sc, and Ga) in the B2 phase have been performed. The calculations predicted the equilibrium lattice constants, which are about 1% greater than experiments for IrAl, 1.81% for IrGa, and 0.71% for IrSc compound. IrAl is shown to be the least compressible, and it is followed by IrGa and the IrSc compound. The phase stability of the studied compounds is checked. The brittleness and ductility properties of IrX (X=Al, Sc, and Ga) are determined by Poisson's ratio ? criterion and Pugh's criterion. IrGa compound is a ductile material; however, IrAl and IrSc show brittleness. The band structure and density of states (DOS), and phonon dispersion curves have been obtained and analyzed. The position of the Fermi level and the contribution of d electrons to the density of states near EF is studied and discussed in detail. We also used the phonon density of states and quasiharmonic approximation to calculate and predict some thermodynamic properties such as constant-volume specific heat capacity of the B2 phase of IrX (X=Al, Sc and Ga) compounds.

Ar?kan, N.; Charifi, Z.; Baaziz, H.; U?ur, ?.; nver, H.; U?ur, G.

2015-02-01

284

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 Quiones, Miguel

2005-08-17

285

Magnetic properties and magnetocaloric effect in the HoNi1-xCuxIn (x=0, 0.1, 0.3, 0.4) intermetallic compounds  

NASA Astrophysics Data System (ADS)

The magnetic properties and magnetocaloric effect (MCE) in HoNi1-xCuxIn (x=0, 0.1, 0.3, 0.4) compounds have been investigated. With the substitution of Cu for Ni, the Ho magnetic moment will cant from the c-axis, and form a complicated magnetic structure. These compounds exhibit two successive magnetic transitions with the increase in temperature. The large reversible magnetocaloric effects have been observed in HoNi1-xCuxIn compounds around Tord, with no thermal and magnetic hysteresis loss. The large reversible isothermal magnetic entropy change (-?SM) is 20.2 J/kg K and the refrigeration capacity (RC) reaches 356.7 J/kg for field changes of 5 T for HoNi0.7Cu0.3In. Especially, the value of -?SM (12.5 J/kg K) and the large RC (132 J/kg) are observed for field changes of 2 T for HoNi0.9Cu0.1In. Additionally, the values of RC are improved to 149 J/K for the field changes of 2 T due to a wide temperature span for the mix of HoNi0.9Cu0.1In and HoNi0.7Cu0.3In compounds with the mass ratio of 1:1. These compounds with excellent MCE are expected to have effective applications in magnetic refrigeration around 20 K.

Mo, Zhao-Jun; Shen, Jun; Yan, Li-Qin; Tang, Cheng-Chun; He, Xiao-Nan; Zheng, Xinqi; Wu, Jian-Feng; Sun, Ji-Rong; Shen, Bao-Gen

2014-03-01

286

Synthesis, Crystal Chemistry, and Physical Properties of Ternary Intermetallic Compounds An2T2X( An=Pu, Am; X=ln, Sn; T=Co, Ir, Ni, Pd, Pt, Rh)  

NASA Astrophysics Data System (ADS)

The synthesis, structural, and physical characterization of nine new ternary intermetallic compounds belonging to the isostructural An2T2Xfamily with the transuranium Pu and Am elements, namely, Pu 2Ni 2In, Pu 2Pd 2In, Pu 2Pt 2In, Pu 2Rh 2In, Pu 2Ni 2Sn, Pu 2Pd 2Sn, Pu 2Pt 2Sn, Am 2Ni 2Sn, and Am 2Pd 2Sn, are reported. From these compounds only Pu 2Rh 2In, Am 2Ni 2Sn, and Am 2Pd 2Sn melt incongruently. All of these compounds crystallize in a tetragonal U 3Si 2-type structure, with the space group P4/ mbm, ( Z=2) as most of the U and Np 2-2-1 compounds already found. In this structure, Anatoms occupy the 4 h( x1, x1+0.5, 0.5), Tthe 4 g( x2, x2+0.5, 0), and Xthe 2 a(0, 0, 0) positions. The average values of x1and x2are, respectively, 0.17 and 0.37. Single-crystal X-ray data were refined to R/ RW=0.045/0.066, 0.043/0.072, 0.066/0.080, 0.070/0.098, 0.029/0.048, 0.055/0.080, 0.073/0.096, 0.048/0.086, 0.048/0.065 for Pu 2Ni 2In, Pu 2Pd 2In, Pu 2Pt 2In, Pu 2Rh 2In, Pu 2Ni 2Sn, Pu 2Pd 2Sn, Pu 2Pt 2Sn, Am 2Ni 2Sn, and Am 2Pd 2Sn, respectively, for seven variables. The variation of the lattice parameters and the range of stability of the 2-2-1 phase are discussed in terms of the substitution of different An(actinide), T(transition metal), and X( p-electron) elements in their crystal structure. The possible role of spin fluctuations in the low-temperature behavior of the Pu samples is indicated by magnetic and electrical resistivity measurements.

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

1997-11-01

287

Simulation of PAC spectra for spin 5/2 probes diffusing via a simple vacancy mechanism in Cu 3 Au-structured intermetallic compounds  

NASA Astrophysics Data System (ADS)

Because of its sensitivity to point defects atomically close to probe nuclei, it is reasonable to expect that perturbed angular correlation (PAC) spectroscopy has the potential to assist in the identification of diffusion mechanisms. It is of interest to characterize under what conditions diffusing defects are visible and how the defects affect relaxation in PAC spectra. This was investigated using a stochastic model to simulate PAC spectra for the special case of non-impurity PAC probes diffusing via a simple vacancy mechanism on the Cu-sublattice in Cu3Au-structured compounds.

Muhammed, Harun; Zacate, Matthew O.; Evenson, William E.

2007-06-01

288

Simulation of PAC spectra for spin 5/2 probes diffusing via a simple vacancy mechanism in Cu3Au-structured intermetallic compounds  

NASA Astrophysics Data System (ADS)

Because of its sensitivity to point defects atomically close to probe nuclei, it is reasonable to expect that perturbed angular correlation (PAC) spectroscopy has the potential to assist in the identification of diffusion mechanisms. It is of interest to characterize under what conditions diffusing defects are visible and how the defects affect relaxation in PAC spectra. This was investigated using a stochastic model to simulate PAC spectra for the special case of non-impurity PAC probes diffusing via a simple vacancy mechanism on the Cu-sublattice in Cu3Au-structured compounds.

Muhammed, Harun; Zacate, Matthew O.; Evenson, William E.

289

Copper/solder intermetallic growth studies.  

PubMed

Copper samples, hot solder (eutectic) dipped and thermally aged, were cross-sectioned and placed in an environmental scanning electronic microscope (ESEM). While in the ESEM the samples were heated for approximately 2.5 h at 170 degrees C to stimulate the growth of additional Cu/Sn intermetallic compound. The intent of the study was to obtain a continuous real-time videotape record of the diffusion process and compare the observations to static SEM images reported to represent long-term, naturally aged intermetallic growth. The video obtained allows the observation of the diffusion process and relativistic growth phenomena at the Cu, Cu3Sn, Cu6Sn5, and solder interfaces as well as effects on the bulk Cu and solder. Effects contrary to earlier reports were observed; for example, growth rates of Cu3Sn were found to greatly exceed those of Cu6Sn5. PMID:8400445

Kirchner, K W; Lucey, G K; Geis, J

1993-08-01

290

Interdiffusion in Intermetallics  

NASA Astrophysics Data System (ADS)

Recently, Tiwari and Mehrotra asserted that the vacancy flux in interdiffusion is driven by a vacancy concentration gradient and also that interdiffusion in intermetallics cannot proceed by the six-jump cycle, triple defect, and antistructural bridge mechanisms. It is shown that those authors' arguments are incorrect according to classical diffusion theory, by the numerous simulations that have been performed, and by analysis of these mechanisms.

Belova, Irina V.; Murch, Graeme E.

2013-10-01

291

Materials Science and Engineering A 443 (2007) 115 Damage evolution in Ti6Al4VAl3Ti metal-intermetallic  

E-print Network

behavior; Damage evolution; Crack density 1. Introduction Intermetallics are phases or compounds formedMaterials Science and Engineering A 443 (2007) 1­15 Damage evolution in Ti6Al4V­Al3Ti metal-intermetallic May 2006; accepted 5 May 2006 Abstract The crack propagation and damage evolution in metal (Ti6Al4V)-intermetallic

Meyers, Marc A.

292

Elastic anisotropy, vibrational, and thermodynamic properties of U2Ti intermetallic compound with AlB2-type structure under high pressure up to 100 GPa  

NASA Astrophysics Data System (ADS)

Structural, elastic anisotropy, dynamical, and thermodynamic properties of U2Ti have been studied by employing density functional theory and density functional perturbative theory. The optimized lattice parameters a, c, unit volume V, bulk modulus B, and bond lengths dU-U, dU-Ti of U2Ti are in favorable agreement with the available experimental data and other theoretical values. The elastic constants under pressure were obtained using "energy-strain" method. The polycrystalline modulus, Poisson's ratio, brittle/ductile characteristics, Debye temperature and the integration of elastic wave velocities over different directions, and hardness under pressure are also evaluated successfully. The anisotropy of the directional bulk modulus and the Young's modulus is systematically predicted for the first time. It turns out that U2Ti should be stabilized mechanically up to 100 GPa, this compound just possesses slightly elastic anisotropy at zero pressure; however, the anisotropy becomes more and more significant with the increasing pressure. In particular, the phonon dispersion curves and phonon density of state under pressure are reported for the first time. The Raman and infrared-active phonon modes at C point are further assigned. Our results indicate that U2Ti is also stable dynamically up to 100 GPa. Additionally, within the calculated phonon density of states, the thermodynamic properties are predicted.

Yang, Jinwen; Gao, Tao; Liu, Benqiong; Sun, Guangai; Chen, Bo

2015-03-01

293

Equiatomic intermetallic compounds YTX (T = Ni, Ir; X = Si, Ge, Sn, Pb): a systematic study by ??Y solid state NMR and ?Sn Mssbauer spectroscopy.  

PubMed

The equiatomic TiNiSi type tetrelides YTX (space group Pnma) with T = Ni, Ir and X = Si, Ge, Sn, Pb were synthesized from the elements by arc-melting or via high-frequency-melting of the elements in sealed niobium ampoules. All samples were characterized by powder X-ray diffraction using the Guinier technique. The structures of YNiGe, YNiPb, YIrSi, YIrGe, and YIrSn were refined from single crystal X-ray diffractometer data. The YTX tetrelides are characterized by a three-dimensional [TX] network that consists of puckered T3X3 hexagons with T-X distances in the order of the sums of the covalent radii. YIrSi and YIrGe show a reverse occupancy of the T and X sites with respect to the remaining YTX compounds, which is most likely a size effect. Solid state NMR studies reveal the sensitivity of (89)Y Knight shifts to electronic structure details. A monotonic dependence on the tetrelide Pauling electronegativity is observed in addition. The stannides YTSn (T = Ni, Rh, Ir, Pt) were further characterized by (119)Sn Mssbauer spectroscopy. They show single signals that are subjected to quadrupole splitting. Comparison of the isomer shifts with the whole series of YTSn stannides gives no hint of obvious correlations as a consequence of the valence electron count but reveals a systematic decrease with atomic number within a given group. PMID:24718868

Hting, Christoph; Eckert, Hellmut; Haarmann, Frank; Winter, Florian; Pttgen, Rainer

2014-06-01

294

Synthesis, structure, and bonding in K12Au21Sn4. A polar intermetallic compound with dense Au20 and open AuSn4 layers  

SciTech Connect

The new phase K{sub 12}Au{sub 21}Sn{sub 4} has been synthesized by direct reaction of the elements at elevated temperatures. Single crystal X-ray diffraction established its orthorhombic structure, space group Pmmn (No. 59), a = 12.162(2); b = 18.058(4); c = 8.657(2) {angstrom}, V = 1901.3(7) {angstrom}{sup 3}, and Z = 2. The structure consists of infinite puckered sheets of vertex-sharing gold tetrahedra (Au{sub 20}) that are tied together by thin layers of alternating four-bonded-Sn and -Au atoms (AuSn{sub 4}). Remarkably, the dense but electron-poorer blocks of Au tetrahedra coexist with more open and saturated Au-Sn layers, which are fragments of a zinc blende type structure that maximize tetrahedral heteroatomic bonding outside of the network of gold tetrahedra. LMTO band structure calculations reveal metallic properties and a pseudogap at 256 valence electrons per formula unit, only three electrons fewer than in the title compound and at a point at which strong Au-Sn bonding is optimized. Additionally, the tight coordination of the Au framework atoms by K plays an important bonding role: each Au tetrahedra has 10 K neighbors and each K atom has 8-12 Au contacts. The appreciably different role of the p element Sn in this structure from that in the triel members in K{sub 3}Au{sub 5}In and Rb{sub 2}Au{sub 3}Tl appears to arise from its higher electron count which leads to better p-bonding (valence electron concentrations = 1.32 versus 1.22).

Li, Bin; Kim, Sung-Jin; Miller, Gordon J.; and Corbett, John D.

2009-10-29

295

Enhanced bioavailability of poorly absorbed hydrophilic compounds through drug complex/in situ gelling formulation.  

PubMed

BCS class III hydrophilic compounds are often associated with low oral bioavailability due to their poor epithelial permeability in the gastrointestinal tract. In this study, we reported an approach of incorporating a drug complex into an in situ gelling muco-adhesive carrier to achieve an improved bioavailability of a poorly absorbed hydrophilic compound. A new molecular entity (RWJ-445167) from Johnson and Johnson was used as a model compound. The compound was first complexed with sodium lauryl sulfate (SLS). The complex was then incorporated into an in situ gelling muco-adhesive carrier Cremophor for formulation characterization and rat pharmacokinetic (PK) studies. The study results showed that RWJ-445167 bound to SLS at a stoichiometric ratio. By complexing with SLS, the compound became lipophilic. The aqueous solubility of RWJ-445167 dropped to 0.58 mg/mL for the complex from 61 mg/mL for the free compound, while the partitioning coefficient of the complex increased to 7.59, compared with 0.05 of the free compound. In the rat PK study, with duodenal administration, the complex in the in situ-gelling formulation achieved 28.24% of bioavailability, compared to 4.26% of the free compound solution. The enhanced bioavailability was also significantly higher than those in the RWJ-445167/SLS physical mixture in Cremophor (14.91%), the complex in non-gelling carrier PEG 400 (9.95%) and the RWJ-445167/SLS physical mixture in PEG 400 carrier (8.60%). The study demonstrates that incorporation of a drug complex into an in situ gelling formulation provides a new approach to improving bioavailability of BCS class III drugs. PMID:24004566

Dai, Wei-Guo; Dong, Liang C; Song, Yanqiu

2013-11-30

296

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

297

Delivery of complex organic compounds from evolved stars to the solar system.  

PubMed

Stars in the late stages of evolution are able to synthesize complex organic compounds with aromatic and aliphatic structures over very short time scales. These compounds are ejected into the interstellar medium and distributed throughout the Galaxy. The structures of these compounds are similar to the insoluble organic matter found in meteorites. In this paper, we discuss to what extent stellar organics has enriched the primordial Solar System and possibly the early Earth. PMID:22139515

Kwok, Sun

2011-12-01

298

Gas chromatographic isolation of individual compounds from complex matrices for radiocarbon dating  

Microsoft Academic Search

This paper describes the application of a novel, practical approach for isolation of individual compounds from complex organic matrices for natural abundance radiocarbon measurement. This is achieved through the use of automated pereparative capillary gas chromatography (PCGC) to separate and recover sufficient quantities of individual target compounds for ¹⁴C analysis by accelerator mass spectrometry (AMS). We developed and tested this

Timothy I. Eglinton; Lihini I. Aluwihare; A. P. McNichol; J. E. Bauer; E. R. M. Druffel

1996-01-01

299

Delivery of Complex Organic Compounds from Planetary Nebulae to the Solar System  

Microsoft Academic Search

Infrared spectroscopic observations of planetary nebulae and proto-planetary nebulae have shown that complex organic compounds are synthesized in these objects over periods as short as a thousand years. These compounds are ejected into the interstellar medium and spread throughout the Galaxy. Evidence from meteorites has shown that these stellar grains have reached the Solar System, and may have showered the

Sun Kwok

2009-01-01

300

Ordered Intermetallics as Electrocatalysts for Fuel Cell  

E-print Network

Ordered Intermetallics as Electrocatalysts for Fuel Cell Applications Hctor D. Abrua) plane Pt-Pt 4.32 #12;Alloys vs. Ordered Intermetallics (A) Alloy; e.g. Pt/Ru (1:1) (B) Ordered Intermetallic e.g. BiPt #12;Bismuth Platinum (BiPt) Intermetallic Phase Powder Refinement for Bi

301

Intermetallics as Novel Supports for Pt Monolayer O2 Reduction Electrocatalysts: Potential for Significantly Improving Properties  

SciTech Connect

We report on a new class of core-shell electrocatalysts for the oxygen-reduction reaction. These electrocatalysts comprise a Pt monolayer shell and ordered intermetallic compounds cores and have enhanced activity and stability compared with conventional ones. These advantages are derived from combining the unique properties of Pt monolayer catalysts (high activity, low metal content) and of the intermetallic compounds (high stability and, possibly, low price). This method holds excellent potential for creating efficient fuel cell electrocatalysts.

Ghosh, T.; Vukmirovic, M.; DiSalvo, F.J.; Adzic, R.R.

2010-01-27

302

Intermetallics as alternative materials  

NASA Technical Reports Server (NTRS)

Aluminum containing intermetallics have B2 cubic crystal structures, exist over a wide range of composition, have large solubilities for third element alloying additions, are capable of both low and high temperature plastic flow, and have very high melting temperatures (approximately 1900 K) except for FeAl. The slow strain rate elevated temperature properties of Fe, Ni, and Co aluminides are investigated. Because of the reported difficulties with traditional melting/casting methods, sound polycrystalling materials are fabricated by hot extrusion of steel canned blended prealloyed powders. These binary aluminides are used to develop base line elevated temperature mechanical properties as well as an understanding of the factors which affect/control the strength and ductility.

Whittenberger, J. D.

1982-01-01

303

Crystalline electric fields and the magnetic ground state of the novel Heusler intermetallic YbRh2Pb  

E-print Network

intermetallic compound with a distorted Heusler structure, YbRh2Pb. We present a study of the magnetic, thermal, synthetic CeRhSn, and natural PbS standards respectively. Matrix elements were calculated using CAMECA PAPCrystalline electric fields and the magnetic ground state of the novel Heusler intermetallic YbRh2

Aronson, Meigan

304

Quantification of volatile sulfur compounds in complex gaseous matrices by solid-phase microextraction  

Microsoft Academic Search

Procedures were assessed for quantifying nine volatile sulfur compounds found in complex gaseous samples collected at a biogas-production plant and a sewage treatment plant. The target compounds were extracted by solid-phase microextraction (using the 75-?m Carboxenpolydimethylsiloxane fiber coating) at 22C for 20 min, and analyzed by GCMS. Detection limits ranged between 1 pptv (v\\/v) for carbon disulfide and 470 pptv

Annika T Nielsen; Susanne Jonsson

2002-01-01

305

Journal of Alloys and Compounds 524 (2012) 5358 Contents lists available at SciVerse ScienceDirect  

E-print Network

concentration, the bulk moduli and shear moduli of Ca­Zn intermetallic compounds increase monoton- ically. Our Ca­Zn intermetallic compounds, considered in this work, are all conductors and thermodynamically that the Ca­Zn system contains eight intermetallic compounds, namely Ca3Zn, Ca7Zn4, CaZn, CaZn2, Ca7Zn20, Ca

Melnik, Roderick

306

Ultrahigh temperature intermetallic alloys  

SciTech Connect

A new family of Cr-Cr{sub 2}Ta intermetallic alloys based on Cr-(6--10)Ta (at.%) is under development for structural use in oxidizing environments in the 1,000-1,300 C (1,832--2,372 F) temperature range. Development objectives relate to high temperature strength and oxidation resistance and room temperature fracture toughness. The 1,200 C (2,192 F) strength goals have been met: yield and fracture strengths of 275 MPa (40 ksi) and 345 MPa (50 ksi), respectively, were achieved. Progress in attaining reasonable fracture toughness of Cr-Cr{sub 2}Ta alloys has been made; current alloys exhibit room-temperature values of about 10--12 MPa{radical}m (1.1 MPa{radical}m = 1 ksi{radical}in.). Oxidation rates of these alloys at 950 C (1,742 F) in air are in the range of those reported for chromia-forming alloys. At 1,100 C (2,012 F) in air, chromia volatility was significant but, nevertheless, no scale spallation and positive weight gains of 1--5 mg/cm{sup 2} have been observed during 120-h, 6-cycle oxidation screening tests. These mechanical and oxidative properties represent substantial improvement over Cr-Cr{sub 2}Nb and Cr-Cr{sub 2}Zr alloys previously developed.

Brady, M.P.; Zhu, J.H.; Liu, C.T.; Tortorelli, P.F.; Wright, J.L.; Carmichael, C.A.

1998-11-01

307

Intermetallics for structural applications  

SciTech Connect

Intermetallics are introduced as possible structural materials. The attributes and useful temperature limits of eight of the most likely candidates have been described. In addition, detailed descriptions are given for chemical compositions, corrosion properties, mechanical properties, melting and processing, and applications of Ni{sub 3}Al and Fe{sub 3}Al-based alloys. Mechanical properties of Ni{sub 3}Al-based alloys are compared with commercially used HU alloys in the cast condition and Haynes 214 in the wrought condition. The mechanical properties of Fe{sub 3}Al-based alloys are compared with an oxide-dispersion-strengthened (ODS) Inco alloy MA-956. Comparisons have shown that Ni{sub 3}Al-based alloys offer the best combination of oxidation and carburization resistance and are significantly stronger than the commercially used HU alloy for many of the furnace-fixture applications. However, the Fe{sub 3}Al-based alloys, which offer the best sulfidation resistance of the commercially available alloys, are significantly weaker in creep than the ODS MA-956 alloy. Even with the current strength level, Fe{sub 3}Al-based alloys are superior as porous, sintered metal filters for hot-gas cleanup in coal gasification systems. Oxide-dispersion strengthening of the Fe{sub 3}Al-based alloys is currently under way to improve their creep strength.

Sikka, V.K.; Deevi, S.C. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

1995-09-01

308

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

309

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 420-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

310

Reversible carbon-carbon bond formation between carbonyl compounds and a ruthenium pincer complex.  

PubMed

This communication describes the reversible reaction of a ruthenium pincer complex with a variety of carbonyl compounds. Both NMR spectroscopic and X-ray crystallographic characterization of isomeric carbonyl adducts are reported, and the equilibrium constants for carbonyl binding have been determined. PMID:23832007

Huff, Chelsea A; Kampf, Jeff W; Sanford, Melanie S

2013-08-18

311

Products of binary complex compounds thermolysis: Catalysts for hydrogen peroxide decomposition  

NASA Astrophysics Data System (ADS)

Samples are obtained via the thermolysis of binary complex compounds in a hydrogen atmosphere. Their catalytic activity in hydrogen peroxide decomposition is studied. The values of the rate constants and activation energies for the catalytic reaction are estimated. The correlation between catalytic activity, composition, specific surface area ( S sp), and particle size of the samples is analyzed.

Domonov, D. P.; Pechenyuk, S. I.; Gosteva, A. N.

2014-06-01

312

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

313

Formation and growth kinetics of interfacial intermetallics in Pb-free solder joint  

Microsoft Academic Search

The formation and growth kinetics of the intermetallic compound (IMC) between lead-free solder and Cu substrate in the surface mount process were studied. Optical and scanning electron microscope (OM and SEM) were used to measure the thickness of intermetallic layers and observe the microstructure evolution of solder joint. The IMC phases were identified by energy dispersive X-ray (EDX) and X-ray

G. Y. Li; B. L. Chen

2003-01-01

314

Gas chromatographic isolation of individual compounds from complex matrices for radiocarbon dating  

SciTech Connect

This paper describes the application of a novel, practical approach for isolation of individual compounds from complex organic matrices for natural abundance radiocarbon measurement. This is achieved through the use of automated pereparative capillary gas chromatography (PCGC) to separate and recover sufficient quantities of individual target compounds for {sup 14}C analysis by accelerator mass spectrometry (AMS). We developed and tested this approach using a suite of samples (plant lipids, petroleums) whose ages spanned the {sup 14}C time scale and which contained a variety of compound types (fatty acids, sterols, hydrocarbons). Comparison of individual compound and bulk radiocarbon signatures for the isotopically homogeneous samples studied revealed that {Delta}{sup 14}C values generally agreed well ({+-}10%). Background contamination was assessed at each stage of the isolation procedure, and incomplete solvent removal prior to combustion was the only significant source of additional carbon. Isotope fractionation was addressed through compound-specific stable carbon isotopic analyses. Fractionation of isotopes during isolation of individual compounds was minimal (<5% for {delta}{sup 13}C), provided the entire peak was collected during PCGC. Trapping of partially coeluting peaks did cause errors, and these results highlight the importance of conducting stable carbon isotopic measurements of each trapped compound in concert with AMS for reliable radiocarbon measurements. 29 refs., 9 figs., 2 tabs.

Eglinton, T.I.; Aluwihare, L.I.; McNichol, A.P. [Woods Hole Oceanographic Inst., MA (United States)] [Woods Hole Oceanographic Inst., MA (United States); Bauer, J.E. [College of Wiliam and Mary, Gloucester Point, VA (United States)] [College of Wiliam and Mary, Gloucester Point, VA (United States); Druffel, E.R.M. [Univ. of California, Irvine, CA (United States)] [Univ. of California, Irvine, CA (United States)

1996-03-01

315

[Mn(en)3]CdSnTe4 and [Mn(en)3]Ag6Sn2Te8: New Intermetallic Tellurides Synthesized in Superheated  

E-print Network

this route, we have recently begun to investigate intermetallic compounds that contain more than one type[Mn(en)3]CdSnTe4 and [Mn(en)3]Ag6Sn2Te8: New Intermetallic Tellurides Synthesized in Superheated intermetallic tellurides, Mn(en)3]CdSnTe4 (I) and [Mn(en)3]Ag6Sn2Te8 (II), have been synthesized in superheated

Li, Jing

316

Pressure tuning of competing magnetic interactions in intermetallic CeFe2  

SciTech Connect

We use high-pressure magnetic x-ray diffraction and numerical simulation to determine the low-temperature magnetic phase diagram of stoichiometric CeFe2. Near 1.5 GPa we find a transition from ferromagnetism to antiferromagnetism, accompanied by a rhombohedral distortion of the cubic Laves crystal lattice. By comparing pressure and chemical substitution we find that the phase transition is controlled by a shift of magnetic frustration from the Ce-Ce to the Fe-Fe sublattice. Notably the dominant Ce-Fe magnetic interaction, which sets the temperature scale for the onset of long-range order, remains satisfied throughout the phase diagram but does not determine the magnetic ground state. Our results illustrate the complexity of a system with multiple competing magnetic energy scales and lead to a general model for magnetism in cubic Laves phase intermetallic compounds.

Wang, Jiyang; Feng, Yejun; Jaramillo, R.; van Wezel, Jasper; Canfield, Paul C.; Rosenbaum, T.F.

2012-07-20

317

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

318

Iron-Targeting Antitumor Activity of Gallium Compounds and Novel Insights Into Triapine-Metal Complexes  

PubMed Central

Abstract Significance: Despite advances made in the treatment of cancer, a significant number of patients succumb to this disease every year. Hence, there is a great need to develop new anticancer agents. Recent Advances: Emerging data show that malignant cells have a greater requirement for iron than normal cells do and that proteins involved in iron import, export, and storage may be altered in cancer cells. Therefore, strategies to perturb these iron-dependent steps in malignant cells hold promise for the treatment of cancer. Recent studies show that gallium compounds and metal-thiosemicarbazone complexes inhibit tumor cell growth by targeting iron homeostasis, including iron-dependent ribonucleotide reductase. Chemical similarities of gallium(III) with iron(III) enable the former to mimic the latter and interpose itself in critical iron-dependent steps in cellular proliferation. Newer gallium compounds have emerged with additional mechanisms of action. In clinical trials, the first-generation-compound gallium nitrate has exhibited activity against bladder cancer and non-Hodgkin's lymphoma, while the thiosemicarbazone Triapine has demonstrated activity against other tumors. Critical Issues: Novel gallium compounds with greater cytotoxicity and a broader spectrum of antineoplastic activity than gallium nitrate should continue to be developed. Future Directions: The antineoplastic activity and toxicity of the existing novel gallium compounds and thiosemicarbazone-metal complexes should be tested in animal tumor models and advanced to Phase I and II clinical trials. Future research should identify biologic markers that predict tumor sensitivity to gallium compounds. This will help direct gallium-based therapy to cancer patients who are most likely to benefit from it. Antioxid. Redox Signal. 00, 000000. PMID:22900955

Antholine, William E.

2013-01-01

319

Spectroscopic investigation on europium complexation with humic acid and its model compounds  

NASA Astrophysics Data System (ADS)

Time resolved fluorescence spectroscopy (TRFS) of Eu(III) (an analogue of trivalent actinides) complexation with humic acid (HA) and its model compounds, namely phthalic acid (PA), mandelic acid (MA) and succinic acid (SA) has been carried out at varying concentration ratios of ligand to metal ion. The emission spectra were recorded in the range of 550-650 nm by exciting at an appropriate wavelength. The intensity of the 616 nm peak of Eu(III) was found to be sensitive to complexation. The ratio of the intensities of 616 and 592 nm peaks was used to determine the stability constants of Eu-phthalate, Eu-mandelate and Eu-succinate complexes. In the case of model compounds, the life-time was found to increase with increasing ligand to metal ratio (L/M) indicating the decrease in quenching of the fluorescence by coordinated water molecules with increasing complexation. On the other hand in the case of HA, the life-time was found to be constant at least up to L/M of 5, indicating the formation of outer sphere complex. Beyond L/M = 5 the life-time value was found to increase which can be attributed to the binding of the metal ion to the higher affinity sites in the HA macromolecule.

Jain, Aishwarya; Yadav, Kartikey; Mohapatra, Manoj; Godbole, S. V.; Tomar, B. S.

2009-06-01

320

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

321

Modeling of Substitutional Site Preference in Ordered Intermetallic Alloys  

NASA Technical Reports Server (NTRS)

We investigate the site substitution scheme of specific alloying elements in ordered compounds and the dependence of site occupancy on compound stoichiometry, alloy concentration. This basic knowledge, and the interactions with other alloying additions are necessary in order to predict and understand the effect of various alloying schemes on the physical properties of a material, its response to various temperature treatments, and the resulting mechanical properties. Many theoretical methods can provide useful but limited insight in this area, since most techniques suffer from constraints in the type of elements and the crystallographic structures that can be modeled. With this in mind, the Bozzolo-Ferrante-Smith (BFS) method for alloys was designed to overcome these limitations, with the intent of providing an useful tool for the theoretical prediction of fundamental properties and structure of complex systems. After a brief description of the BFS method, its use for the determination of site substitution schemes for individual as well as collective alloying additions to intermetallic systems is described, including results for the concentration dependence of the lattice parameter. Focusing on B2 NiAl, FeAl and CoAl alloys, the energetics of Si, Ti, V, Cr, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Hf, Ta and W alloying additions are surveyed. The effect of single additions as well as the result of two simultaneous additions, discussing the interaction between additions and their influence on site preference schemes is considered. Finally, the BFS analysis is extended to ternary L1(sub 2) (Heusler phase) alloys. A comparison between experimental and theoretical results for the limited number of cases for which experimental data is available is also included.

Bozzolo, Guillermo; Noebe, Ronald D.; Honecy, Frank

1998-01-01

322

Study of bulk ground state properties of cerium intermetallics by linear dichroism in 4f resonant inelastic X-ray scattering  

E-print Network

Study of bulk ground state properties of cerium intermetallics by linear dichroism in 4f resonant resonant inelastic X-ray scattering in the M5 region of intermetallic compounds of cerium (CeRh2, CePd3, Ce

Marcon, Marco

323

Structural considerations of intermetallic electrodes for lithium batteries  

NASA Astrophysics Data System (ADS)

Although metal alloys and intermetallic compounds have been researched extensively as possible negative electrodes for lithium batteries, only recently have efforts been made to monitor the phase transitions that occur during their reaction with lithium by in situ X-ray diffraction. These studies have lead to attempts to exploit those systems that show strong structural relationships between a parent structure and its lithiated products. In this paper, an overview of several systems is presented, particularly those that operate by lithium insertion/metal displacement reactions with a host metal array at room temperature. An analogy between these reactions and the high-temperature electrochemical reaction of sodium/nickel chloride cells, which is 100% efficient, is provided. On this basis, a prognosis for using intermetallic electrodes in lithium-ion cells is given.

Thackeray, M. M.; Vaughey, J. T.; Johnson, C. S.; Kropf, A. J.; Benedek, R.; Fransson, L. M. L.; Edstrom, K.

324

NMR study of trialuminide intermetallics  

Microsoft Academic Search

We present a systematic study of the DO22-structure trialuminide intermetallic alloys using 27Al NMR spectroscopy. The quadrupole splittings, Knight shifts, and spin-lattice relaxation times on Al3Ti, Al3V, Al3Nb, and Al3Ta have been identified. Knight-shift tensors were isolated by observation of quadrupole satellite lines and fitting to the central-transition powder patterns. The results are associated with the local electronic density of

Chin-Shan Lue; Suchitra Chepin; James Chepin; Joseph H. Ross Jr.

1998-01-01

325

Stress-Induced Martensitic Phase Transformation in Intermetallic Nickel  

E-print Network

Stress-Induced Martensitic Phase Transformation in Intermetallic Nickel Aluminum Nanowires Harold S simulations are utilized to demonstrate a stress-induced martensitic phase transformation in intermetallic. In this letter, we demonstrate that intermetallic nanowires also show such multifunctional potential

Lin, Xi

326

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

PubMed

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 an intermediate product of the vinyl chloride process in the petrochemical complex, was the most abundant volatile organic compound, followed by ethyl alcohol and acetone. Evaluations based on wind direction clearly indicated that ambient VOC concentrations measured were affected by the refinery and petrochemical complex emissions. VOC concentrations showed seasonal variations at all sampling sites. Concentrations were highest in summer, followed by autumn, probably due to increased evaporation of VOCs from fugitive sources as a result of higher temperatures. VOC concentrations generally increased with temperature and wind speed. Temperature and wind speed together explained 1-60% of the variability in VOC concentrations. The variability in ambient VOC concentrations that could not be explained by temperature and wind speed can be attributed to the effect of other factors (i.e. wind direction, other VOC sources). PMID:12873403

Cetin, Eylem; Odabasi, Mustafa; Seyfioglu, Remzi

2003-08-01

327

Detection and Differentiation of Neutral Organic Compounds by [superscript 19]F NMR with a Tungsten Calix[4]arene Imido Complex  

E-print Network

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 ...

Zhao, Yanchuan

328

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

329

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

330

Method for making devices having intermetallic structures and intermetallic devices made thereby  

DOEpatents

A method and system for making a monolithic intermetallic structure are presented. The structure is made from lamina blanks which comprise multiple layers of metals which are patternable, or intermetallic lamina blanks that are patternable. Lamina blanks are patterned, stacked and registered, and processed to form a monolithic intermetallic structure. The advantages of a patterned monolithic intermetallic structure include physical characteristics such as melting temperature, thermal conductivity, and corrosion resistance. Applications are broad, and include among others, use as a microreactor, heat recycling device, and apparatus for producing superheated steam. Monolithic intermetallic structures may contain one or more catalysts within the internal features.

Paul, Brian Kevin (Oregon State University, Corvallis, OR); Wilson, Rick D.; Alman, David E.

2004-01-06

331

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

332

First-principles study on alloying stability, electronic structure, and mechanical properties of Al-based intermetallics  

Microsoft Academic Search

First-principles calculations were performed to study on alloying stability, electronic structure, and mechanical properties of Al-based intermetallic compounds (AlCu3, AlCu2Zr, and AlZr3). The calculated results show that the lattice parameters obtained after full relaxation of crystalline cells are consistent with experimental data. The calculation of cohesive energies indicated that the structure stability of these Al-based intermetallics will become higher with

Y. Z. Guan; H. Y. Zhang; W. Li

2011-01-01

333

Spin crossover in iron(II)-containing complex compounds under a pressure (Review Article)  

NASA Astrophysics Data System (ADS)

The spin crossover phenomenon consists in switching between two spin states of the central ion of a transition 3d- metal in a molecular complex. The spin crossover can be induced and controlled by temperature, pressure, light radiation etc. The present review addresses all aspects of the effect of hydrostatic pressure on spin-crossover properties of iron(II) complex compounds. The applied hydrostatic pressure allows us to influence the crystal lattice, revealing the role of elastic fields in the cooperative interaction of spin-crossover complexes, and to change directly the volume characteristics of the complex molecules, the distances between the central ion and ligand atoms, and thus affect the strength of the crystal field. The experimental results for all types of iron(II)-containing spin-crossover structures are discussed in details, and the theoretical consideration of the observed effects is given. The physical principles of spin crossover at the molecular level are adequately described by the ligand field theory while the macroscopic properties are understood on the basis of electron-phonon coupling and elastic properties of the crystal lattice.

Levchenko, G. G.; Khristov, A. V.; Varyukhin, V. N.

2014-07-01

334

Molecular identification of organic compounds in atmospheric complex mixtures and relationship to atmospheric chemistry and sources.  

PubMed Central

This article describes a chemical characterization approach for complex organic compound mixtures associated with fine atmospheric particles of diameters less than 2.5 m (PM2.5). It relates molecular- and bulk-level chemical characteristics of the complex mixture to atmospheric chemistry and to emission sources. Overall, the analytical approach describes the organic complex mixtures in terms of a chemical mass balance (CMB). Here, the complex mixture is related to a bulk elemental measurement (total carbon) and is broken down systematically into functional groups and molecular compositions. The CMB and molecular-level information can be used to understand the sources of the atmospheric fine particles through conversion of chromatographic data and by incorporation into receptor-based CMB models. Once described and quantified within a mass balance framework, the chemical profiles for aerosol organic matter can be applied to existing air quality issues. Examples include understanding health effects of PM2.5 and defining and controlling key sources of anthropogenic fine particles. Overall, the organic aerosol compositional data provide chemical information needed for effective PM2.5 management. PMID:12634131

Mazurek, Monica A

2002-01-01

335

Suppressors made from intermetallic materials  

DOEpatents

Disclosed are several examples of apparatuses for suppressing the blast and flash produced as a projectile is expelled by gases from a firearm. In some examples, gases are diverted away from the central chamber to an expansion chamber by baffles. The gases are absorbed by the expansion chamber and desorbed slowly, thus decreasing pressure and increasing residence time of the gases. In other examples, the gases impinge against a plurality of rods before expanding through passages between the rods to decrease the pressure and increase the residence time of the gases. These and other exemplary suppressors are made from an intermetallic material composition for enhanced strength and oxidation resistance at high operational temperatures.

Klett, James W; Muth, Thomas R; Cler, Dan L

2014-11-04

336

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

337

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

338

LJournal of Alloys and Compounds 326 (2001) 166173 www.elsevier.com/locate/jallcom  

E-print Network

-earth (R) and Fe sublattices in R­Fe based intermetallic compounds is normally a cooperative phenomenon a magnetic6 6 moment, the magnetic ordering processes of the R and Fe Intermetallic compounds which containLJournal of Alloys and Compounds 326 (2001) 166­173 www.elsevier.com/locate/jallcom Invited talk

Ryan, Dominic

339

LJournal of Alloys and Compounds 340 (2002) 199206 www.elsevier.com/locate/jallcom  

E-print Network

intermetallic compounds often form with melting temperatures much higher than those of the constitutive pure-melting-temperature intermetallic compounds, and it diagram presented by Hansen and Anderko [12] with the often results in a lessLJournal of Alloys and Compounds 340 (2002) 199­206 www.elsevier.com/locate/jallcom Thermodynamic

Chen, Long-Qing

340

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-, Stafurt- 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 (NDLER 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 NDLER, 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.; Ndler, K.; Geyer, T.; Sauter, M.

2012-04-01

341

Emission of complex fragments for compound nuclei formed far from the stability line for A{approx}120  

SciTech Connect

Experiments and calculations are presented for the emission of complex fragments (Z>2) from compound nuclei around mass 120 and for bombarding energies below 15 MeV/nucleon. It is shown that a strong enhancement in the emission of complex fragments (especially for Z=6) is expected for compound nuclei formed close or at the N=Z line. Several predictions are given that could be tested with the radioactive beams soon to be available. Also results from a recent experiment that utilizes the emission of complex fragments for {gamma}-ray nuclear spectroscopy studies are presented.

Gomez Del Campo, J.

1996-10-01

342

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

Microsoft Academic Search

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

R. G. Buchheit

1995-01-01

343

An analysis of intermetallics formation of gold and copper ball bonding on thermal aging  

Microsoft Academic Search

In IC packages, thermosonic wire bonding is the preferred method for making electrical connections between the die pad and lead frame. These interconnect are made using fine metal wires. On thermal aging (under 175C for 5h) gold aluminide easily forms in gold ball bonds while formation of intermetallic compound is absent in case of copper ball bonds. An analysis of

S. Murali; N. Srikanth; Charles J Vath

2003-01-01

344

The chemical phenol extraction of intermetallic particles from casting AlSi5Cu1Mg alloy.  

PubMed

This paper presents a chemical extraction technique for determination of intermetallic phases formed in the casting AlSi5Cu1Mg aluminium alloy. Commercial aluminium alloys contain a wide range of intermetallic particles that are formed during casting, homogenization and thermomechanical processing. During solidification, particles of intermetallics are dispersed in interdendritic spaces as fine primary phases. Coarse intermetallic compounds that are formed in this aluminium alloy are characterized by unique atomic arrangement (crystallographic structure), morphology, stability, physical and mechanical properties. The volume fraction, chemistry and morphology of the intermetallics significantly affect properties and material behaviour during thermomechanical processing. Therefore, accurate determination of intermetallics is essential to understand and control microstructural evolution in Al alloys. Thus, in this paper it is shown that chemical phenol extraction method can be applied for precise qualitative evaluation. The results of optical light microscopy LOM, scanning electron microscopy SEM and X-ray diffraction XRD analysis reveal that as-cast AlSi5Cu1Mg alloy contains a wide range of intermetallic phases such as Al(4)Fe, gamma- Al(3)FeSi, alpha-Al(8)Fe(2)Si, beta-Al(5)FeSi, Al(12)FeMnSi. PMID:20500407

Mrwka-Nowotnik, G; Sieniawski, J; Nowotnik, A

2010-03-01

345

Potentialities of a Multidetector System to Study Cascade ? Decay of a Compound State of Complex Nuclei  

NASA Astrophysics Data System (ADS)

Decades of investigation of the compound-state ?-decay of complex nuclei (A?100) have not given sufficient information about this process. Traditional (``rough'') studies of ?-spectra using best modern detectors cannot provide full information. So one should look for a new approach to the experimental study of this process. It seems that the most effective way is to distinguish cascades of two, three or more ?-transitions with total energy being equal to the neutron binding energy Bn or to the corresponding difference between Bn and excitation energy of some low-lying states. The Laboratory of Neutron Physics, JINR, has been measuring the cascades with energies E1+E2=Bn since 1982. For the present time they have been studied in 15 nuclei (in 137Ba, 181Hf and 187W-jointly with IP AS LatvSSR). The main information obtained is a decay-scheme of levels excited by cascades with a threshold intensity i???310-4 per decay up to an excitation energy not lower than 3-4 MeV. Very important are also the two-quanta cascade intensities averaged over transition energy (and in some cases, over excitation energy of a nucleus). (First estimates of radiative strength functions of soft primary transitions were evaluated too.) These averaged intensities could be easily compared with those calculated in the frame of any of the models of excited states density and partial widths. The experiment reveals a large enough portion of the total intensity of all the primary transitions in compound-state decay as illustrated in the table. Sometimes the sum i??+i? (see the table) amounts to 80% of the total radiative width of a compound-state. This fact means that the problem of the complete experimental investigation of ?-decay of several nuclei is near to its practical solution.

Khitrov, V. A.; Popov, Yu. P.; Sukhovoj, A. M.

1991-10-01

346

Process for synthesizing compounds from elemental powders and product  

DOEpatents

A process for synthesizing intermetallic compounds from elemental powders. 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.

Rabin, Barry H. (Idaho Falls, ID); Wright, Richard N. (Idaho Falls, ID)

1993-01-01

347

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

SciTech Connect

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, X.; Wai, C.M.; Fisher, D.R.

2000-06-13

348

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

349

Intermetallic NaAu2 as a heterogeneous catalyst for low-temperature CO oxidation.  

PubMed

The enhanced stability and modified electronic structure of intermetallic compounds provide discovery of superior catalysts for chemical conversions with high activity, selectivity, and stability. We find that the intermetallic NaAu2 is an active catalyst for CO oxidation at low temperatures. From density functional theory calculations, a reaction mechanism is suggested to explain the observed low reaction barrier of CO oxidation by NaAu2, in which a CO molecule reacts directly with an adsorbed O2 to form an OOCO* intermediate. The presence of surface Na increases the binding energy of O2 and decreases the energy barrier of the transition states. PMID:23758405

Xiao, Chaoxian; Wang, Lin-Lin; Maligal-Ganesh, Raghu V; Smetana, Volodymyr; Walen, Holly; Thiel, Patricia A; Miller, Gordon J; Johnson, Duane D; Huang, Wenyu

2013-07-01

350

Intermetallic matrix composites prepared by mechanical alloyinga review  

Microsoft Academic Search

This paper reviews research on intermetallic matrix composites synthesized by mechanical alloying. Mechanical alloying, as a powder processing method, results in discontinuous second phases, i.e. dispersoids\\/discontinuous reinforcements, in the intermetallic matrix. After a discussion of earlier work on dispersoids in intermetallics, intermetallic matrix composites prepared by mechanical alloying will be reviewed for the important structural intermetallics Fe40 at.% Al, NiAl,

C. C Koch

1998-01-01

351

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

352

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. 2 figs.

Plucknett, K.; Tiegs, T.N.; Becher, P.F.

1999-05-18

353

Structures and phase transitions in some Pb2B?B?O6 complex perovskite-type compounds  

Microsoft Academic Search

In order to study the influence of substitutions and of the ionic radii of B ions on structure and phase transitions, we present some physical measurements and data on Pb2B?B?O6 (B=W, Nb, Mo) complex perovskite compounds. By Mn and Fe substitution for Mg in Pb2MgWO6 compound a change in lattice parameters and shift of antiferroelectric transition temperature is observed. It

I. Barbur; I. Ardelean

2001-01-01

354

Air monitoring for volatile organic compounds at the Pilot Plant Complex, Aberdeen Proving Ground, Maryland  

SciTech Connect

The US Army`s Aberdeen Proving Ground has been a test site for a variety of munitions, including chemical warfare agents (CWA). The Pilot Plant Complex (PPC) at Aberdeen was the site of development, manufacture, storage, and disposal of CWA. Deterioration of the buildings and violations of environmental laws led to closure of the complex in 1986. Since that time, all equipment, piping, and conduit in the buildings have been removed. The buildings have been declared free of surface CWA contamination as a result of air sampling using the military system. However, no air sampling has been done to determine if other hazardous volatile organic compounds are present in the PPC, although a wide range of toxic and/or hazardous materials other than CWA was used in the PPC. The assumption has been that the air in the PPC is not hazardous. The purpose of this air-monitoring study was to screen the indoor air in the PPC to confirm the assumption that the air does not contain volatile organic contaminants at levels that would endanger persons in the buildings. A secondary purpose was to identify any potential sources of volatile organic contaminants that need to be monitored in subsequent sampling efforts.

Schneider, J.F.; O`Neill, H.J.; Raphaelian, L.A.; Tomczyk, N.A.; Sytsma, L.F.; Cohut, V.J.; Cobo, H.A.; O`Reilly, D.P.; Zimmerman, R.E.

1995-03-01

355

The effect of hybridization on local magnetic interactions at highly diluted Ce ions in tetragonal intermetallic compounds RERh2Si2 (RE=Ce, Pr, Nd, Gd, Tb, Dy).  

PubMed

The contribution of the 4f electron to the local magnetic field at highly diluted Ce atoms in RERh(2)Si(2) (RE = Ce, Pr, Nd, Gd, Tb, Dy) has been investigated as a function of temperature through the measurement of the magnetic hyperfine field in (140)Ce nuclei by time differential perturbed gamma-gamma angular correlation spectroscopy. Samples of the studied compounds were characterized by x-ray diffraction and zero-field resistance to determine the crystal structure and transport properties. DC magnetic susceptibility was measured for NdRh(2)Si(2). It was observed that the variation of the magnetic hyperfine field with temperature follows the expected behaviour for the host magnetization, with the exception of GdRh(2)Si(2), which showed a strong deviation from such a behaviour. It is shown that the hybridization of the d band of the host with the f band of the Ce impurity, which is stronger in GdRh(2)Si(2) than in other compounds, is responsible for the observed deviation from the expected temperature dependence of the hyperfine field. The origin of this stronger hybridization is ascribed to the relatively small magnetic anisotropy observed in GdRh(2)Si(2) when compared with the other compounds of the series, as shown by resistance measurements. PMID:23006536

Cabrera-Pasca, G A; Carbonari, A W; Bosch-Santos, B; Mestnik-Filho, J; Saxena, R N

2012-10-17

356

The effect of hybridization on local magnetic interactions at highly diluted Ce ions in tetragonal intermetallic compounds RERh2Si2 (RE=Ce, Pr, Nd, Gd, Tb, Dy)  

NASA Astrophysics Data System (ADS)

The contribution of the 4f electron to the local magnetic field at highly diluted Ce atoms in RERh2Si2 (RE = Ce, Pr, Nd, Gd, Tb, Dy) has been investigated as a function of temperature through the measurement of the magnetic hyperfine field in 140Ce nuclei by time differential perturbed gamma-gamma angular correlation spectroscopy. Samples of the studied compounds were characterized by x-ray diffraction and zero-field resistance to determine the crystal structure and transport properties. DC magnetic susceptibility was measured for NdRh2Si2. It was observed that the variation of the magnetic hyperfine field with temperature follows the expected behaviour for the host magnetization, with the exception of GdRh2Si2, which showed a strong deviation from such a behaviour. It is shown that the hybridization of the d band of the host with the f band of the Ce impurity, which is stronger in GdRh2Si2 than in other compounds, is responsible for the observed deviation from the expected temperature dependence of the hyperfine field. The origin of this stronger hybridization is ascribed to the relatively small magnetic anisotropy observed in GdRh2Si2 when compared with the other compounds of the series, as shown by resistance measurements.

Cabrera-Pasca, G. A.; Carbonari, A. W.; Bosch-Santos, B.; Mestnik-Filho, J.; Saxena, R. N.

2012-10-01

357

Forming metal-intermetallic or metal-ceramic composites by self-propagating high-temperature reactions  

DOEpatents

Industrial applications of composites often require that the final product have a complex shape. In this invention intermetallic or ceramic phases are formed from sheets of unreacted elemental metals. The process described in this invention allows the final product shape be formed prior to the formation of the composite. This saves energy and allows formation of shaped articles of metal-intermetallic composites composed of brittle materials that cannot be deformed without breaking.

Rawers, James C. (Albany Research Center, Bureau of Mines, Department of the Interior, 1450, Albany, OR 97321); Alman, David E. (Albany Research Center, Bureau of Mines, Department of the Interior, 1450, Albany, OR 97321); Petty, Jr., Arthur V. (Albany Research Center, Bureau of Mines, Department of the Interior, 1450, Albany, OR 97321)

1996-01-01

358

Melt fragility of near-intermetallic composition  

NASA Astrophysics Data System (ADS)

The dynamic viscosities of In-Bi and Ag-Yb alloy systems are measured by the torsional oscillation viscometer and the corresponding melt fragilities (M) are calculated from the temperature dependence of viscosities fitted by the Arrhenius equation. It was found that the melt fragility of the intermetallics is larger than that of the alloys with near-intermetallic compositions, but is smaller than that of the alloys with near-intermetallic compositions with a peritectic reaction. From the thermodynamics and kinetics points of view, the origins for the compositions near intermetallics as potential hosts of glass formers were well demonstrated. Our study confirms the universality of melt fragility and gives implications on the physical mechanisms for the glass forming alloys.

Wang, Xinzhu; Bian, Xiufang; Song, Kaikai; Zhao, Xiaolin; Bai, Yanwen

2012-10-01

359

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

360

Complexation of amino compounds by 18C6 improves selectivity by IMS-IMS-MS: application to petroleum characterization.  

PubMed

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 )H(2n+3)N 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

2011-05-01

361

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

362

Vanadocene(IV) dicyanide complexes: the evidence super-hyperfine coupling for compounds with 13CN ligands.  

PubMed

An EPR study of the vanadocene complexes (C(5)H(5))2V(CN)2 and (CH(3)C(5)H(4))2V(CN)2 was carried out. Such compounds show strong super-hyperfine coupling (|a(iso)(13C)| approximately 1.27 mT) when 13C labeled cyanide is used for their preparation. Super-hyperfine splitting was observed in the isotropic spectra of solution samples as well as in the anisotropic spectra of frozen solutions. Such studies were supplemented with structural characterization of the parent compounds. Molecular structure of the complex (CH(3)C(5)H(4))2V(CN)2 was determined by single-crystal X-ray diffraction analysis. Both compounds were characterized by infrared and Raman spectroscopy. PMID:17431860

Honzcek, Jan; Vinklrek, Jaromr; Cernosek, Zdenek; Csarov, Ivana

2007-06-01

363

INTERNATIONAL TOXICITY EQUIVALENCY FACTOR (I-TEF) METHOD OF RISK ASSESSMENT FOR COMPLEX MIXTURES OF DIOXINS AND RELATED COMPOUNDS  

EPA Science Inventory

The International Toxicity Equivalency Factor (I-TEF) Method of Risk Assessment for Complex Mixtures of Dioxins and Related Compounds is a revised interim procedure for estimating the risks considered with exposures to mixtures of dioxins and furons such as incinerator fly ash, c...

364

Clinical use of an herbal-derived compound (Huperzine A) to treat putative complex partial seizures in a dog  

Microsoft Academic Search

A Bernese mountain dog was diagnosed with complex partial seizures that were supported by electroencephalographic findings. Clinical signs of the problem included star gazing, fly snapping, licking, vacuous chewing, and ongoing anxiety. Treatment with Huperzine A, a compound isolated from Chinese club moss with NMDA receptor blocking activity, anticholinesterase activity, and anticonvulsant properties, produced useful suppression of the abnormal behavior

Barbara M. Schneider; Nicholas H. Dodman; Dominik Faissler; Niwako Ogata

2009-01-01

365

Personal volatile organic compound (VOC) exposure of children attending elementary schools adjacent to industrial complex  

NASA Astrophysics Data System (ADS)

The major deficiency in linking the effects of environmental exposure to children's health is the lack of data on the exposure of children to hazardous environmental pollutants. Accordingly, the present study compared the personal volatile organic compound (VOC) exposure of children from four elementary schools at different proximities to the Daegu Dyeing Industrial Complex (DDIC) and adjacent to different traffic densities. The personal air concentrations of four VOCs (toluene, m, p-xylenes, and o-xylene) were significantly higher for the children attending the school (S1) closest to the boundary of the DDIC compared to the children attending the school (S2) further away. The DDIC was the likely primary cause for the elevated personal air concentrations of the four VOCs in the children attending the school nearest the DDIC. The personal exposure to toluene and methyl tertiary-butyl ether (MTBE) for the children attending the school near a major roadway with a high traffic density was significantly higher than that for the children attending the school near a roadway with a low traffic density. The difference in the breath concentrations was generally similar to the difference in the personal air concentrations among the children from the four schools. In contrast to the children attending schools in low-income areas, the children attending schools in high-income areas exhibited no significant difference in the concentrations of any of the target VOCs in the personal air and breath samples between the children living with and without a smoker in the home.

Park, Kun-Ho; Jo, Wan-Kuen

366

Complex Organic and Inorganic Compounds in Shells of Lithium-rich K Giant Stars  

E-print Network

Hydrocarbon organic material, as found in the interstellar medium, exists in complex mixtures of aromatic and aliphatic forms. It is considered to be originated from carbon enriched giant stars during their final stages of evolution, when very strong mass loss occurs in a few thousand years on their way to become planetary nebulae. We show here that the same organic compounds appear to be formed in previous stages of the evolution of giant stars. More specifically, during the first ascending giant branch K-type stars. According to our model this happens only when these stars are being abruptly enriched with lithium together with the formation of a circumstellar shell with a strong mass loss during just a few thousand years. This sudden mass loss is, on an average, a thousand times larger than that of normal Li-poor K giant stars. This shell would later be detached, specially when the star stops its Li enrichment and a rapid photospheric Li depletion occurs. In order to gain extra carbon-based material to form...

de la Reza, Ramiro; Oliveira, Isa; Rengaswamy, Sridharan

2015-01-01

367

Identification of plant compounds that disrupt the insect juvenile hormone receptor complex.  

PubMed

Insects impact human health through vector-borne diseases and cause major economic losses by damaging crops and stored agricultural products. Insect-specific growth regulators represent attractive control agents because of their safety to the environment and humans. We identified plant compounds that serve as juvenile hormone antagonists (PJHANs). Using the yeast two-hybrid system transformed with the mosquito JH receptor as a reporter system, we demonstrate that PJHANs affect the JH receptor, methoprene-tolerant (Met), by disrupting its complex with CYCLE or FISC, formation of which is required for mediating JH action. We isolated five diterpene secondary metabolites with JH antagonist activity from two plants: Lindera erythrocarpa and Solidago serotina. They are effective in causing mortality of mosquito larvae at relatively low LD50 values. Topical application of two diterpenes caused reduction in the expression of Met target genes and retardation of follicle development in mosquito ovaries. Hence, the newly discovered PJHANs may lead to development of a new class of safe and effective pesticides. PMID:25624480

Lee, Seok-Hee; Oh, Hyun-Woo; Fang, Ying; An, Saes-Byeol; Park, Doo-Sang; Song, Hyuk-Hwan; Oh, Sei-Ryang; Kim, Soo-Young; Kim, Seonghyun; Kim, Namjung; Raikhel, Alexander S; Je, Yeon Ho; Shin, Sang Woon

2015-02-10

368

The influence of heterocyclic compound-PAMAM dendrimer complexes on evoked electrical responses in slices of hypoxic brain tissue.  

PubMed

We used complexes between a fourth generation polyamidoamine (PAMAM) dendrimer and one of two heterocyclic compounds - 1-(6-hydroxyhexyl)-3-(5-phenyl-isoxazole-3-yl)-urea or 5-phenyl-isoxazole-3-carboxylic acid - to reduce oxygen consumption in transverse slices of the hippocampus taken from 4-week old male rats. In vitro electrophysiological experiments revealed that the inhibitory effect of the hypoxic state on the evoked responses was enhanced in the presence of the complexes. The data were analyzed in terms of the potential antitumor effects of these complexes. PMID:24764142

Potkin, Vladimir I; Shcharbin, Dzmitry; Denisov, Andrey A; Paschkevich, Svetlana G; Bryszewska, Maria; Petkevich, Sergey K; Kletskov, Alexey V; Lapotko, Dmitri O; Kazbanov, Vladimir V; Gurinovich, Tatiana A; Kulchitsky, Vladimir A

2014-06-01

369

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

370

NMR study of trialuminide intermetallics  

NASA Astrophysics Data System (ADS)

We present a systematic study of the DO22-structure trialuminide intermetallic alloys using 27Al NMR spectroscopy. The quadrupole splittings, Knight shifts, and spin-lattice relaxation times on Al3Ti, Al3V, Al3Nb, and Al3Ta have been identified. Knight-shift tensors were isolated by observation of quadrupole satellite lines and fitting to the central-transition powder patterns. The results are associated with the local electronic density of states for each crystallographic site. Universally small isotropic Knight shifts and long T1's are consistent with low Fermi-surface densities of states indicating the importance of Fermi-surface features for the phase stability of these alloys. Larger anisotropic Knight shifts occurring at aluminum site I indicate strong hybridization at this site, and the electric-field-gradient tensors confirm the strong ab plane bonding configuration. Local-moment magnetism is found in Al3V, yet electrically this material appears very similar to the other DO22 aluminides.

Lue, Chin-Shan; Chepin, Suchitra; Chepin, James; Ross, Joseph H., Jr.

1998-03-01

371

Effect of intermetallic phases on the anodic oxidation and corrosion of 5A06 aluminum alloy  

NASA Astrophysics Data System (ADS)

Intermetallic phases were found to influence the anodic oxidation and corrosion behavior of 5A06 aluminum alloy. Scattered intermetallic particles were examined by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) after pretreatment. The anodic film was investigated by transmission electron microscopy (TEM), and its corrosion resistance was analyzed by electrochemical impedance spectroscopy (EIS) and Tafel polarization in NaCl solution. The results show that the size of Al-Fe-Mg-Mn particles gradually decreases with the iron content. During anodizing, these intermetallic particles are gradually dissolved, leading to the complex porosity in the anodic film beneath the particles. After anodizing, the residual particles are mainly silicon-containing phases, which are embedded in the anodic film. Electrochemical measurements indicate that the porous anodic film layer is easily penetrated, and the barrier plays a dominant role in the overall protection. Meanwhile, self-healing behavior is observed during the long immersion time.

Li, Song-mei; Li, Ying-dong; Zhang, You; Liu, Jian-hua; Yu, Mei

2015-02-01

372

Wet chemical synthesis of intermetallic Pt3Zn nanocrystals via weak reduction reaction together with UPD process and their excellent electrocatalytic performances.  

PubMed

Platinum based alloy nanocrystals are promising catalysts for a variety of important practical process. However, it remains a great challenge to synthesize platinum-based intermetallic compound nanocrystals with well-defined surface structures. In this communication, taking the synthesis of concave cubic intermetallic Pt3Zn nanocrystals with {hk0} facets as an example, we proposed a new synthesis strategy for intermetallic compounds by reduction of noble metal precursors via a slow reduction process and reduction of transition metal ions via an underpotential deposition (UPD) process in wet chemical synthesis. The as-prepared intermetallic Pt3Zn nanocrystals exhibited superior CO poisoning tolerance and high electro-catalytic activity in both methanol and formic acid oxidation reactions in comparison with solid solution Pt3Zn nanocrystals and Pt/C. PMID:24841616

Chen, Qiaoli; Zhang, Jiawei; Jia, Yanyan; Jiang, Zhiyuan; Xie, Zhaoxiong; Zheng, Lansun

2014-06-21

373

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

374

DNA Cleavage, Cytotoxic Activities, and Antimicrobial Studies of Ternary Copper(II) Complexes of Isoxazole Schiff Base and Heterocyclic Compounds  

PubMed Central

Novel mixed ligand bivalent copper complexes [Cu. L. A. ClO4] and [Cu. L. A] where L is Schiff bases, namely 2-((3,4-dimethylisoxazol-5-ylimino)methyl)-4-bromophenol (DMIIMBP)/2-((3,4-dimethylisoxazol-5-ylimino)methyl)-4-chlorophenol (DMIIMCP), and A is heterocyclic compound, such as 1,10-phenanthroline (phen)/2,21-bipyridyl (bipy)/8-hydroxyquinoline (oxine)/5-chloro-8-hydroxyquinoline (5-Cl-oxine), have been synthesized. These complexes have been characterized by IR, UV-Vis, ESR, elemental analysis, magnetic moments, TG, and DTA. On the basis of spectral studies and analytical data, five-coordinated square pyramidal/four-coordinated square planar geometry is assigned to all complexes. The ligands and their ternary complexes with Cu(II) have been screened for antimicrobial activity against bacteria and fungi by paper disc method. The antimicrobial studies of Schiff bases and their metal complexes showed significant activity and further it is observed that the metal complexes showed more activity than corresponding Schiff bases. In vitro antitumor activity of Cu(II) complexes was assayed against human cervical carcinoma (HeLa) cancer cells and it was observed that few complexes exhibit good antitumor activity on HeLa cell lines. The DNA cleavage studies have also been carried out on pBR 322 and it is observed that these Cu(II) complexes are capable of cleaving supercoiled plasmid DNA in the presence of H2O2 and UV light. PMID:24895493

Chityala, Vijay Kumar; Sathish Kumar, K.; Macha, Ramesh; Tigulla, Parthasarathy; Shivaraj

2014-01-01

375

Optimisation of a multiphase intermetallic metal metal composite material  

E-print Network

Optimisation of a multiphase intermetallic metal metal composite material J. D. Robson, N; accepted 7 August 2000. # 2001 IoM Communications Ltd. Introduction Single phase intermetallic materials strength. Many efforts have therefore focused on the development of multiphase intermetallic materials

Cambridge, University of

376

International Symposium on Structural Intermetallics Seven Springs Resort, Pennsylvania  

E-print Network

1 International Symposium on Structural Intermetallics Seven Springs Resort, Pennsylvania September B2 INTERMETALLICS STUDIED BY PAC Gary S. Collins* , Jiawen Fan and Bin Bai Department of Physics structural intermetallics have been studied using perturbed angular correlation of gamma rays (PAC), by which

Collins, Gary S.

377

Determination of catecholamines and related compounds by capillary electrophoresis with postcolumn terbium complexation and sensitized luminescence detection.  

PubMed

A method has been developed for the determination of catecholamines and related compounds (DA, E, NE, DOPA, DOPAC, DOPAG) in urine samples. The compounds of interest were separated by capillary electrophoresis with a borate buffer as background electrolyte. Detection was based on the sensitized luminescence of terbium ions. Using a homemade postcolumn reactor, a basic solution containing a stoichiometric mixture of terbium(III) chloride and EDTA was added postcolumn to the separation buffer. The ternary catechol-EDTA-terbium complexes formed in the reaction mixture showed a strong luminescence with excitation and emission maxima at 300 and 545 nm, respectively. By optimization of the experimental conditions, zone broadening could be restrained and plate numbers up to 130,000 appeared to be possible. Detection limits found were in the order of 10(-7) mol L-1. The catecholic compounds could be determined in urine samples after a standard cleanup and preconcentration procedure. PMID:9322438

Zhu, R; Kok, W T

1997-10-01

378

Intelligent processing of intermetallic composite consolidation  

NASA Technical Reports Server (NTRS)

Intermetallic composites based upon titanium aluminide matrices and silicon carbide of aluminum oxide fibers are emerging candidates for future hypersonic vehicle airframes and engines. To tailor the properties of these 'engineered' materials for specific application, to increase process yield, and to reduce costs, 'intelligent processing of materials' (IPM) control strategies are being explored for their processing. Recent progress is evaluated in the development of predictive process models, advanced sensors and control methodologies (the components of the IPM approach) for the critical near net-shape consolidation process step of continuous fiber reinforced intermetallic composite manufacture.

Wadley, H. N. G.; Elzey, D. M.; Hsiung, L. M.; Lu, Y.; Duva, J. M.

1990-01-01

379

Effects of intermetallic particles on the SCC initiation of zirconium alloys  

NASA Astrophysics Data System (ADS)

In order to investigate effects of intermetallic particles on SCC initiation of zirconium alloys, tensile tests were conducted in an iodine atmosphere using zirconium plates with different amounts of impurities, and Zircaloy-2 plates. SCC susceptibility of zirconium increased significantly with its iron content. Even small amounts of iron could form the intermetallic compound ZrFe 2 whose particle size and number increased with iron content. In the case of Zircaloy-2, two different types of ternary compounds were detected, namely Zr(CrFe) 2 and Zr 2(NiFe). Metallographic examinations showed that the particles located at grain boundaries were important sites of SCC initiation in zirconium alloys. The initiation probability increased significantly with the amount of the particles, which supported the strong correlation between SCC susceptibility of zirconium and its iron content.

Kubo, T.; Wakashima, Y.; Imahashi, H.; Nagai, M.

1985-06-01

380

Kinetics of Cisplatin and Its Monohydrated Complex with Sulfur-Containing Compounds Designed for Local Otoprotective Administration  

Microsoft Academic Search

The anticancer drug cisplatin can cause permanent inner ear damage. We have determined the second-order degradation rate constant, kNu, of cisplatin and its more toxic monohydrated complex (MHC) in the presence of each of the sulfur-containing nucleophiles N-acetyl-L-cysteine, L-cysteine methyl ester, 1,3- dimethyl-2-thiourea, D-methionine, and thiosulfate, compounds that are under evaluation for local administration to prevent cisplatin-induced ototoxicity. MHC was

PERNILLA VIDEHULT; GORAN LAURELL; INGER WALLIN; HANS EHRSSON

381

Dinitrogen Tetroxide Complexes of Iron and Copper Nitrates as New Reagents for Selective Mono and Dinitration of Phenolic Compounds  

Microsoft Academic Search

Fe(NO3)3. 1.5 N2O4 and Cu(NO3)2. N2O4 are easily prepared reagents for the efficient and selective mono- or dinitration of phenolic compounds. In comparison with metal nitrates, these complexes resemble a synergetic effect on the rates and the yields of the reactions. High ratio of p-nitrophenol formation vs o-nitrophenol is also observed in the mononitration reactions.

H. Firouzabadi; N. Iranpoor; M. A. Zolfigol

1997-01-01

382

Hydrolysis activities of the particle of agarose-Ce 4+ complex for compounds containing phosphodiester or peptide bonds  

Microsoft Academic Search

Hydrolysis activities of PACC (particle of agarose-Ce4+ complex, newly made through double emulsification) for compounds containing phosphodiester or peptide bonds were studied.\\u000a The results showed that PACC could hydrolyze organophosphorous pesticides not only in water but also in vegetable juice or\\u000a tea extract. Hydrolysis rates of methamidophos, omethoate and chlorpyrifos in water are 32.39%, 27.12% and 46.62% respectively,\\u000a those of

Lina Yu; Dongfeng Wang; Lin Su; Yi Luo; Liping Sun; Changhu Xue

2005-01-01

383

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

384

PdGa intermetallic hydrogenation catalyst: an NMR and physical property study.  

PubMed

The PdGa intermetallic compound is a highly selective and stable heterogeneous hydrogenation catalyst for the semi-hydrogenation of acetylene. We have studied single crystals of PdGa grown by the Czochralski technique. The (69)Ga electric-field-gradient (EFG) tensor was determined by means of NMR spectroscopy, giving experimental confirmation of both the recently refined structural model of PdGa and the theoretically predicted Pd-Ga covalent bonding scheme. The hydrogenation experiment has detected no hydrogen uptake in the PdGa, thus preventing in situ hydride formation that leads to a reduction of the catalytic selectivity. We have also determined bulk physical properties (the magnetic susceptibility, the electrical resistivity, the thermoelectric power, the Hall coefficient, the thermal conductivity and the specific heat) of single-crystalline PdGa. The results show that PdGa is a diamagnet with metallic electrical resistivity and moderately high thermal conductivity. The thermoelectric power is negative with complicated temperature dependence, whereas the Hall coefficient is positive and temperature-dependent, indicating complexity of the Fermi surface. Partial fulfillment of the NMR Korringa relation reveals that the charge carriers are weakly correlated. Specific heat measurements show that the density of electronic states (DOS) at the Fermi energy of PdGa is reduced to 15% of the DOS of the elemental Pd metal. PMID:22310701

Klanjek, M; Gradiek, A; Kocjan, A; Bobnar, M; Jegli?, P; Wencka, M; Jagli?i?, Z; Pop?evi?, P; Ivkov, J; Smontara, A; Gille, P; Armbrster, M; Grin, Yu; Dolinek, J

2012-02-29

385

PdGa intermetallic hydrogenation catalyst: an NMR and physical property study  

NASA Astrophysics Data System (ADS)

The PdGa intermetallic compound is a highly selective and stable heterogeneous hydrogenation catalyst for the semi-hydrogenation of acetylene. We have studied single crystals of PdGa grown by the Czochralski technique. The 69Ga electric-field-gradient (EFG) tensor was determined by means of NMR spectroscopy, giving experimental confirmation of both the recently refined structural model of PdGa and the theoretically predicted Pd-Ga covalent bonding scheme. The hydrogenation experiment has detected no hydrogen uptake in the PdGa, thus preventing in situ hydride formation that leads to a reduction of the catalytic selectivity. We have also determined bulk physical properties (the magnetic susceptibility, the electrical resistivity, the thermoelectric power, the Hall coefficient, the thermal conductivity and the specific heat) of single-crystalline PdGa. The results show that PdGa is a diamagnet with metallic electrical resistivity and moderately high thermal conductivity. The thermoelectric power is negative with complicated temperature dependence, whereas the Hall coefficient is positive and temperature-dependent, indicating complexity of the Fermi surface. Partial fulfillment of the NMR Korringa relation reveals that the charge carriers are weakly correlated. Specific heat measurements show that the density of electronic states (DOS) at the Fermi energy of PdGa is reduced to 15% of the DOS of the elemental Pd metal.

Klanjek, M.; Gradiek, A.; Kocjan, A.; Bobnar, M.; Jegli?, P.; Wencka, M.; Jagli?i?, Z.; Pop?evi?, P.; Ivkov, J.; Smontara, A.; Gille, P.; Armbrster, M.; Grin, Yu; Dolinek, J.

2012-02-01

386

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

Microsoft Academic Search

This study explored the effect of Ag as the substrate or alloying element of solders on the interfacial reaction in Sn-Zn\\u000a 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

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

2005-01-01

387

Enhanced growth of intermetallic phases in the NiTi system by current effects  

Microsoft Academic Search

The effect of direct current upon interfacial reactions in the NiTi system was investigated. Isothermal diffusion couple experiments were conducted under varying current densities to de-couple Joule heating from intrinsic effects of the current flux. Current densities of up to 2546 A cm?2 were used in the temperature range of 625850 C. All of the intermetallic compounds (NiTi, Ni3Ti and

J. E. Garay; U. Anselmi-Tamburini; Z. A. Munir

2003-01-01

388

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 120C. 15nm of alumina prevented the reaction at 230C. 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

389

Selective synthesis and superconductivity of In-Sn intermetallic nanowires sheathed in carbon nanotubes  

NASA Astrophysics Data System (ADS)

We demonstrate a simple and reproducible technique to synthesize crystalline and superconducting In-Sn intermetallic nanowires sheathed in carbon nanotubes (CNTs). The method is based on the catalytic reaction of C2H2 over a mixture of both SnO2 and In2O3 particles. Importantly, tetragonal ?-In3Sn and hexagonal ?-InSn4 nanowires with diameters of less than 100 nm are selectively synthesized at different SnO2 to In2O3 weight ratios. CNTs may serve as cylindrical nanocontainers for continuous growth of liquid-phased In1-xSnx nanowires during growth process as well as for their solidification into In-Sn intermetallic nanowires during the cooling process. Microscopic and spectroscopic analyses clearly reveal evidence of a core-shell structure of the CNT-sheathed In-Sn intermetallic nanowires. Magnetization measurements show that the superconducting In-Sn nanowires have a critical magnetic field higher than the value of their bulk intermetallic compounds. Our method can be adopted to the nanofabrication of analogous binary and ternary alloys.

Jeong, Namjo; Yeo, Jeong-gu

2012-07-01

390

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

391

Correlation between intermetallic thickness and roughness during solder reflow  

NASA Astrophysics Data System (ADS)

The evolution of Cu-Sn and Ni-Sn intermetallic compound (IM) morphologies during isochronal reflow of a PbSn solder with Cu and electroless-Ni was investigated. The root mean square roughness of the Cu-Sn and Ni-Sn IM layers exhibited a linear dependence on average thickness, with gradients () of 0.33 and 0.65, respectively. The difference in values was attributed to different thickness distributions resulting from morphological dissimilarity of the IM layers. The apparent activation energies for growth and roughness evolution of both IM were found to be similar and suggest that both IM thickness and roughness evolution are controlled by the same mechanism.

Zuruzi, A. S.; Lahiri, S. K.; Burman, P.; Siow, K. S.

2001-08-01

392

cis-trans Germanium chains in the intermetallic compounds ALi{sub 1-x}In{sub x}Ge{sub 2} and A{sub 2}(Li{sub 1-x}In{sub x}){sub 2}Ge{sub 3} (A=Sr, Ba, Eu)-experimental and theoretical studies  

SciTech Connect

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{sub 0.91(1)}In{sub 0.09}Ge{sub 2}, SrLi{sub 0.95(1)}In{sub 0.05}Ge{sub 2} and BaLi{sub 0.99(1)}In{sub 0.01}Ge{sub 2}, which crystallize in the orthorhombic space group Pnma (BaLi{sub 0.9}Mg{sub 0.1}Si{sub 2} structure type, Pearson code oP16). The lattice parameters are a=7.129(4)-7.405(4) A; b=4.426(3)-4.638(2) A; and c=11.462(7)-11.872(6) A. The second type includes Eu{sub 2}Li{sub 1.36(1)}In{sub 0.64}Ge{sub 3} and Sr{sub 2}Li{sub 1.45(1)}In{sub 0.55}Ge{sub 3}, which adopt the orthorhombic space group Cmcm (Ce{sub 2}Li{sub 2}Ge{sub 3} structure type, Pearson code oC28) with lattice parameters a=4.534(2)-4.618(2) A; b=19.347(8)-19.685(9) A; and c=7.164(3)-7.260(3) A. 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 {pi}-p delocalization along the Ge chains, accounting for the experimentally confirmed substitution of Li forIn. -- Graphical abstract: Presented are the single-crystal structures of two types of closely related intermetallics, as well as their band structures, calculated using tight-binding linear muffin-tin orbital (TB-LMTO-ASA) method. Display Omitted

You, Tae-Soo [Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716 (United States); Bobev, Svilen, E-mail: bobev@udel.ed [Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716 (United States)

2010-12-15

393

Quaternary borocarbides: New class of intermetallic superconductors  

SciTech Connect

The authors recent discovery of superconductivity (SC) in the four-element multiphase Y-Ni-B-C system at an elevated temperature (TC approximately 12 K) has opened up great possibilities of identifying new superconducting materials and generating new physics. Superconductivity with Tc (greater than 20 K) higher than that known so far in bulk intermetallics has been observed in multiphase Y-Pd-B-C and Th-Pd-B-C systems and a family of single phase materials RENi2B2C (RE= Y, rare earth) have been found. The authors investigations show YNi2B2C to be a strong coupling hard type-II SC. HC2(T) exhibits an unconventional temperature dependence. Specific heat and magnetization studies reveal coexistence of SC and magnetism in RNi2B2C (R = Ho, Er, Tm) with magnetic ordering temperatures (Tc approximately 8 K, 10.5 K, 11 K and Tm approximately 5 K, approximately 7K, approximately 4 K respectively) that are remarkably higher than those in known magnetic superconductors . Mu-SR studies suggest the possibility of Ni atoms carrying a moment in TmNi2B2C. Resistivity results suggests a double re-entrant transition (SC-normal-SC) in HoNi2B2C. RENi2B2C (RE = Ce, Nd, Gd) do not show SC down to 4.2 K. The Nd- and Gd-compounds order magnetically at approximately 4.5 K and approximately 19.5 K, respectively. Two SC transitions are observed in Y-Pd-B-C (Tc approximately 22 K, approximately 10 K) and in Th-Pd-B-C (Tc approximately 20 K, approximately 14 K) systems, which indicate that there are at least two structures which support SC in these borocarbides. In the multiphase ThNi2B2C the authors observe SC at approximately 6 K. No SC was seen in multiphase UNi2B2C, UPd2B2C, UOs2Ge2C and UPd5B3C(0.35) down to 4.2 K. Tc in YNi2B2C is depressed by substitutions (Gd, Th and U at Y-sites and Fe, Co at Ni-sites).

Nagarajan, R.; Gupta, L.C.; Dhar, S.K.; Mazumdar, C.; Hossain, Z.; Godart, C.; Levy-Clement, C.; Padalia, B.D.; Vijayaraghavan, R. [Indian Inst. of Tech., Bombay (India); [Centre National de la Recherche Scientifique, Meudon (France)

1995-04-01

394

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

395

Milling of intermetallics and attempts at their ductilization  

SciTech Connect

Considerable effort is devoted at the present time to understanding the defects produced during milling of intermetallics, as well as using milling and consolidation processes to prepare intermetallics of ultrafine grain size, often in the hope of obtaining desirable material properties, such as improved ductility. This study examines the defects produced during milling from the viewpoint of the deformation mechanisms selected by the material. These mechanisms will typically vary depending o the complexity of the crystal structure of the phase being deformed, as well as depending on the characteristics of the faults associated with the dislocation structures or produced by dislocation movement. It is the mode of deformation that will dictate how the material becomes defective during milling. Secondly, the conditions required for powder consolidation to healthy material are briefly considered and the consequences for structural coarsening emphasized. Finally, the role of microstructure scale on the chances of achieving ductility are examined in detail, emphasizing the importance of considering the relative variations of flow stress and flow dimensions as the grain size decreases. In the present section the authors consider the changes in crystal structure and accumulation of defects during the milling of an initially chemically-homogeneous material--that is they do not take into account the initial stages of milling of elemental constituents when layer refinement and chemical homogenization is occurring.

Morris, D.G.; Morris, M.A. [Univ. of Neuchatel (Switzerland). Inst. of Structural Metallurgy] [Univ. of Neuchatel (Switzerland). Inst. of Structural Metallurgy

1996-01-01

396

Metastable phase formation in Be-Nb intermetallic compounds  

SciTech Connect

Amorphous structures or metastable crystalline phases are produced in sputter-deposited Beryllium-Niobium (Be-Nb) alloys (5-15 at. % Nb) depending on the substrate temperature. The metastable phases transform to the stable Be{sub 12}Nb, Be{sub 17}Nb{sub 2}Nb phases on annealing at temperatures >800{degree}C. No Be{sub 5}Nb phase was found and the Be{sub 17}Nb{sub 2} phase is stable to low temperature. The Be{sub 12}Nb phase appeared to have a stoichiometric range of about 5.5 to 7.7 at. % Nb. The formation of the metastable phases is consistent with current models and theories. 17 refs., 1 fig., 2 tabs.

Brimhall, J.L.; Charlot, L.A.; Bruemmer, S.M.

1990-11-01

397

Study of irradiation-induced amorphization in intermetallic compounds  

SciTech Connect

Irradiation-induced amorphization was studied in situ in the high voltage electron microscope interfaced to a tandem accelerator. Variation of elastic properties during irradiation was studied with Brillouin scattering spectroscopy, and its relation to amorphization were explored. Four important topics were investigated. (1) The temperature dependence of the critical dose for amorphization and its correlation with chemical disordering were studied in CuTi and Zr{sub 3}Al with 1-MeV electron irradiation from 10 to 295 K. Similar temperature dependence was observed in CuTi between the critical dose for amorphization and the chemical disordering rate. Chemical disordering is a major driving force for amorphization. The critical dose for amorphization of Zr{sub 3}Al was twenty times larger than that of CuTi and attributed to the differences in point defect mobility and ordering energy. (2) Projectile mass dependence of amorphization behavior was studied in CuTi irradiated with Ne{sup +},Kr{sup +},Xe{sup +}ions. The dose dependence of the amorphous volume fraction indicated that with increasing mass from Ne{sup +} to Kr{sup +} amorphization kinetics changes from the cascade overlap to the direct-impact amorphization. In relation to the kinetics variation, the critical temperature increased with increasing projectile mass and explained in terms of the thermal stability of the primary damage. (3) Effects of simultaneous and sequential irradiation with Kr+ and electrons were studied in CuTi and Zr{sub 3}Al. Both additive and retardation effects were observed depending on temperature and the electron-to-Kri dose rate ratio and explained as the interaction between point defects and cascade damages. (4) Study of elastic properties during Kr{sup +} irradiation revealed that in FeTi, a large dilation and shear modulus softening accompanied with chemical disordering preceded amorphization, but not observed in NiAl.

Koike, J.

1989-01-01

398

Dislocation dissociation in the intermetallic compound MoSi2  

Microsoft Academic Search

The identity of dislocations which contribute to plastic deformation of polycrystalline MoSi2 when compressed at 1400C has been determined using transmission electron microscopy. It has been confirmed that dislocations with Burgers vectors lying parallel to ? 100 ? and ? 111 ? are activated in response to the applied stress. In addition, the deformation microstructure is characterized by the presence

D. J. Evans; S. A. Court; P. M. Hazzledine; H. L. Fraser

1993-01-01

399

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

400

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

401

Trinuclear complexes and coordination polymers of redox-active guanidino-functionalized aromatic (GFA) compounds with a triphenylene core.  

PubMed

Herein, we report on the synthesis, redox activity, and coordination chemistry of 2,3,6,7,10,11-hexakis(tetramethylguanidino)triphenylene. CV measurements indicated that the new compound could be oxidized in three separate reversible two-electron oxidation events. The HOMO and LUMO energies were estimated from the oxidation wave and the onset of absorption in the UV/vis spectrum. Our discussion also includes the related new compound 2,3,6,7,10,11-hexakis(N,N'-dimethylethyleneguanidino)triphenylene. Then trinuclear Cu(I) and Cu(II) complexes of the new triphenylene ligands were characterized, and their electronic properties are discussed. In contrast to previously studied redox-active GFA ligands, oxidation of trinuclear copper(I) iodide complexes with I2 leads to copper instead of ligand oxidation. In the tetra-coordinated Cu(II) complexes, the coordination mode is intermediate between tetrahedral and square planar. The optical properties of the complexes were studied, and low-energy electronic transitions were assigned to ligand-to-metal charge-transfer (LMCT) excitations. We then extended our analysis to trinuclear Ni(II) and Co(II) complexes. The magnetic coupling mediated through the triphenylene ligand in the trinuclear Cu(II) and Co(II) complexes was studied by SQUID magnetometry, revealing ferromagnetic coupling of the spin centers and different degrees of spin delocalization into the guanidino groups. Finally, we show that the GFA ligands could be linked to one- or two-dimensional coordination polymers and porous materials with a layer structure by reaction with silver halides. PMID:25188743

Lebkcher, Anna; Wagner, Christoph; Hbner, Olaf; Kaifer, Elisabeth; Himmel, Hans-Jrg

2014-09-15

402

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

403

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

404

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...

405

Reduced workfunction intermetallic seed layers allow growth of porous n-GaN and low resistivity, ohmic electron transport.  

PubMed

Porous GaN crystals have been successfully grown and electrically contacted simultaneously on Pt- and Au-coated silicon substrates as porous crystals and as porous layers. By the direct reaction of metallic Ga and NH(3) gas through chemical vapor deposition, intermetallic metal-Ga alloys form at the GaN-metal interface, allowing vapor-solid-solid seeding and subsequent growth of porous GaN. Current-voltage and capacitance-voltage measurements confirm that the intermetallic seed layers prevent interface oxidation and give a high-quality reduced workfunction contact that allows exceptionally low contact resistivities. Additionally, the simultaneous formation of a lower workfunction intermetallic permits ohmic electron transport to n-type GaN grown using high workfunction metals that best catalyze the formation of porous GaN layers and may be employed to seed and ohmically contact a range of III-N compounds and alloys for broadband absorption and emission. PMID:23167596

Bilousov, Oleksandr V; Carvajal, Joan J; Drouin, Dominique; Mateos, Xavier; Daz, Francesc; Aguil, Magdalena; O'Dwyer, Colm

2012-12-01

406

Polymer complexes. LVII. Supramolecular assemblies of novel polymer complexes of dioxouranium(VI) with some substituted allyl azo dye compounds  

NASA Astrophysics Data System (ADS)

A novel method to synthesize some dioxouranium(VI) polymer complexes of the general formula [UO2(Ln)2(OAc)2] (where HLn = azo allyl rhodanine). The structure of the novel mononuclear dioxoutranium(VI) polymer complexes was characterized using elemental analysis, spectral (electronic, infrared, 1H &13C NMR) studies, magnetic susceptibility measurements and thermal analysis. The molar conductivities show that all the polymer complexes are non-electrolytes. The IR showed that the ligand HLn act as bidentate neutral through carbonyl group and imine group nitrogen atom forming thereby a six-membered chelating ring and concomitant formation of an intramolecular hydrogen bond. The ?3 frequency of UO2+2 has been shown to be an excellent molecular probe for studying the coordinating power of the ligands. The values of ?3 of the prepared complexes containing UO2+2 were successfully used to calculate the force constant, FUO (10-8 N/) and the bond length RUO () of the Usbnd O bond. A strategy based upon both theoretical and experimental investigations has been adopted. The theoretical aspects are described in terms of the well-known theory of 5d-4f transitions. Wilson's, matrix method, Badger's formula, and Jones and El-Sonbati equations were used to calculate the Usbnd O bond distances from the values of the stretching and interaction force constants. The most probable correlation between Usbnd O force constant to Usbnd O bond distance were satisfactorily discussed in term of Badger's rule and the equations suggested by Jones and El-Sonbati. The effect of Hammet constant is also discussed.

Diab, M. A.; El-Sonbati, A. Z.; El-Bindary, A. A.; Balboula, M. Z.

2013-05-01

407

The ?3 model of acids and bases: extending the Lewis theory to intermetallics.  

PubMed

A central challenge in the design of new metallic materials is the elucidation of the chemical factors underlying the structures of intermetallic compounds. Analogies to molecular bonding phenomena, such as the Zintl concept, have proven very productive in approaching this goal. In this Article, we extend a foundational concept of molecular chemistry to intermetallics: the Lewis theory of acids and bases. The connection is developed through the method of moments, as applied to DFT-calibrated Hckel calculations. We begin by illustrating that the third and fourth moments (?(3) and ?(4)) of the electronic density of states (DOS) distribution tune the properties of a pseudogap. ?(3) controls the balance of states above and below the DOS minimum, with ?(4) then determining the minimum's depth. In this way, ?(3) predicts an ideal occupancy for the DOS distribution. The ?(3)-ideal electron count is used to forge a link between the reactivity of transition metals toward intermetallic phase formation, and that of Lewis acids and bases toward adduct formation. This is accomplished through a moments-based definition of acidity which classifies systems that are electron-poor relative to the ?(3)-ideal as ?(3)-acidic, and those that are electron-rich as ?(3)-basic. The reaction of ?(3) acids and bases, whether in the formation of a Lewis acid/base adduct or an intermetallic phase, tends to neutralize the ?(3) acidity or basicity of the reactants. This ?(3)-neutralization is traced to the influence of electronegativity differences at heteroatomic contacts on the projected DOS curves of the atoms involved. The role of ?(3)-acid/base interactions in intermetallic phases is demonstrated through the examination of 23 binary phases forming between 3d metals, the stability range of the CsCl type, and structural trends within the Ti-Ni system. PMID:22420716

Stacey, Timothy E; Fredrickson, Daniel C

2012-04-01

408

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

409

Medicinal herb extract and a single-compound drug confer similar complex pharmacogenomic activities in mcf-7 cells.  

PubMed

Metabolite profiling and DNA microarray analysis of global gene expression profiles were employed to characterize the bioactivities of the herbal extract of Anoectochilus formosanus (AF), a popular folk medicine with anticancer activity, in MCF-7 cancer cells. The pharmacogenomic activities of this plant extract as a crude phytocompound mixture were compared to those conferred by the single-compound drug, plumbagin. A similar level of complexity in transcriptional regulation at the genomic level was observed for both AF extract- and plumbagin-treated MCF-7 cells, as revealed by the number of up- or downregulated genes as well as by the specific but distinct patterns found in the gene-clustering analysis. This finding offers evidence to support the search for fractionated medicinal herb extracts or phytocompound mixtures, in addition to single-compound drugs, as defined therapeutic agents. PMID:15067226

Yang, Ning-Sun; Shyur, Lie-Fen; Chen, Chih-Huai; Wang, Sheng-Yang; Tzeng, Chi-Meng

2004-01-01

410

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

411

First-principles study of the binary intermetallics in the Au-Rb system  

NASA Astrophysics Data System (ADS)

First-principles calculations within density functional theory (DFT) with the projector augmented wave (PAW) technique were used to investigate the stabilities of intermetallics in the Au-Rb system at 0 K. Four intermetallics: Au7Rb3, Au3Rb2, Au5Rb and AuRb were investigated in their observed experimental structures. The Au2Rb compound, reported in the Au-Rb phase diagrams without specifying explicitly its structure, was also investigated by inspecting several hypothetical structures. A suspect compound (AuRb2) was also investigated. Results show that: (i) The Au3Rb2 and Au7Rb3 compounds, which were never reported in any Au-Rb phase diagram, are stable at 0 K. (ii) The Au2Rb compound is not a ground state for all the tested structures. (iii) Stability of the Au5Rb and AuRb compounds was confirmed. (iv) The new compound AuRb2, not yet reported experimentally, is found mechanically stable at 0 K.

Benmechri, Achraf; Djaballah, Yassine; Amer, Ahmed Said; Belgacem-Bouzida, Aissa; Bouderba, Hichem

2014-06-01

412

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

413

This journal is c The Royal Society of Chemistry 2010 Chem. Commun., 2010, 46, 91439145 9143 Europium(II) compounds: simple synthesis of a molecular complex in  

E-print Network

Europium(II) compounds: simple synthesis of a molecular complex in water and coordination polymers with 2 of the instability of europium in the divalent state, it is not surprising that such materials containing Eu2+ ions

Paris-Sud XI, Universit de

414

Complexes between lanthanide picrates and N,N-dimethylacetamide (DMA). Synthesis, characterization and structure of the samarium compound  

Microsoft Academic Search

Complexes with the composition Ln(pic)3.3DMA (Ln?La?Lu, Y; pic, picrate; DMA, N,N-dimethylacetamide) were synthesized and characterized. They behave as non-electrolytes in nitromethane and acetonitrile. According to X-ray powder patterns, three different types of diffractograms were obtained: (a) La?Pr; (b) Nd?Yb, Y; (c) Lu. Single-crystal X-ray analysis of the samarium compound indicates that Sm3+ is coordinated by six oxygen donors from three

C. V. P. de Melo; G. Vicentini; E. E. Castellano; J. Zukerman-Schpector

1995-01-01

415

Efficient Dehydrogenation of Amines and Carbonyl Compounds Catalyzed by a Tetranuclear Ruthenium-?-Oxo-?-Hydroxo-Hydride Complex  

PubMed Central

The tetranuclear ruthenium-?-oxo?-hydroxo-hydride complex {[(PCy3)(CO)RuH]4(?4-O)(?3-OH)(?2-OH)} (1) was found to be a highly effective catalyst for the transfer dehydrogenation of amines and carbonyl compounds. For example, the initial turnover rate of the dehydrogenation of 2-methylindoline was measured to be 1.9 s-1 with the TON of 7950 after 1 h at 200 C. The extensive H/D scrambling patterns observed from the dehydrogenation reaction of indoline-N-d1 and indoline-?-d2 suggest a monohydride mechanistic pathway with the C-H bond activation rate-limiting step. PMID:20119477

Yi, Chae S.; Lee, Do W.

2009-01-01

416

JOURNAL DE PHYSIQUE CoIloque C 1,supplkment au no 2-3, Tome 32, Fkvrier-Mars 1971,page C 1 -668 MAGNETIC PROPERTIES OF IRON COMPOUNDS  

E-print Network

as the order temperaturesvariation. The intermetallic compounds that exist in the rare earth-iron system accuracy, each type of intermetallic compounds with yttrium and with lutetium exhibits the same absolute MAGNETIC PROPERTIES OF IRON COMPOUNDS WITH YTTRIUM, LUTETIUM AND GADOLINIUM D. GIVORD, F. GIVORD, R

Boyer, Edmond

417

Cluster Compounds DOI: 10.1002/anie.200601805  

E-print Network

of the two types of atoms, as in a true intermetallic compound. The novel cluster was synthesized duringCluster Compounds DOI: 10.1002/anie.200601805 [Zn9Bi11]5? : A Ligand-Free Intermetalloid Cluster species and solid-state compounds with extended structures.[1] Small, cage-like clusters have been

418

Fluorimetric determination of some sulfur containing compounds through complex formation with terbium (Tb+3) and uranium (U+3).  

PubMed

Two simple, sensitive and specific fluorimetric methods have been developed for the determination of some sulphur containing compounds namely, Acetylcysteine (Ac), Carbocisteine (Cc) and Thioctic acid (Th) using terbium Tb+3 and uranium U+3 ions as fluorescent probes. The proposed methods involve the formation of a ternary complex with Tb+3 in presence of Tris-buffer method (I) and a binary complex with aqueous uranyl acetate solution method (II). The fluorescence quenching of Tb+3 at 510, 488 and 540 nm (lambda(ex) 250, 241 and 268 nm) and of uranyl acetate at 512 nm (lambda(ex) 240 nm) due to the complex formation was quantitatively measured for Ac, Cc and Th, respectively. The reaction conditions and the fluorescence spectral properties of the complexes have been investigated. Under the described conditions, the proposed methods were applicable over the concentration range (0.2-2.5 microg ml(-1)), (1-4 microg ml(-1)) and (0.5-3.5 microg ml(-1)) with mean percentage recoveries 99.74+/-0.36, 99.70+/-0.52 and 99.43+/-0.23 for method (I) and (0.5-6 microg ml(-1)), (0.5-5 microg ml(-1)), and (1-6 microg ml(-1)) with mean percentage recoveries 99.38+/-0.20, 99.82+/-0.28 and 99.93+/-0.32 for method (II), for the three cited drugs, respectively. The proposed methods were successfully applied for the determination of the studied compounds in bulk powders and in pharmaceutical formulations, as well as in presence of their related substances. The results obtained were found to be in agree statistically with those obtained by official and reported ones. The two methods were validated according to USP guidelines and also assessed by applying the standard addition technique. PMID:17440799

Taha, Elham Anwer; Hassan, Nagiba Yehya; Aal, Fahima Abdel; Fattah, Laila El-Sayed Abdel

2007-05-01

419

Intermetallic phase formation in thin solid-liquid diffusion couples  

NASA Astrophysics Data System (ADS)

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 m) of intermetallic phase 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 ?-Cu6Sn6 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.

Bartels, F.; Morris, J. W.; Dalke, G.; Gust, W.

1994-08-01

420

Transient liquid phase bonding of intermetallics  

Microsoft Academic Search

The present work was undertaken to examine the applicability of transient liquid phase bonding to structural intermetallics. This research was based on an investigation of the mechanisms governing microstructural development in the joint and adjacent substrates during the joining process. The bonding systems investigated included polycrystalline NiAl\\/Cu\\/Ni, polycrystalline NiAl\\/Cu\\/superalloys (Martin-Marietta (MM)-247, Inconel (IN) 718 and Nimonic 90), single-crystal NiAl (with

Yimin Guan

1998-01-01

421

Arc Casting Intermetallic Alloy (Materials Preparation Center)  

SciTech Connect

Arc casting of intermetallic (La-Ni-Sn) AB5 alloy used for metal hydride hydrogen storage. Upon solidification the Sn is partially rejected and increases in concentration in the remaining liquid. Upon completing solidification there is a great deal of internal stress in the ingot. As the ingot cools further the stress is relieved. This material was cast at the Ames Laboratorys Materials Preparation Center http://www.mpc.ameslab.gov

None

2010-01-01

422

Crystal structure of patatin-17 in complex with aged and non-aged organophosphorus compounds.  

PubMed

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

423

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

424

An approach toward quantification of organic compounds in complex environmental samples using high-resolution electrospray ionization mass spectrometry  

SciTech Connect

Quantitative analysis of individual compounds in complex mixtures using high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) is complicated by differences in the ionization efficiencies of analyte molecules in the mixture, resulting in signal suppression during ionization. However, the ability to obtain concentration estimates of compounds in an environmental sample is important for data interpretation and comparison. We introduce an approach for estimating mass concentrations of analytes observed in a multicomponent mixture by HR-ESI-MS, without prior separation. The approach relies on a calibration of the instrument using appropriate standards added to the mixture of studied analytes. An illustration of how the proposed calibration can be applied in practice is provided for aqueous extracts of isoprene photooxidation organic aerosol, with multifunctional organic acids standards. We show that the observed ion sensitivities in ESI-MS are positively correlated with the adjusted mass, defined as a product of the molecular mass and the H/C ratio in the molecule (adjusted mass = H/C x molecular mass). The correlation of the observed ESI sensitivity with adjusted mass is justified by considering trends of the physical and chemical properties of organic compounds that affect ionization in the positive ion mode, i.e., gas-phase basicity, polarizability, and molecular size.

Nguyen, Tran B.; Nizkorodov, Sergey; Laskin, Alexander; Laskin, Julia

2013-01-07

425

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

426

Radionuclide-binding compound, a radionuclide delivery system, a method of making a radium complexing compound, a method of extracting a radionuclide, and a method of delivering a radionuclide  

DOEpatents

The invention pertains to compounds which specifically bind radionuclides, and to methods of making radionuclide complexing compounds. In one aspect, the invention includes a radionuclide delivery system comprising: a) a calix[n]arene-crown-[m]-ether compound, wherein n is an integer greater than 3, and wherein m is an integer greater than 3, the calix[n]arene-crown-[m]-ether compound comprising at least two ionizable groups; and b) an antibody attached to the calix[n]arene-crown-[m]-ether compound. In another aspect, the invention includes a method of making a radium complexing compound, comprising: a) providing a calix[n]arene compound, wherein n is an integer greater than 3, the calix[n]arene compound comprising n phenolic hydroxyl groups; b) providing a crown ether precursor, the crown ether precursor comprising a pair of tosylated ends; c) reacting the pair of tosylated ends with a pair of the phenolic hydroxyl groups to convert said pair of phenolic hydroxyl groups to ether linkages, the ether linkages connecting the crown ether precursor to the calix[n]arene to form a calix[n]arene-crown-[m]-ether compound, wherein m is an integer greater than 3; d) converting remaining phenolic hydroxyl groups to esters; e) converting the esters to acids, the acids being proximate a crown-[m]-ether portion of the calix[n]arene-crown-[m]-ether compound; and f) providing a Ra.sup.2+ ion within the crown-[m]-ether portion of the calix[n]arene-crown-[m]-ether compound.

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

2000-01-01

427

Intermetallic phase formation in thin solid-liquid diffusion couples  

Microsoft Academic Search

Conducting joints with low fabrication temperatures and high thermal stability are useful in modern electronics. This paper\\u000a discusses the potential use of intermetallic phases in making such joints. Thin interconnection layers that consist entirely\\u000a of intermetallic phases have been produced by joining planar Cu substrates that are coated with thin films of Sn. Thin layers\\u000a (1-5 m) of intermetallic phase

F. Bartels; J. W. Jr. Morris; G. Dalke; W. Gust

1994-01-01

428

Complexation of estragole as pure compound and as main component of basil and tarragon essential oils with cyclodextrins.  

PubMed

Inclusion complexes of estragole (ES) as pure compound and as main component of basil and tarragon essential oils (EOs) with ?-cyclodextrin (?-CD), ?-cyclodextrin (?-CD), hydroxypropyl-?-cyclodextrin (HP-?-CD), randomly methylated-?-cyclodextrin (RAMEB), a low methylated-?-cyclodextrin (CRYSMEB) and ?-cyclodextrin (?-CD) were characterized. Formation constants (Kf) of the complexes were determined in aqueous solution by nonlinear regression analysis using static headspace gas chromatography (SH-GC) and UV-visible spectroscopy. Solid inclusion complexes were prepared by the freeze-drying method for different CD:ES molar ratios and were characterized by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR). Inclusion complexes formation allowed the controlled release of ES. Moreover, increased DPPH radical scavenging activity and photostability of ES and ES containing EOs (ESEOs) were observed in the presence of CDs. These findings suggest that encapsulation with CDs could be an efficient tool to improve the use of ES and ESEOs in aromatherapy, cosmetic and food fields. PMID:25542121

Kfoury, Miriana; Auezova, Lizette; Ruellan, Steven; Greige-Gerges, Hlne; Fourmentin, Sophie

2015-03-15

429

Addition of organolithium compounds to tricarbonyl(tropone)iron complexes: experimental and structural studies  

Microsoft Academic Search

The regioselectivity (1,2 vs. 1,4) in the nucleophilic addition of organolithium reagents to tropone(tricarbonyl)iron complexes has been studied and found to be correlated with the relative hardness of the nucleophile (HSAB principle). X-ray structures of several 1,2 and 1,4 adducts are reported.

Yoann Coquerel; Jean-Pierre Deprs; Andrew E. Greene; Christian Philouze

2002-01-01

430

Evaluations of an Enhanced Total Hydrocarbon Analyzer With Complex Mixtures of Volatile Organic Compounds  

NASA Technical Reports Server (NTRS)

From the earliest manned missions, the volatile organic compound (VOC) content of spacecraft air has been a concern because of a much greater potential for contamination than air in most terrestrial settings. First, the volume of air is small compared to the mass of man- made materials comprising the interior furnishings of the spacecraft. These man-made materials offgas VOCs trapped during manufacture. Second, the nitrogen fraction of the air is recycled. Any VOCs not scrubbed out with charcoal filters or aqueous condensate (mainly water expired by the crew) will accumulate in the air. Third, the crew emits metabolic VOCs. Fourth, experimental payloads can also offgas or accidentally release a VOC; in fact a major organic constituent of the atmosphere is the disinfectant isopropanol released from swabs used in medical experiments.

Cross, John H.; Limero, Thomas F.; James, John T.; Breach, James; Hinton, Mark

1995-01-01

431

New 3,4-diaminobenzoic acid Schiff base compounds and their complexes: Synthesis, characterization and thermodynamics  

NASA Astrophysics Data System (ADS)

Some new tetradentate Schiff base ligands (H3L) were prepared via condensation of 3,4-diaminobenzoic acid with 2-hydroxybenzaldehyde derivatives, such as 3,4-bis((E)-2,4-dihydroxybenzylideneamino)benzoic acid (H3L1), 3,4-bis((E)-2-hydroxy-3-methoxybenzylideneamino)benzoic acid (H3L2) and 3,4-bis((E)-5-bromo-2-hydroxybenzylideneamino)benzoic acid (H3L4). Additionally, a tetradentate Schiff base ligand 3,4-bis((E)-2-hydroxybenzylideneamino)benzoic acid (H3L3) and its complexes were synthesized. Their metal complexes of Co(II), Ni(II), Cu(II) and Zn(II) were prepared in good yields from the reaction of the ligands with the corresponding metal acetate. They were characterized based on IR, 1H NMR, Mass spectroscopy and UV-Vis spectroscopy. Also, the formation constants of the complexes were measured by UV-Vis spectroscopic titration at constant ionic strength 0.1 M (NaClO4), at 25 C in dimethylformamide (DMF) as a solvent.

Mohammadi, Khosro; Niad, Mahmood; Jafari, Tahereh

2014-03-01

432

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 Mssbauer spectroscopic studies. The room temperature Mssbauer 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

433

An experimental investigation of a limited-ductility intermetallic  

NASA Astrophysics Data System (ADS)

The need for efficient testing to collect both greater quantities of data and data that are more useful is argued. This need arises from the many degrees-of-freedom typical in modern, stochastic, multi-scale, nonlinear, physics-based modeling. Novel techniques developed to acquire full-field displacement and strain fields are presented, building on previous work in this area. The two main areas of this experimental-mechanics effort concerned the development of techniques for (1) scanning across a region-of-interest (ROI) of a solid for better resolution of displacements and strains over a large area and (2) studying nonlinear behavior through the analysis of multiple images of the same ROI under different loading conditions. The application of the concepts and the experimental techniques discussed above to a representative alloy of an important class of materials, intermetallics, is presented. The limited ductility of this class of materials has been a hindrance to their wide applicability, but it is hoped that through the knowledge gained through this and similar efforts, a practical design system for these materials, heretofore elusive, can be developed. Efforts to model the behavior of these materials have been severely hampered by the lack of data previously available for verifying and calibrating the complex models that have been developed. Discussion of the utility of the concepts and techniques developed and their application to limited-ductility intermetallics are presented. A semi-empirical method for applying the results of this application to design is presented. In addition, it is argued that the concepts and techniques presented here are applicable to a wide variety of material systems. It is hoped that the general philosophy presented in the thesis and supported by its specific application to a significant class of materials will be an important model for the close integration of modeling and experimentation in the future.

Johnson, David Alan

434

Intermetallics Characterization of Lead-Free Solder Joints under Isothermal Aging  

NASA Astrophysics Data System (ADS)

Solder interconnect reliability is influenced by environmentally imposed loads, solder material properties, and the intermetallics formed within the solder and the metal surfaces to which the solder is bonded. Several lead-free metallurgies are being used for component terminal plating, board pad plating, and solder materials. These metallurgies react together and form intermetallic compounds (IMCs) that affect the metallurgical bond strength and the reliability of solder joint connections. This study evaluates the composition and extent of intermetallic growth in solder joints of ball grid array components for several printed circuit board pad finishes and solder materials. Intermetallic growth during solid state aging at 100C and 125C up to 1000 h for two solder alloys, Sn-3.5Ag and Sn-3.0Ag-0.5Cu, was investigated. For Sn-3.5Ag solder, the electroless nickel immersion gold (ENIG) pad finish was found to result in the lowest IMC thickness compared to immersion tin (ImSn), immersion silver (ImAg), and organic solderability preservative (OSP). Due to the brittle nature of the IMC, a lower IMC thickness is generally preferred for optimal solder joint reliability. A lower IMC thickness may make ENIG a desirable finish for long-life applications. Activation energies of IMC growth in solid-state aging were found to be 0.54 0.1 eV for ENIG, 0.91 0.12 eV for ImSn, and 1.03 0.1 eV for ImAg. Cu3Sn and Cu6Sn5 IMCs were found between the solder and the copper pad on boards with the ImSn and ImAg pad finishes. Ternary (Cu,Ni)6Sn5 intermetallics were found for the ENIG pad finish on the board side. On the component side, a ternary IMC layer composed of Ni-Cu-Sn was found. Along with intermetallics, microvoids were observed at the interface between the copper pad and solder, which presents some concern if devices are subject to shock and vibration loading.

Choubey, Anupam; Yu, Hao; Osterman, Michael; Pecht, Michael; Yun, Fu; Yonghong, Li; Ming, Xu

2008-08-01

435

Photodissociation dynamics of organometallic compounds: Study of the dihydride complex H2Fe(CO)4  

SciTech Connect

The photodissociation of the dihydride complex H2Fe(CO)4 has been investigated by a theoretical approach, involving time-dependent wave packet propagations on potential energy surfaces (PES) obtained from CASSCF-MRCI calculations. A two dimensions simulation is proposed, allowing the study of two concurrents processes, namely photoinduced elimination of molecular hydrogen vs loss of a carbonyl ligand. Three singlet excited states {sup 1}bA1(x{sup 2}-y{sup 2}{yields}{sigma}g*), {sup 1}aB2(x{sup 2}-y{sup 2}{yields}{sigma}u*), {sup 1}aB1(yz{yields}{sigma}g*) has been identified in the range of energy corresponding to the experimental absorption spectrum. Wave packets propagations performed separately on the three PES describe the elementary processes contributing to the photochemical behavior of the molecule. The absorption spectrum reflecting these different processes, has been calculated, using the time dependent formalism.

Heitz, M. C.; Daniel, C. [Laboratoire de Chimie Quantique UPR139 du CNRS Universite Louis Pasteur, Institut Le Bel 4, rue Blaise Pascal, 67000 Strasbourg (France)

1996-04-01

436

Hydrolysis activities of the particle of agarose-Ce4+ complex for compounds containing phosphodiester or peptide bonds  

NASA Astrophysics Data System (ADS)

Hydrolysis activities of PACC (particle of agarose-Ce4+ complex, newly made through double emulsification) for compounds containing phosphodiester or peptide bonds were studied. The results showed that PACC could hydrolyze organophosphorous pesticides not only in water but also in vegetable juice or tea extract. Hydrolysis rates of methamidophos, omethoate and chlorpyrifos in water are 32.39%, 27.12% and 46.62% respectively, those of chlorpyrifos and methamidophos in mung sprout juice 38.28% and 35.45% respectively, and that of chlorpyrifos in tea extract 59.76%. Hydrolysis rates of BSA (bovine serum albumin) in water and protein in tea extract by PACC increase by 54.30% and 86.46% respectively as compared with the control.

Yu, Lina; Wang, Dongfeng; Su, Lin; Luo, Yi; Sun, Liping; Xue, Changhu

2005-07-01

437

Clinical use of an herbal-derived compound (Huperzine A) to treat putative complex partial seizures in a dog.  

PubMed

A Bernese mountain dog was diagnosed with complex partial seizures that were supported by electroencephalographic findings. Clinical signs of the problem included "star gazing," fly snapping, licking, vacuous chewing, and ongoing anxiety. Treatment with Huperzine A, a compound isolated from Chinese club moss with NMDA receptor blocking activity, anticholinesterase activity, and anticonvulsant properties, produced useful suppression of the abnormal behavior for more than months. A relapse occurred when the dog was treated with tramadol for joint pain and the improvement that had been made was not recaptured with Huperzine A. At this stage, phenobarbital therapy was instituted and the dog improved greatly. The role of Huperzine A in controlling seizures is discussed. PMID:19616481

Schneider, Barbara M; Dodman, Nicholas H; Faissler, Dominik; Ogata, Niwako

2009-08-01

438

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

439

Complexes of iron with phenolic compounds from soybean nodules and other legume tissues: prooxidant and antioxidant properties.  

PubMed

The low-molecular-mass fraction of the soybean nodule cytosol contains Fe capable of catalyzing free radical production through Fenton chemistry. A large portion of the pool of catalytic Fe, measured as bleomycin-detectable Fe, was characterized as complexes of Fe with phenolic compounds of three classes: phenolic acids, cinnamic acids, and flavonoids. Many of these compounds, along with other phenolics present in legume tissues, were used for a systematic structure-activity relationship study. All phenolics tested were able to chelate Fe, as judged from their inhibitory effect on site-specific deoxyribose degradation (minus EDTA assay). However, only those having catechol, pyrogallol, or 3-hydroxy-4-carbonyl groupings were potent chelators and reductants of Fe3+ at pH 5.5. The same phenolics promoted oxidative damage to DNA (bleomycin assay) and to deoxyribose (plus EDTA assay), but inhibited linolenic acid peroxidation by chelating and reducing Fe3+ and by neutralizing lipid radicals. Also, phenolics having a pyrogallol nucleus attenuated the free radical-mediated inactivation of glutamine synthetase, which was used as a model system, by chelating Fe2+. It is reasoned that under the microaerobic (10-20 nM O2) and acidic (pH 5.5-6.4) conditions prevailing in nodules, phenolics are likely to act primarily as antioxidants, decreasing oxidative damage to biomolecules. PMID:9119255

Moran, J F; Klucas, R V; Grayer, R J; Abian, J; Becana, M

1997-01-01

440

Formation of intermetallics by ion implantation of multilatered Al/Ti nano-structures  

NASA Astrophysics Data System (ADS)

The effects of Ar+ ion irradiation on Al/Ti multilayers at room temperature were investigated. Eight (Al/Ti) bilayers were deposited by d.c. ion sputtering on (1 0 0) Si wafers to a total thickness of 300 nm. Ion irradiations were performed by 180 keV Ar+ ions with doses 1-6 1016 ions cm-2. After implantation the samples were vacuum annealed at 400 oC for 30 min. Ion irradiations induced intermixing of layer constituents, and for the highest fluence formation of AlTi and AlTi3 intermetallic phases in the vicinity of the mid projected range of the impact ions. Subsequent vacuum annealing of sample implanted to 6 1016 ions cm-2 lead to transformation of all deposited layers into AlTi3 and ?-AlTi intermetallic phases, except for 3-4 layers close to the substrate which were out of range of the effects induced by ion implantation. It is assumed that Al-Ti reaction was initiated by thermal spikes and further enhanced by chemical driving forces, but only in the intermixed region. This procedure may be interesting for fabrication of Al-Ti intermetallic compounds tightly adhered on different substrates.

Peruko, D.; Petrovi?, S.; Stojanovi?, M.; Mitri?, M.; ?izmovi?, M.; Panjan, M.; Milosavljevi?, M.

2012-07-01

441

Investigations of mechanical and electronic properties for Al-based intermetallics with different Ti content  

NASA Astrophysics Data System (ADS)

Electronic structure, mechanical properties and work function of Al-based intermetallic compounds with different content of Ti (AlCu3, AlCu2Ti and AlTi3) are investigated by using first-principles method. Our calculated lattice constants agree well with the experimental data. Effects of different Ti content on the electronic structures and mechanical properties of Al-based intermetallics are further analyzed and discussed in view of the density of states and charge density. Since the decreasing of cohesive energy has been observed when Ti content increases, work function calculations present the same tendency. Moreover, the ratio of the bulk modulus to shear modulus was calculated to account for good ductility of these three crystals and we obtained that AlCu3 has the best ductility. Finally, our results of DOS indicate that AlTi3 has the most intense chemical bonds among these three Al-based intermetallics because of its strongest hybridization. This is a disadvantage for its ductility. Charge density distributions also provide an evident of the strong binding in AlTi3.

Feng, Xiang-Zheng; Peng, Jin-Zhang; Xu, Zhong-Fei; Ouyang, Shi-Liang

2015-01-01

442

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

443

Organometallic compounds of the lanthanides. 42/sup 1/ bis(dimethyloxyethane)lithium bis(cyclopentadienyl)bis(trimethylsilyl)lanthanide complexes  

SciTech Connect

The trichlorides of Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu react with NaC/sub 5/H/sub 5/ in tetrahydrofuran in the presence of dimethoxyethane (dme) with formation of bis(cyclopentadienyl)lanthanide chloride complexes of the types (C/sub 5/H/sub 5/)/sub 2/Ln(/mu/-Cl)/sub 2/Na(dme). The reactions of these organolanthanide halide complexes with (trimethylsilyl)lithium in dme yield compounds of the type (Li(dme)/sub 2/)((C/sub 5/H/sub 5/)/sub 2/Ln(SiMe/sub 3/)/sub 2/) (Ln = Sm, Dy, Ho, Er, Tm, Lu). C/sub 5/H/sub 5//sub 2/Sm(/mu/-Cl)/sub 2/Na(dme) reacts with (trimethylgermyl)lithium in dme/pentane with formation of (Li(dme)/sub 3/)((C/sub 5/H/sub 5/)/sub 3/SmClSm(C/sub 5/H/sub 5/)/sub 3/) (7a.). The new compounds have been characterized by elemental analyses and IR and NMR spectra. The structure of (Li(dme)/sub 3/)(C/sub 5/H/sub 5/)/sub 3/SmClSm(C/sub 5/H/sub 5/)/sub 3/ (7a) has been elucidated through complete X-ray analysis. The crystals are monoclinic with a = 14.00 (1) /angstrom/, b = 13.38 (2) /angstrom/, c = 23.49 (3) /angstrom/, /beta/ = 93.37 (9)/degree/, space group P2/sub 1//n,Z = 4, and R = 0.0411 for 4671 reflections. The (Cp/sub 3/SmClSmCp/sub 3/)/sup /minus// anion consists of two Cp/sub 3/Sm units bridged by a chlorine atom with Sm-Cl distances of 2.827 (2) and 2.798 (2) /angstrom/.

Schumann, H.; Nickel, S.; Loebel, J.; Pickardt, J.

1988-09-01

444

The developmental neurotoxicity study of platinum compounds. Effects of cisplatin versus a novel Pt(II) complex on rat cerebellum.  

PubMed

In the field of experimental oncology, many efforts are being carried out to search new platinum-based drugs overcoming the CNS toxicity and drug resistance. One of the adopted strategies is the synthesis of platinum compounds able to form Pt-DNA adducts different from the cisplatin ones or to react with other subcellular targets. In this context a novel Pt(II) complex, [Pt(O,O'-acac)(?-acac)(DMS)](PtAcacDMS), was synthesized which reacts preferentially with protein thiols or thioethers. In this work we investigated the in vivo effects of cisplatin and PtAcacDMS on normal development. Moreover, to verify the dose-dependence of the effects, different groups of animals were treated with 5 ?g/g or 10 ?g/g body weight of cisPt and PtAcacDMS. We have focused our attention on the cerebellum because it provides a useful model system to evaluate the outcomes of perinatal treatment with chemotherapeutic agents on key CNS developmental processes such as neural cells proliferation, migration and differentiation. We have demonstrated the ability of both cisPt and PtAcacDMS to reach the brain tissue once injected. The brain platinum content after PtAcacDMS treatment was notably higher (approximately 4-fold as much) than after cisPt. The platinum accumulation in the brain was still considerable 7 days after PtAcacDMS administration. However, compared with cisplatin, PtAcacDMS induces less severe changes on fundamental events of neuroarchitecture development, such as no high apoptotic events, less altered granule cell migration and Purkinje cell dendrite growth, suggesting a low neurotoxicity of this new Pt complex for normal CNS. The mild damages could be attributable to the different subcellular target of this